2,308 research outputs found

    Synthesis of titanium-containing ZSM-48

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    Titanium-containing ZSM-48 is synthesized with silicon to titanium ratios of 26 or larger; changes in unit cell volume and IR data show that titanium is incorporated into framework positions

    Opciones y criterios de adaptación de lentes de contacto híbridas: revisión bibliográfica

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    Este trabajo de revisión analiza toda la bibliografía encontrada en MEDLINE a través de PubMed y Ovid sobre lentes de contacto híbridas. En él se presenta la evolución de este tipo de lentes hasta los últimos estudios sobre las lentes SynergEyes. Se dan unas pautas de adaptación para alguno de estos tipos de lentes y se analizan sus diferentes usos. Se estudia la adaptación de lentes en casos de queratocono y otras ectasias corneales, comparando los distintos tipos de lentes utilizados así como los resultados que ofrecen las lentes de contacto híbridas en estos casos. Se comenta la función de este tipo de lentes en casos de córnea irregular poscirugía refractiva, así como en casos de posqueratoplastia. Por último, se analizan brevemente los nuevos avances realizados por los laboratorios especializados en este tipo de lentes de contacto

    Hydrotreating of Guaiacol and Acetic Acid Blends over Ni2P/ZSM-5 Catalysts: Elucidating Molecular Interactions during Bio-Oil Upgrading

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    [EN] Catalytic hydrodeoxygenation (HDO) is an effective technology for upgrading pyrolysis bio-oils. Although, in the past years, this process has been extensively studied, the relevance of the cross-reactivity between the numerous chemical components of bio-oil has been scarcely explored. However, molecular coupling can be beneficial for improving the bio-oil characteristics. With the aim of gaining a better understanding of these interactions, this work investigates the catalytic hydrodeoxygenation of mixtures of two typical components of pyrolysis bio-oils: guaiacol and acetic acid. The catalytic tests were carried out employing a bifunctional catalyst based on nickel phosphide (Ni2P) deposited over a commercial nanocrystalline ZSM-5 zeolite. The influence of both hydrogen availability and temperature on the activity and product distribution, was evaluated by carrying out reactions under different H2 pressures (40¿10 bar) and temperatures (between 260 and 300 °C). Using blends of both substrates, a partial inhibition of guaiacol HDO occurred because of the competence of acetic acid for the catalytic active sites. Nevertheless, positive interactions were also observed, mainly esterification and acylation reactions, which could enhance the bio-oil stability by reducing acidity, lowering the oxygen content, and increasing the chain length of the components. In this respect, formation of acetophenones, which can be further hydrogenated to yield ethyl phenols, is of particular interest for biorefinery applications. Increasing the temperature results in an increment of conversion but a decrease in the yield of fully deoxygenated molecules due to the production of higher proportion of catechol and related products. Additional experiments performed in the absence of hydrogen revealed that esterification reactions are homogeneously self-catalyzed by acetic acid, while acylation processes are mainly catalyzed by the acidic sites of the zeolitic support.The authors thank to the Spanish “Ministry of Economy and Competiveness” for their financial support through the project CATPLASBIO (CTQ2014-60209-R), as well as to the “Regional Government of Madrid” and European Structural Funds for the RESTOENE2 (S2013/MAE-2882) project

    Two Neolithic structures at the archaeological site of Casa Garrido Nord II (Moixent, Valencia)

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    Es presenten les restes de cronologia neolítica documentades a les obres de canalització de gas a la vall de Montesa. Concretament, dues sitges del Neolític II de la seqüència regional, aparegudes al jaciment de Casa Garrido Nord, al terme municipal de Moixent. Encara que els materials són poc significatius, es tracta de les primeres estructures de cronologia neolítica, de les quals tenim constància, en què s’ha realitzat una excavació arqueològica sistemàtica a la comarca de la Costera. Paraules clau: Casa Garrido Nord II. Sitja. Neolític II. La Costera. Assentaments en pla.Es presenten les restes de cronologia neolítica documentades a les obres de canalització de gas a la vall de Montesa. Concretament, dues sitges del Neolític II de la seqüència regional, aparegudes al jaciment de Casa Garrido Nord, al terme municipal de Moixent. Encara que els materials són poc significatius, es tracta de les primeres estructures de cronologia neolítica, de les quals tenim constància, en què s’ha realitzat una excavació arqueològica sistemàtica a la comarca de la Costera. Paraules clau: Casa Garrido Nord II. Sitja. Neolític II. La Costera. Assentaments en pla.Herewith we submit the remains of Neolithic chronology found at the gas piping works performed at the Valley of Montesa (Valencia). They are specifically two Neolithic II underground storage places of a regional sequence, which appeared at the Casa Garrido Nord archaeological site, within the Moixent municipal borough (in the province of Valencia). Although the materials are not very meaningful, they represent the first structures of Neolithic chronology known to us, and therefore we have carried out a systematic archaeological excavation in the area of La Costera (Valencia). Key words: Casa Garrido Nord II. Silo. Neolithic II. La Costera. Settlements on flat lands

    Analysing the effect of land use and vegetation cover on soil infiltration in three contrasting environments in Northeast Spain

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    Este estudio presenta el análisis conjunto de la información obtenida a partir de 195 ensayos de infiltración en el campo, que fueron realizados mediante dispositivos de doble anillo. Los experimentos se realizaron en 20 situaciones contrastadas de usos del suelo, los cuales se encuentran distribuidos en tres contextos geográficos (costa NE de Cataluña, monte bajo del sector central del valle del Ebro y montaña media de la vertiente Sur del Pirineo central). El objetivo de esta investigación es determinar los factores más importantes que explican la variabilidad de la infiltración: uso del suelo, tipo de cubierta vegetal, características del suelo y del substrato rocoso, humedad del suelo y altitud. El análisis de los datos se realizó mediante la comparación de las variables a partir de distintos métodos estadísticos: test de correlación lineal bivariada, ANOVA y comparaciones múltiples de Bonferroni. Los resultados muestran que la variabilidad de la infiltración está principalmente asociada al tipo de uso del suelo, siendo el factor más determinante. El tipo de cubierta vegetal se mostró como el segundo factor en importancia, mientras la humedad del suelo no presentó correlación con la infiltración. La interpretación de estos resultados sugiere que las características de las áreas de estudio son más determinantes que las variaciones temporales del estado hídrico del suelo, aunque la humedad pueda tener un grado de influencia mayor o menor en cada uso del suelo. La validez de los resultados obtenidos en este estudio está avalada porque se ha analizado un amplio espectro de escenarios de uso del suelo/cubierta vegetal, incluso teniendo en cuenta que se han comparado zonas con distintas características geográficas y geológicas. This study presents a joint analysis of the information from 195 field infiltration experiments, using double ring devices. The experiments were carried out in 20 contrasting types of land use, distributed across three geographic contexts (coast of NE Catalonia, low mountains in the central Ebro Valley and mid-height mountains from the southern range of the Central Pyrenees). The objective of this research was to determine the most important factors explaining infiltration variability: land use, type of vegetation cover, soil and bedrock characteristics, soil moisture and altitude. Data analysis was performed by comparing variables using statistical methods: bivariate lineal correlation, ANOVA and Bonferroni multiple comparison tests. Results show that infiltration variability is the most important factor and mainly linked to land use, followed by vegetation type. In contrast, soil moisture did not show any relation with infiltration. The interpretation of these results suggests that the characteristics of the study areas are more decisive than temporal variations of soil water content, although humidity can influence land use to a greater or lesser degree. The validity of the results obtained in this study is supported by the wide range of land use and land cover analysed, located in areas with different geographical and geological characteristics

    Removal of NO at low concentration from air in urban built environments by activated miscanthus biochar

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    This work presents an innovative and sustainable approach to remove NO emissions from urban ambient air in confined areas (underground parking areas or tunnels) using low-cost activated carbons obtained from Miscanthus biochar (MSP700) by physical activation (with CO2 or steam) at temperatures ranging from 800 to 900 °C. The NO removal capacity of the activated biochars was evaluated under different conditions (temperature, humidity and oxygen concentration) and compared against a commercial activated carbon. This last material showed a clear dependence on oxygen concentration and temperature, exhibiting a maximum capacity of 72.6% in air at 20 °C, whilst, its capacity notably decreased at higher temperatures, revealing that physical NO adsorption is the limiting step for the commercial sample that presents limited oxygen surface functionalities. In contrast, MSP700-activated biochars reached nearly complete NO removal (99.9%) at all tested temperatures in air ambient. Those MSP700-derived carbons only required low oxygen concentration (4 vol%) in the gas stream to achieve the full NO removal at 20 °C. Moreover, they also showed an excellent performance in the presence of H2O, reaching NO removal higher than 96%. This remarkable activity results from the abundance of basic oxygenated surface groups, which act as active sites for NO/O2 adsorption, along with the presence of a homogeneous microporosity of 6 Å, which enables intimate contact between NO and O2. These features promote the oxidation of NO to NO2, which is further retained over the carbon surface. Therefore, the activated biochars studied here could be considered promising materials for the efficient removal of NO at low concentrations from air at moderate temperatures, thus closely approaching real-life conditions in confined spaces.J. Fermoso gratefully acknowledges the financial support from the Comunidad de Madrid through the Talent Attraction Programme (2018-T1/AMB-10023)

    Crianza de animales domésticos como factor de riesgo de fascioliasis humana

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    The aim of this study was to determine the association of fascioliasis with the breeding of animals, housing characteristics and food consumption of children in the district of Santa María de Chicmo, Apurimac, Peru. Serological samples were taken from 493 children aged 6 to 16 years, males and females, with the informed consent of their parents. The prevalence, determined by the immunoblot technique was 5.3% (95% CI = 3.2% -7.4%, 26/493). The univariate analysis showed that the breeding of cattle and cats, and raising three or more pigs were factors associated with fascioliasis. The breeding of more than five sheep resulted as a protection factor. Fascioliasis in children was not associated with the characteristics of the dwellings or the consumption of food. It is concluded that the district of Santa María de Chicmo is mesoendemic for fascioliasis in children, and that the rearing of some species of domestic animals involves risk of human fascioliasis.  El estudio tuvo como objetivo determinar la asociación de fascioliasis con la crianza de animales, características de la vivienda y consumo de alimentos de niños del distrito de Santa María de Chicmo, Apurímac, Perú. Se tomaron muestras serológicas a 493 niños de 6 a 16 años, de ambos sexos, con el consentimiento informado de sus padres. La prevalencia, determinada mediante la técnica de inmunoblot fue de 5.3% (IC95%=3.2%-7.4%; 26/493). El análisis univariado demostró que la crianza de bovinos y gatos, así como la crianza de tres o más cerdos fueron factores asociados a fascioliasis. La crianza de más de cinco ovinos configuró un factor de protección. La fascioliasis en niños no estuvo asociada a las características de las viviendas ni al consumo de alimentos. Se concluye que el distrito de Santa María de Chicmo es mesoendémico para fascioliasis en niños, y que la crianza de algunas especies de animales domésticos implica riesgo de fascioliasis humana

    Modelamiento y Simulación de Redes de Transporte Urbano: Seis Casos en Lima

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    Studies of urban transport networks in many cities are not well focused, since they do not include tools for their planning and control, making decisions to solve the multiple problems regarding traffic congestion expensive and not adequate, generating discomfort in the users, and many times it aggravates the problems, since its impact is not evaluated. Currently exist a variety of simulators that are helpful for traffic simulation and online monitoring. An alternative to this are traffic simulators, which currently exist in variety, however, they are not easily accessible, a formal study and a relationship with the research center that provides it is required, their personalized reports are limited and they comply to another reality. In the present work, six frequent cases of urban transport networks in Lima are modeled, simulated and validated: intersection, oval, union, by-pass, clover and T; by using Arena (general-purpose simulator), known statistical and simulation techniques. The T model was validated with an average confidence level of 95%, in addition, personalized information could be obtained for decision making.Los estudios de las redes de transporte urbano en muchas ciudades no están bien enfocados, pues no contemplan herramientas para su planificación y control, haciendo que las decisiones para solucionar los múltiples problemas respecto a la congestión vehicular sean caros y no adecuadas, generando malestar en los usuarios, y muchas veces agrava los problemas, pues no se evalúa su impacto. Una alternativa a ello son los simuladores de tráfico, que en la actualidad existen en variedad, sin embargo, no son de fácil acceso, se requiere un estudio formal y una relación con el centro de investigación que lo provee, sus reportes personalizados son limitados y obedecen a otra realidad. En el presente trabajo se modela, simula seis casos frecuentes de redes de transporte urbano en Lima: Intersección, Ovalo, Unión, By-Pass, Trébol y T; mediante el uso de Arena (simulador de propósito general), técnicas estadísticas y de simulación conocidas. Se validó el modelo T con un nivel de confianza promedio del 95%, además, se pudo obtener información personalizada para la toma de decisión

    Towards the improvement of methane production in CO2 photoreduction using Bi2WO6/TiO2 heterostructures

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    Russelite bismuth tungstate (Bi2WO6) has been widely reported for the photocatalytic degradation and mineralization of a myriad of pollutants as well as organic compounds. These materials present perovskite-like structure with hierarchical morphologies, which confers excellent optoelectronic properties as potentials candidates for photocatalytic solar fuels production. Here, we propose the development of Bi2WO6/TiO2 heterojunctions for CO2 photoreduction, as a promising solution to produce fuels, alleviate global warming and tackle fossil fuel shortage. Our results show an improvement of the photocatalytic activity of the heterojunctions compared to the pristine semiconductors. Near Ambient Pressure X-ray Photoelectron Spectroscopy (NAP-XPS) experiments reveals a preferential CO2 adsorption over TiO2. On the other hand, transient absorption spectroscopy measurements show that the charge transfer pathway in Bi2WO6/TiO2 hybrids leads to longer-lived photogenerated carriers in spatially separated redox active sites, which favor the reduction of CO2 into highly electron demanding fuels and chemicals, such as CH4 and C2H6Financial support has been received from the European Research Council (ERC), through HYMAP project (grant agreement No. 648319), under the European Union's Horizon 2020 research and innovation program, as well as from the Marie Sklodowska-Curie grant agreement No. 754382. L.C. acknowledges funding from the project ARMONIA (PID2020–119125RJ-I00) funded by MCIN/AEI/10.13039/ 501100011033. Financial support has also been received from AEIMINECO/FEDER (Nympha Project, PID2019–106315RB-I00), "Comunidad de Madrid" regional government, and the European Structural Funds (FotoArt-CM project, S2018/NMT-4367). Authors also acknowledge financial support from the grant PLEC2021–007906 funded by MCIN/AEI/10.13039/501100011033 and the "European Union NextGenerationEU/PRTR"
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