Development of innovative materials used in electrochemical devices for the renewable production of hydrogen and electricity

One of the most important challenges for our society is providing powerful devices for renewable energy production. Many technologies based on renewable energy sources have been developed, which represent a clean energy sources that have a much lower environmental impact than conventional energy technologies. Nowadays, many researches focus their attention on the development of renewable energy from solar, water, organic matter and biomass, which represent abundant and renewable energy sources. This research is mainly focused on the development of promising electrode materials and their potential application on emerging technologies such as artificial photosynthesis and microbial fuel cell (MFC). According to desired proprieties of functional materials, this research was focused on two main materials: (1) TiO2 for the development of electrodes for the water splitting reaction due to its demonstrated application potential as photocatalyst material and (2) carbon-based materials for the development of electrodes for MFC. In the first part of the investigation, different TiO2 nanostructures have been studied including: synthesis, characterization and test of TiO2-based materials with the aim of improving the limiting factors of the photocatalytic reaction: charge recombination and separation/migration processes. The photo-catalytic properties of different TiO2 nanostructures were evaluated including: TiO2 nanoparticles (NPs) film, TiO2 nanotubes (NTs) and ZnO@TiO2 core-shell structures. Photo-electrochemical activity measurements and electrochemical impedance spectroscopy analysis showed an improvement in charge collection efficiency of 1D-nanostructures, related to a more efficient electron transport in the materials. The efficient application of both the TiO2 NTs and the ZnO@TiO2 core-shell photoanodes opens important perspectives, not only in the water splitting application field, but also for other photo-catalytic applications (e.g. photovoltaic cells, degradation of organic substances), due to their chemical stability, easiness of preparation and improved transport properties. Additionally, in order to improve the photo-catalytic activity of TiO2 NPs, PANI/TiO2 composite film was synthesized. PANI/TiO2 composite film was successfully applied as anode material for the PEC water splitting reaction showing a significant increase in the photocatalytic activity of TiO2 NPs composite film essentially attributed to the efficient separation of the generated electron and hole pairs. To date, no cost-effective materials system satisfies all of the technical requirements for practical hydrogen production under zero-bias conditions. For this propose, to promote the sustainability of the process, the bias require to conduct PEC water splitting reaction could be powered by MFC systems in which many efforts have been done to improve power and electricity generation as is explained below. In this work, different strategies were also applied in order to improve the performance of anode materials for MFCs. The investigation of commercial carbon-based materials demonstrated that these materials, normally used for other ends are suitable electrodes for MFC and their use could reduce MFC costs and improve the energy sustainability of the process. In addition, to enhance power generation in MFC by using low-cost and commercial carbon-based materials, nitric acid activation (C-HNO3) and PANI deposition (C-PANI) were performed on commercial carbon felt (C-FELT) in order to increase the performance of MFC. Electrochemical determinations performed in batch-mode MFC reveled a strong reduction of the activation losses contribution and an important decrease of the internal resistance of the cell using C-HNO3 and C-PANI of about 2.3 and 4.4 times, respectively, with respect to C-FELT. Additionally, with the aim of solvent different MFC operational problems such as: biofouling, low surface area and large-scale MFC, an innovative three-dimensional material effectively developed and used as anode electrode. The conductive carbon-coated Berl saddles (C-SADDLES) were successfully used as anode electrode in batch-mode MFC. Electrochemical results suggested that C-SADDLES offer a low-cost solution to satisfy either electrical or bioreactor requirements, increasing the reliability of the MFC processes, and seems to be a valid candidate for scaled-up systems and for continuous mode application of MFC technology. In addition, the electrochemical performance and continuous energy production of the most promising materials obtained during this work were evaluated under continuous operation MFC in a long-term evaluation test. Remarkable results were obtained for continuous MFCs systems operated with three different anode materials: C-FELT, C-PANI and C-SADDLES. From polarization curves, the maximum power generation was obtained using C-SADDLES (102 mW•m-2) with respect to C-FELT (93 mW•m-2) and C-PANI (65 mW•m-2) after three months of operation. The highest amount of electrical energy was produced by C-PANI (1803 J) with respect to C-FELT (1664 J) and C-SADDLES (1674 J). However, it is worth to note that PANI activity was reduced during time by the operating conditions inside the anode chamber. In order to demonstrate the wide application potential MFC, this work reports on merging heterogeneous contributions and combining the advantages from three separate fields in a system which enables the ultra-low-power monitoring of a microbial fuel cell voltage status and enables pressure monitoring features of the internal conditions of a cell. The solution is conceived to provide an efficient energy source, harvesting wastewater, integrating energy management and health monitoring capabilities to sensor nodes which are not connected to the energy grid. Finally, this work presented a general concept of the integration of both devices into a hybrid device by interfacing PEC and MFC devices (denoted as PEC-MFC), which is proposed to generate electricity and hydrogen using as external bias the potential produce by microbial fuel cel

Perception of future mathematics teachers on the promotion of self-regulation of learning

Supported by the MINECO/FEDER, UE, Research Project PGC2018- 098603-B-I00

Electrochemical and impedance characterization of Microbial Fuel Cells based on 2D and 3D anodic electrodes working with seawater microorganisms under continuous operation

A mixed microbial population naturally presents in seawater was used as active anodic biofilm of two Microbial Fuel Cells (MFCs), employing either a 2D commercial carbon felt or 3D carbon-coated Berl saddles as anode electrodes, with the aim to compare their electrochemical behavior under continuous operation. After an initial increase of the maximum power density, the felt-based cell reduced its performance at 5months (from 7 to 4μWcm(-2)), while the saddle-based MFC exceeds 9μWcm(-2) (after 2months) and maintained such performance for all the tests. Electrochemical impedance spectroscopy was used to identify the MFCs controlling losses and indicates that the mass-transport limitations at the biofilm-electrolyte interface have the main contribution (>95%) to their internal resistance. The activation resistance was one order of magnitude lower with the Berl saddles than with carbon felt, suggesting an enhanced charge-transfer in the high surface-area 3D electrode, due to an increase in bacteria population growth

La mediación penal en caso de incesto

En su gran mayoría, los casos de incesto no se develan, la situación abusiva se repite de una forma u otra y la niña queda encerrada en su terrible secreto. Por otro lado en los escasos casos que pasan a mano de la justicia, el padre está botado en una cárcel donde suele estar maltratado por los otros presos, y la niña vive una culpabilidad intensa por este mismo hecho. La mediación penal, un proceso judicial llevado a cabo bajo la responsabilidad de un fiscal, permite, sin ocuparse de dictar sanciones, restablecer una relación de palabras entre la hija y su padre, y de este modo ayudar a una re-inscripción de ambos en una sociedad fundada en la Ley Universal de Prohibición del Incesto

Mi entrenamiento, mi ritmo: Los principios de la metodología de Victoria Santa Cruz para la exploración de un training actoral desde la intimidad

Estudiar el trabajo de Victoria Santa Cruz representa una gran oportunidad para insertar más voces femeninas y afrodescendientes en las líneas de estudio artístico de la Facultad. Su legado es materia de estudio histórico, político y artístico desde la óptica de los movimientos antirracistas y afrofeministas. En vista de que esta creadora invita a reconocer el saber corporal como igualmente válido que el conocimiento intelectual, resulta relevante investigar el aporte de su enfoque a las artes. La presente investigación desde la práctica busca analizar el “ritmo interior” y la “memoria ancestral”, conceptos acuñados por Santa Cruz, como medios para explorar rutas para un training actoral que integre el autoconocimiento y la memoria corporal íntima. Para este fin, los sustentos teóricos que guían el estudio son: el análisis de Heidi Feldman sobre la metodología de Santa Cruz, los principios del entrenamiento actoral según Varley y Carreri, el estudio del cuerpo como generador de conocimiento de Bardet y la teoría del archivo y repertorio de Taylor. A partir de un diseño de laboratorio, esta investigación encuentra que la memoria ancestral vincula al cuerpo de la actriz con sus raíces culturales a través del movimiento y la performatividad del archivo familiar y/o cultural. Asimismo, el ritmo interior requiere partir de la propia identidad e historia, permitiendo que la actriz se reconozca como un cuerpo íntegro que actúa con aquello que es dentro y fuera de la profesión. Por ello, la conclusión principal de esta investigación sugiere que ambos conceptos insertan al entrenamiento en una búsqueda de la enunciación propia en la escena, en tanto permiten trabajar en un descubrimiento y desarrollo de la verdad escénica propia de la actriz. Los conceptos invitan a manifestar un repertorio personal vinculado a nuestros orígenes, nuestra historia, nuestras luchas y nuestros placeres

Libro: Aprender a enseñar matemáticas en educación primaria:

Considerant que aprendre a ensenyar matemàtiques no és una tasca fàcil, aquesta pràctica ha de ser un objectiu sistemàtic i constant de tots els professors, més encara si es tracta dels diversos processos matemàtiques que s'han de desenvolupar a educació primària, com per exemple el raonament, les representacions, la resolució de problemes, les connexions, etc. El llibre "Aprendre a ensenyar matemàtiques a educació primària" abasta els diferents tipus de pensament matemàtic i com promoure'ls en el context de l'aula primària des d'una mirada competencial i centrada en l'alumnat. El text fa una mirada a cada àrea del currículum de primària, com els números naturals, les fraccions, l'atzar i l'estadística, el concepte de mesura i la geometria. En cada un d'ells es detallen certs aspectes teòrics i s'entreguen diverses directius per a dur a terme activitats idònies, com també es mostren exemples d'aules dels propis autors que han tingut resultats d'èxit. A més, es parla de la importància de la presència d'errors en els processos de comprensió de cada contingut matemàtic. .Book review: Aprender a enseñar matemáticas en Educación Primaria.Considerando que aprender a enseñar matemáticas no es tarea fácil, dicha práctica debe ser un objetivo sistemático y constante de todo profesor, más aún si hablamos de los diversos procesos matemáticos que se deben desarrollar en la educación primaria, como el razonamiento, las representaciones, la resolución de problemas, las conexiones, entre otros. El libro Aprender a Enseñar Matemáticas en Educación Primaria aborda los distintos tipos de pensamiento matemático y cómo promoverlos en el aula de primaria desde una mirada competencial y centrada en el alumno. El texto da una mirada a cada área del currículo de primaria, como los números naturales, las fracciones, el azar y la estadística, el concepto de medida y la geometría. En cada uno de ellos se detallan ciertos aspectos teóricos y se entregan diversas directrices para llevar a cabo actividades idóneas, como también se muestran ejemplos de aulas de los propios autores que han tenido resultados exitosos. Adicionalmente, se habla de la importancia de la presencia de  errores en los procesos de comprensión de cada contenido matemático

La docencia de danzas folclóricas peruanas como posible práctica de apropiación cultural en Lima del siglo XXI

El presente texto pretende determinar de qué manera la docencia de danzas folclóricas peruanas podría ser considerada una práctica de apropiación cultural en Lima de la actualidad. La respuesta tentativa ante ello es que su docencia puede llegar a ser apropiación cultural hoy en día en la capital; debido a que se trataría de una extracción de la danza de su contexto histórico social que la valora solo a nivel estético y comercial, perpetuando de esta manera la desigualdad social entre el extractor y la colectividad autora de la danza. Para determinar la validez de esta hipótesis, se toman evidencias históricas como lo son la colonización, la Independencia y la República peruanas. Estas demuestran la manipulación permanente de nuestra diversidad cultural por parte de los distintos grupos de poder de cada etapa, a costa de una constante discriminación étnico racial. A su vez, se explica que este hecho originó el interés por la docencia de danzas folclóricas en Lima y cómo esta, desde sus inicios, fue un tema polémico en cuanto a su “autenticidad”. Se debaten también las posibilidades de tomar las danzas folclóricas como herramienta de reparación de brechas sociales ante el racismo y etnocentrismo perpetuados desde la colonia. Por otro lado, se presenta la influencia del capitalismo y la globalización en la perpetuación de la desigualdad social, empobrecimiento e invisibilización de las colectividades originarias. Ello se da debido a la facilidad de mercantilización, manipulación e instrumentalización de las manifestaciones culturales de dichas comunidades; lo cual es causado por una falta de políticas de protección de su patrimonio cultural. Frente a ello, se propone la práctica de principios interculturales que permitan el intercambio igualitario de la diversidad cultural y la implementación de leyes especialmente diseñadas para el entendimiento y protección del patrimonio.This text aims to determine in what way the teaching of Peruvian folk dances could be considered a practice of cultural appropriation in Lima today. The tentative answer to this is that their teaching can become cultural appropriation today in the capital; because it would be an extraction of the dance from its social historical context that values it only on an aesthetic and commercial level, thus perpetuating the social inequality between the extractor and the community that created the dance. To determine the validity of this hypothesis, historical evidence such as the Peruvian colonization, Independence and Republic are taken. These demonstrate the permanent manipulation of our cultural diversity by the different power groups of each stage, at the cost of constant ethnic-racial discrimination. In turn, it is explained that this fact originated the interest in teaching folk dances in Lima and how this, from its beginnings, was a controversial issue regarding its “authenticity”. The possibilities of taking folk dances as a tool to repair social gaps in the face of racism and ethnocentrism perpetuated since the colony are also debated. On the other hand, the influence of capitalism and globalization is presented in the perpetuation of social inequality, impoverishment and invisibility of the original collectivities. This occurs due to the ease of commercialization, manipulation and instrumentalization of the cultural manifestations of these communities; which is caused by a lack of protection policies for their cultural heritage. Faced with this, the practice of intercultural principles that allow the equal exchange of cultural diversity and the implementation of laws specially designed for the understanding and protection of heritage is proposed

Estudio crítico sobre el papel de las microfinanzas en el sistema económico actual

A lo largo de este trabajo se analizará, desde un punto de vista crítico, el papel de las microfinanzas en la actualidad, y concretamente el microcrédito. Dicha herramienta, surgiría de la mano de organizaciones sociales, con un firme objetivo de ayudar a las personas de las capas más pobres a mejorar sus condiciones de vida. Pero en la actualidad, la rentabilidad de las microfinanzas ha convertido a las personas con menos recursos en nicho de mercado atractivo, en el que cada vez son más las organizaciones que buscan en él nuevas oportunidades de negocio con las que incrementar sus beneficios, destacando la creciente presencia de los bancos comerciales. Dentro de la lógica del libre mercado, hoy en día, las microfinanzas representan el puente de acceso para el sector financiero hacia la base de la pirámide, en su objetivo de continuar expandiéndose. De esta manera, el fin social con el que surge el microcrédito, formará parte de la fuerte estrategia de responsabilidad social en la que se apoyará el sector financiero para justificar su negocio con las personas más vulnerables.Departamento de Sociología y Trabajo SocialMáster en Cooperación Internacional para el Desarroll

An experimental and modelling exploration of the host-sanction hypothesis in legume-rhizobia mutualism

Despite the importance of mutualism as a key ecological process, its persistence in nature is difficult to explain since the existence of exploitative, 'cheating' partners that could erode the interaction is common. By analogy with the proposed policing strategy stabilizing intraspecific cooperation, host sanctions against non N2 fixing, cheating symbionts have been proposed as a force stabilizing mutualism in legume-Rhizobium symbiosis. Following this proposal, penalizations would include decreased nodular rhizobial viability and/or early nodule senescence in nodules occupied by cheating rhizobia. In this work, we analyze the stability of Rhizobium-legume symbiosis when "cheating" strains are present, using an experimental and modelling approach. We used split-root experiments with soybean plants inoculated with two rhizobial strains, a cooperative, normal N2 fixing strain and an isogenic non-fixing, “perfect” cheating mutant derivative that lacks nitrogenase activity but has the same nodulation abilities inoculated to split-root plants. We found no experimental evidence of functioning plant host sanctions to cheater rhizobia based on nodular rhizobia viability and nodule senescence and maturity molecular markers. Based on these experiments, we developed a population dynamic model with and without the inclusion of plant host sanctions. We show that plant populations persist in spite of the presence of cheating rhizobia without the need of incorporating any sanction against the cheater populations in the model, under the realistic assumption that plants can at least get some amount of fixed N2 from the effectively mutualistic rhizobia occupying some nodules. Inclusion of plant sanctions merely reduces the time needed for reaching plant population equilibrium and leads to the unrealistic effect of ultimate extinction of cheater strains in soil. Our simulation results are in agreement with increasing experimental evidence and theoretical work showing that mutualisms can persist or even improve in presence of cheating partners

Potencial metanogénico de residuos lignocelulósicos específicos disponibles en las fincas agrícolas costarricenses para cogeneración

Proyecto de Graduación (Licenciatura en Ingeniería Ambiental) Instituto Tecnológico de Costa Rica, Escuela de Química, 2014.In Costa Rica agricultural residues do not have efficient management to exploit them as an energy source, therefore this study evaluates methane yield from elephant grass, banana stem and pineapple and malanga waste leaves for cogeneration. The experiment consisted of four series of batch anaerobic reactors with 6% and 8% of substrate (including co-digestion), incubated for 60 days, 50 days, 35 days. Alkaline treatment (NaOH 6%) and effective microorganisms were used to accelerate the hydrolysis of lignocellulose. The process stability was diagnosed with the study of alkalinity; and the methanogenic yield was analyzed by calculation of Specific Methanogenic Activity (SMA) and modeling Biochemical Methane Potential (BMP) with the Gauss Newton iterative method. The results show that the alkaline buffer capacity of the system is presented in relation HCO3-/CO32- and not only as a result of HCO3-, this is due to the concentration of NaOH; and did not exceed 500 mg CaCO3/L for most of the reactors. This indicates a significant production of volatile fatty acids which confirms the efficiency of alkaline and biological treatment. Methane generation was continuous and without stagnation, this made it difficult for the adjustment of the experimental data with the model of BMP. Methane yield per kg of daily volatile solids (max of 0,0024 Nm3 CH4/kgSV.d with elephant grass) equals to 14 m3 of methane per ton of fresh matter and approximately 36 kWh per month, this can meet the daily electricity demand of four middle class residences in Costa Rica. Finally AME results, more favorable for cogeneration (up to 1980 kWh), are the basis for forecasting increased methane yield by implementing optimal conditions in the digesters