Microstructure evolution of GaN buffer layer on MgAl2O4 substrate

Microstructure of GaN buffer layer grown on (111)MgAl2O4 substrate by metalorganic vapor phase epitaxy (MOVPE) was studied by transmission electron microscopy (TEM). It has been observed that the early deposition of GaN buffer layer on the substrate at a relatively low temperature formed a continual island-sublayer (5 nm thick) with hexagonal crystallographic structure, and the subsequent GaN buffer deposition led to crystal columns which are composed of nano-crystal slices with mixed cubic and hexagonal phases. After high-temperature annealing, the crystallinity of nano-crystal slices and island-sublayer in the buffer layer have been improved. The formation of threading dislocations in the GaN him is attributed not only to the lattice mismatch of GaN/MgAl2O4 interface, but also to the stacking mismatches at the crystal column boundaries. (C) 1998 Published by Elsevier Science B.V. All rights reserved.

The thinking child resource book : brain-based learning for the early years foundation stage.

Ofrece a los profesores, estudiantes y padres, prácticas y sugerencias para la aplicación del aprendizaje, basado en cómo está configurado el cerebro del niño en sus primeros años de vida. Se enumeran ideas sobre cómo usar técnicas de aprendizaje que incluyen las formas de promover la autoestima y la inteligencia emocional, las ideas para la enseñanza a través del juego, música y movimiento, actividades para la hora de la asamblea, asesoramiento sobre el manejo de la conducta positiva y fomento de las relaciones con padres y cuidadores. Los estudios de casos, tomados de una variedad de entornos, dan una idea de cómo las técnicas basadas en el cerebro pueden ser utilizados para enriquecer la experiencia de aprendizaje de los niños pequeños.

Polishable and Renewable DNA Hybridization Biosensors

Routine applications of DNA hybridization biosensors are often restricted by the need for regenerating the single-stranded (ss) probe for subsequent reuse. This note reports on a viable alternative to prolonged thermal or chemical regeneration schemes through the mechanical polishing of oligonucleotide-bulk-modified carbon composite electrodes. The surface of these biocomposite hybridization biosensors can be renewed rapidly and reproducibly by a simple extrusion/polishing protocol. The immobilized probe retains its hybridization activity on confinement in the interior of the carbon paste matrix, with the use of fresh surfaces erasing memory effects and restoring the original target response, to allow numerous hybridization/measurement cycles. We expect that such reusable nucleic acid modified composite electrodes can be designed for a wide variety of biosensing applications.