Abstract not available

Even though electrophoretic NMR (eNMR) experiments may provide unique chemical information and have been performed for three decades, the technique is still rarely applied, mainly because several experimental sources of artifacts have to be controlled to achieve accurate results. In this thesis, new experimental setups and protocols for accurate and precise eNMR experiments are presented. These include a novel eNMR sample cell, a radiofrequency filter and methods to suppress bulk flow effects. These developments improved the signal-to-noise ratio by roughly an order of magnitude compared to the U-tube setup previously used for eNMR. Convection-compensated pulse sequences in combination with a phase correction method were found to efficiently suppress bulk flow effects in the experiments and greatly increase experimental accuracy. These experimental setups and protocols were applied to probe association of ions and molecules in solution. It is particularly illustrated that the combination of diffusion and eNMR has great potential to provide quantitative results on ionic and molecular association in a variety of systems. The extent to which ionic surfactants associate with uncharged cyclodextrin probed by eNMR yielded very similar results to those obtained by diffusion NMR experiments. Complexation of a large set of small mono- and polyvalent metal cations to poly(ethylene oxide) was quantified by estimating the effective charge of the polymer through combined diffusion and eNMR information. Significant association was found for cations that have a surface charge density below a critical value. Ion pairing between tetramethylammonium cations and a series of anions in several solvents was also probed by diffusion NMR and eNMR experiments. For the monovalent anions in ethanol and ethanol-water mixture a dependence on ionic size was demonstrated. In water, dimethylsulfoxide, and methanol no such trend and very little pairing was observed. In acetonitrile, a different pattern was seen that did not correlate well with any single ionic parameter. An experimental cell and procedures for electrokinetic studies of solvated proton-conducting polymer materials is also presented. Electro-osmotic flow and diffusion were studied for each molecular component in water-methanol mixtures that swell Nafion membranes. / Elektroforetisk NMR (eNMR) är en experimentell metod som funnits i tre decennier och som kan ge unik kemisk information. Ändå används den sällan då flera experimentella artefakter måste korrigeras för, om man ska få korrekta resultat. I denna avhandling presenteras nya experimentella uppställningar och protokoll ämnade att uppnå korrekta och noggranna resultat. Dessa inkluderar en ny mätcell, ett radiofrekvensfilter och metoder för att minimera effekten av samtidiga bulkflöden i provlösningen. Sammantaget uppnås ungefär en storleksordning högre signal-brus-förhållande jämfört med den U-rörsuppställning som tidigare använts. Konvektions-kompenserande pulssekvenser i kombination med en faskorrektionsteknik minskade också bulkflödeseffekter effektivt, vilket ökade resultatens noggrannhet högst avsevärt. De experimentella uppställningarna och protokollen användes här för att mäta association av joner och molekyler i lösning. Mätningarna visar att kombinationen diffusions- och eNMR har en stor potential att kvantitativt kunna bestämma associationgraden i många olika typer av kemiska system. Associationsgraden mellan joniska tensider och cyklodextriner undersöktes både med eNMR och diffusions-NMR, och resultaten var mycket lika. Komplex-bildningen mellan en serie enkel- och flerladdade metalljoner och poly-(etylenoxid) kvantifierades genom att uppskatta polymerens effektiva laddning från kombinerad diffusions- och eNMR. Betydande komplexbildning hittades för katjoner med ytladdningstäthet under ett kritiskt värde. Jonparbildning mellan tetrametylammoniumjoner och en serie av anjoner i flera olika lösningsmedel undersöktes också med diffusions- och eNMR. För de monovalenta anjonerna i etanol och etanol-vatten-blandning påvisades ett samband med jonstorleken. I vatten, dimetylsulfoxid och metanol var däremot jonparbildningen låg och inget liknande samband hittades. I acetonitril observerades ett annat mönster, som inte korrelerade bra med någon av anjonernas normala joniska karakteristika. Slutligen presenteras en mätcell och procedurer för elektrokinetiska studier i de solvatiserade protonledande polymermaterial som bland annat används i bränsleceller. Elektroosmotiskt flöde och diffusion uppmättes för varje molekylär komponent i Nafion-membran solvatiserade av vatten-metanol-blandningar. / QC20100709

Staphylococcus aureus is one of the most important pathogens both in community- or hospital-acquired infections. The first part of this study analyzed the similarity of molecular types of S. aureus isolates cultured from nares and blood in patients with S. aureus bacteremia (SAB) by pulse-fielded gel electrophoresis (PFGE) of digested chromosomal DNA by Sma I at Kaohsiung Veterans General Hospital from August 1, 2000 through July 31, 2001. The results showed that the PFGE types of 78 (82.1%) paired nare and blood isolates of the 95 SAB patients having nasal carriage of S. aureus were clonally identical; identical in 89.7% patients of nosocomial group and 62.9% in community-acquired group. This provides the powerful evidence in close relationship between nasal carriage of S. aureus and acquisition of it in bacteremia. The data also showed that the rate of methicillin resistance occurred in SAB patients with nasal carriage in isolates of nosocomial SAB was 85.3%, and 31.3% in community-acquired group. The second part of this study analyzed the distribution of PFGE types of 163 nosocomial SAB isolates. The most predominant type was type A and composed 51.5% (84 strains) of 163 nosocomial SAB isolates. They were further divided into 7 subtypes. The second prevailing type was type B, 6.1%(10 strains). The evidence that an endemic stain (type A) occurred in >50% of nosocomial bacteremic isolates demonstrates horizontal dissemination of a single endemic strain of S. aureus in the SAB patients was common in the hospital. These results provide support for strategies to endorse more intensive procedures in infection control and to prevent systemic S. aureus infections by eliminating S. aureus nasal carriage.

Thesis (Ph. D.)--University of Missouri-Columbia, 2000. / Typescript. Vita. Includes bibliographical references (leaves 120-126). Also available on the Internet.

Thesis (Ph. D.)--University of Missouri-Columbia, 2000. / Typescript. Vita. Includes bibliographical references (leaves 120-126). Also available on the Internet.

This thesis presents results from three studies conducted in a veterinary teaching hospital (VTH). Study 1 retrospectively examined a collection of enterococci from clinical infections. Five recurring strains of Enterococcus faecium, and one strain of Enterococcus faecalis were identified using pulsed-field gel electrophoresis (PFGE) as causing clinical infections. Study 2 examined the gastrointestinal tract enterococci as a source of enteroccocal infections in dogs. Enterococcal catheter-associated bacteriuria (CA-bacteriuria) rate was 8%. In 3 of 4 sets of bacteriuria and rectal isolates, CA-bacteriuria isolates were indistinguishable from rectal isolates suggesting that the patient’s fecal enterococci represented the infection source. In all 3 sets of wound and rectal isolates, fecal carriage of the infection isolate was observed. Study 3 examined the prevalence of bacterial species and the overall CA-bacteriuria rate. CA-bacteriuria rate was 24%, with Enterococcus spp., E. coli, Staphylococcus spp., Streptococcus spp. and Enterobacter spp., as the most prevalent bacteria in listed order. / PetTrust

Thesis (M.S.)--University of Alabama at Birmingham, 2006. / Title from first page of PDF file (viewed Feb. 19, 2009). Includes bibliographical references (p. 35-44).

Thesis (Ph. D.)--University of Washington, 1998. / Vita. Includes bibliographical references (leaves [67]-81).

Magnetic resonance (MR) is a highly versatile technique with great potential for use in industrial applications; from the in situ study of unit operations to the optimisation of product properties. This thesis, concerned with the latter, is divided into two parts. Firstly, dynamic MR is applied to characterise the flow behaviour, or rheology, of process fluids. Such characterisation is typically performed using conventional rheometry methods operating offline, with an online, or inline, method sought for process control and optimisation. Until recently, MR was an unlikely choice for this application due to the requirement of high-field MR hardware. However, recent developments in low-field MR hardware mean that the potential of MR in such applications can now be realised. Since the implementation of MR flow imaging is challenging on low-field MR hardware, two new approaches to MR rheometry are described using pulsed field gradient (PFG) MR. A cumulant analysis of the PFG MR signal is first used to characterise the rheology of model power-law fluids, namely xanthan gum-in-water solutions, accurate to within 5% of conventional rheometry, the data being acquired in only 6% of the time required when using MR flow imaging. The second approach utilises a Bayesian analysis of the PFG MR signal to characterise the rheology of model Herschel--Bulkley fluids, namely Carbopol 940-in-water solutions; data are acquired in only 12% of the time required for analysis using MR flow imaging. The suitability of the Bayesian MR approach to study process fluids is demonstrated through experimental study on an alumina-in-acetic acid slurry used by Johnson Matthey. Secondly, MR imaging is used to provide insights into the origins and mechanisms of colloidal gel collapse. Many industrial products are colloidal gels, a space-spanning network of attractive particles with a yield stress. Colloidal gels are, however, known to undergo gravitational collapse after a latency period, thus limiting the shelf-life of products. This remains poorly understood, with a more detailed understanding of both fundamental interest and practical importance. To this end, MR imaging is applied offline to investigate the phase behaviour of colloidal gels. In particular, a comparison of the simulated and experimental phase diagrams suggests gravitational gel collapse to be gravity-driven. Furthermore, measurement of the colloid volume fraction using MR imaging indicates the formation of clusters of colloids at the top of the samples. Whether such clusters initiate gravitational gel collapse is yield stress-dependent; the gravitational stress exerted by a cluster must be sufficient to yield the colloidal gel.

This cumulative dissertation is a compilation of eight peer-reviewed, published scientific papers on the subject of two microscopic techniques of diffusion measurement, namely infrared (IR) microimaging and pulsed field gradient (PFG) NMR. The dissertation contains mainly five chapters. The first chapter introduces diffusion phenomena in general and concisely explains the importance and the current challenges of the investigation of molecular diffusion in nanoporous materials, which are the primary motivations behind the present work. To rise the challenges, it proposes an option of employing IR microimaging in parallel with PFG NMR in the measurement of the molecular diffusion. The second chapter describes the basic principles of the two diffusion measurement techniques and what they are capable of. Chapters 3 and 4 deliver convincing demonstrations of their applicability and potential in diffusion studies. Lastly, Chapter 5 concludes the present work by discussing complementary benefits of the two techniques, along with the novel application of the two-region model for assessing mass transfer in hierarchically porous materials.:Table of Contents CHAPTER 1. Introduction CHAPTER 2. Basics of diffusion measurement techniques 2.1. Introduction to infrared microscopy (IRM) 2.1.1. Working principle 2.1.2. Experimental setup 2.2. Introduction to pulsed field gradient nuclear magnetic resonance (PFG NMR) 2.2.1. Self-diffusion and propagator 2.2.2. Theory of PFG NMR CHAPTER 3. Applicability and potential of IRM • Publication 3.1. Anomaly in the chain length dependence of n-alkane diffusion in ZIF 4 metal-organic frameworks • Publication 3.2. Metal-organic framework Co-MOF-74-based host-guest composites for resistive gas sensing • Publication 3.3. Revealing the transient concentration of CO2 in a mixed-matrix membrane by IR microimaging and molecular modeling • Publication 3.4. IR microimaging of direction-dependent uptake in MFI-type crystals CHAPTER 4. Importance of PFG NMR in diffusion studies • Publication 4.1. NMR diffusometry with guest molecules in nanoporous materials • Publication 4.2. Structural characterisation of hierarchically porous silica monolith by NMR cryo-porometry and -diffusometry CHAPTER 5. Complementary benefits of IR microimaging and PFG NMR • Publication 5.1. Diffusion in nanopores: correlating experimental findings with 'first-principles' predictions • Publication 5.2. Diffusion analysis in pore hierarchies by the two-region model Bibliography Appendix A. Supporting information Appendix B. Author contributions