| tubular vision | A constriction of the visual field, as though one were looking through a hollow cylinder or tube. Synonym: tunnel vision. (05 Mar 2000) |
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| tunnel vision | A constriction of the visual field, as though one were looking through a hollow cylinder or tube. Synonym: tunnel vision. (05 Mar 2000) |
| twilight vision | Vision when the eye is dark-adapted. See: dark adaptation, dark-adapted eye. Synonym: night vision, rod vision, scotopia, twilight vision. (05 Mar 2000) |
| facial vision | <physiology> Sensing the proximity of objects by the nerves of the face, presumed in the case of the blind and also in sighted persons who are blindfolded or in darkness. (05 Mar 2000) |
| yellow vision | <ophthalmology> A form of chromatopsia in which objects looked at appear yellow. Origin: Gr. Opsis = vision (11 May 1997) |
| line of vision | The straight line extending from the object seen, through the centre of the pupil, to the macula lutea of the retina. Synonym: line of vision. (05 Mar 2000) |
| Abbe theory of image formation | <optics, physics> Abbe's theory is based on the fact that a non-self-luminous particle, which is illuminated by an extraneous source, gives rise to diffracted light rays, in addition to the dioptric pencil. He stated that to form a good microscopical image as many of the diffracted rays as possible should be intercepted by the objective. With closely ruled lines, his theory is easily demonstrated by observing the back lens of the objective, for here the diffracted rays can be observed directly if the aperture diaphragm is closed. It can be shown that, when the illumination is arranged to exclude the diffracted images, resolution is lost. (11 Mar 1998) |
| adsorption theory of narcosis | That a drug becomes concentrated at the surface of the cell as a result of adsorption, and thus alters permeability and metabolism. (05 Mar 2000) |
| Altmann's theory | A theory that protoplasm consists of granular particles (called bioblasts) that are clustered and enclosed in indifferent matter. (05 Mar 2000) |
| Arrhenius-Madsen theory | That the reaction of an antigen with its antibody is a reversible reaction, the equilibrium being determined according to the law of mass action by the concentrations of the reacting substances. (05 Mar 2000) |
| atomic theory | That chemical compounds are formed by the union of atoms in certain definite proportions; in its modern form, first advanced in 1803 by John Dalton. (05 Mar 2000) |
| Baeyer's theory | That carbon bonds are set at fixed angles (109 |
| balance theory | In social psychology, a theory which assumes that steady and unsteady states can be specified for cognitive units, such as an individual and his or her attitudes or acts, and that such units tend to seek steady states (balance); e.g., balance exists when both parts of a unit are evaluated the same, but disequilibrium arises when both parts are not evaluated the same, which causes either cognitive reevaluation of the parts or their segregation. See: cognitive dissonance theory, consistency principle. (05 Mar 2000) |
| beta-oxidation-condensation theory | <biochemistry> That the two carbon fragments split from the fatty acid molecule by beta-oxidation are converted to acetic acid and then condensed to acetoacetic acid. (05 Mar 2000) |
| Bohr's theory | That spectrum lines are produced 1) by the quantised emission of radiant energy when electrons drop from an orbit of a higher to one of a lower energy level, or 2) by absorption of radiation when an electron rises from a lower to a higher energy level. (05 Mar 2000) |