The central slope of dark matter cores in dwarf galaxies: Simulations vs. THINGS

We make a direct comparison of the derived dark matter (DM) distributions between hydrodynamical simulations of dwarf galaxies assuming a LCDM cosmology and the observed dwarf galaxies sample from the THINGS survey in terms of (1) the rotation curve shape and (2) the logarithmic inner density slope alpha of mass density profiles. The simulations, which include the effect of baryonic feedback processes, such as gas cooling, star formation, cosmic UV background heating and most importantly physically motivated gas outflows driven by supernovae (SNe), form bulgeless galaxies with DM cores. We show that the stellar and baryonic mass is similar to that inferred from photometric and kinematic methods for galaxies of similar circular velocity. Analyzing the simulations in exactly the same way as the observational sample allows us to address directly the so-called "cusp/core" problem in the LCDM model. We show that the rotation curves of the simulated dwarf galaxies rise less steeply than CDM rotation curves and are consistent with those of the THINGS dwarf galaxies. The mean value of the logarithmic inner density slopes alpha of the simulated galaxies' dark matter density profiles is ~ -0.4 +- 0.1, which shows good agreement with \alpha = -0.29 +- 0.07 of the THINGS dwarf galaxies. The effect of non-circular motions is not significant enough to affect the results. This confirms that the baryonic feedback processes included in the simulations are efficiently able to make the initial cusps with \alpha ~ -1.0 to -1.5 predicted by dark-matter-only simulations shallower, and induce DM halos with a central mass distribution similar to that observed in nearby dwarf galaxies.Comment: 13 pages, 7 figures; Accepted for publication in AJ; minor correction

Pressure Support in Galaxy Disks: Impact on Rotation Curves and Dark Matter Density Profiles

Rotation curves constrain a galaxy's underlying mass density profile, under the assumption that the observed rotation produces a centripetal force that exactly balances the inward force of gravity. However, most rotation curves are measured using emission lines from gas, which can experience additional forces due to pressure. In realistic galaxy disks, the gas pressure declines with radius, providing additional radial support to the disk. The measured tangential rotation speed will therefore tend to lag the true circular velocity of a test particle. The gas pressure is dominated by turbulence, and we evaluate its likely amplitude from recent estimates of the gas velocity dispersion and surface density. We show that where the amplitude of the rotation curve is comparable to the characteristic velocities of the interstellar turbulence, pressure support may lead to underestimates of the mass density of the underlying dark matter halo and the inner slope of its density profile. These effects may be significant for galaxies with rotation speeds <75km/s, but are unlikely to be significant in higher mass galaxies. We find that pressure support can be sustained over long timescales, because any reduction in support due to the conversion of gas into stars is compensated for by an inward flow of gas. However, we point to many uncertainties in assessing the importance of pressure support in galaxies. Thus, while pressure support may alleviate possible tensions between rotation curve observations and LambdaCDM on kiloparsec scales, it should not be viewed as a definitive solution at this time.Comment: Accepted to the Astrophysical Journal; 18 pages including 5 pages of figure

High-Resolution Rotation Curves and Galaxy Mass Models from THINGS

We present rotation curves of 19 galaxies from THINGS, The HI Nearby Galaxy Survey. The high spatial and velocity resolution of THINGS make these the highest quality HI rotation curves available to date for a large sample of nearby galaxies, spanning a wide range of HI masses and luminosities. The high quality of the data allows us to derive the geometrical and dynamical parameters using HI data alone. We do not find any declining rotation curves unambiguously associated with a cut-off in the mass distribution out to the last measured point. The rotation curves are combined with 3.6 um data from SINGS (Spitzer Infrared Nearby Galaxies Survey) to construct mass models. Our best-fit, dynamical disk masses, derived from the rotation curves, are in good agreement with photometric disk masses derived from the 3.6 um images in combination with stellar population synthesis arguments and two different assumptions for the stellar Initial Mass Function (IMF). We test the Cold Dark Matter-motivated cusp model, and the observationally motivated central density core model and find that (independent of IMF) for massive, disk-dominated galaxies, all halo models fit apparently equally well; for low-mass galaxies, however, a core-dominated halo is clearly preferred over a cuspy halo. The empirically derived densities of the dark matter halos of the late-type galaxies in our sample are half of what is predicted by CDM simulations, again independent of the assumed IMF.Comment: Accepted for publication in the AJ special THINGS issue. For a high-resolution version visit: http://www.mpia.de/THINGS/Publications.html [v2 typo fixed

Cluster analysis of inflammatory biomarker expression in the International Severe Asthma Registry (ISAR)

Funding: ISAR is conducted by Optimum Patient Care Global Ltd, and co-funded by OPC Global Ltd and AstraZeneca.Peer reviewedPublisher PD

Threshold intensity factors as lower boundaries for crack propagation in ceramics

BACKGROUND: Slow crack growth can be described in a v (crack velocity) versus K(I )(stress intensity factor) diagram. Slow crack growth in ceramics is attributed to corrosion assisted stress at the crack tip or at any pre-existing defect in the ceramic. The combined effect of high stresses at the crack tip and the presence of water or body fluid molecules (reducing surface energy at the crack tip) induces crack propagation, which eventually may result in fatigue. The presence of a threshold in the stress intensity factor, below which no crack propagation occurs, has been the subject of important research in the last years. The higher this threshold, the higher the reliability of the ceramic, and consequently the longer its lifetime. METHODS: We utilize the Irwin K-field displacement relation to deduce crack tip stress intensity factors from the near crack tip profile. Cracks are initiated by indentation impressions. The threshold stress intensity factor is determined as the time limit of the tip stress intensity when the residual stresses have (nearly) disappeared. RESULTS: We determined the threshold stress intensity factors for most of the all ceramic materials presently important for dental restorations in Europe. Of special significance is the finding that alumina ceramic has a threshold limit nearly identical with that of zirconia. CONCLUSION: The intention of the present paper is to stress the point that the threshold stress intensity factor represents a more intrinsic property for a given ceramic material than the widely used toughness (bend strength or fracture toughness), which refers only to fast crack growth. Considering two ceramics with identical threshold limits, although with different critical stress intensity limits, means that both ceramics have identical starting points for slow crack growth. Fast catastrophic crack growth leading to spontaneous fatigue, however, is different. This growth starts later in those ceramic materials that have larger critical stress intensity factors

An ecological quantification of the relationships between water, sanitation and infant, child, and maternal mortality

<p>Abstract</p> <p>Background</p> <p>Water and sanitation access are known to be related to newborn, child, and maternal health. Our study attempts to quantify these relationships globally using country-level data: How much does improving access to water and sanitation influence infant, child, and maternal mortality?</p> <p>Methods</p> <p>Data for 193 countries were abstracted from global databases (World Bank, WHO, and UNICEF). Linear regression was used for the outcomes of under-five mortality rate and infant mortality rate (IMR). These results are presented as events per 1000 live births. Ordinal logistic regression was used to compute odds ratios for the outcome of maternal mortality ratio (MMR).</p> <p>Results</p> <p>Under-five mortality rate decreased by 1.17 (95%CI 1.08-1.26) deaths per 1000, <it>p </it>< 0.001, for every quartile increase in population water access after adjustments for confounders. There was a similar relationship between quartile increase of sanitation access and under-five mortality rate, with a decrease of 1.66 (95%CI 1.11-1.32) deaths per 1000, <it>p </it>< 0.001. Improved water access was also related to IMR, with the IMR decreasing by 1.14 (95%CI 1.05-1.23) deaths per 1000, <it>p </it>< 0.001, with increasing quartile of access to improved water source. The significance of this relationship was retained with quartile improvement in sanitation access, where the decrease in IMR was 1.66 (95%CI 1.11-1.32) deaths per 1000, <it>p </it>< 0.001. The estimated odds ratio that increased quartile of water access was significantly associated with increased quartile of MMR was 0.58 (95%CI 0.39-0.86), <it>p </it>= 0.008. The corresponding odds ratio for sanitation was 0.52 (95%CI 0.32-0.85), <it>p </it>= 0.009, both suggesting that better water and sanitation were associated with decreased MMR.</p> <p>Conclusions</p> <p>Our analyses suggest that access to water and sanitation independently contribute to child and maternal mortality outcomes. If the world is to seriously address the Millennium Development Goals of reducing child and maternal mortality, then improved water and sanitation accesses are key strategies.</p

Effectiveness of initiating biologics in severe asthma patients with high steroid exposure

Peer reviewedPostprin

Epigenetic control of nuclear architecture

The cell nucleus is a highly structured compartment where nuclear components are thought to localize in non-random positions. Correct positioning of large chromatin domains may have a direct impact on the localization of other nuclear components, and can therefore influence the global functionality of the nuclear compartment. DNA methylation of cytosine residues in CpG dinucleotides is a prominent epigenetic modification of the chromatin fiber. DNA methylation, in conjunction with the biochemical modification pattern of histone tails, is known to lock chromatin in a close and transcriptionally inactive conformation. The relationship between DNA methylation and large-scale organization of nuclear architecture, however, is poorly understood. Here we briefly summarize present concepts of nuclear architecture and current data supporting a link between DNA methylation and the maintenance of large-scale nuclear organization

Impact of pre-biologic impairment on meeting domain-specific biologic responder definitions in patients with severe asthma

The authors acknowledge Mr Aivaras Cepelis for his contribution during the development of the manuscript. The authors thank Ms Pui Yee Lai (M.A.), of the Observational and Pragmatic Research Institute (OPRI), and Ms Andrea Lim (BSc, Hons) of the Observational Pragmatic Research Institute (OPRI) for their editorial and formatting assistance that supported the development of this publication.Peer reviewe

The Local Volume HI Survey: Galaxy Kinematics

We present a detailed analysis of the neutral hydrogen kinematics of 12 nearby dwarf irregular galaxies observed as part of the Local Volume HI Survey (LVHIS) conducted at the Australia Telescope Compact Array. For each galaxy we measure the disk parameters (inclination, position angle) and the HI rotation curve. Six galaxies in our sample (AM0605-341, Argo Dwarf, ESO059-G001, ESO137-G018, ESO174-G?001, ESO308-G022) have their atomic hydrogen distribution studied for the first time. AM0605-341 was found to have an extension of redshifted HI which we propose is due to a tidal interaction with NGC2188. There is evidence that ESO215-G?009 has extraplanar HI gas. We also compare the global galaxy properties, in particular the integrated HI flux density and velocity widths of the observed HI spectra with the results from the low angular resolution HI Parkes All Sky Survey (HIPASS). We discuss under what circumstances the 21cm emission line profile can accurately predict the galaxy's rotation velocity, an observational parameter crucial to study the classical and baryonic Tully-Fisher relations.Comment: 22 pages, 14 figures, accepted for publication by MNRA