| electrophoresis, gel, pulsed-field | Electrophoresis in which the direction of the electric field is changed periodically. This technique is similar to other electrophoretic methods normally used to separate double-stranded DNA molecules ranging in size up to tens of thousands of base-pairs. However, by alternating the electric field direction one is able to separate DNA molecules up to several million base-pairs in length. (12 Dec 1998) |
|---|---|
| electrostatic field | <radiobiology> The region surrounding an electric charge in which another charge experiences a force. (16 Dec 1997) |
| toroidal field coils | <radiobiology> Coils in a toroidal system, typically wound around the torus in a solenoid-like arrangement, used to generate the toroidal magnetic field. Each turn completely surrounds the plasma. (09 Oct 1997) |
| track and field | Sports performed on a track, field, or arena and including running events and other competitions, such as the pole vault, shot put, etc. (12 Dec 1998) |
| unit of magnetic field intensity | See: gauss, tesla. (05 Mar 2000) |
| field | <radiobiology> In physics, any macroscopic quantity which exists (and typically varies) throughout a region of space. Standard examples include Electric and Magnetic fields, velocity flow fields, gravitational fields, etc. (09 Oct 1997) |
| field block | Regional anaesthesia produced by infiltration of local anaesthetic solution into tissues surrounding an operative field. (05 Mar 2000) |
| field block anaesthesia | Conduction anaesthesia in which small nerves are not anaesthetised individually, as in nerve block anaesthesia, but instead are blocked en masse by local anaesthetic solution injected to form a barrier proximal to the operative site. (05 Mar 2000) |
| field dependence-independence | The ability to respond to segments of the perceptual experience rather than to the whole. (12 Dec 1998) |
| field depth | <microscopy> The thickness of the object space within which objects focused by a lens will all appear in good simultaneous focus. Penetration is a synonym. (05 Aug 1998) |
| field diaphragm | <microscopy> In a photomicrographic system particularly, an iris diaphragm that is imaged in the field of view with Kohler illumination. This limits the extent of the illuminated field and eliminates much extraneous light. The iris diaphragm that is located in front of the collecting lens of the light source. With Kohler illumination, the condenser focuses the image of the field diaphragm onto the image plane. (05 Aug 1998) |
| field-emission microscope | <instrument, microscopy> Either one of two kinds of point-projection microscopes, both invented by E. W. Muller: (1) The older device (1936) is a specialised cathode-ray tube, employing field-emission of electrons from a negatively charged tip of a very sharp needle in a vacuum, by point-projection of the image onto a positively charged, fluorescent screen. (2) A later device (field-ion-mission microscope, 1950) emits absorbed helium ions from an anode. (05 Aug 1998) |
| field emission tube | An X-ray tube that uses a cold cathode, relying on the tube voltage to pull electrons from it to the anode. (05 Mar 2000) |
| field fever | A leptospirosis caused by leptospira. Synonym: canefield fever. (05 Mar 2000) |
| field gradient | In magnetic resonance imaging, a magnetic field that varies with location, superimposed on the uniform field of the magnet, to alter the resonant frequency of nuclei and allow recovery of their spatial position. Synonym: field gradient. (05 Mar 2000) |