The initial stages of GaAs overgrowth over self-assembled coherently strained InAs quantum dots (QDs) are studied. For small GaAs coverages (below 5 nm), atomic force microscopy (AFM) images show partially covered island structures with a regular size distribution which are elongated in the [011] direction. Analysis of the AFM profiles show that a large anisotropic redistribution of the island material is taking place during the initial GaAs overgrowth. Short time annealing experiments together with photoluminescence spectroscopy on annealed QDs are consistent with a Ga and In intermixing during the overgrowth. Surface QDs capped with 5 nm or more GaAs show a strong luminescence intensity indicating that surface QDs are remarkably insensitive to surface recombination effects.
Two novel P450 cDNAs, CYP6A36 and CYP6A37, were isolated from house-flies. Putative protein sequences deduced from the cDNA sequences shared 58% identity. Predicted protein sequences of CYP6A36 and CYP6A37 from pyrethroid-resistant ALHF house-flies were identical to their corresponding orthologues in susceptible aabys flies. Expression of CYP6A36 was developmentally regulated with significant overexpression in ALHF compared with susceptible CS flies. Overexpression of CYP6A36 was detected in ALHF abdomen, where the primary detoxification organs of the midgut and fat body are located. CYP6A37, however, was expressed in all tested life stages, with no significant difference in expression between ALHF and CS. Genetic linkage analysis located CYP6A36 on autosome 5; overexpression of CYP6A36 was linked to the factors on autosomes 1 and 2, corresponding to the linkage of P450-mediated resistance in ALHF. This evidence suggests the importance of CYP6A36 in detoxification of insecticides and evolution of insecticide resistance in ALHF.
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