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  • Pyrrhophyta (organism)

    Dinoflagellate, (division Dinoflagellata), any of numerous one-celled aquatic organisms bearing two dissimilar flagella and having characteristics of both plants and animals. Most are marine, though some live in freshwater habitats. The group is an important component of phytoplankton in all but

  • pyrrhotite (mineral)

    Pyrrhotite, iron sulfide mineral (Fe1–xS) in the niccolite group; in it, the ratio of iron to sulfur atoms is variable but is usually slightly less than one. It commonly is found with pentlandite and other sulfides in silica-poor igneous rocks, as at Kongsberg, Nor.; Andreas-Berg, Ger.; Trentino,

  • pyrrhuloxia (bird)

    cardinal: The desert cardinal (C. sinuatus) is common to the thorn scrub of the American Southwest. Less showy than the northern cardinal, this gray bird with a red mask is also called pyrrhuloxia (formerly part of the bird’s scientific name, combining the Latin name for the bullfinch…

  • Pyrrhus (king of Epirus)

    Pyrrhus, king of Hellenistic Epirus whose costly military successes against Macedonia and Rome gave rise to the phrase “Pyrrhic victory.” His Memoirs and books on the art of war were quoted and praised by many ancient authors, including Cicero. Upon becoming ruler at the age of 12, Pyrrhus allied

  • Pyrrhus (Greek mythology)

    Neoptolemus, in Greek legend, the son of Achilles, the hero of the Greek army at Troy, and of Deïdamia, daughter of King Lycomedes of Scyros; he was sometimes called Pyrrhus, meaning “Red-haired.” In the last year of the Trojan War the Greek hero Odysseus brought him to Troy after the Trojan seer

  • Pyrroglaux podargina (bird)

    owl: General features: …birds; others, such as the Palau owl (Pyrroglaux podargina) and the Seychelles owl (Otus insularis), are endemic island species with small populations. Owls often attain higher population densities than hawks and have survived better in areas of human activity. Their nocturnal habits and inconspicuous daytime behaviour provide them some protection…

  • pyrrole (chemical compound)

    Pyrrole, any of a class of organic compounds of the heterocyclic series characterized by a ring structure composed of four carbon atoms and one nitrogen atom. The simplest member of the pyrrole family is pyrrole itself, a compound with molecular formula C4H5N. The pyrrole ring system is present in

  • pyrrolidine (chemical compound)

    heterocyclic compound: Comparison with carbocyclic compounds: …atom of nitrogen, the compound pyrrolidine, a chemical relative of pyrrole, is produced. The structural formula of pyrrolidine is written:

  • Pyrrophycophyta (organism)

    Dinoflagellate, (division Dinoflagellata), any of numerous one-celled aquatic organisms bearing two dissimilar flagella and having characteristics of both plants and animals. Most are marine, though some live in freshwater habitats. The group is an important component of phytoplankton in all but

  • Pyrrophyta (organism)

    Dinoflagellate, (division Dinoflagellata), any of numerous one-celled aquatic organisms bearing two dissimilar flagella and having characteristics of both plants and animals. Most are marine, though some live in freshwater habitats. The group is an important component of phytoplankton in all but

  • Pyrularia pubera (plant)

    Santalaceae: …oil, or buffalo, nut (Pyrularia pubera), the oil-filled, pear-shaped fruit of a North American parasite, are other commonly known members of the family.

  • Pyrus (tree and fruit)

    Pear, (genus Pyrus), genus of some 20–45 trees and shrubs in the rose family (Rosaceae), including the common pear (Pyrus communis). One of the most important fruit trees in the world, the common pear is cultivated in all temperate-zone countries of both hemispheres. The fruit is commonly eaten

  • Pyrus communis (fruit)

    pear: …rose family (Rosaceae), including the common pear (Pyrus communis). One of the most important fruit trees in the world, the common pear is cultivated in all temperate-zone countries of both hemispheres. The fruit is commonly eaten fresh or is canned. It is used to produce perry, an alcoholic beverage. Several…

  • pyruvate (chemical compound)

    carboxylic acid: Hydroxy and keto acids: …the form of its salt pyruvate) is involved in the normal metabolism of carbohydrates as the final product of a series of some 11 or 12 steps starting from glucose or fructose. It is then converted (by loss of carbon dioxide) to acetyl coenzyme A, which enters the tricarboxylic acid…

  • pyruvate dehydrogenase complex (biochemistry)

    metabolism: The oxidation of pyruvate: … and coenzymes collectively called the pyruvate dehydrogenase complex; i.e., a multienzyme complex in which the substrates are passed consecutively from one enzyme to the next, and the product of the reaction catalyzed by the first enzyme immediately becomes the substrate for the second enzyme in the complex. The overall reaction…

  • pyruvate kinase (enzyme)

    metabolism: The formation of ATP: …PEP to ADP, catalyzed by pyruvate kinase [10], is also highly exergonic and is thus virtually irreversible under physiological conditions.

  • pyruvic acid (chemical compound)

    Pyruvic acid, (CH3COCOOH), is an organic acid that probably occurs in all living cells. It ionizes to give a hydrogen ion and an anion, termed pyruvate. Biochemists use the terms pyruvate and pyruvic acid almost interchangeably. Pyruvic acid is a key product at the crossroads between the catabolism

  • Pyryatyn (Ukraine)

    Pyryatyn, city, east-central Ukraine, on the Uday River. Pyryatyn dates at least from 1155, when it is first documented, and was incorporated in 1781. Before the Russian Revolution of 1917, it was an administrative centre and later became a railway junction. Its varied industries have produced such

  • pyrylium (chemical compound)

    heterocyclic compound: Six-membered rings with one heteroatom: Positively charged ions (cations) of pyrylium and thiopyrylium are the parent six-membered, aromatic, monocyclic oxygen and sulfur compounds of their respective groups.

  • Pyshma River (river, Russia)

    Pyshma River, river in Sverdlovsk and Tyumen oblasti, Russia, a right-bank tributary of the Tura River, part of the Ob River basin. The Pyshma drains a basin of approximately 7,600 square miles (19,700 square km). The river rises on the eastern slopes of the central Ural Mountains, just north of

  • Pyšma River (river, Russia)

    Pyshma River, river in Sverdlovsk and Tyumen oblasti, Russia, a right-bank tributary of the Tura River, part of the Ob River basin. The Pyshma drains a basin of approximately 7,600 square miles (19,700 square km). The river rises on the eastern slopes of the central Ural Mountains, just north of

  • Pythagoras (Greek philosopher and mathematician)

    Pythagoras, Greek philosopher, mathematician, and founder of the Pythagorean brotherhood that, although religious in nature, formulated principles that influenced the thought of Plato and Aristotle and contributed to the development of mathematics and Western rational philosophy. (For a fuller

  • Pythagoras (Greek sculptor)

    Pythagoras, noted Greek sculptor of Rhegium (present-day Reggio di Calabria, Italy), a contemporary of Myron and Polyclitus and their rival in making statues of athletes. One of those, that of the boxer Euthymus of Locri, was erected after the latter’s third victory at Olympia in 472 bce.

  • Pythagorean comma (music)

    comma: …which is audible, is the Pythagorean comma.

  • Pythagorean number (mathematics)

    number game: Pythagorean triples: The study of Pythagorean triples as well as the general theorem of Pythagoras leads to many unexpected byways in mathematics. A Pythagorean triple is formed by the measures of the sides of an integral right triangle—i.e., any set of three positive integers such…

  • Pythagorean scale (music)

    South Asian arts: Qualities of the scales: …found in the ancient Greek Pythagorean scale. Thus, if in a mode the consonance ri-pa (E–A) were needed, one would tune to the madhyamagrama scale. But, if the consonance sa-pa (D–A) were important, it could be obtained with the sadjagrama tuning. There was a further development in this system caused…

  • Pythagorean theorem (mathematics)

    Pythagorean theorem, the well-known geometric theorem that the sum of the squares on the legs of a right triangle is equal to the square on the hypotenuse (the side opposite the right angle)—or, in familiar algebraic notation, a2 + b2 = c2. Although the theorem has long been associated with Greek

  • Pythagorean triple (mathematics)

    mathematics: Geometric and algebraic problems: (Such solutions are sometimes called Pythagorean triples.) A tablet in the Columbia University Collection presents a list of 15 such triples (decimal equivalents are shown in parentheses at the right; the gaps in the expressions for h, b, and d separate the place values in the sexagesimal numerals):

  • Pythagorean tuning (music)

    tuning and temperament: Classic tuning systems: …in the Middle Ages, one, Pythagorean tuning, makes all the fifths perfectly consonant. As a result, all the major thirds and major sixths are sharp (too wide) by 22 cents (a cent is 1/1200 of an octave) or by the ratio of 81:80. This amount is called a comma of…

  • Pythagoreanism

    Pythagoreanism, philosophical school and religious brotherhood, believed to have been founded by Pythagoras of Samos, who settled in Croton in southern Italy about 525 bce. The character of the original Pythagoreanism is controversial, and the conglomeration of disparate features that it displayed

  • Pytheas (Greek explorer)

    Pytheas, navigator, geographer, astronomer, and the first Greek to visit and describe the British Isles and the Atlantic coast of Europe. Though his principal work, On the Ocean, is lost, something is known of his ventures through the Greek historian Polybius (c. 200–c. 118 bc). Sailing from the

  • Pythia (Greek religion)

    ecstasy: The Pythia (priestess) of the Greek oracle at Delphi often went into an ecstatic state during which she uttered sounds revealed to her by the python (the snake, the symbol of resurrection), after drinking water from a certain spring. Her “words” were then interpreted by a…

  • Pythiales (chromist order)

    fungus: Annotated classification: Order Pythiales Pathogenic in plants, algae, and fungi, some are saprotrophic in soil or water; hyphae may grow within or between cells of plants, causing root rot; example genera include Pythium, Phytophthora, and Pythiogeton. Order Rhipidiales Aquatic, saprotrophic, often found in

  • Pythian Games (Greek games)

    Pythian Games, in ancient Greece, various athletic and musical competitions held in honour of Apollo, chiefly those at Delphi. The musicians’ contest there dated from very early times. In 582 bc it was made quadrennial, and athletic events including foot and chariot races were added in emulation

  • Pythidae (insect family)

    coleopteran: Annotated classification: …temperate region; example Pyrochroa Family Pythidae Few species widely distributed in Eurasia and America; example Pytho. Family Rhipiphoridae (wedge-shaped beetles) About 400 species, many with specialized parasitic habits on other insects; complicated life cycle; examples Pelecotoma, Metoecus.

  • pythiosis (disease)

    Pythium: insidiosum causes pythiosis, a rare and deadly tropical disease found in dogs, horses, humans, and certain other mammals.

  • Pythium (chromist genus)

    Pythium, genus of destructive root parasites of the family Pythiaceae (phylum Oomycota, kingdom Chromista). Pythium species have filamentous sporangia, smooth-walled spherical oogonia, and stalked antheridia. Several are often responsible for serious diseases in plants, such as damping-off and rot.

  • Pythium insidiosum (chromist)

    Pythium: P. insidiosum causes pythiosis, a rare and deadly tropical disease found in dogs, horses, humans, and certain other mammals.

  • Pythius (Greek architect)

    Priene: Built by Pythius, probable architect of the Mausoleum of Halicarnassus, the temple was recognized in ancient times as the classic example of the pure Ionic style. Priene is laid out on a grid plan, with 6 main streets running east-west and 15 streets crossing at right angles,…

  • Pytho (Greek religion)

    ecstasy: The Pythia (priestess) of the Greek oracle at Delphi often went into an ecstatic state during which she uttered sounds revealed to her by the python (the snake, the symbol of resurrection), after drinking water from a certain spring. Her “words” were then interpreted by a…

  • python (snake group)

    Python, any of about 40 species of snakes, all but one of which are found in the Old World tropics and subtropics. Most are large, with the reticulated python (Python reticulatus) of Asia attaining a maximum recorded length of 9.6 metres (31.5 feet). Eight species of genus Python live in

  • Python (Greek mythology)

    Python, in Greek mythology, a huge serpent that was killed by the god Apollo at Delphi either because it would not let him found his oracle, being accustomed itself to giving oracles, or because it had persecuted Apollo’s mother, Leto, during her pregnancy. In the earliest account, the Homeric Hymn

  • Python 3 (weapon)

    tactical weapons system: Air-to-air systems: …Israeli missile system, known as Python 3, is said to have shot down 50 Syrian aircraft in the invasion of Lebanon in 1982. When that system detects an airplane within range, it lights an indicator lamp and sounds a warning in the cockpit of the aircraft carrying the missile. The…

  • Python molurus (snake)

    python: sebae), India (P. molurus), New Guinea (L. papuanus), and Australia (L. amethistinus) regularly exceed 3 metres (10 feet). Despite their large size, some of these species survive in urban and suburban areas, where their secretive habits and recognized value as rat catchers par excellence serve to…

  • Python molurus bivittatus (snake)

    Florida panther: Prey and conservation status: …some ecologists fear that the Burmese python (Python molurus bivittatus), an invasive species that competes with the Florida panther for prey, is reducing prey populations and thus contributing to increased panther mortality.

  • Python reticulatus (snake)

    python: Most are large, with the reticulated python (Python reticulatus) of Asia attaining a maximum recorded length of 9.6 metres (31.5 feet).

  • Python sebae (snake)

    python: …metre, but some pythons of Africa (P. sebae), India (P. molurus), New Guinea (L. papuanus), and Australia (L. amethistinus) regularly exceed 3 metres (10 feet). Despite their large size, some of these species survive in urban and suburban areas, where their secretive habits and recognized value as rat catchers par…

  • Pyu (people)

    Myanmar: The Pyu state: Between the 1st century bce and the 9th century ce, speakers of Tibeto-Burman languages known as the Pyu established city-kingdoms in Myanmar at Binnaka, Mongamo, Shri Kshetra, and Halingyi. At the time, a long-standing trade route between China and India passed through northern…

  • pyx (Christian vessel)

    Pyx, in Christianity, vessel containing the consecrated bread used in the service of Holy Communion. Although pyxes were made in various shapes, such as that of a dove, the most common form was that of a small cylindrical box fitted with a cover, which is generally conical. An English pyx dating

  • Pyxidiophorales (order of fungi)

    fungus: Annotated classification: Order Pyxidiophorales Ectoparasitic on mandibulate arthropods, may be mycoparasitic; mycelial; anamorphs lack vesiculate conidiophores; example genus includes Pyxidiophora. Class Lecanoromycetes Forms lichens; thick ascal apex with narrow canal; includes subclasses Acarosporomycetidae, Lecanoromycetidae, and Ostropomycetidae; contains 10

  • Pyxis (astronomy)

    Pyxis, (Latin: “Compass”) constellation in the southern sky at about 9 hours right ascension and 30° south in declination. Its brightest star is Alpha Pyxidis, with a magnitude of 3.7. The French astronomer Nicolas Louis de Lacaille formed this constellation in 1754 from stars near what was

  • Pyynikki Open Air Theatre (theatre, Tampere, Finland)

    Finland: Theatre, opera, and music: …in the country is the Pyynikki Open Air Theatre of Tampere, the revolving auditorium of which can be moved to face any of the natural sets. There are innumerable institutions connected with the theatre in Finland, including the Central Federation of Finnish Theatrical Organizations. There is a wide repertory of…

  • Pz. 61 (tank)

    tank: Gun calibre: …gun was adopted for the Pz. 61 and Pz. 68 tanks produced in Switzerland, the West German Leopard 1, the Swedish S-tank, the Japanese Type 74, and the Mark 1 and 2 versions of the Israeli Merkava. It was also retained in the original version of the U.S. M1 Abrams…

  • Pz. I (tank)

    panzer: Pz. I: The Pz. I was a light tank intended as a training vehicle for the new panzer divisions until the more powerful Pz. II, III, and IV tanks could be put into service. The Pz. I went into production in 1934. It was lightly…

  • Pz. IB (tank)

    panzer: Pz. I: …and an improved version, the IB, was used in large numbers by the German army in the invasions of Poland (1939) and France (1940). The lightly armed and armoured IB performed adequately in these campaigns because it was used in massed formations and because opposing forces made poor use of…

  • Pz. II (tank)

    panzer: Pz. II: The Pz. II was larger and more heavily armed and armoured than the Pz. I, but it was still a light tank. It was nevertheless the mainstay of the panzer divisions in the first two years of the war, because of delays encountered…

  • Pz. III (tank)

    tank: Interwar developments: …cruiser tanks, and the German Pz. III also required support from more heavily armed tanks if they were to engage in fighting of any intensity. The need for tanks with more powerful 75-mm guns was clearly recognized in Germany, leading in 1934 to the design of the Pz. IV. The…

  • Pz. IV (tank)

    tank: World War II: The German Pz. IV and Soviet T-34 were rearmed in 1942 with longer-barreled, higher-velocity guns; soon afterward these began to be displaced by more powerfully armed tanks. In 1943 the Germans introduced the Panther medium tank with a long 75-mm gun having a muzzle velocity of 936…

  • Pz. V (tank)

    tank: World War II: …1943 the Germans introduced the Panther medium tank with a long 75-mm gun having a muzzle velocity of 936 metres (3,070 feet) per second, compared with 384 metres (1,260 feet) per second for the original Pz. IV and 750 metres (2,460 feet) per second for its 1942 version. The 43-ton…

  • Pz. VI (tank)

    Ferdinand Porsche: …designed military vehicles, notably the Tiger tank. After the war the elder Porsche was imprisoned by the French for a time. In 1950 the Porsche sports car was introduced. The Porsche Museum opened in Zuffenhausen, a suburb of Stuttgart, in 2009.

  • PZPR (political party, Poland)

    Poland: Political process: …Poland was governed by the Polish United Workers’ Party (PUWP; Polska Zjednoczona Partia Robotnicza), the country’s communist party, which was modeled on the Communist Party of the Soviet Union. The postwar government was run as a dual system in which state organs were controlled by parallel organs of the PUWP.…

  • PZT (instrument)

    time: Time determination: The photographic zenith tube (PZT) is a telescope permanently mounted in a precisely vertical position. The light from a star passing almost directly overhead is refracted by the lens, reflected from the perfectly horizontal surface of a pool of mercury, and brought to a focus just…

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