Theses and Dissertations from UMD
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New submissions to the thesis/dissertation collections are added automatically as they are received from the Graduate School. Currently, the Graduate School deposits all theses and dissertations from a given semester after the official graduation date. This means that there may be up to a 4 month delay in the appearance of a give thesis/dissertation in DRUM
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Item EXAMINING QUINONE CONTRIBUTION TO THE OPTICAL PROPERTIES OF CHROMOPHORIC DISSOLVED ORGANIC MATTER(2024) Ashmore, Rachel; Blough, Neil; Chemistry; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Chromophoric Dissolved Organic Matter (CDOM) in natural waters is largely responsiblefor absorption of light and photochemistry in the water, impacting environmental reactions and aquatic life. The composition of CDOM is greatly varied based on source, photochemical reactions, and natural cycles. The impact of quinone moieties on this structure and photochemical and redox reactions involving CDOM remains the subject of controversy. To investigate the impact of quinone structure on optical properties, model quinone compounds were thoroughly characterized by their optical properties and reactions with sodium dithionite and sodium sulfite. A series of methyl-substituted p-benzoquinones, a methoxy p-benzoquinone, and a range of napthoquinones and anthraquinones were investigated. These model compounds were characterized according to their quinone and hydroquinone molar absorptivities and fluorescence quantum yields. Sodium dithionite reduction of quinones and the impact of structure on the products of this reaction was investigated by reducing the quinones with both sodium dithionite and sodium sulfite and comparing the optical properties of the products to those of the quinone and hydroquinone. The spectra of dithionite reduced p-benzoquinones and napthoquinones suggested the presence of products other than the hydroquinone. Sulfite is produced in solution as a result of dithionite reduction of quinones. Model quinones were therefore also reduced with sodium sulfite to investigate the impact of this side reaction on the dithionite reduction products. High performance liquid chromatography (HPLC) was used to further investigate and quantify the products of dithionite reduction of quinones and the importance of sulfite interference. Although some of the model quinones react with sulfite to form a proposed sulfonated hydroquinone product, based on the observed extent of this reaction in dithionite reductions, the structures of quinones likely to be found in CDOM, and their relatively small contribution to CDOM optical properties, the sulfite reaction was determined to not significantly impact the study of quinone moieties in CDOM. Dithionite selectively reduces quinones, while borohydride reduces ketones, aldehydes, and quinones. Therefore, in CDOM samples, dithionite can be used to isolate the effects of quinone moieties on the optical properties. Dithionite reduction was used to analyse CDOM standards and natural water extracts from the North Pacific Ocean and the Chesapeake Bay to investigate quinone contribution to their optical properties. These results are compared to borohydride reduction results from Cartisano and McDonnell to compare the contribution of quinones to that of ketones and aldehydes. (1, 2) Dithionite reduction showed small impacts on absorbance and fluorescence, whereas significant changes in both were observed for borohydride reduction. Therefore, the optical changes observed under borohydride reduction are attributed to primarily ketones and aldehydes rather than quinones. Model quinones showed significant changes in fluorescence intensity due to dithionite reduction, which are largely not observed for CDOM standards and natural water extracts, further supporting the conclusion that their role in CDOM optical properties is small.Item CAPTURING SOUND: THE METHODS OF ARRANGING AND EXECUTING INSTRUMENTAL SOUNDS BETWEEN ORCHESTRA AND PIANO(2020) Koelzer, Christopher; Sloan, Rita; Music; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)The piano stands today as a romantic instrument, designed to produce large amounts of sound, a wide range of dynamic contrasts, and infinite voicing possibilities. The piano’s ability to create and sustain harmonies across its over seven- octave range provides composers a single instrument to express the harmonic expanses of an entire orchestra. Through the nineteenth century, composers around the world imbued orchestral characteristics into their pianistic writing. In contrast, some composers took the opposite route and began orchestrating solo piano works. This dissertation explored several orchestral works transcribed for piano across selected genres in order to portray the techniques necessary to most accurately represent the intricate collaboration of orchestral textures and production of sound through the piano. The pieces performed were as follows: Claude Debussy’s Nocturnes, arranged by Maurice Ravel for two piano, four-hands; Igor Stravinsky’s Le sacre du printemps, arranged by the composer for one piano, four-hands; Johannes Brahms’ Variations on a Theme of Haydn, originally scored for two pianos, four-hands; and Sergei Rachmaninoff’s Symphonic Dances, arranged by the composer for two pianos, four- hands. Collaborators included pianists Dr. Nadežda Mijatović-Sekicki and Dr. Alexei Ulitin. These works were presented at the University of Maryland’s Gildenhorn Recital Hall on September 30, 2018, and December 8, 2019. In lieu of performing the third D.M.A. lecture recital, this dissertation encompassed additional chapters of detailed processes and suggestions on how to facilitate transcriptions and reductions at the piano. Recital recordings can be found in the Digital Repository at the University of Maryland (DRUM).Item The Metaphysics of Multi-Level Explanation(2013) McElhoes, David; Frisch, Mathias; Philosophy; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)It is widely presumed that the world exhibits hierarchical structure: that the objects of science can be arranged into levels and that some of those levels are higher than others. Organisms, on this view, are at a higher level than cells, which are at a higher level than molecules, which are at a higher level than atoms. Although it is popular, this "layered worldview" faces notable challenges. Some critics contend that it is hopelessly idealized or even ultimately incoherent. Others contend that it makes no difference to our explanatory practices and has no metaphysical or epistemic significance. I argue that these critics are mistaken. By undertaking a comprehensive analysis of the logical and metaphysical nature of hierarchical structures and their application within contemporary philosophy and ecology, I argue for three claims: that hierarchies exist (insofar as the objects of scientific discourse exist); that the domain of ecological interests is hierarchically structured in a way that is incompatible with ontological reductionism - the idea that everything in the scientific domain is, in fact, contained within the "fundamental level of reality"; and that the hierarchical structure of the world often (but not always) justifies the practice of describing, explaining, and analyzing things using hierarchical terms. My analysis begins with a review of the existing accounts of hierarchies in ecology, biology, sociology, and economics. Arguing that these accounts are inadequate, I then develop an improved account called Core Hierarchy Theory (CHT). CHT, I argue, is an improvement over its predecessors in two respects: generality and simplicity. Other accounts are either too narrow (e.g., failing to count branching hierarchies as genuine hierarchies) or make unnecessary theoretical commitments. Using a formalized version of CHT, I then prove four theorems that are relevant to well-known philosophical debates that involve hierarchies. For example, I show that two of the core metaphysical commitments of the ontological reductionist - that the higher level sciences reduce to fundamental science and that all of reality is, in fact, contained within the fundamental level - are in fact inconsistent with the most basic and unrestricted conception of hierarchical structures provided by CHT.Item USE OF TARTARIC ACID AND ISOPROPYL ALCOHOL IN THE REDUCTION OF HEXAVALENT CHROMIUM AND APPLICATION TO CHROMIUM CONTAMINATED SOILS AND CHROMITE ORE PROCESSING RESIDUE(2012) Brose, Dominic A.; James, Bruce R; Environmental Science and Technology; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Although chromium (Cr) is a naturally occurring metal, in the oxidation state +(VI), it is a health concern when present in soils and natural waters due to its solubility and toxicity. Tartaric acid and isopropyl alcohol were evaluated for reduction of Cr(VI) at environmentally relevant pH values, in the presence of soils, and from chromite ore processing residue (COPR). Soil samples were taken from profiles located in delineations of five soil mapping units in Maryland, USA: Christiana-Russett Complex, Askecksy, Annapolis, Jackland, and Ingleside. In solution, the rate of reduction of Cr(VI) by the tartaric acid-Cr-isopropyl alcohol complex was lowered from 0.128 to 0.011 h-1 as pH was raised from 3.0 to 5.0; however, in the presence of the Russett and Jackland soils, the rates of reduction were 0.037 and 0.020 h-1, respectively despite pH values of 5.3 and 5.0. In addition to Cr(VI) reduction, 97.6 and 89.9 µM Mn(II), and 427 and 67.6 µM Fe(II) were solubilized from the Russett and Jackland soils, respectively. Adding soluble Mn2+ and Fe3+ to the five soils with tartaric acid and isopropyl alcohol enhanced reduction of Cr(VI) in all soils, with the addition of Mn2+ enhancing reduction by an additional 0.27 mM Cr(VI) in the Jackland soil and to 1.46 mM in the Downer soil. Furthermore, the addition of tartaric acid and isopropyl alcohol to Mn-oxide coated sand (1.8x10-1 µmol Mn/mg) showed reductive dissolution of Mn(III,/IV)(hydr)oxides, and the resulting Mn(II) enhanced reduction to 1.24 mM (62%) of Cr(VI). When applied to COPR, tartaric acid-Cr-isopropyl alcohol or tartaric acid-Cr-Mn complexes reduced 0.3 mM (30%) Cr(VI), although when COPR was mixed with the Atsion, Collington, or Russett soils, pH values remained below 5.0 and 0.84 mM (84%) of the Cr(VI) was reduced. This work showed that a tartaric acid and isopropyl alcohol solution reductively dissolves Mn(III,/IV)(hydr)oxides from soils, and the resulting Mn(II) enhances reduction of Cr(VI), which can be potentially applied to the reduction of COPR-derived Cr(VI) in a soil remediation strategy.Item Oxidation-Reduction Transformations of Chromium in Aerobic Soils and the Role of Electron-Shuttling Quinones in Chemical and Microbiological Pathways(2008-05-05) Brose, Dominic; James, Bruce R; Plant Science and Landscape Architecture (PSLA); Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Soils from three toposequences in Maryland with minimal heavy metal contamination were sampled to investigate oxidation-reduction transformations of chromium in whole soil samples. Chromium (VI) reduction to Cr(III) was observed in all 18 samples, and 11 demonstrated enhanced reduction with the electron shuttle anthraquinone-2,6-disulfonate (AQDS). Oxidation of Cr(III) to Cr(VI) was observed in 12 samples, and 7 samples demonstrated diminished oxidation with AQDS. Lactate was added to the Watchung series to enhance biological activity, and high salt concentration was added to inhibit it. Both treatments reduced Cr(VI) to below detection limits by 11 d, suggesting abiotic reduction. The control treatment demonstrated reduction of Cr(VI) without soil. To further investigate, increasing lactate concentrations were added to Cr(VI) and AQDS. Reduction increased with increasing concentration; 60 mM lactate reduced all Cr(VI) within 1 hr. Other organic acids were tested for similar interactions; tartrate and citrate reduced Cr(VI), which was enhanced with AQDS.