Thesis (Ph. D.)--University of Oregon, 2005. / Typescript. Includes vita and abstract. Includes bibliographical references (leaves 75-82). Also available for download via the World Wide Web; free to University of Oregon users.

Thesis (MS)--Montana State University--Bozeman, 2009. / Typescript. Chairperson, Graduate Committee: Clain Jones. Includes bibliographical references.

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With the gradual depletion of the non-renewable fossil fuel resources and the emerging environmental concerns, the need of exploring renewable synthesis routes of our daily basic stocks is rising. Due to the large contribution to the global primary energy (up to 40% in some countries), biomass has recently been advocated to be one of the most promising alternatives for fossil fuel. This thesis focuses on the catalytic transformations of biomass or biomass derived molecules into valuable small alcohols such as methanol, ethanol, and propanol, which can be used as both fuel and chemical synthesis intermediates. Novel catalysts with high activity and selectivity toward target products are desperately required in the development of renewable chemical synthesis routes. In the past 200 years, platinum metal catalysts have been widely used in the industry. But nowadays, Pd is attracting increasing attentions due to (i) its similar physicochemical properties to those of Pt, (ii) its higher natural abundance than Pt. Alloying has been demonstrated as an effective method in enhancing the catalytic properties of noble metals. In this thesis, a new and facile method for the preparation of supported bimetallic NPs with tunable compositions is developed. Through the establishment of a type II hetero-junction in support, controllable amounts of metallic atoms can be derived from the reduction of the metal oxide support, with the assistance of a supported noble metal. A series of extremely small Pd-based bimetallic NPs with a variety of modifier atoms at tunable compositions, namely PdFe, PdCo, PdNi and PdZn, have been synthesized by this method. These novel bimetallic NPs are applied to the catalytic conversion of biomass or biomass derived molecules containing repeating vicinal diol units. It is demonstrated that the catalytic performance of Pd in bimetallic phase is governed by the d-band structure. The high degree of d-band filling and high d-band center position favour the selective C-O cleavage in hydrogenolysis of vicinal diol units. On the other hand, the selective C-C cleavage can be achieved by lowering the d-band filling of the Pd-based bimetallic NPs. The specificity of C-C bond rupture over that of C-O increases in order of PdZn < PdNi < PdCo < PdFe, with progressive d-band filling reduction, eventually reaches 95% in a series of vicinal diols hydrogenolysis. As a result, small alcohols are produced with high selectivity as the degradation products of biomass molecules when PdFe bimetallic NPs are employed as catalyst. Conversely, by incorporating Co atoms at high concentration, PdCo exhibits a high selectivity in breaking C-O bond of ethylene glycol due to the raised d-band center position and gives ethanol as the main product. Pd@Zn bimetallic NPs with an imperfect core(Pd)-shell(Zn) structure were used in a methanol synthesis route from biomass transformation via CO₂ hydrogenation (CO₂/H₂ is produced from low temperature reforming of biomass resource). The Zn shell not only enhances the catalytic activity of Pd metal towards methanol synthesis, but also suppresses the reverse water gas shift (RWGS) reaction in which CO is produced as a by-product. Methanol can be produced as the main product over CO on the Zn rich Pd@Zn surface, even at low pressure. The methanol turnover frequency (TOF) on the exposed Pd site reaches 1.9 ×10^-1 s^-1 with a selectivity of 70% at 2 MPa. The enhancement is attributed to the increasing d-band filling of Pd@Zn bimetallic NPs by the progressive decoration of Zn on Pd surface, which selectively stabilizes the precursor of methanol (HCOO) over that of CO (COOH). Also, the PdZn catalyst with high ability in dissociating H2 reduces the activation barrier for methanol synthesis. The results presented in this thesis, for the first time, signify the possibility of fine-tuning of product specificity of biomass conversion simply by rationally modifying the electronic properties of the Pd-based catalysts. More importantly, these catalysts will help to diversify the energy generation and relieve our dependence on fossil fuels.

xvii, 183 p. : ill. (some col.) A print copy of this thesis is available through the UO Libraries. Search the library catalog for the location and call number. / In recent years, nanoscience has evolved from a multidisciplinary research concept to a primary scientific frontier. Rapid technological advancements have led to the development of nanoscale device components, advanced sensors, and novel biomimetic materials. However, potential negative impacts of nanomaterials are sometimes overlooked during the discovery phase of research. The implementation of green chemistry principles can enhance nanoscience by maximizing safety and efficiency while minimizing the environmental and societal impacts of nanomaterials. This dissertation introduces the concept of green nanosynthesis, demonstrating the application of green chemistry to the synthesis of nanornaterials. A comprehensive review of the synthesis of metal nanomaterials is presented, demonstrating how individual green chemistry principles can improve traditional synthetic routes as well as guide the design of new materials. Detailed examples of greener syntheses of functionalized gold nanoparticles with core diameters of 2-10 nm are described in subsequent chapters, beginning with a method for functionalizing citrate-stabilized gold nanoparticles that are desirable for advanced applications. Although citrate-stabilized gold nanoparticles can be easily produced from a classic procedure using mild reagents and benign methods, functionalization via ligand exchange is often unsuccessful. It was discovered that an ill-defined layer comprised of citrate and other ligands interferes with functionalization processes. By removing excess citrate in a manner where overall structure and stability is maintained, gold cores produced by this route are readily functionalized by incoming thiols, affording unprecedented control over surface composition and functionality. A direct route to functional nanomaterials using Bunte salt precursors is discussed next, describing the use of easily synthesized shelf-stable alternatives to thiols in the preparation of water-soluble gold nanoparticles. Control of core size and surface chemistry is demonstrated through simple manipulation of reagent ratios, yielding products similar to those produced by traditional direct syntheses which rely on the use of thiols. The use of functionalized nanoparticles as "building blocks" for more complex structures was demonstrated in self-assembly processes. Cationic gold particles were deposited upon DNA scaffolds to create linear arrays. A discussion of the future outlook of green nanosynthesis concludes this work, identifying immediate challenges and long-term goals. This dissertation contains previously published and co-authored materials. / Adviser: James E. Hutchison

Made available in DSpace on 2014-06-12T18:03:00Z (GMT). No. of bitstreams: 2 arquivo7692_1.pdf: 156573 bytes, checksum: efbcda03282532417ac013b427e5ca96 (MD5) license.txt: 1748 bytes, checksum: 8a4605be74aa9ea9d79846c1fba20a33 (MD5) Previous issue date: 2000 / A versão de ALCANC infinito da hamiltoniana de Hubbard pode ser resolvida exatamente em qualquer dimensão. Em banda semi-cheia, o modelo apresenta uma transição metal-isolante (Mott) como função da interação quando seu valor é exatamente igual à largura da banda. Em nosso trabalho, estudamos este modelo em uma dimensão, onde o calculo exato da função de Green de 1- partícula permite obter a densidade de estudos modificada pela interação. Um diagrama de fase é então obtido. Obtemos também a função de correlação densidade-densidade e a susceptibilidade magnética do sistema. Em dimensão d>2, utilizamos uma densidade de estados parabólica e obtivemos numericamente várias das quantidades acima mencionadas. Nossos resultados evidenciaram diversas características microscópicas da transição Mott neste modelo

Orientador: Jose Bellandi Filho / Dissertação (mestrado) - Universidade Estadual de Campinas, Instituto de Fisica Gleb Wataghin / Made available in DSpace on 2018-07-15T03:55:20Z (GMT). No. of bitstreams: 1 Oliveira_EdmundoCapelasde_M.pdf: 755219 bytes, checksum: 80ba55e1d5a784ef3a819212b87f373f (MD5) Previous issue date: 1979 / Resumo: Não informado / Abstract: Not informed. / Mestrado / Física / Mestre em Física

The role of juvenile hormone (JH) in alate-apterous polymorphism was investigated in the green peach aphid, Myzus persicae. At higher concentrations (65 ppm), the juvenile hormone analogue (JHA), kinoprene, was immediately toxic to apteriform nymphs. At lower concentrations (10 ppm), the compound was non-toxic and exhibited no apparent morphological activity in apteriform stages. In contrast, 65 ppm kinoprene administered to alatiform nymphs had juvenilizing and apterizing effects. The extent of these effects depended upon when the kinoprene was applied. Fourth instar alatiforms were the least sensitive as kinoprene-treated nymphs developed into normal adults with reduced sclerotization and pigmentation. Kinoprene-treated third instars underwent a supernumerary moult before metamorphosing into adults with malformed wings. Sclerotization and pigmentation were also lacking in these insects. When first and second instar alatiformsiwere treated with kinoprene, they also underwent a supernumerary moult. The adults which emerged exhibited both larval and apterous characteristics. Wing development was almost totally inhibited; the cauda and genital plate were poorly developed. In addition, sclerotization and pigmentation were reduced and ocell lacking. The secondary antennal sensoria were also malformed. These findings clearly (1) demonstrate that kinoprene can be employed as a JH mimic to alter the normal programming of the epidermal cells in alatiform nymphs and (2) indicate that JH plays an important role in aphid morphogenesis and polymorphism. The differential responses of the four alatiform nymphal instars suggest that elevated JH levels during the first and second instars are particularly important in inhibiting wing development. To determine the prenatal effects of JH on wing development and morphogenesis, kinoprene was also administered to newly ecdysed apterous adults. Even though conditions favoured alate production, 75% of the offspring produced by kinoprene-treated virginoparae developed into normal apterae. This suggests that elevated JH titers in maternal haemolymph inhibit wing development and promote development of apterae. Topical application of the anti-allatotropin, precocene-II, had variable effects on apteriform nymphs and adults. In all stages, precocene produced a significant decline in larvi-position. The effects were more pronounced in first and second instar apteriform nymphs and apterous adults than in third and fourth instar nymphs. When kinoprene was applied to these insects, larviposition increased significantly after 2 days. The findings demonstrate that JH stimulates reproduction in viviparous morphs of persicae. / Land and Food Systems, Faculty of / Graduate

Orientadores : Attilio Jose Giarola, Sergio B. de A. Fonseca / Tese (doutorado) - Universidade Estadual de Campinas, Faculdade de Engenharia de Campinas / Made available in DSpace on 2018-07-16T18:33:48Z (GMT). No. of bitstreams: 1 Soares_AntonioJoseMartins_D.pdf: 1995125 bytes, checksum: 3ee7443edb950e6d9a67d3b1be90b26a (MD5) Previous issue date: 1986 / Resumo: Neste trabalho apresenta-se uma análise da propagação de ondas eletromagnéticas em meios com N camadas cilíndricas concêntricas, usando-se o formalismo das funções de Green diádicas. Expressões integrais para os campos são determinadas, através do método da superposição por.espalhamento, para uma distribuição de corrente arbitrária. Sistemas de equações lineares que permitem a obtenção dos coeficientes do campo espalhado são incluídas numa forma generalizada. Como resultados, mostra-se a influência das ondas de superfície na eficiência e no diagrama de radiação da antena de microfita do tipo envólucro, que é composta de uma tira metálica colocada sobre e ao redor de uma camada dielétrica que cobre um cilíndro circular condutor. Também são obtidos os campos excitados por um anel filamentar de corrente magnética localizado numa região com duas camadas cilíndricas dielétricas, e em particular, uma antena dielétrica tubular é examinada / Abstract: In this work an analysis of the electromagnetic wave propagation in media with N cylindrical concentric layers is presented by using dyadic Green's functions. The method of scattering superposition is used to obtain integral expressions for the fields resulting from sources having an arbitrary current distribution. Systems of linear equations for the evaluation of the scattered fields coefficients are shown in a generalized form. As results, the influence of this surface waves on the efficiency and radiation pattern of microstrip wraparound antennas is shown. These antennas consist of a metal strip wrapped around a dielectric layer that covers a circular cylindrical conductor. In addition, the fields produced by a filament ring of magnetic current located in a region with two cylindrical concentric dielectric layers are obtained. In particular, a hollow-rod dielectric antenna is examined / Doutorado / Doutor em Engenharia Elétrica

The phenomenon and increasing rate of urbanisation is causing many researchers to look deeper at life in cities. Increasingly recognised are the benefits of urban green space and their associated recreational parks and nature reserves. While there is a growing literature on the environmental services provided by these areas; so too is there a growing literature on the numerous social benefits that recreational green spaces in particular afford their users. Although imagined and generally designed as salubrious public spaces, many parks often fall short of this. In fact research has shown that a park's design, its surroundings, and its management can all combine to exclude certain types of people. In this study I conducted ethnographic research to participate in and observe the activities of visitors to False Bay Nature Reserve in Cape Town. False Bay Nature Reserve includes a series of nature reserves and the Cape Flats Waste Water Treatment Works, and is situated in the area of Cape Town known as the Cape Flats. Much of the Cape Flats is beset by poverty, unemployment, and violent drug - related crime carried out by notorious gangs. Despite the challenges of the surrounding areas, my study reveals that False Bay Nature Reserve provides relative safety to its users as well a range of enjoyable re creational activities. Some of the key recreational activities are separated distinctively between two key sites in the reserve. Furthermore the visitors of these sites differ markedly in race, ethnicity and income. The legacy of apartheid almost certainly accounts for much of this separation; however, the study indicates that the barriers of this legacy are eroding and can potentially be further dismantled with engaged and informed management strategies. Due to its surroundings, the reserve is vulnerable and recently experienced a period where crime was prevalent, vegetation was overgrown, and it was feared by many of its users, particularly women. The reserve had in many ways become what researchers call a landscape of fear, a not so uncommon description of parks around the world. However, management and the majority of visitors feel the reserve has recovered from this period. This is in large part due to upgrades that improved recreational facilities and security in the reserve. Accounts from visitors high light how important a sense of safety is for people frequenting this reserve, most of who live in nearby neighbourhoods. The reserve still faces some challenges today, but is a significant asset to the City of Cape Town and many of its more marginalised residents. This study challenges much of the literature on the benefits of urban green space and associated parks. It shows that particularly in cities of the Global South such as Cape Town, parks require specific management strategies that prioritise safety and in doing so promote and ensure inclusivity for all.