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A Hilbert--Mumford criterion for generalised Monge--Ampère equations
No full textWe give a new numerical criterion in the spirit of GIT for existence of solutions to inverse Hessian equations, including in particular the J-equation. Our criterion is formulated in terms of stability of pairs in the sense of Paul. To that end, we build on previous work of the author with Dervan, and generalise a result of Zhang, proving isometry between generalised Chow line bundles and mixed Deligne pairings
Experimental demonstration of optical energy transfer between the 0th and −1st orders diffracted by an all-dielectric resonant waveguide grating
No full textInternational audienceThe energy transfer between the reflected 0th and −1st orders diffracted by a grating in the vicinity of the Littrow angle is experimentally demonstrated for the first time with an all-dielectric resonant waveguide grating under TE polarization. This effect has already been described in a theoretical approach but never proved by measurements. Contrary to classical configuration, the dielectric resonant diffractive structure is probed here from the grating backside to avoid signal disturbance. A transparent layer of very high refractive index (hydrogenated amorphous silicon: a-Si:H) is structured by e-beam lithography and plasma etching to create a resonant grating waveguide on a BK7 substrate. Agreement between modeling and experimental characterizations validates the energy transfer effect, opening the way to all-dielectric sensing devices
Ischemia-Reperfusion Dynamics in Acute Myocardial Infarction Experimental Swine Model: New Insights from Quantitative CMR
No full textInternational audienceAims To reveal the pattern and dynamics of myocardial edema induced by myocardial infarction (MI) during ischemia and subsequent reperfusion, that remain largely unknown, as are the factors that contribute to reperfusion injury. To propose a time-resolved dynamic myocardial tissue characterization by quantitative CMR, with T1&T2 mapping and Pixel-wise standardized analysis to circumvent inter-animal differences and subjective ROI positioning. Methods and Results We measured T1&T2 relaxation times at baseline, during a 40-minutes transient coronary occlusion, and after reperfusion in an open-chest swine MI model (n=20; 2 shams) using MRI. Myocardial function, early and late gadolinium enhancement were also assessed. Pixel-wise standardized analysis was used to compare the image contents at each pixel across individuals and time points. A significant increase in cardiac T1&T2 times in the ischemic regions occurred during ischemia compared to baseline (mean ΔT1=118.8ms i.e. +11.1%, ΔT2=5.6ms i.e. +11.3%; p<0.05). A global significant and marked increase in T1&T2 times further appeared immediately after reperfusion (mean ΔT1=256.8ms i.e. +23.3% mean ΔT2=11.9ms i.e. +23.6%, p<0.001). This increase was associated with myocardial wall thickness changes, with regional and global dysfunction in the ischemic myocardium. Three different reperfusion patterns were differentiated by the pixel-wise T1 signal analysis: effective reperfusion with microvascular obstruction (MVO), effective reperfusion without MVO and absence of effective reperfusion. We found no correlations between baseline, per-ischemia, and post-reperfusion native T1&T2 times when effective reperfusion occurred. Conclusions Objective quantification of tissue response by pixel-wise analysis demonstrated rapid and significant changes in myocardial water content status post-reperfusion, with three different early-reperfusion patterns observed, suggesting distinct reperfusion mechanisms. The water content after reperfusion does not reflect its state before and it does not provide insight into the final tissue status observed within 3 hours after recanalization
Corporate social responsibility as a signal in the labor market
No full textInternational audienceWorking for a firm engaged in Corporate Social Responsibility (CSR) appeals to potential workers by boosting their self-image and sense of purpose. We propose an additional mechanism: CSR signals a firm's future treatment of workers. Our model links CSR engagement with a firm's propensity to support workers during unforeseen times of need. Under this assumption, a potential future need of the worker leads to more firms engaging in CSR and to a higher workers' willingness to accept lower wages. Our experiment manipulates potential future needs across treatments. While the aggregate analysis does not fully support our theory, exploratory analysis reveals that male workers respond as predicted, whereas female workers do not. Consistently, in a risky environment, male employers increase their CSR engagement, which raises the acceptance rate among male workers. These results do not hold for female employers and workers.</div
Determinants of virological outcomes in kidney transplant recipients treated with maribavir for refractory cytomegalovirus infection
No full textInternational audienceMaribavir has demonstrated promising efficacy in treating refractory cytomegalovirus (CMV) infections among solid organ transplant recipients; however, factors influencing favorable outcomes remain uncertain. We conducted a retrospective cohort study that involved 88 kidney transplant recipients (KTRs) from 22 transplantation centers, all of whom had refractory CMV infections treated with maribavir (63 with and 25 without ganciclovir resistance mutations). CMV clearance at week 8 was achieved in 45 KTRs (51.1%). Among the 49 KTRs (55.7%) who achieved CMV clearance within 16 weeks, 37 (42%) did not develop CMV recurrence. Notably, CMV DNA levels <10 000 international unit/mL at the time of maribavir initiation (odds ratio, 3.21; 95% confidence interval, 1.29-9.54; P = .016) and asymptomatic CMV infection (odds ratio, 3.22; 95% confidence interval, 1.28-9.0; P = .017) were identified as independent factors associated with CMV clearance within 16 weeks without recurrence. Maribavir resistance mutations were identified in 18 KTRs (20.45%), predominantly among those who failed to achieve CMV clearance (35.9%) and those who experienced CMV recurrence (33.3%). In summary, refractory CMV infections characterized by high levels of CMV DNAemia or symptomatic presentations are more challenging to treat with maribavir. These findings may support the development of new strategies for patients at risk of poor outcomes
Opportunities from energy-loss near-edge fine structure analysis to track chemical and structural damage in zircon
No full textInternational audienceZircon (ZrSiO4) is the oldest-known mineral of Earth and an ubiquitous silicate in geochronology. More specifically, the accumulation of alpha decay damage in zircon over time significantly affects its physical and chemical properties, and can lead to a disturbance of the ages measured in this mineral. Therefore, analytical tools that enable comprehensive structural and chemical information at the nanoscale in this compound are highly sought after. In this context, we explore the electron energy-loss fine structures resulting from the excitation of O1s and Si2p core electrons in zircon, which are interpreted from ab initio calculations in a single-particle framework. An excellent agreement is obtained between the experimental and calculated fine structures, emphasizing the large distortion of the final electronic states induced by the core-hole potential. The O-K edge is particularly rich in information, with intense peaks dominated by O2p - Zr4d and O2p - Si3sp hybrids. This work suggests that the near-edge structures from the O1s and Si2p excitations accessible from electron energy-loss spectroscopy or X-ray absorption spectroscopy could be used as tools to follow, interpret and understand structural and chemical modifications in zircon subject to natural radiation damage. We illustrate the potential of this approach through the evolution of near-edge fine structures in a zircon sample that exhibits a locally amorphized zone formed by ultrafast laser excitation
Stiffness-sensitive gene regulation in human mesenchymal stem cells: Modelling mechanotransduction to predict mineralization and bone protein expression
No full textInternational audienceThe goal of our study was to establish how a specific part of the bone Gene Regulatory Network (GRN) controls mineralization in response to stiffness. We hypothesized that a system of differential equations model stiffness-sensitive gene regulation in human mesenchymal stem cells through the epistatic genetic interactions between stiffness (e.g. WNT-β catenin pathway) and five of the main transcription factors and bone proteins (e.g. RUNX2, BSP, OSX, OC, and OPN). To test this hypothesis, we (i) performed in-vitro experiments culturing bone cells on different stiffness, (i) adapted our previously published model from being continuously time-dependent to continuously stiffness-sensitive, and (iii) simulated protein production in function of stiffness and other protein production from the best estimate of parameters coming from the experimental work. Our experimental findings reveal a non-parametric relationship between stiffness and RUNX2 production, with no discernible linear trends for other proteins. Modeling results demonstrate that continuous variations in stiffness enable simulation of bone GRN gene expression, fitting our novel experimental dataset. Specifically, our computational results indicate that OPN production peaks at low stiffness (8 kPa), while RUNX2, OSX, and OC achieve maximum production at higher stiffness levels (64 kPa). This alignment underscores the model's capacity to replicate experimental data accurately. Additionally, our approach predicts that WNT-β-catenin activation serves as an enhancer for OPN and BSP production. The model also highlights a negative feedback-like interaction between OC and BSP production. Stiffness variations were shown to have a significant impact on OC and BSP production and a moderate effect on OPN production. By employing a stiffness-sensitive gene regulation model, we provide insights into one of the mineralization patterns through the prediction of bone protein expression dynamics
Tracing a Wet Past and Diverse Provenances in Gale Crater, Mars, With Lithium Content Using ChemCam on the Curiosity Rover
No full textInternational audienceThe incompatible behavior of Lithium during magmatic differentiation and high mobility during aqueous alteration make it a valuable tracer of crustal processes on Mars. Its preferential incorporation into secondary phyllosilicates further links Li to clay-forming environments, which are critical for evaluating past aqueous activity and habitability. The ChemCam instrument aboard the Mars Science Laboratory Curiosity rover enables remote Li detection through laser-induced breakdown spectroscopy (LIBS) and has provided the first in situ measurements of Li in Martian rocks. Here, we present the first stratigraphically contextualized analysis of Li abundance and variability in Gale crater based on almost 14,000 ChemCam observations across seven major bedrock classes. Lithium abundances are elevated relative to Martian meteorites, particularly shergottites, and broadly track phyllosilicate distribution, increasing in clay-rich units and decreasing where phyllosilicates are absent. However, this relationship breaks down in the Clay-sulfate Transition region, where Li remains elevated despite low phyllosilicate content. The persistence of high Li in this region, as well as in basaltic rocks, points to the presence of a Li-enriched igneous provenance near Gale crater and emphasizes that the Martian crust is more compositionally diverse than that inferred from Martian meteorites alone
Où implanter des Solutions fondées sur la Nature pour répondre à la surchauffe urbaine et à la fragmentation des réseaux écologiques des insectes pollinisateurs : cas d'étude sur la Ville de Lyon
No full textInternational audienceEn France, chaque année, environ 31000 ha passent du statut d'Espace Naturel, Agricole ou Forestier à celui d'artificialisé (Fosse, 2021). Dans la ville de Lyon, 56% de l'occupation du sol est composée de bâtiments et de leurs espaces artificialisés associés ce qui engendre localement de la surchauffe urbaine, et globalement, le phénomène d'îlot de chaleur urbain (Elliot et al., 2020). Parallèlement, l'homogénéisation des modes de cultures et l'utilisation massive de produits phytosanitaires conduisent les insectes pollinisateurs à délaisser les espaces agricoles environnants pour trouver refuge dans les zones urbaines (Baldock et al., 2015; Hall et al., 2017). Les Solutions fondées sur la Nature (SfN), actions visant à améliorer les conditions de la biodiversité tout en répondant à des questions sociétales, ont été récemment développées sur le territoire lyonnais afin de répondre de la meilleure manière aux deux problématiques.Ce travail cherche à tester où des SfN peuvent être implantées dans la ville de Lyon pour permettre de favoriser la connectivité écologique des insectes pollinisateurs tout en tentant de réduire la surchauffe urbaine.À partir d'une cartographie d'occupation des sols modifiée depuis la base CosIA de l'IGN (ajout de hauteur de bâtiments, des routes et des surfaces enherbées sous les canopées), un premier graphe paysager est réalisé pour un groupe d'insectes pollinisateurs. Ce graphe permet d'identifier les ruptures de continuités écologiques à Lyon et de vérifier leur corrélation avec les zones de surchauffe urbaine. De nouveaux nœuds sont ensuite ajoutés dans les secteurs précédemment identifiés. Ils représentent d'hypothétiques SFN (toits verts, murs végétalisés) pensée pour répondre à la fois aux problématiques humaines et animales. Plusieurs scénarios sont étudiés en fonction des spécificités écologiques des pollinisateurs, en termes de ressources nécessaires à leur implantation, leur distance de déplacement (quotidien, dispersion) et des hauteurs atteignables en déplacement vertical par les individus