2+-dependent processes in a wide variety of cells. In the yeast, Saccharomyces cerevisiae, calcineurin effects Ca 2+ -dependent changes in gene expression through regulation of the Crz1p transcription factor. We show here that calcineurin dephosphorylates Crz1p and that this results in translocation of Crz1p to the nucleus. We identify a region of Crz1p that is required for calcineurin-dependent regulation of its phosphorylation, localization, and activity, and show that this region has significant sequence simlarity to a portion of NF-AT, a family of mammalian transcription factors whose localization is also regulated by calcineurin. Thus, the mechanism of Ca 2+ /calcineurin-dependent signaling shows remarkable conservation between yeast and mammalian cells. Received January 25, 1999; accepted February 5, 1999. Calcineurin is a conserved Ca 2+ /calmodulin-dependent protein phosphatase that plays a critical role in Ca 2+ signaling. The activation of T lymphocytes by antigen requires calcineurin, and the immunosuppressive drugs, FK506 and cyclosporin A, act by inhibiting this phosphatase (Friedman and Weissman 1991;Liu et al. 1991a;Clipstone and Crabtree 1992;O'Keefe et al. 1992). NF-AT, a family of mammalian transcription factors, is the critical target of calcineurin-dependent regulation for Tcell activation as well as for other other processes such as cardiac development and hypertrophy (Clipstone and Crabtree 1992;O'Keefe et al. 1992;Rao et al. 1997;de la Pompa et al. 1998;Molkentin et al. 1998;Ranger et al. 1998). Dephosphorylation of NF-AT by calcineurin results in its translocation to the nucleus, where it activates transcription (Flanagan et al. 1991;Jain et al. 1993;Shaw et al. 1995;Beals et al. 1997).In the yeast Saccharomyces cerevisiae, calcineurin is required for cell viability under specific environmental conditions. Calcineurin is a heterodimer of a catalytic subunit (encoded by the CNA1 and CNA2 genes) and a regulatory subunit (encoded by CNB1) (Cyert et al. 1991;Liu et al. 1991b;Cyert and Thorner 1992 , or alkaline pH, and lose viability during prolonged incubation with mating pheromone (Nakamura et al. 1993;Mendoza et al. 1994;Moser et al. 1996;Pozos et al. 1996;Withee et al. 1997). All of these conditions, as well as addition of Ca 2+ to the growth medium, induce Ca 2+ / calcineurin-dependent gene expression (Mendoza et al. 1994;Mazur et al. 1995;Cunningham and Fink 1996).Previously, we elucidated the mechanism by which transcription of one target gene, FKS2, is activated in response to Ca 2+. A 24 bp region of the FKS2 promoter, the CDRE, is sufficient to direct Ca 2+ -induced gene expression, and this transcription requires both calcineurin and the Crz1p transcription factor (Stathopoulos and Cyert 1997). crz1⌬ mutants fail to activate calcineurin-dependent transcription, and display growth and viability defects similar to those of calcineurin mutants (Matheos et al. 1997;Stathopoulos and Cyert 1997). Thus, many of the physiological functions of calcineurin in yeast are mediated by its reg...
Partial discharge (PD) as one of well-known signatures of defects in the insulation system of high voltage equipment has been studied over eight decades. It is of a great interest to power grid operators and owners to identify and distinguish local weak spots in insulation system of the key components of power system by using the obtained PD information to make timely decision thus to avoid any unexpected failures in the system. This article reviews the research progress of PD in high voltage apparatus, including motors and generators, cables, transformers and gas insulated equipment, with attempts to assess the severity of different types of PD initiating defects as well as key PD features that can be selected for classifying defects. Experimental and on-site test results for each type of discharge and defect associated are summarized and discussed. Also, development of these defects during operation of equipment caused by changes in physical and chemical parameters of defect and/or insulation, and its impact on phaseresolved PD pattern variation are thoroughly explained. It is expected that this paper can provide a comprehensive guideline for PD data analysis of available PD information extracted by conventional PD acquisition instruments for both engineers and asset managers of high voltage apparatus. INDEX TERMSPartial Discharge (PD), high voltage motor, power cable, power transformer, GIS, GIL. Tohid Shahsavarian received the Bachelor's degree in Electrical Engineering from the University of Tabriz in 2011, and the Master's degree from the University of Science and Technology (IUST) in 2013. Then, he worked in the Department of Transmission and Distribution in Monenco Iran Consulting Engineers Company.He is currently working toward the Ph.D. degree at the Electrical and Computer Engineering Department of the University of Connecticut, and his research interests include the partial discharge analysis and risk assessment of AC and DC power cables, enhancement of insulation performance in electrical and electronic components for aerospace application, reliability analysis and protection of HVAC/HVDC grids, geomagnetic disturbances (GMD).
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