Cluster magnetic fields from active galactic nuclei

Active galactic nuclei (AGN) found at the centers of clusters of galaxies are a possible source for weak cluster-wide magnetic fields. To evaluate this scenario, we present 3D adaptive mesh refinement MHD simulations of a cool-core cluster that include injection of kinetic, thermal, and magnetic energy via an AGN-powered jet. Using the MHD solver in FLASH 2, we compare several sub-resolution approaches that link the estimated accretion rate as measured on the simulation mesh to the accretion rate onto the central black hole and the resulting feedback. We examine the effects of magnetized outflows on the accretion history of the black hole and discuss the ability of these models to magnetize the cluster medium.Comment: 4 pages, 2 figures, submitted to conference proceedings "The Monster's Fiery Breath: Feedback in Groups, Galaxies, and Clusters

The Influence of AGN Feedback on Galaxy Cluster Observables

Galaxy clusters are valuable cosmological probes. However, cluster mass estimates rely on observable quantities that are affected by complicated baryonic physics in the intracluster medium (ICM), including feedback from active galactic nuclei (AGN). Cosmological simulations have started to include AGN feedback using subgrid models. In order to make robust predictions, the systematics of different implementations and parametrizations need to be understood. We have developed an AGN subgrid model in FLASH that supports a few different black hole accretion models and feedback models. We use this model to study the effect of AGN on X-ray cluster observables and its dependence on model variations.Comment: minor error corrected, to appear in proceedings of the conference "The Monster's Fiery Breath: Feedback in Galaxies, Groups, and Clusters", June 2009, Madison, Wisconsi

Atom clusters and vibrational excitations in chemically-disordered Pt357Fe

Inelastic nuclear resonant scattering spectra of Fe-57 atoms were measured on crystalline alloys of Pt3Fe-57 that were chemically disordered, partially ordered, and L1(2) ordered. Phonon partial density of states curves for Fe-57 were obtained from these spectra. Upon disordering, about 10% of the spectral intensity underwent a distinct shift from 25 to 19 meV. This change in optical modes accounted for most of the change of the vibrational entropy of disordering contributed by Fe atoms, which was (+0.10 +/- 0.03) k(B) (Fe atom)(-1). Prospects for parametrizing the vibrational entropy with low-order cluster variables were assessed. To calculate the difference in vibrational entropy of the disordered and ordered alloys, the clusters must be large enough to account for the abundances of several of the atom configurations of the first-nearest-neighbor shell about the Fe-57 atoms

A first phase in the habitat classification for the Zeeschelde: Bed form classification

Within the scope of the long term vision of the Schelde Estuary and the Development Outline 2010 low dynamic intertidal and shallow water areas are considered to be of high ecological value. Little is known about the occurrence of such valuable reas in the Schelde Estuary, nor are the physical and morphological processes which determine the occurrence of these areas fully understood. Based on the results and recommendations of a 2008-2009 research project in the Westerschelde, a new research project was defined to determine relationships between abiotic (bedforms, hydrodynamics, sediment) and biotic (benthos) characteristics in the Zeeschelde (Belgium) and to set up a classification of deep and undeep subtidal areas. A first phase in the habitat classification comprises of the analysis of bed form occurrence and the setup of a bed form classification based on multibeam echo sounding data. Results show within the different sub areas a variation in bed forms going from hard bed layers to no bed forms to ripples (H ~ 0,1 to 0,3 m | L ~ 10 m) and smaller dunes (H ~ 0,5 to 1 m | L ~ 15 to 25 m). On-going research investigates relationships between the bed form characteristics and flow and sediment characteristics. Preliminary results

Paediatric HERMES: European accreditation of training centres in paediatric respiratory medicine

HERMES: European accreditation of training centres in paediatric respiratory medicine http://ow.ly/ZBmUg

Point-of-care CRP matters : normal CRP levels reduce immediate antibiotic prescribing for acutely ill children in primary care : a cluster randomized controlled trial

Objective: Antibiotics are prescribed too often in acutely ill children in primary care. We examined whether a Point-of-Care (POC) C-reactive Protein (CRP) test influences the family physicians' (FP) prescribing rate and adherence to the Evidence Based Medicine (EBM) practice guidelines. Design: Cluster randomized controlled trial. Setting: Primary care, Flanders, Belgium. Intervention: Half of the children with non-severe acute infections (random allocation of practices to perform POC CRP or not) and all children at risk for serious infection were tested with POC CRP. Subjects: Acutely ill children consulting their FP. Main outcome measure: Immediate antibiotic prescribing. Results: 2844 infectious episodes recruited by 133 FPs between 15 February 2013 and 28 February 2014 were analyzed. A mixed logistic regression analysis was performed. Compared to episodes in which CRP was not tested, the mere performing of POC CRP reduced prescribing in case EBM practice guidelines advise to prescribe antibiotics (adjusted odds ratio (aUR) 0.54 (95% Confidence Interval (CI) 0.33-0.90). Normal CRP levels reduced antibiotic prescribing, regardless of whether the advice was to prescribe (aOR 0.24 (95%CI 0.11-0.50) or to withhold (aOR 031 (95%CI 0.17-037)). Elevated CRP levels did not increase antibiotic prescribing. Conclusion: Normal CRP levels discourage immediate antibiotic prescribing, even when EBM practice guidelines advise differently. Most likely, a normal CRP convinces FPs to withhold antibiotics when guidelines go against their own gut feeling. Future research should focus on whether POC CRP can effectively identify children that benefit from antibiotics more accurately, without increasing the risks of under-prescribing

Towards Graphene Nanoribbon-based Electronics

The successful fabrication of single layer graphene has greatly stimulated the progress of the research on graphene. In this article, focusing on the basic electronic and transport properties of graphene nanoribbons (GNRs), we review the recent progress of experimental fabrication of GNRs, and the theoretical and experimental investigations of physical properties and device applications of GNRs. We also briefly discuss the research efforts on the spin polarization of GNRs in relation to the edge states.Comment: 9pages,10figure

Three-Dimensional Fermi Surface of Overdoped La-Based Cuprates

We present a soft x-ray angle-resolved photoemission spectroscopy study of the overdoped high-temperature superconductors La$_{2-x}$Sr$_x$CuO$_4$ and La$_{1.8-x}$Eu$_{0.2}$Sr$_x$CuO$_4$. In-plane and out-of-plane components of the Fermi surface are mapped by varying the photoemission angle and the incident photon energy. No $k_z$ dispersion is observed along the nodal direction, whereas a significant antinodal $k_z$ dispersion is identified. Based on a tight-binding parametrization, we discuss the implications for the density of states near the van-Hove singularity. Our results suggest that the large electronic specific heat found in overdoped La$_{2-x}$Sr$_x$CuO$_4$ can not be assigned to the van-Hove singularity alone. We therefore propose quantum criticality induced by a collapsing pseudogap phase as a plausible explanation for observed enhancement of electronic specific heat

Gamma-Ray Spectroscopy of Λ16^{16}_\LambdaO and Λ15^{15}_\LambdaN Hypernuclei via the 16^{16}O(K−,π−)(K^-, \pi^-) reaction

he bound-state level structures of the $^{16}_{\Lambda}$O and $^{15}_{\Lambda}$N hypernuclei were studied by $\gamma$-ray spectroscopy using a germanium detector array (Hyperball) via the $^{16}$O ($K^-, \pi^- \gamma$) reaction. A level scheme for $^{16}_{\Lambda}$O was determined from the observation of three $\gamma$-ray transitions from the doublet of states ($2^-$,$1^-$) at $\sim 6.7$ MeV to the ground-state doublet ($1^-$,$0^-$). The $^{15}_{\Lambda}$N hypernuclei were produced via proton emission from unbound states in $^{16}_{\Lambda}$O . Three $\gamma$ -rays were observed and the lifetime of the $1/2^+;1$ state in $^{15}_{\Lambda}$N was measured by the Doppler shift attenuation method. By comparing the experimental results with shell-model calculations, the spin-dependence of the $\Lambda N$ interaction is discussed. In particular, the measured $^{16}_{\Lambda}$O ground-state doublet spacing of 26.4 $\pm$ 1.6 $\pm$ 0.5 keV determines a small but nonzero strength of the $\Lambda N$ tensor interaction.Comment: 22 pages, 17 figure