magnetic null point
noqte-ye nul-e meqnâtisi
Fr.: point nul magnétique
A region of the → solar corona where the → magnetic field vanishes.
1) nul; 2) nulidan
Fr.: 1) nul; 2) rendre nul
1a) General: Being or amounting to nothing; nil; nonexistent; without value, effect,
From M.Fr. nul, from L. nullus "not any, none," from ne- "not, no" → non- + illus "any," dimunitive of unus "one."
Nul, from na-, → non-, + -ul a variant of the Pers. suffix → -al. Nulidan, infinitive from nul.
Fr.: géodésique nulle
1) The path taken by a light ray in a curved → space-time
just as a → timelike geodesic describes the path of a
Fr.: hypothèse nulle
Statistics: The assumption of the absence of a particular pattern in a set of data. The null hypothesis, denoted by H0, is put forward to be rejected in order to support an → alternative hypothesis.
→ null; → hypothesis.
A lens used in the optical testing of an aspheric surface. It converts a spherical wavefront into one that precisely matches the surface under test. When the wavefront is reflected from that surface, it reverses its path and, if the surface is perfect, results in a perfect emerging spherical wavefront, which is easily evaluated.
Fr.: matrice nulle
An m × n matrix whose elements are all zeros. Also known as zero matrix.
Fr.: méthode de zéro
A method of comparing, or measuring, forces, electric currents, etc., by so opposing them that the pointer of an indicating apparatus remains at, or is brought to, zero, as contrasted with methods in which the deflection is observed directly. Same as zero method.
A device using the → nulling interferometry technique.
Agent noun of the verb → null.
nulling fraction (NF)
Fr.: fraction de phase d'arrêt
The fraction of time that a → pulsar undergoes → pulse nulling. For most → nulling pulsars this fraction can range from zero (for the → Vela pulsar) to more than 50%.
Fr.: interférométrie annulante
A technique for blocking the light of a bright source in order to reveal a faint source near it. This technique uses destructive → interference between two or more → coherent beams from a number of telescopes to make the bright center dark. Nulling interferometry can be used to search the region immediately around a star for → extrasolar planets and → circumstellar dust clouds by suppressing the star's glare.
Nulling, from → null; → interferometry.
Fr.: pulsar à phase d'arrêt
A → pulsar that undergoes → pulse nulling.
Fr.: phase d'arrÃªt de pulsar
A phenomenon in which the → pulsar → emission abruptly drops to zero or near zero for a certain number of → pulse → periods, then suddenly returns to normal. Nulling is relatively common in pulsars. The → nulling fraction can be more than 80%. Investigating the emission behaviors of → nulling pulsars is important to understand the pulsar emission mechanism.
Fr.: arrÃªt de pulsation
A phenomenon seen in the → radio → emission of many → pulsars where the emission appears to cease, or is greatly diminished, for a certain number of pulse periods. Typical time scales of nulling are of the order of a few pulse periods, however it may last for up to many hours in certain pulsars. For example, PSR B0826-34 is active for only about 20% of the time. Same as → pulsar nulling.