Publications scientifiques de l'Université de Reims Champagne-Ardenne
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Macro-scale damage characterization of Wharton’s jelly membrane undergoing tension
No full textInternational audienceThe Wharton’s jelly, a mucoid connective tissue of the umbilical cord, is promising for regenerative medicine applications. However it is relatively new and poorly documented especially from a mechanical point of view. To help filling the gap in the literature lack of data, this study seeks to address the Wharton’s jelly damage behavior by providing first key results through an efficient analytical approach. The tensile and damage behavior of Wharton’s jelly membranes is studied using tensile tests conducted up to failure under close physiological conditions. The Wharton’s jelly mechanical response has been characterized using an hyperelastic constitutive model based on the Ogden formulation, enhanced with continuum damage mechanics to capture analytically the damage behavior. To support the mechanical analysis, optical coherence tomography was used to assess the stress-free microstructural arrangement of the collagen fibers, revealing a transversely isotropic architecture. This qualitative insight into the internal structure enriched the interpretation of the mechanical behavior. Overall, this analytical study enabled the identification of a comprehensive set of material parameters characterizing both elastic and damage responses. Pearson correlation matrices were used to reveal meaningful relationships between parameters, potential predictive descriptors, and model’s limitations. These findings provide a solid foundation for future modeling developments through numerical simulation and offer new outlooks for surgery and dressing applications
Influence of electrical properties on thermal boundary conductance at metal/semiconductor interface
No full textInternational audienceRecent experimental investigations have demonstrated that doping a semiconductor is a route to increase the thermal boundary conductance at metal/semiconductor interfaces. In this work, the influence of the electrical properties on heat transfer across metal/doped semiconductor junctions is investigated. Specifically, thermal boundary conductance at the interfaces between p- and n-doped silicon and titanium is measured by employing frequency-domain photothermal radiometry under varying external conditions. The influence of the doping level of the semiconductor, the barrier height, and the space charge area is analyzed. In particular, a 40% increase in the interface thermal conductance with the application of a current at n-doped silicon/titanium interfaces is reported. The enhancement of the thermal boundary conductance is explained by the shrinking of the surface charga area induced by the electric current. This study opens the way to modulating interfacial heat transfer at metal/semiconductor interfaces through fine tuning of electrical effects
Effets en France des jugements établissant la filiation des enfants nés d'une GPA à l'étranger : la Cour de cassation maintient ses positions
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Entre la Pologne et l’Orne, une trajectoire féminine et nobiliaire transnationale : la marquise Albert Gicquel des Touches, née Miriam Czacka (1863-1948)
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Influence of geometric partitioning on the finite element analysis of a face-centered cubic (FCC) lattice cell under mechanical loading
No full textMon parcours :Depuis Décembre 2024 : Doctorant en thèse à l'Université de Reims Champagne-Ardenne. Sujet de thèse : «Modélisation multi-échelle et optimisation des performances en cas de crash de structures cellulaires à gradient de porosité obtenues par fabrication additive»International audienceFinite element analysis of lattice structures proves very useful for predicting their behavior under mechanical stress. In this article, we propose a geometric partitioning of a facecentered cubic (FCC) lattice cell. From the resulting new geometry, which enables the hexahedral meshing of the entire cell, we perform a finite element analysis of its compression under quasi-static and dynamic regimes using the ABAQUS software. The results obtained are compared with those of the analysis of the same cell with a standard (unpartitioned) geometry and a default tetrahedral mesh. The results obtained with the two mesh types are quite similar, with only slight differences. However, it is worth noting that the hexahedral mesh (known for its higher numerical accuracy) of the cell generates nearly 8 times fewer elements and nodes than the tetrahedral mesh of the same size. Furthermore, the simulation calculation time with the hexahedral mesh is almost 7 times shorter in quasi-static regime and almost 10 times shorter in dynamic regime than with the tetrahedral mesh. The overall results obtained in this study demonstrate that the proposed geometric partitioning for the FCC lattice cell allows for a more precise and, above all, much faster finite element analysis. This geometric partitioning technique could therefore be a highly effective tool for improving finite element analysis of FCC lattice structures containing multiple cells.</div
Metal-free visible-light carbonylation of alkyl iodides to amides <i>via</i> consecutive photoinduced electron transfer
No full textInternational audienceA visible-light-driven, metal-free carbonylation of unactivated alkyl iodides is reported, enabling the directsynthesis of 35 structurally diverse amides in good to excellent yields. The reaction shows broad functional-group tolerance toward both amines and alkyl iodides, including bioisosteric motifs and complex naturalproduct derivatives, underscoring its potential for late-stage functionalization. Mechanistic investigationscombining flash photolysis, spectroelectrochemistry, irradiated thin-layer cyclic voltammetry, and EPRspectroscopy reveal a consecutive photoinduced electron transfer (ConPET) mechanism that divergesfrom conventional single-photon photoredox catalysis. DFT calculations elucidate the key radicalcarbonylation steps governing reactivity and selectivity. This sustainable and operationally simple methodoffers a transition-metal-free approach to carbonylation, expanding the toolbox for highly reducingtransformations under mild conditions
Rire de la comptabilité et « changer le monde ». La mise en débats des normes extra-financières dans Parlement
No full textNational audienceL’article montre comment la saison 2 de Parlement, série politique et humoristique, fait de la comptabilité un ressort comique pour mieux expliquer ses enjeux et l’évolution possible des normes extra-financières. En suivant des scènes clés, il éclaire l’intégration de la nature et de la biodiversité à la comptabilité et les choix de société qu’elle suppose, corrige des approximations, explicite les notions mobilisées et confronte des visions de la soutenabilité, invitant à « compter autrement »
Geometric Reinterpretation of Partial Differential Equations and Applications
No full textInternational audienceWe obtain improved regularity estimates on solutions of partial differential equations by combining the method of Fuchsian Reduction with geometric transformations. Examples include the meron problem and the regularity of the conformal radius. In each case, Reduction needs to be combined with a reinterpretation of the underlying geometry. We argue that the geometric meaning assigned to a problem has an influence, positive or negative, on the range of methods envisioned for its solution, and that the Euler–Poisson–Darboux (EPD) equation cannot be properly understood within a single geometric framework. This explains the central position of EPD-like equations
