K-edge X-ray absorption spectra in transition metal oxides beyond the single particle approximation: shake-up many body effects

The near edge structure (XANES) in K-edge X-ray absorption spectroscopy (XAS) is a widely used tool for studying electronic and local structure in materials. The precise interpretation of these spectra with the help of calculations is hence of prime importance, especially for the study of correlated materials which have a complicated electronic structure per se. The single particle approach, for example, has generally limited itself to the dominant dipolar cross-section. It has long been known however that effects beyond this approach should be taken into account, both due to the inadequacy of such calculations when compared to experiment and the presence of shake-up many-body satellites in core-level photoemission spectra of correlated materials. This effect should manifest itself in XANES spectra and the question is firstly how to account for it theoretically and secondly how to verify it experimentally. By using state-of-the-art first principles electronic structure calculations and 1s photoemission measurements we demonstrate that shake-up many-body effects are present in K-edge XAS dipolar spectra of NiO, CoO and CuO at all energy scales. We show that shake-up effects can be included in K-edge XAS spectra in a simple way by convoluting the single-particle first-principles calculations including core-hole effects with the 1s photoemission spectra. We thus describe all features appearing in the XAS dipolar cross-section of NiO and CoO and obtain a dramatic improvement with respect to the single-particle calculation in CuO. These materials being prototype correlated magnetic oxides, our work points to the presence of shake-up effects in K-edge XANES of most correlated transition metal compounds and shows how to account for them, paving the way to a precise understanding of their electronic structure.Comment: 6 pages, 4 picture

CC9 Livestock-Associated Staphylococcus aureus Emerges in Bloodstream Infections in French Patients Unconnected With Animal Farming

We report 4 bloodstream infections associated with CC9 agr type II Staphylococcus aureus in individuals without animal exposure. We demonstrate, by microarray analysis, the presence of egc cluster, fnbA, cap operon, lukS, set2, set12, splE, splD, sak, epiD, and can, genomic features associated with a high virulence potential in human

A recessive form of hyper-IgE syndrome by disruption of ZNF341-dependent STAT3 transcription and activity.

Heterozygosity for human () dominant-negative (DN) mutations underlies an autosomal dominant form of hyper-immunoglobulin E syndrome (HIES). We describe patients with an autosomal recessive form of HIES due to loss-of-function mutations of a previously uncharacterized gene, ZNF341 is a transcription factor that resides in the nucleus, where it binds a specific DNA motif present in various genes, including the promoter. The patients\u27 cells have low basal levels of STAT3 mRNA and protein. The autoinduction of STAT3 production, activation, and function by STAT3-activating cytokines is strongly impaired. Like patients with DN mutations, ZNF341-deficient patients lack T helper 17 (T17) cells, have an excess of T2 cells, and have low memory B cells due to the tight dependence of STAT3 activity on ZNF341 in lymphocytes. Their milder extra-hematopoietic manifestations and stronger inflammatory responses reflect the lower ZNF341 dependence of STAT3 activity in other cell types. Human ZNF341 is essential for the transcription-dependent autoinduction and sustained activity of STAT3

THERMAL DISORDER OF SURFACE ATOMS STUDIED BY SURFACE EXAFS

Nous avons étudié l'anisotropie du facteur Debye-Waller de surface qui régit l'amortissement des oscillations EXAFS. Pour cela, nous avons mesuré l'absorption au delà du seuil K du cobalt pour une monocouche de Cobalt adsorbée sur la face (111) du cuivre. Le facteur Debye-Waller est déduit de la dépendance en température de l'amortissement du signal EXAFS. L'utilisation du rayonnement synchrotron, qui est linéairement polarisé, a permis de séparer le signal dû à une liaison entre deux atomes de surface de celui dû à une liaison entre un atome de surface et un atome de la couche inférieure. On a pu ainsi déterminer l'anisotropie de vibration des atomes de surface. Ces résultats expérimentaux ont été comparés aux déplacements carrés moyens relatifs des atomes de surface calculés dans l'approximation harmonique. Le bon accord entre les résultats expérimentaux et les calculs montrent la capacité de l'EXAFS à fournir une information quantitative sur l'amplitude des vibrations thermiques des atomes de surface.We have studied the anisotropy of the surface Debye-Waller factor involved in a surface extended X-ray absorption fine structure (SEXAFS) experiment. It was performed at the CoK edge on a monolayer of cobalt deposited on the (111) face of copper. Experimentally, the Debye-Waller factor is deduced from the temperature dependence of the damping of the EXAFS oscillations. The use of polarized synchrotron radiation allows to distinguish between bonds involving two surface atoms or one surface atom only and then determine the anisotropy of the surface atom vibrations. These experimental results have been compared to the mean square relative displacements of surface atoms calculated in the harmonic approximation. The agreement between theoretical and experimental results is good and shows the ability of EXAFS as a valuable tool for the study of the amplitude of surface vibrations

Boundary conditions at a fluid–porous interface: An a priori estimation of the stress jump coefficients

International audienceThe velocity boundary condition that must be imposed at an interface between a porous medium anda free fluid is investigated. A heterogeneous transition zone characterized by rapidly varying properties is introducedbetween the two homogeneous porous and free fluid regions. The problem is solved using the method of matchedasymptotic expansions and boundary conditions between the two homogeneous regions are obtained. The continuityof the velocity is recovered and a jump in the stress built using the viscosity (and not the effective viscosity) appears.This result also provides an explicit dependence of the stress jump coefficient to the internal structure of the transitionzone and its sensitivity to this micro structure is recovere

An Improved SCFlip Decoder for Polar Codes

International audienceThis paper focuses on the recently introduced Successive Cancellation Flip (SCFlip) decoder of polar codes. Our contribution is twofold. First, we propose the use of an optimized metric to determine the flipping positions within the SCFlip decoder, which improves its ability to find the first error that occurred during the initial SC decoding attempt. We also show that the proposed metric allows closely approaching the performance of an ideal SCFlip decoder. Second, we introduce a generalisation of the SCFlip decoder to a number of í µí¼ nested flips, denoted by SCFlip-í µí¼, using a similar optimized metric to determine the positions of the nested flips. We show that the SCFlip-2 decoder yields significant gains in terms of decoding performance and competes with the performance of the CRC-aided SC-List decoder with list size í µí°¿ = 4, while having an average decoding complexity similar to that of the standard SC decoding, at medium to high signal to noise ratio

Method of polyvinyl alcohol substitution in aqueous magnetic colloids

A method of freezing the spatial distribution of magnetic grains in a water-base ferrofluid is described. The procedure is based on the progressive substitution of the water by a polyvinyl alcohol. The resulting samples are solid and can be studied by electron micrography. With a system of Fe 3O4 grains with a diameter of 100 A and a 3 % volume fraction of magnetite, we find spheroidal aggregates of average size 0.5 μ at zero magnetic field. At a field of ∼ 100 G, the aggregates appear as long chains.On décrit une méthode pour figer la distribution spatiale des grains magnétiques dans un ferrofluide à base d'eau. La méthode est basée sur un remplacement progressif de l'eau par un alcool polyvinylique. Les échantillons obtenus sont solides et peuvent être étudiés par microscopie électronique. Pour un système de grains de Fe3O 4 (diamètre 100 A) et une fraction de volume de magnétite de 3 %, on observe des agrégats sphéroïdaux d'une taille moyenne de 0,5 μ en l'absence de champ magnétique. Pour un champ appliqué de ∼ 100 G, les agrégats prennent la forme de longues chaines