A specialist in → biophysics.
The science that deals with biological structures and processes involving the application of physical principles and methods.
The part of a planet or moon within which life can occur. It may include the crust, oceans, and atmosphere.
qânun-e Biot-Savart (#)
Fr.: loi de Biot-Savart
The → magnetic field due to → electric current flowing in a long straight conductor is directly proportional to the current and inversely proportional to the distance of the point of observation from the conductor. The law is derivable from → Ampere's law, but was obtained experimentally by the authors.
Named after the French physicists Jean-Baptiste Biot (1774-1862) and Félix Savart (1791-1841); → law.
Fr.: environnement biotique
Ecology: The environment consisting of living organisms, which interact with each other and with their non-living surroundings.
The science concerned with the functions of life, or vital activity and force.
Having two poles; having two opposite main structures or components.
Fr.: flot bipolaire
Same as → bipolar outflow.
Fr.: jet bipolaire
One of two beams of high-temperature, ionized gas ejected in two opposite directions associated with a → protostar. The collimated jets, a consequence of the → accretion process, can extend over distances of several → light-years.
Fr.: nébuleuse bipolaire
An interstellar cloud of ionized gas with two main lobes which lie symmetrically on either side of a central star. The bipolar shape is generally due to the ejection of material by the central star in opposing directions.
Fr.: flot bipolaire
A flow of gaseous material in two opposite directions emanating from protostellar regions or from → evolved stars during the early post-→ AGB evolution. In protostellar regions → molecular outflows are pushed by → bipolar jets.
A property of some crystalline materials (e.g. calcite, quartz) which have different indices of refraction associated with different crystallographic directions. Therefore, the crystal splits incident transmitted light into two beams, each polarized perpendicularly to the other. Also called double refraction.
Došekast, from do- "two," → bi- + šekast "breaking," from šekastan "to break up," Mid.Pers. škastan, Av. skand- "to break."
došekastgar, došekasti (#)
Of or relating to → birefringence.
pâlâye-ye došekastgar, ~ došekasti
Fr.: filtre biréfringent
A type of narrow-band filter that uses the birefringence to produce selective absorption of polarized light.
Fr.: vide biréfringent
Empty space undergoing → vacuum birefringence.
Fr.: théorème de Birkhoff
For a four dimensional → space-time, the → Schwarzschild metric is the only solution of → Einstein's field equations which describes the gravitational field created by a spherically symmetrical distribution of mass. The theorem implies that the gravitational field outside a sphere is necessarily static, and that the metric inside a spherical shell of matter is necessarily flat.
The theorem was first demonstrated in 1923 by George David Birkhoff (1884-1944), an American mathematician; → theorem
1) zâymân; 2) zâdmân, zâd; 3) zâyeš
Fr.: 1) acouchement; 2;3 ) naissance
1) The act or process of bearing or bringing forth offspring.
M.E. byrthe; O.E. gebyrd; cf. O.H.G. giburt, Ger. geburt; PIE *bhrto, from *bher- "to bear."
1) Zâymân, from zây present stem of zâyidan, zâdan "to give birth"
Av. zan- "to bear, give birth to a child, be born,"
infinitive zazāite, zāta- "born;"
cf. Skt. janati "begets, bears;"
Gk. gignesthai "to become, happen;" L. gignere
"to beget," gnasci "to be born;" PIE base *gen-
"to give birth, beget") + -mân a suffix forming verbal nouns,
birth binary population (BBP)
porineš-e dorinhâ hengâm-e zâdmân
Fr.: population binaire à la naissance
In star formation models, the population of binary components formed via random pairing of stars distributed according to the → canonical IMF.
Fr.: ligne de naissance
The path in the → H-R diagram that continuously → accreting stars follow. Stars on the birthline are difficult to observe, because they are hidden by the → accretion disk and a dense → cocoon of → interstellar matter. The star becomes visible once a sufficient amount of the surrounding matter has been dispersed. It follows that the young starsare observed generally between the birthline and the → zero-age main sequence (ZAMS). Before hydrogen ignition, gravitational contraction and deuterium burning are the main energy sources for the star. The localization of the birthline depends on the deuterium → accretion rate. First introduced by R. Behrend & A. Maeder, 2001 (A&A 373, 190).