Sol-Gel Process for Making Pt-Ru Fuel-Cell Catalysts

A sol-gel process has been developed as a superior alternative to a prior process for making platinum-ruthenium alloy catalysts for electro-oxidation of methanol in fuel cells. The starting materials in the prior process are chloride salts of platinum and ruthenium. The process involves multiple steps, is time-consuming, and yields a Pt-Ru product that has relatively low specific surface area and contains some chloride residue. Low specific surface area translates to incomplete utilization of the catalytic activity that might otherwise be available, while chloride residue further reduces catalytic activity ("poisons" the catalyst). In contrast, the sol-gel process involves fewer steps and less time, does not leave chloride residue, and yields a product of greater specific area and, hence, greater catalytic activity. In this sol-gel process (see figure), the starting materials are platinum(II) acetylacetonate [Pt(C5H7O2)2, also denoted Pt-acac] and ruthenium(III) acetylacetonate [Ru(C5H7O2)3, also denoted Ru-acac]. First, Pt-acac and Ru-acac are dissolved in acetone at the desired concentrations (typically, 0.00338 moles of each salt per 100 mL of acetone) at a temperature of 50 C. A solution of 25 percent tetramethylammonium hydroxide [(CH3)4NOH, also denoted TMAH] in methanol is added to the Pt-acac/Ruacac/ acetone solution to act as a high-molecular-weight hydrolyzing agent. The addition of the TMAH counteracts the undesired tendency of Pt-acac and Ru-acac to precipitate as separate phases during the subsequent evaporation of the solvent, thereby helping to yield a desired homogeneous amorphous gel. The solution is stirred for 10 minutes, then the solvent is evaporated until the solution becomes viscous, eventually transforming into a gel. The viscous gel is dried in air at a temperature of 170 C for about 10 hours. The dried gel is crushed to make a powder that is the immediate precursor of the final catalytic product. The precursor powder is converted to the final product in a controlled-atmosphere heat treatment. Desirably, the final product is a phase-pure (Pt phase only) Pt-Ru powder with a high specific surface area. The conditions of the controlled- atmosphere heat are critical for obtaining the aforementioned desired properties. A typical heat treatment that yields best results for a catalytic alloy of equimolar amounts of Pt and Ru consists of at least two cycles of heating to a temperature of 300 C and holding at 300 C for several hours, all carried out in an atmosphere of 1 percent O2 and 99 percent N2. The resulting powder consists of crystallites with typical linear dimensions of <10 nm. Tests have shown that the powder is highly effective in catalyzing the electro-oxidation of methanol

Internet y conducta sexual de riesgo para VIH/SIDA en jóvenes

Objective: To determine whether the use of online sexual material influences sexual risk behavior for HIV / AIDS in young university students. Concepts of Social Cognitive Theory were used.Enfermería Global Nº 38 Abril 2015 Página 138Methods: A descriptive correlational design, involving 200 university students selected by systematic random sampling (k = 11).Results: Young people who used sexual material online rich media to masturbation (rs =.34), arousal (rs = 29), stimulation (rs = 29), adventure (rs = 30), meeting people (rs =.27), images (rs =.17) and cybersex (rs =.25) showed greater sexual risk behavior for HIV / AIDS (p &lt;.01). The use of sexual material online for masturbation (R2 = 6.4%, F [1,189] = 12.80, p &lt;.001), seeking adventures (R2 = 4.8%, F [1,189] = 9.56, p &lt;.01), meeting people (R2 = 5.9%, F [1,189] = 11.88, p &lt;.01) and have cybersex (R2 = 4.1%, F [1,189] = 8.07, p &lt;.01) had a significant positive effect on behavior sexual risk for HIV/AIDS.Conclusions: The use of online sexual material influences sexual risk behavior for HIV/AIDS.Objetivo: Determinar si el uso de material sexual en línea influye en la conducta sexual de riesgo para VIH/SIDA en los jóvenes universitarios. Se utilizaron conceptos de la Teoría Cognitiva Social.Método: Diseño descriptivo correlacional, participaron 200 jóvenes universitarios, seleccionados por muestreo aleatorio sistemático (k = 11).Resultados: Los jóvenes que usaron material sexual en línea en medios ricos para masturbarse (rs = .34), excitarse (rs = .29), estimularse (rs = .29), buscar una aventura (rs = .30), conocer gente (rs = .27), imágenes (rs = .14) y cibersexo (rs = .25) mostraron mayor conducta sexual de riesgo para VIH/SIDA (p &lt; .01). El uso de material sexual en línea para masturbarse (R2 = 6.4%, F [1,189] = 12.80, p &lt; .001), buscar una aventura (R2 = 4.8%, F [1,189] = 9.56, p &lt; .01), conocer gente (R2 = 5.9%, F [1,189] = 11.88, p &lt; .01) y tener cibersexo (R2 = 4.1%, F [1,189] = 8.07, p &lt; .01) presentó un efecto positivo y significativo en la conducta sexual de riesgo para VIH/SIDA.Conclusiones: El uso de material sexual en línea influye en la conducta sexual de riesgo para VIH/SIDA

Funcionando con la computadora

En este trabajo se presenta la descripción y resultados de la segunda etapa de una experiencia planteada con el objetivo de indagar la manera en que los alumnos determinan e interpretan funciones que explican situaciones problemáticas valiéndose de una nueva forma de trabajo en el aula: la utilización de la computadora como herramienta y un programa asistente matemático. La primera etapa consistió en el desarrollo de un taller optativo con alumnos de entre 14 y 15 años de edad del Colegio Dr. Arturo Illia de la Universidad Nacional de Mar del Plata (Argentina) y sus conclusiones fueron expuestas en el trabajo “FUNCIONando con la computadora. Una experiencia con un asistente matemático” en RELME 16

Técnica didáctica "Normas de convivencia" para disminuir la agresividad escolar, Institución Educativa Leoncio Prado, Chachapoyas, 2015.

La presente investigación surge a partir de la observación reiterada de conductas agresivas en educandos de una institución educativa ubicada en zona periférica de Chachapoyas; planteándose como objetivo, evaluar los efectos que produce la técnica didáctica "Normas de convivencia" en la disminución de la agresividad de los educandos del primer grado de la institución educativa Leoncio Prado de Chachapoyas; siendo la hipótesis: si se experimenta la técnica didáctica "Normas de convivencia", entonces disminuye significativamente la agresividad en los educandos del primer grado de la Institución Educativa Leoncio Prado de Chachapoyas en un determinado período del año 2015; se trabajó con una muestra de 08 educandos. El tipo de investigación es del nivel pre experimental, con diseño de pre test y post test con un solo grupo, en la recolección de datos se utilizó como técnica descriptiva e instrumento tipo lista de cotejo. La metodología en el proceso de investigación se ha basado en el método científico, en términos de paradigmas se ha empleado el análisis cuali-cuantitativo. Sin embargo, para la sistematicidad de la técnica se ha empleado el método de investigación propio de ciencias sociales integrado por tres procedimientos: abstracción, concretización progresiva y verificación. Los resultados del pre test permiten apreciar que un 75 y 25% de estudiantes muestran conductas de agresividad psicológica severa y significativa respectivamente; mientras que en el post test un 37,5 y 62.5% de los educandos muestran conductas agresivas psicológicas, mínima y moderada; en cuanto a agresividad física, en el pre test, el 50% de educandos presentaron agresividad significativa y ell2.5%, agresividad severa; en el post test, se aprecia que el 37.5% demuestran agresividad física mínima y el 62,5% lograron superar las conductas agresivas físicas. Los resultados permiten afirmar que la técnica didáctica "Normas de convivencia" disminuye significativamente las conductas agresivas psicológica y física.Tesi

Positive Ecological Interactions and the Success of Seagrass Restoration

Seagrasses provide multiple ecosystem services including nursery habitat, improved water quality, coastal protection, and carbon sequestration. However, seagrasses are in crisis as global coverage is declining at an accelerating rate. With increased focus on ecological restoration as a conservation strategy, methods that enhance restoration success need to be explored. Decades of work in coastal plant ecosystems, including seagrasses, has shown that positive species relationships and feedbacks are critical for ecosystem stability, expansion, and recovery from disturbance. We reviewed the restoration literature on seagrasses and found few studies have tested for the beneficial effects of including positive species interactions in seagrass restoration designs. Here we review the full suite of positive species interactions that have been documented in seagrass ecosystems, where they occur, and how they might be integrated into seagrass restoration. The few studies in marine plant communities that have explicitly incorporated positive species interactions and feedbacks have found an increase in plant growth with little additional resource investment. As oceans continue to change and stressors become more prevalent, harnessing positive interactions between species through innovative approaches will likely become key to successful seagrass restoration

Positive ecological interactions and the success of seagrass restoration

Seagrasses provide multiple ecosystem services including nursery habitat, improved water quality, coastal protection, and carbon sequestration. However, seagrasses are in crisis as global coverage is declining at an accelerating rate. With increased focus on ecological restoration as a conservation strategy, methods that enhance restoration success need to be explored. Decades of work in coastal plant ecosystems, including seagrasses, has shown that positive species relationships and feedbacks are critical for ecosystem stability, expansion, and recovery from disturbance. We reviewed the restoration literature on seagrasses and found few studies have tested for the beneficial effects of including positive species interactions in seagrass restoration designs. Here we review the full suite of positive species interactions that have been documented in seagrass ecosystems, where they occur, and how they might be integrated into seagrass restoration. The few studies in marine plant communities that have explicitly incorporated positive species interactions and feedbacks have found an increase in plant growth with little additional resource investment. As oceans continue to change and stressors become more prevalent, harnessing positive interactions between species through innovative approaches will likely become key to successful seagrass restoration