# kb

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


id: perturbed-angular-correlation-20260505-5
file: data/en.wikipedia.org/wiki/Perturbed_angular_correlation-5.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:
W ( k → 1 , k → 2 ) = ∑ M i , M f , σ 1 , σ 2 | ∑ M ⟨ M f | H 2 | M ⟩ ⟨ M | H 1 | M i ⟩ | 2 {\displaystyle W({\vec {k}}_{1},{\vec {k}}_{2})=\sum _{M_{i},M_{f},\sigma _{1},\sigma _{2}}\left|\sum _{M}\langle M_{f}|{\mathcal {H}}_{2}|M\rangle \langle M|{\mathcal {H}}_{1}|M_{i}\rangle \right|^{2}} W ( k → 1 , k → 2 ) = W ( Θ ) = ∑ k g e r a d e k m a x A k ( 1 ) A k ( 2 ) P k ( cos ⁡ Θ ) {\displaystyle W({\vec {k}}_{1},{\vec {k}}_{2})=W(\Theta )=\sum _{k_{gerade}}^{k_{max}}A_{k}(1)A_{k}(2)P_{k}(\cos {\Theta })} 0 ≤ k ≤ {\displaystyle 0\leq k\leq } Minimum von ( 2 I , l 1 + l 1 ′ , l 2 + l 2 ′ ) {\displaystyle (2I,l_{1}+l_{1}',l_{2}+l_{2}')} W ( Θ , t ) = ∑ k = 2 , 4 A k k P k ( cos ⁡ Θ ) {\displaystyle W(\Theta ,t)=\sum _{k=2,4}A_{kk}P_{k}(\cos {\Theta })} | M a ⟩ → Λ ( t ) | M a = ∑ M b | M b ⟩ ⟨ M b | Λ ( t )


id: phase-shift-interferometry-20260505-0
file: data/en.wikipedia.org/wiki/Phase_Shift_Interferometry-0.md
category: reference
title: Phase Shift Interferometry
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Phase_Shift_Interferometry
date_saved: 2026-05-05T10:05:42.390129+00:00
instance: kb-cron
parent: phase-shift-interferometry-20260505-0
summary:
Phase Shift Interferometry (PSI) is a technique for areal surface characterisation that focuses on digitising the interference data acquired during a controlled phase shift, usually introduced by the mechanical oscillation of an interference objective. The technique provides full 3D images with typical height measurement repeatability of less than 1 nm, independent of field size. It is a powerful method that allows analysing interferograms to recover phase information. Traditionally, interferograms were measured by locating the centre of a fringe and then tracing along it. Phase shift interferometry avoids the need to track the location of fringes and enables a point-by-point reconstruction of the wavefront. PSI offers significantly lower measurement noise, potentially as low as 0.01 nm. It is the preferred technique for measuring the surface roughness of super-smooth surfaces. == Principle of Operation == Interferometers utilize the wave properties of light to analyse surface characteristics, particularly surface height variations. For evaluating areal surface topography, interferometers separate the source light so that it follows two independent paths: one includes a reference surface and the other the object surface. The separated light beams then recombine and are directed to a digital camera that measures the resultant light intensity over multiple image points simultaneously.


id: photoactivated-localization-microscopy-20260505-0
file: data/en.wikipedia.org/wiki/Photoactivated_localization_microscopy-0.md
category: reference
title: Photoactivated localization microscopy
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Photoactivated_localization_microscopy
date_saved: 2026-05-05T10:05:43.599525+00:00
instance: kb-cron
parent: photoactivated-localization-microscopy-20260505-0
summary:
Photo-activated localization microscopy (PALM or FPALM) and stochastic optical reconstruction microscopy (STORM) are widefield (as opposed to point scanning techniques such as laser scanning confocal microscopy) fluorescence microscopy imaging methods that allow obtaining images with a resolution beyond the diffraction limit. The methods were proposed in 2006 in the wake of a general emergence of optical super-resolution microscopy methods, and were featured as Methods of the Year for 2008 by the Nature Methods journal. The development of PALM as a targeted biophysical imaging method was largely prompted by the discovery of new species and the engineering of mutants of fluorescent proteins displaying a controllable photochromism, such as photo-activatible GFP. However, the concomitant development of STORM, sharing the same fundamental principle, originally made use of paired cyanine dyes. One molecule of the pair (called activator), when excited near its absorption maximum, serves to reactivate the other molecule (called reporter) to the fluorescent state. A growing number of dyes are used for PALM, STORM and related techniques, both organic fluorophores and fluorescent proteins. Some are compatible with live cell imaging, others allow faster acquisition or denser labeling. The choice of a particular fluorophore ultimately depends on the application and on its underlying


id: photoactivated-localization-microscopy-20260505-1
file: data/en.wikipedia.org/wiki/Photoactivated_localization_microscopy-1.md
category: reference
title: Photoactivated localization microscopy
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Photoactivated_localization_microscopy
date_saved: 2026-05-05T10:05:43.599525+00:00
instance: kb-cron
parent: photoactivated-localization-microscopy-20260505-0
summary:
where N is the number of collected photons, a is the pixel size of the imaging detector, b 2 {\displaystyle b^{2}} is the average background signal and s i {\displaystyle s_{i}} is the standard deviation of the point spread function. The requirement of localizing at the same time multiple fluorophores simultaneously over an extended area determines the reason why these methods are wide-field, employing as a detector a CCD, EMCCD or a CMOS camera. The requirement for an enhanced signal-to-noise ratio to maximize localization precision determines the frequent combination of this concept with widefield fluorescent microscopes allowing optical sectioning, such as total internal reflection fluorescence microscopes (TIRF) and light sheet fluorescence microscopes. == Super-resolution image == The resolution of the final image is limited by the precision of each localization and the number of localizations, instead of by diffraction. The super resolution image is therefore a pointillistic representation of the coordinates of all the localized molecules. The super resolution image is commonly rendered by representing each molecule in the image plane as a two dimensional Gaussian with amplitude proportional to the number of photons collected, and the standard deviation depending on the localization precision. == Applications == === Multicolor PALM/STORM


id: photochemical-action-plots-20260505-0
file: data/en.wikipedia.org/wiki/Photochemical_action_plots-0.md
category: reference
title: Photochemical action plots
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Photochemical_action_plots
date_saved: 2026-05-05T10:05:44.791207+00:00
instance: kb-cron
parent: photochemical-action-plots-20260505-0
summary:
Photochemical action plots are a scientific tool used to understand the effects of different wavelengths of light on photochemical reactions. The methodology involves exposing a reaction solution to the same number of photons at varying monochromatic wavelengths, monitoring the conversion or reaction yield of starting materials and/or reaction products. Such global high-resolution analysis of wavelength-dependent chemical reactivity has revealed that maxima in absorbance and reactivity often do not align. Photochemical action plots are historically connected to (biological) action spectra. == Historical development == The study of biological responses to specific wavelengths dates back to the late 19th century. Research primarily focused on assessing photodamage from solar radiation using broad-band lamps and narrow filters. These studies quantified effects such as cell viability, production of erythema, vitamin D3 degradation, DNA changes, and skin cancer appearance. The first biological action spectrum was recorded by Engelmann, who used a prism to produce different colors of light and then illuminated cladophora in a bacteria suspension. He discovered the effects of different light wavelengths on photosynthesis, marking the first recorded action spectrum of photosynthesis. Critical evaluations of active wavelength regions in these studies helped identify contributing chromophores to processes such as photosynthesis. These chromophores are key


id: photoconductive-atomic-force-microscopy-20260505-0
file: data/en.wikipedia.org/wiki/Photoconductive_atomic_force_microscopy-0.md
category: reference
title: Photoconductive atomic force microscopy
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Photoconductive_atomic_force_microscopy
date_saved: 2026-05-05T10:05:46.030587+00:00
instance: kb-cron
parent: photoconductive-atomic-force-microscopy-20260505-0
summary:
Photoconductive atomic force microscopy (PC-AFM) is a variant of atomic force microscopy that measures photoconductivity in addition to surface forces. == Background == Multi-layer photovoltaic cells have gained popularity since mid 1980s. At the time, research was primarily focused on single-layer photovoltaic (PV) devices between two electrodes, in which PV properties rely heavily on the nature of the electrodes. In addition, single layer PV devices notoriously have a poor fill factor. This property is largely attributed to resistance that is characteristic of the organic layer. The fundamentals of pc-AFM are modifications to traditional AFM and focus on the use of pc-AFM in PV characterization. In pc-AFM the major modifications include: a second illumination laser, an inverted microscope and a neutral density filter. These components assist in the precise alignment of the illumination laser and the AFM tip within the sample. Such modifications must complement the existing principals and instrumental modules of pc-AFM so as to minimize the effect of mechanical noise and other interferences on the cantilever and sample. The original exploration of the PV effect can be accredited to research published by Henri Becquerel in 1839. Becquerel noticed the generation of a photocurrent after illumination when he submerged platinum


id: photoconductive-atomic-force-microscopy-20260505-1
file: data/en.wikipedia.org/wiki/Photoconductive_atomic_force_microscopy-1.md
category: reference
title: Photoconductive atomic force microscopy
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Photoconductive_atomic_force_microscopy
date_saved: 2026-05-05T10:05:46.030587+00:00
instance: kb-cron
parent: photoconductive-atomic-force-microscopy-20260505-0
summary:
== Theory == The fundamental principles of photoconductive atomic force microscopy (pc-AFM) are based on those of traditional atomic force microscopy (AFM) in that an ultrafine metallic tip scans the surface of a material to quantify topological features. The working premises for all types of AFM techniques are largely dependent on the fundamentals of the AFM cantilever, metallic tip, scanning piezo-tube and the feedback loop that transfers information from lasers that guide the motion of the probe across the surface of a sample. The ultra-fine dimensions of the tip and the way the tip scans the surface produces lateral resolutions of 500 nm or less. In AFM, the cantilever and tip functions as a mass on a spring. When a force acts on the spring (cantilever), the spring response is directly related to the magnitude of the force. k is defined as the force constant of the cantilever. Hooke's law for cantilever motion: f = − k d {\displaystyle f=-kd} The forces acting on the tip are such that the spring (cantilever) remains soft but responds to the applied force, with a detectable resonant frequency, fo. In Hooke's law, k is the spring constant of the cantilever and mo is


id: photoconductive-atomic-force-microscopy-20260505-2
file: data/en.wikipedia.org/wiki/Photoconductive_atomic_force_microscopy-2.md
category: reference
title: Photoconductive atomic force microscopy
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Photoconductive_atomic_force_microscopy
date_saved: 2026-05-05T10:05:46.030587+00:00
instance: kb-cron
parent: photoconductive-atomic-force-microscopy-20260505-0
summary:
The principles of the piezo-tube is dependent upon how the piezo-electric material reacts with an applied voltage to either the interior or exterior of the tube. When voltage is applied to the two electrodes connected to the scanner, the tube will expand or contract causing motion to the AFM tip in the direction of this movement. This phenomenon is illustrated as the piezo-tube becomes displaced by an angle, θ. As the tube is displaced, the sample that, in traditional AFM is fixed to the tube generates lateral translation and rotation relative to the AFM tip, thus movement of the tip is generated in the x and y directions When voltage is applied of the inside of the tube, movement in the z-direction is implemented. The relationship between the movement of the piezo-tube and the direction of the displacement of the AFM tip assumes that the tube is perfectly symmetric. When no voltage is applied to the tube the z-axis bisects the tube, sample and sample stage symmetrically. When a voltage is applied to the exterior of the tube (x and y motion), the expansion of the tube can be understood as a circular arc. In this equation, the r term


id: photoconductive-atomic-force-microscopy-20260505-3
file: data/en.wikipedia.org/wiki/Photoconductive_atomic_force_microscopy-3.md
category: reference
title: Photoconductive atomic force microscopy
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Photoconductive_atomic_force_microscopy
date_saved: 2026-05-05T10:05:46.030587+00:00
instance: kb-cron
parent: photoconductive-atomic-force-microscopy-20260505-0
summary:
In traditional instrumentation, the stage is a cylindrical piezo-tube scanner that minimizes the effect of mechanical noise. Most cylindrical piezos are between 12 and 24 mm in length and 6 and 12 mm in diameter. The exterior of the piezo-tube is coated with a thin layer of conducting metal so that this region can sustain an electric field. The interior of the cylinder is divided into four regions (x and y regions) by non-conducting metallic strips. Electrical leads are fixed to one end and the exterior wall of the cylinder so that a current can be applied. When a voltage is applied to the exterior, the cylinder expands in x and y direction. Voltage along the interior of the tube causes cylinder expansion in the z-direction and thus movement of the tip in the z-direction. The placement of the piezo tube is dependent upon the type of AFM performed and the mode of analysis. However the z-piezo must always be fixed above the tip and cantilever to control the z-motion. This configuration is most often seen in the c-AFM and pc-AFM modifications to make room for additional instrumental components which are placed below the scanning stage. This is particularly true


id: photoconductive-atomic-force-microscopy-20260505-4
file: data/en.wikipedia.org/wiki/Photoconductive_atomic_force_microscopy-4.md
category: reference
title: Photoconductive atomic force microscopy
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Photoconductive_atomic_force_microscopy
date_saved: 2026-05-05T10:05:46.030587+00:00
instance: kb-cron
parent: photoconductive-atomic-force-microscopy-20260505-0
summary:
The main components and instrumentation of c-AFM instrumentation are identical to that required for a pc-AFM module. The only modifications are the illumination source, filter and inverted microscope objective that are located beneath the sample substrate. In fact, most pc-AFM instruments are simply modified from existing cp-AFM instrumentation. The first report of this instrumental modification came in 2008. In that paper, Lee and coworkers implemented the aforementioned modifications to examine the resolution of photocurrent imaging. Their design consisted of three main units: a conductive mirror plate, steering mirror and laser source. The main difficulty with the previously existing c-AFM instrumentation is the inability of the technique for characterizing photonic devices. Specifically, it is difficult to measure changes in local and nano-scale electrical properties that result from the photonic effect. The optical illumination component (laser) was added to the c-AFM module in order to make such properties visible. Early in development, the main concerns regarding pc-AFM include: physical configuration, laser disturbance and laser alignment. Although many of these concerns have been resolved pc-AFM modules are still widely modified from c-AFM and traditional AFM instruments. The first main concern deals with component configuration and whether or not there is physically enough space


id: photoconductive-atomic-force-microscopy-20260505-5
file: data/en.wikipedia.org/wiki/Photoconductive_atomic_force_microscopy-5.md
category: reference
title: Photoconductive atomic force microscopy
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Photoconductive_atomic_force_microscopy
date_saved: 2026-05-05T10:05:46.030587+00:00
instance: kb-cron
parent: photoconductive-atomic-force-microscopy-20260505-0
summary:
== Applications == Although there is significant insight as to how OPVs work, it is still difficult to relate the device's functionality to local film structures. This difficulty may be attributed to the minimal current generation at a given point within OPVs. Through pc-AFM, OPV devices can be probed at nano-scale level and can help to increase our fundamental knowledge of mechanisms involved in OPVs at nano-scale level. pc-AFM is capable of gathering information such as the mapping of photocurrents, differences in film morphology, determination of donor-acceptor domains, current density-voltage plots, quantum efficiencies, and approximate charge carrier mobilities. One of the other notable characteristics of pc-AFM is its ability to provide concurrent information regarding the topological and photocurrent properties of the device at nano-scale. Using this concurrent sampling method, the sample handling is minimized and can provide more accurate results. In a study by Pingree et al., pc-AFM was used to measure how spatial deviations in the photocurrent generation developed with different processing techniques. The authors were able to compare these photocurrent variations to the duration of the annealing process. They have concluded that lengthening the annealing time allows for improved nano-scale phase separation as well as created a more


id: photoconductive-atomic-force-microscopy-20260505-6
file: data/en.wikipedia.org/wiki/Photoconductive_atomic_force_microscopy-6.md
category: reference
title: Photoconductive atomic force microscopy
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Photoconductive_atomic_force_microscopy
date_saved: 2026-05-05T10:05:46.030587+00:00
instance: kb-cron
parent: photoconductive-atomic-force-microscopy-20260505-0
summary:
Once the sample preparation is complete, the sample is placed onto the scanning stage of the pc-AFM module. This scanning stage is used for x-y piezo translation, completely independent of the z-direction while using a z-piezo scanner. The piezo-electric material within this scanner converts a change in the applied potential into mechanical motion which moves the samples with nanometer resolution and accuracy. There are two variations in which the z-piezo scanner functions; one is contact mode while the other is tapping mode. Many commercial AFM cantilever tips have pre-measured resonant frequencies and force constants which are provided to the customer. As sampling proceeds, the cantilever tip's position changes, which causes the scanning laser wavelength (650 nm) to deviate from its original position on the detector. The z-piezo scanner then recognizes this deviation and moves vertically to return the laser spot to its set position. This vertical movement by the z-piezo scanner is correlated to a change in voltage. Sampling in contact mode relies upon intermolecular forces between the tip and surface as depicted by Van der Waals force. As the sampling begins, the tip is moved close to the sample which creates a weakly attractive force between them. Another force


id: photoconductive-atomic-force-microscopy-20260505-7
file: data/en.wikipedia.org/wiki/Photoconductive_atomic_force_microscopy-7.md
category: reference
title: Photoconductive atomic force microscopy
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Photoconductive_atomic_force_microscopy
date_saved: 2026-05-05T10:05:46.030587+00:00
instance: kb-cron
parent: photoconductive-atomic-force-microscopy-20260505-0
summary:
The range of bias commonly applied is usually limited to between −5 V to +5 V for most studies. This can be achieved by applying a forward bias or reverse bias to the sample through the spotted gold contact. By adjusting this bias, along with the current passing through the cantilever, one can adjust the repulsive/attractive forces between the sample and the tip. When a reverse bias is applied (tip is negative relative to the sample), the tip and the sample experience attractive forces between them. This current density measurement is then combined with the topographical information previously gathered from the AFM tip and cantilever. The resulting image displays the local variations in morphology with the current density measurements superimposed onto of them. Several methods have been employed to help reduce both mechanical and acoustic vibrations within the system. Mechanical vibrations are mainly attributed to traffic in and out of a building Other sources of mechanical vibrations have often been seen in the higher stories of a building due to reduced damping from building supports. This source of vibrational noise is easily controlled through the use of a vibration isolation table. Acoustical vibrations are far more common than mechanical vibrations.


id: photon-induced-near-field-electron-microscopy-20260505-0
file: data/en.wikipedia.org/wiki/Photon-Induced_Near-field_Electron_Microscopy-0.md
category: reference
title: Photon-Induced Near-field Electron Microscopy
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Photon-Induced_Near-field_Electron_Microscopy
date_saved: 2026-05-05T10:05:47.220980+00:00
instance: kb-cron
parent: photon-induced-near-field-electron-microscopy-20260505-0
summary:
Photon-Induced Near-field Electron Microscopy (PINEM) is a variant of the Ultrafast Transmission Electron Microscopy technique and is based on the inelastic coupling between electrons and photons in presence of a surface or a nanostructure. This method allows one to investigate time-varying nanoscale electromagnetic fields in an electron microscope. For visible light, such inelastic coupling between electrons and light, i.e. direct absorption or emission of photons, is forbidden in free space (vacuum) since it is not possible to simultaneously conserve both energy and momentum. This constraint can be circumvented when photon momentum is broadened as a result of light being reflected or scattered from a surface or nanostructure. This process would then generate evanescently confined near-fields with a broad momentum distribution, reaching high intensities in a nanoconfined space and thus also boosting the cross section of electron-light coupling. Theoretically, the analytical description of the phenomenon has been provided by Park et al., Garcia de Abajo et al. and Feist et al. In these works the authors demonstrated that the strength of electron-light interaction depends on the linear coupling to the electric field projection along the electron propagation direction. In particular, Feist et al. also experimentally demonstrated that the interaction process results


id: photonic-force-microscope-20260505-0
file: data/en.wikipedia.org/wiki/Photonic_force_microscope-0.md
category: reference
title: Photonic force microscope
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Photonic_force_microscope
date_saved: 2026-05-05T10:05:48.403870+00:00
instance: kb-cron
parent: photonic-force-microscope-20260505-0
summary:
Photonic force microscopy (PFM) is an optical-tweezers-based microscopy technique. A small dielectric particle (20 nm to several micrometres) is held by a strongly focused laser beam. The forward scattered light, i.e. the light whose orientation is slightly changed while passing through the particle, and unscattered light are collected by a lens and projected onto a Quadrant Photo-Diode (QPD), i.e. a Position sensitive device (PSD). These two components interfere in the detector and produce signals, which permit the detection of the bead's position in three dimensions. The precision is very good (as low as 0.1 nm) and the recording speed is very high (up to 1 MHz). Brownian motion deflects the bead from the resting position. A time sequence of measured positions allows one to derive the optical potential in which the particle is held. The PFM is sensitive to the environment of the particle and has been used in a variety of different experiments that e.g. monitor space that can be filled by particles inside agarose or the fate of small latex beads captured by macrophages. A similar concept of scanning a bead with an optical trap over a surface was invented in 1993 by Ghislain and W. W. Webb.


id: porosimetry-20260505-0
file: data/en.wikipedia.org/wiki/Porosimetry-0.md
category: reference
title: Porosimetry
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Porosimetry
date_saved: 2026-05-05T10:05:49.544741+00:00
instance: kb-cron
parent: porosimetry-20260505-0
summary:
Porosimetry is an analytical technique used to determine various quantifiable aspects of a material's porous structure, such as pore diameter, total pore volume, surface area, and bulk and absolute densities. The technique involves the intrusion of a non-wetting liquid (often mercury) at high pressure into a material through the use of a porosimeter. The pore size can be determined based on the external pressure needed to force the liquid into a pore against the opposing force of the liquid's surface tension. A force balance equation known as Washburn's equation for the above material having cylindrical pores is given as: P L − P G = − 4 σ cos ⁡ θ D P {\displaystyle P_{L}-P_{G}=-{\frac {4\sigma \cos \theta }{D_{P}}}} P L {\displaystyle P_{L}} = pressure of liquid P G {\displaystyle P_{G}} = pressure of gas σ {\displaystyle \sigma } = surface tension of liquid θ {\displaystyle \theta } = contact angle of intrusion liquid D P {\displaystyle D_{P}} = pore diameter Since the technique is usually performed within a vacuum, the initial gas pressure is zero. The contact angle of mercury with most solids is between 135° and 142°, so an average of 140° can be taken without much error.


id: protein-chemical-shift-prediction-20260505-0
file: data/en.wikipedia.org/wiki/Protein_chemical_shift_prediction-0.md
category: reference
title: Protein chemical shift prediction
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Protein_chemical_shift_prediction
date_saved: 2026-05-05T10:05:50.752609+00:00
instance: kb-cron
parent: protein-chemical-shift-prediction-20260505-0
summary:
Protein chemical shift prediction is a branch of biomolecular nuclear magnetic resonance spectroscopy that aims to accurately calculate protein chemical shifts from protein coordinates. Protein chemical shift prediction was first attempted in the late 1960s using semi-empirical methods applied to protein structures solved by X-ray crystallography. Since that time protein chemical shift prediction has evolved to employ much more sophisticated approaches including quantum mechanics, machine learning and empirically derived chemical shift hypersurfaces. The most recently developed methods exhibit remarkable precision and accuracy. == Protein chemical shifts == NMR chemical shifts are often called the mileposts of nuclear magnetic resonance spectroscopy. Chemists have used chemical shifts for more than 50 years as highly reproducible, easily measured parameters to map out the covalent structure of small organic molecules. Indeed, the sensitivity of NMR chemical shifts to the type and character of neighbouring atoms, combined with their reasonably predictable tendencies has made them invaluable for both deciphering and describing the structure of thousands of newly synthesized or newly isolated compounds The same sensitivity to a variety of important protein structural features has made protein chemical shifts equally valuable to protein chemists and biomolecular NMR spectroscopists. In particular, protein chemical shifts are sensitive not


id: qemscan-20260505-0
file: data/en.wikipedia.org/wiki/QEMSCAN-0.md
category: reference
title: QEMSCAN
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/QEMSCAN
date_saved: 2026-05-05T10:05:51.918183+00:00
instance: kb-cron
parent: qemscan-20260505-0
summary:
QEMSCAN is the name for an integrated automated mineralogy and petrography system providing quantitative analysis of minerals, rocks and man-made materials. QEMSCAN is an abbreviation standing for quantitative evaluation of materials by scanning electron microscopy, and a registered trademark owned by FEI Company since 2009. Prior to 2009, QEMSCAN was developed, marketed and sold by Intellection Pty Ltd (a company owned by CSIRO) and also marketed and sold by LEO (Leica electron optics, a company jointly owned by Leica and Zeiss). The integrated system comprises a scanning electron microscope (SEM) with a large specimen chamber, up to four light-element energy-dispersive X-ray spectroscopy (EDS) detectors, an electron backscatter detector, and proprietary software and hardware controlling automated data acquisition. The offline software package iDiscover provides data processing and reporting functionality. == Mineral identification and quantification == QEMSCAN creates phase assemblage maps of a specimen surface scanned by a high-energy accelerated electron beam along a predefined raster scan pattern. Low-count energy-dispersive X-ray spectra (EDX) are generated and provide information on the elemental composition at each measurement point. The elemental composition in combination with back-scattered electron (BSE) brightness and x-ray count rate information is converted into mineral phases. QEMSCAN data includes bulk mineralogy and


id: random-coil-index-20260505-0
file: data/en.wikipedia.org/wiki/Random_coil_index-0.md
category: reference
title: Random coil index
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Random_coil_index
date_saved: 2026-05-05T10:05:53.091599+00:00
instance: kb-cron
parent: random-coil-index-20260505-0
summary:
Random coil index (RCI) predicts protein flexibility by calculating an inverse weighted average of backbone secondary chemical shifts and predicting values of model-free order parameters as well as per-residue RMSD of NMR and molecular dynamics ensembles from this parameter. The key advantages of this protocol over existing methods of studying protein flexibility are it does not require prior knowledge of a protein's tertiary structure, it is not sensitive to the protein's overall tumbling and it does not require additional NMR measurements beyond the standard experiments for backbone assignments. The application of secondary chemical shifts to characterize protein flexibility is based on an assumption that the proximity of chemical shifts to random coil values is a manifestation of increased protein mobility, while significant differences from random coil values are an indication of a relatively rigid structure. Even though chemical shifts of rigid residues may adopt random coil values as a result of comparable contributions of shielding and deshielding effects (e.g. from torsion angles, hydrogen bonds, ring currents, etc.), combining the chemical shifts from multiple nuclei into a single parameter allows one to decrease the influence of these flexibility false positives. The improved performance originates from the different probabilities of random coil


id: recurrence-tracking-microscope-20260505-0
file: data/en.wikipedia.org/wiki/Recurrence_tracking_microscope-0.md
category: reference
title: Recurrence tracking microscope
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Recurrence_tracking_microscope
date_saved: 2026-05-05T10:05:54.290181+00:00
instance: kb-cron
parent: recurrence-tracking-microscope-20260505-0
summary:
A recurrence tracking microscope (RTM) is a microscope that is based on the quantum recurrence phenomenon of an atomic wave packet. It is used to investigate the nano-structure on a surface. == History == In 2006, Farhan Saif used quantum recurrence phenomena of wave packet as a probe to study nano-structures on a surface, naming it Recurrence Tracking Microscope (RTM). == Background == The tunneling phenomenon is used as a probe to study nano-structure on a surface with the help of scanning tunneling microscope (STM). The STM is a powerful device for viewing surfaces at the atomic level. The STM can be used not only in an ultra-high vacuum, but also in air and a variety of other media and at temperatures ranging from nearly zero to hundreds of kelvin. This idea was enhanced to create the atomic force microscope (AFM), which is a very high-resolution type of scanning probe microscope with resolution of fractions of a nanometer. The AFM is one of the foremost tools for imaging, measuring and manipulating matter at the nanoscale. The application of RTM includes the visualization and measurement of surface features having sizes and dimensions as small as one nanometer in research and development


id: reflectance-difference-spectroscopy-20260505-0
file: data/en.wikipedia.org/wiki/Reflectance_difference_spectroscopy-0.md
category: reference
title: Reflectance difference spectroscopy
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Reflectance_difference_spectroscopy
date_saved: 2026-05-05T10:05:55.479852+00:00
instance: kb-cron
parent: reflectance-difference-spectroscopy-20260505-0
summary:
Reflectance difference spectroscopy (RDS) is a spectroscopic technique which measures the difference in reflectance of two beams of light that are shone in normal incident on a surface with different linear polarizations. It is also known as reflectance anisotropy spectroscopy (RAS). It is calculated as: R D S = 2 r α − r β r α + r β , r ∈ C {\displaystyle RDS=2{\frac {r_{\alpha }-r_{\beta }}{r_{\alpha }+r_{\beta }}},r\in \mathbb {C} } r α {\displaystyle r_{\alpha }} and r β {\displaystyle r_{\beta }} are the reflectance in two different polarizations. The method was introduced in 1985 for the study optical properties of the cubic semiconductors silicon and germanium. Due to its high surface sensitivity and independence of ultra-high vacuum, its use has been expanded to in situ monitoring of epitaxial growth or the interaction of surfaces with adsorbates. To assign specific features in the signal to their origin in morphology and electronic structure, theoretical modelling by density functional theory is required. == References ==


id: reststrahlen-effect-20260505-0
file: data/en.wikipedia.org/wiki/Reststrahlen_effect-0.md
category: reference
title: Reststrahlen effect
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Reststrahlen_effect
date_saved: 2026-05-05T10:05:56.711908+00:00
instance: kb-cron
parent: reststrahlen-effect-20260505-0
summary:
The Reststrahlen effect (German: “residual rays”) is a reflectance phenomenon in which electromagnetic radiation within a narrow energy band cannot propagate within a given medium due to a change in refractive index concurrent with the specific absorbance band of the medium in question; this narrow energy band is termed the Reststrahlen band. As a result of this inability to propagate, normally incident Reststrahlen-band radiation experiences strong reflection or total reflection from that medium. The energies at which Reststrahlen bands occur vary and are particular to the individual compound. Numerous physical attributes of a compound will have an effect on the appearance of the Reststrahlen band. These include phonon band-gap, particle/grain size, strongly absorbing compounds, compounds with optically opaque bands in the infrared. == Appearance == The term Reststrahlen was coined following the observation by Heinrich Rubens in 1898 that repeated reflection of an infrared beam at the surface of a given material suppresses radiation at all wavelengths except for certain spectral intervals, and Rubens detected wavelengths of sizes around 60 μm. The measured intensity for these special intervals (the Reststrahlen range) indicates a reflectance of up to 80% or even more, while the maximum reflectance due to infrared bands of


id: rutherford-backscattering-spectrometry-20260505-0
file: data/en.wikipedia.org/wiki/Rutherford_backscattering_spectrometry-0.md
category: reference
title: Rutherford backscattering spectrometry
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Rutherford_backscattering_spectrometry
date_saved: 2026-05-05T10:05:57.856664+00:00
instance: kb-cron
parent: rutherford-backscattering-spectrometry-20260505-0
summary:
Rutherford backscattering spectrometry (RBS) is an analytical technique used in materials science. Sometimes referred to as high-energy ion scattering (HEIS) spectrometry, RBS is used to determine the structure and composition of materials by measuring the backscattering of a beam of high energy ions (typically protons or alpha particles) impinging on a sample. == Geiger–Marsden experiment == Rutherford backscattering spectrometry is named after Lord Rutherford, a physicist sometimes referred to as the father of nuclear physics. Rutherford supervised a series of experiments carried out by Hans Geiger and Ernest Marsden between 1909 and 1914 studying the scattering of alpha particles through metal foils. While attempting to eliminate "stray particles" they believed to be caused by an imperfection in their alpha source, Rutherford suggested that Marsden attempt to measure backscattering from a gold foil sample. According to the then-dominant plum-pudding model of the atom, in which small negative electrons were spread through a diffuse positive region, backscattering of the high-energy positive alpha particles should have been nonexistent. At most small deflections should occur as the alpha particles passed almost unhindered through the foil. Instead, when Marsden positioned the detector on the same side of the foil as the alpha particle source, he


id: rutherford-backscattering-spectrometry-20260505-1
file: data/en.wikipedia.org/wiki/Rutherford_backscattering_spectrometry-1.md
category: reference
title: Rutherford backscattering spectrometry
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Rutherford_backscattering_spectrometry
date_saved: 2026-05-05T10:05:57.856664+00:00
instance: kb-cron
parent: rutherford-backscattering-spectrometry-20260505-0
summary:
where Z 1 {\displaystyle Z_{1}} and Z 2 {\displaystyle Z_{2}} are the atomic numbers of the incident and target nuclei. This equation is written in the centre of mass frame of reference and is therefore not a function of the mass of either the projectile or the target nucleus. The scattering angle in the laboratory frame of reference θ 1 {\displaystyle \theta _{1}} is not the same as the scattering angle in the centre of mass frame of reference θ {\displaystyle \theta } (although for RBS experiments they are usually very similar). However, heavy ion projectiles can easily recoil lighter ions which, if the geometry is right, can be ejected from the target and detected. This is the basis of the Elastic Recoil Detection (ERD, with synonyms ERDA, FRS, HFS) technique. RBS often uses a He beam which readily recoils H, so simultaneous RBS/ERD is frequently done to probe the hydrogen isotope content of samples (although H ERD with a He beam above 1 MeV is not Rutherford: see http://www-nds.iaea.org/sigmacalc). For ERD the scattering angle in the lab frame of reference is quite different from that in the centre of mass frame of reference. Heavy ions cannot backscatter from light


id: rutherford-backscattering-spectrometry-20260505-2
file: data/en.wikipedia.org/wiki/Rutherford_backscattering_spectrometry-2.md
category: reference
title: Rutherford backscattering spectrometry
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Rutherford_backscattering_spectrometry
date_saved: 2026-05-05T10:05:57.856664+00:00
instance: kb-cron
parent: rutherford-backscattering-spectrometry-20260505-0
summary:
An ion source, usually alpha particles (He2+ ions) or, less commonly, protons. A linear particle accelerator capable of accelerating incident ions to high energies, usually in the range 1-3 MeV. A detector capable of measuring the energies of backscattered ions over some range of angles. Two common source/acceleration arrangements are used in commercial RBS systems, working in either one or two stages. One-stage systems consist of a He+ source connected to an acceleration tube with a high positive potential applied to the ion source, and the ground at the end of the acceleration tube. This arrangement is simple and convenient, but it can be difficult to achieve energies of much more than 1 MeV due to the difficulty of applying very high voltages to the system. Two-stage systems, or "tandem accelerators", start with a source of He− ions and position the positive terminal at the center of the acceleration tube. A stripper element included in the positive terminal removes electrons from ions which pass through, converting He− ions to He++ ions. The ions thus start out being attracted to the terminal, pass through and become positive, and are repelled until they exit the tube at ground. This arrangement, though more


id: rutherford-backscattering-spectrometry-20260505-3
file: data/en.wikipedia.org/wiki/Rutherford_backscattering_spectrometry-3.md
category: reference
title: Rutherford backscattering spectrometry
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Rutherford_backscattering_spectrometry
date_saved: 2026-05-05T10:05:57.856664+00:00
instance: kb-cron
parent: rutherford-backscattering-spectrometry-20260505-0
summary:
R = 2 Z 1 Z 2 e 2 L E 0 {\displaystyle R=2{\sqrt {\frac {Z_{1}Z_{2}e^{2}L}{E_{0}}}}} When an ion is scattered from deep inside a sample, it can then re-scatter off a second atom, creating a second blocked cone in the direction of the scattered trajectory. This can be detected by carefully varying the detection angle relative to the incident angle. Channeling is observed when the incident beam is aligned with a major symmetry axis of the crystal. Incident nuclei which avoid collisions with surface atoms are excluded from collisions with all atoms deeper in the sample, due to blocking by the first layer of atoms. When the interatomic distance is large compared to the radius of the blocked cone, the incident ions can penetrate many times the interatomic distance without being backscattered. This can result in a drastic reduction of the observed backscattered signal when the incident beam is oriented along one of the symmetry directions, allowing determination of a sample's regular crystal structure. Channeling works best for very small blocking radii, i.e. for high-energy, low-atomic-number incident ions such as He+. The tolerance for the deviation of the ion beam angle of incidence relative to the symmetry direction depends


id: rutherford-backscattering-spectrometry-20260505-4
file: data/en.wikipedia.org/wiki/Rutherford_backscattering_spectrometry-4.md
category: reference
title: Rutherford backscattering spectrometry
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Rutherford_backscattering_spectrometry
date_saved: 2026-05-05T10:05:57.856664+00:00
instance: kb-cron
parent: rutherford-backscattering-spectrometry-20260505-0
summary:
=== Bibliography === Rhodes, Richard (1988) [1986]. The Making of the Atomic Bomb. Simon & Schuster. ISBN 978-0-684-81378-3. Oura, K.; Lifshits, V.G.; Saranin, A.A.; Zotov, A.V.; et al. (2003). Surface Science: An Introduction. Springer-Verlag. ISBN 3-540-00545-5. Feldman, L.C.; Mayer, J.W.; Picraux, S.T. (1982). Materials Analysis by Ion Channeling. Academic Press. Feldman, L.C.; Mayer, J.W. (1986). Fundamentals of Surface and Thin Film Analysis. Prentice-Hall. "RBS Theory Tutorial". Evans Analytical Group: Training. Retrieved 2007-10-10. "RBS Instrumentation Tutorial". Evans Analytical Group: Training. Retrieved 2007-10-10. Hobbs, C.P.; McMillan, J.W.; Palmer, D.W. (1988). "The effects of surface topography in nuclear microprobe Rutherford backscattering analysis". Nuclear Instruments and Methods in Physics Research B. 30 (3): 342–348. Bibcode:1988NIMPB..30..342H. doi:10.1016/0168-583X(88)90023-7. Frenken, J.W.M.; Maree, P.M.J.; van der Veen, J.F. (1986). "Observation of surface-initiated melting". Phys. Rev. B. 34 (11): 7506–7516. Bibcode:1986PhRvB..34.7506F. doi:10.1103/PhysRevB.34.7506. hdl:1887/71635. PMID 9939429. S2CID 27028634. Maragkos, F.; Dimitrakopoulos, N.; Georgali, E.; Kokkoris, M.; Lagogiannis, A.; Ntemou, E.; Patronis, N.; Tsakiris, Th.; Ziagkova, A. (2021-11-15). "Differential cross-section measurements for proton elastic scattering on natSi in the energy range Ep, lab = 3–5 MeV, suitable for EBS". Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms. 507: 20–26. Bibcode:2021NIMPB.507...20M. doi:10.1016/j.nimb.2021.09.006. ISSN 0168-583X. S2CID


id: scanning-confocal-electron-microscopy-20260505-0
file: data/en.wikipedia.org/wiki/Scanning_confocal_electron_microscopy-0.md
category: reference
title: Scanning confocal electron microscopy
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Scanning_confocal_electron_microscopy
date_saved: 2026-05-05T10:05:59.015556+00:00
instance: kb-cron
parent: scanning-confocal-electron-microscopy-20260505-0
summary:
Scanning confocal electron microscopy (SCEM) is an electron microscopy technique analogous to scanning confocal optical microscopy (SCOM). In this technique, the studied sample is illuminated by a focussed electron beam, as in other scanning microscopy techniques, such as scanning transmission electron microscopy or scanning electron microscopy. However, in SCEM, the collection optics are arranged symmetrically to the illumination optics to gather only the electrons that pass the beam focus. This results in superior depth resolution of the imaging. The technique is relatively new and is being actively developed. == History == The idea of SCEM logically follows from SCOM and thus is rather old. However, practical design and construction of scanning confocal electron microscope is a complex problem first solved by Nestor J. Zaluzec. His first scanning confocal electron microscope demonstrated the 3D properties of the SCEM, but have not realized the sub-nanometer lateral spatial resolution achievable with high-energy electrons (lateral resolution of only ~80 nm has been demonstrated). Several groups are currently working on construction of atomic resolution SCEM. In particular, atomically resolved SCEM images have already been obtained == Operation == The sample is illuminated by a focused electron beam, and the beam is re-focused on the detector,


id: scanning-electron-cryomicroscopy-20260505-0
file: data/en.wikipedia.org/wiki/Scanning_electron_cryomicroscopy-0.md
category: reference
title: Scanning electron cryomicroscopy
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Scanning_electron_cryomicroscopy
date_saved: 2026-05-05T10:06:00.207402+00:00
instance: kb-cron
parent: scanning-electron-cryomicroscopy-20260505-0
summary:
Scanning electron cryomicroscopy (CryoSEM) is a form of electron microscopy where a hydrated but cryogenically fixed sample is imaged on a scanning electron microscope's cold stage in a cryogenic chamber. The cooling is usually achieved with liquid nitrogen. CryoSEM of biological samples with a high moisture content can be done faster with fewer sample preparation steps than conventional SEM. In addition, the dehydration processes needed to prepare a biological sample for a conventional SEM chamber create numerous distortions in the tissue leading to structural artifacts during imaging. == See also == Electron microscopy Electron cryomicroscopy Transmission electron cryomicroscopy == References ==


id: scanning-electron-microscope-20260505-0
file: data/en.wikipedia.org/wiki/Scanning_electron_microscope-0.md
category: reference
title: Scanning electron microscope
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Scanning_electron_microscope
date_saved: 2026-05-05T10:06:01.397531+00:00
instance: kb-cron
parent: scanning-electron-microscope-20260505-0
summary:
A scanning electron microscope (SEM) is a type of electron microscope that produces images of a sample by scanning the surface with a focused beam of electrons. The electrons interact with atoms in the sample, producing various signals that contain information about the surface topography and composition. The electron beam is scanned in a raster scan pattern, and the position of the beam is combined with the intensity of the detected signal to produce an image. In the most common SEM mode, secondary electrons emitted by atoms excited by the electron beam are detected using a secondary electron detector (Everhart–Thornley detector). The number of secondary electrons that can be detected, and thus the signal intensity, depends, among other things, on specimen topography. Some SEMs can achieve resolutions better than 1 nanometer. Specimens are observed in high vacuum in a conventional SEM, or in low vacuum or wet conditions in a variable pressure or environmental SEM, and at a wide range of cryogenic or elevated temperatures with specialized instruments. == History == An account of the early history of scanning electron microscopy has been presented by McMullan. Although Max Knoll produced a photo with a 50 mm object-field-width showing channeling contrast


id: scanning-electron-microscope-20260505-1
file: data/en.wikipedia.org/wiki/Scanning_electron_microscope-1.md
category: reference
title: Scanning electron microscope
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Scanning_electron_microscope
date_saved: 2026-05-05T10:06:01.397531+00:00
instance: kb-cron
parent: scanning-electron-microscope-20260505-0
summary:
SEM samples have to be small enough to fit on the specimen stage, and may need special preparation to increase their electrical conductivity and to stabilize them, so that they can withstand the high vacuum conditions and the high energy beam of electrons. Samples are generally mounted rigidly on a specimen holder or stub using a conductive adhesive. SEM is used extensively for defect analysis of semiconductor wafers, and manufacturers make instruments that can examine any part of a 300 mm semiconductor wafer. Many instruments have chambers that can tilt an object of that size to 45° and provide continuous 360° rotation. Nonconductive specimens collect charge when scanned by the electron beam, and especially in secondary electron imaging mode, this causes scanning faults and other image artifacts. For conventional imaging in the SEM, specimens must be electrically conductive, at least at the surface, and electrically grounded to prevent the accumulation of electrostatic charge. Metal objects require little special preparation for SEM except for cleaning and conductively mounting to a specimen stub. Non-conducting materials are usually coated with an ultrathin coating of electrically conducting material, deposited on the sample either by low-vacuum sputter coating, electroless deposition or by high-vacuum evaporation. Conductive


id: scanning-electron-microscope-20260505-2
file: data/en.wikipedia.org/wiki/Scanning_electron_microscope-2.md
category: reference
title: Scanning electron microscope
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Scanning_electron_microscope
date_saved: 2026-05-05T10:06:01.397531+00:00
instance: kb-cron
parent: scanning-electron-microscope-20260505-0
summary:
In a typical SEM, an electron beam is thermionically emitted from an electron gun fitted with a tungsten filament cathode. Tungsten is normally used in thermionic electron guns because it has the highest melting point and lowest vapor pressure of all metals, thereby allowing it to be electrically heated for electron emission, and because of its low cost. Other types of electron emitters include lanthanum hexaboride (LaB6) cathodes, which can be used in a standard tungsten filament SEM if the vacuum system is upgraded, or field emission guns (FEG), which may be of the cold-cathode type using tungsten single crystal emitters or the thermally assisted Schottky type, that use emitters of tungsten single crystals coated in zirconium oxide. The electron beam, which typically has an energy ranging from 0.2 keV to 40 keV, is focused by one or two condenser lenses to a spot about 0.4 nm to 5 nm in diameter. The beam passes through pairs of scanning coils or pairs of deflector plates in the electron column, typically in the final lens, which deflect the beam in the x and y axes so that it scans in a raster fashion over a rectangular area of the sample surface.


id: scanning-electron-microscope-20260505-3
file: data/en.wikipedia.org/wiki/Scanning_electron_microscope-3.md
category: reference
title: Scanning electron microscope
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Scanning_electron_microscope
date_saved: 2026-05-05T10:06:01.397531+00:00
instance: kb-cron
parent: scanning-electron-microscope-20260505-0
summary:
Backscattered electrons (BSE) consist of high-energy electrons originating in the electron beam, that are reflected or back-scattered out of the specimen interaction volume by elastic scattering interactions with specimen atoms. Since heavy elements (high atomic number) backscatter electrons more strongly than light elements (low atomic number), and thus appear brighter in the image, BSEs are used to detect contrast between areas with different chemical compositions. The Everhart–Thornley detector, which is normally positioned to one side of the specimen, is inefficient for the detection of backscattered electrons because few such electrons are emitted in the solid angle subtended by the detector, and because the positively biased detection grid has little ability to attract the higher energy BSE. Dedicated backscattered electron detectors are positioned above the sample in a "doughnut" type arrangement, concentric with the electron beam, maximizing the solid angle of collection. BSE detectors are usually either of scintillator or of semiconductor types. When all parts of the detector are used to collect electrons symmetrically about the beam, atomic number contrast is produced. However, strong topographic contrast is produced by collecting back-scattered electrons from one side above the specimen using an asymmetrical, directional BSE detector; the resulting contrast appears as illumination


id: scanning-electron-microscope-20260505-4
file: data/en.wikipedia.org/wiki/Scanning_electron_microscope-4.md
category: reference
title: Scanning electron microscope
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Scanning_electron_microscope
date_saved: 2026-05-05T10:06:01.397531+00:00
instance: kb-cron
parent: scanning-electron-microscope-20260505-0
summary:
Conventional SEM requires samples to be imaged under vacuum, because a gas atmosphere rapidly spreads and attenuates electron beams. As a consequence, samples that produce a significant amount of vapour, e.g. wet biological samples or oil-bearing rock, must be either dried or cryogenically frozen. Processes involving phase transitions, such as the drying of adhesives or melting of alloys, liquid transport, chemical reactions, and solid-air-gas systems, in general cannot be observed with conventional high-vacuum SEM. In environmental SEM (ESEM), the chamber is evacuated of air, but water vapor is retained near its saturation pressure, and the residual pressure remains relatively high. This allows the analysis of samples containing water or other volatile substances. With ESEM, observations of living insects have been possible. The first commercial development of the ESEM in the late 1980s allowed samples to be observed in low-pressure gaseous environments (e.g. 1–50 Torr or 0.1–6.7 kPa) and high relative humidity (up to 100%). This was made possible by the development of a secondary-electron detector capable of operating in the presence of water vapour and by the use of pressure-limiting apertures with differential pumping in the path of the electron beam to separate the vacuum region (around the gun and


id: scanning-electron-microscope-20260505-5
file: data/en.wikipedia.org/wiki/Scanning_electron_microscope-5.md
category: reference
title: Scanning electron microscope
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Scanning_electron_microscope
date_saved: 2026-05-05T10:06:01.397531+00:00
instance: kb-cron
parent: scanning-electron-microscope-20260505-0
summary:
=== SEM image coloring === Very often, published SEM images are artificially colored. This may be done for aesthetic effect, to clarify structure or to add a realistic appearance to the sample and generally does not add information about the specimen. Coloring may be performed manually with photo-editing software, or semi-automatically with dedicated software using feature-detection or object-oriented segmentation. Alternately, when additional information from other detectors like EDX, EBSD, ECCI or cathodoluminescence is available, it can be merged as color channel(s) to provide rich material information in a single, high-resolution image. === Color built using multiple electron detectors === In some configurations more information is gathered per pixel, often by the use of multiple detectors. As a common example, secondary electron and backscattered electron detectors are superimposed and a color is assigned to each of the images captured by each detector, with a result of a combined color image where colors are related to the density of the components. This method is known as density-dependent color SEM (DDC-SEM). Micrographs produced by DDC-SEM retain topographical information, which is better captured by the secondary electrons detector and combine it to the information about density, obtained by the backscattered electron detector. === Analytical


id: scanning-electron-microscope-20260505-6
file: data/en.wikipedia.org/wiki/Scanning_electron_microscope-6.md
category: reference
title: Scanning electron microscope
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Scanning_electron_microscope
date_saved: 2026-05-05T10:06:01.397531+00:00
instance: kb-cron
parent: scanning-electron-microscope-20260505-0
summary:
=== Applications of 3D SEM === One possible application is measuring the roughness of ice crystals. This method can combine variable-pressure environmental SEM and the 3D capabilities of the SEM to measure roughness on individual ice crystal facets, convert it into a computer model and run further statistical analysis on the model. Other measurements include fractal dimension, examining fracture surface of metals, characterization of materials, corrosion measurement, and dimensional measurements at the nano scale (step height, volume, angle, flatness, bearing ratio, coplanarity, etc.). SEM is also used by art conservationists to discern threats to paintings' surface stability due to aging, such as the formations of complexes of zinc ions with fatty acids. Forensic scientists use SEM to detect art forgeries. == Gallery of SEM images == The following are examples of images taken using an SEM. == See also == == References == == External links == General HowStuffWorks – How Scanning Electron Microscopes Work Learn to use an SEM – An online learning environment for people wanting to use an SEM. Provided by Microscopy Australia Virtual SEM – sparkler – an interactive simulation of a scanning electron microscope (SEM) Multichannel color SEM imaging – and with BSE Video on


id: scanning-joule-expansion-microscopy-20260505-0
file: data/en.wikipedia.org/wiki/Scanning_joule_expansion_microscopy-0.md
category: reference
title: Scanning joule expansion microscopy
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Scanning_joule_expansion_microscopy
date_saved: 2026-05-05T10:06:02.583665+00:00
instance: kb-cron
parent: scanning-joule-expansion-microscopy-20260505-0
summary:
In microscopy, scanning joule expansion microscopy (SJEM) is a form of scanning probe microscopy heavily based on atomic force microscopy (AFM) that maps the temperature distribution along a surface. Resolutions down to 10 nm have been achieved and 1 nm resolution is theoretically possible. Thermal measurements at the nanometer scale are of both academic and industrial interest, particularly in regards to nanomaterials and modern integrated circuits. == Basic Principles == Scanning joule expansion microscopy is based on the contact operation model of atomic force microscopy. During the operation, the tip on the cantilever is brought into contact with the surface of the sample. AC or pulsed electrical signal is applied to the sample creating Joule heating and resulting in periodic thermal expansion. At the same time, the laser, which is focused on the top surface of the cantilever and the photodiode of the equipment, detects the displacement of the cantilever. The detecting photodiode is composed of two segments, which normalizes the incoming signal deflected from the cantilever. This differential signal is proportional to the cantilever deflection. The deflection signals are caused not only by sample topography, but also by the thermal expansion caused by Joule heating. Since AFM has feedback


id: scanning-joule-expansion-microscopy-20260505-1
file: data/en.wikipedia.org/wiki/Scanning_joule_expansion_microscopy-1.md
category: reference
title: Scanning joule expansion microscopy
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Scanning_joule_expansion_microscopy
date_saved: 2026-05-05T10:06:02.583665+00:00
instance: kb-cron
parent: scanning-joule-expansion-microscopy-20260505-0
summary:
=== Electrostatic force interaction === When a bias is applied to the sample for Joule heating, there is also an electrostatic force interaction between the tip and the sample. The tip-sample electrostatic force can be represented as F = 1 2 d ⁡ C d ⁡ z V 2 {\displaystyle F{=}{\frac {1}{2}}{\operatorname {d} C \over \operatorname {d} z}V^{2}} , in which C is the tip sample capacitance, and V is the voltage, Z is the tip and sample distance. This force also depends on V 2 {\displaystyle V^{2}} , the same as the expansion signal. Usually electrostatic force is small because the sample has been covered with a polymer layer. However, when applied voltage is large, this force needs to be considered. Electrostatic force does not depend on the frequency of the applied AC signal, therefore allowing for a simple method to differentiate and account for this contribution. === Thermal expansion === This is primary mode of signal and the main goal of SJEM. The substrate expands when Joule heated, resulting in change in the measured profile by the cantilever, resulting in a change in signal. However, thermal expansion coefficients can vary significantly. For example, the thermal expansion coefficients of


id: scanning-joule-expansion-microscopy-20260505-2
file: data/en.wikipedia.org/wiki/Scanning_joule_expansion_microscopy-2.md
category: reference
title: Scanning joule expansion microscopy
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Scanning_joule_expansion_microscopy
date_saved: 2026-05-05T10:06:02.583665+00:00
instance: kb-cron
parent: scanning-joule-expansion-microscopy-20260505-0
summary:
=== Integrated circuit transistors === Understanding thermal properties of transistors are vital for the semiconductor industry as well. Similar to interconnects, repeated thermal stresses can eventually lead to device failure. However, more importantly, electrical behavior, and therefore device parameters change significantly with temperature. SJEM has been used to map local hotspots in thin film transistors. By determining the location of these hotspots, they can be better understood and reduced or eliminated. One disadvantage to this method is that, like AFM, only the surface can be mapped. Consequently, additional processing steps would be required in order to map buried features, such as most features in modern IC transistors. === Nanoscale materials === Nanoscale materials are becoming widely investigated for their many advantages in commercial electronics. In particular, these materials are known for excellent mobility as well as ability to carry high current densities. In addition, new applications have been realized for these materials including thermoelectrics, solar cells, fuel cells, etc. However, significant decrease in size scale in conjunction with increases in current density and device density leads to extreme temperature rises in these devices. These temperature fluctuations can influence electrical behavior and lead to device failure. Therefore, these thermal effects must


id: scanning-transmission-x-ray-microscopy-20260505-0
file: data/en.wikipedia.org/wiki/Scanning_transmission_X-ray_microscopy-0.md
category: reference
title: Scanning transmission X-ray microscopy
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Scanning_transmission_X-ray_microscopy
date_saved: 2026-05-05T10:06:03.946842+00:00
instance: kb-cron
parent: scanning-transmission-x-ray-microscopy-20260505-0
summary:
Scanning transmission X-ray microscopy (STXM) is a type of X-ray microscopy in which a zone plate focuses an X-ray beam onto a small spot, a sample is scanned in the focal plane of the zone plate and the transmitted X-ray intensity is recorded as a function of the sample position. A stroboscopic scheme is used where the excitation is the pump and the synchrotron X-ray flashes are the probe. X-ray microscopes work by exposing a film or charged coupled device detector to detect X-rays that pass through the specimen. The image formed is of a thin section of specimen. Newer X-ray microscopes use X-ray absorption spectroscopy to heterogeneous materials at high spatial resolution. The essence of the technique is a combination of spectromicroscopy, imaging with spectral sensitivity, and microspectroscopy, recording spectra from very small spots. == Benefits of STXM == === Radiation damage === Electron energy loss spectroscopy (EELS) in combination with transmission electron microscopy has modest spectral resolution and is rather damaging to the sample material. STXM with variable X-ray energy gives high spectral resolution. Radiation damage effects are typically two orders of magnitude lower than for EELS. Radiation concerns are also relevant with organic materials. === Samples with


id: seec-microscopy-20260505-0
file: data/en.wikipedia.org/wiki/SEEC_microscopy-0.md
category: reference
title: SEEC microscopy
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/SEEC_microscopy
date_saved: 2026-05-05T10:06:05.131624+00:00
instance: kb-cron
parent: seec-microscopy-20260505-0
summary:
Surface-enhanced ellipsometric contrast microscopy (SEEC) uses an upright or inverted optical microscope in a crossed polarization configuration and specific supporting plates called surfs on which the sample is deposited for observation. It is described as an optical nanoscopy technique. SEEC relies on precise control of the reflection properties of polarized light on a surface, improving the axial sensitivity of an optical microscope by two orders of magnitude without reducing its lateral resolution. Applications could include real-time visualization of films as thin as 0.3 micrometers and isolated nano-objects in air and in water. == Principles == A 2006 study on polarized light coherence led to the development of new supports (the surfs) having contrast amplification properties for standard optical microscopy in cross-polarizer mode. Made of optical layers on an opaque or transparent substrate, these supports do not modify the light polarization after reflection even if the numerical aperture of the incident source is significant. This property is modified when a sample is present on a surf; a non-null light component is then detected after it has been analyzed, rendering the sample visible. The performance of these supports is evaluated by measuring the contrast (C) of the sample defined as: C =


id: single-cell-analysis-20260505-0
file: data/en.wikipedia.org/wiki/Single-cell_analysis-0.md
category: reference
title: Single-cell analysis
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Single-cell_analysis
date_saved: 2026-05-05T10:06:06.277163+00:00
instance: kb-cron
parent: single-cell-analysis-20260505-0
summary:
In cell biology, single-cell analysis and subcellular analysis refer to the study of genomics, transcriptomics, proteomics, metabolomics, and cell–cell interactions at the level of an individual cell, as opposed to more conventional methods which study bulk populations of many cells. The concept of single-cell analysis originated in the 1970s. Before the discovery of heterogeneity, single-cell analysis mainly referred to the analysis or manipulation of an individual cell within a bulk population of cells under the influence of a particular condition using optical or electron microscopy. Due to the heterogeneity seen in both eukaryotic and prokaryotic cell populations, analyzing the biochemical processes and features of a single cell makes it possible to discover mechanisms which are too subtle or infrequent to be detectable when studying a bulk population of cells; in conventional multi-cell analysis, this variability is usually masked by the average behavior of the larger population. Technologies such as fluorescence-activated cell sorting allow the precise isolation of selected single cells from complex samples, while high-throughput single-cell partitioning technologies enable the simultaneous molecular analysis of hundreds or thousands of individual unsorted cells; this is particularly useful for the analysis of variations in gene expression between genotypically identical cells, allowing the definition


id: single-cell-analysis-20260505-1
file: data/en.wikipedia.org/wiki/Single-cell_analysis-1.md
category: reference
title: Single-cell analysis
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Single-cell_analysis
date_saved: 2026-05-05T10:06:06.277163+00:00
instance: kb-cron
parent: single-cell-analysis-20260505-0
summary:
Controlled priming and PCR amplification: Adapter-Linker PCR WGA Random priming and PCR amplification: DOP-PCR, MALBAC Random priming and isothermal amplification: MDA The Adapter-Linker PCR WGA is reported in many comparative studies to be the best-performing technique for diploid single-cell mutation analysis, thanks to its very low Allelic Dropout effect, and for copy number variation profiling due to its low noise, both with aCGH and with NGS low Pass Sequencing. This method is only applicable to human cells, both fixed and unfixed. One widely adopted WGA technique is called degenerate oligonucleotide–primed polymerase chain reaction (DOP-PCR). This method uses the well established DNA amplification method PCR to try and amplify the entire genome using a large set of primers. Although simple, this method has been shown to have very low genome coverage. An improvement on DOP-PCR is Multiple displacement amplification (MDA), which uses random primers and a high fidelity enzyme, usually Φ29 DNA polymerase, to accomplish the amplification of larger fragments and greater genome coverage than DOP-PCR. Despite these improvements MDA still has a sequence-dependent bias (certain parts of the genome are amplified more than others because of their sequence, causing some parts to be overrepresented in the resulting genomic dataset). The


id: single-cell-analysis-20260505-2
file: data/en.wikipedia.org/wiki/Single-cell_analysis-2.md
category: reference
title: Single-cell analysis
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Single-cell_analysis
date_saved: 2026-05-05T10:06:06.277163+00:00
instance: kb-cron
parent: single-cell-analysis-20260505-0
summary:
==== Antibody–based methods ==== The antibody based methods use designed antibodies to bind to proteins of interest, allowing the relative abundance of multiple individual targets to be identified by one of several different techniques. Imaging: Antibodies can be bound to fluorescent molecules such as quantum dots or tagged with organic fluorophores for detection by fluorescence microscopy. Since different colored quantum dots or unique fluorophores are attached to each antibody it is possible to identify multiple different proteins in a single cell. Quantum dots can be washed off of the antibodies without damaging the sample, making it possible to do multiple rounds of protein quantification using this method on the same sample. For the methods based on organic fluorophores, the fluorescent tags are attached by a reversible linkage such as a DNA-hybrid (that can be melted/dissociated under low-salt conditions) or chemically inactivated, allowing multiple cycles of analysis, with 3-5 targets quantified per cycle. These approaches have been used for quantifying protein abundance in patient biopsy samples (e.g. cancer) to map variable protein expression in tissues and/or tumors, and to measure changes in protein expression and cell signaling in response to cancer treatment. Mass Cytometry: rare metal isotopes, not normally found in


id: single-cell-analysis-20260505-3
file: data/en.wikipedia.org/wiki/Single-cell_analysis-3.md
category: reference
title: Single-cell analysis
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Single-cell_analysis
date_saved: 2026-05-05T10:06:06.277163+00:00
instance: kb-cron
parent: single-cell-analysis-20260505-0
summary:
====== SIMS ====== Secondary-ion mass spectrometry (SIMS) is a technique similar to DESI, but while DESI is an ambient ionization technique, SIMS happens in vacuum. The solid sample surface is bombarded by a highly focused beam of primary ions. As they hit the surface, molecules are emitted from the surface and ionized. The choice of primary ions determines the size of the beam and also the extent of ionization and fragmentation. Pareek et al. performed metabolomics to trace how purines are synthesized within purinosomes and used isotope labeling and SIMS imaging to directly observe hotspots of metabolic activity within frozen HeLa cells. ====== MALDI ====== In matrix-assisted laser desorption and ionization (MALDI), the sample is incorporated in a chemical matrix that is capable of absorbing energy from a laser. Similar to SIMS, ionization happens in vacuum. Laser irradiation ablates the matrix material from the surface and results in charged gas phase matrix particles, with the analyte molecules ionized from this charged chemical matrix. Liu et al. used MALDI-MS to detect eight phospholipids from single A549 cells. MALDI MS imaging can be used for spatial metabolomics and single-cell analysis. === Purpose === The purpose of studying the proteome is to better


id: single-molecule-fret-20260505-0
file: data/en.wikipedia.org/wiki/Single-molecule_FRET-0.md
category: reference
title: Single-molecule FRET
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Single-molecule_FRET
date_saved: 2026-05-05T10:06:07.449461+00:00
instance: kb-cron
parent: single-molecule-fret-20260505-0
summary:
Single-molecule fluorescence (or Förster) resonance energy transfer (or smFRET) is a biophysical technique used to measure distances at the 1-10 nanometer scale in single molecules, typically biomolecules. It is an application of FRET wherein a pair of donor and acceptor fluorophores are excited and detected at a single molecule level. In contrast to "ensemble FRET" which provides the FRET signal of a high number of molecules, single-molecule FRET is able to resolve the FRET signal of each individual molecule. The variation of the smFRET signal is useful to reveal kinetic information that an ensemble measurement cannot provide, especially when the system is under equilibrium with no ensemble/bulk signal change. Heterogeneity among different molecules can also be observed. This method has been applied in many measurements of intramolecular dynamics such as DNA/RNA/protein folding/unfolding and other conformational changes, and intermolecular dynamics such as reaction, binding, adsorption, and desorption that are particularly useful in chemical sensing, bioassays, and biosensing. == Methodology == Single-molecule FRET measurements are typically performed on fluorescence microscopes, either using surface-immobilized or freely-diffusing molecules. Single FRET pairs are illuminated using intense light sources, typically lasers, in order to generate sufficient fluorescence signals to enable single-molecule detection. Wide-field multiphoton microscopy is


id: single-molecule-fret-20260505-1
file: data/en.wikipedia.org/wiki/Single-molecule_FRET-1.md
category: reference
title: Single-molecule FRET
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Single-molecule_FRET
date_saved: 2026-05-05T10:06:07.449461+00:00
instance: kb-cron
parent: single-molecule-fret-20260505-0
summary:
== Data analysis == Typical smFRET data of a two-dye system are time trajectories of the fluorescent emission intensities of the donor dye and the acceptor dye, called the two channels. Mainly two methods are used to obtain the emission of the two dyes: (1) accumulative measurement uses a fixed exposure time of the cameras for each frame, such as PMT, APD, EMCCD, and CMOS camera; (2) single-photon arriving time sequence measured using PMT or APD detectors. The principle is to use optical filters or dichroic mirrors to separate the emissions of the two dyes and measure them in two channels. For example, a setup using two halves of a charge-coupled device (CCD) camera is explained in the literature. For a two-dye system, the emission signals are then used to calculate the FRET efficiency between the dyes over time. The FRET efficiency is the number of photons emitted from the acceptor dye over the sum of the emissions of the donor and the acceptor dye. The time trajectories produced in every experiment may contain signals from incomplete or incorrect labeling or even aggregates. To account for this multiple research groups have developed sophisticated tools for the time trace selection based


id: single-molecule-fret-20260505-2
file: data/en.wikipedia.org/wiki/Single-molecule_FRET-2.md
category: reference
title: Single-molecule FRET
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Single-molecule_FRET
date_saved: 2026-05-05T10:06:07.449461+00:00
instance: kb-cron
parent: single-molecule-fret-20260505-0
summary:
The camera blurring signal comes from the discrete nature of the measurements. The emission signal has a mismatch with the real transition signal because one or both are stochastic (random). When a state transition happens between the readout of two emission reading intervals, the signal is the average of the two parts in the same measuring window, which then affects the state identification accuracy and eventually the rate constant analysis. This is less of a problem when the measuring frequency is much faster than the transition rate but becomes a real problem when they approach each other (figure on the right). In order to reflect the camera blurring effect in the simulated smFRET trajectories, one must simulate the data in a higher time resolution (e.g. 10 times faster) than the data collection time and then bin the data into the final trajectories. See GitHub (postFRET) for an example MATLAB codes to simulate smFRET time trajectories with a faster time resolution then bin it to the measuring time resolution (integration time) to simulate the camera blurring effect. === Photoblinking and photobleaching === The time trajectories also contain the photoblinking and photobleaching information of the two dyes. This information has to be


id: single-molecule-fret-20260505-3
file: data/en.wikipedia.org/wiki/Single-molecule_FRET-3.md
category: reference
title: Single-molecule FRET
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Single-molecule_FRET
date_saved: 2026-05-05T10:06:07.449461+00:00
instance: kb-cron
parent: single-molecule-fret-20260505-0
summary:
where i is the initial state, f is the final state of the transition, N is the number of these transitions in the time trajectories, n is the total number of states, k is the rate constant, t is the time of each state before the transition happens. For example, one measures 130 seconds (s) of smFRET time trajectories. The total time of a molecule stays on state one is t1 = 100 second (s), state two t2 = 20 s, and state three is t3 = 10 s. Among the 100 s the molecule stays state one, it transfers to state two 70 times and transfers to state three 30 times at the end of its dwell times, the rate constant of state 1 to state 2 is thus k12 = 70/100 = 0.7 s−1, the rate constant of state 1 to state 3 is k13 = 30/100 = 0.3 s−1. Typically the probabilities of the lengths of the 70 times or the 30 times transition (dwell times) are exponentially distributed (right figure). The average dwell times of the two distributions of state one, i.e. the two lifetimes, τ12 and τ13, are both the same at 1 s for


id: single-molecule-fret-20260505-4
file: data/en.wikipedia.org/wiki/Single-molecule_FRET-4.md
category: reference
title: Single-molecule FRET
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Single-molecule_FRET
date_saved: 2026-05-05T10:06:07.449461+00:00
instance: kb-cron
parent: single-molecule-fret-20260505-0
summary:
SmFRET allows for a more precise analysis of heterogeneous populations and has a few advantages when compared to ensemble FRET. One benefit of studying distances in single molecules is that heterogeneous populations can be studied more accurately with values specific for each molecule rather than computing an average based on an ensemble. This allows for the study of specific homogeneous populations within a heterogeneous population. For example, if two existing homologous populations within a heterogeneous population have different FRET values, an ensemble FRET analysis will produce a weighted averaged FRET value to represent the population as a whole. Thus, the obtained FRET value does not produce data on the two distinct populations. In contrast, smFRET would be able to differentiate between the two populations and would allow an analysis of the existing homologous populations. SmFRET also provides dynamic temporal resolution of an individual molecule that cannot be accomplished through ensemble FRET measurements. Ensemble FRET has the ability to detect well-populated transition states that accumulate in a population, but it lacks the ability to characterize intermediates that are short-lived and do not accumulate. This limit is addressed by smFRET which offers a direct way to observe the intermediates of single molecules


id: single-molecule-fret-20260505-5
file: data/en.wikipedia.org/wiki/Single-molecule_FRET-5.md
category: reference
title: Single-molecule FRET
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Single-molecule_FRET
date_saved: 2026-05-05T10:06:07.449461+00:00
instance: kb-cron
parent: single-molecule-fret-20260505-0
summary:
== Applications == A major application of smFRET is to analyze the minute biochemical nuances that facilitate protein folding. In recent years, multiple techniques have been developed to investigate single-molecule interactions that are involved in protein folding and unfolding. Force-probe techniques, using atomic force microscopy and laser tweezers, have provided information on protein stability. smFRET allows researchers to investigate molecular interactions using fluorescence. Forster resonance energy transfer (FRET) was first applied to single molecules by Ha et al. and applied to protein folding in work by Hochstrasser, Weiss, et al. The benefit that smFRET as a whole has afforded to analyze molecular interactions is the ability to test single molecule interactions directly without having to average ensembles of data. In protein folding analysis, ensemble experiments involve taking measurements of multiple proteins that are in various states of transition between their folded and unfolded state. When averaged, the protein structure that can be inferred from the ensemble of data only provides a rudimentary structural model of protein folding. However, a true understanding of protein folding requires deciphering the sequence of structural events along the folding pathways between the folded and unfolded states. It is this particular branch of research that smFRET


id: single-molecule-fret-20260505-6
file: data/en.wikipedia.org/wiki/Single-molecule_FRET-6.md
category: reference
title: Single-molecule FRET
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Single-molecule_FRET
date_saved: 2026-05-05T10:06:07.449461+00:00
instance: kb-cron
parent: single-molecule-fret-20260505-0
summary:
== Limitations == Despite making approximate estimates, a limitation of smFRET is the difficulty of obtaining the correct distance involved in energy transfer. Requiring an accurate distance estimate gives rise to a major challenge because the fluorescence of the donor and acceptor fluorophores, as well as the energy transfer, is dependent on the environment and how the dyes are oriented, which can vary depending on the flexibility of where the fluorophores are bound. In addition, the actual distance of a given state can be dynamic and the measured value represents the average distance within the collection time frame. This issue, however, is not particularly relevant when the distance estimation of the two fluorophores does not need to be determined with exact and absolute precision. Extracting kinetic information from a complicated biological system with a transition rate of around a few milliseconds or below remains challenging. The current time resolutions of such measurements are typically at the millisecond level with a few reports at the microsecond level. There is a theoretical limitation to dye photophysics. The lifetime of the excited state of a typical organic dye molecule is about 1 nanosecond. In order to obtain statistical confidence of the FRET values,


id: solid-state-nuclear-magnetic-resonance-20260505-0
file: data/en.wikipedia.org/wiki/Solid-state_nuclear_magnetic_resonance-0.md
category: reference
title: Solid-state nuclear magnetic resonance
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Solid-state_nuclear_magnetic_resonance
date_saved: 2026-05-05T10:06:08.691434+00:00
instance: kb-cron
parent: solid-state-nuclear-magnetic-resonance-20260505-0
summary:
Solid-state nuclear magnetic resonance (ssNMR) is a spectroscopy technique used to characterize atomic-level structure and dynamics in solid materials. ssNMR spectra are broader due to nuclear spin interactions which can be categorized as dipolar coupling, chemical shielding, quadrupolar interactions, and j-coupling. These interactions directly affect the lines shapes of experimental ssNMR spectra which can be seen in powder and dipolar patterns. There are many essential solid-state techniques alongside advanced ssNMR techniques that may be applied to elucidate the fundamental aspects of solid materials. ssNMR is often combined with magic angle spinning (MAS) to remove anisotropic interactions and improve the sensitivity of the technique. The applications of ssNMR further extend to biology and medicine. == Nuclear spin interactions == The resonance frequency of a nuclear spin depends on the strength of the magnetic field at the nucleus, which can be modified by isotropic (e.g. chemical shift, isotropic J-coupling) and anisotropic interactions (e.g. chemical shift anisotropy, dipolar interactions). In a classical liquid-state NMR experiment, molecular tumbling coming from Brownian motion averages anisotropic interactions to zero and they are therefore not reflected in the NMR spectrum. However, in media with no or little mobility (e.g. crystalline powders, glasses, large membrane vesicles, molecular aggregates),


id: solid-state-nuclear-magnetic-resonance-20260505-1
file: data/en.wikipedia.org/wiki/Solid-state_nuclear_magnetic_resonance-1.md
category: reference
title: Solid-state nuclear magnetic resonance
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Solid-state_nuclear_magnetic_resonance
date_saved: 2026-05-05T10:06:08.691434+00:00
instance: kb-cron
parent: solid-state-nuclear-magnetic-resonance-20260505-0
summary:
A powder pattern arises in powdered samples where crystallites are randomly oriented relative to the magnetic field so that all molecular orientations are present. In presence of a chemical shift anisotropy interaction, each orientation with respect to the magnetic field gives a different resonance frequency. If enough crystallites are present, all the different contributions overlap continuously and lead to a smooth spectrum. Fitting of the pattern in a static ssNMR experiment gives information about the shielding tensor, which are often described by the isotropic chemical shift δ i s o {\displaystyle \delta _{iso}} , the chemical shift anisotropy parameter Δ C S {\displaystyle \Delta _{CS}} , and the asymmetry parameter η {\displaystyle \eta } . === Dipolar pattern === The dipolar powder pattern (also Pake pattern) has a very characteristic shape that arises when two nuclear spins are coupled together within a crystallite. The splitting between the maxima (the "horns") of the pattern is equal to the dipolar coupling constant d {\displaystyle d} .: d = ℏ ( μ 0 4 π ) 1 r 3 γ 1 γ 2 {\displaystyle d=\hbar \left({\frac {\mu _{0}}{4\pi }}\right){\frac {1}{r^{3}}}\gamma _{1}\gamma _{2}} where γ1 and γ2 are the gyromagnetic ratios of the dipolar-coupled


id: solid-state-nuclear-magnetic-resonance-20260505-2
file: data/en.wikipedia.org/wiki/Solid-state_nuclear_magnetic_resonance-2.md
category: reference
title: Solid-state nuclear magnetic resonance
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Solid-state_nuclear_magnetic_resonance
date_saved: 2026-05-05T10:06:08.691434+00:00
instance: kb-cron
parent: solid-state-nuclear-magnetic-resonance-20260505-0
summary:
ξ ∝ ( γ H γ X ) 3 / 2 ( W X W H ) 1 / 2 ( Q H Q X ) 1 / 2 {\displaystyle \xi \propto \left({\frac {\gamma _{H}}{\gamma _{X}}}\right)^{3/2}\left({\frac {W_{X}}{W_{H}}}\right)^{1/2}\left({\frac {Q_{H}}{Q_{X}}}\right)^{1/2}} where γ {\displaystyle \gamma } are the gyromagnetic ratios, W {\displaystyle W} represent the NMR line widths, and Q {\displaystyle Q} represent the quality factor of the probe resonances. === MAS-Dynamic Nuclear Polarisation (MAS-DNP) === Magic angle spinning dynamic nuclear polarization (MAS-DNP) is a technique that increases the sensitivity of NMR experiments by several orders of magnitude. It involves transferring the very high electron polarisation from unpaired electrons to nearby nuclei. This is achieved at cryogenic temperatures through a continuous microwave irradiation from a klystron or a gyrotron, with a frequency close to the corresponding electron paramagnetic resonance (EPR) frequency. The development in the MAS-DNP instrumentation, and the improvement of polarising agents (TOTAPOL, AMUPOL, TEKPOL, etc. ) to achieve a more efficient transfer of polarisation has dramatically reduced experiments times which enabled the observation of surfaces, insensitive isotopes, and multidimensional experiments on low natural abundance nuclei, and diluted species. === Beta-Detected Nuclear Magnetic Resonance (β-NMR) === Beta-detected nuclear magnetic resonance (β-NMR) is


id: spectroscopy-20260505-0
file: data/en.wikipedia.org/wiki/Spectroscopy-0.md
category: reference
title: Spectroscopy
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Spectroscopy
date_saved: 2026-05-05T10:06:09.862940+00:00
instance: kb-cron
parent: spectroscopy-20260505-0
summary:
Spectroscopy is the field of study that measures and interprets electromagnetic spectra as it interacts with matter. In narrower contexts, spectroscopy is the precise study of color as generalized from radiated visible light to all bands of the electromagnetic spectrum. Spectroscopy, primarily in the electromagnetic spectrum, is a fundamental exploratory tool in the fields of astronomy, chemistry, materials science, and physics, allowing the composition, physical and electronic structure of matter to be investigated at the atomic, molecular and macro scale, and over astronomical distances. Historically, spectroscopy originated as the study of the wavelength dependence of the absorption by gas phase matter of visible light dispersed by a prism. Current applications of spectroscopy include biomedical spectroscopy in the areas of tissue analysis and medical imaging. Matter waves and acoustic waves can be considered forms of radiative energy, and recently gravitational waves have been associated with a spectral signature in the context of the Laser Interferometer Gravitational-Wave Observatory (LIGO). == Introduction == Spectroscopy is a branch of science concerned with the spectra of electromagnetic radiation as a function of its wavelength or frequency, as measured by spectrographic equipment and other techniques, in order to obtain information concerning the structure and properties of


id: spectroscopy-20260505-1
file: data/en.wikipedia.org/wiki/Spectroscopy-1.md
category: reference
title: Spectroscopy
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Spectroscopy
date_saved: 2026-05-05T10:06:09.862940+00:00
instance: kb-cron
parent: spectroscopy-20260505-0
summary:
where I 0 {\displaystyle I_{0}} is the light intensity before passing through the sample, I {\displaystyle I} is the output intensity, ε {\displaystyle \varepsilon } is the extinction coefficient, ℓ {\displaystyle \ell } is the path length through the sample, and c {\displaystyle c} is the concentration of the sample. The extinction coefficient depends on the wavelength selected and the molecule being sampled. Resonances by the frequency were first characterized in mechanical systems such as pendulums, which have a frequency of motion noted famously by Galileo. In quantum mechanical systems, the analogous resonance is a coupling of two quantum mechanical stationary states of a system, such as two atomic orbitals, via an oscillatory source of energy such as a photon. The coupling of the two states is strongest when the source energy matches the energy difference between the two states. That is, a photon at the right energy is more likely to cause an electron to jump between two orbitals, a process called electron excitation. The energy E of a photon is related to its frequency ν by E = hν where h is the Planck constant, and so a spectrum of the system response vs. photon frequency will peak


id: spectroscopy-20260505-2
file: data/en.wikipedia.org/wiki/Spectroscopy-2.md
category: reference
title: Spectroscopy
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Spectroscopy
date_saved: 2026-05-05T10:06:09.862940+00:00
instance: kb-cron
parent: spectroscopy-20260505-0
summary:
Atomic spectroscopy was the first application of spectroscopy. Atomic absorption spectroscopy and atomic emission spectroscopy involve visible and ultraviolet light. These absorptions and emissions, often referred to as atomic spectral lines, are due to electronic transitions of outer shell electrons as they rise and fall from one electron orbit to another. Atoms have distinct X-ray spectra that are attributable to the excitation of inner shell electrons to excited states. Atoms of different elements have distinct spectra and therefore atomic spectroscopy allows for the identification and quantitation of a sample's elemental composition. After Robert Bunsen and Gustav Kirchhoff invented the spectroscope, Bunsen discovered cesium and rubidium by observing their emission spectra. Atomic absorption lines are observed in the solar spectrum and referred to as Fraunhofer lines after their discoverer. A comprehensive explanation of the hydrogen spectrum was an early success of quantum mechanics and explained the Lamb shift observed in the hydrogen spectrum, which further led to the development of quantum electrodynamics. Modern implementations of atomic spectroscopy for studying visible and ultraviolet transitions include flame emission spectroscopy, inductively coupled plasma atomic emission spectroscopy, glow discharge spectroscopy, microwave induced plasma spectroscopy, and spark or arc emission spectroscopy. Techniques for studying X-ray spectra


id: spectroscopy-20260505-3
file: data/en.wikipedia.org/wiki/Spectroscopy-3.md
category: reference
title: Spectroscopy
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Spectroscopy
date_saved: 2026-05-05T10:06:09.862940+00:00
instance: kb-cron
parent: spectroscopy-20260505-0
summary:
Acoustic resonance spectroscopy is based on sound waves primarily in the audible and ultrasonic regions. Auger electron spectroscopy is a method used to study surfaces of materials on a micro-scale. It is often used in connection with electron microscopy. Cavity ring-down spectroscopy enables measurement of absolute optical extinction by samples that scatter and absorb light. Circular dichroism spectroscopy measures the differential absorption of left- and right-handed circularly polarized light. Coherent anti-Stokes Raman spectroscopy is a recent technique that has high sensitivity and powerful applications for in vivo spectroscopy and imaging. Cold vapour atomic fluorescence spectroscopy is a subclass of the atomic emission spectroscopy technique that measures trace amounts of volatile heavy metals in the air, such as mercury. Correlation spectroscopy encompasses several types of two-dimensional NMR spectroscopy. Deep-level transient spectroscopy measures concentration and analyzes parameters of electrically active defects in semiconducting materials. Dielectric spectroscopy measures the dielectric properties of a medium as a function of frequency. Dual-polarization interferometry measures the real and imaginary components of the complex refractive index. Electron energy loss spectroscopy in transmission electron microscopy. Electron phenomenological spectroscopy measures the physicochemical properties and characteristics of the electronic structure of multicomponent and complex molecular systems. Electron paramagnetic resonance spectroscopy


id: spectroscopy-20260505-4
file: data/en.wikipedia.org/wiki/Spectroscopy-4.md
category: reference
title: Spectroscopy
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Spectroscopy
date_saved: 2026-05-05T10:06:09.862940+00:00
instance: kb-cron
parent: spectroscopy-20260505-0
summary:
Determining the atomic structure of a sample Studying spectral emission lines of the sun and distant galaxies Space exploration Cure monitoring of composites using optical fibers. Estimating weathered wood exposure times using near infrared spectroscopy Measurement of different compounds in food samples by absorption spectroscopy both in visible and infrared spectrum Measurement of toxic compounds in blood samples Non-destructive elemental analysis by X-ray fluorescence Electronic structure research with various spectroscopes Redshift to determine the speed and velocity of a distant object Determining the metabolic structure of a muscle Monitoring dissolved oxygen content in freshwater and marine ecosystems Altering the structure of drugs to improve effectiveness Characterization of proteins Respiratory gas analysis in hospitals Finding the physical properties of a distant star or nearby exoplanet using the Relativistic Doppler effect. In-ovo sexing: spectroscopy allows to determine the sex of the egg while it is hatching. Developed by French and German companies, both countries decided to ban chick culling, mostly done through a macerator, in 2022. Process monitoring in Industrial process control == History == The history of spectroscopy began with Isaac Newton's optics experiments (1666–1672). According to Andrew Fraknoi and David Morrison, "In 1672, in the first paper that he submitted


id: spin-echo-20260505-0
file: data/en.wikipedia.org/wiki/Spin_echo-0.md
category: reference
title: Spin echo
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Spin_echo
date_saved: 2026-05-05T10:06:10.999636+00:00
instance: kb-cron
parent: spin-echo-20260505-0
summary:
In magnetic resonance, a spin echo or Hahn echo is the refocusing of spin magnetisation by a pulse of resonant electromagnetic radiation. Modern nuclear magnetic resonance (NMR) and magnetic resonance imaging (MRI) make use of this effect. The NMR signal observed following an initial excitation pulse decays with time due to both spin relaxation and any inhomogeneous effects which cause spins in the sample to precess at different rates. The first of these, relaxation, leads to an irreversible loss of magnetisation. But the inhomogeneous dephasing can be removed by applying a 180° inversion pulse that inverts the magnetisation vectors. Examples of inhomogeneous effects include a magnetic field gradient and a distribution of chemical shifts. If the inversion pulse is applied after a period t of dephasing, the inhomogeneous evolution will rephase to form an echo at time 2t. In simple cases, the intensity of the echo relative to the initial signal is given by e–2t/T2 where T2 is the time constant for spin–spin relaxation. The echo time (TE) is the time between the excitation pulse and the peak of the signal. Echo phenomena are important features of coherent spectroscopy which have been used in fields other than magnetic resonance including


id: spin-echo-small-angle-neutron-scattering-20260505-0
file: data/en.wikipedia.org/wiki/Spin_echo_small_angle_neutron_scattering-0.md
category: reference
title: Spin echo small angle neutron scattering
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Spin_echo_small_angle_neutron_scattering
date_saved: 2026-05-05T10:06:12.163464+00:00
instance: kb-cron
parent: spin-echo-small-angle-neutron-scattering-20260505-0
summary:
Spin echo small angle neutron scattering (SESANS) measures structures from around 20 to 2000 nm in size. The information is presented as a real-space (similar to g(r)) as opposed to a reciprocal space (q(r)) mapping. This can simplify the interpretation for some systems. SESANS is useful for studying processes that occur over relatively long time scales, as data collection is often slow, but large length scales. Aggregation of colloids, block copolymer micelles, Stöber silica particles being a prime examples. The technique offers some advantages over SANS but there are fewer SESANS instruments available than SANS instruments. Facilities for SESANS exist at TUDelft (Netherlands) and Rutherford Appleton Laboratory (UK). == References ==


id: spin-polarized-electron-energy-loss-spectroscopy-20260505-0
file: data/en.wikipedia.org/wiki/Spin-polarized_electron_energy_loss_spectroscopy-0.md
category: reference
title: Spin-polarized electron energy loss spectroscopy
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Spin-polarized_electron_energy_loss_spectroscopy
date_saved: 2026-05-05T10:06:13.330154+00:00
instance: kb-cron
parent: spin-polarized-electron-energy-loss-spectroscopy-20260505-0
summary:
Spin-polarized electron energy loss spectroscopy or SPEELS is a technique mainly used to measure the dispersion relation of the collective excitations, over the whole Brillouin zone. Spin waves are collective perturbations in a magnetic solid. Their properties depend on their wavelength (or wave vector). For long wavelength (short wave vector) spin waves, the resulting spin precession has a very low frequency and the spin waves can be treated classically. Ferromagnetic resonance (FMR) and Brillouin light scattering (BLS) experiments explain the long wavelength spin waves in ultrathin magnetic films and nanostructures. If the wavelength is comparable to the lattice constant, the spin waves are governed by the microscopic exchange coupling and a quantum mechanical description is needed. Therefore, experimental information on these short wavelength (large wave vector) spin waves in ultrathin films is highly desired and may lead to fundamentally new insights into the spin dynamics in reduced dimensions in the future. SPEELS is one of the few techniques that can be used to measure the dispersion of such short wavelength spin waves in ultrathin films and nanostructures. == The first experiment == For the first time Kirschner's group in Max Planck institute of Microstructure Physics showed that the signature of


id: staining-20260505-0
file: data/en.wikipedia.org/wiki/Staining-0.md
category: reference
title: Staining
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Staining
date_saved: 2026-05-05T10:06:14.460722+00:00
instance: kb-cron
parent: staining-20260505-0
summary:
Staining is a technique used to enhance contrast in samples, generally at the microscopic level. Stains and dyes are frequently used in histology (microscopic study of biological tissues), in cytology (microscopic study of cells), and in the medical fields of histopathology, hematology, and cytopathology that focus on the study and diagnoses of diseases at the microscopic level. Stains may be used to define biological tissues (highlighting, for example, muscle fibers or connective tissue), cell populations (classifying different blood cells), or organelles within individual cells. In biochemistry, it involves adding a class-specific (DNA, proteins, lipids, carbohydrates) dye to a substrate to qualify or quantify the presence of a specific compound. Staining and fluorescent tagging can serve similar purposes. Biological staining is also used to mark cells in flow cytometry, and to flag proteins or nucleic acids in gel electrophoresis. Light microscopes are used for viewing stained samples at high magnification, typically using bright-field or epi-fluorescence illumination. Staining is not limited to only biological materials, since it can also be used to study the structure of other materials; for example, the lamellar structures of semi-crystalline polymers or the domain structures of block copolymers. == In vivo vs In vitro == In vivo


id: staining-20260505-1
file: data/en.wikipedia.org/wiki/Staining-1.md
category: reference
title: Staining
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Staining
date_saved: 2026-05-05T10:06:14.460722+00:00
instance: kb-cron
parent: staining-20260505-0
summary:
=== Negative staining === A simple staining method for bacteria that is usually successful, even when the positive staining methods fail, is to use a negative stain. This can be achieved by smearing the sample onto the slide and then applying nigrosin (a black synthetic dye) or India ink (an aqueous suspension of carbon particles). After drying, the microorganisms may be viewed in bright field microscopy as lighter inclusions well-contrasted against the dark environment surrounding them. Negative staining is able to stain the background instead of the organisms because the cell wall of microorganisms typically has a negative charge which repels the negatively charged stain. The dyes used in negative staining are acidic. Note: negative staining is a mild technique that may not destroy the microorganisms, and is therefore unsuitable for studying pathogens. === Positive staining === Unlike negative staining, positive staining uses basic dyes to color the specimen against a bright background. While chromophore is used for both negative and positive staining alike, the type of chromophore used in this technique is a positively charged ion instead of a negative one. The negatively charged cell wall of many microorganisms attracts the positively charged chromophore which causes the specimen to


id: staining-20260505-2
file: data/en.wikipedia.org/wiki/Staining-2.md
category: reference
title: Staining
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Staining
date_saved: 2026-05-05T10:06:14.460722+00:00
instance: kb-cron
parent: staining-20260505-0
summary:
Papanicolaou staining, or PAP staining, was developed to replace fine needle aspiration cytology (FNAC) in hopes of decreasing staining times and cost without compromising quality. This stain is a frequently used method for examining cell samples from a variety of tissue types in various organs. PAP staining has endured several modifications in order to become a “suitable alternative” for FNAC. This transition stemmed from the appreciation of wet fixed smears by scientists preserving the structures of the nuclei opposed to the opaque appearance of air dried Romanowsky smears. This led to the creation of a hybrid stain of wet fixed and air dried known as the ultrafast papanicolaou stain. This modification includes the use of nasal saline to rehydrate cells to increase cell transparency and is paired with the use of alcoholic formalin to enhance colors of the nuclei. The papanicolaou stain is now used in place of cytological staining in all organ types due to its increase in morphological quality, decreased staining time, and decreased cost. It is frequently used to stain Pap smear specimens. It uses a combination of haematoxylin, Orange G, eosin Y, Light Green SF yellowish, and sometimes Bismarck Brown Y. === PAS === Periodic acid-Schiff


id: staining-20260505-3
file: data/en.wikipedia.org/wiki/Staining-3.md
category: reference
title: Staining
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Staining
date_saved: 2026-05-05T10:06:14.460722+00:00
instance: kb-cron
parent: staining-20260505-0
summary:
=== Acridine orange === Acridine orange (AO) is a nucleic acid selective fluorescent cationic dye useful for cell cycle determination. It is cell-permeable, and interacts with DNA and RNA by intercalation or electrostatic attractions. When bound to DNA, it is very similar spectrally to fluorescein. Like fluorescein, it is also useful as a non-specific stain for backlighting conventionally stained cells on the surface of a solid sample of tissue (fluorescence backlighted staining). === Bismarck brown === Bismarck brown (also Bismarck brown Y or Manchester brown) imparts a yellow colour to acid mucins and an intense brown color to mast cells. One default of this stain is that it blots out any other structure surrounding it and makes the quality of the contrast low. It has to be paired with other stains in order to be useful. Some complementing stains used alongside Bismark brown are Hematoxylin and Toluidine blue which provide better contrast within the histology sample. === Carmine === Carmine is an intensely red dye used to stain glycogen, while Carmine alum is a nuclear stain. Carmine stains require the use of a mordant, usually aluminum. === Coomassie blue === Coomassie brilliant blue nonspecifically stains proteins a strong blue colour.


id: staining-20260505-4
file: data/en.wikipedia.org/wiki/Staining-4.md
category: reference
title: Staining
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Staining
date_saved: 2026-05-05T10:06:14.460722+00:00
instance: kb-cron
parent: staining-20260505-0
summary:
=== Methyl green === Methyl green is used commonly with bright-field, as well as fluorescence microscopes to dye the chromatin of cells so that they are more easily viewed. === Methylene blue === Methylene blue is used to stain animal cells, such as human cheek cells, to make their nuclei more observable. Also used to stain blood films in cytology. === Neutral red === Neutral red (or toluylene red) stains Nissl substance red. It is usually used as a counterstain in combination with other dyes. === Nile blue === Nile blue (or Nile blue A) stains nuclei blue. It may be used with living cells. === Nile red === Nile red (also known as Nile blue oxazone) is formed by boiling Nile blue with sulfuric acid. This produces a mix of Nile red and Nile blue. Nile red is a lipophilic stain; it will accumulate in lipid globules inside cells, staining them red. Nile red can be used with living cells. It fluoresces strongly when partitioned into lipids, but practically not at all in aqueous solution. === Osmium tetroxide (formal name: osmium tetraoxide) === Osmium tetraoxide is used in optical microscopy to stain lipids. It dissolves in fats, and is


id: thermally-stimulated-depolarization-current-20260505-0
file: data/en.wikipedia.org/wiki/Thermally_stimulated_depolarization_current-0.md
category: reference
title: Thermally stimulated depolarization current
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Thermally_stimulated_depolarization_current
date_saved: 2026-05-05T10:06:15.643505+00:00
instance: kb-cron
parent: thermally-stimulated-depolarization-current-20260505-0
summary:
Thermally stimulated depolarization current (TSDC) is a scientific technique used to measure dielectric properties of materials. It can be used to measure the thermally stimulated depolarization of molecules within a material. One method of doing so is to place the material between two electrodes, cool the material in the presence of an external electric field, remove the field once a desired temperature has been reached, and measure the current between the electrodes as the material warms. The external electric field must be applied at a sufficiently high temperature to allow the molecular dipoles time to align with the field. Because the dielectric relaxation time increases exponentially on cooling, the polarization caused by their alignment with the field gets "frozen-in". So when the field is removed and the material begins to warm the dipoles begin to "thaw" whereby losing their net alignment and thus the material become depolarized. This depolarization can be measured if the material is sandwiched between two ohmic electrodes and the current is measured on warming. As the material depolarizes, charges are pulled to (or pushed away from) the electrodes which causes a current through the measuring device. == References ==


id: thermomechanical-analysis-20260505-0
file: data/en.wikipedia.org/wiki/Thermomechanical_analysis-0.md
category: reference
title: Thermomechanical analysis
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Thermomechanical_analysis
date_saved: 2026-05-05T10:06:16.802929+00:00
instance: kb-cron
parent: thermomechanical-analysis-20260505-0
summary:
Thermomechanical analysis (TMA) is a technique used in thermal analysis, a branch of materials science which studies the properties of materials as they change with temperature. Thermomechanical analysis is a subdiscipline of the thermomechanometry (TM) technique. == Related techniques and terminology == Thermomechanometry is the measurement of a change of a dimension or a mechanical property of the sample while it is subjected to a temperature regime. An associated thermoanalytical method is thermomechanical analysis. A special related technique is thermodilatometry (TD), the measurement of a change of a dimension of the sample with a negligible force acting on the sample while it is subjected to a temperature regime. The associated thermoanalytical method is thermodilatometric analysis (TDA). TDA is often referred to as zero force TMA. The temperature regime may be heating, cooling at a rate of temperature change that can include stepwise temperature changes, linear rate of change, temperature modulation with a set frequency and amplitude, free (uncontrolled) heating or cooling, or maintaining a constant increase in temperature. The sequence of temperatures with respect to time may be predetermined (temperature programmed) or sample controlled (controlled by a feedback signal from the sample response). Thermomechanometry includes several variations according to the


id: thermomechanical-analysis-20260505-1
file: data/en.wikipedia.org/wiki/Thermomechanical_analysis-1.md
category: reference
title: Thermomechanical analysis
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Thermomechanical_analysis
date_saved: 2026-05-05T10:06:16.802929+00:00
instance: kb-cron
parent: thermomechanical-analysis-20260505-0
summary:
==== Cross-linking ==== Cross-linking will restrict the molecular response to temperature change since degree of freedom for segmental motions are reduced as molecules become irreversibly linked. Cross-linking chemically links molecules, while crystallinity and fillers introduce physical constraints to motion. Mechanical properties such as derived from stress-strain testing are used to calculate crosslink density that is usually expressed as the molar mass between crosslinks (Mc). The sensitivity of zero stress TMA to crosslinking is low since the structure receives minimum disturbance. Sensitivity to crosslinks requires high strain such that the segments between crosslinks become fully extended. Zero force TM will only be sensitive to changes in the bulk that are expressed as a change in a linear dimension of the material. The measured change will be the resultant of all processes occurring as the temperature is changed. Some of the processes will be reversible, others irreversible, and others time-dependent. The methodology must be chosen to best detect, distinguish and resolve the thermal expansion or contractions observable. The TM instrument need only apply sufficient stress to keep the probe in contact with the specimen surface, but it must have high sensitivity to dimensional change. The experiment must be conducted at a temperature


id: thermomechanical-analysis-20260505-2
file: data/en.wikipedia.org/wiki/Thermomechanical_analysis-2.md
category: reference
title: Thermomechanical analysis
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Thermomechanical_analysis
date_saved: 2026-05-05T10:06:16.802929+00:00
instance: kb-cron
parent: thermomechanical-analysis-20260505-0
summary:
== Static force thermomechanometry experimental == Creep and stress relaxation measures the elasticity, viscoelasticity and viscous behaviour of materials under a selected stress and temperature. Tensile geometry is the most common for creep measurements. A small force is initially imparted to keep the specimen aligned and straight. The selected stress is applied rapidly and held constant for the required time; this may be 1 h or more. During application of force the elastic property is observed as an immediate elongation or strain. During the constant force period the time dependent elastic response or viscoelasticity, together with the viscous response, result in further increase in strain. The force is removed rapidly, though the small alignment force is maintained. The recovery measurement time should be four times the creep time, so in this example the recovery time should be 4 h. Upon removal of the force the elastic component results in an immediate contraction. The viscoelastic recovery is exponential as the material slowly recovers some of the previously imparted creep strain. After recovery there is a permanent unrecovered strain due to the viscous component of the properties. Analysis of the data is performed using the four component viscoelastic model where the elements


id: time-resolved-mass-spectrometry-20260505-0
file: data/en.wikipedia.org/wiki/Time-resolved_mass_spectrometry-0.md
category: reference
title: Time-resolved mass spectrometry
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Time-resolved_mass_spectrometry
date_saved: 2026-05-05T10:06:34.290244+00:00
instance: kb-cron
parent: time-resolved-mass-spectrometry-20260505-0
summary:
Time-resolved mass spectrometry (TRMS) is a strategy in analytical chemistry that uses mass spectrometry platform to collect data with temporal resolution. Implementation of TRMS builds on the ability of mass spectrometers to process ions within sub-second duty cycles. It often requires the use of customized experimental setups. However, they can normally incorporate commercial mass spectrometers. As a concept in analytical chemistry, TRMS encompasses instrumental developments (e.g. interfaces, ion sources, mass analyzers), methodological developments, and applications. == Applications == An early application of TRMS was in the observation of flash photolysis process. It took advantage of a time-of-flight mass analyzer. TRMS currently finds applications in the monitoring of organic reactions, formation of reactive intermediates, enzyme-catalyzed reactions, convection, protein folding, extraction, and other chemical and physical processes. == Temporal resolution == TRMS is typically implemented to monitor processes that occur on second to millisecond time scale. However, there exist reports from studies in which sub-millisecond resolutions were achieved. == References ==


id: total-internal-reflection-fluorescence-microscope-20260505-0
file: data/en.wikipedia.org/wiki/Total_internal_reflection_fluorescence_microscope-0.md
category: reference
title: Total internal reflection fluorescence microscope
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Total_internal_reflection_fluorescence_microscope
date_saved: 2026-05-05T10:06:35.424390+00:00
instance: kb-cron
parent: total-internal-reflection-fluorescence-microscope-20260505-0
summary:
A total internal reflection fluorescence microscope (TIRFM) is a type of microscope with which a thin region of a specimen, usually less than 200 nanometers can be observed. TIRFM is an imaging modality which uses the excitation of fluorescent cells in a thin optical specimen section that is supported on a glass slide. The technique is based on the principle that when excitation light is totally internally reflected in a transparent solid coverglass at its interface with a liquid medium, an electromagnetic field, also known as an evanescent wave, is generated at the solid-liquid interface with the same frequency as the excitation light. The intensity of the evanescent wave exponentially decays with distance from the surface of the solid so that only fluorescent molecules within a few hundred nanometers of the solid are efficiently excited. Two-dimensional images of the fluorescence can then be obtained, although there are also mechanisms in which three-dimensional information on the location of vesicles or structures in cells can be obtained. == History == Widefield fluorescence was introduced in 1910 which was an optical technique that illuminates the entire sample. Confocal microscopy was then introduced in 1960 which decreased the background and exposure time of the


id: total-internal-reflection-fluorescence-microscope-20260505-1
file: data/en.wikipedia.org/wiki/Total_internal_reflection_fluorescence_microscope-1.md
category: reference
title: Total internal reflection fluorescence microscope
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Total_internal_reflection_fluorescence_microscope
date_saved: 2026-05-05T10:06:35.424390+00:00
instance: kb-cron
parent: total-internal-reflection-fluorescence-microscope-20260505-0
summary:
== Overview == The idea of using total internal reflection to illuminate cells contacting the surface of glass was first described by E.J. Ambrose in 1956. This idea was then extended by Daniel Axelrod at the University of Michigan, Ann Arbor in the early 1980s as TIRFM. A TIRFM uses an evanescent wave to selectively illuminate and excite fluorophores in a restricted region of the specimen immediately adjacent to the glass-water interface. The evanescent electromagnetic field decays exponentially from the interface, and thus penetrates to a depth of only approximately 100 nm into the sample medium. Thus the TIRFM enables a selective visualization of surface regions such as the basal plasma membrane (which are about 7.5 nm thick) of cells. Note, however, that the region visualized is at least a few hundred nanometers wide, so the cytoplasmic zone immediately beneath the plasma membrane is necessarily visualized in addition to the plasma membrane during TIRF microscopy. The selective visualization of the plasma membrane renders the features and events on the plasma membrane in living cells with high axial resolution. TIRF can also be used to observe the fluorescence of a single molecule, making it an important tool of biophysics and quantitative


id: total-internal-reflection-fluorescence-microscope-20260505-2
file: data/en.wikipedia.org/wiki/Total_internal_reflection_fluorescence_microscope-2.md
category: reference
title: Total internal reflection fluorescence microscope
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Total_internal_reflection_fluorescence_microscope
date_saved: 2026-05-05T10:06:35.424390+00:00
instance: kb-cron
parent: total-internal-reflection-fluorescence-microscope-20260505-0
summary:
=== Excitation beam === For complex fluoroscope microscopy techniques, lasers are the preferred light source as they are highly uniform, intense, and near-monochromatic. However, it is noted that ARC LAMP light sources and other types of sources may also work. Typically the wavelength of excitation beam is designated by the requirements of the fluorophores within the sample, with most common excitation wavelengths being in the 400–700 nm range for biological samples. In practice, a lightbox will generate a high intensity multichromatic laser, which will then be filtered to allow the desired wavelengths through to excite the sample. For objective-based TIRFM, the excitation beam and fluoresced emission beam will be captured via the same objective lens. Thus, to split the beams, a dichromatic mirror is used to reflect the incoming excitation beam towards the objective lens, and allow the emission beam to pass through into the detector. Additional filtering may be required to further separate emission and excitation wavelengths. === Emission beam === When excited with specific wavelengths of light, fluorophore dyes will reemit light at longer wavelengths (which contain less energy). In the context of TIRFM, only fluorophores close to the interface will be readily excited by the evanescent field,


id: total-internal-reflection-fluorescence-microscope-20260505-3
file: data/en.wikipedia.org/wiki/Total_internal_reflection_fluorescence_microscope-3.md
category: reference
title: Total internal reflection fluorescence microscope
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Total_internal_reflection_fluorescence_microscope
date_saved: 2026-05-05T10:06:35.424390+00:00
instance: kb-cron
parent: total-internal-reflection-fluorescence-microscope-20260505-0
summary:
=== Image artifact and noise === Most fluorescence imaging techniques exhibit background noise due to illuminating and reconstructing large slices (in the z-direction) of the samples. Since TIRFM uses an evanescent wave to fluoresce a thin slice of the sample, there is inherently less background noise and artifacts. However, there are still other noises and artifacts such as poisson noise, optical aberrations, photobleaching, and other fluorescence molecules. Poissonian noise are fundamental uncertainties with the measurement of light. This will cause uncertainties during the detection of fluorescence photons. If N photons are measured in a particular measurement, there is a 63% probability that the true average value is in the range between N +√N and N −√N. This noise may cause misrepresentation of the object at incorrect pixel locations. Optical aberrations can arise from diffraction of fluorescence light or microscope and objective misalignment. Diffraction of light on the sample slide can spread the fluorescence signal and result in blurring in the convoluted images. Similarly, if there is a misalignment between the objective lens, filter, and detector, the excitation or emission beam may not be in focus and can cause blurring in the images. Photobleaching can occur when the covalent or noncovalent


id: transmission-electron-microscopy-20260505-0
file: data/en.wikipedia.org/wiki/Transmission_electron_microscopy-0.md
category: reference
title: Transmission electron microscopy
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Transmission_electron_microscopy
date_saved: 2026-05-05T10:06:36.644553+00:00
instance: kb-cron
parent: transmission-electron-microscopy-20260505-0
summary:
Transmission electron microscopy (TEM) is a microscopy technique in which a beam of electrons is transmitted through a specimen to form an image. The specimen is most often an ultrathin section less than 100 nm thick or a suspension on a grid. An image is formed from the interaction of the electrons with the sample as the beam is transmitted through the specimen. The image is then magnified and focused onto an imaging device, such as a fluorescent screen, a layer of photographic film, or a detector such as a scintillator attached to a charge-coupled device or a direct electron detector. Transmission electron microscopes are capable of imaging at a significantly higher resolution than light microscopes, owing to the smaller de Broglie wavelength of electrons. This enables the instrument to capture fine detail—even as small as a single column of atoms, which is thousands of times smaller than a resolvable object seen in a light microscope. Transmission electron microscopy is a major analytical method in the physical, chemical and biological sciences. TEMs find application in cancer research, virology, and materials science as well as pollution, nanotechnology and semiconductor research, but also in other fields such as paleontology and palynology. TEM


id: transmission-electron-microscopy-20260505-1
file: data/en.wikipedia.org/wiki/Transmission_electron_microscopy-1.md
category: reference
title: Transmission electron microscopy
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Transmission_electron_microscopy
date_saved: 2026-05-05T10:06:36.644553+00:00
instance: kb-cron
parent: transmission-electron-microscopy-20260505-0
summary:
=== Improving resolution === At the time, electrons were understood to be charged particles of matter; the wave nature of electrons was not fully realized until the PhD thesis of Louis de Broglie in 1924. Knoll's research group was unaware of this publication until 1932, when they realized that the de Broglie wavelength of electrons was many orders of magnitude smaller than that for light, theoretically allowing for imaging at atomic scales. (Even for electrons with a kinetic energy of just 1 electronvolt the wavelength is already as short as 1.18 nm.) In April 1932, Ruska suggested the construction of a new electron microscope for direct imaging of specimens inserted into the microscope, rather than simple mesh grids or images of apertures. With this device successful diffraction and normal imaging of an aluminium sheet was achieved. However the magnification achievable was lower than with light microscopy. Magnifications higher than those available with a light microscope were achieved in September 1933 with images of cotton fibers quickly acquired before being damaged by the electron beam. At this time, interest in the electron microscope had increased, with other groups, such as that of Paul Anderson and Kenneth Fitzsimmons of Washington State University


id: transmission-electron-microscopy-20260505-2
file: data/en.wikipedia.org/wiki/Transmission_electron_microscopy-2.md
category: reference
title: Transmission electron microscopy
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Transmission_electron_microscopy
date_saved: 2026-05-05T10:06:36.644553+00:00
instance: kb-cron
parent: transmission-electron-microscopy-20260505-0
summary:
From the top down, the TEM consists of an emission source or cathode, which may be a tungsten filament, a lanthanum hexaboride (LaB6) single crystal or a field emission gun. The gun is connected to a high voltage source (typically ~100–300 kV) and emits electrons either by thermionic or field electron emission into the vacuum. In the case of a thermionic source, the electron source is mounted in a Wehnelt cylinder to provide preliminary focus of the emitted electrons into a beam while also stabilizing the current using a passive feedback circuit. A field emission source uses instead electrostatic electrodes called an extractor, a suppressor, and a gun lens, with different voltages on each, to control the electric field shape and intensity near the sharp tip. The combination of the cathode and these first electrostatic lens elements is collectively called the "electron gun". After it leaves the gun, the beam is typically accelerated until it reaches its final voltage and enters the next part of the microscope: the condenser lens system. These upper lenses of the TEM then further focus the electron beam to the desired size and location on the sample. Manipulation of the electron beam is performed using


id: transmission-electron-microscopy-20260505-3
file: data/en.wikipedia.org/wiki/Transmission_electron_microscopy-3.md
category: reference
title: Transmission electron microscopy
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Transmission_electron_microscopy
date_saved: 2026-05-05T10:06:36.644553+00:00
instance: kb-cron
parent: transmission-electron-microscopy-20260505-0
summary:
A TEM is composed of several components, which include a vacuum system in which the electrons travel, an electron emission source for generation of the electron stream, a series of electromagnetic lenses, as well as electrostatic plates. The latter two allow the operator to guide and manipulate the beam as required. Also required is a device to allow the insertion into, motion within, and removal of specimens from the beam path. Imaging devices are subsequently used to create an image from the electrons that exit the system. === Vacuum system === To increase the mean free path of the electron gas interaction, a standard TEM is evacuated to low pressures, typically on the order of 10−4 Pa. The need for this is twofold: first the allowance for the voltage difference between the cathode and the ground without generating an arc, and secondly to reduce the collision frequency of electrons with gas atoms to negligible levels—this effect is characterized by the mean free path. TEM components such as specimen holders and film cartridges must be routinely inserted or replaced requiring a system with the ability to re-evacuate on a regular basis. As such, TEMs are equipped with multiple pumping systems and


id: transmission-electron-microscopy-20260505-4
file: data/en.wikipedia.org/wiki/Transmission_electron_microscopy-4.md
category: reference
title: Transmission electron microscopy
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Transmission_electron_microscopy
date_saved: 2026-05-05T10:06:36.644553+00:00
instance: kb-cron
parent: transmission-electron-microscopy-20260505-0
summary:
TEM specimen stage designs include airlocks to allow for insertion of the specimen holder into the vacuum with minimal loss of vacuum in other areas of the microscope. The specimen holders hold a standard size of sample grid or self-supporting specimen. Standard TEM grid sizes are 3.05 mm diameter, with a thickness and mesh size ranging from a few to 100 μm. The sample is placed onto the meshed area having a diameter of approximately 2.5 mm. Usual grid materials are copper, molybdenum, gold or platinum. This grid is placed into the sample holder, which is paired with the specimen stage. A wide variety of designs of stages and holders exist, depending upon the type of experiment being performed. In addition to 3.05 mm grids, 2.3 mm grids are sometimes, if rarely, used. These grids were particularly used in the mineral sciences where a large degree of tilt can be required and where specimen material may be extremely rare. Electron transparent specimens have a thickness usually less than 100 nm, but this value depends on the accelerating voltage. Once inserted into a TEM, the sample has to be manipulated to locate the region of interest to the beam, such as


id: transmission-electron-microscopy-20260505-5
file: data/en.wikipedia.org/wiki/Transmission_electron_microscopy-5.md
category: reference
title: Transmission electron microscopy
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Transmission_electron_microscopy
date_saved: 2026-05-05T10:06:36.644553+00:00
instance: kb-cron
parent: transmission-electron-microscopy-20260505-0
summary:
where A is the Richardson's constant, Φ is the work function and T is the temperature of the material. This equation shows that in order to achieve sufficient current density it is necessary to heat the emitter, taking care not to cause damage by application of excessive heat. For this reason materials with either a high melting point, such as tungsten, or those with a low work function (LaB6) are required for the gun filament. Furthermore, both lanthanum hexaboride and tungsten thermionic sources must be heated in order to achieve thermionic emission, this can be achieved by the use of a small resistive strip. To prevent thermal shock, there is often a delay enforced in the application of current to the tip, to prevent thermal gradients from damaging the filament, the delay is usually a few seconds for LaB6, and significantly lower for tungsten. === Electron lens === Electron lenses are designed to act in a manner emulating that of an optical lens, by focusing parallel electrons at some constant focal distance. Electron lenses may operate electrostatically or magnetically. The majority of electron lenses for TEM use electromagnetic coils to generate a convex lens. The field produced for the lens


id: transmission-electron-microscopy-20260505-6
file: data/en.wikipedia.org/wiki/Transmission_electron_microscopy-6.md
category: reference
title: Transmission electron microscopy
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Transmission_electron_microscopy
date_saved: 2026-05-05T10:06:36.644553+00:00
instance: kb-cron
parent: transmission-electron-microscopy-20260505-0
summary:
The figure on the right shows the two basic operation modes of TEM – imaging and diffraction modes. In both cases the specimen is illuminated with the parallel beam, formed by electron beam shaping with the system of Condenser lenses and Condenser aperture. After interaction with the sample, on the exit surface of the specimen two types of electrons exist – unscattered (which will correspond to the bright central beam on the diffraction pattern) and scattered electrons (which change their trajectories due to interaction with the material). In Imaging mode, the objective aperture is inserted in a back focal plane (BFP) of the objective lens (where diffraction spots are formed). If using the objective aperture to select only the central beam, the transmitted electrons are passed through the aperture while all others are blocked, and a bright field image (BF image) is obtained. If we allow the signal from a diffracted beam, a dark field image (DF image) is received. The selected signal is magnified and projected on a screen (or on a camera) with the help of Intermediate and Projector lenses. An image of the sample is thus obtained. In Diffraction mode, a selected area aperture may be used


id: transmission-electron-microscopy-20260505-7
file: data/en.wikipedia.org/wiki/Transmission_electron_microscopy-7.md
category: reference
title: Transmission electron microscopy
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Transmission_electron_microscopy
date_saved: 2026-05-05T10:06:36.644553+00:00
instance: kb-cron
parent: transmission-electron-microscopy-20260505-0
summary:
Samples can exhibit diffraction contrast, whereby the electron beam undergoes diffraction which in the case of a crystalline sample, disperses electrons into discrete locations in the back focal plane. By the placement of apertures in the back focal plane, i.e. the objective aperture, the desired reciprocal lattice vectors can be selected (or excluded), thus only parts of the sample that are causing the electrons to scatter to the selected reflections will end up projected onto the imaging apparatus. If the reflections that are selected do not include the unscattered beam (which will appear up at the focal point of the lens), then the image will appear dark wherever no sample scattering to the selected peak is present, as such a region without a specimen will appear dark. This is known as a dark-field image. Modern TEMs are often equipped with specimen holders that allow the user to tilt the specimen to a range of angles in order to obtain specific diffraction conditions, and apertures placed above the specimen allow the user to select electrons that would otherwise be diffracted in a particular direction from entering the specimen. Applications for this method include the identification of lattice defects in crystals. By


id: transmission-electron-microscopy-20260505-8
file: data/en.wikipedia.org/wiki/Transmission_electron_microscopy-8.md
category: reference
title: Transmission electron microscopy
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Transmission_electron_microscopy
date_saved: 2026-05-05T10:06:36.644553+00:00
instance: kb-cron
parent: transmission-electron-microscopy-20260505-0
summary:
As TEM specimen holders typically allow for the rotation of a sample by a desired angle, multiple views of the same specimen can be obtained by rotating the angle of the sample along an axis perpendicular to the beam. By taking multiple images of a single TEM sample at differing angles, typically in 1° increments, a set of images known as a "tilt series" can be collected. This methodology was proposed in the 1970s by Walter Hoppe. Under purely absorption contrast conditions, this set of images can be used to construct a three-dimensional representation of the sample. The reconstruction is accomplished by a two-step process, first images are aligned to account for errors in the positioning of a sample; such errors can occur due to vibration or mechanical drift. Alignment methods use image registration algorithms, such as autocorrelation methods to correct these errors. Secondly, using a reconstruction algorithm, such as filtered back projection, the aligned image slices can be transformed from a set of two-dimensional images, Ij(x, y), to a single three-dimensional image, I′j(x, y, z). This three-dimensional image is of particular interest when morphological information is required, further study can be undertaken using computer algorithms, such as isosurfaces and


id: transmission-electron-microscopy-20260505-9
file: data/en.wikipedia.org/wiki/Transmission_electron_microscopy-9.md
category: reference
title: Transmission electron microscopy
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Transmission_electron_microscopy
date_saved: 2026-05-05T10:06:36.644553+00:00
instance: kb-cron
parent: transmission-electron-microscopy-20260505-0
summary:
Before sectioning, biological tissue is often embedded in an epoxy resin block and first trimmed using a razor blade into a trapezoidal block face. Thick sections are then cut from the block face. The thick sections are crudely stained with toluidine blue and examined for specimen and block orientation before thin sectioning. Biological tissue is then thinned to less than 100 nm on an ultramicrotome. The resin block is fractured as it passes over a glass or diamond knife edge. This method is used to obtain thin, minimally deformed samples that allow for the observation of tissue ultrastructure. Inorganic samples, such as aluminium, may also be embedded in resins and ultrathin sectioned in this way, using either coated glass, sapphire or larger angle diamond knives. To prevent charge build-up at the sample surface when viewing in the TEM, tissue samples need to be coated with a thin layer of conducting material, such as carbon. === Sample staining === TEM samples of biological tissues need high atomic number stains to enhance contrast. The stain absorbs the beam electrons or scatters part of the electron beam which otherwise is projected onto the imaging system. Compounds of heavy metals such as osmium, lead,


id: transmission-electron-microscopy-20260505-10
file: data/en.wikipedia.org/wiki/Transmission_electron_microscopy-10.md
category: reference
title: Transmission electron microscopy
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Transmission_electron_microscopy
date_saved: 2026-05-05T10:06:36.644553+00:00
instance: kb-cron
parent: transmission-electron-microscopy-20260505-0
summary:
A TEM can be modified into a scanning transmission electron microscope (STEM) by the addition of a system that rasters a convergent beam across the sample to form the image, when combined with suitable detectors. Scanning coils are used to deflect the beam, such as by an electrostatic shift of the beam, where the beam is then collected using a current detector such as a Faraday cup, which acts as a direct electron counter. By correlating the electron count to the position of the scanning beam (known as the "probe"), the transmitted component of the beam may be measured. The non-transmitted components may be obtained either by beam tilting or by the use of annular dark field detectors. Fundamentally, TEM and STEM are linked via Helmholtz reciprocity. A STEM is a TEM in which the electron source and observation point have been switched relative to the direction of travel of the electron beam. See the ray diagrams in the figure on the right. The STEM instrument effectively relies on the same optical set-up as a TEM, but operates by flipping the direction of travel of the electrons (or reversing time) during operation of a TEM. Rather than using an aperture


id: transmission-electron-microscopy-20260505-11
file: data/en.wikipedia.org/wiki/Transmission_electron_microscopy-11.md
category: reference
title: Transmission electron microscopy
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Transmission_electron_microscopy
date_saved: 2026-05-05T10:06:36.644553+00:00
instance: kb-cron
parent: transmission-electron-microscopy-20260505-0
summary:
High resolution of TEM allows for monitoring the sample in question on a length scale ranging from hundreds of nanometres to several angstroms. This allows for the visualization of both elastic and plastic deformation via strain fields as well as the motion of crystallographic defects such as lattice distortions and dislocation motion. By simultaneously observing deformation phenomena and measuring mechanical response in situ, it is possible to connect nano-mechanical testing information to models that describe both the subtlety and complexity of how materials respond to stress and strain. The material properties and data accuracy obtained from such nano-mechanical tests is largely determined by the mechanical straining holder being used. Current straining holders have the ability to perform tensile tests, nano-indentation, compression tests, shear tests and bending tests on materials. ==== Classical mechanical holders ==== One of the pioneers of classical holders was Heinz G.F. Wilsdorf, who conducted a tensile test inside a TEM in 1958. In a typical experiment, electron transparent TEM samples are cut to shape and glued to a deformable grid. Advances in micromanipulators have also enabled the tensile testing of nanowires and thin films. The deformable grid attaches to the classical tensile holder which stretches the sample


id: transmission-electron-microscopy-20260505-12
file: data/en.wikipedia.org/wiki/Transmission_electron_microscopy-12.md
category: reference
title: Transmission electron microscopy
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Transmission_electron_microscopy
date_saved: 2026-05-05T10:06:36.644553+00:00
instance: kb-cron
parent: transmission-electron-microscopy-20260505-0
summary:
It is possible to reach temporal resolution far beyond that of the readout rate of electron detectors with the use of pulsed electrons. Pulses can be produced by either modifying the electron source to enable laser-triggered photoemission or by installation of an ultrafast beam blanker. This approach is termed ultrafast transmission electron microscopy when stroboscopic pump-probe illumination is used: an image is formed by the accumulation of many ultrashort electron pulses (typically of hundreds of femtoseconds) with a fixed time delay between the arrival of the electron pulse and the sample excitation. On the other hand, the use of single or a short sequence of electron pulses with a sufficient number of electrons to form an image from each pulse is called dynamic transmission electron microscopy. Temporal resolution down to hundreds of femtoseconds and spatial resolution comparable to that available with a Schottky field emission source is possible in ultrafast TEM. Using the Photon-gating approach, the temporal resolution in ultrafast electron microscope reaches to 30-fs allowing the imaging of ultrafast atomic and electron dynamics of matter. However, the technique can only image reversible processes that can be reproducibly triggered millions of times. Dynamic TEM can resolve irreversible processes down to


id: transmission-electron-microscopy-dna-sequencing-20260505-0
file: data/en.wikipedia.org/wiki/Transmission_electron_microscopy_DNA_sequencing-0.md
category: reference
title: Transmission electron microscopy DNA sequencing
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Transmission_electron_microscopy_DNA_sequencing
date_saved: 2026-05-05T10:06:37.867972+00:00
instance: kb-cron
parent: transmission-electron-microscopy-dna-sequencing-20260505-0
summary:
Transmission electron microscopy DNA sequencing is a single-molecule sequencing technology that uses transmission electron microscopy techniques. The method was conceived and developed in the 1960s and 70s, but lost favor when the extent of damage to the sample was recognized. In order for DNA to be clearly visualized under an electron microscope, it must be labeled with heavy atoms. In addition, specialized imaging techniques and aberration corrected optics are beneficial for obtaining the resolution required to image the labeled DNA molecule. In theory, transmission electron microscopy DNA sequencing could provide extremely long read lengths, but the issue of electron beam damage may still remain and the technology has not yet been commercially developed. == History == Only a few years after James Watson and Francis Crick deduced the structure of DNA, and nearly two decades before Frederick Sanger published the first method for rapid DNA sequencing, Richard Feynman, an American physicist, envisioned the electron microscope as the tool that would one day allow biologists to "see the order of bases in the DNA chain". Feynman believed that if the electron microscope could be made powerful enough, then it would become possible to visualize the atomic structure of any and all


id: transmission-electron-microscopy-dna-sequencing-20260505-1
file: data/en.wikipedia.org/wiki/Transmission_electron_microscopy_DNA_sequencing-1.md
category: reference
title: Transmission electron microscopy DNA sequencing
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Transmission_electron_microscopy_DNA_sequencing
date_saved: 2026-05-05T10:06:37.867972+00:00
instance: kb-cron
parent: transmission-electron-microscopy-dna-sequencing-20260505-0
summary:
Annular dark-field imaging measures the scattering of electrons as they deflect off the nuclei of the atoms in the transmission electron microscopy sample. This is best suited to samples containing heavy atoms, as they cause more scattering of electrons. The technique has been used to image atoms as light as boron, nitrogen, and carbon; however, the signal is very weak for such light atoms. If annular dark-field microscopy is put to use for transmission electron microscopy DNA sequencing, it will certainly be necessary to label the DNA bases with heavy atoms so that a strong signal can be detected. Annular bright-field imaging detects electrons transmitted directly through the sample, and measures the wave interference produced by their interactions with the atomic nuclei. This technique can detect light atoms with greater sensitivity than annular dark-field imaging methods. In fact, oxygen, nitrogen, lithium, and hydrogen in crystalline solids have been imaged using annular bright-field electron microscopy. Thus, it is theoretically possible to obtain direct images of the atoms in the DNA chain; however, the structure of DNA is much less geometric than crystalline solids, so direct imaging without prior labeling may not be achievable. === Step 5 – Data analysis === Dark


id: transmission-electron-microscopy-dna-sequencing-20260505-2
file: data/en.wikipedia.org/wiki/Transmission_electron_microscopy_DNA_sequencing-2.md
category: reference
title: Transmission electron microscopy DNA sequencing
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Transmission_electron_microscopy_DNA_sequencing
date_saved: 2026-05-05T10:06:37.867972+00:00
instance: kb-cron
parent: transmission-electron-microscopy-dna-sequencing-20260505-0
summary:
== Strengths and weaknesses == Compared to other second- and third-generation DNA sequencing technologies, transmission electron microscopy DNA sequencing has a number of potential key strengths and weaknesses, which will ultimately determine its usefulness and prominence as a future DNA sequencing technology. === Strengths === Longer read lengths: ZS Genetics has estimated potential read lengths of transmission electron microscopy DNA sequencing to be 10,000 to 20,000 base pairs with a rate of 1.7 billion base pairs per day. Such long read lengths would allow easier de novo genome assembly and direct detection of haplotypes, among other applications. Lower cost: Transmission electron microscopy DNA sequencing is estimated to cost just US$5,000-US$10,000 per human genome, compared to the more expensive second-generation DNA sequencing alternatives. No dephasing: Dephasing of the DNA strands due to loss in synchronicity during synthesis is a major problem of second-generation sequencing technologies. For transmission electron microscopy DNA sequencing and several other third-generation sequencing technologies, synchronization of the reads is unnecessary as only one molecule is being read at a time. Shorter turnaround time: The capacity to read native fragments of DNA renders complex template preparation an unnecessary step in the general workflow of whole genome sequencing. Consequently, shorter


id: transmission-kikuchi-diffraction-20260505-0
file: data/en.wikipedia.org/wiki/Transmission_Kikuchi_diffraction-0.md
category: reference
title: Transmission Kikuchi diffraction
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Transmission_Kikuchi_diffraction
date_saved: 2026-05-05T10:06:39.042429+00:00
instance: kb-cron
parent: transmission-kikuchi-diffraction-20260505-0
summary:
Transmission Kikuchi diffraction (TKD), also sometimes called transmission electron backscatter diffraction (t-EBSD), is a method for orientation mapping at the nanoscale. It’s used for analysing the microstructures of thin transmission electron microscopy (TEM) specimens in the scanning electron microscope (SEM). This technique has been widely utilised in the characterization of nano-crystalline materials, including oxides, superconductors, and metallic alloys. TKD offers improved spatial resolution, enabling effective characterization of nanocrystalline materials and heavily deformed samples where high dislocation densities can prevent successful characterization using conventional Electron backscatter diffraction. Many studies have reported sub-10 nm resolution using TKD. The main difference between diffraction spots and Kikuchi bands is that in TEM, discrete diffraction spots arise from coherent scattering of the incident beam, while the formation of Kikuchi bands is described as a two-step process consisting of incoherent scattering of the primary beam followed by coherent scattering of these forward biased electrons. TKD has also been applied to analyse fine-grained ultramylonite peridotite samples in a scanning electron microscope. The preparation of TKD samples can be done with standard methods used for transmission electron microscopy (TEM). == Description == Transmission Kikuchi diffraction (TKD or t-EBSD) is an Electron backscatter diffraction (EBSD) technique that is used


id: two-dimensional-correlation-analysis-20260505-0
file: data/en.wikipedia.org/wiki/Two-dimensional_correlation_analysis-0.md
category: reference
title: Two-dimensional correlation analysis
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Two-dimensional_correlation_analysis
date_saved: 2026-05-05T10:06:40.213046+00:00
instance: kb-cron
parent: two-dimensional-correlation-analysis-20260505-0
summary:
Two dimensional correlation analysis is a mathematical technique that is used to study changes in measured signals. As mostly spectroscopic signals are discussed, sometime also two dimensional correlation spectroscopy is used and refers to the same technique. In 2D correlation analysis, a sample is subjected to an external perturbation while all other parameters of the system are kept at the same value. This perturbation can be a systematic and controlled change in temperature, pressure, pH, chemical composition of the system, or even time after a catalyst was added to a chemical mixture. As a result of the controlled change (the perturbation), the system will undergo variations which are measured by a chemical or physical detection method. The measured signals or spectra will show systematic variations that are processed with 2D correlation analysis for interpretation. When one considers spectra that consist of few bands, it is quite obvious to determine which bands are subject to a changing intensity. Such a changing intensity can be caused for example by chemical reactions. However, the interpretation of the measured signal becomes more tricky when spectra are complex and bands are heavily overlapping. Two dimensional correlation analysis allows one to determine at which positions in


id: two-dimensional-correlation-analysis-20260505-1
file: data/en.wikipedia.org/wiki/Two-dimensional_correlation_analysis-1.md
category: reference
title: Two-dimensional correlation analysis
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Two-dimensional_correlation_analysis
date_saved: 2026-05-05T10:06:40.213046+00:00
instance: kb-cron
parent: two-dimensional-correlation-analysis-20260505-0
summary:
Ψ is the 2D asynchronous spectrum ν1 en ν2 are two spectral channels yν is the vector composed of the signal intensities in E in column ν n the number of signals in the original dataset N the Noda-Hilbert transform matrix The values of N, Nj, k are determined as follows: 0 if j = k 1 π ( k − j ) {\displaystyle {\frac {1}{\pi (k-j)}}} if j ≠ k where: j the row number k the column number == Interpretation == Interpretation of two-dimensional correlation spectra can be considered to consist of several stages. === Detection of peaks of which the intensity changes in the original dataset === As real measurement signals contain a certain level of noise, the derived 2D spectra are influenced and degraded with substantial higher amounts of noise. Hence, interpretation begins with studying the autocorrelation spectrum on the main diagonal of the 2D synchronous spectrum. In the 2D synchronous main diagonal signal on the right 4 peaks are visible at 10, 20, 30, and 40 (see also the 4 corresponding positive autopeaks in the 2D synchronous spectrum on the right). This indicates that in the original dataset 4 peaks of changing intensity are present.


id: ultraviolet-visible-spectroscopy-20260505-0
file: data/en.wikipedia.org/wiki/Ultraviolet–visible_spectroscopy-0.md
category: reference
title: Ultraviolet–visible spectroscopy
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Ultraviolet–visible_spectroscopy
date_saved: 2026-05-05T10:06:41.378064+00:00
instance: kb-cron
parent: ultraviolet-visible-spectroscopy-20260505-0
summary:
Ultraviolet–visible spectrophotometry (UV–Vis or UV-VIS) refers to absorption spectroscopy or reflectance spectroscopy in part of the ultraviolet and the full, adjacent visible regions of the electromagnetic spectrum. Being relatively inexpensive and easily implemented, this methodology is widely used in diverse applied and fundamental applications. The only requirement is that the sample absorb in the UV–Vis region, i.e. be a chromophore. Absorption spectroscopy is complementary to fluorescence spectroscopy. Parameters of interest, besides the wavelength of measurement, are absorbance (A) or transmittance (%T) or reflectance (%R), and its change with time. A UV–Vis spectrophotometer is an analytical instrument that measures the amount of ultraviolet (UV) and visible light that is absorbed by a sample. It is a widely used technique in chemistry, biochemistry, and other fields, to identify and quantify compounds in a variety of samples. UV–Vis spectrophotometers work by passing a beam of light through the sample and measuring the amount of light that is absorbed at each wavelength. The amount of light absorbed is proportional to the concentration of the absorbing compound in the sample. == Optical transitions == Most molecules and ions absorb energy in the ultraviolet or visible range, i.e., they are chromophores. The absorbed photon excites an


id: ultraviolet-visible-spectroscopy-20260505-1
file: data/en.wikipedia.org/wiki/Ultraviolet–visible_spectroscopy-1.md
category: reference
title: Ultraviolet–visible spectroscopy
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Ultraviolet–visible_spectroscopy
date_saved: 2026-05-05T10:06:41.378064+00:00
instance: kb-cron
parent: ultraviolet-visible-spectroscopy-20260505-0
summary:
A = log 10 ⁡ ( I 0 / I ) = ε c L {\displaystyle A=\log _{10}(I_{0}/I)=\varepsilon cL} , where A is the measured absorbance (formally dimensionless but generally reported in absorbance units (AU)), I 0 {\displaystyle I_{0}} is the intensity of the incident light at a given wavelength, I {\displaystyle I} is the transmitted intensity, L the path length through the sample, and c the concentration of the absorbing species. For each species and wavelength, ε is a constant known as the molar absorptivity or extinction coefficient. This constant is a fundamental molecular property in a given solvent, at a particular temperature and pressure, and has units of 1 / M ∗ c m {\displaystyle 1/M*cm} . The absorbance and extinction ε are sometimes defined in terms of the natural logarithm instead of the base-10 logarithm. The Beer–Lambert law is useful for characterizing many compounds but does not hold as a universal relationship for the concentration and absorption of all substances. A 2nd order polynomial relationship between absorption and concentration is sometimes encountered for very large, complex molecules such as organic dyes (xylenol orange or neutral red, for example). UV–Vis spectroscopy is also used in the semiconductor industry


id: ultraviolet-visible-spectroscopy-20260505-2
file: data/en.wikipedia.org/wiki/Ultraviolet–visible_spectroscopy-2.md
category: reference
title: Ultraviolet–visible spectroscopy
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Ultraviolet–visible_spectroscopy
date_saved: 2026-05-05T10:06:41.378064+00:00
instance: kb-cron
parent: ultraviolet-visible-spectroscopy-20260505-0
summary:
Stray light in a UV spectrophotometer is any light that reaches its detector that is not of the wavelength selected by the monochromator. This can be caused, for instance, by scattering of light within the instrument, or by reflections from optical surfaces. Stray light can cause significant errors in absorbance measurements, especially at high absorbances, because the stray light will be added to the signal detected by the detector, even though it is not part of the actually selected wavelength. The result is that the measured and reported absorbance will be lower than the actual absorbance of the sample. The stray light is an important factor, as it determines the purity of the light used for the analysis. The most important factor affecting it is the stray light level of the monochromator. Typically a detector used in a UV–VIS spectrophotometer is broadband; it responds to all the light that reaches it. If a significant amount of the light passed through the sample contains wavelengths that have much lower extinction coefficients than the nominal one, the instrument will report an incorrectly low absorbance. Any instrument will reach a point where an increase in sample concentration will not result in an increase


id: ultraviolet-visible-spectroscopy-20260505-3
file: data/en.wikipedia.org/wiki/Ultraviolet–visible_spectroscopy-3.md
category: reference
title: Ultraviolet–visible spectroscopy
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Ultraviolet–visible_spectroscopy
date_saved: 2026-05-05T10:06:41.378064+00:00
instance: kb-cron
parent: ultraviolet-visible-spectroscopy-20260505-0
summary:
The UV–visible spectrophotometer can also be configured to measure reflectance. In this case, the spectrophotometer measures the intensity of light reflected from a sample ( I {\displaystyle I} ), and compares it to the intensity of light reflected from a reference material ( I o {\displaystyle I_{o}} ) (such as a white tile). The ratio I / I o {\displaystyle I/I_{o}} is called the reflectance, and is usually expressed as a percentage (%R). The basic parts of a spectrophotometer are a light source, a holder for the sample, a diffraction grating or a prism as a monochromator to separate the different wavelengths of light, and a detector. The radiation source is often a tungsten filament (300–2500 nm), a deuterium arc lamp, which is continuous over the ultraviolet region (190–400 nm), a xenon arc lamp, which is continuous from 160 to 2,000 nm; or more recently, light emitting diodes (LED) for the visible wavelengths. The detector is typically a photomultiplier tube, a photodiode, a photodiode array or a charge-coupled device (CCD). Single photodiode detectors and photomultiplier tubes are used with scanning monochromators, which filter the light so that only light of a single wavelength reaches the detector at one time. The


id: ultraviolet-visible-spectroscopy-20260505-4
file: data/en.wikipedia.org/wiki/Ultraviolet–visible_spectroscopy-4.md
category: reference
title: Ultraviolet–visible spectroscopy
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Ultraviolet–visible_spectroscopy
date_saved: 2026-05-05T10:06:41.378064+00:00
instance: kb-cron
parent: ultraviolet-visible-spectroscopy-20260505-0
summary:
== Microspectrophotometry == UV–visible spectroscopy of microscopic samples is done by integrating an optical microscope with UV–visible optics, white light sources, a monochromator, and a sensitive detector such as a charge-coupled device (CCD) or photomultiplier tube (PMT). As only a single optical path is available, these are single beam instruments. Modern instruments are capable of measuring UV–visible spectra in both reflectance and transmission of micron-scale sampling areas. The advantages of using such instruments is that they are able to measure microscopic samples but are also able to measure the spectra of larger samples with high spatial resolution. As such, they are used in the forensic laboratory to analyze the dyes and pigments in individual textile fibers, microscopic paint chips and the color of glass fragments. They are also used in materials science and biological research and for determining the energy content of coal and petroleum source rock by measuring the vitrinite reflectance. Microspectrophotometers are used in the semiconductor and micro-optics industries for monitoring the thickness of thin films after they have been deposited. In the semiconductor industry, they are used because the critical dimensions of circuitry is microscopic. A typical test of a semiconductor wafer would entail the acquisition of


id: weisz-prater-criterion-20260505-0
file: data/en.wikipedia.org/wiki/Weisz–Prater_criterion-0.md
category: reference
title: Weisz–Prater criterion
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Weisz–Prater_criterion
date_saved: 2026-05-05T10:06:42.548723+00:00
instance: kb-cron
parent: weisz-prater-criterion-20260505-0
summary:
The Weisz–Prater criterion is a method used to estimate the influence of pore diffusion on reaction rates in heterogeneous catalytic reactions. If the criterion is satisfied, pore diffusion limitations are negligible. The criterion is N W − P = R R p 2 C s D e f f ≤ 3 β {\displaystyle N_{W-P}={\dfrac {{\mathfrak {R}}R_{p}^{2}}{C_{s}D_{eff}}}\leq 3\beta } Where R {\displaystyle {\mathfrak {R}}} is the reaction rate per volume of catalyst, R p {\displaystyle R_{p}} is the catalyst particle radius, C s {\displaystyle C_{s}} is the reactant concentration at the particle surface, and D e f f {\displaystyle D_{eff}} is the effective diffusivity. Diffusion is usually in the Knudsen regime when average pore radius is less than 100 nm. For a given effectiveness factor, η {\displaystyle \eta } , and reaction order, n, the quantity β {\displaystyle \beta } is defined by the equation: η = 3 R p 3 ∫ 0 R p [ 1 − β ( 1 − r / R p ) n ] r 2 d r {\displaystyle \eta ={\dfrac {3}{R_{p}^{3}}}\int _{0}^{R_{p}}[1-\beta (1-r/R_{p})^{n}]r^{2}\ dr} for small values of beta this can be approximated using the binomial theorem: η = 1 − n β 4 {\displaystyle


id: x-ray-crystal-truncation-rod-20260505-0
file: data/en.wikipedia.org/wiki/X-ray_crystal_truncation_rod-0.md
category: reference
title: X-ray crystal truncation rod
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/X-ray_crystal_truncation_rod
date_saved: 2026-05-05T10:06:43.719814+00:00
instance: kb-cron
parent: x-ray-crystal-truncation-rod-20260505-0
summary:
X-ray crystal truncation rod scattering is a powerful method in surface science, based on analysis of surface X-ray diffraction (SXRD) patterns from a crystalline surface. For an infinite crystal, the diffracted pattern is concentrated in Dirac delta function like Bragg peaks. Presence of crystalline surfaces results in additional structure along so-called truncation rods (linear regions in momentum space normal to the surface). Crystal Truncation Rod (CTR) measurements allow detailed determination of atomic structure at the surface, especially useful in cases of oxidation, epitaxial growth, and adsorption studies on crystalline surfaces. == Theory == A particle incident on a crystalline surface with momentum K 0 {\displaystyle K_{0}} will undergo scattering through a momentum change of Q {\displaystyle \mathbf {Q} } . If x {\displaystyle x} and y {\displaystyle y} represent directions in the plane of the surface and z {\displaystyle z} is perpendicular to the surface, then the scattered intensity as a function of all possible values of Q {\displaystyle \mathbf {Q} } is given by Where α {\displaystyle \alpha } is the penetration coefficient, defined as the ratio of x-ray amplitudes scattered from successive planes of atoms in the crystal, and a x {\displaystyle a_{x}} , a y {\displaystyle a_{y}}


id: x-ray-fluorescence-20260505-0
file: data/en.wikipedia.org/wiki/X-ray_fluorescence-0.md
category: reference
title: X-ray fluorescence
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/X-ray_fluorescence
date_saved: 2026-05-05T10:06:44.876284+00:00
instance: kb-cron
parent: x-ray-fluorescence-20260505-0
summary:
X-ray fluorescence (XRF) is the emission of characteristic "secondary" (or fluorescent) X-rays from a material that has been excited by being bombarded with high-energy X-rays or gamma rays. When a material is illuminated with high-energy X-rays, its atoms can become excited and emit their own unique, characteristic X-rays—a process similar to how a blacklight makes certain colors fluoresce. By measuring the energy and intensity of these emitted "secondary" X-rays, scientists can identify which elements are present in the sample and in what quantities. Thus, XRF is the basis of a non-destructive analytical technique widely used for elemental analysis and chemical analysis, particularly in the investigation of metals, glass, ceramics and building materials, and for research in geochemistry, forensic science, archaeology and art objects such as paintings. == Underlying physics == When materials are exposed to short-wavelength X-rays or to gamma rays, ionization of their component atoms may take place. Ionization consists of the ejection of one or more electrons from the atom, and may occur if the atom is exposed to radiation with an energy greater than its ionization energy. X-rays and gamma rays can be energetic enough to expel tightly held electrons from the inner orbitals of the atom.


id: x-ray-fluorescence-20260505-1
file: data/en.wikipedia.org/wiki/X-ray_fluorescence-1.md
category: reference
title: X-ray fluorescence
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/X-ray_fluorescence
date_saved: 2026-05-05T10:06:44.876284+00:00
instance: kb-cron
parent: x-ray-fluorescence-20260505-0
summary:
In energy-dispersive analysis, dispersion and detection are a single operation, as already mentioned above. Proportional counters or various types of solid-state detectors (PIN diode, Si(Li), Ge(Li), silicon drift detector SDD) are used. They all share the same detection principle: An incoming X-ray photon ionizes a large number of detector atoms with the amount of charge produced being proportional to the energy of the incoming photon. The charge is then collected and the process repeats itself for the next photon. Detector speed is obviously critical, as all charge carriers measured have to come from the same photon to measure the photon energy correctly (peak length discrimination is used to eliminate events that seem to have been produced by two X-ray photons arriving almost simultaneously). The spectrum is then built up by dividing the energy spectrum into discrete bins and counting the number of pulses registered within each energy bin. EDXRF detector types vary in resolution, speed and the means of cooling (a low number of free charge carriers is critical in the solid state detectors): proportional counters with resolutions of several hundred eV cover the low end of the performance spectrum, followed by PIN diode detectors, while the Si(Li), Ge(Li) and


id: x-ray-fluorescence-20260505-2
file: data/en.wikipedia.org/wiki/X-ray_fluorescence-2.md
category: reference
title: X-ray fluorescence
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/X-ray_fluorescence
date_saved: 2026-05-05T10:06:44.876284+00:00
instance: kb-cron
parent: x-ray-fluorescence-20260505-0
summary:
==== Processing ==== Considerable computer power is dedicated to correcting for pulse-pile up and for extraction of data from poorly resolved spectra. These elaborate correction processes tend to be based on empirical relationships that may change with time, so that continuous vigilance is required in order to obtain chemical data of adequate precision. Digital pulse processors are widely used in high performance nuclear instrumentation. They are able to effectively reduce pile-up and base line shifts, allowing for easier processing. A low pass filter is integrated, improving the signal to noise ratio. The digital pulse processor requires a significant amount of energy to run, but it provides precise results. ==== Usage ==== Energy-dispersive X-ray (EDX) spectrometers are different from wavelength dispersive X-ray (WDX) spectrometers in that they are smaller, simpler in design and have fewer engineered parts; however, the accuracy and resolution of EDX spectrometers are lower than for WDX. EDX spectrometers can also use miniature X-ray tubes or gamma sources, which makes them cheaper and allows miniaturization and portability. This type of instrument is commonly used for portable quality control screening applications, such as testing toys for lead (Pb) content, sorting scrap metals, and measuring the lead content of residential


id: x-ray-fluorescence-20260505-3
file: data/en.wikipedia.org/wiki/X-ray_fluorescence-3.md
category: reference
title: X-ray fluorescence
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/X-ray_fluorescence
date_saved: 2026-05-05T10:06:44.876284+00:00
instance: kb-cron
parent: x-ray-fluorescence-20260505-0
summary:
===== Flat crystal with Söller collimators ===== A Söller collimator is a stack of parallel metal plates, spaced a few tenths of a millimeter apart. To improve angular resolution, one must lengthen the collimator, and/or reduce the plate spacing. This arrangement has the advantage of simplicity and relatively low cost, but the collimators reduce intensity and increase scattering, and reduce the area of sample and crystal that can be "seen". The simplicity of the geometry is especially useful for variable-geometry monochromators. ===== Curved crystal with slits ===== The Rowland circle geometry ensures that the slits are both in focus, but in order for the Bragg condition to be met at all points, the crystal must first be bent to a radius of 2R (where R is the radius of the Rowland circle), then ground to a radius of R. This arrangement allows higher intensities (typically 8-fold) with higher resolution (typically 4-fold) and lower background. However, the mechanics of keeping Rowland circle geometry in a variable-angle monochromator is extremely difficult. In the case of fixed-angle monochromators (for use in simultaneous spectrometers), crystals bent to a logarithmic spiral shape give the best focusing performance. The manufacture of curved crystals to acceptable tolerances


id: x-ray-fluorescence-20260505-4
file: data/en.wikipedia.org/wiki/X-ray_fluorescence-4.md
category: reference
title: X-ray fluorescence
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/X-ray_fluorescence
date_saved: 2026-05-05T10:06:44.876284+00:00
instance: kb-cron
parent: x-ray-fluorescence-20260505-0
summary:
==== Detectors ==== Detectors used for wavelength dispersive spectrometry need to have high pulse processing speeds in order to cope with the very high photon count rates that can be obtained. In addition, they need sufficient energy resolution to allow filtering-out of background noise and spurious photons from the primary beam or from crystal fluorescence. There are four common types of detector: gas flow proportional counters sealed gas detectors scintillation counters semiconductor detectors Gas flow proportional counters are used mainly for detection of longer wavelengths. Gas flows through it continuously. Where there are multiple detectors, the gas is passed through them in series, then led to waste. The gas is usually 90% argon, 10% methane ("P10"), although the argon may be replaced with neon or helium where very long wavelengths (over 5 nm) are to be detected. The argon is ionized by incoming X-ray photons, and the electric field multiplies this charge into a measurable pulse. The methane suppresses the formation of fluorescent photons caused by recombination of the argon ions with stray electrons. The anode wire is typically tungsten or nichrome of 20–60 μm diameter. Since the pulse strength obtained is essentially proportional to the ratio of the detector


id: x-ray-fluorescence-20260505-5
file: data/en.wikipedia.org/wiki/X-ray_fluorescence-5.md
category: reference
title: X-ray fluorescence
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/X-ray_fluorescence
date_saved: 2026-05-05T10:06:44.876284+00:00
instance: kb-cron
parent: x-ray-fluorescence-20260505-0
summary:
X-ray absorption X-ray enhancement sample macroscopic effects All elements absorb X-rays to some extent. Each element has a characteristic absorption spectrum which consists of a "saw-tooth" succession of fringes, each step-change of which has wavelength close to an emission line of the element. Absorption attenuates the secondary X-rays leaving the sample. For example, the mass absorption coefficient of silicon at the wavelength of the aluminium Kα line is 50 m2/kg, whereas that of iron is 377 m2/kg. This means that fluorescent X-rays generated by a given concentration of aluminium in a matrix of iron are absorbed about seven times more (that is 377/50) compared with the fluorescent X-rays generated by the same concentration of aluminium, but in a silicon matrix. That would lead to about one seventh of the count rate, once the X-rays are detected. Mass absorption coefficients are well known and can be calculated. However, to calculate the absorption for a multi-element sample, the composition must be known. For analysis of an unknown sample, an iterative procedure is therefore used. To derive the mass absorption accurately, data for the concentration of elements not measured by XRF may be needed, and various strategies are employed to estimate these. As


id: x-ray-telescope-20260505-0
file: data/en.wikipedia.org/wiki/X-ray_telescope-0.md
category: reference
title: X-ray telescope
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/X-ray_telescope
date_saved: 2026-05-05T10:06:46.164760+00:00
instance: kb-cron
parent: x-ray-telescope-20260505-0
summary:
An X-ray telescope (XRT) is a telescope that is designed to observe remote objects in the X-ray spectrum. X-rays are absorbed by the Earth's atmosphere, so instruments to detect X-rays must be taken to high altitude by balloons, sounding rockets, and satellites. The basic elements of the telescope are the optics (focusing or collimating), that collects the radiation entering the telescope, and the detector, on which the radiation is collected and measured. A variety of different designs and technologies have been used for these elements. Many X-ray telescopes on satellites are compounded of multiple small detector-telescope systems whose capabilities add up or complement each other, and additional fixed or removable elements (filters, spectrometers) that add functionalities to the instrument. == History of X-ray telescopes == X-ray telescopes were first used for astronomy to observe the Sun, which was the only source in the sky bright enough in X-rays for those early telescopes to detect. Because the Sun is so bright in X-rays, early X-ray telescopes could use a small focusing element and the X-rays would be detected with photographic film. The first X-ray picture of the Sun from a rocket-borne telescope was taken by John V. Lindsay of the NASA


id: x-ray-telescope-20260505-1
file: data/en.wikipedia.org/wiki/X-ray_telescope-1.md
category: reference
title: X-ray telescope
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/X-ray_telescope
date_saved: 2026-05-05T10:06:46.164760+00:00
instance: kb-cron
parent: x-ray-telescope-20260505-0
summary:
a high resolution imaging a high telescope sensitivity: since radiation is focused on a small area, Signal-to-noise ratio is much higher for this kind of instruments. The mirrors can be made of ceramic or metal foil coated with a thin layer of a reflective material (typically gold or iridium). Mirrors based on this construction work on the basis of total reflection of light at grazing incidence. This technology is limited in energy range due to the fact that the critical angle for total reflection is inversely proportional to the X-ray photon energy, meaning that higher energy photons require smaller incidence angles and therefore longer telescope designs. The limit in the early 2000s with Chandra and XMM-Newton X-ray observatories was about 15 kilo-electronvolt (keV) light. Using new multi-layered coated mirrors, the X-ray mirror for the NuSTAR telescope pushed this up to 79 keV light. To reflect at this level, glass layers were multi-coated with tungsten (W)/silicon (Si) or platinum (Pt)/silicon carbide(SiC). === Collimating optics === While earlier X-ray telescopes were using simple collimating techniques (e.g. rotating collimators, wire collimators), the technology most used in the present day employs coded aperture masks. This technique uses a flat aperture patterned grille in front


id: x-ray-telescope-20260505-2
file: data/en.wikipedia.org/wiki/X-ray_telescope-2.md
category: reference
title: X-ray telescope
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/X-ray_telescope
date_saved: 2026-05-05T10:06:46.164760+00:00
instance: kb-cron
parent: x-ray-telescope-20260505-0
summary:
A scintillator is a material which exhibits the property of luminescence when excited by ionizing radiation. Luminescent materials, when struck by an incoming particle, such as an X-ray photon, absorb its energy and scintillate, i.e. reemit the absorbed energy in the form of a small flash of light, typically in the visible range. The scintillation X-ray detector were used on Vela 5A and its twin Vela 5B; the X-ray telescope onboard OSO 4 consisted of a single thin NaI(Tl) scintillation crystal plus phototube assembly enclosed in a CsI(Tl) anti-coincidence shield. OSO 5 carried a CsI crystal scintillator. The central crystal was 0.635 cm thick, had a sensitive area of 70 cm2, and was viewed from behind by a pair of photomultiplier tubes. The PHEBUS had two independent detectors, each detector consisted of a bismuth germinate (BGO) crystal 78 mm in diameter by 120 mm thick. The KONUS-B instrument consisted of seven detectors distributed around the spacecraft that responded to photons of 10 keV to 8 MeV energy. They consisted of NaI(Tl) scintillator crystals 200 mm in diameter by 50 mm thick behind a Be entrance window. Kvant-1 carried the HEXE, or High Energy X-ray Experiment, which employed a phoswich of


id: scientific-theory-20260505-0
file: data/en.wikipedia.org/wiki/Scientific_theory-0.md
category: reference
title: Scientific theory
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Scientific_theory
date_saved: 2026-05-05T10:06:47.725273+00:00
instance: kb-cron
parent: scientific-theory-20260505-0
summary:
A scientific theory is an explanation of an aspect of the natural world that can be or that has been repeatedly tested and has corroborating evidence in accordance with the scientific method, using accepted protocols of observation, measurement, and evaluation of results. Where possible, theories are tested under controlled conditions in an experiment. In circumstances not amenable to experimental testing, theories are evaluated through principles of abductive reasoning. Established scientific theories have withstood rigorous scrutiny and embody scientific knowledge. A scientific theory differs from a scientific fact: a fact is an observation, while a theory connects and explains multiple observations. Furthermore, a theory is expected to make predictions which could be confirmed or refuted with additional observations. Stephen Jay Gould wrote that: "...facts and theories are different things, not rungs in a hierarchy of increasing certainty. Facts are the world's data. Theories are structures of ideas that explain and interpret facts." A theory differs from a scientific law in that a law is an empirical description of a relationship between facts and/or other laws. For example, Newton's Law of Gravity is a mathematical equation that can be used to predict the attraction between bodies, but it is not a theory


id: scientific-theory-20260505-1
file: data/en.wikipedia.org/wiki/Scientific_theory-1.md
category: reference
title: Scientific theory
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Scientific_theory
date_saved: 2026-05-05T10:06:47.725273+00:00
instance: kb-cron
parent: scientific-theory-20260505-0
summary:
It can be subjected to minor adaptations to account for new data that do not fit it perfectly, as they are discovered, thus increasing its predictive capability over time. It is among the most parsimonious explanations, economical in the use of proposed entities or explanatory steps as per Occam's razor. This is because for each accepted explanation of a phenomenon, there may be an extremely large, perhaps even incomprehensible, number of possible and more complex alternatives, because one can always burden failing explanations with ad hoc hypotheses to prevent them from being falsified; therefore, simpler theories are preferable to more complex ones because they are more testable. === Definitions from scientific organizations === The United States National Academy of Sciences defines scientific theories as follows: The formal scientific definition of theory is quite different from the everyday meaning of the word. It refers to a comprehensive explanation of some aspect of nature that is supported by a vast body of evidence. Many scientific theories are so well established that no new evidence is likely to alter them substantially. For example, no new evidence will demonstrate that the Earth does not orbit around the Sun (heliocentric theory), or that living things


id: scientific-theory-20260505-2
file: data/en.wikipedia.org/wiki/Scientific_theory-2.md
category: reference
title: Scientific theory
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Scientific_theory
date_saved: 2026-05-05T10:06:47.725273+00:00
instance: kb-cron
parent: scientific-theory-20260505-0
summary:
== Modification and improvement == If experimental results contrary to a theory's predictions are observed, scientists first evaluate whether the experimental design was sound, and if so they confirm the results by independent replication. A search for potential improvements to the theory then begins. Solutions may require minor or major changes to the theory, or none at all if a satisfactory explanation is found within the theory's existing framework. Over time, as successive modifications build on top of each other, theories consistently improve and greater predictive accuracy is achieved. Since each new version of a theory (or a completely new theory) must have more predictive and explanatory power than the last, scientific knowledge consistently becomes more accurate over time. If modifications to the theory or other explanations seem to be insufficient to account for the new results, then a new theory may be required. Since scientific knowledge is usually durable, this occurs much less commonly than modification. Furthermore, until such a theory is proposed and accepted, the previous theory will be retained. This is because it is still the best available explanation for many other phenomena, as verified by its predictive power in other contexts. For example, it has been


id: scientific-theory-20260505-3
file: data/en.wikipedia.org/wiki/Scientific_theory-3.md
category: reference
title: Scientific theory
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Scientific_theory
date_saved: 2026-05-05T10:06:47.725273+00:00
instance: kb-cron
parent: scientific-theory-20260505-0
summary:
=== Theories and facts === A scientific theory does not turn into a fact. Scientific facts are observations that theories organize and explain. As new facts appear, a theory may be revised or new theories may emerge that encompass these additional facts. While American vernacular speech uses "theory" as similar to a "guess" in opposition to a "fact", in science the word "theory" means a model that is expected to explain a wide range of facts. == About theories == === Theories as axioms === The logical positivists thought of scientific theories as statements in a formal language. First-order logic is an example of a formal language. The logical positivists envisaged a similar scientific language. In addition to scientific theories, the language also included observation sentences ("the sun rises in the east"), definitions, and mathematical statements. The phenomena explained by the theories, if they could not be directly observed by the senses (for example, atoms and radio waves), were treated as theoretical concepts. In this view, theories function as axioms: predicted observations are derived from the theories much like theorems are derived in Euclidean geometry. However, the predictions are then tested against reality to verify the predictions, and the "axioms"


id: scientific-theory-20260505-4
file: data/en.wikipedia.org/wiki/Scientific_theory-4.md
category: reference
title: Scientific theory
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Scientific_theory
date_saved: 2026-05-05T10:06:47.725273+00:00
instance: kb-cron
parent: scientific-theory-20260505-0
summary:
...it is incorrect to speak of an assumption as either true or false, since there is no way of proving it to be either (If there were, it would no longer be an assumption). It is better to consider assumptions as either useful or useless, depending on whether deductions made from them correspond to reality...Since we must start somewhere, we must have assumptions, but at least let us have as few assumptions as possible. Certain assumptions are necessary for all empirical claims (e.g. the assumption that reality exists). However, theories do not generally make assumptions in the conventional sense (statements accepted without evidence). While assumptions are often incorporated during the formation of new theories, these are either supported by evidence (such as from previously existing theories) or the evidence is produced in the course of validating the theory. This may be as simple as observing that the theory makes accurate predictions, which is evidence that any assumptions made at the outset are correct or approximately correct under the conditions tested. Conventional assumptions, without evidence, may be used if the theory is only intended to apply when the assumption is valid (or approximately valid). For example, the special theory of relativity


id: scientific-theory-20260505-5
file: data/en.wikipedia.org/wiki/Scientific_theory-5.md
category: reference
title: Scientific theory
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Scientific_theory
date_saved: 2026-05-05T10:06:47.725273+00:00
instance: kb-cron
parent: scientific-theory-20260505-0
summary:
It is easy to obtain confirmations, or verifications, for nearly every theory—if we look for confirmations. Confirmations should count only if they are the result of risky predictions; that is to say, if, unenlightened by the theory in question, we should have expected an event which was incompatible with the theory—an event which would have refuted the theory. Every "good" scientific theory is a prohibition: it forbids certain things from happening. The more a theory forbids, the better it is. A theory which is not refutable by any conceivable event is non-scientific. Irrefutability is not a virtue of a theory (as people often think) but a vice. Every genuine test of a theory is an attempt to falsify it or to refute it. Testability is falsifiability; but there are degrees of testability: some theories are more testable, more exposed to refutation, than others; they take, as it were, greater risks. Confirming evidence should not count except when it is the result of a genuine test of the theory, and this means that it can be presented as a serious but unsuccessful attempt to falsify the theory. (I now speak in such cases of "corroborating evidence".) Some genuinely testable theories, when


id: scientific-theory-20260505-6
file: data/en.wikipedia.org/wiki/Scientific_theory-6.md
category: reference
title: Scientific theory
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Scientific_theory
date_saved: 2026-05-05T10:06:47.725273+00:00
instance: kb-cron
parent: scientific-theory-20260505-0
summary:
A theory is something other than myself. It may be set out on paper as a system of rules, and it is the more truly a theory the more completely it can be put down in such terms. Mathematical theory reaches the highest perfection in this respect. But even a geographical map fully embodies in itself a set of strict rules for finding one's way through a region of otherwise uncharted experience. Indeed, all theory may be regarded as a kind of map extended over space and time. A scientific theory can also be thought of as a book that captures the fundamental information about the world, a book that must be researched, written, and shared. In 1623, Galileo Galilei wrote: Philosophy [i.e. physics] is written in this grand book—I mean the universe—which stands continually open to our gaze, but it cannot be understood unless one first learns to comprehend the language and interpret the characters in which it is written. It is written in the language of mathematics, and its characters are triangles, circles, and other geometrical figures, without which it is humanly impossible to understand a single word of it; without these, one is wandering around in a


id: decompression-theory-20260505-0
file: data/en.wikipedia.org/wiki/Decompression_theory-0.md
category: reference
title: Decompression theory
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Decompression_theory
date_saved: 2026-05-05T10:06:49.112339+00:00
instance: kb-cron
parent: decompression-theory-20260505-0
summary:
Decompression theory is the study and modelling of the transfer of the inert gas component of breathing gases from the gas in the lungs to the tissues and back during exposure to variations in ambient pressure. In the case of underwater diving and compressed air work, this mostly involves ambient pressures greater than the local surface pressure, but astronauts, high altitude mountaineers, and travellers in aircraft which are not pressurised to sea level pressure, are generally exposed to ambient pressures less than standard sea level atmospheric pressure. In all cases, the symptoms caused by decompression occur during or within a relatively short period of hours, or occasionally days, after a significant pressure reduction. The term "decompression" derives from the reduction in ambient pressure experienced by the organism and refers to both the reduction in pressure and the process of allowing dissolved inert gases to be eliminated from the tissues during and after this reduction in pressure. The uptake of gas by the tissues is in the dissolved state, and elimination also requires the gas to be dissolved, however a sufficient reduction in ambient pressure may cause bubble formation in the tissues, which can lead to tissue damage and the symptoms


id: decompression-theory-20260505-1
file: data/en.wikipedia.org/wiki/Decompression_theory-1.md
category: reference
title: Decompression theory
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Decompression_theory
date_saved: 2026-05-05T10:06:49.112339+00:00
instance: kb-cron
parent: decompression-theory-20260505-0
summary:
=== Dissolved phase gas dynamics === Solubility of gases in liquids is influenced by the nature of the solvent liquid and the solute, the temperature, pressure, and the presence of other solutes in the solvent. Diffusion is faster in smaller, lighter molecules of which helium is the extreme example. Diffusivity of helium is 2.65 times faster than nitrogen. The concentration gradient, can be used as a model for the driving mechanism of diffusion. In this context, inert gas refers to a gas which is not metabolically active. Atmospheric nitrogen (N2) is the most common example, and helium (He) is the other inert gas commonly used in breathing mixtures for divers. Atmospheric nitrogen has a partial pressure of approximately 0.78 bar at sea level. Air in the alveoli of the lungs is diluted by saturated water vapour (H2O) and carbon dioxide (CO2), a metabolic product given off by the blood, and contains less oxygen (O2) than atmospheric air as some of it is taken up by the blood for metabolic use. The resulting partial pressure of nitrogen is about 0,758 bar. At atmospheric pressure the body tissues are therefore normally saturated with nitrogen at 0.758 bar (569 mmHg). At increased ambient


id: decompression-theory-20260505-2
file: data/en.wikipedia.org/wiki/Decompression_theory-2.md
category: reference
title: Decompression theory
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Decompression_theory
date_saved: 2026-05-05T10:06:49.112339+00:00
instance: kb-cron
parent: decompression-theory-20260505-0
summary:
=== Bubble mechanics === Equilibrium of forces on the surface is required for a bubble to exist. The sum of the Ambient pressure and pressure due to tissue distortion, exerted on the outside of the surface, with surface tension of the liquid at the interface between the bubble and the surroundings must be balanced by the pressure on the inside of the bubble. This is the sum of the partial pressures of the gases inside due to the net diffusion of gas to and from the bubble. The force balance on the bubble may be modified by a layer of surface active molecules which can stabilise a microbubble at a size where surface tension on a clean bubble would cause it to collapse rapidly, and this surface layer may vary in permeability, so that if the bubble is sufficiently compressed it may become impermeable to diffusion. If the solvent outside the bubble is saturated or unsaturated, the partial pressure will be less than in the bubble, and the surface tension will be increasing the internal pressure in direct proportion to surface curvature, providing a pressure gradient to increase diffusion out of the bubble, effectively "squeezing the gas out of the


id: decompression-theory-20260505-3
file: data/en.wikipedia.org/wiki/Decompression_theory-3.md
category: reference
title: Decompression theory
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Decompression_theory
date_saved: 2026-05-05T10:06:49.112339+00:00
instance: kb-cron
parent: decompression-theory-20260505-0
summary:
=== Isobaric counterdiffusion (ICD) === Isobaric counterdiffusion is the diffusion of gases in opposite directions caused by a change in the composition of the external ambient gas or breathing gas without change in the ambient pressure. During decompression after a dive this can occur when a change is made to the breathing gas, or when the diver moves into a gas filled environment which differs from the breathing gas. While not strictly speaking a phenomenon of decompression, it is a complication that can occur during decompression, and that can result in the formation or growth of bubbles without changes in the environmental pressure. Two forms of this phenomenon have been described by Lambertsen: Superficial ICD (also known as Steady State Isobaric Counterdiffusion) occurs when the inert gas breathed by the diver diffuses more slowly into the body than the inert gas surrounding the body. An example of this would be breathing air in an heliox environment. The helium in the heliox diffuses into the skin quickly, while the nitrogen diffuses more slowly from the capillaries to the skin and out of the body. The resulting effect generates supersaturation in certain sites of the superficial tissues and the formation of inert


id: decompression-theory-20260505-4
file: data/en.wikipedia.org/wiki/Decompression_theory-4.md
category: reference
title: Decompression theory
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Decompression_theory
date_saved: 2026-05-05T10:06:49.112339+00:00
instance: kb-cron
parent: decompression-theory-20260505-0
summary:
Vascular bubbles formed in the systemic capillaries may be trapped in the lung capillaries, temporarily blocking them. If this is severe, the symptom called "chokes" may occur. If the diver has a patent foramen ovale (or a shunt in the pulmonary circulation), bubbles may pass through it and bypass the pulmonary circulation to enter the arterial blood. If these bubbles are not absorbed in the arterial plasma and lodge in systemic capillaries they will block the flow of oxygenated blood to the tissues supplied by those capillaries, and those tissues will be starved of oxygen. Moon and Kisslo (1988) concluded that "the evidence suggests that the risk of serious neurological DCI or early onset DCI is increased in divers with a resting right-to-left shunt through a PFO. There is, at present, no evidence that PFO is related to mild or late onset bends." Bubbles form within other tissues as well as the blood vessels. Inert gas can diffuse into bubble nuclei between tissues. In this case, the bubbles can distort and permanently damage the tissue. As they grow, the bubbles may also compress nerves as they grow causing pain. Extravascular or autochthonous[a] bubbles usually form in slow tissues such as


id: decompression-theory-20260505-5
file: data/en.wikipedia.org/wiki/Decompression_theory-5.md
category: reference
title: Decompression theory
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Decompression_theory
date_saved: 2026-05-05T10:06:49.112339+00:00
instance: kb-cron
parent: decompression-theory-20260505-0
summary:
Two rather different concepts have been used for decompression modelling. The first assumes that dissolved gas is eliminated while in the dissolved phase, and that bubbles are not formed during asymptomatic decompression. The second, which is supported by experimental observation, assumes that bubbles are formed during most asymptomatic decompressions, and that gas elimination must consider both dissolved and bubble phases. Early decompression models tended to use the dissolved phase models, and adjusted them by more or less arbitrary factors to reduce the risk of symptomatic bubble formation. Dissolved phase models are of two main groups. Parallel compartment models, where several compartments with varying rates of gas absorption (half time), are considered to exist independently of each other, and the limiting condition is controlled by the compartment which shows the worst case for a specific exposure profile. These compartments represent conceptual tissues and are not intended to represent specific organic tissues, merely to represent the range of possibilities for the organic tissues. The second group uses serial compartments, where gas is assumed to diffuse through one compartment before it reaches the next. A recent variation on the serial compartment model is the Goldman interconnected compartment model (ICM). More recent models attempt


id: decompression-theory-20260505-6
file: data/en.wikipedia.org/wiki/Decompression_theory-6.md
category: reference
title: Decompression theory
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Decompression_theory
date_saved: 2026-05-05T10:06:49.112339+00:00
instance: kb-cron
parent: decompression-theory-20260505-0
summary:
=== Tissue compartments === One attempt at a solution was the development of multi-tissue models, which assumed that different parts of the body absorbed and eliminated gas at different rates. These are hypothetical tissues which are designated as fast and slow to describe the rate of saturation. Each tissue, or compartment, has a different half-life. Real tissues will also take more or less time to saturate, but the models do not need to use actual tissue values to produce a useful result. Models with from one to 16 tissue compartments have been used to generate decompression tables, and dive computers have used up to 20 compartments. For example: Tissues with a high lipid content can take up a larger amount of nitrogen, but often have a poor blood supply. These will take longer to reach equilibrium, and are described as slow, compared to tissues with a good blood supply and less capacity for dissolved gas, which are described as fast. Fast tissues absorb gas relatively quickly, but will generally release it quickly during ascent. A fast tissue may become saturated in the course of a normal recreational dive, while a slow tissue may have absorbed only a small part of


id: decompression-theory-20260505-7
file: data/en.wikipedia.org/wiki/Decompression_theory-7.md
category: reference
title: Decompression theory
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Decompression_theory
date_saved: 2026-05-05T10:06:49.112339+00:00
instance: kb-cron
parent: decompression-theory-20260505-0
summary:
==== The critical supersaturation approach ==== J.S. Haldane originally used a critical pressure ratio of 2 to 1 for decompression on the principle that the saturation of the body should at no time be allowed to exceed about double the air pressure. This principle was applied as a pressure ratio of total ambient pressure and did not take into account the partial pressures of the component gases of the breathing air. His experimental work on goats and observations of human divers appeared to support this assumption. However, in time, this was found to be inconsistent with incidence of decompression sickness and changes were made to the initial assumptions. This was later changed to a 1.58:1 ratio of nitrogen partial pressures. Further research by people such as Robert Workman suggested that the criterion was not the ratio of pressures, but the actual pressure differentials. Applied to Haldane's work, this would suggest that the limit is not determined by the 1.58:1 ratio but rather by the critical pressure difference of 0.58 atmospheres between tissue pressure and ambient pressure. Most Haldanean tables since the mid 20th century, including the Bühlmann tables, are based on the critical difference assumption. The M-value is the maximum


id: decompression-theory-20260505-8
file: data/en.wikipedia.org/wiki/Decompression_theory-8.md
category: reference
title: Decompression theory
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Decompression_theory
date_saved: 2026-05-05T10:06:49.112339+00:00
instance: kb-cron
parent: decompression-theory-20260505-0
summary:
A saturation exposure is where the time exposed to pressure is sufficient for all tissues to reach equilibrium with the inert gases in the breathing mixture. For practical purposes this is usually taken as 6 times the half time of the slowest tissue in the model. === No-stop limits === A no-stop limit, also called no decompression limit (NDL) is the theoretical maximum dissolved gas content of each tissue compartment of the whole body, which can be decompressed directly to surface pressure at the chosen ascent rate used by the model, without a need to stop to outgas at any depth, which has an acceptable risk of developing symptomatic decompression sickness. No decompression limit is a misnomer as the ascent at the specified ascent rate is decompression, but the term has historical inertia and continues to be used. === Decompression ceiling, floor and window === Once the gas loading of one or more tissue compartments exceeds the maximum level accepted for the no-stop limit, there is a minimum depth to which the diver can ascend at the appropriate ascent rate, at an acceptable risk for decompression sickness. This depth is known as the decompression ceiling. It may be considered a


id: decompression-theory-20260505-9
file: data/en.wikipedia.org/wiki/Decompression_theory-9.md
category: reference
title: Decompression theory
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Decompression_theory
date_saved: 2026-05-05T10:06:49.112339+00:00
instance: kb-cron
parent: decompression-theory-20260505-0
summary:
=== Residual inert gas === Gas bubble formation has been experimentally shown to significantly inhibit inert gas elimination. A considerable amount of inert gas will remain in the tissues after a diver has surfaced, even if no symptoms of decompression sickness occur. This residual gas may be dissolved or in sub-clinical bubble form, and will continue to outgas while the diver remains at the surface. If a repetitive dive is made, the tissues are preloaded with this residual gas which will make them saturate faster. In repetitive diving, the slower tissues can accumulate gas day after day, if there is insufficient time for the gas to be eliminated between dives. This can be a problem for multi-day multi-dive situations. Multiple decompressions per day over multiple days can increase the risk of decompression sickness because of the build up of asymptomatic bubbles, which reduce the rate of off-gassing and are not accounted for in most decompression algorithms. Consequently, some diver training organisations make extra recommendations such as taking "the seventh day off". == Decompression models in practice == === Deterministic models === Deterministic decompression models are a rule based approach to calculating decompression. These models work from the idea that "excessive"


id: decompression-theory-20260505-10
file: data/en.wikipedia.org/wiki/Decompression_theory-10.md
category: reference
title: Decompression theory
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Decompression_theory
date_saved: 2026-05-05T10:06:49.112339+00:00
instance: kb-cron
parent: decompression-theory-20260505-0
summary:
==== Perfusion limited tissues and parallel tissue models ==== The assumption that perfusion is the limiting mechanism leads to a model comprising a group of tissues with varied rates of perfusion, but supplied by blood of approximately equivalent gas concentration. It is also assumed that there is no gas transfer between tissue compartments by diffusion. This results in a parallel set of independent tissues, each with its own rate of ingassing and outgassing dependent on the rate of blood flowing through the tissue. Gas uptake for each tissue is generally modelled as an exponential function, with a fixed compartment half-time, and gas elimination may also be modelled by an exponential function, with the same or a longer half time, or as a more complex function, as in the exponential-linear elimination model. The critical ratio hypothesis predicts that the development of bubbles will occur in a tissue when the ratio of dissolved gas partial pressure to ambient pressure exceeds a particular ratio for a given tissue. The ratio may be the same for all tissue compartments or it may vary, and each compartment is allocated a specific critical supersaturation ratio, based on experimental observations. John Scott Haldane introduced the concept of


id: decompression-theory-20260505-11
file: data/en.wikipedia.org/wiki/Decompression_theory-11.md
category: reference
title: Decompression theory
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Decompression_theory
date_saved: 2026-05-05T10:06:49.112339+00:00
instance: kb-cron
parent: decompression-theory-20260505-0
summary:
For example, a diver ascends from a maximum depth of 60 metres (200 ft), where the ambient pressure is 7 bars (100 psi), to a decompression stop at 20 metres (66 ft), where the pressure is 3 bars (40 psi). The first Pyle stop would take place at the halfway pressure, which is 5 bars (70 psi) corresponding to a depth of 40 metres (130 ft). The second Pyle stop would be at 30 metres (98 ft). A third would be at 25 metres (82 ft) which is less than 9 metres (30 ft) below the first required stop, and therefore is omitted. The value and safety of deep stops additional to the decompression schedule derived from a decompression algorithm is unclear. Decompression experts have pointed out that deep stops are likely to be made at depths where ingassing continues for some slow tissues, and that the addition of deep stops of any kind should be included in the hyperbaric exposure for which the decompression schedule is computed, and not added afterwards, so that such ingassing of slower tissues can be taken into account. Deep stops performed during a dive where the decompression is calculated in real-time are simply part


id: decompression-theory-20260505-12
file: data/en.wikipedia.org/wiki/Decompression_theory-12.md
category: reference
title: Decompression theory
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Decompression_theory
date_saved: 2026-05-05T10:06:49.112339+00:00
instance: kb-cron
parent: decompression-theory-20260505-0
summary:
In contrast to the independent parallel compartments of the Haldanean models, in which all compartments are considered risk bearing, the Goldman model posits a relatively well perfused "active" or "risk-bearing" compartment in series with adjacent relatively poorly perfused "reservoir" or "buffer" compartments, which are not considered potential sites for bubble formation, but affect the probability of bubble formation in the active compartment by diffusive inert gas exchange with the active compartment. During compression, gas diffuses into the active compartment and through it into the buffer compartments, increasing the total amount of dissolved gas passing through the active compartment. During decompression, this buffered gas must pass through the active compartment again before it can be eliminated. If the gas loading of the buffer compartments is small, the added gas diffusion through the active compartment is slow. The interconnected models predict a reduction in gas washout rate with time during decompression compared with the rate predicted for the independent parallel compartment model used for comparison. The Goldman model differs from the Kidd-Stubbs series decompression model in that the Goldman model assumes linear kinetics, where the K-S model includes a quadratic component, and the Goldman model considers only the central well-perfused compartment to


id: decompression-theory-20260505-13
file: data/en.wikipedia.org/wiki/Decompression_theory-13.md
category: reference
title: Decompression theory
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Decompression_theory
date_saved: 2026-05-05T10:06:49.112339+00:00
instance: kb-cron
parent: decompression-theory-20260505-0
summary:
=== Probabilistic models === Probabilistic decompression models, also referred to as evidence-based decompression models, are designed to calculate the risk (or probability) of decompression sickness (DCS) occurring on a given decompression profile, based on actual outcomes of a statistically robust set of data. Statistical analysis is well suited to compressed air work in tunneling operations due to the large number of subjects undergoing similar exposures at the same ambient pressure and temperature, with similar workloads and exposure times, with the same decompression schedule. Large numbers of decompressions under similar circumstances have shown that it is not reasonably practicable to eliminate all risk of DCS, so it is necessary to set an acceptable risk, based on the other factors relevant to the application. For example, easy access to effective treatment in the form of hyperbaric oxygen treatment on site, or greater advantage to getting the diver out of the water sooner, may make a higher incidence acceptable, while interfering with work schedule, adverse effects on worker morale or a high expectation of litigation would shift acceptable incidence rate downward. Efficiency is also a factor, as decompression of employees occurs during working hours. These methods can vary the decompression stop depths and


id: decompression-theory-20260505-14
file: data/en.wikipedia.org/wiki/Decompression_theory-14.md
category: reference
title: Decompression theory
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Decompression_theory
date_saved: 2026-05-05T10:06:49.112339+00:00
instance: kb-cron
parent: decompression-theory-20260505-0
summary:
Saturation decompression is a physiological process of transition from a steady state of full saturation with inert gas at raised pressure to standard conditions at normal surface atmospheric pressure. It is a long process during which inert gases are eliminated at a very low rate limited by the slowest affected tissues, and a deviation can cause the formation of gas bubbles which can produce decompression sickness. Most operational procedures rely on experimentally derived parameters describing a continuous slow decompression rate, which may depend on depth and gas mixture. In saturation diving all tissues are considered saturated and decompression which is safe for the slowest tissues will theoretically be safe for all faster tissues in a parallel model. Direct ascent from air saturation at approximately 7 msw produces venous gas bubbles but not symptomatic DCS. Deeper saturation exposures require decompression to saturation schedules. The safe rate of decompression from a saturation dive is controlled by the partial pressure of oxygen in the inspired breathing gas. The inherent unsaturation due to the oxygen window allows a relatively fast initial phase of saturation decompression in proportion to the oxygen partial pressure and then controls the rate of further decompression limited by the half-time


id: decompression-theory-20260505-15
file: data/en.wikipedia.org/wiki/Decompression_theory-15.md
category: reference
title: Decompression theory
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Decompression_theory
date_saved: 2026-05-05T10:06:49.112339+00:00
instance: kb-cron
parent: decompression-theory-20260505-0
summary:
==== Effects of inert gas component changes ==== Gas switching during decompression on open circuit is done primarily to increase the partial pressure of oxygen to increase the oxygen window effect, while keeping below acute toxicity levels. It is well established both in theory and practice, that a higher oxygen partial pressure facilitates a more rapid and effective elimination of inert gas, both in the dissolved state and as bubbles. In closed circuit rebreather diving the oxygen partial pressure throughout the dive is maintained at a relatively high but tolerable level to reduce the ongassing as well as to accelerate offgassing of the diluent gas. Changes from helium-based diluents to nitrogen during ascent are desirable for reducing the use of expensive helium, but have other implications. It is unlikely that changes to nitrogen based decompression gas will accelerate decompression in typical technical bounce dive profiles, but there is some evidence that decompressing on helium-oxygen mixtures is more likely to result in neurological DCS, while nitrogen based decompression is more likely to produce other symptoms if DCS occurs. However, switching from helium rich to nitrogen rich decompression gas is implicated in inner ear DCS, connected with counter-diffusion effects. This risk can


id: decompression-theory-20260505-16
file: data/en.wikipedia.org/wiki/Decompression_theory-16.md
category: reference
title: Decompression theory
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Decompression_theory
date_saved: 2026-05-05T10:06:49.112339+00:00
instance: kb-cron
parent: decompression-theory-20260505-0
summary:
=== Practical effectiveness of models === Bubble models for decompression were popular among technical divers in the early 2000s, although there was little data to support the effectiveness of the models in practice. Since then, several comparative studies have indicated relatively larger numbers of venous gas emboli after decompression based on bubble models, and one study reported a higher rate of decompression sickness. The deeper decompression stops earlier in the ascent appear to be less effective at controlling bubble formation than the hypotheses suggested. This failure may be due to continued ingassing of slower tissues during the extended time at greater depth, resulting in these tissues being more supersaturated at shallower depths. The optimal decompression strategy for deep bounce dives remains unknown (2016). The practical efficacy of gas switches from helium-based diluent to nitrox for accelerating decompression has not been demonstrated convincingly. These switches increase risk of inner ear decompression sickness due to counterdiffusion effects. Besides the basic dive profile and gas mixes, and the residual gas load from previous dives, three groups of factors are considered likely to have significant influence on decompression stress, the evolution of bubbles in the diver, and development of symptoms. These are exercise, before,


id: disease-theory-of-alcoholism-20260505-0
file: data/en.wikipedia.org/wiki/Disease_theory_of_alcoholism-0.md
category: reference
title: Disease theory of alcoholism
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Disease_theory_of_alcoholism
date_saved: 2026-05-05T10:06:50.381723+00:00
instance: kb-cron
parent: disease-theory-of-alcoholism-20260505-0
summary:
The modern disease theory of alcoholism states that problem drinking is sometimes caused by a disease of the brain, characterized by altered brain structure and function. Today, alcohol use disorder (AUD) is used as a more scientific and suitable approach to alcohol dependence and alcohol-related problems. The largest association of physicians – the American Medical Association (AMA) – declared that alcoholism was an illness in 1956. In 1991, the AMA further endorsed the dual classification of alcoholism by the International Classification of Diseases under both psychiatric and medical sections. == Theory == Under the model of alcoholism, alcohol use disorder is viewed as chronic problem for which abstinence is required. A brain disease model of addiction, based on the extent of neuroadaptation and impaired control, is main position advanced for proposing a disease model of alcohol use disorder. However, if managed properly, damage to the brain can be stopped and to some extent reversed. In addition to problem drinking, the disease is characterized by symptoms including an impaired control over alcohol, compulsive thoughts about alcohol, and distorted thinking. Alcoholism can also lead indirectly, through excess consumption, to physical dependence on alcohol, and diseases such as cirrhosis of the liver. The


id: disease-theory-of-alcoholism-20260505-1
file: data/en.wikipedia.org/wiki/Disease_theory_of_alcoholism-1.md
category: reference
title: Disease theory of alcoholism
tags: science, encyclopedia
source_url: https://en.wikipedia.org/wiki/Disease_theory_of_alcoholism
date_saved: 2026-05-05T10:06:50.381723+00:00
instance: kb-cron
parent: disease-theory-of-alcoholism-20260505-0
summary:
My observations authorize me to say, that persons who have been addicted to them, should abstain from them suddenly and entirely. 'Taste not, handle not, touch not' should be inscribed upon every vessel that contains spirits in the house of a man, who wishes to be cured of habits of intemperance. Rush argued that "habitual drunkenness should be regarded not as a bad habit but as a disease", describing it as "a palsy of the will". Rush expounded his views in a book published in 1808. His views are described by Valverde, Levine Spode, and Perkins-McVey. Already in 1802 the prominent German physician Christoph Wilhelm Hufeland had published a book on the "brandy plague" stating that the "infection" with spirits makes it "inevitably necessary to drink ever more." Later he wrote an enthusiastic preface to the book On the addiction to drink and a rational cure of it by German-Russian physician C. von Brühl-Cramer. As Spode points out, this study marked the birth of a consistent "paradigm" of addiction as a mental illness, although it took many decades until this view was accepted. Perkins-McVey argues that Rush, Trotter, and Brühl-Cramer each independently developed their own disease theories of alcoholism as


