# kb

id: storm-chasing-20260505-3
file: data/en.wikipedia.org/wiki/Storm_chasing-3.md
category: reference
title: Storm chasing
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Storm_chasing
date_saved: 2026-05-05T10:03:24.090775+00:00
instance: kb-cron
parent: storm-chasing-20260505-0
summary:
=== Incidents === For nearly sixty years, the only known chaser deaths were driving-related. As of 25 December 2025, there are four known direct storm chasing deaths and twelve indirect deaths. Nearly half of the indirect deaths are a result of hydroplaning in conditions after a chase. The first was Christopher Phillips, a University of Oklahoma (OU) undergraduate student, who died in a hydroplaning accident when swerving to miss a rabbit in 1984. Other incidents included Jeff Wear driving home in East Texas from a Hurricane Dennis chase in 2005, and Fabian Guerra swerving to miss a deer while driving to a chase on I-80 in Iowa in 2009. A wrong-way driver resulted in a head-on collision that killed Andy Gabrielson who was on the Turner Turnpike (I-44) near Sapulpa, Oklahoma, returning to Luverne, Minnesota, from a chase in 2012. On 31 May 2013, an extreme event led to the first known chaser deaths inflicted directly by weather when the widest tornado ever recorded struck near El Reno, Oklahoma. Engineer Tim Samaras, his photographer son Paul, and meteorologist Carl Young were killed on a rural road by the tornado while doing in situ probe and infrasonic field research. An amateur


id: storm-chasing-20260505-4
file: data/en.wikipedia.org/wiki/Storm_chasing-4.md
category: reference
title: Storm chasing
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Storm_chasing
date_saved: 2026-05-05T10:03:24.090775+00:00
instance: kb-cron
parent: storm-chasing-20260505-0
summary:
Historically, storm chasing relied on either in-field analysis or in some cases nowcasts from trained observers and forecasters. The first in-field technology consisted of radio gear for communication. Much of this equipment could also be adapted to receive radiofax data which was useful for receiving basic observational and analysis data. The primary users of such technology were university or government research groups who often had larger budgets than individual chasers. Radio scanners were also heavily used to listen in on emergency services and storm spotters so as to determine where the most active or dangerous weather was located. A number of chasers were also radio amateurs, and used mobile (or portable) amateur radio to communicate directly with spotters and other chasers, allowing them to keep abreast of what they could not themselves see. It was not until the mid- to late 1980s that the evolution of the laptop computer would begin to revolutionize storm chasing. Early on, some chasers carried acoustic couplers to download batches of raw surface and upper air data from payphones. The technology was too slow for graphical imagery such as radar and satellite data; and during the first years this wasn't available on any connection over


id: storm-chasing-20260505-5
file: data/en.wikipedia.org/wiki/Storm_chasing-5.md
category: reference
title: Storm chasing
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Storm_chasing
date_saved: 2026-05-05T10:03:24.090775+00:00
instance: kb-cron
parent: storm-chasing-20260505-0
summary:
Chasers used paper maps for navigation and some of those now using GPS still use these as a backup or for strategizing with other chasers. Foldable state maps can be used but are cumbersome due to the multitude of states needed and only show major roads. National atlases allow more detail and all states are contained in a single book, with AAA favored and Rand McNally followed by Michelin also used. The preferred atlases due to great detail in rural areas are the "Roads of..." series originally by Shearer Publishing, which first included Texas but expanded to other states such as Oklahoma and Colorado. Covering every state of the union are the DeLorme "Atlas and Gazetteer" series. DeLorme also produced early GPS receivers that connected to laptops and for years was one of two major mapping software creators. DeLorme Street Atlas USA or Microsoft Streets & Trips were used by most chasers until their discontinuations in 2013. Chasers now use Google Maps, Waze, and/or Apple Maps or other web mapping on mobile devices as no comparably robust mapping software emerged although operating systems later implemented the apps Windows Maps and Apple Maps. To ensure mapping availability without an active internet


id: storm-chasing-20260505-6
file: data/en.wikipedia.org/wiki/Storm_chasing-6.md
category: reference
title: Storm chasing
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Storm_chasing
date_saved: 2026-05-05T10:03:24.090775+00:00
instance: kb-cron
parent: storm-chasing-20260505-0
summary:
Some handsets can be used as WiFi hotspots and wireless cards may also be used to avoid committing a handset to tethering or operating as a hotspot. Some hotspots operate as mobile broadband MNVO devices using any radio spectrum that is both available and is in contract with a service provider. Such devices may expand mobile data range beyond a single carrier's service area and typically can work on month-to-month contracts. Adoption of tablet computers expanded by the early 2010s. 4G LTE was adopted early, when available, and was especially useful for uploading HD video. 5G is used with some chasers selecting carriers based on network coverage. Connected car technology includes Wi-Fi which can be used to augment, or even supplant, connectivity via mobile phones. A gradual uptick of those selecting mirrorless interchangeable-lens cameras (MILCs) began in the mid-2010s. Usage of DSLR for video capture, called HDSLR, is common, although camcorders remain relatively popular due to their greater functionality (many chasers still shoot both). Through the 2020s the use of 8K devices is gradually expanding and by the mid-2020s a few chasers are experimenting with 360-degree video. Chasers also carry common travel articles and vehicle maintenance items, and sometimes first


id: storm-chasing-20260505-7
file: data/en.wikipedia.org/wiki/Storm_chasing-7.md
category: reference
title: Storm chasing
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Storm_chasing
date_saved: 2026-05-05T10:03:24.090775+00:00
instance: kb-cron
parent: storm-chasing-20260505-0
summary:
== Ethics == A growing number of experienced storm chasers advocate the adoption of a code of ethics in storm chasing featuring safety, courtesy, and objectivity as the backbone. Storm chasing is a highly visible recreational activity (which is also associated with science) that is vulnerable to sensationalist media promotion. Veteran storm chasers Chuck Doswell and Roger Edwards deemed reckless storm chasers as "yahoos". Doswell and Edwards believe poor chasing ethics at TV news stations add to the growth of "yahoo" storm chasing. A large lawsuit was filed against the parent company of The Weather Channel in March 2019 for allegedly keeping on contract storm chaser drivers with a demonstrated pattern of reckless driving which ultimately led to a fatal collision (killing themselves and a storm spotter in the other vehicle) when running a stop sign in Texas in 2017. Edwards and Rich Thompson, among others, also expressed concern about pernicious effects of media profiteering with Matt Crowther, among others, agreeing in principle but viewing sales as not inherently corrupting. Self-policing is predominantly seen as the means to mold the hobby. There is occasional discussion among chasers that at some point government regulation may be imposed due to increasing numbers


id: studying-children-in-context-20260505-0
file: data/en.wikipedia.org/wiki/Studying_Children_in_Context-0.md
category: reference
title: Studying Children in Context
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Studying_Children_in_Context
date_saved: 2026-05-05T10:03:25.259826+00:00
instance: kb-cron
parent: studying-children-in-context-20260505-0
summary:
Studying Children in Context: Theories, Methods, and Ethics is a 1998 book on qualitative research methods for working with young children. It was written by M. Elizabeth Graue and Daniel J. Walsh and published by SAGE Publications. == Notes == == References ==


id: theory-driven-evaluation-20260505-0
file: data/en.wikipedia.org/wiki/Theory-driven_evaluation-0.md
category: reference
title: Theory-driven evaluation
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Theory-driven_evaluation
date_saved: 2026-05-05T10:03:26.493485+00:00
instance: kb-cron
parent: theory-driven-evaluation-20260505-0
summary:
Theory-driven evaluation (also theory-based evaluation) is an umbrella term for any approach to program evaluation – quantitative, qualitative, or mixed method – that develops a theory of change and uses it to design, implement, analyze, and interpret findings from an evaluation. More specifically, an evaluation is theory-driven if it: formulates a theory of change using some combination of social science, lived experience, and program-related professionals' expertise; develops and prioritizes evaluation questions using the theory; uses the theory to guide the design and implementation of the evaluation; uses the theory to operationalize contextual, process, and outcome variables; provides a causal explanation of how and why outcomes were achieved, including whether the program worked and/or had any unintended consequences (desirable or harmful); and explains what factors moderate outcomes. By investigating the mechanisms leading to outcomes, theory-driven approaches facilitate learning to improve programs and how they are implemented, and help knowledge to accumulate – including across ostensibly different programs. This is in contrast to methods-driven "black box" evaluations, which focus on following the steps of a method (for instance, randomized experiment or focus group) and only assess whether a program achieves its intended outcomes. Theory-driven approaches can also improve the validity of evaluations,


id: theory-driven-evaluation-20260505-1
file: data/en.wikipedia.org/wiki/Theory-driven_evaluation-1.md
category: reference
title: Theory-driven evaluation
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Theory-driven_evaluation
date_saved: 2026-05-05T10:03:26.493485+00:00
instance: kb-cron
parent: theory-driven-evaluation-20260505-0
summary:
The target population includes a specification of who participants are and how they are recruited. The implementing organization (for instance a clinic or school) and its staff of implementers (for instance therapists or teachers) are responsible for allocating resources, training, and delivering the interventions. Intervention and service delivery protocols would include therapy manuals or subject curricula. Associated organizations and community partners refers to organisations other than the implementing organisation. In the case of a psychotherapy intervention, this may include schools or general practitioners who advertise the program or refer beneficiaries to it. Ecological context refers to aspects of the environment, for instance family, friends, co-workers, other students, etc., that may moderate the effects of a program. == Theory-driven methods == The full-range of research methods has been argued to apply. Chen (2015) provides examples using randomized experiments, quasi-experimental designs, process and outcome monitoring, and qualitative methods. Although proponents of theory-driven evaluation are critical of "black box" experiments, Chen and Rossi (1983, p. 292) argue that theory-driven experiments are possible and desirable: [A]dvocates of the black box experimental paradigm often neglect the fact that after randomization exogenous variables are still correlated with outcome variables. Knowing how such exogenous factors affect outcomes


id: trend-analysis-20260505-0
file: data/en.wikipedia.org/wiki/Trend_analysis-0.md
category: reference
title: Trend analysis
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Trend_analysis
date_saved: 2026-05-05T10:03:27.621466+00:00
instance: kb-cron
parent: trend-analysis-20260505-0
summary:
Trend analysis is the practice of collecting information and attempting to spot a pattern. In some fields of study, the term has more formally defined meanings. Although trend analysis is often used to predict future events, it could be used to estimate uncertain events in the past, such as how many ancient kings probably ruled between two dates, based on data such as the average years which other known kings reigned. == Project management == In project management, trend analysis is a mathematical technique that uses historical results to predict future outcome. This is achieved by tracking variances in cost and schedule performance. In this context, it is a project management quality control tool. == Statistics == In statistics, trend analysis often refers to techniques for extracting an underlying pattern of behavior in a time series which would otherwise be partly or nearly completely hidden by noise. If the trend can be assumed to be linear, trend analysis can be undertaken within a formal regression analysis, as described in Trend estimation. If the trends have other shapes than linear, trend testing can be done by non-parametric methods, e.g. Mann-Kendall test, which is a version of Kendall rank correlation coefficient. Smoothing


id: trend-receiver-20260505-0
file: data/en.wikipedia.org/wiki/Trend_Receiver-0.md
category: reference
title: Trend Receiver
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Trend_Receiver
date_saved: 2026-05-05T10:03:28.802758+00:00
instance: kb-cron
parent: trend-receiver-20260505-0
summary:
The Trend Receiver Concept is a method for developing Customer Foresight (Baumgarth, 2018, Lüken 2020, van Deth 2020) and has been overall identified as an approach to develop foresight (Rohrbeck et al. 2015; Schwarz et al. 2018). At the core of the Trend Receiver Concept is the identification of suitable conversation partners, so called Trend Receivers, when developing foresight on the future demands and habits of consumers. “Trend Receivers are individuals who perceive changes and potentials of the new in a specific domain in a highly sensitive and differentiated way”. The concept contributes to a firm's mid and long-term vision and strategy by combining both customers and foresight. The Trend Receiver Concept provides a guideline to identifying suitable individuals (Trend Receivers) and to designing resulting conversations with them. == Characteristics of Trend Receivers == Trend Receivers are very well connected, have profound opinions about what motivates individuals and observe changes in society in a very reflective way. Trend Receivers can further be characterized as follows (Hofmann 2020): Context experience: Trend Receivers have a profound understanding of the specific context due to their consumption and usage experiences and are thus familiar with the motive and value sets of consumers. Self-abstraction ability:


id: virtual-colony-count-20260505-0
file: data/en.wikipedia.org/wiki/Virtual_colony_count-0.md
category: reference
title: Virtual colony count
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Virtual_colony_count
date_saved: 2026-05-05T10:03:29.986616+00:00
instance: kb-cron
parent: virtual-colony-count-20260505-0
summary:
Virtual colony count (VCC) is a kinetic, 96-well microbiological assay originally developed to measure the activity of defensins. It has since been applied to other antimicrobial peptides including LL-37. It utilizes a method of enumerating bacteria called quantitative growth kinetics, which compares the time taken for a bacterial batch culture to reach a threshold optical density with that of a series of calibration curves. The name VCC has also been used to describe the application of quantitative growth kinetics to enumerate bacteria in cell culture infection models. Antimicrobial susceptibility testing (AST) can be done on 96-well plates by diluting the antimicrobial agent at varying concentrations in broth inoculated with bacteria and measuring the minimum inhibitory concentration that results in no growth. However, these methods cannot be used to study some membrane-active antimicrobial peptides, which are inhibited by the broth itself. The virtual colony count procedure takes advantage of this fact by first exposing bacterial cells to the active antimicrobial agent in a low-salt buffer for two hours, then simultaneously inhibiting antimicrobial activity and inducing exponential growth by adding broth. The growth kinetics of surviving cells can then be monitored using a temperature-controlled plate reader. The time taken for each growth


id: virtual-colony-count-20260505-1
file: data/en.wikipedia.org/wiki/Virtual_colony_count-1.md
category: reference
title: Virtual colony count
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Virtual_colony_count
date_saved: 2026-05-05T10:03:29.986616+00:00
instance: kb-cron
parent: virtual-colony-count-20260505-0
summary:
== Virtual colony count == The traditional colony count method could be modified to measure antimicrobial activity in the 96-well plate without the need for sampling the wells and spreading surviving cells on agar plates by simply adding an equal volume of twice-concentrated broth after the two hour incubation in the low salt buffer. There would need to be a way to determine how many cells survived at the end of the incubation period using batch cultures. Fortunately, the mathematics of exponential growth offers a way to do just that. If the turbidity, or optical density, of the batch cultures within the 96-well plate is monitored in real time, and the amount of time required for a well to reach a threshold is recorded, and the doubling time of the exponentially growing cells is known, then the number of cells originally present in the inoculum can be calculated. This starting number of cells is equal to the number of surviving cells at the end of the two hour incubation with the antimicrobial agent. Because this procedure requires no actual colony formation or colony counting, it is termed "virtual colony count". Thus far the VCC technique has been limited to antimicrobial


id: virtual-colony-count-20260505-2
file: data/en.wikipedia.org/wiki/Virtual_colony_count-2.md
category: reference
title: Virtual colony count
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Virtual_colony_count
date_saved: 2026-05-05T10:03:29.986616+00:00
instance: kb-cron
parent: virtual-colony-count-20260505-0
summary:
The method of enumeration of surviving cells used by VCC is termed quantitative growth kinetics (QGK). It relates the kinetic time taken for the turbidity of a bacterial batch microbiological culture in a well of a 96-well microplate to reach a threshold difference in turbidity to a 10-fold dilution series of calibration growth curves. Quantification of the number of viable cells is done using a process mathematically identical to quantitative real-time polymerase chain reaction (QPCR), except with QGK cells, rather than copies of PCR products, grow exponentially. The time taken to reach the threshold is called the "threshold time", Tt, which is equivalent to the QPCR value "cycle time" or Ct. There are at least five processes that cause delays in threshold times in VCC assays: Adhesion, causing cells to stick to the microplate and possibly form biofilms. Unless these cells happen to be directly in the light path, their growth will not affect optical density readings. Cohesion, causing cells to aggregate into clumps of various sizes instead of a homogeneous suspension of individual cells undergoing binary fission. Cohesion can cause imprecision and fluctuations in Tt. Cohesive clumps may also be adhesive, leading to both imprecision due to cohesion and


id: virtual-colony-count-20260505-3
file: data/en.wikipedia.org/wiki/Virtual_colony_count-3.md
category: reference
title: Virtual colony count
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Virtual_colony_count
date_saved: 2026-05-05T10:03:29.986616+00:00
instance: kb-cron
parent: virtual-colony-count-20260505-0
summary:
== Inoculum effect == An inoculum effect has been previously described for many antimicrobial agents, such that the agent is less effective when more bacteria are added to the assay. This effect is often observed with beta lactams when assayed against beta lactamase producing bacteria. The inoculum effect was potentially relevant to a study of HNP1, pro LL-37 and LL-37 that included both traditional colony counting and VCC side by side. In that report, it was found that traditional colony count survival values were less than virtual survival values for all peptides and strains tested. Because the inoculum of bacteria was 20-fold greater in the VCC assay compared to the standardized traditional colony count protocol used, the difference could have been due to an inoculum effect, although the effect would have been the reverse of the inoculum effect normally seen with other antimicrobial agents, since the higher inoculum showed more activity. This possibility was investigated in a series of VCC experiments mainly focusing on the defensin HNP1 and the bacterial strains E. coli, S. aureus and B. cereus. The results of six experiments demonstrated a pronounced inoculum effect of HNP1 against E. coli. == Algorithms to analyze quantitative growth kinetics


id: visual-ethnography-20260505-0
file: data/en.wikipedia.org/wiki/Visual_ethnography-0.md
category: reference
title: Visual ethnography
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Visual_ethnography
date_saved: 2026-05-05T10:03:31.166378+00:00
instance: kb-cron
parent: visual-ethnography-20260505-0
summary:
Visual ethnography is an approach to ethnography (the study of people and cultures) that uses visual methods such as photography, film and video. There are many methods available to conduct visual ethnography. According to Sarah Pink, visual ethnography is a research methodology that brings “theory and practice of visual approaches to learning and knowing about the world and communicating these to others”. As a methodology, visual ethnography can guide the design of research as well as the methods to choose for data collection. Visual ethnography suggests a negotiation of the participants’ view of reality and a constant questioning on the part of the researcher. == Historical development == Beginning in the early 1900s, researchers have recognized the importance of visual methods which has largely emerged from anthropology. That is when photography as well as video became ways of recording targeted populations during field work which are called “salvage ethnography” or “salvage anthropology.” Flaherty's Nanook of the North (1922), Margaret Mead's and Gregory Bateson's video and photos of the Balinese, and Evans-Prichard's photographs of the Nuer are examples of this “salvage ethnography (Pink, 2006, cited in van den Scott, 2018). Boas as explained by Pink was an early user of photography


id: vivisection-20260505-0
file: data/en.wikipedia.org/wiki/Vivisection-0.md
category: reference
title: Vivisection
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Vivisection
date_saved: 2026-05-05T10:03:32.979340+00:00
instance: kb-cron
parent: vivisection-20260505-0
summary:
Vivisection (from Latin vivus 'alive' and sectio 'cutting') is surgery conducted for experimental purposes on a living organism, typically animals with a central nervous system, to view living internal structure. The word is, more broadly, used as a pejorative catch-all term for experimentation on live animals by organizations opposed to animal experimentation, but the term is rarely used by practicing scientists. Human vivisection, such as live organ harvesting, has been perpetrated as a form of torture. == Animal vivisection == === Regulations and laws === Research requiring vivisection techniques that cannot be met through other means is often subject to an external ethics review in conception and implementation, and in many jurisdictions use of anesthesia is legally mandated for any surgery likely to cause pain to any vertebrate. In the United States, the Animal Welfare Act explicitly requires that any procedure that may cause pain use "tranquilizers, analgesics, and anesthetics" with exceptions when "scientifically necessary". The act does not define "scientific necessity" or regulate specific scientific procedures, but approval or rejection of individual techniques in each federally funded lab is determined on a case-by-case basis by the Institutional Animal Care and Use Committee, which contains at least one veterinarian, one


id: vivisection-20260505-1
file: data/en.wikipedia.org/wiki/Vivisection-1.md
category: reference
title: Vivisection
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Vivisection
date_saved: 2026-05-05T10:03:32.979340+00:00
instance: kb-cron
parent: vivisection-20260505-0
summary:
The Cruelty to Animals Act, 1876 in Britain determined that one could only conduct vivisection on animals with the appropriate license from the state, and that the work the physiologist was doing had to be original and absolutely necessary. The stage was set for such legislation by physiologist David Ferrier. Ferrier was a pioneer in understanding the brain and used animals to show that certain locales of the brain corresponded to bodily movement elsewhere in the body in 1873. He put these animals to sleep, and caused them to move unconsciously with a probe. Ferrier was successful, but many decried his use of animals in his experiments. Some of these arguments came from a religious standpoint. Some were concerned that Ferrier's experiments would separate God from the mind of man in the name of science. Some of the anti-vivisection movement in England had its roots in Evangelicalism and Quakerism. These religions already had a distrust for science, only intensified by the recent publishing of Darwin's Theory of Evolution in 1859. Neither side was pleased with how the Cruelty to Animals Act 1876 was passed. The scientific community felt as though the government was restricting their ability to compete with the


id: wildlife-observation-20260505-0
file: data/en.wikipedia.org/wiki/Wildlife_observation-0.md
category: reference
title: Wildlife observation
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Wildlife_observation
date_saved: 2026-05-05T10:03:34.170673+00:00
instance: kb-cron
parent: wildlife-observation-20260505-0
summary:
Wildlife observation is the practice of noting the occurrence or abundance of animal species at a specific location and time, either for research purposes or recreation. Common examples of this type of activity are bird watching and whale watching. The process of scientific wildlife observation includes the reporting of what (diagnosis of the species), where (geographical location), when (date and time), who (details about observer), and why (reason for observation, or explanations for occurrence). Wildlife observation can be performed if the animals are alive, with the most notable example being face-to-face observation and live cameras, or are dead, with the primary example being the notifying of where roadkill has occurred. This outlines the basic information needed to collect data for a wildlife observation; which can also contribute to scientific investigations of distribution, habitat relations, trends, and movement of wildlife species. Wildlife observation allows for the study of organisms with minimal disturbance to their ecosystem depending on the type of method or equipment used. The use of equipment such as unmanned aerial vehicles (UAVs), more commonly known as drones, may disturb and cause negative impacts on wildlife. Specialized equipment can be used to collect more accurate data. == History == Wildlife


id: wildlife-observation-20260505-1
file: data/en.wikipedia.org/wiki/Wildlife_observation-1.md
category: reference
title: Wildlife observation
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Wildlife_observation
date_saved: 2026-05-05T10:03:34.170673+00:00
instance: kb-cron
parent: wildlife-observation-20260505-0
summary:
=== Birdwatching === One of the most popular forms of wildlife observation, birdwatching, is typically performed as a recreational pleasure. Those looking to birdwatch typically travel into a forest or other wooded area with a pair of binoculars in hand to aid the process. Birdwatching has become all the more important with the amount of deforestation that has been occurring in the world. Birds are arguably the most important factor in the balance of environmental systems: "They pollinate plants, disperse seeds, scavenge carcasses and recycle nutrients back into the earth." A decrease in the total number of birds would cause destruction to much of the environmental system. The plants and trees around the world would die at an alarming rate which would, in turn, set off a chain reaction that would cause many other animals to die due to the environment change and habitat loss. One of the ways that birdwatching has an effect on the environment as a whole is that through consistent birdwatching, an observer would be able to identify whether they are seeing less of a certain species of bird. If this happens, there typically is a reasons for the occurrence, whether it be because of an


id: wildlife-observation-20260505-2
file: data/en.wikipedia.org/wiki/Wildlife_observation-2.md
category: reference
title: Wildlife observation
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Wildlife_observation
date_saved: 2026-05-05T10:03:34.170673+00:00
instance: kb-cron
parent: wildlife-observation-20260505-0
summary:
=== Online systems and mobile apps === Many states have already begun to set up websites and systems for the public. The main purpose behind the movement is so that they can notify other individuals about road-killed wildlife. If enough people fill out the forms located on the websites, the government will become notified that there have been occurrences of a loss of animal life and will take the steps required to prevent it. Typically, the step that is taken is the posting of a wildlife crossing sign that, in turn, allows the public to know where there are common animal crossings. Maine and California are the states that have been the pioneers of this movement and this process has become particularly important on heavily traveled roads as no one would like endanger the animals or themselves. Currently, there is an app (available on both iPhone and Android devices) made specifically for the purpose of identifying road-kill called “Mobile Mapper.” The app is a partner of the HerpMapper website. The purpose of the website is to use the user recorded observations for research and conservation purposes. On average, the cost of repairing a car that has been damaged by a


id: wildlife-observation-20260505-3
file: data/en.wikipedia.org/wiki/Wildlife_observation-3.md
category: reference
title: Wildlife observation
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Wildlife_observation
date_saved: 2026-05-05T10:03:34.170673+00:00
instance: kb-cron
parent: wildlife-observation-20260505-0
summary:
=== Pollution === Pollution is another crucial threat to animal life, and human life, across the world. Every form of pollution has an effect on wildlife, whether it be through the air, water, or ground. While sometimes the origin and form of pollution is visible and easy to determine, other times it can be a mystery as to what exactly is causing the death of animals. Through constant and consistent observation of habitat analysis, humans can help prevent the loss of animal life by recognizing the early signs of pollution before the problem becomes too large. ==== Ocean and water pollution ==== Pollution can enter bodies of water in many different ways - Through toxic runoff from pesticides and fertilizers, containers of oil and other hazardous materials falling off of ships, or just from debris from humans that has not been picked up. No matter what the form of pollution is, the effects water pollution has on animal life can be drastic. For example, the BP oil spill which occurred in 2010 impacted over 82,000 birds, 6,000 sea turtles, approximately 26,000 marine animals, and hundreds of thousands of fish. While the observation of how animal life was and has been


id: wildlife-observation-20260505-4
file: data/en.wikipedia.org/wiki/Wildlife_observation-4.md
category: reference
title: Wildlife observation
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Wildlife_observation
date_saved: 2026-05-05T10:03:34.170673+00:00
instance: kb-cron
parent: wildlife-observation-20260505-0
summary:
=== Costs that observation prevents === Referring back to the example from the "Deceased Wildlife Observation" section, it becomes apparent how animal observation can save families and the government money. With the average cost of repairing a car that has damage from a large sized animal being $2,000, families and the government could save money by making the public aware that they should proceed with caution in areas where animals have been hit. Additionally, approximately $44 million of the $4.3 billion spent on water purity is spent each year on protecting aquatic species from nutrient pollution. It is encouraging that the government is willing to spend the money to help save animals' lives, sometimes the effects of the pollution take effect before they are able to stop them entirely. One million seabirds and hundred thousand aquatic mammals and fish that are killed as a result of water pollution each year and that has its economic effects, both directly and indirectly. Directly, the loss of aquatic mammals and fish has a direct impact on the sales of food. The EPA estimated recently that the effects of pollution cost the fishing industry tens of millions of dollars in sales. Indirectly, the loss


id: absorption-spectroscopy-20260505-0
file: data/en.wikipedia.org/wiki/Absorption_spectroscopy-0.md
category: reference
title: Absorption spectroscopy
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Absorption_spectroscopy
date_saved: 2026-05-05T10:03:35.666525+00:00
instance: kb-cron
parent: absorption-spectroscopy-20260505-0
summary:
Absorption spectroscopy is spectroscopy that involves techniques that measure the absorption of electromagnetic radiation, as a function of frequency or wavelength, due to its interaction with a sample. The sample absorbs energy, i.e., photons, from the radiating field. The intensity of the absorption varies as a function of frequency, and this variation is the absorption spectrum. Absorption spectroscopy is performed across the electromagnetic spectrum. Absorption spectroscopy is employed as an analytical chemistry tool to determine the presence of a particular substance in a sample and, in many cases, to quantify the amount of the substance present. Infrared and ultraviolet–visible spectroscopy are particularly common in analytical applications. Absorption spectroscopy is also employed in studies of molecular and atomic physics, astronomical spectroscopy and remote sensing. There is a wide range of experimental approaches for measuring absorption spectra. The most common arrangement is to direct a generated beam of radiation at a sample and detect the intensity of the radiation that passes through it. The transmitted energy can be used to calculate the absorption. The source, sample arrangement and detection technique vary significantly depending on the frequency range and the purpose of the experiment. Following are the major types of absorption spectroscopy: ==


id: absorption-spectroscopy-20260505-1
file: data/en.wikipedia.org/wiki/Absorption_spectroscopy-1.md
category: reference
title: Absorption spectroscopy
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Absorption_spectroscopy
date_saved: 2026-05-05T10:03:35.666525+00:00
instance: kb-cron
parent: absorption-spectroscopy-20260505-0
summary:
=== Relation to scattering and reflection spectra === The scattering and reflection spectra of a material are influenced by both its refractive index and its absorption spectrum. In an optical context, the absorption spectrum is typically quantified by the extinction coefficient, and the extinction and index coefficients are quantitatively related through the Kramers–Kronig relations. Therefore, the absorption spectrum can be derived from a scattering or reflection spectrum. This typically requires simplifying assumptions or models, and so the derived absorption spectrum is an approximation. == Applications == Absorption spectroscopy is useful in chemical analysis because of its specificity and its quantitative nature. The specificity of absorption spectra allows compounds to be distinguished from one another in a mixture, making absorption spectroscopy useful in wide variety of applications. For instance, Infrared gas analyzers can be used to detect pollutants in the air, distinguishing them from nitrogen, oxygen, water, and other expected constituents. The specificity also allows unknown samples to be identified by comparing a measured spectrum with a library of reference spectra. In many cases, qualitative information about a sample can be determined even if it is not in a library. Infrared spectra, for instance, have characteristic absorption bands that indicate if


id: absorption-spectroscopy-20260505-2
file: data/en.wikipedia.org/wiki/Absorption_spectroscopy-2.md
category: reference
title: Absorption spectroscopy
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Absorption_spectroscopy
date_saved: 2026-05-05T10:03:35.666525+00:00
instance: kb-cron
parent: absorption-spectroscopy-20260505-0
summary:
=== Basic approach === The most straightforward approach to absorption spectroscopy is to generate radiation with a source, measure a reference spectrum of that radiation with a detector and then re-measure the sample spectrum after placing the material of interest in between the source and detector. The two measured spectra can then be combined to determine the material's absorption spectrum. The sample spectrum alone is not sufficient to determine the absorption spectrum because it will be affected by the experimental conditions—the spectrum of the source, the absorption spectra of other materials between the source and detector, and the wavelength dependent characteristics of the detector. The reference spectrum will be affected in the same way, though, by these experimental conditions and therefore the combination yields the absorption spectrum of the material alone. A wide variety of radiation sources are employed in order to cover the electromagnetic spectrum. For spectroscopy, it is generally desirable for a source to cover a broad swath of wavelengths in order to measure a broad region of the absorption spectrum. Some sources inherently emit a broad spectrum. Examples of these include globars or other black body sources in the infrared, mercury lamps in the visible and ultraviolet,


id: acoustic-paramagnetic-resonance-20260505-0
file: data/en.wikipedia.org/wiki/Acoustic_paramagnetic_resonance-0.md
category: reference
title: Acoustic paramagnetic resonance
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Acoustic_paramagnetic_resonance
date_saved: 2026-05-05T10:03:36.866337+00:00
instance: kb-cron
parent: acoustic-paramagnetic-resonance-20260505-0
summary:
In acoustics, acoustic paramagnetic resonance (APR) is a phenomenon of resonant absorption of sound by a system of magnetic particles placed in an external magnetic field. It occurs when the energy of the sound wave quantum becomes equal to the splitting of the energy levels of the particles, the splitting being induced by the magnetic field. APR is a variation of electron paramagnetic resonance (EPR) where the acoustic rather than electromagnetic waves are absorbed by the studied sample. APR was theoretically predicted in 1952, independently by Semen Altshuler and Alfred Kastler, and was experimentally observed by W. G. Proctor and W. H. Tanttila in 1955. == History == After discovery of EPR in 1944, Evgeny Zavoisky predicted that the resonance phenomenon should not be restricted to radio or microwave absorption but could be extended to the sound waves. This idea was theoretically developed by his collaborator Semen Altshuler in 1952 and independently by Alfred Kastler; whereas Altshuler reported the effect on electron spins, Kastler calculated a nuclear spin system. The first experimental detection of the APR was reported in 1955 using 35Cl nuclei in single crystals of sodium chlorate. This nuclear-APR work was extended to electron-APR in 1959. Further applications


id: analytical-light-scattering-20260505-0
file: data/en.wikipedia.org/wiki/Analytical_light_scattering-0.md
category: reference
title: Analytical light scattering
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Analytical_light_scattering
date_saved: 2026-05-05T10:03:38.039413+00:00
instance: kb-cron
parent: analytical-light-scattering-20260505-0
summary:
Analytical light scattering (ALS), also loosely referred to as SEC-MALS, is the implementation of static light scattering (SLS) and dynamic light scattering (DLS) techniques in an online or flow mode. A typical ALS instrument consists of an HPLC/FPLC chromatography system coupled in-line with appropriate light scattering and refractive index detectors. The advantage of ALS over conventional steady-state light scattering methods is that it allows separation of molecules/macromolecules on a chromatography column prior to analysis with light scattering detectors. Accordingly, ALS enables one to determine hydrodynamic properties of a single monodisperse species as opposed to bulk or average measurements on a sample afforded by conventional light scattering. == References ==


id: anisotropic-terahertz-microspectroscopy-20260505-0
file: data/en.wikipedia.org/wiki/Anisotropic_terahertz_microspectroscopy-0.md
category: reference
title: Anisotropic terahertz microspectroscopy
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Anisotropic_terahertz_microspectroscopy
date_saved: 2026-05-05T10:03:39.205651+00:00
instance: kb-cron
parent: anisotropic-terahertz-microspectroscopy-20260505-0
summary:
Anisotropic terahertz microspectroscopy (ATM) is a spectroscopic technique in which molecular vibrations in an anisotropic material are probed with short pulses of terahertz radiation whose electric field is linearly polarized parallel to the surface of the material. The technique has been demonstrated in studies involving single crystal sucrose, fructose, oxalic acid, and molecular protein crystals in which the spatial orientation of molecular vibrations are of interest. == Explanation == When the electric field of a propagating beam of light oscillates in a direction perpendicular to its direction of propagation, it is said to be a polarized transverse wave. Light with an electric field constrained to a particular angle in the transverse plane is said to be linearly polarized. When linearly polarized light is transmitted through an isotropic material — a material that exhibits the same physical properties in all spatial directions — the amount of light absorbed by the material is the same when measured for all angles of the polarized light. The resulting absorbance spectrum is featureless as a function of the polarization angle. A material said to be anisotropic exhibits different physical properties, like absorbance, refractive index, conductivity and so on, along different spatial directions. Thus, when a


id: anisotropic-terahertz-microspectroscopy-20260505-1
file: data/en.wikipedia.org/wiki/Anisotropic_terahertz_microspectroscopy-1.md
category: reference
title: Anisotropic terahertz microspectroscopy
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Anisotropic_terahertz_microspectroscopy
date_saved: 2026-05-05T10:03:39.205651+00:00
instance: kb-cron
parent: anisotropic-terahertz-microspectroscopy-20260505-0
summary:
==== Instrument Design ==== An ATM designed with a rotated sample is typically a far-field measurement configuration using a time-domain spectroscopy strategy. A high power infrared laser is typically used. Its beam is split by a beamsplitter into two optical paths: a probe beam and a THz generation beam. The THz generation beam typically receives the greater fraction of NIR power in order to maximize the power of the THz light commonly generated by a voltage-pulsed photoconductive antenna. The generated THz light is collected through a hyper-hemispherical silicon lens and passed to an off-axis parabolic mirror that collimates the THz beam for polarization by a THz polarizer that is often made of a simple wire-grid. The linearly polarized THz beam is then focused by a second off-axis parabolic mirror onto the sample. The THz beam transmitted through the sample is again collected by a third off-axis parabolic mirror, collimated onto a fourth parabolic mirror that then focuses the beam onto an electro-optic (EO) crystal whose birefringence is perturbed by the strength of the THz beam. The NIR probe beam is passed through the EO crystal to probe the induced degree of birefringence caused by the THz beam and passed to


id: anisotropic-terahertz-microspectroscopy-20260505-2
file: data/en.wikipedia.org/wiki/Anisotropic_terahertz_microspectroscopy-2.md
category: reference
title: Anisotropic terahertz microspectroscopy
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Anisotropic_terahertz_microspectroscopy
date_saved: 2026-05-05T10:03:39.205651+00:00
instance: kb-cron
parent: anisotropic-terahertz-microspectroscopy-20260505-0
summary:
===== THz Quarter Waveplate ===== One strategy to provide full 360° rotation of THz polarization of equal electric field magnitude at the sample is to generate a circular state of polarization, then select particular linear polarization states from the circularly polarized beam with a THz polarizer. A circular polarization state may be generated by a quarter waveplate, however, common optical waveplates are typically designed for visible, near- and mid-infrared regions of the electromagnetic spectrum. A quarter waveplate designed for use in the THz frequency range consists of a right-angle silicon prism together with metal-coated planar mirrors as input/output. In particular, the silicon prism acts analogously to a Fresnel rhomb with a single total internal reflection on the longer face of the prism and is a passive broadband component that permits a wide frequency sweep during measurements. == Advantages == A few advantages of ATM over other related microspectroscopy techniques include the orientation of the THz electric field at the sample and the ability to readily measure materials that are sensitive to environmental conditions like hydration, cryo-cooling, and evacuation. === THz polarization orientation at the sample === A key characteristic of ATM is the orientation of the polarized electric field of


id: anomalous-x-ray-scattering-20260505-0
file: data/en.wikipedia.org/wiki/Anomalous_X-ray_scattering-0.md
category: reference
title: Anomalous X-ray scattering
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Anomalous_X-ray_scattering
date_saved: 2026-05-05T10:03:40.354899+00:00
instance: kb-cron
parent: anomalous-x-ray-scattering-20260505-0
summary:
Anomalous X-ray scattering (AXRS or XRAS) is a non-destructive determination technique within X-ray diffraction that makes use of the anomalous dispersion that occurs when a wavelength is selected that is in the vicinity of an absorption edge of one of the constituent elements of the sample. It is used in materials research to study nanometer sized differences in structure. == Atomic scattering factors == In X-ray diffraction the scattering factor f for an atom is roughly proportional to the number of electrons that it possesses. However, for wavelengths that approximate those for which the atom strongly absorbs radiation the scattering factor undergoes a change due to anomalous dispersion. The dispersion not only affects the magnitude of the factor but also imparts a phase shift in the elastic collision of the photon. The scattering factor can therefore best be described as a complex number: f = fo + Δf' + iΔf" == Contrast variation == The anomalous aspects of X-ray scattering have become the focus of considerable interest in the scientific community because of the availability of synchrotron radiation. In contrast to desktop X-ray sources that only operate at certain fixed wavelengths, synchrotron radiation is generated by accelerating electrons and using


id: arterial-spin-labelling-20260505-0
file: data/en.wikipedia.org/wiki/Arterial_spin_labelling-0.md
category: reference
title: Arterial spin labelling
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Arterial_spin_labelling
date_saved: 2026-05-05T10:03:41.600359+00:00
instance: kb-cron
parent: arterial-spin-labelling-20260505-0
summary:
Arterial spin labeling (ASL), also known as arterial spin tagging, is a magnetic resonance imaging technique used to quantify cerebral blood perfusion by labelling blood water as it flows throughout the brain. ASL specifically refers to magnetic labeling of arterial blood below or in the imaging slab, without the need of gadolinium contrast. A number of ASL schemes are possible, the simplest being flow alternating inversion recovery (FAIR) which requires two acquisitions of identical parameters with the exception of the out-of-slice saturation; the difference in the two images is theoretically only from inflowing spins, and may be considered a 'perfusion map'. The ASL technique was developed by John S. Leigh Jr, John A. Detre, Donald S. Williams, and Alan P. Koretsky in 1992. == Physics == Arterial spin labeling utilizes the water molecules circulating with the brain, and using a radiofrequency pulse, tracks the blood water as it circulates throughout the brain. After a period of time in microseconds (enough to allow the blood to circulate through the brain), a 'label' image is captured. A 'control' image is also acquired before the labeling of the blood water. A subtraction technique gives a measurement of perfusion. In order to increase SNR,


id: arterial-spin-labelling-20260505-1
file: data/en.wikipedia.org/wiki/Arterial_spin_labelling-1.md
category: reference
title: Arterial spin labelling
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Arterial_spin_labelling
date_saved: 2026-05-05T10:03:41.600359+00:00
instance: kb-cron
parent: arterial-spin-labelling-20260505-0
summary:
== Analysis of ASL images == ASL maps can mainly be analyzed using the same tools to analyze fMRI and VBM. Many ASL-specific toolboxes have been developed to assist in ASL analysis, such as BASIL (Bayesian inference for arterial spin labelling MRI), part of the FSL neuroimaging package and also Ze Wang's ASL toolbox (using MATLAB) to assist in the subtraction and averaging of the tagged/control pairs. A visual quality check is often needed to make sure that the perfusion map is valid (such as correct registration, or correct segmentation of non-cerebral materials such as the dura mater). A whole brain/voxel-wise approach can be analyzed by registering the ASL map into MNI space for group comparisons. A region of interest approach can be analyzed by registering the ASL map into a selected cluster, or an atlas, like a standard (such as the Harvard-Oxford Cortical atlas) or an individual atlas developed by software like FreeSurfer. The recommended procedure of ASL registration for voxel-wise analysis is to register the perfusion map to a gray matter segmentation of each individual in a non-rigid procedure. Gray matter often requires more oxygenation and is the source of more brain activity compared to white matter. Therefore,


id: ash-chemistry-20260505-0
file: data/en.wikipedia.org/wiki/Ash_(chemistry)-0.md
category: reference
title: Ash (chemistry)
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Ash_(chemistry)
date_saved: 2026-05-05T10:03:42.741481+00:00
instance: kb-cron
parent: ash-chemistry-20260505-0
summary:
In analytical chemistry, ashing or ash content determination is the process of mineralization by complete combustion for preconcentration of trace substances prior to a chemical analysis, such as chromatography, or optical analysis, such as spectroscopy. == Overview == The ash content of a sample is a measure of the amount of inorganic noncombustible material it contains. The residues after a sample is completely burnt - in contrast to the ash remaining after incomplete combustion - typically consist of oxides of the inorganic elements present in the original sample. Ash is one of the components in the proximate analysis of biological materials, consisting mainly of salty, inorganic constituents. It includes metal salts which are important for processes requiring ions such as Na+ (sodium), K+ (potassium), and Ca2+ (calcium). It also includes trace minerals which are required for unique molecules, such as chlorophyll and hemoglobin. Procedures for ash content determination are similar to procedures for loss on ignition. Typically, the term ash is used for primarily organic material such as fuels and foodstuffs, while the term loss on ignition is used for primarily inorganic material such as rocks and combusted ash. A crucible can be used to determine the percentage of ash


id: atom-probe-20260505-0
file: data/en.wikipedia.org/wiki/Atom_probe-0.md
category: reference
title: Atom probe
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Atom_probe
date_saved: 2026-05-05T10:03:43.942629+00:00
instance: kb-cron
parent: atom-probe-20260505-0
summary:
The atom probe was introduced at the 14th Field Emission Symposium in 1967 by Erwin Wilhelm Müller and J. A. Panitz. It combined a field ion microscope with a mass spectrometer having a single particle detection capability and, for the first time, an instrument could “... determine the nature of one single atom seen on a metal surface and selected from neighboring atoms at the discretion of the observer”. Atom probes are unlike conventional optical or electron microscopes, in that the magnification effect comes from the magnification provided by a highly curved electric field, rather than by the manipulation of radiation paths. The method is destructive in nature removing ions from a sample surface in order to image and identify them, generating magnifications sufficient to observe individual atoms as they are removed from the sample surface. Through coupling of this magnification method with time of flight mass spectrometry, ions evaporated by application of electric pulses can have their mass-to-charge ratio computed. Through successive evaporation of material, layers of atoms are removed from a specimen, allowing for probing not only of the surface, but also through the material itself. Computer methods are used to rebuild a three-dimensional view of the sample,


id: atom-probe-20260505-1
file: data/en.wikipedia.org/wiki/Atom_probe-1.md
category: reference
title: Atom probe
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Atom_probe
date_saved: 2026-05-05T10:03:43.942629+00:00
instance: kb-cron
parent: atom-probe-20260505-0
summary:
=== Imaging Atom Probe === The Imaging Atom-Probe (IAP) was introduced in 1974 by J. A. Panitz. It incorporated the features of the 10-cm Atom-Probe yet “... departs completely from [previous] atom probe philosophy. Rather than attempt to determine the identity of a surface species producing a preselected ion-image spot, we wish to determine the complete crystallographic distribution of a surface species of preselected mass-to-charge ratio. Now suppose that instead of operating the [detector] continuously, it is turned on for a short time coincidentally with the arrival of a preselected species of interest by applying a gate pulse a time T after the evaporation pulse has reached the specimen. If the duration of the gate pulse is shorter than the travel time between adjacent species, only that surface species having the unique travel time T will be detected and its complete crystallographic distribution displayed.” It was patented in 1975 as the Field Desorption Spectrometer. The Imaging Atom-Probe moniker was coined by A. J. Waugh in 1978 and the instrument was described in detail by J. A. Panitz in the same year. === Atom Probe Tomography (APT) === Modern day atom probe tomography uses a position sensitive detector aka a FIM


id: atom-probe-20260505-2
file: data/en.wikipedia.org/wiki/Atom_probe-2.md
category: reference
title: Atom probe
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Atom_probe
date_saved: 2026-05-05T10:03:43.942629+00:00
instance: kb-cron
parent: atom-probe-20260505-0
summary:
given a known flight distance. F, for the ion, and a known flight time, t, U = f t {\displaystyle U={\frac {f}{t}}} and thus one can substitute these values to obtain the mass-to-charge for the ion. m n = − 2 e V 1 ( t f ) 2 {\displaystyle {\frac {m}{n}}=-2eV_{1}\left({\frac {t}{f}}\right)^{2}} Thus for an ion which traverses a 1 m flight path, across a time of 2000 ns, given an initial accelerating voltage of 5000 V (V in Si units is kg.m^2.s^-3.A^-1) and noting that one amu is 1×10−27 kg, the mass-to-charge ratio (more correctly the mass-to-ionisation value ratio) becomes ~3.86 amu/charge. The number of electrons removed, and thus net positive charge on the ion is not known directly, but can be inferred from the histogram (spectrum) of observed ions. === Magnification === The magnification in an atom is due to the projection of ions radially away from the small, sharp tip. Subsequently, in the far-field, the ions will be greatly magnified. This magnification is sufficient to observe field variations due to individual atoms, thus allowing in field ion and field evaporation modes for the imaging of single atoms. The standard projection model for the atom probe is


id: atom-probe-20260505-3
file: data/en.wikipedia.org/wiki/Atom_probe-3.md
category: reference
title: Atom probe
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Atom_probe
date_saved: 2026-05-05T10:03:43.942629+00:00
instance: kb-cron
parent: atom-probe-20260505-0
summary:
=== System layout === At a minimum, an atom probe will consist of several key pieces of equipment. A vacuum system for maintaining the low pressures (~10−8 to 10−10 Pa) required, typically a classic 3 chambered UHV design. A system for the manipulation of samples inside the vacuum, including sample viewing systems. A cooling system to reduce atomic motion, such as a helium refrigeration circuit - providing sample temperatures as low as 15K. A high voltage system to raise the sample standing voltage near the threshold for field evaporation. A high voltage pulsing system, use to create timed field evaporation events A counter electrode that can be a simple disk shape (like earlier generation atom probes), or a cone-shaped Local Electrode. The voltage pulse (negative) is typically applied to the counter electrode. A detection system for single energetic ions that includes XY position and TOF information. Optionally, an atom probe may also include laser-optical systems for laser beam targeting and pulsing, if using laser-evaporation methods. In-situ reaction systems, heaters, or plasma treatment may also be employed for some studies as well as a pure noble gas introduction for FIM. === Performance === Collectable ion volumes were previously limited to several


id: atomic-absorption-spectroscopy-20260505-0
file: data/en.wikipedia.org/wiki/Atomic_absorption_spectroscopy-0.md
category: reference
title: Atomic absorption spectroscopy
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Atomic_absorption_spectroscopy
date_saved: 2026-05-05T10:03:45.133964+00:00
instance: kb-cron
parent: atomic-absorption-spectroscopy-20260505-0
summary:
Atomic absorption spectroscopy (AAS) is an elemental analysis method for determining the concentration of metals in a given sample. The principle of AAS relies on the vaporization of metals within a sample when introduced to a flame. Every ground state metal absorbs light radiation (and excites) at a different wavelength. This uniqueness allows each metallic element to have its own absorption spectrum that corresponds to its identity. The total absorbed radiation at a specific wavelength by an element in the sample is proportional to the density of atoms of the element. The quantification of this relationship is used to determine the concentration of specific metals in the sample. == History == The modern form of AAS was largely developed during the 1950s by a team of Australian chemists led by Sir Alan Walsh at the Commonwealth Scientific and Industrial Research Organisation, Division of Chemical Physics, in Melbourne, Australia. Alan Walsh first described AAS in an article titled "The Application of Atomic Absorption Spectra to Chemical Analysis" published in 1955 by the journal Spectrachemica Acta. In this article, Walsh emphasizes the importance of establishing a new technique that can provide an absolute method that can produce reliable chemical standards, which was


id: atomic-absorption-spectroscopy-20260505-1
file: data/en.wikipedia.org/wiki/Atomic_absorption_spectroscopy-1.md
category: reference
title: Atomic absorption spectroscopy
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Atomic_absorption_spectroscopy
date_saved: 2026-05-05T10:03:45.133964+00:00
instance: kb-cron
parent: atomic-absorption-spectroscopy-20260505-0
summary:
==== Line Source AAS ==== In line source AAS (LS AAS), the high resolution that is required for the measurement of atomic absorption is provided by the narrow line emission of the radiation source. The monochromator has to resolve the analytical line from other radiation emitted by the lamp. This can usually be accomplished with a band pass between 0.2 and 2 nm, i.e., a medium-resolution monochromator. Another feature to make LS AAS element-specific is modulation of the primary radiation and the use of a selective amplifier that is tuned to the same modulation frequency, as already postulated by Alan Walsh. This way any (unmodulated) radiation emitted for example by the atomizer can be excluded, which is imperative for LS AAS. Simple monochromators of the Littrow or (better) the Czerny-Turner design are typically used for LS AAS. Photomultiplier tubes are the most frequently used detectors in LS AAS, although solid state detectors might be preferred because of their better signal-to-noise ratio. ==== Continuum Source AAS ==== When a continuum radiation source is used for AAS, a high-resolution monochromator is required. The resolution must be equal to or better than the half-width of an atomic absorption line (about 2 pm) in


id: atomic-absorption-spectroscopy-20260505-2
file: data/en.wikipedia.org/wiki/Atomic_absorption_spectroscopy-2.md
category: reference
title: Atomic absorption spectroscopy
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Atomic_absorption_spectroscopy
date_saved: 2026-05-05T10:03:45.133964+00:00
instance: kb-cron
parent: atomic-absorption-spectroscopy-20260505-0
summary:
Electrothermal AAS (ET AAS) using graphite tube atomizers was pioneered by Boris V. L'vov at the Saint Petersburg Polytechnical Institute, Russia, since the late 1950s, and investigated in parallel by Hans Massmann at the Institute of Spectrochemistry and Applied Spectroscopy (ISAS) in Dortmund, Germany. Although a wide variety of graphite tube designs have been used over the years, typical dimensions are 20–25 mm in length and 5–6 mm inner diameter. With this technique liquid/dissolved, solid, and gaseous samples may be analyzed directly. A measured volume (typically 10–50 μL) or a weighed mass (typically around 1 mg) of a solid sample is introduced into the graphite tube and subject to a temperature program. This typically consists of stages of drying – the solvent is evaporated; pyrolysis – the majority of the matrix constituents are removed; atomization – the analyte element is released to the gaseous phase; and cleaning – residues left in the graphite tube are removed at high temperature. The graphite tubes are heated via their ohmic resistance using a low-voltage high-current power supply; the temperature in the individual stages can be controlled very closely, and temperature ramps between the individual stages facilitate the separation of sample components. Tubes may


id: atomic-absorption-spectroscopy-20260505-3
file: data/en.wikipedia.org/wiki/Atomic_absorption_spectroscopy-3.md
category: reference
title: Atomic absorption spectroscopy
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Atomic_absorption_spectroscopy
date_saved: 2026-05-05T10:03:45.133964+00:00
instance: kb-cron
parent: atomic-absorption-spectroscopy-20260505-0
summary:
== Background absorption and background correction == The relatively small number of atomic absorption lines (compared to atomic emission lines) and their narrow width (a few pm) make spectral overlap rare; there are only few examples known that an absorption line from one element will overlap with another. Molecular absorption, in contrast, is much broader, so that it is more likely that some molecular absorption band will overlap with an atomic line. This kind of absorption might be caused by un-dissociated molecules of concomitant elements of the sample or by flame gases. We have to distinguish between the spectra of di-atomic molecules, which exhibit a pronounced fine structure, and those of larger (usually tri-atomic) molecules that don't show such fine structure. Another source of background absorption, particularly in ET AAS, is scattering of the primary radiation at particles that are generated in the atomization stage, when the matrix could not be removed sufficiently in the pyrolysis stage. All these phenomena, molecular absorption and radiation scattering, can result in artificially high absorption and an improperly high (erroneous) calculation for the concentration or mass of the analyte in the sample. There are several techniques available to correct for background absorption, and they


id: atomic-absorption-spectroscopy-20260505-4
file: data/en.wikipedia.org/wiki/Atomic_absorption_spectroscopy-4.md
category: reference
title: Atomic absorption spectroscopy
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Atomic_absorption_spectroscopy
date_saved: 2026-05-05T10:03:45.133964+00:00
instance: kb-cron
parent: atomic-absorption-spectroscopy-20260505-0
summary:
==== Background correction using a least-squares algorithm ==== The above technique can obviously not correct for a background with fine structure, as in this case the absorbance will be different at each of the correction pixels. In this case, HR-CS AAS is offering the possibility to measure correction spectra of the molecule(s) that is (are) responsible for the background and store them in the computer. These spectra are then multiplied with a factor to match the intensity of the sample spectrum and subtracted pixel by pixel and spectrum by spectrum from the sample spectrum using a least-squares algorithm. This might sound complex, but first of all the number of di-atomic molecules that can exist at the temperatures of the atomizers used in AAS is relatively small, and second, the correction is performed by the computer within a few seconds. The same algorithm can actually also be used to correct for direct line overlap of two atomic absorption lines, making HR-CS AAS the only AAS technique that can correct for this kind of spectral interference. == Applications == AAS is typically used to measure the concentration of metals in a wide variety of substances. For example, AAS has been used to


id: atomic-emission-spectroscopy-20260505-0
file: data/en.wikipedia.org/wiki/Atomic_emission_spectroscopy-0.md
category: reference
title: Atomic emission spectroscopy
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Atomic_emission_spectroscopy
date_saved: 2026-05-05T10:03:46.298080+00:00
instance: kb-cron
parent: atomic-emission-spectroscopy-20260505-0
summary:
Atomic emission spectroscopy (AES) is a method of chemical analysis that uses the intensity of light emitted from a flame, plasma, arc, or spark at a particular wavelength to determine the quantity of an element in a sample. The wavelength of the atomic spectral line in the emission spectrum gives the identity of the element while the intensity of the emitted light is proportional to the number of atoms of the element. The sample may be excited by various methods. Atomic Emission Spectroscopy allows us to measure interactions between electromagnetic radiation and physical atoms and molecules. This interaction is measured in the form of electromagnetic waves representing the changes in energy between atomic energy levels. When elements are burned by a flame, they emit electromagnetic radiation that can be recorded in the form of spectral lines. Each element has its own unique spectral line because each element has a different atomic arrangement, so this method is an important tool for identifying the makeup of materials. Robert Bunsen and Gustav Kirchhoff were the first to establish atomic emission spectroscopy as a tool in chemistry. When an element is burned in a flame, its atoms move from the ground electronic state to


id: atomic-force-microscopy-20260505-0
file: data/en.wikipedia.org/wiki/Atomic_force_microscopy-0.md
category: reference
title: Atomic force microscopy
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Atomic_force_microscopy
date_saved: 2026-05-05T10:03:47.482245+00:00
instance: kb-cron
parent: atomic-force-microscopy-20260505-0
summary:
Atomic force microscopy (AFM) or scanning force microscopy (SFM) is a very-high-resolution type of scanning probe microscopy (SPM), with demonstrated resolution on the order of fractions of a nanometer, more than 1000 times better than the optical diffraction limit. == Overview == Atomic force microscopy (AFM) gathers information by "feeling" or "touching" the surface with a mechanical probe. Piezoelectric elements that facilitate tiny but accurate and precise movements on (electronic) command enable precise scanning. Despite the name, the Atomic Force Microscope does not use the nuclear force. === Abilities and spatial resolution === The AFM has three major abilities: force measurement, topographic imaging, and manipulation. In force measurement, AFMs can be used to measure the forces between the probe and the sample as a function of their mutual separation. This can be applied to perform force spectroscopy, to measure the mechanical properties of the sample, such as the sample's Young's modulus, a measure of stiffness. For imaging, the reaction of the probe to the forces that the sample imposes on it can be used to form an image of the three-dimensional shape (topography) of a sample surface at a high resolution. This is achieved by raster scanning the position of


id: atomic-force-microscopy-20260505-1
file: data/en.wikipedia.org/wiki/Atomic_force_microscopy-1.md
category: reference
title: Atomic force microscopy
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Atomic_force_microscopy
date_saved: 2026-05-05T10:03:47.482245+00:00
instance: kb-cron
parent: atomic-force-microscopy-20260505-0
summary:
==== Image formation ==== This section applies specifically to imaging in § Contact mode. For other imaging modes, the process is similar, except that "deflection" should be replaced by the appropriate feedback variable. When using the AFM to image a sample, the tip is brought into contact with the sample, and the sample is raster scanned along an x–y grid. Most commonly, an electronic feedback loop is employed to keep the probe-sample force constant during scanning. This feedback loop has the cantilever deflection as input, and its output controls the distance along the z axis between the probe support (2 in fig. 3) and the sample support (8 in fig 3). As long as the tip remains in contact with the sample, and the sample is scanned in the x–y plane, height variations in the sample will change the deflection of the cantilever. The feedback then adjusts the height of the probe support so that the deflection is restored to a user-defined value (the setpoint). A properly adjusted feedback loop adjusts the support-sample separation continuously during the scanning motion, such that the deflection remains approximately constant. In this situation, the feedback output equals the sample surface topography to within a


id: atomic-force-microscopy-20260505-2
file: data/en.wikipedia.org/wiki/Atomic_force_microscopy-2.md
category: reference
title: Atomic force microscopy
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Atomic_force_microscopy
date_saved: 2026-05-05T10:03:47.482245+00:00
instance: kb-cron
parent: atomic-force-microscopy-20260505-0
summary:
=== Imaging modes === AFM operation is usually described as one of three modes, according to the nature of the tip motion: contact mode, also called static mode (as opposed to the other two modes, which are called dynamic modes); tapping mode, also called intermittent contact, AC mode, or vibrating mode, or, after the detection mechanism, amplitude modulation AFM; and non-contact mode, or, again after the detection mechanism, frequency modulation AFM. Despite the nomenclature, repulsive contact can occur or be avoided both in amplitude modulation AFM and frequency modulation AFM, depending on the settings. ==== Contact mode ==== In contact mode, the tip is "dragged" across the surface of the sample and the contours of the surface are measured either using the deflection of the cantilever directly or, more commonly, using the feedback signal required to keep the cantilever at a constant position. Because the measurement of a static signal is prone to noise and drift, low stiffness cantilevers (i.e. cantilevers with a low spring constant, k) are used to achieve a large enough deflection signal while keeping the interaction force low. Close to the surface of the sample, attractive forces can be quite strong, causing the tip to "snap-in"


id: atomic-force-microscopy-20260505-3
file: data/en.wikipedia.org/wiki/Atomic_force_microscopy-3.md
category: reference
title: Atomic force microscopy
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Atomic_force_microscopy
date_saved: 2026-05-05T10:03:47.482245+00:00
instance: kb-cron
parent: atomic-force-microscopy-20260505-0
summary:
==== Non-contact mode ==== In non-contact atomic force microscopy mode, the tip of the cantilever does not contact the sample surface. The cantilever is instead oscillated at either its resonant frequency (frequency modulation) or just above (amplitude modulation) where the amplitude of oscillation is typically a few nanometers (<10 nm) down to a few picometers. The van der Waals forces, which are strongest from 1 nm to 10 nm above the surface, or any other long-range force that extends above the surface acts to decrease the resonance frequency of the cantilever. This decrease in resonant frequency combined with the feedback loop system maintains a constant oscillation amplitude or frequency by adjusting the average tip-to-sample distance. Measuring the tip-to-sample distance at each (x,y) data point allows the scanning software to construct a topographic image of the sample surface. Non-contact mode AFM does not suffer from tip or sample degradation effects that are sometimes observed after taking numerous scans with contact AFM. This makes non-contact AFM preferable to contact AFM for measuring soft samples, e.g. biological samples and organic thin film. In the case of rigid samples, contact and non-contact images may look the same. However, if a few monolayers of adsorbed


id: atomic-force-microscopy-20260505-4
file: data/en.wikipedia.org/wiki/Atomic_force_microscopy-4.md
category: reference
title: Atomic force microscopy
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Atomic_force_microscopy
date_saved: 2026-05-05T10:03:47.482245+00:00
instance: kb-cron
parent: atomic-force-microscopy-20260505-0
summary:
=== Topographic image of FM-AFM === When the distance between the probe and the sample is brought to the range where atomic force may be detected, while a cantilever is excited in its natural eigenfrequency (f0), the resonance frequency f of the cantilever may shift from its original resonance frequency. In other words, in the range where atomic force may be detected, a frequency shift (df =f–f0) will also be observed. When the distance between the probe and the sample is in the non-contact region, the frequency shift increases in negative direction as the distance between the probe and the sample gets smaller. When the sample has concavity and convexity, the distance between the tip-apex and the sample varies in accordance with the concavity and convexity accompanied with a scan of the sample along x–y direction (without height regulation in z-direction). As a result, the frequency shift arises. The image in which the values of the frequency obtained by a raster scan along the x–y direction of the sample surface are plotted against the x–y coordination of each measurement point is called a constant-height image. On the other hand, the df may be kept constant by moving the probe upward


id: atomic-force-microscopy-20260505-5
file: data/en.wikipedia.org/wiki/Atomic_force_microscopy-5.md
category: reference
title: Atomic force microscopy
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Atomic_force_microscopy
date_saved: 2026-05-05T10:03:47.482245+00:00
instance: kb-cron
parent: atomic-force-microscopy-20260505-0
summary:
== Probe == An AFM probe has a sharp tip on the free-swinging end of a cantilever that protrudes from a holder. The dimensions of the cantilever are in the scale of micrometers. The radius of the tip is usually on the scale of a few nanometers to a few tens of nanometers. (Specialized probes exist with much larger end radii, for example probes for indentation of soft materials.) The cantilever holder, also called the holder chip—often 1.6 mm by 3.4 mm in size—allows the operator to hold the AFM cantilever/probe assembly with tweezers and fit it into the corresponding holder clips on the scanning head of the atomic force microscope. This device is most commonly called an "AFM probe", but other names include "AFM tip" and "cantilever" (employing the name of a single part as the name of the whole device). An AFM probe is a particular type of SPM probe. AFM probes are manufactured with MEMS technology. Most AFM probes used are made from silicon (Si), but borosilicate glass and silicon nitride are also in use. AFM probes are considered consumables as they are often replaced when the tip apex becomes dull or contaminated or when the cantilever


id: atomic-force-microscopy-20260505-6
file: data/en.wikipedia.org/wiki/Atomic_force_microscopy-6.md
category: reference
title: Atomic force microscopy
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Atomic_force_microscopy
date_saved: 2026-05-05T10:03:47.482245+00:00
instance: kb-cron
parent: atomic-force-microscopy-20260505-0
summary:
f m = − 2 π R γ L ( cos ⁡ θ + cos ⁡ ϕ ) ( 1 − d h d D ) {\displaystyle f_{m}=-2\pi R\gamma _{L}(\cos \theta +\cos \phi )\left(1-{\frac {dh}{dD}}\right)} for dry on wet, f m = − 2 π R γ L d r 0 d D {\displaystyle f_{m}=-2\pi R\gamma _{L}{\frac {dr_{0}}{dD}}} for wet on wet, where θ is the contact angle of the dry sphere and φ is the immersed angle, as shown in the figure For a conical tip, the formula becomes: f m = − 2 π R γ L tan ⁡ δ cos ⁡ δ ( cos ⁡ θ + sin ⁡ δ ) ( h D ) ( 1 − d h d D ) {\displaystyle f_{m}=-2\pi R\gamma _{L}{\frac {\tan \delta }{\cos \delta }}(\cos \theta +\sin \delta )(hD)\left(1-{\frac {dh}{dD}}\right)} for dry on wet f m = − 2 π R γ L ( 1 cos ⁡ δ + sin ⁡ δ ) ( r 0 ) ( d r 0 d D ) {\displaystyle f_{m}=-2\pi R\gamma _{L}\left({\frac {1}{\cos \delta }}+\sin \delta \right)(r_{0})\left({\frac {dr_{0}}{dD}}\right)} for wet on wet where δ is the half cone angle and r0 and h are


id: atomic-force-microscopy-20260505-7
file: data/en.wikipedia.org/wiki/Atomic_force_microscopy-7.md
category: reference
title: Atomic force microscopy
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Atomic_force_microscopy
date_saved: 2026-05-05T10:03:47.482245+00:00
instance: kb-cron
parent: atomic-force-microscopy-20260505-0
summary:
== Piezoelectric scanners == AFM scanners are made from piezoelectric material, which expands and contracts proportionally to an applied voltage. Whether they elongate or contract depends upon the polarity of the voltage applied. Traditionally the tip or sample is mounted on a "tripod" of three piezo crystals, with each responsible for scanning in the x,y and z directions. In 1986, the same year as the AFM was invented, a new piezoelectric scanner, the tube scanner, was developed for use in STM. Later tube scanners were incorporated into AFMs. The tube scanner can move the sample in the x, y, and z directions using a single tube piezo with a single interior contact and four external contacts. An advantage of the tube scanner compared to the original tripod design, is better vibrational isolation, resulting from the higher resonant frequency of the single element construction, in combination with a low resonant frequency isolation stage. A disadvantage is that the x-y motion can cause unwanted z motion resulting in distortion. Another popular design for AFM scanners is the flexure stage, which uses separate piezos for each axis, and couples them through a flexure mechanism. Scanners are characterized by their sensitivity, which is the


id: atomic-force-microscopy-20260505-8
file: data/en.wikipedia.org/wiki/Atomic_force_microscopy-8.md
category: reference
title: Atomic force microscopy
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Atomic_force_microscopy
date_saved: 2026-05-05T10:03:47.482245+00:00
instance: kb-cron
parent: atomic-force-microscopy-20260505-0
summary:
AFM images can also be affected by nonlinearity, hysteresis, and creep of the piezoelectric material and cross-talk between the x, y, z axes that may require software enhancement and filtering. Such filtering could "flatten" out real topographical features. However, newer AFMs utilize real-time correction software (for example, feature-oriented scanning) or closed-loop scanners, which practically eliminate these problems. Some AFMs also use separated orthogonal scanners (as opposed to a single tube), which also serve to eliminate part of the cross-talk problems. As with any other imaging technique, there is the possibility of image artifacts, which could be induced by an unsuitable tip, a poor operating environment, or even by the sample itself, as depicted on the right. These image artifacts are unavoidable; however, their occurrence and effect on results can be reduced through various methods. Artifacts resulting from a too-coarse tip can be caused for example by inappropriate handling or de facto collisions with the sample by either scanning too fast or having an unreasonably rough surface, causing actual wearing of the tip. Due to the nature of AFM probes, they cannot normally measure steep walls or overhangs. Specially made cantilevers and AFMs can be used to modulate the probe sideways


id: attenuated-total-reflectance-20260505-0
file: data/en.wikipedia.org/wiki/Attenuated_total_reflectance-0.md
category: reference
title: Attenuated total reflectance
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Attenuated_total_reflectance
date_saved: 2026-05-05T10:03:48.746520+00:00
instance: kb-cron
parent: attenuated-total-reflectance-20260505-0
summary:
Attenuated total reflection (ATR) is a sampling technique used in conjunction with infrared spectroscopy which enables samples to be examined directly in the solid or liquid state without further preparation. ATR uses a property of total internal reflection resulting in an evanescent wave. A beam of infrared light (IR) is passed through the ATR crystal in such a way that it reflects at least once off the internal surface in contact with the sample. This reflection forms the evanescent wave which extends into the sample. The penetration depth into the sample is typically between 0.5 and 2 micrometres, with the exact value determined by the wavelength of light, the angle of incidence and the indices of refraction for the ATR crystal and the medium being probed. The number of reflections may be varied by varying the angle of incidence. The beam is then collected by a detector as it exits the crystal. Most modern infrared spectrometers can be converted to characterise samples via ATR by mounting the ATR accessory in the spectrometer's sample compartment. The accessibility, rapid sample turnaround and ease of use of ATR with Fourier transform infrared spectroscopy (FTIR) has led to substantial use by the scientific community.


id: automated-mineralogy-20260505-0
file: data/en.wikipedia.org/wiki/Automated_mineralogy-0.md
category: reference
title: Automated mineralogy
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Automated_mineralogy
date_saved: 2026-05-05T10:03:49.957984+00:00
instance: kb-cron
parent: automated-mineralogy-20260505-0
summary:
Automated mineralogy is a generic term describing a range of analytical solutions, areas of commercial enterprise, and a growing field of scientific research and engineering applications involving largely automated and quantitative analysis of minerals, rocks and man-made materials. == Technology == Automated mineralogy analytical solutions are characterised by integrating largely automated measurement techniques based on Scanning Electron Microscopy (SEM) and Energy-dispersive X-ray spectroscopy (EDS). Commercially available lab-based solutions include QEMSCAN and Mineral Liberation Analyzer (MLA) from FEI Company, Mineralogic from Zeiss, AZtecMineral from Oxford Instruments, the TIMA (Tescan integrated mineral analyzer) from TESCAN, AMICS from Bruker, and MaipSCAN from Rock Scientific. The first oil & gas wellsite solution was launched jointly by Zeiss and CGG Veritas in 2011 called RoqSCAN. This was followed approximately 6 months later by the release of QEMSCAN Wellsite by FEI Company. More recently in 2016, a ruggedized mine site solution for mining and mineral processing was launched by Zeiss called MinSCAN. == Business == The business of automated mineralogy is concerned with the commercialisation of the technology and software in terms of development and marketing of integrated solutions. This includes all aspects of: service; maintenance; customer support; R&D; marketing and sales. Customers of automated mineralogy


id: bet-theory-20260505-0
file: data/en.wikipedia.org/wiki/BET_theory-0.md
category: reference
title: BET theory
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/BET_theory
date_saved: 2026-05-05T10:03:51.162056+00:00
instance: kb-cron
parent: bet-theory-20260505-0
summary:
Brunauer–Emmett–Teller (BET) theory aims to explain the physical adsorption of gas molecules on a solid surface and serves as the basis for an important analysis technique for the measurement of the specific surface area of materials. The observations are very often referred to as physical adsorption or physisorption. In 1938, Stephen Brunauer, Paul Hugh Emmett, and Edward Teller presented their theory in the Journal of the American Chemical Society. BET theory applies to systems of multilayer adsorption that usually utilizes a probing gas (called the adsorbate) that does not react chemically with the adsorptive (the material upon which the gas attaches to) to quantify specific surface area. Nitrogen is the most commonly employed gaseous adsorbate for probing surface(s). For this reason, standard BET analysis is most often conducted at the boiling temperature of N2 (77 K). Other probing adsorbates are also utilized, albeit less often, allowing the measurement of surface area at different temperatures and measurement scales. These include argon, carbon dioxide, and water. Specific surface area is a scale-dependent property, with no single true value of specific surface area definable, and thus quantities of specific surface area determined through BET theory may depend on the adsorbate molecule utilized and


id: bet-theory-20260505-1
file: data/en.wikipedia.org/wiki/BET_theory-1.md
category: reference
title: BET theory
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/BET_theory
date_saved: 2026-05-05T10:03:51.162056+00:00
instance: kb-cron
parent: bet-theory-20260505-0
summary:
Adsorptions occur only on well-defined sites of the sample surface (one per molecule) The only molecular interaction considered is the following one: a molecule can act as a single adsorption site for a molecule of the upper layer. The uppermost molecule layer is in equilibrium with the gas phase, i.e. similar molecule adsorption and desorption rates. The desorption is a kinetically limited process, i.e. a heat of adsorption must be provided: these phenomena are homogeneous, i.e. same heat of adsorption for a given molecule layer. it is E1 for the first layer, i.e. the heat of adsorption at the solid sample surface the other layers are assumed similar and can be represented as condensed species, i.e. liquid state. Hence, the heat of adsorption is EL is equal to the heat of liquefaction. At the saturation pressure, the molecule layer number tends to infinity (i.e. equivalent to the sample being surrounded by a liquid phase) Consider a given amount of solid sample in a controlled atmosphere. Let θi be the fractional coverage of the sample surface covered by a number i of successive molecule layers. Let us assume that the adsorption rate Rads,i-1 for molecules on a layer (i-1) (i.e. formation


id: bet-theory-20260505-2
file: data/en.wikipedia.org/wiki/BET_theory-2.md
category: reference
title: BET theory
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/BET_theory
date_saved: 2026-05-05T10:03:51.162056+00:00
instance: kb-cron
parent: bet-theory-20260505-0
summary:
∑ n = 1 ∞ θ n = θ 0 + c θ 0 x ∑ n = 0 ∞ x n = θ 0 + c θ 0 x 1 − x , | x | < 1 {\displaystyle \sum _{n=1}^{\infty }\theta _{n}=\theta _{0}+c\theta _{0}x\sum _{n=0}^{\infty }x^{n}=\theta _{0}+c\theta _{0}{\frac {x}{1-x}},\quad |x|<1} Lastly, defining the excess coverage as V excess = V ads / V mono {\displaystyle V_{\text{excess}}=V_{\text{ads}}/V_{\text{mono}}} , the excess volume relative to the volume of an adsorbed mono-layer becomes V excess = ∑ n = 0 ∞ n θ n 1 = ∑ n = 0 ∞ n θ n ∑ n = 0 ∞ θ n = c x ( 1 − x ) ( 1 + ( c − 1 ) x ) {\displaystyle V_{\text{excess}}={\frac {\sum _{n=0}^{\infty }n\theta _{n}}{1}}={\frac {\sum _{n=0}^{\infty }n\theta _{n}}{\sum _{n=0}^{\infty }\theta _{n}}}={\frac {cx}{(1-x)(1+(c-1)x)}}} where the last equality was obtained by making use of the series expansions presented above. The constant c {\displaystyle c} must be interpreted as the relative binding affinity the substance A has towards a surface, relative to its own liquid. If c > 1 {\displaystyle c>1} then the initial part of the isotherm will be reminiscent of the Langmuir


id: bet-theory-20260505-3
file: data/en.wikipedia.org/wiki/BET_theory-3.md
category: reference
title: BET theory
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/BET_theory
date_saved: 2026-05-05T10:03:51.162056+00:00
instance: kb-cron
parent: bet-theory-20260505-0
summary:
=== Catalysis === In the field of solid catalysis, the surface area of catalysts is an important factor in catalytic activity. Inorganic materials such as mesoporous silica and layered clay minerals have high surface areas of several hundred m2/g calculated by the BET method, indicating the possibility of application for efficient catalytic materials. === Specific surface area calculation === The ISO 9277 standard for calculating the specific surface area of solids is based on the BET method. The method has also been adapted for determination of specific area of ceramics and non-ferrous metal powders. === Thermal desorption === In 2023, researchers in the United States developed a method to determine BET surface areas using a thermogravimetric analyzer (TGA). This method uses a TGA to heat a porous sample loaded with an adsorbate, the produced plot of sample mass vs. temperature is then mapped into a standard isotherm to which BET theory is applied as normal. Common fluids, e.g. water or toluene, can be used as adsorbates for the TGA method allowing the specific interactions of different adsorbates to be determined, as these frequently differ from the commonly used nitrogen. == See also == Adsorption Capillary condensation Langmuir adsorption model Mercury


id: bimodal-atomic-force-microscopy-20260505-0
file: data/en.wikipedia.org/wiki/Bimodal_atomic_force_microscopy-0.md
category: reference
title: Bimodal atomic force microscopy
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Bimodal_atomic_force_microscopy
date_saved: 2026-05-05T10:03:52.382038+00:00
instance: kb-cron
parent: bimodal-atomic-force-microscopy-20260505-0
summary:
Bimodal Atomic Force Microscopy (bimodal AFM) is an advanced atomic force microscopy technique characterized by generating high-spatial resolution maps of material properties. Topography, deformation, elastic modulus, viscosity coefficient or magnetic field maps might be generated. Bimodal AFM is based on the simultaneous excitation and detection of two eigenmodes (resonances) of a force microscope microcantilever. == History == Numerical and theoretical considerations prompted the development of bimodal AFM. The method was initially thought to enhance topographic contrast in air environments. Three subsequent advances such as the capability to detect non-topography properties such electrostatic and magnetic interactions; imaging in liquid and ultra-high vacuum and its genuine quantitative features set the stage for further developments and applications. == Principles of Bimodal AFM == The interaction of the tip with the sample modifies the amplitudes, phase shifts and frequency resonances of the excited modes. Those changes are detected and processed by the feedback of the instrument. Several features make bimodal AFM a very powerful surface characterization method at the nanoscale. (i) Resolution. Atomic, molecular or nanoscale spatial resolution was demonstrated. (ii) Simultaneity. Maps of different properties are generated at the same time. (iii) Efficiency. A maximum number of four data points per pixel are


id: bimodal-atomic-force-microscopy-20260505-1
file: data/en.wikipedia.org/wiki/Bimodal_atomic_force_microscopy-1.md
category: reference
title: Bimodal atomic force microscopy
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Bimodal_atomic_force_microscopy
date_saved: 2026-05-05T10:03:52.382038+00:00
instance: kb-cron
parent: bimodal-atomic-force-microscopy-20260505-0
summary:
where T = T 1 T 2 {\displaystyle T=T_{1}T_{2}} is a time where the oscillation of both modes are periodic; Q i {\displaystyle Q_{i}} the quality factor of mode i. Bimodal AFM operation might be involve any pair of eigenmodes. However, experiments are commonly performed by exciting the first two eigenmodes. The theory of bimodal AFM provides analytical expressions to link material properties with microscope observables. For example, for a paraboloid probe (radius R {\displaystyle R} ) and a tip-sample force given by the linear viscoelastic Kelvin-Voigt model, the effective elastic modulus E e f f {\displaystyle E_{eff}} of the sample, viscous coefficient of compressibility η c o m {\displaystyle \eta _{com}} , loss tangent tan ⁡ ρ {\displaystyle \tan \rho } or retardation time τ {\displaystyle \tau } are expressed by E e f f = 4 2 Q 1 R k 2 2 k 1 Δ f 2 2 f 02 2 A 1 3 / 2 A 01 2 − A 1 2 {\displaystyle E_{eff}=4{\sqrt {2}}{\frac {Q_{1}}{\sqrt {R}}}{\frac {k_{2}^{2}}{k_{1}}}{\frac {\Delta f_{2}^{2}}{f_{02}^{2}}}{\frac {A_{1}^{3/2}}{A_{01}^{2}-A_{1}^{2}}}\,} η c o m = E e f f ω 1 [ A 01 sin ⁡ ϕ 1 − A 1 A 01 cos ⁡


id: cathodoluminescence-20260505-0
file: data/en.wikipedia.org/wiki/Cathodoluminescence-0.md
category: reference
title: Cathodoluminescence
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Cathodoluminescence
date_saved: 2026-05-05T10:03:53.622728+00:00
instance: kb-cron
parent: cathodoluminescence-20260505-0
summary:
Cathodoluminescence is an optical and electromagnetic phenomenon in which electrons impacting on a luminescent material such as a phosphor, cause the emission of photons which may have wavelengths in the visible spectrum. A familiar example is the generation of light by an electron beam scanning the phosphor-coated inner surface of the screen of a television that uses a cathode-ray tube. Cathodoluminescence is the inverse of the photoelectric effect, in which electron emission is induced by irradiation with photons. == Origin == Luminescence in a semiconductor results when an electron in the conduction band recombines with a hole in the valence band. The difference energy (band gap) of this transition can be emitted in form of a photon. The energy (color) of the photon, and the probability that a photon and not a phonon will be emitted, depends on the material, its purity, and the presence of defects. First, the electron has to be excited from the valence band into the conduction band. In cathodoluminescence, this occurs as the result of an impinging high energy electron beam onto a semiconductor. However, these primary electrons carry far too much energy to directly excite electrons. Instead, the inelastic scattering of the primary electrons


id: cathodoluminescence-20260505-1
file: data/en.wikipedia.org/wiki/Cathodoluminescence-1.md
category: reference
title: Cathodoluminescence
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Cathodoluminescence
date_saved: 2026-05-05T10:03:53.622728+00:00
instance: kb-cron
parent: cathodoluminescence-20260505-0
summary:
In scanning electron microscopes a focused beam of electrons impinges on a sample and induces it to emit light that is collected by an optical system, such as an elliptical mirror. From there, a fiber optic will transfer the light out of the microscope where it is separated into its component wavelengths by a monochromator and is then detected with a photomultiplier tube. By scanning the microscope's beam in an X-Y pattern and measuring the light emitted with the beam at each point, a map of the optical activity of the specimen can be obtained (cathodoluminescence imaging). Instead, by measuring the wavelength dependence for a fixed point or a certain area, the spectral characteristics can be recorded (cathodoluminescence spectroscopy). Furthermore, if the photomultiplier tube is replaced with a CCD camera, an entire spectrum can be measured at each point of a map (hyperspectral imaging). Moreover, the optical properties of an object can be correlated to structural properties observed with the electron microscope. The primary advantages to the electron microscope based technique is its spatial resolution. In a scanning electron microscope, the attainable resolution is on the order of a few ten nanometers, while in a (scanning) transmission electron microscope (TEM),


id: cell-unroofing-20260505-0
file: data/en.wikipedia.org/wiki/Cell_unroofing-0.md
category: reference
title: Cell unroofing
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Cell_unroofing
date_saved: 2026-05-05T10:03:54.816547+00:00
instance: kb-cron
parent: cell-unroofing-20260505-0
summary:
Cell unroofing encompasses various methods used to isolate and expose the cell membrane of cells. Unlike the more common membrane extraction protocols performed with multiple steps of centrifugation (which aims to separate the membrane fraction from a cell lysate), cell unroofing aims to tear and preserve patches of the plasma membrane to perform in situ experiments using microscopy and biomedical spectroscopy. == History == The first observation of the bi-layer cell membrane was made in 1959 on a cell section using the electron microscope. However, the first micrograph of the internal side of a cell dates back to 1977 by M.V. Nermut. Professor John Heuser made substantial contributions in the field, imaging the detailed internal structure of the membrane and the cytoskeleton bound to it with extensive use of the electron microscope. It was only after the development of atomic force microscope operated in liquid that it became possible to image cell membranes in almost-physiological conditions and to test their mechanical properties. == Methods == Freeze-fracturing of monolayers Quick-freeze deep-etch electron microscopy and cryofixation Sonication for atomic force microscopy Single-cell unroofing == See also == Sonoporation Lysis == References ==


id: charge-modulation-spectroscopy-20260505-0
file: data/en.wikipedia.org/wiki/Charge_modulation_spectroscopy-0.md
category: reference
title: Charge modulation spectroscopy
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Charge_modulation_spectroscopy
date_saved: 2026-05-05T10:03:56.033551+00:00
instance: kb-cron
parent: charge-modulation-spectroscopy-20260505-0
summary:
Charge modulation spectroscopy is an electro-optical spectroscopy technique tool. It is used to study the charge carrier behavior of organic field-effect transistors. It measures the charge introduced optical transmission variation by directly probing the accumulation charge at the burning interface of semiconductor and dielectric layer where the conduction channel forms. == Principles == Unlike ultraviolet–visible spectroscopy which measures absorbance, charge modulation spectroscopy measures the charge introduced optical transmission variation. In other words, it reveals the new features in optical transmission introduced by charges. In this setup, there are mainly four components: lamp, monochromator, photodetector and lock-in amplifier. Lamp and monochromator are used for generating and selecting the wavelength. The selected wavelength passes through the transistor, and the transmitted light is recorded by the Photodiode. When the signal to noise ratio is very low, the signal can be modulated and recovered with a Lock-in amplifier. In the experiment, a direct current plus an alternating current bias are applied to the organic field-effect transistor. Charge carriers accumulate at the interface between the dielectric and the semiconductor (usually a few nanometers). With the appearance of the accumulation charge, the intensity of the transmitted light changes. The variation of the light intensity (§ Bleaching


id: chemical-ionization-20260505-0
file: data/en.wikipedia.org/wiki/Chemical_ionization-0.md
category: reference
title: Chemical ionization
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Chemical_ionization
date_saved: 2026-05-05T10:03:57.240704+00:00
instance: kb-cron
parent: chemical-ionization-20260505-0
summary:
Chemical ionization (CI) is a soft ionization technique used in mass spectrometry. This was first introduced by Burnaby Munson and Frank H. Field in 1966. This technique is a branch of gaseous ion-molecule chemistry. Reagent gas molecules (often methane or ammonia) are ionized by electron ionization to form reagent ions, which subsequently react with analyte molecules in the gas phase to create analyte ions for analysis by mass spectrometry. Negative chemical ionization (NCI), charge-exchange chemical ionization, atmospheric-pressure chemical ionization (APCI) and atmospheric pressure photoionization (APPI) are some of the common variants of the technique. CI mass spectrometry finds general application in the identification, structure elucidation and quantitation of organic compounds as well as some utility in biochemical analysis. Samples to be analyzed must be in vapour form, or else (in the case of liquids or solids), must be vapourized before introduction into the source. == Principles of operation == The chemical ionization process generally imparts less energy to an analyte molecule than does electron impact (EI) ionization, resulting in less fragmentation and usually a simpler spectrum. The amount of fragmentation, and therefore the amount of structural information produced by the process can be controlled to some degree by selection of


id: chemical-ionization-20260505-1
file: data/en.wikipedia.org/wiki/Chemical_ionization-1.md
category: reference
title: Chemical ionization
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Chemical_ionization
date_saved: 2026-05-05T10:03:57.240704+00:00
instance: kb-cron
parent: chemical-ionization-20260505-0
summary:
== Advantages and limitations == One of the main advantages of CI over EI is the reduced fragmentation as noted above, which for more fragile molecules, results in a peak in the mass spectrum indicative of the molecular weight of the analyte. This proves to be a particular advantage for biological applications where EI often does not yield useful molecular ions in the spectrum. The spectra given by CI are simpler than EI spectra and CI can be more sensitive than other ionization methods, at least in part to the reduced fragmentation which concentrates the ion signal in fewer and therefore more intense peaks. The extent of fragmentation can be somewhat controlled by proper selection of reagent gases. Moreover, CI is often coupled to chromatographic separation techniques, thereby improving its usefulness in identification of compounds. As with EI, the method is limited to compounds that can be vapourized in the ion source. The lower degree of fragmentation can be a disadvantage in that less structural information is provided. Additionally, the degree of fragmentation and therefore the mass spectrum, can be sensitive to source conditions such as pressure, temperature, and the presence of impurities (such as water vapour) in the source.


id: chemical-shift-index-20260505-0
file: data/en.wikipedia.org/wiki/Chemical_shift_index-0.md
category: reference
title: Chemical shift index
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Chemical_shift_index
date_saved: 2026-05-05T10:03:58.435699+00:00
instance: kb-cron
parent: chemical-shift-index-20260505-0
summary:
The chemical shift index or CSI is a widely employed technique in protein nuclear magnetic resonance spectroscopy that can be used to display and identify the location (i.e. start and end) as well as the type of protein secondary structure (beta strands, helices and random coil regions) found in proteins using only backbone chemical shift data The technique was invented by David S. Wishart in 1992 for analyzing 1Hα chemical shifts and then later extended by him in 1994 to incorporate 13C backbone shifts. The original CSI method makes use of the fact that 1Hα chemical shifts of amino acid residues in helices tends to be shifted upfield (i.e. towards the right side of an NMR spectrum) relative to their random coil values and downfield (i.e. towards the left side of an NMR spectrum) in beta strands. Similar kinds of upfield and downfield trends are also detectable in backbone 13C chemical shifts. == Implementation == The CSI is a graph-based technique that essentially employs an amino acid-specific digital filter to convert every assigned backbone chemical shift value into a simple three-state (-1, 0, +1) index. This approach generates a more easily understood and much more visually pleasing graph of protein


id: coherent-diffraction-imaging-20260505-0
file: data/en.wikipedia.org/wiki/Coherent_diffraction_imaging-0.md
category: reference
title: Coherent diffraction imaging
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Coherent_diffraction_imaging
date_saved: 2026-05-05T10:03:59.662514+00:00
instance: kb-cron
parent: coherent-diffraction-imaging-20260505-0
summary:
Coherent diffractive imaging (CDI) is a computational microscopy method that reconstructs images from coherent diffraction patterns without the use of lenses. It was first experimentally demonstrated in 1999 by Miao and collaborators using synchrotron X-rays and iterative phase retrieval. CDI has been applied to image structures such as nanotubes, nanocrystals, porous nanocrystalline layers, defects, potentially proteins, and more. In CDI, a highly coherent beam of X-rays, electrons or other wavelike particle or photon is incident on an object. The beam scattered by the object produces a diffraction pattern downstream which is then collected by a detector. This recorded pattern is then used to reconstruct an image via an iterative feedback algorithm. Effectively, the objective lens in a typical microscope is replaced with software to convert from the reciprocal space diffraction pattern into a real space image. The advantage in using no lenses is that the final image is aberration–free and so resolution is only diffraction and dose limited (dependent on wavelength, aperture size and exposure). Applying a simple inverse Fourier transform to information with only intensities is insufficient for creating an image from the diffraction pattern due to the missing phase information. This is called the phase problem. == Imaging


id: coherent-diffraction-imaging-20260505-1
file: data/en.wikipedia.org/wiki/Coherent_diffraction_imaging-1.md
category: reference
title: Coherent diffraction imaging
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Coherent_diffraction_imaging
date_saved: 2026-05-05T10:03:59.662514+00:00
instance: kb-cron
parent: coherent-diffraction-imaging-20260505-0
summary:
== Reconstruction == In a typical reconstruction the first step is to generate random phases and combine them with the amplitude information from the reciprocal space pattern. Then a Fourier transform is applied back and forth to move between real space and reciprocal space with the modulus squared of the diffracted wave field set equal to the measured diffraction intensities in each cycle. By applying various constraints in real and reciprocal space the pattern evolves into an image after enough iterations of the HIO process. To ensure reproducibility the process is typically repeated with new sets of random phases with each run having typically hundreds to thousands of cycles. The constraints imposed in real and reciprocal space typically depend on the experimental setup and the sample to be imaged. The real space constraint is to restrict the imaged object to a confined region called the "support". For example, the object to be imaged can be initially assumed to reside in a region no larger than roughly the beam size. In some cases this constraint may be more restrictive, such as in a periodic support region for a uniformly spaced array of quantum dots. Other researchers have investigated imaging extended objects,


id: coherent-diffraction-imaging-20260505-2
file: data/en.wikipedia.org/wiki/Coherent_diffraction_imaging-2.md
category: reference
title: Coherent diffraction imaging
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Coherent_diffraction_imaging
date_saved: 2026-05-05T10:03:59.662514+00:00
instance: kb-cron
parent: coherent-diffraction-imaging-20260505-0
summary:
Two wave sources are coherent when their frequency and waveforms are identical; this property of waves allows for stationary interference in which the wave is temporally or spatially constant and the waves are either added or subtracted from one another. Coherence is important in the context of CDI as the coherence of the two sources allows for the continuous emission of waves to occur. A constant phase difference and the coherence of a wave are necessary in order to obtain any type of interference pattern. Clearly a highly coherent beam of waves is required for CDI to work since the technique requires interference of diffracted waves. Coherent waves must be generated at the source (synchrotron, field emitter, etc.) and must maintain coherence until diffraction. It has been shown that the coherence width of the incident beam needs to be approximately twice the lateral width of the object to be imaged. However determining the size of the coherent patch to decide whether the object does or does not meet the criterion is subject to debate. As the coherence width is decreased, the size of the Bragg peaks in reciprocal space grows and they begin to overlap leading to decreased image resolution.


id: coherent-diffraction-imaging-20260505-3
file: data/en.wikipedia.org/wiki/Coherent_diffraction_imaging-3.md
category: reference
title: Coherent diffraction imaging
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Coherent_diffraction_imaging
date_saved: 2026-05-05T10:03:59.662514+00:00
instance: kb-cron
parent: coherent-diffraction-imaging-20260505-0
summary:
== In situ CDI == Incomplete measurements have been a problem observed across all algorithms in CDI. Since the detector is too sensitive to absorb a particle beam directly, a beamstop or hole must be placed at its center to prevent direct contact (Pham 2020). Furthermore, detectors are often constructed with multiple panels with gaps between them where data again cannot be collected (Pham 2020). Ultimately, these qualities of the detector result in missing data within the diffraction patterns. In situ CDI is a new method of this imaging technology that could increase resistance to incomplete measurements. In situ CDI images a static region and a dynamic region that changes over time as a result of external stimuli (Hung Lo 2018). A series of diffraction patterns are collected over time with interference from the static and dynamic regions (Hung Lo 2018). Because of this interference, the static region acts as a time invariant constraint that phases patterns together in fewer iterations (Hung Lo 2018). Enforcing this static region as a constraint makes in situ CDI more robust to incomplete data and noise interference in the diffraction patterns (Hung Lo 2018). Overall, in situ CDI provides clearer data collection in fewer


id: collision-induced-dissociation-20260505-0
file: data/en.wikipedia.org/wiki/Collision-induced_dissociation-0.md
category: reference
title: Collision-induced dissociation
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Collision-induced_dissociation
date_saved: 2026-05-05T10:04:00.852527+00:00
instance: kb-cron
parent: collision-induced-dissociation-20260505-0
summary:
Collision-induced dissociation (CID), also known as collisionally activated dissociation (CAD), is a mass spectrometry technique to induce fragmentation of selected ions in the gas phase. The selected ions (typically molecular ions or protonated molecules) are usually accelerated by applying an electrical potential to increase the ion kinetic energy and then allowed to collide with neutral molecules (often helium, nitrogen, or argon). In the collision, some of the kinetic energy is converted into internal energy which results in bond breakage and the fragmentation of the molecular ion into smaller fragments. These fragment ions can then be analyzed by tandem mass spectrometry. CID and the fragment ions produced by CID are used for several purposes. Partial or complete structural determination can be achieved. In some cases, identity can be established based on previous knowledge without determining structure. Another use is in simply achieving more sensitive and specific detection. By detecting a unique fragment ion, the precursor ion can be detected in the presence of other ions of the same m/z value (mass-to-charge ratio), reducing the background and increasing the limit of detection. == Low-energy CID and high-energy CID == Low-energy CID is typically carried out with ion kinetic energies less than approximately


id: combustion-analysis-20260505-0
file: data/en.wikipedia.org/wiki/Combustion_analysis-0.md
category: reference
title: Combustion analysis
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Combustion_analysis
date_saved: 2026-05-05T10:04:02.028558+00:00
instance: kb-cron
parent: combustion-analysis-20260505-0
summary:
Combustion analysis is a method used in both organic chemistry and analytical chemistry to determine the elemental composition (more precisely empirical formula) of a pure organic compound by combusting the sample under conditions where the resulting combustion products can be quantitatively analyzed. Once the number of moles of each combustion product has been determined the empirical formula or a partial empirical formula of the original compound can be calculated. Applications for combustion analysis involve only the elements of carbon (C), hydrogen (H), nitrogen (N), and sulfur (S) as combustion of materials containing them convert these elements to their oxidized form (CO2, H2O, NO or NO2, and SO2) under high temperature high oxygen conditions. Notable interests for these elements involve measuring total nitrogen in food or feed to determine protein percentage, measuring sulfur in petroleum products, or measuring total organic carbon (TOC) in water. == History == The method was invented by Joseph Louis Gay-Lussac. Justus von Liebig studied the method while working with Gay-Lussac between 1822 and 1824 and improved the method in the following years to a level that it could be used as standard procedure for organic analysis. == Combustion train == A combustion train is an analytical


id: confocal-microscopy-20260505-0
file: data/en.wikipedia.org/wiki/Confocal_microscopy-0.md
category: reference
title: Confocal microscopy
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Confocal_microscopy
date_saved: 2026-05-05T10:04:03.194579+00:00
instance: kb-cron
parent: confocal-microscopy-20260505-0
summary:
Confocal microscopy, most frequently confocal laser scanning microscopy (CLSM) or laser scanning confocal microscopy (LSCM), is an optical imaging technique for increasing optical resolution and contrast of a micrograph by means of using a spatial pinhole to block out-of-focus light in image formation. Capturing multiple two-dimensional images at different depths in a sample enables the reconstruction of three-dimensional structures (a process known as optical sectioning) within an object. This technique is used extensively in the scientific and industrial communities and typical applications are in life sciences, semiconductor inspection and materials science. Light travels through the sample under a conventional microscope as far into the specimen as it can penetrate, while a confocal microscope only focuses a smaller beam of light at one narrow depth level at a time. The CLSM achieves a controlled and highly limited depth of field. == Basic concept == The principle of confocal imaging was patented in 1957 by Marvin Minsky and aims to overcome some limitations of traditional wide-field fluorescence microscopes. In a conventional (i.e., wide-field) fluorescence microscope, the entire specimen is flooded evenly in light from a light source. All parts of the sample can be excited at the same time and the resulting


id: confocal-microscopy-20260505-1
file: data/en.wikipedia.org/wiki/Confocal_microscopy-1.md
category: reference
title: Confocal microscopy
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Confocal_microscopy
date_saved: 2026-05-05T10:04:03.194579+00:00
instance: kb-cron
parent: confocal-microscopy-20260505-0
summary:
Four types of confocal microscopes are commercially available: Confocal laser scanning microscopes use multiple mirrors (typically 2 or 3 scanning linearly along the x- and the y- axes) to scan the laser across the sample and "descan" the image across a fixed pinhole and detector. This process is usually slow and does not work for live imaging, but can be useful to create high-resolution representative images of fixed samples. Spinning-disk (Nipkow disk) confocal microscopes use a series of moving pinholes on a disc to scan spots of light. Since a series of pinholes scans an area in parallel, each pinhole is allowed to hover over a specific area for a longer amount of time thereby reducing the excitation energy needed to illuminate a sample when compared to laser scanning microscopes. Decreased excitation energy reduces phototoxicity and photobleaching of a sample often making it the preferred system for imaging live cells or organisms. Microlens enhanced or dual spinning-disk confocal microscopes work under the same principles as spinning-disk confocal microscopes except a second spinning-disk containing micro-lenses is placed before the spinning-disk containing the pinholes. Every pinhole has an associated microlens. The micro-lenses act to capture a broad band of light and focus


id: confocal-microscopy-20260505-2
file: data/en.wikipedia.org/wiki/Confocal_microscopy-2.md
category: reference
title: Confocal microscopy
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Confocal_microscopy
date_saved: 2026-05-05T10:04:03.194579+00:00
instance: kb-cron
parent: confocal-microscopy-20260505-0
summary:
== Uses == CLSM is widely used in various biological science disciplines, from cell biology and genetics to microbiology and developmental biology. It is also used in quantum optics and nano-crystal imaging and spectroscopy. === Biology and medicine === Clinically, CLSM is used in the evaluation of various eye diseases, and is particularly useful for imaging, qualitative analysis, and quantification of endothelial cells of the cornea. It is used for localizing and identifying the presence of filamentary fungal elements in the corneal stroma in cases of keratomycosis, enabling rapid diagnosis and thereby early institution of definitive therapy. Research into CLSM techniques for endoscopic procedures (endomicroscopy) is also showing promise. In the pharmaceutical industry, it was recommended to follow the manufacturing process of thin film pharmaceutical forms, to control the quality and uniformity of the drug distribution. Confocal microscopy is also used to study biofilms — complex porous structures that are the preferred habitat of microorganisms. Some of temporal and spatial function of biofilms can be understood only by studying their structure on micro- and meso-scales. The study of microscale is needed to detect the activity and organization of single microorganisms. === Optics and crystallography === CLSM is used as the


id: confocal-microscopy-20260505-3
file: data/en.wikipedia.org/wiki/Confocal_microscopy-3.md
category: reference
title: Confocal microscopy
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Confocal_microscopy
date_saved: 2026-05-05T10:04:03.194579+00:00
instance: kb-cron
parent: confocal-microscopy-20260505-0
summary:
=== 1969: The first confocal laser scanning microscope === In 1969 and 1971, M. David Egger and Paul Davidovits from Yale University, published two papers describing the first confocal laser scanning microscope. It was a point scanner, meaning just one illumination spot was generated. It used epi-Illumination-reflection microscopy for the observation of nerve tissue. A 5 mW Helium-Neon-Laser with 633 nm light was reflected by a semi-transparent mirror towards the objective. The objective was a simple lens with a focal length of 8.5 mm. As opposed to all earlier and most later systems, the sample was scanned by movement of this lens (objective scanning), leading to a movement of the focal point. Reflected light came back to the semitransparent mirror, the transmitted part was focused by another lens on the detection pinhole behind which a photomultiplier tube was placed. The signal was visualized by a CRT of an oscilloscope, the cathode ray was moved simultaneously with the objective. A special device allowed to make Polaroid photos, three of which were shown in the 1971 publication. The authors speculate about fluorescent dyes for in vivo investigations. They cite Minsky's patent, thank Steve Baer, at the time a doctoral student at the


id: crucible-20260505-0
file: data/en.wikipedia.org/wiki/Crucible-0.md
category: reference
title: Crucible
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Crucible
date_saved: 2026-05-05T10:04:04.364838+00:00
instance: kb-cron
parent: crucible-20260505-0
summary:
A crucible is a container in which metals or other substances may be melted or subjected to very high temperatures. Although crucibles have historically tended to be made out of clay, they can be made from any material that withstands temperatures high enough to melt or otherwise alter its contents. == History == === Typology and chronology === The form of the crucible has varied through time, with designs reflecting the process for which they are used, as well as regional variation. The earliest crucible forms derive from the sixth/fifth millennium B.C. in Eastern Europe and Iran. === Chalcolithic === Crucibles used for copper smelting were generally wide shallow vessels made from clay that lacks refractory properties which is similar to the types of clay used in other ceramics of the time. During the Chalcolithic period, crucibles were heated from the top by using blowpipes. Ceramic crucibles from this time had slight modifications to their designs such as handles, knobs or pouring spouts allowing them to be more easily handled and poured. Early examples of this practice can be seen in Feinan, Jordan. These crucibles have added handles to allow for better manipulation, however, due to the poor preservation of


id: crucible-20260505-1
file: data/en.wikipedia.org/wiki/Crucible-1.md
category: reference
title: Crucible
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Crucible
date_saved: 2026-05-05T10:04:04.364838+00:00
instance: kb-cron
parent: crucible-20260505-0
summary:
=== Medieval period === Smelting and melting of copper and its alloys such as leaded bronze was done in crucibles similar to those of the Roman period which have thinner walls and flat bases to sit within the furnaces. The technology for this type of smelting started to change at the end of the medieval period with the introduction of new tempering material for the ceramic crucibles. Some of these copper alloy crucibles were used in the making of bells. Bell foundry crucibles had to be larger at about 60 cm. These later medieval crucibles were a more mass-produced product. The cementation process, which was lost from the end of the Roman to the early medieval period, continued in the same way with brass. Brass production increased during the medieval period due to a better understanding of the technology behind it. Furthermore, the process for carrying out cementation for brass did not change greatly until the 19th century. However, during this period a vast and highly important technological innovation happened using the cementation process, the production of crucible steel. Steel production using iron and carbon works similarly to brass, with the iron metal being mixed with carbon to produce steel.


id: crucible-20260505-2
file: data/en.wikipedia.org/wiki/Crucible-2.md
category: reference
title: Crucible
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Crucible
date_saved: 2026-05-05T10:04:04.364838+00:00
instance: kb-cron
parent: crucible-20260505-0
summary:
In the area of chemical analysis, crucibles are used in quantitative gravimetric chemical analysis (analysis by measuring mass of an analyte or its derivative). Common crucible use may be as follows. A residue or precipitate in a chemical analysis method can be collected or filtered from some sample or solution on special "ashless" filter paper. The crucible and lid to be used are pre-weighed very accurately on an analytical balance. After some possible washing and/or pre-drying of this filtrate, the residue on the filter paper can be placed in the crucible and fired (heated at very high temperature) until all the volatiles and moisture are driven out of the sample residue in the crucible. The "ashless" filter paper is completely burned up in this process. The crucible with the sample and lid is allowed to cool in a desiccator. The crucible and lid with the sample inside are weighed very accurately again only after it has completely cooled to room temperature (higher temperature would cause air currents around the balance giving inaccurate results). The mass of the empty, pre-weighed crucible and lid is subtracted from this result to yield the mass of the completely dried residue in the crucible. A


id: cryofixation-20260505-0
file: data/en.wikipedia.org/wiki/Cryofixation-0.md
category: reference
title: Cryofixation
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Cryofixation
date_saved: 2026-05-05T10:04:05.506913+00:00
instance: kb-cron
parent: cryofixation-20260505-0
summary:
Cryofixation is a technique for fixation or stabilisation of biological materials as the first step in specimen preparation for the electron microscopy and cryo-electron microscopy. Typical specimens for cryofixation include small samples of plant or animal tissue, cell suspensions of microorganisms or cultured cells, suspensions of viruses or virus capsids and samples of purified macromolecules, especially proteins. Types of cryo-fixation are freezing-drying, freezing-substitution and freezing-etching. == Plunge freezing == The method involves ultra-rapid cooling of small tissue or cell samples to the temperature of liquid nitrogen (−196 °C) or below, stopping all motion and metabolic activity and preserving the internal structure by freezing all fluid phases solid. Typically, a sample is plunged into liquid nitrogen or into liquid ethane or liquid propane in a container cooled by liquid nitrogen. The ultimate objective is to freeze the specimen so rapidly (at 104 to 106 K per second) that ice crystals are unable to form, or are prevented from growing big enough to cause damage to the specimen's ultrastructure. The formation of samples containing specimens in amorphous ice is the "holy grail" of biological cryomicroscopy. In practice, it is very difficult to achieve high enough cooling rates to produce amorphous ice in


id: cryogenic-electron-microscopy-20260505-0
file: data/en.wikipedia.org/wiki/Cryogenic_electron_microscopy-0.md
category: reference
title: Cryogenic electron microscopy
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Cryogenic_electron_microscopy
date_saved: 2026-05-05T10:04:06.678811+00:00
instance: kb-cron
parent: cryogenic-electron-microscopy-20260505-0
summary:
Cryogenic electron microscopy (cryo-EM) is a transmission electron microscopy technique applied to samples cooled to cryogenic temperatures. Developed in the 1970s, advances in detector technology and software allow biomolecular structures to be imaged at near-atomic resolution. The approach has become a popular alternative to X-ray crystallography or NMR spectroscopy in structural biology. When scanning biological specimens, sample structure is preserved by embedding the specimens in vitreous ice. An aqueous sample solution is applied to a grid-mesh and plunge-frozen in liquid ethane or a mixture of liquid ethane and propane. The 2017 Nobel Prize in Chemistry was awarded to Jacques Dubochet, Joachim Frank, and Richard Henderson "for developing cryo-electron microscopy for the high-resolution structure determination of biomolecules in solution." Nature Methods also named cryo-EM as the "Method of the Year" in 2015. == History == === Early development === In the 1960s, transmission electron microscopy of biological samples was limited because of radiation damage from the high energy electron beams. Scientists hypothesized that examining specimens at low temperatures would reduce beam-induced radiation damage. Both liquid helium (−269 °C or 4 K or −452 °F) and liquid nitrogen (−195.79 °C or 77 K or −320 °F) were considered as cryogens, however high


id: cryogenic-electron-microscopy-20260505-1
file: data/en.wikipedia.org/wiki/Cryogenic_electron_microscopy-1.md
category: reference
title: Cryogenic electron microscopy
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Cryogenic_electron_microscopy
date_saved: 2026-05-05T10:04:06.678811+00:00
instance: kb-cron
parent: cryogenic-electron-microscopy-20260505-0
summary:
Scanning electron cryomicroscopy (cryoSEM) is a scanning electron microscopy technique with a scanning electron microscope's cold stage in a cryogenic chamber. === Technique of use and data analysis === ==== Electron cryotomography ==== In electron cryotomography (cyro-ET), many pictures of a sample are taken from different angles using a tilting mechanism. The images are combined to create a 3D model (map) of ~1–4 nm resolution. ==== Single particle analysis ==== SPA or single-particle cyro-EM is the method used to obtain near-atomic resolution (<1 nm) models of biomolecules. It is what the 2017 Nobel Prize refers to. In SPA, a large collection of cyro-TEM images are automatically sorted into classes. Within each class, the images are combined to reduce noise and to create a 3D model of the class of particles, a 3D "map". The main innovation compared to cyro-ET is the combination of images from similar objects. When combined with a knowledge of time progression, the result is time-resolved cyro-TEM. ===== Comparisons to X-ray crystallography ===== Traditionally, X-ray crystallography has been the most popular technique for determining the 3D structures of biological molecules. However, the aforementioned improvements in cryo-EM have increased its popularity as a tool for examining the details


id: cryogenic-electron-microscopy-20260505-2
file: data/en.wikipedia.org/wiki/Cryogenic_electron_microscopy-2.md
category: reference
title: Cryogenic electron microscopy
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Cryogenic_electron_microscopy
date_saved: 2026-05-05T10:04:06.678811+00:00
instance: kb-cron
parent: cryogenic-electron-microscopy-20260505-0
summary:
== Image processing in cryo-TEM == Even though in the majority of approaches in electron microscopy one tries to get the best resolution image of the material, it is not always the case in cryo-TEM. Besides all the benefits of high resolution images, the signal to noise ratio remains the main hurdle that prevents assigning orientation to each particle. For example, in macromolecule complexes, there are several different structures that are being projected from 3D to 2D during imaging and if they are not distinguished the result of image processing will be a blur. That is why the probabilistic approaches become more powerful in this type of investigation. There are two popular approaches that are widely used nowadays in cryo-EM image processing, the maximum likelihood approach that was discovered in 1998 and relatively recently adapted Bayesian approach. The maximum likelihood estimation approach comes to this field from the statistics. Here, all the possible orientations of particles are summed up to get the resulting probability distribution. We can compare this to a typical least square estimation where particles get exact orientations per image. This way, the particles in the sample get "fuzzy" orientations after calculations, weighted by corresponding probabilities. The whole


id: cyclotron-motion-20260505-0
file: data/en.wikipedia.org/wiki/Cyclotron_motion-0.md
category: reference
title: Cyclotron motion
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Cyclotron_motion
date_saved: 2026-05-05T10:04:07.875335+00:00
instance: kb-cron
parent: cyclotron-motion-20260505-0
summary:
In physics, cyclotron motion, also known as gyromotion, refers to the circular motion exhibited by charged particles in a uniform magnetic field. The circular trajectory of a particle in cyclotron motion is characterized by an angular frequency referred to as the cyclotron frequency or gyrofrequency and a radius referred to as the cyclotron radius, gyroradius, or Larmor radius. For a particle with charge q {\displaystyle q} and mass m {\displaystyle m} initially moving with speed v ⊥ {\displaystyle v_{\perp }} perpendicular to the direction of a uniform magnetic field B {\displaystyle B} , the cyclotron radius is: r c = m v ⊥ | q | B {\displaystyle r_{\rm {c}}={\frac {mv_{\perp }}{|q|B}}} and the cyclotron frequency is: ω c = | q | B m . {\displaystyle \omega _{\rm {c}}={\frac {|q|B}{m}}.} An external oscillating field matching the cyclotron frequency, ω = ω c , {\displaystyle \omega =\omega _{c},} will accelerate the particles, a phenomenon known as cyclotron resonance. This resonance is the basis for many scientific and engineering uses of cyclotron motion. In quantum mechanical systems, the energies of cyclotron orbits are quantized into discrete Landau levels, which contribute to Landau diamagnetism and lead to oscillatory electronic phenomena like the


id: dark-field-x-ray-microscopy-20260505-0
file: data/en.wikipedia.org/wiki/Dark-field_X-ray_microscopy-0.md
category: reference
title: Dark-field X-ray microscopy
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Dark-field_X-ray_microscopy
date_saved: 2026-05-05T10:04:09.080940+00:00
instance: kb-cron
parent: dark-field-x-ray-microscopy-20260505-0
summary:
Dark-field X-ray microscopy (DFXM or DFXRM) is an imaging technique used for multiscale structural characterisation. It is capable of mapping deeply embedded structural elements with nm-resolution using synchrotron X-ray diffraction-based imaging. The technique works by using scattered X-rays to create a high degree of contrast, and by measuring the intensity and spatial distribution of the diffracted beams, it is possible to obtain a three-dimensional map of the sample's structure, orientation, and local strain. == History == The first experimental demonstration of dark-field X-ray microscopy was reported in 2006 by a group at the European Synchrotron Radiation Facility in Grenoble, France. Since then, the technique has been rapidly evolving and has shown great promise in multiscale structural characterization. Its development is largely due to advances in synchrotron X-ray sources, which provide highly collimated and intense beams of X-rays. The development of dark-field X-ray microscopy has been driven by the need for non-destructive imaging of bulk crystalline samples at high resolution, and it continues to be an active area of research today. However, dark-field microscopy, dark-field scanning transmission X-ray microscopy, and soft dark-field X-ray microscopy has long been used to map deeply embedded structural elements. == Principles and instrumentation == In this


id: dark-field-x-ray-microscopy-20260505-1
file: data/en.wikipedia.org/wiki/Dark-field_X-ray_microscopy-1.md
category: reference
title: Dark-field X-ray microscopy
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Dark-field_X-ray_microscopy
date_saved: 2026-05-05T10:04:09.080940+00:00
instance: kb-cron
parent: dark-field-x-ray-microscopy-20260505-0
summary:
Differential-aperture X-ray structural microscopy (DAXM): DAXM is a synchrotron X-ray method capable of delivering precise information about the local structure and crystallographic orientation in three dimensions at a spatial resolution of less than one micron. It also provides angular precision and local elastic strain with high accuracy a wide range of materials, including single crystals, polycrystals, composites, and materials with varying properties. Bragg Coherent diffraction imaging (BCDI): BCDI is an advanced microscopy technique introduced in 2006 to study crystalline nanomaterials' 3D structure. BCDI has applications in diverse areas, including in situ studies of corrosion, probing dissolution processes, and simulating diffraction patterns to understand atomic displacement. Ptychography is a computational imaging method used in microscopy to generate images by processing multiple coherent interference patterns. It provides advantages such as high-resolution imaging, phase retrieval, and lensless imaging capabilities. Diffraction Contrast Tomography (DCT): DCT is a method that uses coherent X-rays to generate three-dimensional grain maps of polycrystalline materials. DCT enables visualization of crystallographic information within samples, aiding in the analysis of materials' structural properties, defects, and grain orientations. Three-dimensional X-ray diffraction (3DXRD): 3DXRD is a synchrotron-based technique that provides information about the crystallographic orientation of individual grains in polycrystalline materials. It can


id: diaphonization-20260505-0
file: data/en.wikipedia.org/wiki/Diaphonization-0.md
category: reference
title: Diaphonization
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Diaphonization
date_saved: 2026-05-05T10:04:10.260401+00:00
instance: kb-cron
parent: diaphonization-20260505-0
summary:
Diaphonization (or diaphonisation), also known as clearing and staining, is a staining technique used on animal specimens that first renders the body of the animal transparent by bathing it in trypsin, and then stains the bones and cartilage with various dyes, usually alizarin red and alcian blue. == History == Diaphonization was first developed by German anatomist Oskar Schultze in 1897, and later was modified by numerous researchers. == Technique == Clearing renders the animals transparent and is achieved by bathing the specimens in a soup of trypsin, a digestive enzyme that slowly breaks down flesh. The dyes alizarin red and alcian blue are most commonly used in the staining of bone and cartilage accordingly. When cleared, the specimen is put in glycerin. Despite its merits, diaphonization is not widely used in the scientific field. Advancements in imaging technology have rendered the practice all but obsolete, though it is expanding as an art form. Diaphonization is not suitable for animals longer than 30 centimeters (except for snakes) due to the limited ability of the trypsin bath to penetrate the tissues of larger animals. It is usually used to preserve animals that are too delicate to dissect, and instead are kept


id: dielectric-thermal-analysis-20260505-0
file: data/en.wikipedia.org/wiki/Dielectric_thermal_analysis-0.md
category: reference
title: Dielectric thermal analysis
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Dielectric_thermal_analysis
date_saved: 2026-05-05T10:04:11.443479+00:00
instance: kb-cron
parent: dielectric-thermal-analysis-20260505-0
summary:
Dielectric thermal analysis (DETA), or dielectric analysis (DEA), is a materials science technique similar to dynamic mechanical analysis except that an oscillating electrical field is used instead of a mechanical force. For investigation of the curing behavior of thermosetting resin systems, composite materials, adhesives and paints, Dielectric Analysis (DEA) can be used in accordance with ASTM E 2038 or E 2039. The great advantage of DEA is that it can be employed not only on a laboratory scale, but also in process. == Measuring principle == In a typical test, the sample is placed in contact with two electrodes (the dielectric sensor) and a sinusoidal voltage (the excitation) is applied to one electrode. The resulting sinusoidal current (the response) is measured at the second electrode. The response signal is attenuated in amplitude and shifted in phase in relation to the mobility of the ions and alignment of the dipoles. Dipoles in the material will attempt to align with the electric field and ions (present as impurities) will move toward the electrode of opposite polarity. The dielectric properties of permittivity ε' and loss factor ε" are then calculated from this measured amplitude and phase change. == References ==


id: differential-dynamic-microscopy-20260505-0
file: data/en.wikipedia.org/wiki/Differential_dynamic_microscopy-0.md
category: reference
title: Differential dynamic microscopy
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Differential_dynamic_microscopy
date_saved: 2026-05-05T10:04:12.670972+00:00
instance: kb-cron
parent: differential-dynamic-microscopy-20260505-0
summary:
Differential dynamic microscopy (DDM) is an imaging-based optical technique that enables performing light scattering-like experiments by means of a conventional optical microscope. It uses time sequences of microscope images to extract dynamic information about microscopic fluctuations over a range of length scales and time delays, analogous to what is obtained in dynamic light scattering (DLS) experiments. DDM is suitable for typical soft materials such as liquids, gels, suspensions of colloids and polymers, liquid crystals and it has been applied to various biological systems including bacteria and cells. == History and developments == The DDM technique was introduced in 2008 by Cerbino & Trappe as a way to probe wavevector-resolved dynamics of colloidal particles using a microscope equipped with a high-speed camera, demonstrating that dynamic information similar to that obtained in DLS can be extracted from time-lapse images taken in real space. This foundational paper has accumulated several citations, establishing the unique capability of DDM to combine imaging capabilities with scattering-based wavevector analysis. Shortly thereafter, Giavazzi et al. discussed extensions to other imaging modalities, also based on fluorescence, and clarified the connections of DDM to related imaging-based scattering methods (see below the section Relationship with other imaging-based scattering methods). Subsequent studies


id: differential-dynamic-microscopy-20260505-1
file: data/en.wikipedia.org/wiki/Differential_dynamic_microscopy-1.md
category: reference
title: Differential dynamic microscopy
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Differential_dynamic_microscopy
date_saved: 2026-05-05T10:04:12.670972+00:00
instance: kb-cron
parent: differential-dynamic-microscopy-20260505-0
summary:
Measurement speed: DDM requires extended acquisition times (minutes to hours) compared to DLS (seconds), making DLS preferred for rapid, routine measurements. Analysis time: Data analysis is computationally intensive. While traditional CPU-based processing required minutes to hours per dataset, recent GPU-accelerated implementations (e.g. fastDDM) reduce this to seconds, enabling high-throughput workflows. Commercial maturity: DLS instruments and software are mature and widely available; DDM requires custom setups or adapted commercial microscopes with specialized analysis software. Optical contrast requirement: DDM performance depends critically on signal contrast. Weakly scattering samples may require careful illumination optimization or fluorescent labeling. Dynamic range trade-offs: Lowest accessible q-values (longest length scales) correspond to very slow dynamics requiring extended acquisition; highest q-values require high magnification and frame rates, creating practical trade-offs in microscope configuration. == Applicability and working principle == The concentration–intensity proportionality, which ensures the validity of the DDM framework, holds in two primary classes of DDM implementations: Scattering-based DDM: where image intensity arises from the interference between a strong transmitted beam and weakly scattered light, as in bright field, phase contrast, or polarized imaging. Fluorescence-based DDM: where images result from the incoherent summation of fluorescence emissions from labeled particles or structures, as in fluorescence or confocal imaging.


id: differential-dynamic-microscopy-20260505-2
file: data/en.wikipedia.org/wiki/Differential_dynamic_microscopy-2.md
category: reference
title: Differential dynamic microscopy
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Differential_dynamic_microscopy
date_saved: 2026-05-05T10:04:12.670972+00:00
instance: kb-cron
parent: differential-dynamic-microscopy-20260505-0
summary:
== Applications == DDM was initially used to characterize the dynamics of colloidal particles undergoing Brownian motion in dilute and concentrated suspensions, extracting diffusion coefficients and other hydrodynamic parameters from the wavevector dependence of decorrelation rates. DDM has been extended to measure dynamics in complex fluids, including aggregation processes of nanoparticles and dynamics of anisotropic colloids. DDM has been widely applied to quantify bacterial motion and motility, providing ensemble-averaged parameters such as population swim speed, diffusivity, and run–tumble statistics without single-particle tracking. Confocal and fluorescence implementations further enable measurements in fluorescent and optically challenging samples, including concentrated and multiply scattering systems. Selected application areas include: Particle sizing and size distributions: DDM can be used for particle sizing by extracting diffusion coefficients and converting them to hydrodynamic sizes via the Stokes–Einstein equation. This can be extended to multimodal size distributions and mixtures, where DDM provides size information even when individual particles are not resolved. Protein sizing and macromolecular characterization: DDM has been extended to characterize proteins at dilute concentrations of a few milligrams per milliliter, achieving hydrodynamic radius measurements in excellent agreement with commercial DLS instruments while requiring only microliters of sample. Turbid and concentrated suspensions: DDM has been used to


id: differential-scanning-calorimetry-20260505-0
file: data/en.wikipedia.org/wiki/Differential_scanning_calorimetry-0.md
category: reference
title: Differential scanning calorimetry
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Differential_scanning_calorimetry
date_saved: 2026-05-05T10:04:13.886915+00:00
instance: kb-cron
parent: differential-scanning-calorimetry-20260505-0
summary:
Differential scanning calorimetry (DSC) is a thermoanalytical technique in which the difference in the amount of heat required to increase the temperature of a sample and a reference is measured as a function of temperature. Both the sample and reference are maintained at nearly the same temperature throughout the experiment. Generally, the temperature program for a DSC analysis is designed such that the sample holder temperature increases linearly as a function of time. The reference sample should have a well-defined heat capacity over the range of temperatures to be scanned. Additionally, the reference sample must be stable, of high purity, and must not experience much change across the temperature scan. Typically, reference standards have been metals such as indium, tin, bismuth, and lead, but other standards such as polyethylene and fatty acids have been proposed to study polymers and organic compounds, respectively. The technique was developed by E. S. Watson and M. J. O'Neill in 1962, and introduced commercially at the 1963 Pittsburgh Conference on Analytical Chemistry and Applied Spectroscopy. The first adiabatic differential scanning calorimeter that could be used in biochemistry was developed by P. L. Privalov and D. R. Monaselidze in 1964 at Institute of Physics in Tbilisi,


id: differential-scanning-calorimetry-20260505-1
file: data/en.wikipedia.org/wiki/Differential_scanning_calorimetry-1.md
category: reference
title: Differential scanning calorimetry
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Differential_scanning_calorimetry
date_saved: 2026-05-05T10:04:13.886915+00:00
instance: kb-cron
parent: differential-scanning-calorimetry-20260505-0
summary:
The result of a DSC experiment is a curve of heat flux versus temperature or versus time. There are two different conventions: exothermic reactions in the sample shown with a positive or negative peak, depending on the kind of technology used in the experiment. This curve can be used to calculate enthalpies of transitions. This is done by integrating the peak corresponding to a given transition. It can be shown that the enthalpy of transition can be expressed using the following equation: Δ H = K A {\displaystyle \Delta H=KA} where Δ H {\displaystyle \Delta H} is the enthalpy of transition, K {\displaystyle K} is the calorimetric constant, and A {\displaystyle A} is the area under the curve. The calorimetric constant will vary from instrument to instrument, and can be determined by analyzing a well-characterized sample with known enthalpies of transition. == Applications == Differential scanning calorimetry can be used to measure a number of characteristic properties of a sample. Using this technique it is possible to observe fusion and crystallization events as well as glass transition temperatures Tg. DSC can also be used to study oxidation, as well as other chemical reactions. Glass transitions may occur as the temperature


id: differential-scanning-calorimetry-20260505-2
file: data/en.wikipedia.org/wiki/Differential_scanning_calorimetry-2.md
category: reference
title: Differential scanning calorimetry
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Differential_scanning_calorimetry
date_saved: 2026-05-05T10:04:13.886915+00:00
instance: kb-cron
parent: differential-scanning-calorimetry-20260505-0
summary:
== Examples == The technique is widely used across a range of applications, both as a routine quality test and as a research tool. The equipment is easy to calibrate, using low melting indium at 156.5985 °C for example, and is a rapid and reliable method of thermal analysis. === Polymers === DSC is used widely for examining polymeric materials to determine their thermal transitions. Important thermal transitions include the glass transition temperature (Tg), crystallization temperature (Tc), and melting temperature (Tm). The observed thermal transitions can be utilized to compare materials, although the transitions alone do not uniquely identify composition. The composition of unknown materials may be completed using complementary techniques such as IR spectroscopy. Melting points and glass transition temperatures for most polymers are available from standard compilations, and the method can show polymer degradation by the lowering of the expected melting temperature. Tm depends on the molecular weight of the polymer and thermal history. The percent crystalline content of a polymer can be estimated from the crystallization/melting peaks of the DSC graph using reference heats of fusion found in the literature. DSC can also be used to study thermal degradation of polymers using an approach such as Oxidative


id: differential-thermal-analysis-20260505-0
file: data/en.wikipedia.org/wiki/Differential_thermal_analysis-0.md
category: reference
title: Differential thermal analysis
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Differential_thermal_analysis
date_saved: 2026-05-05T10:04:15.065279+00:00
instance: kb-cron
parent: differential-thermal-analysis-20260505-0
summary:
Differential thermal analysis (DTA) is a thermoanalytic technique that is similar to differential scanning calorimetry. In DTA, the material under study and an inert reference are made to undergo identical thermal cycles, (i.e., same cooling or heating programme) while recording any temperature difference between sample and reference. This differential temperature is then plotted against time, or against temperature (DTA curve, or thermogram). Changes in the sample, either exothermic or endothermic, can be detected relative to the inert reference. Thus, a DTA curve provides data on the transformations that have occurred, such as glass transitions, crystallization, melting and sublimation. The area under a DTA peak is the enthalpy change and is not affected by the heat capacity of the sample. == Apparatus == A DTA consists of a sample holder, thermocouples, sample containers and a ceramic or metallic block; a furnace; a temperature programmer; and a recording system. The key feature is the existence of two thermocouples connected to a voltmeter. One thermocouple is placed in an inert material such as Al2O3, while the other is placed in a sample of the material under study. As the temperature is increased, there will be a brief deflection of the voltmeter if the


id: dna-encoded-chemical-library-20260505-0
file: data/en.wikipedia.org/wiki/DNA-encoded_chemical_library-0.md
category: reference
title: DNA-encoded chemical library
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/DNA-encoded_chemical_library
date_saved: 2026-05-05T10:04:16.238098+00:00
instance: kb-cron
parent: dna-encoded-chemical-library-20260505-0
summary:
DNA-encoded chemical libraries (DECL) is a technology for the synthesis and screening on an unprecedented scale of collections of small molecule compounds. DECL is used in medicinal chemistry to bridge the fields of combinatorial chemistry and molecular biology. The aim of DECL technology is to accelerate the drug discovery process and in particular early phase discovery activities such as target validation and hit identification. DECL technology involves the conjugation of chemical compounds or building blocks to short DNA fragments that serve as identification bar codes and in some cases also direct and control the chemical synthesis. The technique enables the mass creation and interrogation of libraries via affinity selection, typically on an immobilized protein target. A homogeneous method for screening DNA-encoded libraries (DELs) has recently been developed which uses water-in-oil emulsion technology to isolate, count and identify individual ligand-target complexes in a single-tube approach. In contrast to conventional screening procedures such as high-throughput screening, biochemical assays are not required for binder identification, in principle allowing the isolation of binders to a wide range of proteins historically difficult to tackle with conventional screening technologies. So, in addition to the general discovery of target specific molecular compounds, the availability of binders to


id: dna-encoded-chemical-library-20260505-1
file: data/en.wikipedia.org/wiki/DNA-encoded_chemical_library-1.md
category: reference
title: DNA-encoded chemical library
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/DNA-encoded_chemical_library
date_saved: 2026-05-05T10:04:16.238098+00:00
instance: kb-cron
parent: dna-encoded-chemical-library-20260505-0
summary:
The concept of DNA-encoding was first described in a theoretical paper by Sydney Brenner and Richard Lerner in 1992 in which was proposed to link each molecule of a chemically synthesized entity to a particular oligonucleotide sequence constructed in parallel and to use this encoding genetic tag to identify and enrich active compounds. In 1993 the first practical implementation of this approach was presented by J Nielsen, S. Brenner and K. Janda and similarly by the group of M.A. Gallop. Brenner and Janda suggested to generate individual encoded library members by an alternating parallel combinatorial synthesis of the heteropolymeric chemical compound and the appropriate oligonucleotide sequence on the same bead in a “split-&-pool”-based fashion (see below). Since unprotected DNA is restricted to a narrow window of conventional reaction conditions, until the end of the 1990s a number of alternative encoding strategies were envisaged (i.e. MS-based compound tagging, peptide encoding, haloaromatic tagging, encoding by secondary amines, semiconductor devices.), mainly to avoid inconvenient solid phase DNA synthesis and to create easily screenable combinatorial libraries in high-throughput fashion. However, the selective amplificability of DNA greatly facilitates library screening and it becomes indispensable for the encoding of organic compounds libraries of this unprecedented size.


id: dna-encoded-chemical-library-20260505-2
file: data/en.wikipedia.org/wiki/DNA-encoded_chemical_library-2.md
category: reference
title: DNA-encoded chemical library
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/DNA-encoded_chemical_library
date_saved: 2026-05-05T10:04:16.238098+00:00
instance: kb-cron
parent: dna-encoded-chemical-library-20260505-0
summary:
=== Split-&-Pool DNA Encoding === In order to apply combinatorial chemistry for the synthesis of DNA-encoded chemical libraries, a Split-&-Pool approach was pursued. Initially a set of unique DNA-oligonucleotides (n) each containing a specific coding sequence is chemically conjugated to a corresponding set of small organic molecules. Consequently, the oligonucleotide-conjugate compounds are mixed ("Pool") and divided ("Split") into a number of groups (m). In appropriate conditions a second set of building blocks (m) are coupled to the first one and a further oligonucleotide which is coding for the second modification is enzymatically introduced before mixing again. This “split-&-pool” steps can be iterated a number of times (r) increasing at each round the library size in a combinatorial manner (i.e. (n x m)r). Alternatively, peptide nucleic acids have been used to encode libraries prepared by "split-&-pool" method. A benefit of PNA-encoding is that the chemistry can be performed by standard SPPS. === Stepwise coupling of coding DNA fragments to nascent organic molecules === A promising strategy for the construction of DNA-encoded libraries is represented by the use of multifunctional building blocks covalently conjugated to an oligonucleotide serving as a “core structure” for library synthesis. In a ‘pool-and-split’ fashion a set of


id: dna-encoded-chemical-library-20260505-3
file: data/en.wikipedia.org/wiki/DNA-encoded_chemical_library-3.md
category: reference
title: DNA-encoded chemical library
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/DNA-encoded_chemical_library
date_saved: 2026-05-05T10:04:16.238098+00:00
instance: kb-cron
parent: dna-encoded-chemical-library-20260505-0
summary:
In 2001 David Liu and co-workers showed that complementary DNA oligonucleotides can be used to assist certain synthetic reactions, which do not efficiently take place in solution at low concentration. A DNA-heteroduplex was used to accelerate the reaction between chemical moieties displayed at the extremities of the two DNA strands. Furthermore, the "proximity effect", which accelerates bimolecular reaction, was shown to be distance-independent (at least within a distance of 30 nucleotides). In a sequence-programmed fashion oligonucleotides carrying one chemical reactant group were hybridized to complementary oligonucleotide derivatives carrying a different reactive chemical group. The proximity conferred by the DNA hybridization drastically increases the effective molarity of the reaction reagents attached to the oligonucleotides, enabling the desired reaction to occur even in an aqueous environment at concentrations which are several orders of magnitude lower than those needed for the corresponding conventional organic reaction not DNA-templated. Using a DNA-templated set-up and sequence-programmed synthesis Liu and co-workers generated a 64-member compound DNA encoded library of macrocycles. == 3-Dimensional proximity-based technology (YoctoReactor technology) == The YoctoReactor (yR) is a 3D proximity-driven approach which exploits the self-assembling nature of DNA oligonucleotides into 3, 4 or 5-way junctions to direct small molecule synthesis at the center


id: dna-encoded-chemical-library-20260505-4
file: data/en.wikipedia.org/wiki/DNA-encoded_chemical_library-4.md
category: reference
title: DNA-encoded chemical library
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/DNA-encoded_chemical_library
date_saved: 2026-05-05T10:04:16.238098+00:00
instance: kb-cron
parent: dna-encoded-chemical-library-20260505-0
summary:
== Decoding of DNA-encoded chemical libraries == Following selection from DNA-encoded chemical libraries, the decoding strategy for the fast and efficient identification of the specific binding compounds is crucial for the further development of the DEL technology. So far, Sanger-sequencing-based decoding, microarray-based methodology and high-throughput sequencing techniques represented the main methodologies for the decoding of DNA-encoded library selections. === Sanger sequencing-based decoding === Although many authors implicitly envisaged a traditional Sanger sequencing-based decoding, the number of codes to sequence simply according to the complexity of the library is definitely an unrealistic task for a traditional Sanger sequencing approach. Nevertheless, the implementation of Sanger sequencing for decoding DNA-encoded chemical libraries in high-throughput fashion was the first to be described. After selection and PCR amplification of the DNA-tags of the library compounds, concatamers containing multiple coding sequences were generated and ligated into a vector. Following Sanger sequencing of a representative number of the resulting colonies revealed the frequencies of the codes present in the DNA-encoded library sample before and after selection. === Microarray-based decoding === A DNA microarray is a device for high-throughput investigations widely used in molecular biology and in medicine. It consists of an arrayed series of microscopic spots (‘features’


id: dna-encoded-chemical-library-20260505-5
file: data/en.wikipedia.org/wiki/DNA-encoded_chemical_library-5.md
category: reference
title: DNA-encoded chemical library
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/DNA-encoded_chemical_library
date_saved: 2026-05-05T10:04:16.238098+00:00
instance: kb-cron
parent: dna-encoded-chemical-library-20260505-0
summary:
Peptide nucleic acids (PNAs) are synthetic oligonucleotides in which the sugar-phosphate backbone of the DNA or RNA is replaced by a neutral N-(2-aminoethyl)-glycine peptide-like backbone . This allows PNAs to hybridize with complementary DNA or RNA with high affinity and specificity, maintaining their ability to be amplified via polymerase chain reaction (PCR). Unlike DNA/RNA, PNAs are able to resist degradation by nucleases and proteases . In a PNA-encoded library system, unique PNA sequences serve as molecular tags that are covalently attached to small molecules that are produced using combinatorial methods that generate large collections of related compounds. These PNA tags act as barcodes that encode the identity of the PNA allowing for downstream identification . PNA libraries are synthesized using solid-phase peptide synthesis (SPPS), allowing library assembly on resin similar to other peptide libraries. This contrasts with DNA-encoded libraries, which often require enzymatic ligation steps and can be limited by the chemical properties of DNA . The neutrality and stability of the PNA backbone means that PNA tags can tolerate conditions that might degrade DNA tags, and the strong hybridization to complementary nucleic acids which allows PNA tags to be decoded wither by direct hybridization or by conversion into DNA,


id: du-no-y-ring-method-20260505-0
file: data/en.wikipedia.org/wiki/Du_Noüy_ring_method-0.md
category: reference
title: Du Noüy ring method
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Du_Noüy_ring_method
date_saved: 2026-05-05T10:04:17.394583+00:00
instance: kb-cron
parent: du-no-y-ring-method-20260505-0
summary:
In surface science, the du Noüy ring method is a technique for measuring the surface tension of a liquid. This technique was proposed by Pierre Lecomte du Noüy in 1925. The measurement is performed with a force tensiometer, which typically uses an electrobalance to measure the excess force caused by the liquid being pulled up and automatically calculates and displays the surface tension corresponding to the force. Earlier, torsion wire balances were commonly used. == Description == The method involves slowly lifting a ring, often made of platinum, from the surface of a liquid. The force, F, required to raise the ring from the liquid's surface is measured and related to the liquid's surface tension γ: F = w ring + 2 π ⋅ ( r i + r a ) ⋅ γ , {\displaystyle F=w_{\text{ring}}+2\pi \cdot (r_{\text{i}}+r_{\text{a}})\cdot \gamma ,} where ri is the radius of the inner ring of the liquid film pulled, and ra is the radius of the outer ring of the liquid film. wring is the weight of the ring minus the buoyant force due to the part of the ring below the liquid surface. When the ring's thickness is much smaller than its diameter, this


id: dynamic-light-scattering-20260505-0
file: data/en.wikipedia.org/wiki/Dynamic_light_scattering-0.md
category: reference
title: Dynamic light scattering
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Dynamic_light_scattering
date_saved: 2026-05-05T10:04:18.544311+00:00
instance: kb-cron
parent: dynamic-light-scattering-20260505-0
summary:
Dynamic light scattering (DLS) is a technique in physics that can be used to determine the size distribution profile of small particles in suspension or polymers in solution. In the scope of DLS, temporal fluctuations are usually analyzed using the intensity or photon autocorrelation function (also known as photon correlation spectroscopy – PCS or quasi-elastic light scattering – QELS). In the time domain analysis, the autocorrelation function (ACF) usually decays starting from zero delay time, and faster dynamics due to smaller particles lead to faster decorrelation of scattered intensity trace. It has been shown that the intensity ACF is the Fourier transform of the power spectrum, and therefore the DLS measurements can be equally well performed in the spectral domain. DLS can also be used to probe the behavior of complex fluids such as concentrated polymer solutions. == Setup == A monochromatic light source, usually a laser, is shot through a polarizer and into a sample. The scattered light then goes through a second polarizer where it is collected by a photomultiplier and the resulting image is projected onto a screen. This is known as a speckle pattern (Figure 1). All of the molecules in the solution are being hit


id: dynamic-light-scattering-20260505-1
file: data/en.wikipedia.org/wiki/Dynamic_light_scattering-1.md
category: reference
title: Dynamic light scattering
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Dynamic_light_scattering
date_saved: 2026-05-05T10:04:18.544311+00:00
instance: kb-cron
parent: dynamic-light-scattering-20260505-0
summary:
== Multiple scattering == Dynamic light scattering provides insight into the dynamic properties of soft materials by measuring single scattering events, meaning that each detected photon has been scattered by the sample exactly once. In principle, the DLS measurements can be performed with the detector positioned at any angle. The choice of the best angle depends on the sample properties, such as turbidity and particle size. Back scattering detection (e.g., 173° or 175°) is particularly interesting for turbid and highly concentrated samples, which contain large particles. Side scattering detection (90°) is recommended for weakly scattering samples, including small particles and transparent samples. Finally, forward scattering detection (e.g., 13° or 15°) is suitable for detection of samples containing small particles with few large particles. Some DLS instruments in the market also allow automatic angle selection based on a continuous transmittance measurement. At the lower end of the turbidity range, the Cavity Amplified Scattering Spectroscopy method makes use of an integrating cavity to elongate photon paths through quasi non-scattering samples. As opposed to conventional DLS instruments, this method is angle independent as it probes samples isotropically from all directions. Even though the DLS measurement using a single-angle detection has been the most


id: dynamic-light-scattering-20260505-2
file: data/en.wikipedia.org/wiki/Dynamic_light_scattering-2.md
category: reference
title: Dynamic light scattering
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Dynamic_light_scattering
date_saved: 2026-05-05T10:04:18.544311+00:00
instance: kb-cron
parent: dynamic-light-scattering-20260505-0
summary:
where λ is the incident laser wavelength, n0 is the solvent refractive index and θ is the angle at which the detector is located with respect to the sample cell. The refractive index of the solvent plays a crucial role in light scattering and is important to calculate the Stokes radius from the Stokes-Einstein equation. Therefore, previous refractive index data from the scattering medium should be evaluated with dedicated instruments, known as refractometers. Alternatively, DLS instruments containing a refractive index measurement module allow a good estimative for this important parameter within ±0.5%, which is the accuracy defined by ISO 22412:2017 for refractive index values required for DLS. Besides the refractive index of the medium, the refractive index of the particles is only necessary when analyzing larger particle size (usually above 100 nm) and volume- or number-weighted size distributions are needed. In these cases, prior knowledge of the refractive index and absorbance of the material is required in order to apply the Mie scattering. Depending on the anisotropy and polydispersity of the system, a resulting plot of (Γ/q2) vs. q2 may or may not show an angular dependence. Small spherical particles will show no angular dependence, hence no anisotropy. A plot


id: dynamic-light-scattering-20260505-3
file: data/en.wikipedia.org/wiki/Dynamic_light_scattering-3.md
category: reference
title: Dynamic light scattering
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Dynamic_light_scattering
date_saved: 2026-05-05T10:04:18.544311+00:00
instance: kb-cron
parent: dynamic-light-scattering-20260505-0
summary:
=== CONTIN algorithm === An alternative method for analyzing the autocorrelation function can be achieved through an inverse Laplace transform known as CONTIN developed by Steven Provencher. The CONTIN analysis is ideal for heterodisperse, polydisperse, and multimodal systems that cannot be resolved with the cumulant method. The resolution for separating two different particle populations is approximately a factor of five or higher and the difference in relative intensities between two different populations should be less than 1:10−5. === Maximum entropy method === The Maximum entropy method is an analysis method that has great developmental potential. The method is also used for the quantification of sedimentation velocity data from analytical ultracentrifugation. The maximum entropy method involves several iterative steps to minimize the deviation of the fitted data from the experimental data and subsequently reduce the χ2 of the fitted data. == Scattering of non-spherical particles == If the particle in question is not spherical, the rotational motion must be considered as well because the scattering of the light will be different depending on orientation. According to Pecora, rotational Brownian motion will affect the scattering when a particle fulfills two conditions; they must be both optically and geometrically anisotropic. Rod-shaped molecules fulfill


id: dynamic-mechanical-analysis-20260505-0
file: data/en.wikipedia.org/wiki/Dynamic_mechanical_analysis-0.md
category: reference
title: Dynamic mechanical analysis
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Dynamic_mechanical_analysis
date_saved: 2026-05-05T10:04:19.735755+00:00
instance: kb-cron
parent: dynamic-mechanical-analysis-20260505-0
summary:
Dynamic mechanical analysis (abbreviated DMA) is a technique used to study and characterize materials. It is most useful for studying the viscoelastic behavior of polymers. A sinusoidal stress is applied and the strain in the material is measured, allowing one to determine the complex modulus. The temperature of the sample or the frequency of the stress are often varied, leading to variations in the complex modulus; this approach can be used to locate the glass transition temperature of the material, as well as to identify transitions corresponding to other molecular motions. == Theory == === Viscoelastic properties of materials === Polymers composed of long molecular chains have unique viscoelastic properties, which combine the characteristics of elastic solids and Newtonian fluids. The classical theory of elasticity describes the mechanical properties of elastic solids where stress is proportional to strain in small deformations. Such response to stress is independent of strain rate. The classical theory of hydrodynamics describes the properties of viscous fluid, for which stress response depends on strain rate. This solidlike and liquidlike behaviour of polymers can be modelled mechanically with combinations of springs and dashpots, making for both elastic and viscous behaviour of viscoelastic materials such as bitumen. ===


id: dynamic-mechanical-analysis-20260505-1
file: data/en.wikipedia.org/wiki/Dynamic_mechanical_analysis-1.md
category: reference
title: Dynamic mechanical analysis
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Dynamic_mechanical_analysis
date_saved: 2026-05-05T10:04:19.735755+00:00
instance: kb-cron
parent: dynamic-mechanical-analysis-20260505-0
summary:
σ ( t ) γ 0 = [ ω ∫ o ∞ G ( s ) sin ⁡ ( ω s ) d s ] ⏟ shear storage modulus G ′ sin ⁡ ( ω t ) + [ ω ∫ o ∞ G ( s ) cos ⁡ ( ω s ) d s ] ⏟ shear loss modulus G ″ cos ⁡ ( ω t ) . {\displaystyle {\frac {\sigma (t)}{\gamma _{0}}}=\underbrace {[\omega \int _{o}^{\infty }G(s)\sin(\omega s)ds]} _{{\text{shear storage modulus }}G'}\sin(\omega t)+\underbrace {[\omega \int _{o}^{\infty }G(s)\cos(\omega s)ds]} _{{\text{shear loss modulus }}G''}\cos(\omega t).\,} with converging integrals, if G ( s ) → 0 {\displaystyle G(s)\rightarrow 0} for s → ∞ {\displaystyle s\rightarrow \infty } , which depend on frequency but not of time. Extension of σ ( t ) = σ 0 ⋅ sin ⁡ ( ω ⋅ t + Δ φ ) {\displaystyle \sigma (t)=\sigma _{0}\cdot \sin(\omega \cdot t+\Delta \varphi )} with trigonometric identity sin ⁡ ( x ± y ) = sin ⁡ ( x ) ⋅ cos ⁡ ( y ) ± cos ⁡ ( x ) ⋅ sin ⁡ ( y ) {\displaystyle \sin(x\pm y)=\sin(x)\cdot \cos(y)\pm \cos(x)\cdot \sin(y)} lead to σ ( t ) γ


id: dynamic-mechanical-analysis-20260505-2
file: data/en.wikipedia.org/wiki/Dynamic_mechanical_analysis-2.md
category: reference
title: Dynamic mechanical analysis
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Dynamic_mechanical_analysis
date_saved: 2026-05-05T10:04:19.735755+00:00
instance: kb-cron
parent: dynamic-mechanical-analysis-20260505-0
summary:
Analyzers are made for both stress (force) and strain (displacement) control. In strain control, the probe is displaced and the resulting stress of the sample is measured by implementing a force balance transducer, which utilizes different shafts. The advantages of strain control include a better short time response for materials of low viscosity and experiments of stress relaxation are done with relative ease. In stress control, a set force is applied to the sample and several other experimental conditions (temperature, frequency, or time) can be varied. Stress control is typically less expensive than strain control because only one shaft is needed, but this also makes it harder to use. Some advantages of stress control include the fact that the structure of the sample is less likely to be destroyed and longer relaxation times/ longer creep studies can be done with much more ease. Characterizing low viscous materials come at a disadvantage of short time responses that are limited by inertia. Stress and strain control analyzers give about the same results as long as characterization is within the linear region of the polymer in question. However, stress control lends a more realistic response because polymers have a tendency to resist a


id: electron-backscatter-diffraction-20260505-0
file: data/en.wikipedia.org/wiki/Electron_backscatter_diffraction-0.md
category: reference
title: Electron backscatter diffraction
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Electron_backscatter_diffraction
date_saved: 2026-05-05T10:04:21.164305+00:00
instance: kb-cron
parent: electron-backscatter-diffraction-20260505-0
summary:
Electron backscatter diffraction (EBSD) is a scanning electron microscopy (SEM) technique used to study the crystallographic structure of materials. EBSD is carried out in a scanning electron microscope equipped with an EBSD detector comprising at least a phosphorescent screen, a compact lens and a low-light camera. In the microscope an incident beam of electrons hits a tilted sample. As backscattered electrons leave the sample, they interact with the atoms and are both elastically diffracted and lose energy, leaving the sample at various scattering angles before reaching the phosphor screen forming Kikuchi patterns (EBSPs). The EBSD spatial resolution depends on many factors, including the nature of the material under study and the sample preparation. They can be indexed to provide information about the material's grain structure, grain orientation, and phase at the micro-scale. EBSD is used for impurities and defect studies, plastic deformation, and statistical analysis for average misorientation, grain size, and crystallographic texture. EBSD can also be combined with energy-dispersive X-ray spectroscopy (EDS), cathodoluminescence (CL), and wavelength-dispersive X-ray spectroscopy (WDS) for advanced phase identification and materials discovery. The change and sharpness of the electron backscatter patterns (EBSPs) provide information about lattice distortion in the diffracting volume. Pattern sharpness can be


id: electron-backscatter-diffraction-20260505-1
file: data/en.wikipedia.org/wiki/Electron_backscatter_diffraction-1.md
category: reference
title: Electron backscatter diffraction
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Electron_backscatter_diffraction
date_saved: 2026-05-05T10:04:21.164305+00:00
instance: kb-cron
parent: electron-backscatter-diffraction-20260505-0
summary:
The sample should be vacuum stable. It is typically mounted using a conductive compound (e.g. an epoxy thermoset filled with Cu), which minimises image drift and sample charging under electron beam irradiation. EBSP quality is sensitive to surface preparation. Typically the sample is ground using SiC papers from 240 down to 4000 grit, and polished using diamond paste (from 9 to 1 μm) then in 50 nm colloidal silica. Afterwards, it is cleaned in ethanol, rinsed with deionised water, and dried with a hot air blower. This may be followed by ion beam polishing, for final surface preparation. Inside the SEM, the size of the measurement area determines local resolution and measurement time. Usual settings for high-quality EBSPs are 15 nA current, 20 kV beam energy, 18 mm working distance, long exposure time, and minimal CCD pixel binning. The EBSD phosphor screen is set at an 18 mm working distance and a map's step size of less than 0.5 μm for strain and dislocations density analysis. Decomposition of gaseous hydrocarbons and also hydrocarbons on the surface of samples by the electron beam inside the microscope results in carbon deposition, which degrades the quality of EBSPs inside the probed area compared


id: electron-backscatter-diffraction-20260505-2
file: data/en.wikipedia.org/wiki/Electron_backscatter_diffraction-2.md
category: reference
title: Electron backscatter diffraction
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Electron_backscatter_diffraction
date_saved: 2026-05-05T10:04:21.164305+00:00
instance: kb-cron
parent: electron-backscatter-diffraction-20260505-0
summary:
If the setup geometry is well described, it is possible to relate the bands present in the diffraction pattern to the underlying crystal and crystallographic orientation of the material within the electron interaction volume. Each band can be indexed individually by the Miller indices of the diffracting plane which formed it. In most materials, only three bands/planes intersect and are required to describe a unique solution to the crystal orientation (based on their interplanar angles). Most commercial systems use look-up tables with international crystal databases to index. This crystal orientation relates the orientation of each sampled point to a reference crystal orientation. Indexing is often the first step in the EBSD process after pattern collection. This allows for the identification of the crystal orientation at the single volume of the sample from where the pattern was collected. With EBSD software, pattern bands are typically detected via a mathematical routine using a modified Hough transform, in which every pixel in Hough space denotes a unique line/band in the EBSP. The Hough transform enables band detection, which is difficult to locate by computer in the original EBSP. Once the band locations have been detected, it is possible to relate these locations to


id: electron-backscatter-diffraction-20260505-3
file: data/en.wikipedia.org/wiki/Electron_backscatter_diffraction-3.md
category: reference
title: Electron backscatter diffraction
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Electron_backscatter_diffraction
date_saved: 2026-05-05T10:04:21.164305+00:00
instance: kb-cron
parent: electron-backscatter-diffraction-20260505-0
summary:
The indexing results are used to generate a map of the crystallographic orientation at each point on the surface being studied. Thus, scanning the electron beam in a prescribed fashion (typically in a square or hexagonal grid, correcting for the image foreshortening due to the sample tilt) results in many rich microstructural maps. These maps can spatially describe the crystal orientation of the material being interrogated and can be used to examine microtexture and sample morphology. Some maps describe grain orientation, boundary, and diffraction pattern (image) quality. Various statistical tools can measure the average misorientation, grain size, and crystallographic texture. From this dataset, numerous maps, charts and plots can be generated. The orientation data can be visualised using a variety of techniques, including colour-coding, contour lines, and pole figures. Microscope misalignment, image shift, scan distortion that increases with decreasing magnification, roughness and contamination of the specimen surface, boundary indexing failure and detector quality can lead to uncertainties in determining the crystal orientation. The EBSD signal-to-noise ratio depends on the material and decreases at excessive acquisition speed and beam current, thereby affecting the angular resolution of the measurement. == Strain measurement == Full-field displacement, elastic strain, and the GND density provide


id: electron-backscatter-diffraction-20260505-4
file: data/en.wikipedia.org/wiki/Electron_backscatter_diffraction-4.md
category: reference
title: Electron backscatter diffraction
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Electron_backscatter_diffraction
date_saved: 2026-05-05T10:04:21.164305+00:00
instance: kb-cron
parent: electron-backscatter-diffraction-20260505-0
summary:
The shifts are measured in the phosphor (detector) plane ( β 3 r 3 = 0 {\displaystyle \beta _{3}r_{3}=0} ), and the relationship is simplified; thus, eight out of the nine displacement gradient tensor components can be calculated by measuring the shift at four distinct, widely spaced regions on the EBSP. This shift is then corrected to the sample frame (flipped around Y-axis) because EBSP is recorded on the phosphor screen and is inverted as in a mirror. They are then corrected around the X-axis by 24° (i.e., 20° sample tilt plus ≈4° camera tilt and assuming no angular effect from the beam movement). Using infinitesimal strain theory, the deformation gradient is then split into elastic strain (symmetric part, where i j = j i {\displaystyle ij=ji} ), e i j {\displaystyle e_{ij}} and lattice rotations (asymmetric part, where i i = j j = 0 {\displaystyle ii=jj=0} ), ω i j {\displaystyle \omega _{ij}} . e i j = 1 2 ( β i j + β i j r ) , ω i j = 1 2 ( β i j − β i j r ) {\displaystyle e_{ij}={1 \over {2}}(\beta _{ij}+\beta _{ij}^{r}),\qquad \omega _{ij}={1 \over {2}}(\beta _{ij}-\beta


id: electron-backscatter-diffraction-20260505-5
file: data/en.wikipedia.org/wiki/Electron_backscatter_diffraction-5.md
category: reference
title: Electron backscatter diffraction
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Electron_backscatter_diffraction
date_saved: 2026-05-05T10:04:21.164305+00:00
instance: kb-cron
parent: electron-backscatter-diffraction-20260505-0
summary:
=== The reference pattern problem === In HR-EBSD analysis, the lattice distortion field is calculated relative to a reference pattern or point (EBSP0) per grain in the map, and is dependent on the lattice distortion at the point. The lattice distortion field in each grain is measured with respect to this point; therefore, the absolute lattice distortion at the reference point (relative to the unstrained crystal) is excluded from the HR-EBSD elastic strain and rotation maps. This 'reference pattern problem' is similar to the 'd0 problem' in X-ray diffraction, and affects the nominal magnitude of HR-EBSD stress fields. However, selecting the reference pattern (EBSP0) plays a key role, as severely deformed EBSP0 adds phantom lattice distortions to the map values, thus, decreasing the measurement precision. The local lattice distortion at the EBSP0 influences the resultant HR-EBSD map, e.g., a reference pattern deformed in tension will directly reduce the HR-EBSD map tensile strain magnitude while indirectly influencing the other component magnitude and the strain's spatial distribution. Furthermore, the choice of EBSP0 slightly affects the GND density distribution and magnitude, and choosing a reference pattern with a higher GND density reduces the cross-correlation quality, changes the spatial distribution and induces more errors


id: electron-backscatter-diffraction-20260505-6
file: data/en.wikipedia.org/wiki/Electron_backscatter_diffraction-6.md
category: reference
title: Electron backscatter diffraction
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Electron_backscatter_diffraction
date_saved: 2026-05-05T10:04:21.164305+00:00
instance: kb-cron
parent: electron-backscatter-diffraction-20260505-0
summary:
=== Integrated EBSD/EDS mapping === When simultaneous EDS/EBSD collection can be achieved, the capabilities of both techniques can be enhanced. There are applications where sample chemistry or phase cannot be differentiated via EDS alone because of similar composition, and structure cannot be solved with EBSD alone because of ambiguous structure solutions. To accomplish integrated mapping, the analysis area is scanned, and at each point, Hough peaks and EDS region-of-interest counts are stored. Positions of phases are determined in X-ray maps, and each element's measured EDS intensities are given in charts. The chemical intensity ranges are set for each phase to select the grains. All patterns are then re-indexed off-line. The recorded chemistry determines which phase/crystal-structure file is used to index each point. Each pattern is indexed by only one phase, and maps displaying distinguished phases are generated. The interaction volumes for EDS and EBSD are significantly different (on the order of micrometres compared to tens of nanometres), and the shape of these volumes using a highly tilted sample may have implications on algorithms for phase discrimination. EBSD, when used together with other in-SEM techniques such as cathodoluminescence (CL), wavelength dispersive X-ray spectroscopy (WDS) and/or EDS can provide a deeper insight


id: electron-beam-induced-current-20260505-0
file: data/en.wikipedia.org/wiki/Electron_beam-induced_current-0.md
category: reference
title: Electron beam-induced current
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Electron_beam-induced_current
date_saved: 2026-05-05T10:04:22.337193+00:00
instance: kb-cron
parent: electron-beam-induced-current-20260505-0
summary:
Electron-beam-induced current (EBIC) is a semiconductor analysis technique performed in a scanning electron microscope (SEM) or scanning transmission electron microscope (STEM). It is most commonly used to identify buried junctions or defects in semiconductors, or to examine minority carrier properties. EBIC is similar to cathodoluminescence in that it depends on the creation of electron–hole pairs in the semiconductor sample by the microscope's electron beam. This technique is used in semiconductor failure analysis and solid-state physics. == Physics of the technique == If the semiconductor sample contains an internal electric field, as will be present in the depletion region at a p-n junction or Schottky junction, the electron–hole pairs will be separated by drift due to the electric field. If the p- and n-sides (or semiconductor and Schottky contact, in the case of a Schottky device) are connected through a picoammeter, a current will flow. EBIC is best understood by analogy: in a solar cell, photons of light fall on the entire cell, thus delivering energy and creating electron hole pairs, and cause a current to flow. In EBIC, energetic electrons take the role of the photons, causing the EBIC current to flow. However, because the electron beam of an SEM


id: electron-channelling-contrast-imaging-20260505-0
file: data/en.wikipedia.org/wiki/Electron_channelling_contrast_imaging-0.md
category: reference
title: Electron channelling contrast imaging
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Electron_channelling_contrast_imaging
date_saved: 2026-05-05T10:04:23.537836+00:00
instance: kb-cron
parent: electron-channelling-contrast-imaging-20260505-0
summary:
Electron channelling contrast imaging (ECCI) is a scanning electron microscope (SEM) diffraction technique used in the study of defects in materials. These can be dislocations or stacking faults that are close to the surface of the sample, low angle grain boundaries or atomic steps. Unlike the use of transmission electron microscopy (TEM) for the investigation of dislocations, the ECCI approach has been called a rapid and non-destructive characterisation technique == Mechanism == The word channelling in ECCI, and, similarly, in electron channelling patterns refers to diffraction of the electron beam on its way in the sample. With enough spatial resolution, very small crystal imperfections would change the phase of the incident electron wave-function, and this, in turn, would be reflected in the backscattering probability, showing up as contrast (sharp change in backscattered intensity) close to a dislocation == Background == While we now talk about ECCI being a SEM technique, there was a significant gap of about thirty years between the prediction that defects ought to show up as contrast in the backscattered electron micrographs of the SEM and the development of ECCI as an accessible technique for the user of a standard SEM. In the meanwhile the field emission


id: electron-energy-loss-spectroscopy-20260505-0
file: data/en.wikipedia.org/wiki/Electron_energy_loss_spectroscopy-0.md
category: reference
title: Electron energy loss spectroscopy
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Electron_energy_loss_spectroscopy
date_saved: 2026-05-05T10:04:24.739987+00:00
instance: kb-cron
parent: electron-energy-loss-spectroscopy-20260505-0
summary:
Electron energy loss spectroscopy (EELS) is a form of electron microscopy in which a material is exposed to a beam of electrons with a known, narrow range of kinetic energies. Some of the electrons will undergo inelastic scattering, which means that they lose energy and have their paths slightly and randomly deflected. The amount of energy loss can be measured via an electron spectrometer and interpreted in terms of what caused the energy loss. Inelastic interactions include phonon excitations, inter- and intra-band transitions, plasmon excitations, inner shell ionizations, and Cherenkov radiation. The inner-shell ionizations are particularly useful for detecting the elemental components of a material. For example, one might find that a larger-than-expected number of electrons comes through the material with 285 eV less energy than they had when they entered the material. This is approximately the amount of energy needed to remove an inner-shell electron from a carbon atom, which can be taken as evidence that there is a significant amount of carbon present in the sample. With some care, and looking at a wide range of energy losses, one can determine the types of atoms, and the numbers of atoms of each type, being struck by the beam.


id: electron-energy-loss-spectroscopy-20260505-1
file: data/en.wikipedia.org/wiki/Electron_energy_loss_spectroscopy-1.md
category: reference
title: Electron energy loss spectroscopy
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Electron_energy_loss_spectroscopy
date_saved: 2026-05-05T10:04:24.739987+00:00
instance: kb-cron
parent: electron-energy-loss-spectroscopy-20260505-0
summary:
There are several basic flavors of EELS, primarily classified by the geometry and by the kinetic energy of the incident electrons (typically measured in kiloelectron-volts, or keV). Probably the most common today is transmission EELS, in which the kinetic energies are typically 100 to 300 keV and the incident electrons pass entirely through the material sample. Usually this occurs in a transmission electron microscope (TEM), although some dedicated systems exist which enable extreme resolution in terms of energy and momentum transfer at the expense of spatial resolution. This approach is especially promising in the regime of low-energy reflection and scanning electron microscope (SEM)-based EELS, in which the lower incident beam energy means that energy filtering of both the source and scattered electrons can be done in smaller form-factors. Other flavors include reflection EELS (including reflection high-energy electron energy-loss spectroscopy (RHEELS)), typically at 10 to 1 keV, and aloof EELS (sometimes called near-field EELS), in which the electron beam does not in fact strike the sample but instead interacts with it via the long-ranged Coulomb interaction. Aloof EELS is particularly sensitive to surface properties but is limited to very small energy losses such as those associated with surface plasmons or direct


id: electron-energy-loss-spectroscopy-20260505-2
file: data/en.wikipedia.org/wiki/Electron_energy_loss_spectroscopy-2.md
category: reference
title: Electron energy loss spectroscopy
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Electron_energy_loss_spectroscopy
date_saved: 2026-05-05T10:04:24.739987+00:00
instance: kb-cron
parent: electron-energy-loss-spectroscopy-20260505-0
summary:
== Thickness measurements == EELS allows quick and reliable measurement of local thickness in transmission electron microscopy. The most efficient procedure is the following: Measure the energy loss spectrum in the energy range about −5..200 eV (wider better). Such measurement is quick (milliseconds) and thus can be applied to materials normally unstable under electron beams. Analyse the spectrum: (i) extract zero-loss peak (ZLP) using standard routines; (ii) calculate integrals under the ZLP (I0) and under the whole spectrum (I). The thickness t is calculated as mfp*ln(I/I0). Here mfp is the mean free path of electron inelastic scattering, which has been tabulated for most elemental solids and oxides. The spatial resolution of this procedure is limited by the plasmon localization and is about 1 nm, meaning that spatial thickness maps can be measured in scanning transmission electron microscopy with ~1 nm resolution. == Pressure measurements == The intensity and position of low-energy EELS peaks are affected by pressure. This fact allows mapping local pressure with ~1 nm spatial resolution. Peak shift method is reliable and straightforward. The peak position is calibrated by independent (usually optical) measurement using a diamond anvil cell. However, the spectral resolution of most EEL spectrometers (0.3-2 eV,


id: electron-ionization-20260505-0
file: data/en.wikipedia.org/wiki/Electron_ionization-0.md
category: reference
title: Electron ionization
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Electron_ionization
date_saved: 2026-05-05T10:04:25.973339+00:00
instance: kb-cron
parent: electron-ionization-20260505-0
summary:
Electron ionization (EI, formerly known as electron impact ionization and electron bombardment ionization) is an ionization method in which energetic electrons interact with solid or gas phase atoms or molecules to produce ions. EI was one of the first ionization techniques developed for mass spectrometry. However, this method is still a popular ionization technique. This technique is considered a hard (high fragmentation) ionization method, since it uses highly energetic electrons to produce ions. This leads to extensive fragmentation, which can be helpful for structure determination of unknown compounds. EI is the most useful for organic compounds which have a molecular weight below 600 amu. Also, several other thermally stable and volatile compounds in solid, liquid and gas states can be detected with the use of this technique when coupled with various separation methods. == History == Electron ionization was first described in 1918 by Canadian-American Physicist Arthur J. Dempster in the article of "A new method of positive ray analysis." It was the first modern mass spectrometer and used positive rays to determine the ratio of the mass to charge of various constituents. In this method, the ion source used an electron beam directed at a solid surface. The anode


id: electron-ionization-20260505-1
file: data/en.wikipedia.org/wiki/Electron_ionization-1.md
category: reference
title: Electron ionization
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Electron_ionization
date_saved: 2026-05-05T10:04:25.973339+00:00
instance: kb-cron
parent: electron-ionization-20260505-0
summary:
A schematic diagram of instrumentation which can be used for electron ionization is shown to the right. The ion source block is made out of metal. As the electron source, the cathode, which can be a thin filament of tungsten or rhenium wire, is inserted through a slit to the source block. Then it is heated up to an incandescent temperature to emit electrons. A potential of 70 V is applied between the cathode and source block to accelerate them to 70 eV kinetic energy to produce positive ions. The potential of the anode (electron trap) is slightly positive and it is placed on the outside of the ionization chamber, directly opposite to the cathode. The unused electrons are collected by this electron trap. The sample is introduced through the sample hole. To increase the ionization process, a weak magnetic field is applied parallel to the direction of the electrons' travel. Because of this, electrons travel in a narrow helical path, which increases their path length. The positive ions that are generated are accelerated by the repeller electrode into the accelerating region through the slit in the source block. By applying a potential to the ion source and maintaining the


id: electron-ionization-20260505-2
file: data/en.wikipedia.org/wiki/Electron_ionization-2.md
category: reference
title: Electron ionization
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Electron_ionization
date_saved: 2026-05-05T10:04:25.973339+00:00
instance: kb-cron
parent: electron-ionization-20260505-0
summary:
==== Analysis of biological fluids ==== The GC-EI-MS can be incorporated for the analysis of biological fluids for several applications. One example is the determination of thirteen synthetic pyrethroid insecticide molecules and their stereoisomers in whole blood. This investigation used a new rapid and sensitive electron ionization-gas chromatography–mass spectrometry method in selective ion monitoring mode (SIM) with a single injection of the sample. All the pyrethroid residues were separated by using a GC-MS operated in electron ionization mode and quantified in selective ion monitoring mode. The detection of specific residues in blood is a difficult task due to their very low concentration since as soon as they enter the body most of the chemicals may get excreted. However, this method detected the residues of different pyrethroids down to the level 0.05–2 ng/ml. The detection of this insecticide in blood is very important since an ultra-small quantity in the body is enough to be harmful to human health, especially in children. This method is a very simple, rapid technique and therefore can be adopted without any matrix interferences. The selective ion monitoring mode provides detection sensitivity up to 0.05 ng/ml. Another application is in protein turnover studies using GC-EI-MS. This measures


id: electron-ionization-20260505-3
file: data/en.wikipedia.org/wiki/Electron_ionization-3.md
category: reference
title: Electron ionization
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Electron_ionization
date_saved: 2026-05-05T10:04:25.973339+00:00
instance: kb-cron
parent: electron-ionization-20260505-0
summary:
=== Fourier transform ion cyclotron resonance mass spectrometry === FT- ICR EI - MS can be used for analysis of three vacuum gas oil (VGO) distillation fractions in 295-319 °C, 319-456 °C and 456-543 °C. In this method, EI at 10 eV allows soft ionization of aromatic compounds in the vacuum gas oil range. The compositional variations at the molecular level were determined from the elemental composition assignment. Ultra-high resolving power, small sample size, high reproducibility and mass accuracy (<0.4ppm) are the special features in this method. The major product was aromatic hydrocarbons in all three samples. In addition, many sulfur-, nitrogen-, and oxygen-containing compounds were directly observed when the concentration of this heteroatomic species increased with the boiling point. Using data analysis it gave the information about compound types (rings plus double bonds), their carbon number distributions for hydrocarbon and heteroatomic compounds in the distillation fractions, increasing average molecular weight (or carbon number distribution) and aromaticity with increasing boiling temperature of the petroleum fractions. === Ion trap mass spectrometry === Ion trap EI MS can be incorporated for the identification and quantitation of nonylphenol polyethoxylate (NPEO) residues and their degradation products such as nonylphenol polyethoxy carboxylates and carboxyalkylphenol ethoxy


id: electron-paramagnetic-resonance-20260505-0
file: data/en.wikipedia.org/wiki/Electron_paramagnetic_resonance-0.md
category: reference
title: Electron paramagnetic resonance
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Electron_paramagnetic_resonance
date_saved: 2026-05-05T10:04:27.171248+00:00
instance: kb-cron
parent: electron-paramagnetic-resonance-20260505-0
summary:
Electron paramagnetic resonance (EPR) or electron spin resonance (ESR) spectroscopy is a method for studying materials that have unpaired electrons. The basic concepts of EPR are analogous to those of nuclear magnetic resonance (NMR), but the spins excited are those of the electrons instead of the atomic nuclei. EPR spectroscopy is useful for analyzing metal ions and organic radicals (compounds with unpaired electrons). The technique reveals some structural information but often simply provides a characteristic "finger print". The measurement requires a large magnet into which the sample is placed. Signals are detected using microwaves. In contrast to NMR and infrared (IR) spectroscopy, EPR spectroscopy is less common. For a given sample, some of the parameters of interest are g-values (analogous to chemical shift), anisotropy (asymmetry), hyperfine coupling constants (analogous to coupling constant J), and relaxation times. == History == EPR was first observed in Kazan State University by Soviet physicist Yevgeny Zavoisky in 1944, and was developed independently at the same time by Brebis Bleaney at the University of Oxford. == Theory == Every electron has a magnetic moment and spin quantum number s = 1 2 {\displaystyle s={\tfrac {1}{2}}} , with magnetic components m s = + 1 2


id: electron-paramagnetic-resonance-20260505-1
file: data/en.wikipedia.org/wiki/Electron_paramagnetic_resonance-1.md
category: reference
title: Electron paramagnetic resonance
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Electron_paramagnetic_resonance
date_saved: 2026-05-05T10:04:27.171248+00:00
instance: kb-cron
parent: electron-paramagnetic-resonance-20260505-0
summary:
=== Maxwell–Boltzmann distribution === In practice, EPR samples consist of collections of many paramagnetic species, and not single isolated paramagnetic centers. If the population of radicals is in thermodynamic equilibrium, its statistical distribution is described by the Boltzmann distribution: n upper n lower = exp ⁡ ( − E upper − E lower k T ) = exp ⁡ ( − Δ E k T ) = exp ⁡ ( − ϵ k T ) = exp ⁡ ( − h ν k T ) {\displaystyle {\frac {n_{\text{upper}}}{n_{\text{lower}}}}=\exp {\left(-{\frac {E_{\text{upper}}-E_{\text{lower}}}{kT}}\right)}=\exp {\left(-{\frac {\Delta E}{kT}}\right)}=\exp {\left(-{\frac {\epsilon }{kT}}\right)}=\exp {\left(-{\frac {h\nu }{kT}}\right)}} where n upper {\displaystyle n_{\text{upper}}} is the number of paramagnetic centers occupying the upper energy state, k {\displaystyle k} is the Boltzmann constant, and T {\displaystyle T} is the thermodynamic temperature. At 298 K, X-band microwave frequencies ( ν {\displaystyle \nu } ≈ 9.75 GHz) give n upper / n lower {\displaystyle n_{\text{upper}}/n_{\text{lower}}} ≈ 0.998, meaning that the upper energy level has a slightly smaller population than the lower one. Therefore, transitions from the lower to the higher level are more probable than the reverse, which is why there is a net absorption of energy. The sensitivity of the EPR method


id: electron-paramagnetic-resonance-20260505-2
file: data/en.wikipedia.org/wiki/Electron_paramagnetic_resonance-2.md
category: reference
title: Electron paramagnetic resonance
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Electron_paramagnetic_resonance
date_saved: 2026-05-05T10:04:27.171248+00:00
instance: kb-cron
parent: electron-paramagnetic-resonance-20260505-0
summary:
In general, the g factor is not a number but a 3×3 matrix. The principal axes of this tensor are determined by the local fields, for example, by the local atomic arrangement around the unpaired spin in a solid or in a molecule. Choosing an appropriate coordinate system (say, x,y,z) allows one to "diagonalize" this tensor, thereby reducing the maximal number of its components from 9 to 3: gxx, gyy and gzz. For a single spin experiencing only Zeeman interaction with an external magnetic field, the position of the EPR resonance is given by the expression gxxBx + gyyBy + gzzBz. Here Bx, By and Bz are the components of the magnetic field vector in the coordinate system (x,y,z); their magnitudes change as the field is rotated, so does the frequency of the resonance. For a large ensemble of randomly oriented spins (as in a fluid solution), the EPR spectrum consists of three peaks of characteristic shape at frequencies gxxB0, gyyB0 and gzzB0. In first-derivative spectrum, the low-frequency peak is positive, the high-frequency peak is negative, and the central peak is bipolar. Such situations are commonly observed in powders, and the spectra are therefore called "powder-pattern spectra". In crystals, the


id: electron-paramagnetic-resonance-20260505-3
file: data/en.wikipedia.org/wiki/Electron_paramagnetic_resonance-3.md
category: reference
title: Electron paramagnetic resonance
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Electron_paramagnetic_resonance
date_saved: 2026-05-05T10:04:27.171248+00:00
instance: kb-cron
parent: electron-paramagnetic-resonance-20260505-0
summary:
For a radical having M equivalent nuclei, each with a spin of I, the number of EPR lines expected is 2MI + 1. As an example, the methyl radical, CH3, has three 1H nuclei, each with I = 1/2, and so the number of lines expected is 2MI + 1 = 2(3)(1/2) + 1 = 4, which is as observed. For a radical having M1 equivalent nuclei, each with a spin of I1, and a group of M2 equivalent nuclei, each with a spin of I2, the number of lines expected is (2M1I1 + 1) (2M2I2 + 1). As an example, the methoxymethyl radical, H2C(OCH3) has two equivalent 1H nuclei, each with I = 1/2 and three equivalent 1H nuclei each with I = 1/2, and so the number of lines expected is (2M1I1 + 1) (2M2I2 + 1) = [2(2)(1/2) + 1] [2(3)(1/2) + 1] = 3×4 = 12, again as observed. The above can be extended to predict the number of lines for any number of nuclei. While it is easy to predict the number of lines, the reverse problem, unraveling a complex multi-line EPR spectrum and assigning the various spacings to specific nuclei, is more difficult. In


id: electron-paramagnetic-resonance-20260505-4
file: data/en.wikipedia.org/wiki/Electron_paramagnetic_resonance-4.md
category: reference
title: Electron paramagnetic resonance
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Electron_paramagnetic_resonance
date_saved: 2026-05-05T10:04:27.171248+00:00
instance: kb-cron
parent: electron-paramagnetic-resonance-20260505-0
summary:
=== Medical and biological === Medical and biological applications of EPR also exist. Although radicals are very reactive, so they do not normally occur in high concentrations in biology, special reagents have been developed to attach "spin labels", also called "spin probes", to molecules of interest. Specially-designed nonreactive radical molecules can attach to specific sites in a biological cell, and EPR spectra then give information on the environment of the spin labels. Spin-labeled fatty acids have been extensively used to study dynamic organisation of lipids in biological membranes, lipid-protein interactions and temperature of transition of gel to liquid crystalline phases. Injection of spin-labeled molecules allows for electron resonance imaging of living organisms. A type of dosimetry system has been designed for reference standards and routine use in medicine, based on EPR signals of radicals from irradiated polycrystalline α-alanine (the alanine deamination radical, the hydrogen abstraction radical, and the (CO−(OH))=C(CH3)NH+2 radical). This method is suitable for measuring gamma and X-rays, electrons, protons, and high-linear energy transfer (LET) radiation of doses in the 1 Gy to 100 kGy range. EPR can be used to measure microviscosity and micropolarity within drug delivery systems as well as the characterization of colloidal drug carriers. The


id: electron-paramagnetic-resonance-20260505-5
file: data/en.wikipedia.org/wiki/Electron_paramagnetic_resonance-5.md
category: reference
title: Electron paramagnetic resonance
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Electron_paramagnetic_resonance
date_saved: 2026-05-05T10:04:27.171248+00:00
instance: kb-cron
parent: electron-paramagnetic-resonance-20260505-0
summary:
=== Electrochemistry applications === EPR is a very important technique in the electrochemical field because it operates to detect paramagnetic species and unpaired electrons. The technique has a long history of being coupled to the field, starting with a report in 1958 using EPR to detect free radicals generated via electrochemistry. In an experiment performed by Austen, Given, Ingram, and Peover, solutions of aromatics were electrolyzed and placed into an EPR instrument, resulting in a broad signal response. While this result could not be used for any specific identification, the presence of an EPR signal validated the theory that free radical species were involved in electron transfer reactions as an intermediate state. Soon after, other groups discovered the possibility of coupling in situ electrolysis with EPR, producing the first resolved spectra of the nitrobenzene anion radical from a mercury electrode sealed within the instrument cavity. Since then, the impact of EPR on the field of electrochemistry has only expanded, serving as a way to monitor free radicals produced by other electrolysis reactions. In more recent years, EPR has also been used within the context of electrochemistry to study redox-flow reactions and batteries. Because of the in situ possibilities, it is


id: electron-paramagnetic-resonance-20260505-6
file: data/en.wikipedia.org/wiki/Electron_paramagnetic_resonance-6.md
category: reference
title: Electron paramagnetic resonance
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Electron_paramagnetic_resonance
date_saved: 2026-05-05T10:04:27.171248+00:00
instance: kb-cron
parent: electron-paramagnetic-resonance-20260505-0
summary:
=== Microwave bridge === The microwave bridge contains both the microwave source and the detector. Older spectrometers used a vacuum tube called a klystron to generate microwaves, but modern spectrometers use a Gunn diode. Immediately after the microwave source there is an isolator which serves to attenuate any reflections back to the source which would result in fluctuations in the microwave frequency. The microwave power from the source is then passed through a directional coupler which splits the microwave power into two paths, one directed towards the cavity and the other the reference arm. Along both paths there is a variable attenuator that facilitates the precise control of the flow of microwave power. This in turn allows for accurate control over the intensity of the microwaves subjected to the sample. On the reference arm, after the variable attenuator there is a phase shifter that sets a defined phase relationship between the reference and reflected signal which permits phase sensitive detection. Most EPR spectrometers are reflection spectrometers, meaning that the detector should only be exposed to microwave radiation coming back from the cavity. This is achieved by the use of a device known as the circulator which directs the microwave radiation


id: electron-probe-microanalysis-20260505-0
file: data/en.wikipedia.org/wiki/Electron_probe_microanalysis-0.md
category: reference
title: Electron probe microanalysis
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Electron_probe_microanalysis
date_saved: 2026-05-05T10:04:28.363360+00:00
instance: kb-cron
parent: electron-probe-microanalysis-20260505-0
summary:
Electron probe microanalysis (EPMA), also known as electron probe X-ray microanalysis, electron microprobe analysis (EMPA) or electron probe analysis (EPA) is a microanalytical and imaging technique used to non-destructively determine the chemical element composition of small volumes of solid materials. The device used for this technique is known as an electron probe microanalyzer (also abbreviated EPMA), often shortened to electron microprobe (EMP) or electron probe (EP). In EPMA, the instrument bombards the sample with a high-intensity electron beam, which then emits X-rays. The X-ray wavelengths emitted are characteristic of particular chemical elements and are analyzed using X-ray spectroscopy. The same principle is also employed in wavelength- or energy-dispersive X-ray spectroscopy (WDX, EDX) commonly used in scanning electron microscopes (SEM), but EPMA is characterized by a fixed electron beam rather than a scanning one and primarily used for elemental analysis rather than imaging. == Principles == An electron gun produces an electron beam focused on the sample through a series of magnetic lenses, much like a SEM. However, a key difference from a SEM is that the electron beam is fixed rather than raster scanning, which makes it incapable of producing scanning electron micrograph images. The electron beam has a significantly


id: electron-probe-microanalysis-20260505-1
file: data/en.wikipedia.org/wiki/Electron_probe_microanalysis-1.md
category: reference
title: Electron probe microanalysis
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Electron_probe_microanalysis
date_saved: 2026-05-05T10:04:28.363360+00:00
instance: kb-cron
parent: electron-probe-microanalysis-20260505-0
summary:
== History == The electron microprobe (electron probe microanalyzer) developed from two technologies: electron microscopy, which uses a focused high energy electron beam to impact a target material, and X-ray spectroscopy, which identifies the photons scattered from the electron beam impact, with the energy/wavelength of the photons characteristic of the atoms excited by the incident electrons. Ernst Ruska and Max Knoll are associated with the prototype electron microscope in 1931. Henry Moseley was involved in the discovery of the direct relationship between the wavelength of X-rays and the identity of the atom from which it originated. Several historical threads combined in the early development of electron beam microanalysis. One was the work of James Hillier and Richard Baker at RCA. In the early 1940s, they built an electron microprobe, combining an electron microscope and an energy loss spectrometer. A patent application was filed in 1944. Electron energy loss spectroscopy is very good for light element analysis and they obtained spectra of C-Kα, N-Kα and O-Kα radiation. In 1947, Hiller patented the concept of using an electron beam to produce analytical X-rays, but never constructed a working model. His design proposed using Bragg diffraction from a flat crystal to select specific


id: electron-probe-microanalysis-20260505-2
file: data/en.wikipedia.org/wiki/Electron_probe_microanalysis-2.md
category: reference
title: Electron probe microanalysis
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Electron_probe_microanalysis
date_saved: 2026-05-05T10:04:28.363360+00:00
instance: kb-cron
parent: electron-probe-microanalysis-20260505-0
summary:
=== Application in metallurgy === At the end of the 1950's, Castaing's innovative work was complemented by an instrument that scanned the electron beam and thus enabled the distribution of trace and alloying elements in a sample of metal to be imaged. From a metallurgist's point of view this constituted the biggest advance in metallography since Henry Clifton Sorby had invented the reflected light microscope a hundred years earlier. For while it is helpful to be able to detect the presence of an element on the micron scale, it is even more valuable to be able to image its distribution. This ability to detect for the first time the presence of alloying or trace elements dissolved in a host metal, and image their distribution advanced the science of metallurgy itself. It enabled the identification of non-metallic inclusions, revealed segregation during solidification, and allowed identification of the sources of grain boundary weakness as well as many other problems. The instrument that first did this, the scanning electron probe microanalyzer, emerged from research at Cambridge University, and development work at the nearby laboratories of British engineering firm Tube Investments (TI). It is one of the early examples of a breakthrough borne of


id: electron-probe-microanalysis-20260505-3
file: data/en.wikipedia.org/wiki/Electron_probe_microanalysis-3.md
category: reference
title: Electron probe microanalysis
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Electron_probe_microanalysis
date_saved: 2026-05-05T10:04:28.363360+00:00
instance: kb-cron
parent: electron-probe-microanalysis-20260505-0
summary:
=== Detailed description === Low-energy electrons are produced from a tungsten filament, a lanthanum hexaboride crystal cathode or a field emission electron source and accelerated by a positively biased anode plate to 3 to 30 thousand electron volts (keV). The anode plate has central aperture and electrons that pass through it are collimated and focused by a series of magnetic lenses and apertures. The resulting electron beam (approximately 5 nm to 10 μm diameter) may be rastered across the sample or used in spot mode to produce excitation of various effects in the sample. Among these effects are: phonon excitation (heat), cathodoluminescence (visible light fluorescence), continuum X-ray radiation (bremsstrahlung), characteristic X-ray radiation, secondary electrons (plasmon production), backscattered electron production, and Auger electron production. When the beam electrons (and scattered electrons from the sample) interact with bound electrons in the innermost electron shells of the atoms of the various elements in the sample, they can scatter the bound electrons from the electron shell producing a vacancy in that shell (ionization of the atom). This vacancy is unstable and must be filled by an electron from either a higher energy bound shell in the atom (producing another vacancy which is in turn


id: electrophoretic-light-scattering-20260505-0
file: data/en.wikipedia.org/wiki/Electrophoretic_light_scattering-0.md
category: reference
title: Electrophoretic light scattering
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Electrophoretic_light_scattering
date_saved: 2026-05-05T10:04:29.562309+00:00
instance: kb-cron
parent: electrophoretic-light-scattering-20260505-0
summary:
Electrophoretic light scattering (also known as laser Doppler electrophoresis and phase analysis light scattering ) is based on dynamic light scattering. The frequency shift or phase shift of an incident laser beam depends on the dispersed particles mobility. With dynamic light scattering, Brownian motion causes particle motion. With electrophoretic light scattering, oscillating electric field performs this function. The method is used for measuring electrophoretic mobility, from which zeta potential can then be calculated. Instruments for applying the method are commercially available from several manufacturers. The last set of calculations requires information on viscosity and dielectric permittivity of the dispersion medium; appropriate electrophoresis theory is also required. Sample dilution is often necessary to eliminate multiple scattering of the incident laser beam and/or particle interactions. == Instrumentation == A laser beam passes through the electrophoresis cell, irradiates the particles dispersed in it, and is scattered by the particles. The scattered light is detected by a photo-multiplier after passing through two pinholes. There are two types of optical systems: heterodyne and fringe. Ware and Flygare developed a heterodyne-type ELS instrument, that was the first instrument of this type. In a fringe optics ELS instrument, a laser beam is divided into two beams. Those


id: electrophoretic-light-scattering-20260505-1
file: data/en.wikipedia.org/wiki/Electrophoretic_light_scattering-1.md
category: reference
title: Electrophoretic light scattering
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Electrophoretic_light_scattering
date_saved: 2026-05-05T10:04:29.562309+00:00
instance: kb-cron
parent: electrophoretic-light-scattering-20260505-0
summary:
| q | = 4 π n λ 0 sin ⁡ ( θ 2 ) ( 5 ) {\displaystyle \ |q|={\frac {4\pi n}{\lambda _{0}}}\sin \left({\frac {\theta }{2}}\right)\qquad (5)} Since velocity V {\displaystyle \ V\,} is proportional to the applied electric field, E {\displaystyle \ E\,} , the apparent electrophoretic mobility μ o b s {\displaystyle \ \mu _{obs}\,} is define by the equation V → = μ o b s E → ( 6 ) {\displaystyle \ {\vec {V}}=\mu _{obs}{\vec {E}}\qquad (6)} Finally, the relation between the Doppler shift frequency and mobility is given for the case of the optical configuration of Fig. 3 by the equation υ D = μ o b s n E λ 0 sin ⁡ θ ( 7 ) {\displaystyle \upsilon _{D}=\mu _{obs}{\frac {nE}{\lambda _{0}}}\sin \theta \qquad (7)} where E {\displaystyle \ E\,} is the strength of the electric field, n {\displaystyle \ n\,} the refractive index of the medium, λ 0 {\displaystyle \ \lambda _{0}\,} , the wavelength of the incident light in vacuum, and θ {\displaystyle \ \theta \,} the scattering angle. The sign of v D {\displaystyle \ v_{D}\,} is a result of vector calculation and depends on the geometry of the


id: electrophoretic-light-scattering-20260505-2
file: data/en.wikipedia.org/wiki/Electrophoretic_light_scattering-2.md
category: reference
title: Electrophoretic light scattering
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Electrophoretic_light_scattering
date_saved: 2026-05-05T10:04:29.562309+00:00
instance: kb-cron
parent: electrophoretic-light-scattering-20260505-0
summary:
=== Biophysics === ELS is useful for characterizing information about the surface of proteins. Ware and Flygare (1971) demonstrated that electrophoretic techniques can be combined with laser beat spectroscopy in order to simultaneously determine the electrophoretic mobility and diffusion coefficient of bovine serum albumin. The width of a Doppler shifted spectrum of light that is scattered from a solution of macromolecules is proportional to the diffusion coefficient. The Doppler shift is proportional to the electrophoretic mobility of a macromolecule. From studies that have applied this method to poly (L-lysine), ELS is believed to monitor fluctuation mobilities in the presence of solvents with varying salt concentrations. It has also been shown that electrophoretic mobility data can be converted to zeta potential values, which enables the determination of the isoelectric point of proteins and the number of electrokinetic charges on the surface. Other biological macromolecules that can be analyzed with ELS include polysaccharides. pKa values of chitosans can be calculated from the dependency of electrophoretic mobility values on pH and charge density. Like proteins, the size and zeta potential of chitosans can be determined through ELS. ELS has also been applied to nucleic acids and viruses. The technique can be extended to


id: energy-dispersive-x-ray-spectroscopy-20260505-0
file: data/en.wikipedia.org/wiki/Energy-dispersive_X-ray_spectroscopy-0.md
category: reference
title: Energy-dispersive X-ray spectroscopy
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Energy-dispersive_X-ray_spectroscopy
date_saved: 2026-05-05T10:04:30.711902+00:00
instance: kb-cron
parent: energy-dispersive-x-ray-spectroscopy-20260505-0
summary:
Energy-dispersive X-ray spectroscopy (EDS, EDX, EDXS or XEDS), sometimes called energy dispersive X-ray analysis (EDXA or EDAX) or energy dispersive X-ray microanalysis (EDXMA), is an analytical technique used for the elemental analysis or chemical characterization of a sample. It relies on an interaction of some source of X-ray excitation and a sample. Its characterization capabilities are due in large part to the fundamental principle that each element has a unique atomic structure allowing a unique set of peaks on its electromagnetic emission spectrum (which is the main principle of spectroscopy). The peak positions are predicted by the Moseley's law with accuracy much better than experimental resolution of a typical EDX instrument. To stimulate the emission of characteristic X-rays from a specimen a beam of electrons or X-ray is focused into the sample being studied. At rest, an atom within the sample contains ground state (or unexcited) electrons in discrete energy levels or electron shells bound to the nucleus. The incident beam may excite an electron in an inner shell, ejecting it from the shell while creating an electron hole where the electron was. An electron from an outer, higher-energy shell then fills the hole, and the difference in energy between


id: energy-dispersive-x-ray-spectroscopy-20260505-1
file: data/en.wikipedia.org/wiki/Energy-dispersive_X-ray_spectroscopy-1.md
category: reference
title: Energy-dispersive X-ray spectroscopy
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Energy-dispersive_X-ray_spectroscopy
date_saved: 2026-05-05T10:04:30.711902+00:00
instance: kb-cron
parent: energy-dispersive-x-ray-spectroscopy-20260505-0
summary:
Minimizing SEM beam current allowing for optimization of imaging under analytical conditions, Reduced sample damage and Smaller beam interaction and improved spatial resolution for high speed maps. Where the X-ray energies of interest are in excess of ~ 30 keV, traditional silicon-based technologies suffer from poor quantum efficiency due to a reduction in the detector stopping power. Detectors produced from high density semiconductors such as cadmium telluride (CdTe) and cadmium zinc telluride (CdZnTe) have improved efficiency at higher X-ray energies and are capable of room temperature operation. Single element systems, and more recently pixelated imaging detectors such as the high energy X-ray imaging technology (HEXITEC) system, are capable of achieving energy resolutions of the order of 1% at 100 keV. In recent years, a different type of EDS detector, based upon a superconducting microcalorimeter, has also become commercially available. This new technology combines the simultaneous detection capabilities of EDS with the high spectral resolution of WDS. The EDS microcalorimeter consists of two components: an absorber, and a superconducting transition-edge sensor (TES) thermometer. The former absorbs X-rays emitted from the sample and converts this energy into heat; the latter measures the subsequent change in temperature due to the influx of heat.


id: environmental-scanning-electron-microscope-20260505-0
file: data/en.wikipedia.org/wiki/Environmental_scanning_electron_microscope-0.md
category: reference
title: Environmental scanning electron microscope
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Environmental_scanning_electron_microscope
date_saved: 2026-05-05T10:04:32.049506+00:00
instance: kb-cron
parent: environmental-scanning-electron-microscope-20260505-0
summary:
The environmental scanning electron microscope (ESEM) is a scanning electron microscope (SEM) that allows for the option of collecting electron micrographs of specimens that are wet, uncoated, or both by allowing for a gaseous environment in the specimen chamber. Although there were earlier successes at viewing wet specimens in internal chambers in modified SEMs, the ESEM with its specialized electron detectors (rather than the standard Everhart–Thornley detector) and its differential pumping systems, to allow for the transfer of the electron beam from the high vacuum in the gun area to the high pressure attainable in its specimen chamber, make it a versatile instrument for imaging specimens in their natural state. The instrument was designed originally by Gerasimos Danilatos while working at the University of New South Wales. == History == Starting with Manfred von Ardenne, early attempts were reported of the examination of specimens inside "environmental" cells with water or atmospheric gas, in conjunction with conventional and scanning transmission types of electron microscopes. However, the first images of wet specimens in an SEM were reported by Lane in 1970 when he injected a fine jet of water vapor over the point of observation at the specimen surface; the gas diffused


id: environmental-scanning-electron-microscope-20260505-1
file: data/en.wikipedia.org/wiki/Environmental_scanning_electron_microscope-1.md
category: reference
title: Environmental scanning electron microscope
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Environmental_scanning_electron_microscope
date_saved: 2026-05-05T10:04:32.049506+00:00
instance: kb-cron
parent: environmental-scanning-electron-microscope-20260505-0
summary:
The specimen chamber sustaining the high-pressure gaseous environment is separated from the high vacuum of the electron optics column with at least two small orifices customarily referred to as pressure-limiting apertures (PLA). The gas leaking through the first aperture (PLA1) is quickly removed from the system with a pump that maintains a much lower pressure in the downstream region (i.e. immediately above the aperture). This is called differential pumping. Some gas escapes further from the low pressure region (stage 1) through a second pressure limiting aperture (PLA2) into the vacuum region of the column above, which constitutes a second stage differential pumping (stage 2). A schematic diagram shows the basic ESEM gas pressure stages including the specimen chamber, intermediate cavity and upper electron optics column. The corresponding pressures achieved are p0>>p1>>p2, which is a sufficient condition for a microscope employing a tungsten type of electron gun. Additional pumping stages may be added to achieve an even higher vacuum as required for a LaB6 and field emission type electron guns. The design and shape of a pressure limiting aperture are critical in obtaining the sharpest possible pressure gradient (transition) through it. This is achieved with an orifice made on a thin


id: environmental-scanning-electron-microscope-20260505-2
file: data/en.wikipedia.org/wiki/Environmental_scanning_electron_microscope-2.md
category: reference
title: Environmental scanning electron microscope
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Environmental_scanning_electron_microscope
date_saved: 2026-05-05T10:04:32.049506+00:00
instance: kb-cron
parent: environmental-scanning-electron-microscope-20260505-0
summary:
In a simple form, the gaseous detection device (GDD) employs an electrode with a voltage up to several hundred volts to collect the secondary electrons in the ESEM. The principle of this SE detector is best described by considering two parallel plates at a distance d apart with a potential difference V generating a uniform electric field E = V/d, and is shown in the accompanying diagram of the GDD. Secondary electrons released from the specimen at the point of beam impingement are driven by the field force towards the anode electrode but the electrons also move radially due to thermal diffusion from collisions with the gas molecules. The variation of electron collection fraction R within anode radius r vs. r/d, for fixed values of anode bias V, at constant product of (pressure·distance) p·d = 1 Pa·m, is given by the accompanying characteristic curves of efficiency of the GDD. All of the secondary electrons are detected if the parameters of this device are properly designed. This clearly shows that practically 100% efficiency is possible within a small radius of collector electrode with only moderate bias. At these levels of bias, no catastrophic discharge takes place. Instead, a controlled proportional multiplication


id: environmental-scanning-electron-microscope-20260505-3
file: data/en.wikipedia.org/wiki/Environmental_scanning_electron_microscope-3.md
category: reference
title: Environmental scanning electron microscope
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Environmental_scanning_electron_microscope
date_saved: 2026-05-05T10:04:32.049506+00:00
instance: kb-cron
parent: environmental-scanning-electron-microscope-20260505-0
summary:
===== Adapted detectors ===== Despite the above developments, devoted BSE detectors in the ESEM have played an important role, since the BSE remain a useful detection mode yielding information not possible to obtain with SE. The conventional BSE detection means have been adapted to operate in the gaseous conditions of the ESEM. The BSE having a high energy are self-propelled to the corresponding detector without significant obstruction by the gas molecules. Annular or quadrant solid-state detectors have been employed for this purpose but their geometry is not easily adaptable to the requirements of ESEM for optimum operation. As a result, not much use has been reported of these detectors on genuine ESEM instruments at high pressure. The "Robinson" BSE detector is tuned for operation up to around 100 Pa at the usual working distance of conventional SEM for the suppression of specimen charging, whilst electron collection at the short working distance and high pressure conditions make it inadequate for the ESEM. However, plastic scintillating materials being easily adaptable have been used for BSE and made to measure according to the strictest requirements of the system. Such work culminated in the use of a pair of wedge-shaped detectors saddling a conical


id: environmental-scanning-electron-microscope-20260505-4
file: data/en.wikipedia.org/wiki/Environmental_scanning_electron_microscope-4.md
category: reference
title: Environmental scanning electron microscope
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Environmental_scanning_electron_microscope
date_saved: 2026-05-05T10:04:32.049506+00:00
instance: kb-cron
parent: environmental-scanning-electron-microscope-20260505-0
summary:
=== Specimen charging === The electron beam impinging on insulating specimens accumulates negative charge, which creates an electrical potential tending to deflect the electron beam from the scanned point in conventional SEM. This appears as charging artifacts on the image, which are eliminated in the SEM by depositing a conductive layer on the specimen surface prior to examination. Instead of this coating, the gas in the ESEM being electrically conductive prevents negative charge accumulation. The good conductivity of the gas is due to the ionization it undergoes by the incident electron beam and the ionizing SE and BSE signals. This principle constitutes yet another deviation from conventional vacuum electron microscopy. Charge contrast imaging is a scanning electron microscope imaging mode which can produce images of otherwise invisible microstructures in insulating materials and in fossils. The technique has been used to detect changes in minerals which reflect compositional differences. Since charge is suppressed in ESEM at sufficient gas pressure, it is possible to regulate the amount of charging by varying the pressure between the SEM vacuum and some low pressure while observing the charging contrast variation effects. See examples with a series of images, also four images of the same field,


id: environmental-scanning-electron-microscope-20260505-5
file: data/en.wikipedia.org/wiki/Environmental_scanning_electron_microscope-5.md
category: reference
title: Environmental scanning electron microscope
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Environmental_scanning_electron_microscope
date_saved: 2026-05-05T10:04:32.049506+00:00
instance: kb-cron
parent: environmental-scanning-electron-microscope-20260505-0
summary:
== Advantages == The presence of gas around a specimen creates new possibilities unique to ESEM: (a) liquid-phase electron microscopy is possible since any pressure greater than 609 Pa allows water to be maintained in its liquid phase for temperatures above 0 °C, in contrast to the SEM where specimens are desiccated by the vacuum condition. (b) Electrically non-conductive specimens do not require the preparation techniques used in SEM to render the surface conductive, such as the deposition of a thin gold or carbon coating, or other treatments, techniques which also require vacuum in the process. Insulating specimens charge up by the electron beam making imaging problematic or even impossible. (c) The gas itself is used as a detection medium producing novel imaging possibilities, as opposed to vacuum SEM detectors. (d) Plain plastic scintillating BSE detectors can operate uncoated without charging. Hence, these detectors produce the highest possible signal-to-noise-ratio at the lowest possible accelerating voltage, because the BSE do not dissipate any energy in an aluminium coating used for the vacuum SEM. As a result, specimens can be examined faster and more easily, avoiding complex and time-consuming preparation methods, without modifying the natural surface or creating artifacts by the preceding


id: environmental-scanning-electron-microscope-20260505-6
file: data/en.wikipedia.org/wiki/Environmental_scanning_electron_microscope-6.md
category: reference
title: Environmental scanning electron microscope
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Environmental_scanning_electron_microscope
date_saved: 2026-05-05T10:04:32.049506+00:00
instance: kb-cron
parent: environmental-scanning-electron-microscope-20260505-0
summary:
== Commercial ESEM == The ESEM has appeared under different manufacturing brand names. The term ESEM is a generic name first publicly introduced in 1980 and afterwards unceasingly used in all publications by Danilatos and almost all users of all ESEM type instruments. The ELECTROSCAN ESEM trademark was obtained intermittently until 1999, when it was allowed to lapse. The word “environmental” was originally introduced in continuation to the prior (historical) use of “environmental” cells in transmission microscopy, although the word “atmospheric” has also been used to refer to an ESEM at one atmosphere pressure (ASEM) but not with any commercial instruments. Other competing manufacturers have used the terms "Natural SEM" (Hitachi), “Wet-SEM” (ISI), “Bio-SEM” (short-lived, AMRAY), “VP-SEM” (variable-pressure SEM; LEO/Zeiss-SMT), “LVSEM” (low-vacuum SEM, often also denoting low-voltage SEM; JEOL), all of which seem to be transient in time according to prevailing manufacturing schedules. Until recently, all these names referred to instruments operating up to about 100 Pa and with BSE detectors only. Lately, the Zeiss-SMT VP-SEM has been extended to higher pressure together with a gaseous ionization or gaseous scintillation as the SE mechanism for image formation. Therefore, it is improper to identify the term ESEM with one only brand


id: field-emission-microscopy-20260505-0
file: data/en.wikipedia.org/wiki/Field-emission_microscopy-0.md
category: reference
title: Field-emission microscopy
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Field-emission_microscopy
date_saved: 2026-05-05T10:04:33.222672+00:00
instance: kb-cron
parent: field-emission-microscopy-20260505-0
summary:
Field-emission microscopy (FEM) is an analytical technique that is used in materials science to study the surfaces of needle apexes. The FEM was invented by Erwin Wilhelm Müller in 1936, and it was one of the first surface-analysis instruments that could approach near-atomic resolution. == Introduction == Microscopy techniques are utilized to generate magnified real-space images of the surface of a tip apex. Typically, microscopy information pertains to the surface crystallography (i.e., how the atoms are arranged at the surface) and surface morphology (i.e., the shape and size of topographic features making the surface). Field-emission microscopy (FEM) was invented by Erwin Müller in 1936. In FEM, the phenomenon of field electron emission was used to obtain an image on the detector based on the difference in work function of the various crystallographic planes on the surface. == Setup and working principle == A field-emission microscope consists of a metallic sample shaped like a sharp tip and a fluorescent screen enclosed within an ultrahigh vacuum chamber. Typically, the tip radius used in this microscope is on the order of 100 nm, and it is made of a metal with a high melting point, such as tungsten. The sample is held at


id: focused-ion-beam-20260505-0
file: data/en.wikipedia.org/wiki/Focused_ion_beam-0.md
category: reference
title: Focused ion beam
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Focused_ion_beam
date_saved: 2026-05-05T10:04:34.384165+00:00
instance: kb-cron
parent: focused-ion-beam-20260505-0
summary:
Focused ion beam, also known as FIB, is a technique used particularly in the semiconductor industry, materials science and increasingly in the biological field for site-specific analysis, deposition, and ablation of materials. A FIB setup is a scientific instrument that resembles a scanning electron microscope (SEM). However, while the SEM uses a focused beam of electrons to image the sample in the chamber, a FIB setup uses a focused beam of ions instead. FIB can also be incorporated in a system with both electron and ion beam columns, allowing the same feature to be investigated using either of the beams. FIB should not be confused with using a beam of focused ions for direct write lithography (such as in proton beam writing). These are generally quite different systems where the material is modified by other mechanisms. == Ion beam source == Most widespread instruments are using liquid metal ion sources (LMIS), especially gallium ion sources. Ion sources based on elemental gold and iridium are also available. In a gallium LMIS, gallium metal is placed in contact with a tungsten needle, and heated gallium wets the tungsten and flows to the tip of the needle, where the opposing forces of surface


id: focused-ion-beam-20260505-1
file: data/en.wikipedia.org/wiki/Focused_ion_beam-1.md
category: reference
title: Focused ion beam
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Focused_ion_beam
date_saved: 2026-05-05T10:04:34.384165+00:00
instance: kb-cron
parent: focused-ion-beam-20260505-0
summary:
=== Etching === Unlike an electron microscope, FIB is inherently destructive to the specimen. When the high-energy gallium ions strike the sample, they will sputter atoms from the surface. Gallium atoms will also be implanted into the top few nanometers of the surface, and the surface will be made amorphous. Because of the sputtering capability, the FIB is used as a micro- and nano-machining tool, to modify or machine materials at the micro- and nanoscale. FIB micro machining has become a broad field of its own, but nano machining with FIB is a field that is still developing. Commonly the smallest beam size for imaging is 2.5–6 nm. The smallest milled features are somewhat larger (10–15 nm) as this is dependent on the total beam size and interactions with the sample being milled. FIB tools are designed to etch or machine surfaces, an ideal FIB might machine away one atom layer without any disruption of the atoms in the next layer, or any residual disruptions above the surface. Yet currently because of the sputter the machining typically roughens surfaces at the sub-micrometer length scales. === Deposition === A FIB can also be used to deposit material via ion beam induced


id: focused-ion-beam-20260505-2
file: data/en.wikipedia.org/wiki/Focused_ion_beam-2.md
category: reference
title: Focused ion beam
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Focused_ion_beam
date_saved: 2026-05-05T10:04:34.384165+00:00
instance: kb-cron
parent: focused-ion-beam-20260505-0
summary:
=== FIB-SEM tomography === The focused ion beam has become a powerful tool for site-specific 3D imaging of sub-micron features in a sample. In this FIB tomography technique, the sample is sequentially milled using an ion beam perpendicular to the specimen while imaging the newly exposed surface using an electron beam. This so-called "slice and view" approach allows larger scale nano-structures to be characterized across the many imaging modes available to an SEM, including secondary electron, backscattered electron, and energy dispersive x-ray measurement. The process is destructive, since the specimen is being sequentially milled away after each image is collected. The collected series of images is then reconstructed to a 3D volume by registering the image stack and removing artifacts. The predominant artifact that degrades FIB-SEM is ion mill curtaining, where mill patterns form large aperiodic stripes in each image. The ion mill curtaining can be removed using destriping algorithms. FIB-SEM can be done at both room and cryo temperatures as well as on both materials and biological samples. It is one of several approaches in Volumetric Electron Microscopy. == History == History of FIB technology 1975: The first FIB systems based on field emission technology were developed by Levi-Setti


id: four-terminal-sensing-20260505-0
file: data/en.wikipedia.org/wiki/Four-terminal_sensing-0.md
category: reference
title: Four-terminal sensing
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Four-terminal_sensing
date_saved: 2026-05-05T10:04:35.541595+00:00
instance: kb-cron
parent: four-terminal-sensing-20260505-0
summary:
In electrical engineering, four-terminal sensing (4T sensing), 4-wire sensing, or 4-point probes method is an electrical impedance measuring technique that uses separate pairs of current-carrying and voltage-sensing electrodes to make more accurate measurements than the simpler and more usual two-terminal (2T) sensing. Four-terminal sensing is used in some ohmmeters and impedance analyzers, and in wiring for strain gauges and resistance thermometers. Four-point probes are also used to measure sheet resistance of thin films (particularly semiconductor thin films). Separation of current and voltage electrodes eliminates the lead and contact resistance from the measurement. This is an advantage for precise measurement of low resistance values. For example, an LCR bridge instruction manual recommends the four-terminal technique for accurate measurement of resistance below 100 ohms. Four-terminal sensing is also known as Kelvin sensing, after William Thomson, Lord Kelvin, who invented the Kelvin bridge in 1861 to measure very low resistances using four-terminal sensing. Each two-wire connection can be called a Kelvin connection. A pair of contacts that is designed to connect a force-and-sense pair to a single terminal or lead simultaneously is called a Kelvin contact. A clip, often a crocodile clip, that connects a force-and-sense pair (typically one to each jaw) is


id: fourier-transform-spectroscopy-20260505-0
file: data/en.wikipedia.org/wiki/Fourier-transform_spectroscopy-0.md
category: reference
title: Fourier-transform spectroscopy
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Fourier-transform_spectroscopy
date_saved: 2026-05-05T10:04:36.785085+00:00
instance: kb-cron
parent: fourier-transform-spectroscopy-20260505-0
summary:
Fourier-transform spectroscopy (FTS) is a measurement technique whereby spectra are collected based on measurements of the coherence of a radiative source, using time-domain or space-domain measurements of the radiation, electromagnetic or not. It can be applied to a variety of types of spectroscopy including optical spectroscopy, infrared spectroscopy (FTIR, FT-NIRS), nuclear magnetic resonance (NMR) and magnetic resonance spectroscopic imaging (MRSI), mass spectrometry and electron spin resonance spectroscopy. There are several methods for measuring the temporal coherence of the light (see: field-autocorrelation), including the continuous-wave and the pulsed Fourier-transform spectrometer or Fourier-transform spectrograph. The term "Fourier-transform spectroscopy" reflects the fact that in all these techniques, a Fourier transform is required to turn the raw data into the actual spectrum, and in many of the cases in optics involving interferometers, is based on the Wiener–Khinchin theorem. == Conceptual introduction == === Measuring an emission spectrum === One of the most basic tasks in spectroscopy is to characterize the spectrum of a light source: how much light is emitted at each different wavelength. The most straightforward way to measure a spectrum is to pass the light through a monochromator, an instrument that blocks all of the light except the light at a certain


id: fourier-transform-spectroscopy-20260505-1
file: data/en.wikipedia.org/wiki/Fourier-transform_spectroscopy-1.md
category: reference
title: Fourier-transform spectroscopy
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Fourier-transform_spectroscopy
date_saved: 2026-05-05T10:04:36.785085+00:00
instance: kb-cron
parent: fourier-transform-spectroscopy-20260505-0
summary:
where I ( ν ~ ) {\displaystyle I({\tilde {\nu }})} is the spectrum to be determined. Note that it is not necessary for I ( ν ~ ) {\displaystyle I({\tilde {\nu }})} to be modulated by the sample before the interferometer. In fact, most FTIR spectrometers place the sample after the interferometer in the optical path. The total intensity at the detector is I ( p ) = ∫ 0 ∞ I ( p , ν ~ ) d ν ~ = ∫ 0 ∞ I ( ν ~ ) [ 1 + cos ⁡ ( 2 π ν ~ p ) ] d ν ~ . {\displaystyle {\begin{aligned}I(p)&=\int _{0}^{\infty }I(p,{\tilde {\nu }})d{\tilde {\nu }}\\&=\int _{0}^{\infty }I({\tilde {\nu }})[1+\cos(2\pi {\tilde {\nu }}p)]\,d{\tilde {\nu }}.\end{aligned}}} This is just a Fourier cosine transform. The inverse gives us our desired result in terms of the measured quantity I ( p ) {\displaystyle I(p)} : I ( ν ~ ) = 4 ∫ 0 ∞ [ I ( p ) − 1 2 I ( p = 0 ) ] cos ⁡ ( 2 π ν ~ p ) d p . {\displaystyle I({\tilde {\nu }})=4\int _{0}^{\infty }\left[I(p)-{\frac {1}{2}}I(p=0)\right]\cos(2\pi {\tilde {\nu }}p)\,dp.} == Pulsed


id: gaseous-detection-device-20260505-0
file: data/en.wikipedia.org/wiki/Gaseous_detection_device-0.md
category: reference
title: Gaseous detection device
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Gaseous_detection_device
date_saved: 2026-05-05T10:04:37.957284+00:00
instance: kb-cron
parent: gaseous-detection-device-20260505-0
summary:
The gaseous detection device (GDD) is a method and apparatus for the detection of signals in the gaseous environment of an environmental scanning electron microscope (ESEM) and all scanned beam type of instruments that allow a minimum gas pressure for the detector to operate. == History == In the course of development of the ESEM, the detectors previously employed in the vacuum of a scanning electron microscope (SEM) had to be adapted for operation in gaseous conditions. The backscattered electron (BSE) detector was adapted by an appropriate geometry in accordance with the requirements for optimum electron beam transmission, BSE distribution and light guide transmission. However, the corresponding secondary electron (SE) detector (Everhart–Thornley detector) could not be adapted, because the high potential required would cause a catastrophic breakdown even with moderate increase of pressure, such as low vacuum. Danilatos (1983) overcame this problem by using the environmental gas itself as the detector, by virtue of the ionizing action of various signals. With appropriate control of electrode configuration and bias, detection of SE was achieved. A comprehensive survey dealing with the theory and operation of GDD has been published, from which the majority of the material presented below has been used. ==


id: gaseous-detection-device-20260505-1
file: data/en.wikipedia.org/wiki/Gaseous_detection_device-1.md
category: reference
title: Gaseous detection device
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Gaseous_detection_device
date_saved: 2026-05-05T10:04:37.957284+00:00
instance: kb-cron
parent: gaseous-detection-device-20260505-0
summary:
where R is the fraction of SE that arrives at the anode inside radius r, V the potential difference between the electrodes placed at distance d, k is the Boltzmann constant, T the absolute gas temperature, e the elementary charge and ε is the ratio of the thermal (agitation and kinetic) energy of the electrons divided by the thermal energy of the host gas; I is the corresponding current collected by the anode inside r, δ is the SE yield coefficient and Ib the incident electron beam current. This provides the spatial distribution of the initial electrons SE as they are acted upon by the uniform electric field that moves them from the cathode to the anode, while the electrons also diffuse away due to thermal collisions with the gas molecules. Plots are provided in the accompanying efficiency characteristics of the GDD, for a set of operating conditions of pressure p and distance d. We note that a 100% collection efficiency is fast approached within a small radius even at moderate field strength. At high bias, a nearly complete collection is achieved within a very small radius, a fact that has favorable design implications. The above radial distribution is valid


id: gaseous-detection-device-20260505-2
file: data/en.wikipedia.org/wiki/Gaseous_detection_device-2.md
category: reference
title: Gaseous detection device
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Gaseous_detection_device
date_saved: 2026-05-05T10:04:37.957284+00:00
instance: kb-cron
parent: gaseous-detection-device-20260505-0
summary:
At the point in time when the charge arrives at the electrode, there is no current flowing in the circuit since υ = 0, only when the charge is in motion between the electrodes do we have a signal current. This is important in the case, for example, when a new electron-ion pair is generated at any point in the space between anode-cathode, say at x distance from the anode. Then, only a fraction ex/d of charge is induced by the electron during its transit to the anode, whilst the remainder fraction of e(d − x)/d charge is induced by the ion during its transit to the cathode. Addition of those two fractions gives a charge equal to the charge of one electron. Thus by counting the electrons arriving at the anode or the ions at the cathode we derive the same figure in current measurement. However, since the electrons have a drift velocity about three orders of magnitude greater (in nanosecond range) than the ions, the induced signal may be separated in two components of different significance when the ion transit time may become greater than the pixel time on the scanned image. The GDD has thus two inherent


id: gaseous-detection-device-20260505-3
file: data/en.wikipedia.org/wiki/Gaseous_detection_device-3.md
category: reference
title: Gaseous detection device
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Gaseous_detection_device
date_saved: 2026-05-05T10:04:37.957284+00:00
instance: kb-cron
parent: gaseous-detection-device-20260505-0
summary:
The diagram showing the principle of GDD constitutes a versatile implementation that includes not only the SE mode but also the BSE and a combination of these. Even if only the SE signal is desirable to use alone, at least one additional concentric electrode is recommended to employ in order to help in the separation from interference of BSE and also from other noise sources such as the skirt electrons scattered out of the primary beam by the gas. This addition may act as a "guard" electrode, and by varying its bias independently from the SE electrode, the image contrast can be controlled purposefully. Alternative control electrodes are used such as a mesh between anode and cathode. A multipurpose array of electrodes below and above the specimen and above the pressure limiting aperture of the ESEM has also been described elsewhere. The development of this detector has required devoted electronics circuitry, especially when the signal is picked up by the anode at high bias, because the floating current amplified must be coupled at full bandwidth to the ground amplifier and video display circuits (developed by ElectroScan). An alternative is to bias the cathode with a negative potential and pickup the


id: gravimetric-analysis-20260505-0
file: data/en.wikipedia.org/wiki/Gravimetric_analysis-0.md
category: reference
title: Gravimetric analysis
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Gravimetric_analysis
date_saved: 2026-05-05T10:04:39.107123+00:00
instance: kb-cron
parent: gravimetric-analysis-20260505-0
summary:
Gravimetric analysis describes a set of methods used in analytical chemistry for the quantitative determination of an analyte (the ion being analyzed) based on its mass. The principle of this type of analysis is that once an ion's mass has been determined as a unique compound, that known measurement can then be used to determine the same analyte's mass in a mixture, as long as the relative quantities of the other constituents are known. The four main types of this method of analysis are precipitation, volatilization, electro-analytical, and miscellaneous physical method. The methods involve changing the phase of the analyte to separate it in its pure form from the original mixture and are quantitative measurements. Gravimetric analysis provides for exceedingly precise analysis. In fact, gravimetric analysis was used to determine the atomic masses of many elements in the periodic table to six figure accuracy. Gravimetry provides very little room for instrument error and does not require a series of standards for calculation of an unknown. Also, gravimetric methods often do not require expensive equipment. Due to its high degree of accuracy, gravimetric analysis can also be used to calibrate other instruments instead of using reference standards. To some extent, gravimetric


id: grazing-incidence-diffraction-20260505-0
file: data/en.wikipedia.org/wiki/Grazing_incidence_diffraction-0.md
category: reference
title: Grazing incidence diffraction
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Grazing_incidence_diffraction
date_saved: 2026-05-05T10:04:40.293115+00:00
instance: kb-cron
parent: grazing-incidence-diffraction-20260505-0
summary:
Grazing incidence diffraction (GID) is a technique for interrogating a material using small incidence angles for an incoming wave, often leading to the diffraction being surface sensitive. It occurs in many different areas: Reflection high-energy electron diffraction (RHEED), where electrons of relatively high energy diffract at small angles from a surface. RHEED is used to interrogate surface structure. Surface X-ray diffraction (SXRD), which is similar to RHEED but uses X-rays, and is also used to interrogate surface structure. X-ray standing waves, another X-ray variant where the intensity decay into a sample from diffraction is used to analyze chemistry. Grazing-incidence small-angle scattering (GISAS) a hybrid approach using small scattering (diffraction) angles with X-rays or neutrons. X-ray reflectivity, yet another related technique, but here the intensity of the specular reflected beam is measured. Grazing incidence atom scattering, where the fact that atoms (and ions) can also be waves is used to diffract from surfaces. Quantum reflection, where very low kinetic energy atoms or molecules are diffracted (reflected) from surfaces. Evanescent waves, which occur with all of the above and also photons where there is no flow of energy into the material. More details and citations on these can be found in the


id: grazing-incidence-small-angle-scattering-20260505-0
file: data/en.wikipedia.org/wiki/Grazing-incidence_small-angle_scattering-0.md
category: reference
title: Grazing-incidence small-angle scattering
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Grazing-incidence_small-angle_scattering
date_saved: 2026-05-05T10:04:41.501851+00:00
instance: kb-cron
parent: grazing-incidence-small-angle-scattering-20260505-0
summary:
Grazing-incidence small-angle scattering (GISAS) is a diffraction technique used to study nanostructured surfaces and thin films. The scattered probe is either photons (grazing-incidence small-angle X-ray scattering, GISAXS) or neutrons (grazing-incidence small-angle neutron scattering, GISANS). GISAS combines the accessible length scales of small-angle scattering (SAS: SAXS or SANS) and the surface sensitivity of grazing incidence diffraction (GID). == Applications == A typical application of GISAS is the characterisation of self-assembly and self-organization on the nanoscale in thin films. Systems studied by GISAS include quantum dot arrays, growth instabilities formed during in-situ growth, self-organized nanostructures in thin films of block copolymers, silica mesophases, and nanoparticles. GISAXS was introduced by Levine and Cohen to study the dewetting of gold deposited on a glass surface. The technique was further developed by Naudon and coworkers to study metal agglomerates on surfaces and in buried interfaces. With the advent of nanoscience other applications evolved quickly, first in hard matter such as the characterization of quantum dots on semiconductor surfaces and the in-situ characterization of metal deposits on oxide surfaces. This was soon to be followed by soft matter systems such as ultrathin polymer films, polymer blends, block copolymer films and other self-organized nanostructured thin films that


id: heat-stabilization-20260505-0
file: data/en.wikipedia.org/wiki/Heat_stabilization-0.md
category: reference
title: Heat stabilization
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Heat_stabilization
date_saved: 2026-05-05T10:04:42.641676+00:00
instance: kb-cron
parent: heat-stabilization-20260505-0
summary:
Heat stabilization is an additive-free preservation technology for tissue samples which stops degradation and changes immediately and permanently. Heat stabilization uses rapid conductive heating, under controlled pressure, to generate a fast, homogeneous and irreversible thermal denaturation of proteins, resulting in a complete and permanent elimination of all enzymatic activity that would otherwise cause further biological changes to the tissue sample ex vivo. Due to the permanent inactivation of enzymes, heat stabilization overcomes the drawbacks of conventional tissue sample preservation techniques, such as snap-freezing followed by inhibitors. Understanding the role of proteins, peptides and small molecules in normal and diseased tissue is crucial to defining their potential use as drugs, drug targets or disease biomarkers. Yet biological changes begin the moment tissue is removed from its native environment. Dramatic alterations at the molecular level occur within seconds e.g. changed metabolism, catabolic fragmentation of large molecules (such as ATP) occurs in order to release energy, leading to disrupted control mechanisms, phosphorylation states are altered and proteins begin to degrade. As a consequence vital information may be lost or distorted, leading to inter-sample variation, risk of incorrect data interpretation and potentially misleading conclusions. Heat stabilization offers significant advantages over conventional approaches to preventing


id: helium-atom-scattering-20260505-0
file: data/en.wikipedia.org/wiki/Helium_atom_scattering-0.md
category: reference
title: Helium atom scattering
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Helium_atom_scattering
date_saved: 2026-05-05T10:04:43.864333+00:00
instance: kb-cron
parent: helium-atom-scattering-20260505-0
summary:
Helium atom scattering (HAS) is a surface analysis technique used in materials science. It provides information about the surface structure and lattice dynamics of a material by measuring the diffracted atoms from a monochromatic helium beam incident on the sample. == History == The first recorded helium diffraction experiment was completed in 1930 by Immanuel Estermann and Otto Stern on the (100) crystal face of lithium fluoride. This experimentally established the feasibility of atom diffraction when the de Broglie wavelength, λ, of the impinging atoms is on the order of the interatomic spacing of the material. At the time, the major limit to the experimental resolution of this method was due to the large velocity spread of the helium beam. It wasn't until the development of high pressure nozzle sources capable of producing intense and strongly monochromatic beams in the 1970s that HAS gained popularity for probing surface structure. Interest in studying the collision of rarefied gases with solid surfaces was helped by a connection with aeronautics and space problems of the time. Plenty of studies showing the fine structures in the diffraction pattern of materials using helium atom scattering were published in the 1970s. However, it wasn't until a


id: helium-atom-scattering-20260505-1
file: data/en.wikipedia.org/wiki/Helium_atom_scattering-1.md
category: reference
title: Helium atom scattering
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Helium_atom_scattering
date_saved: 2026-05-05T10:04:43.864333+00:00
instance: kb-cron
parent: helium-atom-scattering-20260505-0
summary:
=== Why use helium atoms? === There are several advantages to using helium atoms as compared with x-rays, neutrons, and electrons to probe a surface and study its structures and phonon dynamics. As mentioned previously, the lightweight helium atoms at thermal energies do not penetrate into the bulk of the material being studied. This means that in addition to being strictly surface-sensitive they are truly non-destructive to the sample. Their de Broglie wavelength is also on the order of the interatomic spacing of materials, making them ideal probing particles. Since they are neutral, helium atoms are insensitive to surface charges. As a noble gas, the helium atoms are chemically inert. When used at thermal energies, as is the usual scenario, the helium atomic beam is an inert probe (chemically, electrically, magnetically, and mechanically). It is therefore capable of studying the surface structure and dynamics of a wide variety of materials, including those with reactive or metastable surfaces. A helium atom beam can even probe surfaces in the presence of electromagnetic fields and during ultra-high vacuum surface processing without interfering with the ongoing process. Because of this, helium atoms can be useful to make measurements of sputtering or annealing, and adsorbate


id: helium-atom-scattering-20260505-2
file: data/en.wikipedia.org/wiki/Helium_atom_scattering-2.md
category: reference
title: Helium atom scattering
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Helium_atom_scattering
date_saved: 2026-05-05T10:04:43.864333+00:00
instance: kb-cron
parent: helium-atom-scattering-20260505-0
summary:
The intensities of the diffraction peaks provide information about the static gas-surface interaction potentials. Measuring the diffraction peak intensities under different incident beam conditions can reveal the surface corrugation (the surface electron density) of the outermost atoms on the surface. Note that the detection of the helium atoms is much less efficient than for electrons, so the scattered intensity can only be determined for one point in k-space at a time. For an ideal surface, there should be no elastic scattering intensity between the observed diffraction peaks. If there is intensity seen here, it is due to a surface imperfection, such as steps or adatoms. From the angular position, width and intensity of the peaks, information is gained regarding the surface structure and symmetry, and the ordering of surface features. == Inelastic measurements == The inelastic scattering of the helium atom beam reveals the surface phonon dispersion for a material. At scattering angles far away from the specular or diffraction angles, the scattering intensity of the ordered surface is dominated by inelastic collisions. In order to study the inelastic scattering of the helium atom beam due only to single-phonon contributions, an energy analysis needs to be made of the scattered


id: helium-3-surface-spin-echo-20260505-0
file: data/en.wikipedia.org/wiki/Helium-3_surface_spin_echo-0.md
category: reference
title: Helium-3 surface spin echo
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Helium-3_surface_spin_echo
date_saved: 2026-05-05T10:04:45.056359+00:00
instance: kb-cron
parent: helium-3-surface-spin-echo-20260505-0
summary:
Helium-3 surface spin echo (HeSE) is an inelastic scattering technique in surface science that has been used to measure microscopic dynamics at well-defined surfaces in ultra-high vacuum. The information available from HeSE complements and extends that available from other inelastic scattering techniques such as neutron spin echo and traditional helium-4 atom scattering (HAS). == Principles == The experimental principles of the HeSE experiment are analogous to those of neutron spin echo, differing in details such as the nature of the probe/sample interactions that give rise to scattering. In outline, a polarized 3He beam is created by a supersonic expansion followed by a spin-filtering stage (polariser). The helium scatters from the experimental sample and is detected at the end of the beamline after another spin-filtering stage (analyser). Before and after the scattering process, the beam passes through magnetic fields that precess the probe spins in the usual sense of a spin echo experiment. The raw data of the experiment are the spin-resolved scattered helium intensities as a function of the incoming magnetic field integral, outgoing field integral and any other variable parameters relevant to specific experiments, such as surface orientation and temperature. In the most general kind of scattering-with-precession experiment, the


id: high-resolution-electron-energy-loss-spectroscopy-20260505-0
file: data/en.wikipedia.org/wiki/High_resolution_electron_energy_loss_spectroscopy-0.md
category: reference
title: High resolution electron energy loss spectroscopy
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/High_resolution_electron_energy_loss_spectroscopy
date_saved: 2026-05-05T10:04:46.244843+00:00
instance: kb-cron
parent: high-resolution-electron-energy-loss-spectroscopy-20260505-0
summary:
High resolution electron energy loss spectroscopy (HREELS) is a tool used in surface science. The inelastic scattering of electrons from surfaces is utilized to study electronic excitations or vibrational modes of the surface of a material or of molecules adsorbed to a surface. In contrast to other electron energy loss spectroscopies (EELS), HREELS deals with small energy losses in the range of 10−3 eV to 1 eV. It plays an important role in the investigation of surface structure, catalysis, dispersion of surface phonons and the monitoring of epitaxial growth. == Overview of HREELS == In general, electron energy loss spectroscopy is based on the energy losses of electrons when inelastically scattered on matter. An incident beam of electrons with a known energy (Ei) is scattered on a sample. The scattering of these electrons can excite the electronic structure of the sample. If this is the case the scattered electron loses the specific energy (ΔE) needed to cause the excitation. Those scattering processes are called inelastic. It may be easiest to imagine that the energy loss is for example due to an excitation of an electron from an atomic K-shell to the M-shell. The energy for this excitation is taken away


id: high-resolution-electron-energy-loss-spectroscopy-20260505-1
file: data/en.wikipedia.org/wiki/High_resolution_electron_energy_loss_spectroscopy-1.md
category: reference
title: High resolution electron energy loss spectroscopy
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/High_resolution_electron_energy_loss_spectroscopy
date_saved: 2026-05-05T10:04:46.244843+00:00
instance: kb-cron
parent: high-resolution-electron-energy-loss-spectroscopy-20260505-0
summary:
The so-called dipole scattering can be applied when the scattered beam is very near to the specular direction. In this case a macroscopic theory can be applied to explain the results. It can be approached using the so-called dielectrical theory introduced by Lucas and Šunjić of which a quantum mechanical treatment was first presented by E. Evans and D.L. Mills in the early 1970s. Alternatively there is a more unfamiliar model which only holds exactly for perfect conductors: A unit cell at the surface does not have a homogeneous surrounding, hence it is supposed to have an electrical dipole moment. When a molecule is adsorbed to the surface there can be an additional dipole moment and the total dipole moment P is present. This dipole moment causes a long range electronic potential in the vacuum above the surface. On this potential the incident electron can scatter inelastically which means it excites vibrations in the dipole structure. The dipole moment can then be written as P + p e I ω t {\displaystyle P+pe^{I\omega t}} . When the adsorbate sticks to a metal surface, imaginary dipoles occur as shown in the figure on the right. Hence for an adsorbed dipole normal


id: high-resolution-electron-energy-loss-spectroscopy-20260505-2
file: data/en.wikipedia.org/wiki/High_resolution_electron_energy_loss_spectroscopy-2.md
category: reference
title: High resolution electron energy loss spectroscopy
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/High_resolution_electron_energy_loss_spectroscopy
date_saved: 2026-05-05T10:04:46.244843+00:00
instance: kb-cron
parent: high-resolution-electron-energy-loss-spectroscopy-20260505-0
summary:
As the electrons used for HREELS are of low energy they do not only have a very short mean free path length in the sample materials but also under normal atmospheric conditions. Therefore, one has to set up the spectrometer in UHV. The spectrometer is in general a computer simulated design that optimizes the resolution while keeping an acceptable electron flux. The electrons are generated in an electron source, by heating a tungsten cathode, which is encapsulated by a negatively charged so called repeller that prevents stray electrons from coming into the detector unit. The electrons can leave the source only through a lens system, like e.g. a slot lens system consisting of several slits all on different potential. The purpose of this system is to focus the electrons on the entrance of the monochromator unit, to get a high initial electron flux. The monochromator is usually a concentric hemispherical analyser (CHA). In more sensitive setups an additional pre-monochromator is used. The task of the monochromator is to reduce the energy of the passing electrons to some eV due to the help of electron lenses. It further lets only those electrons pass which have the chosen initial energy. To achieve


id: high-performance-liquid-chromatography-20260505-0
file: data/en.wikipedia.org/wiki/High-performance_liquid_chromatography-0.md
category: reference
title: High-performance liquid chromatography
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/High-performance_liquid_chromatography
date_saved: 2026-05-05T10:04:47.433046+00:00
instance: kb-cron
parent: high-performance-liquid-chromatography-20260505-0
summary:
High-performance liquid chromatography (HPLC), formerly referred to as high-pressure liquid chromatography, is a technique in analytical chemistry used to separate, identify, and quantify specific components in mixtures. The mixtures can originate from food, chemicals, pharmaceuticals, biological, environmental and agriculture, etc., which is a liquid or has been dissolved into a liquid. It relies on high pressure pumps, which deliver mixtures of various solvents, called the mobile phase, which flows through the system, collecting the sample mixture on the way, delivering it into a cylinder, called the column, filled with solid particles, made of adsorbent material, called the stationary phase. Each component in the sample interacts differently with the adsorbent material, causing different elution rates for each component. These different rates lead to separation as the species flow out of the column into a specific detector such as UV detectors. The output of the detector is a graph, called a chromatogram. Chromatograms are graphical representations of the signal intensity versus time or volume, showing peaks, which represent components of the sample. Each sample appears in its respective time, called its retention time, having area proportional to its amount. HPLC is widely used for manufacturing (e.g., during the production process of pharmaceutical


id: high-performance-liquid-chromatography-20260505-1
file: data/en.wikipedia.org/wiki/High-performance_liquid_chromatography-1.md
category: reference
title: High-performance liquid chromatography
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/High-performance_liquid_chromatography
date_saved: 2026-05-05T10:04:47.433046+00:00
instance: kb-cron
parent: high-performance-liquid-chromatography-20260505-0
summary:
The liquid chromatograph is complex and has sophisticated and delicate technology. In order to properly operate the system, there should be a minimum basis for understanding of how the device performs the data processing to avoid incorrect data and distorted results. HPLC is distinguished from traditional ("low pressure") liquid chromatography because operational pressures are significantly higher (around 50–1400 bar), while ordinary liquid chromatography typically relies on the force of gravity to pass the mobile phase through the packed column. Due to the small sample amount separated in analytical HPLC, typical column dimensions are 2.1–4.6 mm diameter, and 30–250 mm length. Also HPLC columns are made with smaller adsorbent particles (1.5–50 μm in average particle size). This gives HPLC superior resolving power (the ability to distinguish between compounds) when separating mixtures in a shorter period of time, which makes it a popular chromatographic technique. The schematic of an HPLC instrument typically includes solvents' reservoirs, one or more pumps, a solvent-degasser, a sampler, a column, and a detector. The solvents are prepared in advance according to the needs of the separation, they pass through the degasser to remove dissolved gasses, mixed to become the mobile phase, then flow through the sampler, which


id: high-performance-liquid-chromatography-20260505-2
file: data/en.wikipedia.org/wiki/High-performance_liquid_chromatography-2.md
category: reference
title: High-performance liquid chromatography
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/High-performance_liquid_chromatography
date_saved: 2026-05-05T10:04:47.433046+00:00
instance: kb-cron
parent: high-performance-liquid-chromatography-20260505-0
summary:
== History and development == Prior to HPLC, scientists used benchtop column liquid chromatographic techniques. Liquid chromatographic systems were largely inefficient due to the flow rate of solvents being dependent on gravity. Separations took many hours, and sometimes days to complete. Gas chromatography (GC) at the time was more powerful than liquid chromatography (LC), however, it was obvious that gas phase separation and analysis of very polar high molecular weight biopolymers was impossible. GC was ineffective for many life science and health applications for biomolecules, because they are mostly non-volatile and thermally unstable at the high temperatures of GC. As a result, alternative methods were hypothesized which would soon result in the development of HPLC. Following on the seminal work of Martin and Synge in 1941, it was predicted by Calvin Giddings, Josef Huber, and others in the 1960s that LC could be operated in the high-efficiency mode by reducing the packing-particle diameter substantially below the typical LC (and GC) level of 150 μm and using pressure to increase the mobile phase velocity. These predictions underwent extensive experimentation and refinement throughout the 60s into the 70s until these very days. Early developmental research began to improve LC particles, for example


id: high-performance-liquid-chromatography-20260505-3
file: data/en.wikipedia.org/wiki/High-performance_liquid_chromatography-3.md
category: reference
title: High-performance liquid chromatography
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/High-performance_liquid_chromatography
date_saved: 2026-05-05T10:04:47.433046+00:00
instance: kb-cron
parent: high-performance-liquid-chromatography-20260505-0
summary:
=== Normal–phase chromatography === Normal–phase chromatography was one of the first kinds of HPLC that chemists developed, but has decreased in use over the last decades. Also known as normal-phase HPLC (NP-HPLC), this method separates analytes based on their affinity for a polar stationary surface such as silica; hence it is based on analyte ability to engage in polar interactions (such as hydrogen-bonding or dipole-dipole type of interactions) with the sorbent surface. NP-HPLC uses a non-polar, non-aqueous mobile phase (e.g., chloroform), and works effectively for separating analytes readily soluble in non-polar solvents. The analyte associates with and is retained by the polar stationary phase. Adsorption strengths increase with increased analyte polarity. The interaction strength depends not only on the functional groups present in the structure of the analyte molecule, but also on steric factors. The effect of steric hindrance on interaction strength allows this method to resolve (separate) structural isomers. The use of more polar solvents in the mobile phase will decrease the retention time of analytes, whereas more hydrophobic solvents tend to induce slower elution (increased retention times). Very polar solvents such as traces of water in the mobile phase tend to adsorb to the solid surface of the


id: high-performance-liquid-chromatography-20260505-4
file: data/en.wikipedia.org/wiki/High-performance_liquid_chromatography-4.md
category: reference
title: High-performance liquid chromatography
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/High-performance_liquid_chromatography
date_saved: 2026-05-05T10:04:47.433046+00:00
instance: kb-cron
parent: high-performance-liquid-chromatography-20260505-0
summary:
Reversed phase HPLC (RP-HPLC) is the most widespread mode of chromatography. It has a non-polar stationary phase and an aqueous, moderately polar mobile phase. In the reversed phase methods, the substances are retained in the system the more hydrophobic they are. For the retention of organic materials, the stationary phases, packed inside the columns, are consisted mainly of porous granules of silica gel in various shapes, mainly spherical, at different diameters (1.5, 2, 3, 5, 7, 10 um), with varying pore diameters (60, 100, 150, 300, A), on whose surface are chemically bound various hydrocarbon ligands such as C3, C4, C8, C18. There are also polymeric hydrophobic particles that serve as stationary phases, when solutions at extreme pH are needed, or hybrid silica, polymerized with organic substances. The longer the hydrocarbon ligand on the stationary phase, the longer the sample components can be retained. Most of the current methods of separation of biomedical materials use C-18 type of columns, sometimes called by a trade names such as ODS (octadecylsilane) or RP-18 (Reversed Phase 18). The most common RP stationary phases are based on a silica support, which is surface-modified by bonding RMe2SiCl, where R is a straight chain alkyl group


id: high-performance-liquid-chromatography-20260505-5
file: data/en.wikipedia.org/wiki/High-performance_liquid_chromatography-5.md
category: reference
title: High-performance liquid chromatography
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/High-performance_liquid_chromatography
date_saved: 2026-05-05T10:04:47.433046+00:00
instance: kb-cron
parent: high-performance-liquid-chromatography-20260505-0
summary:
=== Size-exclusion chromatography === Size-exclusion chromatography (SEC) separates polymer molecules and biomolecules based on differences in their molecular size (actually by a particle's Stokes radius). The separation process is based on the ability of sample molecules to permeate through the pores of gel spheres, packed inside the column, and is dependent on the relative size of analyte molecules and the respective pore size of the absorbent. The process also relies on the absence of any interactions with the packing material surface. Two types of SEC are usually termed: Gel permeation chromatography (GPC)—separation of synthetic polymers (aqueous or organic soluble). GPC is a powerful technique for polymer characterization using primarily organic solvents. Gel filtration chromatography (GFC)—separation of water-soluble biopolymers. GFC uses primarily aqueous solvents (typically for aqueous soluble biopolymers, such as proteins, etc.). The separation principle in SEC is based on the fully, or partially penetrating of the high molecular weight substances of the sample into the porous stationary-phase particles during their transport through column. The mobile-phase eluent is selected in such a way that it totally prevents interactions with the stationary phase's surface. Under these conditions, the smaller the size of the molecule, the more it is able to penetrate


id: high-performance-liquid-chromatography-20260505-6
file: data/en.wikipedia.org/wiki/High-performance_liquid_chromatography-6.md
category: reference
title: High-performance liquid chromatography
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/High-performance_liquid_chromatography
date_saved: 2026-05-05T10:04:47.433046+00:00
instance: kb-cron
parent: high-performance-liquid-chromatography-20260505-0
summary:
=== Aqueous normal-phase chromatography === Aqueous normal-phase chromatography (ANP) is also called hydrophilic interaction liquid chromatography (HILIC). This is a chromatographic technique which encompasses the mobile phase region between reversed-phase chromatography (RP) and organic normal phase chromatography (ONP). HILIC is used to achieve unique selectivity for hydrophilic compounds, showing normal phase elution order, using "reversed-phase solvents", i.e., relatively polar mostly non-aqueous solvents in the mobile phase. Many biological molecules, especially those found in biological fluids, are small polar compounds that do not retain well by reversed phase-HPLC. This has made hydrophilic interaction LC (HILIC) an attractive alternative and useful approach for analysis of polar molecules. Additionally, because HILIC is routinely used with traditional aqueous mixtures with polar organic solvents such as ACN and methanol, it can be easily coupled to MS. == Isocratic and gradient elution == A separation in which the mobile phase composition remains constant throughout the procedure is termed isocratic (meaning constant composition). The word was coined by Csaba Horvath who was one of the pioneers of HPLC. The mobile phase composition does not have to remain constant. A separation in which the mobile phase composition is changed during the separation process is described as a gradient


id: high-performance-liquid-chromatography-20260505-7
file: data/en.wikipedia.org/wiki/High-performance_liquid_chromatography-7.md
category: reference
title: High-performance liquid chromatography
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/High-performance_liquid_chromatography
date_saved: 2026-05-05T10:04:47.433046+00:00
instance: kb-cron
parent: high-performance-liquid-chromatography-20260505-0
summary:
The parameters are largely derived from two sets of chromatographic theory: plate theory (as part of partition chromatography), and the rate theory of chromatography / van Deemter equation. Of course, they can be put in practice through analysis of HPLC chromatograms, although rate theory is considered the more accurate theory. They are analogous to the calculation of retention factor for a paper chromatography separation, but describes how well HPLC separates a mixture into two or more components that are detected as peaks (bands) on a chromatogram. The HPLC parameters are the: efficiency factor(N), the retention factor (kappa prime), and the separation factor (alpha). Together the factors are variables in a resolution equation, which describes how well two components' peaks separated or overlapped each other. These parameters are mostly only used for describing HPLC reversed phase and HPLC normal phase separations, since those separations tend to be more subtle than other HPLC modes (e.g., ion exchange and size exclusion). Void volume is the amount of space in a column that is occupied by solvent. It is the space within the column that is outside of the column's internal packing material. Void volume is measured on a chromatogram as the first component


id: high-performance-liquid-chromatography-20260505-8
file: data/en.wikipedia.org/wiki/High-performance_liquid_chromatography-8.md
category: reference
title: High-performance liquid chromatography
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/High-performance_liquid_chromatography
date_saved: 2026-05-05T10:04:47.433046+00:00
instance: kb-cron
parent: high-performance-liquid-chromatography-20260505-0
summary:
=== Pump pressure === Pumps vary in pressure capacity, but their performance is measured on their ability to yield a consistent and reproducible volumetric flow rate. Pressure may reach as high as 60 MPa (6000 lbf/in2), or about 600 atmospheres. Modern HPLC systems have been improved to work at much higher pressures, and therefore are able to use much smaller particle sizes in the columns (<2 μm). These "ultra high performance liquid chromatography" systems or UHPLCs, which could also be known as ultra high pressure chromatography systems, can work at up to 120 MPa (17,405 lbf/in2), or about 1200 atmospheres. The term "UPLC" is a trademark of the Waters Corporation, but is sometimes used to refer to the more general technique of UHPLC. === Detectors === HPLC detectors fall into two main categories: universal or selective. Universal detectors typically measure a bulk property (e.g., refractive index) by measuring a difference of a physical property between the mobile phase and mobile phase with solute while selective detectors measure a solute property (e.g., UV-Vis absorbance) by simply responding to the physical or chemical property of the solute. HPLC most commonly uses a UV-Vis absorbance detector; however, a wide range of other chromatography


id: high-performance-liquid-chromatography-20260505-9
file: data/en.wikipedia.org/wiki/High-performance_liquid_chromatography-9.md
category: reference
title: High-performance liquid chromatography
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/High-performance_liquid_chromatography
date_saved: 2026-05-05T10:04:47.433046+00:00
instance: kb-cron
parent: high-performance-liquid-chromatography-20260505-0
summary:
=== Medical and health sciences === Medical use of HPLC typically use mass spectrometer (MS) as the detector, so the technique is called LC-MS or LC-MS/MS for tandem MS, where two types of MS are operated sequentially. When the HPLC instrument is connected to more than one detector, it is called a hyphenated LC system. Pharmaceutical applications are the major users of HPLC, LC-MS and LC-MS/MS. This includes drug development and pharmacology, which is the scientific study of the effects of drugs and chemicals on living organisms, personalized medicine, public health and diagnostics. While urine is the most common medium for analyzing drug concentrations, blood serum is the sample collected for most medical analyses with HPLC. One of the most important roles of LC-MS and LC-MS/MS in the clinical lab is the Newborn Screening (NBS) for metabolic disorders and follow-up diagnostics. The infants' samples come in the shape of dried blood spot (DBS), which is simple to prepare and transport, enabling safe and accessible diagnostics, both locally and globally. Other methods of detection of molecules that are useful for clinical studies have been tested against HPLC, namely immunoassays. In one example of this, competitive protein binding assays (CPBA) and HPLC


id: high-resolution-transmission-electron-microscopy-20260505-0
file: data/en.wikipedia.org/wiki/High-resolution_transmission_electron_microscopy-0.md
category: reference
title: High-resolution transmission electron microscopy
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/High-resolution_transmission_electron_microscopy
date_saved: 2026-05-05T10:04:48.671041+00:00
instance: kb-cron
parent: high-resolution-transmission-electron-microscopy-20260505-0
summary:
High-resolution transmission electron microscopy is an imaging mode of specialized transmission electron microscopes that allows for direct imaging of the atomic structure of samples. It is a powerful tool to study properties of materials on the atomic scale, such as semiconductors, metals, nanoparticles and sp2-bonded carbon (e.g., graphene, nanotubes). While this term is often also used to refer to high resolution scanning transmission electron microscopy, mostly in high angle annular dark field mode, this article describes mainly the imaging of an object by recording the two-dimensional spatial wave amplitude distribution in the image plane, similar to a "classic" light microscope. For disambiguation, the technique is also sometimes referred to as phase contrast transmission electron microscopy. At present, the highest point resolution realised in high resolution transmission electron microscopy is around 0.5 ångströms (0.050 nm). At these small scales, individual atoms of a crystal and defects can be resolved. For 3-dimensional crystals, it is necessary to combine several views, taken from different angles, into a 3D map. This technique is called electron tomography. One of the difficulties with high resolution transmission electron microscopy is that image formation relies on phase contrast. In phase-contrast imaging, contrast is not intuitively interpretable, as the


id: high-resolution-transmission-electron-microscopy-20260505-1
file: data/en.wikipedia.org/wiki/High-resolution_transmission_electron_microscopy-1.md
category: reference
title: High-resolution transmission electron microscopy
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/High-resolution_transmission_electron_microscopy
date_saved: 2026-05-05T10:04:48.671041+00:00
instance: kb-cron
parent: high-resolution-transmission-electron-microscopy-20260505-0
summary:
where Cs is the spherical aberration coefficient, λ is the electron wavelength, and Δf is the defocus. In transmission electron microscopy, defocus can easily be controlled and measured to high precision. Thus one can easily alter the shape of the contrast transfer function by defocusing the sample. Contrary to optical applications, defocusing can increase the precision and interpretability of the micrographs. The aperture function cuts off beams scattered above a certain critical angle (given by the objective pole piece for ex), thus effectively limiting the attainable resolution. However it is the envelope function E(u) which usually dampens the signal of beams scattered at high angles, and imposes a maximum to the transmitted spatial frequency. This maximum determines the highest resolution attainable with a microscope and is known as the information limit. E(u) can be described as a product of single envelopes: E ( u ) = E s ( u ) E c ( u ) E d ( u ) E v ( u ) E D ( u ) , {\displaystyle E(u)=E_{s}(u)E_{c}(u)E_{d}(u)E_{v}(u)E_{D}(u),\,} due to Es(u): angular spread of the source Ec(u): chromatic aberration Ed(u): specimen drift Ev(u): specimen vibration ED(u): detector Specimen drift and vibration can be minimized


id: high-resolution-transmission-electron-microscopy-20260505-2
file: data/en.wikipedia.org/wiki/High-resolution_transmission_electron_microscopy-2.md
category: reference
title: High-resolution transmission electron microscopy
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/High-resolution_transmission_electron_microscopy
date_saved: 2026-05-05T10:04:48.671041+00:00
instance: kb-cron
parent: high-resolution-transmission-electron-microscopy-20260505-0
summary:
==== Gabor defocus ==== Gabor defocus is used in electron holography where both amplitude and phase of the image wave are recorded. One thus wants to minimize crosstalk between the two. The Gabor defocus can be expressed as a function of the Scherzer defocus as Δ f Gabor = 0.56 Δ f Scherzer {\displaystyle \Delta f_{\text{Gabor}}=0.56\Delta f_{\text{Scherzer}}} ==== Lichte defocus ==== To exploit all beams transmitted through the microscope up to the information limit, one relies on a complex method called exit wave reconstruction which consists in mathematically reversing the effect of the contrast transfer function to recover the original exit wave φe(x,u). To maximize the information throughput, Hannes Lichte proposed in 1991 a defocus of a fundamentally different nature than the Scherzer defocus: because the dampening of the envelope function scales with the first derivative of χ(u), Lichte proposed a focus minimizing the modulus of dχ(u)/du Δ f Lichte = − 0.75 C s ( u max λ ) 2 , {\displaystyle \Delta f_{\text{Lichte}}=-0.75C_{s}(u_{\max }\lambda )^{2},} where umax is the maximum transmitted spatial frequency. For the CM300 with an information limit of 0.8 Å Lichte defocus lies at −272 nm. === Exit wave reconstruction === To calculate back to


id: high-throughput-screening-20260505-0
file: data/en.wikipedia.org/wiki/High-throughput_screening-0.md
category: reference
title: High-throughput screening
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/High-throughput_screening
date_saved: 2026-05-05T10:04:49.891793+00:00
instance: kb-cron
parent: high-throughput-screening-20260505-0
summary:
High-throughput screening (HTS) is a method for scientific discovery especially used in drug discovery and relevant to the fields of biology, materials science and chemistry. Using robotics, data processing/control software, liquid handling devices, and sensitive detectors, high-throughput screening allows a researcher to quickly conduct millions of chemical, genetic, or pharmacological tests. Through this process one can quickly recognize active compounds, antibodies, or genes that modulate a particular biomolecular pathway. The results of these experiments provide starting points for drug design and for understanding the noninteraction or role of a particular location. == Assay plate preparation == The key labware or testing vessel of HTS is the microtiter plate, which is a small container, usually disposable and made of plastic, that features a grid of small, open divots called wells. In general, microplates for HTS have either 96, 192, 384, 1536, 3456 or 6144 wells. These are all multiples of 96, reflecting the original 96-well microplate with spaced wells of 8 x 12 with 9 mm spacing. Most of the wells contain test items, depending on the nature of the experiment. These could be different chemical compounds dissolved e.g. in an aqueous solution of dimethyl sulfoxide (DMSO). The wells could also


id: high-throughput-screening-20260505-1
file: data/en.wikipedia.org/wiki/High-throughput_screening-1.md
category: reference
title: High-throughput screening
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/High-throughput_screening
date_saved: 2026-05-05T10:04:49.891793+00:00
instance: kb-cron
parent: high-throughput-screening-20260505-0
summary:
A good plate design helps to identify systematic errors (especially those linked with well position) and determine what normalization should be used to remove/reduce the impact of systematic errors on both QC and hit selection. Effective analytic QC methods serve as a gatekeeper for excellent quality assays. In a typical HTS experiment, a clear distinction between a positive control and a negative reference such as a negative control is an index for good quality. Many quality-assessment measures have been proposed to measure the degree of differentiation between a positive control and a negative reference. Signal-to-background ratio, signal-to-noise ratio, signal window, assay variability ratio, and Z-factor have been adopted to evaluate data quality. Strictly standardized mean difference (SSMD) has recently been proposed for assessing data quality in HTS assays. === Hit selection === A compound with a desired size of effects in an HTS is called a hit. The process of selecting hits is called hit selection. The analytic methods for hit selection in screens without replicates (usually in primary screens) differ from those with replicates (usually in confirmatory screens). For example, the z-score method is suitable for screens without replicates whereas the t-statistic is suitable for screens with replicates. The


id: high-throughput-screening-20260505-2
file: data/en.wikipedia.org/wiki/High-throughput_screening-2.md
category: reference
title: High-throughput screening
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/High-throughput_screening
date_saved: 2026-05-05T10:04:49.891793+00:00
instance: kb-cron
parent: high-throughput-screening-20260505-0
summary:
=== Recent advances === Automation and low volume assay formats were leveraged by scientists at the NIH Chemical Genomics Center (NCGC) to develop quantitative HTS (qHTS), a paradigm to pharmacologically profile large chemical libraries through the generation of full concentration-response relationships for each compound. With accompanying curve fitting and cheminformatics software qHTS data yields half maximal effective concentration (EC50), maximal response, Hill coefficient (nH) for the entire library enabling the assessment of nascent structure activity relationships (SAR). In March 2010, research was published demonstrating an HTS process allowing 1,000 times faster screening (100 million reactions in 10 hours) at 1-millionth the cost (using 10−7 times the reagent volume) than conventional techniques using drop-based microfluidics. Drops of fluid separated by oil replace microplate wells and allow analysis and hit sorting while reagents are flowing through channels. In 2010, researchers developed a silicon sheet of lenses that can be placed over microfluidic arrays to allow the fluorescence measurement of 64 different output channels simultaneously with a single camera. This process can analyze 200,000 drops per second. In 2013, researchers have disclosed an approach with small molecules from plants. In general, it is essential to provide high-quality proof-of-concept validations early in the drug


id: high-throughput-screening-20260505-3
file: data/en.wikipedia.org/wiki/High-throughput_screening-3.md
category: reference
title: High-throughput screening
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/High-throughput_screening
date_saved: 2026-05-05T10:04:49.891793+00:00
instance: kb-cron
parent: high-throughput-screening-20260505-0
summary:
== Increasing use of HTS in academia for biomedical research == HTS is a relatively recent innovation, made feasible largely through modern advances in robotics and high-speed computer technology. It still takes a highly specialized and expensive screening lab to run an HTS operation, so in many cases a small- to moderate-size research institution will use the services of an existing HTS facility rather than set up one for itself. There is a trend in academia for universities to be their own drug discovery enterprise. These facilities, which normally are found only in industry, are now increasingly found at universities as well. UCLA, for example, features an open access HTS laboratory Molecular Screening Shared Resources (MSSR, UCLA), which can screen more than 100,000 compounds a day on a routine basis. The open access policy ensures that researchers from all over the world can take advantage of this facility without lengthy intellectual property negotiations. With a compound library of over 200,000 small molecules, the MSSR has one of the largest compound deck of all universities on the west coast. Also, the MSSR features full functional genomics capabilities (genome wide siRNA, shRNA, cDNA and CRISPR) which are complementary to small molecule efforts:


id: illite-crystallinity-20260505-0
file: data/en.wikipedia.org/wiki/Illite_crystallinity-0.md
category: reference
title: Illite crystallinity
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Illite_crystallinity
date_saved: 2026-05-05T10:04:51.050119+00:00
instance: kb-cron
parent: illite-crystallinity-20260505-0
summary:
Illite crystallinity is a technique used to classify low-grade metamorphic activity in pelitic rocks. Determining the "illite crystallinity index" allows geologists to designate what metamorphic facies and metamorphic zone the rock was formed in and to infer what temperature the rock was formed. Several crystallinity indices have been proposed in recent years, but currently the Kübler index is being used due to its reproducibility and simplicity. The Kübler index is experimentally determined by measuring the full width at half maximum for the X-ray diffraction reflection peak along the (001) crystallographic axis of the rock sample. This value is an indirect measurement of the thickness of illite/muscovite packets which denote a change in metamorphic grade. The method can be used throughout the field of geology in areas such as the petroleum industry, plate tectonics. == Progression == As stated above, the Kübler index was not always the preferred index for illite crystallinity studies in the past. Prior to the introduction of the Kübler index, there were several other indices used to classify low grade metamorphic rocks. Two of the more popular methods of the past are the Weaver index and the Weber index, introduced in 1960 and 1972 respectively. These studies


id: inductively-coupled-plasma-atomic-emission-spectroscopy-20260505-0
file: data/en.wikipedia.org/wiki/Inductively_coupled_plasma_atomic_emission_spectroscopy-0.md
category: reference
title: Inductively coupled plasma atomic emission spectroscopy
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Inductively_coupled_plasma_atomic_emission_spectroscopy
date_saved: 2026-05-05T10:04:52.213071+00:00
instance: kb-cron
parent: inductively-coupled-plasma-atomic-emission-spectroscopy-20260505-0
summary:
Inductively coupled plasma atomic emission spectroscopy (ICP-AES), also referred to as inductively coupled plasma optical emission spectroscopy (ICP-OES), is an analytical technique used for the detection of chemical elements. It is a type of emission spectroscopy that uses the inductively coupled plasma to produce excited atoms and ions that emit electromagnetic radiation at wavelengths characteristic of a particular element. The plasma is a high temperature source of ionised source gas (often argon). The plasma is sustained and maintained by inductive coupling from electrical coils at megahertz frequencies. The source temperature is in the range from 6000 to 10,000 K. The intensity of the emissions from various wavelengths of light are proportional to the concentrations of the elements within the sample. == Mechanism == The ICP-AES is composed of two parts: the ICP and the optical spectrometer. The ICP torch consists of 3 concentric quartz glass tubes. The output or "work" coil of the radio frequency (RF) generator surrounds part of this quartz torch. Argon gas is typically used to create the plasma. Modern innovation has made it possible to use nitrogen gas for the ICP The ICPs have two operation modes, called capacitive (E) mode with low plasma density and


id: inductively-coupled-plasma-mass-spectrometry-20260505-0
file: data/en.wikipedia.org/wiki/Inductively_coupled_plasma_mass_spectrometry-0.md
category: reference
title: Inductively coupled plasma mass spectrometry
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Inductively_coupled_plasma_mass_spectrometry
date_saved: 2026-05-05T10:04:53.426335+00:00
instance: kb-cron
parent: inductively-coupled-plasma-mass-spectrometry-20260505-0
summary:
Inductively coupled plasma mass spectrometry (ICP-MS) is a type of mass spectrometry that uses an inductively coupled plasma to ionize the sample. It atomizes the sample and creates atomic and small polyatomic ions, which are then detected. It is known and used for its ability to detect metals and several non-metals in liquid samples at very low concentrations. It can detect different isotopes of the same element, which makes it a versatile tool in isotopic labeling. Compared to atomic absorption spectroscopy, ICP-MS has greater speed, precision, and sensitivity. However, compared with other types of mass spectrometry, such as thermal ionization mass spectrometry (TIMS) and glow discharge mass spectrometry (GD-MS), ICP-MS introduces many interfering species: argon from the plasma, component gases of air that leak through the cone orifices, and contamination from glassware and the cones. == Components == === Inductively coupled plasma === An inductively coupled plasma is a plasma that is energized (ionized) by inductively heating the gas with an electromagnetic coil, and contains a sufficient concentration of ions and electrons to make the gas electrically conductive. Not all of the gas needs to be ionized for the gas to have the characteristics of a plasma; as little as


id: inductively-coupled-plasma-mass-spectrometry-20260505-1
file: data/en.wikipedia.org/wiki/Inductively_coupled_plasma_mass_spectrometry-1.md
category: reference
title: Inductively coupled plasma mass spectrometry
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Inductively_coupled_plasma_mass_spectrometry
date_saved: 2026-05-05T10:04:53.426335+00:00
instance: kb-cron
parent: inductively-coupled-plasma-mass-spectrometry-20260505-0
summary:
=== Mass spectrometry === For coupling to mass spectrometry, the ions from the plasma are extracted through a series of cones into a mass spectrometer, usually a quadrupole. The ions are separated on the basis of their mass-to-charge ratio and a detector receives an ion signal proportional to the concentration. The concentration of a sample can be determined through calibration with certified reference material such as single or multi-element reference standards. ICP-MS also lends itself to quantitative determinations through isotope dilution, a single point method based on an isotopically enriched standard. In order to increase reproducibility and compensate for errors by sensitivity variation, an internal standard can be added. Other mass analyzers coupled to ICP systems include double focusing magnetic-electrostatic sector systems with both single and multiple collector, as well as time of flight systems (both axial and orthogonal accelerators have been used). == Applications == One of the largest volume uses for ICP-MS is in the medical and forensic field, specifically, toxicology. A physician may order a metal assay for a number of reasons, such as suspicion of heavy metal poisoning, metabolic concerns, and even hepatological issues. Depending on the specific parameters unique to each patient's diagnostic plan, samples


id: inductively-coupled-plasma-mass-spectrometry-20260505-2
file: data/en.wikipedia.org/wiki/Inductively_coupled_plasma_mass_spectrometry-2.md
category: reference
title: Inductively coupled plasma mass spectrometry
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Inductively_coupled_plasma_mass_spectrometry
date_saved: 2026-05-05T10:04:53.426335+00:00
instance: kb-cron
parent: inductively-coupled-plasma-mass-spectrometry-20260505-0
summary:
Cosmetics, such as lipstick, recovered from a crime scene may provide valuable forensic information. Lipstick smears left on cigarette butts, glassware, clothing, bedding; napkins, paper, etc. may be valuable evidence. Lipstick recovered from clothing or skin may also indicate physical contact between individuals. Forensic analysis of recovered lipstick smear evidence can provide valuable information on the recent activities of a victim or suspect. Trace elemental analysis of lipstick smears could be used to complement existing visual comparative procedures to determine the lipstick brand and color. Single Particle Inductively Coupled Plasma Mass Spectroscopy (SP ICP-MS) was designed for particle suspensions in 2000 by Claude Degueldre. He first tested this new methodology at the Forel Institute of the University of Geneva and presented this new analytical approach at the 'Colloid 2oo2' symposium during the spring 2002 meeting of the EMRS, and in the proceedings in 2003. This study presents the theory of SP ICP-MS and the results of tests carried out on clay particles (montmorillonite) as well as other suspensions of colloids. This method was then tested on thorium dioxide nanoparticles by Degueldre & Favarger (2004), zirconium dioxide by Degueldre et al (2004) and gold nanoparticles, which are used as a substrate


id: inductively-coupled-plasma-mass-spectrometry-20260505-3
file: data/en.wikipedia.org/wiki/Inductively_coupled_plasma_mass_spectrometry-3.md
category: reference
title: Inductively coupled plasma mass spectrometry
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Inductively_coupled_plasma_mass_spectrometry
date_saved: 2026-05-05T10:04:53.426335+00:00
instance: kb-cron
parent: inductively-coupled-plasma-mass-spectrometry-20260505-0
summary:
=== Elemental analysis === The ICP-MS allows determination of elements with atomic mass ranges 7 to 250 (Li to U), and sometimes higher. Some masses are prohibited, such as 40 Da, due to the abundance of argon in the sample. Other interference regions may include mass 80 (due to the argon dimer) and mass 56 (due to ArO), the latter of which greatly hinders Fe detection unless the instrument is fitted with a reaction chamber. Such interferences can be reduced by using a high resolution ICP-MS (HR-ICP-MS) which uses two or more slits to constrict the beam and distinguish between nearby peaks. This comes at the cost of sensitivity. For example, distinguishing iron from argon requires a resolving power of about 10,000, which may reduce the iron sensitivity by around 99%. Interfering species can alternatively be distinguished through the use of a collision chamber, which can filter gasses by either chemical reaction or physical collision. A single collector ICP-MS may use a multiplier in pulse counting mode to amplify very low signals, an attenuation grid or a multiplier in analogue mode to detect medium signals, and a Faraday cup/bucket to detect larger signals. A multi-collector ICP-MS may have more than


id: inductively-coupled-plasma-mass-spectrometry-20260505-4
file: data/en.wikipedia.org/wiki/Inductively_coupled_plasma_mass_spectrometry-4.md
category: reference
title: Inductively coupled plasma mass spectrometry
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Inductively_coupled_plasma_mass_spectrometry
date_saved: 2026-05-05T10:04:53.426335+00:00
instance: kb-cron
parent: inductively-coupled-plasma-mass-spectrometry-20260505-0
summary:
=== Sample introduction === The first step in analysis is the introduction of the sample. This has been achieved in ICP-MS through a variety of means. The most common method is the use of analytical nebulizers. A nebulizer converts liquids into an aerosol, and that aerosol can then be swept into the plasma to create the ions. Nebulizers work best with simple liquid samples (i.e. solutions). However, there have been instances of their use with more complex materials like a slurry. Many varieties of nebulizers have been coupled to ICP-MS, including pneumatic, cross-flow, Babington, ultrasonic, and desolvating types. The aerosol generated is often treated to limit it to only smallest droplets, commonly by means of a Peltier cooled double pass or cyclonic spray chamber. Use of autosamplers makes this easier and faster, especially for routine work and large numbers of samples. A Desolvating Nebuliser (DSN) may also be used; this uses a long heated capillary, coated with a fluoropolymer membrane, to remove most of the solvent and reduce the load on the plasma. Matrix removal introduction systems are sometimes used for samples, such as seawater, where the species of interest are at trace levels, and are surrounded by much more


id: inductively-coupled-plasma-mass-spectrometry-20260505-5
file: data/en.wikipedia.org/wiki/Inductively_coupled_plasma_mass_spectrometry-5.md
category: reference
title: Inductively coupled plasma mass spectrometry
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Inductively_coupled_plasma_mass_spectrometry
date_saved: 2026-05-05T10:04:53.426335+00:00
instance: kb-cron
parent: inductively-coupled-plasma-mass-spectrometry-20260505-0
summary:
==== Advantage of argon ==== Making the plasma from argon, instead of other gases, has several advantages. First, argon is abundant (in the atmosphere, as a result of the radioactive decay of potassium) and therefore cheaper than other noble gases. Argon also has a higher first ionization potential than all other elements except He, F, and Ne. Because of this high ionization energy, the reaction (Ar+ + e− → Ar) is more energetically favorable than the reaction (M+ + e− → M). This ensures that the sample remains ionized (as M+) so that the mass spectrometer can detect it. Argon can be purchased for use with the ICP-MS in either a refrigerated liquid or a gas form. However it is important to note that whichever form of argon purchased, it should have a guaranteed purity of 99.9% Argon at a minimum. It is important to determine which type of argon will be best suited for the specific situation. Liquid argon is typically cheaper and can be stored in a greater quantity as opposed to the gas form, which is more expensive and takes up more tank space. If the instrument is in an environment where it gets infrequent use, then


id: inductively-coupled-plasma-mass-spectrometry-20260505-6
file: data/en.wikipedia.org/wiki/Inductively_coupled_plasma_mass_spectrometry-6.md
category: reference
title: Inductively coupled plasma mass spectrometry
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Inductively_coupled_plasma_mass_spectrometry
date_saved: 2026-05-05T10:04:53.426335+00:00
instance: kb-cron
parent: inductively-coupled-plasma-mass-spectrometry-20260505-0
summary:
=== Ion optics === Before mass separation, a beam of positive ions has to be extracted from the plasma and focused into the mass-analyzer. It is important to separate the ions from UV photons, energetic neutrals and from any solid particles that may have been carried into the instrument from the ICP. Traditionally, ICP-MS instruments have used transmitting ion lens arrangements for this purpose. Examples include the Einzel lens, the Barrel lens, Agilent's Omega Lens and Perkin-Elmer's Shadow Stop. Another approach is to use ion guides (quadrupoles, hexapoles, or octopoles) to guide the ions into mass analyzer along a path away from the trajectory of photons or neutral particles. Yet another approach is Varian patented used by Analytik Jena ICP-MS 90 degrees reflecting parabolic "Ion Mirror" optics, which are claimed to provide more efficient ion transport into the mass-analyzer, resulting in better sensitivity and reduced background. Analytik Jena ICP-MS PQMS is the most sensitive instrument on the market. A sector ICP-MS will commonly have four sections: an extraction acceleration region, steering lenses, an electrostatic sector and a magnetic sector. The first region takes ions from the plasma and accelerates them using a high voltage. The second uses may use a


id: inelastic-electron-tunneling-spectroscopy-20260505-0
file: data/en.wikipedia.org/wiki/Inelastic_electron_tunneling_spectroscopy-0.md
category: reference
title: Inelastic electron tunneling spectroscopy
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Inelastic_electron_tunneling_spectroscopy
date_saved: 2026-05-05T10:04:54.648481+00:00
instance: kb-cron
parent: inelastic-electron-tunneling-spectroscopy-20260505-0
summary:
Inelastic electron tunneling spectroscopy (IETS) is an experimental tool for studying the vibrations of molecular adsorbates on metal oxides. It yields vibrational spectra of the adsorbates with high resolution (< 0.5 meV) and high sensitivity (< 1013 molecules are required to provide a spectrum). An additional advantage is the fact that optically forbidden transitions may be observed as well. Within IETS, an oxide layer with molecules adsorbed on it is put between two metal plates. A bias voltage is applied between the two contacts. An energy diagram of the metal-oxide-metal device under bias is shown in the top figure. The metal contacts are characterized by a constant density of states, filled up to the Fermi energy. The metals are assumed to be equal. The adsorbates are situated on the oxide material. They are represented by a single bridge electronic level, which is the upper dashed line. If the insulator is thin enough, there is a finite probability that the incident electron tunnels through the barrier. Since the energy of the electron is not changed by this process, it is an elastic process. This is shown in the left figure. Some of the tunneling electrons can lose energy by exciting vibrations


id: ion-cyclotron-resonance-20260505-0
file: data/en.wikipedia.org/wiki/Ion_cyclotron_resonance-0.md
category: reference
title: Ion cyclotron resonance
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Ion_cyclotron_resonance
date_saved: 2026-05-05T10:04:55.782835+00:00
instance: kb-cron
parent: ion-cyclotron-resonance-20260505-0
summary:
Ion cyclotron resonance is a phenomenon related to the movement of ions in a magnetic field. It is used for accelerating ions in a cyclotron, and for measuring the masses of an ionized analyte in mass spectrometry, particularly with Fourier transform ion cyclotron resonance mass spectrometers. It can also be used to follow the kinetics of chemical reactions in a dilute gas mixture, provided these involve charged species. == Definition of the resonant frequency == An ion in a static and uniform magnetic field will move in a circle due to the Lorentz force. The angular frequency of this cyclotron motion for a given magnetic field strength B is given by ω = 2 π f = z e B m , {\displaystyle \omega =2\pi f={\frac {zeB}{m}},} where z is the number of positive or negative charges of the ion, e is the elementary charge and m is the mass of the ion. An electric excitation signal having a frequency f will therefore resonate with ions having a mass-to-charge ratio m/z given by m z = e B 2 π f . {\displaystyle {\frac {m}{z}}={\frac {eB}{2\pi f}}.} The circular motion may be superimposed with a uniform axial motion, resulting in


id: isothermal-titration-calorimetry-20260505-0
file: data/en.wikipedia.org/wiki/Isothermal_titration_calorimetry-0.md
category: reference
title: Isothermal titration calorimetry
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Isothermal_titration_calorimetry
date_saved: 2026-05-05T10:04:56.942229+00:00
instance: kb-cron
parent: isothermal-titration-calorimetry-20260505-0
summary:
In chemical thermodynamics, isothermal titration calorimetry (ITC) is a physical technique used to determine the thermodynamic parameters of interactions in solution. ITC is the only technique capable of comprehensively characterizing thermodynamic and kinetic profiles of a molecular interaction by simultaneously determining binding constants ( K a {\displaystyle K_{a}} ), reaction stoichiometry ( n {\displaystyle n} ), enthalpy ( Δ H {\displaystyle \Delta H} ), Gibbs free energy ( Δ G {\displaystyle \Delta G} ) and entropy ( Δ S {\displaystyle \Delta S} ) within a single experiment. It consists of two cells which are enclosed in an adiabatic jacket. The compounds to be studied are placed in the sample cell, while the other cell, the reference cell, is used as a control and contains the buffer in which the sample is dissolved. The technique quantifies the heat released or absorbed during the binding process by incrementally adding one reactant (via a syringe) to another (in the sample cell) while maintaining constant temperature and pressure. Heat-sensing devices within the ITC detect temperature variations between two cells, transmitting this information to heaters that adjust accordingly to restore thermal equilibrium between the cells. This energy is converted into binding enthalpy using the information


id: isothermal-titration-calorimetry-20260505-1
file: data/en.wikipedia.org/wiki/Isothermal_titration_calorimetry-1.md
category: reference
title: Isothermal titration calorimetry
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Isothermal_titration_calorimetry
date_saved: 2026-05-05T10:04:56.942229+00:00
instance: kb-cron
parent: isothermal-titration-calorimetry-20260505-0
summary:
An isothermal titration calorimeter is composed of two identical cells made of a highly efficient thermally conducting and chemically inert material such as Hastelloy alloy or gold, surrounded by an adiabatic jacket. In this setup, one of the cells, the sample cell, holds the solution of one reactant, and the other cell, the reference cell, is filled with either a buffer or water. The second reactant, which has a higher concentration than the first, is placed in a syringe and gradually injected into the sample cell in small aliquots throughout the titration process. This process is semi-automated and the sensitive thermopile/thermocouple circuits are used to detect temperature differences between the reference cell (filled with buffer or water) and the sample cell containing the macromolecule. Prior to addition of ligand, a constant power (<1 mW) is applied to the reference cell. This directs a feedback circuit, activating a heater located on the sample cell. During the experiment, ligand is titrated into the sample cell in precisely known aliquots, causing heat to be either taken up or evolved (depending on the nature of the reaction). Measurements consist of the time-dependent input of power required to maintain equal temperatures between the sample and


id: isothermal-titration-calorimetry-20260505-2
file: data/en.wikipedia.org/wiki/Isothermal_titration_calorimetry-2.md
category: reference
title: Isothermal titration calorimetry
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Isothermal_titration_calorimetry
date_saved: 2026-05-05T10:04:56.942229+00:00
instance: kb-cron
parent: isothermal-titration-calorimetry-20260505-0
summary:
=== Post-hoc analysis and proton inventory === It is necessary to conduct a post-hoc analysis to determine the buffer or solvent-independent enthalpy from the experimental thermodynamics. The collected experimental data reflects not only the binding thermodynamics of the interaction of interest, but any contributing competing equilibria associated to it. A post-hoc analysis can be performed to determine the buffer or solvent-independent enthalpy from the experimental thermodynamics, by simply going through the process of Hess' law. Below example shows a simple interaction between a metal ion (M) and a ligand (L). B represents the buffer used for this interaction and H + {\displaystyle {\ce {H+}}} represents protons. M − B ↽ − − ⇀ M + B {\displaystyle {\ce {M - B <=> M + B}}} − Δ H MB {\displaystyle {\ce {-\Delta H_{MB}}}} L − H ↽ − − ⇀ L + H + {\displaystyle {\ce {L - H <=> L + H+}}} − ( n H + ) Δ H L H {\displaystyle -(n_{H+})\Delta H_{LH}} H + + B ↽ − − ⇀ H − B {\displaystyle {\ce {H+ + B <=> H - B}}} ( n H + ) Δ H B H {\displaystyle (n_{H+})\Delta H_{BH}} M +


id: isothermal-titration-calorimetry-20260505-3
file: data/en.wikipedia.org/wiki/Isothermal_titration_calorimetry-3.md
category: reference
title: Isothermal titration calorimetry
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Isothermal_titration_calorimetry
date_saved: 2026-05-05T10:04:56.942229+00:00
instance: kb-cron
parent: isothermal-titration-calorimetry-20260505-0
summary:
=== Chiral chemistry === Applying the ideas above, chirality of organometallic compounds can be deduced as well with this technique. Each chiral compound has its own unique properties and binding mechanisms that are comparable to each other, which leads to differences in thermodynamic properties. By binding chiral solutions in a binding site can deduce the type of chirality and depending on the purpose, which chiral compound is more suitable for binding. === Metal binding interactions === Binding metal ions to protein and other components of biological material is one of the most popular uses of ITC, since ovotransferrin to ferric iron binding study published by Lin et al. from MicroCal Inc. This is due to some of the metal ions utilized in biological systems having d10 electron configuration which cannot be studied with other common techniques such as UV-vis spectrophotometry or electron paramagnetic resonance. It is also closely related to biochemical and medicinal studies due to the large abundance of metal binding enzymes in biological systems. === Carbon nanotubes and related materials === The technique has been well utilized in studying carbon nanotubes to determine thermodynamic binding interactions with biological molecules and graphene composite interactions. Another notable use of ITC


id: isotope-dilution-20260505-0
file: data/en.wikipedia.org/wiki/Isotope_dilution-0.md
category: reference
title: Isotope dilution
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Isotope_dilution
date_saved: 2026-05-05T10:04:58.243186+00:00
instance: kb-cron
parent: isotope-dilution-20260505-0
summary:
Isotope dilution analysis is a method of determining the quantity of chemical substances. In its most simple conception, the method of isotope dilution comprises the addition of known amounts of isotopically enriched substance to the analyzed sample. Mixing of the isotopic standard with the sample effectively "dilutes" the isotopic enrichment of the standard and this forms the basis for the isotope dilution method. Isotope dilution is classified as a method of internal standardisation, because the standard (isotopically enriched form of analyte) is added directly to the sample. In addition, unlike traditional analytical methods which rely on signal intensity, isotope dilution employs signal ratios. Owing to both of these advantages, the method of isotope dilution is regarded among chemistry measurement methods of the highest metrological standing. Isotopes are variants of a particular chemical element which differ in neutron number. All isotopes of a given element have the same number of protons in each atom. The term isotope is formed from the Greek roots isos (ἴσος "equal") and topos (τόπος "place"), meaning "the same place"; thus, the meaning behind the name is that different isotopes of a single element occupy the same position on the periodic table. == Early history == Analytical


id: isotope-dilution-20260505-1
file: data/en.wikipedia.org/wiki/Isotope_dilution-1.md
category: reference
title: Isotope dilution
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Isotope_dilution
date_saved: 2026-05-05T10:04:58.243186+00:00
instance: kb-cron
parent: isotope-dilution-20260505-0
summary:
n A = n B R B − R A B R A B − R A × 1 + R A 1 + R B {\displaystyle n_{\mathrm {A} }=n_{\mathrm {B} }{\frac {R_{\mathrm {B} }-R_{\mathrm {AB} }}{R_{\mathrm {AB} }-R_{\mathrm {A} }}}\times {\frac {1+R_{\mathrm {A} }}{1+R_{\mathrm {B} }}}} In a typical gas chromatography analysis, isotopic dilution can decrease the uncertainty of the measurement results from 5% to 1%. It can also be used in mass spectrometry (commonly referred to as isotopic dilution mass spectrometry or IDMS), in which the isotopic ratio can be determined with precision typically better than 0.25%. === Optimum composition of the blend === In a simplified manner, the uncertainty of the measurement results is largely determined from the measurement of RAB: u ( n A ) 2 ∝ ( ∂ n A ∂ R A B ) 2 u ( R A B ) 2 = n A 2 ( R A − R B ) 2 ( R A − R A B ) 2 ( R A B − R B ) 2 u ( R A B ) 2 {\displaystyle u(n_{\mathrm {A} })^{2}\propto \left({\frac {\partial {n_{\mathrm {A} }}}{\partial R_{\mathrm {AB} }}}\right)^{2}u(R_{\mathrm {AB} })^{2}=n_{\mathrm {A}


id: job-plot-20260505-0
file: data/en.wikipedia.org/wiki/Job_plot-0.md
category: reference
title: Job plot
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Job_plot
date_saved: 2026-05-05T10:04:59.395475+00:00
instance: kb-cron
parent: job-plot-20260505-0
summary:
Within chemistry, a Job plot, otherwise known as the method of continuous variation or Job's method, is a method used in analytical chemistry to determine the stoichiometry of a binding event. The method is named after Paul Job and is also used in instrumental analysis and advanced chemical equilibrium texts and research articles. Job first published his method in 1928, while studying the associations of ions in solution. By plotting the UV absorbance of a solution of Tl(NO3)/NH3 against the mole fraction of Tl(NO3), he produced a graph which provided information about the equilibrium complexes present in solution. == Theory == In solutions where two species are present (i.e. species A and species B), one species (A) may bind to the other species (B). In some cases, more than one A will bind with a single B. One way to determine the amount of A binding to B is by using a Job plot. In this method, the sum of the molar concentrations of the two binding partners (e.g. a protein and ligand or a metal and a ligand) is held constant, but their mole fractions are varied. An observable that is proportional to complex formation (such as absorption signal


id: kymograph-20260505-0
file: data/en.wikipedia.org/wiki/Kymograph-0.md
category: reference
title: Kymograph
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Kymograph
date_saved: 2026-05-05T10:05:00.622856+00:00
instance: kb-cron
parent: kymograph-20260505-0
summary:
A kymograph (from Greek κῦμα, swell or wave + γραφή, writing; also called a kymographion) is a type of two-dimensional plot that represents spatial position or signal intensity over time. In its modern usage, a kymograph is typically a space–time plot used in fields such as microscopy, cell biology, and speech science to track dynamic processes. These plots are generated by extracting intensity values along a predefined path across sequential image frames. The resulting image reduces the dimension to show time on one axis and sequential spatial information on the other. Using this technique allows for the visualization of dynamics within the image sequence, often by measuring the resulting slope of lines or streaks. This allows researchers to quantify velocity and directionality of movement, especially in applications like mitochondrial transport, vesicle trafficking, or vocal fold vibration. Although they reduce spatial information to a one-dimensional line, kymographs offer high temporal resolution and are often used alongside or in place of particle tracking techniques. == Kymograph device == A kymograph is also an analog device that draws a graphical representation of spatial position over time. The graphical representation is a graph in which the y axis shows position and the x axis


id: laser-microprobe-mass-spectrometer-20260505-0
file: data/en.wikipedia.org/wiki/Laser_microprobe_mass_spectrometer-0.md
category: reference
title: Laser microprobe mass spectrometer
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Laser_microprobe_mass_spectrometer
date_saved: 2026-05-05T10:05:01.795644+00:00
instance: kb-cron
parent: laser-microprobe-mass-spectrometer-20260505-0
summary:
A laser microprobe mass spectrometer (LMMS), also laser microprobe mass analyzer (LAMMA), laser ionization mass spectrometer (LIMS), or laser ionization mass analyzer (LIMA) is a mass spectrometer that uses a focused laser for microanalysis. It employs local ionization by a pulsed laser and subsequent mass analysis of the generated ions. == Methods == In laser microprobe mass analysis, a highly focused laser beam is pulsed on a micro sample usually with a volume of approximately 1 microliter. The resulting ions generated by this laser are then analyzed with time-of-flight mass spectrometry to give composition, concentration, and in the case of organic molecules structural information. Unlike other methods of microprobe analysis which involve ions or electrons, the LMMS microproble fires an ultraviolet pulse in order to create ions. == Advantages == LMMS is relatively simple to operate compared to other methods. Furthermore, its strengths include its ability to analyze biological materials to detect certain compounds (such as metals or organic materials). == Sample preparation == LAMMA is particular about the sample which is used. The sample must be small and thin. Ionization of too much material results in a large microplasma whose time spread and ion energy distribution entering the mass


id: laser-induced-breakdown-spectroscopy-20260505-0
file: data/en.wikipedia.org/wiki/Laser-induced_breakdown_spectroscopy-0.md
category: reference
title: Laser-induced breakdown spectroscopy
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Laser-induced_breakdown_spectroscopy
date_saved: 2026-05-05T10:05:02.976424+00:00
instance: kb-cron
parent: laser-induced-breakdown-spectroscopy-20260505-0
summary:
Laser-induced breakdown spectroscopy (LIBS) is a type of atomic emission spectroscopy which uses a highly energetic laser pulse as the excitation source. The laser is focused to form a plasma, which atomizes and excites samples. The formation of the plasma only begins when the focused laser achieves a certain threshold for optical breakdown, which generally depends on the environment and the target material. == 2000s developments == From 2000 to 2010, the U.S. Army Research Laboratory (ARL) researched potential extensions to LIBS technology, which focused on hazardous material detection. Applications investigated at ARL included the standoff detection of explosive residues and other hazardous materials, plastic landmine discrimination, and material characterization of various metal alloys and polymers. Results presented by ARL suggest that LIBS may be able to discriminate between energetic and non-energetic materials. === Research === Broadband high-resolution spectrometers were developed in 2000 and commercialized in 2003. Designed for material analysis, the spectrometer allowed the LIBS system to be sensitive to chemical elements in low concentration. ARL LIBS applications studied from 2000 to 2010 included: Tested for detection of Halon alternative agents Tested a field-portable LIBS system for the detection of lead in soil and paint Studied the spectral emission


id: laser-induced-breakdown-spectroscopy-20260505-1
file: data/en.wikipedia.org/wiki/Laser-induced_breakdown_spectroscopy-1.md
category: reference
title: Laser-induced breakdown spectroscopy
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Laser-induced_breakdown_spectroscopy
date_saved: 2026-05-05T10:05:02.976424+00:00
instance: kb-cron
parent: laser-induced-breakdown-spectroscopy-20260505-0
summary:
== LIBS for food analysis == Recently, LIBS has been investigated as a fast, micro-destructive food analysis tool. It is considered a potential analytical tool for qualitative and quantitative chemical analysis, making it suitable as a PAT (Process Analytical Technology) or portable tool. Milk, bakery products, tea, vegetable oils, water, cereals, flour, potatoes, palm date and different types of meat have been analyzed using LIBS. Few studies have shown its potential as an adulteration detection tool for certain foods. LIBS has also been evaluated as a promising elemental imaging technique in meat. In 2019, researchers of the University of York and of the Liverpool John Moores University employed LIBS for studying 12 European oysters (Ostrea edulis, Linnaeus, 1758) from the Late Mesolithic shell midden at Conors Island (Republic of Ireland). The results highlighted the applicability of LIBS to determine prehistoric seasonality practices as well as biological age and growth at an improved rate and reduced cost than was previously achievable. == See also == Atomic spectroscopy Laser ablation Laser-induced fluorescence List of surface analysis methods Photoacoustic spectroscopy Raman spectroscopy Spectroscopy == References == Lee, Won-Bae; Wu, Jianyong; Lee, Yong-Ill; Sneddon, Joseph (2004). "Recent Applications of Laser-Induced Breakdown Spectrometry: A Review


id: length-measurement-20260505-0
file: data/en.wikipedia.org/wiki/Length_measurement-0.md
category: reference
title: Length measurement
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Length_measurement
date_saved: 2026-05-05T10:05:04.164620+00:00
instance: kb-cron
parent: length-measurement-20260505-0
summary:
Length measurement, distance measurement, or range measurement (ranging) all refer to the many ways in which length, distance, or range can be measured. The most commonly used approaches are the rulers, followed by transit-time methods and the interferometer methods based upon the speed of light. Surveying is one ancient use of measuring long distances. For tiny objects such as crystals and diffraction gratings, diffraction is used with X-ray light, or even electron beams. Measurement techniques for three-dimensional structures very small in every dimension use specialized instruments such as ion microscopy coupled with intensive computer modeling. These techniques are employed, for example, to measure the tiny features on wafers during the manufacture of chips. == Standard rulers == The ruler the simplest kind of length measurement tool: lengths are defined by printed marks or engravings on a stick. The metre was initially defined using a ruler before more accurate methods became available. Gauge blocks are a common method for precise measurement or calibration of measurement tools. For small or microscopic objects, microphotography where the length is calibrated using a graticule can be used. A graticule is a piece that has lines for precise lengths etched into it. Graticules may be fitted


id: length-measurement-20260505-1
file: data/en.wikipedia.org/wiki/Length_measurement-1.md
category: reference
title: Length measurement
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Length_measurement
date_saved: 2026-05-05T10:05:04.164620+00:00
instance: kb-cron
parent: length-measurement-20260505-0
summary:
In many practical circumstances, and for precision work, measurement of dimension using transit-time measurements is used only as an initial indicator of length and is refined using an interferometer. Generally, transit time measurements are preferred for longer lengths, and interferometers for shorter lengths. The figure shows schematically how length is determined using a Michelson interferometer: the two panels show a laser source emitting a light beam split by a beam splitter (BS) to travel two paths. The light is recombined by bouncing the two components off a pair of corner cubes (CC) that return the two components to the beam splitter again to be reassembled. The corner cube serves to displace the incident from the reflected beam, which avoids some complications caused by superposing the two beams. The distance between the left-hand corner cube and the beam splitter is compared to that separation on the fixed leg as the left-hand spacing is adjusted to compare the length of the object to be measured. In the top panel the path is such that the two beams reinforce each other after reassembly, leading to a strong light pattern (sun). The bottom panel shows a path that is made a half wavelength longer


id: length-measurement-20260505-2
file: data/en.wikipedia.org/wiki/Length_measurement-2.md
category: reference
title: Length measurement
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Length_measurement
date_saved: 2026-05-05T10:05:04.164620+00:00
instance: kb-cron
parent: length-measurement-20260505-0
summary:
== Far and moving targets == Ranging is technique that measures distance or slant range from the observer to a target, especially a far and moving target. Active methods use unilateral transmission and passive reflection. Active rangefinding methods include laser (lidar), radar, sonar, and ultrasonic rangefinding. Other devices which measure distance using trigonometry are stadiametric, coincidence and stereoscopic rangefinders. Older methodologies that use a set of known information (usually distance or target sizes) to make the measurement, have been in regular use since the 18th century. Special ranging makes use of actively synchronized transmission and travel time measurements. The time difference between several received signals is used to determine exact distances (upon multiplication by the speed of light). This principle is used in satellite navigation. In conjunction with a standardized model of the Earth's surface, a location on that surface may be determined with high accuracy. Ranging methods without accurate time synchronization of the receiver are called pseudorange, used, for example, in GPS positioning. With other systems ranging is obtained from passive radiation measurements only: the noise or radiation signature of the object generates the signal that is used to determine range. This asynchronous method requires multiple measurements to obtain


id: light-scanning-photomacrography-20260505-0
file: data/en.wikipedia.org/wiki/Light_scanning_photomacrography-0.md
category: reference
title: Light scanning photomacrography
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Light_scanning_photomacrography
date_saved: 2026-05-05T10:05:05.349110+00:00
instance: kb-cron
parent: light-scanning-photomacrography-20260505-0
summary:
Light Scanning Photomacrography (LSP), also known as Scanning Light Photomacrography (SLP) or Deep-Field Photomacrography, is a photographic film technique that allows for high magnification light imaging with exceptional depth of field (DOF). This method overcomes the limitations of conventional macro photography, which typically only keeps a portion of the subject in acceptable focus at high magnifications. == Historical background == The principles of LSP were first documented in the early 1960s by Dan McLachlan Jr., who highlighted its capability for extreme focal depth in microscopy and in 1968 patented the process. The technique was revived and further developed in the 1980s by photographers such as Darwin Dale and Nile Root, a faculty member at the Rochester Institute of Technology. In the early 1990s, William Sharp and Charles Kazilek, both researchers at Arizona State University, also published articles describing their technique and system setup for capturing SLP images. == Predecessor to stack image photography == Light Scanning Photomacrography offered a powerful analog tool for high-detail imaging in the age of film photography. It provided a comprehensive depth of field, making it invaluable in scientific and biomedical photography. As technology and techniques continue to evolve, LSP has been replaced by digital image


id: low-voltage-electron-microscope-20260505-0
file: data/en.wikipedia.org/wiki/Low-voltage_electron_microscope-0.md
category: reference
title: Low-voltage electron microscope
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Low-voltage_electron_microscope
date_saved: 2026-05-05T10:05:06.529035+00:00
instance: kb-cron
parent: low-voltage-electron-microscope-20260505-0
summary:
A Low-voltage electron microscope (LVEM) is an electron microscope which operates in transmission mode at accelerating voltages of a few kiloelectronvolts (keV) or less. By contrast, high-voltage transmission electron microscopes use accelerating voltages in the range of 80-1000 keV. While the architecture of these devices is very similar to a conventional transmission electron microscopes, they have a few key differences that enable them to take advantage of low voltage electron sources, but trading off many advantages of higher voltage operations, including higher resolution and the possibility of electron energy-loss spectroscopy (EELS), etc. A representative example of this newer class of instruments is the LVEM 25E, a compact low-voltage transmission electron microscope that operates at accelerating voltages up to 25 kV. The LVEM 25E combines the high-contrast imaging advantages of low-voltage operation with improved penetration depth and analytical capability compared to earlier systems. In addition to TEM and STEM imaging modes, it integrates energy-dispersive X-ray spectroscopy (EDS), enabling elemental analysis of thin specimens. This extended voltage range allows the examination of biological and soft-matter samples with thicknesses approaching 100 nm, bridging the gap between traditional LVEM systems and conventional high-voltage TEMs. An earlier, low cost alternative is the LVEM 5 tabletop


id: low-energy-electron-diffraction-20260505-0
file: data/en.wikipedia.org/wiki/Low-energy_electron_diffraction-0.md
category: reference
title: Low-energy electron diffraction
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Low-energy_electron_diffraction
date_saved: 2026-05-05T10:05:07.719146+00:00
instance: kb-cron
parent: low-energy-electron-diffraction-20260505-0
summary:
Low-energy electron diffraction (LEED) is a technique for the determination of the surface structure of single-crystalline materials by bombardment with a collimated beam of low-energy electrons (30–200 eV) and observation of diffracted electrons as spots on a fluorescent screen. LEED may be used in one of two ways: Qualitatively, where the diffraction pattern is recorded and analysis of the spot positions gives information on the symmetry of the surface structure. In the presence of an adsorbate the qualitative analysis may reveal information about the size and rotational alignment of the adsorbate unit cell with respect to the substrate unit cell. Quantitatively, where the intensities of diffracted beams are recorded as a function of incident electron beam energy to generate the so-called I–V curves. By comparison with theoretical curves, these may provide accurate information on atomic positions on the surface at hand. == Historical perspective == An electron-diffraction experiment similar to modern LEED was the first to observe the wavelike properties of electrons, but LEED was established as a ubiquitous tool in surface science only with the advances in vacuum generation and electron detection techniques. === Davisson and Germer's discovery of electron diffraction === The theoretical possibility of the occurrence of


id: low-energy-electron-diffraction-20260505-1
file: data/en.wikipedia.org/wiki/Low-energy_electron_diffraction-1.md
category: reference
title: Low-energy electron diffraction
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Low-energy_electron_diffraction
date_saved: 2026-05-05T10:05:07.719146+00:00
instance: kb-cron
parent: low-energy-electron-diffraction-20260505-0
summary:
An electron gun from which monochromatic electrons are emitted by a cathode filament that is at a negative potential, typically 10–600 V, with respect to the sample. The electrons are accelerated and focused into a beam, typically about 0.1 to 0.5 mm wide, by a series of electrodes serving as electron lenses. Some of the electrons incident on the sample surface are backscattered elastically, and diffraction can be detected if sufficient order exists on the surface. This typically requires a region of single crystal surface as wide as the electron beam, although sometimes polycrystalline surfaces such as highly oriented pyrolytic graphite (HOPG) are sufficient. A high-pass filter for scattered electrons in the form of a retarding field analyzer, which blocks all but elastically scattered electrons. It usually contains three or four hemispherical concentric grids. Because only radial fields around the sampled point would be allowed and the geometry of the sample and the surrounding area is not spherical, the space between the sample and the analyzer has to be field-free. The first grid, therefore, separates the space above the sample from the retarding field. The next grid is at a negative potential to block low energy electrons, and is called


id: low-energy-electron-diffraction-20260505-2
file: data/en.wikipedia.org/wiki/Low-energy_electron_diffraction-2.md
category: reference
title: Low-energy electron diffraction
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Low-energy_electron_diffraction
date_saved: 2026-05-05T10:05:07.719146+00:00
instance: kb-cron
parent: low-energy-electron-diffraction-20260505-0
summary:
The interaction between the scatterers present in the surface and the incident electrons is most conveniently described in reciprocal space. In three dimensions the primitive reciprocal lattice vectors are related to the real space lattice {a, b, c} in the following way: a ∗ = 2 π b × c a ⋅ ( b × c ) , b ∗ = 2 π c × a b ⋅ ( c × a ) , c ∗ = 2 π a × b c ⋅ ( a × b ) . {\displaystyle \mathbf {a} ^{*}=2\pi {\frac {\mathbf {b} \times \mathbf {c} }{\mathbf {a} \cdot (\mathbf {b} \times \mathbf {c} )}},\quad \mathbf {b} ^{*}=2\pi {\frac {\mathbf {c} \times \mathbf {a} }{\mathbf {b} \cdot (\mathbf {c} \times \mathbf {a} )}},\quad \mathbf {c} ^{*}=2\pi {\frac {\mathbf {a} \times \mathbf {b} }{\mathbf {c} \cdot (\mathbf {a} \times \mathbf {b} )}}.} For an incident electron with wave vector k i = 2 π / λ i {\displaystyle \mathbf {k} _{i}=2\pi /\lambda _{i}} and scattered wave vector k f = 2 π / λ f {\displaystyle \mathbf {k} _{f}=2\pi /\lambda _{f}} , the condition for constructive interference and hence diffraction of scattered electron waves is given by


id: low-energy-electron-diffraction-20260505-3
file: data/en.wikipedia.org/wiki/Low-energy_electron_diffraction-3.md
category: reference
title: Low-energy electron diffraction
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Low-energy_electron_diffraction
date_saved: 2026-05-05T10:05:07.719146+00:00
instance: kb-cron
parent: low-energy-electron-diffraction-20260505-0
summary:
For a commensurate superstructure the symmetry and the rotational alignment with respect to adsorbent surface can be determined from the LEED pattern. This is easiest shown by using a matrix notation, where the primitive translation vectors of the superlattice {as, bs} are linked to the primitive translation vectors of the underlying (1×1) lattice {a, b} in the following way a s = G 11 a + G 12 b , b s = G 21 a + G 22 b . {\displaystyle {\begin{aligned}{\textbf {a}}_{s}&=G_{11}{\textbf {a}}+G_{12}{\textbf {b}},\\{\textbf {b}}_{s}&=G_{21}{\textbf {a}}+G_{22}{\textbf {b}}.\end{aligned}}} The matrix for the superstructure then is G = ( G 11 G 12 G 21 G 22 ) . {\displaystyle {\begin{aligned}G=\left({\begin{array}{cc}G_{11}&G_{12}\\G_{21}&G_{22}\end{array}}\right).\end{aligned}}} Similarly, the primitive translation vectors of the lattice describing the extra spots {a∗s, b∗s} are linked to the primitive translation vectors of the reciprocal lattice {a∗, b∗} a s ∗ = G 11 ∗ a ∗ + G 12 ∗ b ∗ , b s ∗ = G 21 ∗ a ∗ + G 22 ∗ b ∗ . {\displaystyle {\begin{aligned}{\textbf {a}}_{s}^{*}&=G_{11}^{*}{\textbf {a}}^{*}+G_{12}^{*}{\textbf {b}}^{*},\\{\textbf {b}}_{s}^{*}&=G_{21}^{*}{\textbf {a}}^{*}+G_{22}^{*}{\textbf {b}}^{*}.\end{aligned}}} G∗ is related to G in the following way G ∗ = ( G − 1 ) T = 1 det (


id: low-energy-electron-diffraction-20260505-4
file: data/en.wikipedia.org/wiki/Low-energy_electron_diffraction-4.md
category: reference
title: Low-energy electron diffraction
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Low-energy_electron_diffraction
date_saved: 2026-05-05T10:05:07.719146+00:00
instance: kb-cron
parent: low-energy-electron-diffraction-20260505-0
summary:
=== Dynamical LEED calculations === The term dynamical stems from the studies of X-ray diffraction and describes the situation where the response of the crystal to an incident wave is included self-consistently and multiple scattering can occur. The aim of any dynamical LEED theory is to calculate the intensities of diffraction of an electron beam impinging on a surface as accurately as possible. A common method to achieve this is the self-consistent multiple scattering approach. One essential point in this approach is the assumption that the scattering properties of the surface, i.e. of the individual atoms, are known in detail. The main task then reduces to the determination of the effective wave field incident on the individual scatters present in the surface, where the effective field is the sum of the primary field and the field emitted from all the other atoms. This must be done in a self-consistent way, since the emitted field of an atom depends on the incident effective field upon it. Once the effective field incident on each atom is determined, the total field emitted from all atoms can be found and its asymptotic value far from the crystal then gives the desired intensities. A common


id: low-energy-electron-microscopy-20260505-0
file: data/en.wikipedia.org/wiki/Low-energy_electron_microscopy-0.md
category: reference
title: Low-energy electron microscopy
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Low-energy_electron_microscopy
date_saved: 2026-05-05T10:05:08.928990+00:00
instance: kb-cron
parent: low-energy-electron-microscopy-20260505-0
summary:
Low-energy electron microscopy, or LEEM, is an analytical surface science technique used to image atomically clean surfaces, atom-surface interactions, and thin (crystalline) films. == Operation == High-energy electrons (15-20 keV) are emitted from an electron gun, focused using a set of condenser optics, and sent through a magnetic beam deflector (usually 60˚ or 90˚). The "fast" electrons travel through an objective lens and begin decelerating to low energies (1-100 eV) near the sample surface because the sample is held at a potential near that of the gun. The low-energy electrons are now termed "surface-sensitive" and the near-surface sampling depth can be varied by tuning the energy of the incident electrons (difference between the sample and gun potentials minus the work functions of the sample and system). The low-energy elastically backscattered electrons travel back through the objective lens, reaccelerate to the gun voltage (because the objective lens is grounded), and pass through the beam separator again. However, now the electrons travel away from the condenser optics and into the projector lenses. Imaging of the back focal plane of the objective lens into the object plane of the projector lens (using an intermediate lens) produces a diffraction pattern (low-energy electron diffraction, LEED)


id: low-energy-electron-microscopy-20260505-1
file: data/en.wikipedia.org/wiki/Low-energy_electron_microscopy-1.md
category: reference
title: Low-energy electron microscopy
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Low-energy_electron_microscopy
date_saved: 2026-05-05T10:05:08.928990+00:00
instance: kb-cron
parent: low-energy-electron-microscopy-20260505-0
summary:
A typical LEEM setup consists of electron gun, used to generate electrons by way of thermionic or field emission from a source tip. In thermionic emission, electrons escape a source tip (usually made of LaB6) by resistive heating and application of an electric field to effectively lower the energy needed for electrons to escape the surface. Once sufficient thermal vibrational energy is attained electrons may overcome this electrostatic energy barrier, allowing them to travel into vacuum and accelerate down the lens column to the gun potential (because the lenses are at ground). In field emission, rather than heating the tip to vibrationally excite electrons from the surface, the source tip (usually tungsten) is sharpened to a small point such that when large electric fields are applied, they concentrate at the tip, lowering the barrier to escape the surface as well as making tunneling of electrons from the tip to vacuum level more feasible. Condenser/illumination optics are used to focus electrons leaving the electron gun and manipulate and/or translate the illumination electron beam. Electromagnetic quadrupole electron lenses are used, the number of which depends on how much resolution and focusing flexibility the designer wishes. However, the ultimate resolution of LEEM is


id: low-energy-electron-microscopy-20260505-2
file: data/en.wikipedia.org/wiki/Low-energy_electron_microscopy-2.md
category: reference
title: Low-energy electron microscopy
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Low-energy_electron_microscopy
date_saved: 2026-05-05T10:05:08.928990+00:00
instance: kb-cron
parent: low-energy-electron-microscopy-20260505-0
summary:
=== Dark field imaging === In dark field imaging (also termed diffraction contrast imaging) researchers choose a desired diffraction spot and use a contrast aperture to pass only those electrons that contribute to that particular spot. In the image planes after the contrast aperture it is then possible to observe where the electrons originate from in real space. This technique allows scientists to study on which areas of a specimen a structure with a certain lattice vector (periodicity) exists. === Spectroscopy === Both (micro-)diffraction as well as bright field and dark field imaging can be performed as a function of the electron landing energy, measuring a diffraction pattern or an image for a range of energies. This way of measuring (often called LEEM-IV) yields spectra for each diffraction spot or sample position. In its simplest form, this spectrum gives a `fingerprint' of the surface, enabling the identification of different surface structures. A particular application of bright field spectroscopy is the counting of the exact number of layers in layered materials such as (few layer) graphene, hexagonal boron nitride and some transition metal dichalcogenides. === Photoemission electron microscopy (PEEM) === In photoemission electron microscopy (PEEM), upon exposure to electromagnetic radiation (photons),


id: low-energy-ion-scattering-20260505-0
file: data/en.wikipedia.org/wiki/Low-energy_ion_scattering-0.md
category: reference
title: Low-energy ion scattering
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Low-energy_ion_scattering
date_saved: 2026-05-05T10:05:10.142162+00:00
instance: kb-cron
parent: low-energy-ion-scattering-20260505-0
summary:
Low-energy ion scattering spectroscopy (LEIS), sometimes referred to simply as ion scattering spectroscopy (ISS), is a surface-sensitive analytical technique used to characterize the chemical and structural makeup of materials. LEIS involves directing a stream of charged particles known as ions at a surface and making observations of the positions, velocities, and energies of the ions that have interacted with the surface. Data that is thus collected can be used to deduce information about the material such as the relative positions of atoms in a surface lattice and the elemental identity of those atoms. LEIS is closely related to both medium-energy ion scattering (MEIS) and high-energy ion scattering (HEIS, known in practice as Rutherford backscattering spectroscopy, or RBS), differing primarily in the energy range of the ion beam used to probe the surface. While much of the information collected using LEIS can be obtained using other surface science techniques, LEIS is unique in its sensitivity to both structure and composition of surfaces. Additionally, LEIS is one of a very few surface-sensitive techniques capable of directly observing hydrogen atoms, an aspect that may make it an increasingly more important technique as the hydrogen economy is being explored. == Experimental setup == LEIS


id: low-energy-ion-scattering-20260505-1
file: data/en.wikipedia.org/wiki/Low-energy_ion_scattering-1.md
category: reference
title: Low-energy ion scattering
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Low-energy_ion_scattering
date_saved: 2026-05-05T10:05:10.142162+00:00
instance: kb-cron
parent: low-energy-ion-scattering-20260505-0
summary:
=== Elemental composition and two-body collision model === Due to the energy range typically used in ion scattering experiments (> 500 eV), effects of thermal vibrations, phonon oscillations, and interatomic binding are ignored since they are far below this range (~a few eV), and the interaction of particle and surface may be thought of as a classical two-body elastic collision problem. Measuring the energy of ions scattered in this type of interaction can be used to determine the elemental composition of a surface, as is shown in the following: Two-body elastic collisions are governed by the concepts of energy and momentum conservation. Consider a particle with mass mx, velocity v0, and energy given as E 0 = 1 2 m x v 0 2 {\displaystyle E_{0}={\tfrac {1}{2}}m_{x}v_{0}^{2}\,\!} impacting another particle at rest with mass my. The energies of the particles after collision are E 1 = 1 2 m x v 1 2 {\displaystyle E_{1}={\tfrac {1}{2}}m_{x}v_{1}^{2}\,\!} and E 2 = 1 2 m y v 2 2 {\displaystyle E_{2}={\tfrac {1}{2}}m_{y}v_{2}^{2}\,\!} where E 0 = E 1 + E 2 {\displaystyle E_{0}=E_{1}+E_{2}\,\!} and thus 1 2 m x v 0 2 = 1 2 m x v 1 2 + 1


id: low-energy-ion-scattering-20260505-2
file: data/en.wikipedia.org/wiki/Low-energy_ion_scattering-2.md
category: reference
title: Low-energy ion scattering
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Low-energy_ion_scattering
date_saved: 2026-05-05T10:05:10.142162+00:00
instance: kb-cron
parent: low-energy-ion-scattering-20260505-0
summary:
Shadowing and blocking are important concepts in almost all types of ion-surface interactions and result from the repulsive nature of the ion-nucleus interaction. As shown at right, when a flux of ions flows in parallel towards a scattering center (nucleus), they are each scattered according to the force of the Coulomb repulsion. This effect is known as shadowing. In a simple Coulomb repulsion model, the resulting region of “forbidden” space behind the scattering center takes the form of a paraboloid with radius r = 2 Z 1 Z 2 e 2 L E 0 {\displaystyle r=2{\sqrt {\tfrac {Z_{1}Z_{2}e^{2}L}{E_{0}}}}} at a distance L from the scattering center. The flux density is increased near the edge of the paraboloid. Blocking is closely related to shadowing, and involves the interaction between scattered ions and a neighboring scattering center (as such it inherently requires the presence of at least two scattering centers). As shown, ions scattered from the first nucleus are now on diverging paths as they undergo interaction with the second nucleus. This interaction results in another “shadowing cone” now called a blocking cone where ions scattered from the first nucleus are blocked from exiting at angles below α c r i t


id: low-energy-ion-scattering-20260505-3
file: data/en.wikipedia.org/wiki/Low-energy_ion_scattering-3.md
category: reference
title: Low-energy ion scattering
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Low-energy_ion_scattering
date_saved: 2026-05-05T10:05:10.142162+00:00
instance: kb-cron
parent: low-energy-ion-scattering-20260505-0
summary:
Alkali ion scattering spectroscopy (AISS) uses alkali ions in place of noble gas ions to give a distinctly different type of interaction. The primary difference between AISS and normal ISS is the increase in ion survival probability when using alkali ions. This is due to the relative stability of alkali (+1) ions as opposed to noble gas ions which have a much stronger energetic incentive for abstracting electrons from the sample. Increasing the ion survival probability results in an increase in ion flux and an improvement in sensitivity, which in turn allows for a reduction in primary ion flux to a point where the method is almost non-destructive. A disadvantage of using alkali ions in place of noble gas ions is the increased likelihood of adsorption or deposition to the sample surface. Impact-collision ion scattering spectroscopy (ICISS) takes advantage of shadowing and blocking in order to make precise determinations about interatomic spacing of the first 1-2 layers in a surface. The specific scattering geometry (180 degrees) ensures detection of only those particles which have undergone head-on collisions with surface atoms (thereby avoiding the complications of multiple scattering events). Starting sampling at a relatively high angle of incidence and scanning over


id: low-energy-ion-scattering-20260505-4
file: data/en.wikipedia.org/wiki/Low-energy_ion_scattering-4.md
category: reference
title: Low-energy ion scattering
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Low-energy_ion_scattering
date_saved: 2026-05-05T10:05:10.142162+00:00
instance: kb-cron
parent: low-energy-ion-scattering-20260505-0
summary:
== Comparison to other analytical techniques == Medium energy ion scattering (MEIS) and Rutherford backscattering (RBS) spectroscopies involve a similar setup to LEIS but use ions in the energy range of ~100 keV (MEIS) and ~1-2 MeV (RBS) to probe surfaces. Surface sensitivity is lost as a result of the use of higher energy particles, so while MEIS and RBS can still provide information about a sample they are incapable of providing true first-layer sensitivity. Secondary ion mass spectrometry (SIMS) involves the detection of ionic species ejected from a surface as a result of energetic particle impact. While SIMS is capable of giving depth profiles of the elemental and molecular composition of a sample, it is an inherently destructive method and is generally does not give structural information. X-ray photoelectron spectroscopy (XPS) is capable of surface elemental analysis, but samples a much more broad region of a sample than LEIS and so is not able to distinguish the first layer from subsurface layers. Since XPS relies on ejection of core-level electrons from atoms it is unable to detect hydrogen or helium atoms in a sample. Low-energy electron diffraction (LEED) is often used in combination with LEIS in order to facilitate


id: magic-angle-spinning-20260505-0
file: data/en.wikipedia.org/wiki/Magic_angle_spinning-0.md
category: reference
title: Magic angle spinning
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Magic_angle_spinning
date_saved: 2026-05-05T10:05:11.323662+00:00
instance: kb-cron
parent: magic-angle-spinning-20260505-0
summary:
In solid-state NMR spectroscopy, magic-angle spinning (MAS) is a technique routinely used to produce better resolution NMR spectra. MAS NMR consists in spinning the sample (usually at a frequency of 1 to 130 kHz) at the magic angle θm (ca. 54.74°, where cos2θm=1/3) with respect to the direction of the magnetic field. Three main interactions responsible in solid state NMR (dipolar, chemical shift anisotropy, quadrupolar) often lead to very broad and featureless NMR lines. However, these three interactions in solids are orientation-dependent and can be averaged to some extent by MAS: The nuclear dipolar interaction has a 3 cos 2 ⁡ θ − 1 {\displaystyle 3\cos ^{2}\theta -1} dependence, where θ {\displaystyle \theta } is the angle between the internuclear axis and the main magnetic field. As a result, the dipolar interaction vanish at the magic angle θm and the interaction contributing to the line broadening is removed. Even though all internuclear vectors cannot be all set to the magic angle, rotating the sample around this axis produces the same effect, provided the frequency is comparable to that of the interaction. In addition, a set of spinning sidebands appear on the spectra, which are sharp lines separated from the isotropic


id: magnetic-susceptibility-20260505-0
file: data/en.wikipedia.org/wiki/Magnetic_susceptibility-0.md
category: reference
title: Magnetic susceptibility
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Magnetic_susceptibility
date_saved: 2026-05-05T10:05:12.480631+00:00
instance: kb-cron
parent: magnetic-susceptibility-20260505-0
summary:
In electromagnetism, the magnetic susceptibility (from Latin susceptibilis 'receptive'; denoted χ, chi) is a measure of how much a material will become magnetized in an applied magnetic field. It is the ratio of magnetization M (magnetic moment per unit volume) to the applied magnetic field intensity H. This allows a simple classification, into two categories, of most materials' responses to an applied magnetic field: an alignment with the magnetic field, χ > 0, called paramagnetism, or an alignment against the field, χ < 0, called diamagnetism. Magnetic susceptibility indicates whether a material is attracted into or repelled out of a magnetic field. Paramagnetic materials align with the applied field and are attracted to regions of greater magnetic field. Diamagnetic materials are anti-aligned and are pushed away, toward regions of lower magnetic fields. On top of the applied field, the magnetization of the material adds its own magnetic field, causing the field lines to concentrate in paramagnetism, or be excluded in diamagnetism. Quantitative measures of the magnetic susceptibility also provide insights into the structure of materials, providing insight into bonding and energy levels. Furthermore, it is widely used in geology for paleomagnetic studies and structural geology. The magnetizability of materials comes


id: magnetic-susceptibility-20260505-1
file: data/en.wikipedia.org/wiki/Magnetic_susceptibility-1.md
category: reference
title: Magnetic susceptibility
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Magnetic_susceptibility
date_saved: 2026-05-05T10:05:12.480631+00:00
instance: kb-cron
parent: magnetic-susceptibility-20260505-0
summary:
For example, the CGS volume magnetic susceptibility of water at 20 °C is 7.19×10−7, which is 9.04×10−6 using the SI convention, both quantities being dimensionless. Whereas for most electromagnetic quantities, which system of quantities it belongs to can be disambiguated by incompatibility of their units, this is not true for the susceptibility quantities. In physics it is common to see CGS mass susceptibility with unit cm3/g or emu/g⋅Oe−1, and the CGS molar susceptibility with unit cm3/mol or emu/mol⋅Oe−1. == Paramagnetism and diamagnetism == If χ is positive, a material can be paramagnetic. In this case, the magnetic field in the material is strengthened by the induced magnetization. Alternatively, if χ is negative, the material is diamagnetic. In this case, the magnetic field in the material is weakened by the induced magnetization. Generally, nonmagnetic materials are said to be para- or diamagnetic because they do not possess permanent magnetization without external magnetic field. Ferromagnetic, ferrimagnetic, or antiferromagnetic materials possess permanent magnetization even without external magnetic field and do not have a well defined zero-field susceptibility. == Experimental measurement == Volume magnetic susceptibility is measured by the force change felt upon a substance when a magnetic field gradient is applied. Early measurements


id: magnetic-susceptibility-20260505-2
file: data/en.wikipedia.org/wiki/Magnetic_susceptibility-2.md
category: reference
title: Magnetic susceptibility
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Magnetic_susceptibility
date_saved: 2026-05-05T10:05:12.480631+00:00
instance: kb-cron
parent: magnetic-susceptibility-20260505-0
summary:
== Application in oil exploration == In oil exploration, magnetic susceptibility can determine prospective hydrocarbon deposites. In 2014, a research conducted in western Ukraine revealed that prospective hydrocarbon deposit locations presented higher values of mass-specific magnetic susceptibility that was calculated in laboratory from rock samples obtained on field. Moreover, magnetic susceptibility can distinguish crude oil from different worldwide oil reservoir. Measuring magnetic susceptibility, it is possible to quantify clay content in clastic shoreface reservoir; minerals as illite and quartz can be measured through mass magnetic susceptibility, high amounts of these components are highly correlated with the presence of clay contents into the reservoir. Final results show that magnetic susceptibility measurements have good correspondences compared with traditional methods of measuring minerals in rocks as gamma ray and XDR. Furthermore, magnetic susceptibility can characterize permeability of reservoir rock. Comparing low field and high field magnetic susceptibility measurements, in the high ones exists a higher correlation between the magnetic susceptibility and the permeability of the reservoir. In a shoreface North Sea oil reservoir was observed a slightly higher correlation with permeability in high field susceptibility (Potter and Ivakhnenko, 2008), and a much higher correlation with permeability and porosity in an Arab-D carbonate reservoir


id: mass-cytometry-20260505-0
file: data/en.wikipedia.org/wiki/Mass_cytometry-0.md
category: reference
title: Mass cytometry
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Mass_cytometry
date_saved: 2026-05-05T10:05:13.680590+00:00
instance: kb-cron
parent: mass-cytometry-20260505-0
summary:
Mass cytometry is a high-dimensional single-cell analysis technique that integrates flow cytometry with time of flight mass spectrometry. It is used for the determination of the properties of cells (cytometry). In this approach, antibodies are conjugated with isotopically pure elements, and these antibodies are used to label cellular proteins. Cells are nebulized and sent through an argon plasma, which ionizes the metal-conjugated antibodies. The metal signals are then analyzed by a time-of-flight mass spectrometer. The approach overcomes limitations of spectral overlap in flow cytometry by utilizing discrete isotopes as a reporter system instead of traditional fluorophores which have broad emission spectra. == History and Development == Tagging technology and instrument development occurred at the University of Toronto and DVS Sciences, Inc. CyTOF (cytometry by time of flight) was initially commercialized by DVS Sciences in 2009. In 2014, Fluidigm acquired DVS Sciences to become a reference company in single cell technology. The technology evolved through models like CyTOF, CyTOF2, Helios (CyTOF3) and CyTOF XT, with the latter announced in 2021. In 2022 Fluidigm received a capitol infusion and changed its name to Standard BioTools. In 2023, Standard BioTools introduced the Hyperion XTi Imaging System, advancing Imaging Mass Cytometry (IMC) with capabilities


id: mass-spectrometry-20260505-0
file: data/en.wikipedia.org/wiki/Mass_spectrometry-0.md
category: reference
title: Mass spectrometry
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Mass_spectrometry
date_saved: 2026-05-05T10:05:14.902784+00:00
instance: kb-cron
parent: mass-spectrometry-20260505-0
summary:
Mass spectrometry (MS) is an analytical technique that is used to measure the mass-to-charge ratio of ions. The results are presented as a mass spectrum, a plot of intensity as a function of the mass-to-charge ratio. Mass spectrometry is used in many different fields and is applied to pure samples as well as complex mixtures. A mass spectrum is a type of plot of the ion signal as a function of the mass-to-charge ratio. These spectra are used to determine the elemental or isotopic signature of a sample, the masses of particles and of molecules, and to elucidate the chemical identity or structure of molecules and other chemical compounds. In a typical MS procedure, a sample, which may be solid, liquid, or gaseous, is ionized, for example by bombarding it with a beam of electrons. This may cause some of the sample's molecules to break up into positively charged fragments or simply become positively charged without fragmenting. These ions (fragments) are then separated according to their mass-to-charge ratio, for example by accelerating them and subjecting them to an electric or magnetic field: ions of the same mass-to-charge ratio will undergo the same amount of deflection. The ions are detected by


id: mass-spectrometry-20260505-1
file: data/en.wikipedia.org/wiki/Mass_spectrometry-1.md
category: reference
title: Mass spectrometry
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Mass_spectrometry
date_saved: 2026-05-05T10:05:14.902784+00:00
instance: kb-cron
parent: mass-spectrometry-20260505-0
summary:
=== Theoretical example === The following describes the operation of a spectrometer mass analyzer, which is of the sector type. (Other analyzer types are treated below.) Consider a sample of sodium chloride (table salt). In the ion source, the sample is vaporized (turned into gas) and ionized (transformed into electrically charged particles) into sodium (Na+) and chloride (Cl−) ions. Sodium atoms and ions are monoisotopic, with a mass of about 23 daltons (symbol: Da or older symbol: u). Chloride atoms and ions come in two stable isotopes with masses of approximately 35 u (at a natural abundance of about 75 percent) and approximately 37 u (at a natural abundance of about 25 percent). The analyzer part of the spectrometer contains electric and magnetic fields, which exert forces on ions traveling through these fields. The speed of a charged particle may be increased or decreased while passing through the electric field, and its direction may be altered by the magnetic field. The magnitude of the deflection of the moving ion's trajectory depends on its mass-to-charge ratio. Lighter ions are deflected by the magnetic force to a greater degree than heavier ions (based on Newton's second law of motion, F = ma).


id: mass-spectrometry-20260505-2
file: data/en.wikipedia.org/wiki/Mass_spectrometry-2.md
category: reference
title: Mass spectrometry
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Mass_spectrometry
date_saved: 2026-05-05T10:05:14.902784+00:00
instance: kb-cron
parent: mass-spectrometry-20260505-0
summary:
== Mass selection == Mass analyzers separate the ions according to their mass-to-charge ratio. The following two laws govern the dynamics of charged particles in electric and magnetic fields in vacuum: F = Q ( E + v × B ) {\displaystyle \mathbf {F} =Q(\mathbf {E} +\mathbf {v} \times \mathbf {B} )} (Lorentz force law); F = m a {\displaystyle \mathbf {F} =m\mathbf {a} } (Newton's second law of motion in the non-relativistic case, i.e. valid only at ion velocity much lower than the speed of light). Here F is the force applied to the ion, m is the mass of the ion, a is the acceleration, Q is the ion charge, E is the electric field, and v × B is the vector cross product of the ion velocity and the magnetic field Equating the above expressions for the force applied to the ion yields: ( m / Q ) a = E + v × B . {\displaystyle (m/Q)\mathbf {a} =\mathbf {E} +\mathbf {v} \times \mathbf {B} .} This differential equation is the classic equation of motion for charged particles. Together with the particle's initial conditions, it completely determines the particle's motion in space and time in terms


id: mass-spectrometry-20260505-3
file: data/en.wikipedia.org/wiki/Mass_spectrometry-3.md
category: reference
title: Mass spectrometry
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Mass_spectrometry
date_saved: 2026-05-05T10:05:14.902784+00:00
instance: kb-cron
parent: mass-spectrometry-20260505-0
summary:
The quadrupole ion trap works on the same physical principles as the quadrupole mass analyzer, but the ions are trapped and sequentially ejected. Ions are trapped in a mainly quadrupole RF field, in a space defined by a ring electrode (usually connected to the main RF potential) between two endcap electrodes (typically connected to DC or auxiliary AC potentials). The sample is ionized either internally (e.g. with an electron or laser beam), or externally, in which case the ions are often introduced through an aperture in an endcap electrode. There are many mass/charge separation and isolation methods but the most commonly used is the mass instability mode in which the RF potential is ramped so that the orbit of ions with a mass a > b are stable while ions with mass b become unstable and are ejected on the z-axis onto a detector. There are also non-destructive analysis methods. Ions may also be ejected by the resonance excitation method, whereby a supplemental oscillatory excitation voltage is applied to the endcap electrodes, and the trapping voltage amplitude and/or excitation voltage frequency is varied to bring ions into a resonance condition in order of their mass/charge ratio. ==== Cylindrical ion trap


id: mass-spectrometry-20260505-4
file: data/en.wikipedia.org/wiki/Mass_spectrometry-4.md
category: reference
title: Mass spectrometry
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Mass_spectrometry
date_saved: 2026-05-05T10:05:14.902784+00:00
instance: kb-cron
parent: mass-spectrometry-20260505-0
summary:
A tandem mass spectrometer is one capable of multiple rounds of mass spectrometry, usually separated by some form of molecule fragmentation. For example, one mass analyzer can isolate one peptide from many entering a mass spectrometer. A collision cell then stabilizes the peptide ions while they collide with a gas, causing them to fragment by collision-induced dissociation (CID). A further mass analyzer then sorts the fragments produced from the peptides. Tandem MS can also be done in a single mass analyzer over time, as in a quadrupole ion trap. There are various methods for fragmenting molecules for tandem MS, including collision-induced dissociation (CID), electron capture dissociation (ECD), electron transfer dissociation (ETD), infrared multiphoton dissociation (IRMPD), blackbody infrared radiative dissociation (BIRD), electron-detachment dissociation (EDD) and surface-induced dissociation (SID). An important application using tandem mass spectrometry is in protein identification. Tandem mass spectrometry enables a variety of experimental sequences. Many commercial mass spectrometers are designed to expedite the execution of such routine sequences as selected reaction monitoring (SRM), precursor ion scanning, product ion scanning, and neutral loss scanning. In SRM, the first analyzer allows only a single mass through and the second analyzer monitors for multiple user-defined fragment ions over longer dwell-times


id: mass-spectrometry-20260505-5
file: data/en.wikipedia.org/wiki/Mass_spectrometry-5.md
category: reference
title: Mass spectrometry
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Mass_spectrometry
date_saved: 2026-05-05T10:05:14.902784+00:00
instance: kb-cron
parent: mass-spectrometry-20260505-0
summary:
Ion mobility spectrometry-mass spectrometry (IMS/MS or IMMS) is a technique where ions are first separated by drift time through some neutral gas under an applied electrical potential gradient before being introduced into a mass spectrometer. Drift time is a measure of the collisional cross section relative to the charge of the ion. The duty cycle of IMS (the time over which the experiment takes place) is longer than most mass spectrometric techniques, such that the mass spectrometer can sample along the course of the IMS separation. This produces data about the IMS separation and the mass-to-charge ratio of the ions in a manner similar to LC-MS. The duty cycle of IMS is short relative to liquid chromatography or gas chromatography separations and can thus be coupled to such techniques, producing triple modalities such as LC/IMS/MS. == Data and analysis == === Data representations === Mass spectrometry produces various types of data. The most common data representation is the mass spectrum. Certain types of mass spectrometry data are best represented as a mass chromatogram. Types of chromatograms include selected ion monitoring (SIM), total ion current (TIC), and selected reaction monitoring (SRM), among many others. Other types of mass spectrometry data are


id: mass-spectrometry-20260505-6
file: data/en.wikipedia.org/wiki/Mass_spectrometry-6.md
category: reference
title: Mass spectrometry
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Mass_spectrometry
date_saved: 2026-05-05T10:05:14.902784+00:00
instance: kb-cron
parent: mass-spectrometry-20260505-0
summary:
Mass spectrometry has both qualitative and quantitative uses. These include identifying unknown compounds, determining the isotopic composition of elements in a molecule, and determining the structure of a compound by observing its fragmentation. Other uses include quantifying the amount of a compound in a sample or studying the fundamentals of gas phase ion chemistry (the chemistry of ions and neutrals in a vacuum). MS is now commonly used in analytical laboratories that study physical, chemical, or biological properties of a great variety of compounds. Quantification can be relative (analyzed relative to a reference sample) or absolute (analyzed using a standard curve method). As an analytical technique it possesses distinct advantages such as: Increased sensitivity over most other analytical techniques because the analyzer, as a mass-charge filter, reduces background interference, Excellent specificity from characteristic fragmentation patterns to identify unknowns or confirm the presence of suspected compounds, Information about molecular weight, Information about the isotopic abundance of elements, Temporally resolved chemical data. A few of the disadvantages of the method is that it often fails to distinguish between optical and geometrical isomers and the positions of substituent in o-, m- and p- positions in an aromatic ring. Also, its scope is limited


