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Solar coronal stability problemsHardie, Ian S. January 1993 (has links)
Magnetohydrodynamic stability theory provides a powerful tool for understanding and testing hypothesized mathematical and physical models of observed phenomena on the surface of the Sun. In this thesis, the problem of applying the 'correct' boundary conditions at the photospheric/coronal interface used in modelling coronal arcades is tackled. Then some aspects of the stability of coronal loops and arcades are investigated using a Fourier truncated series approximation for the equation of motion. The problem involving the boundary conditions has been the subject of a controversy for the past decade with two principal conditions suggested, the 'rigid-wall' conditions where all perturbations vanish at the interface, and 'flow-through' conditions where flows parallel to the equilibrium magnetic field take place. By modelling the photosphere and corona as two different density regions and then varying the ratio of the densities of the two regions, growth rates and eigen-functions of both ideal and resistive modes are investigated in order to follow the evolution of the modes as the density ratio is increased. In order to simplify the analysis, the 2-D equations are reduced to 1-D equations by taking a WKB approximation for the spatial variations across the field to give a localized ballooning approach with ordinary differential equations along the fieldlines. Stability of coronal loops to kink modes transformed to localized modes by increasing the poloidal wavenumber, m, is investigated. Two fields generated numerically from the Grad-Shafranov equation and three analytic fields are investigated in detail and the effect of pressure on the marginal loop length is found, both for near force-free conditions such as is found in the solar corona, and away from force-free conditions. It was found that for near force-free conditions, kink modes are the most unstable with localized modes the most stable. As pressure and pressure gradients become important, there is a reversal in the most unstable modes with localized modes the most unstable.
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Internal rotation about C-C and C-N bondsHamlin, Sally-Anne January 1978 (has links)
A study of the historical and more recent work on rotation about carbon-carbon and carbon-nitrogen bonds was the basis for the further investigation of three series of compounds: 1. 2,2'-disubstituted biphenyls, 2. N-benzyl-N-tosyl substituted anilines, 3. substituted quinone-anils. From this work it was established that, in certain compounds, the free energy (ΔG*) for hindered rotation cannot be discussed solely in steric terms but that electronic influences should also be considered. In. the substituted aniline series, it was concluded that a Hammett type correlation existed between the electronegativity of the substituents para to the amino group and the value of ΔG*. This correlation was extrapolated to explain the electronic influence of the substituents ortho to the amino group. Consideration was paid to the possibility that, for the ortho substituents, steric factors may outweigh electronic factors. An attempt was made to extend this correlation to explain the electronic influence of 2'- and 4'-substituents upon the ΔG* values and rates of racemization of-substituted biphenyls. However, it was found that the simple Hammett correlation was not followed and that, for the racemization studies, the entropy of activation (ΔS*) became a significant factor. The values of ΔG* for hindered rotation were obtained from the analysis of 100MHz n.m.r. spectra. The validity of these ΔG* values was discussed with respect to their accuracy and with respect to the effect of entropy. The synthetic routes used to obtain the three series of compounds were also discussed. The discussion of the synthetic routes includes the attempted preparations of a number of quinone-anils via the condensation of 2,6-di-t-butyl-l,4-benzoquinone with 4-substituted 2-benaylanilines. This was complicated by the production of impure samples of 2-benzylaniline and 2-benayl-4-chloroaniline. The synthesis of 2-benzyl-4-nitroaniline was not reproducible. The condensation reaction resulted in a number of products. These were separated by crystallization techniques and identified by high pressure liquid chromatography, I.R. spectroscopy, -13C and proton n.m.r. The structure of a new compound based on a dihydroindole containing one spiro carbon joined to a substituted quinone ring is proposed.
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Reactive intermediates in the reactions of aryl halides with basesHall, Julia Kathleen Aylmer January 1969 (has links)
The reaction of a series of 2,6-dimethylaryl halides with strong base has been investigated. Debromination to give polymethylbenzenes has been found to occur in all the systems studied and varying amounts of higher-boiling products, mainly polymethyl-bibenzyls, have also been obtained. Various mechanisms for these new reactions are discussed and the participation of an unusual triplet carbene intermediate is suggested. The related thermal decomposition of sodium o-halophenates has also been investigated. The participation of a similar carbene intermediate in this reaction appears to be unlikely. Possible mechanisms for the formation of diphenylmethanes obtained in the decomposition of sodium pentachlorophenate in methylbenzenes, are discussed.
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The whisky industry and the regional Scottish economy : an economic analysis of the impact of imminent innovations in public policyHaines, Paul January 1998 (has links)
This dissertation analyses imminent innovations in public policy that will impact upon the whisky industry, and, through linkage adjustments, the regional Scottish economy. An analysis of the interconnectedness between the whisky industry and the wider Scottish economy reveals that such linkages are substantial. A holistic conspectus of the whisky industry in the first part of the dissertation reveals that the predominant form of structural change in the past has been merger & acquisition. Such consolidation has permitted economies in marketing & distribution, but it is contended that in this arena at least there is scope for further performance improvement in the industry. Nevertheless, with taxation forming such a significant proportion of the final price of the product, realising a sustained increase in demand is deemed to be largely outwith the capability of the industry. It is advanced, therefore, that two tax-related developments in public policy in the next few years will impact not merely upon the whisky industry, but materially upon the regional Scottish economy as well. The first of these imminent innovations examined is the proposed abolition of the intra-EU duty free concession in 1999. Whilst it is concluded that such a move is inevitable (and economically logical), it is nonetheless determined that this will have a meaningful detrimental impact upon the whisky industry and Scottish economy. Secondly, the current proposals of the European Commission for the harmonisation of alcohol excises across the European Union are critically appraised, and are shown to be grounded on no logical economic principles, but instead, enshrine protection for European vinicultures. The rationale for alcohol taxation is considered de novo, concluding that within the United Kingdom & across the European Union, at a minimum all alcoholic beverages should be taxed on an equal basis according to alcoholic content, at a level sufficient to cover an estimate of the negative externalities associated with alcohol consumption. Mindful of the importance of the whisky industry to the Scottish economy, it is revealed that in times past, the public authorities have been proactive in intervening to secure the continuing prosperity of the whisky industry, and it is contended that such a stance may be required of the present government. The dissertation concludes by advocating a set of reforms to the structure of alcohol excises in the United Kingdom. An approximate halving of the excise applied to spirits, such that all alcoholic beverages are taxed equally according to alcoholic content, would ensure that the whisky industry & government could lobby with credibility for comparable structures to be adopted overseas, particularly in any revised proposals for European excise harmonisation. In addition, it is suggested that the fillip such a reform would give to domestic sales of whisky would mitigate the negative effects upon the whisky industry & regional Scottish economy of losing the intra-EU duty free concession in 1999.
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Estudo da eletro-oxidação da mistura H2/CO utilizando eletrocatalisadores à base de Pt/C e Céria dopada com Ítria ou Rutênio para aplicação em células a combustível de membrana polimérica condutora de prótons / Study of electro-oxidation the mix H2/CO using Pt/C Etek and yttria or ruthenium doped ceria electrocatalysts for proton exchange membrane fuel cellLulio, Ligia Cristina D'Aloia 06 August 2012 (has links)
As formulações de eletrocatalisadores Pt:(Ce0,9Y0,1O2)+Pt/C Etek, Pt:(Ce0,9Ru0,1O2)+Pt/C Etek, Pt:Ce0,9Y0,1O2/C e Pt:Ce0,9Ru0,1O2+RuO2/C foram preparados pelo método da redução por álcool e caracterizados por difração de raios X (DRX) e microscopia eletrônica de transmissão (MET). A tolerância ao CO foi estudada utilizando o stripping de CO e medidas de curvas de polarização em células unitárias alimentadas com misturas de H2/CO no ânodo e oxigênio no cátodo, na temperatura de 80ºC e pressão absoluta de 2 bar para ânodo e cátodo. Os testes em células a combustível tipo PEMFC mostraram que a oxidação do CO adsorvido a CO2 na superfície da platina ocorre em potenciais menos positivos quando comparado com o catalisador comercial, Pt/C Etek, mostrando tolerância ao CO adsorvido nos eletrocatalisadores de Pt:Ce0,9Y0,1O2/C e Pt:(Ce0,9Ru0,1O2+RuO2)/C. / Pt:(Ce0,9Y0,1O2)+Pt/C Etek, Pt:(Ce0,9Ru0,1O2)+Pt/C Etek, Pt:Ce0,9Y0,1O2/C e Pt:Ce0,9Ru0,1O2+RuO2/C electrocatalysts, were prepared by an alcohol reduction process. The electrocatalysts were characterized by X-Ray Difratometry (XRD) end Transmission Electronic Microscopy (TEM). the CO tolerance was studied using CO stripping and measurements of polarization curves single-cell fed with H2/CO mixture at the anode and oxygen at the cathode, at a temperature of 85ºC and absolute pressure of 2 bar for anode and cathode. The results showed that the oxidation of CO adsorbed to CO2 on the surface of platinum occur at less positive potentials compared to Pt/C Etek showing the tolerance to CO adsorbed on these Pt:Ce0,9Y0,1O2/C e Pt:(Ce0,9Ru0,1O2+RuO2)/C electrocatalysts.
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Estudo da eletro-oxidação da mistura H2/CO utilizando eletrocatalisadores à base de Pt/C e Céria dopada com Ítria ou Rutênio para aplicação em células a combustível de membrana polimérica condutora de prótons / Study of electro-oxidation the mix H2/CO using Pt/C Etek and yttria or ruthenium doped ceria electrocatalysts for proton exchange membrane fuel cellLigia Cristina D'Aloia Lulio 06 August 2012 (has links)
As formulações de eletrocatalisadores Pt:(Ce0,9Y0,1O2)+Pt/C Etek, Pt:(Ce0,9Ru0,1O2)+Pt/C Etek, Pt:Ce0,9Y0,1O2/C e Pt:Ce0,9Ru0,1O2+RuO2/C foram preparados pelo método da redução por álcool e caracterizados por difração de raios X (DRX) e microscopia eletrônica de transmissão (MET). A tolerância ao CO foi estudada utilizando o stripping de CO e medidas de curvas de polarização em células unitárias alimentadas com misturas de H2/CO no ânodo e oxigênio no cátodo, na temperatura de 80ºC e pressão absoluta de 2 bar para ânodo e cátodo. Os testes em células a combustível tipo PEMFC mostraram que a oxidação do CO adsorvido a CO2 na superfície da platina ocorre em potenciais menos positivos quando comparado com o catalisador comercial, Pt/C Etek, mostrando tolerância ao CO adsorvido nos eletrocatalisadores de Pt:Ce0,9Y0,1O2/C e Pt:(Ce0,9Ru0,1O2+RuO2)/C. / Pt:(Ce0,9Y0,1O2)+Pt/C Etek, Pt:(Ce0,9Ru0,1O2)+Pt/C Etek, Pt:Ce0,9Y0,1O2/C e Pt:Ce0,9Ru0,1O2+RuO2/C electrocatalysts, were prepared by an alcohol reduction process. The electrocatalysts were characterized by X-Ray Difratometry (XRD) end Transmission Electronic Microscopy (TEM). the CO tolerance was studied using CO stripping and measurements of polarization curves single-cell fed with H2/CO mixture at the anode and oxygen at the cathode, at a temperature of 85ºC and absolute pressure of 2 bar for anode and cathode. The results showed that the oxidation of CO adsorbed to CO2 on the surface of platinum occur at less positive potentials compared to Pt/C Etek showing the tolerance to CO adsorbed on these Pt:Ce0,9Y0,1O2/C e Pt:(Ce0,9Ru0,1O2+RuO2)/C electrocatalysts.
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The date of the call of the Prophet Jeremiah : texts and issuesHastings, Robert Scott January 1999 (has links)
This dissertation entitled, "The Date of the Call of the Prophet Jeremiah: Texts and Issues," attempts to demonstrate that the most plausible date for the beginning of the prophetic career of Jeremiah is that provided in the tradition itself, i.e. the thirteenth year of Josiah (627). In supporting this, two main topics are addressed. First, the alternative dates which have been forwarded in modern scholarship are examined, and shown to be based upon untenable ideas. Secondly, the various objections which have been proffered against the 627 date are analysed, and the case is made that these objections are invalid. Finally, an attempt is made to explain the message and activity of the prophet within the historical milieu of Judah in the years 627-622. The current study develops this thesis in seven chapters. The first chapter discusses the historical context of the years 640-609, and Josiah's reforms. In chapter two it is argued that the prose sermons should be attributed to Jeremiah, and represent a style of the seventh century. Chapter three demonstrates the implausibility of the alternative dating proposals, while in chapter four it is proposed that the threatened invader of the foe from the north oracles was not originally identified by Jeremiah. The issue of Isaiah and the reforms of Hezekiah as a comparable example is handled in chapter five. Chapter six addresses Jeremiah's attitude toward the cultic reforms of Josiah and the appearance of Deuteronomy in 622, and it is shown that the prophet did speak out in support of the newly published law book. Finally in chapter seven, Jeremiah's relative withdrawal from public activity during the period 622-609 is demonstrated, and the prophet's message is explained in light of the setting of the years 627-622.
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Organisational culture and service quality : an exploratory case study based investigation of Scottish universities' residential functionHammady, Sherief H. January 1999 (has links)
Research on the relationship between organisational culture and service quality is still in its early stages. Mostly, the evidence in such research tends to be either prescriptive or anecdotal. Based on the literature survey conducted it is the purpose of this study to offer a framework by which both concepts could be integrated. Utilising an exploratory case study design, qualitative and quantitative data from two Scottish Universities' student residential service has been collected. Quantitative data was collected through student service quality questionnaires. Performance based measurement was deemed the most appropriate. Qualitative data was gathered through in-depth interviews with members of the service as well as the examination of organisational publications. Association between questionnaire variables as well as the coding of the qualitative data, formed the backbone of two case studies examining the interaction between organisational culture and service quality. It has been demonstrated from the data the utility of the framework, in terms of data fit as well as explanatory power. It has been found in the results that the existing organisational cultures put more of an emphasis on tangible aspects of the service package. However, this research aims to demonstrate that an equal emphasis on the intangible service aspects is needed. That is potentially, the intangibles may offer more in terms of the enhancement of the service experience. Consequently, organisational culture analysis is put forward as the means for enhancing the intangibles of the service.
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Noble Gas Collision Induced Vibrational Relaxation of (v=1) para-H2Weir, Douglas January 2001 (has links)
Close coupling scattering calculations have been conducted for the para spin modification of H<sub>2</sub>-{He, Ne and Ar}. The XC(fit) potential energy surfaces for H<sub>2</sub>-Ne and H<sub>2</sub>-Ar have been used for calculations for these two systems, while a newly fitted version of the Schaefer and Kohler potential energy surface was used for the H<sub>2</sub>-He system. The fitting procedure employs nine modified Lennard-Jones oscillator functions to describe accurately 90% of the original tabulated potential energy surface to better than 12% error. The scattering calculations for H<sub>2</sub>-Arfailed at higher energies due to the presence of a previously undocumented potential energy surface turn-over at R less than 1. 0 Angstroms. Manifold-to-manifold v=1 vibrational relaxation calculations for each of these systems are compared with other experimental and theoretical calculations. These comparisons demonstrate a common discrepancy between previous calculations and the current calculations for each system. The current vibrational relaxation rate constants are generally too small when compared to low temperature values of Audibert et al. and Orlikowski, and the high temperature values obtained by Flower et al. and Dove andTeitelbaum. The current calculations indicate the presence of a dramatic up-turn in the low temperature H<sub>2</sub>-He rate constants. Other experimental and theoretical treatments do not exhibit this same up-turn, which is puzzling. A set of follow-up calculations featuring a larger basis set (such as the {16,12,10,8} Flower et al. basis set) and a larger manifold of included relaxation pathways are needed to improve these calculations.
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Noble Gas Collision Induced Vibrational Relaxation of (v=1) para-H2Weir, Douglas January 2001 (has links)
Close coupling scattering calculations have been conducted for the para spin modification of H<sub>2</sub>-{He, Ne and Ar}. The XC(fit) potential energy surfaces for H<sub>2</sub>-Ne and H<sub>2</sub>-Ar have been used for calculations for these two systems, while a newly fitted version of the Schaefer and Kohler potential energy surface was used for the H<sub>2</sub>-He system. The fitting procedure employs nine modified Lennard-Jones oscillator functions to describe accurately 90% of the original tabulated potential energy surface to better than 12% error. The scattering calculations for H<sub>2</sub>-Arfailed at higher energies due to the presence of a previously undocumented potential energy surface turn-over at R less than 1. 0 Angstroms. Manifold-to-manifold v=1 vibrational relaxation calculations for each of these systems are compared with other experimental and theoretical calculations. These comparisons demonstrate a common discrepancy between previous calculations and the current calculations for each system. The current vibrational relaxation rate constants are generally too small when compared to low temperature values of Audibert et al. and Orlikowski, and the high temperature values obtained by Flower et al. and Dove andTeitelbaum. The current calculations indicate the presence of a dramatic up-turn in the low temperature H<sub>2</sub>-He rate constants. Other experimental and theoretical treatments do not exhibit this same up-turn, which is puzzling. A set of follow-up calculations featuring a larger basis set (such as the {16,12,10,8} Flower et al. basis set) and a larger manifold of included relaxation pathways are needed to improve these calculations.
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