Marco económico del negocio : Análisis de eficiencia empresarial de los subsectores Construcción y Electricidad, Gas y Agua en la región de La Plata, Berisso y Ensenada

Objetivos de la investigación: • Identificar parámetros de eficiencia de los sub sectores «Construcción» y Electricidad, Gas y Agua de la región para poder caracterizar las notas salientes del contexto en este ámbito. • Generar información relativa a la eficiencia de los sub sectores «Construcción» y «Electricidad, Gas y Agua» de la región, capaz de hacer trascender características salientes de la realidad económica. • Analizar patrones de eficiencia sub-sectoriales y comparar con los generales de este estudio.Facultad de Ciencias Económica

The chemistry involved in the third explosion limit of H₂–O₂ mixtures

The third explosion limit of hydrogen oxidation in closed vessels has always been thought to be the result of the competition between homogeneous gas-phase reactions and diffusion of hydroperoxyl radicals to the walls, where they are destroyed. It has recently been observed that this species actually follows a chemical-kinetic steady state in this regime, with the consequence that its diffusive rate toward the catalytic walls becomes irrelevant. Here we show that the critical explosion conditions are determined instead by the fate of hydrogen peroxide, which emerges as the controlling reactant for the resulting gas-phase chemistry. A simple, accurate analytic expression for the third explosion limit follows from identification of the critical conditions for existence of weakly reactive, diffusion&-reaction solutions, thereby providing the answer to a long-standing problem that in early work was characterized as being hopelessly difficult.This work was supported by the US AFOSR Grant # FA9550-12-1-0138, by the Comunidad de Madrid through Project #P2009/ENE-1597, and by the Spanish MCINN through Project #CSD2010-00011

Hydrogen-air mixing-layer ignition at temperatures below crossover

This paper addresses ignition histories of diffusion flames in unstrained hydrogen-air mixing layers for initial conditions of temperature and pressure that place the system below the crossover temperature associated with the second explosion limit of hydrogen–oxygen mixtures. It is seen that a two-step reduced chemical-kinetic mechanism involving as main species H₂, O₂, H₂O, and H₂O₂, derived previously from a detailed mechanism by assuming all radicals to follow a steady-state approximation, suffices to describe accurately the ignition process. The strong temperature sensitivity of the corresponding overall rates enables activation-energy asymptotics to be employed for the analysis, following the ideas developed for mixing-layer ignition by Liñán and Crespo in 1976 on the basis of one-step Arrhenius model chemistry. When the initial temperatures of both reactants differ by a relative amount that is of the order of or smaller than the ratio of this temperature to the effective activation temperature, the chemical reaction is seen to occur at a significant rate all across the mixing layer. The ignition time is then determined as a thermal runaway in a parabolic problem describing the evolution of the temperature increment and the H₂O₂ concentration, with local accumulation, chemical reaction, and transverse convection and diffusion, all being important. By way of contrast, when the air side is sufficiently hotter than the hydrogen side, as often occurs in applications, ignition occurs in a thin layer close to the air-side boundary, enabling a simplified description to be developed in which the ignition time is determined by analyzing the existence of solutions to a two-point boundary-value problem involving quasi-steady diffusion–reaction ordinary differential equations.This work was supported by the US AFOSR Grant # FA9550-12-1-0138, by the Comunidad de Madrid through Project # P2009/ENE-1597, and by the Spanish MCINN through Project #CSD2010-00011

A Chandrasekhar Mass Progenitor for the Type Ia Supernova Remnant 3C 397 from The Enhanced Abundances of Nickel and Manganese

Despite decades of intense efforts, many fundamental aspects of Type Ia supernova (SNe Ia) remain elusive. One of the major open questions is whether the mass of the exploding white dwarf (WD) is close to the Chandrasekhar limit. Here we report the detection of strong K-shell emission from stable Fe-peak elements in the Suzaku X-ray spectrum of the Type Ia supernova remnant (SNR) 3C 397. The high Ni/Fe and Mn/Fe mass ratios (0.11-0.24 and 0.018-0.033, respectively) in the hot plasma component that dominates the K-shell emission lines indicate a degree of neutronization in the SN ejecta which can only be achieved by electron captures in the dense cores of exploding WDs with a near-Chandrasekhar mass. This suggests a single-degenerate origin for 3C 397, since Chandrasekhar mass progenitors are expected naturally if the WD accretes mass slowly from a companion. Together with other results supporting the double-degenerate scenario, our work adds to the mounting evidence that both progenitor channels make a significant contribution to the SN Ia rate in star-forming galaxies.Comment: Accepted by ApJL; 6 pages with 4 figures and 1 tabl

Hypoxia Augments Outgrowth Endothelial Cell (OEC) Sprouting and Directed Migration in Response to Sphingosine-1-Phosphate (S1P)

Therapeutic angiogenesis provides a promising approach to treat ischemic cardiovascular diseases through the delivery of proangiogenic cells and/or molecules. Outgrowth endothelial cells (OECs) are vascular progenitor cells that are especially suited for therapeutic strategies given their ease of noninvasive isolation from umbilical cord or adult peripheral blood and their potent ability to enhance tissue neovascularization. These cells are recruited to sites of vascular injury or tissue ischemia and directly incorporate within native vascular endothelium to participate in neovessel formation. A better understanding of how OEC activity may be boosted under hypoxia with external stimulation by proangiogenic molecules remains a challenge to improving their therapeutic potential. While vascular endothelial growth factor (VEGF) is widely established as a critical factor for initiating angiogenesis, sphingosine-1-phosphate (S1P), a bioactive lysophospholipid, has recently gained great enthusiasm as a potential mediator in neovascularization strategies. This study tests the hypothesis that hypoxia and the presence of VEGF impact the angiogenic response of OECs to S1P stimulation in vitro. We found that hypoxia altered the dynamically regulated S1P receptor 1 (S1PR1) expression on OECs in the presence of S1P (1.0 mu M) and/or VEGF (1.3 nM). the combined stimuli of S1P and VEGF together promoted OEC angiogenic activity as assessed by proliferation, wound healing, 3D sprouting, and directed migration under both normoxia and hypoxia. Hypoxia substantially augmented the response to S1P alone, resulting in similar to 6.5-fold and similar to 25-fold increases in sprouting and directed migration, respectively. Overall, this report highlights the importance of establishing hypoxic conditions in vitro when studying ischemia-related angiogenic strategies employing vascular progenitor cells.University of California, DavisAmerican Heart Association (AHA)Univ Calif Davis, Dept Biomed Engn, Davis, CA 95616 USAUniversidade Federal de São Paulo, Dept Biophys, São Paulo, BrazilUniv Calif Davis, Dept Neurobiol Physiol & Behav, Davis, CA 95616 USAUniversidade Federal de São Paulo, Dept Biophys, São Paulo, BrazilAmerican Heart Association (AHA): 15PRE22930044Web of Scienc

Flammability conditions for ultra-lean hydrogen premixed combustion based on flame-ball analyses

Proceeding of: 10th International Conference on Clean Energy 2010, 15-17 September 2010, Famagusta, North CyprusIt has been reasoned that the structures of strongly cellular flames in very lean mixtures approach an array of flame balls, each burning as if it were isolated, thereby indicating a connection between the critical conditions required for existence of steady flame balls and those necessary for occurrence of self-sustained premixed combustion. This is the starting assumption of the present study, in which structures of near-limit steady sphericosymmetrical flame balls are investigated with the objective of providing analytic expressions for critical combustion conditions in ultra-lean hydrogen-oxygen mixtures diluted with N2 and water vapor. If attention were restricted to planar premixed flames, then the lean-limit mole fraction of H2 would be found to be roughly ten percent, more than twice the observed flammability limits, thereby emphasizing the relevance of the flame-ball phenomena. Numerical integrations using detailed models for chemistry and radiation show that a onestep chemical-kinetic reduced mechanism based on steady-state assumptions for all chemical intermediates, together with a simple, optically thin approximation for water-vapor radiation, can be used to compute near-limit fuel-lean flame balls with excellent accuracy. The previously developed one-step reaction rate includes a crossover temperature that determines in the first approximation a chemical-kinetic lean limit below which combustion cannot occur, with critical conditions achieved when the diffusion-controlled radiation-free peak temperature, computed with account taken of hydrogen Soret diffusion, is equal to the crossover temperature. First-order corrections are found by activation-energy asymptotics in a solution that involves a near-field radiation-free zone surrounding a spherical flame sheet, together with a far-field radiation-conduction balance for the temperature profile. Different scalings are found depending on whether or not the surrounding atmosphere contains water vapor, leading to different analytic expressions for the critical conditions for flame-ball existence, which give results in very good agreement with those obtained by detailed numerical computations. The one-step chemistry employed in the present work, which involves a non-Arrhenius rate having a cutoff at the crossover temperature, applies with excellent accuracy to the description of lean premixed hydrogen-air combustion, i.e, for f(0:5 at atmospheric pressure, and could be used for instance in the numerical simulation of the propagation of curved or cellularflames in ultra-lean reactive atmospheres, of interest for safety analyses related to the storage, transport, and handling of hydrogen.This work was supported by the Comunidad de Madrid through project #P2009/ENE-1597. The first three authors also acknowledge support from the Spanish MCINN through projects # ENE2008-06515 and CSD2010-00011

A multipurpose reduced mechanism for ethanol combustion

New multipurpose skeletal and reduced chemical-kinetic mechanisms for ethanol combustion are developed, along the same philosophical lines followed in our previous work on methanol. The resulting skeletal mechanism contains 66 reactions, only 19 of which are reversible, among 31 species, and the associated reduced mechanism contains 14 overall reactions among 16 species, obtained from the skeletal mechanism by placing CH3CHOH, CH2CH2OH, CH3CO, CH2CHO, CH2CO, C2H3, C2H5, C2H6, S - CH2, T - CH2, CH4, CH2OH, CH3O, HCO, and O in steady state. For the reduced mechanism, the steady-state relations and rate expressions are arranged so that computations can be made sequentially without iteration. Comparison with experimental results for autoignition, laminar burning velocities, and counterflow flame structure and extinction, including comparisons with the 268-step, 54-species detailed San Diego Mechanism and five other mechanisms in the literature, support the utility of the skeletal and reduced mechanisms, showing, for example, that, in comparison with the San Diego mechanism, they reduced the computational time by a factor of 4 (71 % faster) and 12 (93 % faster), respectively. Measures of computation times and of extents of departures from experimental values are defined and employed in evaluating results. Besides contributing to improvements in understanding of the mechanisms, the derived simplifications may prove useful in a variety of computational studies.This work was supported by projects ENE2015-65852-C2-1-R (MINECO/FEDER, UE) and BYNV-ua37crdy (Fundacion Iberdrola Espaha)

The structure of lean hydrogen-air flame balls

An analysis of the structure of flame balls encountered under microgravity conditions, which are stable due to radiant energy losses from H₂O, is carried out for fuel-lean hydrogen-air mixtures. It is seen that, because of radiation losses, in stable flame balls the maximum flame temperature remains close to the crossover temperature, at which the rate of the branching step H + O₂ -> OH + O equals that of the recombination step H + O₂ + M -> HO₂ + M. Under those conditions, all chemical intermediates have very small concentrations and follow the steady-state approximation, while the main species react according to the overall step 2H₂ + O₂-> 2H₂O; so that a one-step chemical-kinetic description, recently derived by asymptotic analysis for near-limit fuel-lean deflagrations, can be used with excellent accuracy to describe the whole branch of stable flame balls. Besides molecular diffusion in a binary-diffusion approximation, Soret diffusion is included, since this exerts a nonnegligible effect to extend the flammability range. When the large value of the activation energy of the overall reaction is taken into account, the leading-order analysis in the reaction-sheet approximation is seen to determine the flame ball radius as that required for radiant heat losses to remove enough of the heat released by chemical reaction at the flame to keep the flame temperature at a value close to crossover. The results are relevant to burning velocities at lean equivalent ratios and may influence fire-safety issues associated with hydrogen utilization.This work was supported by the Spanish MCINN through Project # ENE2008-06515 and by the Comunidad de Madrid through Project #S2009/ENE-159

Energías renovables: desafíos y oportunidades para la ingeniería en Latinoamérica

Los vastos potenciales de recursos sin explotar de la región son una oportunidad motivadora para el despliegue de las energías renovables. La inversión en energías renovables ofrece un amplio margen para generar oportunidades de empleo, cuestión que reviste una importancia capital en las políticas públicas de muchos países de la región. El desarrollo de proyectos, la construcción y la instalación de tecnologías de energías renovables lleva aparejado un potencial de empleo considerable, en especial para los ingenieros. A medida que el sector de las energías renovables se expande en la región, las oportunidades de empleo seguirán creciendo. Sin embargo, la realización plena de los beneficios de las energías renovables requiere de una amplia gama de instrumentos de políticas transversales que deben contemplar entre otros el desarrollo de habilidades y la capacitación. No contar con los profesionales adecuados aumenta los costos laborales y daña la productividad. El presente trabajo analiza la potencialidad de empleo que despliega el sector de energías renovables para los ingenieros de la región y el desafío que presenta en términos de educación.Facultad de Ingeniería (FI

Infraestructura de la producción: consumo de energía en industrias de la región de La Plata, Berisso y Ensenada

Objetivos de la investigación: - Conocer el mercado de consumo energético para las industrias de la región de La Plata, Berisso y Ensenada. - Destacar la importancia de la energía en el sector industrial. - Obtener información del PBG de la región bajo estudio. - Relacionar las variables para obtener conclusiones dentro del sector industrial. (Párrafo extraído del texto a modo de resumen)Facultad de Ingenierí