Engineering Commons^™

The Scaffolds To Guide Fast Angiogenesis, Tianhong Zhou

McKelvey School of Engineering Theses & Dissertations

Angiogenesis is one of the most challenging problems in bone structure repair. The different types of 3D fibrous morphology structure of the extracellular matrix for fasting angiogenesis have been studied. Due to the densely packed constructs and limited porosity of scaffold, the challenge still remains for scaffold fabrication. In this study, we fabricated PCL scaffold with growth factors and cells to guide fast angiogenesis by electro-spinning and electro-spray simultaneously. We developed a technique that electro-spinning encapsulates growth factors OPN(Recombinant Human Osteopontin) and SDF-1α(CXCL12) in poly(lactide-co-glycolide) (PLGA) microspheres into PCL 3D structures scaffold fibers. We also developed a new technique to …

Three-Dimensional Image Reconstruction In Transcranial Photoacoustic Computed Tomography, Joemini Poudel

McKelvey School of Engineering Theses & Dissertations

Photoacoustic computed tomography (PACT) is an emerging imaging modality that exploitsoptical contrast and ultrasonic detection principles to form images of the photoacousticallyinduced initial pressure distribution within tissue. The PACT reconstruction problemcorresponds to an inverse source problem in which the initial pressure distribution is recoveredfrom measurements of the radiated pressure wavefield. A major challenge in transcranialPACT brain imaging is compensation for aberrations in the measured data due to the presenceof the skull. Ultrasonic waves undergo absorption, scattering and longitudinal-to-shear wavemode conversion as they propagate through the skull. To properly account for these effects, awave-equation-based inversion method should be employed that can …

Anion Exchange And Bipolar Membranes For Electrochemical Energy Conversion And Storage, Zhongyang Wang

McKelvey School of Engineering Theses & Dissertations

Anion exchange and bipolar membrane fuel cells generate electrical energy directly from chemical fuels and have attracted considerable interests as alternate power sources for large market applications, such as transportation (hydrogen fuel cells) and unmanned vehicles (sodium borohydride fuel cells). Anion exchange membrane (AEM), generally composed of a polymer with covalently tethered ionic groups, is the central component of the fuel cell serving as the electrolyte, conducting hydroxide ions from cathode to anode, where fast ionic conduction is directly related to power output. However, AEMs currently used in fuel cells (H2 fuel cells and sodium borohydride fuel cells) exhibit ion …

Contemporary Problems In Aerosol Aggregation And Gelation, Pai Liu

McKelvey School of Engineering Theses & Dissertations

Aggregation of nanoparticles in aerosols is a fundamental phenomenon with important implications to diverse fields ranging from material synthesis to pollutant control. The past few decades have witnessed extensive research on investigating the structure and growth mechanism of aerosol aggregates with sizes spanning across several orders of magnitude. This dissertation focuses on some contemporary problems that remain unaddressed in this topical area. Aerosol aggregates in sub-micron regimes, which are formed via the irreversible collision and aggregation of solid nanoparticle monomers, are fractal-like in their morphology. A mathematical description of this seemingly random structure dates to the seminal works by Forest …

Rhodococcus Opacus Pd630 Genetic Tool Development To Enable The Conversion Of Biomass, Drew Michael Delorenzo

McKelvey School of Engineering Theses & Dissertations

The discovery of fossil fuels facilitated a new era in human history and allowed many firsts, such as the mass production of goods, the ability to travel and communicate long distances, the formation of population dense cities, and unprecedented improvements in quality of life. Alternative sources of energy and chemicals are needed, however, as hydrocarbon reserves continue to deplete and the effects of burning fossils on the planet become better understood. Lignocellulosic biomass is the most abundant raw material in the world and a viable alternative to petroleum-derived products. The pre-treatment of lignocellulose (e.g., thermocatalytic depolymerization, enzymatic hydrolysis, pyrolysis, etc.) …

Development Of High-Speed Photoacoustic Imaging Technology And Its Applications In Biomedical Research, Yun He

McKelvey School of Engineering Theses & Dissertations

Photoacoustic (PA) tomography (PAT) is a novel imaging modality that combines the fine lateral resolution from optical imaging and the deep penetration from ultrasonic imaging, and provides rich optical-absorption–based images. PAT has been widely used in extracting structural and functional information from both ex vivo tissue samples to in vivo animals and humans with different length scales by imaging various endogenous and exogenous contrasts at the ultraviolet to infrared spectrum. For example, hemoglobin in red blood cells is of particular interest in PAT since it is one of the dominant absorbers in tissue at the visible wavelength.The main focus of …

Longitudinal Acoustic Traps: Design, Fabrication, And Evaluation For Biological Applications, Michael Moore Binkley

McKelvey School of Engineering Theses & Dissertations

Acoustofluidics combine ultrasonic actuation with small-volume microfluidic channels to enable precise, contactless object manipulation for a range of applications from serial chemical processing to blood component separation and single-cell analysis. Micron- to millimeter-scale vibrational waves generate reproducible pressure fields within the microfluidic channels and chambers. By exploiting the material property mismatch between a particle (polymeric and silica beads, cells, etc.) and a suspending fluid, the acoustic radiation force is used to move particles toward regions of low (nodes) or high pressure (antinodes). An understanding of these field-particle interactions is applied to design and implement complicated channel architectures for preferential segregation …

Corrosion-Resistant Non-Carbon Electrocatalyst Supports For Proton Exchange Membrane Fuel Cells, Cheng He

McKelvey School of Engineering Theses & Dissertations

Proton exchange membrane fuel cells (PEMFCs) are a promising portable power source due to their low operating temperature, minimal pollutant generation and fast startup. However, several challenges remain concerning lifetime, reliability, and cost. A critical issue is PEMFC component durability. Platinum supported on high surface area carbon has been one of the most widely used electrocatalysts in PEMFCs. However, carbon corrosion over the course of normal PEMFC operation occurs due to the relatively low standard electrode potential for the carbon dioxide/carbon redox couple (0.207V vs. standard hydrogen electrode). Considering this challenge, it is imperative to identify alternative support materials to …

Kernel Methods For Graph-Structured Data Analysis, Zhen Zhang

McKelvey School of Engineering Theses & Dissertations

Structured data modeled as graphs arise in many application domains, such as computer vision, bioinformatics, and sociology. In this dissertation, we focus on three important topics in graph-structured data analysis: graph comparison, graph embeddings, and graph matching, for all of which we propose effective algorithms by making use of kernel functions and the corresponding reproducing kernel Hilbert spaces.For the first topic, we develop effective graph kernels, named as "RetGK," for quantitatively measuring the similarities between graphs. Graph kernels, which are positive definite functions on graphs, are powerful similarity measures, in the sense that they make various kernel-based learning algorithms, for …

The Role Of Multi-Charged Responses: Construction And Application Of A Tandem Differential Mobility Analyzer (Tdma), Christopher Ray Oxford

McKelvey School of Engineering Theses & Dissertations

Atmospheric aerosols impact health outcomes, visibility, and the energy balance of the earth. The atmosphere contains a variety of compounds, and the volatility (phase change enthalpy and vapor pressure) of each compound determines its partitioning between the gas phase and the particle phase. The hygroscopicity (an aerosol’s affinity for water) of an atmospheric aerosol particle is determined by the many compounds present in the particle, and thus, the volatility impacts hygroscopicity. Changes in hygroscopicity alter the fraction of the aerosol deposited in the lungs and the fraction of the aerosol activated into cloud droplets. Thus, understanding the volatility and hygroscopicity …

Dynamics And Control In Spiking Neural Networks, Fuqiang Huang

McKelvey School of Engineering Theses & Dissertations

In the brain, neurons (brain cells) produce electrical impulses, or spikes, that are thought to be the substrate of information processing and computation. Through enigmatic processes, these spikes are ultimately decoded into perceptions and actions. The nature of this encoding and decoding is one of the most pervasive questions in theoretical neuroscience. In other words, what are the specific functions enacted by neural circuits, through their biophysics and dynamics? This thesis examines the dynamics of neural networks from the perspective of control theory and engineering. The pivotal concept is that of the normative synthesis of neural circuits, wherein neural dynamics …

Molecular Dynamics Studies Of Thin-Film Evaporation: The Effect Of Graphene-Coated Silicon On Water Evaporation Behavior, Rui Zhou

McKelvey School of Engineering Theses & Dissertations

Conventional single-phase air or liquid cooling methods are insufficient to dissipate the high heat flux of next-generation electronic systems. Thin-film evaporation is one of the most promising solutions, because it takes advantage of the large amount of latent heat in the phase change process. It is important to understand the relationship between interfacial thermal resistance, surface wettability, and thin-film evaporation behavior. In this study, non-equilibrium molecular dynamics simulations are used to study mass and heat transfer in thin-film evaporation of water on a silicon substrate, and equilibrium molecular dynamics simulations are used to study the surface wettability by measuring contact …

Expanding The Palette: Synthesizing Microencapsulated Organic Phase Change Materials In Metallic Matrices For Transient Thermal Applications, Melissa Kate Mccann

McKelvey School of Engineering Theses & Dissertations

As the demand for smaller and faster electronics increases, it becomes increasingly challenging to effectively manage the generated heat without hindering device performance in applications whose thermal profiles are dominated by pulsed thermal loads. Heat propagation in a system can be characterized by steady or transient state heat transfer. In steady state, the temperature at any particular point remains constant after thermal equilibrium is reached. In a transient state, the temperature within a system varies over time. The changing parameters and time dependency associated with a transient regime make heat transfer calculations far more complex than in a steady state. …

Ph-Sensitive Oxygen Release Microspheres To Enhance Cell Survival In Ischemic Condition, Zhongting Liu

McKelvey School of Engineering Theses & Dissertations

Ischemic diseases such as myocardial infarction, stroke and limb ischemia are severe cardiovascular diseases with high rate of death and millions of people suffered from these diseases. Under ischemic environment, cells die due to deficient supply of nutrient and oxygen. To regenerate ischemic tissues, stem cell therapy is a promising approach because stem cells can differentiate into cells necessary for the regeneration. However, stem cell therapy has limitations. For example, few cells can survive under harsh ischemic environment. To enhance stem cells survival, implantation of oxygen release microspheres to sustained supply cells with oxygen represents an effective strategy. Previously, our …

Enhanced Heat Transfer Performance By Shape Optimization Of A Non-Axisymmetric Droplet Evaporating On A Heated Micropillar, Haotian Wu

McKelvey School of Engineering Theses & Dissertations

Abstract

Enhanced Heat Transfer Performance by Shape Optimization of a Non-axisymmetric Droplet Evaporating on a Heated Micropillar

By

Haotian Wu

Department of Mechanical Engineering and Materials Science

Washington University in St. Louis, 2019

Research Advisor: Professor Damena Agonafer

The stacked multilayer 3D IC structure used in next generation high-powered electronics poses great challenges in dissipating their large heat flux, which causes extreme difficulties for traditional cooling technologies. In response, more advanced two-phase liquid cooling technologies, such as droplet evaporation, which utilizes the latent heat of vaporization to remove excessive heat, have been widely investigated. Compared to traditional single-phase cooling techniques, …

Modeling The Effects Of Distribution System Topology On Water Quality, Chun-Ying Chao

McKelvey School of Engineering Theses & Dissertations

Inadequate treatment of drinking water causes the formation of disinfection by-products and the regrowth of harmful microbial species. Various studies have addressed the problem of water quality monitoring, but very few have employed topological analysis, a valuable mathematical tool widely applied in biological, business, and social research. This thesis examines the relationship between the topological properties of water distribution systems and water-quality models. In particular, the research proposes a novel framework for mapping network topological attributes to water-quality models. This research adopts topological metrics to assess the accuracy of the predictions of chlorine concentrations in dead ends. It examines four …

Systemic Risk In Financial Networks, Tathagata Banerjee

McKelvey School of Engineering Theses & Dissertations

In this dissertation, I have used the network model based approach to study systemic risk in financial networks. In particular, I have worked on generalized extensions of the Eisenberg--Noe [2001] framework to account for realistic financial situations viz. pricing of corporate debt while accounting for network effects, asset liquidation mechanisms during fire sales, dynamic clearing and impact of contingent payments such as insurance and credit default swaps. First, I present formulas for the valuation of debt and equity of firms in a financial network under comonotonic endowments. I demonstrate that the comonotonic setting provides a lower bound to the price …

Understanding Excitation Energy Quenching In Isia, Hui-Yuan Steven Chen

McKelvey School of Engineering Theses & Dissertations

Cyanobacteria are photoautotrophic organisms that contribute a significant amount of global primary productivity. They are found in freshwater, marine and even some extremely severe environments. Among those environments, iron deficiency is one of the most common stress conditions in cyanobacterial habitats. To survive, cyanobacteria have evolved and developed several strategies to alleviate the damage caused by iron deficiency.

Iron stress-inducible protein (IsiA) is a chlorophyll-binding membrane protein found in cyanobacteria grown in iron-deficient conditions. During the past decades, considerable effort has been put on understanding how IsiA functions to help cyanobacteria survive iron deficiency. It has been reported that IsiA …

Metabolic Engineering Of Cyanobacteria For Production Of Chemicals, Po-Cheng Lin

McKelvey School of Engineering Theses & Dissertations

Concerns over the impact of climate change caused by CO2 emission have driven the research and development of renewable energies. Microbial production of chemicals is being viewed as a feasible approach to reduce the use of fossil fuels and minimize the impact of climate change. With recent advances in synthetic biology, microorganisms can be engineered to synthesize petroleum-based chemicals and plant-derived compounds. Cyanobacteria are photosynthetic prokaryotes that use only sunlight, CO2, and trace minerals for growth. Compared to other microbial hosts, cyanobacteria are attractive platforms for sustainable bioproduction, because they can directly convert CO2 into products. However, the major challenge …

Role Of Submicrometer Particles In Advanced Technologies Of Carbon Capture, Zhichao Li

McKelvey School of Engineering Theses & Dissertations

Oxy-combustion and post-combustion carbon capture technologies are two of the most promising strategies for carbon capture and storage (CCS), which is a commonly accepted approach to address the challenge of climate change. Pressurized oxy-combustion has been actively studied due to its great potential to enhance the power plant energy efficiency by recovering latent heat from water vapor condensation without incurring additional gas compression cost. On the other hand, amine-based CO2 scrubbers have been demonstrated to have high removal efficiency of CO2 with the possibility to recycle amine solutions, which makes the technology a promising candidate for post-combustion carbon capture. Nonetheless, …

Multi-Dimensional Extension Of The Alternating Minimization Algorithm In X-Ray Computed Tomography, Jingwei Lu

McKelvey School of Engineering Theses & Dissertations

X-ray computed tomography (CT) is an important and effective tool in medical and industrial

imaging applications. The state-of-the-art methods to reconstruct CT images have had

great development but also face challenges. This dissertation derives novel algorithms to

reduce bias and metal artifacts in a wide variety of imaging modalities and increase performance

in low-dose scenarios.

The most widely available CT systems still use the single-energy CT (SECT), which is

good at showing the anatomic structure of the patient body. However, in SECT image

reconstruction, energy-related information is lost. In applications like radiation treatment

planning and dose prediction, accurate energy-related information …

On The Fabrication And Development Of Tissue On A Chip Devices With Included Perfused Vasculatures, Usama Ismail

McKelvey School of Engineering Theses & Dissertations

The advent of Tissue-on-a-Chip (TiOC) devices has provided a novel way for researchers to approach biological study and drug development. As a platform that enables human in vivo conditions to be accurately replicated ex vivo, TiOC can accelerate both fundamental biological research to answer basic questions regarding tissue behavior and function (e.g., cell-cell interactions in the tumor microenvironment (TME)) and translational research that includes testing of standard and novel therapeutics. The reported work focuses on development of processes and technologies common to two classes of TiOC. The first device is a single-layer, multi-compartment microfluidic device for investigation of pancreatic …

Decoupling Information And Connectivity Via Information-Centric Transport, Hila Ben Abraham

McKelvey School of Engineering Theses & Dissertations

The power of Information-Centric Networking architectures (ICNs) lies in their abstraction for communication --- the request for named data. This abstraction was popularized by the HyperText Transfer Protocol (HTTP) as an application-layer abstraction, and was extended by ICNs to also serve as their network-layer abstraction. In recent years, network mechanisms for ICNs, such as scalable name-based forwarding, named-data routing and in-network caching, have been widely explored and researched. However, to the best of our knowledge, the impact of this network abstraction on ICN applications has not been explored or well understood. The motivation of this dissertation is to address this …

Development And Application Of New Methods For Magnetic Resonance Elastography Of The Brain, Charlotte Anne Guertler

McKelvey School of Engineering Theses & Dissertations

Accurate mechanical properties of the intact, living brain are essential for modeling traumatic brain injury (TBI). However, the properties of brain tissue in vivo have traditionally been measured in ex vivo samples. Magnetic resonance elastography (MRE) can be used to measure motion and estimate material properties of soft tissues in vivo, but MRE typically assumes tissue isotropy and homogeneity. The objective of this thesis is to improve MRE of soft tissue, like the brain, by developing and evaluating methods for in vivo estimation of heterogeneous, anisotropic properties. This was achieved through pursuit of the following aims: (1) quantifying the differences …

Polarization Division Multiplexing For Optical Data Communications, Darko Ivanovich

McKelvey School of Engineering Theses & Dissertations

Multiple parallel channels are ubiquitous in optical communications, with spatial division multiplexing (separate physical paths) and wavelength division multiplexing (separate optical wavelengths) being the most common forms. In this research work, we investigate the viability of polarization division multiplexing, the separation of distinct parallel optical communication channels through the polarization properties of light. We investigate polarization division multiplexing based optical communication systems in five distinct parts. In the first part of the work, we define a simulation model of two or more linearly polarized optical signals (at different polarization angles) that are transmitted through a common medium (e.g., air), filtered …

Role Of Submicrometer Particles In Advanced Technologies Of Carbon Capture, Zhichao Li

McKelvey School of Engineering Theses & Dissertations

Oxy-combustion and post-combustion carbon capture technologies are two of the most promising strategies for carbon capture and storage (CCS), which is a commonly accepted approach to address the challenge of climate change. Pressurized oxy-combustion has been actively studied due to its great potential to enhance the power plant energy efficiency by recovering latent heat from water vapor condensation without incurring additional gas compression cost. On the other hand, amine-based CO2 scrubbers have been demonstrated to have high removal efficiency of CO2 with the possibility to recycle amine solutions, which makes the technology a promising candidate for post-combustion carbon capture. Nonetheless, …

Metabolic Engineering Of Cyanobacteria For Production Of Chemicals, Po-Cheng Lin

McKelvey School of Engineering Theses & Dissertations

Concerns over the impact of climate change caused by CO2 emission have driven the research and development of renewable energies. Microbial production of chemicals is being viewed as a feasible approach to reduce the use of fossil fuels and minimize the impact of climate change. With recent advances in synthetic biology, microorganisms can be engineered to synthesize petroleum-based chemicals and plant-derived compounds. Cyanobacteria are photosynthetic prokaryotes that use only sunlight, CO2, and trace minerals for growth. Compared to other microbial hosts, cyanobacteria are attractive platforms for sustainable bioproduction, because they can directly convert CO2 into products. However, the major challenge …

Mechanosensitive Epithelial Cell Scattering And Migration On Layered Matrices, Christopher Michael Walter

McKelvey School of Engineering Theses & Dissertations

Epithelial cells form multi-layered tissue scaffolding that makes up every organ in the body. Along with epithelial cells, the basement membrane (BM) and connective tissue are composed of various proteins that sculpt the organs and protect them from foreign macromolecules. Epithelial cells respond to various cues, both chemical and mechanical, from their surrounding matrices to aid in maintenance and repair of these layers through degradation and deposition of extracellular matrix (ECM) proteins. In cancer progression, epithelial cells lose their normal function of supporting tissue structure and instead adopt more aggressive behaviors through an epithelial-to-mesenchymal transition (EMT) of their cellular traits. …

A Modular Approach For Modeling, Detecting, And Tracking Freezing Of Gait In Parkinson Disease Using Inertial Sensors, Prateek Gundannavar Vijay

McKelvey School of Engineering Theses & Dissertations

Parkinson disease, the second most common neurodegenerative disorder, is caused by the loss of dopaminergic subcortical neurons. Approximately 50% of people with Parkinson disease experience freezing of gait (FOG), a brief, episodic absence or marked reduction of forward progression of the feet despite the intention to walk. FOG causes falls and is resistant to medication in more than 50% of cases. FOG episodes can often be interrupted by mechanical interventions (e.g., a verbal reminder to march), but it is often not practical to apply these interventions on demand (e.g., there is not usually another person to detect an FOG episode …

Joint Reconstruction For Single-Shot Edge Illumination Phase-Contrast Tomography (Eixpct), Yujia Chen

McKelvey School of Engineering Theses & Dissertations

Edge illumination X-ray phase-contrast tomography (EIXPCT) is an emerging X-ray phasecontrast tomography technique for estimating the complex-valued X-ray refractive index distribution of an object with laboratory-based X-ray sources. Conventional image reconstruction approaches for EIXPCT require multiple images to be acquired at each tomographic view angle. This contributes to prolonged data-acquisition times and elevated radiation doses, which can hinder in vivo applications. In this dissertation, a new “single-shot” method without restrictive assumptions related to the object, imaging geometry or hardware is proposed for joint reconstruction (JR) of the real and imaginary-valued components of the refractive index distribution from a tomographic data …