Zinc polyoxometalate on activated carbon: an efficient catalyst for selective oxidation of alcohols with hydrogen peroxide

[PW₁₁ZnO₃₉]^5? was immobilized on activated carbon and characterized using Fourier transform infrared, X‐ray diffraction, Brunauer–Emmett–Teller and elemental analysis techniques. Effective oxidation of various alcohols with hydrogen peroxide was performed in the presence of this catalyst. Easy separation of the catalyst from the reaction mixture, cheapness, high activity and selectivity, stability as well as retained activity in subsequent catalytic cycles make this supported catalyst suitable for small‐scale synthesis. Copyright © 2015 John Wiley & Sons, Ltd.     

Cup products in Hopf-cyclic cohomology

We construct cup products of two different kinds for Hopf-cyclic cohomology. When the Hopf algebra reduces to the ground field our first cup product reduces to Connes' cup product in ordinary cyclic cohomology. The second cup product generalizes Connes–Moscovici's characteristic map for actions of Hopf algebras on algebras. To cite this article: M. Khalkhali, B. Rangipour, C. R. Acad. Sci. Paris, Ser. I 340 (2005).     

An effective modeling and solution approach for the generalized independent set problem

The generalized independent set (GIS) problem was first introduced by Hochbaum and Pathria (Forest Sci 43(4), 544–554, 1997) and independently explored in greater detail by Hochbaum (Manage Sci 50(6), 709–123, 2004). This problem, with applications in forest management and a variety of related areas, is a generalization of the classical maximum independent set problem. In this paper we highlight a natural, nonlinear formulation for the problem that is an attractive alternative to the linear model found in the literature. The effectiveness of this alternative formulation is demonstrated by computational experience on test problems of varying size and density, disclosing a dramatic reduction in the time to obtain optimal and near optimal solutions and an ability to solve much larger problems.     

Roughness induced surface acoustic resonances

The vibrational and electronic spectra of a semi-infinite crystal with a planar surface is modified in presence of surface inhomogeneities or roughness such as ridges or grooves, quantum wires or tips… Using a Green's function formalism, we present an exact numerical method for obtaining the variation of the density of states associated with the adsorption of a ridge on a flat surface or with a groove cut into an otherwise planar surface. This general method is applied to the determination of the acoustic resonances of shear horizontal polarization associated with such deterministic surface protuberances or indentations. The positions and widths of the peaks in the total or local densities of states give the frequencies and lifetimes of the resonances, which may be more or less pronounced features depending on the relative parameters of the substrate and ridge materials. We also investigate the modifications of these acoustic surface shape resonances due to the interaction between two such defects. This calculation can also be transposed to the study of electronic structure of a wire near a flat surface, in the framework of an effective mass model.     

The Importance of Polarity/Polarizability Interaction on the Acidity Behavior of 9,10-Anthraquinone and 9-Anthrone Derivatives in Methanol-Water Mixed Solvents Using Target Factor Analysis and QSPR Approaches

The influence of solvent properties on acidity constants of some newly synthesized 9,10-anthraquinone and 9-anthrone derivatives was studied in methanol-water mixtures in a composition range of 0.57 to 1.0 methanol mole fraction. The model was established by using both multiple linear regression and target factor analysis. Both methods revealed that the solvent polarity/polarizability parameter ^* is a major factor in controlling the acidity behavior of the anthraquinones and anthrones studied in binary methanol-water mixed solvents. A QSPR study was conducted to drive the relationships between the ^* coefficient s and the polarity/polarizability of molecules. Both dipole moment and polarizability were found to have a linear relationship with s. The results confirm that, in the dipolar protic solvents used, the dipole-dipole interaction (for neutral molecules) and the ion-dipole interaction (for ionized molecules) are the major factors controlling the acidity behavior of these compounds.     

Electronic structure of some mesoscopic systems: II. Electronic composites

We study the electronic properties of a mesoscopic system composed of an array of straight, infinite rods made of an isotropic medium and embedded in a regular way in an isotropic background. Such a composite system has two-dimensional periodicity in the plane perpendicular to the rods. Using a Fourier series expansion, the corresponding Schrödinger equation is solved within the effective-mass approximation. The electronic band structure is computed for the wave vector in the transverse plane, and is illustrated by dispersion curves along the principal directions of the two-dimensional Brillouin zone as well as by the histograms of the density of states. The main result is the appearance of absolute energy gaps in the two-dimensional band structure.     

Regio- and Stereoselective Reactions of 17-Phenyl-18,19,20-trinorprostaglandin F(2)(alpha) Isopropyl Ester

Novel prostaglandin F(2)(alpha) derivatives, functionalized at C13 and C14, have been prepared. 17-Phenyl-18,19,20-trinorprostaglandin F(2)(alpha) isopropyl ester [(15S)-1] and its epimer [(15R)-1] were stereoselectively epoxidized, using Sharpless conditions, to produce each of the four diastereomeric epoxides (15S)-2, (15S)-3, (15R)-2, and (15R)-3. Treatment of the four epoxides with LiOH stereospecifically-produced the pentahydroxy substituted analogues 12 and 13. Alternatively, epoxides 2 and 3were allowed to react with thiophenolate ion. The attack of the sulfur nucleophile on the epoxide occurred at either C13 or C14 depending on the stereochemistry of the epoxide and of C15.     

Simple models of adsorbed polymers: Vibrational properties

The vibrational properties of polymers adsorbed on surfaces are investigated within the frame of two simple models. First the surface is modelled as a one-dimensional infinite harmonic chain. Polymeric “ molecules ” are represented as harmonic chains of finite length. The coupling between the polymers and the surface is treated within the frame of the Interface Response Theory. Upon adsorption of polymers, resonant vibrational modes appear as well defined peaks in the variation of the density of states of the system. The effect of the interaction between adsorbed polymers via phonons is investigated and shown to lead to antiresonances in the spectral density of states and the formation of gaps in the density of states as the surface coverage is increased. A second more realistic model is introduced where the same finite harmonic chains (polymers) are grafted on a two dimensional [001] surface cut through a cubic harmonic crystal. Again the variation in density of states exhibits resonant modes between the polymers and the substrate. However, in this case, the interaction between polymers is short range. Adsorption of a film of polymers produces resonant modes which remain well-defined features within the substrate bulk band.