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By means of X-ray fluorescence (XRF), archaeological artifacts made of obsidian and obsidian geological samples were analyzed in order to determine their unknown origin. Obsidian is produced in volcanoes during the expulsion and rapid cooling of felsic lava with minimal crystal growth. The archaeological sampling sites are in the influence area of the San Agustin culture, specifically in the site known as Mesitas, located within the San Agustin Archaeological Park, in the Department of Huila, Colombia. The archaeological artifacts belong to the Early Formative, Middle Formative, Late Formative, Regional Classic and Recent periods of this culture. The outcrop and collection sites of the obsidian geological samples are located in five areas near the Colombian archaeological park and another one in the neighboring country of Ecuador. The results of this research indicate that the aboriginal population of the archaeological park did not use obsidian extracted from nearby geological zones. Consequently, the obsidian would have come from areas far from the park, as a result of trade exchanges with distant social groups that would have greater access to outcrops of these volcanic rocks. The results show the validity and reliability of the XRF as a methodology to support archaeological research. [ABSTRACT FROM AUTHOR]

Copyright of Bistua: Revista de la Facultad de Ciencias Básicas is the property of Facultad de Ciencias Basicas de la Universidad de Pamplona and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Innotec is the property of Laboratorio Tecnologico del Uruguay and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Geominas is the property of FUNDA-GEOMINAS. (Fundacion de Egresados d Amigos de la Escuela de Ingenieria Geologica y de Minas) and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Inventum. Ingenieria, Tecnologia e Investigacion is the property of Corporacion Universitaria Minuto de Dios and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

This study evaluates the effect of annealing on optical, structural, and morphological properties of poly (3-hexiltiofeno) (P3HT), methyl ester of phenyl-C61-butyric acid (PCBM), and (P3HT: PCBM) blend thin films grown on alkaline glass substrates by spin coating, varying temperature between 80 to 120 °C and the annealing time between 0 and 45 minutes. These properties were evaluated through absorbance, XRD, and fluorescence microscopy measurements. The study allowed to find the optimal annealing condictions (120 °C, 30 min) required to prepare PCBM:p3HT blends with the adequated properties to be used as active layer in organic solar cells fabricated with bulk heterojunction type structure. Under these conditions, the samples prepared present a preferential growth along the (001) plane, with high degree of crystollagraphic ordering, high absorbance in the visible region, and high density of PCBM/p3HT heterointerfaces. Fluorescence images performed with fluorescence microscopy, allowed us to study the effect of temperature and annealing time on the fluorescence of the p3HT:PCBM blend and its components; besides, we identified formation of micrometric fibers of PCBM at annealing temperatures greather than 120 °C. [ABSTRACT FROM AUTHOR]

Multi-walled carbon nanotubes were synthesized using methane as carbon source and Colombian natural limonite ore as catalyst precursor. Catalyst was evaluated in reduced form in the reaction decomposition of methane at 700°C. Multi walled carbon nanotubes were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), scanning electron microscopy (SEM) and thennogravimetric analysis (TGA). Finally, TEM micrographs showed that the MWCNTs have inner diameters ranging from 5 to 30 nm and outer diameters up to about 60 nm, and several microns in length. [ABSTRACT FROM AUTHOR]

Copyright of Revista ION is the property of Universidad Industrial de Santander and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

A model that describes the complementary agitation effect produced by the propagation of a mechanical pulses train through a viscous medium with the presence of crystals and its influence on operational and crystallization conductors is discussed. It was experimentally verified that the propagation of mechanical pulses of low frequency during the growth for cooling of suspensions of sucrose crystals in natural liquors, brings about a solution-crystal relative displacement that allows a considerable reduction in the formation of mother liquor inclusions, as well as the elimination of the formation of clusters and their adherence on the surface of heat exchange. It is also observed an improvement on the fluidity of the system that has a great impact on a heat transfer, a larger exhaustion of the liquors and, therefore, in [ABSTRACT FROM AUTHOR]

In order to improve the workability of alloys CuNiSiCr a study of the conditions of homogenizing heat treatment and assessed their behavior through mechanical tests traction. Standardized tests were conducted at 850, 950 and 1025°C with time-keeping 0, 1.5 and 6 hours and a subsequent double aged. It was observed that the optimum workability for the alloys occurs at the 850°C and 6 hours. This improvement in ductility is associated with the presence of a microstructure containing a small amount of discontinuous precipitates in limiting grain and rounded precipitates inside the grains. It is concluded that the homogenizing heat treatment is and adequate method to increase the workability of the alloy. [ABSTRACT FROM AUTHOR]

In this paper we study the dependence of magnetic Barkhausen noise (RMB) with the various microstructural parameters of the steel AISI / SAE 1005, 1020, 1045, 1070; Determining the dependence of various parameters of the signal RMB as are the power spectral density, the amplitude of the peak, the noise envelope and shape of the peaks of noise, with the size grain. Besides using a model to explain the dependence of the above parameters RMB with the grain size. [ABSTRACT FROM AUTHOR]

A deep study of the different equipment of clarification and crystallization areas on the process of a sugar cane factory is done, making a real comparation with standard equipment where the best efficiency indicators are obtained on such areas in the production process. On the basis of this study it is found that if the equipment installed is the one that is really needed for the process, alternatives are proposed in order to find out greater efficiency with cost reduction. In the crystallizators will be analyzed the crystallizator type, the staying time, principal constructive characteristics, possible alternatives for the diminishing of the staying time and greater amount of mixtures that allow better results. [ABSTRACT FROM AUTHOR]

Se considera un modelo para la optimización del tamaño de cristalización en una planta azucarera cubana. Se describen las características operativas que definen el modelo, se indican las condiciones que optimizan el proceso y se define un factor de corrección para lograr una mejor distribución de tamaños de cristales.

Se presenta un estudio de la naturaleza fractal de los patrones que se forman durante la electrodeposición del zinc. Se indica la dimensión fractal (Df) para las diversas concentraciones de solución de sulfato de zinc, valores de corriente y de voltaje. Se concluye que los resultados obtenidos concuerdan con el modelo DLA (Diffusion Limited Aggregation) de crecimiento de cristales