| 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) |
| acid wave | A temporary increase in the acidity of the urine occurring during fasting. Synonym: acid wave. (05 Mar 2000) |
| alkaline wave | A period of urinary neutrality or even alkalinity after meals due to withdrawal of hydrogen ion for the purpose of secretion of the highly acid gastric juice. Synonym: alkaline wave. (05 Mar 2000) |
| alpha wave | Brain waves in the encephalogram which have a frequency of 8 to 13 per second. They are typical of the normal person awake and in a quiet resting state, and occur principally in the occipital region. (12 Dec 1998) |
| arterial wave | A wave in the jugular phlebogram due to transmission of carotid artery pulsation. B wave, the initial positive deflection in the electroretinogram, possibly arising from the inner nuclear layer of the retina. (05 Mar 2000) |
| A wave | The initial negative deflection in the electroretinogram, presumably reflecting retinal photoreceptor activity, an atrial deflection in an electrocardiogram recorded from within the atrium of the heart, the first positive deflection of the atrial and venous pulses due to atrial systole. (05 Mar 2000) |
| beta wave | <neurology> Brain waves in the electroencephalogram which have a frequency of 18 to 30 per second. They are typical during periods of intense activity of the nervous system, and occur principally in the parietal and frontal regions. (12 Dec 1998) |
| brain wave | Colloquialism for electroencephalogram. (05 Mar 2000) |
| brain wave complex | A specific combination of fast and slow electroencephalographic activity that recurs frequently enough to be identified as a discrete phenomenon. (05 Mar 2000) |
| brain wave cycle | The complete upward and downward excursion of a single wave, complex, or impulse as seen on an electroencephalogram. (05 Mar 2000) |
| brain wave test | <investigation> A diagnostic test which measures the electrical activity of the brain (brain waves) using high sensitive recording equipment attached to the scalp by fine electrodes. Commonly employed in the evaluation of neurological disease (for example seizures, epilepsy, etc.). Acronym: EEG (13 Nov 1997) |