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Electronic Structure and Optical Properties of Silicon Nanocrystals along their Aggregation Stages

The structural control of silicon nanocrystals is an important technological problem. Typically a distribution of nanocrystal sizes and shapes emerges under the uncontrolled aggregation of smaller clusters. The aim of this computational study is to investigate the evolution of the nanocrystal electronic states and their optical properties throughout their aggregation stages. To realistically tackle such systems, an atomistic electronic structure tool is required that can accommodate about tens of thousand nanocrystal and embedding lattice atoms with very irregular shapes. For this purpose, a computationally-efficient pseudopotential-based electronic structure tool is developed that can handle realistic nanostructures based on the expansion of the wavefunction of the aggregate in terms of bulk Bloch bands of the constituent semiconductors. With this tool, the evolution of the electronic states as well as the polarization-dependent absorption spectra correlated with the oscillator strengths over their aggregation stages are traced. The low-lying aggregate nanocrystal states develop binding and anti-binding counterparts of the isolated states. Such information may become instrumental with the maturity of the controlled aggregation of these nanocrystals.Comment: 5 pages, 7 figure

Pedagogical participatory experiences to promote Public Interest Technology from volunteer work

Public Interest Technologies allow practices and learning opportunities for the sustainable improvement of living conditions. Our analysis of participatory pedagogical experiences, from the perspective of student volunteer tourism, adds elements to this emerging field of study by analyzing the steps, main opportunities, and challenges as a basis for the implementation of PIT in higher education. In six case studies, students from the Northern hemisphere reached out to vulnerable communities in Lima (Peru) through universities and local NGOs, in events ranging from welfarism to co-design and participation. Experiences of Practice Based Education promoted direct interaction with different local realities, enhancing communication, socialization and empathy, key skills in the training of a new generation of professionals that will work in the implementation of new inclusive and participatory policies in our communities. Technology becomes an ally of processes once trust has been consolidated, seeking sustainability in the public interest

Plants rustication in a solar greenhouse

La producción por propagación agámica o asexual mediante estacas semileñosas se realiza tradicionalmente en dos etapas, una destinada al enraizamiento y la otra al fortalecimiento radicular y crecimiento de la planta en condiciones próximas al aire libre. Este método presenta un bajo porcentaje de sobrevivencia, menor que el 45 %, debido especialmente al cambio brusco de hábitat que sufren las estacas. La solución que se propone es la incorporación un invernadero de plástico acondicionado térmicamente con energía solar como etapa intermedia del sistema de producción, para favorecer la adaptación del plantón, disminuir el estrés térmico y su estadía en la casa de vegetación (enraizamiento). El sistema se basa principalmente en colectar la radiación solar incidente y extraer el excedente de calor del aire del invernadero durante el día, para acumularlo y usarlo en el momento que sea necesario para calentar el aire y el suelo del mismo. En el presente trabajo se analizan los resultados experimentales y de la simulación numérica del sistema en pleno funcionamiento, utilizando una analogía térmica - eléctrica y el programa para resolución de circuitos eléctricos SCEPTRE. La desviación promedio diaria de la temperatura del aire interior al mismo fue de 1,4 °C con un error relativo promedio de 8,3 %. Se han logrado niveles de energía suficiente para asegurar un nivel térmico adecuado a las necesidades de las plantas para los días con condiciones climáticas típicas de la zona. Desde el punto de vista agronómico los resultados fueron muy satisfactorios lográndose un 100 % de sobrevivencia, una alta tasa de crecimiento y un material vegetal de excelente calidad.Production by agamic or asexual propagation using cuttings is traditionally carried out in two stages, one for rooting, and the other for root strengthening and plant growing in the open air. This method has a low percentage of survival. To reduce thermal stress and the period of staying in the vegetation house the present work proposed an intermediate step to facilitate the planton adaptation. The system is mainly based on collecting solar incident radiation and extracting air heating surplus in the greenhouse during the day and use it when necessary to heat the air and soil in the greenhouse. Experimental results and numeric simulation are analyzed using thermo – electric analogy and the program for electric circuit resolution SCEPTRE. Daily mean deviation of air temperature within the greenhouse was 14° C with a relative error average of 8.3%.. From the agronomic point of view, results were very satisfactory.Fil: Iriarte, Adolfo Antonio. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Salta. Instituto de Investigaciones en Energía no Convencional. Universidad Nacional de Salta. Facultad de Ciencias Exactas. Departamento de Física. Instituto de Investigaciones en Energía no Convencional; ArgentinaFil: Saravia Mathon, Luis Roberto. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Salta. Instituto de Investigaciones en Energía no Convencional. Universidad Nacional de Salta. Facultad de Ciencias Exactas. Departamento de Física. Instituto de Investigaciones en Energía no Convencional; ArgentinaFil: Matias, C.. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Salta. Instituto de Investigaciones en Energía no Convencional. Universidad Nacional de Salta. Facultad de Ciencias Exactas. Departamento de Física. Instituto de Investigaciones en Energía no Convencional; ArgentinaFil: Tomalino, L.. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Salta. Instituto de Investigaciones en Energía no Convencional. Universidad Nacional de Salta. Facultad de Ciencias Exactas. Departamento de Física. Instituto de Investigaciones en Energía no Convencional; Argentin

The Present and Future of Academical Dress in Spain: Catalogue of Guidelines on the Use of Academical Dress and its Colours in Spanish Universities

The Association for the Study of University Protocol, founded in 1997, brings together professionals in Spanish universities who are responsible for the organization of academic ceremonies, university traditions, as well as the new activities derived from those traditions which maintain the university in its place. In the course of the activities of the Association it soon became apparent that it was necessary to understand with the greatest possible degree of accuracy ways in which academical dress was used and that it was important to establish a catalogue of suggestions on its use and of the current use of colours. The fruits of this labour, co-ordinated by the authors of this article, were elaborated in such a Catalogue. [Excerpt from Introduction]

Study of adsorption process of iron colloid substances on activated carbon by ultrasound

The paper reports on the adsorption of iron colloid substances on activated carbon (PAC) Norit SA UF with using ultrasound. It is found that time of adsorption is equal to three hours. High-frequency electrical oscillation is 35 kHz. The adsorption capacity of activated carbon was determined and it is equal to about 0.25 mg iron colloid substances /mg PAC. The iron colloid substances size ranging from 30 to 360 nm was determined. The zeta potential of iron colloid substances which consists of iron (III) hydroxide, silicon compounds and natura organic substances is about (-38mV). The process of destruction iron colloid substances occurs with subsequent formation of a precipitate in the form of Fe(OH)[3] as a result of the removal of organic substances from the model solution

Setaria pflanzii Pensiero

El Cevilar (al norte de El Salvador-CIMBOC)publishedVersio

Estudio geométrico de un concentrador solar térmico de reflector lineal fijo

This paper addresses a new research line in which a solar thermal concentrator fixed linear reflector with mobile absorber develops. In this publication the geometric optical study of two types of reflectors, realized through ray tracing analysis. This allowed to find the advantages and disadvantages of each of the options to define the final configuration, as well as determine the focal length (f) and aperture (w) of the reflector. It was built a prototype for optical testing which allowed to determine the system behavior at different angles of incident radiation.Se está presentando una nueva línea de trabajo abordada por el equipo de investigación en la cual se desarrolla un concentrador solar térmico de reflector lineal fijo con absorbedor móvil. En esta publicación se describe el estudio óptico geométrico de dos tipos de reflectores para el sistema, realizado a través del análisis de la marcha de rayos. Este permitió encontrar las ventajas y desventajas de cada una de las opciones para definir la configuración final del concentrador, como así también determinar la distancia focal (f) y la apertura (w) del reflector. Se construyó el prototipo sobre el cual se realizaron ensayos ópticos, que permitieron determinar el comportamiento del sistema frente a distintos ángulos de radiación incidente.Tema 3: Energía solar, aplicaciones térmicas y químicas.Facultad de Arquitectura y Urbanism

Estudio geométrico de un concentrador solar térmico de reflector lineal fijo

This paper addresses a new research line in which a solar thermal concentrator fixed linear reflector with mobile absorber develops. In this publication the geometric optical study of two types of reflectors, realized through ray tracing analysis. This allowed to find the advantages and disadvantages of each of the options to define the final configuration, as well as determine the focal length (f) and aperture (w) of the reflector. It was built a prototype for optical testing which allowed to determine the system behavior at different angles of incident radiation.Se está presentando una nueva línea de trabajo abordada por el equipo de investigación en la cual se desarrolla un concentrador solar térmico de reflector lineal fijo con absorbedor móvil. En esta publicación se describe el estudio óptico geométrico de dos tipos de reflectores para el sistema, realizado a través del análisis de la marcha de rayos. Este permitió encontrar las ventajas y desventajas de cada una de las opciones para definir la configuración final del concentrador, como así también determinar la distancia focal (f) y la apertura (w) del reflector. Se construyó el prototipo sobre el cual se realizaron ensayos ópticos, que permitieron determinar el comportamiento del sistema frente a distintos ángulos de radiación incidente.Tema 3: Energía solar, aplicaciones térmicas y químicas.Facultad de Arquitectura y Urbanism