2,143 research outputs found
Inclusive and Direct Photons in S + Au Central Collisions at 200A GeV/c
A hadron and string cascade model, JPCIAE, which is based on LUND string
model, PYTHIA event generator especially, is used to study both inclusive
photon production and direct photon production in 200A GeV S + Au central
collisions. The model takes into account the photon production from the
partonic QCD scattering process, the hadronic final-state interaction, and the
hadronic decay and deals with them consistently. The results of JPCIAE model
reproduce successfully both the WA93 data of low p_T inclusive photon
distribution and the WA80 data of transverse momentum dependent upper limit of
direct photon. The photon production from different decay channels is
investigated for both direct and inclusive photons. We have discussed the
effects of the partonic QCD scattering and the hadronic final-state interaction
on direct photon production as well.Comment: 6 pages with 5 figure
Intensified partner notification and repeat testing can improve the effectiveness of screening in reducing Chlamydia trachomatis prevalence: a mathematical modelling study.
BACKGROUND
The Australian Chlamydia Control Effectiveness Pilot (ACCEPt) was a cluster randomised controlled trial designed to assess the effectiveness of annual chlamydia testing through general practice in Australia. The trial showed that testing rates increased among sexually active men and women aged 16-29 years, but after 3 years the estimated chlamydia prevalence did not differ between intervention and control communities. We developed a mathematical model to estimate the potential longer-term impact of chlamydia testing on prevalence in the general population.
METHODS
We developed an individual-based model to simulate the transmission of Chlamydia trachomatis in a heterosexual population, calibrated to ACCEPt data. A proportion of the modelled population were tested for chlamydia and treated annually at coverage achieved in the control and intervention arms of ACCEPt. We estimated the reduction in chlamydia prevalence achieved by increasing retesting and by treating the partners of infected individuals up to 9 years after introduction of the intervention.
RESULTS
Increasing the testing coverage in the general Australian heterosexual population to the level achieved in the ACCEPt intervention arm resulted in reduction in the population-level prevalence of chlamydia from 4.6% to 2.7% in those aged 16-29 years old after 10 years (a relative reduction of 41%). The prevalence reduces to 2.2% if the proportion retested within 4 months of treatment is doubled from the rate achieved in the ACCEPt intervention arm (a relative reduction of 52%), and to 1.9% if the partner treatment rate is increased from 30%, as assumed in the base case, to 50% (a relative reduction of 59%).
CONCLUSION
A reduction in C. trachomatis prevalence could be achieved if the level of testing as observed in the ACCEPt intervention arm can be maintained at a population level. More substantial reductions can be achieved with intensified case management comprising retesting of those treated and treatment of partners of infected individuals
The WiggleZ Dark Energy Survey: Star-formation in UV-luminous galaxies from their luminosity functions
We present the ultraviolet (UV) luminosity function of galaxies from the
GALEX Medium Imaging Survey with measured spectroscopic redshifts from the
first data release of the WiggleZ Dark Energy Survey. This sample selects
galaxies with high star formation rates: at 0.6 < z < 0.9 the median star
formation rate is at the upper 95th percentile of optically-selected (r<22.5)
galaxies and the sample contains about 50 per cent of all NUV < 22.8, 0.6 < z <
0.9 starburst galaxies within the volume sampled.
The most luminous galaxies in our sample (-21.0>M_NUV>-22.5) evolve very
rapidly with a number density declining as (1+z)^{5\pm 1} from redshift z = 0.9
to z = 0.6. These starburst galaxies (M_NUV<-21 is approximately a star
formation rate of 30 \msuny) contribute about 1 per cent of cosmic star
formation over the redshift range z=0.6 to z=0.9. The star formation rate
density of these very luminous galaxies evolves rapidly, as (1+z)^{4\pm 1}.
Such a rapid evolution implies the majority of star formation in these large
galaxies must have occurred before z = 0.9.
We measure the UV luminosity function in 0.05 redshift intervals spanning
0.1<z<0.9, and provide analytic fits to the results. At all redshifts greater
than z=0.55 we find that the bright end of the luminosity function is not well
described by a pure Schechter function due to an excess of very luminous
(M_NUV<-22) galaxies. These luminosity functions can be used to create a radial
selection function for the WiggleZ survey or test models of galaxy formation
and evolution. Here we test the AGN feedback model in Scannapieco et al.
(2005), and find that this AGN feedback model requires AGN feedback efficiency
to vary with one or more of the following: stellar mass, star formation rate
and redshift.Comment: 27 pages; 13 pages without appendices. 22 figures; 11 figures in the
main tex
The WiggleZ Dark Energy Survey: improved distance measurements to z = 1 with reconstruction of the baryonic acoustic feature
We present significant improvements in cosmic distance measurements from the WiggleZ Dark Energy Survey, achieved by applying the reconstruction of the baryonic acoustic feature technique. We show using both data and simulations that the reconstruction technique can often be effective despite patchiness of the survey, significant edge effects and shot-noise. We investigate three redshift bins in the redshift range 0.2 < z < 1, and in all three find improvement after reconstruction in the detection of the baryonic acoustic feature and its usage as a standard ruler. We measure model-independent distance measures DV(rsfid/rs) of 1716 ± 83, 2221 ± 101, 2516 ± 86 Mpc (68 per cent CL) at effective redshifts z = 0.44, 0.6, 0.73, respectively, where DV is the volume-averaged distance, and rs is the sound horizon at the end of the baryon drag epoch. These significantly improved 4.8, 4.5 and 3.4 per cent accuracy measurements are equivalent to those expected from surveys with up to 2.5 times the volume of WiggleZ without reconstruction applied. These measurements are fully consistent with cosmologies allowed by the analyses of the Planck Collaboration and the Sloan Digital Sky Survey. We provide the DV(rsfid/rs) posterior probability distributions and their covariances. When combining these measurements with temperature fluctuations measurements of Planck, the polarization of Wilkinson Microwave Anisotropy Probe 9, and the 6dF Galaxy Survey baryonic acoustic feature, we do not detect deviations from a flat Λ cold dark matter (ΛCDM) model. Assuming this model, we constrain the current expansion rate to H₀ = 67.15 ± 0.98 km s⁻¹Mpc⁻¹. Allowing the equation of state of dark energy to vary, we obtain wDE = −1.080 ± 0.135. When assuming a curved ΛCDM model we obtain a curvature value of ΩK = −0.0043 ± 0.0047
-scaling and Information Entropy in Ultra-Relativistic Nucleus-Nucleus Collisions
The -scaling method has been applied to ultra-relativistic p+p, C+C
and Pb+Pb collision data simulated using a high energy Monte Carlo package,
LUCIAE 3.0. The -scaling is found to be valid for some physical
variables, such as charged particle multiplicity, strange particle multiplicity
and number of binary nucleon-nucleon collisions from these simulated
nucleus-nucleus collisions over an extended energy ranging from = 20
to 200 A GeV. In addition we derived information entropy from the multiplicity
distribution as a function of beam energy for these collisions.Comment: 4 pages, 4 figures, 1 table; to appear in the July Issue of Chin.
Phys. Lett.. Web Page: http://www.iop.org/EJ/journal/CP
Differential co-expression framework to quantify goodness of biclusters and compare biclustering algorithms
<p>Abstract</p> <p>Background</p> <p>Biclustering is an important analysis procedure to understand the biological mechanisms from microarray gene expression data. Several algorithms have been proposed to identify biclusters, but very little effort was made to compare the performance of different algorithms on real datasets and combine the resultant biclusters into one unified ranking.</p> <p>Results</p> <p>In this paper we propose differential co-expression framework and a differential co-expression scoring function to objectively quantify quality or goodness of a bicluster of genes based on the observation that genes in a bicluster are co-expressed in the conditions belonged to the bicluster and not co-expressed in the other conditions. Furthermore, we propose a scoring function to stratify biclusters into three types of co-expression. We used the proposed scoring functions to understand the performance and behavior of the four well established biclustering algorithms on six real datasets from different domains by combining their output into one unified ranking.</p> <p>Conclusions</p> <p>Differential co-expression framework is useful to provide quantitative and objective assessment of the goodness of biclusters of co-expressed genes and performance of biclustering algorithms in identifying co-expression biclusters. It also helps to combine the biclusters output by different algorithms into one unified ranking i.e. meta-biclustering.</p
The WiggleZ Dark Energy Survey: Survey Design and First Data Release
The WiggleZ Dark Energy Survey is a survey of 240,000 emission line galaxies
in the distant universe, measured with the AAOmega spectrograph on the 3.9-m
Anglo-Australian Telescope (AAT). The target galaxies are selected using
ultraviolet photometry from the GALEX satellite, with a flux limit of NUV<22.8
mag. The redshift range containing 90% of the galaxies is 0.2<z<1.0. The
primary aim of the survey is to precisely measure the scale of baryon acoustic
oscillations (BAO) imprinted on the spatial distribution of these galaxies at
look-back times of 4-8 Gyrs. Detailed forecasts indicate the survey will
measure the BAO scale to better than 2% and the tangential and radial acoustic
wave scales to approximately 3% and 5%, respectively.
This paper provides a detailed description of the survey and its design, as
well as the spectroscopic observations, data reduction, and redshift
measurement techniques employed. It also presents an analysis of the properties
of the target galaxies, including emission line diagnostics which show that
they are mostly extreme starburst galaxies, and Hubble Space Telescope images,
which show they contain a high fraction of interacting or distorted systems. In
conjunction with this paper, we make a public data release of data for the
first 100,000 galaxies measured for the project.Comment: Accepted by MNRAS; this has some figures in low resolution format.
Full resolution PDF version (7MB) available at
http://www.physics.uq.edu.au/people/mjd/pub/wigglez1.pdf The WiggleZ home
page is at http://wigglez.swin.edu.au
The frequency of osteogenic activities and the pattern of intermittence between periods of physical activity and sedentary behaviour affects bone mineral content: the cross-sectional NHANES study
BACKGROUND: Sedentary behaviours, defined as non exercising seated activities, have been shown to have deleterious effects on health. It has been hypothesised that too much sitting time can have a detrimental effect on bone health in youth. The aim of this study is to test this hypothesis by exploring the association between objectively measured volume and patterns of time spent in sedentary behaviours, time spent in specific screen-based sedentary pursuits and bone mineral content (BMC) accrual in youth. METHODS: NHANES 2005–2006 cycle data includes BMC of the femoral and spinal region via dual-energy X-ray absorptiometry (DEXA), assessment of physical activity and sedentary behaviour patterns through accelerometry, self reported time spent in screen based pursuits (watching TV and using a computer), and frequency of vigorous playtime and strengthening activities. Multiple regression analysis, stratified by gender was performed on N = 671 males and N = 677 females aged from 8 to 22 years. RESULTS: Time spent in screen-based sedentary behaviours is negatively associated with femoral BMC (males and females) and spinal BMC (females only) after correction for time spent in moderate and vigorous activity. Regression coefficients indicate that an additional hour per day of screen-based sitting corresponds to a difference of −0.77 g femoral BMC in females [95% CI: -1.31 to −0.22] and of −0.45 g femoral BMC in males [95% CI: -0.83 to −0.06]. This association is attenuated when self-reported engagement in regular (average 5 times per week) strengthening exercise (for males) and vigorous playing (for both males and females) is taken into account. Total sitting time and non screen-based sitting do not appear to have a negative association with BMC, whereas screen based sedentary time does. Patterns of intermittence between periods of sitting and moderate to vigorous activity appears to be positively associated with bone health when activity is clustered in time and inter-spaced with long continuous bouts of sitting. CONCLUSIONS: Some specific sedentary pursuits (screen-based) are negatively associated with bone health in youth. This association is specific to gender and anatomical area. This relationship between screen-based time and bone health is independent of the total amount of physical activity measured objectively, but not independent of self-reported frequency of strengthening and vigorous play activities. The data clearly suggests that the frequency, rather than the volume, of osteogenic activities is important in counteracting the effect of sedentary behaviour on bone health. The pattern of intermittence between sedentary periods and activity also plays a role in bone accrual, with clustered short bouts of activity interspaced with long periods of sedentary behaviours appearing to be more beneficial than activities more evenly spread in time
The WiggleZ Dark Energy Survey: Direct constraints on blue galaxy intrinsic alignments at intermediate redshifts
Correlations between the intrinsic shapes of galaxy pairs, and between the
intrinsic shapes of galaxies and the large-scale density field, may be induced
by tidal fields. These correlations, which have been detected at low redshifts
(z<0.35) for bright red galaxies in the Sloan Digital Sky Survey (SDSS), and
for which upper limits exist for blue galaxies at z~0.1, provide a window into
galaxy formation and evolution, and are also an important contaminant for
current and future weak lensing surveys. Measurements of these alignments at
intermediate redshifts (z~0.6) that are more relevant for cosmic shear
observations are very important for understanding the origin and redshift
evolution of these alignments, and for minimising their impact on weak lensing
measurements. We present the first such intermediate-redshift measurement for
blue galaxies, using galaxy shape measurements from SDSS and spectroscopic
redshifts from the WiggleZ Dark Energy Survey. Our null detection allows us to
place upper limits on the contamination of weak lensing measurements by blue
galaxy intrinsic alignments that, for the first time, do not require
significant model-dependent extrapolation from the z~0.1 SDSS observations.
Also, combining the SDSS and WiggleZ constraints gives us a long redshift
baseline with which to constrain intrinsic alignment models and contamination
of the cosmic shear power spectrum. Assuming that the alignments can be
explained by linear alignment with the smoothed local density field, we find
that a measurement of \sigma_8 in a blue-galaxy dominated, CFHTLS-like survey
would be contaminated by at most +/-0.02 (95% confidence level, SDSS and
WiggleZ) or +/-0.03 (WiggleZ alone) due to intrinsic alignments. [Abridged]Comment: 18 pages, 12 figures, accepted to MNRAS; v2 has correction to one
author's name, NO other changes; v3 has minor changes in explanation and
calculations, no significant difference in results or conclusions; v4 has an
additional footnote about model interpretation, no changes to
data/calculations/result
The WiggleZ Dark Energy Survey: the growth rate of cosmic structure since redshift z=0.9
We present precise measurements of the growth rate of cosmic structure for
the redshift range 0.1 < z < 0.9, using redshift-space distortions in the
galaxy power spectrum of the WiggleZ Dark Energy Survey. Our results, which
have a precision of around 10% in four independent redshift bins, are well-fit
by a flat LCDM cosmological model with matter density parameter Omega_m = 0.27.
Our analysis hence indicates that this model provides a self-consistent
description of the growth of cosmic structure through large-scale perturbations
and the homogeneous cosmic expansion mapped by supernovae and baryon acoustic
oscillations. We achieve robust results by systematically comparing our data
with several different models of the quasi-linear growth of structure including
empirical models, fitting formulae calibrated to N-body simulations, and
perturbation theory techniques. We extract the first measurements of the power
spectrum of the velocity divergence field, P_vv(k), as a function of redshift
(under the assumption that P_gv(k) = -sqrt[P_gg(k) P_vv(k)] where g is the
galaxy overdensity field), and demonstrate that the WiggleZ galaxy-mass
cross-correlation is consistent with a deterministic (rather than stochastic)
scale-independent bias model for WiggleZ galaxies for scales k < 0.3 h/Mpc.
Measurements of the cosmic growth rate from the WiggleZ Survey and other
current and future observations offer a powerful test of the physical nature of
dark energy that is complementary to distance-redshift measures such as
supernovae and baryon acoustic oscillations.Comment: 17 pages, 11 figures, accepted for publication by MNRA
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