| radiofrequency | 1. Radiant energy of a certain frequency range; e.g., radio and television employ radiant energy having a frequency between 105-1011 Hz, while diagnostic X-rays have a frequency in the range of 3 × 1018 Hz. 2. In magnetic resonance imaging, the energy applied to switch or create a gradient in the magnetic field. (05 Mar 2000) |
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| radio frequency or radiofrequency | <physics> Term used to describe electromagnetic radiation with frequencies less than infrared, but greater than audio frequencies, i.e., greater than about 15,000 Hz. Wavelengths are therefore less than about 20,000 km and greater than about 0.01 mm. (These numbers are not precise.) (09 Oct 1997) |
| radiofrequency plugging | <radiobiology> Use of axial ponderomotive force to plug an open-ended device. First demonstrated on RFC-XX, Institute of Plasma Physics, Nagoya University, Nagoya, Japan, and later demonstrated in the Phaedrus device at the University of Wisconsin. (09 Oct 1997) |
| radiofrequency pulse | In nuclear magnetic resonance, a short electromagnetic signal used to change the direction of the magnetic field. See: sequence pulse. (05 Mar 2000) |
| radiofrequency trapping | <radiobiology> Use of RF waves to pitch angle scatter particles flowing axially into a magnetic mirror cell. The particles are scattered out of the loss cone and are trapped. (See entries for pitch angle scattering, magnetic mirror, loss cone.) (09 Oct 1997) |
| bacterial interference | The condition in which colonization by one bacterial strain prevents colonization by another strain. (05 Mar 2000) |
| viral interference | A phenomenon in which infection by a first virus results in resistance of cells or tissues to infection by a second, unrelated virus. (12 Dec 1998) |
| microscopy, interference | Microscopy in which physiological and photometric contrast in the image is influenced or produced by the action of optical components which regulate interference. (12 Dec 1998) |
| cuspal interference | A condition of tooth contact's which diverts the mandible from a normal path of closure to centric jaw relation. Synonym: cuspal interference, interceptive occlusal contact, premature contact. (05 Mar 2000) |
| Newton's interference colours | <microscopy> Newton's series of colours by interference results when two wave-trains of white light meet. For some wavelengths (colours) there will be destructive interference (darkness) but for other wavelengths there will be reinforcement (colour). They are most frequently observed in very thin films, only wavelengths thick, for example, oil on water. The interference is caused by partially reflected light from the interfaces. Newton's series of colours appears in sequence in the Michel-Levy chart. (05 Aug 1998) |
| differential interference contrast | <technique> A mode of contrast generation in microscopy that yields an image with a shadow relief. The relief reflects the gradient of optical path difference. Differential Interference Contrast, which is a form of interferenc microscopy that uses polarizing beam splitters, can be of the Smith or Nomarski type. Acronym: DIC (05 Aug 1998) |
| dissociation by interference | The simultaneous operation of two separate cardiac pacemaking foci that are unassociated because of interference (a normal physiologic phenomenon) due to rendering their respective territories refractory to each other. Usually atrioventricular dissociation is indicated, the rates being quite close to each other with the atrial rate slightly faster than that of the pacemaker in control of the ventricles. Capture is in either direction, usually the ventricle by the atrium, in incomplete dissociation. H Synonym: dissociation by interference. (05 Mar 2000) |
| interference | Opposition or hampering of an action or procedure. Origin: L. Ferire = to strike (18 Nov 1997) |
| interference beat | Ventricular capture in forms of A-V dissociation due to interference. (05 Mar 2000) |
| interference colours | <microscopy> Michel-Levy colour chart of birefringence/retardation vs. Thickness. (05 Aug 1998) |