Knotted wave dislocation with the hopf invariant

We study the wave dislocations with an induced gauge potential. The topological current characterized the wave dislocations is constructed with the dual of Abelian gauge field. And the topological charges and locations of the wave dislocations are determined by the phi-mapping topological current theory. Furthermore, it is shown that the knotted wave dislocations can be described with a Hopf invariant in the wave field. At last we discussed the evolution of the knotted wave dislocations.

Risk of dislocation using large- vs. small-diameter femoral heads in total hip arthroplasty.

BACKGROUND: Dislocation remains a difficult problem in total hip arthroplasty. Large-diameter femoral heads may lower the incidence of dislocation by enhancing the jump distance and decreasing impingement, but their performance against small-diameter heads has not been assessed. This study compared the mid-term radiographic and functional outcomes of two matched cohorts of patients undergoing total hip arthroplasty who had a high pre-operative risk for dislocation and who received either small-diameter (26- or 28-millimeters) or large-diameter (≥36-millimeters) femoral heads. METHODS: All patients who received large-diameter heads (≥36-millimeter) between 2002 and 2005, and who had pre-operative risk factors for dislocation, were identified in the institution's joint registry. Forty-one patients (52 hips) who received large-diameter heads were identified, and these patients were matched to 48 patients (52 hips) in the registry who received small-diameter femoral heads. RESULTS: At mean final follow-up of 62 months (range, 49 to 101 months), both groups achieved excellent functional outcomes as measured by Harris Hip scores, with slightly better final scores in the large-diameter group (90 vs. 83 points). No patient showed any radiographic signs of loosening. No patient dislocated in the large-diameter femoral head group; the smaller-diameter group had a greater rate of dislocation (3.8%, 2 out of 52). CONCLUSIONS: Large-diameter femoral head articulations may reduce dislocation rates in patients who have a high pre-operative risk for dislocation while providing the same functional improvements and safety as small-diameter bearings.

Atomistic studies of <110] screw dislocation core structures and glide in γ-TiAl

The core structure of <110] superdislocations in L10 TiAl was investigated with a view to clarifying their dissociation abilities and the mechanisms by which they may become sessile by self-locking. A detailed knowledge of the fine structure of dislocations is essential in analysing the origin of the various deformation features. Atomistic simulation of the core structure and glide of the screw <110] superdislocation was carried out using a bond order potential for ?-TiAl. The core structure of the screw <110] superdislocation was examined, starting with initial unrelaxed configurations corresponding to various dislocation dissociations discussed in the literature. The superdislocation was found to possess in the screw orientation either planar (glissile) or non-planar (sessile) core structures. The response of the core configurations to externally applied shear stress was studied. Some implications were considered of the dissociated configurations and their response to externally applied stress on dislocation dynamics, including the issue of dislocation decomposition, the mechanism of locking and the orientation dependence of the dislocation substructure observed in single-phase ?-TiAl. An unexpectedly rich and complex set of candidate core structures, both planar and non-planar, was found, the cores of which may transform under applied stress with consequent violation of Schmid's law.

Direct evidence for cation non-stoichiometry and Cottrell atmospheres around dislocation cores in functional oxide interfaces

Long-range strain fields associated with dislocation cores at an oxide interface are shown to be sufficient enough to create significant variations in the chemical composition around the core (Cottrell atmospheres). Such stress-assisted diffusion of cations towards the cores is proposed to significantly impact the properties of nanoscale functional devices. The figure shows a Z-contrast image of a single dislocation core at an oxide interface.

The Hybridity of Violence : Location, Dislocation, and Relocation in Contemporary Canadian Multicultural and Indigenous Writing

Cette thèse explore la relation entre les littératures autochtones et multiculturelles du Canada. Même si les critiques littéraires examinent les littératures dites mineures de plus en plus, ces dernières sont rarement étudiées sans la présence médiatrice de la littérature canadienne considérée comme étant dominante. Afin de produire une telle analyse, cette thèse mobilise le concept d’hybridité en tant que catégorie d’analyse de texte qui, en plus de son histoire raciale et coloniale, décrit convenablement les formes d’expérimentations stylistiques que les écrivains autochtones et multiculturels emploient afin de représenter et questionner leur marginalisation. Ne voulant pas reproduire les interprétations fétichistes qui réduisent les littératures autochtones et multiculturelles à leurs représentations de concepts d’altérité, j’examine ces textes dans leurs relations avec différents discours et débats ayant marqué les études littéraires canadiennes, notamment, le long poème canadien, l’écriture des prairies canadiennes, la littérature urbaine, le multiculturalisme, et les premières nations. Ma méthode d’analyse repose sur la façon dont chaque texte étudié alimente ces catégories d’analyse littéraire tout en les modifiant radicalement. De plus, je développe un cadre conceptuel et théorique permettant l’étude de la relation entre les textes autochtones et multiculturels sans toutefois confondre ou réduire les contextes d’où proviennent ces littératures. Ma thèse et ma méthode d’analyse se concrétise par l’interprétation des textes écrits par Armand Garnet Ruffo, Suzette Mayr, Rawi Hage, et Jeannette Armstrong. Le chapitre d’introduction détaille la façon dont la relation entre les textes autochtones et multiculturels a été appréhendée jusqu’à présent. J’y élabore mon cadre théorique qui joint et réinterprète de manière critique diverses théories, dont celle du postcolonialisme, de l’hybridité, et de la mondialisation, et la façon dont ces théories se rapportent aux études littéraires canadiennes. Dans mon deuxième chapitre, j’analyse le long poème d’Armand Garnet Ruffo, Grey Owl: The Mystery of Archie Belaney, en m’attardant particulièrement aux stratégies d’expérimentations stylistiques et génériques que Ruffo développe afin de rendre le genre du long poème canadien autochtone et de questionner l’identité de Grey Owl. Mon troisième chapitre examine Venous Hum, un roman de Suzette Mayr. Ce texte remet en question la tradition de « prairie writing », le multiculturalisme canadien, et le conservatisme albertain à travers son style expérimental, son usage des métaphores et du réalisme magique. Mon quatrième chapitre interprète le roman montréalais Cockroach, de Rawi Hage, en examinant la façon dont ses unités locales, nationales, et globales rencontrent le colonialisme et contestent les discours nationaux une fois que sa critique de la mondialisation se trouve réarticulée dans une approbation des discours d’interventions humanitaires de l’occident. Mon dernier chapitre explore le roman de Jeannette Armstrong, Whispering in Shadows, afin de démontrer les limites de ma méthode d’analyse. Puisque l’hybridité sous-entend inévitablement la notion d’assimilation, son application dans le contexte de l’œuvre d’Armstrong s’avèrerait réductrice. Pour cette raison, ce chapitre utilise des concepts autochtones définis par Armstrong afin de développer une méthode de lecture non-hégémonique. Ma thèse examine donc la façon dont chaque texte déploie le concept d’hybridité pour à la fois contester et enrichir les discours critiques qui tentent de contenir ces textes. Elle contribue aux études postcoloniales de la littérature canadienne en élargissant leur champ habituel pour inclure les complexités des théories de la mondialisation, et en examinant quelles stratégies littéraires les textes autochtones et multiculturels partagent, mais mobilisent à des fins différentes.

Statistical dynamics of dislocation systems: The influence of dislocation-dislocation correlations.

During plastic deformation of crystalline materials, the collective dynamics of interacting dislocations gives rise to various patterning phenomena. A crucial and still open question is whether the long range dislocation-dislocation interactions which do not have an intrinsic range can lead to spatial patterns which may exhibit well-defined characteristic scales. It is demonstrated for a general model of two-dimensional dislocation systems that spontaneously emerging dislocation pair correlations introduce a length scale which is proportional to the mean dislocation spacing. General properties of the pair correlation functions are derived, and explicit calculations are performed for a simple special case, viz pair correlations in single-glide dislocation dynamics. It is shown that in this case the dislocation system exhibits a patterning instability leading to the formation of walls normal to the glide plane. The results are discussed in terms of their general implications for dislocation patterning.

Depinning transition of dislocation assemblies: Pileups and low-angle grain boundaries

We investigate the depinning transition occurring in dislocation assemblies. In particular, we consider the cases of regularly spaced pileups and low-angle grain boundaries interacting with a disordered stress landscape provided by solute atoms, or by other immobile dislocations present in nonactive slip systems. Using linear elasticity, we compute the stress originated by small deformations of these assemblies and the corresponding energy cost in two and three dimensions. Contrary to the case of isolated dislocation lines, which are usually approximated as elastic strings with an effective line tension, the deformations of a dislocation assembly cannot be described by local elastic interactions with a constant tension or stiffness. A nonlocal elastic kernel results as a consequence of long-range interactions between dislocations. In light of this result, we revise statistical depinning theories of dislocation assemblies and compare the theoretical results with numerical simulations and experimental data.

The threading of [(CuCN)(2)(mu-4,4 '-bpy)] sheets by CuCN chains

Yellow (CuCN)(2)[(CuCN)(2)(mu-4,4'-bpy)], formed in the hydrothermal reaction of CuCN with 4,4'-bipyridine at 453 K, contains two types of infinite CuCN chains. One set of CuCN chains is linked by 4,4'-bpy ligands to form almost flat sheets of composition [(CuCN)(2)(mu-4,4'-bpy)]. Holes in these sheets are aligned to allow pairs of approximately linear, infinite -(CuCN)- chains to thread through them. The closest interatomic approach between copper atoms in the threading chains and host sheets (similar to2.74 Angstrom) does not appear to represent a significant covalent bond as it leads to only a small distortion of the -(CuCN)- chains from linearity The relationship of this material to the previously determined structures of the host [(CuCN)(2)(mu-4,4'-bpy)] sheets and (CuCN)(3)[(CuCN)(2)(mu-4,4'-bPY)](2), in which these sheets are threaded by single -(CuCN)- chains, is discussed.

The Genomic Threading Database: a comprehensive resource for structural annotations of the genomes from key organisms

Currently, the Genomic Threading Database (GTD) contains structural assignments for the proteins encoded within the genomes of nine eukaryotes and 101 prokaryotes. Structural annotations are carried out using a modified version of GenTHREADER, a reliable fold recognition method. The Gen THREADER annotation jobs are distributed across multiple clusters of processors using grid technology and the predictions are deposited in a relational database accessible via a web interface at http://bioinf.cs.ucl.ac.uk/GTD. Using this system, up to 84% of proteins encoded within a genome can be confidently assigned to known folds with 72% of the residues aligned. On average in the GTD, 64% of proteins encoded within a genome are confidently assigned to known folds and 58% of the residues are aligned to structures.