printmaking Art form consisting of the production of images, usually on paper but occasionally on fabric, parchment, plastic, or other support, by various techniques of multiplication, under the direct supervision of or by the hand of the artist. Such fine prints are considered original works of art, even though they can exist in multiple copies. The major techniques are relief printing, where the background is cut away, leaving a raised image; intaglio printing, where the image is incised directly into the plate; surface printing such as lithography, where the image is painted or drawn onto a stone; and stencil printing, where the design is cut out and printed by spraying paint or ink through the stencil. The history of printmaking parallels the history of art and is one of the oldest art forms. Though he had several predecessors, the first important engraver was a 15th-century German, Martin Schongauer. In the 16th century Albrecht Durer created prints of the highest quality, and in the 17th century the etchings of Rem¬ brandt were especially fine. Japanese printmaking originated in the 17th century with the ukiyo-e school of woodcuts; the best-known artists were Hokusai and Hiroshige. Important 18th-century Western artists who made prints include William Hogarth, Francisco Goya, and Giambattista Piranesi. Among the works of 19th-century printmakers, those of Honore Daumier and of many of the French Impressionists are notable. Experimentation in new styles and new directions proliferated in the 20th century, with art¬ ists from the century’s major movements—including Expressionism, Sur¬ realism, Pop art, Minimalism, and Neo- Expressionism —all pursuing printmaking. See also engraving; etching; mezzotint; woodcut.
prion Vpre-,an\ Disease-causing agent, discovered by Stanley Prusiner, responsible for various fatal neurodegenerative diseases called transmis¬ sible spongiform encephalopathies. An abnormal form of a normally harmless protein found in mammals and birds, the disease-causing prion can enter the brain through infection, or it can arise from a mutation in the gene that encodes the protein. Once present in the brain it causes nor¬ mal proteins to refold into the abnormal shape. As prion proteins multi¬ ply, they accumulate within nerve cells, destroying them and eventually causing brain tissue to become riddled with holes. Diseases caused by prions include Creutzfeldt-Jakob disease, mad cow disease, and scrapie. Pri¬ ons are unlike all other known disease-causing organisms in that they appear to lack nucleic acid (DNA or RNA).
Pripet Vpri-.peA Marshes Vast marsh region, southern Belarus and northwestern Ukraine. The largest swamp of the European continent, the marshes lie in the thickly forested basin of the Pripet River. They cover an area of about 104,000 sq mi (270,000 sq km). Densely wooded and largely uninhabited, the region has supported a diversified lumber industry. A vast amount of land reclamation took place during the 20th century, including the regulation of water drainage, permitting the development of agricul¬ tural areas.
Pripet \'pri-,pet\ River Belarusian Prypyats' River Ukrainian Pryp'yat River River, northwestern Ukraine and southern Belarus. Rising in northwestern Ukraine near the Polish border, it flows east
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Priscian ► Privy Council I 1549
through the Pripet Marshes to Mazyr, then joins the Dnieper River in the Kiev Reservoir after a course of 480 mi (775 km). It is navigable for 300 mi (483 km) and is connected by canals with the Bug and Neman rivers.
Priscian Vpri-shsn \ Latin Priscianus Caesariensis (b. c. 500, Cae¬ sarea, Mauretania) Latin grammarian. He used the writings of Apollonius Dyscolus on Greek grammar as a guide in producing his own classic works on Latin grammar. His Institutiones grammaticae (“Grammatical Foun¬ dations”), with citations from Latin authors, became the standard work for teaching grammar in the Middle Ages. His other writings include trea¬ tises on weights and measures and on the metres of Terence.
prism Piece of glass or other transparent material cut with precise angles and plane faces. Prisms are useful for analyzing and refracting light (see refraction). A triangular prism can separate white light into its constitu¬ ent colours by refracting each different wavelength of light by a different amount. The longer wavelengths (those at the red end of the spectrum) are bent the least, the shorter ones (those at the violet end) the most. The result is the spectrum of visible light, or the rainbow. Prisms are used in certain kinds of spectroscopy and in various optical systems.
prison Institution for the confinement of people convicted of crimes. Prisons are administered by state, provincial, or national governments and house inmates for relatively long terms. They thus differ from jails, which usually are under local jurisidiction and house inmates serving short sen¬ tences. Until the late 18th century, prisons were used mainly for the con¬ finement of debtors who could not meet their obligations, of accused persons waiting to be tried, and of convicts who were waiting for their sentences of death or banishment to be put into effect. Later, imprison¬ ment itself came to be accepted as a means of punishing convicted crimi¬ nals. In early U.S. prisons, prisoners were kept in isolation; in the 19th century, they were permitted to work together, but only in silence. At the end of the 19th century, prison reformers successfully advocated segre¬ gation of criminals by type of crime, age, and sex; rewards for good behaviour; indeterminate sentencing; vocational training; and parole. In the late 20th century, prison populations in many countries began to explode as arrests for violent offenses and for possession of small amounts of illegal drugs increased.
prisoner's dilemma Imaginary situation employed in game theory. One version is as follows. Two prisoners are accused of a crime. If one confesses and the other does not, the one who confesses will be released immediately and the other will spend 20 years in prison. If neither con¬ fesses, each will be held only a few months. If both confess, they will each be jailed 15 years. They cannot communicate with one another. Given that neither prisoner knows whether the other has confessed, it is in the self-interest of each to confess himself. Paradoxically, when each prisoner pursues his self-interest, both end up worse off than they would have been had they acted otherwise. See egoism.
Pristina Vpresh-te-,na\ City (pop., 2000 est.: 186,611), Kosovo region, Serbia, Serbia and Montenegro. It is the capital of the Kosovo region (administered by the UN from mid-1999). Pristina was the capital of the Serbian state before the Turks defeated the Balkan Christian armies in 1389 at the Battle of Kosovo. It is also a cultural centre for Kosovar Alba¬ nians, though it lost many of its ethnic Albanian inhabitants in 1999 when they were driven out by the Serbian campaign of “ethnic cleansing” (see Kosovo conflict). Many returned after a peace accord was signed in June 1999, however.
Pritchett, Sir V(ictor) S(awdon) (b. Dec. 16, 1900, Ipswich, Suf¬ folk, Eng.—d. March 20, 1997, London) British novelist, short-story writer, and critic. A full-time journalist from 1922 and a literary critic for the New Statesman (1928—65), Pritchett became known for his perceptive essays and reviews and for his penetrating and finely crafted short stories. His collections, which offer lively, ironic portraits of middle-class life, include You Make Your Own Life (1938), Blind Love (1969), and A Care¬ less Widow (1989). He also wrote novels, travel books, and the admired memoirs A Cab at the Door (1968) and Midnight Oil (1971).