nulling fraction (NF)
Fr.: fraction de phase d'arrêt
Fr.: activité optique
The property possessed by some substances and their solutions of rotating the plane of vibration of → polarized light. When a beam of → linearly polarized light is sent through an optically active substance, such as crystalline quartz and sugar solution, the direction of vibration of the emerging linearly polarized light is found to be different from the original direction. Those which rotate the → plane of polarization to the right, for an observer looking in the incoming beam, are called → dextrorotatory or right handed; those which rotate it to the left, → levorotatory or left handed. Optical activity may be due to an asymmetry of molecules of a substance (solutions of cane sugar) or it may be a property of a crystal as a whole (crystalline quartz).
Fr.: optiquement actif
Relating to → optical activity.
barxe-ye anbâštegi (#)
Fr.: coefficient de tassement
The difference between the isotopic mass of a nuclide and its mass number divided by its mass number. The packing fraction is a measure of the stability of the nucleus.
Packing, from the verb pack "to put together in a pack," from the noun pack, from M.E. pak, packe, from M.D. pac or perhaps M.L.G. pak; → fraction.
Barxé, → fraction; anbâštegi quality noun of anbâštan, anbârdan "to fill, to replete;" Mid.Pers. hambāridan "to fill;" from Proto-Iranian *ham-par-, from prefix ham- + par- "to fill;" cf. Av. par- "to fill," parav-, pauru-, pouru- "full, much, many;" O.Pers. paru- "much, many;" Mid.Pers. purr "full;" Mod.Pers. por "full, much, very;" PIE base *pelu- "full," from *pel- "to be full;" cf. Skt. puru- "much, abundant;" Gk. polus "many," plethos "great number, multitude;" O.E. full.
Of or pertaining to a parallax.
Adj. form of → parallax.
Fr.: angle parallactique
Of an object in the sky, the angle between the → celestial pole, the object, and the → zenith. Since parallactic angle describes the orientation on the sky of the object for a particular observer, it can be an important quantity in some observations.
Fr.: ellipse de parallaxe
The path on the sky of the apparent position of a star as seen from the Earth, due to the Earth's annual motion around the Sun.
Fr.: inégalité parallactique
An irregularity in the Moon's motion caused by the Sun's gravitational attraction, which sets the Moon ahead or behind its normal orbital position. The Moon is about 2 arcminutes ahead of its expected position at first quarter, and a similar amount behind at last quarter.
Fr.: mouvement parallactique
The proper motion of a star due to the effect of the Sun's motion relative to the → local standard of rest.
Of or pertaining to a → perigalacticon.
The point in an object's orbit around a galaxy when the object lies closest to the galactic center; opposite of → apogalacticon.
Fr.: fraction de polarisation
The ratio expressed by P = (Ipar - Iper) / (Ipar + Iper), where Ipar and Iper are the light intensities with the electric field vector respectively parallel and perpendicular to the incident beam.
That can be done or used or put into practice.
Concerned with practice, as opposed to → theory.
1) varzidan (#); 2) varzé (#)
Fr.: 1) pratiquer; 2) pratique
1a) To do habitually or regularly.
M.E. practisen, practizen; O.Fr. practiser "to practice," from M.L. practicare "to do, perform," from L.L. practicus "practical," from Gk. praktikos "practical."
1) Varzidan "to practice, perform; to accustom oneself to; to labor; to sow a field;"
Mid.Pers. warz- "to work, do, practice;"
Av. varəz- "to work, do, perform, exercise;" cf.
Gk. ergon "work;" Arm. gorc "work;" Lith. verziu "tie, fasten, squeeze,"
vargas "need, distress;" Goth. waurkjan; O.E. wyrcan "work,"
wrecan "to drive, hunt, pursue;" E. work;
PIE base *werg- "to work."
Actively following a specified career or way of life.
A professional man, especially in medicine and the law.
principle of action and reaction
parvaz-e žireš va vâžireš, ~ koneš va vâkoneš
Fr.: principe d'action et de réaction
Newton's third law of motion, which states that for every action there must be an equal and opposite reaction.
principle of least action
parvaz-e kamtarin žireš, ~ ~ koneš
Fr.: principe de moindre action
The principle that, for a system whose total mechanical energy is conserved, the path to be taken for the system from one configuration to another is the one whose action has the least value relative to all other possible paths and from the same configurations. Also called Maupertuis' principle, least-action principle.
A → radioactive → chemical element which is a malleable, shiny silver-gray metal; symbol Pa. → atomic number 91; → mass number of most stable isotope 231; → melting point greater than 1,600°C; → boiling point 4,026°C; calculated → specific gravity 15.37; → valence +4, +5. Protactinium has 24 → isotopes of which only three are found in nature. The most stable is protactinium-231 (→ half-life about 32,500 years); it is also the most common, being found in nature in all uranium ores in about the same abundance as radium. The element was discovered by Otto Hahn and Lise Meitner, who found one of its isotopes in 1917. It was isolated in 1934, by Aristid von Grosse.