| double bond | <chemistry> A covalent bond resulting from the sharing of two pairs of electrons; e.g., H2C==CH2 (ethylene). (05 Mar 2000) |
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| double bubble sign | <radiology> Gas in stomach and duodenal bulb, duodenal atresia, annular pancreas, Ladd's bands, congenital duodenal web (or diaphragm) (12 Dec 1998) |
| double-channel catheter | A catheter with two lumens, allowing irrigation and aspiration. Synonym: two-way catheter. (05 Mar 2000) |
| double chin | A fatty puffing under the chin. Synonym: double chin. Origin: L. Dim. Of bucca, cheek (05 Mar 2000) |
| double compartment hydrocephalus | Independent supra-and infra-tentorial hydrocephalus usually due to a veil occlusion of the aqueduct of Sylvius. (05 Mar 2000) |
| double concave lens | A lens that is concave on two opposing surfaces. Synonym: concavoconcave lens, double concave lens. (05 Mar 2000) |
| double congenital athetosis | A type of cerebral palsy manifested predominantly as bilateral involuntary movements, beginning at about the age of 3 years, and preceded by generalised hypotonia and delayed motor development. Due to various causes, including kernicterus and birth hypoxia. Synonym: congenital choreoathetosis, double congenital athetosis, Vogt syndrome. (05 Mar 2000) |
| double consciousness | A condition in which one lives in two seemingly unrelated mental states, being, while in one, unaware of the other or of the acts performed in the other. See: dual personality. (05 Mar 2000) |
| double contrast enema | After evacuation of a barium enema and injection of air into the rectum, radiographs show fine details of mucosa of the rectum and colon. (05 Mar 2000) |
| double convex lens | A lens with both surfaces convex. Synonym: convexoconvex lens, double convex lens. (05 Mar 2000) |
| double crossover | <genetics, molecular biology> Two events of recombination occuring on the same chromosome. (09 Oct 1997) |
| double decidual sac | <radiology> DDS, visualization correlates with presence of pregnancy in 98%, may be seen at less than 5 weeks on transvaginal scans see: gestational sac (12 Dec 1998) |
| double digestion | <molecular biology> Treating DNA with two different restriction enzymes, or enzymes which will cleave DNA at specific nucleotide sequences. (09 Oct 1997) |
| double displacement mechanism | A special multisubstrate reaction in which, for a two-substrate, two-product (i.e., bi-bi) system, an enzyme reacts with one substrate to form a product and a modified enzyme, the latter then reacting with a second substrate to form a second, final product, and regenerating the original enzyme. An example of such a mechanism is found in the aminotransferases. More complex ping-pong mechanisms exist for enzymes having more than two substrates. Synonym: double displacement mechanism. (05 Mar 2000) |
| double-ender | A locomotive with pilot at each end. Source: Websters Dictionary (01 Mar 1998) |