Doctor of Philosophy / Department of Anatomy and Physiology / Bruce D. Schultz / The first aim of this project is to define the cellular mechanisms that account for the low Na[superscript]+ concentration in human milk. MCF10A cells, which were derived from human mammary epithelium and grown on permeable supports, exhibit amiloride- and benzamil-sensitive short circuit current (I[subscript]sc), suggesting activity of the epithelial Na[superscript]+ channel, ENaC. When cultured in the presence of cholera toxin (Ctx), MCF10A cells exhibit greater amiloride sensitive I[subscript]sc at all time points tested, an effect that is not reduced with Ctx washout for 12 hours or by cytosolic pathways inhibitors. Ctx increases the abundance of both beta and gamma-ENaC in the apical membrane and increases its monoubiquitination but without changing total protein and mRNA levels. Additionally, Ctx increases the levels of both the phosphorylated and the nonphosphorylated forms of Nedd4-2, a ubiquitin-protein ligase that regulates ENaC degradation. The results reveal a novel mechanism in human mammary gland epithelia by which Ctx regulates ENaC-mediated Na[superscript]+ transport. The second project aim is to develop a protocol to isolate mammary gland epithelia for subsequent in vitro culture. Caprine (1[superscript]0CME) and bovine mammary epithelia (1[superscript]0BME) were isolated and cultured on permeable supports to study hormone- and neurotransmitter-sensitive ion transport. Both 1[superscript]0CME and 1[superscript]0BME cells were passed for multiple subcultures and all passages formed electrically tight barriers. 1[superscript]0CME were cultured in the presence of hydrocortisone and exhibited high electrical resistance and amiloride-sensitive I[subscript]sc, suggesting the presence of ENaC-mediated Na[superscript]+ transport. 1[superscript]0BME were grown in a complex media in the presence or absence of dexamethasone. In contrast to 1[superscript]0CME, 1[superscript]0BME exhibited no detectable amiloride-sensitive I[subscript]sc in either culture condition. However, 1[superscript]0BME monolayers responded to an adrenergic agonist, norepinephrine, and a cholinergic agonist, carbamylcholine, with rapid increases in I[subscript]sc. Thus, this protocol for isolation and primary cell culture can be used for future studies that focus on mammary epithelial cell regulation and functions. In conclusion, the results from these projects demonstrate that mammary epithelial cells form electrically tight monolayers and can exhibit neurotransmitter- and/or hormone-induced net ion transport. The mechanisms that regulate Na[superscript]+ transport across mammary gland may provide clues to prevent or treat mastitis.

Esta dissertação une antropologia e música para analisar processos contemporâneos de produção de discos e músicos na cidade de São Paulo. A questão central que permeia todo texto é a seguinte: por que ainda se grava discos na era da música digital compartilhada no ciberespaço através da internet? Em outras palavras, por que no mesmo período em que as vendas de discos físicos (CDs e discos de vinil) diminuíram, colocando as grandes companhias fonográficas numa crise sem precedentes, um grupo de compositores urbanos passou a produzir e lançar discos físicos de forma autônoma, contínua e intensa? Acompanhando processos criativos e produtivos de três compositores paulistas Kiko Dinucci, Rodrigo Campos e Tatá Aeroplano , o disco emergiu como agente fundamental realizando as mediações que possibilitam aos compositores se constituírem enquanto artistas, construindo uma imagem pública (e uma sonoridade), e conquistando reconhecimento coletivo. O mesmo processo de digitalização que desencadeou a pirataria musical na internet, desencadeou um curto-circuito entre arte e técnica no fazer musical, e um curto-circuito entre artista e público, reconfigurando o lugar social dos discos para esse grupo de compositores que ainda faz questão de gravar e lançar músicas próprias. No primeiro capítulo, baseado numa etnografia dentro de estúdios, acompanhei a gravação dos discos Bahia Fantástica (Rodrigo Campos), Tatá Aeroplano (Tatá Aeroplano) e Metal Metal (Kiko Dinucci). Identifiquei dinâmicas coletivas de arranjo das canções que caracterizam um processo criativo no qual as atividades de todos os envolvidos são permeáveis entre si, e em que arte e técnica se interpenetram. No segundo capítulo, realizei uma experimentação musical com a teoria da agência de Alfred Gell, para analisar como os discos agem fora dos estúdios transformando a vida dos envolvidos em sua produção. Os discos, tratados aqui como indexes musicais, se mostraram sujeitos atuantes nos processos de construção dos artistas. No terceiro e último capítulo, segui os três compositores na internet mapeando alguns usos e estratégias de ação no ciberespaço. Procurei descrever como os discos são disponibilizados no mundo digital, especialmente em redes sociais que possibilitam uma comunicação direta entre artistas e público. Os três capítulos juntos descrevem como os discos gravam os artistas, tanto quanto os artistas gravam os discos. / This dissertation connect anthropology and music to analyze contemporary process of record production and musicians in São Paulo. The central question that permeates the entire text is the following one: why does it still record albuns in the age of digital music shared on cyberspace through internet? In other words, why at the same time when the physical record sales decreased (CDs and vinyl records), placing large companies in an unprecedented crisis, a group of urban composers is recording and releasing physical records with autonomy, intensity and continuity? Following creative and productive processes of three composers from São Paulo Kiko Dinucci, Rodrigo Campos e Tatá Aeroplano , the disc has emerged as a central agent performing the mediations that enable the composers to build themselves as artists, building a public image (and a sonority), and acquiring collective recognition. The same digitalization process that has triggered musical piracy on internet, has triggered a shortcircuit between art and technique in the music making, and a short-circuit between artist and public, reconfiguring the records social position inside this group of composers that still record and release their songs. In the first chapter, based on an ethnography inside the studios, I followed the recording process of Bahia Fantástica (Rodrigo Campos), Tatá Aeroplano (Tatá Aeroplano) e Metal Metal (Kiko Dinucci). I have indentified songs collective dynamics of arrangements that characterize a creative process where the activities of all people involved are together permeable, and where art and technique intertwine. In the second chapter, I have conducted a musical experiment with Alfred Gells agency theory, to analyze how the records act outside the studios, transforming the social life from the people involved with its production. The records, treated here as musical indexes, have presented it selves as acting subjects in the process of an artist construction. In the third and last chapter, I have followed the composers, while mapping their uses and strategies of action on cyberspace. I have tried to describe how the records are available in the digital world, especially in social networks enabling a straight communication between artists and public. All the three chapters together describe how the album record the artists, as much as the artists record the albums.

The rapid development in renewable generation technologies and flexible distribution networks requires current infrastructure to be modified and developed to adapt high penetration levels of distributed generation. Existing distribution networks were not initially designed and anticipated to accommodate generators on large scale. Short circuit studies ensure the effectiveness of protection equipment settings and coordination is maintained in case of short circuit, despite any additional distributed generation is connected to the distribution network. This research aims to study and compare the different network fault situations for wind energy systems with induction generators, photovoltaic energy systems, and diesel generators connected to distribution networks. The simulation study will be conducted on the existing IEEE case study systems including 13 bus and 30 bus distribution test systems, using ETAP software. Short circuit analysis will be performed twice to include the ANSI/IEEE and the IEC methods for short circuit currents calculation. Simulated results showed that the wind energy systems have significant impact on the short circuit currents, whereas the photovoltaic energy systems are found to have inconsequential effect. The most moderate solution is found to be a distributed generation mix.

In this study, we add an additional layer above and under the CIGS absorber layer as a secondary absorption layer respectively. We made the conventional structure of ZnO/CdS/CIGS/Mo becomes the structure of ZnO/CdS/CIGS/InGaP/Mo and ZnO/CdS/InGaP/CIGS/Mo which can improve the conversion efficiency. And we translate the thickness proportion of Ga and the doping concentration to find out the best parameter. According to the simulation, the wavelength of EQE in 600 nm ~ 1200 nm for our proposed CIGS solar cell which the additional layer under CIGS layer has been improved when compared to the conventional CIGS solar cell. The short-circuit current density has been increased about 9 %. And the conversion efficiency has also been increased about 9 %.When the additional layer above the CIGS absorber layer, according to the simulation, the wavelength of EQE in 300 nm ~ 600 nm for our proposed CIGS solar cell is improved when compared with the conventional CIGS solar cell. The short-circuit current density has been improved about 7.7 %, the open-circuit voltage about 7.1 %, and the conversion efficiency about 20.6 %. The main reason is that when the InGaP absorption layer under the CIGS layer which can catch the light which can¡¦t be absorbed by CIGS layer. The InGaP absorption layer above the CIGS layer which can catch the light immediately.

PCWE has been used widely in oriental traditional medicine in treating edema and diarrhea. Recent studies have shown that PCWE may also have anti-tumor and anti-inflammation acts. However, few studies have been conducted to reveal the mechanisms of these effects. In the present study, we tried to elucidate the mechanisms by investigating the effects on PCWE on the regulation of ion transport across the epithelial membranes of colon, which is also useful in explaining the anti-diarrhea and anti-edema effects. Alternation in membrane potential and short-circuit current (Isc) were examined using the Ussing chamber technique. Our results showed that PCWE decreased Isc upon application to the apical side. Amiloride inhibited this Isc induced by PCWE indicating that PCWE acted on amiloride-sensitive sodium channel of the epithelium. However, when PCWE was applied to the serosal side, the Isc was not changed, indicating a minimal influence of this substance on ATP-driving Na+/K+ counter transporters. Our data also showed that the Isc decreased by PCWE could be inhibited by bumetanide and chlorothiazide (Cl¡Â channel inhibitors). We therefore concluded that PCWE could both enhance sodium transport and stimulate the secretion of Cl¡Â in colon epithelium.

Existing models describing the dynamic behavior of a six-pulse rectifier during a short-circuit fault condition are derived from switch models using time-domain average value parametric functions. Unlike these models, novel non-parametric dynamic models have been developed using analytical average-value modeling approach in this work. In this modeling approach, depending upon the number of switches conducting during a switching cycle, the operating point of the rectifier is brought into one of three modes of operation of a six-pulse rectifier. The model for each mode is represented by a differential equation. During output current calculation for the rectifier the operating model is selected based on firing angle and overlap angle functions derived in this paper. They completely characterize the dynamic behavior of current flowing through the dc inductor for a wide range of operating conditions with the exception of harmonics and asymmetrical currents which are dominant for faults occurring at the terminals of the rectifier upstream of the smoothing inductor. The results from the average value model and few other simple models have been applied for Thevenin ac source and synchronous generator supplied rectifier models to determine the characteristics of short circuit current from the rectifier. / text

Modeling of wind farms to determine their short circuit contribution in response to faults is a crucial part of system impact studies performed by power utilities. Short circuit calculations are necessary to determine protective relay settings, equipment ratings and to provide data for protection coordination. The plethora of different factors that influence the response of wind farms to short circuits makes short circuit modeling of wind farms an interesting, complex, and challenging task. Low voltage ride through (LVRT) requirements make it necessary for the latest generation of wind generators to be capable of providing reactive power support without disconnecting from the grid during and after voltage sags. If the wind generator must stay connected to the grid, a facility has to be provided to by-pass the high rotor current that occurs during voltage sags and prevent damage of the rotor side power electronic circuits. This is done through crowbar circuits which are of two types, namely active and passive crowbars, based on the power electronic device used in the crowbar triggering circuit. Power electronics-based converters and controls have become an integral part of wind generator systems like the Type 3 doubly fed induction generator based wind generators. The proprietary nature of the design of these power electronics makes it difficult to obtain the necessary information from the manufacturer to model them accurately. Also, the use of power electronic controllers has led to phenomena such as sub-synchronous control interactions (SSCI) in series compensated Type 3 wind farms which are characterized by non-fundamental frequency oscillations. SSCI affects fault current magnitude significantly and is a crucial factor that cannot be ignored while modeling series compensated Type 3 wind farms. These factors have led to disagreement and inconsistencies about which techniques are appropriate for short circuit modeling of wind farms. Fundamental frequency models like voltage behind transient reactance model are incapable of representing the majority of critical wind generator fault characteristics such as sub-synchronous interactions. The Detailed time domain models, though accurate, demand high levels of computation and modeling expertise. Voltage dependent current source modeling based on look up tables are not stand-alone models and provide only a black-box type of solution. The short circuit modeling methodology developed in this research work for representing a series compensated Type 3 wind farm is based on the generalized averaging theory, where the system variables are represented as time varying Fourier coefficients known as dynamic phasors. The modeling technique is also known as dynamic phasor modeling. The Type 3 wind generator has become the most popular type of wind generator, making it an ideal candidate for such a modeling method to be developed. The dynamic phasor model provides a generic model and achieves a middle ground between the conventional electromechanical models and the cumbersome electromagnetic time domain models. The essence of this scheme to model a periodically driven system, such as power converter circuits, is to retain only particular Fourier coefficients based on the behavior of interest of the system under study making it computationally efficient and inclusive of the required frequency components, even if non-fundamental in nature. The capability to model non-fundamental frequency components is critical for representing sub-synchronous interactions. A 450 MW Type 3 wind farm consisting of 150 generator units was modeled using the proposed approach. The method is shown to be highly accurate for representing faults at the point of interconnection of the wind farm to the grid for balanced and unbalanced faults as well as for non-fundamental frequency components present in fault currents during sub-synchronous interactions. Further, the model is shown to be accurate also for different degrees of transmission line compensation and different transformer configurations used in the test system.

This thesis presents an investigation into the power transmission limitations imposed on a VSC-HVdc converter by ac system strength and ac system impedance characteristics, quantified by the short circuit ratio (SCR). An important result of this study is that the operation of the converter is not only affected by the SCR’s magnitude, but is also significantly affected by the ac system’s impedance angle at the fundamental frequency. As the ac impedance becomes more resistive, the minimum SCR required at the rectifier side increases from that required for ideally inductive ac impedance, but it decreases at the inverter side. The finite megavolt ampere (MVA) limit of the VSC imposes a further limitation on power transfer, requiring an increase in the value of the minimum SCR. This limitation can be mitigated if additional reactive power support is provided at the point-common-connection. A state-space VSC model was developed and validated with a fully detailed non-linear EMT model. The model showed that gains of the phased-locked-loop (PLL), particularly at low SCRs greatly affect the operation of the VSC-HVdc converter and that operation at low SCRs below about 1.6 is difficult. The model also shows that the theoretically calculated power-voltage stability limit is not attainable in practice, but can be approached if the PLL gains are reduced. The thesis shows that as the VSC-HVdc converter is subject to large signal excitation, a good controller design cannot rely on small signal analysis alone. The thesis therefore proposes the application of optimization tools to coordinate the controls of multiple converters in a dc grid. A new method, the "single converter relaxation method", is proposed and validated. The design procedure of control gains selection using the single converter relaxation method for a multi-converter system is developed. A new method for selecting robust control gains to permit operation over a range of operation conditions is presented. The coordination and interaction of control parameters of multi-terminal VSC are discussed. Using the SCR information at converter bus, the gain scheduling approach to optimal gains is possible. However, compared to robust control gains setting, this approach is more susceptible to system instability.

The performance of the High voltage dc systems is dependent on the stiffness of the ac bus, it is connected to. With the traditional synchronous reference frame-phase locked loops (SRF-PLL), voltage source converters (VSC) systems with large PLL gains, connected to weak ac networks are shown to be prone to instabilities, when subject to disturbances. In this thesis a new Adaptive PLL is designed with a pre-filter topology which extracts the fundamental positive sequence component of the input voltage, to be fed into the SRF-PLL for tracking of its phase angle. Compared with other traditional PLL topologies, this Adaptive PLL shows superior immunity to voltage distortions, and also has a faster dynamic performance. The thesis presents a comparative analysis of the performance of the traditional SRF-PLL with the Adaptive PLL in a VSC control system, and its impact on stability for VSCs connected to weak ac systems (up to SCR=1.3).

This thesis presents an investigation into the power transmission limitations imposed on a VSC-HVdc converter by ac system strength and ac system impedance characteristics, quantified by the short circuit ratio (SCR). An important result of this study is that the operation of the converter is not only affected by the SCR’s magnitude, but is also significantly affected by the ac system’s impedance angle at the fundamental frequency. As the ac impedance becomes more resistive, the minimum SCR required at the rectifier side increases from that required for ideally inductive ac impedance, but it decreases at the inverter side. The finite megavolt ampere (MVA) limit of the VSC imposes a further limitation on power transfer, requiring an increase in the value of the minimum SCR. This limitation can be mitigated if additional reactive power support is provided at the point-common-connection. A state-space VSC model was developed and validated with a fully detailed non-linear EMT model. The model showed that gains of the phased-locked-loop (PLL), particularly at low SCRs greatly affect the operation of the VSC-HVdc converter and that operation at low SCRs below about 1.6 is difficult. The model also shows that the theoretically calculated power-voltage stability limit is not attainable in practice, but can be approached if the PLL gains are reduced. The thesis shows that as the VSC-HVdc converter is subject to large signal excitation, a good controller design cannot rely on small signal analysis alone. The thesis therefore proposes the application of optimization tools to coordinate the controls of multiple converters in a dc grid. A new method, the "single converter relaxation method", is proposed and validated. The design procedure of control gains selection using the single converter relaxation method for a multi-converter system is developed. A new method for selecting robust control gains to permit operation over a range of operation conditions is presented. The coordination and interaction of control parameters of multi-terminal VSC are discussed. Using the SCR information at converter bus, the gain scheduling approach to optimal gains is possible. However, compared to robust control gains setting, this approach is more susceptible to system instability.