Influence of surface roughness on the charging of insulating spacers in vacuum

This paper describes the charging phenomena of cylindrical insulators made of PMMA, PTFE, or Al₂O₃ under ramped and stepped dc voltage. It is primarily concerned with the influence of surface roughness on the formation of charging for various insulating spacers. By using an electrostatic probe located on the cathode, we conducted real‐time observations of the electric field induced by the surface charge. It was found that the surface roughness positively affects the charging, which becomes more pronounced in insulators polished to a higher degree. Furthermore, polished insulators are characterized by a shorter time lag. These results show the importance of surface treatment for insulating spacers in vacuum. © 2001 Scripta Technica, Electr Eng Jpn, 135(3): 16–25, 2001     

Application of DBR mode-locked lasers in millimeter-wavefiber-radio system

An actively mode-locked laser (MLLD) integrated with a distributed Bragg reflector (DBR) was used as a light source for optical subcarrier transmission. The millimeter (mm)-wave power penalty due to fiber dispersion is suppressed within 4 dB by operating this laser in a symmetric four-mode configuration. The experimental results agree well with the calculation of dispersion-induced penalty for a four-component-lightwave source. Optical subcarrier transmission free from dispersion-induced penalty within experimental error is achieved by further suppression of the end-modes of the DBR-MLLD using a fiber Bragg grating (FBG)     

EELS analysis of {1 1 1} Σ3 and {1 1 2} Σ3 twin boundaries and their junctions in phosphor-doped cast polycrystalline silicon

{1 1 1} Σ3 and {1 1 2} Σ3 twin boundaries and their junctions in a phosphor-doped cast polycrystalline silicon were investigated by EELS using HREM to study the local electrical properties and impurity effects at these boundaries and junctions. FWHMs of the silicon plasmon-loss peaks are wider at the grain boundary junctions and {1 1 2} Σ3 twin boundary as compared with other area partly because of the overlapped effect of plasmon loss of SiO₂ and carbon. In the inner-shell edge part of EELS spectrum, the grain boundary junction having distorted structure shows slightly strong intensity at around 110 eV, suggesting the formation of nano-size SiO₂, even though the presence of the SiO₂ could not be observed by HREM. The effects of carbon K-edge can be recognized in the EELS spectra acquired at {1 1 1} Σ3 and {1 1 2} Σ3 boundaries and their junctions, suggesting the grain boundary segregation of carbon atoms.     

Enhancement of electrochemical ion/electron-transfer reaction at solid|liquid interface by polymer coating on solid surface

Controlling the ion/electron-transfer reaction at the electrode|electrolyte (solid/liquid) interface is a necessary and vitally important point for improving the operation of various electrochemical devices. In this paper, we propose a polymer coating technique which enhances the Li⁺ ion-transfer reaction at the LiCoO₂|electrolyte interface, and confirm the effects of the polymer coating by cyclic voltammetry (CV) and AC impedance techniques. The results from the experiments indicated that the application of an F-introduced polymer on the LiCoO₂ (LCO) surface decreased the activation barrier for Li⁺ ion transfer. Besides the electrochemical studies, the present computational results indicated that the Li⁺ exchange process between two states, which are both solved with ethylene carbonate (EC) and coordinated with an F-introduced polymer, might occur due to the close energy levels of Li⁺ stability. Accordingly, we inferred that the transition state of this exchange process promotes the observed decrease in activation energy for the interfacial Li⁺-transfer reaction.     

Serum levels of tumor necrosis factor alpha and soluble tumor necrosis factor-receptor I in asthmatic patients and patients with chronic respiratory tract infection

In order to investigate the role of tumor necrosis factor alpha (TNF-alpha) in bronchial asthma or chronic respiratory infection, we measured serum levels of TNF-alpha and serum soluble tumor necrosis factor-receptor I (sTNF-RI) in asthmatic patients (n = 11) and patients (n = 10) with chronic respiratory infection by Pseudomonas aeruginosa. We also measured serum levels of eosinophil cationic protein (ECP) in the asthmatic patients. The serum levels of TNF-alpha in the asthmatic patients, patients with chronic respiratory tract infection and control group were 2.864 +/- 0.719 g/ml, 2.564-1.384 pg/ml and 0.681 +/- 0.453 pg/ml respectively. The levels of the former two groups were higher than those of the control group (p < 0.05). The serum levels of sTNF-RI in the asthmatic patients, the patients with chronic respiratory tract infection, and the control group was 758 +/- 268 pg/ml, 999 +/- 242 pg/ml and 909 +/- 268 pg/ml respectively. The levels of the former two groups did not differ significantly from those of the control group. There were significant correlations between TNF-alpha and sTNF-RI in the control group and in the patients with chronic respiratory tract infection, but there was no significant correlation in the asthmatic patients. In the asthmatic patients. TNF-alpha/s TNF-RI correlated with %best of PEF (r = 0.691, n = 9, p 0.0373). The serum levels of ECP correlated significantly with TNF-alpha, but not with sTNF-RI in the asthmatic patients. It is suggested that TNF-alpha plays a significant role in the pathogenesis of bronchial asthma and chronic respiratory tract infection as a factor causing inflammation and that the increase of TNF-alpha/sTNF-RI reflects the activation of eosinophil functions in an asthmatic attack.     

Atrial electrograms and activation sequences in the transition between atrial fibrillation and atrial flutter

INTRODUCTION: The electrophysiologic mechanism of atrial fibrillation (AF) has a wide spectrum, and it seems that some atrial regions are essential for the occurrence of a particular type of AF. We focused on one type of AF: AF associated with typical atrial flutter (AFL), which was right atrial (RA) arrhythmia, and sought to investigate intra-atrial electrograms and activation sequences in the transition between AF and AFL. METHODS AND RESULTS: Intra-atrial electrograms and activation sequences in the RA free wall and the septum were evaluated in the transition between AF and AFL in seven patients without organic heart disease (all men; mean age 57+/-11 years). In five episodes of the conversion of AFL into AF, the AFL cycle length was shortened (from 211+/-6 msec in stable AFL to 190+/-15 msec before the conversion, P, 0.001). Interruption of the AFL wavefront and an abrupt activation sequential change induced by a premature atrial impulse resulted in fractionation and disorganization of the septal electrograms. During sustained AF, septal electrograms were persistently fractionated with disorganized activation sequences. However, the RA free-wall electrograms were organized, and the activation sequence was predominantly craniocaudal rather than caudocranial throughout AF. In 12 episodes of the conversion of AF into AFL, the AF cycle length measured in the RA free wall increased (from 165+/-26 msec at the onset of AF to 180+/-24 msec before the conversion, P, 0.001). AFL resumed when fractionated septal electrograms were separated and organized to the caudocranial direction, despite the RA free-wall electrograms remaining discrete and sharp with an isoelectric line. CONCLUSION: Changes of the electrogram and activation sequence in the atrial septum played an important role in the transition between AF and AFL.     

Effects of magnetic field on the carrier density distribution of semiconductor power device operated in pulsed power conditions

Turn‐on characteristics of semiconductor power devices are evaluated under external magnetic field to study the effects of external magnetic field generated in a pulsed power circuit. Two pin diodes that have a basic structure of power devices are connected in parallel and driven by a pulsed voltage source. It was found the magnetic field applied to one diode in the perpendicular direction of current‐flow changed the current balance between the diodes. Besides the on‐resistance of a diode was increased under external magnetic field. The carrier‐density distribution inside of the diodes was measured by using a free carrier absorption method. The data show that the carrier‐density distribution changes from nearly the uniform one to the one‐sided one. It can be concluded that the effects of magnetic‐field have to be considered for the evaluation of switching characteristic in pulsed power operations. © 2004 Wiley Periodicals, Inc. Electr Eng Jpn, 147(1): 10–16, 2004; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/eej.10271