The use of Lorentz microscopy for the determination of magnetic reversal mechanism of exchange-biased Co30Fe70/NiMn bilayer

Lorentz transmission electron microscopy (LTEM) combined with in-situ magnetizing experiments is a powerful tool for the investigation of the magnetization of the reversal process at the micron scale. We have implemented this tool on a conventional transmission electron microscope (TEM) to study the exchange anisotropy of a polycrystalline Co35Fe65/NiMn bilayer. Semi-quantitative maps of the magnetic induction were obtained at different field values by the differential phase contrast (DPC) technique adapted for a TEM (SIDPC). The hysteresis loop of the bilayer has been calculated from the relative intensity of magnetic maps. The curve shows the appearance of an exchange-bias field reveals with two distinct reversal modes of the magnetization: the first path corresponds to a reversal by wall propagation when the applied field is parallel to the anisotropy direction whereas the second is a reversal by coherent rotation of magnetic moments when the field is applied antiparallel to unidirectional anisotropy direction

Do not forget the electrochemical characteristics of the membrane electrode assembly when designing a Proton Exchange Membrane Fuel Cell stack

International audienceThe membrane electrode assembly (MEA) is the key component of a PEMFC stack. Conventional MEAs are composed of catalyzed electrodes loaded with 0.1-0.4 mgPt cm−2 pressed against a Nafion® membrane, leading to cell performance close to 0.8 W cm−2 at 0.6 V. Due to their limited stability at high temperatures, the cost of platinum catalysts and that of proton exchange membranes, the recycling problems and material availability, the MEA components do not match the requirements for large scale development of PEMCFs at a low cost, particularly for automotive applications. Novel approaches to medium and high temperature membranes are described in this work, and a composite polybenzimidazole-poly(vinylphosphonic) acid membrane, stable up to 190 ◦C, led to a power density of 0.5 W cm−2 at 160 ◦C under 3 bar abs with hydrogen and air. Concerning the preparation of efficient electrocatalysts supported on a Vulcan XC72 carbon powder, the Bönnemann colloidal method and above all plasma sputtering allowed preparing bimetallic platinum-based electrocatalysts with a low Pt loading. In the case of plasma deposition of Pt nanoclusters, Pt loadings as low as 10 g cm−2 were achieved, leading to a very high mass power density of ca. 20 kW g−1 Pt . Finally characterization of the MEA electrical properties by Electrochemical Impedance Spectroscopy (EIS) based on a theoretical model of mass and charge transport inside the active and gas diffusion layers, together with the optimization of the operating parameters (cell temperature, humidity, flow rate and pressure) allowed obtaining electrical performance greater than 1.2 W cm−2 using an homemade MEA with a rather low Pt loading

Latitudinal patterns of forest ecosystem stability across spatial scales as affected by biodiversity and environmental heterogeneity

Our planet is facing a variety of serious threats from climate change that are unfolding unevenly across the globe. Uncovering the spatial patterns of ecosystem stability is important for predicting the responses of ecological processes and biodiversity patterns to climate change. However, the understanding of the latitudinal pattern of ecosystem stability across scales and of the underlying ecological drivers is still very limited. Accordingly, this study examines the latitudinal patterns of ecosystem stability at the local and regional spatial scale using a natural assembly of forest metacommunities that are distributed over a large temperate forest region, considering a range of potential environmental drivers. We found that the stability of regional communities (regional stability) and asynchronous dynamics among local communities (spatial asynchrony) both decreased with increasing latitude, whereas the stability of local communities (local stability) did not. We tested a series of hypotheses that potentially drive the spatial patterns of ecosystem stability, and found that although the ecological drivers of biodiversity, climatic history, resource conditions, climatic stability, and environmental heterogeneity varied with latitude, latitudinal patterns of ecosystem stability at multiple scales were affected by biodiversity and environmental heterogeneity. In particular, α diversity is positively associated with local stability, while β diversity is positively associated with spatial asynchrony, although both relationships are weak. Our study provides the first evidence that latitudinal patterns of the temporal stability of naturally assembled forest metacommunities across scales are driven by biodiversity and environmental heterogeneity. Our findings suggest that the preservation of plant biodiversity within and between forest communities and the maintenance of heterogeneous landscapes can be crucial to buffer forest ecosystems at higher latitudes from the faster and more intense negative impacts of climate change in the future

Quelle place pour les adventices dans l’épidémiosurveillance ? Rapport au Comité National d’Epidémiosurveillance

La gestion des adventices est à juste titre considérée comme un frein majeur à l’adoption deméthodes intégrées de conduite des cultures peu dépendantes en produits phytosanitaires.Leur dynamique d’infestation se construisant sur plusieurs saisons culturales du fait du stock desemences dans le sol, les plantes adventices ne peuvent être gérées comme le seraient d’autresravageurs dépendant des seuls paramètres saisonniers pour déclencher leur épidémie. Pourautant notre groupe conclut que l’épidémiosurveillance des adventices peut être utile à unerationalisation des moyens de lutte. Elle peut permettre, sur le pas de temps court, d’optimiseren saison le choix tactique et le timing des interventions de tout ordre ayant un impact sur lesadventices et doit pour cela apparaître clairement dans les Bulletins de Santé du Végétal (BSV).Sa compilation sur plusieurs saisons permettra de mieux saisir l’évolution de la flore et depointer du doigt les facteurs responsables sous-jacents. Ceux-ci constituent autant d’éléments àintégrer dans l’analyse du risque et les préconisations stratégiques qui peuvent en découler. (...

Clinical practice guidelines for BRCA1 and BRCA2 genetic testing

BRCA1 and BRCA2 gene pathogenic variants account for most hereditary breast cancer and are increasingly used to determine eligibility for PARP inhibitor (PARPi) therapy of BRCA-related cancer. Because issues of BRCA testing in clinical practice now overlap with both preventive and therapeutic management, updated and comprehensive practice guidelines for BRCA genotyping are needed. The integrative recommendations for BRCA testing presented here aim to (1) identify individuals who may benefit from genetic counselling and risk-reducing strategies; (2) update germline and tumour-testing indications for PARPi-approved therapies; (3) provide testing recommendations for personalised management of early and metastatic breast cancer; and (4) address the issues of rapid process and tumour analysis. An international group of experts, including geneticists, medical and surgical oncologists, pathologists, ethicists and patient representatives, was commissioned by the French Society of Predictive and Personalised Medicine (SFMPP). The group followed a methodology based on specific formal guidelines development, including (1) evaluating the likelihood of BRCAm from a combined systematic review of the literature, risk assessment models and expert quotations, and (2) therapeutic values of BRCAm status for PARPi therapy in BRCA-related cancer and for management of early and advanced breast cancer. These international guidelines may help clinicians comprehensively update and standardise BRCA testing practices

Treatment of Community-Acquired Pneumonia in Immunocompromised Adults:A Consensus Statement Regarding Initial Strategies

Background Community-acquired pneumonia (CAP) guidelines have improved the treatment and outcomes of patients with CAP, primarily by standardization of initial empirical therapy. But current society-published guidelines exclude immunocompromised patients. Research Question There is no consensus regarding the initial treatment of immunocompromised patients with suspected CAP. Study Design and Methods This consensus document was created by a multidisciplinary panel of 45 physicians with experience in the treatment of CAP in immunocompromised patients. The Delphi survey methodology was used to reach consensus. Results The panel focused on 21 questions addressing initial management strategies. The panel achieved consensus in defining the population, site of care, likely pathogens, microbiologic workup, general principles of empirical therapy, and empirical therapy for specific pathogens. Interpretation This document offers general suggestions for the initial treatment of the immunocompromised patient who arrives at the hospital with pneumonia

Matériaux magnétiques doux hétérogènes à combinaison d'aimantation élevée et de grande anisotropie utilisant le couplage d'échange pour des applications microondes.

Thèse d'Université de Limoge

Matériaux magnétiques doux hétérogènes à combinaison d'aimantation élevée et de grande anisotropie utilisant le couplage d'échange, pour application microondes

Dans le domaine de la microélectronique haute fréquence, les dimensions des composants passifs sont un frein à la miniaturisation des circuits. Dans ce contexte, la réduction des tailles pour les inductances spirales planaires a fait appel récemment à l utilisation de films minces ferromagnétiques doux. Les concepteurs de circuits pour la communication mobile en lien avec les développeurs de matériaux ont alors pensé à étendre ces matériaux à d autres domaines d application à la frontière du micro-onde et du millimétrique. Ceci ne pourra être réalisé seulement si des films à forte perméabilité ( 'DC) et à fréquence de résonance (fFMR) très élevée sont développés. Cependant, une très forte aimantation (4pMs) et une grande anisotropie (Hk) sont très difficiles à combiner naturellement dans les alliages conventionnels. Afin de surmonter cette limitation, nous proposons une démarche en rupture pour le développement traditionnel pour les matériaux magnétiques doux avec l utilisation de films de CoFe à très forte aimantation mais non doux naturellement, couplés avec un matériau antiferromagnétique (AF). Durant ma thèse, j ai développé par PVD des structures Antiferromagnétique/Ferromagnétique/Antiferromagnétique (AF/F/AF) en couches minces. Les principales études ont été réalisées avec le Co90Fe10 (4pMs = 17.5 kG) et Co35Fe65 (4pMs = 23.5 kG), ce dernier présentant l aimantation ultime, en tant que couche F et avec Ni50Mn50 en tant que couche AF. Pour des applications pratiques, ces matériaux seront utilisés en multicouches épais [NiMn/CoFe]*n afin d obtenir une épaisseur fonctionnelle suffisante (typiquement >= 0.5 m). Cependant, ces matériaux sont susceptibles de souffrir de limitations principalement dues aux courants de Foucault, en raison d un facteur de remplissage non favorable (fr = eF/eAF) = 0.5 m). However, these materials might suffer from limitations (mainly eddy currents) due to an unfavourable filling ratio (fr = eF/eAF) < 1) and too large conductivities with FeCo and NiMn. We have enlarged the study to others AF layers such as IrMn and NiO. We have also developed new soft F-layers as CoFeN and CoFeHfN exhibiting high resistivity ( 180 .cm). As the exchange bias strength, critical thickness and temperature-dependence are known to strongly depend on the nature of the AF-layer, systematic investigations vs eAF and eF have been conducted. This work includes structural analyses (XRD, TEM) and annealing temperature investigations. Static properties have been investigated with VSM and Kerr effect. Dynamical properties have been investigated with a single coil permeameter up to 6 GHz and with coplanar wave guide lines up to 20 GHz. Large interfacial exchange energy densities Jex are achievable (1 erg.cm 2) with the AF/F/AF configuration which allows to adjust the pinning field (Hex) over a large range according to the classical 1/eF dependence. The combination of ultra high 4pMs and unique large Hk (50-700 Oe) has been successfully achieved, leading to the highest fFMR 10 GHz frequencies associated with 'DC 50 never reported so far. Microwave permeability spectra agree LLG model and exhibit conventional damping parameter (0.01- 0.02), suitable for RF applications. Furthermore, microwave properties of such films are adequate regarding temperature stability : NiMn-coupled films do not show any significant changes up to 150C. Finally, we have investigated the integration of such multilayered films in real devices. A new type of RF-inductor on silicon has been developed based on coplanar copper lines covered with the magnetic film. The realization features a new topology where the central stripe is fully encapsulated with the magnetic film including flanges. As a best result, the closed inductor exhibit the highest linear density of inductance with 1.5 nH.mm 1 being optimized up to 5 GHz. Indeed, the ratio between the operating frequency (Qmax) and the gyromagnetic frequency is found much more suitable than with spirals for Q optimization, considering moderate damping parameters. Integrated coplanar wave lines have been shown adequate for unusual high frequency permeability investigation (up to 20 GHz) while macroscopic techniques do not exceed 6 GHz typically. However, this advantage is balanced by a more complex interpretation of a which includes now extrinsic contributions to the material but realistic in terms of excitation.LIMOGES-BU Sciences (870852109) / SudocSudocFranceF

A fast constant-voltage technique to determine the rating performance with application to solid-state batteries

International audienceOne of the main characterization necessary to compare different battery technology is the extraction of the rating performance [1]. In Ragone or Ragone-like plot [2], [3] the evolution of the available capacity as a function of the discharge/charge current or power is plotted for different technology in such a way to compare them not only at a particular discharge condition, but on the whole spectrum of available current density. This comparison is of paramount interest because it may lead to unexpected results, as in the case of nanostructured electrode (e.g., Carbon nanofibers based electrode). That kind of electrode usually shows a poor capacity, compared to standard slurry electrode, at low current density, due to the intrinsic loss of active material linked to the 3D porous structure. Notwithstanding, when the comparison spans multiple decades of current density, the former technology will prove far better of the latter due to a superior electrolyte permeation and hence an almost zero loss of capacity with increasing current density[4]. Nowadays, the extraction of the rating performance is accomplished by discharging a cell at multiple current density and the final capacity value correspond to a single point on the rating plot. The corresponding test time is very high (>100h) even if lots of test channel are available. The test time will always be at least the time required to discharge a cell at the lowest probed current density. In the present work, we propose different and faster methods to acquire the same information and compare them to the standard protocol both in terms of quality of results and total test time. Solid state Enfilm [5] has been considered as a test vehicle for this work The first corresponds to start discharging a cell with the highest current under test and each time the voltage limit (e.g., 3V) is reached, to restart the discharge with a lower current, down to the minimum current under test. The resulting discharge profile while be composed by N-current step. This method limits the time at which the cell is discharge at the lowest current and strongly increases the amount of data: each test provides data for all probed current and not only one as in the case of the standard protocol. The second method consists in discharging the cell at constant voltage. The voltage is fixed equal to the limiting voltage (i.e., 3V) and the current is registered. In this case, no previous knowledge of the maximum current is required and the number of points in the final plot are equal to the sampling of the measurement. The rating performance is directly available on the current versus capacity plot. The capacity available for each current density is obtained by integrating the discharge curve up to the desired current. This method can be considered the limit of the N-current step method for N approaching infinity. Theoretical discussion and validity of application of the technique will be further discussed

Minimal architecture lithium batteries: toward high energy density storage solutions

International audienceThe coupling of thick and dense cathodes with anode-free lithium metal configuration is a promising path to enable the next generation of high energy density solid-state batteries. In this work, LiCoO$_2$ (30 µm)/LiPON/Ti is considered as a model system to study the correlation between fundamental electrode properties and cell electrochemical performance, and a physical model is proposed to understand the governing phenomena. The first cycle loss is demonstrated to be constant and independent of both cathode thickness and anode configuration, and only ascribed to the diffusion coefficient's abrupt fall at high lithium contents. Subsequent cycles achieve close to 100% coulombic efficiency. The examination of the effect of cathode thickness demonstrate a nearly linear correlation with areal specific capacity for sub-100 µm LiCoO$_2$ and 0.1 mA cm$^{−2}$ current density. These findings bring new insights to better understand the energy density limiting factors and to suggest potential optimization approaches