Three-Phase PWM Inverter and Rectifier with Two-Switch Auxiliary Resonant DC Link Snubber-Assisted

Nagai Shinichiro,Sato Shinji,Matsumoto Takayuki The Korean Institute of Power Electronics 2005 JOURNAL OF POWER ELECTRONICS Vol.5 No.3

In this paper, a new conceptual circuit configuration of a 3-phase voltage source, soft switching AC-DC-AC converter using an IGBT module, which has one ARCPL circuit and one ARDCL circuit, is presented. In actuality, the ARCPL circuit is applied in the 3-phase voltage source rectifier side, and the ARDCL circuit is in the inverter side. And more, each power semiconductor device has a novel clamp snubber circuit, which can save the power semiconductor device from voltage and current across each power device. The proposed soft switching circuits have only two active power semiconductor devices. These ARCPL and ARDCL circuits consist of fewer parts than the conventional soft switching circuit. Furthermore, the proposed 3-phase voltage source soft switching AC-DC-AC power conversion system needs no additional sensor for complete soft switching as compared with the conventional 3-phase voltage source AC-DC-AC power conversion system. In addition to this, these soft switching circuits operate only once in one sampling term. Therefore, the power conversion efficiency of the proposed AC-DC-AC converter system will get higher than a conventional soft switching converter system because of the reduced ARCPL and ARDCL circuit losses. The operation timing and terms for ARDCL and ARCPL circuits are calculated and controlled by the smoothing DC capacitor voltage and the output AC current. Using this control, the loss of the soft switching circuits are reduced owing to reduced resonant inductor current in ARCPL and ARDCL circuits as compared with the conventional controlled soft switching power conversion system. The operating performances of proposed soft switching AC-DC-AC converter treated here are evaluated on the basis of experimental results in a 50kVA setup in this paper. As a result of experiment on the 50kVA system, it was confirmed that the proposed circuit could reduce conduction noise below 10 MHz and improve the conversion efficiency from 88. 5% to 90.5%, when compared with the hard switching circuit.

Cellular analysis of cleavage-stage chick embryos reveals hidden conservation in vertebrate early development

Nagai, Hiroki,Sezaki, Maiko,Kakiguchi, Kisa,Nakaya, Yukiko,Lee, Hyung Chul,Ladher, Raj,Sasanami, Tomohiro,Han, Jae Yong,Yonemura, Shigenobu,Sheng, Guojun The Company of Biologists 2015 Development (Cambridge) Vol.142 No.7

<▼1><P>Birds and mammals, phylogenetically close amniotes with similar post-gastrula development, exhibit little conservation in their post-fertilization cleavage patterns. Data from the mouse suggest that cellular morphogenesis and molecular signaling at the cleavage stage play important roles in lineage specification at later (blastula and gastrula) stages. Very little is known, however, about cleavage-stage chick embryos, owing to their poor accessibility. This period of chick development takes place before egg-laying and encompasses several fundamental processes of avian embryology, including zygotic gene activation (ZGA) and blastoderm cell-layer increase. We have carried out morphological and cellular analyses of cleavage-stage chick embryos covering the first half of pre-ovipositional development, from Eyal-Giladi and Kochav stage (EGK-) I to EGK-V. Scanning electron microscopy revealed remarkable subcellular details of blastomere cellularization and subgerminal cavity formation. Phosphorylated RNA polymerase II immunostaining showed that ZGA in the chick starts at early EGK-III during the 7th to 8th nuclear division cycle, comparable with the time reported for other yolk-rich vertebrates (e.g. zebrafish and <I>Xenopus</I>). The increase in the number of cell layers after EGK-III is not a direct consequence of oriented cell division. Finally, we present evidence that, as in the zebrafish embryo, a yolk syncytial layer is formed in the avian embryo after EGK-V. Our data suggest that several fundamental features of cleavage-stage development in birds resemble those in yolk-rich anamniote species, revealing conservation in vertebrate early development. Whether this conservation lends morphogenetic support to the anamniote-to-amniote transition in evolution or reflects developmental plasticity in convergent evolution awaits further investigation.</P></▼1><▼2><P><B>Summary:</B> Early chick embryos share previously unappreciated features with anamniote embryos such as the timing of zygotic gene activation and yolk syncytial layer formation.</P></▼2>

Synchronization of Circadian Oscillation of Phosphorylation Level of KaiC In Vitro

Nagai, T.,Terada, T.P.,Sasai, M. Biophysical Society ; Published for the Biophysica 2010 Biophysical journal Vol.98 No.11

In recent experimental reports, robust circadian oscillation of the phosphorylation level of KaiC has been reconstituted by incubating three cyanobacterial proteins, KaiA, KaiB, and KaiC, with ATP in vitro. This reconstitution indicates that protein-protein interactions and the associated ATP hydrolysis suffice to generate the oscillation, and suggests that the rhythm arising from this protein-based system is the circadian clock pacemaker in cyanobacteria. The mechanism of this reconstituted oscillation, however, remains elusive. In this study, we extend our previous model of oscillation by explicitly taking two phosphorylation sites of KaiC into account and we apply the extended model to the problem of synchrony of two oscillatory samples mixed at different phases. The agreement between the simulated and observed data suggests that the combined mechanism of the allosteric transition of KaiC hexamers and the monomer shuffling between them plays a key role in synchronization among KaiC hexamers and hence underlies the population-level oscillation of the ensemble of Kai proteins. The predicted synchronization patterns in mixtures of unequal amounts of two samples provide further opportunities to experimentally check the validity of the proposed mechanism. This mechanism of synchronization should be important in vivo for the persistent oscillation when Kai proteins are synthesized at random timing in cyanobacterial cells.

In Vitro Production of Porcine Embryos

Nagai, T.,Kikuchi, K. 한국수정란이식학회 2002 한국수정란이식학회 학술대회 Vol.2002 No.1

There have been intensive attempts to establish reliable methods far in vitro production (IVP) methods for of porcine embryos. Although a great deal of progress has been made, our current IVP systems still need to be improved. In this review, we focused on studies about in vitro maturation and fertilization (IVM-IVF) of porcine oocytes and their in vitro culture (IVC), especially on an excellent piglets production system using modified IVP system producing porcine blastocysts with high Quality.

Phenotypic Modulation of Vascular Smooth Muscle Cell : Dissection of Transcriptional Regulatory Mechanisms

Nagai,Ryozo 한국지질학회 2001 韓國脂質學會誌 Vol.11 No.3

Immortalized human microglial cell line: Phenotypic expression

Nagai, Atsushi,Mishima, Seiji,Ishida, Yuri,Ishikura, Hiroto,Harada, Takayuki,Kobayashi, Shotai,Kim, Seung U. Wiley Subscription Services, Inc., A Wiley Company 2005 JOURNAL OF NEUROSCIENCE RESEARCH - Vol.81 No.3

<P>Microglia are a major neuroglial component of the CNS, playing an important role as resident immunocompetent and phagocytic cells in the CNS in the event of injury and disease. To understand the role of microglia in the CNS in health and diseases, we have recently established an immortalized clonal cell line of human microglia, HMO6, from human embryonic telencephalon tissue by using a retroviral vector encoding v-myc. This immortalized microglia HMO6 cell line exhibits cell-type-specific antigens for microglia, including CD11b (Mac-1), CD68, CD86 (B7-2), HLA-ABC, HLA-DR, and RCA-1 lectin, and actively phagocytoses latex beads. © 2005 Wiley-Liss, Inc.</P>

Two-Switch Auxiliary Resonant DC Link Snubber-Assisted Three-Phase Soft Switching PWM Sinewave Power Conversion System with Minimized Commutation Power Losses

Nagai, Shinichiro,Sato, Shinji,Ahmed, Tarek,Nakaoka, Mutsuo The Korean Institute of Power Electronics 2003 JOURNAL OF POWER ELECTRONICS Vol.3 No.4

This paper presents a high-efficient and cost effective three-phase AC/DC-DC/AC power conversion system with a single two-switch type active Auxiliary Resonant DC Link (ARDCL) snubber circuit, which can minimize the total power dissipation. The active ARDCL snubber circuit is proposed in this paper and its unique features are described. Its operation principle in steady-state is discussed for the three phase AC/DC-DC/AC converter, which is composed of PWM rectifier as power factor correction (PFC) converter, sinewave PWM inverter. In the presented power converter system not only three-phase AC/DC PWM rectifier but also three-phase DC/AC inverter can achieve the stable ZVS commutation for all the power semiconductor devices. It is proved that the proposed three-phase AC/DC-DC/AC converter system is more effective and acceptable than the previous from the cost viewpoint and high efficient consideration. In addition, the proposed two-switch type active auxiliary ARDCL snubber circuit can reduce the peak value of the resonant inductor injection current in order to maximize total system actual efficiency by using the improved DSP based control scheme. Moreover the proposed active auxiliary two-switch ARDCL snubber circuit has the merit so that there is no need to use any sensing devices to detect the voltage and current in the ARDCL sunbber circuit for realizing soft-switching operation. This three-phase AC/DC-DC/AC converter system developed for UPS can achieve the 1.8% higher efficiency and 20dB lower conduction noise than those of the conventional three-phase hard-switching PWM AC/DC-DC/AC converter system. It is proved that actual efficiency of the proposed three-phase AC/DC-DC/AC converter system operating under a condition of soft switching is 88.7% under 10kw output power.

Pathophysiological Roles of ASK1-MAP Kinase Signaling Pathways

Nagai, Hiroaki,Noguchi, Takuya,Takeda, Kohsuke,Ichijo, Hidenori Korean Society for Biochemistry and Molecular Biol 2007 Journal of biochemistry and molecular biology Vol.40 No.1

Apoptosis signal-regulating kinase 1 (ASK1) is a mitogenactivated protein kinase (MAPK) kinase kinase that activates JNK and p38 kinases. ASK1 is activated by various stresses, such as reactive oxygen species (ROS), endoplasmic reticulum (ER) stress, lipopolysaccharide (LPS) and calcium influx which are thought to be responsible for the pathogenesis or exacerbations of various human diseases. Recent studies revealed the involvement of ASK1 in ROS- or ER stressrelated diseases, suggesting that ASK1 may be a potential therapeutic target of various human diseases. In this review, we focus on the current findings for the relationship between pathogenesis and ASK1-MAPK pathways.

Topical Membrane Adhesive Drug Delivery System

Nagai, Tsuneji The Korean Society of Pharmaceutical Sciences and 1985 Journal of Pharmaceutical Investigation Vol.15 No.4

BEHAVIOR OF SOLUTIONS TO A PARABOLIC-ELLIPTIC SYSTEM MODELLING CHEMOTAXIS

Nagai, Toshitaka Korean Mathematical Society 2000 대한수학회지 Vol.37 No.5

A paeabolic-elliptic system modelling chemotaxis is analysed. We study the behavior of solutions, especially the finite-time blowup of nonradial dolutions, to parabolic-elliptic system of n(n 2).