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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.
351

Synthesis and Characterization of Sulfonated Poly(arylene ether sulfone)s for Membrane Separations

Lane, Ozma Redd 01 February 2016 (has links)
Sulfonated poly(arylene ether sulfone)s are a class of engineering thermoplastics well-known for their mechanical properties and chemical/oxidative stability. The research in this dissertation focuses on modifying the structure of sulfonated poly(arylene ether sulfone)s to improve membrane performance. Blends of a 20% disulfonated poly(arylene ether sulfone) (BPS20) with poly(ethylene glycol) (PEG) were investigated with the objective of promoting water flux across a reverse osmosis membrane. It was considered desirable to investigate poly(arylene ether sulfone)s with a hydroquinone unit that could be controllably post-sulfonated without degradation, providing a polymer with controlled sulfonation through controlling hydroquinone content. It also avoided the disadvantages noted previously in polymers with post-sulfonated biphenol units. Initial experiments focused on determining sulfonation conditions to confirm quantitative sulfonation of the hydroquinone without side reactions or degradation. A polymer with 29 mole % hydroquinone-containing units was used to study the rate of sulfonation. Successful post-sulfonation was confirmed and reaction conditions were applied to a series of polymers with varying hydroquinone comonomer contents. These polymers were sulfonated, characterized and evaluated for transport properties. Of interest was the high sodium rejection in the presence of calcium, which in the directly copolymerized disulfonated materials is compromised. The post-sulfonated poly(arylene ether sulfone)s showed no compromise in sodium rejection in a mixed-feed of sodium chloride and calcium chloride. In the membrane electrolysis of water, Nafion's high permeability to hydrogen, particularly above about 80 C, results in back-diffusion of hydrogen across the membrane. This reduces efficiency, product purity, and long-term electrode stability. Hydrophilic-hydrophobic multiblock copolymers based on disulfonated and non-sulfonated poly(arylene ether sulfone) oligomers feature a lower gas permeability. Various multiblock compositions and casting conditions were investigated and transport properties were characterized. A multiblock poly(arylene ether sulfone) showed a significant improvement in performance over Nafion at 95°C. Multiblock hydrophilic-hydrophobic poly(arylene ether sulfone)s have been extensively investigated as alternatives for proton exchange membrane fuel cells. One concern with these materials is the complicated multi-step synthesis and processing of oligomers, followed by coupling to produce a multiblock copolymer. An streamlined synthetic process was successful for synthesizing membranes with comparable morphologies and performance to a multiblock synthesized via the traditional method. / Ph. D.
352

Investigating Predation in the Fossil Record: Modern Analogs

Tyler, Carrie Leigh 29 March 2012 (has links)
Predation is considered a powerful ecological force influencing community structure, diversity, and abundance. Paleoecology offers a unique perspective, allowing us to examine ecological processes such as predation over evolutionary timescales. The three studies summarized below include two case studies testing the role of predation in evolution and one method-oriented project, which explores new tools with which to examine predator-prey interactions in the fossil record. Considering the importance of community interactions in the current global biodiversity crisis, understanding ecological and evolutionary dimensions of predation is critical to conservation biology and ecology, as predators are thought to play a vital role in maintaining ecosystem health and biodiversity. Predation has been dismissed as a causal mechanism for some major prey groups. For example, the evolutionary decline and cryptic or antitropical distribution of brachiopods is often explained as due to the potentially low energetic value and suspected non-palatability or toxicity of brachiopod tissues. Here we demonstrate that multiple invertebrate marine predators (crustaceans, echinoderms, and gastropods) are willing and able to consume brachiopods, and that predation pressure on the living brachiopod population may be consequential. Examination of the fossil record is consistent with this interpretation: evidence for drilling and repair of brachiopod shells is found throughout the fossil record in multiple orders. This suggests that although brachiopods may be unwanted prey in the presence of energetically more desirable targets, they do appear to be edible and are subject to intense predator-prey interactions. Limpets are important prey for some crab species, yet little is known about the role of durophagy in the evolution of the limpet shell. Feeding trials using three common species of Pacific Northwest limpets (Lottia digitalis, L. pelta and Tectura scutum) were conducted to assess how different shell morphologies affect mortality and handling time. We predicted that large size, shell ornament, and low-spires would result in either increased survivorship, and/or longer handling times. Contrary to our expectation that ridges resist predation, individuals with smooth morphologies experienced significantly lower mortality, as did those with low-spires. As species possessing high-spires and ridges typically occur high in the intertidal where predation risk due to crabs is relatively low, these morphologies are likely adaptions to physical factors such as thermal stress. One of the major caveats of using gastropod drill holes to assess predator-prey interactions in both the modern and the ancient is the correct identification of drill holes of predatory origin. By examining known predatory drill holes using environmental scanning electron microscopy, we aim to refine the development of a novel technique for augmenting their identification, and to explore the relationship between predator body size, predatory radula dentition, and radular microrasping marks observed on the shells of prey organisms. Electron micrographs were used to measure the spacing of microrasping marks produced by the radula, and the intercusp spacing of the radula dentition. A relationship between predator body size and microrasping marks makes it possible to infer predator size from these microtraces in both modern and fossil specimens, augmenting our ability to examine predator-prey interactions throughout the history of this important ecological interaction. Proxies for predation intensity such as predation traces or antipredatory morphologies provide an invaluable method to examine predation in both modern communities, and the fossil record. Our understanding of the importance of predation in regulating biodiversity and in evolution will continue to grow with the development of new methodologies, and a comprehensive understanding of predatory defenses. / Ph. D.
353

Map Creation and Position Correction for an Off the Shelf Mobile Robotic System

Barry, Jeremy Jude 28 May 2004 (has links)
Robots are widely used in domestic and commercial applications. These applications typically involve robots built for a specific the task, thus leading to efficiency in task completion. However, with the increase in completion efficiency comes an increase in the time required for completion of the whole system. Specific tasks create the need for many different robots, all with differing capabilities, causing an increase in development cost and time needed. This raises the issue of whether using an off the shelf system with minor modifications can accurately perform the same tasks. If so, more time can be spent on refining the process leading to completion of the task, resulting in less time spent developing the robot. Consequently, less cost in the life cycle of the system leads to less cost for the end user, thus allowing robots to be used for more applications. This thesis explores using a commercially available robot, Acroname Inc.'s Garcia, to perform mapping and localization tasks. As the robot travels it gathers data about the environment. This data is processed in Matlab and the result of the algorithm is a map. In the creation of the map, mathematical morphology is explored as a means to reduce noise. When the robot has located a corner, Matlab provides the robot with a position estimate correction. This correction allows the robot to better estimate its location resulting in a more accurate map. As the results of this thesis illustrate, with very minor modifications, the robot is capable of accurately performing mapping and localization tasks. The results demonstrate that an off the shelf system is capable of accurately performing tasks for which it was not specifically designed. / Master of Science
354

Bio-based composites that mimic the plant cell wall

Li, Zhuo 04 June 2009 (has links)
Nature creates high performance materials under modest conditions, i.e., neutral pH and ambient temperature and pressure. One of the most significant materials is the plant cell wall. The plant cell wall is a composite of oriented cellulose microfibrils reinforcing a lignin/hemicellulose matrix. In principle, the plant cell wall composite is designed much like a synthetic fiber-reinforced polymer composite. Unlike synthetic composites, the plant cell wall has an excellent combination of high modulus, strength, toughness and low density that originates in the optimal interactions between the biopolymers. Therefore, to produce high performance composites, a unique route may be to mimic a biological system like the plant cell wall. The present work focuses on understanding the thermodynamics of biopolymer assembly to exploit the process in vitro. In our system, we use an already polymerized nanocellulose template and polymerize phenolic monomers on the template using a peroxidase enzyme. In the first part, we have polymerized phenol using horseradish peroxidase (HRP) in the presence of TEMPO-oxidized nanocellulose. Similar to native plant cell wall structures, the polyphenol-nanocellulose composite had intimate mixing of polyphenol and cellulose at the nanoscale with the presence of cellulose promoting a uniquely organized structure. The obtained composite material showed synergy that enhanced the thermal stability, hydrophobicity, and possibly mechanical properties. In the second part, monolignol coniferyl alcohol was polymerized in the presence of nanocellulose by the same procedure. A comparison between the polyphenol composite and poly(coniferyl alcohol) (PCA) composite revealed that the propanyl substitution imparted flexibility to the PCA molecules so that they could bend and form a hollow globule structure to envelope nanocellulose inside. Polyphenol could not do this because of its rigidity. / Master of Science
355

Dual effect of thiol addition on fluorescent polymeric micelles: ON-to-OFF emissive switch and morphology transition

Mabire, A.B., Robin, M.P., Willcock, H., Pitto-Barry, Anaïs, Kirby, N., O'Reilly, R.K. 07 August 2014 (has links)
Yes / The morphology transition from micelles to vesicles of a solution-state self-assembled block copolymer, containing a fluorescent dye at the core–shell interface, has been induced by an addition–elimination reaction using a thiol, and has been shown to be coupled to a simultaneous ON-to-OFF switch in particle fluorescence. / EPSRC and the IAS at the University of Warwick
356

Genetic and morphological variation among populations of Sargassum hemiphyllum (phaeophyta).

January 2003 (has links)
Cheang Chi-chiu. / Thesis (M.Phil.)--Chinese University of Hong Kong, 2003. / Includes bibliographical references (leaves 126-136). / Abstracts in English and Chinese. / Abstract --- p.i / Acknowledgements --- p.vi / Contents --- p.viii / List of Tables --- p.xi / List of Figures --- p.xiii / Chapter CHAPTER 1: --- Introduction and Background --- p.1 / Chapter 1.1 --- Ecology and distribution of the genus Sargassum --- p.1 / Chapter 1.2 --- Classical taxonomy of the genus Sargassum and associated problems --- p.2 / Chapter 1.3 --- Recent approaches on taxonomic studies of Sargassum --- p.4 / Chapter 1.3.1 --- Morphological studies --- p.4 / Chapter 1.3.2 --- Genetic studies --- p.5 / Chapter 1.3.3 --- Integration of genetic and morphological studies --- p.7 / Chapter 1.4 --- Phylogeographic distribution and population dispersal --- p.8 / Chapter 1.5 --- Description of species --- p.11 / Chapter 1.6 --- Objectives --- p.14 / Chapter 1.7 --- Layout of the thesis --- p.15 / Chapter CHAPTER 2: --- Morphological Examination on Sargassum hemiphyllum --- p.17 / Chapter 2.1 --- Introduction --- p.17 / Chapter 2.2 --- Methodology --- p.18 / Chapter 2.2.1 --- Sampling locations and treatment of specimens --- p.18 / Chapter 2.2.2 --- Morphological measurement --- p.22 / Chapter 2.2.3 --- Data analysis and statistical tests --- p.28 / Chapter 2.3 --- Results --- p.31 / Chapter 2.3.1 --- Choosing parameters from preliminary results --- p.31 / Chapter 2.3.2 --- Analysis on the main data set --- p.40 / Chapter 2.3.2.1 --- Layout of the data set --- p.40 / Chapter 2.3.2.2 --- Spatially conservable vs. variable parameters --- p.51 / Chapter 2.3.3 --- Conservable morphological parameters- consensus of specimens --- p.58 / Chapter 2.3.4 --- Variable morphological parameters- variation among specimens based on categorical parameters --- p.58 / Chapter 2.3.5 --- Differentiation of populations based on measurable and numerical parameters --- p.63 / Chapter 2.4 --- Discussion --- p.74 / Chapter 2.4.1 --- Temporal vs. spatial variation in the morphology of Sargassum hemiphyllum --- p.74 / Chapter 2.4.2 --- Spatially conservable characters for the taxonomic identification of Sargassum hemiphyllum --- p.77 / Chapter 2.4.3 --- Variation within Sargassum hemiphyllum --- p.77 / Chapter 2.4.4 --- Variation along the biogeographical gradient --- p.79 / Chapter CHAPTER 3: --- Genetic Analysis of RbcL-S Spacer in Sargassum hemiphyllum --- p.82 / Chapter 3.1 --- Introduction --- p.82 / Chapter 3.2 --- Methodology --- p.87 / Chapter 3.2.1 --- Extraction and purification of DNA --- p.87 / Chapter 3.2.2 --- Polymerase chain reaction (PCR) and gel electrophoresis --- p.87 / Chapter 3.2.3 --- Purification of PCR product --- p.90 / Chapter 3.2.4 --- DNA sequencing --- p.90 / Chapter 3.2.5 --- RFLP study --- p.92 / Chapter 3.2.6 --- Sequence alignment and analysis --- p.92 / Chapter 3.3 --- Results --- p.93 / Chapter 3.3.1 --- Extraction and PCR amplification --- p.93 / Chapter 3.3.2 --- Pilot study --- p.97 / Chapter 3.3.3 --- RFLP study --- p.103 / Chapter 3.4 --- Discussion --- p.108 / Chapter 3.4.1 --- Suitability of RbcL-S spacer as genetic marker at population level --- p.108 / Chapter 3.4.2 --- Two clades vs. two varieties of S. hemiphyllum --- p.109 / Chapter 3.4.3 --- Reproductive barrier --- p.110 / Chapter CHAPTER 4: --- General Discussion --- p.113 / Chapter 4.1 --- Morphological and genetic data- consistence or conflict --- p.113 / Chapter 4.2 --- Latitudinal gradient of seawater temperature in the Pacific NW --- p.115 / Chapter 4.3 --- Fluctuation in seawater salinity in the Pacific NW --- p.118 / Chapter 4.4 --- Possible initiation of speciation --- p.122 / Chapter 4.5 --- Works to be done in the future --- p.123 / References --- p.126
357

INFERENTIAL-REALIZATIONAL MORPHOLOGY AND AFFIX ORDERING: EVIDENCE FROM THE AGREEMENT PATTERNS OF BASQUE AUXILIARY VERBS

Brody, Parker 01 January 2014 (has links)
“No aspect of Basque linguistics has received more attention over the years than the morphology of the verb.” (Trask 1981:1) The current study examines the complex morphological agreement patterns found in the Basque auxiliary verb system as a case in point for discussion of theoretical approaches to inflectional morphology. The traditional syntax-driven treatment of these auxiliaries is contrasted with an inferential, morphology-driven analysis within the Paradigm Function Morphology framework. Additionally, a computational implementation of the current analysis using the DATR lexical knowledge representation language is discussed.
358

Spatial, temporal and ecological correlates of morphological variation among North American freshwater fishes

Jacquemin, Stephen J. 04 May 2013 (has links)
This dissertation outlines the contribution of evolutionary and environmental factors on North American freshwater fish morphological variation. A more thorough understanding of the factors which result in morphological variation is essential to describing patterns of evolutionary diversification, distribution, ecological niche, ontogeny, sexual dimorphism, ecosystem role, community assembly, invasion dynamics, and conservation. This dissertation makes a unique contribution to understanding morphological diversity in freshwater fishes by linking intraspecific and interspecific variation to phylogeny, allometry, sex, habitat niche, geographic niche, hydrology, and long term environmental change. This dissertation is comprised of three chapters which detail large scale macroevolutionary patterns in morphological variation for North American freshwater fishes, long term morphological changes with hydrological alterations in Cyprinidae, and phenotypic plasticity of freshwater drum in the Wabash River. Overall, North American fishes tend to be deeper bodied and more robust with larger body size, in females, in low flow and lentic hydrological conditions, and in taxa with smaller geographic range that occupy more specialized habitat niches. Further, macroevolutionary analysis suggests that the majority of morphological diversification occurred relatively early on in the evolutionary history of North American fishes. / Evolution of North American freshwater fish morphology with variation in habitat use and geographic range -- 100 years of hydrologic alterations and morphological variation in Cyprinidae -- Effects of allometry, sex and river location on morphological variation of freshwater drum Aplodinotus grunniens in the Wabash River, USA. / Department of Biology
359

Influence of etched seedcoats on the durability of soybean seed during conditioning, weatherability in the field, and the effect of cultural practices on the incidence of etched seedcoats in a seedlot

Burchett, Clyde Alan January 2011 (has links)
Typescript (photocopy). / Digitized by Kansas Correctional Industries
360

Pollen morphology of the Leontodontinae (Asteraceae: Lactuceae)

Zeleznak, Kathleen J. January 1978 (has links)
Call number: LD2668 .T4 1978 Z44 / Master of Science

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