• Refine Query
  • Source
  • Publication year
  • to
  • Language
  • 1210
  • 278
  • 187
  • 183
  • 153
  • 65
  • 62
  • 47
  • 31
  • 23
  • 14
  • 12
  • 9
  • 5
  • 5
  • Tagged with
  • 2874
  • 583
  • 477
  • 301
  • 300
  • 290
  • 265
  • 251
  • 227
  • 212
  • 209
  • 180
  • 163
  • 147
  • 142
  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
1001

Cardiac function in hereditary transthyretin amyloidosis : an echocardiographic study / Hjärtfunktion vid ärftlig transtyretin-amyloidos : en ekokardiografisk studie

Arvidsson, Sandra January 2016 (has links)
Background: Hereditary transthyretin amyloidosis (ATTR) is a lethal disease in which misfolded transthyretin (TTR) proteins accumulate as insoluble aggregates in tissues throughout the body. A common mutation is the exchange of valine to methionine at place 30 (TTR V30M), a form endemically found in the northern parts of Sweden. The main treatment option for ATTR amyloidosis is liver transplantation as the procedure halts production of mutated transthyretin. The disease is associated with marked phenotypic diversity ranging from predominant cardiac complications to pure neuropathy. Two different types of fibril composition – one in which both fragmented and full-length TTR are present (type A) and one consisting of only full-length TTR (type B) have been suggested to account for some phenotypic differences. Cardiac amyloidosis is associated with increased myocardial thickness and the disease could easily be mistaken for other entities characterised by myocardial thickening, such as sarcomeric hypertrophic cardiomyopathy (HCM). The aims in this thesis were to investigate echocardiographic characteristics in Swedish ATTR amyloidosis patients, and to identify markers aiding in differentiating ATTR heart disease from HCM. Another objective was to examine the impact of fibril composition and sex on the phenotypic variation in amyloid heart disease. Methods: A total of 122 ATTR amyloidosis patients that had undergone thorough echocardiographic examinations were included in the studies. Analyses of ventricular geometry as well as assessment of systolic and diastolic function were performed, using both conventional echocardiographic methods and speckle tracking technique. ECG analysis was conducted in study I, allowing measurement of QRS voltage. In study I and study II ATTR patients were compared to patients with HCM. In addition, 30 healthy controls were added to study II. Results: When parameters from ECG and echocardiography were investigated, the results revealed that the combination of QRS voltage <30 mm (<3 mV) and an interventricular/posterior wall thickness quotient <1.6 could differentiate cardiac ATTR amyloidosis from HCM. Differences in degree of right ventricular involvement were also demonstrated between HCM and ATTR amyloidosis, where ATTR patients displayed a right ventricular apical sparing pattern whereas the inverse pattern was found in HCM. Analysis of fibril composition revealed increased LV wall thickness in type A patients compared to type B, but in addition type A women displayed both lower myocardial thickness and more preserved systolic function as compared to type A males. When cardiac geometry and function were evaluated pre and post liver transplantation in type A and B patients, significant deterioration was detected in type A but not in type B patients after liver transplantation. Conclusions: Increasing awareness of typical cardiac amyloidotic signs by echocardiography is important to reduce the risk of delayed diagnosis. Our classification model based on ECG and echocardiography could aid in differentiating ATTR amyloidosis from HCM. Furthermore, the apical sparing pattern found in the right ventricle may pose another clue for amyloid heart disease, although it requires to be studied further. Furthermore, we disclosed that type A fibrils, male sex and increasing age were important determinants of increased myocardial thickness. As type A fibril patients displayed rapid cardiac deterioration after liver transplantation other treatment options should probably be sought for this group of patients.
1002

Efeito de dois sistemas de soldagem na alteração dimensional nas ligas de cobalto-cromo verificado por meio de análise por extensometria linear elétrica e resistência à flexão

Castilho, Anderson Almeida [UNESP] 13 July 2009 (has links) (PDF)
Made available in DSpace on 2014-06-11T19:28:57Z (GMT). No. of bitstreams: 0 Previous issue date: 2009-07-13Bitstream added on 2014-06-13T19:58:20Z : No. of bitstreams: 1 castilho_aa_me_sjc.pdf: 568029 bytes, checksum: 0b5b31953733da6dcf83b1d44aeb677d (MD5) / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) / O objetivo neste estudo foi avaliar a alteração dimensional provocada pelos procedimentos de soldagem nas infra-estruturas de próteses fixas impanto-suportadas por meio de análise de extensometria linear elétrica assim como se determinar a resistência flexão de dois tipos de juntas soldadas (Arco-Plasma e Laser) em liga Odontológica Co-Cr. Para tanto, estruturas metálicas foram fundidas pelo método de indução para pilares tipo micro-unit. Para esse estudo, foram investigados três grupos: Grupo controle (G I: fundição em Monobloco, n=10), Grupo Arco-Plasma (G II: fundição segmentada e soldagem da estrutura em Arco-Plasma, n=10) e Grupo Laser (G III: fundição segmentada e soldagem da estrutura em LASER, n=10) as quais após assentamento em modelo de análise extensométrica, foram coletadas três leituras de microdeformação (με) para cada amostra. Os grupos, após ensaio de extensometria linear elétrica, foram submetidos ao teste de resistência à flexão (MPa) em máquina de ensaios universal (EMIC, 0,5 mm/min, 500Kg). As médias ±DP dos valores de microdeformação observados para as condições foram para o grupo Monobloco:461,9με; para o grupo Arco-Plasma: 637,0με e para o grupo Laser : 526,8με. Os resultados obtidos após o teste de resistência à flexão foram: para o grupo Monobloco: 1857,2MPa; para o grupo Arco-Plasma: 1820MPa e para o grupo Laser : 1068Mpa. Uma comparação em análise extensométrica entre os três grupos, quanto à distribuição dos valores de alteração dimensional, foi efetuada por meio do teste de Kruskal-Wallis. Verificou-se que a distribuição dos valores de alteração dimensional não difere Estatisticamente (estatística kw = 1,77; gl = 2; p = 0,414 > 0,05). Uma comparação entre os três grupos, quanto à distribuição dos valores... / The aim of this study was to evaluate the dimensional changes caused by the welding procedures in implant-supported prostheses infrastructure by strain gauge analysis as well as to determine the flexural strength values of two types of welded joints (Arc-Plasm and Laser) in Co-Cr dental alloy. Thus, metal structures were casted by induction method for micro-unit type abutment. For this study, three groups were evaluated: Control Group (G I: monoblock casting, n = 10), Arc-Plasm Group (G II: casting and welding of structures in Arc-Plasm, n = 10) and Laser Group (G III: casting and welding of structures in Laser, n = 10), in which were, after placing the samples in the strain gauge analysis model, three micro strain (με) measurements for each specimen were collected. The groups, after strain gauge analysis, were submitted to flexural strength (MPa) test in an universal testing machine (EMIC, 0.5 mm / min, 500Kg). Mean ± SD values of microstrain conditions observed for the Monoblock group were: 461.9 mε; for the Arc-Plasm group: 637.0 mε and the Laser group: 526.8 mε. The results, after flexural strength test, were: Monoblock group: 1857.2 MPa; Arc-Plasm group: 1820 MPa and Laser group: 1068 MPa. The strain gauge comparison analysis between the three groups, as well the distribution of dimensional changes values were made by Kruskal- Wallis test. It was found that the values´ distribution of dimensional changes do not differ statistically (KW statistic = 1.77, df = 2, p = 0.414> 0.05). A comparison between the three groups, in relation to the 108 distribution of the values of flexural strength, was performed by Kruskal- Wallis test. It was found that the values distribution of flexural strength differ statistically... (Complete abstract click electronic access below)
1003

Extensometria: estudo das deformações ao redor de três implantes cone morse, com posicionamento linear, sob carga axial

Abreu, Celina Wanderley de [UNESP] 03 February 2009 (has links) (PDF)
Made available in DSpace on 2014-06-11T19:28:57Z (GMT). No. of bitstreams: 0 Previous issue date: 2009-02-03Bitstream added on 2014-06-13T18:58:12Z : No. of bitstreams: 1 abreu_cw_me_sjc.pdf: 508442 bytes, checksum: 720d525ea366cc2fd0575e67a37ba04e (MD5) / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) / Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP) / O objetivo desse estudo foi avaliar a aplicação de carga e distribuição das microdeformações ao redor de implantes com conexão protética cone morse. Três implantes foram inseridos num bloco de poliuretano e pilares microunit foram instalados nos implantes com torque de 20 Ncm. Três coifas usinadas foram adaptadas nos pilares para configurar a supraestrutura protética (n=5) e comparar com as supra-estruturas obtidas com coifas plásticas. Quatro extensômetros foram colados na superfície superior do bloco. Uma carga vertical estática de 30 Kg foi aplicada em cinco pontos das supra-estruturas. Os registros obtidos dos extensômetros foram submetidos ao teste estatístico ANOVA e Tukey (α=5%). As medidas derivadas dessa simulação revelaram que durante a aplicação de carga: (1) existiu uma relação direta do local de aplicação e na distribuição da microdeformação ao redor dos implantes; (2) não existiu diferença na microdeformação entre coifas plásticas e usinadas. / The aim of this study was to evaluate the load transfer and strain distribution by an implant-supported fixed partial prosthesis. Three implants Morse Taper were inserted in a polyurethane block and abutments microunit were installed on the implants with a torque of 20 Ncm. Plastic cylinders and prefabricated cylinders were adapted on abutments to fabricate the framework (n=5). Four strain gauges were attached on the superior surface of the block and then each framework was tight on the abutments with a torque of 10 Ncm and vertical load of 30Kg was applied to five points on the framework. The data obtained in the strain gauge analysis were submitted to the statistical tests ANOVA and Tukey (α=5%). The measurements derived from this simulation revealed that: (1) there was a direct proportion between the strain distribution in the metal framework and stresses created in the supporting structure around the implants; (2) there was not a strain difference between plastic and prefabricated cylinders during the load transfer
1004

Aspectos da deformacao do aluminio em ensaios de tracao

QUADROS, NEY F. de 09 October 2014 (has links)
Made available in DSpace on 2014-10-09T12:31:55Z (GMT). No. of bitstreams: 0 / Made available in DSpace on 2014-10-09T13:56:40Z (GMT). No. of bitstreams: 1 02238.pdf: 7874589 bytes, checksum: 2508ea5b8a12f7656ab705c285fb99b3 (MD5) / Tese (Doutoramento) / IPEN/T / Instituto de Pesquisas Energeticas e Nucleares - IPEN/CNEN-SP
1005

Contribution à la caractérisation expérimentale et à la modélisation des champs de pression, de deformations et de contraintes induits par un contact élastique entre composants mécaniques. / Contribution to experimental caracterisation and modelisation of pressure field, strain field and stress field due to elesatic contact between mecanical components.

Solle, Julien 16 October 2013 (has links)
L'objectif du travail présenté dans ce mémoire de thèse est d'évaluer par des mesures les champs de pression, de déformation et de contraintes induits par un contact élastique localisé entre deux pièces mécaniques. Après avoir exploré les différentes méthodes existantes, un constat a été fait : la grande majorité des techniques de mesure passent par l'évaluation de grandeurs physiques seulement indirectement liées aux grandeurs recherchées. En cherchant une approche plus directe, l'idée de caractériser la déformation de la surface de contact entre deux pièces a permis de trouver un moyen de mesure : la microscopie confocale chromatique. Ainsi, en mesurant, cette surface, par transparence, et en utilisant la théorie des potentiels de Boussinesq et Cerrutti, il a été possible d'une part de calculer le champ de pression au contact entre les pièces mais aussi d'évaluer les autres champs élastiques associés. Cette approche a aussi permis de mettre au point une méthode de simulation de contact localisé originale et performante s'appliquant à toute géométrie de contact. / The aim of this thesis is to evaluate pressure, strain and stress fields induced by a localized contact between mechanical parts. As the different methods have been explored, it appeared that all existent methods just measure physical quantities only indirectly related to the data of interest. By searching a more direct method, the idea of characterizing the deformation of the surface of contact between parts allowed to find a way of measurement: chromatic confocal microscopy. Thus, measuring this surface by transparency and using Boussinesq and Cerrutti potential theory allows first to calculate the pressure field at the contact between the parts but also to evaluate the other associated elastic fields. This approach also helped to develop an original and highly simulation method of localized contact applying to any contact geometry.
1006

[en] APPLICATION OF A CONTINUATED METHOD OF FINITE ELASTICITY PROBLEMS OF INCOMPRESSIBLE MATERIALS / [pt] APLICAÇÃO DO MÉTODO DE CONTINUAÇÃO A PROBLEMAS DE ELASTICIDADE FINITA DE MATERIAIS INCOMPRESSÍVEIS

EDGAR NOBUO MAMIYA 15 March 2018 (has links)
[pt] Apresenta-se aqui uma aplicação do método de continuação, baseado no algoritmo de Euler-Quase Newton, a problemas de equilíbrio de materiais hiperelásticos incompressíveis sujeitos a grandes deformações. Discretiza-se o problema misto estado deformado-campo de pressão pela utilização do método dos elementos finitos, prevendo-se a compatibilidade LBB entre os espaços envolvidos. Propõe-se a utilização de uma função densidade de energia de deformação para o material de Mooney-Rivlin distinta daquela apresentada na literatura clássica, devido ao mal comportamento do Hessiano associado à formulação original. / [en] The application of a continuation method based on the Euler-Chord algorithm to equilibrium problems of incompressible, hyperelastic materials subjected to large deformations is here presented. The mixed strained state-pressure field problem is discretized by means of the finite element method, taking into account the LBB compatibility condition between the involved spaces. The utilization of a strain energy density function diverse from the one presented in the classical literature, is proposed, due to the ill behavior of the Hessian associated with the original formulation.
1007

Germanium déformé pour l'émission de lumière / Strained germanium for light emission

Guilloy, Kévin 05 July 2016 (has links)
Malgré le caractère indirect de sa bande interdite, le germanium est un bon candidat comme source de lumière pour la photonique silicium puisque l'application de déformations en tension réduit l'écart entre l'énergie de son gap direct et celle de son gap indirect. Cependant, l'application de très fortes déformations soulève un certain nombre de questions, tant d'un point de vue technologique que de la connaissance des propriétés de ce matériau. Après avoir posé les bases théoriques du problème, deux approches pour déformer le germanium sont employées : la première utilisant des nanofils crus selon le mécanisme Vapeur-Liquide-Solide, la seconde utilisant une micro-structuration de substrats de germanium sur isolant.Pour la première, une étude du dopage n des nanofils crus par CVD en utilisant des mesures électriques 4 pointes et la spectroscopie EDX révèle que ceux-ci atteignent une concentration atomique en phosphore de 7 1019 cm-3, ceux-ci étant complètement activés. Un procédé de micro-fabrication est ensuite utilisé pour mettre en tension des nanofils uniques, ce qui permet d'atteindre 1.5 % d'élongation uniaxiale mesurée par micro-diffraction de rayons X. La déformation est corrélé à une mesure du gap direct par spectroscopie de photocourant, en bon accord avec les prédictions théoriques de la littérature.Le dernier chapitre présente le procédé de fabrication de structures obtenues par amplification de la contrainte résiduelle des couches de germanium sur isolant. La diffraction de rayon X, couplée à la spectroscopie Raman, révèle qu'elles atteignent 4.9 % d'extension uniaxiale et 1.9 % d'extension biaxiale. La relation entre le décalage Raman et la déformation diffère significativement des modèles publiés dans la littérature au delà de quelques pourcents de déformation. Enfin, la mesure des transitions directes avec les bandes de trous lourds et légers par spectroscopie d'électro-absorption montre que leur dépendance en déformation s'avère ne plus être en complet accord avec la théorie des potentiels de déformation au-delà de 2 % mais en accord avec des prédictions effectués par modèle des liaisons fortes. / Despite the indirect nature of its bandgap, germanium is a promising candidate as a potential light source for silicon photonic, since the application of tensile strain reduces the energy difference between its direct and indirect bandgaps. However, the application of very large strains raises a number of issues, from a technological point of vue as well as for the determination of the material properties. After laying the theoretical fondations of this problem, two straining approaches are employed : the first one using nanowires grown by the Vapor-Liquid-Solid mechanism, the second using micro-structuration of germanium-on-insulator substrates.For the first one, a study of the n-type doping of CVD-grown nanowires using 4-probes electrical measurements and EDX spectroscopy reveals that they reach a phosphorus atomic concentration of 7 1019 cm-3, these dopants being fully activated. A micro-fabrication process is then used to apply tensile strain to single nanowires, reaching 1.5 % uniaxial stretch measured by X-ray micro-diffraction. The strain measurement is correlated with a direct bandgap measurement by photocurrent spectroscopy, leading to a good agreement with theoretical predictions from the literature.The last chapter describes the fabrication process of structures obtained by amplification of the residual stress of germanium layers on insulator. X-ray diffraction, coupled to Raman spectroscopy, reveals that the structures reach 4.9 % uniaxial stretch and 1.9 % biaxial stretch. The relation between Raman-shift and strain differs significantly from models published in the literature above a few percents of strain. Finally, the measurement of the direct transition with the light- and heavy-holes bands by electro-absorption spectroscopy shows that their strain dependence is not in complete agreement with the deformation potential theory above 2 % but in agreement with predictions from tight-binding simulations.
1008

Hamstringsruptur – en fotbollsspelares svåraste motståndare : En litteraturstudie framtagen för att hjälpa fotbollstränare att förebygga och behandla hamstringsrupturer / Hamstring strain – a soccer player 's most difficult opponent : A literature study presented to help soccer coaches to prevent and treat hamstring strains

Bylinder Westerberg, Frida, Magnusson, Gabriella January 2018 (has links)
Introduktion: Fotboll är en av de mest skadedrabbade idrotterna. 70-90% av skadorna är lokaliserade i nedre extremiteter. Den vanligaste skadan är hamstringsruptur och utgör 37% av skador i nedre extremiteter. Det finns idag mycket forskning gjord på hamstringsrupturer hos manliga fotbollsspelare, men skadefrekvensen för hamstringsrupturen minskar inte. Syfte: Studiens syfte är att bidra med ökad medvetenhet och kunskap om uppkomst, rehabilitering och preventiva åtgärder på hamstringsrupturer för tränare i manliga fotbollslag. Metod: Studien har sammanställt redan befintlig litteratur om de valda område för att besvara studiens syfte. Studiens valda metod är en litteraturstudie. Resultat: (1) Uppkomst: Höghastighetssprint & förlängning. (2) Rehabilitering: Individuell konservativ behandling. (3) Preventiva åtgärder: Excentriska övningar ex: Nordic hamstrings exercise, Asklings glider. Slutsats: Mer kunskap behövs inom området, både för tränare och spelare i idrottsföreningar, och kunskapen måste presenteras på ett användbart sätt. / Introduction: Soccer is one of the most injured sports. 70-90% of the injuries are located in the lower extremities. The most common injury is hamstring strain and accounts for 37% of lower limb damage. There is a lot of research done today on hamstring strains for male soccer players, but the injury rate for hamstring strains is not diminishing. Purpose: This study wants to contribute to increased awareness and knowledge of the origin, rehabilitation and prevention of hamstring strains for coaches in male football teams. Method: The study has complied already existing literature on the chosen areas to answer the purpose of the study. The chosen method on the study is a literature study. Result: (1) Origin: High Speed Sprint & extension. (2) Rehabilitation: Individual conservative treatment. (3) Preventive measures: Eccentric exercises eg: Nordic hamstrings training, Askling Glider. Conclusion: More knowledge is needed in the field, for both athletes and coaches, and the knowledge must be presented in a useful way.
1009

Self-Control and the Consequences of Maladaptive Coping: Specifying a New Pathway between Victimization and Offending

January 2011 (has links)
abstract: The link between victimization and offending is well established in the literature, yet an unexplored causal pathway within this relationship is concerned with why some individuals engage in maladaptive coping in response to victimization. In particular, those with low self-control may be attracted to problematic yet immediately gratifying forms of coping post-victimization (e.g., substance use), which may increase their likelihood of violent offending in the future. Using three waves of adolescent panel data from the Gang Resistance Education and Training (GREAT) program, this research examines: (1) whether individuals with low-self control are more likely to engage in substance use coping following violent victimization, and (2) whether victims with low self-control who engage in substance use coping are more likely to commit violent offenses in the future. The results from negative binomial regressions support these hypotheses, even after controlling for prior offending, peer influences, prior substance abuse, and other forms of offending. The implications for integrating general strain and self-control theories, as well as for our understanding of the victimization-offending overlap, are discussed. / Dissertation/Thesis / M.S. Criminology and Criminal Justice 2011
1010

Advanced Nanostructured Concepts in Solar Cells using III-V and Silicon-Based Materials

January 2011 (has links)
abstract: As existing solar cell technologies come closer to their theoretical efficiency, new concepts that overcome the Shockley-Queisser limit and exceed 50% efficiency need to be explored. New materials systems are often investigated to achieve this, but the use of existing solar cell materials in advanced concept approaches is compelling for multiple theoretical and practical reasons. In order to include advanced concept approaches into existing materials, nanostructures are used as they alter the physical properties of these materials. To explore advanced nanostructured concepts with existing materials such as III-V alloys, silicon and/or silicon/germanium and associated alloys, fundamental aspects of using these materials in advanced concept nanostructured solar cells must be understood. Chief among these is the determination and predication of optimum electronic band structures, including effects such as strain on the band structure, and the material's opto-electronic properties. Nanostructures have a large impact on band structure and electronic properties through quantum confinement. An additional large effect is the change in band structure due to elastic strain caused by lattice mismatch between the barrier and nanostructured (usually self-assembled QDs) materials. To develop a material model for advanced concept solar cells, the band structure is calculated for single as well as vertical array of quantum dots with the realistic effects such as strain, associated with the epitaxial growth of these materials. The results show significant effect of strain in band structure. More importantly, the band diagram of a vertical array of QDs with different spacer layer thickness show significant change in band offsets, especially for heavy and light hole valence bands when the spacer layer thickness is reduced. These results, ultimately, have significance to develop a material model for advance concept solar cells that use the QD nanostructures as absorbing medium. The band structure calculations serve as the basis for multiple other calculations. Chief among these is that the model allows the design of a practical QD advanced concept solar cell, which meets key design criteria such as a negligible valence band offset between the QD/barrier materials and close to optimum band gaps, resulting in the predication of optimum material combinations. / Dissertation/Thesis / Ph.D. Electrical Engineering 2011

Page generated in 0.0487 seconds