Portail HAL de l'Université Picardie Jules Verne
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Porous NaTi<sub>2</sub>(PO<sub>4</sub>)<sub>3</sub>-PVDF Composite Granules as Negolyte Boosters for Sodium-Based Redox-Targeting Flow Batteries
No full textInternational audienceRedox-Targeting Flow Batteries (RTFBs) are promising alternatives to classical vanadium-based batteries for large-scale and stationary energy storage. Typically, RTFBs are marked by higher energy densities thanks to the addition of solid boosters within aqueous systems, taking care to limit the use of critical raw materials. This work subsequently investigates the case of sodium titanium phosphate (NTP, NaTi2(PO4)3, 132.8 mAh/g) as a potential booster material for the negolyte side of aqueous RTFBs. Pure NTP and carbon-coated NTP (C-NTP) particles were synthesized and characterized by various techniques (X-ray, TEM, TGA, Raman). So-obtained NTP and C-NTP particles were found to be suitable for creating innovative porous composite boosters formed as centimeter-sized granules by dry processing. Porous composite granules with an open porosity of 65% and 50 wt % of immobilized NTP or C-NTP were successfully produced by an extrusion–dissolution process using a regular PVDF binder and PEO as a porogen agent. Subsequently, intensive electrochemical tests were performed using an innovative dual-mediator reaction system (Fe-Tiron and 2,7-AQDS). High NTP reactivity, with booster utilization rates of up to 84% of its theoretical capacity, can be achieved under flow conditions, with an increase in volumetric capacity by a factor of 1.5, from 4 Ah L–1 to 6 Ah L–1. The mediator concentration (10 – 100 mM) and the mediator/booster ratio (0.5 – 1) play key roles in NTP reactivity. The fundamental work also highlights the benefit of C-NTP, allowing higher reactivity at low mediator concentrations. The study consequently validates the potential of NTP as an interesting booster material in future RTFB applications, with its scalable extrusion–dissolution technique to create innovative porous booster granules
The bloomy rind sign: An underrecognized MRI feature in the diagnosis of carcinomatosis
No full textInternational audienc
MODÈFONE - Modèle fantôme pour pression intracrânienne
No full textThis report presents the MODÈFONE project, whose objective is to develop a simplified experimental model of the cerebrospinal system in order to investigate fluid-structure interactions and physiological adaptations under altered gravity conditions, with a particular focus on microgravity. The experimental setup is based on a pulsatile hydraulic circuit reproducing systolic and diastolic dynamics, coupled with deformable elements simulating vascular compliance and a cranial compartment immersed in a fluid representing cerebrospinal fluid. This model enables the analysis of cranial and spinal pressures as well as their pulsatility. The purpose of this report is to describe the design and the results of the experimental setup.Ce rapport présente le projet MODÈFONE, dont l’objectif est de développer un modèle expérimental simplifié du système cérébrospinal afin d’étudier les interactions fluide–structure et les adaptations physiologiques en conditions de gravité modifiée, en particulier en micropesanteur.Le dispositif expérimental repose sur un circuit hydraulique pulsatile reproduisant la dynamique systolique et diastolique, couplé à des éléments déformables simulant la compliance vasculaire et à un compartiment crânial immergé dans un fluide représentant le liquide cérébrospinal. Ce modèle permet d’analyser les pressions crânienne et spinale ainsi que leur pulsatilité.L’objectif de ce rapport est de décrire la conception et les résultats du dispositif expérimental
Faut-il en finir avec les incitations à mieux gérer nos déchets ? Le problème posé par les sciences comportementales
No full textInternational audiencePour réduire les déchets, les politiques publiques misent de plus en plus sur les sciences comportementales, comme les « nudges » (dispositifs de suggestion). Cette idée est séduisante, mais elle déplace la responsabilité d’un problème systémique vers les individus. Les défauts de tris et autres dépôts sauvages sont alors souvent requalifiés comme de « mauvais comportements ». Le problème de cette approche ? Elle invisibilise les déterminants matériels, sociaux et politiques de la production des déchets
3D morphological characteristics of gravel bars in an engineered river using LiDAR data and aerial photographs
No full textInternational audienceRivers are fundamental water bodies supporting a wide range of ecosystem services. However, during the last century, river dynamics have been considerably modified by human engineering, notably channelized and dyked to prevent floods. In many Alpine rivers, this has led to the formation of a complex of alternate bars, gradually colonized by vegetation. Therefore, assessing spatial and temporal dynamics over large extents of these alternate bar systems represents a challenge to better understand the functioning of ecosystems in Alpine river and eventually to prevent flood risk. The three objectives of this study were 1) to create a database characterizing bars along a 30 km segment of the River Arc, in the French Alps, 2) to create a bar typology and to compare it to expert point of view, and 3) to assess the dynamics of the system after a 10‐year return period flood event that occurred in June 2013. High‐resolution LiDAR data and aerial photographs were used to localize major bed evolutions through a DEM of Difference (DoD), and to delineate and characterize gravel bars, including their volume, between two dates covering the flood event (in Sept. 2010 and Nov. 2013, respectively). Other river parameters such as sinuosity and river width were also calculated. A hierarchical clustering applied to the whole dataset revealed some bar morphological patterns, with three types of bars, depending in their functioning and age: large old vegetated bars with no mobility, very young, small and low elevated free bars without vegetation, and less mobile and more elongated bars, mostly corresponding to hybrid alternate bars. The results also highlight strong sediment dynamics resulting from the June 2013 flood. Bars were indeed statistically slightly thinner and shorter in 2013 than in 2010, corresponding to an enlargement of the main channel. Finally, these results proved the strong potential of remote sensing data—especially LiDAR data—to characterize sediment bars in channelized river over large extents
Bottleneck size manipulation through the introduction of large-radius alkali ions in Na sites of a NaSICON solid electrolyte: A computational proof of concept
No full textInternational audienceNaSICON electrolytes, such as Na1+xZr2(SiO4)x(PO4)3–x (NZSP), constitute promising candidates for solid-state battery (SSB) development. Research on such fast superionic conductors has primarily focused on two key phenomena acting specifically on Na+ ion migration: (i) the Na-concentration-driven modulation effect and (ii) the incidence of substitution. While numerous experimental and computational studies have established the fundamental role of concerted migration in ionic conduction, the precise influence of bottleneck size along with its dependence on NaSICON composition remains elusive. In view of participating in this research field and following an experimentally tested strategy, suggesting that the migration bottleneck can be expanded by partially substituting diffusing Na+ ions with larger-radius alkali elements, we investigated the impact of the introduction of such point defects (i.e. K+ or Cs+ replacing Na+) on structural and Na+ diffusion aspects in the NZSP crystal structure. A proof of concept of the interest linked to this unconventional doping approach has been searched for. Theoretical investigations relying on density functional theory (DFT) and subsequent kinetic Monte Carlo simulations were involved to unravel interrelations between the ionic radius of the substituting ion and bottleneck sizes, structural changes, diffusion pathways, and ionic conductivity features. Apart from an opening of the bottleneck along the migration path as a common feature, a clear differentiation between both kinds of substituents was evidenced on various aspects, K-NZSP outperforming the undoped counterpart and effectively enabling the maximization of ionic conductivity in these envisaged NaSICON-type matrices. Furthermore, the identification─emerging from this study─of a critical bottleneck size in such systems may contribute to provide a further key clue and lead to well thought-out crystal chemical engineering of improved materials for this research area.</p
Fabrication of Centimeter‐Scale MoWS 2 ‐Based High Performing Solar Cells
No full textInternational audienceThe growing demand for efficient, scalable, and lightweight photovoltaic (PV) technologies has intensified interest in WS 2 and MoS 2 ‐based devices. Despite notable advances, achieving simultaneously high performance and long‐term operational stability remains a key barrier to broader adoption. Here, we address this challenge by fabricating p–n heterojunction solar cells through a single‐step chemical vapor deposition process that directly deposits WS 2 , MoS 2 , and their alloy MoWS 2 onto p‐type silicon substrates. The MoWS 2 alloy exhibits a reduced bandgap and enhanced optoelectronic properties, which translate into substantially improved PV output and device robustness. The MoWS 2 ‐based solar cell achieves a power conversion efficiency of 5.8%, outperforming the WS 2 and MoS 2 counterparts, which reach 1.12% and 3.6%, respectively. In addition, MoWS 2 displays markedly enhanced light‐harvesting capability, with an external quantum efficiency of 80%, compared to 30% for WS 2 and 50% for MoS 2 . Stability assessments further demonstrate that MoWS 2 retains its performance over a 30‐day test period, confirming its superior long‐term durability. By establishing the viability of MoWS 2 as a high‐potential photoactive material for lightweight PVs, this work sets the stage for future research and paves the way toward practical implementation of alloy‐engineered 2D semiconductor solar technologies
Toward Zero-Waste Valorization of Isatis tinctoria: A Preliminary Study Regarding Antioxidant Properties of Organic Extract
No full textInternational audienceIntroduction: Isatis tinctoria is a non-food Brassica plant that was extensively cultivated in Europe between the 12th and 17th centuries for the production of the blue indigo naturalis dye pigment. Presently, a project is underway to reintroduce the species to several European regions. However, the mere production of the pigment does not necessarily guarantee the economic viability of its cultivation. A considerable body of research has been dedicated to examining the antioxidant capacity of this plant. Extensive studies have demonstrated that extracts obtained from the cauline leaves exhibit notable antioxidant properties. Consequently, a direct incompatibility exists in the valorization of the plant between the production of pigment and the production of antioxidant compounds. Method: This study aims to circumvent this competitive dynamic; a zero-waste valorization of Isatis tinctoria can be posited. The antioxidant potential of both leaf residues after pigment extraction and roots was evaluated from a hydroponic culture of Isatis tinctoria. The antioxidant capacity of the obtained extracts was evaluated according to four colorimetric tests: ABTS, DPPH, FRAP, and CUPRAC. Results: The results of the study indicate that the re-use of the cauline leaves of Isatis tinctoria is possible, in particular through its DPPH (544 μmol TE/100g DW) and CUPRAC (807 μmol TE/100g DW) activities. Nevertheless, the drying process following pigment extraction must be enhanced to ensure the reproducibility of results. It has been observed that the roots of Isatis tinctoria exhibit a degree of interest, albeit to a more moderate extent, in terms of metal reduction activities (FRAP: 120 μmol TE/100g FW; CUPRAC: 250 μmol TE/100g FW). Discussion: However, it is imperative to optimize both the drying step and the extraction methodology. Furthermore, the components constituting both extracts must be characterized. Conclusion: The subsequent study demonstrated that Isatis tinctoria leaves, a byproduct of indigo extraction, can be valorized through a biocascade approach for the production of an antioxidant extract. Furthermore, the study suggests that plant zero-waste valorization can be achieved through the extraction of antioxidants from Isatis tinctoria roots
A QUIVER ANALOGUE OF HIGMAN'S CONJECTURE
No full textAn unresolved conjecture by Graham Higman states that for all n ≥ 1 the number of conjugacy classes of the group of n × n unitriangular matrices with entries in the finite field Fq is a polynomial in q.In this paper we introduce a new quiver generalization of the conjecture. Motivated by this generalization, we prove that certain operations on quivers leave the relevant counts unchanged. Based on these invariance properties, we solve the introduced conjecture for quivers containing no path of length exceeding two, providing explicit formulas.</p
A comprehensive review of EEG electrode technologies: Advancements, applications, and future directions
No full textInternational audienceElectroencephalography remains a fundamental tool in neurological diagnostics, cognitive research, and emerging consumer applications. This comprehensive review critically examines the technological landscape of non-invasive EEG electrodes through a novel comparative framework rather than a conventional chronological analysis. We systematically evaluate wet, semi-dry, and dry electrode technologies across four key dimensions: material and design innovations, signal quality metrics, clinical and research applications, and implementation challenges. Our analysis reveals that while standard wet electrodes remain the gold standard for signal fidelity, they nevertheless require extensive setup, cause notable discomfort—particularly for children and long-term users, and demand ongoing gel reapplication, all of which limit their practicality in many real-world settings. Significant advancements in semi-dry electrodes now address these shortcomings by offering comparable performance with reduced preparation time and enhanced usability. Dry electrodes, despite inherently higher impedance, demonstrate increasing viability for long-term and ambulatory monitoring when paired with appropriate signal processing techniques. This review provides a decision framework for selecting optimal electrode technologies based on specific application requirements, subject characteristics, and recording environments. We identify critical research gaps, particularly in standardization methods, cross-population validation, and integration with emerging materials. As EEG applications expand beyond traditional clinical settings into consumer markets, this review offers valuable guidance for researchers, clinicians, and technology developers navigating the rapidly evolving landscape of EEG electrode technologies