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Atmospheric plasma spraying is attractive for manufacturing solid oxide fuel cells (SOFCs) because it allows functional layers to be built rapidly with controlled microstructures. The technique allows SOFCs that operate at low temperatures (600 to 750°C) to be fabricated by spraying directly onto robust and inexpensive metallic supports. Processes were developed to manufacture metal-supported SOFC cathodes by axial-injection plasma spraying. Cathodes consisted of LSCF (La0.6Sr0.4Co0.2Fe0.8O3-δ) or SSC (Sm0.5Sr0.5CoO3) as the primary material. Initially, the plasma spray process parameters were varied, and x-ray diffraction analyses were performed on the cathode coatings to detect material decomposition and the formation of undesired phases. These results determined the envelope of plasma spray parameters in which coatings of LSCF and SSC can be manufactured, and the range of conditions in which composite cathode coatings could potentially be manufactured. Subsequently, composite cathodes were fabricated by mixing up to 40 wt. % of the ionic conducting SDC (Ce0.8Sm0.2O1.9) material into the feedstock. The deposition efficiencies of these cathodes were calculated based on the mass of the sprayed cathode. Particle surface temperatures were measured in-flight to enhance understanding of the relationship between spray parameters, microstructure, and deposition efficiency. Electrochemical impedance spectroscopy was performed in symmetrical cells: at 750°C, LSCF-SDC cathodes had polarization resistances as low as 0.101 Ωcm², and SSC cathodes had polarization resistances as low as 0.0056 Ωcm². Finer mixing of the ceramic phases was achieved by using a nano-structured feedstock that contained both LSCF and SDC phases agglomerated together in larger particles. Fuel cells containing a yttria-stabilized zirconia (YSZ) electrolyte and a nickel-YSZ anode were fabricated, and the effect of the cathode microstructure on cell impedance was studied using the analysis of differential impedance spectra. The degradation of composite LSCF-SDC cathodes on porous 430 stainless steel supports was also investigated. To reduce degradation, La2O3 and Y2O3 reactive element oxide coatings were deposited on the internal pore surfaces of the metal supports. As a result, polarization resistance degradation rates as low as 0.00256 Ω·cm2 /1000 h were observed over 100 hours on coated substrates, compared to 0.1 Ω·cm2 /1000 h on uncoated substrates.

Atmospheric plasma spraying is attractive for manufacturing solid oxide fuel cells (SOFCs) because it allows functional layers to be built rapidly with controlled microstructures. The technique allows SOFCs that operate at low temperatures (600 to 750°C) to be fabricated by spraying directly onto robust and inexpensive metallic supports. Processes were developed to manufacture metal-supported SOFC cathodes by axial-injection plasma spraying. Cathodes consisted of LSCF (La0.6Sr0.4Co0.2Fe0.8O3-δ) or SSC (Sm0.5Sr0.5CoO3) as the primary material. Initially, the plasma spray process parameters were varied, and x-ray diffraction analyses were performed on the cathode coatings to detect material decomposition and the formation of undesired phases. These results determined the envelope of plasma spray parameters in which coatings of LSCF and SSC can be manufactured, and the range of conditions in which composite cathode coatings could potentially be manufactured. Subsequently, composite cathodes were fabricated by mixing up to 40 wt. % of the ionic conducting SDC (Ce0.8Sm0.2O1.9) material into the feedstock. The deposition efficiencies of these cathodes were calculated based on the mass of the sprayed cathode. Particle surface temperatures were measured in-flight to enhance understanding of the relationship between spray parameters, microstructure, and deposition efficiency. Electrochemical impedance spectroscopy was performed in symmetrical cells: at 750°C, LSCF-SDC cathodes had polarization resistances as low as 0.101 Ωcm², and SSC cathodes had polarization resistances as low as 0.0056 Ωcm². Finer mixing of the ceramic phases was achieved by using a nano-structured feedstock that contained both LSCF and SDC phases agglomerated together in larger particles. Fuel cells containing a yttria-stabilized zirconia (YSZ) electrolyte and a nickel-YSZ anode were fabricated, and the effect of the cathode microstructure on cell impedance was studied using the analysis of differential impedance spectra. The degradation of composite LSCF-SDC cathodes on porous 430 stainless steel supports was also investigated. To reduce degradation, La2O3 and Y2O3 reactive element oxide coatings were deposited on the internal pore surfaces of the metal supports. As a result, polarization resistance degradation rates as low as 0.00256 Ω·cm2 /1000 h were observed over 100 hours on coated substrates, compared to 0.1 Ω·cm2 /1000 h on uncoated substrates.

A presente pesquisa procura estudar uma mudança organizacional de larga escala em uma rede hoteleira multinacional. Esta mudança tem como foco a implementação de um Centro de Serviços Compartilhados (CSC) que passa a realizar de forma centralizada as rotinas e processos administrativos, contábeis e financeiros de mais de quarenta unidades hoteleiras do grupo. Na implementação de mudanças desta magnitude, é necessário lidar com as resistências internas da organização que se apresentam no decorrer do processo. Neste sentido, esta pesquisa objetiva estudar quais são as principais resistências que envolvem um processo de mudança, tomando como ponto base os elementos da resistência apontados por Burns e Scapens (2000). Este construto foi desenvolvido para dar um foco intraorganizacional aos processos de mudança, sendo influenciado pela Old Institutional Economics (OIE), e procura sanar algumas críticas postas às primeiras pesquisas da New Institutional Sociology (NIS) pelas quais esta última estaria descrevendo os processos de mudança como lineares e inevitáveis, nos quais os atores se tornavam voluntariamente isomórficos às instituições. Com base neste construto, este trabalho procura analisar os elementos de resistência (i) por existência de conflito de interesses; (ii) por falta de competência (conhecimento e / ou experiência); e (iii) por apego às instituições postas no ambiente, identificando quais são as mais importantes e como estas resistências se relacionam ao processo de institucionalização posto por Burns e Scapens (2000), no processo de codificação, incorporação, repetição e institucionalização. Assim, por meio de um estudo descritivo, com o uso de técnicas qualitativas e quantitativas, entrevistas, questionários e das ferramentas multivariadas Análise de Conglomerados, Análise de Correspondência (ANACOR), análise de homogeneidade (HOMALS) e da Categorical Principal Component Analysys (CAPTCA), procura-se analisar e observar como os gestores operacionais (gerentes gerais e subgerentes das unidades hoteleiras) e os gestores corporativos (alta diretoria e condutores da mudança) assimilam e percebem a mudança promovida pela implementação de um CSC. O CSC, por sua vez um modelo recente nas organizações, foi implementado para 42 unidades hoteleiras do grupo, distribuídas em cinco marcas com características distintas, através de um cronograma de migração de dezoito meses de duração. Os achados permitem concluir que as principais resistências existentes ao processo estão relacionadas com a resistência por falta de competência e por apego às instituições existentes. É preciso considerar que os elementos da resistência estão todos eles entrelaçados e todos devem ser analisados em planos de ação que visem à institucionalização completa no novo modelo do CSC. Os resultados desta pesquisa levantam insumos para considerar que a identificação das principais resistências em um processo de institucionalização, dentro do construto descrito por Burns e Scapens (2000), é bastante útil para direcionar ações e estratégias que visem à completa institucionalização do modelo. Nestes estudo, a análise dos elementos da resistência lança luz sobre as possíveis causas da resistência dos gestores operacionais pela falta de conhecimento principalmente com os temas essenciais relacionados à análise das informações contábeis e financeiras. Adicionalmente, levantam-se argumentos sobre as possíveis causas da resistência destes mesmos gestores por apego às instituições, especificamente nas marcas superiores, onde se demandam informações específicas e diferenciadas em função da complexidade maior destas unidades. Ambas as conclusões servem como um importante direcionador, tanto para a organização foco de estudo como para outras organizações que passem por processos de mudança similares ou que estejam procurando implementar um centro de serviços compartilhados, solução recente e em franca expansão no Brasil. / The following research brings a study on a large-scale organizational change in an international hotel chain. The change has as its focus the implementation of a Shared Service Center (SSC) that accomplishes the administrative, accounting and financial processes in a centralized way in more than forty hotel unities of the group. In order to implement changes of such magnitude, it is necessary to deal with internal resistances within the organization that appear during the process. In this sense, this research aims to study which are the main resistances involved in a change process, based on the resistance elements indicated by Burns and Scapens (2000). Influenced by the Old Institutional Economics (OIE), the present research has been developed to bring an intra-organizational focus to the change processes, and it intends to solve some criticism brought toward the first researches developed by the New Institutional Sociology (NIS). Those researches would describe the change processes as being linear and unavoidable, and, through such processes, the actors supposedly became voluntarily isomorphic to the institutions. Based on those ideas, this paper intends to analyze the following elements of resistance: (i) formal and overt due to competing interests; (ii) by lack of capability (knowledge and experience); and (iii) by attachment to the institutions set in the environment, identifying which are the most important resistances and how they would relate to the process of institutionalization considered by Burns and Scapens (2000) in the encoding, enacting, reproduction and institutionalization process. Thus, through descriptive research, using qualitative and quantitative techniques, interviews, surveys and through multivariate analysis such as Conglomerate Analysis, Correspondence Analysis (ANACOR), Homogeneity Analysis (HOMALS) and Categorical Principal Component Analysis (CAPTCA), the research aims to analyze and observe how operational managers (general managers and assistant managers of the hotel unities) and corporative managers (board members) assimilate and realize the change promoted by the implementation of a SSC. On its turn, the SSC, being a recent model on the organizations, was implemented in 42 hotel unities of the group, distributed in five brands with distinct characteristics, through a migration chronogram lasting 18 months. The findings led to the conclusion that the main resistances to the process are related to the resistance by lack of capability and by attachment to the existing institutions. It is necessary to consider that the elements of the resistance are interconnected, and they should be analyzed in action plans aiming the complete institutionalization within the new model of the SSC. The results of this research bring inputs to consider that the identification of the main resistances in an institutionalization process, as described by Burns and Scarpens (2000). Those inputs are very useful to lead actions and strategies, in order to guide the complete institutionalization of the model. In this specific case observed, the analysis of the elements of resistance illuminates the possible reasons for which there is, by the operational managers, resistance by lack of knowledge, resistance which is mainly connected to the essential subjects related to the analysis of accounting and financial information. Additionally, the research raises arguments on the possible causes of the resistance of such operational managers, caused by attachment to the institutions, specifically on the superior brands, in which there is a demand for specific and different information because of the complexity of those unities when compared to the economical brands. The conclusions work as an important guide, both to the organization focused in this study and to the ones that possibly may go through similar change processes or that may be trying to implement a center of shared services, a recent solution that is in expansion in Brazil.

Sulfide Stress Cracking (SSC) resistance of the newly developed API-X100 High Strength Low Alloy (HSLA) steel was investigated in the NACE TM0177 "A" solution. The NACE TM0177 "A" solution is a hydrogen sulfide (H2S) saturated solution containing 5.0 wt.% sodium chloride (NaC1) and 0.5 wt.% acetic acid (CH3COOH). The aim of this thesis was to study the effect of microstructure, non-metallic inclusions and alloying elements of the X100 on H2S corrosion and SSC susceptibility. The study was conducted by means of electrochemical polarization techniques and constant load (proof ring) testing. Microstructural analysis and electrochemical polarization results for X100were compared with those for X80, an older generation HSLA steel. Uniaxial constant load SSC testing was conducted using X100 samples and the results were compared with those reported for older generation HSLA steels. Addition of H2S to the NACE TM0177 "A" solution increased the corrosion rate of X100from 51.6 to 96.7 mpy. The effect of H2S on the corrosion rate was similar for X80. The corrosion rate for X80 increased from 45.2 to 80.2 mpy when H2S was added to the test solution. Addition of H2S enhanced the anodic kinetics by forming a catalyst (FeHSads) on the metal surface and as a result, shifted the anodic polarization curve to more current densities. Moreover, the cathodic half cell potential increased due to the decrease in pH, from 2.9 to 2.7, which shifted the cathodic polarization curve to more current densities. The increase in both the anodic and cathodic currents, after H2S addition, caused the rise in the corrosion current density. In H2S saturated NACE TM-0177 "A" solution, the X100 steel corrosion rate was higher than the X80 steel by 20%. Longer phase boundaries and larger nonmetallic inclusions in the X100 microstructure generated more areas with dissimilar corrosion potentials and therefore, a stronger driving force for corrosion. Higher density of second phase regions and larger nonmetallic inclusions acted as an increased cathode area on the X100 surface which increased the cathodic current density and consequently, increased the corrosion current density. Proof ring tests on the X100 gave a threshold stress value, C5th, of 46% YS, 343.1 MPa(49.7 ksi). The main failure was caused by SSC cracking. SSC nucleated at corrosion pits on the metal surface and microcracks in the metal body and propagated perpendicular to the applied stress. Hydrogen Induced Cracking (HIC) was observed in the X100. HIC cracks nucleated at banded martensite-ferrite interfaces and propagated along the rolling direction parallel to the applied tensile stress through the softer ferrite phase. When compared to older HSLA grades, the X100 tested in this study had a high SSC susceptibility and therefore, is not be recommended for H2S service applications. The high X100 SSC susceptibility was caused by the material high corrosion rates in H2Smedia which formed corrosion pits that acted as crack initiation sites on the metal surface and provided more hydrogen that migrated into the steel. In addition, the X100 inhomogeneous microstructure provided a high density of hydrogen traps in front of the main crack tip which promoted SSC microcrack formation inside the metal. Microcracks in the metal body connected with the main crack tip that originated from corrosion pits which assisted SSC propagation. / Applied Science, Faculty of / Materials Engineering, Department of / Graduate

In our Laboratory of Developmental Biology there was established a long term culture derived from Xenopus tropicalis testes. It contains pre-Sertoli cells mostly. They compose a feeder layer allowing cultivation of stem cells, revealing the morphology of spermatogonial stem cells. This diploma thesis was focused on a preparation of two growth factors, FGF2 (fibroblast growth factor 2) and GDNF (glial cell line-derived neurotrophic factor), with the subsequent characterization of their influence at cell culture mentioned above. Factors were selected on the basis of the microenvironmental niche theory, according which FGF2 and GDNF are the most important factors for spermatogonial stem cells proliferation and self-renewal. FGF2 recombinant factor was gained using the expression plasmid pET-15b. Its characterization in the testicular culture brought surprising result. Even a low concentration of FGF2 factor (2.5ng/ml) caused cell detaching and dying. Similar result was previously shown in differentiating osteoblast culture only. More experiments need to be done to prove if apoptose take place and why do testicular cells act this way. Key words: Xenopus tropicalis, FGF2, GDNF, SSC, pre-Seroli cells

京都大学 / 0048 / 新制・課程博士 / 博士(工学) / 甲第20678号 / 工博第4375号 / 新制||工||1680(附属図書館) / 京都大学大学院工学研究科社会基盤工学専攻 / (主査)教授 中川 一, 教授 平石 哲也, 准教授 川池 健司 / 学位規則第4条第1項該当 / Doctor of Philosophy (Engineering) / Kyoto University / DFAM

New analytical and numerical solutions are developed to both the kinematic approximation to the St Venant equations and the Hairsine-Rose (HR) soil erosion model in order to gain a better physical understanding of soil erosion and sediment transport in shallow overland flow. The HR model is unique amongst physically based erosion models in that it is the only one that: considers the entire distribution of the soil s sediment size classes, considers the development of a layer of deposited non-cohesive sediment having different characteristics to the original underlying cohesive soil and considers separately the erosion processes of rainfall detachment, runoff entrainment and gravitational deposition. The method of characteristics and the method of lines were used to develop both the analytical and numerical solutions respectively. These solutions were obtained for boundary and initial conditions typical of those used in laboratory flume experiments along with physically realistic constant and time dependent excess rainfall rates. Depending on the boundary and initial conditions, interesting new solutions of the kinematic wave equation containing expansion waves, travelling shocks as well as solutions which split into an upslope and downslope drying profiles were found. Numerical solutions of the HR model were applied to the experimental flume data of Polyakov and Nearing (2003) obtained under flow conditions which periodically cycled between net erosion and net deposition conditions. While excellent agreement was found with suspended sediment data, the analysis suggested that an additional transport mechanisms, traditionally not included in soil erosion models, was occurring. While the inclusion of bed-load transport improved the ii overall model prediction, it was still not sufficient. Subsequent asymptotic analysis then showed that the interaction of the flow with an evolving bed morphology was in fact far more important than bed load transport. A very interesting finding from this work showed that the traditional criterion of validating sediment transport model based solely on suspended sediment data was not sufficient as reliable predictions could be obtained even when important transport mechanisms were neglected. Experimental plots of sediment discharge or suspended sediment concentration against water discharge in overland flow have been shown to contain significant hysteresis between the falling and rising limbs of the discharge hydrograph. In the final Chapter, the numerical solution developed for the complete system of soil erosion and kinematic flow was used to show that it was possible for the HR model to simulate three of the four hysteresis loops identified in the literature. Counter clock-wise loops, clock-wise loops and figure 8 loops could all be produced as a result of starting with different initial conditions, being mi(x; 0) = 0, mi(x; 0) = pimt and mi(x; 0) = 0:5pimt respectively. This is the first time that these types of hysteresis loops have been produced by any erosion model. The generation of these hysteresis loops are physically explainable in terms of sediment availability and is consistent with data obtained on the field scale.

Spermatogonial stem cells (SSC) self-renew and differentiate into spermatozoa throughout the life of the male. SSC transplantation is a potential method for the propagation of genetically important males. These cells have been isolated in different mammalian species using specific cell surface markers, but not in felines. The goal of this study was to explore a relevant strategy for conservation of endangered felids by characterizing domestic cat (Felis catus) SSCs and assessing their ability for self-renewal after transplantation. Firstly, SSC and pluripotent surface markers, identified in non-feline species, were tested for expression in mixed germ cells from adults by immunocytochemistry and flow cytometry, with immunohistochemical confirmation of expression in prepubertal and adult testis tissue. Secondly, subpopulations were purified through fluorescence-activated cell sorting using spermatogonia-specific markers and molecularly characterized to ascertain levels of pluripotent transcription factors expressed in cat embryos. Thirdly, subpopulations of mixed germ cells and purified spermatogonial cells were transplanted to prepubertal cats to determine: 1) if SSCs capable of colonization were present, and 2) the value of using adolescent domestic cats without depletion of endogenous germ cells as recipients. Fourthly, various culture conditions were evaluated to identify proteins and factors required to maintain proliferation of cat SSCs. Lastly, adult lion testis tissue was characterized with the same surface markers, and mixed germ cells were transplanted to cat testes to evaluate the cat as a suitable host for lion SSC colonization and differentiation. Pluripotent surface markers were more reliable than the common SSC surface markers for isolating cat SSCs. Varying expression levels of pluripotent transcription factors between the different purified cell populations identified spermatogonial subpopulations. Cell purification was not necessary to colonize recipient testes, and transplantation validated the use of prepubertal males as recipients without depletion of endogenous cells. Unlike spermatogonia within mixed germ cells, purified spermatogonia were not maintained under various culture conditions; therefore, SSC culture conditions must be optimized. Similarities in the expression patterns of surface markers in lion and cat spermatogonia were revealed, and colonization of lion SSCs in cat testes provided further evidence of the domestic cat’s relevance as a model for exotic felid SSC transplantation.

O objetivo deste trabalho foi a preparação de um revestimento inteligente com resina epóxi, capaz de autorreparar-se quando o sofre um defeito mecânico. A autorreparação é possibilitada pela presença de microcápsulas, dispersas na resina (revestimento de epóxi sem pigmentos) e que contêm no seu núcleo o agente de autorreparação, o óleo de linhaça. Estas cápsulas foram preparadas por uma emulsão de óleo de linhaça em água para formar micelas e sobre estas uma parede ou casca exterior de poliuréia-formaldeído. Para a avaliação da resistência à corrosão e do efeito de autorreparação do revestimento, chapas de aço carbono foram revestidas e avaliadas pela técnica de espectroscopia de impedância eletroquímica (EIE) em 0.1molL-1 1 NaCl e também foram avaliadas pelo teste acelerado de corrosão em câmara de névoa salina (SSC). Após a cura do revestimento aditivado com as microcápsulas, aplicado sobre placas de aço carbono, as medidas eletroquímicas de impedância foram realizadas em corpos de prova com um defeito mecânico provocado de forma controlada e reprodutível. Uma célula de três eletrodos foi utilizada. Estas medidas foram efetuadas após 0h, 24h e 48h da execução da incisão ou defeito mecânico. Para comparação, as mesmas medidas foram realizadas com as placas pintadas com o revestimento não-aditivado, com a mesma espessura total de 120 m. Os resultados mostraram que as cápsulas foram quebradas e se liberou o óleo de linhaça, reparando a área da incisão o defeito após pelo menos 24 horas de exposição natural ao ar ambiente. Verificou-se que para as placas revestidas sem defeito, os valores de | Z | mantiveram-se elevados. No entanto, o revestimento sem as microcápsulas, após 24 horas, mostrou uma diminuição considerável no valor de módulo de impedância, |Z|. Assim, usando a técnica de EIE foi possível avaliar quantitativamente o mecanismo de autorreparação do revestimento aditivado com microcápsulas que contêm óleo de linhaça. Os ensaios acelerados de corrosão (SSC) mostraram resultados em estreita concordância com os obtidos por EIE. / The aim of this work was the preparation of a smart coating with epoxy resin which is able to repair itself (self-healing effect) after suffering a mechanical defect. Self-healing is possible due to the presence of microcapsules, dispersed in the resin (clear type epoxy coating) and contain in their core the self-healing agent, the linseed oil. These capsules were prepared in an emulsion of linseed oil in water to form micelles and an outer skin or wall of poly(urea-formaldehyde) was formed. For the corrosion resistance and the self-healing effect evaluation of the coating, carbon steel plates were coated and tested by electrochemical impedance spectroscopy technique (EIS) in 0.1molL-1 NaCl solution and by accelerated corrosion test in salt spray chamber (SSC). After curing of the capsules additivated epoxy based clear coating applied on carbon steel plates, electrochemical impedance measurements were performed on plates with a controlled and reproducible mechanical defect. A three-electrode electrochemical cell was used. These measurements were performed after 0h, 24h and 48h of making the incision or mechanical defect. For comparison, the same measurements were performed with the plates painted with a non- capsules additivated clear coating of the same total thickness of 120 m. The results showed that the capsules were broken and released the linseed oil, which indeed have repaired the incision area after at least 24 hours of natural air aging. It was found that for the plates coated without a defect, the values of impedance modulus, |Z|, remained high. However, the coating without the capsules after 24 hours, showed a considerable decrease in |Z|. So, using EIS it was possible to quantitatively assess the mechanism of self-healing of the additivated coating using microcapsules containing linseed oil. The SSC accelerated corrosion tests showed results in close agreement with those obtained by EIS.