XMM-Newton Reflection Grating Spectrometer Observations of the Prototypical Starburst Galaxy M82

We present results from XMM-Newton Reflection Grating Spectrometer observations of the prototypical starburst galaxy M82. These high resolution spectra represent the best X-ray spectra to date of a starburst galaxy. A complex array of lines from species over a wide range of temperatures is seen, the most prominent being due to Lyman-alpha emission from abundant low Z elements such as N, O, Ne, Mg and Si. Emission lines from Helium-like charge states of the same elements are also seen in emission, as are strong lines from the entire Fe-L series. Further, the OVII line complex is resolved and is seen to be consistent with gas in collisional ionization equilibrium. Spectral fitting indicates emission from a large mass of gas with a differential emission measure over a range of temperatures (from 0.2 keV to 1.6 keV, peaking at 0.7 keV), and evidence for super-solar abundances of several elements is indicated. Spatial analysis of the data indicates that low energy emission is more extended to the south and east of the nucleus than to the north and west. Higher energy emission is far more centrally concentrated.Comment: 5 pages, 4 figures, MNRAS accepte

The m->0 limit for massive graviton in dS_4 and AdS_4. How to circumvent the van Dam-Veltman-Zakharov discontinuity

We show that, by considering physics in dS_4 or AdS_4 spacetime, one can circumvent the van Dam - Veltman - Zakharov theorem which requires that the extra polarization states of a massive graviton do not decouple in the massless limit. It is shown that the smoothness of the m->0 limit is ensured if the H (``Hubble'') parameter, associated with the horizon of the dS_4 or AdS_4 space, tends to zero slower than the mass of the graviton m.Comment: 11 pages, references added, minor typos correcte

Attack Rates Assessment of the 2009 Pandemic H1N1 Influenza A in Children and Their Contacts: A Systematic Review and Meta-Analysis

Background: The recent H1N1 influenza A pandemic was marked by multiple reports of illness and hospitalization in children, suggesting that children may have played a major role in the propagation of the virus. A comprehensive detailed analysis of the attack rates among children as compared with their contacts in various settings is of great importance for understanding their unique role in influenza pandemics. Methodology/Principal Findings: We searched MEDLINE (PubMed) and Embase for published studies reporting outbreak investigations with direct measurements of attack rates of the 2009 pandemic H1N1 influenza A among children, and quantified how these compare with those of their contacts. We identified 50 articles suitable for review, which reported school, household, travel and social events. The selected reports and our meta-analysis indicated that children had significantly higher attack rates as compared to adults, and that this phenomenon was observed for both virologically confirmed and clinical cases, in various settings and locations around the world. The review also provided insight into some characteristics of transmission between children and their contacts in the various settings. Conclusion/Significance: The consistently higher attack rates of the 2009 pandemic H1N1 influenza A among children, as compared to adults, as well as the magnitude of the difference is important for understanding the contribution of children to disease burden, for implementation of mitigation strategies directed towards children, as well as more precise mathematical modeling and simulation of future influenza pandemics

Principles for the post-GWAS functional characterisation of risk loci

Several challenges lie ahead in assigning functionality to susceptibility SNPs. For example, most effect sizes are small relative to effects seen in monogenic diseases, with per allele odds ratios usually ranging from 1.15 to 1.3. It is unclear whether current molecular biology methods have enough resolution to differentiate such small effects. Our objective here is therefore to provide a set of recommendations to optimize the allocation of effort and resources in order maximize the chances of elucidating the functional contribution of specific loci to the disease phenotype. It has been estimated that 88% of currently identified disease-associated SNP are intronic or intergenic. Thus, in this paper we will focus our attention on the analysis of non-coding variants and outline a hierarchical approach for post-GWAS functional studies

Integration of the WUDAPT, WRF, and ENVI-met models to simulate extreme daytime temperature mitigation strategies in San Jose, California

An obstacle to the modeling of strategies to mitigate extreme urban temperatures is frequently the lack of on-site meteorological data. The current study thus reports on a method that used the Weather Research and Forecasting (WRF) model to generate inputs for the ENVI-met model to produce building-scale canyon temperatures within a 300 m square near downtown San Jose. A land use distribution was generated for WRF by a WUDAPT classification, and the days of interest were then the hottest day in California history and a typical summer day. The source of meteorological data for ENVI-met, run with a 1.5 m cubic grid, was either an urbanized version of WRF; its default version; or observations at the closest NWS site. All WRF simulations were run on a 1 km grid, and output at its grid closest to the study area provided ENVI-met with lateral boundary conditions. The mitigation strategy was comprised of three parts, which either increased vegetation, rooftop albedo, or architectural shade elements. Results showed all strategies with only negligible impacts on ENVI-met nighttime 1 m level street canyon temperatures. Increased vegetation, however, was the most effective daytime strategy on both days, as it affected the largest area. The maximum vegetative cooling on the extreme and average days was −3.5 and −3.3 °C, respectively. While increased rooftop albedos produced near negligible impacts, increased architectural shading produced corresponding values of −1.6 and −1.7 °C, respectively

A new bigravity model with exclusively positive branes

We propose a new ``bigravity'' model with two positive tension AdS_4 branes in AdS_5 bulk and no negative tension branes. The bounce of the ``warp'' factor mimics the effect of a negative brane and thus gives rise to an anomalously light graviton KK mode. This configuration satisfies the weak energy condition and has no ghost state. In addition, the extra polarization states of the massive graviton practically decouple and thus it does not contradict to Einsteinian gravity. However, the model has certain phenomenological difficulties associated with the presence of a negative cosmological constant on the branes.Comment: 17 pages, 1 axodraw figure, comments added in the introduction, references added, minor typos correcte

HST observations of the Local Group dwarf galaxy Leo I

We present deep HST F555W (V) and F814W (I) observations of a central field in the Local Group dwarf spheroidal (dSph) galaxy Leo I. The resulting color-magnitude diagram (CMD) reaches I \simeq 26 and reveals the oldest ~10-15 Gyr old turnoffs. Nevertheless, a horizontal branch is not obvious in the CMD. Given the low metallicity of the galaxy, this likely indicates that the first substantial star formation in the galaxy may have been somehow delayed in Leo I in comparison with the other dSph satellites of the Milky Way. The subgiant region is well and uniformly populated from the oldest turnoffs up to the 1 Gyr old turnoff, indicating that star formation has proceeded in a continuous way, with possible variations in intensity but no big gaps between successive bursts, over the galaxy's lifetime. The structure of the red-clump of core He-burning stars is consistent with the large amount of intermediate-age population inferred from the main sequence and the subgiant region. In spite of the lack of gas in Leo I, the CMD clearly shows star formation continuing until 1 Gyr ago and possibly until a few hundred Myrs ago in the central part of the galaxy.Comment: 26 pages with 8 figures (fig 2 not available electronically). To be published in ApJ, April 1 1999 (vol.514, #2