Electrical and light-emitting properties from (111)-oriented homoepitaxial diamond p–i–n junctions

We have succeeded in fabricating a (111)-oriented diamond p–i–n junction with high crystalline quality intrinsic layer and with low series resistance. The series resistance of this diamond p–i–n junction was improved by decreasing the resistivity and specific contact resistance of n-type layer, which is allowed to inject higher current while maintaining lower junction temperature. Current density–voltage characteristics showed a rectification ratio of 10⁶ at ± 15 V at room temperature. A clear ultraviolet emission at around 235 nm due to free exciton recombination was observed at a forward current, while the broad visible light emission from deep levels was significantly suppressed. Moreover, stronger excitonic emission by two orders of magnitude than that of (001)-oriented diamond p–i–n junctions with high series resistance was realized.     

Operating tests with a 6.6‐kV reduced model of rectifying‐type fault current limiter system

Fault current limiters (FCL) are extensively needed to suppress fault currents, particularly for trunk power systems heavily connected to high‐voltage transmission lines, such as the 500‐kV‐class power system which constitutes the nucleus of the electric power system. In this paper, we propose a new FCL system, consisting of solid‐state diodes, a dc coil, and a bypass ac coil, and describe the specifications of the trunk electric power system and the 6.6‐kV reduction model. Also we propose a 6.6‐kV trial model and describe an efficiency test with a short circuit generator, which we have trial produced for the new FCL system. © 2001 Scripta Technica, Electr Eng Jpn, 137(3): 29–36, 2001     

A novel outer membrane lipoprotein, LolB (HemM), involved in the LolA (p20)-dependent localization of lipoproteins to the outer membrane of Escherichia coli

The Escherichia coli major outer membrane lipoprotein (Lpp) is released from the inner membrane into the periplasm as a complex with a carrier protein, LolA (p20), and is then specifically incorporated into the outer membrane. An outer membrane protein playing a critical role in Lpp incorporation was identified, and partial amino acid sequences of the protein, named LolB, were identical to those of HemM, which has been suggested to play a role in 5-aminolevulinic acid synthesis in the cytosol. In contrast to this suggested role, the deduced amino acid sequence of HemM implied that the gene encodes a novel outer membrane lipoprotein. Indeed, an antibody raised against highly purified LolB revealed its outer membrane localization, and inhibited in vitro Lpp incorporation into the outer membrane. Furthermore, LolB was found to be synthesized as a precursor with a signal sequence and then processed to a lipid-modified mature form. An E.coli strain possessing chromosomal hemM under the control of the lac promoter-operator required IPTG for growth, indicating that hemM (lolB) is an essential gene. Outer membrane prepared from LolB-depleted cells did not incorporate Lpp. When the Lpp-LolA complex was incubated with a water-soluble LolB derivative, Lpp was transferred from LolA to LolB. Based on these results, the outer membrane localization pathway for E.coli lipoprotein is discussed with respect to the functions of LolA and LolB.     

Electrochemical studies of acid-promoted disproportionation of nitroxyl radical

The acid-promoted disproportionation of 2,2,6,6-tetramethylpiperidinyl-1-oxyl (TEMPO) was studied in order to elucidate the recycling process of the catalytic oxidation of alcohol by nitroxides. Potentiometry, cyclic and hydrodynamic voltammetries with a rotating disk electrode (RDE) have been used to investigate the formation of a nitrosonium cation and a hydroxylamine by disproportionation of nitroxides in acetonitrile. The addition of p-toluenesulfonic acid caused the rest potential of the TEMPO/nitrosonium cation couple to shift in a more positive direction and decreased the peak current in the cyclic voltammograms. The subsequent addition of 2,6-lutidine as a Lewis base made the rest potential and the peak current recover. These phenomena corresponded to the recycling of the catalytic process by TEMPO in a basic aprotic solution.     

Epinephrine-induced ventricular premature complexes due to early afterdepolarizations and effects of verapamil and propranolol in a patient with congenital long QT syndrome

We report a patient with congenital long QT syndrome in whom early afterdepolarizations (EADs) were demonstrated on monophasic action potential (MAP) recordings in the left ventricular mid-base inferior wall. Epinephrine infusion at 5 micrograms/min increased the amplitude of the EADs and the late component of the T(U) wave. Epinephrine also induced ventricular premature complexes (VPCs) with right bundle branch block morphology and left-axis deviation that occurred from the peak of the EADs. Verapamil injection (5 mg) during continuous epinephrine infusion abolished all VPCs with a slight reduction in the amplitude of the EADs. Propranolol injection (5 mg) in addition to verapamil further reduced the amplitude of the EADs and the late component of the T(U) wave. These findings suggest that the epinephrine-induced VPCs were closely related to triggered rhythm arising from the EADs, and that both verapamil and propranolol were effective for the suppression of VPCs and EADs.     

Mixing characteristics of a submerged jet measured using an isokinetic sampling probe

The flow properties and mixing characteristics of a submerged gas jet near the injection point were measured using an isokinetic sampling probe in a water model. The radial and axial profiles of gas velocity, water velocity, and void fraction were measured. Since the gas velocity was always larger than that of the water, the existence of a slip velocity between gas and water was confirmed. A one-dimensional mathematical model was developed using the dimensionless slip velocity as a parameter. The dimensionless slip velocity (S) was estimated to be 0.3 to 0.6 for the nitrogen-water system. TheS of the He-water system was slightly larger than that of the nitrogen-water system. When the model was applied to calculate the gas fraction in the jet for the nitrogen-mercury system,S was estimated to be 0.95 to 0.97. A large slip velocity between gas and liquid is expected for gas-metal systems. Formerly Research Associate, the Research Institute of Mineral Dressing and Metallurgy, Tohoku University     

Evaluation of performance of photovoltaic system with maximum power point (MPP)

Performance of the photovoltaic system is highly influenced by the weather, especially the irradiation and the temperature. To simplify the design of solar generator power, a mathematical model and its validity of the solar cell are required. In this work, the value of the parameters in the mathematical model is obtained by the measurement of the I–V curve of the module. To get an I–V curve, one of the modules in the system was radiated and loaded by a load simulator. A photovoltaic pumping system with maximum power point tracker was built and tested. The results were analyzed and evaluated by using the parameters and the photovoltaic system was shown to be well optimized.     

A new differential LSI space-based probabilistic document classifier

We have developed a new effective probabilistic classifier for document classification by introducing the concept of differential document vectors and DLSI (differential latent semantic indexing) spaces. A combined use of the projections on and the distances to the DLSI spaces introduced from the differential document vectors improves the adaptability of the LSI (latent semantic indexing) method by capturing unique characteristics of documents. Using the intra- and extra-document statistics, both a simple posteriori calculation on a small example and an experiment on a large Reuters-21578 database demonstrate the advantage of the DLSI space-based probabilistic classifier over the LSI space-based classifier in classification performance.