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Theses/Dissertations

Publicly Accessible Penn Dissertations

2011

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Full-Text Articles in Engineering

Computer-Aided, Multi-Modal, And Compression Diffuse Optical Studies Of Breast Tissue, David R. Busch Jr Dec 2011

Computer-Aided, Multi-Modal, And Compression Diffuse Optical Studies Of Breast Tissue, David R. Busch Jr

Publicly Accessible Penn Dissertations

Diffuse Optical Tomography and Spectroscopy permit measurement of important physiological parameters non-invasively through ~10 cm of tissue. I have applied these techniques in measurements of human breast and breast cancer. My thesis integrates three loosely connected themes in this context: multi-modal breast cancer imaging, automated data analysis of breast cancer images, and microvascular hemodynamics of breast under compression. As per the first theme, I describe construction, testing, and the initial clinical usage of two generations of imaging systems for simultaneous diffuse optical and magnetic resonance imaging. The second project develops a statistical analysis of optical breast data from many spatial ...


Economics Of Spectrum Allocation In Cognitive Radio Networks, Gaurav S. Kasbekar Dec 2011

Economics Of Spectrum Allocation In Cognitive Radio Networks, Gaurav S. Kasbekar

Publicly Accessible Penn Dissertations

Cognitive radio networks (CRNs) are emerging as a promising technology for the efficient use of radio spectrum. In these networks, there are two levels of networks on each channel, primary and secondary, and secondary users can use the channel whenever the primary is not using it. Spectrum allocation in CRNs poses several challenges not present in traditional wireless networks; the goal of this dissertation is to address some of the economic aspects thereof. Broadly, spectrum allocation in CRNs can be done in two ways- (i) one-step allocation in which the spectrum regulator simultaneously allocates spectrum to primary and secondary users ...


Plasmon Enhanced Photoconduction In Porphyrin-Gold Nanoparticle Assemblies, David Conklin Dec 2011

Plasmon Enhanced Photoconduction In Porphyrin-Gold Nanoparticle Assemblies, David Conklin

Publicly Accessible Penn Dissertations

This thesis describes a series of experiments to both determine the origins of charge transport and enhanced photoconduction in metal nanoparticle arrays linked with zinc-porphyrin complexes, but to also determine the nucleation and growth mechanisms related to Ferroelectric Nanolithography (FNL) as a platform for hybrid devices. The development of test structures on glass substrates was undertaken to not only allow the study of the mechanisms controlling charge transport but the photoconduction of zinc-porphyrin linked gold nanoparticle (AuNP) arrays. In this study, the dominate charge transport mechanism was determined to be thermally assisted tunneling and the origins of enhanced photoconduction in ...


Mind Economy: Dynamic Graph Analysis Of Communications, Alexy Khrabrov Dec 2011

Mind Economy: Dynamic Graph Analysis Of Communications, Alexy Khrabrov

Publicly Accessible Penn Dissertations

Social networks are growing in reach and impact but little is known about their structure, dynamics, or users’ behaviors. New techniques and approaches are needed to study and understand why these networks attract users’ persistent attention, and how the networks evolve. This thesis investigates questions that arise when modeling human behavior in social networks, and its main contributions are:

• an infrastructure and methodology for understanding communication on graphs;

• identification and exploration of sub-communities;

• metrics for identifying effective communicators in dynamic graphs;

• a new definition of dynamic, reciprocal social capital and its iterative computation

• a methodology to study influence in social ...


Dynamic Vertical Climbing: Bioinspiration, Design, And Analysis, Goran Lynch Dec 2011

Dynamic Vertical Climbing: Bioinspiration, Design, And Analysis, Goran Lynch

Publicly Accessible Penn Dissertations

Biologists have proposed a pendulous climbing model, the Full-Goldman (F-G) template, that abstracts remarkable similarities in dynamic wall scaling behavior exhibited by radically different animal species. This thesis presents a progression of work related to dynamic vertical climbing based on that model.

We begin by describing the inspiration, design, implementation of and experimentation with the first dynamical vertical climbing robot. We study numerically a version of the pendulous climbing template dynamically re-scaled for applicability to utilitarian payloads with conventional electronics and actuation, revealing that the incorporation of passive compliance can compensate for an artifact’s poorer power density and scale ...


Optimization And Translation Of Msc-Based Hyaluronic Acid Hydrogels For Cartilage Repair, Isaac E. Erickson Dec 2011

Optimization And Translation Of Msc-Based Hyaluronic Acid Hydrogels For Cartilage Repair, Isaac E. Erickson

Publicly Accessible Penn Dissertations

Traumatic injury and disease disrupt the ability of cartilage to carry joint stresses and, without an innate regenerative response, often lead to degenerative changes towards the premature development of osteoarthritis. Surgical interventions have yet to restore long-term mechanical function. Towards this end, tissue engineering has been explored for the de novo formation of engineered cartilage as a biologic approach to cartilage repair. Research utilizing autologous chondrocytes has been promising, but clinical limitations in their yield have motivated research into the potential of mesenchymal stem cells (MSCs) as an alternative cell source. MSCs are multipotent cells that can differentiate towards a ...


Enhancing Meniscus Repair Through Biomaterial Design, Lara Ionescu Silverman Dec 2011

Enhancing Meniscus Repair Through Biomaterial Design, Lara Ionescu Silverman

Publicly Accessible Penn Dissertations

The knee meniscus is prone to damage, which leads to pain and inhibits mobility in the joint long term. Due to the minimal vascularity, low cellularity and large mechanical forces imparted on the meniscus with normal use, endogenous repair is limited. Resection of the damaged region of the tissue (meniscectomy) remains the most common treatment for a torn meniscus, but this procedure results in cartilage degradation and other adverse changes in the knee joint. Given the prevalence of meniscus damage, there is thus a pressing need for novel approaches to meniscus repair. To address this issue, this thesis developed in ...


The Nanoaquarium: A Nanofluidic Platform For In Situ Transmission Electron Microscopy In Liquid Media, Joseph M. Grogan Dec 2011

The Nanoaquarium: A Nanofluidic Platform For In Situ Transmission Electron Microscopy In Liquid Media, Joseph M. Grogan

Publicly Accessible Penn Dissertations

There are many scientifically interesting and technologically relevant nanoscale phenomena that take place in liquid media. Examples include aggregation and assembly of nanoparticles; colloidal crystal formation; liquid phase growth of structures such as nanowires; electrochemical deposition and etching for fabrication processes and battery applications; interfacial phenomena; boiling and cavitation; and biological interactions. Understanding of these fields would benefit greatly from real-time, in situ transmission electron microscope (TEM) imaging with nanoscale resolution. Most liquids cannot be imaged by traditional TEM due to evaporation in the high vacuum environment and the requirement that samples be very thin. Liquid-cell in situ TEM has ...


Cerebral Hemodynamics In High-Risk Neonates Probed By Diffuse Optical Spectroscopies, Erin M. Buckley Aug 2011

Cerebral Hemodynamics In High-Risk Neonates Probed By Diffuse Optical Spectroscopies, Erin M. Buckley

Publicly Accessible Penn Dissertations

Advances in medical and surgical care of the critically ill neonates have decreased
mortality, yet a significant number of these neonates suffer from neurodevelopmental
delays and failure in school. Thus, clinicians are now focusing on prevention of
neurologic injury and improvement of neurocognitive outcome in these high-risk infants. Assessment of cerebral oxygenation, cerebral blood volume, and the regulation of cerebral blood flow (CBF) during the neonatal period is vital for evaluating brain health. Traditional CBF imaging methods fail, however, for both ethical and logistical reasons. In this dissertation, I demonstrate the use of non-invasive optical modalities, i.e., diffuse optical ...


Energy Transport And Conversion In Semiconductor Nanocrystal Solids, Dong Kyun Ko Aug 2011

Energy Transport And Conversion In Semiconductor Nanocrystal Solids, Dong Kyun Ko

Publicly Accessible Penn Dissertations

Solids constructed with single and multicomponent nanocrystal represent an exciting new form of condensed matter, as they can potentially capture not only the quantum features of the individual building blocks but also novel collective properties that arise from coupling of nanocrystal components. In this thesis, measurement and interpretation of temperature-dependent thermopower in semiconductor nanocrystal solids are used to elucidate the Fermi energy level and the density of state distribution. The physical understating of temperature dependence of thermopower is, in turn, utilized to develop a powerful tool with which to monitor doping in PbTe nanocrystal solids with different concentrations of Ag ...


High Throughput Screening For The Enhancement Of Adeno-Associated Virus Type 2 Transduction, Alexis J. Wallen Aug 2011

High Throughput Screening For The Enhancement Of Adeno-Associated Virus Type 2 Transduction, Alexis J. Wallen

Publicly Accessible Penn Dissertations

Adeno-associated virus (AAV) is a promising vector for human gene therapy. Although more effective than non-viral vectors, AAV still requires improvement in efficacy in order to become a successful gene therapy vector. With this in mind, we have sought to identify and examine identified enhancers of adeno-associated virus type 2 (AAV2) transduction. Using a high throughput screening system with recombinant AAV2 carrying the luciferase reporter gene (AAV2-Luc), we found siRNA sequences and chemical compounds which increase AAV2 reporter gene expression. We specifically identified a hexamer seed region 5’-UGUUUC-3’ which facilitated AAV2 transduction. Chemical compound enhancers included ellagic acid, 1 ...


Size-Dependent Metal-Insulator Transition In Pt-Dispersed Sio2 Thin Film: A Candidate For Future Non-Volatile Memory, Albert B. Chen Aug 2011

Size-Dependent Metal-Insulator Transition In Pt-Dispersed Sio2 Thin Film: A Candidate For Future Non-Volatile Memory, Albert B. Chen

Publicly Accessible Penn Dissertations

Non-volatile random access memories (NVRAM) are promising data storage and processing devices. Various NVRAM, such as FeRAM and MRAM, have been studied in the past. But resistance switching random access memory (RRAM) has demonstrated the most potential for replacing flash memory in use today. In this dissertation, a novel RRAM material design that relies upon an electronic transition, rather than a phase change (as in chalcogenide Ovonic RRAM) or a structural change (such in oxide and halide filamentary RRAM), is investigated. Since the design is not limited to a single material but applicable to general combinations of metals and insulators ...


Structure And Properties Of Bi-Containing Mixed A-Site Perovskites, David M. Stein Aug 2011

Structure And Properties Of Bi-Containing Mixed A-Site Perovskites, David M. Stein

Publicly Accessible Penn Dissertations

This thesis describes a series of studies undertaken to explore the criteria for the stabilization of Bi3+ in a perovskite through the formation of mixed A-site solid solutions. Electronically similar to Pb2+ but with a smaller ionic radius, Bi3+ has the potential to replace and improve upon Pb-based counterparts for dielectric and piezoelectric applications.

Building off the discovery that Bi(Zn1/2Ti1/2)O3 increases the tetragonality of PbTiO3, the first part of this work identified a new substituent, Bi(Zn3/4W1/4)O6, that is also able ...


Communication For Teams Of Networked Robots, Jonathan Fink Aug 2011

Communication For Teams Of Networked Robots, Jonathan Fink

Publicly Accessible Penn Dissertations

There are a large class of problems, from search and rescue to environmental monitoring, that can benefit from teams of mobile robots in environments where there is no existing infrastructure for inter-agent communication. We seek to address the problems necessary for a team of small, low-power, low-cost robots to deploy in such a way that they can dynamically provide their own multi-hop communication network. To do so, we formulate a situational awareness problem statement that specifies both the physical task and end-to-end communication rates that must be maintained. In pursuit of a solution to this problem, we address topics ranging ...


Understanding Molecular Chemistry Of Nanocrystals And Nanostructures: Precursor, Ligand, And Surface Chemistry, Weon-Kyu Koh Aug 2011

Understanding Molecular Chemistry Of Nanocrystals And Nanostructures: Precursor, Ligand, And Surface Chemistry, Weon-Kyu Koh

Publicly Accessible Penn Dissertations

The aim of this dissertation is to understand the molecular chemistry of nanomaterials and to correlate their structures to their functions. The first part of this dissertation explores how we can use precursor chemistry to develop a synthetic approach to novel structures of nanomaterials. There will be a demonstration of morphology control in lead chalcogenide nanocrystals following an investigation of the precursor chemistry which gives valuable information on precursor decomposition during the crystal growth. At the same time, there will be a discussion about how we can understand structure-dependent properties of nanomaterials using advanced spectroscopic techniques. Well-established synthetic approaches discussed ...


Dynamics In Polymer Nanocomposites, Sangah Gam Aug 2011

Dynamics In Polymer Nanocomposites, Sangah Gam

Publicly Accessible Penn Dissertations

Polymer diffusion and matrix morphology are investigated in polymer nanocomposites (PNCs). Using elastic recoil detection, tracer diffusion coefficients (D) of dPS and dPMMA are measured in PNCs containing polystyrene (PS) with phenyl-capped (Ph) silica, and poly(methyl methacrylate) (PMMA) with hydroxyl-terminated (OH) silica nanoparticles (NPs), respectively. As NP volume fraction increases or NP size decreases, polymer diffusion slows down. Moreover, D plotted relative to diffusion in a pure PS matrix (i.e., D/D0) falls on a master curve when plotted against the interparticle distance of NPs relative to the tracer radius of gyration, ID/2Rg. This ...


Microfluidic Pumping With Surface Tension Force And Magnetohydrodynamic Drive, Mian Qin Aug 2011

Microfluidic Pumping With Surface Tension Force And Magnetohydrodynamic Drive, Mian Qin

Publicly Accessible Penn Dissertations

Micropumping is difficult to design and control as compared to their macro-scale counterparts due to the size limitation.

The first part of this dissertation focuses on micropumping with surface tension forces. A simple, single-action, capillary pump/valve consisting of a bi-phase slug confined in a non-uniform conduit is described. At low temperatures, the slug is solid and seals the conduit. Once heated above its melting temperature, the liquid slug moves spontaneously along a predetermined path due to surface tension forces imbalance. This technique can be easily combined with other propulsion mechanisms such as pressure and magnetohydrodynamics (MHD).

The second part ...


Miniaturization Methods For Modular Robotics: External Actuation And Dielectric Elastomer Actuation, Paul J. White Aug 2011

Miniaturization Methods For Modular Robotics: External Actuation And Dielectric Elastomer Actuation, Paul J. White

Publicly Accessible Penn Dissertations

A conventional robot with fixed form cannot change its morphology to respond to changes in its environment or suit a specific task. In contrast, a self-reconfigurable modular robot can rearrange its modules to adapt to a task or its environment. Module miniaturization would enable applications requiring fine resolution such as dexterous manipulation and accurate three-dimensional physical representation. As the module's actuators limit its minimum size, we present two novel methods for enabling module miniaturization: external actuation and dielectric elastomer actuation.

With external actuation, modules reconfigure using forces provided by a controlled environment rather than internal actuators. The environment imposes ...


An An Vitro And In Silico Investigation Of The Role Of Nmda Receptor Subtypes Following Mechanical Injury, Pallab Singh Aug 2011

An An Vitro And In Silico Investigation Of The Role Of Nmda Receptor Subtypes Following Mechanical Injury, Pallab Singh

Publicly Accessible Penn Dissertations

The N-methyl D-aspartate receptor (NMDAR), a common glutamate receptor found throughout the brain, has long been implicated as the major mediator of the pathology seen after traumatic brain injury (TBI). However, given their critical role in physiologic function of neural networks, complete inhibition of these receptors is an unsuitable therapeutic strategy. Thus, further investigation into how these receptors respond to injury is required to identify more directed therapeutic targets. Here, we aimed to use two unique experimental models to further investigate the role of NMDARs in the neuronal response to TBI, with specific emphasis on the contribution of different NMDAR ...


Multiscale Modeling Of The Erbb Receptor Tyrosine Kinase Signaling Network Through Theory And Experiment, Shannon E. Telesco Aug 2011

Multiscale Modeling Of The Erbb Receptor Tyrosine Kinase Signaling Network Through Theory And Experiment, Shannon E. Telesco

Publicly Accessible Penn Dissertations

The biochemical processes occurring within a living cell span a spectrum of scales in space and time, ranging from the nano- to the macro-scale. We note that a single cellular process often operates on multiple spatial and temporal scales, and thus it becomes necessary to combine modeling techniques in multiscale approaches, in which different levels of theory are synergized to describe a system at a number of scales or resolutions. In this work we apply a multiscale modeling framework to investigate the molecular regulatory mechanisms governing the activation of the ErbB receptor tyrosine kinases, a family of kinases which are ...


Chemical And Biological Strategies For Improving The Sensitivity Of Spio-Enhanced Mr Imaging, Andrew Elias Aug 2011

Chemical And Biological Strategies For Improving The Sensitivity Of Spio-Enhanced Mr Imaging, Andrew Elias

Publicly Accessible Penn Dissertations

The prevalence of cancer has seen significant growth over the last three decades, with the American Cancer Society now reporting that one in every three Americans will be afflicted with some form of cancer in their lifetime. The debilitating effects of cancer permeate beyond obvious biological ramifications, often adversely affecting patients on emotional and financial levels as well. While significant progress has been made in diagnosing and treating cancer, advancements are still needed in detecting and treating cancers at earlier stages, where clinical outcomes will be more favorable. The field of cellular and molecular imaging has emerged as a cutting-edge ...


Entropic Elasticity Of Polymers And Their Networks, Tianxiang Su Aug 2011

Entropic Elasticity Of Polymers And Their Networks, Tianxiang Su

Publicly Accessible Penn Dissertations

The elastic energy for many biopolymer systems is comparable to the thermal energy at room temperature. Therefore, biopolymers and their networks are constantly under thermal fluctuations. From the point of view of thermodynamics, this suggests that entropy plays a crucial role in determining the mechanical behaviors of these filamentous biopolymers. One of the main goals of this thesis is to understand how thermal fluctuations affect the mechanical properties and behaviors of filamentous networks, and also how stress affects the thermal fluctuations.

Filaments and filamentous networks are viewed as mechanical structures, whose static equilibrium states under the action of loads or ...


Coordination Of Multirobot Teams And Groups In Constrained Environments: Models, Abstractions, And Control Policies, Nora Ayanian Aug 2011

Coordination Of Multirobot Teams And Groups In Constrained Environments: Models, Abstractions, And Control Policies, Nora Ayanian

Publicly Accessible Penn Dissertations

Robots can augment and even replace humans in dangerous environments, such as search and rescue and reconnaissance missions, yet robots used in these situations are largely tele-operated. In most cases, the robots' performance depends on the operator's ability to control and coordinate the robots, resulting in increased response time and poor situational awareness, and hindering multirobot cooperation.

Many factors impede extended autonomy in these situations, including the unique nature of individual tasks, the number of robots needed, the complexity of coordinating heterogeneous robot teams, and the need to operate safely. These factors can be partly addressed by having many ...


Quantitative Mapping Of Lung Ventilation Using Hyperpolarized Gas Magnetic Resonance Imaging, Kiarash Emami May 2011

Quantitative Mapping Of Lung Ventilation Using Hyperpolarized Gas Magnetic Resonance Imaging, Kiarash Emami

Publicly Accessible Penn Dissertations

The main objective of this project was to develop and implement techniques for high-resolution quantitative imaging of ventilation in lungs using hyperpolarized gas magnetic resonance imaging (MRI). Pulmonary ventilation is an important aspect of lung function and is frequently compromised through several different mechanisms and at varying degrees in presence of certain lung conditions, such as chronic obstructive pulmonary diseases. The primary focus of this development is on large mammalian species as a steppingstone towards translation to human subjects. The key deliverables of this project are a device for real-time mixing and delivery of hyperpolarized gases such as 3He ...


Modeling Memes: A Memetic View Of Affordance Learning, Benjamin D. Nye May 2011

Modeling Memes: A Memetic View Of Affordance Learning, Benjamin D. Nye

Publicly Accessible Penn Dissertations

This research employed systems social science inquiry to build a synthesis model that would be useful for modeling meme evolution. First, a formal definition of memes was proposed that balanced both ontological adequacy and empirical observability. Based on this definition, a systems model for meme evolution was synthesized from Shannon Information Theory and elements of Bandura's Social Cognitive Learning Theory. Research in perception, social psychology, learning, and communication were incorporated to explain the cognitive and environmental processes guiding meme evolution. By extending the PMFServ cognitive architecture, socio-cognitive agents were created who could simulate social learning of Gibson affordances. The ...


Design And Fabrication Of Photonic Microstructures By Holographic Lithography And Pattern Transformation, Xuelian Zhu May 2011

Design And Fabrication Of Photonic Microstructures By Holographic Lithography And Pattern Transformation, Xuelian Zhu

Publicly Accessible Penn Dissertations

The creation of periodic structures in nano- or micro-scale is an exciting challenge of materials science. Meanwhile, the structures with alternating periodic dielectric constants, known as photonic crystals, are great potentials for many applications in optical integrated circuits. In this dissertation, we design and fabricate periodic two- (2D) and three-dimensional (3D) photonic microstructures with desired symmetry, scalable size or novel functionality (e.g. anisotropic feature) using holographic lithography (HL) technique and via harnessing mechanical instability in different polymer systems. In fabrication of 3D diamond-like photonic structure via four-beam single-exposure HL, we quantitatively analyze the lattice distortion due to refraction effect ...


On The Economic Viability Of Network Systems And Architectures, Soumya Sen May 2011

On The Economic Viability Of Network Systems And Architectures, Soumya Sen

Publicly Accessible Penn Dissertations

Understanding the relationship between technology and economics is fundamental to making judicious policy and design decisions. Many technologies that are successful in meeting their technical goals often fail to get adopted due to economic factors. This holds true even for networked systems, e.g., the Internet, which witnessed failures in the adoption of QoS solutions, IPv6 migration etc., due to factors such as high costs, lack of demand, and weight of incumbency. To gain better insights into these issues, researchers need access to analytical frameworks that account for both technological and economic factors and provide useful design guidelines. This dissertation ...


Systems Biology Of Blood Coagulation And Platelet Activation, Manash S. Chatterjee May 2011

Systems Biology Of Blood Coagulation And Platelet Activation, Manash S. Chatterjee

Publicly Accessible Penn Dissertations

Blood clotting is a highly conserved physiological response that prevents excessive blood loss following vessel injury. It involves a sequence of plasma reactions leading to the formation of thromin (the coagulation cascade) as well as tightly controlled intracellular reactions mediating platelet activation. These two events are inextricably coupled, with the active platelet surface serving as a cofactor for coagulation factor assembly and thrombin serving as a potent platelet agonist. Using the technologies of automated liquid handling, high throughput experimental systems were developed that allowed individual exploration of these two components of the thrombotic response under diverse initial conditions. Based on ...


A Study Of Red./Ox. Thermodynamic And Catalytic Properties Of Metal Oxide Materials, Ivan S. Baldychev May 2011

A Study Of Red./Ox. Thermodynamic And Catalytic Properties Of Metal Oxide Materials, Ivan S. Baldychev

Publicly Accessible Penn Dissertations

Redox thermodynamic properties and catalytic activities of metal oxides were studied to gain insight into the fundamental relationships between those properties. Catalysts based on iron oxides, vanadium oxides, and molybdenum oxides were studied because of their industrial importance to the water-gas-shift and partial-oxidation reactions.

Redox properties of 5wt% and 15wt% V2O5/Al2O3 catalysts calcined at 753 K and 973 K were measured using coulometric titration at 748 K. 5wt% V2O5/Al2O3 was found to be thermally stable and its reduction from V+5 to V+4 occurred at P(O2) values between 10-4 and 10-19 atm and from V+4 ...


Indirect Detection Of Axonal Architecture With Q-Space Imaging, Henry H. Ong May 2011

Indirect Detection Of Axonal Architecture With Q-Space Imaging, Henry H. Ong

Publicly Accessible Penn Dissertations

Evaluating axon morphology would provide insights into connectivity, maturation, and disease pathology. Conventional diffusion MRI can provide metrics that are related to axon morphology, but cannot measure specific parameters such as mean axon diameter (MAD) and intracellular fraction (ICF). Q-space imaging (QSI) is an advanced diffusion MRI technique that may be able to provide more information on axon morphology. However, QSI has several limitations that affect its implementation and accuracy.

The main objective of this dissertation was to address these limitations and to evaluate the potential of QSI to accurately assess axon morphology. First, a custom-built high-amplitude gradient coil was ...