Electron affinity of Al13: a correlated electronic structure study

Neutral and anionic 13-atom aluminum clusters are studied with high-level, fully ab initio methods: second-order perturbation theory (MP2) and coupled cluster theory with singles, doubles, and perturbative triples (CCSD(T)). Energies and vibrational frequencies are reported for icosahedral and decahedral isomers, and are compared with density functional theory results. At the MP2 level of theory, with all of the basis sets employed, the icosahedral structure is energetically favored over the decahedral structure for both the neutral and anionic Al(13) clusters. Hessian calculations imply that only the icosahedral structures are potential energy minima. The CCSD(T)/aug-cc-pVTZ adiabatic electron affinity of Al(13) is found to be 3.57 eV, in excellent agreement with experiment.     

Rhodium(I)-catalyzed addition of arylboronic acids to (benzyl-/arylsulfonyl)acetonitriles: efficient synthesis of (Z)-β-sulfonylvinylamines and β-keto sulfones

An efficient rhodium(I)-catalyzed addition of arylboronic acids to (benzyl-/arylsulfonyl)acetonitrile is described. Novel β-sulfonylvinylamine products are formed in a stereoselective fashion (Z-alkene). Upon hydrolysis, useful β-keto sulfones are obtained with a broad scope of aryl and sulfonyl substituents.     

Improving Physical Properties via C?H Oxidation: Chemical and Enzymatic Approaches

Physicochemical properties constitute a key factor for the success of a drug candidate. Whereas many strategies to improve the physicochemical properties of small heterocycle‐type leads exist, complex hydrocarbon skeletons are more challenging to derivatize because of the absence of functional groups. A variety of C H oxidation methods have been explored on the betulin skeleton to improve the solubility of this very bioactive, yet poorly water‐soluble, natural product. Capitalizing on the innate reactivity of the molecule, as well as the few molecular handles present on the core, allowed oxidations at different positions across the pentacyclic structure. Enzymatic oxidations afforded several orthogonal oxidations to chemical methods. Solubility measurements showed an enhancement for many of the synthesized compounds.     

Lifting,superadditivity, mixed integer rounding and single node flow sets revisited

In this survey we attempt to give a unified presentation of a variety of results on the lifting of valid inequalities, as well as a standard procedure combining mixed integer rounding with lifting for the development of strong valid inequalities for knapsack and single node flow sets. Our hope is that the latter can be used in practice to generate cutting planes for mixed integer programs. The survey contains essentially two parts. In the first we present lifting in a very general way, emphasizing superadditive lifting which allows one to lift simultaneously different sets of variables. In the second, our procedure for generating strong valid inequalities consists of reduction to a knapsack set with a single continuous variable, construction of a mixed integer rounding inequality, and superadditive lifting. It is applied to several generalizations of the 0–1 single node flow set. This paper appeared in 4OR, 1, 173–208 (2003). The first author is supported by the FNRS as a chercheur qualifié. This paper presents research results of the Belgian Program on Interuniversity Poles of Attraction initiated by the Belgian State, Prime Minister’s Office, Science Policy Programming. The scientific responsibility is assumed by the authors.     

Experimental investigation of reflection coefficients for lossy liquid-solid-liquid systems

The reflection coefficient for a bounded ultrasonic beam incident on a liquid-solid-liquid system (LSL) is studied. Systematic measurements were carried out to investigate the variations of the amplitude of the reflection modulus ∣R_LSL∣ with incident angle and parameter Fd (frequency-thickness of the plate). The experimental plots confirm the theoretical works of Claeys et al¹ and Bogy and Gracewski². It is shown that the attenuation of the media has a great influence on the variations of this coefficient as has been already mentioned in the literature, for liquid-solid configurations.     

The determination of hexadecapole deformation parameters in actinide nuclei and their variation near the nuclear surface

By computing self consistently the nuclear density of²³⁸U with the Skyrme SIII effective force, the hexadecapole deformation parameter has been found to vary considerably in the nuclear surface. This suggests an explanation for some discrepancies observed betweenβ ₄ parameters estimated from different inelastic scattering experiments.     

Elastoacoustic model with uncertain mechanical properties for ultrasonic wave velocity prediction: application to cortical bone evaluation

The axial transmission technique can measure the longitudinal wave velocity of an immersed solid. An elementary model of the technique is developed with a set of source and receivers placed in a semi-infinite fluid coupled at a plane interface with a semi-infinite solid. The acoustic fluid is homogeneous. The solid is homogeneous, isotropic, and linearly elastic. The work is focused on the prediction of the measured velocity (apparent velocity) when the solid is considered to have random material properties. The probability density functions of the random variables modeling each mechanical parameter of the solid are derived following the maximum entropy principle. Specific attention is paid to the modeling of Poisson's ratio so that the second-order moments of the velocities remain finite. The stochastic solver is based on a Monte Carlo numerical simulation and uses an exact semianalytic expression of the acoustic response derived with the Cagniard-de Hoop method. Results are presented for a solid with the material properties of cortical bone. The estimated mean values and confidence regions of the apparent velocity are presented for various dispersion levels of the random parameters. A sensibility analysis with respect to the source and receivers locations is presented.     

On differential Galois groups of strongly normal extensions

We revisit Kolchin's results on definability of differential Galois groups of strongly normal extensions, in the case where the field of constants is not necessarily algebraically closed. In certain classes of differential topological fields, which encompasses ordered or p‐valued differential fields, we find a partial Galois correspondence and we show one cannot expect more in general. In the class of ordered differential fields, using elimination of imaginaries in , we establish a relative Galois correspondence for relatively definable subgroups of the group of differential order automorphisms.     

A nullstellensatz and a positivstellensatz for ordered differential fields

We use the model completeness and axiomatisation of the theory of closed ordered differential fields to give a differential version of Dubois, Krivine and Risler's nullstellensatz and Stengle's positivstellensatz for ordered fields.