Research Center of Radioisotopes at University of Osaka Prefecture Radiocarbon Dates I

Abstract

The radiocarbon dating laboratory has been in operation since 1984 at the Radiation Center of Osaka Prefecture (OR), predecessor of the Research Center of Radioisotopes, University of Osaka Prefecture. We use liquid scintillation counting (LSC), following sample conversion to methanol through combustion and LiAlH4 reduction. This method was developed by Yamada et al. (Yamada, Higashimura and Shidei 1966; Yamada and Kobashigawa 1986). In cooperation with Yamada, we somewhat modified their procedure: 1) sample charcoal is burned at 700° in the presence of CuO needles and Sulfix grains to remove sulfur and halogen compounds produced during the combustion; 2) the combustion is carried out by using N2-O2 mixed gas of minimized O2 content and stopped when a small amount of the charcoal still remains unchanged, because precise investigation of methanol preparation revealed that O2 gas stimulates byproduct formation during LiAlH4 reduction (Shibata et al. 1985; Shibata et al. 1993). Usually, methanol is prepared directly from sample charcoal in a reaction apparatus (“direct method”). When the sample quantity is insufficient, generated CO2 is isolated as CaCO3 and diluted with inactive commercial CaCO3 if necessary (< 40 g of CaCO3 yield). Then CaCO3 is hydrolyzed with HCl to CO2 for methanol preparation in the usual way (“separate method”). We use standard oxalic acid SRM 4990C (HOxII) for determination of modern 14C (Stuiver 1983). The acid is oxidized to CO2 using the wet method of Valastro, Land and Valera (1977) followed by methanol preparation in the same manner as for unknown samples.

Formulation for nonaxisymmetric uniformly rotating equilibrium configurations in the second post-Newtonian approximation of general relativity

“…( 2.24) as it is, equations for Ω and C become implicit equations for Ω. As found in a previous paper [15], in such a situation, the convergence to a solution is very slow. Therefore, we transform those equations into other forms in which the potentials as well as Eq.…”

“…As a result, the number of Poisson equations we need to solve in each step of iteration reaches 29. However, source terms of the Poisson equations decrease rapidly enough, at worst O(r −4 ), in the region far from the source, so that we can solve accurately these equations as the boundary value problem like in the case of the first PN calculations [15]. Thus, the present formalism will be useful to obtain equilibrium configurations for synchronized BNS's or the Jacobi ellipsoid.…”

“…In our formalism, we extract terms depending on the angular velocity Ω from the can solve accurately these equations as the boundary value problem like in the case of the first PN calculations [15]. Thus, the present formalism will be useful to obtain equilibrium configurations for synchronized BNS's or the Jacobi ellipsoid.…”

“…In numerical calculation, the standard method to obtain equilibrium configurations is as follows [19,20,15];…”

“…In section 3, we rewrite the Poisson equation for potential functions, which are described in section 2, into useful forms in which the source terms of the Poisson equations decrease rapidly enough(O(r −4 )). In section 4, we show a formulation to obtain numerically equilibrium solutions of uniformly rotating fluid in the 2PN approximation: Taking into account the formulation in the first PN approximation [15], we further rewrite potentials defined in section 3 into a polynomial form in the angular velocity, Ω. Then, we transform the integrated Euler equation into the polynomial form in Ω 2 so that the convergence property in iteration procedures may be much improved.…”