a research instrument primarily used in physics to accelerate streams of charged subnuclear particles to high velocities in order to sort and analyze them.
This technique is now also used to count carbon isotope atoms for radiocarbon dating.
Specific changes in its amino acid structure (racemization or epimerization) which occur at a slow, relatively uniform rate, are measured after the organism's death.
The basis for the technique is the fact that almost all amino acids change from optically active to optically passive compounds (racemize) over a period of time.
Proteins are composed of different combinations of amino acids assembled in chain-like molecules.
However, when the organism dies, the amount of c14 declines such that the longer the time since death the lower the levels of c14 in organic tissue.
SYNONYMS OR RELATED TERMS: amino-acid dating; aminostratigraphy; amino-acid racemization, amino acid racemization CATEGORY: technique DEFINITION: A method of absolute (chronometric) dating which is hoped to fill the gap between radiocarbon dates and potassium-argon dates.
It is used for human and animal bone and other organic material.
Artifacts are usually relatively portable objects such as projectile points, ceramic pots, and relative dating of early human sites by association with index fossils uncovered in the same strata as human evidence.
The assumption is that both the people and the species that is now an index fossil must have lived at about the same of a relative dating method that measures somewhat irregular occurring natural phenomena that have been cross-dated with at least one chronometric technique so that the dates are somewhat comparable from sites in one region to another.