Fr.: neutrons retardés
Neutrons resulting from nuclear fission which are emitted with a measurable time delay. Delayed neutrons are responsible for the ability to control the rate at which power can rise in a reactor. → prompt neutrons.
delayed supernova explosion
oskaft-e bâderang-e abar-now-axtar
Fr.: explosion retardée de supernova
A mechanism predicted by theoretical models of → supernova explosion that operates after the → supernova shock fails to deliver a → prompt supernova explosion. The delayed supernova explosion mechanism assumes that a few tenth of a second after the → iron core collapse, the supernova shock is stalled due to energy dissipation. The material between the → protoneutron star and the stalled shock is mainly disintegrated into neutrons and protons due to the high temperatures (a few MeV) in this region. As the → neutrinos coming from the protoneutron star run through this material, a fraction of the neutrinos are captured by the → nucleons, and their energy is deposited in the material. As a result, the material behind the shock is heated by the neutrinos. If this neutrino heating is efficient enough, the stalled shock can be reinvigorated to bring about a supernova explosion.
Fr.: barrer, rayer
To strike out or remove (something written or printed); cancel; erase.
L. deletus, p.p. of delere "destroy, blot out, efface," from delevi, fro delinere "to erase by smudging," from → de- "from, away" + linere "to smear, wipe."
Rušidan, from Kurd. rušê "to be wiped off through rubbing;" cf. Av. fra.uruxti- "destruction;" Wakhi riz-, rəz-/rəzd- "to tear apart, rip up a seam;" Yaghnobi ruc/ructa, rušta "to shave off the skin, skin off;" Proto-Ir. *rauj- "to break, bust" (Cheung 2007).
1) An act or instance of deleting. The state of being deleted. A deleted word, passage, etc.
Verbal noun from → delete.
1) Fine in texture, quality, construction, etc.
M.E. delicat, from L. delicatus "alluring, delightful, dainty," of uncertain origin.
Dârmé, from Mid.Pers. dârmag "delicate;" cf. (dialect of Ferdows) dermi "fine thread," Sogd. žâm, žam "delicate."
L. delphinus, from Gk. delphin-, delphis; akin to Gk. delphys womb, cf. Skt. garbha- "womb; interior."
Dolfin loanword from Gk.
1) The fourth letter of the Greek alphabet (δ, Δ).
M.E. deltha, from L. delta, from Gk. delta; from the Phoenician name of the corresponding letter daleth "tent door."
Fr.: Delta Cephée
The prototype of classical → Cepheid variables, which is a pulsating → yellow supergiant. John Goodricke was the first in 1784 to discover its variability. The star shows a quick and sharp rise from minimum to maximum, and slowly declines to its minimum again. The changes in brightness are accompanied by and principally caused by changes in stellar temperature and also by changes in radius. δ Cephei was actually the second Cepheid variable to be discovered. The first one, Eta Aquilae, had been discovered earlier the same year by Edward Pigott. δ Cephei varies with a period of 5.366341 days (or 5 days 8 hours 37.5 minutes) from magnitude 3.48, spectral type F5 Ib in its maximum to magnitude 4.37, spectral type G2 Ib in its minimum. It lies at a distance of 1,340 → light-years.
râne-ye deltâ , ~ vâkil
Fr.: entraînement en déclinaison
Fr.: fonction delta
Same as → Dirac function.
Fr.: offset en déclinaison
Fr.: delta Orionis
Same as → Mintaka.
Delta Scuti variable
Fr.: variable δ Scuti
A member of a class of → pulsating stars with periods less than 0.3 days, → spectral types A or F, and visual light amplitudes in the range from a few thousands of a magnitude to about 0.8 mag. On the → H-R diagram, δ Scuti stars form a group which lies in an → instability strip which includes the classical → Cepheids at its brightest end and the pulsating → white dwarfs at its faintest limit. These stars can show very complex light variations since, while some of them are pulsating in one radial mode only, others may be pulsating simultaneously in several radial and non-radial modes.
Deltâ T (ΔT)
Fr.: Delta T (ΔT)
A measure of the variation in → Earth's rotation, which is the difference between → Terrestrial Time (TT) and → Universal Time (UT). TT is uniform and related to the → International Atomic Time, whereas UT, which is directly tied to the Earth's rotation, is not strictly uniform and shows small erratic fluctuations. Between 1970 and 1990, ΔT changed from +40 to +57 seconds, and was +67 seconds for 2010.
Δ, Gk. letter of alphabet indicating a difference; T for → time.
In communications, the process of recovering the original information from a modulated signal wave. → modulation.
From L. dæmon "spirit," from Gk. daimon "deity, fate, fortune."
Pari "a good genius, a fairy," from Mid.Pers. parîk "sorceress, witch;" from Av. pairikā- "sorceress, witch."
1) To make evident or establish by arguments or reasoning; prove.
From L. demonstratus, p.p. of demonstrare "to show, point out," from → de- + monstrare "to show," from monstrum "sign, portent."
Padišidan, from Sogd. padēš "to show," ultimately from Proto-Ir. *apa-dais-, from *dais- "to show," cf. Av. daēs- "to show," related to andiš, → think.
1) The → act or → circumstance
of proving or being → proved conclusively, as
by → reasoning or a show of → evidence.
Verbal noun of → demonstrate.
A person or thing that demonstrates (Dictionary.com).
The removal of mystery or confusion surrounding a topic or idea.