Fr.: couche d'inversion
Meteo.: The atmospheric layer in which the temperature gradient is
inverted, that is increases; → inversion. The inversion layer
tends to prevent the air below it from rising, thus trapping any pollutants that are present.
Fr.: inververtir, renverser
To turn upside down.
From M.Fr. invertir, from L. invertere "turn upside down, turn about," from → in- "in, on" + vertere "to turn;" cf. Pers. gardidan, gaštan "to turn, to change;" Mid.Pers. vartitan; Av. varət- "to turn, revolve;" Skt. vartati; O.H.G. werden "to become;" PIE base *wer- "to turn, bend."
Vâgardândan, from vâ-, → re-, +
gardândan, from gardidan "to turn; to change,"
from Mid.Pers. vartitan;
Av. varət- "to turn, revolve;" cf.
Skt. vrt- "to turn, roll," vartate "it turns round, rolls;"
L. vertere "to turn;" O.H.G. werden "to become;"
PIE base *wer- "to turn, bend."
porineš-e vâgardânidé, ~ vârun
Fr.: population inversée
In atomic physics, a condition in which there are more electrons in an upper energy level than in a lower one, while under normal conditions of thermal equilibrium the reverse is true. → optical pumping.
Fr.: non visqueux
The act of invoking.
Verbal noun of → invoke.
1) to call for with earnest desire; make supplication or pray for.
Io (Jupiter I)
1) The fifth of → Jupiter's known moons and
the third largest. It is the innermost of the
→ Galilean satellites.
With a diameter of 3630 km, Io is slightly larger than Earth's Moon. It revolves at
a mean distance of 422,000 km from Jupiter.
Its mass is 8.93 x 1022 kg (about 1.2 Earth Moons) and its
→ orbital period 1.8 Earth days.
The mean → surface temperature
of Io is -155 °C.
Io's yellow color derive from → sulfur
and molten → silicate rock. The unusual
surface of Io is kept very young by its system of active
The intense → tidal force
of Jupiter stretches Io and
damps wobbles caused by Jupiter's other Galilean moons. The resulting
friction greatly heats Io's interior, causing molten rock to explode
through the surface. Io's volcanoes are so active that they are
effectively turning the whole moon inside out. Some of Io's volcanic
lava is so hot it glows in the dark.
In Gk. mythology, Io was a maiden who was seduced by Zeus (Jupiter). When Hera came upon their rendez-vous, Zeus transformed the maiden into a white heifer.
A nonmetallic chemical element; symbol I; atomic number 53; atomic weight 126.9045; melting point 113.5°C; boiling point 184.35°C.
Iodine, coined 1814 by British chemist Sir Humphry Davy from Fr. iode "iodine," coined 1812 by Fr. chemist Joseph Louis Gay-Lussac (who proved it was an element) from Gk. ioeides "violet-colored," because of its violet vapors. Despite the priority rights dispute between Davy and Gay-Lussac, both acknowledged Courtois as the discoverer of the element.
Yod, from Fr. iode, as above.
An atom that has lost or gained one or more electrons and has become electrically charged as the result.
Ion (introduced in 1834 by E. physicist and chemist Michael Faraday), from Gk ion " going," neut. pr.p. of ienai "to go," from PIE base *ei- "to go, to walk," eimi "I go;" cf. Pers. ây-, â- present stem of âmadan "to come;" O.Pers. aitiy "goes;" Av. ay- "to go, to come," aēiti "goes;" Skt. e- "to come near," eti "arrival;" L. ire "to go;" Goth. iddja "went," Lith. eiti "to go;" Rus. idti "to go."
Yon, from Fr., from Gk., as above.
partowhâ-ye yoni (#)
Fr.: rayons ioniques
The thin glowing streamers in a comet's ion tail.
donbâle-ye yoni (#)
Fr.: queue d'ions
Of a comet, same as → gas tail.
Of or pertaining to ions; occurring in the form of ions.
Fr.: abondance ionique
A quantity, pertaining to an ion of a chemical element, expressing the relative number of the ion with respect to that of hydrogen.
Fr.: molécule ionique
A molecule that consists of the ions of the chemical elements that make up the molecule.
The process by which ions are produced, typically occurring by interaction with electromagnetic radiation ("photoionization"), or by collisions with atoms or electrons ("collisional ionization").
Verbal noun of → ionize.
ionization correction factor (ICF)
karvand-e aršâyeš-e yoneš
Fr.: facteur de correction d'ionisation
A quantity used in studies of → emission nebulae to convert the → ionic abundance of a given chemical element to its total → elemental abundance. The elemental abundance of an element relative to hydrogen is given by the sum of abundances of all its ions. In practice, not all the ionization stages are observed. One must therefore correct for unobserved stages using ICFs. A common way to do this was to rely on → ionization potential considerations. However, → photoionization models show that such simple relations do not necessarily hold. Hence, ICFs based on grids of photoionization models are more reliable. Nevertheless here also care should be taken for several reasons: the atomic physics is not well known yet, the ionization structure of a nebula depends on the spectral energy distribution of the stellar radiation field, which differs from one model to another, and the density structure of real nebulae is more complicated than that of idealized models (see, e.g., Stasińska, 2002, astro-ph/0207500, and references therein).
Fr.: énergie d'ionisation
Same as → ionization potential.
Fr.: front d'ionisation
An abrupt discontinuity between an H II region and the molecular cloud in which it has formed. In this transition region interstellar gas changes from a mostly neutral state to a mostly ionized state.
Fr.: paramètre d'ionisation
A ratio representing the number of ionizing photons to the number of electrons in a nebular emitting region.
Fr.: potentiel d'ionisation
The energy required to remove an electron from an isolated atom or molecule. The ionization potential for hydrogen is 13.6 eV, which corresponds to an ultraviolet ionizing photon with a wavelength of 912 A. Also called → ionization energy.