cyclic carxe-yi (#) Fr.: cyclique Of, pertaining to, or constituting a cycle or cycles. |
cyclic coordinate hamârâ-ye nâdidé engâshté Fr.: coordonnée ignorée Same as → ignorable coordinate. → cyclic; → coordinate. |
cyclic group goruh-e carxe-yi Fr.: groupe cyclic A group in which each element can be expressed as a power of any other element. |
cyclic process farâravand-e carxe-yi Fr.: processus cyclique Any sequence of changes in a → thermodynamic system that returns the system into its → initial → state. |
cyclic quadrilateral cahârbar-e carxe-yi Fr.: quadrilatère cyclique A quadrilateral in which all four vertices lie on the circumference of a circle. → cyclic; → quadrilateral. |
epicyclic apicarxe-yi Fr.: épicyclique Of or pertaining to an → epicycle. |
epicyclic frequency basâmad-e apicarxe-yi Fr.: fréquence épicyclique In the → epicyclic theory of Galactic rotation, the frequency at which a star in the → Galactic disk describes an ellipse around its mean circular orbit. The epicyclic frequency relates to the → Oort's constants. In the solar neighborhood the epicyclic frequency is about 32 km s-1 kpc-1. |
epicyclic oscillation naveš-e apicarxe-yi Fr.: oscillation épicyclique In a → disk galaxy, the motion of a star about the orbital → guiding center when it is displaced radially. See also → epicyclic frequency, → epicyclic theory. → epicyclic; → oscillation. |
epicyclic theory negare-ye apicarxe-yi Fr.: théorie épicyclique The theory that describes the Galactic dynamics, that is the orbits of stars and gas clouds in the → Galactic disk, as well as the spiral → density wave. Formulated by Bertil Lindblad (1895-1965), the epicyclic theory assumes that orbits are circular with small deviations. Star orbits are described by the superposition of two motions: i) a rotation of the star (epicenter) around the Galactic center at the circular angular velocity, Ω, and ii) a retrograde elliptical motion at → epicyclic frequency, κ. The epicyclic motion in the Galactic plane occurs in a retrograde sense to conserve → angular momentum. In general Ω and κ are different and, therefore, orbits do not close. However, seen by an observer who rotates with the epicenter, orbits are closed ellipses. |
polycyclic aromatic hydrocarbons (PAHs) hidrocarburhâ-ye aromâtik-e polisiklik, ~ ~ bol-carxe-yi Fr.: hydrocarbures aromatiques polycycliques 1) Chemistry: A family of → organic molecules composed
of carbon and hydrogen atoms (→ hydrocarbons) in which
→ carbon atoms appear in multiple loops (polycyclic)
with strong chemical → bonds that exist between them (aromatic).
PAHs are formed during the incomplete burning of coal, oil and gas, garbage, or other
organic substances like tobacco or charbroiled meat. As a pollutant, they are of
concern because some compounds (benzo(a)pyrene) have been identified as tending to
cause cancer. → poly-; → cyclic; → aromatic; → hydrocarbon. |