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101.
Sandi R. Copeland Matt Sponheimer Julia A. Lee-Thorp Petrus J. le Roux Darryl J. de Ruiter Michael P. Richards 《Journal of archaeological science》2010
This study tests the precision and accuracy of laser ablation multi-collector inductively coupled plasma mass spectrometry (LA-MC-ICP-MS) for measuring strontium isotope ratios (87Sr/86Sr) in fossil teeth from Swartkrans and Sterkfontein in South Africa, and explores the extent of diagenesis in these specimens. Compared to solution MC-ICP-MS or thermal ionization mass spectrometry (TIMS) methods, LA-MC-ICP-MS can be faster and less expensive, but has lower precision and accuracy. We found that 87Sr/86Sr ratios in fossil rodent teeth measured by LA-MC-ICP-MS were offset from solution values by a mean of 0.0005 ± 0.0010 (2σ). Because of the very wide spread of biologically available 87Sr/86Sr ratios (∼0.710 to ∼0.790) in the region, LA-MC-ICP-MS is more than sufficient for assessing the geographic origins of the fossil rodents. The concentration of strontium in modern and fossil enamel from the area is statistically indistinguishable, as is the range of 87Sr/86Sr ratios in modern rodents and fossil rodents from Swartkrans. Thus, there is little evidence of diagenetic Sr in the fossil enamel. In contrast, the fossil dentine may contain up to ∼50% diagenetic strontium, although many dentine 87Sr/86Sr ratios are still far removed from the background cave value of 0.729. We propose that LA-MC-ICP-MS will also be of use for investigating the geographic origins of other, non-rodent fossil teeth from the Sterkfontein and Swartkrans collections, and may prove of similar utility at other suitable sites. 相似文献
102.
Valérie Tesnière Corinne Bouquin 《Revue de synthèse / Centre international de synthèse》2014,135(2-3):175-202
The statistical survey of 1 385 french titles, starting with annales, journal or revue, helps to understand the development of “scientific” journals in France from the beginning of the 19th century until today. This 200 years history provides perspectives about the growth and decline of publishing. It includes scientific titles within the publishing production and underscores the importance of stimulation of the flow of ideas and information, through frequency and growth analysis. 相似文献
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Pierre Voinchet Gongming Yin Christophe Falguères Chunru Liu Fei Han Xuefeng Sun Jean Jacques Bahain 《Geochronometria》2013,40(4):341-347
The ESR dating method requires to describe the evolution of the ESR signal intensities vs. increasing gamma doses, then to extrapolate the equivalent dose of radiation received by the sample since its deposition using mathematical fitting. The function classically used to describe the growth curves of ESR aluminium signal in quartz was recently discussed and challenged for Lower Pleistocene sediments. In the present work, some alluvial sediments sampled in Upper Pleistocene fluvial terraces of the Yellow River system (China) permit us to test the application of another extrapolation function (linear + exponential) recently proposed for Lower Pleistocene sediments. The equivalent doses obtained here for the recent deposits of the Yellow River system and the corresponding ages are promising and indicate the potential of ESR to date quartz deposits from Upper Pleistocene times. 相似文献
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