Actores y mirones

La profunda transformación y reestructuración industrial y social de los últimos años permitió a los países industrializados modernizar y adaptar sus estructuras a ese nuevo sistema productivo

Energy supply optimization for unregulated consumers

El presente artículo propone un modelo de optimización del portafolio de abastecimiento de energía eléctrica para consumidores finales no regulados en el mercado de electricidad colombiano. El propósito del modelo es determinar la cantidad óptima de energía que debe ser suministrada por cada una de las tres formas de abastecimiento disponibles para el usuario: compra basada en mercado spot, compra mediante contratos bilaterales y cogeneración, minimizando el costo esperado de abastecimiento de energía y el valor en riesgo asociado. Para este objetivo se usa un modelo de optimización estocástica y el indicador de riesgo empleado es el valor en riesgo condicional ( Conditional Value at Risk-CVaR). Finalmente, se estudian los resultados del modelo a través de escenarios de precios simulados basados en los precios reportados en el sistema de información NEON administrado por XM S.A., operador del mercado de electricidad colombiano y se selecciona el mejor ejemplo de aversión al riesgo. Abstract A supply electricity portfolio optimization model for unregulated consumers in the Colombian electricity market is proposed in this paper. The purpose is to choose between three supply alternatives available to the consumers: spot market purchase, purchase by bilateral contracts and self-generation, minimizing the total expected cost and the risk associated to these decisions. For this objective, a stochastic optimization model is used and the risk indicator is the conditional value at risk (CVaR). Finally, the model results are analyzed through the application of simulated prices based on real price observations from the database managed by XM – the Colombian Market Operator, and the best instance of risk aversion is selected

MicroRNA as crucial regulators of gene expression in estradiol-treated human endothelial cells.

Background/Aims: Estrogen signalling plays an important role in vascular biology as it modulates vasoactive and metabolic pathways in endothelial cells. Growing evidence has also established microRNA (miRNA) as key regulators of endothelial function. Nonetheless, the role of estrogen regulation on miRNA profile in endothelial cells is poorly understood. In this study, we aimed to determine how estrogen modulates miRNA profile in human endothelial cells and to explore the role of the different estrogen receptors (ERα, ERβ and GPER) in the regulation of miRNA expression by estrogen. Methods: We used miRNA microarrays to determine global miRNA expression in human umbilical vein endothelial cells (HUVEC) exposed to a physiological concentration of estradiol (E2; 1 nmol/L) for 24 hours. miRNA-gene interactions were computationally predicted using Ingenuity Pathway Analysis and changes in miRNA levels were validated by qRT-PCR. Role of ER in the E2-induced miRNA was additionally confirmed by using specific ER agonists and antagonists. Results: miRNA array revealed that expression of 114 miRNA were significantly modified after E2 exposition. Further biological pathway analysis revealed cell death and survival, lipid metabolism, reproductive system function, as the top functions regulated by E2. We validated changes in the most significantly increased (miR-30b-5p, miR-487a-5p, miR-4710, miR-501-3p) and decreased (miR-378h and miR-1244) miRNA and the role of ER in these E2-induced miRNA was determined. Results showed that both classical, ERα and ERβ, and membrane-bound ER, GPER, differentially regulated specific miRNA. In silico analysis of validated miRNA promoters identified specific ER binding sites. Conclusion: Our findings identify differentially expressed miRNA pathways linked to E2 in human endothelial cells through ER, and provide new insights by which estrogen can modulate endothelial function

Study of the neutron ux distribution in acylindrical reactor

[EN] n the Energy Engineering Degree of the Universitat Polit ecnica de Val encia, the students attend to theNuclear Technology course, in which the basic knowledge of this technology is presented. A main objectiveof this technology is to obtain neutron population distribution inside a reactor core, in order to maintainthe ssion reaction chain. As this activity cannot be experimentally developed, mathematical modelling isof great importance to achieve such objective. One of the computer laboratories proposed consists in theneutron ux determination analytically and numerically in a cylindrical geometry. The analytical solutionmakes use of the Bessel functions and is a good example of their applications. Alternatively, a numericalsolution based on nite di erences is used to obtain an approximate solution of the neutron ux. In thiswork, di erent discretizations of the cylindrical geometry are implemented and their results are compared[ES] Dentro del Grado de Ingeniería de la Energía, impartido en la Universitat Politècnica de València, se encuentra la asignatura de Tecnología Nuclear, en la que los alumnos adquieren los conocimientos básicos sobre esta tecnología. Un objetivo primordial en este tipo de generación energética es el conocimiento de la distribución de la población neutrónica dentro de un reactor, con la finalidad de mantener la reacción en cadena. Es evidente que esta actividad no puede desarrollarse de forma experimental, por lo que los modelos matemáticos son de gran importancia para lograr este objetivo. Así, una de las prácticas que se propone a los alumnos es la obtención del perfil del flujo neutrónico en una geometría cilíndrica, que es un modelo aproximado del núcleo de un reactor, de forma analítica aprovechando para introducirlas funciones de Bessel y dar un ejemplo de su utilización. Como método alternativo para obtener una aproximación de la solución del problema se utiliza el método de diferencias finitas. Se estudian distintas discretizaciones del reactor cilíndrico y se comparan las soluciones obtenidas.Vidal-Ferràndiz, A.; Carlos, S.; Verdú, G. (2017). Estudio del flujo neutrónico en un reactor cilíndrico. Modelling in Science Education and Learning. 10(2):5-20. doi:10.4995/msel.2017.6678SWORD520102Oliveira, F. R., Bodmann, B. E. J., Vilhena, M. T., & Carvalho, F. (2017). On an analytical formulation for the mono-energetic neutron space-kinetic equation in full cylinder symmetry. Annals of Nuclear Energy, 99, 253-257. doi:10.1016/j.anucene.2016.08.032Hébert A. (2009).Applied Reactor Physics. Presses internationales Polytechnique, Quebec, Canada, ISBN 9782553014369. Burden R., Faires J. (2007).Análisis numérico.International Thomson Editores, ISBN 9789706861344.Temme, N. M. (1996). Special Functions. doi:10.1002/9781118032572Stacey, W. M. (2007). Nuclear Reactor Physics. doi:10.1002/9783527611041Saad, Y. (2003). Iterative Methods for Sparse Linear Systems. doi:10.1137/1.978089871800

Impact of different hyperbaric storage conditions on microbial, physicochemical and enzymatic parameters of watermelon juice

Hyperbaric storage (HS) of raw watermelon juice, up to 10days at 50, 75, and 100MPa at variable/uncontrolled room temperature (18-23°C, RT) was studied and compared with storage at atmospheric pressure (AP) under refrigeration (4°C, RF) and RT, being evaluated microbiological (endogenous and inoculated), physicochemical parameters, and enzymatic activities. Ten days of storage at 50MPa resulted in a microbial growth evolution similar to RF, while at 75/100MPa were observed microbial load reductions on endogenous and inoculated microorganisms (Escherichia coli and Listeria innocua, whose counts were reduced to below the detection limit of 1.00 log CFU/mL), resulting in a shelf-life extension compared to RF. The physicochemical parameters remained stable at 75MPa when compared to the initial raw juice, except for browning degree that increased 1.72-fold, whilst at 100MPa were observed higher colour variations, attributed to a lycopene content decrease (25%), as well as reductions on peroxidase residual activity (16.8%) after 10days, while both polyphenol oxidase and pectin methylesterase residual activities were similar to RF. These outcomes hint HS as a reliable alternative to RF as a new food preservation methodology, allowing energy savings and shelf-life extension of food products. This is the first paper studying the effect of HS on inoculated microorganisms and on a broad number of physicochemical parameters and on endogenous enzymatic activities, for a preservation length surpassing the shelf-life by RF

Análisis del espacio de trabajo de un robot paralelo de 3RRR

Comunicación presentada en las XXIX Jornadas de Automática, Tarragona, 3-5 Septiembre 2008.El objetivo de este artículo es realizar el análisis del espacio de trabajo de un robot paralelo esférico del tipo 3RRR mediante una herramienta matemática desarrollada en Matlab. Este 3RRR contiene una particularidad que lo diferencia con respecto a los robots esféricos comunes debido a las exigencias de su aplicación: su centro de rotación no se encuentra en el centro del robot. Basándonos en un parámetro que define la habilidad o destreza del robot (dexterity), calcularemos el valor de las variables que optimizan su espacio de trabajo

Synthesis and Electrocatalytic Properties of H2SO4-Induced (100) Pt Nanoparticles Prepared in Water-in-Oil Microemulsion

The increasing number of applications for shape-controlled metal nanoparticles (NPs) has led to the need for easy, cheap, and scalable methodologies. We report the synthesis of (100) preferentially oriented Pt NPs, with a particle size of 9 nm, by using a water-in-oil microemulsion method. The specific surface structure of the NPs is induced by the presence of H2SO4 in the water phase of the microemulsion. Interestingly, the results reported herein show how increasing amounts of H2SO4 lead to the formation of Pt NPs containing a larger amount of (100) sites on their surface. This preferential surface orientation is confirmed electrochemically by using the so-called hydrogen adsorption/desorption process. In addition, transmission electron microscopy measurements confirm the presence of cubic-like Pt NPs. Finally, the electrocatalytic properties of the Pt NPs are evaluated towards ammonia and CO electro-oxidations, which are (100) structure-sensitive reactions.This work has been financially supported by the MCINN-FEDER (Spain) (project CTQ 2010-16271), Generalitat Valenciana (project PROMETEO/2009/045) and in part by NASA-URC Grant No. NNX10AQ17A and NSF-NSEC Center for Hierarchical Manufactur-ing Grant No. CHM-CMMI-0531171. R. M-R is grateful to the Becas Iberoamérica, Santander Universidades-España 2012 and PR-LSAMP Bridge to Doctorate Fellowship programs

Clinical ethical dilemmas for vascular surgeons (The vascuethics study) : are self-interest attitudes related to profeccional seniority

Producción CientíficaObjective. To evaluate the association between professional seniority and self-interest (PSI) attitudes in the resolution of vascular ethical dilemmas (VED). Design. Cross-sectional. Subjects. Vascular surgeons (residents included) from the 28 vascular teaching departments of Spain. Measurements. Multidisciplinary team-designed questionnaire of 5 VED. Each VED had 3 different answers (attitudes): 2 favouring legitimate ethical attitudes (LEA) and 1 favouring PSI. The questionnaire was self-administered and all participants stated their degree of agreement with each answer on a continuous Likert scale. PSI was evaluated by: (1) adding the magnitudes of the 5 answers favouring PSI (absPSI); and (2) by comparing in each case the magnitude of the PSI answer with that of the 2 LEA (relPSI). Statistics. Linear regression adjusted by confounding factors. Results. Two hundred and fifty-three vascular surgeons from the 26 participating teaching vascular departments of public hospitals completed the questionnaire (87.5% surgeons/department). Surgeon characteristics were: (1) median age 37 years; (2) 187 (74%) male; (3) 59 (23%) brought up with a health professional relative; (4) 94 (38%) had additional private practice; (5) 133 (65%) professed religious beliefs; and (6) 1–10 years of experience in 116 (47%), 11–20 years in 58 (24%), 21–30 years in 57 (23%), and .30 years in 15 (6%). The multivariate analysis disclosed that for every 10-years rise in professional seniority there was a 3.2% increase in absPSI (p ¼ 0.007, adjusted by variables 3 and 4), and a 3.4% increase in relPSI (p ¼ 0.002, adjusted by variable 5). Conclusions. Professional seniority is associated with a slight increase in pro-PSI attitudes in cases of vascular ethical dilemma. Both vascular surgeons and health institutions should promote the reversal of this worrying tendency

Notional defined contribution pension schemes: Why does only Sweden distribute the survivor dividend?

The aim of this paper is to analyse the role of the survivor dividend in notional defined contribution (NDC) pension schemes. At present, this feature can only be found in the Swedish defined contribution scheme. We develop a model that endorses the idea that the survivor dividend has a strong basis for enabling the NDC scheme to achieve financial equilibrium and that not including the dividend is a non-transparent way of compensating for increases in longevity and/or legacy costs from old pension systems. We also find that the average effect of the dividend remains unchanged for any constant annual rate of population growth, that contribu-tors who reach retirement age always get a higher return than the scheme does, and that population growth enables cohorts with more years of contributions to benefit to a greater extent from the dividend effect