京都大学 / 0048 / 新制・課程博士 / 博士(農学) / 甲第19936号 / 農博第2186号 / 新制||農||1044(附属図書館) / 学位論文||H28||N5009(農学部図書室) / 33022 / 京都大学大学院農学研究科森林科学専攻 / (主査)教授 木村 恒久, 教授 西尾 嘉之, 教授 髙野 俊幸 / 学位規則第4条第1項該当 / Doctor of Agricultural Science / Kyoto University / DGAM

No description available.

Molecular structures of biomaterials have close relation to their functions. We are interested in how biological building blocks assemble into the structures of native biomaterials and the hierarchy of those structures. We tackled the problem mainly with X-ray diffraction experiments and developed a thorough analysis technique to assign the X-ray signals to protein secondary structures and chitin. Three different types of biomaterials were examined: vimentin fibres, squid pens, and human hair. In vimentin fibres, we found that the secondary protein structures play an important role in the strength of the fibres. In native squid pens, we found a self-similar, hierarchical structure from millimetres down to nanometres. In human hair, we compared the signals corresponding to keratin proteins, intermediate filaments, and lipids between different subjects, and found small deviations. The structures of these three biomaterials, which encompass different orders of length scales, were described both quantitatively and graphically. We hope that this work will eventually allow us to understand how and why nature builds biomaterials this way. / Thesis / Master of Science (MSc)

X-ray diffraction experiments have been used to determine the structure of cesium methylsulfonate (CsCH₃SO₃), lithium hydrazinium sulfate (LiN₂H₅SO₄), above 160ºC and triclinic potassium dichromate (K₂Cr₂O₇). The solved CsCH₃SO₃ structure is compared with BaSO₄ and the CsCH₃SO₃⁻¹ ion stereochemistry is dicussed in terms of a current theory of bonding for such groups. The previously known structure of room temperature ferroelectric LiN₂H₅SO₄ has recieved additional refinement and a comparison is made with the structure determined above 160ºC. The symmetry and structure found for K₂Cr₂O₇ are compared with similar compounds and predictions are given for the yet unsolved structures of other K₂Cr₂O₇ phases. The first accurate data for the Cr₂O₇⁻² ion stereochemistry is presented. This ion is compared to similar ones, and the possibility of extending a bonding theory to such ions involving chromium is discussed. / Thesis / Doctor of Philosophy (PhD)

No description available.

Thermal Barrier Coatings have been used for decades to impose a thermal gradient between the hot combustion gases and the underlying superalloy substrate in engine turbine blades. Yttria Stabilized Zirconia (YSZ) is an industry standard high temperature ceramic for turbine applications. The protective coating is adhered to the substrate using a nickel based alloy bond coat. Through exposure to high temperature, a Thermally Grown Oxide (TGO) layer develops at the bond coat-YSZ interface. Large residual stresses develop in these layers due to thermal expansion mismatch that occurs during cool down from high temperature spraying and cyclic operating conditions. Despite their standard use, much is to be determined as to how these residual stresses are linked to the various failure modes. This study developed techniques to monitor the strain and stress in these internal layers during thermal gradient and mechanical conditions representing operating conditions. The thermal gradient is applied across the coating thickness of the tubular samples from infrared heating of the outer coating and forced air internal cooling of the substrate. While thermal and mechanical loading conditions are applied, 2-dimensional diffraction measurements are taken using the high-energy Synchrotron X-Rays and analyzed to provide high-resolution depth-resolved strain. This study will include fatigue comparisons through use of samples, which are both 'as-coated' as well as aged to various stages in a TBC lifespan. Studies reveal that variations in thermal gradients and mechanical loads create corresponding trends in depth resolved strains with the largest effects displayed at or near the bond coat/TBC interface. Single cycles as well as experiments targeting thermal gradient and mechanical effects were conducted to capture these trends. Inelastic behavior such as creep was observed and quantified for the different layers at high temperatures. From these studies more accurate lifespan predictions, material behaviors, and causes of failure modes can be determined. The work further develops measurement and analysis techniques for diffraction measurements in internal layers on a coated tubular sample which can be used by various industries to analyze similar geometries with different applications.

<p>Various transition metal oxides with interesting magnetic properties (often based on the perovskite structure) were prepared using conventional solid-state methodologies and fully characterized using a variety of techniques such as powder X-ray diffraction, variable temperature neutron diffraction, SEM-EDS, TEM-EDS, SQUID magnetometry and heat capacity measurements.</p> <p>One family of compounds that was investigated intensively were the 'pillared perovskites'. In this structure type, perovskite-like layers of comer shared octahedra are separated. by about 10 A by diamagnetic edge-shared octahedral dimer 'pillars'. Despite this long distance between layers, long-range order is present in both the La5Re3Co016 and La5Re3Ni016 members. In fact, a new magnetic structure was discovered for the Ni compound consisting of ferromagnetically ordered layers, coupled antiferromagnetically.</p> <p>In addition, for the first time, substitution of the 5+ ion within the layer was successful, yielding compounds with general formula, La5Re3-xTaxB016 (B =Mn, Fe, Co, Ni; x ~ 0.5). Surprisingly, despite replacing about half of the magnetic ions within the perovskite layers with non-magnetic tantalum, the materials had the same ordering temperatures and magnetic structures as their unsubstituted analogues. This observation is evidence that the longer interlayer coupling pathway is the key to long-range ordering in this structure type.</p> <p>The lanthanum rhenium oxide, La3Re20 10, involves the edge-shared octahedral dimer 'pillar' unit from the pillared perovskite structure, but with one unpaired electron per dimer unit. Prepared for the first time by solid-state synthesis, and studied magnetically in depth, long-range order was evident at 18 K. Theoretical investigations hinted that the magnetic structure consists of antiferromagnetically coupled chains of dimers, coupled antiferromagnetically.</p> <p>The magnetic properties of the double perovskite, SrLaRuNi06, were also explored for the first time. This study demonstrates the power of neutron diffraction at elucidating magnetic information, such as the ordering temperature and magnetic structure, despite the presence of a ferromagnetic impurity that dominated much of the measurements.</p> <p>The candidate's examination of the magnetism of the rock-salt oxides, Na2Cu2Te06 and Na3Cu2Sb06 has raised some controversy in the literature, as the exact nature of the one-dimensional order (either antiferromagnetic-antiferromagnetic or antiferromagnetic-ferromagnetic alternating linear chains) is uncertain. Again, theoretical calculations and comparison with other magnetic data can aide in the ultimate understanding of the overriding magnetism.</p> <p>This thesis has focused on the synthesis and study of transition metal oxides with interesting or unusual magnetic properties. In many cases, the compounds exhibited long-range magnetic order despite convoluted or non-existent magnetic superexchange pathways.</p> / Thesis / Doctor of Philosophy (PhD)

The crystal structures of Co₃(AsO₄)₂, Co₂₄ٜ₂As₉O₄₈, Co₂As₂O₇ and Co₇As₃ٜ₆O₁₆ have been determined by x-ray diffraction methods. The crystal structure of Mg₃(VO₄)₂ have been refined using single crystal x-ray diffraction data. General structural relations between M₃(XO₄)₂ type compounds where M refers to a divalent cation with radius comparable to that of cobalt, and x = As or V, are discussed. The deviations from ideality in cation polyhedral groups in crystal structures are analysed. / Thesis / Doctor of Philosophy (PhD)

京都大学 / 0048 / 新制・課程博士 / 博士(医学) / 甲第20071号 / 医博第4164号 / 新制||医||1018(附属図書館) / 33187 / 京都大学大学院医学研究科医学専攻 / (主査)教授 黒田 知宏, 教授 松田 文彦, 教授 楠見 明弘 / 学位規則第4条第1項該当 / Doctor of Medical Science / Kyoto University / DFAM

The crystal structures of (NH4)2TeBr6 and Ce2TeBr6 have been reinvestigated using X-ray diffraction from powders and single crystals. Three dimensional single crystal intensity data obtained photographically have been used to refine these structures, which are of the cubic K2PtCl6 type, by a full matrix least squares analysis. The Te-Br bond is found to be 2.70* in both crystals after correction for the thermal notion of the atoms. A phase transition in (NH4)2TeBr6 has been observed at about 183°K. Pros an examination of Weissenberg photographs taken at 163°K, the low temperature phase is found to be tetragonal, space group p4/mnc (D64h) with a « 7.501+/-0.005* and c =10.765*+/-0.005*. The transformation in this case is probably similar to that reported in other isomorphous crystals, e.g., K2snBr6. A review of other crystals with similar structure is included in this thesis and the theory of X-ray diffraction as applicable to the present problem is discussed briefly. / Thesis / Master of Science (MSc)