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Total synthesis of cyclotripeptide natural products with a quinazolinopiperazine structure
No full textInternational audienc
Theoretical and Experimental Investigations of the Hock rearrangement with InCl3 as catalyst
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From total synthesis to photosynthesis, a detective journey to the site of action of a phytotoxic natural product
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Rearrangement-based total syntheses of oxacyclic natural products
No full textInternational audienceOxacycles are commonly found in natural products. Some compounds of interest to us, due to their complexity and biological properties, are based on the seven-membered oxepane or oxepin motif, like the fungal cyclotripeptides janoxepin and varioxepin A, or the plant 2,5-dihydrobenzoxepin radulanin A. Numerous strategies have been described in the literature for their synthesis through C-C (e.g. metathesis) or C-O (e.g. Mitsunobu reaction) bond formation. However, these strategies use long synthetic sequences to reach the precursors. In this poster, we want to disclose our latest results on the synthesis of oxacycles. Several rearrangement-based methodologies will be described. First, the retro-Claisen [3,3] rearrangement of cis-2-vinylcyclopropane carboxaldehydes allowed us to synthesize two different natural products using a fragment-based strategy: janoxepin1 and radulanin A.2 Second, an interrupted Hock cleavage of 1-hydroperoxycycloalkanes led to new oxacycles and allowed us to synthesize substituted benzoxepanes and chromanes like the natural product erythrococcamide B. In addition, a photochemical rearrangement should complete this panel of methodologies.Our total synthesis of janoxepin, including a strong methodological development for each key step, uses a fragment-based strategy leading to an important increase of complexity through the retro-Claisen rearrangement. The completion of the synthesis was particularly challenging, when it came to oxidize the dihydrooxepin intermediate into the oxepin ring. Our total synthesis of radulanine A employed a similar rearrangement but here, the challenge lied on the aromatization step. Overall, these works show that the retro-Claisen rearrangement can be useful in total synthesis
Approche numérique pour l’étude de l’influence du choix d’une équation d’état dans un écoulement autour d’une aile, à haute pression et température
No full textInternational audienc
Détermination de l’équation d’état dans la direction hors plan du Tensylon® (UHMWPE)
No full textInternational audienceLe développement de nouveaux matériaux, plus légers, plus économiquement et écologiquement performant et mécaniquement supérieurs permet aux industries de relever de nouveaux défis technologiques. Les matériaux composites occupent une place devenue majeure dans la conception de structures et d’assemblages destinés à soutenir des sollicitations extrêmes, notamment dans le secteur aérospatial et de la défense. Un matériau composite d’intérêt pour ses performances mécanique et sa recyclabilité est le polyéthylène haute densité (PE-HD). Sous forme de plis composites d’orientation [0-90°], il constitue à lui seul une protection balistique contre les projectiles de petits calibres. Dans le cadre du développement de protections balistiques, il est primordial de connaître le comportement de ce matériau sous sollicitations dynamiques de type ondes de choc. Il convient donc de déterminer la loi de comportement, d’endommagement ainsi que l’équation d’état sous choc pour renseigner un outil numérique de type éléments-finis explicite (LS DYNA, RADIOSS, ABAQUS …). Le présent travail a pour objectif de déterminer les paramètres de l’équation d’état sous choc d’un PE-HD particulier, le Tensylon HSBD30 A fabriqué par DuPont®. Une brève revue de nos travaux antérieurs est donnée, puis la démarche analytique et expérimentale a permis d’obtenir les données de l’équation d’état sous choc. Enfin, étant donné que trop peu d’essais valables ont pu être obtenus, une méthode bayésienne et proposée pour discuter des incertitudes applicables à nos résultats
Experimental heat transfer measurement applied to CO2 hydrate formation kinetic study
No full textInternational audienceCO2 hydrate slurry is a promising phase change material for secondary refrigeration cold distribution issues, due to its high latent heat (about 500 kJ.kg-1 of water, higher than that of ice-333 kJ.kg-1) and wide melting temperature range suitable for air conditioning application. While the thermodynamic properties of CO2 hydrates are now well established, knowledge of crystallization kinetics phenomena is still a challenge. Trying to understand and control the formation of gas hydrates is a key factor since their discovery in pipeline plugs by Hammerschmidt, but unlike that case, the goal here is to promote the rate of CO2 hydrate formation. Most laboratory-scale hydrate reactors are equipped with pressure and temperature loggers, and mass balance on CO2 allows formation kinetic studies, but with assumptions on CO2 concentration in liquid phase in the liquid phase and the hydration number. The present work investigates the kinetics of CO2 hydrate crystallization for different types of stirrers and stirring speed conditions in a jacketed stirred batch reactor. Heat balance obtain experimentally using a specially developed sensor installed on the cooling jacket. The mass fraction of crystallized hydrate determine directly from the heat balance on the cooling jacket. First, tests on water heating and cooling steps and ice crystallization allowed the method validation before to apply it to CO2 hydrate crystallization. Experimental results described with an empirical model and compared to other mass balance based kinetic determinations. Finally, the development of a simplified thermal model improved this kinetic determination by estimating heat flows inside the reactor and with the environment
Deep learning based higher-order approximation for multiple knife edge diffraction
No full textInternational audienceWe introduce an hybrid approach for computing multiple knife-edge diffraction attenuation. First, we show that the well-known Epstein-Peterson method can be considered as the first order approximation of the Vogler method. In the other words, the Vogler method is a combination of the Epstein-Peterson method and an higher order approximation. Then, we propose to learn the approximation based on deep learning methods. The key advantage of this approach is the significant reduction of generating training data to approximate the Vogler method while still offering a good accuracy and fast computation. Comparison to the state-of-the-art methods demonstrates the effectiveness of our proposed approach
Pushing the Frontier in the Design of Laser-Based Electron Accelerators with Groundbreaking Mesh-Refined Particle-In-Cell Simulations on Exascale-Class Supercomputers
No full textInternational audienceWe present a first-of-kind mesh-refined (MR) massively parallel Particle-In-Cell (PIC) code for kinetic plasma simulations optimized on the Frontier, Fugaku, Summit, and Perlmutter supercomputers. Major innovations, implemented in the WarpX PIC code, include: (i) a three level parallelization strategy that demonstrated performance portability and scaling on millions of A64FX cores and tens of thousands of AMD and Nvidia GPUs (ii) a groundbreaking mesh refinement capability that provides between 1.5 x to 4 x savings in computing requirements on the science case reported in this paper, (iii) an efficient load balancing strategy between multiple MR levels. The MR PIC code enabled 3D simulations of laser-matter interactions on Frontier, Fugaku, and Summit, which have so far been out of the reach of standard codes. These simulations helped remove a major limitation of compact laser-based electron accelerators, which are promising candidates for next generation high-energy physics experiments and ultra-high dose rate FLASH radiotherapy
