| A [band] | the dark-staining zone of a striated muscle |
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| AR | absolute risk; accounts receivable; achievement ratio; actinic reticuloid [syndrome]; active resista... |
| ARA | Academy of Rehabilitative Audiometry; acetylene reduction activity; American Rheumatism Association;... |
| ARR | aortic root replacement |
| ATZ | atypical transformation zone |
| zone | 1. A girdle; a cincture. "An embroidered zone surrounds her waist." (Dryden) "Loose were her tresses seen, her zone unbound." (Collins) 2. <geography> One of the five great divisions of the earth, with respect to latitude and temperature. The zones are five: the torrid zone, extending from tropic to tropic 46 deg 56 min, or 23 deg 28 min on each side of the equator; two temperate or variable zones, situated between the tropics and the polar circles; and two frigid zones, situated between the polar circles and the poles. "Commerce . . . Defies every wind, outrides every tempest, and invades." (Bancroft) 3. <mathematics> The portion of the surface of a sphere included between two parallel planes; the portion of a surface of revolution included between two planes perpendicular to the axis. 4. A band or stripe extending around a body. A band or area of growth encircling anything; as, a zone of evergreens on a mountain; the zone of animal or vegetable life in the ocean around an island or a continent; the Alpine zone, that part of mountains which is above the limit of tree growth. 5. <chemistry> A series of planes having mutually parallel intersections. 6. Circuit; circumference. Abyssal zone. To girdle; to encircle. <physics> A straight line passing through the center of a crystal, to which all the planes of a given zone are parallel. Origin: F. Zone, L. Zona, Gr.; akin to to gird, Lith. Jsta to gird, Zend yah. Source: Websters Dictionary (01 Mar 1998) |
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| zone 1, 2, 3, 4 of West | In pulmonary physiology, defines the levels in a vertical lung according to the relationships of alveolar gas pressure, capillary blood pressure, and pulmonary venous pressure. (05 Mar 2000) |
| zone centrifugation | <technique> High-speed centrifugation inwhich molecules float at a point wheretheir density equals that in a gradient of cesium chloride or sucrose. (12 Jan 1998) |
| zone electrophoresis | <chemistry, procedure> A type of electrophoresis used by physical chemists. In it, the components of a mixture are separated into distinct zones by moving the solution through a porous medium such as filter paper. (06 May 1997) |
| zone of inhibition | <microbiology> The area of no bacterial browth around an antimicrobial agent in the disk-diffusion test. (09 Oct 1997) |
| zone of optimal proportion | <chemistry> A zone in a solution of mixed antigen in which the two biomolecules are totally combined. (11 May 1997) |
| zone of polarizing activity | <cell biology> The small group of mesenchyme cells in avian limb buds that is located at the posterior margin of the developing bud and that produces a substance, possibly retinoic acid, that provides positional information to the developing limb bud. (18 Nov 1997) |
| foetal zone | An extensive area of the adrenal gland present in primates during foetal life and for a short period after birth; located between the definitive cortex and the medulla, it contains large steroid-secreting cells arranged in a reticular pattern; involution of this zone in humans is largely completed by three months after birth. Synonym: androgenic zone, foetal reticularis, foetal zone, provisional cortex. (05 Mar 2000) |
| language zone | A large area of the cerebral cortex on the left side (in right-handed persons) considered by some to embrace all the centres of memories and associations connected with language. (05 Mar 2000) |
| latent zone | That portion of the cerebral cortex, the stimulation of which produces no movement and a lesion of which produces no symptoms; mainly the more anterior areas of the frontal lobes. (05 Mar 2000) |
| frontal zone contraction theory | Model proposed to account for the movement of giant amoebae in which cytoplasmic contraction at the front of the leading pseudopod (fountain zone) pulls viscoelastic cytoplasm forward in the centre of the cell and forms a tube of more rigid cytoplasm immediately below the plasma membrane behind the active region. The peripheral contracted cytoplasm relaxes into a weaker gel at the rear and is pulled forward in its turn. Contrasts with the ectoplasmic tube contraction model. (18 Nov 1997) |
| Lissauer's marginal zone | A longitudinal bundle of thin, unmyelinated and poorly myelinated fibres capping the apex of the posterior horn of the spinal gray matter, composed of posterior root fibres and short association fibres that interconnect neighboring segments of the posterior horn. Synonym: fasciculus dorsolateralis, tractus dorsolateralis, dorsolateral tract, fasciculus marginalis, Lissauer's bundle, Lissauer's column, Lissauer's fasciculus, Lissauer's marginal zone, Lissauer's tract, marginal fasciculus, Spitzka's marginal tract, Spitzka's marginal zone, Waldeyer's tract, Waldeyer's zonal layer. (05 Mar 2000) |
| alum root | <botany> A North American herb (Heuchera Americana) of the Saxifrage family, whose root has astringent properties. Source: Websters Dictionary (01 Mar 1998) |
| anatomical root | That portion of a tooth extending from the cervical line to its apical extremity. (05 Mar 2000) |
| angelica root | The root of Angelica archangelica (family Umbelliferae); a tonic and stimulant that may cause nausea; used as a carminative, diuretic, and externally as a counterirritant. (05 Mar 2000) |