Evolution of electronic and ionic structure of Mg-clusters with the growth cluster size

The optimized structure and electronic properties of neutral and singly charged magnesium clusters have been investigated using ab initio theoretical methods based on density-functional theory and systematic post-Hartree-Fock many-body perturbation theory accounting for all electrons in the system. We have systematically calculated the optimized geometries of neutral and singly charged magnesium clusters consisting of up to 21 atoms, electronic shell closures, binding energies per atom, ionization potentials and the gap between the highest occupied and the lowest unoccupied molecular orbitals. We have investigated the transition to the hcp structure and metallic evolution of the magnesium clusters, as well as the stability of linear chains and rings of magnesium atoms. The results obtained are compared with the available experimental data and the results of other theoretical works.Comment: 30 pages, 10 figures, 3 table

Close-Packing of Clusters: Application to Al_100

The lowest energy configurations of close-packed clusters up to N=110 atoms with stacking faults are studied using the Monte Carlo method with Metropolis algorithm. Two types of contact interactions, a pair-potential and a many-atom interaction, are used. Enhanced stability is shown for N=12, 26, 38, 50, 59, 61, 68, 75, 79, 86, 100 and 102, of which only the sizes 38, 75, 79, 86, and 102 are pure FCC clusters, the others having stacking faults. A connection between the model potential and density functional calculations is studied in the case of Al_100. The density functional calculations are consistent with the experimental fact that there exist epitaxially grown FCC clusters starting from relatively small cluster sizes. Calculations also show that several other close-packed motifs existwith comparable total energies.Comment: 9 pages, 7 figure

Epidémiologie et traitement des lymphomes non hodgkiniens chez la personne âgée

L'incidence des lymphomes non hodgkiniens (LNH) chez les patients de plus de 60 ans est en nette augmentation depuis une vingtaine d'années. La survie globale à 5 ans de ces patients est environ de 50% pour les lymphomes de bas degré de malignité et de 30% ou moins pour les lymphomes de haut degré de malignité. Les facteurs pronostiques sont les mêmes que chez les adultes, en dehors de l'âge qui est un facteur indépendant. En ce qui concerne les LNH de bas degré de malignité, il n'y a pas de bénéfice à traiter précocement les malades asymptomatiques. Les agents alkylants restent le traitement de choix pour les patients symptomatiques, mais les analogues des purines sont des agents prometteurs. Le CHOP reste le traitement standard des LNH de haut degré de malignité. Il est important de recruter ces patients dans des études cliniques prospectives