Determining optimal conditions to produce activated carbon from barley husks using single or dual optimization.

When producing activated carbons from agricultural by-products, certain properties, such as yield and specific surface area, are very important for obtaining an economical and promising adsorbent material. Nevertheless, many researchers have not simultaneously optimized these properties and have obtained different optimal conditions for the production of activated carbon that either increases specific surface area but decreases yield or vice versa. In this research, the production of activated carbon from barley husks (BH) by chemical activation with zinc chloride was optimized by using a 2(3) factorial design with replicates at the central point, followed by a central composite design with two responses (the yield and iodine number) and three factors (the activation temperature, activation time, and impregnation ratio). Both responses were simultaneously optimized by using the desirability functions approach to determine the optimal conditions of this process. The findings reveal that after the simultaneous dual optimization, the maximal response values were obtained at an activation temperature of 436 °C, an activation time of 20 min, and an impregnation ratio of 1.1 g ZnCl2/g BH, although the results after the single optimization of each response were quite different. At these conditions, the predicted values for the iodine number and yield were 829.58 ± 78.30 mg/g and 46.82 ± 2.64%, respectively, whereas experimental tests produced values of 901.86 mg/g and 48.48%, respectively. Moreover, activated carbons from BH obtained at the optimal conditions primarily developed a porous structure (mesopores > 71% and micropores > 28%), achieving a high surface area (811.44 m(2)/g) that is similar to commercial activated carbons and lignocellulosic-based activated carbons. These results imply that the pore width and surface area are large enough to allow the diffusion and adsorption of pollutants inside the adsorbent particles. In summary, two responses were optimized to determine the optimal conditions for the production of activated carbons because it is possible to increase both the specific surface area and yield.

Experimental design for the optimization of copper biosorption from aqueous solution by Aspergillus terreus.

An experimental design methodology was applied to study the effects of temperature, pH, biomass dose, and stirring speed on copper removal from aqueous solutions by Aspergillus terreus in a biosorption batch system. To identify the effects of the main factors and their interactions on copper removal efficiency and to optimize the process, a full 2(4) factorial design with central points was performed. Four factors were studied at two levels, including stirring speed (50-150 min(-1)), temperature (30-50°C), pH (4-6) and biosorbent dose (0.01-0.175 g). The main factors observed were pH and biomass dose, along with the interactions between pH and biomass, and stirring speed. The optimal operational conditions were obtained using a response surface methodology. The adequacy of the proposed model at 99% confidence level was confirmed by its high adjusted linear coefficient of determination (R(Adj)(2)=0.9452). The best conditions for copper biosorption in the present study were: pH 6, biosorbent dose of 0.175 g, stirring speed of 50 min(-1) and temperature of 50°C. Under these conditions, the maximum predicted copper removal efficiency was 68.52% (adsorption capacity of 15.24 mg/g). The difference between the experimental and predicted copper removal efficiency at the optimal conditions was 4.8%, which implies that the model represented very well the experimental data.

Tratamiento endovascular de fístula arteriovenosa del muñón renal postnefrectomía con Amplatzer vascular plug II / Embolization of a postnephrectomy renal stump fistula with Amplatzer vascular plug II

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Una revisión de algunos autoinformes para la medida del constructo hostilidad/ira/agresión (HIA) / A brief review on the main selfreport instruments in measuring hostility

Los autoinformes son una parte crítica en el estudio de la relación entre enfermedad coronaria (EC) y el constructo hostilidad/ira/agresión (HIA); sin embargo, si echamos una ojeada a la literatura podemos observar que hay problemas especiales en la medida de este constructo, los cuales dificultan el estudio de dicha relación. Creemos que estos problemas pueden deberse en parte al desacuerdo existente con respecto a la terminología y formulación del constructo, pero también es posible que puedan ser atribuidos a la utilización de instrumentos sin que haya existido una comprobación previa de sus propiedades psicométricas. En la revisión de la literatura hemos encontrado referencia a un número relativamente elevado de autoinformes para la evaluación de este constructo, aunque no todos van a ser objeto de nuestra atención. En concreto, el objetivo de este trabajo es ofrecer una visión clara del estado actual de algunos de los instrumentos de medida del constructo HIA, intentando clarificar en qué grado esta serie de instrumentos son capaces de evaluar los diversos componentes que forman parte del constructo de acuerdo con criterios psicométricos adecuados (AU)