42,772 articles
PEGylation
PEGylation, also called PEG labeling, is the covalent attachment of polyethylene glycol chains to therapeutic molecules such as proteins to prolong their circulation half-life, first FDA-approved in 1990.
Peierls transition
The Peierls transition is a metal-to-insulator phase transition in which a one-dimensional metal spontaneously distorts its lattice with period twice the Fermi wavevector, opening an energy gap at the Fermi level.
Pekka Pyykkö
Pekka Pyykkö, born 1941 in Finland, is a theoretical chemist and professor emeritus at the University of Helsinki, known for relativistic quantum chemistry of gold and widely used covalent radii.
Pelagic zone
The pelagic zone, also called the open ocean, is the entire water column of the sea, away from the bottom and shore, and Earth's largest habitat.
Pelargonic acid
Pelargonic acid, also called nonanoic acid, is a naturally occurring nine-carbon saturated fatty acid found in geranium oil and many foods, used as a contact herbicide, blossom thinner for fruit trees, and food additive.
Pelican optimization algorithm
The pelican optimization algorithm (POA) is a nature-inspired metaheuristic introduced by Pavel Trojovský and Mohammad Dehghani in Sensors in 2022, simulating how pelicans hunt for prey.
Pell numbers
Pell numbers are the integer sequence 0, 1, 2, 5, 12, 29, ... that solves the Pell equation and approximates the square root of 2.
Pell's equation
Pell's equation, also called the Pellian equation, is the Diophantine equation x² − Dy² = 1, solved via continued fractions and studied since Brahmagupta in 628.
Pellet injection
Pellet injection launches small cryogenic pellets of hydrogen, deuterium, or tritium ice into a magnetically confined plasma at high speed, to refuel the core, control density, and mitigate disruptions.
Pellet pacing for ELM control
Pellet pacing is an ELM control technique for tokamaks in which small frozen fuel pellets trigger frequent, smaller edge localized modes, first demonstrated on ASDEX Upgrade.
Pelletron
A Pelletron is an electrostatic particle accelerator charged by a chain of metal pellets linked by nylon, developed by Raymond Herb in the mid 1960s.
Penalized regression
Penalized regression is a family of regression methods that adds a penalty on coefficient size to improve prediction, including ridge regression, the lasso, and the elastic net.
Penalty method
The penalty method is a numerical optimization technique that turns a constrained minimization problem into a sequence of unconstrained problems by penalizing constraint violations in the objective function.
Peñasquito mine
Peñasquito is a polymetallic open-pit mine in Mazapil, Zacatecas, Mexico, producing gold, silver, lead, and zinc since 2009. Owned by Newmont, it is Mexico's largest gold mine.
Pendant drop tensiometry
Pendant drop tensiometry is an optical method that measures surface or interfacial tension from the shape of a drop hanging from a needle, fitting the Young–Laplace equation.
Pendulum
A pendulum is a weight, called a bob, suspended from a pivot so it swings under gravity; its regular period made it the regulator of mechanical clocks from 1657 until electronic timekeeping.
Penetrative convection
Penetrative convection is a form of turbulent convection in which surface cooling drives plumes that overshoot into stratified water below, entraining it and deepening a lake's mixed layer.
Peng Wu (molecular biologist)
Peng Wu (吴鹏) is a chemical biologist and professor at Scripps Research in La Jolla, California, known for chemoenzymatic methods that edit cell-surface glycans and target cancer immunotherapy.
Peng–Robinson equation
The Peng–Robinson equation of state is a cubic equation of state published in 1976 by Ding-Yu Peng and Donald B. Robinson, used to calculate vapor–liquid equilibria of hydrocarbon mixtures.
Peng–Robinson equation of state
The Peng–Robinson equation of state is a cubic equation of state published in 1976 by Ding-Yu Peng and Donald B. Robinson, widely used in the chemical and petroleum industries.
Pengcheng Dai
Pengcheng Dai is a Chinese American experimental condensed matter physicist, the Sam and Helen Worden Professor at Rice University, known for neutron scattering studies of high-temperature superconductors.
Penicillamine
Penicillamine (D-penicillamine) is a chelating drug derived from penicillin, first isolated at Oxford in 1943 and introduced by John Walshe in 1956 as the first oral treatment for Wilson's disease.
Penicillanic Acid
Penicillanic acid is the bicyclic nucleus of the penicillin antibiotics; its 6-amino derivative, 6-aminopenicillanic acid (6-APA), isolated in 1959, is the raw material for semisynthetic penicillins like ampicillin.
Penman–Monteith equation
The Penman–Monteith equation estimates evapotranspiration from standard weather variables, combining surface energy balance with aerodynamic vapor transfer; FAO-56 adopted it as its sole standard in 1998.
Penning ionization
Penning ionization is a collisional ionization process in which a metastable excited atom transfers energy to a partner, ionizing it, first suggested by F. M. Penning in 1927.
Penning trap
A Penning trap is a device that confines charged particles with static electric and magnetic fields, underpinning precision measurements of particle masses, magnetic moments, and antiproton research.
Pennsylvanian (geology)
The Pennsylvanian, or Pennsylvanian Period, is the younger half of the Carboniferous Period, from 323.2 to 298.9 million years ago, named for Pennsylvania's coal-bearing rocks.
Penrose diagram
A Penrose diagram, also called a conformal diagram, is a spacetime diagram that fits an infinite spacetime into a finite picture while preserving light-ray paths, introduced by Roger Penrose in 1963.
Penrose inequality
The Penrose inequality is a conjecture in general relativity relating the total mass of a spacetime to the area of the black hole horizons it contains.
Penrose interpretation
The Penrose interpretation is Roger Penrose's proposal that quantum wave function collapse is a real physical process caused by gravity rather than measurement, known quantitatively as the Diósi–Penrose model.