Physical Sciences and Mathematics Commons^™

Computational Approaches To The Design And Analysis Of Stability Of Polypeptide Multilayer Thin Films, Bin Zheng

Doctoral Dissertations

The focus of this research is the development of computational approaches to understanding the physical basis of layer-by-layer assembly (LBL), a key methodology of nanomanufacturing. The results provided detailed information on structure which cannot be obtained directly by experiments.

The model systems chosen for study are polypeptide chains. Reasons for this are that polypeptides are no less polyelectrolytes than the more usual polyions, and one can control the primary structure of a polypeptide on a residue-by-residue basis using modern synthetic methods. Moreover, as peptides constitute one of the four major classes of biological macromolecules, research in this direction is expected …

Sense -Based Text Classification By Semantic Hierarchy Representation, Xiaogang Peng

Doctoral Dissertations

Automatic classification of web pages is an effective way to facilitate the process of retrieving information from the Internet. Currently, two major classification methods are used in this area: keyword-based classification and sense-based classification. For keyword-based classification, keywords often have different semantic meanings, and the correct keyword matching is largely based on using exactly the same keywords. Thus, the classification results of keyword-based classification are not always satisfying. Many sense-based classification algorithms and systems have been presented, but they pay little attention to the relationship between senses. In this dissertation, we present a method to automatically classify documents based on …

Effect Of Nanoscale Confinement On The Structure And Properties Of Single Conjugated Polymer Molecules, Pradeep K. Koyadankizhakkedath

Doctoral Dissertations

The research presented in this thesis was motivated by questions on the effect of nanoscale confinement on molecular conformation and related photophysical properties of conjugated polymers. Using microdroplet techniques as a method of isolating single molecules of various poly[phenylene vinylenes] we discovered that poly[2-methoxy-5- (2’-ethyl-hexyloxy)-1,4-phenylene vinylene] (MEH-PPV) and poly[2-Methoxy-5-(2'- ethylhexyloxy)-1,4-(cyanovinylene)phenylene] (CN-PPV) can be deposited on precleaned glass substrates with unique transition moment orientation. Structural investigation using a combination of fluorescence emission pattern imaging, atomic force microscopy and polarization anisotropy measurements revealed that individual polymer nanostructures had a high degree of intra-molecular with the long axis of the conjugated segment oriented …

Inter- And Intra-Species Variation In Three Crown Condition Indicators For Seven Tree Species In The Southeastern United States, Kadonna Cheryl Randolph

Doctoral Dissertations

The USDA Forest Service utilizes assessments of tree crowns, specifically crown density, crown dieback, and foliage transparency, to accomplish in part its mission of reporting the long-term status, changes, and trends in forest ecosystem health in the United States. To aid interpretation and provide general guidelines of health across all species the crown condition assessments are classed into categories ranging from “good” to “poor.” The purpose of this research was to evaluate and describe the variation in crown density, crown dieback, and foliage transparency between and within species, and to critique the appropriateness of the current threshold levels. In addition, …

Decidability In Algebraic Geometry, John James Iskra

Doctoral Dissertations

The central theme of our investigation is the concept of Decidability in Algebra/Algebraic Geometry. To the best of our knowledge this seems to be novel in the sense that there is no work known to isolate or to focus on the concept of Decidability in the context of Commutative Algebra. Decidability is more restrictive than Grothendieck's concept of formally unramified, but weaker than the concept of étale. In this article we study these relationships by characterizing Decidability for ring-extensions of essentially finite type. In the absence of essential finiteness we can only show, at present, that a separable algebraic …

Fibrator Properties Of Pl Manifolds, Violeta Vasilevska

Doctoral Dissertations

In the early 90s, R.Daverman defined the concept of the PL fibrator ([12]). PL fibrators, by definition, provide detection of PL approximate fibrations. Daver- man defines a closed, connected, orientable PL n-manifold to be a codimension-k PL orientable fibrator if for all closed, connected, orientable PL (n + k)-manifolds M and PL maps p : M → B, where B is a polyhedron, such that each fiber collapses to an n-complex homotopy equivalent to Nⁿ, p is always an approximate fibration.

If N is a codimension-k PL orientable fibrator for all k > 0, …

A High -Order Finite Difference Method For Solving Bioheat Transfer Equations In Three-Dimensional Triple -Layered Skin Structure, Haofeng Yu

Doctoral Dissertations

Investigations on instantaneous skin burns are useful for an accurate assessment of burn-evaluation and for establishing thermal protections for various purposes. Meanwhile, hyperthermia with radiation is important in the treatment of cancer, and it is essential for developers and users of hyperthermia systems to predict, and interpret correctly the biomass thermal and vascular response to heating. In this dissertation, we employ the well-known Pennes' bioheat transfer equation to predict the degree of skin burn and the temperature distribution in hyperthermia cancer treatment.

A fourth-order compact finite difference scheme is developed to solve Pennes' bioheat transfer equation in a three-dimensional single …

Alpha And Gamma-Ray Spectroscopic Studies Of Au, Pt, And Ir Nuclei Near The Proton Dripline, Tuck-Meng Goon

Doctoral Dissertations

This dissertation reports the observation of α-decay and in-beam level structures in the neutron-deficient nuclei ^176,174Au, ^173,174Pt, and ¹⁷⁵Ir from an experiment which was performed at Argonne National Laboratory (ANL). A beam of ⁸⁴Sr projectiles was used to bombard ^92,94,96Mo targets. From these reactions, the ^176,178,180Hg compound nuclei were made which eventually decayed into more than 20 product nuclei. The experiment was performed with the Atlas accelerator and utilized the Gammasphere array at the target position in conjunction with the Fragment Mass Analyzer (FMA) for mass identification and a Double-Sided Silicon Strip Detector (DSSD), …

Compatibilizing Polymer Blends Using Reactive Telechelic Oligomers And Copolymers, Charles Paul O'Brien

Doctoral Dissertations

The compatbilization of polymer blends via reactive compatibilization and block copolymers was studied. The result presented in this thesis suggest that the process of reactive compatibiliaztion provides a mechanism by which blocky copolymeric compatibilizers can be formed during processing, as demonstrated by the changes in the mechanical and optical properties of the phase separated polymer blends. The results also show, however, that the presence of unreacted smaller oligomers can act as a plasticizer in the blend and can thus detrimentally affect the mechanical properties of the blend if any remains after processing. Careful control of the mixing conditions or post …

Structural Studies Of Superacidic Systems Using Neutron And High Energy X-Ray Diffraction, Syliva Ellen Mclain

Doctoral Dissertations

The structure of two superacids in the liquid phase, hydrogen fluoride and fluorosulfuric acid, have been determined by neutron and high energy X-ray diffraction in this study. In addition the structure of a molecular Lewis acid, BF₃, has been determined for the liquid state as well as the supercritical state. Experiments were also performed on solutions of the hydronium ion in fluorosulfuric acid by neutron and X-ray diffraction as well as by Raman spectroscopy.

In addition this thesis presents the design and construction of sample cells for neutron and X-ray scattering experiments and the design and construction of …

The Internet Backplane Protocol: Shared Storage For Enhanced Network Infrastructure, Wael Rashad Elwasif

Doctoral Dissertations

Presented here are results pertaining to the utilization of distributed shared storage infrastructure to facilitate application management of remote state. The proposed infrastructure relies on non-privileged storage servers deployed by users at various location in the network. Applications utilize network topology information and storage servers profiles to develop and deploy data access and movement policies that enhance application performance and/or functionality. The combined management of storage and communication resources afforded by the proposed model enable a wide array of new applications that depart from the end-to-end model at the core of the existing Internet. However, this departure is done at …

A Parametric Reactive Distillation Study: Economic Feasibility And Design Heuristics, Craig Alan Hoyme

Doctoral Dissertations

The integration of reaction and distillation into a single column is called reactive distillation or catalytic distillation. Reactive distillation provides many benefits such as reduced capital and operating costs, circumventing non-reactive azeotropes, and overcoming equilibrium limited reactions. Industry has been successful in applying reactive distillation; however the integration of reaction and distillation is not applicable for all reaction/separation systems and it is not always clear when reactive distillation is a feasible design alternative.

Heuristics or rules-of-thumb are an integral part of process systems engineering and are used to provide initial guidance and insight for the analysis of process feasibility and …

Development Of Novel Substrates And Sampling Techniques For The Analysis Of Drugs And Model Environmental Pollutants Via Surface Enhanced Raman Spectroscopy (Sers), Marco Antonio De Jesús

Doctoral Dissertations

Surface Enhanced Raman Spectroscopy (SERS) has shown promise for the analysis of environmental and pharmaceutically relevant compounds due to its tremendous enhancement of Raman signals and the large amount of structural information provided by the technique. Despite these advantages, SERS has not been established as a routine analytical tool due to limitations in the analytical figures of merit such as reproducibility and linear dynamic range. This is due in part to the fact that the continuous irradiation of the laser beam over the SERS substrate can promote the rapid decomposition of sample analytes which significantly broaden and diminish the intensities …

Mathematical And Empirical Modeling Of Chemical Reactions In A Microreactor, Jing Hu

Doctoral Dissertations

This dissertation is concerned with mathematical and empirical modeling to simulate three important chemical reactions (cyclohexene hydrogenation and dehydrogenation, preferential oxidation of carbon monoxide, and the Fischer-Tropsch (F-T) synthesis in a microreaction system.

Empirical modeling and optimization techniques based on experimental design (Central Composite Design (CCD)) and response surface methodology were applied to these three chemical reactions. Regression models were built, and the operating conditions (such as temperature, the ratio of the reactants, and total flow rate) which maximize reactant conversion and product selectivity were determined for each reaction.

A probability model for predicting the probability that a certain species …

Computational Magnetohydrodynamic Investigation Of Flux Compression And Implosion Dynamics In A Z-Pinch Plasma With An Azimuthally Opposed Magnetic Field Configuration, Kyle John Peterson

Doctoral Dissertations

Magnetic flux compression is a well established technique for the generation of ultrahigh magnetic fields, large currents, and large energy densities. It has been suggested as a means for power density amplification on Z-pinch generators such as Decade Quad, at Arnold Engineering Development Center, and it may be especially suitable as a means for producing higher powers of K-shell radiation from high atomic number loads such as titanium. Although many one-dimensional models of flux compression on Z-pinch generators exist, an improvement in understanding is needed about the physics and implosion dynamics on a two-dimensional level. To this end, a two-dimensional …

“Design Of Molecular Mechanics Modeling Techniques For Exploring Molecular Recognition Using Cyclodextrins., Shannon Bradley Fox

Doctoral Dissertations

Molecular mechanics modeling techniques have been developed to study the behavior of cyclodextrins (CDs) in capillary electrophoresis (CE) separations. Using the commercial computational package, Sybyl, the mechanisms of molecular recognition between organic analytes and CDs are investigated.

Cyclodextrin-modified capillary electrochromatography (CDCE) experiments were conducted to separate neutral derivitized naphthalene solutes using carboxymethyl-beta-cyclodextrin (CM-b-CD). Grid conformation-searching programs were developed to explore the interaction space between CD and solute and to calculate their interaction energies using molecular mechanics. The interaction energies correlated remarkably well with the separation behavior. It was found that extensive minimization (more than 3000 iterations) was required at each …

Production In Au-Au Collisions, Robert Jason Newby

Doctoral Dissertations

This thesis presents the first J/ Ψ production analysis of Au+Au reactions at forward rapidity at p √sNN = 200 GeV. In the second year of RHIC running, design energy was achieved in the collisions of both Au+Au ions and proton+proton reactions. The production of the J/Ψ is measured by the PHENIX experiment in Au+Au collisions as well as in proton-proton collisions. The scientific goal is to investigate the nature of hot, dense nuclear matter capitalizing on the unique properties of the J/ Ψ as a probe of this matter. Recent experimental results by the NA50 collaboration at CERN …

A High Shear-Rate Optical Rheometer For Complex Fluids, Khaled S. Mriziq

Doctoral Dissertations

A parallel-plate optical rheometer in a magnetic-disc drive configuration has been designed and constructed of optically transparent materials and operating with a very small gap to obtain rheological and structural measurements at very high shear rates.

The friction force at the disk-slider interface has been measured as a function of sliding speed while the film thickness was monitored in situ using a capacitance technique. The shear rate is calculated from the film thickness and the sliding speed. A thin film can be applied on the disk, which allows very high-shear-rate measurements at low sliding speeds with negligible viscous heating.

Both …

Modeling Of The Inverse Heat -Conduction Problem With Application To Laser Chemical Vapor Deposition And Bioheat Transfer, Peng Zhen

Doctoral Dissertations

This dissertation consists of two parts. Part one deals with three-dimensional laser induced chemical vapor deposition (3D-LCVD), whereas part two deals with a Pennes model of a 3D skin structure. LCVD is an important technique in manufacturing complex micro-structures with high aspect ratio. In part one, a numerical model was developed for simulating kinetically-limited growth of an axisymmetric cylindrical rod by pre-specifying the surface temperature distribution required for growing the rod and then by obtaining optimized laser power that gives rise to the pre-specified temperature distribution. The temperature distribution at the surface of the rod was assumed to be at …

Strategies For Enhancing The Performance Of Chemical Sensors Based On Microcantilever Sensors, Christopher Tipple

Doctoral Dissertations

Microcantilever (MC) based chemical sensors have become more widely used during the past 10 years due to the advantages they possess over other chemical sensors. One of the most significant characteristics is their extremely high surface to volume ratio. This key facet allows surface forces that can be ignored on a macroscale to become a significant sensing transduction mechanism. MC based sensors also exhibit a higher mass sensitivity to adsorbates than do many other chemical sensor platforms. Under many conditions, MC based sensors directly translate changes in Gibbs free energies due to analyte-surface interactions into mechanical responses. However, the widespread …

Thermodynamics And Kinetics Of Defects At Surfaces, Tianjiao Zhang

Doctoral Dissertations

Fundamental understanding of the various electronic and structural properties at surfaces is a prerequisite for improved control of nanometer-scale patterning of surfaces for potential technological applications. In this dissertation, we have used multi-scale theoretical approaches to investigate the thermodynamic and kinetic properties of a few elemental types of surface defects. The multi-scale approaches range from first-principles calculations within density functional theory to empirical embedded atom method (EAM) to statistical analysis to kinetic Monte Carlo simulations. In studying the thermodynamic properties of intrinsic line defects on a vicinal TaC(910) surface, our Monte Carlo simulations in comparison with scanning tuning microscope (STM) …

Data Access In Wide Area Networks Of Heterogeneous Workstations, Kim Buckner

Doctoral Dissertations

The accessibility of data in wide area networks can be difficult. This research shows the use of the Internet Backplane Protocol (IBP) along with a modified version of the C standard I/O library that can allow data to be easily accessible without having to make major modifications to legacy code. In fact if legacy programs only use standard input and output routines, they need only be recompiled to effect a homogeneous file system. It also demonstrates that this access is predictable enough to make decisions on what data to access and in what fashion that access is most effective.

“Enhancement Of Sensitivity And Selectivity Of Chemical Sensors Through Thin Film Coatings And Surface Modifications, Joseph Jeremy Headrick

Doctoral Dissertations

Chemical sensors have become major analytical tools for how we monitor
and obtain information about the chemical nature of ourselves and our
surroundings. Two characteristics of chemical sensors that are under constant
development and improvement are their selectivity and their sensitivity.
Selectivity is a concern of any chemical sensor, without it the signal obtained by
a chemical sensor cannot be related to the target species concentration with any
confidence. With chemical sensors the selectivity is generally created by the
used of a chemical recognition layer such as a permeable membrane, or a thin
chemical film. The sensitivity of a chemical …

Eigenvalue Dependence On Problem Parameters For Stieltjes Sturm-Liouville Problems, Laurie Elizabeth Battle

Doctoral Dissertations

This work examines generalized Stieltjes Sturm-Liouville boundary value problems with particular consideration of self-adjoint problems. Of central importance is determining conditions under which the eigenvalues depend continuously and differentiably on the problem data. These results can be applied to various physical problems, such as constructing beams to maximize the fundamental frequency of vibration, or constructing columns to maximize the height without buckling. These problems involve maximizing the smallest eigenvalues of Sturm-Liouville equations, and the continuous dependence of the eigenvalues on the problem parameters can be used to accomplish this.

We first consider the generalized 2n-dimensional initial value problem dy …

Computational Models For Diusion Of Second Messengers In Visual Transduction, Harihar Khanal

Doctoral Dissertations

The process of phototransduction, whereby light is converted into an electrical response in retinal rod and cone photoreceptors, involves, as a crucial step, the diffusion of cytoplasmic signaling molecules, termed second messengers. A barrier to mathematical and computational modeling is the complex geometry of the rod outer segment which contains about 1000 thin discs. Most current investigations on the subject assume a well stirred bulk aqueous environment thereby avoiding such geometrical complexity. We present theoretical and computational spatio-temporal models for phototransduction in vertebrate rod photoreceptors, which are pointwise in nature and thus take into account the complex geometry of the …

A Preemption-Based Meta-Scheduling System For Distributed Computing, Sathish Vadhiyar

Doctoral Dissertations

This research aims at designing and building a scheduling framework for distributed computing systems with the primary objectives of providing fast response times to the users, delivering high system throughput and accommodating maximum number of applications into the systems. The author claims that the above mentioned objectives are the most important objectives for scheduling in recent distributed computing systems, especially Grid computing environments.

In order to achieve the objectives of the scheduling framework, the scheduler employs arbitration of application-level schedules and preemption of executing jobs under certain conditions. In application-level scheduling, the user develops a schedule for his application using …

Studies Of Electroosmotic Flow Dynamics During Electrophoretic Separations, Jason Lasseter Pittman

Doctoral Dissertations

Instrumentation and techniques for monitoring electroosmotic flow (EOF) during capillary electrophoretic (CE) separations in both fused-silica capillaries and glass microfluidic devices are presented. These techniques were applied under conventional and sample stacking separation conditions. The instrumentation developed for monitoring EOF was also used to develop optically gated vacancy separations in microfluidic devices.

A recently developed technique for monitoring EOF in capillary electrophoresis by periodic photobleaching of a neutral fluorophore added to the running buffer was further characterized and optimized and then applied to monitoring EOF during a typical capillary electrophoresis separation. The concentration of neutral fluorophore (rhodamine B) added to …

The Role Of Surface States In Electron-Phonon Coupling On The Open Surfaces Of Simple Metals, Shu-Jung Tang

Doctoral Dissertations

Symmetry is the beauty of nature. It is the mirror of the way nature minimizes the energy of the system, and achieves the stable state. In the bulk crystal, 3D symmetry has ensured the minimum of free energy contributed by electrostatic energy, vibrational energy and many body self-energy. When the crystal is broken to form two surfaces, the 3D symmetry is destroyed, leading to high free energy on the surface. In order to minimize the free energy, the electronic charge on or near the surface rearranges to form an electronic and lattice structure quite distinct from the bulk. My research …

“Applications Of Coherent Electron Beams, Alexander Erwin Thesen

Doctoral Dissertations

The use of coherent beams for interferometric measurements has gained great popularity in light optics over the last several decades. The availability of coherent electron sources has now opened the door to apply the concept of holographic imaging in many new areas. Off-axis holograms can now be recorded in field emission transmission electron microscopes equipped with the electron optical equivalent of a biprism. This technique allows the accurate retrieval of phase and amplitude of the electron wave, which has been transmitted through a sample. The sensitivity of the phase of the electron wave to electrical potentials makes it possible to …

Aspects Of Black Hole Scattering, Suphot Musiri

Doctoral Dissertations

We discuss various aspects of black hole scattering. Firstly, we consider nonextremal rotating black branes. We solve the wave equation for a massless scalar field and calculate the absorption cross section. We obtain a function of two temperature parameters once we move away from extremality, which is similar to the case of Kerr- Newman black holes. We discuss the implications of this result to the AdS/CFT correspondence. Secondly, we study a system of maximally-charged slowly-moving black holes and take the limit of a continuous self-interacting matter distribution (black string). We quantize the system by using the path integral method. We …