| ACS | acrocallosal syndrome; acrocephalosyndactyly; acute chest syndrome; acute confusional state; Alcon C... |
|---|---|
| APC | acetylsalicylic acid, phenacetin, and caffeine; activated protein C; adenoidal-pharyngeal-conjunctiv... |
| NA | Avogadro constant or number; nalidixic acid; Narcotics Anonymous; network administrator; neuraminida... |
| c.gl. | correction with glasses |
| s.gl. | without correction without glasses |
| CF | Correction Factor |
|---|---|
| TACT | Tuned Aperture Computed Tomography |
| AC | attenuation correction |
| N.A. | numerical aperture |
| aperture correction | <microscopy> An electronic process used in some high-resolution video cameras and monitors that compensates for the loss in sharpness of detail due to the finite dimensions (aperture) of the scanning beam. (05 Aug 1998) |
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| correction | A setting right, as the provision of specific lenses for the improvement of vision or an arbitrary adjustment made in values or devices in performance of experimental procedures. Origin: L. Correctio = straightening out, amendment (18 Nov 1997) |
|---|---|
| correction collar | <microscopy> An adjustment collar provided on some high-numerical aperture, microscope objective lenses. Rotation of the collar adjusts the height of certain lens elements in the objective lens to compensate for variations in coverslip thickness or immersion media. at high numerical apertures, even a small deviation of the coverslip thickness (by as little as a few micrometres in some cases), or refractive index of the immersion medium from the designated standard, can introduce significant aberrations. (05 Aug 1998) |
| spontaneous correction of placenta previa | The upward "migration" of the placenta away from the internal os by the differential growth rates of upper and lower uterine segments. (05 Mar 2000) |
| occlusal correction | The correction of malocclusion, by whatever means is employed, elimination of disharmony of occlusal contacts. (05 Mar 2000) |
| angle of aperture | <ophthalmology, optics> The angle formed by lines drawn from the ends of the diameter of a lens to its point of focus. See: angular aperture. (05 Mar 2000) |
| angular aperture | The angle, in air, of light that passes from the object to the ends of the diameter of the front lens of the microscope objective. (05 Mar 2000) |
| anterior nasal aperture | The anterior nasal opening in the skull. Synonym: apertura piriformis, piriform opening. (05 Mar 2000) |
| aperture | <physics> The opening in an optical system which restricts the size of the bundle of rays incident on a given surface. (Usually circular and specified by diameter.) (09 Oct 1997) |
| aperture, angular | <microscopy> The angle between the most divergent rays that can pass through a lens to form the image of an object. The angle subtended between the axis of a lens and the largest accepted angle of the image-forming rays. With microscope objectives the trigonometric sine of this angle is used to define numerical aperture but as measured from the axial object point. (05 Aug 1998) |
| aperture diaphragm | A metal device that limits the area of the beam emerging from an X-ray tube. (05 Mar 2000) |
| aperture, effective | <microscopy> The diameter of the entrance pupil: it is the apparent diameter of the limiting aperture measured from the front. (05 Aug 1998) |
| aperture for electron microscopy | <technique> Anode aperture: The opening in the accelerating voltage anode shield of the electron gun through which the electrons must pass to irradiate the specimen. Condenser aperture: An opening in the condenser lens controlling the number of electrons entering the lens and the angular aperture of the electron beam. The angular aperture can also be controlled by the condenser lens current. Physical objective aperture: A metallic diaphragm, with a small central hole, used to limit the cone of electrons accepted by the objective lens. This improves image-contrast since highly scattered electrons are prevented from arriving at the Gaussian image plane and therefore cannot contribute to background fog. Aplanatic. Free from spherical aberration and coma. (05 Aug 1998) |
| aperture function | <microscopy> In a diffraction-limited optical system, the function that determines the relationship between the image and each point in the object. Modifying the aperture function changes the image according to the modified Fourier-filtering (or optical filtration) property of the aperture. (05 Aug 1998) |
| aperture of mastoid antrum | The orifice leading from the epitympanic recess to the mastoid antrum. Synonym: aditus ad antrum. (05 Mar 2000) |
| aperture of orbit | The somewhat quadrangular anterior entrance to the orbit which forms the base of the pyramid-shaped orbital cavity. It is bounded by the sharp supra-, infra-, and lateral orbital margins and a less obvious medial margin on each side of the upper nose. Synonym: aditus orbitae, aperture of orbit. (05 Mar 2000) |
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