Towards a Precision Cosmology from Starburst Galaxies at z>2

This work investigates the use of a well-known empirical correlation between the velocity dispersion, metallicity, and luminosity in H beta of nearby HII galaxies to measure the distances to HII-like starburst galaxies at high redshifts. This correlation is applied to a sample of 15 starburst galaxies with redshifts between z=2.17 and z=3.39 to constrain Omega_m, using data available from the literature. A best-fit value of Omega_m = 0.21 +0.30 -0.12 in a Lambda-dominated universe and of Omega_m = 0.11 +0.37 -0.19 in an open universe is obtained. A detailed analysis of systematic errors, their causes, and their effects on the values derived for the distance moduli and Omega_m is carried out. A discussion of how future work will improve constraints on Omega_m by reducing the errors is also presented.Comment: 7 pages, 3 figures, accepted for publication in MNRA

Nuevo índice de estabilidad de tensión para mejorar la operación en redes radiales de distribución

Este artículo presenta un nuevo índice de estabilidad de voltaje aplicado a redes radiales de distribución. Fue resuelto el problema de reconfiguración de alimentadores primarios usando el algoritmo genético de Chu-Beasley, en el cual el índice propuesto es usado como función objetivo. Dos sistemas de pruebas han sido utilizados, el primero de ellos cuenta con 33 nodos y 37 ramas, y el segundo, posee 136 nodos y 156 ramas. Los resultados muestran que el índice propuesto presenta resultados satisfactorios, es confiable y fácil de implementar al ser comparado con dos índices de estabilidad propuestos en la literatura técnica

Nuevo índice de estabilidad de tensión para mejorar la operación en redes radiales de distribución

Este artículo presenta un nuevo índice de estabilidad de voltaje aplicado a redes radiales de distribución. Fue resuelto el problema de reconfiguración de alimentadores primarios usando el algoritmo genético de Chu-Beasley, en el cual el índice propuesto es usado como función objetivo. Dos sistemas de pruebas han sido utilizados, el primero de ellos cuenta con 33 nodos y 37 ramas, y el segundo, posee 136 nodos y 156 ramas. Los resultados muestran que el índice propuesto presenta resultados satisfactorios, es confiable y fácil de implementar al ser comparado con dos índices de estabilidad propuestos en la literatura técnica

Nuevo índice de estabilidad de tensión para mejorar la operación en redes radiales de distribución

Este artículo presenta un nuevo índice de estabilidad de voltaje aplicado a redes radiales de distribución. Fue resuelto el problema de reconfiguración de alimentadores primarios usando el algoritmo genético de Chu-Beasley, en el cual el índice propuesto es usado como función objetivo. Dos sistemas de pruebas han sido utilizados, el primero de ellos cuenta con 33 nodos y 37 ramas, y el segundo, posee 136 nodos y 156 ramas. Los resultados muestran que el índice propuesto presenta resultados satisfactorios, es confiable y fácil de implementar al ser comparado con dos índices de estabilidad propuestos en la literatura técnica

Reducción de operaciones en la solución de sistemas de ecuaciones lineales de gran escala aplicando simulated annealing

Este documento describe una novedosa técnica basada en un algoritmo metaheurístico denominado Simulated Annealing aplicado al ordenamiento de ecuaciones lineales en el proceso de solución, y con el cual, se busca reducir el aparecimiento de elementos de relleno que surgen en dicho proceso. Sedescribe en detalle la metodología aplicada y, para validarla, se pone a pruebaen redes estándares IEEE de diferente complejidad

Evolution of Gaseous and Particulate Pollutants in the Air: What Changed after Five Lockdown Weeks at a Southwest Atlantic European Region (Northwest of Spain) Due to the SARS-CoV-2 Pandemic?

[Abstract] Due to the exponential growth of the SARS-CoV-2 pandemic in Spain (2020), the Spanish Government adopted lockdown measures as mitigating strategies to reduce the spread of the pandemic from 14 March. In this paper, we report the results of the change in air quality at two Atlantic Coastal European cities (Northwest Spain) during five lockdown weeks. The temporal evolution of gaseous (nitrogen oxides, comprising NOₓ, NO, and NO₂; sulfur dioxide, SO₂; carbon monoxide, CO; and ozone, O₃) and particulate matter (PM₁₀; PM₂․₅; and equivalent black carbon, eBC) pollutants were recorded before (7 February to 13 March 2020) and during the first five lockdown weeks (14 March to 20 April 2020) at seven air quality monitoring stations (urban background, traffic, and industrial) in the cities of A Coruña and Vigo. The influences of the backward trajectories and meteorological parameters on air pollutant concentrations were considered during the studied period. The temporal trends indicate that the concentrations of almost all species steadily decreased during the lockdown period with statistical significance, with respect to the pre-lockdown period. In this context, great reductions were observed for pollutants related mainly to fossil fuel combustion, road traffic, and shipping emissions (−38 to −78% for NO, −22 to −69% for NO₂, −26 to −75% for NOₓ, −3 to −77% for SO₂, −21% for CO, −25 to −49% for PM₁₀, −10 to −38% for PM₂․₅, and −29 to −51% for eBC). Conversely, O₃ concentrations increased from +5 to +16%. Finally, pollutant concentration data for 14 March to 20 April of 2020 were compared with those of the previous two years. The results show that the overall air pollutants levels were higher during 2018–2019 than during the lockdown period.This work was supported by Ministerio de Ciencia, Innovación y Universidades (MCIU), Agencia Estatal de Investigación (AEI) and Fondo Europeo de Desarrollo Regional (FEDER) (Programa Estatal de I+D+i Orientada a los Retos de la Sociedad, ref: RTI 2018-101116-B-I00), Xunta de Galicia (Programa de Consolidación y Estructuración de Unidades de Investigación Competitivas ref: ED431C 2017/28-2017-2020) and FEDER-MINECO (UNLC15-DE-3097, financed together (80/20%) with Xunta de Galicia). Joel Sánchez-Piñero acknowledges the Xunta de Galicia and the European Union (European Social Fund-ESF) for a predoctoral grant (ED481A-2018/164). María Fernández-Amado acknowledges the Ministerio de Ciencia, Innovación y Universidades (PTA2017-13607-I)

Strontium hexaferrite platelets: a comprehensive soft X-ray absorption and Mössbauer spectroscopy study

IBERMÖSS-2019, Bilbao, 30-31 may 2019. --https://www.ehu.eus/es/web/ibermossmeetingStrontium ferrite (SFO, SrFe12O19) is a ferrite employed for permanent magnets due to its high magnetocrystalline anisotropy. Since its discovery in the mid-20th century, this hexagonal ferrite has become an increasingly important material both commercially and technologically, finding a variety of uses and applications. Its structure can be considered a sequence of alternating spinel (S) and rocksalt (R) blocks. All the iron cations are in the Fe3+ oxidation state and it has a ferrimagnetic configuration with five different cationic environments for the iron (three octahedral sites, a tetraedrical site and a bipiramidal site)[1,2]. We have studied the properties of SrFe 12O19 in the shape of platelets, up to several micrometers in width, and tens of nanometers thick, synthesized by a hydrothermal method. We have characterized the structural and magnetic properties of these platelets by Mössbauer spectroscopy, x-ray transmission microscopy (TMX), transmission electron microscopy (TEM), x-ray diffraction (XRD), vibrating-sample magnetometry (VSM), x-ray absorption spectroscopy (XAS), x-ray circular magnetic dichroism (XMCD) and photoemission electron microscopy (PEEM). To the best of our knowledge this is the first time that the x-ray absorption spectra at the Fe L 2,3 edges of this material in its pure form have been reported. The Mössbauer results recorded from these platelets both in the electron detection and transmission modes have helped to understand the iron magnetic moments determined by XMCD (Fig.1). The experimental results have been complemented with multiplet calculations aimed at reproducing the observed XAS and XMCD spectra at the Fe L 2,3 absorption edge, and by density functional theory (DFT) calculations to reproduce the oxygen K- absorption edge. Finally the domain pattern measured in remanence is in good agreement with micromagnetic simulations [3]