Modules for Experiments in Stellar Astrophysics (MESA)
An open-source, one-dimensional astrophysical code which is capable of calculating the evolution of stars in a wide range of environments. It works according to the → Henyey method and uses many modules that deal with various aspects of the theoretical models, such as the → equation of state (EOS), → nuclear reaction networks, → chemical composition, micro-physics, or macro-physics. The EOS and corresponding opacities or nuclear networks are provided in tabulated formats and can be selected by the user, while the micro-physics and macro-physics can be controlled by inlists of relevant parameters and settings (Paxton et al. 2015, ApJS 220, 15 and references therein).
Fr.: période naturelle
Of a body or system, the period of → free oscillation.
Fr.: température de bruit
A means for specifying the noise generated as unwanted → electromagnetic radiation in a receiver system or one of its components. It is usually measured in terms of the equivalent temperature in a → Rayleigh-Jeans spectrum. Noise temperature is used mainly in radio astronomy.
Fr.: milieu non dispersif
A medium in which the → phase velocity is independent of frequency.
Fr.: dispersion normale
The capability of being put into use, operation, or practice.
Capable of operating or of being operated.
To function or work; to make something function or work.
From L. operari "to work, labor," L. opus "a work, labor, exertion," Av. *āpah-, *apah- "to do, operate," see below, Skt. ápas- "work, action, religious act;" O.H.G. uoben "to start work, to practice, to honor;" Ger. üben "to exercise, practice;" Du. oefenen; O.E. æfnan "to perform, work, do," afol "power"); PIE base *op- "to work, perform."
Âpâridan, from âpâr-, from Av. *āp(ah)- "to do, operate," as above, + suffix -ar (as in vadar- "weapon," zafar- "jaw," baēvar- "thousand," and so on), shifted to -âr, + -idan suffix of infinitives. The Av. *āpah- "to do, operate," is extant in Mod.Pers. xub "good;" Mid.Pers. hwp, xub "good;" from Av. huuāpah- "doing good work, masterly," from huu-, hv- "good" → eu- + āpah- "work, deed," hauuapanha- "creativity;" cf. Skt. sv-ápas- "doing good work, skillful;" PIE base *op-, as above.
operating system (OS)
Fr.: système d'exploitation
1) General: An act or instance, process, or manner of functioning or operating.
Verbal noun of → operate
Pertaining to a process or series of actions for achieving a result.
Adj. of → operation.
Fr.: calcul opérationnel
A method of mathematical analysis which in many cases makes it possible to reduce the study of differential operators, pseudo-differential operators and certain types of integral operators, and the solution of equations containing them, to an examination of simpler algebraic problems. It is also known as operational analysis.
In the philosophy of science, the view that → concepts are defined in terms of measuring operations which determine their applicability. Same as operationism.
Math.: Something that acts on another function to produce another function. In linear algebra an "operator" is a linear operator. In calculus an "operator" may be a differential operator, to perform ordinary differentiation, or an integral operator, to perform ordinary integration.
dowre-ye medâri (#)
Fr.: période orbitale
The time interval between two successive passages of an object through the same point in its orbit around another object.
abar-now-axtar-e nâpâydâri-ye joft
Fr.: supernova à instabilité de paires
A special type of → supernova that would result from the → pair instability in → supermassive stars with a mass range between 140 and 260 Msun in a low → metallicity environment. Such objects descended from the → Population III stars in the early history of the Universe. Such supernovae are the most powerful thermonuclear explosions in the Universe. Pair-instability supernovae may have played an important role in the synthesis of → heavy elements. Moreover, the energetic feedback of the processed elements to their surroundings could have affected the structure and evolution of the early Universe (See, e.g., Fryer et al. 2001, ApJ 550, 372; Heger & Woosley 2002, ApJ 567, 532). See also → pulsational pair-instability supernova.
The hypothesis that life exists and is distributed throughout the Universe in the form of "seeds" that develop in the right environment. The oldest record of this idea may be traced back to the ancient Greek philospher Anaxagoras, who lived in the fifth century B.C.
N.L., from Gk. panspermia "mixture of all seeds," from → pan- + -sperm, a combining form of sperma "seed" + -ia a noun suffix.
Pân-dâne-vari, sarâsar-dâne-vari, from pân-, sarâsar-, → pan-, + dâné "seed, grain" (Mid.Pers. dân, dânag "seed, corn," Av. dânô- in dânô.karš- "carrying grains; an ant," Skt. dhânâ- "corn, grain," Tokharian B tâno "grain," cf. Lith. duona "corn, bread") + -var suffix of possession, variant -ur (Mid.Pers. -uwar, -war; from O.Pers. -bara, from bar- "to bear, carry") + -i noun suffix.
1) kâqaz; 2) vetâr (#)
1) A thin sheet made from fibrous material (wood pulp, rags, straw, etc.)
suitable for writing or printing on.
From M.E. papire, from L. papyrus "paper," from Gk. papyros "any plant of the paper plant genus," may be of Egyptian origin.
Kâqaz "paper," probably a transliteration of old Chinese gu zhi; cf. Sogd. kāγaδā "paper," Skt. kakali, kakari, Marathi kagad, Tamil kagidam, Malayalam kayitam (Y. Kumar, 2005, A History of Sino-Indian Relations).
parts per million (ppm)
pâr dar milion
Fr.: partie par million
A fraction of a whole number in units of 1/1000,000. It is usually used to describe chemical concentrations, very small amounts of pollutants in air, water, body fluids, and uncertainty. For example 30 ppm is 3 x 10-5 or 0.003%.
Pascal's barrel experiment
âzmâyeš-e celik-e Pascal
Fr.: expérience du tonneau de Pascal
An experiment carried out by Blaise Pascal in 1646 to demonstrate the hydraulic pressure. A long and narrow vertical pipe was connected to the content of a closed wooden barrel already full of water. He poured a small quantity of water into the pipe, whereby the height of the fluid within the pipe sharply increased. Due to the increase in hydrostatic pressure and → Pascal's law, the barrel could leak and even burst.