prolapse Protrusion of an internal organ out of its normal place, usu¬ ally of the rectum or uterus outside the body when supporting muscles weaken. The membrane lining the rectum can push out through the anus, most often in old people with constipation who strain during defecation. Chronic rectal prolapse requires surgical repair. The uterus may prolapse into the vagina after gravity adds to weakness from childbirth injuries. Temporary supports and pelvic exercises can relieve mild uterine pro¬ lapse, but severe prolapse may require hysterectomy.
proletariat \,pro-b-'ter-e-3t\ The lowest, or one among the lowest, economic and social classes in a society. In ancient Rome, the proletariat were poor landless freemen who, crowded out of the labour market by the extension of slavery, became parasites on the economy. Karl Marx used the term to refer to the class of wage earners engaged in industrial pro¬ duction only (the broader term working class included all those obliged to work for a living). Another of Marx’s categories, the lumpenproletar- iat (lumpen meaning “rags”), comprised marginal and unemployable workers, paupers, beggars, and criminals. Marxian theory predicted a transitional phase between the abolition of capitalism and the establish-
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proline ► property tax I 1553
ment of communism during which a “dictatorship of the proletariat” would suppress resistance to the socialist revolution by the bourgeoisie, destroy the social relations of production underlying the class system, and create a new, classless society.
proline \'pro- l len\ One of the nonessential amino acids, found in many proteins, especially collagen. Because the nitrogen atom of its amino group is part of a ring structure (making it a heterocyclic compound), its chemi¬ cal properties differ from those of the other amino acids in proteins. It is used in biochemical, nutritional, and microbiological research and as a dietary supplement.
promenade V.pra-mo-'nad, .pra-mo-'nadX Public place where people walk (or, in the past, rode) at leisure for pleasure, exercise, or display. Promenades are pedestrian avenues pleasingly landscaped or command¬ ing a view, often located along waterfronts and in parks. Vehicular traffic may or may not be restricted.
Prometheus Xpra-'me-the-osV In Greek religion, one of the Titans and a god of fire. He was a master craftsman and a supreme trickster, and he was sometimes associated with the creation of humans. According to leg¬ end, Prometheus stole fire from the gods and gave it to humans. In ven¬ geance, Zeus created Pandora, who married Prometheus’s brother and set loose all the evils of the world. Another tale held that Zeus had Prometheus chained to a mountain and sent an eagle to devour his liver, which regen¬ erated every night so that he could suffer the same torment the next day.
promissory note Short-term credit instrument consisting of a written promise by one person to pay a specified amount of money to another on demand or at a given future date. Promissory notes were in use in Europe as early as the Renaissance. They are often negotiable and may be secured by the pledge of collateral. The instrument changed substantially during the 20th century, when various clauses were added regarding payment and other provisions—for example, authorizing the sale of collateral, permit¬ ting extensions of time, and allowing acceleration of payment in the event of default. See also bill of exchange.
Promoters Revolution (1932) Bloodless coup that put an end to absolute monarchy in Siam (Thailand) and initiated the Constitutional Era. The coup was headed by the Promoters, a group that included mem¬ bers of the Thai elite, noted intellectuals, and disaffected army officers. Their first constitution, the Temporary Constitution, stripped the king of power and put it in the hands of the Promoters themselves. The Perma¬ nent, or December, Constitution restored some of the royal prestige and dignity and introduced some liberal, Western-style reforms. None of Thai¬ land’s subsequent constitutions effectively limited political power or pro¬ vided a means by which political contests could be decided. See also Luang Phibunsongkhram; Pridi Phanomyong.
pronghorn Ruminant (Antilocapra americana) of North American plains and semideserts, the only liv¬ ing member of the family Antiloca- pridae. The pronghorn stands 30-40 in. (80-100 cm) tall. It is reddish brown with a short, dark-brown mane, white underparts, two white bands on the throat, and a circular white patch on the rump. Both sexes bear erect, two-pronged horns; the longer prong curves backward, the shorter prong forward. Pronghorns live alone or in small bands in sum¬ mer, and in large herds in winter. The fastest mammal of North America, the pronghorn can run 45 mph (70 kph) and can bound up to 20 ft (6 m). Though tens of millions once roamed the West, they were nearly exterminated by hunters in the early 20th century; conservation efforts have since allowed their populations to increase.
proof In logic and mathematics, an argument that establishes a propo¬ sition’s validity. Formally, it is a finite sequence of formulas generated according to accepted rules. Each formula either is an axiom or is derived from a previously established theorem, and the last formula is the state¬ ment that is to be proven. The essence of deductive reasoning (see deduc¬ tion), this is the basis of Euclidean geometry and all scientific methods inspired by it. An alternative form of proof, called mathematical induc¬
tion, applies to propositions defined through processes based on the count¬ ing numbers. If the proposition holds for n = 1 and can be shown to hold for n = k + 1 whenever n = k (a constant) is also true, then it holds for all values of n. An example is the assertion that the sum of the first n count¬ ing numbers is n(n + l)/2.
propaganda Manipulation of information to influence public opinion. The term comes from Congregatio de Propaganda Fide (Congregation for the Propagation of the Faith), a missionary organization established by the pope in 1622. Propagandists emphasize the elements of information that support their position and deemphasize or exclude those that do not. Misleading statements and even lies may be used to create the desired effect in the public audience. Lobbying, advertising, and missionary activ¬ ity are all forms of propaganda, but the term is most commonly used in the political arena. Prior to the 20th century, pictures and the written media were the principal instruments of propaganda; radio, television, motion pictures, and the Internet later joined their ranks. Authoritarian and totali¬ tarian regimes use propaganda to win and keep the support of the popu¬ lace. In wartime, propaganda directed by a country at its own civilian population and military forces can boost morale; propaganda aimed at the enemy is an element of psychological warfare.
propane Colourless, easily liquefied hydrocarbon gas (C 3 H 8 or, more fully, CH 3 CH 2 CH 3 ). Separated in large quantities from natural gas, light crude oil, and oil-refinery gases, it is available as liquefied propane or as a major constituent of liquefied petroleum gas (LPG). It is an important raw material for the manufacture of ethylene and for the petrochemical industry. It is also used as a refrigerant, extractant, solvent, aerosol pro¬ pellant, and fuel for portable cooking appliances, torches, and lighters.