Abbe number adad-e Abbe Fr.: nombre d'Abbe The reciprocal of the → dispersive power of a substance. Also known as constringence. → Abbe sine condition; → number. |
aberrational day number šomâre-ye ruz-e birâheši Fr.: nombre de jours d'aberration A → Besselian day number denoted by C or D. → aberration; → -al; → day; → number. |
Alfvén Mach number adad-e Mach-e Alfvéni Fr.: nombre de Mach alfvénique The ratio of the flow velocity to the → Alfvén speed in a medium. → Alfvén wave; → number. |
Alfven Mach number adad-e Mach-e Alfvéni Fr.: nombre de Mach alfvénique The ratio of the flow velocity to the → Alfvén speed in a medium. → Alfvén wave; → number. |
algebraic number adad-e jabri (#) Fr.: nombre algébrique A number, → real or → complex, that is a → root of a → non-zero polynomial equation whose → coefficients are all → rational. For example, the root x of the polynomial x^{2} - 2x + 1 = 0 is an algebraic number, because the polynomial is non-zero and the coefficients are rational numbers. The imaginary number i is algebraic, because it is the solution to x^{2} + 1 = 0. |
atomic mass number (A-number) adad-e jerm-e atomi (#) Fr.: nombre de masse atomique The total number of protons and neutrons in the nucleus of an atom. For example, Oxygen-16 has a mass number of sixteen, because it has eight protons and eight neutrons. |
atomic number adad-e atomi (#) Fr.: nombre atomique The number of → protons in an atomic → nucleus. Same as → Z-number. |
Avogadro's number adad-e Avogâdro (#) Fr.: Nombre d'Avogadro The number of atoms in 12 grams of ^{12}C; by extension, the number of atoms in a gram-atom (or the number of molecules in a → mole) of any substance: 6.02 × 10^{23}. Named after Amedeo Avogadro (1776-1856), whose law allowed other physicists to calculate Avogadro's number; → number. |
azimuthal quantum number adad-e kuântomi-ye sugâni Fr.: nombre quantique azimutal In quantum mechanics, a quantum number that distinguishes the different shapes of the orbitals. Azimuthal, adj. from → azimuth; → quantum number. |
baryon number adad-e bâriyoni (#) Fr.: nombre baryonique 1) The difference between the total number of → baryons and
the total number of → antibaryons in a system of
→ subatomic particles.
It is a measure of → baryon asymmetry and is
defined by the quantity
η = (n_{b} - n_{b-})/n_{γ},
called the → baryon-photon ratio,
where n_{b} is the → comoving number
density of baryons, n_{b-} is the number of
antibaryons, and n_{γ} is that of photons. The value of η for
the → cosmic microwave background radiation (CMBR)
has been very well determined by the → WMAP satellite to be
η = (6.14 ± 0.25) x 10^{-10}. The baryon number is assumed to be
constant. The photons created in
stars amount to only a small fraction, less than 1%, of those in the CMBR. |
Besselian day number šomâre-ye ruz-e Besseli Fr.: Any of the five quantities denoted by A, B, C, D, and E used in conjunction with → Besselian star constants for the reduction of a star's → mean catalog place to its → apparent place. |
binary number system râžmân-e adadhâ-ye dirini Fr.: système des nombres binaires A → numeral system that has 2 as its base and uses only two digits, 0 and 1. The positional value of each digit in a binary number is twice the place value of the digit of its right side. Each binary digit is known as a bit. The decimal numbers from 0 to 10 are thus in binary 0, 1, 10, 11, 100, 101, 110, 111, 1000, 1001, and 1010. And, for example, the binary number 11101_{2} represents the decimal number (1 × 2^{4}) + (1 × 2^{3}) + (1 × 2^{2}) + (0 × 2^{1}) + (1 × 2^{0}), or 29. In electronics, binary numbers are the flow of information in the form of zeros and ones used by computers. Computers use it to manipulate and store all of their data including numbers, words, videos, graphics, and music. |
cardinal number adad-e agrâ Fr.: nombre cardinal An ordinary number such as 0, 1, 2, or 3, as opposed to an → ordinal number such as 1st, 2nd, or 3rd. Cardinal numbers can be → zero or → positive and are used for counting the things that are assumed to be not divisible. |
complex number adad-e hamtâft (#) Fr.: nombre complexe Any number of the form u = a + bi, where a and b are → real numbers and i imaginary, i.e. i^{2} = -1. |
composite number adad-e hamnehâdé Fr.: nombre composite A whole number which is the product of whole numbers other than itself and 1. The opposite of prime number. → compound number. |
compound number adad-e hamnehâdé Fr.: nombre composé A quantity expressed as the sum of two or more quantities of differing units. For example 5 hours and 15 minutes or 4 meters and 20 centimeters. → composite number. |
congruent number adad-e damsâz Fr.: nombre congru Number theory: An → integerN if there exists a → right triangle with → rational sides so that the area of the triangle is N. For example, the number N = 6, because of the 3-4-5 triangle. |
conjugate complex number adad-e hamtâft hamyuq (#) Fr.: nombre complexe conjugé The conjugate of a → complex number, expressed by ū = a - bi. The complex number and its conjugate have the same real part. Same as → complex conjugate. |
coordination number šomêr-e hamârâyeš Fr.: nombre de coordination 1) Crystallography: The
number of nearest neighbors of an atom or ion in a → crystal lattice.
A large coordination number indicates that the structure is more closely packed. → coordination; → number. |
data number (DN) šomâr-e dâdehâ Fr.: Unit of the analog-to-digital conversion system of a CCD apparatus. For example a 16 bit system may use a maximum of 65536 DN. The acronym ADU, for analog-to-digital unit, is also used. |