Effect of creep deformation on oxidation behavior of nickel‐based alloy with Re‐based diffusion barrier coating

Oxidation and creep behaviors of a Ni‐Mo‐based alloy (Hastelloy‐X) with a diffusion barrier coating consisting of duplex, inner Re‐based alloy, and outer β‐NiAl layers were investigated at 1243 K in air with an external tensile stress of 22.5 MPa. For comparison the alloys, as‐received, heat treated, and with the Ni‐aluminide coating, were oxidized under creep deformation. Creep rapture time for the diffusion barrier‐coated alloy was longer than those for the bare alloy and with the β‐NiAl‐coated alloy. After creep deformation to a strain of 3.5% for 190 h, it was found that the Re‐based alloy layer has few cracks and flaws and the β‐NiAl layer has the similar structure and composition before and after the creep test. The external scale mainly consisted of θ‐Al₂O₃ at the early stage of creep, and with further oxidation the external scale became a duplex layer, inner, equi‐axed α‐Al₂O₃, and outer, plate‐like θ‐Al₂O₃, which exfoliated significantly. It was concluded that the Re‐based alloy layer acts effectively as a barrier against inward Al diffusion and outward diffusion of alloy elements under creep deformation.     

Perioperative management for partial resection of a lymphangioma of the tongue

Twelve month old boy had been suffering from a neck lymphangioma. Partial resection was carried out in his newborn period at another hospital, and he was obliged to be tracheostomied because of severe airway obstruction due to postoperative edema. He was scheduled for partial glossectomy since his tongue had increased in mass, which could easily be injured by teeth, and he had difficulties in swallowing recently. His airway was not obstructive even during sleep and preoperative MRI showed adequate space around the larynx. We induced anesthesia by a mask and he was subseqently intubated with a fiberscope via his nose because his huge and less mobile tongue could not allow the insertion of a laryngoscope and this might cause bleeding. We did not extubate the endotracheal tube for fear of airway obstruction attributable to postoperative edema. Marked edema around the neck persisted longer than we expected. We tried to evaluate the degree of diminution of edema with MRI twice to decide when extubation could be attempted. However, examination with MRI could not give us useful informations. Consequently we evaluated the timing of extubation by examining whether he could close his mouth or not, whether his tongue could move freely and the degree of edema. We realized lymphangioma caused marked and extensive edema after the operation and we should keep in mind that lymphangioma of the tongue might cause various anesthetic problems especially on airways.     

Calcium Signaling and Meiotic Exit at Fertilization in Xenopus Egg

Calcium is a universal messenger that mediates egg activation at fertilization in all sexually reproducing species studied. However, signaling pathways leading to calcium generation and the mechanisms of calcium-induced exit from meiotic arrest vary substantially among species. Here, we review the pathways of calcium signaling and the mechanisms of meiotic exit at fertilization in the eggs of the established developmental model, African clawed frog, Xenopus laevis. We also discuss calcium involvement in the early fertilization-induced events in Xenopus egg, such as membrane depolarization, the increase in intracellular pH, cortical granule exocytosis, cortical contraction, contraction wave, cortical rotation, reformation of the nuclear envelope, sperm chromatin decondensation and sister chromatid segregation.     

Efficient cleavage of RNA at high temperatures by a thermostable DNA-linked ribonuclease H

To construct a DNA-linked RNase H, which cleaves RNA site-specificallyat high temperatures, the 15-mer DNA, which is complementaryto the polypurine-tract sequence of human immunodeficiency virus-1RNA (PPT-RNA), was cross-linked to the unique thiol group ofCys135 in the Thermus thermophilus RNase HI variant. The resultantDNA-linked enzyme (d15-C135/TRNH), as well as the d15-C135/ERNH,in which the RNase H portion of the d15-C135/TRNH is replacedby the Escherichia coli RNase HI variant, cleaved the 15-merPPT-RNA site-specifically. The mixture of the unmodified enzymeand the unlinked 15-mer DNA also cleaved the PPT-RNA but ina less strict manner. In addition, this mixture cleaved thePPT-RNA much less effectively than the DNA-linked enzyme. Theseresults indicate that the cross-linking limits but acceleratesthe interaction between the enzyme and the DNA/RNA substrate.The d15-C135/TRNH cleaved the PPT-RNA more effectively thanthe d15-C135/ERNH at temperatures higher than 50°C. Thed15-C135/TRNH showed the highest activity at 65°C, at whichthe d15-C135/ERNH showed little activity. Such a thermostableDNA-linked RNase H may be useful to cleave RNA molecules withhighly ordered structures in a sequence-specific manner.     

Novel isoflavone diglycoside in groundnut (Apios americana Medik)

In the present HPLC-based analysis of the isoflavone profile of groundnut (Apios americana Medik) tubers, we identified a major peak that did not correspond to any known isoflavones. A water extract of groundnut tubers prepared at 4 °C showed the major and genistin peaks, whereas that prepared at 45 °C did not yield these peaks but showed a peak for genistein on HPLC analysis. When the extract was treated with β-glucosidase after the inactivation of endogenous enzymes, the major peak decreased over time and the genistin peak also decreased after a transient increase, changes which were accompanied by the appearance of a genistein peak. The HPLC elution pattern of the β-glucosidase-treated extract was markedly similar to that observed for the extract prepared at 45 °C.     

Succession of a microbial community during stable operation of a semi-continuous garbage-decomposing system

The microbial community in a garbage-decomposing system was analyzed using denaturing gradient gel electrophoresis (DGGE) on the basis of 16S rDNA. The system treated 1 kg of garbage everyday for two months at ambient temperature with almost constant decomposition efficiency, although a transient pH increase occurred. Succession of the banding pattern of the DGGE profile suggested that the bacterial community was not directly affected by the continuous addition of non-sterilized garbage into the open system, but changed with the fluctuation of pH. These resistance and resilience characteristics of the community structure may be effective to keep the decomposition efficiency stable. The analyses of the DNA sequences from the DGGE bands suggested the existence of uncultured or novel bacteria as well as Lactobacillus sp., Corynebacterium spp., Enterococcus spp., and Staphylococcus sp. A specific PCR detection was performed to evaluate the existence of Escherichia coli within the community. E. coli 16S rDNAs were not detected from the decomposing system.     

Improvement of thermal efficiency and reduction of NOx emissions by burning a controlled jet plume in high-pressure direct-injection hydrogen engines

A new combustion process called the Plume Ignition Combustion Concept (PCC), in which the plume tail of the hydrogen jet is spark-ignited immediately after the completion of fuel injection to accomplish combustion of a rich mixture has been proposed by the authors. This PCC combustion process markedly reduces nitrogen oxides (NOx) emissions in the high-output region while maintaining high levels of thermal efficiency and power. On the other hand, as burning lean mixture of fuel and air is the conventional way to improve thermal efficiency and reduce NOx, a high λ premixed mixture of hydrogen and air formed by injecting hydrogen in the early stage of the compression stroke has been used in direct-injection hydrogen engines. It was recently reported, however, that this mixture condition does not always offer expected improved thermal efficiency under even lean mixture conditions by increasing unburned hydrogen emissions caused by incomplete flame propagation in the non-uniform and extremely lean portion of the mixture. In this study, the effect of retarding the injection timing to late in the compression stroke but slightly advanced from original PCC was examined as a way of reducing unburned hydrogen emissions and improving thermal efficiency. These effects result from a centroidal axially stratified mixture that positions a fairly rich charge near the spark plug. This stratified mixture is presumably effective in reducing incomplete flame propagation thought to be the cause of unburned hydrogen emissions and also promoting increasing burning velocity of the mixture that improve thermal efficiency. Finally, this research is characterized by measuring the hydrogen fuel concentration at the point and the time of spark ignition quantitatively by spark-induced breakdown spectroscopy in order to identify the changes in mixture ratio mentioned above caused by the parameters involved.     

Development of series of gateway binary vectors, pGWBs, for realizing efficient construction of fusion genes for plant transformation

We developed a new series of binary vectors useful for Gateway cloning to facilitate transgenic experiments in plant biotechnology. The new system, Gateway Binary Vectors (pGWBs) realized efficient cloning, constitutive expression using the cauliflower mosaic virus (CaMV) 35S promoter and the construction of fusion genes by simple clonase reaction with an entry clone. The reporters employable in this system are beta-glucuronidase (GUS), synthetic green fluorescent protein with S65T mutation (sGFP), luciferase (LUC), enhanced yellow fluorescent protein (EYFP), and enhanced cyan fluorescent protein (ECFP). The tags available are 6xHis, FLAG, 3xHA, 4xMyc, 10xMyc, GST, T7-epitope, and tandem affinity purification (TAP). In total, 13 kinds of reporter or tag were arranged and were almost applicable to both N- and C-fusions. The pGWBs could be used for many purposes, such as promoter::reporter analysis, observation of subcellular localization by the expression of proteins fused to a reporter or tag, and analysis of protein-protein interaction by copurification and immunodetection experiments. The pGWBs were constructed with modified pBI101 containing a CaMV35S promoter-driven hygromycin phosphotransferase (HPT) gene as the second selection marker. We also constructed pGWBs with the marker HPT driven by the nopaline synthase promoter. By using the pGWB system, the expression of tagged proteins, and the localization of GFP-fused proteins were easily analyzed. Moreover, tissue-specific and inducible gene expression using a promoter was also monitored with pGWBs. It is expected that, the pGWB system will serve as a powerful tool for plasmid construction in plant research.