M.A. / The Nigeria-Biafra War has elicited a corpus of literature which thematises the hydra-headed problematic of nationhood that embodies ethnicity, politics and history. A recent contribution is Chimamanda Ngozi Adichie’s award-winning Half of a Yellow Sun (henceforth, Yellow Sun) which reveals interesting affinities between Adichie and Chinua Achebe, and suggests the influence of Achebe on her. The centrality of Biafra to these writers (both are of Igbo or ‘Biafran’ extraction) foregrounds concerns about the links between literary production, identity politics and the narrative of the nation. At a time marked by the resurgence of sub-nationalist notions in Nigeria, it becomes fitting to review the growing ‘Biafra discourse’ as enunciated in recent Nigerian fiction. It is argued that in Yellow Sun and Achebe's most recent novel Anthills of the Savannah (henceforth, Anthills) both writers espouse notions of nationhood which privilege the ethnic group mainly through a valorisation of the Igbo people of south-eastern Nigeria who constituted the defunct Biafra republic. This dissertation examines how both novels depict difference and deploy historical revision to fetishise ethnic identity in their enunciation of ethno-nationalism. It also explores the degree to which Yellow Sun may reflect the influence of Anthills, both ideologically and stylistically. In this regard, the study interrogates the peculiar narratological features of both novels. The predominant research method applied is close reading, and the theoretical framework incorporates theories of narratology, influence and intertextuality as well as postcolonial notions of nationalism, historicisation, difference and representation. The study draws significantly on the scholarship of Frederic Jameson, Mieke Bal, Harold Bloom and Imre Szeman among others. Keywords: narratology, nationalism, historicisation, representation, ethnicity, difference, other/otherness/othering, representation, intertextuality, Nigeria, Biafra, civil war.

This thesis investigates the growth of intermetallic compounds by co-sputtering from single elemental targets. The preliminary work involved constructing a sputtering set-up to grow abinary alloy (Sm-Co) and investigating how to control the composition spread that was obtained. Having achieved this, a larger sputtering flange was built up to grow the ternary Heusler alloy, Co₂MnSi. Co₂MnSi has been predicted to be a half-metallic ferromagnet, which means that there is an energy gap in the minority spin band at the Fermi energy. This leads to 100% spin polarised conduction electrons, which would enable ideal spin-device performance to be obtained. Co₂MnSi is particularly promising because it is predicted to have a large energy gap in the minority band of ~0.4 eV and has the highest Curie temperature among the known Heuslers of 985 K. Initially, Co₂MnSi was grown on a-plane sapphire and stoichiometric films were single phase and highly (110) textured, without the use of a seed layer. They exhibited the bulk value of the saturation magnetisation, Ms and films grown at the highest deposition temperature (715 K) showed the lowest resistivity (47 μΩcm at 4.2 K) and the lowest room temperature coercivity (18 Oe). The spin polarisation of the transport current, Pt of a 400 nm film grown at this deposition temperature was 54%, consistent with measurements on bulk single crystals. Ms decreased with decreasing film thickness indicating a graded disorder. By growing on GaAs (001), which has a similar lattice parameter to Co₂MnSi it was expected that this disordered region would be confined to the first few atomic layers. However, this was not the case because interfacial reactions resulted in the formation of an epitaxial Mn-As region, and a thin interfacial layer that was Co-Ga rich. This prevented the lattice matching of the Co₂MnSi to the GaAs(001) hence hindering epitaxial growth of the Heusler. The reaction zone also meant that films exhibited a Ms slightly below the bulk value. The expected fourfold anisotropy was not obtained for this cubic material, which is most likely due to the anisotropy of the reconstructed GaAs surface. Inspite of this anomalous behaviour, Pt was 55%, similar to the result obtained on sapphire, indicating that either Pt is independent of orientation or that the Heusler surface reconstructs in the same way. Films showed some improved properties to films grown on a-plane sapphire, indicating the potential of growing on this technologically important substrate. With this in mind, pseudo spin valves involving Co₂MnSi as one of the ferromagnetic electrodes were fabricated in both the CIP and CPP configurations. Clear low-field spin-valve contributions were observed at 15 K but the MR values are much lower than that expected from a PSV with a predicted 100% spin polarised electrode.

Estruturas de dados volumétricas são de extrema utilidade em várias aplicações, e em particular na área de Visualização Científica. Essas estruturas são úteis em duas etapas do processo de visualização. A primeira é na representação de dados, isto é, de informações associadas aos valores, medidos ou simulados, os quais se deseja visualizar. A outra fase que necessita de uma estrutura de dados é a fase de exploração, ou seja, o modelo criado é usado tanto para exploração interativa quanto para a realização de simulações sobre o mesmo, por exemplo, numa cirurgia virtual. Está em desenvolvimento no ICMC, uma estrutura de dados volumétrica, chamada Singular Half-Face, que tem como característica a modelagem explícita das singularidades presentes no modelo, além de outros elementos topológicos. Este trabalho de mestrado visa testar a viabilidade da estrutura num contexto de visualização em fluxo de dados, incorporando-a à biblioteca gráfica de visualização Visualization ToolKit (VTK), que possui definição extremamente pobre da topologia dos objetos que representa. Adicionando essa nova classe e realizando sobre ela técnicas convencionais de visualização e exploração de dados, é estudada sua capacidade de apoiar todas as fases do processo de visualização. / Volumetric data structures are of extreme utility in various applications, and particularly in the area of Scientific Visualization. These structures are useful in two stages of the visualization process. The first one is in data representation, that is, in the organization of information associated with the values, measured or simulated, to be visualized. The other phase of the visualization data flow that needs a data structure is the exploration phase. It would be useful to have a model designed to be used both for interactive exploration and for simulation in a number of application, for example, in virtual surgery. A volumetric data structure, named Singular Half-Face (SHF) is being developed at the ICMC, that has as its main characteristic the explicit modeling of singularities present in the model, besides other essential topological elements. This dissertation aims at testing the viability of this structure in a context of visualization in data flow, by incorporating it in the Visualization ToolKit (VTK) class library, whose data structures are extremely poor in definition of the topology of the objects that they represent. By adding SHF to this library and carrying out conventional visualization and data exploration on it, we wish to study its support to all the phases of the visualization process.

Oxide heterostructures are attracting huge interest in recent years due to the special functionalities of quasi two-dimensional quantum gases. In this thesis, the electronic states at the interface between perovskite oxides and pyrite compounds have been studied by first-principles calculations based on density functional theory. Optimization of the atomic positions are taken into account, which is considered very important at interfaces, as observed in the case of LaAlO3/SrTiO3. The creation of metallic states at the interfaces thus is explained in terms of charge transfer between the transition metal and oxygen atoms near the interface. It is observed that with typical thicknesses of at least 10-12 °A the gases still extend considerably in the third dimension, which essentially determines the magnitude of quantum mechanical effects. To overcome this problem, we propose incorporation of highly electronegative cations (such as Ag) in the oxides. A fundamental interest is also the thermodynamic stability of the interfaces due to the possibility of atomic intermixing in the interface region. Therefore, different cation intermixed configurations are taken into account for the interfaces aiming at the energetically stable state. The effect of O vacancies is also discussed for both polar and non-polar heterostructures. The interface metallicity is enhanced for the polar system with the creation of O vacancies, while the clean interface at the non-polar heterostructure exhibits an insulating state and becomes metallic in presence of O vacancy. The O vacancy formation energies are calculated and explained in terms of the increasing electronegativity and effective volume of A the side cation. Along with these, the electronic and magnetic properties of an interface between the ferromagnetic metal CoS2 and the non-magnetic semiconductor FeS2 is investigated. We find that this contact shows a metallic character. The CoS2 stays quasi half metallic at the interface, while the FeS2 becomes metallic. At the interface, ferromagnetic ordering is found to be energetically favorable as compared to antiferromagnetic ordering. Furthermore, tensile strain is shown to strongly enhance the spin polarization so that a virtually half-metallic interface can be achieved, for comparably moderate strain. Our detailed study is aimed at complementing experiments on various oxide interfaces and obtaining a general picture how factors like cations, anions, their atomic weights and elecronegativities, O vacancies, lattice mismatch, lattice relaxation, magnetism etc play a combined role in device design.

京都大学 / 0048 / 新制・課程博士 / 博士(医学) / 甲第20270号 / 医博第4229号 / 新制||医||1021(附属図書館) / 京都大学大学院医学研究科医学専攻 / (主査)教授 山田 亮, 教授 福原 俊一, 教授 小川 修 / 学位規則第4条第1項該当 / Doctor of Medical Science / Kyoto University / DFAM

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Yes / Half-sandwich metal complexes are of considerable interest in medicine, material, and nanomaterial chemistry. The design of libraries of such complexes with particular reactivity and properties is therefore a major quest. Here, we report the unique and peculiar reactivity of eight apparently 16-electron half-sandwich metal (ruthenium, osmium, rhodium, and iridium) complexes based on benzene-1,2-dithiolato and 3,6-dichlorobenzene-1,2-dithiolato chelating ligands. These electron-deficient complexes do not react with electron-donor pyridine derivatives, even with the strong σ-donor 4-dimethylaminopyridine (DMAP) ligand. The Ru, Rh, and Ir complexes accept electrons from the triphenylphosphine ligand (σ-donor, π-acceptor), whilst the Os complexes were found to be the first examples of non-electron-acceptor electron-deficient metal complexes. We rationalized these unique properties by a combination of experimental techniques and DFT/TDFT calculations. The synthetic versatility offered by this family of complexes, the low reactivity at the metal center, and the facile functionalization of the non-innocent benzene ligands is expected to allow the synthesis of libraries of pseudo electron-deficient half-sandwich complexes with unusual properties for a large range of applications.

Fighting bankruptcy, the owner of the last traveling circus train in America must improve the act and generate ticket sales or it's curtains for him and his eclectic cast and crew.