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<p> This thesis focuses on the use of time-resolved fluorescence anisotropy (TRF A) for the analysis of peptide-silica and protein-silica interactions. Previous studies from our group have shown that strong ionic binding of the cationic probe rhodamine 6G (R6G) to the anionic surface of silica particles in water provides a convenient labeling procedure to study both particle growth kinetics and surface modification by time-resolved fluorescence anisotropy (TRF A). The decays for R6G dispersed in diluted Ludox silica sols usually fit to a sum of picosecond and nanosecond decay components, along with a significant residual anisotropy component. The first objective of my work was to assess the nature of the R6G:silica interaction to determine the origin of the nanosecond decay component, and ultimately validate the model used to fit the TRFA data and gain further insight into the physical meaning of the anisotropy decay parameters. Our results show the origin of the nanosecond decay component ( ¢2) is due to the presence of a subpopulation of small nanoparticles in the Ludox sol. </p> <p> With the correct physical model in place, we have been able use TRFA ofR6G in aqueous Ludox to monitor peptide adsorption onto the silica particles in situ. Steady-state anisotropy and TRF A of R6G in Ludox sols were measured to characterize the extent of the ionic binding of the probe to silica particles in the presence of varying levels of tripeptides of varying charge, including Lys-Trp-Lys (KWK), N-acetylated Lys-Trp-Lys (Ac-KWK), Glu-Trp-Glu (EWE) and N-acetylated Glu-Trp-Glu (Ac-EWE). R6G showed significant decreases in anisotropy in the presence of cationic peptides, consistent with the addition of cationic peptides blocking the adsorption of the dye to the silica surface. The study shows that the competitive binding method can be used to assess the binding of various biologically relevant compounds onto silica surfaces, and demonstrates the potential of TRF A for probing peptide: silica and protein: silica interactions. </p> <p> We have also extended the application of TRF A to monitor protein adsorption onto plain and modified silica particles using a recently reported cationic long-lifetime quinolinium dye, CG437, which strongly binds to anionic silica particles through electrostatic interactions. In this case, alterations in the rotational correlation time of Ludox particles resulting from increases in the diameter of the rotating body upon binding of protein to the silica surface were monitored. The study shows that TRFA analysis of long-lived cationic probes such as CG437 can provide an effective method to investigate interactions between proteins and modified silica surfaces, extending the utility of the TRF A method. </p> / Thesis / Master of Science (MSc)

A generating voltmeter capable of measuring one, two, or found million volts has been designed and constructed for use with the Virginia Polytechnical Institute electrostatic accelerator. The voltmeter is a grounded shutter type, the rectified output of which is measured by a vacuum tube voltmeter. The voltmeter was calibrated by known nuclear resonances of fluoride. The calibration showed the meter to be accurate to within five percent at half scale deflation on the one million volts range the less than plus or minus three percent on the two million volts range. / Master of Science

A magnetic analyzer capable of bending the four million electron volt bean of the Virginia Polytechnic Institute electrostatic accelerator has been constructed. The magnet is the circumferential yoke, double-focusing type. Tests show its field to be uniform within one percent along its 16-inch radius, its magnetization curve to agree with the design requirements, and its cooling system to be more than adequate. A motor-generator set and a motor amplydine have been obtained for the magnet power supply, delivery now awaited. A voltage feedback system has been designed for field stabilization, and the considerations in supplying nuclear magnetic resonance equipment to field stabilization have been examined. / Master of Science

Piezoceramic fiber composite (PFC) actuators and sensors offer many advantages over conventional monolithic piezoceramic devices. Conformable, durable and, when equipped with interdigitated electrodes (IDEs), more responsive than regular monolithic devices, PFCs promise to revolutionize the application of piezoelectric materials. Developed by the NASA-Langley Research Center, the Macro-Fiber Composite (MFC) actuator and sensor is the most sophisticated PFC device yet invented. With superior qualities among PFCs in performance, behavior repeatability and manufacturability, the MFC has spawned great interest in the commercial and academic community as a tool in multitudinous engineering applications. While the MFC's characteristics render it a singularly useful device, limited characterization and modeling research on the MFC exists. Empirically designed and assembled, the MFC is poorly understood, especially in terms of its underlying operating principles, its dependence on design parameters and its electrical properties. The majority of published MFC studies focus on experimental quantification of MFC mechanical and actuation properties, and the research that attempts to model the MFC relies totally on finite element analysis. Published works widely assume that analytical models of the MFC are totally impossible. Rectifying gaps in the current body of MFC research, this study presents the first accurate analytical model of the static electrical field properties of the MFC. Implementing the techniques of conformal mapping, a branch of complex analysis, the following chapters derive a closed-form, exact analytical solution describing the electrical potential field and electrical field of the MFC's dual-IDE structure. Based on the conformal mapping solution for the MFC's electrical field, the electrical field of the commercially available MFC is examined and analyzed, introducing an intuitive knowledge of the MFC's operation. Demonstrating the utility of this solution in modeling the MFC, this work also predicts the capacitance and induced strain properties of a continuum of potential MFC designs and offers final suggestions on improving the current commercial MFC design. After establishing the theoretical underpinnings of the analytical MFC model, this report derives the conformal mapping solutions for the MFC, discusses the computational application of the resulting equations and then presents the results of numerical analyses executed using the new analytical model. / Master of Science

This thesis describes testing of an electrostatic precipitator that has a portion of the main precipitator flow drawn through a porous (fabric) collecting surface. Tests investigated effects of flow through the collecting surface (side flow) on precipitator turbulence and particulate removal efficiency. Particulate removal tests were conducted at both ambient temperature and boiler slipstream conditions. Side flow was shown to reduce turbulence in the boundary layers of the collecting plates, but to have no significant effect on turbulence in the main gas stream (beyond the boundary layer). Side flow was shown to create a more uniform horizontal velocity profile within the precipitator. Side flow was shown to have little effect on the reentrainment of single particles, but appears to reduce reentrainment of an established dust layer. Reentrainment was shown to be an important concern primarily for particles greater than three micrometers in diameter. This research strongly indicated the advisability of using two stage electrostatic precipitation for the collection of particles less than three micrometers in size. / Master of Science

No description available.

Thesis (M.S.)--Ohio University, November, 2008. / Title from PDF t.p. Includes bibliographical references.

In atomic force microscopy (AFM), the measured force between tip and substrate is used to produce images with subatomic resolution. In this thesis, plausible electrostatic interactions between tip-substrate is studied and compared with the experimental results in the report Vibrations of a molecule in an external force field by Okabayashi et al.. A simplified model gives by hand that the interaction between substrate and tip is dominated by a point charge - point charge relation due to the interatomic distances in AFM. We find that the electrostatic interaction can reproduce the experiment down to a limit of z ~ 3 Å. Further, we find that the tip interacts with the sample as a point charge with an induced dipole moment obtained by the electric field of the substrate. By analyzing electrostatic forces and compare them with the results in the Okabayashi et al. report, the AFM images in the report could be reproduced. / <p>Rättande lärare: Cecilia Holmqvist</p>

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