Physical world and mathematics

Proton-coupled electron transfer

Proton-coupled electron transfer (PCET) is a class of chemical reactions in which an electron and a proton transfer together or in linked steps, first named in 1981 by Thomas J. Meyer's group.

Proton-coupled electron transfer catalysis

Proton-coupled electron transfer (PCET) catalysis uses reactions that exchange an electron and a proton together, often in one concerted step, to generate radicals under mild conditions.

Proton-coupled electron transfer in CO2 electrocatalysis

Proton-coupled electron transfer in CO2 electrocatalysis is the coupled movement of electrons and protons that converts carbon dioxide into reduced products, by sequential or concerted steps that set pH dependence and selectivity.

Proton-coupled electron transfer in organic synthesis

Proton-coupled electron transfer (PCET) in organic synthesis is the use of redox steps that exchange an electron and proton together to cleave bonds and generate radicals under mild conditions.

Proton-detected local field spectroscopy

Proton-detected local field (PDLF) spectroscopy is a solid-state NMR method measuring proton heteronuclear dipolar couplings, such as ¹H–¹³C, to determine molecular orientation and dynamics in ordered materials like liquid crystals.

Proton-driven plasma wakefield acceleration

Proton-driven plasma wakefield acceleration is an accelerator technique in which proton bunches drive wakefields that accelerate electrons, developed at CERN by the AWAKE experiment, which first demonstrated it in 2018.

Proton-transfer-reaction mass spectrometry

Proton-transfer-reaction mass spectrometry (PTR-MS) is an analytical technique that ionizes trace volatile organic compounds directly in air using hydronium ions, introduced in 1995 and used in breath analysis and atmospheric monitoring.

Proton–proton chain

The proton–proton chain, or pp chain, is a nuclear fusion process that produces about 99 percent of the Sun's energy by converting four protons into helium-4.

Protonolysis

Protonolysis is the cleavage of a chemical bond by a proton donor, typically acid breaking a polar metal–carbon bond; in palladium chemistry it is called protodepalladation.

Protoplanetary disk

A protoplanetary disk, also called a planet-forming disk, is a rotating disk of gas and dust around a young star where dust grains collide and grow into planets.

Protoplanetary disk streamer

A protoplanetary disk streamer is a narrow, elongated channel of gas that funnels material from the surrounding cloud onto the disk around a young star, first confirmed as freely infalling gas in 2020.

Protoscience

Protoscience is a philosophy of science term for a research field that is not yet an established science but may become one, as when alchemy led to chemistry.

Protostar

A protostar is a mass of interstellar gas and dust collapsing to form a star, gathering mass through an accretion disk until hydrogen fusion can power it.

Oct 15, 2026

Provability logic

Provability logic is a modal logic, centered on the system GL, that studies what arithmetical theories like Peano Arithmetic can prove about their own provability.

Proxima Centauri

Proxima Centauri, also called Alpha Centauri C, is a red dwarf star in Centaurus and the nearest star to the Sun, orbiting Alpha Centauri A and B.

Proxima Centauri b

Proxima Centauri b, also known as Proxima b, is an exoplanet orbiting Proxima Centauri, the Sun's closest neighbor, detected in 2016 with a minimum mass of about 1.2 Earth masses.

Proxima Centauri d

Proxima Centauri d (also written Proxima d) is a terrestrial exoplanet orbiting Proxima Centauri, the closest star to the Sun, with a minimum mass of about 0.26 Earth masses.

Proximate analysis

Proximate analysis is a set of standardized laboratory tests that partitions a solid fuel such as coal, coke, or biomass into moisture, volatile matter, fixed carbon, and ash fractions.

Oct 15, 2026

Proximity effect (electromagnetism)

The proximity effect is the redistribution of alternating current in a conductor caused by the time-varying magnetic field of a neighboring conductor, increasing effective AC resistance.

Proximity sensor

A proximity sensor, or proximity detector, detects nearby objects without physical contact, converting their presence into an electrical signal through electromagnetic, electric, light, sound, or magnetic fields.

Proximity-induced bioorthogonal chemistry

Proximity-induced bioorthogonal chemistry is a chemical biology strategy in which molecular recognition, such as ligand binding, brings two reactive groups close, triggering a bioorthogonal reaction at a chosen site.

Proximity-induced spin–orbit coupling and spin Hall effect in graphene

Proximity-induced spin–orbit coupling in graphene is the transfer of strong spin–orbit coupling from a adjacent transition-metal dichalcogenide such as WS2 or MoS2 into graphene, enabling the spin Hall effect.

Proximity-induced spin–orbit coupling in graphene/TMD heterostructures

Proximity-induced spin–orbit coupling in graphene/TMD heterostructures is the transfer of strong spin–orbit interaction from an adjacent TMD such as WS2 or WSe2 into graphene through wavefunction overlap, raising it by up to two orders of magnitude.

Proximity-induced superconductivity

Proximity-induced superconductivity is the induction of superconducting behavior in a non-superconducting material placed in electrical contact with a superconductor; it underlies Josephson junctions and weak links.

Prussian blue

Prussian blue, also known as Berlin blue or Berliner Blau, is a dark blue pigment accidentally discovered in Berlin around 1704, the first modern synthetic pigment.

Prussian blue analogues

Prussian blue analogues are a family of cyanide-bridged coordination polymers related to Prussian blue, with other transition metals replacing iron, studied for batteries and electrocatalysis.

Prussian blue nanoparticles

Prussian blue nanoparticles (PBNPs) are nanoscale particles of Prussian blue, a mixed-valence iron coordination compound studied in nanomedicine as drug carriers, imaging contrast agents, antidotes, photothermal agents, and enzyme-mimicking catalysts.