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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
161

Charakterisierung und Modifizierung poröser Cellulosepartikel für die flüssige Hochleistungs-Chromatographie und ihr Einsatz zur Untersuchung von Protein-Wechselwirkungen

Wieland, Christoph 01 March 2010 (has links)
Perlcellulose stellt ein interessantes Material für den Einsatz in der wässrigen Größenausschlusschromatgraphie (SEC) dar. Sie ist aufgrund ihrer guten Modifizierbarkeit zudem ein perfektes Ausgangsmaterial für Protein-Aggregationsuntersuchungen. Ein Protein von besonderem praktischem Interesse ist Insulin. Dessen Fehlfaltung und Aggregation verursacht eine Reihe von schwerwiegenden Problemen (z.B. in Drug-Delivery-Systemen). Hierbei erfolgt eine Umwandlung von alpha-Helix- in beta-Faltblatt-Strukturen wobei sich unlösliche Fibrillen bilden. Deren Rückfaltung mit Hilfe fluorierter Alkohole sowie mit fluorierten Nanopartikeln wurde in der Literatur beschrieben. Der Ansatzpunkt dieser Arbeit war es zu untersuchen, ob Fluor auf Oberflächen mit hohem Anteil von Hydroxygruppen eine Rückfaltung von Proteinen wie Insulin bewirken kann. Das Ziel war es, schaltbare stationäre Phasen zu erhalten, mit denen sowohl eine Rückfaltung als auch die Trennung von Proteinen durchgeführt werden können. Zunächst erfolgte die Charakterisierung geeigneter Perlcellulosen, wobei erstmals eine Kombination der „klassischen“ Porosimetrie (Hg-Intrusion, N2-Sorption) mit SAXS und Inverser SEC zur Untersuchung der Porenstruktur von Cellulose angewandt wurde. Es konnte die reversible Schrumpfung der Poren während der Trockungsprozesse beschrieben werden. Die Immobilisierung von Fluor auf der Oberfläche von Cellulosepartikeln erfolgte u.a. durch Pfropfung von fluorierten Acrylaten mittels Cer(IV)-Redoxinitiierung. Es gelang eine homopolymerfreie Pfropfung, wobei es zu keiner Veränderung der Porenstruktur kam. Die Kontrolle der Proteinadsorption auf der modifizierten Oberfläche mittels chemischer Stimuli konnte beschrieben werden. Aggregationsuntersuchungen mittels SEC, DLS und SAXS ergaben, dass fluormodifizierte Perlcellulose keine Verzögerung der Insulinaggregation bewirkt. Jedoch zeigte sich, dass unmodifizierte Perlcellulose eine signifikante Verzögerung der Aggregation bewirken kann. / Porous bead cellulose is an interesting material for the application in aqueous size exclusion chromatography (SEC). Its good modifiability makes it furthermore to a perfect starting material for protein aggregation studies. A protein with huge practical importance is insulin. Misfolding and aggregation of insulin creates serious problems e.g. in drug delivery systems. Thereby it undergoes a change from alpha-helix to beta-sheet structure and forms insoluble fibrils. A back-folding with (toxic) fluorinated alcohols and fluorinated nanoparticles was already shown in literature. The approach for this work was that fluorine (CF3-) on a surface with high hydroxyl-content can induce the back folding of proteins like insulin. The purpose was to get stationary phases that can induce back folding and separation of proteins on a single column. At first a characterization of suitable cellulose beads with focus on different porosimetry methods was done. For the first time a combination of “classical” porosimetry methods (Hg-Intrusion; N2-Sorption) with SAXS and inverse SEC was applied for porous cellulose particles. A reversible shrinking of pores during drying process was shown. Immobilization of fluorine on the surface of cellulose beads was done by grafting of fluorinated acrylates via cer(IV)-redox-initiation and by polymer analogous reaction with fluorinated iodo alkanes. Homopolymer free graft-copolymerization was achieved, whereas no effect on pore structure was observed. The control of protein adsorption on surface by chemical stimuli was shown. Aggregation studies using SEC, DLS and SAXS showed that fluoro-modified cellulose beads do not delay insulin-aggregation due to strong adsorption effects. Though a significant aggregation delay for insulin with unmodified cellulose beads was discovered.
162

Remoção de alquilbenzeno linear sulfonado (LAS) e caracterização microbiana em reator anaeróbio de leito fluidificado / Removal of linear alkylbenzene sulfonate (LAS) and microbial characterization in anaerobic fluidized bed reactor

Lorena Lima de Oliveira 19 February 2010 (has links)
Nesse trabalho foi estudado a degradação anaeróbia do alquilbenzeno linear sulfonado (LAS), um surfactante amplamente utilizado na fabricação de detergentes e presente em esgoto doméstico e águas residuárias industriais. Para isso foi utilizado reator anaeróbio de leito fluidificado em escala de bancada (1,2 L) preenchido com material suporte para imobilização da biomassa. Quatro diferentes suportes foram testados previamente em reatores de leito fluidificado em menor escala (350 ml): carvão ativado (R1), argila expandida (R2), pérolas de vidro (R3) e areia (R4). Todos os reatores foram inoculados com lodo proveniente de reator UASB utilizado no tratamento de dejetos de suinocultura e alimentados com substrato sintético acrescido de LAS. Os reatores foram mantidos a 30°C e operados com tempo de detenção hidráulica (TDH) de 18 horas. Foi possível constatar que os quatro reatores foram aptos na remoção de matéria orgânica (acima de 84%) e LAS (acima de 81%), respectivamente para concentração inicial média de 550 mg/L e 16,5 mg/L. No entanto, carvão ativado e argila expandida sofreram processo de fragmentação durante a operação do reator. Assim, areia foi o material escolhido para preencher o reator em escala de bancada devido aos bons resultados de remoção do LAS (99%), menor custo e facilidade de aquisição, quando comparada a pérola de vidro. Após 270 dias de operação, com concentrações crescentes de LAS e média de 32,3 mg/L, constatou-se que o reator em escala de bancada removeu 93% de LAS. Todos os suportes adsorveram pouco LAS (máximo de 0,43 mgLAS/gargila) não interferindo significativamente no processo de remoção biológica. Exames microscópicos realizados durante a operação dos reatores mostraram que estiveram presentes microrganismos com morfologias semelhantes a espiroquetas, bacilos, bactérias filamentosas e cocos, entre outros. A biomassa presente no final da operação do reator em escala de bancada e nos reatores menores preenchidos com pérolas de vidro (R3) e areia (R4) foi submetida à técnica de clonagem e sequenciamento do gene 16S RNAr para o Domínio Bacteria. Observou-se que os reatores apresentaram clones relacionados a diversos Filos como Bacteroidetes, Proteobacteria, Verrucomicrobia e Firmicutes, entre outros. / This work presents the anaerobic degradation of linear alkylbenzene sulphonate (LAS), a surfactant widely used in the production of detergents and present in domestic and industrial wastewaters. It was used an anaerobic fluidized bed reactor in bench scale (1,2L) filled with support material for biomass immobilization. Four different supports were previously tested in small scale fluidized bed reactors (350 ml): activated charcoal (R1), expanded clay (R2), glass beads (R3) and sand (R4). All reactors were inoculated with sludge from a UASB reactor treating swine wastewater and were fed with a synthetic substrate supplemented with LAS. The reactors were kept at 30ºC and operated with a hydraulic retention time (HRT) of 18 h. It was possible to note that the four tested reactors were able to remove organic matter (higher than 84%) and LAS (higher than 81%), respectively, to initial mean value of 550 mg/L and 16.5 mg/L. However, activated charcoal and expanded clay both produced shearing during reactor operation. Thus, sand was the chosen material to fill the bench scale reacto because of good results of LAS removal (99%) and smaller cost and affordability compared to glass beads. After 270 days of operation, with crescent LAS concentrations and average of 32,3 mg/L, it was found that the bench scale reactor was able to remove LAS in 93%. All supports adsorb a few LAS (maximun of 0.43 mgLAS/gclay). This value does not interfere in biologic removal process. Microscopic tests done during the reactor´s operation presented microorganisms with morphologies similar to spirochetes, bacillus, filamentous, cocci and others. 16S rRNA gene sequencing and phylogenetic analysis of samples from the bench scale reactor and smaller reactor filled with glass beads (R3) and sand (R4) revealed that these reactors gave rise to broad microbial diversity, with microorganisms belonging to the phyla Bacteroidetes, Proteobacteria, Verrucomicrobia and Firmicutes, and others.
163

Análisis de la Visibilidad y la Resistencia al Deslizamiento de las Marcas Viales Retrorreflectantes en Carretera Convencional

Coves García, José Andrés 15 January 2016 (has links)
El sistema de señalización vial horizontal para carretera convencional es uno de los elementos del equipamiento viario que guarda mayor relación con la seguridad vial. Por ello, la investigación de nuevos materiales y sistemas de aplicación que contribuyan a la mejora de los parámetros físico-ópticos de las marcas viales es vital para el aumento del nivel de servicio de la carretera y, además, para colaborar en la disminución de la siniestralidad en carretera. Por tal motivo, en la presente tesis doctoral se han estudiado las características esenciales de las marcas viales: visibilidad diurna, visibilidad nocturna, resistencia al deslizamiento y durabilidad en busca de la óptima señalización vial horizontal en carretera convencional. Para ello se han desarrollado tres estudios de investigación en tres campos de prueba ejecutados in-situ en distintas carreteras convencionales. En cada uno de ellos se ha evaluado y se han extraído conclusiones que nos han permitido seguir avanzando en la misma línea de investigación a través de los siguientes estudios. En el primer estudio llevado a cabo, se analizaron 81 combinaciones de materiales, aplicadas en el campo de pruebas in-situ nº 1 localizado en la CV-9006 con tipología de travesía, variando el tipo de material base, el material de post-mezclado, sus dosificaciones y los sistemas de aplicación. Para ello se estudiaron los dos parámetros fundamentales: factor de luminancia β y la retrorreflexión RL en seco, para las probetas recién aplicadas, al mes y a los seis meses de antigüedad. Para el segundo estudio se utilizaron materiales y sistemas de aplicación nuevos consiguiendo 14 probetas en cada sentido de circulación, que forman un total de 28 probetas. Éstas fueron ejecutadas in-situ en la CV-8354 y se analizaron los parámetros esenciales de las marcas viales: factor de luminancia β, retrorreflexión RL en seco y coeficiente de rozamiento SRT. El tercer estudio se compuso de 18 combinaciones de materiales para cada sentido de circulación, con un total de 36 probetas, en el campo de pruebas nº 3 de la carretera CV-904. En este caso, los parámetros característicos analizados de las probetas fueron: factor de luminancia β, coordenadas cromáticas (x,y), coeficiente de luminancia en iluminación difusa Qd, retrorreflexión RL en seco, retrorreflexión RL en húmedo y coeficiente de rozamiento SRT para las 36 probetas recién aplicadas, al mes, a los 6 meses, a los 12 meses y a los 18 meses desde su fabricación. Finalmente, tras el análisis cuantitativo y cualitativo de todos los parámetros fotométricos que caracterizan las marcas viales, se ha conseguido establecer el sistema de señalización vial horizontal óptimo para carretera convencional y sus pautas de comportamiento a lo largo del tiempo.
164

Entre le Saguenay et la Huronie : les perles de verre du lac Abitibi et la route du Nord au XVIIe siècle

Lee-Hone, Chloe 02 1900 (has links)
No description available.
165

Application of Raman and Fluorescence Spectroscopy to Single Chromatographic Beads

Larsson, Mina January 2005 (has links)
<p>Chromatography is a powerful technique, essential in chemical analyses and preparative separation in industry and research. Many different kinds of chromatographic material are needed, due to the large variety of applications. Detailed methods of characterisation are needed to design new chromatographic materials and understand their properties. In this thesis, confocal Raman spectroscopy and surface enhanced Raman spectroscopy (SERS) have been applied to micrometer-size chromatographic beads, for which these techniques have not been used earlier. New methodology, optimized for use with the chromatographic beads, has been developed and evaluated. </p><p>Confocal spectroscopy has been used to determine distributions of functional groups within single chromatographic beads. This distribution is of great importance in determining the chromatographic properties, since the material is porous and the solute molecules can diffuse inside the beads. Most of the confocal experiments have been performed with Raman spectroscopy; fluorescence spectroscopy, using Nd<sup>3+</sup> ions or dye-labelled proteins as fluorescence probes, has been used for comparison. </p><p>The concentration of adsorbed analytes is very low within the beads. SERS was therefore used to enhance the Raman signal. SERS-active surfaces were prepared by incorporating gold nano-particles into the interior of the bead. TEM measurements showed that the gold nano-particles could be observed throughout, and it was possible to record analyte spectra from different positions within the bead. Enhanced spectra could be obtained both for small test molecules and for larger bio-molecules, although the spectra for the smaller analytes were much more intense.</p>
166

Interconnections : Glass beads and trade in southern and eastern Africa and the Indian Ocean - 7th to 16th centuries AD

Wood, Marilee January 2012 (has links)
Glass beads comprise the most frequently found evidence of trade between southern Africa and the greater Indian Oceanbetween the 7th and 16th centuries AD.  In this thesis beads recovered from southern African archaeological sites are organized into series, based on morphology and chemical composition determined by LA-ICP-MS analysis.  The results are used to interpret the trade patterns and partners that linked eastern Africa to the rest of the Indian Ocean world, as well as interconnections between southern Africa andEast Africa.   Comprehensive reports on bead assemblages from several archaeological sites are presented, including: Mapungubwe, K2 and Schroda in the Shashe-Limpopo Basin; Chibuene in southern Mozambique; Hlamba Mlonga in eastern Zimbabwe; Sibudu Cave in KwaZulu-Natal, Kaole Ruins in Tanzania and Mahilaka in northwest Madagascar.  The conclusions reached show that trade relationships and socio-political development in the south were different from those on the East Coast and that changes in bead series in the south demonstrate it was fully integrated into the cycles of the Eurasian and African world-system.
167

Transmission Electron Microscopy of Graphene and Hydrated Biomaterial Nanostructures : Novel Techniques and Analysis

Akhtar, Sultan January 2012 (has links)
Transmission Electron Microscopy (TEM) on light element materials and soft matters is problematic due to electron irradiation damage and low contrast. In this doctoral thesis techniques were developed to address some of those issues and successfully characterize these materials at high resolution. These techniques were demonstrated on graphene flakes, DNA/magnetic beads and a number of water containing biomaterials. The details of these studies are given below. A TEM based method was presented for thickness characterization of graphene flakes. For the thickness characterization, the dynamical theory of electron diffraction is used to obtain an analytical expression for the intensity of the transmitted electron beam as a function of thickness. From JEMS simulations (experiments) the absorption constant λ in a low symmetry orientation was found to be ~ 208 nm (225 ± 9 nm). When compared to standard techniques for thickness determination of graphene/graphite, the method has the advantage of being relatively simple, fast and requiring only the acquisition of bright-field (BF) images. Using the proposed method, it is possible to measure the thickness change due to one monolayer of graphene if the flake has uniform thickness over a larger area. A real-space TEM study on magnetic bead-DNA coil interaction was conducted and a statistical analysis of the number of beads attached to the DNA-coils was performed. The average number of beads per DNA coil was calculated around 6 and slightly above 2 for samples with 40 nm and 130 nm beads, respectively. These results are in good agreement with magnetic measurements. In addition, the TEM analysis supported an earlier hypothesis that 40 nm beads are preferably attached interior of the DNA-coils while 130 nm beads closer to the exterior of the coils. A focused ion-beam in-situ lift-out technique for hydrated biological specimens was developed for cryo-TEM. The technique was demonstrated on frozen Aspergillus niger spores which were frozen with liquid nitrogen to preserve their cellular structures. A thin lamella was prepared, lifted out and welded to a TEM grid. Once the lamella was thinned to electron transparency, the grid was cryogenically transferred to the TEM using a cryo-transfer bath. The structure of the cells was revealed by BF imaging. Also, a series of energy filtered images was acquired and C, N and Mn elemental maps were produced. Furthermore, 3 Å lattice fringes of the underlying Al support were successfully resolved by high resolution imaging, confirming that the technique has the potential to extract structural information down to the atomic scale. The experimental protocol is ready now to be employed on a large variety of samples e.g. soft/hard matter interfaces.
168

Application of Raman and Fluorescence Spectroscopy to Single Chromatographic Beads

Larsson, Mina January 2005 (has links)
Chromatography is a powerful technique, essential in chemical analyses and preparative separation in industry and research. Many different kinds of chromatographic material are needed, due to the large variety of applications. Detailed methods of characterisation are needed to design new chromatographic materials and understand their properties. In this thesis, confocal Raman spectroscopy and surface enhanced Raman spectroscopy (SERS) have been applied to micrometer-size chromatographic beads, for which these techniques have not been used earlier. New methodology, optimized for use with the chromatographic beads, has been developed and evaluated. Confocal spectroscopy has been used to determine distributions of functional groups within single chromatographic beads. This distribution is of great importance in determining the chromatographic properties, since the material is porous and the solute molecules can diffuse inside the beads. Most of the confocal experiments have been performed with Raman spectroscopy; fluorescence spectroscopy, using Nd3+ ions or dye-labelled proteins as fluorescence probes, has been used for comparison. The concentration of adsorbed analytes is very low within the beads. SERS was therefore used to enhance the Raman signal. SERS-active surfaces were prepared by incorporating gold nano-particles into the interior of the bead. TEM measurements showed that the gold nano-particles could be observed throughout, and it was possible to record analyte spectra from different positions within the bead. Enhanced spectra could be obtained both for small test molecules and for larger bio-molecules, although the spectra for the smaller analytes were much more intense.
169

Microfluidic bead-based methods for DNA analysis

Russom, Aman January 2005 (has links)
With the completion of the human genome sequencing project, attention is currently shifting toward understanding how genetic variation, such as single nucleotide polymorphism (SNP), leads to disease. To identify, understand, and control biological mechanisms of living organisms, the enormous amounts of accumulated sequence information must be coupled to faster, cheaper, and more powerful technologies for DNA, RNA, and protein analysis. One approach is the miniaturization of analytical methods through the application of microfluidics, which involves the manipulation of fluids in micrometer-sized channels. Advances in microfluidic chip technology are expected to play a major role in the development of cost-effective and rapid DNA analysis methods. This thesis presents microfluidic approaches for different DNA genotyping assays. The overall goal is to combine the potential of the microfluidic lab-on-a-chip concept with biochemistry to develop and improve current methods for SNP genotyping. Three genotyping assays using miniaturized microfluidic approaches are addressed. The first two assays are based on primer extension by DNA polymerase. A microfluidic device consisting of a flow-through filter chamber for handling beads with nanoliter liquid volumes was used in these studies. The first assay involved an allelespecific extension strategy. The microfluidic approach took advantage of the different reaction kinetics of matched and mismatched configurations at the 3’-ends of a primer/template complex. The second assay consisted of adapting pyrosequencing technology, a bioluminometric DNA sequencing assay based on sequencing-bysynthesis, to a microfluidic flow-through platform. Base-by-base sequencing was performed in a microfluidic device to obtain accurate SNP scoring data on nanoliter volumes. This thesis also presents the applications of monolayer of beads immobilized by microcontact printing for chip-based DNA analysis. Single-base incorporation could be detected with pyrosequencing chemistry on these monolayers. The third assay developed is based on a hybridization technology termed Dynamic Allele-Specific Hybridization (DASH). In this approach, monolayered beads containing DNA duplexes were randomly immobilized on the surface of a microheater chip. DNA melting-curve analysis was performed by dynamically heating the chip while simultaneously monitoring the DNA denaturation profile to determine the genotype. Multiplexing based on single-bead analysis was achieved at heating rates more than 20 times faster than conventional DASH provides. / QC 20101008
170

Delar av en grav och glimtar av en tid : Om yngre romersk järnålder, Tuna i Badelunda i Västmanland och personen i grav X / Parts of a Grave and Glimpses of a Time : A discussion of the Late Roman Iron Age, Tuna in Badelunda in Västmanland and the person in Grave X

Fernstål, Lotta January 2004 (has links)
Grave X was found in 1952 during construction work in Tuna in Badelunda parish, in the province of Västmanland. Objects from this 3rd Century grave were dispersed and the stone grave covering and cist-like wooden burial chamber were cut almost in half as a result of the construction work that unearthed it. The purpose of this dissertation is to create a better understanding of Tuna in Badelunda and to place Grave X and the person buried there in context. Due to my interest in Grave X and the person in this grave, the scope of the study is limited to Tuna during the Late Roman Iron Age. What kind of place may Tuna in Badelunda have been during that time? Which kinds of knowledge may the person in Grave X have possessed and what roles may this person have had in local society? How may this person have acted in Tuna in Badelunda in particular? Why was this person buried in the specific type of structure that was Grave X? To answer these questions, ancient monuments and phenomena in the Tuna area, objects from the grave and construction details of the grave are discussed. Specifically, I examine the name Tuna, stone enclosures, hillforts of Bejby borg-character and travel routes, beads, golden rings in the shape of snakes, vessels and serving utensils, and the stone grave covering and cist-like chamber. Since Grave X was partly ruined when discovered, comparisons are made to about 20 similar graves from other parts of Scandinavia in order to get an idea of what may have been lost from Grave X. A performative-constructive gender perspective is of importance in this dissertation, as well as the concept of creolization. The kinds of knowledge and the societal roles the person in Grave X may have had can be summarized in five categories or contexts of action: production within the (social-political) economy of the farm, ritual performances, physical communication, textile production, and oral performances with the telling of stories and relating of memories. Possible personal strategies in relation to the activities the person in question was involved in are seen as important. One way this dissertation takes up this subject is through the discussion of the role the person may have had in greetings and farewells in the yard of the farm (Sw. tun, gårdsplan). Greetings and farewells were probably of importance, and Tuna is discussed as a crossroads. This means that although a local perspective is advocated in this dissertation, Tuna may not be seen as an isolated community, but rather as a small place that to a great extent partook in the larger world. This can also be seen in Grave X; when the person in this grave was buried, the living made choices that both expressed local traditions and made reference to far-away places. In contrast to the surrounding graves, the person in Grave X was not cremated. One of many possible reasons may have been a desire to emphasize the person’s personality and gender as well as roles in society. / <p>Auktoriserad namnform i LIBRIS: Fernstål, Charlotte, 1974-</p>

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