Crystallization monitoring by quantitative image analysis

Crystals have well defined geometric characteristics. A geometry-based algorithm has been developed to study images of crystals and to calculate their macroscopic structural characteristics. The procedure has been applied to single monocrystals and crystal populations for which shape distributions can be determined and used to quantify the shape homogeneity of a crystallizer production.     

Weakly continuous mappings on Banach spaces

It is shown that every n-homogeneous continuous polynomial on a Banach space E which is weakly continuous on the unit ball of E is weakly uniformly continuous on the unit ball of E. Applications of the result to spaces of polynomials and holomorphic mappings on E are given.     

N-phtalimidoazetioines par reactions d'isonitriles avec les N-phtalimidoazirioines,Ylures d'azomethine potentiels ; transposition en imines.

The reactions of isocyanides RNC with the 1-phtalimido 2-cyano 2-methoxycarbonyl 3-aryl aziridines gives N-phtalimido azetidines. Rearrangement of azetidines with R = tert-butyle or tert-octyle yields isomeric imines.     

Ag6(PMo10V2O40](CH3COO).8H2O: A 3D macrocationic polyoxometallic Keggin complex

Silver atoms and strongly interlinking Keggin units ensure the tridimensionnal macrocationic structure of [Ag(6)(PMo(10)V(2)O(40))](CH(3)COO).8H(2)O, which catalyzes O(2)-based oxidation of p-methoxytoluene in acetic acid by air.     

Integrated allosteric regulation in the <Emphasis Type="Italic">S. cerevisiae</Emphasis> carbamylphosphate synthetase – aspartate transcarbamylase multifunctional protein

Background  

The S. cerevisiae carbamylphosphate synthetase – aspartate transcarbamylase multifunctional protein catalyses the first two reactions of the pyrimidine pathway. In this organism, these two reactions are feedback inhibited by the end product UTP. In the present work, the mechanisms of these integrated inhibitions were studied.     

Structure of colloidal complexes obtained from neutral/poly- electrolyte copolymers and oppositely charged surfactants

We report on the phase behavior and scattering properties of colloidal complexes made from block copolymers and surfactants. The copolymer is poly(sodium acrylate)-b-poly(acrylamide), hereafter abbreviated as PANa-PAM, with molecular weight 5000 g/mol for the first block and 30000 g/mol for the second. In aqueous solutions and neutral pH, poly(sodium acrylate) is a weak polyelectrolyte, whereas poly(acrylamide) is neutral and in good-solvent conditions. The surfactant is dodecyltrimethylammonium bromide (DTAB) and is of opposite charge with respect to the polyelectrolyte block. Combining dynamical light scattering and small-angle neutron scattering, we show that in aqueous solutions PANa-PAM diblocks and DTAB associate into colloidal complexes. For surfactant-to-polymer charge ratios Z lower than a threshold (Z(C) approximately 0.3), the complexes are single surfactant micelles decorated by few copolymers. Above the threshold, the colloidal complexes reveal an original core-shell microstructure. We have found that the core of typical radius 100-200 A is constituted from densely packed surfactant micelles connected by the polyelectrolyte blocks. The outer part of the colloidal complex is a corona and is made from the neutral poly(acrylamide) chains. Typical hydrodynamic sizes for the whole aggregate are around 1000 A. The aggregation numbers expressed in terms of numbers of micelles and copolymers per complex are determined and found to be comprised between 100-400, depending on the charge ratio Z and on the total concentration. We have also shown that the sizes of the complexes depend on the exact procedure of the sample preparation. We propose that the driving mechanism for the complex formation is similar to that involved in the phase separation of homopolyelectrolyte/surfactant systems. With copolymers, the presence of the neutral blocks prevents the macroscopic phase separation from occurring.     

Simple technique for measuring the Goos-Hänchen effect with polarization modulation and a position-sensitive detector

An original approach to directly measuring the Goos-H?nchen longitudinal shift between TE and TM polarization states during a total internal reflection is introduced. The technique is based on the modulation of the polarization state of a laser by an electro-optic modulator combined with a precise measurement of the resulting spatial displacement with a position-sensitive detector. This method presents many advantages over other techniques and allows measurements at different wavelengths over a broad range for the incident angle.     

Size-based separation of synthetic polyelectrolytes in entangled polymer solution capillary electrophoresis: the effect of binary mixtures of separating polymers differing in molecular mass

The influence on the electrophoretic behavior of polystyrenesulfonates of the percentage of high-molecular-mass chains in an entangled poly(ethylene oxide) solution having a bimodal molecular mass distribution has been investigated and compared with the results obtained for similar solutions of unimodal molecular mass distribution. The comparisons between the different separating polymer solutions were made at a constant total mass concentration, so as to keep constant the mesh size and to highlight the sole effect of the network dynamics. The use of binary polymer mixtures of two different molecular masses but of same nature can be a convenient alternative to modulate the dynamics of the network and the viscosity of the separating medium. A 20-30% content of high-molecular-mass chains in an entangled poly(ethylene oxide) solution having a binary molecular mass distribution appears to be a good compromise for a moderate viscosity and a good separation selectivity in comparison with a solution containing only chains of high molecular mass at the same concentration.