alkaline earth metal Any of the six chemical elements in the second leftmost group of the periodic table (beryllium, magnesium, calcium, strontium, barium, and radium). Their name harks back to medieval alchemy. Their atoms have two electrons in the outermost shell, so they react readily, form numerous compounds, and are never found free in nature.
alkaloid Basic (see base) organic compounds of plant origin, contain¬ ing combined nitrogen. Alkaloids are amines, so their names usually end in “ine” (e.g., caffeine, nicotine, morphine, quinine). Most have complex chemical structures of multiple ring systems. They have diverse, impor¬ tant physiological effects on humans and other animals, but their func¬ tions in the plants that produce them are poorly understood. Some plants (e.g., opium poppy, ergot fungus) produce many different alkaloids, but most produce only one or a few. Certain plant families, including the poppy fam¬ ily (Papaveraceae) and the nightshade family (Solanaceae), are particularly rich in them. Alkaloids are extracted by dissolving the plant in dilute acid.
Alkamenes See Alcamenes
alkane or paraffin Any of a class of hydrocarbons whose molecules consist only of carbon and hydrogen atoms joined by single covalent bonds (general formula C„H (2n + 2 ))- The simplest is methane (CH 4 ). Alkanes with more than three carbon atoms may have straight and branched isomers. Cycloalkanes have ring structures (but are not aromatic compounds) with two fewer hydrogen atoms per molecule than the cor¬ responding alkane; many have more than one ring. Commercial sources include petroleum and natural gas. Uses, often as mixtures, include fuels, solvents, and raw materials. See also paraffin.
alkene See olefin
All Saints' Day In Christianity, a day commemorating all the saints of the church, known and unknown. It is celebrated on November 1 in the Western churches and on the first Sunday after Pentecost in the Eastern churches. The first general observance of All Saints’ Day was ordered by Pope Gregory IV in 837. In medieval England the festival was called All Hallows, and its eve is still known as Halloween.
All Souls' Day In the Roman Catholic church, a day commemorating all the Christians believed to be in purgatory. Celebrated on November 2, it was first established by Odilo (d. 1049), abbot of Cluny, in the 11th century, and it was widely celebrated by the 13th century. The date fol¬ lows All Saints' Day, with the idea that remembering the saints in heaven should be followed by remembering the souls awaiting release from pur¬ gatory. Roman Catholic doctrine holds that the prayers of the faithful on earth will help cleanse these souls in order to prepare them for heaven.
Allah Arabic "God" Standard Arabic word for God, used by Arab Christians as well as by Muslims. According to the Qur’an, Allah is the creator and judge of humankind, omnipotent, compassionate, and merci¬ ful. The Muslim profession of faith affirms that there is no deity but God and emphasizes that he is inherently one: “nothing is like unto him.” Everything that happens occurs by his commandment; submission to God is the basis of Isiam. The Qur’an and the Hadith contain the 99 “most beau¬ tiful names” of God, including the One and Only, the Living One, the Real Truth, the Hearer, the Seer, the Benefactor, and the Constant For¬ given
Allahabad Va-la-ha-,bad\ ancient Prayag City (pop., 2001: metro, area, 1,042,229), south-central Uttar Pradesh state, northern India, on the Ganges (Ganga) and Yamuna rivers. An ancient holy city sacred to Hindu pilgrims, it is the site of the Pillar of Ashoka (erected c. 240 bc). The Mughal emperor Akbar founded the present-day city in 1583; it was ceded to the British in 1801. Allahabad was the scene of a serious outbreak in the 1857 Indian Mutiny. As the home of the Nehru family, it was later a centre of the Indian independence movement. It is the site of the Jami Masjid (Great Mosque) and the University of Allahabad.
Allbutt, Sir Thomas Clifford (b. July 20, 1836, Dewsbury, York¬ shire, Eng.—d. Feb. 22, 1925, Cambridge, Cambridgeshire) English phy¬ sician. He introduced the modern clinical thermometer (the thermometer had previously been a foot-long instrument that required 20 minutes to register temperature) and outlined the use of the ophthalmoscope to inspect the interior of the eye. He demonstrated the aortic origin of angina pectoris. His investigations improved treatment of arterial diseases and
resulted in, among other works, Diseases of the Arteries (1915). His chief publication was Systems of Medicine (8 vol., 1896-99).
Alleghenian orogeny V.al-o-'ga-ne-on-o-'ra-jo-n e\ formerly Appa¬ lachian Revolution Mountain-building event that affected the Appa¬ lachian Geosyncline in the late Permian period (c. 286-248 million years ago). The Alleghenian orogeny is most pronounced in the central and southern Appalachian Mountains and produced the different effects in various subregions: compressional folding and faulting of the Valley and Ridge Province, westward thrusting of the Blue Ridge, and folding and minor metamorphism and igneous intrusion in the Piedmont Province. It may have resulted from the collision (see plate tectonics) of the central and southern Appalachian continental margin with that of North Africa in the Permian period.
Allegheny \,al-3-'ga-ne\ Mountains Ranges of the Appalachian sys¬ tem in Pennsylvania, Maryland, Virginia, and West Virginia, U.S., west of and generally parallel to the Blue Ridge Mountains. Part of the Allegh¬ eny Plateau that spans the entire upland area from the Cumberland Pla¬ teau to the Mohawk Valley in New York, the Allegheny Mountains extend some 500 mi (800 km) south-southwestward, with heights of more than 4,800 ft (1,460 m). The eastern slope is sometimes called the Allegheny Front.
Allegheny River River in Pennsylvania and New York, U.S. It rises in Potter county. Pa., loops northwest into New York, turns back into Pennsylvania, and unites with the Monongahela to form the Ohio River at Pittsburgh, Pa. It is 325 mi (523 km) long; its chief tributaries are the Clarion, the Kiskiminetas, and French Creek. Several dams make the river navigable from Pittsburgh to East Brady, Pa.
allegory Work of written, oral, or visual expression that uses symbolic figures, objects, and actions to convey truths or generalizations about human conduct or experience. It encompasses such forms as the fable and parable. Characters often personify abstract concepts or types, and the action of the narrative usually stands for something not explicitly stated. Symbolic allegories, in which characters may also have an identity apart from the message they convey, have frequently been used to represent political and historical situations and have long been popular as vehicles for satire. Edmund Spenser’s long poem The Faerie Queen is a famous example of a symbolic allegory.
allele \3-'lel\ Any one of two or more alternative forms of a gene that may occur alternatively at a given site on a chromosome. Alleles may occur in pairs, or there may be multiple alleles affecting the expression of a par¬ ticular trait. If paired alleles are the same, the organism is said to be homozygous for that trait; if they are different, the organism is heterozy¬ gous. A dominant allele will override the traits of a recessive allele in a heterozygous pairing (see dominance and recessiveness). In some traits, alleles may be codominant (i.e., neither acts as dominant or recessive). An individual cannot possess more than two alleles for a given trait. All genetic traits are the result of the interactions of alleles.
allemande Val-o-.mandX Processional couple dance with stately flow¬ ing steps, fashionable in the 16th century, especially in France. A line of couples extended their paired hands forward and paraded back and forth the length of the ballroom. It was revived in the 18th century as a figure dance for four couples, in which each pair performed intricate turns under each other’s arms, a figure that partly survives in the “allemand” of the U.S. square dance. In the late 17th century a stylized version of the dance in 14 time began to be used by composers as the first movement of the SUITE.