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1
Bosomworth, P. A. "Thermal stress damage resistance of gel-bonded magnesia refractories." Thesis, University of Leeds, 1986. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.371841.
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Miyafuji, Hisashi. "Wood-Inorganic Composites with Fire-Resistance as Prepared by the Sol-Gel Process." Kyoto University, 2000. http://hdl.handle.net/2433/68743.
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Guadagnin, Hellen Costerano. "Corrosion resistance study of AA2524 anodized in sulphuric-tartaric acid and sealed with hybrid coatings." Universidade de São Paulo, 2017. http://www.teses.usp.br/teses/disponiveis/3/3137/tde-20072017-152947/.
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Aluminium alloys are widely used in the aerospace industry due to their lightweight and high specific strength. However, these alloys are particularly sensitive to localized corrosion in chloride environments and need to be protected by a robust system. One of the protection methodologies consists in anodizing. The produced layer increases the corrosion resistance and also serves as anchoring site for organic coatings application. Chromium-based anodizing has been usually employed, nevertheless, as chromate compounds are toxic for health and the environment, chromium-based surface treatments will be prohibited in the aerospace industry in a near future. Tartaric-sulphuric acid (TSA) anodizing is a promising environment compliant alternative, which is already being used at industrial level with appropriate corrosion protection and paint adhesion properties. This study aims at proposing a hybrid sol-gel treatment after TSA anodizing of AA2524 specimens in order to improve the corrosion resistance of the anodized layer while maintaining its compatibility with organic coatings. For this, anodic aluminium oxides (AAO) were produced at different anodizing voltages and protected by dip-coating with a hybrid sol-gel layer obtained from a tetraethoxysilane (TEOS) and 3-glycidoxypropyltrimethoxysilane (GPTMS) hydrolysis solution with high water content. Corrosion resistance evaluation was carried out by means of electrochemical impedance spectroscopy (EIS) in NaCl 0.1 mol L-1 and salt-spray chamber exposure (ASTM B117-11 standard). The morphology of the anodic porous layer was investigated by means of FE-SEM, whereas glow discharge optical emission spectroscopy (GDOES) was employed to evaluate the distribution of the sol-gel layer within the porous AAO. FE-SEM characterization confirmed that the layer properties (pore distribution, porosity and thickness) were strongly dependent on the anodizing conditions, whereas GDOES depth profile showed penetration of the hybrid coating within the pores of the anodized layer. The two characterization techniques showed inefficient surface sol-gel coverage for the samples anodized at higher voltage, likely due to insufficient sol-gel deposition. The results of the EIS characterization tests up to 1008 h (42 days) showed that, irrespectively to the anodizing voltage, the hybrid sol-gel protected AAO was stable with only slight evolution of the diagrams with immersion time. Moreover, the hybrid coating protected samples presented higher low frequency impedance modulus than hydrothermally sealed (HTSed) reference TSA anodized samples, which was confirmed by electrical equivalent circuit (EEC) fitting of the EIS data. EEC fitting also revealed that the resistance of the pores to electrolyte penetration was increased by the application of the sol-gel coating when compared to the resistance of the HTSed reference samples and indicated better anticorrosion performance for the sample anodized at 16 V. These results were confirmed by the salt-spray tests. Investigation on the ageing of the hybrid sol-gel hydrolysis solution showed that its viscosity hardly changed up to two weeks of test and that hybrid coatings applied from these solutions were stable and afforded good corrosion protection to the TSA anodized substrate, an improvement of the anticorrosion properties of the hybrid coating was verified for an ageing time of 168 h. Preliminary tests performed with a solvent-free organic coating (epoxy) indicated good compatibility with the hybrid TEOS-GPTMS coating characterized by very high impedance and good stability upon exposure to the salt-spray chamber.Ligas de alumínio são muito utilizadas na indústria aeronáutica por serem materiais leves e altamente resistentes. Porém, essas ligas são particularmente sensíveis à corrosão localizada em meios que contêm cloretos, e precisam de sistemas robustos de proteção. Uma das metodologias de proteção consiste em anodização. A camada produzida aumenta a resistência à corrosão e também serve como sítio de ancoragem para aplicação de revestimentos orgânicos. A anodização crômica tem sido usualmente empregada na indústria aeronáutica. No entanto, como compostos contendo íons cromato são tóxicos para a saúde e para o meio-ambiente, tratamentos de superfície à base de cromo serão proibidos na indústria espacial em um futuro próximo. Anodização em banho de ácido sulfúrico-tartárico (TSA) é uma alternativa promissora e ambientalmente compatível, a qual já está sendo usada industrialmente com apropriada proteção à corrosão e adesão para pintura. Este estudo tem como objetivo propor um tratamento utilizando um revestimento híbrido sol-gel para melhorar a resistência à corrosão da liga AA2524 anodizada em TSA e que mantenha sua compatibilidade com revestimentos orgânicos. Para isso, camadas anodizadas de alumínio (CAA) foram produzidas em diferentes voltagens e protegidas por camada de híbrido sol-gel obtida pela hidrólise de tetraetilortosilano (TEOS) e glicidóxipropiltrimetóxisilano (GPTMS) em solução com alto teor de água e aplicada pela técnica de dip-coating. A avaliação da resistência à corrosão foi realizada através de espectroscopia de impedância eletroquímica (EIS) em NaCl 0,1 mol.L-1 e por exposição à câmara de névoa salina (norma ASTM B117-11). A morfologia da camada porosa foi investigada por MEV e a espectroscopia de emissão óptica por descarga luminescente (GDOES) foi empregada para avaliar a distribuição do híbrido sol-gel no interior dos poros da camada porosa. As caracterizações por MEV confirmaram que as propriedades da camada (distribuição dos poros, porosidade e espessura) são fortemente dependentes das condições de anodização, e a composição em profundidade obtida por GDOES mostrou que o revestimento híbrido penetrou nos poros da camada anodizada. As duas técnicas de caracterização mostraram uma cobertura ineficiente da camada sol-gel para as amostras anodizadas nas voltagens mais elevadas, provavelmente devido à deposição insuficiente do híbrido. Os testes de EIS com duração de até 1008 h (42 dias) mostraram que, independentemente da voltagem de anodização empregada, a camada anódica coberta com sol-gel ficou estável ocorrendo apenas pequenas evoluções dos diagramas com o tempo de imersão. Além do mais, as amostras protegidas com o revestimento híbrido apresentaram maiores valores de módulo de impedância em baixa frequência do que as amostras anodizadas em TSA e hidrotermicamente seladas (HTsed) usadas como referências. Essa tendência foi confirmada pelo ajuste com circuitos elétricos equivalentes (EEC) dos resultados de EIS que também mostrou que a aplicação do sol-gel híbrido torna mais difícil a penetração do eletrólito agressivo nos poros da camada anodizada quando comparada com as amostras HTSed, e indicou melhor desempenho anticorrosivo para a amostra anodizada em 16 V. Esses resultados foram confirmados pelos testes de névoa salina. A investigação do envelhecimento da solução de sol-gel mostrou pouca mudança na viscosidade da solução de hidrólise em duas semanas de testes e que os revestimentos híbridos aplicados a partir dessas soluções foram estáveis e promoveram boa proteção à corrosão para as amostras anodizadas em TSA, com melhora das propriedades anticorrosivas após 168 h de envelhecimento. Testes preliminares realizados com revestimento orgânico livre de solvente (epóxi) indicaram boa compatibilidade deste com o revestimento híbrido TEOS-GPTMS. O revestimento epóxi propiciou valores de módulo de impedância elevados e estáveis e também boa estabilidade após exposição à câmara de névoa salina quando aplicado sobre o revestimento híbrido aplicado sobre a liga 2524.
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Hendry, Jason. "The fretting corrosion resistance of sol-gel and PVD surface-modified orthopaedic implant alloys." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1999. http://www.collectionscanada.ca/obj/s4/f2/dsk1/tape8/PQDD_0002/MQ46101.pdf.
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Casbonne-Renaud, Frédérique. "Comportement aux cycles gel-dégel des bétons de granulats calcaires." Vandoeuvre-les-Nancy, INPL, 1998. http://www.theses.fr/1998INPL053N.
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Le but de cette étude est de caractériser le comportement aux cycles gel-dégel de bétons réalisés à base de granulats calcaires, et de le comparer à celui d'un béton classique réalisé avec des granulats siliceux. Des bétons ont été soumis à des cycles gel-dégel accélérés en enceinte climatique, différents de ceux des normes, en ajoutant des paliers de gel et de dégel. Des analyses au microscope électronique à balayage ont montré l'apparition d'ettringite secondaire dans tous les bétons dégradés (siliceux et calcaires). L’ettringite apparait au cours des paliers et peut entrainer une aggravation des désordres lors de sa cristallisation par poussée cristalline. Des mesures de vitesse des ondes ultrasonores, de perméabilité au gaz et de résistance à la compression simple ont permis de montrer différents types de comportements aux cycles gel-dégel en fonction des types de granulats utilisés et des dosages en ciment. La liaison continue entre la pate et les granulats calcaires sublithographiques supprime la zone de faiblesse existant à ce niveau dans le cas des granulats siliceux. L’utilisation de granulats calcaires sublithographiques améliore donc la résistance au gel. Pour des calcaires plus poreux oolithiques, la liaison pate-granulat est très compacte, ce qui entraine dans certains cas des gradients de contrainte pouvant conduire à la formation de fissures. Leur utilisation demandera donc des études préalables.
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Vance, Lindsey. "The Inhibitory Effects of a Novel Gel on Staphylococcus aureus Biofilms." Digital Commons @ East Tennessee State University, 2018. https://dc.etsu.edu/honors/435.
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Antibiotic resistance is an ever-growing topic of concern within the medical field causing researchers to examine the mechanisms of resistance to develop new antimicrobials. Bacteria’s ability to form biofilms is one mechanism which aids in antimicrobial resistance. Staphylococcus aureus is of special interest as it is one of the most frequent biofilm-forming bacteria found on medical devices causing infections and posing dangerous threats in a clinical setting. A recently developed antimicrobial gel has been shown to have profound effects on treating bacterial infections and wound healing. This research is centered upon examining the antimicrobial effects of this gel on the three different stages of biofilm formation in clinical and laboratory strains of S. aureus. Through a series of experiments examining the effects this gel has on S. aureus at the stages of biofilm attachment, maturation, and dispersion, the gel has shown significant levels of inhibition. These findings indicate that the novel gel disrupts biofilm forming processes of S. aureus, which provides useful information for fighting infections in the medical field. Further research on the uses and effects of this new gel could lead possibility using the antimicrobial compound for a variety of clinical purposes.
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Nguyen, Vinh Xuan. "Mecanismes de la resistance au gel de l'embryon de pommier (pyrus malus l. Cv. Golden delicious)." Paris 6, 1987. http://www.theses.fr/1987PA066554.
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Des pommes (pyrus malus l. Cv. "golden delicious" ont ete entreposees apres la recolte, a 0,12 et 35**(o)c. Apres 4 semaines, des lots de fruits ont ete transferes de 0 a 12**(o)c ou inversement de 12 a 0**(o)c. Les basses temperatures (0**(o)c) favorisent la levee de dormance, tandis que les temperatures elevees (12 et 35**(o)c) sont favorables a une meilleure resistance au gel et ces 2 phenomenes sont independants. L'analyse thermique differentielle a montre que l'embryon de pommier ne peut survivre au gel qu'en evitant la congelation intracellulairegrace a une surfusion prolongee. Plus la temperature de conservation des fruits est elevee, plus la temperature de surfusion est basse
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Serafini, Gabriele Maria Callegaro. "Açúcar granulado ou gel no tratamento de feridas em cães." Universidade Federal de Santa Maria, 2012. http://repositorio.ufsm.br/handle/1/10117.
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Coordenação de Aperfeiçoamento de Pessoal de Nível SuperiorSugar is one of the most widely used products in the treatment of wounds in veterinary medicine. Its main advantage is the hygroscopic effect on tissues and the bacterial death by plasmolysis, making it a bactericidal agent due to the physical effect observed, without leading to bacterial resistance as it might occur with antibiotic therapy. The objective of this experiment was to compare cicatricial evolution in cutaneous wounds with the topical use of sugar both granulated and in the form of a gel. For such, 16 canine wounds were treated, where eight received treatment with granulated sugar (group A) and eight with sugar gel (group G). Evaluations such as mensurations of the wounded areas, bacteriological cultures and observation of the aspect of the lesions were done weekly from the moment of the first examination until the formation of enough granulation tissue to suspend the use of the products. When comparing the decline in the area between groups no statistical difference was observed at any time. However, when the areas were analyzed in each group's interval, it was possible to notice a statistically significant decline between days 1-14 and 7-14 in the group treated with sugar. In the group treated with the gel, beside those intervals, a significant decline was also noticed between days 1-7. In terms of the frequency of negative bacteriological culture, there was no statistical difference between groups, not even in the different moments of each group. The time taken for the granulation tissue to be fully formed varied from 7 to 14 days in both groups. As to applicability, the gel showed better adhesion to the wounds and filling of the product subcutaneously more effectively than the granulated sugar. The conclusion reached is that both the sugar and the gel were effective in healing the animals' wounds in this experiment, the gel having demonstrated precocity in cicatricial retraction in the first seven days.
O açúcar é um dos produtos mais utilizados para tratamento de feridas em medicina veterinária. Sua principal vantagem é o efeito higroscópico nos tecidos e morte das bactérias por plasmólise, tornando-o um bactericida pelo efeito físico realizado, sem levar à resistência bacteriana, como poderia ocorrer na terapia antibiótica. O objetivo desse experimento foi comparar a evolução cicatricial de feridas cutâneas com o uso tópico de açúcar na forma granulada e na forma de gel. Para tal, foram tratadas 16 feridas de cães, onde oito receberam tratamento com açúcar granulado (grupo A) e oito com gel de açúcar (grupo G). Avaliações como mensurações das áreas das feridas, culturas bacteriológicas e observação quanto ao aspecto das lesões foram realizadas semanalmente desde o momento do atendimento até a formação de tecido de granulação suficiente para suspender o uso dos produtos. Na comparação da diminuição da área entre os grupos não se observou diferença estatística em nenhum momento. Entretanto, quando as áreas foram analisadas nos intervalos de cada grupo, pôde-se perceber diminuição estatisticamente significativa entre os dias 1 e 14 e 7 e 14 no grupo tratado com açúcar. No grupo tratado com gel, além desses intervalos, também se percebeu diminuição significativa entre os dias 1 e 7. Com relação a frequência de cultura bacteriológica negativa, não houve diferença estatística entre os grupos, nem nos diferentes momentos de cada grupo. O tempo para completa formação de tecido de granulação variou entre sete e 14 dias em ambos os grupos. Quanto à aplicabilidade, o gel demonstrou melhor adesão nas feridas e preenchimento do produto no subcutâneo de forma mais efetiva que o açúcar granulado. Conclui-se que tanto o gel quanto o açúcar foram efetivos na cicatrização das feridas dos animais desse experimento, sendo que o gel demonstrou precocidade na retração cicatricial nos primeiros sete dias.
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Vivar, Mora Laura. "The impact on mechanical properties and corrosion resistance of silica nanoparticles on a sol-gel based coating." Thesis, University of Leeds, 2018. http://etheses.whiterose.ac.uk/20390/.
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Corrosion has a huge impact on metallic structures which not just affect the economy but also assets, environment and society. Finding measures to reduce and prevent corrosion damage is crucial. Organic coatings (epoxies), and inorganic coatings (polysiloxanes), have long been used to mitigate corrosion. Combining the best features of both organic and inorganic coatings to create high performance protective coatings is still a challenge. Many studies have reported increased corrosion protection and durability through the use of these hybrid coatings which could be further enhanced with the incorporation of nanoparticles. Many nanoadditives are now commercially available and many more in the development stage, but integration into coatings is a key challenge since modifies its physical and mechanical properties. The purpose within this investigation was to identify preliminary design rules by studying the effect and impact of these key materials in order to start establishing a materials by design approach which can be further developed and will help the integration of novel materials into industrial applications. A sol-gel based coating was created to modify it with unfunctionalised and functionalised silica nanoparticles and study both their interaction with the coating matrix and their influence on coating morphology and mechanical durability. It was found that non-functionalised silica led to improved barrier properties, however, when the same silica was surface treated the corrosion resistance was further enhanced. Following that line of investigation, three functionalisation levels as well as three loading levels of functionalised silica were examined. This study showed that the highest loading (20 wt.%) of the lowest functionalised silica (T0.1) led to coatings with improved properties and durability. This functionalised silica was homogeneously distributed within the polysiloxane-based matrix with no signs of agglomeration, highlighting the importance of the relation between nanoparticles, matrix and nanoparticle distribution as a key factor to improve coating performance.
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Kang, Min. "Alkali/steam corrosion resistance of commercial SiC products coated with sol-gel deposited Mg-doped Al₂TiO₅ and CMZP." Thesis, Virginia Tech, 1994. http://hdl.handle.net/10919/42006.
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The corrosion resistance of two commercially available SiC filter materials coated with Mg-doped
Al2 Ti05 and (Ca 0.6.6' Mg0.52)
Zr4P6024 (CMZP) was investigated in high-temperature high pressure
(HTHP) alkali-steam environments. Coated specimen properties, including cold and hot
compressive strengths, bulk density, apparent porosity, permeability, and weight change,
dete~ed after exposure to 92% air-S% steam 10 ppm Na at 8OO°C and 1.8 MPs for 500 h were
compared with those of uncoated specimens. Procedures for applying homogeneous coatings of
Mg-doped Al2 Ti05 and CMZP to porous SiC filters were established and coating of the materials
was successfully accomplished. Efforts to stabilize the Al2 Ti05 coating composition at elevated
temperature were successful. Coatings show promise for providing improved corrosion resistance
of the materials in pressurized fluidized bed combustion (PFBC) environments as evidenced by
higher compressive strengths exhibited by coated SiC specimens than by uncoated SiC specimens
following HTHP alkali-steam exposure.
Master of Science
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Leng, Zhongtai. "Distribution and mobility of antibiotic resistant genes in oral/urogentital [sic] bacteria." Thesis, Connect to this title online; UW restricted, 1998. http://hdl.handle.net/1773/9273.
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Karsli, Kadir. "Vanadium Oxide (vox) Thin Films Elaborated By Sol-gel Method For Microbolometer Applications." Master's thesis, METU, 2012. http://etd.lib.metu.edu.tr/upload/12614078/index.pdf.
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Infrared detector technologies have been developing each day. Thermal detectors take great attention in commercial applications due to their low power consumption and low costs. The active material selection and the deposition of the material are highly important performance effective factors for microbolometer detector applications. In that sense, developing vanadium oxide (VOx) microbolometer active material by sol-gel method might be feasible approach to achieve good performance microbolometer detectors.
In this study, vanadium oxide thin films are prepared by sol-gel method is deposited on silicon or silicon nitride wafers as active material by spin coating. The films are annealed under different hydrogen concentration of H2/N2 environments at 410
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OBADIA, BAROGHEL SYLVIA. "Frittage de melanges al::(2)o::(3) + sio::(2) gel pour moules de fonderie : developpement des microstructures et deformation a chaud." Paris, ENMP, 1987. http://www.theses.fr/1987ENMP0079.
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Etude du frittage reactif de melanges prepares a partir de la silice colloidale et l'alumine alpha entrant dans la composition des moules. Influence du temps, de la temperature et de la composition initiale sur l'affaissement des moules carapaces de fonderies pour la coulee/solidification dirigee des aubes de turbine des reacteurs d'avions
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Bouteille, Sébastien. "Outils de caractérisation et analyse du comportement des matériaux cimentaires soumis à des cycles de gel-dégel en présence de sels." Thesis, Paris Est, 2013. http://www.theses.fr/2013PEST1024/document.
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Un béton exposé à des cycles de gel-dégel peut subir des dégradations généralement identifiées sous deux formes. Le gel interne, d’une part, qui affecte le coeur du matériau et peut aboutir à une microfissuration généralisée de la pâte cimentaire. La sensibilité d’un béton courant à ce mode de détérioration peut être diminuée par la présence d’un réseau de bulles d’air au sein de la pâte cimentaire. L’écaillage, d’autre part, qui est une détérioration de surface. Cette dernière est le plus souvent quantifiée par la perte de masse sur la surface exposée. Cette forme de dégradation est fortement influencée par la présence d’une solution aqueuse proche de la surface de béton exposée et de sa concentration en sels fondants (généralement du chlorure de sodium). Lorsque la formulation d’un béton courant n’est pas adaptée pour résister à ce type d’environnement, les dégradations liées au gel interne et à l’écaillage peuvent pénaliser l’exploitation de l’ouvrage concerné dans des conditions de services attendues. Des essais laboratoire, exposant des corps d’épreuve en béton à des cycles de gel-dégel accélérés, permettent d’évaluer la résistance d’un béton face à ces deux formes de détériorations. La communauté scientifique s’accorde sur les essais permettant de caractériser la détérioration par le gel interne et l’aspect protecteur d’un réseau de bulles d’air. Par contre, l’écaillage est encore abordé par diverses procédures expérimentales qui ne font pas consensus et ont peu évolué depuis le milieu des années 1990 (...)A concrete submitted to freeze-thaw cycles may undergo damages generally identified under two forms. On one hand, the internal frost affects the whole volume of the concrete. It can resul in generalized microcracks into the ciment paste. The sensibility of a common concrete to this deterioration can be decreased by the presence of a network of air bubbles within the ciment paste. On the other hand, the scaling, is a surface deterioration generaly quantified by the loss of mass from the exposed surface. The scaling is strongly influenced by the presence of a solution and its concentration in salts (generally some sodium chloride), over the exposed concrete surface. When a common concrete is not correctly formulated to resist this environment, its degradation can penalize the exploitation of the concerned structure in expected conditions of services. Laboratory tests exposing bodies of concrete to accelerated freeze-thaws cycles, allow to estimate the concrete resistance when exposed to these two kinds of deteriorations. The scientific community agrees on the internal frost laboratory test and on the protective aspect of a network of air bubbles. But the scaling is still approached by experimental procedures which do not make consensus and have little evolved since the middle of the 1990s (...)
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Segro, Scott S. "Surface-Bonded Sol-Gel Sorbents for On-Line Hyphenation of Capillary Microextraction with High-Performance Liquid Chromatography." Scholar Commons, 2010. https://scholarcommons.usf.edu/etd/1762.
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High-performance liquid chromatography (HPLC) is the most widely used analysis technique. However, its sensitivity is limited. Sample preconcentration methods, such as fiber-based solid-phase microextraction (SPME) and in-tube SPME (capillary microextraction) offer improved detection limits. It is, however, difficult to couple fiber SPME on-line with HPLC due to the need for complicated desorption devices. Such coupling is further complicated due to the limited solvent stability of the extracting phase both in the fiber and in-tube formats of SPME. In this research, surface-bonded sol-gel sorbents were developed to provide the solvent stability required for effective on-line hyphenation of capillary microextraction (CME) with HPLC. These sol-gel sorbents were prepared using (1) silica-based, (2) titania-based, and (3) germania-based sol-gel precursors. Sol-gel reactions were performed within fused silica capillaries to create a number of organic-inorganic hybrid sorbents in the form of surface-bonded coatings: (1) alkyl (methyl, octyl, octadecyl), (2) polydimethyldiphenylsiloxane, (3) titania poly(tetrahydrofuran), and (4) germania tri-block polymer. The sol-gel coated microextraction capillaries were capable of efficiently extracting a wide variety of analytes, including polycyclic aromatic hydrocarbons, ketones, aldehydes, aromatic compounds, amines, alcohols, and phenols with ng/L to pg/L detection limits. The sol-gel methyl coating demonstrated a counterintuitive ability to extract polar analytes. Sol-gel polydimethyldiphenylsiloxane coatings were found to be resistant to high temperature solvent exposure (150°C and 200°C), making them suitable for use in high-temperature liquid phase separations. To better understand how extraction takes place, effects of alkyl chain length and sol-gel precursor concentration were evaluated in the study on sol-gel alkyl coatings. The sol-gel titania poly(tetrahydrofuran) coating was also capable of extracting underivatized aromatic acids and polypeptides at pHs near their respective isolectric points. The sol-gel titania poly(tetrahydrofuran) coatings and the sol-gel germania tri-block polymer coatings demonstrated impressive resistance to extreme pH conditions, surviving prolonged exposure to 1.0 M HCl (pH approx. 0.0) and 1.0 M NaOH (pH approx. 14.0) with virtually no change in extraction behavior. Sol-gel germania tri-block polymer coatings were also stable under high temperature solvent conditions (200°C). In addition, for the first time, the analyte distribution constants between a sol-gel germania coating and the aqueous samples (Kcs) were determined.
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Walker, Luke Sky. "Processing of Ultra High Temperature Ceramics." Diss., The University of Arizona, 2012. http://hdl.handle.net/10150/228496.
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For hypersonic flight to enable rapid global transport and allow routine space access thermal protection systems must be developed that can survive the extreme aerothermal heating and oxidation for extended periods of time. Ultra high temperature ceramics (UHTCs) are the only potential materials capable of surviving the extreme hypersonic environment however extensive research in processing science and their oxidation properties are required before engineering systems can be developed for flight vehicles. Investigating the role of oxides during processing of ultra high temperature ceramics shows they play a critical role in both synthesis of ceramic powders and during densification. During spark plasma sintering of UHTCs the oxides can result in the formation of vapor filled pores that limit densification. A low temperature heat treatment can remove the oxides responsible for forming the vapor pores and also results in a significant improvement of the densification through a particle surface physical modification. The surface modification breaks up the native continuous surface oxide increasing the surface energy of the powder and removing the oxide as a barrier to diffusion that must be overcome before densification can begin. During synthesis of UHTCs from sol-gel the B₂O₃ phase acts as the main structure of the gel limiting the transition metal oxide network. While heat treating to form diborides the transition metal oxide undergoes preferential reduction forming carbides that reduce B₂O₃ while at high temperature encourage particle growth and localized extreme coarsening. To form phase pure borides B₂O₃ is required in excessive quantities to limit residual carbides, however carbide reduction and grain growth are connected. When the UHTC systems of ZrB₂-SiC are exposed to oxidation, either as dense ceramics or coatings on Carbon-Carbon composites, at high temperatures they undergo a complex oxidation mechanism with simultaneous material transport, precipitation and evaporation of oxide species that forms a glass ceramic protective oxygen barrier on the surface. The composite effect observed between the oxides of ZrB₂-SiC enables them to survive extreme oxidizing environments where traditional SiC oxidation barrier coatings fail.
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Venugopal, Saranya. "Synthesis and processing of sub-micron hafnium diboride powders and carbon-fibre hafnium diboride composite." Thesis, Loughborough University, 2013. https://dspace.lboro.ac.uk/2134/12532.
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A vehicle flying at hypersonic speeds, i.e. at speeds greater than Mach 4, needs to be able to withstand the heat arising from friction and shock waves, which can reach temperatures of up to 3000oC. The current project focuses on producing thermal protection systems based on ultra high temperature ceramic (UHTC) impregnated carbon-carbon composites. The carbon fibres offer low mass and excellent resistance to thermal shock; their vulnerability is to oxidation above 500oC. The aim of introducing HfB2, a UHTC, as a coating on the fibre tows or as particulate reinforcement into the carbon fibre preform, was to improve this property. The objectives of this project were to: i) identify a low temperature synthesis route for group IV diborides, ii) produce a powder fine enough to reduce the difficulties associated with sintering the refractory diborides, iii) develop sol-gel coating of HfB2 onto carbon fibre tows iv) improve the solid loading of the particulate reinforcement into the carbon fibre preform, which should, in turn, increase the oxidation protection. In order to achieve the above set objectives, fine HfB2 powder was synthesized through a low temperature sol gel and boro/carbothermal reduction process, using a range of different carbon sources. Study of the formation mechanism of HfB2 revealed an intermediate boron sub-oxide and/or active boron formation that yielded HfB2 formation at 1300oC. At higher temperatures the formation of HfB2 could be via intermediate HfC formation and/or B4C formation. Growth mechanism analysis showed that the nucleated particles possessed screw dislocations which indicated that the formation of HfB2 was not only through a substitution reaction, but there could have been an element of a precipitation nucleation mechanism that lead to anisotropic growth under certain conditions. The effect of carbon sources during the boro/carbothermal reduction reaction on the size of the final HfB2 powders was analysed and it was found that a direct relation existed between the size and level of agglomeration of the carbon sources and the resulting HfB2 powders. A powder phenolic resin source led to the finest powder, with particle sizes in the range 30 to 150 nm. SPS sintering of the powder revealed that 99% theoretical density could be achieved without the need for sintering aids at 2200oC. Sol-gel coatings and slurry impregnation of HfB2 on carbon fibres tows was performed using dip coating and a 'squeeze-tube' method respectively. Crack free coatings and non-porous matrix infiltration were successfully achieved. The solid loading of the fine HfB2 into the carbon fibre preform was carried out through impregnation of a HfB2 / phenolic resin/acetone slurry using vacuum impregnation. Although the sub-micron Loughborough (LU) powders were expected to improve the solid loading, compared to the commercially available micron sized powders, due to the slurry made from them having a higher viscosity because of the fine particle size, the solids loading achieved was consequently decreased. Optimisation of the rheology of the slurry with LU HfB2 still requires more work. A comparison of the oxidation and ablation resistance of the Cf-HfB2 composites prepared with both commercial micron sized HfB2 powder and Loughborough sub-micron sized HfB2 powder, each with similar level of solid loading, was carried out using oxyacetylene torch testing. It was found that the composite containing the finer, Loughborough powders suffered a larger erosion volume than the composite with the coarser commercial powders indicating that the former offered worse ablation and oxidation resistance than the latter. A full investigation of the effect of solids loading and particle size, including the option of using mixtures of fine and coarse powders, is still required.
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Nelson, Tasha K. "A New All-Natural Wound Treatment Gel Shows Strong Inhibitory Activity Against Staphylococcus aureus and Other Wound Pathogens." Digital Commons @ East Tennessee State University, 2021. https://dc.etsu.edu/etd/3911.
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Skin related injuries are some of the most dangerous forms of wounds. In addition to treating the wound itself, health care providers must be cautious of microbial infections. In this study, we evaluate a novel all-natural antimicrobial gel compound (AMG) designed to kill planktonic bacteria, penetrate bacterial biofilms, and accelerate wound healing. In -vitro experiments demonstrate that AMG is effective in inhibiting planktonic growth and biofilm development of eight common pathogens. LIVE/DEAD staining and confocal microscopy reveal that planktonic growth and three-dimensional structure of biofilms were significantly reduced. Reverse Transcriptase Polymerase Chain Reaction (RT-PCR) was used to investigate a small panel of genes (PrsA, Sprx) and showed potential targets for future study. A physiologically relevant wound model was created for treating S. aureus infections by using AMG alone or in combination with a common topical antibiotic, Mupirocin. AMG is a safe and effective treatment option for skin related infection.
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Rosin, Ana Paula Marchi. "Avaliação do perfil clonal, resistência e virulência de isolados de Enterococci resistente à vancomicina em pacientes com doenças hematológicas ou submetidos a transplante de medula óssea." Universidade de São Paulo, 2017. http://www.teses.usp.br/teses/disponiveis/5/5134/tde-29012018-130636/.
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Introdução: Enterococcus resistente à vancomicina (VRE do inglês Vancomycin Resistant Enterococcus) é uma importante causa de infecção relacionada a assistência à saúde com alta morbidade e mortalidade principalmente nos pacientes imunocomprometidos sendo a segunda causa mais comum de infecções hospitalares nessa população de pacientes em alguns centros. O uso prolongado da terapia antimicrobiana com vancomicina e outras drogas, são fatores de risco associados com a disseminação desse patógeno. Além disso, espécies de enterococos podem apresentar fatores de virulência tais como: substância de agregação (asa1), gelatinase (gelE), citolisina (cylA), proteína de superfície enterococo (esp) e hidrolase glicosil (hylefm). Entretanto, o papel da virulência na colonização e infecção por VRE é controverso. Objetivos: Avaliar o perfil clonal, virulência e resistência de 86 isolados de VRE (80 E. faecium e 06 E. faecalis) de infecção e colonização de 76 pacientes com doenças hematológicas e/ou submetidos a transplante de Medula Óssea (TMO) internados no Hospital das Clínicas da Faculdade de Medicina da Universidade de São Paulo (HCFMUSP) no período de 10 anos (2005-2014). Material e Métodos: Foram realizadas concentração inibitória mínima para: vancomicina, teicoplanina, linezolida, gentamicina e estreptomicina em alta concentração (HLAR); Avaliação da clonalidade por eletroforese em campo pulsado (PFGE); Detecção dos mecanismos de resistência (vanA e vanB) e de virulência (esp, asa1, gelE, cylA e hylefm) pela técnica de PCR e sequenciamento total do genoma de dezoito isolados selecionados de acordo com a clonalidade. Foi criado um banco de dados no programa Epiinfo (CDC) com variáveis clinicas e demográficas dos pacientes. A proporção de isolados de colonização portadores de genes de virulência foi comparada com os isolados de infecção assim como a proporção de isolados de infecção portadores de genes de virulência que evoluíram para óbito. O valor de p < 0,005 foi considerado significativo. Resultados: Trinta e quatro pacientes eram colonizados e 42 infectados por VRE (28 eram infecção de corrente sanguínea), 48 pacientes eram transplantados dos quais 32 eram alogênicos. A mortalidade em 14 dias foi de 21.0% e durante a hospitalização de 53.9%. Todos os isolados foram resistentes à vancomicina e 87,3% à teicoplanina. Resistência a gentamicina e estreptomicina em alta concentração (HLAR) foi observada em 08 e 59 isolados respectivamente. Um isolado apresentou resistência a linezolida identificado pela primeira vez na unidade. O gene vanA foi detectado em todos os isolados. Quanto aos genes de virulência, 96,5% de isolados foram positivos para o gene esp e 69,8% para os genes gelE e asa1. Isolados de infecção de E. faecium carrearam mais genes de virulência: esp (100%), gelE (80,0%) e asa1 (75,5%) e o gene gelE foi significativamente mais frequente entre isolados de infecção que de colonização (p=0,008). Infecções causadas por isolados de E. faecium positivos para o gene asa1 foram significantemente associadas com maior mortalidade (p < 0,05). Quinze diferentes Pulsed field type (PFT) foram observados entre os isolados de E. faecium e 06 entre os isolados de E. faecalis. Dezessete E. faecium foram sequenciados e diferentes sequencias tipo (ST) foram observadas (ST412, ST478, ST78 e ST896) já descritas em outros estudos no Brasil. O isolado resistente a linezolida apresentou mutação no domínio V do gene 23S rRNA com um perfil alélico diferente, caracterizando um novo ST (ST987) descrito pela primeira vez no Brasil. Todos os ST observados nos isolados de E. faecium pertencem ao complexo clonal 17, dos quais dois STs (ST963, ST792) foram descritos pela primeira vez no país. O isolado de E. faecalis sequenciado pertencia ao ST9 e ao complexo clonal 9 já descrito por outros autores. Conclusão: Nosso estudo observou que E. faecium foi predominante em nosso hospital e os ST circulantes pertenciam ao CC17. Os isolados de infecção foram mais virulentos que os isolados de colonização e o gene gelE foi significativamente mais frequente nos isolados de infecção. Infecções causadas por isolados de E. faecium positivos para o gene asa1 foram associadas com a alta mortalidade. Este achado pode ser útil para controlar a disseminação de E. faecium no ambiente hospitalar e em pacientes hematológicosIntroduction: Vancomycin Resistant Enterococcus (VRE) is a important cause of health care-associated infection with high morbidity and mortality, mainly in immunocompromised patients, being the second most common cause of hospital infections in this population of patients in some centers. Prolonged use of antimicrobial therapy with vancomycin and other drugs are risk factors associated with the spread of this pathogen. In addition, enterococcal species may present virulence factors such as: aggregation substance (asa1), gelatinase (gelE), cytolysin (cylA), enterococcal surface protein (esp) and glycosyl hydrolase (hylefm). However, the role of virulence on VRE colonization and infection is controversial. Objectives: To evaluate the clonal profile, virulence and resistance of 86 isolates of VRE (80 E. faecium and 06 E. faecalis) from infection and colonization of 76 patients with hematological diseases and / or submitted to bone marrow transplantation (BMT) at Hospital das Clinics of the Medical School of the University of São Paulo (HC-FMUSP) in the period of 10 years (2005-2014). Material and Methods: Minimum inhibitory concentration to vancomycin, teicoplanin, linezolid, gentamicin and streptomycin in high concentration (HLAR) was performed; Clonality of isolates by pulsed field electrophoresis (PFGE) was evaluated; Detection of resistance (vanA and vanB) and virulence (esp, asa1, gelE, cylA and hylefm) genes by PCR technique and whole genome sequencing of eighteen isolates selected based on clonality. Results: All isolates were resistant to vancomycin and 87.3% to teicoplanin. Resistance to gentamicin and streptomycin in high concentration (HLAR) was observed in 08 and 59 isolates respectively. One isolate presented resistance to linezolid observed for the first time in the unit. The vanA gene was detected in all isolates. Regarding virulence genes, 96.5% of isolates were positive for the esp gene and 69.8% for the gelE and asa1 genes. Isolates of E. faecium infection carried more virulence genes: esp (100%), gelE (80.0%) and asa1 (75.5%) and gelE gene was significantly more frequent among infection isolates than colonization (p = 0.008). Infections caused by E. faecium isolates carrying the asa1 gene were significantly associated with higher mortality (p < 0.05). Fifteen different Pulsed field type (PFT) were observed among the isolates of E. faecium and 06 among E. faecalis isolates. Seventeen E. faecium were sequenced and the following sequences type (ST) were observed (ST412, ST478, ST78 and ST896) all of them already described in Brazil. The linezolid-resistant isolate showed the 23S gene Vdomain mutation with a different allelic profile, characterizing a new ST (ST987) described for the first time in our study. All STs observed in E. faecium isolates belong to clonal complex 17. Two other STs (ST963, ST792) were identified for the first time in the country. The E. faecalis isolate belong to ST9 and clonal complex 9 already described by other authors in Brazil. Conclusion: Our study observed that E. faecium was predominant in our hospital and the circulating STs belonged to CC17 a virulent lineage. E. faecium infection isolates were more virulent than colonization isolates and harbored significantly more gelE gene. It appears that infections caused by E. faecium isolates carrying asa1 gene evolved more frequently to death. This finding may be useful to control the spread of E. faecium in the hospital environment and in haematological patients
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Gao, Tongzhai. "Anticorrosive Organic/Inorganic Hybrid Coatings." University of Akron / OhioLINK, 2014. http://rave.ohiolink.edu/etdc/view?acc_num=akron1412775013.
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Coaker, Gitta Laurel. "Genetic and biochemical characterization of resistance to bacterial canker of tomato caused by Clavibacter michiganensis subsp. michiganensis." The Ohio State University, 2003. http://rave.ohiolink.edu/etdc/view?acc_num=osu1069188955.
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Box, Matthew. "Multiple-locus variable-number tandem-repeat analysis (MLVA) for clonal characterization of methicillin resistant Staphylococcus aureus strains." Thesis, Birmingham, Ala. : University of Alabama at Birmingham, 2006. https://www.mhsl.uab.edu/dt/2008r/box.pdf.
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Meinerz, Cristiane Claudia. "Indução de mecanismos bioquímicos de defesa em sorgo (Sorghum bicolor) por frações obtidas do decocto de avenca (Adiantum capillus-veneris)." Universidade Estadual do Oeste do Paraná, 2010. http://tede.unioeste.br:8080/tede/handle/tede/1413.
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Induction of resistance involves the activation of plant defense mechanisms in response to treatment with biotic or abiotic elicitors. The application of plant extracts in order to induce resistance mechanisms is an interesting alternative to chemical control, however, besides the presence of inducers, can occur the presence of suppressors. This study aimed to partially purificate through gel filtration chromatography (GFC) and precipitation with ammonium sulfate (SA), compounds present in decoct of Adiantum capillus-veneris, capable to induce defense mechanisms in sorghum mesocotyls, including phytoalexins and peroxidase, polyphenoloxidase (PPO), phenylalanine ammonia-lyase (PAL) and chitinase. The decoct 1% was fractionated with concentrations of ammonium sulfate, 0-20%, 20-40%, 40-60%, 60-80% and 80-100% of SA and those fractions were subjected to GFC. We obtained nine protein peaks and one glucosic peak for decoct with molecular weights ranging from 0.61 to 0.01 KDa; to fraction 0-20% were obtained two protein and two glucosic peaks, with molecular weights lower than 0.01 KDa, and concentration of sugars ranging from 4.1 to 17.5 mg mL-1; to fraction 20-40% were obtained three protein peaks (0.98 to 111.5 KDa) and five glucosic peaks (11.3 to 73.7 mg mL-1); to fraction 40-60% were obtained two protein peaks (0.09 to 111.5 KDa) and two glucosic peaks (5.6 to 7.5 mg mL-1); to fraction 60-80% were obtained six protein peaks (lower than 0.02 KDa) and two glucosic peaks (16.5 to 51.3 mg mL-1); and to fraction 80-100% were obtained three protein peaks (lower than 0.09 KDa). Sorghum mesocotyl were treated with fractions from the GFC, and decoct, acibenzolar-S-methyl (ASM) (125 mg L-1 of a. i. as elicitor of reference) and sodium phosphate buffer 10 mM pH 6.0. After incubation of 96 h were measured the levels of phytoalexins in mesocotyls and the activity of defense-related enzymes in leaves. Treatment with peak II (0,09 KDa) induced phytoalexin 6.68% more than. Among the fractionn, 60-80% increased 76% compared to ASM. To peroxidase the peak IV (lower than 0,01 KDa) increased 21% the activity compared to control water, and 44% compared to ASM. For the fraction 0-20% the protein peak II (lower than 0,01 KDa) increased 39% the activity in relation to the fraction 0-20% and 19% in relation to decoct. The fraction, 80-100% increased 89% compared to, ASM. For the PPO the peak VI (lower than 0,01 KDa) from decoct decreased 88% the activity compared to ASM. For PAL the peak II (lower than 0,01 KDa) from fraction 0-20% was 91% higher than decoct. For chitinase 1% peak IV (lower than 0,01 KDa) from decoct was 68% higher than the ASM. It was possible to induce defense mechanisms in sorghum by the application of partially purified fractions from A. capillus-veneris, which can allow to obtain new molecules and development alternative methods to control plant diseases
A indução de resistência envolve a ativação de mecanismos de defesa latentes existentes nas plantas em resposta ao tratamento com agentes bióticos ou abióticos. A aplicação de extratos vegetais visando à indução de mecanismos de resistência é uma alternativa interessante ao controle químico, entretanto, nestes extratos pode ocorrer além da presença de indutores, a presença de supressores. Este trabalho teve por objetivo a purificação parcial, por meio de cromatografia de filtração em gel (CFG) e precipitação com sulfato de amônio (SA), de compostos presentes em decocto de avenca (Adiantum capillus-veneris), eficientes na indução de mecanismos de defesa em mesocótilos de sorgo, incluindo as fitoalexina deoxiantocianidinas e as proteínas peroxidase, polifenoloxidase, fenilalanina amônia-liase e quitinase, buscando selecionar frações potencialmente eficientes na indução de resistência em plantas. Decocto (EA 1%) de A. capillus-veneris foi fracionado com concentrações de sulfato de amônio de 0-20%, 20-40%, 40-60%, 60-80% e 80-100% e esses cortes foram submetidos à cromatografia de filtração em gel (CFG). Foram obtidos nove picos protéicos e um pico glicídico para EA 1% com massas moleculares variando de 0,61 à 0,01 KDa; no corte 0-20% foram obtidos dois picos protéicos e dois glicídicos, com massas moleculares menores que 0,01 KDa, e concentração de açúcares redutores variando de 4,1 a 17,5 µg mL-1; no corte 20-40% três picos protéicos (111,5 à 0,98 KDa) e cinco glicídicos (11,3 a 73,7 µg mL-1 de açúcares); no corte 40-60% dois picos protéicos (111,5 à 0,09 KDa) e dois glicídicos (5,6 a 7,5 µg mL-1); no corte 60-80% seis picos protéicos (menor que 0,02 KDa) e dois glicídicos (16,5 a 51,3 µg mL-1); e no corte 80-100% três picos protéicos (menor que 0,09 KDa). Mesocótilos de sorgo foram tratados com as frações provenientes da CFG, além do decocto a 1%, acibenzolar-S-metil (ASM) (125 mg. L-1 do i.a. como elicitor de referência) e tampão fosfato de sódio 10 mM pH 6,0, totalizando 42 tratamentos. Após incubação por um período de 96 h, avaliou-se dos teores de fitoalexinas nos mesocótilos e análises bioquímicas dos folíolos. O tratamento pico II (0,09 KDa) do EA 1% mostrou-se eficiente na indução de fitoalexinas, sendo superior em 6,68% ao ASM. Entre os cortes, 60-80% permitiu incremento de 76% em relação ao ASM. Para peroxidase o pico IV (menor que 0,01 KDa) do EA 1% incrementou 21% a atividade em relação a testemunha água e 44% ao ASM. Para os precipitados 0-20% o pico protéico II (menor que 0,01 KDa) promoveu incremento de 39% na atividade em relação ao corte 0-20% e 19% para o EA 1%. O precipitado 80-100% foi superior 89% ao ASM. Para polifenoloxidase o pico protéico VI (menor que 0,01 KDa) do EA1% reduziu 88% a atividade em relação ao ASM. Para fenilalanina amônia-liase o pico protéico II (menor que 0,01 KDa) do corte 0-20% foi 91% superior ao EA 1%. Para quitinase o pico protéico IV (menor que 0,01 KDa) do EA 1% foi 68% superior ao ASM. Foi possível induzir mecanismos de defesa em sorgo pela aplicação de frações parcialmente purificadas de A. capillus-veneris, o que pode permitir a obtenção de novas moléculas e o desenvolvimento de métodos alternativos para controle de doenças em plantas
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Macalík, Michal. "Tenkovrstvé elektrody pro elektrochromní prvky." Doctoral thesis, Vysoké učení technické v Brně. Fakulta elektrotechniky a komunikačních technologií, 2009. http://www.nusl.cz/ntk/nusl-233501.
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The work deals with the deposition of layers for electrochromic device with different methods. Transparent electrically conductive layer of SnO2 was deposited by pyrolytic decomposition of peroxostannate solution. Hydrogen peroxide in starting solution contributes to the oxidation process of growth layers and to increase the electrical conductivity. Active electrochromic layer of WO3 was electrolytic deposited from the peroxotungstic acid solution. Optimal deposition time and the optimal annealing temperature of deposited layers were found. Passive electrochromic layer of V2O5 was deposited using dip-coating method from peroxovanadate solution. A contribution of solution diluted with distilled water was investigated. Found results were used to construct complete electrochromic device with polymer gel electrolyte.
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Wang, Dongxin. "Preparation and characterisation of transparent conducting oxides and thin films." Thesis, Loughborough University, 2010. https://dspace.lboro.ac.uk/2134/7042.
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Transparent conducting oxide (TCOs) thin films, including non-stoichiometric tin doped indium oxide (ITO) and aluminium doped zinc oxide (AZO), have found considerable applications in various displays, solar cells, and electrochromic devices, due to their unique combination of high electrical conductivity and optical transparency. TCO thin films are normally fabricated by sputtering, thermal vapour deposition and sol-gel method. Among them, sol-gel processing, which was employed in this project, is no doubt the simplest and cheapest processing method, The main objectives of this project were to produce indium tin oxides (ITO) and zinc aluminium oxides (AZO) nanoparticles with controlled particle size and morphology and to fabricate TCO thin films with high optical transmittance and electrical conductivity. In this research, hydrothermal method was used to synthesise ITO and AZO nanoparticles. Tin oxides, zinc oxides, ITO and AZO particles with the particle size ranging from 10 nm to several micrometers and different morphologies were synthesised through controlling the starting salts, alkaline solvents and hydrothermal treatment conditions. ITO and AZO thin films were fabricated via sol-gel technique through dip coating method. The effects of the starting salts, alkaline solvents, surfactant additives and coating and calcination conditions on the formation of thin films were investigated. XRD, TEM, FEG-SEM, DSC-TGA, UV-Vis spectrometer and four-point probe resistance meter were used to characterise the crystallinity, particle size, morphology, optical transmittance and sheet resistance of the particles and thin films. Crack-free thin films with high optical transmittance (>80% at 550 nm) and low sheet resistances (2.11 kΩ for ITO and 26.4 kΩ for AZO) were obtained in optimised processing conditions.
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Valmary, Laurence. "Phénotypes de résistance aux bêta-lactamines des souches de "Klebsiella" isolées dans un hôpital de long et moyen séjour : différenciation des souches résistantes par analyse du polymorphisme enzymatique." Paris 5, 1994. http://www.theses.fr/1994PA05P147.
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Iurkiv, Luciana. "Purificação parcial de compostos biologicamente ativos a partir de Pycnoporus sanguineus para o controle de ferrugem asiática em soja." Universidade Estadual do Oeste do Paraná, 2009. http://tede.unioeste.br:8080/tede/handle/tede/1343.
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Previous issue date: 2009-02-04Coordenação de Aperfeiçoamento de Pessoal de Nível Superior
Induced resistance involves the activation of latent defense mechanisms in plants in response to the treatment with biotic or abiotic agents. The use of crude extracts aimed at inducing resistance mechanisms is an interesting alternative to chemical control, however, in this extracts can occurs besides de presence of inducers, the presence of suppressors. This work objectived a partial purification, through gel filtration chromatography (GFC) and by ammonium sulphate (AS) precipitation, of compounds in basidiocarps crude extracts from Pycnoporus sanguineus efficient to the control of Asian rust in soybean by induction of resistance. Crude extracts from P. sanguineus were submited to gel filtration chromatography (GFC), and five proteins and one carbohydrate peaks were obtained, with molecular weight ranging from 1,82 to 5,18 KDa. It was made the fractionated protein purification from 100 mL of crude extract from P. sanguineus. The fractions obtained were: 0-20%, 20-40%, 40-60%, 60-80% and 80-100% of ammonium sulphate. Incised soybean cotyledons were treated with fractions from GFC and AS precipitation, crude extract 20% (EB 20%), Saccharomyces cerevisiae (25 mg mL-1) and water. After incubation during 20 h, was made biochemical analyses to verify the phytoalexins content and peroxidases, polyphenoloxidases, β-1,3 glucanases and phenylalanine ammonia-lyase activities. The treatments from GFC, protein fractions III (3,44 KDa), IV (2,79 KDa) and V (1,82 KDa), and carbohydrate fraction, fractions 40-60%, 60-80% and 80-100%, obtained by ammonium sulphate precipitation, crude extract (CE) of basidiocarps at 20%, besides control treatments fungicide (tebuconazole, 0,5 g a.i. L-1) and water were used to evaluate the antimicrobial activity and induction of resistance in soybean against P. pacchirhizi in greenhouse. Soybean plants were treated and after three days were inoculated with the pathogen. Samples were collected 0, 1, 3, 6 and 9 days after the treatment for biochemical analyses and the severity was evaluated after 13 days. The data referring to evaluation of antimicrobial activity show that the fractions do not have inhibiting activity of germination of spores. As for severity, the treatments protein fraction III and CE 20% were efficient in the reduction of the number of injuries for cm2. For peroxidase the CE 20% presented tendency in reducing the enzymatic activity. Chitinases and polifenoloxidases did not presented statistical differences between the treatments. For β-1,3 glucanases there was local induction for the treatments with glicide fraction and protein fractions III and V, and fractions 40-60% and 60-80%, while CE 20% presented systemic induction for this enzyme. For phenylalanine ammonia-lyase the purified fractions of P. sanguineus reduced the enzymatic activity, except for CE 20%. It was possible to induce defense mechanisms in soybean against P. pachyrhizi for the application of partially purified fractions from P. sanguineus, indicating its possible use as an alternative method for controling this pathogen
A indução de resistência envolve a ativação de mecanismos de defesa latentes existentes nas plantas em resposta ao tratamento com agentes bióticos ou abióticos. A aplicação de extratos brutos visando à indução de mecanismos de resistência é uma alternativa interessante ao controle químico, entretanto, nestes extratos pode ocorrer além da presença de indutores, a presença de supressores. Este trabalho teve por objetivo a purificação parcial, por meio de cromatografia de filtração em gel (CFG) e precipitação com sulfato de amônio (SA), de compostos presentes em extrato bruto de Pycnoporus sanguineus, eficientes no controle de ferrugem asiática em soja por indução de resistência. Extrato bruto de P. sanguineus foi submetido à cromatografia de filtração em gel, sendo obtidos cinco picos protéicos e um pico glícido, com pesos moleculares variando de 1,82 a 5,18 KDa. Foi efetuada a precipitação fracionada das proteínas presentes em 100 mL de extrato bruto de basidiocarpos de P. sanguineus. As frações obtidas foram: 0-20%, 20-40%, 40-60%, 60-80% e 80-100% de SA. Cotilédones de soja incisados foram tratados com as frações provenientes da CFG e precipitação com SA, além dos tratamentos extrato bruto a 20% (EB 20%), Saccharomyces cerevisiae (25 mg mL-1) e água. Após incubação pelo período de 20 h efetuou-se análises bioquímicas dos cotilédones para verificar os teores de fitoalexinas, peroxidases, polifenoloxidases, β-1,3 glucanases e fenilalanina amônia-liase. Os tratamentos obtidos por CFG frações protéicas III (3,44 KDa), IV (2,79 KDa) e V (1,82 KDa), e glícida, além das frações 40-60, 60-80 e 80-100% obtidos por saturação com SA foram selecionados para avaliação de atividade antimicrobiana e de indução de resistência em soja contra P. pacchirhizi em casa de vegetação, utilizou-se também extrato bruto (EB) 20% de basidiocarpo de P. sanguineus e as testemunhas fungicida tebuconazole (0,5 g i.a. L-1) e água. Visando avaliar o controle da doença ferrugem asiática e indução de enzimas relacionadas à defesa, montou-se ensaio em casa de vegetação onde plantas foram tratadas e após três dias inoculadas com o patógeno. Amostras foram coletadas 0, 1, 3, 6 e 9 dias após os tratamentos para análises bioquímicas e a severidade foi avaliada após 13 dias. Os dados referentes à avaliação de atividade antimicrobiana mostram que as frações não possuem atividade inibidora da geminação de esporos. Quanto à severidade, a fração III e o EB 20% foram eficientes na redução do número de lesões por cm2. Para peroxidases, o EB 20% apresentou tendência em reduzir a atividade enzimática. Quitinases e polifenoloxidases não apresentaram diferenças estatísticas entre os tratamentos. Para β-1,3 glucanases houve indução local pelas frações glícida e protéicas III e V, e pelas frações 40-60% e 60-80% em relação ao EB 20%, sendo que o mesmo apresentou indução sistêmica para essa enzima. Para fenilalaniana amônia-liase as frações purificadas de P. sanguineus apresentaram tendência em reduzir a atividade enzimática, com exceção para EB 20%. Foi possível induzir mecanismos de defesa em soja contra P. pachyrhizi pela aplicação de frações parcialmente purificadas de P. sanguineus, o que pode permitir o desenvolvimento de métodos alternativos para controle desse patógeno
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Trevisoli, Edilaine Della Valentina Gonçalves. "Purificação de eliciadores de defesa vegetal em soja e feijoeiro a partir de nematoides fitopatogênicos." Universidade Estadual do Oeste do Paraná, 2016. http://tede.unioeste.br:8080/tede/handle/tede/1475.
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Previous issue date: 2016-02-25Coordenação de Aperfeiçoamento de Pessoal de Nível Superior
The induction of resistance in plants to pathogens is an alternative method of disease control, wich involves activation of plant resistance mechanisms such as induction of phytoalexins. The elicitors molecules are able to induce and activate those responses, and therefore, techniques have sought to isolate and characterize fractions with elicitor character. The study aimed to purify, through ion exchange chromatography and gel filtration chromatography, eliciting molecules from pathogenic nematodes, and test them in phaseolin induction in beans hypocotyls beans and gliceolin in soybean cotyledons. The buffer solution Tris HCl 0.05 M (pH 6.8) was used as control and the acibenzolar-S-methyl (50 mg a.i. L-1) and Saccharomyces cerevisiae (20 mg mL-1) were used as induction standard treatments. Ion exchange chromatography (IEC) and gel filtration chromatography (GC) were performed to separate fractions with eliciting power from 500 female nematodes of Meloidogyne incognita and Meloidogyne javanica. For purification of elicitors from Meloidogyne javanica, through IEC, six glycidic fractions and six glycoproteins were obtained. These were purified on GC, obtaining sixty-three fractions. They have been classified according to their nature, as twenty-six glycidic and thirty-seven glycoprotein with molecular weights ranging from 29.19 to 2989.25 kDa. Regarding the elicitors purification of Meloidogyne incognita through IEC, nine glycidic and five glycoprotein fractions were obtained. From these fractions, a total of fifty-eight fractions was obtained through GC, twenty-five glycidic and thirty-three glycoprotein with molecular weights ranging from 37.42 to 200.32 kDa. From the fractions purified from Meloidogyne javanica eight had inducing potential of phaseolin. For gliceolin fifteen fractions showed inducing effect. Regarding the fractions purified from Meloidogyne incognita, no fraction has inductive potential of phaseolin superior to the standard treatment. However, twenty-two fractions suppressed phytoalexin inducing activity. For gliceolin ten fractions induced the same, whereas, twenty-three fractions suppressed the induction of gliceolin. Chromatography was efficient in the purification of elicitors compounds. Compounds with suppressing characteristics of gliceolin and phaseolin were checked in bioassays. For those fractions obtained through IEC, and then submitted to GC that did not induce phytoalexin, it is suggested that molecules need to act together to have elicitor effect and thus induce defense response in the plant
A indução de resistência em plantas contra patógenos é um método de controle alternativo de doenças, e que envolve a ativação dos mecanismos de resistência da planta, como a indução de fitoalexinas. As moléculas eliciadoras possuem a capacidade de induzir e ativar tais repostas, e assim sendo, técnicas têm buscado isolar e caracterizar frações com caráter eliciador. O trabalho teve por objetivo purificar, por cromatografia de troca iônica cromatografia de filtração em gel, moléculas eliciadoras a partir de nematoides fitopatogênicos, e testá-las na indução de faseolina em hipocótilos de feijoeiro e gliceolina em cotilédones de soja. O tampão Tris HCl 0,05 M (pH 6,8) foi utilizado como tratamento controle e o acibenzolar-S-metil (50 mg i.a. L-1) e o Saccharomyces cerevisiae (20 mg mL-1) foram utilizados como tratamento padrão de indução. Cromatografia de troca iônica (CTI) e cromatografia de filtração em gel (CFG) foram realizadas para separar frações com poder eliciador a partir de quinhentas fêmeas de nematoides de Meloidogyne incognita e Meloidogyne javanica. Para a purificação de eliciadores a patir de Meloidogyne javanica, por CTI, foram obtidos seis frações glicídicas e seis glicoproteicas. Estas, por sua vez, foram purificadas em CFG, sendo obtidos no total sessenta e três frações. As mesmas foram classificadas de acordo com sua natureza, sendo vinte e seis glicídicas e trinta e sete glicoproteicas, com massas moleculares variando de 29,19 a 2.989,25 kDa. Em relação a purificação de eliciadores de Meloidogyne incognita por CTI, foram obtidos nove frações glicídicas e cinco glicoproteicas. A partir destas, foram obtidos por CFG um total de cinquenta e oito frações, sendo vinte e cinco glicídicas e trinta e três glicoproteicas, com massas moleculares variando de 37,42 a 200,32 kDa. Das frações purificadas a partir de Meloidogyne javanica oito apresentaram potencial indutor de faseolina. Para gliceolina quinze frações mostraram efeito indutor. Em relação as frações purificadas a partir de Meloidogyne incognita, nenhuma fração apresentou potencial indutor de faseolina superior ao tratamento padrão. Entretanto, vinte e duas frações suprimiram a atividade de indução de fitoalexina. Para gliceolina dez frações induziram a mesma, enquanto que, vinte e três frações suprimiram a indução da gliceolina. A cromatografia foi eficiente na purificação de compostos eliciadores. Compostos com características supressoras de gliceolina e faseolina foram verificadas nos bioensaios. Para aquelas frações obtidas por CTI e posteriormente submetidas a CFG que não induziram fitoalexina, sugere-se que as moléculas necessitam atuar juntas para haver efeito eliciador e assim induzir a resposta de defesa no vegetal
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Hossain, Mir Ashad. "Does SABP2 Exist As a Dimer?" Digital Commons @ East Tennessee State University, 2011. https://dc.etsu.edu/etd/2255.
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Salicylic acid binding protein 2 (SABP2) is one of the key enzymes in salicylic acid-dependent plant defense pathway. SABP2 is a 29 kDa protein present in extremely low abundance in plants and it catalyzes the conversion of signaling molecule methyl salicylate into salicylic acid. Although it has been shown that 6x His-tagged SABP2 over expressed in E. coli is a homodimer, its exact conformation in planta is still unknown. Therefore, we proposed to determine if SABP2 exist as a dimer and/or monomer under natural condition. To verify the exact conformation of native SABP2 protein in plant, SABP2 was purified from wild type tobacco using a 5-step purification protocol. Analysis of purified SABP2 in gel filtration and immunoblot assay suggested that SABP2 exists as a monomer in tobacco plant. Studies on SABP2 conformation will give us insight into the structure and functional relationship of this protein in salicylic acid-dependent disease resistance pathway.
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Khan, Ghazanfar Ali. "Monitoring anti-infectives and antibiotic resistance genes : with focus on analytical method development, effects of antibiotics and national perspectives." Doctoral thesis, Umeå universitet, Kemiska institutionen, 2012. http://urn.kb.se/resolve?urn=urn:nbn:se:umu:diva-61682.
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Antibiotics are biologically active and are globally used in humans and animal medicine for treatment and in sub-therapeutic amounts as growth promoters in animal husbandry, aquaculture and agriculture. After excretion, inappropriate disposal and discharge from drug production facilities they enter into water bodies either as intact drugs, metabolites or transformed products. In water environments they promote development of antibiotic resistance genes (ARGs) which could serve as a reservoir and be horizontally transferred to human-associated bacteria and thus contribute to AR proliferation. Measurement of antibiotics has been revolutionized with the usage of solid phase extraction (SPE) for enrichment followed by Liquid chromatography mass spectrometry (LC-MS). On-line SPE coupled to LC-MS/MS has the advantages of high sample throughput, low sample preparation time and minimal solvent utilization. Constructed wetlands (CWs) are potential alternatives to conventional treatment plants to remove organic pollutants. A study at Plönninge, Halmstad was performed to assess the impact of bacterial community pattern and development of resistance in spiked (n=4) and control (n=4). CWs were spiked with antibiotics at environmentally relevant concentrations continuously for 25 days. Shannon Index (H’) were used to determine the bacterial diversity and real-time PCR detected and quantified antibiotic resistance genes (ARGs) sulI, tetA, tetB, erm, dfrA1, qnrS and vanB and class 1 integrons intI1. No significant differences in bacterial compositions or in ARGs or integron concentrations could be discerned between exposed and control wetlands. A study conducted in Northern Pakistan showed that the antibiotic levels in most studied rivers were comparable to surface water measurements in unpolluted sites in Europe and the US. However, high levels of antibiotics were detected in the river in close vicinity of the 10 million city Lahore, e.g. 4600 ng L−1 sulfamethoxazole. Highest detected levels were at one of the drug formulation facilities, with measured levels up to 49000 ng L−1 of sulfamethoxazole for example. The highest levels of ARGs detected, sul1 and dfrA1, were directly associated with the antibiotics detected at the highest concentrations, sulfamethoxazole and trimethoprim. In the study in UK, sewage epidemiology surveillance is used to measure the oseltamivir carboxylate (OC), metabolite of oseltamivir (parent drug) in twenty four time proportional hourly influent samples from two WWTPs and then back-calculations were made to assess the compliance of drug. Predicted users of oseltamivir, based on measured OC in waste water, ranged from 3-4 and 120-154 people for the two WWTP catchments, respectively, which are consistent with the projected use from national antiviral allocation statistics, 3-8 and 108-270, respectively. Scenario analysis suggests compliance was likely between 45-60% in the study regions.
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Widerström, Micael. "Molecular epidemiology of coagulase-negative staphylococci in hospitals and in the community." Doctoral thesis, Umeå universitet, Klinisk bakteriologi, 2010. http://urn.kb.se/resolve?urn=urn:nbn:se:umu:diva-34289.
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Background Coagulase-negative staphylococci (CoNS) and in particular Staphylococcus epidermidis have emerged as major pathogens primarily causing nosocomial infections in patients with indwelling medical devices. These infections are often caused by multidrug-resistant strains of S. epidermidis (MDRSE). Other clinical entities due to CoNS are lower urinary tract infections (UTI) in women and native valve endocarditis. The purpose of this work was to investigate the frequency of antibiotic resistance and the molecular epidemiology of both hospital and community-associated isolates of S. epidermidis in order to examine if certain clones are related to MDRSE infections. Furthermore, we aimed to explore if specific clones of S. saprophyticus are associated with UTI in women. Methods A total of 359 hospital-associated methicillin-resistant isolates of CoNS obtained from 11 hospitals in northern Europe and 223 community-associated staphylococcal isolates were examined. Furthermore, 126 isolates of S. saprophyticus isolated from women with uncomplicated UTI from five different locations in northern Europe were analyzed. Pulsed-field gel electrophoresis (PFGE) was used for genotyping. Additionally, some of the S. epidermidis isolates were analyzed with multilocus sequence typing (MLST). Antibiotic susceptibility was determined for all isolates by the disc diffusion test. Results 293 of the 359 (82%) hospital-associated and 124 of the 223 (56%) community-associated isolates belonged to the species S. epidermidis. Among the hospital-associated S. epidermidis isolates, two dominating PFGE types (type A and B) were distinguished, comprising 78 (27%) and 51 (17%) isolates, respectively. Type A, which was detected in a Norwegian and eight Swedish hospitals, corresponded with a novel sequence type (ST215). Type B was discovered in a German, a Danish and seven Swedish hospitals and corresponded with ST2. In contrast, community-associated isolates of S. epidermidis were genetically extremely diverse with no predominating genotype, and showed a low rate of antibiotic resistance; only two (1.6%) methicillin-resistant strains were detected. Among 126 analyzed isolates of S. saprophyticus, 47 different PFGE profiles were identified. Several clusters of genetically highly related isolates were detected among isolates obtained from different locations and periods of time. Conclusion We have demonstrated the occurrence, persistence and potential dissemination of two multidrug-resistant S. epidermidis (MDRSE) genotypes, including a novel sequence type (ST215), within hospitals in northern Europe. Community-associated isolates of S. epidermidis showed a low rate of methicillin-resistance and were genetically heterogeneous. These results indicate that MDRSE by large are confined to the hospital setting in our region. Moreover, although the S. saprophyticus population was quite heterogeneous, indistinguishable isolates of S. saprophyticus causing lower UTI in women were identified in different countries 11 years apart, indicating the persistence and geographical spread of some clones of S. saprophyticus.
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Parry, Glenn Charles. "Scratch resistant coatings produced by sol-gel techniques." Thesis, University of Cambridge, 2001. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.620938.
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Guinchard, Marie-Pierre. "Comportement hivernal du trèfle blanc (Trifolium repens l. ) : morphogénèse et rôle des composés carbonés." Vandoeuvre-les-Nancy, INPL, 1995. http://docnum.univ-lorraine.fr/public/INPL_T_1995_GUINCHARD_M_P.pdf.
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La pérennité du trèfle blanc (Trifolium repens l. ) est en partie conditionnée par sa survie hivernale et sa reprise printanière. L’objectif du présent travail est de déterminer les effets des basses températures sur la morphogénèse et sur l'évolution des réserves carbonées du trèfle blanc. Des suivis expérimentaux réalisés en plein champ montrent que la morphogénèse du trèfle est principalement sous la dépendance de la température et notamment de l'indice actinothermique. Des réserves carbonées (amidon et sucres solubles) sont accumulées dans les stolons, les racines et les feuilles, caractérisant un endurcissement de la plante aux basses températures. Les plus fortes mortalités foliaires observées pendant l'hiver sont dues aux alternances rapides de gels et dégels, notamment en début d'hiver et qui conduisent à une forte consommation de l'amidon stocké dans les stolons. Des gels simulés en conditions contrôlées induisent une déshydratation des plantes, moins forte chez les plantes endurcies. En réponse aux basses températures positives, on observe une accumulation de solutés dans les cellules, conduisant à un ajustement osmotique. Les sucres solubles contribuent pour 20 à 30% à cet ajustement osmotique, indiquant que des composés autre que les sucres interviennent. Une comparaison variétale montre que dans nos conditions expérimentales, Aberherald présente un taux d'émission des feuilles identique à Huia. Le meilleur rendement en matière sèche de Aberherald observé au champ à la première coupe est du à des feuilles plus grosses, des pétioles et des stolons plus longs et plus épais. Ainsi Aberherald possède une valeur adaptative au froid supérieure à Huia. En période hivernale et printanière, les réserves carbonées ne limitent pas le taux d'émission des feuilles mais influencent la croissance des organes émis. Les réponses de la plante au froid concernant la morphogénèse et les réserves carbonées sont discutées en termes de mécanismes de tolérance, de résistance et d'adaptation
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Grundwürmer, Matthias. "Development and characterisation of liquid impact resistant sol-gel coatings." Düsseldorf VDI-Verl, 2008. http://d-nb.info/990760251/04.
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Li, Chenghong. "Inorganic-Organic Sol-Gel Derived Hybrid Materials as Abrasion Resistant Coatings." Diss., Virginia Tech, 1999. http://hdl.handle.net/10919/39013.
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Inorganic-organic hybrid materials have been developed using sol-gel reactions of a trialkoxysilylated organic compound and a metal or semi-metal alkoxide and applied as coatings on polymeric or metallic substrates. Many of these coatings have demonstrated good to excellent abrasion resistance.
Abrasion resistant coatings were prepared by hydrolysis and condensation of mixtures of a triethoxysilylated diethylenetriamine (f-DETA), tetramethoxysilane (TMOS), water and an alcohol in the presence of an acid catalyst (a one-step hydrolysis approach). The influences of many formulation and processing variables on the gelation time, optical properties, hardness and abrasion resistance were investigated. An aminolysis mechanism was also proposed to explain the adhesion between sol-gel derived coatings and polycarbonate substrates promoted by a 3-aminopropyltriethoxysilane (3-APS) primer. FT-IR, GPC, 1H and 13C NMR, XPS experiments were conducted to support this mechanism.
The f-DETA/TMOS system is essentially a binary system of an alkyltriethoxysilane (T) and a tetraalkoxysilane (Q). At pH 0-2 and pH 4-5, the relative condensation reactivities of the T and Q species in this system were compared using 29Si NMR spectroscopy. After thermal curing, 13C or 29Si solid state NMR spectroscopy was used to estimate the extent of hydrolysis of the urea linkages in f-DETA, the concentration of residual alkoxysilane groups, and the extent of condensation for both T and Q species. The dependence of the morphology of f-DETA/TMOS gels on the pH and the water concentration was also investigated using AFM, SEM and SAXS.
Many other trialkoxysilylated organic compounds containing urea, urethane, epoxy and siloxane linkages were also synthesized and utilized to prepare abrasion resistant coatings via a one-step hydrolysis approach, a two-step hydrolysis approach or a moisture-curing approach. Coatings derived from many of these systems or approaches demonstrated abrasion resistance comparable to that of the f-DETA/TMOS coating. Thin coatings were also derived from cubic octasilicate monomers via hydrosilylation or sol-gel reactions. These coatings were very transparent but unfortunately lacked abrasion resistance.Ph. D.
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Jordens, Kurt. "Hybrid Inorganic-Organic Materials: Novel Poly(Propylene Oxide) Based Ceramers, Abrasion Resistant Sol-Gel Coatings for Metals, and Epoxy-Clay Nanocomposites. With an Additional Chapter On: Metallocene Catalyzed Linear Polyethylene." Diss., Virginia Tech, 1999. http://hdl.handle.net/10919/30194.
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The sol-gel process has been employed to generate hybrid inorganic-organic network materials. Unique ceramers were prepared based on an alkoxysilane functionalized soft organic oligomer, poly(propylene oxide) (PPO), and tetramethoxysilane (TMOS). Despite the formation of covalent bonds between the inorganic and organic constituents, the resulting network materials were phase separated, composed of a silicate rich phase embedded in a matrix of the organic oligomer chains. The behavior of such materials was similar to elastomers containing a reinforcing filler. The study focused on the influence of initial oligomer molecular weight, functionality, and tetramethoxysilane, water, and acid catalyst content on the final structure, mechanical and thermal properties. The sol-gel approach has also been exploited to generate thin, transparent, abrasion resistant coatings for metal substrates. These systems were based on alkoxysilane functionazized diethylenetriamine (DETA) with TMOS, which generated hybrid networks with very high crosslink densities. These materials were applied with great success as abrasion resistant coatings to aluminum, copper, brass, and stainless steel. In another study, intercalated polymer-clay nanocomposites were prepared based on various epoxy networks montmorillonite clay. This work explored the influence of incorporated clay on the adhesive properties of the epoxies. The lap shear strength decreased with increasing clay content. This was due to a reduction in the toughness of the epoxy. Also, the delaminated (or exfoliated) nanocomposite structure could not be generated. Instead, all nanocomposite systems possessed an intercalated structure.
The final project involved the characterization of a series of metallocene catalyzed linear polyethylenes, produced at Phillips Petroleum. Polyolefins synthesized with such new catalyst systems are becoming widely available. The influence of molecular weight and thermal treatment on the mechanical, rheological, and thermal behavior was probed. Although the behavior of this series of metallocene polyethylenes was not unlike that of traditionally catalyzed materials, this work is one of the first comprehensive studies of these new linear polyethylenes. The main distinction between the metallocene and traditional Ziegler-Natta catalyzed polyethylenes is the narrow molecular weight distributions produced by the former (for this series of materials, 2.3< Mw  Mn <3.6).Ph. D.
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Wang, Lin. "Mass Transfer and GDL Electric Resistance in PEM Fuel Cells." Scholarly Repository, 2010. http://scholarlyrepository.miami.edu/oa_dissertations/486.
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Many modeling studies have been carried out to simulate the current distribution across the channel and shoulder direction in a proton exchange membrane (PEM) fuel cell. However the modeling results do not show agreement on the current density distribution. At the same time, no experimental measurement result of current density distribution across the channel and the shoulder direction is available to testify the modeling studies. Hence in this work, an experiment was conducted to separately measure the current densities under the channel and the shoulder in a PEM fuel cell by using the specially designed membrane electrode assemblies. The experimental results show that the current density under the channel is lower than that under the shoulder except when the fuel cell load is high. Afterwards two more experiments were carried out to find out the reason causing the higher current density under the shoulder. The effects of the electric resistance of gas diffusion layer (GDL) in the lateral and through-plane directions on the current density distribution were studied respectively. The experimental results show that it is the through-plane electric resistance that leads to the higher current density under the shoulder. Moreover, a three-dimensional fuel cell model is developed using FORTRAN. A new method of combining the thin-film model and homogeneous model is utilized to model the catalyst layer. The model is validated by the experimental data. The distribution of current density, oxygen concentration, membrane phase potential, solid phase potential and overpotential in a PEM fuel cell have been studied by the model. The modeling results show that the new modeling method provides better simulations to the actual transport processes and chemical reaction in the catalyst layer of a PEM fuel cell.
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Betrabet, Chinmay Suresh. "Inorganic-organic hybrid materials and abrasion resistant coatings based on a sol-gel approach." Diss., Virginia Tech, 1993. http://hdl.handle.net/10919/40188.
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Novel inorganic-organic hybrid materials made previously in the laboratory have
utilized acids catalysts such as HCI, acetic acid, toluene sulfonic acid and polystyrene sulfonic acid to catalyze the sol-gel reaction. The sol-gel reaction can also be catalyzed under near neutral (i.e. 5 < pH < 7) and basic conditions. The effects of synthesizing hybrid materials under near basic and basic conditions has not been studied.
Attempts to synthesize hybrid materials from polytetramethylene oxide (PTMO) end functionalized with triethoxy silyl groups and, tetraethylorthosilicate (TEOS) under basic conditions met with only partial success. The films obtained had low mechanical stability. This was attributed to the low reactivity of the triethoxy species under neutral and basic conditions. In contrast, films with good mechanical stability were obtained when the TEOS was replaced with titanium tetraisopropoxide (TIOPR). The microstructure of the TIOPRlPTMO hybrid synthesized under near neutral conditions was generally similar to the acid catalyzed PTMOffIOPR hybrids.Ph. D.
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Schwartz, Anne. "Characterization of normal and androgen resistant-genital skin fibroblasts using high-resolution two-dimensional gel electrophoresis." Thesis, McGill University, 1985. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=63378.
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O'Neill, Michelle. "A role for lipoxygenase in stress responses in Pisum sativum L." Thesis, University of East Anglia, 1997. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.389268.
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Rajamani, Deepika. "Processing and Properties of Environmentally-Friendly Corrosion Resistant Hybrid Nanocomposite Coatings for Aluminum Alloy AA2024." University of Cincinnati / OhioLINK, 2006. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1138811300.
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Gebeyehu, Setegn. "Physiological response to drought stress of common bean (Phaseolus vulgaris L.) genotypes differing in drought resistance." Göttingen Cuvillier, 2006. http://geb.uni-giessen.de/geb/volltexte/2006/3726/index.html.
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Cox, Ryan Yinghua. "Development of a Humidity-Resistant Coating to Impart High Oxygen Barrier Performance to Food Packaging Films." DigitalCommons@CalPoly, 2017. https://digitalcommons.calpoly.edu/theses/1764.
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Oxygen barrier coatings have the potential to greatly extend the lifetime of certain food products by incorporating them into existing food packaging. Present technologies face definite challenges of maintaining high performance, while attaining simple and inexpensive preparation methods. The oxygen barrier effect obtained with these coatings is also susceptible to a plasticization effect when exposed to high humidity, since water vapor molecules are readily soluble in typically hydrophilic resins. In this work, we demonstrate a 1 – 2 micron thick oxygen barrier coating, prepared on a 12 micron poly(ethylene terephthalate) substrate, that has oxygen transmission rates as low as 1.44 cc m-2 day-1 under standard conditions and can maintain similar oxygen barrier performance at high humidity. This degree of oxygen barrier meets the standard of 1 – 10 cc m-2 day-1 established for food packaging applications. The coating is prepared through use of sol-gel chemistry between poly(vinyl alcohol) and vinyltrimethoxsilane molecules, which form a strong network resin through hydrolysis and condensation reactions. The formulation of these oxygen barrier coatings allows for variability of solids percentage and viscosity without significant change in performance. The ability to scale up the preparation of these coated films was tested successfully on an industrial flexographic printing press.
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Pereira, Luís Filipe Mendes. "As diferentes modalidades da crioterapia e os seus efeitos na resistência passiva muscular." Bachelor's thesis, [s.n.], 2011. http://hdl.handle.net/10284/2869.
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Trabalho apresentado à Universidade Fernando Pessoa como parte dos requisitos para obtenção do grau de Licenciado em FisioterapiaObjectivo: A aplicação de crioterapia no tratamento de lesões faz parte do quotidiano dos fisioterapeutas e desportistas. Apesar do seu efeito analgésico e anti-inflamatório ser consensual, existe actualmente pouca informação relativamente ao seu efeito ao nível das propriedades visco-elásticas do tecido muscular. Deste modo, este estudo pretende analisar as diferentes modalidades da crioterapia e os seus efeitos, bem como o efeito da crioterapia na resistência passiva muscular. Método: Foi realizada uma revisão da literatura na B-On através da Medline, Pubmed, Scielo e EBSCO e no Google Scholar. Resultados: Após a análise dos estudos seleccionados verificou-se os métodos de crioterapia mais utilizados, nomeadamente o gelo picado, compressas de gelo, pacotes de gel congelado e imersão em água fria. Contudo nem todos os estudos apresentaram efeitos significativos na resistência passiva muscular após a crioterapia. Conclusão: O presente estudo, sugere que os efeitos agudos após a aplicação de crioterapia não produz alteração na resistência passiva muscular, devido à rigidez, embora os seus efeitos analgésicos e a rápida recuperação da função neuromuscular sejam comprovados. Objective: The application of cryotherapy in the treatment of injuries is part of everyday physical therapists and sports. Despite its analgesic and anti-inflammatory to be consensual, there is currently little information on the effect in terms of visco-elastic properties of muscle tissue. Therefore, this study aims to analyze the different forms of cryotherapy and its effects, as well as the effect of cryotherapy on muscle passive resistance. Method: We performed a literature review on the B-On through the Medline, Pubmed, Scielo and EBSCO and Google Scholar. Results: After analysis of selected studies it was found the most commonly used methods of cryotherapy, including the crushed ice, ice packs, frozen gel packs and immersion in cold water. However not all studies showed a significant effect on passive muscle strength after cryotherapy. Conclusions: This study suggests that the acute effects after application of cryotherapy produces no change in muscle passive resistance due to stiffness, although their analgesic effects and rapid recovery of neuromuscular function are proven.
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Caston, Terry Brett. "Design of a gas diffusion layer for a polymer electrolyte membrane fuel cell with a graduated resistance to flow." Thesis, Georgia Institute of Technology, 2010. http://hdl.handle.net/1853/34790.
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Due to escalating energy costs and limited fossil fuel resources, much attention has been given to polymer electrolyte membrane (PEM) fuel cells. Gas diffusion layers (GDLs) play a vital role in a fuel cell such as (1) water removal, (2) cooling, (3) structural backing, (4) electrical conduction and (5) transporting gases towards the active catalyst sites where the reactions take place. The power density of a PEM fuel cell in part is dependent upon how uniform the gases are distributed to the active sites. To this end, research is being conducted to understand the mechanisms that influence gas distribution across the fuel cell. Emerging PEM fuel cell designs have shown that higher power density can be achieved; however this requires significant changes to existing components, particularly the GDL. For instance, some emerging concepts require higher through-plane gas permeability than in-plane gas permeability (i.e., anisotropic resistance) which is contrary to conventional GDLs (e.g., carbon paper and carbon cloth), to obtain a uniform gas distribution across the active sites. This is the foundation on which this thesis is centered. A numerical study is conducted in order to investigate the effect of the gas permeability profile on the expected current density in the catalyst layer. An experimental study is done to characterize the effects of the weave structure on gas permeability in woven GDLs. Numerical simulations are developed using Fluent version 6.3.26 and COMSOL Multiphysics version 3.5 to create an anisotropic resistance profile in the unconventional GDL, while maintaining similar performance to conventional GDL designs. The effects of (1) changing the permeability profile in the in-plane and through-plane direction, (2) changing the thickness of the unconventional GDL and (3) changing the gas stoichiometry on the current density and pressure drop through the unconventional GDL are investigated. It is found that the permeability profile and thickness of the unconventional GDL have a minimal effect on the average current density and current density distribution. As a tradeoff, an unconventional GDL with a lower permeability will exhibit a higher pressure drop. Once the fuel cell has a sufficient amount of oxygen to sustain reactions, the gas stoichiometry has a minimal effect on increases in performance. Woven GDL samples with varying tightness and weave patterns are made on a hand loom, and their in-plane and through-plane permeability are measured using in-house test equipment. The porosity of the samples is measured using mercury intrusion porosimetry. It is found that the in-plane permeability is higher than the through-plane permeability for all weave patterns tested, except for the twill weave with 8 tows/cm in the warp direction and 4 tows/cm in the weft direction, which exhibited a through-plane permeability which was 20% higher than the in-plane permeability. It is also concluded that the permeability of twill woven fabrics is higher than the permeability of plain woven fabrics, and that the percentage of macropores, ranging in size from 50-400 µm, is a driving force in determining the through-plane permeability of a woven GDL. From these studies, it was found that the graduated permeability profile in the unconventional GDL had a minimal effect on gas flow. However, a graduated permeability may have an impact on liquid water transport. In addition, it was found that graduating the catalyst loading, thereby employing a non-uniform catalyst loading has a greater effect on creating a uniform current density than graduating the permeability profile.
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McCarrick, Jessica Anne. "Differential Regulation of Steroid Receptors in Breast Cancer by the Rho GEF Vav3." Scholarly Repository, 2008. http://scholarlyrepository.miami.edu/oa_theses/124.
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Recently reported data demonstrate that Vav3, a Rho Guanine Nucleotide Exchange Factor (Rho GEF) is overexpressed in breast tumors, coexpressed with ER, necessary for proliferation in breast cancer cells, and predictive of response to neoadjuvant endocrine therapies in patients with ER+ tumors. Such data beg the question as to what roles Vav3 plays in modulation of steroid receptor activity in breast cancer and in resistance to current hormonal therapies. Using reporter assays, I provide novel evidence that Vav3 potentiates Estrogen Receptor activity and represses Androgen Receptor activity in breast cancer cells. Vav3 potentiates ligand-dependent estrogen receptor activity in the MCF-7. A truncated, constitutively active form of Vav3, caVav3 potentiates ligand dependent ER activity in both MCF-7 and T47D. Vav3 activates Rho GTPases through its GEF domain. ER potentiation by caVav3 is dependent upon GEF activity. A caVav3 mutant with defective GEF function represses basal and ligand-mediated ER activity in T47D. Although other studies have shown that Vav3 could activate various Rho GTPases, only constitutively active Rac1 mutants potentiated ER activity in both cell lines. Contrastingly, reporter assays were used to show that caVav3 inhibits ligand-mediated AR activity in the AR+ T47D cell line by both R1881 and DHT stimulation. caVav3-mediated repression of AR activity is GEF-dependent, as caVav3 GEF mutants potentiate AR activity. Constitutively active forms of Rho GTPases were found to repress AR activity to different extents, but R1881-mediated AR activity was only significantly repressed by caCdc42. My studies of the effect of androgens on AR protein by western blot show that androgens downregulate AR protein in the highly Vav3 positive T47D cell line. Previous studies have demonstrated that androgens stabilize AR protein in MCF-7, and I now provide evidence that overexpression of Vav3 or caVav3 reverses hormone-mediated AR protein stabilization in MCF-7. These data are especially relevant given recently published data that decreased AR protein levels contributed to failure of response to MPA in patients with metastatic breast cancer. Further breast cancer studies may prove Vav3 to be a potential drug target in hormone dependent, hormone independent, and metastatic disease.
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Roberts, Jill Carolyne. "Characterization of Community-acquired Methicillin-resistant Staphylococcus aureus by Pulsed-field Gel Electrophoresis, Multilocus Sequence Typing, and Staphylococcal Protein A Sequencing: Establishing a Strain Typing Database." [Tampa, Fla] : University of South Florida, 2006. http://purl.fcla.edu/usf/dc/et/SFE0001489.
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Rodrigues, Binoy Johann. "DYNAMIC FRICTIONAL RESPONSE OF GRANULAR MATERIALS UNDER SEISMICALLY RELEVANT CONDITIONS USING A NOVEL TORSIONAL KOLSKY BAR APPARATUS." Case Western Reserve University School of Graduate Studies / OhioLINK, 2018. http://rave.ohiolink.edu/etdc/view?acc_num=case1508455191610014.
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Lucena, Valeska Silva. "Caracteriza??o da resist?ncia do algodoeiro a Ramularia areola e variabilidade molecular do pat?geno." Universidade Federal do Rio Grande do Norte, 2007. http://repositorio.ufrn.br:8080/jspui/handle/123456789/16781.
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Previous issue date: 2007-02-23This research was conducted with the aim to study the genetic and pathogenic structure of Ramularia areola isolates collected in Brazil and to characterize the resistance response in cotton plants to ramularia spot. The genetic variability of 28 isolates of R. areola was studied using RAPD markers. The pathogenicity evaluation was realized by the inoculation of 6 isolates on cotton varieties Guazuncho-2 (Gossypium hirsutum) and VH8-4602 (Gossypium barbadense). The inheritance of disease resistance was studied using an artificially inoculated population of F2 individuals derived from the intercross of Guazuncho-2 (susceptible variety) end VH8-4602 (resistant variety), and also the parents and F1 individuals. Molecular polymorphism between the G. hisutum varieties DeltaOpal (suscetible) and CNPA CO-11612 (resistant) was estimated by 118 SSR and 24 AFLP markers. The parental genotypes Guazuncho-2 and VH8-4602 were selected for mapping, and then Recombinant Inbred Lines (RIL?s) derived from this crossing were evaluated with SSR 12 markers. The analysis of population structure of R. areola revealed that the three subpopulations were genetically simillar (Gst=0.18), and the isolates from Goi?s and Minas Gerais were more similar to each other (0,92). This probability can be related to the relatively high gene flow among the three subpopulations (Nm=2.20). The isolates R. areola 9.1, from Minas Gerais State and 8.1 and 8.3 from Goi?s State were the most aggressive ones to the susceptible variety Guazuncho-2. The variety VH8-4602 presented high level of resistance to ramularia spot. No differential interaction was observed between the pathogens and the analyzed varieties, and the resistance was classified as horizontal. The quantification of disease by number of necrotic lesions and number of spores in individual plants of F1 and F2 generations from the crossing between the varieties Guazuncho-2 and VH8-4602 presented continuous distribution, suggesting polygenic resistance. The resistance is probabilly recessive, since necrotic lesions and sporulation were observed on F1 plants. The molecular polymorphism between DeltaOpal e CNPA CO-11612 lineages was low (6%), then would be difficult to accomplish molecular mapping of disease resistance using this intercross. With the genotyping of the RIL s it was verified that 25% of the markers segregated in the proportions proposed by Mendel s Law and 75% of the studied markers presented segregation distortion in favor to the parental G. hirsutum. Both the low genetic variability of the pathogen and the number of resistance genes suggest that durable genetic resitance may be achieved
Este estudo teve como objetivos estudar a estrutura gen?tica e patog?nica de isolados de Ramularia areola do Brasil e caracterizar a resposta de resist?ncia no algodoeiro ? mancha-de-ramul?ria. Foi avaliada a variabilidade gen?tica de 28 isolados do pat?geno, utilizando-se marcadores RAPD. A avalia??o da patogenicidade de 6 desses isolados foi realizada ap?s a inocula??o nas variedades Guazuncho-2 (Gossypium hirsutum) suscet?vel e VH8-4602 (Gossypium barbadense) resistente ? doen?a. A heran?a da resist?ncia no algodoeiro ? doen?a foi caracterizada pela medi??o de intensidade da doen?a nas variedades Guazuncho-2 (G. hirsutum), suscet?vel, e VH8-4602 (G. barbadense), resistente ? doen?a, e nas gera??es F1 e F2 provenientes do cruzamento entre elas. O polimorfismo molecular entre as linhagens de G. hirsutum DeltaOpal e CNPA CO11612, contrastantes fenotipicamente quanto ? resist?ncia ? doen?a foi avaliado utilizando-se 118 marcadores SSR e 24 AFLP. Para mapeamento molecular dos genes de resist?ncia, linhagens recombinantes RIL s derivadas do cruzamento entre Guazuncho-2 e VH8-4602 foram genotipadas utilizando marcadores SSR. A an?lise da estrutura da popula??o de R. areola revelou que as tr?s subpopula??es foram semelhantes geneticamente (Gst=0.18). Os isolados de Goi?s e Minas Gerais obtiveram maior similaridade gen?tica (0,92), que pode estar associada com o alto fluxo gen?tico existente entre as subpopula??es que foi de (Nm=2.20). Quanto ? patogenicidade, os isolados de R. areola 9.1, coletado no estado de Minas Gerais, 8.2 e 8.3 de Goi?s, foram mais agressivos na variedade suscet?vel Guazuncho-2. A variedade VH8-4602 apresentou alto n?vel de resist?ncia ? doen?a. N?o foi observada intera??o diferencial entre os pat?genos e as variedades analisadas, sendo a resist?ncia classificada como horizontal. Na an?lise dos indiv?duos das gera??es F1 e F2, provenientes do cruzamento entre Guazuncho-2 e VH8-4602, a quantifica??o de sintomas da doen?a atrav?s da contagem de manchas necr?ticas e pelo n?mero de esporos mostrou varia??o cont?nua da resist?ncia ? doen?a nos indiv?duos da gera??o F2, indicando que a heran?a ? polig?nica. O aparecimento de sintomas e esporula??o nos indiv?duos F1 mostrou que a resist?ncia ? recessiva. O polimorfismo molecular entre as linhagens de G. hirsutum, DeltaOpal e CNPA CO11612 foi de 6%, portanto baixo, para realizar o mapeamento. Durante genotipagem das RIL?s foi verificado que 25% dos marcadores segregaram de acordo com as propor??es das leis de Mendel, e 75% desses marcadores apresentaram distor??o de segrega??o, com aumento da propor??o de genes do parental G. hirsutum. A baixa variabilidade do pat?geno e n?mero de genes de resist?ncia sugere que a resist?ncia gen?tica ao pat?geno tenha alta durabilidade
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Nguyen, Duc Bach, Van Hai Tong, Van Hung Nguyen, and Huu Ton Phan. "Collection, conservation, exploitation and development of rice genetic resource of Vietnam." Saechsische Landesbibliothek- Staats- und Universitaetsbibliothek Dresden, 2015. http://nbn-resolving.de/urn:nbn:de:bsz:14-qucosa-190749.
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Genetic resources are important for the development of every country and for humanity. Collection, conservation and reasonable utilization of genetic resource is required mission. Understanding the importance of genetic resource, especially rice germplasm, since 2001, Center for conservation and development of crop genetic resources (CCD-CGR) of Hanoi University of Agriculture (Vietnam National University of Agriculture) has been collected, conserved and evaluated rice germplasm from different provinces of Vietnam for breeding programs. So far, 1090 accessions of local rice of Vietnam have been collected. Evaluation of agronomic properties and screening of some important genes using DNA molecular markers have revealed that Vietnamese rice germplasm has high level diversity and containing important genes for quality and resistance for disease and pests. These genetic resources are potential materials for national breeding programs. Based on the collected germplasm, 3 new glutinous rice varieties have been successfully created with high yield and good quality. In addition, the degradation of local rice varieties is also a matter of concern. So far, 4 specialty rice varieties Deo Dang, Ble chau, Pu de and Khau dao have been successfully restored for the north provinces of Vietnam. The main results of this study are germplasms for rice breeding programs and new improved varieties that bring economic benefits to farmers and the countryNguồn gene là tài nguyên sống còn của mỗi quốc gia và của toàn nhân loại. Vì vậy thu thập, bảo tồn, đánh giá và khai thác hợp lý nguồn tài nguyên này có ý nghĩa rất lớn. Nhận thức được tầm quan trọng của nguồn gen nhất là nguồn gen cây lúa, ngay từ đầu những năm 2000, Trung tâm bảo tồn và phát triển nguồn gene cây trồng thuộc Trường Đại học nông nghiệp, nay là Học Viện nông nghiệp Việt Nam đã tiến hành thu thập, lưu giữ, đánh giá và khai thác nguồn gene lúa. Kết quả đã thu thập, lưu giữ được 1090 mẫu giống lúa địa phương Việt Nam. Đánh giá đặc điểm nông sinh học và phát hiện một số gene quy định các tính trạng chất lượng và kháng sâu bệnh bằng chỉ thị phân tử DNA. Đây là nguồn gene quan trọng cho chọn tạo giống. Dựa vào nguồn gene thu thập được, cho đến nay, Trung tâm bảo tồn và phát triển nguồn gene cây trồng đã lai và chọn tạo được thành công 03 giống lúa nếp chất lượng cao. Ngoài ra, thoái hóa giống cũng là vấn đề đang được quan tâm. Cho đến nay 4 giống lúa đặc sản Đèo đàng, Ble châu, Pu đe và Khẩu dao đã được phục tráng và đưa vào sản xuất. Kết quả của những nghiên cứu này là ngân hàng các giống lúa làm nguồn gene để chọn tạo giống mới đem lại lợi ích kinh tế cho người nông dân và đất nước