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uncertainty principle

(Encyclopedia)uncertainty principle, physical principle, enunciated by Werner Heisenberg in 1927, that places an absolute, theoretical limit on the combined accuracy of certain pairs of simultaneous, related measur...

quantum theory

(Encyclopedia)quantum theory, modern physical theory concerned with the emission and absorption of energy by matter and with the motion of material particles; the quantum theory and the theory of relativity togethe...

gamma radiation

(Encyclopedia)gamma radiation, high-energy photons emitted as one of the three types of radiation resulting from natural radioactivity. It is the most energetic form of electromagnetic radiation, with a very short ...

foreign aid

(Encyclopedia)foreign aid, economic, military, technical, and financial assistance given on an international, and usually intergovernmental level. U.S. foreign aid programs have included at least three different ob...

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...

spectrum

(Encyclopedia)CE5 Dispersion of white light by a triangular prism spectrum, arrangement or display of light or other form of radiation separated according to wavelength, frequency, energy, or some other propert...

disarmament, nuclear

(Encyclopedia)disarmament, nuclear, the reduction and limitation of the various nuclear weapons in the military forces of the world's nations. The atomic bombs dropped (1945) on Japan by the United States in World ...

nuclear reactor

(Encyclopedia)CE5 Power reactor system nuclear reactor, device for producing controlled release of nuclear energy. Reactors can be used for research or for power production. A research reactor is designed to pr...

Henderson, Donald Ainslie

(Encyclopedia)Henderson, Donald Ainslie, 1928–2016, American physician instrumental in eradicating smallpox, b. Lakewood, Ohio, M.D. Univ. of Rochester, 1954, M.P.H. Johns Hopkins, 1960. He joined (1955) the Epid...

Michigan, University of

(Encyclopedia)Michigan, University of, main campus at Ann Arbor; state supported; coeducational; chartered 1817 at Detroit as the Catholepistemiad, or Univ., of Michigania, rechartered 1821 (as Univ. of Mich.) and ...