| FR | failure rate; film-screen radiograph; fasciculus retroflexus; febrile reaction; feedback regulation;... |
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| FRAT | free radical assay technique |
| ORS | olfactory reference syndrome; oral rehydration solution; oral surgery, oral surgeon; Orthopaedic Res... |
| RAD | radial artery catheter; radiation absorbed dose; radical; radiography or radiographic; reactive airw... |
| rad | radiation absorbed dose; radial; radian; radical; radius; root [Lat. radix] |
| colour radical | The part of a visibly coloured molecule responsible for light absorption over a range of wavelengths thus giving rise to the colour. By extension the term may be applied to UV or IR absorbing parts of molecules. Do not confuse with chromatophores. (18 Nov 1997) |
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| hydroxyl radical | <chemical> Hydroxyl. The univalent radical oh. This radical is characteristic of hydroxides, oxygen acids, alcohols, glycols, phenols, and hemiacetals. Chemical name: Hydroxyl (12 Dec 1998) |
| oxygen radical | <chemistry> Any oxygen species that carries an unpaired electron (except free oxygen). Examples are the hydroxyl radical and the superoxide anion. These radicals are very powerful oxidizing agents and cause structural damage to proteins and nucleic acids. They mediate the damaging effects of ionising radiation. (18 Nov 1997) |
| free radical | A chemically active atom or molecular fragment containing a chemical charge due to an excess or deficient number of electrons. Radicals seek to receive or release electrons in order to achieve a more stable configuration, a process that can damage the large molecules within cells. See: Oxidation. (09 Oct 1997) |
| free radical reductase | <enzyme> Catalyses conversion of carbon-centreed lipid radicals into an inactive species by utilizing vitamin e at one end and glutathione at the other Registry number: EC 1.8.4.- (26 Jun 1999) |
| free radical scavengers | Substances that influence the course of a chemical reaction by ready combination with free radicals. Among other effects, this combining activity protects pancreatic islets against damage by cytokines and prevents myocardial and pulmonary perfusion injuries. (12 Dec 1998) |