Although the Dyke is conventionally dated to the Early Middle Ages of Anglo-Saxon England, research in recent decades using techniques such as radioactive carbon dating has challenged the conventional historiography and theories about the earthwork.
32.
The carbon dates ( which depend on the kinds of radioactive carbon atoms in the sample ) are always expressed as a probability, such as : " Two thousand years before present, plus or minus 750 years ."
33.
Ahmed, 62, was arrested Thursday and charged with illegal possession of radioactive material after investigators seized three briefcases, a suit and a desk all contaminated with radioactive carbon 14 at his home, said Tori Richards, a spokeswoman for the Orange County district attorney.
34.
Therefore, in D 2 O with natural oxygen, 21 % of neutron captures are on oxygen, rising higher as 17 O builds up from neutron capture on 16 O . Also, 17 O may emit an alpha particle on neutron capture, producing radioactive carbon-14.
35.
Martin D . Kamen, one of the scientists who discovered radioactive carbon-14 and in doing so helped lay a foundation for deciphering the chemical processes in plants and animals, died on Aug . 31 at his home in Santa Barbara, Calif . He was 89.
36.
But Goodyear says radioactive carbon dating of small quantities of burned plant remains found deeply buried alongside simple stone tools at the remote Allendale County site appear to confirm that primitive people were there well before the peak of the last ice age, around 22, 000 years ago.
37.
The scientists used the latest and most sophisticated techniques based on the known decay rates of radioactive carbon in organic material to date the age of the buried vegetation and tree stumps they collected, and they found that none of the samples could have been drowned _ either by subsidence or tsunami _ earlier than 1660 or later than 1730.
