| radioactive | Giving off radiation. (12 Dec 1998) |
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| radioactive atom | <chemistry, physics> An atom with an unstable nucleus, which emits particulate or electromagnetic radiation (radioactive emission) to achieve greater stability. See: radionuclide, half-life, Becquerel. (05 Mar 2000) |
| radioactive constant | <physics, radiobiology> The fraction of the amount of a radionuclide that undergoes transition per unit time. Formally: Lamda=dP/dt Where dP is the probability of a given nucleus undergoing spontaneous nuclear transition in the time interval dt. (16 Dec 1997) |
| radioactive contamination | <radiobiology> Radioactive substance dispersed in material or places where it is undesirable. (16 Dec 1997) |
| radioactive cow | Colloquialism for radionuclide generator. See: cow. (05 Mar 2000) |
| radioactive decay | <physics> The process by which a spontaneous change in nuclear state takes place. This process is accompanied by the emission of energy in various specific combinations of electromagnetic and corpuscular radiation and neutrinos. (16 Dec 1997) |
| radioactive equilibrium | <radiobiology> That condition in which the activities of the members of a radioactive chain decrease exponentially in time with the half-life of the chain precursor. Such radioactive equilibrium is only possible when the half-life of the precursor is longer than that of any other chain member. If the precursor half-life is so long that the change in the precursor population during the period of interest can be ignored, all the activities become sensibly equal and the equilibrium is said to be secular, otherwise it is said to be transient. (16 Dec 1997) |
| 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) |
| 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) |
| air pollutants, radioactive | Pollutants, present in air, which exhibit radioactivity. (12 Dec 1998) |
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| gold colloid, radioactive | <chemical> A radioactive suspension of minute particles of metallic gold, made by exposure to neutrons. It is used in the pleural cavity to treat lung cancer. Pharmacological action: antineoplastic agent, radiopharmaceuticals. (12 Dec 1998) |
| rose bengal radioactive test | A test of liver function used as a means of measuring hepatic blood flow and for scintillation scanning of the liver to determine size and contour of the liver, or the presence of space-occupying masses in the liver. (05 Mar 2000) |
| water pollutants, radioactive | Pollutants, present in water or bodies of water, which exhibit radioactivity. (12 Dec 1998) |
| colloidal radioactive gold | A radioactive isotope of gold emitting negative beta particles and gamma radiation, with a half-life of 2.7 days; formerly used for irradiation of closed serous cavities in the palliative treatment of ascites and pleural effusion due to metastatic malignancies, and for liver scans. Synonym: 198Au colloid, colloidal radioactive gold. (05 Mar 2000) |
| soil pollutants, radioactive | Pollutants, present in soil, which exhibit radioactivity. (12 Dec 1998) |
| elements, radioactive | Chemical elements which spontaneously transmute into another element with corpuscular or electromagnetic radiation. The natural radioactive elements are all those with an atomic number above 83, and some other elements, such as potassium (atomic number 19) and rubidium (atomic number 7), which are very weakly radioactive. (12 Dec 1998) |