An Etymological Dictionary of Astronomy and Astrophysics
English-French-Persian

To send data from one's computer to another computer. See also: → loading, → download.

→ up-; → load.

Bârgozâštan, literally "to put load," from bâr, → load, + gozâštan "to put, to place," → passage.

Higher, as in place, position, pitch, or in a scale.

Upper, from → up, → hyper-.

Bâlâ, → up; zabarin, → superior.

The part of the → arm between the → shoulder and the → elbow.

→ upper; → arm.

Bâzu "arm," from Mid.Pers. bâzûk "arm;" Av. bāzu- "arm;" Mod.Pers. bâhu "stick, staff; arm;" cf. Skt. bāhu- "arm, forearm;" Gk. pechys "forearm, arm, ell;" O.H.G. buog "shoulder;" Ger. Bug "shoulder;" Du. boeg; O.E. bôg, bôh "shoulder, bough;" E. bough " a branch of a tree;" PIE *bhaghu- "arm").

The general term applied to the atmosphere above the → troposphere.

→ upper; → atmosphere.

Same as → superior culmination.

→ upper; → culmination.

In atomic physics, an initial energy state in an emission transition.

→ upper; → level.

Of an integral operator, the point at which the integration ends.

→ upper; → limit.

A → main sequence star with a mass above 1.5 Msun. Upper main sequence stars have high central temperatures so that they produce their energy through the → CNO cycle. The outward energy flux is very high and therefore this flux cannot be maintained by → radiative transfer. Thus, upper main sequence stars have → convective cores. Outside the core, there is a → radiative zone. The mass of the convective core gradually diminishes as the hydrogen is consumed. The surface hydrogen is fully ionized and the → opacity is due to → electron scattering The opacity due to electron scattering.

→ upper; → main; → sequence.

The upper part of the Earth's → mantle which begins at the base of the → crust around 35 km and extends downward to about 410 km.

→ upper; → mantle.

Same as → upper mass limit.

→ upper; → mass; → cut-off.

The highest mass range admitted in a star formation model. The high mass end of the → initial mass function. The upper mass limit is a critical parameter in understanding → stellar populations, → star formation, and → massive star feedback in galaxies.

→ upper; → mass; → limit.

The movement of a celestial body across a celestial meridian's upper branch. Same as → upper culmination.

→ upper; → transit.

1) Toward or in the higher part of a stream; against the current. → downstream
2) Directed upstream; situated upstream.

→ up; → stream.

Farâz, → height; water, → water.

A → radioactive metallic → chemical element; symbol U. → Atomic number 92; → atomic weight 238.0289; → melting post 1,132 °C; → boiling point 3,818°C; → specific gravity 19.1 at 25 °C. Uranium has 14 known → isotopes of which ²³⁸U is the most abundant in nature. This isotope (→ half-life 4.5 billion years) is 138 times more abundant than ²³⁵U (half-life 710 million years). The metal was first isolated by the French chemist Eugène-Melchior Peligot in 1841. See also: → uranium oxide, → uranium conversion, → uranium dioxide, → uranium enrichment, → uranium hexafluoride, → uranium-233, → uranium-235, → uranium-238, → plutonium, → fissile isotope, → fertile isotope, → yellowcake.

From the name of the planet → Uranus. The German chemist Martin-Heinrich Klaproth discovered the element in 1789, following the German/English astronomer William Hershel's discovery of the planet in 1781.

A chemical process converting the → yellowcake to → uranium hexafluoride. The uranium hexafluoride is heated to become a gas and loaded into cylinders. When it cools, it condenses into a solid.

→ uranium; → conversion.

A black crystalline solid (UO_{2pitchblende, carnotite, and autunite and is used chiefly as a source of nuclear energy by fission of the radioisotope uranium-235. After the → uranium hexafluoride is enriched, a fuel fabricator converts it into uranium dioxide powder and presses the powder into fuel pellets.}

→ uranium; → dioxide.

The process by which the percentage of → fissile uranium in a sample is increased. Uranium obtained from mining contains several → isotopes of uranium in different compositions, such as U-238 (~99%), U-235 (~0.7%), and U-234 (~0.02%). Among them, U-235 is the only one that is fissile, i.e. can be used in a → nuclear reactor to produce heat (and consequently electricity) in a controlled manner. As such, the concentration of U-235 as a fuel used in a reactor needs to be increased, which is done using several techniques, such as → gaseous diffusion.

→ uranium; → enrichment.

A white solid compound (UF₆) of → uranium and → fluorine obtained by chemical treatment of → yellowcake, forming a vapor at temperatures above 56 °C. It contains both of the naturally occurring → isotopes of uranium U-235 and U-238. The isotopes are separated on the basis of differences in their diffusion properties. UF₆ is the process medium for all separation processes for → uranium enrichment. It is essential that fluoride be a pure element and therefore solely the mass differences of U-235 and U-238 determine the separation process.

→ uranium; → hexa-; → fluoride.

A chemical compound made up of → uranium and → oxygen. The most common forms of uranium oxide are U₃O₈ and UO₂. Both oxide forms are solids that have low solubility in water and are relatively stable over a wide range of environmental conditions. Triuranium octaoxide (U₃O₈) is the most stable form of uranium and is the form most commonly found in nature. → Uranium dioxide (UO₂) is the form in which uranium is most commonly used as a → nuclear reactor fuel. At ambient temperatures, UO₂ will gradually convert to U₃O₈.

→ uranium; → oxide.

A → fissile isotope bred by the → fertile isotope thorium-232. It is similar in weapons quality to → plutonium-239.

→ uranium.