All articles starting with P
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Positron emission
Positron emission, also called beta-plus (β+) decay, is a mode of radioactive decay in which a proton in the nucleus becomes a neutron, emitting a positron and an electron neutrino.
Positron emission tomography
Positron emission tomography (PET) is a nuclear medicine imaging method using positron-emitting tracers such as F-18 FDG and annihilation coincidence detection, chiefly for cancer staging via PET/CT, with PET/MRI emerging.
Positron fraction excess
The positron fraction excess is the unexpected rise in the cosmic-ray positron fraction above roughly 10 GeV, observed by PAMELA and confirmed by AMS-02 in 2013.
Positronic brain
A positronic brain is a fictional device invented by Isaac Asimov as the thinking organ of his robots, built around the Three Laws of Robotics.
Positronium
Positronium (Ps) is an exotic hydrogen-like atom in which an electron is bound to a positron, its antiparticle, making it the simplest bound state in physics.
Posiva
Posiva is a Finnish company, founded in 1995–1996 and owned by TVO and Fortum, building the world's first deep geological repository for spent nuclear fuel at Olkiluoto.
POSIX
POSIX, formally the Portable Operating System Interface and once proposed as IEEE-IX, is a family of IEEE standards defining a C API, shell, and utilities for application portability.
POSIX ACLs
POSIX ACLs are access control lists for files and directories that extend the traditional UNIX permission model with per-user and per-group entries, as in the withdrawn POSIX 1003.1e draft.
POSIX threads
POSIX threads, commonly called Pthreads, is the POSIX.1 standard interface for threaded programming in C, first standardized as IEEE Std 1003.1c-1995 and now part of POSIX.1-2024.
POSM process
The POSM process (propylene oxide/styrene monomer process), also called PO/SM or SMPO, co-produces propylene oxide and styrene monomer from ethylbenzene and propylene; it was commercialized in 1969.
Posolsky Prikaz
The Posolsky Prikaz (Посольский приказ, Ambassadorial Chancellery) was the Russian state's foreign affairs office from 1549 until its replacement by the Collegium of Foreign Affairs in 1720.
Pospiviroidae
Pospiviroidae, named after potato spindle tuber viroid (PSTVd), is the larger family of viroids: circular single-stranded RNAs of 246–375 nt with a rod-like structure, CCR, nuclear asymmetric rolling-circle replication via host RNA polymerase II, five genera, 40 species.
Posse (1993 film)
Posse is a 1993 American revisionist Western directed by and starring Mario Van Peebles, about Black soldiers defending a Black town from the Ku Klux Klan.
Posse comitatus
Posse comitatus is a federal statute enacted in 1878 that criminalizes the willful deployment of the Army, Navy, Marine Corps, Air Force, or Space Force for law enforcement.
Posse Comitatus (organization)
Posse Comitatus ("power of the county"): American far-right organization founded 1969 in Portland, Oregon by Mike Beach and William Potter Gale; held the county sheriff to be supreme authority; precursor of sovereign citizen and militia movements.
Posse Comitatus Act
Posse Comitatus Act (18 U.S.C. §1385), an 1878 U.S. criminal statute barring federal military forces from domestic law enforcement except when authorized by the Constitution or Congress; principal exception is the Insurrection Act; amended in 2021 to cover all service branches.
Possessed (band)
Possessed: San Francisco death/thrash metal band formed 1983; regarded as the first death metal band. Seven Churches (1985) and its song "Death Metal" named and defined the genre; Jeff Becerra leads the 2007-reformed band.
Possession (1981 film)
Possession (1981), Andrzej Żuławski's French-West German horror-drama starring Isabelle Adjani and Sam Neill, depicts a divorcing couple in West Berlin, a tentacled monster, Cannes Best Actress win, video-nasty ban, and cult legacy.
Possession (2027 film)
Possession (2027) is Parker Finn's Paramount remake of Andrzej Żuławski's 1981 cult horror film, starring Margaret Qualley and Callum Turner as a divorcing couple, produced with Robert Pattinson, releasing June 11, 2027.
Possession (British TV series)
Possession (formerly Inheritance) is a 2026 five-part Sky Original supernatural thriller created by Karla Crome, directed by Storm Saulter, starring Gugu Mbatha-Raw as a lawyer contesting a £50m inheritance on a haunted Jamaican slave plantation.
Possession trance disorder
Possession trance disorder, ICD-11 code 6B63, is a dissociative disorder in which a possessing spirit or deity involuntarily replaces a person's identity, causing distress; diagnosis excludes cultural or religious practices.
Possessional peasants
Possessional peasants (Посессионные крестьяне) were Russian serfs bound to a factory or manufactory rather than an individual owner, created by a decree of Peter I in 1721.
Possessive
Possessive constructions in linguistics: how languages mark possession (English 's, genitive, head-marking, particles), alienability splits, obligatory possessive inflection, and Ye's universals on independent versus dependent possessive forms (mine/my).
Possessor (film)
Possessor is a 2020 Canadian-British sci-fi horror thriller written and directed by Brandon Cronenberg, starring Andrea Riseborough as assassin Tasya Vos, who uses brain-implant technology to control others' bodies; Sundance 2020 premiere, Sitges award winner.
Posset
Posset: historic British drink of milk curdled with wine, ale, or citrus, sweetened and spiced; layered grace, custard, and alcohol; obsolete by 1800, revived as lemon posset dessert.
Possibility theory
Possibility theory is a mathematical framework for reasoning under uncertainty from incomplete or imprecise information rather than randomness, introduced by Lotfi Zadeh in 1978 and developed by Dubois and Prade.
Possible Love (가능한 사랑)
Possible Love (가능한 사랑, Ga-neung-han Sa-rang) is a 2026 South Korean drama by Lee Chang-dong, his first film since Burning (2018), starring Jeon Do-yeon, Sul Kyung-gu, Zo In-sung, and Cho Yeo-jeong; it won the Venice Silver Lion and is Korea's 99th Academy Awards submission.
Possible reserves
Possible reserves are the most uncertain category of petroleum reserves, less likely to be recoverable than probable reserves, with at least a 10% recovery probability.
Possible world
A possible world, also called a possible universe, is a complete way things could have been, used in modal logic to define possibility and necessity.
Possibly the Greatest Alchemist of All Time
Izure Saikyou no Renkinjutsushi? (いずれ最強の錬金術師？), known in English as Possibly the Greatest Alchemist of All Time, is Kogitsunemaru's isekai light novel series from AlphaPolis about salaryman Takumi Iruma, accidentally summoned to Mildgard and granted an all-creating alchemy skill; adapted into manga and a 2025 Studio Comet anime with season 2 announced.