# kb

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


id: mass-spectrometry-20260505-7
file: data/en.wikipedia.org/wiki/Mass_spectrometry-7.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 is an important method for the characterization and sequencing of proteins. The two primary methods for ionization of whole proteins are electrospray ionization (ESI) and matrix-assisted laser desorption/ionization (MALDI). In keeping with the performance and mass range of available mass spectrometers, two approaches are used for characterizing proteins. In the first, intact proteins are ionized by either of the two techniques described above, and then introduced to a mass analyzer. This approach is referred to as "top-down" strategy of protein analysis. The top-down approach however is largely limited to low-throughput single-protein studies. In the second, proteins are enzymatically digested into smaller peptides using proteases such as trypsin or pepsin, either in solution or in gel after electrophoretic separation. Other proteolytic agents are also used. The collection of peptide products are often separated by chromatography prior to introduction to the mass analyzer. When the characteristic pattern of peptides is used for the identification of the protein the method is called peptide mass fingerprinting (PMF), if the identification is performed using the sequence data determined in tandem MS analysis it is called de novo peptide sequencing. These procedures of protein analysis are also referred to as the "bottom-up" approach, and


id: list-of-materials-analysis-methods-20260505-0
file: data/en.wikipedia.org/wiki/List_of_materials_analysis_methods-0.md
category: reference
title: List of materials analysis methods
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/List_of_materials_analysis_methods
date_saved: 2026-05-05T10:05:16.127432+00:00
instance: kb-cron
parent: list-of-materials-analysis-methods-20260505-0
summary:
This is a list of analysis methods used in materials science. Analysis methods are listed by their acronym, if one exists. == Symbols == μSR – see muon spin spectroscopy χ – see magnetic susceptibility == A == AAS – Atomic absorption spectroscopy AED – Auger electron diffraction AES – Auger electron spectroscopy AFM – Atomic force microscopy AFS – Atomic fluorescence spectroscopy Analytical ultracentrifugation APFIM – Atom probe field ion microscopy APS – Appearance potential spectroscopy ARPES – Angle resolved photoemission spectroscopy ARUPS – Angle resolved ultraviolet photoemission spectroscopy ATR – Attenuated total reflectance == B == BET – BET surface area measurement (BET from Brunauer, Emmett, Teller) BiFC – Bimolecular fluorescence complementation BKD – Backscatter Kikuchi diffraction, see EBSD BRET – Bioluminescence resonance energy transfer BSED – Back scattered electron diffraction, see EBSD == C == CAICISS – Coaxial impact collision ion scattering spectroscopy CARS – Coherent anti-Stokes Raman spectroscopy CBED – Convergent beam electron diffraction CCM – Charge collection microscopy CDI – Coherent diffraction imaging CE – Capillary electrophoresis CET – Cryo-electron tomography CL – Cathodoluminescence CLSM – Confocal laser scanning microscopy COSY – Correlation spectroscopy Cryo-EM – Cryo-electron microscopy Cryo-SEM – Cryo-scanning electron microscopy CV –


id: list-of-materials-analysis-methods-20260505-1
file: data/en.wikipedia.org/wiki/List_of_materials_analysis_methods-1.md
category: reference
title: List of materials analysis methods
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/List_of_materials_analysis_methods
date_saved: 2026-05-05T10:05:16.127432+00:00
instance: kb-cron
parent: list-of-materials-analysis-methods-20260505-0
summary:
== P == PAS – Positron annihilation spectroscopy Photoacoustic spectroscopy PAT or PACT – Photoacoustic tomography or photoacoustic computed tomography PAX – Photoemission of adsorbed xenon PC or PCS – Photocurrent spectroscopy Phase contrast microscopy PhD – Photoelectron diffraction PD – Photodesorption PDEIS – Potentiodynamic electrochemical impedance spectroscopy PDS – Photothermal deflection spectroscopy PED – Photoelectron diffraction PEELS – parallel electron energy loss spectroscopy PEEM – Photoemission electron microscopy (or photoelectron emission microscopy) PES – Photoelectron spectroscopy PINEM – photon-induced near-field electron microscopy PIGE – Particle (or proton) induced gamma-ray spectroscopy, see nuclear reaction analysis PIXE – Particle (or proton) induced X-ray spectroscopy PL – Photoluminescence Porosimetry Powder diffraction PTMS – Photothermal microspectroscopy PTS – Photothermal spectroscopy == Q == QENS – Quasielastic neutron scattering QCM-D – Quartz crystal microbalance with dissipation monitoring == R == Raman spectroscopy RAXRS – Resonant anomalous X-ray scattering RBS – Rutherford backscattering spectrometry REM – Reflection electron microscopy RDS – Reflectance difference spectroscopy RHEED – Reflection high energy electron diffraction RIMS – Resonance ionization mass spectrometry RIXS – Resonant inelastic X-ray scattering RR spectroscopy – Resonance Raman spectroscopy == S == SAD – Selected area diffraction SAED – Selected area electron diffraction SAM –


id: maximum-acceptable-toxicant-concentration-20260505-0
file: data/en.wikipedia.org/wiki/Maximum_acceptable_toxicant_concentration-0.md
category: reference
title: Maximum acceptable toxicant concentration
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Maximum_acceptable_toxicant_concentration
date_saved: 2026-05-05T10:05:17.305648+00:00
instance: kb-cron
parent: maximum-acceptable-toxicant-concentration-20260505-0
summary:
The maximum acceptable toxicant concentration (MATC) is a value that is calculated through aquatic toxicity tests to help set water quality regulations for the protection of aquatic life. Using the results of a partial life-cycle chronic toxicity test, the MATC is reported as the geometric mean between the No Observed Effect Concentration (NOEC) and the lowest observed effect concentration (LOEC). The MATC is used to set regulatory standards for priority pollutants under the US federal Clean Water Act. Regulatory guidelines give two acceptable concentrations of pollutants to protect against effects: chronic or acute. Since the MATC should only be reported in chronic toxicity tests, there is a widely accepted method to convert the chronic MATC to a concentration that protects against acute effects. The MATC is calculated and reported from the results of a number of standard procedures designed by the United States Environmental Protection Agency (US EPA) and other organizations to maintain high accuracy and precision among all toxicity tests for regulatory purposes. == Calculation == === Chronic toxicity tests === In a toxicity test, the NOEC and LOEC are derived as a comparison from the negative control, or the experimental group that does not contain the chemical in


id: maximum-acceptable-toxicant-concentration-20260505-1
file: data/en.wikipedia.org/wiki/Maximum_acceptable_toxicant_concentration-1.md
category: reference
title: Maximum acceptable toxicant concentration
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Maximum_acceptable_toxicant_concentration
date_saved: 2026-05-05T10:05:17.305648+00:00
instance: kb-cron
parent: maximum-acceptable-toxicant-concentration-20260505-0
summary:
== Advantages and limitations == Using the MATC to derive regulatory guidelines has been accompanied with some debate. Hypothesis testing, or statistical tests performed with data sets that only report a significant difference, are not considered the most statistically robust. There are no confidence intervals to show a measure of uncertainty in a NOEC and LOEC. In addition, the NOEC and LOEC can only be concentrations in the test, and nothing in between. Because of these reasons, values that are derived through curve fitting methods, such as an LC50, or EC10 (the concentration that causes the measured effect in 10% of organisms) would be preferred if it was possible more often. From a regulatory standpoint, there are advantages to using results from hypothesis tests. NOEC and LOEC's were used more often in the past, and there are more test results reporting NOEC and LOEC's than EC10's. The time and effort required to perform all of the previous tests to derive a different value is not seen as a good use of resources. In addition, the use of NOEC and LOEC's allows for reporting of one number to regulatory agencies. Water Quality Criteria are reported as one number that the actual


id: methods-of-detecting-exoplanets-20260505-0
file: data/en.wikipedia.org/wiki/Methods_of_detecting_exoplanets-0.md
category: reference
title: Methods of detecting exoplanets
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Methods_of_detecting_exoplanets
date_saved: 2026-05-05T10:05:19.616921+00:00
instance: kb-cron
parent: methods-of-detecting-exoplanets-20260505-0
summary:
Methods of detecting exoplanets usually rely on indirect strategies – that is, they do not directly image the planet but deduce its existence from another signal. Any planet is an extremely faint light source compared to its parent star. For example, a star like the Sun is about a billion times as bright as the reflected light from any of the planets orbiting it. In addition to the intrinsic difficulty of detecting such a faint light source, the glare from the parent star washes it out. For those reasons, very few of the exoplanets reported as of June 2025 have been detected directly, with even fewer being resolved from their host star. == Established detection methods == The following methods have proven successful at least once for discovering a new planet or detecting an already discovered planet: === Radial velocity === A star with a planet will move in its own small orbit in response to the planet's gravity. This leads to variations in the speed with which the star moves toward or away from Earth, i.e. the variations are in the radial velocity of the star with respect to Earth. The radial velocity can be deduced from the displacement


id: methods-of-detecting-exoplanets-20260505-1
file: data/en.wikipedia.org/wiki/Methods_of_detecting_exoplanets-1.md
category: reference
title: Methods of detecting exoplanets
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Methods_of_detecting_exoplanets
date_saved: 2026-05-05T10:05:19.616921+00:00
instance: kb-cron
parent: methods-of-detecting-exoplanets-20260505-0
summary:
==== Technique, advantages, and disadvantages ==== While the radial velocity method provides information about a planet's mass, the photometric method can determine the planet's radius. If a planet crosses (transits) in front of its parent star's disk, then the observed visual brightness of the star drops by a small amount, depending on the relative sizes of the star and the planet. For example, in the case of HD 209458, the star dims by 1.7%. However, most transit signals are considerably smaller; for example, an Earth-size planet transiting a Sun-like star produces a dimming of only 80 parts per million (0.008 percent). A theoretical transiting exoplanet light curve model predicts the following characteristics of an observed planetary system: transit depth (δ), transit duration (T), the ingress/egress duration (τ), and period of the exoplanet (P). However, these observed quantities are based on several assumptions. For convenience in the calculations, we assume that the planet and star are spherical, the stellar disk is uniform, and the orbit is circular. Depending on the relative position that an observed transiting exoplanet is while transiting a star, the observed physical parameters of the light curve will change. The transit depth (δ) of a transiting light curve


id: methods-of-detecting-exoplanets-20260505-2
file: data/en.wikipedia.org/wiki/Methods_of_detecting_exoplanets-2.md
category: reference
title: Methods of detecting exoplanets
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Methods_of_detecting_exoplanets
date_saved: 2026-05-05T10:05:19.616921+00:00
instance: kb-cron
parent: methods-of-detecting-exoplanets-20260505-0
summary:
===== False positives ===== Many points of light in the sky have brightness variations that may appear as transiting planets by flux measurements. False-positives in the transit photometry method arise in three common forms: blended eclipsing binary systems, grazing eclipsing binary systems, and transits by planet sized stars. Eclipsing binary systems usually produce deep eclipses that distinguish them from exoplanet transits, since planets are usually smaller than about 2RJ, but eclipses are shallower for blended or grazing eclipsing binary systems. Blended eclipsing binary systems consist of a normal eclipsing binary blended with a third (usually brighter) star along the same line of sight, usually at a different distance. The constant light of the third star dilutes the measured eclipse depth, so the light-curve may resemble that for a transiting exoplanet. In these cases, the target most often contains a large main sequence primary with a small main sequence secondary or a giant star with a main sequence secondary. Grazing eclipsing binary systems are systems in which one object will just barely graze the limb of the other. In these cases, the maximum transit depth of the light curve will not be proportional to the ratio of the squares of the


id: methods-of-detecting-exoplanets-20260505-3
file: data/en.wikipedia.org/wiki/Methods_of_detecting_exoplanets-3.md
category: reference
title: Methods of detecting exoplanets
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Methods_of_detecting_exoplanets
date_saved: 2026-05-05T10:05:19.616921+00:00
instance: kb-cron
parent: methods-of-detecting-exoplanets-20260505-0
summary:
==== History ==== The first exoplanet for which transits were observed for HD 209458 b, which was discovered using radial velocity technique. These transits were observed in 1999 by two teams led David Charbonneau and Gregory W. Henry. The first exoplanet to be discovered with the transit method was OGLE-TR-56b in 2002 by the OGLE project. A French Space Agency mission, CoRoT, began in 2006 to search for planetary transits from orbit, where the absence of atmospheric scintillation allows improved accuracy. This mission was designed to be able to detect planets "a few times to several times larger than Earth" and performed "better than expected", with two exoplanet discoveries (both of the "hot Jupiter" type) as of early 2008. In June 2013, CoRoT's exoplanet count was 32 with several still to be confirmed. The satellite unexpectedly stopped transmitting data in November 2012 (after its mission had twice been extended), and was retired in June 2013.In March 2009, NASA mission Kepler was launched to scan a large number of stars in the constellation Cygnus with a measurement precision expected to detect and characterize Earth-sized planets. The NASA Kepler Mission uses the transit method to scan a hundred thousand stars for planets.


id: methods-of-detecting-exoplanets-20260505-4
file: data/en.wikipedia.org/wiki/Methods_of_detecting_exoplanets-4.md
category: reference
title: Methods of detecting exoplanets
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Methods_of_detecting_exoplanets
date_saved: 2026-05-05T10:05:19.616921+00:00
instance: kb-cron
parent: methods-of-detecting-exoplanets-20260505-0
summary:
A separate novel method to detect exoplanets from light variations uses relativistic beaming of the observed flux from the star due to its motion. It is also known as Doppler beaming or Doppler boosting. The method was first proposed by Abraham Loeb and Scott Gaudi in 2003. As the planet tugs the star with its gravitation, the density of photons and therefore the apparent brightness of the star changes from observer's viewpoint. Like the radial velocity method, it can be used to determine the orbital eccentricity and the minimum mass of the planet. With this method, it is easier to detect massive planets close to their stars as these factors increase the star's motion. Unlike the radial velocity method, it does not require an accurate spectrum of a star, and therefore can be used more easily to find planets around fast-rotating stars and more distant stars. One of the biggest disadvantages of this method is that the light variation effect is very small. A Jovian-mass planet orbiting 0.025 AU away from a Sun-like star is barely detectable even when the orbit is edge-on. This is not an ideal method for discovering new planets, as the amount of emitted and reflected


id: methods-of-detecting-exoplanets-20260505-5
file: data/en.wikipedia.org/wiki/Methods_of_detecting_exoplanets-5.md
category: reference
title: Methods of detecting exoplanets
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Methods_of_detecting_exoplanets
date_saved: 2026-05-05T10:05:19.616921+00:00
instance: kb-cron
parent: methods-of-detecting-exoplanets-20260505-0
summary:
The transit timing variation method considers whether transits occur with strict periodicity, or if there is a variation. When multiple transiting planets are detected, they can often be confirmed with the transit timing variation method. This is useful in planetary systems far from the Sun, where radial velocity methods cannot detect them due to the low signal-to-noise ratio. If a planet has been detected by the transit method, then variations in the timing of the transit provide an extremely sensitive method of detecting additional non-transiting planets in the system with masses comparable to Earth's. It is easier to detect transit-timing variations if planets have relatively close orbits, and when at least one of the planets is more massive, causing the orbital period of a less massive planet to be more perturbed. The main drawback of the transit timing method is that usually not much can be learnt about the planet itself. Transit timing variation can help to determine the maximum mass of a planet. In most cases, it can confirm if an object has a planetary mass, but it does not put narrow constraints on its mass. There are exceptions though, as planets in the Kepler-36 and Kepler-88 systems orbit


id: methods-of-detecting-exoplanets-20260505-6
file: data/en.wikipedia.org/wiki/Methods_of_detecting_exoplanets-6.md
category: reference
title: Methods of detecting exoplanets
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Methods_of_detecting_exoplanets
date_saved: 2026-05-05T10:05:19.616921+00:00
instance: kb-cron
parent: methods-of-detecting-exoplanets-20260505-0
summary:
Gravitational microlensing occurs when the gravitational field of a star acts like a lens, magnifying the light of a distant background star. This effect occurs only when the two stars are almost exactly aligned. Lensing events are brief, lasting for weeks or days, as the two stars and Earth are all moving relative to each other. More than a thousand such events have been observed over the past ten years. If the foreground lensing star has a planet, then that planet's own gravitational field can make a detectable contribution to the lensing effect. Since that requires a highly improbable alignment, a very large number of distant stars must be continuously monitored in order to detect planetary microlensing contributions at a reasonable rate. This method is most fruitful for planets between Earth and the center of the galaxy, as the galactic center provides a large number of background stars. In 1991, astronomers Shude Mao and Bohdan Paczyński proposed using gravitational microlensing to look for binary companions to stars, and their proposal was refined by Andy Gould and Abraham Loeb in 1992 as a method to detect exoplanets. Successes with the method date back to 2002, when a group of Polish astronomers


id: methods-of-detecting-exoplanets-20260505-7
file: data/en.wikipedia.org/wiki/Methods_of_detecting_exoplanets-7.md
category: reference
title: Methods of detecting exoplanets
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Methods_of_detecting_exoplanets
date_saved: 2026-05-05T10:05:19.616921+00:00
instance: kb-cron
parent: methods-of-detecting-exoplanets-20260505-0
summary:
Direct imaging can give only loose constraints of the planet's mass, which is derived from the age of the star and the temperature of the planet. Mass can vary considerably, as planets can form several million years after the star has formed. The cooler the planet is, the less the planet's mass needs to be. In some cases it is possible to give reasonable constraints to the radius of a planet based on planet's temperature, its apparent brightness, and its distance from Earth. The spectra emitted from planets do not have to be separated from the star, which eases determining the chemical composition of planets. Sometimes observations at multiple wavelengths are needed to rule out the planet being a brown dwarf. Direct imaging can be used to accurately measure the planet's orbit around the star. Unlike the majority of other methods, direct imaging works better with planets with face-on orbits rather than edge-on orbits, as a planet in a face-on orbit is observable during the entirety of the planet's orbit, while planets with edge-on orbits are most easily observable during their period of largest apparent separation from the parent star. The planets detected through direct imaging currently fall into two


id: methods-of-detecting-exoplanets-20260505-8
file: data/en.wikipedia.org/wiki/Methods_of_detecting_exoplanets-8.md
category: reference
title: Methods of detecting exoplanets
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Methods_of_detecting_exoplanets
date_saved: 2026-05-05T10:05:19.616921+00:00
instance: kb-cron
parent: methods-of-detecting-exoplanets-20260505-0
summary:
==== Data reduction techniques ==== Post-processing of observational data to enhance signal strength of off-axial bodies (i.e. exoplanets) can be accomplished in a variety of ways. All methods are based on the presence of diversity in the data between the central star and the exoplanet companions: this diversity can originate from differences in the spectrum, the angular position, the orbital motion, the polarisation, or the coherence of the light. The most popular technique is Angular Differential Imaging (ADI), where exposures are acquired at different parallactic angle positions and the sky is left to rotate around the observed central star. The exposures are averaged, each exposure undergoes subtraction by the average, and then they are (de-)rotated to stack the faint planetary signal all in one place. Specral Differential Imaging (SDI) performs an analogous procedure, but for radial changes in brightness (as a function of spectra or wavelength) instead of angular changes. Combinations of the two are possible (ASDI, SADI, or Combined Differential Imaging "CODI"). === Polarimetry === Light given off by a star is un-polarized, i.e. the direction of oscillation of the light wave is random. However, when the light is reflected off the atmosphere of a planet, the light waves


id: methods-of-detecting-exoplanets-20260505-9
file: data/en.wikipedia.org/wiki/Methods_of_detecting_exoplanets-9.md
category: reference
title: Methods of detecting exoplanets
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Methods_of_detecting_exoplanets
date_saved: 2026-05-05T10:05:19.616921+00:00
instance: kb-cron
parent: methods-of-detecting-exoplanets-20260505-0
summary:
Astrometry is the oldest search method for extrasolar planets, and was originally popular because of its success in characterizing astrometric binary star systems. It dates back at least to statements made by William Herschel in the late 18th century. He claimed that an unseen companion was affecting the position of the star he cataloged as 70 Ophiuchi. The first known formal astrometric calculation for an extrasolar planet was made by William Stephen Jacob in 1855 for this star. Similar calculations were repeated by others for another half-century until finally refuted in the early 20th century. For two centuries claims circulated of the discovery of unseen companions in orbit around nearby star systems that all were reportedly found using this method, culminating in the prominent 1996 announcement, of multiple planets orbiting the nearby star Lalande 21185 by George Gatewood. None of these claims survived scrutiny by other astronomers, and the technique fell into disrepute. Unfortunately, changes in stellar position are so small—and atmospheric and systematic distortions so large—that even the best ground-based telescopes cannot produce precise enough measurements. All claims of a planetary companion of less than 0.1 solar mass, as the mass of the planet, made before 1996 using this


id: methods-of-detecting-exoplanets-20260505-10
file: data/en.wikipedia.org/wiki/Methods_of_detecting_exoplanets-10.md
category: reference
title: Methods of detecting exoplanets
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Methods_of_detecting_exoplanets
date_saved: 2026-05-05T10:05:19.616921+00:00
instance: kb-cron
parent: methods-of-detecting-exoplanets-20260505-0
summary:
=== Magnetospheric (auroral) radio emissions === Auroral radio emissions from exoplanet magnetospheres could be detected with radio telescopes. The emission may be caused by the exoplanet's magnetic field interacting with a stellar wind, adjacent plasma sources (such as Jupiter's volcanic moon Io travelling through its magnetosphere) or the interaction of the magnetic field with the interstellar medium. Although several discoveries have been claimed, thus far, none have been verified. The most sensitive searches for direct radio emissions from exoplanet magnetic fields, or from exoplanet magnetic fields interacting with those from their host stars, have been conducted with the Arecibo radio telescope. In addition to allowing for a study of exoplanet magnetic fields, radio emissions may be used to measure the interior rotation rate of an exoplanet. === Optical interferometry === In March 2019, ESO astronomers, employing the GRAVITY instrument on their Very Large Telescope Interferometer (VLTI), announced the first direct detection of an exoplanet, HR 8799 e, using optical interferometry. === Modified interferometry === By looking at the wiggles of an interferogram using a Fourier-Transform-Spectrometer, enhanced sensitivity could be obtained in order to detect faint signals from Earth-like planets. === Detection of dust trapping around Lagrangian points === Identification of


id: micro-x-ray-fluorescence-20260505-0
file: data/en.wikipedia.org/wiki/Micro-X-ray_fluorescence-0.md
category: reference
title: Micro-X-ray fluorescence
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Micro-X-ray_fluorescence
date_saved: 2026-05-05T10:05:20.786161+00:00
instance: kb-cron
parent: micro-x-ray-fluorescence-20260505-0
summary:
Micro x-ray fluorescence (μXRF) is an elemental analysis technique that relies on the same principles as x-ray fluorescence (XRF). Synchrotron X-rays may be used to provide elemental imaging with biological samples. The spatial resolution diameter of micro x-ray fluorescence is many orders of magnitude smaller than that of conventional XRF. While a smaller excitation spot can be achieved by restricting x-ray beam using a pinhole aperture, this method blocks much of the x-ray flux which has an adverse effect on the sensitivity of trace elemental analysis. Two types of x-ray optics, polycapillary and doubly curved crystal focusing optics, are able to create small focal spots of just a few micrometers in diameter. By using x-ray optics, the irradiation of the focal spot is much more intense and allows for enhanced trace element analysis and better resolution of small features. Micro x-ray fluorescence using x-ray optics has been used in applications such as forensics, small feature evaluations, elemental mapping, mineralogy, electronics, multi-layered coating analysis, micro-contamination detection, film and plating thickness, biology and environment. == Application in forensic science == Micro x-ray fluorescence is among the newest technologies used to detect fingerprints. It is a new visualization technique which rapidly reveals the


id: microtechnique-20260505-0
file: data/en.wikipedia.org/wiki/Microtechnique-0.md
category: reference
title: Microtechnique
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Microtechnique
date_saved: 2026-05-05T10:05:21.963883+00:00
instance: kb-cron
parent: microtechnique-20260505-0
summary:
Microtechnique is an aggregate of methods used to prepare micro-objects for studying. It is currently being employed in many fields in life science. Two well-known branches of microtechnique are botanical (plant) microtechnique and zoological (animal) microtechnique. With respect to both plant microtechnique and animal microtechnique, four types of methods are commonly used, which are whole mounts, smears, squashes, and sections, in recent micro experiments. Plant microtechnique contains direct macroscopic examinations, freehand sections, clearing, maceration, embedding, and staining. Moreover, three preparation ways used in zoological micro observations are paraffin method, celloidin method, and freezing method. == History == The early development of microtechnique in botany is closely related to that in zoology. Zoological and botanical discoveries are adopted by both zoologists and botanists. The field of microtechnique lasted from at the end of the 1930s when the principle of dry preparation emerged. The early development of microtechnique in botany is closely related to that in zoology. Zoological and botanical discoveries are adopted by both zoologists and botanists. Since Hooke discovered cells, microtechnique had also developed with the emergence of early microscopes. Microtechnique then had advanced over the period of 1800–1875. After 1875, modern micro methods have emerged. In recent years, both


id: microtechnique-20260505-1
file: data/en.wikipedia.org/wiki/Microtechnique-1.md
category: reference
title: Microtechnique
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Microtechnique
date_saved: 2026-05-05T10:05:21.963883+00:00
instance: kb-cron
parent: microtechnique-20260505-0
summary:
=== Maceration === Macerating tissues is the process of separating the constituent cells of tissues. This method enables observers to study the whole cell in third-dimensional detail. Chemical maceration method means the using chemicals to process organs or part to soften tissue and dissolving the cells so that different cell can be identified. === Embedding === Embedding technique is a medium stage when doing a sectioning process. When preparing specimens, it is difficult to make uniform slices since the tissue is soft. Therefore, it is necessary to soak the tissue with a certain substance to harden the whole tissue, to facilitate the slicing. This process is called embedding. The substance used to embed tissue is embedding media, which is chosen depends on the category of the microscope, category of the micro tome, and category of tissue. Paraffin wax, whose melting point is from 56 to 62°C, is commonly used for embedding. === Staining === Since few plant tissues have a color, there is little chromatically difference between plant tissues makes it difficult to differentiate botanical structure. Material is usually dyed before installation. This process is called staining, which can be used to prepare botanical specimens so that it is possible


id: microtechnique-20260505-2
file: data/en.wikipedia.org/wiki/Microtechnique-2.md
category: reference
title: Microtechnique
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Microtechnique
date_saved: 2026-05-05T10:05:21.963883+00:00
instance: kb-cron
parent: microtechnique-20260505-0
summary:
=== Freezing method === Freezing technique is the most commonly used sectioning method. This method can preserve the immune activity of various antigens well. Both fresh tissue and fixed tissue can be frozen. Moreover, it is also a technique used for freezing sections of either fresh or fixed plant tissues. During the freezing procedure, the water in tissues is easy to form ice crystals, which often affects the antigen localization. It is generally believed that when ice crystals are small, the effect is small, and when ice crystals are large, the damage to the tissue structure is large, and the above phenomenon is more likely to occur in tissues with more moisture components. The size of an ice crystal is directly proportional to its growth rate and inversely proportional to the nucleation rate (formation rate), that is, the larger the number of ice crystal formation, the smaller it is, and the more serious the impact on the structure. Therefore, the number of ice crystals should be minimized. The freezing method allows sectioning tissues rapidly and biopsy without using reagents. This procedure should be rapidly in case of the form of ice crystal. == See also == Microtechnology Histology == References


id: monolithic-hplc-column-20260505-0
file: data/en.wikipedia.org/wiki/Monolithic_HPLC_column-0.md
category: reference
title: Monolithic HPLC column
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Monolithic_HPLC_column
date_saved: 2026-05-05T10:05:23.177025+00:00
instance: kb-cron
parent: monolithic-hplc-column-20260505-0
summary:
A monolithic HPLC column, or monolithic column, is a column used in high-performance liquid chromatography (HPLC). The internal structure of the monolithic column is created in such a way that many channels form inside the column. The material inside the column which separates the channels can be porous and functionalized. In contrast, most HPLC configurations use particulate packed columns; in these configurations, tiny beads of an inert substance, typically a modified silica, are used inside the column. Monolithic columns can be broken down into two categories, silica-based and polymer-based monoliths. Silica-based monoliths are known for their efficiency in separating smaller molecules while, polymer-based are known for separating large protein molecules. == Technology overview == In analytical chromatography, the goal is to separate and uniquely identify each of the compounds in a substance. Alternatively, preparative scale chromatography is a method of purification of large batches of material in a production environment. The basic methods of separation in HPLC rely on a mobile phase (water, organic solvents, etc.) being passed through a stationary phase (particulate silica packings, monoliths, etc.) in a closed environment (column); the differences in reactivity among the solvent of interest and the mobile and stationary phases distinguish compounds from


id: monolithic-hplc-column-20260505-1
file: data/en.wikipedia.org/wiki/Monolithic_HPLC_column-1.md
category: reference
title: Monolithic HPLC column
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Monolithic_HPLC_column
date_saved: 2026-05-05T10:05:23.177025+00:00
instance: kb-cron
parent: monolithic-hplc-column-20260505-0
summary:
== Technology development == The roots of liquid chromatography extend back over a century ago to 1900, when Russian botanist Mikhail Tsvet began experimenting with plant pigments in chlorophyll. He noted that, when a solvent was applied, distinct bands appeared that migrated at different rates along a stationary phase. For this new observation, he coined the term “chromatography,” a colored picture. His first lecture on the subject was presented in 1903, but his most important contribution occurred three years later, in 1906, when the paper “Adsorption analysis and chromatographic method. Applications on the chemistry of chlorophyll,” was published. Rivalry with a colleague who readily and vocally denounced his work meant that chromatographic analysis was shelved for almost 25 years. The great irony of the matter is that it was his rival's students who later took up the chromatography banner in their work with carotins. Greatly unchanged from Tswett's time until the 1940s, normal phase chromatography was performed by passing a gravity-fed solvent through small glass tubes packed with pellicular adsorbent beads. It was in the 1940s, however, that there was a great revolution in gas chromatography (GC). Although GC was a wonderful technique for analyzing inorganic compounds, less than 20%


id: monolithic-hplc-column-20260505-2
file: data/en.wikipedia.org/wiki/Monolithic_HPLC_column-2.md
category: reference
title: Monolithic HPLC column
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Monolithic_HPLC_column
date_saved: 2026-05-05T10:05:23.177025+00:00
instance: kb-cron
parent: monolithic-hplc-column-20260505-0
summary:
== Industry evolution == Liquid chromatography as we know it today really got its start in 1969, when the first modern HPLC was designed and marketed as a nucleic acid analyzer. Columns throughout the 1970s were unreliable, pump flow rates were inconsistent, and many biologically active compounds escaped detection by UV and fluorescence detectors. Focus on purification methods in the '70s morphed into faster analyses in the 1980s, when computerized controls were integrated into HPLC equipment. Higher degrees of computerization then led to emphasis on more precise, faster, automated equipment in the 1990s. Atypical of many technologies of the '60s and '70s, the emphasis in improvements was not on “bigger and better,” but on “smaller and better”. At the same time the HPLC user-interface was improving, it was critical to be able to isolate hundreds of peptides or biomarkers from ever decreasing sample sizes. Laboratory analytical instrumentation has only been recognized as a separate and distinct industry by NAICS and SIC since 1987. This market segmentation includes not only gas and liquid chromatography, but also mass spectrometry and spectrophotometric instruments. Since first recognized as a separate market, sales of analytical laboratory equipment increased from about $3.5 billion in 1987 to


id: monolithic-hplc-column-20260505-3
file: data/en.wikipedia.org/wiki/Monolithic_HPLC_column-3.md
category: reference
title: Monolithic HPLC column
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Monolithic_HPLC_column
date_saved: 2026-05-05T10:05:23.177025+00:00
instance: kb-cron
parent: monolithic-hplc-column-20260505-0
summary:
== Industry applications == The liquid chromatography marketplace is incredibly diverse. Five to ten firms are consistently market leaders, yet nearly half of the market is made up of small, fragmented companies. This section of the report will focus on the roles that a few companies have had in bringing monolith column technologies to the commercial market. In 1998, start-up biotechnology company BIA Separations of Ljubljana, Slovenia, came into being. The technology was originally developed by Tatiana Tennikova and Frantisek Svec during a collaboration between their respective institutes. The patent for these columns was acquired by BIA Separations and Ales Podgornik and Milos Barut developed the first commercially available monolith column in the form of a short disc encapsulated in a plastic housing. Trademarked CIM, BIA Separations has since introduced full lines of reversed-phase, normal-phase, ion-exchange, and affinity polymeric monoliths. Ales Podgornik and Janez Jancar then went on to develop large scale tube monolithic columns for industrial use. The largest column currently available is 8L. In May 2008, LC instrumentation powerhouse Agilent technologies agreed to market BIA Separations’ analytical columns based on monolith technology. Agilent's commercialized the columns with strong and weak ion exchange phases and Protein A in September


id: monolithic-hplc-column-20260505-4
file: data/en.wikipedia.org/wiki/Monolithic_HPLC_column-4.md
category: reference
title: Monolithic HPLC column
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Monolithic_HPLC_column
date_saved: 2026-05-05T10:05:23.177025+00:00
instance: kb-cron
parent: monolithic-hplc-column-20260505-0
summary:
== Economic impact == Though the many advances of HPLC and monoliths are highly visible within the confines of the analytical and pharmaceutical industries, it is unlikely that general society is aware of these developments. Currently, consumers may witness technology developments in the analytical sciences industry in the form of a broader array of available pharmaceutical products of higher purity, advanced forensic testing in criminal trials, better environmental monitoring, and faster returns on medical tests. In the future, presumably, this may not be the case. As medicine becomes more individualized over time, consumer awareness that something is improving their quality of care seems more likely. The further thought that monoliths or HPLC are involved is unlikely to concern the general public, however. There are two main cost drivers behind technological change in this industry. Though many different analytical areas use LC, including food and beverage industries, forensics labs, and clinical testing facilities, the largest impetus toward technology developments comes from the research and development and production arms of the pharmaceutical industry. The areas in which high-throughput monolithic column technologies are likely to have the largest economic impact are R&D and downstream processing. From the Research and Development field comes the


id: m-ssbauer-spectroscopy-20260505-0
file: data/en.wikipedia.org/wiki/Mössbauer_spectroscopy-0.md
category: reference
title: Mössbauer spectroscopy
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Mössbauer_spectroscopy
date_saved: 2026-05-05T10:05:24.346490+00:00
instance: kb-cron
parent: m-ssbauer-spectroscopy-20260505-0
summary:
Mössbauer spectroscopy is a spectroscopic technique based on the Mössbauer effect. This effect, discovered by Rudolf Mössbauer (sometimes written "Moessbauer", German: "Mößbauer") in 1958, consists of the nearly recoil-free emission and absorption of nuclear gamma rays in solids. The consequent nuclear spectroscopy method is exquisitely sensitive to small changes in the chemical environment of certain nuclei. Typically, three types of nuclear interactions may be observed: the isomer shift due to differences in nearby electron densities (also called the chemical shift in older literature), quadrupole splitting due to atomic-scale electric field gradients; and magnetic splitting due to non-nuclear magnetic fields. Due to the high energy and extremely narrow line widths of nuclear gamma rays, Mössbauer spectroscopy is a highly sensitive technique in terms of energy (and hence frequency) resolution, capable of detecting changes of just a few parts in 1011. == Basic principle == Just as a gun recoils when a bullet is fired, conservation of momentum requires a nucleus (such as in a gas) to recoil during the emission or absorption of a gamma ray. If a nucleus at rest emits a gamma ray, the energy of the gamma ray is slightly less than the natural energy of the transition,


id: m-ssbauer-spectroscopy-20260505-1
file: data/en.wikipedia.org/wiki/Mössbauer_spectroscopy-1.md
category: reference
title: Mössbauer spectroscopy
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Mössbauer_spectroscopy
date_saved: 2026-05-05T10:05:24.346490+00:00
instance: kb-cron
parent: m-ssbauer-spectroscopy-20260505-0
summary:
Isomer shift (δ) (also sometimes called chemical shift, especially in the older literature) is a relative measure describing a shift in the resonance energy of a nucleus (see Fig. 2) due to the transition of electrons within its s orbitals. The whole spectrum is shifted in either a positive or negative direction depending upon the s electron charge density in the nucleus. This change arises due to alterations in the electrostatic response between the non-zero probability s orbital electrons and the non-zero volume nucleus they orbit. Only electrons in s orbitals have a non-zero probability of being found in the nucleus (see atomic orbitals). However, p, d, and f electrons may influence the s electron density through a screening effect. Isomer shift can be expressed using the formula below, where K is a nuclear constant, the difference between Re2 and Rg2 is the effective nuclear charge radius difference between excited state and the ground state, and the difference between [Ψs2(0)]a and [Ψs2(0)]b is the electron density difference in the nucleus (a = source, b = sample). The Chemical Isomer shift as described here does not change with temperature, however, Mössbauer spectra do have a temperature sensitivity due to a relativistic


id: m-ssbauer-spectroscopy-20260505-2
file: data/en.wikipedia.org/wiki/Mössbauer_spectroscopy-2.md
category: reference
title: Mössbauer spectroscopy
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Mössbauer_spectroscopy
date_saved: 2026-05-05T10:05:24.346490+00:00
instance: kb-cron
parent: m-ssbauer-spectroscopy-20260505-0
summary:
=== Combination of all === The three Mössbauer parameters, isomer shift, quadrupole splitting, and hyperfine splitting, can often be used to identify a particular compound by comparison to spectra for standards. In some cases, a compound may have more than one possible position for the Mössbauer active atom. For example, the crystal structure of magnetite (Fe3O4) supports two different sites for the iron atoms. Its spectrum has 12 peaks, a sextet for each potential atomic site, corresponding to two sets of Mössbauer parameters. Many times all effects are observed: isomer shift, quadrupole splitting, and magnetic splitting. In such cases the isomer shift is given by the average of all lines. The quadrupole splitting when all the four excited sub-states are equally shifted (two sub-states are lifted and the other two are lowered) is given by the shift of the outer two lines relative to the inner four lines (all inner four lines shift in opposition to the outermost two lines). Usually fitting software is used for accurate values. In addition, the relative intensities of the various peaks reflect the relative concentrations of compounds in a sample and can be used for semi-quantitative analysis. Also, since ferromagnetic phenomena are size-dependent, in


id: m-ssbauer-spectroscopy-20260505-3
file: data/en.wikipedia.org/wiki/Mössbauer_spectroscopy-3.md
category: reference
title: Mössbauer spectroscopy
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Mössbauer_spectroscopy
date_saved: 2026-05-05T10:05:24.346490+00:00
instance: kb-cron
parent: m-ssbauer-spectroscopy-20260505-0
summary:
where c is the speed of light, Bint is the internal magnetic field of the metallic iron (33 T), μN is the nuclear magneton (3.1524512605×10−8 eV/T), Eγ is the excitation energy (14.412497(3) keV), gn is the ground state nuclear splitting factor (0.090604/(I), where Isospin I = 1⁄2) and gen is the excited state splitting factor of 57Fe (-0.15532/(I), where I = 3⁄2). By substituting the above values one would get V = 10.6258 mm/s. Other values are sometimes used to reflect different qualities of iron foils. In all cases, any change in V only affects the isomer shift and not the quadrupole splitting. As the IBAME, the authority for Mössbauer spectroscopy, does not specify a particular value, anything between 10.60 mm/s to 10.67 mm/s can be used. For this reason it is highly recommended to provide the isomer shift values relative to the source used, not to the iron foil, mentioning the details of the source (centre of gravity of the folded spectrum). == See also == Alpha-particle spectroscopy Gamma probe Gamma ray spectrometer Isomeric shift Liquid scintillation counting Mass spectrometry Mössbauer effect Nuclear isomer Pandemonium effect Perturbed angular correlation Scintillation counter Total absorption spectroscopy X-ray spectroscopy == References ==


id: multiangle-light-scattering-20260505-0
file: data/en.wikipedia.org/wiki/Multiangle_light_scattering-0.md
category: reference
title: Multiangle light scattering
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Multiangle_light_scattering
date_saved: 2026-05-05T10:05:25.515516+00:00
instance: kb-cron
parent: multiangle-light-scattering-20260505-0
summary:
Multiangle light scattering (MALS) describes a technique for measuring the light scattered by a sample into a plurality of angles. It is used for determining both the absolute molar mass and the average size of molecules in solution, by detecting how they scatter light. A collimated beam from a laser source is most often used, in which case the technique can be referred to as multiangle laser light scattering (MALLS). The insertion of the word laser was intended to reassure those used to making light scattering measurements with conventional light sources, such as Hg-arc lamps that low-angle measurements could now be made. Until the advent of lasers and their associated fine beams of narrow width, the width of conventional light beams used to make such measurements prevented data collection at smaller scattering angles. In recent years, since all commercial light scattering instrumentation use laser sources, this need to mention the light source has been dropped and the term MALS is used throughout. The "multi-angle" term refers to the detection of scattered light at different discrete angles as measured, for example, by a single detector moved over a range that includes the particular angles selected or an array of detectors fixed


id: multiangle-light-scattering-20260505-1
file: data/en.wikipedia.org/wiki/Multiangle_light_scattering-1.md
category: reference
title: Multiangle light scattering
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Multiangle_light_scattering
date_saved: 2026-05-05T10:05:25.515516+00:00
instance: kb-cron
parent: multiangle-light-scattering-20260505-0
summary:
== Background == The measurement of scattered light from an illuminated sample forms the basis of the so-called classical light scattering measurement. Historically, such measurements were made using a single detector rotated in an arc about the illuminated sample. The first commercial instrument (formally called a "scattered photometer") was the Brice-Phoenix light scattering photometer introduced in the mid-1950s and followed by the Sofica photometer introduced in the late 1960s. Measurements were generally expressed as scattered intensities or scattered irradiance. Since the collection of data was made as the detector was placed at different locations on the arc, each position corresponding to a different scattering angle, the concept of placing a separate detector at each angular location of interest was well understood, though not implemented commercially until the late 1970s. Multiple detectors having different quantum efficiency have different response and hence needs to be normalized in this scheme. An interesting system based upon the use of high speed film was developed by Brunsting and Mullaney in 1974. It permitted the entire range of scattered intensities to be recorded on the film with a subsequent densitometer scan providing the relative scattered intensities. The then-conventional use of a single detector rotated about an


id: multiangle-light-scattering-20260505-2
file: data/en.wikipedia.org/wiki/Multiangle_light_scattering-2.md
category: reference
title: Multiangle light scattering
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Multiangle_light_scattering
date_saved: 2026-05-05T10:05:25.515516+00:00
instance: kb-cron
parent: multiangle-light-scattering-20260505-0
summary:
== Theory == The interpretation of scattering measurements made at the multiangular locations relies upon some knowledge of the a priori properties of the particles or molecules measured. The scattering characteristics of different classes of such scatterers may be interpreted best by application of an appropriate theory. For example, the following theories are most often applied. Rayleigh scattering is the simplest and describes elastic scattering of light or other electromagnetic radiation by objects much smaller than the incident wavelength. This type of scattering is responsible for the blue color of the sky during the day and is inversely proportional to the fourth power of wavelength. The Rayleigh–Gans approximation is a means of interpreting MALS measurements with the assumption that the scattering particles have a refractive index, n1, very close to the refractive index of the surrounding medium, n0. If we set m = n1/n0 and assume that |m - 1| << 1, then such particles may be considered as composed of very small elements, each of which may be represented as a Rayleigh-scattering particle. Thus each small element of the larger particle is assumed to scatter independently of any other. Lorenz–Mie theory is used to interpret the scattering of light


id: multiangle-light-scattering-20260505-3
file: data/en.wikipedia.org/wiki/Multiangle_light_scattering-3.md
category: reference
title: Multiangle light scattering
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Multiangle_light_scattering
date_saved: 2026-05-05T10:05:25.515516+00:00
instance: kb-cron
parent: multiangle-light-scattering-20260505-0
summary:
With the advent of size exclusion chromatography (SEC), MALS measurements began to be used in conjunction with an on-line concentration detector to determine absolute molar mass and size of sample fractions eluting from the column, rather than depending on calibration techniques. These flow mode MALS measurements have been extended to other separation techniques such as field flow fractionation, ion exchange chromatography, and reversed-phase chromatography. The angular dependence of light scattering data is shown below in a figure of mix of polystyrene spheres which was separated by SEC. The two smallest samples (farthest to the right) eluted last and show no angular dependence. The sample, second to the right shows a linear angular variation with the intensity increasing at lower scattering angles. The largest sample, on the left, elutes first and shows non-linear angular variation. === Utility of MALS measurements === ==== Molar mass and size ==== Coupling MALS with an in-line concentration detector following a sample separation means like SEC permits the calculation of the molar mass of the eluting sample in addition to its root-mean-square radius. The figure below represents a chromatographic separation of BSA aggregates. The 90° light scattering signal from a MALS detector and the molar mass


id: muon-spin-spectroscopy-20260505-0
file: data/en.wikipedia.org/wiki/Muon_spin_spectroscopy-0.md
category: reference
title: Muon spin spectroscopy
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Muon_spin_spectroscopy
date_saved: 2026-05-05T10:05:26.758138+00:00
instance: kb-cron
parent: muon-spin-spectroscopy-20260505-0
summary:
Muon spin spectroscopy, also known as μSR, is an experimental technique based on the implantation of spin-polarized muons in matter and on the detection of the influence of the atomic, molecular or crystalline surroundings on their spin motion. The motion of the muon spin is due to the magnetic field experienced by the particle and may provide information on its local environment in a very similar way to other magnetic resonance techniques, such as electron spin resonance (ESR or EPR) and, more closely, nuclear magnetic resonance (NMR). == Introduction == Muon spin spectroscopy is an atomic, molecular and condensed matter experimental technique that exploits nuclear detection methods. In analogy with the acronyms for the previously established spectroscopies NMR and ESR, muon spin spectroscopy is also known as μSR. The acronym stands for muon spin rotation, relaxation, or resonance, depending respectively on whether the muon spin motion is predominantly a rotation (more precisely a precession around a still magnetic field), a relaxation towards an equilibrium direction, or a more complex dynamic dictated by the addition of short radio frequency pulses. μSR does not require any radio-frequency technique to align the probing spin. More generally speaking, muon spin spectroscopy includes any study


id: muon-spin-spectroscopy-20260505-1
file: data/en.wikipedia.org/wiki/Muon_spin_spectroscopy-1.md
category: reference
title: Muon spin spectroscopy
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Muon_spin_spectroscopy
date_saved: 2026-05-05T10:05:26.758138+00:00
instance: kb-cron
parent: muon-spin-spectroscopy-20260505-0
summary:
=== Energy classes of muon beams === Muon beams are classified into three types based on the energy of the muons being produced: high-energy, surface or "Arizona", and ultra-slow muon beams. High-energy muon beams are formed by the pions escaping the production target at high energies. They are collected over a certain solid angle by quadrupole magnets and directed onto a decay section consisting of a long superconducting solenoid with a field of several tesla. If the pion momentum is not too high, a large fraction of the pions will have decayed before they reach the end of the solenoid. In the laboratory frame the polarization of a high-energy muon beam is limited to about 80% and its energy is of the order of ~40-50MeV. Although such a high energy beam requires the use of suitable moderators and samples with sufficient thickness, it guarantees a homogeneous implantation of the muons in the sample volume. Such beams are also used to study specimens inside of recipients, e.g. samples inside pressure cells. Such muon beams are available at PSI, TRIUMF, J-PARC and RIKEN-RAL. The second type of muon beam is often called the surface or Arizona beam (recalling the pioneering work of


id: muon-spin-spectroscopy-20260505-2
file: data/en.wikipedia.org/wiki/Muon_spin_spectroscopy-2.md
category: reference
title: Muon spin spectroscopy
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Muon_spin_spectroscopy
date_saved: 2026-05-05T10:05:26.758138+00:00
instance: kb-cron
parent: muon-spin-spectroscopy-20260505-0
summary:
=== Muon implantation === The muons are implanted into the sample of interest where they lose energy very quickly. Fortunately, this deceleration process occurs in such a way that it does not jeopardize a μSR measurement. On one side it is very fast (much faster than 100 ps), which is much shorter than a typical μSR time window (up to 20 μs), and on the other side, all the processes involved during the deceleration are Coulombic (ionization of atoms, electron scattering, electron capture) in origin and do not interact with the muon spin, so that the muon is thermalized without any significant loss of polarization. The positive muons usually adopt interstitial sites of the crystallographic lattice, markedly distinguished by their electronic (charge) state. The spectroscopy of a muon chemically bound to an unpaired electron is remarkably different from that of all other muon states, which motivates the historical distinction in paramagnetic and diamagnetic states. Note that many diamagnetic muon states really behave like paramagnetic centers, according to the standard definition of a paramagnet. For example, in most metallic samples, which are Pauli paramagnets, the muon's positive charge is collectively screened by a cloud of conduction electrons. Thus, in metals, the


id: muon-spin-spectroscopy-20260505-3
file: data/en.wikipedia.org/wiki/Muon_spin_spectroscopy-3.md
category: reference
title: Muon spin spectroscopy
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Muon_spin_spectroscopy
date_saved: 2026-05-05T10:05:26.758138+00:00
instance: kb-cron
parent: muon-spin-spectroscopy-20260505-0
summary:
A more general case is when the initial muon spin direction (coinciding with the detector axis) forms an angle θ {\displaystyle \theta } with the field direction. In this case the muon spin precession describes a cone which results in both a longitudinal component, A cos 2 ⁡ θ {\displaystyle A\cos ^{2}\theta } , and a transverse precessing component, A sin 2 ⁡ θ cos ⁡ ω t {\displaystyle A\sin ^{2}\theta \cos \omega t} , of the total asymmetry. ZF μSR experiments in the presence of a spontaneous internal field fall into this category as well. == Applications == Muon spin rotation and relaxation are mostly performed with positive muons. They are well suited to the study of magnetic fields at the atomic scale inside matter, such as those produced by various kinds of magnetism and/or superconductivity encountered in compounds occurring in nature or artificially produced by modern material science. The London penetration depth is one of the most important parameters characterizing a superconductor because its inverse square provides a measure of the density ns of Cooper pairs. The dependence of ns on temperature and magnetic field directly indicates the symmetry of the superconducting gap. Muon spin spectroscopy provides a


id: nano-ftir-20260505-0
file: data/en.wikipedia.org/wiki/Nano-FTIR-0.md
category: reference
title: Nano-FTIR
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Nano-FTIR
date_saved: 2026-05-05T10:05:27.989654+00:00
instance: kb-cron
parent: nano-ftir-20260505-0
summary:
Nano-FTIR (nanoscale Fourier transform infrared spectroscopy) is a scanning probe technique that utilizes as a combination of two techniques: Fourier transform infrared spectroscopy (FTIR) and scattering-type scanning near-field optical microscopy (s-SNOM). As s-SNOM, nano-FTIR is based on atomic-force microscopy (AFM), where a sharp tip is illuminated by an external light source and the tip-scattered light (typically back-scattered) is detected as a function of tip position. A typical nano-FTIR setup thus consists of an atomic force microscope, a broadband infrared light source used for tip illumination, and a Michelson interferometer acting as Fourier-transform spectrometer. In nano-FTIR, the sample stage is placed in one of the interferometer arms, which allows for recording both amplitude and phase of the detected light (unlike conventional FTIR that normally does not yield phase information). Scanning the tip allows for performing hyperspectral imaging (i.e. complete spectrum at every pixel of the scanned area) with nanoscale spatial resolution determined by the tip apex size. The use of broadband infrared sources enables the acquisition of continuous spectra, which is a distinctive feature of nano-FTIR compared to s-SNOM. Nano-FTIR is capable of performing infrared (IR) spectroscopy of materials in ultrasmall quantities and with nanoscale spatial resolution. The detection of a


id: nano-ftir-20260505-1
file: data/en.wikipedia.org/wiki/Nano-FTIR-1.md
category: reference
title: Nano-FTIR
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Nano-FTIR
date_saved: 2026-05-05T10:05:27.989654+00:00
instance: kb-cron
parent: nano-ftir-20260505-0
summary:
The breakthrough in nano-FTIR came upon the development of high-power broadband mid-IR laser sources, which provided large spectral irradiance in a sufficiently large bandwidth (mW-level power in ~1000 cm-1 bandwidth) and enabled truly broadband nanoscale-resolved material spectroscopy capable of detecting even the weakest vibrational resonances. Particularly, it has been shown that nano-FTIR is capable of measuring molecular fingerprints which match well with far-field FTIR spectra, owing to the asymmetry of the nano-FTIR spectrometer that provides phase and thus gives access to the molecular absorption. Recently, the first nanoscale-resolved infrared hyperspectral imaging of a co-polymer blend was demonstrated, which allowed for the application of statistical techniques such as multivariate analysis – a widely used tool for heterogeneous sample analysis. Additional boost to the development of nano-FTIR came from the utilization of the synchrotron radiation that provide extreme bandwidth, yet at the expense of weaker IR spectral irradiance compared to broadband laser sources. == Commercialization == The nano-FTIR technology has been commercialized by neaspec – a Germany-based spin-off company of the Max Planck Institute of Biochemistry founded by Ocelic, Hillenbrand and Keilmann in 2007 and based on the original patent by Ocelic and Hillenbrand. The detection module optimized for broadband illumination sources


id: nano-ftir-20260505-2
file: data/en.wikipedia.org/wiki/Nano-FTIR-2.md
category: reference
title: Nano-FTIR
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Nano-FTIR
date_saved: 2026-05-05T10:05:27.989654+00:00
instance: kb-cron
parent: nano-ftir-20260505-0
summary:
=== Cryogenic environment === Reveling the fundamentals of phase transitions in superconductors, correlated oxides, Bose-Einstein condensates of surface polaritons, etc. require spectroscopic studies at the characteristically nanometer length scales and in cryogenic environment. Nano-FTIR is compatible with cryogenic s-SNOM that has already been utilized for reveling a nanotextured coexistence of metal and correlated Mott insulator phases in Vanadium oxide near the metal-insulator transition. === Special atmosphere environments === Nano-FTIR can be operated in different atmospheric environments by enclosing the system into an isolated chamber or a glove box. Such operation has already been used for the investigation of highly reactive Lithium-ion battery components. == Applications == Nano-FTIR has a plenitude of applications, including polymers and polymer composites, organic films, semiconductors, biological research (cell membranes, proteins structure, studies of single viruses), chemistry and catalysis, photochemistry, minerals and biominerals, geochemistry, corrosion and materials sciences, low-dimensional materials, photonics, energy storage, cosmetics, pharmacology and environmental sciences. === Materials and chemical sciences === Nano-FTIR has been used for the nanoscale spectroscopic chemical identification of polymers and nanocomposites, for in situ investigation of structure and crystallinity of organic thin films, for strain characterization and relaxation in crystalline materials and for high-resolution spatial mapping of catalytic reactions,


id: nano-ftir-20260505-3
file: data/en.wikipedia.org/wiki/Nano-FTIR-3.md
category: reference
title: Nano-FTIR
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Nano-FTIR
date_saved: 2026-05-05T10:05:27.989654+00:00
instance: kb-cron
parent: nano-ftir-20260505-0
summary:
I ~ n ( ω ) ∝ E r e f , 0 ∗ E n f , n {\displaystyle {\tilde {I}}_{n}(\omega )\propto E_{\rm {ref,0}}^{*}E_{{\rm {nf}},n}} This way, besides providing the interferometric gain, the asymmetric interferometer utilized in nano-FTIR also eliminates the multiplicative background, which otherwise could be a source of various artifacts and is often overlooked in other s-SNOM based spectroscopies. === Normalization === Following the standard FTIR practice, spectra in nano-FTIR are normalized to those obtained on a known, preferably spectrally-flat reference material. This eliminates the generally unknown reference field and any instrumental functions, yielding spectra of the near-field contrast: η n ( ω ) = I ~ n ( ω ) I ~ n r e f ( ω ) = E n f , n ( ω ) E n f , n r e f ( ω ) {\displaystyle \eta _{n}(\omega )={\frac {{\tilde {I}}_{n}(\omega )}{{\tilde {I}}_{n}^{\rm {ref}}(\omega )}}={\frac {E_{{\rm {nf}},n}(\omega )}{E_{{\rm {nf}},n}^{\rm {ref}}(\omega )}}} Near-field contrast spectra are generally complex-valued, reflecting on the possible phase delay of the sample-scattered field with respect to the reference. Near-field contrast spectra depend nearly exclusively on the dielectric properties of sample material and can be used for its identification


id: neutron-activation-analysis-20260505-0
file: data/en.wikipedia.org/wiki/Neutron_activation_analysis-0.md
category: reference
title: Neutron activation analysis
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Neutron_activation_analysis
date_saved: 2026-05-05T10:05:29.163002+00:00
instance: kb-cron
parent: neutron-activation-analysis-20260505-0
summary:
Neutron activation analysis (NAA) is a nuclear process used for determining the concentrations of elements in many materials. NAA allows discrete sampling of elements as it disregards the chemical form of a sample, and focuses solely on atomic nuclei. The method is based on neutron activation and thus requires a neutron source. The sample is bombarded with neutrons, causing its constituent elements to form radioactive isotopes. The radioactive emissions and radioactive decay paths for each element have long been studied and determined. Using this information, it is possible to study spectra of the emissions of the radioactive sample, and determine the concentrations of the various elements within it. A particular advantage of this technique is that it does not destroy the sample, and thus has been used for the analysis of works of art and historical artifacts. NAA can also be used to determine the activity of a radioactive sample. If NAA is conducted directly on irradiated samples it is termed instrumental neutron activation analysis (INAA). In some cases, irradiated samples are subjected to chemical separation to remove interfering species or to concentrate the radioisotope of interest; this technique is known as radiochemical neutron activation analysis (RNAA). NAA can perform


id: neutron-activation-analysis-20260505-1
file: data/en.wikipedia.org/wiki/Neutron_activation_analysis-1.md
category: reference
title: Neutron activation analysis
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Neutron_activation_analysis
date_saved: 2026-05-05T10:05:29.163002+00:00
instance: kb-cron
parent: neutron-activation-analysis-20260505-0
summary:
== Variations == NAA can vary according to a number of experimental parameters. The kinetic energy of the neutrons used for irradiation will be a major experimental parameter. The above description is of activation by slow neutrons, slow neutrons are fully moderated within the reactor and have KE <0.5 eV. Medium KE neutrons may also be used for activation, these neutrons have been only partially moderated and have KE of 0.5 eV to 0.5 MeV, and are termed epithermal neutrons. Activation with epithermal neutrons is known as Epithermal NAA (ENAA). High KE neutrons are sometimes used for activation, these neutrons are unmoderated and consist of primary fission neutrons. High KE or fast neutrons have a KE >0.5 MeV. Activation with fast neutrons is termed Fast NAA (FNAA). Another major experimental parameter is whether nuclear decay products (gamma rays or particles) are measured during neutron irradiation (prompt gamma), or at some time after irradiation (delayed gamma, DGNAA). PGNAA is generally performed by using a neutron stream tapped off the nuclear reactor via a beam port. Neutron fluxes from beam ports are the order of 106 times weaker than inside a reactor. This is somewhat compensated for by placing the detector very


id: neutron-activation-analysis-20260505-2
file: data/en.wikipedia.org/wiki/Neutron_activation_analysis-2.md
category: reference
title: Neutron activation analysis
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Neutron_activation_analysis
date_saved: 2026-05-05T10:05:29.163002+00:00
instance: kb-cron
parent: neutron-activation-analysis-20260505-0
summary:
== Analytical capabilities == NAA can detect up to 74 elements depending upon the experimental procedure, with minimum detection limits ranging from 0.1 to 1 million ng/g depending on element under investigation. Heavier elements have larger nuclei, therefore they have a larger neutron capture cross-section and are more likely to be activated. Some nuclei can capture a number of neutrons and remain relatively stable, not undergoing transmutation or decay for many months or even years. Other nuclei decay instantaneously or form only stable isotopes and can only be identified by PGNAA. == Applications == Neutron Activation Analysis has a wide variety of applications including within the fields of archaeology, soil science, geology, forensics, and the semiconductor industry. Forensically, hairs subjected to a detailed forensic neutron analysis to determine whether they had sourced from the same individuals was first used in the trial of John Norman Collins. Archaeologists use NAA in order to determine the elements that comprise certain artifacts. This technique is used because it is nondestructive and it can relate an artifact to its source by its chemical signature. This method has proven to be very successful at determining trade routes, particularly for obsidian, with the ability of NAA


id: non-contact-atomic-force-microscopy-20260505-0
file: data/en.wikipedia.org/wiki/Non-contact_atomic_force_microscopy-0.md
category: reference
title: Non-contact atomic force microscopy
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Non-contact_atomic_force_microscopy
date_saved: 2026-05-05T10:05:30.401388+00:00
instance: kb-cron
parent: non-contact-atomic-force-microscopy-20260505-0
summary:
Non-contact atomic force microscopy (nc-AFM), also known as dynamic force microscopy (DFM), is a mode of atomic force microscopy, which itself is a type of scanning probe microscopy. In nc-AFM a sharp probe is moved close (order of angstroms) to the surface under study, the probe is then raster scanned across the surface, the image is then constructed from the force interactions during the scan. The probe is connected to a resonator, usually a silicon cantilever or a quartz crystal resonator. During measurements the sensor is driven so that it oscillates. The force interactions are measured either by measuring the change in amplitude of the oscillation at a constant frequency just off resonance (amplitude modulation) or by measuring the change in resonant frequency directly using a feedback circuit (usually a phase-locked loop) to always drive the sensor on resonance (frequency modulation). == Modes of operation == The two most common modes of nc-AFM operation, frequency modulation (FM) and amplitude modulation (AM), are described below. === Frequency modulation === Frequency modulation atomic force microscopy, introduced by Albrecht, Grütter, Horne and Rugar in 1991, is a mode of nc-AFM where the change in resonant frequency of the sensor is tracked directly, by


id: non-contact-atomic-force-microscopy-20260505-1
file: data/en.wikipedia.org/wiki/Non-contact_atomic_force_microscopy-1.md
category: reference
title: Non-contact atomic force microscopy
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Non-contact_atomic_force_microscopy
date_saved: 2026-05-05T10:05:30.401388+00:00
instance: kb-cron
parent: non-contact-atomic-force-microscopy-20260505-0
summary:
A qPlus sensor is used in many ultra-high vacuum nc-AFMs. The sensor was originally made from a quartz tuning fork from a wristwatch. In contrast to a quartz tuning fork sensor that consists of two coupled tines that oscillate opposed to each other, a qPlus sensor has only one tine that oscillates. The tuning fork is glued to a mount such that one tine of the tuning fork is immobilised, a tungsten wire, etched to have a sharp apex, is then glued to the free prong. The sensor was invented in 1996 by physicist Franz J. Giessibl. The AFM deflection signal is generated by the piezoelectric effect, and can be read from the two electrodes on the tuning fork. As the tungsten tip wire is conductive, the sensor can be used for combined STM/nc-AFM operation. The tip can either be electrically connected to one of tuning fork electrodes, or to a separate thin (~30μm diameter) gold wire. The advantage of the separate wire is that it can reduce crosstalk between the tunnel current and the deflection channels, however the wire will have its own resonance, which can affect the resonant properties of the sensor. New versions of the qPlus sensor


id: non-contact-atomic-force-microscopy-20260505-2
file: data/en.wikipedia.org/wiki/Non-contact_atomic_force_microscopy-2.md
category: reference
title: Non-contact atomic force microscopy
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Non-contact_atomic_force_microscopy
date_saved: 2026-05-05T10:05:30.401388+00:00
instance: kb-cron
parent: non-contact-atomic-force-microscopy-20260505-0
summary:
=== Lateral force measurements === It is possible to perform lateral force measurements using a nc-AFM probe oscillating normal to the surface under study. This method uses a similar method to force spectroscopy except the tip is moved parallel to the surface while the frequency shift is recorded, this is repeated at multiple heights above the surface, starting far from the surface and moving closer. After any change to the surface, for example moving an atom on the surface, the experiment is stopped. This leaves a 2D grid of measured frequency shifts. Using an appropriate force spectroscopy calculation each of the vertical frequency shift vectors can be converted into a vector of forces in the z-direction, thus creating a 2D grid of calculated forces. These forces can be integrated vertically to produce a 2D map of the potential. It is then possible to differentiate the potential horizontally to calculate the lateral forces. As this method relies on heavy mathematical processing, in which each state assumes a vertical motion of the tip, it is critical that the sensor is not angled, and that the tip length is very short compared to the length of the sensor. A direct measurement of lateral


id: nuclear-magnetic-resonance-20260505-0
file: data/en.wikipedia.org/wiki/Nuclear_magnetic_resonance-0.md
category: reference
title: Nuclear magnetic resonance
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Nuclear_magnetic_resonance
date_saved: 2026-05-05T10:05:31.644050+00:00
instance: kb-cron
parent: nuclear-magnetic-resonance-20260505-0
summary:
Nuclear magnetic resonance (NMR) is a physical phenomenon in which nuclei in a strong constant magnetic field are disturbed by a weak oscillating magnetic field (in the near field) and respond by producing an electromagnetic signal with a frequency characteristic of the magnetic field at the nucleus. This process occurs near resonance, when the oscillation frequency matches the intrinsic frequency of the nuclei, which depends on the strength of the static magnetic field, the chemical environment, and the magnetic properties of the isotope involved; in practical applications with static magnetic fields up to ca. 20 tesla, the frequency is similar to VHF and UHF television broadcasts (60–1000 MHz). NMR results from specific magnetic properties of certain atomic nuclei. High-resolution nuclear magnetic resonance spectroscopy is widely used to determine the structure of organic molecules in solution and study molecular physics and crystals as well as non-crystalline materials. NMR is also routinely used in advanced medical imaging techniques, such as in magnetic resonance imaging (MRI). The original application of NMR to condensed matter physics is nowadays mostly devoted to strongly correlated electron systems. It reveals large many-body couplings by fast broadband detection and should not be confused with solid state NMR, which


id: nuclear-magnetic-resonance-20260505-1
file: data/en.wikipedia.org/wiki/Nuclear_magnetic_resonance-1.md
category: reference
title: Nuclear magnetic resonance
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Nuclear_magnetic_resonance
date_saved: 2026-05-05T10:05:31.644050+00:00
instance: kb-cron
parent: nuclear-magnetic-resonance-20260505-0
summary:
Nuclear magnetic resonance was first described and measured in molecular beams by Isidor Rabi in 1938, by extending the Stern–Gerlach experiment, and in 1944, Rabi was awarded the Nobel Prize in Physics for this work. In 1946, Felix Bloch and Edward Mills Purcell expanded the technique for use on liquids and solids, for which they shared the Nobel Prize in Physics in 1952. Russell H. Varian filed the "Method and means for correlating nuclear properties of atoms and magnetic fields", U.S. patent 2,561,490 on October 21, 1948 and was accepted on July 24, 1951. Varian Associates developed the first NMR unit called NMR HR-30 in 1952. Purcell had worked on the development of radar during World War II at the Massachusetts Institute of Technology's Radiation Laboratory. His work during that project on the production and detection of radio frequency power and on the absorption of such RF power by matter laid the foundation for his discovery of NMR in bulk matter. Rabi, Bloch, and Purcell observed that magnetic nuclei, like 1H and 31P, could absorb RF energy when placed in a magnetic field and when the RF was of a frequency specific to the identity of the nuclei. When this


id: nuclear-magnetic-resonance-20260505-2
file: data/en.wikipedia.org/wiki/Nuclear_magnetic_resonance-2.md
category: reference
title: Nuclear magnetic resonance
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Nuclear_magnetic_resonance
date_saved: 2026-05-05T10:05:31.644050+00:00
instance: kb-cron
parent: nuclear-magnetic-resonance-20260505-0
summary:
=== Nuclear spins and magnets === All nucleons, that is neutrons and protons, composing any atomic nucleus, have the intrinsic quantum property of spin, an intrinsic angular momentum analogous to the classical angular momentum of a spinning sphere. The overall spin of the nucleus is determined by the spin quantum number S. If the numbers of both the protons and neutrons in a given nuclide are even then S = 0, i.e. there is no overall spin. Then, just as electrons pair up in nondegenerate atomic orbitals, so do even numbers of protons or even numbers of neutrons (both of which are also spin-⁠1/2⁠ particles and hence fermions), giving zero overall spin. However, an unpaired proton and unpaired neutron will have a lower energy when their spins are parallel, not anti-parallel. This parallel spin alignment of distinguishable particles does not violate the Pauli exclusion principle. The lowering of energy for parallel spins has to do with the quark structure of these two nucleons. As a result, the spin ground state for the deuteron (the nucleus of deuterium, the 2H isotope of hydrogen), which has only a proton and a neutron, corresponds to a spin value of 1, not of zero.


id: nuclear-magnetic-resonance-20260505-3
file: data/en.wikipedia.org/wiki/Nuclear_magnetic_resonance-3.md
category: reference
title: Nuclear magnetic resonance
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Nuclear_magnetic_resonance
date_saved: 2026-05-05T10:05:31.644050+00:00
instance: kb-cron
parent: nuclear-magnetic-resonance-20260505-0
summary:
As a result, the different nuclear spin states have different energies in a non-zero magnetic field. In less formal language, we can talk about the two spin states of a spin ⁠1/2⁠ as being aligned either with or against the magnetic field. If γ is positive (true for most isotopes used in NMR) then m = ⁠1/2⁠ ("spin up") is the lower energy state. The energy difference between the two states is: Δ E = γ ℏ B 0 , {\displaystyle \Delta {E}=\gamma \hbar B_{0}\,,} and this results in a small population bias favoring the lower energy state in thermal equilibrium. With more spins pointing up than down, a net spin magnetization along the magnetic field B0 results. ==== Precession of the spin magnetization ==== A central concept in NMR is the precession of the spin magnetization around the magnetic field at the nucleus, with the angular frequency ω = − γ B {\displaystyle \omega =-\gamma B} where ω = 2 π ν {\displaystyle \omega =2\pi \nu } relates to the oscillation frequency ν {\displaystyle \nu } and B is the magnitude of the field. This means that the spin magnetization, which is proportional to the sum of the spin


id: nuclear-magnetic-resonance-20260505-4
file: data/en.wikipedia.org/wiki/Nuclear_magnetic_resonance-4.md
category: reference
title: Nuclear magnetic resonance
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Nuclear_magnetic_resonance
date_saved: 2026-05-05T10:05:31.644050+00:00
instance: kb-cron
parent: nuclear-magnetic-resonance-20260505-0
summary:
==== Radiation Damping ==== In 1949, Suryan first suggested that the interaction between a radiofrequency coil and a sample's bulk magnetization could explain why experimental observations of relaxation times differed from theoretical predictions. Building on this idea, Bloembergen and Pound further developed Suryan's hypothesis by mathematically integrating the Maxwell–Bloch equations, a process through which they introduced the concept of "radiation damping." Radiation damping (RD) in Nuclear Magnetic Resonance (NMR) is an intrinsic phenomenon observed in many high-field NMR experiments, especially relevant in systems with high concentrations of nuclei like protons or fluorine. RD occurs when transverse bulk magnetization from the sample, following a radio frequency pulse, induces an electromagnetic field (emf) in the receiver coil of the NMR spectrometer. This generates an oscillating current and a non-linear induced transverse magnetic field which returns the spin system to equilibrium faster than other mechanisms of relaxation. RD can result in line broadening and measurement of a shorter spin-lattice relaxation time ( T 1 {\displaystyle T_{1}} ). For instance, a sample of water in a 400 MHz NMR spectrometer will have T R D {\displaystyle T_{RD}} around 20 ms, whereas its T 1 {\displaystyle T_{1}} is hundreds of milliseconds. This effect is often


id: nuclear-magnetic-resonance-20260505-5
file: data/en.wikipedia.org/wiki/Nuclear_magnetic_resonance-5.md
category: reference
title: Nuclear magnetic resonance
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Nuclear_magnetic_resonance
date_saved: 2026-05-05T10:05:31.644050+00:00
instance: kb-cron
parent: nuclear-magnetic-resonance-20260505-0
summary:
The precessing nuclei can also fall out of alignment with each other and gradually stop producing a signal. This is called T2, "spin-spin" or transverse relaxation. Because of the difference in the actual relaxation mechanisms involved (for example, intermolecular versus intramolecular magnetic dipole-dipole interactions), T1 is usually (except in rare cases) longer than T2 (that is, slower spin-lattice relaxation, for example because of smaller dipole-dipole interaction effects). In practice, the value of T2*, which is the actually observed decay time of the observed NMR signal, or free induction decay (to ⁠1/e⁠ of the initial amplitude immediately after the resonant RF pulse), also depends on the static magnetic field inhomogeneity, which may be quite significant. (There is also a smaller but significant contribution to the observed FID shortening from the RF inhomogeneity of the resonant pulse). In the corresponding FT-NMR spectrum—meaning the Fourier transform of the free induction decay— the width of the NMR signal in frequency units is inversely related to the T2* time. Thus, a nucleus with a long T2* relaxation time gives rise to a very sharp NMR peak in the FT-NMR spectrum for a very homogeneous ("well-shimmed") static magnetic field, whereas nuclei with shorter T2* values give


id: nuclear-magnetic-resonance-20260505-6
file: data/en.wikipedia.org/wiki/Nuclear_magnetic_resonance-6.md
category: reference
title: Nuclear magnetic resonance
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Nuclear_magnetic_resonance
date_saved: 2026-05-05T10:05:31.644050+00:00
instance: kb-cron
parent: nuclear-magnetic-resonance-20260505-0
summary:
Most applications of NMR involve full NMR spectra, that is, the intensity of the NMR signal as a function of frequency. Early attempts to acquire the NMR spectrum more efficiently than simple CW methods involved illuminating the target simultaneously with more than one frequency. A revolution in NMR occurred when short radio-frequency pulses began to be used, with a frequency centered at the middle of the NMR spectrum. In simple terms, a short pulse of a given "carrier" frequency "contains" a range of frequencies centered about the carrier frequency, with the range of excitation (bandwidth) being inversely proportional to the pulse duration, i.e. the Fourier transform of a short pulse contains contributions from all the frequencies in the neighborhood of the principal frequency. The restricted range of the NMR frequencies for most light spin-⁠1/2⁠ nuclei made it relatively easy to use short (1 - 100 microsecond) radio frequency pulses to excite the entire NMR spectrum. Applying such a pulse to a set of nuclear spins simultaneously excites all the single-quantum NMR transitions. In terms of the net magnetization vector, this corresponds to tilting the magnetization vector away from its equilibrium position (aligned along the external magnetic field). The out-of-equilibrium magnetization


id: nuclear-magnetic-resonance-20260505-7
file: data/en.wikipedia.org/wiki/Nuclear_magnetic_resonance-7.md
category: reference
title: Nuclear magnetic resonance
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Nuclear_magnetic_resonance
date_saved: 2026-05-05T10:05:31.644050+00:00
instance: kb-cron
parent: nuclear-magnetic-resonance-20260505-0
summary:
This technique complements X-ray crystallography in that it is frequently applicable to molecules in an amorphous or liquid-crystalline state, whereas crystallography, as the name implies, is performed on molecules in a crystalline phase. In electronically conductive materials, the Knight shift of the resonance frequency can provide information on the mobile charge carriers. Though nuclear magnetic resonance is used to study the structure of solids, extensive atomic-level structural detail is more challenging to obtain in the solid state. Due to broadening by chemical shift anisotropy (CSA) and dipolar couplings to other nuclear spins, without special techniques such as MAS or dipolar decoupling by RF pulses, the observed spectrum is often only a broad Gaussian band for non-quadrupolar spins in a solid. Professor Raymond Andrew at the University of Nottingham in the UK pioneered the development of high-resolution solid-state nuclear magnetic resonance. He was the first to report the introduction of the MAS (magic angle sample spinning; MASS) technique that allowed him to achieve spectral resolution in solids sufficient to distinguish between chemical groups with either different chemical shifts or distinct Knight shifts. In MASS, the sample is spun at several kilohertz around an axis that makes the so-called magic angle θm


id: nuclear-magnetic-resonance-20260505-8
file: data/en.wikipedia.org/wiki/Nuclear_magnetic_resonance-8.md
category: reference
title: Nuclear magnetic resonance
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Nuclear_magnetic_resonance
date_saved: 2026-05-05T10:05:31.644050+00:00
instance: kb-cron
parent: nuclear-magnetic-resonance-20260505-0
summary:
1H, the most commonly used spin-⁠1/2⁠ nucleus in NMR investigations, has been studied using many forms of NMR. Hydrogen is highly abundant, especially in biological systems. It is the nucleus providing the strongest NMR signal (apart from 3H, which is not commonly used due to its instability and radioactivity). Proton NMR has a narrow chemical-shift range but gives sharp signals in solution state. Fast acquisition of quantitative spectra (with peak integrals in stoichiometric ratios) is possible due to short relaxation time. The 1H nucleus has provided the sole diagnostic signal for clinical magnetic resonance imaging (MRI). 2H, a spin-1 nucleus, is commonly utilized to provide a signal-free medium in the form of deuterated solvents for proton NMR, to avoid signal interference from hydrogen-containing solvents in measurement of 1H NMR of solutes. It is also used in determining the behavior of lipids in lipid membranes and other solids or liquid crystals as it is a relatively non-perturbing label which can selectively replace 1H. Alternatively, 2H can be detected in media specially labeled with 2H. Deuterium resonance is commonly used in high-resolution NMR spectroscopy to monitor drift of the magnetic field strength (lock) and to monitor the homogeneity of the external magnetic


id: nuclear-magnetic-resonance-20260505-9
file: data/en.wikipedia.org/wiki/Nuclear_magnetic_resonance-9.md
category: reference
title: Nuclear magnetic resonance
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Nuclear_magnetic_resonance
date_saved: 2026-05-05T10:05:31.644050+00:00
instance: kb-cron
parent: nuclear-magnetic-resonance-20260505-0
summary:
=== Chemistry === The aforementioned chemical shift came as a disappointment to physicists who had hoped that the resonance frequency of each nuclear species would be constant in a given magnetic field. But about 1951, chemist S. S. Dharmatti pioneered a way to determine the structure of many compounds by studying the peaks of nuclear magnetic resonance spectra. It can be a very selective technique, distinguishing among many atoms within a molecule or collection of molecules of very similar type but which differ only in terms of their local chemical environment. NMR spectroscopy is used to unambiguously identify known and novel compounds, and as such, is usually required by scientific journals for identity confirmation of synthesized new compounds. See the articles on carbon-13 NMR and proton NMR for detailed discussions. A chemist can determine the identity of a compound by comparing the observed nuclear precession frequencies to known or predicted frequencies. Further structural data can be elucidated by observing spin–spin coupling, a process by which the precession frequency of a nucleus can be influenced by the spin orientation of a chemically bonded nucleus. Spin–spin coupling is easily observed in NMR of hydrogen-1 (1H NMR) since its natural abundance is nearly


id: nuclear-magnetic-resonance-20260505-10
file: data/en.wikipedia.org/wiki/Nuclear_magnetic_resonance-10.md
category: reference
title: Nuclear magnetic resonance
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Nuclear_magnetic_resonance
date_saved: 2026-05-05T10:05:31.644050+00:00
instance: kb-cron
parent: nuclear-magnetic-resonance-20260505-0
summary:
P u r i t y = w s t d × n [ H ] s t d × M W s p l w s p l × M W s t d × n [ H ] s p l × P {\displaystyle \mathrm {Purity} ={\frac {w_{\mathrm {std} }\times n[\mathrm {H} ]_{\mathrm {std} }\times MW_{\mathrm {spl} }}{w_{\mathrm {spl} }\times MW_{\mathrm {std} }\times n[\mathrm {H} ]_{\mathrm {spl} }}}\times P} Where: wstd: weight of internal standard wspl: weight of sample n[H]std: the integrated area of the peak selected for comparison in the standard, corrected for the number of protons in that functional group n[H]spl: the integrated area of the peak selected for comparison in the sample, corrected for the number of protons in that functional group MWstd: molecular weight of standard MWspl: molecular weight of sample P: purity of internal standard === Non-destructive testing === Nuclear magnetic resonance is extremely useful for analyzing samples non-destructively. Radio-frequency magnetic fields easily penetrate many types of matter and anything that is not highly conductive or inherently ferromagnetic. For example, various expensive biological samples, such as nucleic acids, including RNA and DNA, or proteins, can be studied using nuclear magnetic resonance for weeks


id: nuclear-magnetic-resonance-20260505-11
file: data/en.wikipedia.org/wiki/Nuclear_magnetic_resonance-11.md
category: reference
title: Nuclear magnetic resonance
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Nuclear_magnetic_resonance
date_saved: 2026-05-05T10:05:31.644050+00:00
instance: kb-cron
parent: nuclear-magnetic-resonance-20260505-0
summary:
In the Earth's magnetic field, NMR frequencies are in the audio frequency range, or the very low frequency and ultra low frequency bands of the radio frequency spectrum. Earth's field NMR (EFNMR) is typically stimulated by applying a relatively strong dc magnetic field pulse to the sample and, after the end of the pulse, analyzing the resulting low frequency alternating magnetic field that occurs in the Earth's magnetic field due to free induction decay (FID). These effects are exploited in some types of magnetometers, EFNMR spectrometers, and MRI imagers. Their inexpensive portable nature makes these instruments valuable for field use and for teaching the principles of NMR and MRI. An important feature of EFNMR spectrometry compared with high-field NMR is that some aspects of molecular structure can be observed more clearly at low fields and low frequencies, whereas other aspects observable at high fields are not observable at low fields. This is because: Electron-mediated heteronuclear J-couplings (spin–spin couplings) are field independent, producing clusters of two or more frequencies separated by several Hz, which are more easily observed in a fundamental resonance of about 2 kHz."Indeed it appears that enhanced resolution is possible due to the long spin relaxation times and


id: nuclear-magnetic-resonance-crystallography-20260505-0
file: data/en.wikipedia.org/wiki/Nuclear_magnetic_resonance_crystallography-0.md
category: reference
title: Nuclear magnetic resonance crystallography
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Nuclear_magnetic_resonance_crystallography
date_saved: 2026-05-05T10:05:32.873771+00:00
instance: kb-cron
parent: nuclear-magnetic-resonance-crystallography-20260505-0
summary:
Nuclear magnetic resonance crystallography (NMR crystallography) is a method which utilizes primarily NMR spectroscopy to determine the structure of solid materials on the atomic scale. Thus, solid-state NMR spectroscopy would be used primarily, possibly supplemented by quantum chemistry calculations (e.g. density functional theory), powder diffraction etc. If suitable crystals can be grown, any crystallographic method would generally be preferred to determine the crystal structure comprising in case of organic compounds the molecular structures and molecular packing. The main interest in NMR crystallography is in microcrystalline materials which are amenable to this method but not to X-ray, neutron and electron diffraction. This is largely because interactions of comparably short range are measured in NMR crystallography. == Introduction == When applied to organic molecules, NMR crystallography aims at including structural information not only of a single molecule but also on the molecular packing (i.e. crystal structure). Contrary to X-ray, single crystals are not necessary with solid-state NMR and structural information can be obtained from high-resolution spectra of disordered solids. E.g. polymorphism is an area of interest for NMR crystallography since this is encountered occasionally (and may often be previously undiscovered) in organic compounds. In this case a change in the molecular structure


id: nuclear-resonance-vibrational-spectroscopy-20260505-0
file: data/en.wikipedia.org/wiki/Nuclear_resonance_vibrational_spectroscopy-0.md
category: reference
title: Nuclear resonance vibrational spectroscopy
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Nuclear_resonance_vibrational_spectroscopy
date_saved: 2026-05-05T10:05:34.044320+00:00
instance: kb-cron
parent: nuclear-resonance-vibrational-spectroscopy-20260505-0
summary:
Nuclear resonance vibrational spectroscopy is a synchrotron-based technique that probes vibrational energy levels. The technique, often called NRVS, is specific for samples that contain nuclei that respond to Mössbauer spectroscopy, most commonly iron. The method exploits the high resolution offered by synchrotron light sources, which enables the resolution of vibrational fine structure, especially those vibrations that are coupled to the position of the Fe centre(s). The method is popularly applied to problems in bioinorganic chemistry, materials science, and geophysics. A novel aspect of the method is the ability to determine the 3D-trajectory of iron atoms within vibrational modes, providing a unique appraisal of DFT-prediction accuracy. Other names for this method include nuclear inelastic scattering (NIS), nuclear inelastic absorption (NIA), nuclear resonant inelastic x-ray scattering (NRIXS), and phonon assisted Mössbauer effect. == Experimental set-up == In the experimental setup, X-rays are released from the particle beam by an undulator; a high-resolution monochromator produces a beam with small energy dispersion (typically 1.0 meV). The sample is irradiated with photons chosen around the resonance of the Mössbauer isotope and further information is provided for the specific isotope. Typical parameters for the experimental scan are –20 meV below recoil-free resonance energy to +100 meV


id: nuclear-spectroscopy-20260505-0
file: data/en.wikipedia.org/wiki/Nuclear_spectroscopy-0.md
category: reference
title: Nuclear spectroscopy
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Nuclear_spectroscopy
date_saved: 2026-05-05T10:05:35.222723+00:00
instance: kb-cron
parent: nuclear-spectroscopy-20260505-0
summary:
Nuclear spectroscopy is a superordinate concept of methods that uses properties of a nucleus to probe material properties. By emission or absorption of radiation from the nucleus information of the local structure is obtained, as an interaction of an atom with its closest neighbours. Or a radiation spectrum of the nucleus is detected. Most methods base on hyperfine interactions, which are the interaction of the nucleus with its interaction of its atom's electrons and their interaction with the nearest neighbor atoms as well as external fields. Nuclear spectroscopy is mainly applied to solids and liquids, rarely in gases. Its methods are important tools in condensed matter physics, solid state chemistry., and analysis of chemical composition (analytical chemistry). == Methods == In nuclear physics these methods are used to study properties of the nucleus itself. Methods for studies of the nucleus: Gamma spectroscopy Hypernuclear spectroscopy Methods for condensed matter studies: Nuclear magnetic resonance (NMR) Mössbauer spectroscopy Perturbed angular correlation (PAC, TDPAC, PAC spectroscopy) Muon spin spectroscopy Nuclear orientation Channeling Nuclear reaction analysis Nuclear quadrupole resonance (NQR) Quasielastic neutron scattering (QENS) Methods for trace element analysis: Neutron activation analysis (NAA) Associated particle imaging (API) == References ==


id: optically-detected-magnetic-resonance-20260505-0
file: data/en.wikipedia.org/wiki/Optically_detected_magnetic_resonance-0.md
category: reference
title: Optically detected magnetic resonance
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Optically_detected_magnetic_resonance
date_saved: 2026-05-05T10:05:36.408472+00:00
instance: kb-cron
parent: optically-detected-magnetic-resonance-20260505-0
summary:
In physics, optically detected magnetic resonance (ODMR) is a technique for detecting quantum systems with spin-dependent optical transitions. In the case of fluorescent point defects (color centers) in crystals, the "ODMR signal" refers to a change in the defect's fluorescence intensity due to a simultaneously applied AC magnetic field. When the magnetic field frequency is resonant with a spin transition, which means that the frequency matches the energy splitting between two spin states, the spin system undergoes Rabi oscillations between the two states. If the two spin states have different fluorescence intensities, this results in a change in the defect's fluorescence. This can be used to measure properties of the spin such as the zero-field splitting and the gyromagnetic ratio. There may be many spin transitions, and their characteristics as observed with ODMR (principally frequency and linewidth) depend sensitively on the conditions of the measurement, motivating the use of ODMR as a technique for quantum sensing. Like electron paramagnetic resonance (EPR), ODMR makes use of the Zeeman effect in unpaired electrons. The negatively charged nitrogen vacancy centre (NV−) has been the target of considerable interest with regards to performing experiments using ODMR. ODMR of NV−s in diamond has applications in


id: osmometer-20260505-0
file: data/en.wikipedia.org/wiki/Osmometer-0.md
category: reference
title: Osmometer
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Osmometer
date_saved: 2026-05-05T10:05:37.557943+00:00
instance: kb-cron
parent: osmometer-20260505-0
summary:
An osmometer is a device for measuring the osmotic strength of a solution, colloid, or compound. There are several different techniques employed in osmometry: Freezing point depression osmometers may also be used to determine the osmotic strength of a solution, as osmotically active compounds depress the freezing point of a solution. This is the most common method in clinical laboratories because it is the most accurate and simple method. Vapor pressure osmometers determine the concentration of osmotically active particles that reduce the vapor pressure of a solution. Membrane osmometers measure the osmotic pressure of a solution separated from pure solvent by a semipermeable membrane. Osmometers are useful for determining the total concentration of dissolved salts and sugars in blood or urine samples. Osmometry is also useful in determining the molecular weight of unknown compounds and polymers. Osmometry is the measurement of the osmotic strength of a substance. This is often used by chemists for the determination of average molecular weight. Osmometry is also useful for estimating the drought tolerance of plant leaves. == See also == Clifton nanolitre osmometer, an example of a freezing point depression osmometer. == References ==


id: parahydrogen-induced-polarization-20260505-0
file: data/en.wikipedia.org/wiki/Parahydrogen-induced_polarization-0.md
category: reference
title: Parahydrogen-induced polarization
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Parahydrogen-induced_polarization
date_saved: 2026-05-05T10:05:38.756117+00:00
instance: kb-cron
parent: parahydrogen-induced-polarization-20260505-0
summary:
Parahydrogen-induced polarization (PHIP) is a hyperpolarization method utilizing parahydrogen (one of the two spin isomers of hydrogen), which can temporarily increase the signal intensity commonly in nuclear magnetic resonance (NMR), and has been explored in many demonstrations using magnetic resonance imaging (MRI) experiments. PHIP methods are commonly categorized in two ways – hydrogenative PHIP and non-hydrogenative PHIP. In hydrogenative PHIP, the parahydrogen is being added directly to the molecular site via hydrogenation reaction. Commonly encountered types of hydrogenative PHIP techniques include PASADENA and ALTADENA. In non-hydrogenative PHIP, spin order transfer from the parahydrogen to the target nuclei of interest occurs through a catalyst in a reversible exchange process. Common types of non-hydrogenative PHIP methods include SABRE. PHIP methods have most commonly been applied to NMR spectroscopy, which can include in-vitro metabolite monitoring, in addition to in-vivo or ex-vivo MRI demonstrations. == Overview == Conventional non 1H NMR and MRI signals can be weak due to low nuclear spin polarization levels at thermal equilibrium and/or low natural abundance of NMR compatible nuclear isotopes (e.g., 13C, 15N, etc.). Common methods to improve sensitivity may include increasing sample concentration or using an instrument containing a larger magnetic field. However, hyperpolarization techniques can enhance


id: parahydrogen-induced-polarization-20260505-1
file: data/en.wikipedia.org/wiki/Parahydrogen-induced_polarization-1.md
category: reference
title: Parahydrogen-induced polarization
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Parahydrogen-induced_polarization
date_saved: 2026-05-05T10:05:38.756117+00:00
instance: kb-cron
parent: parahydrogen-induced-polarization-20260505-0
summary:
== Applications in chemistry of materials == In chemistry of materials, PHIP has been used as a tool for studying polymer hyperpolarization, and varying catalyst formats/platforms (e.g., immobilized onto polymeric materials). In the context of PHIP, the types of polymers can include synthetic polymers and biopolymers/macromolecules, where PHIP helps to counter the sensitivity limitations by conventional NMR for these categories. The following polymer-related chemistry of materials applications in PHIP can include hyperpolarizing polymeric targets, or polymer-enabled hyperpolarization platforms. For hyperpolarizing polymeric targets, this depends on whether the polymeric architecture includes PHIP reactive sites/handles (e.g., unsaturated bond) for hydrogenative PHIP, which can be placed at the terminal chain end, or side chains. An example application includes the works of Münnemann et al. in their article titled “Hyperbranched polymers for molecular imaging: designing polymers for parahydrogen induced polarisation (PHIP).” Additionally, inclusion of polymer-related platforms used in PHIP can be in the form of catalyst immobilization, which can enable improved recyclability of catalyst, and improved polymer support engineering for solvent compatibility. An example of polymer supports compatible with a specific solvent (e.g., water) for catalyst immobilization to enable recyclability can be found in the works of Min et al., in the article titled


id: parahydrogen-induced-polarization-20260505-2
file: data/en.wikipedia.org/wiki/Parahydrogen-induced_polarization-2.md
category: reference
title: Parahydrogen-induced polarization
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Parahydrogen-induced_polarization
date_saved: 2026-05-05T10:05:38.756117+00:00
instance: kb-cron
parent: parahydrogen-induced-polarization-20260505-0
summary:
== Non-hydrogenative PHIP == Non-hydrogenative PHIP refers to reversible exchange methods, typically entailing SABRE (Signal Amplification By Reversible Exchange). This method does not add hydrogen to the target molecule via hydrogenation reaction, in contrast to hydrogenative PHIP, which achieves this via pairwise addition to an unsaturated bond. Reversible exchange refers to the way in which parahydrogen binds to the metal containing catalyst (commonly iridium-based), where the singlet spin order of parahydrogen gets converted to observable magnetization via spin-spin transfer interactions to the target nuclei of interest. Once the target nuclei are hyperpolarized, the molecule unbinds the catalyst (hence reversible). This process of hyperpolarizing with a new set of parahydrogen and soon-to-be hyperpolarized substrate can occur in repeated polarization cycles with zero structural changes. Note that while SABRE almost always entails a non-hydrogenative process, less commonly it can include hydrogen exchange methods. The source of the signal enhancement in non-hydrogenative PHIP comes from the singlet ordered parahydrogen, and through the metal catalyst, that spin order is transferred to the target nuclei (non-zero spin quantum number) through the scalar coupling network (i.e., J-coupling network, spin coupling network), which results in observable magnetization. The efficiency of the spin order transfer strongly depends on


id: parahydrogen-induced-polarization-20260505-3
file: data/en.wikipedia.org/wiki/Parahydrogen-induced_polarization-3.md
category: reference
title: Parahydrogen-induced polarization
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Parahydrogen-induced_polarization
date_saved: 2026-05-05T10:05:38.756117+00:00
instance: kb-cron
parent: parahydrogen-induced-polarization-20260505-0
summary:
== Hydrogenative PHIP == Hydrogenative PHIP is a branch of PHIP that involves chemically adding parahydrogen to an unsaturated bond of the target substrate via a hydrogenation reaction. Such unsaturated bonds are commonly seen as alkene or alkyne functionalities, where both of the hydrogen atoms in parahydrogen are added via pairwise addition. Specifically, pairwise addition is key to preserving the singlet spin order derived from parahydrogen. This is in large contrast to non-hydrogenative PHIP methods, such as SABRE-related methods, where reversible exchange occurs while the targeted molecule remains chemically unchanged. Intuitively, the molecule detected in hydrogenative PHIP is the hydrogenated product, not the original unsaturated precursor. The transfer of singlet spin order from the pairwise addition of parahydrogen to the hydrogenated product results in signal readout in NMR/MRI. The parahydrogen’s singlet state is NMR silent, thus not directly observable. The two added hydrogen atoms are typically magnetically inequivalent, hence allow for an observable enhanced magnetic resonance signal that may result in antiphase signals, and can even lead to spin order transfer from the hydrogen nuclei to a targeted nucleus (e.g., 13C, 15N). Features listed, such as enhanced NMR signals and antiphase signal patterns are dependent on the chemical nature of


id: particle-mass-analyser-20260505-0
file: data/en.wikipedia.org/wiki/Particle_mass_analyser-0.md
category: reference
title: Particle mass analyser
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Particle_mass_analyser
date_saved: 2026-05-05T10:05:39.990756+00:00
instance: kb-cron
parent: particle-mass-analyser-20260505-0
summary:
A Particle mass analyser (PMA) is an instrument for classifying aerosol particles according to their mass-to-charge ratio using opposing electrical and centrifugal forces. This allows the classifier to select particles of a specified mass-to-charge ratio independent of particle shape. It one of the three types of monodisperse aerosol classifier, the others being the differential mobility analyser (DMA, for electrical mobility size), and the aerodynamic aerosol classifier (AAC, for relaxation time, or aerodynamic diameter). The corresponding three quantities are related by the expression τ = mB, where τ is relaxation time, m is mass and B is mobility. Further work improved the technique by engineering the centrifugal force to match the electrostatic force across the whole classification region, thus increasing the throughput. == References ==


id: perturbed-angular-correlation-20260505-0
file: data/en.wikipedia.org/wiki/Perturbed_angular_correlation-0.md
category: reference
title: Perturbed angular correlation
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Perturbed_angular_correlation
date_saved: 2026-05-05T10:05:41.189355+00:00
instance: kb-cron
parent: perturbed-angular-correlation-20260505-0
summary:
The perturbed γ-γ angular correlation, PAC for short or PAC-Spectroscopy, is a method of nuclear solid-state physics with which magnetic and electric fields in crystal structures can be measured. In doing so, electrical field gradients and the Larmor frequency in magnetic fields as well as dynamic effects are determined. With this very sensitive method, which requires only about 10–1000 billion atoms of a radioactive isotope per measurement, material properties in the local structure, phase transitions, magnetism and diffusion can be investigated. The PAC method is related to nuclear magnetic resonance and the Mössbauer effect, but shows no signal attenuation at very high temperatures. Today only the time-differential perturbed angular correlation (TDPAC) is used. == History and development == PAC goes back to a theoretical work by Donald R. Hamilton from 1940. The first successful experiment was carried out by Brady and Deutsch in 1947. Essentially spin and parity of nuclear spins were investigated in these first PAC experiments. However, it was recognized early on that electric and magnetic fields interact with the nuclear moment, providing the basis for a new form of material investigation: nuclear solid-state spectroscopy. Step by step the theory was developed. After Abragam and Pound published their


id: perturbed-angular-correlation-20260505-1
file: data/en.wikipedia.org/wiki/Perturbed_angular_correlation-1.md
category: reference
title: Perturbed angular correlation
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Perturbed_angular_correlation
date_saved: 2026-05-05T10:05:41.189355+00:00
instance: kb-cron
parent: perturbed-angular-correlation-20260505-0
summary:
PAC is a statistical method: Each radioactive probe atom sits in its own environment. In crystals, due to the high regularity of the arrangement of the atoms or ions, the environments are identical or very similar, so that probes on identical lattice sites experience the same hyperfine field or magnetic field, which then becomes measurable in a PAC spectrum. On the other hand, for probes in very different environments, such as in amorphous materials, a broad frequency distribution or no is usually observed and the PAC spectrum appears flat, without frequency response. With single crystals, depending on the orientation of the crystal to the detectors, certain transition frequencies can be reduced or extinct, as can be seen in the example of the PAC spectrum of zinc oxide (ZnO). == Instrumental setup == In the typical PAC spectrometer, a setup of four 90° and 180° planar arrayed detectors or six octahedral arrayed detectors are placed around the radioactive source sample. The detectors used are scintillation crystals of BaF2 or NaI. For modern instruments today mainly LaBr3:Ce or CeBr3 are used. Photomultipliers convert the weak flashes of light into electrical signals generated in the scintillator by gamma radiation. In classical instruments these


id: perturbed-angular-correlation-20260505-2
file: data/en.wikipedia.org/wiki/Perturbed_angular_correlation-2.md
category: reference
title: Perturbed angular correlation
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Perturbed_angular_correlation
date_saved: 2026-05-05T10:05:41.189355+00:00
instance: kb-cron
parent: perturbed-angular-correlation-20260505-0
summary:
=== Diffusion === In the diffusion method, the radioactive probe is usually diluted in a solvent applied to the sample, dried and it is diffused into the material by tempering it. The solution with the radioactive probe should be as pure as possible, since all other substances can diffuse into the sample and affect thereby the measurement results. The sample should be sufficiently diluted in the sample. Therefore, the diffusion process should be planned so that a uniform distribution or sufficient penetration depth is achieved. === Added during synthesis === PAC probes may also be added during the synthesis of sample materials to achieve the most uniform distribution in the sample. This method is particularly well suited if, for example, the PAC probe diffuses only poorly in the material and a higher concentration in grain boundaries is to be expected. Since only very small samples are necessary with PAC (about 5 mm), micro-reactors can be used. Ideally, the probe is added to the liquid phase of the sol-gel process or one of the later precursor phases. === Neutron activation === In neutron activation, the probe is prepared directly from the sample material by converting very small part of one of


id: perturbed-angular-correlation-20260505-3
file: data/en.wikipedia.org/wiki/Perturbed_angular_correlation-3.md
category: reference
title: Perturbed angular correlation
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Perturbed_angular_correlation
date_saved: 2026-05-05T10:05:41.189355+00:00
instance: kb-cron
parent: perturbed-angular-correlation-20260505-0
summary:
g {\displaystyle g} is the Landé g-factor und u N {\displaystyle u_{N}} is the nuclear magneton. With N = M − M ′ {\displaystyle N=M-M'} follows: E m a g n ( M ) − E m a g n ( M ′ ) = − ( M − M ′ ) g μ N B z = N ℏ ω L {\displaystyle E_{magn}(M)-E_{magn}(M')=-(M-M')g\mu _{N}B_{z}=N\hbar \omega _{L}} From the general theory we get: G k 1 k 2 N N = ( 2 k 1 + 1 ) ( 2 k 2 + 1 ) ⋅ e − i N ω L t × ∑ M ( I I k 1 M ′ − M N ) ( I I k 2 M ′ − M N ) {\displaystyle G_{k_{1}k_{2}}^{NN}={\sqrt {(2k_{1}+1)(2k_{2}+1)}}\cdot e^{-iN\omega _{L}t}\times \sum _{M}{\begin{pmatrix}I&I&k_{1}\\M'&-M&N\\\end{pmatrix}}{\begin{pmatrix}I&I&k_{2}\\M'&-M&N\\\end{pmatrix}}} For the magnetic interaction follows: G k 1 k 2 N N = e ( − i N ω L t ) {\displaystyle G_{k_{1}k_{2}}^{NN}=e^{\left({-iN\omega _{L}t}\right)}} === Static electric quadrupole interaction === The energy of the hyperfine electrical interaction between the charge distribution of the core and the extranuclear static electric field can be extended to multipoles. The monopole term only causes an energy shift and


id: perturbed-angular-correlation-20260505-4
file: data/en.wikipedia.org/wiki/Perturbed_angular_correlation-4.md
category: reference
title: Perturbed angular correlation
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Perturbed_angular_correlation
date_saved: 2026-05-05T10:05:41.189355+00:00
instance: kb-cron
parent: perturbed-angular-correlation-20260505-0
summary:
G k 1 k 2 N N = ∑ n s n N k 1 k 2 cos ⁡ ( n ω Q 0 t ) {\displaystyle G_{k_{1}k_{2}}^{NN}=\sum _{n}s_{nN}^{k_{1}k_{2}}\cos {(n\omega _{Q}^{0}t)}} With the factor for the probabilities of the observed frequencies: s n N k 1 k 2 = ( 2 k 1 + 1 ) ( 2 k 2 + 1 ) ⋅ ∑ M , M ′ ( I I k 1 M ′ − M N ) ( I I k 2 M ′ − M N ) {\displaystyle s_{nN}^{k_{1}k_{2}}={\sqrt {(2k_{1}+1)(2k_{2}+1)}}\cdot \sum _{M,M'}{\begin{pmatrix}I&I&k_{1}\\M'&-M&N\\\end{pmatrix}}{\begin{pmatrix}I&I&k_{2}\\M'&-M&N\\\end{pmatrix}}} As far as the magnetic dipole interaction is concerned, the electrical quadrupole interaction also induces a precision of the angular correlation in time and this modulates the quadrupole interaction frequency. This frequency is an overlap of the different transition frequencies ω n {\displaystyle \omega _{n}} . The relative amplitudes of the various components depend on the orientation of the electric field gradient relative to the detectors (symmetry axis) and the asymmetry parameter η {\displaystyle \eta } . For a probe with different probe nuclei, one needs a parameter that allows a direct comparison: Therefore, the quadrupole coupling constant ν Q {\displaystyle \nu _{Q}} independent


