La física en la realidad diaria

En los primeros capítulos de la memoria se ha desarrollado las causas por las que la metodología tradicional a veces no funciona y esto hace que se pierda la motivación de los alumnos por la ciencia. Es evidnete que ante un entorno de continuo cambio, la metodología en la educación (en este caso en ciencias) ha de cambiar también y ofrecer nuevas perspectivas a los estudiantes. En el último capítulo de la presente memoria, se desarrollan tres bloques dirigidos a contenidos de Física de 2º de bachillerato que se han tratado desde otro puento de vista respecto a la metodología tradicional. Lo que se ha pretendido es incentivar al alumno con propuestas que se les hayan poddido ocurrir en algún momento de sus vidas (la formación del arco iris, un radar de velocidad o la pantalla de sus teléfonos móviles). Una vez se despierte el interés habrá que introducir el fundamento teórico correspondiente pero buscando continuamente un realismo a las ecuaciones o enunciados.Departamento de Química AnalíticaMáster en Profesor de Educación Secundaria Obligatoria y Bachillerato, Formación Profesional y Enseñanzas de Idioma

Defect characterization of UMG mc-Si solar cells using LBIC and luminescence imaging techniques

Upgraded metallurgical-grade silicon (UMG Si) solar cells with different ranges of efficiencies were characterized through electroluminescence imaging (ELi) and light-beam induced current (LBIC) measurements. The results showed a good correlation between the EL intensity and the efficiency of the solar cells. ELi images gave a bright contrast at the defects, grain boundaries and intragrain defects, and dark contrast inside the grain bodies. Metallic impurities are much more present in some cells due to the directional solidification of the Si ingot. Local short-circuit current mapping with LBIC measurements revealed a bright zone in the neighborhoods of the defects due to the depletion of impurities. Internal quantum efficiencies (IQE) and effective diffusion lengths (Leff) were calculated using different excitation wavelengths. High resolution LBIC measurements revealed micrometric clusters of impurities around intragrain defectsSpanish MINECO project, ref. ENE2014-56069-C4-4-R and “Junta de Castilla y León (Spain)” project number VA081U1

Improving the sustainability of heterogeneous Fenton-based methods for micropollutant abatement by electrochemical coupling

Advanced oxidation processes such as Fenton reaction-based processes have attracted great interest in recent years as a promising alternative for the removal of persistent pollutants in wastewater. The use of nanocatalysts in advanced oxidation processes overcomes the limitations of homogeneous Fenton processes, where acidic pH values are required, and a large amount of sludge is generated after treatment. Aiming at maximizing the catalytic potential of the process, different configurations include coupling photocatalysis or electrochemistry to Fenton reactions. This manuscript presents a comparative environmental and economic analysis of different heterogeneous Fenton-based process using magnetic nanoparticles: Fenton, photo-Fenton, electro-Fenton and photoelectron-Fenton. These alternatives encompass not only different reaction conditions but also varying degradation kinetics, which control the treatment capability in each specific case. It is not only important to determine the technological feasibility of the proposal based on the removal performance of the target compounds, but also to identify the environmental profile of each configuration. In this regard, the Life Cycle Assessment methodology was applied considering a combination of primary and secondary data from process modeling. Moreover, and aiming towards the future large-scale implementation of the technology, an economic analysis of each configuration was also performed to provide a better understanding about the costs associated to the operation of Fenton-based wastewater treatmentsThis research was supported by HP-NANOBIO (PID2019-111163RB-I00), funded by Agencia Estatal de Investigación (AEI), and SPOTLIGHT (PDC2021-121540-I00) projects, funded by Agencia Estatal de Investigación (AEI) and European Union NextGenerationEU/PRTR. J.J.C. acknowledges Xunta de Galicia financial support through a postdoctoral fellowship (Grant reference ED481B-2021/015). S.E. and J.G.-R. predoctoral fellowships were funded by Agencia Estatal de Investigación (AEI) and by “ESF Investing in your future” (Grant references PRE2020-092074 and FPU19/004612, respectively). The authors belong to the Galician Competitive Research Group (GRC) ED432C-2021/37S

Photoluminescence Imaging and LBIC Characterization of Defects in mc-Si Solar Cells

Today’s photovoltaic market is dominated by multicrystalline silicon (mc-Si) based solar cells with around 70% of worldwide production. In order to improve the quality of the Si material, a proper characterization of the electrical activity in mc-Si solar cells is essential. A full-wafer characterization technique such as photoluminescence imaging (PLi) provides a fast inspection of the wafer defects, though at the expense of the spatial resolution. On the other hand, a study of the defects at a microscopic scale can be achieved through the light-beam induced current technique. The combination of these macroscopic and microscopic resolution techniques allows a detailed study of the electrical activity of defects in mc-Si solar cells. In this work, upgraded metallurgical grade Si solar cells are studied using these two techniques.Ministerio de Economía, Industria y Competitividad (ENE2014-56069-C4-4-R)Junta de Castilla y León (programa de apoyo a proyectos de investigación – Ref. Project VA081U16

Electroluminescence Imaging and Light-Beam Induced Current as characterization techniques of Multi-Crystalline Si Solar Cells

There is an increasing demand for characterizing multicrystalline solar cells at different stages of its service life. Luminescence techniques, e.g. electroluminescence (EL) and photoluminescence (PL), have acquired a paramount interest in the last years. These techniques are used in imaging mode, allowing to take a luminescence picture at a full wafer/cell scale. This imaging approach is fast and sensitive, but has a low spatial resolution, which avoids a detailed analysis of the defect distribution, which can led to misinterpretations about critical parameters as the minority carrier diffusion length, or the internal and external quantum efficiencies. If one complements these techniques with high spatial resolution techniques, such as light beam induced current (LBIC), one can study the electrical activity of the defects at a micrometric scale, providing additional understanding about the role played by the defects in full wafer/cell luminescence images. The combination of the macroscopic and microscopic resolution scales is necessary for the analysis of the full luminescence images in mc-Si solar cells.Proyecto de Investigación ENE2014-56069-C4- 4-R (MCIN)Proyecto de Investigación ENE2017-89561-C4-3-R (MCIN)Proyecto de Investigación VA081U16 (Junta de Castilla y León

Daylight luminescence system for silicon solar panels based on a bias switching method

Among the many characterization techniques for solar panel testing, two, electroluminescence (EL) and photoluminescence (PL), can provide useful visual information about the presence of different types of cell defects. EL is performed outdoors by night in commercial solar plants due to the very weak luminescence emission compared to sunlight. PL faces the added difficulty of needing to find a large-area homogeneous light source to excite the modules. Since nighttime work poses many drawbacks and risks, a daylight outdoor EL/PL system would be useful for offering safe inspection of solar plants. We present daylight luminescence techniques based on a bias switching method, in which a pulsed luminescence signal is obtained by alternating the polarization state of the solar panels, synchronizing it with the luminescence image detection by an InGaAs camera. Fast switching and selecting an optimized exposure time are key to achieving high-quality images. The daylight luminescence method described herein allows both EL and PL luminescence images to be obtained, even under high solar irradiance conditions.Proyecto de Investigación ENE2014-56069-C4- 4-R (MCIN)Proyecto de Investigación ENE2017-89561-C4-3-R (MCIN)Proyecto de Investigación RTC-2017-6712-3 (MCIN)Proyecto IDI-20151194 (CDTI)Proyecto de Investigación VA081U16 (Junta de Castilla y León)Proyecto de Investigación VA283P18 (Junta de Castilla y León

The evolution of the ventilatory ratio is a prognostic factor in mechanically ventilated COVID-19 ARDS patients

Background: Mortality due to COVID-19 is high, especially in patients requiring mechanical ventilation. The purpose of the study is to investigate associations between mortality and variables measured during the first three days of mechanical ventilation in patients with COVID-19 intubated at ICU admission. Methods: Multicenter, observational, cohort study includes consecutive patients with COVID-19 admitted to 44 Spanish ICUs between February 25 and July 31, 2020, who required intubation at ICU admission and mechanical ventilation for more than three days. We collected demographic and clinical data prior to admission; information about clinical evolution at days 1 and 3 of mechanical ventilation; and outcomes. Results: Of the 2,095 patients with COVID-19 admitted to the ICU, 1,118 (53.3%) were intubated at day 1 and remained under mechanical ventilation at day three. From days 1 to 3, PaO2/FiO2 increased from 115.6 [80.0-171.2] to 180.0 [135.4-227.9] mmHg and the ventilatory ratio from 1.73 [1.33-2.25] to 1.96 [1.61-2.40]. In-hospital mortality was 38.7%. A higher increase between ICU admission and day 3 in the ventilatory ratio (OR 1.04 [CI 1.01-1.07], p = 0.030) and creatinine levels (OR 1.05 [CI 1.01-1.09], p = 0.005) and a lower increase in platelet counts (OR 0.96 [CI 0.93-1.00], p = 0.037) were independently associated with a higher risk of death. No association between mortality and the PaO2/FiO2 variation was observed (OR 0.99 [CI 0.95 to 1.02], p = 0.47). Conclusions: Higher ventilatory ratio and its increase at day 3 is associated with mortality in patients with COVID-19 receiving mechanical ventilation at ICU admission. No association was found in the PaO2/FiO2 variation

Clustering COVID-19 ARDS patients through the first days of ICU admission. An analysis of the CIBERESUCICOVID Cohort

Background Acute respiratory distress syndrome (ARDS) can be classified into sub-phenotypes according to different inflammatory/clinical status. Prognostic enrichment was achieved by grouping patients into hypoinflammatory or hyperinflammatory sub-phenotypes, even though the time of analysis may change the classification according to treatment response or disease evolution. We aimed to evaluate when patients can be clustered in more than 1 group, and how they may change the clustering of patients using data of baseline or day 3, and the prognosis of patients according to their evolution by changing or not the cluster.Methods Multicenter, observational prospective, and retrospective study of patients admitted due to ARDS related to COVID-19 infection in Spain. Patients were grouped according to a clustering mixed-type data algorithm (k-prototypes) using continuous and categorical readily available variables at baseline and day 3.Results Of 6205 patients, 3743 (60%) were included in the study. According to silhouette analysis, patients were grouped in two clusters. At baseline, 1402 (37%) patients were included in cluster 1 and 2341(63%) in cluster 2. On day 3, 1557(42%) patients were included in cluster 1 and 2086 (57%) in cluster 2. The patients included in cluster 2 were older and more frequently hypertensive and had a higher prevalence of shock, organ dysfunction, inflammatory biomarkers, and worst respiratory indexes at both time points. The 90-day mortality was higher in cluster 2 at both clustering processes (43.8% [n = 1025] versus 27.3% [n = 383] at baseline, and 49% [n = 1023] versus 20.6% [n = 321] on day 3). Four hundred and fifty-eight (33%) patients clustered in the first group were clustered in the second group on day 3. In contrast, 638 (27%) patients clustered in the second group were clustered in the first group on day 3.Conclusions During the first days, patients can be clustered into two groups and the process of clustering patients may change as they continue to evolve. This means that despite a vast majority of patients remaining in the same cluster, a minority reaching 33% of patients analyzed may be re-categorized into different clusters based on their progress. Such changes can significantly impact their prognosis

Outcomes from elective colorectal cancer surgery during the SARS-CoV-2 pandemic

This study aimed to describe the change in surgical practice and the impact of SARS-CoV-2 on mortality after surgical resection of colorectal cancer during the initial phases of the SARS-CoV-2 pandemic

Características financieras de las empresas escindidas en España: Aproximación mediante un modelo logit

The aim of this study is the characterisation of the financial and economic structure of Spanish companies that decide to spin off and, thus, find out which are the circumstances that push companies to face this kind of corporate restructuration. To do so, we have worked on two samples taken in two different time periods: 2001-2003, a stage of economic stability in Spain; and 2011, a period of economic crisis. Both samples include companies that decided to spin off, and companies that didn't. The results obtained are clearly significant and show some of the characteristics that differentiate companies that spin off from those that don't, throughout time.El objetivo del presente trabajo es caracterizar la estructura económica y financiera de las empresas españolas que toman la decisión de escindirse y, así, conocer las circunstancias o determinantes que empujan a las empresas a acogerse a este tipo de reestructuración empresarial. Para ello, hemos trabajado con dos muestras obtenidas en etapas muy distintas: la primera muestra, en el periodo 2001-2003, momento de gran estabilidad económica en España; y la segunda muestra, del año 2011, periodo de crisis económica. Ambas muestras contienen datos de empresas escindidas y no escindidas. Los resultados obtenidos resultan claramente significativos y nos han permitido exponer algunas características que diferencian a las empresas escindidas de las no escindidas a lo largo del tiempo