42,772 articles
PETG
PETG, or polyethylene terephthalate glycol-modified, is an amorphous thermoplastic copolyester in which some ethylene glycol is replaced with CHDM, keeping it transparent and tough; the CHDM also makes it a popular, less brittle 3D printing filament.
Petra E. de Jongh
Petra E. de Jongh is a Dutch materials chemist, professor of catalysts and energy materials at Utrecht University, known for nanoparticle catalysts and hydrogen storage research.
PETRA III
PETRA III is a high-brilliance synchrotron X-ray source at DESY in Hamburg, Germany, converted from the PETRA storage ring and opened to users in 2010.
Petra Nova
Petra Nova is a carbon capture project that removes CO2 from the flue gas of NRG Energy's W.A. Parish coal plant near Houston, Texas, operating since 2017.
Petra Schwille
Petra Schwille, born 1968, is a German biophysicist directing the Department of Cellular and Molecular Biophysics at the Max Planck Institute of Biochemistry, known for reconstituting E. coli's Min proteins.
Petrel (reservoir software)
Petrel is a subsurface software platform, developed by Technoguide in Norway and owned by SLB, that geoscientists use for seismic interpretation, 3D geological modeling, and reservoir simulation.
Petri dish
A Petri dish, also called a Petri plate or culture dish, is a shallow lidded laboratory container for growing microorganisms and cells, named after Julius Richard Petri.
Petri net
A Petri net, or PT net, is a mathematical model of concurrent computation in which places and transitions exchange tokens, introduced by Carl Adam Petri in 1962.
Petrichor
Petrichor is the earthy scent produced when rain falls on dry soil, especially after a dry spell, named by two Australian CSIRO scientists in 1964.
Petrified wood
Petrified wood, also known as fossilwood or opalised wood, is fossilized vegetation in which minerals, usually silica, replace the organic material while preserving the wood's three-dimensional cellular structure.
Petrochronology
Petrochronology is the branch of geoscience that links radiometric dates on individual mineral zones to the specific rock-forming processes that produced them, combining isotopic dating with petrographic context.
Petrographic analysis
Petrographic analysis identifies minerals, textures, and modal composition in a rock by polarized-light microscopy of a thin section ground to a standard 30 µm thickness, a low-cost alternative to SEM and X-ray diffraction.
Petrography
Petrography is the systematic description and classification of rocks, most often by examining rock slices about 30 µm thick under a polarizing microscope; it is a subdiscipline of petrology, the broader science of rocks.
Petroleum
Petroleum, often called crude oil, is a naturally occurring mixture of hydrocarbons found underground, including crude oil, natural gas, and asphaltic compounds in tar sands and oil shales.
Petroleum ether
Petroleum ether, also called pet ether or ligroin, is a mixture of low-boiling aliphatic hydrocarbons from petroleum used as a nonpolar laboratory solvent despite containing no ether.
Petroleum jelly
Petroleum jelly, also called petrolatum or soft paraffin, is a purified semisolid hydrocarbon mixture from petroleum, used as an occlusive moisturizer and ointment base; it was patented as Vaseline by Robert Chesebrough in 1872.
Petroleum play
A petroleum play is a set of oil and gas accumulations sharing similar geologic, geographic, and temporal properties, used as the working unit for exploration.
Petroleum system
A petroleum system, also called a hydrocarbon system, is a petroleum geology concept linking a source rock to the oil and gas it generated, formalized by Magoon and Dow in 1994.
Petros Koumoutsakos
Petros Koumoutsakos is a Greek computational scientist, a Harvard professor who applies computing and AI to fluid flows, elected to the US National Academy of Engineering in 2018.
Petros Tzeferacos
Petros Tzeferacos is a plasma physicist at the University of Rochester who directs the Flash Center for Computational Science and won a 2025 PECASE award.
Petrov classification
The Petrov classification, introduced by A. Z. Petrov in 1954 and independently derived by Felix Pirani in 1957, sorts four-dimensional Lorentzian spacetimes into six types based on the Weyl tensor's algebraic structure.
Petrov–Galerkin method
The Petrov–Galerkin method is a finite element technique for solving partial differential equations in which trial and test functions come from different function spaces, improving stability.
PETSc
PETSc, the Portable, Extensible Toolkit for Scientific Computation, is a library for the scalable, parallel solution of scientific applications modeled by partial differential equations, running from laptops to GPU-based supercomputers.
Petter Minnhagen
Petter Minnhagen is a theoretical physicist known for work on the Kosterlitz–Thouless transition in two-dimensional superconductors; his theory appears in the 2016 Nobel Prize in Physics background.
Petzval field curvature
Petzval field curvature, also called field curvature, is an optical aberration in which a flat object is focused onto a curved image surface rather than a flat plane.
PeVatron
A PeVatron is a natural astrophysical accelerator that boosts cosmic-ray particles, mainly protons, to energies of 1 PeV or more, explaining the knee in the cosmic-ray spectrum.
Pfaffian
The Pfaffian is a polynomial in the entries of a skew-symmetric matrix whose square equals the determinant, defined for even-order matrices and named by Cayley in 1852.
Pfaffian constraint
A Pfaffian constraint is a constraint on a mechanical system's motion that is linear in the generalized velocities; nonintegrable cases are nonholonomic, like a car that cannot slide sideways.
PffBT4T-2OD
PffBT4T-2OD, also known as PCE11, is a low band gap donor polymer used in bulk-heterojunction organic solar cells, notable for its high efficiency in thick active layers around 300 nm.
PG 1159-035
PG 1159-035, also known as GW Vir, is a hot, hydrogen-deficient pre-white dwarf in Virgo and the prototype of both the PG 1159 class and GW Vir pulsators.