| MRF | Markov random field; medical record file; melanocyte-[stimulating hormone]-releasing factor; mesence... |
|---|---|
| RAM | random-access memory; rapid alternating movements; rectus abdominis muscle; rectus abdominis myocuta... |
| RBS | random blood sugar; Roberts syndrome; Rutherford backscattering |
| RDB | random double-blind [trial] |
| RM | radical mastectomy; random migration; radon monitor; range of movement; red marrow; reference materi... |
| random sample | A group selected randomly, solely by chance. (12 Dec 1998) |
|---|---|
| random sampling | A selection of elements by a formal randomizing device for purposes of inference about a population of inference from that population in such a way that the probability of each possible outcome may be precisely specified in advance; the inferences are necessarily stochastic. (05 Mar 2000) |
| random variable | A variable that may assume a set of values, each with fixed probabilities or probability densities (its distribution), in such a way that the total probability assigned to the distribution is unity; the random variable may be discrete, continuous, or mixed discrete-continuous. (05 Mar 2000) |
| random walk | <cell biology> A description of the path followed by a cell or particle when there is no bias in movement. The direction of movement at any instant is not influenced by the direction of travel in the preceding period. If changes of direction are very frequent, then the displacement will be small, unless the speed is very great and the object will appear to vibrate on the spot. Although the behaviour of moving cells in a uniform environment can be described as a random walk in the long term, this is not true in the short term because of persistence. (18 Nov 1997) |
| random waves | Wave's in the electroencephalogram which occur paroxysmally and asynchronously. (05 Mar 2000) |
| genetic equilibrium | A condition in which the rate of an allele's forward mutation is cancelled out by its rate of reverse mutation. (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) |
| chemical equilibrium | <chemistry> A state in a reversible chemical reaction at which the reactants are turning into products at the same rate as the products are turning back into the reactants, so that the amounts of each reactant and product remains constant. (09 Oct 1997) |
| mixed discrete-continuous random variable | <statistics> A random variable that may assume some values with probabilities and others with probability densities. For example, in a 35-year-old man with familial polyposis of the colon, the distribution of time until malignant disease occurs consists of a probability that he already has cancer (which would be assigned the waiting time 0), a probability density of developing it in the future and a probability that he will die of some other cause before he develops cancer. (05 Mar 2000) |
| physiologic equilibrium | nutritive equilibrium |
| continuous random variable | Continuous variable that may randomly assume any value in its domain but any particular value has no probability of occurring, only a probability density. (05 Mar 2000) |
| Hardy-Weinberg equilibrium | <genetics> In a population containing the genotypes of AA, aa, and Aa, the frequency of AA will be p2, the frequency of aa will be q2, and the frequency of Aa will be 2 pq at equilibrium, where p is the frequency of A and q is the frequency of a. By the Hardy-Weinberg law, a ramdonly-mating population will eventually reach these frequencies and be at this equilibrium as long as there are no selection pressures on the population. (09 Oct 1997) |
| sample, random | A group selected randomly, solely by chance. (12 Dec 1998) |
| secular equilibrium | A type of radioactive equilibrium in which the half-life of the precursor (parent) radioisotope is so much longer than that of the product (daughter) that the radioactivity of the daughter becomes equal to that of the parent with time. Stable equilibrium, equilibrium in which, after every small perturbation, the original state will tend to be restored. Transient equilibrium, a type of radioactive equilibrium in which the half-life of the parent radioisotope is longer than that of the daughter so that the ratio of activities of parent and daughter become constant as they decrease with time. Unstable equilibrium, equilibrium in which the response to a small perturbation will tend to make the perturbation greater (e.g., a logged feedback process of zero order). (05 Mar 2000) |
| homeostatic equilibrium | See: homeostasis. Nitrogenous equilibrium, a condition in which the amount of nitrogen excreted from the body equals that taken in with the food; nutritive equilibrium so far as protein is concerned. Nutritive equilibrium, condition in which there is a perfect balance between intake and excretion of nutritive material, so that there is no increase or loss in weight. Synonym: physiologic equilibrium. (05 Mar 2000) |