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Pacific storm track
The Pacific storm track is the band over the North Pacific where migrating cyclones and anticyclones are most active, supplying much of western North America's winter weather.
Pacific Time Zone
Pacific Time Zone (PT): North American zone using PST (UTC−8) in winter and PDT (UTC−7) in summer, covering the US West Coast, British Columbia, Yukon, and Baja California; created by railroads in 1883.
Pacific Tsunami Warning Center
The Pacific Tsunami Warning Center (PTWC) is a National Weather Service facility at ʻEwa Beach, Hawaii, established in 1949 to warn of tsunamis across the Pacific and Caribbean.
Pacific–North American pattern
The Pacific–North American pattern (PNA) is a prominent teleconnection pattern of atmospheric circulation variability over the North Pacific and North America, tracked by a NOAA index since 1950.
Packed bed reactor
A packed bed reactor, or fixed bed reactor, is a chemical reactor where reactants flow through a stationary bed of solid catalyst pellets inside a vessel.
Packing fraction (mass spectrometry)
The packing fraction, introduced by Francis William Aston in the 1920s, measures how far an isotope's mass deviates from its whole-number mass number, reflecting nuclear binding energy.
Packing problems
A packing problem asks how to arrange objects in a region without overlap, optimizing density or number of items, from sphere packing to bin packing.
Packstone
Packstone is a limestone in the Dunham classification of carbonate rocks, defined in 1962 as grain supported but containing carbonate mud between the sand-sized grains.
Paddle-wheel mechanism
The paddle-wheel mechanism is a proposed ion-transport process in solid electrolytes, coined in the 1980s for superionic sulfates like Li₂SO₄, where rotating anion groups assist cation motion.
Padé approximant
A Padé approximant is a rational function whose power series expansion matches a given function's series to the highest possible order, often beating truncated Taylor series near poles.
Padmini Rangamani
Padmini Rangamani is an Indian-born American theoretical biophysicist, professor at UC San Diego, and 2017 recipient of the Presidential Early Career Award for Scientists and Engineers.
Padovan sequence
The Padovan sequence, also called the Cordonnier sequence, is an integer sequence defined by P(n) = P(n−2) + P(n−3), named by Ian Stewart in 1996.
Paeoniflorin
Paeoniflorin is a water-soluble monoterpene glycoside, the principal active glucoside of peony roots (Paeonia lactiflora), isolated in 1963 and studied for anti-inflammatory, neuroprotective, and cardiovascular effects.
PAGASA
PAGASA, the Philippine Atmospheric, Geophysical and Astronomical Services Administration, is the national weather service of the Philippines under the Department of Science and Technology, issuing forecasts, typhoon warnings, and flood bulletins.
PAGASA name lists for tropical cyclones
PAGASA name lists are four rotating sets of 25 Filipino names, each with a 10-name auxiliary list, that PAGASA assigns to tropical cyclones entering the Philippine Area of Responsibility.
Page curve
The Page curve is the expected entanglement entropy of Hawking radiation from an evaporating black hole, rising to a peak at the Page time and then falling to zero.
Painlevé analysis
Painlevé analysis is a singularity-based technique testing whether nonlinear differential equations have only pole-type movable singularities, used to detect integrability and construct exact solutions, Lax pairs, and Bäcklund transformations.
Painlevé paradox
The Painlevé paradox is a breakdown of determinism in rigid-body equations with Coulomb friction, identified by Paul Painlevé in 1895: the equations admit no solution or several.
Pair distribution function
The pair distribution function is a real-space structural measure giving the probability of finding atom pairs a distance r apart, used for glasses, liquids, and nanomaterials.
Pair plasma
A pair plasma is a quasi-neutral plasma of particles and their antiparticles, typically electrons and positrons, with no ion component, found in pulsar magnetospheres, relativistic jets, and gamma-ray bursts.
Pair production
Pair production, or pair creation, converts a high-energy photon into an electron and a positron in the field of a nucleus, requiring at least 1.022 MeV.
Pair production cascade
A pair production cascade is an electromagnetic cascade in intergalactic space where TeV gamma rays absorbed by the extragalactic background light regenerate GeV gamma rays through inverse Compton scattering.
Pair-density wave
The pair-density wave (PDW) is a proposed superconducting state in which Cooper pairs carry finite momentum, making the superconducting order parameter oscillate in space rather than stay uniform.
Pair-density-wave order in cuprates
Pair-density-wave (PDW) order in cuprates is a proposed superconducting state in which the order parameter oscillates spatially, giving Cooper pairs finite momentum, proposed as a mother order behind charge order and the pseudogap.
Pair-instability mass gap
The pair-instability mass gap is a predicted range of black hole masses, roughly 50 to 130 solar masses, where pair-instability supernovae disrupt very massive stars completely.
Pair-instability supernova
A pair-instability supernova (PISN) is a thermonuclear explosion that completely disrupts a very massive star when pair creation removes core pressure support, leaving no neutron star or black hole behind.
Paired electrosynthesis
Paired electrosynthesis is an electrochemical synthesis strategy in which both the anode and the cathode yield valuable compounds, achieving up to 200% current efficiency and improving sustainability.
Pairwise comparison
A pairwise comparison is a statistical evaluation of one pair of treatments or items at a time, used to test differences between group means or to rank items from preferences.
Pairwise independence
Pairwise independence is a property in probability theory where every pair of random variables or events is independent, even though the collection as a whole may not be mutually independent.
Päivi Törmä
Päivi Törmä is a Finnish physicist and professor of applied physics at Aalto University, where she leads the Quantum Dynamics group and studies nanoplasmonics and superconductivity.