Growth and optical characterization of indirect-gap AlxGa1−xAs alloys

Nonintentionally doped AlxGa1−xAs layers with 0.38 x 0.84 were grown on (100) GaAs substrates by liquid phase epitaxy (LPE) under near-equilibrium conditions. The crystalline quality of the samples was studied by photoluminescence at 2 K and room temperature Raman spectroscopy. The peculiar behavior in the photoluminescence intensities of the indirect bound exciton line and the donor–acceptor pair transition is explained from the evolution of the silicon donor binding energy according to the aluminum composition. It was also possible to observe the excitonic transition corresponding to the AlxGa1−xAs/GaAs interface, despite the disorder and other factors which are normally involved when growing high-aluminum-content layers by this technique. Furthermore, Raman measurements show the quadratic variations of longitudinal optical phonon frequencies with aluminum concentration in good agreement with previous experimental results. In this work we show that high quality indirect-gap AlxGa1−xAs samples can be grown by LPE under near-equilibrium [email protected]

Visual impact produced by mining activity in the Punta Gorda ore body, Moa

Open-pit mining has adverse impacts on the landscape of the mining area. This article describes the visual impact resulting from surface mining activities being conducted in the Punta Gorda laterite ore body located in Moa. The implementation of the indirect method Bureau of Land Management by means of computer tools, such as Surfer 8.0, Didger 3.02, Gemcom 4.11, Autocad Civil 3d allowed the determination of visual landscape units and the main visual basins according to the method of selection used. This investigation also includes an analysis on the visual basin soil, color, texture and luminosity. Observation locations were selected based on their topographical characteristics or because of their being located in the highest altitudes. It was concluded that the visual impact of mining activities on the landscape investigated covers more than 50% of the visual basin. This research paves the way to a new field in the visual impact assessment of open-pit mining in Cuba. It constitutes a practical contribution providing information of interest on landscapes for the decision making associated with ore body management and planning and it stands out for being useful to ensure a successful mining and environmental planning of a region

Polipectomía gástrica por vía endoscópica

Se han extirpado 16 lesiones elevadas de estómago en 13 pacientes, 9 hombres y 5 mujeres, con edades entre 28 y 68 años, mediante la técnica de la polipectomía endoscópica, usando corriente de alta frecuencia. Las lesiones fueron clasificadas según el criterio de Yamada y el estudio histopatológico demostró: 10 pólipos hiperplásicos, 5 adenomatosos y 1 páncreas aberrante. La ulceración postpolipectomía cicatrizó entre 2 a 4 semanas y no se registraron complicaciones durante y después del procedimiento.