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from The American Heritage® Dictionary of the English Language, 4th Edition

  • n. Any of a class of cell membrane proteins that function as intermediaries between hormone receptors and effector enzymes and enable the cell to regulate its metabolism in response to hormonal changes.


From GTP-binding regulatory protein.
(American Heritage® Dictionary of the English Language, Fourth Edition)


  • Vale representatives said last week at the Brazilian Mining Institute's biannual congress that the company had discovered "safe" radioactive elements at the Salobo site that could be classified as rare-earth minerals.

    Brazil's Vale Discovers Rare Earths in Amazon

  • The region is also a key producer of so-called rare-earth elements, which are increasingly in demand in high-tech manufacturing, and are almost exclusively mined in China, which accounts for about 97% of global output.

    China Makes Effort to Cool Unrest in Inner Mongolia

  • Today, that mine, chock-full of so-called rare-earth metals, is responsible for one of the fastest windfalls in private-equity history: Turning $200 million into a paper profit of about $2.3 billion in just 30 months, or roughly $2.6 million in profit each day.

    Molycorp Pays Off for Buyout Believers

  • In recent years, concern has focused on the supply of so-called rare-earth elements - which include lanthanum, cerium and neodymium - as China produces about 95 percent of them, Graedel said.

    U.S. urged to safeguard supply of 'energy-critical elements'

  • Over the past few years, a spotlight has focused on supply concerns with so-called rare-earth elements - which include lanthanum, cerium and neodymium - as China now produces about 95 percent of these, Graedel said.

    U.S. urged to swiftly secure supplies of 'energy-critical elements'

  • These chemicals, known as rare-earth elements, are vital for the high-tech, defense and green-energy industries. - Top Stories

  • Some resources are really scarce on earth (PGMs for example) or geographically very unevenly distributed (Japan and China currently compete over relatively abundant rare-earth metals, and lithium in Bolivia)

    Why the Moon? Here's Why. - NASA Watch

  • At the time, the decision was overshadowed by the global uproar over China's move to restrict the export of rare-earth metals for political reasons.

    Lower China Molybdenum Output Stirs North American Production

  • Its locking system uses a rare-earth magnet as a key.

    Cute Co-Workers

  • Hybrid cars and wind turbines need rare-earth minerals that come with their own hefty environmental price tag.

    The California Experiment


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