| double back cross | A mating that is a back cross at each of two loci of interest; of special value and importance in linkage analysis. (05 Mar 2000) |
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| double bind | A type of personal interaction in which one receives two mutually conflicting verbal or nonverbal instructions or demands from the same person or different individuals, resulting in a situation in which either compliance or noncompliance with either alternative threatens one of the needed relationships. (05 Mar 2000) |
| double bind theory | Contradictions in verbal and behavioural communication between parent and child (patient) which entrap the child because he is unable to comment on the incongruity or to escape from the situation. (12 Dec 1998) |
| double-blind | <statistics> A kind of clinical study in which neither the participants nor the person administering treatment know which treatment any particular subject is receiving. Usually the comparison is between an experimental drug and a placebo or standard comparison treatment. This method is believed to achieve the most accuracy because neither the doctor nor the patient can affect the observed results with their psychological bias. (10 Oct 1997) |
| double-blind experiment | <statistics> An experiment conducted with neither experimenter nor subjects knowing which experiment is the control; prevents bias in recording results. See: double-masked experiment. (05 Mar 2000) |
| double-blind method | <statistics> A method of studying a drug or procedure in which both the subjects and investigators are kept unaware of who is actually getting which specific treatment. (12 Dec 1998) |
| 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) |
| 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) |