| OIF | observed intrinsic frequency; oil immersion field; Osteogenesis Imperfecta Foundation |
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| LCM | latent cardiomyopathy; left costal margin; leukocyte-conditioned medium; lowest common multiple; lym... |
| LED | light-emitting diode; lowest emitting dose; lupus erythematosus disseminatus |
| LEMO | lowest empty molecular orbital |
| LETD | lowest effective toxic dose |
| Mach effect | The appearance of a light or dark line on a radiograph where there is a concave or convex interface in the subject, a physiological optical form of edge enhancement. See: Mach's band. (05 Mar 2000) |
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| raman effect | <radiobiology> A phenomenon observed in the scattering of light as it passes through a transparent medium, the light undergoes a change in frequency and a random alteration in phase due to a change in rotational or vibrational energy of the scattering molecules. (09 Oct 1997) |
| gene dosage effect | In codominant alleles, the more or less linear relationship between the phenotypic value and the number of genes of one type substituted by another type. (05 Mar 2000) |
| generation effect | Variation in health status arising from the different causal factors of disease to which each successive generation born is exposed as it passes through life. (05 Mar 2000) |
| rebound effect | The characteristic of a drug to produce reverse effects when either the effect of the drug has passed or when the patient no longer responds to the drug. (18 Nov 1997) |
| Venturi effect | Term applied to the operation of a Venturi tube and similar systems. (05 Mar 2000) |
| mass effect | <neurology> Damage to the brain due the bulk of a tumour, the blockage of fluid or excess accumulation of fluid within the skull. (16 Dec 1997) |
| red drop effect | Experimental observation that the photosynthetic efficiency of monochromatic light is greatly reduced above 680 nm, even though chlorophyll absorbs well up to 700 nm. Led to the discovery of the two light reactions of photosynthesis. See: photosystems I and II. (18 Nov 1997) |
| 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) |
| maternal effect gene | Gene, usually required for early embryonic development, whose product is secreted into the egg by the mother. The phenotype is thus determined by the mother's, rather than the egg's, genotype. Compare:. Zygotic effect gene. See: egg polarity gene. (18 Nov 1997) |
| Pasteur effect | <biochemistry> Decrease in the rate of carbohydrate breakdown that occurs in yeast and other cells when switched from anaerobic to aerobic conditions. Results from a relatively slow flux of material through the biochemical pathways of respiration compared with those of fermentation. (18 Nov 1997) |
| Pasteur's effect | The inhibition of fermentation by oxygen, first observed by Pasteur; either not observed, or only slightly observed, in malignant tumours. Compare: Crabtree effect. (05 Mar 2000) |
| glucose effect | <biochemistry> The ability of the sugar glucose to block sugar metabolism by keeping the genes which make the enzymes involved in the early steps of sugar metabolism from making those enzymes. (09 Oct 1997) |
| greenhouse effect | The effect of certain gases in the Earth's atmosphere in trapping heat from the sun. (05 Dec 1998) |
| Rivero-Carvallo effect | Inspiratory increase in the systolic murmur of tricuspid insufficiency; the characteristic distinguishing tricuspid insufficiency from mitral insufficiency. (05 Mar 2000) |