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A discrete fracture model for coupled simulation of water flow and electrical current in fractured vadose zone
No full text(IF 5.9;Q1)International audienceFractures and conduits in the vadose zone can significantly affect the groundwater-surface runoff interaction. Electrical geophysical methods have the potential to provide important information regarding saturation evolution in the fractured vadose zone in the field. Integrating numerical models with the field data can improve the interpretation of the field electrical measurements. In this study we develop and present an advanced method for coupled simulation of variably saturated fluid flow and electrical current distribution in an explicitly fractured porous media. In this model, the fractures are simulated with the hybrid-dimension approach (i.e. 1D fracture elements and 2D matrix elements) discrete fracture matrix model. Mixed hybrid finite element method, previously shown to be significantly more efficient that the conventional finite element method for highly heterogeneous domains, has been used as the numerical method of discretization for both fluid flow and electrical current. The results of the numerical solution are validated by comparing against the results obtained by a finite element based package for three synthetic configurations and the results show that the developed model exceeds the computation performance of the finite element counterpart. The developed model is then used to investigate impact of fracture geometry and the influence of electrical dipole configurations on the simulated electrical response. This work is the preliminary study of a highly efficient new tool for the coupled simulation of water flow and electrical current in fractured vadose zone
Climate risks and economic activity in France: Evidence from media coverage
No full textInternational audienceThis study investigates the impact of climate risks on economic activity in France. Using natural language processing methods on three major French newspapers (Le Monde, Les Echos, and Le Figaro) from 2000 to 2023, we construct a measure of climate risks that we disentangle into physical and transition-risk components. Our findings highlight several transmission channels through which climate risks affect the economy: the business cycle channel, the precautionary savings channel, the inflation channel, and the banking/credit channel. Moreover, while we document the existence of heterogeneous responses to our measures of physical and transition risks, we find that the tone of media coverage of climate risks matters beyond the frequency of published articles. These results remain robust to newspapers’ political slant and ruling political parties’ orientation. Finally, the impact of climate risks also depends on the stringency of environmental policies, with more lenient policies leading to a stronger sensitivity of our economic and financial variables to the media-related climate risk index
Invited Paper: Liquid flow electrification phenomenon: Review
No full textInternational audienceFlow electrification phenomenon is particularly complex as it involves materials, physics, chemistry, and fluid mechanics. It originates from the electric double layer (EDL) present at each solid/liquid interface, which results in a polarization of the interface. This physics equilibrium is determined by the nature of the materials and their physico-chemical properties. It is disrupted by the liquid flow toward a new equilibrium, described by the flow electrification phenomenon. Studied within the research framework in electrochemistry, colloid chemistry, and electrical engineering, EDL remains poorly understood. It relies on models whose viability has yet to be confirmed, as well as on often indirect experimental approaches. Zeta-metry and the flow electrification measurements constitute the main methods of study.The evaluation and control of electrostatic hazard in an industrial and applied context can be achieved either by acting on the genesis of charge generation at interfaces or by addressing the various parameters governing the phenomenon of electrification through flow. Thus, after a description of the EDL, the phenomenon of electrification through flow will be analyzed in detail for both laminar and turbulent regimes. Particular attention will be given to studying this phenomenon in the context of electrostatic hazard in power transformers. Then, a new theoretical analysis of the flow electrification phenomenon under turbulent flows is described. Finally, an overview of new experimental approaches for analyzing the EDL will be presented
Iron-rich microband formation in marine sediments by hydrothermal iron cycling bacteria at Lucky Strike
No full textInternational audienceModels describing banded iron formation deposition beneath oxygenated Paleoproterozoic marine shelf waters assume that microaerophilic iron-oxidizing microorganisms were significant contributors. However, direct evidence for this mechanism is lacking, and it remains unclear how associated primary organic biomass and biogenic iron oxyhydroxides transformed into organic carbon-poor iron oxide/ carbonate-rich bands in banded iron formations. Here we explore in situ modern Zetaproteobacterial iron-oxidizing mats thriving in the Lucky Strike hydrothermal vent field to develop an empirical model that explains the potential contribution of iron-based metabolisms to deposition of rocks resembling banded iron formations. Petrographic, mineralogical, and geochemical data suggest that abundant production of Zetaproteobacterial stalks nucleates and drives spontaneous biotic/abiotic ferrihydrite precipitation in the mats. Subsequent early diagenetic anaerobic microbial oxidation of dead biomass as the mats aged, coupled to microbial reduction of iron oxyhydroxides/oxides, generates ferrous carbonates and mixed valence magnetite. Collectively, this forms crystalline iron-rich organic carbonlean 13C-depleted layers reminiscent of Precambrian banded iron formation microbands
Arc Blanc: a real time ocean simulation framework
No full textInternational audienceThe oceans cover the vast majority of the Earth. Therefore, their simulation has many scientific, industrial and military interests, including computer graphics domain. By fully exploiting the multi-threading power of GPU and CPU, current state-of-the-art tools can achieve real-time ocean simulation, even if it is sometimes needed to reduce the physical realism for large scenes. Although most of the building blocks for implementing an ocean simulator are described in the literature, a clear explanation of how they interconnect is lacking. Hence, this paper proposes to bring all these components together, detailing all their interactions, in a comprehensive and fully described real-time framework that simulates the free ocean surface and the coupling between solids and fluid. This article also presents several improvements to enhance the physical realism of our model. The two main ones are: calculating the real-time velocity of ocean fluids at any depth; computing the input of the solid to fluid coupling algorithm.Les océans couvrent la grande majorité de la Terre. Leur simulation présente donc de nombreux intérêts scientifiques, industriels et militaires, y compris dans le domaine de l'informatique graphique. En exploitant pleinement la puissance du multithreading sur les GPU et les CPU, les outils actuels peuvent réaliser une simulation des océans en temps réel, même s'il est parfois nécessaire de réduire le réalisme physique pour les scènes de grande taille. Bien que la plupart des éléments constitutifs de la mise en œuvre d'un simulateur d'océan soient décrites dans la littérature, il n'existe pas d'explication claire sur la manière dont ils sont interconnectés. Cet article propose donc de rassembler tous ces composants, en détaillant toutes leurs interactions, dans un framework en temps réel qui simule la surface libre de l'océan et le couplage entre les solides et les fluides. Cet article présente également plusieurs améliorations visant à renforcer le réalisme physique de notre modèle. Les deux principales sont : le calcul en temps réel de la vitesse des fluides océaniques à n'importe quelle profondeur ; le calcul de l'entrée de l'algorithme de couplage du solide vers le fluide
La Boétie, Etienne de, Discours de la servitude volontaire. Translation en français moderne (revue) et dossier "Défendre et entretenir la liberté"
No full textInternational audienceTranslation en français moderne (revue par rapport à celle de 2008) et dossier Bac français "Défendre et entretenir la liberté", en collaboration avec Anne Dalsuet.Chronologie, Présentation de l'oeuvre, Histoire littéraire, Groupements de textes, Préparer l'écrit, Préparer l'oral, Exercices d'appropriation, Histoire des art
Selection and characterization of DNA aptamers targeting the surface Borrelia protein CspZ with high-throughput cross-over SELEX
No full textInternational audienceLyme borreliosis (LB) is the most prevalent tick-borne illness, with an estimated 700 000 cases annually in the United States and Europe. The LB diagnosis based on a two-tiered serology remains controversial due to its indirect nature and low sensitivity during the early stage of the disease. Aptamers are single-stranded DNA or RNA oligonucleotides that exhibit high selectivity and specificity for their target due to their unique three-dimensional structure. By applying cross-over-SELEX process, an enrichment of DNA oligonucleotide sequences against a surface protein of Borrelia, named CspZ, has been performed and monitored using absorbance at 260 nm, melting curves and NGS analyses. Beyond sequence enrichment, oligonucleotides binding to CspZ were observed during the selection rounds by Dot Blot and beads assays. Thirteen unique and highly redundant oligonucleotide sequences were further characterized using multiple approaches such as Dot Blot, BioLayer Interferometry and Surface Plasmon Resonance. The selected aptamers showed K D values from tens of nanomolar to the micromolar range by BLI and SPR. Two aptamers, Apta9 and Apta10, characterized by flow cytometry and epifluorescence microscopy, were able to specifically recognize Borrelia burgdorferi sensu stricto. This strategy holds promise for the development of an improved diagnostic assay.</div
Low back pain reduces reliance on the segment rotation mechanism for postural control in challenging postural conditions
No full textInternational audienceIntroduction. Low back pain (LBP) is considered to alter postural control, yet postural control results remain heterogenous in the LBP population. A potential explanation is that postural control has been predominantly characterised by the 'center of pressure' (CoP) mechanism in non-challenging anatomical conditions, omitting the contribution of the 'segment rotation' mechanism (i.e. modification of whole-body angular momentum). The objective of this study was to characterise the impact of LBP on postural control in non-challenging and challenging bipedal upright postures, using indicators illustrating the contribution of both the CoP and segment rotation mechanisms to postural control. Methods. Twenty adults with chronic LBP and twenty age-matched adults without LBP stood quietly on a forceplate in four postural conditions: anatomical with eyes open, anatomical with eyes closed, tandem with eyes open and tandem with eyes closed. ANOVAs were used to compare indicators illustrating the contribution of the CoP and segment rotation mechanisms between groups and conditions.Results. No difference in indicators of the CoP mechanism were observed between the two groups. Smaller results in mediolateral indicators accounting for the segment rotation mechanism were observed for the LBP group in the tandem with eyes closed condition, compared to the control group.Discussion. These findings suggest that LBP impairs reliance on the segment rotation mechanism (i.e. modification of whole-body angular momentum) for postural control, when its contribution is substantial and cannot be compensated by visual feedbacks. Consequently, the segment rotation mechanism should be quantified complementarily to the CoP mechanism in the LBP population
SBA-15 supported Ni-Cu catalysts for hydrodeoxygenation of m-cresol to toluene
No full textInternational audienceAmidst concerns over fossil fuel dependency and environmental sustainability, the utilization of biomass-derived aromatic compounds emerges as a viable solution across diverse industries. In this scheme, the conversion of biomass involves pyrolysis, followed by a hydrodeoxygenation (HDO) step to reduce the oxygen content of pyrolysis oils and stabilize the end products including aromatics. In this study, we explored the properties of size controlled NiCu bimetallic catalysts supported on ordered mesoporous silica (SBA-15) for the catalytic gas-phase HDO of m-cresol, a lignin model compound. We compared their performances with monometallic Ni and Cu catalysts. The prepared catalysts contained varying Ni to Cu ratios and featured an average particle size of approximately 2 nm. The catalytic tests revealed that the introduction of Cu alongside Ni enhanced the selectivity for the direct deoxygenation (DDO) pathway, yielding toluene as the primary product. Optimal performance was observed with a catalyst composition comprising 5 wt.% Ni and 5 wr.% Cu, achieving 85 % selectivity to toluene. Further increasing the Cu content improved turnover frequency (TOF) values, but reduced DDO selectivity. These findings underscore the importance of catalyst design in facilitating biomass-derived compound transformations and offer insights into optimizing catalyst composition for more selective HDO reactions