Radiocarbon dating (sometimes simply known as carbon dating) is a radiometric dating method that uses the naturally occurring radioisotope carbon-14 (C) to estimate the age of carbon-bearing materials up to about 58,000 to 62,000 years. Raw, i.e. uncalibrated, radiocarbon ages are usually reported in radiocarbon years "Before Present" (BP), "Present" being defined as 1950. Such raw ages can be calibrated to give calendar dates. One of the most frequent uses of radiocarbon dating is to estimate the age of organic remains from archaeological sites. When plants fix atmospheric carbon dioxide (CO2) into organic material during photosynthesis they incorporate a quantity of C that approximately matches the level of this isotope in the atmosphere (a small difference occurs because of isotope fractionation, but this is corrected after laboratory analysis). After plants die or they are consumed by other organisms (for example, by humans or other animals) the C fraction of this organic material declines at a fixed exponential rate due to the radioactive decay of C. Comparing the remaining C fraction of a sample to that expected from atmospheric C allows the age of the sample to be
Graphene layers dramatically reduce wear and friction on sliding steel surfaces
(Phys.org) —Sometimes, all it takes is an extremely small amount of material to make a big difference. Scientists at Argonne National Laboratory have recently discovered that they could substitute one-atom-thick ...
Apr 26, 2013
4.8 / 5 (23)
9
|
Study finds fungi, not plant matter, responsible for most carbon sequestration in northern forests
(Phys.org) —A new study undertaken by a diverse group of scientists in Sweden has found that contrary to popular belief, most of the carbon that is sequestered in northern boreal forests comes about due ...
Mar 29, 2013
4.8 / 5 (10)
3
|
Microbes surviving deep inside oceanic crust
(Phys.org) —A new study shows for the first time that microorganisms are thriving deep within the oceanic crust under the sea floor, and hence far from light or oxygen.
Mar 15, 2013
5 / 5 (7)
8
|
Researchers studying nanotube toxicity develop method for finding them in soils
(Phys.org)—Carbon nanotubes (CNTs) could pave the way for remarkable technology, from improved computer chips, flexible computer screens or body armor, to health applications such as bone healing and cancer treatments.
Oct 19, 2012
4.5 / 5 (2)
0
Research shows graphene nanopores can be controlled
(Phys.org)—Engineers at the University of Texas at Dallas have used advanced techniques to make the material graphene small enough to read DNA.
Oct 02, 2012
5 / 5 (4)
1
|
Graphene films—highly resistant to damage—could protect metals in harsh environments
(Phys.org)—A coating so thin it's invisible to the human eye has been shown to make copper nearly 100 times more resistant to corrosion, creating tremendous potential for metal protection even in harsh ...
Sep 27, 2012
5 / 5 (11)
12
|
New technique controls graphite to graphene transition
(Phys.org) -- University of Arkansas physicists have found a way to systematically study and control the transition of graphite, the “lead” found in pencils, to graphene, one of the strongest, lightest ...
Jul 02, 2012
5 / 5 (1)
1
|
