| CSR | central supply room; chart-stimulated recall [test]; Cheyne-Stokes respiration; continued stay revie... |
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| ESR | Einstein stoke radius; electric skin resistance; electron spin resonance; equipment service report; ... |
| SECRET | stiffness of joint, elderly individuals, constitutional symptoms, arthritis, elevated erythrocyte se... |
| SED | sedimentation rate; skin erythema dose; spondyloepiphyseal dysplasia; standard error of deviation; s... |
| sed | sedimentation; stool [Lat. sedes] |
| concentration gradient | <chemistry> A column of liquid in which the density varies continually with position, usually as a consequence of variation of concentration of a solute. Such gradients may be established by progressive mixing of solutions of different density as for example: sucrose gradients) or by centrifuge induced redistribution of solute (as for caesium chloride gradients). Density gradients are widely used for centrifugal and gravity induced separations of cells, organelles and macromolecules. The separations may exploit density differences between particles or primarily differences in size, in which latter case the function of the gradient is chiefly to stabilise the liquid column against mixing. (12 Jan 1998) |
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| critical gradient | <botany> The maximum stable inclination of an unsupported slope under the most adverse conditions that it will likely experience, as determined by current engineering technology. (09 Oct 1997) |
| 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) |
| pseudospatial gradient sensing | <cell biology> Mechanism for sensing a gradient of a diffusible chemical in which the cell sends protrusions out at random, up gradient protrusions are stabilised by positive feedback (because receptor occupancy is rising with time) and others are transitory because of adaptation. Possibly the mechanism by which neutrophils sense chemotactic gradients. (18 Nov 1997) |
| 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) |
| sense of equilibrium | The sense that makes possible a normal physiologic posture. Synonym: static sense. (05 Mar 2000) |
| systolic gradient | The difference in pressure during systole between two communicating cardiovascular chambers, e.g., between the left ventricle and aorta in aortic stenosis. (05 Mar 2000) |
| 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) |
| dynamic equilibrium | Balance A condition in which no further net change is occuring in a system, and free energy is minimimal. (09 Oct 1997) |
| thermodynamic equilibrium | <radiobiology> There is a very general result from statistical mechanics which states that, if a system is in thermodynamic equilibrium with another (or several other) system, all processes by which the systems can exchange energy must be exactly balanced by their reverse processes, so that there is no net exchange of energy. For plasma systems in thermodynamic equilibrium, ionisation must be balanced by recombination, Bremsstrahlung by absorption, and so on. When thermodynamic equilibrium exists, the distribution function of particle energies and excited energy levels of the atoms can be obtained from the Maxwell-Boltzmann distribution (which is a function only of the temperature). The Saha equation is a special application of this. (09 Oct 1997) |
| electrochemical gradient | A measure of the tendency of an ion to move passively from one point to another, taking into consideration the differences in its concentration and in the electrical potentials between the two points; commonly expressed as the additional voltage needed to achieve equilibrium. (05 Mar 2000) |
| equilibrium | Balance A condition in which no further net change is occuring in a system, and free energy is minimimal. (09 Oct 1997) |
| equilibrium centrifugation | A type of density gradient centrifugation used to separate proteins or nucleic acids from a mixture. (09 Oct 1997) |
| equilibrium constant | <chemistry> The ratio of the reverse and forward rate constants for a reaction of the type: A + B = AB at equilibrium the equilibrium constant (K) equals the product of the concentrations of reactants divided by the concentration of product and has dimensions of concentration. Kd = (concentration A.concentration B) / (concentration AB). The affinity constant (Ka) is the reciprocal of the equilibrium constant. Dimension: moles per litre. In general the concept of Kd is more readily understood than that of Ka, for example: in considering the conversion of A to AB by the binding of ligand B, the Kd = B when A = AB. Thus Kd is equal to the ligand concentration which produces half maximal conversion (response). (10 Jan 1998) |