| k | <physics> Mathematical symbol usually used for Boltzmann's Constant. Value is 1.4 x 10^-23 Joules/Kelvin (in SI units), or 1.4 x 10^-16 ergs/Kelvin (in cgs units). (09 Oct 1997) |
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| K antigen | Capsular antigens of bacteria usually polysaccharide. (18 Nov 1997) |
| K antigens | <haematology, immunology> Blood type classification based on a group of erythrocyte antigens that is characterised by an antibody called anti-K. Multiple erythrocytic antigens that comprise at least three pairs of alternates and amorphs, determined by one complex gene or possibly several genes at closely linked loci. The system is important in transfusion reactions. Its expression involves the X chromosome. (21 Jun 2000) |
| K blood group | K blood group See Kell blood group, Blood Groups appendix. (05 Mar 2000) |
| K capture | <radiobiology> Nuclear decay process whereby a proton in the nucleus absorbs an orbiting electron and converts to a neutron. (09 Oct 1997) |
| K cell | 1. <immunology> Mammalian cells which can lyse antibody coated target cells. They have a receptor for the Fc portion of IgG and are probably of the mononuclear phagocyte lineage, though some may be lymphocytes. Not to be confused with cytotoxic T-cells which recognise targets by other means and are clearly a sub set of T lymphocytes. This confusion exists in the early literature. 2. Natural killer cell are CD3 negative large granular lymphocytes, mediating cytolytic reactions that do not require expression of Class I or II major histocompatibility antigens on the target cell. 3. Lymphokine activated killer cells are NK cells activated by interleukin-2 (LAK cells). (13 Nov 1997) |
| K cells | Lymphocyte-like effector cells which mediate antibody-dependent cell cytotoxicity. They kill antibody-coated target cells which they bind with their fc receptors. (12 Dec 1998) |
| K complex | High amplitude, diphasic frontocental slow waves in the electroencephalogram related to arousal from sleep by a sound; characteristic of sleep stages 2, 3, and 4. (05 Mar 2000) |
| K luyvera | Newly named genus of Enterobacteriaceae. (05 Mar 2000) |
| K region | Carbons 9 and 10 of the phenanthrene ring system; thought by some to be the reactive spot in the various hydrocarbon carcinogens. (05 Mar 2000) |
| k selection | <zoology> In evolution, the selection of traits that aid an organisms competitive capability when the population is at or near its carrying capacity. (21 Mar 1998) |
| K shell | The innermost electron orbit or shell; it can hold two electrons. (05 Mar 2000) |
| K virus | A polyomavirus, family Papovaviridae, that causes pneumonia in young mice by various routes of inoculation. (05 Mar 2000) |
| K+-translocating Kdp-ATPase | <enzyme> An inducible high affinity k+ transporter in E coli Registry number: EC 3.6.1.- Synonym: potassium kdp atpase, kdp-atpase, kdpb protein (26 Jun 1999) |
| K-radiation | Usually a very penetrating form of x-radiation excited by cathode rays (high speed electrons) impinging upon a metal anode such as tungsten; the energy of the radiation is a function of the binding energy of the K-shell electrons of the metal anode. (05 Mar 2000) |