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  • Heston, Leonard (behaviour genetics)

    behaviour genetics: Methods of study: …1966 by American behavioral geneticist Leonard Heston showed that children adopted away from their schizophrenic biological mothers at birth were just as likely to become schizophrenic (about 10 percent) as were children reared by their schizophrenic biological mothers. A 20-year study begun in the 1970s in the United States of…

  • Heston, William Martin (American athlete)

    Willie Heston, U.S. collegiate halfback who played with Fielding Yost’s University of Michigan (Ann Arbor) teams that from 1901 through 1904 scored 2,326 points in 44 games to their opponents’ 40 points. Heston graduated from Grant’s Pass (Oregon) High School and played football at San Jose

  • Heston, Willie (American athlete)

    Willie Heston, U.S. collegiate halfback who played with Fielding Yost’s University of Michigan (Ann Arbor) teams that from 1901 through 1904 scored 2,326 points in 44 games to their opponents’ 40 points. Heston graduated from Grant’s Pass (Oregon) High School and played football at San Jose

  • Hesychasm (Eastern Orthodoxy)

    Hesychasm, in Eastern Christianity, type of monastic life in which practitioners seek divine quietness (Greek hēsychia) through the contemplation of God in uninterrupted prayer. Such prayer, involving the entire human being—soul, mind, and body—is often called “pure,” or “intellectual,” prayer or

  • Hesychius of Alexandria (Greek lexicographer)

    Hesychius of Alexandria, author of the most important Greek lexicon known from antiquity, valued as a basic authority for the dialects and vocabularies of ancient inscriptions, poetic text, and the Greek Church Fathers. Although nothing is known of his life, Hesychius indicated the comprehensive

  • Hesychius of Jerusalem (Eastern Orthodox monk)

    Hesychius Of Jerusalem, priest-monk, renowned in the Eastern Church as a theologian, biblical commentator, and preacher. He played a prominent role in the 5th-century controversy on the nature of Christ and was acclaimed as having annotated the whole of sacred Scripture. Serving as a priest in the

  • Hesychius of Miletus (Byzantine historian)

    Hesychius Of Miletus , Byzantine historian and literary biographer whose chronicle of world history influenced later Byzantine historical accounts and provided singular data on the history of Constantinople. His works are also a valuable source for the history of Greek literature. A native of

  • HET (telescope, Texas, United States)

    Hobby-Eberly Telescope (HET), telescope that is one of the largest in the world, with a mirror measuring 11.1 by 9.8 metres (36.4 by 32.2 feet). It is located on Mount Fowlkes (2,024 metres [6,640 feet]) at the University of Texas at Austin’s McDonald Observatory near Fort Davis, Texas, U.S. The

  • Het uur U (poetry by Nijhoff)

    Martinus Nijhoff: “Awater” and Het uur U (1942; “U-Hour”), the story of a stranger’s shattering effect on a self-satisfied community, firmly establish Nijhoff as one of Europe’s foremost 20th-century poets.

  • hét, A (Hungarian periodical)

    Hungarian literature: Writers of the late 19th century: The periodical A hét (“The Week”), founded in 1890 by József Kiss, became the organ of a number of gifted writers, including Zoltán Ambrus and Sándor Bródy.

  • hetaera (ancient Greek courtesan)

    Hetaira, (Greek: “female companion”) one of a class of professional independent courtesans of ancient Greece who, besides developing physical beauty, cultivated their minds and talents to a degree far beyond that allowed to the average Attic woman. Usually living fashionably alone, or sometimes two

  • hetaira (ancient Greek courtesan)

    Hetaira, (Greek: “female companion”) one of a class of professional independent courtesans of ancient Greece who, besides developing physical beauty, cultivated their minds and talents to a degree far beyond that allowed to the average Attic woman. Usually living fashionably alone, or sometimes two

  • hetairoi (Macedonian cavalry)

    Alexander the Great: Campaign eastward to Central Asia: The Companion cavalry was reorganized in two sections, each containing four squadrons (now known as hipparchies); one group was commanded by Alexander’s oldest friend, Hephaestion, the other by Cleitus, an older man. From Phrada, Alexander pressed on during the winter of 330–329 up the valley of…

  • Hetch Hetchy Reservoir (reservoir, Yosemite National Park, California, United States)

    dam: Rise of environmental and economic concerns: …San Francisco to build a reservoir in Hetch Hetchy Valley. Located more than 900 metres (3,000 feet) above sea level, the Hetch Hetchy site offered a good storage location in the Sierra Nevada for water that could be delivered without pumping to San Francisco via an aqueduct nearly 270 km…

  • HETE-2 (international satellite)

    High Energy Transient Explorer-2 (HETE-2), international satellite designed to study gamma-ray bursts (GRBs), intense flashes of gamma rays from very distant objects. HETE-2 was launched on October 9, 2000, near Kwajalein Atoll in the Pacific Ocean by a Pegasus launch vehicle dropped from the

  • Hetepheres (queen of Egypt)

    Hetepheres, ancient Egyptian queen, wife of the king Snefru, who bore the title “Daughter of God” and represented the direct royal blood line of the 4th dynasty (c. 2575–c. 2465 bce). Snefru probably married her in the middle of the reign of his predecessor, Huni, in order to establish his claim to

  • Hetepsekhemwy (king of Egypt)

    ancient Egypt: The 2nd dynasty (c. 2775–c. 2650 bce): …whose first king’s Horus name, Hetepsekhemwy, means “peaceful in respect of the two powers” and may allude to the conclusion of strife between two factions or parts of the country, to the antagonistic gods Horus and Seth, or to both. Hetepsekhemwy and his successor, Reneb, moved their burial places to…

  • Heteralocha acutirostris (extinct bird)

    Callaeidae: ; Creadion carunculatus), and the huia (Heteralocha acutirostris). The first two are rare and in danger of extinction; the huia has been extinct since the early 19th century.

  • Heteranthera (plant)

    Mud plantain, any aquatic annual or perennial plant of the genus Heteranthera of the pickerelweed family (Pontederiaceae), consisting of about 10 species, distributed primarily in tropical America. The broad or ribbonlike leaves of these plants have leafstalks that form sheaths around the long

  • Heteranthera dubia (plant)

    mud plantain: Water star grass (H. dubia) is widely distributed throughout North America; it has yellow star-shaped flowers.

  • heterarchy (social science)

    Heterarchy, form of management or rule in which any unit can govern or be governed by others, depending on circumstances, and, hence, no one unit dominates the rest. Authority within a heterarchy is distributed. A heterarchy possesses a flexible structure made up of interdependent units, and the

  • Heterenchelyidae

    eel: Annotated classification: Family Heterenchelyidae (mud eels) No fins, mouth large. 2 genera with 8 species. Tropical Atlantic. Family Moringuidae (spaghetti eels) Anus in posterior half of body, degenerate, burrowing. 2 genera with about 6 species. Tropical Indo-Pacific and western Atlantic. Suborder

  • heteroaromatic compound (chemical compound)

    heterocyclic compound: The nature of heteroaromaticity: Aromaticity denotes the significant stabilization of a ring compound by a system of alternating single and double bonds—called a cyclic conjugated system—in which six π electrons generally participate. A nitrogen atom in a ring can carry a positive or a negative charge, or it…

  • heteroatom (chemistry)

    chemical compound: Functional groups: …carbon or hydrogen (termed a heteroatom) is bonded to carbon. All heteroatoms have a greater or lesser attraction for electrons than does carbon. Thus, each bond between a carbon and a heteroatom is polar, and the degree of polarity depends on the difference between the electron-attracting properties of the two…

  • heterocarpy (botany)
  • Heterocentrotus mammillatus (invertebrate)

    sea urchin: The slate-pencil urchin (Heterocentrotus mammillatus) of the Indo-Pacific has 12-cm spines that may be 1 cm thick—stout enough to be used for writing. Lytechinus variegatus, a pale-greenish urchin of the southeastern coast of the United States and the Caribbean, and the large, short-spined Psammechinus (sometimes Echinus)…

  • Heterocephalus glaber (rodent)

    blesmol: Blesmol genera: Smallest is the naked blesmol, more commonly called the naked mole rat (Heterocephalus glaber), which weighs 80 grams (2.8 ounces) or less and has a body only 8 to 9 cm long and a tail of 3 to 5 cm. Its wrinkled skin is pinkish and bald except…

  • Heteroceridae (insect)

    coleopteran: Annotated classification: Family Heteroceridae (variegated mud-loving beetles) About 500 widely distributed species; example Heterocerus. Family Limnichidae (minute marsh-loving beetles) Similar to Dryopidae; a few widely distributed species. Family Lutrochidae (travertine

  • heterochain polymer (chemistry)

    major industrial polymers: Heterochain polymers: A wide variety of heterochain polymers—that is, polymers in which the backbone contains elements such as oxygen, nitrogen, sulfur, or silicon in addition to carbon—are in commercial use. Many of these compounds are complex in structure. In this section the major heterochain polymer…

  • heterochlorid (protozoan order)

    Heterochlorid, any protozoan of the plantlike flagellate order Heterochlorida. Heterochlorids have two flagella of unequal length and chromatophores with yellow to yellow-green pigments. Food reserves are stored as leucosin (a carbohydrate) and lipids. Some genera may be amoeboid during part of

  • Heterochlorida (protozoan order)

    Heterochlorid, any protozoan of the plantlike flagellate order Heterochlorida. Heterochlorids have two flagella of unequal length and chromatophores with yellow to yellow-green pigments. Food reserves are stored as leucosin (a carbohydrate) and lipids. Some genera may be amoeboid during part of

  • heterocycle (chemistry)

    Heterocyclic compound, any of a major class of organic chemical compounds characterized by the fact that some or all of the atoms in their molecules are joined in rings containing at least one atom of an element other than carbon (C). The cyclic part (from Greek kyklos, meaning “circle”) of

  • heterocyclic compound (chemistry)

    Heterocyclic compound, any of a major class of organic chemical compounds characterized by the fact that some or all of the atoms in their molecules are joined in rings containing at least one atom of an element other than carbon (C). The cyclic part (from Greek kyklos, meaning “circle”) of

  • heterocyst (cell)

    blue-green algae: …that have specialized cells called heterocysts. The heterocysts are thick-walled cell inclusions that are impermeable to oxygen; they provide the anaerobic (oxygen-free) environment necessary for the operation of the nitrogen-fixing enzymes. In Southeast Asia, nitrogen-fixing cyanobacteria often are grown in rice paddies, thereby eliminating the need to apply nitrogen fertilizers.

  • Heterodera rostochiensis (species of nematode)

    plant disease: Nematode diseases: The golden nematode of potatoes (Heterodera rostochiensis) is a menace of the European potato industry. Great efforts have been made to control it. The speck-sized golden cysts that dot infested plant roots are the remains of female bodies. Each cyst may contain up to 500 eggs,…

  • Heterodera schachtii (worm)

    plant disease: Nematode diseases: A related, cyst-forming species, the sugar beet nematode (H. schachtii), is a pest that has restricted acreage of sugar beets in Europe, Asia, and America.

  • Heterodon (reptile, genus Heterodon)

    Hognose snake, (genus Heterodon), any of three species of North American nonvenomous snakes belonging to the family Colubridae. They are named for the upturned snout, which is used for digging. These are the harmless but often-avoided puff adders, or blow snakes, of North America. When threatened,

  • Heterodon nasicus (snake)

    hognose snake: …(Heterodon platyrhinos) and western (H. nasicus). Both are heavy-bodied and blotchy; their usual length is about 60 to 80 cm (24 to 31 inches).

  • Heterodon platyrhinos (snake)

    hognose snake: …species are the eastern (Heterodon platyrhinos) and western (H. nasicus). Both are heavy-bodied and blotchy; their usual length is about 60 to 80 cm (24 to 31 inches).

  • heterodont (dinosaur family)

    ornithopod: …of several subgroups, including Fabrosauridae, Heterodontosauridae, Hypsilophodontidae, Iguanodontidae, and Hadrosauridae (the duck-billed dinosaurs). The fabrosaurs were the earliest and most primitive of the ornithopods; these small, lightly built dinosaurs reached lengths of 60–120 cm (2–4 feet). The heterodontosaurs began to develop the horny beaks and specialized teeth typical of ornithischians.…

  • Heterodonta (bivalve subclass)

    bivalve: Annotated classification: Subclass Heterodonta Shell highly variable; hinge plate teeth may be reduced or absent; shell comprises crossed-lamellar, complex crossed-lamellar, or prismatic layers, but never nacreous; primitively isomyarian but with wide range of adductor muscle configurations; ctenidia eulamellibranch; mantle margins extensively fused, particularly posteriorly, often to form long…

  • Heterodontidae (shark family)

    chondrichthyan: Annotated classification: Family Heterodontidae (horned sharks, bullhead sharks, Port Jackson sharks) Oviparous; egg case screw-shaped, a double spiral flange extending from the egg’s apex to large end. Teeth in upper and lower jaws alike, those in front incisor-like, those on sides much larger and molar-like. Size up to…

  • Heterodontoidei (shark suborder)

    chondrichthyan: Annotated classification: Suborder Heterodontoidei 5 gill openings on each side of body; anal fin present; 2 dorsal fins, each preceded by a spine. Marine. Late Devonian to present. Family Heterodontidae (horned sharks, bullhead sharks, Port Jackson sharks) Oviparous; egg case screw-shaped, a double spiral flange extending from the…

  • heterodontosaur (dinosaur family)

    ornithopod: …of several subgroups, including Fabrosauridae, Heterodontosauridae, Hypsilophodontidae, Iguanodontidae, and Hadrosauridae (the duck-billed dinosaurs). The fabrosaurs were the earliest and most primitive of the ornithopods; these small, lightly built dinosaurs reached lengths of 60–120 cm (2–4 feet). The heterodontosaurs began to develop the horny beaks and specialized teeth typical of ornithischians.…

  • Heterodontosauridae (dinosaur family)

    ornithopod: …of several subgroups, including Fabrosauridae, Heterodontosauridae, Hypsilophodontidae, Iguanodontidae, and Hadrosauridae (the duck-billed dinosaurs). The fabrosaurs were the earliest and most primitive of the ornithopods; these small, lightly built dinosaurs reached lengths of 60–120 cm (2–4 feet). The heterodontosaurs began to develop the horny beaks and specialized teeth typical of ornithischians.…

  • Heterodontus (fish)

    Bullhead shark, any shark of the genus Heterodontus, which contains about 10 species and constitutes the family Heterodontidae (order Heterodontiformes). This exclusively marine group is found only in the tropical reaches of the Pacific and Indian oceans and in the eastern Pacific from California

  • Heterodontus francisci (shark)

    chondrichthyan: Reproduction and development: …less pillow-shaped; those of the horned sharks (Heterodontus francisci) are screw-shaped with a spiral flange. The eggs of chimaeras are elliptic, spindle-shaped, or tadpole-shaped and open to the exterior through pores and slits that permit entrance of water during incubation. An egg of the whale shark found in the Gulf…

  • Heterodontus philippi (shark)

    bullhead shark: The Port Jackson shark (H. philippi or portusjacksoni), found in Australian Pacific waters, reaches a length of 1.5 m (5 feet).

  • Heterodontus portusjacksoni (shark)

    bullhead shark: The Port Jackson shark (H. philippi or portusjacksoni), found in Australian Pacific waters, reaches a length of 1.5 m (5 feet).

  • heterodonty (teeth)

    primate: Teeth: …different kinds of teeth (heterodonty)—incisors, canines, and cheek teeth—is characteristic of all primates and indeed of mammals generally. Heterodonty is a primitive characteristic, and primates have evolved less far from the original pattern than most mammals. The principal changes are a reduction in the number of teeth and an…

  • heterodox problem (chess composition)

    chess: Heterodox problems: The 20th century was marked by investigation of heterodox problems and greater elaboration of direct-mate problem themes. These problems, also called fairy chess, are distinguished from the orthodox problems considered so far by their unusual stipulations or by the use of nonstandard rules…

  • Heterodoxia (work by Sábato)

    Ernesto Sábato: …model for social structures, and Heterodoxia (1953; “Heterodoxy”), on the problems of modern civilization and what Sábato saw as an attendant loss of earlier moral and metaphysical foundations.

  • Heterodoxus spiniger (insect)

    louse: Ecology: Heterodoxus spiniger, which is parasitic on domestic dogs in tropical regions, was most likely acquired relatively recently from an Australian marsupial.

  • heteroduplex (biology)

    nucleic acid: General recombination: …identical will be a “heteroduplex”—that is, a molecule in which mismatched bases will be present at some positions in the helix. Thus, in the specialized recombination that takes place during meiosis, one round of replication is necessary before the mosaic chromosomes produced by recombination are properly matched. Enzymes are…

  • heterodyne beat (electronics)

    Alexander Meissner: …amplification systems, and developed the heterodyne principle for radio reception. In 1911 Meissner designed the first rotary radio beacon to aid in the navigation of the Zeppelin airships. In 1913 he was the first to amplify high-frequency radio signals by using feedback in a vacuum triode; this principle made it…

  • heterodyne principle (electronics)

    Alexander Meissner: …amplification systems, and developed the heterodyne principle for radio reception. In 1911 Meissner designed the first rotary radio beacon to aid in the navigation of the Zeppelin airships. In 1913 he was the first to amplify high-frequency radio signals by using feedback in a vacuum triode; this principle made it…

  • heteroepitaxy (crystallography)

    crystal: Growth from the melt: Heteroepitaxy, on the other hand, is the growth of one crystal on the substrate of another. Silicon substrates are often used since they are readily available in atomically smooth form. Many different semiconductor crystals can be grown on silicon, such as gallium arsenide, germanium, cadmium…

  • heterogamy (biology)

    plant reproductive system: The cellular basis: , heterogamous). The larger gamete, or egg, is nonmotile; the smaller gamete, or sperm, is motile. The last type of gametic difference, egg and sperm, is often designated as oogamy. In oogamous reproduction, the union of sperm and egg is called fertilization. Isogamy, heterogamy, and oogamy…

  • Heterogastridiales (order of fungi)

    fungus: Annotated classification: Order Heterogastridiales Mycoparasitic; basidiocarps may be pycnidioid; example genus includes Heterogastridium. Order Microbotryales Pathogenic in plants (some cause smut); violet teliospores; example genera include Microbotryum and Ustilentyloma.

  • heterogeneous catalysis (chemistry)

    catalysis: Heterogeneous catalysis: Many catalytic processes are known in which the catalyst and the reactants are not present in the same phase—that is, state of matter. These are known as heterogeneous catalytic reactions. They include reactions between gases or liquids or both at the surface of…

  • heterogeneous nucleation (crystallography)

    atmosphere: Condensation: When ice nuclei are present, heterogeneous ice nucleation can occur at warmer temperatures.

  • heterogeneous reaction (chemical reaction)

    Heterogeneous reaction, any of a class of chemical reactions in which the reactants are components of two or more phases (solid and gas, solid and liquid, two immiscible liquids) or in which one or more reactants undergo chemical change at an interface, e.g., on the surface of a solid catalyst.

  • heterogeneous shopping goods (economics)

    marketing: Shopping goods: With heterogeneous shopping goods, product features become more important to the consumer than price. Such is often the case with the purchase of major appliances, clothing, furniture, and high-tech equipment. In this situation, the item purchased must be a certain size or colour and must perform…

  • heterogenesis (biology)

    Alternation of generations, in biology, the alternation of a sexual phase and an asexual phase in the life cycle of an organism. The two phases, or generations, are often morphologically, and sometimes chromosomally, distinct. In algae, fungi, and plants, alternation of generations is common. It is

  • Hétérogénie (work by Pouchet)

    Félix-Archimède Pouchet: In his major work, Hétérogénie (1859), he detailed the conditions under which living organisms supposedly were produced by chemical processes such as fermentation and putrefaction. His supporters were primarily among those whose religious or philosophical beliefs required the concept of spontaneous generation. Pouchet’s theory was discredited when Louis Pasteur…

  • heterogloss (linguistics)

    dialect: Geographic dialects: …own boundary line, called an isogloss (or sometimes heterogloss). Isoglosses of various linguistic phenomena rarely coincide completely, and by crossing and interweaving they constitute intricate patterns on dialect maps. Frequently, however, several isoglosses are grouped approximately together into a bundle of isoglosses. This grouping is caused either by geographic obstacles…

  • heteroglycan (biochemistry)

    carbohydrate: Heteropolysaccharides: In general, heteropolysaccharides (heteroglycans) contain two or more different monosaccharide units. Although a few representatives contain three or more different monosaccharides, most naturally occurring heteroglycans contain only two different ones and are closely associated with lipid or protein. The complex nature of these substances…

  • heterograft (surgery)

    cardiovascular disease: Valvular disease: …human beings after death) and heterograft valves (secured from animals) is widespread. One of the advantages of both types is the absence of clotting, which occurs occasionally with the use of artificial valves. Most homograft and heterograft valves have a durability of 10–15 years. There is a risk of endocarditis…

  • Heterohyrax (mammal)

    hyrax: The bush hyraxes (Heterohyrax) and the rock hyrax (Procavia capensis) are terrestrial animals that live in groups among rocks and are active by day. The tree hyraxes (Dendrohyrax) are arboreal, solitary, and nocturnal. All are primarily vegetarian.

  • heterojunction (electronics)

    semiconductor device: Metal-semiconductor field-effect transistors: …performance of the MESFET, various heterojunction field-effect transistors (FETs) have been developed. A heterojunction is a junction formed between two dissimilar semiconductors, such as the binary compound GaAs and the ternary compound AlxGa1 − xAs. Such junctions have many unique features that are not readily available in the conventional p-n…

  • heterokont (organism)
  • Heterolobosea (protist)

    protozoan: Annotated classification: Heterolobosea Many exhibit amoeboid, flagellated, and encysted forms. Pseudopodia are unique compared with those found in Amoebozoa. Many are heterotrophic. Positioned within Excavata on basis of genetic similarity, although the classification of heteroloboseans remains a source of debate; euglenozoans and heteroloboseans are closely related and…

  • heterolobosean (protist)

    protozoan: Annotated classification: Heterolobosea Many exhibit amoeboid, flagellated, and encysted forms. Pseudopodia are unique compared with those found in Amoebozoa. Many are heterotrophic. Positioned within Excavata on basis of genetic similarity, although the classification of heteroloboseans remains a source of debate; euglenozoans and heteroloboseans are closely related and…

  • heterolysis (chemistry)

    reaction mechanism: Homolysis and heterolysis: When a covalent bond (a nonionic chemical bond formed by shared electrons) is made up of two electrons, each of which is supplied by a different atom, the process is called colligation; the reverse process, in which the electrons of a covalent bond are…

  • heterolytic reaction (chemistry)

    reaction mechanism: Homolysis and heterolysis: When a covalent bond (a nonionic chemical bond formed by shared electrons) is made up of two electrons, each of which is supplied by a different atom, the process is called colligation; the reverse process, in which the electrons of a covalent bond are…

  • heteromerous thallus (lichen)

    lichen: …of fungal cells, while the heteromerous thallus has a predominance of fungal cells.

  • heteromorph (ammonoid)

    Triassic Period: Invertebrates: …the Late Triassic evolved bizarre heteromorphs with loosely coiled body chambers, such as Choristoceras, or with helically coiled whorls, such as Cochloceras. These aberrant forms were short-lived, however. A small group of smooth-shelled forms with more complex suture lines, the phylloceratids, also arose in the Early Triassic. They are regarded…

  • heteromorphosis (biology)

    regeneration: Atypical regeneration: …that which is regenerated is very different from the original. Among the arthropods there are cases in which the stump of an antenna grows a leg, while a cut eyestalk regenerates an antenna. More commonly, the regenerated part may be a reasonable facsimile of the original but will differ in…

  • Heteromyidae (rodent family)

    pocket mouse: Classification and paleontology: …are classified in the family Heteromyidae, meaning “different mouse,” or “other mouse,” in Greek. This family also includes kangaroo rats and kangaroo mice. Within Heteromyidae, the silky and coarse-haired pocket mice constitute the subfamily Perognathinae, and the spiny pocket mice constitute the subfamily Heteromyinae. Spiny pocket mice are more ratlike…

  • Heteromys (rodent)

    pocket mouse: Natural history: The seven species of forest spiny pocket mice (genus Heteromys) are the largest, weighing from 37 to 85 grams and having 11- to 18-cm bodies and long scantily haired tails. Forest pocket mice range from southern Mexico to northern South America, where they live from sea level upward into…

  • Heteromysis cotti (crustacean)

    opossum shrimp: Some species, such as Heteromysis cotti of the Canary Islands, live in caves and are either blind or have poorly developed eyes.

  • heteron (philosophy)

    Eleaticism: The decline of Eleaticism: …of every Not-Being as a heteron (i.e., as a being characterized only by its difference from “another” being) is neither in Gorgias nor in the Parmenides but in the Sophist of Plato. There Plato argued that the antinomy between on and mē-on (Being and Not-Being) does not really exist, the…

  • Heteronetta atricapilla (bird)

    anseriform: Reproductive behaviour: Only one species, the black-headed duck (Heteronetta atricapilla) of South America, is an obligate nest-parasite, always laying in the nests of other species.

  • heteronomy (theology and philosophy)

    Paul Tillich: Early life and education: …theological work: the relation of heteronomy to autonomy and their possible synthesis in theonomy. Heteronomy (alien rule) is the cultural and spiritual condition when traditional norms and values become rigid, external demands threatening to destroy individual freedom. Autonomy (self-rule) is the inevitable and justified revolt against such oppression, which nevertheless…

  • heteronuclear molecule

    polarity: …at each end of a heteronuclear bond (i.e., a bond between atoms of different elements) gives rise to an electric dipole. The magnitude of this dipole is expressed by the value of its dipole moment, μ, which is the product of the magnitude of the partial charges times their separation…

  • heteronym (literature)

    Fernando Pessoa: …innovation of what Pessoa called heteronyms, or alternative personae. Rather than alter egos—alternative identities that serve as counterparts to or foils for an author’s own ideas—Pessoa’s heteronyms were presented as distinct authors, each of whom differed from the others in terms of poetic style, aesthetic, philosophy, personality, and even gender…

  • heterophil (leukocyte)

    Neutrophil, type of white blood cell (leukocyte) that is characterized histologically by its ability to be stained by neutral dyes and functionally by its role in mediating immune responses against infectious microorganisms. Neutrophils, along with eosinophils and basophils, constitute a group of

  • heterophony (music)

    Heterophony, in music, texture resulting from simultaneous performances of melodic variants of the same tune, typical of Middle Eastern practices as well as of a vast array of folk music. Balkan Slavic epic singers, for example, accompany themselves heterophonically on the gusle (fiddle). In

  • heteroplasmy (genetics)

    human genetic disease: Mitochondrial DNA mutations: …reflect the combined effects of heteroplasmy (i.e., mixed populations of both normal and mutant mitochondrial DNA in a single cell) and other confounding genetic or environmental factors. There are close to 50 mitochondrial genetic diseases currently known.

  • Heteropodidae (arachnid family)

    spider: Annotated classification: Family Sparassidae or Heteropodidae (huntsman spiders, tarantulas in Australia) Found in most tropical regions. Eyes in 2 rows; legs extended sideways; large, slightly flattened body. Family Tetragnathidae (long-jawed orb weavers) 1,000 species worldwide. Males with long chelicerae; epigynum often

  • Heteropogon (plant genus)

    grassland: Biota: Heteropogon and Sorghum dominate grasslands in moister, northern areas, and Astrebla (Mitchell grass) is prevalent in seasonally arid areas, especially on cracking clay soils in the east. Other grass species are usually subordinate but may dominate in spots. Woody plants, particularly Acacia in arid areas…

  • heteropolar bond (chemistry)

    Ionic bond, type of linkage formed from the electrostatic attraction between oppositely charged ions in a chemical compound. Such a bond forms when the valence (outermost) electrons of one atom are transferred permanently to another atom. The atom that loses the electrons becomes a positively

  • heteropolar machine (generator)

    electric generator: Inductor alternators: In the heteropolar type, the field coils are in slots in the stator.

  • heteropoly acid (chemical compound)

    coordination compound: Isopoly and heteropoly anions: …or silicic acids) to form heteropoly acids, which can form heteropoly salts. The condensation reactions, which occur reversibly in dilute aqueous solution, involve formation of oxo bridges by elimination of water from two molecules of the weak acid. The best-known and simplest example is the condensation of yellow chromate ion…

  • heteropoly anion

    coordination compound: Isopoly and heteropoly anions: The amphoteric metals of groups VB (vanadium, niobium, and tantalum) and VIB (chromium, molybdenum, and tungsten) in the +5 and +6 oxidation states, respectively, form weak acids that readily condense (polymerize) to form anions

  • heteropoly salt (chemical compound)

    coordination compound: Isopoly and heteropoly anions: …heteropoly acids, which can form heteropoly salts. The condensation reactions, which occur reversibly in dilute aqueous solution, involve formation of oxo bridges by elimination of water from two molecules of the weak acid. The best-known and simplest example is the condensation of yellow chromate ion (CrO42−) to form the orange…

  • heteropolymolybdate (chemical compound)

    coordination compound: Isopoly and heteropoly anions: …and salts, of which the heteropolymolybdates and heteropolytungstates are the best known, have very high molecular weights (some above 4,000) as compared with other inorganic electrolytes, are very soluble in water and organic solvents, are almost always highly hydrated with several hydrates existing, and are highly coloured. Some are strong…

  • heteropolysaccharide (biochemistry)

    carbohydrate: Heteropolysaccharides: In general, heteropolysaccharides (heteroglycans) contain two or more different monosaccharide units. Although a few representatives contain three or more different monosaccharides, most naturally occurring heteroglycans contain only two different ones and are closely associated with lipid or protein. The complex nature of these substances…

  • heteropolytungstate (chemical compound)

    coordination compound: Isopoly and heteropoly anions: …of which the heteropolymolybdates and heteropolytungstates are the best known, have very high molecular weights (some above 4,000) as compared with other inorganic electrolytes, are very soluble in water and organic solvents, are almost always highly hydrated with several hydrates existing, and are highly coloured. Some are strong oxidizing agents…

  • Heteroptera (insect order)

    Heteropteran, any member of the insect order Heteroptera, which comprises the so-called true bugs. (Some authorities use the name Hemiptera; others consider both the heteropterans and the homopterans to be suborders of the Hemiptera.) This large group of insects, consisting of more than 40,000

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