| visual extinction | A condition in which individual stimuli are seen correctly, but when the nasal visual field of one eye and the temporal visual field of the fellow eye are stimulated simultaneously, one field is blind. Synonym: visual extinction. (05 Mar 2000) |
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| molar extinction coefficient | Absorbance (of light) per unit path length (usually the centimeter) and per unit of concentration (moles per liter); a fundamental unit in spectrophotometry. Synonym: absorbancy index, absorptivity, molar absorbancy index, molar absorptivity, molar extinction coefficient. (05 Mar 2000) |
| high extinction microscopy | <technique> Polarized-light, interference, fluorescence, and other modes of microscopy using polarization rectifiers and other devices to achieve a high degree of back- ground extinction in order to bring out the signal originating from a very small degree of birefringence, optical path difference, fluorescence etc. (05 Aug 1998) |
| specific extinction | Absorbance (of light) per unit path length (usually the centimeter) and per unit of mass concentration. Compare: molar absorption coefficient. Synonym: absorbancy index, absorptivity, extinction coefficient, specific extinction. (05 Mar 2000) |
| extinction | 1. <ecology> The death of an entire species. 2. <psychology> The procedure of presenting the conditioned stimulus without reinforcement to an organism previously conditioned. It refers also to the diminution of a conditioned response resulting from this procedure. (27 Jun 1999) |
| extinction angle | <microscopy> The angle between the nearer vibration direction and a prominent direction of the crystal. It never exceeds 45 degrees (05 Aug 1998) |
| extinction coefficient | <chemistry> A constant used in the Beer-Lambert Law which relates the concentration of the substance being measured (in moles) to the absorbance of the substance in solution (how well the substance in solution blocks light beamed through it from getting out on the other side). (09 Oct 1997) |
| extinction factor | <microscopy> In a polarizing or Differential Interference Contrast microscope, the ratio of the amount of light that is transmitted with the axes of the polars parallel over the amount transmitted with their axes crossed. Unless the lenses are rectified, the extinction factor drops exponentially as the numerical aperture is increased. Acronym: EF (26 Mar 1998) |
| extinction oblique | <microscopy> Vibration directions oblique to the long direction of the crystal or fibre. (05 Aug 1998) |
| extinction parallel | <microscopy> Vibration directions parallel and perpendicular to the long direction of the crystal or fibre. (05 Aug 1998) |
| extinction symmetrical | <microscopy> Vibration directions bisecting a prominent crystal profile angle. (05 Aug 1998) |
| undulose extinction | <microscopy> Nonuniform extinction of a substance between crossed polars. The areas of complete extinction move progressively with a fanlike motion across the surface of the substance as the stage is rotated. (05 Aug 1998) |
| abscopal effect | A reaction produced following irradiation but occurring outside the zone of actual radiation absorption. (05 Mar 2000) |
| additive effect | <biochemistry, chemistry> An additive effect is the overall biological effect two chemicals acting together and which is the simple sum of the effects of the chemicals acting independently. Compare: antagonism. (15 Jan 1998) |
| adverse effect | This is an abnormal or harmful effect to an organism caused by exposure to a chemical. It is indicated by some result such as death, a change in food or water consumption, altered body and organ weights, altered enzyme levels, or visible illness. An effect may be classed as adverse if it causes functional or anatomical damage, causes irreversible change in the homeostasis of the organism, or increases the susceptibility of the organism to other chemical or biological stress. A non-adverse effect will usually be reversed when the organism is no longer being exposed to the chemical. (09 Oct 1997) |