Primordial magnetic field and spectral distortion of cosmic background radiation

The role played by a primordial magnetic field during the pre-recombination epoch is analysed through the cyclotron radiation (due to the free electrons) it might produce in the primordial plasma. We discuss the constraint implied by the measurement or lack thereof COBE on this primordial field.Comment: to appear in International Journal of Mod. Phy

Compressed sensing imaging techniques for radio interferometry

Radio interferometry probes astrophysical signals through incomplete and noisy Fourier measurements. The theory of compressed sensing demonstrates that such measurements may actually suffice for accurate reconstruction of sparse or compressible signals. We propose new generic imaging techniques based on convex optimization for global minimization problems defined in this context. The versatility of the framework notably allows introduction of specific prior information on the signals, which offers the possibility of significant improvements of reconstruction relative to the standard local matching pursuit algorithm CLEAN used in radio astronomy. We illustrate the potential of the approach by studying reconstruction performances on simulations of two different kinds of signals observed with very generic interferometric configurations. The first kind is an intensity field of compact astrophysical objects. The second kind is the imprint of cosmic strings in the temperature field of the cosmic microwave background radiation, of particular interest for cosmolog

Formation of Low Mass Stars in Elliptical Galaxy Cooling Flows

X-ray emission from hot (T = 10^7 K) interstellar gas in massive elliptical galaxies indicates that 10^{10} M_sun has cooled over a Hubble time, but optical and radio evidence for this cold gas is lacking. We provide detailed theoretical support for the hypothesis that this gas has formed into low luminosity stars. Within several kpc of the galactic center, interstellar gas first cools to T = 10^4 K where it is heated by stellar UV and emits the observed diffuse optical line emission. This cooling occurs at a large number (10^6) of isolated sites. After less than a solar mass of gas has accumulated (10^{-6} M_sun/yr) at a typical cooling site, a neutral (HI or H_2) core develops in the HII cloud where gas temperatures drop to T = 15 K and the ionization level (from thermal X-rays) is very low (x = 10^{-6}). We show that the maximum mass of cores that become gravitationally unstable is only about 2 M_sun. No star can exceed this mass. Fragmentation of collapsing cores produces a population of low mass stars with a bottom-heavy IMF and radial orbits. Gravitational collapse and ambipolar diffusion are rapid. The total mass of star-forming (dust-free) HI or H_2 cores in a typical bright elliptical is only 10^6 M_sun, below current observational thresholds.Comment: 23 pages in AASTEX LaTeX with 8 figures; accepted by Astrophysical Journa

Effet de deux agents de blanchiment sur la surface de l’émail. Etude in vitro

We present a study «in vitro» of the effect of bleaching agents on dental surfaces using the «Walking bleaching technique». We found that hydrogen peroxide bleached more quickly than carbamide although, after a period of six weeks, the results were the same as far as wheitening was concerned. In the scanning electron microscope we observed significantly different changes in each case. Carbamide caused a regular and uniform opening of the enamel prisms of the surface while hydrogen peroxide produced more severe superficial destructuration with the appearance of patterning similar to the acid etching, and the presence of some crystalline areas emerging from the body of the prisms.Nous présentons une étude in vitro de l’effet sur la surface dentaire de deux agents de blanchiment utilisés par la technique «Walking bleaching». Nous observons que le peroxyde d’hydrogène blanchit plus vite que le peroxyde de carbamide même si dans un délai de 6 semaines les résultats sont les mêmes en ce qui concerne le blanchiment. Au MEB, nous observons des changements significativement différents dans l’un et l’autre cas. Le peroxyde de carbamide provoque une ouverture des prismes sur la surface de l’émail de manière régulière et uniforme, alors que le peroxyde d’hydrogène produit des destructurations superficielles plus importantes avec l’apparition d’un maître-modèle comme celui de mordançage acide avec la présence sur certaines zones de cristaux qui émergent du corps des prismes

Free Zn2+ determination in natural freshwater of the Pyrenees: towards on-site measurements with AGNES

An on-site methodology has been developed for the direct determination of free Zn2+ with AGNES (Absence of Gradients and Nernstian Equilibrium Stripping) in freshwaters. This implementation includes: i) the use of screen printed electrodes, which provide good limits of detection and easy transportation and deployment; ii) no need for sample purging; iii) a calibration in a synthetic river solution that reproduces well the speciation changes of the natural samples and allows the oxygen interferences to be minimised; iv) the addition of a background electrolyte up to 0.01 mol L-1 in both the calibration and freshwater samples; v) chemical stripping chronopotentiometry as the quantification stage of AGNES. This procedure minimizes the effects of working at low ionic strength and in the presence of dissolved oxygen. In the laboratory, the methodology was checked with different natural samples taken from rivers Garonne, Gave de Cauterets and Gave de Pau in the Pyrenees. Results appeared in good agreement with theoretical estimations computed from Visual Minteq. On-site measurements were performed for the first time with AGNES in the Gave de Cauterets in Soulom (France) and the results were corroborated with purged measurements performed in the laboratory.English language editing by Holly Pearson is acknowledged. The authors acknowledge support for this research from the Communaut e d’Agglom eration de Pau Pyr en ees (CDAPP), from the Spanish Ministerio de Ciencia e Innovacio´n (project numbers CTM2012–39183 and CTM2013– 48967), from the European Community EFA15/08 (PyrMet) and from the Comissionat d’Universitats i Recerca de la Generalitat de Catalunya (project number 2014SGR1132)

HD/H2 Molecular Clouds in the Early Universe: The Problem of Primordial Deuterium

We have detected new HD absorption systems at high redshifts, z_abs=2.626 and z_abs=1.777, identified in the spectra of the quasars J0812+3208 and Q1331+170, respectively. Each of these systems consists of two subsystems. The HD column densities have been determined: log(N(HD),A)=15.70+/-0.07 for z_A=2.626443(2) and log(N(HD),B)=12.98+/-0.22 for z_B=2.626276(2) in the spectrum of J0812+3208 and log(N(HD),C)=14.83+/-0.15 for z_C=1.77637(2) and log(N(HD),D)=14.61+/-0.20 for z_D=1.77670(3) in the spectrum of Q1331+170. The measured HD/H2 ratio for three of these subsystems has been found to be considerably higher than its values typical of clouds in our Galaxy. We discuss the problem of determining the primordial deuterium abundance, which is most sensitive to the baryon density of the Universe \Omega_{b}. Using a well-known model for the chemistry of a molecular cloud, we have estimated the isotopic ratio D/H=HD/2H_2=(2.97+/-0.55)x10^{-5} and the corresponding baryon density \Omega_{b}h^2=0.0205^{+0.0025}_{-0.0020}. This value is in good agreement with \Omega_{b}h^2=0.0226^{+0.0006}_{-0.0006} obtained by analyzing the cosmic microwave background radiation anisotropy. However, in high-redshift clouds, under conditions of low metallicity and low dust content, hydrogen may be incompletely molecularized even in the case of self-shielding. In this situation, the HD/2H_2 ratio may not correspond to the actual D/H isotopic ratio. We have estimated the cloud molecularization dynamics and the influence of cosmological evolutionary effects on it

Compressed sensing imaging techniques for radio interferometry

Radio interferometry probes astrophysical signals through incomplete and noisy Fourier measurements. The theory of compressed sensing demonstrates that such measurements may actually suffice for accurate reconstruction of sparse or compressible signals. We propose new generic imaging techniques based on convex optimization for global minimization problems defined in this context. The versatility of the framework notably allows introduction of specific prior information on the signals, which offers the possibility of significant improvements of reconstruction relative to the standard local matching pursuit algorithm CLEAN used in radio astronomy. We illustrate the potential of the approach by studying reconstruction performances on simulations of two different kinds of signals observed with very generic interferometric configurations. The first kind is an intensity field of compact astrophysical objects. The second kind is the imprint of cosmic strings in the temperature field of the cosmic microwave background radiation, of particular interest for cosmology.Comment: 10 pages, 1 figure. Version 2 matches version accepted for publication in MNRAS. Changes includes: writing corrections, clarifications of arguments, figure update, and a new subsection 4.1 commenting on the exact compliance of radio interferometric measurements with compressed sensin

Simulations of Hot Bubbles in the ICM

We review the general properties of the intracluster medium (ICM) in clusters that host a cooling flow, and in particular the effects on the ICM of the injection of hot plasma by a powerful active galactic nucleus (AGN). It is observed that, in some cases, the hot plasma produces cavities in the ICM that finally detach and rise, perhaps buoyantly. The gas dynamics induced by the rising bubbles can help explain the absence of a cooled gas component in clusters with a cooling flow. This scenario is explored using numerical simulations.Comment: 13 pages, no figures. Accepted for publication in Modern Physics Letters

Chemical composition and bioactivity potential of the new endosequence BC Sealer formulación hiflow

Aim To evaluate in a laboratory setting the effects of Endosequence BC Sealer HiFlow (Brasseler USA, Savannah, GA, USA), a novel calcium silicate-based sealer developed for use in warm canal filling techniques, on human periodontal ligament stem cells (hPDLSCs). Methodology Eluates of EndoSequence BC Sealer HiFlow (BCHiF) (Brasseler USA), EndoSequence BC Sealer (BCS) (Brasseler USA) and AH Plus (AHP) (Dentsply DeTrey GmbH, Konstanz, Germany), were placed in contact with hPDLSCs. The characterisation of the chemical elements of the root canal sealers was assessed using Scanning Electron Microscopy and Energy Dispersive X-ray analysis (SEM-EDX). Inductively Coupled Plasma Mass Spectrometry (ICP-MS) was used to determine the ion release of the sealers. MTT assay and wound healing techniques were used to determine cell viability and migration, respectively. Cell morphology and cell attachment were assessed using a direct contact technique of hPDLSCs onto the surface of the sealers and analysed by SEM. The bioactivity potential was carried out with the Alizarin Red and qPCR testing methods. The statistical differences were evaluated using one-way ANOVA and Tukey´s test (p0.05). Both BCS and BCHiF had similar rates of cell migration to the control group at 24 and 48 hours. Cell morphology and adhesion capacity were also similar for BCS and BCHiF groups, while the AHP group was associated with reduced adhesion capacity. The Alizarin Red assay revealed a significant difference between the BCS and the control group (p<0.001), as well as for the BCHiF group (p<0.001). Finally, BCS and BCHiF promoted overexpression of osteo/cementogenic genes. Conclusions In general, EndoSequence BC Sealer HiFlow possesses suitable biological properties to be safely used as a root canal filling material and promote increased expression of oste/cementogenic genes by hPDLSCs

neXtProt: a knowledge platform for human proteins

neXtProt (http://www.nextprot.org/) is a new human protein-centric knowledge platform. Developed at the Swiss Institute of Bioinformatics (SIB), it aims to help researchers answer questions relevant to human proteins. To achieve this goal, neXtProt is built on a corpus containing both curated knowledge originating from the UniProtKB/Swiss-Prot knowledgebase and carefully selected and filtered high-throughput data pertinent to human proteins. This article presents an overview of the database and the data integration process. We also lay out the key future directions of neXtProt that we consider the necessary steps to make neXtProt the one-stop-shop for all research projects focusing on human proteins