Genomics of industrial Aspergilli and comparison with toxigenic relatives

Aspergillus oryzae has been used in Japanese fermentation industries for more than a thousand years. The species produces large amounts of various hydrolytic enzymes and has been successfully applied to modern biotechnology. The size of the A. oryzae genome (37.5 Mb) is very close to that of A. flavus and A. niger, and 20-30% larger than that of either A. nidulans or A. fumigatus. A. oryzae and A. flavus have exactly the same number of aspartic proteinase genes, of which each orthologous pair shares highly conserved amino acid sequences. Synteny analysis with A. fumigatus and A. nidulans showed that the A. oryzae genome has a mosaic structure consisting of syntenic and non-syntenic blocks. In the microorganisms to be compared, the density of the genes having homologs was obviously higher on the syntenic than on the non-syntenic blocks. Expression analysis by the DNA microarray supported the significantly lower expression of genes on the non-syntenic than on the syntenic blocks.     

Corrosion evaluation of Au-Cu-Pd ternary alloys

The corrosion resistivity of single-phase Au-Cu-11 at% Pd alloys was evaluated by using a parameterQ which represented the total amount of anodic reaction in a potentiostatic polarization test. The result was compared with those for binary Au-Cu, ternary Au-Cu-11 at % Ag and some commercial alloys. The validity of usingQ as a corrosion parameter was confirmed by the good agreement between the analysed and calculated values of copper ion dissolved into the test solution. By replacing a part of the copper in Au-Cu alloys with palladium the corrosion resistivity can be greatly improved, but silver has no such significant effect. The value ofQ decreased by both treatments of homogenization and grain refinement of the alloy. One of the advantages of the alloy having a single-phase structure is that inhomogeneity in the distribution of the constituents is small even in the as-cast state, which results in a small galvanic effect.     

Characteristics including electron velocity overshoot for0.1-μm-gate-length GaAs SAINT MESFET's

Short-channel effects, substrate leakage current, and average electron velocity are investigated for 0.1-μm-gate-length GaAs MESFETs fabricated using the SAINT (self-aligned implantation for n⁺-layer technology) process. The threshold-voltage shift was scaled by the aspect ratio of the channel thickness to the gate length ( a/L_g). The substrate leakage current in a sub-quarter-micrometer MESFET is completely suppressed by the buried p layers and shallow n⁺-layers. The average electron velocity for 0.1- to 0.2-μm-gate-length FETs is estimated to be 3×10⁶ cm/s from the analysis of intrinsic FET parameters. This high value indicates electron velocity overshoot. Moreover, a very high f_T of 93.1 GHz has been attained by the 0.1-μm SAINT MESFET     

On a fast reactor cycle scheme that incorporates a thoria-based minor actinide-containing cermet fuel

A fast reactor cycle scheme that incorporates a thoria-based minor actinide-containing cermet fuel is given. The present cermet fuel consists of an oxide solid solution of Th and minor actinides and Mo-inert matrix. It has been proposed as a high-performance device that can enhance minor actinide incineration in a fast reactor cycle. It is used in an independent small sub-cycle, whereby dedicated cycle technologies are adopted. Two-step reprocessing process was proposed for the present cermet fuel; it consists of a pre-removal of Mo-inert matrix and an actinide recovery. A preliminary test for the pre-removal of Mo-inert matrix was carried out using a surrogate cermet fuel. Burnup characteristics of a fast reactor core loaded with the cermet fuel were investigated by using neutronic calculation codes. It was revealed that a heterogeneous composition of Mo-inert matrix in inner and outer cores may lead to an effective transmutation of minor actinides and a flattened power density. It was concluded that the present cermet fuel was potentially promising as a high-performance incineration device of minor actinides for fast reactors.     

Molecular characterization of Xenopus embryo heparan sulfate. Differential structural requirements for the specific binding to basic fibroblast growth factor and follistatin

Enzymatic elimination of heparan sulfate (HS) causes abnormal mesodermal and neural formation in Xenopus embryos, and HS plays an indispensable role in establishing the embryogenesis and tissue morphogenesis during early Xenopus development (Furuya, S., Sera, M., Tohno-oka, R., Sugahara, K., Shiokawa, K., and Hirabayashi, Y. (1995) Dev. Growth Differ. 37, 337-346). In this study, HS was purified from Xenopus embryos to investigate its disaccharide composition and binding ability to basic fibroblast growth factor (bFGF) and follistatin (FS), the latter being provided in two isoforms with core sequences of 315 and 288 amino acids (designated FS-315 and FS-288) originating from alternative mRNA splicing. Disaccharide composition analysis of the purified Xenopus HS showed the preponderance of a disulfated disaccharide unit with uronic acid 2-O-sulfate and glucosamine 2-N-sulfate, which has been implicated in the interactions with bFGF. Specific binding of the HS to bFGF and FS-288, the COOH-terminal truncated form, was observed in the filter binding assay, whereas HS did not bind to FS-315, indicating that the acidic Glu-rich domain of FS-315 precluded the binding. The binding of the HS to bFGF or FS-288 was markedly inhibited by heparin (HP) and various HS preparations, but not by chondroitin sulfate, supporting the binding specificity of HS. The binding specificity was further investigated using FS-288 and bovine intestinal [3H]HS. Competitive inhibition assays of the HS binding to FS-288 using size-defined HP oligosaccharides revealed that the minimum size required for significant inhibition was a dodecasaccharide, which is larger than the pentasaccharide required for bFGF binding. The binding affinity of FS to HS increased in the presence of activin, a growth/differentiation factor, which could be inactivated by direct binding to FS. These results, taken together, indicate that the structural requirement for binding of HS to bFGF and FS is different. HS may undergo dynamic changes in its structure during early Xenopus embryogenesis in response to the temporal and spatial expression of various growth/differentiation factors.     

Microstructural change of ultrafine-grained aluminum during high-speed plastic deformation

Effect of strain rate on microstructural change in deformation of the ultrafine grained (UFG) aluminum produced by severe plastic deformation (SPD) was studied. Commercial purity 1100 aluminum sheets were highly strained up to an equivalent strain of 4.8 by the Accumulative Roll-Bonding (ARB) process at ambient temperature. The ARB-processed sheets were found to be filled with pancake-shaped ultrafine grains surrounded by high-angle grain boundaries. The ultrafine grains had a mean grain thickness of 200 nm and a mean grain length of 1100 nm. The ultrafine-grained aluminum sheets were deformed at various strain rates ranging from 2 to 6.0×10⁴ s⁻¹ by conventional rolling, ultra-high-speed rolling, and impact compression. High-speed plastic deformation generates a large amount of heat, inducing coarsening of the ultrafine grains during and after deformation. On the other hand, it was also suggested that high-speed plastic deformation is effective for grain-subdivision, in other words, ultra-grain refinement, if the effect of heat generation is extracted.