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Fluorination Strategies for Mn₃O₄ Nanoparticles: Enhancing Reversibility and Capacity in Li-Ion Batteries
No full textInternational audienceTransition metal oxides (TMOs) occupy an increasing share in the search for new electrode materials for Li-Ion batteries. Despite promising electrochemical performances (up to 1000 mAh g−1 in the case of conversion), these materials have poor cyclability linked primarily to hysteresis phenomena. To improve their electrochemical performance, one strategy consists of reducing the particle size. A second strategy relies on the incorporation of fluorine directly into electrode materials to limit the solid–electrolyte interface (SEI). Our study focuses on the impact of fluorination on the electrochemical performance of manganese oxide obtained by solid combustion synthesis (SCS). Two fluorinating agents were used: pure gaseous molecular fluorine F2 and radical fluorine F• through xenon difluoride XeF2 decomposition. The use of F2 results in strong fluorination localized primarily at the particle surface while XeF2 diffuses deeper into the particle, resulting in the removal of residual carbon from the synthesis by combustion. The electrochemical performance of the oxide fluorinated with XeF2 reaches more than 750 mAh g−1 after 160 cycles, whereas that of the oxide fluorinated by F2 barely exceeds that of the non-fluorinated oxide, less than 200 mAh g−1 after 200 cycles
Exploring a conservative staggered scheme for Boussinesq-type equations: Insights into numerical diffusion, dispersion, and wave-breaking
No full textInternational audienceAccurate and efficient modeling of coastal wave transformation, particularly under wave-breaking conditions, remains a major challenge for Boussinesq-type models. To address this, we introduce and validate a conservative staggered-grid scheme to discretize a set of weakly nonlinear Boussinesq-type equations. The presented approach revisits the staggered finite-difference strategy by ensuring a momentum-conserving solution designed to enhance numerical stability and improve shock-capturing properties. The scheme's performance is assessed through a series of numerical tests involving monochromatic and spectral linear wave propagation. These tests demonstrate that the conservative staggered scheme is much less sensitive to grid resolution, resulting in approximately one order of magnitude lower numerical diffusion in contrast to the well-established HLLC scheme, while maintaining comparable dispersive accuracy despite using a lower-order spatial reconstruction. Additionally, the scheme introduces a slight negative phase error that compensates for the positive dispersion error inherent in the underlying equations, resulting in improved overall phase accuracy relative to the HLLC scheme. Beyond linear wave propagation, the numerical approach is validated against standard benchmark tests with solitary and spectral breaking waves. In these highly non-linear cases, coupling the conservative staggered scheme with a turbulent kinetic energy (TKE)-based eddy viscosity model yields localized and physically consistent dissipation while preserving the dispersive characteristics of the solution. Compared to conventional hybrid breaking approaches, the TKE-based closure provides enhanced stability, reduced grid sensitivity, and a more accurate representation of energy dissipation during wave breaking. These results underscore the potential of the conservative staggered scheme as an efficient and robust framework for computing complex coastal and nearshore wave processes.</div
Siderophore‐Dependent and ‐Independent Iron Acquisition Pathways in Marinobacter Nauticus SP17
No full textInternational audienceWe explored the iron acquisition pathways of Marinobacter nauticus SP17, which exhibits distinct growth modes, manifesting as a planktonic population on acetate and forming a biofilm while utilising n ‐alkanes or triglycerides as substrates. The expression of genes encoding iron‐containing proteins and growth yields measured under varying iron concentrations suggest that the balance between iron demand and availability plays a key role in regulating these genes in response to the carbon source and/or growth mode. Phenotypic studies of a petrobactin‐deficient mutant revealed that, although this siderophore is important, it is not essential for growth on all substrates under iron‐deplete conditions. This suggests the presence of petrobactin‐independent iron acquisition pathways. One such pathway involves the ferric ion‐binding protein FbpA, as a ΔfbpA mutant exhibits reduced growth on all substrates tested under iron limitation. Notably, the double mutant (Δ asbABF Δ fbpA ) failed to grow, demonstrating that petrobactin and FbpA contribute to two distinct major iron acquisition pathways. The siderophore‐dependent and ‐independent pathways appear to be largely functionally redundant and are involved in iron acquisition in all growth modes on all carbon sources tested
Biotransformation of Selenium in Yeast—Speciation and Nanostructural Analysis
No full textInternational audienceSelenium (Se) is an essential trace element for human and animal health, and its deficiency in the diet can lead to metabolic disorders. Se-enriched yeast could be an alternative Se supplement for humans. This study aimed to evaluate the bioaccumulation, the biotransformation, and the production of selenium nanoparticles (SeNPs) in Saccharomyces cerevisiae ATCC 7090 as a conventional yeast compared to Rhodotorula glutinis CCY 20–2-26. Identifying selenium compounds and characterizing nanoparticles (SeNPs) formed in their cells using RP-HPLC-ICP-MS and UHPLC-ESI-Orbitrap-MS. In S. cerevisiae ATCC 7090 at the concentration of 10-mg Se4+/L in medium, selenium in the cells (1559 μg Se4+/g) accumulated higher amounts than in R. glutinis CCY 20–2-26 (1202 μg Se4+/g). Additionally, several selenium species were identified in S. cerevisiae ATCC 7090 cells, commonly known in the conventional yeast, whereas only two selenium species were found in R. glutinis CCY 20–2-26. The size distribution of SeNPs was a range of 60 to 180 nm in S. cerevisiae ATCC 7090 and 40 to 260 nm in R. glutinis CCY 20–2-26. Even though the size of SeNPs were comparable to a therapeutic range (≤ 200 nm), SeNPs were less uniform in R. glutinis CCY 20–2-26. Thus, the overall selenium levels and SeNPs produced by R. glutinis CCY 20–2-26 were significantly lower than the conventional yeast (S. cerevisiae ATCC 7090). The content of SeNPs in the biomass of yeast S. cerevisiae and R. glutinis was 13 and 9 µg/g, respectively. The findings highlight these yeasts’ biotechnological potential in producing selenium-rich dietary supplements and nanomaterials
La fonction poïétique de la minéralogie dans l’œuvre céramique de Bernard Palissy
No full textNational audienc
Caractérisation des mécanismes moléculaires de TXNDC5 et de son rôle dans la réponse au squalène à l'aide de divers systèmes d'administration de médicaments dans la lignée cellulaire AML12
No full textMetabolic dysfunction-associated steatotic liver disease (MASLD), previously known as non-alcoholic fatty liver disease (NAFLD) is induced by fat accumulation within the liver. Endoplasmic reticulum (ER) stress, oxidative stress, and mitochondrial dysfunction are necessary elements in the development of MASLD. Thioredoxin domain-containing 5 (TXNDC5) is a member of the thioredoxin family and plays a pivotal role as an ER chaperone involved in maintaining cellular homeostasis in stress conditions. Nevertheless, the precise molecular mechanisms through which TXNDC5 exerts its effects on hepatocytes under conditions of oxidative and ER stress remain incompletely understood. The objective of this study was to investigate the effects of TXNDC5 on squalene action, a natural antioxidant found in virgin olive oil, delivered through various drug delivery systems to enhance its bioavailability. Squalene was encapsulated in PLGA and chitosan nanoparticles with the aim of enhancing its cellular uptake in AML12 (alpha mouse liver) cells and TXNDC5-deficient AML12 cells (KO) produced by CRISPR/Cas9 technology. Characterization of the nanoparticles by electron microscopy, dynamic light scattering, zeta potential analysis, and high-performance liquid chromatography confirmed efficient encapsulation and inclusion of squalene at different concentrations. The encapsulation of squalene in chitosan nanoparticles demonstrated a significantly enhanced cellular uptake in comparison to the PLGA and ethanol drug carriers. This enables the administration of higher doses, which enhance hepatocyte viability and reduce ROS levels, effectively compensating for the adverse effects of TXNDC5 deficiency in the context of hepatocyte stress protection.Cell viability assays showed that TXNDC5 has an important role in modulating cell viability under conditions of oxidative and ER stress, as evidenced by the fact that squalene effectively reduced ROS in AML12 cells while increasing ROS in TXNDC5-deficient cells. Squalene was observed to enhance cell viability under conditions of ER stress by decreasing the expression of ER stress markers, including ERN1 and EIF2AK3, and by inducing the expression of protective proteins such as GPx4. To ascertain the function of TXNDC5 in AML12 and KO cell lines, tunicamycin, palmitic acid, and thapsigargin were utilized as stressors. The results from protein expression of the most prominent ER stress markers revealed that among them, the proteins ERN1 and EIF2AK3 were downregulated and HSPA5 was upregulated. Tunicamycin has disrupted the protein levels of HSPA5, ERN1, and EIF2AK3 in KO cells. Palmitic acid modified the protein levels of the ER stress sensors, such as ATF6, HSPA5, and EIF2AK3. TXNDC5 interacted with PRDX6 and HSPA9, proteins involved in the redox regulation of lipid peroxidation and glutathione, and with the loss of TXNDC5, these pathways do have reduced activities, as was recorded by reduced lipid and glutathione peroxidation. Thereby, loss of TXNDC5 impacted mitochondrial functions and specifically disrupted the mRNA levels coding genes that participate in an oxidative stress response and protein folding process.In conclusion, these findings show that TXNDC5 is a modulator of multiple signaling pathways involved in oxidative and ER-induced stresses in hepatocytes, which squalene, given through PLGA and chitosan nanoparticles, prevents the action of these stresses and supports its protective action by the underlying therapeutic implications for modulation of TXNDC5 with a drug-target delivery system to protect the liver.Maladie hépatique stéatosique associée à un dysfonctionnement métabolique (MASLD), anciennement connue sous le nom de stéatose hépatique non alcoolique (NAFLD) est induite par l'accumulation de graisse dans le foie. Le stress du réticulum endoplasmique (RE), le stress oxydatif et le dysfonctionnement mitochondrial sont des éléments nécessaires au développement de la MASLD. La protéine qui contient la thioredoxine de type 5 (TXNDC5) est un membre de la famille des thioredoxines et joue un rôle central en tant que chaperon du RE impliqué dans le maintien de l'homéostasie cellulaire dans des conditions de stress. L'objectif de cette étude était d'étudier les effets du TXNDC5 sur l'action du squalène, un antioxydant naturel présent dans l'huile d'olive vierge, délivré par divers systèmes d'administration de médicaments pour améliorer sa biodisponibilité. Le squalène a été encapsulé dans des nanoparticules de PLGA et de chitosane dans le but d'améliorer son absorption cellulaire dans les cellules AML12 (foie de souris alpha) et les cellules AML12 déficientes en TXNDC5 (KO) produites par la technologie CRISPR/Cas9. La caractérisation des nanoparticules par microscopie électronique, diffusion dynamique de la lumière, analyse du potentiel zêta et chromatographie liquide haute performance a confirmé l'encapsulation et l'inclusion efficaces du squalène à différentes concentrations. L'encapsulation du squalène dans des nanoparticules de chitosane a démontré une absorption cellulaire significativement améliorée par rapport aux vecteurs de médicaments PLGA et éthanol. Cela permet l'administration de doses plus élevées, qui améliorent la viabilité des hépatocytes et réduisent les niveaux de ROS, compensant efficacement les effets indésirables du déficit en TXNDC5 dans le contexte de la protection contre le stress des hépatocytes.Les tests de viabilité cellulaire ont montré que TXNDC5 joue un rôle important dans la modulation de la viabilité cellulaire dans des conditions de stress oxydatif et ER, comme en témoigne le fait que le squalène réduit efficacement les ROS dans les cellules AML12 tout en augmentant les ROS dans les cellules déficientes en TXNDC5. Il a été observé que le squalène améliore la viabilité cellulaire dans des conditions de stress ER en diminuant l'expression des marqueurs de stress ER, notamment ERN1 et EIF2AK3, et en induisant l'expression de protéines protectrices telles que GPx4. Pour déterminer la fonction de TXNDC5 dans les lignées cellulaires AML12 et KO, la tunicamycine, l'acide palmitique et la thapsigargine ont été utilisés comme facteurs de stress. Les résultats de l'expression protéique des marqueurs de stress ER les plus importants ont révélé que parmi eux, les protéines ERN1 et EIF2AK3 étaient régulées à la baisse et HSPA5 était régulée à la hausse. La tunicamycine a perturbé les niveaux de protéines de HSPA5, ERN1 et EIF2AK3 dans les cellules KO. L'acide palmitique a modifié les niveaux de protéines des capteurs de stress du RE, tels que ATF6, HSPA5 et EIF2AK3. TXNDC5 a interagi avec PRDX6 et HSPA9, des protéines impliquées dans la régulation redox de la peroxydation lipidique et du glutathion, et avec la perte de TXNDC5, ces voies ont des activités réduites, comme cela a été enregistré par la réduction de la peroxydation lipidique et du glutathion.En conclusion, ces résultats montrent que TXNDC5 est un modulateur de multiples voies de signalisation impliquées dans les stress oxydatifs et induits par le RE dans les hépatocytes, que le squalène, administré par l'intermédiaire de nanoparticules de PLGA et de chitosane, empêche l'action de ces stress et soutient son action protectrice par les implications thérapeutiques sous-jacentes de la modulation de TXNDC5 avec un système d'administration de médicaments ciblés pour protéger le foie
Towards a model for continuous embedded LES (CELES)
No full textNational audienceThe aim of this work is to develop a novel strategy for embedded LES in the context of continuous/global hybrid RANS/LES (HRL) approaches, called continuous embedded LES (CELES). The issues of Modelled-Stress Depletion (MSD) and Log-Layer Mismatch (LLM), originating due to the presence of the grey-area, are tackled through the use of an active forcing approach wherein the commutation errors due to the hybrid filter are modelled by a fluctuating force introduced in the momentum equation. The Active HRL model thus developed forms the basis for the CELES approach, which is validated in the case of a wall-mounted cube.L’objectif de ce travail est de développer une nouvelle stratégie pour la LES embarquée dans le contexte des approches hyrbides RANS/LES (HRL) continues/globales, appelée LES embarquée continue (CELES). Les problèmes de Modelled-Stress Depletion (MSD) et de Log-Layer Mismatch (LLM), dus à la présence de la zone grise, sont traités par l’utilisation d’une approche de forçage actif dans laquelle les erreurs de commutation dues au filtre hybride sont modélisées par une force fluctuante introduite dans l’équation de la quantité de mouvement. Le modèle HRL actif ainsi développé constitue la base de l’approche CELES, qui est validée dans le cas d’un cube posé sur une paroi
"Unfiction" : internet horror storytelling in the Midst of the Covid-19 pandemic
No full textHorror fiction on the Internet saw a prominent rise in quantity and popularity around the Covid-19 Pandemic. One of the most common traits of the Internet being its complicated relation to what is real and what isn’t, this style of fiction is characterised by its want to appear as believable as it can by its appropriation of the various codes and trends established online. This type of fiction is far from new, but it is important to note how massive it became during the Pandemic, where it was easily able to find a larger audience and gain further recognition than ever before, as it finally was attributed its defined name of “Unfiction.”This research paper’s goal is to find an explanation to this sudden popularity which Unfiction gained during the period between the end of 2019 and the start of 2023. Through this thesis I plan to explore the question: What were the links between Unfiction works created during this time and the general climate of the Pandemic?To answer this problematic question, this paper will firstly recontextualise Unfiction in a broader way to further understand what it brought during such a period of crisis, before carrying out a more thorough analysis of some examples of Unfiction from between 2019 and 2023 to concretely define the themes emanating from this type of fiction at that time. Through these two developments I conclude that Unfiction inserts itself in the continuation of the Horror genre and its main principle of adapting itself around troublesome times to extract and exploit its associated fears, here serving to channel the frustration and growing anxiety surrounding Covid. This idea is further confirmed by the various themes discussed in Unfiction sub-genres and works developed during this time (isolation, nostalgia, powerlessness, technological dependence, etc.).With the direction taken by Unfiction during those years fully established, it would be interesting to pay more attention to what is now being made in this genre of fiction to observe its evolution following its past rise and see what has been maintained, abandoned, or added to its formula. Another possible avenue to think about could be to focus some research on the creative process behind Unfiction to see how one might come to create such a narrative.La fiction à charactère horrifique sur Internet a vu une grande monté en quantité et en popularité aux alentours de la Pandémie causée par le Covid-19. Cette fiction portant énormément des traits d’Internet dans sa façon de se présenter, elle est principalement caractérisée par sa volonté de paraitre aussi vraisemblable que possible par le biais des codes et des tendances partagés sur le Web. Même si ce type de fiction n’est pas nouveau, il reste notable que c’est en grande partie pendant cette Pandémie que celle-ci à trouver une audience bien plus importante qu’auparavant et une reconnaissance plus poussée, lui valant récemment l’adoption de son nom courant sur Internet : la Unfiction. Ce travail de recherche a pour but d’apporter une explication derrière la soudaine popularité de la Unfiction principalement survenu sur la période de fin 2019 à début 2023. Par ce mémoire je compte explorer la question : Quelles sont les liens entre la Unfiction paru à cette période et le climat créé par la Pandémie ? La réponse à cette problématique est développée tout d’abord par une recontextualisation complète de la Unfiction pour davantage comprendre son apport à une période de crise tel que celle-ci, suivi par une analyse poussée de certains exemples surgit entre 2019 et 2023 pour définir concrètement les thèmes émanant de ce type de fiction à ce moment-là. Par ces deux développements j’en conclus que la Unfiction continue un des principes majeurs de l’Horreur de s’adapter et de se construire autour de période de troubles pour en tirer et en exploiter ses peurs associées, ici servant de canal pour exprimer une frustration et une anxiété grandissante au moment de la Pandémie. Cette conclusion est d’autant plus confirmée par les différents thèmes majeurs repris par la Unfiction et ses sous-genres lors du Covid (isolation, nostalgie, impuissance, dépendance à la technologie, etc.). Avec la direction qu’a pris la Unfiction pendant ces quelques années, il serait intéressant de porter d’avantage attention à ce qui émane dorénavant de ce genre pour en constater son évolution suivant son explosion passé et en voir ce qui est maintenu, ce qui est abandonné, et ce qui est apporté. Une plus grande réflexion sur le processus créatif derrière ce type de fiction peut également être une avenue à suivre