Digital Commons Network^™

The Effects Of Fast Secondary Electrons On Low Voltage Electron Beam Lithography, Mehdi Bolorizadeh

Doctoral Dissertations

In 1981 Prof. Sir Alec Broers suggested that the spatial limit of direct writing electron beam lithography (DWEBL) would be limited to ~10 nm by the laterally scattered fast secondary electrons (FSE) even in atomically thin resist. Experiments and simulations have been carried out to quantify the contribution of FSE to the energy deposition that results in exposure of the resist over high beam energies. One possible solution to this restriction would be to use low energy electrons.

To examine Broers' hypothesis in low voltage electron beam lithography (EBL), studies in the low energy range on the effects of FSE …

The Effect Of Mobile Phase Composition And Temperature On The Adsorption Behavior Of Tryptophan, Tarab Jamil Ahmad

Doctoral Dissertations

Single-component adsorption isotherm data were acquired by frontal analysis for tryptophan on a C₁₈-Kromasil packed column, using acetonitrile-water solutions of various compositions (2.5, 5, and 7.5% ACN + 1% ACOH). These isotherms have a complex behavior, exhibiting at least one clear inflection point at an intermediate concentration and, possibly, another such point, close to the origin. The isotherm for 2.5 % ACN has the strongest curvature. At high concentrations, all these isotherms tend toward a limit, showing that the adsorbent has a finite saturation capacity. At low concentrations, these isotherms seem to exhibit langmuirian behavior. The isotherm model …

Linear And Nonlinear Chiroptical Effects, Watheq Ahmad Al-Basheer

Doctoral Dissertations

Chiroptical effects of linear and nonlinear nature are investigated by employing a variety of spectroscopic methods, such as linear and nonlinear circular dichroism, optical rotation, vibrational Raman scattering, infrared absorption and Vibrational Circular Dichroism. (2+1) Resonance Enhanced Multiphoton Ionization Circular Dichroism (REMPICD) is a direct demonstration of the nonlinear chiroptical effects of a sample of R-(+)-3-methylcyclopentanone. Solvent effects on circular dichroism is studied for 35 common solvents, which is significantly attributed to the solute- solvent electrostatic and Van der waals interactions for CD and ORD of R3MCP. Hartree-Fock and Density Function Theoretical calculations of R3MCP CD and …

Combined Study Of Reactor And Terrestrial Antineutrinos With Kamland, Mikhail Batygov

Doctoral Dissertations

This dissertation presents a combined study of antineutrinos of terrestrial and reactor origin detected by Kamioka Liquid scintillator Anti-Neutrino Detector (KamLAND). Of special physical interest are neutrino oscillation parameters and the terrestrial antineutrino flux, the former being of a profound importance for new physics beyond the Standard Model, and the latter having significant implications for geophysics. The analysis described here uses a comprehensive likelihood model to naturally combine terrestrial and reactor antineutrino studies within a single framework. The use of this likelihood model and better event reconstruction tools allowed to obtain narrower limits for the oscillation parameters and the terrestrial …

Interference Effects Among J = 3/2+ Resonances In 19Ne System & Searching For Resonances In The Unbound 6Be Nucleus, Kyung Yuk Chae

Doctoral Dissertations

The ¹⁸F(p,α)¹⁵O reaction plays a crucial role in understanding γ-ray emission from novae. Because of the importance of understanding the ¹⁸F + p reactions, a number of studies of the A=19 isobars have been made using stable and exotic beams. The interference effects among J ^π = 3/2⁺ resonances in the ¹⁸F + p system, however, have never been measured, but they can change the S-factor by a factor of 20 at nova energies. R-matrix calculations indicate that the cross sections above the Ec.m. = 665 keV resonance are sensitive …

Single-Molecule Detection With Active Transport, David Allan Ball

Doctoral Dissertations

A glass capillary is used near the focal region of a custom-built confocal microscope to investigate the use of active transport for single-molecule detection in solution, with both one and two-photon laser excitation. The capillary tip has a diameter of several microns and is carefully aligned nearby to the sub-micron laser beam waist, collinear to the optical axis, so that a negative pressure-difference causes molecules to be drawn into the capillary, along the laser beam axis. The flow of solution, which is characterized by fluorescence correlation spectroscopy (FCS), can increase the single-molecule detection rate for slowly diffusing proteins by over …

Regularization Of The Particle-Particle Interaction In The Nuclear Density Functional Theory, Piotr Jerzy Borycki

Doctoral Dissertations

In this work we show how to regularize the ultraviolet divergences appearing in the local pairing term of the energy density functional. Our approach, entirely rooted in the framework of the Density Functional Theory, is based on the regularization of local densities and currents and can be applied to various classes of energy density functionals. We demonstrated, that for the particular choice of the pairing term of energy density functional, our procedure gives the same regularization scheme to the one obtained earlier by the means of the pairing gap regularization.

We also investigated the non-unitarity of the Bogoliubov tranformation due …

Thermodynamic And Neutron Structural Studies Of Hydrocarbon Adsorption On Mgo Nanocubes, Richard E. Cook

Doctoral Dissertations

Presented is a series of thermodynamic and neutron scattering experiments used to probe the nature of the hydrocarbon - MgO (100) interaction. High-resolution volumetric isotherms are used to probe the wetting, layer transitions, heats of adsorption, two-dimensional compressibilities, and identify possible phase transitions of thin films of benzene, ethane, and n - pentane on MgO powders. Neutron diffraction experiments were used to probe the structure and identify any phase transitions within monolayer films of ethane, butane and n -pentane.

Benzene adsorption, while showing no visible layering steps, shows a shift in the shape of the isotherm for p/p_o > 0.7. …

Characterization Of Aβ Aggregates Using Hydrogen/Deuterium Exchange Mass Spectrometry, Maolian Chen

Doctoral Dissertations

The work presented in this dissertation aimed to localize the hydrogen-bonding interaction sites within Aβ aggregates associated with Alzheimer’s disease using hydrogen/deuterium exchange mass spectrometry (HDX-MS) coupled with proteolysis. Toward this end, an on-line digestion system utilizing a triaxial electrospray probe as the front end to MS was developed. Using this approach, regions of Aβ(1-40) fibrils and protofibrils that are protected from HDX have been identified. The HDX data show that the C-terminal segment 35-40 and the N-terminal segment 1-19 are highly exposed to exchange in both fibrils and protofibrils, while the internal fragment 20-34 is highly protected from exchange …

Direct Integration Of Surface Enhanced Raman Spectroscopy As A Detection Mode For Microfluidic Separations And Fluid Handling: Μfluidic-Sers, Raynella Magdalene Connatser

Doctoral Dissertations

The arena of microfluidics (µfluidics) has grown over the past decade to encompass myriad separation techniques and exploit copious detection modes. The direct integration of a vibrational spectroscopic detection technique, rich with structural information, onto a platform that is portable and potentially highly controllable such as µfluidics, could offer redress for some of the problems inherent in many of the electrophoretically driven separations carried out on said devices. Herein, this direct integration is explored, and methods of device fabrication, spectroscopic data collection conditions, analytical figures of merit of the detection technique, and separations method development results are discussed. The creation …

Management Of Requirements Changes In Sequence-Based Software Specifications, Lan Lin

Doctoral Dissertations

The sequence-based software specification method was developed to convert ordinary, or typical requirements and requirements statements into mathematically precise specifications, at an acceptable level of abstraction, for deterministic systems. In view of the iterative nature of modern software developing process, requirements, once defined, are not frozen; changes are integrated continuously that need to be accommodated and validated.

The need for managing changes of requirements in sequence-based specifications arises both as a consequence of practicing this method and as a general topic in software requirements engineering. In this research we have explored the theoretical consequences of three major requirements changes in …

The Reaction Of Telechelic Polymers At Multicomponent Interfaces: A Molecular Loop Study, James Kevin Rice

Doctoral Dissertations

The work presented in this dissertation attempts to form an understanding of the reaction parameters that govern the reaction of telechelic polymers to form multiply bound polymer chains, resulting in polymer loop formation, at both soft and hard polymeric interfaces. Both theoretical and experimental studies offer evidence that blocky copolymers, as opposed to random or alternating morphologies, are the best compatibilizers of a given polymer blend system. This has been attributed to the fact that blocky copolymers spread across the interface, with each block lying in or near the homopolymer region in which it is miscible, effectively “stitching” the interface …

Measurement Of The 32S(P,D)31S Reaction And Its Astrophysical Implications, Zhanwen Ma

Doctoral Dissertations

The ³⁰P(p,γ)³¹S reaction plays a crucial role in the synthesis of heavier nuclear species, from Si to Ca, in nova outbursts on ONe White Dwarfs [26, 28, 35]. However, its rate is very uncertain as a result of the lack of spectroscopic information on the levels above proton threshold in ³¹S. The currently adopted rate of this reaction, based on statistical Hauser-Feshbach calculations [36], could have an uncertainty as much as a factor of 100 higher or lower under nova conditions [26].

To reduce these uncertainties, we have measured differential cross sections for the ³²S(p,d) …

Multiple Approaches To The Separation Of Amino Acids And Biologically-Relevant Compounds, Lance Andrew Riddle

Doctoral Dissertations

The branch of analytical chemistry known as separations has continued to grow and expand ever since its beginnings a century ago. With all the technological advances occurring to make separations a more powerful technique, the main goal continues to be the desired separation of the compounds of interest in a mixture. Although a desired separation may be achieved, there can always be room for improvement with regards to the time necessary for the separation as well as better resolution of closely-related species as well as enantiomers of the same analyte.

In this work, a variety of separation methods and variations …

Synthesis And Radiolabeling Of Potassium Trifluoroborate Benzylidene Anabaseine Derivatives, Aaron Landon Smith

Doctoral Dissertations

Anabaseine has demonstrated a high, non-selective, affinity for the α7- bungarotoxin sensitive neuronal nicotinic acetylcholine receptor binding site found in small cell lung carcinoma. The benzylidene anabaseine derivatives of anabaseine have shown a selective affinity for these binding sites. These studies suggest that radiolabeled benzylidene anabaseine derivatives could act as potential imaging agents to aid in the early detection of lung cancer.

This dissertation outlines the strategy and methods employed in the synthesis of a family of potassium trifluoroborate derivatives of benzylidene anabaseine and their subsequent halogenation. Two of the trifluoroborate salts were converted to their radiolabeled analogues for potential …

Scheduling Tasks With Precedence Constraints On Heterogeneous Distributed Computing Systems, Zhiao Shi

Doctoral Dissertations

Efficient scheduling is essential to exploit the tremendous potential of high performance computing systems. Scheduling tasks with precedence constraints is a well studied problem and a number of heuristics have been proposed.

In this thesis, we first consider the problem of scheduling task graphs in heterogeneous distributed computing systems (HDCS) where the processors have different capabilities. A novel, list scheduling-based algorithm to deal with this particular situation is proposed. The algorithm takes into account the resource scarcity when assigning the task node weights. It incorporates the average communication cost between the scheduling node and its node when computing the Earliest …

Adsorption Of Small Molecules On Mgo And Graphite, Peter Nikolaivich Yaron

Doctoral Dissertations

The physical adsorption of molecules on metal oxide surfaces has direct implications in a number of industrial applications such as; catalysis, electronics, and fuel cells to name a few. Despite the large number of adsorption studies to date, only a small number of systems can be explained with the most advanced ab initio calculations currently available.

One of the simplest metal oxide systems to study is magnesium oxide due to its simple cubic rock-salt structure. Using a patented method, nearly defect-free MgO cubes can be synthesized with a narrow size distribution exposing exclusively the (100) equilibrium crystal face. The use …

Synthesis And Characterization Of Complex Polymer Architectures, Brandon Scott Farmer

Doctoral Dissertations

Anionic polymerization based upon high vacuum technique has been used to synthesize different star polymers using varying linking techniques. In particular chlorosilanes, divinylbenzene, and polyhedral oligomeric silsesquioxane (POSS) chlorosilane derivatives were used in the synthesis of star polymers. These polymers, along with polymers synthesized by others, have been characterized by a range of methods in this work.

A series of polyisoprene (PI) stars were synthesized from dimethylaminopropyllithium (DMAPLi) and subsequently hydrogenated to form poly (ethylene-co-propylene) (PEP) these were characterized by size exclusion chromatography (SEC) coupled with online two angle laser light scattering (TALLS). These polymers were synthesized in an attempt …

A Measurement Of The Top Quark Mass With A Matrix Element Method, Adam Paul Gibson '96

Doctoral Dissertations

We present a measurement of the mass of the top quark. Our event sample is selected from proton-antiproton collisions, at 1.96 TeV center-of-mass energy, observed with the CDF detector at Fermilab's Tevatron. We consider a 318 pb^-1 dataset collected between March 2002 and August 2004. We select events that contain one energetic lepton, large missing transverse energy, exactly four energetic jets, and at least one displaced vertex b tag. Our analysis uses leading-order tt and background matrix elements along with parameterized parton showering to construct event-by-event likelihoods as a function of top quark mass. From the 63 events observed …

Membrane Systems With Limited Parallelism, Bianca Daniela Popa

Doctoral Dissertations

Membrane computing is an emerging research field that belongs to the more general area of molecular computing, which deals with computational models inspired from bio-molecular processes. Membrane computing aims at defining models, called membrane systems or P systems, which abstract the functioning and structure of the cell. A membrane system consists of a hierarchical arrangement of membranes delimiting regions, which represent various compartments of a cell, and with each region containing bio-chemical elements of various types and having associated evolution rules, which represent bio-chemical processes taking place inside the cell.

This work is a continuation of the investigations aiming to …

Potential Subsurface Structures And Hydrocarbon Reservoirs In The Southern Appalachian Basin Beneath The Cumberland Plateau And Eastern Highland Rim, Tennessee, Kentucky, And Southwestern Virginia, Jonathan Charles Evenick

Doctoral Dissertations

Oil and gas exploration in the southern Appalachian basin is typically concentrated around areas with historically proven reserves and very limited prospecting is conducted elsewhere in the region. To remove possible correlation problems and promote regional prospecting a standardized picking methodology was established in geophysical logs for the Middle Ordovician carbonate lithofacies (Nashville-Stones River Groups). This methodology was then used to correlate the units across Cumberland Plateau of Tennessee, Kentucky, and Virginia, from the Nashville-Jessamine domes to the Clinchport-Whiteoak Mountain thrust in the Valley and Ridge. The same lithofacies may extend in Ohio, Pennsylvania, and New York, suggesting a standardized …

Solute Transport And U(Vi) Reactivity In Natural Heterogeneous Sediments, Melanie A. Mays

Doctoral Dissertations

The primary goal of this research was to determine the relationship between sedimentary geology and solute transport parameters. The overall hypothesis was that the transport of reactive and nonreactive solutes can be predicted using observable sedimentary depositional characteristics. The objective was to test this hypothesis by performing a variety of quantitative transport experiments in intact layered sediment samples. In this study, I used natural materials to explore 1) how mineralogical composition influenced the fate and transport of uranium(VI), 2) the relationship between heterogeneous sedimentary layering and preference for direction of flow, and 3) the mechanisms of solute transport in a …

Growth And Superconductivity Of Pb And Pb-Bi Alloys In The Quantum Regime, Mustafa Murat Ozer

Doctoral Dissertations

Superconductivity is a collective quantum phenomenon that is inevitably suppressed in reduced dimensionality. Questions of how thin superconducting wires or films can be before they lose their superconducting properties have important technological ramifications and go to the heart of understanding formation, coherence, and robustness of the superconducting state in quantum confined geometries. Suppression of superconductivity in low dimensions is usually attributed to thermal or quantum fluctuations, or to pair-breaking Coulomb interactions in the presence of strong disorder. Control and quantification of a film’s disorder length scale remained a critical experimental obstacle, however. Here, we exploit quantum confinement of itinerant electrons …

Ab-Initio Calculations Of The Charge-Density Response In Complex Materials, Oscar Dario Restrepo Tovar

Doctoral Dissertations

Our main goal is to have a realistic description of the charge excitations in complex materials in the range of energies such as the coulomb energy U, which is in the eV range. Spectra of these charge excitations, for a large range of wave vector transfers, may provide signatures of the underlying electronic structures. The charge-density response function calculated within Time-dependent Density functional (TDDFT) is an ideal theoretical framework for the calculation of these excitations, since comparison with experimental data (in particular with non-resonant inelastic x-ray scattering experiments) can be done in absolute units (without the need of any adjustable …

Asymtre: Building Coalitions For Heterogeneous Multi-Robot Teams, Fang Tang

Doctoral Dissertations

This dissertation addresses the problem of synthesizing task solution strategies for a hetero- geneous robot team to accomplish multi-robot tasks by sharing sensory and computational resources. The approach I developed is called ASyMTRe, which stands for Automated Synthesis of Multi-robot Task solutions through software Reconfiguration, pronounced “Asymmetry”. When dealing with heterogeneous teams, it is challenging to determine how the capabilities of each team member can be appropriately utilized to facilitate the accomplishment of the team-level goal. The ASyMTRe approach provides a way for the robots to reason about how to solve a task depending on their individual capabilities. The fundamental …

Neutron Scat- Tering In The Novel Quantum Magnets: Livo2 And Dmacucl3, Wei Tian

Doctoral Dissertations

The behavior of magnetic systems in the extreme quantum limit is one of the most interesting forefront areas in condensed matter physics. This dissertation investigates two particularly interesting quantum magnets: LiVO₂ and DMACuCl₃. Systematic studies were performed on single crystal samples using different experimental techniques, especially inelastic neutron scattering. Detailed experimental results and corresponding model calculations are presented and discussed in this dissertation.

LiVO₂ is a good candidate to study the interplay between “magnetic frustration” and orbital ordering. V³⁺ ions in LiVO₂ form a triangular lattice involving threefold degenerate t_2g orbitals. LiVO2 undergoes …

Manifestations Of Broken Symmetry: The Surfaces Phases Of Ca2−XSrXRuo4, Robert G. Moore Ii

Doctoral Dissertations

The discovery of superconductivity in Sr₂RuO₄ has renewed vigor in the study of correlated electron systems. The evolution of a p-wave superconducting state from a para- magnetic 2-dimensional Fermi liquid shows the ruthenate superconductivity is anything but conventional. Sr₂RuO₄ is isostructural with La₂CuO₄, the parent compound for the high temperature superconducting family La2_−xSr_xRuO₄. The substitution of Ca²⁺ for Sr²⁺ generates a different structure involving a static rotation and tilt of the RuO₆ octahedral, however, the antiferromagnetic insulating ground state of Ca …

Three Population Models Applied To Competition, Disease And Invasion, Erika Asano

Doctoral Dissertations

In this work, we present three diffrent types of population models. The first two models are examined in the context of optimal control problems. The third involves the construction of an invasion model using a significant amount of data.

The first model describes the interaction of three populations, motivated by a combat scenario. One of the three populations can switch the mode of alliance with the other two populations between cooperation and competition. The other two populations always compete with each other. In this system of parabolic partial differential equations, the control is the function which measures the strength of …

Two Biological Applications Of Optimal Control To Hybrid Differential Equations And Elliptic Partial Differential Equations, Wandi Ding

Doctoral Dissertations

In this dissertation, we investigate optimal control of hybrid differential equations and elliptic partial differential equations with two biological applications. We prove the existence of an optimal control for which the objective functional is maximized. The goal is to characterize the optimal control in terms of the solution of the opti- mality system. The optimality system consists of the state equations coupled with the adjoint equations. To obtain the optimality system we differentiate the objective functional with respect to the control. This process is applied to studying two prob- lems: one is a type of hybrid system involving ordinary differential …

Cohomological Dimension With Respect To Nonabelian Groups, Atish Jyoti Mitra

Doctoral Dissertations

This dissertation addresses three aspects of cohomological dimension of metric spaces with respect to nonabelian groups.

In the first part we examine when the Eilenberg-Maclane space (n = 1) of the abelianization of a solvable group being an absolute extensor of a metric space implies the Eilenberg-Maclane space of the group itself is an absolute extensor. We also give an elementary approach to this problem in the case of nilpotent groups and 2-dimensional metric spaces.

The next part of the dissertation is devoted to generalizations of the Cencelj- Dranishnikov theorems relating extension properties of nilpotent CW complexes to its homology …