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Ambiphilic Reactivity of SF<sub>5</sub>‐Alkynes Applied to Regioselective and Stereodivergent Halogenation Reactions: An Experimental and Theoretical Case Study
No full textInternational audienceWe explored the ambiphilic reactivity of SF 5 ‐alkynes, and we proved they can act as both nucleophiles and electrophiles. We selected halogenation reactions as benchmark reactions and developed highly selective stereodivergent hydrohalogenation (I, Br, Cl, F) reactions of SF 5 ‐alkynes. The stereochemistry is finely controlled thanks to the nature of the acids used (strong or soft) in the presence of halide source, while the high regioselectivity is governed by the strong polarization of SF 5 ‐alkynes. Mechanistic studies supported by DFT calculations shed light on two different reaction mechanisms responsible of the excellent stereocontrol. This stereoselectivity was quantitatively rationalized with the ASM and EDA methods. A few dihalogenation reactions are reported and DFT calculations rationalize this cis ‐stereoselectivity. Relative configuration of all the SF 5 ‐haloalkenes was unambiguously determined by X‐ray diffraction. Noteworthy, several post‐functionalization reactions such as cross‐couplings, cyanation and reductions are described to strengthen the synthetic potential
Passive Polarized Vision for Autonomous Vehicles: A Review
No full textInternational audienceThis review article aims to address common research questions in passive polarized vision for robotics. What kind of polarization sensing can we embed into robots? Can we find our geolocation and true north heading by detecting light scattering from the sky as animals do? How should polarization images be related to the physical properties of reflecting surfaces in the context of scene understanding? This review article is divided into three main sections to address these questions, as well as to assist roboticists in identifying future directions in passive polarized vision for robotics. After an introduction, three key interconnected areas will be covered in the following sections: embedded polarization imaging; polarized vision for robotics navigation; and polarized vision for scene understanding. We will then discuss how polarized vision, a type of vision commonly used in the animal kingdom, should be implemented in robotics; this type of vision has not yet been exploited in robotics service. Passive polarized vision could be a supplemental perceptive modality of localization techniques to complement and reinforce more conventional ones
Heterogenization of [Ru(bpy)3].Cl2 on ordered mesoporous silica materials for photocatalytic applications
No full textInternational audienceHerein, the preparation and characterization of three Ru-based heterogeneous photocatalysts supported on ordered mesoporous silica materials are reported. The photocatalytic activity of these catalysts was evaluated through oxidation, reduction, cycloaddition and carboxylation reactions and their efficiencies are comparable to the parent [Ru(bpy)3]Cl2 in homogeneous conditions. These photocatalysts are efficiently recovered even after five reactions cycles offering new opportunities in sustainable chemistr
Traduire la littérature grand public et la vulgarisation / Translating Popular Fiction and Science
No full textInternational audienceCe volume réunit 16 contributions de chercheurs internationaux autour d’un sujet encore peu étudié en traductologie, à savoir la traduction de la littérature grand public et de la vulgarisation. Par leur vocation populaire, la vulgarisation scientifique et la littérature grand public souffrent traditionnellement d’un manque de reconnaissance dans la recherche, malgré un lectorat très vaste.La vulgarisation scientifique s’inscrit aujourd’hui dans une démarche reconnue et encouragée, qui consiste à diffuser les résultats de la recherche en dehors des cercles des initiés. Elle procède de la simplification d’un discours plus spécialisé via une démarche de réécriture, voire de traduction intralinguistique.La littérature grand public partage les mêmes objectifs de large diffusion et d’accessibilité, sans pour autant procéder d’une réécriture à partir de formes plus spécialisées. Romans populaires, paralittérature, bestsellers sont autant de termes qui essayent de cerner une catégorie fuyante, vouée à évoluer au cours de l’histoire et à canoniser parfois les feuilletons d’antan. Le critère d’inclusion dans nos analyses est le succès public de ces ouvrages, ce qui permet d’élargir le spectre à des textes littéraires n’affichant pas nécessairement une vocation « populaire » — vocation par ailleurs difficile à identifier — mais qui touchent un public large.L’ouvrage est organisé en 5 grandes sections : Approches théoriques, Approches historiques, Vulgarisation scientifique, Littérature grand public, Expériences de traduction. Le lecteur y trouvera des réflexions théoriques, des études de cas à l’échelle européenne et des retours d’expérience de deux traducteurs de bestsellers littéraires. Textes de : Nicolas Froeliger, Gary Massey, Muguras Costantinescu, Regina Solova, Justyna Lukaszwiecz, Natalia Paprocka, Agnieszka Wandel, Fabio Regattin, Tatiana Musinova, Mathilde Fontanet, Enrico Monti, Elżbieta Skibińska, Jerzy Brzozowski, Julie Loison-Charles, Francesco Laurenti, Muauia Alabdulmagid, Dominique Defert
Nonaqueous potassium-ion full-cells: Mapping the progress and identifying missing puzzle pieces
No full textInternational audienceThis review addresses the growing interest for potassium-ion full-cells (KIFCs) in view of the transition from potassium-ion half-cells (KIHCs) toward commercial K-ion batteries (KIBs). It focuses on the key parameters of KIFCs such as the electrode/electrolyte interfaces challenge, major barriers, and recent advancements in KIFCs. The strategies for enhancing KIFC performance, including interfaces control, electrolyte optimization, electrodes capacity ratio, electrode material screening and electrode design, are discussed. The review highlights the need to evaluate KIBs in full-cell configurations as half-cell results are strongly impacted by the K metal reactivity. It also emphasizes the importance of understanding solid electrolyte interphase (SEI) formation in KIFCs and explores promising nonaqueous as well as quasi- and all-solid-state electrolytes options. This review thus paves the way for practical, cost-effective, and scalable KIBs as energy storage systems by offering insights and guidance for future research
Minimizing grid capacity in preemptive electric vehicle charging orchestration: Complexity, exact and heuristic approaches
No full textInternational audienceUnlike refueling an internal combustion engine vehicle, charging electric vehicles is time-consuming and results in higher energy consumption. Hence, charging stations will face several challenges in providing high-quality charging services when the adoption of electric vehicles increases. These charging infrastructures must satisfy charging demands without overloading the power grid. In this work, we investigate the problem of scheduling the charging of electric vehicles to reduce the maximum peak power while satisfying all charging demands. We consider a charging station where the installed chargers deliver a preemptive constant charging power. These chargers can either be identical or non-identical. For both cases, we address two optimization problems. First, we study the problem of finding the minimum number of chargers needed to plug a set of electric vehicles giving different arrival and departure times and required energies. We prove that this problem belongs to the complexity class P, and we provide polynomial-time algorithms. Then, we study the problem of minimizing the power grid capacity. For identical chargers, we prove that the problem is polynomial, whereas it is NP-hard in the case of non-identical chargers. We formulate these problems as a mixed-integer linear programming model for both cases. To obtain near-optimal solutions for the NP-hard problem, we propose a heuristic and an iterated local search metaheuristic. Through computational results, we demonstrate the effectiveness of the proposed approaches in terms of reducing the grid capacity
Zwischen Politik und Wissenschaft : Handlungsmöglichkeiten des deutschen Ethnologenund diskreten Kommunisten Paul Kirchhoff in Grossbritannien 1932/1933
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Pyrolysis and combustion of de-oiled yeast biomass: comparison of the thermogravimetric profiles and kinetic modeling
No full textInternational audienceYeast biomass is a heterogeneous mixture of carbohydrates, proteins, lipid and nucleic acids. De-oiled yeast was derived from yeast biomass after solvent extraction. Pyrolysis experiments were carried out on the raw and treated yeast biomass under the temperature ramp of 5 °C/min. Five components or stages can be identified for both materials in the conversion and conversion rate curves, although these curves present differences in the position and height of each peak and shoulder. Simulations of these pyrolysis experiments were performed using the Extended Independent Parallel Reaction model considering the five components and the first-order reaction function. The associated activation energies lie between 40.2 and 100.2 kJ/mol for the raw yeast sample and between 58.2 and 160.2 kJ/mol for the de-oiled yeast sample. In the two cases, the determination coefficients for the conversion and conversion rate curves are higher than 0.98, which prove the quality of the simulations
Simulations of combustion experiments performed on spherical magnesium particles
No full textCombustion experiments were performed on spherical magnesium particles in a fluidized bed reactor and in a pilot burner. In the fluidized bed, isothermal temperatures of 530, 550 and 570 °C were applied with a gas flux composed of oxygen (20%) and helium (80%). For such temperatures, a heterogeneous reaction prevailed for the oxidation of Mg to MgO. The oxidation rate of Mg was characterized by in-line oxygen measurement. Simulations were performed using a single reaction with Avrami-Erofeev reaction functions of orders 2 or 3, and with Mampel-Delmon model. In the pilot burner, self-sustained combustion experiments were performed. The temperature of the swirled flame was higher than 2000 °C and a mechanism of homogeneous reaction prevailed. Simulations were tentatively performed with the software Fluent, decomposing the problem in four steps. The experimental conditions will be presented, together with the results of the simulations
High-temperature oxidation of metal particles in a fluidized bed reactor
No full textInternational audienceMagnesium (Mg) and iron (Fe) are promising fuels for the metal-enabled cycle of renewable energy. It has also been proposed to use magnesium in combustion-based space power systems. However, the existing methods for combustion of metal powders have difficulties with maintaining flame stability, and the oxidation mechanisms of Mg and Fe particles at high temperatures are not well understood. The objectives of the present work are to demonstrate the feasibility of stable high-temperature oxidation of a spherical metal powder in a fluidized bed reactor, to investigate the oxidation kinetics of this powder by conducting isothermal tests in this reactor at different temperatures, and to determine the associated kinetic models and parameters based on the obtained experimental data. Specifically, a fluidized bed reactor was used to study oxidation of spherical Mg and Fe particles in an oxygen/helium environment at temperatures between 530 and 570 °C. A quartz reactor (inner diameter and height of the main section: 1.3 cm and 29 cm), was installed inside an electric furnace. Approximately 200 mg of Mg or Fe powder with particle diameter between 50 and 70 µm were injected from the top of the reactor onto the quartz sintered grid. Oxygen/helium (20:80 mole ratio) mixture entered the reactor at the bottom, fluidized the metal particles, and exited at the top. The height of the bed was 3 mm at rest and slightly over 10 mm when fluidized. The extent of conversion was determined based on the measured oxygen concentration in the exhaust gas. The curves of the extent of conversion and of the conversion rate obtained for Mg were analyzed using the Avrami-Erofeev and Mampel-Delmon models. The former assumes that both nucleation and growth occur in the bulk, whereas in the latter the nuclei appear randomly on the surface and then grow with the rate-controlling step at the reactant-product interface. The activation energy for Mg obtained with the Avrami-Erofeev equation is 191 or 198 kJ∙mol-1, depending on the equation’s dimension (3 or 2, respectively). The Mampel-Delmon approach has shown that the activation energies of nucleation and growth are equal to 189 and 120 kJ∙mol-1, respectively, i.e., the former is close to the apparent activation energy obtained with the Avrami-Erofeev model at a dimension of 3. With increasing temperature, the rate of nucleation rises faster than the rate of growth. The results for iron particles will also be presented