220 research outputs found

    QENS study of methane diffusion in Mo/H-ZSM-5 used for the methane dehydroaromatisation reaction

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    There is commercial interest in understanding the deactivation of Mo loaded H-ZSM-5 catalyst by coke fouling during the methane dehydroaromatization reaction (MDA). The effect of coke on methane diffusion inside the zeolite pores was studied by quasielastic neutron scattering (QENS) measurements on Mo/H-ZSM-5 samples reacted with methane for 0, 7, 25 and 60 min. Catalytic activity of the samples followed by mass spectrometry indicate that the induction period in which Mo species are carburized lasts for ∼9 min; after this period the material shows selectivity to aromatics. Characterization by TGA and N2physisorption suggest that practically no carbon is deposited during the induction period. The ∼2 wt % of coke formed after one hour of reaction has a negligible effect in the zeolite crystal structurebut a small effect on the micropore volume. The QENS studies show that the methane transport by jump diffusion is however not measurably affected by the accumulated coke in the samples

    Detection of key transient Cu intermediates in SSZ-13 during NH3-SCR deNOx by modulation excitation IR spectroscopy

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    The small pore zeolite Cu-SSZ-13 is an efficient material for the standard selective catalytic reduction of nitrogen oxides (NOx) by ammonia (NH3). In this work, Cu-SSZ-13 has been studied at 250 °C under high conversion using a modulation excitation approach and analysed with phase sensitive detection (PSD). While the complementary X-ray absorption near edge structure (XANES) spectroscopy measurements showed that the experiments were performed under cyclic Cu+/Cu2+ redox, Diffuse Reflectance Infrared Fourier Transform Spectroscopy (DRIFTS) experiments provide spectroscopic evidence for previously postulated intermediates Cu–N([double bond, length as m-dash]O)–NH2 and Cu–NO3 in the NH3-SCR deNOx mechanism and for the role of [Cu2+(OH−)]+. These results therefore help in building towards a more comprehensive understanding of the reaction mechanism which to date has only been postulated in silico

    Congreso online como herramienta docente para estudiantes de tercer ciclo en Electroquímica

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    Los congresos científicos son una buena herramienta para que los estudiantes de tercer ciclo puedan ampliar sus conocimientos. Sin embargo, las intervenciones donde los estudiantes plantean dudas o preguntas son prácticamente nulas. Con el objetivo de fomentar la participación de los estudiantes en los congresos científicos, la nueva red continua con el trabajo anteriormente realizado, llevando a cabo la II edición del Congreso online de estudiantes dentro del programa interuniversitario “Electroquímica. Ciencia y Tecnología”. La red busca concienciar acerca de la importancia que para un investigador tiene un congreso científico y a su vez, incrementar y mejorar su participación. Para ello, se utiliza un formato más atractivo que en la edición anterior, que mejora el entorno de trabajo y favorece la interacción entre los estudiantes. Asimismo, se emplean estrategias de comunicación más desarrolladas para hacer crecer el número de participantes. Finalmente, se establecerán diferentes parámetros para evaluar la actividad durante el congreso y se entregarán premios para motivar la participación

    Dry selection and wet evaluation for the rational discovery of new anthelmintics

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    Helminths infections remain a major problem in medical and public health. In this report, atom-based 2D bilinear indices, a TOMOCOMD-CARDD (QuBiLs-MAS module) molecular descriptor family and linear discriminant analysis (LDA) were used to find models that differentiate among anthelmintic and non-anthelmintic compounds. Two classification models obtained by using non-stochastic and stochastic 2D bilinear indices, classified correctly 86.64% and 84.66%, respectively, in the training set. Equation 1(2) correctly classified 141(135) out of 165 [85.45%(81.82%)] compounds in external validation set. Another LDA models were performed in order to get the most likely mechanism of action of anthelmintics. The model shows an accuracy of 86.84% in the training set and 94.44% in the external prediction set. Finally, we carry out an experiment to predict the biological profile of our ‘in-house’ collections of indole, indazole, quinoxaline and cinnoline derivatives (∼200 compounds). Subsequently, we selected a group of nine of the theoretically most active structures. Then, these chemicals were tested in an invitro assay and one good candidate (VA5-5c) as fasciolicide compound (100% of reduction at concentrations of 50 and 10 mg/L) was discovered.Yovani Marrero-Ponce acknowledges the support from USFQ with partial finance of project ID5455Peer Reviewe

    La formación técnico profesional en el nivel superior no universitario de Argentina

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    El presente trabajo pretende problematizar la Formación Técnico Profesional en el Nivel Superior No Universitario en Argentina, habida cuenta de que la misma se constituye en el objeto de conocimiento del proceso de investigación que está desarrollando un equipo docente de la Facultad de Educación de la Universidad Católica de Córdoba de nuestro país, dirigido por el Dr. Horacio A. Ferreyra.Luego de una breve caracterización de las principales políticas públicas para la Educación Superior No Universitaria en Argentina en las últimas dos décadas (1990-2009), se presenta un marco teórico y conceptual producto de un relevamiento del estado del arte en el tema para abordar el estudio y análisis de este subsistema de la Educación Superior Argentina.Finalmente, este trabajo propone alternativas de mejoramiento de la calidad a modo de anticipaciones de sentido y posibles líneas de investigación a futuro. La convicción que moviliza el Proyecto y la Ponencia es la necesidad e importancia de construir aportes y propuestas para reorientar la transformación del subsistema ligado a las políticas de desarrollo socio-económico de la región y del país

    Brief cognitive assessment instruments in schizophrenia and bipolar patients, and healthy control subjects: A comparison study between the Brief Cognitive Assessment Tool for Schizophrenia (B-CATS) and the Screen for Cognitive Impairment in Psychiatry (SCIP)

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    Cognitive impairment in schizophrenia and psychosis is ubiquitous and acknowledged as a core feature of clinical expression, pathophysiology, and prediction of functioning. However, assessment of cognitive functioning is excessively time-consuming in routine practice, and brief cognitive instruments specific to psychosis would be of value. Two screening tools have recently been created to address this issue, i.e., the Brief Cognitive Assessment Tool for Schizophrenia (B-CATS) and the Screen for Cognitive Impairment in Psychiatry (SCIP). The aim of this research was to examine the comparative validity of these two brief instruments in relation to a global cognitive score. 161 patients with psychosis (96 patients diagnosed with schizophrenia and 65 patients diagnosed with bipolar disorder) and 76 healthy control subjects were tested with both instruments to examine their concurrent validity relative to a more comprehensive neuropsychological assessment battery. Scores from the B-CATS and the SCIP were highly correlated in the three diagnostic groups, and both scales showed good to excellent concurrent validity relative to a Global Cognitive Composite Score (GCCS) derived from the more comprehensive examination. The SCIP-S showed better predictive value of global cognitive impairment than the B-CATS. Partial and semi-partial correlations showed slightly higher percentages of both shared and unique variance between the SCIP-S and the GCCS than between the B-CATS and the GCCS. Brief instruments for assessing cognition in schizophrenia and bipolar disorders, such as the SCIP-S and B-CATS, seem to be reliable and promising tools for use in routine clinical practice

    Pt-Richcore/Sn-Richsubsurface/Ptskin Nanocubes As Highly Active and Stable Electrocatalysts for the Ethanol Oxidation Reaction

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    Direct ethanol fuel cells are one of the most promising electrochemical energy conversion devices for portable, mobile and stationary power applications. However, more efficient and stable and less expensive electrocatalysts are still required. Interestingly, the electrochemical performance of the electrocatalysts toward the ethanol oxidation reaction can be remarkably enhanced by exploiting the benefits of structural and compositional sensitivity and control. Here, we describe the synthesis, characterization, and electrochemical behavior of cubic Pt–Sn nanoparticles. The electrochemical activity of the cubic Pt–Sn nanoparticles was found to be about three times higher than that obtained with unshaped Pt–Sn nanoparticles and six times higher than that of Pt nanocubes. In addition, stability tests indicated the electrocatalyst preserves its morphology and remains well-dispersed on the carbon support after 5000 potential cycles, while a cubic (pure) Pt catalyst exhibited severe agglomeration of the nanoparticles after a similar stability testing protocol. A detailed analysis of the elemental distribution in the nanoparticles by STEM-EELS indicated that Sn dissolves from the outer part of the shell after potential cycling, forming a ∼0.5 nm Pt skin. This particular atomic composition profile having a Pt-rich core, a Sn-rich subsurface layer, and a Pt-skin surface structure is responsible for the high activity and stability.This work has been supported by Fundación Cajacanarias (project BIOGRAF) and the Ministry of Economy and Competitiveness (MINECO) through the projects CTQ2011-28913-C02-02 and ENE2014-52158-C2-2-R (cofunded by FEDER). We acknowledge the SEGAI services of Universidad de La Laguna for important technical assistance, and R.R. acknowledges the funding received from MINECO (EEBB-I-16-11762) to carry out a predoctoral stay in a foreign R&D center. E.P. acknowledges support from an electron microscopy facility supported by the NSF MRSEC program (DMR 1120296) and an NSF MRI grant (DMR 1429155). J.S.G. acknowledges financial support from VITC (Vicerrectorado de Investigación y Transferencia de Conocimiento) of the University of Alicante
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