| E/M | electron microscope, electron microscopy; evaluation and management |
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| ACTA | American Cardiology Technologists Association; automatic computerized transverse axial [scanning] |
| CSLM | confocal scanning microscopy |
| MBPS | multigated blood pool scanning |
| OpScan | optical scanning |
| Scanning Probe Microscopy | <technique> Initially called Atomic Force Microscopy, this technique is now more typically termed Scanning Force Microscopy or Scanning Probe Microscopy. This instrument is essentially an extremely high resolution profilometre. A sharp tip, typically fabricated from silicon nitride, is scanned across the surface of a sample at a constant force by three piezoelectric ceramics. The piezoelectric ceramics are computer controlled via a feedback loop which monitors the position of the tip by means of an optical lever. (A laser is focused on the top of the tip support and the beam reflected into a position sensitive detector). The changes in height of the tip are used to form an image as the tip is scanned across the sample. Acronym: SPM (26 Mar 1998) |
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| scanning speech | Measured or metered, often slow speech. (05 Mar 2000) |
| scanning tunnelling microscopy | <procedure> A form of ultra high resolution microscopy of a surface in which a very small current is passed through a surface and is detected by a microprobe of atomic dimnensions at its tip that scans the surface by use of a piezodrive. In the simplest form the current transferred to the probe is recorded as an indication of the contours of molecules on the surface above the local plane. In more complex forms feedback is used to hold the probe at a constant difference and the signal in the feedback loop indicates the contours of the molecule. Capable of resolving single atoms and known to work for nonconducting molecules as well as conducting ones. (18 Nov 1997) |
| linker scanning | A type of deletion mutagenesis where the distance and/or reading frame between potentially important regions is maintained by replacement with a synthetic oligonucleotide of known sequence. (05 Mar 2000) |
| aperture for electron microscopy | <technique> Anode aperture: The opening in the accelerating voltage anode shield of the electron gun through which the electrons must pass to irradiate the specimen. Condenser aperture: An opening in the condenser lens controlling the number of electrons entering the lens and the angular aperture of the electron beam. The angular aperture can also be controlled by the condenser lens current. Physical objective aperture: A metallic diaphragm, with a small central hole, used to limit the cone of electrons accepted by the objective lens. This improves image-contrast since highly scattered electrons are prevented from arriving at the Gaussian image plane and therefore cannot contribute to background fog. Aplanatic. Free from spherical aberration and coma. (05 Aug 1998) |
| Auger electron | An electron ejected from a lower energy orbital after a photoelectric interaction of an X-ray photon with a K-shell electron by the characteristic radiation photon; the Auger electron recoils with energy equal to the characteristic radiation less the difference in shell binding energies. See: photoelectric effect. (05 Mar 2000) |
| backscattered electron | <microscopy> Produced by an incident electron colliding with the nucleus of an atom in the specimen. The incident electron is then scattered backward about 180 degrees with no appreciable loss of energy, an elastic collision. (05 Aug 1998) |
| backscattered electron imaging | <microscopy> The production of backscattered electrons from a sample varies directly with the specimen's average atomic number, higher atomic number elements produce more backscattered electrons than lower atomic number ones. Detection of Backscattered Electrons is achieved by using a donut shaped solid state saemiconductor device mounted on the bottom of the objective lens. When Backscattered Electrons strike the detector electron-hole pairs are created which are then counted. This quantity is translated into a pixel intensity and displayed on the CRT, forming the image. By splitting the detector into halves (or quadrants) differences in the signal level on the individual detector segments provide surface topography information. (05 Aug 1998) |
| valence electron | One of the electron's that take part in chemical reactions of an atom. (05 Mar 2000) |
| Parallel Electron Energy Loss Spectroscopy | <technique> Electron energy loss spectroscopy analyses the inelastically scattered electrons present in the beam after it has been transmitted through the sample. An electron energy loss spectrum typically consists of a monatomic decreasing background on which are superimposed a number of peaks. Each peak is characteristic of the scattering process that has occurred in the sample. The peaks can be used to obtain information about the chemical composition and electronic structure of the sample. Electron energy loss spectra are acquired typically in a magnetic sector spectrometer located under the camera chamber of the transmission electron microscope. Spatial resolution is typically limited by the minimum probe diameter of the microscope. Electron energy loss spectroscopy tends to be complimentary to EDS in that it can be used to analyse very thin samples of low Z materials. Acronym: PEELS (05 Aug 1998) |
| reverse electron transport | <chemistry> The energy-dependent movement of electrons against the thermodynamic gradient to form a strong reductant from a weaker electron donor. (11 Jan 1998) |
| microscope, electron | <microscopy> An electron-optical device which produces a magnified image of an object. Detail may be revealed by virtue of selective transmission, reflection, or emission of electrons by the object. (05 Aug 1998) |
| microscopy, electron | Visual and photographic microscopy in which electron beams with wavelengths thousands of times shorter than visible light are used in place of light, thereby allowing much greater magnification. (12 Dec 1998) |
| Conventional Transmission Electron Microscopy | <technique> A term applied to 'normal' transmission electron microscopy imaging. The electron beam is passed through a thin film sample (typically ~1-200 nm thick). Bright field diffraction contrast images are formed with the direct (undiffracted) beam. Dark field images are formed with a selected diffracted beam. CTEM imaging is used in the general observation of samples and careful selection of the diffracting conditions of the sample will allow the analysis of defect structures within the sample. (05 Aug 1998) |
| Convergent Beam Electron Diffraction | <microscopy> An electron probe is tightly focused on a transmission electron microscopy specimen and the resulting pattern of diffracted electrons is observed. The patterns contains information on the crystal symmetry and atomic and electronic structure of the sample. Regions as small as 0.2 nm may be examined. Acronym: CBED (05 Aug 1998) |