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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.
11

Incorporation of Organic Molecules in the Tunnels of the Sepiolite Clay Mineral

Blank, Katrin 13 September 2011 (has links)
Sepiolite is a clay mineral, a complex magnesium silicate, a typical formula for which is (OH2)4(OH)4Mg8Si12O30•8H2O. It is formed by blocks and cavities (tunnels) growing in the direction of the fibres. The tunnels, 3.7 x 10.6 Å in cross-section, are responsible for the high specific surface area and sorptive properties of sepiolite. The co-intercalation of 3-methyl cyclohex-2-en-1-one (MCH), the Douglas-Fir beetle anti-aggregation pheromone, with methanol, ethanol, acetone, or benzene into sepiolite tunnels was studied. The resulting nanohybrid materials were characterized by means of various techniques, such as multinuclear solid-state NMR spectroscopy, porosity studies and Thermal Gravimetric Analysis (TGA). This was done in the hope of obtaining slow and controlled release of MCH from the sepiolite tunnels. It was demonstrated by 13C MAS NMR (carbon-13 magic angle spinning nuclear magnetic resonance) that at room temperature there are two different MCH molecules: one MCH inside the tunnels and the other one outside the tunnels of the sepiolite. Heating nanohybrid materials at 60˚C for 20 hours removes the external MCH molecules from the sepiolite. 13C MAS NMR showed that by further heating nanohybrid materials at 120˚C for 20 hours, methanol, ethanol, or acetone peaks were greatly reduced; however, the benzene peak was not reduced. To better understand how benzene acts inside sepiolite, intercalation of d6-benzene, and co-intercalations of d6-benzene with MCH and d6-benzene with pyridine into sepiolite tunnels were carried out, and these samples were studied by the same techniques. Another technique was used in order to see whether the slow and controlled release of MCH from the sepiolite tunnels could be obtained: sepiolite-MCH nanohybrids were treated with 20 ml of 0.5 M HCl solution. It was found that when 1 gram of MCH-sepiolite sample was acid treated at room temperature, about 35% of intercalated MCH was removed from the sepiolite. The role of sepiolite clay was also studied in Maya-Blue representative structure sepiolite-indigo adduct. It is known that upon heating the sepiolite and indigo mixture, the stability that is present in Maya-Blue is achieved. It is still a mystery, however, how exactly indigo and sepiolite interact with each other.
12

Studying food-related demineralisation of teeth with atomic force microscopy (AFM) and nanoindentation

Finke, Manuela January 2001 (has links)
No description available.
13

Incorporation of Organic Molecules in the Tunnels of the Sepiolite Clay Mineral

Blank, Katrin January 2011 (has links)
Sepiolite is a clay mineral, a complex magnesium silicate, a typical formula for which is (OH2)4(OH)4Mg8Si12O30•8H2O. It is formed by blocks and cavities (tunnels) growing in the direction of the fibres. The tunnels, 3.7 x 10.6 Å in cross-section, are responsible for the high specific surface area and sorptive properties of sepiolite. The co-intercalation of 3-methyl cyclohex-2-en-1-one (MCH), the Douglas-Fir beetle anti-aggregation pheromone, with methanol, ethanol, acetone, or benzene into sepiolite tunnels was studied. The resulting nanohybrid materials were characterized by means of various techniques, such as multinuclear solid-state NMR spectroscopy, porosity studies and Thermal Gravimetric Analysis (TGA). This was done in the hope of obtaining slow and controlled release of MCH from the sepiolite tunnels. It was demonstrated by 13C MAS NMR (carbon-13 magic angle spinning nuclear magnetic resonance) that at room temperature there are two different MCH molecules: one MCH inside the tunnels and the other one outside the tunnels of the sepiolite. Heating nanohybrid materials at 60˚C for 20 hours removes the external MCH molecules from the sepiolite. 13C MAS NMR showed that by further heating nanohybrid materials at 120˚C for 20 hours, methanol, ethanol, or acetone peaks were greatly reduced; however, the benzene peak was not reduced. To better understand how benzene acts inside sepiolite, intercalation of d6-benzene, and co-intercalations of d6-benzene with MCH and d6-benzene with pyridine into sepiolite tunnels were carried out, and these samples were studied by the same techniques. Another technique was used in order to see whether the slow and controlled release of MCH from the sepiolite tunnels could be obtained: sepiolite-MCH nanohybrids were treated with 20 ml of 0.5 M HCl solution. It was found that when 1 gram of MCH-sepiolite sample was acid treated at room temperature, about 35% of intercalated MCH was removed from the sepiolite. The role of sepiolite clay was also studied in Maya-Blue representative structure sepiolite-indigo adduct. It is known that upon heating the sepiolite and indigo mixture, the stability that is present in Maya-Blue is achieved. It is still a mystery, however, how exactly indigo and sepiolite interact with each other.
14

Production and Secretion of Recombinant Human Fibrinogen by the Transgenic Murine Mammary Gland

Butler, Stephen P. 19 June 1997 (has links)
The mammary gland of lactating transgenic animals has several advantages for production of heterologous proteins including a high cell density that results in high concentrations of secreted protein and the ability to perform several types of post-translational modifications. Transgenes were constructed from the 4.1 kbp murine Whey Acidic Protein promoter (mWAP) and the three cDNAs coding for the Aα, Bβ and γ fibrinogen chains to evaluate the requirements of the transgenic murine mammary gland for high level secretion of fully assembled human fibrinogen. After introducing the constructs into the murine zygotes by microinjection, secretion of fully assembled fibrinogen into milk was measured at concentrations between 10 ug/ml to 200 ug/ml. In one line of mice the total secretion of fibrinogen and unassembled subunits approached 700 ug/ml in milk. The level of assembled fibrinogen was proportional to the lowest amount of subunit produced where both the Bβ and γ chains were rate limiting. Also, the subunit complexes γ₂, Aαγ₂ and the individual subunits Aα, Bβ and γ were found as secretion products. This is the first time that secretion of individual Bβ-subunits by any cell type has been reported and suggests the organization of the secretion pathway in mammary epithelia is different from that in liver. Glycosylated forms of individual Bβ-chain contained a complex saccharide with low mannose. Glycosylation of the γ-chain was also observed. These results suggest the 4.1 mWAP promoter can drive expression of fibrinogen cDNAs to high levels and that the amount of fully assembled fibrinogen secreted is equal to the level of the lowest expressing chain. / Master of Science
15

The role of astrocytes in murine models of toxic demyelination

Menken, Lena 22 June 2016 (has links)
No description available.
16

Hydrologie et modélisation hydrologique des tourbières acides du Massif Central (France) / Hydrology and hydrological modelling of acidic mires in central France

Duranel, Arnaud 23 March 2016 (has links)
L'objet de la présente thèse est de caractériser, quantifier et modéliser les flux d'eau au sein de la Réserve Naturelle Nationale de la Tourbière des Dauges, située en Limousin (Massif Central, France) et qui inclue une tourbière acide de fond de vallon et son bassin versant. Un ensemble de techniques, incluant la description de coupes superficielles existantes, la réinterprétation de sondages géologiques profonds, la tomographie de résistivité électrique et une modélisation de la distribution spatiale des formations affleurantes, ont été utilisées pour caractériser la nature et la géométrie des formations d'altération du granite. Les dépôts alluviaux et tourbeux ont été caractérisés et cartographiés par sondage à la tarière et à la tige filetée, et leur conductivité hydraulique estimée par choc hydraulique. Les précipitations, les paramètres météorologiques nécessaires au calcul de l'évapotranspiration potentielle, les débits et niveaux dans les ruisseaux, et les niveaux piézométriques dans la tourbe et les formations minérales sous jacentes ont été mesurés en continu pendant trois ans. Le modèle hydrologique distribué à base physique MIKE SHE / MIKE 11 a été utilisé pour modéliser les écoulements et les niveaux piézométriques au sein de la tourbière et de son bassin versant avec un pas de temps quotidien et une résolution spatiale de IO m. Il est montré que les apports souterrains issus de la zone fissurée du granite et suintant au travers du dépôt tourbeux constituent une part quantitativement importante et fonctionnellement essentielle de la balance hydrique de la zone humide. La présence d'une nappe affleurante entraîne une évacuation rapide vers les cours d'eau des apports par ruissellement ou par précipitation directe du fait de la saturation des histosols. Toutefois, il est montré que le fonctionnement hydrologique à l'échelle locale peut s'éloigner de ce schéma général du fait d'une grande hétérogénéité du taux d'humification et de la conductivité hydraulique de la tourbe, de la présence de dépôts alluviaux très perméables sous ou au sein du dépôt tourbeux et de perturbations anthropiques passées. Une fois calibré, le modèle hydrologique, qui représente la zone fissurée du socle granitique comme un milieu poreux équivalent, donne des résultats satisfaisants à très bons selon les indicateurs de performance utilisés: il est capable de reproduire les débits dans les cours d'eau au niveau des quatre stations de jaugeage disponibles, et le niveau de la nappe dans la plupart des piézomètres installés. A l'échelle du bassin versant étudié, le niveau moyen de la nappe simulé par le modèle montre une très bonne concordance avec la distribution observée des végétations de zone humide, cartographiée de manière indépendante. Les analyses de sensibilité ont montré que la porosité efficace et la conductivité hydraulique horizontale de la zone fissurée du granite sont les paramètres auxquels les débits et les niveaux de nappe (y compris dans la tourbe) simulés par le modèle sont les plus sensibles, ce qui démontre l'importance d'une meilleure caractérisation des formations d'altération du granite dans tout le bassin versant pour la compréhension et la modélisation du fonctionnement hydrologique de ce type de zone humide. Le modèle a été utilisé pour simuler l'impact potentiel d'un changement d'occupation des sols au sein du bassin versant sur la balance hydrique et les niveaux de nappe dans la zone humide, ainsi que sur les débits dans les cours d'eau. Le modèle suggère que le remplacement des végétations conduirait à une réduction substantielle des apports de surface et souterrains à la tourbière et à un abaissement conséquent des niveaux de nappe dans les histosols en période estivale. / This thesis identifies, quantifies and models water fluxes within the Dauges National Nature Reserve, an acidic valley mire in the French Massif Central. A range of techniques were used to investigate the nature and geometry of granite weathering formations and of peat deposits. Rainfall, reference evapotranspiration, stream discharge, stream stage, groundwater table depths and piezometric heads were monitored over a three-year period. The distributed, physics-based hydrological model MIKE SHE / MIKE 11 was used to model water flow within the mire and its catchment. lt was shown that the mire is mostly fed by groundwater flowing within the densely fissured granite zone and upwelling through the peat deposits. Upwelling to the peat layer and see page to overland flow were highest along the mire boundaries. However hydrological functioning differs from this general conceptual model in some locations due to the high variability of the peat hydraulic characteristics, the presence of highly permeable alluvial deposits of past human interference including drainage. The equivalent porous medium approach used to mode groundwater flow within the fissured granite zone gave satisfactory results : the model was able to reproduce discharge at several locations within the high-relief catchment and groundwater table depth in most monitoring points. Sensitivity analyses showed that the specific yield and horizontal hydraulic conductivity of the fissured zone are the parameter to which simulated stream discharge and groundwater table depth, including in peat, are most sensitive. The model was forced with new vegetation pararneters to assess the potential impacts of changes in catchment land use on the mire hydrological conditions. Replacement of the broad leaf woodlands that currently cover most of the catchment with conifer plantations would lead to a substantial reduction in surface and groundwater intlows to the mire and to a substantial drop in summer groundwater table depths, particularly along the mire margins.
17

Experimental Practice in order to Increasing Efficiency of Biogas Production by Treating Digestate Sludge.

Khorshidi, Nasrin, Arikan, Beyza January 2008 (has links)
According to national and international policies in order to protect environment regarding renewable sources of energy, biogas is one of the best alternative to reduce waste and pollution and getting energy. Biogas is the gas that is produced by some kinds of microorganisms in anaerobic condition from organic waste treatment. Technology of biogas plants is varies and there is no standard procedure that is applicable worldwide. Methane (biogas), which is produced from wastes and it is known widely since 1973. By organic waste degradation methane is produced and waste volume will be reduced. Some surveys prove that during anaerobic digestion only 50% of organic matter is degraded. Anaerobic degradation has some steps that are hydrolysis, acidogenesis, acetogenesis and methanogenesis. Since hydrolysis is rate-limited step it can be improved by some pretreatment and some action like improving monitoring system can show that the efficiency of biogas will increase. There are three main pretreatment methods. During this study digestate sludge from different waste treatment plants were pretreated. First experience was pretreating digestate sludge from Sobacken, Falköping, Västerås by Enzyme Addition (Cellolase) and the measuring of biogas (methane) has done by Gas Chromatograph (GC). Second experience was pretreating digestate sludge by Acid (Sulfuric acid). The data of those measurements are shown that the amount of biogas was increased two times in the case of Västerås by enzyme addition, which is about 70% of theoretical expectation of this pretreatment and pretreating digestate sludge of Sobacken by acid pretreatment could increase the amount of biogas two times as well that was about 60% of theoretical estimation. By proper gas chromatograph and choosing one kind of waste and pretreating that by just one kind of pretreatment in each experience and following the results and going further the biogas efficiency will increase significantly because still 50% organic matter is inside the digester. / Uppsatsnivå: D
18

FATE OF LIMESTONE DISSOLUTION PRODUCTS IN ACIDIC METALCONTAMINATED SOIL MESOCOSMS

Driscoll, Kendra 17 March 2014 (has links)
The impact of liming (10 t ha-1 of calcitic and dolomitic limestone, separately) on the soil solution and soil matrix was investigated in an acidic metal-contaminated soil from Sudbury, ON. A soil mesocosm experiment was performed; columns were leached with simulated rainwater and the soil solution collected at various locations throughout the soil column. The dissolution rate of calcitic limestone used for this experiment was found to be approximately double that of the dolomitic limestone investigated. Calcium and Mg released during limestone dissolution migrated through the soil profile to the Bf-BC interface. The addition of limestone increased the pH and decreases the bioavailability of Ni, Cu, Co, Cd, As, Ba, Mn, and Zn the LFH horizon. Amending acid, contaminated soils with calcitic or dolomitic limestone has profound effects on soil solution chemistry.
19

The dynamics of manganese phytotoxicity: Implications for diagnosis and management of excess manganese in acid upland soils

Bajita, Jocelyn 12 1900 (has links)
Manganese (Mn) in excess of crop requirements is a serious problem when manganiferous soils become acid, waterlogged or amended with organic materials. We investigated the dynamics of manganese phytotoxicity and tested management options for growing crops in acid soils with excess Mn. We hypothesized that Mn phytotoxicity is governed by water use and expressed as continuous negative interaction between current plant/leaf growth rate (RGR PLant/Leaf) and future Mn accumulation rate (RAR Mn); and that under growth conditions where RGRPlant/Leaf exceeds RAR Mn, excess Mn can be managed by maximizing RGR Plant/Leaf and minimizing RAR Mn. The parameters RGR Plant/Leaf and RAR Mn were calculated using the conventional growth analysis techniques. The dynamics of Mn phytotoxicity was investigated by growing Mn-tolerant Lee and Mn-sensitive Forrest soybeans in the greenhouse using Wahiawa series, a manganiferous Oxisol in Hawaii. The soybeans were grown at soil pHs 4.78, 5.5, and 6.00 and five growth conditions (control, 80-90% field capacity, 40% shading, green manure and phosphorus at 150 mg kg-1). RAR Mn consistently exceeded RGR Leaf in most treatments. Over the range of soil pH and growth conditions, we found strong positive correlation between RGR Leaf and RAR Mn, this correlation mediated by a more fundamental correlation of both rate processes to plant water use. The dynamics of Mn phytotoxicity, referred to as the 'dual feedback effect' model described a continuous negative interaction between current RGR Leaf and future RAR Mn and between current RAR Mn and future RGR Leaf. Manganese accumulation rate exceeded plant growth rate, leaf Mn increased with time and growth treatments did not affect growth rate unless soil pH was increased to eliminate excessive Mn in the soil. Field experiments were conducted in Rugao series, an acid Alfisol in Northern Philippines. The soil is acid (pH 4.40) with abundant Fe-Mn concretions within the surface 20-cm. Preliminary field experiment showed Mn phytotoxicity in local soybeans cv. PSB Sy2 and PSB Sy6 as leaf symptoms in addition to low plant growth rates and grain yields associated with leaf Mn exceeding a critical value of 500 mg kg-1. Results of a second field experiment showed that cultivar, liming, and the management of phosphorus (P), manure and mulching modified plant growth rate and enhanced tolerance to excess soil Mn. Lime control (2 t ha-1) neutralized half of the exchangeable AI while keeping saturated paste Mn in excess. Mulching did not affect saturated paste-and increased RAR Mn without affecting RGR Leaf. Increases in RGR Leaf due to P and manure were accompanied by increases in RAR Mn. This increase in RGR Leaf translated to increased yields even when RAR Mn and soil solution Mn were increased as in the case of manure addition. Increases in grain yield due to manure exceeded the increases due to lime or P. Chicken manure was more effective than green manure in increasing grain yield. Plant growth rate exceeded Mn accumulation rate, leaf Mn decreased with time and manure treatments alleviated Mn phytotoxicity despite an increase in soil Mn.
20

Recycled organic products to reduce the negative impact of salinity and sodicity on acidic soil properties and plant growth

Raue, Judith Doris January 2008 (has links)
Salt affected soils and their effects on land and water resources have been identified as one of the most severe environmental problems facing Australia. This current study focused on the incorporation of recycled organic products (RO) into an acidic saline soil that had been irrigated with an industrial effluent (IE), specifically to investigate the potential for these organics to be used in rehabilitation. Compost incorporated into the acidic saline soil was able to raise pH to more favourable levels required for plant growth (pH 6 – 7.5). Plant growth was however dependent on the input material of the compost as well as the irrigation scheme. The soils amended with this compost generally showed higher and more rapid microbial activity, measured by CO2 emissions, in all amendment rates than the plant derived compost. Overall it could be concluded that the application of RO on saline soils improved the establishment and growth of plants and alleviated to some degree the negative effects of IE. However great care should be taken at the selection of the input material, as high rates of ammonium, calcium and other soluble salts can increase the EC of an amended soil further.

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