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Articles 1 - 18 of 18
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The Effects Of Parkinson's On Fixational Stability, Erin L. Mallahan
The Effects Of Parkinson's On Fixational Stability, Erin L. Mallahan
Theses and Dissertations
Parkinson's disease (PD) is a progressive, neurological movement disorder. The stability of eye movements in PD is not well understood but many patients report difficulty doing tasks that require stabilized fixation and gaze. The ability to stabilize an image on the retina is critical is acquiring visual information. The purpose of this study was to compare the stability of fixational eye movements of PD patients to those of age-matched controls. Eye movements during simple fixation tasks were recorded from 66 subjects (ages 52 to 84), and 36 age-matched controls (ages 58-85). The absolute velocity of the fixational eye movements were …
A Study On The Nature Of Anomalous Current Conduction In Gallium Nitride, Joshua K. Spradlin
A Study On The Nature Of Anomalous Current Conduction In Gallium Nitride, Joshua K. Spradlin
Theses and Dissertations
Current leakage in GaN thin films limits reliable device fabrication. A variety of Ga and N rich MBE GaN thin films grown by Rf, NH3, and Rf+ NH3, are examined with electrical measurements on NiIAu Schottky diodes and CAFM. Current-voltage (IV) mechanisms will identify conduction mechanisms on diodes, and CAFM measurements will investigate the microstructure of conduction in GaN thin films. With CAFM, enhanced conduction has been shown to decorate some extended defects and surface features, while CAFM spectroscopy on a MODFET structure indicates a correlation between extended defects and field conduction behavior at room temperature. A remedy for poor …
Design, Fabrication And Performance Evaluation Of An Impedimetric Urea Biosensor System, Vandana Gupta
Design, Fabrication And Performance Evaluation Of An Impedimetric Urea Biosensor System, Vandana Gupta
Theses and Dissertations
An impedance bioanalyzer system comprising an in-vitro biotransducer, instrumentation and control software for the measurement of urea, potentially in blood dialysate, has been developed. The biotransducer comprises of a microlithographically fabricated interdigitated microsensor electrode (IME) onto which was cast a biorecognition layer conferred with the specificity of the enzyme urease. Urease hydrolysis of urea produces NH4+, HC03- and OH- ions that decrease the device's impedance. The temporal rate of change (kinetic) and the extent of change (equilibrium) of ion concentration were measured as the sensor's response. Five formats: [i) unPEGylated urease-containing poly(hydroxyethylmethacrylate) [p(HEMA)] hydrogel, ii) PEGylated urease-containing p(HEMA) hydrogel, iii) …
Synthesis And Characterization Of Methylene Bis (P-Cyclohexyl Isocyanate)-Poly (Tetramethyl Oxide) Based Polyurethane Elastomers, Kennard Marcellus Brunson
Synthesis And Characterization Of Methylene Bis (P-Cyclohexyl Isocyanate)-Poly (Tetramethyl Oxide) Based Polyurethane Elastomers, Kennard Marcellus Brunson
Theses and Dissertations
This research concerns the development and characterization of methylene bis (p-cyclohexyl isocyanate/butanediol) (HMDI/BD) based polyurethanes used in connection with surface-active anti-microbial polyurethanes. Previously studied polyurethanes having an isophorone diisocyanate/butanediol (IPDI/BD) hard block contaminated water during dynamic contact angle (DCA) analyses. This contamination by unknown species confounds results from biocidal studies and jeopardizes the use of the polyurethane as a matrix polyurethane. By contrast, polyurethanes with methylene bis (p-cyclohexyl isocyanate)/butanediol hard block showed no contamination during DCA analysis. For this reason, further study of HMDI/BD/PTMO polyurethanes was conducted. HMDI/BD polyurethanes were synthesized with 15-50wt% hard block and a soft block of …
Numerical Modeling Of Synthetic Jets In Quiescent Air With Moving Boundary Conditions, Nicholas D. Castro
Numerical Modeling Of Synthetic Jets In Quiescent Air With Moving Boundary Conditions, Nicholas D. Castro
Theses and Dissertations
Flow control is a key factor in optimizing the performance of any vehicle moving through fluids. Particularly, in aerodynamics there are many potential benefits for implementing synthetic jets to achieve aircraft designs with less moving parts, uper- maneuverability, and separation control for fuel economy. Piezoelectric synthetic jets are of special interest because of their lightweight and low power consumption. Numerous publications on such jets are available. Actuator properties and boundary conditions relevant to this particular application however are often overlooked. The focus of this project is to numerically model synthetic jets in quiescent air to study the influence of cavity …
Analysis And Shape Modeling Of Thin Piezoelectric Actuators, Makram Mouhli
Analysis And Shape Modeling Of Thin Piezoelectric Actuators, Makram Mouhli
Theses and Dissertations
The field of smart materials is an increasingly growing area of research. In aerodynamics applications especially, transducers have to fulfill a series of requirements such as light weight, size, energy consumption, robustness and durability. Piezoelectric transducers, devices which transform an electrical signal into motion, fulfill many of these requirements. Specifically, piezoelectric composites are of interest due to their added toughness and ease of integration into a structure. Resulting composites have a characteristic initial curvature with accompanying residual stresses that are responsible for enhanced performance, relative to flat actuators, when the active material is energized. A number of transducer designs based …
Characterization Of Electrosprayed Poly(Vinylidene Fluoride)/Cnt Nanocomposite, Ihab Maher Abdelsayed
Characterization Of Electrosprayed Poly(Vinylidene Fluoride)/Cnt Nanocomposite, Ihab Maher Abdelsayed
Theses and Dissertations
PVDF, Poly(vinylidene fluoride), is a polymer that has been studied for over four decades due to its good electromechanical properties, stability, and durability in various environments. Currently, PVDF is the only commercially available piezoelectric polymer. PVDF is a polymorph, which indicates the presence of several crystalline phases such as α, β, γ, and δ-phase. Oriented β-phase PVDF exhibits ferroelectric properties and displays the largest piezoelectricity amongst the four phases, which makes it the most desirable phase. Preparing oriented β-phase PVDF is a multi-step process, which is cost intensive, due to the time, labor and energy utilized. The main goal of …
The Extraction Of Type Ii Collagen And The Electrospinning Of Nano-Fibrous Scaffolds, Danielle Careen Knapp
The Extraction Of Type Ii Collagen And The Electrospinning Of Nano-Fibrous Scaffolds, Danielle Careen Knapp
Theses and Dissertations
Articular cartilage lining joints, such as in the knee, functions to reduce friction and absorb shock. Collagen type II is the largest constituent in the extracellular matrix of articular cartilage and its restoration is of the highest interest to tissue engineers. Cartilage has little ability to naturally regenerate due to the absence of vascularity and the inability of the chondrocytes to proliferate at a high rate. It would be ideal to create a mimicking extracellular matrix/scaffold from type II collagen that could possibly be used to replace damaged articular cartilage that has the same function and morphology. Three different groups …
Electromechanical Characterization Of Poly(Dimethyl Siloxane) Based Electroactive Polymers, Wrutu Deepak Parulkar
Electromechanical Characterization Of Poly(Dimethyl Siloxane) Based Electroactive Polymers, Wrutu Deepak Parulkar
Theses and Dissertations
The main objectives of this thesis are 1) to evaluate the effect of cross-linking polar cyano phenyl (CN) groups on poly (dimethyl siloxane) (PDMS) and 2) to characterize the electromechanical properties of the resulting CN-PDMS blend as an electroactive actuator. Materials responding to an external stimulus are referred to as electroactive materials. There are several phenomena, which govern the mechanism in these materials, such as piezoelectricity, Maxwell's effect, ferroelectricity, electrostriction to name a few. These electroactive materials can be employed in several applications such as biomedical devices, robots, MEMs, aerospace vehicles, where the application is governed by the specific mechanism. …
Myocardial Perfusion Imaging With Rb-82 Pet, George Nittil Francis
Myocardial Perfusion Imaging With Rb-82 Pet, George Nittil Francis
Theses and Dissertations
Myocardial perfusion imaging (MPI) is an effective technique used to study the left ventricular ejection function (LVEF), myocardial perfusion, wall motion, and wall thickening. Positron emission tomography (PET) and single photon emission computed tomography (SPECT) are two modalities that can be used to quantify the left global and regional perfusion at rest and stress. While PET and SPECT rely on similar principles to produce images, important differences in instrumentation and experimental applications are dictated by inherent differences in their respective physics of radioactive decay. With a sensitivity > 90% in combination with a high specificity, PET is today the best available …
Investigation Of Surface States And Device Surface Charging In Nitride Materials Using Scanning Kelvin Probe Microscopy, Mohammed Shahriar Sabuktagin
Investigation Of Surface States And Device Surface Charging In Nitride Materials Using Scanning Kelvin Probe Microscopy, Mohammed Shahriar Sabuktagin
Theses and Dissertations
In this work Scanning Kelvin Probe Microscopy (SKPM) was used to characterize surface states and device surface charging in nitride materials. Samples grown by Molecular Beam Epitaxy (MBE), Metal Organic Chemical Vapor Deposition (MOCVD) and Hydride Vapor Phase Epitaxy (HVPE) typically show a high surface band bending of about 1 eV. In an n-type sample with 3X1017 cm-3 carrier concentration, 1 eV upward band bending corresponds to 1.7X1012 cm-2 trapped charge density in the surface states. Under continuous ultraviolet (UV) illumination up to 0.6 eV surface photo voltage effect could be observed in some samples, which further indicates that surface …
The Use Of Computerized Dynamic Posturography To Assess The Balance In Individuals With Parkinson's Disease, Theresa Erin Mcguirk
The Use Of Computerized Dynamic Posturography To Assess The Balance In Individuals With Parkinson's Disease, Theresa Erin Mcguirk
Theses and Dissertations
Postural instability is one of the hallmarks of Parkinson's disease (PD), currently evaluated using several subjective tools. However, the nature and degree of the resulting balance deficit is not well specified by these tools. Computerized dynamic posturography (CDP) provides an objective assessment by isolating and quantifying sensory and motor contributions to balance control. The purpose of this study was to compare balance in individuals with PD to a control group using CDP (NeuroCom Smart Balance Master® system). Testing took place at the Southeast Parkinson's disease Research Education and Clinical Center (PADRECC), an interdisciplinary center of excellence for people with PD …
Reentrainment Of Submicron Solid Particles, Ramin Mortazavi
Reentrainment Of Submicron Solid Particles, Ramin Mortazavi
Theses and Dissertations
In this work, an experimental method is developed to study the effects of particle size, flow rate, pulsation, particle/substrate material, and temperature on the short-term reentrainment of submicron particles. The particles tested are in the size range of 10-900 nm and are deposited by wetting the inside of capillary tubes with a liquid suspension. The tubes are then dried in a desiccator. The particles are reentrained under turbulent dry air flow conditions and a condensation particle counter is used to measure the number of entrained particles.There has been very limited work done with nanoscale particles in general and no previous …
Characterization Of Fluoropolymer Powders Made By Supercritical Assisted Mixing With Crystalline Additives, Ntoh Atem-Tambe
Characterization Of Fluoropolymer Powders Made By Supercritical Assisted Mixing With Crystalline Additives, Ntoh Atem-Tambe
Theses and Dissertations
This research project investigates a new technique to efficiently mix crystalline solid additives with polymers by gentle ball milling with steel balls in the presence of carbon dioxide (C02) at 17 to 30°C and 1300 to 2500 psig. As the ball milling system is agitated, the steel balls transfer mechanical energy to the fluoropolymer and additive thereby converting them to powders. C02 is added into the chamber to expand the polymer and make it amenable to impregnation by the additive. At the end of the mixing process, a free flowing powder is produced consisting of the additive coated with fluoropolymer. …
Joint Center Movement Analysis And 3d Motion Modeling Of Upper Arm - Comparison Of Several Algorithms With The Visual 3-D Program, Leena Joseph
Theses and Dissertations
600 out of every 100,000 people in the United States today suffer from some form of cerebellar disease that causes major abnormalities in the equilibrium and aligned, coordinated movement of the body. Hence it becomes essential to diagnose the extent of the movement and gait disorder and provide required therapy to the patients. Various developments have been made in the designing and application of interactive software system for body positioning. Object oriented design techniques are used in the field of software engineering for interactive geometric representation of system behavior. Motion analysis of the upper and lower extremities of the body …
Iterative Methods For The Reconstruction Of Tomographic Images With Unconventional Source-Detector Configurations, Abey Mukkananchery
Iterative Methods For The Reconstruction Of Tomographic Images With Unconventional Source-Detector Configurations, Abey Mukkananchery
Theses and Dissertations
X-ray computed tomography (CT) holds a critical role in current medical practice for the evaluation of patients, particularly in the emergency department and intensive care units. Expensive high resolution stationary scanners are available in radiology departments of most hospitals. In many situations however, a small, inexpensive, portable CT unit would be of significant value. Several mobile or miniature CT scanners are available, but none of these systems have the range, flexibility or overall physical characteristics of a truly portable device. The main challenge is the design of a geometry that optimally trades image quality for system size. The goal of …
Real Time Frequency Analysis Of Signals From Lasso Catheter For Radiofrequency Ablation During Atrial Fibrillation, Prashant Yadav
Real Time Frequency Analysis Of Signals From Lasso Catheter For Radiofrequency Ablation During Atrial Fibrillation, Prashant Yadav
Theses and Dissertations
Real time spectrum analysis of signals obtained through lasso catheter during radiofrequency ablation of pulmonary vein was performed to determine the channel with dominant frequency. Threshold algorithm was used for signals which could be classified as type I and type II AF. Type III AF Signals which were highly fractionated or differentiated were evaluated for frequency content by performing Fast Fourier Transform. Data from Seven patients was collected and an episode of 180 ± 40 seconds was recorded and analyzed for each pulmonary vein that showed electrical activation. Frequency spectra for one second segment of signal for each channel were …
Experimental Design And Analysis Of Piezoelectric Synthetic Jets In Quiescent Air, Poorna Mane
Experimental Design And Analysis Of Piezoelectric Synthetic Jets In Quiescent Air, Poorna Mane
Theses and Dissertations
Flow control can lead to saving millions of dollars in fuel costs each year by making an aircraft more efficient. Synthetic jets, a device for active flow control, operate by introducing small amounts of energy locally to achieve non-local changes in the flow field with large performance gains. These devices consist of a cavity with an oscillating diaphragm that divides it, into active and passive sides. The active side has a small opening where a jet is formed, whereas and the passive side does not directly participate in the fluidic jet.Research has shown that the synthetic jet behavior is dependent …