Thesis (M.S.)--Oregon State University, 1996. / Typescript (photocopy). Includes bibliographical references (leaves 108-123). Also available on the World Wide Web.

Thesis (Ph. D.)--Syracuse University, 1988. / Includes bibliographical references.

Thesis (Ph. D.)--University of Texas at Austin, 2008. / Vita. Includes bibliographical references.

Thesis (M.Sc.D.)--Boston University, School of Graduate Dentistry, 1973. (Pedodontics) / Bibliography included.

Four negative stains, hafnium chloride and europium, samarium and gadolinium nitrates, were tested in single particle electron microscopy as potential alternatives to uranyl acetate, which is recently being widely restricted for its toxicity. The new stains were applied to a structurally well-described plant photosystem I, visualized by a transmission electron microscope and classified in a single particle analysis. The quality of the stains was evaluated by the obtained resolution and ability to provide reliable structural information.

Made available in DSpace on 2014-06-11T19:31:26Z (GMT). No. of bitstreams: 0 Previous issue date: 2008-03-13Bitstream added on 2014-06-13T19:20:25Z : No. of bitstreams: 1 santos_pa_dr_arafo.pdf: 1139131 bytes, checksum: 18d63c9cbe7759346d5e8465937304eb (MD5) / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) / O objetivo deste estudo foi avaliar a influência da fonte de luz na estabilidade de cor da resina composta nanoparticulada Filtek Supreme submetida a diferentes meios e tempos de imersão. Para isso, foram utilizadas três fontes de luz: um LED UltraLume LED 5/ UltraDent; um aparelho de lâmpada halógena convencional – Curing Light XL 3000/ 3M/ESPE; e um de luz halógena de alta densidade de potência – Jet Lite 4000 Plus/ JMorita. Os espécimes (n=180) foram confeccionados em matriz de metal circular (10mm x 2mm) apoiada em placa de vidro e tira de poliéster. A resina composta foi inserida na matriz num único incremento e fotoativada por 40 segundos. Os espécimes foram divididos em três grupos (equipamento de fotopolimerização) e quatro subgrupos experimentais (meios de imersão: café, Coca-Cola®, chá e saliva artificial). Os espécimes permaneceram imersos em saliva artificial por 24 horas e foram submetidos à análise da cor no espectrofotômetro de colorimetria (CB-6807 color-guide /BYK-Gardner) pelo sistema CIELab. A partir desse período, passaram a ser mergulhados nos diferentes meios por cinco minutos, três vezes ao dia, por 60 dias, e nos intervalos foram mantidos em estufa à 37°C ± 1°C. A leitura da alteração de cor foi realizada após 24 e 48 horas, 7, 14, 21, 30 e 60 dias do início da imersão. Os dados foram analisados pelo teste não-paramétrico Kruskall-Wallis para os fatores fonte de luz e meio de imersão (p<0,05), enquanto, para o fator tempo, utilizou-se o teste ANOVA a dois critérios e o teste de Fisher (p<0,05). Os resultados mostraram que, para o fator fonte de luz, o Ultralume LED 5 apresentou a menor alteração de cor em comparação aos aparelhos halógenos. Em relação ao meio de imersão, o café mostrou a maior alteração de cor e de luminosidade (ΔE=8,40; _L=-5,21), a Coca-Cola® apresentou os menores valores... / The aim of this study was to evaluate the influence of light sources on color stability of a composite resin and the effect of immersion media. In this test, three light sources were used: a conventional halogen curing light unit (XL3000 – 3M/ESPE), a high power density halogen unit (Jet Lite 4000 Plus – JMorita) and a high power density LED unit (Ultralume LED 5 - Ultradent). There were four media immersion: coffee, tea, Coke® and artificial saliva. One nanofilled composite resin was selected: Filtek Supreme. A stainless steel matrix (10mmx2mm) was used to prepare 180 specimens. After this, all specimens were immersed in artificial saliva for 24hs at 37oC ± 1ºC and its initial color was measured with a spectrophotometer (Color Guide 45/0, BYKGardner) by CIELab system. Then, the specimens were divided into 4 subgroups according to each medium and were immersed in the respective medium three times a day during 5 minutes for 60 days. Color changes were recorded after 24hs, 48hs, 7, 14, 21, 30 and 60 days of immersion. Data from the color change and luminosity were analyzed and subjected to Kruskall-Wallis test to light source and immersion media factor (p<0,05). To immersion time, data were subjected to two-way ANOVA test and Fisher’s test (p<0,05). The light source that more contributed to color stability was Ultralume LED 5. In relation to solutions, coffee caused an intense color alteration (ΔE=8,40; ΔL=-5,21) and Coke® showed the lowest color changes (ΔE=1,43; ΔL=0,36). Then, it might be concluded that Ultralume LED 5 was the light-curing unit that allowed better color stability and coffee was the immersion medium that promoted the highest influence on color stability of the studied composite resin.

Nesta pesquisa in vitro verificou-se a possibilidade de remoção do manchamento causado por café ou vinho tinto em cinco resinas compostas disponíveis comercialmente, após serem submetidas ao processo de envelhecimento. Trinta e seis espécimes de cada resina composta foram confeccionados em uma matriz de teflon, com 10 mm de diâmetro e 1,5 mm de espessura. Os espécimes foram mantidos em água destilada a 37ºC por 24 horas e, em seguida, polidos com irrigação na politriz (Ecomet Buehler USA) nas duas superfícies, com lixa de carbureto de silício com granulação de número 600, até atingirem a espessura de 1,3 ±0,01 mm. Após o polimento, a cor dos espécimes foi aferida com espectrofotômetro Cintra 10 UV (Visible Spectrometer, GBC, Austrália). Todos os espécimes foram submetidos à ciclagem térmica com temperaturas de 5 e 55ºC, com tempo de imersão de 1 minuto, por 1000 ciclos em solução de 75% álcool-água. Após a ciclagem térmica, os espécimes foram mantidos imersos em água destilada a 37ºC até completar o período de 7 dias da confecção das amostras. Após esse período, todos os espécimes foram levados ao espectrofotômetro para leitura da cor. Os espécimes foram divididos em três grupos, cada um com n=12, de acordo com as soluções em que foram imersos: água destilada (controle), café e vinho tinto. Para que o processo de manchamento acontecesse em uma única superfície do espécime, uma das faces e a superfície lateral do espécime foram isoladas com cera branca. Os espécimes foram imersos nas diferentes soluções e mantidos a 37ºC por 14 dias. Após o período de manchamento, a cera foi removida e a superfície submetida ao manchamento passou por escovação com escova elétrica (Escova Elétrica Braun Oral-B Procter & Gamble do Brasil S.A., Manaus, Brasil) por 30 segundos com pressão leve. Os espécimes foram secos com papel absorvente e novamente levados ao espectrofotômetro para medição da cor. Em seguida, os espécimes foram submetidos a três desgastes de 20 m e a cor foi aferida após cada um dos desgastes. O cálculo da diferença de cor foi realizado através da fórmula CIEDE2000. De acordo com a metodologia utilizada neste estudo, concluiuse que o manchamento provocado por café e vinho tinto nos compósitos avaliados foi superficial e um desgaste de 20 m foi suficiente para remoção de tal manchamento. / This in vitro research verified the possible elimination of staining caused by coffee and red wine in five commercial composite resins, after being submitted to thermal cycling. Thirty six specimens were prepared in a teflon mold with 10 mm in diameter and 1.5 mm thick. The specimens were immersed in water at 37ºC for 24 h and polished (Ecomet Buehler - USA) in both surfaces with a # 600 grit silicon carbide paper until achieve 1.3 ±0.01 mm thickness. After polishing, specimens color was measured in a spectrophotometer Cintra 10 UV (Visible Spectrometer, GBC, Austrália). All specimens were submitted to thermal cycling with temperatures of 5 and 55ºC with a dwell time of 1 minute, for 1000 cycles in a 75% ethanol/water solution. After thermal cycling the specimens were immersed in water at 37ºC until complete 7 days from the preparation of the specimens. All the specimens were then taken into spectrophotometer for measuring the color. The specimens were divided into 3 groups (n=12): distilled water (control), coffee and red wine. For the purpose of the staining process to occur in only one surface, all the side and one of the surfaces were isolated with white wax. The specimens were immersed in one of the solutions at 37ºC for 14 days. After the staining period, the wax was removed and the specimens were brushed with electric toothbrush (Braun Oral-B, Procter & Gamble do Brasil S.A., Manaus, Brasil) for 30 seconds with a slight pressure. The specimens were dry with a tissue paper and were taken to spectrophotometer for measuring the color. Following, the specimens were submitted to three wears of 20 m and the color was measured after each one of the wears. The calculation of the color difference was made through CIEDE2000 formula. According to the methodology used in this research, it was concluded that the staining caused by coffee and red wine was superficial and one wear of 20 m was enough for removing the discoloration.

No description available.

Sinorhizobium meliloti is a model bacterium for the study of symbiotic nitrogen fixation (SNF). It infects the roots of alfalfa as well as some other legumes and differentiates into N2-fixing bacteroids within the plant cells of specialized nodule organs. To understand genes essential for SNF and, in the longer term, to facilitate the manipulation of this SNF process for agricultural purposes, it is highly desirable to construct the minimal genome for SNF in this organism. S. meliloti harbors two replicons required for SNF, a 1.7-Mb chromid (pSymB) and a 1.4-Mb megaplasmid (pSymA). A previous deletion analysis revealed that only four gene regions, accounting for <12% of the total sequences of pSymA and pSymB that, were essential for SNF. In the first part of the thesis, I report the cloning of these two pSymA SNF-essential regions on a plasmid (pTH3255) in Escherichia coli, and the integration of this plasmid into the genome of a ∆pSymA S. meliloti derivative strain (the strain was named as RmP4291 after integration). Plant root dry weight and nitrogenase-catalyzed acetylene reduction assays were carried out on RmP4291 with four host plants, including Medicago sativa, Medicago truncatula, Melilotus alba and Melilotus officinalis. Nodule kinetic assays were also performed on RmP4291 and RmP110(wt). The results showed that the SNF-essential regions from pSymA were sufficient to restore the symbiotic capabilities to the ∆pSymA derivative strain with all the host plants tested, except a significant reduction (~40%) in SNF by RmP4291 was noticed on M. officinalis compared to that by wildtype S. meliloti. A higher alfalfa nodulation efficiency of RmP4291 compared to that of wildtype RmP110 was also discovered. In the second part of the thesis, a histochemical staining method for S. meliloti nodules was developed by integrating the marker genes gusA (β-glucuronidase) and celB (β-glucosidase) into the S. meliloti genome. This staining method was found to be useful in the study of nodule competitiveness. A nodule competition assay was carried out between RmP4291 and RmP110 using the new staining method. RmP4291 was found to be significantly reduced in nodulation competitiveness compared to wildtype S. meliloti. The development of the histochemical staining method for S. meliloti nodules will accelerate the identification of genes required for nodule competitiveness in the organism, which will be of crucial importance to the construction of the minimal genome strains with high SNF efficiency. / Thesis / Master of Science (MSc) / Nitrogen is one of the critical elements for life. Biological nitrogen fixation plays a crucial role in providing fixed nitrogen for the ecosystem on Earth. Our Laboratory has endeavored to establish a minimal symbiotic genome in Sinorhizobium meliloti, a model nitrogen fixing bacterium which forms symbiosis with certain kinds of legumes. Building this minimal symbiotic genome will improve our understanding of the symbiotic nitrogen fixation process in S. meliloti at gene level. It may also help in eventually introducing a nitrogen fixation system into other organisms. In this study, the minimal symbiotic genome of the pSymA replicon in S. meliloti was constructed. In addition, a staining method to detect specific S. meliloti strains in nodules was established. This method is potentially useful in finding genes related to nodule competitiveness, and these are potentially important for augmenting the genes that constitute the minimal symbiotic genome.

Thesis (doctoral)--Swedish University of Agricultural Sciences, 2006. / Thesis documentation sheet inserted. Errata sheet inserted. Appendix reprints four papers and manuscripts co-authored with others. Includes bibliographical references. Issued also electronically via World Wide Web in PDF format; online version lacks appendix.