119 Matching Results

Search Results

prev Results: 97 - 119
open access

The Correlation Between Carbon-Proton and Proton-Proton Coupling Constants

Description: The correlation between the carbon-proton and proton-proton coupling constants have been studied in various 13 systems. Isocrotonic acid-carboxyl-3C, crotonic acid- 13 13 carboxyl-3C, and 5-norbornene-2-carboxylic acid-carboxyl-3C- 1,5,6,7,7-hexachloro were synthesized and their carbonproton coupling constants were analyzed. Nmr studies showed the magnitudes of the carbon-proton coupling constants to correlate well with analogous protonproton coupling constants, although the values of the coupl… more
Date: December 1975
Creator: Seiwell, Ruth R.
Item Type: Refine your search to only Thesis or Dissertation
Partner: UNT Libraries
open access

Denaturation, Renaturation and Other Structural Studies on Phosphoglucose Isomerases

Description: Structural properties of phosphoglucose isomerases isolated from a variety of species have been compared by peptide fingerprinting, predicted amino acid sequence homologies and by denaturation and renaturation studies. The enzymes are more readily denatured in guanidinium chloride than in urea, and the isomerase isolated from yeast is more stable toward acid pH than the rabbit muscle enzyme. The rates of guanidinium chloride-induced denaturation are markedly increased by ionic strength and decr… more
Date: December 1975
Creator: Young, Clint D.
Item Type: Refine your search to only Thesis or Dissertation
Partner: UNT Libraries
open access

Long-Range Carbon-13--Carbon-13 Spin-Spin Coupling Constants

Description: The study consists of three major areas of research. First, the dihedral angle dependence of vicinal carbon-carbon coupling constants is determined for aliphatic and alicyclic carboxylic acids wherein the formal hybridization and substituents are held constant. Second, the magnitudes and relative signs of long-range carbon-carbon coupling constants in a. triple- 13 C-labeled system are determined and compared with carbon-proton and/or proton-proton coupling constants in geometrically similar co… more
Date: December 1974
Creator: Miller, Denis E.
Item Type: Refine your search to only Thesis or Dissertation
Partner: UNT Libraries
open access

A Materials Approach to Silicon Wafer Level Contamination Issues from the Wet Clean Process

Description: Semiconductor devices are built using hyperpure silicon and very controlled levels of doping to create desired electrical properties. Contamination can alter these precisely controlled electrical properties that can render the device non-functional or unreliable. It is desirable to determine what impurities impact the device and control them. This study consists of four parts: a) determination of acceptable SCI (Standard Clean 1) bath contamination levels using VPD-DSE-GFAAS (Vapor Phase Decomp… more
Date: December 1996
Creator: Hall, Lindsey H. (Lindsey Harrison)
Item Type: Refine your search to only Thesis or Dissertation
Partner: UNT Libraries
open access

Rearrangement of Alkylhaloketene-Cyclopentadiene Adducts in Basic Solution--A New Synthesis of 2-Alkyltropones

Description: This research is concerned with determining whether the previously reported synthesis of tropolone by the solvolysis of the dichloroketene-cyclopentadiene adduct in sodium acetate and acetic acid could be used to prepare 2-alkyltropones from the adducts of alkylhaloketenes and cyclopentadiene. The information obtained from these rearrangements could be useful in determining the mechanism of the ring expansion of halogenated ketene-cyclopentadiene adducts to tropone derivatives.
Date: December 1971
Creator: Hieble, Jacob Paul, 1948-
Item Type: Refine your search to only Thesis or Dissertation
Partner: UNT Libraries
open access

Structure-Activity Studies of Halopyrethroids

Description: The structures of the new pyrethroids were elucidated utilizing nuclear magnetic spectroscopy and elemental analysis. The biological activity of the pyrethroids has been evaluated for houseflies and yellow fever mosquitoes. A correlation of increase in rapid knockdown and toxicity with decrease in size of halogen has been made. The most effective compound, the difluorovinyl ester, has a toxicity of 123 times greater than pyrethrins. This degree of toxicity has not previously been reported for a… more
Date: December 1974
Creator: Brown, Dale Gordon
Item Type: Refine your search to only Thesis or Dissertation
Partner: UNT Libraries
open access

Isolation, Physical and Chemical Characterization of Lecithin:Cholesterol Acyltransferase from Human Plasma

Description: The physiological role of LCAT has been the subject of a number of recent articles (Glomset, 1979; Nilsson-Ehle et al., 1980). According to most current theories, the enzyme functions in combination with high-density lipoproteins in the reverse cholesterol transport pathway which presumably returns peripheral cholesterol to the liver where cholesterol catabolism takes place. Despite the exciting potential for studies on the catalytic function and the nature of the enzyme-substrate complex, the … more
Date: December 1981
Creator: Chong, Kui Song
Item Type: Refine your search to only Thesis or Dissertation
Partner: UNT Libraries
open access

Silver(I) and Copper(I) Complexes from Homoleptic to Heteroleptic: Synthesis, Structure and Characterization

Description: A plethora of novel scientific phenomena and practical applications, such as solid-state molecular solar cells and other optoelectronic devices for energy harvesting and lighting technologies, have catalyzed us to synthesize novel compounds with tunable properties. Synthetic routes, single crystal structures, and spectral and materials properties are described. Reactions of Ag(I) and Cu(I) precursors with various types of ligands -- including the azolates, diimines, and diiphosphines -- lead to… more
Date: December 2018
Creator: Almotawa, Ruaa Mohammed
Item Type: Refine your search to only Thesis or Dissertation
Partner: UNT Libraries

Pressure Controlled Topochemical Polymerization in Two-Dimensional Hybrid Perovskite

Description: Mechanical pressure offers unique control over the energy landscape of chemical reactions, opening up pathways that are inaccessible through conventional thermochemistry. We hypothesize that the reduced dimensionality defines the conformational space of the high-pressure reaction, giving rise to new selectivity that is unavailable in 3D systems. Here, we demonstrate this concept through the pressure-controlled topochemical polymerization of the diacetylene molecule deca‐3,5‐diyn‐1‐amine (DDA) i… more
Date: December 2021
Creator: Abu-Amara, Lama Marwan
Item Type: Refine your search to only Thesis or Dissertation
Partner: UNT Libraries
open access

A Comprehensive Investigation of Photoinduced Electron Transfer and Charge Transfer Mechanisms in Push-Pull Donor-Acceptor Systems: Implications for Energy Harvesting Applications

Description: Donor-acceptor systems exhibit distinctive attributes rendering them highly promising for the emulation of natural photosynthesis and the efficient capture of solar energy. This dissertation is primarily devoted to the investigation of these unique features within diverse donor-acceptor system typologies, encompassing categories such as closely covalently linked, push-pull, supramolecular, and multi-modular donor- acceptor conjugates. The research encompasses an examination of photosynthetic an… more
Date: December 2023
Creator: Alsaleh, Ajyal Zaki
Item Type: Refine your search to only Thesis or Dissertation
Partner: UNT Libraries

Surface Engineering of Materials for Beyond-Microelectronics

Description: All oxide heterostructure Cr2O3/TiO2-x was deposited on Al2O3(0001) single crystal via MBE. The analysis of interfacial interactions involving two metal oxides resulting in magnetic properties gave insights for using such heterostructures as potential spintronic device materials. The corundum phase epitaxial growth of TiO2-x on Al2O3 was characterized using XPS, AES, EELS, and LEED. The data obtained gives evidence of presence of two-dimensional electron gas at titania surface due to oxygen vac… more
This item is restricted from view until January 1, 2029.
Date: December 2023
Creator: Anwar, Fatima
Item Type: Refine your search to only Thesis or Dissertation
Partner: UNT Libraries
open access

Kinetics and Thermochemistry of Halogen and Nitrogen Compounds

Description: Halogen and nitrogen containing compounds play a key role in the atmospheric chemistry of the Earth. Through a mixed computational and experimental approach, the kinetics of these compounds with radicals common to the atmosphere have been explored. Using fundamental measurements such as the IR absorption cross-section, the rate constants of atmospheric reactions and the properties of product molecules have been derived. These results have been further extended to environmental applications such… more
Date: December 2023
Creator: Rawling, George
Item Type: Refine your search to only Thesis or Dissertation
Partner: UNT Libraries

Directing Transition Metal Catalysis of Second and Third Row Metals through Ligand Design

Description: Ligand design is important due to a ligand's ability to tune properties of the transition metals, such as catalytic activity and selectivity. Gold(I) catalysts can be directly impacted by ligands electronically as well as with steric bulk when undergoing enantioselective and regioselective reactions. In the dissertation, a series of gold(I) acyclic diaminocarbenes were synthesized and used to explore the 1,6 enyne cyclization/hydroarylation. The use of metal templated synthesis of the gold(I) a… more
This item is restricted from view until January 1, 2025.
Date: December 2023
Creator: Nguyen, John
Item Type: Refine your search to only Thesis or Dissertation
Partner: UNT Libraries

Synthesis, Characterization, Standardization, and Validation of Luminescence Optical Chemosensors for the Detection of Carbon Dioxide, Aluminum Ions, and Silver Ions for Real-Life Applications

Description: The presented dissertation encompasses three distinct investigations into novel complexes with diverse applications. Firstly, a Europium-based complex, K[Eu(hfa)4], exhibits remarkable potential for detecting dissolved CO2 in an ethylene glycol medium, offering a low limit of detection, rapid response times, and high signal-to-noise ratios. This complex demonstrates promise for quantifying CO2 concentrations and finds utility in sugar fermentation monitoring. Secondly, an innovative ratiometric… more
This item is restricted from view until January 1, 2025.
Date: December 2023
Creator: Perera, Nawagamu Appuhamilage Kasun
Item Type: Refine your search to only Thesis or Dissertation
Partner: UNT Libraries
open access

Cross-Conjugation Effects on Fused β, β'–π–Extended Porphyrins

Description: Cross-conjugation in molecules has been seen in nature for many years but was not pursued due to the difficulty of their synthesis and their lack of stability. Recently, it has become more interesting due to the rise of molecular electronics. Linear conjugation serves well as the wires to conduct electrons, but molecular electronics are made up of more than just wires. Molecules are needed that possess an on/off switch that can allow or deter conduction. Cross-conjugated systems show promise in… more
Date: December 2023
Creator: Washburn, Spenser L.
Item Type: Refine your search to only Thesis or Dissertation
Partner: UNT Libraries
open access

Kinetics and Atmospheric Chemistry Studies of Halogenated Species

Description: Quantitative information about halogenated hydrocarbons is important for understanding their impact on atmospheric ozone chemistry and climate change, their regulation, and the devising of improved substitutes. The Montreal Protocol aimed to regulate the utilization and manufacturing of hydrochlorofluorocarbon compounds (HCFCs), contributing to ozone layer depletion. The 2016 Kigali Amendment to the Montreal Protocol agreement, Annex C listed 274 HCFCs. Only 16 of them have been measured experi… more
Date: December 2023
Creator: Sapkota, Ramesh
Item Type: Refine your search to only Thesis or Dissertation
Partner: UNT Libraries

Design and Development of a Paper Spray Air Sampling Device for Use in Clinical, Defense, and Environmental Applications

Description: Environmental monitoring is becoming increasingly important, primarily in urban areas due to the concentrated levels of human activities. The air sampling device presented is a novel method to sample air which harnesses the power of paper spray ionization paired with the intrinsic advantages of mass spectrometry such as high sensitivity, high selectivity, high throughput, and the ability to monitor multiple compounds at once.
This item is restricted from view until January 1, 2025.
Date: December 2023
Creator: Murillo, Wilbert Alberto
Item Type: Refine your search to only Thesis or Dissertation
Partner: UNT Libraries

Nitrogen Reduction Reaction: Deposition, Characterization and Selectivity of Transition Metal (V, Co and Ti) Oxynitrides as Electrocatalysts

Description: The electrocatalytic nitrogen reduction reaction (NRR) is of considerable interest due to its potential for less energy intensive and environmentally friendly ammonia production which is critical for agricultural and clean energy applications. However, the selectivity of NRR compared to the hydrogen evolution reaction (HER) often poses challenges for various catalysts, including Earth-abundant transition metal oxynitrides like Ti, V, and Co. In this work, a comparative analysis of the selectivi… more
This item is restricted from view until January 1, 2025.
Date: December 2023
Creator: Chukwunenye, Precious O.
Item Type: Refine your search to only Thesis or Dissertation
Partner: UNT Libraries
open access

Acenaphthene and 1,10-Phenanthroline-Fused Βeta-Functionalized Porphyrins

Description: A series of acene-fused porphyrins and 1,10-phenanthroline-fused porphyrins were synthesized and characterized via NMR spectroscopy and mass spectrometry. The acene-fused porphyrins exhibit unique optoelectronic properties, most notably they exhibit highly red-shifted absorption bands. The 1,10-phenanthroline-fused porphyrins are of interest for their ability to bond to as variety of metals to form chelation complexes.
Date: December 2023
Creator: Arvidson, Jacob Randall
Item Type: Refine your search to only Thesis or Dissertation
Partner: UNT Libraries
open access

Metal Nitride Complexes as Potential Catalysts for C-H and N-H Bonds Activation

Description: Recognizing the dual ability of the nitride ligand to react as a nucleophile or an electrophile – depending on the metal and other supporting ligands – is a key to their broad-range reactivity; thus, three DFT studies were initiated to investigate these two factors effects (the metal and supporting ligands) for tuning nitride ligand reactivity for C-H and N-H bond activation/functionalization. We focused on studying these factors effects from both a kinetic and thermodynamic perspective in ord… more
Date: December 2023
Creator: Alharbi, Waad Sulaiman S.
Item Type: Refine your search to only Thesis or Dissertation
Partner: UNT Libraries

Corrosion Mechanism and Prevention of Wire Bonded Device in Microelectronic Manufacturing and Spectroscopic Investigation of Copper Etch Chemical Equilibria for High Density Interconnect Application

Description: In the first part of this dissertation work, Al bond pad corrosion behavior was investigated in the presence of common industrial contaminants such as chloride (Cl-) and fluoride (F-). Al corrosion while in direct contact with Cu displayed rapid hydrogen (H2) gas evolution and dendrite propagation. In contrast, Al without bimetallic contact showed only minor surface roughening. This observed difference in the corrosion mechanism between Cl- and F- is attributed to the solubility of the corrosio… more
Date: December 2021
Creator: Ashok Kumar, Goutham Issac
Item Type: Refine your search to only Thesis or Dissertation
Partner: UNT Libraries
open access

Instrumental Development and Implementation of Portable Membrane Inlet Mass Spectrometry for Homeland Security and Environmental Applications

Description: A rapidly growing topic of great interest is the adaptation of benchtop analytical instrumentation for use in outdoor harsh environments. Some of the areas that stand to benefit from field instrumentation development include government agencies involved with the preservation of the environment and institutions responsible for the safety of the general public. Detection systems are at the forefront of the miniaturization movement as the interest in analyte identification and quantitation appears… more
Date: December 2021
Creator: Anguiano Virgen, Camila
Item Type: Refine your search to only Thesis or Dissertation
Partner: UNT Libraries

Homoleptic and Heteroleptic Platinum(II) Complexes for Organic Light Emitting Diodes and Humidity Sensors: Synthesis, Characterization, and Applications

Description: This dissertation focuses on the design, synthesis, characterization of platinum (II) pyridylazolate complexes and develop high performance organic light emitting diodes (OLEDs) and design and execute high-sensitivity humidity sensors based on the luminescent metal-organic complexes of platinum. A majority of existing platinum compounds do not dissolve in organic solvents, making it difficult to analyze the photophysical characteristics of complexes in solution, a key part of understanding chem… more
This item is restricted from view until January 1, 2029.
Date: December 2023
Creator: Farvid, Seyedmajid
Item Type: Refine your search to only Thesis or Dissertation
Partner: UNT Libraries
Back to Top of Screen