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Václav Chvátal-Research-Chvátal is also known for proving the art gallery theorem, for researching a self-describing digital sequence, for his work with David Sankoff on the Chvátal–Sankoff constants controlling the behavior of the longest common subsequence problem on random inputs, and for his work with Endre Szemeré... | milkshake721/2.1M-wiki-STEM |
Václav Chvátal-Books-Vašek Chvátal (1983). Linear Programming. W.H. Freeman. ISBN 978-0-7167-1587-0.. Japanese translation published by Keigaku Shuppan, Tokyo, 1986.
C. Berge and V. Chvátal (eds.) (1984). Topics on Perfect Graphs. Elsevier. ISBN 978-0-444-86587-8. {{cite book}}: |author= has generic name (help) David L... | milkshake721/2.1M-wiki-STEM |
Cloud tree-Cloud tree-A cloud tree is a tree shaped using topiary techniques. The leaves are pruned into a ball or cloud shape, leaving the stems thin and exposed. The shape of the tree as a whole resembles a set of clouds.
Cloud trees differ from bonsai trees because they are not miniature. Typically, cloud trees are ... | milkshake721/2.1M-wiki-STEM |
Calendar (Windows)-Calendar (Windows)-Calendar is a personal calendar application made by Microsoft for Microsoft Windows. It offers synchronization of calendars using Microsoft Exchange Server, Outlook.com Apple's iCloud calendar service, and Google Calendar. It supports the popular iCalendar 2.0 format. | milkshake721/2.1M-wiki-STEM |
Calendar (Windows)-History-Microsoft first included a Calendar application (shortened to app) in Windows 1.0, which was included through Windows 3.1, and was replaced by Schedule+ in Windows for Workgroups and Windows NT 3.1. Schedule+ was later moved from Windows to the Microsoft Office suite, and Windows did not incl... | milkshake721/2.1M-wiki-STEM |
Calendar (Windows)-History-Windows Vista This version supports sharing, subscribing, and publishing of calendars on WebDAV-enabled web servers and network shares. It has always supported .ics files, and the subscription feature enables syncing with Google Calendar. Its interface matches Windows Vista Mail's, but the tw... | milkshake721/2.1M-wiki-STEM |
Calendar (Windows)-History-On the calendar taskbar applet, there is a date grid on the left side and a skeuomorphistic analogue clock and a digital clock underneath on the right side. Additional clocks displaying different time zones can be added to the view. On the date grid (left side), dates far in the past or futur... | milkshake721/2.1M-wiki-STEM |
Calendar (Windows)-History-Windows 8 A new version of Calendar with a text-heavy was added to Windows 8 as one of many apps written to run full-screen or snapped as part of Microsoft's Metro design language philosophy. It is one of three apps on Windows that originate from Microsoft Outlook, the other two being Mail an... | milkshake721/2.1M-wiki-STEM |
Calendar (Windows)-History-Windows 10 Calendar has preset server configurations for Outlook.com, Exchange, Google Calendar, and iCloud Calendar. Users can set it to use the system theme or choose a custom accent color, background image, and light/dark preference. Windows 10 Calendar has multi-window support for viewing... | milkshake721/2.1M-wiki-STEM |
Doral (cigarette)-Doral (cigarette)-Doral is an American brand of cigarettes, currently owned and manufactured by the R.J. Reynolds Tobacco Company. | milkshake721/2.1M-wiki-STEM |
Doral (cigarette)-History-Doral was introduced in 1969 and is available nationwide in the United States.Originally a premium brand, the cigarettes were re-branded in 1984 as a savings brand. This made Doral the officially first branded cigarette to be in the value-savings market.In 1984, The New York Times tested vario... | milkshake721/2.1M-wiki-STEM |
Doral (cigarette)-Advertisement-R.J. Reynolds made various poster adverts to promote the Doral brand. Magazine advertisements were done in comic strip format; such as one with a lion tamer worried about what his Doral pack sang.Doral's current slogan is "Premium Taste, Guaranteed". An early slogan was "Taste me!" done ... | milkshake721/2.1M-wiki-STEM |
MathWorks-MathWorks-MathWorks is an American privately held corporation that specializes in mathematical computing software. Its major products include MATLAB and Simulink, which support data analysis and simulation. | milkshake721/2.1M-wiki-STEM |
MathWorks-History-The company's key product, MATLAB, was created in the 1970s by Cleve Moler, who was chairman of the computer science department at the University of New Mexico at the time. It was a free tool for academics. Jack Little, who would eventually set up the company, came across the tool while he was a gradu... | milkshake721/2.1M-wiki-STEM |
MathWorks-History-In 1999, MathWorks relocated to the Apple Hill office complex in Natick, Massachusetts, purchasing additional buildings in the complex in 2008 and 2009, ultimately occupying the entire campus. MathWorks expanded further in 2013 by buying Boston Scientific's old headquarters campus, which is near to Ma... | milkshake721/2.1M-wiki-STEM |
MathWorks-Products-The company's two lead products are MATLAB, which provides an environment for scientists, engineers and programmers to analyze and visualize data and develop algorithms, and Simulink, a graphical and simulation environment for model-based design of dynamic systems. MATLAB and Simulink are used in aer... | milkshake721/2.1M-wiki-STEM |
MathWorks-Corporate affairs-Intellectual property and competition In 1999, the U.S. Department of Justice filed a lawsuit against MathWorks and Wind River Systems alleging that an agreement between them violated antitrust laws. The agreement in question stipulated that the two companies agreed to stop competing in the ... | milkshake721/2.1M-wiki-STEM |
MathWorks-Corporate affairs-Logo The logo represents the first vibrational mode of a thin L-shaped membrane, clamped at the edges, and governed by the wave equation, which was the subject of Moler's thesis. | milkshake721/2.1M-wiki-STEM |
MathWorks-Corporate affairs-Community The company annually sponsors a number of student engineering competitions, including EcoCAR, an advanced vehicle technology competition created by the United States Department of Energy (DOE) and General Motors (GM). MathWorks sponsored the mathematics exhibit at London's Science ... | milkshake721/2.1M-wiki-STEM |
Crossover (genetic algorithm)-Crossover (genetic algorithm)-In genetic algorithms and evolutionary computation, crossover, also called recombination, is a genetic operator used to combine the genetic information of two parents to generate new offspring. It is one way to stochastically generate new solutions from an exi... | milkshake721/2.1M-wiki-STEM |
Crossover (genetic algorithm)-Crossover (genetic algorithm)-Different algorithms in evolutionary computation may use different data structures to store genetic information, and each genetic representation can be recombined with different crossover operators. Typical data structures that can be recombined with crossover... | milkshake721/2.1M-wiki-STEM |
Crossover (genetic algorithm)-Crossover for binary arrays-Traditional genetic algorithms store genetic information in a chromosome represented by a bit array. Crossover methods for bit arrays are popular and an illustrative example of genetic recombination.
One-point crossover A point on both parents' chromosomes is pi... | milkshake721/2.1M-wiki-STEM |
Crossover (genetic algorithm)-Crossover for binary arrays-Two-point and k-point crossover In two-point crossover, two crossover points are picked randomly from the parent chromosomes. The bits in between the two points are swapped between the parent organisms. Two-point crossover is equivalent to performing two single... | milkshake721/2.1M-wiki-STEM |
Crossover (genetic algorithm)-Crossover for binary arrays-Uniform crossover In uniform crossover, typically, each bit is chosen from either parent with equal probability. Other mixing ratios are sometimes used, resulting in offspring which inherit more genetic information from one parent than the other.
In a uniform cr... | milkshake721/2.1M-wiki-STEM |
Crossover (genetic algorithm)-Crossover for integer or real-valued genomes-For the crossover operators presented above and for most other crossover operators for bit strings, it holds that they can also be applied accordingly to integer or real-valued genomes whose genes each consist of an integer or real-valued number... | milkshake721/2.1M-wiki-STEM |
Crossover (genetic algorithm)-Crossover for integer or real-valued genomes-Discrete recombination If the rules of the uniform crossover for bit strings are applied during the generation of the offspring, this is also called discrete recombination. | milkshake721/2.1M-wiki-STEM |
Crossover (genetic algorithm)-Crossover for integer or real-valued genomes-Intermediate recombination In this recombination operator, the allele values of the child genome ai are generated by mixing the alleles of the two parent genomes ai,P1 and ai,P2 :αi=αi,P1⋅βi+αi,P2⋅(1−βi)withβi∈[−d,1+d] randomly equally distri... | milkshake721/2.1M-wiki-STEM |
Crossover (genetic algorithm)-Crossover for permutations-For combinatorial tasks, permutations are usually used that are specifically designed for genomes that are themselves permutations of a set. The underlying set is usually a subset of N or N0 . If 1- or n-point or uniform crossover for integer genomes is used fo... | milkshake721/2.1M-wiki-STEM |
Crossover (genetic algorithm)-Crossover for permutations-In the following, two crossover operators are presented as examples, the partially mapped crossover (PMX) motivated by the TSP and the order crossover (OX1) designed for order-based permutations. A second offspring can be produced in each case by exchanging the p... | milkshake721/2.1M-wiki-STEM |
Crossover (genetic algorithm)-Crossover for permutations-Partially mapped crossover (PMX) The PMX operator was designed as a recombination operator for TSP like Problems. The explanation of the procedure is illustrated by an example: Order crossover (OX1) The order crossover goes back to Davis in its original form and ... | milkshake721/2.1M-wiki-STEM |
Crossover (genetic algorithm)-Crossover for permutations-Further crossover operators for permutations Over time, a large number of crossover operators for permutations have been proposed, so the following list is only a small selection. For more information, the reader is referred to the literature. | milkshake721/2.1M-wiki-STEM |
Crossover (genetic algorithm)-Crossover for permutations-cycle crossover (CX) order-based crossover (OX2) position-based crossover (POS) edge recombination voting recombination (VR) alternating-positions crossover (AP) maximal preservative crossover (MPX) merge crossover (MX) sequential constructive crossover operator ... | milkshake721/2.1M-wiki-STEM |
Isochronous signal-Isochronous signal-In telecommunication, an isochronous signal is a signal in which the time interval separating any two significant instants is equal to the unit interval or a multiple of the unit interval. Variations in the time intervals are constrained within specified limits.
"Isochronous" is a ... | milkshake721/2.1M-wiki-STEM |
Transmission electron microscopy-Transmission electron microscopy-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 i... | milkshake721/2.1M-wiki-STEM |
Transmission electron microscopy-Transmission electron microscopy-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 co... | milkshake721/2.1M-wiki-STEM |
Transmission electron microscopy-Transmission electron microscopy-TEM instruments have multiple operating modes including conventional imaging, scanning TEM imaging (STEM), diffraction, spectroscopy, and combinations of these. Even within conventional imaging, there are many fundamentally different ways that contrast i... | milkshake721/2.1M-wiki-STEM |
Transmission electron microscopy-Transmission electron microscopy-The first TEM was demonstrated by Max Knoll and Ernst Ruska in 1931, with this group developing the first TEM with resolution greater than that of light in 1933 and the first commercial TEM in 1939. In 1986, Ruska was awarded the Nobel Prize in physics f... | milkshake721/2.1M-wiki-STEM |
Transmission electron microscopy-History-Initial development In 1873, Ernst Abbe proposed that the ability to resolve detail in an object was limited approximately by the wavelength of the light used in imaging or a few hundred nanometers for visible light microscopes. Developments in ultraviolet (UV) microscopes, led ... | milkshake721/2.1M-wiki-STEM |
Transmission electron microscopy-History-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 reali... | milkshake721/2.1M-wiki-STEM |
Transmission electron microscopy-History-Research continued on the electron microscope at Siemens in 1936, where the aim of the research was the development and improvement of TEM imaging properties, particularly with regard to biological specimens. At this time electron microscopes were being fabricated for specific g... | milkshake721/2.1M-wiki-STEM |
Transmission electron microscopy-History-Further research After World War II, Ruska resumed work at Siemens, where he continued to develop the electron microscope, producing the first microscope with 100k magnification. The fundamental structure of this microscope design, with multi-stage beam preparation optics, is st... | milkshake721/2.1M-wiki-STEM |
Transmission electron microscopy-History-With the development of TEM, the associated technique of scanning transmission electron microscopy (STEM) was re-investigated and remained undeveloped until the 1970s, with Albert Crewe at the University of Chicago developing the field emission gun and adding a high quality obje... | milkshake721/2.1M-wiki-STEM |
Transmission electron microscopy-Background-Electrons Theoretically, the maximum resolution, d, that one can obtain with a light microscope is limited by the wavelength of the photons (λ) and the numerical aperture NA of the system. | milkshake721/2.1M-wiki-STEM |
Transmission electron microscopy-Background-sin NA where n is the index of refraction of the medium in which the lens is working and α is the maximum half-angle of the cone of light that can enter the lens (see numerical aperture). Early twentieth century scientists theorized ways of getting around the limitations of t... | milkshake721/2.1M-wiki-STEM |
Transmission electron microscopy-Background-Electron source 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 electr... | milkshake721/2.1M-wiki-STEM |
Transmission electron microscopy-Background-Optics The lenses of a TEM are what gives it its flexibility of operating modes and ability to focus beams down to the atomic scale and magnify them to get an image. A lens is usually made of a solenoid coil nearly surrounded by ferromagnetic materials designed to concentrate... | milkshake721/2.1M-wiki-STEM |
Transmission electron microscopy-Background-Equally important to the lenses are the apertures. These are circular holes in thin strips of heavy metal. Some are fixed in size and position and play important roles in limiting x-ray generation and improving the vacuum performance. Others can be freely switched among sever... | milkshake721/2.1M-wiki-STEM |
Transmission electron microscopy-Background-The electron-optical system also includes deflectors and stigmators, usually made of small electromagnets. The deflectors allow the position and angle of the beam at the sample position to be independently controlled and also ensure that the beams remain near the low-aberrati... | milkshake721/2.1M-wiki-STEM |
Transmission electron microscopy-Background-Typically a TEM consists of three stages of lensing. The stages are the condenser lenses, the objective lenses, and the projector lenses. The condenser lenses are responsible for primary beam formation, while the objective lenses focus the beam that comes through the sample i... | milkshake721/2.1M-wiki-STEM |
Transmission electron microscopy-Background-Reciprocity The optical reciprocity theorem, or principle of Helmholtz reciprocity, generally holds true for elastically scattered electrons, as is often the case under standard TEM operating conditions. The theorem states that the wave amplitude at some point B as a result o... | milkshake721/2.1M-wiki-STEM |
Transmission electron microscopy-Background-Display and detectors The key factors when considering electron detection include detective quantum efficiency (DQE), point spread function (PSF), modulation transfer function (MTF), pixel size and array size, noise, data readout speed, and radiation hardness.Imaging systems ... | milkshake721/2.1M-wiki-STEM |
Transmission electron microscopy-Components-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 g... | milkshake721/2.1M-wiki-STEM |
Transmission electron microscopy-Components-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 witho... | milkshake721/2.1M-wiki-STEM |
Transmission electron microscopy-Components-The vacuum system for evacuating a TEM to an operating pressure level consists of several stages. Initially, a low or roughing vacuum is achieved with either a rotary vane pump or diaphragm pumps setting a sufficiently low pressure to allow the operation of a turbo-molecular ... | milkshake721/2.1M-wiki-STEM |
Transmission electron microscopy-Components-High-voltage TEMs require ultra-high vacuums on the range of 10−7 to 10−9 Pa to prevent the generation of an electrical arc, particularly at the TEM cathode. As such for higher voltage TEMs a third vacuum system may operate, with the gun isolated from the main chamber either ... | milkshake721/2.1M-wiki-STEM |
Transmission electron microscopy-Components-Poor vacuum in a TEM can cause several problems ranging from the deposition of gas inside the TEM onto the specimen while viewed in a process known as electron beam induced deposition to more severe cathode damages caused by electrical discharge. The use of a cold trap to ads... | milkshake721/2.1M-wiki-STEM |
Transmission electron microscopy-Components-Specimen stage 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. Standar... | milkshake721/2.1M-wiki-STEM |
Transmission electron microscopy-Components-Once inserted into a TEM, the sample has to be manipulated to locate the region of interest to the beam, such as in single grain diffraction, in a specific orientation. To accommodate this, the TEM stage allows movement of the sample in the XY plane, Z height adjustment, and ... | milkshake721/2.1M-wiki-STEM |
Transmission electron microscopy-Components-A TEM stage is required to have the ability to hold a specimen and be manipulated to bring the region of interest into the path of the electron beam. As the TEM can operate over a wide range of magnifications, the stage must simultaneously be highly resistant to mechanical dr... | milkshake721/2.1M-wiki-STEM |
Transmission electron microscopy-Components-Two main designs for stages in a TEM exist, the side-entry and top entry version. Each design must accommodate the matching holder to allow for specimen insertion without either damaging delicate TEM optics or allowing gas into TEM systems under vacuum. | milkshake721/2.1M-wiki-STEM |
Transmission electron microscopy-Components-The most common is the side entry holder, where the specimen is placed near the tip of a long metal (brass or stainless steel) rod, with the specimen placed flat in a small bore. Along the rod are several polymer vacuum rings to allow for the formation of a vacuum seal of suf... | milkshake721/2.1M-wiki-STEM |
Transmission electron microscopy-Components-Insertion procedures for side-entry TEM holders typically involve the rotation of the sample to trigger micro switches that initiate evacuation of the airlock before the sample is inserted into the TEM column. | milkshake721/2.1M-wiki-STEM |
Transmission electron microscopy-Components-The second design is the top-entry holder consists of a cartridge that is several cm long with a bore drilled down the cartridge axis. The specimen is loaded into the bore, possibly using a small screw ring to hold the sample in place. This cartridge is inserted into an airlo... | milkshake721/2.1M-wiki-STEM |
Transmission electron microscopy-Components-Electron gun The electron gun is formed from several components: the filament, a biasing circuit, a Wehnelt cap, and an extraction anode. By connecting the filament to the negative component power supply, electrons can be "pumped" from the electron gun to the anode plate and ... | milkshake721/2.1M-wiki-STEM |
Transmission electron microscopy-Components-The thermionic emission current density, J, can be related to the work function of the emitting material via Richardson's law exp (−ΦkT), 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 t... | milkshake721/2.1M-wiki-STEM |
Transmission electron microscopy-Components-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 electrom... | milkshake721/2.1M-wiki-STEM |
Transmission electron microscopy-Components-The components include the yoke, the magnetic coil, the poles, the polepiece, and the external control circuitry. The pole piece must be manufactured in a very symmetrical manner, as this provides the boundary conditions for the magnetic field that forms the lens. Imperfectio... | milkshake721/2.1M-wiki-STEM |
Transmission electron microscopy-Components-Apertures Apertures are annular metallic plates, through which electrons that are further than a fixed distance from the optic axis may be excluded. These consist of a small metallic disc that is sufficiently thick to prevent electrons from passing through the disc, whilst pe... | milkshake721/2.1M-wiki-STEM |
Transmission electron microscopy-Imaging methods-Imaging methods in TEM use the information contained in the electron waves exiting from the sample to form an image. The projector lenses allow for the correct positioning of this electron wave distribution onto the viewing system. The observed intensity, I, of the image... | milkshake721/2.1M-wiki-STEM |
Transmission electron microscopy-Imaging methods-I(x)=kt1−t0∫t0t1ΨΨ∗dt Different imaging methods therefore attempt to modify the electron waves exiting the sample in a way that provides information about the sample, or the beam itself. From the previous equation, it can be deduced that the observed image depends not on... | milkshake721/2.1M-wiki-STEM |
Transmission electron microscopy-Imaging methods-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 interac... | milkshake721/2.1M-wiki-STEM |
Transmission electron microscopy-Imaging methods-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 al... | milkshake721/2.1M-wiki-STEM |
Transmission electron microscopy-Imaging methods-In Diffraction mode, a selected area aperture may be used to determine more precisely the specimen area from which the signal will be displayed. By changing the strength of current to the intermediate lens, the diffraction pattern is projected on a screen. Diffraction is... | milkshake721/2.1M-wiki-STEM |
Transmission electron microscopy-Imaging methods-Contrast formation The contrast between two adjacent areas in a TEM image can be defined as the difference in the electron densities in image plane. Due to the scattering of the incident beam by the sample, the amplitude and phase of the electron wave change, which resul... | milkshake721/2.1M-wiki-STEM |
Transmission electron microscopy-Imaging methods-Amplitude–contrast is obtained due to removal of some electrons before the image plane. During their interaction with the specimen some of electrons will be lost due to absorption, or due to scattering at very high angles beyond the physical limitation of microscope or a... | milkshake721/2.1M-wiki-STEM |
Transmission electron microscopy-Imaging methods-Figure on the right shows a TEM image (a) and the corresponding diffraction pattern (b) of Pt polycrystalline film taken without an objective aperture. In order to enhance the contrast in the TEM image the number of scattered beams as visible in the diffraction pattern s... | milkshake721/2.1M-wiki-STEM |
Transmission electron microscopy-Imaging methods-There are two types of amplitude contrast – mass–thickness and diffraction contrast. First, let's consider mass–thickness contrast. When the beam illuminates two neighbouring areas with low mass (or thickness) and high mass (or thickness), the heavier region scatters ele... | milkshake721/2.1M-wiki-STEM |
Transmission electron microscopy-Imaging methods-Diffraction contrast occurs due to a specific crystallographic orientation of a grain. In such a case the crystal is oriented in a way that there is a high probability of diffraction. Diffraction contrast provides information on the orientation of the crystals in a polyc... | milkshake721/2.1M-wiki-STEM |
Transmission electron microscopy-Imaging methods-Diffraction contrast 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 ... | milkshake721/2.1M-wiki-STEM |
Transmission electron microscopy-Imaging methods-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 ... | milkshake721/2.1M-wiki-STEM |
Transmission electron microscopy-Imaging methods-Applications for this method include the identification of lattice defects in crystals. By carefully selecting the orientation of the sample, it is possible not just to determine the position of defects but also to determine the type of defect present. If the sample is o... | milkshake721/2.1M-wiki-STEM |
Transmission electron microscopy-Imaging methods-Phase contrast Crystal structure can also be investigated by high-resolution transmission electron microscopy (HRTEM), also known as phase contrast. When using a field emission source and a specimen of uniform thickness, the images are formed due to differences in phase ... | milkshake721/2.1M-wiki-STEM |
Transmission electron microscopy-Imaging methods-Diffraction As previously stated, by adjusting the magnetic lenses such that the back focal plane of the lens rather than the imaging plane is placed on the imaging apparatus a diffraction pattern can be generated. For thin crystalline samples, this produces an image tha... | milkshake721/2.1M-wiki-STEM |
Transmission electron microscopy-Imaging methods-Diffraction patterns can have a large dynamic range, and for crystalline samples, may have intensities greater than those recordable by CCD. As such, TEMs may still be equipped with film cartridges for the purpose of obtaining these images, as the film is a single use de... | milkshake721/2.1M-wiki-STEM |
Transmission electron microscopy-Imaging methods-Analysis of diffraction patterns beyond point-position can be complex, as the image is sensitive to a number of factors such as specimen thickness and orientation, objective lens defocus, and spherical and chromatic aberration. Although quantitative interpretation of the... | milkshake721/2.1M-wiki-STEM |
Transmission electron microscopy-Imaging methods-Electron energy loss spectroscopy (EELS) Using the advanced technique of electron energy loss spectroscopy (EELS), for TEMs appropriately equipped, electrons can be separated into a spectrum based upon their velocity (which is closely related to their kinetic energy, and... | milkshake721/2.1M-wiki-STEM |
Transmission electron microscopy-Imaging methods-Three-dimensional imaging 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 o... | milkshake721/2.1M-wiki-STEM |
Transmission electron microscopy-Imaging methods-As TEM samples cannot typically be viewed at a full 180° rotation, the observed images typically suffer from a "missing wedge" of data, which when using Fourier-based back projection methods decreases the range of resolvable frequencies in the three-dimensional reconstru... | milkshake721/2.1M-wiki-STEM |
Transmission electron microscopy-Imaging methods-All the above-mentioned methods involve recording tilt series of a given specimen field. This inevitably results in the summation of a high dose of reactive electrons through the sample and the accompanying destruction of fine detail during recording. The technique of lo... | milkshake721/2.1M-wiki-STEM |
Transmission electron microscopy-Imaging methods-Non-tomographic variants on this method, referred to as single particle analysis, use images of multiple (hopefully) identical objects at different orientations to produce the image data required for three-dimensional reconstruction. If the objects do not have significan... | milkshake721/2.1M-wiki-STEM |
Transmission electron microscopy-Sample preparation-Sample preparation in TEM can be a complex procedure. TEM specimens should be less than 100 nanometers thick for a conventional TEM. Unlike neutron or X-ray radiation the electrons in the beam interact readily with the sample, an effect that increases roughly with ato... | milkshake721/2.1M-wiki-STEM |
Transmission electron microscopy-Sample preparation-Materials that have dimensions small enough to be electron transparent, such as powdered substances, small organisms, viruses, or nanotubes, can be quickly prepared by the deposition of a dilute sample containing the specimen onto films on support grids. Biological sp... | milkshake721/2.1M-wiki-STEM |
Transmission electron microscopy-Sample preparation-Tissue sectioning Biological tissue is often embedded in a resin block 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 t... | milkshake721/2.1M-wiki-STEM |
Transmission electron microscopy-Sample preparation-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 osm... | milkshake721/2.1M-wiki-STEM |
Transmission electron microscopy-Sample preparation-Mechanical milling Mechanical polishing is also used to prepare samples for imaging on the TEM. Polishing needs to be done to a high quality, to ensure constant sample thickness across the region of interest. A diamond, or cubic boron nitride polishing compound may be... | milkshake721/2.1M-wiki-STEM |
Transmission electron microscopy-Sample preparation-Chemical etching Certain samples may be prepared by chemical etching, particularly metallic specimens. These samples are thinned using a chemical etchant, such as an acid, to prepare the sample for TEM observation. Devices to control the thinning process may allow the... | milkshake721/2.1M-wiki-STEM |
Transmission electron microscopy-Sample preparation-Ion etching Ion etching is a sputtering process that can remove very fine quantities of material. This is used to perform a finishing polish of specimens polished by other means. Ion etching uses an inert gas passed through an electric field to generate a plasma strea... | milkshake721/2.1M-wiki-STEM |
Transmission electron microscopy-Sample preparation-Ion etching by argon gas has been recently shown to be able to file down MTJ stack structures to a specific layer which has then been atomically resolved. The TEM images taken in plan view rather than cross-section reveal that the MgO layer within MTJs contains a larg... | milkshake721/2.1M-wiki-STEM |
Transmission electron microscopy-Sample preparation-Ion milling (FIB) More recently focused ion beam methods have been used to prepare samples. FIB is a relatively new technique to prepare thin samples for TEM examination from larger specimens. Because FIB can be used to micro-machine samples very precisely, it is poss... | milkshake721/2.1M-wiki-STEM |
Transmission electron microscopy-Sample preparation-Nanowire assisted transfer For a minimal introduction of stress and bending to transmission electron microscopy (TEM) samples (lamellae, thin films, and other mechanically and beam sensitive samples), when transferring inside a focused ion beam (FIB), flexible metalli... | milkshake721/2.1M-wiki-STEM |
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