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Full-Text Articles in Physical Sciences and Mathematics

Mixed Quantum-Classical Molecular Dynamics Study Of A Hydrated Electron And An Investigation Of Temperature Control Algorithms, Janet Aremu-Cole Aug 2007

Mixed Quantum-Classical Molecular Dynamics Study Of A Hydrated Electron And An Investigation Of Temperature Control Algorithms, Janet Aremu-Cole

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The use of classical and quantum mechanics has been employed in this dissertation to study temperature control algorithms and a hydrated electron. A comparison of the effects of four commonly used temperature control algorithms on the energetics and dynamics of liquid water has been executed, in efforts to better understand the non-equipartitioning effects caused by some thermostats. The Berendsen, Andersen, Langevin, and velocity rescaling temperature control algorithms were applied to both dimer and bulk water systems, using the TIP4P water model. The two deterministic thermostats, Berendsen and velocity rescaling, display the 'flying ice cube effect' that had been noticed earlier …


Synthesis, Reactions, And Applications Of Bis-Ortho-Diynyl Arene (Boda) Monomers, Polymers, And Derivatives, Mark Perpall May 2007

Synthesis, Reactions, And Applications Of Bis-Ortho-Diynyl Arene (Boda) Monomers, Polymers, And Derivatives, Mark Perpall

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Bis-ortho-diynyl arenes (BODA) monomers contain two arenediyne functional groups with variable functionality at both the linker group, X, and the alkyne terminal group, R. These arenediyne moieties undergo thermal Bergman reactions to cycloaromatize to naphthyl diradical species. The inclusion of two of these arenediyne functionalities allows the polymer to grow without losing processability and solubility as most aromatic polymers do. The second functionality acts as a solubilizing group until all functionalities are consumed in the fully cured network polymer.
When heated above 800 °C, BODA polymer converts to a high-yield glassy carbon material. This work has been extended …


Exploratory Synthesis And Characterization Of New Mixed-Framework Chalcohalides And Oxyhalide And Its Potential Applications For Diluted Magnetic Semiconductor, Lei Wang May 2007

Exploratory Synthesis And Characterization Of New Mixed-Framework Chalcohalides And Oxyhalide And Its Potential Applications For Diluted Magnetic Semiconductor, Lei Wang

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Due to the excellent diverse properties and performance, solid-state material with low-dimensional crystal structure has always been interested by solid-state scientists. Besides the interesting properties, the low-dimensional-structured materials are used as the platform for further research and application of semiconductor and optical devices, as well as theoretic studies. My dissertation research mainly focuses on two aspects: discovery of solids with low-dimensional crystal structure; fabrication and investigation of new materials using the discovered materials as the platform.
The idea of mixed-anion-framework has been used in synthesis of novel low-dimensional-structured solid-state materials. The stereo-active Sb3+/Bi3+ chalcogenides building units and …


Hydrothermal Crystal Growth Of Oxides For Optical Applications, Colin Mcmillen May 2007

Hydrothermal Crystal Growth Of Oxides For Optical Applications, Colin Mcmillen

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There is great interest in obtaining coherent radiation in all regions of the optical spectrum. This dissertation explores the hydrothermal growth of crystals that function in two regions currently inaccessible by solid state devices. The first gap exists in the deep-UV region, particularly below 200 nm. Some materials such as LBO and BBO can generate coherent light at wavelengths as low as 205 nm. The growth of these materials was explored to investigate the feasibility of the hydrothermal method as a new technique for growing these crystals. Particular attention was paid to the descriptive chemistry surrounding these systems, and several …


Adaptive Treatment Of Van Der Waals Interactions In Empirical Bond-Order Potentials With Application To Junction Formation In Carbon Nanotubes, Aibing Liu May 2007

Adaptive Treatment Of Van Der Waals Interactions In Empirical Bond-Order Potentials With Application To Junction Formation In Carbon Nanotubes, Aibing Liu

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Molecular dynamics (MD) simulation of reactive condensed-phase hydrocarbon systems is a challenging research area. The AIREBO potential is particularly useful in this area because it can simulate bond breaking and bond forming during chemical reactions. It also includes non-bonded interactions for systems with significant intermolecular interactions.

The first part of this dissertation describes a method to adaptively incorporate van der Waals interaction of carbon atoms into the AIREBO force field. In bond-order potentials, the covalent bonding interactions adapt to the local chemical environment, allowing bonded interactions to change in response to local chemical changes.
Non-bonded interactions should adjust to their …


The Glow Discharge - A Multifaceted Optical Emission Source: From Solids Analysis To Metalloproteins, Timothy Brewer May 2007

The Glow Discharge - A Multifaceted Optical Emission Source: From Solids Analysis To Metalloproteins, Timothy Brewer

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Glow discharges (GD) are well known for their application to direct solids elemental analysis of metals and alloys by optical emission spectroscopy (GD-OES). The most successful application of GD-OES has been the analysis of solid materials since the GD provides rapid, direct bulk and depth profiling analysis of solids, metals, powders, polymers, glasses and ceramics. However, solids analysis has typically suffered from the lack of true analytical blanks and the inability to study particulate solids in their native state. An approach for the analysis of solid powdered material entrapped in a sol-gel matrix by radio frequency glow discharge optical emission …


Functionalized Nanomaterials: Synthesis, Characterization, And Applications, Liangwei Qu May 2007

Functionalized Nanomaterials: Synthesis, Characterization, And Applications, Liangwei Qu

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Due to their unique electronic, optical, catalytic and mechanical properties, nanomaterials (nanoparticles and nanotubes) have been attracting much attention over the past decades. In this dissertation, polymeric nanoparticles bearing derivatized D-mannose and galactose molecules were prepared via dispersion polymerization and their interactions with various bacterial cells were studied. The results show that there are strong adhesin-specific interactions of the nanoparticles with E. coli cells, resulting significant nanoparticles-madiated cell agglutination.
Poly(ethylene glycol)-coated magnetic polymer nanoparticles were synthesized through miniemulsion polymerization by using macromonomer as both a comonomer and a surfactant. The resulting magnetic polymer nanoparticles were successfully used for bio-detection and …


Analysis Of Nutraceuticals For Toxic Metals: Development And Validation Of Sample Preparation Method, Julia Cooper May 2007

Analysis Of Nutraceuticals For Toxic Metals: Development And Validation Of Sample Preparation Method, Julia Cooper

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With increasing numbers of health-conscious consumers purchasing nutraceutical supplements, total sales in the nutrition industry have soared to over $200 billion in 2006. It is important to assess the safety of these nutraceutical products, with specific regards to toxic metals, including arsenic, cadmium, lead, and mercury. Because species of these metals may be more toxic than others, they can have hazardous health effects if ingested in excess quantities. The work described in this thesis focuses on the development of a sample preparation method for nutraceutical products, specifically ethanolic tinctures and glycerin-based matrices, and analysis of these products by inductively coupled …


Incorporation Of Capillary-Channeled Polymer (C-Cp) Fibers Into Micropipette Tips For Solid Phase Extraction With Applications In Bioanalysis, Donald Fornea Dec 2006

Incorporation Of Capillary-Channeled Polymer (C-Cp) Fibers Into Micropipette Tips For Solid Phase Extraction With Applications In Bioanalysis, Donald Fornea

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Solid phase extraction (SPE), is a widely used sample preparation method that is currently experiencing a surge in research interest, clever architecture/format development, and stationary phase characterization.1-3 SPE devices commonly exist in syringe, cartridge, disk, and micropipette tip formats.4 Micropipette tip SPE has enhanced the determination of proteins by electrospray ionization (ESI) and matrix assisted laser desorption ionization (MALDI) mass spectrometry (MS) by handling micro-liter volumes of sample and buffer removal/solvent exchange.5-7 Buffers have deleterious effects on ionization taking place in MS sources due to preferential ionization, ion suppression effects, and the formation of adduct species competing for ionization in …


Perfluoroalkyl (Aryl) Sulfonimide Zwitterions, Hua Mei Dec 2006

Perfluoroalkyl (Aryl) Sulfonimide Zwitterions, Hua Mei

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This research focuses on superacid perfluoroalkyl(aryl) sulfonimides and their derivatives as a source of stable zwitterionic salts. The strong resonance stabilization of sulfonimides imparts unexpected stability to the zwitterions.
Two types of zwitterions were investigated. The first are symmetrical diaryliodonium zwitterions (DZs) as potential photo acid generators (PAGs) for microlithography. Driven by the demand for smaller feature sizes in the microelectronics industry, microlithography using shorter wavelength light has evolved and new PAGs are of interest. New DZs are potentially useful because they have good thermal stability and may be structurally modified to alter their spectral absorption characteristics. As an extension …


Characterization Of Capillary-Channeled Polymer Fibers As Stationary Phases For High-Performance Liquid Chromatography Of Macromolecules, Dwella Nelson Dec 2006

Characterization Of Capillary-Channeled Polymer Fibers As Stationary Phases For High-Performance Liquid Chromatography Of Macromolecules, Dwella Nelson

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Capillary-channeled polymer (C-CP) fibers are being developed and characterized as high-performance liquid chromatography (HPLC) stationary phases for reversed-phase separations of proteins. Conventional porous phases are not well suited for separating large macromolecules due to the slow diffusivity of the molecules, large diffusional distances, and stagnant mobile phase zones within the column. Stationary phases are continually being developed to address the challenges associated with HPLC of proteins and other macromolecules in general. C-CP fiber stationary phases are an alternative to conventional bead technology and offer a variety of chemical and physical advantages. The fibers can be selected for their chemical functionality …


Path Integral Formulation Of Langeinv Dynamics With Applications To Rare-Event Systems, Bradley Dickson Dec 2006

Path Integral Formulation Of Langeinv Dynamics With Applications To Rare-Event Systems, Bradley Dickson

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In the last decade great efforts have been made to efficiently study the behaviors of rare-event systems. The methods and theories developed in pursuit of this goal are far from unified and are instead applied on a case-by-case basis where one makes a best educated guess as to which approach may afford the greatest chance of studying the rare-event system in question. The work contained here is directed at further development of one of these sets of methods and theories. Specifically, a new theory of dynamics in the Langevin path space is developed with emphasis on generating and sampling Langevin …


The Interaction Between Hydrogen And Various Carbon Allotropes Calculated Using Bond-Order Potentials, Michael Knippenberg Nov 2006

The Interaction Between Hydrogen And Various Carbon Allotropes Calculated Using Bond-Order Potentials, Michael Knippenberg

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Carbon-based materials are an exciting component of materials science. The understanding of interactions at the atomic level provide useful information for creating materials with specific properties. This dissertation examines three hydrocarbon systems: amorphous carbon (with and without hydrogenation), hydrogen adsorption in carbon nanotubes, and reconstructions of the diamond surface.
A melting/quenching procedure is used to produce amorphous carbon films at 2.0, 2.6, and 3.0 g/cm3. The sp3 fraction at each density is calculated and found to be qualitatively similar to experimental data at low densities. The inclusion of hydrogen in the amorphous film causes the sp3 …


New Enantioselective Lewis Acid Catalysts, Mustafa Guzel Dec 1996

New Enantioselective Lewis Acid Catalysts, Mustafa Guzel

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Recently, many organic chemists have been ultimately interested in research in the synthesis of enantiomerically pure organics which are useful to synthesis of biologically active agents and prodrug substances. In the past decades, the new concepts in catalyst design unexpectedly explored the direction of natural product synthesis. In many cases, using enantioselective catalysts are the most suitable and efficient method into enantiopure systems.