| tenth-value layer | <radiobiology> Thickness of a specified substance which, when introduced into the path of a given beam of radiation, reduces the absorbed dose index or dose-equivalent index to one-tenth. The magnitude of the tenth-value layer may be different for absorbed dose index and dose equivalent index. (16 Dec 1997) |
|---|---|
| thiocyanogen value | The number of grams of thiocyanogen taken up by 100 g of fat; analogous to the iodine number, except that thiocyanogen will not add to all the double bonds in polyunsaturated fatty acids as will iodine. Synonym: thiocyanogen value. (05 Mar 2000) |
| threshold limit value | The maximum concentration of a chemical recommended by the American Conference of Government Industrial Hygienists for repeated exposure without adverse health effects on workers. (05 Mar 2000) |
| economic value of life | The evaluation of the monetary value of a life lost or a life saved. (12 Dec 1998) |
| law of initial value | The direction of response of a body function to any agent depends to a large degree on the initial level of that function. Synonym: law of initial value. (05 Mar 2000) |
| lower heating value | (LHV) The potential energy in a fuel if the water vapour from combustion of hydrogen is not condensed. (05 Dec 1998) |
| biological | Pertaining to biology. (18 Nov 1997) |
| biological agent | <microbiology> A disease-causing microorganism or virus, or other toxic biological matter, which is used as a weapon during war. (21 Mar 1998) |
| biological assay | <technique> Once a pharmaceutical protein is isolated from the cells in which it was grown, researchers perform tests to measure the protein's biological activity. It must maintain a certain minimal level of biological activity to be used for animal or clinical testing or, later, for market. Researchers also test to confirm that the isolated protein is identical to the desired protein. (21 Mar 1998) |
| biological assessment | A specific process required as part of an environmental assessment. An evaluation of potential effects of a proposed project on proposed, endangered, threatened, and sensitive animal and plant species and their habitats. (05 Dec 1998) |
| biological availability | The extent to which the active ingredient of a drug dosage form becomes available at the site of drug action or in a biological medium believed to reflect accessibility to a site of action. (12 Dec 1998) |
| biological chemistry | The scientific study of the chemistry of living cells, tissues, organs and organisms. (09 Oct 1997) |
| biological clock | <biology, physiology> An internal biological mechanism which controls certain biological rhythms and biocycles, such as metabolism, sleep cycles, photosynthesis. (21 Mar 1998) |
| biological clocks | The physiological mechanisms that govern the rhythmic occurrence of certain biochemical, physiological, and behavioural phenomena in plants and animals. The pineal gland, which receives input from the optic nerves and connects to the hypothalamus, may be the biological clock in humans. (12 Dec 1998) |
| biological coefficient | Rarely used term denoting the energy expended by the body at rest. (05 Mar 2000) |