The mechanism of the anodic formation of S2O2−8 ions on a Ti-supported IrO2 electrode in mixed aqueous solutions of H2SO4, (NH4)4SO4 and NH4F

The mechanism for the anodic formation of peroxydisulfate ion on a Ti-supported IrO₂ electrode was investigated in mixed aqueous solutions of H₂SO₄, (NH₄)SO₄ and NH₄F.Peroxydisulfate ion can be formed in higher yield at lower overpotential on the Ti-supported IrO₂ electrode, compared with smooth Pt electrode. The most probable mechanism under Langmuir conditions of intermediate adsorption was proposed as

     

Effect of heat treatment of ti substrate on service life of ti-supported IrO2 electrode in mixed aqueous solutions of H2SO4, (NH4)2SO4 and NH4F

The effect of the heat treatment of Ti substrate on the service life of Ti-supported IrO₂ electrode was investigated in mixed aqueous solutions of H₂SO₄, (NH₄)₂SO₄ and NH₄F. The service life was prolonged by the heat treatment of Ti substrate prior to the coating of IrO₂. Such effect was attributed to the increase in thickness of TiO₂ layer existing at the Ti/IrO₂ interface.     

Hot Isostatic Processing of Shocked Si3N4 Powder

To enhance the sinter ability of Si₃N₄, powders mixed with 0, 2, and 5 wt% Y₂O₃ were explosively shock-treated. Compacts of these powders were encapsulated in 96% silica glass containers and isostatically hot-pressed. The shocked Si₃N₄ with 5 wt% Y₂O₃ was pressed to a density of 3.09 g/cm³ (95.4% of theoretical) at 1400°C under 430 MPa for 3 h, whereas the unshocked material attained only 82.4% of theoretical density under the same hot isostatic pressing conditions.     

Diagnostic system to measure spatial and temporal profiles of shock front using compact two-stage light-gas gun and line reflection method

A diagnostic system has been developed to obtain spatial and temporal profiles of shock front. A two-stage light-gas gun is used to accelerate impactors in velocity range with 4-9 km/s. The system consists of the Faraday-type electromagnetic sensors to measure impactor velocity, optical system with high-speed streak camera to measure shock-wave velocities, and the delay trigger system with self-adjustable pre-event pulse generator. We describe the specifications and performance of this system and data-analysis technique on the tilt and distortion of the shock front. Finally, we obtained the Hugoniot data of copper for system demonstration.     

Loss analysis of permanent magnet synchronous machines by considering circulating currents of armature windings

In this paper, we investigate the losses caused by circulating currents generated in armature windings of permanent magnet synchronous machines by using electromagnetic field analysis. In the analysis, each parallel connected wire in the windings is modeled by finite elements in order to consider the difference in the electromotive forces and the generation of the circulating currents. The calculated losses are compared with experimental results. It is clarified that the armature copper loss in permanent magnet machines with parallel connected wires considerably increases by the circulating currents.     

Blue Color Formation of Cyanobacteria with β-Cyclocitral

Volatile compounds, such as β-cyclocitral, geosmin, and 2-methylisoborneol, from cyanobacteria showed a lytic activity against cyanobacteria. Particularly, β-cyclocitral caused an interesting color change in the culture broth from green to blue during the lysis process. In the present study, the lytic behavior of various cyanobacteria with β-cyclocitral was investigated, and a mechanism for the blue color formation was developed. β-Cyclocitral lysed both the laboratory strains of any genera and bloom samples including many species of cyanobacteria, and caused the characteristic color change from green to blue. β-Cyclocitral provided a characteristic behavior, such that the absorption maxima of chlorophyll-a and β-carotene disappeared, but that of phycocyanin still remained after 12 h, which indicated that β-cyclocitral decomposed chlorophyll-a and β-carotene rapidly, so that the inherent colors from the tolerant water-soluble pigments became observable in the cultured broth. This phenomenon was confirmed by another experiment using Phormidium (NIES-611), which showed a pink color derived from phycoerythrin. β-Cyclocitral was more easily oxidized when compared with similar aldehyde compounds, so that the pH of the solution quickly decreased to 4.5. An oxidation product of β-cyclocitral in water solution was isolated and identified as 2,6,6-trimethylcyclohexene-1-carboxylic acid. This study provides support that β-cyclocitral derived from cyanobacteria plays an important role in the lysis of cyanobacteria and participates in the blue color formation under natural conditions.     

Lantibiotics: insight and foresight for new paradigm

Lantibiotics are a unique type of antimicrobial peptide produced by a large number of gram-positive bacteria that contain unusual amino acids, such as lanthionine and dehydrated amino acids. Ribosomally synthesized lantibiotic prepeptide consists of an N-terminal leader peptide followed by a C-terminal propeptide moiety that undergoes several post-translational modification events to yield a biologically active lantibiotic. Research on lantibiotics has drawn much attention in recent years and has undergone extensive progress as a step forward to the next paradigm. Unusual amino acids in lantibiotics solely contribute to their biological activity and also enhance their structural stability. Thus, enzymes involved in lantibiotic biosynthesis would have a high potential for peptide engineering by introducing unusual amino acids into desired peptides, which may establish a universal approach to advance the structural design of novel peptides, termed lantibiotic engineering. In this review, we focus on recent development with contemporary innovations and perspective of lantibiotic research.     

A novel approach to practical matrix converter motor drive system with reverse blocking IGBT

This paper proposes a novel control strategy and a protection circuit and shows the advantage of utilizing a newly developed reverse blocking insulated gate bipolar transistor (RB-IGBT), to solve several practical problems of the matrix converter. The proposed control strategy is based on a virtual indirect control method with a virtual rectifier and a virtual inverter. Pulse-width modulated (PWM) pulses for the matrix converter are obtained by combining PWM pulses for the virtual rectifier and inverter. As a result, the control part of the input current and output voltage can be clearly separated. Thus, the conventional inverter control algorithms can be applied to the virtual inverter control. The advantage of this method is confirmed by experimental results with a 22-kW induction motor drive system. Good sinusoidal waveforms are obtained for the input and output currents, and the total harmonic distortion (THD) of the input and output current are 5.1% and 1.4%, respectively. The conduction loss of the RB-IGBT is decreased to about two-thirds of the conventional ac switch with series connection diode. Thus, the converter loss is about a half to the conventional PWM rectifier-inverter system with the same capacity. Furthermore, the protection problem is solved by a dynamic clamp method without an electrolytic capacitor. This protection circuit directly dissipates reactive load energy by dynamic clamp operation of an IGBT.     

Significant increase in recombinant protein production of a virus-infected Sf-9 insect cell culture of low MOI under low dissolved oxygen conditions

Spodoptera frugiperda Sf-9 insect cells were infected with recombinant Autographa californica nuclear polyhedrosis virus at a low multiplicity of infection (MOI) (0.1), and the effect of dissolved oxygen (DO) on the production of a polyhedrin promoter-driven recombinant protein (beta-galactosidase), intrinsic proteases (carboxyl and cysteine proteases), and the virus was determined. The DO concentrations used in the present study were 45%, 25%, 5%, and 1.3% of air saturation. At 5% DO the cell growth following viral infection was greatest and beta-galactosidase was about 5-fold increased in volumetric yield compared to that at 45% and 25% DO, whereas the growth at 1.3% DO was extremely poor. The virus titer in the medium at 4-8 d post-infection (dpi) was also highest at 5% DO, but the titer was significantly decreased by further increasing the culture time. This was in part attributed to the fact that baculovirus is susceptible to oxidative inactivation under aerobic conditions. The DO dependency of the specific oxygen consumption rate of virus-infected and uninfected Sf-9 cells was expressed by a Monod-type equation. A critical DO, above which the rate of oxygen utilization is not limited by DO, was estimated to be 3.5% of air saturation for virus-infected Sf-9 cells. These results indicated that for a baculovirus-infected Sf-9 insect cell culture of low MOI, the optimal DO was likely to be approximately 5% of air saturation, which is above the critical DO for the infected Sf-9 cells but sufficiently low to reduce the possibility of the oxidative inactivation of virus. For the production of carboxyl and cysteine proteases, the accumulation behavior and concentrations did not significantly vary with DO, except that a peak of cysteine protease activity was observed intracellularly only at 5% DO, coinciding with beta-galactosidase production.     

Molecular breeding of Aspergillus kawachii overproducing cellulase and its application to brewing barley shochu

In order to improve fermentation of barley without addition of commercial cellulase, a white koji mold, Aspergillus kawachii IFO4308, was transformed with the egl1 gene encoding endoglucanase I (EGI) of Trichoderma viride and the endogenous cekA gene encoding endoglucanase (CekA). Transformants with egl1 under the control of the strong glaA promoter produced EGI in both submerged and solid-state cultures. However, the EGI produced in solid-state culture was unstable due to the acidic condition of this culture. A transformant N10 with two additional copies of the cekA gene exhibited endoglucanase activities against carboxymethyl-cellulose, which are 21- and 1.8-fold higher than that of the wild-type (wt) strain when the cells were cultivated in submerged and solid-state cultures, respectively. Cultivation of strain N10 in steamed barley for preparing koji followed by fermentation with Saccharomyces cerevisiae resulted in improved fermentation assessed based on higher productions of ethanol, amino acids, and organic acids, the reduction of residual sugar, and the low viscosity of barley mash. The overall fermentation result for the transformant carrying cekA was comparable with that for the wt strain using commercial cellulase. These results demonstrate that acquisition of only two-fold CekA activity by A. kawachii in the solid-state culture allows us to improve the brewing of barley shochu.