Positron Lifetime Spectroscopy Applied to Pure Tellurium

High-purity crystalline Tellurium has been investigated using positron lifetime spectroscopy technique in order to determine basic information missing in the current experimental knowledge of the positron annihilation spectroscopy field. Three different pairs of samples have been studied in the as-received state and, in order to eliminate the vacancy-type defects, after consecutive isothermal treatments at 300 C. Lifetime corresponding to the annihilation in the Tellurium bulk has been determined as 282(1) ps. Previous theoretical calculations present in the bibliography that used different methods and parameterization provided a wide range of values for the annihilation lifetime of the positron in the bulk of Tellurium. The obtained result has been used to identify the most accurate results among them.This research was supported by the Universidad Carlos III de Madrid and by the Comunidad de Madrid (Spain)—multiannual agreement with UC3M (“Excelencia para el Profesorado Universitario”—EPUC3M14)—Fifth regional research plan 2016–2020

Positron lifetime spectroscopy applied to pure sulphur and selenium

High purity crystalline orthorhombic Sulphur and hexagonal Selenium have been investigated using Positron Lifetime Spectroscopy technique. Annealed for 3 h at 120 °C Selenium lifetime (308(1) ps) has been compared with previous Positron Lifetime Spectroscopy knowledge in order to validate the measurements and the analysis procedure, and also compared with theoretical calculations available in literature, including different methods and parametrizations, resulting on the best match of LMTO-ASA method with GGA parametrization. Annealed for 3 h at 80 °C Sulphur samples were studied by the same means providing a single lifetime component with value 300(1) ps that has been assigned to the positron annihilation in the bulk that is not present in the current literature.This research was supported by the Universidad Carlos III de Madrid and by the Comunidad de Madrid (Spain)-multiannual agreement with UC3M ('Excelencia para el Profesorado Universitario'-EPUC3M14)-Fifth regional research plan 2016-2020, and by Agencia Estatal de Investigación (PID2019-105325RB-C33 / AEI /10.13039/501100011033)

Online review courses as preparation for first term remedial exams

[EN] At Universidad Carlos III de Madrid we have developed a review course (R-Course) with a SPOC structure intended for students who failed the first term regular exams. The purpose of the course is to help students prepare for the remedial exams at the same time they study the second term courses. The R-Course is implemented in an Open-EDX platform that holds digital documents, both theory and solved exercise videos, platform integrated exercises, and forums. The content of the course is divided in videos of less than 10 minutes in length, allowing students to include the R-Course in any schedule and making it compatible with the second term courses. Interactive platform integrated exercises have been devised under different types of methodologies to increase the motivation of the students, and the platform forums give students and tutors a space to discuss and interact for a well-rounded academic experience.The authors wish to acknowledge the financial and structural support from Universidad Carlos III the Madrid, in particular from the UTEID (Unidad de Tecnología Educativa e Innovación Docente) and the encouragement from professors Carlos Delgado-Kloos and Luis Raúl Sánchez Fernández.Domínguez-Reyes, R.; Meléndez, J.; Hernández-Pérez, A. (2015). Online review courses as preparation for first term remedial exams. Multidisciplinary Journal for Education, Social and Technological Sciences. 2(2):139-152. doi:10.4995/muse.2015.3687.SWORD1391522

Almacenamiento termoquímico en plantas CSP basado en calcium-looping: retos y oportunidades

Libro de Actas del XVI Congreso Ibérico y XII Congreso Iberoamericano de Energía Solar, 20 – 22 de junio de 2018 Madrid, EspañaLa integración de sistemas termoquímicos de energía en plantas CSP está ganando interés en los últimos años. De entre los posibles sistemas termoquímicos, el proceso de Calcium-looping (CaL), basado en la calcinación/carbonatación multicíclica de CaCO3, está considerado como uno de los más prometedores. Tras la aparente sencillez del proceso se encuentran una serie de retos que deben ser resueltos para que la tecnología pueda alcanzar una escala comercial. En el presente trabajo se muestra un análisis crítico del estado actual de la tecnología con el objetivo de evaluar los retos y oportunidades que presenta la integración del CaL como sistema de almacenamiento termoquímico en plantas CSP. El proyecto SOCRATCES, financiado dentro del programa H2020, tiene como principal objetivo desarrollar un prototipo a escala piloto de la integración CSP-CaL en Sevilla (España).Thermochemical energy storage is gaining attention in last years to be integrated in CSP plants. Among the various possibilities, the Calcium-looping (CaL) process, based on the multicyclic calcination/carbonation of CaCO3, is considered as one of the most promising systems. However, for a commercial deployment of CSP, several challenges must be solved. This work presents a critical analysis on the status of the technology with the aim of evaluating the main challenges and opportunities of the CSP-CaL integration. The SOCRATCES project, founded from the European Union’s Horizon 2020 research and innovation programme, aims to develop a CSP-CaL prototype at pilot scale in Seville (Spain)

Modular 3-D-printed education tool for blind and visually impaired students oriented to net structures

Contribution: This article presents the design, creation, testing, and results after the use of a 3-D-printed educational tool that helped a blind student learning electric circuits theory in higher education. Background: Educational tools oriented to visually impaired and blind students in higher education are limited or even nonexistent in the STEM area. Previous developments on the field present in the literature, including other 3-D printing solutions, have been revised and compared to the proposed educational tool. Intended Outcomes: The tool was tested by a blind student in order to test the potential of the design to achieve a better understanding of the topology and performance of electric circuits. The main purpose of the tool described in this work is helping to increase the resources available in the field of teaching students with visual impairments. Application Design: 3-D technology has the potential to be used to create accessibility tools for visually impaired and blind individuals. Modular systems can be used to create complex structures using simple elements. A modular 3-D-printed tool was fabricated to help blind and visually impaired students to learn net structures. Findings: The 3-D tool has allowed the blind student to work autonomously in the study of simple electric circuits and supplies the teacher with a resource to communicate with the student in an easy and fast way. Updated design can be used to describe more complex net structures that can be applied to most electric circuits despite their complexity. The use of the modular system provided the blind student with a direct representation of the whole subject, even when it involved a great amount of graphical information and manipulation.This work was supported by the "Programa de Atención a Estudiantes con Discapacidad" from Universidad Carlos III de Madrid

High-heat flux Cu-0.8Y alloys investigated by positron annihilation spectroscopy

This work studies the thermal stability of the microstructure and the evolution of the defects of two high-heat flux Cu-0.8 wt%Y alloys fabricated following two alternative powder metallurgy routes. One batch was produced by direct hot isostatic pressing (HIP) consolidation of Cu-0.8 wt%Y pre-alloyed atomized powders while an additional ball milling processing step was introduced before HIP sintering for the second alloy. The stability and recovery characteristics of the vacancy type defects in these alloys in the as-produced state and after processing by severe equal channel angular pressing to achieve a refine microstructure have been investigated by positron lifetime and coincidence Doppler broadening measurements in samples subjected to isochronal annealing from room temperature to 900 °C. Microhardness measurements and electron transmission microscopy analysis have also been performed to support the results obtained from the positron annihilation spectroscopy analysis techniques. The recovery curves of the positron lifetime and S-W plots show a recovery stage in agreement with the recovery stage V for Cu. However, a full recovery is not accomplished, and a stage that reverts the previous recovery takes place after annealing above ~600 °C, that leads to the formation of very stable defects at temperatures up to 900 °C, identified as vacancy aggregates and nanocavities. The characteristic shape of the coincidence Doppler broadening indicates that the dispersed Y-O particles in the Cu matrix appear to be responsible for stabilizing the vacancy aggregates and nanocavities for temperatures above 600-700 °C.This research was supported by the Spanish Ministerio de Economia y Competitividad (MINECO) in the form of Project ENE2015-70300-C3-2-R and by the Regional Government of Madrid (Spain) through TECHNOFUSIÓN(III)CM (S2018/EMT-4437), and Comunidad de Madrid (Spain) - multiannual agreement with UC3M ("Excelencia para el Profesorado Universitario" EPUC3M14) - Fifth regional research plan 2016-2020; and also Spanish Ministerio de Ciencia e Innovación through project DAMAINSOL [grant number RTI2018-101020-B-I00]

Curvas de crecimiento en bovinos Limousin de raza pura y cruzados

The objective was to fit a non-linear model (NLM) to evaluate the growth curve in purebred (PB) Limousin cattle and in five degrees of crossbreeding (DCBs: 1/2, 3/4, 7/8, 15/16, 31/32 Limousin). Live weight, the birth weight interval at 500 d of age, was analyzed. Four NLMs were evaluated: Brody, Bertalanffy, Gompertz, and logistic. Growth parameters were estimated: adult weight (ADW); growth rate (GR); age (AIP; months) and weight (WIP; kg) at inflection point; age (months; A50M) to reach 50 % maturity and degree of maturity at 15 mo (DM15). The growth curve in DCB was characterized using the NLM selected for BP. The best-fitting model was Bertalanffy. The ADW for purebred (PB) males was 566.1, for crossbred (CB) males it was in the range of 446.9 to 527.4; for CB females it was in the range of 374.5 to 419.9, and for PB females, it was 443.0. The NLMs exhibited correlations below -0.75 between ADW and GR. In PB heifers, AIP was estimated at 3.7, and WIP, at 131.2; in CB heifers, AIP and WIP were in the ranges of 2.9 to 3.7 and 110.9 to 124.4, respectively. A50M for PB females was 10.6, and for CB females, within the range of 8.9 to 10.5. DM15 for CB females, the average was 90.5 %, and 87.9 % for PB females. PB males reach A50M at the age of 13 mo.El objetivo fue el ajuste de un modelo no lineal (MNL) para evaluar la curva de crecimiento en bovinos Limousin, en pureza de raza (PRZ) y cinco grados de cruzamiento (GPZ; 1/2, 3/4, 7/8, 15/16, 31/32 de Limousin). Se analizó el peso vivo, el intervalo de peso al nacer a 500 días de edad. Se evaluaron cuatro MNL: Brody, Bertalanffy, Gompertz y logístico. Se estimaron parámetros de crecimiento: peso adulto (PAD); tasa de crecimiento (TAC); edad (EPI; meses) y peso (PPI; kg) al punto de inflexión; edad (meses; E50M) para alcanzar 50% de madurez y madurez a 15 meses (GM15). Con el MNL seleccionado en PRZ se caracterizó la curva de crecimiento en GPZ. El modelo de mejor ajuste fue Bertalanffy. El PAD para machos PRZ fue 566.1, para GPZ estuvo en el intervalo de 446.9 a 527.4; para hembras, en GPZ estuvo en el intervalo de 374.5 a 419.9, en PRZ fue 443.0. Los MNL presentaron correlaciones por debajo de -0.75 entre PAD y TAC. En vaquillas de PRZ, EPI se estimó a 3.7 con 131.2 para PPI; en GPZ, EPI y PPI estuvieron en los intervalos de 2.9 a 3.7 y 110.9 a 124.4, respectivamente. E50M para hembras, en PRZ fue a 10.6 y para GPZ en el intervalo de 8.9 a 10.5. GM15 para hembras, en GPZ el promedio fue 90.5 % en PRZ fue de 87.9 %. Los machos en PRZ alcanzan E50M a partir de 13 meses

Producción verde de un poliéster alifático

En este trabajo de investigación se realizó la preparación, caracterización y evaluación del poliéster 2-metil-2,4-pentano-etanodioico. La discusión se centra en variables de síntesis como el tiempo, temperatura y composición. Se utilizó un ácido dicarboxílico y un glicol para llevar a cabo una reacción de esterificación y obtener el poliéster. Los tiempos de reacción por calentamiento convencional son elevados, aproximadamente 2 horas. Por ende, se procedió a optimizar la reacción empleando las microondas como energía alternativa, utilizando los principios de la Química Verde que tiene como fundamento minimizar el impacto ambiental de ciertas reacciones empleando formas de energía más eficiente que el calentamiento convencional o reduciendo el uso de reactivos peligrosos buscando diversos sustitutos. Lo anterior permitió que la reacción en estudio se llevará a cabo en un tiempo de 13 minutos, en este proceso se utiliza vacío a 0.3 kgf/cm² para evitar el uso de un medio desecante, la identificación del poliéster se realizó mediante Espectroscopia de Resonancia Magnética Nuclear (RMN) y de Espectroscopia Infrarrojo por Transformada de Fourier (FTIR). Los resultados obtenidos permitieron conocer la influencia de las propiedades del polímero y la relación que existe entre la relación molar y el peso molecular del polímero.In this research the preparation, characterization and evaluation of polyester 2-methyl-2,4-pentane-ethanedioic was performed. The discussion focuses on synthesis variables such as time, temperature and composition. a dicarboxylic acid and a glycol was used to carry out an esterification reaction and obtain the polyester. Reaction times by conventional heating are high, approximately 2 hours. Therefore, we proceeded to optimize the reaction using microwaves as alternative energy, using the principles of Green Chemistry whose foundation minimize the environmental impact of certain reactions using forms of energy more efficient than conventional heating or reducing the use of reagents dangerous looking various substitutes. This allowed the reaction study will take place in a time of 13 minutes in this process is used empty to 0.3 kgf/cm² to avoid the use of a drying medium identification polyester was performed by Magnetic Resonance Spectroscopy (MRI) and Infrared Spectroscopy Fourier Transform (FTIR). The results obtained allowed to determine the influence of the properties of the polymer and the relationship between the molar ratio and the molecular weight of the polymer

Estudio transversal analítico de las características y desenlaces clínicos de niños hospitalizados con COVID-19 en Lima, Perú

Introduction: Coronavirus 2019 (SARS-CoV-2) infection in children occurred in Peru as of March 2020, leading to pediatric patients' hospitalization in areas adapted for this purpose at the Edgardo Rebagliati Martins National Hospital. In the beginning, the demand for hospitalization was low, but it increased gradually. Consistent with international reports, the majority of patients presented mild or moderate symptoms. Nonetheless, there were also severe cases, even fatal ones. Objectives: To describe the characteristics and clinical outcome of pediatric patients with COVID-19 hospitalized in a referral hospital in Lima, Peru, between March and August 2020. Methods: A descriptive and inferential cross-sectional study was carried out. The population includes all hospitalized patients in the Department of Pediatrics, with clinical and surgical diagnoses associated with COVID-19. Results: We included 100 patients, with an average age of 83.4 ± 54 months, with a predominance of male patients (55%). Hospitalized patients were grouped into five categories: respiratory failure (17%), multisystemic inflammatory syndrome (MIS-C) (31%), neurological presentation (19%), acute abdomen (20%), and patients with oncological problems (13%). Most of the patients (74%) had comorbidities. Regarding the presenting symptoms, intestinal pain predominated in the appendicitis group (90%, p < 0.001), fever was present in most patients with respiratory failure (64.7%); multisystemic inflammatory syndrome (90.3%), neurological manifestations (15.8%), acute abdomen (50%) and oncological conditions (61.5%) were also present in these patients. Kawasaki symptoms were found in 38.7% of the patients with multisystemic inflammatory syndrome. Mortality was 4%. Respiratory problems (29.4%) and multisystemic inflammatory syndrome (22.6%) required admission to intensive care, more frequently than the other presentations (p = 0.008). Conclusions: We conclude that the vulnerability in the pediatric population is the one that has preexisting conditions. We divided our patients according to presentation, diagnosis, and complications, which were predominantly respiratory. We also had oncological patients with COVID-19.Introducción: La infección por coronavirus 2019 (SARS-CoV-2) en niños se presentó en Perú desde marzo del 2020. Desde entonces fue necesario internar pacientes pediátricos en el Hospital Nacional Edgardo Rebagliati Martins, en el área de hospitalización adaptada para dicho propósito. Al inicio, la demanda de hospitalización era baja y se fue incrementando progresivamente. Coincidiendo con los reportes internacionales, la mayoría presentó cuadros leves o moderados, pero también hubo casos graves e incluso mortales. Objetivos: Describir las características y el desenlace clínico de los pacientes pediátricos con COVID-19 hospitalizados en un hospital de referencia en Lima, Perú, entre marzo y agosto de 2020. Métodos: Se realizó un estudio transversal descriptivo e inferencial. La población incluyó a todos los pacientes que se hospitalizaron en el Departamento de Pediatría Clínica, con diagnósticos clínicos y quirúrgicos asociados a COVID-19. Resultados: Incluimos 100 pacientes, con edad promedio de 83,4 ± 54 meses, con predominio de varones (55%). Los pacientes hospitalizados fueron agrupados en cinco categorías: insuficiencia respiratoria (17%), síndrome inflamatorio multisistémico (31%), presentación neurológica (19%), abdomen agudo (20%) y pacientes con problemas oncológicos (13%). La mayoría de los pacientes (74%) tenían comorbilidades. Respecto a los síntomas de presentación, el dolor intestinal predominó en el grupo de apendicitis (90%, p < 0,001), la fiebre estuvo presente en la mayoría de los pacientes con falla respiratoria (64,7%), el síndrome inflamatorio multisistémico se registró en 90,3%, la sintomatología neurológica en 15,8%, el abdomen agudo 50% y oncológicos en 61,5% de los pacientes. Los síntomas de Kawasaki estuvieron presentes en 38,7% de los pacientes con síndrome inflamatorio multisistémico. La mortalidad fue de 4%. En 29,4% de problemas respiratorios y en 22,6% de síndrome inflamatorio multisistémico, se requirió de admisión en cuidados intensivos, lo que fue más frecuente que las otras presentaciones (p = 0,008). Conclusiones: Se concluye que la población pediátrica vulnerable es aquella con comorbilidades preexistentes. La división de pacientes en nuestro estudio fue definida por la presentación, diagnóstico y complicaciones predominantemente con problemas respiratorios, y en pacientes oncológicos con COVID-19.Revisión por pare

Astrophysical S factor for the He-4(He-3,gamma)Be-7 reaction at medium energies

3 pags., 1 tab. -- Nuclear Physics in Astrophysics V 3–8 April 2011, Eilat, IsraelThe astrophysical S factor for the He-4(He-3,gamma)Be-7 direct capture reaction plays a major role in the context of solar neutrino flux and primordial Li-7 abundances that demand accurate information on the reaction. We report here our recent cross section measurements using the activation method in the region of E-CM=900-2800 keV, that aim to shed light on the discrepancies in the existing data and lead to a more accurate extrapolation of the S factor