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Occupational Safety and Health Administration

(Encyclopedia)Occupational Safety and Health Administration (OSHA), U.S. agency established (1970) in the Dept. of Labor (see Labor, United States Department of) to develop and enforce regulations for the safety an...

Río

(Encyclopedia)Río and Rio, respectively Spanish and Portuguese terms for river. For those not listed here, see under the second element of the name. Thus, for Río Lerma, see Lerma. ...

International Union of Pure and Applied Chemistry

(Encyclopedia)International Union of Pure and Applied Chemistry (IUPAC), an international organization est. 1919 to advance the chemical sciences and contribute to the application of chemistry to the service of hum...

molecule

(Encyclopedia)molecule mŏlˈəkyo͞ol [key] [New Lat.,=little mass], smallest particle of a compound that has all the chemical properties of that compound. A single atom is usually not referred to as a molecule, a...

Xiang

(Encyclopedia)Xiang shyäng, syäng [key], river, 715 mi (1,151 km) long, rising in NE Guangxi prov. and flowing N through Hunan prov. to Dongting Lake, SE China. The river is navigable to large vessels for most of...

ozone

(Encyclopedia)ozone ōˈzōn [key], an allotropic form of the chemical element oxygen (see allotropy). Pure ozone is an unstable, faintly bluish gas with a characteristic fresh, penetrating odor. The gas has a dens...

Levitt, Michael

(Encyclopedia)Levitt, Michael, 1947–, British-Israeli-American biophysicist, b. South Africa, Ph.D. Cambridge, 1971. Levitt was a faculty member at Cambridge from 1974 to 1979 and at the Weizmann Institute in Isr...

Karplus, Martin

(Encyclopedia)Karplus, Martin, 1930–, Austrian-American theoretical chemist, b. Vienna, Ph.D. California Institute of Technology, 1953. He has been a professor at Harvard since 1967, studying the electronic struc...

Warshel, Arieh

(Encyclopedia)Warshel, Arieh, 1940–, Israeli-American chemist, b. Kibbutz Sde Nahum (in what is now Israel), Ph.D. Weizmann Institute, 1969. He has been a professor at the Univ. of Southern California since 1976....

atomic mass

(Encyclopedia)atomic mass, the mass of a single atom, usually expressed in atomic mass units (amu). Most of the mass of an atom is concentrated in the protons and neutrons contained in the nucleus. Each proton or n...