Transporte de informação directamente sobre sistemas de comunicação ópticos

Mestrado em Engenharia ElectrónicaNum futuro próximo, a informação transmitida entre vários utilizadores, seja áudio, vídeo ou dados, poderá ser transportada directamente sobre redes ópticas. Neste sentido, têm sido estudadas e analisadas várias tecnologias emergentes de redes ópticas, que culminaram com o aparecimento de soluções que permitem a integração de redes IP (Internet Protocol) sobre redes ópticas. Tendo em vista este cenário, o objectivo deste trabalho foi o estudo dos mecanismos de transporte de informação sobre sistemas de comunicação ópticos. Foi dada especial relevância a tecnologias ópticas multicanal utilizadas actualmente, o Wavelength Division Multiplexing (WDM) e o Multiprotocol Label Switching (MPLS). Uma vez que uma das formas usuais de avaliar o impacto da camada física nos sistemas de comunicação é através das taxa de erro binários, foi efectuada a caracterização da camada física em termos de taxas de erros binários e da probabilidade de erros na transmissão de pacotes de informação. Este estudo englobou várias fases, nomeadamente a caracterização do meio de transmissão, a fibra (através da taxa de erros binários e do factor Q), e a análise do impacto dos erros binários nas camadas de ligação de dados, de rede e de transporte, traduzida na probabilidade de erros em sequências de bits. Foi também abordado o impacto dos esquemas de detecção e/ou de correcção de erros utilizados nas várias camadas protocolares. Finalmente, foi analisado e caracterizado o comportamento da rede em função das características físicas do canal de transmissão.In a near future, information (audio, video and data) may be transmitted between several users directly over optical networks. Several emerging technologies on optical networks, which allow the IP (Internet Protocol) integration in the optical domain, have already been widely studied and analyzed. Keeping in mind this scenario, the goal of this work was the study of the information transport mechanisms over optical communication systems. Special attention was given to technologies currently used, the Wavelength Division Multiplexing (WDM) and the Multiprotocol Label Switching (MPLS). The Bit Error Rate (BER) is used as a measure of the negative effects of all physical impairments on the fibre, being usually a comprehensive criterion for the evaluation of the signal transmission quality. This way, the physical layer characterization was made in terms of BER and/or packet error rate (PER). This study concerned several stages: the fibre characterization in terms of BER and Q-factor, the study of the impact of the binary errors in the network behaviour, and the study and analysis of the error detection and correction schemes used in the several layers. Finally, the network behaviour was analysed and characterized as a function of the channel physical characteristics and constraints

Quantification of oxidative stress biomarkers: development of a method by ultra performance liquid chromatography

Thiol and purine compounds are widely distributed in nature. They are involved in physiological processes, such as, homeostasis and redox signalling, and disturbances of these functions are the basis of many human diseases. Therefore, there has been a great effort to better understand the metabolomics of these compounds. The goal of the present work was to optimize an Ultra-High Performance Liquid Chromatography method for simultaneous detection and quantification of some thiol, and purine compounds in cells lysates and biological fluids. For this purpose, an UPLC® system, equipped with an HSS T3 column, with fluorescence and photodiode array detection was used. Preliminary experiences to optimize chromatographic separation of standard compounds were accomplished and involved testing of conditions for sample pre-analytical treatments, mobile phase compositions and detection conditions. A good resolution and separation was obtained for the standards tested. The thiols Glutathione, Cysteine and Homocysteine eluted at 0.655 0.005, 2.189 0.000 and 3.752 0.001 minutes. Intra-day precision of the method was 12.05, 9.87 and 9.06% for areas. Farther, inter-day precision for the retention times were 29.49, 1.63 and 2.24% and for areas were 41.55, 28.28 and 29.46%, respectively. Purines Adenosine and Inosine eluted at 2.249 0.001 and 2.584 0.005 minutes. Inter-day precision for the retention times were 0.06 and 0.01% and for areas were 6.99 and 6.63%, respectively. Linearity was tested in a range of concentrations from 5 to 100 M for thiols and 25 to 500 M for purines, with good results. Additionally, the detection and quantification limits were too high. Unfortunately, our analyses do not shown intra or inter-day precision. Therefore, the validation was not completed because reproducibility was inconsistent due to the mechanical failure of the chromatographic equipment used. However, we concluded that the identification of these analytes is possible with the methods established.Os compostos tiólicos e as purinas encontram-se amplamente distribuídos na natureza. Estão envolvidos em vários processos fisiológicos, como a homeostasia e a sinalização redox. Perturbações destas funções estão na base de muitas patologias humanas. Por essa razão, existe um grande esforço da comunidade científica para entender estes compostos, particularmente ao nível da metabolómica. O objetivo deste trabalho foi otimizar um método de cromatografia líquida de ultra precisão para a deteção e quantificação destes compostos, em lisados celulares e fluidos biológicos. Com este propósito, foi usado o sistema cromatográfico UPLC®, equipado com uma coluna HSS T3 acoplado a detetores de fluorescência e fotodiodos em série para os tióis e purinas, respetivamente. Foram realizadas diversas experiências preliminares de otimização da separação dos padrões, onde foram testadas várias condições de pré-tratamento das amostras, diversas composições das fases móveis e condições de deteção. Foi possível obter uma boa resolução com os compostos tiólicos e com as purinas. O Glutatião, a Cisteína e a Homocisteína eluíram aos 0.655 0.005, 2.189 0.000 e 3.752 0.001 minutos. A precisão inter-diária dos tempos de retenção foi de 29.49, 1.63 e 2.24% e das áreas foi de 41.55, 28.28 e 29.46%, respetivamente. A linearidade do método foi testada numa gama de concentrações entre 5 e 100 M, com bons coeficientes de correlação. Os compostos purínicos Adenosina e Inosina eluíram aos 2.249 0.001 e 2.584 0.005 minutos. A precisão inter-diária dos tempos de retenção foi 0.06 e 0.01% e das áreas 6.99 e 6.63%, respetivamente. A linearidade do método foi testada numa gama de concentrações entre 25 e 500 M, com bons coeficientes de correlação. Infelizmente os resultados foram inconsistentes e a validação não foi alcançada, devido a falhas mecânicas do equipamento cromatográfico utilizado. Conclui-se que a identificação dos analitos é possível com os métodos estabelecidos

Optimization Methods Applied to Power Systems Ⅱ

Electrical power systems are complex networks that include a set of electrical components that allow distributing the electricity generated in the conventional and renewable power plants to distribution systems so it can be received by final consumers (businesses and homes). In practice, power system management requires solving different design, operation, and control problems. Bearing in mind that computers are used to solve these complex optimization problems, this book includes some recent contributions to this field that cover a large variety of problems. More specifically, the book includes contributions about topics such as controllers for the frequency response of microgrids, post-contingency overflow analysis, line overloads after line and generation contingences, power quality disturbances, earthing system touch voltages, security-constrained optimal power flow, voltage regulation planning, intermittent generation in power systems, location of partial discharge source in gas-insulated switchgear, electric vehicle charging stations, optimal power flow with photovoltaic generation, hydroelectric plant location selection, cold-thermal-electric integrated energy systems, high-efficiency resonant devices for microwave power generation, security-constrained unit commitment, and economic dispatch problems

Catalytic Asymmetric Reactions between Alkenes and Aldehydes

This doctoral work describes catalytic asymmetric reactions between alkenes and aldehydes, enabled by the development of chiral Brønsted acids. Valuable and functionalized enantiomerically enriched cyclic compounds were efficiently furnished from inexpensive and commercially available reagents with high degrees of atom economy. In the first part of this thesis, the first highly enantioselective organocatalytic intramolecular carbonyl−ene cyclization of olefinic aldehydes is presented. In the second part, asymmetric cyclizations via oxocarbenium ions are described. One is a general asymmetric catalytic Prins cyclization of aldehydes with homoallylic alcohols, in which the oxocarbenium ion is attacked intramolecularly by a pendent alkene. The other one is an asymmetric oxa-Pictet−Spengler reaction between aldehydes and homobenzyl alcohols, in which the oxocarbenium ion is trapped by an intramolecular arene. The first general asymmetric [4+2]-cycloaddition of simple and unactivated dienes with aldehydes is developed in the last part of this thesis. This methodology is extremely robust and scalable. Valuable enantiomerically enriched dihydropyran compounds could be readily obtained from inexpensive and abundant dienes and aldehydes. New types of confined Brønsted acids were rationally designed and synthesized, including imino-imidodiphosphates (iIDPs), nitrated imidodiphosphates (nIDPs), and imidodiphosphorimidates (IDPis). Beyond the application of these catalysts in various asymmetric reactions between simple alkenes and aldehydes, mechanistic investigations are also disclosed in this doctoral work

Monitoring antibiotics in the environment. Study of Quinoxaline derivatives bioactivity

Dissertação para obtenção do Grau de Doutor em Química SustentávelAntimicrobial agents have revolutionized medicine and promoted an increase in average life expectancy of human populations worldwide. These drugs are used not only in human medicine but also in veterinary practice, in the treatment and prevention of infections, and in some regions in the world, as well as growth promoters, ensuring a greater and better animal production. The use of antimicrobial agents in animal production causes contamination of the final product with drug residues that are eventually distributed in human food chain. Residues of antimicrobial agents provenient from human and animal consumption are also present in sewage, surface water or ground water. It is still unknown all the consequences of this contamination, but there are indications of changes in indigenous microbiota. The use of these drugs was quickly followed by the emergence of resistance, which led to decreased efficacy and compounds available. Therefore, the spread of antimicrobial agents in the environment is also associated with increased resistance to such drugs. The presented work intended to establish methods for monitoring the presence of antibiotics in animal foods, evaluate if the presence of antimicrobial agents in the environment at sub-inhibitory concentrations can contribute to the selection of resistant bacteria and characterize the biological activity of a number of compounds of the quinoxaline family as potential new antimicrobial agents. In order to achieve these objectives, chromatographic techniques were used for detection and quantification of antimicrobial agents, methods of microbiology and molecular biology to evaluate the behavior of bacteria under selective pressure. Various strains of prokaryotes and eukaryotes microorganisms were also used to evaluate the antimicrobial activity of N-oxide derivatives of quinoxaline. We used, also, cell cultures to assess the potential toxicity of these new antibiotics. A new chromatographic method was developed to quantify the reduced and oxidized forms of glutathione, in order to infer the cellular oxidative stress induced by exposure to the quinoxaline derivative compounds with proven antimicrobial activity. The results confirm that the chromatographic HPLC-DAD methods are powerful tools in monitoring food quality. They also indicate that the presence of subinhibitory amounts of ciprofloxacin in water may influence the dynamic of susceptible and resistant to ciprofloxacin Escherichia coli population. An assessment of the biological activity of quinoxaline derivatives indicated the compounds studied as potential new antimicrobial agents who have shown low toxicity in cell lines and oxidative cell damage in small extent.Fundação para a Ciência e Tecnologia - bolsa de doutoramento SFRH / BD /48116 / 200

Biochemical characterization of a haloalcohol dehalogenase from Arthrobacter sp H10a

Haloalcohols are an important class of industrial pollutants some of which are believed to be carcinogenic. Bacteria that are capable of efficient degradation of these compounds have been isolated. In our laboratory several soil isolates have been isolated by enrichment on 1,3-dichloro-2-propanol and have been subject of biochemical and physiological characterization. In order to shed more light on the biochemical and molecular mechanisms of dehalogenation an Arthrobaxter SP H10a was chosen for this study. Arthrobacter sp strain H10a possesses two enzymes capable of dehalogenating halohydrins (haloalcohol dehalogenases). These dehalogenases designated as Deh1 and Deh2 are expressed constitutively but levels of enzyme activity can be increased 3 to 4 fold in the presence of glycidol. The Deh1 enzyme showed higher activity towards 1,3-DCP while the Deh2 dehalogenase showed higher activity towards CPD. The analysis of the ratio of dehalogenation rate for both CPD and 1,3-DCP showed that addition of haloalcohols to the growth medium resulted in an increase in the Deh2 enzyme activity in relation to the Deh1 activity, whilst epoxides had an opposite effect. In an attempt to understand the mechanisms of dehalogenation the Deh1 haloalcohol dehalogenase was purified and characterized. The enzyme is constituted by two subunits of 31.5 and 34 kDa molecular weight, that associate with other proteins to form a large protein complex of 200 kDa. Peptide mapping with different proteases and amino acid micro-sequence analysis of tryptic digests showed 100% identity between the two Deh1 subunits. The Deh1 haloalcohol dehalogenase catalyzed the conversion of civinal halohydrins to epoxides and the reverse reaction in the presence of an excess of halogen. This enzyme showed maxium activity at 50°C and a broad pH optimum from 8.5 to 10.5. The apparent K/(_m/) and V$_{max}$ values for dehalogenation of 1,3-DCP and CPD were 0.11mM, 236 μmol min$^{-1}$ mg$^{-1}$, respectively. The enzyme activity was inhibited by MCA and DCA. The inhibition pattern suggested a mixed type inhibition predominantly uncompetitive. Amino acid modifying experiments have shown that one of more cysteine and arginine residues may be involved in catalysis or play important roles in maintenance of the enzyme structure. Modification of histidine, lysine, aspartic and glumatic acids had no effect on the dehalogenase activity. Studies of the stereospecificity of the epoxides formed by the Deh1 haloalcohol dehalogenase revealed that (R)-ECH was selectively produced from 1,3-DCP. During the reverse reaction (R)-ECH was stereoselectively halogenated to 1,3-DCP if the halogen in the reaction mixture of chloride. However, if chloride was substituted by bromide, the (S)-isomer was halogenated preferentially. Although the enantiomeric excess and the yields of ECH obtained were low it was shown that it is possible to produce both isomers of ECH if the reaction conditions were optimized. An antibody raised against the Deh1 enzyme was used to screen other bacterial isolates in the laboratory culture collection. This antibody showed immunocross-reactivity with a haloalcohol dehalogenase from strain H10c. This enzyme revealed the same electrophoretic mobility as the Deh1 protein under both native and denaturing conditions. The Deh1 antibody also showed cross-reaction with a 31.5 kDa protein from strain H10f. No immunological cross-reactivity was found between this antibody and the total protein extracts from haloacid and haloalkane degrading bacteria

Television broadcast from space systems: Technology, costs

Broadcast satellite systems are described. The technologies which are unique to both high power broadcast satellites and small TV receive-only earth terminals are also described. A cost assessment of both space and earth segments is included and appendices present both a computer model for satellite cost and the pertinent reported experience with the Japanese BSE