<< < -he Haf hal har har He hea hel hel Her Her hid hig hip hom hor hot Hub Hug hur hyd hyd hyg hyp > >>
hydrography âbnegâri (#) Fr.: hydrographie The study, measurement, and description of depths and currents in open seas, lakes, estuaries, and rivers. |
hydrologic cycle carxe-ye âbšenâsik (#), ~ âbšenâxti (#) Fr.: cycle hydrologique The vertical and horizontal transport of water in all its states between the earth, the atmosphere, and the seas; often called the water cycle. |
hydrology âbšenâsi (#) Fr.: hydrologie The study of the waters of the earth, especially with relation to the effects of precipitation and evaporation upon the occurrence and character of water in streams, lakes, and on or below the land surface. |
hydromagnetics hidromeqnâtik Fr.: hydromagnétisme Same as → magnetohydrodynamics. |
hydron hidron (#) Fr.: hydron The general name for the atomic hydrogen → cation H+. |
hydronium hidroniom Fr.: hydronium A → water, → molecule with an additional hydrogen ion (H3O+). Also called hydronium ion. Hydronium is an abundant molecular ion in the interstellar diffuse and dense molecular clouds (→ Sagittarius B2, → Orion molecular cloud OMC-1) as well as the plasma tails of → comets (→ Halley, → Hale-Bopp). From hydr-, → hydro- + -onium a suffix used in the names of complex cations, extrcated from ammonium "ionized ammonia" (NH4+). |
hydrosphere âbsepehr (#) Fr.: hydrosphère A term denoting the water portion of the Earth's surface. |
hydrostatic hidristâik Fr.: hydrostatique Of or pertaining to → hydrostatics. |
hydrostatic equation hamugeš-e hidristâik Fr.: équation hydrostatique The equation describing the → hydrostatic equilibrium in a star, expressed as: dP/dr = -GMρ/r2, where P and M are the mass and pressure of a spherical shell with thickness dr at some distance r around the center of the star, ρ is the density of the gas, and G the → gravitational constant. → hydrostatic; → equation. |
hydrostatic equilibrium tarâzmandi-ye hidristâik Fr.: équilibre hydrostatique 1) The physical situation reached in a fluid when complete balance exists between
the internal pressure at any point and the weight of the material above the point. → hydrostatic; → equilibrium. |
hydrostatic halo hâle-ye hidristâ Fr.: halo hydrostatique A model of the → Milky Way galaxy in which the → Galactic halo (composed of → gas, → magnetic fields, and → cosmic rays) is assumed to be in → hydrostatic equilibrium. Parker (1966) presented the first study of stability considerations between gas, magnetic fields and cosmic rays in an equilibrium configuration. He found that it is difficult to maintain a stable configuration due to magnetohydrodynamic self-attraction (→ Parker instability). Subsequent works taking into account turbulent motions showed that turbulent pressure can mitigate the influence of Parker instabilities. This enabled new attempts to find conditions under which a stable equilibrium configuration of the Galaxy could exist. → hydrostatic; → halo. |
hydrostatic pressure fešâr-e hidrotavânik Fr.: pression hydrodynamique The term ρgz in the → Bernoulli equation. It is not pressure in a real sense, because its value depends on the reference level selected. → hydrostatic; → pressure. |
hydrostatics hidristâyik Fr.: hydrostatique A branch of physics that deals with the characteristics of → fluids at rest and especially with the pressure in a fluid or exerted by a fluid on an immersed body. |
hydrothermal hidro-garmâyi Fr.: hydrothermique Geology: Relating to or caused by high temperature underground water or gas heated by natural processes. |
hydroxide hidroksid (#) Fr.: hydroxide A diatomic ion containing one oxygen and one hydrogen atom with chemical formula OH-. |
hydroxyl group (OH) goruh-e hidroksil (#) Fr.: groupe hydroxyle The univalent radical or group consisting of one hydrogen and one oxygen atom, forming a part of a molecule of a compound. From → hydro- + ox(y)- a combining form meaning "sharp, acute, pointed, acid," used in the formation of compound words, from Gk, oxys "sharp, keen, acid" + -yl a suffix used in the names of chemical radicals, from Fr. -yle, from Gk. hyle "matter, substance;" → group. |
Hydrus âbmâr (#) Fr.: Hydre mâle The Male Water Snake. A minor constellation with three main stars, one of the 15 → circumpolar constellations in the southern hemisphere. It first appeared in Johann Bayer's Uranometria of 1603. It is often confused with → Hydra, the large constellation further north. It is also referred to as "male Hydra" or "little Hydra." Abbreviation: Hyi; genitive: Hydri. From L., from Gk. hydros "water serpent." Âbmâr "water snake," from âb "water" (Mid.Pers. âb "water;" O. Pers. ap- "water;" Av. ap- "water;" cf. Skt. áp- "water;" Hitt. happa- "water;" PIE āp-, ab- "water, river;" cf. Gk. Apidanos, proper noun, a river in Thessalia; L. amnis "stream, river" (from *abnis); O.Ir. ab "river," O.Prus. ape "stream," Lith. upé "stream;" Latv. upe "brook") + mâr "snake, serpent" (Mid.Pers. mâr "snake;" Av. mairya- "snake, serpent"). |
hygro- nam- (#) Fr.: hygro- A combining form meaning "wet, moist, moisture," used in the formation of compound words: → hygrogram; → hygrograph; → hygrometer . Hygro-, from Gk, combining form of hygros "wet, moist." Nam "humidity, moisture" + -negâšt, → -gram. The first component nam, from Mid.Pers. nam, namb "moisture;" Av. napta- "moist," nabās-câ- "cloud," nabah- "sky;" cf. Skt. nábhas- "moisture, cloud, mist;" Gk. nephos "cloud, mass of clouds," nephele "cloud;" L. nebula "mist," nimbus "rainstorm, rain cloud;" O.H.G. nebul; Ger. Nebel "fog;" O.E. nifol "dark;" from PIE *nebh- "cloud, vapor, fog, moist, sky." |
hygrogram namnegâšt (#) Fr.: hygrogramme The graphical record made by a → hygrograph. |
hygrograph namnegâš (#) Fr.: hygrographe An instrument that records the hygrometer's measure of water vapor. |
<< < -he Haf hal har har He hea hel hel Her Her hid hig hip hom hor hot Hub Hug hur hyd hyd hyg hyp > >>