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In view of its varied concepts and interpretations, and because of the discrepancies produced by the previous utilization of polydispersed dextrans, a study using extremely narrow-range molecular weight dextran fractions was initiated to reevaluate and consolidate some of the aspects of capillary permeability. A portion of the study was performed under decreased barometric pressure in order to clarify further some of the mechanisms involved in particulate transfer across the capillary endothelial membranes. Gel filtration procedures augmented the study as an assessment of the polydispersity effects of the dextrans employed.

L’objectif principal de la thèse a été d’identifié expérimentalement les comportements mécaniques et rhéologiques de milieux granulaires dans un environnement à complexité croissante. En particulier, je me suis intéressé aux phénomènes de fluage sous contrainte en essayant de mieux comprendre l’impact des vibrations et la présence d’une faible quantité d’eau piégée entre les pores. J’ai monté un système cissométrique permettant de réaliser des tests mécaniques de fluage. Une originalité de mon montage a été de mettre au point un système de lit fluidisé qui, en alliant flux d’air et vibration, m’a permis de fabriquer des empilements à compacité initiale contrôlée. J’ai étudié les propriétés fondamentales de fluage sous contrainte d’un empilement granulaire de billes de verre de taille d = 200μm sous le seuil de Coulomb. Cette étude a mis en évidence que les seuils de Coulomb varient fortement avec la compacité, mais en plus, on a mis en évidence une contrainte appelée " contrainte de première rupture " qui traduit des réorganisation internes dans l’empilement et qui est d’environ 1/3 de la contrainte seuil maximale. En outre, grâce à la précision de la mesure de déformation, on a obtenu les réponses élastiques à de petits cycles en contrainte et on a établi que le module cisaillement élastique G augmente linéairement en fonction de la compacité, en accord avec le modèle d’élasticité non-linéaire de Hertz (modèle de champ moyen). Nous avons réalisé aussi une étude paramétrique complète du fluage en variant systématiquement la compacité et la contrainte de cisaillement. Notre étude sur les seuils de contrainte, l’élasticité effective et la dynamique de fluage, a été prolongée pour des empilements sous vibration générés par des transducteurs piézo-électriques enfouis sous la surface. Ce montage permet en outre par injection dans le granulaire d’un gaz saturé en vapeur d’eau, d’imposer sous un faible gradient thermique une condensation et d’obtenir une quantité contrôlée d’eau piégée dans l’empilement. Cette méthode permettra par la suite d’aborder le cas de granulaires cohésifs. / The main objective of the thesis was to identify experimentally the mechanical and rheological behavior of granular media in an environment varying in complexity. In particular, I was interested to creep phenomenon under stress in trying to understand better the impact of vibration and the presence of a small amount of water trapped between the grains. I set up a system to perform mechanical creep tests. Originality of my setup was the fluidized bed which uses air flow and vibration, and thus allows the control of the initial packing fraction. I studied the basic properties of creep strain of a granular resulting from a packing of glass beads of size d = 200 μm under the Coulomb threshold. This study showed that the Coulomb thresholds vary strongly with the packing fraction. In addition, it showed a stress called "the first rupture", that results from internal reorganizations in the granular medium and which is approximately 1/3 of the maximum stress threshold. Moreover, thanks to the precision of measuring deformation, we obtained the elastic response with small stress cycles, and we found that the shear elastic modulus G increases linearly with the packing fraction, in agreement with the model of nonlinear elasticity of Hertz (mean field). We performed a parametric study of creep in varying the packing fraction and shear stress. In all cases, we found the dynamics of logarithmic strain for long times. Our study on stress threshold, the elastic modulus and dynamics of creep, has been extended to granular medium under vibration generated by piezoelectric transducers buried under the surface. A small amount of water can be added and thus modifies the mechanical properties by the presence of capillary bridges. Preliminary experiments show the dependence of the Coulomb threshold of the elastic response and dynamic creep with an amount of water content.

For a number of reasons, miniaturization of chromatographic columns has been a general trend over the past three decades. Methods designed to enhance selectivity and efficiency can offer improved separation power and speed, expanding on the advantages of miniaturized columns. This dissertation describes novel approaches in this direction, focusing on two areas: the development of affinity-type sorbents for capillary HPLC derived from molecular imprinted polymers (MIPs) and the study of perfusive electroosmosotic flow (EOF) and its effect on efficiency in capillary electrochromatography (CEC). MIPs are synthetic polymers capable of selectively binding a template molecule incorporated prior to polymerization. MIPs prepared using nortripyline, a tricyclic antidepressant drug, were employed to screen a simulated chemical library, consisting of a series of structural analogs and related compounds. A parameter was introduced to quantify the selective retention of the analytes. Library compounds containing the major structural features of the template (ring structure and pendant 2�� amine) exhibited the highest affinity for the MIP. The use of macroporous packings under conditions of electroosmotic perfusion can result in improved chromatographic efficiencies. In this work, the performance of CEC columns packed with particles having different nominal pore diameters was investigated. The results indicate that perfusive EOF can yield significant gains in efficiency and speed, especially when wide pore packings and dilute buffers are employed. A model was developed that estimates the extent of perfusive EOF expressed as an effective particle diameter, d[subscript p,eff] The results suggest that the observed efficiency gains are not entirely due to smaller d[subscript p,eff] values and could perhaps be due to a decreased A term in the wide pore packings. The electrical conductivity of CEC columns was used to assess intraparticle flow permeability under conditions of perfusion. Results for the narrow pore (100 ��) column were in agreement with theory for nonporous spheres, indicating intraparticle current was negligible, while the wide pore (1000 and 4000��) columns exceeded theoretical values by a factor of two. These results provide evidence of the existence of "through-pores" and that intraparticle flow permeability (and potential for improved efficiency with perfusion) is greatest with wide pore packings. / Graduation date: 2001

The synthesis of the sodium salt of heptakis (2, 3-di-O-acetyl-6-O-sulfo)-β-cyclodextrin was modified to increase the isomeric purity to 98.5%. This salt was used to obtain the organic-solvent-soluble, single-isomer, charged tetrabutylammonium salt of heptakis (2, 3-di-O-acetyl-6-O-sulfo)-β-cyclodextrin. Its isomeric purity was higher than 99%, as determined by CE, and its structure was confirmed by NMR and ESI-MS analysis. The hydrophobic single-isomer cyclodextrin was utilized to separate the enantiomers of weak base analytes in aprotic media by capillary electrophoresis. The effective mobilities and separation selectivities follow trends observed with negatively charged cyclodextrins in amphiprotic solvents. The properties of the dissolved cyclodextrin are altered by its counter ion, thereby affecting the separations of enantiomers. The aprotic media allow the modification of the separation selectivity, since the binding strength of the enantiomers to the cyclodextrin is intermediate between that reported in aqueous and methanolic buffers.

Chromosomal mediated antimicrobial resistance in Neisseria gonorrhoeae can develop as a result of three main processes including the alteration of target enzymes, changes in transmembrane transport channels and active efflux pump function. Single nucleotide polymorphisms (SNPs) of target genes such as DNA gyrase (gyrA) and topoisomerase (parC), together with mutations in the promoter regions of the efflux pumps norM and mtr can confer resistance to the macrolides, penicillins and fluoroquinolones. These SNPs were analyzed using the SNaPshot method to allow for rapid detection of resistant isolates. Oligonucleotides were developed in the 5’ to the 3’ direction, ending one nucleotide adjacent to the specific SNP of interest. Single base extension reactions were performed and were detected using capillary electrophoresis. The SNaPshot procedure from Applied Biosystems employed in this study adds a single fluorescently-labelled nucleotide complementary to this SNP at the 3’ end by a primer extension polymerase reaction. Then using capillary electrophoresis, the labelled nucleotide is detected, enabling differentiation between A, C, T, or G. SNP results obtained were verified using DNA sequencing and both single and multiplexed reactions were carried out to increase the efficiency of the procedure. Spiked urine samples were also observed to determine if SNPs could be detected clinically. Single reactions enabled the characterization of all confirmed and relevant SNPs. With multiplex primer extension, multiple peaks were observed, each corresponding to one of the SNPs in the gene. This technique was explored for its applicability to detect SNPs of gyrA and parC mutations. Observable SNP detection limits were seen in spiked urine samples at 108 cells/mL in as early as 4 hours. DNA sequencing results confirmed the SNPs identity in each case. Thus, capillary electrophoresis using the SNaPshot protocol is another way to rapidly identify clinically resistant strains of Neisseria gonorrhoeae. This technique has also been shown to reduce analysis time compared to DNA sequencing and produces the same results. / February 2005