Submitted by Luciana Ferreira (lucgeral@gmail.com) on 2017-02-09T10:36:15Z No. of bitstreams: 2 Dissertação - Nara Lígia Leão Casa - 2015.pdf: 3128154 bytes, checksum: 290faf6f7e255eb06dcfd7b0baf48e03 (MD5) license_rdf: 0 bytes, checksum: d41d8cd98f00b204e9800998ecf8427e (MD5) / Approved for entry into archive by Luciana Ferreira (lucgeral@gmail.com) on 2017-02-09T10:36:36Z (GMT) No. of bitstreams: 2 Dissertação - Nara Lígia Leão Casa - 2015.pdf: 3128154 bytes, checksum: 290faf6f7e255eb06dcfd7b0baf48e03 (MD5) license_rdf: 0 bytes, checksum: d41d8cd98f00b204e9800998ecf8427e (MD5) / Made available in DSpace on 2017-02-09T10:36:36Z (GMT). No. of bitstreams: 2 Dissertação - Nara Lígia Leão Casa - 2015.pdf: 3128154 bytes, checksum: 290faf6f7e255eb06dcfd7b0baf48e03 (MD5) license_rdf: 0 bytes, checksum: d41d8cd98f00b204e9800998ecf8427e (MD5) Previous issue date: 2015-12-02 / Introduction: Lumbar disc herniation (LDH) is the most common diagnosis among the degenerative changes in the lumbar spine and it can lead to functional limitations. Although several studies have shown a positive association between polymorphisms in the aggrecan gene and LDH, results are conflicting and vary across populations. Until now, such studies have not been carried out in Brazil. An understanding of this association can help in the prevention and intervention processes in patients with LDH. Objective: Investigate the association between polymorphisms in the aggrecan gene and LDH. Methods: This is a Case-Control study, paired by gender and age. A total of 119 male and female individuals from Goiania (Brazil) participated in the study; 39 individuals in the Case Group (CaG) and 80 in the Control Group (CtG). For each individual, sociodemographic and clinical data were collected as well as blood samples for genetic analysis. DNA was isolated and genotyped at the variable number of tandem repeats (VNTR) region of the aggrecan gene using polymerase chain reaction. Results: Both groups were homogeneous for socio-demographic, anthropometric, and life style variables. The sum of allele sizes at the VNTR region of the aggrecan gene were significantly lower in individuals with LDH, with allele A22 showing significantly higher frequency in this group. Comparison of allele size distribution indicated that shorter alleles (i.e., A13-A25) were more frequent in individuals with LDH, whereas alleles with a higher number of repeats were more frequent among healthy individuals. It should be noted, however, that differences were not significant. The most frequent alleles in both groups were A28, A27 and A29, respectively. Genotype A26/A26 was the most common among individuals in the CaG. Conclusions: An association between short alleles and LDH was observed in this study. This finding is in agreement with other reports in the literature, corroborating the hypothesis that individuals with shorter alleles have an aggrecan gene with fewer repeats. Therefore, a smaller number of chondroitin sulfate chains bind to the aggrecan in the intervertebral disc, leading to a decrease in its physiological function of hydration of the intervertebral disc, and thus to an increase in LDH susceptibility. / Introdução: A hérnia de disco lombar (HDL) é um diagnóstico frequente dentre as alterações degenerativas da coluna lombar e causa limitações funcionais importantes. Alguns estudos apontam para uma associação positiva entre polimorfismos no gene aggrecan e a HDL, porém os resultados ainda são conflitantes e variam entre as populações, não havendo pesquisas sobre o tema na população brasileira até o momento. Compreender essa associação pode auxiliar na prevenção e intervenção junto às pessoas com HDL. Objetivo: Investigar a associação entre polimorfismos no gene aggrecan com a hérnia de disco lombar. Métodos: Estudo caso-controle, pareado em quinquênio por idade e sexo. Participaram do estudo 119 pessoas de ambos os sexos, domiciliadas em Goiânia (Brasil), sendo 39 no Grupo Caso (Ca) e 80 no Controle (Ct). Foram coletados dados sociodemográficos e clínicos e amostras de sangue periférico; o DNA foi isolado para posterior genotipagem do número variável de repetições em Tandem (VNTR) do gene aggrecan (ACAN) através de PCR convencional. Resultados: Os grupos mostraram-se homogêneos quanto às variáveis sociodemográficas, antropométricas e hábitos de vida. O escore alélico do VNTR do gene aggrecan foi significativamente menor nos voluntários com HDL; o alelo A22 mostrou-se significativamente mais prevalente nesse mesmo grupo; no grupo Ca houve maior frequência dos alelos pequenos A13 - A25, enquanto no Ct maior frequência dos alelos grandes, porém, sem diferença estatisticamente significativa; em ambos os grupos os alelos mais frequentes foram A28, A27 e A29, respectivamente; o genótipo A26/A26 foi significativamente mais comum no Grupo Ca. Conclusões: Houve associação entre alelos pequenos com a HDL nos adultos pesquisados e compatibilidade com a literatura internacional, corroborando a hipótese de que indivíduos que possuem alelos pequenos possuem um aggrecan com menor número de repetições. Portanto, um número menor de cadeias de sulfato de condroitina se ligam no aggrecan do disco intervertebral, o que resulta na diminuição da sua função fisiológica de hidratação do disco e, consequentemente, aumenta a susceptibilidade individual à HDL.

INTRODUÇÃO: A degeneração do disco intervertebral (DIV) é um processo crônico e apontado como o maior causador de cervicalgia e lombalgia. Esse processo geralmente conta com a degradação da matriz extracelular, expressão de citocinas inflamatórias e fatores angiogênicos e axonogênicos. Entretanto, muito pouco se sabe sobre esse processo em DIVs assintomáticos durante o envelhecimento, principalmente no segmento cervical. O objetivo desse estudo foi de delinear o perfil de moléculas relacionadas à degeneração discal em DIVs cervicais e lombares. MÉTODOS: Discos intervertebrais humanos cervicais e lombares (C4-C6 e L4-S1) foram coletados em autópsia de 30 indivíduos presumivelmente assintomáticos e divididos em grupos jovem (GJ < 35 anos, n=60) e idoso (GI > 65 anos, n=60). O nível de degeneração foi constatado pela escala de Thompson, e foi correlacionado com a detecção imuno-histoquímica das moléculas de MMP-1, -2, -3, TIMP-1, IL-1beta, TNF-alfa, VEGF, NGF-beta e BDNF. RESULTADOS: Todos os DIVs mostraram algum grau de degeneração, embora mais acentuadas no GI. As moléculas empenhadas no estudo foram identificadas em ambos grupos. A detecção imuno-histoquímica foi prevalente no citoplasma das células nativas do DIV e na região de interseção entre a placa vertebral e o arranjo fibro-colágeno. O envelhecimento propiciou, no disco cervical, maior expressão de MMP-2, -3, VEGF, NGF-beta e BDNF, enquanto que no disco lombar, a maior expressão foi de MMP-1, -2 -3, TIMP-1, TNF-alfa, VEGF e NGF-beta. DISCUSSÃO: O envelhecimento de DIVs cervicais e lombares caracterizou-se por exibir um processo catabólico e extensivo remodelamento da matriz extracelular, os quais podem ser interpretados como eventos que antecipam a doença degenerativa discal. Esse processo é capaz de levar a angiogênese e axonogênese de modo a ampliar o metabolismo aeróbio do DIV e captar informação nociceptiva como forma de defesa, uma vez que até nos discos lombares de indivíduos jovens essa última característica pôde ser observada. Discos assintomáticos também exibem moléculas relacionadas à doença degenerativa discal e talvez a inibição de parte dessas possa resultar em terapia preventiva / INTRODUCTION: Degeneration of the intervertebral disc (DIV) is a chronic process that pointed as a major cause of neck and low back pain. This process generally includes an extracellular matrix degradation, expression of inflammatory cytokines, angiogenesis and axonogenesis factors. However, there is a little known about this process in asymptomatic DIVs during aging, especially in the cervical region. The aim of this study was to delineate the profile of molecules related to disc degeneration in the cervical and lumbar discs. METHODS: Human cervical and lumbar intervertebral discs (C4-C6 e L4-S1) were harvested at autopsy from 30 asymptomatic individuals, and divided according to age with young (GJ < 35 years old, n=60) and elderly (GI > 65 years old, n=60) groups. Gross degeneration was graded according to the Thompson scale and this was correlated to the immunohistochemical detection of molecules of MMP-1, -2, -3, TIMP-1, IL-1beta, TNF-alfa, VEGF, NGF-beta e BDNF. RESULTS: Discs from GJ were significantly less degenerated than those of GI. The molecules involved in the study were identified in both groups. The immunohistochemical detection was prevalent in the cytoplasm of native disc cells and the region between the vertebral plate and fibrous collagen arrangement (intersection). Aging provided in cervical disc, increased expression of MMP-2, -3, VEGF, NGF and BDNF-beta, whereas in the lumbar disc the highest expression of MMP-1, -2, -3, TIMP-1, TNF-alfa, VEGF and NGF-beta was seen. DISCUSSION: The aging of cervical and lumbar DIV was marked by catabolic process and a extensive remodeling on extracellular matrix which can be interpreted as a predict event of the degenerative disc disease. This process can lead to angiogenesis and axonogenesis in order to expand the aerobic metabolism of the DIV and get nociceptive information as a defense, since even in the lumbar discs of young individuals this last feature can be observed. Asymptomatic discs also exhibit molecules related to degenerative disc disease and perhaps the inhibition some of these can result in preventive therapy

La dégénérescence des disques intervertébraux (DD) est un processus naturel qui touche une grande partie de la population. Toutefois, elle peut devenir pathologique et ainsi être accélérée par de multiples facteurs et conduire à un dysfonctionnement précoce des disques lombaires. La DD est un phénomène asymptomatique, ce qui le rend délicat à diagnostiquer précocement. Dans ce cadre, le présent travail vise à développer une méthodologie de diagnostic de la DD utilisant imagerie médicale et modélisation biomécanique.Les disques intervertébraux (DIV) sont des articulations fibro-cartilagineuses qui lient les vertèbres du rachis entre elles. Ils ont pour rôle de supporter et redistribuer les chargements appliqués au rachis tout en assurant sa mobilité. Le DIV peut être assimilé d’un point de vue mécanique à un milieu poreux biologique dont le squelette est formé par la matrice extracellulaire (MEC) et la phase fluide par son contenu hydrique. C’est un milieu hétérogène et anisotrope. Possédant une pression osmotique interne élevée, les DIV ne sont pas vascularisés et possèdent un contenu hydrique important dans lesquels les nutriments cellulaires diffusent à partir des vertèbres adjacentes. Cette particularité rend le fonctionnement des disques très dépendant de la régulation en eau en particulier lorsque ces derniers sont soumis à des sollicitations mécaniques non physiologiques.L’une des clés dans l’élaboration d’un diagnostic fiable de la DD peut être de déterminer de manière objective certaines des caractéristiques internes au disque relatives à son hydratation. Dans le présent travail, une méthodologie de diagnostic quantitatif de la viabilité discale et plus largement de la DD est ainsi proposée. Cette méthodologie se base sur un couplage entre l’imagerie médicale et l’analyse par modélisation du comportement biomécanique du DIV. Un modèle physique biphasique du DIV est développé à l’aide de données déduites d’images IRM. Ce modèle tient compte de l’anisotropie du DIV et des effets induits par les déformations mécaniques sur le processus de transport nutritif.La partie mécanique du modèle est tout d’abord validée en utilisant des résultats d’essais de relaxation réalisés précédemment par l’équipe de biomécanique d’IRPHE. Le modèle est à même de reproduire la distribution de la porosité à l’intérieur du DIV et la perte d’eau suite à un effort mécanique. Cela permet de confirmer la fiabilité de la méthodologie de diagnostic développée pour les cas étudiés. En intégrant le couplage mécano-métabolique, la réponse biomécanique du DIV à des chargements quasi statiques et cycliques est ensuite analysée. / Intervertebral disc degeneration (DD) is a natural process affecting a large part of the population. However, it can be accelerated by several factors and then become associated to lumbar disc pathologies. Given that the DD is symptomless, it is complicated to diagnostic it early. In this context, the present work aims to develop a new methodology of DD diagnostic based on medical imaging and biomechanical modeling.The intervertebral discs (IVD) are fibro-cartilaginous joints that connect vertebrae together ensuring their relative motion. They support and distribute loads applied on the spine. Mechanically, the IVD can be assimilated to a biological porous media in which the solid phase is composed of the extracellular matrix (MEC) and the fluid phase is formed by water content. It is a non-homogeneous and anisotropic component. The IVD is nonvascularized and characterized by a high water content in which cell nutrients diffuses from the adjacent vertebrae. Given this latter particularity, the porosity of the IVD presents a key factor in in its functioning especially when exposed to mechanical non-physiological loads. One of the main keys in the elaboration of a reliable DD diagnostic is to determine objectively some of the IVD interne properties related to its water content. In the present work, a new quantitative methodology of DD diagnostic is proposed. This method is based on a coupling between the medical imaging and the IVD biomechanical behavior modeling. A biphasic IVD model is developed using data from MRI imaging. This model takes into account the anisotropy of the IVD and the effect of the mechanical deformation on the nutrient transport process.The mechanical part of the developed model was firstly validated using results of relaxation tests previously performed by the biomechanics staff of IRPHE. The model is able to predict water distribution within the IVD and the water loss as response to a mechanical load. These results confirm the reliability of the developed diagnostic methodology for the studied cases. The biomechanical response to quasi-static and cyclic loads is then analyzed. The present work proposes and evaluates a new methodology of DD quantitative diagnostic. It also analyzes and compares mechanical and metabolic responses to quasi-static and cyclic loads.

The intervertebral disc (IVD), situated between adjoining vertebrae, consists of the gelatinous nucleus pulposus (NP) in the centre surrounded by the tougher annulus fibrosus (AF). Its main roles are to distribute loads and to act as joints. With aging, degenerative disc disease (DDD) occurs due to an imbalance in anabolic and catabolic events in the IVD, which results in a loss of function. Lower back pain (LBP) affects 84% of people at some point in their lifetime and is strongly associated with DDD. Current LBP treatments have limited long term efficacy and are symptomatic rather than curative. Cell-based therapies are regarded to hold great potential for the treatment of DDD as it has been hypothesised that they could regenerate the damaged tissue and alleviate LBP. A number of natural and synthetic biomaterials have been investigated as NP tissue engineering scaffolds with varying results. In this study, a self assembling peptide hydrogel (SAPH) was investigated for its potential as a cell carrier and/or scaffold for NP tissue engineering. SAPHs display the advantages of natural polymer hydrogels such as biocompatibility and biodegradability whilst combining the advantages of synthetic materials such as controlled structural and mechanical propertiesCharacterisation determined that the SAPH nanofibrous architecture had features that were of similar scale to extracellular matrix (ECM) components of the human NP. The mechanical properties of the SAPH could be optimised to closely match the native tissue. The system could shear thin and self-heal making the system ideally suited to delivery via minimally invasive procedure. The three dimensional (3D) culture of bovine NP cells (bNPCs) in the SAPH demonstrated that the NP phenotype could be restored after de-differentiation during monolayer culture. Gene expression results demonstrated that ‘traditional’ and ‘novel’ NP markers were highly expressed throughout in vitro culture. Cell viability was high, cell population remained stable and bNPCs adopted the characteristic rounded morphology of native NPCs. Finally, type II collagen and aggrecan, the main ECM components of the NP, were deposited with increasing production over culture period. Growth differentiation factor 6 (GDF-6) has been identified as the most promising current growth factor for inducing discogenic differentiation from human bone marrow mesenchymal stem cell (h-BMMSCs). After samples were stimulated with GDF-6, gene expression results confirmed that a NP-like phenotype could be induced with high expression of ‘traditional’ and ‘novel’ NP markers. Cell viability was high, cell population remained stable and NP associated ECM components were deposited with cells displaying a rounded morphology. Interestingly, when h-BMMSCs were cultured without GDF-6, it was strongly suggested that spontaneous discogenic differentiation occurred after culture in the SAPHs as ‘traditional’ and ‘novel’ NP markers were highly expressed, morphology was comparable to native NPCs and type II collagen and aggrecan were deposited extracellularly. If these findings were accurate then this is the first study to demonstrate that a NP-like phenotype could be induced from MSCs without use of an exogenous growth factor or a discogenic bioactive motif. Despite exciting and novel results, further work is required to confirm the potential of SAPHs for NP tissue engineering scaffolds.

L'étude de la composition chimique et de la cinématique des étoiles de la Voie Lactée est essentielle afin de comprendre comment les grandes structures de notre Galaxie se sont formées. Les étoiles de faible masse gardent en mémoire dans leur atmosphère la composition chimique du milieu interstellaire dans lequel elles sont nées, et leur cinématique est essentielle afin de caractériser les différentes populations stellaires. Dans cette thèse, nous étudions le disque galactique, composante majeure de notre Galaxie. Dans le cadre de la mission spatiale Gaia, nous avons développé une procédure automatique de mesure d'abondances chimiques, GAUGUIN, utilisée dans le cadre du Gaia-ESO Survey GES (abondances chimiques d'éléments alpha et du pic du fer pour 10000 étoiles) et du projet AMBRE (abondances de lithium pour 7300 étoiles). GAUGUIN va être intégré au pipeline d'analyse des spectres RVS de Gaia. Nous avons étudié l'évolution des dispersions des vitesses dans le disque galactique en fonction du [Mg/Fe], utilisé comme proxy de l'âge. A partir de 6800 étoiles de GES, nous avons détecté la présence d'étoiles du disque épais cinématiquement froides mais avec des valeurs élevées du rapport [Mg/Fe], donc possiblement âgées. Dans le contexte d'un milieu turbulent, nous discutons la présence de ces étoiles dans le cadre des différents modèles de formation du disque galactique. Nous avons également montré que l'abondance du lithium dans le disque montre une croissance avec la métallicité sur le domaine -1<[M/H]<+0 dex et décroît pour les métallicités super-solaires. Enfin, le disque mince et le disque épais seraient caractérisés par des évolutions chimiques différentes en abondance de lithium. / Studying both the chemical composition and kinematics of Milky Way stars is essential to understand how big structures of our Galaxy are formed. Indeed, low-mass stars retain in their photosphere the chemical composition of the interstellar medium is which they were born. Additionally, the kinematics are essential to characterize stellar populations. In this thesis, we focus on the galactic disc, a major component of the Milky Way. In the context of the Gaia mission, we have developed an automatic procedure GAUGUIN, devoted to deriving chemical abundances. We first applied our method to the Gaia-ESO Survey (GES) data to derive alpha and iron-peak chemical abundances for 10000 stars. We then derived lithium abundances for 7300 stars from the AMBRE project. GAUGUIN is well adapted to massive spectroscopic surveys, both in terms of computation time and accuracy. GAUGUIN will be soon integrated into the RVS DPAC analysis pipeline of the Gaia mission. We studied the velocity dispersions in the galactic disc as a function of the [Mg/Fe] ratio, used as an age proxy. Thanks to 6800 GES stars, we detected thick disc stars with cool kinematics and high [Mg/Fe] ratio, so presumably old. In the generally turbulent context of the primitive galactic disc, this thesis places these results in the framework of the different disc formation and evolution scenarios. We also showed that the lithium abundance in the galactic disc increases as a function of the metallicity in the domain -1<[M/H]+0 dex and decreases at super-solar metallicities. Finally, the thin and the thick discs could be characterized by different lithium abundance evolutions.

Pollution is the single largest cause of transmission/distribution line outages, next to lightning, which result in expensive power outages. A major significance of the problem is that it can repeatedly occur even at normal working voltages. As a result, it has become the most detrimental factor affecting the safe operation of extra and ultra high voltage (EHV/UHV) transmission lines and substations. In reality, the phenomenon of pollution-induced flashover is a very complex, and vexatious problem that continues to challenge high voltage engineers even today. In spite of knowing this phenomenon for the past several decades, a solution has remained still elusive. Although there exist some remedial measures, there are associated limitations, which will become evident on long runs. The guaranteed solution seems to be the washing and cleaning of insulators for which utilities spend significant amount of money. Therefore, there is a need to develop a suitable mitigation technique which is cost effective and yield better performance in the field. Motivated by this, the present study is undertaken and it essentially aims to seek simple alternative solutions for the problem for strings with ceramic insulator discs. All the ten types (normal and anti fog) ceramic insulators, which are commonly employed in our country, are considered in the study. Amongst the several controllable and uncontrollable physical quantities leading to the pollution flashover phenomena, the maximum surface field identified as on of the major influencing factor. In fact, the field concentration near the pin can lead to early formation of dry band and scintillation/partial arcs. Considering this, it is intended to seek possible minimization of the maximum surface field occurring at the pin region. This is expected to yield enhanced pollution/contamination flashover strength and in addition, show an improvement in normal operation. The intended study requires a detailed knowledge on field distribution. However, the required data is found to be rather scarce. In view of this a detailed study on field distribution is taken up for all the ten types of disc insulators used in our country. For the problem under investigation, the governing equation has been identified for both clean and polluted conditions along with pertinent boundary conditions. Considering the open geometry nature of the problem along with presence of multiple dielectrics, Surface Charge Simulation (SCSM) methodology was found to be most suitable and hence adopted for the work. In particular, the Galerkin method with piecewise linear interpolation function is employed in the formulation. The method employed and the codes developed are verified with suitable examples. First, a detailed quantification of the field distribution under clean conditions is made for all the ten types of discs in single disc and string configuration. Subsequently, the task of reducing the maximum surface field gradient, which occurs at the pin, is attempted. Several consideration lead to an artificial extension of pin as one of best feasible choice. However, any attempt to extend the pin would lead to some reduction in total creepage length, possible enhancement of bulk stress in air and enhancement of stress in triple junction. After a careful study, involving several experimental trials, a novel field control element (FCE) is developed both for normal and anti-fog types of insulator discs. From the electric field simulation study, it is shown that the use of field control element for uniform pollution deposition prevailing under laboratory test conditions yields a significant reduction of maximum surface field for discs by about 47 to 54%. Similarly a reduction of about 37% to 55% in case of 3-disc string (for 33 kV class), 30% to 52% in case of 9-disc string (for 132 kV class), 27% to 52% in case of 14-disc string (220 kV class), 27% to 54% in case of 23/20 disc string (for 400 kV class) and 41% to 48% in case of 35/29 disc strings (for 765kV class) is achieved respectively for different strings. It is anticipated that this will lead to retardation in inception of scintillations/partial arcs, which in turn can reduce the risk of pollution induced flashover. Subsequently, it was aimed to experimentally evaluate the impact of field control element on the performance of disc/string under normal and that during polluted conditions. For this a national level unique artificial pollution test facility as per the international standards has been established for conducting pollution studies on disc insulator/strings up to 132kV system voltage (The rating of test source: 150kV/2A,100kV/3A,50kV/6A of 300kVA). Experimental investigations for the normal operation involving dry and wet power frequency flashover strengths, lightning impulse strength, radio interference level (RIV), visible discharge inception (Corona) level and voltage distribution along the string are carried out. The study showed that with the insertion of field control element, performance under normal condition is maintained and in fact noticeably improved in certain cases. Subsequently pollution flashover strength is evaluated using solid layer and cold fog methods. The pollution flashover strength exhibited an overall improvement 15 to 20% for all types of discs considered in the study. Similarly an improvement of 16 to 19% and 12-14% is observed for 3-disc string and 6-disc string respectively. The reasons for relatively lower gain in the pollution flashover strength as compared to reduction in maximum surface field are investigated. In particular, the reduction in improvement with number of discs in a string is dealt with. The non-uniform wet-ting against highly non-uniform drying of insulator surface and discs in a string, are identified as the cause for deviation. For an experimental verification of the same, the pollution layer resistance of individual discs in a 3-disc string is measured prior to and immediately after flashover. It is shown that the resistances of the different units become grossly different even though initial values were substantially the same. The values measured immediately after flashover show that the resistance of the top unit develops voltage enough to result in its flashover and subsequently, the flashover of the whole string. In summary, the main contribution of the present work is the development of novel field control element (FCE) for both normal and anti-fog type of ceramic disc insulators, which will enhance their pollution flashover strength. The actual cost of these elements is estimated to be about 1-2% of the cost of the disc, while the gain in strength is shown to be more than 12 - 20%.

This Master's thesis project was provided by Epiroc Rock Drills AB and conducted at Camatec Industriteknik AB in Karlstad, Sweden. The project is centered around the cutter wheel in the mechanical rock excavator Mobile Miner 40V.  This cutter wheel is equipped with cutter discs that grind rock into debris as the wheel rotates and thrusts forward. The internal system consisting of a bearing constellation and the components in its vicinity has experienced a certain degree of wear in the form of scuffing and this was detected on the surfaces of some of the components in the system. The reasons for this occurrence are unknown and per the request of the thesis provider, this was to be determined. The thesis provider also requested a new Finite Element Analysis (FEA) model of the system along with feasible load cases that can be applied to said model. The project was deemed extensive and was therefore decided to be conducted by two students. This thesis covers the determination of the load cases as well as the optimization of the current design of the system inside the cutter wheel. During the pre-study, relevant background data was obtained for the cutter wheel and the internal system. Methods and models considered to potentially be useful were also gathered. The system in question was divided into two separate models; one consisted of a tribo-system with two components in sliding contact and the other consisted of the bearing constellation along with the outer-most section of the cutter wheel. The purpose of the first model was to use it to determine the contact pressure between the tribo-surfaces and by doing so, be able to determine the expected lubrication regime for the oil in the tribo-system. A material selection process was also conducted on the tribo-surface that had experienced the most severe surface damage. Additionally, minor reconstructions were made with the purpose of optimizing the system. The purpose of the second model was to apply the calculated load cases to the cutter disc attachments located on the outer-most section of the cutter wheel and then determine the contact pressures that develop on the bearing roller elements. The results of the thesis work consist of five potential material options, two reconstructions and 60 different load cases for the FEA model. With the load cases, the largest contact pressures on the bearing roller elements was determined. In addition, the cause of the severe surface damage that had occurred in the system is believed to have been identified. Further work on the project work is believed to be required. Future work of interest are determining load cases that incorporate multiple cutter discs simultaneously in contact with the rock, reconstruction solutions for the oil inlet and outlet pipes, a more thorough materials selection process and a criterion for the expected lubrication regime in the tribo-system based on tests performed with materials that are more identical to the ones in this project. / Detta examensarbete tillhandahölls av Epiroc Rock Drills AB och genomfördes hos Camatec Industriteknik i Karlstad, Sverige. Projektet är centrerat kring cutterhjulet i maskinen Mobile Miner 40V som är avsedd för mekanisk bergavverkning. Cutterhjulet är utrustat med cutter discar som maler berget till mindre flisor genom att hjulet roterar och trycks framåt. Det inre systemet bestående av en lagring med närliggande komponenter har utsatts för en viss grad av nötning i form av scuffing och detta upptäcktes på ytorna hos vissa av komponenterna i systemet. De bakomliggande anledningarna för denna förekomst är okända och utifrån begäran från projektgivaren skulle dessa anledningar fastställas. Projektgivaren eftersökte även en ny FEM-modell av systemet tillsammans med rimliga lastfall som ska kunna appliceras på modellen i fråga. Projektet ansågs tämligen omfattande och det bedömdes därför att två studenter krävdes för att genomföra arbetet. Denna uppsats behandlar framtagningen av lastfallen såväl som optimeringen av den nuvarande designen av systemet inuti cutterhjulet. Under förstudien hämtades relevant bakgrundsdata för cutterhjulet och det interna systemet. Metoder och teorier som ansågs vara potentiellt användbara samlades även in. Systemet i fråga delades in i två separata modeller; en bestod av ett tribo-system bestående av två tribo-ytor i glidande kontakt och den andra bestod av lagringen tillsammans med den yttersta sektionen hos cutterhjulet. Syftet med den förstnämnda modellen var att använda den för att bestämma kontakttrycket mellan tribo-ytorna, och genom detta kunna fastställa den förväntade smörjningsregimen hos oljan i tribo-systemet. En materialvalsprocess utfördes även för tribo-ytan som hade utsatts för den mest allvarliga skadan. Även smärre omkonstruktioner utfördes med syftet att optimera systemet. Syftet hos den andra modellen var att kunna applicera de beräknade lastfallen på cutter discarnas infästningar som återfinns i den yttersta sektionen hos cutterhjulet och sedan bestämma kontakttrycken som uppstår på rullarna i lagren. Resultaten från arbetet består av fem potentiella materialval, två konstruktionsändringar och 60 olika lastfall för FEM-modellen. Genom att applicera lastfallen bestämdes de största kontakttrycken på lagrens rullar. Utöver detta anses det att anledningen för den allvarliga ytskadan som hade skett i systemet har identifierats. Det anses att fortsatt arbete krävs för projektet. Kompletterande arbete som anses vara av intresse är lastfall som inkluderar flera cutter discar i ingrepp samtidigt med berget, konstruktionslösningar för tillförsel och bortförsel av oljan, en mer djupgående materialvalsprocess och ett kriterium för förväntad smörjningsregim hos tribo-systemet baserat på tester utförda med material som är mer identiska med dem som förekommer i projektet.

The main target of this work is a design of the program for border localization of the optic disc in OCT data. Part of this program is also localization of the „optic cup“ and calculation of several values that characterize optic disc. The work is also dealing with a description of the optical coherence tomography principle which is used in ophthalmology. One chapter describes some published methods of optic cup localization. Success of the program and its comparison with OCT Zeiss Stratus 3000 is evaluated at the end of the work.

Degenerative Veränderungen der Lendenwirbelsäule beginnen bereits im Alter von unter 20 Jahren und betreffen vor allem die unteren 3 Bewegungssegmente. Die degenerativen Veränderungen an der Bandscheibe gehen mit einer Kalzifizierung der Grund- und Deckplatten der Wirbelkörper einher, was zu einer Reduktion der Nährstoffversorgung der Bandscheibe und damit zu einem Untergang der matrixbildenden Zellen und konsekutiv zu einem Flüssigkeitsverlust in der Bandscheibe führt. Als Folge nimmt die Belastung der Bandscheibe weiter ab. Die aktuellen Therapieoptionen umfassen sowohl die konservative als auch die operative Therapie, wobei allerdings nur die Folgen der Degeneration behandelt werden. Ziel einer Zelltransplantation ist es, der Bandscheibe wieder matrixbildende Zellen zur Verfügung zu stellen, damit die nutritiven Veränderungen auszugleichen und eventuell reversibel zu machen. Dieser Effekt konnte im Tierversuch nachgewiesen werden, woraufhin eine klinische Studie initiiert wurde. Im Rahmen der publizierten klinischen prospektiven, randomisierten Studie konnte gezeigt werden, dass die Transplantation autologer Chondrozyten, die bei einer notwendigen operativen Therapie eines sequestrierten Bandscheibenvorfalls gewonnen wurden, einen sowohl klinisch als auch bildmorphologisch positiven Effekt auf die degenerierten Bandscheiben hat. Es kam zu einer signifikanten Reduktion der Schmerzsymptomatik und einer Steigerung der Lebensqualität in der Gruppe der transplantierten Patienten. Die Bandscheibenhöhe zeigt sich stabil über den Beobachtungszeitraum von 2 Jahren.

During tightening of a screw, the variation in friction will affect the force acting on the joint, especially when tightening using torque as a control parameter. So, it is crucial to have a proper understanding of the contact mechanism and friction in the screw head to joint and thread interfaces. This will make it possible to develop tightening strategies that compensate for the friction variation to assure a better quality of the joint. This understating could be achieved through conducting experiments using a pin on disc tribometer. In the present study, the frictional behavior of three different coatings has been investigated using a tribometer. The study comprises both the experimental and numerical procedures. Experimental tests have been conducted to find the required material inputs for numerical modeling, and also, to log the results required for validation of the simulation results. The Central Composite Design (CCD) method has been employed for the design of experiments where the normal pressure and sliding velocity have been selected as the test parameters (design factors). For the numerical part of the study, the localized finite element model of the contact region of the pin and coated disc has been made in ANSYS. The model represents a portion of the test specimen used in the tribometer so that a high level of refinement could be applied. Two different approaches have been implemented in ANSYS to model the friction coefficient as a function of normal pressure and sliding velocity. The both approaches are based on a mathematical model for friction coefficient which has nine constants that could be determined using the experimental tests’ results. Also, a correction scheme for the contact stiffness has been implemented so that the mesh dependency of the model could be reduced significantly. Finally, the results of the numerical modeling have been compared with those obtained from experiments for friction force. The comparison shows a good agreement between them, proving the accuracy of the utilized numerical model and the correction scheme employed. / Vid åtdragning av en skruv kommer variationen i friktion att påverka kraften som verkar på fogen, speciellt vid åtdragning med vridmoment som styrparameter. Så det är avgörande att ha en ordentlig underskattning av kontaktmekanismen och friktionen i skruvhuvudet till skarvar och gänggränssnitt. Detta kommer att göra det möjligt att utveckla åtdragningsstrategier som kompenserar för friktionsvariationen för att säkerställa en bättre kvalitet på fogen. Denna underskattning kan uppnås genom att utföra experiment med en stift på skivtribometer. I föreliggande studie har friktionsbeteendet hos tre olika beläggningar undersökts med hjälp av en tribometer. Studien omfattar både de experimentella och numeriska procedurerna. Experimentella tester har genomförts för att hitta nödvändiga materialingångar för numerisk modellering, och även för att logga de resultat som krävs för validering av simuleringsresultaten. Central Composite Design (CCD) metod har använts för design av experiment där det normala trycket och glidhastigheten har valts som testparametrar (designfaktorer). För den numeriska delen av studien har den lokaliserade finita elementmodellen av kontaktområdet för stiftet och den belagda skivan gjorts i ANSYS. Modellen representerar en del av testexemplaret som används i tribometern så att en hög nivå av förfining kunde tillämpas. Två olika tillvägagångssätt har implementerats i ANSYS för att modellera friktionskoefficienten som en funktion av normalt tryck och glidhastighet. Båda tillvägagångssätten är baserade på en matematisk modell för friktionskoefficient som har nio konstanter som kan bestämmas med hjälp av de experimentella testernas resultat. Dessutom har ett korrigeringsschema för kontaktstyvheten implementerats så att modellens meshberoende kan reduceras avsevärt. Slutligen har resultaten av den numeriska modelleringen jämförts med de som erhållits från experiment för friktionskraft. Jämförelsen visar en god överensstämmelse mellan dem, vilket bevisar noggrannheten hos den använda numeriska modellen och det använda korrigeringsschemat.