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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.
71

Influence of drying technique on Pt/In₂O₃ aerogels for methanol steam reforming

Thoni, Lukas, Metzkow, Nadia, Eychmüller, Alexander 22 May 2024 (has links)
In this paper we present a comparison of aerogels which are dried under different conditions. Of those, most important are the solvent, temperature, and pressure. Criteria of comparison rely mostly on results from analysis of nitrogen adsorption experiments, as well as transmission electron microscopy imaging. Platinum loaded indium oxide aerogels were picked as a model system for this study as they can be used as highly effective heterogeneous catalysts in methanol steam reforming. The compared drying methods include supercritical drying from CO2, supercritical CO2 - ethanol mixture, freeze drying from tert-butanol and ambient conditions drying from acetone and 1-Methoxyheptafluoropropane. High porosities and large specific surface areas can be achieved via supercritical, freeze- and ambient conditions drying, while retaining the original gel morphology in this system for most methods except freeze drying and ambient conditions drying from acetone.
72

The Onsager heat of transport at the liquidvapour interface of p-tert-butyltoluene

Biggs, Georgina Aimee January 2007 (has links)
The Onsager heat of transport for p-tert-butyltoluene was measured, as part of a series of preliminary experiments towards the determination of the importance of temperature gradients on the air-sea flux of carbon dioxide. The results presented in this thesis imply that the temperature gradient is a major contributor to the magnitude of the air-sea flux. The heat of transport has been measured for the p-tert-butyltoluene system by measuring stationary-state pressure changes for known temperature differences on the vapour side of the interface. At the pressure ranges used the number of mean free paths was always outside the Knudsen zone, but the values of Q* were approximately 100 % of the latent heat of vaporisation. Departures from linearity of plots of P against ΔT are attributed to temperature jumps at the surface of the dry upper plate. Both the results taken for p-tert-butyltoluene and the earlier results for water from this laboratory fit to a Type III BET isotherm, where the c parameter is not constant. They also reveal the importance of the temperature gradient in determining the value of the thermal accommodation coefficient, and provide a new method of measuring thermal accommodation coefficients for a variety of surfaces and vapours
73

Preparação e caracterização de catalisadores de V2O5 suportados em TiO2. / Preparation and characterization of V2O5 catalyst supported TiO2.

Rodella, Cristiane Barbieri 02 May 2001 (has links)
Uma série de amostras do sistema catalítico V2O5/TiO2 foi preparada pelo método sol-gel com diferentes teores da fase ativa (de 0 a 9% em massa de V2O5) e calcinada em diferentes temperaturas (de 250 a 6000C). Sistema similar foi obtido pelo método de impregnação para a comparação. Os catalisadores foram caracterizados quanto suas propriedades texturais e estruturais pelas técnicas de Adsorção de N2 a 77K, Difratometria de Raios-X (DRX), Espectroscopia Raman, Ressonância Paramagnética Eletrônica (EPR), Espectroscopia de Fotoelétrons Excitados por Raios-X (XPS) e Espectroscopia de Absorção de Raios-X (XAS). Testes catalíticos para a verificação da atividade e seletividade foram realizados frente à reação de conversão do metanol. O sistema obtido pelo método sol-gel apresentou elevada área superficial e porosidade, as quais foram ampliadas com o aumento do teor de vanádio e reduzidos com o aumento da temperatura de calcinação. O sistema preparado por impregnação apresentou as mesmas propriedades texturais do suporte comercial. A análise de DRX identificou a existência de TiO2 nas formas cristalográficas anatásio e rutilo, não foi identificada a presença de V2O5 na forma cristalina. No sistema preparado por impregnação a estrutura cristalográfica do suporte se mantém, independente do teor de vanádio, porém a partir de 6% de V2O5 foi identificado à presença de V2O5 cristalino. Os espectros de Raman mostraram a presença de dois grupos superficiais de vanádio, os vanadilos monoméricos e os vanadatos poliméricos mesmo em elevados teores de vanádio, nos sistemas preparados pelo processo sol-gel. Nos catalisadores obtidos por impregnação foram identificados modos vibracionais referentes ao V2O5 cristalino.Os resultados obtidos por XAS confirmaram os obtidos por DRX e indicaram a presença de vanádio V4+ e V5+, porém com simetria diferente da forma cristalina V2O5. A determinação da razão entre os átomos V/Ti superficiais feita por XPS mostrou ser crescente com o aumento do teor de vanádio. Os espectros de EPR indicaram a presença de pelo menos três famílias de íons V4+ em diferentes simetrias, duas delas inseridas na matriz da titânia na fase rutilo e a outra dispersa na superfície. O sistema obtido por impregnação apresentou poucos íons V4+. Os testes catalíticos revelaram que a atividade e seletividade catalítica foram praticamente as mesmas para os sistemas preparados pelos dois métodos. Entretanto, a estabilidade catalítica do sistema obtido via sol-gel foi superior ao sistema preparado por impregnação. / A series of samples of the catalytic system V2O5/TiO2 was prepared by the sol-gel method with different proportions of the active phase (from 0 to 9% in mass of V2O5) and calcined in different temperatures (from 250 to 6000C). A similar system was obtained by the impregnation method for comparison. The catalyst were characterized by their textural and structural properties by Adsorption of N2 at 77K, X-Ray Diffraction (XRD), Raman Spectroscopy, Electronic Paramagnetic Resonance (EPR), X-Ray Photoelectron Spectroscopy (XPS) and X-Ray Absorption Spectroscopy (XAS). Catalytic tests for the verification of the activity and selectivity were performed by the conversion reaction of the methanol. The system obtained by the sol-gel method presented a high superficial area and porosity, which were enlarged by the increase of vanadium proportion and reduced with increase of the calcinations temperature. The system prepared by impregnation presented the same textural proprieties of the commercial support. XRD analysis identified the existence of TiO2 in two crystallographic forms, anatase and rutile. It was not identified the presence of V2O5 in the crystalline form. In the system prepared by impregnation the crystallographic structure of the support keeps, independent of the vanadium content, however starting from 6% of the vanadia was identified crystalline V2O5. Raman spectra showed the presence of two superficial groups of vanadium, the monomeric vanadyls and the polymeric vanadates even for elevated contents of vanadium, in the system prepared by the impregnation method vibrational modes were identified referring to V2O5 crystalline. The results obtained by XAS confirmed the obtained by XRD and indicated the presence of V4+ and V5+, however with different symmetry from the V2O5 in a crystalline form. The determination of the proportion between the surface V/Ti atoms determined by XPS showed to be increased with the increase of the vanadium content. EPR spectra indicated the presence of at least three V4+ion families in different symmetries; two of them inserted in the matrix of titania in the rutile phase and to other dispersed on the surface. The system obtained by impregnation presented few V4+ ions. The catalytic tests reveled that the catalytic activity and selectivity were practically the same for the systems prepared by both methods. However, the catalytic stability of the system obtained via sol-gel was superior to the system prepared by impregnation.
74

The Bromodomain Proteins GTE9 and GTE11 Associate with BT2-based E3 Ligase Complex and Mediate Responses to Multiple Signals in Arabidopsis thaliana.

Misra, Anjali 2011 December 1900 (has links)
BT2 is an Arabidopsis thaliana protein with N-terminal BTB, central TAZ and a C-terminal calmodulin binding domain and associates with Cullin3 to form an E3 ubiquitin ligase. We have shown previously that BT2 regulates telomerase activity in mature vegetative organs and controls a variety of hormone, stress and metabolic responses in Arabidopsis thaliana. Loss of BT2 results in plants that are hypersensitive to inhibition of germination by ABA and sugars. Conversely, overexpression of BT2 results in resistance to ABA and sugars, suggesting that BT2 is a negative regulator of ABA and sugar responses. Here, we report the roles of BT2-interacting partners GTE9 and GTE11, bromodomain and extraterminal-domain proteins of Global Transcription Factor Group E, in BT2-mediated responses to sugars and hormones. Loss-of-function mutants gte9-1 and gte11-1 phenocopy the bt2-1-null mutant responses; germination in all three mutants is hypersensitive to inhibition by glucose and ABA. Loss of either GTE9 or GTE11 in a BT2 over-expressing background blocks resistance to sugars and ABA, indicating that both GTE9 and GTE11 are required for BT2 function. Additionally, loss of GTE9 or GTE11, similar to loss of BT2, suppresses transcriptional gene activation mediated by CaMV 35S enhancers in Arabidopsis. The suppressed phenotype was accompanied by decreased transcription and hypermethylation of the 35S enhancers in the activation-tagged lines. We showed that BT2 and GTE9 co-immunoprecipitate and physically interact in vivo to mediate diverse responses to biotic and abiotic signals and 35S enhancer activity. Our working model is that the GTE9 and GTE11 function as chromatin adaptors that localize the BT2-CULLIN3 E3 ubiquitin ligase complex to acetylated chromatin on transcriptionally competent promoters in response to calcium signals detected by BT2’s calmodulin-binding domain.
75

The deposition of silica on titanium dioxide surfaces

Furlong, Donald Neil January 1975 (has links)
The deposition of amorphous silica from aqueous solution on to rutile particles has been studied with the aim of elucidating the nature of the silica-titania interactions occurring and of following the progressive build up of the silica coating. The coating process, which involves the addition of an aqueous sodium silicate solution to an aqueous dispersion of titanium dioxide, has been investigated by performing a series of controlled preparations and using the technique of microelectrophoresis. Prepared silica-coated rutile samples ranging from partial to full silica coatings have been characterized using transmission electron microscopy, microelectrophoresis and nitrogen, argon and water sorption. Nitrogen and argon adsorption isotherms have been analysed using the equation of Brunauer, Emmett and Teller (BET). Differential energies of adsorption of nitrogen and argon have been determined calorimetrically. Water sorption isotherms have been analysed using the BET equation and the Frenkel - Halsey - Hill (FHH) equation. It has been shown that uniform silica coatings can be produced if adsorption of monomeric silica is followed by polymerization of silica at the solid/liquid interface. Surface cations on rutile may be hydroxylated or co-ordinately bound to water molecules and it appears that monomeric silica adsorbs preferentially by replacing ligand water molecules. Rutile particles with silica coatings thicker than approximately 2.5nm exhibit characteristics typical of silica and not of the base rutile. Silica coatings deposited at pH 10 contain narrow channels which are accessible to water molecules but not to nitrogen or argon. Neutralization to pH 7 reduces the volume in the coating accessible to water molecules.
76

The Onsager heat of transport at the liquidvapour interface of p-tert-butyltoluene

Biggs, Georgina Aimee January 2007 (has links)
The Onsager heat of transport for p-tert-butyltoluene was measured, as part of a series of preliminary experiments towards the determination of the importance of temperature gradients on the air-sea flux of carbon dioxide. The results presented in this thesis imply that the temperature gradient is a major contributor to the magnitude of the air-sea flux. The heat of transport has been measured for the p-tert-butyltoluene system by measuring stationary-state pressure changes for known temperature differences on the vapour side of the interface. At the pressure ranges used the number of mean free paths was always outside the Knudsen zone, but the values of Q* were approximately 100 % of the latent heat of vaporisation. Departures from linearity of plots of P against ΔT are attributed to temperature jumps at the surface of the dry upper plate. Both the results taken for p-tert-butyltoluene and the earlier results for water from this laboratory fit to a Type III BET isotherm, where the c parameter is not constant. They also reveal the importance of the temperature gradient in determining the value of the thermal accommodation coefficient, and provide a new method of measuring thermal accommodation coefficients for a variety of surfaces and vapours
77

Controversial Industries: does it pay to ignore social norms?

van Nuenen, M.R.T.M. January 2018 (has links)
This paper investigates the impact of social norms on the performance and valuation of “controversial stocks”- publicly traded companies involved in the production of Adult Entertainment, Alcohol, Gambling, Nuclear Energy, Tobacco, Uranium, and Weapons. Their performance and valuation is directly compared with compare non-controversial stocks. The paper consider an international sample of 941 controversial stocks. Employing a multi-factor performance measure, seven countries provide a significant outperformance of controversial stocks across all relevant control factors. The valuation analysis, however, provide mixed results on a country level, but on the global market-to-book ratio provide a significant overvaluation of controversial stocks compared to comparable non-controversial stocks, which contradicts the prediction of an undervaluation.JEL classification:
78

Immunological Effects of TBE Vaccination : Increased Expression of Transcription factor T-bet Indicates Activation of Th1-like Cellular Immunity

Andersson, Pär January 2007 (has links)
Tick-borne encephalitis virus is the cause of much morbidity and sometimes a fatal infection. A vaccine based on formaldehyde inactivated virus is currently the only available way of preventing disease. This vaccine gives a high rate of seroconversion but there are reports of vaccination breakthrough, even in people who have demonstrated a neutralizing antibody response. The T cell response to inactivated TBE vaccine is largely unknown, but could be of importance for the effect of the vaccine. This study characterizes aspects of the T cell response by investigating the expression of two transcription factors, T-bet and GATA-3 with RT-PCR. T-bet is expressed in CD4+ T cells of the Th1 type, while GATA-3 is expressed in CD4+ T cells of the Th2 type. Our data show that vaccination with inactivated TBE vaccine leads to increase in expression of the T-bet gene when cells of vaccinated subjects are cultured with TBE virus. In contrast, the expression of GATA-3 remains unaffected by vaccination. Thus, this study suggests that the inactivated TBE vaccine leads to a Th1-like immune response in humans.
79

Využití Poissonova rozdělení pro předpovědi výsledků sportovních utkání / Use of Poisson distribution for prediction of sports matches results

Svoboda, Ondřej January 2017 (has links)
The aim of this master thesis is to verify possibility to use Poisson distribution for predicting soccer matches. At first for analysis is applied the original model from English statisticians Mark J. Dixon and Stuart G. Coles from 1997. Thereafter the model is extended in the thesis. All models are based on the maximum likelihood method. Chosen league for deducing conclusions is the first English league - Premier League. The matches are played in the period from season 2004/2005 to half of season 2015/2016. For identification of models performance are used the most market odds from American bookmaker Pinnacle. In the theoretical part are described models and statistical methods that are used in the practical part. In the practical part are realized calculations. Counted performance of models is based on profit from market odds. In the period ex-post are calculated optimum model parameters that are used in the ex-ante period, where is calculated performance of the model. The thesis answers question: Are these models gaining from public database effective in modern age?
80

Preparação e caracterização de catalisadores de V2O5 suportados em TiO2. / Preparation and characterization of V2O5 catalyst supported TiO2.

Cristiane Barbieri Rodella 02 May 2001 (has links)
Uma série de amostras do sistema catalítico V2O5/TiO2 foi preparada pelo método sol-gel com diferentes teores da fase ativa (de 0 a 9% em massa de V2O5) e calcinada em diferentes temperaturas (de 250 a 6000C). Sistema similar foi obtido pelo método de impregnação para a comparação. Os catalisadores foram caracterizados quanto suas propriedades texturais e estruturais pelas técnicas de Adsorção de N2 a 77K, Difratometria de Raios-X (DRX), Espectroscopia Raman, Ressonância Paramagnética Eletrônica (EPR), Espectroscopia de Fotoelétrons Excitados por Raios-X (XPS) e Espectroscopia de Absorção de Raios-X (XAS). Testes catalíticos para a verificação da atividade e seletividade foram realizados frente à reação de conversão do metanol. O sistema obtido pelo método sol-gel apresentou elevada área superficial e porosidade, as quais foram ampliadas com o aumento do teor de vanádio e reduzidos com o aumento da temperatura de calcinação. O sistema preparado por impregnação apresentou as mesmas propriedades texturais do suporte comercial. A análise de DRX identificou a existência de TiO2 nas formas cristalográficas anatásio e rutilo, não foi identificada a presença de V2O5 na forma cristalina. No sistema preparado por impregnação a estrutura cristalográfica do suporte se mantém, independente do teor de vanádio, porém a partir de 6% de V2O5 foi identificado à presença de V2O5 cristalino. Os espectros de Raman mostraram a presença de dois grupos superficiais de vanádio, os vanadilos monoméricos e os vanadatos poliméricos mesmo em elevados teores de vanádio, nos sistemas preparados pelo processo sol-gel. Nos catalisadores obtidos por impregnação foram identificados modos vibracionais referentes ao V2O5 cristalino.Os resultados obtidos por XAS confirmaram os obtidos por DRX e indicaram a presença de vanádio V4+ e V5+, porém com simetria diferente da forma cristalina V2O5. A determinação da razão entre os átomos V/Ti superficiais feita por XPS mostrou ser crescente com o aumento do teor de vanádio. Os espectros de EPR indicaram a presença de pelo menos três famílias de íons V4+ em diferentes simetrias, duas delas inseridas na matriz da titânia na fase rutilo e a outra dispersa na superfície. O sistema obtido por impregnação apresentou poucos íons V4+. Os testes catalíticos revelaram que a atividade e seletividade catalítica foram praticamente as mesmas para os sistemas preparados pelos dois métodos. Entretanto, a estabilidade catalítica do sistema obtido via sol-gel foi superior ao sistema preparado por impregnação. / A series of samples of the catalytic system V2O5/TiO2 was prepared by the sol-gel method with different proportions of the active phase (from 0 to 9% in mass of V2O5) and calcined in different temperatures (from 250 to 6000C). A similar system was obtained by the impregnation method for comparison. The catalyst were characterized by their textural and structural properties by Adsorption of N2 at 77K, X-Ray Diffraction (XRD), Raman Spectroscopy, Electronic Paramagnetic Resonance (EPR), X-Ray Photoelectron Spectroscopy (XPS) and X-Ray Absorption Spectroscopy (XAS). Catalytic tests for the verification of the activity and selectivity were performed by the conversion reaction of the methanol. The system obtained by the sol-gel method presented a high superficial area and porosity, which were enlarged by the increase of vanadium proportion and reduced with increase of the calcinations temperature. The system prepared by impregnation presented the same textural proprieties of the commercial support. XRD analysis identified the existence of TiO2 in two crystallographic forms, anatase and rutile. It was not identified the presence of V2O5 in the crystalline form. In the system prepared by impregnation the crystallographic structure of the support keeps, independent of the vanadium content, however starting from 6% of the vanadia was identified crystalline V2O5. Raman spectra showed the presence of two superficial groups of vanadium, the monomeric vanadyls and the polymeric vanadates even for elevated contents of vanadium, in the system prepared by the impregnation method vibrational modes were identified referring to V2O5 crystalline. The results obtained by XAS confirmed the obtained by XRD and indicated the presence of V4+ and V5+, however with different symmetry from the V2O5 in a crystalline form. The determination of the proportion between the surface V/Ti atoms determined by XPS showed to be increased with the increase of the vanadium content. EPR spectra indicated the presence of at least three V4+ion families in different symmetries; two of them inserted in the matrix of titania in the rutile phase and to other dispersed on the surface. The system obtained by impregnation presented few V4+ ions. The catalytic tests reveled that the catalytic activity and selectivity were practically the same for the systems prepared by both methods. However, the catalytic stability of the system obtained via sol-gel was superior to the system prepared by impregnation.

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