Digital Commons Network^™

Improving The Stimulation Selectivity In The Human Cochlea By Strategic Selection Of The Current Return Electrode, Ozan Cakmak

Dissertations

The hearing quality provided by cochlear implants are poorly predicted by computer simulations. A realistic cochlear anatomy is crucial for the accuracy of predictions. In this study, the standard multipolar stimulation paradigms are revisited and Rattay’s Activating Function is evaluated in a finite element model of a realistic cochlear geometry that is based on µ-CT images and a commercial lead. The stimulation thresholds across the cochlear fibers were investigated for monopolar, bipolar, tripolar, and a novel (distant) bipolar electrode configuration using an active compartmental nerve model based on Schwartz-Eikhof-Frijns membrane dynamics. The results suggest that skipping of the stimulation point …

Photonic Monitoring Of Atmospheric Fauna, Adrien P. Genoud

Dissertations

Insects play a quintessential role in the Earth’s ecosystems and their recent decline in abundance and diversity is alarming. Monitoring their population is paramount to understand the causes of their decline, as well as to guide and evaluate the efficiency of conservation policies. Monitoring populations of flying insects is generally done using physical traps, but this method requires long and expensive laboratory analysis where each insect must be identified by qualified personnel. Lack of reliable data on insect populations is now considered a significant issue in the field of entomology, often referred to as a “data crisis” in the field. …

Twitter Sentiment Analysis: Applications In Healthcare And Finance, Jiali Wang

Dissertations

This research explores the influence of Twitter sentiment on healthcare and finance industries. It assesses how Twitter sentiment and culture measure influence COVID-19 statistics, and it investigates the impact of Twitter sentiment on S&P 1500 stock mispricing. Furthermore, it examines how tweet sentiment predicts major industry returns.

The first part examines how Hofstede’s Culture Dimensions (HCD) and Twitter economic uncertainty index (TEU) relate to COVID-19 infection rate and death rate. The results show certain aspects in HCD, such as power distance index (PDI) and masculinity (MAS) both are negatively and significantly associated with the infection rate, while indulgence (IVR) and …

Integrated Machine Learning And Optimization Approaches, Dogacan Yilmaz

Dissertations

This dissertation focuses on the integration of machine learning and optimization. Specifically, novel machine learning-based frameworks are proposed to help solve a broad range of well-known operations research problems to reduce the solution times. The first study presents a bidirectional Long Short-Term Memory framework to learn optimal solutions to sequential decision-making problems. Computational results show that the framework significantly reduces the solution time of benchmark capacitated lot-sizing problems without much loss in feasibility and optimality. Also, models trained using shorter planning horizons can successfully predict the optimal solution of the instances with longer planning horizons. For the hardest data set, …

Faceted Nanomaterial Synthesis, Characterizations And Applications In Reactive Electrochemical Membrane Filtration, Qingquan Ma

Dissertations

Facet engineering of nanomaterials, especially metals and metal oxides has become an important strategy for tuning catalytic properties and functions from heterogeneous catalysis to electrochemical catalysis, photocatalysis, biomedicine, fuel cells, and gas sensors. The catalytic properties are highly related to the surface electronic structures, surface electron transport characteristics, and active center structures of catalysts, which can be tailored by surface facet control. The aim of this doctoral dissertation research is to study the facet-dependent properties of metal or metal oxide nanoparticles using multiple advanced characterization techniques. Specifically, the novel atomic force microscope-scanning electrochemical microscope (AFM-SECM) and density functional theory (DFT) …

Helioseismic Diagnostics Of Active Regions And Their Magnetic Fields, John T. Stefan

Dissertations

While two and a half decades of nearly constant observation by the Solar and Heliospheric Observatory (SOHO) and the Solar Dynamics Observatory (SDO) spacecraft have yielded key insights into the structure and dynamics of active regions, it is still unclear if active regions can be identified before emerging on the solar surface and, once emerged, whether the subsurface structure of an active region’s magnetic field can be measured. Regarding the dynamical processes associated with active regions, the height and mechanism of sunquake excitation remains poorly understood. To answer these questions, a comprehensive survey of active region magnetic fields and their …

Hydrodynamic Investigation Of The Discharge Of Complex Fluids From Dispensing Bottles Using Experimental And Computational Approaches, Baran Teoman

Dissertations

The discharge of non-Newtonian, complex fluids through orifices of industrial tanks, pipes, dispensers, or packaging containers is a ubiquitous but often problematic process because of the complex rheology of such fluids and the geometry of the containers. This, in turn, reduces the discharge rate and results in residual fluid left in the container, often referred to as heel. Heel formation is undesired in general, since it causes loss of valuable material, container fouling, and cross-contamination between batches. Heel may be of significant concern not only in industrial vessels but also in consumer packaging. Despite its relevance, the research in this …

The Future Of The Urban Street In The United States: Visions Of Alternative Mobilities In The Twenty-First Century, Esther Zipori

Dissertations

This dissertation is concerned with the present and future of urban streets in the United States. The goal is to document and analyze current visions, policies, and strategies related to the form and use of American urban streets. The dissertation examines current mobility trends and offers a framework for organizing visions of the future of urban streets, evaluating them through three lenses: safety, comfort, and delight: assessing physical conditions in accordance with livability standards toward sustainable development. At the same time, it demonstrates the way 12 scenarios (NACTO Blueprint for Autonomous Urbanism, Sidewalk Labs: Quayside Project, Public Square by FXCollaborative, …

Interactions Of Amyloid Peptides With Lipid Membranes, Yanxing Yang

Dissertations

The aggregation of amyloid proteins into fibrils is a hallmark of several diseases including Alzheimer’s (AD), Parkinson’s, and Type II diabetes. This aggregation process involves the formation of small size oligomers preceding the formation of insoluble fibrils. Recent studies have shown that these oligomers are more likely to be responsible for cell toxicity than fibrils. A possible mechanism of toxicity involves the interaction of oligomers with the cell membrane compromising its integrity. In particular, oligomers may form pore-like structures in the cell membrane affecting its permeability or they may induce lipid loss via a detergent-like effect. This dissertation aims to …

Microhydrodynamic, Kinetic And Thermal Modeling Of Wet Media Milling For Process Optimization And Intensification, Gulenay Guner

Dissertations

Nanoparticle production by wet stirred media milling (WSMM) is a common method for the formulation of poorly water-soluble drugs. While most of the studies in the WSMM literature focus on the formulation aspects to overcome the stability challenges, a thorough mechanistic understanding of the process is lacking, and the process is slow, costly, and energy-intensive. This dissertation presents experimental and modeling work with the ultimate goals of (i) gaining a deeper and more mechanistic understanding of the WSMM process and breakage kinetics of the particles using a microhydrodynamic model with various improvements and advancements, (ii) examining the heat dissipation during …

Machine Learning-Based Data Analytics For Understanding Space Weather And Climate, Yasser Abduallah

Dissertations

This dissertation addresses multiple crucial problems in space weather and climate, presenting new machine learning-based data analytics algorithms and models for tackling the problems.

First, the dissertation presents two new approaches to predicting solar flares. One approach, called DeepSun, predicts solar flares by utilizing a machine-learning-as-a-service (MLaaS) platform. The DeepSun system provides a friendly interface for Web users and an application programming interface (API) for remote programming users. It adopts an ensemble learning method that employs several machine learning algorithms to perform multiclass flare prediction. The other approach, named SolarFlareNet, forecasts the occurrence of solar flares within the next 24 …

Bioremediation Of Petroleum Hydrocarbons In Coastal Sediments, Charbel Abou Khalil

Dissertations

The biodegradation of dispersed crude oil in the ocean is relatively rapid (a half-life of a few weeks). However, it is often much slower on shorelines, usually attributed to low moisture content, nutrient limitation, and higher oil concentrations in beaches than in dispersed plumes. Another factor may be the increased salinity of the upper intertidal and supratidal zones since these parts of the beach are potentially subject to prolonged evaporation and only intermittent inundation. Therefore, two laboratory experiments are conducted to investigate whether such an increase in porewater salinity results in additional inhibitory effects on oil biodegradation in seashores.

In …

Combustion Soot Nanoparticles: Mechanism Of Restructuring And Mechanical Properties, Ali Hasani

Dissertations

Soot, a product of incomplete combustion of fossil fuels, is a global warming agent. The effect of soot particles on climate depends on their morphology. Freshly released soot particles are fractal lacey aggregates, but they often appear collapsed in atmospheric samples collected away from emission sources. A body of work has concluded that the collapse is caused by liquid shells when they form by vapor condensation around soot aggregates. However, some recent studies argue that soot remains fractal even when engulfed by the shells, collapsing only when the shells evaporate. To reconcile this disagreement, the effects of the condensation and …

Monitoring Climate Change With Machine Learning And Uncertainty Quantification, Firas Gerges

Dissertations

The impact of climate change on the environment has become increasingly visible today. One important topic in climate change monitoring is to forecast future climate events, which relies on long-term prediction of climate variables at a local regional scale. This topic is crucial for disaster risk management and for resolving climate change at the local level. General Circulation Models (GCMs) allow for the simulation of several climate variables, decades into the future. GCM simulations, however, are at a global large scale and are too coarse to monitor climate change at the local small scale. This dissertation explores new machine learning …

Amphiphilic Block Copolymers And The Applications In Therapeutics Delivery, Jie Dou

Dissertations

Well-defined thermo-responsive triblock copolymers containing polyethylene oxide (PEO) and poly(N-isopropyl acrylamide) PNIPAM are synthesized by a type of living controlled polymerization, named iniferter polymerization. The polymers are amphiphilic in nature and are self-assembled into a micelle. Their properties and application are characterized and investigated in this work.

Foremost, the initiator of the polymerization (iniferter) is designed and synthesized by condensation polymerization, where PEO is incorporated into the structure to improve biocompatibility, which has great potential for biological application. Moreover, this iniferter reagent could be applied to more than 70 percent of vinyl monomers.

NIPAM, a commercial vinyl monomer, is chosen …

Biotransformation And Biodefluorination Of Fluorotelomer Carboxylic Acids, Chen Wu

Dissertations

Per- and polyfluoroalkyl substances (PFASs), a class of emerging contaminants of concern, have attacked unprecedented attention given their prevalent detection and adverse health effects. Primary regulatory attention has been focused on PFOA, PFOS, and other perfluoroalkyl acids (PFAAs). Recent investigations revealed that fluorotelomer carboxylic acid (FTCAs), particularly 5:3 FTCA and 6:2 FTCA, were dominant in landfill leachates and other environmental matrixes. FTCAs are also found as common intermediates during the biotransformation of PFAA precursors. Unfortunately, FTCAs have higher bioaccumulating potential and are at least two orders more toxic than their corresponding PFCAs. However, information regarding the potentials and mechanisms of …

A Novel Biomaterial Platform For Cardiac Tissue Engineering, Andrew House

Dissertations

Heart disease is one of the leading causes of death in the world. With a growing demand for in vitro cardiac models that can recapitulate the complex physiology of the cardiac tissue, there is a desire to create novel therapies and treatments. However, due to a lack of fundamental understanding of the heart's inflammatory response to myocardial infarction, the development of new therapies is both time consuming and costly. In this work, a novel approach to fabricating a dynamic hydrogel cardiac platform is reported. This platform better mimics the dynamic changes occurring in the native cardiac tissue microenvironment during cardiac …

Angiogenic Supports For Microvascular Engineering, Zain Siddiqui

Dissertations

Ischemic tissue disease is caused by a lack of circulation / blood supply to tissue. This can be treated by introducing a number of angiogenic (pro-blood vessel forming) factors into the tissue. This work presents strategies for ischemic tissue treatment utilizing a novel proangiogenic self-assembling peptide hydrogel platform. To demonstrate the utility of this platform, its use alone as an angiogenic therapeutic (both alone as a self-assembling hydrogel and with two-component systems), and its ability to vascularize implants is explored. Due to these angiogenic scaffolds demonstrating efficacy to regenerate microvasculature, this work evaluates diseases that can be treated by the …

Polymeric Nitrogen: Computational Catalysis And Materials Design, Safa Alzaim

Dissertations

The urgent climactic crisis currently endangering all life on earth is largely due to the combustion of fossil fuels as an energy source. This work combines physics, chemistry, mathematics and computer science to develop new ways to harvest, store and use sustainable energy. In particular, this work centers on polymeric nitrogen (PN). PN is highly desirable because the energy density is extremely high. This energy density lends PN to applications such as rocket fuel and energetic materials. Recently, the polymeric phase N₈ was shown to be highly active for oxygen reduction reactions (ORR); the material is an excellent electrocatalyst …

Nondirect Line-Of-Sight Free-Space Optical Communications And Networks, Paa Kwesi Affir Esubonteng

Dissertations

Nondirect Line-of-Sight Free-Space Optical Communications (NLoS-FSOC) uses diffuse reflected light to establish communication between two or more stations that are with or without line-of-sight (LoS) to each other. Different from free-space optical communications (FSOC), NLoS-FSOC uses a diffuse reflector (DR) between a transmitter and a receiver so that LoS is not required between them but between the station and the DR. Unlike a mirror, the DR reflects the incident light to all directions and except to itself. That multidirectional reflection broadcast the optical transmission to all receivers with LoS to the DR. The optical broadcast channel establishes a true optical …

Naturally Derived Fibrous Scaffolds Containing Metabolic Factors For Bone Tissue Engineering, Apurva Limaye

Dissertations

More than 500,000 bone grafting procedures are performed each year to treat bone defects, trauma, and non-unions. Current strategies, including autografts and allografts, face limitations that include donor site morbidity and poor integration, respectively. Treatments using the delivery of the growth factor, bone morphogenetic protein-2 (BMP2), result in ectopic bone formation and adverse effects at high doses. Tissue engineering strategies are utilized to combat these challenges. Natural biomaterials are commonly used as tissue engineering scaffolds due to their biocompatibility, biodegradability, and they can promote cellular function. However, animal-derived materials can have limitations in availability, lot to lot variability and potential …

Microplastics And Genetic Vectors Promoting The Dissemination Of Antimicrobial Resistance In Municipal Wastewater Treatment Processes, Ngoc Dung Pham

Dissertations

The spread of antimicrobial resistance in the environment and especially its transfer into human pathogens have emerged as global issues. Activated sludge units at municipal wastewater treatment plants are "hotspots" converging a multitude of contaminants, including antibiotics, antibiotic-resistant bacteria (ARB), human pathogens, and microplastics. The prevalence of antibiotics can induce stress response of sludge microbial communities and promote the development of new resistance mechanisms and transmission venues, through which the dissemination of antibiotic resistance genes (ARGs) arises as mediated by mobile genetic elements (MGEs). In this doctoral dissertation, the impacts of microplastics and genetic vectors (i.e., MGEs and bacterial hosts) …

Platinum Nanoparticles, Targeted Therapy For Triple Negative Breast Cancer, Aida Lopez Ruiz

Dissertations

Nanotechnology is a multidisciplinary field that has many different applications including cancer treatment and detection. Noble metal nanoparticles such as gold, silver or palladium, have shown major potential in the field of medicine and pharmaceutics. In particular, platinum nanoparticles (Pt NPs) have been reported with promising anticancer results. The activity of nanoparticles is based on their small size and high surface area; these properties allow them to penetrate biofilms as well as influence intracellular mechanisms. Recent studies indicate that Pt NPs can be used as a therapy for cancer showing a limited toxicity to healthy cells. Hence, in this work, …

The Impact Of Job Satisfaction On Retention And Motivation For Leadership Advancement Of The U. S. Citizenship And Immigration Services (Uscis) Millennial Supervisors, Kelvin Medlock

Dissertations

Purpose: This explanatory mixed-methods study aimed to identify the job satisfaction level of millennial supervisors at the five service centers of the U. S. Citizenship and Immigration Services (USCIS). Additionally, it identified the impact that job satisfaction levels have on their job retention and motivation for leadership advancement.

Methodology: An explanatory sequential design data collection method was used to identify and describe the level of job satisfaction of USCIS millennial supervisors. This Minnesota Satisfaction Questionnaire (MSQ) was completed by the participants and was followed by an open-ended interview designed to collect in-depth data on job satisfaction factors’ impact on retention …

Implementing A Smoking Cessation Protocol In Type 2 Diabetics In A Podiatry Clinic Using The Five A'S Model, Guerlyne Henson

Dissertations

Smoking is an independent risk factor for DMT2 making it essential for providers to address smoking cessation consistently. The purpose of this quantitative, quasiexperimental quality improvement (QI) project was to evaluate if or to what degree the implementation of a tobacco cessation protocol using the Five A's model would impact the patient's motivation, nicotine dependence, and provider compliance with assessing tobacco use in adult diabetic smokers in a podiatry clinic for four weeks in the northeastern United States. The transtheoretical model (TTM) was utilized to evaluate patient motivation to quit smoking and determine appropriate cessation interventions. Data on the motivation …

Evaluation And Revision Of The Practice Environment Scale Of The Nursing Work Index For Acute Care Hospital Staff Nurses, Caitlin M. Campbell

Dissertations

The Practice Environment Scale of the Nursing Work Index (PES-NWI) is the most frequently used instrument for measuring the nursing work environment. The original PES-NWI obtained its items directly from the parent instrument, the Nursing Work Index, which was developed in the 1980s. However, potential value change among younger generations and vast historical, social, and technological transformations in the way healthcare is provided may have led to different factors that compose a favorable work environment for nurses working today.

Implementation Of The Family Help Protocol: A Feasibility Project For A West Texas Icu, Rebecca Mcclay

Dissertations

The purpose of this project was to determine if there is sufficient bedside ICU nurse buy-in to the Family HELP protocol to make implementation feasible at one county hospital in West Texas.

Implementation Of An Adverse Childhood Experiences (Ace) Screening Protocol For Adults At An Outpatient Medical Psychology Practice: A Dnp Project, Jennifer E. Allain

Dissertations

This DNP project aimed to educate and train staff and providers on ACE screening and implement an ACE screening policy and protocol at an outpatient medical psychology practice. The two expected outcomes of this project, provider knowledge after ACE training and provider compliance with the ACE screening protocol, were measured to determine if a clinical practice change occurred. A paired-samples t-test compared the participants' knowledge of ACEs before and after the ACE educational intervention with a pre/post-test. There was a statistically significant difference in the pre-test and post-test scores. These findings reflected a change in knowledge based on education …

"Cameras Don’T Kill People": Community-Based Organizations And The Expansion Of Surveillance Systems In St. Louis, Missouri, Claire Greene

Dissertations

In many cities, private camera ownership and video sharing partnerships with law enforcement are on the rise. These private surveillance networks have dramatically increased the reach of law enforcement and intensified the monitoring of urban life. Although police use of private cameras has become the subject of contentious debate, our understanding of private camera systems and how they are used by the police remains quite limited, largely focusing on either utopian or dystopian narratives. Drawing on interviews with community organizations in St. Louis, Missouri, that have installed neighborhood surveillance systems, this dissertation seeks to provide some insight into the rise …

Daily Rounding To Reduce Catheter-Associated Urinary Tract Infections In A Rehabilitation Facility, Folashade Oluwafunmi

Dissertations

Despite national efforts to reduce catheter-associated urinary tract infections (CAUTIs), healthcare facilities continue to report CAUTI events. The project site reported CAUTI rates above local and national benchmarks even though a CAUTI bundle was in use. The purpose of this quantitative quasi-experimental quality improvement project was to determine if the implementation of daily rounding by organizational CAUTI champions, using the Agency for Healthcare Research and Quality (AHRQ) Comprehensive Unitbased Safety Program (CUSP), would impact CAUTI rates among adult residents in a rehabilitation facility in Northern California for four weeks. Lewin's change theory and the IOWA evidence-based practice model were the …