(from the article "Russia") The decline of Kiev led to regional developments so striking that the subsequent period has often been called the "Period of Feudal Partition." This phrase is misleading: feudal is hardly ...
(from the article "Earth") ...(less eccentric) than are the orbits of all but two of the other planets, Venus and Neptune. Earth makes one revolution, or one complete orbit of the Sun, in about ...
(from the article "galaxy") ...of the Milky Way Galaxy, was one of the first to appreciate the importance of the Magellanic Clouds in terms of the nature of spiral nebulae. To gauge the distance ...
(from the article "comet") ...from cometary passages during the last three centuries. The 1,292 cometary apparitions of Marsden's catalog involve only 810 individual comets; the remainder represents the repeated returns of periodic comets.
(from the article "trigonometry") ...there are similar relations for the other five functions. These results may be expressed by saying that the trigonometric functions are periodic and have a period of 360° or 180°.
(from the article "brick and tile") In so-called periodic kilns the bricks are placed with sufficient air space to allow the heat from the fires to reach all surfaces. They are placed directly from the drier, ...
in chemistry, the generalization that there is a recurring pattern in the properties of the elements when they are arranged in order of increasing atomic number-i.e., the ... [12 Related Articles]
in physics, motion repeated in equal intervals of time. Periodic motion is performed, for example, by a rocking chair, a bouncing ball, a vibrating tuning fork, a swing in motion, ... [2 Related Articles]
any of the forms of a rare disorder that is characterized by relatively short-term, recurrent attacks of muscle weakness. Usually the disorder is inherited; it occurs three times more often ... [2 Related Articles]
(from the article "celestial mechanics") ...a net regression. Such a change that is always in the same direction as time increases is called a secular perturbation. Superposed on the secular perturbation of the longitude of ...
(from the article "continental landform") The concept of periodic random dominance as an aspect of landform evolution carries with it the implication of polygenetic landforms and landscapes where geomorphic system dominance fails to develop. Indeed, ...
(from the article "Physical Sciences") The periodic table of the elements once contained only 92 naturally occurring elements, from hydrogen (the lightest building block of matter, with atomic number 1) to uranium (the heaviest, with ...
(from the article "property law") ...or 99 years. The tenant may also have an interest for a specific term that is renewed automatically unless the landlord or the tenant gives notice within a fixed period ...
(from the article "homopteran") The life cycle of three species of periodical cicadas is the longest known for insects, lasting 17 years. In the temperate zone enormous numbers of orange-winged adults emerge in spring, ...
(from the article "rhythm") ...accent, metre, and tempo. As in the closely related subjects of verse and metre, opinions differ widely, at least among poets and linguists, on the nature and movement of rhythm. ...
fleshy tissue between tooth and tooth socket that holds the tooth in place, attaches it to the adjacent teeth, and enables it to resist the stresses of chewing. It develops ... [2 Related Articles]
dental specialty concerned with the prevention, diagnosis, and treatment of functional and structural diseases of the periodontal membrane and related tissues that surround and support the teeth. Degeneration or inflammation ... [1 Related Articles]
inflammation of the soft tissues around the teeth, characterized by swollen, tender gums, that may lead to the eventual loss of teeth. Periodontitis begins with the deposition of bacterial plaque ... [1 Related Articles]
(from the article "sports") ...officials conducted quadrennial athletic contests. Sacred games also were held at Delphi (in honour of Apollo), Corinth, and Nemea. These four events were known as the periodos, ...
dense fibrous membrane covering the surfaces of bones, consisting of an outer fibrous layer and an inner cellular layer (cambium). The outer layer is composed mostly of collagen and contains ... [3 Related Articles]
(from the article "bivalve") The bivalve shell is made of calcium carbonate embedded in an organic matrix secreted by the mantle. The periostracum, the outermost organic layer, is secreted by the inner surface of ...
(from the article "Aristotle") ...the city boundary, he established his own school in a gymnasium known as the Lyceum. He built a substantial library and gathered around him a group of brilliant research students, ...
(from the article "social behaviour in animals") Peripatus and its relatives, the onychophorans, are intermediate between annelid worms and arthropods and have well-developed parental systems. Some Australian forms lay eggs, but others keep the eggs inside until ...
the turning point in a drama after which the plot moves steadily to its denouement. It is discussed by Aristotle in the Poetics as the shift of the tragic protagonist's ... [1 Related Articles]
(from the article "ear, human") ...have two sets of processes, or fibres, that extend from opposite ends of the cell body. The longer, central fibres, also called the primary auditory fibres, form the cochlear nerve, ...
(from the article "air-cushion machine") ...slot running entirely around the circumference, the air would flow toward the centre of the vessel, forming an external curtain that would effectively contain the cushion. This system is known ...
(from the article "Romance languages") ...measures, standard Italian is a "central" language (i.e., it is quite close and often readily intelligible to all other Romance languages), whereas French and Romanian are peripheral (they lack similarity ...
(from the article "nervous system, human") The peripheral nervous system is a channel for the relay of sensory and motor impulses between the central nervous system on one hand and the body surface, skeletal muscles, and ...
the use of a longer phrasing in place of a possible shorter form of expression; a roundabout or indirect manner of writing or speaking. In literature periphrasis is sometimes used ... [1 Related Articles]
(from the article "inland water ecosystem") ...as well as microbes (see marine ecosystem: Marine biota: Plankton); the shoreline macrophytes; the benthos (bottom-dwelling organisms); the nekton (free-swimming forms in the water column); the periphyton (microscopic biota on ...
optical instrument used in land and sea warfare, submarine navigation, and elsewhere to enable an observer to see his surroundings while remaining under cover, behind armour, or submerged.
(from the article "seed and fruit") ...but the reserve materials are present elsewhere-e.g., in the cotyledons, or seed leaves, of the embryo, as in beans, lettuce, and peanuts, or in a tissue derived from the nucellus, ...
any member of the order Perissodactyla, a group of herbivorous mammals characterized by the possession of either one or three hoofed toes on each hindfoot. They include the horses, asses, ... [5 Related Articles]
involuntary movements of the longitudinal and circular muscles, primarily in the digestive tract but occasionally in other hollow tubes of the body, that occur in progressive wavelike contractions. Peristaltic waves ... [9 Related Articles]
(from the article "circulation") ...of a blood vessel down which passes a wave of muscular contraction, called peristalsis, that forces the enclosed blood in the direction of contraction. Valves may or may not be ...
(from the article "locomotion") Peristaltic locomotion is a common locomotor pattern in elongated, soft-bodied invertebrates, particularly in segmented worms, such as earthworms. It involves the alternation of circular- and longitudinal-muscle-contraction waves. Forward movement is ...
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 ... [1 Related Articles]
(from the article "bryophyte") ...with thickened midrib; cells usually lacking corner thickenings; oil bodies, if present, not complex; jacket of sporangium often with stomata; sporangium usually opening by apical cap (operculum); peristome teeth usually ...
(from the article "domus") ...subdivided around the perimeter into different spaces for conversation and relaxation; it was reached from the street through the prothyrum, an entrance passageway. Located between the atrium and peristyle was ...
(from the article "Signs of pathogen presence in diseased plants") ...Ascomycota (kingdom Fungi). It arises from vegetative filaments (hyphae) after sexual reproduction has been initiated. The ascocarp (in forms called apothecium, cleistothecium [cleistocarp], or perithecium) contain saclike structures (asci) that ...
(from the article "Principal national parks of the world") Perito Francisco P. Moreno National Park has an area of 444 square miles (1,150 square km) and includes the Andean divide between Pacific and Atlantic drainage. Los Glaciares National Park, ...
(from the article "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 ...
(from the article "renal system disease") There are two main techniques of dialysis in current use. In peritoneal dialysis, the patient's own abdominal cavity is used as the container of fluid; the fluid is run in, ...
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 ... [3 Related Articles]
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, ... [3 Related Articles]
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 ... [1 Related Articles]
(from the article "echinoderm") ...Internal to the dermis are circular and longitudinal muscle layers. The extensive body cavity (coelom) is modified to form several specialized regions. Two subdivisions of the coelom are the perivisceral ...
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 ... [2 Related Articles]
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 ...
river and lake in southern Kerala state, southwestern India. The river, 140 mi (225 km) long, rises in the Western Ghats range near the border with Tamil Nadu state and ... [3 Related Articles]
wildlife preserve in Idukki district, Kerala state, southern India. The sanctuary is noted for herds of elephants, sometimes numbering 50 members. In addition, bonnet monkey, nilgai, langur, porcupine, sloth bear, ... [1 Related Articles]
(from the article "Dutch literature") ...extremes of sentimentality and anarchy, iconoclasm and utopianism. Although poetry as a convention was anathema to him, Dekker was greatly admired by the young men of the new generation, such ...
(from the article "Perkin, Sir William Henry") ...and held a monopoly on its manufacture for several years. In 1867 he discovered a chemical process for preparing unsaturated acids. The following year he used this process, which became ...
American actor who was best remembered for his portrayal of murderous motel owner Norman Bates in the Alfred Hitchcock thriller Psycho (1960); he reprised this role in three sequels (1983, ...
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 ... [2 Related Articles]
Australian civil servant and activist (b. June 16, 1936, Alice Springs, N.Terr.-d. Oct. 18, 2000, Sydney, N.S.W.), was the first indigenous Australian to head a government department and the most ...
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 ... [1 Related Articles]
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, ...
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 ... [3 Related Articles]
(from the article "computer programming language") PERL (practical extraction and report language) was developed in the late 1980s, originally for use with the UNIX operating system. It was intended to have all the capabilities of earlier ...
(from the article "Hebrew literature") ...by the Edict of Toleration (1781) of the emperor Joseph II. By supporting some of its aims, Hebrew writers incurred hatred and persecution. Their chief weapon was satire, and the ...
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 ... [3 Related Articles]
(from the article "chondrostean") ...large gular (i.e., in the throat region) plates; small opercular (i.e., gill cover) apparatus. One family, Europe and North America.Lower to Upper Triassic. With ganoid (i.e., bony, diamond-shaped, and ...
Polish-born French pianist (b. May 26, 1904, Kovno, Russian Empire [now Kaunas, Lithuania]-d. Sept. 4, 2002, Paris, France), became one of the 20th century's foremost interpreters of the works of ...
(from the article "romance") ...in the other, Balain (who strikes the Dolorous Stroke) are contrasted with Galahad, a type of the Redeemer. The conflict between earthly chivalry and the demands of religion is absent ...
a natural glass with concentric cracks such that the rock breaks into small, pearllike bodies. It is formed by the rapid cooling of viscous lava or magma. Perlite has a ... [1 Related Articles]
Israeli-born 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 ... [1 Related Articles]
(from the article "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 ...
(from the article "calligraphy") ...texts from the end of the 10th century, probably mainly in monastic houses in Constantinople, was one with plain, neat, rounded letters; this style became known as
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 ...
city and administrative centre of Perm oblast (province), western Russia. The city stands on both banks of the Kama River below its confluence with the Chusovaya.
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 ... [12 Related Articles]
(from the article "permafrost") Permafrost with no water, and thus no ice, is termed dry permafrost. The upper surface of permafrost is called the permafrost table. In permafrost areas the surface layer of ground ...
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 ... [3 Related Articles]
(from the article "human rights") The Permanent Arab Commission on Human Rights, founded by the Council of the League of Arab States in September 1968, has been preoccupied primarily with the rights of Arabs living ...
(from the article "Palmer, Timothy") Palmer's most noted 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 ...
(from the article "human disease") ...Of the three categories of human cells-(1) the labile cells, which multiply throughout life, (2) the stable cells, which do not multiply continuously but can do so when necessary, and ...
(from the article "map") ...the forms and applications that are to be used in government maps and documents. This function is exercised in the United States by the Board on Geographic Names and in ...
(from the article "American States, Organization of") ...or chiefs of state. The General Assembly controls the OAS's budget and supervises various specialized organizations. In case of attack or an act of aggression within or between member states, ...
(from the article "Poland") 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, ...
(from the article "Hague Convention") ...prohibiting the discharges of projectiles or explosives from balloons. Last, and most important, was the adoption of the Convention for the Pacific Settlement of International Disputes, creating the Permanent Court ...
(from the article "International Court of Justice") ...the various conferences that produced the Hague Conventions in the late 19th and early 20th centuries. The body subsequently established, the Permanent Court of Arbitration, was the precursor of the ...
(from the article "drought") 1. Permanent drought characterizes the driest climates; the sparse vegetation is adapted to aridity, and agriculture is impossible without continuous irrigation.
(from the article "fortification") in military science, any work erected to strengthen a position against attack. Fortifications are usually of two types: permanent and field. Permanent fortifications include elaborate forts and troop shelters and ...
(from the article "baldness") the lack or loss of hair. Two primary types of baldness can be distinguished: permanent hair loss arising from the destruction of hair follicles, and temporary hair loss arising from ...
(from the article "insurance") ...from country to country, ranging from 50 percent of the employee's wage to 100 percent; the most common benefits are 66 23 percent and 75 percent. Third is a permanent ...
(from the article "consumption function") Economist Milton Friedman advocated a simplified version of this model, known as the "permanent income hypothesis," which abstracts from retirement saving decisions. The figure shows the consumption function that emerges ...
(from the article "cobalt processing") About 25 percent of the world's cobalt output goes into magnets. The best permanent magnets contain a substantial quantity of cobalt.hysteresis loop
(from the article "spectroscopy") ...range and even those that can be tuned, such as dye lasers, must be driven by a pump laser and for a given dye have a limited tuning range. This ...
(from the article "mandate") Theoretically, exercise of the mandates 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. ...
(from the article "digestive system, human") ...gradually between the ages of six months and two years. As the jaws grow and expand, these teeth are replaced one by one by the teeth of the secondary set. ...
(from the article "cosmetic") ...intended to give gloss and body to the hair, such as resin-based sprays, brilliantines, and pomades, as well as alcohol-based lotions; and hair conditioners that are designed to treat damaged ...
(from the article "electric generator") 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 ...
(from the article "electric motor") 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 ...
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 ... [10 Related Articles]
(from the article "nervous system") ...in which the flux rate of the diffusing material is controlled by the permeability of the membrane, which in turn is dictated by the size of the pores and is ...
