| beta pleated sheet | <cell biology> Beta secondary structure in proteins consists of two almost fully extended polypeptide chains lying side by side, linked by interchain hydrogen bonds between peptide C=O and N H groups. The chains may run in the same or opposite directions (yielding parallel or antiparallel structures, respectively). When multiple chains are involved, an extended sheet, the pleated sheet, is formed. (18 Nov 1997) |
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| sheet | 1. To furnish with a sheet or sheets; to wrap in, or cover with, a sheet, or as with a sheet. "The sheeted dead." "When snow the pasture sheets." 2. To expand, as a sheet. "The star shot flew from the welkin blue, As it fell from the sheeted sky." (J. R. Drake) To sheet home, to haul upon a sheet until the sail is as flat, and the clew as near the wind, as possible. Origin: Sheeted; Sheeting. In general, a large, broad piece of anything thin, as paper, cloth, etc.; a broad, thin portion of any substance; an expanded superficies. Specifically: A broad piece of cloth, usually linen or cotton, used for wrapping the body or for a covering; especially, one used as an article of bedding next to the body. "He fell into a trance, and saw heaven opened, and a certain vessel descending unto him, as it had been a great sheet knit at the four corners." (Acts x. 10, 11) "If I do die before thee, prithee, shroud me In one of those same sheets." (Shak) A broad piece of paper, whether folded or unfolded, whether blank or written or printed upon; hence, a letter; a newspaper, etc. A single signature of a book or a pamphlet; in pl, the book itself. "To this the following sheets are intended for a full and distinct answer." (Waterland) A broad, thinly expanded portion of metal or other substance; as, a sheet of copper, of glass, or the like; a plate; a leaf. A broad expanse of water, or the like. "The two beautiful sheets of water." . A sail. <geology> An extensive bed of an eruptive rock intruded between, or overlying, other strata. 2. [AS. Sceata. See the Etymology above. A rope or chain which regulates the angle of adjustment of a sail in relation in relation to the wind; usually attached to the lower corner of a sail, or to a yard or a boom. Pl. The space in the forward or the after part of a boat where there are no rowers; as, fore sheets; stern sheets. Sheet is often used adjectively, or in combination, to denote that the substance to the name of which it is prefixed is in the form of sheets, or thin plates or leaves; as, sheet brass, or sheet-brass; sheet glass, or sheet-glass; sheet gold, or sheet-gold; sheet iron, or sheet-iron, etc. A sheet in the wind, half drunk. Both sheets in the wind, very drunk. In sheets, lying flat or expanded; not folded, or folded but not bound; said especially of printed sheets. Sheet bend, a bend or hitch used for temporarily fastening a rope to the bight of another rope or to an eye. Sheet lightning, Sheet piling, etc. See Lightning, Piling, etc. Origin: OE. Shete, schete, AS. Scte, scte, fr. Sceat a projecting corner, a fold in a garment (akin to D. Schoot sheet, bosom, lap, G. Schoss bosom, lap, flap of a coat, Icel. Skaut, Goth. Skauts the hem of a garment); originally, that which shoots out, from the root of AS. Sceotan to shoot. See Shoot. Source: Websters Dictionary (01 Mar 1998) |
| draw-sheet | A narrow sheet placed crosswise on the bed under the patient, with a rubber sheet of the same width beneath it; used to assist in moving the patient or in changing soiled bed coverings. (05 Mar 2000) |
| 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) |
| acetone test | A test for ketonuria; the suspected urine is shaken up with a few drops of sodium nitroprusside, and strong ammonia water is then gently poured over the mixture; if acetone is present, a magenta ring forms at the line of contact; tablets containing sodium nitroprusside and alkali are now more commonly used. (05 Mar 2000) |
| achievement test | A standardised test used to measure acquired learning, e.g., competence in a specific subject area such as reading or arithmetic, in contrast to an intelligence test which is a useful index of potential ability or learning. (05 Mar 2000) |
| acidified serum test | Lysis of the patient's red cells in acidified fresh serum, specific for paroxysmal nocturnal haemoglobinuria. Synonym: Ham's test. (05 Mar 2000) |
| acid loading test | <nephrology> This is a test used in the diagnosis of renal tubular acidosis. The patient takes ammonium chloride capsules for 3 days to acidify the blood (lower blood pH). A sample of the urine and the blood is then collected and the results are interpreted. (27 Sep 1997) |
| acid perfusion test | <gastroenterology, investigation> A test used to diagnosis gastrooesophageal reflux disease. This investigation requires that the patient swallow 3 tiny tubes into the stomach. A mixture of hydrochloric acid (like stomach acid) and saline are alternatively injected into the tubes. The patient then reports any symptoms they may have. Some patients may vomit. (13 Nov 1997) |
| acid phosphatase test for semen | A screening test for semen by determining acid phosphatase content; because seminal fluid contains high concentrations of acid phosphatase, while other body fluids and extraneous foreign materials have very low concentrations, high values of acid phosphatase on vaginal aspirate or lavage, or on wash fluid from stains, render positive identification of semen, even if the male is aspermic. (05 Mar 2000) |
| acid reflux test | A test to detect gastroesophageal reflux by monitoring oesophageal pH by an electrode in the distal oesophagus either basally or after acid is instilled into the stomach. (05 Mar 2000) |
| ACTH stimulation test | A test for adrenal cortical function; ACTH administered by continuous intravenous infusion, or intramuscularly, evokes an increase in plasma cortisol in normal persons; in adrenal cortical insufficiency, the expected increase in plasma cortisol is limited or nonexistent. (05 Mar 2000) |
| ACTH suppression test | <investigation> A test that measures the response of the adrenal glands to ACTH. In this case, dexamethasone is given to the patient and then blood cortisol levels are measured. Under normal conditions, cortisol levels should drop in response to dexamethasone. In this test one milligram of dexamethasone is administered in the morning and then the blood is drawn for analysis the following morning. Abnormal test results can indicate Cushing's syndrome. (27 Sep 1997) |
| adhesion test | The diagnostic application of the immune adhesion phenomenon. Synonym: erythrocyte adherence test, immune adhesion test, red cell adherence test. (05 Mar 2000) |
| Adler's test | A test for blood; the suspected fluid is treated with glacial acetic acid and ether, and the latter is then decanted and treated with hydrogen peroxide and a solution of benzidine in acetic acid; the presence of blood is indicated by a bluish colour turning to purple. Synonym: Adler's test. (05 Mar 2000) |