The dissociation of (a+c) misfit dislocations at the InGaN/GaN interface

In hexagonal materials, ( a+c ) dislocations are typically observed to dissociate into partial dislocations. Edge ( a+c ) dislocations are introduced into (0001) nitride semiconductor layers by the process of plastic relaxation. As there is an increasing interest in obtaining relaxed InGaN buffer layers for the deposition of high In content structures, the study of the dissociation mechanism of misfit ( a+c ) dislocations laying at the InGaN/GaN interface is then crucial for understanding their nucleation and glide mechanisms. In the case of the presented plastically relaxed InGaN layers deposited on GaN substrates, we observe a trigonal network of ( a+c ) dislocations extending at the interface with a rotation of 3° from <1 $\overline{1}$00> directions. High-resolution microscopy studies show that these dislocations are dissociated into two Frank–Shockley 1/6<2 $\overline{2}$03> partial dislocations with the I₁ BSF spreading between them. Atomistic simulations of a dissociated edge ( a+c ) dislocation revealed a 3/5-atom ring structure for the cores of both partial dislocations. The observed separation between two partial dislocations must result from the climb of at least one of the dislocations during the dissociation process, possibly induced by the mismatch stress in the InGaN layer.     

Metabolic Activation of Anthanthrene: Significance of Stable Radicals Derived from its Key Metabolite 3-Hydroxyanthanthrene

Anthanthrene (dibenzo[def,mno]chrysene), a hexacyclic aromatic hydrocarbon lacking the structural element of a bay-region is found to be metabolized to 3-hydroxyanthanthrene (3-HA) and anthanthrene 3,6-quinone by rat liver microsomes. Two further metabolites of anthanthrene are are also derived as metabolites of 3-HA. 3-HA forms stable radicals in the presence of horseradish peroxidase and hydrogen peroxide as revealed by electron spin resonance spectroscopy. These radical species which are also formed spontaneously from 3-HA could be responsible for the genotoxic properties of anthanthrene.     

Numerical investigation of transient current density distributions for multi-ion electrolytes at a rotating disk electrode

A versatile model for the simulation of transient multiion transport and reaction processes is applied to investigate current density distributions over a rotating disk electrode for linear voltammetric sweep experiments. The model accounts for ion transport by convection, diffusion, and migration, in combination with Butler-Volmer type electrode reactions. For several process conditions (reversible and irreversible reactions, excess or lack of supporting electrolyte), the current density distribution over the disk surface is examined and the transient current response is compared to results from the more commonly used one-dimensional axial approach. The impact of migrational effects on the nonuniform local process conditions over the disk surface is illustrated, and the resulting effect on the current peak height, width, and position is investigated. A mathematical correlation for the current peak height as a function of the reacting ion transference number is established.     

Structure and Activity of NADPH‐Dependent Reductase Q1EQE0 from Streptomyces kanamyceticus,which Catalyses the R‐Selective Reduction of an Imine Substrate

NADPH‐dependent oxidoreductase Q1EQE0 from Streptomyces kanamyceticus catalyzes the asymmetric reduction of the prochiral monocyclic imine 2‐methyl‐1‐pyrroline to the chiral amine (R)‐2‐methylpyrrolidine with >99 % ee, and is thus of interest as a potential biocatalyst for the production of optically active amines. The structures of Q1EQE0 in native form, and in complex with the nicotinamide cofactor NADPH have been solved and refined to a resolution of 2.7 Å. Q1EQE0 functions as a dimer in which the monomer consists of an N‐terminal Rossman‐fold motif attached to a helical C‐terminal domain through a helix of 28 amino acids. The dimer is formed through reciprocal domain sharing in which the C‐terminal domains are swapped, with a substrate‐binding cleft formed between the N‐terminal subunit of monomer A and the C‐terminal subunit of monomer B. The structure is related to those of known β‐hydroxyacid dehydrogenases, except that the essential lysine, which serves as an acid/base in the (de)protonation of the nascent alcohol in those enzymes, is replaced by an aspartate residue, Asp187 in Q1EQE0. Mutation of Asp187 to either asparagine or alanine resulted in an inactive enzyme.     

Development of a product model for specifying new lines of seafood products

New product development in the seafood industries is increasingly based on extension of product lines. These must be tailored to the retailer and customer needs and be available with short lead-times. One possibility for seafood companies to meet this challenge is to utilise the benefits and prospects of an IT approach to product modelling. The approach used is developed for non-food specification tasks and coupled with the experience gained in a seafood company. IT application prototype that consisted mainly of earlier product solutions and knowledge related to the specification tasks was developed. Testing of the prototype has indicated possibilities for speeding up the specification process in the company and it is assumed that similar results can be obtained in other food product development processes.     

High resolution mapping of surface reduction in ceria nanoparticles

Surface reduction of ceria nano octahedra with predominant {111} and {100} type surfaces is studied using a combination of aberration-corrected Transmission Electron Microscopy (TEM) and spatially resolved electron energy-loss spectroscopy (EELS) at high energy resolution and atomic spatial resolution. The valency of cerium ions at the surface of the nanoparticles is mapped using the fine structure of the Ce M(4,5) edge as a fingerprint. The valency of the surface cerium ions is found to change from 4+ to 3+ owing to oxygen deficiency (vacancies) close to the surface. The thickness of this Ce(3+) shell is measured using atomic-resolution Scanning Transmission Electron Microscopy (STEM)-EELS mapping over a {111} surface (the predominant facet for this ceria morphology), {111} type surface island steps and {100} terminating planes. For the {111} facets and for {111} surface islands, the reduction shell is found to extend over a single fully reduced surface plane and 1-2 underlying mixed valency planes. For the {100} facets the reduction shell extends over a larger area of 5-6 oxygen vacancy-rich planes. This finding provides a plausible explanation for the higher catalytic activity of the {100} surface facets in ceria.     

Etching Effect on CMP of Different GaN Layers

Chemical mechanical polishing (CMP) was used to etch various GaN materials, such as GaN layers on sapphire and silicon carbide substrates grown by metal-organic chemical vapor deposition and thick GaN layers grown by physical vapor transport. It was found that CMP could reveal the dislocations in GaN surfaces due to a selective etching component. After the optimization of CMP condition, the surface finish improved and the subsurface damage was almost completely removed, demonstrated by atomic force microsco...     

Agglomeration dynamics of business services

An important characteristic of the economic development in Europe and North America during the last few decades is a fast expansion of the business-service sector. The present paper aims at modeling the location dynamics of three categories of firms: (i) knowledge-intensive business-service firms, (ii) ordinary business-service firms and other firms, where the latter form the rest of the economy. In the theoretical framework, business-service firms have random-choice preferences and respond in a non-linear way to time distances in their contact efforts to customer firms. Business-service firms make their location decisions in response to local, intra-regional and extra-regional access to market demand. The econometric analysis makes use of information about time distances between zones in urban areas as well as between urban areas in the same agglomeration and between urban areas in different agglomerations. The empirical analysis shows how the number of jobs in the different sectors change in response to accessibility to purchasing power. The estimation results show that the change processes feature non-linear dependencies with varying spatial reach.     

Analytic modelling and optimization of slip synchronous permanent magnet wind turbine generator topologies

The modular slip‐synchronous permanent magnet generator (SSPMG) is viewed as an induction‐synchronous machine pair that is electromagnetically decoupled by a free‐rotating rotor that in turn houses two different sets of permanent magnets. This machine pair combines the advantages of both conventional induction and permanent magnet synchronous machines. It therefore has the potential to realize a new path in reliable, robust and cost‐effective wind turbine drivetrains. However, which electromagnetic SSPMG topology is best and how does it compare with conventional drivetrain designs for various capacities? To date, the most published SSPMG advances are specific to winding design, torque quality and performance optimization in the small capacity range. This paper presents optimized analytic electrical designs of modular, radially and axially separable, radial flux SSPMG topologies of capacities ranging from 100 kW to 5 MW. Designs are based on lumped analytic models and are optimized for minimum specific active mass (mass/torque). A rated efficiency of 95 % and an inductive power factor of 0.95 are applied to all designs. The analytic models are validated with transient two‐dimensional finite element analysis results. The best SSPMG topologies are determined and compared with conventional drivetrain designs. The axially separable topology seems to be the best SSPMG design. Copyright © 2014 John Wiley & Sons, Ltd.     

Effect of Carbon‐Based Materials on the Early Hydration of Tricalcium Silicate

Two types of carbon‐based materials, i.e., mesoporous carbon and HNO₃‐oxidized carbon nanotubes, with nearly the same specific surface area and abundant in surface oxygen‐containing functional groups were selected in order to examine their effect on the hydration of tricalcium silicate (C₃S), the main portland cement component, in early stages. Different methods, including XPS and TG‐MS analyses, electrokinetic potential measurements, as well as determination of adsorption capacity for calcium ions from aqueous solutions, were used to investigate the physicochemical surface properties of the selected carbon‐based materials. It was found that the carbon‐based materials with high specific surface area and rich in oxygen‐containing functional groups on their surfaces have a catalytic effect on early C₃S hydration. It was observed that the modification of C₃S paste with the selected materials added in high concentrations (1 wt% and higher) led to an increase in the rate and degree of C₃S hydration in the early stages. The mechanism of early C₃S hydration accelerated by carbon‐based materials rich in surface functional groups was clarified by the example of the mesoporous carbon. It was found that the oxygen‐containing functional groups present on the carbon surface have both an influence on the content of calcium ions in the aqueous phase of the C₃S paste and an indirect positive effect in relation to the specific surface of C₃S.