| basic reproductive rate, ratio | <epidemiology> See Reproductive Ratio. (05 Dec 1998) |
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| body-weight ratio | Body weight (in grams) divided by stature (in centimeters). (05 Mar 2000) |
| branching ratio | <radiobiology> In a fusion reaction involving two nuclei, there are typically a variety of possible sets of products which can form. The branching ratio for a particular set of products is the probability that that set of products will be produced. (09 Oct 1997) |
| cardiothoracic ratio | The ratio of the horizontal diameter of the heart to the inner diameter of the rib cage at its widest point as determined on a chest roentgenogram. (05 Mar 2000) |
| magnetogyric ratio | In nuclear magnetic resonance, the ratio of the magnetic dipole moment of the nucleus to the nuclear spin angular momentum; the gyromagnetic ratio is a unique value for each type of nucleus. Synonym: magnetogyric ratio. (05 Mar 2000) |
| variance ratio | The distribution of the ratio of two independent estimates of the same variance from a gaussian distribution based on samples of sizes (n + 1) and (m + 1) respectively. Estimates are usually based on one such sample analyzed in such a way as to make them independent e.g., analysis of variance; and F may be used to test a null hypothesis that the observed differences among sample means is no greater than could readily be accounted for by chance. (05 Mar 2000) |
| G+C ratio | <molecular biology> In DNA (or RNA) from any organism, the percent of the total nucleic acid that consists of guanine plus cytosine bases. (20 Mar 1998) |
| ratio | 1. <mathematics> The relation which one quantity or magnitude has to another of the same kind. It is expressed by the quotient of the division of the first by the second; thus, the ratio of 3 to 6 is expressed by 3/6/ or 1/2; of a to b by a/b; or (less commonly) the second is made the dividend; as, a:b = b/a. Some writers consider ratio as the quotient itself, making ratio equivalent to a number. The term ratio is also sometimes applied to the difference of two quantities as well as to their quotient, in which case the former is called arithmetical ratio, the latter, geometrical ratio. The name ratio is sometimes given to the rule of three in arithmetic. See Rule. 2. Hence, fixed relation of number, quantity, or degree; rate; proportion; as, the ratio of representation in Congress. Compound ratio, Duplicate ratio, Inverse ratio, etc. See Compound, Duplicate, etc. Ratio of a geometrical progression, the constant quantity by which each term is multiplied to produce the succeeding one. Origin: L, fr. Reri, ratus, to reckon, believe, think, judge. See Reason. Source: Websters Dictionary (01 Mar 1998) |
| ratio imaging fluorescence microscopy | <procedure> A method of measurement of intracellular pH or intracellular calcium levels, using a fluorescent probe molecule (see fura-2), in which the two different excitation wavelengths are used and the emitted light levels compared. If emission at one wavelength is sensitive to the intracellular ion level and emission at the other wavelength is not, then standardisation for intracellular probe concentration, efficiency of light collection, inactivation of probe and thickness of cytoplasm can all be performed automatically. (17 Dec 1997) |
| ratio of decayed and filled surfaces | An index of decayed and filled permanent surfaces per person, per full complement of 122 tooth surfaces. (05 Mar 2000) |
| ratio of decayed and filled teeth | An index of decayed and filled permanent teeth per person, per full complement of 28 teeth. (05 Mar 2000) |
| ratio scale | A scale that involves physical units and demonstrates their relations. (05 Mar 2000) |
| ventilation-perfusion ratio | The ratio of alveolar ventilation to simultaneous alveolar capillary blood flow in any part of the lung. (12 Dec 1998) |
| ventilation/perfusion ratio | The ratio of alveolar ventilation to simultaneous alveolar capillary blood flow in any part of the lung; because both ventilation and perfusion are expressed per unit volume of tissue and per unit time, which cancel, the units become liters of gas per liter of blood. (05 Mar 2000) |
| mass-action ratio | The ratio of the product of all of the product concentrations divided by the product of all of the reactant concentrations of a particular reaction; when the reaction has been completed (i.e., t = ∞), then this ratio is equal to the equilibrium constant. (05 Mar 2000) |