228 research outputs found
C-banding And Fish In Chromosomes Of The Blow Flies Chrysomya Megacephala And Chrysomya Putoria (diptera, Calliphoridae).
The blow flies Chrysomya putoria and C. megacephala have 2n=12 chromosomes, five metacentric pairs of autosomes and an XX/XY sex chromosome pair. There are no substantial differences in the karyotype morphology of these two species, except for the X chromosome which is subtelocentric in C. megacephala and metacentric in C. putoria and is about 1.4 times longer in C. putoria. All autosomes were characterized by the presence of a C band in the pericentromeric region; C. putoria also has an interstitial band in pair III. The sex chromosomes of both species were heterochromatic, except for a small region at the end of the long arm of the X chromosome. Ribosomal genes were detected in meiotic chromosomes by FISH and in both species the NOR was located on the sex chromosomes. These results confirm that C. putoria was the species introduced into Brazil in 1970s, and not C. chloropyga as formerly described.96371-
Collective modes in relativistic npe matter at finite temperature
Isospin and density waves in neutral neutron-proton-electron (npe) matter are
studied within a relativistic mean-field hadron model at finite temperature
with the inclusion of the electromagnetic field. The dispersion relation is
calculated and the collective modes are obtained. The unstable modes are
discussed and the spinodals, which separate the stable from the unstable
regions, are shown for different values of the momentum transfer at various
temperatures. The critical temperatures are compared with the ones obtained in
a system without electrons. The largest critical temperature, 12.39 MeV, occurs
for a proton fraction y_p=0.47. For y_p=0.3 we get =5 MeV and for
y_p>0.495 MeV.
It is shown that at finite temperature the distillation effect in asymmetric
matter is not so efficient and that electron effects are particularly important
for small momentum transfers.Comment: 10 pages, 6 figure
Instabilities in asymmetric nuclear matter
The existence of phase transitions from liquid to gas phases in asymmetric
nuclear matter (ANM) is related with the instability regions which are limited
by the spinodals. In this work we investigate the instabilities in ANM
described within relativistic mean field hadron models, both with constant and
density dependent couplings at zero and finite temperatures. In calculating the
proton and neutron chemical potentials we have used an expansion in terms of
Bessel functions that is convenient at low densities. The role of the isovector
scalar -meson is also investigated in the framework of relativistic
mean field models and density dependent hadronic models. It is shown that the
main differences occur at finite temperature and large isospin asymmetry close
to the boundary of the instability regions.Comment: 13 pages, 5 figures; to appear in Phys. Rev.
Light clusters and the pasta phase
The effects of including light clusters in nuclear matter at low densities
are investigated within four different parametrizations of relativistic models
at finite temperature. Both homogeneous and inhomogeneous matter (pasta phase)
are described for neutral nuclear matter with fixed proton fractions. We
discuss the effect of the density dependence of the symmetry energy, the
temperature and the proton fraction on the non-homogeneous matter forming the
inner crust of proto-neutron stars. It is shown that the number of nucleons in
the clusters, the cluster proton fraction and the sizes of the Wigner Seitz
cell and of the cluster are very sensitive to the density dependence of the
symmetry energy.Comment: 14 pages, 14 figures; Accepted for publication in Phys. Rev.
Compositeness effects, Pauli's principle and entanglement
We analyse some compositeness effects and their relation with entanglement.
We show that the purity of a composite system increases, in the sense of the
expectation values of the deviation operators, with large values of the
entanglement between the components of the system. We also study the validity
of Pauli's principle in composite systems. It is valid within the limits of
application of the approach presented here. We also present an example of two
identical fermions, one of them entangled with a distinguishable particle,
where the exclusion principle cannot be applied. This result can be important
in the description of open systems
Relativistic Mean-Field Hadronic Models under Nuclear Matter Constraints
Relativistic mean-field (RMF) models have been widely used in the study of
many hadronic frameworks because of several important aspects not always
present in nonrelativistic models, such as intrinsic Lorentz covariance,
automatic inclusion of spin, appropriate saturation mechanism for nuclear
matter, causality and, therefore, no problems related to superluminal speed of
sound. With the aim of identifying the models which best satisfy well known
properties of nuclear matter, we have analyzed parameterizations of seven
different types of RMF models under three different sets of constraints related
to symmetric nuclear matter, pure neutron matter, symmetry energy, and its
derivatives. One of these (SET1) is formed of the same constraints used in a
recent work [M. Dutra et al., Phys. Rev. C 85, 035201 (2012)] in which we
analyzed Skyrme parameterizations. The results pointed to models
consistent with all constraints. By using another set of constraints, namely,
SET2a, formed by the updated versions of the previous one, we found models
approved simultaneously. Finally, in the third set, named SET2b, in which the
values of the constraints are more restrictive, we found consistent models.
Another interesting feature of our analysis is that the results change
dramatically if we do not consider the constraint regarding the volume part of
the isospin incompressibility (). In this case, we have
approved models in SET2a and in SET2b.Comment: 63 pages, 3 figures and 9 tables. Version accepted for publication in
PR
Density Dependent Parametrization Models: Formalism and Applications
In this work we derive a formalism to incorporate asymmetry and temperature
effects in the Brown-Rho (BR) scaled lagrangian model in a mean field theory.
The lagrangian density discussed in this work requires less parameters than the
usual models with density dependent couplings. We also present the formalism
with the inclusion of the eight lightest baryons, two lightest leptons, beta
equilibrium and charge neutrality in order to apply the BR scaled model to the
study of neutron stars. The results are again compared with the ones obtained
from another density dependent parametrization model. The role played by the
rearrangement term at T=0 for nuclear or neutron star matter and at finite
temperature is investigated. The BR scaled model is shown to be a good tool in
studies involving density dependent effective masses and in astrophysics
applications.Comment: 23 pages, 10 figure
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