Electromethanogenesis at medium-low temperatures: Impact on performance and sources of variability

.In this study we aimed to understand the impact of medium–low temperatures on the two main steps that usually comprise the electromethanogenesis (EM) process: electrothrophic hydrogenesis and hydrogenothrophic methanogenesis. Results revealed that pure CO2 could effectively be converted into a high-purity biogas (∼90:10 CH4/CO2) at 30 °C. However, when temperature was reduced to 15 °C, methane richness greatly decreased (∼40:60 CH4/CO2). This deterioration in performance was mostly attributed to a decline in methanogenic activity (represented mainly by Methanobacterium and Methanobrevibacter). In contrast, the hydrogenic activity (mostly Desulfomicrobium) did not suffer any significant decay. Results also seemed to indicate that methanogenesis, rather than hydrogenesis, is the main source of variability in EM. Increasing the temperature again to 30 °C restored previous performance, which highlights the resilience of EM to wide temperature fluctuations (from 30 to 15 and back 30 °C).S

Microbial electromethanogenesis for energy storage: Influence of acidic pH on process performance

[EN] Microbial electromethanogenesis (EM) has positioned itself as a promising technology for electrical energy storage using CO2 as a feedstock. However, the selectivity of the final product remains a challenge, being highly dependent of the operating conditions (temperature, pH, conductivity, etc.). This study tries to understand the role that pH plays on the start-up, performance and the structure of microbial communities of an EM system. To that end, two EM reactors were started at pH 7.0 and 5.5 respectively and were subsequently subjected to pH variations between 7.5 and 3.5. The reactor inoculated at pH 5.5 started to produce CH4 earlier than that inoculated at pH 7.0, and the acetogenic activity was gradually displaced by methanogenesis during the start-up period, regardless of the pH. In addition, as the pH of the catholyte became more acidic, the performance improved in terms of methane production, current density and columbic efficiency. Acidic environments – pH around 4.5 – promoted higher methane production due to the selection of Methanobacterium, an acid-tolerant hydrogenotrophic archaea. When pH was set at 3.5, the overall performance declined sharply, probably because it induced unfavourable physiological conditions.SIMinisterio de Ciencia e Innovació

Propuesta del sistema de gestión de seguridad y salud en el trabajo para la facultad de ciencias económicas de la Universidad de Guayaquil bajo los lineamientos del SART.

Este documento contiene archivo en PDF.El desarrollo de la presente tesis se basa en el análisis preliminar de los trabajos de titulación de los Ingenieros Industriales Perlaza Nazareno Marcos David, Choez Pibaque Gabriel Ricardo, Plaza Santos Félix Luis, los mismos que al finalizar el diagnóstico del Sistema de Auditorías de Riesgos de Trabajo obtuvieron un puntaje del 11,42%, en la Facultad de Ciencias Económicas de la Universidad de Guayaquil sobre el 80% como mínimo requerido del SART. Partiendo la matriz y el cuadro de estratificación de riesgos se propone la elaboración e implementación de planes de respuestas a Emergencias, vigilancia de la salud de los trabajadores, inspecciones planeadas de seguridad, señalización, implementación de factores de indicadores reactivos y proactivos, información interna y externa, monitoreo de factores de riesgos, desarrollo de competencias, plan de vacunación y otros. Estableciendo un presupuesto global de $ 256.088,20 dólares. Se recomienda la aplicación del método basado en Excel Grafico Radar, para monitorear el detalle de avances del Sistema de Gestión de Prevención de Riesgos, bajo el esquema del SART. El método Radar o también denominado diagrama de araña es una herramienta muy útil para mostrar visualmente los avances entre el estado actual y el futuro de gestión de prevención y presentar claramente las características de desempeño del sistema de gestión de prevención. Esta metodología permite establecer que los avances más significativos en este estudio son la Gestión de los Procedimientos y Programas Operativos Básicos y Administrativa establecidos en el artículo 9 numeral 1 y 4, seguido por la Gestión Técnica y de Talento Humano establecidos en el artículo 9 numeral 2 y 3 y sus literales de la Resolución 333 CD-IESS.The development of this thesis is based on preliminary analysis of the work of certification of Industrial Engineers Perlaza Nazareno Marcos David, Choez Pibaque Gabriel Ricardo, Plaza Santos Félix Luis, the same as at the end of the diagnostic system of Workplace Audits average score of 11,42% , Faculty of Administrative Sciences at the University of Guayaquil on 80% minimum required SART. From the table matrix and risk stratification developing and implementing emergency response plans, monitoring the health of workers, planned safety inspections, signaling factors implementation of proactive and reactive indicators, aims and internal information external, monitoring risk factors, skills development, and other vaccination plan. Establishing an overall budget of 256.088,20 US dollars. The method based on Excel Graphic Radar method is recommended to monitor the detailed progress Management System Risk Prevention, under the scheme of the SART. The Radar method or also called spider diagram is very useful for displaying the progress between the current state and future prevention and management clearly have the characteristics of performance management system prevention tool. This methodology allows for the most significant advances in this study are Management Procedures and Basic Administrative and Operational Programmes set out in Article 9, paragraph 1 and 4, followed by the Technical Management and Talent established in Article 9 paragraph 2 and 3 and their literal Resolution 333 CD-IESS

El plan director de la vega baja de Toledo, España: paisaje patrimonial, ecológico y urbano.

La Vega Baja de Toledo constituye un gran vacío urbano que, por avatares históricos, se ha mantenido al margen del crecimiento de la ciudad, rodeada por el casco histórico de Toledo, los barrios del ensanche norte y el río Tajo. Su localización privilegiada, junto a la riqueza patrimonial y ecológica del espacio, han sido las bases de la propuesta del Plan Director de la Vega Baja (PDVB). El objetivo del PDVB ha sido articular este vacío y abrirlo a la población, a la vez que proteger y regenerar sus valores ecológicos y culturales. Para ello ha sido necesario integrar distintos elementos: la fachada urbana de Toledo, el río Tajo con su vegetación de ribera y sus bienes patrimoniales que testimonian la sucesión de aprovechamientos históricos, y como cuerpo central del ámbito, el yacimiento arqueológico de lo que puede ser una gran ciudad visigoda. El planteamiento general del PDVB ha sido tratar el espacio como un continuo abierto, una sucesión de paisajes con su propio carácter, que alberguen distintos usos y funciones: Desde el jardín clásico que rodearía al circo romano, llegando hasta el río, con una vegetación, mobiliario y recorridos acordes con las ruinas existentes; pasando por el jardín patrimonial del yacimiento, para el que se proponen plantaciones e itinerarios efímeros que cambien a la par que avanzan las excavaciones; hasta el paisaje más puramente agrícola del vivero o paisaje de ribera, de gran valor ecológico en relación con la fauna aviar

Reduced graphene oxide improves the performance of a methanogenic biocathode

.Microbial electrosynthesis (MES), a sub-branch of bioelectrochemical processes, takes advantage of a certain type of electroactive microorganism to produce added value products (such as methane) from carbon dioxide (CO2). The aim of this study is to quantify the benefits of using a carbon felt electrode modified with reduced graphene-oxide (rgoCF) as a methanogenic biocathode. The current density generated by the rgoCF was almost 30% higher than in the control carbon felt electrode (CF). In addition, charge transfer and ohmic resistances were, on average, 50% lower in the rgoCF electrode. These improvements were accompanied by a larger presence of bacteria (31% larger) and archaea (18% larger) in the rgoCF electrode. The microbial communities were dominated by hydrogenotrophic methanogenic archaea (Methanobacterium) and, to a lesser extent, by a low-diversity group of bacteria in both biocathodes. Finally, it was estimated that for a CO2 feeding rate in the range 15–30 g CO2 per m2 of electrode per day, it is possible to produce a high-quality biogas (>95% methane concentrationS

Effects of a thermal inversion experiment on STEM students learning and application of damped harmonic motion

There are diverse teaching methodologies to promote both collaborative and individual work in undergraduate physics courses. However, few educational studies seek to understand how students learn and apply new knowledge through open-ended activities that require mathematical modeling and experimentation focused on environmental problems. In this work, we propose a novel home experiment to simulate the dynamics of a particulate under temperature inversion and model it as damped harmonic motion. Twenty six first year students enrolled in STEM majors answered six qualitative questions after designing and developing the experiment. These questions helped analyze the students epistemological beliefs about their learning process of physics topics and its applications. Results showed that this type of open-ended experiments could facilitate the students understanding of physics phenomena. In addition, this experiment showed that it could help physics professors to promote students epistemological development by giving their students the opportunity to search for different sources of knowledge and becoming self-learners instead of looking at the professor as the epistemological authority. At the end, students described this activity as a positive experience that helped them realize alternative ways to apply physics topics in different contexts of their environment.Comment: 23 pages, 5 figure

Microbial electrosynthesis for CO2 conversion and methane production: Influence of electrode geometry on biofilm development

[EN] Electromethanogenesis is a process of microbial electrosynthesis (MES) in whichelectroactive microorganisms reduce carbon dioxide (CO2) to produce methane (CH4), using a cathodeas an electron donor. The efficiency of this reaction is greatly determined by the establishment of arobust microbial community on the biocathodes, which eventually affects the global performance of thebioreactor. Moreover, the development of the biofilm depends on several characteristics of theelectrodes, more specifically their material and geometry. Since electrode geometry is a crucialparameter, this study aims at evaluating the sole influence of the electrode shape by installingcarbon-based electrodes with two different constructions (brush and carbon felt) of biocathodes in anelectromethanogenic reactor for CO2capture. The overall performance of the reactors showedcoulombic efficiencies around 100%, with high-quality biogas reaching methane concentrations above90%. The results reveal that the electrode geometry affects the individual biocathode performance, andthe carbon brush showed a bigger contribution to current generation and electrical capacitance,exhibiting higher peak hydrogen production compared to the carbon felt, which could be reflected inhigher CO2capture and methane generation. Both geometries showed a greater proliferation of archaeaover bacteria (between 53 and 85%), which was more significant on the brush than on the carbon felt.Archaea community was dominated byMethanobacteriumin carbon felt electrodes and codominatedwithMethanobrevibacterin brush electrodes, while bacteria analyses showed a very similar communityfor both geometriesS

La innovación tecnológica: creando competitividad en las empresas desarrolladoras de software

In this research, the general purpose is to ascertain to what extent technological innovation impacts competitivity in Guayaquil´ software development companies. This research has a correlational scope and its approach is quantitative. Results reveal a statistically significant Spearman rho correlation coefficient of 0.877, which indicates that there is statistical evidence to prove that technological innovation impacts competitivity. This fact leads us to think that there have been advances and improvements in companies that develop software in the city of Guayaquil; this responds to the strategies generated to develop competitive advantages by improving the competitivity level in this industry.En la presente investigación el propósito general es determinar en qué medida la innovación tecnológica impacta a la competitividad en las empresas desarrolladoras de software de la ciudad de Guayaquil. Esta investigación tiene un alcance correlacional y su enfoque es cuantitativo. Los resultados revelan un coeficiente de correlación rho de Spearman de 0.877 estadísticamente significativo, lo que señala que existe evidencia estadística para demostrar y afirmar que la innovación tecnológica sí impacta a la competitividad en las empresas. Este hecho conduce a pensar que sí se han dado avances y mejoras en las empresas que desarrollan software en la ciudad de Guayaquil, lo que responde a las estrategias generadas para generar ventajas competitivas mejorando los niveles de competitividad en esta industria

Manifestaciones de cultura de violencia y afectación a derechos de adolescentes

La violencia en El Salvador es un problema social de gran impacto, que en las últimas décadas ha afectado comunidades enteras, familias e individuos al haber generado luto por el alza de homicidios y feminicidios, desplazamientos internos forzados y desapariciones forzadas, dejando severos efectos tanto a nivel social, económico y de salud, que en conjunto han debilitado el tejido social, trascendiendo al aparato policial como al sistema judicial. El país cuenta con un historial de violencia, entre estos, el conflicto armado surgido en la década de los 80, al que se le pusiera fin con la firma de los Acuerdos de Paz el 16 de enero de 1992, dejando un escenario de setenta y cinco mil muertes, según lo revela el Informe de la Comisión de la Verdad (Acuerdos de El Salvador. ONUSAL, San Salvador, nov, 1993