Simplicité abstraite des groupes de Kac–Moody non affines

We announce the simplicity of non-affine Kac–Moody lattices (modulo center). The groups under consideration are minimal Kac–Moody groups. They were defined by Jacques Tits by means of a presentation à la Steinberg. The ground field is finite, assumed to be of cardinality greater than the rank of the buildings these groups naturally act upon. We work in the general combinatorial context of twin root data. To cite this article: P.-E. Caprace, B. Rémy, C. R. Acad. Sci. Paris, Ser. I 342 (2006).     

M?ssbauer spectroscopy: analysis and predictions for Li-ion batteries

Due to their high storage capacity Sn-based materials are of considerable interest as negative electrode for Li-ion batteries. However the strong volume change occurring during the alloy formation strongly limits the electrochemical performances (cycle and time life). Analysis by M?ssbauer spectroscopy using model compounds (Sn, Sn-Li and transition metal-Sn alloys) shows that the volume expansion is related to the structural change from a Sn based network to a Li based network. Two types of materials are proposed here to overcome this problem: tin dispersion in an electrochemically inactive oxide matrix with buffer role to absorb volume changes or tin alloying with an inactive transition metal to minimize the volume expansion. The use of M?ssbauer spectroscopy (in situ operando mode) allows a dynamic approach which is essential to understand the fundamental causes of ageing on cycling and to define then the key issues to be solved for material’s application.     

Efficient stereochemical controllers in biaryl Suzuki coupling reactions: benzylic carbinols bearing in beta-position thioether, dimethylamino, or sulfoxide groups

Highly atropo-diastereoselective Suzuki coupling between aryl halides bearing stereogenic benzylic carbinols with sulfoxide, thioether, or dimethylamino groups as efficient internal chelating ligands and 2-methoxy-1-naphthylboronic acid were performed with high yields; a palladacycle is proposed as a potential transition state. [reaction: see text]     

On the rate of convergence to equilibrium in the Becker-Döring equations

We provide an explicit rate of convergence to equilibrium for solutions of the Becker-Döring equations using the energy/energy-dissipation relation. The main difficulty is the structure of equilibria of the Becker-Döring equations, which do not correspond to a Gaussian measure, such that a logarithmic Sobolev-inequality is not available. We prove a weaker inequality which still implies for fast decaying data that the solution converges to equilibrium as e^−ct1/3.     

Giant field dependence of the low temperature relaxation of the magnetization in a dysprosium(III)-DOTA complex

The square antiprismatic Na[Dy(DOTA)(H(2)O)]·4H(2)O complex was characterised by single crystal X-ray diffraction and ac magnetic susceptometry. Two competing mechanisms for magnetic relaxation as well as the remarkable increase of six orders of magnitude in the relaxation time upon application of a static magnetic field were detected.     

On mean-field limits and quantitative estimates with a large class of singular kernels: Application to the Patlak–Keller–Segel model

In this note, we propose a modulated free energy combination of the methods developed by P.-E. Jabin and Z. Wang [Inventiones (2018)] and by S. Serfaty [Proc. Int. Cong. Math. (2018) and references therein] to treat more general kernels in mean-field limit theory. This modulated free energy may be understood as introducing appropriate weights in the relative entropy developed by P.-E. Jabin and Z. Wang (in the spirit of what has been recently developed by D. Bresch and P.-E. Jabin [Ann. of Math. (2) (2018)]) to cancel the most singular terms involving the divergence of the flow. Our modulated free energy allows us to treat singular potentials that combine large smooth part, small attractive singular part, and large repulsive singular part. As an example, a full rigorous derivation (with quantitative estimates) of some chemotaxis models, such as the Patlak–Keller–Segel system in subcritical regimes, is obtained.     

The photoelectron spectra of perfluoro-2-butyne and perfluorohexa-2,4-diyne. The perfluorination effect

The He(I) photoelectron spectra of perfluoro-2-butyne and perfluorohexa-2,4-diyne are reported and discussed in comparison with the photoelectron spectra of 2-butyne and hexa-2,4-diyne. Large π shifts (ca. 2 eV) towards higher ionization energies are observed as a consequence of complete substitution of hydrogen by fluorine. EXTHUC and CNDO/S calculations are found to be in good agreement with the experimental data. A new vibrational analysis of the first band of the perfluoro-2-butyne is proposed.     

Reflection rigidity of 2-spherical Coxeter groups

We prove that each finitely generated, irreducible and 2-sphericalCoxeter system (W, S) is strongly reflection rigid wheneverthe group W is of infinite order. This means in particular thatall reflection-preserving automorphisms of such a group areinner-by-graph. Our result can be seen as a first major steptowards a proof of the conjecture that all infinite, irreducibleCoxeter systems are strongly reflection rigid if they do notadmit diagram twists.     

Remodeling of ordered membrane domains by GPI-anchored intestinal alkaline phosphatase

Glycosylphosphatidyl-inositol (GPI)-anchored proteins preferentially localize in the most ordered regions of the cell plasma membrane. Acyl and alkyl chain composition of GPI anchors influence the association with the ordered domains. This suggests that, conversely, changes in the fluid and in the ordered domains lipid composition affect the interaction of GPI-anchored proteins with membrane microdomains. Validity of this hypothesis was examined by investigating the spontaneous insertion of the GPI-anchored intestinal alkaline phophatase (BIAP) into the solid (gel) phase domains of preformed supported membranes made of dioleoylphosphatidylcholine/dipalmitoylphosphatidylcholine (DOPC/DPPC), DOPC/sphingomyelin (DOPC/SM), and palmitoyloleoylphosphatidylcholine/SM (POPC/SM). Atomic force microscopy (AFM) showed that BIAP inserted in the gel phases of the three mixtures. However, changes in the lipid composition of membranes had a marked effect on the protein containing bilayer topography. Moreover, BIAP insertion was associated with a net transfer of phospholipids from the fluid to the gel (DOPC/DPPC) or from the gel to the fluid (POPC/SM) phases. For DOPC/SM bilayers, transfer of lipids was dependent on the homogeneity of the gel SM phase. The data strongly suggest that BIAP interacts with the most ordered lipid species present in the gel phases of phase-separated membranes. They also suggest that GPI-anchored proteins might contribute to the selection of their own microdomain environment.     

Characterization of phospholipid bilayer formation on a thin film of porous SiO2 by reflective interferometric Fourier transform spectroscopy (RIFTS)

Classical methods for characterizing supported artificial phospholipid bilayers include imaging techniques such as atomic force microscopy and fluorescence microscopy. The use in the past decade of surface-sensitive methods such as surface plasmon resonance and ellipsometry, and acoustic sensors such as the quartz crystal microbalance, coupled to the imaging methods, have expanded our understanding of the formation mechanisms of phospholipid bilayers. In the present work, reflective interferometric Fourier transform spectrocopy (RIFTS) is employed to monitor the formation of a planar phospholipid bilayer on an oxidized mesoporous Si (pSiO(2)) thin film. The pSiO(2) substrates are prepared as thin films (3 μm thick) with pore dimensions of a few nanometers in diameter by the electrochemical etching of crystalline silicon, and they are passivated with a thin thermal oxide layer. A thin film of mica is used as a control. Interferometric optical measurements are used to quantify the behavior of the phospholipids at the internal (pores) and external surfaces of the substrates. The optical measurements indicate that vesicles initially adsorb to the pSiO(2) surface as a monolayer, followed by vesicle fusion and conversion to a surface-adsorbed lipid bilayer. The timescale of the process is consistent with prior measurements of vesicle fusion onto mica surfaces. Reflectance spectra calculated using a simple double-layer Fabry-Perot interference model verify the experimental results. The method provides a simple, real-time, nondestructive approach to characterizing the growth and evolution of lipid vesicle layers on the surface of an optical thin film.