Fr.: réaction proton-proton
Fr.: réaction pycnonucléaire
A nuclear reaction that takes place at high densities and relatively low temperatures. Pycnonuclear reactions are almost temperature independent and occur even at zero temperature. These reactions are extremely slow at densities typical for normal stars but intensify with increasing density. For example, carbon burns into heavier elements at densities over 1010 g cm-3.
quantum of action
Fr.: quantum d'action
Possessing, or pertaining to, → radioactivity.
sen yâbi-ye partow-žirâ
Fr.: datation radioactive
Determining the age of an object from the → radioactive decay of its constituting material. The technique consists of comparing the → abundance ratio of a → radioactive isotope to its → decay product. This will yield the number of half-lives that have occurred since the sample was formed. More specifically, if an object is made up of 50 % decay product then it has gone through 1 → half-life. 75% decay product equals 2 half-lives, 87.5% decay product equals 3 half-lives, 93.76% decay product equals 4 half-lives, and so on. For example, the decay product of → uranium-238 (238U) is → lead-206 (206Pb). The half-life of 238U is 4.5 billion years. Hence, if the sample has gone through two half-lives, it is 9 billion years old. See also: → radiocarbon dating.
Fr.: désintégration radioactive
Spontaneous emission by a nucleus of photons or particles.
Fr.: isotope radioactif
A → nuclide that is radioactive.
Fr.: nucléide radioactif
Fr.: déchets radioactifs
The radioactive by-products from the operation of a nuclear reactor or from the reprocessing of depleted nuclear fuel. Also known as nuclear waste.
The spontaneous disintegration of certain atomic nuclei, which is accompanied by the emission of either α- or β- particles and/or a γ rays.
The state of being rarefied, less dense.
M.E. rarefien, from M.Fr. rarefier, from L. rarefacere "make rare," from rarus "loose, wide apart, thin, infrequent."
Verbal noun from âlar present stem of âlaridan→ rarefy + -š, a suffix.
Fr.: onde de raréfaction
A pressure wave in a fluid generated by rarefaction. It travels in the opposite direction to that of a shock wave in the medium.
1) To act in response to an agent, influence, or stimulus.
The opposition to the flow of alternating current caused by the inductance and capacitance in a circuit rather than by resistance.
From → react + -ance a suffix of nouns.
Vâžirâyi state noun of vâžirâ agent noun of vâžiridan→ react.
1) General: A person or thing that reacts.
From → react + -ant.
1) General: Action in response to some influence, event, stimulus.
Verbal noun of → react.
Fr.: taux de réaction
Tending to react. Pertaining to or characterized by reaction.
From → react + -ive a suffix of adjectives expressing tendency, disposition, function, connection, etc.
1) General: The quality or condition of being reactive.
1) A device for introducing reactance into an electrical circuit (e.g. a capacitor).