Browsing Radiocarbon, Volume 29, Number 1 (1987) by Title
Now showing items 1-17 of 17
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Available PublicationsAmerican Journal of Science, 1987-01-01
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Comparative Study of the Radiocarbon Dating of Different Bone Collagen PreparationsFour different bone collagen preparation procedures were compared and were found useful as a means of assessing the nature of contaminants present in a sample. Weathered bone however appeared to contain contaminants that could not be eliminated by any of the procedures studied.
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Comparison of Oceanic 14C Data with Those of GEOSECS: Vertical Profiles in 1973 (GEOSECS) and in 1980 at (30 Degrees N, 170 Degrees E) in the Northwestern Pacific OceanThe vertical profile of radiocarbon at (30 degrees N, 170 degrees E) measured in 1980 was compared with the GEOSECS data measured in 1973. 14C was extracted from 200L of sea water, converted to C2H2, and analyzed with a gas proportional counter. Our profile and that of GEOSECS were in good agreement below 700m depth without systematic deviation of Delta-14C values between both measurements. On the other hand, a Delta-14C increase was observed above 700m depth, reflecting the transient addition, in 6.6 years, of bomb 14C to the intermediate layer from the atmosphere.
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Drastic Increase of Background in the Gliwice Radiocarbon Laboratory During Late April, 1986, and Its Time ChangesPreliminary observations of changes of the background of three proportional counters during May and June,1986, are presented. Some isotopes contributing to the rise of background were identified on the basis of their half-life determinations.
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Evaluation and Status of Liquid Scintillation Counting for Radiocarbon DatingAn international review of liquid scintillation low-level counting procedures and instrumentation made it possible to assess in detail those elements which lead to high-precision liquid scintillation radiocarbon dating with a Figure of Merit of 32,000. Current research is documented and future possibilities are alluded to.
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New Books in ArchaeologyAmerican Journal of Science, 1987-01-01
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Radiocarbon Content of Tropospheric CO2 at China Lake, California 1977-1983The measurements reported here are a continuation of tropospheric radiocarbon measurements in carbon dioxide carried out since 1961 at our China Lake, California collection facility. The data show a continued decrease in radiocarbon activity from ca 330 per mil in 1977 to 215 per mil in 1983 in agreement with similar analyses in Europe for the same time interval.
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Radiocarbon, Volume 29, Number 1 (1985)American Journal of Science, 1987-01-01
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Scintillation Counter Performance at the SMU Radiocarbon LaboratoryResults are presented of a study of counter performance and vial characteristics for three liquid scintillation counters used at the SMU Radiocarbon Laboratory: the Intertechnique LS20, Packard Tri-Garb 460C, and LKB Wallac Rack Beta 1217. Modifications to photomultiplier tube high voltage, pre-amplifier gain, energy window settings, counting vial design, and sample holder design have resulted in reduced background, higher counting efficiency, and greater long-term stability for the Intertechnique and Packard counters. Square quartz counting vials are used in the Intertechnique and Packard counters with excellent results. Use of Teflon vials in the LKB counter requires careful cleaning procedures and long counting times.
