| quantum yield | The number of photons required for the formation of one oxygen molecule in photosynthesis. Varies from 8-14 depending on the system used to measure it. (18 Nov 1997) |
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| sputtering yield | <radiobiology> Number of target particles sputtered per incident particle, varies with target and plasma species and energy. (09 Oct 1997) |
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| sustained yield | The maintenance in perpetuity of regular, periodic harvest of wood resources from forest land without damaging the productivity of the land. (05 Dec 1998) |
| yield | <botany> Standing crop expressed as a rate, i.e., grams dry weight per metre square per day. (09 Oct 1997) |
| yield strength | The amount of stress at which a permanent (plastic) deformation in a component becomes measurable (usually taken as 0.2% permanent strain). (05 Mar 2000) |
| yield stress | The critical stress that must be applied to a material before it begins to flow, as in a Bingham plastic. (05 Mar 2000) |
| quantum | <unit> The fundamental unit of electromagnetic energy. (09 Oct 1997) |
| quantum efficiency | The number of photons required for the formation of one oxygen molecule in photosynthesis. Varies from 8-14 depending on the system used to measure it. (18 Nov 1997) |
| quantum evolution | An extremely rapid evolutionarychange in a single genetic lineage, thought to result from a sudden and radical change in the species'environment. (09 Oct 1997) |
| quantum limit | The shortest wavelength found in an X-ray spectrum. (05 Mar 2000) |
| quantum mottle | Mottle caused by the statistical fluctuation of the number of photons absorbed by the intensifying screens to form the light image on the film; faster screens produce more quantum mottle. (05 Mar 2000) |
| quantum rectum | See: Q.R. Origin: L. However much is correct (05 Mar 2000) |
| quantum requirement | The number of quanta of light absorbed required for the transformation of one molecule; the inverse of the quantum yield. (05 Mar 2000) |
| quantum satis | See: q.s. Origin: L. However much is enough Quantum sink, in radiological imaging, the stage at which statistical information reaches its lowest level because of a low photon flux. (05 Mar 2000) |
| quantum speciation | The rapid evolution of a newspecies from a small population that ispartially or totally isolated from the parent population, the rapidspeciation occurs due to geneticdrift and founder effect and usuallyinvolves a few mutations that have a big impact on the organisms' observable physical traits. (09 Oct 1997) |
| quantum sufficiat | See: q.s. Origin: L. However much is enough (05 Mar 2000) |