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second

(Encyclopedia)second, abbr. sec or s, fundamental unit of time in all systems of measurement. In practical terms, the second is 1/60 of a minute, 1/3,600 of an hour, or 1/86,400 of a day. Since the length of the da...

psoriasis

(Encyclopedia)psoriasis sôrīˈəsĭs [key], occasionally acute but usually chronic and recurrent inflammation of the skin. The exact cause is unknown, but the disease appears to be an inherited, possibly autoimmu...

glacial periods

(Encyclopedia)glacial periods, times during which large portions of the earth's surface were covered with thick glacial ice sheets. In the Pleistocene epoch, in the Carboniferous and Permian periods of the Paleozoi...

breast cancer

(Encyclopedia)breast cancer, cancer that originates in the breast. Breast cancer is the second leading cause of cancer death in women (following lung cancer). Although the vast majority of the cases occur in women,...

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...

Giacconi, Riccardo

(Encyclopedia)Giacconi, Riccardo, 1931–2018, Italian-American astrophysicist, b. Milan, Italy, Ph.D. Univ. of Milan 1954. He was a researcher at American Science and Engineering Corporation (1959–73), professor...

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...

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...

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...