| Poiseuille's viscosity coefficient | An expression of the viscosity as determined by the capillary tube method; the coefficient η = (πPr4t/8vl), where P is the pressure difference between the inlet and outlet of the tube, r the radius of the tube, l its length, and v the volume of liquid delivered in the time t. If volume is in cm3, time is in seconds, and l and r are in cm, then n will be in poise. (05 Mar 2000) |
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| correlation coefficient | A measure of association that indicates the degree to which two variables have a linear relationship; this coefficient, represented by the letter r, can vary between +1 and -1; when r = +1, there is a perfect positive linear relationship in which one variable relates directly with the other; when r = -1, there is a perfect negative linear relationship between the variables. (05 Mar 2000) |
| population diffusion coefficient | <cell biology> Coefficient that describes the tendency of a population of motile cells to diffuse through the environment. Its use presupposes that the cells move in a random walk. (18 Nov 1997) |
| creatinine coefficient | The number of milligrams of creatinine excreted daily per kilogram of body weight. (05 Mar 2000) |
| Hill coefficient | A measure of cooperativity in a binding process. A Hill coefficient of 1 indicates independent binding, a value of greater than 1 shows positive cooperativity binding of one ligand facilitates binding of subsequent ligands at other sites on the multimeric receptor complex. Worked out originally for the binding of oxygen to haemoglobin (Hill coefficient of 2.8). (18 Nov 1997) |
| sedimentation coefficient | <physics> The ratio of the velocity of sedimentation of a molecule to the centrifugal force required to produce this sedimentation. It is a constant for a particular species of molecule and the value is given in Svedberg units that, it should be noted, are nonadditive. (18 Nov 1997) |
| selection coefficient | The proportion of progeny or potential progeny not surviving to sexual maturity; usually defined artificially by expressing the fitness of a phenotype as a fraction of the mean or optimal fitness to give the relative fitness, and subtracting this fraction from unity. If the mean size of family in the population is 3.2 and that for a particular genotype is 2.4 then the fitness of the phenotype is 2.4/3.2 =0.75 and the selection coefficient =1-0.75 =.25 = 5 (05 Mar 2000) |
| hygienic laboratory coefficient | A figure expressing the disinfecting power of any substance; it is obtained by dividing the figure indicating the degree of dilution of the disinfectant that kills a microorganism in a given time by that indicating the degree of dilution of phenol which kills the organism in the same space of time under similar conditions. Synonym: hygienic laboratory coefficient, phenol coefficient. (05 Mar 2000) |
| specific absorption coefficient | Absorbance (of light) per unit path length (usually the centimeter) and per unit of mass concentration. Compare: molar absorption coefficient. Synonym: absorbancy index, absorptivity, extinction coefficient, specific extinction. (05 Mar 2000) |
| diffusion coefficient | For the translational diffusion of solutes, diffusion is described by Fick's First Law, that states that the amount of a substance crossing a given area is proportional to the spatial gradient of concentration and the diffusion constant (D), that is related to molecular size and shape. A useful derived relationship is that the mean square distance moved by molecules in time t is 6Dt. (18 Nov 1997) |
| distribution coefficient | The ratio of concentrations of a substance in two immiscible phases at equilibrium; the basis of many chromatographic separation procedures. Synonym: partition coefficient. (05 Mar 2000) |
| inbreeding, coefficient of | A statistical way of gauging how close two people are as to their genes. The coefficient of inbreeding (symbolised as f) is the probability that a person with two identical genes received both genes from an identical ancestor. Take, for example, first cousins. They share a set of grandparents. For any particular allele (gene) in the father, the chance that the mother inherited the same allele from the same source is 1/8. For any gene the father passes to his child, the chance is 1/8 that the mother has the same gene and 1/2 that she transmits that gene to the child so 1/8 x 1/2 = 1/16. Thus, a first-cousin marriage has a coefficient of inbreeding f =1/16. The added risks to the offspring of first cousins depend not only upon this coefficient of inbreeding but also upon the genetic family history and, in some cases, upon test results (as to beta thalassaemia, for instance, for first cousins of italian descent). There are always added risks from the mating of closely related persons. (12 Dec 1998) |
| isotonic coefficient | The amount of salts in the blood plasma, or the amount that should be added to distilled water in order to prepare an isotonic solution. (05 Mar 2000) |
| Ostwald's solubility coefficient | The milliliters of gas dissolved per milliliter of liquid and per atmosphere (760 mm of Hg) partial pressure of the gas at any given temperature. This differs from Bunsen's solubility coefficient (a) in that the amount of dissolved gas is expressed in terms of its volume at the temperature of the experiment, instead of STPD. Thus, lambda = a (1 + 0.00367t), where t = temperature in degrees Celsius. (05 Mar 2000) |
| oxygen utilization coefficient | The extraction coefficient for oxygen in any given tissue. (05 Mar 2000) |