| DA | dark adaptation; dark agouti [rat]; daunomycin; degenerative arthritis; delayed action; Dental Assis... |
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| CR | calculation rate; calculus removed; calorie-restricted; cardiac rehabilitation; cardiac resuscitatio... |
| PETH | pink-eyed, tan-hooded [rat] |
| TAN | total adenine nucleotide; total ammonia nitrogen |
| tan | tandem translocation; tangent |
| TAN | Total adenine nucleotide |
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| BBTV | Banana bunchy top virus |
| BCTV | Beet curly top virus |
| TOP | termination of pregnancy |
| D | Dark |
| tan | 1. To convert (the skin of an animal) into leather, as by usual process of steeping it in an infusion of oak or some other bark, whereby it is impregnated with tannin, or tannic acid (which exists in several species of bark), and is thus rendered firm, durable, and in some degree impervious to water. The essential result in tanning is due to the fact that the tannins form, with gelatins and albuminoids, a series of insoluble compounds which constitute leather. Similar results may be produced by the use of other reagents in place of tannin, as alum, and some acids or chlorides, which are employed in certain processes of tanning. 2. To make brown; to imbrown, as by exposure to the rays of the sun; as, to tan the skin. Origin: F. Tanner, LL. Tannare. See Tan. 1. The bark of the oak, and some other trees, bruised and broken by a mill, for tanning hides; so called both before and after it has been used. Called also tan bark. 2. A yellowish-brown colour, like that of tan. 3. A brown colour imparted to the skin by exposure to the sun; as, hands covered with tan. <botany> Tan bed, a bed made of tan; a bark bed. Tan pickle, the liquor used in tanning leather. Tan spud, a spud used in stripping bark for tan from trees. Tan stove. See Bark stove, under Bark. Tan vat, a vat in which hides are steeped in liquor with tan. Origin: F. Tan, perhaps fr. Armor. Tann an oak, oak bar; or of Teutonic origin; cf. G. Tanne a fir, OHG. Tanna a fir, oak, MHG. Tan a forest. Cf. Tawny. Source: Websters Dictionary (01 Mar 1998) |
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| top | 1. To cover on the top; to tip; to cap; chiefly used in the past participle. "Like moving mountains topped with snow." (Waller) "A mount Of alabaster, topped with golden spires." (Milton) 2. To rise above; to excel; to outgo; to surpass. "Topping all others in boasting." (Shak) "Edmund the base shall top the legitimate." (Shak) 3. To rise to the top of; to go over the top of. "But wind about till thou hast topped the hill." (Denham) 4. To take off the or upper part of; to crop. "Top your rose trees a little with your knife." (Evelyn) 5. To perform eminently, or better than before. "From endeavoring universally to top their parts, they will go universally beyond them." (Jeffrey) 6. To raise one end of, as a yard, so that that end becomes higher than the other. To top off, to complete by putting on, or finishing, the top or uppermost part of; as, to top off a stack of hay; hence, to complete; to finish; to adorn. 1. A child's toy, commonly in the form of a conoid or pear, made to spin on its point, usually by drawing off a string wound round its surface or stem, the motion being sometimes continued by means of a whip. 2. A plug, or conical block of wood, with longitudital grooves on its surface, in which the strands of the rope slide in the process of twisting. Origin: CF. OD. Dop, top, OHG, MNG, & dial. G. Topf; perhaps akin to G. Topf a pot. 1. The highest part of anything; the upper end, edge, or extremity; the upper side or surface; summit; apex; vertex; cover; lid; as, the top of a spire; the top of a house; the top of a mountain; the top of the ground. "The star that bids the shepherd fold, Now the top of heaven doth hold." (Milton) 2. The utmost degree; the acme; the summit. "The top of my ambition is to contribute to that work." (Pope) 3. The highest rank; the most honorable position; the utmost attainable place; as, to be at the top of one's class, or at the top of the school. "And wears upon hisbaby brow the round And top of sovereignty." (Shak) 4. The chief person; the most prominent one. "Other . . . Aspired to be the top of zealots." (Milton) 5. The crown of the head, or the hair upon it; the head. "From top to toe" "All the stored vengeance of Heaven fall On her ungrateful top !" (Shak) 6. The head, or upper part, of a plant. "The buds . . . Are called heads, or tops, as cabbageheads." (I. Watts) 7. A platform surrounding the head of the lower mast and projecting on all sudes. It serves to spead the topmast rigging, thus strengheningthe mast, and also furnishes a convenient standing place for the men aloft. 8. A bundle or ball of slivers of comkbed wool, from which the noils, or dust, have been taken out. 9. Eve; verge; point. "He was upon the top of his marriage with Magdaleine." 10. The part of a cut gem between the girdle, or circumference, and the table, or flat upper surface. Top is often used adjectively or as the first part of compound words, usually self-explaining; as, top stone, or topstone; top-boots, or top boots; top soil, or top-soil. Top and but, a phrase used to denote a method of working long tapering planks by bringing the but of one plank to the top of the other to make up a constant breadth in two layers. <zoology> Top minnow, a small viviparous fresh water fish (Gambusia patruelis) abundant in the Southern United States. Also applied to other similar species. Origin: AS. Top; akin to OFries. Top a tuft, D. Top top, OHG. Zopf end, tip, tuft of hair, G. Zopf tuft of hair, pigtail, top of a tree, Icel. Toppr a tuft of hair, crest, top, Dan. Top, Sw. Topp pinnacle, top; of uncertain origin. Cf. Tuft. Source: Websters Dictionary (01 Mar 1998) |
| top-shaped | <botany> Having the shape of a top; cone-shaped, with the apex downward; turbinate. Source: Websters Dictionary (01 Mar 1998) |
| top-shell | <zoology> Any one of numerous species of marine top_shaped shells of the genus Thochus, or family Trochidae. Source: Websters Dictionary (01 Mar 1998) |
| turban-top | <botany> A kind of fungus with an irregularly wrinkled, somewhat globular pileus (Helvella, or Gyromitra, esculenta). Source: Websters Dictionary (01 Mar 1998) |
| flat top waves | Activity in the electroencephalogram having a pattern suggesting a flat top; these wave's are often found in temporal lobe discharges. (05 Mar 2000) |
| cardioid dark field condenser | <microscopy> A condenser designed with two reflecting surfaces, the first, a spherical surface which reflects the rays to a second, cardioid (heart-shaped) surface. The virtue in such an arrangement is that, if the cardioid surface is of true figure, the lens is both achromatic and aplanatic. It has a limiting numerical aperture of about 1.0. Thus objectives of a greater numerical aperture cannot be used successfully with it. A true cardioid figure is the trace of a point on the circumference of a circle rolling around an equal, fixed circle. (05 Aug 1998) |
| paraboloid dark field condenser | <microscopy> A lens of parabolic shape. The vertex end is ground back so that its focus can be brought into coincidence with the specimen on the slide. A central stop is provided to block the central rays. It is used chiefly for medium- power work. (05 Aug 1998) |
| condenser, dark field | <microscopy> A condenser forming a hollow cone of light with its apex (or focal point) in the plane of the specimen. When used with an objective having a numerical aperture lower than the minimum numerical aperture of the hollow cone, only light deviated by the specimen enters the objective. Objects are seen as bright images against a dark background. The ordinary bright field condenser of low power, used with a central stop, makes a good dark field condenser. They all form a dark field while illuminating the specimen with a hollow cone of light. The lower limiting aperture of the condenser must be greater than the numerical aperture of the objective with which it is to be used. Thus, no direct light enters the objective, the specimen is seen by reflected or scattered light on a dark background. See: condensers See: special dark field condensers: paraboloid, cardioid and Cassegrainian. (05 Aug 1998) |
| dark adaptation | The adjustment of the eye occurring under reduced illumination in which the sensitivity to light is greatly increased or the light threshold is greatly reduced. Dark adaptation is slower than light adaptation. During dark adaptation rhodopsin is built up in the retinal rods. (12 Dec 1998) |
| dark-adapted eye | An eye that has been in darkness or semidarkness and has undergone regeneration of rhodopsin (visual purple), which renders it more sensitive to reduced illumination. Synonym: scotopic eye. (05 Mar 2000) |
| dark cell | Cell's in eccrine sweat glands having many ribosomes and mucoid secretory granules. (05 Mar 2000) |
| dark current | <physiology> Current caused by constant influx of sodium ions into the rod outer segment of retinal photoreceptors and that is blocked by light (leading to hyperpolarization). The plasma membrane sodium channel is controlled through a cascade of amplification reactions initiated by photon capture by rhodopsin in the disc membrane. (18 Nov 1997) |
| dark-field condenser | An apparatus for throwing reflected light through the microscope field, so that only the object to be examined is illuminated, the field itself being dark. (05 Mar 2000) |
| dark field illumination | <microscopy> Any method of illumination which illuminates the specimen but does not admit light directly to the objective. It may be by substage (dark field) condensers, by stagespot lighting, by special condensers fitted around special objectives for reflected illumination or by the slit ultramicroscope. (05 Aug 1998) |
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