2017 UMKC Dissertations - Freely Available Online
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Item Design of Instrumentation and Methodologies for Determination of Free Neutron Characteristics(University of Missouri -- Kansas City, 2017) Hoshor, Cory Blake; Caruso, Anthony N.Measuring neutron source‐dependent free neutron properties over a large neutron energy range, with human‐portable instrumentation, continues to push the frontier of neutron detection instrumentation design and analysis techniques. In addition, a variety of nuclear nonproliferation and health physics applications require instrumentation that can provide free neutron property measurement and analysis in real time. To overcome the challenges inherent to these applications and advance the state of the current art in neutron detection instrumentation, the first representatives of a new class of solid-state moderating-type neutron spectrometer have been designed, modeled, fabricated, and tested. This work introduces state-of-the-art human-portable instruments by discussing the fundamental theory of their operation, investigating and analyzing—via Monte Carlo simulation—the principle considerations for optimal instrument design, and empirically evaluating the capability of each of the fabricated spectrometers to meet the application needs. Utilizing the unique three dimensional neutron thermalization information afforded by this new class of instrumentation, novel algorithmic methodologies are introduced to determine free neutron characteristics of interest to the aforementioned applications in real time.Item Practical Memristor Emulator Circuit Development Techniques for Analog Applications(University of Missouri -- Kansas City, 2017) Alharbi, Abdullah G.; Chowdhury, Masud H.Emerging memristor technology is drawing widespread attention during recent time due to its potential diverse applications in nanoelectronic memories, logic and neu romorphic computer architectures, digital and analog modulations system, and oscillator circuits. There has been a surge of interest to study memristor. However, as of now there is no single device available in the market that can truly exhibit the memristive be havior for a certain frequency range. Due to the absence of a real fabricated memristor, researchers are still relying on the memristor emulators to investigate the behavior and applications of memristor. Memristor emulator circuits are intended to understand and mimic the perceived behavior and properties of memristor. In addition, memristor has recently been recognized as a new and the fourth passive element that has the potential for many applications in digital, analog, and mixed signal domains. In the absence of a physical memristor, these emulator circuits would be of great importance to understand the fundamental concepts and potential applications related to memristor,becausetheseemulatorcircuitscanbebuiltinthelaboratoryusinginexpensive off-the-shelf circuit components. One of the most widely used ideal memristor models developedbytheHPLabdoesnotfittheanticipatednonlinearbehaviorofarealmemris tor. Therefore, this dissertation has proposed generic and practical emulator circuits for a current-controlled and voltage-controlled memristor, which can be used to mimic the behavior of the well-known memristor models like-Simmons Tunneling Barrier Model (STBM), ThrEshold Adaptive Memristor (TEAM) Model, and Voltage ThrEshold Adap tive Memristor (VTEAM) in addition to the simple Hewlett Packard (HP) model. Prior emulators can only emulate the linear electrical behavior. Moreover, the proposed emulator circuit development techniques can be config ured for both floating and grounded models. In addition to the mathematical modeling and analysis of the proposed emulator, we provide SPICE simulation and experimental results. The analytical observations and the experimental results show that the proposed circuits can mimic the nonlinear behavior of real memristors for certain frequency range. Furthermore, the proposed emulator has been used to verify some applications like Wien bridge oscillator. Both series and parallel connectivity of the proposed emulator circuits have been studied experimentally. Finally, a brief comparison with the previously pub lished emulators is presented to highlight the advantages of the proposed design.Item Understanding and Adapting to Crowd Behavior: A Study of Wireless Networks and Entrepreneurial Crowdfunding(University of Missouri -- Kansas City, 2017) Tonhozi de Oliveira, Pedro; Beard, CoryThe advances of the future will demand scholars have a systemic vision to solve problems. Integration across disciplines is needed to study, explain, inquire and discover beyond the traditional borders of academic areas. In this research,we consider the effects of crowd behavior in wireless networks and funding. First,we seek to demonstrate how to improve the allocation of wireless network resources based on the use of aggregate data from crowds’ mobile phones and dynamically improve the wireless network around them. The data is used to develop an optimization allowing a more efficient management of the network. Second,using tool sets from engineering and entrepreneurship,we study the interaction of herding and speed to goal towards success on the crowdfunding environment using the liability of newness as a theoretical lens. Finally, we advance entrepreneurial crowdfunding literature through developing a new framework to understand the different paths to success. One of the challenges of deploying dense networks is unpredicted human mobility behavior. Today, the static allocation of carriers results in a suboptimal use of spectrum resources. In this essay, we introduce the concept of Dynamic Carrier Allocation as the ability of dynamically move carriers from one cell to another based on the demand. Simulation results demonstrate on average 25% higher efficiency when compared with the previous static allocation schemes. Crowdfunding has become a popular substitute for traditional sources of funding for new ventures. While some research has been done to explain the reasons an entrepreneur is successful in this environment, the understanding of the interaction between the early and late stages of the campaign still cloudy. In this essay, we use the liability of newness theory and over 2,400 crowdfunding projects to discuss the connection between the timing of the herding effect and the speed in which the campaign is funded. We also look how the size of the goal moderates this effect. Then, we propose a taxonomy for the different paths towards crowdfunding success. The conceptual and empirical findings of this work extend our understanding of entrepreneurial legitimacy and the roles played by early stage funding strategies in overcoming internal and external liabilities of newness.Item Addressing On-Chip Power Conversion and Dissipation Issues in Many-Core System-on-a-Chip based on Conventional Silicon and Emerging Nanotechnologies(University of Missouri -- Kansas City, 2017) Ashenafi, Emeshaw; Chowdhury, Masud H.Integrated circuits (ICs) are moving towards system-on-a-chip (SOC) designs. SOC allows various small and large electronic systems to be implemented in a single chip. This approach enables the miniaturization of design blocks that leads to high density transistor integration, faster response time, and lower fabrication costs. To reap the benefits of SOC and uphold the miniaturization of transistors, innovative power delivery and power dissipation management schemes are paramount. This dissertation focuses on on-chip integration of power delivery systems and managing power dissipation to increase the lifetime of energy storage elements. We explore this problem from two different angels: On-chip voltage regulators and power gating techniques. On-chip voltage regulators reduce parasitic effects, and allow faster and efficient power delivery for microprocessors. Power gating techniques, on the other hand, reduce the power loss incurred by circuit blocks during standby mode. Power dissipation (Ptotal = Pstatic and Pdynamic) in a complementary metal-oxide semiconductor (CMOS) circuit comes from two sources: static and dynamic. A quadratic dependency on the dynamic switching power and a more than linear dependency on static power as a form of gate leakage (subthreshold current) exist. To reduce dynamic power loss, the supply power should be reduced. A significant reduction in power dissipation occurs when portions of a microprocessor operate at a lower voltage level. This reduction in supply voltage is achieved via voltage regulators or converters. Voltage regulators are used to provide a stable power supply to the microprocessor. The conventional off-chip switching voltage regulator contains a passive floating inductor, which is difficult to be implemented inside the chip due to excessive power dissipation and parasitic effects. Additionally, the inductor takes a very large chip area while hampering the scaling process. These limitations make passive inductor based on-chip regulator design very unattractive for SOC integration and multi-/many-core environments. To circumvent the challenges, three alternative techniques based on active circuit elements to replace the passive LC filter of the buck convertor are developed. The first inductorless on-chip switching voltage regulator architecture is based on a cascaded 2nd order multiple feedback (MFB) low-pass filter (LPF). This design has the ability to modulate to multiple voltage settings via pulse with modulation (PWM). The second approach is a supplementary design utilizing a hybrid low drop-out scheme to lower the output ripple of the switching regulator over a wider frequency range. The third design approach allows the integration of an entire power management system within a single chipset by combining a highly efficient switching regulator with an intermittently efficient linear regulator (area efficient), for robust and highly efficient on-chip regulation. The static power (Pstatic) or subthreshold leakage power (Pleak) increases with technology scaling. To mitigate static power dissipation, power gating techniques are implemented. Power gating is one of the popular methods to manage leakage power during standby periods in low-power high-speed IC design. It works by using transistor based switches to shut down part of the circuit block and put them in the idle mode. The efficiency of a power gating scheme involves minimum Ioff and high Ion for the sleep transistor. A conventional sleep transistor circuit design requires an additional header, footer, or both switches to turn off the logic block. This additional transistor causes signal delay and increases the chip area. We propose two innovative designs for next generation sleep transistor designs. For an above threshold operation, we present a sleep transistor design based on fully depleted silicon-on-insulator (FDSOI) device. For a subthreshold circuit operation, we implement a sleep transistor utilizing the newly developed silicon-on ferroelectric-insulator field effect transistor (SOFFET). In both of the designs, the ability to control the threshold voltage via bias voltage at the back gate makes both devices more flexible for sleep transistors design than a bulk MOSFET. The proposed approaches simplify the design complexity, reduce the chip area, eliminate the voltage drop by sleep transistor, and improve power dissipation. In addition, the design provides a dynamically controlled Vt for times when the circuit needs to be in a sleep or switching mode.Item Long Term Ocular Drug Delivery with Novel Pentablock Copolymers; Part I: Composite Nanoformulation of Macromolecules For Back of the Eye Diseases, Part II: Dexamethasone Nanoparticle to Develop an In Vitro Model for Glaucoma(University of Missouri -- Kansas City, 2017) Agrahari, Vibhuti; Mitra, Ashim K., 1954-Pentablock (PB) copolymers have been successfully synthesized for long term delivery in the treatment of posterior segment ocular diseases. PB copolymers are comprised of FDA approved biodegradable polymer such as polyethylene glycol (PEG), polycaprolactone (PCL), polylactic acid (PLA) and polyglycolic acid (PGA). PB copolymers of different composition, molecular weights and block arrangements were synthesized by ring opening bulk copolymerization method and analyzed by NMR, GPC FT-IR and XRD analyses. Further, these PB copolymers have been utilized to develop the macromolecule embedded thermosensitive gels or nanoparticles (NPs) or composite nanoformulation (NPs suspended in gel) for a sustained drug delivery. PBG (PLA-PCL-PEG-PCL-PLA; PBG-1 and PEG-PCL-PLA-PCL-PEG; PBG-2) gelling copolymers were evaluated for their utility as injectable in situ hydrogel forming depot for controlled ocular delivery of macromolecules (proteins, peptides and Fab fragments). A wide variety of macromolecules (Octreotide, IgG-Fab, IgG-Fab‘ and IgG) with molecular weights ranging from 1 - 150 kDa have been used for this purpose. The kinematic viscosity of the copolymer solution was studied at different polymer concentration with different block arrangment. It was observed that viscosity of hydrophobic polymer (PBG-1) was considerably higher relative to PBG-2 copolymer. Sol-gel transition curves for PBG-1 and PBG-2 copolymer was compared to understand the effect of hydrophobicity and effect of block arrangement on the sol-gel behavior of block copolymers. Sol-gel transition and rheology revealed that PBG block arrangements were easy to handle at room temperature and easy to administer through small gauge needle. Cell viability and cytotoxicity studies confirmed that PBG copolymers are superior biomaterials for ocular delivery. It was observed that the in vitro release pattern was depended on the molecular weight of the macromolecules and amphiphilic nature of the PBG copolymers. It is anticipated that much longer release can be obtained by altering block composition or change in hydrophobicity and/or hydrophilicity of the gelling polymer. The in vitro release pattern was in conjunction with the facts that amorphous and hydrophilic polymer degrades fast. CD spectroscopy results revealed no changes in the secondary structure of macromoelcules (studied for IgG as a model macromoelcule). The in vitro degradation study for PBG-2 copolymer was performed under four different conditions; (i) in pH 7.4 PBS at 37°C, (ii) in presence of enzymes acetylcholinesterase (14.7 mU/mL) and butyrylcholinesterase (5.9 mU/mL), (iii) in pH 9.0 borate buffer at 37°C and (iv) in pH 7.4 PBS at 40°C. The samples were analyzed by XRD and GPC to determine the weight loss of the PBG-2 copolymer. It was observed that accelerated conditions such as pH 9.0 (37°C) and high temperature (40°C) exhibited weight loss of ~45% and ~40%, respectively which were significantly higher than weight loss observed under normal condition (pH - 7.4, 37°C) i.e., ~35%. No significant effect of enzymes was observed on polymer degradation. Besides, in vivo assessment of PBG-2 copolymer provided a safe environment and was well tolerated in the rabbit eyes analyzed up to 33 weeks. Further, PB-NPs were formulated with different molecular weights of PB copolymer (PCL-PLA-PEG-PLA-PCL) to study the release pattern of macromolecules (lysozyme, IgG-Fab, ranibizumab and IgG). The macromolecules encapsulated in PB NPs were prepared by W1/O/W2 double emulsion solvent evaporation method. The macromolecules were optimized to achieve a high drug loading (~17%) and entrapment efficiency (~66%) in the NPs. PB-NPs alone exhibited significant burst release in the first few days however, the dual approach i.e., composite nanoformulations (macromolecules encapsulated PB-NPs dispersed in thermosensitive gel) eliminated the burst release effect and exhibited nearly zero-order protein release for significantly longer durations (~3-6 months). In order to compare the duration of in vitro release, PB copolymers with different molecular weight have been studied. The enzymatic activity of lysozyme with its respective enzymatic assays was used to investigate the activity of released macromolecule. Anti-VEGF activity of ranibizumab released from composite nanoformulation was analyzed by indirect ELISA. It was observed that macromolecules maintained their structural integrity and bioactivity during the preparation of the nanoformulation and also during the drug release process. The mean particle size distribution of NPs in PBS was found in the range of ~150 nm and was consistent throughout the study in different media analyzed up to 10 days. The results confirmed the higher stability of NPs in different cell culture media. In vitro cell viability, cytotoxicity and biocompatibility studies performed on various ocular cells, confirmed the safety of PB copolymers for ocular applications. PART II: DEXAMETHASONE NANOPARTICLE TO DEVELOP AN IN VITRO MODEL FOR GLAUCOMA The aim of the present study was to examine the elevation of myocillin (MYOC); one of the extra cellular matrix related proteins whose expression is altered in presence of long-term treatment of Glucocorticoids. In this study, dexamethasone (DEX) was selected as model drug. The different strains of primary cultures of human trabecular meshwork (HTM) cell line (HTM120, 136, 126, 134 and 141) were used to develop the in vitro cell culture model of glaucoma. To obtain a long-term delivery of DEX, pentablock (PB) copolymer was synthesize using the ring opening bulk copolymerization method and characterized by NMR, GPC and XRD analyses. PB copolymer was used to formulate the DEX encapsulated nanoparticles (NPs) with entrapment efficiency of ~63% and drug loading of ~11% w/w. The mean particle size distribution of NPs was analyzed by NTA in PBS was found in the range of ~109 nm. The biomaterial was further studied for in vitro cytotoxicity and cell viability. Results showed that neither cell viability nor cytotoxicity was affected up to 12 weeks of treatment. DEX-PB-NPs or control NPs treatments were given to the HTM cells and cell culture supernatant was collected/replaced with fresh 1% DMEM once/week for 12 weeks. DEX or vehicle was used as controls to compare MYOC secretion levels by Western blot (WB). Four HTM cell strains tested showed similar MYOC secretion patterns, having robust responses for the entire monitoring period. In contrast, one cell strain responded only for a few weeks. Quantitation of WB data from five HTM cell strains showed that MYOC increased by 5.2 ± 1.3, 7.4 ± 4.3, and 2.8 ± 1.1 fold at 4, 8, and 12 weeks in the presence of DEX-PB-NPs compared to 9.2 ± 3.8, 2.2 ± 0.5, and 1.5 ± 0.3 fold at 4, 8, and 12 weeks in control DEX treatment group. Based on the decline in MYOC levels after withdrawal of DEX from control wells, results indicate that DEX-PB-NPs released biologically active DEX for at least 10 weeks. By comparison, MYOC levels in vehicle treated control wells remained unchanged. Moreover, PB copolymers were biocompatible and didn‘t modifying the cellular functions of HTM cells. Although the PB copolymers did not show any sign of cytotoxicity to HTM cells in this long-term study, they did modify HTM cell morphology. HTM cell elongation was present in all cell strains after both Con-NPs and DEX-PB-NPs treatment. Morphological modification of HTM cells by the polymers may accompany functional changes those were not measured in the present study, but needs further investigations. Meanwhile, this study provides the evidence that our in vitro system developed in this study is a valuable tool for analyzing the safety of the polymers and biological effects of steroids released from the polymers. In addition, histological observations in the C57BL/6 mice showed normal phenomenon in ocular tissue morphology.