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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
1

Thermal Analysis of Milkweed Floss Using TG/FTIR

Gu, Pei 01 April 1992 (has links)
The thermal analysis of milkweed and several individual commercial samples of .similar chemical composition has been carried out. By combining a two-stage thermal process. (pyrolysis-combustion) with TG-FTIR, it has been possible to identify the major organic volatile products during pyrolysis and to correlate gas evolution with the decomposition of the individual components (cellulose, hemicellulose and lignin) of the floss. During pyrolysis, acetic acid, formic acid and methanol are formed 1n addition to CO2, and H2O. The data also show that pyrolytic decomposition of the three chemical constituents of milkweed occur without any apparent synergistic interaction. The combustion of milkweed produced CO2 and H2O, as expected, but the removal of the waxy coating from the fibers results in an increased susceptibility to combustion. The coating displays no effect on the process of pyrolysis.
2

Sulfur dioxide oxidation and nitric oxide decomposition over copper oxide on ʏ-alumina sorbents/catalysts: an infrared diffuse reflectance study

Porbeni, Francis Ebikefe 01 July 1997 (has links)
Copper (II) oxide on ʏ-alumina sorbents/catalysts generated from the thermolysis of supported copper acetylacetonate complex, have shown potential for the possible removal of SO2and NO in a gas stream. These supported metal complexes were prepared by the non-aqueous impregnation of the catalyst precursor {CU(acac)2} on alumina. Diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) was used to investigate the nature of interaction between the support and the π-electron structure of the complex. SO2 adsorption in the absence of added oxygen produced aluminum sulfate species even at 30ºC on all sorbents. The formation of sulfates without added oxygen is suggested to be due to the high dispersion of the metal. Oxidation of chemisorbed SO2 species yielded a copper sulfate band at 1125cm-1. NO adsorption shows that the copper exists primarily as Cu2+ ions on the catalysts. The decomposition of NO is inferred via the formation of a copper-nitrito complex identified at 1628cm-1 absorption band. A sulfated surface appears to stabilize the cupric ions thereby enhancing the NO adsorption.
3

Fluorine analogs of some biologically active adamantanes II. The synthesis of 1--(3-Fluoroadamantyl) ureas

Randolph, Betty Jane 01 December 1975 (has links)
No description available.
4

Pyrolysis Studies of Copper and Copper Phosphate Mixtures on a Tungsten Surface

Poudyal Kharel, Aryashree 24 February 2016 (has links)
<p> The purpose of this research is to identify the chemical species present on a tungsten filament atomizer in the moment prior to the atomization. The first sample prepared was used to investigate the effects of copper samples with phosphate modifier and the second sample investigated the effect of copper samples with pyrophosphate. The aim of this thesis is to investigate the thermal decomposition of copper phosphate on a tungsten surface. An alumina crucible was used to understand the role of tungsten. The project sought to identify the possible copper compounds that remain after drying and pyrolysis in electrothermal atomic absorption spectroscopy. This was carried out by examining the effect of mass loss with the time and temperature. Dry sample residues, prior to and following heating, were studied using thermogravimetric analysis (TGA). X-ray diffraction showed that the starting material before performing TGA analysis was copper phosphate hydrate. The observation showed the formation of copper pyrophosphate at around 600&deg;C for different concentrations of sample prepared. The X-ray diffraction (X-RD) spectra from TGA confirmed the formation of crystalline copper pyrophosphate at around 600 &deg;C. The well separated endo thermal effects correlate to the mass loss steps and characterize thermal behavior of copper pyrophosphate.</p>
5

Development of Ion Mobility and Mass Spectrometry Strategies in Support of Integrated Omics and Systems Biology

Lareau, Nichole Marie 11 March 2016 (has links)
Systems biology greatly enhances the study of complex biological processes by expanding on reductionist approaches that have traditionally focused on individual biological components (i.e. glycomics). Systems biology strategies allow for the comprehensive analysis of biological samples as a whole. To advance these systems analyses strategies, we have developed ion mobility-mass spectrometry (IM-MS) techniques to study biological systems in the gas phase through class specific structural separations. Proteins, lipids, and carbohydrates, which exhibit overlapping signals in a 1-D mass spectrum, are separated in IM-MS because each biomolecular class occupies a unique region of conformational space. Thus, IM-MS analysis is able to differentiate molecules present in complex biological samples with minimal sample purification, greatly improving upon current methodologies. Here, a simple LC-IM-MS method for non-derivatized glycans was described for simultaneous glycomics and proteomics analyses. Glycans released from fetuin were separated on a reverse phase column such that analyses were compatible with proteomics workflows. Novel sequencing workflows were developed utilizing multi-modal fragmentation techniques to obtain finer structural detail of glycoconjugates and glycoproteins. These multi-modal techniques were applied to a carcinoembryonic antigen and show great promise as a more comprehensive sequencing strategy. As many metabolites of interest are decorated with carbohydrate and peptide moieties, parallel studies aim to develop technologies to address the challenges associated with the analysis of these structurally unique small molecules. High throughput chip-based HPLC-IM-MS technologies are well suited for metabolite analysis and lead target prioritization. A series of small molecules were analyzed by chip-based HPLC-IM-MS to compile a database of four-dimensional descriptors to assist dereplication efforts. IM-MS provides broad scale biological structural descriptors, which can be further honed to describe subclass and multiclass descriptors. Combining broad and fine structural studies in this manner creates a toolbox for extensive analyses of metabolomics, glycomics and more generally, integrated omics at large.
6

Ultrafast and Nonlinear Spectroscopy of Colloidal Nanomaterials

Karam, Tony Eugene 15 March 2016 (has links)
In the first part of this dissertation, the adsorption isotherms, resonance coupling, and fluorescence of molecular dyes on the surface of plasmonic nanoparticles are investigates. SHG is also used to investigate the growth of a silver shell on the surface of gold nanoparticles in real time. Additionally, gold-silver-gold core-shell-shell nanoparticles possess extinction peak wavelengths that can be controlled over the visible and near-infrared regions and enhanced photothermal effect. Transient absorption measurements determine that the phonon-phonon scattering lifetime is considerably faster in the core-shell-shell nanoparticles than in the gold nanospheres and gold nanorods, which contributes to the higher photothermal efficiencies. Transient absorption is also used to investigate the ultrafast excited-state relaxation dynamics of the different dyes adsorbed on the core-shell-shell surface and the size-dependent dynamics o interfacial charge transfer between the gold nanoclusters and the TiO2 bandgap in TiO2-Au nanocomposites. In the second part of this dissertation, the ultrafast spectroscopy of size-selected ([Ru(bipy)3][BETI]2) nanoGUMBPS are reported. The nanoGUMBOS show spectral shifts and size-dependent relaxation dynamics. Long-lived acoustic phonon oscillations with size-dependent frequencies are also observed, where the phonon frequency increases as the nanoparticle size increases, suggesting a very low coupling between electronic and phonon degrees of freedom and a strong hydrophobic interaction with the aqueous solvent. Furthermore, Transient absorption measurements of porphyrin-based nanoGUMBOS reveal that efficient electron transfer and energy transfer is observed between the porphyrin groups leading to shorter excited-state lifetimes. Additionally, the excited-state dynamics of brilliant green BETI and carbazole BETI nanoGUMBOS are investigated using pump-probe transient absorption. Brilliant green BETI nanoGUMBOS exhibit enhanced NIR fluorescence compared to the parent dye in water. The overall excited-state dynamics of brilliant green molecular dye in water are longer than those in the colloidal nanoGUMBOS. The torsional degrees of freedom of the phenyl ring in brilliant green are hindered in the nanoGUMBOS. Additionally, the SHG signal of [BG][BETI] nanoGUMBOS is remarkably enhanced due to the increase of the second order susceptibility tensor χ^((2)) of the nanoGUMBOS. Transient absorption measurement of carbazole BETI nanoGUMBOS reveal the presence of optical gain and stimulated emission during the excited-state relaxation dynamics.
7

Contemporary Organic Transformations Enabled by Novel Cationic Processes

Ayala, Caitlan Elizabeth 13 April 2016 (has links)
This dissertation focuses on the development of synthetic methodologies in organic synthesis in two different areas. Chapter 1 discusses the more recent examples of transforming alcohols to their corresponding alkyl chlorides. The first area of our groups research interest is the development of a mild chlorination method from unactivated alcohols, detailed in Chapter 2. Chapter 3 provides an insight into the history of oxyallyl cations, the basis of the second methodology development project in our laboratory. This chapter focuses on the traditional reactions that utilize these reactive intermediates, and it also showcases the concept of direct nucleophilic addition and the applications of the á-indole ketones. Chapters 4 through 7 detail the discovery and development of a novel method involving the use of protected oxyallyl cation intermediates. In these chapters, the reactivity of starting materials, nucleophilic additives, solvents, and catalysts are described in regards to the formation of a variety of distinctive small molecules.
8

Boron Functionalization of BODIPY Dyes, and Their Evaluation as Bioimaging Agents

Nguyen, Alex Long 14 April 2016 (has links)
BODIPY, also known as porphyrins little sister, belongs to a class of fluorescent dyes. It contains a dipyrromethene π-system with a disubstituted boron atom. The basic 4,4-difluoro-4-bora-3a,4a-diaza-s-indacene (BODIPY) is known for its numerous useful applications in the fields of biology and materials. Modification of this well-known fluorophore has been shown to change its photophysical and chemical properties. There has been great interest in the modification at the boron center in recent years for synthesizing new dyads and cascade-type dyes. This work focuses on functionalization at the boron center with carbon and oxygen nucleophiles for further investigation as bioimaging agents. Chapter 1 of this dissertation describes an overview of BODIPYs including synthetic development, post-synthetic functionalization strategies, and how BODIPYs can be involved in many biological applications. Chapter 2 discusses the synthesis, characterization, and computational studies of 4,4-dialkoxy BODIPY and its derivatives. Preliminary studies with various Lewis acids and alcohols will be investigated and discussed. In collaboration with Dr. Petia Bobadova-Parvanova of Rockhurst University, the photophysical properties were studied using computational analysis. The structural, spectroscopic and fluorescence properties of all the synthesized BODIPYs will be studied and be compared. Chapter 3 presents the synthesis and characterization of 4,4-dicyano-BODIPYs. A novel route for preparation of 4,4-difunctionalized BODIPYs bearing phenyl and various substituents at the boron center was developed. These compounds were synthesized in a three step one-pot reaction between dipyrromethenes and dichlorophenylborane, followed by replacement of chloride with fluoride and various carbon- and oxygen-centered nucleophiles. These BODIPYs structural, spectroscopic, and fluorescence properties are reported and discussed. Chapter 4 represents the investigation of six 1,2,3-triazole-BODIPYs under the Cu(I)-catalyzed Huisgen cycloaddition reaction conditions. A novel BODIPY bearing a chiral moiety was synthesized using method C and X-ray crystallography confirmed its identity. Chapter 5 reports the synthesis of chloroalcohol compounds via triphosgene-triethylamine activation. An asymmetric SN1 reaction was investigated through the use of an oxazolidinone.
9

Scanning Electrochemical Microscopy Investigations of Monolayer-protected Gold Nanoparticles and Shewanella oneidensis

Crisostomo, David Allen 28 March 2016 (has links)
As climate change and population growth increase the demand for energy and clean water, research must be to alleviate the increased pressure on the energy-water nexus. In this work, two potential solutions to this problem were investigated: gold nanoparticles and Shewanella oneidensis. Monolayer protected gold nanoparticles have recently been proposed as possible components of improved photovoltaics as nanocapacitors. In order to effectively implement nanoparticles in this field, it is important to understand the electron transfer properties of a variety of protecting ligands. In this research, we determined the forward heterogeneous electron-transfer rate constant of wired organic-soluble and water-soluble monolayer protected gold NPs using the scanning electrochemical microscope (SECM). Using SECM approach curves, we were able to determine the electron transfer rates of nanoparticles protected with a variety of ligands. By altering the monolayer composition through place exchange as well as changing the ligand charge by adjusting solution pH, we demonstrate effective means of modulating electron transfer rates. Shewanella oneidensis bacteria have been noted for potential use in clean energy production and water purification due to its capability to metabolize a variety of species, including insoluble metal oxides and toxic metal species. Again using SECM, we investigated these dissimilarity metal reduction pathways and spatially determine flavin production and consumption of S. oneidensis biofilms. This understanding of the DMR mechanisms is necessary in the optimization for use of S. oneidensis in bioenergy and bioremediation applications.
10

Absolute Quantitative Matrix-Assisted Laser Desorption/Ionization Mass Spectrometry and Imaging Mass Spectrometry of Pharmaceutical Drugs from Biological Specimens

Chumbley, Chad Walter 30 March 2016 (has links)
Matrix-assisted laser desorption/ionization (MALDI) mass spectrometry (MS) allows for the high-throughput analysis of plasma samples for pharmaceutical drugs. A new multiplexing time-of-flight instrument with a continuous raster laser was used to improve the accurate quantitation of drugs in plasma samples using internal standards. This instrument has the capability of isolating and fragmenting multiple analytes of interest from a single laser shot. Quantitative assays of plasma for enalapril using ramipril as the internal standard and for verapamil, enalapril, and promethazine with their respective isotopically labeled internal standards were developed using this instrumentation. Verapamil, enalapril, and ramipril are all drugs used to treat hypertension, while promethazine is an antihistamine. The quantitative accuracies and precision for each analyte improved greatly upon normalization to their respective internal standard. MALDI imaging mass spectrometry (IMS) allows for the elucidation of the distribution of pharmaceutical drugs within tissue sections. Absolute pixel-to-pixel quantitation by MALDI IMS is challenging because of matrix and tissue heterogeneities. Through careful application of isotopically labeled internal standards, accurate quantitative results can be obtained. A homogenously dosed standard tissue was developed to assess different methods of internal standard application. Internal standards with calibration standards on an adjacent non-dosed section were then used to quantitatively determine the distributions of rifampicin, an antibiotic used to treat tuberculosis, and of promethazine when dosed in animal models. The quantitative distribution of rifampicin was elucidated in rabbit livers, while the quantitative distribution of promethazine was elucidated in mouse livers and kidneys. The MALDI IMS data were compared to conventional quantitation methods using HPLC-MS/MS for further validation. The results from all experiments compared favorably to HPLC-MS/MS (>90% similarities), but quantitative MALDI IMS provided the localization of the drugs within the tissue sections. This information is lost when homogenizing the tissue for HPLC-MS/MS analysis. These studies allow for the direct quantitation of pharmaceutical drugs in relation to histological and anatomical features within tissue sections, providing unparalleled information about drugs and their targets.

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