| AD | accident dispensary; acetate dialysis; active disease; acute dermatomyositis; addict, addiction; ade... |
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| ADC | adult day care [facility]; affective disorders clinic; Aid to [Families with] Dependent Children; AI... |
| ADT | Accepted Dental Therapeutics; adenosine triphosphate; admission, discharge, transfer; agar-gel diffu... |
| AGDD | agar gel double diffusion |
| CDC | calculated date of confinement; cancer diagnosis center; capillary diffusion capacity; cell division... |
| gel diffusion | Diffusion in a gel, as in the case of gel diffusion precipitin tests in which the immune reactants diffuse in agar. See: immunodiffusion. (05 Mar 2000) |
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| gel diffusion precipitin tests | Precipitin test's in which the immune precipitate forms in a gel medium (usually agar) into which one or both reactants have diffused; generally classified in two types, in one dimension, and in two dimensions. Synonym: gel diffusion reactions. (05 Mar 2000) |
| gel diffusion precipitin tests in one dimension | Precipitin test's in which antigen solution and antibody incorporated in agar are layered in tubes, permitting effective diffusion in the vertical dimension; the antibody-containing agar may be overlaid directly with antigen solution (single (gel) diffusion in one dimension). (05 Mar 2000) |
| gel diffusion precipitin tests in two dimensions | Precipitin test's made in a layer of agar that permits radial diffusion, in both of the horizontal dimensions, of one or both reactants. Double (gel) diffusion in two dimensions (Ouchterlony test, technique, or method) incorporates antigen and antibody solutions placed in separate wells in a sheet of plain agar, permitting radial diffusion of both reactants; this method is widely used to determine antigenic relationships; the bands of precipitate that form where the reactants meet in optimal concentration are of three patterns, referred to as reaction of identity, reaction of partial identity (cross-reaction), and reaction of nonidentity. (05 Mar 2000) |
| gel diffusion reactions | Precipitin test's in which the immune precipitate forms in a gel medium (usually agar) into which one or both reactants have diffused; generally classified in two types, in one dimension, and in two dimensions. Synonym: gel diffusion reactions. (05 Mar 2000) |
| passive diffusion | See: facilitated transport. (05 Mar 2000) |
| classical diffusion | <radiobiology> In plasma physics, diffusion due solely to scattering (collisions) of charged particles (with unlike charges) via electrical (Coulomb) interactions. (See also diffusion.) (09 Oct 1997) |
| population diffusion coefficient | <cell biology> Coefficient that describes the tendency of a population of motile cells to diffuse through the environment. Its use presupposes that the cells move in a random walk. (18 Nov 1997) |
| neoclassical diffusion | <radiobiology> In a magnetised plasma, _classical_ diffusion refers to transport of particles due to Coulomb collisions, taking the spiral orbits in the magnetic field into account. In a toroidal magnetic field, the actual rate of diffusive transport is much higher due to slow changes in the positions of the centres of the spirals, known as banana orbits. This faster transport is called _neo-classical_. With very few exceptions the transport in toroidal devices is observed to be 10-100 times larger still, presumably due to small-scale turbulence. The observed transport is called _anomalous_ (although it actually is the normal state). (09 Oct 1997) |
| diffusion | The process of becoming diffused or widely spread, the spontaneous movement of molecules or other particles in solution, owing to their random thermal motion, to reach a uniform concentration throughout the solvent, a process requiring no addition of energy to the system. (18 Nov 1997) |
| diffusion anoxia | Diffusion hypoxia severe enough to result in the absence of oxygen in alveolar gas. (05 Mar 2000) |
| diffusion chambers, culture | Devices used in a technique by which cells or tissues are grown in vitro or, by implantation, in vivo within chambers permeable to diffusion of solutes across the chamber walls. The chambers are used for studies of drug effects, osmotic responses, cytogenic and immunologic phenomena, metabolism, etc., and include tissue cages. (12 Dec 1998) |
| diffusion coefficient | For the translational diffusion of solutes, diffusion is described by Fick's First Law, that states that the amount of a substance crossing a given area is proportional to the spatial gradient of concentration and the diffusion constant (D), that is related to molecular size and shape. A useful derived relationship is that the mean square distance moved by molecules in time t is 6Dt. (18 Nov 1997) |
| diffusion constant | For the translational diffusion of solutes, diffusion is described by Fick's First Law, that states that the amount of a substance crossing a given area is proportional to the spatial gradient of concentration and the diffusion constant (D), that is related to molecular size and shape. A useful derived relationship is that the mean square distance moved by molecules in time t is 6Dt. (18 Nov 1997) |
| diffusion hypoxia | Abrupt transient decrease in alveolar oxygen tension when room air is inhaled at the conclusion of a nitrous oxide anaesthesia, because nitrous oxide diffusing out of the blood dilutes the alveolar oxygen. (05 Mar 2000) |