16,089 research outputs found
The Variation of Gas Mass Distribution in Galaxy Clusters: Effects of Preheating and Shocks
We investigate the origin of the variation of the gas mass fraction in the
core of galaxy clusters, which was indicated by our work on the X-ray
fundamental plane. The adopted model supposes that the gas distribution
characterized by the slope parameter is related to the preheated temperature.
Comparison with observations of relatively hot (~> 3 keV) and low redshift
clusters suggests that the preheated temperature is about 0.5-2 keV, which is
higher than expected from the conventional galactic wind model and possibly
suggests the need for additional heating such as quasars or gravitational
heating on the largest scales at high redshift. The dispersion of the preheated
temperature may be attributed to the gravitational heating in subclusters. We
calculate the central gas fraction of a cluster from the gas distribution,
assuming that the global gas mass fraction is constant within a virial radius
at the time of the cluster collapse. We find that the central gas density thus
calculated is in good agreement with the observed one, which suggests that the
variation of gas mass fraction in cluster cores appears to be explained by
breaking the self-similarity in clusters due to preheated gas. We also find
that this model does not change major conclusions on the fundamental plane and
its cosmological implications obtained in previous papers, which strongly
suggests that not only for the dark halo but also for the intracluster gas the
core structure preserves information about the cluster formation.Comment: 17 pages, to be published in Ap
Three-body spin-orbit forces from chiral two-pion exchange
Using chiral perturbation theory, we calculate the density-dependent
spin-orbit coupling generated by the two-pion exchange three-nucleon
interaction involving virtual -isobar excitation. From the
corresponding three-loop Hartree and Fock diagrams we obtain an isoscalar
spin-orbit strength which amounts at nuclear matter
saturation density to about half of the empirical value of MeVfm. The
associated isovector spin-orbit strength comes out about a
factor of 20 smaller. Interestingly, this three-body spin-orbit coupling is not
a relativistic effect but independent of the nucleon mass . Furthermore, we
calculate the three-body spin-orbit coupling generated by two-pion exchange on
the basis of the most general chiral -contact interaction. We find
similar (numerical) results for the isoscalar and isovector spin-orbit
strengths and with a strong dominance of
the p-wave part of the -contact interaction and the Hartree
contribution.Comment: 8 pages, 4figure, published in : Physical Review C68, 054001 (2003
Reflectivity measurements in uniaxial superconductors: a methodological discussion applied to the case of La(2-x)Sr(x)CuO(4)
Most of the novel superconductors are uniaxial crystals, with metallic planes
() orthogonal to an insulating axis (). Far-infrared measurements of the
reflectivity provide valuable information on their low-energy
electrodynamics, but involve delicate experimental issues. Two of them are a
possible contamination of from the c axis and the
extrapolation of the data to =0, both above and below .
Here we discuss quantitatively these issues with particular regard to
LaSrCuO, one of the most studied high- materials.Comment: 13 pages with 3 Fig
Validation of a novel scoring system for changes in skeletal manifestations of hypophosphatasia in newborns, infants, and children: The Radiographic Global Impression of Change scale
Hypophosphatasia (HPP) is the heritable metabolic disease characterized by impaired skeletal mineralization due to low activity of the tissue-nonspecific isoenzyme of alkaline phosphatase. Although HPP during growth often manifests with distinctive radiographic skeletal features, no validated method was available to quantify them, including changes over time. We created the Radiographic Global Impression of Change (RGI-C) scale to assess changes in the skeletal burden of pediatric HPP. Site-specific pairs of radiographs of newborns, infants, and children with HPP from three clinical studies of asfotase alfa, an enzyme replacement therapy for HPP, were obtained at baseline and during treatment. Each pair was scored by three pediatric radiologists ( raters ), with nine raters across the three studies. Intrarater and interrater agreement was determined by weighted Kappa coefficients. Interrater reliability was assessed using intraclass correlation coefficients (ICCs) and by two-way random effects analysis of variance (ANOVA) and a mixed-model repeated measures ANOVA. Pearson correlation coefficients evaluated relationships of the RGI-C to the Rickets Severity Scale (RSS), Pediatric Outcomes Data Collection Instrument Global Function Parent Normative Score, Childhood Health Assessment Questionnaire Disability Index, 6-Minute Walk Test percent predicted, and Z-score for height in patients aged 6 to 12 years at baseline. Eighty-nine percent (8/9) of raters showed substantial or almost perfect intrarater agreement of sequential RGI-C scores (weighted Kappa coefficients, 0.72 to 0.93) and moderate or substantial interrater agreement (weighted Kappa coefficients, 0.53 to 0.71) in patients aged 0 to 12 years at baseline. Moderate-to-good interrater reliability was observed (ICC, 0.57 to 0.65). RGI-C scores were significantly (p ≤ 0.0065) correlated with the RSS and with measures of global function, disability, endurance, and growth in the patients aged 6 to 12 years at baseline. Thus, the RGI-C is valid and reliable for detecting clinically important changes in skeletal manifestations of severe HPP in newborns, infants, and children, including during asfotase alfa treatment. © 2018 The Authors. Journal of Bone and Mineral Research Published by Wiley Periodicals Inc
Numerically flat Higgs vector bundles
After providing a suitable definition of numerical effectiveness for Higgs
bundles, and a related notion of numerical flatness, in this paper we prove,
together with some side results, that all Chern classes of a Higgs-numerically
flat Higgs bundle vanish, and that a Higgs bundle is Higgs-numerically flat if
and only if it is has a filtration whose quotients are flat stable Higgs
bundles. We also study the relation between these numerical properties of Higgs
bundles and (semi)stability.Comment: 11 page
The effects of regional insolation differences upon advanced solar thermal electric power plant performance and energy costs
The performance and cost of the 10 MWe advanced solar thermal electric power plants sited in various regions of the continental United States were determined. The regional insolation data base is discussed. A range for the forecast cost of conventional electricity by region and nationally over the next several cades are presented
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