depletion allowance In tax law, the deductions from gross income allowed investors in exhaustible commodities (such as minerals, oil, or gas) for the depletion of the deposits. The depletion allowance is intended as an incentive to stimulate investment in this high-risk industry, though critics argue that mineral deposits are valuable enough to justify high lev¬ els of investment even without tax incentives. See also depreciation.
deposit account Either of two basic bank deposit accounts. The demand deposit is payable on demand (see check). Theoretically, the time deposit is payable only after a fixed interval of time; in practice, with¬ drawals from most small time-deposit accounts are paid on demand.
depreciation Accounting charge for the decline in value of an asset spread over its economic life. Depreciation includes deterioration from use, age, and exposure to the elements, as well as decline in value caused by obsolescence, loss of usefulness, and the availability of newer and more efficient means of serving the same purpose. It does not include sudden losses caused by fire, accident, or disaster. Depreciation is often used in assessing the value of property (e.g., buildings, machinery) or other assets of limited life (e.g., a leasehold or copyright) for tax pur¬ poses. See also depletion allowance; investment credit.
depression In economics, a major downswing in the business cycle char¬ acterized by sharply reduced industrial production, widespread unemploy¬ ment, a serious decline or cessation of growth in construction, and great reductions in international trade and capital movements. Unlike recessions, which may be limited to a single country, severe depressions such as the Great Depression encompass many nations. See also deflation; inflation.
depression Neurotic or psychotic disorder marked by sadness, inac¬ tivity, difficulty in thinking and concentration, a significant increase or decrease in appetite and time spent sleeping, feelings of dejection and hopelessness, and sometimes suicidal tendencies. Probably the most com¬ mon psychiatric complaint, depression has been described by physicians from at least the time of Hippocrates, who called it melancholia. Its course is extremely variable from person to person; it may be fleeting or perma¬ nent, mild or severe. Depression is more common in women than in men. The rates of incidence increase with age in men, while the peak for women is between the ages of 35 and 45. Its causes can be both psychosocial (e.g., the loss of a loved one) and biochemical (chiefly, reduced quanti¬ ties of the monoamines norepinephrine and serotonin). Treatment is usu¬ ally a combination of psychotherapy and drug therapy (see antidepressant).
A person who experiences alternating states of depression and extreme elation is said to suffer from bipolar disorder.
Depression of T 929 See Great Depression
Depretis \da-'pre-tes\, Agostino (b. Jan. 13, 1813, Mezzana Corti, Kingdom of Italy—d. July 29, 1887, Stradella, Italy) Italian politician. In 1848 he was elected to the first Piedmontese parliament and was reelected thereafter until his death. After Italy was unified, he served in several cabinet posts (1862-67). He became premier in 1876 and was the domi¬ nant force in Italian politics until 1887. Among his notable achievements were the signing of the Triple Alliance and his government policy of tras- formismo, bringing together members of different parties in the same cabinet.
depth charge or depth bomb Weapon used by ships or aircraft to attack submerged submarines. Developed by the British in World War I for use against German submarines, it consisted of a canister filled with explosives and dropped off the stern of a ship near a submerged subma¬ rine. It rarely exploded close enough to sink the submarine, but its shock waves loosened the submarine’s joints and damaged its instruments, forc¬ ing it to the surface, where naval gunfire could finish it off. Modem depth charges can be fired as far as 2,000 yards (1,800 m) from a ship’s deck or launched from aircraft. Atomic depth charges have a nuclear warhead and a vastly increased killing radius.
Derain \d3-'raii\, Andre (b. June 10, 1880, Chatou, Fr.—d. Sept. 8, 1954, Garches) French painter, graphic artist, and designer. After study¬ ing in Paris at the Academie Carriere and Academie Julian, he developed his early style in association with his friends Maurice de Vlaminck and Henri Matisse; the three were the principal exponents of Fauvism. Their land¬ scapes and figure studies featured brilliant colours, broken brushstrokes, and impulsive lines. By the 1920s, however, Derain had turned to the Neoclassical style (see Classicism and Neoclassicism). He produced numer¬ ous book illustrations and designs for stage sets, notably for Sergey Diaghi- lev’s Ballets Russes.
Derby One of the classic English horse races (established 1780), run in June over a 1 Vi-mi (2,400 m) course at Epsom Downs, Surrey. Many other horse races have been named for the Derby (e.g., the Kentucky Derby), and the term itself has come to signify a race or contest of any type.
Derby \'dar-be\, Edward (George Geoffrey Smith) Stanley, 14th earl of (b. March 29, 1799, Knowsley Park, Lancashire, Eng.—d. Oct. 23, 1869, London) English statesman. Having entered Parliament as a Whig in 1820, he later joined the Conservatives and became leader of the Conservative Party (1846-68) and prime minister (1852, 1858, and 1866-68). Legislation adopted during his tenure included the removal of Jewish discrimination in Parliament membership, the transfer of India’s administration from the East India Company to the crown, and the Reform Bill of 1 867. He is remembered as one of England’s greatest parliamen¬ tary orators.
Derbyshire \'dar-be-,shir\ or Derby \'dar-be\ Administrative (pop., 2001: 734,581), geographic, and historic county, central England. The landscape varies from the moorlands of the north to the Trent lowlands in the south. Industry ranges from tourism in the High Peak district to mining and engineering in the eastern and southern coalfields. Apart from gaining the rural district of Tintwistle from Cheshire, the traditional county was unaltered by the administrative reorganization in 1974; its county seat is Matlock.
derivative In mathematics, a fundamental concept of differential calculus representing the instantaneous rate of change of a function. The first deriva¬ tive of a function is a function whose values can be interpreted as slopes of tangent lines to the graph of the original function at a given point. The derivative of a derivative (known as the second derivative) describes the rate of change of the rate of change, and can be thought of physically as acceleration. The process of finding a derivative is called differentiation.
derivative, partial See partial derivative
derivatives In finance, contracts whose value is derived from another asset, which can include stocks, bonds, currencies, interest rates, com¬ modities, and related indexes. Purchasers of derivatives are essentially wagering on the future performance of that asset. Derivatives include such widely accepted products as futures and options. Concern over the risky nature of derivatives grew after some well-publicized corporate losses in 1994 involving Procter & Gamble, Metallgesellschaft AG of Germany, and
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dermatitis ► desalination I 535
Orange County, Calif. Anxiety intensified after the collapse in 1995 of the London-based merchant bank Barings PLC (now part of the Dutch ING Group NV). Securities regulators from 16 countries then agreed on mea¬ sures to improve control of derivatives.
dermatitis or eczema \ig-'ze-ms, 'eg-z3-m3\ Inflammation of the skin, usually itchy, with redness, swelling, and blistering. Causes and patterns vary. Contact dermatitis appears at the site of contact with an irritating substance or allergen. Atopic dermatitis, with patches of dry skin, occurs in infants, children, and young adults with genetic hypersensitivities (atopy). Stasis dermatitis affects the ankles and lower legs because of chronic poor blood flow in the veins. Seborrheic dermatitis appears as scaly skin, most often on the scalp (dandruff) and areas rich in sebaceous glands. Neurodermatitis is apparently caused by repeated scratching of an itchy skin area.