| GDS | geriatric depression scale; Global Deterioration Scale; Gordon Diagnostic System [for attention diso... |
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| IRD | infantile Refsum syndrome; isorhythmic dissociation |
| ODC | oritidine decarboxylase; ornithine decarboxylase; oxygen dissociation curve |
| B0 | constant magnetic field in nuclear magnetic resonance |
| Bo | constant magnetic field in a magnetic resonance scanner |
| sedimentation constant | The constant s in Svedberg's equation for estimating the molecular weight of a protein from the rate of movement in a centrifugal field:where M is the molecular weight, R the gas constant, T the absolute temperature, D the diffusion constant (in square centimeters per second), V the partial specific volume of the protein, ρ the density of the solvent. The constant s, with dimensions of time per unit of field force (s = drb/dt /ω2ro where rb is the position at time t, r0 is the position at time 0, and ω is the angular velocity) is usually between 1 × 10-13 and 200 × 10-13 second. The Svedberg unit (S) is arbitrarily set at 1 × 10-13 second and is very often used to describe the sedimentation rate of macromolecules; e.g., 4 S RNA. Synonym: sedimentation coefficient. (05 Mar 2000) |
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| specificity constant | Ratio of the maximum velocity (Vmax) or kcat to the true Km value for a specific substrate in an enzyme-catalyzed reaction. (05 Mar 2000) |
| Newtonian constant of gravitation | A universal constant relating the gravitational force, f., attracting two masses, m1 and m2, toward each other when they are separated by a distance, r, in the equation: f = G(m1m2/r2); it has the value of 6.67259 × 10-8 dyne cm2 g-2 = 6.67259 × 10-11 m3 kg-1 s-2 in SI units. (05 Mar 2000) |
| decay constant | <physics, radiobiology> The fraction of the amount of a radionuclide that undergoes transition per unit time. Formally: Lamda=dP/dt Where dP is the probability of a given nucleus undergoing spontaneous nuclear transition in the time interval dt. (16 Dec 1997) |
| diffusion constant | For the translational diffusion of solutes, diffusion is described by Fick's First Law, that states that the amount of a substance crossing a given area is proportional to the spatial gradient of concentration and the diffusion constant (D), that is related to molecular size and shape. A useful derived relationship is that the mean square distance moved by molecules in time t is 6Dt. (18 Nov 1997) |
| disintegration constant | <physics, radiobiology> The fraction of the amount of a radionuclide that undergoes transition per unit time. Formally: Lamda=dP/dt Where dP is the probability of a given nucleus undergoing spontaneous nuclear transition in the time interval dt. (16 Dec 1997) |
| immunoglobulin constant region | That region of the immunoglobulin (antibody) molecule that is invariable in its amino acid sequence within any class of immunoglobulins. It confers the biological specificity to the ig and is grossly species specific. It comprises the c-terminus half of the light chains and three quarters or more of the heavy chains, all of the fc fragment, and the c-terminus half of the fab fragment. (12 Dec 1998) |
| time constant | That part of a circuit that determines the time interval over which the rate of electrical events will be averaged; in pulmonary physiology, the factors determining rate of flow in the airways. (05 Mar 2000) |
| transformation constant | <physics, radiobiology> The fraction of the amount of a radionuclide that undergoes transition per unit time. Formally: Lamda=dP/dt Where dP is the probability of a given nucleus undergoing spontaneous nuclear transition in the time interval dt. (16 Dec 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) |
| universal gas constant | <radiobiology> R = 8.314 x 10^7 ergs per degree C per mole. (09 Oct 1997) |
| flotation constant | Characteristic sedimentation behaviour of a lipoprotein fraction of plasma in a centrifugal field in a medium of appropriate density, achieved by adding a salt or D2O to the plasma. Synonym: negative S, Svedberg of flotation. (05 Mar 2000) |
| law of constant numbers in ovulation | The number of ova discharged at each ovulation is nearly constant for any given species. (05 Mar 2000) |
| acid-base balance | The normal balance between acid and base in the blood plasma, expressed in the hydrogen ion concentration or pH, resulting from the relative amounts of acidic and basic materials ingested and produced by body metabolism, compared to the relative amounts of acidic and basic materials excreted from the body and consumed by body metabolism; the normal state of acid-base balance is not one of neutrality, with equal concentrations of hydrogen and hydroxyl ions, but a more alkaline state with a certain excess of hydroxyl ions. Synonym: acid-base equilibrium. (05 Mar 2000) |
| acid-base equilibrium | A condition in which the net rate of acid or alkali production by the body is balanced by the net rate of acid or alkali excretion from the body, resulting in a stable concentration of hydrogen ions in the body fluids. (12 Dec 1998) |