383 research outputs found
Learning from the Success of MPI
The Message Passing Interface (MPI) has been extremely successful as a
portable way to program high-performance parallel computers. This success has
occurred in spite of the view of many that message passing is difficult and
that other approaches, including automatic parallelization and directive-based
parallelism, are easier to use. This paper argues that MPI has succeeded
because it addresses all of the important issues in providing a parallel
programming model.Comment: 12 pages, 1 figur
Multiscale Bone Remodelling with Spatial P Systems
Many biological phenomena are inherently multiscale, i.e. they are
characterized by interactions involving different spatial and temporal scales
simultaneously. Though several approaches have been proposed to provide
"multilayer" models, only Complex Automata, derived from Cellular Automata,
naturally embed spatial information and realize multiscaling with
well-established inter-scale integration schemas. Spatial P systems, a variant
of P systems in which a more geometric concept of space has been added, have
several characteristics in common with Cellular Automata. We propose such a
formalism as a basis to rephrase the Complex Automata multiscaling approach
and, in this perspective, provide a 2-scale Spatial P system describing bone
remodelling. The proposed model not only results to be highly faithful and
expressive in a multiscale scenario, but also highlights the need of a deep and
formal expressiveness study involving Complex Automata, Spatial P systems and
other promising multiscale approaches, such as our shape-based one already
resulted to be highly faithful.Comment: In Proceedings MeCBIC 2010, arXiv:1011.005
Boost operators in Coulomb-gauge QCD: the pion form factor and Fock expansions in phi radiative decays
In this article we rederive the Boost operators in Coulomb-Gauge Yang-Mills
theory employing the path-integral formalism and write down the complete
operators for QCD. We immediately apply them to note that what are usually
called the pion square, quartic... charge radii, defined from derivatives of
the pion form factor at zero squared momentum transfer, are completely blurred
out by relativistic and interaction corrections, so that it is not clear at all
how to interpret these quantities in terms of the pion charge distribution. The
form factor therefore measures matrix elements of powers of the QCD boost and
Moeller operators, weighted by the charge density in the target's rest frame.
In addition we remark that the decomposition of the eta' wavefunction in
quarkonium, gluonium, ... components attempted by the KLOE collaboration
combining data from phi radiative decays, requires corrections due to the
velocity of the final state meson recoiling against a photon. This will be
especially important if such decompositions are to be attempted with data from
J/psi decays.Comment: 14 pages, 4 figure
Phantom Field with O(N) Symmetry in Exponential Potential
In this paper, we study the phase space of phantom model with O(\emph{N})
symmetry in exponential potential. Different from the model without O(\emph{N})
symmetry, the introduction of the symmetry leads to a lower bound on the
equation of state for the existence of stable phantom dominated attractor
phase. The reconstruction relation between the potential of O(\textit{N})
phantom system and red shift has been derived.Comment: 5 pages, 3 figures, replaced with the version to appear on Phys. Rev.
D*-->Dpi and D*-->Dgamma decays: Axial coupling and Magnetic moment of D* meson
The axial coupling and the magnetic moment of D*-meson or, more specifically,
the couplings g(D*Dpi) and g(D*Dgamma), encode the non-perturbative QCD effects
describing the decays D*-->Dpi and D*-->Dgamma. We compute these quantities by
means of lattice QCD with Nf=2 dynamical quarks, by employing the Wilson
("clover") action. On our finer lattice (a=0.065 fm) we obtain: g(D*Dpi)=20 +/-
2, and g(D0*D0gamma)=[2.0 +/- 0.6]/GeV. This is the first determination of
g(D0*D0gamma) on the lattice. We also provide a short phenomenological
discussion and the comparison of our result with experiment and with the
results quoted in the literature.Comment: 22 pages, 3 figure
Ultra-High Energy Neutrino Fluxes and Their Constraints
Applying our recently developed propagation code we review extragalactic
neutrino fluxes above 10^{14} eV in various scenarios and how they are
constrained by current data. We specifically identify scenarios in which the
cosmogenic neutrino flux, produced by pion production of ultra high energy
cosmic rays outside their sources, is considerably higher than the
"Waxman-Bahcall bound". This is easy to achieve for sources with hard injection
spectra and luminosities that were higher in the past. Such fluxes would
significantly increase the chances to detect ultra-high energy neutrinos with
experiments currently under construction or in the proposal stage.Comment: 11 pages, 15 figures, version published in Phys.Rev.
Prenatal exposure to per-and polyfluoroalkyl substances, umbilical cord blood DNA methylation, and cardio-metabolic indicators in newborns: The healthy start study
BACKGROUND: Per-and polyfluoroalkyl substances (PFAS) are environmentally persistent chemicals widely detected in women of reproductive age. Prenatal PFAS exposure is associated with adverse health outcomes in children. We hypothesized that DNA methylation changes may result from prenatal PFAS exposure and may be linked to offspring cardio-metabolic phenotype. OBJECTIVES: We estimated associations of prenatal PFAS with DNA methylation in umbilical cord blood. We evaluated associations of methylation at selected sites with neonatal cardio-metabolic indicators. METHODS: Among 583 mother–infant pairs in a prospective cohort, five PFAS were quantified in maternal serum (median 27 wk of gestation). Umbilical cord blood DNA methylation was evaluated using the Illumina HumanMethylation450 array. Differentially methylated positions (DMPs) were evaluated at a false discovery rate (FDR) <0:05 and differentially methylated regions (DMRs) were identified using comb-p (Šidák-adjusted p <0:05). We estimated associations between methylation at candidate DMPs and DMR sites and the following outcomes: newborn weight, adiposity, and cord blood glucose, insulin, lipids, and leptin. RESULTS: Maternal serum PFAS concentrations were below the median for females in the U.S. general population. Moderate to high pairwise correla-tions were observed between PFAS concentrations (q =0:28 − 0:76). Methylation at one DMP (cg18587484), annotated to the gene TJAP1, was associated with perfluorooctanoate (PFOA) at FDR < 0:05. Comb-p detected between 4 and 15 DMRs for each PFAS. Associated genes, some common across multiple PFAS, were implicated in growth (RPTOR), lipid homeostasis (PON1, PON3, CIDEB, NR1H2), inflammation and immune activity (RASL11B, RNF39), among other functions. There was suggestive evidence that two PFAS-associated loci (cg09093485, cg09637273) were associated with cord blood triglycerides and birth weight, respectively (FDR < 0:1). DISCUSSION: DNA methylation in umbilical cord blood was associated with maternal serum PFAS concentrations during pregnancy, suggesting potential associations with offspring growth, metabolism, and immune function. Future research should explore whether DNA methylation changes mediate associations between prenatal PFAS exposures and child health outcomes. https://doi.org/10.1289/EHP6888
System Size and Energy Dependence of Jet-Induced Hadron Pair Correlation Shapes in Cu+Cu and Au+Au Collisions at sqrt(s_NN) = 200 and 62.4 GeV
We present azimuthal angle correlations of intermediate transverse momentum
(1-4 GeV/c) hadrons from {dijets} in Cu+Cu and Au+Au collisions at sqrt(s_NN) =
62.4 and 200 GeV. The away-side dijet induced azimuthal correlation is
broadened, non-Gaussian, and peaked away from \Delta\phi=\pi in central and
semi-central collisions in all the systems. The broadening and peak location
are found to depend upon the number of participants in the collision, but not
on the collision energy or beam nuclei. These results are consistent with sound
or shock wave models, but pose challenges to Cherenkov gluon radiation models.Comment: 464 authors from 60 institutions, 6 pages, 3 figures, 2 tables.
Submitted to Physical Review Letters. Plain text data tables for the points
plotted in figures for this and previous PHENIX publications are (or will be)
publicly available at http://www.phenix.bnl.gov/papers.htm
Improved Measurement of Double Helicity Asymmetry in Inclusive Midrapidity pi^0 Production for Polarized p+p Collisions at sqrt(s)=200 GeV
We present an improved measurement of the double helicity asymmetry for pi^0
production in polarized proton-proton scattering at sqrt(s) = 200 GeV employing
the PHENIX detector at the Relativistic Heavy Ion Collider (RHIC). The
improvements to our previous measurement come from two main factors: Inclusion
of a new data set from the 2004 RHIC run with higher beam polarizations than
the earlier run and a recalibration of the beam polarization measurements,
which resulted in reduced uncertainties and increased beam polarizations. The
results are compared to a Next to Leading Order (NLO) perturbative Quantum
Chromodynamics (pQCD) calculation with a range of polarized gluon
distributions.Comment: 389 authors, 4 pages, 2 tables, 1 figure. Submitted to Phys. Rev. D,
Rapid Communications. Plain text data tables for the points plotted in
figures for this and previous PHENIX publications are (or will be) publicly
available at http://www.phenix.bnl.gov/papers.htm
Dilepton mass spectra in p+p collisions at sqrt(s)= 200 GeV and the contribution from open charm
The PHENIX experiement has measured the electron-positron pair mass spectrum
from 0 to 8 GeV/c^2 in p+p collisions at sqrt(s)=200 GeV. The contributions
from light meson decays to e^+e^- pairs have been determined based on
measurements of hadron production cross sections by PHENIX. They account for
nearly all e^+e^- pairs in the mass region below 1 GeV/c^2. The e^+e^- pair
yield remaining after subtracting these contributions is dominated by
semileptonic decays of charmed hadrons correlated through flavor conservation.
Using the spectral shape predicted by PYTHIA, we estimate the charm production
cross section to be 544 +/- 39(stat) +/- 142(syst) +/- 200(model) \mu b, which
is consistent with QCD calculations and measurements of single leptons by
PHENIX.Comment: 375 authors from 57 institutions, 18 pages, 4 figures, 2 tables.
Submitted to Physics Letters B. v2 fixes technical errors in matching authors
to institutions. Plain text data tables for the points plotted in figures for
this and previous PHENIX publications are (or will be) publicly available at
http://www.phenix.bnl.gov/papers.htm
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