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Nb2O5 based photocatalysts for efficient generation of H2 by Photoreforming of aqueous solutions of ethanol
No full textInternational audienceA series of Nb 2 O 5 semiconductors and their composites with TiO 2 have been prepared following a hydrothermal treatment at varied synthetic conditions, and tested for the photoreforming of aqueous solutions of ethanol. The photo-reforming activity has been tested under UV and natural solar light irradiation, both in the absence and in the presence of Pt as co-catalyst. Our data has shown that the Nb 2 O 5 -TiO 2 composite prepared by a hydrothermal treatment of three days displayed the highest photocatalytic activity, with a hydrogen production of 138 mmol H 2 •h -1 •g -1 under UV light (apparent quantum yield of ca. 44 %) and 40 mmol H 2 •kJ -1 •g -1 under natural solar light (apparent quantum yield of ca. 85 % considering only the UV fraction of sunlight). The exalted photocatalytic activity of this material was attributed to the concomitance of two favorable events, namely the possible formation of a heterojunction between the two semiconductors and the optimal ratio of them in this composite.</div
Deconvolution of the finite strainfield from the western French Massif Central: implications on the exhumation of HP rocks and Variscan geodynamics
No full textInternational audienceThe French Massif Central (FMC) forms the hinterland of the west-European Variscan belt and underwent numerous tectonic and metamorphic events from Devonian to Permian periods. The accreted tectonic units belonging to Gondwana and Laurussia were involved in subduction, nappe stacking and syn-to post-orogenic extension to varying degrees. This orogenic evolution suggests that the resulting finite structure likely reflects the interference between fabrics formed at different stages of the orogenic cycle with varying degrees of overprinting, depending on different factors such as spatial strain gradients, lithologies, structural levels or the degree of partial melting. We present a model of finite strain field of the western FMC, based on new structural data from the Limousin area and an extensive compilation of available data. Lineations and foliations were analyzed and interpolated at regional to local scales, using geostatistics. Ductile fabrics within autochthonous units and syn-collisional plutons are poorly disturbed and reflect the transition from syn-thickening to extensional lateral flow of the partially molten mid-lower crust. In contrast, allochthonous units are affected by numerous perturbations, including polyphased ductile shearing, folding and faulting, which induce local block rotations. Considering the overprint of late tectonic events, we show that early fabrics related to high pressure metamorphism or nappe stacking (D1, D2) have undergone significant reorientation. As a result, the finite trend of the associated lineations (L1-L2) must be treated with caution and may not always reflect the original direction of stretching and shearing that occurred during the early compressional stages. By re-analyzing the Lauriéras and Argentat seismic profiles (Limousin), we propose that the allochthonous units are affected by block-tilting induced by listric normal faults that merge at depth, forming the top of an extensional gneiss dome. Consequently, ductile fabrics within allochthonous units are early and should not be interpreted as related to NW-SE syn to post-orogenic extension, as recently proposed for the eastern FMC. Considering i) the spatial distribution and various degrees of reorientation of these early fabrics, and ii) the deconvolution of these disturbances, we propose the following:-The high dispersion of lineation trends in allochthonous units of Limousin can be explained by passive rotations, during later isoclinal folding under dextral transpressional conditions, rather than by two superposed tectonic phases (the so-called D1& D2), as previously inferred,-The allochthonous units from the Limousin form a single tectonic unit,-This main event of ductile deformation in the allochthonous units may be related to the exhumation of the subducted continental crust rather than nappe stacking,-The formation of Variscan orogenic prism in the western FMC may only result of continuous south-directed thrusting rather than a switch from NE-SW to NW-SE thrusting
Changer pour durer, ou le travail en tension. Influence des ressources sur deux trajectoires d’agriculteurs
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Exploring the Coordination Chemistry and Potential Applications of PC3PA-Based Lanthanide Complexes: Synthesis, Solution Structure, Luminescence, and Relaxation Properties
No full textInternational audienceThe novel ligand H3PC3PA was synthesized from pyclen and methyl-6-(bromomethyl)picolinate with 82% overall yield, and its rare-earth complexes (La, Eu, Gd, Tb, Lu, Y) were isolated and characterized by HR-MS and analytical HPLC. Solution 1H and 13C NMR studies of the diamagnetic [Lu(PC3PA)] and [Y(PC3PA)] chelates evidenced non-coordination of the picolinate moiety at the N6 position to the metal. The 1H NMR spectrum of [Lu(PC3PA)] showed diastereotopic CH2 signals corresponding to a single, rigid isomer in solution, while [Y(PC3PA)] displayed sharp signals at higher temperatures, and diffusion-ordered NMR spectroscopy (DOSY) confirmed a single monomer species. [Eu(PC3PA)] and [Tb(PC3PA)] in water showed broad absorption bands at 269 nm due to the picolinate chromophore. [Eu(PC3PA)] displays red emission with a splitting of the 7FJ manifold characteristic of a low-symmetry coordination environment, while [Tb(PC3PA)] shows typical 5D4-7FJ transitions of Tb3+. Emission lifetimes confirmed monohydration of both complexes, in accordance with a non-coordinating picolinate pendant. The relaxivity of [Gd(PC3PA)], r1p = 3.97 mM-1 s-1 (20 MHz, 298 K), is comparable to that of commercial MRI contrast agents. The dissociation half-life of [Gd(PC3PA)] (22 min at pH 1, 25 °C) is short in comparison to that of analogous complexes, evidencing that the non-coordinating picolinate accelerates proton-assisted dissociation
Water Redistribution and Carbonation in Drying Unsaturated Porous Media
No full textInternational audienceEvaporation is a key process in porous hydrosystems affected by human activities or climate-driven underground changes. Basically, it is influenced by complex interactions between the pore structure and external boundary conditions such as relative humidity [1]. Extensive drying not only reduces available pore water but also establishes capillary conditions that modify geochemical dynamics by influencing the driving forces of solid-gas-liquid interactions. [2]; yet these impacts remain largely unexplored at column-scale. In this study, we investigated how evaporation influences pore water redistribution and carbonation reactions in an unsaturated sand-brucite column (Fig. 1). A non-reactive gas with 50% relative humidity was injected from the bottom for over five weeks, and water evaporation was monitored using Time Domain Reflectometry (TDR) sensors and weight measurements. Gas injection initially caused evaporation from bottom and subsequent increasing saturation at top, while continued injection led to evaporation throughout the column, reducing total saturation from 30% to 5% (Fig. 2). At this stage, CO₂ was introduced into the injected gas, triggering brucite carbonation. The CO₂ breakthrough analysis showed less carbonation at the bottom due to limited water availability, while a stepwise trend in the breakthrough curve suggests a possible role of capillarity in CO₂ transport and reaction progression. A separate experiment at the same final saturation (5%) revealed that evaporation history significantly affects water redistribution and carbonation reaction. These findings highlight that water saturation during evaporation does not change in a linear or continuous manner, and the limited water availability induces capillary effects that influence the carbonation reaction. Understanding these effects is essential for predicting long-term processes in diverse subsurface applications such as arid soils management, or geothermal, CO₂ and energy storage systems
Approche interdisciplinaire des unités phraséologiques (UP) dans les langues du mondeLinguistique - TAL & IA - Traduction - Littérature
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Modélisation et structuration d’un dictionnaire bilingue français-chinoisdes expressions idiomatiques : approche lexicographique et ontologique
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Le neurodéveloppement: Une dimension transnosographique
No full textInternational audienceThe neurodevelopmental dimension represents a major challenge for the future of precision psychiatry. It provides a transdiagnostic framework, that allows for the redefinition of psychiatric disorders beyond traditional diagnostic categories, such as autism spectrum disorders, attention-deficit/hyperactivity disorder, schizophrenia, and bipolar disorder. This model is based on the identification of deviations in brain developmental trajectories during critical periods of vulnerability. Using multimodal approaches that integrate clinical, biological, neuroimaging, and neurophysiological data, this framework aims to define an individualized neurodevelopmental burden, opening up new prospects for stratification and the development of personalized treatments tailored to each developmental profile.La dimension neurodéveloppementale est un enjeu majeur pour l’avenir de la psychiatrie de précision. Elle propose un cadre transnosographique, offrant la possibilité de redéfinir les troubles psychiatriques au-delà des catégories diagnostiques classiques, tels que les troubles du spectre de l’autisme, le trouble du déficit de l’attention avec ou sans hyperactivité, la schizophrénie, et le trouble bipolaire. Ce modèle repose sur l’identification de déviations dans les trajectoires du développement cérébral à des périodes critiques de vulnérabilité. Grâce à des approches multimodales combinant des données cliniques, biologiques, de neuroimagerie et de neurophysiologie, cette approche vise à définir une charge neurodéveloppementale individualisée, ouvrant de nouvelles perspectives de stratification et de traitements personnalisés adaptés à chaque profil développemental
