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281.
The Cu‐catalyzed intramolecular CH insertion of phenyliodonium ylide 1b was investigated at 0° in the presence of several chiral ligands. Enantioselectivities varied in the range 38–72%, and were higher than those resulting from reaction of the diazo compound 1c at 65°. The intramolecular insertion of the enantiomerically pure methyl diazoacetate (R)‐ 20 and of the corresponding phenyliodonium ylide (R)‐ 21 proceeded to (R)‐ 23 with retention of configuration with [Cu(hfa)2] (hfa=hexafluoroacetylacetone=1,1,1,5,5,5‐hexafluoropentane‐2,4‐dione) and [Rh2(OAc)4]. These results are consistent with a carbenoid mechanism for the Cu‐catalyzed insertion with phenyliodonium ylides. However, the insertion of the perfluorosulfonated phenyliodonium ylide (R)‐ 29 afforded with [Cu(hfa)2] as well as with [Rh2(OAc)4] the cyclopentanone derivative 30 as a cis/trans mixture with only 56–67% enantiomeric excess. 相似文献
282.
Henri Vahabi Fouad Laoutid Elnaz Movahedifar Reza Khalili Negar Rahmati Christelle Vagner Marianne Cochez Loic Brison Franck Ducos Mohammad Reza Ganjali Mohammad Reza Saeb 《先进技术聚合物》2019,30(8):2056-2066
This work visualizes the complementary actions of organic and mineral additives in model thermoplastic polymer composites in terms of Flame Retardancy Index (FRI). Thermal and flame retardancy behaviors of ethylene‐vinyl acetate copolymer (EVA) composites containing calcium carbonate (CC) mineral and ammonium polyphosphate (APP) organic additives were studied varying composition of additives in the 80/20 EVA/(xCC + (20 ? x)APP) composites with x denoting 0, 5, 10, 15, and 20 wt%. Thermogravimetric analysis (TGA) revealed that the onset temperature of composites and the remaining residue were increased by combination of APP and CC, while cone calorimetry results were indicative of a promising flame retardancy performance at a given composition of APP and CC. Based on FRI values, we made distinguished samples from flame retardancy performance viewpoint, where the best flame retardancy was obtained by combination of 15 wt% APP and 5 wt% CC, as reflected in FRI value of 3.08. By contrast, samples containing only APP or CC revealed low resistance against flame, as signaled by FRI values of 0.99 and 0.89, respectively. X‐ray diffraction (XRD) analysis was made on remaining residue collected at the end of cone calorimetry measurements. Moreover, Raman analysis confirmed barrier effect of flame retardancy for EVA/(5APP + 15CC) sample, featured by a higher graphitization level as well as a thicker yet more homogenous char layer. Mechanical behavior analysis of composites revealed an acceptable level of properties, particularly high elongation at break, which was almost independent of formulation. However, a minor loss in yield stress was observed, especially for EVA(10CC + 10APP) sample. 相似文献
283.
Christelle Combescure Hélène Dumontet François Voldoire 《International Journal of Solids and Structures》2013
A new stress resultant constitutive model for reinforced concrete plates under cyclic solicitations is presented. This model is built by the periodic homogenisation approach using the averaging method and couples damage of concrete and periodic debonding between concrete and steel rebar. In one-dimensional situations, we derive a closed-form solution of the local problem useful to verify and set up the plate problem. The one dimensional macroscopic constitutive model involves a limited number of parameters, the sensibility of which is studied. Comparison to experimental results underlines the pertinence of the model by considering internal debonding in order to properly represent the mechanical dissipation occurring during cyclic loadings on reinforced concrete panels. 相似文献
284.
285.
Dr. Charlène Esmieu Guillaume Ferrand Dr. Valentina Borghesani Dr. Christelle Hureau 《Chemistry (Weinheim an der Bergstrasse, Germany)》2021,27(5):1777-1786
In vitro Cu(Aβ1–x)-induced ROS production has been extensively studied. Conversely, the ability of N-truncated isoforms of Aβ to alter the Cu-induced ROS production has been overlooked, even though they are main constituents of amyloid plaques found in the human brain. N-Truncated peptides at the positions 4 and 11 (Aβ4–x and Aβ11–x) contain an amino-terminal copper and nickel (ATCUN) binding motif (H2N-Xxx-Zzz-His) that confer them different coordination sites and higher affinities for CuII compared to the Aβ1–x peptide. It has further been proposed that the role of Aβ4–x peptide is to quench CuII toxicity in the brain. However, the role of CuI coordination has not been investigated to date. In contrast to CuII, CuI coordination is expected to be the same for N-truncated and N-intact peptides. Herein, we report in-depth characterizations and ROS production studies of Cu (CuI and CuII) complexes of the Aβ4–16 and Aβ11–16 N-truncated peptides. Our findings show that the N-truncated peptides do produce ROS when CuI is present in the medium, albeit to a lesser extent than the unmodified counterpart. In addition, when used as competitor ligands (i.e., in the presence of Aβ1–16), the N-truncated peptides are not able to fully preclude Cu(Aβ1–16)-induced ROS production. 相似文献
286.
Highly selective and sensitive assays are required for detection and quantitation of the small masses of DNA typically encountered in clinical and forensic settings. High detection sensitivity is achieved using fluorescent labeling dyes and detection techniques such as spectrofluorometers, microplate readers and cytometers. This work describes the use of a laser-induced fluorescence (LIF) detector in conjunction with a commercial capillary electrophoresis instrument for DNA quantitation. PicoGreen and YO-PRO-1, two fluorescent DNA labeling dyes, were used to assess the potential of the system for routine DNA analysis. Linearity, reproducibility, sensitivity, limits of detection and quantitation, and sample stability were examined for the two assays. The LIF detector response was found to be linear (R2 > 0.999) and reproducible (RSD < 9%) in both cases. The PicoGreen assay displayed lower limits of detection and quantitation (20 pg and 60 pg, respectively) than the YO-PRO-1 assay (60 pg and 260 pg, respectively). Although a small variation in fluorescence was observed for the DNA/dye complexes over time, quantitation was not significantly affected and the solutions were found to be relatively stable for 80 min. The advantages of the technique include a 4- to 40-fold reduction in the volume of sample required compared to traditional assays, a 2- to 20-fold reduction in the volume of reagents consumed, fast and automated analysis, and low cost (no specific instrumentation required). 相似文献
287.
Marine Cotte Victor Gonzalez Frederik Vanmeert Letizia Monico Catherine Dejoie Manfred Burghammer Loïc Huder Wout de Nolf Stuart Fisher Ida Fazlic Christelle Chauffeton Gilles Wallez Núria Jimnez Francesc Albert-Tortosa Nati Salvad Elena Possenti Chiara Colombo Marta Ghirardello Daniela Comelli Ermanno Avranovich Clerici Riccardo Vivani Aldo Romani Claudio Costantino Koen Janssens Yoko Taniguchi Joanne McCarthy Harald Reichert Jean Susini 《Molecules (Basel, Switzerland)》2022,27(6)
The European Synchrotron Radiation Facility (ESRF) has recently commissioned the new Extremely Brilliant Source (EBS). The gain in brightness as well as the continuous development of beamline instruments boosts the beamline performances, in particular in terms of accelerated data acquisition. This has motivated the development of new access modes as an alternative to standard proposals for access to beamtime, in particular via the “block allocation group” (BAG) mode. Here, we present the recently implemented “historical materials BAG”: a community proposal giving to 10 European institutes the opportunity for guaranteed beamtime at two X-ray powder diffraction (XRPD) beamlines—ID13, for 2D high lateral resolution XRPD mapping, and ID22 for high angular resolution XRPD bulk analyses—with a particular focus on applications to cultural heritage. The capabilities offered by these instruments, the specific hardware and software developments to facilitate and speed-up data acquisition and data processing are detailed, and the first results from this new access are illustrated with recent applications to pigments, paintings, ceramics and wood. 相似文献
288.
Stéphane Mabic Christelle Franot 《Journal of the American Society for Mass Spectrometry》1997,8(12):1255-1256
The electron-induced mass spectrometry of 1-substituted-4-phenyl-1,2-dihydropyridines is characterized by a [M-1] peak that accounts for the base peak, and a fragment corresponding to the loss of the N-substituent in every example examined. 相似文献
289.
Marielle Drommi Clment Rulmont Charlne Esmieu Christelle Hureau 《Molecules (Basel, Switzerland)》2021,26(24)
We here report the synthesis of three new hybrid ligands built around the phenanthroline scaffold and encompassing two histidine-like moieties: phenHH, phenHGH and H’phenH’, where H correspond to histidine and H’ to histamine. These ligands were designed to capture Cu(I/II) from the amyloid-β peptide and to prevent the formation of reactive oxygen species produced by amyloid-β bound copper in presence of physiological reductant (e.g., ascorbate) and dioxygen. The amyloid-β peptide is a well-known key player in Alzheimer’s disease, a debilitating and devasting neurological disorder the mankind has to fight against. The Cu-Aβ complex does participate in the oxidative stress observed in the disease, due to the redox ability of the Cu(I/II) ions. The complete characterization of the copper complexes made with phenHH, phenHGH and H’phenH’ is reported, along with the ability of ligands to remove Cu from Aβ, and to prevent the formation of reactive oxygen species catalyzed by Cu and Cu-Aβ, including in presence of zinc, the second metal ions important in the etiology of Alzheimer’s disease. The importance of the reduced state of copper, Cu(I), in the prevention and arrest of ROS is mechanistically described with the help of cyclic voltammetry experiments. 相似文献
290.
Christelle Perreur Jean‐Pierre Habas Jean Peyrelasse Alain Lapp Jeanne Francois 《Macromolecular Symposia》2001,166(1):127-138
The physico‐chemical properties of Tetronic® 908 in aqueous solution have been explored on a wide range of temperature and concentration. This system presents interesting rheological properties depending on the polymer concentration in solution, and temperature. For weight percentage p comprised between 5% and 20%, the viscosity of the solution passes through a maximum. Small angle neutron scattering experiments show that the increase in the viscosity is due to the progressive aggregation of the chains. For higher weight percentages, the viscosity of the system diverges and the mixture becomes “gel‐like”. SANS studies of the same solution indicate that the micelles are organized in a cubic structure. We have developed a model which suitably describes the SANS curves of the system in the region where micelles are formed. It allows the calculation of several parameters (volume fraction of the micelles, size, composition). The evolution of these parameters with temperature and polymer concentration is detailed. Comparisons with models of literature are discussed. 相似文献