Paul Hamm (U.S.) competes on the parallel bars during the 2004 Olympic Games in Athens.
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Budgerigar (Melopsittacus undulatus), a popular parakeet.
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paramagnetism ► parchment I 1447
bone or joint disease, fracture, or tumour affecting the vertebrae; inflam¬ matory and degenerative diseases; or pernicious anemia) paralyzes the body at and below the level of the damage (paraplegia if the legs and lower body only; quadriplegia if arms and legs). Poliomyelitis and polyneuritis (neuritis of multiple nerves) result in paralysis with muscle wasting. Bell palsy (a type of neuritis) paralyzes the muscles of one side of the face. Muscular dystrophy causes paralysis by attacking muscle. Metabolic causes include myasthenia gravis. Paralysis may also have psychiatric causes (see hysteria).
paramagnetism Kind of magnetism that occurs in materials weakly attracted by a strong magnet. Compounds containing iron, palladium, platinum, and the rare-earth elements exhibit strong paramagnetism because they have atoms with some incomplete inner electron shells. Their unpaired electrons make the atoms behave like tiny permanent magnets that align with and strengthen an applied magnetic field. As the tempera¬ ture rises, strong paramagnetism decreases because of the greater random motion of the atoms. Weak paramagnetism, found in many solid metallic elements, is independent of temperature.
Paramaribo \,pa-ra-'ma-re-bo\ City (pop., 1999 est.: 233,000), sea¬ port, and capital of Suriname. Located on the Suriname River near the Atlantic Ocean, it was originally an Indian village before becoming a French settlement (c. 1640). In 1651 it became a British colony but was ceded to the Dutch in 1667. It is built on a shingle reef that stands 16 ft (5 m) above the river at low tide. Much of the distinctive Dutch colonial architecture and a canal system remain. Since 1945 the city has grown considerably because of tourism and industries.
paramecium V.par-o-'me-se-onA Any of the free-living, single-celled protozoans that make up the genus Paramecium. Most are about the size of the period at the end of this sentence. They vary in shape and are sur¬ rounded by a rigid protein layer (pellicle) covered with hundreds of cilia that beat rhythmically to propel them and to direct bacteria and other food particles into their oral groove. Food particles are collected into food vac¬ uoles, where digestion takes place. Two (occasionally three) contractile vacuoles close to the surface near the ends of the cell expand and con¬ tract as they discharge metabolic wastes and excess fluid. Paramecia have two kinds of nuclei: a large macronucleus (the centre of all metabolic activities) and at least one small micronucleus (which stores the genetic material necessary for sexual reproduction). See illustration opposite.
Paramount Communications Media and communications corpo¬ ration. It was founded (as Paramount Pictures Corp.) by W. W. Hodkin- son in 1914 as a film distributor. It became a motion-picture company two years later and won attention with stars such as Mary Pickford, Glo¬ ria Swanson, and Rudolph Valentino. In the late 1920s and 1930s the stu¬ dio added Claudette Colbert, Gary Cooper, and Marlene Dietrich to its roster. Forced to declare bankruptcy after its chain of theaters suffered losses during the transition to sound, the company was reorganized two years later as Paramount Pictures, Inc. Among its successes of the 1940s and ’50s were the films of Preston Sturges and Billy Wilder. In 1966 Gulf & Western Industries took control of Paramount, and the new company later changed its name to Paramount Communications. In 1994 it was acquired by Viacom Inc., which in 2000 merged with CBS.
Parana \,pa-ra-'na\ River River, South America. It is the continent’s second longest river (after the Amazon River) and rises on the plateau of southeast-central Brazil. It flows generally south 3,032 mi (4,880 km) to join the Uruguay River and form the Rio de la Plata estuary on the Atlan¬ tic Ocean. Its drainage basin includes most of southeastern Brazil, Para¬ guay, eastern Bolivia, and northern Argentina. From its origin at the confluence of the Grande and Paranafba rivers to its junction with the Paraguay River, it is known as the Alto (Upper) Parana. Completion of the Itaipii Dam between Paraguay and Brazil in the 1980s submerged the massive Guafra Falls and created a large reservoir.
paranoia Mental disorder characterized by delusions of persecution or grandeur, usually without hallucinations. Paranoia was formerly classified as a distinct psychosis but is now generally treated as one of several vari¬ eties of schizophrenia or, in milder cases, of personality disorder. The para¬ noid person generally suffers from exaggerated self-reference, a tendency to construe independent events and acts as pertaining to him- or herself.
parapsychology V.par-o-.sI-'ka-b-jeV Discipline concerned with investigating events that cannot be accounted for by natural law and knowledge that cannot have been obtained through the usual sensory
cytosome
(gullet)
food
vacuole
General features of a paramecium.
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abilities. Parapsychology studies the cognitive phenomena often called extrasensory perception, in which a person acquires knowledge of other people’s thoughts or of future events through channels apparently beyond the five senses. It also examines physical phenomena such as the levita¬ tion of objects and the bending of metal through psychokinesis. Though belief in such phenomena may be traced to earliest times, parapsychol¬ ogy as a subject of serious research originated in the late 19th century, partly in reaction to the growth of the spiritualist movement. The Society of Psychical Research was established in London in 1882, and similar societies were later founded in the U.S. and in many European countries. In the 20th century research into parapsychology was also conducted at some universities, notably at Duke University under J. B. Rhine.
parasitism Vpar-o-so-.ti-zomX Relationship between two species in which one benefits at the expense of the other. Ectoparasites live on the body surface of the host; endoparasites live in their hosts’ organs, tissues, or cells and often rely on a third organism (the carrier, or vector) to trans¬ mit them to the host. The cuckoo and cowbird practice brood parasitism, laying eggs in other birds’ nests to be raised by the foster parents. In social parasitism, one type of animal parasitizes animals of the same type (e.g., one ant species on different ant species). Hyperparasitism occurs when parasites are parasitized (e.g., protozoans hyperparasitize a flea on a dog). See also predation.
parathyroid gland Endocrine gland, two to eight of which are embedded in each side of the thyroid gland. It secretes parathyroid hor¬ mone, which regulates blood calcium and phosphorus levels. When cal¬ cium in body fluids drops, increased hormone secretion releases calcium from bone into the bloodstream (see calcium deficiency). The hormone also increases excretion of phosphate in the urine, lowering blood concentra¬ tions, and may play a role in magnesium metabolism. When thyroid removal is required, the parathyroid glands must be separated out and left in place. See also endocrine system.
parchment Processed skins of certain animals (chiefly sheep, goats, and calves) that have been prepared for the purpose of writing on them. Parchment was probably invented in Greece in the 2nd century bc. Skins had been used for writing material even earlier (c. 2400 bc), but the new, more thorough method of cleaning, stretching, and scraping made pos¬ sible the use of both sides of a manuscript leaf, leading to the replace-
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1448 I pardo ► Paris
ment of the rolled manuscript by the bound book (codex). Especially fine parchment is known as vellum. In modern usage, the terms “parchment” and “vellum” are sometimes used for a type of high-quality paper.