| Gibbs' theorem | Substances that lower the surface tension of the pure dispersion medium tend to collect in its surface, whereas substances that raise the surface tension tend to remain out of the surface film. (05 Mar 2000) |
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| bayes theorem | A theorem in probability theory named for thomas bayes (1702-1761). In epidemiology, it is used to obtain the probability of disease in a group of people with some characteristic on the basis of the overall rate of that disease and of the likelihoods of that characteristic in healthy and diseased individuals. The most familiar application is in clinical decision analysis where it is used for estimating the probability of a particular diagnosis given the appearance of some symptoms or test result. (12 Dec 1998) |
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| Bernoulli's theorem | <physics> When friction is negligible, the velocity of flow of a gas or fluid through a tube is inversely related to its pressure against the side of the tube; i.e., velocity is greatest and pressure lowest at a point of constriction. Synonym: Bernoulli's principle, Bernoulli's theorem. (05 Mar 2000) |
| central limit theorem | The sum (or average) of n realizations of the same process, provided only that it has a finite variance, will approach the gaussian distribution as n becomes indefinitely large. This theory provides a broad warrant for the use of normal theory even for nongaussian data. In the form stated here, it constitutes the classical version; more general versions allow serious relaxation of the usual assumptions. (05 Mar 2000) |
| theorem | 1. That which is considered and established as a principle; hence, sometimes, a rule. "Not theories, but theorems, the intelligible products of contemplation, intellectual objects in the mind, and of and for the mind exclusively." (Coleridge) "By the theorems, Which your polite and terser gallants practice, I re-refine the court, and civilize Their barbarous natures." (Massinger) 2. <mathematics> A statement of a principle to be demonstrated. A theorem is something to be proved, and is thus distinguished from a problem, which is something to be solved. In analysis, the term is sometimes applied to a rule, especially a rule or statement of relations expressed in a formula or by symbols; as, the binomial theorem; Taylor's theorem. See the Note under Proposition. Binomial theorem. <mathematics> A theorem which extends to any quantity without restriction. Origin: L. Theorema, Gr. A sight, speculation, theory, theorem, fr. To look at, a spectator: cf. F. Theoreme. See Theory. Source: Websters Dictionary (01 Mar 1998) |
| Gibbs | J. Willard, U.S. Mathematician and physicist, 1839-1903. See: Gibbs-Donnan equilibrium, Gibbs-Helmholtz equation, Helmholtz-Gibbs theory, Gibbs' theorem, Gibbs free energy, Gibbs energy of activation. (05 Mar 2000) |
| gibbs-donnan effect | The observation that charged molecules starting on one side of a semipermeable membrane sometimes will not evenly distribute themselves by diffusion on both sides of the membrane. This effect is probably because there are other charged substances already present which cannot move through the membrane themselves and which are creating an electric field that influences the movement of the incoming charged molecules. (09 Oct 1997) |
| Gibbs-Donnan equilibrium | An equilibrium established between a charged, immobile colloid (such as clay, ion exchange resin or cytoplasm) and a solution of electrolyte. Characteristics: ions of like charge to the colloid tend to be excluded, ions of opposite charge tend to be attracted, the colloid compartment is electrically polarized relative to the solution in the same direction as the colloid charges (a Donnan potential) and the osmotic pressure is higher in the colloid compartment. (18 Nov 1997) |
| Gibbs energy of activation | The Gibbs energy that must be added to that already possessed by a molecule or molecules in order to initiate a reaction. (05 Mar 2000) |
| gibbs free energy | The total amount of energy which is either used up or released during a chemical reaction. Gibbs free energy (delta G) = (delta H) - t (delta s): where (delta H) is the change in enthalpy, calculated by adding up the amount of energy released or used up to break or form chemical bonds during the reaction, t is the temperature at which the reaction took place, and (delta S) is the change in entropy, or amount of disorder, that occurs in the molecules involved during the reaction. (09 Oct 1997) |
| Gibbs-Helmholtz equation | An equation expressing the relationship in a galvanic cell between the chemical energy transformed and the maximal electromotive force obtainable. (05 Mar 2000) |
| Helmholtz-Gibbs theory | An equation expressing the relationship in a galvanic cell between the chemical energy transformed and the maximal electromotive force obtainable. (05 Mar 2000) |
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