Electrochemical polymerization of pyrrole in supercritical carbon dioxide-in-water emulsion

Supercritical carbon dioxide is an environmentally benign solvent but its low polarity limits electrochemical reactions in it. We now report the electrochemical polymerization of pyrrole in a supercritical carbon dioxide-in-water (C/W) emulsion in the presence of a surfactant. Black polypyrrole films were formed on Pt electrodes, whose conductivity was comparable with non-oriented polypyrrole prepared in conventional solvents. The structure of the polypyrrole films was confirmed by IR and Raman spectroscopic measurements. p-Toluenesulfonic acid was a suitable supporting electrolyte among the electrolytes examined for the electrochemical polymerization in the C/W emulsion. A typical nodular morphology was observed on the basis of the SEM and AFM measurements. Confocal scanning microscope revealed the formation of a fine uneven texture on the film prepared in the C/W emulsion.     

Calculation of damping torque of power systems compensated with TCSC

The thyristor‐controlled series capacitor (TCSC) is being developed to improve the transmission capability of power systems. The TCSC is thought to compensate transmission line reactance without causing subsynchronous resonance (SSR). However, in order to evaluate its effect quantitatively, we must calculate the frequency response of the generator damping torque. Simulations need a long computing time, and it is hard to choose the frequency freely. In this paper, we propose a method of analytically calculating the damping torque. First, when a generator rotor oscillates at some frequency, two voltage components appear. We analytically calculate the damping torque from small current variations due to the voltage components. The damping characteristic changes depending on the method of firing thyristors. The best characteristic is obtained when triggering with reference to the fundamental wave of TCSC voltage or current is used. By choosing an appropriate firing angle, we can drastically reduce negative damping by the TCSC. The damping characteristic is closely related to the system impedance. The fact that the TCSC has large resistance in the 0 to 60 Hz range helps significantly in improving the characteristic. Lastly, numerical simulations of SSR are used to examine the validity of our investigation. © 2003 Wiley Periodicals, Inc. Electr Eng Jpn, 143(1): 39–49, 2003; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/eej.10068     

Ion conducting properties of hydrogen-containing Ta2O5 thin films prepared by reactive sputtering

Hydrogen-containing Ta₂O₅ (Ta₂O₅:H) thin films are considered to be a candidate for a proton-conducting solid-oxide electrolyte. In this study, Ta₂O₅:H thin films were prepared by reactively sputtering a Ta metal target in an O₂ + H₂O mixed gas. The effects of sputtering power and post-deposition heat treatment on the ion conducting properties of the Ta₂O₅:H thin films were studied. The ionic conductivity of the films was improved by decreasing the RF power and a maximum conductivity of 2 × 10⁻⁹ S/cm was obtained at an RF power of 20 W. The ionic conductivity decreased by heat-treatment in air, and no ion-conduction was observed after treatment at 300 °C due to the decrease in hydrogen content in the films.     

Development of Strategic Establishment of Technology Bases for a Fusion DEMO Reactor in Japan

The strategic establishment of technology bases required for the development of a fusion demonstration reactor (DEMO) has been discussed by joint endeavors throughout the Japanese fusion community. The mission of Fusion DEMO is to demonstrate the technological and economic feasibility of fusion energy. The basic concept of Fusion DEMO has been identified and the structure of technological issues to ensure the feasibility of this DEMO concept has been examined. The Joint-Core Team consisting of experts from the Japanese fusion community including industry has pointed out that DEMO should be aimed at steady power generation beyond several hundred thousand kilowatts, availability which must be extensible to commercialization, and overall tritium breeding sufficient to achieve fuel-cycle self-sufficiency. The necessary technological issues and activities have been sorted out along with 11 identified elements of DEMO, such as superconducting coils, blanket, divertor, and others. These will be arranged within a time line to lead to the Japanese fusion roadmap.     

Image cross-connector using a photorefractive polymer

We propose an image cross-connector using an organic photorefractive polymer. With this device, it is possible to perform a reconfigurable connection between multiple input–output image ports by setting the incident angle of individual control beams to minute levels. The use of a polymer can reduce the thickness of the index grating to be induced inside the medium, which can also reduce the distortion of the output image and bring about high precise image connection without an additional optical system. We conduct an experiment with a hole-transport polymer PATPD to verify the operations of an image cross-connector, in which different images from a vertical array of input images would be connected separately to two output ports by two control beams that were injected at different angles.     

Functional expression of a plant hydroxynitrile lyase in Escherichia coli by directed evolution: creation and characterization of highly in vivo soluble mutants

Low protein solubility of recombinantly expressed proteins in Escherichia coli is a major factor hindering their application and analysis. We generated highly in vivo soluble mutants of a hydroxynitrile lyase in E.coli using protein engineering. Structure-guided saturation mutagenesis caused high solubility of single Lys-Pro mutations at positions 176, 199 and 224 of this low soluble wild-type enzyme. The triple Lys-Pro mutant generated at these surface conserved residues showed up to 8-fold increase in specific activity in the cell-free extract. Random mutagenesis also created a mutant of His103Met with 18.5-fold increase. The main expression form was reversed from insoluble to the soluble fraction following both types of above-mentioned mutations in E.coli at 37°C. The findings challenge the rationale of producing recombinant proteins in this host at 37°C. Formerly wild type low soluble protein was then present as soluble protein by these mutations, which also elevated the total soluble protein fraction in E.coli. Saturation mutagenesis of His103 provided other highly soluble mutants with hydrophobic substitutions. These mutations caused only minor secondary structural changes as determined by circular dichroism and Fourier-transform infrared spectroscopy and affected catalytic efficiency slightly for the purified mutants (0.82-1.6-fold for benzaldehyde and 0.9-1.9-fold for mandelonitrile). The stability of the mutants was differed from that of the wild type at high temperatures and at pH >8. Exchanging the buried basic-polar residue His103 with hydrophobic amino acids is in line with the overall structure of the enzyme, i.e. having hydrophilic residues in solvent-exposed areas and hydrophobic residues in the core.     

Soluble High-Temperature Polymers Containing a Tetraphenylthiophene Unit

Soluble high-temperature polymers containing a tetraphenylthiophene unit were successfully prepared. Four types of tetraphenylthiophene monomers—diamine, diisocyanate, dicarboxylic acid chloride, and dibromide—were synthesized starting from tetraphenylthiophene, which was readily obtained by the reaction of benzyl chloride and sulfur. Aromatic polyimides and copolyimides were prepared by the reactions of tetraphenylthiophene diamine with tetracarboxylic dianhydrides, tetraphenylthiophene diisocyanate with tetracarboxylic dianhydrides, and tetraphenylthiophene diamine with tetracarboxylic dithioanhydrides. Aromatic polyamides and copolyamides were obtained from the reaction pairs of tetraphenylthiophene diamine and dicarboxylic acid chlorides, tetraphenylthiophene dicarboxylic acid chloride and diamines, and tetraphenylthiophene dibromide, diamines, and carbon monoxide. Similarly aromatic polyamide-imides were prepared by the reaction of tetraphenylthiophene diamine with 4-chloroformylphthalic anhydride, and tetraphenylthiophene diisocyanate with trimellitic anhydride. The reaction of tetraphenylthiophene dicarboxylic dichloride with bisphenols and aminophenols afforded aromatic polyesters and polyamide-esters, respectively. Aromatic polyazomethines were prepared by the reaction of tetraphenylthiophene diamine and dialdehydes. All the polymers were obtained in high molecular weights, and all were soluble in organic solvents and had high glass transition temperatures around 300°C.     

Effects of Addition of Na and S to Alumina Catalyst for the Selective Reduction of Nitrogen Monoxide with Ethene in Excess Oxygen

The addition of Na and S into alumina catalysts brought about a decrease in the catalytic activity for the reduction of NO with ethane in excess oxygen. Aluminas containing Na or S in different amounts were subjected to activity tests for the related reactions to elucidate the causes of the suppressive effects of the addition of Na and S on the reduction of NO. The reactions taken as test reactions were the oxidation of NO with oxygen, the reaction of NO₂ with ethene in the absence of oxygen, and the reaction of ethene with oxygen. The addition of Na suppressed the oxidation of NO, and the reaction of NO₂ with ethene to form N₂, but promoted the reaction of ethene with oxygen to a great extent. The addition of Na also caused the formation of NO in the reaction of NO₂ with ethene. The changes which the addition of Na brought about are all unfavorable directions for the reduction of NO. The most important effect of the addition of Na on the decrease in the reduction of NO is suggested to be due to the enhancement of the reaction of ethene with oxygen. The addition of S suppressed the oxidation of NO to a great extent, but did not affect much the reaction of ethene with oxygen. Like the case of the Na addition, the addition of S caused the formation of NO in the reaction of NO₂ with ethene.     

Grain size control of lead-free Li0.06(Na0.5K0.5)0.94NbO3 piezoelectric ceramics by Ba and Ti doping

In this study, Ba- and Ti-doped Li_0.06(Na_0.5K_0.5)_0.94NbO₃ [(1 ? x)Li_0.06(Na_0.5K_0.5)_0.94NbO₃–xBaTiO₃ (x = 0–0.07)] ceramics were prepared by using conventional solid state reaction method, and the microstructure and electric properties of these samples were investigated. The grain size distribution of non-doped Li_0.06(Na_0.5K_0.5)_0.94NbO₃ ceramics was relatively wide. The microstructure was composed of grains ranging 1.1–5.0 μm in size. However, with increasing Ba and Ti content, the grain size distribution became narrow and the average grain size decreased from 2.0 to 0.9 μm in size. In particular, the microstructure of x = 0.07 sample was composed of grains ranging 0.5–2.2 μm in size. As a result, the frequency dispersion of dielectric constant for the (1 ? x)Li_0.06(Na_0.5K_0.5)_0.94NbO₃–xBaTiO₃ (x = 0–0.07) ceramics was reduced and the mechanical quality factor Q_m was enhanced with increasing Ba and Ti content.