low-temperature physics, science concerned with the production and maintenance of temperatures much below normal, down to almost absolute zero, and with various phenomena that occur only at such temperatures. The temperature scale used in low-temperature physics is the Kelvin temperature scale, or absolute temperature scale, which is based on the behavior of an idealized gas (see gas laws; kinetic-molecular theory of gases). Low-temperature physics is also known as cryogenics, from the Greek meaning "producing cold." Low temperatures are achieved by removing energy from a substance. This may be done in various ways. The simplest way to cool a substance is to bring it into contact with another substance that is already at a low temperature. Ordinary ice, dry ice (solid carbon dioxide), and liquid air may be used successively to cool a substance down to about 80°K; (about -190°C;). The heat is removed by conduction, passing from the substance to be cooled to the colder substance in contact with it. If the colder substance is a liquefied gas (see liquefaction), considerable heat can be removed as the liquid reverts to its gaseous state, since it will absorb its latent heat of vaporization during the transition. Various liquefied gases can be used in this manner to cool a substance to as low as 4.2°K;, the boiling point of liquid helium. If the vapor over the liquid helium is continually pumped away, even lower temperatures, down to less than 1°K;, can be achieved because more helium must evaporate to maintain the proper vapor pressure of the liquid helium. Most processes used to reduce the temperature below this level involve the heat energy that is associated with magnetization (see magnetism). Successive magnetization and demagnetization under the proper combination of conditions can lower the temperature to only about a millionth of a degree above absolute zero. Reaching such low temperatures becomes increasingly difficult, as each temperature drop requires finding some kind of energy within the substance and then devising a means of removing this energy. Moreover, according to the third law of thermodynamics, it is theoretically impossible to reduce a substance to absolute zero by any finite number of processes. Superconductivity and superfluidity have traditionally been thought of as phenomena that occur only at temperatures near absolute zero, but by the late 1980s several materials that exhibit superconductivity at temperatures exceeding 100°K; had been found. Superconductivity is the vanishing of all electrical resistance in certain substances when they reach a transition temperature that varies from one substance to another; this effect can be used to produce powerful superconducting magnets. Superfluidity occurs in liquid helium and leads to the tendency of liquid helium to flow over the sides of any container it is placed in without being stopped by friction or gravity.

low-temperature fusion: see cold fusion.

Warming, Johannes Eugenius Bülow, 1841-1924, Danish botanist, a founder of the science of plant ecology. He was a professor at the Univ. of Copenhagen (1885-1911) and wrote a pioneer work in his field, Plantesamfund (1895), which, rewritten and enlarged, appeared in English as Oecology of Plants (1909). He also wrote A Handbook of Systematic Botany (1878; tr., 2d ed. 1904).

Low, Sir David, 1891-1963, British cartoonist, b. New Zealand. In 1919 Low went to England, where he worked on the London Star (1919-27). Thereafter he successively joined the staff of the Evening Standard (1927-50), the Daily Herald (1950-53), and finally the Manchester Guardian (from 1953). At the Standard he became noted for his sharp and perceptive caricatures and cartoons on national and international affairs. He created "Colonel Blimp," a caricature of the pompous British ultraconservative. Low's cartoons have been collected in A Cartoon History of Our Times (1939), Low on the War (1941), Years of Wrath (1946), which covers the period from 1931 to 1945, and The Fearful Fifties (1960).

Low, Seth, 1850-1916, American political reformer and college president, b. Brooklyn, N.Y., grad. Columbia, 1870. He entered his father's tea and silk importing firm, but became interested in politics and was reform mayor of the city of Brooklyn for two terms (1882-86). His support of Grover Cleveland in 1884 angered his fellow Republicans and cost Low a third term. As president of Columbia (1889-1901) he reorganized the existing schools, added to their number, increased affiliations with other institutions, supervised the removal of the university to Morningside Heights (1897), and gave it a library building in memory of his father. In 1901 he was elected mayor of Greater New York City (including the present five boroughs) as Fusion candidate against Tammany, then under Richard Croker. He reformed the police and education departments, reorganized the city finances, compelled the electrification of the New York Central RR within the city, and attacked the continued existence of unsanitary tenements. He was not reelected. Low was a delegate to the First Hague Conference.

Low, Juliette Gordon, 1860-1927, American founder of the Girl Scouts, b. Savannah, Ga., as Juliette Magill Kinzie Gordon. From a prominent Southern family, she met Robert Baden-Powell, founder of the Boy Scouts and Girl Guides, in England in 1911 and began organizing Girl Guide troops in Great Britain. Returning to the United States, she founded a Girl Guide troop in Savannah in 1912 and worked to spread the group, renamed Girl Scouts of America in 1913, throughout the country. At the time of her death the organization's had 168,000 members.

Low Countries, region of NW Europe comprising the Netherlands, Belgium, and the Grand Duchy of Luxembourg. The northern parts of the Netherlands and Belgium form a low plain bordering on the North Sea, but S Belgium and Luxembourg are part of the Ardennes plateau. The name Low Countries is a political and historic term rather than a strictly geographic concept. One of the wealthiest areas of medieval and modern Europe, it has also been a chronic battle site. For a history of the Low Countries, see articles on the individual nations and provinces (e.g., Flanders; Brabant, duchy of; Holland). See also Netherlands, Austrian and Spanish.

Low Church: see England, Church of.

Low Archipelago: see Tuamotu Archipelago.

Dodge, David Low, 1774-1852, American merchant and pacifist, b. Brooklyn, Conn. In 1815 he founded the New York Peace Society, possibly the first such organization to be established. In 1828 other peace societies joined with it to form the American Peace Society; Dodge served as a director and as a member of the executive committee until 1836.

De Vinne, Theodore Low, 1828-1914, American printer, b. Stamford, Conn. He learned his trade in the office of the Newburgh (N.Y.) Gazette and in 1848 entered the shop of Francis Hart in New York City. In 1858 he was made a junior partner, and after Hart's death in 1877 De Vinne became owner of the business. It continued as Theo. L. De Vinne & Company until 1908, when it was incorporated as the De Vinne Press. De Vinne became the best-known American printer of his day and did much by his writings and by his example of workmanship to advance the cause of good printing. He printed the Century Magazine and the Century Dictionary, both of them considered fine specimens of the art in that period. He also printed many of the Grolier Club books. He was a close student of types and did much to make American printers type conscious. De Vinne helped to bring reproduction and illustration processes to new standards of excellence. His numerous books include The Invention of Printing (1876), The Practice of Typography (4 vol., 1900-1904), and Notable Printers of Italy during the Fifteenth Century (1910).

Bülow, Hans Guido, Freiherr von, 1830-94, German pianist and conductor. After hearing Wagner's Lohengrin in 1850 at Weimar under Liszt's direction, he studied piano with Liszt and later conducted the premieres of several of Wagner's operas. In 1857 he married Liszt's daughter Cosima, who left him in 1869 and later became the wife of Wagner. While retaining his admiration of Wagner's music, Bülow became the most ardent champion of Brahms. He framed the aphorism that Bach, Beethoven, and Brahms are the three B's of music. One of the first pianists to be concerned with stylistically proper performances, Bülow made critical editions of the works of many composers. The first of the modern virtuoso conductors, he achieved his greatest distinction as conductor (1880-85) of the ducal orchestra at Meiningen.

Bülow, Friedrich Wilhelm, Freiherr von, 1755-1816, Prussian general in the Napoleonic Wars. After his victories (1813) over the French at Gross Beeren and at Dennewitz he was created count of Dennewitz. In 1815 he played a conspicuous part in the Waterloo campaign.

Bülow, Bernhard Heinrich Martin, Fürst von, 1849-1929, German chancellor. He held many diplomatic posts before he became, through the influence of Friedrich von Holstein, foreign secretary in 1897 and succeeded Hohenlohe-Schillingsfürst as chancellor in 1900. He inadvertently increased German isolation by his failure to gain the friendship of England and by his aggressive foreign policy. He antagonized France by his actions in the Moroccan crisis of 1905 (see Morocco). Bülow later alienated Russia in the Bosnian crisis of 1908 by thwarting Russian goals for the opening of the Dardanelles and supporting Austria-Hungary's annexation of Bosnia and Herzegovina. As a result he strengthened the Triple Entente between Great Britain, France, and Russia (see Triple Alliance and Triple Entente). Bülow lost the confidence of Emperor William II in the Daily Telegraph affair (Oct., 1908) in which William indiscreetly revealed his foreign policy toward Britain in an interview with the London newspaper; the interview caused a national uproar. Bülow had approved the text of William's remarks, but had not read them. Bülow subsequently lost support in the Reichstag over a proposed tax and was forced to resign in 1909. He later (1914-15) was ambassador to Italy.

Regulating food intake to improve physical condition, especially to lose weight. Examples include diets low in fat for weight loss, low in saturated fat and cholesterol to prevent or help treat coronary heart disease, or high in carbohydrates and protein to build muscle. Weight-loss diets are based on reducing calorie intake in different proportions of fat, carbohydrate, or protein; most result in some weight loss, but often the weight is gained back within a few years. Diets must include adequate nutrition and are most effective combined with exercise. Appetite suppressants may have dangerous side effects. Excessive weight loss may be a sign of anorexia nervosa.

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or low blood pressure

Condition in which blood pressure is abnormally low. It may result from reduced blood volume (e.g., from heavy bleeding or plasma loss after severe burns) or increased blood-vessel capacity (e.g., in syncope). Orthostatic hypotension—drop in blood pressure on standing—results from failure of the reflexes that contract muscles and constrict blood vessels in the legs to offset gravity as one rises. Hypotension is also a factor in poliomyelitis, shock, and barbiturate poisoning.

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Severe atmospheric disturbance in tropical oceans. Tropical cyclones have very low atmospheric pressures in the calm, clear centre (the eye) of a circular structure of rain, cloud, and very high winds. In the Atlantic and Caribbean they are called hurricanes; in the Pacific they are known as typhoons. Because of the Earth's rotation, tropical cyclones rotate clockwise in the Southern Hemisphere and counterclockwise in the Northern. They may be 50–500 mi (80–800 km) in diameter, and sustained winds in excess of 100 mph (160 kph) are common. In the eye, however, the winds drop abruptly to light breezes or even complete calm. The lowest sea-level pressures on Earth occur in or near the eye.

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Any large system of winds that circulates about a centre of low atmospheric pressure in a counterclockwise direction north of the Equator and in a clockwise direction south of it. Cyclones that occur in the mid- and high latitudes are known as extratropical cyclones; they are frequently preceded by thickening and lowering clouds, followed by precipitation. Cyclones that form in the lower latitudes are known as tropical cyclones; smaller than extratropical cyclones, they tend to be more violent and can cause considerable damage (see tropical cyclone). Wind systems that circulate around a high-pressure centre in directions opposite to that of cyclones are known as anticyclones.

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Coastal region, northwestern Europe, consisting of Belgium, The Netherlands, and Luxembourg. Known as the Low Countries because much of the land along the North Sea is below or at sea level, they are often called the Benelux countries, from the initial letters of their names.

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