| biological half-life | <biochemistry, biology> This is the time required for one-half of the total amount of a particular substance in a biological system to be consumed or broken down by biological processes when the rate of removal is approximately exponential. Toxic chemicals with a long biological half-life (such as some pesticides) will tend to accumulate in the body and are, therefore, more likely to be harmful. A substance with a short biological half-life may still accumulate if a portion of it it becomes tightly bound to bone or other tissues, even if most of it is quickly cleared from the body. (21 Mar 1998) |
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| vegetative life | The simple metabolic and reproductive activity of humans or animals, apart from the exercise of conscious mental or psychic processes. (05 Mar 2000) |
| germ-free life | Animals not contaminated by or associated with any foreign organisms. (12 Dec 1998) |
| change of life | Colloquialism for menopause, climacteric. (05 Mar 2000) |
| RNA life | <biology, molecular biology> A hypothetical life form lacking DNA and protein which may have existed on early earth and in which RNA served both a genetic coding and a catalytic function. (23 Aug 1998) |
| physical half-life | The time required for half the atoms of a radionuclide to undergo disintegration. (05 Mar 2000) |
| wrongful life | In civil law a cause of action which alleges that a defendant has wrongfully caused a child to be born. (12 Dec 1998) |
| postnatal life | That interval of life after birth; in man, usually divided into periods: neonatal, infancy, childhood, adolescence, and adulthood. (05 Mar 2000) |
| half-life | 1. <pharmacology> The period over which the concentration of a specified chemical or drug takes to fall to half its original concentration in the specified fluid or blood. 2. <radiobiology> The time required to reduce the amount of a radionuclide to one-half the amount originally present. Physical or radioactive half-life refers to reduction of activity by radioactive decay, biological half-life refers to biological elimination from the body and effective half-life refers to the combined action of radioactive decay and biological elimination. (16 Dec 1997) |
| prenatal life | That interval of life between conception and birth; in humans, usually divided into embryonic and foetal periods. (05 Mar 2000) |
| sexual life | In psychiatry and psychoanalysis, the specifically erotic or sexual interests, fantasies, inclinations, and conduct of the patient. (05 Mar 2000) |
| direct life cycle | <epidemiology> A life cycle in which a parasite is transmitted directly from one host to the next without an intermediate host or vector of another species. (05 Dec 1998) |
| drug half-life | The amount of time it takes for one-half of an administered drug to be lost through biological processes (metabolism and elimination). (27 Sep 1997) |
| immediately dangerous to life concentration | <radiobiology> This is a regulatory value defined as the maximum exposure concentration in the workplace from which one could escape within 30 minutes without suffering symptoms which would interfere with escaping and without suffering any irreversible health effects. (04 Nov 1997) |
| indirect life cycle | <epidemiology> A life cycle which requires one or more intermediate hosts before the definitive host species is reinfected. Compare direct, nondirect. (05 Dec 1998) |