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Objective: To explore development and testing of a new patient positioning device during wrist MRI. To evaluate rheumatoid arthritis (RA) wrist 3T MRI with computerised image analysis tools including bone segmentation techniques, semiquantitative scoring and dynamic contrast enhanced (DCE-MRI) for synovitis measures, with similar assessments on healthy subjects. To examine the relationship between X-ray/MRI disease activity measures and bone mineral density loss using computerised digital X-ray radiogammetry (DXR). Methods: Preliminary study was about development and evaluation of a new patient positioning device for wrist imaging and its evaluation against current standard positions. In the main longitudinal MRI study, 13 RA and 10 healthy subjects (HV) were recruited with 10 RA and 7 HV completing the study. Hand/wrist MRI and radiographs were performed over a year and assessed using semi-quantitative scoring and exploratory computerised image analysis tools, which included pilot work on bone segmentation techniques, including manual and semi-automated methods; bone mineral density loss assessment using DXR-online and its comparison with MRI disease activity measures; and dynamic contrast enhanced MRI (DCE-MRI) analysis using Dynamika software. Result: A developed bridge patient positioning device allowed for comfortable, good quality and reproducible imaging as compared to standard positions (Bridge vs hand by the side vs hand above head position: comfort score (out of 10) (mean±std) – 7.3±0.7 vs 7.1±0.8 vs 6.1±1.6, and image quality (Signal to noise/contrast to noise ratio) – 6.1±1.7/3.1±0.5 vs 5.3±1.5/2.6±0.5 vs 7.7±1.1/4±0.5), with subsequent use in a longitudinal study (Comfort score: RA/HV:9.1/8.1). The semi-automated bone segmentation method was much quicker than manual technique (10/8 vs 165/132 minutes for two readers), with good inter and intra-observer similarity for manual method and in between the two methods, though the semi-automated method failed in an advanced RA patient. The manual segmentation using SliceOmatic software was also time consuming - 3256 minutes for 2196 slices, but with image registration and transformation a visual analysis of future images was possible. In the main longitudinal study, there were stable moderate DAS 28 disease activity scores (Day 1 – 3.9 and week 52 – 4.0). MRI disease activity measures showed good correlation. Bone marrow oedema (BME) correlated with erosions, and automated early 3 month rate of metacarpal digital x-ray radiogrammetric bone mineral density loss (RC-BMD) correlated with 1 year wrist BME change (p=0.035). No significant change was seen for MRI, radiographic or any disease activity measure over the year, though there was small increase in MRI erosion: 2.4 (1.6%), BME: 0.4 (0.8%) and radiographic: 1.8 (0.4%) mean scores. In HV, no radiographic erosions were seen, but MRI showed erosion-like changes, low grade BME and low-moderate synovial enhancement. It was also demonstrated that dynamic contrast enhancement does occur in healthy volunteers, and the inherent variability of perfusion measures obtained with the quantitative DCE-MRI method was small both in HV and stable RA patients on routine treatment. Conclusion: A new MRI wrist patient positioning device was developed, tested and successfully used in a longitudinal study. New and exploratory computerised image analysis techniques in RA, including bone segmentation, DXR and DCE-MRI have a potential role in longitudinal RA clinical trials.

In recent years the role of pi and delta complexes in electrophilic aromatic substitutions has aroused much controversy. Olah has argued that the transition state in electrophilic aromatic substitution is not a fixed one. With strong electrophiles it can occur early along the reaction coordinate resembling a pi complex, with weak electrophiles the tranistion state occures late, resembling a pi complex. This argument is based on a number of benzoylations and benzylations on benzene and toluene in which the electrophilicity of the electrophile has been varied. These conclusions have come under strong criticism and in order to shed light on the exact mechanism the following research was undertaken. This study is centered around the Friedel-Crafts acid catalysed cyclodehydration of 2-benzylbenzoic acids although the cyclodehydration of 2-naphthoylbenzoic acid and 2-benzoylbenzoic acids were also studied. The cyclodehydrations were effected mainly with methanesulphonic acid, but sulphuric acid, polyphosphoric acid and trifluoromethanesulphonic acid were also employed. Rate constants were measured and products of cyclodehydration were identified for all model compounds. The cyclodehydration was investigated by varying the electrophilicity on both the substrate and the electrophile. Consequently many new substituted 2-benzylbenzoic acids were synthesised. Hammett plots were also made and p values calculated. In addition to this the deuterium isotope effect was also investigated, but none was observed. Acidity function work (HR) was also carried out on methanesulphonic acid to try to extend the range to 100% acidity. Analysis of the rate constants and product distributions shows that the transition state resembles a delta complex rather than a pi complex. Hammett and acidity function studies do, however, indicate that the rate limiting step in the reaction is variable. This is dependent on whether there are electron withdrawing or electron donating groups present in the substrate. With electron donating groups the loss of water in the formation of the electrophile is the rate limiting step whereas with electron withdrawing groups the formation of the delta complex is rate limiting.

Parents’ math engagement in the home is important for their children’s math skill development prior to school entry (Daucourt et al., 2021). Both the frequency and type of parental number talk (discussions of number concepts) is related to children’s math performance (Levine et al., 2010; Gunderson & Levine, 2011). However, previous research exploring numeracy engagement in the home focused primarily on mothers of young children, and particularly those with preschool- and school-aged children. This project aimed to investigate the joint and unique influences of mothers and fathers on their toddlers’ number knowledge, by comparing the frequency and type of number talk mothers and fathers use with their toddlers during semi-structured interactions, and how these may predict children’s number skills. In a sample of 133 children aged 2-3 years (M=30.8 months, SD=3.36 months, 52% female) and their mothers and fathers, we found that mothers and fathers of two- to three-year-olds used relatively similar proportions of number talk, t(132) = 1.92, p = 0.057, with mothers tending to use slightly more number talk. Additionally, both mothers and fathers most frequently used quantifiers, labeling, and counting when talking about numerical concepts, and unexpectedly, neither parents’ frequency of number talk significantly predicted children’s numeracy scores (assessed as performance in Point-to-X and Give-N tasks). Exploratory analyses suggested that fathers’ use of labeling set sizes significantly predicted toddlers’ number skills (r = .22, p = .011), and more work is needed to understand how this may contribute to children’s number knowledge over time. Overall, this study presents novel findings in how mothers and fathers compare in their frequency and categorical use of number talk with their toddlers.

Improved understanding of solid surface energy and its role in the overall mechanical properties is of great interest due to the emerging manufacturing techniques of nanostructures, coatings, and synthetic/biological bilayer-polymer hybrids. Continuum numerical modeling of surface stresses efficiently incorporates a zero-thickness membrane bonded to a bulk, intrinsically accounting for surface tension and surface elasticity. Compressive surface stresses are not possible in a purely membrane formulation, ignoring the surface flexural resistance. The extension of material surfaces to account for flexural resistance, i.e., the Steigmann–Ogden model, requires spatial derivatives of second order, posing significant challenges to standard discretization techniques. Hence, the effect of surface curvature resistance on the overall mechanical behavior of complex geometries remains elusive. Here, we develop a three-dimensional computational formulation of curvature-dependent surface energetics at finite strains using surface-enriched isogeometric analysis. Coupled with a hyperelastic bulk, bending-resistance of material surfaces furnishes a new physical length scale, i.e., the elastobending length. We quantify the effect of elastobending deformations for several numerical examples involving soft materials with thin coatings and liquid-shell surfaces, capturing budding-like behavior observed at cell membranes. Our results demonstrate a stiffer overall mechanical behavior when material surfaces resist bending deformations and illustrate how curvature effects lead to complex budding deformations at non-zero initial curvature states. The proposed methodology provides a robust computational foundation to help improve our understanding and mechanical characterization of soft solids, nanostructures, and biological membranes at small scales.

As the population of immigrant-origin adolescents in the United States increases, it is critical to understand the social position these adolescents occupy in school, namely whether they are included and excluded among peers. A well-established body of literature documents that immigrant-origin youth self-report experiencing higher rates of victimization than their non- immigrant counterparts (i.e., of the third generation and beyond). Yet, it is not clear whether the broader peer collective is similarly exclusionary of the immigrant adolescents. Moreover, their positive relationships (i.e., social inclusion) remain unexamined insofar as identifying which peers are most socioemotionally supportive across the adolescent years. The current dissertation aimed to examine these questions across two studies, examining the positive and negative peer relations of immigrant-origin youth from multiple perspectives, over the three years of middle school. Study 1 examined several indicators of peer inclusion and social exclusion mainly from the perspective of peers. It was found that while immigrant-origin youth are just as socially included by peers as their non-immigrant counterparts, they are significantly more neglected iii (i.e., ignored) among the peer landscape. Immigrant-origin youth were no more likely to be perceived as a “victim” at school than non-immigrant youth. However, immigrant adolescents self-reported significantly more victimization than non-immigrants, highlighting a key discrepancy between peer and self-perceptions of social exclusion. Study 2 focused specifically on friendships from the immigrant youths’ perspective to identify the demographic characteristics (i.e., racial/ethnic background, immigrant generational status) of their friends, as well as the quality and duration. The analyses aimed to test the hypothesis that friendships with other immigrant-origin peers would be highest in quality and duration, relative to friendships with non-immigrant peers. Analyses revealed a significant tendency among immigrant-origin youth to befriend other immigrant-origin peers. While immigrant-origin youths’ friendships with immigrant-origin peers were similar in quality to their friendships with non-immigrants, the friendships with immigrant peers were significantly greater in duration regardless of friend race/ethnicity. The findings demonstrate the importance of befriending similar others who understand the immigrant experience. Together, the dissertation studies contribute to a more nuanced and sophisticated understanding of the social position and social relationships of immigrant-origin youth during the early adolescent period. Implications for theory and future research are discussed.

The object of this work is to exploit various constructions of string theory and M-theory to yield new insights into supersymmetric theories in both four and three dimensions. In 4d, we extend work on Seiberg-Witten theory to study and compute BPS spectra of the class of complete N = 2 theories. The approach we take is based on the program of geometric engineering, in which 4d theories are constructed from compactifications of type IIB strings on Calabi-Yau manifolds. In this setup, the natural candidates for BPS states are D3 branes wrapped on supersymmetric 3-cycles in the Calabi-Yau. Our study makes use of the mathematical structure of quivers, whose representation theory encodes the notion of stability of BPS particles. Except for 11 exceptional cases, all complete theories can be constructed by wrapping stacks of two M5 branes on Riemann surfaces. By exploring the connection between quivers and M5 brane theories, we develop a powerful algorithm for computing BPS spectra, and give an in-depth study of its applications. In particular, we compute BPS spectra for all asymptotically free complete theories, as well as an infinite set of conformal \(SU(2)^k\) theories with certain matter content. From here, we go on to apply the insight gained from our 4d study to 3d gauge theories. We consider the analog of the M5 brane construction in the case of 3d N = 2 theories: pairs of M5 branes wrapped on a 3-manifold. Using the ansantz of R-flow, we study 3-manifolds consisting of Riemann surfaces fibered over R. When the construction is non-singular, the resulting IR physics is described by a free abelian Chern-Simons theory. The mathematical data of a tangle captures the data of the gauge theory, and the Reidemeister equivalances on tangles correspond to dualities of physical descriptions. To obtain interacting matter, we allow singularities in the construction. By extending the tangle description to these singular cases, we find a set of generalized Reidemeister moves that capture non-trivial mirror symmetries of 3d gauge theories. These results give a geometric origin to these well-known 3d dualities., Physics

Intracortical brain-computer interfaces (iBCIs) can restore functional upper limb movements to individuals with chronic tetraplegia by converting neural signals into the movement of an external effector, such as a robotic limb or paralyzed arm reanimated through functional electrical stimulation (FES). While most human-operated iBCIs have extracted intended kinematic parameters such as position and velocity from the motor cortex, restoring natural grasping and object interaction capabilities also requires the control of kinetic parameters such as force. The development of hybrid iBCIs that incorporate both movement kinematics and kinetics requires an understanding of how kinetic information is represented within the human motor cortex, and how this representation is affected by additional motor and non-motor parameters during intended actions. Here, we investigated in a person with chronic tetraplegia how motor cortical neural activity was modulated by three discrete force levels over a range of volitional states (i.e., observed, imagined, and attempted forces) and hand and arm postures.Four major findings emerged from this work. First, this study showed quantitative, electrophysiological evidence that force-related activity persists in motor cortex, even after tetraplegia, in three individuals. Second, it showed that neural force representation depends on volitional state. Attempted forces were represented to a greater degree, and were more accurately predicted from neural data, than observed and imagined forces. Third, we found that attempted forces had both grasp-independent and grasp-dependent neural representations. Specifically, while attempted forces could be predicted from the neural activity at levels above chance across up to five hand and arm postures in two participants, these arm and hand postures significantly impacted the accuracy of attempted force predictions. Finally, this study showed that force-related information was represented to a lesser degree than other parameters, including volitional state and grasp, possibly due to deafferentation-induced changes in somatosensory feedback.This study provides relevant information towards the development of a hybrid kinetic and kinematic iBCI. While the study results indicate that incorporating force control into iBCIs is feasible, force iBCIs will likely need to account for the impacts of additional motor and non-motor parameters in order to maximize performance.

Changes in the mean and extreme climate characteristics are undeniably evident in observational records. Over the United States, the mean temperature has approximately increased by 1oC since the late 19th century and an additional warming of up to 2.2oC is projected by the mid 21st century. Similarly, changes in the temperature and precipitation extremes are also visible through a decreasing trend in the number of rain days and an increasing trend in the frequency of droughts, heat waves and heavy downpours. Discernable evidence suggests that such changes in hydroclimate characteristic are impacting human systems such as energy, agriculture and critical infrastructure. Within this context, this research investigates the responses of regional hydroclimate over the United States to projected increases in radiative forcing in the near term future and its implications for the human systems. This investigation is divided in four parts. The first part quantifies potential changes in county-level residential space heating and cooling requirements as a result of projected changes in heating and cooling degree days. The second part investigates the characteristics of dry versus humid heatwaves and the associated thermodynamic changes in the present and warmer future climate. The third part studies changes in the spatial and temporal characteristics of precipitation events, including extent, intensity and frequency in response to increase in radiative forcing. The fourth part evaluates potential changes in the magnitude of probable maximum precipitation, which is used as a design criteria for critical infrastructure, in the warmer and moister future climate over a hydrological basin in the southeastern United States. Overall, this research should enable development of rigorous analytical frameworks for better planning to cope with the challenges posed by climate change.

Abstract: The tools of atomic physics enable researchers to explore rich quantum mechanical phenomena by way of light-matter interactions. In some applications, light is used to manipulate or modify the properties of a material medium, for instance, laser-cooling and optical trapping of neutral atoms and ions; electromagnetically-induced-transparency (EIT); and Bose- Einstein-Condensation (BEC). Likewise, there are applications where matter is used to manipulate the properties of light, as for example, non-linear optical processes; atomic quantum memories; and quantum-information-processing. This thesis explores two routes towards manipulating light using matter and vice versa in our lab. The work presented in this thesis falls under two categories, one is the experimental side where we have designed and built a laser system to cool a thermal gas of 39K atoms to sub-Doppler temperatures, using the ‘Gray Molasses’ technique. This work is motivated by the long term goal of performing quantum simulation experiments with degenerate quantum gas of K. The second category is on the theoretical (numerical) side, where we introduce a novel quantum memory protocol for coherent storage and processing of broadband light pulses, based on a fundamental physical process in atomic physics, called the ‘Autler-Townes’ effect. Ultracold quantum gases are one of the most versatile systems in the field of cold atom physics; these atomic systems can be experimentally controlled and manipulated with high degree of precision and are thus, widely used to model the behavior of other complex quantum mechanical systems. Laser cooling is the first and indeed a crucial stage towards creating an ultracold gas of atoms. In this thesis, we describe an optical setup for producing a laser-cooled and trapped gas of bosonic 39K atoms, using D1 and D2 atomic transition-lines. The optical setup is built to generate appropriate laser frequencies for implementing various stages of the experiment: red- detuned two and three-dimensional magneto-optical traps (MOT) on the D2-line; a blue-detuned gray molasses phase on the D1-line; as well as optical pumping, imaging and push beams on the D2-line. We also highlight the underlying physics behind the blue-detuned gray molasses cooling and the advantages it offers in cooling species like K and Li. We also discuss in detail, the techniques used for frequency locking our lasers, namely, saturated absorption spectroscopy (SAS) and beatnote locking. The second part of the thesis describes a new atomic quantum-memory scheme for storing broadband pulses of light, which we call the ‘Autler- Townes Splitting (ATS)’ protocol. We show the light storage and retrieval operation in three different configurations, via numerical simulation of Maxwell-Bloch equations. We also discuss the strategies for getting high storage and retrieval efficiency in the ATS memory in terms of only two phenomenological parameters, both of which are experimentally accessible. We have shown that a near-unity efficiency is achievable for a wideband signal, under moderate values of atomic density and laser powers; this significantly relaxes the technical requirements of our protocol when compared to other broadband storage schemes.

ABSTRACT OF THE THESISLiquid Phase Epitaxy Doping for High-Performance Emitters in Silicon Solar CellsbyTulika RastogiMaster of ScienceUniversity of California San Diego, 2018Professor David Fenning, ChairRecombination in the emitter is a primary contributor to recombination current in modern industrial silicon solar cells. This loss is primarily due to recombination that occurs because of the inflexible constraints of solid-state diffusion kinetics during conventional emitter formation that result in a heavily-doped, difficult-to-passivate front surface. P-n junction formation by gas diffusion is also one of the costliest steps in the cell process due to equipment capital expenditure, the large thermal budget required, and the low-throughput batch nature of the process [1]. Liquid phase epitaxy doping (LPE-D) is proposed as a facile low-temperature, low-cost replacement for boron and/or phosphorus diffusion. This doping process decouples the emitter formation from the slow solid-state kinetics of gas diffusion. The doping profile formed is largely time-independent – theoretically, doping could be done in a brief firing step or during bulk impurity gettering, allowing throughput to be optimized without constraining cell architecture in next generation solar cells. The liquid phase epitaxy approach results in a nearly uniform doping concentration profile with the potential for significantly lower saturation currents and improved surface passivation in comparison to existing and proposed industrial diffused emitters. We examine the performance of emitters doped via liquid phase epitaxy using simulation and present experimental demonstration.

Validation of Autonomous Vehicle behavior algorithms requires thorough testing against a wide range of test scenarios. It is not financially and practically feasible to conduct these tests entirely in a real world setting. We discuss the design and implementation of a VR based simulation testbed that allows such testing to be conducted virtually, linking a computer-generated environment to the system running the autonomous vehicle's decision making algorithms and operating in real-time. We illustrate the system by further discussing the design and implementation of an application that builds upon the VR simulation testbed to visually evaluate the performance of an Advance Driver Assist System (ADAS), namely Cooperative Adaptive Cruise Control (CACC) controller against an actor using vehicular navigation data from real traffic within a virtual 3D environment of Clemson University's campus. With this application, our goal is to enable the user to achieve spatial awareness and immersion of physically being inside a test car within a realistic traffic scenario in a safe, inexpensive and repeatable manner in Virtual Reality. Finally, we evaluate the performance of our simulator application and conduct a user study to assess its usability.

We present methods where sessile or suspended microdroplets are used to develop applications in the areas of bio-detection, photonics, drug delivery and catalysis. The first technique we report is for droplet-on-a-chip microbioassays. The assays are performed in droplet micro-containers suspended on the surface of high density fluorinated oil and are based on the process of agglutination of antibody-coated particles. Droplet microbioassays for the detection of Ricin were designed and their performance was compared to the standard handheld field assays. These droplet microbioassays were found to be 10 times more sensitive in terms of analyte concentration while requiring 100 times smaller volumes. We developed a model for the agglutination kinetics and mass transfer processes inside the droplets, which correlates well with the experimental data. The second technique that we developed uses droplet templates dispensed on superhydrophobic substrates for the fabrication of a new class of three dimensional hierarchical microsphere assemblies. The technique is termed Dry Self Assembly (DSA) since the fabricated supraparticles are easily detached from the substrate and collected unlike methods where assembled structures are suspended in liquid environment. The sessile droplet templates cast the final supraparticles into light diffracting near-spherical assemblies. When illuminated with a collimated beam of light, the structures exhibit unique ring shaped color diffraction patterns on their surface. The experimental observations for the angular position and wavelength corresponding to a spot on the rings are interpreted using a surface diffraction grating model. We also tailored the DSA method to produce both shape-anisotropic and composition-anisotropic supraparticles. The shape anisotropy was demonstrated by fabricating "doughnut" assemblies using droplets of both pure silica suspensions and silica mixed with gold nanoparticles. The composition anisotropy was realized by redistribution of magnetic nanoparticles in droplets containing mixtures of latex and magnetic particle suspensions. The redistribution is dictated by the pattern of magnetic field to which the droplet templates are introduced during drying. We developed new types of patchy magnetic particles that can find application in targeted drug delivery. The latex matrix can be infused with a drug and the magnetic patch(es) facilitate remote manipulation of the carrier. A new microfluidic chip was developed for the in-vitro characterization of drug/material release rate from the porous latex network in a live environment. The release rate of dye (drug simulant) from the porous supports is quantified and interpreted on the basis of diffusion/dissolution based mass transfer models. The technique has the potential to perform simultaneous screening of multiple samples and replace the conventional bulk laboratory setup needed for determining the release profiles in drug development process.

Chronic diseases can often be managed by constantly delivering therapeutic amounts of drug for prolonged periods. A controlled release for extended duration would replace the need for multiple and frequent dosing. Local drug release would provide added benefit as a lower dose of drug at the target site will be needed as opposed to higher doses required by whole body administration. This would provide maximum efficacy with minimum side effects. Nonetheless, a problem with the known implantable drug delivery devices is that the delivery rate cannot be controlled, which leads to drug being released in an unpredictable pattern resulting in poor therapeutic management of patients. This dissertation is the result of development of an implantable drug delivery system that is capable of long-term zero order local release of drugs. The device can be optimized to deliver any pharmaceutical agent for any time period up to several years maintaining a controlled and desired rate. Initially significant efforts were dedicated to the characterization, biocompatibility, and loading capacity of nanoporous metal surfaces for controlled release of drugs. The physical characterization of the nanoporous wafers using Scanning electron microscropy (SEM) and atomic force microscopy techniques (AFM) yielded 3.55 x 10⁴ nm³ of pore volume / μm² of wafer surface. In vitro drug release study using 2 - octyl cyanoacrylate and methyl orange as the polymer-drug matrix was conducted and after 7 days, 88.1 ± 5.0 % drug was released. However, the initial goal to achieve zero order drug release rates for long periods of time was not achieved. The search for a better delivery system led to the design of a perforated microtube. The delivery system was designed and appropriate dimensions for the device size and hole size were estimated. Polyimide microtubes in different sizes (125-1000 μm) were used. Micro holes with dimensions ranging from 20-600 μm were fabricated on these tubes using photolithography, laser drilling, or manual drilling procedures. Small molecules such as crystal violet, prednisolone, and ethinyl estradiol were successfully loaded inside the tubes in powder or solution using manual filling or capillary filling methods. A drug loading of 0.05 – 5.40 mg was achieved depending on the tube size and the drug filling method used. The delivery system in different dimensions was characterized by performing in vitro release studies in phosphate buffered saline (pH 7.1-7.4) and in vitreous humor from the rabbit’s eye at 37.0 ± 1.0°C for up to four weeks. The number of holes was varied between 1 and 3. The tubes were loaded with crystal violet (CV) and ethinyl estradiol (EE). Linear release rates with R²>0.9900 were obtained for all groups with CV and EE. Release rates of 7.8±2.5, 16.2±5.5, and 22.5±6.0 ng/day for CV and 30.1±5.8 ng/day for EE were obtained for small tubes (30 μm hole diameter; 125 μm tube diameter). For large tubes (362-542 μm hole diameter; 1000 μm tube diameter), a release rate of 10.8±4.1, 15.8±4.8 and 22.1±6.7 μg/day was observed in vitro in PBS and a release rate of 5.8±1.8 μg/day was observed ex vivo in vitreous humor. The delivery system was also evaluated for its ability to produce a biologically significant amounts in cells stably transfected with an estrogen receptor/luciferase construct (T47D-KBluc cells). These cells are engineered to produce a constant luminescent signal in proportion to drug exposure. The average luminescence of 1144.8±153.8 and 1219.9±127.7 RLU/day, (RLU = Relative Luminescence Units), yet again indicating the capability of the device for long-term zero order release. The polyimide device was characterized for biocompatibility. An automated goniometer was used to determine the contact angle for the device, which was found to be 63.7±3.7degreees indicating that it is hydrophilic and favors cell attachment. In addition, after 72 h incubation with mammalian cells (RAW 267.4), a high cell distribution was observed on the device’s surface. The polyimide tubes were also investigated for any signs of inflammation using inflammatory markers, TNF-α and IL-1β. No significant levels of either TNF-α or IL-1β were detected in polyimide device. The results indicated that polyimide tubes were biocompatible and did not produce an inflammatory response.

Performance and power consumption are most important issues while designing embedded systems. Several studies have shown that cache memory consumes about 50% of the total power in these systems. Thus, the architecture of the cache governs both performance and power usage of embedded systems. A new N-way reconfigurable data cache is proposed especially for embedded systems. This thesis explores the issues and design considerations involved in designing a reconfigurable cache. The proposed reconfigurable data cache architecture can be configured as direct-mapped, two-way, or four-way set associative using a mode selector. The module has been designed and simulated in Xilinx ISE 9.1i and ModelSim SE 6.3e using the Verilog hardware description language.

The ability to pattern functional polymers at different length scales is important for the advancement of modern science and technology. This dissertation mainly describes the work done on the high resolution patterning of polymer thin films that have a variety of potential uses. The nanoscale patterning of spun-coated polar polymers was demonstrated using environmentally benign supercritical carbon dioxide (scCO2) as a processing solvent. The use of scCO2 as a processing solvent has several technical advantages that help resolve some of the key problems faced in lithography. In addition, it helps reduce the energy and resource usage that can negatively affect the environment. scCO2 is generally a poor solvent for high molecular weight polymers that are used as standard photoresists. Chapter 2 describes a series of fluorinated quaternary ammonium salts that were synthesized and used as CO2 compatible additives to aid the dissolution of polar polymer photoresists in scCO2. Using these dissolution aids, patterns as small as 100 nm lines were obtained with scCO2 development. Chapters 3 and 4 focus on the patterning of high-tech thin polymer films referred to as polymer brushes. In these films the polymer chains are covalently attached to a surface. A direct method of patterning polymer brushes in a single step using electron beam lithography has been described. Polymer brushes of different structures such as poly(methyl methacrylate) (PMMA) brushes , poly(2-hydroxyethyl methacrylate) (PHEMA) brushes, poly(isobutyl methacrylate) (PIBMA) brushes, poly(neopentyl methacrylate) (PNPMA) brushes and poly(2,2,2-trifluoroethyl methacrylate) (PTFEMA) brushes were grown via atom transfer radical polymerization. These brushes were directly patterned using e-beam and their sensitivity to e-beam patterning has been compared and explained. This direct patterning approach produced polymer brush patterns down to 50 nm lines. Due to the number of advantages of using scCO2 as a processing solvent, the dry development of a directly patterned low surface energy coating composed of PTFEMA brushes in scCO2 has been demonstrated in Chapter 4. Using scCO2 as a developer, patterned PTFEMA brushes with 150 nm lines were obtained. Polymer brushes have been used to prepare biocompatible surfaces with reduced non-specific adsorption. Chapter 5 describes the synthesis of a new oligo(ethylene glycol) containing ATRP intiator to prevent non-specific adsorption of biomolecules on polymer brush coated gold electrodes. The adsorption of non-specific antibodies on modified gold electrodes was studied using cyclic voltammetry. Poly(acrylic acid) brushes grown using this new ATRP initiator showed reduced nonspecific binding of the gold electrodes. There has been a continuing need for developing new medical countermeasures for emerging infectious diseases. Chapter 6 describes the role of functionalized poly(acrylic acid) brushes in the development of a biosensor based on sensitive electrochemical detection of the intrinsic catalytic activity of antibodies. Poly(acrylic acid) brushes have been functionalized with 2,4-dinitrophenyl groups (model antigen) and Ni-NTA to immobilize specific antibodies on the sensor surface. The modification of gold surfaces with polymer brushes provides a bio- and electronically compatible substrate with high density of specific haptens with reduced non-specific adsorption.

In an integrated heterogeneous wireless network (IHWN), a user can connect itself to different types of networks on anytime, anywhere basis. Any of the following networks: cellular networks, WLANs, and ad hoc and sensor networks can constitute an IHWN network. The user is free to roam within networks seamlessly based on his needs and network availability. However, the security concerns associated with the IHWN count for some of the challenges involved in its implementation. These concerns combined with the different security requirements of various constituent wireless networks may have made security a serious issue. Seamless transfer of user’s credentials is a major requirement when considering security during vertical handoff between two different types of networks. A security scheme that can fit all types of networks is difficult to propose. However, a reasonable architecture that keeps both security and user convenience into consideration can be designed. The existing security schemes fail to address mobility and scalability requirements. Considering the importance of these aspects in securing a global network, we propose a novel security scheme that uses two different security algorithms depending on the number of vertical handoffs made by the mobile node after the first authentication in the home network. It makes use of existing network elements, such as RADIUS and Diameter protocols and supports scalability, mobility, and secure key exchange. We also introduce a time factor which is pre-set between the home network and foreign network. It delegates the task of authorizing subsequent requests from mobile node to connect to a different foreign network. Finally, we evaluate the efficiency and scalability of the scheme and prove its superiority over the existing schemes. The simulation results show a significant improvement over messages exchanged during key distribution at the time of vertical handoff. They also show how the scheme provides an excellent solution for delegated authentication. For a fair comparison, we also analyze the existing key distribution schemes and discuss their limitations in supporting the user security needs in current wireless networks.

Part-1: Degradation of PCBs by Ferrous-Peroxymonosulfate oxidation systemPolychlorinated biphenyls (PCBs) in the environment pose long-term risk to public health because of their persistent and toxic nature. This study investigates the degradation of PCBs using sulfate radical-based advanced oxidation processes (SR-AOPs). These processes are based on the generation of sulfate radicals through iron (Fe(II),Fe(III)) mediated activation of peroxymonosulfate (KHSO 5, PMS) or persulfate(Na 2S 2O 8, PS). This study is the first instance for coupling of Fe(II)/Fe(III) with Oxone for PCB degradation in aqueous and sediment systems. The high oxidation efficiencies of the free radicals (SO 4 -•), in combination with the slow rate of consumption of the oxidants, make these processes very effective for the degradation of recalcitrant organic compounds. The effectiveness of the process was evaluated based on the degradation of a model polychlorinated biphenyl, 2-chlorobiphenyl and total organic carbon (TOC) removal. The kinetics of 2-chlorobiphenyl degradation along with the effect of oxidant and catalyst concentrations on the degradation efficiency were studied. Near complete removal of 2-chlorobiphenyl was observed when Fe(II) was used with PMS or PS. Fe(II) acts as a sulfate radical scavenger at higher concentrations indicating that there is an optimum concentration of Fe(II) that leads to most effective degradation of the target contaminant. A chelating agent, sodium citrate, was used to control the quantity of iron in the solution for activation of the oxidant. For the first time, we studied the feasibility of the activation of Oxone using iron-citrate complexes for PCB degradation. In the presence of sodium citrate, increase in degradation efficiency was observed up to a metal: ligand ratio of 1:2, after which the increase in citrate concentration led to a decrease in removal efficiency. Fe(II)/PMS systems were found to be very effective in degrading PCB in a sediment slurry system with more than 90% PCB removal being observed within 24 h. Part-2: Destruction of Chlorophenols by novel radical based oxidation processesThis study examines the feasibility and applications of novel advanced oxidation technologies (AOTs) based on sulfate radicals (SO 4 -•) for US EPA priority pollutants, chlorophenols. A novel class of sulfate radical based homogeneous AOTs (Fe(II)/PS, Fe(II)/PMS,Fe(II)/H 2O 2) was successfully tested for the degradation of series of chlorophenols ( 4-CP, 2,4-CP, 2,4,6-CP, 2,3,4,5-CP). The main objective of the present study was to evaluate the effectiveness of three common peroxide (PMS, PS, H 2O 2) activation by Fe(II) complexes of three representative chelating agents (Citrate, EDDS, and Pyrophosphate) at neutral pH conditions. Short term (4 h) and long term (7 d) experiments were conducted to evaluate the kinetics and longevity of different oxidative systems for 4-chlorophenol degradation. In degradation experiments, remaining contaminant (4-CP), oxidant and soluble iron were monitored with time in an attempt to clearly understand the process of oxidant activation by iron complexes of these three chelating agents. To our best knowledge, this is the first study evaluating the effectiveness of PMS, PS and H 2O 2(common oxidations) for chlorophenol degradation at neutral pH using citrate, pyrophosphate and EDDS as chelating agent. Results showed that certain iron-chelating agent couples were much superior in activating particular oxidant and consequently 4-CP degradation. In case of Fe(II)/PMS system, the inorganic chelating agent pyrophosphate showed the best activation of PMS whereas very fast dissociation of PMS was recorded in case of Fe(II)/EDDS without any apparent 4-CP degradation. In Fe(II)/H 2O 2system, Fe(II)/EDDS complexes were proven to be the most effective and Fe(II)/Pyrophosphate complexes could not activate hydrogen peroxide. Fe(II)/Citrate system showed moderate activation of all three oxidants. Overall, PMS was found the more universal oxidant which was activated by all three iron-chelating agent systems and Fe(II)/Citrate was most universal chelating agent system, which was able to activate all three oxidants up a certain extent.

In order to satisfy the high accuracy and continuity constraints for avionics related applications of Global Positioning System (GPS), it is important to develop methods to correct and prevent anomalies that can hinder navigation. This thesis aims at building a user-friendly tool to analyze the GPS signal anomalies and attempts to identify causes so that appropriate preventive measures can be utilized or explored. Graphical User Interfaces (GUIs) are developed in MATLAB™ which can process 10 seconds of GPS radio frequency data using batch processing algorithms in a Software-Defined Radio (SDR). One GUI gives a quick look at the signal abnormalities for all satellites while the second GUI gives a detailed look at parameters such as carrier phase, carrier to noise ratio, carrier frequency, navigation data bits and accumulated Doppler, for one satellite signal. Radio Frequency Interference (RFI) anomalies are simulated to test the software and to observe the effects on the GPS signals.

Critical infrastructures such as wireless network systems demand dependability. Dependability attributes addressed in this thesis include availability, reliability, maintainability and survivability (ARMS). This research uses computer simulation and artificial intelligence to introduce a new approach to measure dependability of wireless networks. The new approach is based on the development of a neural network, which is trained to investigate ARMS attributes of a wireless network capable of serving 100,000 subscribers. Given the reliability and maintainability of wireless infrastructure components, the resulting impact on network availability and survivability are determined. Component mean time to failure (MTTF) is used to model reliability, while mean time to restore (MTR) is used for maintainability. Here, unavailability, the complement of availability, is defined as the fraction of time the entire network system is down, while survivability is the fraction of network users who have service. Both availability and survivability can be instantaneous or averaged over some period. The simulation output is used to train the neural network, which is obtained from simulation experiments for a range of component’s MTTF and MTTR values. In turn, the NN is used to gain insights not easily apparent from simulation results. The NN also assists in estimating the number of FCC-Reportable outages of a wireless network. Lastly, a variety of reliability/maintainability growth and deterioration scenarios is analyzed with the NN. Besides focusing on questions regarding availability and survivability under reliability and maintainability growth/deterioration scenarios, this research also focuses on the relative performance of neural network modeling compared to analytical and simulation techniques.

The NASA SeaWinds scatterometer is a radar remote sensor which operates on two satellites; NASA's QuikSCAT launched in June 1999 and on Japan's ADEOS-II satellite launched in December 2002. The purpose of SeaWinds is to provide global measurements of the ocean surface wind vector. On QuikSCAT, a ground data processing algorithm was developed, which allowed the instrument to function as a QuikSCAT Radiometer (QRad) and measure the ocean microwave emissions (brightness temperature, Tb) simultaneously with the backscattered power. When SeaWinds on ADEOS was launched, this same algorithm was applied, but the results were anomalous. The initial SRad brightness temperatures exhibited significant, unexpected, ascending/descending orbit Tb biases. This thesis presents an empirical correction algorithm to correct the anomalous SeaWinds Radiometer (SRad) ocean brightness temperature measurements. I use the Advanced Microwave Scanning Radiometer (AMSR) as a brightness temperature standard to calibrate and then, with independent measurements, validate the corrected SRad Tb measurements. AMSR is a well-calibrated multi-frequency, dual-polarized microwave radiometer that also operates on ADEOS-II. These results demonstrate that, after tuning the Tb algorithm, good quality SRad brightness temperature measurements are obtained over the oceans.

Many existing hospitals have problems with their ward layouts. However, the increase in construction costs and the decrease in the number of hospitals have made renovation more economical than building new facilities. Compounding the problem of inefficient floor layouts is the increasing severity of cases treated on an inpatient basis. This research was designed to evaluate the problems faced by nurses working on long corridor patient wards in Montgomery Regional Hospital in Blacksburg, Virginia. It was shown in the study and through previous studies in the literature that these types of wards have physical design problems that affect adversely nurses’ activities in patient care. This study used a time travel method to evaluate the amount of time the nurses spent traveling between the nurses’ station, patient rooms, and other functional areas. Nurses’ perspectives concerning their physical environment and layout were also studied using a questionnaire. It was found that the travel time on the ward was directly related to the geometry of the ward. It was also shown that the total travel time was dependant on the number of patients in the ward. The average amount of time nurses spent traveling in Ward-A was more than the average time they spent in patient rooms. The average time the nurses spent traveling in Ward-B was less than the average time they spent in patient rooms. In addition to a discussion of the time travel data the study also posed several design solutions to problems found in Montgomery Regional Hospital.

Structural analyses are developed to determine the linear elastic and the geometrically nonlinear elastic response of an internally pressurized, orthogonally stiffened, composite material cylindrical shell. The configuration is a long circular cylindrical shell stiffened on the inside by a regular arrangement of identical stringers and identical rings. Periodicity permits the analysis of a unit cell model consisting of a portion of the shell wall centered over one stringer-ring joint. The stringer-ring- shell joint is modeled in an idealized manner; the stiffeners are mathematically permitted to pass through one another without contact, but do interact indirectly through their mutual contact with the shell at the joint. Discrete beams models of the stiffeners include a stringer with a symmetrical cross section and a ring with either a symmetrical or an asymmetrical open section. Mathematical formulations presented for the linear response include the effect of transverse shear deformations and the effect of warping of the ring’s cross section due to torsion. These effects are important when the ring has an asymmetrical cross section because the loss of symmetry in the problem results in torsion and out-of-plane bending of the ring, and a concomitant rotation of the joint at the stiffener intersection about the circumferential axis. Data from a composite material crown panel typical of a large transport fuselage structure are used for two numerical examples. Although the inclusion of geometric nonlinearity reduces the "pillowing" of the shell, it 1s found that bending is localized to a narrow region near the stiffener. Including warping deformation of the ring into the analysis changes the sense of the joint rotation. Transverse shear deformation models result in increased joint flexibility.