Zeune's law 맹인의 수는 적도에 가까운 열대지방에서 증가한다.
zidovudin
| Abbe test plate | <equipment> A long, wedge-shaped coverslip about 0.20 mm thick at one end and 0.10 to 0.12 mm at the other end coated chemically with a silver film on which are ruled horizontal lines. at each variation in thickness of 0.01 mm there are vertical lines. By means of oblique illumination and by focusing on different portions of the plate, it is possible to determine the optimum coverslip thickness for any objective and also, for microscopes with drawtubes, the tube length for best objective performance. The approximate freedom from spherical and chromatic aberrations can also be estimated. Small isolated bits of silver near the edges of the lines form good objects for the star test (05 Aug 1998) |
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| 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) |
| anterior limiting layer of cornea | A transparent homogeneous acellular layer, 6 to 9 um thick, lying between the basal lamina of the outer layer of stratified epithelium and the substantia propria of the cornea; considered to be a basement membrane. Synonym: lamina limitans anterior corneae, anterior elastic layer, Bowman's membrane, lamina elastica anterior, limiting layers of cornea. (05 Mar 2000) |
| anterior limiting ring | The periphery of the cornea marking the termination of Descemet's membrane and the anterior border of the trabecular meshwork; an important landmark in gonioscopy. Synonym: Schwalbe's ring. (05 Mar 2000) |
| rate-limiting step | <biochemistry> The slowest step in a metabolic pathway, or the step in an enzymatic reaction that requires the greatest amount of energy to initiate. (17 Dec 1997) |
| glial limiting membrane | A dense, resilient membrane forming the true capsule of the brain and spinal cord, composed of the processes of astrocytes (macroglia cells) and covered throughout by the pia mater, which firmly adheres to it; the two membranes are collectively called the pial-glial membrane. Synonym: membrana limitans gliae. (05 Mar 2000) |
| condenser, Abbe | <microscopy> Originally a two-lens substage condenser combination designed by Ernst Abbe. It lacks chromatic correction though designed for a minimum of spherical aberration and has only a very low-angle aplanatic cone. It may be rated with a numerical aperture as high as 1.3. (05 Aug 1998) |
| posterior limiting layer of cornea | A transparent homogeneous acellular layer between the substantia propria and the endothelial layer of the cornea; considered to be a highly developed basement membrane. Synonym: lamina limitans posterior corneae, membrana vitrea, Descemet's membrane, Duddell's membrane, entocornea, hyaloid membrane, lamina elastica posterior, limiting layers of cornea, membrana hyaloidea, posterior elastic layer, tunica vitrea, vitreous membrane. (05 Mar 2000) |
| internal limiting membrane | Formed by the expanded inner ends of Muller's fibres, outer limiting membrane, not a membrane but a row of junctional complexes. Synonym: membrana limitans. (05 Mar 2000) |
| Ernst Abbe | <person> German mathematician and physicist, professor at Jena, and inventor of much optical apparatus at the Zeiss works. His inventions include the apochromatic objective, the compensating ocular, the Abbe condenser, a well corrected oil-immersion achromatic condenser, the immersion objective, Abbe apertometre, Abbe refractometre, and the drawing camera, he evolved the Abbe theory of resolution and microscope imagery, the numerical aperture formula, and other optical theories. Lived: 1840-1905. (05 Aug 1998) |
| limiting angle | The angle of incidence at which a ray of light, in passing between two media, changes from refraction to total reflection. Synonym: limiting angle. (05 Mar 2000) |
| limiting factor | Environmental factor that limits the growth or activities of an organism or that restricts the size of a population or its geographical range. (09 Oct 1997) |
| limiting layers of cornea | anterior limiting layer of cornea, posterior limiting layer of cornea |
| limiting membrane of retina | One of two layers of the retina: (05 Mar 2000) |
| limiting sulcus | The medial longitudinal groove on the inner surface of the neural tube separating the alar and basal plates. Synonym: sulcus limitans. (05 Mar 2000) |