| radioactive fallout | The material that descends to the earth or water well beyond the site of a surface or subsurface nuclear explosion. (12 Dec 1998) |
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| radioactive iodide uptake test | A test of thyroid function in which 131I-iodide is given orally; after 24 hours, the amount present in the thyroid gland is measured and compared with normal values. Synonym: radioactive iodide uptake test, RAI test. (05 Mar 2000) |
| radioactive iodine | Iodine that gives off radiation. See radioiodine. (12 Dec 1998) |
| radioactive isotope | <physics, radiobiology> An isotope of an element that has an unstable nucleus, it tries to stabilise itself by giving off ionising radiation. (09 Oct 1997) |
| radioactive pollutants | Radioactive substances which act as pollutants. They include chemicals whose radiation is released via radioactive waste, nuclear accidents, fallout from nuclear explosions, and the like. (12 Dec 1998) |
| radioactive probe | A nucleic acid fragment, labelled by a radioisotope, biotin, etc., that is complementary to a sequence in another nucleic acid (fragment) and that will, by hydrogen binding to the latter, locate or identify it and be detected; a diagnostic technique based on the fact that every species of microbe possesses some unique nucleic acid sequences which differentiate it from all others, and thus can be used as identifying markers or "fingerprints." (05 Mar 2000) |
| radioactive thyroxine | Thyroxine in which a radioisotope of iodine (125I or 131I) is incorporated into its molecule; used in experiments tracing the metabolism of thyroxine. Synonym: labelled thyroxine, radiolabelled thyroxine, radiothyroxin. (05 Mar 2000) |
| radioactive tracer | <physics, radiobiology> A radioisotope is an element which has the same atomic number as another but a different atomic weight, exhibiting the property of spontaneous decomposition. Decomposition gives off radiation (gamma rays) that can be detected with a counter. If a radioisotope is attached to a biological compound and injected into the body, its path may be traced through the body (resulting in an image). (27 Sep 1997) |
| radioactive tracers | Radioactive substances added in minute amounts to the reacting elements or compounds in a chemical process and traced through the process by appropriate detection methods, e.g., geiger counter. Compounds containing tracers are often said to be tagged or labelled. (12 Dec 1998) |
| radioactive waste | <radiobiology> Equipment and materials from nuclear operations which are radioactive and for which there is no further anticipated use. Wastes are generally classified as high-level (having radioactivity concentrations of hundreds to thousands of curies per gallon or cubic foot), low-level (in the range of 1 microcurie per gallon or cubic foot), or intermediate (between high and low). See: curie. (09 Oct 1997) |
| radioactivity | <radiobiology> The quality of emitting or the emission of corpuscular or electromagnetic radiations consequent to nuclear disintegration, a natural property of all chemical elements of atomic number above 83 and possible of induction in all other known elements. (18 Nov 1997) |
| radioallergosorbent test | An allergy test done on a sample of blood. The aim with rast, as with skin tests, is to check for allergic sensitivity to specific substances. Rast stands for radioallergosorbent test. (12 Dec 1998) |
| radioautogram | Older term for autoradiograph. (05 Mar 2000) |
| radioautography | <technique> A specimen containing radioactive atoms is overlaid with a photographic emulsion (X-ray film), which is subsequently developed, revealing the localisation of radioactivity as a pattern of silver grains. Resolution is determined by the path length of the radiation and so the low energy beta emitting isotope, tritium, is usually used. The technique can be used to visualise radioactively labelled molecules or fragments of molecules, used in analyzing length and number of DNA fragments after they are separated by gel electrophoresis. (12 Mar 1998) |
| radiobicipital | Relating to the radius and the biceps muscle. (05 Mar 2000) |