1,584 research outputs found
Evolutionary history and identification of conservation units in the giant otter, Pteronura brasiliensis.
The giant otter, Pteronura brasiliensis, occupies a range including the major drainage basins of South America, yet the degree of structure that exists within and among populations inhabiting these drainages is unknown. We sequenced portions of the mitochondrial DNA (mtDNA) cytochrome b (612 bp) and control region (383 bp) genes in order to determine patterns of genetic variation within the species. We found high levels of mtDNA haplotype diversity (h = 0.93 overall) and support for subdivision into four distinct groups of populations, representing important centers of genetic diversity and useful units for prioritizing conservation within the giant otter. We tested these results against the predictions of three hypotheses of Amazonian diversification (Pleistocene Refugia, Paleogeography, and Hydrogeology). While the phylogeographic pattern conformed to the predictions of the Refugia Hypothesis, molecular dating using a relaxed clock revealed the phylogroups diverged from one another between 1.69 and 0.84 Ma, ruling out the influence of Late Pleistocene glacial refugia. However, the role of Plio-Pleistocene climate change could not be rejected. While the molecular dating also makes the influence of geological arches according to the Paleogeography Hypothesis extremely unlikely, the recent Pliocene formation of the Fitzcarrald Arch and its effect of subsequently altering drainage pattern could not be rejected. The data presented here support the interactions of both climatic and hydrological changes resulting from geological activity in the Plio-Pleistocene, in shaping the phylogeographic structure of the giant otter
Lambda-proton correlations in relativistic heavy ion collisions
The prospect of using lambda-proton correlations to extract source sizes in
relativistic heavy ion collisions is investigated. It is found that the strong
interaction induces a large peak in the correlation function that provides more
sensitive source size measurements than two-proton correlations under some
circumstances. The prospect of using lambda-proton correlations to measure the
time lag between lambda and proton emissions is also studied.Comment: 4 pages, 3 figure, revtex style. Two short paragraphs are added at
referees' recommendations. Phys. Rev. Lett. in pres
Ecologia de populações de porco monteiro no Pantanal do Brasil
O porco monteiro chegou ao Pantanal há cerca de dois séculos e, desde então, tem sido considerado como a principal espécie cinegética (de interesse para a caça) na região. Suas populações vivem livres na planície e independentes da atividade humana, exceto pelo manejo tradicional que age como fator de controle populacional dos rebanhos. Considerando que a espécie apresenta potencial para utilização econômica e que pode vir a compor a pauta de produtos com certificação de origem no Pantanal, informações sobre a ecologia das populações presentes na planície são estratégicas. Este artigo apresenta um apanhado sobre as informações disponíveis a respeito da espécie e discute aspectos da dinâmica de suas populações, com base em projeções obtidas utilizando-se o software VORTEX 9.6.bitstream/CPAP-2010/57340/1/DOC106.pd
Effective Field Theory for Bulk Properties of Nuclei
Recent progress in Lorentz-covariant quantum field theories of the nuclear
many-body problem ({\em quantum hadrodynamics}, or QHD) is discussed. The
importance of modern perspectives in effective field theory and density
functional theory for understanding the successes of QHD is emphasized. The
inclusion of hadronic electromagnetic structure and of nonanalytic terms in the
energy functional is also considered.Comment: 11 pages, 0 figures, REVTeX 3.0; Invited talk at the 11th Conference
on Recent Progress in Many-Body Theories (MB 11), Manchester, UK, July 9--13,
200
Phenomenological Lambda-Nuclear Interactions
Variational Monte Carlo calculations for (ground and
excited states) and are performed to decipher information on
-nuclear interactions. Appropriate operatorial nuclear and
-nuclear correlations have been incorporated to minimize the
expectation values of the energies. We use the Argonne two-body
NN along with the Urbana IX three-body NNN interactions. The study demonstrates
that a large part of the splitting energy in () is
due to the three-body NN forces. hypernucleus is
analyzed using the {\it s}-shell results. binding to nuclear matter
is calculated within the variational framework using the
Fermi-Hypernetted-Chain technique. There is a need to correctly incorporate the
three-body NN correlations for binding to nuclear matter.Comment: 18 pages (TeX), 2 figure
Variational calculations of the -seperation energy of the O hypernucleus
Variational Monte Carlo calculations have been made for the O hypernucleus using realistic two- and three-baryon
interactions. A two pion exchange potential with spin- and space-exchange
components is used for the N potential. Three-body two-pion exchange
and strongly repulsive dispersive NN interactions are also included.
The trial wave function is constructed from pair- and triplet-correlation
operators acting on a single particle determinant. These operators consist of
central, spin, isospin, tensor and three- baryon potential components. A
cluster Monte Carlo method is developed for noncentral correlations and is used
with up to four-baryon clusters in our calculations. The three-baryon
NN force is discussed.Comment: 24 pages, 2 figs available by fax., for publication in Phys. Rev.
Detectability of Strange Matter in Heavy Ion Experiments
We discuss the properties of two distinct forms of hypothetical strange
matter, small lumps of strange quark matter (strangelets) and of hyperon matter
(metastable exotic multihypernuclear objects: MEMOs), with special emphasis on
their relevance for present and future heavy ion experiments. The masses of
small strangelets up to A = 40 are calculated using the MIT bag model with
shell mode filling for various bag parameters. The strangelets are checked for
possible strong and weak hadronic decays, also taking into account multiple
hadron decays. It is found that strangelets which are stable against strong
decay are most likely highly negative charged, contrary to previous findings.
Strangelets can be stable against weak hadronic decay but their masses and
charges are still rather high. This has serious impact on the present high
sensitivity searches in heavy ion experiments at the AGS and CERN facilities.
On the other hand, highly charged MEMOs are predicted on the basis of an
extended relativistic mean-field model. Those objects could be detected in
future experiments searching for short-lived, rare composites. It is
demonstrated that future experiments can be sensitive to a much wider variety
of strangelets.Comment: 26 pages, 5 figures, uses RevTeX and epsf.st
Relativistic Mean Field Approximation in a Density Dependent Parametrization Model at Finite Temperature
In this work we calculate the equation of state of nuclear matter for
different proton fractions at zero and finite temperature within the Thomas
Fermi approach considering three different parameter sets: the well-known NL3
and TM1 and a density dependent parametrization proposed by Typel and Wolter.
The main differences are outlined and the consequences of imposing
beta-stability in these models are discussed.Comment: 13 pages, 10 figure
The extended, relativistic hyperon star model
In this paper an equation of state of neutron star matter which includes
strange baryons in the framework of Zimanyi and Moszkowski (ZM) model has been
obtained. We concentrate on the effects of the isospin dependence of the
equation of state constructing for the appropriate choices of parameters the
hyperons star model. Numerous neutron star models show that the appearance of
hyperons is connected with the increasing density in neutron star interiors.
Various studies have indicated that the inclusion of delta meson mainly affects
the symmetry energy and through this the chemical composition of a neutron
star. As the effective nucleon mass contributes to hadron chemical potentials
it alters the chemical composition of the star. In the result the obtained
model of the star not only excludes large population of hadrons but also does
not reduce significantly lepton contents in the star interior.Comment: 22 pages, revtex4, 13 figure
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