Voltage-gated ion channels mediate electrical excitability of cellular membranes. Re- duced models of the voltage sensor (VS) of Kv channels produce insight into the electrostatic physics underlying the response of the highly positively charged S4 transmembrane domain to changes in membrane potential and other electrostatic parameters. By calculating the partition function computed from the electrostatic energy over translational and/or rotational degrees of freedom, I compute expectations of charge displacement, energetics, probability distributions of translation & rotation and Maxwell stress for arrangements of S4 positively charged residues and S2 & S3 negatively charged counter-charges; these computations can then be compared with experimental results to elucidate the role of various putative atomic level features of the VS. A "paddle" model (Jiang et al., 2003) is rejected on electrostatic grounds, owing to unfavorable energetics, insufficient charge displacement and excessive Maxwell stress. On the other hand, a "sliding helix" model (Catterall, 1986) with three local counter-charges, a protein dielectric coefficient of 4 and a 2/3 interval of counter-charge positioning relative to the S4 alpha-helix period of positive residues is electrostatically reasonable, comparing well with Shaker (Seoh et al., 1996). Lack of counter-charges destabilizes the S4 in the membrane; counter-charge interval helps determine the number and shape of energy barriers and troughs over the range of motion of the S4; and the local dielectric coefficient of the protein (S2, S3 & S4) constrains the height of energy maxima relative to the energy troughs. These "sliding helix" models compare favorably with experimental results for single & double mutant charge experiments on Shaker by Seoh et al. (1996). Single S4 positive charge mutants are predicted quite well by this model; single S2 or S3 negative counter-charge mutants are predicted less well; and double mutants for both an S4 charge and an S2 or S3 counter-charge are characterized least well by these electrostatic models (which do not include gating load, unlike their biological analogs). Further computational and experimental investigation of S2 & S3 counter-charge structure for voltage-gated ion channels is warranted.

Kv channel interacting proteins (KChIPs) are Ca2+-binding proteins with four EF-hands and well-known to modulate Kv4.2 channel gating. The present study is carried out to investigate the molecular mechanism related to regulate the interaction of KChIP2.2 and KChIP4a with Kv channel. In comparison with KChIP4a, the interaction of KChIP2.2 with Kv4.2 was more obvious in the absence of Ca2+ or Mg2+. However the binding of KChIP2.2 and KChIP4a toward Kv4.2 increased with increasing Ca2+ and Mg2+ concentration. Nevertheless, no individual regions within KChIP2.2 and KChIP4a could exclusively fulfill the interaction between KChIPs mutants and Kv channel. Fluorescence measurement showed that KChIP2.2 possessed both high affinity and low affinity Ca2+-binding sites, but only low affinity Ca2+-binding site was observed with KChIP4a. However, both of them have only one Mg2+-binding site. Studies on the truncated mutants revealed that the EF-hand 4 of KChIP2.2 was related to high affinity binding with Ca2+, and the integrity of molecular structure of KChIP2.2 and KChIP4a was important for Ca2+ -and Mg2+-binding. The thermal stability of KChIP2.2 and KChIP4 was found to be differentiately affected by Ca2+ and Mg2+. Proteolytic digestion and thiol reactivity assays also supported that Ca2+ and Mg2+-induced conformational change of KChIP2.2 was differed from KChIP4a. Moreover, in cells co-transfected with Kv4.2 cDNA, it was formed that KChIP2.2 trafficking to the cell surface was increased by elevating intracellular Ca2+ concentration, but no noticeable change was observed for KChIP4a. Taken together, these results suggest that the conformational changes of KChIP2.2 and KChIP4a differently induced by Ca2+ and Mg2+ affect their binding with Kv channel and/or cellular distribution.

In the nervous system, the roles of Kv channels are well established as being critical for regulating action potential frequency, membrane potential, and neurotransmitter release. However, their role in glial cells, a non-excitable cell type, is yet to be fully understood. Whole-cell current kinetics, pharmacology, immunocytochemistry and RT-PCR were used to characterize A-type current in hippocampal astrocyte cultures to better understand its function. Pharmacological analysis suggests that ~70%, 10% and less than 5% of total A current is associated with Kv4, Kv3 and Kv1 channels, respectively. In addition, pharmacology and kinetics provide novel evidence for a significant contribution of KChIP accessory proteins to astrocytic A-channel composition. Localization of the Shaw Kv3.4 channel to astrocytic processes and the Shal Kv4.3 channel to soma suggest that these channels serve a specific function. Since astrocytes are known to be subjected to neuronal firing frequencies of up to 200 Hz in the hippocampus, the role of A currents in membrane voltage oscillations was assessed. Although TEA-sensitive delayed-rectifying currents are involved in the extent of repolarization, 4-AP-sensitive A currents serve to increase the rate. Astrocytes and HEK293 cells were used to investigate the mechanism of the previously found GABAA induced anion-mediated reduction of Kv channels in more detail. Astrocytes demonstrate an anion concentration specific depolarizing effect on inactivating A-type (also termed transient voltage-gated) K+ channel activation kinetics whereas a hyperpolarizing effect was seen upon expression of Kv4.2 or Kv1.4 in HEK293 cells, but only after disruption of the cytoskeleton using cytochalasin D. It is hypothesized that cytoskeletal interactions and Cl -mediated effects are mediated through N-terminal conformational stabilities. <p>In summary, the results indicate that hippocampal astrocytes in vitro express multiple A type Kv channel á subunits with accessory, Ca2+-sensitive cytoplasmic subunits that appear to be specifically localized to subcellular membrane compartments. Functions of these channels remain to be determined in a physiological setting, but suggest that A-type Kv channels enable astrocytes to respond rapidly with membrane voltage oscillations to high frequency incoming signals, possibly synchronizing astrocyte function to neuronal activity. Furthermore, studies of anion and cytoskeletal effects on Kv channels demonstrate channel function to be highly localized/targeted and susceptible to changes in ionic environment.

In the nervous system, the roles of Kv channels are well established as being critical for regulating action potential frequency, membrane potential, and neurotransmitter release. However, their role in glial cells, a non-excitable cell type, is yet to be fully understood. Whole-cell current kinetics, pharmacology, immunocytochemistry and RT-PCR were used to characterize A-type current in hippocampal astrocyte cultures to better understand its function. Pharmacological analysis suggests that ~70%, 10% and less than 5% of total A current is associated with Kv4, Kv3 and Kv1 channels, respectively. In addition, pharmacology and kinetics provide novel evidence for a significant contribution of KChIP accessory proteins to astrocytic A-channel composition. Localization of the Shaw Kv3.4 channel to astrocytic processes and the Shal Kv4.3 channel to soma suggest that these channels serve a specific function. Since astrocytes are known to be subjected to neuronal firing frequencies of up to 200 Hz in the hippocampus, the role of A currents in membrane voltage oscillations was assessed. Although TEA-sensitive delayed-rectifying currents are involved in the extent of repolarization, 4-AP-sensitive A currents serve to increase the rate. Astrocytes and HEK293 cells were used to investigate the mechanism of the previously found GABAA induced anion-mediated reduction of Kv channels in more detail. Astrocytes demonstrate an anion concentration specific depolarizing effect on inactivating A-type (also termed transient voltage-gated) K+ channel activation kinetics whereas a hyperpolarizing effect was seen upon expression of Kv4.2 or Kv1.4 in HEK293 cells, but only after disruption of the cytoskeleton using cytochalasin D. It is hypothesized that cytoskeletal interactions and Cl -mediated effects are mediated through N-terminal conformational stabilities. <p>In summary, the results indicate that hippocampal astrocytes in vitro express multiple A type Kv channel á subunits with accessory, Ca2+-sensitive cytoplasmic subunits that appear to be specifically localized to subcellular membrane compartments. Functions of these channels remain to be determined in a physiological setting, but suggest that A-type Kv channels enable astrocytes to respond rapidly with membrane voltage oscillations to high frequency incoming signals, possibly synchronizing astrocyte function to neuronal activity. Furthermore, studies of anion and cytoskeletal effects on Kv channels demonstrate channel function to be highly localized/targeted and susceptible to changes in ionic environment.

Mutagenesis studies on the four EF-hands of KChIP2.2 (Potassium channel-interacting protein 2.2) were carried out to explore the conformational transition upon the binding of Ca2+ and Mg2+ and the subsequent effect on the interaction between KChIP2.2 and Kv4.2. CD spectra indicated that Ca2+- and Mg2+-loaded wild-type and mutated KChIP2.2 altered the secondary structure contents. In contrast to other mutants, mutation on EF1 caused a notably change in the secondary structure of KChIP2.2. Fluorescence measurement revealed that EF-hands 3 and 4 were high affinity Ca2+-binding sites within KChIP2.2 molecule, but the binding of Mg2+ with KChIP2.2 was marginally affected by EF-hand mutations. The results of size-exclusion chromatography showed that mutations on EF-1, EF-2 and EF-3 induced the oligomerization of KChIP2.2 and the extent of oligomerization was enhanced by Ca2+ and Mg2+. No significant differences were noted when wild-type and mutated KChIP2.2 bound with porcine brain membrane and liposome either in the absence or presence of Ca2+- and Mg2+. Pull down assay showed that KChIP2.2 and EF-hand mutants could bind with Kv4.2 in the absence of Ca2+ and Mg2+, but the interaction was enhanced by Ca2+ and Mg2+. However, the binding capability of mutants for Kv4.2 was notably lower than that observed for wild-type KChIP2.2. It was found that, in sharp contrast to that EF1 mutant exclusively localized in the nucleus, the other EF-hand mutants and wild-type protein distributed within nucleus as well as cytoplasm. Elevating intracellular Ca2+ concentration caused the translocation of EF1 mutant to cytoplasm but no appreciable effect on other mutants and wild-type KChIP2.2. . Taken together, these results suggest that the integrity of the four EF-hands are involved in function to stabilize conformation for binding with Kv channel, but this conformational transition is not essential for the binding to cell membrane.

Šiame darbe nagrinėjamos skirstomojo tinklo 0,4- 10 kV linijų gedimų problemos, remiantis mokslinės literatūros analize ir praktinio darbo patirties apibendrinimu. Nustatomi Šiaulių regiono kiekvieno rajono elektros tinklų 0,4-10 kV linijų gedimų skaičius, atjungtų vartotojų skaičius, atjungimų trukmės ir priežastys. Apskaičiuojami Šiaulių regiono kiekvieno rajono elektros tinklo patikimumo rodikliai, daugiausiai gendančios elektros linijos parengties ir priverstinės prastovos koeficientai bei veikimo ir gedimo tikimybės per 12 mėnesių. / This paper deals with the distribution network of 0.4 and 10 kV line fault problems based on the scientific literature and practical experience. The number of faults, the number of disconnections, the disconnections times and reasons of 0.4-10 kV grid lines of Šiauliai region have been investigated. Reliability indicators of electrical network of Šiauliai region have been calculated. Working and failure probabilities of the electrical network during 12 months have been calculated.

Detta arbete har utförts hos Varberg Energi AB och syftat till att presentera olika koncept som alternativ till konventionella 130 kV luftisolerade fördelningsstationer. Arbetet är tänkt att kunna vara en del i en uppdragsbeskrivning för en kommande ombyggnation. De alternativ som står tillbuds bygger ofta på att någon eller flera komponenter innehåller svavelhexafluorid, SF6, vilken har en stor negativ påverkan på växthuseffekten om den släpps ut i atmosfären. De alternativ av komponenter, exempelvis brytare, som inte innehåller SF6 är få och väsentligt mycket dyrare. Dock är fortfarande konceptlösningar som använder sig av luft som isolationsmedium till komponenter som inte är brytare, frånskiljare eller dylikt de billigaste.  Alternativen som framkommit i denna rapport och studerats närmare är ABB:s Urban-koncept, GIS med SF6 och Siemens Blue GIS med renad luft och vakuumbrytare. Fokus har varit lösningarnas beskaffenhet gällande säkerhet för tredje man, enkelhet i underhåll, klimatpåverkan och tillförlitlighet. Önskvärt är en helhetslösning där underhåll eller reparationer kan utföras i de olika facken i 130 kV-stationen utan att det påverkar driften och orsakar ett avbrott. Att finna en lösning som inte kräver SF6-gas i någon del av fördelningsstationen ger många lättnader i regelverk, mindre övervakning och kostnader förknippade med denna. En balansgång behöver göras mellan ekonomiska intressen, miljöpåverkan, inspektionsintervall, felavhjälpning och eventuella framtida miljökrav för högspänningsanläggningar. Det förstärkta sabotageskyddet som en byggnad ger har varit en klar fördel som lyfts fram hos de besökta anläggningarna. Vid val av konceptlösning kan storleken hos och kompetensen inom den egna organisationen vara en faktor att ta hänsyn till. Även utformning och val av lösning för tidigare och framtida stationer kan behöva tas hänsyn till.

Como parte de um projeto de pesquisa e desenvolvimento (P&D) mais amplo, que está sendo desenvolvido pela Escola de Engenharia de São Carlos - USP e Companhia Paulista de Força Luz (CPFL), com previsão de conclusão para 2010, este trabalho tem por objetivo apresentar os principais procedimentos para a realização da repotenciação de linhas de subtransmissão de 34,5 KV para 69 KV. Para atingir esse objetivo, é realizada inicialmente uma apreciação do estágio atual dos estudos sobre o tema, abordando inclusive outros métodos além daquele que será objeto específico desse estudo. Em seguida, discutem-se tópicos relevantes dos métodos apresentados de forma que, esse estudo, além de cumprir o já mencionado objetivo específico de apresentar soluções para aumentar a capacidade de transmissão de uma determinada linha, mantendo a sua faixa de servidão, indicará parâmetros válidos para a realização de outros projetos da mesma natureza. Sequencialmente são apresentadas as etapas desenvolvidas para a operacionalização da repotenciação de uma linha, a começar pela escolha da mais adequada, a seleção do método a ser utilizado, levando-se em consideração tanto a alteração do limite térmico da linha quanto à elevação de sua tensão operativa e os aspectos ambientais que envolvem a repotenciação. Finalmente, fazendo uso dos softwares ATP, através da interface gráfica ATPDraw (empregado para as XIV simulações de transitórios eletromagnéticos) e do Flux®, para as simulações dos campos elétricos em torno dos isoladores, realizou-se um conjunto de simulações computacionais pertinentes para um bom conhecimento do funcionamento da linha de subtransmissão a ser repotenciada na classe de interesse. Todas as etapas e as conclusões preliminares sobre o assunto delineado serão apresentadas neste documento. / As part of a wider research and development project, which is being developed between Escola de Engenharia de São Paulo USP and Companhia Paulista de Força e Luz (CPFL), scheduled to be finished in 2010, this work aims to present the main procedures to perform a repowering on subtransmission lines from 34.5 KV to 69 KV. To achieve this purpose, an assessment of the current studies about the subject is carried out, including an approach of other methods besides the one which is going to be the specific object of this study. After this, relevant points about the main methods are discussed in such a way that this study, in addition to serve its specific purpose, that is to present solutions in order to increase the transmission capacity of a determined line, keeping its right-of-way, can also point out valuable parameters which can be used to develop other projects of similar nature. Sequentially, the steps followed to operationalize the line repowering are presented, starting with the choice of the most suitable line, the selection of the method to be used, and taking into consideration both the change in the line thermal limit and the elevation on its operating voltage and also the environmental aspects involving repowering. At last, making use of ATP software throughout ATPDraw graphical interface (which is used to simulate electromagnetic transients) and Flux®, that simulates electrical fields around insulators, it is carried out a set of computational XVI simulations which are relevant to a good knowledge of the line subtransmission running. All the steps and preliminary conclusions about the subject are going to be outlined on this document.

Este trabalho visa apresentar uma análise metodológica para viabilizar a realização da repotenciação, elevando a classe de tensão de linhas de distribuição de 34,5 kV para a classe de subtransmissão de 69 kV. Foi realizado um levantamento de casos de repotenciação de linhas de transmissão, inclusive para a alternativa de elevação da tensão de operação da linha. Foram analisados modelos matemáticos apropriados para a representação da linha frente a transitórios eletromagnéticos como curtos-circuitos e descargas atmosféricas e ainda, um estudo sobre o procedimento a ser realizado dispondo-se de um software baseado na teoria de elementos finitos para a verificação do nível básico de isolamento das estruturas pertencentes à linha. Assim, a linha piloto foi representada no software ATP, utilizando-se a interface ATPDraw, e foi submetida a diversos transitórios eletromagnéticos. A partir dos valores de tensão observados nesses distúrbios, iniciaram-se novas simulações computacionais por meio do software FLUX®, que é baseado na teoria dos elementos finitos, para avaliar o comportamento do campo elétrico nas diferentes estruturas da linha, considerando a cruzeta de madeira e os isoladores cerâmicos. Dessa forma, esse estudo, avalia as simulações computacionais realizadas e aponta quais as estruturas da linha estão aptas a operar na classe de tensão de 69 kV, ou ainda, quais alterações permitirão que estruturas menos seguras possam operar neste novo nível de tensão. Todas as etapas e as conclusões finais sobre o assunto delineado são apresentadas neste documento. / This work presents a methodological analysis to make repowering distribution line possible, raising the voltage level from 34.5 kV to 69 kV (sub transmission level). A literature review of transmission line upgrading was accomplished, including the alternative of raising the line operating voltage. Proper mathematical models were analyzed for the line representation facing electromagnetic transients such as short circuits and lightning. In addition, a software based on finite elements theory for the verification of the basic insulation level of the structures (poles and crossarms) belonging to the line was utilized. Thus, a pilot line was modeled in the ATP software, using the ATPDraw interface, and it was subjected to various electromagnetic transients. From the voltage values observed in these disturbances, new computer simulations were carried out using FLUX®, a finite elements theory based software capable of evaluating the electrical field behavior in different structures of the line, considering wooden crossarms and ceramic insulators. In this context, the present study analyze the computer simulations and points out which line structures are able to operate in the 69 kV voltage level, or even indicates which alterations will enable the less secure structures to operate in this new voltage level. All the stages and final conclusions about the outlined subject are presented in this document.

Como parte de um projeto de pesquisa e desenvolvimento (P&D) mais amplo, que está sendo desenvolvido pela Escola de Engenharia de São Carlos - USP e Companhia Paulista de Força Luz (CPFL), com previsão de conclusão para 2010, este trabalho tem por objetivo apresentar os principais procedimentos para a realização da repotenciação de linhas de subtransmissão de 34,5 KV para 69 KV. Para atingir esse objetivo, é realizada inicialmente uma apreciação do estágio atual dos estudos sobre o tema, abordando inclusive outros métodos além daquele que será objeto específico desse estudo. Em seguida, discutem-se tópicos relevantes dos métodos apresentados de forma que, esse estudo, além de cumprir o já mencionado objetivo específico de apresentar soluções para aumentar a capacidade de transmissão de uma determinada linha, mantendo a sua faixa de servidão, indicará parâmetros válidos para a realização de outros projetos da mesma natureza. Sequencialmente são apresentadas as etapas desenvolvidas para a operacionalização da repotenciação de uma linha, a começar pela escolha da mais adequada, a seleção do método a ser utilizado, levando-se em consideração tanto a alteração do limite térmico da linha quanto à elevação de sua tensão operativa e os aspectos ambientais que envolvem a repotenciação. Finalmente, fazendo uso dos softwares ATP, através da interface gráfica ATPDraw (empregado para as XIV simulações de transitórios eletromagnéticos) e do Flux®, para as simulações dos campos elétricos em torno dos isoladores, realizou-se um conjunto de simulações computacionais pertinentes para um bom conhecimento do funcionamento da linha de subtransmissão a ser repotenciada na classe de interesse. Todas as etapas e as conclusões preliminares sobre o assunto delineado serão apresentadas neste documento. / As part of a wider research and development project, which is being developed between Escola de Engenharia de São Paulo USP and Companhia Paulista de Força e Luz (CPFL), scheduled to be finished in 2010, this work aims to present the main procedures to perform a repowering on subtransmission lines from 34.5 KV to 69 KV. To achieve this purpose, an assessment of the current studies about the subject is carried out, including an approach of other methods besides the one which is going to be the specific object of this study. After this, relevant points about the main methods are discussed in such a way that this study, in addition to serve its specific purpose, that is to present solutions in order to increase the transmission capacity of a determined line, keeping its right-of-way, can also point out valuable parameters which can be used to develop other projects of similar nature. Sequentially, the steps followed to operationalize the line repowering are presented, starting with the choice of the most suitable line, the selection of the method to be used, and taking into consideration both the change in the line thermal limit and the elevation on its operating voltage and also the environmental aspects involving repowering. At last, making use of ATP software throughout ATPDraw graphical interface (which is used to simulate electromagnetic transients) and Flux®, that simulates electrical fields around insulators, it is carried out a set of computational XVI simulations which are relevant to a good knowledge of the line subtransmission running. All the steps and preliminary conclusions about the subject are going to be outlined on this document.