Labile Base-Stabilized Silyliumylidene Ions. Non-Metallic Species Capable of Activating Multiple Small Molecules

Several base-stabilized silyliumylidene ions ( 2 and 3 ) with different ligands were synthesized. Their behaviour appeared strongly dependent on the nature of ligand. Indeed, in contrast to the poorly reactive silyliumylidene ions 3 c,d stabilized by strongly donating ligands (DMAP, NHC), the silylene- and sulfide-supported one ( 2-H and 3 a ) exhibits higher reactivity toward various small molecules. Furthermore, their capability to successively activate multiple small molecules was clearly demonstrated by processes involving successive reactions with silane/formamide, CO₂ and H₂. Moreover, HBPin adduct of 3 a ( 8-C ) catalyzes the hydroboration of pyridine. Of particular interest, silylene-supported silyliumylidene complex 2-H is one of the rare species able to activate two H₂ molecules.     

Complexes of Dichlorogermylene with Phosphine/Sulfoxide-Supported Carbone as Ligand

Due to their remarkable electronic features, recent years have witnessed the emergence of carbones L₂C, which consist in two donating L ligands coordinating a central carbon atom bearing two lone pairs. In this context, the phosphine/sulfoxide-supported carbone 4 exhibits a strong nucleophilic character, and here, we describe its ability to coordinate dichlorogermylene. Two original stable coordination complexes were obtained and fully characterized in solution and in the solid state by NMR spectroscopy and X-ray diffraction analysis, respectively. At 60 °C, in the presence of 4, the Ge(II)-complex 5 undergoes a slow isomerization that transforms the bis-ylide ligand into an yldiide.     

A penalization method applied to the wave equation

In this Note we investigate the mathematical properties of the volume penalization method applied to the one-dimensional wave equation. Generally speaking, the penalization method allows one to handle complex geometries by simply adding a term to the equation to impose the boundary conditions. We study the convergence of the method with regards to the penalization parameter and we present error and stability analyses for the wave equation. Numerical simulations using a finite difference scheme illustrate the results. To cite this article: A. Paccou et al., C. R. Mecanique 333 (2005).     

Metastability release of the form alpha of trehalose by isothermal solid state vitrification

Kinetic investigations of the polymorphic form alpha of anhydrous trehalose have been performed below its apparent melting temperature (Tm) by differential scanning calorimetry (DSC) and X-ray diffraction. The results reveal a spontaneous isothermal vitrification process which indicates that the phase alpha is in a very unusual superheating situation. This behavior has been attributed to the fact that the effective melting temperature (Tm(eff)) of the phase alpha is likely to be located far below the glass transition temperature (Tg) of this compound. The high viscosity of the liquid trehalose between Tm(eff) and Tg is thus invoked to explain the long lifetime of the phase alpha in this temperature range.     

Visualizing Microglia with a Fluorescence Turn‐On Ugt1a7c Substrate

Microglia, the brain‐resident macrophage, are involved in brain development and contribute to the progression of neural disorders. Despite the importance of microglia, imaging of live microglia at a cellular resolution has been limited to transgenic mice. Efforts have therefore been dedicated to developing new methods for microglia detection and imaging. Using a thorough structure–activity relationships study, we developed CDr20, a high‐performance fluorogenic chemical probe that enables the visualization of microglia both in vitro and in vivo. Using a genome‐scale CRISPR‐Cas9 knockout screen, the UDP‐glucuronosyltransferase Ugt1a7c was identified as the target of CDr20. The glucuronidation of CDr20 by Ugt1a7c in microglia produces fluorescence.     

Raman identification of H2CO in aqueous solutions

Aqueous formaldehyde solutions of mole fraction from 0.05 to 0.20 were studied by Raman spectroscopy at temperatures up to 180 °C. The previously unreported Raman spectrum of formaldehyde under its non‐hydrated form H₂CO has been identified, in addition to the already known bands from methanediol CH₂(OH)₂ and poly(oxymethylene)glycols HO(CH₂O)_nH formed by hydration and subsequent polymerization of the formaldehyde molecules. The experimental spectrum of formaldehyde in solutions agrees perfectly with the theoretical calculations. Copyright © 2010 John Wiley & Sons, Ltd.     

Analysis of high molecular mass proteins larger than 150 kDa using cyanogen bromide cleavage and conventional 2-DE

Proteomic approaches including high-resolution 2-DE are providing the tools needed to discover disease-associated biomarkers in complex biological samples. Although 2-DE is an extremely powerful approach to analyze the proteome, the separation of proteins with extreme molecular masses still remains an issue requiring improvement. Because high molecular mass (HMM) proteins larger than 150 kDa have already been observed to be differentially expressed in several pathologies such as cancer, we developed an original strategy to analyze this part of the proteome that is not easily separated by 2-DE in polyacrylamide gels. This strategy is based on the 2-DE separation of cyanogen bromide (CNBr) fragments of purified HMM protein fractions, and combines techniques including SEC fractionation, TCA precipitation, CNBr cleavage, 2-DE and MS analysis. The method was first tested on a model protein, the BSA. Preliminary results obtained using colonic tissues led to the identification of six HMM proteins with M(r) comprised between 163 and 533 kDa in their reduced state. These results demonstrated that our CNBr/2-DE approach should provide a powerful tool for identification of new biomarkers larger than 150 kDa.     

A study on the limitations of a vane rheometer for mineral suspensions using image processing

This study presents the results from the rheological measurement of clay suspensions using vane geometry in a wide gap configuration. It focuses on how measurement of viscosity cannot be effective for two reasons: the limits of the vane geometry itself and the limits of the material depending on its content of solid particles. Image analysis of the flow while shearing the material is carried out to relate the flow behavior. Several approaches to compute the shear flow curve from torque-rotational velocity data are used. The results demonstrate that the applied setpoint while applying a logarithmic shear rate ramp can be very different from the calculated shear rate from existing theories. Depending on the solid volume fraction of the particles in the mixture, we relate the macroscopic behavior using image analysis and the shear flow curves to the rheophysical regime of the flow of the suspensions. Therefore, this paper has two simultaneous goals: the first one is to describe the physical phenomena which control macroscopic behavior and the second one is to highlight the limits of the vane geometry for viscosity measurement of mineral suspensions like kaolinite pastes.     

Quantification of ignition time uncertainty based on the classical ignition theory and Fourier analysis

This study aims at modeling the effect of incoming heat flux fluctuations, on solid material ignition. In order to propose a general methodology based on the classical ignition theory that can be applied to any kind of solid target, kernels accounting for the target temperature response regarding an incoming heat flux are considered for thermally thick and thin solids with low or high thermal inertia. A Fourier decomposition of the incoming heat flux is then used to calculate the target response to harmonic heat fluxes. Finally, effects of harmonic fluctuations on ignition are discussed based on the previous analytical results, allowing us to discriminate situations where ignition time is expected to be rather predictable from situations where ignition time is expected to be less predictable thanks to an uncertainty quantification of the ignition time.