2,504 research outputs found
Curculionidae and Chrysomelidae Found in Aquatic Habitats in Wisconsin
(excerpt)
We became interested in aquatic weevils (Curculionidae) and leaf beetles (Chryso- melidae) during the Aquatic Entomology Course at the University of Wisconsin, in the
spring of 1971. Many collections, taken from a variety of aquatic habitats in Wisconsin, contained weevils and leaf beetles. Most of the species were not fully treated in the keys found in aquatic entomology texts. We thought it would be useful to compile keys from the literature and present what is known of the distribution of these insects in Wisconsin. Nine species of weevils have been found in aquatic habitats in Wisconsin, representing seven genera, all belonging to the subtribe Hydronomi, and twenty-five species of leaf beetles, representing five genera in three subfamilies
Dirac Hartree-Fock for Finite Nuclei Employing realistic Forces
We discuss two different approximation schemes for the self-consistent
solution of the {\it relativistic} Brueckner-Hartree-Fock equation for finite
nuclei. In the first scheme, the Dirac effects are deduced from corresponding
nuclear matter calculations, whereas in the second approach the local-density
approximation is used to account for the effects of correlations. The results
obtained by the two methods are very similar. Employing a realistic
one-boson-exchange potential (Bonn~A), the predictions for energies and radii
of O and Ca come out in substantially better agreement with
experiment as compared to non-relativistic approaches. As a by-product of our
study, it turns out that the Fock exchange-terms, ignored in a previous
investigation, are not negligible.Comment:
Relativistic Equation of State of Nuclear Matter for Supernova and Neutron Star
We construct the equation of state (EOS) of nuclear matter using the
relativistic mean field (RMF) theory in the wide density, temperature range
with various proton fractions for the use of supernova simulation and the
neutron star calculations. We first construct the EOS of homogeneous nuclear
matter. We use then the Thomas-Fermi approximation to describe inhomogeneous
matter, where heavy nuclei are formed together with free nucleon gas. We
discuss the results on free energy, pressure and entropy in the wide range of
astrophysical interest. As an example, we apply the resulting EOS on the
neutron star properties by using the Oppenheimer-Volkoff equation.Comment: 15 pages, LaTeX, 14 ps-figures, accepted for publication in
Nucl.Phys.
Spin-orbit coupling in nuclei and realistic nucleon-nucleon potentials
We analyze the spin-orbit coupling term in the nuclear energy density
functional in terms of a zero-range NN-contact interaction and finite-range
contributions from two-pion exchange. We show that the strength of the
spin-orbit contact interaction as extracted from high-precision nucleon-nucleon
potentials is in perfect agreement with that of phenomenological Skyrme forces
employed in non-relativistic nuclear structure calculations. Additional
long-range contributions from chiral two-pion exchange turn out to be
relatively small. These explicitly density-dependent contributions reduce the
ratio of the isovector to the isoscalar spin-orbit strength significantly below
the Skyrme value 1/3. We perform a similar analysis for the strength function
of the -term and find values not far from those of
phenomenological Skyrme parameterizations.Comment: 10 pages, 3 figures, accepted for publication in Physical Review C70
(2004
Relativistic Structure of the Nucleon Self-Energy in Asymmetric Nuclei
The Dirac structure of the nucleon self-energy in asymmetric nuclear matter
cannot reliably be deduced from the momentum dependence of the single-particle
energies. It is demonstrated that such attempts yield an isospin dependence
with even a wrong sign. Relativistic studies of finite nuclei have been based
on such studies of asymmetric nuclear matter. The effects of these isospin
components on the results for finite nuclei are investigated.Comment: 9 pages, Latex 4 figures include
Thematic mapper research in the earth sciences: Small scale patches of suspended matter and phytoplankton in the Elbe River Estuary, German Bight and Tidal Flats
A Thematic Mapper (TM) field experiment was followed by a data analysis to determine TM capabilities for analysis of suspended matter and phytoplankton. Factor analysis showed that suspended matter concentration, atmospheric scattering, and sea surface temperature can be retrieved as independent factors which determine the variation in the TM data over water areas. Spectral channels in the near infrared open the possibility of determining the Angstrom exponent better than for the coastal zone color scanner. The suspended matter distribution may then be calculated by the absolute radiance of channel 2 or 3 or the ratio of both. There is no indication of whether separation of chlorophyll is possible. The distribution of suspended matter and sea surface temperature can be observed with the expected fine structure. A good correlation between water depth and suspended matter distribution as found from ship data can now be analyzed for an entire area by the synoptic view of the TM scenes
Joint assembly and genetic mapping of the Atlantic horseshoe crab genome reveals ancient whole genome duplication
Horseshoe crabs are marine arthropods with a fossil record extending back
approximately 450 million years. They exhibit remarkable morphological
stability over their long evolutionary history, retaining a number of ancestral
arthropod traits, and are often cited as examples of "living fossils." As
arthropods, they belong to the Ecdysozoa}, an ancient super-phylum whose
sequenced genomes (including insects and nematodes) have thus far shown more
divergence from the ancestral pattern of eumetazoan genome organization than
cnidarians, deuterostomes, and lophotrochozoans. However, much of ecdysozoan
diversity remains unrepresented in comparative genomic analyses. Here we use a
new strategy of combined de novo assembly and genetic mapping to examine the
chromosome-scale genome organization of the Atlantic horseshoe crab Limulus
polyphemus. We constructed a genetic linkage map of this 2.7 Gbp genome by
sequencing the nuclear DNA of 34 wild-collected, full-sibling embryos and their
parents at a mean redundancy of 1.1x per sample. The map includes 84,307
sequence markers and 5,775 candidate conserved protein coding genes. Comparison
to other metazoan genomes shows that the L. polyphemus genome preserves
ancestral bilaterian linkage groups, and that a common ancestor of modern
horseshoe crabs underwent one or more ancient whole genome duplications (WGDs)
~ 300 MYA, followed by extensive chromosome fusion
Effective DBHF Method for Asymmetric Nuclear Matter and Finite Nuclei
A new decomposition of the Dirac structure of nucleon self-energies in the
Dirac Brueckner-Hartree-Fock (DBHF) approach is adopted to investigate the
equation of state for asymmetric nuclear matter. The effective coupling
constants of , , and mesons with a density
dependence in the relativistic mean field approach are deduced by reproducing
the nucleon self-energy resulting from the DBHF at each density for symmetric
and asymmetric nuclear matter. With these couplings the properties of finite
nuclei are investigated. The agreement of charge radii and binding energies of
finite nuclei with the experimental data are improved simultaneously in
comparison with the projection method. It seems that the properties of finite
nuclei are sensitive to the scheme used for the DBHF self-energy extraction. We
may conclude that the properties of the asymmetric nuclear matter and finite
nuclei could be well described by the new decomposition approach of the G
matrix.Comment: 16 pages, 5 figure
Quark mean field model with density dependent couplings for finite nuclei
The quark mean field model, which describes the nucleon using the constituent
quark model, is applied to investigate the properties of finite nuclei. The
couplings of the scalar and vector mesons with quarks are made density
dependent through direct coupling to the scalar field so as to reproduce the
relativistic Brueckner-Hartree-Fock results of nuclear matter. The present
model provides satisfactory results on the properties of spherical nuclei, and
predicts an increasing size of the nucleon as well as a reduction of the
nucleon mass in the nuclear environmentComment: 8 pages, REVTeX, 8 ps figures, accepted for publication in Phys. Rev.
STEPS - an approach for human mobility modeling
In this paper we introduce Spatio-TEmporal Parametric Stepping (STEPS) - a simple parametric mobility model which can cover a large spectrum of human mobility patterns. STEPS makes abstraction of spatio-temporal preferences in human mobility by using a power law to rule the nodes movement. Nodes in STEPS have preferential attachment to favorite locations where they spend most of their time. Via simulations, we show that STEPS is able, not only to express the peer to peer properties such as inter-ontact/contact time and to reflect accurately realistic routing performance, but also to express the structural properties of the underlying interaction graph such as small-world phenomenon. Moreover, STEPS is easy to implement, exible to configure and also theoretically tractable
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