978 resultados para Horizontal wells


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This paper discusses the theoretical and experimental results obtained for the excitonic binding energy (Eb) in a set of single and coupled double quantum wells (SQWs and CDQWs) of GaAs/AlGaAs with different Al concentrations (Al%) and inter-well barrier thicknesses. To obtain the theoretical Eb the method proposed by Mathieu, Lefebvre and Christol (MLC) was used, which is based on the idea of fractional-dimension space, together with the approach proposed by Zhao et al., which extends the MLC method for application in CDQWs. Through magnetophotoluminescence (MPL) measurements performed at 4 K with magnetic fields ranging from 0 T to 12 T, the diamagnetic shift curves were plotted and adjusted using two expressions: one appropriate to fit the curve in the range of low intensity fields and another for the range of high intensity fields, providing the experimental Eb values. The effects of increasing the Al% and the inter-well barrier thickness on E b are discussed. The Eb reduction when going from the SQW to the CDQW with 5 Å inter-well barrier is clearly observed experimentally for 35% Al concentration and this trend can be noticed even for concentrations as low as 25% and 15%, although the Eb variations in these latter cases are within the error bars. As the Zhao's approach is unable to describe this effect, the wave functions and the probability densities for electrons and holes were calculated, allowing us to explain this effect as being due to a decrease in the spatial superposition of the wave functions caused by the thin inter-well barrier. © 2013 Elsevier B.V.

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Informe de reunion sobre cooperacion horizontal en administracion de recursos hidricos en America Latina y el Caribe. Contiene: organizacion de los trabajos, resumen de los debates, resultado de los debates de los Grupos de Trabajo y conclusiones y recomendaciones.

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Aim To compare the effect of recombinant human bone morphogenetic protein-2 (rhBMP-2) in an absorbable collagen sponge carrier (ACS) with autogenous bone graft for augmentation of the edentulous atrophic anterior maxilla. Methods Twenty-four subjects were enrolled in a randomized, controlled, parallel-group, open-label clinical trial. Subjects either received rhBMP-2/ACS (1.5 mg/ml) or particulated autogenous bone harvested from the mandibular retromolar region. A titanium-mesh was used to provide space and wound stability. A guide was used to standardize clinical recordings using an analogue caliper. Alveolar ridge width was also assessed using cone-beam computed tomography. Results rhBMP-2/ACS yielded significantly greater radiographic horizontal bone gain compared with autogenous bone graft at immediate subcrestal levels (1.5 ± 0.7 versus 0.5 ± 0.9 mm; p = 0.01); non-significant differences were observed at mid- (2.9 ± 0.8 versus 2.9 ± 0.9 mm; p = 0.98) and apical (1.7 ± 0.9 versus 1.8 ± 1.1 mm; p = 0.85) crestal levels. No significant differences in clinical horizontal bone gain were observed at 6 months between rhBMP-2/ACS and autogenous bone graft (3.2 ± 0.9 mm versus 3.7 ± 1.4 mm; p = 0.31). Sixty-two implants were placed after 6 month of healing with no significant differences between groups for number of implants, implant size, primary stability and survival. Conclusions rhBMP-2/ACS appears a realistic alternative for augmentation of the edentulous atrophic anterior maxilla. © 2013 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd.

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Se refiere a las actividades que sirven de antecedente a las actuales iniciativas de la CEPAL en el Caribe; describe los objetivos y el alcance de la cooperación horizontal; examina la experiencia del Caribe en materia de cooperación horizontal en el sector del agua potable y del saneamiento ambiental, y sobre esa base, identifica para el Caribe las principales consideraciones relativas al fortalecimiento de la cooperación técnica y económica en el sector.

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Se refiere a las actividades que sirven de antecedente a las actuales iniciativas de la CEPAL en el Caribe; describe los objetivos y el alcance de la cooperación horizontal; examina la experiencia del Caribe en materia de cooperación horizontal en el sector del agua potable y del saneamiento ambiental, y sobre esa base, identifica para el Caribe las principales consideraciones relativas al fortalecimiento de la cooperación técnica y económica en el sector.

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Presenta proyectos de cooperacion horizontal para el desarrollo del sector minero-metalurgico propuestos por Argentina, Bolivia, Colombia, Ecuador, Guatemala, Panama, Paraguay, Peru y Republica Dominicana, los cuales han sido clasificados en proyectos de caracter regional o subregional y en proyectos de caracter multinacional.

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Pós-graduação em Ciências Sociais - FFC