Marie Van Zandt: …in March 1880 in an Opéra-Comique production of Ambroise Thomas’s Mignon. Her performance there won her a five-year contract, and she attained popular stardom with dizzying speed. The height of her Paris career came in April 1883, when she created the title role in Lakmé, which Leo Delibes reportedly wrote…

operant conditioning, in psychology and the study of human and animal behaviour, a mechanism of learning through which humans and animals come to perform or to avoid performing certain behaviours in response to the presence or absence of certain environmental stimuli. The behaviours are

modinha: …of modinhas are in the Óperas Portuguesas (1733–41) by António José da Silva, who interspersed the songs into the prose dialogue of his dramas. Originally simple melodies, modinhas often were embellished with intricate and elaborate musical effects when performed at court or for the nobility. Modinhas were introduced in Brazil…

opera, a staged drama set to music in its entirety, made up of vocal pieces with instrumental accompaniment and usually with orchestral overtures and interludes. In some operas the music is continuous throughout an act; in others it is broken up into discrete pieces, or “numbers,” separated either

Dame Adeline Genée: …was originally called, became the Royal Academy of Dancing, at the helm of which Genée remained as founder-president until 1954. In 1950 she was made a Dame of the British Empire, the first member of the dance profession to be so honoured.

Andrea Bocelli: Musical experimentation: …by the press as “popera”) in an effort to expand his audience base. Criticized by some reviewers as being too lightweight to be taken seriously by the opera world, Bocelli nevertheless performed in The Merry Widow in 1999, singing three arias, and made his American operatic debut later that…

operating room (OR), specially designed medical facility where surgical procedures are performed under sterile conditions to prevent infection and ensure patient safety. It is equipped with advanced surgical instruments, an anesthesia machine, monitoring systems, and specialized lighting, which

modem: Operating parameters: …must follow matching protocols, or operating standards. Worldwide standards for voiceband modems are established by the V-series of recommendations published by the Telecommunication Standardization sector of the International Telecommunication Union (ITU). Among other functions, these standards establish the signaling by which modems initiate and terminate communication, establish compatible modulation and…

operating system (OS), program that manages a computer’s resources, especially the allocation of those resources among other programs. Typical resources include the central processing unit (CPU), computer memory, file storage, input/output (I/O) devices, and network connections. Management tasks

operating room (OR), specially designed medical facility where surgical procedures are performed under sterile conditions to prevent infection and ensure patient safety. It is equipped with advanced surgical instruments, an anesthesia machine, monitoring systems, and specialized lighting, which

operating room (OR), specially designed medical facility where surgical procedures are performed under sterile conditions to prevent infection and ensure patient safety. It is equipped with advanced surgical instruments, an anesthesia machine, monitoring systems, and specialized lighting, which

thetan: An operating thetan (OT) is one who not only is free from engrams but also operates as a fully conscious and functioning thetan according to the church’s most sacred teachings.

statistics: Hypothesis testing: A graph known as an operating-characteristic curve can be constructed to show how changes in the sample size affect the probability of making a type II error.

Operation Bagration, large-scale Soviet offensive against Nazi Germany that occurred from June 23 to August 19, 1944, on the Eastern Front during World War II. It was launched in support of the Normandy Invasion. By mid-1944, the Nazis’ military power was in irreversible decline, and Germany’s

Operation Blue Star, Indian military operation in June 1984 ordered by Prime Minister Indira Gandhi to root out a group of militant Sikh separatists who had occupied the Golden Temple, the Sikhs’ holiest shrine. The leader of the group was Jarnail Singh Bhindranwale, a Sikh fundamentalist who

Operation Breadbasket, program begun in 1962 by the Southern Christian Leadership Conference (SCLC) that aimed at improving the economic status of African Americans through a boycott of white-owned and white-operated businesses that refused to employ African Americans or to buy products sold by

Liam Neeson: The 2000s and beyond: …a hit man, and in Operation Chromite (2016), about the Inch’ŏn (Incheon) landing during the Korean War, he played U.S. Gen. Douglas MacArthur. Neeson’s other credits from 2016 included A Monster Calls, in which he portrayed the title character, who helps a boy cope with the impending loss of his…

Mohammed bin Salman: In charge of defense and economic policy: Known as Operation Decisive Storm, the campaign intended to give the government of Yemeni Pres. Abd Rabbuh Mansur Hadi a decisive advantage against the Shiʿi Houthi insurgency in the north of the country. It was thought that a Houthi victory might give Iran, Saudi Arabia’s main regional…

Battle of Iwo Jima: Battle: …and Marines to carry out Operation Detachment. At its disposal was an armada of 11 warships that were intended to soften up Japanese defenses with sustained bombardment. Maj. Gen. Harry Schmidt took charge of Marine operations. He fielded the largely veteran 3rd, 4th, and 5th Marine divisions, totaling some 70,000…

Operation Eagle Claw, failed mission by the U.S. military in April 1980 to rescue Americans who were held during the Iran hostage crisis. The mission highlighted deficiencies within the U.S. military command structure and led to the creation of the United States Special Operations Command (SOCOM).

Libya bombings of 1986, U.S. air attacks on selected targets in Libya, launched on April 15, 1986, in retaliation for that country’s perceived terrorist activities. Ten days before the attacks, a bomb exploded in a discotheque in West Berlin frequented by U.S. soldiers, killing two people and

2026 Iran war, conflict centered on Iran that was initiated by the United States and Israel on February 28, 2026, and has upended the dynamics of the Middle East. The opening salvo took out the heart of the Iranian regime, Supreme Leader Ali Khamenei, and triggered a torrent of hundreds of

Ben Kingsley: Later works: …by the United Nations, and Operation Finale, portraying Adolf Eichmann, a former Nazi officer, as he is tracked and captured in Argentina by a team of secret agents determined to bring him to justice. In 2019 Kingsley played a member of Mossad in both The Red Sea Diving Resort and…

Operation Fortitude, during World War II, an Allied deception operation that was intended to make Nazi Germany’s high command believe that the main Allied invasion of Europe in 1944 would not be at Normandy. Organized by Allied military officials beginning in 1943, Operation Fortitude—which was one

Jason Statham: Acting career: …up for the action comedy Operation Fortune: Ruse de Guerre (2023), about the hunt to find a stolen briefcase.

Operation Just Cause, U.S. military action (December 1989–January 1990) that centered on the invasion of Panama for the purposes of removing Gen. Manuel Noriega, the country’s dictatorial de facto ruler, from power and extraditing him to the U.S. to face charges of drug trafficking and money

Blake Edwards: Early life and work: …for the Jack Lemmon comedies Operation Mad Ball (1957) and The Notorious Landlady (1962). At the same time, he began writing for television. His first films as a director were Bring Your Smile Along (1955) and He Laughed Last (1956), both of which starred Frankie Laine and were also written…

Operation Market Garden, Allied pursuit of Nazi Germany’s forces across France, and a failed strategic airborne attempt to advance into Germany by way of Holland during World War II, from September 17 to 27, 1944, during World War II. Field Marshal Sir Bernard Montgomery persuaded the Supreme

Pres. Donald Trump surged back to the presidency in 2025 in part by pledging an unprecedented crackdown on unauthorized immigration. His administration moved quickly to fulfill this promise, empowering U.S. Immigration and Customs Enforcement (ICE) and U.S. Customs and Border Protection (CBP) to

Colin Firth: Later credits: …the World War II film Operation Mincemeat (2021), Firth starred with Toni Collette in The Staircase (2022), a true-crime miniseries about the death of a writer’s wife. He also had a role in the drama Empire of Light (2022) and a cameo in the romantic comedy Rye Lane (2023). In…

Operation Mincemeat, covert operation by British intelligence in 1943, designed to mislead Nazi Germany about the Allied powers’ plans to invade Sicily during World War II. The operation involved secret documents placed on a dead body; the fake documents successfully misled the Axis powers into

Operation Mincemeat: Aftermath and legacy: A book titled Operation Mincemeat: The True Spy Story That Changed the Course of World War II (2010) by well-known British author Ben Macintyre was adapted into an eponymous 2021 Netflix film starring Colin Firth and Matthew Macfadyen.

Project Paperclip, U.S. government program that sponsored the post-World War II immigration of German and Austrian scientists and technicians to the United States in order to exploit their knowledge for military and industrial purposes. Project Paperclip itself lasted less than two years, but

Ex Parte Quirin: …1941 Nazi plan, known as Operation Pastorius, in which German submarines put two teams of infiltrators ashore in New York and Florida to sabotage defense-related industries in the United States. All of the saboteurs had been born in Germany, lived in the United States, and then returned to their homeland.…

Blake Edwards: Early life and work: …hit with the military comedy Operation Petticoat (1959), which starred Cary Grant.

Jamie Lee Curtis: Scream Queen: …appear in television shows, notably Operation Petticoat, which was based on a 1959 film starring her father and Cary Grant. The show was canceled in 1978, and that year she made her big-screen debut, starring in John Carpenter’s Halloween. She played Laurie Strode, a shy studious babysitter terrorized by the…

Jesse Jackson: The PUSH era: Operation PUSH was born.

Treblinka: …Belzec and Sobibor—as part of Operation Reinhard, an effort to exterminate the Jews of occupied Poland.

Anselm Kiefer: …Germany’s Spiritual Heroes (1973) and Operation Sea Lion (1975) Kiefer was able to develop an array of visual symbols by which he could continue to comment with irony and sarcasm on certain tragic aspects of German history and culture, in particular the Nazi period. These paintings used garish, sombre colours…

Philip Roth: …he had won previously for Operation Shylock (1993) and The Human Stain. Everyman also marked the start of a period during which Roth produced relatively brief novels, all focused on issues of mortality. Exit Ghost (2007) revisits Zuckerman, who has been reawoken to life’s possibilities after more than a decade…

Operation Torch, major Allied amphibious operation in French North Africa during World War II. It began on November 8, 1942, with the landing of 107,000 British and U.S. troops at Casablanca, Morocco, and the Algerian cities of Algiers and Oran. French authorities concluded an armistice with the

U.S. invasion of Grenada, (October 25, 1983), U.S.-led invasion of the Caribbean country of Grenada to overthrow a military government that had taken power in a bloody coup days earlier. Grenada achieved independence from the United Kingdom on February 7, 1974, and the transition was marked by

Operation Wetback, U.S. immigration law enforcement campaign during the summer of 1954 that resulted in the mass deportation of Mexican nationals—1,100,000 persons according to the U.S. Immigration and Naturalization Service (INS), though most estimates put the figure closer to 300,000. Drafted by

Operation Wrath of God, covert assassination campaign carried out by Israel to avenge the kidnapping and murder of 11 Israeli athletes by Palestinian militants in September 1972 at the Munich Olympics. Although Israel had historically targeted the leaders of organizations such as Fatah, the

Gregory Ratoff: Return to acting: …drama starring Bette Davis, and Operation X (originally called My Daughter Joy), which he also directed; the latter starred Cummins as the daughter of a tycoon (Edward G. Robinson). Ratoff helmed several more films—including Abdullah’s Harem (1955) and Oscar Wilde (1960), his last directing credit—but by then his interest had…

analog computer: Their basic component was an operational amplifier, a device whose output current was proportional to its input potential difference. By causing this output current to flow through appropriate components, further potential differences were obtained, and a wide variety of mathematical operations, including inversion, summation, differentiation, and integration, could be carried…

operations research: Model construction: …be necessary to resort to operational experiments to determine which variables are relevant and how they affect system performance.

combat fatigue, a neurotic disorder caused by the stress involved in war. This anxiety-related disorder is characterized by (1) hypersensitivity to stimuli such as noises, movements, and light accompanied by overactive responses that include involuntary defensive jerking or jumping (startle

operations research: Simulation: …real decision makers is called “operational gaming.” Such simulations are commonly used in the study of interactions of decision makers as in competitive situations. Military gaming has long been used as a training device, but only relatively recently has it been used for research purposes. There is still considerable difficulty,…

intelligence: Levels of intelligence: Tactical intelligence, sometimes called operational or combat intelligence, is information required by military field commanders. Because of the enormous destructive power of modern weaponry, the decision making of political leaders often must take into account information derived from tactical as well as strategic intelligence; major…

operations research, application of scientific methods to the management and administration of organized military, governmental, commercial, and industrial processes. Operations research attempts to provide those who manage organized systems with an objective and quantitative basis for decision; it

operations research: History: …which in 1954 became the Operational Research Society. The Operations Research Society in America was formed in 1952. Many other national societies appeared; the first international conference on operations research was held at Oxford University in 1957. In 1959 an International Federation of Operational Research Societies was formed.

operations research: History: The first scholarly journal, the Operational Research Quarterly, published in the United Kingdom, was initiated in 1950; in 1978 its name was changed to the Journal of the Operational Research Society. It was followed in 1952 by the Journal of the Operations Research Society of America, which was renamed Operations…

operations research: History: …which in 1954 became the Operational Research Society. The Operations Research Society in America was formed in 1952. Many other national societies appeared; the first international conference on operations research was held at Oxford University in 1957. In 1959 an International Federation of Operational Research Societies was formed.

operationalism, In the philosophy of science, the attempt to define all scientific concepts in terms of specifically described operations of measurement and observation. The length of a rod, for example, may be defined as the number of times a certain stick can be laid end to end alongside it.

production management, planning and control of industrial processes to ensure that they move smoothly at the required level. Techniques of production management are employed in service as well as in manufacturing industries. It is a responsibility similar in level and scope to other specialties

operations research, application of scientific methods to the management and administration of organized military, governmental, commercial, and industrial processes. Operations research attempts to provide those who manage organized systems with an objective and quantitative basis for decision; it

operations research: History: …by the Journal of the Operations Research Society of America, which was renamed Operations Research in 1955. The International Federation of Operational Research Societies initiated the International Abstracts in Operations Research in 1961.

Central Intelligence Agency: Organization and responsibilities: The Directorate of Operations is responsible for spying (i.e., espionage, or the clandestine collection of intelligence) and special covert and often illegal operations, including subversion. Clandestine activities are carried out under various covers, including the diplomatic cloak used by virtually every intelligence service, as well as…

history of logic: Ernst Schröder: His first work, Der Operations-kreis des Logikkalkuls (1877; “The Circle of Operations of the Logical Calculus”), was an equational algebraic logic influenced by Boole and Grassmann but presented in an especially clear, concise, and careful manner; it was, however, intensional in that letters stand for concepts, not classes…

Joseph Lister: Education: …hospital disease (now known as operative sepsis—infection of the blood by disease-producing microorganisms) would be greatly decreased in their new building. The hope proved vain, however. Lister reported that, in his Male Accident Ward, between 45 and 50 percent of his amputation cases died from sepsis between 1861 and 1865.

operator, in mathematics, any symbol that indicates an operation to be performed. Examples are x (which indicates the square root is to be taken) and ddx (which indicates differentiation with respect to x is to be performed). An operator may be regarded as a function, transformation, or map, in the

Richard Boleslavsky: Operator 13 (1934) was an American Civil War drama that centred on a Union spy (Marion Davies) disguised in blackface who falls for a Confederate officer (Gary Cooper). The Painted Veil (1934) starred Greta Garbo as a neglected wife who embarks on an affair with…

blood group: Blood groups and genetic linkage: …depends on the existence of operator genes, which turn the activity of closely linked structural genes on or off. The operator genes are themselves controlled by regulator genes. The operator genes are responsible for the quantity of Rh antigens, while the structural genes are responsible for their qualitative characteristics.

John von Neumann: Princeton, 1930–42: …of operators, now known as von Neumann algebras (1929 through the 1940s). Other achievements include a proof of the quasi-ergodic hypothesis (1932) and important work in lattice theory (1935–37). It was not only the new physics that commanded von Neumann’s attention. A 1932 Princeton lecture, “On Certain Equations of Economics…

Niels Fabian Helge von Koch: …part of the theory of linear operators, which are fundamental in the study of quantum mechanics. He also worked on the Riemann hypothesis (see Riemann zeta function) and the prime number theorem.

cirripede: Diversity and distribution: There are two types of sessile barnacle: symmetrical and asymmetrical. The two symmetrical sessile barnacles are the extinct suborder Brachylepadomorpha (Brachylepas) and the extant suborder Balanomorpha, or acorn barnacles (e.g., Balanus, Semibalanus, and Chthamalus). An acorn barnacle is a conical, sessile animal whose soft body is contained within a cavity…

moss animal: Zooids: …the cheilostome colonies, and the operculum seems to have been significant in the evolution of the specialized zooids of this order. The avicularium type of zooid has a small body and a rudimentary polypide; the operculum, however, is proportionally larger, has strong adductor (closing) muscles, and has become, in effect,…

bryophyte: Form and function: …of an apical lid (the operculum). When the operculum falls, there is exposed a ring of teeth that controls the release of the spores over an extended period of time. These teeth usually respond to slight moisture changes and pulsate inward and outward, carrying spores out of the sporangium on…

amphibian: Common features: …airborne (columella) or seismic (operculum) signals.

Eugenio Beltrami: Beltrami’s four-volume work, Opere Matematiche (1902–20), published posthumously, contains his comments on a broad range of physical and mathematical subjects, including thermodynamics, elasticity, magnetism, optics, and electricity. Beltrami was a member of the scientific Accademia dei Lincei, serving as president in 1898; he was elected to the Italian

operetta, musical-dramatic production similar in structure to a light opera but characteristically having a romantically sentimental plot interspersed with songs, orchestral music, and rather elaborate dancing scenes, along with spoken dialogue. The operetta originated in part with the tradition of

Zhang Ziyi: …in Operetta tanuki goten (Princess Raccoon), an elaborate musical adaptation of a Japanese folktale that was directed by legendary Japanese filmmaker Suzuki Seijun. Her subsequent films include Ye yan (2006; The Banquet), which was loosely based on William Shakespeare’s Hamlet; Mei Lanfang (2008), a biopic about the jingxi (Peking…

Giacomo Leopardi: …enlarged collection of poems; and Operette morali (1827; “Minor Moral Works”), an influential philosophical exposition, mainly in dialogue form, of his doctrine of despair.

operon, genetic regulatory system found in bacteria and their viruses in which genes coding for functionally related proteins are clustered along the DNA. This feature allows protein synthesis to be controlled coordinately in response to the needs of the cell. By providing the means to produce

Opet, ancient Egyptian festival of the second month of the lunar calendar. In the celebration of Opet, the god Amon, Mut, his consort, and Khons, their son, made a ritual journey from their shrines at Karnak to the temple of Luxor (called Ipet resyt in pharaonic Egyptian, hence the name of the

Taurt: Another goddess, called Opet (or Apet), was depicted in the same form.

Fritz von Unruh: …1916 at Verdun, published 1919; Way of Sacrifice) and, on a mythical level, in the tragedy Ein Geschlecht (1916; “A Family”)—strengthened his antimilitaristic attitude and led to such later works as Heinrich von Andernach (1925), a festival play and a great plea for love among men.

Yiddish literature: Writers in Poland and the Soviet Union: His masterpiece Opgang (1920; Departing) conveys the decline of the shtetl using techniques such as internal monologue, dream sequences, nonlinear narrative, and a roving narrative eye that views the town from the perspective of many different characters. When the novel opens, its main character has already died of uncertain…

Ophelia, daughter of Polonius, sister to Laertes, and rejected lover of Hamlet in William Shakespeare’s tragedy Hamlet. Ophelia’s mad scene (Act IV, scene 5) is one of the best known in Western literature, and her tragic figure, that of innocence gone mad, has often been portrayed in

Ophelia, oil painting that was created in 1851–52 by John Everett Millais and first exhibited at the Royal Academy of Arts in 1852. It is regarded as a masterpiece of the Pre-Raphaelite Brotherhood. Ophelia is one of the most popular Pre-Raphaelite paintings, produced when the youthful enthusiasm

annelid: Annotated classification: …10 cm; examples of genera: Ophelia, Polyophthalmus, Scalibregma. Order Capitellida No prostomial appendages; 1 or 2 anterior segments without setae; parapodia biramous; setae all simple; size, 1 to 20 or more cm; examples of genera: Capitella,

Uranus: The ring system: …innermost two moons, Cordelia and Ophelia, orbit on either side of the Epsilon ring at exactly the right radii required for shepherding. Shepherds for the other rings were not observed, perhaps because the moons are too small to be seen in the Voyager images. Small moons may also be reservoirs…

Naomi Watts: Later credits: In Ophelia (2018), a retelling of William Shakespeare’s play from the female perspective, Watts portrayed Gertrude, Hamlet’s mother, and also played Gertrude’s invented sister. After the drama Penguin Bloom (2020), Watts was cast as a scientist in the sci-fi thriller Boss Level (2021). She then starred

annelid: Annotated classification: Order Opheliida No prostomial appendages; body with limited number of segments; setae all simple; size, 1 to 10 cm; examples of genera: Ophelia, Polyophthalmus, Scalibregma. Order Capitellida No prostomial appendages; 1 or 2

Hypsipyle: …was acting as nurse to Opheltes, the king’s infant son, she left her charge in order to help the Seven Against Thebes find water; in her absence the child was bitten by a snake and died. (The seer Amphiaraus saw that this episode portended the failure of the expedition of…

green snake: aestivus), often called vine snake, is about 75 cm (23 inches) long.

green snake: The smooth green snake (Opheodrys vernalis), sometimes called green grass snake, is about 50 cm (20 inches) long. The rough, or keeled (ridged), green snake (O. aestivus), often called vine snake, is about 75 cm (23 inches) long.

alopecia areata: Types: …thins across the scalp, and ophiasis alopecia, in which hair loss occurs in a band along the sides and back of the head.

snake eel, any of numerous marine fishes in the family Ophichthidae (order Anguilliformes). Representatives of the more than 200 species are found throughout the world, mostly in tropical or temperate waters. These snakelike creatures are more benign than their aggressive relatives, the morays. The

snake eel: The spotted snake eel (Ophichthus ophis) of the southern Atlantic and Caribbean attains a length of 120 centimetres (4 feet).

ophicleide, brass wind musical instrument with a cup-shaped mouthpiece and padded keys, the bass version of the old keyed bugle. The name (from Greek ophis and kleid, “serpent” and “key”) alludes to its improvement on the military band “upright serpents” (now-obsolete S-shaped bass instruments

cusk eel, any of about 30 species of slim, eel-like marine fishes of the family Ophidiidae, found worldwide in warm and temperate waters. Cusk eels are characterized by the union of their dorsal, anal, and tail fins into a single long fin, and by the position of their feeler-like pelvic fins, which

paracanthopterygian: General features: …and about 385 species of ophidiiforms (that is, the pearlfishes and cusk-eels).

paracanthopterygian: General features: …and about 385 species of ophidiiforms (that is, the pearlfishes and cusk-eels).

avoidance behaviour: Specific stimuli: …disturbed by the sight of snakes—the notion of a legless object perhaps being a key stimulus. Human responses to spiders and centipedes with conspicuous legs also may be intense. In the reaction to snakes at least, notwithstanding Freudian explanations that they symbolize male sex organs, the behaviour of people may…

Sabiaceae: …and is known as the snake nut. Meliosma, with about 80 species, has two anthers that open explosively after being held under tension by two or three complex staminodes (sterile stamens). Sabia, with some 30 species, and the small genus Kingsboroghia are the other two genera of the family.

echinoderm: Annotated classification: †Class Ophiocistioidea Lower Ordovician to Upper Silurian about 395,000,000–500,000,000 years ago; dome-shaped body partly or completely covered by well-developed test; 5 ambulacral tracts carry plated tube feet relatively enormous in size. Class Holothuroidea (sea cucumbers) Fossil and living forms (Ordovician about 460,000,000

zombie-ant fungus, (Ophiocordyceps unilateralis), species of parasitic fungus that infects ants and dramatically alters their behavior before killing them. The fungus is largely pantropical and primarily infects carpenter ants (genus Camponotus). Its taxonomy is contentious, with some research

brittle star: …best-known littoral species are the green brittle star (Ophioderma brevispina), found from Massachusetts to Brazil, and the common European brittle star (Ophiothrix fragilis). Brittle stars typically hide under rocks or in crevices during the day and emerge at night to feed.