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The tetractys. The tetractys (Greek: τετρακτύς), or tetrad, [1] or the tetractys of the decad [2] is a triangular figure consisting of ten points arranged in four rows: one, two, three, and four points in each row, which is the geometrical representation of the fourth triangular number.
The tetrad is the four spores produced after meiosis of a yeast or other Ascomycota, Chlamydomonas or other alga, or a plant. After parent haploids mate, they produce diploids. Under appropriate environmental conditions, diploids sporulate and undergo meiosis. The meiotic products, spores, remain packaged in the parental cell body to produce ...
Tetrads are clusters of four cocci arranged within the same plane such as Micrococcus sp.). Sarcina describes a pack-like cuboidal arrangement of eight cocci such as Sarcina ventriculi . Gram-positive cocci
Inex and saros for tetrads between AD 1000 and 2500, showing the tetradia. In astronomy, a tetrad is a set of four total lunar eclipses within two consecutive years. [1] The frequency of tetrads varies by century with the frequency of total lunar eclipses. This repeating cycle is called a tetradia. See Eclipse cycle for more information.
In metaphase I of meiosis I, the pairs of homologous chromosomes, also known as bivalents or tetrads, line up in a random order along the metaphase plate. [10] The random orientation is another way for cells to introduce genetic variation.
Tetrad (astronomy), four total lunar eclipses within two years; Tetrad (chromosomal formation) Tetrad (general relativity), or frame field Tetrad formalism, an approach to general relativity; Tetrad (geometry puzzle), a set of four simply connected disjoint planar regions in the plane; Tetrad (meiosis), the four cells produced by meiotic cell ...
Tetrad Disease Tetralogy of Fallot: pulmonary stenosis, ventricular septal defect, right ventricular hypertrophy, overriding aorta: Tetralogy of Fallot Ménière's disease: vertigo, tinnitus, fluctuating low frequency hearing loss, aural fullness: Ménière's disease zoonotic tetrad: scrub typhus, chiggers, rodents and birds, scrub vegetation
A frame field in general relativity (also called a tetrad or vierbein) is a set of four pointwise-orthonormal vector fields, one timelike and three spacelike, defined on a Lorentzian manifold that is physically interpreted as a model of spacetime.