RESUMO
We report the observation of coupling of single InGaAs quantum dots with the surface plasmon resonance of a metal nanocrystal, which leads to clear enhancement of the photoluminescence in the spectral region of the surface plasmon resonance of the metal structures. Sharp emission lines, typical for single quantum dot emission, are observed, whereas for reference samples, only weak continuous background emission is visible. The composite metal-semiconductor structure is prepared by molecular beam epitaxy utilizing the principle of strain-driven adatom migration for the positioning of the metal nanocrystals with respect to the quantum dots without use of any additional processing steps.
RESUMO
The expression patterns of two true ras genes, Ppras1 and Ppras2and one rap gene, Pprap1were examined in four Physarum polycephalum developmental stages: uninucleate amoebae, plasmodia (multinucleate syncytia), spherules (a vegetative, dormant stage) and fruiting bodies. Ppras1 and Pprap1 are expressed in all stages examined with the maximum levels of their transcripts in amoebae and fruiting bodies, respectively, and the minimum levels in plasmodia, whereas the Ppras2 transcript is only detectable in amoebae and fruiting bodies. The results obtained indicate that P. polycephalum is an organism possessing a developmentally regulated ras gene family and presents a convenient system to study the role of ras/rap genes in control of growth and differentiation of lower eukaryotic organisms.Copyright 1997 Academic Press Limited Copyright 1997Academic Press Limited
RESUMO
The authors present the case of a 19 year old man with a continuous murmurin the right latero-thoracic region, with no functional symptomatology. Complementary examination demonstrated the presence of an angiomatosis which had developed at the expense of the right internal and external mammary vessels, and communicating with the pulmonary arterio-venous system.