Дисертації: "Silicon alternatives"

1

Rostkowska, Cristina. "Efeito da infusão de Artemisia annua cultivada em solo com aplicação de silicato de cálcio e magnésio sobre o controle de Toxoplasma gondii in vitro." Universidade Federal de Uberlândia, 2012. https://repositorio.ufu.br/handle/123456789/16579.

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Fundação de Amparo a Pesquisa do Estado de Minas Gerais
Toxoplasmosis is an important zoonotic disease due to ability of its causal agent, Toxoplasma gondii, to infect large number of vertebrates and to be associated with congenital infection or opportunistic disease in immunosuppressed patients. As the traditional treatment has shown adverse effects, low-toxicity compounds including artemisinin and its derivatives have been researched, as well Artemisina annua tea infusion. The use of silicon in the soil of A. annua crops and its role on artemisinin content has not been studied yet. This study aimed to investigate the effects of silicon on A. annua plant physiology and the role of the tea infusion obtained from these plants in the control of T. gondii infection in cell culture. The experimental design was a completely randomized design (CRD), in which A. annua was planted in the soil with five different doses of calcium/magnesium silicate (0, 200, 400, 800 and 1600 kg ha-1) and five replications, and maintained in a greenhouse. Analysis of foliar macronutrients showed a significant increase only for nitrogen, in the presence of the highest dose of silicate in the soil. The foliar micronutrient and Si concentrations as well the plant height were not significantly changed with any silicate doses in the soil. The use of 400 kg ha-1 of silicate induced the highest total glandular trichome area that was also associated with the intact glandular trichomes, as observed by scanning electron microscopy, and with the highest artemisinin content in plant leaves and tea infusion, as determined by thin layer chromatography (TLC) and high performance liquid chromatography (HPLC), respectively. HeLa cell treatments along with or after T. gondii infection, with infusion of A. annua grown in the soil without or with silicate (400 kg ha-1), induced a decrease of parasite proliferation in a dose-dependent manner, as also seen for cell treatment with pure artemisinin. In conclusion, the use of silicon had positive effect on the glandular trichome areas and artemisinin contents, but this outcome was not associated with a better efficacy of A. annua tea infusion on T. gondii replication. These findings suggest that other components rather than artemisinin could be contributing to this effect, such as flavonoids present in its leaves, which may act in synergism with the artemisinin and improve its efficacy.
A toxoplasmose é uma zoonose importante devido à capacidade de seu agente causal, Toxoplasma gondii, de infectar um grande número de vertebrados e ser associada com infecção congênita ou doença oportunista em pacientes imunocomprometidos. O tratamento tradicional mostra efeitos adversos levando à pesquisa de compostos de baixa toxicidade como a artemisinina, seus derivados e a infusão da planta Artemisia annua. A utilização de silício no solo de culturas de A. annua e seu papel no conteúdo de artemisinina ainda não foram estudados. O objetivo deste estudo foi investigar os efeitos do silício sobre a fisiologia da planta A. annua e o papel da infusão destas plantas sobre o controle da infecção de T. gondii em cultura celular. Foi utilizado o delineamento inteiramente ao acaso (DIC), no qual A. annua foi plantada em solo com aplicação de cinco diferentes dosagens de silicato de cálcio/magnésio (0, 200, 400, 800 e 1600 kg ha-1), em cinco repetições e mantida em casa de vegetação. A análise de macronutrientes foliares mostrou um aumento significativo apenas para o nitrogênio, na presença da maior dosagem de silicato no solo. As quantidades de micronutrientes e silício foliares bem como a altura da planta não foram significativamente alteradas em quaisquer dosagens de silicato no solo. A aplicação de 400 kg ha-1 de silicato induziu a maior área de tricomas glandulares totais que foi associada com os tricomas glandulares intactos, como observado por microscopia eletrônica de varredura, e com o mais alto conteúdo de artemisinina nas folhas e na infusão da planta, como determinado por cromatografia em camada fina (TLC) e cromatografia líquida de alta eficiência (HPLC), respectivamente. Os tratamentos de células HeLa, simultaneamente ou após a infecção por T. gondii, com infusão de A. annua cultivada sem ou com silicato (400 kg ha-1) aplicado ao solo, induziram decréscimo dependente da dose na proliferação parasitária, como também verificado para o tratamento das células com artemisinina pura. Em conclusão, o uso de silício teve efeito positivo sobre as áreas de tricomas glandulares e seu conteúdo de artemisinina, mas este resultado não foi associado com melhor eficácia da infusão de A. annua sobre a replicação intracelular de T. gondii. Estes resultados sugerem que outros componentes além da artemisinina poderiam contribuir para este efeito, como os flavonóides presentes nas folhas de A. annua que podem atuar em sinergismo com a artemisinina e melhorar a sua eficácia.
Doutor em Imunologia e Parasitologia Aplicadas

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2

Åkerblom, Denize, and Erik Göranzon. "Greener Water Repellency? Feasible alternatives to fluoro chemicals for DWOR treatments on textiles." Thesis, Högskolan i Borås, Institutionen Textilhögskolan, 2014. http://urn.kb.se/resolve?urn=urn:nbn:se:hb:diva-17695.

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BACKGROUND: Perfluorinated compounds (PFCs) have been used as durable water and oil repellent treatments in clothing for more than 50 years. The reason for its popularity is related to the chemical structure, which also makes these compounds persistent in the environment. Numerous studies have shown negative environmental and health effects related to high concentrations of perfluorinated compounds in blood serum. Due to these studies, this paper aimed to find out if perfluorinated compounds could be replaced by non-perfluorinated without compromising performance related to water and oil repellency. METHODOLOGY: A reference sample impregnated with fluorocarbons was compared with the following non-perfluorinated treatments, aliphatic polyurethane (comb polymer) organic silicone and acid (comb polymer) and hydrocarbon (dendrimer). Impregnations were subjected to abrasion, UV-radiation and washing and after each destructive treatment; oil and water repellency tests were conducted. The environmental and health effect of all treatments were examined in a theoretical study. RESULTS: Due to difficulties with the impregnation process, comparable results could only be concluded with the perfluorinated and the hydrocarbon compound. The hydrocarbon was superior the perfluorinated compound to abrasion but for usage simulation methods that allowed chemical reactions, hence UV-radiation and washing, the fluorocarbons showed better resistance. CONCLUSION: Results show that the hydrocarbon treatment could replace perfluorinated treatments commercially when only water and not oil repellency is required. The alternative treatments in this study are not yet sufficiently examined with respect to environmental and health and can therefore not be called greener with certainty.
Program: Textilingenjörsutbildningen

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3

Daubriac, Richard. "Caractérisation de techniques d'implantations ioniques alternatives pour l'optimisation du module source-drain de la technologie FDSOI 28nm." Thesis, Toulouse, INSA, 2018. http://www.theses.fr/2018ISAT0031/document.

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Durant ces dernières années, l’apparition de nouvelles architectures (FDSOI, FinFETs ou NW-FETs) et l’utilisation de nouveaux matériaux (notamment SiGe) ont permis de repousser les limites des performances des dispositifs MOS et de contourner l’effet canal court inhérent à la miniaturisation des composants. Cependant, pour toutes ces nouvelles architectures, la résistance de contact se dégrade au fil des nœuds technologiques. Celle-ci dépend fortement de deux paramètres physiques : la concentration de dopants actifs proches de la surface du semi-conducteur et de la hauteur de barrière Schottky du contact siliciuré. De multiples procédés avancés ont été proposé pour améliorer ces deux paramètres physiques (pré-amorphisation, recuit laser, ségrégation de dopants, etc…). Afin d’optimiser les conditions expérimentales de ces nouvelles techniques de fabrication, il est primordial de pouvoir caractériser avec fiabilité leur impact sur les deux grandeurs physiques citées. Dans le cadre de cette thèse, deux thématiques dédiées à l’étude de chacun des paramètres sont abordées, explicitant les méthodes de caractérisation développées ainsi que des exemples concrets d’applications. La première partie concerne l’étude de la concentration de dopants actifs proches de la surface du semi-conducteur. Dans cet axe, nous avons mis en place une méthode d’Effet Hall Différentiel (DHE). Cette technique combine gravures successives et mesures par effet Hall conventionnel afin d’obtenir le profil de concentration de dopants actifs en fonction de la profondeur. Nous avons développé et validé une méthode de gravure chimique et de mesure électrique pour des couches ultra-minces de SiGe et de Si dopées. Les profils de concentration générés ont une résolution en profondeur inférieure à 1 nm et ont permis d’étudier de façon approfondie dans les premiers nanomètres proches de la surface de couches fabriquées grâce à des techniques d’implantation et de recuit avancées comme par exemple, la croissance en phase solide activée par recuit laser. La deuxième partie porte sur la mesure de hauteurs de barrière Schottky pour des contacts siliciurés. Durant cette étude, nous avons transféré une technique se basant sur des diodes en tête bêche pour caractériser l’impact de la ségrégation de différentes espèces à l’interface siliciure/semi-conducteur sur la hauteur de barrière Schottky d’un contact en siliciure de platine. Cette méthode de mesure associée à des simulations physiques a permis d’une part, d’extrairer avec fiabilité des hauteurs de barrières avec une précision de 10meV et d’autre part, d’effectuer une sélection des meilleures conditions de ségrégation de dopants pour la réduction de la hauteur de barrière Schottky. Pour conclure, ce projet a rendu possible le développement de méthodes de caractérisation pour l’étude de matériaux utilisés en nanoélectronique. De plus, nous avons pu apporter des éclaircissements concernant l’impact de techniques d’implantation ionique alternatives sur des couches de Si et SiGe ultrafines, et ce, dans le but de réduire la résistance de contact entre siliciure et semi-conducteur dans le module source-drain de transistors ultimes
During the past few decades, the emergence of new architectures (FDSOI, FinFETs or NW-FETs) and the use of new materials (like silicon/germanium alloys) allowed to go further in MOS devices scaling by solving short channel effect issues. However, new architectures suffer from contact resistance degradation with size reduction. This resistance strongly depends on two parameters: the active dopant concentration close to the semi-conductor surface and the Schottky barrier height of the silicide contact. Many solutions have been proposed to improve both of these physical parameters: pre-amorphisation, laser annealing, dopant segregation and others. In order to optimize the experimental conditions of these fabrication techniques, it is mandatory to measure precisely and reliably their impact on cited parameters.Within the scope of this thesis, two parts are dedicated to each lever of the contact resistance, each time precising the developed characterization method and concrete application studies. The first part concerns the study of the active dopant concentration close to the semi-conductor surface. In this axis, we developed a Differential Hall Effet method (DHE) which can provide accurate depth profiles of active dopant concentration combining successive etching processes and conventional Hall Effect measurements. To do so, we validated layer chemical etching and precise electrical characterization method for doped Si and SiGe. Obtained generated profiles have a sub-1nm resolution and allowed to scan the first few nanometers of layers fabricated by advanced ion implantation and annealing techniques, like solid-phase epitaxy regrowth activated by laser annealing. In the second part, we focused on the measurement of Schottky barrier height of platinum silicide contact. We transferred a characterization method based on back-to-back diodes structure to measure platinum silicide contacts with different dopant segregation conditions. The electrical measurements were then fitted with physical models to extract Schottky barrier height with a precision of about 10meV. This combination between measurements and simulations allowed to point out the best ion implantation and annealing conditions for Schottky barrier height reduction.To conclude, thanks to this project, we developed highly sensitive characterization methods for nanoelectronics application. Moreover, we brought several clarifications on the impact of alternative ion implantation and annealing processes on Si and SiGe ultra-thin layers in the perspective of contact resistance reduction in FDSOI source-drain module

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Karecki, Simon Martin. "Alternative chemistries for etching of silicon dioxide and silicon nitride." Thesis, Massachusetts Institute of Technology, 1996. http://hdl.handle.net/1721.1/43304.

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Thesis (M.S.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 1997.
Includes bibliographical references (p. 123-126).
by Simon Martin Karecki.
M.S.

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Madhavan, Atul. "Alternative designs for nanocrystalline silicon solar cells." [Ames, Iowa : Iowa State University], 2009. http://gateway.proquest.com/openurl?url_ver=Z39.88-2004&rft_val_fmt=info:ofi/fmt:kev:mtx:dissertation&res_dat=xri:pqdiss&rft_dat=xri:pqdiss:3403005.

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6

Orellana, Pérez Teresa. "Mechanical behavior of alternative multicrystalline silicon for solar cells." Doctoral thesis, Technische Universitaet Bergakademie Freiberg Universitaetsbibliothek "Georgius Agricola", 2013. http://nbn-resolving.de/urn:nbn:de:bsz:105-qucosa-117455.

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The usage of more inexpensive silicon feedstock for the crystallization of multicrystalline silicon blocks promises cost reduction for the photovoltaic industry. Less expensive substrates made out of metallurgical silicon (MG-Si) are used as a mechanical support for the epitaxial solar cell. Moreover, conventional inert solar cells can be produced from up-graded metallurgical silicon (UMG-Si). This feedstock has higher content of impurities which influences cell performance and mechanical strength of the wafers. Thus, it is of importance to know these effects in order to know which impurities should be preferentially removed or prevented during the crystallization process. Solar cell processing steps can also exert a change in the values of mechanical strength of processed multicrystalline silicon wafers until the fabrication of a solar cell. Bending tests, fracture toughness and dynamic elastic modulus measurements are performed in this work in order to research the mechanical behavior of multicrystalline silicon crystallized with different qualities of silicon feedstock. Bending tests and residual stress measurements allows the quantification of the mechanical strength of the wafers after every solar cell processing step. The experimental results are compared with theoretical models found in the classical literature about the mechanical properties of ceramics. The influence of second phase particles and thermal processes on the mechanical strength of silicon wafers can be predicted and analyzed with the theoretical models. Metals like Al and Cu can decrease the mechanical strength due to micro-cracking of the silicon matrix and introduction of high values of thermal residual stress. Additionally, amorphous silicon oxide particles (SiOx) lower the mechanical strength of multicrystalline silicon due to thermal residual stresses and elastic mismatch with silicon. Silicon nitride particles (Si3N4) reduce fracture toughness and cause failure by radial cracking in its surroundings due to its thermal mismatch with silicon. Finally, silicon carbide (SiC) and crystalline silicon oxide (SiOx) introduce thermal residual stresses but can have a toughening effect on the silicon matrix and hence, increase the mechanical strength of silicon wafers if the particles are smaller than a certain size. The surface of as-cut wafers after multi-wire sawing presents sharp micro-cracks that control their mechanical behavior. Subsequent removal of these micro-cracks by texture or damage etching approximately doubles the mechanical strength of silicon wafers. The mechanical behavior of the wafers is then governed by defects like cracks and particles formed during the crystallization of multicrystalline silicon blocks. Further thermal processing steps have a minor impact on the mechanical strength of the wafers compared to as-cut wafers. Finally, the mechanical strength of final solar cells is comparable to the mechanical strength of as-cut wafers due to the high residual thermal stress introduced after the formation of the metallic contacts which makes silicon prone to crack.

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Nortey, Philip Tetteybuah. "Alternative methods for the formation of chemically bonded phases for liquid chromatography." Thesis, Birkbeck (University of London), 2000. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.340537.

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Silva, Raphael Tavares da. "Desenvolvimento de uma abordagem computacional para a tradução in silico de variantes de splicing detectadas no transcriptoma humano." reponame:Repositório Institucional da FIOCRUZ, 2012. https://www.arca.fiocruz.br/handle/icict/6406.

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Fundação Oswaldo Cruz. Instituto Oswaldo Cruz. Rio de Janeiro, RJ, Brasil.
Um dos mecanismos capaz de aumentar a diversidade do proteoma de eucariotos é o splicing alternativo nos pré-mRNAs. Este mecanismo celular ocorre durante a transcrição dos genes, sendo ocasionado por um ou mais dos seguintes eventos: retenção de íntrons, uso alternativo de sítio de splice 5', uso alternativo de sítio de splice 3' e uso alternativo de éxons. Análises recentes de Bioinformática utilizando experimentos de RNA-Seq mostram que aproximadamente 90% dos genes humanos produzem mais de um transcrito decorrente de eventos de splicing alternativo. O impacto do splicing alternativo no proteoma humano vem sendo alvo de algumas abordagens de Bioinformática, sendo esperado que uma grande porção de tais transcritos alternativos possa alterar o conteúdo da cadeia polipeptídica obtida após a sua tradução. Devido à sua importância, diversos trabalhos já foram desenvolvidos com o objetivo de facilitar a identificação de eventos de splicing alternativo a partir de dados provenientes de cDNA, bem como sua associação com a estrutura das proteínas de suas isoformas. Entretanto, são poucas as abordagens que realizaram a tradução in silico do transcriptoma humano na busca por variantes de splicing e a utilização de dados oriundos de sequenciadores de segunda geração (NGS) ainda é muito pouco explorada para tratar do tema. Desta maneira, o presente projeto tem como objetivo a aplicação de uma nova abordagem para a identificação e tradução de variantes de splicing alternativo usando dados de NGS. Foram utilizadas leituras da plataforma de sequenciamento Roche/454 oriundas de estudos de câncer para um enriquecimento de nosso banco de dados original que continha previamente mRNAs completos e ESTs. Após o enriquecimento, a metodologia empregada pelo nosso grupo conseguiu detectar 4.574 variantes de splicing inéditas em nosso banco. O novo banco gerado foi traduzido levando a criação de um repertório proteico contendo 159.638 sequências polipeptídicas não redundantes. Na busca por variantes inéditas utilizando dados de proteômica, foram identificadas três possíveis nos genes humanos tubulina 2b, tubulina 4b e actina. Dados de sequenciamento da plataforma Illumina também foram utilizados para uma avaliação da sua contribuição em número de variantes e sequências polipeptídicas traduzidas em nosso repertório. Encontramos que a nossa abordagem foi capaz de anotar 53% mais sequências polipeptídicas quando comparada ao repertório de ENSEMBL Gene. Desta forma, acreditamos que o presente projeto pode auxiliar no melhoramento da anotação de peptídeos encontrados por técnicas de proteômica, bem como no descobrimento de novos marcadores moleculares.
Alternative splicing of pre-mRNAs is one of the mechanisms capable to increase the proteome diversity in eukaryotes. This cellular mechanism occurs during the transcription of genes and is associated with one or more of the following events: intron retention, 5’ alternative splice, 3’ alternative splice and exon skipping. Recent Bioinformatics analysis using RNA-Seq experiments showed that approximately 90% of human genes produce more than one transcript due to alternative splicing events. The impact of alternative splicing in the human proteome has been the focus of some Bioinformatics approaches and is expected that the majority part of these alternative transcripts can alter the polypeptide chain produced after its translation. Due to its importance, many studies have been developed focused on facilitating the identification of alternative splicing events based on cDNA data, as well as to study the protein structure of its isoforms. However, few studies performed the in silico translation of the human transcriptome to search for new splicing isoforms using Next Generation Sequencing (NGS) data. In this way, our project aims to the development of a new approach to identify and translate alternative splicing isoforms using NGS data. Roche/454 reads of cancer studies were used to enrich our initial database, which was previously populated with full-length mRNAs and ESTs data. After the enrichment step, the methodology developed by our group could detect 4,574 new splicing variants in our database. The enriched database was translated, producing a protein repository with 159,638 non-redundant polypeptide sequences. Searching for new isoforms using experimental proteomic data, three possible new isoforms were identified for the human genes tubulin 2b, tubulin 4b and actin. Illumina sequencing data was used to assess its contribution for the number of new isoforms and the translated polypeptide sequences on our database. We realized that our approach was capable to annotate 53% more polypeptide sequences when compared with the ENSEMBL Gene repository. In this way, we believe that our project can support the improvement of peptide annotation found by proteomic techniques, as well as to discover new molecular markers.

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Moreira, Ricco Isabel Maria. "Alternative oxidants and processing procedures for pyrotechnic time delays." Pretoria : [s.n.], 2004. http://upetd.up.ac.za/thesis/available/etd-09132005-115831.

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Li, Sonia Mary Seiwei. "Alternative approaches to silicon germanium modulation doped field effect transistor processing." Thesis, Imperial College London, 2004. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.408012.

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Kwapil, Wolfram [Verfasser]. "Alternative materials for crystalline silicon solar cells : risks and implications / Wolfram Kwapil." Konstanz : Bibliothek der Universität Konstanz, 2010. http://d-nb.info/1017235988/34.

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Stodilka, Danielle O. "Silicon carbide MIS and MOS development using alternative nitride and oxide dielectrics." [Gainesville, Fla.] : University of Florida, 2005. http://purl.fcla.edu/fcla/etd/UFE0013116.

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Pysch, Damian [Verfasser]. "Assembly and Analysis of Alternative Emitter Systems for Silicon Solar Cells / Damian Pysch." München : Verlag Dr. Hut, 2011. http://d-nb.info/1015608159/34.

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Zhu, Xingguang Williams John R. "Alternative growth and interface passivation techniques for SiO2 on 4H-SiC." Auburn, Ala, 2008. http://hdl.handle.net/10415/1494.

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Kalkandjiev, Kiril [Verfasser], and Roland [Akademischer Betreuer] Zengerle. "Microfluidics based on silicon, polymer and all-polymer technologies as an alternative to silicon, glass: a case study for TopSpot printheads." Freiburg : Universität, 2015. http://d-nb.info/1119805597/34.

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Chan, Julia Kam Chu 1972. "Alternative passivation for silicon (100), environmentally benign manufacturing, and cooperative strategy in semiconductor industry." Thesis, Massachusetts Institute of Technology, 2000. http://hdl.handle.net/1721.1/8850.

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Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Materials Science and Engineering; and, (S.M.)--Massachusetts Institute of Technology, Technology and Policy Program, 2000.
Includes bibliographical references (p. 118-120).
My personal involvement, as a research graduate student, sponsored by Engineering Research Center, a center created by National Science Foundation and Semiconductor Research Corporation demonstrates that, through industrial research staffs' mentoring, university research can bring innovative environmentally benign manufacturing methods to the U.S. semiconductor industry. Our group has used methoxy to protect the bare silicon surface, because we have identified that the industrial standard, hydrogen passivation of silicon (H-Si) degrades rapidly when exposes to air. In this thesis, two new processing steps are added to make this methoxy passivation compatible to industrial practice. In addition, a preliminary gate oxide test demonstrated that this methoxy terminated silicon (MeO-Si) yielded a thinner ultra thin gate oxide than those wafers cleaned by IBM's conventional RCA and dilute hydrofluoric acid last clean without compromising its reliability. Furthermore, particle count results shown that this MeO-Si has the same particle resistance as H-Si. Further mechanistic and thermodynamic studies are performed such that this process is optimized. As a result, MeO-Si is 49 times more stable than H-Si against air degradation. Through this center, an Environmental Safety and Health incorporated Cost of Ownership is developed in this thesis. This is done by using in vitro studies to evaluate the toxicity of new chemicals used, and by using lifecycle analysis to calculate the amount of untreated chemical, which leaks to the environment. Both of these will give rise to an environmental figure of merit to modify the conventional cost of ownership. In the last section, a strategic analysis of this Engineering Research Center is performed to demonstrated that students are a very important media to (1) facilitating technology transfer to industry, (2) enhancing collaboration along the chain of semiconductor industrial participants.
by Julia Kam Chu Chan.
S.M.

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Adams, Curtis. "Studies on nitrogen and silicon deficiency in microalgal lipid production." DigitalCommons@USU, 2013. https://digitalcommons.usu.edu/etd/1955.

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Microalgae are a rich, largely untapped source of lipids. Algae are underutilized, in part, because lipid formation generally is stimulated by stress, such as nutrient deficiency. Nutrient deficiencies reduce growth, resulting in a tradeoff between elevated cellular lipids and abundant cell division. This tradeoff is not well understood. We also have a poor understanding of the physiological drivers for this lipid formation. Here we report on three sets of research: 1) Assessment of species differences in growth and lipid content tradeoffs with high and low level nitrogen deficiency; 2) Investigation of physiological drivers of lipid formation, by mass balance accounting of cellular nitrogen with progressing deficiency; 3) Examination of the effects of sodium chloride and silicon on lipid production in a marine diatom. 1) Nitrogen deficiency typically had disproportionate effects on growth and lipid content, with profound differences among species. Optimally balancing the tradeoff required a wide range in the rate of nitrogen supply to species. Some species grew first and then accumulated lipids, while other species grew and accumulated lipids concurrently--a characteristic that increased lipid productivity. High lipid content generally resulted from a response to minimal stress. 2) Commonalities among species in cellular nitrogen at the initiation of lipid accumulation provided insight into the physiological drivers for lipid accumulation in nitrogen deficient algae. Total nitrogen uptake and retention differed widely among species, but the ratio of minimum retained nitrogen to nitrogen at the initiation of lipid accumulation was consistent among species at 0.5 ± 0.04. This suggests that lipid accumulation was signaled by a common magnitude of nitrogen deficiency. Among the cellular pools of nitrogen at the initiation of lipid accumulation, the concentration of RNA and the protein to RNA ratio were most similar among species with averages of 3.2 ± 0.26 g L-1 (8.2% variation) and 16 ± 1.5 (9.2% variation), respectively. This implicates critical levels of these parameters as potential signals initiating the accumulation of lipids. 3) In a marine diatom, low levels of either sodium chloride or silicon resulted in at least 50% increases in lipid content. The synergy of simultaneous, moderate sodium chloride and silicon stress resulted in lipid content up to 73%. There was a strong sodium chloride/silicon interaction in total and ash-free dry mass densities that arose because low sodium chloride was inhibitory to growth, but the inhibition was overcome with excessive silicon supply. This suggests that low sodium chloride may have affected metabolism of silicon.

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LIMA, Meridiana Araújo Gonçalves. "Óleos essenciais e silício para controle da murcha bacteriana do tomateiro." Universidade Federal Rural de Pernambuco, 2016. http://www.tede2.ufrpe.br:8080/tede2/handle/tede2/6023.

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Coordenação de Aperfeiçoamento de Pessoal de Nível Superior - CAPES
Bacterial wilt caused by Ralstonia solanacearum (Rs) is one of the most important tomato diseases in Brazil. The effectiveness of ginger and melaleuca at 1%, rosemary at 0.50% and bergamot, lemongrass, clove, citronella, eucalyptus, sweet orange, palmrose and sage at 0.14% (v/v) essential oils was evaluated in vitro and via biofumigation of the soil infested with Rs. It was analyzed the in vitro growth; the population of Rs in soil before and seven days after biofumigation; and the components of resistance to disease and the growth of tomato plants cv. TY 2006, 15 days after transplanting. The clove oil was fractioned and its major chemical component was compared with the essencial oil in relation to the variables already cited. The in vitro growth of Rs was reduced by 100% with rosemary, lemongrass, citronella, clove, eucalyptus and palmrose oils. The population of Rs in soil was reduced by rosemary, clove, lemongrass, ginger, melaleuca and palmrose oils, with emphases for clove oil, which reduced Rs populations by 42.3%. The biofumigation with clove oil reduced the disease incidence, bacterial wilt index (BWI), and area under the disease curve progress (AUDPC) by 90.2, 97 and 98.8%, respectively and elevated the latent period by 10 days compared as the control with tween 20. The eugenol was the major constituent (87%) of the clove oil showing the same reduction effects of the components of disease resistance. The clove oil and the eugenol acetate did not reduce the height, and the fresh and dry biomass of plants. In asecond experiment, it was also evaluated the effect of silicon (Si) supplementation on the production of tomato transplants cultivars (cvs.) Santa Clara, TY 2006 and Yoshimatsu 4-11. The transplants were produced in substrate without Si (-Si) or with 3 g of calcium silicate de calcium/kg of substrate (+Si) and transplanted to Rs infected soil. After 15 days of growing it was evaluated the resistance components; the plant growth by measuring height, and the fresh and dry biomass of plants; the chlorophyll index; the Si content in plant tissues; the Rs population in stem base; and the enzymatic activity of phenylalanine amonia-lyases (PAL), β-1,3 glucanases (GLU) and peroxidases (POX). The Si supplementation on cvs. Santa Clara and TY 2006 reduced severity (33.2 and 42%), AUDPC (23.1 and 19.2%) and BWI (21.7 and 10%), respectively. The Si supplementation in the substrate did not affect plant growth, the chlorophyll index; the Si content in plant tissues and the Rs population in stem. Higher activities of PAL and GLU were evidenced on +Si plants. Therefore, the soil biofumigation with clove oil at 0.14% and the production of tomato transplants in substrate with Si have the potential to be integrated in the bacterial wilt management.
A murcha bacteriana causada por Ralstonia solanacearum (Rs) é uma das doenças economicamente mais importantes em tomateiro. Os óleos essenciais de gengibre e melaleuca a 1%, alecrim a 0,50% e bergamota, capim limão, cravo, citronela, eucalipto, laranja doce palmarosa e sálvia a 0,14% (v/v) foram testados in vitro e pela biofumigação do solo infestado com Rs. Foram avaliados o crescimento in vitro, a população de Rs no solo antes e sete dias depois da biofumigação, os componentes de resistência à doença e o crescimento das plantas em tomateiros da cv. TY 2006, aos 15 dias após o transplantio. O óleo de cravo foi fracionado e seu constituinte químico majoritário foi comparado com o óleo essencial quanto a redução da doença e demais variáveis citadas anteriormente. No ensaio in vitro, os óleos de alecrim, capim limão, citronela, cravo, eucalipto e palmarosa inibiram completamente o crescimento de Rs. A população de Rs no solo foi reduzida pelos óleos de alecrim, cravo, capim limão, gengibre, melaleuca e palmarosa, destacando-se o cravo com redução de 42,3%. A biofumigação com o óleo de cravo reduziu a incidência, o índice de murcha bacteriana (IMB) e a área abaixo da curva de progresso da doença (AACPD) em 90,2; 97 e 98,8%, respectivamente e elevou o período de latência - PL50 em 10 dias com relação a testemunha com Tween 20. Este óleo apresentou o eugenol como constituinte majoritário (87%), com os mesmos efeitos na redução dos componentes de resistência da doença. O óleo de cravo e o acetato de eugenol não reduziram a altura, biomassa fresca e seca das plantas. Em um segundo experimento, foi avaliado o efeito da suplementação do silício (Si) na produção de mudas de tomateiro das cultivares (cvs.) Santa Clara, TY 2006 e Yoshimatsu 4-11. As mudas foram produzidas em substrato sem silício (-Si) ou com 3 g de silicato de cálcio/kg de substrato (+Si) e transplantadas para solo com Rs. Aos 15 dias de cultivo, foram avaliados os componentes de resistência à doença; o crescimento das plantas, medindo-se a altura e o peso da biomassa fresca e seca, o índice reativo de clorofila; o conteúdo de Si na planta; a população de Rs no caule; e as atividades enzimáticas de fenilalanina amônia-liases (FAL), β-1,3 glucanases (GLU) e peroxidases (POX). A suplementação com Si nas cvs. Santa Clara e TY 2006 promoveu redução da doença avaliada pela severidade (33,2 e 42%), AACPD (23,1 e 19,2%) e IMB (21,7 e 10%), respectivamente. A suplementação com Si no substrato não afetou de forma significativa o crescimento das plantas, o índice reativo de clorofila, o acúmulo de Si nos tecidos das plantas e a população de Rs nos tecidos do caule. Foi evidenciada maior atividade enzimática de FAL e GLU nas plantas tratadas (+Si). Desta forma, a biofumigação do solo com o óleo de cravo a 0,14 % e a produção de mudas em substrato tratado com Si têm potencial como medidas a serem utilizadas no manejo da murcha bacteriana em tomateiro.

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19

Petkowicz, Diego Ivan. "Zeólitas sintetizadas com fontes alternativas de silício e alumínio: aplicação em fotocatálise." reponame:Biblioteca Digital de Teses e Dissertações da UFRGS, 2009. http://hdl.handle.net/10183/16779.

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No presente estudo, casca de arroz submetida à calcinação e lixívia ácida, crisotila na forma natural e após lixívia ácida, uma sílica oriunda de rejeito e papel alumínio foram utilizados com fontes de silício e alumínio na síntese da zeólita A. Para fins comparativos, sílica pirogênica comercial também foi empregada como fonte de silício. As matérias-primas, bem como os produtos obtidos, foram caracterizados por um conjunto de técnicas espectroscópicas, térmicas, eletroquímicas, volumétricas e microscópicas, a saber: Difratometria de raios-X (XRD), espectroscopia fotoeletrônica de Raios-X (XPS), espectroscopia molecular de absorção no infravermelho com Transformada de Fourier (FTIR), espectroscopia de reflectância difusa no infravermelho com Transformada de Fourier (DRIFTS), adsorção de nitrogênio, análise termogravimétrica (TGA), espectroscopia de reflectância difusa no ultravioleta-visível (DRS), microscopia de força atômica (AFM), microscopia eletrônica de varredura (SEM), microscopia eletrônica de varredura com espectroscopia de emissão de Raios-X por dispersão de energia (SEM-EDX) e voltametria cíclica diferencial (DPV). Os parâmetros de síntese avaliados foram: (i) natureza da fonte de silício e alumínio; (ii) tempo de cristalização; (iii) razões molares Si/Al no gel de síntese e (iv) influência da agitação na cristalização. Excetuando a crisotila natural, para todas as demais situações, zeólita A com alta cristalinidade e pureza foi obtida. A zeólita A sintetizada a partir da crisotila lixiviada mostrou alta estabilidade estrutural por períodos mais longos de síntese. A variação da razão molar Si/Al levou à formação da zeólita Y pura, quando usada a casca de arroz calcinada a 600ºC como fonte de Si, e uma mistura de zeólita A e Y quando usada a crisotila lixiviada. Zeólitas A, com alta cristalinidade e com grandes tamanhos de grãos foram obtidas a partir da síntese usando sílica oriunda de rejeito, crisotila lixiviada e casca de arroz calcinada a 600ºC como fonte de silício e papel alumínio como fonte de alumínio. A degradação de corantes (azul de metileno, azul direto 71 e amarelo direto 8) e fármaco (paracetamol) foi avaliada para uma série de catalisadores suportados de titânia obtidos pela impregnação do TiCl4 em zeólitas, sintetizadas usando casca de arroz e crisotila como fonte de silício, submetidas posteriormente à calcinação. A titânia gerada apresenta-se na forma anatase. Atividade catalítica elevada foi observada para as amostras com 10% de Ti, apresentando atividade catalítica comparável àquela da titânia comercial (P25) após uma hora de irradiação com luz UV. Experimentos realizados com luz solar levou à decomposição de 92 % do corante azul de metileno. A atividade fotocatalítica de um catalisador de titânia suportada foi monitorada por vários ciclos, permanecendo constante até o quinto ciclo.
In the present study, alternative silicon and aluminum sources for zeolite A synthesis were exploited, namely: rice husk submitted to calcination and to acid leaching, chrysotile in its natural form and after acid leaching, silica from reject material and aluminum foil. For comparative reasons, commercial pyrogenic silica was also employed as a silicon source. Raw materials, as well as the corresponding resulting ones were characterized by a group of spectroscopical, thermal, electrochemical, volumetric and microscopy techniques, namely: X-ray Diffraction (XRD) spectrometry, X-ray photoelectron spectroscopy (XPS), transmittance Fourier Transform infrared spectroscopy (FTIR), Diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS), nitrogen adsorption, thermogravimetric analysis (TGA), ultraviolet-visible diffuse reflectance spectroscopy (DRS), atomic force microscopy (AFM), scanning electron microscopy (SEM), electron scanning microscopy combined with energy dispersive X-ray analysis (SEMEDX) and differential pulse voltammetry (DPV). For the zeolite synthesis, the evaluated parameters were: (i) nature of the silicon and aluminum sources; (ii) crystallization time; (iii) Si/Al molar ratio on the synthesis gel and (iv) influence of the stirring in the crystallization. Excepting for raw chrisotile, the other cases afforded the production of zeolite A with higy crystallinity and purity. The synthesized zeolite A started from the leached chrysotile showed high structural stability for longer periods of synthesis. Variation in Si/Al molar ratio led to the formation of the zeolite Y, which was pure when rice calcinated to 600ºC was employed as the source of silicon and, which resulted in a mixture of zeolite A and Y when used the leached crisotila. Zeolite A with high crystalinity and with big size grains were obtained in the case of using silica (reject), leached chrysotile and rice calcined at 600ºC as silicon source and aluminum foil as the source of aluminum. Degradation of dyes (methylene blue, direct blue 71 and yellow direct 8) and pharmaceutical (paracetamol) was evaluated by a series of in situ generated titania supported catalysts obtained from the impregnation of TiCl4 onto a series of zeolite, synthesized using rice husk and chrysotile as the silicon source, whice were later submitted to calcination. The resulting titania were in the form of anatase phase. The highest catalyst activity was reached with samples having 10 wt.% Ti, being comparable to that exhibited by commercial P25 after one hour of UV light exposition. Experiments carried out in natural sunlight reached 92% decomposition of the methylene blue dye. The catalyst activity of a supported titania catalyst was shown to be kept until five cycles.

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Sexton, Alexandra Elizabeth. "Eating for the post-Anthropocene : alternative proteins, Silicon Valley and the (bio)politics of food security." Thesis, King's College London (University of London), 2018. https://kclpure.kcl.ac.uk/portal/en/theses/eating-for-the-postanthropocene(2e88cc17-8f6f-4f86-9f8f-fdb485ebd0cd).html.

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This thesis explores the emergence of a new generation of alternative proteins (APs) – including cellular agriculture, edible insects and plant-based proteins – that aim to provide more sustainable, healthy and ethical alternatives to conventional livestock products. It examines APs within the broader context of Anthropocenic debates, situating this activity as a reaction to contemporary food-related ‘crises’ and, ultimately, as solutions for global food security. Drawing on interviews, policy analysis and visceral autoethnographic work in the leading hubs of recent AP activity in Europe and the US, the thesis demonstrates how APs both reinforce (‘simulate’) and challenge (‘disrupt’) the existing imaginaries, materialities and political economic factors of the global food system. Through exploring this negotiation between simulation and disruption, the thesis critically examines the enthusiastic and at-times bombastic promissory narratives that have characterised the sector to date. It calls into question to whom and in what ways APs cause disruption, arguing that while they have indeed disturbed the geographies, actors and practices involved in protein production, the political economic underpinnings of the global food system (i.e. inequality, bio-corporatisation, Western-based power) remain largely intact. Drawing on Foucauldian thought, the thesis also argues that APs represent a new site of food biopolitics – introduced as the ‘biopolitics of edibility’ – through which we see a continuation of consumer responsibilisation wherein personal food choice acts as a means for creating a better self and planet. By analysing the material and discursive strategies used to make APs into ‘food’, the thesis also explores these products as an important case for thinking through the material and visceral (bio)politics of eating, as well as the limits of disgust and mistrust posed by food-technology interactions and the precarious relationship between (non)human bodies. Through its theoretical and empirical contributions, the thesis intervenes in critical food geography by bringing together recent debates on the geographies of production and consumption, the material and visceral politics of eating, and the biopolitics of food. It also engages with economic geography and STS theorisations of innovation to think through the material and promissory trajectories that APs have taken to date. Through examining the negotiation of simulation and disruption, the recent AP movement is problematised as both entangled and implicit in politics around ‘good’ eating and the individualised project of Anthropocenic solutions.

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21

Demchikhin, Sergey. "Alternativy likvidace fotovoltaických článků jako potenciální ekologické zátěže." Master's thesis, Vysoké učení technické v Brně. Fakulta elektrotechniky a komunikačních technologií, 2012. http://www.nusl.cz/ntk/nusl-219643.

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The first part of this master’s thesis contain the history of photovoltaic technology and types of PV cells. Gave a consideration to advantages and disadvantages of solar cells. Compared their effectiveness and important parameters. In the next part described the recycling technology of modules at the end of their lifetime. Described certain recycled materials. At the end of the work described possible improvements to existing technologies used for encapsulating of cell. And wich would improve the recycling process.

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22

Dehouck, Yves. "Développement de potentiels statistiques pour l'étude in silico de protéines et analyse de structurations alternatives." Doctoral thesis, Universite Libre de Bruxelles, 2005. http://hdl.handle.net/2013/ULB-DIPOT:oai:dipot.ulb.ac.be:2013/211040.

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Cette thèse se place dans le cadre de l'étude in silico, c'est-à-dire assistée par ordinateur, des liens qui unissent la séquence d'une protéine à la (ou aux) structure(s) tri-dimensionnelle(s) qu'elle adopte. Le décryptage de ces liens présente de nombreuses applications dans divers domaines et constitue sans doute l'une des problématiques les plus fascinantes de la recherche en biologie moléculaire.

Le premier aspect de notre travail concerne le développement de potentiels statistiques dérivés de bases de données de protéines dont les structures sont connues. Ces potentiels présentent plusieurs avantages: ils peuvent être aisément adaptés à des représentations structurales simplifiées, et permettent de définir un nombre limité de fonctions énergétiques qui incarnent l'ensemble complexe d'interactions gouvernant la structure et la stabilité des protéines, et qui incluent également certaines contributions entropiques. Cependant, leur signification physique reste assez nébuleuse, car l'impact des diverses hypothèses nécessaires à leur dérivation est loin d'être clairement établi. Nous nous sommes attachés à l'étude de certaines limitations des ces potentiels: leur dépendance en la taille des protéines incluses dans la base de données, la non-additivité des termes de potentiels, et l'importance souvent négligée de l'environnement protéique spécifique ressenti par chaque résidu. Nous avons ainsi mis en évidence que l'influence de la taille des protéines de la base de données sur les potentiels de distance entre résidus est spécifique à chaque paire d'acides aminés, peut être relativement importante, et résulte essentiellement de la répartition inhomogène des résidus hydrophobes et hydrophiles entre le coeur et la surface des protéines. Ces résultats ont guidé la mise au point de fonctions correctives qui permettent de tenir compte de cette influence lors de la dérivation des potentiels. Par ailleurs, la définition d'une procédure générale de dérivation de potentiels et de termes de couplage a rendu possible la création d'une fonction énergétique qui tient compte simultanément de plusieurs descripteurs de séquence et de structure (la nature des résidus, leurs conformations, leurs accessibilités au solvant, ainsi que les distances qui les séparent dans l'espace et le long de la séquence). Cette fonction énergétique présente des performances nettement améliorées par rapport aux potentiels originaux, et par rapport à d'autres potentiels décrits dans la littérature.

Le deuxième aspect de notre travail concerne l'application de programmes basés sur des potentiels statistiques à l'étude de protéines qui adoptent des structures alternatives. La permutation de domaines est un phénomène qui affecte diverses protéines et qui implique la génération d'un oligomère suite à l'échange de fragments structuraux entre monomères identiques. Nos résultats suggèrent que la présence de "faiblesses structurales", c'est-à-dire de régions qui ne sont pas optimales vis-à-vis de la stabilité de la structure native ou qui présentent une préférence marquée pour une conformation non-native en absence d'interactions tertiaires, est intimement liée aux mécanismes de permutation. Nous avons également mis en évidence l'importance des interactions de type cation-{pi}, qui sont fréquemment observées dans certaines zones clés de la permutation. Finalement, nous avons sélectionné un ensemble de mutations susceptibles de modifier sensiblement la propension de diverses protéines à permuter. L'étude expérimentale de ces mutations devrait permettre de valider, ou de raffiner, les hypothèses que nous avons proposées quant au rôle joué par les faiblesses structurales et les interactions de type cation-{pi}. Nous avons également analysé une autre protéine soumise à d'importants réarrangements conformationnels: l'{alpha}1-antitrypsine. Dans le cas de cette protéine, les modifications structurales sont indispensables à l'exécution de l'activité biologique normale, mais peuvent sous certaines conditions mener à la formation de polymères insolubles et au développement de maladies. Afin de contribuer à une meilleure compréhension des mécanismes responsables de la polymérisation, nous avons cherché à concevoir rationnellement des protéines mutantes qui présentent une propension à polymériser contrôlée. Des tests expérimentaux ont été réalisés par le groupe australien du Professeur S.P. Bottomley, et ont permis de valider nos prédictions de manière assez remarquable.

The work presented in this thesis concerns the computational study of the relationships between the sequence of a protein and its three-dimensional structure(s). The unravelling of these relationships has many applications in different domains and is probably one of the most fascinating issues in molecular biology.

The first part of our work is devoted to the development of statistical potentials derived from databases of known protein structures. These potentials allow to define a limited number of energetic functions embodying the complex ensemble of interactions that rule protein folding and stability (including some entropic contributions), and can be easily adapted to simplified representations of protein structures. However, their physical meaning remains unclear since several hypotheses and approximations are necessary, whose impact is far from clearly understood. We studied some of the limitations of these potentials: their dependence on the size of the proteins included in the database, the non-additivity of the different potential terms, and the importance of the specific environment of each residue. Our results show that residue-based distance potentials are affected by the size of the database proteins, and that this effect can be quite strong, is residue-specific, and seems to result mostly from the inhomogeneous partition of hydrophobic and hydrophilic residues between the surface and the core of proteins. On the basis of these observations, we defined a set of corrective functions in order to take protein size into account while deriving the potentials. On the other hand, we developed a general procedure of derivation of potentials and coupling terms and consequently created an energetic function describing the correlations between several sequence and structure descriptors (the nature of each residue, the conformation of its main chain, its solvent accessibility, and the distances that separate it from other residues, in space and along the sequence). This energetic function presents a strongly improved predictive power, in comparison with the original potentials and with other potentials described in the literature.

The second part describes the application of different programs, based on statistical potentials, to the study of proteins that adopt alternative structures. Domain swapping involves the exchange of a structural element between identical proteins, and leads to the generation of an oligomeric unit. We showed that the presence of “structural weaknesses”, regions that are not optimal with respect to the folding mechanisms or to the stability of the native structure, seems to be intimately linked with the swapping mechanisms. In addition, cation-{pi} interactions were frequently detected in some key locations and might also play an important role. Finally, we designed a set of mutations that are likely to affect the swapping propensities of different proteins. The experimental study of these mutations should allow to validate, or refine, our hypotheses concerning the importance of structural weaknesses and cation-{pi} interactions. We also analysed another protein that undergoes large conformational changes: {alpha}1-antitrypsin. In this case, the structural modifications are necessary to the proper execution of the biological activity. However, under certain circumstances, they lead to the formation of insoluble polymers and the development of diseases. With the aim of reaching a better understanding of the mechanisms that are responsible for this polymerisation, we tried to design mutant proteins that display a controlled polymerisation propensity. An experimental study of these mutants was conducted by the group of Prof. S.P. Bottomley, and remarkably confirmed our predictions.

Doctorat en sciences appliquées
info:eu-repo/semantics/nonPublished

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Touma, Wissam Elias. "Alkali-silica reaction in Portland cement concrete : testing methods and mitigation alternatives /." Digital version accessible at:, 2000. http://wwwlib.umi.com/cr/utexas/main.

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Tarvornpanich, Tarnkamol. "Recycled colourless soda-lime-silica glass as an alternative flux in whitewares." Thesis, University of Sheffield, 2007. http://etheses.whiterose.ac.uk/14505/.

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The most common type of container glass which is landfilled in the UK is soda-limesilica glass, comprising typically 7I-75wt% silica, 12-I6wt% soda and 1O-15wt% lime. Considering its chemical similarity to that of the fluxing materials commonly used in whiteware bodies, it is sensible to investigate the use of SLS waste glass as replacement for these fluxes in whitewares. The present study aimed at the incorporation of colourless SLS waste glass into a standard whiteware formulation (Le. 50wt% kaolinite clay, 25wt% quartz and 25wt% nepheline syenite) as a flux, and at the examination of the microstructural development on firing. Bulk samples with two (e.g. clay and quartz, SLS glass and clay, etc.), three (standard and fully SLS-fluxed whiteware) and four (mixed nepheline syenite SLS glass as flux system) components were studied in depth. After firing 3h at 1100Ã‚Â°C, batches containing 6.25wt% SLS glass and 18.75wt% nepheline syenite attained open-pore closure and a bulk density of 2.40 g/cm3 , comparable to that of the standard body fired at 1200Ã‚Â°C. SLS glass softens and melts, conferring early densification and overfiring on whitewares fired at commercially-applied firing temperatures. Severe bloating ruled out the use of higher amounts of SLS glass. The microstructural evolution examined using XRD, SEMlEDS, and TEMIEDS revealed the formation of a variable composition plagioclase, wollastonite, and cristobalite in batches containing SLS glass, in addition to primary and secondary mullites, partially dissolved quartz, and a glassy matrix as found in the standard whiteware. Na+ and Ca2+ions from SLS glass migrate towards clay mineral relicts to form plagioclase, limiting the extent of mullite crystallization in SLS containing batches. Wollastonite and cristobalite crystallize from the devitrification of SLS glass. The flexural strength of the body containing 6.25wt% SLS glass fired at 1l00Ã‚Â°C (-71.2 MPa) was higher, modulus of elasticity slightly lower, and fracture toughness comparable to those of the standard whiteware body fired at 1200Ã‚Â°C. The Weibull modulus of the partially SLS-fluxed whiteware was lower due to the presence of crystals inhomogeneously distributed over a complex microstructure. From the physical and mechanical properties investigated in this study, SLS glass can be used as part of the fluxing system of some fully densified whitewares.

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Miotti, Leonardo. "Transporte atômico e estabilidade em dielétricos alternativos para a tecnologia do Si." reponame:Biblioteca Digital de Teses e Dissertações da UFRGS, 2007. http://hdl.handle.net/10183/10724.

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Анотація:

Esta tese trata do estudo experimental de fenômenos de transporte atômico e reação química em filmes ultra-finos dielétricos sobre Si. Esses dielétricos são materiais alternativos ao óxido de silício utilizado em dispositivos basedos na estrutura metal-óxido-semicondutor. Foram investigados os seguintes materiais: silicato e aluminato de háfnio, aluminato de lantânio e bicamada óxido de alumínio/ óxido de háfnio. O tema principal da investigação aqui descrita é a estabilidade destas estruturas frente à duas etapas críticas do processo de fabricação. A primeira é o tratamento térmico após deposição do filme, usualmente realizada à temperaturas entre 600 e 800 C. A segunda é a ativação de dopantes de fonte e dreno dos transistores à efeito de campo do tipo metal-óxido-semicondutor. Esta etapa é realizada a temperaturas ao redor de 1000 C, durante intervalos de tempo ao redor de 10 s. Para a produção destas estruturas foram utilizados diversos métodos, entre eles pulverização catódica reativa e deposição por camada atômica. Para a observação dos fenômenos induzidos por tratamentos térmico, foram usados diferentes métodos de caracterização, entre eles os de análises por espalhamento de íons de altas, médias e baixas energias, análise por reações nucleares ressonantes ou não ressonantes, espectroscopia de fotoelétrons, microscopia eletrônica de transmissão, determinação de características I×V e C×V e outras. Os resultados mostram que estas etapas críticas do processo de fabricação de dispositivos microeletrônicos avançados com dimensões nanoscópicas induzem transporte atômico de várias espécies e reações químicas nas interfaces dos dielétricos investigados e o substrato de Si. Muitas vezes isto acontece contrariando as expectativas formadas quando se considera apenas as energias de formação dos diferentes compostos. Esta tendência é fortemente modificada de acordo com a atmosfera em que é realizado o tratamento térmico (nitrogênio, oxigênio e suas misturas), bem como pela introdução de nitrogênio nos filmes.
This thesis reports on experimental investigation of atomic transport and chemical reaction phenomena in ultrathin dielectric films on Si. These materials are alternative to silicon oxide used in metal-oxide-semiconductors based devices. The dielectrics investigated were: hafnium silicate and aluminate, lanthanum aluminate, and aluminum oxide/hafnium oxide bilayers. The main aim of the investigation here reported is the stability of structures against two critical steps of the fabrication process. The first one is post-deposition annealing, usually performed at temperatures between 600 and 800 C. The second one is source and drain dopant activation of the fabricated metal-oxide-semiconductor field effect transistors, which is usually performed at temperatures around 1000 C for times around 10 s. The production of the structures was accomplished by different deposition methods, among them reactive sputtering and atomic layer deposition. The observation of the thermal stability induced phenomena was accomplished with different characterization methods, such as high, medium, and low energy ion scattering, narrow nuclear reaction profiling, photoelectron spectroscopy, atomic resolution electron microscopy, and I×V and C×V characteristics. The results showed that the critical fabrication steps of advanced, nanoscopic microelectronic devices lead to atomic transport of different species and interfacial chemical reactions in the dielectrics on Si. In many cases this is not in agreement with the expectations based only on the formation energy of the concerned compounds. This trend is strongly modified according to the annealing atmospheres (nitrogen, oxygen, and their mixtures) as well by the introduction of nitrogen in the films.

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26

Beaudoing, Emmanuel. "Etude in silico de la polyadénylation alternative, un système de régulation post-transcriptionnelle de l'expression génique." Aix-Marseille 2, 2001. http://www.theses.fr/2001AIX22036.

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27

Redondo, Simone Ungari Azzolino. "Avaliação da potencialidade do uso de fibras de Eucalyptus como reforço alternativo em compositos de silicona." [s.n.], 2003. http://repositorio.unicamp.br/jspui/handle/REPOSIP/250501.

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Анотація:

Orientadores: Inez Valeria Pagotto Yoshida e Maria do Carmo Gonçalvez
Tese (doutorado) - Universidade Estadual de Campinas, Instituto de Quimica
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Doutorado

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28

Matt, Hughes. "Silica supported transition metal phosphides : alternative materials for the water-gas shift reaction." Thesis, University of Glasgow, 2014. http://theses.gla.ac.uk/5548/.

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Transition metal phosphides remain relatively unexplored as water-gas shift catalysts; however the little that has been done has produced promising results in terms of performance due to the presence of oxygen rich phases. They can be produced through a number of approaches, the most common being reduction of the phosphate precursor using hydrogen. Bimetallic phosphides have also generated interest recently, e.g. with the addition of cerium there are improvements to the phosphides' activity and with the addition of palladium a decrease in reduction temperature is evident in the precursor material. Nickel phosphide and a range of bimetallic derivatives on a silica support were investigated for their activity in both high and low temperature water-gas shift reactions. All of the catalysts were tested using a continuous flow, fixed bed reactor. Characterization of the catalysts was carried out using XRD, EXAFS, XPS, FTIR, SEM and TEM. The comparison of supported nickel phosphide and an iron based industrial catalyst shows supported nickel phosphide to have good mass normalized activity in comparison to the industrial counterpart under high temperature water-gas shift conditions. The results complement previous studies with regards to potential of nickel phosphide as a water-gas shift catalyst. In view of the results obtained so far for other transition metal phosphides, Ni2P appears to be superior for the water-gas shift reaction. One of the most promising aspects of using nickel phosphide in the water-gas shift reaction is its potential resistance to sulfur. Catalyst poisoning caused by impurities such as sulfur are known to deactivate current commercial catalysts for both high and low temperature shift conditions, therefore a catalyst which is resistant to sulfur is an attractive prospect. The sulfur resistant properties of the nickel phosphide catalysts were highlighted by testing them under high temperature water-gas shift conditions in the presence of sulfur. Whilst the catalysts deactivated under the conditions, they showed some residual catalytic activity still remained after sulfur was removed from the feed. Compared with the industrial catalyst, nickel phosphide displayed greater resistance to deactivation.

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29

Filho, José Cândido de Souza. "Uma geometria alternativa para detecção do espalhamento de luz LASER por partículas e micro-rugosidades em superfícies de silício." Universidade de São Paulo, 2008. http://www.teses.usp.br/teses/disponiveis/3/3140/tde-30092008-145835/.

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Neste trabalho é proposta uma geometria alternativa para detecção do espalhamento de luz LASER, com o objetivo de determinar o tamanho e o número de partículas aderidas em lâminas de silício com diferentes acabamentos superficiais. Neste trabalho foi utilizado um modelo teórico que descreve o espalhamento de luz por partículas dielétricas previamente depositadas sobre superfícies polidas. Esse modelo baseia-se na teoria analítica de espalhamento por partículas dielétricas suspensas num meio desenvolvida por Gustav Mie26, adaptado para partículas aderidas em superfícies28,29. Para caracterizar o equipamento por nós construído, foram utilizadas amostras contendo diferentes características ou feições superficiais: partículas de LATEX com quatro diâmetros diferentes (0,1 mm, 0,6 mm, 1,1 mm e 5,0 mm) previamente depositadas, amostras de lâminas de silício contendo padrões de linhas com alturas, larguras e espaçamentos conhecidos e amostras com micro-gotas de glicerina de diversos diâmetros (500 1800 mm). Obtivemos a intensidade total de luz espalhada em função das seções de espalhamento de cada elemento citado. Também foram feitas medidas de contagem de partículas e, em alguns casos, uma medida da assimetria horizontal das partículas presentes nas superfícies. Os resultados das medidas de espalhamento de luz por partículas e micro-gotas de glicerina foram comparados com os resultados previstos pelo modelo da reflexão desobstruída (URM) através de um programa implementado no MATLAB para o cálculo de seções de espalhamento, elaborado com base numa rotina de cálculo proposta por Bohren e Huffman.
In this work, it is proposed an alternative geometry to detect LASER light scattering to obtain the average size and concentration of particles adhered on silicon wafers with different surface finishing. It was used a theoretical model for light scattering from dieletric particles which were previously deposited onto polished surfaces. This model is based on the analitical scattering theory of suspended particles developed by Gustav Mie26 which was adapted for particles adhered on silicon surfaces28,29. To characterize our Home-Built Equipment, it was used different samples with different surface features: silicon wafers with LATEX spheres of four different diameters (0.1 mm, 0.6 mm, 1.1 mm and 5.0 mm), surface lines with different width, height and inter-spacing, and liquid micro-drops of glicerine with several diameters (500-1800 mm). We have obtained the total intensity of scattered light as a function of the scattering section for each mentioned feature. Also, particle counting and, in some cases, measurements of horizontal assimetry of the particles were done. The light scattering measurements of particles and micro-drops were modeled using the Unbstructed Reflection Model to obtain the scattering sections with the aid of a calculation routine as proposed by Bohren and Huffman.

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30

Taillet, Brice. "Procédés alternatifs pour l'élaboration de matériaux composites à matrice céramique." Thesis, Bordeaux, 2014. http://www.theses.fr/2014BORD0203/document.

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L’ouverture du marché de l’aéronautique civil aux matériaux composites à matrice céramique impose le développement de nouveaux procédés d’élaboration compatibles avec les cadences de production et les coûts de fabrication du secteur.À cette fin, des travaux expérimentaux ont été menés pour élaborer une matrice à base d’oxynitrure de silicium (Si2N2O) par procédé SHS, ou synthèse par combustion, à partir d’un mélange de poudres réactives.L’oxynitrure de silicium est une céramique thermostructurale prometteuse, caractérisée par de bonnes propriétés mécaniques, mais également par une résistance à l’oxydation supérieure à celle du carbure de silicium.Le procédé SHS est un procédé d’élaboration rapide dont le moteur est une réaction chimique suffisamment exothermique pour s’entretenir sans apport d’énergie extérieur.Les poudres sont préalablement broyées, mises en suspension, puis imprégnées dans une préforme fibreuse composée de fibres en carbure de silicium de dernière génération (Hi-Nicalon S). La réaction SHS est ensuite réalisée dans un réacteur spécialement conçu et dédié à cette étude.Une attention particulière a été portée sur l’optimisation des paramètres d’élaboration pour la synthèse d’une matrice à base Si2N2O. La synthèse s’effectue par la nitruration sous pression d’un mélange dans les bonnes proportions d’une poudre de silicium et d’une poudre de silice. La réaction chimique s’amorce à la température de fusion du silicium. La pression d’élaboration et la vitesse de montée en température constituent les paramètres principaux régissant la composition et la microstructure de la matrice. Ces paramètres ont fait l’objet d’une étude expérimentale approfondie pour parvenir à une matrice homogène, composée à plus de 90% d’oxynitrure de silicium et assurant un taux de porosité résiduelle du composite inférieur à 10%. Ce travail a été complété par le calcul des propriétés élastoplastiques de la matrice, par la caractérisation mécanique à l’échelle du composite, et par un test de vieillissement en température sous air humide
The opening of the civil aviation market to ceramic matrix composite materials requires the development of new methods of producing compatible with the production rates and manufacturing costs of the sector.For this purpose, experimental work was conducted to develop a silicon oxynitride matrix (Si2N2O) by combustion synthesis (or SHS), from reactive powders. In recent years, Si2N2O has emerged as a promising new high-temperature ceramic material, characterized by not only good mechanical properties, but also by a higher oxidation resistance than silicon carbide. The underlying basis of SHS relies on the ability of highly exothermic reactions to be self-sustaining and, therefore, energetically efficient. Powders are first milled, dispersed and stabilized in aqueous media, and then impregnated into a fibrous preform composed of the latest generation of silicon carbide fibers (Hi-Nicalon S). SHS reaction is then carried out in a reactor specially designed and dedicated to this study. Particular attention was focused on the optimization of experimental parameters for the synthesis of a Si2N2O based matrix. Silicon metal in a mixture with silica powder was combusted under pressurized nitrogen gas into silicon oxynitride. The pressure and the temperature rise rate were the principal parameters for the composition and microstructure of the matrix. These parameters have been the subject of extensive experimental work to reach a homogeneous matrix with a very high formation rate for silicon oxynitride (more than 90wt%) and with a level of residual porosity lower than 10%. This work was completed by the calculation of the physical properties of the matrix, by the mechanical characterization of the composite material, and finally by a temperature aging test under moist air

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31

Zhang, Yugao. "An alternative preparation of organofunctionalized silica gels and their characterization by solid-state NMR spectroscopy." Thesis, University of British Columbia, 1991. http://hdl.handle.net/2429/29889.

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The theoretical consideration and experimental techniques required to obtain high -resolution solid-state NMR spectra of silica gels and their organofunctionalized derivatives are presented. A series of organofunctionalized silica gels has been prepared by the copolymerization of the two components, tetraethoxysilane (TEOS), (EtO)₄Si, and methyltriethoxysilane (MTES) (EtO)₃SiCH₃, which is an alternative to the conventional anchoring method. CP/MAS solid-state NMR techniques have been used to elucidate the structures of the organofunctionalized silica gels. The copolymerization method is superior to the anchoring method in that more functional groups can be incorporated into a silica gel matrix. CP/MAS solid-state NMR has been successfully applied in the investigation of the thermal stabilities of the functionalized silica gels as a complementary technique to the more traditional DSC technique and it has been concluded that in an inert gas (N₂) environment, the methyl groups on the methylsilica gel made by copolymerization method are more thermally stable to decomposition than that made by the anchoring method and both are much more stable than in a normal atmospheric environment. Two-dimensional heteronuclear ¹H-²⁹Si correlation NMR spectroscopy has been used to characterize three different types of modified silica gels; methylsilica gel prepared by the anchoring method; methylsilica gel prepared by the copolymerization method; and a mechanical mixture of silica gel and polymethylsiloxane. This technique successfully demonstrated the structural differences among the three materials which cannot be easily distinguished by other analytical techniques. It is shown that methylsilica gel prepared by the anchoring method consists of two distinct phases when the functional group loading is high (i.e., polymethylsiloxane built up "horizontally" on the surface of silica gel), and it is very like the mechanical mixture of silica gel and polymethylsiloxane. On the other hand, the methylsilica gel prepared by the copolymerization method consists of a distribution of the two components, i.e., there is no domain structure between silica gel and polymethylsiloxane. The methyl protons and hydroxyl protons in the functionalized silica gels were found to be sources of cross-polarization transfer to the Si(0-)₄ framework silicons, but the physically absorbed water does not contribute to this transfer.
Science, Faculty of
Chemistry, Department of
Graduate

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32

Field, M. "In vitro and in silico examination of the alternative respiratory NADH dehydrogenase family in Arabidopsis thaliana and other species." Thesis, University College London (University of London), 2007. http://discovery.ucl.ac.uk/1444705/.

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The respiratory electron transport chain (ETC) in plants, fungi and many bacteria incorporates additional enzymes not present in mammalian counterparts. The alternative NADH dehydrogenase (NDH2) performs the same enzymatic function as Complex I---the oxidation of NADU and reduction of membrane-bound quinone---but without the concomitant translocation of hydrogen ions across the ETC membrane, and thus does not contribute directly to the proton-motive potential. Three genes in Saccharomyces cerevisiae and as many as seven putative genes have been identified in Arabidopsis thaliana encoding NDH2 enzymes yet their structure, enzymatic kinetics and the benefits they confer on the organisms remain speculative. This thesis reports the investigation of these enzymes using a combination of computational and biochemical techniques. cDNA clones were produced from Arabidopsis leaf tissue and subcloned into an E. coli expression vector from which a high yield of protein was obtained, but this aggregated as inclusion bodies. Refolding assays using dialysis and injection diffusion techniques failed to obtain active protein. NDH2 gene sequences from all species were reviewed in detail both to determine expression patterns and to identify gene-specific motifs. The latter were used in a novel homology modelling process which has determined key structural elements, including residues specific for NADH or NADPH and the fact that these enzymes have been incorrectly annotated as "NADH disulphide oxidoreductases". The modelling analysis yielded other enzyme properties pertinent to biochemical expression, such as the absence of disulphide bridges in the tertiary structure.

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33

Potié, Alexis. "Etude de la croissance de nanofils de Si Ge et caractérisation par microscopie à force atomique." Phd thesis, Université de Grenoble, 2012. http://tel.archives-ouvertes.fr/tel-00767918.

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Étude de la croissance de nanofils de SiGe par dépôt chimique en phase vapeur et caractérisation par microscopie à force atomique. Les nanofils semi-conducteurs constituent des briques de bases au potentiel prometteur pour l'amélioration des dispositifs du futur. D'autre part, l'alliage SiGe permet de contrôler les propriétés électroniques de la matière telles que les mobilités des porteurs et la largeur de bande. Dans le cadre de ce travail de thèse, nous étudions les mécanismes de croissance catalysée de nanofils de SiGe et développons des méthodes de caractérisation de nanofils par AFM.Dans un premier temps, la croissance par CVD de nanofils de SiGe est étudiée en utilisant l'or comme catalyseur. Nous étudions l'influence du HCl en phase gazeuse qui permet un contrôle de la croissance de nanofils de SiGe et modélisons son action.Dans un deuxième temps, nous étudions la croissance de nanofils SiGe catalysée par siliciures compatibles CMOS, et la croissance de nanofils de Ge pur à basse température. Nous nous intéressons également à l'élaboration d'hétérostructures.Enfin, nous étudions le module de Young de NF unique de Si, GaN et ZnO par AFM et une nouvelle méthode de génération de potentiel piézoélectrique sur NF de GaN a été développée.

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34

Amit, Kumar. "Food irradiation and development of an alternative method for the detection of 2-Alkylcylcyclobutanone." Kansas State University, 2008. http://hdl.handle.net/2097/592.

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Master of Science
Food Science Institute
J. Scott Smith
Food irradiation is one of the most important food processing methods utilized to reduce microbial load and extend shelf life. In 1995 the World Health Organization (WHO) declared irradiated foods to be safe from a nutritional and toxicological point of view. Various methods have been applied to detect irradiated foods. Detection of 2-alkylcyclobutanones has been found to be a useful method in identifying irradiated foods. The solvent extraction method utilizes a Soxhlet apparatus for lipid extraction followed by clean up with Florisil. However, this method is very time consuming. The other methods available to detect 2-alkylcyclobutanone include supercritical fluid extraction (SFE), and accelerated solvent extraction method using a Dionex ASE 200 instrument. The SFE is a fast method to detected 2-alkylcyclobutanone. All the above mentioned methods involve costly equipment. The aim of this study was to eliminate the requirement of costly extraction equipment for lipid extraction before clean up or direct isolation of 2-alkylcyclobutanone as in case of SFE instrument using Florisil cartridges. In this study, the manual solvent extraction method was applied to isolate alkylcylcobutanone followed by clean up with 2 g silica cartridge. The clean up extract was injected to gas chromatography-flame ionization detector (GC-FID) for detection of 2-dodecylcyclobutanone (2-DCB). Gas chromatography-mass spectrometry (GC-MS) was used to confirm that the compound detected was 2-dodecylcyclobutanone. The ions m/z 98 and 112 were selected for 2-DCB for monitoring in selected ion monitoring (SIM) mode of GC-MS. The results showed that this method was able to detect 2-DCB from irradiated ground beef. The manual method does not require costly equipment such as supercritical fluid extractor, Dionex, or Soxlet apparatus for extraction process.

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35

Orellana, Pérez Teresa [Verfasser], Hans Joachim [Akademischer Betreuer] Möller, Hans Joachim [Gutachter] Möller, and Cano Jose Ygnacio [Gutachter] Pastor. "Mechanical behavior of alternative multicrystalline silicon for solar cells / Teresa Orellana Pérez ; Gutachter: Hans Joachim Möller, Jose Ygnacio Pastor Cano ; Betreuer: Hans Joachim Möller." Freiberg : Technische Universitaet Bergakademie Freiberg Universitaetsbibliothek "Georgius Agricola", 2013. http://d-nb.info/122083727X/34.

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36

Garros, Xavier. "Caractérisation et modélisation de l'oxyde d'hafnium comme alternative à la silice pour les futures technologies CMOS submicroniques." Aix-Marseille 1, 2004. http://www.theses.fr/2004AIX11067.

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L'oxyde d'hafnium a récemment été proposé pour remplacer l'oxyde thermique classique. Le but de cette thèse était de faire un point sur les propriétés électriques de ce nouveau matériau. Cette thèse est organisée en quatre chapitres : L'EOT (Epaisseur Equivalente Oxyde), la conduction à travers l'isolant, les défauts électriques dans l'oxyde et la fiabilité du diélectrique. Dans le premier chapitre, il est démontré que l'EOT dépend principalement des conditions de recuit RTP à travers l'épaisseur de la couche interfaciale. Dans le chapitre 2, la conduction à travers le diélectrique est analysée. De manière générale, HfO2 apporte un bénéfice appréciable en terme de courant de fuite par rapport à SiO2. Dans le chapitre 3, les défauts électriques dans HfO2 (pièges d'interfaces et de volume, charges fixes) sont évalués. Dans le dernier chapitre, la bonne fiabilité de ce matériau est démontrée.

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37

LIMA, Liliane Andrade. "Síntese de peneiras moleculares MCM-41 impregnadas com Co e Co/Ru utilizando fontes alternativas de sílica." Universidade Federal de Campina Grande, 2015. http://dspace.sti.ufcg.edu.br:8080/jspui/handle/riufcg/433.

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Este trabalho teve como objetivo sintetizar e caracterizar a peneira molecular mesoporosa MCM-41, utilizando diferentes fontes de sílica, e desenvolver catalisadores a base de cobalto e rutênio. As peneiras moleculares MCM-41 foram sintetizadas utilizando-se como fonte de sílica as cinzas de casca de arroz, cinzas de bagaço de cana-de-açúcar, argila chocolate B e Sílica Aerosil 200 com a seguinte base molar: 1,0 CTMABr:4,0 SiO2:1 Na2O:200 H2O. As peneiras moleculares MCM41 obtidas foram calcinadas em mufla a 600 °C por 7 horas. A deposição dos metais (cobalto e rutênio) sobre o suporte MCM-41 foi realizada por meio de impregnação úmida e depois calcinada. As amostras obtidas foram caracterizadas pelas técnicas de Espectroscopia de Fluorescência e Raios X por Energia Dispersiva (FRX-ED), Difração de raios X (DRX), Adsorção Física de Nitrogênio, Microscopia Eletrônica de Varredura (MEV) e Espectroscopia na Região do Infravermelho com Transformada de Fourier (FTIR). Os resultados mostraram ser possível obter a peneira molecular MCM-41 com diferentes fontes de sílica, pelas micrografias observa-se que os materiais apresentam morfologias similares, constituídas por aglomerados com forma esponjosa. Os difratogramas dos catalisadores mostraram que após a impregnação dos metais e calcinação, não ocorreram modificações na estrutura hexagonal. A partir dos resultados de Adsorção Física de N2, observou-se isotermas de adsorção do tipo IV, típico de materiais mesoporosos e altos valores de área superficial. Os catalisadores apresentaram composições de metais nas proporções pré-definidas e após impregnação do rutênio obteve melhor dispersão dos metais sobre a peneira molecular. Os espectros apresentaram bandas na região de 500 - 4000 cm-1, características das vibrações fundamentais dos grupos funcionais específicos presentes na estrutura da peneira molecular MCM-41 e bandas referentes a estrutura do óxido de cobalto (Co3O4).
This study aimed to synthesize and characterize the molecular sieve mesoporous MCM-41, using different sources of silica, and develop cobalt-based catalysts and ruthenium. The MCM-41 molecular sieves were synthesized using as silica source the rice husk ash, ash from sugarcane bagasse, clay chocolate B and silica Aerosil 200 with the following molar basis: 1.0 CTMABr: 4.0 SiO2: 1 Na2O: 200 H2O. The MCM-41 molecular sieves were obtained calcined in a muffle at 600 ° C for 7 hours. The deposition of metals (cobalt and ruthenium) on the supporting MCM-41 was performed by wet impregnation and then calcined. The samples obtained were characterized by spectroscopy techniques Fluorescence and X-rays by Energy Dispersive (FRX-ED), X-ray diffraction (XRD), Adsorption Nitrogen Physics, Scanning Electron Microscopy (SEM) and Fourier transform infrared spectroscopic (FTIR). The results proved possible to obtain MCM-41 molecular sieve having different silica sources, the micrographs it is noted that the materials have similar morphology, consisting of spongy form agglomerates. The XRD patterns of the catalysts showed that after impregnation and calcination of the metal, there were no changes in the hexagonal structure. From the results of Physical Adsorption of N2 was observed adsorption isotherms of type IV, typical of mesoporous materials and high surface area values. The metal catalyst compositions presented in predefined proportions and after impregnation of the obtained ruthenium better dispersion of metals on the molecular sieve. The spectra showed bands in the region of 500 - 4000 cm-1, characteristic of the fundamental vibrations of the specific functional groups present in the structure of the molecular sieve MCM-41 and bands related to the structure of the cobalt oxide (Co3O4).

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38

Kelly, Brennan James. "Experimental and Simulated Analysis of Voltage Stress Within a Bar-Wound Synchronous Machine Excited by a Silicon Carbide Inverter." The Ohio State University, 2021. http://rave.ohiolink.edu/etdc/view?acc_num=osu1619111736344023.

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39

Kostura, Patrik. "Vývoj vysokohodnotného pórobetonu při využití alternativních zdrojů." Master's thesis, Vysoké učení technické v Brně. Fakulta stavební, 2019. http://www.nusl.cz/ntk/nusl-392332.

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With the growing trend of construction, the demand for building materials is growing steadily. Porous concrete is widely used in the building industry, that makes efforts to discount production and simultaneously save the environment. The aim of this thesis is to develop high-quality porous concrete by using alternative raw materials as a substitute for silicate sand. As a possible substitute were chosen: Silica masonry, foundry sand and fireclay boulders. The influence of two key parameters - the specific surface (130, 240 and 350 m2·kg-1) and the amount of silica sand substitution (10, 30 and 50 %) were monitored. Two autoclaving modes (7 and 12 hours of isothermal durations at 190 ° C) were tested. Based on the physico-mechanical and mineralogical characteristics of the porous concrete composites was chosen the ideal surface area of 240 m2·kg-1 and time of isothermal endurance was determined at 7 hours (temperature 190 ° C, pressure 1,4 MPa). From the optimal intentions were created samples with a macroporous structure, using an aluminum powder. Physical-mechanical properties and microstructural analysis (XRD, SEM) were subsequently determined on the samples. Ideal recipes were proposed with 50% sand substitution of fireclay boulders and 10% substitution of foundry sand. This was due to a 10% higher compressive strenght and an increase of the coefficient of constructiveness, compared to the reference sample.

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Santos, Felipe Antunes. "Vitrocerâmica à base de silicato de lítio para uso como material dentário utilizando casca de arroz como fonte alternativa de silica." Universidade de São Paulo, 2013. http://www.teses.usp.br/teses/disponiveis/97/97133/tde-08102013-084019/.

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O presente trabalho sugere a substituição da sílica comercial pela sílica obtida da casca de arroz como fonte alternativa para obtenção do dissilicato de lítio, material que pode ser utilizado em aplicações odontológicas. Para esse fim foram desenvolvidos materiais com estequiometria base de 33,33%mol. Li2O e 66,67%mol. SiO2 com e sem adição de óxidos complementares, visando à obtenção de vitrocerâmicas de maior tenacidade, por meio das duas fontes de sílica, comercial e da casca de arroz. Como caracterizações iniciais, foram realizadas difrações de raios X (DRX) para as misturas iniciais das matérias-primas antes e após a fusão para obtenção dos vidros. Para o caso dos materiais sem adição dos óxidos, a caracterização quanto à sua devitrificação, foi realizada por análise térmica diferencial (ATD), utilizando diferentes taxas de aquecimento e granulometrias, para ambas as fontes de sílica. Valores de temperatura de pico de cristalização (Tp), sem adição dos óxidos, ficaram na faixa de 640°C para os materiais de ambas as fontes de sílica. Também por ATD foi analisado o fenômeno de devitrificação dos materiais com adição dos óxidos. Além disso, para observar a existência de fases intermediárias no sistema, foram também realizadas análises por DRX com variação térmica. Para visualizar a alteração microestrutural, de acordo com a variação da temperatura de tratamento térmico (TT), fonte de sílica e influência dos óxidos, foram realizadas caracterizações por microscopia eletrônica de varredura (MEV). O comportamento citotóxico dos materiais frente às colônias celulares foi observado por meio do ensaio de citotoxicidade. As propriedades mecânicas, de acordo com as alterações das variáveis estudadas, foram obtidas por meio de cálculos de dureza e tenacidade à fratura por ensaio Vickers. Foram encontrados valores de tenacidade à fratura de aproximadamente 1,75 MPam1/2 para ambas as fontes de sílica, com adição de óxidos a 660°C (TT). Diante dos resultados obtidos é possível afirmar grande potencialidade na substituição da sílica comercial pela sílica da casca de arroz.
This work suggests the replacement of commercial silica by silica obtained from rice husk as alternative source for obtaining lithium disilicate material that can be used in dental application. The lithium disilicate as dental material is a glass-ceramic that has good mechanical properties and chemical stability. For these developments the materials have been obtained using stoichiometry of 33.33%mol. Li2O and 66.67%mol. SiO2, without complementary oxide addition or with, seeking better fracture toughness comportment, to both sources of silica, commercial and from rice husk. As initial characterization X-ray diffraction (XRD) was performed for the mixtures of materials before and after the fusion to obtain the glasses. For materials without oxide addition, the two materials developed were characterized for their devitrification, in other words, the transition from glass to glass-ceramic was observed by differential thermal analysis (DTA), using different heating rates and granulometries. Peak crystallization temperatures (Tp), to both silica sources, heat rate 10°C/min and 1mm of granulometry, was in average values of 640°C. The DTA was used to verify the devitrification in material with oxide addition too. In addition, to observe the possible formation of intermediate phases on stoichiometric system of lithium disilicate, were also carried out high temperature X-ray diffractomery (HTXRD). To view the microstructural changes occurring in the system, according to the variation of heat treatments temperatures (HT), silica source and oxides influence, characterizations were performed by scanning electron microscopy (SEM). The cytotoxic behavior of the materials in cell colonies was observed by the cytotoxicity test. Mechanical properties, Vickers hardness and fracture toughness, were determined by calculus, using Vickers test data. Values of approximately 1.75 MPam½ were obtained for both silica sources with oxide addition to 660°C (HT). Results obtained show great potential in the replacement of commercial silica by rice husk silica.

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Roberts, Alan Clive. "The Development of Facial Prosthetics and Adhesives in Plastic and Reconstructive Surgery. A study in the application of prosthetic materials and devices used in plastic and reconstructive surgery together with tissue adhesives as an alternative to conventional ligation." Thesis, University of Bradford, 1988. http://hdl.handle.net/10454/5065.

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Various silicone elastomers have been evaluated for use in the prosthetic reconstruction of facial defects. Their strength, texture, flexibility, hardness, ease of preparation, pigment receptivity and retention, and their resistance to cleaning were compared and the data consulted when an elastomer was chosen to restore defects, improve aesthetics and reestablish the confidence of a selection of patients. Detailed case reports are provided, together with information on the adhesives or mechanical methods available for retaining the facial prosetheses. Cyanoacrylate adhesives for use on skin surfaces and as tissue adhesives have been studied in detail. A novel n-butyl 413 cyanoacrylate has been developed with a viscosity, haemostatic property and stability to make it particularly suitable for use in skin grafting and tissue repair. It has already been used with good results on patients with severe burns. An improved formulation, containing a fluorescent dye, can be precisely applied through a specially constructed foot-controlled dispenser illuminated by a fibre-optic supplying UV-light. Cyanoacrylates are already being used as tissue adhesives in place of the conventional but potentially disfiguring suture. The availability of improved, imperceptible adhesives and a precision applicator, which can be used in a modern operating theatre, will extend their effectiveness and satisfy some of the needs of Plastic, and Oral and Maxillo-Facial Surgeons. Portable applicators have potential use in battlefield and in veterinary surgery and overcome the imprecision characteristic of earlier methods.

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Abedrrabba, Sarra. "Solutions innovantes pour des filtres de fréquences volumiques et semi-volumiques performants, en céramique, silice fondue et thermoplastique COC/COP... : nouvelles alternatives pour les futurs programmes de satellite multimédia." Thesis, Brest, 2017. http://www.theses.fr/2017BRES0126/document.

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L’émergence des satellites très haut débit pour la couverture des zones rurales s’accompagne de nombreuses contraintes technologiques. Dans le cadre du plan France très haut débit, le projet THD-sat proposé par le CNES se base sur l’utilisation des bandes Q et V pour assurer les liaisons avec les stations au sol et libérer de la ressource sur la bande Ka communément utilisée par les satellites ancienne génération. Avec la montée en fréquence, les besoins en termes de filtrage deviennent très stricts nécessitant des considérations particulières. Le premier chapitre reprend le contexte de l’étude et expose les différents éléments permettant de justifier le choix de la technologie SIW qui profite à la fois des bons facteurs de qualité des modes volumiques se propageant dans le substrat et de l’aisance du procédé technologique et de l’intégration des structures planaires. Les performances des cavités SIW restent néanmoins intimement liées à l’épaisseur de substrat qui doit être augmentée pour atteindre de meilleurs facteurs de qualité. L’augmentation de l’épaisseur de substrat s’accompagne de deux principales limitations : le rallongement des fils de « bonding » utilisés pour le câblage du filtre à son environnement MIC d’épaisseur 254 μm et l’élargissement de la ligne d’accès 50 Ω induisant des problèmes de discontinuités et d’excitations de modes parasites. L’approche suivie consiste à considérer des formes 3D permettant l’adaptation de mode et d’épaisseur entre une ligne microruban sur substrat de 254 μm d’épaisseur et le SIW d’épaisseur plus importante. Une nouvelle transition 3D est dès lors imaginée. Le chapitre II reprend les différents procédés technologiques utilisés pour la mise en forme et la métallisation des substrats 3D. Les substrats considérés sont l’alumine et la silice fondue mis en forme par ablation laser et le thermoplastique COP mis en forme par moulage. La principale limitation de l’ablation laser concerne les épaisseurs de substrat accessibles. Nous nous limitons à 635 μm dans le cas de l’alumine et à 500 μm dans le cas de la silice fondue. Le moulage polymère permet de s’affranchir de cette limitation et de viser des substrats plus épais (2 mm pour la solution COP).Le chapitre III reprend les étapes de conception des différentes solutions de filtrage avec la nouvelle transition 3D. Des résultats de mesures de différents prototypes réalisés sont par ailleurs présentés. Ces résultats sont globalement encourageants mais nécessitent d’être davantage développés pour être mieux exploitables
The emergence of satellite high-speed internet for the coverage of rural zones is accompanied by numerous technological constraints. The current trend is to use higher frequency bands to release the satellite capacity for users. The increasing frequency requires new considerations especially for filtering needs which become notably strict in terms of performance and integration in small integrated circuits. This work introduces filtering solutions based on high quality factor Substrate Integrated Waveguides (SIW) using a novel 3D transition for a better integration in widely planar Hybrid ICs.The first chapter introduces the study’s context and the different elements justifying the use of the SIW technology.In fact, these structures profit from both the good quality factors of TE-modes propagating in the substrate and the easy fabrication process and integration of planar circuits. However, to increase the SIW quality factor, the substrate’s height should be increased which induces interconnection limitations such as long bond wires with high parasitic effects and large microstrip access lines with discontinuity problems and the propagation of parasitic modes. The adopted approach consists in imagining 3D shapes providing both mode and thickness matching between a microstrip line etched on a thin substrate and a high substrate SIW.The second chapter introduces the different manufacturing processes used for the substrate’s shaping and metallization. Three substrates are considered: Alumina, fused Silica and Cyclo Olefin Polymer COC. Alumina is widely used in space applications and has a well-mastered process. For equivalent dielectric losses, fused silica has a lower permittivity for bigger structures with less manufacturing tolerance sensitivity. Both Alumina and fused silica substrates are shaped using a laser ablation. The reachable substrate’s height using this machining method is relatively low. The polymer solution (COP) is elaborated using a molding process allowing higher substrates heights.The last chapter outlines the design steps of the different solutions and the measurement results of the first prototypes. These results are on the whole encouraging but require further development

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Jerban, Majid. "Performance of concrete incorporating amorphous silica residue and biomass fly ash." Mémoire, Université de Sherbrooke, 2016. http://hdl.handle.net/11143/9807.

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L'industrie du ciment est l'une des principales sources d'émission de dioxyde de carbone. L'industrie mondiale du ciment contribue à environ 7% des émissions de gaz à effet de serre dans l'atmosphère. Afin d'aborder les effets environnementaux associés à la fabrication de ciment exploitant en permanence les ressources naturelles, il est nécessaire de développer des liants alternatifs pour fabriquer du béton durable. Ainsi, de nombreux sous-produits industriels ont été utilisés pour remplacer partiellement le ciment dans le béton afin de générer plus d'économie et de durabilité. La performance d'un additif de ciment est dans la cinétique d'hydratation et de la synergie entre les additions et de ciment Portland. Dans ce projet, deux sous-produits industriels sont étudiés comme des matériaux cimentaires alternatifs: le résidu de silice amorphe (RSA) et les cendres des boues de désencrage. Le RSA est un sous-produit de la production de magnésium provenant de l'Alliance Magnésium des villes d'Asbestos et Thedford Mines, et les cendres des boues de désencrage est un sous-produit de la combustion des boues de désencrage, l'écorce et les résidus de bois dans le système à lit fluidisé de l'usine de Brompton située près de Sherbrooke, Québec, Canada. Récemment, les cendres des boues de désencrage ont été utilisées comme des matériaux cimentaires alternatifs. L'utilisation de ces cendres comme matériau cimentaire dans la fabrication du béton conduit à réduire la qualité des bétons. Ces problèmes sont causés par des produits d'hydratation perturbateurs des cendres volantes de la biomasse quand ces cendres sont partiellement mélangées avec du ciment dans la fabrication du béton. Le processus de pré-mouillage de la cendre de boue de désencrage avant la fabrication du béton réduit les produits d'hydratation perturbateurs et par conséquent les propriétés mécaniques du béton sont améliorées. Les approches pour étudier la cendre de boue de désencrage dans ce projet sont : 1) caractérisation de cette cendre volante régulière et pré-humidifiée, 2) l'étude de la performance du mortier et du béton incorporant cette cendre volante régulière et pré-humidifiée. Le RSA est un nouveau sous-produit industriel. La haute teneur en silice amorphe en RSA est un excellent potentiel en tant que matériau cimentaire dans le béton. Dans ce projet, l'évaluation des RSA comme matériaux cimentaires alternatifs compose trois étapes. Tout d'abord, la caractérisation par la détermination des propriétés minéralogiques, physiques et chimiques des RSA, ensuite, l'optimisation du taux de remplacement du ciment par le RSA dans le mortier, et enfin l'évaluation du RSA en remplacement partiel du ciment dans différents types de béton dans le système binaire et ternaire. Cette étude a révélé que le béton de haute performance (BHP) incorporant le RSA a montré des propriétés mécaniques et la durabilité, similaire du contrôle. Le RSA a amélioré les propriétés des mécaniques et la durabilité du béton ordinaire (BO). Le béton autoplaçant (BAP) incorporant le RSA est stable, homogène et a montré de bonnes propriétés mécaniques et la durabilité. Le RSA avait une bonne synergie en combinaison de liant ternaire avec d'autres matériaux cimentaires supplémentaires. Cette étude a montré que le RSA peut être utilisé comme nouveaux matériaux cimentaires dans le béton.
Abstract : Cement manufacturing industry is one of the carbon dioxide emitting sources. The global cement industry contributes about 7% of greenhouse gas emission to the earth’s atmosphere. In order to address environmental effects associated with cement manufacturing and constantly depleting natural resources, there is necessity to develop alternative binders to make sustainable concrete. Thus, many industrial by-products have been used to partially substitute cement in order to generate more economic and durable concrete. The performance of a cement additive depends on kinetics hydration and synergy between additions and Portland cement. In this project, two industrial by-products are investigated as alternative supplementary cementitious materials (ASCMs), non-toxic amorphous silica residue (AmSR) and wastepaper sludge ash (WSA). AmSR is by-product of production of magnesium from Alliance Magnesium near of Asbestos and Thetford Mines Cities, and wastepaper sludge ash is by-product of combustion of de-inking sludge, bark and residues of woods in fluidized-bed system from Brompton mill located near Sherbrooke, Quebec, Canada. The AmSR is new industrial by-products. Recently, wastepaper sludge ash has been used as cementitious materials. Utilization of these ashes as cementitious material in concrete manufacturing leads to reduce the mechanical properties of concretes. These problems are caused by disruptive hydration products of biomass fly ash once these ashes partially blended with cement in concrete manufacturing. The pre-wetting process of WSA before concrete manufacturing reduced disruptive hydration products and consequently improved concrete mechanical properties. Approaches for investigation of WSA in this project consist on characterizing regular and pre-wetted WSA, the effect of regular and pre-wetted WSA on performance of mortar and concrete. The high content of amorphous silica in AmSR is excellent potential as cementitious material in concrete. In this project, evaluation of AmSR as cementitious materials consists of three steps. Characterizing and determining physical, chemical and mineralogical properties of AmSR. Then, effect of different rates of replacement of cement by AmSR in mortar. Finally, study of effect of AmSR as partial replacement of cement in different concrete types with binary and ternary binder combinations. This study revealed that high performance concrete (HPC) incorporating AmSR showed similar mechanical properties and durability, compared to control mixture. AmSR improved mechanical properties and durability of ordinary concrete. Self-consolidating (SCC) concrete incorporating AmSR was stable, homogenous and showed good mechanical properties and durability. AmSR had good synergy in ternary binder combination with other supplementary cementitious materials (SCMs). This study showed AmSR can be use as new cementitious materials in concrete.

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Montenegro, Danielle Lobo. "Reforma a seco de metano com catalisadores Ni/MCM-41 sintetizados a partir de fontes alternativas de s?lica." Universidade Federal do Rio Grande do Norte, 2013. http://repositorio.ufrn.br:8080/jspui/handle/123456789/12986.

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Conselho Nacional de Desenvolvimento Cient?fico e Tecnol?gico
The production of synthesis gas has received renewed attention due to demand for renewable energies to reduce the emissions of gases responsible for enhanced greenhouse effect. This work was carried out in order to synthesize, characterize and evaluate the implementation of nickel catalysts on MCM-41 in dry reforming reactions of methane. The mesoporous molecular sieves were synthesized using as silica sources the tetraethyl orthosilicate (TEOS) and residual glass powder (PV). The sieves were impregnated with 10% nickel to obtain the metallic catalysts (Ni/MCM-41). These materials were calcined and characterized by Thermogravimetric Analysis (TG), Infrared spectroscopy (FTIR), X-ray Diffraction (XRD), Temperature-Programmed Reduction (TPR) and N2 Adsorption/Desorption isotherms (BET/BJH). The catalytic properties of the samples were evaluated in methane dry reforming with CO2 in order to produce synthesis gas to be used in the petrochemical industry. The materials characterized showed hexagonal structure characteristic of mesoporous material MCM-41 type, being maintained after impregnation with nickel. The samples presented variations in the specific surface area, average volume and diameter of pores based on the type of interaction between the nickel and the mesoporous support. The result of the the catalytic tests showed conversions about 91% CO2, 86% CH4, yelds about 85% CO and 81% H2 to Ni/MCM-41_TEOS_C, and conversions about 87% CO2, 82% CH4, yelds about 70% CO and 59% H2 to Ni/MCM-41_PV_C. The similar performance confirms that the TEOS can be replaced by a less noble materials
A produ??o de g?s de s?ntese tem recebido muita import?ncia devido a procura por fontes de energias renov?veis para reduzir as emiss?es dos gases respons?veis pelo aumento do efeito estufa. Este trabalho foi realizado com o objetivo de sintetizar, caracterizar e avaliar a aplica??o dos catalisadores de n?quel sobre MCM-41, em rea?oes de reforma a seco de metano. As peneiras moleculares mesoporosas foram sintetizadas utilizando como fontes de s?lica o Tetraetil Ortosilicato (TEOS) e o res?duo de p? de vidro (PV). As peneiras foram impregnadas com 10% de n?quel para forma??o dos catalisadores met?licos (Ni/MCM-41). Esses materiais foram calcinados e caracterizados por Termogravimetria (TG), Espectroscopia na Regi?o do Infravermelho (FTIR), Difratometria de raios X (DRX), Redu??o de Temperatura Programada (TPR) e Adsor??o e Dessor??o de N2 (BET/BJH). As propriedades catal?ticas das amostras foram avaliadas na reforma a seco de metano com CO2, tendo como objetivo a produ??o de g?s de s?ntese para utiliza??o na ind?stria petroqu?mica. Os materiais caracterizados apresentaram estrutura hexagonal caracter?stica do material mesoporoso tipo MCM-41, sendo mantida ap?s a impregna??o com n?quel. As amostras apresentaram varia??es quanto ? ?rea superficial espec?fica e volume m?dio de poros, em fun??o do tipo de intera??o existente entre o n?quel e o suporte mesoporoso. Os resultados dos testes catal?ticos mostraram convers?es de 86% de CH4 e 91% de CO2 e rendimento de 85% de CO e 81% de H2 para o material Ni/MCM-41_TEOS_C, e convers?es de 82% de CH4 e 87% de CO2 e rendimentos na produ??o do g?s de s?ntese de 70% de CO e 59% de H2 para o material Ni/MCM-41_PV. Esse comportamento semelhante comprova que o TEOS pode ser substitu?do por um material menos nobre

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Vankeuren, Jody L. "Parasites Predators and Symbionts." Kent State University / OhioLINK, 2021. http://rave.ohiolink.edu/etdc/view?acc_num=kent1619475426952694.

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Silva, José Geraldo da, and 69-99903-7010. "Estudo da temperatura de pastas com substituição parcial da silica ativa ao cimento utilizando o método semi-adiabático." Universidade Federal do Amazonas, 2017. https://tede.ufam.edu.br/handle/tede/6541.

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The increasing requests for shorter execution times in concrete using concrete results in a consequent demand for thermal control. This work aims to evaluate the use of silica in the reduction of temperature in cement reactions through tests on cement pastes using device and semi-adiabatic method developed in this research. For that, an equipment and method of use was developed. This work presents a method, including the design of the semi-adiabatic reaction measuring device, with the application of suitable materials to obtain the results, as well as an adequate experimental planning, allowing the evaluation of the active silica as a thermal control proposal. The results showed the different temperature indications, according to the respective dosages of active silica. The dosages of cement were substituted by silica in the proportions of 0, 7, 14 and 20% both with respect to w / c relation of 0.5. The silica was presented increasing or decreasing the temperatures of the reactions according to dosage, aspect, therefore, determinant to the process of application of the same for such purpose according to the data observed.
As crescentes solicitações de menores prazos de execução em projetos utilizando concreto massa traz consequente demanda ao controle térmico. Este trabalho tem o objetivo de avaliar a utilização da sílica na redução da temperatura em reações cimentícias através de ensaios em pastas de cimento empregando dispositivo e método semi-adiabático desenvolvidos nesta pesquisa. Para tanto foi elaborada um equipamento e método de uso. Este trabalho apresenta um método, incluindo o projeto do dispositivo de medição semi-adiabática da reação, contando com a aplicação de materiais adequados a obtenção dos resultados, bem como um planejamento experimental adequado possibilitando obter avaliação da sílica ativa como proposta de controle térmico. Os resultados mostraram as diferentes indicações de temperatura, conforme as respectivas dosagens de sílica ativa. Foram praticadas as dosagens de sílica em substituição ao cimento nas proporções de 0, 7, 14 e 20% ambas com relação a/c de 0,5. A sílica apresentou-se aumentando ou diminuindo as temperaturas das reações conforme dosagem, aspecto, portanto, determinante ao processo de aplicação da mesma para tal finalidade segundo os dados observados.

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Hofgård, Daniel, and John Sundkvist. "Climate enhanced concrete in the civil engineering industry." Thesis, KTH, Betongbyggnad, 2020. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-278216.

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In 2017, the Swedish Parliament stated a new climate law with the goal that Sweden should be climate neutral by 2045. The concrete industry has developed a roadmap on how the goal for 2045 can be achieved, where one way to reduce the carbon emissions from concrete is by replacing a part of the cement clinker with alternative binders in the concrete mix. Ground granulated blast furnace slag (GGBS), fly ash, silica fume and trass are alternative binders that are possible to use in concrete mixes to reduce the amount of ordinary Portland cement (OPC). GGBS, fly ash and silica fume are by-products from other industries, while trass is volcanic ash that can be extracted. Besides the positive environmental impact that comes from using alternative binders and reducing the amount of cement clinker, the alternative binders have other properties, both positive and negative, that affect the concrete. The aim of this thesis was to investigate whether concrete with alternative binders does fulfill the regulations set by Swedish standards and how concrete with alternative binders does affect the material parameters. The concrete mixes were divided into three different types of concrete: concrete for bridges (w/c ratio 0.4), hydropower structures (w/c ratio 0.45) and wind powerplant foundations (w/c ratio 0.55). A total of seven concrete mixes were cast in a laboratory and the concrete mixes were investigated in the three hardening stages of concrete: fresh, young and hardened. The analyzed material parameters were compressive strength, shrinkage, frost resistance, workability, air voids and temperature development. Beyond the experimental testing, a global warming potential (GWP) comparison was made to compare the reduction of GWP for each concrete mix compared to a reference concrete for each usage area. The mix containing a CEM II/A-V fly ash cement and 15% GGBS showed great potential regarding the different material parameters. This mix, however, is according to Swedish standards not possible to certify for structures in exposure class XF4, such as bridges, but is possible to certify for structures in exposure class XF3, such as wind powerplant foundations. The mix containing 30% GGBS and 5% silica fume also showed beneficiary properties, but superplasticizers are required in this mix to ensure good workability. For hydropower structures, the mix containing 35% GGBS showed a great compressive strength but a high temperature development and low workability. The mix containing trass had a notably low temperature development, but with an increase in shrinkage and low workability. Moreover, all concrete mixes showed a frost resistance which, according to standard, is classified as “Very Good”.
Sveriges regering antog 2017 ett nytt klimatpolitiskt ramverk med målet att Sverige ska ha noll nettoutsläpp av växthusgaser år 2045. Betongindustrin har tagit fram en färdplan för hur betong kan bli klimatneutralt, där ett sätt att reducera klimatpåverkan från betong är att byta ut en del av cementklinkern mot alternativa bindemedel. Mald granulerad masugnsslagg (GGBS), flygaska, silikastoft och trass är alternativa bindemedel som är möjliga att använda i betongblandningar för att reducera mängden Portlandcement. GGBS, flygaska och silikastoft är restprodukter från andra industrier medan trass är en vulkanisk aska som kan utvinnas. Utöver den positiva miljöeffekten som erhålls när alternativa bindemedel ersätter cementklinker, så har de alternativa bindemedlen andra egenskaper, både positiva och negativa, som påverkar betongen. Målet med denna studie var att undersöka och jämföra om betongblandningar där en del av cementklinkern har ersatts med alternativa bindemedel når upp till de krav som ställs i nuvarande regelverk. Utöver det så undersöktes även hur betongblandningarnas materialparametrar påverkades av alternativa bindemedel. Betongblandningarna delades in i tre olika typer av betong: betong för broar (vct 0.4), vattenbyggnader (vct 0.45) och vindkraftverksfundament (vct 0.55), där totalt sju betongblandningar tillverkades i ett laboratorium. Betongblandningarna undersöktes i de tre olika faserna för hårdnande av betong, vilka är färsk, ung och hårdnad betong. De materialparametrar som analyserades var tryckhållfasthet, krympning, frostresistens, arbetbarhet, luftporhalt och temperaturutveckling. Förutom de experimentella testerna gjordes en jämförelse kring hur mycket koldioxid som kan reduceras för varje betongblandning, jämfört med en referensbetong för varje användningsområde. Betongblandningen med ett CEM II/A-V flygaska-cement och 15% GGBS visade stor potential med avseende på de olika materialparametrarna. Denna blandning är dock enligt svensk standard inte möjlig att certifiera för betongbyggnad i exponeringsklass XF4, exempelvis broar, men kan certifieras för betongbyggnad i exponeringsklass XF3, exempelvis fundament för vindkraftverk. Blandningen med 30% GGBS och 5% silikastoft visade även positiva egenskaper, men flyttillsatsmedel måste användas i denna blandning för att erhålla en god arbetbarhet. För vattenbyggnadsbetong så visade blandningen med 35% GGBS en hög tryckhållfasthet, men samtidigt en hög temperaturutveckling och en låg arbetbarhet. Blandningen med trass hade en noterbart låg temperaturutveckling, men med ökad krympning samt låg arbetbarhet. Avslutningsvis så uppvisade alla blandningar en frostresistens som enligt standard klassificeras som ”Mycket bra”.

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Moscoso, Ramírez Pedro Antonio. "Aproximaciones a una estrategia integrada para el control no contaminante de las podredumbres verde y azul en poscosecha de cítricos." Doctoral thesis, Universitat Politècnica de València, 2013. http://hdl.handle.net/10251/34626.

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Las podredumbres verde y azul causadas por los hongos patógenos Penicillium digitatum (Pers.: Fr.) Sacc y Penicillium italicum Wehmer, respectivamente, son las responsables de grandes pérdidas económicas en poscosecha de cítricos a nivel mundial. En España, las pudriciones de la fruta en poscosecha fluctúan del 3 al 6% durante una estación típica. Sin embargo, bajo condiciones favorables a la enfermedad, las pérdidas pueden alcanzar el 50%. Las podredumbres verde y azul son las enfermedades de poscosecha más importante de los cítricos en España, California y todas las áreas de producción caracterizadas por lluvias escasas en verano (Ecker y Eaks, 1989). Se han logrado avances importantes en estudios de resistencia adquirida sistémica (SAR) y resistencia sistémica inducida (ISR) tanto natural como artificial (Terry y Joyce, 2004; Tavallali et al., 2008). También se está avanzando en la evaluación de sustancias conocidas como GRAS (Generally Regarded as Safe), o en el uso del calor y la luz ultravioleta (Palou et al., 2008; Montesinos et al., 2009). Todos estos enfoques constituyen estrategias de control alternativo no contaminante. Sin embargo, actualmente seguimos dependiendo del uso de fungicidas químicos sintéticos convencionales para controlar las enfermedades de poscosecha de fruta fresca en general y de cítricos en particular. Asimismo, existe un incremento de la demanda de los mercados internacionales de frutas y hortalizas frescas de buena calidad e inocuas. Además, el uso de fungicidas convencionales conlleva el problema del desarrollo de resistencia en cepas de P. digitatum y P. italicum. Por otro lado, los resultados en efectividad de la mayoría de los métodos de control no contaminantes no han sido equivalentes a los obtenidos con métodos de control químico convencional. Por todo ello sigue siendo un reto la búsqueda e implementación comercial de estrategias no contaminantes efectivas para el control de las podredumbres verde y azul de los cítricos. Un importante mediador de la respuesta en la patogénesis de estos hongos es el gas etileno, ya que su biosíntesis se incrementa durante la interacción planta-patógeno o después de la aplicación de químicos inductores de resistencia. Además, la producción del etileno puede ser una señal para activar mecanismos de defensa contra patógenos como hongos, bacterias o virus (Ecker y Davis, 1987). Se han realizado estudios orientados a buscar relaciones entre el etileno y la patogenicidad de hongos causantes de enfermedades en poscosecha (Brown, 1973). Sin embargo, discrepancias en los resultados han sido observadas. El etileno es aplicado durante la desverdización de los frutos cítricos, que es una práctica comercial común realizada en muchas partes del mundo (Smilanick et al., 2006), incluyendo España, y se estima que más de 1,2 millones de toneladas de fruta de mandarina de estación temprana se desverdiza anualmente (Martínez-Jávega et al., 2007). Por lo tanto, es de importancia primordial determinar el efecto de esta práctica en la susceptibilidad y desarrollo de las podredumbres verde y azul de los frutos cítricos. Los objetivos serán los siguientes: 1) Evaluar sustancias químicas con antecedentes de potencial de inducción de resistencia para controlar las podredumbres verde y azul de poscosecha en frutos cítricos, 2) Evaluar sustancias conocidas como GRAS (General Regarded as Safe), solas o combinadas con fungicidas para controlar las podredumbres verde y azul en frutos cítricos y, 3) Determinar el efecto del desverdizado comercial con etileno sobre la incidencia y desarrollo de las podredumbres verde y azul en mandarinas y naranjas de estación temprana; así como el efecto del desverdizado comercial sobre los atributos de calidad del fruto.
Moscoso Ramírez, PA. (2013). Aproximaciones a una estrategia integrada para el control no contaminante de las podredumbres verde y azul en poscosecha de cítricos [Tesis doctoral no publicada]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/34626
TESIS

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Jin, Yawei. "Simulation methodology to compare emerging technologies for alternatives to silicon gigascale logic device." 2006. http://www.lib.ncsu.edu/theses/available/etd-09192006-231837/unrestricted/etd.pdf.

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"Electrical and Thermal Transport in Alternative Device Technologies." Master's thesis, 2013. http://hdl.handle.net/2286/R.I.20942.

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abstract: The goal of this research work is to develop a particle-based device simulator for modeling strained silicon devices. Two separate modules had to be developed for that purpose: A generic bulk Monte Carlo simulation code which in the long-time limit solves the Boltzmann transport equation for electrons; and an extension to this code that solves for the bulk properties of strained silicon. One scattering table is needed for conventional silicon, whereas, because of the strain breaking the symmetry of the system, three scattering tables are needed for modeling strained silicon material. Simulation results for the average drift velocity and the average electron energy are in close agreement with published data. A Monte Carlo device simulation tool has also been employed to integrate the effects of self-heating into device simulation for Silicon on Insulator devices. The effects of different types of materials for buried oxide layers have been studied. Sapphire, Aluminum Nitride (AlN), Silicon dioxide (SiO2) and Diamond have been used as target materials of interest in the analysis and the effects of varying insulator layer thickness have also been investigated. It was observed that although AlN exhibits the best isothermal behavior, diamond is the best choice when thermal effects are accounted for.
Dissertation/Thesis
M.S. Electrical Engineering 2013

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Дисертації з теми "Silicon alternatives"

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