| Mach number | A number representing the ratio between the speed of an object moving through a fluid medium, such as air, and the speed of sound in the same medium. (05 Mar 2000) |
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| magnetic mach number | <physics> A dimensionless number equal to the ratio of the velocity of a fluid to the velocity of Alfven waves in that fluid. (13 Nov 1997) |
| mass number | The mass of the atom of a particular isotope relative to hydrogen-1 (or to 1/12 the mass of carbon-12), generally very close to the whole number represented by the sum of the protons and neutrons in the atomic nucleus of the isotope (indicated in the name or symbol of the isotope; e.g., oxygen-16, 16O); not to be confused with the atomic weight of an element, which may include a number of isotopes in natural proportion. (05 Mar 2000) |
| Reichert-Meissl number | An index of the volatile acid content of a fat; the number of milliliters of 0.1 n KOH required to neutralise the soluble volatile fatty acids in 5 g of fat that has been saponified, acidified to liberate the fatty acids, and then steam-distilled. Synonym: volatile fatty acid number. (05 Mar 2000) |
| volatile fatty acid number | An index of the volatile acid content of a fat; the number of milliliters of 0.1 n KOH required to neutralise the soluble volatile fatty acids in 5 g of fat that has been saponified, acidified to liberate the fatty acids, and then steam-distilled. Synonym: volatile fatty acid number. (05 Mar 2000) |
| gold number | A unit of power of the protective colloids; the number of milligrams of protective colloid just sufficient to prevent the precipitation of 10 ml of a 0.0053 to 0.0058% gold solution by the action of 1 ml of a 10% sodium chloride solution. Synonym: gold number. (05 Mar 2000) |
| Reynolds number | A dimensionless number that describes the tendency for a flowing fluid, such as blood, to change from laminar flow to turbulent flow or vice versa. (05 Mar 2000) |
| Reynold's number | <physiology> A constant without dimensions that relates the inertial and viscous drag acting to hinder a body moving through fluid medium. For cells the Reynold's number is very small, viscous drag is dominant and inertial resistance can be neglected. (18 Nov 1997) |
| MIM number | The catalog assignment for a mendelian trait in the MIM system. If the initial digit is 1, the trait is deemed autosomal dominant; if 2, autosomal recessive; if 3, then X-linked. Wherever a trait defined in this dictionary has a MIM number the number from the tenth edition of MIM is given in square brackets with or without an asterisk as appropriate e.g., Pelizaeus-Merzbacher disease is a well-established, autosomal, dominant, mendelian disorder. (05 Mar 2000) |
| wave number | <microscopy> The number of waves or cycles of light flux or radiant energy, measured through a distance of 1 cm. (05 Aug 1998) |
| writhing number | <molecular biology> The number of times the axis of a DNA helix crosses itself while the molecule is in the process of supercoiling. (09 Oct 1997) |
| copy number | The number of molecules of a particular type on or in a cell or part of a cell. Usually applied to specific genes or to plasmids within a bacterium. (18 Nov 1997) |
| Polenske number | The number of milliliters of 0.1 n KOH required to neutralise the nonvolatile fatty acids obtained from 5 g of a saponified fat or oil. (05 Mar 2000) |
| CT number | A normalised value of the calculated X-ray absorption coefficient of a pixel (picture element) in a computed tomogram, expressed in Hounsfield units, where the CT number of air is -1000 and that of water is zero. Synonym: Hounsfield number. (05 Mar 2000) |
| haploid number | <cell biology, genetics> The haploid number is the total number of chromosomes in a single set, such as would be found in a gamete or a haploid somatic cell (such as in fungus or gametophyte plants). In humans, the haploid number would be 23. (09 Oct 1997) |