| free energy | A thermodynamic term used to describe the energy that may be extracted from a system at constant temperature and pressure. In biological systems the most important relationship is: _G = RTln(Keq), where Keq is an equilibrium constant. (18 Nov 1997) |
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| free field | A field (three-dimensional space) in a homogeneous, isotropic medium free from boundaries; in practice, a field in which boundary effects are negligible. (05 Mar 2000) |
| free flap | Island flap in which the donor vessels are severed proximally, the flap is transported as a free object to the recipient area, and the flap is revascularised by anastomosing its supplying vessels to vessels there. (05 Mar 2000) |
| free gingiva | That portion of the gingiva that surrounds the tooth and is not directly attached to the tooth surface; the outer wall of the gingival sulcus. (05 Mar 2000) |
| free graft | A graft transplanted without its normal attachments, or a pedicle, from one site to another. (05 Mar 2000) |
| free induction decay | In magnetic resonance imaging, the decay curve that is detected by the radiofrequency coil after the application of an excitation pulse, without additional pulses (free). (05 Mar 2000) |
| free macrophage | An actively motile macrophage typically found in sites of inflammation. (05 Mar 2000) |
| free mandibular movements | Any mandibular movement's made without tooth interference, any uninhibited movement's of the mandible. (05 Mar 2000) |
| free margin | Unattached edge of a sturcture, often opposite the attached edge. See: free border of nail, free border of ovary. Synonym: margo liber, free margin. (05 Mar 2000) |
| free margin of eyelids | The unattached inferior edge of the upper lid and superior edge of the lower lid, where the anterior (cutaneous) surface of the eyelid meets the posterior (conjunctival) surface of the eyelid. The free margins of the eyelids bound the rima palpebrarum, and each free margin has an anterior and posterior border. See: borders of eyelids. (05 Mar 2000) |
| free nerve endings | A form of peripheral ending of sensory nerve fibres in which the terminal filaments end freely in the tissue. Synonym: terminationes nervorum liberae. (05 Mar 2000) |
| 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) |
| free radicals | Highly reactive molecules with an unsatisfied electron valence pair. Free radicals are produced in both normal and pathological processes. They are proven or suspected agents of tissue damage in a wide variety of circumstances including radiation, damage from environment chemicals, and aging. Natural and pharmacological prevention of free radical damage is being actively investigated. (12 Dec 1998) |