| Bertrand lens | <physics> A small, low-power lens, usually on a slide for insertion into the drawtube between analyser and ocular. It is used to observe the back focal plane of the objective so as to examine interference figures or as an aid in achieving interference figures. It is apt to be strongly astigmatic. It is used to image the lamp filament in setting up Kohler illumination as well as for centreing dispersion staining stops to the substage aperture diaphragm. (05 Aug 1998) |
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| Bertrand, Ivan Georges | <person> 20th century French neurologist. See: Canavan-van Bogaert-Bertrand disease. (05 Mar 2000) |
| Canavan-van Bogaert-Bertrand disease | Autosomal recessive degenerative disease of infancy; mostly in Jewish infants; onset typically within first 3-4 months of birth, consisting of blindness, psychomotor regression, enlarged head, optic atrophy, hypotonia, spasticity, increased N-acetylaspartic acid urinary excretion. MRI shows enlarged brain, decreased attenuation of cerebral and cerebellar white matter, and normal ventricles. Pathologically, there is increased brain volume and weight, and spongy degeneration in the subcortical white matter. See: leukodystrophy. Synonym: Canavan's sclerosis, Canavan-van Bogaert-Bertrand disease, spongy degeneration of infancy. (05 Mar 2000) |
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| lens, Bertrand | <microscopy> A small convergent lens placed between objectives and eyepiece. The lens focuses an image of the upper focal plane of the objective on the focal plane of the eyepiece. It is chiefly used with polarized light for inspecting the interference figure. It is also convenient for quickly verifying centreing, size, and uniform illumination of an aperture. (05 Aug 1998) |
| Bertrand | English philosopher and mathematician who collaborated with Whitehead (1872-1970) |
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| Bertrand | English philosopher and mathematician who collaborated with Whitehead (1872-1970) |
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