Reactivity indexes for different geometries of palladium leads

Electronic transport through metallic break junctions or molecules is clearly dependent not only on the electronic structure of the central nanodevice connecting the leads, but also the shape and crystalline orientation of the contacts which can define the possible conduction channels. In this work we examine different geometries of contacts of palladium characterizing them through global and local reactivity indexes as electrophilicity, chemical hardness and Fukui functions. In molecules, these indicators are essentially defined by the energies of the frontier molecular orbitals and in solids they are related with the local and partial density of states. We use for this purpose an ab-initio based code (FIREBALL), applied to plane contacts with (001) fcc faces and also pyramidal tips grown following a (001) and (111) packaging. The results allow us to have an insight about the chemical features of this type of nanojunctions.Fil: Gómez Carrillo, Sandra Carolina. Universidad Nacional del Litoral. Facultad de Ingeniería Química. Departamento de Física; ArgentinaFil: Ortega, J.. Universidad Autónoma de Madrid; EspañaFil: Bolcatto, Pablo Guillermo. Universidad Nacional del Litoral; Argentin

Infinite-time concentration in aggregation-diffusion equations with a given potential

Typically, aggregation-diffusion is modeled by parabolic equations that combine linear or nonlinear diffusion with a Fokker-Planck convection term. Under very general suitable assumptions, we prove that radial solutions of the evolution process converge asymptotically in time towards a stationary state representing the balance between the two effects. Our parabolic system is the gradient how of an energy functional, and in fact we show that the stationary states are minimizers of a relaxed energy. Here, we study radial solutions of an aggregation-diffusion model that combines nonlinear fast diffusion with a convection term driven by the gradient of a potential, both in balls and the whole space. We show that, depending on the exponent of fast diffusion and the potential, the steady state is given by the sum of an explicit integrable function, plus a Dirac delta at the origin containing the rest of the mass of the initial datum. Furthermore, it is a global minimizer of the relaxed energy. This splitting phenomenon is an uncommon example of blow-up in inffinite time.Depto. de Análisis Matemático y Matemática AplicadaFac. de Ciencias MatemáticasFALSEUnión Europea. Horizonte 2020Ministerio de Ciencia e Innovación (MICINN)pu

Efectos moduladores de la personalidad y la valoración subjetiva en la respuesta autonómica ante una tarea de hablar en público

El objetivo de este estudio fue examinar en una muestra de 16 mujeres, el efecto los de rasgos de personalidad y la valoración subjetiva ante un estresor social de laboratorio (hablar en público) en la respuesta cardiovascular y electrodérmica. Se midieron las respuestas de conductancia de la piel, la frecuencia cardiaca (FC) y el volumen del pulso periférico (VPP) durante un periodo de descanso, preparación, tarea y recuperación ante un discurso académico. Los sujetos fueron clasificados según sus puntuaciones altas o bajas en el cuestionario de personalidad EPQ, el STAI y en las medidas subjetivas. Los sujetos mostraron un aumento de la activación fisiológica significativo durante las fases de preparación y ejecución del discurso, esta activación estuvo modulada por las variables de personalidad y la valoración subjetiva. Los sujetos más extrovertidos mostraron mayor frecuencia de respuestas electrodérmicas (RED) a lo largo de todo el registro. Los sujetos que percibieron la tarea como más difícil mostraron los valores más altos en frecuencia cardiaca. Por último, aquéllos que percibieron un mayor estrés y esfuerzo mostraron un porcentaje de cambio mayor en volumen de pulso. Estos resultados apoyan el uso de la tarea de hablar en público como un buen estresor de laboratorio y la importancia de la experiencia subjetiva y los rasgos de personalidad del individuo como variables que modulan dicha respuesta

Las mil y una noches. Español

En el texto impreso, página 7, figura "A la memoria del pensador poeta Stéfane Mallarmé esta obra que él tanto amaba. Enero 1899"

El Taiji Quan y Qigong en la promoción de la salud y en el afrontamiento del estrés

Exercise and physical activity improves psychological and physical health in users. However, rarely it is examined the quantitative effects of Tai Chi in cardiovascular, locomotor, mental, cognitive and psychosocial systems among others. The effects on stress, blood pressure and cardiopulmonary risk, breathing capacity and its impact on diseases of this system, balance, muscle elasticity on the locomotor system, anxiety, depression and disorders of systematically reviewed mood in both eastern and western populations. 53 studies were considered and 5875 subject were studied. Tai Chi appears to be associated with improvements in the vast majority of systems that analyze the authors but stresses the psychological well-being, including reducing stress, anxiety, depression and improvements to musculoskeletal level. Conclusion: these are limited due to variation in design, the various results and incorrect quality controls. Randomized trials are necessary to ensure the evidence.El ejercicio y la actividad física mejoran la salud psicológica y física de los usuarios. Sin embargo, pocas veces se han examinado los efectos cuantitativos del Tai Chi Chuan en los sistemas cardiovascular, locomotor, mental, cognitivo y psicosocial entre otros. Se revisaron sistemáticamente los efectos sobre el estrés, la presión arterial y el riesgo cardiopulmonar, la capacidad respiratoria y su incidencia sobre patologías de este sistema, el equilibrio, la elasticidad muscular sobre el sistema locomotor, la ansiedad, la depresión y trastornos del estado de ánimo en las poblaciones orientales y occidentales. Se han considerado 53 estudios con una muestra de 5.875 sujetos y 13 meta análisis. Hay que resaltar que el Tai Chi parece estar asociado con mejoras en la gran mayoría de los sistemas que analizan los autores pero destaca el bienestar psicológico, incluyendo la reducción del estrés, ansiedad, depresión así como las mejoras a nivel musculo esquelético. Las conclusiones definitivas son limitadas debido a la variación en los diseños, los resultados diversos y los controles incorrectos de calidad. Son necesarios más ensayos aleatorios que garanticen la evidencia

Influence of Boron, Tungsten and Molybdenum Modifiers on Zirconia Based Pt Catalyst for Glycerol Valorization

The influence of boron, tungsten and molybdenum modifiers on zirconia-based Pt catalyst was studied for glycerol valorization. Zirconia modified supports were prepared by impregnation of ZrO2 with either boric, silicontungstic or phosphomolybdic acids to obtain supports with enhanced Brönsted acidic properties. The modified supports were subsequently impregnated with chloroplatinic acid to obtain Pt-based catalysts. Pt incorporation resulted in the increase in Lewis acidity of the solids, being more significant for the Pt//W/ZrO2 catalyst. Reduced Pt catalysts were tested for the liquid-phase glycerol hydrogenolysis, observing a synergistic effect between catalyst acid sites and metal function that proved to be crucial in glycerol hydrogenolysis. The Pt//W/ZrO2 catalyst was the most active catalyst in this reaction, being the only leading to 1,3-PDO (45% sel., 160 °C) while Pt//Mo/ZrO2 is the best option for 1,2-PDO (49% sel., 180 °C). Reusability studies carried out for Pt//W/ZrO2 showed that catalytic activity dropped after the first use, remaining constant for the second and subsequent ones. Selectivity to reaction products also changes during reuses. Therefore, the selectivity to 1,2 PDO increases in the first reuse in detriment to the selectivity to n-propanol whereas the selectivity to 1,3-PDO remains constant along the uses. This behavior could be associated to the lixiviation of W species and/or catalyst fouling during reaction runs

Treatment of spent pickling baths coming from hot dip galvanizing by means of an electrochemical membrane reactor

The performance of a one (OCR) and a two-compartment electrochemical reactor in the presence of a cation-exchange membrane (CEM) for the zinc recovery present in the spent pickling baths is analyzed in this paper under galvanostatic control. These solutions, which mainly contain ZnCl2 and FeCl2 in aqueous HCl media, come from the hot dip galvanizing industry. The effect of the applied current, the dilution factor of the baths and the presence or absence of initial cathodic zinc is also studied. For the 1:50 diluted spent bath, OCR experiments initially present higher values of the figures of merit than those obtained in the presence of the CEM since zinc is close to the cathode from the first electrolysis instants. However, at long electrolysis times, OCR presents zinc redissolution for all the current values tested due to the chlorine and iron presence close to the zinc deposits. In addition, the iron codeposition phenomenon is also observed in the OCR experiments when pH values are close to 2. On the other hand, CEM experiments become very similar to the OCR experiments at long time values since the CEM under these experimental conditions prevents zinc redissolution phenomenon and also iron codeposition. When the 1:50 diluted bath is concentred to 1:10, OCR experiments present the same tendency as that observed for the 1:50 dilution factor but the effect of zinc redissolution is increased due to the greater amount of chlorine generated in the anode. Under these experimental conditions, iron deposition has also been observed in the presence of the cation-exchange membrane as the rate of zinc deposition is greater than that of zinc transport through the membrane, and the zinc/iron ratio in the cathodic compartment is not high enough to prevent iron codeposition. In both cases, the pH values when iron codeposits with zinc are close to 2 and the zinc/iron ratio is below 0.6. The presence of initial zinc in the cathodic compartment of the electrochemical reactor enhances the reactor performance since it allows the zinc–iron separation in one single step and avoids the zinc redissolution phenomenon.The authors want to express their gratitude to the Generalitat Valenciana for a postgraduate grant (GV/2010/029) and to the Ministerio de Economia y Competitividad for financing the project number CTQ2012-37450-C02-01/PPQ.Carrillo Abad, J.; García Gabaldón, M.; Pérez Herranz, V. (2014). Treatment of spent pickling baths coming from hot dip galvanizing by means of an electrochemical membrane reactor. Desalination. 343:38-47. https://doi.org/10.1016/j.desal.2013.11.040S384734

Study of the chlorfenvinphos pesticide removal under different anodic materials and different reactor configuration

The present manuscript focuses on the study of the electrochemical oxidation of the insecticide Chlorfenvinphos (CVP). The assays were carried out under galvanostatic conditions using boron-doped diamond (BDD) and lowcost tin dioxide doped with antimony (Sb-doped SnO2) as anodes. The influence of the operating variables, such as applied current density, presence or absence of a cation-exchange membrane and concentration of supporting electrolyte, was discussed. The results revealed that the higher applied current density the higher degradation and mineralization of the insecticide for both anodes. The presence of the membrane and the highest concentration of Na2SO4 studied (0.1 M) as a supporting electrolyte benefited the oxidation process of CVP using the BDD electrode, while with the ceramic anode the elimination of CVP was lower under these experimental conditions. Although the BDD electrode showed the best performance, ceramic anodes appear as an interesting alternative as they were able to degrade CVP completely for the highest applied current density values. Toxicity tests revealed that the initial solution of CVP was more toxic than the samples treated with the ceramic electrode, while using the BDD electrode the toxicity of the sample increased

Enhanced Atenolol oxidation by ferrites photoanodes grown on ceramic SnO2-Sb2O3 anodes

The increase in the consumption of pharmaceutical compounds has caused the increment of their presence in different body waters. β-blockers are one of the most dangerous even at low concentrations (ng L−1). Anodic oxidation with a boron-doped diamond (BDD) anode presents good results to remove these compounds. However, since this anode is expensive, some cheaper materials are under study. In this work, Sb-doped SnO2 ceramic anodes (BCE) coated with Zn or Cd ferrites, in order to provide photocatalytic properties, have been applied to the degradation of the Atenolol (ATL) β-blocker. Increasing the applied current increased ATL degradation and mineralization but caused a decrease in mineralization current efficiency (MCE) and an increase in energy consumption (ETOC). Additionally, light irradiation enhanced the ATL mineralization rate between 10% and 20% for both ferrites, although this increase was higher for the cadmium ferrite one. Finally, when the ferrites were compared with BDD and BCE anodes, the oxidizing power of the different anodic materials can be ordered as follows BDD> Cd-Fe> Zn-Fe> BCE. Therefore, both ferrites improved the BCE performance but only the cadmium one appeared as an alternative to the BDD, especially for MCE and ETOC, reaching values of 15% and 0.5 kWh gTOC−1, respectively