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Discontinuous Thermal Expansions and Phase Transformations in Crystals at Higher Temperatures

Description: The purpose of this investigation is to make more detailed studies of transformations. Fourteen compounds have been examined by high temperature X-ray diffraction for this purpose. The investigations have been carried out in such a way as to reveal: 1. the existence of transformations, 2. the influence of polarizability on thermal expansion, 3. the anisotropy of expansion, and 4. the discontinuity of thermal expansion.
Date: 1967
Creator: Hsu, Yuan Tsun
Item Type: Refine your search to only Thesis or Dissertation
Partner: UNT Libraries
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Applications of Metallic Clusters and Nanoparticles via Soft Landing Ion Mobility, from Reduced to Ambient Pressures

Description: Nanoparticles, simple yet groundbreaking objects have led to the discovery of invaluable information due to their physiological, chemical, and physical properties, have become a hot topic in various fields of study including but not limited to chemistry, biology, and physics. In the work presented here, demonstrations of various applications of chemical free nanoparticles are explored, from the determination of a non-invasive method for the study of the exposome via using soft-landing ion mobil… more
Date: August 2018
Creator: Aguilar Ayala, Roberto
Item Type: Refine your search to only Thesis or Dissertation
Partner: UNT Libraries
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Knowledge Discovery of Nanotube Mechanical Properties With an Informatics-Molecular Dynamics Approach

Description: Carbon nanotubes (CNT) have unparalleled mechanical properties, spanning several orders of magnitude over both length and time scales. Computational and experimental results vary greatly, partly due to the multitude of variables. Coupling physics-based molecular dynamics (MD) with informatics methodologies is proposed to navigate the large problem space. The adaptive intermolecular reactive empirical bond order (AIREBO) is used to model short range, long range and torsional interactions. A … more
Date: May 2012
Creator: Borders, Tammie L.
Item Type: Refine your search to only Thesis or Dissertation
Partner: UNT Libraries
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Computational Modeling of Small Molecules

Description: Computational chemistry lies at the intersection of chemistry, physics, mathematics, and computer science, and can be used to explain the behavior of atoms and molecules, as well as to augment experiment. In this work, computational chemistry methods are used to predict structural and energetic properties of small molecules, i.e. molecules with less than 60 atoms. Different aspects of computational chemistry are examined in this work. The importance of examining the converged orbitals obtained … more
Date: December 2015
Creator: Weber, Rebecca J.
Item Type: Refine your search to only Thesis or Dissertation
Partner: UNT Libraries
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Novel Carborane Derived Semiconducting Thin Films for Neutron Detection and Device Applications

Description: Novel carborane (B10C2H12) and aromatic compounds (benzene, pyridine, diaminobenzene) copolymers and composite materials have been fabricated by electron beam induced cross-linking and plasma enhanced chemical vapor deposition (PECVD) respectively. Chemical and electronic structure of these materials were studied using X-ray and ultra-violet photoelectron spectroscopy (XPS and UPS). UPS suggest that the systematic tuning of electronic structure can be achieved by using different aromatic compou… more
Date: August 2015
Creator: James, Robinson
Item Type: Refine your search to only Thesis or Dissertation
Partner: UNT Libraries
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Surface and Interfacial Studies of Metal-Organic Chemical Vapor Deposition of Copper

Description: The nucleation and successful growth of copper (Cu) thin films on diffusion barrier/adhesion promoter substrates during metal-organic chemical vapor deposition (MOCVD) are strongly dependent on the initial Cu precursor-substrate chemistry and surface conditions such as organic contamination and oxidation. This research focuses on the interactions of bis(1,1,1,5,5,5-hexafluoroacetylacetonato)copper(II), [Cu(hfac)2], with polycrystalline tantalum (Ta) and polycrystalline as well as epitaxial tita… more
Date: December 1997
Creator: Nuesca, Guillermo M.
Item Type: Refine your search to only Thesis or Dissertation
Partner: UNT Libraries
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The Pure Rotational Spectra of Diatomics and Halogen-Addition Benzene Measured by Microwave and Radio Frequency Spectrometers

Description: Two aluminum spherical mirrors with radii of 203.2 mm and radii of curvature also of 203.2 mm have been used to construct a tunable Fabry-Perót type resonator operational at frequencies as low as 500 MHz. The resonator has been incorporated into a pulsed nozzle, Fourier transform, Balle-Flygare spectrometer. The spectrometer is of use in recording low J transitions of large asymmetric molecules where the spectra are often greatly simplified compared to higher frequency regions. The resonators u… more
Date: August 2010
Creator: Etchison, Kerry C.
Item Type: Refine your search to only Thesis or Dissertation
Partner: UNT Libraries
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Properties of Molecular Rydberg States

Description: Many of the bands in the vapor-phase far-ultraviolet absorption spectra of simple molecules can often be fit to mathematical progressions referred to as molecular Rydberg series. The name Rydberg arises from the similarity between the Rydberg formula for the atomic hydrogen spectrum and the formulae for the progressions found in molecular spectra. The theories of molecular Rydberg transitions and states are discussed in terms of the inferences that have been made in the past from the available … more
Date: December 1974
Creator: Scott, John Delmoth
Item Type: Refine your search to only Thesis or Dissertation
Partner: UNT Libraries
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Design and Development of Soft Landing Ion Mobility: A Novel Instrument for Preparative Material Development

Description: The design and fabrication of a novel soft landing instrument Soft Landing Ion Mobility (SLIM) is described here. Topics covered include history of soft landing, gas phase mobility theory, the design and fabrication of SLIM, as well as applications pertaining to soft landing. Principle applications devised for this instrument involved the gas phase separation and selection of an ionized component from a multicomponent gas phase mixture as combing technique to optimize coatings, catalyst, and a … more
Date: August 2011
Creator: Davila, Stephen Juan
Item Type: Refine your search to only Thesis or Dissertation
Partner: UNT Libraries
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The Development of an Analytical Microwave Electromagnetic Pulse Transmission Probe and Preliminary Test Results

Description: Within this educational endeavor instrumental development was explored through the investigation of microwave induce stable electromagnetic waves within a non-linear yttrium iron garnet ferromagnetic waveguide. The resulting magnetostatic surface waves were investigated as a possible method of rapid analytical evaluation of material composition. Initial analytical results indicate that the interaction seen between wave and material electric and magnetic fields will allow phase coherence recover… more
Date: May 2011
Creator: Griffith, William Francis
Item Type: Refine your search to only Thesis or Dissertation
Partner: UNT Libraries

Parameterization of Ionic Liquids and Applications in Various Chemical Systems

Description: In this work, the development of parameters for a series of imidazolium-based ionic liquids molecules, now included in the AMOEBA force field, is discussed. The quality of obtained parameters is tested in a variety of calculations to reproduce structural, thermodynamic, and transport properties. First, it is proposed a novel method to parameterize in a faster, and more efficient way parameters for the AMOEBA force field that can be applied to any imidazolim-based cation. Second, AMOEBA-IL polar… more
This item is restricted from view until January 1, 2028.
Date: December 2022
Creator: Vazquez Cervantes, Jose Enrique
Item Type: Refine your search to only Thesis or Dissertation
Partner: UNT Libraries

Machine Learning in Computational Chemistry

Description: Machine learning and artificial intelligence are increasingly becoming mainstream in our daily lives, from smart algorithms that recognize us online to cars that can drive themselves. In this defense, the intersection of machine learning and computational chemistry are applied to the generation of new PFAS molecules that are less toxic than those currently used today without sacrificing the unique properties that make them desirable for industrial use. Additionally, machine learning is used t… more
This item is restricted from view until June 1, 2024.
Date: May 2022
Creator: Kuntz, David Micah
Item Type: Refine your search to only Thesis or Dissertation
Partner: UNT Libraries
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Miniature Mass Spectrometry: Theory, Development and Applications

Description: As mass analyzer technology has continued to improve over the last fifty years, the prospect of field-portable mass spectrometers has garnered interest from many research groups and organizations. Designing a field portable instrument entails more than the scaling down of current commercial systems. Additional considerations such as power consumption, vacuum requirements and ruggedization also play key roles. In this research, two avenues were pursued in the initial development of a portable… more
Date: December 2013
Creator: Fox, James D.
Item Type: Refine your search to only Thesis or Dissertation
Partner: UNT Libraries
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Thermochemical Study of Crystalline Solutes Dissolved in Ternary Hydrogen-Bonding Solvent Mixtures

Description: The purpose of this dissertation is to investigate the thermochemical properties of nonelectrolyte solutes dissolved in ternary solvent mixtures, and to develop mathematical expressions for predicting and describing behavior in the solvent mixtures. Forty-five ternary solvent systems were studied containing an ether (Methyl tert-butyl ether, Dibutyl ether, or 1,4-Dioxane), an alcohol (1-Propanol, 2-Propanol, 1-Butanol, 2-Butanol, or 2-Methyl-1-propanol), and an alkane (Cyclohexane, Heptane, or… more
Date: May 2001
Creator: Pribyla, Karen J.
Item Type: Refine your search to only Thesis or Dissertation
Partner: UNT Libraries
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Nuclear Magnetic Resonance Spectra of Some 1,2,4-triazoles

Description: In the work undertaken here, NMR has been used to ascertain the structure of some 1,2,4-triazoles. The investigation provides information concerning the structure of potentially tautomeric triazoles such as hydroxy- and aminotriazole. Connected with this aspect of triazole chemistry is the larger problem of mesohydric tautomerism. The present study also yields information for a comparison of substituent effects in triazoles, N-heteroaromatic substances and benzene.
Date: January 1967
Creator: Creagh, Linda Truitt
Item Type: Refine your search to only Thesis or Dissertation
Partner: UNT Libraries
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Examining and Characterizing Changes in First Year High School Chemistry Curricula

Description: Many students currently entering college are able to solve mathematical problems but often do not understand the chemistry concepts underlying their calculations. High school chemistry teachers from Texas and the United States (US) were surveyed as to what topics they teach in their chemistry classes. A subset of Texas teachers was also interviewed about their instruction. The survey indicated that less-experienced Texas teachers are omitting a number of topics from their chemistry instruction,… more
Date: August 2010
Creator: Holley, Kerry Kathleen McGee
Item Type: Refine your search to only Thesis or Dissertation
Partner: UNT Libraries
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Computational Study of Intermolecular Interactions in Complex Chemical Systems

Description: This work discusses applications of computational simulations to a wide variety of chemical systems, to investigate intermolecular interactions to develop force field parameters and gain new insights into chemical reactivity and structure stability. First, we cover the characterization of hydrogen-bonding interactions in pyrazine tetracarboxamide complexes employing quantum topological analyses. Second we describe the use of quantum mechanical energy decomposition analysis (EDA) and non-covalen… more
Date: May 2020
Creator: Vazquez Montelongo, Erik Antonio
Item Type: Refine your search to only Thesis or Dissertation
Partner: UNT Libraries
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Interfacial Electrochemistry and Surface Characterization: Hydrogen Terminated Silicon, Electrolessly Deposited Palladium & Platinum on Pyrolyzed Photoresist Films and Electrodeposited Copper on Iridium

Description: Hydrogen terminated silicon surfaces play an important role in the integrated circuit (IC) industry. Ultra-pure water is extensively used for the cleaning and surface preparation of silicon surfaces. This work studies the effects of ultra-pure water on hydrogen passivated silicon surfaces in a short time frame of 120 minutes using fourier transform infrared spectroscopy – attenuated total reflection techniques. Varying conditions of ultra-pure water are used. This includes dissolved oxygen poor… more
Date: December 2003
Creator: Chan, Raymond
Item Type: Refine your search to only Thesis or Dissertation
Partner: UNT Libraries
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Affordances of Instrumentation in General Chemistry Laboratories

Description: The purpose of this study is to find out what students in the first chemistry course at the undergraduate level (general chemistry for science majors) know about the affordances of instrumentation used in the general chemistry laboratory and how their knowledge develops over time. Overall, students see the PASCO™ system as a useful and accurate measuring tool for general chemistry labs. They see the probeware as easy to use, portable, and able to interact with computers. Students find that the … more
Date: August 2010
Creator: Sherman, Kristin Mary Daniels
Item Type: Refine your search to only Thesis or Dissertation
Partner: UNT Libraries
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Impact of Texas High School Science Teacher Credentials on Student Performance in High School Science

Description: A study was conducted to determine the relationship between the credentials held by science teachers who taught at a school that administered the Science Texas Assessment on Knowledge and Skills (Science TAKS), the state standardized exam in science, at grade 11 and student performance on a state standardized exam in science administered in grade 11. Years of teaching experience, teacher certification type(s), highest degree level held, teacher and school demographic information, and the percen… more
Date: August 2012
Creator: George, Anna Ray Bayless
Item Type: Refine your search to only Thesis or Dissertation
Partner: UNT Libraries
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A Study of Silver: an Alternative Maldi Matrix for Low Weight Compounds and Mass Spectrometry Imaging

Description: Soft-landing ion mobility has applicability in a variety of areas. The ability to produce material and collect a sufficient amount for further analysis and applications is the key goal of this technique. Soft-landing ion mobility has provided a way to deposit material in a controllable fashion, and can be tailored to specific applications. Changing the conditions at which soft-landing ion mobility occurs effects the characteristics of the resulting particles (size, distribution/coverage on t… more
Date: May 2014
Creator: Walton, Barbara Lynn
Item Type: Refine your search to only Thesis or Dissertation
Partner: UNT Libraries
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Stoichiometry and Deposition Temperature Dependence of the Microstructural and Electrical Properties of Barium Strontium Titanate Thin Films

Description: Barium Strontium Titanate (BST) was deposited on Pt/ZrO2 / SiO2/Si substrates using liquid source metal organic chemical vapor deposition. A stoichiometry series was deposited with various GrII/Ti ratios (0.658 to 1.022) and a temperature series was deposited at 550 to 700°C. The thin films were characterized using transmission electron microscopy. Both series of samples contained cubic perovskite BST and an amorphous phase. The grain size increased and the volume fraction of amorphous phase de… more
Date: May 1998
Creator: Pena, Piedad
Item Type: Refine your search to only Thesis or Dissertation
Partner: UNT Libraries
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Molecular Modeling Study of Oxidative Degradation of Polyperfluoroethers Catalyzed by Iron Fluoride Surfaces : An Extended Hückel Theory Approach

Description: Extended Hückel methods are known to be a useful tool in understanding surface phenomena. Important quantities about atoms and chemical bonds can be obtained from this computationally simple method, although caution must be exercised in interpreting the results. Application of Extended Hückel calculations to large metal clusters reveals the role of d orbitals in solids. Basic ideas of constructing model compounds have been developed. Several model systems for surface chemisorption processes are… more
Date: May 1995
Creator: Wang, Yanbin
Item Type: Refine your search to only Thesis or Dissertation
Partner: UNT Libraries
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