5,153 research outputs found
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 , being 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 paÃses de América Latina. Los años noventa mostró una importante transformación en los sectores de servicios públicos que se inició en los paÃses centrales pero que tuvo su mayor difusión e impacto en América Latina. AsÃ, por ejemplo un 48% de la inversión directa en infraestructura y un 35% del total de proyectos de participación privada durante ese perÃodo tuvieron como destino paÃses 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-RodrÃguez, A.. Universidad de Mar del Plata. Laboratorio de Componentes Electrónicos; ArgentinaFil: MartÃn-Pirchio, F. N.. Universidad Nacional del Sur. Departamento de IngenierÃa Eléctrica y de Computadoras; ArgentinaFil: Julian, Pedro Marcelo. Consejo Nacional de Investigaciones CientÃficas y Técnicas. Centro CientÃfico Tecnológico Conicet - BahÃa Blanca. Instituto de Investigaciones en IngenierÃa Eléctrica "Alfredo Desages". Universidad Nacional del Sur. Departamento de IngenierÃa Eléctrica y de Computadoras. Instituto de Investigaciones en IngenierÃa Eléctrica "Alfredo Desages"; ArgentinaFil: Mandolesi, Pablo Sergio. Universidad Nacional del Sur. Departamento de IngenierÃa 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 categorÃas 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
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 edÃficas
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
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