Three-body effects, which are effects of three-body force and three-hotly correlation, are introduced into the two-body nuclear force in a semi-phenomenological way to reproduce the nuclear saturation over all nuclei by the lowest order Brueckner theory. On the hasis of the reaction matrix calculation of nuclear matter with this two-body force including the three· body effects, a new effective potential is proposed which includes two independent parameters, namely, nuclear density and starting-energy. Because of the effect of three-body force, this effective potential is more attractive in the 'E state, compared with the usual one, and assures overall saturation without any artificial modification. The starting-energy dependence of the effective potential is also strengthened by the three-body force. The starting-energy dependence is found to work well for nuclear saturation together with the density dependence. Present density dependence is weaker than that of the usual clensity dependent effective potentials. The effective potential is decomposed into central, spin-orbit and tensor components. § I. IntroductionOn the basis of the realistic nuclear force, properties of nuclear matter and finite nuclei have been investigated and fruitful successes are accumulated. 1 l In particular, the Density-Dependent Hartree-Fock method (DDHF) has yielded remarkably good results for binding energies, density distributions, single particle energies and compressibilities of some finite nuclei.'J However, it should be noted that effective potentials used in DDHF are artificially adjusted by arbitrary factors to reproduce the nuclear saturation. This would be a weak point of DDHF to be investigated.In the reaction matrix theory, 3 l realistic two-body forces ensure about 10"'"' 12MeV I A for the binding energy of nuclear matter, while the empirical value is 16 MeV I A. It is also known from many calculations that with only the two-body force we could not reproduce the empirical binding energy and saturation density simultaneously.") Tamagaki 5 l pointed out this fact and Coester et al. 6 l showed that sufficient binding energy would be obtained only at too high equilibrium density as far as we use two-body forces. Thus it is necessary to seek for some origins which give an additional binding and shift the equilibrium density to the empirical one. Two of the present authors (T.K. and Y.A.) and co-vvorkersn.sJ have pointed at University of British Columbia on June 18, 2015 http://ptp.oxfordjournals.org/ Downloaded from

The contribution of two~pion exchange three-body force from the P-wave 77-N scat-te~ing to the binding energy of nuclear matter is investigated. The three-body force (TBF) is derived as the effective two-body force under consideration ~f the correlations between all the pairs of nucleons concerned with TBF. The reaction-matrix equations are solved self-consistently with two-and three-(effective two-)body potential. The binding energy contribution from TBF is about 3.5 MeV attraction for the c~se of the Ramada-Johnston potential and 4.1 MeV for Tamagaki's OPEH potential. The characteristic effect of TBF is discussed in connection with the binding energy and the saturation density. In nuclear matter calculation with two-nucleon· potentials, there seems to be that the energy gain has generally been accompanied by increasing the saturation density, but our results show that TBF gives the energy gain, but does not increase the saturation density so much as two-body force does.

Residual organophosphorus pesticides (OPP) in rice decrease when rice is cooked, but the extent of the decrease varies largely with the kind of pesticide used, ranging from 20% for Dimethoate to 93.5% for Ronnel. To determine the mechanism of this decrease, 14 kinds of pesticides were tested in a model experiment designed to determine their thermal decomposition and steam distillation behavior. From the results of the experiment, the test pesticides can be classified into three groups: 1) compounds resistant to both thermal decomposition and steam distillation (e.g., Dimethoate), 2) compounds thermally stable but susceptible to steam distillation (e.g., Fenitrothion=MEP), and 3) compounds thermally unstable and susceptible to steam distillation (e.g., Diazinon). The experimental results accounted well for the behavior of residual. OPPs in rice during the cooking process, and the residual amounts of OPPs after cooking can be estimated from the results.

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