| constant field equation | An equation derived to predict membrane potentials in terms of the membrane's permeability to ions and their concentrations on either side. Synonym: constant field equation, Goldman-Hodgkin-Katz equation, GHK equation. (05 Mar 2000) |
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| poloidal field | <physics> In toroidal devices, the magnetic field that encircles the plasma axis. (i.e., loops around the torus the short way.) (09 Oct 1997) |
| poloidal field coil | <radiobiology> In toroidal devices (e.g., tokamaks), the sets of windings which are (typically) aligned along the plasma axis and produce poloidal fields. These include ohmic heating, shaping, vertical, equilibrium, and divertor windings. (09 Oct 1997) |
| curvature of field | <microscopy> A property of lens that causes the image of a plane to be focused into a curved surface instead of a plane. The image plane formed by a single lens is naturally curved. While one part of the field will be in good focus, the rest will need refocusing to be sharp. While the eye may partially correct for this, a camera lens will not, and the final image as photographed will not be in perfect focus over the entire image plane. (05 Aug 1998) |
| prerubral field | See: fields of Forel. (05 Mar 2000) |
| pulsed-field gel electrophoresis | Gel electrophoresis in which, after electrophoretic migration has begun, the current is briefly stopped and reapplied in a different orientation; allows for the purification of long DNA molecules. Synonym: pulsed-field gel electrophoresis. (05 Mar 2000) |
| pulse field electrophoresis | <investigation> A method used for high resolution electrophoretic separation of very large (megabase) fragments of DNA. Electric fields 100 |
| pulse-field gel electrophoresis | Gel electrophoresis in which, after electrophoretic migration has begun, the current is briefly stopped and reapplied in a different orientation; allows for the purification of long DNA molecules. Synonym: pulsed-field gel electrophoresis. (05 Mar 2000) |
| nerve field | The regional distribution of nerve terminals. (05 Mar 2000) |
| dark-field condenser | An apparatus for throwing reflected light through the microscope field, so that only the object to be examined is illuminated, the field itself being dark. (05 Mar 2000) |
| dark field illumination | <microscopy> Any method of illumination which illuminates the specimen but does not admit light directly to the objective. It may be by substage (dark field) condensers, by stagespot lighting, by special condensers fitted around special objectives for reflected illumination or by the slit ultramicroscope. (05 Aug 1998) |
| dark field imaging | <microscopy> Using a single diffracted beam to form the image in a transmission electron microscope. This causes all regions of the specimen not of the same crystal structure and orientation as the region which produced the diffracted beam to be represented as very dark in the final image, allowing phase differentiation visually in the transmission electron microscope. (05 Aug 1998) |
| dark-field microscope | <instrument> A microscope that has a special condenser and objective with a diaphragm or stop that scatters light from the object observed, with the result that the object appears bright on a dark background. (05 Mar 2000) |
| dark field microscopy | <procedure> A system of microscopy in which particles are illuminated at a very low angle from the side so that the background appears dark and the objects are seen by diffracted and reflected patches of light against a dark background. (18 Nov 1997) |
| dark field objective | <microscopy> Certain objectives for high-power, dark fieldwork equipped with iris diaphragms or funnel stops so that their apertures may be reduced to correspond to the dark field con-denser with which they are used. (05 Aug 1998) |