Electro-adsorption of polyethyleneimine on the anion exchange membrane: Application to the nitrate removal from loaded solutions

Anion exchange membrane has been modified by fixation of polyethyleneimine. The modification has been carried out aiming to achieve a separation of anions according to their hydration radii and their sizes. The performances of the modified membranes were compared with the unmodified one by applying Donnan dialysis of nitrate ion using Cl⁻ in the strip compartment. The transfer of nitrate ions in the presence of chloride was enhanced by using immersion modified membrane. The presence of a thin layer of PEI on the strip side of the membrane improves Cl⁻ transference, by creating a chemical potential difference which increases the transfer.     

Pyrroloquinolines,a New Platform for Developing Organic Photosensitizers: When Synthetic Methodology Meets Photophysics†

New molecular architectures with triplet sensitization properties can have a big impact on photochemistry and photobiology. In their recent work, de Bonfils et al. have tackled this challenge in a very systematic way using a powerful synthetic strategy. This consists of an elegant yet practical organocatalyzed cyclization/oxidation rearrangement sequence which they now apply to the synthesis of pyrroloquinolines, a new scaffold for photosensitizers. However, beyond this new class of compounds, the strategy has potential to produce a myriad of compact organic chromophores with promising photoinduced intersystem crossing properties. The study therefore provides interesting clues to serve the rational design of biocompatible molecular photosensitizers but also raises puzzling questions on the intriguing excited state reactivity of these molecular architectures.     

Spectral and oscillatory properties of a linear pencil of fourth-order differential operators

The paper deals with the spectral and oscillatory properties of a linear operator pencilA ? λB, where the coefficient A corresponds to the differential expression (py″)″ and the coefficient B corresponds to the differential expression ?y″ + cry. In particular, it is shown that all negative eigenvalues of the pencil are simple and, under some additional conditions, the number of zeros of the corresponding eigenfunctions is related to the serial number of the corresponding eigenvalue.     

Synthesis and X-ray structure of neutral Pd(IV) hydride complexes supported by β-ketoimine ligands

A series of neutral palladium(IV) hydride complexes supported by β-ketoimine ligands was synthesized. Reaction of dichlorobis(acetonitrile)palladium(II) with β-ketoamines (1–4) in dichloromethane at room temperature generated dark red solids of [PdCl₂(β-ketoimine)(H)] (6–9) in which the central carbon of the ketoimine ligand is σ-bound to the palladium. All the new complexes have been characterized by NMR and IR spectroscopy. The structure of complex(9) has been solved by X-ray crystallography.     

Synthesis, crystal structure and optical investigation of the new phosphates: Na7Mg13Ln(PO4)12 (Ln=La, Eu)

Two new isostructural rare earth phosphates Na₇Mg₁₃Ln(PO₄)₁₂ (Ln=La, Eu) have been synthesized and investigated by X-ray diffraction and optical measurements. They crystallize in the orthorhombic system with the Cmc2₁ space group (Z=4). The crystal structure exhibits a new type of framework built up from LnO₈ (Ln=La, Eu), MO₆ (M=0.5Mg+0.5Na) and MgO_x (x=5, 6) polyhedra and PO₄ tetrahedra linked by common corner, edge or face. It can be described in terms of [Mg₄MP₄O₂₂]_∞ layers stacked along the a direction. These layers are interconnected by [Mg₄LnP₄O₃₆]_∞ undulating chains spreading along the b direction. This framework delimits 6 distinct cavities occupied by Na⁺ cations. The results of the optical study of Na₇Mg₁₃La_1−xEu_x(PO₄)₁₂ (x=0, 0.02, 0.1, 1) reveal the presence of two different Eu³⁺ ion environments whereas the X-ray study predicts the existence of only one Eu site. This difference can be explained by the possible presence of the europium element in the sodium sites with small occupancies which cannot be detected by the X-ray structural determination.     

Formulation fonction-courant et tourbillon du problème de Stokes dans un domaine bidimensionnel multiplement connexe

We consider the formulation of the Stokes problem in a multiply connected two-dimensional domain where the unknowns are the stream-function and the vorticity. We derive its equivalence with a finite system of several variational problems. This leads to the construction of a finite element discretization of this problem. The analysis and a numerical experiment prove the convergence of the method. To cite this article: M. Amara et al., C. R. Acad. Sci. Paris, Ser. I 342 (2006).