Adaptability is one of the reasons for the success of bacteria, allowing them to survive in conditions where no other organisms would be able to thrive. Nitrogen deficiency, for example, can be a limiting factor for the growth of micro-organisms, as this element is an essential part of almost all types of biomolecules. As such, some bacteria have evolved specific mechanisms to overcome nitrogen limitation. Nitrogen fixing bacteria, or diazotrophs, use a specific enzyme complex, nitrogenase, in order to harness this element from the enormous reservoir that is the Earth’s atmosphere. However, nitrogen fixation is a demanding process for the cells, requiring vast amounts of energy and tight regulation. In this thesis we explore the mechanisms regulating nitrogen fixation in Rhodospirillum rubrum, a purple non-sulphur photosynthetic bacterium. Using proteomics tools, we show how the regulation of both the nitrogen and carbon fixation processes is interconnected, possibly in order to maintain the intracellular redox balance. Using a new detergent molecule, we also demonstrate how nitrogen availability affects the chromatophore membrane proteome. Our studies have revealed the crucial role of the cellular pool of 2-oxoglutarate (2OG) for adequate signaling through the PII proteins and the effects resulting from artificially manipulating this metabolite’s concentration. In R. rubrum nitrogenase is also subjected to post-translational control (the “switch-off” effect) and this work shows for the first time that the enzyme modifying nitrogenase (Dinitrogenase Reductase ADP-ribsosyl Transferase or DRAT) forms a complex with the PII protein GlnB. This complex allows DRAT activation and its formation – and, therefore, DRAT activity – is regulated by binding of ADP:ATP and 2OG to GlnB. Upon light withdrawal, nitrogenase activity anaerobically in the dark is also here demonstrated to be dependent on the activity of the pathway starting in pyruvate formate-lyase and we show how different nitrogen sources influence the switch-off response. This response can, in some conditions, be modified by addition of pyruvate and we have studied how this metabolite influences nitrogenase activity and switch-off regulation. This study allows a better understanding of the underlying processes controlling the metabolic routes in R. rubrum and also provides new insights into regulation of enzyme activity, paving the road for the complete establishment of the mechanisms regulating nitrogenase switch-off. / <p>At the time of the doctoral defense, the following papers were unpublished and had a status as follows: Paper 2: In press. Paper 3: Submitted. Paper 4: Manuscript. Paper 5: Submitted.</p>

The sharing of the terrestrial TV frequency spectrum with Secondary Users (SUs) is presently the focus point of numerous research efforts worldwide. In many regulatory domains, contiguous blocks of VHF and UHF spectrum are available for exclusive use by the terrestrial TV broadcasting incumbents. However, this notion is currently challenged by the spectrum management paradigm of Dynamic Spectrum Access (DSA), advocating that this spectrum may be shared on a dynamic basis with SUs. The migration of analogue terrestrial TV to Digital Terrestrial Television (DTT) has also catalysed the notion that the terrestrial TV frequency spectrum will no longer be exclusively used for terrestrial broadcasting. Some administrations have already embraced this technology, reforming spectrum policy to allow unlicensed secondary access to the Spectral Opportunities (SOs) present in the terrestrial TV frequency bands. The Independent Communications Authority of South Africa (ICASA) has expressed early interest in the possibilities of TV white space technology and its possible utility in exploiting the SOs that exist in the terrestrial TV frequency bands. Core to the issues mentioned above is the quantification of the Spectral Opportunity (SO) available. To this end, the work presented in this thesis gives a quantified estimate of the SO available in South Africa. This work is the first of its kind for the South African environment and uncovers new knowledge regarding SO in South Africa. SO is analysed and quantified on provincial and national level for three discrete points in time: before the start of dual-illumination, during dual illumination and after analogue switch-off. A system model that is able to produce the required geo-referenced field strength coverage and SO maps is conceptualised and implemented. A complete standards compliant model is implemented from scratch, verified and validated, with design decisions specific to the South African context. The analysis methodology is developed with rigour. The construction of the TV transmitter database, definition of incumbent protection criteria and development of the required analysis metrics to quantify SO are presented. SO in the VHF and UHF terrestrial TV frequency bands is quantified by expressing SO in terms of the number of available channels, weighted respectively by land area and population density. The analysis results indicate that significant SO is available for exploitation by TV white space devices in the terrestrial TV spectrum in South Africa. The effects of radio astronomy advantage areas on the SO available are also investigated. The probability of finding contiguous channels in the Very High Frequency (VHF) and Ultra High Frequency (UHF) bands is also quantified. A comparative study, comparing the SO for South Africa with related work in Europe and the United States of America (USA), is also performed. Finally, maps that visualise the SO available are constructed for the three discrete time periods evaluated. / Thesis (PhD (Computer Engineering))--North-West University, Potchefstroom Campus, 2013

The sharing of the terrestrial TV frequency spectrum with Secondary Users (SUs) is presently the focus point of numerous research efforts worldwide. In many regulatory domains, contiguous blocks of VHF and UHF spectrum are available for exclusive use by the terrestrial TV broadcasting incumbents. However, this notion is currently challenged by the spectrum management paradigm of Dynamic Spectrum Access (DSA), advocating that this spectrum may be shared on a dynamic basis with SUs. The migration of analogue terrestrial TV to Digital Terrestrial Television (DTT) has also catalysed the notion that the terrestrial TV frequency spectrum will no longer be exclusively used for terrestrial broadcasting. Some administrations have already embraced this technology, reforming spectrum policy to allow unlicensed secondary access to the Spectral Opportunities (SOs) present in the terrestrial TV frequency bands. The Independent Communications Authority of South Africa (ICASA) has expressed early interest in the possibilities of TV white space technology and its possible utility in exploiting the SOs that exist in the terrestrial TV frequency bands. Core to the issues mentioned above is the quantification of the Spectral Opportunity (SO) available. To this end, the work presented in this thesis gives a quantified estimate of the SO available in South Africa. This work is the first of its kind for the South African environment and uncovers new knowledge regarding SO in South Africa. SO is analysed and quantified on provincial and national level for three discrete points in time: before the start of dual-illumination, during dual illumination and after analogue switch-off. A system model that is able to produce the required geo-referenced field strength coverage and SO maps is conceptualised and implemented. A complete standards compliant model is implemented from scratch, verified and validated, with design decisions specific to the South African context. The analysis methodology is developed with rigour. The construction of the TV transmitter database, definition of incumbent protection criteria and development of the required analysis metrics to quantify SO are presented. SO in the VHF and UHF terrestrial TV frequency bands is quantified by expressing SO in terms of the number of available channels, weighted respectively by land area and population density. The analysis results indicate that significant SO is available for exploitation by TV white space devices in the terrestrial TV spectrum in South Africa. The effects of radio astronomy advantage areas on the SO available are also investigated. The probability of finding contiguous channels in the Very High Frequency (VHF) and Ultra High Frequency (UHF) bands is also quantified. A comparative study, comparing the SO for South Africa with related work in Europe and the United States of America (USA), is also performed. Finally, maps that visualise the SO available are constructed for the three discrete time periods evaluated. / Thesis (PhD (Computer Engineering))--North-West University, Potchefstroom Campus, 2013

Com o sistema binário e a convergência digital das mídias, dispositivos de comunicação como celulares, computadores e até mesmo aparelhos receptores de televisão deixam de desempenhar apenas a função principal para a qual foram desenvolvidos e passam a se constituir, devido à interoperabilidade de sistemas e à internet, em meios para os quais confluem serviços e linguagens. Se olharmos especialmente para a televisão, notaremos imediatamente que a forma de vê-la ganha novos moldes. O aparelho separa-se do conteúdo. O sinal da TV deixa seu corpo físico e passa a navegar pelo horizonte binário. Ela fica, assim, emancipada do seu corpo material - o aparelho televisor -, e pode ser acompanhada em outras plataformas e dispositivos, aumentando, desse modo, a sua difusão e as possibilidades de canal de retorno para emissores e receptores. Esta pesquisa acompanha o cenário de implantação da TV digital no Brasil e no mundo e reflete acerca das influências e transformações trazidas ao cotidiano da sociedade e aos espaços públicos pelo sistema digital e pela internet. A tese foi estruturada em cinco capítulos, que perpassam diferentes aspectos relacionados à televisão: a sua história e cronologia, os princípios tecnológicos que regem o seu funcionamento, as linguagens que a caracterizam, a sua colocação no cenário convergente e a sua influência no cotidiano das pessoas. No trabalho, trago o resultado de um estudo de caso realizado no ano de 2014, durante um Estágio de Pesquisa no Exterior na Universidade Sapienza de Roma e uma visita técnica às universidades de Brighton e Portsmouth. Essa etapa da pesquisa permitiu-me conhecer in loco o panorama atual desses países, dois anos após a conclusão do switch off, analisar a relação dos italianos e ingleses com a mídia televisiva e com as outras mídias de comunicação digital e a relação/abertura das suas emissoras televisivas para com as novas modalidades de transmissão de conteúdos nas plataformas digitais. Para isso, além buscar fontes bibliográficas, entrevistei pesquisadores e profissionais da área de radiodifusão e telecomunicações que participaram diretamente do processo de transição analógico-digital da TV. Na tese, também faço o relato de uma pesquisa de campo realizada na zona leste de São Paulo, desenvolvida em conjunto com educadores e educandos do Intermídia Cidadã, um coletivo pertencente ao Núcleo de Comunicação Comunitária da Fundação Tide Setubal. A experiência, realizada com base na Produção Partilhada do Conhecimento, serviu para divulgar a chegada da televisão digital e do apagão analógico, refletir sobre os conteúdos da TV aberta brasileira e observar as possibilidades trazidas pela TV digital para o exercício da comunicação comunitária. A pesquisa, de cunho qualitativo e quantitativo, empregou os métodos de procedimento experimental e comparativo e levantou dados através de questionário, entrevistas em áudio e vídeo, oficinas, debates e consultas bibliográficas. Dentre os autores citados, posso destacar: Mikhail Bakhtin, Lúcia Santaella, Sérgio Bairon, Arlindo Machado, Jesús Martín-Barbero, Gérman Rey, Nicholas Negroponte, Arlindo Machado, Eugênio Bucci, Manuel Castells, Clay Shriky, Henry Jenkins, Alberto Marinelli, Néstor García Canclini, Almir Almas, Jay David Bolter, Richard Grusin, Walter Benjamin, Rafael Ruiz e Márcia Tiburi. / With the emergence of the binary system and the convergence of digital media, communication devices such as cellular phones, computers and even television receivers have now taken on more than just the main functions for which each was developed. They are now part of, due to the interoperability between systems and the Internet, systems of which services and languages are now integrated to as well. If one was to focus entirely on television, it can be observed that television watching has now received new forms. The device itself is separate from the content. The TV signal moves away from its physical form and begins to navigate on the binary field. Thus, it is emancipated of its material form - the television device - and can now be seen on other platforms and devices, hence raising the signal\'s distribution and the possibilities of return channels to transmitters and receivers. This research has closely followed the digital television implementation scenario in Brazil and in the world, and observes the influences and transformations in introduced to society\'s daily routine and to the public arena by the digital system and the Internet. The thesis is structured in five parts that run through the different aspects related to television: its timeline and history, the technological principles that command its operation, the languages that distinguish it, its placement in the converging scenario, and is influence in society\'s daily routine. This project presents the result of a case study performed in 2014, during my Research Internship at the University of Sapienza, in Rome. It also includes data gathered during technical visits to the universities in Brighton and Portsmouth. This stage of the research allowed me to observe the current panorama of these countries in loco, two years after the switch off. It also gave me the opportunity to analyze the relationship of the Italians and the English with television media, as well as with other digital communications media and the relationship/opening of the television transmitters of each country to new transmission modalities of content on digital platforms. In order to perform this leg of the research, in addition to searching in bibliographical sources, I interviewed researchers and professionals of the radio broadcasting and telecommunications fields, who had directly participated in the analogue-digital TV transition process. In this thesis, I also present a report of a field study done in the East Side of São Paulo city. This study was developed with the help of educators and pupils of Intermídia Cidadã, a collaboration that belongs to the Community Communication Nucleus of the Tide Setubal Foundation. The experience, based on the Shared Production of Information, was helpful to showcase the arrival of digital television and the analogue blackout. It was also useful to consider the content of public TV in Brazil and to analyze the possibilities now available through digital TV for community communication. This research, of qualitative and quantitative intent, applied comparative and experimental methods and collected data through surveys, audio and video interviews, workshops, debates and bibliographic research. Among the authors mentioned, I would like to make special reference to the following: Mikhail Bakhtin, Lúcia Santaella, Sérgio Bairon, Arlindo Machado, Jesús Martín-Barbero, Gérman Rey, Nicholas Negroponte, Arlindo Machado, Eugênio Bucci, Manuel Castells, Clay Shriky, Henry Jenkins, Alberto Marinelli, Néstor García Canclini, Almir Almas, Jay David Bolter, Richard Grusin, Walter Benjamin, Rafael Ruiz and Márcia Tiburi.

Com o sistema binário e a convergência digital das mídias, dispositivos de comunicação como celulares, computadores e até mesmo aparelhos receptores de televisão deixam de desempenhar apenas a função principal para a qual foram desenvolvidos e passam a se constituir, devido à interoperabilidade de sistemas e à internet, em meios para os quais confluem serviços e linguagens. Se olharmos especialmente para a televisão, notaremos imediatamente que a forma de vê-la ganha novos moldes. O aparelho separa-se do conteúdo. O sinal da TV deixa seu corpo físico e passa a navegar pelo horizonte binário. Ela fica, assim, emancipada do seu corpo material - o aparelho televisor -, e pode ser acompanhada em outras plataformas e dispositivos, aumentando, desse modo, a sua difusão e as possibilidades de canal de retorno para emissores e receptores. Esta pesquisa acompanha o cenário de implantação da TV digital no Brasil e no mundo e reflete acerca das influências e transformações trazidas ao cotidiano da sociedade e aos espaços públicos pelo sistema digital e pela internet. A tese foi estruturada em cinco capítulos, que perpassam diferentes aspectos relacionados à televisão: a sua história e cronologia, os princípios tecnológicos que regem o seu funcionamento, as linguagens que a caracterizam, a sua colocação no cenário convergente e a sua influência no cotidiano das pessoas. No trabalho, trago o resultado de um estudo de caso realizado no ano de 2014, durante um Estágio de Pesquisa no Exterior na Universidade Sapienza de Roma e uma visita técnica às universidades de Brighton e Portsmouth. Essa etapa da pesquisa permitiu-me conhecer in loco o panorama atual desses países, dois anos após a conclusão do switch off, analisar a relação dos italianos e ingleses com a mídia televisiva e com as outras mídias de comunicação digital e a relação/abertura das suas emissoras televisivas para com as novas modalidades de transmissão de conteúdos nas plataformas digitais. Para isso, além buscar fontes bibliográficas, entrevistei pesquisadores e profissionais da área de radiodifusão e telecomunicações que participaram diretamente do processo de transição analógico-digital da TV. Na tese, também faço o relato de uma pesquisa de campo realizada na zona leste de São Paulo, desenvolvida em conjunto com educadores e educandos do Intermídia Cidadã, um coletivo pertencente ao Núcleo de Comunicação Comunitária da Fundação Tide Setubal. A experiência, realizada com base na Produção Partilhada do Conhecimento, serviu para divulgar a chegada da televisão digital e do apagão analógico, refletir sobre os conteúdos da TV aberta brasileira e observar as possibilidades trazidas pela TV digital para o exercício da comunicação comunitária. A pesquisa, de cunho qualitativo e quantitativo, empregou os métodos de procedimento experimental e comparativo e levantou dados através de questionário, entrevistas em áudio e vídeo, oficinas, debates e consultas bibliográficas. Dentre os autores citados, posso destacar: Mikhail Bakhtin, Lúcia Santaella, Sérgio Bairon, Arlindo Machado, Jesús Martín-Barbero, Gérman Rey, Nicholas Negroponte, Arlindo Machado, Eugênio Bucci, Manuel Castells, Clay Shriky, Henry Jenkins, Alberto Marinelli, Néstor García Canclini, Almir Almas, Jay David Bolter, Richard Grusin, Walter Benjamin, Rafael Ruiz e Márcia Tiburi. / With the emergence of the binary system and the convergence of digital media, communication devices such as cellular phones, computers and even television receivers have now taken on more than just the main functions for which each was developed. They are now part of, due to the interoperability between systems and the Internet, systems of which services and languages are now integrated to as well. If one was to focus entirely on television, it can be observed that television watching has now received new forms. The device itself is separate from the content. The TV signal moves away from its physical form and begins to navigate on the binary field. Thus, it is emancipated of its material form - the television device - and can now be seen on other platforms and devices, hence raising the signal\'s distribution and the possibilities of return channels to transmitters and receivers. This research has closely followed the digital television implementation scenario in Brazil and in the world, and observes the influences and transformations in introduced to society\'s daily routine and to the public arena by the digital system and the Internet. The thesis is structured in five parts that run through the different aspects related to television: its timeline and history, the technological principles that command its operation, the languages that distinguish it, its placement in the converging scenario, and is influence in society\'s daily routine. This project presents the result of a case study performed in 2014, during my Research Internship at the University of Sapienza, in Rome. It also includes data gathered during technical visits to the universities in Brighton and Portsmouth. This stage of the research allowed me to observe the current panorama of these countries in loco, two years after the switch off. It also gave me the opportunity to analyze the relationship of the Italians and the English with television media, as well as with other digital communications media and the relationship/opening of the television transmitters of each country to new transmission modalities of content on digital platforms. In order to perform this leg of the research, in addition to searching in bibliographical sources, I interviewed researchers and professionals of the radio broadcasting and telecommunications fields, who had directly participated in the analogue-digital TV transition process. In this thesis, I also present a report of a field study done in the East Side of São Paulo city. This study was developed with the help of educators and pupils of Intermídia Cidadã, a collaboration that belongs to the Community Communication Nucleus of the Tide Setubal Foundation. The experience, based on the Shared Production of Information, was helpful to showcase the arrival of digital television and the analogue blackout. It was also useful to consider the content of public TV in Brazil and to analyze the possibilities now available through digital TV for community communication. This research, of qualitative and quantitative intent, applied comparative and experimental methods and collected data through surveys, audio and video interviews, workshops, debates and bibliographic research. Among the authors mentioned, I would like to make special reference to the following: Mikhail Bakhtin, Lúcia Santaella, Sérgio Bairon, Arlindo Machado, Jesús Martín-Barbero, Gérman Rey, Nicholas Negroponte, Arlindo Machado, Eugênio Bucci, Manuel Castells, Clay Shriky, Henry Jenkins, Alberto Marinelli, Néstor García Canclini, Almir Almas, Jay David Bolter, Richard Grusin, Walter Benjamin, Rafael Ruiz and Márcia Tiburi.

In theoretical part Master’s thesis deals with processing acoustic signal before speech recognition. There are described methods of automatic speech recognition and capture attributes. Those methods are short-term energy of signal, short-term autocorrelation analysis, linear predictive analysis etc. In practical part has been created software, which has to switch off of electrical tool, if the keyword “zastav” has been spoken. In the second part of this thesis software has been optimized for work in real conditions (noise generated by electrical tools).

Hydropower is the most important power balancing resource in the Swedish electrical power system, regulating the power supply to match the load. Consequently, several hydropower plants have periods of stand-by operation where the power production is absent but where several devices within a plant are still active. Such a device is the step-up power transformer, which during stand-by operation still generates no-load energy losses. These losses can accumulate to a considerable amount of energy and costs during the long technical lifetime of the apparatus. One option to minimize these no-load energy losses is by turning the transformer off when its generating unit is in stand-by operation. However, when this transformer operational change has been explained to experts in the field, the most common response has been that a more frequent reenergizing of a transformer leads to higher risks for errors or transformer breakdowns. This study aimed to analytically investigate three effects from this operational change. First, the potential of fatigue failure for the windings due to the increased sequences of inrush current. Secondly, the thermal cycling as a consequence of change in present losses. Lastly, the energy and economic saving potentials for hydropower plants where this operational adjustment is applied. The study used both established as well as analytical tools explicitly created for this study. These were then applied on currently active transformers in different plant categories in Fortum’s hydropower fleet.  The study primarily showed three things. Firstly, risk of fatigue failure due to the increased presence of inrush currents did not affect the transformer’s technical lifetime. Secondly, the thermal cycling changes were slightly larger with absent no-load losses during stand-by operation. The average temperature for the transformer decreased, which in general is seen as a positive indicator for a longer insulation lifetime and thus the transformer’s technical lifetime. Finally, the created frameworks showed the potential of saving energy and money for all plant categories, where the potential grew with the installed production capacity and the stand-by operation timeshare. Despite the simplifications made to describe the complex reality of a transformer operating in a hydropower plant, this thesis contributes to lay a foundation for future investigation of an easy adjustment to avoid unnecessary energy losses and costs for transformers in hydropower plants.

Hydropower is the most important power balancing resource in the Swedish electrical power system, regulating the power supply to match the load. Consequently, several hydropower plants have periods of stand-by operation where the power production is absent but where several devices within a plant are still active. Such a device is the step-up power transformer, which during stand-by operation still generates no-load energy losses. These losses can accumulate to a considerable amount of energy and costs during the long technical lifetime of the apparatus. One option to minimize these no-load energy losses is by turning the transformer off when its generating unit is in stand-by operation. However, when this transformer operational change has been explained to experts in the field, the most common response has been that a more frequent reenergizing of a transformer leads to higher risks for errors or transformer breakdowns. This study aimed to analytically investigate three effects from this operational change. First, the potential of fatigue failure for the windings due to the increased sequences of inrush current. Secondly, the thermal cycling as a consequence of change in present losses. Lastly, the energy and economic saving potentials for hydropower plants where this operational adjustment is applied. The study used both established as well as analytical tools explicitly created for this study. These were then applied on currently active transformers in different plant categories in Fortum’s hydropower fleet. The study primarily showed three things. Firstly, risk of fatigue failure due to the increased presence of inrush currents did not affect the transformer’s technical lifetime. Secondly, the thermal cycling changes were slightly larger with absent no-load losses during stand-by operation. The average temperature for the transformer decreased, which in general is seen as a positive indicator for a longer insulation lifetime and thus the transformer’s technical lifetime. Finally, the created frameworks showed the potential of saving energy and money for all plant categories, where the potential grew with the installed production capacity and the stand-by operation timeshare. Despite the simplifications made to describe the complex reality of a transformer operating in a hydropower plant, this thesis contributes to lay a foundation for future investigation of an easy adjustment to avoid unnecessary energy losses and costs for transformers in hydropower plants