1,290 research outputs found
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
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.
An HFB scheme in natural orbitals
We present a formulation of the Hartree-Fock-Bogoliubov (HFB) equations which
solves the problem directly in the basis of natural orbitals. This provides a
very efficient scheme which is particularly suited for large scale calculations
on coordinate-space grids.Comment: 5 pages RevTeX, (Postscript-file also available at
http://www.th.physik.uni-frankfurt.de/~bender/nucl_struct_publications.html
or at ftp://th.physik.uni-frankfurt.de/pub/bender ), accepted for publication
in Z. Phys.
Pest Flies of Pastured Cattle and Horses
NYS IPM Type: Livestock Fact SheetIntegrated pest management (IPM) of pest flies, midges, and mosquitoes of pastured cattle and Horses incorporates several key components: correct arthropod pest identification, monitoring, management action (i.e., treatment), and evaluation of the action. This fact sheet is intended to help the livestock producer identify arthropod pests and not to be a how-to document. For information on the other steps to successful pest management please consult one or more of the suggested readings or web sites provided in the references section
Integrated Management of Flies in and around Dairy and Livestock Barns
NYS IPM Type: Livestock Fact SheetIn the past, management of flies in dairy and livestock barns often relied solely on insecticide use. But this single-tactic approach can aggravate fly populations' resistance to insecticides and inadvertently destroy natural enemies of flies. Today successful farmers are combining careful use of pesticides with other integrated pest management (IPM) practices
Seasonal Variation in Carcinops pumilio (Coleoptera: Histeridae) Dispersal and Potential for Suppression of Dispersal Behavior
Seasonal dispersal of Carcinops pumilio (Erichson) was evaluated using two trapping methods-a black-light pitfall trap and a mesh-bottomed trap placed on poultry manure. The black-light trap collected larger numbers than the mesh-bottomed trap from March through June. The mesh-bottomed trap gathered larger numbers of beetles from June through August and numbers were less variable throughout the year. Often, when very low numbers of beetles were recovered from manure cores, large numbers of beetles could be collected with the black-light trap suggesting that beetle density may not be an important factor in dispersal behavior. The greatest dispersal in the dispersal arenas (≈90%) occurred using beetles collected by both trap types in June 2000. Beginning in March and ending in August, a cyclic rise and then fall pattern in both laboratory dispersal and beetle collections was observed. Trap collection patterns were similar in both years of the study. In January and March, we were unable to prevent dispersal behavior of beetles captured in black-light traps. However, in May, after beetles had been in a dispersal phase for several months, we were able to suppress dispersal. In contrast, dispersal behavior among beetles captured with the mesh-bottomed trap did not change following the photoperiod-altered exposur
House Fly (Musca domestica L.) Survival after Mechanical Incorporation of Poultry Manure into Field Soil
Land application is often a routine part of manure management. Not only is it a practical means of disposing large amounts of poultry wastes, it is an efficient use of an organic fertilizer. Unfortunately, poultry manure may contain a large number of house fly larvae and pupae that can become a nuisance if they complete development. Mechanical incorporation of poultry manure is often recommended to help reduce odor; it has also been though to reduce the potential for a fly outbreak. This study examined fly survival following burial in field soil at depths of 0, 1, 3, 6, 9, and 12 in. One quarter of the adult house flies developing from pupae were able to crawl through 12 in. of soil to reach the surface. Survival of flies buried closer to the surface was greater. We compared house fly survival following disk, harrow, and moldboard plow incorporation of manure to surface application. No method of incorporation was better than the surface application. Adult flies reached outbreak proportions 10 days following application and the outbreak lasted another 11 day
Individual and Combined Releases of Muscidifurax raptor and M. raptorellus (Hymenoptera: Pteromalidae) as a Biological Control Tactic Targeting House Flies in Dairy Calf Facilities
The impact of commercially reared house fly parasitoids released into nine dairy calf coverall facilities were evaluated over 3 yr. Individual and equally mixed ratios of the pteromalid parasitoids Muscidifurax raptor Girault and Saunders and M. raptorellus Kogan and Legner were released at a rate of 500 parasitoids per calf per week for 8 wk. Prerelease, release, and postrelease parasitism was monitored using nearly 100,000 sentinel house fly, Musca domestica L., pupae during the 3 yr study. In general, very few adult parasitoids were recovered during the prerelease period and on the no-release farms during any period. However, considerable numbers of M. raptor and M. raptorellus were recovered from sentinel pupae on respective release farms. As expected, the greatest successful parasitism occurred during release periods, with a drop during postrelease periods. High successful parasitism and uneclosed pupae on M. raptorellus release farms suggests that this parasitoid was aggressive in attacking hosts with progeny production at approximately four wasps per pupa. Solitary releases of M. raptor provided sentinel mortality between 31 and 38%, whereas sentinel mortality on M. raptorellus-release farms was double, at 59-80%. Using mixed releases of the two species, overall fly mortality was slightly lower than that observed on M. raptorellus-only farms. This study documents the advantage of releasing M. raptorellus rather than M. raptor on New York dairy calf facilities, as supported by higher parasitism rates and lower costs (35-75%) for purchase of these gregarious wasps, as 75-80% fewer parasitized pupae are needed to achieve similar adult parasitoid level
Potential energy surfaces of superheavy nuclei
We investigate the structure of the potential energy surfaces of the
superheavy nuclei 258Fm, 264Hs, (Z=112,N=166), (Z=114,N=184), and (Z=120,N=172)
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 parametrisation 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.Comment: 8 pages RevTeX, 6 figure
Nuclear Ground State Observables and QCD Scaling in a Refined Relativistic Point Coupling Model
We present results obtained in the calculation of nuclear ground state
properties in relativistic Hartree approximation using a Lagrangian whose
QCD-scaled coupling constants are all natural (dimensionless and of order 1).
Our model consists of four-, six-, and eight-fermion point couplings (contact
interactions) together with derivative terms representing, respectively, two-,
three-, and four-body forces and the finite ranges of the corresponding mesonic
interactions. The coupling constants have been determined in a self-consistent
procedure that solves the model equations for representative nuclei
simultaneously in a generalized nonlinear least-squares adjustment algorithm.
The extracted coupling constants allow us to predict ground state properties of
a much larger set of even-even nuclei to good accuracy. The fact that the
extracted coupling constants are all natural leads to the conclusion that QCD
scaling and chiral symmetry apply to finite nuclei.Comment: 44 pages, 13 figures, 9 tables, REVTEX, accepted for publication in
Phys. Rev.
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