X-ray and Sunyaev-Zel'dovich scaling relations in galaxy clusters

[Abridged] We present an analysis of the scaling relations between X-ray properties and Sunyaev-Zel'dovich (SZ) parameters for a sample of 24 X-ray luminous galaxy clusters observed with Chandra and with measured SZ effect. These objects are in the redshift range 0.14--0.82 and have X-ray bolometric luminosity L>10^45 erg/s. We perform a spatially resolved spectral analysis and recover the density, temperature and pressure profiles of the ICM, just relying on the spherical symmetry of the cluster and the hydrostatic equilibrium hypothesis. We observe that the correlations among X-ray quantities only are in agreement with previous results obtained for samples of high-z X-ray luminous galaxy clusters. On the relations involving SZ quantities, we obtain that they correlate with the gas temperature with a logarithmic slope significantly larger than the predicted value from the self-similar model. The measured scatter indicates, however, that the central Compton parameter y_0 is a proxy of the gas temperature at the same level of other X-ray quantities like luminosity. Our results on the X-ray and SZ scaling relations show a tension between the quantities more related to the global energy of the system (e.g. gas temperature, gravitating mass) and the indicators of the structure of the ICM (e.g. gas density profile, central Compton parameter y_0), showing the most significant deviations from the values of the slope predicted from the self-similar model in the L-T, L-M_{tot}, M_{gas}-T, y_0-T relations. When the slope is fixed to the self-similar value, these relations consistently show a negative evolution suggesting a scenario in which the ICM at higher redshift has lower both X-ray luminosity and pressure in the central regions than the expectations from self-similar model.Comment: MNRAS in press - Minor revision to match published versio

Spin Chains in an External Magnetic Field. Closure of the Haldane Gap and Effective Field Theories

We investigate both numerically and analytically the behaviour of a spin-1 antiferromagnetic (AFM) isotropic Heisenberg chain in an external magnetic field. Extensive DMRG studies of chains up to N=80 sites extend previous analyses and exhibit the well known phenomenon of the closure of the Haldane gap at a lower critical field H_c1. We obtain an estimate of the gap below H_c1. Above the lower critical field, when the correlation functions exhibit algebraic decay, we obtain the critical exponent as a function of the net magnetization as well as the magnetization curve up to the saturation (upper critical) field H_c2. We argue that, despite the fact that the SO(3) symmetry of the model is explicitly broken by the field, the Haldane phase of the model is still well described by an SO(3) nonlinear sigma-model. A mean-field theory is developed for the latter and its predictions are compared with those of the numerical analysis and with the existing literature.Comment: 11 pages, 4 eps figure

P99Nrg1beta enhances glucose uptake in cardiomyocytes via mTOR, Src and Akt

Background: Neuregulin (Nrg)1β is a growth factor that activates PI3K/Akt and Src/FAK via the ErbB2/ErbB4receptors. Although it is currently in clinical trial to treat haert failure, itremains unclear which cellular mechanisms are responsible for its cardioprotective actions. Here we tested if Nrg1β regulates glucose uptake in cardiomyocytes and analyzed the underlying signaling mechanisms. Methods: Neonatal rat ventricular myocytes were treated with Nrg1β (10ng/ml) in combination with the mTOR inhibitors PP242 (2mM) and rapamycin (20ng/ml), the ErbB2 inhibitor lapatinib (1mM), the Src inhibitor PP2 (5mM), the Akt inhibitor VIII (20mM), or vehicle. Cells were pre-incubated for 30 min with the inhibitors and proteins extracted 30 min after the addition of Nrg1β for analysis by Western blot. Glucose uptake was assessed by measuring the incorporation of 3H-D-glucose for 30 min. ErbB2 or ErbB4 receptors were knocked down withsiRNAfor 48h before Nrg1β treatment. Results: Similar to IGF-I and Insulin, Nrg1β caused a 1.9 fold increase in 3H-D-glucose incorporation (P< 0.01).Nrg1β induced phosphorylation of mTOR (S2448), Akt (S308) and FAK (Y861), as well as of the mTORC1 targets 4E-BP1, p70-S6K1 and ULK and the mTORC2 target Akt (S473). Lapatinib, PP242 and Akt inhibitor VIII blocked the Nrg1β-induced Akt-, mTOR-, p70-S6K1-, ULK-, and 4E-BP1-phosphorylation, indicating that these effects require ErbB2 and are mediated by Akt and mTOR. However, only lapatinib and Akt inhibitor VIII fully blocked the Nrg1β-induced glucose uptake; PP242 partially blocked it and rapamycin did not block it at all. These results suggest that Akt is required for Nrg1β-induced glucose uptake, and that mTORC2-dependent Akt phosphorylation mediates, at least in part, this response. PP2 blocked phosphorylation of FAK as expected, and it also partially blocked phosphorylation of Akt (S473) and p70-S6K1. PP2 also decreased general glucose uptake (0.6-fold of Ctl, p<0.05) and Nrg1β-induced glucose uptake (1.06-fold of Ctl, p=ns). Knock-down of ErbB4 receptor alone was sufficient to decrease both mTORC1 and mTORC2 signaling, whereas knock-down of ErbB2 affected only the mTORC2 targets. Conclusions: Our results show that Nrg1β increases glucose uptake in cardiomyocytes via Akt. We also show that Nrg1β activates mTORC1 via ErbB4 and mTORC2 via the ErbB2/ErbB4 heterodimer. Our data also support the hypothesis that Src/FAK is upstream of mTORC2 and mediates the Nrg1β-induced phosphorylation of Akt and glucose uptak

Folds and Buckles at the Nanoscale: Experimental and Theoretical Investigation of the Bending Properties of Graphene Membranes

The elastic properties of graphene crystals have been extensively investigated, revealing unique properties in the linear and nonlinear regimes, when the membranes are under either stretching or bending loading conditions. Nevertheless less knowledge has been developed so far on folded graphene membranes and ribbons. It has been recently suggested that fold-induced curvatures, without in-plane strain, can affect the local chemical reactivity, the mechanical properties, and the electron transfer in graphene membranes. This intriguing perspective envisages a materials-by-design approach through the engineering of folding and bending to develop enhanced nano-resonators or nano-electro-mechanical devices. Here we present a novel methodology to investigate the mechanical properties of folded and wrinkled graphene crystals, combining transmission electron microscopy mapping of 3D curvatures and theoretical modeling based on continuum elasticity theory and tight-binding atomistic simulations

CAUSA INCONSUETA DI COIN LESION

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LBT/MODS spectroscopy of globular clusters in the irregular galaxy NGC 4449

We present intermediate-resolution (R$\sim$1000) spectra in the $\sim$3500-10,000 A range of 14 globular clusters in the magellanic irregular galaxy NGC 4449 acquired with the Multi Object Double Spectrograph on the Large Binocular Telescope. We derived Lick indices in the optical and the CaII-triplet index in the near-infrared in order to infer the clusters' stellar population properties. The inferred cluster ages are typically older than $\sim$9 Gyr, although ages are derived with large uncertainties. The clusters exhibit intermediate metallicities, in the range $-1.2\lesssim$[Fe/H]$\lesssim-0.7$, and typically sub-solar [$\alpha/Fe$] ratios, with a peak at $\sim-0.4$. These properties suggest that i) during the first few Gyrs NGC 4449 formed stars slowly and inefficiently, with galactic winds having possibly contributed to the expulsion of the $\alpha$-elements, and ii) globular clusters in NGC 4449 formed relatively "late", from a medium already enriched in the products of type Ia supernovae. The majority of clusters appear also under-abundant in CN compared to Milky Way halo globular clusters, perhaps because of the lack of a conspicuous N-enriched, second-generation of stars like that observed in Galactic globular clusters. Using the cluster velocities, we infer the dynamical mass of NGC 4449 inside 2.88 kpc to be M($<$2.88 kpc)=$3.15^{+3.16}_{-0.75} \times 10^9~M_\odot$. We also report the serendipitous discovery of a planetary nebula within one of the targeted clusters, a rather rare event.Comment: Accepted for publication in MNRAS; corrected typo in author lis

3D Modeling of the Magnetization of Superconducting Rectangular-Based Bulks and Tape Stacks

In recent years, numerical models have become popular and powerful tools to investigate the electromagnetic behavior of superconductors. One domain where this advances are most necessary is the 3D modeling of the electromagnetic behavior of superconductors. For this purpose, a benchmark problem consisting of superconducting cube subjected to an AC magnetic field perpendicular to one of its faces has been recently defined and successfully solved. In this work, a situation more relevant for applications is investigated: a superconducting parallelepiped bulk with the magnetic field parallel to two of its faces and making an angle with the other one without and with a further constraint on the possible directions of the current. The latter constraint can be used to model the magnetization of a stack of high-temperature superconductor tapes, which are electrically insulated in one direction. For the present study three different numerical approaches are used: the Minimum Electro-Magnetic Entropy Production (MEMEP) method, the $H$-formulation of Maxwell's equations and the Volume Integral Method (VIM) for 3D eddy currents computation. The results in terms of current density profiles and energy dissipation are compared, and the differences in the two situations of unconstrained and constrained current flow are pointed out. In addition, various technical issues related to the 3D modeling of superconductors are discussed and information about the computational effort required by each model is provided. This works constitutes a concrete result of the collaborative effort taking place within the HTS numerical modeling community and will hopefully serve as a stepping stone for future joint investigations

Gli aneurismi dell'aorta addominale. Diagnosi e trattamento [Aneurysms of the abdominal aorta. Diagnosis and treatment]

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