High voltage power transformer is one of the most important and expensive components in today's power transmission and distribution systems. Any overlooked critical fault generated inside a power transformer may lead to a transformer catastrophic failure which could not only cause a disruption to the power system but also significant equipment damage. Accurate and prompt information on the health state of a transformer is thus the critical prerequisite for an asset manager to make a vital decision on a transformer with suspicious conditions. Partial discharge (PD) is not only a precursor of insulation degradation, but also a primary factor to accelerate the deterioration of the insulation system in a transformer. Monitoring of PD activities and the concentration of PD generated combustible gases dissolved in the transformer oil has been proven to be an effective procedure for transformer health state estimation. However current commercially available sensors can only be installed outside of transformers and offer indirect or delayed information. This research is aimed to investigate and develop several sensor techniques for transformer health monitoring. The first work is an optical fiber extrinsic Fabry-Perot interferometric sensor for PD detection. By filling SF6 into the sensor air cavity of the extrinsic Fabry-Perot interferometer sensor, the last potential obstacle that prevents this kind of sensors from being installed inside transformers has been removed. The proposed acoustic sensor multiplexing system is stable and more economical than the other sensor multiplexing methods that usually require the use of a tunable laser or filters. Two dissolved gas analysis (DGA) methods for dissolved hydrogen or acetylene measurement are also proposed and demonstrated. The dissolved hydrogen detection is based on hydrogen induced fiber loss and the dissolved acetylene detection is by direct oil transmission measurement. / Ph. D.

The power industry relies on high voltage transformers as the backbone of power distribution networks. High voltage transformers are designed to handle immense electrical loads in hostile environments. Long term placement is desired, however by being under constant heavy load transformers face mechanical, thermal, and electrical stresses which lead to failures of the protection systems in place. The service life of a transformer is often limited by the life time of its insulation system. Insulation failures most often develop from thermal faults, or hotspots, and electrical faults, or partial discharges. Detecting hotspots and partial discharges to predict transformer life times is imperative and much research is focused towards these topics. As these protection systems fail they often generate gas or acoustic signals signifying a problem. Research has already been performed discovering new ways integrate optical fiber sensors into high voltage transformers. This thesis is a continuation of that research by attempting to improve sensor sensitivity for hydrogen and acetylene gasses. Of note is the fabrication of new hydrogen sensing fiber for operation around a larger absorption peak and also the improvement of the acetylene sensor's light source stability. Also detailed is the manufacturing of a field testable prototype and the non-sensitivity testing of several other gasses. The developed sensors are capable but still could be improved with the use of more powerful and stable light sources. / Master of Science

In der vorliegenden Arbeit konnte erstmals gezeigt werden, dass die Konvertierung von Methan zu Acetylen mit Ausbeuten von über 99 % und Selektivitäten größer als 200:1 mit dem Einsatz von „continious wave“ (cw) Mikrowellenplasmen großtechnisch möglich ist. Im Gegensatz zu vorangegangenen Arbeiten[1,3,5,6] konnte der Vorteil von cw Mikrowellenplasmen in Bezug auf Ausbeute und Selektivität herausgestellt werden. Die vielfach beschriebenen Probleme der Rußbildung[7,8] konnten mit dem Einsatz der CYRANNUS® MW Plasmareaktoren gelöst werden. Des Weiteren besteht die Möglichkeit das Produktgas als chemischen Energiespeicher von regenerativen Überschussstrom (aus Photovoltaik oder Windkraft) zu nutzen. Hierbei sei der Bezug zu „power to gas“ (PtG) zu nennen. Der gebildete Wasserstoff eröffnet weitere vielfältige Nutzungsmöglichkeiten in diesem Rahmen. Im Rahmen der Aktivierung von Kohlenstoffdioxid (aus fossilen oder regenerativen Quellen) sei die Umsetzung von Methan und Kohlenstoffdioxid zu Synthesegas (CO + H2) genannt. Diese Reaktion könnte als Grundlage für sog. „Biosynthesegas“ dienen. Eingesetzt werden hierbei Edukte aus einer Biomassevergärungsanlage (Biogasanlage = BGA). Im Rahmen des Vergärungsprozesses entsteht eine Mischung aus CH4 und CO2. Eine Weiterverarbeitung zu Biosynthesegas und anschließend zu „liquid fuels“ als Biotreibstoff; z.B. im Rahmen einer Fischer-Tropsch-Synthese erscheint äußerst vielversprechend. Unter dem Aspekt der Energiewende ist es bei Einsatz von 100 % regenerativen Strom und der Zuführung von Eduktgas, welches aus Biomasse gewonnen wurde, auf diesem Weg möglich, „grüne“ Grundchemikalien in sehr guten Ausbeuten zu synthetisieren. / In the present study it was demonstrated for the first time, that the conversion of methane to acetylene with yields of over 99 % and selectivity greater than 200:1 with the use of "continious wave" (cw) micro wave Plasmas is possible in an industrial scale. In contrast to previous works[1,3,5,6] the advantage regarding yield and selectivity could be put out by using cw microwave plasmas. The often described problems of soot formation[7,8] could be solved with the use of the CYRANNUS® MW plasma reactors. In addition, the possibility is to use the product gas as a chemical energy storage by regenerative surplus electricity (photovoltaic or wind power). This was the reference to mention "power to gas" (PtG). In this context the formed hydrogen opens more possibilities of use. In case of the activation of carbon dioxide (from fossil or renewable sources) the reaction of methane and carbon dioxide to synthesis gas (CO + H2) is mentioned here. This reaction could serve as the basis for so-called organic synthesis gas. In the fermentation process a mixture formed CH4 and CO2 is formed. A further preparation for the organic synthesis gas and then to "liquid fuels" as biofuel; for example, in the frame of a Fischer-Tropsch synthesis appears very promising. Under the aspect of the energy revolution it is possible to synthesize "green" chemicals in excellent yields when using 100 % renewable electricity and the supply of reactant gas, which was obtained from biomass.

Manguezais são ecossistemas de transição entre ambientes terrestres e marinhos encontrados em regiões tropicais e subtropicais. A ampla faixa de variações de salinidade e teor oxigênio, típica desses ambientes, está entre os principais fatores condicionantes da colonização e desenvolvimento da biota. Apesar disso, são ambientes com elevada produção primária. Entre os nutrientes, o nitrogênio é um dos principais fatores limitantes que afetam o desenvolvimento da vegetação do manguezal e somente baixa disponibilidade de formas reduzidas está presente. Portanto, há a necessidade de determinar os micro-organismos fixadores de nitrogênio que colonizam os ecossistemas de manguezais. Dentre esses, existem as cianobactérias, um grupo bem conhecido de micro-organismos fotossintéticos oxigênicos e fixadores de nitrogênio. Neste estudo, 50 linhagens de cianobactérias foram isoladas de amostras ambientais de solos, água e material perifítico, coletadas nos ecossistemas de manguezais da Ilha do Cardoso e Bertioga, São Paulo. Essas linhagens foram isoladas usando meios específicos de crescimento e análises morfológicas identificaram representantes das ordens Chroococcales (35 linhagens, 70%), Oscillatoriales (9 linhagens, 18%) e Nostocales (6 linhagens, 12%). Dezesseis linhagens distribuídas entre as ordens Chroococcales e Nostocales foram selecionadas para os estudos de filogenia usando o gene rpoC1. A maioria das sequências de rpoC1 geradas pela amplificação por PCR usando o conjunto específico de primer rpoC1-1/rpoC1-T mostraram baixas similaridades (menor que 90%) com seqüências disponíveis no GenBank, indicando que estas linhagens de cianobactérias são únicas. As exceções foram somente duas linhagens (Synechococcus sp. CENA177 and Cyanothece sp. CENA169) que apresentaram altas similaridades com sequências de cianobactérias isoladas de ambientes de água doce do Brasil. A análise filogenética Neighbor-Joining mostrou que várias das novas linhagens cianobactérias dos manguezais se agruparam, sem relação com a descrição taxonômica baseada na caracterização morfotípica. Uma busca pelo gene funcional nifH, o qual codifica para a redutase da nitrogenase, em 27 isolados dos manguezais, revelou a sua presença em 21 linhagens (77%) dispersas entre as ordens Chroococcales, Oscillatoriales e Nostocales. Os 21 fragmentos do gene nifH amplificados foram clonados e seqüenciados e todas as sequências também mostram baixas similaridades (menor que 95%) com seqüências de cianobactérias disponíveis no GenBank. A análise filogenética do gene nifH posicionou as novas linhagens de cianobactérias dos manguezais em vários agrupamentos distribuídos ao longo da árvore, e como também observado para o gene rpoC1, sem correlação com a descrição taxonômica baseada na caracterização morfotípica. Atividade da nitrogenase, avaliada pela técnica de redução de acetileno, foi encontrada em cinco linhagens pertencentes à ordem Nostocales e em uma linhagem pertencente à ordem Chroococcales. A estimativa da fixação biológica de nitrogênio por essas linhagens variaram de 327,01 a 1.954,15 pmol N2.g-1 de biomassa seca.dia-1. / Mangroves are transitional ecosystems between terrestrial and marine environments found in tropical and subtropical regions. The broad range of variations of salinity and oxygen content, typical of these environments, is among the main constraint factors for the establishment and development of biota. Nevertheless, mangroves have high primary production. Among the nutrients, nitrogen is one of the most important limiting factors affecting the development of mangrove vegetation and only low availability of reduced forms is present. Therefore, there is a need to determine the nitrogen fixing microorganisms that colonize mangrove ecosystems. Among those, there are the cyanobacteria, a well known group of oxygenic photosynthetic and nitrogen fixing microorganisms. In this study, 50 cyanobacterial strains were isolated from environmental samples of soil, water and periphytic material collected in the Cardoso Island and Bertioga mangrove ecosystems, São Paulo. These strains were isolated using specific growth media and morphological analyses identified representatives of the orders Chroococcales (35 strains, 70%), Oscillatoriales (9 strains, 18%) and Nostocales (6 strains, 12%). Sixteen strains belong to the orders Chroococcales and Nostocales were selected for phylogeny studies using the gene rpoC1. The majority of rpoC1 sequences generated by PCR amplification using the specific set primer rpoC1-1/rpoC1-T showed low similarities (below 90%) with sequences available in the GenBank, indicating that these cyanobacterial strains are unique. The exceptions were only two strains (Synechococcus sp. CENA177 and Cyanothece sp. CENA169) that had high similarities with cyanobacterial sequences isolated from Brazilian freshwater environments. The Neighbor-Joining phylogenetic analysis showed that several of the new mangrove cyanobacterial strains clustered together, with no relationship with the taxonomical description based on morphotypic characterization. A search for the functional nifH gene, which coding for nitrogenase reductase, on 27 mangrove isolates revealed its presence in 21 strains (77%) dispersed among the orders Chroococcales, Oscillatoriales and Nostocales. The 21 amplified fragments of nifH were cloned and sequenced, and all the sequences also showed low similarities (below 95%) with cyanobacterial sequences available in the GenBank. The phylogenetic analysis of nifH gene positioned the new mangrove cyanobacterial strains in several clusters distributed along the tree, and as also observed for rpoC1 gene, with no correlation with the taxonomical description based on morphotypic characterization. Nitrogenase activity, measured by the acetylene reduction technique, was found in five strains belonging to the order Nostocales and one strain belonging to the order Chroococcales. The estimation of biological nitrogen fixation by these strains ranged from 327.01 to 1954.15 pmol N2.g-1 dry biomass.day-1.

Μελετήθηκε το φαινόμενο της ηλεκτροχημικής ενίσχυσης για τις αντιδράσεις της εκλεκτικής υδρογόνωσης του ακετυλενίου προς αιθυλένιο σε καταλύτη Pd εναποτεθειμένο σε β\"-Al2O3 και της οξείδωσης του βουταδιενίου προς προϊόντα εκλεκτικής οξείδωσης σε καταλύτη Ag0.73V2O5.365 εναποτεθειμένο σε YSZ. Το φαινόμενο της ηλεκτροχημικής ενίσχυσης (Electrochemical Promotion) αφορά την τροποποίηση της ενεργότητας καταλυτών που είναι εναποτεθειμένοι πάνω σε στερεούς ηλεκτρολύτες κατά την επιβολή δυναμικού στη διεπιφάνεια καταλύτη | στερεού ηλεκτρολύτη. Στην παρούσα διατριβή μελετήθηκαν αντιδράσεις βιομηχανικού ενδιαφέροντος σε συνθήκες παρόμοιες με αυτές της βιομηχανικής πρακτικής. Υδρογόνωση Ακετυλενίου: Βρέθηκε ότι η αύξηση της κάλυψης της καταλυτικής επιφάνειας με ιόντα Na+ έχει σαν αποτέλεσμα την σημαντική αύξηση της εκλεκτικότητας προς αιθυλένιο. Το φαινόμενο είναι πλήρως αντιστρεπτό δηλαδή η απομάκρυνση των ιόντων Na+ από την καταλυτική επιφάνειας έχει σαν συνέπεια την επιστροφή των καταλυτικών ρυθμών στους αρχικούς που αντιστοιχούν σε επιφάνεια καθαρή από ιόντα Na+. Ο ηλεκτροχημικά ενισχυμένος καταλύτης της παρούσας βρέθηκε ότι είναι πιο εκλεκτικός (κατά 1.5%) σε σχέση με τον βιομηχανικό καταλύτη για υψηλή μετατροπή ακετυλενίου Εκλεκτική οξείδωση βουταδιενίου: Βρέθηκε ότι είναι δυνατή η ηλεκτροχημική ενίσχυση της οξείδωσης τόσο του αιθυλενίου, η οποία εξετάστηκε ως αντίδραση “μοντέλο”, όσο και του βουταδιενίου με χρήση ενός μη αγώγιμου οξειδοαναγωγικού καταλύτη όπως αυτού της παρούσας μελέτης. Η επιβολή θετικών δυναμικών δηλαδή η μεταφορά ιόντων οξυγόνου στην καταλυτική επιφάνεια έχει σαν αποτέλεσμα της αύξηση των καταλυτικών ρυθμών για τα περισσότερα προϊόντα εκλεκτικής οξείδωσης ενώ μικρότερες αυξήσεις παρατηρούνται κατά την επιβολή αρνητικών δυναμικών. Βρέθηκε επίσης ότι η οξειδωτική κατάσταση του καταλύτη επηρεάζει σημαντικά τόσο την κατανομή των προϊόντων όσο και το μέγεθος της ηλεκτροχημικής ενίσχυσης. / The phenomenon of Electrochemical Promotion was studied for two catalytic reactions of industrial importance: for the hydrogenation of acetylene on Pd catalytic films deposited on β\"-Al2O3 solid electrolyte and for the selective oxidation of butadiene on Ag0.73V2O5.365, industrial catalyst, deposited on YSZ solid electrolyte. The Electrochemical Promotion concerns the modification of catalytic activity and selectivity of conductive catalysts deposited on solid electrolytes by applying electrical currents or potential between the catalyst and the counter electrode also deposited on the solid electrolyte. Acetylene Hydrogenation: It was found that the selectivity to C2H4 is significantly enhanced upon increasing the coverage of catalytic surface with electrochemically supplied sodium ions. The phenomenon is reversible that is the electrochemical removing of sodium ions from the catalytic surface results to the return of catalytic activity and selectivity at the initial values corresponding to the unpromoted catalyst. The electrochemical promoted catalyst appears to be more selective (by 1.5%) than the industrial catalyst in the high acetylene conversion region Selective Oxidation of Butadiene: It was found that both ethylene oxidation, which is studied as “model” reaction and selective oxidation of butadiene can be enhanced electrochemically on a non conductive redox catalyst. It was found that the oxygen species, which are carried electrochemically from YSZ solid electrolyte to the catalytic surface, by applying positive potential or current, enhance the catalytic rates for all partial oxidation products. Minor increases to the catalytic rates observed by applying negative potential or current. It was also found that the oxidation state of catalyst affects significantly both the reaction rates and the magnitude of electrochemical promotion.

Manguezais são ecossistemas de transição entre ambientes terrestres e marinhos encontrados em regiões tropicais e subtropicais. A ampla faixa de variações de salinidade e teor oxigênio, típica desses ambientes, está entre os principais fatores condicionantes da colonização e desenvolvimento da biota. Apesar disso, são ambientes com elevada produção primária. Entre os nutrientes, o nitrogênio é um dos principais fatores limitantes que afetam o desenvolvimento da vegetação do manguezal e somente baixa disponibilidade de formas reduzidas está presente. Portanto, há a necessidade de determinar os micro-organismos fixadores de nitrogênio que colonizam os ecossistemas de manguezais. Dentre esses, existem as cianobactérias, um grupo bem conhecido de micro-organismos fotossintéticos oxigênicos e fixadores de nitrogênio. Neste estudo, 50 linhagens de cianobactérias foram isoladas de amostras ambientais de solos, água e material perifítico, coletadas nos ecossistemas de manguezais da Ilha do Cardoso e Bertioga, São Paulo. Essas linhagens foram isoladas usando meios específicos de crescimento e análises morfológicas identificaram representantes das ordens Chroococcales (35 linhagens, 70%), Oscillatoriales (9 linhagens, 18%) e Nostocales (6 linhagens, 12%). Dezesseis linhagens distribuídas entre as ordens Chroococcales e Nostocales foram selecionadas para os estudos de filogenia usando o gene rpoC1. A maioria das sequências de rpoC1 geradas pela amplificação por PCR usando o conjunto específico de primer rpoC1-1/rpoC1-T mostraram baixas similaridades (menor que 90%) com seqüências disponíveis no GenBank, indicando que estas linhagens de cianobactérias são únicas. As exceções foram somente duas linhagens (Synechococcus sp. CENA177 and Cyanothece sp. CENA169) que apresentaram altas similaridades com sequências de cianobactérias isoladas de ambientes de água doce do Brasil. A análise filogenética Neighbor-Joining mostrou que várias das novas linhagens cianobactérias dos manguezais se agruparam, sem relação com a descrição taxonômica baseada na caracterização morfotípica. Uma busca pelo gene funcional nifH, o qual codifica para a redutase da nitrogenase, em 27 isolados dos manguezais, revelou a sua presença em 21 linhagens (77%) dispersas entre as ordens Chroococcales, Oscillatoriales e Nostocales. Os 21 fragmentos do gene nifH amplificados foram clonados e seqüenciados e todas as sequências também mostram baixas similaridades (menor que 95%) com seqüências de cianobactérias disponíveis no GenBank. A análise filogenética do gene nifH posicionou as novas linhagens de cianobactérias dos manguezais em vários agrupamentos distribuídos ao longo da árvore, e como também observado para o gene rpoC1, sem correlação com a descrição taxonômica baseada na caracterização morfotípica. Atividade da nitrogenase, avaliada pela técnica de redução de acetileno, foi encontrada em cinco linhagens pertencentes à ordem Nostocales e em uma linhagem pertencente à ordem Chroococcales. A estimativa da fixação biológica de nitrogênio por essas linhagens variaram de 327,01 a 1.954,15 pmol N2.g-1 de biomassa seca.dia-1. / Mangroves are transitional ecosystems between terrestrial and marine environments found in tropical and subtropical regions. The broad range of variations of salinity and oxygen content, typical of these environments, is among the main constraint factors for the establishment and development of biota. Nevertheless, mangroves have high primary production. Among the nutrients, nitrogen is one of the most important limiting factors affecting the development of mangrove vegetation and only low availability of reduced forms is present. Therefore, there is a need to determine the nitrogen fixing microorganisms that colonize mangrove ecosystems. Among those, there are the cyanobacteria, a well known group of oxygenic photosynthetic and nitrogen fixing microorganisms. In this study, 50 cyanobacterial strains were isolated from environmental samples of soil, water and periphytic material collected in the Cardoso Island and Bertioga mangrove ecosystems, São Paulo. These strains were isolated using specific growth media and morphological analyses identified representatives of the orders Chroococcales (35 strains, 70%), Oscillatoriales (9 strains, 18%) and Nostocales (6 strains, 12%). Sixteen strains belong to the orders Chroococcales and Nostocales were selected for phylogeny studies using the gene rpoC1. The majority of rpoC1 sequences generated by PCR amplification using the specific set primer rpoC1-1/rpoC1-T showed low similarities (below 90%) with sequences available in the GenBank, indicating that these cyanobacterial strains are unique. The exceptions were only two strains (Synechococcus sp. CENA177 and Cyanothece sp. CENA169) that had high similarities with cyanobacterial sequences isolated from Brazilian freshwater environments. The Neighbor-Joining phylogenetic analysis showed that several of the new mangrove cyanobacterial strains clustered together, with no relationship with the taxonomical description based on morphotypic characterization. A search for the functional nifH gene, which coding for nitrogenase reductase, on 27 mangrove isolates revealed its presence in 21 strains (77%) dispersed among the orders Chroococcales, Oscillatoriales and Nostocales. The 21 amplified fragments of nifH were cloned and sequenced, and all the sequences also showed low similarities (below 95%) with cyanobacterial sequences available in the GenBank. The phylogenetic analysis of nifH gene positioned the new mangrove cyanobacterial strains in several clusters distributed along the tree, and as also observed for rpoC1 gene, with no correlation with the taxonomical description based on morphotypic characterization. Nitrogenase activity, measured by the acetylene reduction technique, was found in five strains belonging to the order Nostocales and one strain belonging to the order Chroococcales. The estimation of biological nitrogen fixation by these strains ranged from 327.01 to 1954.15 pmol N2.g-1 dry biomass.day-1.

No description available.

No description available.

Carbon-carbon bond formation is one the fundamental reactions in organic synthesis. The quest for the development of new and more efficient processes for the construction of this bond has been an ongoing focus for years. The transformations that permit the use of simple precursors to access complex structural architectures in the absence of stoichiometric quantities by-products are highly desirable. Hydrogen is a cheapest and cleanest reductant available to the mankind. The catalytic hydrogenation has been widely utilized in the industry, however the construction of the carbon-carbon bond under hydrogenative conditions has been achieved only for alkene hydroformylations and Fisher-Tropsh process and limited to the use of carbon monoxide. The extension of the hydrogenative carbon-carbon bond formations beyond aforementioned processes would be of a great significance to the synthetic community. The overview of allene use in the metal catalyzed reactions to achieve carbonyl and imine allylation and vinylation is presented in Chapter 1. The following chapter vii discusses the development of metal catalyzed hydrogenative and transfer hydrogenative coupling of allenes and carbonyl compounds to afford allylation products. These studies have resulted in the development of the first carbonyl allylation from the alcohol oxidation level. Chapter 3 discusses efforts towards achieving highly enantioselective hydrogenative coupling of alkynes to carbonyl compounds. / text

Atoms construct the molecules and molecules construct the material substances (with the exceptions as well, e.g.., metals, where atoms directly construct the material substances). Intermolecular interactions play an important role in most of the branches of sciences, ranging from material sciences to biological sciences. Van der Waals interactions are weak intermolecular interactions while hydrogen bonding varies in strength from weak to strong (1 to 40 kcal/mol). The present work focuses on applying some theoretical methods (ab initio and Atoms in Molecules theory) on these interactions to differentiate them with physically meaningful parameters such as hydrogen bond radii and atoms in molecules theory parameters. 1)Defining and calculating H-bond radii have been done using atoms in molecules theory approach which can explain ruling out the presence or absence of an H-bond in an intermolecular interaction. 2) A blue-shift of 200 cm-1 for a weakly bound complex is unprecedented. Our studies on weakly bound complexes showed the blue-shift of 200 cm-1 for H3C•••CIF and shift has been found to be purely from the mixing of normal modes and not because of an interaction. 3)Methane, a symmetric top molecule can act both as H-bond acceptor and donor. The present work shows that methane is rather a better H-bond acceptor than a donor and all the calculated parameters are in favor of this description. 4) Microwave spectrometer is an ultimate tool (at least at present) for structural characterization of the weakly bound complexes accurately. The rotational spectrum of the weakly bound isotopomer weakly bound complexes accurately. The rotational spectrum of the weakly bound isotopomer 13CC5H6•••Ar, which is a symmetric top and gives only “B” rotational constant. Moreover, the A rotational constant of the complex is the same as the rotational constant for 13CC5H6, which has no dipole moment. C2H2 molecule is an astrophysically important molecule as it is present in asymptotic giant branch and T-type stars (Teff<3000K). Due to its various infrared active vibrational modes, C2H2 is one of the most important sources in cool stars. The production of C2H2 infrared spectroscopic data at high temperature is therefore essential to trace back physical characteristics of these objects and to model the radiative transfer in their envelope. The databases such as “HITRAN”, do not have enough data available for stimulating high temperature spectra. Keeping all these objectives in mind, high temperature emission spectrum of acetylene has been recorded around 3µm region of acetylene.