coefficient (ko-e-fish´ent)

1. The expression of the amount or degree of any quality possessed by a substance, or of the degree of physical or chemical change normally occurring in that substance under stated conditions. 2. The ratio or factor that relates a quantity observed under one set of conditions to that observed under standard conditions, usually when all variables are either 1 or a simple power of 10. [L. co- + efficio (exfacio), to accomplish]
absorption c. 1. the milliliters of a gas at standard temperature and pressure that will saturate 100 ml of liquid; 2. the amount of light absorbed in passing through 1 cm of a 1 molar solution of a given substance, expressed as a constant in Beer-Lambert law; Cf. specific absorption c. 3. in x-ray, a measure of the rate of decrease of intensity of a beam in its passage through a substance, resulting from a combination of scattering and conversion to other forms of energy.
activity c. (gamma) See activity (2).
biological c. rarely used term denoting the energy expended by the body at rest.
Bunsen's solubility c. (a) the milliliters of gas STPD dissolved per milliliter of liquid and per atmosphere (760 mm Hg) partial pressure of the gas at any given temperature.
c. of consanguinity c. of inbreeding
correlation c. a measure of association that indicates the degree to which two variables have a linear relationship; this c., 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.
creatinine c. the number of milligrams of creatinine excreted daily per kilogram of body weight.
diffusion c. the mass of material diffusing across a unit area in unit time under a concentration gradient of unity.diffusion constant;
distribution c. the ratio of concentrations of a substance in two immiscible phases at equilibrium; the basis of many chromatographic separation procedures.partition c;
economic c. in growth and cultivation of microorganisms, the ratio of the mass produced to the substrate consumed.
extinction c. (epsi) specific absorption c
extraction c. the percentage of a substance removed from the blood or plasma in a single passage through a tissue; e.g., the extraction c. for p-aminohippuric acid (PAH) in the kidney is the difference between arterial and renal venous plasma PAH concentrations, divided by the arterial plasma PAH concentration.
filtration c. a measure of a membrane's permeability to water; specifically, the volume of fluid filtered in unit time through a unit area of membrane per unit pressure difference, taking into account both hydraulic and osmotic pressures.
Hill c. the slope of the line in a Hill plot; a measure of the degree of cooperativity.Hill constant;
hygienic laboratory c. Rideal-Walker c
c. of inbreeding the probability that the individual concerned is homozygous by descent at an autosomal locus picked at random; equal to the c. of kinship of the parents.c. of consanguinity;
isotonic c. 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.
c. of kinship the probability that two genes at the same locus, picked at random from each of two individuals, are identical by descent.
lethal c. that concentration of disinfectant that kills bacteria at 20-25°C in the shortest period of time.
linear absorption c. that fraction of ionizing radiation absorbed in a unit thickness of a substance or tissue. See also absorption c. (3).
Long's c. Long's formula
molar absorption c. (epsi) absorbance (of light) per unit path length (usually the centimeter) and per unit of concentration (moles per liter); a fundamental unit in spectrophotometry.absorbancy index (2) , absorptivity (2) , molar absorbancy index, molar absorptivity, molar extinction c;
molar extinction c. molar absorption c
Ostwald's solubility c. (LAMBDA) 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 c. (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.
oxygen utilization c. the extraction c. for oxygen in any given tissue.
partition c. distribution c
permeability c. a c. associated with simple diffusion through a membrane that is proportional to the partition coefficient and the diffusion coefficient and inversely proportional to membrane thickness.
phenol c. Rideal-Walker c
Poiseuille's viscosity c. an expression of the viscosity as determined by the capillary tube method; the coefficient eta = (piPr4t / 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.
reflection c. (sigma) a measure of the relative permeability of a particular membrane to a particular solute; calculated as the ratio of observed osmotic pressure to that calculated from van't Hoff's law; also equal to 1 minus the ratio of the effective pore areas available to solute and to solvent.
c. of relationship the probability that a gene present in one mate is also present in the other and is derived from the same source.
reliability c. an index of the consistency of measurement often based on the correlation between scores obtained on the initial test and a retest (test-retest reliability) or between scores on two similar forms of the same test (equivalent-form reliability).
respiratory c. respiratory quotient
Rideal-Walker c. 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.hygienic laboratory c., phenol c;
sedimentation c. (s) sedimentation constant
selection c. (s) 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
specific absorption c. (a) absorbance (of light) per unit path length (usually the centimeter) and per unit of mass concentration. Cf. molar absorption c. absorbancy index (1) , absorptivity (1) , extinction c., specific extinction;
temperature c. the fractional change in any physical property per degree rise in temperature.
ultrafiltration c. the filtration c. of a semipermeable membrane.
c. of variation (CV) the ratio of the standard deviation to the mean.
velocity c. the rate of transformation of a unit mass of substance in a chemical reaction.
c. of viscosity the value of the force per unit area required to maintain a unit relative velocity between two parallel planes a unit distance apart.


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