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Iron porphyrin flanked by viologen redox units for persistent carbon dioxide reduction in the presence of oxygen
No full textInternational audienceThe electrocatalytic reduction of CO2 to energy-rich forms such as CO or hydrocarbons is typically realized with pure CO2. This is primarily to exclude O2, which is a far better oxidant and a major competitor upon reduction of the CO2/O2 feed gas. Furthermore, the presence of O2 can deactivate the catalytic material and reduce its effectiveness for CO2 reduction. To confront this major challenge, different strategies are being pursued. We utilize a molecular design approach by adjoining to a known catalyst a redox active module that can competitively divert the deleterious O2 activity. We tailored an iron porphyrin, a prominent catalyst for CO2 reduction, flanked by viologen units known for their efficient O2 reduction. Electrochemical studies on the homogeneous phase of the pre-catalyst, the iron(III)-m-oxo form, show the independent activity of both modules. When heterogenized with carbon nanotubes on a carbon paper electrode, we found that the catalyst could sustain the aerobic (5% O2) reduction of CO2 to CO with a faradaic efficiency of 62%, while the activity of the unmodified iron porphyrin fell to 18% under the same experimental conditions
Enhancing Epoxy Nanocomposites for High‐Impact Applications: Dynamic Performance of Carbon Black‐Reinforced DGEBA Under SHPB Testing
No full textInternational audienceABSTRACT This study presents a novel investigation into the dynamic mechanical behavior of epoxy nanocomposites reinforced with carbon black (CB) nanoparticles. While the static mechanical enhancement of DGEBA epoxy by CB has been widely reported, its performance under high strain rate loading remains insufficiently explored. To address this gap, epoxy nanocomposites containing 1, 2, and 5 wt.% CB were fabricated and tested using a Split Hopkinson Pressure Bar (SHPB) at impact pressures of 1.5, 2, and 4 bar. The results demonstrate that a 1 wt.% CB concentration provides the best balance of stiffness, strength, and toughness without compromising elasticity. At this level, the material exhibited a 60% increase in maximum stress and a 50.8% increase in toughness compared to neat epoxy at 1.5 bar. In contrast, 5 wt.% CB led to nanoparticle agglomeration, reducing energy absorption and elastic recovery. Scanning Electron Microscopy (SEM) and numerical simulations confirmed the influence of CB dispersion on mechanical performance. This work contributes a comprehensive understanding of CB‐reinforced epoxy systems under dynamic loading, offering new insights for advanced structural applications requiring impact resistance
Composite Nanoarchitectonics of Poly(butylene adipate-co-terephthalate) Reinforced with Metal-Organic Framework (MOF-2) and Epoxy-Functionalized Graphene (EFG) for Sustainable Food Packaging
No full textInternational audiencePoly(butylene adipate-co-terephthalate) (PBAT)-based nanocomposites were successfully fabricated via melt blending by incorporating 3–7 wt% of either MOF-2 or a hybrid nanofiller system consisting of MOF-2 and epoxy-functionalized graphene (EFG) in equal parts. MOF-2 was selected for its porosity and tunable chemistry to enhance barrier properties, while EFG was added for its high surface area and epoxy groups to improve interfacial adhesion and synergistic reinforcement. Comprehensive physicochemical characterization demonstrated that both the nanofiller type and concentration substantially influenced the structural and functional performance of the PBAT matrix. Improved nanofiller dispersion and interfacial adhesion were confirmed by XRD and SEM, particularly at 5 and 7 wt% hybrid loadings. Rheological analyses revealed enhanced viscoelastic behavior, indicating stronger polymer–nanofiller interactions. Thermal analyses showed increased thermal stability and crystallinity, with the crystallinity rising from 5.78% in neat PBAT to 10.63% in the 7 wt% hybrid system. Dynamic mechanical analysis also confirmed reinforcement through higher storage moduli. Barrier property measurements revealed notable enhancements: water vapor permeability decreased from 3.41 to 2.10 × 10⁻¹¹ g/m·s·Pa, while oxygen transmission rate dropped from 1052 to 374 ml/m²/day. These improvements are attributed to the formation of a tortuous path by the nanofillers, which effectively hinders gas and moisture diffusion. Furthermore, surface energy increased with nanofiller content, from 46.84 mJ/m² in neat PBAT to 55.64 mJ/m² in the hybrid-filled sample, accompanied by a reduced water contact angle (from 85.86° to 74.38°), indicating enhanced polarity and hydrophilicity. A slight density increase was also observed. Altogether, the synergistic use of MOF-2 and EFG significantly improved the multifunctional properties of PBAT, making these nanocomposites excellent candidates for sustainable and high-performance food packaging
How does gender influence student learning, stress and career choice in endodontics?
No full textInternational audienceThe influence of gender is underexplored in endodontic educational research. This review examines the effect of gender on learning within the domains of skill acquisition, performance and difficulties encountered. It also analyses the stress and confidence experienced by male and female students during clinical endodontics, as well as their preparedness at the end of their undergraduate studies. Finally, this review analyses the influence of gender on student career choices in dentistry with a focus on endodontics. The review highlights that gender is invariably studied as a secondary outcome in endodontic education. Based on current evidence, it appears that female students tend to underestimate their skills and knowledge more than male counterparts in endodontics. They are also often more stressed than males, feeling less confident and not as prepared. A recognition of gender differences in learning and stress management is important. Student aspirations regarding their choice of endodontic postgraduate speciality appear to be relatively well balanced in terms of gender. Finally, there is a need for further research to elucidate more clearly the impact of gender in endodontic education and endodontic career choice
Soil contamination by microplastics in a small French agricultural watershed
No full textInternational audienc
Conditions de réparation des conséquences médicales d'une vaccination obligatoire
No full textInternational audienceNote sous CE, 20 mars 2025, no 472778 (Lebon T.
Les termes utilisés dans une fiche de poste ne suffisent pas à justifier l'attribution d'un logement de fonction
No full textInternational audienceObservations sous CAA Versailles, 28 mars 2025, no 23VE01751, Cne de Viry-Châtillo
3D Concrete Printing: State of the Art and Applications
No full textInternational audienceThis book presents a comprehensive overview of the state of the art in additive manufacturing in the world of concrete construction. 3D Concrete Printing tackles its subject from several angles, including issues relating to concrete materials (such as their formulation or fresh-state behavior), the various printing processes that have been developed, and how to describe the mechanical behavior and architectural and structural designs of printed structures. This book also considers the transition to application and industrialization, and the relevance of these new technologies in reducing the environmental impact of the construction sector. Finally, material characterization methodologies are presented with a view to describing the behavior of materials both before and after printing, and the modeling tools used to simulate the process are listed
Incremental bending of a three-dimensional beam with circular cross section into a regular helix using Castigliano’s second theorem
No full textInternational audienceThis study aims to find a semi-analytical solution to the three-dimensional bending of a circular cross section beam into a regular helix. As though analytical methods exist in literature for in-plane finite bending, few were presented in the case of an out-of-plane, three-dimensional beam. After solving a spring under tip moment problem, a simple incremental method using Castigliano’s second theorem is formulated. The results are then compared with finite elements method (FEM) results, which will serve as reference. The effects of the input parameters such as the number of increments, winding angle and number of revolutions, and their impact on the result are also analyzed. The method’s results show good agreement with those found using FEM in terms of displacement under end moment load, and internal stress components. It is found that the method converges to the helical solution by the use of smaller increments. To bend the initially straight beam into one with multiple revolutions or coils, a higher number of increments are necessary to obtain a more accurate result, as the bending load is naturally larger. The case of beams with rectangular cross section is discussed at the end