In addition, samples for which a magnesium precursor flux had been present during the coalescence of the GaN stripes also exhibited p-type doping. From an analysis of the spatial distribution of the unintentional doping in the ELOG material, it has been possible to propose that the incorporation of the n-type dopant was slower on the (0001) facet than the 11 (2) over bar2 facets. This facet dependent difference in incorporation rates also helps to explain the nonuniformity in thickness of n-type conductive layers seen at the GaN/sapphire interface when a three-dimensional,growth
mode is employed in the early stages of growth. (C) 2009 American Institute of Physics. [doi: 10.1063/1.3259379]“
“Oxidation of dopamine to aminochrome seems to be a normal process leading LDK378 supplier to aminochrome polymerization to form neuromelanin, since normal individuals have this pigment in their dopaminergic neurons in the substantia nigra. The neurons lost in individuals with
Parkinson’s disease are dopaminergic see more neurons containing neuromelanin. This raises two questions. First, why are those cells containing neuromelanin lost in this disease? Second, what is the identity of the neurotoxin that induces this cell death? We propose that aminochrome is the agent responsible for the death of dopaminergic neurons containing neuromelanin in individuals with Parkinson’s disease. The normal oxidative pathway of dopamine, in which aminochrome polymerizes to form neuromelanin, can be neurotoxic if DT-diaphorase selleck is inhibited under certain conditions. Inhibition of DT-diaphorase allows two neurotoxic reactions to proceed: (i) the
formation of aminochrome adducts with alpha-synuclein, which induce and stabilize the formation of neurotoxic protofibrils; and (ii) the one electron reduction of aminochrome to the neurotoxic leukoaminochrome o-semiquinone radical. Therefore, we propose that DT-diaphorase is an important neuroprotective enzyme in dopaminergic neurons containing neuromelanin.”
“Nanoparticles of tin dioxide embedded in silica matrix were synthesized by ion implanting a Sn+ ion beam in a silica slide and by annealing, in oxidizing atmosphere at 800 degrees C. A detailed structural and optical characterization was performed by using glancing incidence x-ray diffraction, transmission electron microscopy, optical absorption, and photoluminescence spectroscopies. Metallic tetragonal, beta-tin crystalline nanoparticles were formed in the as-irnplanted sample. The annealing in oxidizing atmosphere promotes the total oxidation of the tin nanoparticles with a preferential migration of the nanoparticles toward the surface of the matrix. A broad blue-violet emission band peaked at 388 nm was observed in the photoluminescence spectra of both the as-implanted and annealed samples, which was attributed to the Sn-related oxygen deficiency center defects and the SnO2 nanoparticles, respectively. (C) 2009 American Institute of Physics. [doi: 10.1063/1.