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The role of boron in interactions between liquid Si,B alloy and SiC at high temperature: Contribution of Raman spectroscopy, electron energy loss spectroscopy (EELS) and atom probe tomography (APT)
No full textInternational audienceThis study examines the protective role of boron towards chemical vapor deposited (CVD) SiC via the synthesisand analysis, at various scales, of model composites representative of SiC/SiC composites prepared by siliconmelt infiltration. Comparing the SiC-Si,B and SiC-Si model composites clearly demonstrates the boron’s protectiveeffect. Yet, the SiC-Si,B sample shows a macroscopic reactivity gradient related to the progression of theSi,B alloy through the porous SiC network. Electron energy loss spectroscopy (EELS) and atom probe tomography(APT) were used to assess elemental composition at the quasi-atomic and trace scales, in the different phases andat SiC/Si,B interfaces. Boron diffuses into bulk SiC, in agreement with thermodynamic calculations, but alsoconcentrates at structural defects in polycrystalline CVD SiC. EELS and APT both revealed a high boron overconcentrationover a few nanometers at SiC/Si,B interfaces, without intermediate layer visible by TEM. Ramanspectroscopy also evidenced a microscale gradient of substituted boron in the Si,B alloy, near SiC/Si,B interfaces,which was related to a high carbon concentration and an unexpected carbon environment. These results led toconclude that the addition of boron cumulates three beneficial effects limiting SiC reactivity: (1) a volume effectin SiC, stabilizing and accommodating structural defects (2) an interfacial effect, with B atoms concentrating andstabilizing SiC/Si,B interfaces, and (3) a volume effect in the Si,B alloy, forming B-C clusters inhibiting carbondiffusion. Further RMS, EELS and APT analyses at different locations in the model composites would be useful toexplain the macroscopic corrosion gradient
Complete genome sequence of a new beny-like virus from winter wheat (Triticum aestivum L.) in France
No full textInternational audienceHere, we report the discovery of a new beny-like virus in winter wheat (Triticum aestivum L.) plants collected in the Brittany and Burgundy regions of France in spring 2022, using a high-throughput sequencing approach. A complete genome sequence, comprising two genomic RNAs of 6734 nt (RNA1) and 4856 nt (RNA2) was obtained. This genome shows a typical benyvirus organization, with the RNA1 encoding a large replication-associated protein and the RNA2 encoding, from 5' to 3', the coat protein and its readthrough domain and a triple gene block. Pairwise sequence comparisons and phylogenetic analysis showed that the new virus is a member of the family Benyviridae and that its closest relatives are the recently described beny-like virus wheat stripe mosaic virus and, somewhat more distantly, other recognized benyviruses. Creation of a new species to accommodate the new virus, with the proposed common name "wheat beny-like virus 1" (WBLV1), is suggested, either in the genus Benyvirus or in another genus to be created within the family Benyviridae. Given that WBLV1 was identified in plants that were coinfected by other viruses, no conclusions can be drawn at this stage on its potential pathogenicit
Meal scheduling corrects obesogenic diet induced-uncoupling of cortico-hippocampal activities supporting memory
No full textInternational audienceBackground: Highly caloric food consumed around the clock perturbs the metabolism and cognitive functioning. We hypothesised that obesogenic food could alter neuronal representations of memory depending on the feeding-fasting cycle.Methods: We tracked memory performance, dendritic spine dynamics and neuronal representations of memory in C57Bl6J mice fed obesogenic food ad libitum from peri-adolescence. We aimed to correct energy rich diet-induced plasticity deficits and cognitive impairment with time-restricted feeding in males and females. We further used chemogenetics, pharmacology and knock-in mice to investigate functional correlates underlying diet-induced neurocognitive impairments.Findings: We found that changes in the feeding-fasting cycle reverted the effects of ad libitum obesogenic food on memory impairment in both sexes (n = 55, p = 0.003). Concurrently, it also corrected the increased dendritic spine maintenance and neuroactivity in hippocampus and the decreased spine maintenance and activity in parietal cortex (n = 48, p < 0.005). Bi-directional effects in cortex and hippocampus mediated by glucocorticoid signalling are causal to behavioural changes (n = 91, p = 0.0008), and scaling hippocampal with cortical activities restored memory in mice fed obesogenic food (n = 44, p = 0.02).Interpretation: These results indicate that meal scheduling is a promising approach to confront glucocorticoid signalling bias and memory deficits caused by obesogenic food
Droit de la peine. Mesure de sûreté - Appel possible contre l'ordonnance du JLD en cas d'irresponsabilité pénale pour cause de trouble mental (Cass. crim., 5 févr. 2025, n° 23-86.184, B : JurisData n° 2025-000896)
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Élaboration d’un substitut osseux en verre bioactif mis en forme par frittage laser recherche expérimentale préliminaire : recherche expérimentale préliminaire
No full textThis thesis focuses on the development of a bioactive glass-based bone substitute, shaped by laser sintering. In a context where the need for bioactive and customizable implantable materials is growing, this research aims to develop a biomaterial capable of promoting bone regeneration while being suitable for additive manufacturing technologies. The main objective is to optimize selective laser sintering parameters to structure a bioactive glass without altering its biological and mechanical properties. An experimental approach was taken, including the preparation of bioactive glass powder and its treatment by laser sintering at different powers and scanning speeds. Samples were characterized by RAMAN spectroscopy and X-ray diffraction to analyze composition, by electron microscopy to study microstructure, and by in vitro tests to assess their ability to induce hydroxyapatite formation. The results obtained provide proof of concept for adapting the process to more complex geometries. They also demonstrate the process' potential for manufacturing custom bone implants. This study is an essential prerequisite for three-dimensional printing, and paves the way for the integration of laser sintering in the manufacture of innovative, customized bioactive glass-based bone substitutes for regenerative medicine.Cette thèse porte sur l’élaboration d’un substitut osseux à base de verre bioactif, mis en forme par frittage laser. Dans un contexte où les besoins en matériaux implantables bioactifs et personnalisables sont croissants, cette recherche vise à développer un biomatériau capable de favoriser la régénération osseuse tout en étant adapté aux technologies de fabrication additive. L’objectif principal est d’optimiser les paramètres de frittage laser sélectif pour structurer un verre bioactif sans en altérer les propriétés biologiques et mécaniques. Une approche expérimentale a été menée, incluant la préparation du verre du verre bioactif en poudre, son traitement par frittage laser à différentes puissances et vitesses de balayage. Les échantillons ont été caractérisés par spectroscopie RAMAN et diffraction des rayons X pour analyser la composition, par microscopie électronique pour étudier la microstructure, ainsi que par des tests in vitro afin d’évaluer leur capacité à induire la formation d’hydroxyapatite. Les résultats obtenus fournissent une preuve de concept pour l’adaptation du procédé à des géométries plus complexes. Ils démontrent le potentiel du procédé pour fabriquer des implants osseux sur mesure. Cette étude constitue une étape préalable essentielle à l’impression tridimensionnelle, et ouvre la voie à l’intégration du frittage laser dans la fabrication de substituts osseux innovants et personnalisés à base de verre bioactif pour la médecine régénérative
Cognitive motivational states impact quality of work life and job effectiveness via proactive behavior: a two-wave study of nurse managers
No full textInternational audiencePurposeThis study examines whether nurse middle managers’ proactive behavior mediates the relationship between cognitive motivational states (role breadth self-efficacy and positive emotions) and outcomes related to quality of work life (job satisfaction and job stress) and job effectiveness (innovative work behavior and job performance).Design/methodology/approachThe study utilizes two-wave survey data from 152 nurse middle managers. Structural equation modeling was used to test whether proactive behavior mediates the effects of role breadth self-efficacy and positive emotions on both quality of work life and job effectiveness outcomes.FindingsFindings indicate that cognitive motivational states (role breadth self-efficacy and positive emotions) significantly influence proactive behavior. Proactive behavior, in turn, enhances both quality of work life and job effectiveness. Additionally, proactive behavior was found to be the mechanism through which role breadth self-efficacy and positive emotions positively impact innovative work behavior.Practical implicationsThese insights provide valuable guidance for hospital management and HR practitioners on how to foster nurse middle managers’ proactivity, ultimately improving job performance and enhancing the quality of work life within healthcare organizations.Originality/valueThe study identifies proactive behavior as a key mediator in the relationship between cognitive motivational states and both work life quality and job effectiveness, emphasizing its role in driving innovative work behavior among nurse middle managers
And the law relaxed the rules. A quasi-experimental study of fatal police shootings in Europe
No full textInternational audienceCan the behavior of civil servants with a large autonomy, the police, be regulated by law? In the case of the use of deadly force, the subject remains understudied in Europe. A 2017 law in France relaxed restrictions and allowed for the first time the national police to use weapons beyond self-defense. This quasi-experimental study examines the impact that this regulatory change, used as an exogenous shock, has had on the number of deaths of occupants of vehicles. The monthly number of killings has significantly increased for the national police (experimental group), who are directly affected by the new regulation, but not other forces unaffected by the regulation such as the French gendarmerie, a military status force (control group 1), and other police forces of two neighboring states (Germany, Belgium, control group 2 and 3). The findings hold after controlling for the variations in level of violence in society, and police exposure to and death in dangerous traffic violations during the study period. When using more conservative specifications, the observed increase in lethal shootings does not reach statistical significance due to a lack of statistical power related to the rarity of police lethal shootings in the European context. We recommend that national regulations governing the use of weapons by police more clearly and unambiguously embed the notions of proportionality and absolute necessity
Direct Observation of a Fundamental Arylium Species Using Photoelectron Spectroscopy: Singlet–Triplet Gap in Phenylium
No full textInternational audienceReactive intermediates such as aryl cations play crucial roles in organic and astrochemical processes, yet their characterization remains a significant experimental challenge. The present study offers the first partially vibrationally resolved photoelectron spectrum of the phenyl radical (C 6 H 5 ), focusing on ionization thresholds to the lowest singlet and triplet states of its cation. Using synchrotron-based photoelectron spectroscopy, we directly determine the adiabatic ionization energy of the first triplet state of phenylium (C 6 H + 5 , IE ad (ã + ← X) = 9.300(10) eV), and use this as an anchor to derive the singlet-triplet energy gap (∆E(S -T) = 1.043(32) eV) with assistance from advanced quantum chemical computations. These findings provide new constraints to thermochemical properties essential in Arylium ground state determination (and thus essential for a better understanding of Arylium chemistry), and establish a framework for future joint spectroscopic-computational studies of more complex arylium compounds.</div
Upstream moisture sources and circulation patterns controls Asian monsoon hydroclimate over the past 20,000 years
No full textInternational audienceSpeleothem oxygen isotope records (δ18O) from caves in the Asian monsoon region have been widely utilized to reconstruct paleo-monsoon variability. However, interpreting these records remains challenging due to conflicting hypotheses about their relationship with Asian Summer Monsoon (ASM) strength and regional rainfall patterns. In this study, we analyzed 15 cave stalagmite δ18O records collected across East and South Asia, covering the last 20,000 years. Our analysis focuses on key climatic events, including Heinrich Stadial 1 (HS1), the Bølling-Allerød warm period (BA), and the Younger Dryas (YD), to explore the driving force of Asian summer monsoons from both high-latitude North Atlantic climate and lower-latitudes atmospheric circulation patterns. The results revealed that speleothem δ18O variations were predominantly influenced by shifts in upstream moisture sources, particularly from low-latitude regions in the Indian and Pacific Oceans, as evidenced by both observational data and model simulations. We demonstrated that δ18O records from Chinese caves reflect not only local rainfall dynamics but also broader influences from upstream moisture sources
