carbon 12

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car·bon 12 (12C),

The standard of atomic mass, 98.90% of natural carbon.
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But the chances of this reaction occurring naturally in a star are incredibly slim, due to the fact that both an alpha particle and a carbon-12 nucleus are highly positively charged.
There's lighter carbon-12 in the atmosphere because the increase in atmospheric carbon levels is due entirely to humans burning fossil fuels.
SAM's mass spectrometer and tunable laser spectrometer independently measured virtually identical ratios of carbon-13 to carbon-12. SAM also includes a gas chromatograph and uses all three instruments to analyze rocks and soil, as well as atmosphere.
Atomic weight is (according to Wikipedia) "the ratio of the average mass of atoms of an element (from a given source) to 1/12 of the mass of an atom of carbon-12." The number 4.003 means nothing without knowing about the formula it is derived from.
Carbon-14, for example, is carbon with 14 neutrons and is an isotope of carbon-12, which has 12 neutrons.
There is a different ratio of carbon-14 and carbon-12 in steroid hormones made from plant sources compared with animal sources.
In a recent project, researchers at the University of Wyoming used the isotopic carbon-13 to carbon-12 ratio to address environmental issues associated with water co-produced with coalbed natural gas.
There is a different ratio of carbon-14 and carbon-12 in steroid hormones that are made from plant sources compared with animal sources.
Most of the shells are made of one isotope of carbon, carbon-12, but the amounts of other carbon isotopes can be quite revealing.
By measuring the ratio of radiocarbon (carbon-14) to the most common form of carbon (carbon-12) using accelerator mass spectrometry and comparing it with the ratio in the atmosphere we can calculate how much time has elapsed since death using a simple mathematical formula for exponential decay.
In nature, the two most abundant stable carbon isotopes are carbon-12 ([sup.12]C) and carbon-13 ([sup.13]C) with natural abundances of 98.89 percent and 1.11 percent, respectively.
In the journal article, Rutgers said the researchers detail a way to facilitate the of anaerobic bacteria in cleaning up MTBE by employing carbon isotope fractionation -- the changes in the isotopic ratios of carbon (its different molecular versions, carbon-12 and carbon-13) brought about from the selective degradation of the carbon-12 form in the case of MTBE.