Fr.: écoulement laminaire
A flow in which the particles of fluid are moving orderly, and in which adjacent layers or laminas glide smoothly over another with little mixing between them. A laminar flow may rapidly transform into a → turbulent flow for large → Reynolds numbers.
Fr.: sous-couche laminaire
A layer in which the fluid undergoes smooth, nonturbulent flow. It is found between any surface and a turbulent layer above.
lâmp (#), cerâq (#)
Any of various devices producing artificial light, as by electricity, gas, or oil.
From O.Fr. lampe, from L. lampas, from Gk. lampas "torch, lamp, beacon, meteor, light," from lampein "to shine," from PIE base *lap- "to shine" (cf. Lith. lope "light," O.Ir. lassar "flame").
Lâmp, loanword from Fr., as above.
xoški (#), zamin (#)
Any part of the earth's surface not covered by a body of water.
M.E., from O.E. land, lond, "ground, soil, territory;" PIE base *lendh- "land, heath" (cf. O.N., O.Fris. Du., Ger., Goth. land; O.Ir. land; Welsh llan "enclosure, church," Breton lann "heath," source of Fr. lande; O.C.S. ledina "waste land, heath," Czech lada "fallow land").
nasim-e xoški (#)
Fr.: brise de terre
A coastal breeze blowing from land to sea after sunset, caused by the temperature difference when the sea surface is warmer than the adjacent land. The warmer air above the water continues to rise, and cooler air from over the land replaces it, creating a breeze.
Xoški "land," from xošk "dry;" Mid.Pers. xušk "dry;" O.Pers. uška- "mainland;" Av. huška- "dry;" cf. Skt. śuska- "dry, dried out;" Gk. auos "dry, dried up;" O.E. sēar "dried up, withered;" Lith. sausas "dry, barren."
Fr.: amortissement de Landau
The process wherein a → plasma gains energy at the expense of the → Langmuir wave. In the presence of the → Landau resonance, the particles in resonance moving slightly faster than the wave lose energy, while those moving slightly slower will gain energy. Since the Maxwellian distribution is decreasing with velocity, in a Maxwellian plasma, near the Landau resonance, there are more particles at lower velocities than at higher velocities. Also called collisionless damping.
Fr.: niveau de Landau
Fr.: résonance de Landau
Fr.: facteur de Landé
The constant of proportionality relating the separations of lines of successive pairs of adjacent components of the levels of a spectral multiplet to the larger of the two J-values for the respective pairs. The interval between two successive components J and J + 1 is proportional to J + 1.
After Alfred Landé (1888-1976), a German-American physicist, known for his contributions to quantum theory; → facteur.
Fr.: équation de Lane-Emden
Named after the American astrophysicist Jonathan Homer Lane (1819-1880) and the Swiss astrophysicist Robert Emden (1862-1940); → equation
Fr.: équation de Langevin
Equation of motion for a weakly ionized cold plasma.
Paul Langevin (1872-1946), French physicist, who developed the theory of magnetic susceptibility of a paramagnetic gas; → equation.
Fr.: onde de Langmuir
A disturbance of a → plasma in the form of a longitudinal, → electrostatic wave that propagates in the plasma due to variations in the plasma's electron density. More specifically, Langmuir waves are collective oscillations of inhomogeneous bunches of electrons displaced from their natural equilibrium, in which the inertia of the relatively massive ions serves to establish an electrostatic restoring force that tries to bring the electrons back to their equilibrium positions. → Landau damping causes dissipation of Langmuir waves as the electrons are either accelerated or decelerated so as to be in resonance with the phase velocity of the waves themselves.
Irving Langmuir (1881-1957), American chemist and physicist, Nobel Prize in Chemistry 1932; → wave.
Any means of conveying or communicating ideas; specifically, human speech.
M.E., from O.Fr. langage, from L. lingua "tongue; speech, language."
Zabân "tongue; language," from Mid.Pers. uzwân "tongue; language;" O.Pers. hzanm, hizânam "tongue," Av. hizuua-, hizū- "tongue;" cf. Skt. jivhā- "tongue;" L. lingua "tongue, speech, language;" O.Ir. tenge; Welsh tafod; Lith. liezuvis; O.C.S. jezyku; M.Du. tonghe; Du. tong; O.H.G. zunga; Ger. Zunge; Goth. tuggo; PIE base *dnghwa-.
Fr.: paléontologie linguistique
An approach in which terms reconstructed in the → proto-language are used to make inferences about its speakers' culture and environment.
Fr.: superamas Laniakea
A → supercluster of galaxies that includes our → Local Group and about 300 to 500 known → galaxy clusters and groups. Also called → Local Supercluster. If approximated as round, it has a diameter of 12,000 km s-1 in units of the → cosmic expansion or 160 megaparsecs, and encompasses about 1017 → solar masses. Our Local Group lies toward the outer regions of Laniakea. Its main components are the four previously known superclusters: → Virgo supercluster (the part where the → Milky Way resides), Hydra-Centaurus Supercluster (including the → Great Attractor, Antlia Wall, known as Hydra Supercluster, → Centaurus supercluster), Pavo-Indus Supercluster, and Southern Supercluster (including Fornax Cluster, Dorado and Eridanus clouds). The most massive galaxy clusters of Laniakea are Virgo, Hydra, Centaurus, Abell 3565, Abell 3574, Abell 3521, Fornax, Eridanus, and Norma. The Laniakea supercluster was discovered by Tully et al. (2014, Nature 513, 71).
From the Hawaiian words lani "heaven," and akea "spacious, immeasurable;" → supercluster.
Any of the series of 15 consecutive → chemical elements in the → periodic table from → lanthanum to lutetium (→ atomic numbers 57 to 71 inclusive). The atoms of these metals have similar configurations and similar physical and chemical properties. They are grouped apart from the rest of the elements in the → Periodic Table because they all behave in a similar way in chemical reactions. Also called → rare-earth element. International Union of Pure and Applied Chemistry currently recommends the name lanthanoid rather than lanthanide.
From the chemical element → lanthanum.
A soft, malleable, ductile, silver-white metallic → chemical element; symbol La. → atomic number 57; → atomic weight 138.9055; → melting point about 920°C; → boiling point about 3,460°C; → specific gravity 6.19 at 25°C; → valence +3. Lanthanum is a member of the → lanthanide group, also called → rare-earth elements. Two naturally occurring → isotopes of lanthanum are known, 139La (more than 99%) and 138La (less than 0.1%). The → half-life of 138La is 1.1 x 1011 years.
From lanthan- + suffix -um, variant of → -ium. The first component from Gk. lanthanein for "to lie hidden, to escape notice" because it hid in cerium ore and was difficult to separate from that rare-earth mineral. It was discovered in the form lanthanium oxide, called lanthana, by the Swedish surgeon and chemist Carl-Gustav Mosander (1797-1858) in 1839. Subsequently, in 1842, Mosander separated his lanthanium sample into two oxides; for one of these he retained the name lanthanum and for the other he gave the name didymium (or twin).
The French great mathematician, physicist, and astronomer Pierre-Simon Marquis de Laplace (1749-1827). → Laplace operator; → Laplace plane; → Laplace resonance; → Laplace transform; → Laplace's demon ; → Laplace's equation ; → Kant-Laplace hypothesis
Fr.: opérateur de Laplace
Same as → Laplacian.