Burgess Shale: …down its plated back; and Opabinia, which had five eyes and a long nozzle, have led many scientists to conclude that the Cambrian Period may have produced many unique phyla. However, deposits discovered in China, Greenland, and elsewhere have demonstrated that at least some of the shale’s oddities (including Hallucigenia…

library: Vehicles for catalogs: …is known as OPAC (on-line public access computer). Further development of this system has made it possible to integrate other library records with the OPAC, so that patrons can reserve materials that are still on order and can determine if items in the library’s collection are already on loan.…

industrial glass: Transparency, opacity, and colour: Because electrons in glass molecules are confined to particular energy levels, they cannot absorb and reemit photons (the basic units of light energy) by skipping from one energy band to another and back again. As a consequence, light energy travels through glass…

opah: One species, Lampris guttatus, is the only known fully warm-blooded fish. Although two species are recognized traditionally, some classifications suggest that anatomical evidence exists to divide L. guttatus into five species.

opah, (genus Lampris), any of two species of large marine fish of the family Lampridae (order Lampridiformes). One species, Lampris guttatus, is the only known fully warm-blooded fish. Although two species are recognized traditionally, some classifications suggest that anatomical evidence exists to

opal, silica mineral extensively used as a gemstone, a submicrocrystalline variety of cristobalite. In ancient times opal was included among the noble gems and was ranked second only to emerald by the Romans. In the Middle Ages it was supposed to be lucky, but in modern times it has been regarded

industrial glass: Silica-based: …not transparent product known as opal glass can be obtained. Another silica-based variation is borosilicate glass, which is used where high thermal shock resistance and high chemical durability are desired—as in chemical glassware and automobile headlamps. In the past, leaded “crystal” tableware was made of glass containing high amounts of…

coloration: Short-term changes: Greenfish, or opaleye (Girella nigricans), kept in white-walled aquariums became very pale during a four-month period, storing about four times the quantity of integumentary guanine as was recoverable from the skins of individuals living in black-walled aquariums but receiving the same kind and amounts of…

Ops: …dating of her festivals (the Opalia on December 19 and the Opiconsiva on August 25) illustrate her affinities with the Saturnalia (December 17) and the Consualia (of Consus; December 15).

opalinid, (subphylum Opalinata), any of about 150 protozoans found in the intestinal tracts of amphibians and some other animals. The nuclei of opalinids vary in number from two (e.g., Zelleriella) to many (e.g., Cepedea); the locomotor organelles (short, hairlike projections) are arranged in

opaline glass, usually opaque glass or crystal, either white or coloured, made in France between approximately 1810 and 1890. Opaline resembles the milk glass of 16th-century Venice and the opaque, white glass associated with Bristol, Eng., in the 18th century. The main centres of production were

opalinid, (subphylum Opalinata), any of about 150 protozoans found in the intestinal tracts of amphibians and some other animals. The nuclei of opalinids vary in number from two (e.g., Zelleriella) to many (e.g., Cepedea); the locomotor organelles (short, hairlike projections) are arranged in

Krzysztof Opaliński was a Polish statesman and writer who was a noted satirist. A highly educated and well-traveled man, and governor (wojewoda) of the province of Poznań, Opaliński figured in the history of Polish literature as the author of Satyry albo przestrogi do naprawy rządu i obyczajów w

ironstone china, type of stoneware introduced in England early in the 19th century by Staffordshire potters who sought to develop a porcelain substitute that could be mass-produced. The result of their experiments was a dense, hard, durable stoneware that came to be known by several names—e.g.,

cereal processing: Corn: These corns, called Opaque-2 and Floury-2, possess certain drawbacks. They are generally lower in yield than dent hybrids, are subject to more kernel damage when combine-harvested, and may be more difficult to process. Nevertheless, these new hybrid corns are expected to become widely cultivated, and the principles involved…

Aleksandr Oparin was a Russian biochemist noted for his studies on the origin of life from chemical matter. By drawing on the insights of chemistry, he extended the Darwinian theory of evolution backward in time to explain how simple organic and inorganic materials might have combined into complex

Aleksandr Oparin was a Russian biochemist noted for his studies on the origin of life from chemical matter. By drawing on the insights of chemistry, he extended the Darwinian theory of evolution backward in time to explain how simple organic and inorganic materials might have combined into complex

Oparin-Haldane theory, idea that organic molecules could be formed from abiogenic materials in the presence of an external energy source—e.g., ultraviolet radiation—and that Earth’s primitive atmosphere was reducing (having very low amounts of free oxygen) and contained ammonia and water vapour,

northern Mexican Indian: …Taracahitic group, the once prominent Ópata, have lost their own language and no longer maintain a separate identity. The Piman languages are spoken by four groups: the Pima Bajo of the Sierra Madre border of Sonora–Chihuahua; the Pima-Papago (O’odham) of northwest Sonora, who are identical with a much larger portion…

Opatija, resort town, one of the best-known coastal resorts in Istria, western Croatia. It is situated at the head of the Kvarner, a gulf of the Adriatic Sea along the eastern side of the Istrian peninsula. The town’s name derives from the old Benedictine opatija (“abbey”) of San Giacomo al Palo,

Opava, city, northeastern Czech Republic. It lies along the Opava River near the Polish border and is northwest of Ostrava, from which it is separated by part of the wooded Oder Hills. First recorded as Oppavia in 1195, it was a principate and fief of the Bohemian crown in the early 14th century

Opava, city, northeastern Czech Republic. It lies along the Opava River near the Polish border and is northwest of Ostrava, from which it is separated by part of the wooded Oder Hills. First recorded as Oppavia in 1195, it was a principate and fief of the Bohemian crown in the early 14th century

torture: Contemporary developments: In 2002 the Optional Protocol to the Convention against Torture (OPCAT) established a Subcommittee on Prevention, an expert body that, unlike the committees and the Special Rapporteur, would have the right and obligation to visit states without further consent of a state party to the protocol. Inspired by…

Organisation for the Prohibition of Chemical Weapons (OPCW), international organization established by the Chemical Weapons Convention (adopted 1992, entered into force 1997) to implement and enforce the terms of the international treaty, which prohibits the use, stockpiling, or transfer of

optics: Seidel sums: …is generally called OPD, meaning optical path difference. It can be shown that OPD is related to x0 and y0 by five constants S1 through S5, and the quantity h′o,Each of these five terms is considered to be a separate “aberration,” the coefficients S1

Ottoman Empire: The 1875–78 crisis: …and a European-controlled organization, the Ottoman Public Debt Administration (OPDA), was set up to collect the payments.

mangabey: …subspecies of the black mangabey, Opdenbosch’s mangabey (L. aterrimus opdenboschi) has a shorter crest, and the thick straight cheek whiskers are black like the body; it is confined to a few gallery forests on the rivers south of the Congo. The kipunji (Rungwecebus kipunji) was initially placed in the genus…

Abiy Ahmed: Entry into politics: …as a member of the Oromo People’s Democratic Organization (OPDO), which was part of the Ethiopian People’s Revolutionary Democratic Front (EPRDF) ruling coalition. In the following years he would go on to earn a master’s degree in transformational leadership (2011) from the International Leadership Institute in Addis Ababa, in partnership…

OPEC, multinational organization that was established to coordinate the petroleum policies of its members and to provide member states with technical and economic aid. OPEC was established at a conference held in Baghdad September 10–14, 1960, and was formally constituted in January 1961 by five

Native American: The mid-Atlantic Algonquians: …1618 his brother and successor, Opechancanough, attempted to force the colonists out of the region. His men initiated synchronized attacks against Jamestown and its outlying plantations on the morning of March 22, 1622. The colonists were caught unawares, and, having killed some 350 of the 1,200 English, Opechancanough’s well-organized operation…

Opel AG, German automotive company, a wholly owned subsidiary of Stellantis NV, specializing in the manufacture of passenger cars and light vans. Its headquarters are in Rüsselsheim, Germany. The company was started in 1898 when the five Opel brothers began converting the bicycle and sewing machine

Fritz von Opel was a German automotive industrialist who took part, with Max Valier and Friedrich Wilhelm Sander, in experiments with rocket propulsion for automobiles and aircraft. He was a grandson of Adam Opel, who in 1862 had founded at Rüsselsheim a firm bearing his name that manufactured

Opelika, city, seat (1866) of Lee county, eastern Alabama, U.S. It is situated about 15 miles (24 km) west of the Chattahoochee River, adjacent to Auburn. The first settlers entered the area following the signing of a final treaty with the Creek in 1832. Opelika is a Creek word meaning “large

Opelousas, city, seat (1805) of St. Landry parish, south-central Louisiana, U.S. It lies on the Gulf Coastal Plain, 20 miles (32 km) north of Lafayette. Founded in 1720 as a French garrison and trading post and named for the Opelousas Indians, it became a sanctuary for Acadians exiled from Nova

museum: Early period of reassessment: …museums at Arnhem, Netherlands (Netherlands Open Air Museum; opened 1912), and at St. Fagans, Wales (the Museum of Welsh Life; opened as the Welsh Folk Museum in 1948). The preservation and restoration of buildings or entire settlements in situ also began; particularly well known is Colonial Williamsburg, founded in…

airport: Open apron and linear designs: …for passenger terminals is the open apron design, in which aircraft park on the apron immediately adjacent to the terminal and passengers walk across the apron to board the aircraft by mobile steps. Frequently, the aircraft maneuver in and out of the parking positions under their own power. As airports…

Netscape Communications Corp.: Browser enhancements: …expanded Navigator’s capabilities; this “open-architecture” approach led in particular to a proliferation of plug-ins for digital audio, video, and animation. Netscape was among the first licensees of Sun Microsystems, Inc.’s Java programming language and virtual-machine technology. Sun and Netscape also collaborated to define JavaScript, a separate language designed to…

breed association: …registered; this is called an open association. The qualifications may be type, colour, or speed. Standardbred horses, for example, are admitted to the registry if they can trot a mile in 2 minutes 30 seconds, or pace a mile in 2 minutes 25 seconds. Older associations generally require that each…

The Open Boat, short story by Stephen Crane, published in the collection The Open Boat and Other Tales of Adventure in 1898. It recounts the efforts of four survivors of a shipwreck—a newspaper correspondent and the ship’s cook, captain, and oiler—as they attempt to remain afloat in a dinghy on

Plymouth Brethren: …Exclusive Brethren; the others, called Open Brethren, maintained a congregational form of church government and less rigorous standards for membership. Exclusive Brethren have suffered further divisions.

caisson: An open caisson, open at both the bottom and the top, is fitted with a cutting bottom edge, which facilitates sinking through soft material while excavation is carried out inside through a honeycomb of large pipes, or dredging wells. As excavating proceeds and the caisson sinks,…

freight car: …since the early 1800s: the open-top car, the boxcar, and the flatcar.

British Open, one of the world’s four major golf tournaments—with the Masters Tournament, the U.S. Open, and the Professional Golfers’ Association (PGA) Championship—and the oldest continually run championship in the sport. Best known outside the United States as the Open Championship or, simply,

animal: Water/vascular systems: Most animals have open circulatory systems. Those few animals with closed circulatory systems have a continuous series of vessels to circulate fluid to the vicinity of all cells, whereas those with open systems have vessels only near the heart. (Actually, no system is entirely closed or open.) In…

Open City, Italian Neorealist film, released in 1945, that portrayed life in Nazi-occupied Rome during World War II. Directed by Roberto Rossellini in a documentary style that was innovative for the time, the movie brought international attention to the Neorealist movement and became one of its

free school, school in which the teaching system is based on an environment structured to encourage the child to become actively involved in the learning process. The free school stresses individualized rather than group instruction, and children proceed from one step to another at their own rate

open cluster, in astronomy, any group of young stars held together by mutual gravitation. See star

craps: …version of the game called money craps, or open craps, is found in simpler or illegal gaming houses and is mostly played for cash on a table without the elaborate layout found in bank craps. The players may gamble with each other on the shooter’s point numbers, but all other…

salt: Use of artificial heat: …quantity is made in so-called open crystallizers or grainers that produce a type of crystal preferred for use in some of the food industries. The brine, natural or artificial, is first pumped into settling tanks, where calcium and magnesium compounds may be removed by chemical treatment. In grainer operations the…

Open Door policy, statement of principles initiated by the United States in 1899 and 1900 for the protection of equal privileges among countries trading with China and in support of Chinese territorial and administrative integrity. The statement was issued in the form of circular notes dispatched

World Economic Forum: …developing countries and introduced the Open Forum Davos (2003), a free public forum held in parallel with the WEF.

John Cornyn: …of open government, championing the OPEN Government Act (2007), a program that revised the Freedom of Information Act to ensure more timely action on the part of government agencies being petitioned. He also proposed legislation that would prohibit Congress from enacting bills that did not have an accompanying statement of…

computer graphics: Processors and programs: The OpenGL (open graphics library) specifies a standard set of graphics routines that may be implemented in computer programming languages such as C or Java. PHIGS (programmer’s hierarchical interactive graphics system) is another set of graphics routines. VRML (virtual reality modeling language) is a graphics description…

open habitat, part of a landscape that is not enclosed by trees. Open habitat may include plains, tundra, polar barrens, forest clear-cuts, and other areas free of tree cover. It may be limited to certain portions of ecosystems, or it may encompass whole ecosystems or biomes, such as grasslands or

Google: Android OS and entry into the smartphone market: …announced the founding of the Open Handset Alliance, a consortium of dozens of technology and mobile telephone companies, including Intel Corporation, Motorola, Inc., NVIDIA Corporation, Texas Instruments Incorporated, LG Electronics, Inc., Samsung Electronics, Sprint Nextel Corporation, and T-Mobile (Deutsche Telekom). The consortium was created in order to

Ellen DeGeneres: …as One Night Stand (1989), Open House (1989–90), and Laurie Hill (1992). In 1994 she starred in These Friends of Mine; its name changed to Ellen the following season. The show was a success, earning nominations for Golden Globe, American Comedy, and Emmy awards. In 1997 DeGeneres revealed that she…

sugar: Open pan sugar: In industrial sugarcane processing, crystallization is conducted under vacuum in order to lower operating temperatures, but some sugar is produced in the tropics by “open pan” processes. In these processes, crudely clarified juices are boiled down in open containers until a sludgy…

keyboard instrument: Flue pipes: … lower in pitch than an open pipe of the same speaking length.

Robert Gober: …in scale from their sources—Open Playpen (1987), for example, lacks the protective bars on one side, while X Playpen (1987) effectively reduces the “play” area to one of two tiny triangular spaces—those sculptures seemed exercises in wistful memory, exposing a stark poetry embedded within the mundane and the domestic.

poker: Stud poker: Each player receives one card facedown—his hole card—and one card faceup. The deal is then interrupted for a betting interval. There follow three rounds of dealing, each deal distributing one card faceup to each active player, with a betting interval after…

fat and oil processing: Pressing machines: In open presses, the ground seed material was confined in cloths of human hair or, less commonly, camel hair. Pressures on the cake varied from approximately 70 to 140 kilograms per square centimetre (1,000 to 2,000 pounds per square inch), and in the closed-type press, in…

primary election: …party members to vote, or open (nonpartisan), enabling all voters to choose which party’s primary they wish to vote in without declaring any party affiliation. Primaries may be direct or indirect. A direct primary, which is now used in some form in all U.S. states, functions as a preliminary election…

ethics: Moore and the naturalistic fallacy: ”) The “open-question argument,” as it came to be known, was in fact used by Sidgwick and to some extent by the 18th-century intuitionists, but Moore’s statement of it somehow caught the imagination of philosophers during the first half of the 20th century. The upshot was that…

open range, in U.S. history, any of several areas of public domain north of Texas where from about 1866 to 1890 more than 5,000,000 head of cattle were driven to fatten and be shipped off to slaughter. The open ranges of western Kansas, Nebraska, the Dakotas, Montana, Wyoming, and other Western

Kevin Costner: …his third film, the western Open Range (2003), in which he also starred. He continued to act in such movies as Thirteen Days (2000), a dramatization of the Cuban missile crisis; the comic dramas The Upside of Anger (2005) and Swing Vote (2008); and the action movie The Guardian (2006).…

economic regionalism: In “open” forms there are no elements of exclusion or discrimination against nonmembers. Trade liberalization and unconditional most-favoured-nation status, in compliance with Article XXIV of the General Agreement on Tariffs and Trade (GATT), are characteristic features of open regionalism. The EU, NAFTA, and APEC contain many…

Martin Lawrence: …his numerous other films are Open Season (2006), Wild Hogs (2007), and College Road Trip (2008). He reunited with Smith for Bad Boys II (2003) and Bad Boys for Life (2020).

Alice Munro: Her book Open Secrets (1994) contains stories that range in setting from the semicivilized hills of southern Ontario to the mountains of Albania. In Runaway (2004) Munro explores the depths of ordinary lives through the use of temporal shifts and realistically rendered reminiscences; it also was awarded…

metalogic: Truth definition of the given language: An open sentence, such as x = 1, is one that may be either true or false depending on the value of x, but a closed sentence, such as 0 = 1 and (∀x) (x = 0) or “All x’s are zero,” is one that has…

topology: Topological space: …sets in T are called open sets and T is called a topology on X. For example, the real number line becomes a topological space when its topology is specified as the collection of all possible unions of open intervals—such as (−5, 2), (1/2, π), (0, 2), …. (An analogous…

union shop: …not join the union) or open shops (which require neither membership nor dues payment). Employees in open shops who benefit from the gains that unions achieve through collective bargaining, without sharing the expenses, are sometimes called “free riders.”

20th-century international relations: Arms control and defense: …stunned the Soviets with his “open skies” proposal. The United States and the Soviet Union, he said, should exchange blueprints of all military installations and each allow the other side to conduct unhindered aerial reconnaissance. After some hesitation, Khrushchev denounced the plan as a capitalist espionage device. The Geneva summit…

minority: An open society, on the other hand, allows the individual to change his role and to benefit from corresponding changes in status. Unlike a closed society, which stresses hierarchical cooperation between social groups, an open society permits different social groups to vie for the same resources,…

F.A. Hayek: Life and major works: …a publisher for Popper’s book The Open Society and Its Enemies (1945). Popper and Hayek would remain lifelong friends.

Alexander Soros: Philanthropy and inheritance of George Soros’s empire: …the board of directors for Open Society Foundations, the family’s philanthropic arm. In December 2022 the board elected him as its chair, replacing his aging father. In June 2023 a spokesperson for George Soros announced that he would hand control of his holdings to the younger Soros.

open source: Hacker culture: …“open” system and formed the Open Software Foundation. This set off the so-called “UNIX wars” among minicomputer enthusiasts.

Wole Soyinka: …ills and Western responsibility in The Open Sore of a Continent (1996) and The Burden of Memory, the Muse of Forgiveness (1999).

open source, social movement, begun by computer programmers, that rejects secrecy and centralized control of creative work in favour of decentralization, transparency, and unrestricted (“open”) sharing of information. Source refers to the human-readable source code of computer programs, as opposed

Linus Torvalds: …under the auspices of the Open Source Development Labs (OSDL), a consortium created by such high-tech companies as IBM, Intel, and Siemens to promote Linux development. In 2007 OSDL merged with the Free Standards Group to form the Linux Foundation. In 2012 he was awarded the Millennium Technology Prize by…

open stage, theatrical stage without a proscenium, projecting into the audience and surrounded on three sides by the audience. The open stage was used in the corrales of Spain’s Golden Age of theatre (beginning about 1570) and in the traditional Noh theatre of Japan. It was also used in the first

stoping: …the operation is known as open stoping. A common open-stoping method is room-and-pillar mining, in which pillars of ore are left standing to support the rock over a flat-lying ore body.

Tim Winton: …35, for his first novel, An Open Swimmer (1982). He won the Miles Franklin Award, Australia’s most prestigious literary prize, for his second novel, Shallows (1984). More novels followed, and by the time his international best seller The Riders (1995) was short-listed for the Booker Prize, Winton had become Australia’s…

telecommunications network: Open systems interconnection: Different communication requirements necessitate different network solutions, and these different network protocols can create significant problems of compatibility when networks are interconnected with one another. In order to overcome some of these interconnection problems, the open systems interconnection (OSI) was approved in…

Joseph Chaikin: …Living Theatre before founding the Open Theatre (1963), which became an influential force in experimental theatre. His celebrated productions, the results of intense collaboration between writer, director, and actors, included America Hurrah (1966), The Serpent (1969), Terminal (1970), The Mutation Show (1971), and Nightwalk (1973). He published his ideas about…

textual criticism: Recension: This is called “horizontal” transmission, and a tradition of this kind is called “open” or “contaminated.” The practice of critics faced with contamination tends to vary, for historical reasons, from field to field. Editors of classical texts generally adopt a controlled eclecticism, classifying the witnesses broadly by groups…

sound: Open tubes: In an open tube, the standing wave of the lowest possible frequency for that particular length of tube (in other words, the fundamental) has antinodes at each end and a node in the centre. This means that an open tube is one-half wavelength…

slide guitar: …slide guitar usually use “open tunings,” in which all the strings are tuned to the pitches of a single chord.

cosmology: Friedmann-Lemaître models: …as negatively curved spaces (“open” universes). The difference between the approaches of Friedmann and Lemaître is that the former set the cosmological constant equal to zero, whereas the latter retained the possibility that it might have a nonzero value. To simplify the discussion, only the Friedmann models are considered…

Netherlands: Education: In addition, the Open University, established in 1984, provides for both university and vocational education through correspondence courses.

Open University, British experiment in higher education for adults. It opened in January 1971 with headquarters at the new town of Milton Keynes, Buckinghamshire. There are no academic prerequisites for enrollment in Open University, the aim of which is to extend educational opportunities to all.

Israel: Education: The Open University of Israel (formerly Everyman’s University) in Tel Aviv opened in 1974, and teachers’ training colleges include two for Arabs. The language of instruction at Israeli universities is Hebrew, while the teaching system represents a mixture of European and American methods. In the 1990s…

animal: Water/vascular systems: Most animals have open circulatory systems. Those few animals with closed circulatory systems have a continuous series of vessels to circulate fluid to the vicinity of all cells, whereas those with open systems have vessels only near the heart. (Actually, no system is entirely closed or open.) In…

Tai languages: Phonological characteristics: …follows: level (using no diacritic), low (using a grave accent), falling (using a circumflex), high (using an acute accent), and rising (using a wedge, or haček); for example, maa (with no diacritic) ‘to come,’ màak (with a grave accent) ‘areca nut,’ mâak (with a circumflex) ‘much,’ máa (with an acute…

construction: Steel: …efficient structural shape is the bar (or open web) joist, a standard truss made with angles for the top and bottom chords, joined by welding to a web made of a continuous bent rod. It is used almost exclusively to support roofs and can span up to 45 metres (150…

The Open Window, frequently anthologized short story by Saki, first published in the collection Beasts and Super-Beasts in 1914. Vera, a charming teenager, plays a practical joke on a nervous visitor, causing him to flee the house. The story’s surprise ending, its witty, concise narrative, and its

solid-waste management: Digesting and processing: …for composting either by the open windrow method or in an enclosed mechanical facility. Windrows are long, low mounds of refuse. They are turned or mixed every few days to provide air for the microbes digesting the organics. Depending on moisture conditions, it may take five to eight weeks for…

Umberto Eco: 1972, 1976; The Open Work), which suggests that in much modern music, Symbolist verse, and literature of controlled disorder (Franz Kafka, James Joyce) the messages are fundamentally ambiguous and invite the audience to participate more actively in the interpretive and creative process. From that work he went…

British Open, one of the world’s four major golf tournaments—with the Masters Tournament, the U.S. Open, and the Professional Golfers’ Association (PGA) Championship—and the oldest continually run championship in the sport. Best known outside the United States as the Open Championship or, simply,

museum: From mouseion to museum: Open-air museums, comprising a series of buildings preserved as objects, and ecomuseums, involving the interpretation of all aspects of an outdoor environment, provide examples of this. In addition, so-called virtual museums exist in electronic form on the Internet. Although virtual museums provide interesting opportunities for…

South Asian arts: Parsi theatre: Sondhi built the Open-Air Theatre, situated on a small artificial hillock in the Lawrence Gardens, one of the finest in all of South Asia. It has remained the centre of dramatic contests and festivals and is a favourite of visiting dancers and actors.