Water composed of two atoms of deuterium (D; a heavy isotope of hydrogen) and one atom of oxygen (O), chemical formula D2O. Water from most natural sources contains about 0.015percnt deuterium oxide; this can be enriched or purified by distillation, electrolysis, or chemical processing. Heavy water is used as a moderator in nuclear power plants, slowing down the fast neutrons so that they can react with the fuel in the reactor. Heavy water is also used in research as an isotopic tracer for chemical reactions and biochemical pathways. Water with tritium (T2O) rather than deuterium may also be called heavy water.
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Sample of crested barite from Missouri
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Type of rock music marked by highly amplified, distorted “power chords” on electric guitar, a hard beat, thumping bass, and often dark lyrics. It evolved in Britain and the U.S. in the late 1960s from the heavy, blues-oriented music of Steppenwolf, Jimi Hendrix, and others. In the 1970s the genre was defined by the music of bands such as Led Zeppelin, Black Sabbath, Kiss, AC/DC, and Aerosmith. After a period of decline, a new generation of bands such as Def Leppard, Iron Maiden, Mötley Crüe, and Van Halen revived heavy metal in the 1980s, along with the careers of many of its pioneers, including Ozzy Osbourne of Black Sabbath.
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