| double product | The product of systolic blood pressure multiplied by the heart frequency; a measure of heart work load. See: Robinson index. (05 Mar 2000) |
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| double protrusion | The excessive forward projection of both the maxilla and the mandible in relation to the cranial base. Synonym: double protrusion. (05 Mar 2000) |
| double quotidian fever | Malaria in which two paroxysms of fever occur daily. (05 Mar 2000) |
| double-reciprocal plot | <statistics> A graph made to analyse how fast an enzyme can convert its substrate into its product, depending on how much substrate is present (its concentration) and to determine its maximum speed (after which the enzyme does not get any faster no matter how high the concentration of substrate gets), called Vmax. It is a plot of 1/v versus 1/[S], where v=rate of product formation and [S]=the concentration of the substrate. Synonym: Lineweaver-Burk plot, Woolf-Lineweaver-Burk plot. (05 Mar 2000) |
| double refraction | <microscopy> The refraction of light in two slightly different directions to form two rays or vector components. Each ray is polarized, and their vibration directions are perpendicular to each other. Furthermore, each ray has a different velocity, and therefore a different refractive index. See: birefringence. (05 Aug 1998) |
| double salt | A salt in which two different positive ions are bonded to the same negative ion, or vice versa; e.g., NaKSO4. (05 Mar 2000) |
| double-shock sound | Applied by J. B. Bouillaud to describe the cadence of a split-second heart sound, or of the second sound followed by an opening snap or early third heart sound. Synonym: double-shock sound. Origin: Fr. Drum-beat (05 Mar 2000) |
| double stain | <technique> A mixture of two dyes, each of which stains different portions of a tissue or cell. (05 Mar 2000) |
| double-strand break | A break in double-stranded DNA in which both strands have been cleaved; however, the two strands have not separated from each other. (05 Mar 2000) |
| double-stranded complimentary DNA | <molecular biology> A duplex DNA molecule copied from a copy DNA template. (09 Oct 1997) |
| double tachycardia | The simultaneous tachycardia of two ectopic pacemakers, e.g., atrial and junctional tachycardia. (05 Mar 2000) |
| double tertian | Denoting malarial infections with two different sets of organisms producing daily paroxysms. See: quotidian malaria. (05 Mar 2000) |
| double tertian malaria | See: quotidian malaria. (05 Mar 2000) |
| double thymidine block | <cell culture, procedure> A lab technique used to synchronise the cell cycles of all the cells in a culture. This is done by adding excessive amounts of thymidine (a deoxynucleoside) to the culture so that DNA replication is blocked. Eventually, all of the cells will reach the same point in the cell cycle and stop. (09 Oct 1997) |
| double track sign | In paediatric radiology, a less common sign of congenital pyloric stenosis, when barium is caught between mucosal folds in the hypertrophied pylorus. (05 Mar 2000) |