| acid etch | <dentistry> A procedure where a weak acid smeared on your teeth to ready your teeth for brackets. The acid etch helps your brackets stay on better. (08 Jan 1998) |
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| acid etch cemented splint | A splint of heavy wire which is cemented to the labial surfaces of teeth with any of the acid etch cement techniques; used to stabilise traumatically displaced or periodontally diseased teeth. (05 Mar 2000) |
| acid etching, dental | Pretreatment of tooth surfaces with etching agents, usually phosphoric acid, to increase the adhesion of various resin systems. (12 Dec 1998) |
| etch | 1. To produce, as figures or designs, on mental, glass, or the like, by means of lines or strokes eaten in or corroded by means of some strong acid. The plate is first covered with varnish, or some other ground capable of resisting the acid, and this is then scored or scratched with a needle, or similar instrument, so as to form the drawing; the plate is then covered with acid, which corrodes the metal in the lines thus laid bare. 2. To subject to etching; to draw upon and bite with acid, as a plate of metal. "I was etching a plate at the beginning of 1875." (Hamerton) 3. To sketch; to delineate. "There are many empty terms to be found in some learned writes, to which they had recourse to etch out their system." (Locke) Origin: D. Etsen, G. Atzen to feed, corrode, etch. MHG. Etzen, causative of ezzen to eat, G. Essen . See Eat. Source: Websters Dictionary (01 Mar 1998) |
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| freeze etch | <microscopy, technique> A method of preparing a cell for study by freezing it, cracking it open to reveal the organelles, freeze drying it, then examining it under the electron microscope. (09 Oct 1997) |
| Rambourg's chromic acid-phosphotungstic acid stain | <technique> A stain for glycoproteins, used with an electron microscope, with which ultrathin tissue sections reveal complex carbohydrates in the same locations as shown by Rambourg's periodic acid-chromic methenamine-silver stain. (05 Mar 2000) |
| a1-acid glycoprotein | <biology> Plasma protein of mammals and birds, 38% carbohydrate. In humans a single chain glycoprotein of 39 kD. Increased levels are associated with inflammation, pregnancy and various diseases. (18 Nov 1997) |
| abscisic acid | <biochemistry> A lipid hormone that inhibits cell growth in plants, it is associated with fruit drop, leaf death and seed dormancy. It is synthesised in the plastids from carotenoids. This hormone helps plants deal with water loss, and its effects can be reversed with gibberellins. (06 May 1997) |
| abscisic acid 8'-hydroxylase | <enzyme> Catalyses conversion of abscisic acid to 8'-hydroxyabscisic acid, which rearranges to phaseic acid Registry number: EC 1.14.99.- Synonym: aba 8'-hydroxylase (26 Jun 1999) |
| acetic acid | <chemical> The acid most commonly associated with vinegar, it is the most commercially important organic acid and is used to manufacture a wide range of chemical products, such as plastics and Acetobacter but, except for making vinegar, is usually made through synthetic processes. Derivatives of acetic acid which may be formed by substitution reactions. Mono- and di-substituted, as well as, halogenated compounds have been synthesised. Experimentally, alpha- and n2- substituted acetic acids have been examined for their anti-inflammatory activity and effect on the central nervous system respectively. Additionally, limited exposure data has been collected on dibromo and dichloroacetic acids to determine whether they pose health effects. Synonym: ethanoic acid. (26 Jun 1999) |
| acetoacetic acid | CH3COCH2COOH;one of the ketone bodies, formed in excess and appearing in the urine in starvation or diabetes. Synonym: diacetic acid. (05 Mar 2000) |
| acetohydroxamic acid | C2H5NO2; N-Hydroxyacetamide;an inhibitor of urease, used as adjunctive therapy in chronic urea-splitting urinary infections. (05 Mar 2000) |
| acetrizoic acid | <chemical> A water-soluble, iodinated radiographic contrast medium, used as sodium acetrizoate in hysterosalpingography. Pharmacological action: contrast media. Chemical name: Benzoic acid, 3-(acetylamino)-2,4,6-triiodo- (12 Dec 1998) |
| acetylsalicylic acid | <drug> An odourless, white, slightly bitter drug used to reduce pain, fever, inflammation and sometimes to prevent blood clotting. Also called aspirin. Some people cannot tolerate it because it can cause stomach bleeding, however. It is soluble in both water and alcoholand melts at 132 to 136 degrees C. (06 May 1997) |
| acetyltannic acid | An astringent used for treatment of diarrhoea. Synonym: diacetyltannic acid, tannylacetate. (05 Mar 2000) |
| acid | <chemical, chemistry> A fundamental category of many compounds whose water-based solutions have a sour taste, turn blue litmus paper red and can combine with metals to form salts. They are chemical compounds which yield hydrogen ions or protons when dissolved in water, whose hydrogen can be replaced by metals or basic radicals, or which react with bases to form salts and water (neutralization). An extension of the term includes substances dissolved in media other than water. Specific types of acids include: Arrhenius acid: any chemical that increases the number of free hydrogen ions (H+) when added to a water-based solution. The more free hydrogens produced, the stronger the acid. Bronsted or Bronsted-Lowry acid: any chemical that acts as a proton donor in a chemical reaction. Lewis acid: any chemical that accepts two electrons to form a covalent bond during a chemical reaction. (13 Nov 1997) |
| acid agglutination | The clumping together of certain microorganisms at high hydrogen ion concentration. (05 Mar 2000) |
| acid anhydride hydrolases | <enzyme> A group of enzymes that catalyze the hydrolysis of diphosphate bonds in compounds such as nucleoside di- and tri-phosphates, and sulfonyl-containing anhydrides such as adenylylsulfate. (enzyme nomenclature, 1992). Registry number: EC 3.6 (12 Dec 1998) |