| Tyndall effect | The visibility of floating particles in gases or liquids when illuminated by a ray of sunlight and viewed at right angles to the illuminating ray. Synonym: Tyndall effect. (05 Mar 2000) |
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| extrapyramidal effect | A combination of neurologic effects which includes tremors, chorea, athetosis and dystonia. A common side effect of neuroleptic agents (phenothiazines). Other medications known to cause these reactions include haloperidol, molindone, perphenazine & amitriptyline, loxapine, pimozide and rarely, benzodiazepines. (27 Sep 1997) |
| Fahraeus-Lindqvist effect | The decrease in apparent viscosity that occurs when a suspension, such as blood, is made to flow through a tube of smaller diameter; observed in tubes less than about 0.3 mm in diameter. Synonym: sigma effect. (05 Mar 2000) |
| Zeeman effect | The splitting of spectral lines into three or more symmetrically placed lines when the light source is subjected to a magnetic field. (05 Mar 2000) |
| Fenn effect | The increased liberation of heat in a stimulated muscle when it is allowed to do mechanical work; the amount of heat liberated is increased in proportion to the distance the muscle is allowed to shorten and in proportion to the tension it must develop (e.g., the weight it lifts) during shortening; thus increased chemical energy is consumed both to liberate increased heat and to do increased mechanical work. (05 Mar 2000) |
| zygotic effect gene | <genetics> A gene whose phenotype is dependent on the genotype of the zygote, rather than the genotype of the mother. See: maternal effect gene. (18 Nov 1997) |
| late effect | Side effects of chemotherapy and/or radiotherapy which only become apparent with long-term monitoring of the patient over a period of years. These are of particular concern in patients below the age of puberty. (18 Nov 1997) |
| founder effect | The establishment of a new population by a few original founders (in an extreme case, by a single fertilized female) which carry only a small fraction of the total genetic variation of the parental population [Ernst Mayr, 1963]. The result is that a given allele, gene, chromosome, or part of a chromosome found in members of the population can be traced back to one ancestral individual. (09 Oct 1997) |