| double-blind study | A study in which neither the experimenter nor any other assessor of the results, including patients, know which group is subject to which procedure, thus helping assure that the biases or expectations of either will not influence the results. (05 Mar 2000) |
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| double bond | <chemistry> A covalent bond resulting from the sharing of two pairs of electrons; e.g., H2C==CH2 (ethylene). (05 Mar 2000) |
| 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) |