| drift feeder | Fish and other predators that forage on invertebrates drifting on the water surface or in the water column. (09 Oct 1997) |
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| feeder | 1. One who, or that which, gives food or supplies nourishment; steward. "A couple of friends, his chaplain and feeder." (Goldsmith) 2. One who furnishes incentives; an encourager. "The feeder of my riots." 3. One who eats or feeds; specifically, an animal to be fed or fattened. "With eager feeding, food doth choke the feeder." (Shak) 4. One who fattens cattle for slaughter. 5. <physics> A stream that flows into another body of water; a tributary; specifically, a water course which supplies a canal or reservoir by gravitation or natural flow. 6. A branch railroad, stage line, or the like; a side line which increases the business of the main line. 7. <chemical> A small lateral lode falling into the main lode or mineral vein. A strong discharge of gas from a fissure; a blower. 8. <machinery> An auxiliary part of a machine which supplies or leads along the material operated upon. 9. <engineering> A device for supplying steam boilers with water as needed. Source: Websters Dictionary (01 Mar 1998) |
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| feeder layer | <cell culture> In order to culture some cells, particularly at low or clonal density, it is necessary to use a layer of less fastidious cells to condition the medium. Often the cells of the feeder layer are irradiated or otherwise treated so that they will not proliferate. In some cases the feeder layer may be producing growth factors or cytokines. (18 Nov 1997) |
| antigenic drift | <immunology> A change that occurs on the molecular level to effect a change in the antigenicity of a bacteria or virus. Antigenic drift occurs naturally and more rapidly in certain viruses (for example HIV). It is antigenic drift which complicates the development of an effective HIV (AIDS) vaccine. (27 Sep 1997) |
| genetic drift | <genetics> The random change of the occurance of a particular gene in a population, genetic drift is thought to be one cause of speciation when a group oforganisms is separated from its parent population. (09 Oct 1997) |
| pure random drift | That which has random components only with an average value of zero and no systematic effects. Brownian movement in a still container shows pure random drift but in the Mississippi shows a steady downstream tendency. (05 Mar 2000) |
| drift | Collectively, stream invertebrates (almost wholly the aquatic larval stages of insects) that voluntarily or accidentally leave the substrate to move or float with the current, as well as terrestrial invertebrates that drop into the stream. Also, any detrital material transported in the water current. (09 Oct 1997) |
| drift cyclotron loss cone instabilities | (DCLC) This is an electrostatic microinstability (frequencies at harmonics of the ion cyclotron frequency) which is of major concern in small mirror devices. Mode is driven by radial gradients in the electron density, and causes loss of ions due to non-conservation of magnetic moment (see adiabatic invariant) as they interact with the mode, and are dispersed in velocity space into the loss cone. Stabilisation is accomplished by increasing the plasma size and by partially filling the loss cone with a continuous extermal warm plasma stream. (09 Oct 1997) |
| drift line | An accumulation of water-carried debris along a contour or at the base of vegetation that provides direct evidence of prior inundation and often indicates the directional flow of flood waters. (09 Oct 1997) |
| drift motion | <radiobiology> Ordinarily particles placed in a magnetic field will simply orbit in circles, but if the magnetic field is not uniform, or curves, or there is an electrical field perpendicular to the magnetic field, or another force is applied perpendicular to the magnetic field, then the guiding centres of the particle orbits will drift (generally perpendicular to the magnetic field and to the applied force). (09 Oct 1997) |
| drift movements | Slow ocular movements of greater amplitude than flicks, occurring during ocular fixation. Synonym: drift movements. (05 Mar 2000) |
| drift pumping | <radiobiology> A process that removes ions trapped in a thermal barrier using radial transport induced by an externally-applied radiofrequency field tuned to resonate with the azimuthal drift frequency. (09 Oct 1997) |
| drift surface | <radiobiology> Surface on which the guiding centre of a particle is constrained to move, due to the effects of the laws of adiabatic invariance on its drift motion. (09 Oct 1997) |
| drift velocity | <radiobiology> Characteristic velocity at which the centre of a particle's orbit (guiding centre) drifts when drift motion (see above) occurs. (09 Oct 1997) |
| drift wave | <radiobiology> Oscillations in a magnetically-confined plasma arising in the presence of density gradients (such as at the plasma's surface). These resemble the waves that propagate at the interface of two fluids with different density in a gravitational field. (09 Oct 1997) |