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Li-Mg alloys as anode for Li batteries in liquid electrolytes: Preparation, shaping, characterization and parametric electrochemical study
No full textInternational audienceLithium-metal batteries offer significant energy density advantages over classical Li-ion technology but their practical implementation is hampered by the poor reversibility of the lithium deposition/stripping processes. To solve this issue, Li-Mg alloys have already been considered as possible alternative and are examined in greater details herein. Homogeneous Li-rich alloys (β-phase) with controlled composition (5–13 at.%Mg) were fabricated and electrochemically reacted with Li to explore the kinetics of the Li-driven β−α phase equilibrium. We showed that the (de)lithiation of the β-phase that occurs at ∼0 Volt vs Li+/Li°, and therefore the most interesting, is strongly limited with the early appearance of Mg-rich α-phase at higher voltages. We demonstrated that this β-domain can be largely extended by using moderate cycling temperature (40 °C), low current density, high initial Li/Mg ratio and rest sequences. Post-cycling observations reveal that repeated (de)alloyings proceed without dendritic growth but rather involve the continuous growth of a porous surface film at the expense of the dense Li-Mg alloy resulting in a sudden drop in capacity when the electrode is becoming completely porous. By limiting the capacity, it is possible to control the progression of this porous layer, improve the efficiency of the Li plating-stripping process, and thus achieve a thousand cycles (0.8 mA.cm-2, 0.8 mAh.cm-2). In full cells, better reversibility is spotted for LiFePO4/Li17Mg compared to LiFePO4/Li cells provided that cycling rate is not pushed over ∼1.2 mAh.cm-2. Overall, we hope these results will provide useful insights for the design of lithium alloy electrodes to improve lithium-metal batteries
Présence Integral Presence at Work as a means to Spiritually Transform Organizations
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Novel Zn-doped Nasicon-based glass-ceramic with superior Li-conductivity and enhanced properties as a solid electrolyte
No full textInternational audienceAmong the diverse array of solid electrolyte options, glass-ceramics hold great promise for application in all-solid-state lithium batteries. In this respect, we have effectively developed novel glasses and glass-ceramics through an innovative approach that integrates a glass-ceramic strategy with the newly introduced zinc-doped Nasicon phase. This was achieved by applying melt-quenching techniques coupled with meticulous control over the crystallization process, guided by a thorough study of crystallization kinetics. The crystallization kinetics have unveiled a two-dimensional nucleation mechanism with an activation energy of 165 kJ.mol-1. X-ray diffraction (XRD) analysis revealed the emergence of a novel Zn-doped Nasicon phase, identified as Li1.6Zn0.3Ti1.7(PO4)3, within the 30Li2O-20ZnO-20TiO2–30P2O5 glass-ceramic, a validation corroborated through Rietveld refinement. Indeed, FT-IR, Raman, and NMR analyses confirmed the formation of Li1+2xZnxTi2-x(PO4)3 Nasicon phase within the glass-ceramics structures. Moreover, SEM images, complemented by TEM observations and density assessments, provide evidence for the creation of a dense, pore-free glass-ceramic with a striped microstructure. The 30Li2O-20ZnO-20TiO2–30P2O5 glass-ceramic demonstrates outstanding chemical durability and robust mechanical properties. Notably, it exhibits high total ionic conductivity, reaching 7.14.10–4 Ω-1.cm-1 at room temperature, while displaying low electronic conductivity of 8.10–9 Ω-1.cm-1, aligning with findings from UV–visible spectroscopy. Additionally, the lithium transference number is confirmed to be 0.99, positioning the developed glass-ceramic as a highly competitive solid electrolyte in the field of energy storage. DFT calculations were conducted on the crystallized Li1.6Zn0.3Ti1.7(PO4)3 NASICON phase to gain detailed insights into its thermodynamic stability and electronic properties
Fluorescein Angiography as a Surrogate Marker of Disease Activity in Susac Syndrome
No full textInternational audienceObjectivesTo evaluate the sensitivity of fluorescein angiography (FA) in detecting disease activity in Susac syndrome. MethodsWe conducted a blinded analysis of all FA, brain MRI, and audiogram examinations performed throughout the follow-up of patients with Susac syndrome. ResultsA total of 79 FA examinations, 85 brain MRI scans, and 49 audiograms were analyzed from 9 patients followed for a mean (SD) period of 6 (4) years. Disease activity was detected in 41.5% of FA examinations, 10.5% of MRI scans, and 25% of audiograms (FA vs MRI, p < 0.0001; FA vs audiogram, p = 0.06; audiogram vs MRI, p < 0.05). Within 3 months of clinical relapses, activity was observed in 57%, 24%, and 27% of FA, MRI, and audiogram examinations, respectively (FA vs MRI, p < 0.05; FA vs audiogram, p = 0.09; audiogram vs MRI, p = 1). Quantitative analysis of FA showed a mean (SD) of 2.5 (2.5) leakages (both eyes) during relapses compared with 1.2 (1.4) during remission (p < 0.05). DiscussionFA, particularly arterial leakage, demonstrated the highest sensitivity in detecting disease activity and may be a valuable tool for treatment management in Susac syndrome. Future studies with larger samples should aim to identify the optimal threshold of FA changes associated with an increased risk of relapse.</div
Responsabilités communes mais différenciées en matière de consommation durable : l’apport des Principes directeurs des Nations unies pour la protection des consommateurs
No full textInternational audienceThe 1985 United Nations Guidelines for Consumer Protection aim at defining the main characteristics consumer protection laws must possess, the institutions responsible for enforcing them, and the mechanisms for guaranteeing such protection. The 1999 and 2015 revised versions of the Guidelines, which were then expanded to sustainable development issues, introduced a reference to the principle of common but differentiated responsibilities (CBDR principle) between member states. Developed in international environmental and climate change law, this principle is traditionally used to introduce a degree of flexibility in the implementation of binding obligations by States in light of their specific situation. Despite being widely discussed in doctrine, the introduction of this principle in the Guidelines and its impact on consumer protection and sustainable consumption remain largely unexplored to date. The present contribution aims to document the little-known interface between the CBDR principle and sustainable consumption, on the one hand, and to question its added value in the context of non-binding recommendations, on the other.Les Principes directeurs des Nations unies pour la protection des consommateurs de 1985 (ci-après les « Principes directeurs ») ont pour triple objectif de définir les principales caractéristiques auxquelles doivent satisfaire la législation, les institutions chargées de la faire respecter et les mécanismes permettant de garantir la protection des consommateurs. Leur élargissement aux enjeux de développement durable en 1999 et 2015 s’est accompagné d’une référence au principe de responsabilités communes mais différenciées (PRCMD) entre États membres. Utilisé principalement en droit international de l’environnement et de la lutte contre les changements climatiques, ce principe est traditionnellement utilisé pour introduire une certaine flexibilité dans la mise en œuvre d’obligations contraignantes, au regard de la situation ou contraintes propres des États concernés. En dépit d’un large traitement en doctrine, la récupération de ce principe par les Principes directeurs et son impact en matière de protection du consommateur et de consommation durable demeurent à ce jour largement inexplorés. La présente contribution vise à documenter l’interface peu connue entre PRCMD et consommation durable, d’une part, et interroger sa valeur ajoutée s’agissant de recommandations non contraignantes, d’autre part
Momentum, vorticity and scalar transport in turbulence: the Taylor–Prandtl controversy
No full textInternational audienceThe ‘vorticity transport’ theory by G. I. Taylor states that, in two-dimensional (2-D) turbulent flows, it is not the momentum of the eddies which is conserved from one step of their random walk to the other (the so-called Reynolds–Prandtl analogy), but their vorticity, implying that the conservation laws for the time-averaged profiles for the velocity u and concentration of a passive scalar c must be different. This theory predicts that, across a 2-D wake or a jet, both fields (scaled by their maximal value) are exactly related to each other by u =c. We reexamine critically this problem on hand of several experiments with plane and round turbulent jets seeded with high and low diffusing scalars, and conclude that the microscopic equations for u and c are identical, but that the differences between the u- and c-fields is a genuine mixing problem, sensitive to the dimensionality of the flow and to the intrinsic diffusivity of the scalar D, through the Schmidt number (Sc =ν/D) dependence of the flow coarsening scale. We observe that u =c with β =2 in plane jets irrespective of Sc, β =3/2 in round jets at Sc =1 and β =1 in round jets for Sc→∞. We explain why, because measurements dating back to the 1930s–40s were all made for heat transport in air (Sc ≈1), agreement with Taylor‘s vision was only coincidental. The experiments and the new representation proposed here are strictly at odds with Reynolds’ analogy, although essentially an adaptation of it to eddies transporting momentum and mass, but liable to exchange mass with a smooth reservoir along their Brownian path
L’employeur est tenu de reclasser rapidement le salarié déclaré inapte
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Abbas Kiarostami, à rebours
No full textInternational audienceLorsqu’Abbas Kiarostami (1940-2016) découvre la vidéo numérique, le support l’enthousiasme immédiatement. Ce nouvel outil répond si bien à sa conception du cinéma qu’il annonce qu’il ne tournera plus jamais en pellicule. Dans une approche analytique, cet essai revient sur les productions numériques du cinéaste iranien, ainsi que sur ses films plus anciens. Argentique ou digital, le cinéma reste, pour lui, un art du temps et du mouvement dans lequel tout est prétexte à une réflexion sur l’image. La caméra numérique lui permet d’acquérir une nouvelle liberté, d’explorer une forme d’autonomie de l’image, et de jouer avec des modes de pensée non filmiques, quand la réalisation d’installations vidéo renouvelle sa conception du cinéma. Le dialogue entre technique et esthétique donne ici à saisir la dimension expérimentale d’une pensée du cinéma en perpétuel mouvement
Repenser les pratiques d'enseignement et d'apprentissage par la robotique éducative : le cas du robot socio-émotionnel Buddy
No full textInternational audienceThis paper explores the use of Buddy in educational and learning contexts, focusing on two key uses. First, at the National Higher Institute of Teaching and Education in Aix-Marseille, with future teachers and digital pedagogy students. Second, as an emotional and artistic mediator in art learning. The paper examines how Buddy can enhance teaching practices by stimulating creativity, interaction, and emotional and educational support. Acting as a mediator between the learner and their environment, particularly in storytelling, art, and informational assistance, Buddy highlights the potential of robotics to develop inclusive pedagogical practices where art and technology converge to promote learning and emotional resilience. Through these experiments, Buddy serves as a learning catalyst, opening avenues for interdisciplinary research involving computer engineering, psychology, and education. The current technical limitations of Buddy offer opportunities to design educational scenarios that demystify artificial intelligence, shedding light on its biases and limitations.Cet article explore l'utilisation de Buddy dans un contexte éducatif et d'apprentissage, avec un focus particulier sur deux usages. Premièrement, à l'Institut National Supérieur du Professorat et de l'Éducation d'Aix-Marseille avec des étudiants futurs profs des écoles, collèges et lycées ainsi que des étudiants en ingénierie pédagogique numérique. Deuxièmement, dans un contexte spécifique comme médiateur artistique et émotionnel dans l'apprentissage de l'art. Cet article s'intéresse à la façon dont ce robot peut enrichir les pratiques pédagogiques en stimulant la créativité, l'interaction et l'accompagnement pédagogique et émotionnel des apprenants. Buddy peut agir comme médiateur entre l'apprenant et son environnement, en particulier dans les domaines de la narration, de l'art et de l'assistance informationnelle. Cette expérimentation du robot Buddy, met en lumière les possibilités de la robotique dans le développement de pratiques pédagogiques inclusives, où l'art et la technologie convergent pour favoriser l'apprentissage et la résilience émotionnelle. À travers ces expériences, le robot devient un catalyseur d'apprentissage et de réflexion, tout en ouvrant des perspectives pour une recherche interdisciplinaire impliquant l'ingénierie informatique, la psychologie et l'éducation. Les limites techniques actuelles de Buddy, loin d'être des obstacles, offrent des opportunités pour concevoir des scénarios pédagogiques visant à démythifier l'intelligence artificielle, en mettant en lumière ses biais et ses limitations
An Alkaliphilic Chitinase Unveils Environment-Dependent Variation in the Canonical Catalytic Machinery of Family-18 Glycoside Hydrolases
No full textInternational audienceChitinases belonging to glycoside hydrolase family-18 (GH18) employ substrate-assisted catalysis and typically have neutral/acidic pH-optima. We describe the structural and functional analysis of CaChiA, a chitinase from the anaerobic alkaliphilic bacterium Chitinivibrio alkaliphilus with an alkaline pH optimum (8.8) and unique active site features, including a noncanonical catalytic HxxExDxE motif, which is DxxDxDxE in other chitinases. Propka calculations indicated a significantly higher pK a for the catalytic acid/base, Glu148, in CaGH18, compared to other GH18 enzymes, aligning with its alkaline pH optimum. Both Propka calculations and functional studies of enzyme variants with mutations in the catalytic center suggested that not the change in the catalytic motif, but rather a unique glutamine, Gln57, modulating the properties of this motif, enables activity at alkaline pH. Further characterization of CaChiA unveiled additional peculiar enzyme properties, such as a unique ability to convert chitin to chitotriose. Thus, CaChiA adds novel catalytic capabilities to the widespread family of GH18 chitinases, made possible by adaptation of an intricate catalytic center