16,415 research outputs found
Neutron-skin thickness of finite nuclei in relativistic mean-field models with chiral limits
We study several structure properties of finite nuclei using relativistic
mean-field Lagrangians constructed according to the Brown-Rho scaling due to
the chiral symmetry restoration at high densities. The models are consistent
with current experimental constraints for the equations of state of symmetric
matter at both normal and supra-normal densities and of asymmetric matter at
sub-saturation densities. It is shown that these models can successfully
describe the binding energies and charge radii of finite nuclei. Compared to
calculations with usual relativistic mean-field models, these models give a
reduced thickness of neutron skin in ^{208}Pb between 0.17 fm and 0.21 fm. The
reduction of the predicted neutron skin thickness is found to be due to not
only the softening of the symmetry energy but also the scaling property of
meson required by the partial restoration of chiral symmetry.Comment: Accepted version to appear in PRC (2007
Small radii of neutron stars as an indication of novel in-medium effects
At present, neutron star radii from both observations and model predictions
remain very uncertain. Whereas different models can predict a wide range of
neutron star radii, it is not possible for most models to predict radii that
are smaller than about 10 km, thus if such small radii are established in the
future they will be very difficult to reconcile with model estimates. By
invoking a new term in the equation of state that enhances the energy density,
but leaves the pressure unchanged we simulate the current uncertainty in the
neutron star radii. This new term can be possibly due to the exchange of the
weakly interacting light U-boson with appropriate in-medium parameters, which
does not compromise the success of the conventional nuclear models. The
validity of this new scheme will be tested eventually by more precise
measurements of neutron star radii.Comment: EPJA (2015) in pres
Large-mass neutron stars with hyperonization
Within a density-dependent relativistic mean-field model using in-medium
meson-hadron coupling constants and meson masses, we explore effects of
in-medium hyperon interactions on properties of neutron stars. It is found that
the hyperonic constituents in large-mass neutron stars can not be simply ruled
out, while the recently measured mass of the millisecond pulsar J1614-2230 can
constrain significantly the in-medium hyperon interactions. Moreover, effects
of nuclear symmetry energy on hyperonization in neutron stars are also
discussed
Effects of medium-induced meson mixing on the equation of state in isospin-asymmetric nuclear matter
We reexamine effects of the meson mixing mediated by nucleon
polarizations on the symmetry energy in isospin-asymmetric nuclear matter.
Taking into account the rearrangement term neglected in previous studies by
others, we evaluate the mixing angle in a novel way within the
Relativistic Mean-Field Models with and without chiral limits. It is found that
the symmetry energy is significantly softened at high densities contrary to the
finding in earlier studies. As the first step of going beyond the lowest-order
calculations, we also solve the RPA equation for the mixing. In
this case, it is found that the symmetry energy is not only significantly
softened by the mixing at supra-saturation densities, similar to
the lowest-order mixing, but interestingly also softened at
subsaturation densities. In addition, the softening of the symmetry energy at
subsaturation densities can be partly suppressed by the nonlinear
self-interaction of the meson.Comment: Significant changes made. Accepted version to appear in PRC (2009
Real-time Data Flow Control for CBM-TOF Super Module Quality Evaluation
Super module assembled with MRPC detectors is the component unit of TOF (Time
of Flight) system for the Compressed Baryonic Matter (CBM) experiment. Quality
of super modules needs to be evaluated before it is applied in CBM-TOF. Time
signals exported from super module are digitalized at TDC (Time to Digital
Converter) station. Data rate is up to 6 Gbps at each TDC station, which brings
a tremendous pressure for data transmission in real time. In this paper, a
real-time data flow control method is designed. In this control method, data
flow is divided into 3 types: scientific data flow, status data flow and
control data flow. In scientific data flow, data of each TDC station is divided
into 4 sub-flows, and then is read out by a parallel and hierarchical network,
which consists of multiple readout mother boards and daughter boards groups. In
status data flow, status data is aggregated into a specific readout mother
board. Then it is uploaded to DAQ via readout daughter board. In control data
flow, control data is downloaded to all circuit modules in the opposite
direction of status data flow. Preliminary test result indicated data of STS
was correctly transmitted to DAQ with no error and three type data flows were
control orderly in real time. This data flow control method can meet the
quality evaluation requirement of supper module in CBM-TOF
Withaferin A promotes proliferation and migration of brain endothelial cells
Purpose: To investigate the effect of withaferin A (WFA) on the proliferation and migration of brain endothelial cells.Methods: BALB-5023 mouse microvascular cells were treated with a range of withaferin A (WFA) concentrations from 10 to 100 ng/mL. Dojindo’s CCK-8 cell proliferation kit was used for the analysis of cell proliferation. Transwell cell culture inserts were used to determine the migration potential of WFAtreated endothelial cells. Absorbance was measured at 450 nm on an enzyme-linked immunosorbent(ELISA) reader.Results: The results revealed a significant increase in the proliferation and migration of endothelial cells following treatment with a low concentration (30 ng/mL) of WFA compared with the higher concentration (> 10 ng/mL). The effect was further enhanced when WFA was used in combination with soluble Fas ligand (sFasL). Autocrine signaling of vascular endothelial growth factor (VEGF) by endothelial cellswas significantly increased following treatment with WFA or in combination with sFasL. WFA increased the expression of Fas on endothelial cells, suggesting the involvement of sFasL in the proliferation and migration of brain endothelial cells.Conclusion: Thus, WFA promotes the proliferation and migration of endothelial cells through increase in the expression of Fas and secretion of VEGF.Keywords: Endothelial cells, Vascular endothelial growth factor, Microvascular, Vascular disease, Withaferin
Mean free paths and in-medium scattering cross sections of energetic nucleons in neutron-rich nucleonic matter within the relativistic impulse approximation
The mean free paths and in-medium scattering cross sections of energetic
nucleons in neutron-rich nucleonic matter are investigated using the nucleon
optical potential obtained within the relativistic impulse approximation with
the empirical nucleon-nucleon scattering amplitudes and the nuclear densities
obtained in the relativistic mean field model. It is found that the
isospin-splitting of nucleon mean free paths, sensitive to the imaginary part
of the symmetry potential, changes its sign at certain high kinetic energy. The
in-medium nucleon-nucleon cross sections are analytically and numerically
demonstrated to be essentially independent of the isospin asymmetry of the
medium and increase linearly with density in the high energy region where the
relativistic impulse approximation is applicable.Comment: 13 pages, 6 figure
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