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  • 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.
21

Fluid management in immersion and imprint microlithography

Bassett, Derek William 31 January 2011 (has links)
The important roles of fluid dynamics in immersion lithography (IL) and step-and-flash imprint lithography (S FIL) are analyzed experimentally and theoretically. In IL there are many challenges with managing a fluid droplet between the lens and the wafer, including preventing separation of the fluid droplet from the lens and deposition of small droplets behind the lens. Fluid management is also critical in S FIL because the imprint fluid creates capillary and lubrication forces, both of which are primarily responsible for the dynamics of the template and fluid motion. The fluid flow and shape of the wafer determine how uniform the gap height between the wafer and the template is, and they affect the resistance during the alignment phase. IL was investigated as a methodology to improve laser lithography for making photomasks. The fluid flow in IL was investigated by building a test apparatus to simulate the motion of the fluid droplet during microlithographic production, and using this apparatus to conduct experiments on various immersion fluids and wafer topcoats to determine what instabilities would occur. A theoretical model was used to predict the fluid separation instabilities. Finite element simulations were also used to model the fluid droplet, and these simulations accurately predict the fluid instabilities and quantitatively agreed with the model and experiments. It is shown that the process is viable: capillary forces are sufficient to keep the fluid droplet stable, heating effects due to the laser are negligible, and other concerns such as evaporation and dissolution are manageable. Euler beam theory and the lubrication equation were used to model the bending of an S FIL template and the flow of the fluid between the template and a non-flat wafer. The template filling time, conformance of the template to the wafer, and the alignment phase are investigated with an analytical model and finite element simulations. Analysis and simulations show that uniformity of the residual film thickness and ease of proper alignment depend greatly on the planarity of the wafer, the properties of the template, and the surface tension of the fluid. / text
22

Avaliação dos efeitos de polimorfismos e da origem parental do alelo na expressão de genes candidatos à característica maciez da carne em bovinos da raça Nelore

Souza, Marcela Maria de 29 February 2012 (has links)
Made available in DSpace on 2016-06-02T20:21:29Z (GMT). No. of bitstreams: 1 4293.pdf: 642637 bytes, checksum: 6b7a62fa5cf6f1f58e418c8414593c06 (MD5) Previous issue date: 2012-02-29 / Financiadora de Estudos e Projetos / Tenderness is the main trait appreciated by consumers of bovine meat, however Nellore animals that comprise the largest part of Brazilian cattle, have lower tenderness when compared with European animals. In this way, it is essential understand the variability of genes associated to tenderness as well as their mechanisms of allelic expression, considering that deviations of expression depending on the parental origin of the allele have been described for some genes, and these phenomena must be understood to be incorporated in animal breeding programs. Therefore, the aim of this study was to evaluate the variability of SNPs in candidate genes for tenderness and investigate the expression pattern of their alleles. For this purpose, genotypes of SNPs in CAST, CAPN1, DGAT1, leptin, KCNJ11 and IGFBP3 genes were determined in 30 sires, in which the genes DGAT1, leptin and IGFBP3 were not polymorphic. After this, polymorphic SNPs in population of sires were genotyped in their offspring by TaqMan® assay in real time PCR, followed by allelic expression analysis. In the expression analysis, to discriminate each allele of the gene it was utilized one SNP, or two in the case of KCNJ11. All genes presented biallelic expression in adult muscular tissue. However, with exception of CAPN1 for which the allelic expression difference was not significant, the allelic expression ratio was significantly different of 1 for SNP of CAST (1.3±0.03) and the two SNPs of KCNJ11 SNP 2126T>C (1.2±0.04) and SNP 2942C>T (1.46±0.04). Differential allelic expression (DAE) found in SNP 2126T>C of KCNJ11 and in CAST were not influenced by parental origin of allele, but the differences in allelic expression for SNP 2942C>T of gene KCNJ11 showed parental origin effect and influence by genotype of the other SNP of KCNJ11. It was conclude that the CAST, CAPN1 and KCNJ11 are polymorphic in this population, they are not imprinted, but CAST and KCNJ11 showed differential allelic expression. / A maciez é o principal atributo apreciado pelos consumidores da carne bovina, no entanto, animais da raça Nelore, que compõem a maior parte do rebanho brasileiro, apresentam carne menos macia, quando comparados a animais de origem europeia. Assim, é fundamental compreender a variabilidade de genes associados à maciez além de seus mecanismos de expressão alélica, já que desvios da expressão em função da origem parental do alelo têm sido descritos para alguns genes e tais fenômenos precisam ser compreendidos para serem incorporados nos programas de melhoramento animal. Portanto, o objetivo deste trabalho foi avaliar a variabilidade de SNPs contidos em genes candidatos a influenciar a maciez da carne e compreender o padrão de expressão de seus alelos. Para isso, os genótipos para SNPs contidos nos genes CAST, CAPN1, DGAT1, leptina, KCNJ11 e IGFBP3 foram determinados em uma população de 30 touros, nos quais os genes DGAT1, leptina e IGFBP3 não se mostraram polimórficos. Os SNPs polimórficos na população de touros foram então genotipados na progênie, por ensaio TaqMan® em PCR em tempo real, seguida da avaliação da expressão alélica dos mesmos. Na análise de expressão utilizou-se um SNP para discriminar cada alelo do gene, ou dois SNPs, no caso do KCNJ11. O padrão de expressão de todos os genes foi bialélico no tecido muscular adulto. Entretanto, com exceção do CAPN1, para o qual a diferença de expressão alélica não foi significativa, as razões de expressão alélica foram significativamente diferentes de 1 para os genes CAST (1,3±0,03) e os dois SNPs analisados do KCNJ11 SNP 2126T>C (1,2±0,04) e SNP 2942C>T (1,46±0,04). A expressão alélica diferencial (EAD) encontrada no SNP 2126T>C do KCNJ11 e no CAST não foram influenciadas pela origem parental do alelo, mas a diferença de expressão alélica no SNP 2942C>T do gene KCNJ11 apresentou efeito de origem parental, além da influencia do genótipo do outro SNP do KCNJ11. Concluiu-se então que os genes CAST, CAPN1 e KCNJ11 são polimórficos na população, não são imprinted, mas os genes CAST e KCNJ11 apresentam expressão alélica diferencial.
23

Homeostase glicêmica na prole de camundongos com obesidade induzida por dieta hiperlipídica : o papel da sinalização da insulina / Glucose homeostasis in the offspring of hyperlipidic diet-induced obese mice : the role of insulin signaling

Guimarães, Nicole Corrêa, 1987- 23 August 2018 (has links)
Orientador: Marcio Alberto Torsoni / Dissertação (mestrado) - Universidade Estadual de Campinas, Instituto de Biologia / Made available in DSpace on 2018-08-23T02:02:19Z (GMT). No. of bitstreams: 1 Guimaraes_NicoleCorrea_M.pdf: 2579384 bytes, checksum: 1c61c716c6c09d41088ff284a70b8461 (MD5) Previous issue date: 2012 / Resumo: A obesidade é precursora de co-morbidades como o Diabetes Mellitus tipo 2 e doenças vasculares. Estudos demonstram que a composição da dieta materna durante a gestação pode modular o metabolismo da prole, promovendo um ajuste funcional conhecido como imprint metabólico, predispondo a prole ao ganho de peso e resistência da insulina (RI). A RI está diretamente relacionada com a adiposidade e com o aumento no nível de citocinas pró-inflamatórias no sangue. Estas citocinas são responsáveis pela ativação de serina-quinases que podem promover a redução do sinal intracelular. Considerando que o hipotálamo desempenha importante função no controle da homeostase energética e do metabolismo periférico, a alteração na expressão e ativação de proteínas chave neste tecido pode trazer conseqüências importantes para o organismo. Desta maneira, o presente estudo avaliou proteínas hipotalâmicas e hepáticas que possam ser moduladas pelo uso materno de dieta rica em gordura animal. Para isso foram utilizadas proles de camundongos fêmeas que fizeram uso de dieta rica em gordura (grupo HN) ou dieta padrão (grupo NN) durante o período de gestação e lactação e com idade de 4 e 12 semanas (4S e 12S) de vida. Inicialmente foram avaliados o ganho de peso, massa adiposa, a tolerância a glicose, os níveis séricos de insulina e citocinas pró-inflamatórias, a deposição hepática de gordura por histologia e o conteúdo de triglicérides hepáticos. As alterações metabólicas relacionadas à manutenção da homeostase glicêmica e do balanço energético foram avaliadas pela análise do conteúdo e/ou ativação das proteínas JNK, IKK, NFKB, AKT, IR, IRS1, IRS2, ACC, FAS, AMPK, PEPCK e HSL nos tecidos hepático, hipotalâmico e adiposo utilizando a técnica de Western Blot. A prole das fêmeas tratadas com a dieta especial apresentou maior ganho de peso e massa adiposa epididimal, menor tolerância à glicose, maior deposição hepática de gordura no fígado e maiores níveis de triglicérides hepáticos (4 e 12S), maiores níveis sanguíneos de insulina, TNF?, IL1? (12S). As serina quinases JNK e iKK estavam mais fosforiladas no fígado (4 e 12S) e hipotálamo (4S). A proteína NFKB estava mais presente no grupo HN em ambos os tecidos (4S). A proteína AKT apresentou menor fosforilação após estímulo com insulina no hipotálamo (4S) e fígado do grupo HN, bem como o IR, IRS1 e 2 (12S). A proteína PEPCK foi encontrada em maior quantidade no fígado dos animais HN (12S), A proteína FAS foi encontrada em maiores níveis no fígado dos animais HN (4S), entretanto o inverso foi observado na idade de 12 semanas. A enzima HSL estava menos fosforilada no tecido adiposo do grupo HN (12s). A proteína ACC hepática do grupo HN estava menos fosforilada em seu estado basal nos dois períodos, no hipotálamo a fosforilação da ACC não foi diferente do grupo NN (4s). O grupo HN apresentou menor desfosforilação da AMPK por estímulo de insulina. A partir destes resultados observamos que a nutrição hiperlipídica pré-natal foi capaz de influenciar negativamente a homeostase glicêmica da prole, além de modular as vias lipogênicas e o controle do balanço energético / Abstract: Obesity is a condition that preceeds co-morbidities as type 2 Diabetes Mellitus and vascular diseases. Studies demonstrate that the composition of the maternal diet during gestation can modulate offspring's metabolism, leading to a functional adjustment known as metabolic imprint, which predisposes the offspring to weight gain and insulin resistance (IR). IR is directly related to adiposity and the blood level of pro-inflammatory cytokines. These cytokines are responsible for the activation of serine-kinases that can promote a reduction of the intracellular signal. Considering that the hypothalamus plays an important role on the control of energetic homeostasis and peripheral metabolism, the alteration on the expression and activation of key proteins in this tissue may lead to important consequences to the organism. This way, the present study evaluated hypothalamic and hepatic proteins that can be modulated by the maternal use of animal fat rich diet. For that, offsprings of female mice fed a high fat diet (HN group) or standard diet (NN group) during pregnancy and lactation, at the ages of 4 and 12 weeks old (4W and 12W) were used. Initially weight gain, adipose mass, glucose tolerance, serum levels of insulin and pro-inflammatory cytokines, liver fat depot by histology, and liver triglycerides content were evaluated. The metabolic alterations related to the maintenance of glycemic homeostasis and energy balance were evaluated through the analysis of the expression and/or activation of the proteins JNK, IKK, NFKB, AKT, IR, IRS1, IRS2, ACC, FAS, AMPK, PEPCK and HSL in the liver, hypothalamus and asipose tissue using western blot technique. The offspring of the dams treated with the special diet presented higher weight gain and epididymal adipose mass, lower glucose tolerance, higher hepatic fat deposition and higher levels of liver triglycerides (4 and 12W), higher levels of blood insulin, TNF? and IL1? (12W). The serine-kinases JNK and IKK were more phosphorylated in the liver (4 and 12W) and hypothalamus (4W). The NFKB was found at a higher amount in both tissues (4W). The AKT presented lower phosphorylation after stimulation with insulin in the hypothalamus (4W) and liver of HN group, as the IR, IRS1 and 2 were more expressed (12W). PEPCK was found in higher quantity in the liver of HN animals (12W). FAS were found in higher levels in the liver of HN animals (4W), however the opposite was observed at the age of 12 weeks. The enzyme HSL was less phosphorylated in the adipose of HN group (12W). Hepatic ACC of HN group was less phosphorylated in its basal state at both ages; in the hypothalamus the phosphorylation of ACC was not different of NN group (4W). HN group showed lower dephosphorylation of AMPK with insulin stimulation. By these results we observe that the pre-natal hyperlipidic nutrition was able to influence negatively the glucose homeostasis of the offspring, besides the modulation of the lipogenic pathways and energy balance control / Mestrado / Bioquimica / Mestre em Biologia Funcional e Molecular
24

Les empreintes environnementales de l'approvisionnement alimentaire : Paris, ses viandes et lait, XIXe-XXIe siècles / The environmental imprint of food consumption : meat and milk supply to Paris, 19th-21st centuries

Chatzimpiros, Petros 24 June 2011 (has links)
Face aux changements globaux et aux défis du développement soutenable, l'approvisionnement alimentaire urbain doit à la fois être analysé à travers les processus qui le sous-tendent et quantifié en termes de mobilisation des ressources naturelles et d'émission des polluants dans l'environnement. On s'est intéressé dans le cadre de cette thèse à comprendre le mécanisme d'approvisionnement en viande et en lait frais de l'agglomération parisienne sur une période longue de deux siècles et à déterminer, produit par produit, l'empreinte environnementale de l'approvisionnement en termes d'emprise spatiale, de mobilisation d'eau et de flux d'azote entre les agro-systèmes et l'environnement au début des XIXe, XXe et XXIe siècles. On a utilisé des données statistiques nationales et internationales de transport et de production agricole pour déterminer et suivre l'évolution de l'aire géographique d'approvisionnement, évaluer la fraction des subsistances régionales que réclame la capitale pour son approvisionnement, reconstituer à l'aide des modèles de rationnement et des tables d'alimentation les rations des animaux approvisionnant Paris, déterminer, en termes à la fois de biomasse, d'énergie et de protéines, le rendement en viande et en lait du fourrage aux différentes dates et enfin calculer, de manière spatialisée, l'étendue des terres agricoles (empreinte spatiale) - et les flux d'azote et d'eau impliqués dans la production. L'empreinte hydrique a pour objectif de mesurer le volume des prélèvements d'eau (pluviale et d'irrigation) et le taux moyen de mobilisation des apports d'origine pluviale. L'empreinte azotée brute désigne le tonnage total d'azote mis en jeu dans la production, dont le partage entre la production d'aliments et les pertes environnementales dépend de la manière dont fonctionnent les agro-systèmes et caractérise la profondeur de l'empreinte urbaine. On propose ainsi d'élargir la notion d'équivalent habitant (Equ/Hab) classiquement considéré comme représentatif des émissions individuelles d'azote dans les eaux usées urbaines et de définir un équivalent habitant amont qui englobe en quelque sorte tous les rejets individuels d'azote en amont de la ville, relatifs à la production de la nourriture d'un citadin. Depuis le début du XIXe siècle, l'étendue de production par habitant s'est réduite d'un facteur six (pour une consommation de viande et de lait égale à environ 2 kg N/hab/an au début du XIXe siècle comme actuellement) – la réduction étant pour 30 % environ relative au doublement du rendement en viande et en lait du fourrage - mais l'intensité d'utilisation de l'eau et la profondeur de l'empreinte par hectare ont respectivement doublé et quadruplé. On estime qu'actuellement, 45 % des pertes d'azote - soit 5,1 kg N/hab/an ou 60 kg N/ha - proviennent des fumures laissées à l'abandon, faute de n'être reconduites à l'agriculture végétale. Etant donné que la somme des importations de viande bovine, porcine et de lait représente 25 % de l'apport protéique total dans l'alimentation du Parisien et sachant que la fraction végétale de l'alimentation est à priori caractérisée par moins de pertes d'azote que la fraction animale, on estime l'équivalent habitant amont de l'ensemble de l'alimentation du Parisien, à environ 7 Equ/Hab / For the sake of the sustainable development as a measure against global environmental change, urban consumption needs to be studied through the processes that underlie production and assessed in terms of resource use and pollutant emissions into the environment. This PhD thesis devotes to understand the mechanisms in supplying meat and milk to Paris over two hundred years and measure the land requirements, water withdrawals and nitrogen flows between agrosystems and the environment to supply each product in the early 19th, 20th and 21st centuries. We used agricultural and transport statistics from French and international data sources to locate the Paris hinterland at each date, quantify the urban food supply as a proportion of the regional potential food production, precisely model the diets of the livestock according to the animal productivity and the feed availability in the regional and global markets at the dawn of each century, compute the nitrogen, energy and feed conversion efficiencies in the meat and milk production and, finally, assess both the size and the geographic pattern of the Paris acreage (spatial imprint) and of the nitrogen and water flows in support of the production. The water imprint is used to account for the water withdrawals (irrigation and rainwater) in terms of volume and use intensity. The N imprint measures on the one hand the total amount of reactive nitrogen entering the agrosystems and the partitioning of these inputs between the food production and the environmental losses. The latter are referred to as “the depth” of the urban imprint which provides a measurement of the indirect contribution of urban areas to the alteration of the N cycle. When expressed on a “per capita” basis (kg N/cap) the depth of the imprint shows the emissions of reactive nitrogen to supply the diet of one person as opposed to the direct individual N discharge in urban wastewater. When expressed on a “per hectare” basis, it shows the intensity of the upstream urban N emissions and can be used as a tool for assessing urban sustainability beyond the city limits. Since the early 19th century, the land requirements for the “per capita” meat and milk consumption in Paris (equaling about 2 kg N/cap/year in both the early 19th and the early 21st centuries) reduced six-fold – with about 30 % of the reduction relating to the doubling of the nutrient conversion efficiencies in the secondary production – but the water use intensity and the “per hectare” depth of the imprint respectively doubled and quadrupled. We estimate that currently, about 45 % of the N losses - meaning 5.1 kg N/per/year or 60 kg N/ha – stem from abandoned manure. As the beef, pork and fresh milk imports to Paris currently account for about 25 % of the protein intake of a Parisian and given that animal production is a priori more wasteful that primary production, we estimate that the “per capita” emissions of N for providing the whole diet equal over 7 times the urban N discharges, meaning that a city's wastewater treatment plants handle less than 15 % of the total (direct and indirect) food related N emissions of the citizens
25

Nouvelles stratégies pour l'analyse protéomique du tissu cérébral et des fluides biologiques dans la maladie de Parkinson / Strategies for proteomic analysis of cerebral tissue and biological fluids in Parkinson's disease

Zaccaria, Affif 15 March 2013 (has links)
L'analyse protéomique du tissu cérébral pathologique dans la maladie de Parkinson (MP) est un enjeu majeur à l'identification des causes moléculaires de la dégénérescence en vue de développer des thérapies curatives. Jusqu'à présent, les études chez l'humain se sont limitées à l'analyse du cerveau post-mortem, trop souvent représentatif d'un stade très avancé de la maladie et potentiellement altéré par différents facteurs. Dans ce travail, nous avons exploité l'accès temporaire au cerveau parkinsonien durant l'implantation d'électrodes de stimulation, pour obtenir une information moléculaire du tissu cérébral, in vivo et à un stade moins avancé de la maladie. Afin d'optimiser notre stratégie, nous avons ensuite développé un outil dédié à la capture tissulaire dont l'efficacité et le caractère non lésionnel ont été validés in vivo chez le primate. Ce travail permet d'envisager l'analyse protéomique du cerveau parkinsonien « vivant » afin d'identifier les causes moléculaires de la MP. En revanche, cette approche tissulaire n'est pas envisageable pour un diagnostic en routine clinique. Aussi, de nombreux groupes s'intéressent à l'analyse protéomique du LCR en vue d'identifier des marqueurs diagnostiques. Dans cette optique, nous avons mis au point une stratégie, basée sur l'utilisation de nanoparticules (NPs) fonctionnalisées qui a permis un enrichissement considérable des profils protéiques observés en spectrométrie de masse. La reproductibilité et la possibilité d'automatiser intégralement la préparation des échantillons font de notre approche une solution adaptée à la recherche de marqueurs moléculaires diagnostiques de la MP dans le LCR. Nous avons aussi démontré l'intérêt de notre approche pour l'analyse protéomique du plasma et du globule rouge. Enfin, nous avons évalué la possibilité d'utiliser ces NPs in vivo, pour une capture des protéines directement dans la circulation sanguine. / Proteomics analysis of pathological brain tissue in Parkinson's disease (PD) is of great importance to understand the molecular aetiology of degeneration and to develop curative treatments. To date, published studies have been restricted to the analysis of human post-mortem tissue samples, frequently derived from advanced disease stage and potentially altered by several factors. In this project we took advantage of the temporary access to PD patient's brain during electrode implantation to obtain in vivo molecular information from cerebral tissue at earlier stage of the disease. We further developed a dedicated tool to improve our tissue harvesting approach, and validated its efficiency and non-lesion effects in vivo in monkeys. This work opens the way to the proteomic analysis of fresh human brain samples to elucidate molecular causes of degeneration in PD. However such tissue investigation approach remains invasive and cannot be used in routine clinical screening for PD diagnosis. Proteomics analysis of cerebrospinal fluid (CSF) constitutes a promising alternative to identify neuropathological diagnosis markers. For this purpose, we developed a nanoparticle-assisted strategy enabling the enrichment of CSF proteins detection by mass spectrometry. Reproducibility and high throughput potentiality of our approach demonstrate its compatibility with clinical proteomics for PD diagnosis biomarker research in CSF. We also demonstrated the interest of this NP strategy for plasma and red blood cells proteome analysis. Finally, we evaluated the ability to use these NPs for in vivo protein harvesting in blood.
26

Les empreintes des corps dans l'oeuvre d'Alice Munro / The imprints of bodies in Alice Munro’s stories

Bentley, Lucile 26 October 2018 (has links)
Cette thèse met en relation la représentation des corps dans l’œuvre d’Alice Munro avec le processus de l’empreinte tel qu’il a été mis au jour par Georges Didi-Huberman. La description des corps des personnages partage la même essence dialectique que l’empreinte : elle saisit une matière tout en laissant entrevoir le mouvement qui a donné naissance à la forme, elle est la conséquence d’un contact mais n’advient que dans la distance et son unicité fait signe vers le multiple. Le corps et son rapport au monde qui l’entoure met aussi en lumière une relation de ressemblance et de contact, une relation mutuelle que les mots eux-mêmes font transparaître dans une expression qui tend vers le lyrisme. Enfin, les corps représentés dans la fiction munrovienne ne sont pas de simples copies du réel mais sont véritablement créateurs en devenant les matériaux interpersonnels de la création artistique. Cette étude de la représentation des corps dans l’œuvre d’Alice Munro tente de montrer les enjeux de l’attention au corps, en particulier ceux du care, et comment cette attention influence l’écriture fictionnelle. / This dissertation examines the relationship between the representation of bodies in Alice Munro’s work and the imprint process as characterized by Georges Didi-Huberman. The description of the characters’ bodies gives evidence of the same dialectical essence as imprints: it attempts to fix the body matter while making movement visible, it is the product of a contact but becomes apparent only from a distance and its unicity foreshadows its multiplicity. The body and its link to the world around also displays a relationship of resemblance and contact based on reciprocity. It is conveyed through words and an expression that tends to lyricism. Finally, bodies represented in Munro’s fiction are not mere copies of the real but are creative and interpersonal as they become the very material of artistic creation. This study of the representation of bodies in Alice Munro’s work attempts to show what being attentive to bodies entails, in particular in the context of care studies, and how this attention to bodies influences fictional writing.
27

On the influence of indenter tip geometry on the identification of material parameters in indentation testing

Guo, Weichao 08 December 2010 (has links)
ABSTRACT The rapid development of structural materials and their successful applications in various sectors of industry have led to increasing demands for assessing their mechanical properties in small volumes. If the size dimensions are below micron, it is difficult to perform traditional tensile and compression tests at such small scales. Indentation testing as one of the advanced technologies to characterize the mechanical properties of material has already been widely employed since indentation technology has emerged as a cost-effective, convenient and non-destructive method to solve this problem at micro- and nanoscales. In spite of the advances in indentation testing, the theory and development on indentation testing are still not completely mature. Many factors affect the accuracy and reliability of identified material parameters. For instance, when the material properties are determined utilizing the inverse analysis relying on numerical modelling, the procedures often suffer from a strong material parameter correlation, which leads to a non-uniqueness of the solution or high errors in parameter identification. In order to overcome that problem, an approach is proposed to reduce the material parameter correlation by designing appropriate indenter tip shapes able to sense indentation piling-up or sinking-in occurring in non-linear materials. In the present thesis, the effect of indenter tip geometry on parameter correlation in material parameter identification is investigated. It may be helpful to design indenter tip shapes producing a minimal material parameter correlation, which may help to improve the reliability of material parameter identification procedures based on indentation testing combined with inverse methods. First, a method to assess the effect of indenter tip geometry on the identification of material parameters is proposed, which contains a gradient-based numerical optimization method with sensitivity analysis. The sensitivities of objective function computed by finite difference method and by direct differentiation method are compared. Subsequently, the direct differentiation method is selected to use because it is more reliable, accurate and versatile for computing the sensitivities of the objective function. Second, the residual imprint mappings produced by different indenters are investigated. In common indentation experiments, the imprint data are not available because the indenter tip itself shields that region from access by measurement devices during loading and unloading. However, they include information about sinking-in and piling-up, which may be valuable to reduce the correlation of material parameter. Therefore, the effect of the imprint data on identification of material parameters is investigated. Finally, some strategies for improvement of the identifiability of material parameter are proposed. Indenters with special tip shapes and different loading histories are investigated. The sensitivities of material parameters toward indenter tip geometries are evaluated on the materials with elasto-plastic and elasto-visoplastic constitutive laws. The results of this thesis have shown that first, the correlations of material parameters are related to the geometries of indenter tip shapes. The abilities of different indenters for determining material parameters are significantly different. Second, residual imprint mapping data are proved to be important for identification of material parameters, because they contain the additional information about plastic material behaviour. Third, different loading histories are helpful to evaluate the material parameters of time-dependent materials. Particularly, a holding cycle is necessary to determine the material properties of time-dependent materials. These results may be useful to enable a more reliable material parameter identification.
28

Study on the thermomechanical properties and workability of Mg-based bulk metallic glasses

Chang, Yu-Chen 10 July 2008 (has links)
In the near couple years, the applications of amorphous alloys have attracted great attention due to their characteristics and future potential. This research is intended to synthesis a lighter Mg-based amorphous alloy as the imprinting materials for micro-electromechanical system (MEMS) with a high glass forming ability (GFA) and lower glass transition temperature (Tg). Also, the workability of the Mg-based metallic glasses is examined in terms of several viscous flow behaviors and parameters obtained from the thermomechanical analysis (TMA). The lighter Mg-based metallic glasses exhibit their superior glass forming ability, and can be cast into bulk metallic glasses (BMGs). Based on the thermal analysis of the Mg-Cu-Y glassy materials, the evaluation of the glass forming ability and thermal stability for searching the optimum alloy composition is conducted. By using Mg58Cu31Y11 amorphous alloy with the best composition as the micro-forming specimens, imprinting was made by hot pressing at 150oC with several applied compressive stresses to form the hexagonal micro-lens arrays. Finite element simulation using 3D Deform software is also applied to trace the microforming evolution, and to compare with the experimental observations. The results demonstrate that the imprinting is feasible and promising. On the other hand, the Mg-Cu-Gd BMGs with even better GFA than Mg-Cu-Y are explored in terms of their thermomechanical properties. Extension of this study is performed partially by Cu replacing by Ag or B for the improvement of maximum diameter and thermal stability. And the workability of these Mg-Cu-(Ag, B)-Gd metallic glasses, namely, Mg65Cu25-xAgxGd10 (x = 0, 3, 10 at %) and Mg65Cu22B3Gd10 is evaluated in terming of the thermomechanical parameters, viscous flow behavior, deformability, and the deformation model. It is found the fragility for viscous deformation would increase with the replacement of Ag or B, leading to the negative factors for the micro-forming and nano-imprinting practices. This conclusion is supported by the many extracted parameters. Thus, even the B-additive Mg based BMG has much higher hardness and Ag-additive Mg based BMG has the larger maximum rod diameter, they are more difficult to be formed, appearing as a negative factor in the micro-forming or nano-imprinting industry. The base Mg65Cu25Gd10 alloy stilly appears to be more promising than the Ag or B-containing alloys when the viscous forming is under consideration.
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Fabrication of pyramid-shaped microlens array

Chen, Jia-lin 12 February 2009 (has links)
Brightness enhancement film (BEF) has been manufactured in foreign factories for backlight module of liquid crystal display (LCD), then it only have some interior factories to put in exploitation. Because of this, the study presents a precision machining and new step-imprint hot embossing process to fabricate pyramid-shaped microlens array. First, a tungsten (W) steel material is manufactured by precision machining. The dimension of a pyramid-shaped microlens on the W steel are about 300 £gm in the base line of three side, 222 £gm in bevel edge of three side, 139 £gm in height of bottom to top, 180 £gm in pitch of the left and right sides between two pyramid-shaped microlens tips, and 85 degree in top angle of three bevel. The W steel mold is used as the first mold. Second, the pyramid peaks of first mold pattern are transferred on bulk metallic glass (BMG) using step-imprint hot embossing method with position adjustable mechanism to form a smaller concave pyramid-shaped microlens array, it can avoid arc radius of cutting tools which is used as the second mold. Another the pyramid peaks are transferred on PMMA (Polymethylmethacrylate) for concave pyramid-shaped microlens array of optical film in the hot embossing system. Finally, the second mold is fabricated to emboss convex pyramid-shaped microlens array of optical film on PMMA. The foregoing method is provided for backlight module of optical films process.
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Imprint lithography and characterization of photosensitive polymers for advanced microelectronics packaging

Rajarathinam, Venmathy 23 June 2010 (has links)
To enable fast and reliable processors, advances must be made in the interconnections on the printed circuit board and in the interconnections from the chip to the printed circuit board. Processing techniques have been demonstrated to fabricate a copper-clad encapsulated air dielectric layer to enable low loss off-chip electrical signal lines using sacrificial polymers and the three dimensional patterning capabilities of imprint lithography. The inclusion of an air gap can eliminate the dielectric loss allowing the signal to propagate over longer lengths. Additionally, the low dielectric constant of air lowers the loss contributions from the conductor and increases the signal propagation velocity reducing delay. The metal shielding could minimize the crosstalk noise and radiation losses that are significant at high frequencies. The three dimensional patterning capabilities of imprint lithography fabricated curved structures and rounded terminations which can reduce reflections at discontinuities. Furthermore, imprint lithography also created planarized surfaces which simplified the buildup process. Since imprint lithography, only uses temperature and pressure to make a pattern it is an inexpensive and simple process advancement. The metal-clad encapsulated air dielectric structures were fabricated in a comparable number of registration steps to traditional transmission lines. Implementation of all copper chip to substrate interconnects would provide high conductivity electrical connections, resistance to electromigration while avoiding formation of brittle intermetallics. High aspect ratio polymer molds for copper electroplating interconnects could enable improved integrated circuit electrical performance. The properties of a new aqueous base develop, negative-tone photosensitive polynorbornene polymer have been characterized to develop mechanically compliant all copper connections between the chip and printed circuit board. High aspect ratio features of 7:1 (height:width) were produced in 70 ìm thick films in a single coat with straight side-wall profiles and high fidelity. The polymer films studied had a contrast of 11.6 and a low absorption coefficient. To evaluate the polymer's suitability to microelectronics applications, epoxy cross-linking reactions were studied as a function of processing condition through Fourier transform infrared spectroscopy, nano-indentation, and dielectric measurements. The fully cross-linked films had an elastic modulus of 2.9 GPa and hardness of 0.18 GPa which can improve the mechanical compliance of the copper interconnections. A photo-imprint lithography process was developed to improve the photo-patterning of the polynorbornene polymer for high aspect ratio hollow structures. A shallow photo-imprint stamp was developed to physically displace material in the polymer core. Since the imprint stamp displaces material in the area of the feature, the effective film thickness is reduced compared to the bulk film. The reduction in film height reduced the effects of scattering in the core and also facilitated transport of developer within the core. The photo-imprint lithography process resulted in high aspect ratio hollow core pillars that exceeded optical resolution capabilities for comparable feature sizes.

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