La narrativa indigenista a la luz del modelo estructural.

Sin resume

Landau parameters for isospin asymmetric nuclear matter based on a relativistic model of composite and finite extension nucleons

We study the properties of cold asymmetric nuclear matter at high density, applying the quark meson coupling model with excluded volume corrections in the framework of the Landau theory of relativistic Fermi liquids. We discuss the role of the finite spatial extension of composite baryons on dynamical and statistical properties such as the Landau parameters, the compressibility, and the symmetry energy. We have also calculated the low-lying collective eigenfrequencies arising from the collisionless quasiparticle transport equation, considering both unstable and stable modes. An overall analysis of the excluded volume correlations on the collective properties is performed.Facultad de Ciencias Exacta

Neutron star structure in a quark model with excluded volume correction

We study the effects of the finite size of baryons on the equation of state of homogeneous hadronic matter. The finite extension of hadrons is introduced in order to improve the performance of field theoretical models at very high densities. We simulate the in-medium averaged baryon-baryon strong repulsion at very short distances by introducing a Van der Waals like normalization of the fields. This is done in the framework of the Quark Meson Coupling model, that allows to take care of the quark structure of baryons. Since within this model the confinement volume evolves with the fields configuration, the treatment is not equivalent to a simple hard-core potential. We investigate the phase transition to quark matter and the structure of neutron stars. We have found significant corrections at high densities.Facultad de Ciencias Exacta

Análisis comparativo de la cobertura de SciELO y Redalyc.org

Objetivo: Conocer la cobertura de las dos principales bases de datos de acceso abierto en América Latina: la Scientific Electronic Library Online (SciELO) y el Sistema de Información Científica Redalyc (redalyc.org), desde una perspectiva comparada de las revistas que indizan ambas plataformas en línea, las cuales comunican artículos científicos en texto completo.Metodología: Se realizó una búsqueda web del 14 al 17 de febrero de 2013 en los sitios: www.scielo.org y www.redalyc.org, con el fin de conocer el número de revistas editadas por país, área de conocimiento y disciplinas dentro de ambas bases de datos.Resultados: Brasil, México y Colombia cuentan con más de 50% del acervo total para cada acervo digital en línea. En SciELO, el área de conocimiento más representativa es ciencias con 47.2% (426 revistas), mientras que en redalyc.org corresponde a ciencias sociales con 59% (475 publicaciones). Las disciplinas con mayor número de revistas son, para el caso de SciELO: medicina (184), salud (61), y biología (54); mientras que en redalyc.org se vinculan con: educación (74), psicología (67), y medicina (59). En total, ambas bases comparten 339 revistas, donde Colombia cuenta con el mayor número de publicaciones comunes (90), y el área de ciencias sociales concentra el mayor número de publicaciones compartidas (167 revistas)

Hyphenation of single-drop microextraction with laser-induced breakdown spectrometry for trace analysis in liquid samples: a viability study

In this work, an analytical methodology based on single drop microextraction (SDME) followed by Laser-Induced Breakdown Spectrometry (LIBS) has been tested for trace metal determination in liquid samples. By this method, analytes in the samples were extracted into a small volume of toluene as ammonium pyrrolidinedithiocarbamate (APDC) chelates. After that, the analyte-enriched toluene was dried on a solid substrate and, finally, the resulting solid residue was analyzed by LIBS. Analyte extraction by the SDME procedure was optimized for the first time by using a multivariate optimization approach. Under optimum SDME conditions, analytical figures of merit of the proposed SDME-LIBS methodology were compared to those of the direct LIBS analysis method (i.e., without the SDME procedure). An estuarine water certified reference material was analyzed for method trueness evaluation. The results obtained in this study indicate that SDME-LIBS methodology leads to a sensitivity increase of about 2.0–2.6 times the ones obtained by LIBS. Detection limits of SDME-LIBS decrease according to the obtained sensitivity improvement, reaching values in the range 21–301 μg kg−1 for the analytes tested. The measurement repeatability was similar in both SDME-LIBS (13–20% RSD) and LIBS (16–20% RSD) methodologies, mainly limited by the LIBS experimental setup used in this work for LIBS analysis of liquid samples. The SDME-LIBS analysis of the certified reference material led to recovery values in the range of 96% to 112%.The authors are grateful to the Spanish Government (projects CTQ2011-23968) and the Regional Government of Valencia (Spain) (ACOMP/2013/072) for the financial support. M.A.A. is grateful to the University of Alicante for his PhD fellowship. This work is part of the PhD degree of M.A.A

Metal applications of liquid-phase microextraction

This review focuses on the combination of elemental detection techniques with liquid-phase microextraction (LPME), namely, single drop microextraction, hollow fiber based liquid-phase microextraction, dispersive liquid-liquid microextraction, and related techniques. General features of different microextraction procedures, historical overview and automation of LPME are described and compared, along with examples of new developments and applications presented to demonstrate its potential for trace and ultra-trace metal analysis. Furthermore, potential applications and an outlook on the combination of LPME and elemental detection techniques for inorganic analysis are presented.The authors would like to thank the Spanish Ministry of Economy and Competitiveness and European Union (FEDER funds) (project n. CTQ2016-79991-R) for the financial support. P. Baile also thanks Ministry of Education, Culture and Sports for her FPU grant (FPU14/04589)

Electrochemical Sensor for the Determination of Methylthiouracil in Meat Samples

Two analytical methods based on miniaturized electrochemical sensors, voltammetric and amperometric sensors, have been developed for the determination of 6-methyl-2-thiouracil (MTU) in meat consumption samples (beef liver and foie). A multivariate approach has been considered to optimize the experimental procedure including extraction and electrochemical detection. Under optimal conditions and at a typical working potential of 1.55 V (vs Ag pseudo-reference electrode), response is linear in the range 0 to 20 µg L−1 MTU concentration range. The empirical limit of detection is 0.13 µg L−1, lower than the maximum concentration established by legislation. The electrochemical methods have been used to analyze MTU-spiked meat samples, and recovery values varying between 85 and 95% with coefficients of variation <30%. The analytical methods developed with the miniaturized electrochemical sensors can successfully determine the concentration of MTU in real meat samples with high accuracy, being the results obtained similar to those provided by other methods such as UV-Vis spectrophotometry. Finally, the degree of sustainability of the electrochemical sensors-based developed method has been quantified by means of the Analytical Eco-Scale.This research was funded by Spanish Ministry of Science and Innovation grant number PID2021-126155OB-I00 and Regional Government of Valencia grant number CIPROM/2021/062, and Spanish Ministry of Science, Innovation and Universities (RED2018-102522-T)

Dispersive liquid–liquid microextraction for metals enrichment: A useful strategy for improving sensitivity of laser-induced breakdown spectroscopy in liquid samples analysis

A rapid and efficient Dispersive Liquid–Liquid Microextraction (DLLME) followed by Laser-Induced Breakdown Spectroscopy detection (LIBS) was evaluated for simultaneous determination of Cr, Cu, Mn, Ni and Zn in water samples. Metals in the samples were extracted with tetrachloromethane as pyrrolidinedithiocarbamate (APDC) complexes, using vortex agitation to achieve dispersion of the extractant solvent. Several DLLME experimental factors affecting extraction efficiency were optimized with a multivariate approach. Under optimum DLLME conditions, DLLME-LIBS method was found to be of about 4.0–5.5 times more sensitive than LIBS, achieving limits of detection of about 3.7–5.6 times lower. To assess accuracy of the proposed DLLME-LIBS procedure, a certified reference material of estuarine water was analyzed.The authors are grateful to the Spanish Government (project no. CTQ2011-23968) and Regional Government of Valencia (Spain) (project no. ACOMP/2013/072) for the financial support

Selective Harmonic Mitigation Technique for High-Power Converters

In high-power applications, the maximum switching frequency is limited due to thermal losses. This leads to highly distorted output waveforms. In such applications, it is necessary to filter the output waveforms using bulky passive filtering systems. The recently presented selective harmonic mitigation pulsewidth modulation (SHMPWM) technique produces output waveforms where the harmonic distortion is limited, fulfilling specific grid codes when the number of switching angles is high enough. The related technique has been previously presented using a switching frequency that is equal to 750 Hz. In this paper, a special implementation of the SHMPWM technique optimized for very low switching frequency is studied. Experimental results obtained applying SHMPWM to a three-level neutral-point-clamped converter using a switching frequency that is equal to 350 Hz are presented. The obtained results show that the SHMPWM technique improves the results of previous selective harmonic elimination pulsewidth modulation techniques for very low switching frequencies. This fact highlights that the SHMPWM technique is very useful in high-power applications, leading its use to an important reduction of the bulky and expensive filtering elements.Ministerio de Ciencia y Tecnología TEC2006-03863Junta de Andalucía EXC/2005/TIC-117