780 research outputs found
Kaon mass in dense matter
The variation of kaon mass in dense, charge-neutral baryonic matter at
beta-equilibrium has been investigated. The baryon interaction has been
included by means of nonlinear Walecka model, with and without hyperons and the
interaction of kaons with the baryons has been incorporated through the
Nelson-Kaplan model. A self-consistant, one-loop level calculation has been
carried out. We find that at the mean field level, the presence of the hyperons
makes the density-dependence of the kaon mass softer. Thus, the kaon
condensation threshold is pushed up in the baryon density. The loop diagrams
tend to lower the kaon condensation point for lower values of . We
also find that the S-wave kaon-nucleon interaction plays the dominant role in
determining the on-set of kaon condensation and the contribution of the P-wave
interaction is insignificant.Comment: Four figures available on reques
Identification of optimal assisted aspiration conditions of oocytes for use in porcine in vitro maturation: a re-evaluation of the relationship between the cumulus oocyte complex and oocyte quality
The quality of porcine oocytes for use in IVF is commonly graded according to the number of layers of cumulus cells surrounding the oocyte; together these form the cumulus oocyte complex (COC). At least three compact layers of cumulus cells is regarded as important for efficient IVP. To test this, oocytes were scored according to cumulus investment, with grade A representing COCs with three or more cumulus layers including granulosa cell-cumulus oocyte complexes, grade B those with an intact corona radiata surrounded by another layer of cumulus cells and grades C and D representing COCs with lower cumulus cell investment. These oocytes were then monitored for in vitro maturation (IVM), as assessed by tubulin immunostaining for meiotic progression, the development of a cortical granule ring, and by glutathione levels. Results indicate that grading correlates closely with nuclear maturation and cytoplasmic maturation, suggesting that grading oocytes by cumulus investment is a reliable method to predict IVM success. Importantly, Grade A and B oocytes showed no significant differences in any measure and hence using a cut-off of two or more cumulus cell layers may be optimal. We also determined the effect of assisted aspiration for oocyte retrieval, comparing the effect of needle size and applied pressure on the retrieval rate. These data indicated that both variables affected oocyte recovery rates and the quality of recovered oocytes. In combination, these experiments indicate that grade A and B oocytes have a similar developmental potential and that the recovery of oocytes of these grades is maximised by use of an 18-gauge needle and 50mmHg aspiration pressure
Gravitational field around a screwed superconducting cosmic string in scalar-tensor theories
We obtain the solution that corresponds to a screwed superconducting cosmic
string (SSCS) in the framework of a general scalar-tensor theory including
torsion. We investigate the metric of the SSCS in Brans-Dicke theory with
torsion and analyze the case without torsion. We show that in the case with
torsion the space-time background presents other properties different from that
in which torsion is absent. When the spin vanish, this torsion is a
-gradient and then it propagates outside of the string. We investigate
the effect of torsion on the gravitational force and on the geodesics of a
test-particle moving around the SSCS. The accretion of matter by wakes
formation when a SSCS moves with speed is investigated. We compare our
results with those obtained for cosmic strings in the framework of
scalar-tensor theory.Comment: 22 pages, LaTeX, presented at the "XXII - Encontro Nacional de Fisica
de Particulas e Campos", Sao Lourenco, MG, Brazi
Prospects of Scintillating Crystal Detector in Low-Energy Low-Background Experiments
Scintillating crystal detector offers potential advantages in low-energy
(keV-MeV range) low-background experiments for particle physics and
astrophysics. The merits are discussed using CsI(Tl) crystal as illustrations.
The various physics topics which can be pursued with this detector technology
are summarized. A conceptual design for a generic detector is presented.Comment: 20 pages, 1 tables, 7 figures, submitted to Astroparticle Physic
Strangeness Production in Neutron Stars
Production of strange quarks in neutron stars is investigated in this work.
Three cases, one in which the energy and neutrinos produced in the strangeness
production reactions are retained in the reaction region, second in which the
neutrinos are allowed to escape the reaction region but the energy is retained
and the third in which both the energy and neutrinos escape the reaction region
are considered. It is shown that the nonleptonic weak process dominates strange
quark production while semileptonic weak processes, which produce neutrinos,
lead to the cooling if the neutrinos escape the reaction region. It is found
that the time required for the saturation of the strangeness fraction is
between and sec, with the shorter time corresponding to the
first two cases. About 0.2 neutrinos/baryon are emitted during the process in
the first two cases where as the neutrino emission is somewhat suppressed in
the last case. The average energy of the neutrinos produced in all the three
cases is found to be several hundred . We also find that a large amount of
energy is released during the strangeness production in the first two cases and
this leads to the heating of the reaction region. Implications of the neutrino
production are investigated.Comment: Latex file. 3 figures available from SKG on request. accepted in Nucl
Phys
A reanalysis of the luminosities of clusters of galaxies in the EMSS sample with 0.3 < z < 0.6
The X-ray luminosities of the Einstein Extended Medium Sensitivity Survey
(EMSS) clusters of galaxies with redshifts 0.3<z<0.6 are remeasured using ROSAT
PSPC data. It is found that the new luminosities are on average 1.18 +/- 0.08
times higher than previously measured but that this ratio depends strongly on
the X-ray core radii we measure. For the clusters with small core radii, in
general we confirm the EMSS luminosities, but for clusters with core radii >250
kpc (the constant value assumed in the EMSS), the new luminosities are 2.2 +/-
0.15 times the previous measurements. The X-ray luminosity function (XLF) at
0.3<z<0.6 is recalculated and is found to be consistent with the local XLF. The
constraints on the updated properties of the 0.3<z<0.6 EMSS sample, including a
comparison with the number of clusters predicted from local XLFs, indicate that
the space density of luminous, massive clusters has either not evolved or has
increased by a small factor ~2 since z=0.4. The implications of this result are
discussed in terms of constraints on the cosmological parameter Omega_0.Comment: 12 pages, 7 figures. Accepted for publication in MNRA
Z boson pair production at LHC in a stabilized Randall-Sundrum scenario
We study the Z boson pair production at LHC in the Randall-Sundrum scenario
with the Goldberger-Wise stabilization mechanism. It is shown that
comprehensive account of the Kaluza-Klein graviton and radion effects is
crucial to probe the model: The KK graviton effects enhance the cross section
of on the whole so that the resonance peak of the radion becomes
easy to detect, whereas the RS effects on the process are
rather insignificant. The and invariant-mass distributions are presented
to study the dependence of the RS model parameters. The production of
longitudinally polarized Z bosons, to which the SM contributions are
suppressed, is mainly due to KK gravitons and the radion, providing one of the
most robust methods to signal the RS effects. The sensitivity bounds
on with are also obtained such that
the effective weak scale of order 5 TeV can be experimentally
probed.Comment: 28 pages, LaTex file, 18 eps figure
- …