Cross-polarization/magic-angle spinning 13C nuclear magnetic resonance study of cellulose I-ethylenediamine complex

Complete assignments of the cross-polarization/magic-angle spinning (CP/MAS) 13C nuclear magnetic resonance (NMR) spectrum of the cellulose I-ethylenediamine (EDA) complex, which is the intermediate of the reaction from cellulose I to cellulose III(I), were performed. In this paper, we used the 13C-enriched cellulose that was biosynthesized by Acetobacter xylinum ATCC10245 strain from culture medium containing D-(2-13C), D-(3-13C), or D-(5-13C)glucose as a carbon source. After conversion into cellulose I-EDA complex by sufficient EDA treatment, the CP/MAS 13C NMR spectra of the 13C-enriched cellulose I-EDA complexes were measured. As a result, 13C resonance lines of each carbon of the cellulose moiety in the complex appeared as a singlet, suggesting that all glucose residues of the complex are magnetically equivalent. The difference in chemical shifts for each carbon between cellulose I-EDA and cellulose I(alpha), I(beta), and III(I), respectively, suggests that the conformation of the cellulose chains for cellulose I-EDA differs from that for cellulose I(alpha), I(beta), and III(I). In addition, fitting analysis of the 13C spectrum of Valonia cellulose I-EDA complex revealed that the complex contains one EDA molecule per two glucose residues in the cellulose chain.     

Cycling behaviour of electrodeposited zinc alloy electrode for secondary lithium batteries

The cycling behaviour of an electroplated lithium-zinc alloy film electrode is examined in 1 M LiC1O₄/propylene carbonate. The cycle life depends on the utilization of lithium in the alloy and is improved by dispersion of 2 to 4 wt.% iron. This improvement is more effective when the discharge cutoff potential is 0.5 V versus Li⁺/Li. In this case, the life cycle is about 150 cycles at 250 mA h g⁻¹ of lithium utilization. The reason for improvement is possibly the suppression of electrode disintegration and the appropriate choice of alloy phases.     

Flow-induced vibrations in closed side branch pipes and their attenuation methods

Some problems due to flow-induced vibrations related to closed side branch pipes have been observed in thermal and nuclear power plants. Fluctuating pressure generated in the main pipes was unusually, acoustically excited in closed side branch pipes, and intense vibrations were caused at pipes and components. For example, flow-excited acoustic resonance in closed side branches of stub pipes of safety relief valves caused the failure of steam dryers in the United States Quad City Unit 2 nuclear power plant. Furthermore, there was a possibility that residual air or gas in a closed side branch pipe unexpectedly caused severe vibrations of low frequency in the feed water piping system. We have investigated the root cause and influence of air on severe vibrations. Intense fluctuating pressure was often caused by water hammer due to valve closure and it became larger in the closed side branch pipes. We showed that an additional side branch with an orifice was very effective to suppress the flow-induced acoustic resonance. Design methods of the orifice to attenuate fluctuating pressure generated by water hammer were presented considering Mach number, the pressure loss coefficient of orifice and the intensity of particle velocity. Moreover, suitability of the characteristic curve method was confirmed for evaluation of the attenuation effect of an orifice on fluctuating pressure generated by water hammer. Finally, we considered some flow-induced vibration problems related to closed side branch pipes and their attenuation methods.     

Diffractive properties of obstructed vector Laguerre-Gaussian beam under tight focusing condition

Diffractive and focusing properties of vector Laguerre-Gaussian beams with obstacle are investigated under tight focusing conditions. Using vector diffraction theory, intensity and polarization distributions near the focus at different orthogonal planes are calculated and analyzed for vector Laguerre-Gaussian beams. It is observed that the beam is able to compensate the distortion produced by obstacles when the size of the obstacle is small. The structural changes in the polarization distribution are not the same in different orthogonal planes. The polarization characteristics of the beam show a significant change when the size of the obstacle is large. A comparative study of the focusing and diffractive properties of vector Laguerre-Gaussian and vector Bessel-Gaussian beams has also been performed.     

Focusing of radially and azimuthally polarized beams through a uniaxial crystal

We calculated and measured the difference between focal positions of radially and azimuthally polarized beams after passing through a uniaxial crystal. Calculations were carried out on the basis of the ray optics and the vector diffraction theory. The results of the calculations were in good agreement with those of the experiment. In addition, we discussed the polarization selection in a hemispherical laser cavity that was used for the generation of a radially polarized beam by use of the birefringence of a c-cut Nd:YVO4 laser crystal [Opt. Lett. 31, 2151 (2006)]. The stability range of the laser cavity length for the generation of a radially polarized beam was also in good agreement with the differences mentioned above.     

Life cycle assessment and economical evaluation of superconducting magnetic energy storage systems in a power system

In recent years, the introduction of superconducting magnetic energy storage systems (SMES) into a power system is drawing considerable research effort because of their high efficiency rate and large storage capacity characteristics. In this paper, the introduction of SMES into a power system and its effects on energy and on environmental issues are addressed. The analysis results show that the introduction of SMES can considerably cut down CO₂ emissions without increasing the production cost if it substitutes for the operation of thermal plants during peak load period. However, to achieve this, nuclear plants are also needed for charging purposes. Thus, an algorithm to find the best generation mix, subject to CO₂ emissions constraints and nuclear plant introduction constraints, is proposed. The inclusion of nuclear plant constraints increases the coal consumption, hence CO₂ emissions. Nevertheless, in most of the analyzed cases, the introduction of SMES could attain important cost savings and environmental conservation. © 2000 Scripta Technica, Electr Eng Jpn, 131(1): 32–44, 2000     

Colorimetric sensing of H2PO4− using a Pb2+ complex of a pyridylazo dye in aqueous solution

This study develops a sensitive and selective colorimetric probe for the detection of dihydrogen phosphate (H₂PO₄⁻) based on a lead ion (Pb²⁺) complex of a commercially available pyridylazo dye (PAPS) in aqueous media under physiological conditions. The complex was made by adding Pb²⁺ to PAPS in a 1:1 stoichiometric ratio (PAPS-Pb²⁺), which was accompanied by the remarkable solution change from yellow to purple. The colorimetric sensing of H₂PO₄⁻ over other anions with PAPS-Pb²⁺ occurred owing to the regeneration of original PAPS by the interaction of H₂PO₄⁻ with Pb²⁺ in a 1:2 molar ratio. Moreover, the H₂PO₄⁻ detection was less affected by the presence of other coexisting competitive anions. The colorimetric naked-eye behaviour of PAPS-Pb²⁺ rendered a useful and convenient probe for the detection of H₂PO₄⁻ via the indicator displacement assay.     

The Synthesis and Photocatalytic Properties of Nitrogen Doped TiO<Subscript>2</Subscript> Films Prepared Using the AC-PLD Method

Synthesis of N doped TiO₂ films were conducted by the atmospheric controlled pulsed laser deposition (AC-PLD) method to generate visible light active photocatalytic films. In this method, the anion doped TiO₂ films were synthesized on a quartz substrate by the irradiation of a pulsed Nd:YAG laser on a TiO₂ target in the presence of gaseous nitrogen containing reagents at reduced pressure. For nitrogen doping, the use of CH₃CN was found to be more effective than the use of NH₃. The visible light absorption properties of the films were very sensitive to the CH₃CN partial pressure during ablation. When using CH₃CN, nitrogen and an equal quantity of carbon was uniformly doped into the TiO₂ films. The resultant films showed better catalytic performance than those which were either un-doped or doped using NH₃. The formation of nitrogen doped TiO₂ is discussed by relating experimental results to thermodynamic considerations. It is also suggested that stronger reducing agents such as carbon are required for doping nitrogen into TiO₂ films.