Consequences of the center-of-mass correction in nuclear mean-field models

We study the influence of the scheme for the correction for spurious center-of-mass motion on the fit of effective interactions for self-consistent nuclear mean-field calculations. We find that interactions with very simple center-of-mass correction have significantly larger surface coefficients than interactions for which the center-of-mass correction was calculated for the actual many-body state during the fit. The reason for that is that the effective interaction has to counteract the wrong trends with nucleon number of all simplified schemes for center-of-mass correction which puts a wrong trend with mass number into the effective interaction itself. The effect becomes clearly visible when looking at the deformation energy of largely deformed systems, e.g. superdeformed states or fission barriers of heavy nuclei.Comment: 12 pages LATeX, needs EPJ style files, 5 eps figures, accepted for publication in Eur. Phys. J.

Shell structure of superheavy nuclei in self-consistent mean-field models

We study the extrapolation of nuclear shell structure to the region of superheavy nuclei in self-consistent mean-field models—the Skyrme-Hartree-Fock approach and the relativistic mean-field model—using a large number of parametrizations which give similar results for stable nuclei but differ in detail. Results obtained with the folded-Yukawa potential which is widely used in macroscopic-macroscopic models are shown for comparison. We focus on differences in the isospin dependence of the spin-orbit interaction and the effective mass between the models and their influence on single-particle spectra. The predictive power of the mean-field models concerning single-particle spectra is discussed for the examples of 208Pb and the spin-orbit splittings of selected neutron and proton levels in 16O, 132Sn, and 208Pb. While all relativistic models give a reasonable description of spin-orbit splittings, all Skyrme interactions show a wrong trend with mass number. The spin-orbit splitting of heavy nuclei might be overestimated by 40%–80%, which exposes a fundamental deficiency of the current nonrelativistic models. In most cases the occurrence of spherical shell closures is found to be nucleon-number dependent. Spherical doubly magic superheavy nuclei are found at 184298114, 172292120, or 184310126 depending on the parametrization. The Z=114 proton shell closure, which is related to a large spin-orbit splitting of proton 2f states, is predicted only by forces which by far overestimate the proton spin-orbit splitting in 208Pb. The Z=120 and N=172 shell closures predicted by the relativistic models and some Skyrme interactions are found to be related to a central depression of the nuclear density distribution. This effect cannot appear in macroscopic-microscopic models or semiclassical approaches like the extended Thomas-Fermi-Strutinski integral approach which have a limited freedom for the density distribution only. In summary, our findings give a strong argument for 172292120 to be the next spherical doubly magic superheavy nucleus

Retinoic acid inhibits the fixation of initial transformational damage in X-irradiated Balb/3T3 mouse fibroblasts in vitro

We have examined the effects of all-trans retinoic acid (RA) on confluent holding recovery (cell survival) and on the fixation of initial transformational damage expressed as the ultimate yield of transformed foci following X-irradiation of density-inhibited cultures of Balb/3T3 cells. Non-cytotoxic concentrations of RA suppressed both recovery of potentially lethal damage and neoplastic transformation in a dosedependent manner when added for 24 h during postirradiation confluent holding after a dose of 5 Gy. At 100 μM, RA inhibited the fixation of initial transformational damage by 80%. These findings are discussed in terms of the hypothesis that retinoids may allow a selective enhancement of the inactivation of certain irradiated tumor cells in vivo while reducing the risk of secondary malignancies in successfully treated patient

Pairing gaps from nuclear mean-field models

We discuss the pairing gap, a measure for nuclear pairing correlations, in chains of spherical, semi-magic nuclei in the framework of self-consistent nuclear mean-field models. The equations for the conventional BCS model and the approximate projection-before-variation Lipkin-Nogami method are formulated in terms of local density functionals for the effective interaction. We calculate the Lipkin-Nogami corrections of both the mean-field energy and the pairing energy. Various definitions of the pairing gap are discussed as three-point, four-point and five-point mass-difference formulae, averaged matrix elements of the pairing potential, and single-quasiparticle energies. Experimental values for the pairing gap are compared with calculations employing both a delta pairing force and a density-dependent delta interaction in the BCS and Lipkin-Nogami model. Odd-mass nuclei are calculated in the spherical blocking approximation which neglects part of the the core polarization in the odd nucleus. We find that the five-point mass difference formula gives a very robust description of the odd-even staggering, other approximations for the gap may differ from that up to 30% for certain nuclei.Comment: 17 pages, 8 figures. Accepted for publication in EPJ

Pest Management Recommendations for Dairy Cattle

NYS IPM Type: Livestock RecommendsNYS IPM Type: Livestock Fact SheetA variety of insect and mite pests affect the dairy industry in the Northeast. House flies, stable flies, face flies, horn flies, horse flies, deer flies, cattle grubs, lice, and mange mites all are common and significant pests of cattle

Einflussfaktoren auf Soziale und Gesellschaftliche Lernprozesse im Wissenssystem Biolandbau

Improved organic farming methods that enable more sustainable use of natural resources are numerous and are applied in almost every region of this planet. However, when it comes to spreading and adapting these methods to specific ecological and socio-economic contexts, we know only little about what factors influence the learning processes involved. This study aims at a thorough assessment of factors that are enabling or hindering knowledge co-production in organic farming in general and of sustainable rice farming in particular. Following a qualitative multilevel analysis, special emphasis is placed on understanding how the socio-economic, cultural and ecological context is constituted (macro-level), how key stakeholder groups collaborate and enhance societal and social learning processes (meso-level), and to what degree these processes lead to enhancement and integration of organic rice farming methods in the farmers’ livelihood systems (micro-level). Case studies in South Korea and Cambodia show that capacity building and institutionalization of key actors such as farmer promoters and farmer researchers, as well as farmer group maintenance with diverse incentives for sustained participation are vital enabling factors

Screening for bid-rigging - does it work?

This paper proposes a method to detect bid-rigging by applying mutually reinforcing screens to a road construction procurement data set from Switzerland in which no prior information about collusion was available. The screening method is particularly suited to deal with the problem of partial collusion, i.e. collusion which does not involve all firms and/or all contracts in a specific data set, implying that many of the classical markers discussed in the corresponding literature will fail to identify bid-rigging. In addition to presenting a new screen for collusion, it is shown how benchmarks and the combination of different screens may be used to identify subsets of suspicious contracts and firms in a data set. The discussed screening method succeeds in isolating a group of “suspicious” firms exhibiting the characteristics of a local bid-rigging cartel operating with cover bids and a – more or less pronounced – bid rotation scheme. Based on these findings the Swiss Competition Commission (ComCo) decided to open an investigation

Potential energy surfaces of superheavy nuclei

We investigate the structure of the potential energy surfaces of the superheavy nuclei 158258Fm100, 156264Hs108, 166278112, 184298114, and 172292120 within the framework of self-consistent nuclear models, i.e., the Skyrme-Hartree-Fock approach and the relativistic mean-field model. We compare results obtained with one representative parametrization of each model which is successful in describing superheavy nuclei. We find systematic changes as compared to the potential energy surfaces of heavy nuclei in the uranium region: there is no sufficiently stable fission isomer any more, the importance of triaxial configurations to lower the first barrier fades away, and asymmetric fission paths compete down to rather small deformation. Comparing the two models, it turns out that the relativistic mean-field model gives generally smaller fission barriers

Evaluation of Two Parasitoids in Dairy Calf Greenhouses

Parasitoids are a critical component of a successful dairy IPM program.  In the first year of this two-year study we compared individual species parasitoid releases.  During Year 2 we compared the best individual parasitoid from Year 1 (M. raptorellus) to a 50:50 ratio of M. raptor and M. raptorellus