HAL Portal Univ Catholille
Not a member yet
19763 research outputs found
Sort by
Beyond Climate Change: The Role of Integrated Soil Fertility Management for Sustaining Future Maize Yield in Sub‐Saharan Africa
No full textInternational audienceClimate change is projected to exacerbate food insecurity in sub‐Saharan Africa (SSA) by reducing crop yields and soil fertility. Many climate change impact studies in SSA have overlooked long‐term effects of soil fertility on crop yield. We evaluated maize yields under different scenarios of soil fertility (using soil organic carbon as a proxy) and climate change (considering changes in temperature, rainfall, and CO2) at four sites in SSA. Using an ensemble of 15 calibrated soil‐crop models, we found a strong consensus that, without fertilization, soil fertility declines over time, impacting maize yields more strongly than changes in temperature, rainfall, or CO2. The model ensemble indicated that when accounting for soil fertility changes, the yield benefits of combined application of organic and mineral inputs increase over time, even under climate change. These findings highlight the importance of considering long‐term change in soil fertility when assessing impacts of climate change and integrated nutrient management on crop production in SSA
Ultrasound-Assisted Depolymerization Process of Kraft Lignin by Laccase-Mediator System from Industrial Black Liquor
No full textInternational audienceThe recycling of industrial biomass waste, such as black liquor rich in lignin from the pulp and paper industry, represents a sustainable strategy to reduce environmental impact and promote resource valorization. Enzymatic depolymerization of lignin is considered a promising approach due to the high specificity of lignin-degrading enzymes. However, lignin's poor solubility in aqueous and acidic conditions, combined with its structural complexity and recalcitrance, limits its enzymatic reactivity. In this study, Trametes versicolor laccase was used to depolymerize lignin following a sonication pretreatment designed to improve its solubility and reactivity. Response surface methodology (RSM) identified lignin concentration and sonication time as the most influential parameters for optimizing pretreatment efficiency. The enzymatic depolymerization process revealed a competition between condensation and depolymerization reactions. Characterization of the reaction products using GPC, FTIR, and NMR confirmed the formation of lignin-derived aromatic compounds. These findings highlight the effectiveness of sonication as a pretreatment method to enhance enzymatic lignin degradation. Future research will focus on integrating depolymerization and product separation processes to limit lignin repolymerization and increase the yield of depolymerized aromatic products
Ultrafiltration-based recovery of kraft lignin from black liquor for depolymerization purposes
No full textInternational audienceLignin, the most abundant aromatic biopolymer on Earth, represents a promising renewable resource for sustainable production of bio-based chemicals and energy carriers. However, in the pulp and paper industry, the majority of the 70 million tons of lignin annually generated in kraft black liquor remains underutilized due to its complex composition. This study explores ultrafiltration (UF) as a purification strategy to recover lignin fractions suitable for enzymatic depolymerization. Softwood black liquor was treated using six polymeric membranes (polyethersulfone, regenerated cellulose) with molecular weight cut-offs of 30, 10, and 5 kDa. UF achieved high lignin retention (>95%) across all membranes, while simultaneously rejecting 70–80% of sugars, indicating the presence of lignin–carbohydrate complexes (LCCs). Structural analyses by 31 P NMR and gel permeation chromatography confirmed that LCCs contributed to elevated apparent molecular weights and influenced membrane performance. An acid precipitation pre-treatment cleaved ether-linked carbohydrates, reducing lignin molecular weight by ~40% and improving UF selectivity. Among the tested configurations, the 5 kDa PES membrane proved most effective, combining high retention with favorable permeability and flux recovery after cleaning. These findings provide new insights into LCC-driven separation mechanisms and identify UF conditions enabling the production of purified lignin fractions compatible with enzymatic depolymerization, thereby supporting the development of integrated and sustainable lignin valorization routes in future biorefineries
Microfabricated alkali-vapor cells with tunable He - Ne buffer-gas mixture using reservoirs with laser-actuated break seals
No full textInternational audienceWe report on the generation of a tunable buffer-gas mixture within microfabricated alkali-vapor cells. We show that the combination of low-permeation windows with sequential openings of laser-actuated break seals enables adjustment of a He -Ne noble gas mixture, fully compatible with alkali-metal dispensers. The gas reservoirs and the main cell cavities are initially sealed at the wafer level under distinct helium and neon atmospheres, respectively. Within each cell, after Cs vapor is released from the dispenser, the break seals are successively actuated to incrementally increase the helium fraction in the buffer-gas mixture. This process shifts the atomic clock frequency inversion temperature toward higher values. As an illustration, one of the fabricated cells was operated at 95∘C in a coherent population trapping clock, achieving a fractional frequency stability of 9 ×10−11 at an integration time of 1 day. These results demonstrate the feasibility of precisely tuning buffer-gas compositions in microfabricated vapor cells and support the suitability of He-Ne mixtures for miniature atomic clock applications
Assessing the thermal efficiency of innovative eco-friendly bricks enhanced with phase change materials
No full textInternational audienc
Target trial emulation to replicate randomised clinical trials using registry data in multiple sclerosis
No full textInternational audienceBackground: Target trial emulation (TTE) offers a formal framework for causal inference using observational data, but its validity must be evaluated in each research domain by replicating randomised clinical trials (RCTs). We aimed to replicate eight RCTs evaluating the efficacy of disease-modifying therapies (DMTs) in multiple sclerosis (MS) using French registry data.Methods: This multicentre, retrospective, observational study was conducted using data extracted in December 2023 from the Observatoire Français de la Sclérose en Plaques (OFSEP) database. For each emulated trial, patients were included when they initiated one of the DMT evaluated in the corresponding RCT and met its inclusion criteria. Clinical outcomes were the annualised relapse rate and 3-month confirmed Expanded Disability Status Scale progression. Radiological outcomes were new/enlarged T2-lesions and new gadolinium-enhanced T1-lesions on a brain MRI. A targeted maximum likelihood estimator was used to estimate the treatment effect adjusted for confounding factors between groups and corrected for censoring and missing outcome assessment.Results: 14 111 patients were included in eight emulated trials: ASSESS (fingolimod vs glatiramer acetate), BEYOND (interferon beta vs glatiramer acetate), CONFIRM (dimethyl fumarate (DMF) vs glatiramer acetate), OPERA (ocrelizumab vs interferon beta), REGARD (interferon beta vs glatiramer acetate), RIFUND-MS (rituximab vs DMF), TENERE (teriflunomide vs interferon beta) and TRANSFORMS (fingolimod vs interferon beta). Treatment effects estimated in emulated trials were concordant with RCT findings in seven of eight trials for relapse rate, and in all six trials assessing disability progression. Radiological outcomes were more challenging to replicate; concordance was achieved in three of five trials for new T2-lesions, and one of four trials for new gadolinium-enhanced T1-lesions.Conclusion: The combined use of a TTE methodology and high-quality registry data is a valid tool to evaluate treatment effectiveness in MS
Differential effects of isopropyl alcohol on glucose-induced insulin secretion in INS-1 and MIN6 cells
No full textInternational audienceBackgroundSolvents such as isopropyl alcohol (IPA, propan-2-ol, also called isopropanol) can occasionally be used for drug solubilization in in vitro screening of antidiabetic agents. However, their potential to interfere with pancreatic β-cell function remains poorly characterized.ObjectiveThis study aimed to assess the effects of IPA on insulin secretion and viability in two widely used β-cell models, INS-1 and MIN6.MethodsINS-1 and MIN6 cells were exposed to increasing concentrations of IPA (0–10% v/v). Cell viability, total insulin content, and glucose-stimulated insulin secretion (GSIS) were evaluated. Mechanistic insights were investigated using co-incubation with the K(ATP) channel opener diazoxide (200 µM), the protein kinase A (PKA) inhibitor H89 (10 µM), and antioxidants N-acetylcysteine (NAC, 2 mM) and quercetin (20 µM).ResultsIPA up to 1% (v/v) was non-cytotoxic in both cell lines. In MIN6 cells, IPA did not affect GSIS. In contrast, IPA dose-dependently enhanced GSIS in INS-1 cells, without altering basal secretion or total insulin content. This effect was unaffected by NAC or quercetin, but it was abolished by diazoxide and significantly reduced by H89, suggesting a mechanism involving K(ATP) channel closure, protein kinase A (PKA) activation, and its downstream signaling. However, intracellular cAMP levels remained unchanged, indicating a cAMP-independent activation of PKA.ConclusionsIPA can enhance insulin secretion in a cell-line-specific manner via PKA-dependent, cAMP-independent pathways involving K(ATP) channels. These findings underscore the importance of solvent choice in drug screening, as IPA may confound β-cell functional assays
[HDR] Jets, Bulles, Films et Particules : quelques problèmes aux interfaces libres
No full textThe work presented in this HDR manuscript is the synthesis of seven years of research focused on the experimental understanding of phenomena involving free interfaces, fluid/solid interactions, and thermal effects. This manuscript develops an approach based on simple yet revealing experiments, complemented by toy models and scaling-law analyses.The first part is devoted to the hydraulic jump, a topic initiated during my PhD and pursued ever since. In particular, we examine the role of surface tension in the formation of the circular hydraulic jump and discuss the limitations of existing theories. We also highlight a regime of spontaneous oscillations of the jump, which we interpret as the signature of cavity modes of the liquid layer present in the outer region.The second part concerns the impact of jets on hot surfaces, a subject in which hydrodynamics and phase-change phenomena are coupled. We describe the different regimes observed: the growth of a drop that detaches in a Leidenfrost state, and a droplet-ejection regime resulting from sheet fragmentation. This latter regime is studied in detail and decomposed into zones: a wetted zone, a detachment zone (vapor film), and the fragmentation region of the liquid sheet. We propose models describing each of these zones using scaling laws. We also open the study to the effects of jet inclination, which lead to different behaviors, such as the appearance of rebound regimes.The third part deals with interactions between bubbles and particles. we analyze how a bubble trapped beneath a particle can generate retention or repulsion forces. We also describe work carried out on “eternal” bubbles, stabilized by particles and by the use of a water–glycerol mixture. Preliminary results concerning armored antibubbles are also presented at the end of this section.Finally, the last part presents a set of exploratory studies on soap films, particularly the dynamics of liquid lenses deposited on such films, their orbiting trajectories, and certain observed instabilities. A striking visual similarity with galaxy-merging mechanisms emerges from these observations. This chapter concludes with a preliminary exploration of a jet impacting a soap film.Les travaux présentés dans ce mémoire d’HDR sont la synthèse de sept années de recherche centrées sur la compréhension expérimentale de phénomènes impliquant des interfaces libres, des interactions fluide/solide, ainsi que des effets thermiques. Ce manuscrit développe une approche fondée sur des expériences simples mais révélatrices, complétées par des modèles jouets et des approches en loi d’échelle.Une première partie est consacrée au ressaut hydraulique, thématique initiée pendant ma thèse et poursuivie depuis. Nous y examinons notamment le rôle de la tension de surface dans la formation du ressaut circulaire et nous discutons les limites de certaines théories existantes. Nous mettons également en évidence un régime d’oscillations spontanées pour le ressaut, que nous interprétons comme la signature des modes de cavité de la couche d’eau présente dans la zone externe.La deuxième partie concerne l’impact de jets sur des surfaces chaudes, sujet où se combinent hydrodynamique et phénomènes de changement de phase. Nous y décrivons les différents régimes observés : croissance d’une goutte qui se détache en Leidenfrost à basse vitesse de jet et régime d’éjection de gouttelettes par fragmentation pour de plus hautes vitesses. Ce dernier régime est étudié en détails et décomposé en zones : zone mouillée, zone de décollement (film de vapeur), puis fragmentation de la nappe liquide. Nous proposons des modèles décrivant chacune de ces zones en utilisant des lois d’échelles. Nous ouvrons enfin ces travaux sur les effets de l’inclinaison du jet, qui conduisent à des comportements différents, comme l’apparition de régimes de rebond.La troisième partie porte sur les interactions entre bulles et particules. Nous y analysons comment une bulle piégée sous une particule peut générer des forces de rétention ou de répulsion. Nous décrivons également des travaux menés sur des bulles « éternelles », stabilisées par des particules et par l’utilisation d’un mélange eau-glycérol. Des résultats préliminaires concernant les antibulles armurées sont également présentés en fin de manuscrit. Enfin, la dernière partie présente un ensemble d’études exploratoires sur les films de savon, en particulier la dynamique de lentilles liquides déposées sur ces films, leurs trajectoires orbitantes et certaines instabilités observées. On y trouve une ressemblance visuelle frappante avec des mécanismes de fusion de galaxie. Ce chapitre se termine sur l’ouverture sur une expérience de jet impactant un film de savon