Scanning tunneling microscopy of adsorbed molecules on metalic surfaces for nearly localized atomic states

We consider a Hubbard-Anderson model which describes localized orbitals in five different sites hybridized both among themselves and with a continuum of extended states. A square planar geometry with an atom at the center is used to represent TBrPP-Co molecules. When the renormalized effective hopping between sites is small compared with a Kondo energy scale determined by the sitecontinuum hybridization, the system can be described as a set of independent Kondo resonances, rather than molecular states. We study the crossover between both regimes and analyze the spectral density of conduction electrons as a function of position. The results are in qualitative agreement with measurements of the differential conductance in a system with TBrPP-Co molecules adsorbed on a Cu(111) surface.Comment: 5 pages, 4 figure

La desregulación de la comercialización de electricidad en Inglaterra y Gales

A partir de 1995, las autoridades regulatorias de Reino Unido han comenzado un proceso de introducción de competencia para ventas minoristas de electricidad. Esta política demandó un gran esfuerzo de organización por parte de los agentes de sistema, cuyos costos de lanzamiento se estiman en alrededor de 500 millones de libras. El presente reporte, en primer lugar, describe el programa de apertura llevado a cabo y evalúa los efectos de la apertura sobre el funcionamiento del sector y los niveles de bienestar de distintos estratos sociales de la población. Finalmente, del estudio de la experiencia británica se pueden extraer lecciones para la implementación futura de similares medidas en otros países.desregulación; comercialización de electricidad;

Quantum interference through gated single-molecule junctions

We discuss the general form of the transmission spectrum through a molec- ular junction in terms of the Green function of the isolated molecule. By introducing a tight binding method, we are able to translate the Green func- tion properties into practical graphical rules for assessing beforehand the possible existence of antiresonances in an energy range for a given choice of connecting sites. The analysis is exemplified with a benzene molecule under a hypothetical local gate, which allows one to continuously tune the on-site energy of single atoms, for various connection topologies and gate positions.Comment: 17 pages, 5 figure

A Benchmarking Exercise on Latin American Water Util

The aim of this study is to estimate both stochastic and mathematical programming cost functions and frontier studies with the ADERASA’s database. ADERASA is a Latin American association of water regulators, which has done a systematic effort on data collection. Econometric and DEA techniques were employed here. This study fills a gap on the understanding of relative efficiency in the Latin American water sector., through a consistent database. Firstly we present a survey of the empirical literature related with cost and production frontiers in the water and sanitation sector. The survey shed light in order to determine the variables to choose in the models to be estimated. Secondly, some models were estimated, differing each other on the specification, and the environmental variables included. The results are satisfactory, with the expected signs and plausible values for the coefficients. Some consistency between methodologies was found.Benchmarking; cost functions; frontier; stochastic model; ADERASA