80 research outputs found

    Passivation of a CoCrMo PVD Alloy with Biomedical Composition under Simulated Physiological Conditions Studied by EQCM and XPS

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    Kinetics of passive film growth on a CoCrMo biomedical alloy have been studied using the Electrochemical Quartz Crystal Microbalance technique (EQCM) in phosphate buffer solution at room temperature and 37◦C. CoCrMo layers were deposited on the quartz crystals by physical vapor deposition (PVD) reaching a dense and compact deposition film with fine-grain structure. EQCM measurements were performed under potentiodynamic and potentiostatic conditions (at applied passive and transpassive potentials). Furthermore, ex-situ X-ray Photoelectron Spectroscopy (XPS) analysis of the each tested sample was performed at the end of the electrochemical test. The use ofEQCMallows distinguishing between electrochemical oxidation, passive and transpassive dissolution and passive film growth. In the passive domain the passive film thickness stabilizes within 200 to 400 s after an initial fast growth. The increase in current at the onset of the transpassive domain does not affect the passive dissolution rate. Only at higher potential dissolution rate increases due to the dissolution of Cr(VI), Co(III) and Mo(VI) species. The observed constant mass loss rate at transpassive potentials indicates that the passive film at these potentials is cracked or porous. Increasing temperature accelerates themass loss through the oxide/electrolyte interface enhancing the passive and transpassive dissolution and increasing the thickness of the oxide filmWe wish to express our gratitude to the Spanish Government, "Ministerio de Educacion" for the economic support and the post-graduate grant (Ref.AP2007-01243) and "Ministerio de Ciencia e Innovacion" for the financial support (Ref.MAT2011-22481), the assistance of N. Xanthopoulos with the XPS measurements and P. Mettraux with the PVD deposits and assistance with the scanning electron micrographs.Valero Vidal, C.; Igual Muñoz, AN.; Olsson, C.; Mischler, S. (2012). Passivation of a CoCrMo PVD Alloy with Biomedical Composition under Simulated Physiological Conditions Studied by EQCM and XPS. Journal of The Electrochemical Society. 159(5):233-243. https://doi.org/10.1149/2.090205jesS2332431595Katti, K. S. (2004). Biomaterials in total joint replacement. Colloids and Surfaces B: Biointerfaces, 39(3), 133-142. doi:10.1016/j.colsurfb.2003.12.002Okazaki, Y. (2002). Effect of friction on anodic polarization properties of metallic biomaterials. Biomaterials, 23(9), 2071-2077. doi:10.1016/s0142-9612(01)00337-4Virtanen, S., Milošev, I., Gomez-Barrena, E., Trebše, R., Salo, J., & Konttinen, Y. T. (2008). Special modes of corrosion under physiological and simulated physiological conditions. Acta Biomaterialia, 4(3), 468-476. doi:10.1016/j.actbio.2007.12.003Milošev, I., & Strehblow, H.-H. (2003). 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    Stability of 3D-porous Ni/Cu cathodes under real alkaline electrolyzer operating conditions and its effect on catalytic activity

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    Despite the development and synthesis of new electrode materials for hydrogen generation in alkaline water electrolyzers has been a research topic widely exploited in the last years, stability tests on the obtained cathodes have been restricted to long-term potentiostatic/galvanostatic experiments which do not fulfil the real operating conditions that take place in those devices. In this work, two different Service Life Tests have been designed and implemented, aiming at including particular conditions (i.e. inverse polarity and short-circuit) in the durability and catalytic activity of cathode characterization. For this purpose, Ni/Cu bilayered porous electrodes were prepared using different Ni electrodeposition times (15, 30 and 45 min) following a double template electrochemical method. It has been confirmed that the electrode with the lowest Ni content can be considered as a promising electrocatalyst for hydrogen production under industrial conditions because of its optimal activity and stability after the two sets of testing conditions. In particular, electrochemical studies demonstrated that an inversion in polarity can positively affect the electrode performance, as a consequence of the synergetic interaction between CuO/Cu(OH)(2) and beta-Ni(OH)(2) species formed at potentials below the oxygen evolution domain.The authors gratefully acknowledge financial support given by the Generalitat Valenciana (PROMETEO/2010/023) and Spanish Government (Ministerio de Ciencia e Innovation) for the postgraduate grants AP2007-01243 (Carlos Valero-Vidal) and AP2007-03737 (Isaac Herraiz-Cardona).Valero Vidal, C.; Herraiz Cardona, I.; Pérez-Herranz, V.; Igual Muñoz, AN. (2016). Stability of 3D-porous Ni/Cu cathodes under real alkaline electrolyzer operating conditions and its effect on catalytic activity. Applied Catalysis B: Environmental. 198:142-153. doi:10.1016/j.apcatb.2016.05.030S14215319

    Ag-Vanadates/GO Nanocomposites by Aerosol-Assisted Spray Pyrolysis: Preparation and Structural and Electrochemical Characterization of a Versatile Material

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    In this article, we describe the deposition by aerosol-assisted spray pyrolysis of different types of silver vanadate nanocomposites with and without graphene oxide (GO) on different substrates (carbon paper (CP) and fluorine-doped tin oxide (FTO)). When deposited on CP, different amounts of GO were added to the Ag and V precursor solution to study the effect of GO on the physicochemical properties of the resulting Ag-vanadate. It is shown that the addition of GO leads mainly to the formation of nanoparticles of the Ag2V4O11 phase, whereas Ag2V4O11 and Ag3VO4 are obtained without the addition of GO. The morphology and chemical properties of the composites were determined by scanning and transmission electron microscopies, X-ray diffraction, X-ray photoemission spectroscopy, and UV\u2013visible and Raman spectroscopies. In addition, the photoelectrochemical (PEC) properties of such composites were studied by CV, linear sweep voltammetry, and electrochemical impedance spectroscopy. The ideal AgxVOy and GO ratio was optimized for obtaining higher photocurrent values and a good stability. The results showed that the presence of GO improves the electrical conductivity of the catalyst layer as well as the electron injection from the oxide to the electrode surface. The deposition of pure Ag2V4O11 on FTO does not lead to samples with stable PEC performances. Samples grown on CP supports showed an efficient electrochemical detection of small amounts of ethylenediamine in water solution

    Co-modification of Ni-based type Raney electrodeposits for hydrogen evolution reaction in alkaline media

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    [EN] In this work, high performance Ni and Ni-Co porous electrodes are prepared using the Raney strategy by galvanic co-deposition for hydrogen evolution reaction (HER) in alkaline solution (KOH 30 wt.%). The incorporation of Co into the Raney Ni matrix causes a surface morphology modification, from cracked to "cauliflower-like", which dominates the superficial structure of the Co-richest obtained material. The evaluation of these electrodes as H-2-evolving cathodes is done through pseudo-steady-state polarization curves and electrochemical impedance spectroscopy (EIS). Ni Raney electrode (without Co) manifests the highest apparent catalytic activity per unit of geometric surface area, which is attributed to the higher surface roughness factor, determined by EIS. HER on the investigated electrocatalysts proceeds via the Volmer-Heyrovsky mechanism, with Heyrovsky as the rate-determining step (rds). From the kinetic parameters it is derived that Co presence, in a composition range of 5-22 at.%, increases the intrinsic catalytic activity of the developed cathodes per unit of true surface area, as a consequence of the synergism between the properties of Ni and of Co. Nevertheless, this improvement does not compensate the lower surface roughness factor, originated by the surface morphology modification as the Co content increases, reporting lower apparent catalytic activities. (C) 2013 Elsevier B.V. All rights reserved.Isaac Herraiz-Cardona is grateful to Fundacion Iberdrola for the economical support by means of the Project: "Desarrollo y caracterizacion de materiales electrodicos porosos estables para la produccion de hidrogeno a partir de la electrolisis alcalina del agua" - II Convocatoria de Ayudas a la Investigacion en Energia y Medio Ambiente. The authors would like to thank the financial support from Generalitat Valenciana (PROMETEO/2010/023) and Universidad Politecnica de Valencia (PAID-06-10-2227).Herraiz Cardona, I.; González Buch, C.; Valero Vidal, C.; Ortega Navarro, EM.; Pérez-Herranz, V. (2013). Co-modification of Ni-based type Raney electrodeposits for hydrogen evolution reaction in alkaline media. Journal of Power Sources. 240:698-704. https://doi.org/10.1016/j.jpowsour.2013.05.041S69870424

    Picos, a hardware task-dependence manager for task-based dataflow programming models

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    Task-based programming Task-based programming models such as OpenMP, Intel TBB and OmpSs are widely used to extract high level of parallelism of applications executed on multi-core and manycore platforms. These programming models allow applications to be expressed as a set of tasks with dependences to drive their execution at runtime. While managing these dependences for task with coarse granularity proves to be highly beneficial, it introduces noticeable overheads when targeting fine-grained tasks, diminishing the potential speedups or even introducing performance losses. To overcome this drawback, we propose a hardware/software co-design Picos that manages inter-task dependences efficiently. In this paper we describe the main ideas of our proposal and a prototype implementation. This prototype is integrated with a parallel task- based programming model and evaluated with real executions in Linux embedded system with two ARM Cortex-A9 and a FPGA. When compared with a software runtime, our solution results in more than 1.8x speedup and 40% of energy savings with only 2 threads.This work is supported by the projects SEV-2015-0493 and TIN2015-65316-P, by the project 2014-SGR-1051 and 2014-SGR-1272, by the RoMoL GA 321253 and by the project cooperation agreement with LG Electronics, and thank the Xilinx University Program.Postprint (published version

    Congreso online: nueva herramienta para fomentar el aprendizaje

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    Los congresos científicos son una herramienta valiosa en el aprendizaje para estudiantes de tercer ciclo. Sin embargo, no son aprovechados al máximo con esta finalidad, puesto que las intervenciones por parte de los estudiantes, en cuanto a plantear cuestiones se refiere, son prácticamente nulas. Con el objetivo de fomentar la participación de los estudiantes de tercer ciclo en los congresos científicos, se presenta una propuesta de congreso online para estudiantes de doctorado en el programa interuniversitario `Electroquímica. Ciencia y Tecnología`, empleando la herramienta Moodle. Este congreso consiste en dar a conocer, de forma visible y con formato de pósters, comunicaciones científicas de los estudiantes, quienes deben hacer preguntas acerca de las mismas y responder a las realizadas sobre su contribución. Además, y siempre con la finalidad de fomentar la participación en forma de preguntas y discusiones científicas, se otorgarán premios tales como al estudiante más participativo y al mejor póster, para lo que se evaluará la defensa del póster por parte del estudiante

    An Energy-Reduced Mediterranean Diet, Physical Activity, and Body Composition

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    [ENG]Importance Strategies targeting body composition may help prevent chronic diseases in persons with excess weight, but randomized clinical trials evaluating lifestyle interventions have rarely reported effects on directly quantified body composition. OBJECTIVE To evaluate the effects of a lifestyle weight-loss intervention on changes in overall and regional body composition. DESIGN, SETTING, AND PARTICIPANTS The ongoing Prevención con Dieta Mediterránea-Plus (PREDIMED-Plus) randomized clinical trial is designed to test the effect of the intervention on cardiovascular disease prevention after 8 years of follow-up. The trial is being conducted in 23 Spanish research centers and includes men and women (age 55-75 years) with body mass index between 27 and 40 and metabolic syndrome. The trial reported herein is an interim subgroup analysis of the intermediate outcome body composition after 3-year follow-up, and data analysis was conducted from February 1 to November 30, 2022. Of 6874 total PREDIMED-Plus participants, a subsample of 1521 individuals, coming from centers with access to a dual energy x-ray absorptiometry device, underwent body composition measurements at 3 time points. INTERVENTION Participants were randomly allocated to a multifactorial intervention based on an energy-reduced Mediterranean diet (MedDiet) and increased physical activity (PA) or to a control group based on usual care, with advice to follow an ad libitum MedDiet, but no physical activity promotion. MAIN OUTCOMES AND MEASURES The outcomes (continuous) were 3-year changes in total fat and lean mass (expressed as percentages of body mass) and visceral fat (in grams), tested using multivariable linear mixed-effects models. Clinical relevance of changes in body components (dichotomous) was assessed based on 5% or more improvements in baseline values, using logistic regression. Main analyses were performed in the evaluable population (completers only) and in sensitivity analyses, multiple imputation was performed to include data of participants lost to follow-up (intention-to-treat analyses). RESULTS A total of 1521 individuals were included (mean [SD] age, 65.3 [5.0] years; 52.1% men). In comparison with the control group (n=761), participants in the intervention arm (n=760) showed greater reductions in the percentage of total fat (between group differences after 1-year, −0.94% [95% CI, −1.19 to −0.69]; 3 years, −0.38% [95% CI, −0.64 to −0.12] and visceral fat storage after 1 year, -126 g [95% CI, −179 to −73.3 g]; 3 years, −70.4 g [95% CI, −126 to −15.2 g] and greater increases in the percentage of total lean mass at 1 year, 0.88% [95% CI, 0.63%-1.12%]; 3-years 0.34% [95%CI, 0.09%-0.60%]). The intervention group was more likely to show improvements of 5% or more in baseline body components (absolute risk reduction after 1 year, 13% for total fat mass, 11% for total lean mass, and 14% for visceral fat mass; after 3-years: 6% for total fat mass, 6% for total lean mass, and 8% for visceral fat mass). The number of participants needed to treat was between 12 and 17 to attain at least 1 individual with possibly clinically meaningful improvements in body composition. CONCLUSIONS AND RELEVANCE The findings of this trial suggest a weight-loss lifestyle intervention based on an energy-reduced MedDiet and physical activity significantly reduced total and visceral fat and attenuated age-related losses of lean mass in older adults with overweight or obesity and metabolic syndrome. Continued follow-up is warranted to confirm the long-term consequences of these changes on cardiovascular clinical end points.S
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