From L. familia "household, the slaves of a household," from famulus "servant," of unknown origin.
Xânevâdé "family," from xâné "house, home, houshold" + vâdé "root, foundation, origin." Xâné, from Mid.Pers. xânak, xân, xôn; cf. L. cunae "cradle;" Gk. kome "village;" Pers. Aftari dialect kiye "house, home;" PIE base *kei- "bed; to lie, to settle; beloved" (other cognates: P.Gmc. *khaim-; O.E. ham "dwelling, house, village;" E. home; Ger. Heim; L. civis "townsman;" Fr. cité; E. city; Skt. śiva- "auspicious, dear").
family of curves
Fr.: famille de courbes
A set of similar curves which are distinguished by the values taken by one or more parameters in their general equation. For example, the general solution of a differential equation is represented by a family of curves.
family of distributions
Fr.: famille de distributions
A set of distributions which have the same general mathematical → formula.
family of sets
Fr.: famille de comètes
In 3D → magnetic reconnection models of solar plasma, a plane or curve surface composed of magnetic field lines emanating from the → magnetic null point (almost radially in the absence of electric currents and spirally if electric currents are present). See also → spine (Lau & Finn. 1990, ApJ 350, 672; Parnell et al. 1996, Physics of Plasmas 3, 759).
M.E., from O.E. fann, from L. vannus "a basket or shovel for winnowing grain," related to ventus, → wind.
Bâdzan "fan, ventilator," from bâd, → wind + zan from zadan "to strike, beat; to play an instrument; to do" (Mid.Pers. zatan, žatan; O.Pers./Av. jan-, gan- "to strike, hit, smite, kill" (jantar- "smiter"); cf. Skt. han- "to strike, beat" (hantar- "smiter, killer"); Gk. theinein "to strike;" L. fendere "to strike, push;" Gmc. *gundjo "war, battle;" PIE *gwhen- "to strike, kill").
Fanaroff-Riley Class I (FR-I)
rade-ye Fanarof-Riley I
Fr.: Fanaroff-Riley de type I
In the → Fanaroff-Riley classification, sources with RFR < 0.5. Fanaroff and Riley (1974) found that nearly all sources with luminosity L(178MHz) ≤ 2 × 1025h100-2 W Hz-1 sr-1 were of class I. FR-I → radio jets are thought to be → subsonic, possibly due to mass entrainment, which makes them amenable to distortions in the interaction with the ambient medium.
Fanaroff-Riley Class II (FR-II)
radeh-ye Fanarof-Riley II
Fr.: Fanaroff-Riley de type II
In the → Fanaroff-Riley classification, → radio sources with hotspots in their lobes at distances from the center which are such that RFR > 0.5. The → radio jets in FR-II sources are expected to be highly → supersonic, allowing them to travel large distances.
Fr.: classification Fanaroff-Riley
A classification scheme for distinguishing a → radio galaxy from an → active galaxy based on their → radio frequency and → luminosity and their kpc-scale appearance. Analyzing a sample of 57 radio galaxies from the → 3CR catalogue, which were clearly resolved at 1.4 GHz or 5 GHz, Fanaroff & Riley (1974) discovered that the relative positions of regions of high and low → surface brightness in the → lobes of extragalactic → radio sources are correlated with their radio luminosity. They divided the sample into two classes using the ratio RFR of the distance between the regions of highest surface brightness on opposite sides of the central galaxy or quasar, to the total extent of the source up to the lowest brightness contour in the map. → Fanaroff-Riley Class I (FR-I) , → Fanaroff-Riley Class II (FR-II). The boundary between the two classes is not very sharp, and there is some overlap in the luminosities of sources classified as FR-I or FR-II on the basis of their structures. The physical cause of the FR-I/II dichotomy probably lies in the type of flow in the → radio jets.
Bernard L. Fanaroff and Julia M. Riley, 1974, MNRAS 167, 31P; → classification.
Fr.: loin, lointain
Being at a great distance; remote in time or place.
O.E. feorr "to a great distance, long ago," from P.Gmc. *ferro (cf. Du. ver, Ger. fern), from PIE *per- "through, across, beyond" (cf. O.Pers. para "on the other side (of);" Av. parə "beyond, more than, superior," parô "except," pərətu- "crossing, bridge;" Mod.Pers. pol "bridge;" Skt. parás "far, further, beyond," Gk. pera "across, beyond," L. per "through").
Dur, from Mid.Pers. dūr "far, distant, remote;" O.Pers. dūra- "far (in time or space)," dūraiy "afar, far away, far and wide;" Av. dūra-, dūirē "far," from dav- "to move away;" cf. Skt. dūrá- "far; distance (in space and time);" PIE base *deu- "to move forward, pass;" cf. Gk. den "for a long time," deros "lasting long."
forusorx-e dur (#)
Fr.: infrarouge lointain
Infrared radiation in the wavelength range (25-40) to (200-350) microns emitted by cold molecular/dust clouds.
far ultraviolet (FUV)
farâbanafš-e dur (#)
Fr.: ultraviolet lointain
Ultraviolet radiation in the wavelength range 912-2000 Å. See also → extreme ultraviolet.
forusorx-e dur (#)
Fr.: infrarouge lointain
Named after the British physicist Michael Faraday (1791-1867), who made several major contributions to the fields of electricity and magnetism.
Fr.: cage de Faraday
An enclosure made of conducting material, such as wire mesh or metal plates, that shields what it contains from external electric fields. According to → Gauss's theorem, the electric field inside a hollow conductor is nil. In order to demonstrate this, Faraday, in 1836, made a large box covered with wire mesh, and went inside it himself with an → electroscope. Powerful charges were applied to the outside of the box, but he detected no effect inside the cage.
Fr.: effet Faraday
Same as → Faraday rotation.
carxeš-e Faraday (#)
Fr.: rotation Faraday
The rotation of the plane of → polarization experienced by a beam of → linearly polarized radiation when the radiation passes through a material containing a magnetic field with a component in the direction of propagation. This effect occurs in → H II regions in which a magnetic field causes a change in the polarized waves passing through. Same as → Faraday effect.
Faraday's law of induction
qânun-e darhazeš-e Faraday
Fr.: loi d'induction de Faraday
The induced → electromotive force in a circuit is equal in magnitude and opposite in sign to the rate of change of the → magnetic flux through the surface bounded by the circuit. Mathematically, it is expressed as: ∇ x E = -∂B/∂t, which is one of the four → Maxwell's equations.
Moving or able to move, operate, function, or take effect quickly; quick; swift; rapid (Dictionary.com).
M.E., from O.E. fæst "firmly fixed, steadfast;" O.Fr. fest, O.N. fastr, Du. vast, Ger. fest.
Tond "swift, rapid, brisk; fierce, severe," → velocity.
fast radio burst (FRB)
belk-e râdioyi-ye tond
Fr.: sursaut radio rapide, impulsion ~ ~
A bright → burst of → radio emission lasting only a few milliseconds, and thought to be of → extragalactic origin. The first ever detected such burst, called the → Lorimer burst, was in 2007. It lasted only 5 milliseconds, but the single radio → pulse was dispersed over a wide range of frequencies (→ dispersion measure). This suggested a → cosmic origin for the burst, because the radiation must have passed through very distant → intergalactic clouds to be so highly dispersed. The second FRB was detected in 2012 in archival data from the Parkes Radio Telescope, the same telescope through which the original burst was seen. No temporally coincident → X-ray or → gamma ray signature was identified in association with the bursts. Most recent results suggest FRBs as a new population of explosive events at cosmological distances of up to 3 → giga → parsecs, that is → redshifts of 0.5 to 1. While physical interpretations for this phenomenon remain speculative, they are thought to involve highly → compact objects, such as → neutron stars. See also → blitzar.