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fallout

(Encyclopedia)fallout, minute particles of radioactive material produced by nuclear explosions (see atomic bomb; hydrogen bomb; Chernobyl) or by discharge from nuclear-power or atomic installations and scattered th...

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...

Orbiting Geophysical Observatory

(Encyclopedia)Orbiting Geophysical Observatory (OGO), series of six orbiting observatories (see observatory, orbiting) launched between 1964 and 1969 by the National Aeronautics and Space Administration (NASA) to s...

Kaposi's sarcoma

(Encyclopedia)Kaposi's sarcoma käpˈəshēˌ, kəpōˈsē [key], a usually fatal cancer that was considered rare until its appearance in AIDS patients. First described by an Austro-Hungarian physician, Moritz Kapo...

PET scan

(Encyclopedia)PET scan pŏzˈĭtrŏnˌ ĭmĭshˈən təmŏgˈrəfē [key], a medical imaging technique that monitors metabolic, or biochemical, activity in the brain and other organs by tracking the movement and co...

plant breeding

(Encyclopedia)plant breeding, science of altering the genetic pattern of plants in order to increase their value. Increased crop yield is the primary aim of most plant-breeding programs; advantages of the hybrids a...

phosphorescence

(Encyclopedia)phosphorescence fŏsˌfərĕsˈəns [key], luminescence produced by certain substances after absorbing radiant energy or other types of energy. Phosphorescence is distinguished from fluorescence in th...

air mass

(Encyclopedia)air mass, large body of air within the earth's atmosphere in which temperature and humidity, although varying at different heights, remain similar throughout the body at any one height. Air masses for...

occupational disease

(Encyclopedia)occupational disease, illness incurred because of the conditions or environment of employment. Unlike with accidents, some time usually elapses between exposure to the cause and development of symptom...