| frequency | 1. <physics> The number of occurrences of a periodic or recurrent process per unit time, for example the number of vibrations of a particle per second or the number of repetitions of a complete wave form (cycles) per second. 2. <statistics> The number of members of a population or statistical sample falling in a particular class. 3. Relative frequency, the average number of occurrences of a particular event in a large number of repeated trials. (07 Apr 1998) |
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| frequency analysis | <ecology, statistics> A method of evaluating vegetation in an area by establishing a transect and counting the occurrences of plant species at various sampling points along the transect. (07 Apr 1998) |
| frequency curve | A systematic grouping of data into classes or categories according to the frequency of occurrence of each successive value or ranges of such values, resulting in a graph of a frequency distribution. Synonym: frequency curve. (05 Mar 2000) |
| frequency distribution | A statistical description of raw data in terms of the number or frequency of items characterised by each of a series or range of values of a continuous variable. (05 Mar 2000) |
| frequency domain | The expression of a function by its amplitude and phase at each component frequency, usually as determined by Fourier analysis. (05 Mar 2000) |
| frequency encoding | In magnetic resonance imaging, a method of varying the magnetic field strength with location to encode the location of each voxel uniquely in one direction. (05 Mar 2000) |
| frequency of micturition | Micturition at short intervals; it may result from increased urine formation, decreased bladder capacity, or lower urinary tract irritation. (05 Mar 2000) |
| frequency of occurrence | The number of times a given event occurs at specified sample points during a defined period. (07 Apr 1998) |
| frequency spectrum | The range of frequencies in a signal, used to describe the resolving power of an imaging system in radiology. (05 Mar 2000) |
| frequency, urinary | Urinating too often, at too frequent intervals, not due to an unusually large volume of urine, but rather to a decrease in the capacity of the bladder to hold urine. (12 Dec 1998) |
| bounce frequency | <physics> The average frequency of oscillation of a particle trapped in a magnetic mirror as it bounces back and forth between its turning points in regions of high magnetic field. (See also trapped particle, turning points, banana orbit). (09 Oct 1997) |
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| radio frequency current drive | <radiobiology> Plasma waves in the radio-frequency range can be used to push plasma particles in such a way that current forms in the plasma, this is a method of non-inductive current drive which would allow for steady-state fusion reactors to operate. (09 Oct 1997) |
| radio frequency heating | <radiobiology> Process for heating the plasma by transferring energy to ions or electrons using waves generated by an external oscillator at an appropriate frequency. (This is similar to how a microwave oven heats food.) There are various types: See: ECRH, ICRH, and Lower Hybrid. (09 Oct 1997) |
| 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) |
| gene frequency | The relative occurence (expressed as a percentage) of a gene in a given population. (09 Oct 1997) |
| recombination frequency | The frequency at which crossingover occurs between two chromosomal loci--the probability that twoloci will become unlinked during meiosis. (09 Oct 1997) |
| resonant frequency | The frequency at which individual magnetic nuclei absorb or emit radiofrequency energy in magnetic resonance studies. Synonym: resonance. (05 Mar 2000) |
| respiratory frequency | The number of breaths per minute. (05 Mar 2000) |
| collision frequency | <chemistry> The rate at which chemical species collide, used in theories of chemical kinetics. Also, the frequency with which gaseous molecules collide. (09 Oct 1997) |
| plasma frequency | <radiobiology> The natural collective oscillation frequency of a charge species (electrons, ions, etc.) in a plasma, in the absence of (or at least parallel to) a magnetic field. Also known as Langmuir or Langmuir-Tonks frequency. See: electrostatic waves, plasma oscillations. (09 Oct 1997) |
| mutational frequency | The proportions of mutations in a population. (05 Mar 2000) |
| critical flicker fusion frequency | The minimal number of flashes of light per second at which an intermittent light stimulus no longer stimulates a continuous visual sensation. (05 Mar 2000) |
| cyclotron frequency | <radiobiology> Number of times per second that a particle orbits a magnetic field line. The frequency is completely determined by the strength of the field and the particle's charge-to-mass ratio. (Often, and incorrectly, called the Larmor frequency. The cyclotron or gyrofrequency is twice the Larmor frequency of precession.) (09 Oct 1997) |
| hearing loss, high-frequency | Hearing loss in frequencies above 1000 hertz. (12 Dec 1998) |
| high frequency current | An alternating electric current having a frequency of 10,000 or more per second; it produces no muscular contractions and does not affect the sensory nerves. Synonym: d'Arsonval current, Tesla current. (05 Mar 2000) |