HAL-Artois
Not a member yet
27242 research outputs found
Sort by
Structural and magnetic properties of mixed-metal (Bi2O2)(Fe 1−xMxF4) Aurivillius oxyfluorides
No full textInternational audienceA series of mixed-metal Aurivillius oxyfluorides of the ideal formula [Bi2O2][Fe1−xMxF4] was synthesized by hydrothermal synthesis with M = Mn, Co, and Ni. We first re-examined the Fe-only compound and deduced that despite the observation of inhomogeneous lattice parameters between batches, the iron valence remains constant around Fe∼2.5+ in all samples measured using Mössbauer spectroscopy. The mixed valency charge compensation is mainly assigned to the formation of Bi vacancies. For the mixed Fe/M phases, the most common observation, using various diffraction techniques, of long-range ordering between tilted [(Fe,M)F6] octahedra in the perovskite layers is reminiscent of the Fe, Co, and Ni parent members. This validates the possibility of well-defined anion-ordering, despite the mixing of cations with different ionic radii. A qualitative matching between the lattice evolution along the Fe/M solid solutions and our DFT relaxed ideal models supports this idea. Differences in the magnetic structures are observed between the single-metal and the mixed Fe/M compositions, while retaining ordered magnetic structures and escaping spin-glass behavior despite disordered Fe/M ions. In contrast to the non-collinear antiferromagnetic spin arrangements obtained in most of the parent cases, the majority of the mixed Fe/M compounds show a collinear structure with spins aligned along the c-axis, similar to the single-metal M = Mn2+ (L = 0) case in which spin–orbit coupling is absent. This suggests the predominant role of the spin contribution to the ordering of the magnetic moments as soon as both Fe and M intervene
Enhancing heat transfer in concentric-tube heat exchangers: A CFD study on multi-tube configurations and design criteria
No full textInternational audienc
Deriving accurate galaxy cluster masses using X-ray thermodynamic profiles and graph neural networks
No full textInternational audiencePrecise determination of galaxy cluster masses is crucial for establishing reliable mass-observable scaling relations in cluster cosmology. We employ graph neural networks (GNNs) to estimate galaxy cluster masses from radially sampled profiles of the intra-cluster medium (ICM) inferred from X-ray observations. GNNs naturally handle inputs of variable length and resolution by representing each ICM profile as a graph, enabling accurate and flexible modeling across diverse observational conditions. We trained and tested GNN model using state-of-the-art hydrodynamical simulations of galaxy clusters from The Three Hundred Project. The mass estimates using our method exhibit no systematic bias compared to the true cluster masses in the simulations. Additionally, we achieve a scatter in recovered mass versus true mass of about 6%, which is a factor of six smaller than obtained from a standard hydrostatic equilibrium approach. Our algorithm is robust to both data quality and cluster morphology and it is capable of incorporating model uncertainties alongside observational uncertainties. Finally, we apply our technique to XMM-Newton observed galaxy cluster samples and compare the GNN derived mass estimates with those obtained with -M scaling relations. Our results provide strong evidence, at 5 level, for a mass-dependent bias in SZ derived masses, with higher mass clusters exhibiting a greater degree of deviation. Furthermore, we find the median bias to be , albeit with significant dispersion due to its mass dependence. This work takes a significant step towards establishing unbiased observable mass scaling relations by integrating X-ray, SZ and optical datasets using deep learning techniques, thereby enhancing the role of galaxy clusters in precision cosmology
The reassessment of Lignosus dimiticus (Basidiomycota, Polyporales), an enigmatic polypore rediscovered in the Central African Republic, and the new genus Microporellopsis (Fibroporiaceae)
No full textInternational audienc
Une intervention de littératie physique de longue durée pour améliorer les indicateurs de santé et les niveaux d'activité physique chez les adolescents en surpoids et obèses
No full textInternational audienceBackground The aim of this study was to present the effects of a long-duration Physical Literacy intervention on the healthof overweight and obese adolescents.Methods CAPACITES 64 was a quasi-experimental study of 14 overweight and obese adolescents. The intervention wasconducted for 15 months, with two measurement times.Results The intervention significantly increased the overall Physical Literacy score (Δ = + 7.6 points; p < 0.05). The%Skeletal Muscle Mass (Δ = + 3.5%; p < 0.05) and the VO2peak(Δ = + 3.4 ml.min.kg−1; p < 0.05) increase significantly,also. Decreases in Z-score Body Mass Index (Δ = -0.5; p < 0.05) and %Body Fat (Δ = -6.1; p < 0.05) were observed. Nosignificant effect on Moderate to Vigorous Physical Activity is identified (Δ = -0.2 min.day−1; p = 0.09).Conclusions This study revealed that a long-duration Physical Literacy intervention had a positive effect on health indicatorsand prevented a decrease in the level of physical activity in overweight and obese adolescents
La « plus petite France » de Vichy mise à nu par ses indésirables
No full textInternational audienceThe Irregulars – exiles, foreigners, and marginalized writers – bore witness to defeated France from a displaced position. Their lucidity in the face of History, their attention to language, and their rejection of heroic narratives shape an alternative memory of the Occupation, built on silence, ambiguity, and discreet forms of resistance – a missing link in our literary history of the Twentieth centuryLes Irréguliers – exilés, étrangers, écrivains en marge – témoignent de la France défaite depuis une position décentrée. Leur lucidité face à l’Histoire, leur attention à la langue et leur rejet des récits héroïques dessinent une autre mémoire de l’Occupation, faite de silences, d’ambiguïtés et de résistancesdiscrètes, qui constitue un chaînon manquant de notre histoire littéraire du xxe siècle
Gold Nanostructures Stabilized on Layered Polydimethylsiloxane-Like Porous Silica Framework as a Solvent-Free Heterogeneous Catalyst for Hydroamination
No full textInternational audienceBifaceted building blocks possessing a layered hydrophobic polydimethylsiloxane (PDMS)-like framework and segment-enriched silica network with permanent porosity have been crafted for hosting and stabilizing gold nanoparticles. The as-prepared solid materials were used as heterogeneous catalysts for solvent-free hydroamination. Unlike mesostructured-type and conventional silica supports, the more pronounced hydrophobicity of PDMSiO2 provides the driving force for preventing imine hydrolysis, allowing consequently for improving the yield to 94% and selectivity to 99%
Urban Agricultural Soil
No full textInternational audienceThis chapter explores the history of urban agriculture, the diversity of urban soils involved and the challenges that cities face in terms of the services provided and their management. The forms of agriculture that have developed are shaped by available space, the nature of the soil, the farming system and on the type of production or again on the distribution channel. There are many different definitions for urban soils depending on whether the approach used is oriented toward spatialization or toward the origin of the soil. The common effects of anthropization on a soil's physicochemical parameters are observable. Urban agriculture projects are inserted into channels for the distribution and consumption of various food products: from personal consumption to more or less short circuit marketing. Many decision-making tools have been developed for urban agriculture in order to meet to needs of agriculture project leaders, the different actors in urban planning or community technical servic
Development of New Anodes based on 1,4-Trans Polymyrcene and Carbon Graphite for Microbial Fuel Cells
No full textInternational audienceThis study investigates the electrolysis of ethanol in 1 M NaCl using a carbon paste electrode (CPE) modified with trans-1,4-polymyrcene, a polymer known for its catalytic properties. The electropolymerization process was performed using both potentiostatic and galvanostatic techniques, each offering distinct benefits to the electrode's performance. The potentiostatic method produced a uniform polymer layer, enhancing catalytic stability and consistency. Significant improvements were observed with the modified CPE/polymer electrode: double-layer capacitance increased from 4.18 μF/cm² to 603.7 μF/cm², and charge transfer resistance decreased from 40.85 kΩ.cm² to 2.01 kΩ.cm². Galvanostatic polymerization optimized polymer density and morphology, improving surface characteristics. Optical microscopy confirmed the polymer layer's uniformity and ideal thickness, improving ethanol oxidation efficiency due to better electron transfer. The polymer’s stability and cost-effectiveness suggest it is suitable for sustainable, repeated use. These results demonstrate the potential of trans-1,4-polymyrcene-modified CPEs for biological catalysis and environmental monitoring, contributing to the development of efficient electrochemical devices
