<p>This thesis is focused on the synthesis and structural determination of a series of quasicrystal approximants in the <i>RE</i>₁₃Zn_~58 (<i>RE</i> = Ce, Pr, Nd, Sm, Gd, Tb, Dy, Ho, Er, Tm, Yb and Lu), Ce₁₃Cd_~58and <i>RE</i>Cd₆ (<i>RE</i> = Tb, Ho, Er, Tm and Lu) systems. Structural studies were performed by single crystal X-ray diffraction methods.</p><p>The <i>RE</i>Cd₆ phases are 1/1 cubic approximants to the stable icosahedral quasicrystals. The structure of quasicrystals cannot be solved by conventional crystallography due to the lack of periodicity in three-dimensional space. On the other hand, quasicrystal approximants exhibit long-range order, which makes their structural determination possible by standard methods. Since they are believed to display the same local arrangement as the quasicrystals, the structures of the quasicrystal approximants play a key role in understanding quasicrystals.</p><p>The <i>RE</i>₁₃Zn_~58 and Ce₁₃Cd_~58 quasicrystal approximants show measurable compositional variations coupled to subtle structural differences. The crystal structures are generally rather more complex than previously reported, and exhibit a number of different ordering and disordering modes.</p>

This thesis is focused on the synthesis and structural determination of a series of quasicrystal approximants in the RE13Zn~58 (RE = Ce, Pr, Nd, Sm, Gd, Tb, Dy, Ho, Er, Tm, Yb and Lu), Ce13Cd~58 and RECd6 (RE = Tb, Ho, Er, Tm and Lu) systems. Structural studies were performed by single crystal X-ray diffraction methods. The RECd6 phases are 1/1 cubic approximants to the stable icosahedral quasicrystals. The structure of quasicrystals cannot be solved by conventional crystallography due to the lack of periodicity in three-dimensional space. On the other hand, quasicrystal approximants exhibit long-range order, which makes their structural determination possible by standard methods. Since they are believed to display the same local arrangement as the quasicrystals, the structures of the quasicrystal approximants play a key role in understanding quasicrystals. The RE13Zn~58 and Ce13Cd~58 quasicrystal approximants show measurable compositional variations coupled to subtle structural differences. The crystal structures are generally rather more complex than previously reported, and exhibit a number of different ordering and disordering modes.

Order-by-disorder is the phenomenon of the selection of a long-ranged ordered state by fluctuations in a many-body system. This mechanism, at first sight, seems paradoxical, since fluctuations (disorder) intuitively tend to suppress the order. However, when ObD happens, disorder works in favour of a particular ordered phase. Order-by-disorder can happen where an accidental degeneracy occurs in classical or mean field treatment of a system. These degeneracies, which are not due to exact symmetries of the system, can then be lifted by quantum or thermal fluctuations. The ObD phenomenon is ubiquitous in condensed matter systems with competing or frustrated interactions. Traditionally, the ObD is studied at $T = 0^+$ where the ground state of the system can be selected by quantum fluctuations. The study of ObD at temperature regimes near criticality, $T \lesssim Tc$ where transition happens from the paramagnetic phase to an ordered phase, however, have not received as much attention. In this thesis, we study the ObD phenomenon in three dimensional frustrated sys- tems close to criticality. We consider 3-component classical Heisenberg spins on pyrochlore lattice and FCC lattice. In the former, the spins interact via a Hamiltonian that can include the most general nearest-neighbour symmetry allowed bilinear interactions, long- range magnetostatic dipole-dipole interaction and second and/or third nearest-neighbour exchange interactions. However, in the latter, the Hamiltonian only consists of long-range magnetostatic dipole-dipole interactions. These two systems, correspond to insulating rare- earth pyrochlore oxides and rare-earth FCC salts. The mean field treatment shows, that accidental $O(4)$ and $U(1)$ symmetries emerge in two different regions of the parameter space of the Hamiltonian of pyrochlore system. While in the FCC system, an accidental $O(3)$ symmetry emerges at the mean field level. We show that fluctuations break these symmetries by respectively introducing cubic (in 4-vector and 3-vector models) and hexag- onal anisotropies to the free-energy of the system. To study these system beyond mean field approximation, we use Monte Carlo simulations, spin wave theory and we develop the E-TAP method which is an extended version of the method originally proposed by Thouless, Anderson and Palmer to study fluctuations in spin glasses.

Magnetic films have gained great attention for decades because of their broad industrial application. Their modern functionality more and more relies on their domain structure. Magnetic films usually form complex domain patterns with unique structures at different length scales due to the competition between short range attractive and long range repulsive interactions. The ensemble of domains is topologically disordered, although each of them possesses orientational spin order. Since simplifying complexity is the key step to understand and transform nature, finding new orders from the ostensible disordered structures would be a fascinating topic. Scattering techniques are well-known powerful tools to detect orders. Coherent soft xray magnetic resonant scattering becomes accessible with the development of synchrotron radiation facilities. We applied the technique to study the domain structure of CoPd/MnIr multilayer films with perpendicular magnetic anisotropy. By tuning incident photon energy to Co 2p&rarr3d transition edge we collected small angle magnetic scattering patterns by a charged coupled device in transmission geometry. Each pattern is an unique fingerprint of the corresponding illuminated domain structure. The patterns were analyzed by an angular correlation method. A variety of striking rotational orders were discovered. Their evolution with applied fields was investigated. The sustainabilities of the orders under the room temperature, exchange biased (EB) state, and non-EB state were compared, which suggests that certain orders can be well manipulated under the EB condition. By simulating magnetic resonant scattering from domain patterns obtained by a direct imaging method, we probed the range of emerging orders and finite size effect. Our study provides a novel approach to characterizing magnetic films and potentially can be extended to any system with a complex microstructure. / 2015-07-11

study documents the occurrence of the intellectual hero in anime, focussing on the anime series of Monster (2004), Paranoia Agent (Kon 2004) and Umineko no Naku Koro ni (Kon 2009). The characters, Doctor Kenzo Tenma, Detective Keiichi Ikari and Battler Ushiromiya represent the concept of the intellectual hero in anime. Each intellectual hero in anime exists as an embodiment of literature pertaining to the hero and the anime hero. The intellectual hero in anime is derived from key aspects of Thomas Carlyle's (1796-1881) writings concerning heroes and hero-worship. Antonia Levi and Susan Napier contribute further aspects pertaining to the depiction of the intellectual hero in anime, by discussing the concept of the anime hero. As such, the intellectual hero in anime exists as a concept encompassing elements of both the traditionally perceived styled hero and anime hero. Carlyle's theories reveal the intellectual hero in anime's preference for intelligence, genius and order versus disorder; while exhibiting aspects of an inborn morality. Levi and Napier document the fallibility, sincerity, the complex divided self, moral ambiguity and turmoil of the anime hero. This combined definition communicates an intelligent and exceptional character experiencing failure during his encounter with the antagonist -- an agent of disorder. This study thus appropriates these concepts on the hero and anime hero to construct a concise and viable definition. Moreover, this study strives to identify and promote the existence of the intellectual hero. The intellectual hero in anime acts as a possible bridge between the traditionally perceived hero and anime hero. By identifying this concept, the study opts to prove the validity of the intellectual hero in anime, by means of a qualitative content analysis. Furthermore, a semiotic analysis documents the visual depiction of the intellectual hero in anime. As such, the aim of the study is to document the occurrence of the intellectual hero in anime by means of a qualitative content analysis and semiotics. / Dissertation (MA)--University of Pretoria, 2016. / Visual Arts / MA / Unrestricted

京都大学 / 0048 / 新制・課程博士 / 博士(工学) / 甲第19317号 / 工博第4114号 / 新制||工||1634(附属図書館) / 32319 / 京都大学大学院工学研究科合成・生物化学専攻 / (主査)教授 北川 進, 教授 松田 建児, 教授 陰山 洋 / 学位規則第4条第1項該当 / Doctor of Philosophy (Engineering) / Kyoto University / DGAM

In this thesis, we investigate strongly correlated phenomena in quantum spin systems. In the first part of this work, we study geometrically frustrated antiferromagnets (AFMs). Generalizing the SU(2) Heisenberg Hamiltonian to Sp(N) symmetry, we obtain, in the large-N limit, the mean-field phase diagrams for the planar pyrochlore and cubic AFMs. We then use gauge theories to consider fluctuation effects about their respective mean-field configurations. We find, in addition to conventional Neel states, a plethora of novel magnetically disordered phases: two kinds of spin liquids, Z2 in 2+1D and U(1)in 3+1D, and several valence bond solids such as two and three-dimensional plaquette and columnar singlet states. We use the same approach to study the diamond lattice AFM which possesses extended classical ground state degeneracy. We demonstrate that quantum and entropic fluctuations lift this degeneracy in different ways. In the second part of the thesis, we study ultracold spinor atoms confined in optical lattices. We first demonstrate the feasibility of experimental realization of rotor models using ultracold spin-one Bose atoms in a spin-dependent and disordered optical lattice. We show that the ground state of such disordered rotor models with quadrupolar interactions can exhibit biaxial nematic ordering in the disorder-averaged sense, and suggest an imaging experiment to detect the biaxial nematicity in such systems. Finally, using variational wavefunction methods, we study the Mott phases and superfluid-insulator transition of spin-three bosons in an optical lattice with an anisotropic two dimensional optical trap. We chart out the phase diagrams for Mott states with n = 1 and n = 2 atoms per lattice site. We show that the long-range dipolar interaction stabilizes a state characterized by antiferromagnetic chains made of ferromagnetically aligned spins. We also obtain the mean-field phase boundary for the superfluid-insulator transition, and show that inside the superfluid phase and near the superfluid-insulator phase boundary, the system undergoes a first order antiferromagnetic-ferromagnetic spin ordering transition.

In this thesis, we investigate strongly correlated phenomena in quantum spin systems. In the first part of this work, we study geometrically frustrated antiferromagnets (AFMs). Generalizing the SU(2) Heisenberg Hamiltonian to Sp(N) symmetry, we obtain, in the large-N limit, the mean-field phase diagrams for the planar pyrochlore and cubic AFMs. We then use gauge theories to consider fluctuation effects about their respective mean-field configurations. We find, in addition to conventional Neel states, a plethora of novel magnetically disordered phases: two kinds of spin liquids, Z2 in 2+1D and U(1)in 3+1D, and several valence bond solids such as two and three-dimensional plaquette and columnar singlet states. We use the same approach to study the diamond lattice AFM which possesses extended classical ground state degeneracy. We demonstrate that quantum and entropic fluctuations lift this degeneracy in different ways. In the second part of the thesis, we study ultracold spinor atoms confined in optical lattices. We first demonstrate the feasibility of experimental realization of rotor models using ultracold spin-one Bose atoms in a spin-dependent and disordered optical lattice. We show that the ground state of such disordered rotor models with quadrupolar interactions can exhibit biaxial nematic ordering in the disorder-averaged sense, and suggest an imaging experiment to detect the biaxial nematicity in such systems. Finally, using variational wavefunction methods, we study the Mott phases and superfluid-insulator transition of spin-three bosons in an optical lattice with an anisotropic two dimensional optical trap. We chart out the phase diagrams for Mott states with n = 1 and n = 2 atoms per lattice site. We show that the long-range dipolar interaction stabilizes a state characterized by antiferromagnetic chains made of ferromagnetically aligned spins. We also obtain the mean-field phase boundary for the superfluid-insulator transition, and show that inside the superfluid phase and near the superfluid-insulator phase boundary, the system undergoes a first order antiferromagnetic-ferromagnetic spin ordering transition.

La fiabilité organisationnelle concerne l’étude des conditions organisationnelles permettant à un système organisé complexe de maintenir des niveaux de fiabilité compatibles à la fois avec les exigences de sécurité et les exigences économiques. Les études effectuées sur le fonctionnement des organisations à haute fiabilité mettent en avant un ensemble de pratiques et de dispositifs mis en place au sein de ces organisations, tant au niveau de l’individu et du groupe qu’au niveau de l’organisation, qui permettent à celles-ci de gérer et d’exploiter efficacement des systèmes techniques complexes à risques. Dans la lignée des différents apports sur ce qui fait la fiabilité au sein de telles entreprises, ce travail vise à démontrer la prise en compte du désordre, comme une des logiques organisationnelles, participant à la fiabilité de l’entreprise. En ce sens, une conceptualisation du désordre en tant qu’organisateur (désordre organisationnel) est proposée. À la suite de cette conceptualisation, la thèse démontre dans quelle mesure le désordre, par le biais de lamise en place d’organisations informelles stratifiées sur l’organisation formelle existante, permet de résorber et de restreindre les effets des perturbations. Le désordre est analysé comme catalyseur intrinsèque de la création de sens, participant à la fiabilité. En discutant la considération du désordre comme étant essence même de l’organisation, ce travail analyse l’approche normative sous-jacente dans la conception même de l’organisation et la fiabilité de celle-ci. / The study of high organizational reliability refers to the examination of conditions that allow a complex organized system to maintain high levels of reliability consistent with both security and economic requirements. Studies on the functioning of High Reliability Organizations (HRO) feature a set of practices and mechanisms implemented within these organizations - at the individual, group and organizational levels - which enable them to manage and operate effectively complex technicalsystems at risk. In line with the contributions on what contribute to high reliability in such companies, this work aims to demonstrate the consideration of disorder, as one of the organizational logics, supporting reliability of the company. In this sense, a conceptualization of disorder as an organizing component (organizational disorder) is proposed. As a result of this conceptualization, the thesis demonstrates to what extent organizational disorder, through the establishment ofinformal organizations stratified on the existing formal ones, can reduce and limit the effects of disruptions. Disorder is analyzed as an intrinsic catalyst of sensemaking, partaking to high reliability. By discussing the consideration of disorder as the very essence of the organization, the thesis also debates upon the underlying normative approach in the very conception of the organization and its ensuant high reliability.

Denna etnografiska studie tar sin utgångspunkt i ett jämförande fältarbete bland lärare på högstadieskolor i två sydligt situerade storstäder i Europa: Malmö i Sverige och Marseille i Frankrike. Studiens fokus ligger på hur lärare begripliggör och brottas med sitt uppdrag att forma och fostra ”goda” medborgare för en nationell gemenskap och sammanhållning. Genom att utforska lärarnas egna strävanden och stretanden i denna fråga belyses de idéer och praktiker som driver detta arbete framåt. Samtidigt synliggörs de vardagliga spänningar som emellanåt komplicerar lärarnas arbete. En central iakttagelse i denna studie är att lärare i både Sverige och Frankrike stundtals finner sig inneslutna i ett slags korstryck. Inpressade i detta kastas de mellan att å ena sidan eftersträva vissa på förhand fastslagna visioner och mål om gemensamt liv, å andra sidan kontinuerligt konfronteras med en oregelbunden och inte alla gånger följsam verklighet. Avhandlingen visar hur lärare handskas med detta korstryck; hur de i händelse av hinder och motstånd i sitt arbete försöker bringa ordning i vad de uppfattar och upplever som ett tillstånd av stor oreda i förhållande till sitt medborgardanande uppdrag. Sammantaget bidrar avhandlingen till ökad kunskap om lärares både levda yrkeserfarenheter och situerade praktiker i vardagen, liksom till en problematiserande diskussion om den roll och betydelse som lärare förväntar sig spela för det gemensamma livet i Sverige och Frankrike i stort. / This ethnographic study is based on comparative fieldwork among teachers at secondary schools in two southern situated cities in Europe: Malmö in Sweden and Marseille in France. The focus of the study is on how teachers make sense of and grapple with their mission to build and foster “good” citizens, which is intended to promote national community and unity. Exploring how the teachers strive and struggle to fulfil this mission provides a better insight into the ideas and practices that permeate their work. At the same time, the everyday tensions that occasionally complicate this task are highlighted. A crucial observation in this study is that teachers in both Sweden and France often find themselves confined to a kind of cross-pressure. Enclosed within it, teachers are torn between, on the one hand, endeavouring to reach certain visions and goals regarding how to instil a sense of national community in their pupils and, on the other, being confronted with an irregular and often far from pliable reality. This study shows how teachers are dealing with this cross-pressure, how – in case of hurdles and friction in their work – they try to maintain order in what they perceive and experience as being a state of great disorder in relation to their educational mission. The thesis contributes to increased knowledge of teachers’ lived professional experiences and situated practices in their day-to-day work. It also brings to light a problematising discussion about the role and importance that teachers expect themselves to play in relation to an overall idea of national community and unity in Sweden and France respectively.