• Radiocarbon, Volume 20, Number 3 (1978)

      American Journal of Science, 1978-01-01
    • Notice to Readers

      American Journal of Science, 1978-01-01
    • Uppsala Natural Radiocarbon Measurements XII

      Olsson, Ingrid U.; El-Daoushy, M. Farid A. F. (American Journal of Science, 1978-01-01)
    • University of Miami Radiocarbon Dates XIII

      Calvert, P. M.; Introne, D. S.; Stipp, J. J. (American Journal of Science, 1978-01-01)
    • University of Lund Radiocarbon Dates XI

      Håkansson, Sören (American Journal of Science, 1978-01-01)
    • University of Georgia Radiocarbon Dates VI

      Brandau, Betty Lee; Noakes, John E. (American Journal of Science, 1978-01-01)
    • Texas A&M University Radiocarbon Dates IV

      Parker, R. A.; Sackett, W. M. (American Journal of Science, 1978-01-01)
      Organic and carbonate carbon in sediments deposited in the Cariaco Basin and on the Mississippi River Delta and the total dissolved inorganic carbon in four water column profiles comprise the samples in this list. Except as noted below the samples were processed using the benzene synthesis and other procedures described by lNTatllews, et al (1972).
    • Tartu Radiocarbon Dates VIII

      Ilves, E. (American Journal of Science, 1978-01-01)
    • Tartu Radiocarbon Dates VII

      Liiva, Arvi; Ekman, Ilpo; Rinne, Toivo (American Journal of Science, 1978-01-01)
    • Tallinn Radiocarbon Dates V

      Punning, J. M.; Rajamäe, R.; Ehrenpreis, M. (American Journal of Science, 1978-01-01)
    • Optimum Operating Conditions of 14C-Methane Isotope Enrichment By Concentric Type Thermal Diffusion Columns for Use in Radiocarbon Dating

      Erlenkeuser, Helmut (American Journal of Science, 1978-01-01)
      The optimum operating conditions providing nlinirnurn run-time and running costs have been studied theoretically for a thermal diffusion plant to be used for the enrichment of the radiocarbon isotope from finite sample size. The calculations are based on a simple approximate model of the enrichment process, regarding the isotope separation column as operating under quasi-stationary state conditions. The temporal variation of the isotope accumulation is given by a single exponential term. From comparison with the numerical solution of the separation tube equation, approximate models of this simple type appear hardly sufficient for analytical work but seem well suited for optimization calculations. For column operation not too close to the equilibrium state, the approximate run-times were found accurate within 0.2 d. The approximate model has been applied to a column of the concentric type, operated on gaseous methane. Cross-section configuration and temperatures were not varied (hot and cold wall radii: 2.0 and 2.6cm, respectively; hot and cold wall temperatures: 400 degrees C and 14 degrees C, respectively). The column transport coefficients used were derived from measurements. Run-time was minimized by optimizing both the operating pressure and the sample collection mode for different total sample size (range studied: 24 to 100 g), mass of enriched sample (1.8, 2.4, and 3.0 g), enrichment factor (12, 15, and 20) and column length (8 to 18 m). Optimum working pressures are between 1 and 2 atm. Usually, about 90 percent of the enriched sample mass is extracted favorably from the column itself, the length of the sampling section being about 2.5 to 5 in. Typical runtimes are between 3 days and 2 weeks, and isotope yield may reach 90 percent. Optimum operating conditions have also been calculated for other column configurations reported in literature and are compared with the experimental results.
    • Marine Resources Research Institute Radiocarbon Dates II

      Mathews, T. D. (American Journal of Science, 1978-01-01)
    • Laboratories

      American Journal of Science, 1978-01-01
    • La Jolla Measurements of Radiocarbon in the Oceans

      Linick, T. W. (American Journal of Science, 1978-01-01)
    • Index: Volume 20, Nos. 1, 2, and 3, 1978

      American Journal of Science, 1978-01-01
    • Gliwice Radiocarbon Dates IV

      Moscicki, Wlodzimierz; Pazdur, Anna; Pazdur, Mieczysław F.; Zastawny, Andrej (American Journal of Science, 1978-01-01)
    • Erratum

      American Journal of Science, 1978-01-01
    • Birbal Sahni Institute Radiocarbon Measurement I

      Rajagopalan, G.; Vishnu, Mittre; Sekar, B. (American Journal of Science, 1978-01-01)
    • Berlin Radiocarbon Dates V

      Kohl, G.; Quitta, H. (American Journal of Science, 1978-01-01)
    • ANU Radiocarbon Date List VI

      Polach, H. A.; Head, M. J.; Gower, J. D. (American Journal of Science, 1978-01-01)