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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.
81

Short-term Comparison of Frictional Properties of Superpave and Balance Mix Design Hot Mix Asphalt Mixes

Matics, Janie Katherine 02 August 2022 (has links)
Hot Mix Asphalt (HMA) design has undergone years of development. Currently, many state agencies use the Superpave mix design method. While the Superpave mix design improved rutting, the implemented level 1 only considered volumetric properties and not mixture performance tests. Therefore, development in the asphalt community has addressed some of the issues with the Superpave mix design, e.g., cracking and raveling, with the Balance Mix Design (BMD) approaches. The Balance Mix Design incorporates performance testing elements that the level 1 Superpave mix design does not. The Virginia Department of Transportation (VDOT) aims to implement the Balance Mix Design by 2023. The objective of this thesis is to evaluate the initial frictional properties of mixes designed using the Balanced Mix Design method to verify that safety is not compromised to support the implementation of the BMD method within VDOT. It provides a further understanding of BMD mixtures surface properties provides insight into volumetric properties that may influence macrotexture. The thesis analyzed the initial friction and macrotexture of a series of experimental sections built to support VDOT BMD implementation efforts. A Side-Force Coefficient Road Investigation Machine (SCRIM) was used to measure friction and texture data on Control (Superpave Mix Design) and Balance Mix Design sections on several VDOT districts. Once the data was collected, it was analyzed using descriptive statistics and mean comparisons to determine any statistical differences in the friction and texture of the Control and BMD Mixes. The analysis showed that although statistically significant differences in friction and macrotexture were observed between some of the Superpave (Control) and Balance Mix Design mixes, the differences seem to be more prominent among districts than between the mix design method. In general, there were no difference in friction between control and BMD mixes in the same locations. On the other hand, there is statistically significant differences in the as-constructed macrotexture of Superpave and BMD mixes evaluated, with more BMD mixes having higher macrotexture than their control counterparts. Further analysis was conducted to create a macrotexture prediction model based on production volumetric properties obtained from VDOT databases. The model provided an initial assessment of the main HMA properties that influence MPD. A comparison of the macrotexture of the constructed in the various locations found that there is strong statistical evidence that the mean macrotexture of the pavement constructed in the various location was different. The analysis also showed that some projects produced sections with more uniform macrotexture than others. Comparison of mixes constructed in different years does not suggest any significant differences over the three-construction season evaluated. / Master of Science / Hot Mix Asphalt (HMA) is derived from various mix designs over the last hundred years. Currently, many highway agencies use the Superpave Mix Design in roadway development but only his basic level has been implemented. Most agencies do not use mechanical tests to verify that the mixes will perform properly when place on the pavement. To address some of issues with the current mix design approach, highway agencies have started to implement and use the Balance Mix Design (BMD). The Balance Mix Design incorporates performance tests for distresses such as rutting and cracking where the Superpave Mix Design did not. The Virginia Department of Transportation (VDOT) is working towards implementing the Balance Mix Design by 2023. The objective of this thesis is to evaluate the initial frictional properties of mixes designed using the Balanced Mix Design method to verify that safety is not compromised to support the implementation of the BMD method within VDOT. It helps agencies understand of BMD mixtures surface properties and what mix design properties may influence the safety of the road surface. The thesis analyzed the initial friction and macrotexture, properties that allow the vehicles to break and maintain control on curves, of a series of experimental sections built to support VDOT BMD implementation efforts. The Side-Force Coefficient Road Investigation Machine (SCRIM) is a large vehicle that continuously measures the pavement surface for friction, texture, and other elements using a skewed wheel and a laser system. The SCRIM was used in this thesis to measure friction and texture data on Control (Superpave Mix Design) and Balance Mix Design sections constructed on several VDOT districts. The data were analyzed using statistical analysis to determine any differences in the friction and texture of the Control and BMD Mixes. In general, there are no differences in friction between control and BMD mixes in the same locations. On the other hand, the analysis showed significant differences in the as-constructed macrotexture of Superpave and BMD mixes evaluated. In general, more BMD mixes had higher macrotexture than their control counterparts. Further analysis was conducted to create a macrotexture prediction model based on production volumetric properties obtained from VDOT databases. A comparison of the macrotexture of the constructed in the various locations found that there is strong statistical evidence that the average macrotexture of the pavement constructed in the various location was different.
82

Estimating the mechanical properties of retinal tissue using contact angle measurements of a spreading droplet

Grant, Colin A., Twigg, Peter C., Savage, M.D., Woon, W.H., Wilson, M.C.T., Greig, D. January 2013 (has links)
No / When a drop of liquid is placed on the surface of a soft material, the surface deformation and the rate of spreading of the triple contact point is dependent on the mechanical properties of the substrate. This study seeks to use drop spreading behavior to infer the mechanical properties of soft biological materials. As an illustration of the value of this technique we have compared the spreading behavior of a liquid droplet on two viscoelastic, soft materials, namely, an elastomer and a low concentration agar gel. The ratio of the mechanical properties of these soft materials obtained in this way is confirmed by atomic force microscopy (AFM) nanoindentation. By comparing the spreading behavior of a liquid on the retina with that of the same liquid on each of two viscoelastic materials, we can then estimate the elastic moduli of the retina: an estimate that is extremely difficult to carry out using AFM.
83

Interfacial study of cell adhesion to liquid crystals using widefield surface plasmon resonance microscopy

Soon, C. F., Khaghani, S. A., Youseffi, M., Nayan, N., Saim, H., Britland, S., Blagden, N., Denyer, M. C. January 2013 (has links)
Widefield surface plasmon resonance (WSPR) microscopy provides high resolution imaging of interfacial interactions. We report the application of the WSPR imaging system in the study of the interaction between keratinocytes and liquid crystals (LC). Imaging of fixed keratinocytes cultured on gold coated surface plasmon substrates functionalized with a thin film of liquid crystals was performed in air using a 1.45NA objective based system. Focal adhesion of the cells adhered to glass and LC were further studied using immunofluorescence staining of the vinculin. The imaging system was also simulated with 2x2 scattering matrix to investigate the optical reflection of the resonant plasmonic wave via the glass/gold/cell and glass/gold/LC/cell layers. WSPR imaging indicated that keratinocytes are less spread and formed distinct topography of cell-liquid crystal couplings when cultured on liquid crystal coated substrates. The simulation indicates that glass/LC shifted the surface plasmon excitation angle to 75.39 degrees as compared to glass/air interface at 44 degrees . The WSPR microcopy reveals that the cells remodelled their topography of adhesion at different interfaces.
84

Différents paramètres physiques exercés par le singe durant l'exploration tactile

Fortier-Poisson, Pascal January 2008 (has links)
Mémoire numérisé par la Division de la gestion de documents et des archives de l'Université de Montréal.
85

Applications of mesostructured carbonaceous materials as supports for fischer-tropsch metal catalyst

Mbileni, Charity Nonkululeko 21 February 2007 (has links)
Student Number : 0303610W - PhD thesis - School of Chemistry - Faculty of Science / Mesoporous MCM-48 was synthesized and used as a template to synthesize mesoporous carbon (MC) materials. Polystyrene, the carbon source, together with sulfuric acid and toluene were added to the template (160 oC for 6 h) and this procedure generated a low surface area carbon supported/MCM-48 material. A repeat addition and carbonization step was needed to form the precursor carbon/MCM-48 material that was pyrolysed at 900 oC to generate graphitic mesoporous carbon materials. After removal of the silica template, mesoporous carbons were characterized by XRD, HR-TEM, Raman spectroscopy and surface area analysis. The effect of the amount of polystyrene as well as the role of the pyrolysis temperature on the final product was investigated. This synthesis methodology can readily be controlled to produce partially ordered graphitic mesoporous carbon supports with predictable pore width and surface area. The methane selectivity was low (below 6%) and stable, and the overall olefin fraction was found to be good for all the supported catalysts studied. The potassium promoter increased the hydrocarbon chain growth to C68 giving α-1 and α-2 both between 0.79 and 0.90 for all supported catalysts with an exception of MCM-48 supported Fe catalyst that selectively produced hydrocarbons up to C28.
86

Estudos de adsorção em interfaces SnO2|H2O / Studies of adsorption on interfaces SnO2|H2O

Longo, Claudia 19 May 1994 (has links)
Estudos da adsorção de prótons e hidroxilas, considerados os íons determinantes de potencial para interfases óxido|H2O, e de surfactantes iônicos e não iônicos foram realizados para duas amostras de SnO2 obtidas através de métodos de preparação distintos. Uma amostra foi obtida pela oxidação de Sn metálico com HNO3 (conc.) e calcinação (amostra I) e a outra pela oxidação de Sn metálico com HCl (conc.), precipitação com ácido oxálico e calcinação (amostra II). A caracterização física das amostras identificou-as como sendo cristalinas, com estrutura de cassiterita e áreas específicas de 11,9 e 8,57 m2/g para as amostras I e II, respectivamente. A adsorção dos íons H+ e OH- foi determinada através de titulações potenciométricas ácido-base de suspensões do óxido em meio de KNO3 10-3 a 0,5 M. Através dos excessos superficiais destes íons, determinaram-se as curvas da variação da densidade de carga superficial (δo) em função do pH e da força iônica das suspensões. O ponto de carga zero da interfase foi determinado através do ponto de intersecção comum das curvas obtidas em diferentes concentrações do eletrólito suporte. Os valores obtidos foram pH (7,9 ± 0,3) para a amostra I e (7,0 ± 0,1) para a amostra II. A comparação das curvas mostrou que a amostra I apresenta valores de δo maiores que os correspondentes da amostra II, para condições de pH inferiores ao pcz. O estudo da adsorção de surfactantes consistiu na obtenção e análise de isotermas de adsorção de dodecilbenzenosulfonato de sódio (DBS), cloreto de benzil-hexadecildimetilamônio (CBz) e Triton X-100 (TX100). As isotermas foram determinadas a 25 °C em três condições nas quais a interfase apresenta valores distintos de δo. Para os surfactantes iônicos, o estudo foi realizado em condições nas quais a interfase apresenta densidades de carga opostas às dos tensoativos; para o TXI00, foram escolhidas condições nas quais a interfase apresenta carga aproximadamente nula. O comportamento apresentado pelas isotermas foi discutido em função das interações eletrostáticas e hidrofóbicas que ocorrem no sistema. A análise das isotermas obtidas para o DBS mostrou que a adsorção é favorecida quanto maiores a acidez e a concentração do eletrólito suporte, ou seja, para valores crescentes de δo. Para o TX100, as variáveis de pH e força iônica não exercem influência significativa na adsorção. Para o CBz, os resultados obtidos não permitiram avaliar a influência das forças de atração eletrostática no processo de adsorção deste sulfactante no sistema estudado. Através dos resultados obtidos, observou-se que a amostra I apresenta maior afinidade por prótons que a amostra II e que ambas as amostras apresentam afinidade aproximadamente equivalente por hidroxilas. No estudo referente à adsorção de sulfactantes, obteve-se que a amostra II apresenta maior capacidade de adsorção que a amostra I, comportamento oposto ao esperado considerando os valores de densidade de carga superficial e área específica determinados para as duas amostras. / The adsorption of H+ and OH- ions, the potential determining ions for the oxide isoIution interface, and the adsorption of ionic surfactants were studied for two distinct SnO2 samples, prepared via two different routes. Sample I was obtained by oxidizing metallic tin with HNO3 (conc) and calcination, while the other one, sample II, was prepared via the oxidation of metallic tin by HCl (conc), precipitation with oxalic acid and calcination. The resulting materials were characterized as cristalline SnO2 with cassiterite structure having specific surface areas equal to 11,9 and 8,57 m2g-1, for samples I and II, respectively. The adsorption of the H+ and OH- ions was studied by means of the potentiometric titration method of SnO2 suspensions in KNO3 aqueous solutions. The resulting point of zero charge were pH (7,9 ± 0,3) for sample I and (7,0 ± 0,1) for sample II. Adsorption isotherms of three different surlfactants: sodium dodecylbenzenesulfonate, benzylcetyldimethylanunonium chloride and Triton X-100 were obtained at 25°C for three different surface charge conditions. The adsorption isotherms were interpreted as a function of electrostatic and hidrophobic interactions. It was observed that Sample I presents a higher affinity for H+ ions while both SnO2 samples show the same extension for affinity for OH- ions. In spite of this, analysis of the surfactant adsorption isotherms showed that Sample II has a higher adsorption ability that Sample I. This behavior is just the opposite than the expected considering the values of the surface charge density and surface area of the samples.
87

Étude des propriétés de surface du bactériophage MS2 et du norovirus murin au cours de différents traitements d’inactivation / Evolution of surface properties of MS2 bacteriophage and murine norovirus during different inactivation treatments

Brié, Adrien 25 January 2017 (has links)
Même si les traitements thermiques ou la désinfection par les oxydants ont démontré leur efficacité virucide, les mécanismes liés à la perte du caractère infectieux ne sont pas connus. Ceci pose un réel problème d’interprétation de la présence de génome viral en matière de risque infectieux dans les aliments. Ce travail de thèse a pour objectif d’étudier l’évolution des propriétés de surface (charge et hydrophobie) de virus modèles, bactériophage MS2 et norovirus murin, au cours de l’inactivation par la chaleur, l’hypochlorite de sodium et l’ozone. Pour nos deux virus, nous démontrons l’existence d’une température critique au-delà de laquelle la particule virale se déstructure en libérant son génome. Un simple traitement à la RNase permettrait alors de ne détecter que des virus infectieux par biologie moléculaire. Le traitement thermique implique aussi une augmentation de l’hydrophobie soulignant des modifications conformationnelles de la capside. L’hypochlorite de sodium ne modifie que peu les propriétés de surface mais des phénomènes d’oxydation ont lieu au niveau de la capside puisque la charge du bactériophage MS2 est légèrement modifiée. Ces modifications diminuent la résistance thermique du virus. Nous démontrons un effet synergique de l’hypochlorite de sodium et la chaleur sur le bactériophage MS2 (inactivation, RNase et hydrophobie). Quant à l’ozone gazeux, nous soulignons son intérêt pour le traitement virucide des aliments fragiles. Ainsi, ce travail précise les mécanismes d’inactivation des virus et ouvre de nouvelles perspectives tant pour discriminer les virus infectieux et non-infectieux que pour proposer l’exploration de nouveaux traitements technologiques / Although heat treatments or disinfections by oxidants have proven their virucidal efficiencies, mechanisms related to the loss of infectivity are not known. This statement could lead to a misinterpretation of the presence of viral genome on infection risk for humans in food matrices. This thesis aimed to study the evolution of surface properties (charge and hydrophobicity) for model viruses, bacteriophage MS2 and murine norovirus, during the heat, sodium hypochlorite and ozone inactivations. For both viruses, the existence of a critical temperature beyond which the viral particle was disrupted and released its genome was demonstrated. Simple treatment with RNase would then only detect infectious virus by molecular biology. The heat treatment also involved a transient increase in the hydrophobicity which highlighted conformational changes of the viral capsid. Sodium hypochlorite slightly modified the surface properties but oxidation phenomena occurred onto capsid since the bacteriophage MS2 charge has changed a little. These changes decreased the thermal resistance of the virus. Synergistic effects of both sodium hypochlorite and heat were observed on the inactivation of MS2 phages, the sensitivity of their genome to RNases and the increase in hydrophobicity of remaining infectious particles. Regarding gaseous ozone, we underlined its interest in the case of virucidal treatment of fragile food matrices. Therefore, this work specified the virus inactivation mechanisms and opened up new perspectives to discriminate infectious from non-infectious viruses but also to propose the exploration of new technological processes
88

Comparative studies on the physical and surface properties of salmeterol xinafoate prepared by spray drying and supercritical fluid processing. / CUHK electronic theses & dissertations collection

January 2003 (has links)
Tong Hoi Yee. / "July, 2003." / Thesis (Ph.D.)--Chinese University of Hong Kong, 2003. / Includes bibliographical references (p. 237-253). / Electronic reproduction. Hong Kong : Chinese University of Hong Kong, [2012] System requirements: Adobe Acrobat Reader. Available via World Wide Web. / Mode of access: World Wide Web. / Abstracts in English and Chinese.
89

Tailormade Surfaces for Extended CE Applications

Ullsten, Sara January 2004 (has links)
<p>The combination of capillary electrophoresis (CE) and mass spectrometry (MS) constitutes a powerful microanalytical system in the fields of biology, medicine and chemistry. This thesis describes the development of three novel capillary coatings and demonstrates how these extend the utility of CE as a high-efficiency separation technique in protein analysis and biopharmaceutical drug screening.</p><p>Due to the rapidly growing interest in characterizing the human proteome, there is an increased need for rapid protein separations. The use of CE in protein analysis is, however, nontrivial due to problems with protein adsorption to the fused-silica capillary walls. In this thesis, this problem was addressed by developing two novel, physically adsorbed, cationic polymer surface coatings, denoted PolyE-323 and Q-agarose. By using simple rinsing protocols, highly reproducible coatings, stable over a wide range of pH 2-11 were generated. Successful protein separations using cationic-coated capillaries in CE-MS, equipped with either electrospray ionization (ESI) or matrix-assisted laser desorption/ionization (MALDI), has been demonstrated.</p><p>In the pharmaceutical industry, favorable pharmacokinetic properties of a candidate drug, such as high bioavailability after oral administration, are crucial for a high success rate in clinical development. Tools for prediction of biopharmaceutically relevant drug properties are important in order to identify and discard poor candidate drugs as soon as possible. In this thesis, a membrane mimetic coating was developed by electrostatically immobilizing liposomes to the capillary wall, via an anchoring sublayer of Q-agarose. The liposome-coated capillaries were demonstrated in on-line CE-MS for prediction of drug membrane permeability.</p>
90

Tailormade Surfaces for Extended CE Applications

Ullsten, Sara January 2004 (has links)
The combination of capillary electrophoresis (CE) and mass spectrometry (MS) constitutes a powerful microanalytical system in the fields of biology, medicine and chemistry. This thesis describes the development of three novel capillary coatings and demonstrates how these extend the utility of CE as a high-efficiency separation technique in protein analysis and biopharmaceutical drug screening. Due to the rapidly growing interest in characterizing the human proteome, there is an increased need for rapid protein separations. The use of CE in protein analysis is, however, nontrivial due to problems with protein adsorption to the fused-silica capillary walls. In this thesis, this problem was addressed by developing two novel, physically adsorbed, cationic polymer surface coatings, denoted PolyE-323 and Q-agarose. By using simple rinsing protocols, highly reproducible coatings, stable over a wide range of pH 2-11 were generated. Successful protein separations using cationic-coated capillaries in CE-MS, equipped with either electrospray ionization (ESI) or matrix-assisted laser desorption/ionization (MALDI), has been demonstrated. In the pharmaceutical industry, favorable pharmacokinetic properties of a candidate drug, such as high bioavailability after oral administration, are crucial for a high success rate in clinical development. Tools for prediction of biopharmaceutically relevant drug properties are important in order to identify and discard poor candidate drugs as soon as possible. In this thesis, a membrane mimetic coating was developed by electrostatically immobilizing liposomes to the capillary wall, via an anchoring sublayer of Q-agarose. The liposome-coated capillaries were demonstrated in on-line CE-MS for prediction of drug membrane permeability.

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