1,718 research outputs found
Self-consistent treatment of the self-energy in nuclear matter
The influence of hole-hole propagation in addition to the conventional
particle-particle propagation, on the energy per nucleon and the momentum
distribution is investigated. The results are compared to the
Brueckner-Hartree-Fock (BHF) calculations with a continuous choice and
conventional choice for the single-particle spectrum. The Bethe-Goldstone
equation has been solved using realistic interactions. Also, the structure
of nucleon self-energy in nuclear matter is evaluated. All the self-energies
are calculated self-consistently. Starting from the BHF approximation without
the usual angle-average approximation, the effects of hole-hole contributions
and a self-consistent treatment within the framework of the Green function
approach are investigated. Using the self-consistent self-energy, the hole and
particle self-consistent spectral functions including the particle-particle and
hole-hole ladder contributions in nuclear matter are calculated using realistic
interactions. We found that, the difference in binding energy between both
results, i.e. BHF and self-consistent Green function, is not large. This
explains why is the BHF ignored the 2h1p contribution.Comment: Preprint 20 pages including 15 figures and one tabl
Scalar FCNC and rare top decays in a two Higgs doublet model "for the top"
In the so called two Higgs doublet model for the top-quark (T2HDM), first
suggested by Das and Kao, the top quark receives a special status, which endows
it with a naturally large mass, and also potentially gives rise to large flavor
changing neutral currents (FCNC) only in the up-quark sector. In this paper we
calculate the branching ratio (BR) for the rare decays t->ch and h->tc (h is a
neutral Higgs) in the T2HDM, at tree level and at 1-loop when it exceeds the
tree-level. We compare our results to predictions from other versions of 2HDM's
and find that the scalar FCNC in the T2HDM can play a significant role in these
decays. In particular, the 1-loop mediated decays can be significantly enhanced
in the T2HDM compared to the 2HDM of types I and II, in some instances reaching
BR~10^-4 which is within the detectable level at the LHC.Comment: added two references. 15 pages, 14 figure
Properties of asymmetric nuclear matter in different approaches
Properties of asymmetric nuclear matter are derived from various many-body
approaches. This includes phenomenological ones like the Skyrme Hartree-Fock
and relativistic mean field approaches, which are adjusted to fit properties of
nuclei, as well as more microscopic attempts like the Brueckner-Hartree-Fock
approximation, a self-consistent Greens function method and the so-called
approach, which are based on realistic nucleon-nucleon interactions
which reproduce the nucleon-nucleon phase shifts. These microscopic approaches
are supplemented by a density-dependent contact interaction to achieve the
empirical saturation property of symmetric nuclear matter. The predictions of
all these approaches are discussed for nuclear matter at high densities in
-equilibrium. Special attention is paid to behavior of the isovector
component of the effective mass in neutron-rich matter.Comment: 16 pages, 7 figure
Overexpression of the scaffold WD40 protein WRAP53β enhances the repair of and cell survival from DNA double-strand breaks
Altered expression of the multifunctional protein WRAP53β (WD40 encoding RNA Antisense to p53), which targets repair factors to DNA double-strand breaks and factors involved in telomere elongation to Cajal bodies, is linked to carcinogenesis. While loss of WRAP53β function has been shown to disrupt processes regulated by this protein, the consequences of its overexpression remain unclear. Here we demonstrate that overexpression of WRAP53β disrupts the formation of and impairs the localization of coilin to Cajal bodies. At the same time, the function of this protein in the repair of DNA double-strand breaks is enhanced. Following irradiation, cells overexpressing WRAP53β exhibit more rapid clearance of phospho-histone H2AX (γH2AX), and more efficient homologous recombination and non-homologous end-joining, in association with fewer DNA breaks. Moreover, in these cells the ubiquitylation of damaged chromatin, which is known to facilitate the recruitment of repair factors and subsequent repair, is elevated. Knockdown of the ubiquitin ligase involved, ring-finger protein 8 (RNF8), which is recruited to DNA breaks by WRAP53β, attenuated this effect, suggesting that overexpression of WRAP53β leads to more rapid repair, as well as improved cell survival, by enhancing RNF8-mediated ubiquitylation at DNA breaks. Our present findings indicate that WRAP53β and RNF8 are rate-limiting factors in the repair of DNA double-strand breaks and raise the possibility that upregulation of WRAP53β may contribute to genomic stability in and survival of cancer cells
Energy and Momentum densities of cosmological models, with equation of state , in general relativity and teleparallel gravity
We calculated the energy and momentum densities of stiff fluid solutions,
using Einstein, Bergmann-Thomson and Landau-Lifshitz energy-momentum complexes,
in both general relativity and teleparallel gravity. In our analysis we get
different results comparing the aforementioned complexes with each other when
calculated in the same gravitational theory, either this is in general
relativity and teleparallel gravity. However, interestingly enough, each
complex's value is the same either in general relativity or teleparallel
gravity. Our results sustain that (i) general relativity or teleparallel
gravity are equivalent theories (ii) different energy-momentum complexes do not
provide the same energy and momentum densities neither in general relativity
nor in teleparallel gravity. In the context of the theory of teleparallel
gravity, the vector and axial-vector parts of the torsion are obtained. We show
that the axial-vector torsion vanishes for the space-time under study.Comment: 15 pages, no figures, Minor typos corrected; version to appear in
International Journal of Theoretical Physic
Enhancement of the superconducting transition temperature in La2-xSrxCuO4 bilayers: Role of pairing and phase stiffness
The superconducting transition temperature, Tc, of bilayers comprising
underdoped La2-xSrxCuO4 films capped by a thin heavily overdoped metallic
La1.65Sr0.35CuO4 layer, is found to increase with respect to Tc of the bare
underdoped films. The highest Tc is achieved for x = 0.12, close to the
'anomalous' 1/8 doping level, and exceeds that of the optimally-doped bare
film. Our data suggest that the enhanced superconductivity is confined to the
interface between the layers. We attribute the effect to a combination of the
high pairing scale in the underdoped layer with an enhanced phase stiffness
induced by the overdoped film.Comment: Published versio
Nucleotide mutations associated with hepatitis B e antigen negativity
Copyright © 2005 Wiley-Liss, Inc., A Wiley CompanyArticleJOURNAL OF MEDICAL VIROLOGY. 76(2): 170-175 (2005)journal articl
Nuclear Self-energy and Realistic Interactions
The structure of nucleon self-energy in nuclear matter is evaluated for
various realistic models of the nucleon-nucleon (NN) interaction. Starting from
the Brueckner-Hartree-Fock approximation without the usual angle-average
approximation, the effects of hole-hole contributions and a self-consistent
treatment within the framework of the Green function approach are investigated.
Special attention is paid to the predictions for the spectral function
originating from various models of the NN interaction which all yield an
accurate fit for the NN phase shifts.Comment: 26 pages, 12 figure
Three heavy jet events at hadron colliders as a sensitive probe of the Higgs sector
Assuming that a non-standard neutral Higgs with an enhanced Yukawa coupling
to a bottom quark is observed at future hadron experiments, we propose a method
for a better understanding of the Higgs sector. Our procedure is based on
"counting" the number of events with heavy jets (where "heavy" stands for a c
or b jet) versus b jets, in the final state of processes in which the Higgs is
produced in association with a single high p_T c or b jet. We show that an
observed signal of the type proposed, at either the Tevatron or the LHC, will
rule out the popular two Higgs doublet model of type II as well as its
supersymmetric version - the Minimal Supersymmetric Standard Model (MSSM), and
may provide new evidence in favor of some more exotic multi Higgs scenarios. As
an example, we show that in a version of a two Higgs doublet model which
naturally accounts for the large mass of the top quark, our signal can be
easily detected at the LHC within that framework. We also find that such a
signal may be observable at the upgraded Tevatron RunIII, if the neutral Higgs
in this model has a mass around 100 GeV and \tan\beta > 50 and if the
efficiency for distinguishing a c jet from a light jet will reach the level of
50%.Comment: Revtex, 11 pages, 4 figures embedded in the text. Main changes with
respect to Version 1: Numerical results re-calculated using the CTEQ5L pdf,
improved discussion on the experimental consequences, new references added.
Conclusions remain unchanged. As will appear in Phys. Rev.
Micro-Electro-Mechanical-Systems (MEMS) and Fluid Flows
The micromachining technology that emerged in the late 1980s can provide micron-sized sensors and actuators. These micro transducers are able to be integrated with signal conditioning and processing circuitry to form micro-electro-mechanical-systems (MEMS) that can perform real-time distributed control. This capability opens up a new territory for flow control research. On the other hand, surface effects dominate the fluid flowing through these miniature mechanical devices because of the large surface-to-volume ratio in micron-scale configurations. We need to reexamine the surface forces in the momentum equation. Owing to their smallness, gas flows experience large Knudsen numbers, and therefore boundary conditions need to be modified. Besides being an enabling technology, MEMS also provide many challenges for fundamental flow-science research
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