Alkaline direct alcohol fuel cells Antolini, E.; Gonzalez, E.R.
Journal of power sources,
06/2010, Letnik:
195, Številka:
11
Journal Article
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The faster kinetics of the alcohol oxidation and oxygen reduction reactions in alkaline direct alcohol fuel cells (ADAFCs), opening up the possibility of using less expensive metal catalysts, as ...silver, nickel and palladium, makes the alkaline direct alcohol fuel cell a potentially low cost technology compared to acid direct alcohol fuel cell technology, which employs platinum catalysts. A boost in the research regarding alkaline fuel cells, fuelled with hydrogen or alcohols, was due to the development of alkaline anion-exchange membranes, which allows the overcoming of the problem of the progressive carbonation of the alkaline electrolyte. This paper presents an overview of catalysts and membranes for ADAFCs, and of testing of ADAFCs, fuelled with methanol, ethanol and ethylene glycol, formed by these materials.
Due their high accessible surface area, low resistance and high stability, conducting polymers have been investigated as carbon-substitute supports for fuel cell catalysts. This paper provides a ...review of the state-of-the-art in the development of metal/polymer composites as electrode materials for low-temperature fuel cells.
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The dependence of the peak current density on the thickness of PPy film for the oxidation peaks (a) at about 0.62
V in the positive-going sweep and (b) at about 0.43
V in the negative-going sweep in the CV of methanol at the Pt/PPy/GC electrode.
Due to their high accessible surface area, low resistance and high stability, conducting polymers have been investigated as carbon-substitute supports for fuel cell catalysts. The main reason for incorporating metallic particles into porous polymeric matrixes is to increase the specific area of these materials and thereby improve the catalytic efficiency. Polymer-supported metal particles also present higher tolerance to poisoning due to the adsorption of CO species, in comparison to the serious problem of poisoning of bulk and carbon-supported metals. Moreover, conducting polymers are not only electron conducting, but also proton conducting materials, so they can replace Nafion in the catalyst layer of fuel cell electrodes and provide enhanced performance. This paper provides a review of the state-of-the-art in the development of metal/polymer composites as electrode materials for low-temperature fuel cells.
Powerful winds driven by active galactic nuclei are often thought to affect the evolution of both supermassive black holes and their host galaxies, quenching star formation and explaining the close ...relationship between black holes and galaxies. Recent observations of large-scale molecular outflows in ultraluminous infrared galaxies support this quasar-feedback idea, because they directly trace the gas from which stars form. Theoretical models suggest that these outflows originate as energy-conserving flows driven by fast accretion-disk winds. Proposed connections between large-scale molecular outflows and accretion-disk activity in ultraluminous galaxies were incomplete because no accretion-disk wind had been detected. Conversely, studies of powerful accretion-disk winds have until now focused only on X-ray observations of local Seyfert galaxies and a few higher-redshift quasars. Here we report observations of a powerful accretion-disk wind with a mildly relativistic velocity (a quarter that of light) in the X-ray spectrum of IRAS F11119+3257, a nearby (redshift 0.189) optically classified type 1 ultraluminous infrared galaxy hosting a powerful molecular outflow. The active galactic nucleus is responsible for about 80 per cent of the emission, with a quasar-like luminosity of 1.5 × 10(46) ergs per second. The energetics of these two types of wide-angle outflows is consistent with the energy-conserving mechanism that is the basis of the quasar feedback in active galactic nuclei that lack powerful radio jets (such jets are an alternative way to drive molecular outflows).
•The PV-CSP system presents a LCOE only 2% higher than the PV-Battery system.•If the ORC is increased to 60 kWe, the LCOE is cheaper than the PV-Battery system.•For a community with demands exceeding ...500 kWe, the LCOE decreases to $0.37 USD/kWh.•LCOE costs can be reduced by up to $0.18 USD/kWh if the system is maximized energetically.
In this work an economic and technical analysis on a hybrid Photovoltaic (PV) – Concentrated solar power (CSP) system, to be used as an energy source in isolated microgrids, is conducted using the microgrid in Puertecitos, Baja California, Mexico as a case study. The PV-CSP system uses a field of solar concentrators with thermal storage to activate a 30 kW organic Rankine cycle, which satisfies the community's energy demand during periods of low or no solar radiation. The PV field provides 73 kW to cover the electrical needs of the community during the daytime, the period in which the CSP field stores sensible heat in tanks for later use. An operational and economic study that compares the hybrid system to the one currently used in the microgrid is presented. The results show that, for the case study, the levelized cost of energy (LCOE) for the PV-CSP hybrid system is 0.524 USD/kWh, only 2% higher than the LCOE for the PV-Battery, 0.51 USD/kWh. However, if the PV-CSP were used in a community with an energy demand 50% larger, the LCOE would be of 0.506 USD/kWh. Furthermore, if the community’s demand exceeds 500 kW, the LCOE of the PV-CSP would be 26% lower. If the system is harnessed to its maximum capacity throughout the year, its LCOE can be comparable to, and as competitive as that of large commercial hybrid plants. The hybridization of these systems allows a manageability and complementarity of energy that, when applied to isolated microgrids, diminishes or eliminates the problem of battery storage, resulting in costs reduction during the useful life of the project.
La relación entre la corteza entorrinal y el hipocampo ha sido estudiada por diferentes autores, que han destacado la importancia de las células de cuadrícula, las células de posicionamiento y la ...conexión trisináptica en los procesos que regulan: la persistencia de la memoria espacial, explícita y reciente, y su posible afección con el envejecimiento.
Observar si existen diferencias en el tamaño y número de células de cuadrícula contenidas en la lámina iii de la corteza entorrinal y en la capa granular del giro dentado del hipocampo de pacientes mayores.
Realizamos estudios posmortem del cerebro de 6 sujetos de edades comprendidas entre los 56 y 87 años. Los cortes de cerebros que contenían el giro dentado del hipocampo y la corteza entorrinal adyacente se tiñeron con el método de Klüver-Barrera, después se midió, mediante el programa Image J, el área neuronal individual, el área neuronal total, así como el número de neuronas, contenidas en cuadrículas rectangulares a nivel de la lámina iii de la corteza entorrinal y la lámina ii del giro dentado y se llevó a cabo un análisis estadístico.
Se ha observado una reducción de la población celular de la capa piramidal externa de la corteza entorrinal, así como de las neuronas de la capa granular del giro dentado relacionada con el envejecimiento.
Nuestros resultados indican que el envejecimiento produce una disminución en el tamaño y la densidad neuronal en las células de cuadrícula de la corteza entorrinal y de posicionamiento del giro dentado.
The relationship between the entorhinal cortex and the hippocampus has been studied by different authors, who have highlighted the importance of grid cells, place cells, and the trisynaptic circuit in the processes that they regulate: the persistence of spatial, explicit, and recent memory and their possible impairment with ageing.
We aimed to determine whether older age causes changes in the size and number of grid cells contained in layer III of the entorhinal cortex and in the granular layer of the dentate gyrus of the hippocampus.
We conducted post-mortem studies of the brains of 6 individuals aged 56-87 years. The brain sections containing the dentate gyrus and the adjacent entorhinal cortex were stained according to the Klüver-Barrera method, then the Image J software was used to measure the individual neuronal area, the total neuronal area, and the number of neurons contained in rectangular areas in layer III of the entorhinal cortex and layer II of the dentate gyrus. Statistical analysis was subsequently performed.
We observed an age-related reduction in the cell population of the external pyramidal layer of the entorhinal cortex, and in the number of neurons in the granular layer of the dentate gyrus.
Our results indicate that ageing causes a decrease in the size and density of grid cells of the entorhinal cortex and place cells of the dentate gyrus.
En este trabajo se analizan las bases de la gestión ambiental frente al cambio climático en los 12 municipios del departamento de Quindío, Colombia. Se efectúo una revisión documental y análisis de ...datos y observaciones obtenidos sobre la gestión ambiental en el marco de cambio y análisis climático en la planificación territorial y planes de desarrollo sobre dos vigencias administrativas (2012–2015 y 2016-2019). Se encontró que las directrices para el progreso no han sido implementadas efectivamente en algunas administraciones o es incompleta la inclusión del tema ambiental y climático, en el ordenamiento territorial de las respectivas administraciones municipales, en el sentido de establecer medidas de protección y prevención ambiental efectivas. Lo anterior se debe al modelo económico imperante y/o en casos, por ejemplo, a los conflictos de interés de las personas que realizan y proyectan las herramientas en el contexto de la planificación y desarrollo sustentable. Por tanto, enfrentar desafíos de gestión ambiental a la luz de los requisitos del cambio climático a nivel de los gobiernos locales requiere una comprensión de las complejas dimensiones del territorio y la coordinación con la identidad del mismo, más allá de un modelo desarrollo impuesto.
En las sociedades desarrolladas existe una aceleración secular del crecimiento. Entre los años 2000 y 2004 hemos valorado el crecimiento en una población caucásica española procedente de Andalucía, ...Barcelona, Bilbao y Zaragoza y hemos comparado los resultados con estudios españoles realizados antes de 1988 en poblaciones caucásicas de Bilbao (BIB 88) y Cataluña (CAT 87).
Estudio transversal que valora el peso, la longitud y el índice de masa corporal (IMC) en 32.064 sujetos (16.607 varones y 15.457 mujeres) desde el nacimiento a la talla adulta: a) 5.796 son recién nacidos a término (2.974 varones y 2.822 mujeres) hijos de madres sanas, de gestaciones únicas; b) 23.701 son niños y adolescentes (12.358 varones y 11.343 mujeres) de 0,25 a 18 años de edad ambos inclusive, y c) 2.567 son adultos jóvenes (1.275 varones y 1.292 mujeres) de 18,1 a 24 años de edad. Todos estaban sanos, eran de raza caucásica y sus padres, de origen español. La distribución percentilada, el valor z-score y el diseño de las gráficas se ha realizado según el método LMS.
Se expresan los valores de la media, desviación estándar, coeficiente de Skewness y percentiles desde el nacimiento la edad adulta, en intervalos de 0,25-0,50 años. Existe un dimorfismo sexual y un incremento en los valores de peso y talla de todos los percentiles respecto a los estudios BIB 88 y CAT 87. Los valores de los percentiles 3, 50 y 97 de la talla adulta son superiores en 1,8, 1,4 y 3,3 cm respecto a BIB 88, y en 2,5, 3,3 y 3,8 cm respecto a CAT 87 en los varones, y 3,5, 2,5 y 4,2 cm respecto a BIB 88 y 3,5, 3,1 y 3,9 cm respecto a CAT 87 en las mujeres. Los correspondientes valores de peso son 5,4, 6,2 y 11,7 kg superiors a los de BIB 88 y 6,7, 6,3 y 10,1 kg superiores a los de CAT 87 en los varones y 1,7, 2,2 y 8,3 kg superiores a los de BIB 88, y 1,8, 2,4 y 3,6 kg superiores CAT 87 en las mujeres. Los respectivos incrementos en el IMC son 2,0, 1,4 y 3,9 respecto a BIB 88 y −0,1, −0,2 y 5,3 respecto a CAT 87 en los varones y 0,9, 0,4 y 3,7 respecto a BIB 88 y −1,8, −0,1 y 4,0 respecto a CAT 87, en las mujeres. Los valores del IMC de 25 y 30 “en la edad adulta” corresponden a los percentiles 80 y 97 en los varones y 85 y 97 en las mujeres.
En ambos sexos los valores de la talla media adulta son similares a los observados en otros estudios longitudinales y transversales españoles recientes y a los observados en estudios europeos y americanos, aunque inferiores a los de la población alemana, sueca y holandesa.
Con relación a estudios españoles previos, existe una aceleración secular de peso y talla, con un incremento desproporcionado en los valores del IMC correspondientes al percentil 75 o superiores, y de forma marcada en los del percentil 97. Este estudio muestra la necesidad de actualizar periódicamente los datos de referencia utilizados en la valoración del crecimiento durante la infancia y adolescencia.
In developed countries a secular trend in growth has been reported. Our aim was to evaluate weight, height and body mass index (BMI) values in a Spanish population coming from Andalusia, Barcelona, Bilbao and Zaragoza, and to compare these values with those obtained before 1988 (BIB 88 and CAT 87 studies).
Cross-sectional evaluation of height, weight and BMI in 32,064 subjects (16,607 males and 15,457 females) from birth to adulthood between the years 2000 and 2004. Three subpopulations were evaluated: a) 5,796 (2,974 males, 2,822 females) newborns at term from normal gestations; b) 23,701 (12,358 males; 11,343 females) children and adolescents 0.25-18 years old, and c) 2,567 (1,275 males, 1,292 females) young adults 18.1-24 years of age. All were healthy caucasians, and their parents from Spanish origin. The LSM method was used.
Mean, standard deviation, Skewness index and percentiles values with a 0.25-0.5 year-period intervals from birth to adulthood are reported. As regards the data obtained previously in Spanish populations, an increase of 1.8 cm, 1.4 cm and 3.3 cm were observed in adult height for percetiles 3, 50 and 97 in males respect to BIB 88 and 2.5 cm, 3.3 cm and 3.8 respect to CAT 87. In females these values were 3.5 cm, 2.5 cm and 4.2 cm respect to BIB 88 and 3.5 cm, 3.1 cm and 3.9 cm respect to CAT 87. The corresponding values for weight, in males, were increased in 5.4 kg, 6.2 kg and 11.7 kg respect to BIB 88 and 6.7 kg, 6.3 kg and 10.1 kg respect to CAT 87; in females these increased were 1.7 kg, 2,2 kg and 8.3 kg respect to BIB 88 and 1.8 kg, 2.4 kg and 3.6 kg respect to CAT 87. The corresponding increased for BMI values, in males, were 2.0, 1.4 and 3.9 respect to BIB 88 and −0.1, −0.2 and 5.3 respect to CAT 87; in females these values were 0.9, 0.4 and 3.7 respect to BIB 88 and −1.8, −0.1 and 4 respect to CAT 87. In young adults, 25 and 30 BMI values correspond to percentiles 80 and 97 in males, and 85 and 97 in females.
Mean values of adult height were similar to those observed in other longitudinal and cross-sectional Spanish, European, and American studies, but lower than those reported for German, Swedish and Netherlands populations.
A secular trend of growth was observed in our population with a non-proportional increased of weight to height ratio (BMI) values, particularly for those corresponding to the 97 percentile. The need of periodical updates of growth data used in the evaluation of children and adolescents is required.
Reactive Oxygen Species are involved in the pathological development of many important human diseases such as neurodegenerative diseases, cardiovascular processes, diabetes and many others. The most ...promising strategy to prevent from the oxidative damage caused by these reactive species is the use of antioxidant molecules. These compounds can act as direct antioxidants through free radical scavenging mechanisms and/or as indirect antioxidants by enhancing the antioxidant status (enzymatic and non-enzymatic). Terpenes, one of the most extensive and varied structural compounds occurring in nature, display a wide range of biological and pharmacological activities. Here we highlight their antioxidant properties. Due to their antioxidant behaviour terpenes have been shown to provide relevant protection under oxidative stress conditions in different diseases including liver, renal, neurodegenerative and cardiovascular diseases, cancer, diabetes as well as in ageing processes. Evidence for this comes from the increasing number of publications on this issue in recent years. This review provides a complete overview of the natural terpenes with potential antioxidant properties, focusing on their source, structures, antioxidant mechanisms through which they exert their pharmacological and possible therapeutic activities.
The performance and durability of low-temperature fuel cells seriously depend on catalyst support materials. Catalysts supported on high surface area carbons are widely used in low temperature fuel ...cells. However, the corrosion of carbonaceous catalyst-support materials such as carbon black has been recognized as one of the causes of performance degradation of low-temperature fuel cells, in particular under repeated start-stop cycles or high-potential conditions. To improve the stability of the carbon support, materials with a higher graphitic character such as carbon nanotubes and carbon nanofibers have been tested in fuel cell conditions. These nanostructured carbons show a several-fold lower intrinsic corrosion rate, however, do not prevent carbon oxidation, but rather simply decrease the rate. Due their high stability in fuel cell environment, ceramic materials (oxides and carbides) have been investigated as carbon-substitute supports for fuel cell catalysts. Moreover, the higher specific electrocatalytic activity of some ceramic supported metals than unsupported and carbon supported ones, suggests the possibility of a synergistic effect by supporting metal catalyst on ceramic supports. This paper presents an overview of ceramic materials tested as a support for fuel cell catalysts, with particular attention addressed to the electrochemical activity and stability of the supported catalysts.
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