magnetic flux density
cagâli-ye šâr-e meqnâtisi (#)
Fr.: densité du flux magnétique
A vector quantity measuring the strength and direction of the magnetic field. It is the → magnetic flux per unit area of a magnetic field at right angles to the magnetic force. Magnetic flux density is expressed in → teslas. Also called → magnetic induction.
Fr.: intensité magnétique
Strength of a magnetic field at a point, denoted H. The force which could be exerted on unit north magnetic pole situated at that point. Measured in oersteds. Same as → magnetic field strength.
Fr.: densité massique
The mass per unit area of the ring material, integrated through the thickness of the ring. Sometimes called → surface density (Ellis et al., 2007, Planetary Ring Systems, Springer).
Fr.: rapport masse-luminosité
The ratio of the mass of a system, expressed in solar masses, to its visual luminosity, expressed in solar luminosities. The Milky Way Galaxy has a mass-luminosity ratio in its inner regions of about 10, whereas a rich cluster of galaxies such as the Coma Cluster has a mass-luminosity ratio of about 200, indicating the presence of a considerable amount of dark matter.
Fr.: relation masse-luminosité
A relationship between luminosity and mass for stars that are on the main sequence, specifying how bright a star of a given mass will be. Averaged over the whole main sequence, it has been found that L = M3.5, where both L and M are in solar units. This means, for example, that if the mass is doubled, the luminosity increases more than 10-fold.
maximum density of water
cagâli-ye bišine-ye âb
Fr.: densité maximale de l'eau
The density of pure water occurring at 3.98 °C, which is 1.0000 g cm-3, or 1000 kg m-3. Water when cooled down contracts normally until the temperature is 3.98 °C, after which it expands. Because the maximum density of water occurs at about 4 °C, water becomes increasingly lighter at 3 °C, 2 °C, 1 °C, and 0 °C (→ freezing point). The density of liquid water at 0 °C is greater than the density of frozen water at the same temperature. Thus water is heavier as a liquid than as a solid, and this is why ice floats on water. When a mass of water cools below 4 °C, the density decreases and allows water to rise to the surface, where freezing occurs. The layer of ice formed on the surface does not sink and it acts as a thermal isolator, thus protecting the biological environment beneath it. This property of water liquid is very unusual; molecules pack more closely than in the crystal structure of ice. The reason is that → hydrogen bonds between liquid water are not stable, they are continuously broken and new bonds are created. In the crystal structure of ice molecules have a fixed pattern creating empty space between molecules.
Fr.: position moyenne
Same as → mean place.
Fr.: proposition moléculaire
Fr.: relation morphologie-densité
An observationally determined relationship between the → morphological classification of galaxies and the → environments in which they are located. Specifically, the morphology-density relation indicates that early-type galaxies (→ ETG) are preferentially located in high density environments, whereas late-type galaxies (→ LTG) are preferentially found in low density environments. Hence, spiral galaxies are rare in the high densities of clusters and are common in the lower density group environments. Early-type galaxies, on the other hand, are common in clusters and are rarely found in isolation.
1) A nebulous form, shape, or mass.
1) The fact of being necessary or indispensable.
neutral density filter
pâlâye-ye cagâli-ye natâr
Fr.: filtre neutre
A filter having a flat response over the range of wavelengths of interest. Also called neutral filter or gray filter.
cagâli-ye haste-yi (#)
Fr.: densité nucléaire
The density of an atomic nucleus (about 1014 g/cm3).
Fr.: densité nmérique
Number of a particular type of object found in each unit volume.
1) ru-be-ru; 2) pâdistin; 3) pâdcem
Fr.: 1) opposé, d'en face; 2) contraire, opposé; 3) antonyme
1) Situated, placed, or lying face to face with something else or each
other, or in corresponding positions with relation to an intervening
line, space, or thing: opposite ends of a room (Dictionary.com).
M.E., from M.Fr., from L. oppositus, p.p. of opponere, → opposition.
1, 2) pâdist; 3, 4) pâdistân
1) The action of opposing, resisting, or combating.
Verbal noun of → oppose.
Pâdist "standing against," from pâd-
"agaist, contrary to," → anti-,
+ ist present stem of istâdan "to stand"
O.Pers./Av. sta- "to stand; to set;"
Av. hištaiti; cf. Skt. sthâ- "to stand;"
Gk. histemi "put, place, weigh," stasis "a standing still;"
L. stare "to stand;" Lith. statau "place;" Goth. standan;
PIE base *sta- "to set, stand").
Fr.: densité optique
The transmittance of a point on a photographic negative equal to the log to the base 10 of the reciprocal of the transmittance through the negative at that point.
Named after the German naturalist Peter Pallas (1741-1811), who first studied such a type of meteorites.
Fr.: luminosité du pic
The → bolometric luminosity of a → supernova corresponding to the highest brightness in its → light curve. The peak luminosity occurs after the → supernova explosion; it is directly linked to the amount of radioactive 56Ni produced in the explosion and can be used to test various explosion models. Following → Arnett's rule, one can derive the 56Ni mass from the peak luminosity of a → Type Ia supernova.