Photocatalytic oxidation of CO with various oxidants by Mo oxide species highly dispersed on SiO2 at 293 K

The photocatalytic oxidation of CO into CO₂ with oxidants such as NO, N₂O and O₂ proceeded efficiently on a Mo/SiO₂ with high Mo dispersion under UV light irradiation. It was found that the reaction rate greatly depended on the kind and concentration of the oxidant. Photoluminescence investigations reveal the close relationship between the reaction rate and the relative concentration of the photo-excited Mo⁶⁺-oxide species, i.e. charge transfer–excited–triplet state (Mo⁵⁺–O⁻)^*, under steady-state reaction conditions. Moreover, the photocatalytic oxidation of CO with O₂ in excess H₂ was carried out to test suitability for applications to supplying pure H₂. This reaction was seen to proceed efficiently on Mo/SiO₂ with a high CO conversion of 100% and CO selectivity of 99% after 180 min under UV light irradiation, showing higher photocatalytic performance than TiO₂ (P-25) photocatalyst. UV–vis, XAFS, photoluminescence and FT-IR investigations revealed that the high reactivity of the charge transfer–excited–triplet state (Mo⁵⁺–O⁻)^*, with CO as well as the high reactivity of the photoreduced Mo-oxide species (Mo⁴⁺-species) with O₂ to produce the original Mo-oxide species (Mo⁶⁺O²⁻), played a crucial role in the reactions.     

Light Transmission by Lotus Plant Stem and Leaf Tissue: Natural Textiles for Optical Fibers

Application of plant stem for optical transmitting devices is considered. This research indicates a possibility of application of vascular bundles as natural textiles for optical fibers. Observations of lotus stem tissue were carried out. Laser beam transmission of lotus stem was confirmed. New functions of photoconduction through lotus stem and confinement of incident light on the leaf surface are discussed.     

Crystal structure and ferroelectric properties of Ca(Cu3−xMx)Ti4O12 (M = Fe and Ni) ceramics

M-substituted Ca(Cu_3−xM_x)Ti₄O₁₂ (CCMTO) ceramics, where M = Fe and Ni, were synthesized and the influence of M substitutions for Cu on the crystal structure and ferroelectric properties of CCMTO ceramics were investigated in this study. From the variations in the lattice parameters of CCMTO ceramics, the solubility limit of Ni substitution for Cu in CaCu_3−xNi_xTi₄O₁₂ (CCNTO) ceramics was x = 0.2, whereas that of CaCu_3−xFe_xTi₄O₁₂ (CCFTO) ceramics was x = 0.05. The crystal structural analysis of CCMTO ceramics revealed that the single phase of CCMTO ceramics belongs to the I23 non-centrosymmetric space group of I23; as a result, the P_r and E_c values of CCFTO ceramics at x = 0.05 were 1.8 μC/cm² and 40 kV/cm, respectively. The ferroelectric behavior of CCMTO ceramics by the M substitutions for Cu may be related to the displacement of a Ti⁴⁺ cation in the TiO₆ octahedra and tilting of the Ti–O–Ti angle because of the non-centrosymmetric space group.     

Development of numerical analysis method of flow-acoustic resonance in stub pipes of safety relief valves

The boiling water reactors (BWRs) have steam dryer in the upper part of the pressure vessel to remove moisture from the steam. The steam dryer in the Quad Cities Unit 2 nuclear power plant was damaged by high-cycle fatigue due to acoustic-induced vibration during extended power uprate operation. The principal source of the acoustic-induced vibration was flow-acoustic resonance at the stub pipes of the safety relief valves (SRVs) in the main steam lines (MSLs). The acoustic wave generated at the SRV stub pipes propagates throughout the MSLs and eventually reaches and damages the steam dryer. Therefore, for power uprate operation of the BWRs, it has been required to predict the flow-acoustic resonance at the SRV stub pipes. The purpose of this article was to propose a numerical analysis method for evaluating the flow-acoustic resonance in the SRV stub pipes. The proposed method is based on the finite difference lattice Boltzmann method (FDLBM). So far, the FDLBM has been applied to flow-acoustic simulations of laminar flows around simple geometries at low Reynolds number. In order to apply the FDLBM to the flow-acoustic resonance simulations of turbulent flows around complicated geometries at the high Reynolds number, we developed computationally efficient model by introducing new function into the governing equation. The proposed method was compared with the conventional FDLBM in the cavity-driven flow simulation. The proposed method was validated by comparisons with the experimental data in the 1/10-scale test of BWR-5 under atmosphere condition. The following three results were obtained; the first is that the proposed method can reduce the computing time by 30% compared with the conventional FDLBM; the second is that the proposed method successfully simulated the flow-acoustic resonance in the SRV stub pipes of the BWR-5, and the pressure fluctuations of the simulation results agreed well with those of the experimental data; and the third is the mechanism of the flow-acoustic resonance in the SRV stub pipes. Acoustic waves causing the flow-acoustic resonance in the SRV stub pipes are generated by the unsteady vortices in the SRV stub pipes.     

Ultrahigh-Q nanocavities written with a nanoprobe

High-Q nanocavities have been extensively studied recently because they are considered key elements in low-power photonic devices and integrated circuits. Here we demonstrate that ultrahigh-Q (>10(6)) nanocavities can be created by employing scanning probe lithography on a prepatterned line defect in a silicon photonic crystal. This is the first realization of ultrahigh-Q nanocavities by the postprocess modification of photonic crystals. With this method, we can form an ultrahigh-Q nanocavity with controllable cavity parameters at an arbitrary position along a line defect. Furthermore, the fabricated nanocavity achieves ultralow power all-optical bistable operation owing to its large cavity enhancement effect. This demonstration indicates the possibility of realizing photonic integrated circuits on demand, where various circuit patterns are written with a nanoprobe on a universal photonic crystal substrate.     

Individual cathodoluminescence and photoluminescence spectroscopy of zinc oxide nanoparticles in combination with in situ transmission electron microscopy

The functions of scanning near-field optical microscopy (SNOM) were installed in high-resolution transmission electron microscopy (TEM) for cathodoluminescence spectroscopy and photoluminescence spectroscopy of individual nanostructures. Optical fiber probes used in SNOM were allowed to approach nanoparticles by piezomanipulation with simultaneous observation by TEM. As an application of this method, cathodoluminescence and photoluminescence from zinc oxide nanoparticles were measured at room temperature and 130 K. It was demonstrated that the present method directly provides the relationships between structural features of individual nanoparticles and spectra.     

Progress in ECRF antenna development for JT-60SA

Structural, mechanical and optical design work on antennas/launchers for the electron cyclotron range of frequency heating and current drive system in JT-60 Super Advanced (JT-60SA) have been advanced based on a linear motion antenna concept. A CAD model of the launcher was built with realistic component sizes. A mock-up of the steering structure consisting of two different bellows sections for poloidal and toroidal beam scanning was fabricated to test movement of the bellows. The poloidal (?40° to +20°) and toroidal (?15° to +15°) injection angle ranges required in JT-60SA were shown to be realized by this steering structure and mirrors.     

Development of high water-content cutting fluids with a new concept: Fire prevention and environmental protection

Using water-insoluble cutting fluids, which are good in lubricity but easy to mist, always risks firing and environmental problems. On the other hand, the current water-soluble coolants fail to deliver sufficient lubricity to heavy cutting applications. This study has newly proposed and developed a high water-content cutting fluid, based upon a new concept of having high lubricity despite of its water-soluble nature. As compared to the commercialized water-insoluble cutting fluid, the new cutting fluids shows a better capability of preventing oil mist and is fully applicable into cutting of various metallic materials, particularly effective in cutting of S45C and SUS304. The study also reveals a fact that a sulfur-type extreme pressure agent is the key element to enhance the cutting performance at high temperature.     

Study on inverse spinel zinc stannate, Zn2SnO4, as transparent conductive films deposited by rf magnetron sputtering

Inverse spinel zinc stannate (Zn₂SnO₄, ZTO) films were deposited onto fused quartz glass substrates heated at 800 °C by rf magnetron sputtering using a ceramic ZTO target (Zn:Sn = 2:1). H₂ flow ratios [H₂/(Ar + H₂)] were controlled from 0 to 30% during the depositions. ZTO films deposited at 800 °C possessed a polycrystalline inverse spinel structure. The lowest resistivity of 1.1 × 10^− 2 Ω cm was obtained for a ZTO film deposited at 20% H₂ flow ratio. The transmittance of the ZTO film was approximately 80% in the visible region.     

Facile Preparation of an Enzyme‐Immobilized Microreactor using a Cross‐Linking Enzyme Membrane on a Microchannel Surface

The enzyme microreactor has considerable potential for use in biotechnological syntheses and analytical studies. Simplifying the procedure of enzyme immobilization in a microreactor is attractive, and it is achievable by utilizing enzyme immobilization techniques and taking advantage of the characteristics of microfluidics. We previously developed a facile and inexpensive preparation method for an enzyme‐immobilized microreactor. The immobilization of enzymes can be achieved by the formation of an enzyme‐polymeric membrane on the inner wall of the microchannel through cross‐linking polymerization in a laminar flow. However, this method is unsuitable for use in conjunction with electronegative enzymes. Therefore, a novel preparation method using poly‐L ‐lysine [poly(Lys)] as a booster and an adjunct for the effective polymerization of electronegative enzymes was developed in this study. Using aminoacylase as a model for an electronegative enzyme, the reaction conditions for the enzyme‐cross‐linked aggregation were optimized. On the basis of the determined conditions, an acylase‐immobilized tubing microreactor was successfully prepared by cross‐linking polymerization in a concentric laminar flow. The resulting microreactor showed a higher stability against heat and organic solvents compared to those of the free enzyme. The developed method using poly(Lys) was applicable to various enzymes with low isoelectric points, suggesting that this microreactor preparation utilizing a cross‐linked enzyme in a laminar flow could be expanded to microreactors in which a broad range of functional proteins are employed.