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latitude varunâ Fr.: latitude The angle between a perpendicular at a location, and the
→ equatorial plane of the Earth.
→ longitude. See also: L. latitudo "breadth, width, size," from latus "wide," from PIE base *stela- "to spread" (cf. O.C.S. steljo "to spread out," Arm. lain "broad"). Varunâ, from var "breadth, side, breast," variant bar, Tabari vari "width," Mid.Pers. var "breast," Av. varah- "breast" (Sk. vara- "width, breadth") + -u a suffix forming adjectives; Av. vouru- "wide;" + -nâ a suffix of dimension. |
lattice jâré Fr.: réseau 1) A regular geometric arrangement of points in a plane or in space. From O.Fr. latiz "lattice," from late "lath, board, plank, batten" (Fr. latte); cf. O.H.G. latta "lath." Jâré, from jarra "net; snare," Afghan jâli "reticulated garment," Tabari jarazin "grilled apparatus used in a watercourse to gather thatch and trash;" cf. Skt. jāla- "net, snare, lattice." |
lattice energy kâruž-e jâré Fr.: énergie réticulaire The energy required to separate an ion from a → crystal to an infinite distance. In other words, the energy released when one → mole of a crystal is formed from gaseous ions. |
latus rectum târ-e râst Fr.: latus rectum The chord through a focus and perpendicular to then major axis of a conic section. L. latus "side;" rectum "straight," → right. Târ "thread, warp, string" (related to tur "net, fishing net, snare," tâl "thread" (Borujerdi dialect), tân "thread, warp of a web," from tanidan, tan- "to spin, twist, weave;" Mid.Pers. tanitan; Av. tan- to stretch, extend;" cf. Skt. tan- to stretch, extend;" tanoti "stretches," tántra- "warp; essence, main point;" Gk. teinein "to stretch, pull tight;" L. tendere "to stretch;" Lith. tiñklas "net, fishing net, snare," Latv. tikls "net;" PIE base *ten- "to stretch." |
lava godâzé (#) Fr.: lave Molten → magma released from a volcanic vent or fissure. Lava, from It. lava "torrent, stream," from L. lavare "to wash;" PIE base *lou- "to wash;" cf. Persian Lori, Kurdi, Malâyeri laf "flood," variants Tabari lé, [Mo'in, Dehxodâ] lur, lây "flood;" Gk. louein "to wash." |
law qânun (#), arté (#) Fr.: loi 1) A rule of conduct or procedure established by custom, agreement,
or authority. M.E., O.E. lagu, from O.N. *lagu, variant of lag "that which is laid down;" cf. Ger. liegen, E. lay, lie; PIE *legh- "To lie, lay;" compare with Hittite laggari "falls, lies," Gk. lekhesthai "to lie down," L. lectus "bed," O.Ir. lige "bed, tomb," Tokharian lake, leke "bed." Qânun, from Ar., ultimately from Gk. kanon "rule." |
law of cosines qânun-e kosinushâ Fr.: loi des cosinus An expression that for any triangle relates the length of a side to the cosine of the opposite angle and the lengths of the two other sides. If a, b, and c are the sides and A, B, and C are the corresponding opposites angles: a^{2} = b^{2} + c^{2} - 2bc cos A; b^{2} = c^{2} + a^{2} - 2ca cos B; c^{2} = a^{2} + b^{2} - 2ab cos C. |
law of excluded middle qânun-e miyâni soklândé Fr.: principe du milieu exclu Same as → principle of excluded middle. |
law of identity qânun-e idâni Fr.: principe d'identité Same as → principle of identity. |
law of inertia qânun-e laxti (#) Fr.: loi d'inertie Same as → Newton's first law. The → reference frames to which the law applies are called → inertial frames. |
law of non-contradiction qânun-e nâpâdguyi Fr.: principe de non-contradiction Same as → principle of non-contradiction. → law; → non-; → contradiction. |
law of reflection qânun-e bâztâb (#) Fr.: loi de réflexion One of the two laws governing reflection of light from a surface: a) The → incident ray, normal to surface, and reflected ray lie in the same plane. b) The → angle of incidence (with the normal to the surface) is equal to the → angle of reflection. → law; → reflection. |
law of refraction qânun-e šekast (#) Fr.: loi de réfraction One of the two laws governing → refraction of light when it enters another transparent medium: a) The → incident ray, normal to the surface, and refracted ray, all lie in the same plane. b) → Snell's law is satisfied. → law; → refraction. |
law of sines qânun-e sinushâ Fr.: loi des sinus In any triangle the sides are proportional to the sines of the opposite angles: a/sin A = b/sin B = c/sin C, where A, B, and C are the three vertices and a, b, and c are the corresponding sides. |
lawrencium lawrensiom (#) Fr.: lawrencium An artificially produced → radioactive→ chemical element; symbol Lr (formerly Lw). → Atomic number 103; → atomic weight of most stable isotope 262; → melting point about 1,627°C; → boiling point and → specific gravity unknown; → valence +3. The longest half-life associated with this unstable element is 3.6 hour ^{262}Lr. Credit for the first synthesis of this element in 1971 is given jointly to American chemists from the University of California laboratory in Berkeley under Albert Ghiorso and the Russian team at the Joint Institute for Nuclear Reactions lab in Dubna, under Georgi N. Flerov. Named the American physicist Ernest 0. Lawrence (1901-1958), who developed the → cyclotron, + → -ium. |
laws of dynamics qânunhâ-ye tavânik Fr.: lois de dynamique The three basic laws of → dynamics which were first formulated by Isaac Newton in his classical work "Mathematical Principles of Natural Philosophy" published in 1687. → Newton's first law of motion; → Newton's second law of motion; → Newton's third law of motion. |
layer lâyé (#) Fr.: couche A thickness of some material laid on or spread over a surface. From M.E. leyer, legger + -er. The first element from layen, leggen "to lay," from O.E. lecgan; cf. Du. leggen; Ger. legen; O.N. legja; Goth. lagjan Lâyé "layer," from lâ, lây "fold" + -é nuance suffix of nouns. |
Layzer-Irvine equation hamugeš-e Layzer-Irvine Fr.: équation de Layzer-Irvine The ordinary Newtonian energy conservation equation when expressed in expanding cosmological coordinates. More specifically, it is the relation between the → kinetic energy per unit mass associated with the motion of matter relative to the general → expansion of the Universe and the → gravitational potential energy per unit mass associated with the departure from a homogeneous mass distribution. In other words, it deals with how the energy of the → Universe is partitioned between kinetic and potential energy. Also known as → cosmic energy equation. In its original form, the Layzer-Irvine equation accounts for the evolution of the energy of a system of → non-relativistic particles, interacting only through gravity, until → virial equilibrium is reached. But it has recently been generalized to account for interaction between → dark matter and a homogeneous → dark energy component. Thus, it describes the dynamics of local dark matter perturbations in an otherwise homogeneous and → isotropic Universe (P. P. Avelino and C. F. V. Gomes, 2013, arXiv:1305.6064). W. M. Irvine, 1961, Ph.D. thesis, Harvard University; D. Layzer, 1963, Astrophys. J. 138, 174; → equation. |
Le Chatelier's Principle parvaz-e Le Chatelier Fr.: principe de Le Chatelier A change in one of the variables (such as temperature, pressure, and concentration of various species) that describe a system at equilibrium produces a shift in the position of the equilibrium that counteracts the effect of this change. Named after the French chemist and engineer Henry Louis Le Chatelier (1850-1936); → principle. |
lead sorb (#) Fr.: plomb A metallic chemical element; symbol Pb (L. plumbum, of unknown origin). Atomic number 82; atomic weight 207.2; melting point 327.502°C; boiling point about 1,740°C. One of the oldest metals used by humanity, because of its relatively low melting point. O.E. lead, from W.Gmc. *loudhom (cf. O.Fris. lad, M.Du. loot "lead," Ger. Lot "weight, plummet"). Sorb, from Mid.Pers. srub "lead;" Av. sru- "lead." |
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