Thesis (Ph. D.)--University of California, San Diego and San Diego State University, 2006. / Includes bibliographical references (leaves 178-191).

abstract: Complex samples, such as those from biological sources, contain valuable information indicative of the state of human health. These samples, though incredibly valuable, are difficult to analyze. Separation science is often used as the first step when studying these samples. Electrophoretic exclusion is a novel separations technique that differentiates species in bulk solution. Due to its ability to isolate species in bulk solution, it is uniquely suited to array-based separations for complex sample analysis. This work provides proof of principle experimental results and resolving capabilities of the novel technique. Electrophoretic exclusion is demonstrated at a single interface on both benchtop and microscale device designs. The benchtop instrument recorded absorbance measurements in a 365 μL reservoir near a channel entrance. Results demonstrated the successful exclusion of a positively-charged dye, methyl violet, with various durations of applied potential (30 - 60 s). This was the first example of measuring absorbance at the exclusion location. A planar, hybrid glass/PDMS microscale device was also constructed. One set of experiments employed electrophoretic exclusion to isolate small dye molecules (rhodamine 123) in a 250 nL reservoir, while another set isolated particles (modified polystyrene microspheres). Separation of rhodamine 123 from carboxylate-modified polystyrene spheres was also shown. These microscale results demonstrated the first example of the direct observation of exclusion behavior. Furthermore, these results showed that electrophoretic exclusion can be applicable to a wide range of analytes. The theoretical resolving capabilities of electrophoretic exclusion were also developed. Theory indicates that species with electrophoretic mobilities as similar as 10-9 cm2/Vs can be separated using electrophoretic exclusion. These results are comparable to those of capillary electrophoresis, but on a very different format. This format, capable of isolating species in bulk solution, coupled with the resolving capabilities, makes the technique ideal for use in a separations-based array. / Dissertation/Thesis / Ph.D. Chemistry 2012

<p> Studies on the isolation and purification of Fraction I protein from various plants are described. Clear differences in the electrophoretic mobilities of Fr I from various species were observed. The genetic implication of observations on the electrophoretic mobilities of Fr I from wheat, rye and triticales are discussed. It is suggested that a non-chromosomal gene codes for Fr I. Conclusions are drawn from the fingerprint, N-terminal amino acid, and amino acid analysis studies. The presence of ribulose diphosphate carboxylase activity in Fr I protein is also investigated.</p> / Thesis / Doctor of Philosophy (PhD)

The discovery that negatively charged aggregates of C60 fullerene are stable in aqueous environments has elicited concerns regarding the potential environmental and health effects of these aggregates. Although many previous studies have used aggregates synthesized using intermediate organic solvents, this work primarily employed an aggregate production method that more closely emulates the fate of C60 upon accidental release into the environment — extended mixing in water. The aggregates formed via this method (aqu/nC60) differ from those produced using the more common solvent exchange methods. The aqu/nC60 aggregates are heterogeneous in size (20 nm and larger) and shape (angular to round), negatively charged, and crystalline in structure — exhibiting a face centered cubic (fcc) system. Solution characteristics such as aqu/nC60 aggregate size and concentration were found to be dependant upon preparation variables such as stirring time, initial C60 concentration, and initial particle size. Additional experiments indicate that aggregate charge, structure, and stability are highly dependant upon the identity of co-solutes (NaCl, CaCl2, sodium citrate) and their concentrations. Citrate concentrations greater than 0.5 mM resulted in the formation of very small (< 20 nm) spherical aqu/nC60 particles. At moderate citrate concentrations (~ 1 mM) a more negative surface charge was observed, which may be an indication of increased nC60 stability. In contrast, high concentrations of monovalent and divalent electrolytes result in aggregation and sedimentation of nC60 out of solution. Our research describes the effect that solution composition has on aggregate formation and stability, and suggests that C60 fate and transport will be a function of solution composition. / Master of Science

<p>The thesis deals partly with methodology including construction</p><p>of hardware and new pulse sequences in the field of electrophoretic</p><p>NMR, and partly with practical use of ENMR and</p><p>diffusion NMR in the investigation of charged colloidal systems.</p><p>Several sources of artefacts are investigated, including gas production</p><p>at the electrodes, electroosmosis and Joule heating</p><p>effects that can cause convection. The electrophoretic double</p><p>stimulated-echo pulse sequence is introduced to suppress these</p><p>artefacts and to increase the feasible measuring range to higher</p><p>electric fields and conductivities.</p><p>The interaction between the non-ionic polymer poly(ethylene</p><p>oxide) PEO and differently charged surfactants is investigated</p><p>using the above mentioned methods. The investigated surfactants</p><p>are the anionic sodium dodecyl sulphate (SDS) and</p><p>potassium laurate (KC12), the cationic dodecyltrimethylammonium</p><p>bromide (CTAB) and the non-ionic octyl β-D-glucoside.</p><p>ENMR is also used to investigate two different mixed micelle</p><p>systems, with SDS as the charged surfactant component and</p><p>dodecyl malono-bis-N-methylglucamide (C12BNMG) respectively</p><p>tetra(ethylene oxide) dodecyl ether (C12EO4) as the nonionic</p><p>surfactant component. A method to calculate the degree</p><p>of counter-ion dissociation, αdissociation, as a function of composition</p><p>is demonstrated.</p><p>Finally diffusion NMR is used to compare transport dynamics</p><p>in gel electrolyte systems based on two differently grafted polymers;</p><p>one amphiphilic system containing polymethacrylate</p><p>grafted partly with polyethylene oxide and partly with fluorocarbons</p><p>and the corresponding nonamphiphilic system grafted</p><p>with only polyethylene oxide. Both systems contain the electrolyte</p><p>lithium bis(trifluoromethylsulfonyl) imide salt dissolved in</p><p>γ-butyrolactone. The results show that the system based on the</p><p>amphiphilic polymer has better transport dynamics and therefore</p><p>is more suited as material for battery</p>

The thesis deals partly with methodology including construction of hardware and new pulse sequences in the field of electrophoretic NMR, and partly with practical use of ENMR and diffusion NMR in the investigation of charged colloidal systems. Several sources of artefacts are investigated, including gas production at the electrodes, electroosmosis and Joule heating effects that can cause convection. The electrophoretic double stimulated-echo pulse sequence is introduced to suppress these artefacts and to increase the feasible measuring range to higher electric fields and conductivities. The interaction between the non-ionic polymer poly(ethylene oxide) PEO and differently charged surfactants is investigated using the above mentioned methods. The investigated surfactants are the anionic sodium dodecyl sulphate (SDS) and potassium laurate (KC12), the cationic dodecyltrimethylammonium bromide (CTAB) and the non-ionic octyl β-D-glucoside. ENMR is also used to investigate two different mixed micelle systems, with SDS as the charged surfactant component and dodecyl malono-bis-N-methylglucamide (C12BNMG) respectively tetra(ethylene oxide) dodecyl ether (C12EO4) as the nonionic surfactant component. A method to calculate the degree of counter-ion dissociation, αdissociation, as a function of composition is demonstrated. Finally diffusion NMR is used to compare transport dynamics in gel electrolyte systems based on two differently grafted polymers; one amphiphilic system containing polymethacrylate grafted partly with polyethylene oxide and partly with fluorocarbons and the corresponding nonamphiphilic system grafted with only polyethylene oxide. Both systems contain the electrolyte lithium bis(trifluoromethylsulfonyl) imide salt dissolved in γ-butyrolactone. The results show that the system based on the amphiphilic polymer has better transport dynamics and therefore is more suited as material for battery

High capacitance devices were developed using rapid electrophoretic deposition (EPD) of barium titanate (BaTiO3) on ultrasonically etched nickel (Ni) substrates. The microstructural and electrical properties of films with varying thicknesses, sintering temperatures and substrate etching times were investigated to study their effect on the capacitance. Although increasing the capacitance was the primary goal, decreasing manufacturing costs and reducing environmental impact was also considered. After confirming the tetragonality and particle size of a 0.2 µm hydrothermal powder, it was dispersed in an aqueous-organic mixture of ethanol, acetone and water. A zeta potential of 50 mV was observed at the EPD pH level (6.8). Flocculation or coagulation was not likely in this situation. Therefore, mixing water with an organic solution was an effective method for reducing environmental impact while maintaining deposition quality. The presence of BaCO3 in the films was proven using X-ray diffraction. Other impurities such as TiO2 and NiO were not detected. A significant variation in the average grain size was not observed for films with different thicknesses whereas films sintered at different temperatures displayed greater variation. A bimodal pore size distribution in the samples suggested that the powder was agglomerated after deposition due to a high deposition voltage (20 V). Rapid deposition times of 2 to 8 seconds offered a potential for cost reduction compared to longer deposition times implemented in industry. Therefore the increased porosity was accepted. The dielectric constant of the films increased from 2900 to 6730 as the thickness increased from 17.75 µm to 47.5 µm. The dissipation factor decreased from 0.27 to 0.06 with increasing thickness. This behavior was attributed to a low dielectric constant interfacial layer and a higher dielectric leakage current at smaller thicknesses. The dielectric constant increased from 1700 to 6350 and the dissipation factor decreased from 0.23 to 0.04 as the sintering temperature increased from 1150°C to 1300°C. This was attributed to an increase in tetragonality with grain size and a decrease in porosity with sintering temperature. Finally, etching a substrate for 60 seconds increased its capacitance by 27.47% and using ultrasonic agitation further increased the capacitance by 8.75%. / Thesis (Master, Mechanical and Materials Engineering) -- Queen's University, 2012-10-12 00:54:53.915

Specific ion effects, identified for more than hundred years, play an important role in a wide range of phenomena and applications. Several mechanisms such as direct ion interaction with molecules have been suggested to explain these effects, but quantitative experimental evidence remains scarce. Electrophoretic NMR (eNMR) has been emerging as a very powerful tool for studying molecular association and ionic transport in a variety of systems. Yet its potential in studying specific ion effect has been unexplored. In this thesis, eNMR was in part developed further as an analytical method and was in part used as one of the main techniques to study ions interacting with macromolecules in aqueous and non-aqueous solutions. The complexation of a large group of cations with poly ethylene oxide (PEO) in methanol was studied with eNMR. The binding of monovalent ions was demonstrated not to follow the Hofmeister order; multivalent cations except barium all showed negligible complexation. As a unifying feature, only cations with surface charge density below a threshold value were able to bind suggesting that ion solvation is critical. The binding mechanism was examined in greater detail for K+ and Ba2+ with oligomeric PEO of different chain lengths. Those two cations exhibited different binding mechanisms. K+ was found to bind to PEO by having at least 6 repeating units wrap around it while retaining the polymer flexibility. On the other hand, Ba2+ (and, to some extent, (BaAnion)+) needs a slightly shorter section to bind, but the molecular dynamics at the binding site slow considerably. The binding of anions with poly (N-isopropylacrylamide) in water was quantified at low salt concentration with eNMR and the binding affinity, though very weak, followed the Hofmeister order. This result indicates the non-electrostatic nature of this specific ion effects. The increase of binding strength with salt concentration is well described by a Langmuir isotherm. The specific ion binding to a protein, bovine serum albumin (BSA), was also studied at pH values where BSA has either net positive and negative charges. Our results show that anions have the same binding affinity irrespective of the surface charge while the binding strength of cations is reversed with the change in net surface charge. This indicates different binding mechanisms for cations and anions. The ionization of cellobiose in alkaline solutions was measured quantitatively by eNMR. The results show a two-step deprotonation process with increasing alkaline strength. Supported by results from 1H-13C HSQC NMR and MD simulation, ionization was proposed to be responsible for the improved solubility of cellulose in alkaline solution. eNMR was also used to characterize the effective charge of tetramethylammonium ions in a variety of solvents. In solvents of high polarity, the results agree well with predictions based on Onsager’s limiting law but for nonpolar solvents deviations were found that were attributed to ion pair formation. / <p>QC 20170216</p>

In 2012 the net world electricity generation was 21.56 trillion kilowatt hours. Photovoltaics only accounted for only 0.1 trillion kilowatt hours, less than 1 % of the total power. Recently there has been a push to convert more energy production to renewable sources. In recent years a great deal of interest has been shown for dye sensitized solar cells. These devices use inexpensive materials and have reported efficiencies approaching 12% in the lab. Here methods have been studied to improve upon these, and other, devices. Different approaches for the addition of gold nanoparticles to TiO2 films were studied. These additions acted as plasmonic and light scattering enhancements to reported dye sensitized devices. These nanoparticle enhancements generated a 10% efficiency in device performance for dye sensitized devices. Quantum dot (QD) sensitized solar cells were prepared by successive ionic layer adsorption and reaction (SILAR) synthesis of QDs in mesoporous films as well as the chemical attachment of colloidal quantum dots using 3-mercaptopropionic acid (3-MPA). Methods of synthesizing a copper sulfide (Cu2S) counter electrode were investigated to improve the device performance. By using a mesoporous film of indium tin oxide nanoparticles as a substrate for SILAR growth of Cu2S catalyst, an increase in device performance was seen over that of devices using platinum. These devices did suffer from construction drawbacks. This lead to the development of 3D nanostructures for use in Schottky photovoltaics. These high surface area devices were designed to overcome the recombination problems of thin film Schottky devices. The need to deposit a transparent top electrode limited the success of these devices, but did lead to the development of highly ordered metal nanotube arrays. To further explore these nanostructures depleted heterojunction devices were produced. Along with these devices a new approach to depositing lead sulfide quantum dots was developed. This electrophoretic deposition technique uses an applied electric field to deposit nanoparticles onto a substrate. This creates the possibility for a low waste method for depositing nanocrystals onto nanostructured substrates.

>Magister Scientiae - MSc / Tuberculosis (TB) is a global health problem and rated as the second leading cause of death after HIV/AIDS. Transmission of TB from one person to the next is very rapid in crowded communities. Therefore, it is crucial to identify people who are infected as quickly as possible not only to provide treatment but also to prevent the spread of the disease. Current TB diagnostic tests such as the culture and sputum smear tests are time-consuming, while rapid tests make use of antibodies that are costly and have low sensitivity and stability. Great improvement has been observed when aptamers are used in place of antibodies in rapid diagnostic tests such as lateral flow devices (LFDs). Therefore, the current study aims to synthesize and identify aptamers against serum biomarkers for development of rapid TB diagnostic tests such as a lateral flow assay. Several TB serum biomarkers have been identified and can be used for the diagnosis of TB. TB biomarkers expressed in serum samples were identified through in silico approach. The biomarkers were expressed in bacterial systems using recombinant DNA technology. The recombinant proteins were purified by affinity chromatography and further used as targets for the selection of aptamers using Systemic Evolution of Ligands by EXponential enrichment (SELEX). Aptamers for the selected biomarkers were synthesized based on magnetic-bead based SELEX and characterized by electrophoretic mobility shift assay (EMSA), Surface Plasmon resonance (SPR) and MicroScale Thermophoresis (MST). Six putative TB serum biomarker proteins were selected from literature, namely, Insulin-like Growth Factor Binding Protein 6 (IGFBP6), Interferon-stimulated Gene 15 (ISG15), Calcium Binding Protein (S100A9), Retinol Binding Protein 4 (RBP4), Granzyme A (GrA), and Transgelin-2 (TAGLN2). The biomarkers were recombinantly expressed and purified after which they were used as targets in SELEX for aptamers synthesis. Aptamers were analysed by in silico method and the ones with highly conserved motifs were selected. The selected aptamers were synthesized and later characterized. The aptamers that show high affinity and specificity for the biomarkers will be used for the fabrication of a rapid lateral flow device for TB screening. Such a test would allow for a short diagnostic turnaround time, and hence expedite treatment.