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carbon-12 |
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carbon-12 [′kär·bən ′twelv] (nuclear physics) A stable isotope of carbon with mass number of 12, forming about 98.9% of natural carbon; used as the basis of the newer scale of atomic masses, having an atomic mass of exactly 12u (relative nuclidic mass unit) by definition. How to thank TFD for its existence? Tell a friend about us, add a link to this page, add the site to iGoogle, or visit webmaster's page for free fun content. |
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The team extracted and purified samples of two MeO-PBDEs, MeO-BDE-47 and MeO-BDE-68, and measured the ratios of the isotopes carbon-14 and carbon-12 in each sample. The ratio of the isotopes of carbon-13 and carbon-12 in the material coating the tubules is lower than that normally found in Earth's crust, a clue that the substance was produced by--or is what's left of--ancient microorganisms. On Earth, methane made by living things has a ratio of carbon-12 to carbon-13 that's slightly elevated compared with methane produced by nonbiological sources. |
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