Technical Change and Catching-up: The Electricity Distribution Sector in South America

The main purpose of this paper is to analyze technical change in the electricity distribution sector in South America, in the period 1994-1997. We do so by estimating a Maximum Likelihood stochastic frontier. We found that there is no evidence of catching up effects in the sector during this period. Besides, there is partial evidence that suggests that countries which reformed their electricity sector had a better performance than those which did not. We also found an increase in the capital share in the countries that made the reform and an increment in the labor share in the ones that did not make the reform.Technical change; Catching-Up; Stochastic frontier

Organic Molecules in the Galactic Center. Hot Core Chemistry without Hot Cores

We study the origin of large abundances of complex organic molecules in the Galactic center (GC). We carried out a systematic study of the complex organic molecules CH3OH, C2H5OH, (CH3)2O, HCOOCH3, HCOOH, CH3COOH, H2CO, and CS toward 40 GC molecular clouds. Using the LTE approximation, we derived the physical properties of GC molecular clouds and the abundances of the complex molecules.The CH3OH abundance between clouds varies by nearly two orders of magnitude from 2.4x10^{-8} to 1.1x10^{-6}. The abundance of the other complex organic molecules relative to that of CH3OH is basically independent of the CH3OH abundance, with variations of only a factor 4-8. The abundances of complex organic molecules in the GC are compared with those measured in hot cores and hot corinos, in which these complex molecules are also abundant. We find that both the abundance and the abundance ratios of the complex molecules relative to CH3OH in hot cores are similar to those found in the GC clouds. However, hot corinos show different abundance ratios than observed in hot cores and in GC clouds. The rather constant abundance of all the complex molecules relative to CH3OH suggests that all complex molecules are ejected from grain mantles by shocks. Frequent (similar 10^{5}years) shocks with velocities >6km/s are required to explain the high abundances in gas phase of complex organic molecules in the GC molecular clouds. The rather uniform abundance ratios in the GC clouds and in Galactic hot cores indicate a similar average composition of grain mantles in both kinds of regions. The Sickle and the Thermal Radio Arches, affected by UV radiation, show different relative abundances in the complex organic molecules due to the differentially photodissociation of these molecules.Comment: 18 pages, 10 Postscript figures, uses aa.cls, aa.bst, 10pt.rtx, natbib.sty, revsymb.sty revtex4.cls, aps.rtx and aalongtabl.sty. Accepted in A&A 2006. version 2. relocated figures and tables. Language editor suggestions. added reference

The Cost of Capital in Regulated Firms: The Argentine Experience

The sustainability of service is one of the fundamental aims of any regulatory system, and this tends to be reflected in the general principles within the legal framework of each public service. The necessity to cover economic costs of service then follows, in order to cover costs in such a way as to guarantee the maintaining and continuity of the system as well as its expansion. These economic costs should necessarily include sufficient retribution for the capital used by investors: the cost of capital. In the case of Argentine regulation, it is usual practice to use an adapted form of the CAPM (Capital Asset Pricing Model) to calculate the opportunity cost of equity, in such a way as to take the country risk into account. In this work we will analyse the components of the adapted formula for the cost of capital, discussing incentives which generate each of the possible outcomes for the regulated firms. Finally, we will present a model of dynamic optimisation for a regulated firm in a country such as Argentina.regulatory system; public service; CAPM; country risk

Compound orbits break-up in constituents: an algorithm

In this paper decomposition of periodic orbits in bifurcation diagrams are derived in unidimensional dynamics system $x_{n+1}=f(x_{n};r)$, being $f$ an unimodal function. We proof a theorem which states the necessary and sufficient conditions for the break-up of compound orbits in their simpler constituents. A corollary to this theorem provides an algorithm for the computation of those orbits. This process closes the theoretical framework initiated in (Physica D, 239:1135--1146, 2010)

A process of rumor scotching on finite populations

Rumor spreading is a ubiquitous phenomenon in social and technological networks. Traditional models consider that the rumor is propagated by pairwise interactions between spreaders and ignorants. Spreaders can become stiflers only after contacting spreaders or stiflers. Here we propose a model that considers the traditional assumptions, but stiflers are active and try to scotch the rumor to the spreaders. An analytical treatment based on the theory of convergence of density dependent Markov chains is developed to analyze how the final proportion of ignorants behaves asymptotically in a finite homogeneously mixing population. We perform Monte Carlo simulations in random graphs and scale-free networks and verify that the results obtained for homogeneously mixing populations can be approximated for random graphs, but are not suitable for scale-free networks. Furthermore, regarding the process on a heterogeneous mixing population, we obtain a set of differential equations that describes the time evolution of the probability that an individual is in each state. Our model can be applied to study systems in which informed agents try to stop the rumor propagation. In addition, our results can be considered to develop optimal information dissemination strategies and approaches to control rumor propagation.Comment: 13 pages, 11 figure

La Determinación del Costo de Capital en América Latina Un Estudio Comparativo de Casos

El objetivo de este trabajo es presentar un análisis comparativo de la determinación del costo de capital en sectores regulados en distintos países de América Latina. Los años noventa mostró una importante transformación en los sectores de servicios públicos que se inició en los países centrales pero que tuvo su mayor difusión e impacto en América Latina. Así, por ejemplo un 48% de la inversión directa en infraestructura y un 35% del total de proyectos de participación privada durante ese período tuvieron como destino países de América Latinacosto de capital; sectores regulados; servicios públicos; inversión directa en infraestructura;

A Verilog HDL digital architecture for delay calculation

A method for the calculation of the delay between two digital signals with central frequencies in the range [20, 300] Hz is presented. The method performs a delay calculation in order to determine the bearing angle of a sound source. Computing accuracy is tested against a previous implementation of the Cross Correlation Derivative method. A Verilog RTL model of the method has been tested on a Xilinx® FPGA in order to evaluate the real performance of the method. Simulations of an ASIC design on a standard CMOS technology predict a power saving of about 25 times per delay stage over previous implementations.Fil: Chacón-Rodríguez, A.. Universidad de Mar del Plata. Laboratorio de Componentes Electrónicos; ArgentinaFil: Martín-Pirchio, F. N.. Universidad Nacional del Sur. Departamento de Ingeniería Eléctrica y de Computadoras; ArgentinaFil: Julian, Pedro Marcelo. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Bahía Blanca. Instituto de Investigaciones en Ingeniería Eléctrica "Alfredo Desages". Universidad Nacional del Sur. Departamento de Ingeniería Eléctrica y de Computadoras. Instituto de Investigaciones en Ingeniería Eléctrica "Alfredo Desages"; ArgentinaFil: Mandolesi, Pablo Sergio. Universidad Nacional del Sur. Departamento de Ingeniería Eléctrica y de Computadoras; Argentin

Participación vegetal en la construcción de los sistemas dunares litorales de Mallorca

[Resumen] Se establecen las relaciones entre la zonación vegetal y las áreas geomorfológicas de los sistemas dunares litorales de la isla de Mallorca. Para ello, se clasifican dichos sistemas en cuatro categorías en base a criterios morfológicos y de vegetación y se analiza la situación actual en cada uno de ellos, definiendose el papel que juega la vegetación en su arquitectura..[Abstract] The relationship between plant zonation and geomorphological areas have been studied in the coastal dunar systems of the island of Mallorca. Trough a four type classification based in vegetation and morphological criteria we point out their state of conservation and the role of the vegetation in their build-up

Conjunctival Melanoma: A New Clinical and Therapeutical Approach

Melanoma involving the conjunctiva is extremely rare. Graver prognosis has been reported with primary conjunctival melanoma than with their cutaneous counterparts [Collin et al.: Aust N Z J Ophthalmol 1986;14:29–34]. Among conjunctival melanomas, two significant risk factors for tumour-related death have been identified: (i) age older than 55 years and (ii) unfavourable tumour location (caruncle, cornea, fornix, palpebral conjunctiva) [Werschnik and Lommatzsch: Am J Clin Oncol 2002;25:248–255]. Here we present a rare case of lentigo maligna involving the palpebral, bulbar conjunctiva and the caruncle. We describe dermoscopic patterns observed and the use of a novel ocular melanoma therapy with topical imiquimod

Distribución espacial de leguminosas en relación con el arbolado

A study was made of tree canopy influence on spatial distribution of leguminosae species and some soil variables in grassland communities. Besides the differentiation according to the tree species, it is possible to establish groups of samples according to their distance frorn the tree trunk. The greatest influence of canopy on vegetation and soil variables has been detected in the samples taken on the northern side of the trees.Se estudia la incidencia del arbolado sobre la distribución espacial de especies pertenecientes a la familia de las leguminosas y sobre algunas variables edáficas, en comunidades de pastizal adehesado. Aparte de la diferenciación atribuible a la especie arbórea, en todos los casos es posible el establecimiento de grupos de acuerdo con la distancia al tronco. La mayor influencia del arbolado se detecta en orientación norte, tanto en lo que se refiere a la vegetación como a las variables edíficas