| 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 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) |
| high extinction microscopy | <technique> Polarized-light, interference, fluorescence, and other modes of microscopy using polarization rectifiers and other devices to achieve a high degree of back- ground extinction in order to bring out the signal originating from a very small degree of birefringence, optical path difference, fluorescence etc. (05 Aug 1998) |
| holographic microscopy | <technique> A mode of light microscopy in which a highly coherent, laser beam is split into a reference and main beam, with the reference beam (usually travelling outside of the microscope) being made to interfere with the main beam that has passed through the specimen. The interference of the two mutually coherent beams forms a hologram. The depth of field gained by viewing the hologram is essentially infinitely great, and the contrast mode or observation can be switched to dark field, phase contrast, interference contrast, etc., after the hologram has been formed by the microscope in bright field. (05 Aug 1998) |
| nanovid microscopy | <procedure> Technique of bright field light microscopy using electronic contrast enhancement and maximum numerical aperture. (18 Nov 1997) |
| dark field microscopy | <procedure> A system of microscopy in which particles are illuminated at a very low angle from the side so that the background appears dark and the objects are seen by diffracted and reflected patches of light against a dark background. (18 Nov 1997) |
| immunoelectron microscopy | <technique> A technique for using an electron microscope to locate specific antigensin cells or tissue. (09 Oct 1997) |
| interference microscopy | <procedure> Although all image formation depends on interference, the term is generally restricted to systems in which contrast comes from the recombination of a reference beam with light that has been retarded by passing through the object. Because the phase retardation is a consequence of the difference in refractive index between specimen and medium and because the the refractive increment is almost the same for all biological molecules, it is possible to measure the amount of dry mass per unit area of the specimen by measuring the phase retardation. Quantification of the phase retardation is usually done by using a compensator to reduce the bright object to darkness (see Senarmont and Ehrlinghaus compensators). Two major optical systems have been used the Jamin Lebedeff system and the Mach Zehnder system. These instruments are often referred to as interferometers, since they are designed for measuring phase retardation. Although their use has passed out of fashion, it may be that they will be employed more frequently in future in conjunction with image analysing systems. (18 Nov 1997) |
| interference reflection microscopy | <procedure> An optical technique for detecting the topography of the side of a cell in contact with a planar substrate and for providing information on the separation of the plasmalemma from the substrate. Interference between the reflections from the substrate medium interface and the reflections from the plasmalemma medium interface generate the image. (18 Nov 1997) |
| time-lapse microscopy | Microscopy in which the same object (e.g., a cell) is photographed at regular time intervals over several hours. (05 Mar 2000) |
| fluorescence microscopy | <procedure> Any type of microscopy in which intrinsic or applied reagents are visualised. Intrinsic fluorescence is often referred to as auto fluorescence. The applied reagents typically include fluorescently labelled proteins that are reactive with sites in the specimen. In particular, fluorescently labelled antibodies are widely used to detect particular antigens in biological specimens. (18 Nov 1997) |
| light microscopy | <procedure> In contrast to electron microscopy. See: bright field, phase contrast, interference, interference contrast, interference reflection, dark field, confocal and fluorescence microscopy. (18 Nov 1997) |
| airbrasive technique | A method of grinding, cutting tooth structure, or roughening the natural tooth surface or the surface of a restoration, by means of a device utilizing a gas-impelled jet of fine Al203 particles which, after striking the tooth, are removed by an aspirator. See: microetching technique. (05 Mar 2000) |
| air-gap technique | Chest radiography performed using a space between the subject and film instead of a grid to absorb scattered radiation; usually requires a target-film distance of 10 feet. (05 Mar 2000) |
| aseptic technique | <procedure> A method used by microbiologists and clinicians to keep cultures, sterile instruments and media, and people free of microbial contamination. (09 Oct 1997) |