593 research outputs found
Parity Violation in Astrophysics
Core collapse supernovae are gigantic explosions of massive stars that
radiate 99% of their energy in neutrinos. This provides a unique opportunity
for large scale parity or charge conjugation violation. Parity violation in a
strong magnetic field could lead to an asymmetry in the neutrino radiation and
recoil of the newly formed neutron star. Charge conjugation violation in the
neutrino-nucleon interaction reduces the ratio of neutrons to protons in the
neutrino driven wind above the neutron star. This is a problem for r-process
nucleosynthesis in this wind. On earth, parity violation is an excellent probe
of neutrons because the weak charge of a neutron is much larger than that of a
proton. The Parity Radius Experiment (PREX) at Jefferson Laboratory aims to
precisely measure the neutron radius of Pb with parity violating
elastic electron scattering. This has many implications for astrophysics,
including the structure of neutron stars, and for atomic parity nonconservation
experiments.}Comment: 4 pages, 2 figures, proceedings of PAVI04 conference in Grenoble,
Franc
Dopaminergic, glutamatergic but not opioidergic mechanisms mediate induction of FOS-like protein by cocaethylene
Cocaethylene is a psychoactive metabolite formed\ud
during the combined consumption of cocaine and ethanol. As\ud
this metabolite has many properties in common with cocaine, it is conceivable that cocaethylene administration may induce the activity of nuclear transcription factors that regulate the expression of late-response genes. Therefore, the temporal induction of FOS-like protein in rat brain was examined following IP administration of 60 mmol/kg cocaethylene. Immunoreactivity for the protein was detectable at 1 h in striatal neurons and had virtually disappeared 6 h after drug treatment. Administration of\ud
specific dopaminergic (SCH-23390; 0.5 mg/kg) and glutamatergic (MK-801; 1 mg/kg) receptor antagonists prior to cocaethylene indicated a significant role for dopamine (D1) and Nmethyl-D-aspartate receptor subtypes in mediating the nuclear induction of the aforementioned transcription factor protein. In contrast, no significant effects on FOS-like protein in discrete neurons of the caudate putamen were found when spiradoline (U-62066), a kappa opioid-receptor agonist, was administered either IP (10 mg/kg) or directly (50 nmol) into the brain parenchyma. In addition, we uncovered a differential sensitivity of Long–Evans rats to the behavioral effects of cocaethylene, with the psychoactive metabolite producing significantly less behavioral activity (e.g., locomotion, rearing, and continuous sniffing)than that produced by cocaine (molar equivalent of 60 mmol/kg cocaethylene). These findings indicate both common and disparate effects of cocaethylene and its parent compound, cocaine, on receptor pathways that regulate target alterations in gene expression and drug-induced motor behavior
Differential Behavioral Responses to\ud Cocaethylene of Long-Evans and\ud Sprague-Dawley Rats: Role of Serotonin
Cocaethylene is a neuroactive metabolite derived from the concurrent consumption of cocaine and ethanol. The effects of cocaethylene on locomotor activity, stereotypy, and rearing in Long-Evans and Sprague-Dawley rats were compared.A single cocaine injection (molar equivalent of 60 ÎĽmol/kg cocaethylene, intraperitoneal) elicited a robust series of motor output behaviors, including locomotion, stereotypy, and rearing over a 30-minute testing period in Long-Evans rats. In contrast, cocaethylene administration,\ud
under comparable testing conditions, produced no significant changes in locomotor and investigatory behaviors. Because cocaethylene has relatively little impact on serotonin (5-HT) reuptake as opposed to reuptake of dopamine, we pretreated Long-Evans rats with fluoxetine (10 mg/kg; IP), a selective 5-HT reuptake inhibitor. Fluoxetine profoundly augmented cocaethylene-stimulated behaviors in this rat phenotype. To examine whether other rat strains exhibit a similar response to cocaethylene, Sprague-Dawley rats were injected (IP) with cocaethylene and their behavior patterns monitored over a 30-minute testing period. Cocaethylene produced marked locomotor and exploratory behaviors in this strain, suggesting therefore that Long-Evans and Sprague-\ud
Dawley rats differ in their response to cocaethylene. To relate these behavioral differences to possible structural differences in the neuronal density of dopaminergic or\ud
serotonergic neurons, Long-Evans and Sprague-Dawley brains were evaluated for tyrosine hydroxylase and 5-HT immunocytochemistry. No gross morphological differences\ud
in neuronal architecture or density were found in the ventral tegmental area or dorsal raphe nucleus of the two rat phenotypes. These results indicate that two commonly used rat strains show a differential response to cocaethylene and the neurochemical basis for this behavioral difference may be related to synaptic 5-HT bioavailability
Effects of cocaethylene on dopamine and serotonin synthesis in Long–Evans and Sprague–Dawley brains
We examined the behavioral and neurochemical effects of cocaethylene treatment in Long–Evans (�LE). and Sprague–Dawley� (SD) rats. Cocaethylene-induced behaviors were significantly less in LE rats. Cocaethylene caused an inhibition of dopamine synthesis in the caudate nucleus and nucleus accumbens that was equivalent in both rat lines. Serotonin synthesis was also suppressed by cocaethylene treatment, however this phenomenon was less pronounced when compared with the effects on dopamine synthesis
Black Hole Entropy and Superconformal Field Theories on Brane-Antibrane Systems
We obtain the enropy of Schwarzschild and charged black holes in D>4 from
superconformal gases that live on p=10-D dimensional brane-antibrane systems
wrapped on T^p. The preperties of the strongly coupled superconformal theories
such as the appearance of hidden dimensions (for p=1,4) and fractional strings
(for p=5) are crucial for our results. In all cases, the Schwarzschild radius
is given by the transverse fluctuations of the branes and antibranes due to the
finite temperature. We show that our results can be generalized to multicharged
black holes.Comment: 24 pages in phyzzx.te
Realistic Neutrino Opacities for Supernova Simulations With Correlations and Weak Magnetism
Advances in neutrino transport allow realistic neutrino interactions to be
incorporated into supernova simulations. We add tensor couplings to
relativistic RPA calculations of neutrino opacities. Our results reproduce
free-space neutrino-nucleon cross sections at low density, including weak
magnetism and recoil corrections. In addition, our opacities are
thermodynamically consistent with relativistic mean field equations of state.
We find antineutrino mean free paths that are considerably larger then those
for neutrinos. This difference depends little on density. In a supernova, this
difference could lead to an average energy of that is larger than
that for by an amount that is comparable to the energy difference
between and Comment: 15 pages, 10 figures, submitted to PRC, minor changes to figs. (9,10
Comment on Counting Black Hole Microstates Using String Dualities
We discuss a previous attempt at a microscopic counting of the entropy of
asymptotically flat non-extremal black-holes. This method used string dualities
to relate 4 and 5 dimensional black holes to the BTZ black hole. We show how
the dualities can be justified in a certain limit, equivalent to a near horizon
limit, but the resulting spacetime is no longer asymptotically flat.Comment: 10 pages, harvmac. v(2) typo correcte
Comment on "The black hole final state"
Horowitz and Maldacena have suggested that the unitarity of the black hole
S-matrix can be reconciled with Hawking's semiclassical arguments if a
final-state boundary condition is imposed at the spacelike singularity inside
the black hole. We point out that, in this scenario, departures from unitarity
can arise due to interactions between the collapsing body and the infalling
Hawking radiation inside the event horizon. The amount of information lost when
a black hole evaporates depends on the extent to which these interactions are
entangling.Comment: 4 pages, REVTe
Relativistic analysis of the 208Pb(e,e'p)207Tl reaction at high momentum
The recent 208Pb(e,e'p)207Tl data from NIKHEF-K at high missing momentum
(p_m>300 MeV/c) are compared to theoretical results obtained with a fully
relativistic formalism previously applied to analyze data on the low missing
momentum (p_m < 300 MeV/c) region. The same relativistic optical potential and
mean field wave functions are used in the two p_m-regions. The spectroscopic
factors of the various shells are extracted from the analysis of the low-p_m
data and then used in the high-p_m region. In contrast to previous analyses
using a nonrelativistic mean field formalism, we do not find a substantial
deviation from the mean field predictions other than that of the spectroscopic
factors, which appear to be consistent with both low- and high-p_m data. We
find that the difference between results of relativistic and nonrelativistic
formalisms is enhanced in the p_m<0 region that will be interesting to explore
experimentally.Comment: 12 pages, LaTeX+Revtex, included 3 postscript figures. To appear in
the Physical Review C (Rapid Communications
Non-Local Effects of Multi-Trace Deformations in the AdS/CFT Correspondence
The AdS/CFT correspondence relates deformations of the CFT by "multi-trace
operators" to "non-local string theories". The deformed theories seem to have
non-local interactions in the compact directions of space-time; in the gravity
approximation the deformed theories involve modified boundary conditions on the
fields which are explicitly non-local in the compact directions. In this note
we exhibit a particular non-local property of the resulting space-time theory.
We show that in the usual backgrounds appearing in the AdS/CFT correspondence,
the commutator of two bulk scalar fields at points with a large enough distance
between them in the compact directions and a small enough time-like distance
between them in AdS vanishes, but this is not always true in the deformed
theories. We discuss how this is consistent with causality.Comment: 24 pages, 6 figures, 2 appendices. v2: added reference
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