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ultrasound

(Encyclopedia)ultrasound or sonography, in medicine, technique that uses sound waves to study and treat hard-to-reach body areas. In scanning with ultrasound, high-frequency sound waves are transmitted to the area ...

Prokhorov, Aleksandr Mikhailovich

(Encyclopedia)Prokhorov, Aleksandr Mikhailovich əlyĭksänˈdər mēkhīˈləvĭch prôˈkhərəf [key], 1916–2002, Russian physicist, b. Atherton, Queensland, Australia. In 1923 he was taken to the Soviet Union...

Achaean League

(Encyclopedia)Achaean League əkēˈən [key], confederation of cities on the Gulf of Corinth. The First Achaean League, about which little is known, was formed presumably before the 5th cent. b.c. and lasted throu...

Banville, John

(Encyclopedia)Banville, John, 1945–, Irish novelist. His novels, which stress language over plot and narrative, are written in a dense, elaborate, and highly original blend of poetry and prose. They are allusive,...

light

(Encyclopedia)light, visible electromagnetic radiation. Of the entire electromagnetic spectrum, the human eye is sensitive to only a tiny part, the part that is called light. The wavelengths of visible light range ...

chromosphere

(Encyclopedia)chromosphere krōˈməsfērˌ [key] [Gr.,=color sphere], layer of rarefied, transparent gases in the solar atmosphere; it measures 6,000 mi (9,700 km) in thickness and lies between the photosphere (th...

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...

magnetron

(Encyclopedia)magnetron măgˈnĭtrŏnˌ [key], vacuum tube oscillator (see electron tube) that generates high-power electromagnetic signals in the microwave frequency range. Its operation is based on the combined ...

Arecibo Observatory

(Encyclopedia)Arecibo Observatory, radio-astronomy facility located near Arecibo, Puerto Rico, part of the National Astronomy and Ionosphere Center. Conceived by, designed by, and built under the supervision of Wil...

Kawasaki disease

(Encyclopedia)Kawasaki disease or Kawasaki syndrome, acute illness characterized by inflammation of the blood vessels that primarily affects young children; it is more common in boys and children of Asian descent. ...