natural line broadening
pahneš-e zâstâri-ye xatt
Fr.: élargissement naturel de raie
The broadening of any spectral line due to the fact that excited levels have mean lives, which, by virtue of the uncertainty principle, implies a spread in the energy values.
Fr.: logarithme naturel
The logarithm in which the → base is the → irrational number e = 2.718281828.... Also called → Napierian logarithm. The natural logarithm is denoted ln, an abbreviation of logarithmus naturalis. Natural logarithms are related to → common logarithms through: ln x = (1/M) log x, with M = (1/ln 10) ≅ 0.434294.
Fr.: nombre naturel
Either a member of the set of positive integers 1, 2, 3, ..., or the set of non-negative integers 0, 1, 2, 3, ... There seems to be no general agreement about whether to include 0 in the set of natural numbers.
Fr.: période naturelle
Of a body or system, the period of → free oscillation.
Fr.: résonance naturelle
A resonance such that the period of the driving force is the same as the natural period of the system.
Fr.: satellite naturel
Fr.: science naturelle
A science that deals with matter, energy, their interrelations and transformations, In other words, natural sciences are concerned with physical processes observable in nature. They can be divided into physical and biological sciences.
Fr.: unités naturelles
Physical units of measurement defined in terms of universal physical constants in such a manner that some chosen physical constants (e.g. the speed of light, Planck's constant, Boltzmann's constant, etc.) are equal to unity. The use of natural units allows these constants to be omitted from mathematical equations, leading to simpler calculations.
Fr.: uranium naturel
Uranium as found in nature. It contains 0.7% uranium-235, 99.3% uranium-238, and a trace of uranium-234 by weight.
Philosophy: 1) The view of the world that takes account only of natural elements
and forces, excluding the supernatural or spiritual.
The natural world as it exists without human beings or civilization.
M.E. natur(e), from O.Fr. nature from L. natura "the things at the outset, as it was when brought into existence; conditions of birth; essence, natural qualities," from natus "born," p.p. of nasci "to be born," from PIE *gen- "to give birth, beget," cognate with Pers. zâdan "to give birth," as below.
Zâstâr, literally "birth," from zâst past stem of [Dehxodâ] zâstan, variant of zâdan "to bring forth, give birth;" (Lâsgardi, Sorxeyi, Aftari) nestor "barren, sterile" (Mid.Pers. zâtan; Av. zan- "to bear, give birth to a child, be born," infinitive zazāite, zāta- "born;" cf. Skt. janati "begets, bears;" L. gignere "to beget," nasci "to be born," as above, PIE base *gen- "to give birth, beget") + suffix -âr (forming verbal nouns as in raftâr, kerdâr, goftâr, didâr, jostâr, and so on; or forming accusative nouns, as in gereftâr, koštâr, etc.).
Fr.: astronomie nautique
The branch of practical astronomy concerned with the determination of position and direction on sea by observation of celestial objects.
Nautical, from M.Fr. nautique, from L. nauticus "pertaining to ships or sailors," from Gk. nautikos, from nautes "sailor," from naus "ship," from PIE *nau- "boat;" cf. Pers. nâv "ship;" O.Pers./Av. *nāv-, O.Pers. nāviyā- "fleet;" Skt. nau-, nava- "ship, boat;" → astronomy.
Axtaršenâsi→ astronomy; daryâ-navardik, relating to daryâ-navardi "sea navigation," from daryâ "sea" (Mid.Pers. daryâp variant zrah; O.Pers. drayah-; Av. zrayah- "sea;" cf. Skt. jráyas- "expanse, space, flat surface") + navardi, noun of navardidan, navardan "to travel, walk, pass by and over" + -ik, → -ic.
Fr.: crépuscule nautique
The period before sunrise and after sunset when the center of the Sun's disk is between 6° and 12° below the horizon.
Fr.: équation de Navier-Stokes
One of a set of differential equations that describes the motion of a fluid as a function of pressure, density, total external force, and viscosity. → Euler equation.
Named after Claude-Louis Navier (1785-1836), a French engineer and physicist, and George Gabriel Stokes (1819-1903), an English mathematician and physicist; → equation.
Fr.: astronomie nautique
Same as → nautical astronomy.
Navigational, adj. of navigation, from L. navigationem (nom. navigatio), from navigatus, p.p. of navigare "to sail, steer a ship," from navis "ship," cognate with Pers. nâv "ship," as below, + root of agere "to drive," → act; → astronomy.
Axtaršenâsi→ astronomy; nâvrâni "navigation," from nâv "ship;" O.Pers./Av. *nāv-, O.Pers. nāviyā- "fleet;" cf. Skt. nau-, nava- "ship, boat" + râni verbal noun of rândan "to drive, to cause to go," causative of raftan "to go, walk, proceed" (present tense stem row-, Mid.Pers. raftan, raw-, Proto-Iranian *rab/f- "to go; to attack").
Fr.: marée de morte-eau
Neap, from M.E. neep, from O.E. nepflod "neap tide" + → tide.
Close; to a point or place not far away.
O.E. near "closer, nearer," comparative of neah, neh "nigh."
Nazdik, from Mid.Pers. nazdik "near," from nazd "close" (Mid.Pers. nazd, nazdik "near," nazdist "first;" O.Pers. ašna- "close;" Av. nazdišta- "nearest, next," nazdyo "nearer to," nas- "to come near, approach, reach;" cf. Skt. nédīyas- "closer, very close," nas- "to approach, to reach") + -ik, → -ic.
farâbanafš-e nazdik (#)
Fr.: proche ultraviolet
The longest wavelengths of the ultraviolet region, which are adjacent to the visible, from 200 to 350 nm.
near-Earth asteroid (NEA)
Fr.: astéroïde géocroiseur
An → asteroid whose orbit lies partly between 0.983 and 1.3 → astronomical units from the Sun, so that it passes close to the Earth. Currently thousands of near-Earth asteroids are known, ranging in size up to about 30 km. Among them, there are between 500 and 1,000 such asteroids larger than one km in diameter. They are divided into three subclasses: → Amor asteroids, → Apollo asteroids, and → Aten asteroids. See also → near-Earth object.
near-Earth object (NEO)
An → asteroid, → comet, or large → meteoroid whose orbit brings it exceptionally close to the Earth, and which may therefore pose a collision danger. Most such objects are in orbits around the Sun with → perihelion distance less than 1.3 → astronomical units. See also → near-Earth asteroid.