Microscopic origin of isotropic non-Heisenberg behavior in highly correlated systems

We have reanalyzed the microscopic origin of the isotropic deviations that are observed from the energy spacings predicted by the HDVV Hamiltonian. Usually, a biquadratic spin operator is added to the HDVV Hamiltonian to account for such deviations. It is shown here that this operator cannot describe the effect of the excited atomic non-Hund states which brought the most important contribution to the deviations. For systems containing more than two magnetic centers, non-Hund states cause additional interactions that are of the same order of magnitude as the biquadratic exchange and should have significant effects on the macroscopic properties of extended systems.Comment: 4 pages, 3 figure

The structure of freight flows in Europe and its implications for EU railway freight policy

We analyse the potential for shifting freight transports to the railways in Western and Cen-tral Europe. This potential arises for large and concentrated freight flows over long distances of about 300 km or more. However, we show that there are only few such freight flows in Europe, and that they are concentrated or connected to the central European population centers, sometimes called the “Blue Banana”. As a consequence, the European railway freight corridors according to EU Regulation 913/2010 should be divided into two distinct groups: first tier and second tier corridors. Substantial innovations should be introduced on the first tier corridors first, in order to increase efficiency and reduce noise. This refers to core innovations for rolling stock like the introduction of automatic couplings, electronic or electro-pneumatic brakes, and modern bogies

Spin-density-functional theory: some open problems and application to inhomogeneous Heisenberg models

Spin-density-functional theory (SDFT) is the most widely implemented and applied formulation of density-functional theory. However, it is still finding novel applications, and occasionally encounters unexpected problems. In this paper we first briefly describe a few of the latter, related to issues such as nonuniqueness, noncollinearity, and currents. In the main part we then turn to an example of the former, namely SDFT for the Heisenberg model. It is shown that time-honored concepts of Coulomb DFT, such as the local-density approximation, can be applied to this (and other) model Hamiltonians, too, once the concept of 'density' has been suitably reinterpreted. Local-density-type approximations for the inhomogeneous Heisenberg model are constructed. Numerical applications to finite-size and impurity systems demonstrate that DFT is a computationally efficient and reasonably accurate alternative to conventional methods of statistical mechanics for the Heisenberg model.Comment: 15 pages, 1 figure, 1 tabl

International Road Freight Transport in France: Experiences from Germany, the Netherlands and Driver Costs Analysis

These last few years, French international road freight transport has been undergoing a loss of influence within Europe while traffic has increased and great manoeuvres are taking place since the opening of the European Union towards East. Some of the French transporters are then focusing back on the French market showing a worrying loss in competitiveness. On the contrary, German and Dutch companies are increasing their shares in the French market and have reorganized themselves within Europe to face Eastern Europe competition: follow-up on customers delocalizing in the East, networking, hyperproductivity, markets segmentation between high quality transport in the West, specific markets and low cost segment in Eastern Germany and East Europe (Poland, Romania, ...), intensive geographical closeness to a great harbour (Rotterdam)... What should France learn from German and Dutch experiences? On the basis of a comparison of our neighbours' driving costs and road freight transport structure, our contribution - a synthesis of two recent studies ordered by the Comite National Routier (CNR, studies free to be downloaded by www.cnr.fr) - will first propose a cooperation with German or Dutch companies in order to propose a winner-winner model based on exchange of competencies: North Africa (Morocco for instance) and Southern Europe for French partners (specialization Storage - Logistics) and transport business model and opening towards the East for the German and Dutch partners

Dérivations et extractions de hamiltoniens modèles pour l'étude de composés à propriétés électroniques remarquables

TOULOUSE3-BU Sciences (315552104) / SudocSudocFranceF

EVALUATION DE LA QUALITE DE VIE DES PERSONNES AGEES ET LEUR SATISFACTION DANS QUATRE INSTITUTIONS ,EN MAYENNE,QUI SONT EN COURS DE CERTIFICATION D'ETABLISSEMENT D'HEBERGEMENT POUR PERSONNES AGEES DEPENDANTES

ANGERS-BU Médecine-Pharmacie (490072105) / SudocPARIS-BIUM (751062103) / SudocSudocFranceF

La responsabilité publique en amont des choix collectifs : les économistes sur la piste du « politique »

La question de la responsabilité publique se trouve généralement posée en aval des décisions et actions publiques. Cette perspective classique laisse cependant de côté une dimension importante de l'analyse de la responsabilité, en amont des décisions publiques. Nous prenons donc comme hypothèse de travail l'idée selon laquelle le rôle principal de la politique est de faire émerger les préférences collectives. Cette perspective, traitée sous un angle strictement économique, conduit à quatre types idéaux de l'analyse économique de la décision publique, issus d'un croisement entre des considérations portant, d'une part, sur le caractère supposé bienveillant ou opportuniste des élus ; et, d'autre part, sur le fait que les préférences individuelles sont connues ou au contraire incertaines. De la vision traditionnelle du « Petit Père des Peuples », ou dictateur bienveillant, on passe alors progressivement à une approche en ternies de quasi-contrats entre les électeurs et les élus. Cette problématique du contrat politique se heurtant à l'incertitude sur les préférences individuelles, nous entrons ensuite dans une logique de benchmarking politique qui rappelle toute la complexité du problème. On revient alors à une bienveillance active des « politiques » lorsqu'ils sont en présence de préférences individuelles incertaines sous forme de pan sur les préférences collectives futures.Crozet Yves, Guihery Laurent. La responsabilité publique en amont des choix collectifs : les économistes sur la piste du « politique ». In: Politiques et management public, vol. 19, n° 3, 2001. Les nouvelles exigences de la responsabilité publique. Actes du dixième colloque international - Paris, jeudi 9 et vendredi 10 mars 2000 - Tome 2. pp. 37-54