The Monte Carlo forward Euler method with uniform time stepping is the standard technique to compute an approximation of the expected payoff of a solution of an Itô SDE. For a given accuracy requirement TOL, the complexity of this technique for well behaved problems, that is the amount of computational work to solve the problem, is O(TOL-3). A new hybrid adaptive Monte Carlo forward Euler algorithm for SDEs with non-smooth coefficients and low regular observables is developed in this thesis. This adaptive method is based on the derivation of a new error expansion with computable leading-order terms. The basic idea of the new expansion is the use of a mixture of prior information to determine the weight functions and posterior information to compute the local error. In a number of numerical examples the superior efficiency of the hybrid adaptive algorithm over the standard uniform time stepping technique is verified. When a non-smooth binary payoff with either GBM or drift singularity type of SDEs is considered, the new adaptive method achieves the same complexity as the uniform discretization with smooth problems. Moreover, the new developed algorithm is extended to the MLMC forward Euler setting which reduces the complexity from O(TOL-3) to O(TOL-2(log(TOL))2). For the binary option case with the same type of Itô SDEs, the hybrid adaptive MLMC forward Euler recovers the standard multilevel computational cost O(TOL-2(log(TOL))2). When considering a higher order Milstein scheme, a similar complexity result was obtained by Giles using the uniform time stepping for one dimensional SDEs. The difficulty to extend Giles' Milstein MLMC method to the multidimensional case is an argument for the flexibility of our new constructed adaptive MLMC forward Euler method which can be easily adapted to this setting. Similarly, the expected complexity O(TOL-2(log(TOL))2) is reached for the multidimensional case and verified numerically.

Liver fat-storing cells (FSC) play an important role in collagen deposition. During the induction of liver cirrhosis, FSC lose their fat droplets, acquire an actin-rich cytoskeleton and transform into myofibroblasts. Myofibroblasts have been associated with increased collagen production in cirrhotic livers. Cultured FSC resemble myofibroblasts. However, it is not known whether regulation of collagen gene expression is similar in FSC obtained from normal or cirrhotic livers. In this communication, we describe the characterization of two fat-storing cell lines, one from normal (NFSC) and one from CCl4-cirrhotic liver (CFSC), obtained after spontaneous immortalization in culture. We studied the effect of serum and various growth factors on cell proliferation. We determined the production of collagen and fibronectin and we analyzed the presence of mRNA transcripts of collagens type I, III, and IV, fibronectin laminin, transforming growth factor-β and interleukin-6. We found that CFSC have a greater serum-dependency than NFSC. NFSC grow with a mixture of insulin and epidermal growth factor, whereas CFSC proliferate only with platelet-derived growth factor. Although we did not find significant differences in the expression of mRNAs for collagen type I, fibronectin and transforming growth factor-β, collagen and fibronectin synthesis was increased 2- and 1.5-fold respectively. NFSC contained 1.6- and 2.0-fold more type III collagen and laminin mRNAs, respectively, than CFSC. Neither cell line expressed type IV collagen mRNA. NFSC but not CFSC produced interleukin-6. These results suggest that, except for the lack of transcripts of collagen type IV, both cell lines resemble primary cultures of FSC. However, significant differences in cell proliferation and interleukin-6 production between the two cell lines were found. We suggest that these cell lines could be useful tools to study possible differences in regulation of matrix production by FSC.

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abstract: The inexorable upsurge in world’s energy demand has steered the search for newer renewable energy sources and photovoltaics seemed to be one of the best alternatives for energy production. Among the various photovoltaic technologies that emerged, organic/polymer photovoltaics based on solution processed bulk-heterojunctions (BHJ) of semiconducting polymers has gained serious attention owing to the use of inexpensive light-weight materials, exhibiting high mechanical flexibility and compatibility with low temperature roll-to-roll manufacturing techniques on flexible substrates. The most widely studied material to date is the blend of regioregular P3HT and PC61BM used as donor and acceptor materials. The object of this study was to investigate and improve the performance/stability of the organic solar cells by use of inexpensive materials. In an attempt to enhance the efficiency of organic solar cells, we have demonstrated the use of hexamethyldisilazane (HMDS) modified indium tin oxide (ITO) electrode in bulk heterojunction solar cell structure The device studies showed a significant enhancement in the short-circuit current as well as in the shunt resistance on use of the hexamethyldisilazane (HMDS) layer. In another approach a p-type CuI hole-transport layer was utilized that could possibly replace the acidic PEDOT:PSS layer in the fabrication of high-efficiency solar cells. The device optimization was done by varying the concentration of CuI in the precursor solution which played an important role in the efficiency of the solar cell devices. Recently a substantial amount of research has been focused on identifying suitable interfacial layers in organic solar cells which has efficient charge transport properties. It was illustrated that a thin layer of silver oxide interfacial layer showed a 28% increase in power conversion efficiency in comparison to that of the control cell. The optoelectronic properties and morphological features of indium-free ZnO/Ag/MoOx electrodes was also studied. Organic solar cells on these composite electrodes revealed good optical and electrical properties, making them a promising alternative indium free and PEDOT:PSS-free organic solar cells. Lastly, inverted solar cells utilizing zinc oxide and yttrium doped zinc oxide electron transport was also created and their device properties revealed that optimum annealing conditions and yttrium doping was essential to obtain high efficiency solar cells. / Dissertation/Thesis / Doctoral Dissertation Chemistry 2015

Made available in DSpace on 2015-03-26T13:35:17Z (GMT). No. of bitstreams: 1 texto completo.pdf: 2702366 bytes, checksum: 02a68d22232b7448fb6511c00ea887ba (MD5) Previous issue date: 2011-07-25 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / In this work were carried out some studies on electrochemical properties of carbon nanotubes (CNT) thin films deposited on ITO (Indium Tin Oxide) electrodes by electrophoretic deposition (EPD). Capacitance and electrochemical area measurements were made with films of three types of nanotubes with different dimensions and previous treatments. All measurements were performed in aqueous and organic solutions in order to notice any behavior difference. Nanotubes films showed higher electrochemical capacitance and area in organic solution compared with those obtained in aqueous solution, demonstrating a greater compatibility with organic solvents. The films consist of smaller nanotubes showed the highest capacitance values, suggesting that the electrochemical capacitance has a direct dependence with the ratio area / mass of CNT's. We analyzed also the effect of functionalization of nanotubes by cyclic voltammetry in solution of H2SO4 on the electrochemical measurements. In these experiments, the electrodes modified with CNT's showed a slight improvement on the electronic transfer, however, the value of the capacitance of these films has increased substantially after this process. Finally, nickel electrodeposition was performed in organic solution and zinc oxide in aqueous solution, on the nanotube films. Images of scanning electron microscopy (SEM) and transmission electron microscopy (TEM) revealed that the deposits resulted only in the ZnO crystal growth micrometric crystallographic hexagonal pattern on the film. In contrast, the nickel deposits produced CNT's quite covered with Ni nanoparticles. All electrochemical characterizations and electrodepositions were carried out at Laboratório de Eletrodeposição, Superfícies e Películas Avançadas (LESPA) of Physics department at UFV. / Neste trabalho foram realizados estudos sobre algumas propriedades eletroquímicas de filmes finos de nanotubos de carbono (CNT, Carbon Nanotube) depositados sobre eletrodos de óxido de titânio dopado com índio (ITO, Indium Tin Oxide) por deposição eletroforética (EPD, Electrophoretic Deposition). Medidas de capacitância e área eletroquímicas foram realizadas em filmes de três tipos de nanotubos que possuem diferentes dimensões e tratamentos prévios. Todas as medidas foram realizadas em soluções orgânicas e aquosas a fim de se verificar alguma diferença de comportamento dos filmes. Inicialmente, foi analisado o efeito da funcionalização destes nanotubos por voltametria cíclica em solução de H2SO4 sobre as medidas eletroquímicas. Nestes experimentos, os eletrodos modificados com CNT s apresentaram uma leve melhora na transferência eletrônica, no entanto, o valor da capacitância destes filmes sofreu um aumento substancial após este processo Os filmes constituídos pelos nanotubos de menores dimensões apresentaram os maiores valores de capacitância, sugerindo que a capacitância eletroquímica tem uma dependência direta com a razão área/massa dos CNT s. Os nanotubos apresentaram maior capacitância e área eletroquímica em solução orgânica comparados com os valores obtidos em solução aquosa, demonstrando uma maior compatibilidade com solventes orgânicos. Por fim, foram realizadas eletrodeposições de níquel em solução orgânica e de óxido de zinco em solução aquosa, sobre os filmes de nanotubo. Imagens de microscopia eletrônica de varredura (SEM, Scanning Electron Microscopy) e de transmissão (TEM, Transmission Electron Microscopy) revelaram que os depósitos de ZnO resultaram apenas no crescimento de cristais micrométricos com padrão cristalográfico hexagonal sobre os filmes. Em contrapartida, os depósitos de níquel produziram CNT s cobertos com nanopartículas deste metal. Todas as caracterizações eletroquímicas e eletrodeposições foram realizadas no Laboratório de Eletrodeposição, Superfícies e Películas Avançadas (LESPA) do Departamento de Física da Universidade Federal de Viçosa.

Die Temperung mittels Xenon-Blitzlampen (Flash Lamp Annealing - FLA) ist ein Kurzzeittemperverfahren mit Pulszeiten im Bereich von Millisekunden, bei dem nur die Oberfläche eines Substrats erhitzt wird. Durch die Blitzlampentemperung kann der Schichtwiderstand von tansparenten leitfähigen Oxidschichten reduziert und die Transmission im sichtbaren Licht erhöht werden. In dieser Arbeit wurde dies am Beispiel von Indium-Zinn-Oxid (ITO), Indium-Zink-Oxid (IZO) und aluminiumdotiertem Zinkoxid (AZO) gezeigt. Es wurde untersucht, welchen Einfluss verschiedene Prozessparameter wie Energiedichte und Pulszeit des Xenonlichtblitzes, die Absorption der zu behandelnden Schicht, die Gasatmosphäre während der Temperung, die Reflexion im Prozessraum und das Substratmaterial auf die optischen und elektrischen Eigenschaften der Schichten haben. Für ITO-Schichten mit einer Schichtdicke von 150 nm kann der Widerstand von 45 auf <14 Ohm verbessert werden, was vergleichbar mit einer konventionellen Temperung im Umluftofen ist.

Die Temperung mittels Xenon-Blitzlampen (Flash Lamp Annealing - FLA) ist ein Kurzzeittemperverfahren mit Pulszeiten im Bereich von Millisekunden, bei dem nur die Oberfläche eines Substrats erhitzt wird. Durch die Blitzlampentemperung kann der Schichtwiderstand von tansparenten leitfähigen Oxidschichten reduziert und die Transmission im sichtbaren Licht erhöht werden. In dieser Arbeit wurde dies am Beispiel von Indium-Zinn-Oxid (ITO), Indium-Zink-Oxid (IZO) und aluminiumdotiertem Zinkoxid (AZO) gezeigt. Es wurde untersucht, welchen Einfluss verschiedene Prozessparameter wie Energiedichte und Pulszeit des Xenonlichtblitzes, die Absorption der zu behandelnden Schicht, die Gasatmosphäre während der Temperung, die Reflexion im Prozessraum und das Substratmaterial auf die optischen und elektrischen Eigenschaften der Schichten haben. Für ITO-Schichten mit einer Schichtdicke von 150 nm kann der Widerstand von 45 auf <14 Ohm verbessert werden, was vergleichbar mit einer konventionellen Temperung im Umluftofen ist.

Ce mémoire est composé de deux articles qui ont pour but commun de lever le voile et de compléter le schéma d’Askey des q–polynômes orthogonaux dans la limite q = −1. L’objectif est donc de trouver toutes les familles de polynômes orthogonaux dans la limite −1, de caractériser ces familles et de les connecter aux autres familles de polynômes orthogonaux −1 déjà introduites. Dans le premier article, une méthode basée sur la prise de limites dans les relations de récurrence est présentée. En utilisant cette méthode, plusieurs nouvelles familles de polynômes orthogonaux sur des intervals continus sont introduites et un schéma est construit reliant toutes ces familles de polynômes −1. Dans le second article, un ensemble de polynômes, orthogonaux sur l’agencement de quatre grilles linéaires, nommé les polynômes de para-Bannai-Ito est introduit. Cette famille de polynômes complète ainsi la liste des parapolynômes. / This master thesis contains two articles with the common goal of unveiling and completing the Askey scheme of q–orthogonal polynomials in the q = −1 limit. The main objective is to find and characterize new families of -1 orthogonal polynomials and connect them to other already known families. In the first article, a method based on applying limits in recurrence relations is presented. This method is used to find many new families of polynomials orthogonal with respect to continuous measure. A −1 scheme containing them is constructed and a compendium containing the properties of all such families is included. In the second article, a new set of polynomials named the para–Bannai–Ito polynomials is introduced. This new set, orthogonal on a linear quadri–lattice, completes the list of parapolynomials, but it is also a step toward the finalization of the -1 scheme of polynomials orthogonal on finite grids.