Fr.: liaison hydrogène
The attractive force between the hydrogen attached to an electronegative atom of one molecule and an electronegative atom of a different molecule. Usually the electronegative atom is oxygen, nitrogen, or fluorine, which has a partial negative charge. The hydrogen then has the partial positive charge.
Fr.: combustion de l'hydrogène
Fr.: chevelure d'hydrogène
The cometary cloud of hydrogen, detectable in ultraviolet light, that is immensely bigger than even the huge visible coma it surrounds. It is produced by the dissociation of water into hydrogen and oxygen and by other processes set into motion by solar radiation and and the solar wind.
hydrogen cyanide (HCN)
siyânur-e hidrožen (#)
Fr.: cyanure d'hydrogène
A colorless or light blue liquid or gas, a triatomic cyanide, which is extremely flammable. HCN is an important industrial chemical and over a million tonnes are produced yearly in the world. It is produced industrially by reacting methane and ammonia in air at high temperature. A wide range of combustion processes produce HCN gas in the smoke or fumes. HCN is found naturally throughout the environment at low levels as it is released from volcanoes and certain plants and bacteria. Hydrogen cyanide is abundant in all kinds of astronomical environments, from dark clouds to star-forming regions and circumstellar envelopes. The first detection of interstellar HCN (at 88.6 GHz) and H13N (at 86.3 GHz) was reported by Buhl & Snyder (1971, ApJ 163, L47). Also called → hydrocyanic acid and → prussic acid.
Fr.: fusion de l'hydrogène
hidron, yon-e hidrož
Fr.: hydron, ion hydrogène
xatt-e hidrožen (#)
Fr.: raie de l'hydrogène
hydrogen shell burning
suzeš-e puste-ye hidrožen
Fr.: combustion de la coquille d'hydrogène
A phase in the life of a star that has left the → main sequence. When no more hydrogen is available in the core, the core will start to contract as it is no longer releasing the necessary energy whose pressure supports the surrounding layers. As a result of this contraction, gravitational energy is converted into thermal energy and the temperature will rise. Therefore a shell of unprocessed material surrounding the original core will be heated sufficiently for hydrogen burning to start. During the evolution of → asymptotic giant branch stars hydrogen shell burning occurs alternatively with helium shell burning. → double shell burning.
To undergo or cause to undergo a reaction with hydrogen. Same as → hydrogenize.
The process of combining or exposing to → hydrogen.
The study, measurement, and description of depths and currents in open seas, lakes, estuaries, and rivers.
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.
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.
Same as → magnetohydrodynamics.
The general name for the atomic hydrogen → cation H+.
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+).
A term denoting the water portion of the Earth's surface.
Of or pertaining to → hydrostatics.
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.