Cubic and hexagonal InGaAsN dilute arsenides by unintentional homogeneous incorporation of As into InGaN

Arsenic alloying is observed for epitaxial layers nominally intended to be In0.75Ga0.25N. Voids form beneath their interfaces with GaAs substrates, acting as sources of Ga + As out-diffusion into the growing epilayers. As a result, heteroepitaxial single-phase quaternary InxGa1-xAsyN1-y, films are formed with x similar to 0.55 and 0.05 menor que y menor que 0,10. While an undoped epilayer retains the wurtzite structure, a Mn-doped sample showed randomly spaced dopant segregations, which, together with a slightly higher As concentration, led to a transformation from the hexagonal to the twinned cubic phase.

Thermal diffusion profile by NRA of Deuterium implanted in solid breeder blanket materials

This paper studies the relationship between aging, physical changes and the results of non-destructive testing of plywood. 176 pieces of plywood were tested to analyze their actual and estimated density using non-destructive methods (screw withdrawal force and ultrasound wave velocity) during a laboratory aging test. From the results of statistical analysis it can be concluded that there is a strong relationship between the non-destructive measurements carried out, and the decline in the physical properties of the panels due to aging. The authors propose several models to estimate board density. The best results are obtained with ultrasound. A reliable prediction of the degree of deterioration (aging) of board is presented. Breeder blanket materials have to produce tritium from lithium while fulfilling several strict conditions. In particular, when dealing with materials to be applied in fusion reactors, one of the key questions is the study of light ions retention, which can be produced by transmutation reactions and/or introduced by interaction with the plasma. In ceramic breeders the understanding of the hydrogen isotopes behaviour and specially the diffusion of tritium to the surface is crucial. Moreover the evolution of the microstructure during irradiation with energetic ions, neutrons and electrons is complex because of the interaction of a high number of processes.

Rhizobium leguminosarum HupE is a highly-specific diffusion facilitator for nickel uptake

Bacteria require nickel transporters for the synthesis of Ni-containing metalloenzymes in natural, low nickel habitats. In this work we carry out functional and topological characterization of Rhizobium leguminosarum HupE, a nickel permease required for the provision of this element for [NiFe] hydrogenase synthesis. Expression studies in the Escherichia coli nikABCDE mutant strain HYD723 revealed that HupE is a medium-affinity permease (apparent Km 227 ! 21 nM; Vmax 49 ! 21 pmol Ni2+ min"1 mg"1 bacterial dry weight) that functions as an energy-independent diffusion facilitator for the uptake of Ni(II) ions. This Ni2+ transport is not inhibited by similar cations such as Mn2+, Zn2+, or Co2+, but is blocked by Cu2+. Analysis of site-directed HupE mutants allowed the identification of several residues (H36, D42, H43, F69, E90, H130, and E133) that are essential for HupE-mediated Ni uptake in E. coli cells. By using translational fusions to reporter genes we demonstrated the presence of five transmembrane domains with a periplasmic N-terminal domain and a C-terminal domain buried in the lipid bilayer. The periplasmic N-terminal domain contributes to stability and functionality of the protein