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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
51

Construction et analyse de mutants de la machinerie de photoproduction d'hydrogène chez la cyanobactérie modèle Synechocystis / Construction and analysis of mutants of the hydrogen photoproduction machine in the model cyanobacterium Synechocystis

Ortega-Ramos, Marcia 13 January 2014 (has links)
Les microorganismes photosynthétiques suscitent un intérêt biotechnologique grandissant pour la production de dihydrogène (H₂) à partir d'eau et d'énergie solaire en préservant l'eau douce et les terres cultivables sans ajout d'engrais. La cyanobactérie modèle Synechocystis PCC 6803 est capable de produire du H₂ de manière faible et transitoire grâce à une hydrogénase [NiFe] bidirectionnelle Hox. Cette enzyme possède 5 sous-unités protéiques (HoxEFUYH) qui catalysent la réaction réversible : 2H⁺ + 2e⁻ ↔ H₂. Le site actif [NiFe] de cette enzyme est assemblé par un complexe de six protéines HypABCDEF. L’hydrogénase est ensuite maturée par une protéase HoxW qui clive la sous-unité HoxH et active le site catalytique [NiFe]. L’ingénierie de cyanobactéries pour la photoproduction biologique d’H₂ passe par une meilleure compréhension du rôle de l'hydrogénase dans le métabolisme cyanobactérien. Au cours de ma thèse, j’ai construit et analysé 7 mutants sophistiqués de Synechocystis permettant la surexpression simultanée (constitutive ou régulée par la température de croissance) des gènes hoxEFUYHW et hypABCDEF. On a ainsi montré que la surproduction simultanée des protéines HoxEFUYHW et HypABCDEF combinée à une augmentation de la disponibilité de nickel dans le milieu conduit à une augmentation de l’activité hydrogénase d’un facteur 20. D’autre part, un mutant dépourvu de l'opéron hoxEFUYH a permis également de montrer que l'hydrogénase n'est pas indispensable à la croissance dans les conditions photoautotrophiques standard. La comparaison des phénotypes des divers mutants construits durant ce travail a permis également de montrer pour la première fois que l’hydrogénase joue un rôle dans la défense cellulaire contre le stress oxydant induit par le H₂O₂, par la présence de glucose ou de glycérol dans le milieu de culture. Par ailleurs, j'ai participé à la caractérisation d'un nouveau régulateur de l'expression de l’hydrogénase. Ce facteur de transcription (AbrB2) qui réprime l’opéron hoxEFUYH est impliqué dans la tolérance au stress induit par le diamide ou le nickel. Un contrôle redox de l'activité de ce régulateur par une modification post-traductionnelle de glutathionylation a été mise en évidence pour la première fois chez les cyanobactéries. L'ensemble de ces résultats démontre que l’on doit combiner plusieurs stratégies génétiques et physiologiques pour augmenter fortement la production d’hydrogène chez Synechocystis, et que nos mutants sont des outils très importants vers cet objectif. / Photosynthetic organisms are attractive organisms for hydrogen production using water and solar energy, while preserving fresh water and arable soils without adding fertilizers. The model cyanobacterium Synechocystis PCC 6803 produces small and transitory amounts of H₂ thanks to its bidirectional [NiFe] hydrogenase Hox. The Hox complex with its 5 protein subunits (HoxEFUYH) catalyzes the reversible reaction 2H⁺ + 2e⁻ ↔ H₂. The [NiFe] catalytic site of the Hox enzyme is assembled using a six-subunits HypABCDEF complex and matured by the HoxW protease that cleaves HoxH and activates its [NiFe]-containing center. Engineering cyanobacteria for hydrogen production relies on a better understanding of the role of hydrogenase in the cyanobacterium metabolism. During my PhD, I have constructed and analyzed 7 sophisticated mutants of Synechocystis, allowing the simultaneous over-expression (constitutive or regulated by the growth temperature) of the hoxEFUYH and hypABCDEF genes. We demonstrated that the simultaneous over-production of the HoxEFUYH and HypABCDEF proteins, combined to an increase in nickel availability led to an approximately 20-fold increase of the active hydrogenase level. Moreover, using a deleted hox-operon mutant we showed that hydrogenase is dispensable in standard phototrophic growth conditions. Comparing the phenotypes of different mutants constructed in this study enables us to demonstrate for the first time that the hydrogenase operates in cell protection against oxidative stress (H₂O₂) and sugar stress (glucose or glycerol). Besides, I have also participated to the characterization of a new regulator (AbrB2) of the expression of the hydrogenase. This transcription factor represses the hoxEFUYH operon and is involved in the tolerance to stress induced by diamide or nickel. For the first time in cyanobacteria, a redox control of the activity of this regulator by a post-translational gluthathionylation was identified. Collectively, our findings showed that several genetic and physiological strategies should be combined in a single strain to strongly increase hydrogen production in Synechocystis. Meanwhile the presently constructed mutants proved to be very powerful tools to achieve this goal.
52

A PRÁTICA COMO COMPONENTE CURRICULAR NA UNIVERSIDADE FEDERAL DO MARANHÃO: Prática como Componente Curricular em Educação Física / PRACTICE IN CURRICULUM COMPONENT Federal University of Maranhão: implications for the Degree Course in Physical Education

Araujo, Raffaelle Andressa dos Santos 30 August 2011 (has links)
Made available in DSpace on 2016-08-17T13:54:23Z (GMT). No. of bitstreams: 1 Dissertacao Completa Raffaelle.pdf: 1717850 bytes, checksum: 79bfd8ac3b2d359e3f59e32570b68ba4 (MD5) Previous issue date: 2011-08-30 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / The practice as component curricular (PCC) in the course of degree course in Physical Education of the Federal University of the Maranhão (UFMA). The practice is investigated like component curricular and if his inclusion has been contributing to the overcoming of the dichotomy between theory and it practices in the Course of Degree course in Physical Education of the UFMA. As for the hard-working methodology, the inquiry is of hallmark exploratory of the type descriptive, whose proposal methodological developed through the combination of bibliographical, documentary inquiry and of field. For so much, it takes office like base to the contributions of Vázquez (1977) about the practice in a dialectic perspective and, o concept of pedagogic practice anchored in the studies of Veiga (1989; 2000), Fonseca (2005) and Schmidt et al (1999). For the collection of data there was used the semi-structured interview devoted to a coordinator, chief of department and seven (7) teachers of the course; and application of questionnaire to twelve (12) pupils properly enroled in the intermediary periods (5th and 6º) and you waste away (8th and 9º). It is ended that the PCC is not being treated inside the above-mentioned course as the PPP of the same thing emanates and what there is no full understanding for part of pupils and teachers as for the above-mentioned practice. In accordance with teachers and pupils interviewed to PCC have contributed to the overcoming of the dichotomy between theory and practice, meantime, there is the need of pedagogic practices more contextual, critical and reflexive. It is believed that the recognition of this necessity is a significant step to rescind the faults and gaps in the process of teaching and apprenticeship, making possible the understanding and transformation of the reality which the teachers are going to influence. / A prática como componente curricular (PCC) no curso de licenciatura em Educação Física da Universidade Federal do Maranhão (UFMA). Investiga-se a prática como componente curricular e se sua inclusão tem contribuído para a superação da dicotomia entre teoria e prática no Curso de Licenciatura em Educação Física da UFMA. Quanto à metodologia aplicada, a pesquisa é de cunho exploratória do tipo descritiva, cuja proposta metodológica desenvolveu-se através da combinação de pesquisa bibliográfica, documental e de campo. Para tanto, assume-se como base as contribuições de Vázquez (1977) acerca da prática numa perspectiva dialética, e o conceito de prática pedagógica, ancorado nos estudos de Veiga (1989; 2000), Fonseca (2005) e Schmidt et al (1999). Para a coleta de dados, utilizou-se a entrevista semi-estruturada aplicada ao coordenador, chefe de departamento e sete (7) professores do curso; e, aplicação de questionário a doze (12) discentes devidamente matriculados nos períodos intermediários (5ª e 6º) e finais (8º e 9º). Conclui-se que a PCC não está sendo tratada dentro do referido curso como emana o PPP do mesmo, e que não há entendimento pleno por parte de alunos e professores quanto à referida prática. De acordo com os docentes e discentes entrevistados, a PCC tem contribuído para a superação da dicotomia entre teoria e prática, entretanto, há a necessidade de práticas pedagógicas mais contextualizadas, críticas e reflexivas. Acredita-se que o reconhecimento dessa necessidade é um passo significativo para rescindir as falhas e lacunas no processo de ensino e aprendizagem, possibilitando a compreensão e transformação da realidade sobre a qual os professores vão atuar.
53

Avaliação da implementação do sistema cook-chill em unidade de alimentação e nutrição - UAN / Evaluation of cook-chill system implementation on foodservice

Karina de Oliveira Calheiros 23 February 2016 (has links)
Eficácia, aperfeiçoar a produção, minimizar custos relativos e otimizar recursos disponíveis são desafios aos quais se deparam os serviços de alimentação coletiva no Brasil. Este estudo procurou avaliar os recursos disponíveis de uma unidade de alimentação e nutrição - UAN, visando subsidiar a implementação do sistema cook-chill. Para realização do estudo foram utilizados dois tipos de proteína animal, o lagarto (músculo semitendinosus) e o peito de frango (pectoralis major) com o emprego das técnicas cook-chill e convencional. O estudo foi divido em três etapas. A primeira avaliou a capacidade instalada a partir da observação dos recursos necessários, tais como, mão de obra empregada, estrutura física relacionada a equipamentos e custo. Os resultados evidenciaram um baixo índice de produtividade de mão de obra quando comparado a outras UAN. O custo total da preparação alimentícia aumentou 2,7% com o emprego da técnica cook-chill quando comparado à técnica convencional. Este aumento foi causado principalmente pelo maior tempo no emprego da mão de obra, de consumo de energia elétrica e no uso da capacidade instalada. Esta, por sua vez pode ser considerada suficiente para a implementação da técnica cook-chill. Na segunda etapa, identificou-se os pontos críticos de controle - PCC - de preparações com o emprego da técnica cook-chill. Testes preliminares definiram o tempo e temperatura do tratamento térmico empregado, devendo ser a temperatura de forno de 160°C até atingir 89°C no centro geométrico por 4 minutos para carne bovina (lagarto) e 2 minutos para carne a base de ave (peito de frango), respectivamente, num tempo total de processo de 2 horas e 25 minutos, binômios suficientes para reduzir 11D do microrganismo alvo do estudo, o Clostridium botulinun type E. Para o emprego da técnica cook-chill, identificou-se como pontos críticos de controle, a partir do método recomendado pelo Codex alimentarius, as etapas de cocção, armazenamento e regeneração, para as duas preparações. Na terceira etapa aplicou-se a técnica cook-chill visando comparar os resultados em relação aos aspectos sensoriais, físicos, químicos e microbiológicos com a técnica convencional. O rendimento total das preparações com o emprego da técnica convencional foi menor quando comparado ao cook-chill, para ambas as proteínas, exceto nas amostras de lagarto com cook-chill que tiveram um rendimento maior no armazenamento durante cinco dias, justificado pela influência da retenção de água provido pelo acondicionamento em saco a vácuo. O emprego da técnica cook-chill e o tempo de armazenamento não influenciaram nos resultados para pH, força de cisalhamento e cor objetiva, para nenhum dos tipos de carnes. As contagens microbiológicas revelaram-se satisfatórias, mesmo para as amostras armazenadas sob refrigeração no período mais longo. Quanto à análise sensorial as duas técnicas obtiveram uma aceitação acima de 60% nos atributos sensoriais avaliados. Concluiu-se que a UAN poderá substituir a técnica convencional, uma vez que obteve resultados satisfatórios de aceitação da técnica cook-chill, principalmente no tempo de armazenamento em até 5 dias a 3°C, e demais análises. Do mesmo modo, essa técnica apresentou-se vantajosa devido à maior facilidade operacional, sugerindo a redução do tempo de produção, a otimização da mão de obra e equipamentos disponíveis o favorecimento do aumento da produção. / Effectiveness, improving the production, minimize costs and optimize available resources are challenges which face the collective power services in Brazil. This study sought to evaluate the resources of a unit of foodservice, aiming to support the implementation of the cook-chill system. To conduct the study were used two types of animal protein, the semitendinosus beef and fillet of chicken breast (pectoralis major) with the use of cook-chill techniques (zero time and five days of storage) and conventional. The study was divided into three stages. First, it was evaluated the installed capacity from observing the necessary resources, such as labour, physical structure related to equipment and cost analysis. While using conventional techniques, the results showed a low labor productivity rate when compared to other foodservice units. The total cost increased to 2.7% with the use of cook-chill technique when compared to the conventional technique, caused mainly by higher use of labor, consumption of electricity and installed capacity, which may be considered sufficient for the implementation of the cook-chill technique. In the second stage, it was identified the critical control points - CCP - of preparations with the use of cook-chill technology. Preliminary tests defined time and temperature of cooking should be 160°C of oven temperature, up to reach 89°C at geometric center for 4 minutes, to semitendinosus beef, and 2 minutes for the chicken breast, respectively, in a total time process of 2 hours and 25 minutes, binomial of time enough to reduce 11D of the study target microorganism, Clostridium botulinun type E. For the implementation of the cook-chill technique it was identified, as critical control points from the method recommended by the Codex alimentarius, the steps of cooking, storage and regeneration, for both of preparations. The third stage applied the cook-chill technique in order to compare its results with the conventional technique, on the sensory, physical, chemical and microbiological aspects. The overall process yield with the conventional technique was lower than in the cook-chill technique for both proteins, except in the lizard samples cook-chill with time of storage of 5 days, that shown a higher process yield, that can be explained by the influence of water retention provided by storage in a vacuum bag. The use of cook-chill technique did not influence the results for pH, shear force, objective color, the storage time, for any of the types of meats, as well as microbiological counts proved to be satisfactory even for the preparations of meats under longer periods of refrigeration. The sensory analysis of two techniques gained acceptance over 60% in the sensory attributes evaluated. In conclusion, the foodservice unit can replace the conventional technique for cook-chill technique, according to satisfactory results of analyzed parameters, particularly for storage time up to 5 days at 3°C, also provides greater operational convenience, reduced production time, and labour optimization creating conditions for further production increase.
54

O irmão que virou irmão: rupturas e permanências na conversão de membros do PCC ao pentecostalismo na Vila Leste - SP

Marques, Vagner Aparecido 21 October 2013 (has links)
Made available in DSpace on 2016-04-25T19:20:28Z (GMT). No. of bitstreams: 1 Vagner Aparecido Marques.pdf: 1256514 bytes, checksum: 2ef5d5a7161c8d07b34c7c55aeaf2c88 (MD5) Previous issue date: 2013-10-21 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / The present dissertation investigates the conversion process of current and former PCC members to the Pentecostalism, in the Eastern area of São Paulo City. Our approach is to analyze a case study, through the journey of Kadu , brother in the church and also brother in the PCC party. The conversion trajectory of Kadu to the Pentecostalism will be seen through a new religious conversion paradigm. In that approach, the conversion is the result of a slow, gradual and not-immediate process, accompanied by numbers of crisis, as shown by a great deal of the religious conversion writings. Kadu´s conversion was not followed by the rupture/asceticism binomial; on the opposite, we could verify continuities along the former network, the PCC. This dual brotherhood is the main focus point of the research. Kadu also open some doors for the analyses of engaging networks existing in the Vila Leste neighborhood and its moral entrepreneurs. In the region of Vila Leste, Pentecostalism and PCC are entangled, and this reality will be analyzed in this work / A presente dissertação investiga o processo de conversão de membros e ex-membros do PCC ao pentecostalismo, no extremo Leste de São Paulo. Nossa proposta é realizar um estudo de caso a partir da trajetória de Kadu, irmão da igreja e também irmão do PCC. A trajetória da conversão de Kadu ao pentecostalismo será observada a partir de um novo paradigma de conversão religiosa. Nesta, a conversão é resultado de um processo lento, gradual e não imediato, e acompanhado de crises conforme mostrará boa parte da literatura sobre sua conversão religiosa. A conversão de Kadu não foi acompanhada pelo binômio rupturas e ascetismo; pelo contrário, verificamos continuidades com a rede anterior, o PCC. Essa sua dupla irmandade é o objeto central desta pesquisa. Kadu também nos abre as portas para analisarmos as redes de engajamento existentes na Vila Leste e seus empreendedores morais. Na Vila Leste, pentecostais e PCC interpenetram-se, e essa realidade será analisada neste estudo
55

Problema da cobertura por caminhos com K-terminais-fixos em grafos de intervalos

Santos, Alander Pereira dos January 2013 (has links)
Orientadora: Gordana Manic / Dissertação (mestrado) - Universidade Federal do ABC, Programa de Pós-Graduação em Ciência da Computação, 2013
56

Characterization of the DNA-Binding Properties of the Cyanobacterial Transcription Factor NtcA

Wisén, Susanne January 2003 (has links)
<p>Nitrogen is an essential building block of proteins and nucleic acids and, therefore, crucial for the biosphere. Nearly 79 % of the air consists of nitrogen, but in the form of nitrogen gas (N<sub>2</sub>), which cannot be utilized by most organisms. Nitrogen-fixing microorganisms such as cyanobacteria have a central role in supplying biologically useful nitrogen to the biosphere. Therefore, it is important to achieve further understanding of control mechanisms involved in nitrogen fixation and related processes. </p><p>This thesis concerns different molecular aspects of the transcription factor NtcA from the heterocystous cyanobacterium <i>Anabaena</i> PCC 7120. Apart from performing oxygenic photosynthesis, <i>Anabaena</i> PCC 7120 is also capable of fixing nitrogen. NtcA is a protein regulating transcription of a wide range of genes and in particular genes involved in cyanobacterial global nitrogen control. NtcA binds as a dimer to the promoter regions of target genes such as those involved in nitrogen fixation and heterocyst differentiation. </p><p>NtcA from <i>Anabaena</i> PCC 7120 was heterologously expressed in <i>E. coli</i> and a high yield of recombinant protein was achieved through purification by Ni-IMAC chromatography. The purified NtcA was used to examine DNA binding motifs preferred by NtcA <i>in vitro </i>using a semi-random library of DNA sequences. The preferred binding sequence for NtcA is TGTA – N<sub>8</sub> – TACA and at least five of the bases in the palindromic binding site are necessary for binding. Differences in the consensus sequence in vivo may reflect variations in the structural conformation of NtcA under various physiological conditions. </p><p>Since an earlier study suggested redox-regulated NtcA-DNA binding the role of the two cysteine residues of NtcA were investigated. Binding studies using three mutants, Cys157Ala, Cys164Ala, and Cys157Ala / Cys164Ala, demonstrated that all these NtcA variants bind to DNA with a slightly higher affinity in the presence of the reducing agent DTT. The studies indicate that the binding mechanism is not dependent on a conformational change of NtcA caused by breaking of intra-molecular disulfide bonds. </p><p>Crystallization followed by structural studies rendered a partial crystal structure of NtcA. The structure verifies that NtcA is a dimeric protein. Each subunit has three domains: the N-terminal domain, a dimerization helix connecting the N-terminal domain with the C-terminal domain, as well as making up the dimer interface, and a C-terminal domain including the DNA binding helix-turn-helix motif.</p><p>Furthermore, an NtcA binding site was found in the promoter region of the<i> hupSL</i> gene, encoding an uptake hydrogenase in <i>Nostoc punctiforme</i> (ATCC 29133), indicating that yet another gene is transcriptionally controlled by NtcA, thereby further emphasizing the multifaceted role of NtcA in cyanobacteria.</p>
57

Characterization of the DNA-Binding Properties of the Cyanobacterial Transcription Factor NtcA

Wisén, Susanne January 2003 (has links)
Nitrogen is an essential building block of proteins and nucleic acids and, therefore, crucial for the biosphere. Nearly 79 % of the air consists of nitrogen, but in the form of nitrogen gas (N2), which cannot be utilized by most organisms. Nitrogen-fixing microorganisms such as cyanobacteria have a central role in supplying biologically useful nitrogen to the biosphere. Therefore, it is important to achieve further understanding of control mechanisms involved in nitrogen fixation and related processes. This thesis concerns different molecular aspects of the transcription factor NtcA from the heterocystous cyanobacterium Anabaena PCC 7120. Apart from performing oxygenic photosynthesis, Anabaena PCC 7120 is also capable of fixing nitrogen. NtcA is a protein regulating transcription of a wide range of genes and in particular genes involved in cyanobacterial global nitrogen control. NtcA binds as a dimer to the promoter regions of target genes such as those involved in nitrogen fixation and heterocyst differentiation. NtcA from Anabaena PCC 7120 was heterologously expressed in E. coli and a high yield of recombinant protein was achieved through purification by Ni-IMAC chromatography. The purified NtcA was used to examine DNA binding motifs preferred by NtcA in vitro using a semi-random library of DNA sequences. The preferred binding sequence for NtcA is TGTA – N8 – TACA and at least five of the bases in the palindromic binding site are necessary for binding. Differences in the consensus sequence in vivo may reflect variations in the structural conformation of NtcA under various physiological conditions. Since an earlier study suggested redox-regulated NtcA-DNA binding the role of the two cysteine residues of NtcA were investigated. Binding studies using three mutants, Cys157Ala, Cys164Ala, and Cys157Ala / Cys164Ala, demonstrated that all these NtcA variants bind to DNA with a slightly higher affinity in the presence of the reducing agent DTT. The studies indicate that the binding mechanism is not dependent on a conformational change of NtcA caused by breaking of intra-molecular disulfide bonds. Crystallization followed by structural studies rendered a partial crystal structure of NtcA. The structure verifies that NtcA is a dimeric protein. Each subunit has three domains: the N-terminal domain, a dimerization helix connecting the N-terminal domain with the C-terminal domain, as well as making up the dimer interface, and a C-terminal domain including the DNA binding helix-turn-helix motif. Furthermore, an NtcA binding site was found in the promoter region of the hupSL gene, encoding an uptake hydrogenase in Nostoc punctiforme (ATCC 29133), indicating that yet another gene is transcriptionally controlled by NtcA, thereby further emphasizing the multifaceted role of NtcA in cyanobacteria.
58

Algoritmo treansgen?tico na solu??o do problema do Caixeiro Viajante

Bagi, Ligia Bariani 09 February 2007 (has links)
Made available in DSpace on 2014-12-17T15:48:11Z (GMT). No. of bitstreams: 1 LigiaBB.pdf: 1036516 bytes, checksum: 36260a287f3ddf0bc38abbb0ec32b82f (MD5) Previous issue date: 2007-02-09 / Coordena??o de Aperfei?oamento de Pessoal de N?vel Superior / The Traveling Purchaser Problem is a variant of the Traveling Salesman Problem, where there is a set of markets and a set of products. Each product is available on a subset of markets and its unit cost depends on the market where it is available. The objective is to buy all the products, departing and returning to a domicile, at the least possible cost defined as the summation of the weights of the edges in the tour and the cost paid to acquire the products. A Transgenetic Algorithm, an evolutionary algorithm with basis on endosymbiosis, is applied to the Capacited and Uncapacited versions of this problem. Evolution in Transgenetic Algorithms is simulated with the interaction and information sharing between populations of individuals from distinct species. The computational results show that this is a very effective approach for the TPP regarding solution quality and runtime. Seventeen and nine new best results are presented for instances of the capacited and uncapacited versions, respectively / O Problema do Caixeiro Comprador ? uma variante do Problema do Caixeiro Viajante, onde existe um conjunto de mercados e um conjunto de produtos. Cada produto est? dispon?vel em um subconjunto de mercados e o pre?o da unidade varia de acordo com o mercado. O objetivo ? comprar todos os produtos, partindo e retornando para o dep?sito, de maneira que a soma do custo da rota e dos produtos seja m?nimo. Um Algoritmo Transgen?tico, algoritmo evolucion?rio com base na endosimbiose, ? utilizado para resolver a vers?o Capacitada e N?o Capacitada desse problema. A evolu??o no algoritmo transgen?tico ? simulada com a intera??o e troca de informa??es entre popula??o de indiv?duos de diferentes esp?cies. Os resultados computacionais mostram que a abordagem ? satisfat?ria para o PCC , tanto na qualidade da solu??o, quanto no tempo de execu??o. Dezessete e nove novas melhores solu??es s?o encontradas para o PCC Capacitado e para o PCC N?o Capacitado, respectivamente
59

Regulation of the chlorophyll biosynthesis in the cyanobacterium \kur{Synechocystis} sp. PCC 6803 / Regulation of the chlorophyll biosynthesis in the cyanobacterium \kur{Synechocystis} sp. PCC 6803

KOPEČNÁ, Jana January 2012 (has links)
The thesis focuses on regulation of the chlorophyll biosynthetic pathway and its coordination with synthesis of chlorophyll-binding proteins in the cyanobacterium Synechocystis sp. PCC 6803. One of the aims was to analyze correlation between syntheses of photosystems and chlorophyll in Synechocystis cells using radioactive labeling of proteins and chlorophyll by 35S and 14C, respectively. I also investigated the role of enzymes catalyzing protochlorophyllide reduction step in the chlorophyll biosynthesis by analyzing the synthesis and accumulation of photosynthetic proteins in Synechocystis mutants lacking one of the enzymes. Further, roles of Ycf54 and Psb27 proteins in stability and assembly of oxidative cyclase and CP43, respectively, are also described.
60

Selective exhaust gas recirculation in combined cycle gas turbine power plants with post-combustion carbon capture

Herraiz Palomino, Laura January 2017 (has links)
Selective Exhaust Gas Recirculation (S-EGR) consists of selectively transferring CO2 from the exhaust gas stream of a gas-fired power plant into the air stream entering the gas turbine compressor. Unlike in “non-selective” Exhaust Gas Recirculation (EGR) technology, recirculation of, principally, nitrogen does not occur, and the gas turbine still operates with a large excess of air. Two configurations are proposed: one with the CO2 transfer system operating in parallel to the post-combustion carbon capture (PCC) unit; the other with the CO2 transfer system operating downstream of, and in series to, the PCC unit. S-EGR allows for higher CO2 concentrations in the flue gas of approximately 13-14 vol%, compared to 6.6 vol% with EGR at 35% recirculation ratio. The oxygen levels in the combustor are approximately 19 vol%, well above the minimum limit of 16 vol% with 35% EGR reported in literature. At these operating conditions, process model simulations show that the current class of gas turbine engines can operate without a significant deviation in the compressor and the turbine performance from the design conditions. Compressor inlet temperature and CO2 concentration in the working fluid are critical parameters in the assessment of the effect on the gas turbine net power output and efficiency. A higher turbine exhaust temperature allows the generation of additional steam which results in a marginal increase in the combined cycle net power output of 5% and 2% in the investigated configurations with S-EGR in parallel and S-EGR in series, respectively. With aqueous monoethanolamine scrubbing technology, S-EGR leads to operation and cost benefits. S-EGR in parallel operating at 70% recirculation, 97% selective CO2 transfer efficiency and 96% PCC efficiency results in a reduction of 46% in packing volume and 5% in specific reboiler duty, compared to air-based combustion CCGT with PCC, and of 10% in packing volume and 2% in specific reboiler duty, compared to 35% EGR. S-EGR in series operating at 95% selective CO2 transfer efficiency and 32% PCC efficiency results in a reduction of 64% in packing volume and 7% in specific reboiler duty, compared to air-based, and of 40% in packing volume and 4% in specific reboiler duty, compared to 35% EGR. An analysis of key performance indicators for selective CO2 transfer proposes physical adsorption in rotary wheel systems as an alternative to selective CO2 membrane systems. A conceptual design assessment with two commercially available adsorbent materials, activated carbon and Zeolite X13, shows that it is possible to regenerate the adsorbent with air at near ambient temperature and pressure. Yet, a significant step change in adsorbent materials is necessary to design rotary adsorption systems with dimensions comparable to the largest rotary gas/gas heat exchanger used in coal-fired power plants, i.e. approximately 24 m diameter and 2 m height. An optimisation study provides guidelines on the equilibrium parameters for the development of materials. Finally, a technical feasibility study of configuration options with rotary gas/gas heat exchangers shows that cooling water demand around the post-combustion CO2 capture system can be drastically reduced using dry cooling systems where gas/gas heat exchangers use ambient air as the cooling fluid. Hybrid cooling configurations reduce cooling and process water demand in the direct contact cooler of a wet cooling system by 67% and 35% respectively, and dry cooling configurations eliminate the use of process and cooling water and achieve adequate gas temperature entering the absorber.

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