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Proton computed microtomography is a technique that reveals the inner content of microscopic samples. The density distribution of the material (in g·cmIn this study, we describe how the 3D variations in the mass density were taken into account in the reconstruction code, in order to quantify the correction according to the position of the proton beam and the position and aperture angle of the X-ray detector. Moreover, we assess the accuracy of the reconstructed densities using Geant4 simulations on numerical phantoms, used as references.The correction process was successfully applied and led, for the largest regions of interest (little affected by partial volume effects), to an accuracy ≤ 4% for phosphorus (compared to about 40% discrepancy without correction).This study demonstrates the accuracy of the correction method implemented in the tomographic reconstruction code for thick samples. It also points out some advantages offered by Geant4 simulations: i) they produce projection data that are totally independent of the inversion method used for the image reconstruction; ii) one or more physical processes (X-ray absorption, proton energy loss) can be artificially turned off, in order to precisely quantify the effect of the different phenomena involved in the attenuation of X-ray spectra.

This work encompasses an in-depth transmission electron microscopy and atom probe tomography study of Ti-stabilized austenitic steel irradiated with Fe-ions. The focus is on radiation induced segregation and precipitation, and in particular on how Ti and TiC affect these processes. A 15-15Ti steel (grade: DIN 1.4970) in two thermo-mechanical states (cold-worked and aged) was irradiated at different temperatures up to a dose of 40 dpa. At low irradiation temperatures, the cold-worked and aged materials evolved to a similar microstructure dominated by small Si and Ni clusters, corresponding to segregation to small point defect clusters. TiC precipitates, initially present in the aged material, were found to be unstable under these irradiation conditions. Elevated irradiation temperatures resulted in the nucleation of nanometer sized Cr enriched TiC precipitates surrounded by Si and Ni enriched shells. In addition, nanometer sized Ti- and Mn-enriched G-phase (M6Ni16Si7) precipitates formed, often attached to TiC precipitates. Post irradiation, larger number densities of TiC were observed in the cold-worked material compared to the aged material. This was correlated with a lower volume fraction of G-phase. The findings suggest that at elevated irradiation temperatures, the precipitate-matrix interface is an important point defect sink and contributes to the improved radiation resistance of this material. The study is a first of its kind on stabilized steel and demonstrates the significance of the small Ti addition to the evolution of the microstructure under irradiation. (C) 2020 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

Recent macroscopic experimental and theoretical evidence on the stress-strain-temperature behavior of NiTi beyond the strain recoverability limits (large strain, high stress, high temperature), where reversible martensitic transformation tends to proceed together with irreversible plastic deformation processes, is reviewed. Model predictions on the transformation – plasticity coupling are laid out based on the mathematical theory of martensitic microstructures and the crystal plasticity theory. A particular attention is paid to the strain compatibility at moving phase interfaces that may have a direct impact on the plasticity accompanying the martensitic transformation. It is suggested that strong transformation-plasticity coupling shall be expected during the reverse martensitic transformation. Macroscopic models from the literature capable of simulation of thermomechanical responses of NiTi polycrystals due to coexisting martensitic transformation and plastic deformation are reviewed. Dedicated thermomechanical loading experiments on superelastic and actuator NiTi wires aimed at improving our understanding of the coupling between martensitic transformation and plasticity are presented. Based on the results of in-situ studies during thermomechanical loading experiments (electric resistance, synchrotron X-ray diffraction, surface strain by DIC, relaxations) and characterization microstructures in deformed wires by TEM, it is shown that: (i) microstructures and consequently functional properties of annealed NiTi wires can be purposely manipulated by thermomechanical processing, (ii) shape setting of NiTi can be performed at relatively low temperatures (

The present work reports on the microstructural evolution of a new heat of 24% cold worked austenitic DIN 1.4970 (15-15Ti) nuclear cladding steel subjected to ageing heat treatments of varying duration between 500 and 800 degrees C (by steps of 100 degrees C). The primary aim was studying the finely dispersed Ti-C nanoprecipitate population, which are thought to be beneficial for creep and swelling resistance during service. Their size distribution and number density were estimated through dark field imaging and bright field Moire imaging techniques in the transmission electron microscope. Nanoprecipitates formed at and above 600 degrees C, which is a lower temperature than previously reported. The observed nucleation, growth and coarsening behavior of the nanoprecipitates were consistent with simple diffusion arguments. The formation of nanoprecipitates coincided with significant dissociation of dislocations as evidenced by weak beam dark field imaging. Possible mechanisms, including Silcock's stacking fault growth model and Suzuki segregation, are discussed. Recrystallization observed after extended ageing at 800 degrees C caused the redissolution of nanoprecipitates. Large primary Ti(C,N) and (Ti,Mo)C precipitates that occur in the as-received material, and M23C6 precipitates that nucleate on grain boundaries at low temperatures were also characterized by a selective dissolution procedure involving filtration, X-ray diffraction and quantitative Rietveld refinement. The partitioning of key elements between the different phases was derived by combining these findings and was consistent with thermodynamic considerations and the processing history of the steel. (C) 2018 Elsevier B.V. All rights reserved.

In order to assess the impact of α-radiolysis of water on the oxidative dissolution of spent fuel, an un-irradiated, annealed MOX fuel pellet with high content of Pu (∼24 wt%), and a specific α-activity of 4.96 GBq/g MOX , was leached in carbonate-containing solutions of low ionic strength. The high Pu content in the pellet stabilizes the (U,Pu)O 2 (s) matrix towards oxidative dissolution, whereas the α-decays emitted from the surface are expected to produce ∼3.6 × 10 −7 mol H 2 O 2 /day, contributing to the oxidative dissolution of the pellet. Two sets of leaching tests were conducted under different redox conditions: Ar gas atmosphere and deuterium gas atmosphere. A relatively slow increase of the U and Pu concentrations was observed in the Ar case, with U concentrations increasing from 1·10-6 M after 1 h to ∼7 × 10-5 M after 58 days. Leaching under an atmosphere starting at 1 MPa deuterium gas was undertaken in order to evaluate any effect of dissolved hydrogen on the radiolytic dissolution of the pellet, as well as to investigate any potential recombination of the α-radiolytic products with dissolved deuterium. For the latter purpose, isotopic analysis of the D/H content was carried out on solution samples taken during the leaching. Despite the continuous production of radiolytic oxidants, the concentrations of U and Pu remained quite constant at the level of ∼3 × 10-8 M during the first 30 days, i.e. as long as the deuterium pressure remained higher than 0.8 MPa. These data rule out any oxidative dissolution of the pellet during the first month. The un-irradiated MOX fuel does not contain metallic e-particles, hence it is mainly the interaction of ra diolytic oxidants and dissolved deuterium with the surface of the mixed actinide oxide that causes the neutralization of the oxidants. This conclusion is supported by the steadily increasing levels of HDO measured in the leachate samples.

The engineering of nanomaterials, because of their specific properties, is increasingly being developed for commercial purposes over the past decades, to enhance diagnosis, cosmetics properties as well as sensing efficiency. However, the understanding of their fate and thus their interactions at the cellular level with bio-organisms remains elusive. Here, we investigate the size-and charge-dependence of the damages induced by silica nanoparticles (SiO 2-NPs) on Gram-negative Escherichia coli bacteria. We show and quantify the existence of a NPs size threshold discriminating toxic and inert SiO 2-NPs with a critical particle diameter (Φ c) in the range 50nm–80nm. This particular threshold is identified at both the micrometer scale via viability tests through Colony Forming Units (CFU) counting, and the nanometer scale via atomic force microscopy (AFM). At this nanometer scale, AFM emphasizes the interaction between the cell membrane and SiO 2-NPs from both topographic and mechanical points of view. For SiO 2-NPs with Φ > Φ c no change in E. coli morphology nor its outer membrane (OM) organization is observed unless the NPs are positively charged in which case reorganization and disruption of the OM are detected. Conversely, when Φ < Φ c , E. coli exhibit unusual spherical shapes, partial collapse, even lysis, and OM reorganization.

International audience; Antibody-mediated rejection (ABMR) is associated with poor transplant outcome. Pathogenic alloantibodies are usually directed against human leukocyte antigens (HLAs). Histological findings suggestive of ABMR usually demonstrate an anti-HLA donor-specific antibody (DSA)-mediated injury, while a small subset of patients develop acute dysfunction with histological lesions suggestive of ABMR in the absence of anti-HLA DSAs. Although this non-HLA ABMR is not well recognized by current diagnostic classifications,itisassociated withgraftdysfunctionandallograft loss. These clinicaldescriptions suggest apathogenic role for non-HLA anti-endothelial cell antibodies. Diverse antigenic targets have been described during the last decade. This review discusses recent findings in the field and addresses the clinical relevance of anti-endothelial cell antibodies (AECAs).

An experimental database at a Reynolds number Reθ based on momentum thickness close to 9800, was obtained in the Laboratoire de Mecanique de Lille wind tunnel with stereo-PIV (SPIV) and Hot Wires Anemometry (HWA) (Delville et al., wallturb joined experiment to assess the large scale structures in a high reynolds number turbulent boundary layer. In: Progress in Wall Turbulence: Understanding and Modeling. Springer; 2011. p. 65–73.); using a Linear Stochastic Estimation procedure based on correlations computation, a 3 component field is reconstructed here at high frequency from stereo-PIV at 4 Hz and hot wire data at 30 kHz. The present paper describes the results obtained on large scale coherent structures (uniform momentum regions and vortices) by post-processing this reconstruction. Structures are characterized (size, intensity and life time), and results are discussed with emphasis on the spatio-temporal organization of the coherent structures and their energetic contribution to the flow.

We investigated the diagnostic reliability of pregnancy detection using changes in interferon stimulated gene (ISG) messenger RNA (mRNA) levels in circulating immune cells in ewes. Two different groups of ewes (an experimental group, experiment 1 and a farm group, experiment 2) were oestrus-synchronized and blood sampled on day 14 (D0=day of insemination in control animals, experiment 1) and day 15 (experiment 2). Real-time PCR were performed to evaluate the abundance of different ISG mRNAs. In the experimental group, peripheral blood mononuclear cells of 29 ewes born and bred in experimental facilities were isolated using a Percoll gradient method. Gene expression for Chemokine (C-X-C motif) ligand 10 (CXCL10), Myxovirus (influenza virus) resistance 1 (MX1) and Signal transducer and activator of transcription 1 (STAT1) mRNA were, respectively, 8.3-fold, 6.1-fold and 2.7-fold higher (P0.10) in CXCL10, STAT1, MX1, Myxovirus (influenza virus) resistance 2 (MX2) and ISG15 ubiquitin-like modifier (ISG15) mRNA expression were found between pregnant and non-pregnant ewes. The ROC curves and the hierarchical classification generated from the real-time PCR data failed to discriminate between pregnant and non-pregnant animals. In this group of animals, our results show a strong variability in ISG expression patterns: 17% of animals identified as non-pregnant by the five tests were in fact pregnant, only 52% of pregnant animals had at least two positive results (two genes above threshold), whereas up to five positive results (five genes above threshold) were needed to avoid misclassification. In conclusion, this study illustrates the high variability in ISG expression levels in immune circulating cells during early pregnancy and, therefore, highlights the limits of using ISG expression levels in blood samples, collected on PAXgene® tubes on farms, for early pregnancy detection in sheep.

International audience; An efficient strategy is described to prepare electron donor/acceptor hybrid nanoparticles by anchoring a low band-gap polymer onto zinc oxide spheres. Functional macromolecules, bearing triethoxysilane or catechol terminal groups, were synthesized by polycondensation, using a ternary blend reaction, i.e. mixing two monomers and an end-capper. Importantly, and in agreement with Carothers theory, the amount of end-capper allowed to control the chains molar mass. ZnO spherical nanoparticles were then grafted with the polymer chains and TEM images confirmed that core@shell materials were formed. The surface morphology of these hybrid materials was anchoring agent dependent. When silane functionalized polymers were used, cross-linked aggregates were obtained due to competition between self-condensation of silanes and reaction with ZnO surface hydroxyl groups. On the contrary, well-dispersed core-shell particles were synthesized with catechol polymers as anchoring agents. This grafting onto methodology led to patchy nanoparticles on which both zinc oxide and polymer surfaces were accessible. The optical properties of the hybrid material were ascertained by UV–visible absorption and photoluminescence to show a specific quenching of the polymer fluorescence by the metal oxide.

International audience; Solute transport in natural or artificial compacted clay porous media is receiving particular attention in the contexts of waste storage and the design of materials with tuneable physical properties. In these contexts, the porosity is commonly considered as a primary parameter controlling the diffusional properties of water and solutes in these systems. However, little attention has been given to the role played by anisotropy in the particle orientation. In this study, the influence of the preferred orientation of clay particles on the water diffusion anisotropy in two kaolinite porous media obtained by compaction and centrifugation methods (for a constant porosity value of ~0.5) was investigated by coupling experiments and simulations. An increase in the preferred orientation of kaolinite particles, as quantified by X-ray scattering analysis, was found to be logically associated with an enhanced anisotropy in water diffusion obtained from pulsed gradient spin echo attenuation measurements by nuclear magnetic resonance of protons. Brownian dynamics simulations performed on three-dimensional virtual porous media, mimicking the shape and orientation of the particles in the samples, led to calculated water diffusion coefficients in agreement with experimental data. Once validated, this computational work was extended to a wide range of degrees in the preferred orientation of particles. The results showed that this parameter leads to an increase and a decrease in pore water diffusion coefficients along and across the mean orientation plane, respectively, up to a factor ~2. The directional diffusion anisotropy was also found to range between 1 and ~5 for the most isotropic and anisotropic organisations, respectively. This study hence provides quantitative insights into the impact of the preferred orientation for the prediction of water diffusion in compacted clay media.

Peer victimization in the form of bullying is a chronic social stressor experienced by many humans during development. Exposure to bullying has been associated with a variety of mental disorders, such as anxiety and depression. Participants pre-selected for the presence or absence of a history of being bullied were brought into a laboratory and placed in a stressful situation. Blood pressure, heart rate, and salivary cortisol levels were measured before the introduction of the stressor (Time 1), at the end of the stressor (Time 2), and after its removal (Time 3). Men with a history of exposure to frequent bullying showed blunted blood pressure responses at Time 2 compared to control men. Bullied and Non-bullied women did not show any differences in any of the measures. Men and women in both groups showed an increase in heart rate in response to the stressor. There were no significant differences in salivary cortisol levels between Bullied and Non-bullied participants. However, salivary cortisol levels and systolic blood pressure were lower in Bullied male participants who reported having no feelings of anger about their experience compared to controls and those who did report anger. These data show altered sympathetic responses to stress in men with a history of victimization as well as suggesting long-term effects on the HPA axis in the most affected individuals.

Les greffes de cellules-souches hematopoietiques (CSH) haplo-identiques, par leurs mismatchs HLA, predisposent a un risque accru immunologique. Elles connaissent cependant un essor important ces dernieres annees du fait d’une amelioration des procedures permettant une diminution de la reaction du greffon contre l’hote (GVH) et de la mortalite liee a la greffe (TRM). Ces progres ont en particulier ete observes avec des techniques de depletion T in vivo par cyclophosphamide ou depletion in vitro des lymphocytes T alpha-beta. Selon les series publiees, entre 11,3 % et 20,2 % des patients greffes en situation haploidentique presentent, avant transplantation, des anticorps diriges contre le donneur (DSA). Le titre de ces DSA est associe a un impact pejoratif sur la survie ainsi que le delai et l’incidence de prise de greffe. Il existe 4 types de strategies de desensibilisation pregreffes derivee de l’experience de la transplantation d’organes solides : – L’elimination des anticorps par plasmapherese ou immunoabsorption ; – l’inhibition de la production d’anticorps par anticorps monoclonaux diriges contre les lymphocytes CD20+ ou par un inhibiteur du proteasome inhibant les plasmocytes ; – la neutralisation d’anticorps a l’aide d’immunoglobuline intraveineuse (IgIV) ou d’antigenes HLA du donneur par transfusions de plaquettes ; – inhibition de la cascade du complement. Ces strategies sont associees les unes aux autres en fonction des techniques et de l’experience de chaque centre. Nous presentons ici 2 strategies d’utilisation de concentres de plaquettes d’apherese dans le cadre de desensibilisation pregreffe CSH haplo-identiques avec immunisation HLA.