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  • Presidential Prayer Breakfast

    The Family: Move to Washington: Known since 1970 as the National Prayer Breakfast, it is regularly addressed by the president of the United States and is conceived of by the movement as a consecration of the governing class to the service of Jesus.

  • presidential primary (politics)

    primary election: Indirect primaries for the presidency of the United States are used in many states. Voters in these elections generally select delegates who attend a national political convention and are bound and pledged to cast their ballots on the basis of the preferences of the voters. Delegates…

  • Presidential Reconstruction (United States [1865-1867])

    Reconstruction: Presidential Reconstruction: Following Lincoln’s assassination in April 1865, Andrew Johnson became president and inaugurated the period of Presidential Reconstruction (1865–67). Johnson offered a pardon to all Southern whites except Confederate leaders and wealthy planters (although most of these subsequently received individual pardons), restoring their political rights…

  • Presidential Recordings and Materials Preservation Act (United States)

    attainder: …Services (1977) held that the Presidential Recordings and Materials Preservation Act was not a bill of attainder even though the law referred to President Richard Nixon by name. This law directed the administrator of the General Services Administration to seize tape recordings, papers, and other materials then in Nixon’s possession.…

  • presidential succession (United States government)

    Speaker of the U.S. House of Representatives: …second in the line of presidential succession, following the vice president.

  • Presidential Symphony Orchestra (Turkish orchestra)

    Ankara: The contemporary city: …the state theatre and the Presidential Symphony Orchestra.

  • Presidential vote for the District of Columbia (United States Constitution)

    Twenty-third Amendment, amendment (1961) to the Constitution of the United States that permitted citizens of Washington, D.C., the right to choose electors in presidential elections. It was proposed by the U.S. Congress on June 16, 1960, and its ratification was certified on March 29, 1961.

  • presidential-parliamentary system (government)

    political system: Constitutional government: …constitutional democracy is the hybrid presidential-parliamentary system, exemplified by the government of France. In such systems there is both a directly elected president with substantial executive powers and a presidentially appointed prime minister, who must retain majority support in the legislature. If the president’s party or coalition also controls a…

  • Presidents of the United States

    As the head of the government of the United States, the president is arguably the most powerful government official in the world. The president is elected to a four-year term via an electoral college system. Since the Twenty-second Amendment was adopted in 1951, the American presidency has been

  • Presidents’ Day (United States holiday)

    Presidents’ Day, in the United States, holiday (third Monday in February) popularly recognized as honouring George Washington and Abraham Lincoln. The day is sometimes understood as a celebration of the birthdays and lives of all U.S. presidents. The origin of Presidents’ Day lies in the 1880s,

  • présidial (French court)

    France: The growth of a professional bureaucracy: …new kind of court, the présidial, whose jurisdiction lay between the parlement and the bailiwick. Each of the 65 new courts had a complement of nine judges; this brought in a sizable revenue but appears to have made little difference to the efficiency of the judicial system. Nor were judicial…

  • Presidio (military base, San Francisco, California, United States)

    San Francisco: City layout: …Golden Gate Bridge, lies the Presidio, a two-century-old military installation that became part of Golden Gate National Recreation Area in 1994; it is remarkable for its parklike lawns and wind-sculptured stands of trees. South of the Presidio is Golden Gate Park, reclaimed from a onetime sandy desert. The rest of…

  • presidium (Soviet government)

    Soviet Union: Postwar: Instead of a Politburo, a Presidium of the Central Committee was nominated, consisting of 25 members and 11 candidate members. This included all the old Politburo members except Andreyev (though Kosygin was now only a candidate). But there were also a number of new members, to whom Stalin looked as…

  • Presidium of the Supreme Soviet (Soviet government)

    Soviet Union: …small group known as the Presidium of the Supreme Soviet, itself strongly influenced by the Politburo of the CPSU, and were unanimously approved by the deputies. The role of the soviets in the individual republics and other territories was primarily to put into effect the decisions made by the Supreme…

  • Preslav (Bulgaria)

    Veliki Preslav, town, eastern Bulgaria. It lies at the foot of the Preslav Mountains, 11 miles (18 km) southwest of Shumen. Founded by the Proto-Bulgarians in the 8th century and called Yeski Stambolchuk (Eski Stambul), it served as capital of Bulgaria under Simeon the Great in the 10th century. It

  • Presley, Elvis (American singer and actor)

    Elvis Presley, American popular singer widely known as the “King of Rock and Roll” and one of rock music’s dominant performers from the mid-1950s until his death. Presley grew up dirt-poor in Tupelo, moved to Memphis as a teenager, and, with his family, was off welfare only a few weeks when

  • Presley, Elvis Aaron (American singer and actor)

    Elvis Presley, American popular singer widely known as the “King of Rock and Roll” and one of rock music’s dominant performers from the mid-1950s until his death. Presley grew up dirt-poor in Tupelo, moved to Memphis as a teenager, and, with his family, was off welfare only a few weeks when

  • Presley, Elvis Aron (American singer and actor)

    Elvis Presley, American popular singer widely known as the “King of Rock and Roll” and one of rock music’s dominant performers from the mid-1950s until his death. Presley grew up dirt-poor in Tupelo, moved to Memphis as a teenager, and, with his family, was off welfare only a few weeks when

  • Presley, Reg (British singer)

    Reg Presley, (Reginald Maurice Ball), British singer (born June 12, 1941, Andover, Hampshire, Eng.—died Feb. 4, 2013, Andover), was the lead singer for the 1960s rock-and-roll band the Troggs; his raspy, innuendo-laden rendition of the group’s smash hit “Wild Thing” (1966) briefly brought them

  • Presnell, George Harvey (American actor)

    Harve Presnell, (George Harvey Presnell), American actor (born Sept. 14, 1933, Modesto, Calif.—died June 30, 2009, Santa Monica, Calif.), enchanted stage and screen audiences with his leading-man looks and rich baritone voice before becoming an austere character actor decades later. Presnell

  • Presnell, Harve (American actor)

    Harve Presnell, (George Harvey Presnell), American actor (born Sept. 14, 1933, Modesto, Calif.—died June 30, 2009, Santa Monica, Calif.), enchanted stage and screen audiences with his leading-man looks and rich baritone voice before becoming an austere character actor decades later. Presnell

  • Prešov (Slovakia)

    Prešov, town, eastern Slovakia, on the Torysa River. First mentioned in documents in 1247, it became a royal free town in 1374. Prešov is now a state historic town; its medieval oval marketplace, Renaissance burgher houses, and three churches representing Gothic, 16th-century Baroque, and

  • Prespa Agreement (Balkan history)

    Balkans: Economic collapse and nationalist resurgence: …Macedonia and Greece signed the Prespa Agreement, under which Macedonia was to be known both domestically and internationally as the Republic of North Macedonia (Macedonian: Republika Severna Makedonija). By January 2019 the Macedonian and Greek legislatures had both approved the measures necessary to pave the way for formal adoption of…

  • Prespa, Lake (lake, Europe)

    Lake Prespa, lake situated on the North Macedonia–Albania–Greece frontier, with an elevation of 2,800 feet (853 metres) above sea level and an area of 106 square miles (274 square km). Fed by underground streams, it is linked by subterranean channels with Lake Ohrid. Most of Lake Prespa is in North

  • Prespansko Ezero (lake, Europe)

    Lake Prespa, lake situated on the North Macedonia–Albania–Greece frontier, with an elevation of 2,800 feet (853 metres) above sea level and an area of 106 square miles (274 square km). Fed by underground streams, it is linked by subterranean channels with Lake Ohrid. Most of Lake Prespa is in North

  • Prespës, Liqueni i (lake, Europe)

    Lake Prespa, lake situated on the North Macedonia–Albania–Greece frontier, with an elevation of 2,800 feet (853 metres) above sea level and an area of 106 square miles (274 square km). Fed by underground streams, it is linked by subterranean channels with Lake Ohrid. Most of Lake Prespa is in North

  • presplitting (excavation technique)

    tunnels and underground excavations: Sound-wall blasting: …met by the technique of presplitting, developed in the United States in the late 1950s. Basically, this technique consists of creating a continuous crack (or presplit) at a desired finished excavation line by initially firing a line of closely spaced, lightly loaded holes drilled there. Next, the interior rock mass…

  • presqualene pyrophosphate (chemical compound)

    isoprenoid: Tail-to-tail coupling of isoprenoids: …containing a three-membered ring, called presqualene pyrophosphate, to accumulate. (OPP represents the pyrophosphate group.)

  • Presque Isle (Maine, United States)

    Presque Isle, city, Aroostook county, northeastern Maine, U.S., on the Aroostook River and its affluent the Presque Isle Stream, near the New Brunswick (Canada) border, 163 miles (262 km) north-northeast of Bangor. Settled in the 1820s as Fairbanks, it was incorporated as a town in 1859 with a name

  • Presque Isle State Park (park, Pennsylvania, United States)

    Erie: Presque Isle State Park, named for Fort-Presque-Isle (built by the French in 1753), is located on a peninsula that forms a natural harbour for the city of Erie, which is the county seat. This lakeside city, Pennsylvania’s only port on the St. Lawrence Seaway (completed…

  • press (weightlifting)

    weightlifting: Lifts: The press was also a two-part lift. As in the clean and jerk, the barbell was brought to the lifter’s shoulders, the same foot motion being allowed. Then the lifter had to stand erect until the referee signaled for the completion of the lift, which was…

  • press

    Journalism, the collection, preparation, and distribution of news and related commentary and feature materials through such print and electronic media as newspapers, magazines, books, blogs, webcasts, podcasts, social networking and social media sites, and e-mail as well as through radio, motion

  • press

    Newspaper, publication usually issued daily, weekly, or at other regular times that provides news, views, features, and other information of public interest and that often carries advertising. Forerunners of the modern newspaper include the Acta diurna (“daily acts”) of ancient Rome—posted

  • press (publishing)

    Magazine, a printed or digitally published collection of texts (essays, articles, stories, poems), often illustrated, that is produced at regular intervals (excluding newspapers). A brief treatment of magazines follows. For full treatment, see publishing: Magazine publishing. The modern magazine

  • press (furniture)

    wardrobe: …was originally known as a press, and at quite an early date its division into two parts—one for hanging garments, the other for laying them out flat—became established. By the 17th century the word wardrobe was coming to be accepted as descriptive of this kind of piece, while the earlier…

  • press (basketball)

    basketball: Principles of play: The press, which can be either man-to-man or zone, is used by a team to guard its opponent so thoroughly that the opposition is forced to hurry its movements and especially to commit errors that result in turnovers. A full-court press applies this pressure defense from…

  • press (machine tool)

    machine tool: Presses: This large class of machines includes equipment used for forming metal parts by applying the following processes: shearing, blanking, forming, drawing, bending, forging, coining, upsetting, flanging, squeezing, and hammering. All of these processes require presses with a movable ram that can be pressed against an…

  • press agency (journalism)

    News agency, organization that gathers, writes, and distributes news from around a nation or the world to newspapers, periodicals, radio and television broadcasters, government agencies, and other users. It does not generally publish news itself but supplies news to its subscribers, who, by sharing

  • press association (journalism)

    News agency, organization that gathers, writes, and distributes news from around a nation or the world to newspapers, periodicals, radio and television broadcasters, government agencies, and other users. It does not generally publish news itself but supplies news to its subscribers, who, by sharing

  • Press Association (British organization)

    Thomson Reuters: The Press Association (PA), an organization representing the provincial press of Great Britain, acquired a majority interest in Reuters in 1925 and full ownership some years later. In 1941 the PA sold half of Reuters to the Newspaper Proprietors’ Association, representing Britain’s national press, and in…

  • press die (technology)

    tool and die making: The fabrication of pressworking dies constitutes the major part of the work done in tool and die shops. Most pressworking dies are utilized in the fabrication of sheet-metal parts that range in size from the finger stop on a dial telephone to the panels of an automobile body.…

  • press mold (technology)

    sculpture: Casting and molding: …low reliefs—can be prepared by pressing clay into a rigid mold. More complex forms can be built up from a number of separately press-cast pieces. Simple terra-cotta molds can be made by pressing clay around a rigid positive form. After firing, these press molds can be used for press casting.

  • press molding (technology)

    sculpture: Casting and molding: …low reliefs—can be prepared by pressing clay into a rigid mold. More complex forms can be built up from a number of separately press-cast pieces. Simple terra-cotta molds can be made by pressing clay around a rigid positive form. After firing, these press molds can be used for press casting.

  • press ram (technology)

    tool and die making: In a working cycle the press ram, on which the male section is mounted, descends into the fixed female section. Any metal interposed between the sections is cut or shaped to a prescribed form. Like the dies, the presses range in size from extremely small to gigantic. A bench press…

  • press section (papermaking)

    papermaking: Formation of paper sheet by machines: The press section increases the solids content of the sheet of paper by removing some of the free water contained in the sheet after it is formed. It then carries the paper from the forming unit to the dryer section without disrupting or disturbing sheet structure…

  • press syndicate (journalism)

    Newspaper syndicate, agency that sells to newspapers and other media special writing and artwork, often written by a noted journalist or eminent authority or drawn by a well-known cartoonist, that cannot be classified as spot coverage of the news. Its fundamental service is to spread the cost of

  • Press Trust of India (news agency)

    Press Trust of India (PTI), news agency cooperatively owned by Indian newspapers, which joined together to take over the management of the Associated Press of India and the Indian outlets of the Reuters news agency of Great Britain. It began operating in February 1949 and is headquartered in

  • press, freedom of the (law)

    censorship: Requirements of self-government: …of speech and of the press, particularly as that freedom permits an informed access to information and opinions about political matters. Even the more repressive regimes today recognize this underlying principle, in that their ruling bodies try to make certain that they themselves become and remain informed about what is…

  • Press, Irina (Soviet athlete)

    Irina Press, Soviet athlete who won two track-and-field Olympic gold medals during a career in which she set 11 world records. Press won a gold medal in the 1960 Olympics in Rome in the 80-metre hurdles, setting an Olympic record (10.6 sec) in the semifinals. Her sister Tamara also competed in Rome

  • press, printing (printing)

    Printing press, machine by which text and images are transferred to paper or other media by means of ink. Although movable type, as well as paper, first appeared in China, it was in Europe that printing first became mechanized. The earliest mention of a printing press is in a lawsuit in Strasbourg

  • Press, Tamara (Soviet athlete)

    Tamara Press , Soviet athlete who won three track-and-field Olympic gold medals and set 12 world records. Press won her first gold medal at the 1960 Olympics in Rome, setting an Olympic record with a shot put of 17.32 metres (56 feet 10 inches). She won the silver medal in the discus (52.59 metres

  • Press-Ewing seismograph (instrument)

    seismograph: Development of the first seismographs: The Press-Ewing seismograph, developed in the United States for recording long-period waves, was widely used throughout the world. That device employed a Milne-type pendulum, but the pivot supporting the pendulum was replaced by an elastic wire to avoid friction.

  • Pressburg (national capital, Slovakia)

    Bratislava, city, capital of Slovakia. It lies in the extreme southwestern part of the country, along the Danube where that river has cut a gorge in the Little Carpathian Mountains near the meeting point of the frontiers of Slovakia, Austria, and Hungary. Vienna is 35 miles (56 km) west.

  • Pressburg, Treaty of (Europe [1805])

    Treaty of Pressburg, (Dec. 26, 1805), agreement signed by Austria and France at Pressburg (now Bratislava, Slovakia) after Napoleon’s victories at Ulm and Austerlitz; it imposed severe terms on Austria. Austria gave up the following: all that it had received of Venetian territory at the Treaty of

  • Pressburg, Treaty of (Europe [1491])

    Maximilian I: Territorial expansion: By the Treaty of Pressburg in 1491, he arranged that the succession to Bohemia and Hungary would pass to the Habsburgs if Vladislas left no male heir.

  • Pressburger, Emeric (British writer)

    Emeric Pressburger, Hungarian-born screenwriter who wrote and produced innovative and visually striking motion pictures in collaboration with British director Michael Powell, most notably The Red Shoes (1948). Pressburger studied engineering in Prague and Stuttgart, but in 1925 he went to Berlin,

  • Pressburger, Imre (British writer)

    Emeric Pressburger, Hungarian-born screenwriter who wrote and produced innovative and visually striking motion pictures in collaboration with British director Michael Powell, most notably The Red Shoes (1948). Pressburger studied engineering in Prague and Stuttgart, but in 1925 he went to Berlin,

  • Presse, Die (Austrian newspaper)

    Die Presse, (German: “The Press”) newspaper published in Vienna, Austria’s leading daily (though far from its largest) and one of Europe’s outstanding journals. It was founded in 1848 during one of the Austro-Hungarian Empire’s intermittent periods of freedom of the press. It emphasized quality,

  • Presse, La (French newspaper)

    history of publishing: Continental Europe and other countries: …the founding in Paris of La Presse (1836) by Émile de Girardin, who might be called one of the first press barons. He introduced new features and serials to raise circulation as high as 20,000 and thus to enable him to lower the price of his newspapers. A prominent contemporary…

  • Presse, La (Canadian newspaper)

    La Presse, (French: “The Press”) French-language daily newspaper published in Montreal. It has long been one of the most widely circulated French-language daily newspapers in Canada, and it remains the biggest standard-size (broadsheet) paper; only the French-language tabloid Le Journal de Montréal

  • pressed glass

    Pressed glass, glassware produced by mechanically pressing molten glass into a plain or engraved mold by means of a plunger. Pressed glass can generally be distinguished from hand-cut glass because of its blunt-edged facets, mold seams (which are often removed by polishing, however), and precise,

  • Presser v. Illinois (law case)

    William B. Woods: …activities of individuals, and in Presser v. Illinois, which declared that the Bill of Rights limited the power of the federal, but not a state, government. Both positions were later reversed.

  • Presser, Jackie (American union leader)

    Jackie Presser, American union leader and president (1983–88) of the International Brotherhood of Teamsters, one of the nation’s largest unions. Presser quit school after the eighth grade, joined the navy at age 17, and served in World War II. He then took a job with a local restaurant workers

  • pressing (forming)

    traditional ceramics: Plastic forming: Foremost among these techniques are pressing and extrusion.

  • pressing (food processing)

    fat and oil processing: Pressing machines: Many different mechanical devices have been used for pressing. The Romans developed a screw press, described by Pliny, for the production of olive oil. Centuries ago, the Chinese employed the same series of operations followed in modern pressing mills—namely, bruising or grinding the…

  • pressing (clothing)

    clothing and footwear industry: Pressing and molding processes: Pressing, pleating, blocking, mangling, steaming, creasing, curing, and casting are trade terms for various molding processes in producing clothing and footwear.

  • Pression barométrique, recherches de physiologie expérimentale, La (work by Bert)

    Paul Bert: …recherches de physiologie expérimentale (1878; Barometric Pressure: Researches in Experimental Physiology, 1943) was of fundamental importance to aviation medicine during World War II and to aerospace research in general.

  • Presson, Jacqueline (American screenwriter and playwright)

    Jay Presson Allen, (Jacqueline Presson), American screenwriter and playwright (born March 3, 1922, Fort Worth, Texas—died May 1, 2006, New York, N.Y.), was best known for the scripts she adapted from novels and was credited with having developed some of the best and most memorable women’s stage a

  • pressoreceptor (physiology)

    Bainbridge reflex: Special pressure sensors called baroreceptors (or venoatrial stretch receptors) located in the right atrium of the heart detect increases in the volume and pressure of blood returned to the heart. These receptors transmit information along the vagus nerve (10th cranial nerve) to the central nervous system. This response results…

  • pressure (physics)

    Pressure, in the physical sciences, the perpendicular force per unit area, or the stress at a point within a confined fluid. The pressure exerted on a floor by a 42-pound box the bottom of which has an area of 84 square inches is equal to the force divided by the area over which it is exerted;

  • pressure altimeter (instrument)

    altimeter: …two main types are the pressure altimeter, or aneroid barometer, which approximates altitude above sea level by measuring atmospheric pressure, and the radio altimeter, which measures absolute altitude (distance above land or water) based on the time required for a radio wave signal to travel from an airplane, a weather…

  • pressure antinode (physics)

    sound: Measuring techniques: …of a tube, while a pressure antinode (corresponding to a displacement or velocity node) occurs at the closed end. Because most microphones respond to changes in pressure, this type of representation may be more useful when discussing experimental observations involving the use of microphones.

  • pressure bomb (plant)

    angiosperm: Process of xylem transport: …ingeniously simple device called the pressure bomb. A small twig is inserted in a container (the pressure bomb), its cut stump emerging from a tightly sealed hole. As pressure is applied to the container and gradually increased, water from the xylem emerges from the cut end as soon as the…

  • pressure bridge (music)

    bridge: In the pressure bridge, the string is fastened at one end to a tuning peg or a wrest pin and at the other to a pin or a tailpiece; it passes over the bridge (or bridges), which may be glued to the soundboard (as in the piano)…

  • pressure cooker

    Pressure cooker, hermetically sealed pot which produces steam heat to cook food quickly. The pressure cooker first appeared in 1679 as Papin’s Digester, named for its inventor, the French-born physicist Denis Papin. The cooker heats water to produce very hot steam which forces the temperature

  • pressure drum (musical instrument)

    Dùndún pressure drum, double-membrane, hourglass-shaped drum of the Yoruba people of southwestern Nigeria. It is capable of imitating the tones and glides of the spoken language and is employed by a skilled musician to render ritual praise poetry to a deity or king. It has counterparts in East

  • pressure filter (chemistry)

    filtration: Filter types: Pressure or vacuum filters usually are used in industry in preference to gravity filters. The driving force that can be supplied by pressure or vacuum is much greater than gravity, thus permitting higher filtration rates. Sand-bed filters are operated under pressure in closed vessels to…

  • pressure flaking technique

    flake tool: Pressure flaking, as the name implies, consists of applying pressure by means of a pointed stick or bone near the edge of a flake or blade, to detach small flakes from both sides. This method was used mostly to put the finishing touches on tools…

  • pressure flow (plant physiology)

    angiosperm: Process of phloem transport: Mass-flow hypotheses include the pressure-flow hypothesis, which states that flow into sieve tubes at source regions (places of photosynthesis or mobilization and exportation of storage products) raises the osmotic pressure in the sieve tube; removal of sugars from sieve tubes in sink regions—i.e., those in…

  • pressure gauge (instrument)

    Pressure gauge, instrument for measuring the condition of a fluid (liquid or gas) that is specified by the force that the fluid would exert, when at rest, on a unit area, such as pounds per square inch or newtons per square centimetre. The reading on a gauge, which is the difference between two

  • pressure group (political science)

    Interest group, any association of individuals or organizations, usually formally organized, that, on the basis of one or more shared concerns, attempts to influence public policy in its favour. All interest groups share a desire to affect government policy to benefit themselves or their causes.

  • pressure leaching (industrial process)

    metallurgy: Leaching: Pressure leaching shortens the treatment time by improving the solubility of solids that dissolve only very slowly at atmospheric pressure. For this process autoclaves are used, in both vertical and horizontal styles. After leaching, the pregnant solution is separated from the insoluble residue and sent…

  • pressure mine (submarine mine)

    mine: Submarine mine: The pressure mine employs the principle that beneath every ship in motion in shallow water there is an area of reduced pressure. The pressure mine contains a chamber divided by a diaphragm, with one side of the chamber open to the sea. Any sudden decrease in…

  • pressure node (physics)

    sound: Measuring techniques: …in Figure 6—that is, a pressure node (corresponding to a displacement or velocity antinode) occurs at the open end of a tube, while a pressure antinode (corresponding to a displacement or velocity node) occurs at the closed end. Because most microphones respond to changes in pressure, this type of representation…

  • pressure receptor (physiology)

    Bainbridge reflex: Special pressure sensors called baroreceptors (or venoatrial stretch receptors) located in the right atrium of the heart detect increases in the volume and pressure of blood returned to the heart. These receptors transmit information along the vagus nerve (10th cranial nerve) to the central nervous system. This response results…

  • pressure remanent magnetization (physics)

    rock: Types of remanent magnetization: PRM (pressure remanent, or piezoremanent, magnetization) arises when a material undergoes mechanical deformation while in a magnetic field. The process of deformation may result from hydrostatic pressure, shock impact (as produced by a meteorite striking the Earth’s surface), or directed tectonic stress. There are magnetization changes with stress in…

  • pressure ridge (ice)

    sea ice: Sea ice formation and features: A pressure ridge is composed of a sail above the waterline and a keel below. In the Arctic most keels are 10–25 m (about 33–80 feet) deep and typically four times the sail height. Keel widths are typically 2–3 times the sail width. Antarctic pressure ridges…

  • pressure sore (ulceration)

    Bedsore, an ulceration of skin and underlying tissue caused by pressure that limits the blood supply to the affected area. As the name indicates, bedsores are a particular affliction for persons who have been bedridden for a long time. The interference with normal blood flow is caused by the

  • pressure staging (engineering)

    turbine: Turbine staging: Pressure staging uses a number of sequential impulse stages similar to those illustrated in Figure 1, except that the stationary passages also become highly curved nozzles. Pressure-staged turbines can range in power capacity from a few to more than 1.3 million kilowatts. Some manufacturers prefer…

  • pressure vessel (reactor part)

    nuclear reactor: Structural components: …gas-controlled reactor (HTGR), a reactor pressure vessel (RPV) is utilized so that the coolant is contained and operated under conditions appropriate for power generation—namely, elevated temperature and pressure. Within the reactor vessel are a number of structural elements: grids for holding the reactor core and solid reflectors, control-rod guide tubes,…

  • pressure wave (physics)

    Longitudinal wave, wave consisting of a periodic disturbance or vibration that takes place in the same direction as the advance of the wave. A coiled spring that is compressed at one end and then released experiences a wave of compression that travels its length, followed by a stretching; a point

  • pressure-assisted sintering

    advanced ceramics: Pressure-assisted sintering: The sintering processes described above can be assisted by the application of pressure. Pressure increases the driving force for densification, and it also decreases the temperature needed for sintering to as low as half the melting point of the ceramic. Furthermore, shape forming…

  • pressure-flow hypothesis (botany)

    angiosperm: Process of phloem transport: Mass-flow hypotheses include the pressure-flow hypothesis, which states that flow into sieve tubes at source regions (places of photosynthesis or mobilization and exportation of storage products) raises the osmotic pressure in the sieve tube; removal of sugars from sieve tubes in sink regions—i.e., those in which sugars are removed…

  • pressure-gradient force (atmospheric science)

    Buys Ballot's law: …between the wind and the pressure gradient is a right angle. This is almost exactly true in the free atmosphere, but not near the surface. Near the ground, the angle is usually less than 90° because of friction between the air and the surface and the turning of the wind…

  • pressure-on-the-face mole (tunnel machine)

    tunnels and underground excavations: Soft-ground moles: A third type is the pressure-on-face mole. Here, only the face is pressurized, and the tunnel proper operates in free air—thus avoiding the high costs of labour under pressure. In 1969 a first major attempt used air pressure on the face of a mole operating in sands and silts for…

  • pressure-ridge cave (geology)

    cave: Other types of lava caves: So-called pressure-ridge caves can be formed beneath the ridges by the mechanical lifting of the roof rock. Such cavities typically measure one to two metres in height, have a roughly triangular cross section, and extend several hundred metres in length. Unlike lava tube caves that are…

  • pressure-sensitive adhesive (adhesive)

    adhesive: Pressure-sensitive adhesives: Pressure-sensitive adhesives, or PSAs, represent a large industrial and commercial market in the form of adhesive tapes and films directed toward packaging, mounting and fastening, masking, and electrical and surgical applications. PSAs are capable of holding adherends together when the surfaces are mated…

  • pressure-temperature-time path (geology)

    metamorphic rock: Pressure-temperature-time paths: Interaction between metamorphic petrologists and geophysicists in the 1980s led to the realization that each metamorphic rock follows its own unique path through pressure- (depth-) temperature space during metamorphism and that these paths bear little or no resemblance to steady-state geotherms. The specific…

  • pressurized-water reactor (nuclear energy)

    nuclear reactor: PWRs and BWRs: …are two basic types: the pressurized-water reactor (PWR) and the boiling-water reactor (BWR). In the PWR, water at high pressure and temperature removes heat from the core and is transported to a steam generator. There the heat from the primary loop is transferred to a lower-pressure secondary loop also containing…

  • pressworking (technology)

    automation: Automated production lines: Pressworking operations involve the cutting and forming of parts from sheet metal. Examples of such parts include automobile body panels, outer shells of major appliances (e.g., laundry machines and ranges), and metal furniture (e.g., desks and file cabinets). More than one processing step is often…

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