1,341 research outputs found
Heavy Quark Radiative Energy Loss - Applications to RHIC
Heavy quark energy loss in a hot QCD plasma is computed taking into account
the competing effects due to suppression of zeroth order gluon radiation bellow
the plasma frequency and the enhancement of gluon radiation due to transition
energy loss and medium induced Bremsstrahlung. Heavy quark medium induced
radiative energy loss is derived to all orders in opacity, .
Numerical evaluation of the energy loss suggest small suppression of high
charm quarks, and therefore provide a possible explanation for the
null effects observed by PHENIX in the prompt electron spectrum in as
and 200 AGeV.Comment: 4 pages, 4 figures, Contributed to 17th International Conference on
Ultra Relativistic Nucleus-Nucleus Collisions (Quark Matter 2004), Oakland,
California, 11-17 Jan 200
Drug resistance in non-B subtype HIV-1: Impact of HIV-1 reverse transcriptase inhibitors
Human immunodeficiency virus (HIV) causes approximately 2.5 million new infections every year, and nearly 1.6 million patients succumb to HIV each year. Several factors, including cross-species transmission and error-prone replication have resulted in extraordinary genetic diversity of HIV groups. One of these groups, known as group M (main) contains nine subtypes (A-D, F-H and J-K) and causes ∼95% of all HIV infections. Most reported data on susceptibility and resistance to anti-HIV therapies are from subtype B HIV infections, which are prevalent in developed countries but account for only ∼12% of all global HIV infections, whereas non-B subtype HIV infections that account for ∼88% of all HIV infections are prevalent primarily in low and middle-income countries. Although the treatments for subtype B infections are generally effective against non-B subtype infections, there are differences in response to therapies. Here, we review how polymorphisms, transmission efficiency of drug-resistant strains, and differences in genetic barrier for drug resistance can differentially alter the response to reverse transcriptase-targeting therapies in various subtypes
On the Steady Nature of Line-Driven Disk Winds: Application to Cataclysmic Variables
We apply the semi-analytical analysis of the steady nature of line-driven
winds presented in two earlier papers to disk winds driven by the flux
distribution of a standard Shakura & Sunyaev (1973) disk for typical
cataclysmic variable (CV) parameters. We find that the wind critical point
tends to be closer to the disk surface towards the inner disk regions. Our main
conclusion, however, is that a line-driven wind, arising from a steady disk
flux distribution of a standard Shakura-Sunyaev disk capable of locally
supplying the corresponding mass flow, is steady. These results confirm the
findings of an earlier paper that studied "simple" flux distributions that are
more readily analyzable than those presented here. These results are consistent
with the steady velocity nature of outflows observationally inferred for both
CVs and quasi-stellar objects (QSOs). We find good agreement with the 2.5D CV
disk wind models of Pereyra and collaborators. These results suggest that the
likely scenario to account for the wind outflows commonly observed in CVs is
the line-driven accretion disk wind scenario, as suggested early-on by Cordova
& Mason (1982). For QSOs, these results show that the line-driven accretion
disk wind continues to be a promising scenario to account for the outflows
detected in broad absorption line (BAL) QSOs, as suggested early-on by Turnshek
(1984), and analyzed in detail by Murray et al. (1995).Comment: 35 pages, 20 figure
Study of electron anti-neutrinos associated with gamma-ray bursts using KamLAND
We search for electron anti-neutrinos () from long and
short-duration gamma-ray bursts~(GRBs) using data taken by the KamLAND detector
from August 2002 to June 2013. No statistically significant excess over the
background level is found. We place the tightest upper limits on
fluence from GRBs below 7 MeV and place first constraints on
the relation between luminosity and effective temperature.Comment: 16 pages and 5 figure
Using the MitoB method to assess levels of reactive oxygen species in ecological studies of oxidative stress
In recent years evolutionary ecologists have become increasingly interested in the effects of reactive
oxygen species (ROS) on the life-histories of animals. ROS levels have mostly been inferred indirectly
due to the limitations of estimating ROS from in vitro methods. However, measuring ROS (hydrogen
peroxide, H2O2) content in vivo is now possible using the MitoB probe. Here, we extend and refine
the MitoB method to make it suitable for ecological studies of oxidative stress using the brown trout
Salmo trutta as model. The MitoB method allows an evaluation of H2O2 levels in living organisms over
a timescale from hours to days. The method is flexible with regard to the duration of exposure and
initial concentration of the MitoB probe, and there is no transfer of the MitoB probe between fish. H2O2
levels were consistent across subsamples of the same liver but differed between muscle subsamples
and between tissues of the same animal. The MitoB method provides a convenient method for
measuring ROS levels in living animals over a significant period of time. Given its wide range of possible
applications, it opens the opportunity to study the role of ROS in mediating life history trade-offs in
ecological settings
KamLAND Sensitivity to Neutrinos from Pre-Supernova Stars
In the late stages of nuclear burning for massive stars (M>8~M_{\sun}), the
production of neutrino-antineutrino pairs through various processes becomes the
dominant stellar cooling mechanism. As the star evolves, the energy of these
neutrinos increases and in the days preceding the supernova a significant
fraction of emitted electron anti-neutrinos exceeds the energy threshold for
inverse beta decay on free hydrogen. This is the golden channel for liquid
scintillator detectors because the coincidence signature allows for significant
reductions in background signals. We find that the kiloton-scale liquid
scintillator detector KamLAND can detect these pre-supernova neutrinos from a
star with a mass of 25~M_{\sun} at a distance less than 690~pc with 3
significance before the supernova. This limit is dependent on the neutrino mass
ordering and background levels. KamLAND takes data continuously and can provide
a supernova alert to the community.Comment: 19 pages, 6 figures, 1 tabl
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Multiparticle azimuthal correlations for extracting event-by-event elliptic and triangular flow in Au + Au collisions at sNN =200 GeV
We present measurements of elliptic and triangular azimuthal anisotropy of charged particles detected at forward rapidity 1<|η|<3 in Au + Au collisions at sNN=200 GeV, as a function of centrality. The multiparticle cumulant technique is used to obtain the elliptic flow coefficients v2{2},v2{4},v2{6}, and v2{8}, and triangular flow coefficients v3{2} and v3{4}. Using the small-variance limit, we estimate the mean and variance of the event-by-event v2 distribution from v2{2} and v2{4}. In a complementary analysis, we also use a folding procedure to study the distributions of v2 and v3 directly, extracting both the mean and variance. Implications for initial geometrical fluctuations and their translation into the final-state momentum distributions are discussed
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