Les systèmes imprimitifs dans lesquels se répartissent les combinaisonsi ài dem éléments par les substitutions du groupe cyclique de degrém

Sans résumé     

A mössbauer investigation of non-bridging oxygens in Na2O-Fe2O3-B2O3 glasses

Mössbauer measurements of sodium borate glasses 4 Fe₂O₃· x Na₂O· (96-x) B₂O₃ (x=6, 10, 15, 20, 25, 30) have been carried out. It was found that Fe³⁺ is present in both octahedral and tetrahedral sites, whereby the tetrahedral sites are preferred. In the range of Na₂O contents higher than about 15 mol%, the isomer shifts and quadrupole splittings for Fe³⁺ decrease continuously with increasing Na₂O concentration. These changes could be attributed to the formation of non-bridging oxygens (NBO) in the neighborhood of ferric ions. Increasing Na₂O content thus gives rise to more NBO increasing the symmetry of the iron polyhedra.     

The exact Mössbauer recoilless fraction in fractals ATT≠0

In this paper a detailed calculation of the Mössbauer fraction for a general non-Euclidean dimensionality is given. The result shows that the contributions to the Mössbauer effect in fractals come from three possible types of transition.     

New reformulations for probabilistically constrained quadratic programs

The mixed integer quadratic programming (MIQP) reformulation by Zheng, Sun, Li, and Cui (2012) for probabilistically constrained quadratic programs (PCQP) recently published in EJOR significantly dominates the standard MIQP formulation ( and ) which has been widely adopted in the literature. Stimulated by the dimensionality problem which Zheng et al. (2012) acknowledge themselves for their reformulations, we study further the characteristics of PCQP and develop new MIQP reformulations for PCQP with fewer variables and constraints. The results from numerical tests demonstrate that our reformulations clearly outperform the state-of-the-art MIQP in Zheng et al. (2012).     

Investigation of the solid-solid surface adsorption of Eu2O3 on amorphous Al2O3

Solid-solid surface adsorption of Eu₂O₃ on anorphous Al₂O₃ have been investigated by the Mössbauer effect, X-ray diffraction analysis (XRD.) and Laser Raman Spectroscopy (LRS). The results of these studies indicate that the structure of EU₂O₃ dispersed onto the support surface depends on the structure of support and that there is an inductive effect of the support on the structure of the Eu₂O₃.     

A Mössbauer study of spin-pinning in the oxide surface layer on fine iron particles

Fine α-Fe particles coated with an oxide surface layer were prepared by the evaporation technique. The spin pinning in the oxide surface layer were studied by means of the Mössbauer effect in an applied field of 6T during a thermal-cycle process. The anisotropy energy on the surface was estimated.     

The Grob/Eschenmoser fragmentation of cycloalkanones bearing β-electron withdrawing groups: a general strategy to acyclic synthetic intermediates

Introduction of a β-electron withdrawing group to cycloalkanones allows facile C-C bond fragmentation. The reaction has been demonstrated with a large range of ring sizes, bearing various leaving and electron withdrawing groups, and using a variety of nitrogen and oxygen containing nucleophiles (>30 examples). The application of fragmentation products to the preparation of substituted γ-lactones has been demonstrated. Mechanistic studies are reported which are suggestive of a Grob/Eschenmoser type reaction.     

On multiple objective programming problems with set functions

The convexity of a subset of a σ-algebra and the convexity of a set function on a convex subset are defined. Related properties are also examined. A Farkas-Minkowski theorem for set functions is then proved. These results are used to characterize properly efficient solutions for multiple objective programming problems with set functions by associated scalar problems.