| adaptive radiation | <chemistry> The evolution of new speciesor sub-species to fill unoccupied ecological niches. (06 May 1997) |
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| adaptive behaviour | Any behaviour that enables an organism to adjust to a particular situation or environment. (05 Mar 2000) |
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| adaptive behaviour scales | A behavioural assessment device to quantify the levels of skills of mentally retarded and developmentally delayed individuals in interacting with the environment; consists of three developmentally related factors: 1) personal self-sufficiency, e.g., eating, dressing; 2) community self-sufficiency, e.g., shopping, communicating; 3) personal and social responsibility, e.g., use of leisure time, job performance. See: intelligence. (05 Mar 2000) |
| adaptive enzyme | Inducible enzyme, an enzyme that can be detected in a growing culture of a microorganism, after the addition of a particular substance (inducer) to the culture medium, but was not detectable prior to the addition and can act on the inducer. A prototype is the beta-galactosidase of Escherichia coli, synthesised upon the addition of various galactosides, whether or not these are good substrates. Compare: constitutive enzyme. Synonym: adaptive enzyme. (05 Mar 2000) |
| adaptive hypertrophy | Thickening of the walls of a hollow organ, like the urinary bladder, when there is obstruction to outflow. (05 Mar 2000) |
| adaptive management | A continuing process of action-based planning, monitoring, researching, evaluating, and adjusting with the objective of improving implementation and achieving the goals of the selected alternative. (05 Dec 1998) |
| adaptive management area | Landscape units designated for development and testing of technical and social approaches to achieving desired ecological, economic, and other social objectives. (05 Dec 1998) |
| abnormalities, radiation-induced | Congenital changes in the morphology of organs produced by exposure to ionizing or non-ionizing radiation. (12 Dec 1998) |
| accidents, radiation | Accidental dispersal of radioactive materials from a radiation source. Accidents at nuclear reactors can involve large groups of the population from dispersion of radioactivity into the environment and through fallout or a few individuals with high injurious doses. (12 Dec 1998) |
| acoustic radiation | The fibres that pass from the medial geniculate body to the transverse temporal gyri of the cerebral cortex by way of the sublentiform part of the internal capsule. Synonym: radiatio acustica. (05 Mar 2000) |
| acute radiation syndrome | <syndrome> A syndrome caused by exposure of the body to large amounts of radiation, (e.g., from certain forms of therapy, accidents, and nuclear explosions; it is divided into three major forms which are, in ascending order of severity, the haematogic, gastrointestinal, and central nervous system-cardiovascular forms; its clinical manifestations are divided into prodromal, latent, overt, and recovery stages. (05 Mar 2000) |
| alpha radiation | <physics, radiobiology> The most easily absorbable type of radiation, it consists of a stream of alpha particles, doubly ionised helium nuclei which are electrically charged and produce intense ionisation in matter. Alpha radiation can be deflected in electromagnetic fields. (09 Oct 1997) |
| annihilation radiation | The radiation resulting when a positron from beta positive decay comes to rest. It encounters an electron, and they annihilate each other and convert their rest mass into two 0.51-MeV gamma rays emitted in exactly opposite directions. (05 Mar 2000) |
| background radiation | <radiobiology> Level of environmental radation due to background sources. Background sources can be natural, such as cosmic rays and natural radioactive elements (principally radon, but including other elements such as isotopes of potassium (which people get substantial amounts of in foods like bananas)). They can also be man-made, such as from fossil-fuel combustion, everyday leakage from nuclear activities, and leftover from atmospheric nuclear weapons tests. Background radiation is usually distinguished from acute radiation, such as from medical X-rays, nuclear accidents, radioisotope therapy, or other short-term doses. The man-made contribution to background radiation is quite small compared to the natural contribution, medical uses dominate human exposure to acute radiation. (09 Oct 1997) |
| beta radiation | <radiobiology> Radiant energy from a source of beta rays. (05 Mar 2000) |
| radiation | <radiobiology> Propagation of energy through space. In the context of this report, it is electromagnetic radiation (X-rays or gamma rays) or corpuscular radiation (alpha particles, electrons, protons, neutrons) capable of producing ionisation. (16 Dec 1997) |