Thesis (Ph. D.)--University of Washington, 2006. / Vita. Includes bibliographical references (leaves 112-124).

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abstract: Bioparticles comprise a diverse amount of materials ubiquitously present in nature. From proteins to aerosolized biological debris, bioparticles have important roles spanning from regulating cellular functions to possibly influencing global climate. Understanding their structures, functions, and properties provides the necessary tools to expand our fundamental knowledge of biological systems and exploit them for useful applications. In order to contribute to this efforts, the work presented in this dissertation focuses on the study of electrokinetic properties of liposomes and novel applications of bioaerosol analysis. Using immobilized lipid vesicles under the influence of modest (less than 100 V/cm) electric fields, a novel strategy for bionanotubule fabrication with superior throughput and simplicity was developed. Fluorescence and bright field microscopy was used to describe the formation of these bilayer-bound cylindrical structures, which have been previously identified in nature (playing crucial roles in intercellular communication) and made synthetically by direct mechanical manipulation of membranes. In the biological context, the results of this work suggest that mechanical electrostatic interaction may play a role in the shape and function of individual biological membranes and networks of membrane-bound structures. A second project involving liposomes focused on membrane potential measurements in vesicles containing trans-membrane pH gradients. These types of gradients consist of differential charge states in the lipid bilayer leaflets, which have been shown to greatly influence the efficacy of drug targeting and the treatment of diseases such as cancer. Here, these systems are qualitatively and quantitatively assessed by using voltage-sensitive membrane dyes and fluorescence spectroscopy. Bioaerosol studies involved exploring the feasibility of a fingerprinting technology based on current understanding of cellular debris in aerosols and arguments regarding sampling, sensitivity, separations and detection schemes of these debris. Aerosolized particles of cellular material and proteins emitted by humans, animals and plants can be considered information-rich packets that carry biochemical information specific to the living organisms present in the collection settings. These materials could potentially be exploited for identification purposes. Preliminary studies evaluated protein concentration trends in both indoor and outdoor locations. Results indicated that concentrations correlate to certain conditions of the collection environment (e.g. extent of human presence), supporting the idea that bioaerosol fingerprinting is possible. / Dissertation/Thesis / Ph.D. Chemistry 2011

Piezoelectric composite materials, consisting of a ferroelectric ceramic in an electrically-inactive polymer matrix, have been shown to greatly outperform single phase materials for certain applications. A new assembly technique, which electrically controls the spatial distribution of the ceramic within the polymer, promises to enhance the sensitivity of 0-3 type piezoelectric composites. The materials so-produced have a quasi 1-3 structure and it is intended that they will exhibit some of the advantages of 1- 3 piezoelectric composites, whilst retaining the simplicity of 0-3 manufacturing. The electric field structuring technique exploits the electrokinetic phenomenon of dielectrophoresis, which is responsible for the electrorheological effect. When a suspension of ceramic particles in an insulating fluid is exposed to a moderate AC electric field, the particles polarize and as a result they exhibit a mutually attractive force. Under suitable conditions the particles assemble into 'pearl-chains', 'fibrils' or columns, oriented parallel to the applied field. If the fluid is a resin pre-polymer, this can then be cured and the newly formed structures frozen into place to form a composite material with anisotropic properties. The key process parameters are explored and the implications of employing this method to produce technologically useful materials are discussed. It is demonstrated, for the first time, that dielectrophoresis can be used to induce anisotropic dielectric and piezoelectric properties in 55%vol. fraction ceramic/polymer composites. A model composite system of pure lead titanate in an epoxy resin is considered in basic detail. A method of producing a lead zirconate titanate (PZT) powder with a narrow particle size distribution, by flux growth, has been shown to be effective. New concepts in multiphase composites are introduced, whereby chains are formed within the confines of a second immiscible fluid or where particles of two different materials are mixed in a suspension, each material having its own 'polarization signature'.

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Abstract The general aim of the present study is to gain insight into physical mechanisms of some auroral forms on the basis of multi-instrumental measurements (satellites, rockets and ground-based magnetic and riometer instruments) in the vicinity of the auroras observed by ground-based all-sky cameras. One part of this work is related to the Auroral Turbulence II sounding rocket experiment. It was launched on February 11th, 1997, at 08:36 UT from Poker Flat Research Range, Alaska, into a moderately active auroral region after a substorm onset. This unique three-payload rocket experiment contained both electric and magnetic in the evening sector (21 MLT), auroral forms at the substorm recovery were investigated, providing details of the quiet and disturbed auroral densities and DC electric patches propagating along them like a luminosity wave. Those evening auroral patches and associated electric fields formed a 200-km spatially-periodic structure along the arc, which propagated westward at a velocity of 3 km s-1. The other part of this study describes ground signatures of dynamic substorm features observed by the IRIS imaging riometer, magnetometers and all-sky camera during late evening hours. The magnetometer data were consistent with the motion of upward data are used to estimate the intensity of FAC associated with these local current-carrying the excitation of the low-frequency turbulence in the upper ionosphere. As a result, a quasi-oscillating regime of anomalous resistivity on the auroral field lines can give rise to the burst-like electron acceleration responsible for simultaneously observed auroral forms and bursts of Pi1B pulsations.

In this thesis we investigate different phases of matter in systems driven out of equilibrium. In particular, we focus on current driven metal insulator transitions and on the physics of negative conductivity in photoexcited metals. We present a new mechanism by which a modest applied electric field can destabilize a correlated insulating phase at finite temperature, without directly exciting carriers across the gap. We investigate the consequences of a metal insulator phase interface, and show that the large difference in Seebeck coefficients leads to a substantial heat generation or removal at the interface depending on the direction of the applied electric current; our findings explain the key features of recent interesting experiments in Calcium Ruthenate. We also analyze a model of a metal coupled to a strongly photoexcited phonon mode and show that under general conditions the system exhibits a negative conductivity, even long after the removal of the pump; we study the phenomenological consequences of such state and find that it leads to a novel and purely non-equilibrium collective mode coupling charge and entropy. The resonance of this mode with probe radiation induces an enhancement of the optical reflectivity and can explain the experimental reports of the non-equilibrium state in photoexcited fullerides.

The first comprehensive study of equatorial- to mid-latitude ionospheric electric fields (plasma drifts) is presented, using extensive incoherent scatter radar measurements from Jicamarca, Arecibo, and Millstone Hill, and F-region ion drift meter data from the polar orbiting DE-2 satellite. Seasonal and solar cycle dependent empirical quiet-time electric field models from equatorial to mid latitudes are developed, which improve and extend existing climatological models. The signatures of electric field perturbations during geomagnetically disturbed periods, associated with changes in the high-latitude currents and the characteristics of storm-time dynamo electric fields driven by enhanced energy deposition into the high-latitude ionosphere, are studied. Analytical empirical models that describe these perturbation drifts are presented. The study provided conclusive evidence for the two basic components of ionospheric disturbance electric fields. It is shown that magnetospheric dynamo electric fields can penetrate with significant amplitudes into the equatorial- to mid-latitude ionosphere, but only for periods up to 1 hour, consistent with results from the Rice Convection Model. The storm-time wind-driven electric fields are proportional to the high-latitude energy input, vary with local time and latitude, and have largest magnitudes during nighttime. These perturbations affect differently the zonal and meridional electric field components. It is shown that equatorial zonal electric fields (vertical drifts) can be disturbed up to 30 hours after large enhancements in the high-latitude currents. These perturbation electric fields are associated with enhanced high-latitude energy deposition taking place predominantly between about 1-12 hours earlier and found to be in good agreement with the Blanc-Richmond disturbance dynamo model. A second class of perturbations occurs around midnight and in the dawn-noon sector with delays of about 18-30 hours between the equatorial- and the high-latitude disturbances , and maximizes during locally quiet geomagnetic times. The latitudinal variation of the meridional disturbance electric fields (zonal drifts) is also presented. It is shown that these perturbation electric fields are predominantly downward/equatorward at all latitudes and due to both prompt penetration and disturbance dynamo electric fields. These results are also generally consistent with predictions from global convection and disturbance dynamo models.

The use of small satellites to measure the native electric field of the earth has historically presented many problems as a result of the generally modest pointing capabilities of small satellites. In spite of this, the cost of small satellites makes them ideal for just such scientic missions. This thesis details many of the constraints of electric field measuring missions as well as the requirements on any spacecraft designed to accomplish such. The data from a small sounding rocket mission is then analyzed and its usefulness discussed. Possible other methods for use are also discussed.

The shear force mechanism has been utilized as a distance regulation method in scanning probe microscopes. However, the origin of shear force is still unclear. One of the most important reasons for the shear-force damping is due to the presence of a water contamination layer at the sample surface in ambient conditions. Understanding the behavior of such mesoscopic fluid-like films is of significance for studies of not only scanning probe microscopy but also other complex surface phenomena, such as nanotribology, lubrication, adhesion, wetting, and the microfluidity of biological membranes. This thesis investigates, in particular, the dynamics of mesoscopic fluids confined between two sliding solid boundaries. When fluids are constrained to nanometer-sized regions, their physical properties can greatly differ from those displayed by bulk liquids. To gain an insight into the fundamental characteristics of the confined fluid films, we exploit the versatile capabilities of the novel shear-force/acoustic near-field microscope (SANM), which is able to concurrently and independently monitor the effects of the fluid-mediated interactions acting on both the microscope's probe and the sample to be analyzed. Two signals are monitored simultaneously during each experimental cycle: the tuning fork signal, which is the oscillation amplitude of the probe and gives access to the shear force; and acoustic signal, which is detected by an acoustic sensor placed under the sample. Systematic experiments are carried out to investigate the effects of probe geometry, environmental humidity, and chemical properties of probe and sample surface (water affinity: hydrophobicity or hydrophilicity) on the probe-sample interactions, expressing the influence of the fluid-like contamination films.