When cosmic rays enter the atmosphere, they undergo various transformations, including the production of neutrons.The resulting neutrons ( but attempts to directly measure the production rate in situ were not very successful.Libby estimated that the radioactivity of exchangeable carbon-14 would be about 14 disintegrations per minute (dpm) per gram of pure carbon, and this is still used as the activity of the modern radiocarbon standard.
In the initial variant of the urea breath test, a diagnostic test for Helicobacter pylori, urea labeled with approximately 37 k Bq (1.0 µCi) carbon-14 is fed to a patient (i.e., 37,000 decays per second). pylori infection, the bacterial urease enzyme breaks down the urea into ammonia and radioactively-labeled carbon dioxide, which can be detected by low-level counting of the patient's breath.
This resemblance is used in chemical and biological research, in a technique called carbon labeling: carbon-14 atoms can be used to replace nonradioactive carbon, in order to trace chemical and biochemical reactions involving carbon atoms from any given organic compound.
These are relatively low energies; the maximum distance traveled is estimated to be 22 cm in air and 0.27 mm in body tissue.
The presence of carbon-14 in the isotopic signature of a sample of carbonaceous material possibly indicates its contamination by biogenic sources or the decay of radioactive material in surrounding geologic strata.
In connection with building the Borexino solar neutrino observatory, petroleum feedstock (for synthesizing the primary scintillant) was obtained with low Since many sources of human food are ultimately derived from terrestrial plants, the carbon that comprises our bodies contains carbon-14 at the same concentration as the atmosphere.