889 research outputs found
Simulation of Light Antinucleus-Nucleus Interactions
Creations of light anti-nuclei (anti-deuterium, anti-tritium, anti-He3 and
anti-He4) are observed by collaborations at the LHC and RHIC accelerators. Some
cosmic ray experiments are aimed to find the anti-nuclei in cosmic rays. To
support the experimental studies of the anti-nuclei a Monte Carlo simulation of
anti-nuclei interactions with matter is implemented in the Geant4 toolkit. The
implementation combines practically all known theoretical approaches to the
problem of antinucleon-nucleon interactions.Comment: 8 pages, 5 figure
Alternative Transcript Initiation and Splicing as a Response to DNA Damage
Humans are exposed to the DNA damaging agent, ionizing radiation (IR), from background radiation, medical treatments, occupational and accidental exposures. IR causes changes in transcription, but little is known about alternative transcription in response to IR on a genome-wide basis. These investigations examine the response to IR at the exon level in human cells, using exon arrays to comprehensively characterize radiation-induced transcriptional expression products. Previously uncharacterized alternative transcripts that preferentially occur following IR exposure have been discovered. A large number of genes showed alternative transcription initiation as a response to IR. Dose-response and time course kinetics have also been characterized. Interestingly, most genes showing alternative transcript induction maintained these isoforms over the dose range and times tested. Finally, clusters of co-ordinately up- and down-regulated radiation response genes were identified at specific chromosomal loci. These data provide the first genome-wide view of the transcriptional response to ionizing radiation at the exon level. This study provides novel insights into alternative transcripts as a mechanism for response to DNA damage and cell stress responses in general
The Microscopic Approach to Nuclear Matter and Neutron Star Matter
We review a variety of theoretical and experimental investigations aimed at
improving our knowledge of the nuclear matter equation of state. Of particular
interest are nuclear matter extreme states in terms of density and/or isospin
asymmetry. The equation of state of matter with unequal concentrations of
protons and neutrons has numerous applications. These include heavy-ion
collisions, the physics of rare, short-lived nuclei and, on a dramatically
different scale, the physics of neutron stars. The "common denominator" among
these (seemingly) very different systems is the symmetry energy, which plays a
crucial role in both the formation of the neutron skin in neutron-rich nuclei
and the radius of a neutron star (a system 18 orders of magnitude larger and 55
orders of magnitude heavier). The details of the density dependence of the
symmetry energy are not yet sufficiently constrained. Throughout this article,
our emphasis will be on the importance of adopting a microscopic approach to
the many-body problem, which we believe to be the one with true predictive
power.Comment: 56 pages, review article to appear in the International Journal of
Modern Physics
Neighborhood crime is differentially associated with cardiovascular risk factors as a function of race and sex
Background: Neighborhood crime may be an important factor contributing to cardiovascular health disparities, and these relations may vary by race and sex. The present investigation evaluated (a) potential differential associations between neighborhood crime and cardiovascular disease (CVD) risk factors within subgroups of African American (AA) and White men and women, and (b) potential mediation by negative affect.
Design and Methods: Participants were 1,718 AAs and Whites (58% AA; 54% female; 59% above poverty; ages 30-64 years) living in Baltimore, Maryland who completed the first wave of the Healthy Aging in Neighborhoods of Diversity across the Life Span study from 2004-2009. CVD risk factors included body mass index, total serum cholesterol, glucose, and systolic and diastolic blood pressure. A negative affect composite was comprised of self-reported depression, anxiety, anger, vigilance, and perceived stress. Hierarchical multiple regression analyses were used to examine associations between per capita overall and violent crime rates, negative affect, and CVD risk factors.
Results: There were significant associations of greater overall crime rate with higher fasting glucose (b=.192, P<0.05), and greater violent crime rate with higher systolic (b=86.50, P<0.05) and diastolic (b=60.12, P<0.05) blood pressure in AA women, but not men. These associations were not explained by negative affect. In Whites, there were no significant associations of overall or violent crime rates with cardiovascular risk factors.
Conclusions: AA women may be particularly vulnerable to the negative impact of crime on cardiovascular risk. Preventative efforts aimed toward this group may help to deter the detrimental effects that living in a high crime area may have on one’s cardiovascular health
Direct observation of nanoscale interface phase in the superconducting chalcogenide KFeSe with intrinsic phase separation
We have used scanning micro x-ray diffraction to characterize different
phases in superconducting KFeSe as a function of temperature,
unveiling the thermal evolution across the superconducting transition
temperature (T32 K), phase separation temperature (T520 K)
and iron-vacancy order temperature (T580 K). In addition to the
iron-vacancy ordered tetragonal magnetic phase and orthorhombic metallic
minority filamentary phase, we have found a clear evidence of the interface
phase with tetragonal symmetry. The metallic phase is surrounded by this
interface phase below 300 K, and is embedded in the insulating texture.
The spatial distribution of coexisting phases as a function of temperature
provides a clear evidence of the formation of protected metallic percolative
paths in the majority texture with large magnetic moment, required for the
electronic coherence for the superconductivity. Furthermore, a clear
reorganization of iron-vacancy order around the T and T is found
with the interface phase being mostly associated with a different iron-vacancy
configuration, that may be important for protecting the percolative
superconductivity in KFeSe.Comment: 6 pages, 4 figure
Neutron star properties and the equation of state of neutron-rich matter
We calculate total masses and radii of neutron stars (NS) for pure neutron
matter and nuclear matter in beta-equilibrium. We apply a relativistic nuclear
matter equation of state (EOS) derived from Dirac-Brueckner-Hartree-Fock (DBHF)
calculations. We use realistic nucleon-nucleon (NN) interactions defined in the
framework of the meson exchange potential models. Our results are compared with
other theoretical predictions and recent observational data. Suggestions for
further study are discussed.Comment: 13 pages, 9 figures, 1 table; Revised version, accepted for
publication in Physical Review
Beta-decay in odd-A and even-even proton-rich Kr isotopes
Beta-decay properties of proton-rich odd-A and even-even Krypton isotopes are
studied in the framework of a deformed selfconsistent Hartree-Fock calculation
with density-dependent Skyrme forces, including pairing correlations between
like nucleons in BCS approximation. Residual spin-isospin interactions are
consistently included in the particle-hole and particle-particle channels and
treated in Quasiparticle Random Phase Approximation. The similarities and
differences in the treatment of even-even and odd-A nuclei are stressed.
Comparison to available experimental information is done for Gamow-Teller
strength distributions, summed strengths, and half-lives. The dependence of
these observables on deformation is particularly emphasized in a search for
signatures of the shape of the parent nucleus.Comment: 29 pages, 16 figure
Microscopically-constrained Fock energy density functionals from chiral effective field theory. I. Two-nucleon interactions
The density matrix expansion (DME) of Negele and Vautherin is a convenient
tool to map finite-range physics associated with vacuum two- and three-nucleon
interactions into the form of a Skyme-like energy density functional (EDF) with
density-dependent couplings. In this work, we apply the improved formulation of
the DME proposed recently in arXiv:0910.4979 by Gebremariam {\it et al.} to the
non-local Fock energy obtained from chiral effective field theory (EFT)
two-nucleon (NN) interactions at next-to-next-to-leading-order (NLO). The
structure of the chiral interactions is such that each coupling in the DME Fock
functional can be decomposed into a cutoff-dependent coupling {\it constant}
arising from zero-range contact interactions and a cutoff-independent coupling
{\it function} of the density arising from the universal long-range pion
exchanges. This motivates a new microscopically-guided Skyrme phenomenology
where the density-dependent couplings associated with the underlying
pion-exchange interactions are added to standard empirical Skyrme functionals,
and the density-independent Skyrme parameters subsequently refit to data. A
Mathematica notebook containing the novel density-dependent couplings is
provided.Comment: 28 pages, 12 figures. Mathematica notebook provided with submission
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A simplified model of aerosol removal by natural processes in reactor containments
Simplified formulae are developed for estimating the aerosol decontamination that can be achieved by natural processes in the containments of pressurized water reactors and in the drywells of boiling water reactors under severe accident conditions. These simplified formulae were derived by correlation of results of Monte Carlo uncertainty analyses of detailed models of aerosol behavior under accident conditions. Monte Carlo uncertainty analyses of decontamination by natural aerosol processes are reported for 1,000, 2,000, 3,000, and 4,000 MW(th) pressurized water reactors and for 1,500, 2,500, and 3,500 MW(th) boiling water reactors. Uncertainty distributions for the decontamination factors and decontamination coefficients as functions of time were developed in the Monte Carlo analyses by considering uncertainties in aerosol processes, material properties, reactor geometry and severe accident progression. Phenomenological uncertainties examined in this work included uncertainties in aerosol coagulation by gravitational collision, Brownian diffusion, turbulent diffusion and turbulent inertia. Uncertainties in aerosol deposition by gravitational settling, thermophoresis, diffusiophoresis, and turbulent diffusion were examined. Electrostatic charging of aerosol particles in severe accidents is discussed. Such charging could affect both the coagulation and deposition of aerosol particles. Electrostatic effects are not considered in most available models of aerosol behavior during severe accidents and cause uncertainties in predicted natural decontamination processes that could not be taken in to account in this work. Median (50%), 90 and 10% values of the uncertainty distributions for effective decontamination coefficients were correlated with time and reactor thermal power. These correlations constitute a simplified model that can be used to estimate the decontamination by natural aerosol processes at 3 levels of conservatism. Applications of the model are described
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