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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.
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Showing 819901 to 819910 of 1984812 (1.184 seconds)| 819901 |
Gold(I)-Catalyzed Synthesis of Polycyclic Frameworks Related to Terpenes: Selective Divergent Synthesis of Fused CarbocyclesBarabe, Francis 07 November 2013 (has links)
Gold catalysis has become an important tool to achieve highly chemoselective p-acid activation. Exceptional reactivity and selectivity are often encountered under mild reaction conditions. These properties have made gold(I) complexes suitable catalysts for tremendous applications in the total synthesis of natural products. The first chapter will highlight a number of total syntheses using gold catalysis as a key step.
The second chapter will cover our application of the gold(I)-catalyzed 6-endo-dig carbocyclization for the synthesis of bridgehead-substituted scaffolds and its use toward the synthesis of PPAP natural products. This research has opened our eyes to the utility of biphenylphosphine ligands, particularly JohnPhos, in gold(I)-catalysis.
The reactivity and selectivity exhibited by gold(I) complexes is modulated by the nature of the ancillary ligand. Recent research rationalizes the impact of these ligands on the divergent reactivity observed between cationic and carbenoid intermediates. Our desire to favor the 6-endo-dig pathway has led us toward the discovery of another example of the diagonal reactivity that NHC carbene and biphenylphosphine ligands can bring to gold(I)-catalysis. Chapter three will explain the development of a selective gold-catalyzed synthesis of fused carbocycles
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Our selective divergent synthesis of fused carbocycles, combined with the Diels–Alder reaction, has brought new synthetic opportunities. Chapter four will describe our approach toward the synthesis of various polycyclic diterpene-related frameworks. Starting with a unique linear precursor, we have developed a new “one-pot” process for the synthesis of three different polycyclic compounds related to the terpenoid family. The facile modulation of the linear precursor and the use of different dienophiles during the Diels–Alder reaction could enable the synthesis of diverse polycyclic analogues based on three principal frameworks.
The gold(I)-catalyzed synthesis of fused carbocycles reached some limitations during our study. Regioselective control was found to be substantially more challenging, with terminal alkynes or alkynes bearing a sterically and electronically neutral methyl substituent. In chapter five, we will discuss how the complementarity of silver(I) catalysis to gold(I) catalysis enabled the selective divergent synthesis of three different fused carbocycles from a unique precursor. Moreover, copper(I) catalysis has given access to the 6-endo-dig pathway on terminal alkynes without the formation of a vinylidene intermediate.
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| 819902 |
Impact of Low Temperature on RNA Splicing of Aberrant Mitochondrial Group II Introns in Wheat EmbryosDalby, Stephen J. 08 November 2013 (has links)
A subset of mitochondrial group II introns of flowering plants has, over evolutionary time, lost characteristic features and employs unconventional splicing pathways. Given the potential impact of cold treatment on RNA folding, as well as on enzymatic activity and import of nuclear-encoded splicing machinery, I have examined the physical excised forms of aberrant introns from wheat embryos subjected to 4oC. My findings suggest a shift in biochemistry with cold treatment to novel splicing pathways that generate heterogeneous in vivo circularized forms for nad1 intron 2, nad2 intron 1 and the cox2 intron, in contrast to predominantly linear excised intron forms at room temperature. Interestingly, the highly degenerate nad1 intron 1, which due to DNA rearrangement has been broken into two halves that interact for splicing in trans, is excised exclusively by first-step hydrolysis at room temperature and under cold treatment. In this case, splicing culminates in two distinct linear half introns that appears correlated with an unusual 5’ terminal insert. This represents the first in vivo demonstration of hydrolytic trans-splicing. Based on northern analysis, cold treatment was further associated with reduced splicing efficiency for all introns surveyed. Moreover, study of precursor transcripts of the nad1a-intron 1a locus suggests the efficiency of end-maturation, including processing of the cotranscribed tRNA-Pro gene, is also reduced in the cold. My findings demonstrate a temperature-sensitivity of transcript maturation, particularly for RNA splicing, providing new insight into the impact of cold growth conditions on plant mitochondrial gene expression.
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| 819903 |
Heritability of Flight Energetics and its Associated Traits in the Bumblebee Bombus ImpatiensBillardon, Fannie 08 November 2013 (has links)
Recent studies suggest a possible correlated evolution of wing morphology, wing beat frequency, muscle biochemistry and flight metabolic rate in bees. In order to investigate the degree to which natural selection can act on these traits, an estimation of heritability was required. Commercial and laboratory reared colonies from wild caught queens were used to estimate narrow-sense (h2) and broad-sense (H2) heritability of flight metabolic rate and its associated traits in the bumblebee Bombus impatiens. h2 estimates obtained from parent-offspring regressions were not statistically significant. H2 estimates were significant for morphological traits (body mass and wing morphology) as well as whole-animal traits (flight and resting metabolic rate, wing beat frequency) in both populations. We suggest that queens have a decrease in flight performance as a result of a trade-off between flight and fecundity, explaining the lack of significance in parent-offspring regressions.
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| 819904 |
In the Coffin of Current U.S. Assimilationist Politics: Reading the Homonormative Politics of Stephanie Meyer's VampireMcFarland, Jami 08 November 2013 (has links)
Broadly, this thesis is a project about queerness and its relationship to Twilight. This thesis seeks to recuperate the queer in the Twilight series. Using discourse analysis, I explore both common and uncommon representations of queerness and the popular and unpopular discourses of Twilight. While both Chapter 1 and 2 offer paranoid readings of the Twilight series and its relationship to queerness, Chapter 3 presents a reparative reading of the text. I argue that Meyer’s tame and conservative vampire, conventionally represented as being either sexually ambiguous or outside the norm, is symptomatic of a modern culture that is becoming more accepting of odd, strange, and/or queer individuals. I maintain, however, that the normalization of specific "ways of being" still comes at the expense of the constitutive “other”. Furthermore, I understand this process of normalizing a monster to be representative of a seemingly apolitical, yet violent, Faludian backlash toward queers.
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| 819905 |
Functional Genetic Analysis Reveals Intricate Roles of Conserved X-box Elements in Yeast Transcriptional RegulationVoll, Sarah 13 November 2013 (has links)
Understanding the functional impact of physical interactions between proteins and
DNA on gene expression is important for developing approaches to correct disease-associated gene dysregulation. I conducted a systematic, functional genetic analysis of protein-DNA interactions in the promoter region of the yeast ribonucleotide reductase
subunit gene RNR3. I measured the transcriptional impact of systematically
perturbing the major transcriptional regulator, Crt1, and three X-box sites on the
DNA known to physically bind Crt1. This analysis revealed interactions between
two of the three X-boxes in the presence of Crt1, and unexpectedly, a significant
functional role of the X-boxes in the absence of Crt1. Further analysis revealed Crt1-
independent regulators of RNR3 that were impacted by X-box perturbation. Taken
together, these results support the notion that higher-order X-box-mediated interactions
are important for RNR3 transcription, and that the X-boxes have unexpected roles in the regulation of RNR3 transcription that extend beyond their interaction with Crt1.
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| 819906 |
Modified Spiegler-Kedem Model to Predict the Rejection and Flux of Nanofiltration Processes at High NaCl ConcentrationsAhmed, Farah N. 13 November 2013 (has links)
Current nanofiltration (NF) models are based on the “diluted solution” assumption and cannot successfully predict permeate fluxes at high salt concentrations. The reasons behind the strong differences between the predicted and observed fluxes are still not fully understood. In this work, it is proposed that these deviations are possibly caused by the electrical charges inside the membrane pores. At a nanoscale level, the complex electrostatic interactions between the highly confined charged solutes and the charges inside membrane pores contribute to flow retardation and this phenomena can be characterized using an additional resistance factor, which is defined as the electric resistance factor in this study. To this extent, experiments were carried out with aqueous sodium chloride (NaCl) solutions in a wide range of concentrations (0.05 – 1.96 M) using two commercial membranes (NF270 and Desal-5 DL). Salt retention was fitted and analysed by means of the classical Spiegler-Kedem model (SK). The model has been modified to include the proposed empirical electric resistance factor, Relec, to account for this additional hydrodynamic flow resistance. The modified Spiegler-Kedem model (MSK) was verified by fitting experimental data at relatively low salt concentration to obtain model parameters and then comparing the model prediction with experimental data at higher concentrations. A mathematical equation was developed to describe the dependence of an important model parameter, reflection coefficient (σ), on operational conditions such as pressure and bulk salt concentration. The thesis also discussed the mechanisms of NF separation, highlighting the electrostatic interaction between the co-ions and the membrane charges in the confined nano-environment inside the NF membrane pores.
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| 819907 |
“Accumulation by Dispossession” by the Global Extractive Industry: The Case of CanadaKinuthia, Wanyee 13 November 2013 (has links)
This thesis draws on David Harvey’s concept of “accumulation by dispossession” and an international political economy (IPE) approach centred on the institutional arrangements and power structures that privilege certain actors and values, in order to critique current capitalist practices of primitive accumulation by the global corporate extractive industry. The thesis examines how accumulation by dispossession by the global extractive industry is facilitated by the “free entry” or “free mining” principle. It does so by focusing on Canada as a leader in the global extractive industry and the spread of this country’s mining laws to other countries – in other words, the transnationalisation of norms in the global extractive industry – so as to maintain a consistent and familiar operating environment for Canadian extractive companies. The transnationalisation of norms is further promoted by key international institutions such as the World Bank, which is also the world’s largest development lender and also plays a key role in shaping the regulations that govern natural resource extraction. The thesis briefly investigates some Canadian examples of resource extraction projects, in order to demonstrate the weaknesses of Canadian mining laws, particularly the lack of protection of landowners’ rights under the free entry system and the subsequent need for “free, prior and informed consent” (FPIC). The thesis also considers some of the challenges to the adoption and implementation of the right to FPIC. These challenges include embedded institutional structures like the free entry mining system, international political economy (IPE) as shaped by international institutions and powerful corporations, as well as concerns regarding ‘local’ power structures or the legitimacy of representatives of communities affected by extractive projects. The thesis concludes that in order for Canada to be truly recognized as a leader in the global extractive industry, it must establish legal norms domestically to ensure that Canadian mining companies and residents can be held accountable when there is evidence of environmental and/or human rights violations associated with the activities of Canadian mining companies abroad. The thesis also concludes that Canada needs to address underlying structural issues such as the free entry mining system and implement FPIC, in order to curb “accumulation by dispossession” by the extractive industry, both domestically and abroad.
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| 819908 |
Adaptive Acquisition Techniques for Spherical Near-Field Antenna MeasurementsBeaulé, Vincent 13 November 2013 (has links)
This thesis presents a practical approach to reduce the overall testing time in a spherical near-field (SNF) antenna measurement environment. The premise of this work is that the acquisition time is mostly dominated by the mechanical movement and the processing electronic. Moreover, it is assumed that the transformation time to go from the near-field domain to the far-field domain (NF-FF transform) is small compared to the acquisition time. Thus this operation can be done repeatedly while the acquisition is on-going without significantly affecting the overall test time.
This situation allows to continuously evaluate the far-field (FF) of the antenna under test (AUT), so that certain decision functions based on the radiation pattern of the antenna can be monitored. Such decision functions are based on the antenna specification, such as the gain, the side lobe level, etc.
We do not proceed with a complete scan of the measurement sphere but effectively allow the probe to follow a directed path under control of an acquisition rule, so that the sampled near-field (NF) datapoints constitute an acquisition map on the sphere. The acquisition can then be terminated based on decision function values, allowing the smallest amount of data needed to ensure accurate determination of the AUT performance measures.
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| 819909 |
Reflections on the Law and Ethics of Regulating Preimplantation Genetic Diagnosis in the United KingdomKrahn, Timothy 14 November 2013 (has links)
The purpose of this thesis is to query the legitimacy of offering preimplantation genetic diagnostic (PGD) testing against Down's syndrome on the basis of United Kingdom (UK) law and policies. I will argue that extending PGD testing for Down’s syndrome as a permissible use of this technology does not (straightforwardly) adhere with the Human Fertilisation and Embryology Authority (HFEA) Code of Practice's stated factors which are to be considered when assessing the appropriateness of PGD applications. Indeed, due consideration of the evidence given in the relevant literature about the capacities and quality of life possible for persons living with Down's syndrome would seriously call into question the validity of a positive judgment recommending PGD as a treatment service for Down's syndrome according to the current UK regulatory instruments. I end the thesis by considering why the HFEA's relatively recent decision to limit client access according to an exclusive list of "serious" and therefore "in principle" test-worthy genetic conditions—understood as legitimate applications for PGD—stands to entrench prejudice, stigma, social bias, and unfair discrimination against the disadvantaged social group of persons living with Down's syndrome.
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| 819910 |
Autobiographical Accounts of Early-Onset Alzheimer's Disease: Obituaries of the Living Dead?Stanley, Daina 14 November 2013 (has links)
The thesis was designed to gain insight into how Alzheimer’s disease influences selfhood from first-personal accounts of illness. The focus of the study was narrowed further by concentrating on the autobiographies of individuals diagnosed with Early-Onset Alzheimer’s disease (EOAD). The purpose of this thesis was to analyze the autobiographies of individuals with EOAD with the aim of understanding their selfhood. In this thesis I argue that, Alzheimer’s disease may influence a change in self, however, the self is not lost entirely. This thesis draws on the philosophical conception of narrated self as it allows for one perpetually constructed self, whereby a change in self does not necessarily mean the self is lost entirely. Through an interpretive analysis of six autobiographical accounts of Alzheimer’s, this thesis demonstrates that Alzheimer’s disease influences a loss of sense of self but that autobiography enables individuals with Alzheimer’s to (re)construct self.
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