Les disques optiques numériques sont utilisés par de nombreux organismes, publics ou privés, pour l’archivage de données. Malgré les espoirs fondés dans l’utilisation de ces supports, des pertes d’information ont été observées, parfois après seulement quelques années d’archivage. Cette évolution a été attribuée au vieillissement des disques, sans préjuger des constituants impliqués. Ce travail de thèse visait à identifier les modifications chimiques et physiques résultant de l’application de différentes contraintes (photochimique, thermique ethydrolytique) sur des constituants de disques optiques : substrats de CD-R en polycarbonate, couches enregistrables de types « phtalocyanine » et « azoïque » et vernis de protection. L’étude de ce dernier constituant a permis d’élargir les recherches au cas du Blu-ray Disc. Ces évolutions physico-chimiques ont ensuite été corrélées à des variations des paramètres analogiques et numériques de disques soumis aux mêmes contraintes. L’objectif ultime de ce travail était de mettre en place une méthodologie générale permettant de comprendre l’origine de la perte d’information de disques optiques numériques exposés à des contraintes. / Optical discs are often used by many private or public organizations to archive essential data. For a long time these media were supposed to be reliable. However, a loss of the stored data was highlighted, sometimes only after a few years of storage. This degradation was attributed to the discs ageing, without any identification of the materials involved in this ageing. This work aimed to determine the chemical and physical modifications resulting from the application of different stresses (photochemical, thermal and hydrolytic) on the materials used in optical discs : the CD-R polycarbonate substrates, the recording layers based on phthalocyanines and azo compounds, and the protective layers. The study of this last component allowed us to extend the researches to the case of the Blu-ray Disc. These physico-chemical modifications were then correlated to variations in digital and analog parameters of discs submitted to the same stresses. The ultimate objective of this work was to propose a general method that could help to understand the origin of the loss of information of optical discs submitted to stresses.

Made available in DSpace on 2014-06-11T19:32:09Z (GMT). No. of bitstreams: 0 Previous issue date: 2009-08-27Bitstream added on 2014-06-13T18:43:07Z : No. of bitstreams: 1 chanut_tgg_dr_guara.pdf: 931615 bytes, checksum: eb9339c7c510483431d4b235ce98cea8 (MD5) / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) / Neste trabalho de tese exploramos a sugestão de Barge e Sommeria (1995) de captura de partículas em vórtices anticiclônicos que se formam devido a instabilidades na nebulosa proto-planetária. O problema dinâmico foi estudado através de simulações de um disco kepleriano bidimensional e incompressível. Examinamos o processo de concentração de partículas dentro de grandes vórtices através das equações do movimento para partículas individuais (com tamanho de 50 cm e 2,12 m) submetidas à gravidade solar e ao arrasto do gás nebular. Os vórtices levam à captura de um grande número de partículas. Mostramos que a eficácia das capturas não depende somente do valor do arrasto gasoso e da elongação do vórtice mas também do modelo do disco proto-planetário escolhido. Um achado muito importante nesse trabalho de tese pode começar a responder à questão sobre a formação planetária: colapso gravitacional ou coagulação? Quando incluímos a auto-gravidade, os resultados que obtivemos mostram que a acumulação das partículas dentro do vórtice é bem mais rápida. É um ponto muito importante na formação dos núcleos planetários até hoje bastante discutido. De fato, a formação dos núcleos planetários dos planetas gigantes precisa da acumulação de material maior que 1MÅ em muito pouco tempo para que o colapso ocorra antes do efeito gravitacional dentro do vórtice começar a expulsar os planetesimais A auto-gravidade até então bastante negligenciada por muitos autores pode ser uma ferramenta essencial a ser incluída no modelo de formação planetária para explicar tal fato. Outro resultado interessante que obtivemos foi que o crescimento por auto-sedimentação das partículas com tamanho sub-métrico, não é muito eficiente para formar planetesimais. Parece que os vórtices capturam partículas com um tamanho preferencial para formar planetesimais ou núcleos planetários. / In this thesis, we explore the suggestion of Barge & Sommeria (1995) of dust-trapping in anticyclonic vortices forming due to instabilities in the protoplanetary nebula. The dynamical problem is studied through numerical simulations of a two-dimensional incompressible Keplerian disc. We examine the process of particle concentration inside large vortex through a non-collisional N body’s code for individual particles (with sizes of 50 cm and 2,12 m) subject to the solar gravity and the nebular gas drag. The vortices tend to capture a large number of particles. We show that the effectiveness of these captures depend not only on the value of the gaseous drag and the elongation of the vortices but also on the model of the protoplanetary disc chosen. A very important finding in this thesis can start to answer the question of the planetary formation: gravitational collapse or coagulation? When we include the self-gravity, the results that we found show that the accumulation of particles inside the vortices is faster. It is a very important point in the formation of planetary embryo until today highly discussed. In fact, the formation of the giant planets embryo need the accumulation of more material than 1MÅ in a very short time such that the collapse occurs before the gravitational effect inside the vortices start to eject the planetesimals. Self-gravity, until now neglected by many authors could be an essential tool to be included in planetary formation model to explain such fact. Another interesting result that we got was that the growth for auto-sedimentation of particles with sub-metric size, is not very efficient to form planetesimal. It seems that vortices capture particles with a preferential size to form planetesimals or planetary cores.

Made available in DSpace on 2014-06-11T19:34:57Z (GMT). No. of bitstreams: 0 Previous issue date: 2011-07-22Bitstream added on 2014-06-13T21:06:51Z : No. of bitstreams: 1 lemos_ff_dr_guara_parcial.pdf: 67760 bytes, checksum: 8abbb6c32f12d888cf49226d69fd138e (MD5) Bitstreams deleted on 2014-10-03T16:24:39Z: lemos_ff_dr_guara_parcial.pdf,Bitstream added on 2014-10-03T16:27:37Z : No. of bitstreams: 2 lemos_ff_dr_guara_parcial.pdf.txt: 11034 bytes, checksum: 59c288b2b373bbe58255effddd89bb52 (MD5) 000671151.pdf: 2407167 bytes, checksum: 0e13b6a8dfac5d68060ec4460476f509 (MD5) Bitstreams deleted on 2014-10-03T16:33:14Z: 000671151.pdf,Bitstream added on 2014-10-03T16:43:28Z : No. of bitstreams: 2 lemos_ff_dr_guara_parcial.pdf.txt: 11034 bytes, checksum: 59c288b2b373bbe58255effddd89bb52 (MD5) 000671151.pdf: 2407167 bytes, checksum: 0e13b6a8dfac5d68060ec4460476f509 (MD5) Bitstreams deleted on 2014-10-03T16:48:54Z: 000671151.pdf,Bitstream added on 2014-10-03T16:49:46Z : No. of bitstreams: 1 000671151.pdf: 2407167 bytes, checksum: 0e13b6a8dfac5d68060ec4460476f509 (MD5) Bitstreams deleted on 2014-10-27T11:47:07Z: 000671151.pdf,Bitstream added on 2014-10-27T11:48:04Z : No. of bitstreams: 1 000671151.pdf: 2407167 bytes, checksum: 0e13b6a8dfac5d68060ec4460476f509 (MD5) / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) / A desidratação do núcleo pulposo que, juntamente com o anulus fibroso, compõe o disco intervertebral, participa do processo de degeneração da coluna vertebral. Torna-se importante entender como este processo de desidratação e a consequente alteração das propriedades mecânicas influenciam na biomecânica dessa articulação. O principal objetivo deste estudo é analisar a influência da desidratação no coeficiente de amortecimento viscoso e como esta variação pode alterar o comportamento mecânico do disco intervertebral lombar. Este estudo é composto de duas etapas: na primeira, o coeficiente de amortecimento viscoso foi obtido experimentalmente de unidades funcionais de colunas lombares suínas antes e após o processo de desidratação das mesmas; na segunda, foi simulado em modelo computacional a resposta harmônica, utilizando-se dados da literatura e do coeficiente de amortecimento viscoso, analisando as diferenças entre uma simulação com o disco intervertebral hidratado e desidratado. O coeficiente de amortecimento viscoso hidratado (4,7) e desidratado (2,7) apresentou diferença estatisticamente significante (p<0,001). Na simulação computacional podese evidenciar uma menor influência da variação do coeficiente de amortecimento viscoso quando analisado de forma isolada do que quando analisado em conjunto com variações nos dados referentes à rigidez, principalmente nas frequências de ressonância e nas amplitudes de pressão intradiscal e deformação do disco intervertebral. Concluiu-se que discos intervertebrais desidratados respondem de forma diferente à vibração, o que pode contribuir para os processos lesivos da coluna vertebral / The dehydration of the nucleus pulposus which, with the anulus fibrosus, composes the intervertebral disc, participates in the process of degeneration of the spine. It is important to understand how this process and the consequent alteration of dehydration of the mechanical properties influence the biomechanics of this joint. The aim of this study is to analyze the influence of dehydration in the viscous damping coefficient and how this variation can change the mechanical behavior of lumbar intervertebral disc. This study consists of two stages: first, the viscous damping coefficient was obtained experimentally in functional units of porcine lumbar spine before and after the dehydration process of them; second, an harmonic response was simulated in a computer model, using literature data and the viscous damping coefficient, analyzing the differences between a simulation with the hydrated and dehydrated intervertebral disc. The hydrated (4.7) and dehydrated (2.7) viscous damping coefficient showed a statistically significant difference (p <0.001). In the computer simulation, a lower influence of variation of the viscous damping coefficient can be detected when analyzed separately than when analyzed together with variation on stiffness data, especially in the resonance frequencies and in the amplitudes of the intradiscal pressure and deformation of the intervertebral disc. We conclude that dehydrated intervertebral discs respond differently to vibration, what can contribute to the damaging processes of the spine

Master of Landscape Architecture / Department of Landscape Architecture/Regional and Community Planning / Howard Hahn / Disc golf is on the rise. Disc golf is a sport based on traditional golf but played with a flying disc instead of a ball and club. It was formalized in the 1970s and has grown steadily ever since, particularly in the last decade. Landscape architecture has largely ignored this phenomenon, except for two MLA theses (Plansky, 2013a; Hutzelman, 2012). This seems unusual, considering that landscape architecture has been called the most relevant degree to disc golf course design (DGCD, 2014). This study assesses the relationship between landscape architecture and disc golf. A general research question guides this study: what added benefit, if any, might landscape architects bring to disc golf course design and development? This guiding question is explored through three subquestions: 1) what services might landscape architects offer disc golf course development, 2) how might landscape architectural services be used by the current state of disc golf course development, and 3) how might future course development types take full advantage of the services provided by landscape architects? This project used literature synthesis, analysis of existing data, and three types of exploratory designs to answer the above questions. The results of these methods showed that landscape architects can add value to disc golf course design and development through their skillsets and process. Not every landscape architect necessarily possesses the skills and experience to design a disc golf course, but landscape architects as a whole can propose disc golf courses if they have a basic knowledge of course requirements. A closer relationship between landscape architects and disc golf would be beneficial for the growth of the profession and the sport. This report concludes with recommendations and an action plan to reach this goal.

Abstract Genetic factors have been implicated to play a role in both degenerative lumbar spinal stenosis (LSS) and intervertebral disc disease (IDD). Sequence variations in the genes coding for collagen IX and inflammatory mediators have been indicated as risk factors for IDD. Nine genes coding for intervertebral disc (IVD) collagens I, II, IX and XI and aggrecan (AGC1) were analyzed for sequence variations in 29 Finnish individuals with LSS. In addition, two polymorphisms in the vitamin D receptor gene and one in the matrix metalloproteinase-3 gene were studied. Study subjects were analyzed both clinically and radiologically. Results indicated an association between the COL11A2 IVS6-4 a to t polymorphism and LSS (p = 0.0016). Moreover, the t/t genotype was found more often in the patient group compared to controls (p = 0.0011). A novel splicing mutation, likely resulting in the synthesis of a truncated protein, was identified in COL9A2. Eight hundred four Chinese individuals were screened for the presence of the Trp2 and Trp3 alleles. The Trp2 allele was found in 20% of the individuals compared to the previously reported 5% in Finnish patients with IDD characterized by sciatica. The Trp2 allele was found to predispose to IVD degeneration and end plate herniations, increasing the risk by 2.4-fold from 40 to 49 years of age. In addition, the degeneration was worse in individuals with the Trp2 allele. The risk for annular tears was 4-fold greater in study subjects from 30 to 39 years of age who were Trp2 positive. Surprisingly, the Trp3 allele was absent even though it was found in about 9% of Finnish individuals. One hundred fifty-five Finnish individuals with IDD characterized by sciatica were analyzed for sequence variations in four genes coding for inflammatory mediators IL1A, IL1B, IL6, and TNFA. In addition, sixteen polymorphisms in inflammatory mediator genes were analyzed. The results identified an association between sciatica and the E5+15T>A polymorphism in IL6 (p = 0.007). A significant association was also seen in the IL6 haplotype analysis (-597 g>a, -572 g>c, -174 g>c and E5+15T>A). The association of the GGGA haplotype with the disease was highly significant (p = 0.0033).

Abstract Genetic factors have been shown to have an important role in intervertebral disc disease. The associations of known genetic risk factors and whole-body vibration, a proposed environmental risk factor, for intervertebral disc disease (IDD) were evaluated. Eleven variations in eight genes (COL9A2, COL9A3, COL11A2, IL1A, IL1B, IL6, MMP-3 and VDR) were genotyped in 150 male train engineers with an average of 21-year exposure to whole-body vibration and 61 male paper mill workers with no occupational exposure to vibration. The number of individuals belonging to the IDD group was significantly higher among train engineers (42% of train engineers vs. 17.5% of sedentary workers; p = 0.005). In addition, the IL1A-889T allele represented a risk factor for the IDD-phenotype. In order to clarify the role of genetic variations in the genes coding for several proinflammatory mediators, hundred fifty-five Finnish individuals with IDD were analyzed for mutations in the genes coding for inflammatory mediators IL-1α, IL-1β, IL-6 and TNF-α. In addition, sixteen single nucleotide polymorphisms (SNPs) in inflammatory mediator genes were genotyped. An association was identified between IDD and IL6 polymorphism +15T>A in exon 5 (p = 0.007). In addition, IL6 haplotype GGGA of -597G>A, -572G>C, -174G>C and +15T>A in exon 5 associated with IDD (p = 0.0033). A functional SNP in the CILP gene has been suggested to cause IDD in the Japanese population. This functional variation was analyzed in 243 Finnish IDD patients and 259 controls, and in 348 Chinese individuals with degenerative MRI findings and 343 Chinese individuals with normal MRI. No association was found in the Finnish and Chinese study populations. In order to reveal chromosomal susceptibility loci and new candidate gene(s) for IDD a genome-wide scan was performed on 14 Finnish families with 186 individuals. Genome-wide and fine mapping analysis provided maximum two-point LOD scores of 2.71, 2.36 and 2.04 for chromosomes 21, 4, and 6, respectively. Second fine mapping confirmed the susceptibility of chromosome 21. Two candidate genes, ADAMTS-1 and ADAMTS-5, were analyzed in the region suggesting linkage, leading to the identification of thirteen sequence variations. However, none of the variations were disease causing.

The purpose of this study was to determine whether magnetic resonance imaging (MRI) accurately predicts surgical findings in dachshund dogs with thoracolumbar intervertebral disc extrusions (TLDE). Sixteen dogs presenting with signs of acute TLDE took part in this investigation. MRI was performed on each dog. This was followed by decompressive surgery with the completion of an intra-operative questionnaire documenting the site of the extrusion and spatial distribution of the disc material for each dog. An independent veterinary radiologist evaluated each MRI study, measured and recorded the same parameters from images, utilising 3 sequences (T1-, T2-weighted and Short T1 Inversion recovery) without knowledge of the surgical findings. The imaging findings were compared with the intra-operative measurements. The specific intervertebral disc (IVD) space from which the material extruded and lateralization of the extruded disc material (EDM) were found to be similar between MRI and surgical observations. Longitudinal distribution of the EDM was described as being cranial, caudal or equally distributed in relation to the affected IVD. A Kappa test showed moderate agreement in longitudinal distribution between MRI and surgery. Circumferential distribution was recorded on transverse images and compared to surgical findings. Recorded distribution only coincided completely in 1 case, although the rest of the cases showed good overlap of findings between the MRI and intraoperative findings.Our results could not demonstrate a statistically significant difference between T1-, T2-weighted or STIR sequences when determining the length of the extruded mass in the vertebral canal. We found that when evaluating the absolute error and range of error for each sequence, that the T2-weighted sequence had a narrower range of errors and was thus more consistent in predicting the size of the lesion pre-surgically. MRI was validated as a very useful imaging modality for neurological disorders in dogs. / Dissertation (MMedVet)--University of Pretoria, 2007. / Companion Animal Clinical Studies / unrestricted

The purpose of this project was to develop a spoken word-recognition task that could be used clinically to evaluate recognition performance of individuals with hearing loss in a background noise. The test instrument incorporated monosyllabic words at seven levels over a 35-dB range presented in a background of "multi-talker" babble that was fixed in level. In Experiment 1, we established normative data on 24 young adult listeners with normal hearing and on 50 older adult listeners with high-frequency hearing loss. In Experiment 2, we examined the effects that age and hearing loss have on understanding speech in multi-talker babble by studying 15 subjects in each decade interval from 20 to 79 years.

No description available.

<p> This study is one of the projects of the artificial joints group conducted by Professor W. R. Newcombe, Department of Mechanical Engineering and Dr. G. R. Viviani, Department of Surgery.</p> <p> A summary of the literature survey of the lower back which is pertinent to the design of a replacement for the lumbar spine is reported. Motions, force system, and strengths of the lumbar intervertebral joint are obtained from the literatures and calculation.</p> <p> Advantages of silicone elastomer and titanium as the biomaterials for the artificial disc are presented. An experiment to test the bond between titanium and silicone reveals that the strength provided by only applying primer is insufficient.</p> <p> Surface structure for prosthetic stabilization and initial fixation is discussed. Proposed design alternatives for artificial discs are presented with the attempts to reduce the number of moulds needed by introducing a prosthesis with a more regular shape.</p> <p> An important part of this thesis is to indicate the direction in which further work in this area should proceed.</p> / Thesis / Master of Engineering (MEngr)