Conventional step-index silica fibers do not possess a second-order optical nonlinearity due to symmetry concerns. However, through the process of poling, the generation of a frozen-in DC field $E^{DC}$, and in turn, a non-zero second-order nonlinearity $\chi^{(2)} = 3\chi^{(3)}E^{DC}$, can be created in optical fibers. In this thesis, I measure the individual $\chi^{(2)}$ tensor elements of birefringent periodically poled fiber via second-harmonic generation and sum-frequency generation experiments. The symmetry of the $\chi^{(2)}$ tensor is consistent with that of the $\chi^{(3)}$ for isotropic media. This is the first study that characterizes all the $\chi^{(2)}$ tensor elements in birefringent poled fiber. Furthermore, I investigate the intermix of the $\chi^{(2)}$ tensor elements by twisting the fiber, which results in the generation of new second-harmonic signals not observed in untwisted fiber. The conversion efficiencies and spectral positions of these new signals can be varied by twisting the fiber.

Conventional step-index silica fibers do not possess a second-order optical nonlinearity due to symmetry concerns. However, through the process of poling, the generation of a frozen-in DC field $E^{DC}$, and in turn, a non-zero second-order nonlinearity $\chi^{(2)} = 3\chi^{(3)}E^{DC}$, can be created in optical fibers. In this thesis, I measure the individual $\chi^{(2)}$ tensor elements of birefringent periodically poled fiber via second-harmonic generation and sum-frequency generation experiments. The symmetry of the $\chi^{(2)}$ tensor is consistent with that of the $\chi^{(3)}$ for isotropic media. This is the first study that characterizes all the $\chi^{(2)}$ tensor elements in birefringent poled fiber. Furthermore, I investigate the intermix of the $\chi^{(2)}$ tensor elements by twisting the fiber, which results in the generation of new second-harmonic signals not observed in untwisted fiber. The conversion efficiencies and spectral positions of these new signals can be varied by twisting the fiber.

In this study, novel bio-inks formulated with horseradish peroxidase, HRP, and some additives were successfully developed for piezoelectric inkjet application. The optimized bio-ink formulation had a reliable jetting performance and maintained the biofunctionality before and after printing. The bio-ink also demonstrated a good storage life for up to 40 days at 4 oC with a negligible loss of biofunctionality. However, it was observed that some additives used in the bio-ink for obtaining necessary operational characteristics had detrimental effects on the enzyme activity. Especially, it was found that various viscosity modifiers typically used in commercial inkjet inks significantly impaired HRP activity prior to printing. Sodium Carboxymethyl Cellulose was shown to be an effective viscosity modifier that had no adverse effect on the biological activity of the HRP enzyme. Using a confocal scanning fluorescent microscope, a method for characterizing the spatial distribution of the active enzyme within the cellulosic paper substrates after inkjet printing was developed. Interestingly, it was found that the active printed HRP enzyme was mostly located in the cell walls of the cellulosic fibers instead of near the pigments or fillers. In an effort to better understand the fundamental interactions between the enzyme and the immobilization substrates, HRP adsorption isotherms on various substrate surfaces were obtained using the depletion method. The substrates included not only pulp fibers with varying degree of hydrophobicity and pigment and latex (the key materials used in papermaking), but also other types of cellulosic fibers of different morphologies, crystallinities, porosities, or surface charge densities. The influence on enzyme adsorption and inactivation behaviour of these substrates was compared with that of polystyrene beads (dialysed), which has been well studied in the literature. Results from this thesis indicated that hydrophobic interactions between the enzyme and the substrate surfaces had a major impact on the HRP adsorption behavior, while electrostatic interactions played a minor role. However, strong hydrophobic interactions could lead to enzyme inactivation. Research findings from this study suggested that cellulosic pulp fibers could be tailor-made into excellent enzyme immobilization supports by using existing fiber surface modification techniques.

Rho GTPases are critical regulators of actin cytoskeletal dynamics. The three most well characterized Rho GTPases, Rac1, RhoA and Cdc42 share a common inhibitor, RhoGDI. It is only recently becoming clear how upstream signals cause the selective release of individual Rho GTPases from RhoGDI. For example, our laboratory showed that diacylglycerol kinase zeta (DGKz), which converts diacylglycerol (DAG) to phosphatidic acid (PA), activates PAK1-mediated RhoGDI phosphorylation on Ser-101/174, causing selective Rac1 release and activation. Phosphorylation of RhoGDI on Ser-34 by PKCa has recently been demonstrated to selectively release RhoA, promoting RhoA activation. Here, I show DGKz is required for optimal RhoA activation and RhoGDI Ser-34 phosphorylation. Both were substantially reduced in DGKz-null fibroblasts and occurred independently of DGKz activity, but required a function DGKz PDZ-binding motif. In contrast, Rac1 activation required DGKz-derived PA, but not PDZ-interactions, indicating DGKz regulates these Rho GTPases by two distinct regulatory complexes. Interestingly, RhoA bound directly to the DGKz C1A domain, the same region known to bind Rac1. By direct interactions with RhoA and PKCa, DGKz was required for the efficient co-precipitation of these proteins, suggesting it is important to assemble a signalling complex that functions as a RhoA-specific RhoGDI dissociation complex. Consequently, cells lacking DGKz exhibited decreased RhoA signalling downstream and disrupted stress fibers. Moreover, DGKz loss resulted in decreased stress fiber formation following the expression of a constitutively active RhoA mutant, suggesting it is also important for RhoA function following activation. This is consistent with the ability of DGKz to bind both active and inactive RhoA conformations. Collectively, these findings suggest DGKz is central to two distinct Rho GTPase activation complexes, each having different requirements for DGKz activity and PDZ interactions, and might regulate the balance of Rac1 and RhoA activity during dynamic changes to the actin cytoskeleton.

This thesis covers two topics. The first subject involves tests run on a ultralite reflux tube supplied by Battelle Pacific Northwest Laboratories (PNL). The second topic involves tests to determine the relative wicking rates of several different fabrics. The ultralite reflux tube supplied by PNL was constructed of copper and Nextel 312. It had a 10 mil thick copper evaporator and a 10 mil thick copper condenser end cap. The bulk of the condenser was 2 mil thick copper covered by a one inch diameter Nextel 312 woven hose. A life test was run within the Heat Pipe Test Facility, a chamber used to simulate low earth orbit. The life test lasted for over 800 hours, during which time the reflux tube operated steadily with no drop in performance. At the end of the test the reflux tube was removed and observed. The only noticeable change was a slight discoloration of the Nextel 312 used to cover the condenser. This discoloration was consistent with previously observed phenomenon. The second topic, fabric wicking rate studies were done as a follow up study to the dry uptake tests previously conducted at Oregon State University. The purpose of the tests were to get a relative feel for the ability of different fabrics to wick water. This was achieved using a drop test in which the fabrics were laid out on a bridge connecting two containers. One of the containers was elevated above the other. The fabrics were allowed to wick water from the upper container to the lower container and the rate at which this was accomplished was measured. The fabrics were all able to move significant amounts of water. The stiffer fabrics seemed to perform better. The major transport mechanism was transport between fabric layers and the fabric and the bridge. / Graduation date: 1993

Composites are combinations of mainly two different components: the matrix and the filler/reinforcement. In the thermoplastic composites industry, natural fibers from agricultural crops have been emerged as alternative fillers. Crops such as wheat straw are renewable and low cost materials that, combined with thermoplastics such as polypropylene, provide engineering products with unique characteristics. The objective of this study was to investigate the influence of processing conditions and composite formulation in the final properties of the composites. For these purposes wheat straw fibres and polypropylene (PP) were compounded in a batch mixer under a number of different thermal conditions and formulations. Fiber loading in the range from 0 to 60 wt-% was examined and the individual effects of two coupling agents (maleic anhydride modified polypropylene and maleic acid ethylene copolymer) and a lubricant were also studied. Particle size, morphology, thermal and mechanical properties and water uptake behaviour were inspected with appropriate techniques. Wheat straw particle size distribution was studied through image analysis; distribution curves for length and width of the particles were recorded in two stages of the project: previous and after compounding the natural material with polypropylene. Morphology of wheat straw particles and wheat straw-polypropylene composites were analyzed by scanning electron microscopy (SEM). Thermal properties including melting temperature and crystallization temperature of composites and pure resin were obtained from differential scanning calorimetry (DSC) performed on the samples; percentage of crystallinity was also calculated from the heat of fusion obtained from those tests. Mechanical properties, such as flexural modulus and flexural yield strength, were accessed in a miniature materials tester. Water absorption of selected composite samples was evaluated after immersion of the samples in a water bath. Water absorption curves were used to calculate the water diffusion coefficient (diffusivity) of the composites. Image analysis revealed the changes in the wheat straw structure due to shear forces during processing and improvement of adhesion between matrix and filler in compositions containing coupling agent. Small changes in the percentage of crystallinity of the thermoplastic phase were observed in all composites tested. Flexural tests revealed behaviour trends for the composites tested. Water uptake appeared to be a severe problem on natural fiber composites due to color fading, dimension instability and significant weight gains. Results from this work allowed the determination of some effects of processing temperature, fiber loading and use of additives on the final properties of wheat straw- polypropylene composites, thus making contributions to the scientific work that has been realized on natural fiber composites.

Composites are combinations of mainly two different components: the matrix and the filler/reinforcement. In the thermoplastic composites industry, natural fibers from agricultural crops have been emerged as alternative fillers. Crops such as wheat straw are renewable and low cost materials that, combined with thermoplastics such as polypropylene, provide engineering products with unique characteristics. The objective of this study was to investigate the influence of processing conditions and composite formulation in the final properties of the composites. For these purposes wheat straw fibres and polypropylene (PP) were compounded in a batch mixer under a number of different thermal conditions and formulations. Fiber loading in the range from 0 to 60 wt-% was examined and the individual effects of two coupling agents (maleic anhydride modified polypropylene and maleic acid ethylene copolymer) and a lubricant were also studied. Particle size, morphology, thermal and mechanical properties and water uptake behaviour were inspected with appropriate techniques. Wheat straw particle size distribution was studied through image analysis; distribution curves for length and width of the particles were recorded in two stages of the project: previous and after compounding the natural material with polypropylene. Morphology of wheat straw particles and wheat straw-polypropylene composites were analyzed by scanning electron microscopy (SEM). Thermal properties including melting temperature and crystallization temperature of composites and pure resin were obtained from differential scanning calorimetry (DSC) performed on the samples; percentage of crystallinity was also calculated from the heat of fusion obtained from those tests. Mechanical properties, such as flexural modulus and flexural yield strength, were accessed in a miniature materials tester. Water absorption of selected composite samples was evaluated after immersion of the samples in a water bath. Water absorption curves were used to calculate the water diffusion coefficient (diffusivity) of the composites. Image analysis revealed the changes in the wheat straw structure due to shear forces during processing and improvement of adhesion between matrix and filler in compositions containing coupling agent. Small changes in the percentage of crystallinity of the thermoplastic phase were observed in all composites tested. Flexural tests revealed behaviour trends for the composites tested. Water uptake appeared to be a severe problem on natural fiber composites due to color fading, dimension instability and significant weight gains. Results from this work allowed the determination of some effects of processing temperature, fiber loading and use of additives on the final properties of wheat straw- polypropylene composites, thus making contributions to the scientific work that has been realized on natural fiber composites.

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