Now showing items 7350-7369 of 20274

• #### F-spin study of rare earth nuclei using F-spin multiplets and angular momentum projected intrinsic states.

The proton-neutron Interacting-Boson Model contains both symmetric and mixed-symmetry proton-neutron boson configurations. These states of different proton-neutron symmetry can be classified in terms of an SU(2) symmetry, called F-spin. This dissertation deals with some new applications of F-spin. Even-even nuclei drawn from the proton and neutron shells 50 < Z < 82 and 82 < N < 126, respectively, are systematically classified in F-spin multiplets and their binding energies are fit with a six-parameter mass-formula. Using particle-hole symmetry conjugation, the energies of the low-lying levels of the neutron-rich nuclei are estimated and their mass excesses determined with the mass-formula. The masses of these nuclei are of interest in astrophysical processes. A novel asymptotic realization of the angular-momentum projected intrinsic-state in the generalized IBM is presented. This approach which uses the Laplace method of asymptotic expansion, is shown to be an improvement over the Gaussian method espoused by Kuyucak and Morrison. The method, herein called the 1/Λ-expansion, is used to derive analytical expressions for different quantities in the framework of the generalized IBM. Particular attention is paid to the M1 summed strength, the mean-excitation energy of the mixed symmetry 1⁺ scissor mode, and the gyromagnetic ratios of the ground-band members, for which formulas are derived. A no-free-parameter calculation is performed for the summed M1 strength and the centroid energy of ⁽¹⁴⁶⁻¹⁵⁸⁾Sm isotopes. The g factors of deformed and transitional nuclei in the rare-earth mass region are also computed. The data in all cases are found to be well reproduced, in general. A weak L dependence is predicted for the g factors, and there appears to be no need to include two-body terms in the T(M1) operator for determining the M1 strength.

• #### Fabrication and Application of Absorption-Based and Interference-Based Micropolarizers

The ability to create arbitrary patterned linear, circular, and elliptical liquid crystal polymer polarizers is demonstrated in this work. The operating wavelength of the thin-film polarizer ranges from 400 to 4200 nm. The linear absorption-based micropolarizer is fabricated using dichroic dye as a guest in liquid crystal polymer host with feature sizes as small as 4 µm. The circular interference-based micropolarizer is fabricated using cholesteric liquid crystal polymers with feature sizes as small as 6.2 µm. The elliptical micropolarizer is achieved using the combination of a microretarder and a micropolarizer. The chemistry, fabrication process, spatial resolution and optical properties of micropolarizers are presented. Alignments of liquid crystal polymers and cholesteric liquid crystal polymers are both achieved using photoalignment technique with polarized photo-lithography. Two different methods, thermal annealing and solvent rinse, are utilized for patterning cholesteric liquid crystal polymers over large areas. In addition to exploring absorption-based and interference-based micropolarizers, arrays of micropolarizers are fabricated for the construction of 580nm and 760nm division-of-focal-plane full-Stokes imaging polarimeters. The polarimeter utilizes a set of four optimized measurements which represent a regular tetrahedron inscribed in the Poincaré sphere. Results from the device fabrication, instrument calibration and characterization for the 580 nm polarimeter are presented. The optimized imaging polarimeter can be used for sampling the polarization signature across a scene with a resolution of 1608 x 1208 x 14-bit at 20 frames/second.
• #### Fabrication and characterization of erbium doped waveguide amplifiers and lasers

Planar waveguide amplifiers and lasers were fabricated using Ag film ion exchange on Er³⁺/Yb³⁺ codoped phosphate glass. The performance of these amplifiers and lasers were studied and characterized. Silver film ion exchange process was thoroughly studied and a process suitable for fabrication of low loss waveguides on Er³⁺/Yb³⁺ codoped phosphate glass was developed. A transmission loss of 0.15 dB/cm was obtained in surface waveguides on phosphate glass. Planar waveguide amplifiers were fabricated on Er³⁺/Yb³⁺ codoped phosphate glass and characterized. A net gain of 7 dB in a sample of length 4.7 cm and gain/cm of 1.5 dB/cm were achieved. Single mode waveguide laser arrays pumped by single mode laser diodes were fabricated. Their performance was characterized in terms of the output power, spectrum of the laser, lasing wavelength dependence on the waveguide width and the relative intensity noise (RIN) of the laser. The tunability of the lasing wavelength to the desired wavelength, after waveguide fabrication, by annealing was demonstrated. A novel planar waveguide laser configuration for single-mode operation around 1550 nm using cost-effective multimode diode pumping was demonstrated. The laser was fabricated by Ag film ion exchange in a hybrid phosphate glass which has active and passive regions monolithically integrated in a single glass chip. Power of 54 mW at 1538 nm was measured from the single-mode output waveguide.
• #### Fabrication and Characterization of Recombinant Silk-elastinlike Protein Fibers for Tissue Engineering Applications

The integration of functional and structural properties makes genetically engineered proteins appealing in tissue engineering. Silk-elastinlike proteins (SELPs), containing tandemly repeated polypeptide sequence derived from natural silk and elastin, are recently under active study due to the interesting structure. The biological, chemical, physical properties of SELPs have been extensively investigated for their possible applications in drug/gene delivery, surgical tissue sealing and spine repair surgery. However, the mechanical aspect has rarely been looked into. Moreover, many other biomaterials have been fabricated into fibers in micrometer and nanometer scale to build extracellular matrix-mimic scaffolds for tissue regeneration, but many have one or mixed defects such as: poor strength, mild toxicity or immune repulsion etc. The SELP fibers, with the intrinsic primary structures, have novel mechanical properties that can make them defects-minimized scaffolds in tissue engineering.In this study, one SELP (SELP-47K) was fabricated into microfibers and nanofibers by the techniques of wet-spinning and electrospinning. Microfibers of meters long were formed and collected from a methanol coagulation bath, and later were crosslinked by glutaraldehyde (GTA) vapor. The resultant microfibers displayed higher tensile strength up to 20 MPa and higher deformability as high as 700% when tested in hydrated state. Electrospinnig of SELP-47K in formic acid and water resulted in rod-like and ribbon-like nanofibrous scaffolds correspondingly. Both chemical (methanol and/or GTA) and physical (autoclaving) crosslinking methods were utilized to stabilize the scaffolds. The chemical crosslinked hydrated scaffolds exhibit elastic moduli of 3.4-13.2 MPa, ultimate tensile strength of 5.7-13.5 MPa, and deformability of 100-130%, closely matching or exceeding the native aortic elastin; while the autoclaved one had lower numbers: 1.0 MPa elastic modulus, 0.3 MPa ultimate strength and 29% deformation. However, the resilience was all above 80%, beyond the aortic elastin, which is 77%. Additionally, Fourier transform infrared spectra showed clear secondary structure transition after crosslinking, explaining the phenomenon of scaffold water-insolubility from structural perspective and showed a direct relationship with the mechanical performance. Furthermore, the in vitro biocompatibility of SELP-47K nanofibrous scaffolds were verified through the culture of NIH 3T3 mouse embryonic fibroblast cells.
• #### Fabrication and characterization of variable groove depth grating waveguide couplers.

Variable groove depth grating waveguide couplers (VGDGWCs) can be used to couple light into or out of planar waveguides. In principle an out-coupled light beam with any arbitrary irradiance profile can be obtained. VGDGWCs that produce out-coupled beams exhibiting a Gaussian irradiance profile are examined in this report. An expression for the grating groove depth variation necessary to produce Gaussian beams from VGDGWCs is derived. The design of a VGDGWC using two different materials for the host planar waveguide is presented. The designs are optimized with a consideration of the waveguide materials, the fabrication process, and the out-coupled beam quality. Two methods, that utilize ion etching to fabricate VGDGWCs are presented. Each method operates by limiting the cross sectional area of an ion beam. A scanning slit is used for one method and a moving variable width aperture is employed for the second. The ion etching process for each of the fabrication methods is characterized by a series of ion beam etching experiments. The results from the ion beam etching experiments are used to optimize the fabrication process. The variable width aperture fabrication method in combination with a post etching process, is found to produce the optimum results. The measured irradiance profile and the wavefront quality of the out-coupled beams from the fabricated VGDGWCs are compared to theory. The variable width aperture fabrication method is found to produce out-coupled beams with a nearly perfect Gaussian irradiance profile. The measured wavefront quality of out-coupled beams shows good agreement with theory.
• #### Fabrication and structural, optical, and electrical characterization of multisource evaporated copper-gallium-selenide polycrystalline thin films.

Theoretical considerations for the use of chalcopyrite ternary I-III-VI₂ compounds in heterojunction photovoltaic conversion devices are presented, followed by an in-depth study of the structural, optical, and electrical characteristics of multi-source evaporated CuGaSe₂ thin films as determined by processing. Film composition was identified as the primary variable for affecting the microstructure and optical-electrical behavior of the films. Film composition was in turn dependent upon elemental flux rates and substrate related effects. Films deposited on glass and bare alumina substrates were richer in selenium than films deposited on molybdenum coated substrates. Cu-poor, near stoichiometeric, and Cu-rich compositions were obtained by varying the Cu/Ga flux ratio. Cu-poor films deposited on bare ceramic substrates were characterized by secondary impurity phase content and a tendency for cubic CuGaSe₂ formation. The cubic nature of optically thin films deposited on glass was substantiated by a lack of crystal field splitting of the valence band as observed by optical absorption measurements. Cubic-tetragonal phase behavior was monitored on optically opaque samples by observation of intensity-independent (112)/(111) x-ray diffraction peak shifts. Cu-poor films on glass were also characterized by surfaces pitting at substrate temperatures in excess of 450°C which may be related to the high surface energy of gallium. Cu-poor films deposited on molybdenum coated alumina substrates exhibited less impurity phase formation and were largely single-phase tetragonal CuGaSe₂. Cu-rich films on all substrates contained CuₓSe impurities and tetragonal CuGaSe₂.
• #### Fabrication of low-loss planar waveguides and development of integrated optical chemical sensors

Applications of planar integrated optical waveguide (IOW) technology to problems in surface spectroscopy and optical chemical sensing have been partly limited by the difficulty of producing high quality glass IOWs is. The fabrication of IOWs by the sol-gel method from methyltriethoxysilane and titanium tetrabutoxide precursors has therefore been developed. The physical, chemical, and optical properties of the films were studied using a variety of analytical techniques. The results show that the catalyst used to accelerate the sol-gel reaction strongly influenced the optical quality of the IOW. A novel optical sensing platform was subsequently developed using a sol-gel derived, laminate planar IOW structure. The sensing element is fabricated by coating a sol-gel IOW with a second, porous sol-gel layer in which optical indicator molecules are physically entrapped, yet remain sterically accessible to analytes that diffuse into the pore network. Formation of a complex between the analyte and entrapped indicator is detected via attenuated total reflection (ATR) of light guided in the IOW. Feasibility was evaluated by constructing IOW-ATR sensors for Pb2+ and pH, based on entrapped xylenol orange and bromocresol purple respectively. The response of both sensors was sensitive and rapid. This work was further extended to the development of a new class of gaseous iodine sensors. The sensing principle is based on the detection of a charge transfer complex formed between iodine and phenyl groups that have been incorporated into a porous, methylated glass film. The sol-gel iodine sensor exhibits a linear response to gaseous I2 in the range of 100 ppb to 15 ppm with response and recovery times less than 15 sec. Langmuir-Blodgett (LB) films have also been deposited on a sol-gel IOW from zinc 1,4,8,11,15,18,22,25-octabutoxy-phthalocyanine (ZnPc). Planar waveguide linear dichroism was used to determine molecular orientation in a ZnPc LB monolayer. The IOW-supported ZnPc monolayer was found to exhibit a sensitive spectral response to gaseous I2. The overall optical sensing approach described in this dissertation is technically simple, inexpensive, and applicable to a wide variety of chemical sensing problems.
• #### Fabrication of Multimodal Organic-Inorganic Hybrid Nanovesicles and Study on their Intracellular Fates in Cancer Cells by Single Particle Tracking

Creation of magic bullets might be the dream of all scientists working on anticancer therapeutics. In reality, there are always pros and cons. Chemotherapeutics such as doxorubicin and paclitaxel can effectively inhibit growth of cancer cells; however, the drugs at a high dosage are not selective and can cause severe damage to normal tissues and/or organs. To minimize its side effects, anticancer therapeutics are often encapsulated using nanovesicles (NVs). Antibodies that target specific cancer cells may be conjugated with drug-carrying NVs to further improve the selectivity of drug delivery. In the design and fabrication of NV-based drug carriers, many structural and micro-environmental factors affect cellular uptake and internalization of drug-carrying NVs, drug release and distribution in tissues, and therapeutic efficiency. Two goals of my dissertation study is (1) to fabricate multimodal NVs for bio-imaging, selective targeting and drug delivery and (2) to unfold interplays between different factors and intracellular fates of these NVs in prostate cancer cells. This proposed work separates into four phases: (1) Novel organic-inorganic liposomal cerasomes will be used as drug carriers for delivery of potent anticancer doxorcubicin (DOX). Liposomes will be stabilized via an addition of inorganic polyorganosiloxane networks on their surfaces, creating liposomal cerasomes, and its potential to store and release DOX will be investigated. (2) Prostate cancer cells will be used as a model system to study endocytic pathway of cerasomes. Among various types of human cancer, prostate cancer is the second leading cause of death for man. It is anticipated that the proposed study will shed new insights into endocytosis drug-carrying NVs. Results from the study may facilitate the development of cerasome-based therapeutics for treating prostate cancer patients. (3) Since diagnostic, imaging and therapy are three major biomedical applications in nanotechnology, multifunctional NVs with combined bio-imaging, therapeutic efficiency and selective targeting modalities are essential as next-generation nano-carriers. Here, we proposed to incooperate fluorophores and prostate cancer targeted antibodies into cerasomes to achieve our multimodal NVs. (4) Single particle tracking (SPT) analysis will be used to study the intracellular fates of cerasome uptake in single cell level. SPT is an advanced imaging technique permits the real-time monitoring of cellular entry, intracellular transport and internalization of multiple NVs. Our main focus is to identify the different in cellular transportation mechanism between targeted and non-targeted vesicles. Moreover, SPT will be integrated into a microfluidic system, which not only minimizes the consumption of reagents/ materials but also allows us to precisely control biochemical environments around cells.
• #### Fabrication of Novel Structures to Enhance the Performance of Microwave, Millimeter Wave and Optical Radiators

This dissertation has three parts which are distinctive from the perspective of their frequency regime of operation and from the nature of their contributions to the science and engineering communities. The first part describes work that was conducted on a vertical-external-cavity surface emitting-laser (VECSEL) in the optical frequency regime. We designed, fabricated, and tested a hybrid distributed Bragg reflector (DBR) mirror for a VECSEL sub-cavity operating at the laser emission wavelength of 1057 nm. The DBR mirror was terminated with a highly reflecting gold surface and integrated with an engineered pattern of titanium. This hybrid mirror achieved a reduction in half of the number of DBR layer pairs in comparison to a previously reported, successful VECSEL chip. Moreover, the output power of our VECSEL chip was measured to be beyond 4.0Wwith an optical-to-optical efficiency of 19.4%. Excellent power output stability was demonstrated; a steady 1.0 W output at 15.0 W pump power was measured for over an hour. The second part reports on an ultrafast in situ pump-probing of the nonequlibrium dynamics of the gain medium of a VECSEL under mode-locked conditions. We proposed and successfully tested a novel approach to measure the response of the inverted carriers in the active region of a VECSEL device while it was operating under passively mode-locked conditions. We employed the dual-frequency-comb spectroscopy (DFCS) technique using an asynchronous optical sampling (ASOPS) method based on modified time-domain spectroscopy (TDS) to measure the nonequilibrium dynamics of the gain medium of a phase-locked VECSEL that we designed and fabricated to operate at the1030 nm emission wavelength. Our spectroscopic studies used a probe pulse of 100 fs and an in situ pump pulse of 13 ps. We probed the gain medium of the VECSEL and recorded a depletion time of 13 ps, a fast recovery period of 17 ps, and 110 ps for the slow recovery time. Our scans thus demonstrated a 140 ps full depletion-recovery cycle in the nonequilibrium state. The third part discusses work in the microwave and millimeter wave frequency regimes. A new method to fabricate Luneburg lenses was proposed and demonstrated. This type of lens is well known; it is versatile and has been used for many applications, including high power radars, satellite communications, and remote sensing systems. Because the fabrication of such a lens requires intricate and time consuming processes, we demonstrated the design, fabrication and testing of a Luneburg lens prototype using a 3-D printing rapid prototyping technique both at the X and Ka-V frequency bands. The measured results were in very good agreement with their simulated values. The fabricated X-band lens had a 12 cm diameter and produced a beam having a maximum gain of 20 dB and a beam directivity (half-power beam width (HPBW)) ranging from 12° to 19°). The corresponding Ka-V band lens had a 7 cm diameter; it produced a beam with a HPBW about the same as the X-band lens, but with a maximum gain of more than 20 dB.
• #### Fabrication, analysis and patterning of sol-gel based silica ultrathin films

A novel approach to sol-gel thin film fabrication has been developed which leads to the production of ultrathin ∼2 nm to 100 nm thick silica and conductively-doped silica films on metal and semiconductor substrates. The research described herein focuses on the development, characterization and potential application of these thin films in current technology. These ultrathin films were fabricated by a sol-gel procedure, which utilized highly diluted silica precursor compounds. The [H₂O]:[Si] ratio ranged from 50 to 1000, far above the typical values (4-10) used in sol-gel film preparation. This dilution leads to highly densified silica when spin-cast onto an appropriately compatible surface. The surface examined included Si(111)/SiO₂; ITO; and 3-(mercaptopropyl)trimethoxysilane (3MPT) modified Au and Ag. These surfaces must act as wetting control agents for the sol-gel precursor, while simultaneously providing adhesion to the nm sized sol-gel aggregates. The 3MPT-Ag monolayer was examined in detail by Tl, Pb and Cd underpotential deposition electrochemistry, to understand the interfacial structure of the molecule. These results show that the 3MPT monolayer is very stable to outside influences (i.e. Tl and Pb reversibly deposit monolayers at the metal surface). The UPD of metal ions is highly size dependent with Tl depositing with fewer kinetic limitations than Pb and Cd not depositing at all. Raman spectral characterization shows that 3MPT undergoes some reversible rearrangement during the UPD process. The electronic properties of the pure silica films were examined in great detail. The results suggested that in solution, a solvated gel layer at the film-solution interface gives rise to an anomalously low capacitance <100 pF/cm², which has no comparison in the current literature. In the dry state, these silica films have a dielectric constant of ε = 3.5, which is close to that of thermally-grown silica on silicon (3.9). These films were doped with 1,1'-bistriethoxysilylferrocene, an electrochemically-active sol-gel material. The results suggest that under the proper precursor solution conditions, thin ( <10 nm), uniform films can be fabricated. By simply adjusting the ratio of the ferrocene moiety in solution, the film composition can be adjusted. XPS verifies that the atom ratio in solution is near to the observed atom ratio in the films, with some indication of surface segregation of the ferrocene moiety. Electrochemical analysis of these films suggests that electron hopping between the ferrocene centers drives the electrochemical response only when there are pinhole defects, to support counterion conduction to the surface. (Abstract shortened by UMI.)
• #### Fabrication, Biocompatibility, and Tissue Engineering Substrate Analysis of Polyvinyl Alcohol-Gelatin Core-Shell Electrospun Nanofibers

Cardiovascular disease is the leading cause of death in the United States with approximately 49% of the cardiovascular related deaths attributed to coronary heart disease (CHD). CHD is the accumulation of plaque resulting in the narrowing of the vessel lumen and a decrease in blood flow to the downstream heart muscle. In order to restore blood flow, arterial by-pass procedures can be undertaken. However, the patient's own arteries/veins may not be suitable for use as a vessel replacement, and synthetic grafts lack the compliancy and durability needed for these small diameter locations (<5 mm). Therefore, the goal of this research is to develop a nanofibrous material that can be used in vascular applications such as this. In this study, we fabricate coaxial electrospun nanofibers with gelatin in the shell and polyvinyl alcohol (PVA) in the core using 1 Gelatin: 1 PVA and 3 Gelatin: 1 PVA mass ratios. Gelatin, derived from collagen, is highly bioactive while PVA, a synthetic polymer, has appealing mechanical properties. Therefore, by combining these materials in a core-shell structure, we hypothesize that the resulting nanofibers will have enhanced mechanical properties, cellular growth and migration, as well as minimal platelet deposition and activation compared to scaffolds composed solely of gelatin or PVA. First, the coaxial scaffolds exhibited an enhanced Young's modulus and ultimate strength compared to scaffolds composed of PVA or gelatin alone. Endothelial cells had high proliferation and migration on the coaxial electrospun scaffolds with higher migration seen on the stiffer, coaxial scaffolds. The smooth muscle cells had less proliferation and lower migration rates on the coaxial scaffolds than the endothelial cells. Using a modified prothrombinase assay, the coaxial scaffolds had minimal platelet activation. Lastly, when pre-seeding the coaxial scaffolds with endothelial cells or smooth muscle cells, the platelet deposition decreased in comparison to platelet deposition with no cell pre-seeding. Overall, the 1 Gel: 1 PVA coaxial scaffolds promoted endothelial cell growth and migration, minimized smooth muscle cell growth and migration, and had minimal platelet activation. Therefore, the 1 Gel: 1 PVA coaxial nanofibers are an intriguing material for use in vascular applications.
• #### Fabrication, Characterization, and Application of Microresonators and Resonant Structures

Optical resonators are structures that allow light to circulate and store energy for a duration of time. This work primarily looks at the fabrication, characterization, and application of whispering gallery mode microresonators and the analysis of organic photonic crystal-like structures and simulation of their resonant effects. Whispering gallery mode (WGM) microresonators are a class of cylindrically symmetric optical resonator which light circulates around the equator of the structure. These resonators are named after acoustic whispering galleries, where a whisper can be heard anywhere along the perimeter of a circular room. These optical structures are known for their ultra high Q-factor and their low mode volume. Q-factor describes the photon lifetime in the cavity and is responsible for the energy buildup within the cavity and sharp spectral characteristics of WGM resonators. The energy buildup is ideal for non-linear optics and the sharp spectral features are beneficial for sensing applications. Characterization of microbubble resonators is done by coupling light from a tunable laser source via tapered optical fiber into the cavity. The fabrication of quality tapered optical fiber on the order of 1-2 μm is critical to working on WGM resonators. The measurement of Q-factors up to 2x10⁸ and mode spectra are possible with these resonators and experimental techniques. This work focuses on microdisk and microbubble WGM resonators. The microdisk resonators are fabricated by femtosecond laser micromachining. The micromachined resonators are fabricated by ablating rotating optical fiber to generate the disk shape and then heated to reflow the surface to improve optical quality. These resonators have a spares mode spectrum and display a Q factor as high as 2x10⁶. The microbubble resonators are hollow microresonators fabricated by heating a pressurized capillary tube which forms a bubble in the area exposed to heat. These have a wall thickness of 2-5 μm and a diameter of 200-400 μm. Applications in pressure sensing and two-photon fluorescence of dye in microbubble resonators is explored. Photonic crystals can have engineered resonant properties by tuning photonic band gaps and introducing defects to create cavities in the photonic structure. In this work, a natural photonic crystal structure is analyzed in the form of diatoms. Diatoms are a type of phytoplankton which are identified by unique ornamentation of each species silica shell, called a frustule. The frustule is composed of a quasi-periodic lattice of pores which closely resembles manmade photonic crystals. The diatom frustules are analyzed using image processing techniques to determine pore-to-pore spacing and identify defects in the quasi-periodic structure which may contribute to optical filtering and photonic band gap effects. The data gathered is used to simulate light propagation through the diatom structure at different incident angles and with different material properties and to verify data gathered experimentally.
• #### Fabrication, experimental investigation and computer modeling of gallium-arsenide nonlinear optical devices.

Nonlinear-optical switching and logic devices based on GaAs nonlinear Fabry-Perot etalons have been investigated theoretically and experimentally. The theoretical modeling has been performed with the first realistic and easily computed theory of GaAs nonlinear optical properties near the band edge. Both steady-state and dynamic calculations have been performed for optical bistability with GaAs etalons. High-transmission operation is predicted for certain etalon detunings from the excitation wavelength. Various logic-gate functions have simulated with the model. An investigation of differential energy gain in transient, one-wavelength operation was performed. The conclusion is that useful differential gain is not achievable in transient, one-wavelength operation if the pulse width is less than about ten times the carrier lifetime in the material. Waveguide structures with single-mode transverse confinement were designed and optical bistability was predicted for long GaAs etalons similar to cleaved waveguides. GaAs nonlinear optical devices were fabricated in forms of interest for application to optical parallel processing and guided wave signal processing. The fabrication work included etalon arrays and waveguide devices fabricated by reactive ion etching. The photolithography and reactive ion etching processes used and developed are described. Preliminary work on ultra-small quantum-confinement structures is described. Optical experiments were performed on the devices fabricated. The etalon arrays demonstrated extremely fast relaxation times for GaAs etalon devices, and demonstrated the ability to control material parameters through the fabrication process, by increasing the surface recombination rate of charge carriers. Fast optical bistability at low powers was also demonstrated in the array devices. Strip-loaded waveguides with cleaved ends were operated as optical bistable devices with conclusive evidence that the mechanism was electronic in origin. Nonlinear phase shifts of greater than $2\pi$ were observed in some waveguides. Such large nonlinear phase shifts are of great interest for the development of other nonlinear-optical waveguide devices.
• #### FABRICATION, INVESTIGATION AND OPTIMIZATION OF GALLIUM-ARSENIDE OPTICAL BISTABLE DEVICES AND LOGIC GATES.

The fundamental components for processing all-optically represented data, namely optical switches and logic gates are investigated. Improved techniques for fabricating nonlinear Fabry-Perot etalons containing GaAs have brought a proliferation of GaAs optical bistable devices. These devices show significant improvements in speed, power requirements, operating temperature and thermal stability. Experiments verify predictions that one can operate a single nonlinear etalon as optical logic gates or two such etalons as a flip-flop. Optimization of the logic gates is then discussed from a systems approach.
• #### A facework-based approach to the elicitation and provision of support in romantic dyads

Social support has been conceptualized as coping assistance (Thoits, 1986) and facilitated reappraisal (Burleson & Goldsmith, 1998). The present investigation sought to explore this conceptualization using a facework-based approach (Goldsmith, 1994a). Specifically, the Communication Model of Facework (Lim & Bowers, 1991) and Burleson's (1985) hierarchical model of comforting sensitivity were used to create the Face Interaction Support Coding Scheme (FISCS). The Communication Model of Facework is built on the premise that individuals want to be accepted for who they are (fellowship face), to be respected for their abilities and accomplishments (competence face), and to be allowed the freedom to make decisions for themselves (autonomy face). The hierarchical model of comforting sensitivity assumes that comforting messages that are more person-centered, rather than position-centered, are often more effective at meeting the needs of distressed persons. The FISCS is intended to assess how person-centered individuals are in meeting their partner's needs for fellowship, competence and autonomy. In addition to examining facework, this study also included an assessment of conversational involvement. Seventy couples participated in an interaction where they discussed a recent stressful event being experienced by one of the partners. Participants completed measures of pre-interaction appraisals of stressfulness and controllability, post-interaction appraisals, communication satisfaction, provider helpfulness, and interaction typicality. Results were analyzed using the Actor-Partner Interdependence Model (Kashy & Kenny, 2000). Results of the analyses revealed that an increased use of fellowship face was related to pre- and post-interaction appraisals of problem stressfulness, as well as perceptions of communication satisfaction, provider helpfulness, and the typicality of the interaction. The partner's use of competence face was related to increased perceptions of provider helpfulness, while one's own use of autonomy face was related to perceiving the problem as less stressful following the interaction. Regarding conversational involvement, involvement and pleasantness exhibited opposite partner effects with controllability: increased partner involvement was related to perceiving the problem as more controllable after the interaction, while increased partner pleasantness was related to appraising the problem as more uncontrollable. Finally, partner involvement was also related to increased communication satisfaction and greater perceptions of interaction typicality.
• #### Facial EMG and the subjective experience of emotion in idiopathic Parkinson's disease in response to affectively laden visual stimuli.

The purpose of the study was to investigate the possible role of facial musculature movement in the subjective experience of emotion. Nineteen nondemented, nondepressed patients with idiopathic Parkinson's disease and 19 demographically matched control subjects were asked to rate valence and arousal dimensions after viewing emotionally laden slides. The patients with Parkinson's disease viewed one set of slides at their peak levodopa dose and one set of slides after at least a 12 hour abstention from their levodopa medication. Normal control subjects underwent two similar testing sessions, although no drug was administered. Mean valence and mean arousal ratings of slides within groups were determined. During the viewing of the slides, bilateral facial electromyographic activity in the zygomatic and corrugator muscle regions was recorded. EMG change scores relative to individual slide presentation were determined. Comparisons were made between and within groups of the mean valence, arousal, and EMG change scores relative to the slide valence type (i.e., positive, neutral, or negative slide content) and on/off drug condition. Results suggest that a subgroup of Parkinson's Disease patients experience similar emotional valence and arousal, to that of normal controls, when confronted with emotional visual stimuli. However, they display significantly less facial muscular movement in the zygomatic muscle region and somewhat less facial muscular movement in the corrugator region than the normal controls. Implications of these results are discussed relative to the James-Lange theory that posits emotional experience to be dependent upon a peripheral "feedback" system versus the Cannon-Bard theory that posits emotion to be mediated centrally. Although the present results lend support to the Cannon-Bard theory of emotion, future research is necessary to determine the role of the skin of the face (with blood and temperature components), rather than the facial musculature per se, in the subjective experience of emotion. It may be that the skin of the face and the sound of one's own voice (among other factors) play important roles in the subjective experience of emotion as posited by S. S. Tomkins. If so, a modified peripheral mediation theory of emotion would be supported.
• #### Facilitating End-of-Life Care Discussions in the Emergency Department

Purpose: The purpose of this Doctor of Nursing Practice project is to increase emergency room nurses’ personal initiative to engage in EOLC discussions by utilizing the PREPARED CPG. Background: While it is the duty of healthcare practitioners (HCP) to initiate end-of-life care (EOLC) discussions with their patients, less than one-third report receiving education in such discussions, and 46% report frequently being unsure of what to say in such discussions. Over 25% of Medicare costs occur in the last year of the patient’s life, attributable to multiple hospitalizations and medically futile, costly interventions being performed. Approximately 75% of Americans do not have an Advance Directive in place. HCP need the tools and support necessary to confidently engage in proactive discussions about EOLC with their patients, ultimately avoiding costly and unwarranted medical interventions. Methods: A quantitative descriptive design was used to assess current personal practice of participants and factors associated with their use of the PREPARED CPG to facilitate EOLC discussions. Thirty emergency department (ED) nurses were educated on the CPG and completed a demographic survey, pre-education survey, and post-education survey. To be considered for inclusion ED nurses had to: (a) be core staff, (b) not in management or administration, and (c) consent. Exclusions included travel, float, and charge nurses. All aspects of project preparation and implementation were aligned with the Joanna Briggs Institute Model of Evidence-based Healthcare. Results: Most participants reported that they “sometimes” educate their patients/families on the difference between “full code” status and “DNR” (n=12, 40%). The most frequently reported reason participants did not engage in EOLC discussions was difficulty with the patient’s family (n=14, 46.7%). Nearly all participants found the PREPARED acronym easy to understand and practical for use in the ED (93.3% and 76.7%, respectively). Most respondents stated they will use this information in their practice and reported a degree of increased confidence to engage in EOLC discussions (93.3% each). Conclusion: Results may be used to identify the need for EOLC discussion education and protocols in healthcare facilities. Feedback elicited may help to identify areas of interest for future research.