(from the article "aldehyde") ...catalyst, but this method is less useful on a smaller scale such as in chemistry laboratories. On a laboratory scale, a number of reagents have been used, most notably pyridinium ...
(from the article "drug") ...this condition because they enhance the action of acetylcholine and enable transmission to occur in spite of the loss of receptors; they do not affect the underlying disease process. Neostigmine ...
(from the article "Bovet, Daniel") ...effect of histamine) is effective in treating allergic reactions. This discovery led to development of the first antihistamine drug for humans in 1942, and in 1944 one of Bovet's own ...
(from the article "drug") ...where chloroquine-resistant Plasmodium falciparum is encountered, however, mefloquine or doxycycline are used for prevention of the disease. Quinine sulfate, along with pyrimethamine and sulfadoxine, is used to ...
any of a class of organic compounds of the heterocyclic series characterized by a ring structure composed of four carbon atoms and two nitrogen atoms. The simplest member of the ... [7 Related Articles]
(from the article "genetic disease, human") Ultraviolet light, when acting on DNA, can lead to covalent linking of adjacent pyrimidine bases. Such pyrimidine dimerization is mutagenic, but this damage can be repaired by an enzyme called ...
a naturally occurring iron disulfide mineral. The name comes from the Greek word pyr, "fire," because pyrite emits sparks when struck by steel. Pyrite is called fool's gold because its ... [10 Related Articles]
(from the article "sulfide mineral") ...crystalling in this manner is galena (PbS), the ore mineral of lead. A type of packing that involves two sulfide ions in each of the octahedral positions in the sodium ...
natural, solid hydrocarbon substance, distinguishable from bitumen (q.v.) by being infusible and insoluble. When heated, however, pyrobitumens generate or transform into bitumen-like liquid or gaseous petroleum compounds. [1 Related Articles]
(from the article "explosive") ...It was first marketed about 1909 and was the most important type of smokeless powder used by the Allies in World War I. It was made from a nitrocotton of ...
(from the article "tyrant flycatcher") ...in black and white. Many have a patch of red or yellow on the crown (often concealed, but erectile, nevertheless). In all but a few, the sexes are marked alike. ...
a complex oxide mineral [(Na, Ca)2Nb2O6(OH,F)] composed of niobium, sodium, and calcium that forms brown to black, glassy octahedral crystals and irregular masses. Tantalum atoms replace niobium atoms in the ... [1 Related Articles]
(from the article "volcano") Pyroclastic cones (also called cinder cones or scoria cones) such as Cerro Negro in Nicaragua are relatively small, steep (about 30°) volcanic landforms built of loose pyroclastic fragments, most of ...
in a volcanic eruption, a fluidized mixture of hot rock fragments, hot gases, and entrapped air that moves at high speed in thick, gray-to-black, turbulent clouds that hug the ground. ... [8 Related Articles]
(from the article "igneous rock") ...and dislocation of solid material. In volcanic environments they generally result from explosive activity or the incorporation of solid fragments by moving lava; as such, they characterize the pyroclastic rocks. ...
(from the article "pyroclastic flow") ...are generally produced by large eruptions that form calderas. Nuees ardentes deposit ash- to block-sized fragments that are denser than pumice. Pyroclastic surges are low-density flows that ...
(from the article "igneous rock") Pyroclastic texture results from the explosive fragmentation of volcanic material, including magma (commonly the light, frothy pumice variety and glass fragments called shards), country rock, and phenocrysts. Fragments less than ...
(from the article "bacteria") ...Most striking was the discovery in the mid-1980s of bacteria and archaea in nutrient-rich, extremely hot hydrothermal vents on the deep seafloor. The archaea in the genus
development of opposite electrical charges on different parts of a crystal that is subjected to temperature change. First observed (1824) in quartz, pyroelectricity is exhibited only in crystallized nonconducting substances ... [1 Related Articles]
an organic compound belonging to the phenol family, used as a photographic film developer and in the preparation of other chemicals. [3 Related Articles]
(from the article "human disease") ...large amounts of tissue have died because of lack of blood supply. Body temperature is controlled by the thermostatic centre in the hypothalamus. Certain protein and polysaccharide substances called pyrogens, ...
(from the article "wood tar") Hardwood tars are obtained from pyroligneous acid, either as a deposit from the acid or as a residue from the distillation of the acid. Crude pyroligneous acid is the condensed, ...
rock consisting of about three parts peridotite and one part basalt. The name was coined to explain the chemical and mineralogic composition of the upper mantle of the Earth. The ...
common manganese mineral, manganese dioxide (MnO2), that constitutes an important ore. Always formed under highly oxidizing conditions, it forms light-gray to black, metallic, moderately heavy coatings, crusts, or fibres that ... [1 Related Articles]
(from the article "carbene") in which R and R' represent two organic groups, which may be the same or different. On either photolysis or pyrolysis (treatment with light or heat, respectively), diazo compounds cleave ...
(from the article "augury") ...each with its own specialist jargon and ritual, were atmospheric phenomena (aeromancy), cards (cartomancy), dice or lots (cleromancy), dots and other marks on paper (geomancy), fire and smoke (pyromancy), the ...
impulse-control disorder characterized by the recurrent compulsion to set fires. The term refers only to the setting of fires for sexual or other gratification provided by the fire itself, not ...
(from the article "metallurgy") Two of the most common pyrometallurgical processes, in both extraction and refining, are oxidation and reduction. In oxidation, metals having a great affinity for oxygen selectively combine with it to ...
(from the article "rock") ...produces apparent layering, or banding, because of the segregation of minerals into separate bands. Metamorphic processes can also occur at the Earth's surface due to meteorite impact events and pyrometamorphism ...
device for measuring relatively high temperatures, such as are encountered in furnaces. Most pyrometers work by measuring radiation from the body whose temperature is to be measured. Radiation devices have ... [3 Related Articles]
phosphate mineral, lead chloride phosphate [Pb5(PO4)3Cl], that is a minor ore of lead. It occurs with galena, cerussite, and limonite in the oxidized zone of lead deposits, where it forms ...
(from the article "cup fungus") ...which contains about 50 widespread species, produces in summer a cup-shaped fruiting body or mushroomlike structure on rotting wood or manure. Fire fungus is the common name for two genera ...
magnesium aluminum garnet (Mg3Al2), the transparent form of which is used as a gemstone. Its colour varies from brownish red to purplish red. A beautiful, deep-red pyrope is often called ... [1 Related Articles]
(from the article "organometallic compound") ...useful organometallic reagents Li(CH3), Zn(CH3)2, B(CH3)3, and Al2(CH3)6 are spontaneously flammable in air (pyrophoric). Accordingly, techniques have been developed to handle these and other pyrophoric compounds. Glass reaction vessels sealed ...
(from the article "click beetle") ...American click beetle, grows to 45 mm (over 1 34 in.) long and has two large black-and-white eyelike spots on the prothorax, a region behind the head. The genus Pyrophorus, ...
(from the article "metabolism") In this series of reactions, n indicates the number of hydrocarbon units (&singlehorzbond;CH2&singlehorzbond;) in the molecule. Because most tissues contain highly active pyrophosphatase enzymes [21a], which catalyze the virtually irreversible ...
(from the article "isoprenoid") The head-to-tail coupling of isosprenoid units in biosynthesis logically follows from expected enzymatic reaction patterns of the pyrophosphate units (see below Biosynthesis of isoprenoids). Tail-to-tail coupling does not appear to follow ...
very soft, pale-coloured silicate mineral, hydrated aluminum silicate, Al2(OH)2 Si4O10, that is the main constituent of some schistose rocks. The most extensive commercial deposits are in North Carolina, but pyrophyllite ... [3 Related Articles]
(from the article "bioluminescence") Among other higher animals, the chordate subphylum Tunicata contains luminous forms. The genus Pyrosoma includes several species that account for the brilliant luminescence among macroplanktons of the seas, giving rise ...
(from the article "tunicate") ...forms; atrial aperture directed toward the rear of each zooid; asexual buds form from a ventral stolon; about 70 species.Zooids embedded in a tube open at one end.Complex ...
(from the article "magnesium processing") Magnesium has been used in military pyrotechnics for many years and has found numerous uses in incendiary devices and flares. In the form of finely divided particles, it has been ...
any of a group of important rock-forming silicate minerals of variable composition, among which calcium-, magnesium-, and iron-rich varieties predominate. [9 Related Articles]
(from the article "pyroxene") ...and FeSiO3 (ferrosilite). Since no true pyroxenes exist with calcium contents greater than that of the diopside-hedenbergite join, the part of this system below this join is known as the ...
(from the article "metamorphic rock") Rocks of the pyroxene-hornfels facies are characteristically formed near larger granitic or gabbroic bodies at depths of a few kilometres or at pressures of a few hundred bars. The mineral ...
dark-coloured, intrusive igneous rock that consists chiefly of pyroxene. Pyroxenites are not abundant; they occur in discrete inclusions, in layered sills (tabular bodies inserted between other rocks) and lopoliths (laccoliths ...
(from the article "Deucalion") in Greek legend, the Greek equivalent of Noah, the son of Prometheus (the creator of humankind), king of Phthia in Thessaly, and husband of Pyrrha; he was also the father ...
(from the article "prosody") Some theorists also admit the spondaic foot ('') and pyrrhic foot (˘˘) into their scansions; however, spondees and pyrrhics occur only as substitutions for other feet, never as determinants of ...
(from the article "ancient Rome") Rome spent the 280s BC putting down unrest in northern Italy, but its attention was soon directed to the far south as well by a quarrel between the Greek city ...
(from the article "dance, Western") Another dance form that originated in Crete and flourished in Greece was the pyrrhiche, a weapon dance. Practiced in Sparta as part of military training, it was a basis for ...
(from the article "Skepticism") The other major form of ancient Skepticism was Pyrrhonism, apparently developed by medical Skeptics in Alexandria. Beginning with Aenesidemus (1st century BC), this movement, named after Pyrrhon, criticized the Academic ...
(from the article "algae") ...Cryptomonas, Falcomonas, and Rhinomonas.Predominantly unicellular flagellates; approximately half of the species are heterotrophic rather than photosynthetic; photosynthetic forms with...dinoflagellate
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 ... [2 Related Articles]
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 ... [9 Related Articles]
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 ... [3 Related Articles]
(from the article "heterocyclic compound") When one of the carbon atoms of cyclopentane is replaced with an atom of nitrogen, the compound pyrrolidine, a chemical relative of pyrrole, is produced. The structural formula of pyrrolidine ...
(from the article "pear") any of several species of the genus Pyrus, especially Pyrus communis, of the rose family (Rosaceae), which is one of the most important fruit trees of the world and is ...
(from the article "carboxylic acid") Pyruvic acid (in 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 ...
(from the article "metabolism") The oxidation of pyruvate involves the concerted action of several enzymes and coenzymes collectively called the pyruvate dehydrogenase complex; i.e., a multienzyme complex in which the substrates are passed consecutively ...
(from the article "metabolism") ...(PEP), water being lost from 2-phosphoglycerate in the process. Phosphoenolpyruvate acts as the second source of ATP in glycolysis. The transfer of the phosphate group from PEP to ADP, catalyzed ...
(from the article "carboxylic acid") Pyruvic acid and acetoacetic acid are the simplest and most important of the alpha-keto and beta-keto acids, respectively.
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 ...
(from the article "heterocyclic compound") Positively charged ions (cations) of pyrylium and thiopyrylium are the parent six-membered, aromatic, monocyclic oxygen and sulfur compounds of their respective groups.
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 ... [20 Related Articles]
noted Greek sculptor of Rhegium, in Italy (present Reggio di Calabria), a contemporary of Myron and Polyclitus and their rival in making statues of athletes. One of these, that of ...
(from the article "comma") ...occurs: . . . A♯, E♯, B♯. This B♯, however, instead of being exactly in tune with C, is slightly higher, by 0.24 of a semitone. This difference, which is ...
(from the article "number game") 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 ...
(from the article "South Asian arts") The two parent scales are complementary and between them supply all the consonances found in the ancient Greek Pythagorean scale. Thus, if in a mode the consonance ri-pa (E-A) were ...
proposition number 47 from Book I of Euclid's Elements, the well-known geometric theorem that the sum of the squares on the legs of a right triangle is ... [10 Related Articles]
(from the article "mathematics") ...of the terms, the third will usually be irrational, but it is possible to find cases in which all three terms are integers: for example, 3, 4, 5 and 5, ...
(from the article "musical sound") ...viewpoint all suffer from one of two mutually exclusive faults: either they lack relationships (intervals) of uniform size, or they are incapable of providing chords that are acceptable to the ...
philosophical school and religious brotherhood, believed to have been founded by Pythagoras of Samos, who settled in Croton in southern Italy about 525 BC. [27 Related Articles]
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 ... [4 Related Articles]
(from the article "oracle") ...the Corinthian Gulf. Traditionally, the oracle first belonged to Mother Earth (Gaea) but later was either given to or stolen by Apollo. At Delphi the medium was a woman over ...
(from the article "fungus") ...and behaving as conidia (asexually produced spores); example genera include Albugo, Peronospora, Bremia, and Plasmopara.Pathogenic in plants, algae, and fungi, some are saprobic in soil or water; hyphae may ...
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 ... [4 Related Articles]
(from the article "Pythium") a genus of destructive root-parasitic fungi of the family Pythiaceae (phylum Oomycota, kingdom Chromista), having filamentous sporangia, smooth-walled, spherical oogonia, and stalked antheridia. Species of Pythium are often responsible for ...
(from the article "Priene") ...of the most beautiful examples of Greek town planning. The city's remains lie on successive terraces that rise from a plain to a steep hill upon which stands the Temple ...
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 ...
any of about 28 species of nonvenomous snakes, all but one of which are found in the Old World tropics and subtropics. Most are large, with the reticulated python ( [1 Related Articles]
(from the article "tactical weapons system") ...the much-used U.S. Sidewinder is guided to the target by the target's heat emission. One French missile is adaptable to either radar or infrared guidance. An Israeli missile system, known ...
(from the article "snake") ...New World tropics, Madagascar, and the southwestern Pacific. Size moderate to very large, 1-8 metres. Pelvic vestiges present. Bears living young.Approximately 30 species in 8 genera of the ...
(from the article "Myanmar") 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 ...
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 ... [1 Related Articles]
(from the article "fungus") ...and penetrates insect exoskeleton to absorb nutrients; spinelike ascoma; example genera include Laboulbenia, Rickia, and Ceratomyces.Ectoparasitic on mandibulate arthropods, may be mycoparasitic; mycelial; anamorphs lack vesiculate conidiophores; example genus ...
(from the article "Finland") ...1872 with Kaarlo Bergbom as producer and manager; its granite building in Helsinki was built in 1902. There are also several other municipal theatres. One of the most exciting in ...
(from the article "tank") The same 105-millimetre 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 ...
(from the article "panzer") 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 ...
(from the article "panzer") ...5.4 tons, had a top road speed of 39 km (24 miles) per hour, and was manned by a crew of two. The Pz. I first saw combat in the ...
(from the article "panzer") 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 ...
(from the article "tank") Apart from being lightly armoured, the Soviet BT, the equivalent British cruiser tanks, and the German Pz. III also required support from more heavily armed tanks if they were to ...
(from the article "tank") The campaigns of 1939-41, in which armoured forces played such an important role, also intensified the technical development of tanks and other armoured vehicles. The German Pz. IV and Soviet ...
(from the article "tank") ...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 ...
(from the article "Porsche, Ferdinand") ...car" and with his son Ferdinand, known as Ferry, was responsible for the initial design of the Volkswagen in 1934. During World War II the Porsches designed military vehicles, notably ...
