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Previous short-term experiments showed that trail following behavior of the Argentine ant, Linepithema humile (Mayr) (Hymenoptera: Formicidae), can be disrupted by a high concentration of synthetic trail pheromone component (Z)-9-hexadecenal. In this study, a long-term field trial was conducted in 100-m2 plots of house gardens in an urban area of Japan to see whether the control effect on Argentine ants can be obtained by permeating synthetic trail pheromone from dispensers. The dispensers were placed in the experimental plots during the ant's active season (April-November) for 2 yr with monthly renewal. To estimate Argentine ant population density, foraging activity of Argentine ants in the study plots was monitored by monthly bait surveys. Throughout the study period, Argentine ant foraging activity was suppressed in the presence of the dispensers, presumably via trail forming inhibition. In contrast, the level of foraging activity was not different between treatment and no-treatment plots when the dispensers were temporarily removed, suggesting that treatment with pheromone dispensers did not suppress Argentine ant density in the treatment plots. Population decline may be expected with larger-scale treatment that covers a significant portion of the ant colony or with improvement in the potency of the disruptant.

We study the nuclear polarizations in the atomic and muonic 208 Pb using the complete set of nuclear excitations constructed by the relativistic mean-field model. We show that the nuclear-polarization energy shift is very sensitive to the contributions of the antinucleon and the effective mass of the nucleon. The persistent anomaly in the nuclear polarization of p-levels in the muonic 208 Pb is analyzed in the light of the present results.

We study the electronic and muonic nuclear polarizations with the nuclear excitations constructed by two nuclear models: the relativistic and nonrelativistic random-phase approximations. The importance of the nuclear dynamics in the level shift of electronic and muonic states is discussed.

We studied transmutation of high-level wastes in a spherical-tokamak reactor. We examined spent fuel, recovered fuel, natural UO2 fuel and reprocessed waste, though the natural UO2 fuel is not a high-level waste. We added a few percent of 239Pu to the former three fuels to increase the tritium breeding ratio and saw the change in the effective multiplication factor keff, number of fissions, multiplication of fusion energy and conversion ratio of 239Pu. We found that 2.5 and 5.5 fissions are needed to obtain the tritium breeding ratio of 1 and 2, respectively. High amplification of fusion energy occurs. Breeding of 239Pu is expected for the natural UO2 fuel even in a subcritical environment. For the reprocessed waste, 93Zr and 99Tc are transmuted efficiently by the (n,γ) reaction and so are 237Np and 241Am by the (n,f) reaction. Fusion neutrons of 100MW will transmute half of those nuclides produced from the generation of 1 GW(e) year in a large pressurized water reactor. However, tritium fuel may not be self-sustained in the reprocessed-waste burner.

Charge conservation for nonrelativistic RPA theory of finite nuclei is investigated. Charge conservation of the RPA is proved with effective one-body operators by taking the angular momentum coupling into account. For LS-closed shell nuclei, it is proved that this charge conservation is valid also in truncated particle-hole spaces.

In light of the recent finding of the discrepancies between theory and experiment in the Δ2p and Δ3p fine-structure splitting energies of muonic 208Pb, we have studied the effect of the electromagnetic transverse interaction on the nuclear-polarization energy shifts of muonic 208Pb. The reasons for this study are that the electric transverse interaction interferes coherently with the Coulomb interaction giving rise to large nuclear-polarization energy shifts, and that the transverse interaction may give nuclear-polarization energies of different muon-spin dependences from those of the Coulomb interaction. The calculation is based on the transition charge and current densities constructed from the random-phase approximation with the density-dependent contact interaction of Migdal and with particle-hole excitations of nearly a full 3 h ω space. The real part of the Feynman propagator was employed in the electromagnetic transverse interaction. The transverse interaction is found to explain 111 eV of the Δ2p binding-energy anomaly, which is one third of the total discrepancy, while it reduces the Δ3p anomaly by 32 eV. Large portions ofthe discrepancies still remain in both cases.

We study the muonic nuclear-polarization corrections, which provide level shifts due to the two-photon exchange process between a bound muon and a nucleus. We choose $^{16}\mathrm{O}$ as a nucleus for the demonstration of the amount and the property of the nuclear polarization in the muonic atoms. The nuclear states of $^{16}\mathrm{O}$ are constructed in the random-phase approximation including the negative-energy states based on the relativistic mean field model. The spatial components of the transition current have large couplings between positive- and negative-energy states. As a result, the contribution from the negative-energy states of nucleus to the nuclear-polarization correction is found to be significant and also essential to achieve gauge invariance. The nuclear-polarization effect in muonic $^{16}\mathrm{O}$ is also calculated using the collective model. We find that the nonrelativistic nuclear model with the effective mass provides similar results as the relativistic one.

We calculate nuclear-polarization energy shifts in muonic ${}^{208}\mathrm{Pb}.$ We employ a relativistic field-theoretical calculation and evaluate the ladder, cross, and seagull terms of the two-photon exchange diagrams in both the Feynman and Coulomb gauges. Gauge independence is very well satisfied with the calculated nuclear-polarization energies. Using these results, we analyze fine-structure splitting energies of muonic ${}^{208}\mathrm{Pb}$ because of the presence of the persisting discrepancies between experiment and calculation. The present nuclear-polarization energies explain about half of the anomaly in the $\ensuremath{\Delta}2p$ fine-structure splitting energy, and only one-fourth of the anomaly in the $\ensuremath{\Delta}3p$ fine-structure splitting energy.

Charge radii of Sn, Ba, Yb, and Pb isotopes are calculated within Hartree-Fock-Bogoliubov theory with a Skyrme force and a density-dependent delta-force pairing. We investigate mean field effects of the pairing upon odd-even staggering of isotope shifts. HFB equations are solved in the canonical basis. Odd nuclei are treated in the blocking approximation., Comment: 10 pages including 20 postscript figures, to be published in Nuclear Physics A

The 26 Mg(d, p) 27 Mg neutron stripping reaction has been studied at 3.1 and 3.5 MeV. Product protons corresponding to levels up to 4.8 MeV in 27 Mg were analysed with the broad range magnetic spectrograph with peak widths of ∼7 keV (FWHM) at eight angles from θ=15° to θ=120°. Cross sections are analysed using the DWBA theory and the statistical theory of Hauser and Feshbach. The angular momentum transfers l n are determined undoubtfully. The spectroscopic factors for respective states are then compared with the shell model calculations of Wildenthal et al. and the predictions of the collective model.

In addition to the rare earth nuclei, there appear band-llke structures in many regions of even-even nuclei whose neutrons are rich or deficient. These band structures are named quasiground, quasi- BETA and quasi- gamma bands as counterparts of these collective states in the well-deformed region. Nuclei having the quasi-ground band are thought to be in transition regions from spherical to deformed and the low-lying quasi- BETA or quasi- gamma band indicates the softness against the BETA or gamma vibration of these nuclei. A method is proposed in order to predict whether a nucleus is preferable to be axially symmetric or gamma -unstable if it is deformed. This method coiisists of introducing an idea of preferred shaPes of the proton and neutron systems in each case. By the preferred shape we mean the preferred direction of deforrnation that the system should have inherently. It can be predicted from the preferred shapes of protons and neutrons whether the deformation of the nucleus is axially symmetric or gamma -unstable. This method is applied to the lighter Ge, Se, Kr and Sr isotopes, the heavier Zr, Mo and Ru isotopes and the lighter Xe, Ba and Ce isotopes and its prediction is compared withmore » the potential energy surfaces of these nuclei calculated within a framework of the time dependent Hartree-Bogoliubov theory with the pairing plus quadrupole force. (auth)« less

Continuing a study on the production of mesons in hydrogen and carbon, a cloud chamber which contained alterrate layers of paraffin, graphite, and lead was operated with a counter hodoscope system at Mt. Norikura (elevation 2840 m) Cosmic-Ray Laboratory, University of Tokyo. Energy distributions of photons originating from neutral pions produced by nuclear interactions in paraffin, graphite, and lead were compared. The results are summarized in tables and graphs. (A.C.)