42,772 articles
Push–relabel maximum flow algorithm
The push–relabel maximum flow algorithm, also known as the push–relabel algorithm or preflow push, is a maximum flow algorithm introduced by Goldberg and Tarjan in 1988.
Pushdown automaton
A pushdown automaton (PDA) is a finite-state machine with a stack as its only auxiliary memory, recognizing exactly the context-free languages, including nested structures like palindromes.
Putana
Putana (Jorgencal, Machuca) is a 5,884 m Holocene stratovolcano on the Chile-Bolivia border in the Central Andean arc, with vigorous summit fumaroles, sulfur mining, a reported 1810 CE eruption, and 2009 uplift unrest.
Puthandu (புத்தாண்டு)
Puthandu (புத்தாண்டு), also called Varusha Pirappu, is the traditional Tamil New Year, observed on the first day of Chithirai, usually 14 April, by Tamil communities in India, Sri Lanka, and the diaspora.
Putrescine
Putrescine, also called butane-1,4-diamine, is a foul-smelling four-carbon diamine produced from ornithine in living cells, a precursor of spermidine and spermine, and a monomer for nylon-4,6.
PX Andromedae
PX Andromedae, cataloged as PG 0027+260 from the Palomar-Green survey, is an eclipsing SW Sextantis-type cataclysmic variable in Andromeda known for its highly variable eclipse depth.
Pycnocline
A pycnocline is the ocean layer where water density changes most rapidly with depth, typically caused by temperature or salinity gradients, which restricts vertical mixing and stabilizes the water column.
Pycnometer
A pycnometer, also called a pyknometer or specific gravity bottle, is a laboratory flask with a close-fitting stopper that delivers a fixed volume so density can be determined by weighing.
Pygmy dipole resonance
The pygmy dipole resonance (PDR) is a concentration of low-energy electric dipole strength in atomic nuclei, often pictured as neutron skin oscillating against the core.
Pymatgen
Pymatgen, short for Python Materials Genomics, is a robust open-source Python library for materials analysis founded by Shyue Ping Ong that powers the Materials Project and is used by thousands of researchers.
Pyocyanin
Pyocyanin is a blue-green, redox-active phenazine pigment produced by Pseudomonas aeruginosa, which gives infected pus its color and acts as a virulence factor in cystic fibrosis.
Pyotr Kapitsa
Pyotr Kapitsa, also known as Pyotr Leonidovich Kapitsa, was a Soviet physicist who won the 1978 Nobel Prize for discovering the superfluidity of liquid helium.
Pyotr Lebedev
Pyotr Nikolaevich Lebedev (Пётр Никола́евич Ле́бедев) was a Russian physicist who in 1899 made the first measurement of light pressure on solids, confirming Maxwell's electromagnetic theory.
Pyotr Rashevsky
Pyotr Konstantinovich Rashevsky (Пётр Константинович Рашевский; 1907–1983) was a Soviet differential geometer who created polimetric geometry, proved the Chow–Rashevskii theorem, and headed Moscow State University's differential geometry department.
Pyramid (geometry)
A pyramid, also called a polygonal pyramid, is a polyhedron with a polygonal base and triangular faces meeting at an apex, with volume one third of base area times height.
Pyramid wavefront sensor
The pyramid wavefront sensor (PWFS) is an adaptive optics wavefront sensor invented by Roberto Ragazzoni in 1996, using a four-sided pyramidal prism to split light into four pupil images.
Pyramidal peak
A pyramidal peak, also called a glacial horn, is a sharp pyramid-shaped summit formed when cirque glaciers erode a mountain from three or more sides; the Matterhorn is the type example.
Pyran
Pyran is a six-membered non-aromatic heterocycle, formula C₅H₆O, with two double bonds and two isomers, 2H-pyran and 4H-pyran, that appears in natural products like sugars and flavonoids.
Pyranometer
A pyranometer is a radiometer that measures solar irradiance on a plane surface from the hemisphere above, the standard instrument for global horizontal irradiance in meteorology and solar energy.
Pyranose
A pyranose is the six-membered cyclic ring form of a monosaccharide, a hemiacetal or hemiketal based on the heterocycle pyran, with terms introduced by Norman Haworth in the 1920s.
Pyrazinamide
Pyrazinamide is a first-line oral antibiotic used to treat tuberculosis, valued for killing slow-growing bacilli; its addition in the 1970s shortened treatment from 12 to 6 months.
Pyrazine
Pyrazine, also known as 1,4-diazine, is an aromatic heterocyclic organic compound with formula C4H4N2, occurring naturally in roasted foods and used as a flavoring agent.
Pyrazole
Pyrazole, also known as 1,2-diazole, is an aromatic heterocyclic compound with a five-membered ring of three carbons and two adjacent nitrogens, found in over 50 marketed drugs and many pesticides.
Pyrene
Pyrene is a polycyclic aromatic hydrocarbon, C₁₆H₁₀, made of four fused benzene rings, a colorless crystalline solid with blue fluorescence found in combustion products and used widely as a fluorescent probe.
Pyrex
Pyrex, or Pyrex glass, is a heat-resistant glassware brand introduced in 1915 by Corning Glass Works of Corning, New York, known for borosilicate laboratory glass and American bakeware.
Pyridazine
Pyridazine, also called 1,2-diazine or orthodiazine, is an aromatic six-membered heterocycle with the formula C4H4N2, two adjacent nitrogen atoms, and the highest dipole moment of the three diazine isomers.
Pyridine
Pyridine (C5H5N), also known as azabenzene, is a six-membered aromatic heterocycle and colorless liquid with a fish-like odor, used as a solvent, weak base, and chemical intermediate.
Pyridinic nitrogen edge-site ORR activity
Pyridinic nitrogen edge-site ORR activity is the catalytic behavior of pyridinic nitrogen at graphene edges in the oxygen reduction reaction, assigned as the active site in 2016.
Pyridinium chlorochromate
Pyridinium chlorochromate (PCC), also called the Corey–Suggs reagent, is a red-orange chromium(VI) salt that selectively oxidizes primary alcohols to aldehydes and secondary alcohols to ketones.
Pyridinoline
Pyridinoline, also called hydroxylysyl pyridinoline (HP), is a non-reducible trivalent collagen cross-link predominant in cartilage and bone; its structure was determined in 1978, and urinary pyridinoline serves as a biochemical marker of bone resorption.