peristerite, iridescent gemstone in the plagioclase (q.v.) series of feldspar minerals. The name (from Greek peristera, “pigeon”) refers to the resemblance of fine specimens such as those from Ontario and Quebec to the commonly iridescent feathers of a pigeon’s neck. In peristerite—usually a form

bryophyte: Annotated classification: …opening by apical cap (operculum); peristome teeth usually surrounding the sporangium mouth and influencing spore release; columella usually present, encircled or overarched by a spore-bearing layer; calyptra capping apex of elongating seta and influencing survival and differentiation of sporangium; spores generally shed over extended period; seta a rigid structure with…

domus: Located between the atrium and peristyle was the tablinum, an open living room that could be curtained off from public view. A hallway, or fauces, was positioned to one side of the tablinum, to provide convenient access to the peristyle.

ascocarp: …called apothecium, cleistothecium [cleistocarp], or perithecium) contain saclike structures (asci) that usually bear four to eight ascospores. Apothecia are stalked and either disklike, saucer-shaped, or cup-shaped with exposed asci. The largest known apothecium, produced by Geopyxis cacabus, has a stalk 1 metre (40 inches) high and a cup 50 centimetres…

Santa Cruz: Perito Francisco P. Moreno National Park, with an area of 444 square miles (1,150 square km) in the northwestern part of the province, includes the Andean divide between Pacific and Atlantic drainage. The northeast-central Petrified Forest National Monument (1954) covers nearly 14 square miles (35…

ascites: …accumulation of fluid in the peritoneal cavity, between the membrane lining the abdominal wall and the membrane covering the abdominal organs. The most common causes of ascites are cirrhosis of the liver, heart failure, tumours of the peritoneal membranes, and escape of chyle (lymph laden with emulsified fats) into the…

renal system disease: Dialysis: In peritoneal dialysis, the patient’s own abdominal cavity is used as the container of fluid; the fluid is run in, allowed to reach equilibrium, and removed, taking with it urea and other wastes. The process has proved suitable for the short-term treatment of acute renal failure,…

laparoscopy, procedure that permits visual examination of the abdominal cavity with an optical instrument called a laparoscope, which is inserted through a small incision made in the abdominal wall. The term comes from the Greek words laparo, meaning “flank,” and skopein, meaning “to examine.” The

peritoneum, large membrane in the abdominal cavity that connects and supports internal organs. It is composed of many folds that pass between or around the various organs. Two folds are of primary importance: the omentum, which hangs in front of the stomach and intestine; and the mesentery, which

peritonitis, inflammation of the peritoneum, the membrane that lines the abdominal wall and then folds in to enclose the abdominal organs. The condition is marked by an accumulation of cells, pus, and other bodily fluids, such as serum and fibrin, in the peritoneal cavity (between the two folds of

quinsy, pus-filled swelling in the throat that develops infrequently as a complication of acute tonsillitis. It extends through the tonsillar capsule into the loose connective tissue of the neck and displaces the involved tonsil toward the midline of the throat. Extreme pain accompanying the

peritrich, any ciliated vase-shaped protozoan of the order Peritrichida (more than 1,000 species), found in both fresh and salt water. Usually nonmotile (sessile), they attach themselves to underwater objects, but a few genera, such as Telotrochidium, are free-swimming. In most peritrichs a

peritrich, any ciliated vase-shaped protozoan of the order Peritrichida (more than 1,000 species), found in both fresh and salt water. Usually nonmotile (sessile), they attach themselves to underwater objects, but a few genera, such as Telotrochidium, are free-swimming. In most peritrichs a

echinoderm: Body wall and body cavity: …of the coelom are the perivisceral coelom and the water-vascular system. The perivisceral coelom is a large, fluid-filled cavity in which the major organs, particularly the digestive tube and sex organs, are suspended. Other regions of the coelom include the axial sinus (absent from adult holothurians and all echinoids), the…

peruke, man’s wig, especially the type popular from the 17th to the early 19th century. It was made of long hair, often with curls on the sides, and was sometimes drawn back on the nape of the neck. Use of the word peruke probably became widespread in the 16th century, when the wearing of wigs

periwinkle, in botany, any of various plants of the genus Vinca of the dogbane family (Apocynaceae). The name periwinkle is possibly taken from pervinka, the Russian name of the flower, which in turn is derived from pervi, “first,” as it is one of the first flowers of spring. The lesser periwinkle

periwinkle, in zoology, any small marine snail belonging to the family Littorinidae (class Gastropoda, phylum Mollusca). Periwinkles are widely distributed shore (littoral) snails, chiefly herbivorous, usually found on rocks, stones, or pilings between high- and low-tide marks; a few are found on

Periyar was an Indian social reformer, politician, and iconoclast who played a pivotal role in shaping modern Tamil politics. Born Erode Venkatappa Ramasamy Naicker, he was popularly called Periyar (“Revered One”). A fierce critic of the caste system, religious orthodoxy, and patriarchy, he led the

Periyar River: …north a short distance to Periyar Lake. It is the longest river in Kerala and is the second largest river basin of Kerala with a catchment area of 2,084 square miles (5,398 square km). Of this, 2,040 square miles (5,284 square km) lies in Kerala, and 44 square miles (114…

Periyar River, river in southern Kerala, southwestern India. Periyar, meaning “big river” in Malayalam and Tamil, is also the name given to a lake in the river’s course. The river, 152 miles (245 km) long, rises in the Sivagiri Hills of the Western Ghats range near the border with Tamil Nadu and

Periyar Wildlife Sanctuary, wildlife preserve in south-central Kerala state, southern India. The sanctuary is noted for herds of Asian elephants, sometimes having 50 members. In addition, bonnet monkeys, nilgai (Indian antelope), langurs, porcupines, sloth bears, tigers, leopards, barking deer,

perjury, in law, the giving of false testimony under oath on an issue or point of inquiry regarded as material. Both traditional and modern legal systems have provisions for taking testimony under oath and mandate penalties for giving false testimony. Islamic law, for example, relies heavily on

fringe benefit, any nonwage payment or benefit (e.g., pension plans, profit-sharing programs, vacation pay, and company-paid life, health, and unemployment insurance programs) granted to employees by employers. It may be required by law, granted unilaterally by employers, or obtained through

Dutch literature: Romanticism: …the new generation, such as Jacques Perk, who wrote sketches in Dekker’s humorous style before composing a sonnet cycle, Mathilde (published posthumously in 1882), which opened a new epoch in Dutch literature.

Sir William Henry Perkin: …which became known as the Perkin reaction, to synthesize coumarin, the first artificial perfume. He also investigated other dyes, salicyl alcohol, and flavourings.

John Ford: …’Tis Pity She’s a Whore; Perkin Warbeck; The Queen; The Fancies, Chaste and Noble; Love’s Sacrifice; and The Lady’s Trial (1638). There are a few contemporary references to Ford, but nothing is known of his personal life, and there is no certain record of him after 1639.

Sir William Henry Perkin was a British chemist who discovered aniline dyes. In 1853 Perkin entered the Royal College of Chemistry, London, where he studied under August Wilhelm von Hofmann. While Perkin was working as Hofmann’s laboratory assistant, he undertook the synthesis of quinine. He

history of the blind: Education and the blind: …Blind (later known as the Perkins School for the Blind)—the second school of its kind in the United States—argued that the blind could be educated and trained to become independent members of society, earning their own way in the world.

Anthony Perkins was an American actor who was best remembered for his portrayal of the murderous motel owner Norman Bates in the Alfred Hitchcock thriller Psycho (1960); he reprised this role in three sequels (1983, 1986, and 1990). (Read Alfred Hitchcock’s 1965 Britannica essay on film

Carl Perkins was an American singer, songwriter, and guitarist whose song “Blue Suede Shoes” was a touchstone of the rockabilly musical movement of the 1950s. A “triple threat” performer—a strong singer, a prolific and imaginative songwriter, and an excellent and influential lead guitarist—Perkins

Charles Perkins was an Australian civil servant and activist who was the first Indigenous Australian to head a government department and the most influential figure in the Aboriginal fight for civil rights; he was often compared to American civil rights leader the Rev. Martin Luther King, Jr.

Charles Perkins was an Australian civil servant and activist who was the first Indigenous Australian to head a government department and the most influential figure in the Aboriginal fight for civil rights; he was often compared to American civil rights leader the Rev. Martin Luther King, Jr.

Charlotte Perkins Gilman was an American feminist, lecturer, writer, and publisher who was a leading theorist of the women’s movement in the United States. Charlotte Perkins grew up in poverty, her father having essentially abandoned the family. Her education was irregular and limited, but she did

Frances Perkins was the U.S. secretary of labor during the presidency of Franklin D. Roosevelt. Besides being the first woman to be appointed to a cabinet post, she also served one of the longest terms of any Roosevelt appointee (1933–45). Perkins graduated from Mount Holyoke College in 1902 and

Frances Perkins was the U.S. secretary of labor during the presidency of Franklin D. Roosevelt. Besides being the first woman to be appointed to a cabinet post, she also served one of the longest terms of any Roosevelt appointee (1933–45). Perkins graduated from Mount Holyoke College in 1902 and

George Walbridge Perkins was a U.S. insurance executive and financier who organized the health insurance agency system and the corporate structures of several large companies. He also served as chairman of Theodore Roosevelt’s Progressive Party, organizing Roosevelt’s 1912 presidential campaign.

Jacob Perkins was an American inventor who produced successful innovations in many fields. About 1790 Perkins built a machine to cut and head nails in one operation, but the plant he opened to exploit it was ruined by an extended lawsuit over the invention. He subsequently devised a method of

Lucy Fitch Perkins was an American writer of children’s books, best remembered for her Twins series of storybooks that ranged in setting among different cultures and times. Lucy Fitch attended the Museum of Fine Arts School in Boston (1883–86). She worked as an illustrator for the Prang Educational

Jack Hanna: …Zoos and Aquariums with the R. Marlin Perkins Award for Professional Excellence.

Maxwell Perkins was an influential American editor who discovered many of the most prominent American writers of the first half of the 20th century. Perkins graduated from Harvard University in 1907. From 1907 to 1910 he worked as a reporter for the New York Times. He then went to work in the

Maxwell Perkins was an influential American editor who discovered many of the most prominent American writers of the first half of the 20th century. Perkins graduated from Harvard University in 1907. From 1907 to 1910 he worked as a reporter for the New York Times. He then went to work in the

The Diary of Anne Frank: …on Anne Frank (played by Millie Perkins) and her family, residents of Amsterdam who go into hiding in 1942, during the Nazi occupation of the Netherlands. Their hiding space, a secret annex within an office building, is shared by another Jewish family, the Van Daans, and Anne soon becomes close…

Jack Hanna: …Zoos and Aquariums with the R. Marlin Perkins Award for Professional Excellence.

Pērkons, sky deity of Baltic religion, renowned as the guardian of law and order and as a fertility god. The oak, as the tree most often struck by lightning, is sacred to him. Pērkons is related in functions and image to the Slavic Perun, Germanic Thor, and Greek Zeus. Often depicted as a vigorous,

Julia Garner: Martha Marcy May Marlene and other early roles: …role of a classmate in The Perks of Being a Wallflower (2012), based on Stephen Chbosky’s 1999 young adult novel, as well as roles in The Last Exorcism: Part II (2013) and Sin City: A Dame to Kill For (2014). Garner then starred as another pregnant teenager, this time in…

Pērkons, sky deity of Baltic religion, renowned as the guardian of law and order and as a fertility god. The oak, as the tree most often struck by lightning, is sacred to him. Pērkons is related in functions and image to the Slavic Perun, Germanic Thor, and Greek Zeus. Often depicted as a vigorous,

Pērkons, sky deity of Baltic religion, renowned as the guardian of law and order and as a fertility god. The oak, as the tree most often struck by lightning, is sacred to him. Pērkons is related in functions and image to the Slavic Perun, Germanic Thor, and Greek Zeus. Often depicted as a vigorous,

Perl, a cross-platform open-source computer programming language used widely in the commercial and private computing sectors. Perl was a favourite in the late 20th and early 21st centuries among Web developers for its flexible, continually evolving text-processing and problem-solving capabilities.

Hebrew literature: Beginnings of the Haskala movement: …satire, and the imitation by Joseph Perl of the Epistolae obscurorum virorum (1515; “Letters of Obscure Men”) of Crotus Rubianus and the essays of Isaac Erter were classics of the genre. One poet, Meir Letteris, and one dramatist, Naḥman Isaac Fischman, wrote biblical plays.

Martin Lewis Perl was an American physicist who received the 1995 Nobel Prize for Physics for discovering a subatomic particle that he named the tau, a massive lepton with a negative charge. The tau, which he found in the mid-1970s, was the first evidence of a third “generation” of fundamental

Otto Perl was a German author and cofounder of the Selbsthilfebund der Körperbehinderten (Self-Help Alliance of the Physically Handicapped, or Otto Perl Alliance; 1919–31), the first emancipatory self-help organization representing the interests of the physically disabled in Germany. Perl grew up

Pearl Islands, archipelago, in the Gulf of Panama, about 50 miles (80 km) southeast of Panama City, Panama, consisting of 183 islands, of which 39 are sizable. The most important islands include the mountainous del Rey Island on which the principal town, San Miguel, is located; San José; Pedro

George Perle was an American composer, music theorist, musicologist, and educator who expanded ways of working with all 12 notes of the Western chromatic scale, from both a music-compositional and an analytical perspective. Perle earned a B.A. (1938) in music from DePaul University, Chicago, and

Prilep, town, North Macedonia, south of Skopje on the Titov Veles–Bitola railway line. Prilep was an important centre during the Middle Ages. St. Nikola’s Church (1299) has valuable frescoes. The Monastery of Archangel Michael and the Church of St. Dimitri both date from the 14th century, during

romance: Arthurian themes: …religion is absent from the Perlesvaus (after 1230?), in which the hero Perlesvaus (that is, Perceval) has Christological overtones and in which the task of knighthood is to uphold and advance Christianity. A 13th-century prose Tristan (Tristan de Léonois), fundamentally an adaptation of the Tristan story to an Arthurian setting,…

Alan Jay Perlis was an American mathematician and computer scientist. He was the first winner, in 1966, of the A.M. Turing Award, given by the Association of Computing Machinery (ACM) and recognized internationally as the highest honour in computer science. In particular, Perlis was cited for “his

perlite, a natural glass with concentric cracks such that the rock breaks into small pearl-like bodies. It is formed by the rapid cooling of viscous lava or magma. Perlite has a waxy to pearly lustre and is commonly gray or greenish but may be brown, blue, or red. Some perlites are of intrusive

Itzhak Perlman is an Israeli-American violinist known for his brilliant virtuoso technique. His refinement of detail led many to regard him as one of the finest performers of the major violin repertoire of his time. Perlman was drawn to the violin after hearing it on the radio when he was three.

Rhea Perlman is an American actress best known for her role as the wisecracking barmaid Carla Tortelli on the award-winning American television sitcom Cheers (1982–93). Perlman is the eldest of two daughters born to Philip Perlman, a Polish immigrant who worked in the toy business, and Adele

Rhea Perlman is an American actress best known for her role as the wisecracking barmaid Carla Tortelli on the award-winning American television sitcom Cheers (1982–93). Perlman is the eldest of two daughters born to Philip Perlman, a Polish immigrant who worked in the toy business, and Adele

Hellboy: The live-action feature film starred Ron Perlman as the title hero, and it was well received by fans and critics alike. Del Toro and Perlman returned for the sequel, Hellboy II: The Golden Army (2008). Hellboy and the B.P.R.D also appeared in the animated films Hellboy: Sword of Storms (2006)…

Saul Perlmutter is an American physicist who was awarded the 2011 Nobel Prize for Physics for his discovery of dark energy, a repulsive force that is the dominant component (73 percent) of the universe. He shared the prize with astronomers Brian Schmidt and Adam Riess. Perlmutter graduated with a

Gestalt therapy: Frederick (“Fritz”) S. Perls, a German-born psychiatrist, founded Gestalt therapy in the 1940s with his wife, Laura. Perls was trained in traditional psychoanalysis, but his dissatisfaction with certain Freudian theories and methods led him to develop his own system of psychotherapy. He was influenced by…

Gestalt therapy: Frederick (“Fritz”) S. Perls, a German-born psychiatrist, founded Gestalt therapy in the 1940s with his wife, Laura. Perls was trained in traditional psychoanalysis, but his dissatisfaction with certain Freudian theories and methods led him to develop his own system of psychotherapy. He was influenced by…

calligraphy: Formal minuscule, 10th to 14th century: …this style became known as Perlschrift from its likeness to small, round beads strung together. A very plain, businesslike, rather staccato style was used in manuscripts with musical notation, most commonly in the 12th and 13th centuries.

Perm, city and administrative centre of Perm kray (territory), western Russia. The city stands on both banks of the Kama River below its confluence with the Chusovaya. In 1723 a copper-smelting works was founded at the village of Yegoshikha (founded 1568), at the junction of the Yegoshikha and Kama

Perm, kray (territory), western Russia. It occupies an area on the western flank of the central Ural Mountains, extending from the crestline in the east across the broad basin of the middle Kama River. The northwest corner of the territory is occupied by the former Komi-Permyak autonomous okrug

permaculture, worldwide holistic agricultural and land management design approach that attempts to mimic patterns found in surrounding natural ecosystems to reduce waste, prevent pollution, maximize sustainability, protect wildlife, and improve the land’s resiliency and biodiversity. In practice,

permafrost, perennially frozen ground, a naturally occurring material with a temperature colder than 0 °C (32 °F) continuously for two or more years. Such a layer of frozen ground is designated exclusively on the basis of temperature. Part or all of its moisture may be unfrozen, depending on the

permafrost: …of permafrost is called the permafrost table. In permafrost areas the surface layer of ground that freezes in the winter (seasonally frozen ground) and thaws in summer is called the active layer. The thickness of the active layer depends mainly on the moisture content, varying from less than a foot…

Permalloy, trademark of the Western Electric Company for nickel-iron alloys having much higher magnetic permeability than iron alone. It is widely used for fabricating the thin pieces that are laminated to form transformer cores. The proportion of nickel may range from 35 to 90 percent, depending

Helen Keller International (HKI), one of the oldest international nonprofit organizations working to prevent blindness and fight malnutrition. Headquarters are in New York City. In 1915 the American merchant George Kessler and his wife, Cora Parsons Kessler, organized in Paris the British, French,

Timothy Palmer: …work was the completely enclosed Permanent Bridge (c. 1806) over the Schuylkill River at Philadelphia. In use until destroyed by fire in 1875, the Permanent Bridge proved the value of, and set the style for, covered bridges in the United States.

human disease: Repair and regeneration: …when necessary, and (3) the permanent cells, incapable of multiplication in the adult—only the permanent cells are incapable of regeneration. These are the brain cells and the cells of the skeletal and heart muscles.

map: Nomenclature: …the United Kingdom by the Permanent Committee on Geographical Names; worldwide these activities are coordinated by the United Nations Conference on the Standardization of Geographical Names.

Poland: Social and economic changes: The newly created Permanent Council, a collegial body composed of five ministries, was the first executive organ for both the Crown and Lithuania. The council achieved progress in financial, police, and administrative fields, although it was seen as a channel for Russian influence and was attacked by the…

Organization of American States: Structure: …or between member states, the Permanent Council, composed of an ambassador from each member state, acts as the provisional organ of consultation until all the member states’ ministers of foreign affairs can assemble. At this consultation meeting of foreign ministers, collective action cannot be undertaken without the approval of two-thirds…

Hague Convention: …of International Disputes, creating the Permanent Court of Arbitration.

International Court of Justice: …was the precursor of the Permanent Court of International Justice (PCIJ), which was established by the League of Nations. From 1921 to 1939 the PCIJ issued more than 30 decisions and delivered nearly as many advisory opinions, though none were related to the issues that threatened to engulf Europe in…

human digestive system: The teeth: …five deciduous teeth and eight permanent teeth in each quarter of the mouth, resulting in a total of 32 permanent teeth to succeed the 20 deciduous ones.

drought: Permanent drought characterizes the driest climates. The sparse vegetation is adapted to aridity, and agriculture is impossible without continuous irrigation.

fortification: Permanent fortifications include elaborate forts and troop shelters and are most often erected in times of peace or upon threat of war. Field fortifications, which are constructed when in contact with an enemy or when contact is imminent, consist of entrenched positions for personnel and…

baldness: …of baldness can be distinguished: permanent hair loss, arising from abnormalities in or destruction of hair follicles, and temporary hair loss, arising from transitory damage to the follicles. The first category is dominated by male pattern baldness (androgenetic alopecia). By age 50, some 30 to 50 of men have been…

insurance: Classes of benefits: Third is a permanent incapacity benefit, which, unless the degree is very small, in which case a lump sum is paid, takes the form of a pension. If the incapacity is total, the pension is usually equal to the temporary incapacity benefit. If the incapacity is partial, the…

consumption function: …model, known as the “permanent income hypothesis,” which abstracts from retirement saving decisions. The figure shows the consumption function that emerges from a standard version of the permanent income hypothesis (assuming uncertain future income and a standard “utility function” that specifies consumers’ attitudes toward the level and riskiness of…

Indus Waters Treaty: …over the years through the Permanent Indus Commission.

International Peace Bureau, international organization founded in 1891 in Bern, Switz., to create a central office through which peace activities of several countries could be coordinated. The Peace Bureau was awarded the Nobel Prize for Peace in 1910, after having been nominated during 7 of the

cobalt processing: Magnetic alloys: The best permanent magnets contain a substantial quantity of cobalt.

spectroscopy: Laser magnetic resonance and Stark spectroscopies: …overcome for molecules that possess permanent magnetic moments or electric dipole moments by using external magnetic or electric fields to bring the energy spacing between levels into coincidence with the frequency of the laser.

mandate: …was supervised by the League’s Permanent Mandates Commission, but the commission had no real way to enforce its will on any of the mandatory powers. The mandate system was replaced by the UN trusteeship system in 1946.

Russell Banks: …on the Roof (2000) and A Permanent Member of the Family (2013). Dreaming Up America (2008) is a nonfiction work scrutinizing the history of destructive and constructive policies pursued by the United States. Banks later published Voyager (2016), a collection of his travel writings.

zooplankton: Permanent plankton, or holoplankton, such as protozoa and copepods (an important food for larger animals), spend their lives as plankton. Temporary plankton, or meroplankton, such as young starfish, clams, worms, and other bottom-dwelling animals, live and feed as plankton until they leave to become adults in their proper…

Edward Snowden: …2019 Snowden released the memoir Permanent Record. On the same day, the U.S. Justice Department sued him to recover all of his earnings from the book, claiming that he had violated his nondisclosure agreements with the CIA and NSA by not submitting the work to them for a prepublication review.

human digestive system: The teeth: …five deciduous teeth and eight permanent teeth in each quarter of the mouth, resulting in a total of 32 permanent teeth to succeed the 20 deciduous ones.

cosmetic: Other cosmetics: Permanent-wave and hair-straightening preparations use a chemical, ammonium thioglycolate, to release hair from its natural set. Hair colorants use permanent or semipermanent dyes to add colour to dull or mousy-coloured hair, and hydrogen peroxide is used to bleach hair to a blond colour.

electric generator: Permanent-magnet generators: For some applications, the magnetic field of the generator may be provided by permanent magnets. The rotor structure can consist of a ring of magnetic iron with magnets mounted on its surface. A magnet material such as neodymium-boron-iron or samarium-cobalt can provide a…

electric motor: Permanent-magnet motors: The magnetic field for a synchronous machine may be provided by using permanent magnets made of neodymium-boron-iron, samarium-cobalt, or ferrite on the rotor. In some motors, these magnets are mounted with adhesive on the surface of the rotor core such that the magnetic…

magnetic permeability, relative increase or decrease in the resultant magnetic field inside a material compared with the magnetizing field in which the given material is located; or the property of a material that is equal to the magnetic flux density B established within the material by a

artesian well: …drilled wherever a gently dipping, permeable rock layer (such as sandstone) receives water along its outcrop at a level higher than the level of the surface of the ground at the well site. At the outcrop the water moves down into the aquifer (water-bearing layer) but is prevented from leaving…

permeability, capacity of a porous material for transmitting a fluid; it is expressed as the velocity with which a fluid of specified viscosity, under the influence of a given pressure, passes through a sample having a certain cross section and thickness. Permeability is largely dependent on the