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CHEXANET: a novel approach to fast-tracking disequilibrium chemistry calculations for exoplanets using neural networks
No full textInternational audienceIn the rapidly evolving field of exoplanetary science with missions like JWST and Ariel, there is a pressing need for fast and accurate simulations of disequilibrium chemistry in exoplanet atmospheres. Methods which assume chemical equilibrium simplify calculations but fail to capture the more complex chemical dynamics observed in actual exoplanets. Accurate estimations require complex kinetic codes that are time-intensive due to the need to solve ordinary differential equations. Given an extensive parameter space that needs to be explored to calculate forward models, kinetic codes will become a significant bottleneck, especially when used to match observations or in retrieval processes. We introduce CHEXANET, a novel U-Net-based neural network architecture designed to efficiently simulate disequilibrium chemistry in exoplanetary atmospheres. By utilizing the thermochemical equilibrium state of a hot-Jupiter’s atmosphere as an initial condition, which computes in seconds, alongside a set of initial parameters such as the C/O ratio, the network effectively learns to predict the atmosphere in disequilibrium. It significantly enhances computational efficiency, reducing the prediction time for atmospheric disequilibrium states to just one second per atmosphere on a standard personal computer – over a hundred times faster than traditional kinetic models like Full and Reduced Exoplanet Chemical Kinetics distiLLed (FRECKLL)
High-Resolution FTIR Spectroscopy of CH3F: Global Effective Hamiltonian Analysis of the Ground State and the 2ν3, ν3 + ν6, and 2ν6 Bands
No full textInternational audienceHigh-resolution Fourier transform infrared (FTIR) spectra of methyl fluoride CH_3F) were recorded in the mid-and far-infrared regions using the Bruker IFS 125HR spectrometer at GSMA (Reims, France) and the SOLEIL synchrotron facility (Saint-Aubin, France). The measurements cover both the pure rotational transitions of the ground state (20 -100 cm-1 ) and the vibrational triad region (1950 -2450 cm-1 ), which includes the 2ν3 , ν3 +ν6 , and 2ν6 bands. Spectra were recorded under various pressure conditions to optimize line visibility, with a high resolution. Line assignments were performed using predictions from the tensorial effective Hamiltonian implemented in the MIRS package, together with a newly developed automated assignment tool, SpectraMatcher, which facilitates line matching and discrimination of CH_3F transitions from overlapping CO_2 features. More than 5000 transitions (up to J = 52 in the ground state and up to J = 45 in the triad and K = 19) were assigned and included in a global fit. The sixth-order tensorial effective Hamiltonian model yielded excellent agreement with experiment, with root-mean-square (RMS) deviations better than 8 × 10-4 cm -1 across all regions. This paper presents the first continuous rovibrational study of CH_3F over both the triad and far-infrared ground state regions. The improved accuracy from previous studies stems from the improved set of effective Hamiltonian parameters which will also form a good basis from future applications in atmospheric modelling and spectroscopic databases
Boza
No full textIn recent decades, emerging challenges such as increased digitalization of social lives and the ongoing processes of border externalization and internalization, have prompted scholars and civil societies to question the ways in which people view, frame and experience migration and draw attention to emerging forms of resistance and mobility justice. This timely Encyclopedia engages with critical epistemologies and practices to provide a comprehensive examination of the field of global migration, activism and cultural production.This contribution explores the term "boza" through migration experiences from Africa to Europe
High coercivity in A0.54Ca0.46Fe6.5Al5.5O19 (A = Ba and Sr) M-type hexaferrite prepared by sol-gel auto-combustion method
No full textInternational audienc
L’inégale perception de la complexité des questions climatiques : perspectives depuis la géographie du secondaire français
No full textInternational audienceThis article looks at the unequal perception of complexity among pupils when it comes to climate issues. How can teaching methods be devised to grasp this issue and develop a more complex understanding of environmental issues? To answer this question, two geography surveys were carried out in French secondary schools, with secondary school pupils (7th, 9th and 10th grades). The first part of the study analyses pupils' perceptions based on questionnaires about their pre-existing knowledge. The second part details two experiential geography schemes designed to transform this spontaneous knowledge into disciplinary and transdisciplinary reasoning. Finally, the third part presents the results, shedding light on the conditions conducive to the conceptualization we developed.Cet article questionne l’inégale perception de la complexité par les élèves concernant les questions climatiques. Comment concevoir des dispositifs didactiques pour saisir cette question et développer une appréhension plus complexe des enjeux environnementaux ? Pour répondre à cette question, deux enquêtes ont été menées en géographie dans le secondaire français, auprès de collégiens (5e et 3e) et de lycéens (2e). La première partie de l’étude analyse les perceptions des élèves à partir de questionnaires sur leurs connaissances préexistantes. La seconde expose deux dispositifs de géographie expérientielle visant à transformer ces savoirs spontanés en raisonnement disciplinaire et transdisciplinaires. Enfin, la troisième partie présente les résultats de l’ensemble de la démarche, éclairant les conditions propices à une conceptualisation plus globale des questions climatiques
Permeation and Selective Retention of Solutes in PEGDA Hydrogel Membranes Containing Free Polymer Chains
No full textInternational audienceWe performed permeation experiments using PEGDA-based hydrogel membranes in which we added free polymer chains. We know from previous studies that free polymer chains can be trapped in the PEGDA matrix. Therefore, we use this property to trigger the retention of solutes through noncovalent interactions (heterogeneous bonds and electrostatic interactions) between the solute and the free polymer chains. We show that proton-donor molecules bearing carboxylic acid groups can be retained by hydrogen interactions at low pH with the free PEG (poly(ethylene glycol)) chains, which are proton acceptors. PEG is a nonionic hydrophilic polymer based on ethylene oxide units (−CH2CH2O−) which is a proton acceptor and can establish hydrogen bonds with proton-donor groups (such as COOH). The extent of retention increases with the number of acidic groups on the solute. By adding PAA (poly(acrylic acid), based on acrylic acid (−CH2CHCOOH), these groups are negatively charged at pH > pKa, i.e., pH > 5) in the PEGDA/PEG membranes, we show that positively charged molecules can be retained inside the membranes at a pH where the PAA is ionized. This retention is reversible, and solute molecules can be flushed out by reducing the pH below the pKa of PAA. By measuring the adsorption isotherm of molecules in the membranes, we obtain the interaction energy between the solute and PAA, which is consistent with electrostatic interactions. Finally, we photopolymerize our membranes directly in a microfluidic chip to perform tangential filtration of a mixture of fluorescein (negatively charged) and rhodamine B (zwitterionic). Fluorescein is repelled by negatively charged PAA and does not penetrate the membrane, while rhodamine B is retained and eventually permeates through. These findings pave the way to functionalization of hydrogel membranes by trapping free polymer chains for selective retention and filtration
Non-Invasive Neonatal Jaundice Detection via Two-Phase Self-Supervised Learning and Vision Transformer
No full textInternational audienceNeonatal jaundice is a potentially serious and prevalent condition that can lead to neurological challenges in newborns if not detected or treated on time. Currently, most approaches employed to diagnose neonatal jaundice are invasive and are often characterized by constraints in accuracy and accessibility, especially in locations with limited resources. To proffer a solution to these challenges, this study presents a vision transformer-based framework, JauNViT, for diagnosing neonatal jaundice. In this framework, a two-phase technique is deployed. The first phase involves the use of Vision Transformer (ViT) to extract deep features from the image data and then use the Self-Relative Clustering (SRC) technique to organize the image data into clinically meaningful clusters and learn discriminative features in the process, facilitating unsupervised learning from limited data. To further enhance the quality of these features, a self-supervised learning strategy based on Linear Centered Kernel Alignment (LCKA) loss was employed to refine the extracted representations. In the second phase, the pre-trained model was fine-tuned on a small labeled dataset, enabling the model to optimize its learned features for efficient neonatal jaundice classification. The proposed dual-phase approach based on ViT yields robust diagnostic accuracy and exhibits prospects of being adaptable to different healthcare settings
Challenges for chlorophyll-a remote sensing: Retrieval of Water Quality Parameters in Creteil Lake Based on Sentinel-2 MSI Imagery
No full textStatut Juridique et Qualité des Hôpitaux : Une Décomposition des Différences de Processus et de Résultats
No full textThe effect of hospital ownership status on quality has been extensively examined in the literature, yet no clear consensus has been reached. Using administrative data from 2014 to 2023 for all acute inpatient stays in France, we aim to study difference in quality between hospital ownership taking into account its multidimensional aspect by using process and outcome indicators. For all indicators, quality in public hospitals is lower than privatehospitals. We apply a Oaxaca-Blinder decomposition to explain mean differences in quality between public, private non-profit, and private for-profit hospitals. We find that, both differences in characteristics (structure, case-mix, environment) and their differences in coefficients explain quality differences but the coefficients effect mainly drive quality differences. The structure characteristics that contribute the most to mean quality differences is the level of specialization. Regarding case-mix, the most important characteristics is the comorbidityindex. Finally, for environment characteristics, GP accessibility is a key contributor. However, when considering the relative importance of all factors, the role of environmental factors is minor compared with structure and case-mix characteristics.L’effet du statut de propriété des hôpitaux sur la qualité a été largement étudié dans la littérature, mais aucun consensus clair n’a encore été atteint. À partir de données administratives de 2014 à 2023 couvrant l’ensemble des séjours hospitaliers en soins aigus en France, nous analysons les différences de qualité selon le statut de propriété des hôpitaux, en tenant compte de sa nature multidimensionnelle au moyen d’indicateurs de processus et de résultat. Pour l’ensemble des indicateurs, la qualité observée dans les hôpitaux publics est inférieure à celle des établissements privés.Nous appliquons une décomposition de Oaxaca-Blinder afin d’expliquer les différences moyennes de qualité entre les hôpitaux publics, privés à but non lucratif et privés à but lucratif. Nos résultats montrent que les différences de caractéristiques (structure, case-mix, environnement) ainsi que les différences de coefficients contribuent toutes deux aux écarts de qualité, mais que l’effet des coefficients constitue le principal déterminant de ces écarts. Parmi les caractéristiques structurelles, le niveau de spécialisation est celui qui contribue le plus aux différences moyennes de qualité. S’agissant du case-mix, la caractéristique la plus importante est l’indice de comorbidité. Enfin, parmi les caractéristiques environnementales, l’accessibilité aux médecins généralistes constitue un facteur clé. Cependant, si l’on considère l’importance relative de l’ensemble des facteurs, le rôle des caractéristiques environnementales reste limité par rapport à celui des caractéristiques de structure et de case-mix