Design optimization of tall tubular lead/acid cells based on an analysis of the reaction distribution

In order to estimate the discharge performance of tall lead/acid cells (with tubular positives), changes in current and potential distributions with discharge progress were calculated with a computer on the basis of plate resistance and the current—potential—time relationship between small facing parts of positive and negative plates. The taller the cell, the larger the voltage drop along the plates. Thus, the discharge time became shorter despite a large amount of available active mass remaining in the bottom part of the plates.Various current-collector designs were evaluated, e.g., one with varying resistance at each height; a side conductor placed along the plates and connected to them at the top, centre and bottom, etc. Results revealed an optimum collector design with which the maximum discharge capacity could be obtained. Furthermore, it was shown that the side conductor markedly improved the discharge performance because the active mass near the connecting parts was appreciably used.     

Development of a fast neutron radiography converter using wavelength-shifting fibers

A fluorescent converter for fast neutron radiography (FNR) comprising a scintillator and hydrogen-rich resin has been developed and applied to electronic imaging. The rate of the reaction between fast neutrons and the converter is increased by thickening the converter, but its opaqueness attenuates emitted light photons before they reach its surface. To improve the luminosity of a fluorescent converter for FNR, a novel type of converter was designed in which wavelength-shifting fibers were adopted to transport radiated light to the observation end face. The performance of the converter was compared with that of a polypropylene-based fluorescent converter in an experiment conducted at the fast-neutron-source reactor YAYOI in the University of Tokyo.     

Effects of cononsolvency on gelation of poly(vinyl alcohol) in mixed solvents of dimethyl sulfoxide and water

We studied the rates of gelation and phase separation of poly(vinyl alcohol) (PVA) solutions in mixtures of dimethyl sulfoxide (DMSO) and water at 25 °C and found that both the rates show a maximum at a volume fraction of DMSO φ_DMSO=0.60 while gelation was not observed either in pure DMSO or pure water, suggesting that water-DMSO is a cononsolvent system for PVA. On the basis of the data by Cowie [Can J Chem 36 (1961) 2240] we concluded that the 1:2 stable complex between one DMSO molecule and two water molecules is the main cause of this cononsolvency.     

A scheme of picosecond pulse shaping using gain saturationcharacteristics of semiconductor laser amplifiers

To obtain high power, well shaped picosecond pulses from gain-switched semiconductor lasers, the use of dynamic gain saturation characteristics of semiconductor laser amplifiers was investigated theoretically and experimentally. A configuration of a reflected-wave amplifier (RWA) with single-side external coupling is introduced for pulse shaping, which is found to be suitable for enhancing dynamic gain saturation. By a combination of a distributed feedback laser oscillator at 1.3 μm in wavelength and a reflected-wave amplifier of 400 μm cavity length with asymmetric facet reflectivities of 0.01% and 30%, single-mode optical pulses with almost no tailing, full width at half maximum of 15 ps, and peak power exceeding 50 mW were obtained without pulse broadening, despite the considerable tail structure of the incident pulse     

X-ray Photoelectron Spectroscopy Investigation on the Low-Temperature Degradation of 2 mol% Y2O3-ZrO2 Ceramics

2 mol% Y₂O₃-ZrO₂ polycrystals were annealed in water and under vacuum to highlight the effect of the presence of H₂O on the low-temperature degradation transformation. The specimen surfaces with monoclinic phases transformed during annealing in the different environments were analyzed by X-ray photoelectron spectroscopy with special interest on the electron binding energy change of the constituent ions of the 2 mol% Y₂O₃-ZrO₂ ceramics after the degradation transformation. It was found that no change occurred for the electron-bonding energies of core levels of zirconium ions after the transformation, whereas Y-OH bonds were formed during annealing in water. This result suggested a possibility that the preferred hydration of yttrium took place at the surface of Y₂O₃-partially-stabilized ZrO₂, which is likely to be the reason for the low-temperature degradation accelerated by the presence of H₂O.     

Discharge behaviour of electrodeposited PbO2 and Pb electrodes

The discharge behaviour of electrodeposited lead dioxide and lead electrodes was investigated under various conditions; the surfaces of the discharged electrodes were observed with a scanning electron microscope. Both the positive and negative electrodes were passivated by a covering of deposited lead sulphate crystals. The amount of lead sulphate required for passivation depended on the size of the crystals.     

Series resonant ZCS‐PFM DC‐DC power converter with high‐frequency high‐voltage transformer link for high‐power magnetron drive

This paper presents a single lossless inductive snubber‐assisted ZCS‐PFM series resonant DC‐DC power converter with a high‐frequency high‐voltage transformer link for industrial‐use high‐power magnetron drive. The current flowing through the active power switches rises gradually at a turned‐on transient state with the aid of a single lossless snubber inductor, and ZCS turn‐on commutation based on overlapping current can be achieved via the wide range pulse frequency modulation control scheme. The high‐frequency high‐voltage transformer primary side resonant current always becomes continuous operation mode, by electromagnetic loose coupling design of the high‐frequency high‐voltage transformer and the magnetizing inductance of the high‐frequency high‐voltage transformer. As a result, this high‐voltage power converter circuit for the magnetron can achieve a complete zero current soft switching under the condition of broad width gate voltage signals. Furthermore, this high‐voltage DC‐DC power converter circuit can regulate the output power from zero to full over audible frequency range via the two resonant frequency circuit design. Its operating performances are evaluated and discussed on the basis of the power loss analysis simulation and the experimental results from a practical point of view. © 2005 Wiley Periodicals, Inc. Electr Eng Jpn, 153(3): 79–87, 2005; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/eej.20126     

Responses of plasma norepinephrine and heart rate during exercise in patients after Fontan operation and patients with residual right ventricular outflow tract obstruction after definitive reconstruction

In a fetal autopsy series, we have explored the occurrence of renal tubular dysgenesis in twins. Renal tubular dysgenesis was found exclusively among those monozygotic twins with evidence of twin transfusion syndrome, particularly in those donor twins with oligohydramnios and growth restriction. We infer that hypotension in the donor twin of the twin transfusion syndrome pair is responsible for the failure of proximal convoluted tubule differentiation, and the disturbance of renal function is manifested as oligohydramnios prenatally, and either oliguria or tubular dysfunction postnatally.     

Thermal expansion behavior of various aromatic polyimides

The thermal expansion behavior for various aromatic polymides was investigated. Usally polymers, including polyimides, have high thermal expansion coefficients (3–6 × 10^?5 K^?1), compared with metals and ceramics. However, there are some polyimides which have very low thermal expansion coefficients below 1 × 10^?5 K^?1. This property was observed for the polymides obtained from pyromellitic dianhydride or 3,3′ 4,4′-biphenyltetracarboxylic dianhydride and aromatic diamines which were constituted of only benzene rings fused at para positions. It was proposed that their low thermal expansion coefficient related to the linearity in their polymer molecular skeltons.     

Regulation of Kv4.2 and Kv1.4 K+ channel expression by myocardial hypertrophic factors in cultured newborn rat ventricular cells

Postnatal development and myocardial hypertrophy are associated with alterations in cardiac voltage-gated K+ channels. To investigate mechanisms underlying this K+ channel remodeling, expression of Kv4.2 and Kv1.4 K+ channel alpha-subunits was examined in cultured newborn rat ventricular myocytes by Western blot analysis using polyclonal antibodies against each of the subunits. At day 5 of cell culture, Kv1.4 protein was expressed at higher level than Kv4.2; as the age of culture progressed, Kv1.4 was significantly diminished while Kv4.2 increased with time in culture and became the predominant K+ channel protein. Such K+ channel isoform switch from Kv1.4 to Kv4.2 resembles that of the development in vivo. A 72-h treatment with exogenous triiodothyronine (T3, 0.1 microM) to cultured neonatal myocytes enhanced the expression of Kv4.2 by 73% and decreased the Kv1.4 expression by 22%. The effects of T3 were associated with an increase in the protein-to-DNA ratio indicating myocyte hypertrophy. On the other hand, a 72-h treatment with cardiac non-myocyte cell (NMC)-conditioned growth medium (NCGM) or phenylephrine (20 microM) induced similar cell hypertrophy, but in sharp contrast to T3, both markedly suppressed the Kv4.2 channel protein level. In addition, the trophic and the Kv4.2-downregulating effects of NCGM could be mimicked by exogenous endothelin-1 (0.1 microM), a paracrine factor secreted from cardiac NMCs. Our observations for the first time suggest that cardiac Kv4.2 and Kv1.4 K+ channel alpha-subunits are differentially regulated by a variety of myocardial hypertrophic factors. That T3 accelerated the developmental K+ channel isoform switch from Kv1.4 to Kv4.2 in vitro indicates the critical importance of thyroid hormone in postnatal K+ channel remodeling. Cardiac NMCs and alpha-adrenoceptor activation may contribute to the reduced outward K+ channel density in hypertrophied cardiomyocytes.