Chimie organométallique de l'aluminum pour la polymérization par métathèse d'ouverture de cycle : compréhension, amélioration et développement de systèmes d'intérêt industriel

Le polydicylopentadiène est un matériau aux propriétés d’usage remarquables. Il est obtenu par polymérisation par métathèse d’ouverture de cycle (ROMP) du dicyclopentadiène. Industriellement, les procédés de fabrication reposent sur le moulage à injection réactive de deux solutions de monomère: la première comprend une source de métal du groupe 6 (Mo, W), et la seconde un mélange de chloroalkyle aluminique, d’alcool et de différents additifs. Leur combinaison génère la formation in situ d’espèces actives en métathèse. Au cours de ces travaux, nous nous sommes focalisés sur la formulation à base d’aluminium. Dans un premier temps, nous avons étudié la chimie organométallique de l’aluminium en lien direct avec les formulations industrielles, ce qui nous a permis de comprendre et rationnaliser les observations faites sur ces systèmes. Puis, sur ces bases, nous avons développé de nouvelles formulations aluminiques pour l’obtention de polydicyclopentadiène en conditions industrielles, selon deux axes : modification du composant alcool, et modification du composant chloroalkyle aluminique. Certaines propriétés mécaniques des matériaux obtenus se sont avérées supérieures à celles obtenues à l’aide des procédés existants. De plus, l’apport de la chimie organométallique a été essentiel pour la compréhension de relations entre les modes de préparation et les performances des systèmes catalytiques. A l’issue de ces travaux, nous proposons une nouvelle solution industrielle pour la production de polydicyclopentadiène par moulage à injection réactive.Polydicylopentadiene is a material featuring remarkable usage properties. It is obtained by ring opening metathesis polymerization (ROMP) of dicyclopentadiene. Industrial processes rely on the reactive injection molding of two monomer solutions: the first one contains a source of group 6 metal (Mo, W), and the second one, a mixture of chloroalkylaluminum, alcohol and various additives. Their combination generates in situ active species that perform metathesis. In the present work, we focused on the aluminum-based formulation. We have first studied the aluminum organometallic chemistry that is directly connected to the industrial formulations, which allowed us to understand and rationalize the observations made on these systems. Then, from this point on, we developed new aluminic formulations for polydicyclopentadiene preparation under industrially relevant conditions, working along two directions: modification avec the alcohol component, and modification of the chloroalkyl aluminum species. Some mechanical properties of the thus obtained materials proved to be better than those resulting from classical processes. Furthermore, the input from organometallic chemistry was critical to the understanding of the relationships between preparation modes and performances of the catalytic systems.From this study, we propose a new industrial solution for the production of polydicyclopentadiene by reactive injection molding

Impact reduction through long-term intervention in recreational runners: midfoot strike pattern versus low-drop/low-heel height footwear

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An Efficient Catalytic Approach to the Synthesis of Wax Esters from Fatty Acid Methyl Esters

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Solvent- and base-free synthesis of wax esters from fatty acid methyl esters by consecutive one-pot, two-step catalysis

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The small secreted protein OmSSP1 is up-regulated in ericoid mycorrhiza and is involved in symbiosis

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V-erbA generates ribosomes devoid of RPL11 and regulates translational activity in avian erythroid progenitors

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Advances in Structural Studies on Alkylaluminum Species in the Solid State via Challenging ²⁷Al–¹³C NMR Spectroscopy and X‑ray Diffraction

Advanced multinuclear solid state NMR experiments were developed to probe the structure of two organometallic aluminum derivatives, Li­[Al­(CH₃)₃CH₂Si­(CH₃)₃] (<b>1</b>) and Li­[Al­(CH₃)₄] (<b>2</b>), which are relevant to olefin polymerization processes. For the first time, NMR observation of ²⁷Al–¹³C covalent bonds in solids is performed with the natural abundance material <b>1</b>. Unprecedented triple-resonance (¹H–¹³C–²⁷Al) and quadruple-resonance (¹H–⁷Li–¹³C–²⁷Al) heteronuclear correlation two-dimensional NMR experiments are also introduced to probe ²⁷Al–¹³C and ¹³C–⁷Li proximities for <b>2</b>. High-resolution solid-state NMR spectra thus obtained provide information on the local structure of these representative organometallic derivatives that proved to be most complementary and in full agreement with the structures obtained by X-ray diffraction

Carotid versus femoral access for transcatheter aortic valve replacement: comparable results in the current era

International audienceAbstract OBJECTIVES The carotid approach for transcatheter aortic valve replacement (TAVR) has been shown to be feasible and safe. The goal of this study was to compare the 30-day outcomes of trans-carotid (TC) and transfemoral (TF) TAVR. METHODS This retrospective study enrolled 500 consecutive patients treated by TC-TAVR (n = 100) or TF-TAVR (n = 400) with percutaneous closure between January 2018 and January 2020 at the Nantes University Hospital. The primary end-point was the occurrence of cardiovascular death and cerebrovascular events at 30 days. RESULTS The mean age was 79.9 ± 8.1 in the TC group and 81.3 ± 6.9 (P = 0.069) in the TF group. The TC group had more men (69% vs 50.5%; P = 0.001) and more patients with peripheral vascular disease (86% vs 14.8%; P &lt; 0.0001). Cardiac characteristics were similar between the groups, and the EuroSCORE II was 3.8 ± 2.6% vs 4.6 ± 6.0%, respectively (P = 0.443). The 30-day mortality was 2% in the TC group versus 1% in the TF group (P = 0.345). TC-TAVR was not associated with an increased risk of stroke (2% vs 2.5%; P = 0.999) or major vascular complications (2% vs 4%; P = 0.548). More permanent pacemakers were implanted in the TF group (14.9% vs 5.6%; P = 0.015), and no moderate or severe aortic regurgitation was observed in the TC group (0 vs 3.3%; P = 0.08). TC-TAVR was not associated with an increased risk of mortality or stroke at 30 days (odds ratio 1.32; 95% confidence interval 0.42–4.21; P = 0.63) in the multivariable analysis. CONCLUSIONS No statistically significant differences between TC-TAVR and TF-TAVR were observed; therefore, TC-TAVR should be the first alternative in patients with anatomical contraindications to the femoral route

The Hydrophobin-Like OmSSP1 May Be an Effector in the Ericoid Mycorrhizal Symbiosis

Mutualistic and pathogenic plant-colonizing fungi use effector molecules to manipulate the host cell metabolism to allow plant tissue invasion. Some small secreted proteins (SSPs) have been identified as fungal effectors in both ectomycorrhizal and arbuscular mycorrhizal fungi, but it is currently unknown whether SSPs also play a role as effectors in other mycorrhizal associations. Ericoid mycorrhiza is a specific endomycorrhizal type that involves symbiotic fungi mostly belonging to the Leotiomycetes (Ascomycetes) and plants in the family Ericaceae. Genomic and RNASeq data from the ericoid mycorrhizal fungus Oidiodendron maius led to the identification of several symbiosis-upregulated genes encoding putative SSPs. OmSSP1, the most highly symbiosis up-regulated SSP, was found to share some features with fungal hydrophobins, even though it lacks the Pfam hydrophobin domain. Sequence alignment with other hydrophobins and hydrophobin-like fungal proteins placed OmSSP1 within Class I hydrophobins. However, the predicted features of OmSSP1 may suggest a distinct type of hydrophobin-like proteins. The presence of a predicted signal peptide and a yeast-based signal sequence trap assay demonstrate that OmSSP1 is secreted. OmSSP1 null-mutants showed a reduced capacity to form ericoid mycorrhiza with Vaccinium myrtillus roots, suggesting a role as effectors in the ericoid mycorrhizal interaction