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pulse, in anatomy

(Encyclopedia)pulse, alternate expansion and contraction of artery walls as heart action varies blood volume within the arteries. Artery walls are elastic. Hence they become distended by increased blood volume duri...

echo, in acoustics

(Encyclopedia)echo, reflection of a sound wave back to its source in sufficient strength and with a sufficient time lag to be separately distinguished. If a sound wave returns within 1⁄10 sec, the human ear is in...

Haas, Arthur Erich

(Encyclopedia)Haas, Arthur Erich häs [key], 1884–1941, American physicist and educator, b. Bohemia. He was professor of physics at Vienna, Leipzig, London, and, from 1936, the Univ. of Notre Dame, South Bend, In...

Michelson, Albert Abraham

(Encyclopedia)Michelson, Albert Abraham mīˈkəlsən [key], 1852–1931, American physicist, b. Strelno, Prussia, grad. Annapolis, 1873, and studied at Berlin, Heidelberg, and Paris. He was professor of physics at...

Roentgen, Wilhelm Conrad

(Encyclopedia)Roentgen or Röntgen, Wilhelm Conrad both: rĕntˈgĭn, rŭntˈ–, Ger. vĭlˈhĕlm kônˈrät röntˈgən [key], 1845–1923, German physicist. His notable research in many fields of physics, especi...

Stern, Otto

(Encyclopedia)Stern, Otto stûrn, Ger. ôˈtō shtĕrn [key], 1888–1969, American physicist, b. Germany, Ph.D. Univ. of Breslau, 1912. After resigning from his post at the Univ. of Hamburg in 1933, he became prof...

Huygens, Christiaan

(Encyclopedia)Huygens, Christiaan krĭsˈtyän hoiˈgəns [key], 1629–95, Dutch mathematician and physicist; son of Constantijn Huygens. He improved telescopic lenses and discovered (1655) a satellite of Saturn a...

complementarity principle

(Encyclopedia)complementarity principle, physical principle enunciated by Niels Bohr in 1928 stating that certain physical concepts are complementary. If two concepts are complementary, an experiment that clearly i...

Thomson, Sir George Paget

(Encyclopedia)Thomson, Sir George Paget, 1892–1975, English physicist; son of Sir Joseph John Thomson. He was professor of natural philosophy at the Univ. of Aberdeen (1922–30) and from 1930 to 1952 was profess...

parity

(Encyclopedia)parity or space parity, in physics, quantity that refers to the relationship between an object or process and the image that it can produce in a mirror. For example, any right-handed object will produ...