Dating of organic materials

In 1947 W. F. Libby and collaborators [17-19] measured for the first time 14C produced by cosmic radiation in the atmosphere. He then proposed the use of this radioisotope for dating of organic material. A unique constellation of factors makes the 14C dating technique a most fascinating and powerful instrument for studies of the last 50,000 y ... 

Another application of carbon isotopes in foraminifera is to distinguish distinct water masses and to trace deep water circulation (Bender and Keigwin 1979 Duplessy et al. 1988). Since dissolved carbonate in the deeper waters becomes iso-topically lighter with time and depths in the area of their formation due to the increasing oxidation of organic material, comparison of sites of similar paleodepth in different areas can be used to trace the circulation of deep waters as they move from their sources. Such a reconstruction can be carried out by analyzing 8 C-values of well-dated foraminifera. 

Fullerenes, Cxy, have internal cavities that can act as containers for metal atoms. The metal reduces Cxy and is trapped in a fullerene cage (Saalfrank 1996). For example, Buck-minsterfullerene C6o can react with two potassium atoms, producing a dianion diradical that is a triplet in its ground state. Alkali metal salts of Buckminsterfullerene C6o possess the highest superconductivity transition temperatures (Tc) to date for organic materials, e.g., K3C60 with Tc = 19 K, Rt Ceo with Tc = 29 K, and Cs2RbC60 with / , 33 K (Haddon... 

In the earliest stages of human history, people and their homi-nid ancestors relied on easily obtainable natural materials, such as wood, stone, and clay. They developed techniques for fashioning these materials into the weapons, tools, buildings, and household items needed in their everyday lives. The earliest recorded tools date to 3.1 to 2.5 million years ago from the Hadar region of Africa. These tools were made of volcanic rock and were probably used to shape household items, weapons, and other tools. If the earliest humans made and used tools of organic materials, such as skin or rope, they would all have decayed, and no record of them remains today. 

Perhaps the most immediate impact on archaeological applications of dating using TAMS has been the major decrease in the amount of organic materials required for a determination. Even at this stage in the development of the technology, reductions of two or more orders of magnitude have been obtained. Our analysis of the Sunnyvale bone sample vividly illustrated the importance of this characteristic of TAMS... 

Carbon was used in various forms from very ancient times. The controlled production of carbon as charcoal may date from as early as 1 million years ago. The name comes from the Latin carbo, meaning charcoal. Carbon exists widely in nature and is known to be present in stars, comets, and the atmospheres of other planets. It is found frequently in combination with other elements, such as oxygen (carbon monoxide and carbon dioxide), as well as in the form of organic material, which by definition must contain a carbon atom. In the form of diamonds, carbon is the hardest naturally occurring material. 

Several authors (Ishiwatari et al., 1966 Ishiwatari, 1970a Kemp and Mudrochova, 1973 Bourbonniere and Meyers, 1978) have published infrared spectra of fulvic acids. These studies show that absorption spectra of fulvic acids extracted from the same sediment sample are not necessarily the same. This may be due to the difficulty of removing inorganic materials and to the existence of many kinds of organic materials in the fraction. However, absorption bands for most fulvic acids appear essentially the same as those for humic acids except for a carboxyl band at 1740 cm for fulvic acids and at 1720 cm for humic acids. To date no reliable data on humin have been obtained by infrared spectroscopy. 

We have initiated investigations intended to characterize homogeneous carbon dioxide reduction processes and our results to date are summarized herein. Specifically, our research centers on mechanistic studies of metal carbonyl anion catalysts, which readily activate CO2 to C-H and C-C bond formation, two of the most important processes in the synthesis of organic materials. 

Radiocarbon dating is a technique used widely by archaeologists to date articles composed of organic material (e.g. wood), and the importance of the method was recognized in 1960 by the award of the Nobel Prize in Chemistry to its developer, W.F. Libby. The method relies on the fact that one isotope of carbon, gC, is radioactive (n = 5730 yr) and decays according to equation 2.34. 

For example, continuous vertical mixing of the ocean provides the surface waters with some abyssal Die that has been removed from contact with atmospheric CO2 for up to 1500 years. This process gives the ocean an average surface water reservoir age of about 400 years (A " C= —50 ppt). A constant correction factor of 400 years often is subtracted from the radiocarbon dates of marine materials (both organic and inorganic). There are regional differences, however, and in upwelling areas the true deviation can approach 1300 years. 

Radiocarbon dating is a technique used widely by archaeologists to date articles composed of organic material (e.g. wood), and the importance of the method was recognized... 

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