Relative permittivity and conductivity of water‐treed region in XLPE estimated by an equivalent circuit

By dividing a water‐treed XLPE sheet sample of 1 mm thickness into a nondegraded region and a water‐treed one, relative permittivity and AC conductivity σ_AC2 of the water‐treed region have been estimated using an equivalent circuit. The variation of and σ_AC2 with the length r of the water‐treed region has been discussed based on the Sillars model. It was concluded that the volume fraction of water in the water‐treed layer is in the range from 0.5% to 1.5% for the most‐degraded XLPE sheet, which depends on the ratio of axes of spheroids to which water‐filled voids and channels are compared. It was also concluded that the AC conductivity of water in the water‐treed region ranges from 3 × 10^?3 S/m to 2 × 10^?2 S/m. © 2004 Wiley Periodicals, Inc. Electr Eng Jpn, 148(3): 7–14, 2004; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/eej.10332     

Traveling wave amplifier using “VP×B” effect

The “v _p ×B” effect is introduced into a traveling wave amplifier trying to increase its output power and efficiency. The numerical calculating results show that by introducing an tapered static magnetic field into a traditional traveling wave amplifier, its output power and efficiency can be increased obviously comparing with an ordinary traveling wave amplifier, because of the effective interactive duration of electron bunches and a rf field is extended by the “v _p ×B” effect.     

Competitive binding of divalent cations to poly(α-hydroxyacrylic acid)

The competitive binding of divalent cations (Mg²⁺, Ca²⁺, Mn²⁺, Co²⁺, Ni²⁺, Cu²⁺ and Zn²⁺) on poly(α-hydroxyacrylic acid) (PHA) and poly(acrylic acid) (PAA) was investigated by equilibrium dialysis. In the Mg/Ca mixed system, binding selectivity for Ca²⁺ over Mg²⁺ was significantly higher in PHA than in PAA; this was attributed to coordination of α-OH groups on PHA to Ca²⁺. The binding ability and selectivity for the transition metal cations were almost the same for PHA and PAA at neutral pH, while PHA maintained appreciably higher degrees of binding than PAA in acidic solutions (pH about 3). This cation binding ability of PHA was ascribed to the lower pK_a value in the relevant pH region. © 1998 SCI.     

Tricycloillicinone, a novel prenylated c6-c3 compound increasing choline acetyltransferase (ChAT) activity, isolated from Illicium tashiroi

Tricycloillicinone (1), a novel tricyclic prenylated C6-C3 compound, has been isolated as a neurotrophic substance from the woods of Illicium tashiroi and its structure has been elucidated by spectroscopic analyses. Compound 1 could increase ChAT activity in culture of P10 rat septal neurons.     

Synthesis and properties of optically functionalized polythiophene having porphyrin side-chain

The synthesis and photochemical properties of poly[1,3-bis(dithienyl)benzene] having a porphyrin group as a side-chain were studied. As a target monomer, 1,3-bis(dithienyl)benzene with an ethynylporphyrin substituent was synthesized by Pd-catalyzed cross-coupling reactions. The electrochemical polymerization of the monomer afforded a conductive polymer film on the ITO-coated glass. The spectroelectrochemistry of the polymer was investigated to clarify the electrochemical oxidation behavior. The current density of the target polymer showed a good photoresponse and the much larger photocurrent was observed as compared with the dark current.     

Influence of water and sediment quality on benthic biota in an acidified river

Water and sediment quality and benthic biota were investigated in all seasons during three years in the River Akagawa that receives the effluent from a mine drainage treatment plant at its upstream site. The upper reaches kept the low pH, the comparatively high concentrations of metals and a large amount of iron deposited on the riverbed. The predominant macroinvertebrates were Protonemura sp., Capnidae, Nemoura sp. and Chironomidae in the upper and middle reaches. In the lowest reaches, the community structure of the macroinvertebrate changed into Chironomidae, Trichoptera (Hydropsychidae) and Ephemeroptera (Baetis sp.) as the pH was increased. From the results of multivariate analyses, it was found that the restoration of pH and attached algae and the increase in the concentrations of nutrients and organic matter promoted the inhabitation of Chironomidae and Hydropsychidae, whereas the dissolved metals in the river water inhibited the inhabitation of these families. Moreover, the sedimentation of metals would cause a severe damage to the inhabitation of Hydropsychidae compared with that of Chironomidae.     

Numerical study on spectral properties of tungsten one-dimensional surface-relief gratings for spectrally selective devices

Spectral properties of one-dimensional tungsten gratings with various depths and widths of grooves were investigated by means of finite-difference time-domain simulation with a multi-Lorentz model. Shallow gratings showed a strong absorption peak due to surface plasmon polaritons when the oscillation of the electric field was parallel to the grating vector. On the other hand, deep gratings with wide grooves showed a different absorption attributed to the microcavity effect when the oscillation of the electric field was perpendicular to the grating vector. With narrowed grooves, another absorption with d-dependence occurred, which was probably due to vertically oscillating surface plasmons to the grooves.     

Effect of rare-earth oxides on fracture properties of ceria ceramics

The influences of the sintering additive content of rare-earth oxide (Y₂O₃, Gd₂O₃, Sm₂O₃) on microstructure and mechanical properties of ceria ceramics were investigated by scanning electron microscopy and small specimen technique. A small punch testing method was employed to determine the elastic modulus and biaxial fracture stress of the ceria-based ceramics, and the fracture toughness was estimated by Vickers indentation method. Grain growth in the rare-earth oxides doped ceria ceramics was significantly suppressed, compared to the pure ceria ceramics. However, the elastic modulus, fracture stress and fracture toughness were decreased significantly with increasing additive content of the rare-earth oxides, possibly due to the oxygen vacancies induced by the rare earth oxides doping. The experimental results suggest that the change in the mechanical properties should be taken into account in the use of ceria-based ceramics for solid oxide fuel cells, in addition to the improvement of oxygen ion conductivity.     

Radiation-induced seeded copolymerization of tetrafluoroethylene with propylene. II. Kinetic analysis

The radiation-induced seeded copolymerization of tetrafluoroethylene with propylene was kinetically analyzed by assuming that growing radical in polymer particle is deactivated by degradative chain transfer to propylene and/or by recombination with newly entered radical which grows for a while before recombination. Apparent rate constant of initiation is 2.6 × 10^?9 mole/liter rad independent of the monomer composition in polymer particles. Apparent rate constant of propagation lies in the range of 10⁵ hr^?1 increasing with tetrafluoroethylene fraction. Change in apparent rate constant of chain transfer with propylene fraction suggests that first-order termination by radical occlusion or radical escape to aqueous phase may occur simultaneously with the degradative chain transfer. Average number of radical in a particle is found to increase with dose rate and levelled off at the value of 0.9. The higher value above 0.5 is explained by Trommsdorff effect. The dose rate exponent of average number of radical changes from 1 to 0 with increasing dose rate. This change is consistent with the dose rate effect on the polymerization rate under the constant number of polymer particles.