Tungsten-Based Composites for Nuclear Fusion Applications

This chapter provides a comprehensive knowledge about the potential role of tungsten-based composites in fusion reactors and the research work which has been done in this very important area of nuclear materials. The characteristics of tungsten, which make it the most potential candidate for plasma-facing applications, have been presented along with the shortcomings in pure tungsten. The research work that has been done so far in the field of tungsten-based composites to overcome the problems with pure tungsten has been included. The fabrication, characterization, types of reinforcements and the classes of composites have been reviewed. The behavior of tungsten-based composites under various kinds of loads (i.e. mechanical and thermal) and environments (radiations and oxidizing etc.) has been summarized

Introduction

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Vertically aligned InGaN nanowires with engineered axial In composition for highly efficient visible light emission.

We report on the fabrication of novel InGaN nanowires (NWs) with improved crystalline quality and high radiative efficiency for applications as nanoscale visible light emitters. Pristine InGaN NWs grown under a uniform In/Ga molar flow ratio (UIF) exhibited multi-peak white-like emission and a high density of dislocation-like defects. A phase separation and broad emission with non-uniform luminescent clusters were also observed for a single UIF NW investigated by spatially resolved cathodoluminescence. Hence, we proposed a simple approach based on engineering the axial In content by increasing the In/Ga molar flow ratio at the end of NW growth. This new approach yielded samples with a high luminescence intensity, a narrow emission spectrum, and enhanced crystalline quality. Using time-resolved photoluminescence spectroscopy, the UIF NWs exhibited a long radiative recombination time (τr) and low internal quantum efficiency (IQE) due to strong exciton localization and carrier trapping in defect states. In contrast, NWs with engineered In content demonstrated three times higher IQE and a much shorter τr due to mitigated In fluctuation and improved crystal quality

Molecular cloning and biochemical characterization of a novel erythrose reductase from Candida magnoliae JH110

<p>Abstract</p> <p>Background</p> <p>Erythrose reductase (ER) catalyzes the final step of erythritol production, which is reducing erythrose to erythritol using NAD(P)H as a cofactor. ER has gained interest because of its importance in the production of erythritol, which has extremely low digestibility and approved safety for diabetics. Although ERs were purified and characterized from microbial sources, the entire primary structure and the corresponding DNA for ER still remain unknown in most of erythritol-producing yeasts. <it>Candida magnoliae </it>JH110 isolated from honeycombs produces a significant amount of erythritol, suggesting the presence of erythrose metabolizing enzymes. Here we provide the genetic sequence and functional characteristics of a novel NADPH-dependent ER from <it>C. magnoliae </it>JH110.</p> <p>Results</p> <p>The gene encoding a novel ER was isolated from an osmophilic yeast <it>C. magnoliae </it>JH110. The ER gene composed of 849 nucleotides encodes a polypeptide with a calculated molecular mass of 31.4 kDa. The deduced amino acid sequence of ER showed a high degree of similarity to other members of the aldo-keto reductase superfamily including three ER isozymes from <it>Trichosporonoides megachiliensis </it>SNG-42. The intact coding region of ER from <it>C. magnoliae </it>JH110 was cloned, functionally expressed in <it>Escherichia coli </it>using a combined approach of gene fusion and molecular chaperone co-expression, and subsequently purified to homogeneity. The enzyme displayed a temperature and pH optimum at 42°C and 5.5, respectively. Among various aldoses, the <it>C. magnoliae </it>JH110 ER showed high specific activity for reduction of erythrose to the corresponding alcohol, erythritol. To explore the molecular basis of the catalysis of erythrose reduction with NADPH, homology structural modeling was performed. The result suggested that NADPH binding partners are completely conserved in the <it>C. magnoliae </it>JH110 ER. Furthermore, NADPH interacts with the side chains Lys252, Thr255, and Arg258, which could account for the enzyme's absolute requirement of NADPH over NADH.</p> <p>Conclusions</p> <p>A novel ER enzyme and its corresponding gene were isolated from <it>C. magnoliae </it>JH110. The <it>C. magnoliae </it>JH110 ER with high activity and catalytic efficiency would be very useful for <it>in vitro </it>erythritol production and could be applied for the production of erythritol in other microorganisms, which do not produce erythritol.</p