thymus Vthl-mosV Pyramid-shaped lymphoid organ (see lymphoid tissue) between the breastbone and the heart. Starting at puberty, it shrinks slowly. It has no lymphatic vessels draining into it and does not filter lymph; instead, stem cells in its outer cortex develop into different kinds of T cells (see lymphocytes). Some migrate to the inner medulla and enter the blood¬ stream; those that do not may be destroyed to prevent autoimmune reac¬ tions. This process is most active during infancy. If a newborn’s thymus is removed, not enough T cells are produced, the spleen and lymph nodes have little tissue, and the immune system fails, causing a gradual, fatal wasting disease. Thymus removal in adults has little effect.
thyroid gland Endocrine gland in the throat that secretes hormones vital to metabolism and growth. Secretion of thyroid hormones—mostly thyroxine (T 4 )—is controlled by thyroid-stimulating hormone (TSH), released by the pituitary gland when the level of thyroid hormones in the blood drops below a certain threshold (see endocrine system). These hor¬ mones’ primary action in adults is to regulate cellular oxygen consump¬ tion (metabolic rate). They also lower blood cholesterol and are necessary for normal growth and development in children. The thyroid also pro¬ duces calcitonin, a hormone that stimulates deposition of calcium from the blood into the bones, balancing the action of parathyroid hormone. See also goitre; Graves disease; iodine deficiency.
thyroxine \thl-'rak-,sen\ or l-tetraiodothyronine Vel-.te-tro-I-.o- do-'thI-r3-,nen\ or T 4 One of the two major hormones (along with the closely related 1-triiodothyronine, or T 3 ) secreted by the thyroid gland. Its principal function is to stimulate oxygen consumption and thus metabolism in all cells and tissues in the body. Thyroxine is formed by the addition of iodine to the amino acid tyrosine while the latter is in a protein-bound form. Thyroxine secretion is excessive in hyperthyroidism and deficient in hypothyroidism.
Thyssen Vtui-sonV Fritz (b. Nov. 9, 1873, Mulheim, Ger.—d. Feb. 8, 1951, Buenos Aires, Arg.) German industrialist and financial backer of Adolf Hitler. Thyssen entered the family iron, steel, and coal business and inherited his father’s fortune and empire in 1926 (see Thyssen Krupp Stahl). He created a family business trust that came to control more than 75% of Germany’s ore reserves and employ 200,000 workers. Distressed by the rise of socialism in Germany, he supported Hitler and helped finance his rise to chancellor. But Thyssen opposed Hitler’s later policies and fled to Switzerland in 1939, enabling Hitler to confiscate Thyssen’s fortune (about $88 million). Thyssen was arrested in France (1941) and impris¬ oned by the Nazis. After the war, he was convicted as a “minor Nazi” and ordered to pay 15% of his property in restitution.
ThyssenKrupp AG German steel company. The Krupp firm began in 1811 when Friedrich Krupp (1787-1826) founded a steel plant in Essen, and it remained in family hands for a century and a half. Known for its high-quality steel and its cannons and other armaments, Krupp prospered with the rise of the German navy. It enjoyed a monopoly on arms manu¬ facturing during World War I; one of its most potent weapons was “Big Bertha.” After the war, Germany was forbidden to manufacture arms, and parts of the Krupp works were dismantled, though it remained a vast industrial empire. Krupp’s factories were central to Germany’s illegal
rearmament under Adolf Hitler in the 1930s. After World War II, Alfried Krupp (1907-67) was convicted of war crimes for using slave labour and ordered to forfeit all his property, but with the outbreak of the Korean War he was granted amnesty and his property restored. In 1968, after his son renounced the Krupp name and fortune, the company went public. In 1992 it merged with Hoesch AG to become Fried Krupp AG Hoesch- Krupp. Thyssen AG originated as a rolling mill founded by August Thys¬ sen (1842-1926). It merged with seven other steelworks to become Vereinigte Stahlwerke AG, but reassumed its own identity in 1953. After the steel divisions of the rival companies were joined in 1997 to form Thyssen Krupp Stahl, the remaining segments of each company merged in 1999, creating ThyssenKrupp AG. Its products include steel, construc¬ tion and automotive components, elevators, and engineering services.
Tiamat \'te-a-,mat\ In Mesopotamian mythology, a primal goddess who is a personification of salt water and the mother of the gods. When con¬ flict between her husband, Apsu, and the other gods resulted in Apsu’s death, Tiamat waged war on the other divinities, backed by an army of demons she had created. Her battle with, and defeat at the hands of, Mar- duk forms the substance of the Babylonian creation epic Enuma elish. From her body Marduk fashioned the heavens and the earth.
Tian or T'ien \'tyen\ Chinese "Heaven" In indigenous Chinese reli¬ gion, the supreme power reigning over humans and lesser gods. The term refers to a deity, to impersonal nature, or to both. As a god, Tian is an impersonal power, in contrast to the supreme ruler Shangdi, but the two are closely identified and their names are sometimes used synonymously. In later references, Tian is likened to nature or fate. Scholars generally agree that Tian was the source of moral law, but they long debated whether Tian responded to pleas and rewarded and punished human actions or whether events merely followed Tian’s order and principles.
Tian Shan See Tien Shan
Tiananmen \'tyan- , an- , men\ Square One of the largest public squares in the world, originally designed and built in Beijing in 1651 and enlarged in 1958. It is named for the massive stone “Gate of Heavenly Peace” (Tiananmen) at its northern end. It contains and is surrounded by halls, museums, and monuments, including the Mao Zedong Memorial Hall, where Mao’s body rests in state. Tiananmen Square has been the rallying point for political demonstrations since 1919, including the large protests in May-June 1989 that were forcibly repressed. See also Fang Lizhi.
Tiancong See Hongtaiji
Tianjin Vtyen-'jhA or T'ien-chin conventional Tientsin Seaport and municipality with provincial status (pop., 2003 est.: city, 4,933,100; 2002 est.: municipality, 10,070,000), northeastern China. The municipality, on the Bo Hai, is bordered by Hebei province and Beijing municipality and has an area of 4,400 sq mi (11,300 sq km). The city, China’s third largest, lies at the head of the short Hai River, which flows into the Bo Hai; Tianjin is connected to the Yangtze River (Chang Jiang) by the Grand Canal. It has been a major transportation and trading centre since the Yuan dynasty in the 13th century. It was a garrison town during the Ming dynasty (1368— 1644). The British and French occupied it during the Second Opium War (1856-60); a treaty signed there in 1858 opened 11 Chinese ports to for¬ eign trade. As a treaty port, it developed rapidly. It was the scene of heavy fighting during the Boxer Rebellion (1900), after which it was placed under an international commission and its walls razed. It is the leading port in northern China and the country’s second largest manufacturing centre. Educational institutions include Tianjin University (1895) and Nankai University (1919).
Tianshi Dao See Five Pecks of Rice
Tiantai \'tyan-'dl\ Japanese Tendai \'ten-'dl\ Buddhist sect founded by Zhiyi in the 6th century ad. Its chief scripture is the Lotus Sutra, and the school is thus known as the Lotus school. Its basic philosophical doctrine is summarized as the Triple Truth: All dharmas lack ontological reality; nevertheless, they have a temporary existence; and they are simulta¬ neously unreal and temporarily existing—an absolute truth that surpasses the others. In Tiantai, all Buddhist learning is arranged in a grand hier¬ archical scheme. In Japan, Saicho attempted to incorporate Zen medita¬ tion, monastic discipline, and esoteric cults. Amalgamation of Shinto and Buddhism was also encouraged.