| selection cutting | The periodic removal at short intervals of the oldest and largest trees in the stand, individually or in small groups. (05 Dec 1998) |
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| selection (genetics) | Differential and non-random reproduction of different genotypes, operating to alter the gene frequencies within a population. (12 Dec 1998) |
| selection pressure | Impact of effective reproduction due to environmental impact on the phenotype. (05 Mar 2000) |
| sexual selection | A form of natural selection in which, according to Darwin's theory, the male or female is attracted by certain characteristics, form, colour, behaviour, etc., in the opposite sex; thus modifications of a special nature are brought about in the species. (05 Mar 2000) |
| natural selection | The hypothesis that genotype environment interactions occurring at the phenotypic level lead to differential reproductive success of individuals and hence to modification of the gene pool of a population. (18 Nov 1997) |
| insurance selection bias | Adverse of favourable selection bias exhibited by insurers or enrollees resulting in disproportionate enrollment of certain groups of people. (12 Dec 1998) |
| k selection | <zoology> In evolution, the selection of traits that aid an organisms competitive capability when the population is at or near its carrying capacity. (21 Mar 1998) |
| atrioventricular gradient | The diastolic pressure difference between the atrium and ventricle. (05 Mar 2000) |
| ventricular gradient | The algebraic sum of (i.e., the net electrical difference between) the area enclosed within the QRS complex and that within the T wave in the electrocardiogram. (05 Mar 2000) |
| voltage gradient | <physiology> Literally, the electric field in a region, defined as the potential difference between two points divided by the distance between them. Used more loosely, the potential difference across a plasma membrane. (18 Nov 1997) |
| centrifugation, density gradient | Separation of particles according to density by employing a gradient of varying densities. at equilibrium each particle settles in the gradient at a point equal to its density. (12 Dec 1998) |
| cesium chloride gradient centrifugation | A type of density gradient centrifugation, a lab technique used to separate or purify nucleic acids. It involves putting cesium chloride and the nucleic acids into a centrifuge to be spun for hours or days. The cesium chloride forms a density gradient (highly dense at the bottom, thinnest at the top), and the different nucleic acids separate along the gradient according to their buoyancies in different densities. (09 Oct 1997) |
| gradient | <physics> Mathematical term for the operator which determines the magnitude and direction of the greatest rate-of-change of a given function with position. Similarly used to describe such a rate-of-change. For instance, at a given point on a hill, the slope of the hill in the steepest uphill direction is the gradient of the altitude function for the hill. (09 Oct 1997) |
| gradient elution | Elution in column chromatography in which a changing pH or ionic strength is used to separate substances. (05 Mar 2000) |
| gradient encoding | In magnetic resonance imaging, the technique of inducing a gradient in the magnetic field in the Y-axis to induce phase differences with location. Synonym: gradient encoding. (05 Mar 2000) |