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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.
41

Estudos de mecanismos redox enzimáticos por eletroquímica e modelagem computacional / Studies of enzymatic redox mechanisms by electrochemistry and computational modeling

Callera, Welder Franzini Amaral [UNESP] 04 August 2017 (has links)
Submitted by WELDER FRANZINI AMARAL CALLERA null (weldercallera@hotmail.com) on 2017-08-28T21:25:00Z No. of bitstreams: 1 TESE - Welder F A Callera OK.pdf: 2324966 bytes, checksum: 979c488a0e341117b537d2d5a1ec77b2 (MD5) / Rejected by Luiz Galeffi (luizgaleffi@gmail.com), reason: Solicitamos que realize uma nova submissão seguindo a orientação abaixo: O arquivo submetido está sem a ficha catalográfica. A versão submetida por você é considerada a versão final da dissertação/tese, portanto não poderá ocorrer qualquer alteração em seu conteúdo após a aprovação. Corrija esta informação e realize uma nova submissão contendo o arquivo correto. Agradecemos a compreensão. on 2017-08-29T18:03:23Z (GMT) / Submitted by WELDER FRANZINI AMARAL CALLERA null (weldercallera@hotmail.com) on 2017-08-29T18:41:29Z No. of bitstreams: 1 TESE - Welder F A Callera OK.pdf: 2349810 bytes, checksum: 0b00e94e2ccb5b74f2521ba559748736 (MD5) / Approved for entry into archive by Luiz Galeffi (luizgaleffi@gmail.com) on 2017-08-29T18:53:53Z (GMT) No. of bitstreams: 1 callera_wfa_dr_araiq.pdf: 2349810 bytes, checksum: 0b00e94e2ccb5b74f2521ba559748736 (MD5) / Made available in DSpace on 2017-08-29T18:53:53Z (GMT). No. of bitstreams: 1 callera_wfa_dr_araiq.pdf: 2349810 bytes, checksum: 0b00e94e2ccb5b74f2521ba559748736 (MD5) Previous issue date: 2017-08-04 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) / Esta tese de doutoramento apresentou o entendimento de processos redox enzimáticos, detalhando o mecanismo envolvido na troca eletrônica, a qual resulta na formação de um produto, por catálise enzimática. Observou-se a influência de um eletrodo sob a ação de um potencial estacionário aplicado (E) na reação enzima/substrato. Realizou-se eletroanálises, como: Voltametria Cíclica (VC) e Espectroscopia de Impedância Eletroquímica (EIE), para a penicilinase. Os resultados obtidos dão indícios de que a reação enzimática se beneficia de determinados potenciais, pois o parâmetro utilizado, Rct, resistência à transferência de cargas, sugere que ocorre maior troca eletrônica em alguns potenciais ótimos (faixa de -0,3 a -0,5 V). A Simulação Molecular serviu para estudar o comportamento atomístico por métodos clássicos (Dinâmica Molecular – DM) para as condições impostas experimentalmente, esclarecendo o mecanismo de reação enzimática por métodos quânticos (DFT – Teoria do Funcional de Densidade) e híbridos (QM/MM), cabendo salientar que a penicilinase não pertence à classe das enzimas oxirredutivas. / This doctoral thesis presented the understanding of enzymatic redox processes, detailing the mechanism involved in the electronic exchange, which results in the formation of a product by enzymatic catalysis. The influence of an electrode under the action of an applied stationary potential (E) on the enzyme/substrate reaction was observed. Electroanalysis was performed, such as: Cyclic Voltammetry (VC) and Electrochemical Impedance Spectroscopy (EIS), for the penicilinase. The results obtained indicate that the enzymatic reaction benefits from certain potentials, since the parameter used, Rct, resistance to the transfer of charges, suggests that there is greater electronic exchange in some optimal potentials (range the -0.3 to -0.5 V). The Molecular Simulation was used to study the atomistic behavior by classical methods (Molecular Dynamics - DM) for experimentally imposed conditions, clarifying the mechanism of enzymatic reaction by quantum methods (DFT) and hybrids (QM/MM). That penicillinase does not belong to the class of oxidoreductive enzymes.
42

Elektrochemisches Modell zur Beschreibung der Konversion von Aluminium durch anodische Oxidation

Sieber, Maximilian 21 December 2016 (has links)
Durch elektrochemische Impedanzspektroskopie während der anodischen Oxidation von Aluminium werden in der vorliegenden Arbeit die elektrochemischen Vorgänge während der Oxidbildung quantitativ und zeitabhängig untersucht. Es wird ein Modell vorgeschlagen und diskutiert, welches das Impedanzverhalten während der anodischen Oxidation in Schwefel-, Oxal- und Phosphorsäure über einen großen Bereich von Konzentrationen und Stromdichten abbilden kann. Aus den gewonnenen Ergebnissen werden die kapazitive Wirkung der Sperrschicht am Porengrund, der Eintritt von Ladungsträgern in die Sperrschicht, der Ionentransport durch die Sperrschicht sowie die Oxidbildungsreaktion selbst als wesentlich für das Impedanzverhalten identifiziert. Die ermittelten Zusammenhänge und Konstanten können als Grundlage für Modellvorstellungen dienen, welche das Verhalten elektrischer Prozessgrößen und die Ausbildung der charakteristischen Oxidstruktur bei der anodischen Oxidation von Aluminium verknüpfen. / In the present work, the electrochemical subprocesses of the oxide formation on aluminium by anodic oxidation are investigated using electrochemical impedance spectroscopy. The time dependence of the impedance behaviour and the quantitative relations between the process parameters and the impedance behaviour are considered. A model for the representation of the electrochemical behaviour during the anodic oxidation in sulphuric, oxalic and phosphoric acid is proposed and discussed for a wide range of anion concentrations and current densities. On the basis of the obtained results, the capacitive effect of the barrier layer, the charge transfer resistance of the barrier layer, the ion transport within the barrier layer and the oxide formation are identified as the dominating effects for the impedance behaviour. The established relations can serve as a basis for models, which interrelate both the electrochemical behaviour and the geometrical formation of the characteristic pore structure.

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