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Carbon-14, C-14, 14 C or radiocarbon, is a radioactive isotope of carbon with an atomic nucleus containing 6 protons and 8 neutrons. Its presence in organic matter is the basis of the radiocarbon dating method pioneered by Willard Libby and colleagues (1949) to date archaeological, geological and hydrogeological samples.
Two are stable and not radioactive: carbon-12 (12 C), and carbon-13 (13 C); and carbon-14 (14 C), also known as "radiocarbon", which is radioactive. The half-life of 14 C (the time it takes for half of a given amount of 14 C to decay) is about 5,730 years, so its concentration in the atmosphere might be expected to decrease over thousands of ...
A good example of the difference in energy of the various radionuclei is the detection window ranges used to detect them, which are generally proportional to the energy of the emission, but vary from machine to machine: in a Perkin elmer TriLux Beta scintillation counter , the hydrogen-3 energy range window is between channel 5–360; carbon-14 ...
When an organism dies, the exchange of 14 C with the environment ends and the incorporated 14 C decays. Given radioactive decay (14 C's half-life is about 5,730 years), the relative amount of 14 C left in the dead organism can be used to calculate how long ago it died. Bomb pulse dating should be considered a special form of carbon dating.
Two common contaminants are humic acid, which can be removed with an alkali wash, and carbonates, which can be removed with an acid.These treatments can damage the structural integrity of the sample and remove significant volumes of material, so the exact treatment decided on will depend on the sample size and the amount of carbon needed for the chosen measurement technique.
Patients swallow urea labelled with an uncommon isotope, either radioactive carbon-14 (nowadays preferred in many countries) or non-radioactive carbon-13.In the subsequent 10–30 minutes, the detection of isotope-labelled carbon dioxide in exhaled breath indicates that the urea was split; this indicates that urease (the enzyme that H. pylori uses to metabolize urea to produce ammonia) is ...
This is similar to a head CT (see table). Other sources include cosmic radiation, dissolved uranium and thorium in water, and internal radiation (humans have radioactive potassium-40 and carbon-14 inside their bodies from birth). [18]
The action of neutrons on stable isotopes can form radioisotopes, for instance the neutron bombardment (neutron activation) of nitrogen-14 forms carbon-14. This radioisotope can be released from the nuclear fuel cycle ; this is the radioisotope responsible for the majority of the dose experienced by the population as a result of the activities ...