Verbal noun of → brake.
Fr.: indice de freinage
A parameter indicating the rate at which a → pulsar slows down. Neutron stars are powered by → rotational energy and lose energy by accelerating particle → winds and by emitting → electromagnetic radiation. The → rotation frequency, Ω, thus decreases with time and this slowdown is usually described by the relation Ω. = - kΩn, where k is a positive constant which depends on the → moment of inertia and the → magnetic dipole moment of the → neutron star and n is the braking index. Conventionally, the braking index is derived by differentiation of the above equation, yielding n = ΩΩ.. / Ω.2. In a highly simplified model in which the spin-down torque arises from dipole radiation at the rotation frequency, one expects n = 3 (Johnston, S., Galloway, D., 1999, arXiv:astro-ph/9905058).
1) šâxé (#); 2) šâxé zadan (#)
Fr.: 1) branche; 2) se ramifier
1a) General: A shoot or arm-like limb of a tree; anything like a
limb of a tree; any offshoot from a main trunk.
M.E., from O.Fr. branche, from L.L. branca "a claw, paw."
1) Šâxé "branch," from Mid.Pers šâk, cf.
Mod.Pers. šâx, šax "branch; horn," Skt. sakha-
"a branch, a limb," Arm. cax, Lit. šaka,
O.S. soxa, PIE *kakhâ "branch."
The act of dividing into branches. → branching ratio.
Fr.: rapport de branchement
A quantity used to describe a → radionuclide that has more than one → decay mode. For a particular decay mode, the ratio of the number of atoms decaying by that decay mode to the number decaying in total: BRi = ki/(k1 + k2 + ...) = ki/k, where k is → decay constant.
In theoretical physics, an entity which can have any number of allowed spatial dimensions. It is usually accompanied by a prefix, i.e. p-brane, indicating the number of dimensions. For example, a 0-brane is a zero-dimensional point-like particle, a 1-brane is a → string, a 2-brane is a "membrane," and so forth. Our Universe is a 3-brane.
Brane, short for membrane, from L. membrana "parchment," from membrum "limb, member of the body," → member.
Breyn, loanword from E., as above.
1) šekastan; boridan; gosastan; 2) šekast; boreš, boré; gosast
Fr.: 1) couper, rompre; 2) brisure, coupure
1) To separate into parts or fragments violently; to become broken.
From break, from M.E. breken, O.E. brecan, from P.Gmc. *brekan (cf. Du. breken, O.H.G. brehhan, Ger. brechen), from PIE base *bhreg- "to break" (see also → fraction).
1) Šekastan, škan- "to break, split;"
Mid.Pers. škastan "to break;" Av. scind-, scand
"to break, cleave;" Proto-Iranian *skand- "to break, cleave;"
PIE sken- "to cut off."
Fr.: luminosité de coupure
A characteristic luminosity around which the → luminosity function of a sample of galaxies changes to a steeper slope or exponentially declines.
Fr.: vitesse de rupture
The velocity of a → rotating star at which the → centrifugal force equals the → gravitational force. Also known as → critical velocity. The simplest expression of the break-up velocity for an OB star, ignoring the → Eddington luminosity, is given by the relation: v = (GM / R)1/2, where M and R are the mass and radius of the star respectively, and G the → gravitational constant. A more realistic expression takes into account not only the → radiation pressure, but also the non-uniformity of the brightness over the stellar surface, as indicated by → von Zeipel theorem. With these conditions, the break-up velocity has a more complicated formula, corresponding to the velocity reached when somewhere on the star the → total gravity becomes zero.
A rock composed of angular fragments (over two millimeter diameter) of older rocks melded together with a matrix of smaller particles or a mineral cement.
From It. breccia "broken (rock)," from a Germanic source akin to O.H.G. brecha "a breaking," ultimately from PIE *bhreg- "to break," → fraction.
Bereš, loan from Fr.
To form as → breccia.
Characterized by, converted into, or resembling a breccia; especially of a rock structure marked by an accumulation of angular fragments, or of an ore texture showing mineral fragments without notable rounding.
Fr.: roche bréchifiée
A rock formed by the process of → brecciation.
The formation of → breccia.
Verbal noun of → brecciate.
A wind or current of air, especially a light or moderate one (2-14 m/sec).
From O.Sp. briza "cold northeast wind;" alternatively from East Frisian brisen "to blow fresh and strong."
Nasim "gentle breeze," from Ar.
Fr.: processus Breit-Wheeler
The production of an → electron-positron pair in the → collision of two → gamma ray → photons (γγ → e+e-). It is the → inverse process of → Dirac annihilation (e+e-→ γγ). The Breit-Wheeler process is the simplest way by which pure → light can be potentially transformed into → matter. However, as of 2014, this process has never been observed in practice because of the difficulty in preparing colliding → gamma ray beams.
Breit, G. & Wheeler, J. A. 1934, Collision of two light quanta. Phys. Rev. 46, 1087; → process.
Fr.: rayonnement de freinage, bremsstrahlung
Bremsstrahlung, from Ger. Bremse "brake" + Strahlung "radiation," from strahlen "to radiate," from Strahl "ray," from O.H.G. strala "arrow, stripe;" PIE *ster- "to spread."
zâviye-ye Brewster (#)
Fr.: angle de Brewster
Fr.: point de Brewster
A → neutral point located 15 to 20° directly below the Sun.
Fr.: loi de Brewster
The amount of the polarization of light reflected from a surface is a maximum when the reflected ray is at right angles to the refracted ray. See also → polarizing angle.
Named after Sir David Brewster (1781-1868), Scottish physicist; → law.