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fermion fermion (#) Fr.: fermion An elementary particle, such as → electron, → proton, or → neutron, having a half integral value of → spin. Fermions obey the → Pauli exclusion principle. |
ferric iron âhan-e ferrik Fr.: fer ferrique, fer trivalent Iron in a plus-3 → oxidation state. Ferric iron needs to share three electrons with an oxygen molecule to make the ion neutral. |
ferrous iron âhan-e fervar Fr.: fer ferreux, fer bivalent Iron in a plus-2 → oxidation state. |
Fibonacci number 'adad-e Fibonacci Fr.: nombre de Fobonacci One of the numbers in the → Fibonacci sequence. → Fibonacci sequence; → number. |
Fibonacci sequence peyâye-ye Fibonacci Fr.: suite de Fibonacci An infinite sequence of integers, starting with 0 and 1, where each element is the sum of the two previous numbers. For example: 0, 1, 1, 2, 3, 5, 8, 13, 21, 34, 55, 89, 144, ... As the sequence develops, the ratio of the consecutive terms converges to the → golden ratio, about 1.618. Leonardo Pisano Fibonacci (1170-1250), medieval Italian mathematician who wrote Liber abaci (1202; Book of the Abacus), the first European work on Indian and Arabian mathematics, which introduced "Arabic" numerals in Europe; → sequence. |
fiction dizan Fr.: fiction 1) Literary works invented by the imagination, such as novels or short stories. M.E., from O.Fr. ficcion "dissimulation, ruse; invention, fabrication" and directly from L. fictionem "a fashioning or feigning," noun of action from p.p. stem of fingere "to shape, form, devise, feign," originally "to knead, form out of clay," from PIE *dheigh- "to build, form, knead;" akin to Skt. dehah "body," literally "that which is formed," dih- "to besmear;" Gk. teikhos "wall;" L. fingere "to form, fashion," Gothic deigan "to smear;" O.Irish digen "firm, solid." Formed on the model of fiction, as above, from diz- "to build, to form;" (related to Pers. dež, dez "fortress"); cf. Mid.Pers. dys-/dēs- "to build;" Sogd. dys "to build;" Av. (+ *pari-) daēz- "to build (around);" Proto-Ir. *daiz- "to build, form;" from PIE *dheigh- "to build, form," as above, + suffix -an. |
field equation hamugeš-e meydân Fr.: équation de champ In a physical theory, an equation that describe how a fundamental force interacts with matter. Einstein's equations of → general relativity are called field equations since they describe the → gravitational field. Similarly, → Maxwell's equations describe the electromagnetic field. |
field horizontal branch star setâre-ye šâxe-ye ofoqi-ye meydâni Fr.: étoile de la branche horizontal du champ A → horizontal branch star with high velocity. → field; → horizontal; → branch; → star. |
field rotation carxeš-e meydân Fr.: rotation de champ The effect of the Earth's rotation on the position of the image formed on the → focal plane of a telescope during long exposures. In the case of → equatorial mounting, the image remains fixed, whereas it turns continuously with an → altazimuth mounting. In the latter case the image motion must be compensated by an appropriate mechanism, → field rotator. |
fine-structure constant pâyâ-ye sâxtâr-e nâzok Fr.: constante de la structure fine A measure of the strength of → interaction between a → charged particle and the → electromagnetic field. It is a → dimensionless number expressed (in → cgs units) by α = e^{2}/ħc, where e is the → electron charge, ħ is the → reduced Planck's constant, and c is the → speed of light. It is approximately equal to 1/137 or 7.3 x 10^{-3}. The smallness of this number is of great importance since it determines the size of → atoms and the → stability of → matter. → fine structure; → constant. |
fingering convection hambaz-e angoštvâr Fr.: A weak yet important kind of mixing that results from → fingering instability in stars within → radiative zones that have an unstable mean → molecular weight → gradient. Also called → thermohaline convection. → finger; → -ing; → convection. |
finite population porineš-e karânmand Fr.: population finie A → statistical population consisting of individuals or items which are finite in number. → finite; → population. |
first approximation nazdin-e naxost Fr.: première approximation 1) Generally, an expression to indicate that a comment or result is
only approximate. → first; → approximation. |
first contact parmâs-e naxost Fr.: premier contact 1) The beginning of a → solar eclipse when the eastern part of
the lunar limb touches the western limb of the Sun, marking
the beginning of an eclipse. |
first degree equation hamugeš-e daraje-ye yekom Fr.: équiation du premier degré A equation in which the highest → exponent of the → variable is 1. Same as → linear equation. |
first-order differential equation hamugeš-e degarsâne-yi-ye râye-ye naxost Fr.: équation différentielle du premier ordre A → differential equation containing only the first → derivative. For example, dy/dx = 3x and 2y(dy/dx) + 3x = 5. → first; → order; → differential; → equation. |
fission šekâft (#) Fr.: fission 1) The act or process of splitting or breaking into parts. Fission, from L. fissionem "a breaking up, cleaving," from root of findere "to split." Šekâft, stem of šekâftan "to split, break, tear," akin to kaftan, kâftan "to split; to dig," Parthian Mid.Pers. q'f- "to split;" Sogdian kβ "to split;" Chorasmian kf- "to split, be split;" Proto-Iranian *kap-, *kaf- "to split." |
fission products farâvardehâ-ye šekâft (#) Fr.: produits de fission Nuclides generated by the fission of higher mass elements or by subsequent radioactive decay of nuclides directly generated by fission. |
fissionable šekâftpazir (#) Fr.: fissile The material that can be fissioned by fast neutrons, such as uranium-238. Commonly used as a synonym for → fissile material. |
fixation barjâyeš Fr.: fixation The act of fixing or the state of being fixed. |
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