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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.
351

Understanding Size-Dependent Structure and Properties of Spinel Iron Oxide Nanocrystals Under 10 nm Diameter

Cooper, Susan 30 April 2019 (has links)
Iron oxide nanoparticles (NPs) are promising materials for use in many applications, including new cancer treatments and in cleaning water, because they exhibit size-dependent magnetic and absorptive properties. NP properties are caused by structural attributes of the NPs, like surface disorder and cation vacancies. However, NP synthetic methods also impact structure, therefore properties, of NPs. Furthermore, the synthetic method is often changed in order to change the core diameter of NPs. Determining if properties are caused by the dimensions of the NP is impossible if there are also structural features present in the NP caused by the synthetic method, like grain boundaries or polycrystalline shells. In Chapter II of this dissertation, we show a new continuous growth synthesis of spinel iron oxide where the diameter of NPs is changed by the amount of precursor added to the reaction, meaning the only structural feature changing between the NPs is size. Continuous growth, therefore, can be used to probe the impact that size has on NP structure and properties. We report that saturation magnetization of NPs produced from continuous growth is size-dependent and higher in magnitude than NPs of the same core diameter made by other syntheses. In chapter III of this dissertation we determine nanoscale structure by Pair Distribution Function (PDF) analysis of Total X-ray Scattering data of NPs isolated from the reaction with core diameters between 3-10 nm. In Chapter IV of this dissertation we monitored the growth of NPs in situ with Total X-ray Scattering to gain insight on the structures of NPs while forming. In situ measurements of Total X-ray Scattering data gave insights into how precursor oxidation state influences the structures formed during formation of NPs, with more oxidized precursor giving a more oxidized product and a reduced precursor yielding a more reduced product even though the NPs formed by either method are indistinguishable by ex situ analysis. This dissertation includes previously published and unpublished co-authored material. / 2021-04-30
352

Números complexos para professores de matemática da educação básica que atuam no ensino médio / Complex number for high school mathematics teachers

Cruz Filho, Robinson Antão da 13 April 2018 (has links)
Um texto sobre o corpo dos números complexos abordando-os de uma forma integrada e direcionada para professores de educação básica que atuam no ensino médio. Apresenta de forma bem fundamentada vários aspectos dos números complexos: par ordenado, vetor do plano, forma algébrica, forma trigonométrica e matricial. Todos os resultados essenciais foram demonstrados. Há um capítulo com alguns problemas resolvidos. / A text on the field of complex numbers in an integrated way and directed to teachers of basic education who work in high school. It presents in a well-founded form several aspects of the complex numbers: ordered pair, plane vector, algebraic form, trigonometric and matrix form. For every essential result, there is a proof. There is a chapter with some solved problems.
353

Search for the Higgs boson decaying to bottom quarks and W boson tagging techniques at the ATLAS experiment at the LHC

Bristow, Timothy Michael January 2016 (has links)
The Standard Model of particle physics is currently the most complete theory of subatomic particles. The discovery of the Higgs boson with a mass of 125 GeV in 2012 further validated the Standard Model, providing evidence for the theory that vector bosons obtain non-zero masses through the Higgs mechanism. Studies are ongoing to determine the exact nature and properties of the Higgs boson. A Higgs boson of this mass is predicted to decay to a pair of b-b quarks with a branching ratio of 58%, however this decay mode has not yet been observed. This thesis presents a search for the associated production of a Higgs boson with a leptonically decaying W boson, WH → ℓvb-b, using 20.3 fb-1 of Run 1 data collected by ATLAS at the LHC from pp collisions at a centre-of-mass energy of ps = 8 TeV. The observed (expected) significance of a Higgs boson with a mass of 125 GeV for the WH → ℓvb-b process is found to be 2:7σ (1:3σ). The measured cross section in units of the expected Standard Model cross section has a best-fit value of μ = μ/μSM = 2:2+0:67-0:64(stat:)+0:7-0:59(syst:) = 2:2+0:97-0:87. The results are combined with the search for ZH → v-vb-b and ZH → ℓ+ℓ-b-b to provide a best-fit value of μ = μ/μSM = 1:1+0:61-0:56. The start of Run 2 of the LHC in 2015 saw the collision energy being raised to √s = 13 TeV, increasing the probability of particles being produced with a large momentum boost. At these high energies there is also a possibility to discover new particles and interactions. An extension of the Standard Model, the Heavy Vector Triplet (HVT) model, describes new heavy vector bosons W¹ and Z¹, which can decay to pairs of heavy bosons (W, Z or Higgs bosons). If the W0 and Z0 bosons are sufficiently heavy, the hadronic decays of the diboson final states produce boosted jets. In this thesis, methods for identifying hadronically decaying boosted bosons are developed, based on techniques that examine the internal substructure of the jet. Multiple substructure variables are combined into a single discriminant using two machine learning techniques: boosted decision trees and deep neural networks. Simulated events of W¹→WZ → q-qq-q are used to develop these boosted W boson taggers. An improvement in the background rejection power, whilst keeping 50% of the signal, over previous boosted W boson taggers of up to 13%-when using deep neural networks-and 36%-when using boosted decision trees-is obtained. The performance of the new boosted W boson taggers are evaluated in a search for a narrow WW resonances from the decay of a Z¹ with boson-tagged jets in 3.2 fb-1 of pp collisions at √s = 13 TeV collected with the ATLAS detector.
354

Ordering phenomena in iron-containing spinels

Perversi, Giuditta January 2018 (has links)
The spinel structure (general formula AB2O4) is widely occurring in natural and synthetic materials, and has a marked technological and scientific significance due to its magnetic, electric and multiferroic behaviours. The presence of transition metal cations with multiple oxidation state and the resulting charge, orbital and spin degrees of freedom of the partially occupied d-orbitals lead to uniquely ordered ground states. The coupling of all the three degrees of freedom can result in a structurally distorted ground state where the direct metal-metal interaction forms atomic clusters, or 'orbital molecules'. The Verwey phase of magnetite (Fe3O4), occurring below TV ~ 125 K, is driven by a cooperative bond distortion that forms linear Fe3+-Fe2+-Fe3+ arrangement (trimeron). The effect of non-stoichiometry and chemical modification on this complex structure has been investigated with a variety of samples through microcrystal synchrotron XRD. A mineral sample (Al, Si, Mg and Mn impurities, TV = 119 K) confirms the Verwey phase as the most complex long-range electronic order known to occur naturally; its relevance in space sciences is discussed. Moreover, the structural analysis of two synthetic magnetites (Fe3(1-δ)O4 with 3δ = 0.012 and TV = 102 K, Fe3-xZnxO4 with x = 0.03 and TV = 90 K) univocally confirmed the persistence of the transition, and its first order, at doping level > 1 %, contrary to previous reports. Moreover, the temperature evolution of the trimerons and their persistence above TV was probed through X-ray Pair Distribution Function analysis on pure Fe3O4: the data analysis between 90 K < T < 923 K show that the Verwey phase goes from long-range ordered (T < 125 K) to short-range ordered (T > 850 K). Magnetite can thus only be considered to have a regular cubic spinel structure above the Curie temperature (TC = 858 K). The pyrochlore lattice of B cations in a spinel gives the structure the potential for frustration upon antiferromagnetic ordering. Fe2GeO4 and γ-Fe2SiO4 were synthesised through conventional solid state routes, with the use of high-pressure synthesis for the latter. Magnetometry and heat capacity measurements highlighted two transitions (Tm1 = 8.6 K and Tm2 = 7.2 K, and Tm1 = 11.2 K and Tm2 = 7.5 K respectively). Powder neutron diffraction data between 2 K < T < 25 K showed that both materials stay undistorted below TN. Magnetic Rietveld refinement led to two highly unconventional magnetic structures, with incommensurate propagation vectors and modulation of the moment magnitude. γ-Fe2SiO4 also shows a spin-ice order below Tm2. The results are unique and unusual for transition metal oxides; the models are systematised by proposing a 'frustration wave' model, in which the degree of frustration is a spatial quantity that can be distributed through the structure in order to stabilise the ground state.
355

Análise multivariada dos fatores de risco aplicada ao estudo da perda auditiva induzida pelo ruído na indústria

Tinoco, Helder Cesar 27 July 2017 (has links)
Submitted by Secretaria Pós de Produção (tpp@vm.uff.br) on 2017-07-27T20:01:54Z No. of bitstreams: 1 D2014 - Helder Cesar Tinoco.pdf: 6602828 bytes, checksum: c205d6b3a325570344d5e51284eee91e (MD5) / Made available in DSpace on 2017-07-27T20:01:54Z (GMT). No. of bitstreams: 1 D2014 - Helder Cesar Tinoco.pdf: 6602828 bytes, checksum: c205d6b3a325570344d5e51284eee91e (MD5) / O ruído ocupacional é responsável por cerca de 20% das perdas auditivas induzidas por ruído (PAIR). Doença oriunda da exposição aos níveis elevados de pressão sonora ao longo dos anos gera perdas auditivas progressivas e irreversíveis, além de sintomas tais como: zumbidos, tontura, dor de cabeça, distúrbios gástricos, estresse e alterações transitórias na pressão arterial, podendo ainda prejudicar a visão, atenção, memória, sono e humor. Neste contexto, o objetivo desta pesquisa é apresentar uma sistemática para verificação dos fatores de risco que impactam na perda auditiva induzida pelo ruído na indústria e na utilização de equipamento de proteção individual auditiva – EPI. Para isso, inicialmente foi realizado um levantamento do estado da arte, com base na estruturação de um quadro referencial teórico dos subconstructos relacionados ao assunto em tela, desde agosto de 2012 até setembro de 2014, baseado numa pesquisa bibliográfica de publicações indexadas ou catalogadas na base de dados do portal de Periódicos Capes. Como opção metodológica, a partir da revisão de literatura definiu-se um total de 14 subconstructos para a pesquisa, sendo eles: idade; sexo; perdas auditivas; conforto do EPI; índice de risco; formação; barreiras; cultura de segurança; percepção do risco; percepção dos efeitos; expectativa; valorização dos resultados; comportamento de risco e produtos químicos ototóxicos. O presente trabalho - incidindo sobre uma amostra de 278 trabalhadores industriais expostos a níveis de pressões sonoras superiores a 80 dB (A) – utilizou como instrumento de análise de dados a análise multivariada pelas técnicas de correlação de Pearson e regressão linear múltipla, aplicadas sobre as variáveis identificadas. Para consolidação dos resultados, a análise fatorial permitiu obter uma estimativa dos efeitos diretos e indiretos de um conjunto de fatores relacionados à PAIR e ao uso do EPI. Concluiu-se que um efetivo entendimento dos empregados acerca do risco ocupacional perante o agente físico ruído mostrou influenciar no uso do EPI auditivo. Verificou-se ainda que a percepção dos efeitos gerados pela PAIR parece influenciar no desenvolvimento desta doença ocupacional, podendo inclusive influenciar positivamente para o desenvolvimento de comportamentos seguros pelos empregados. / Occupational noise is responsible for about 20% of noise-induced hearing loss (NIHL). Disease arising from exposure to high sound pressure levels over the years causes progressive and irreversible hearing loss, and symptoms such as tinnitus, dizziness, headache, stomach upset, transient changes in blood pressure, stress, vision disturbances, attention, memory, sleep and mood. In this context, the objective of this research is to present a systematic check of the risk factors that impact the industry in noise-induced hearing loss in industry and in the use of hearing protective equipment - PPE. A survey of the state of the art was done based on the structure of a framework of theoretical subconstructs related to the subject was conducted from August 2012 until September 2014, based on a literature search of publications indexed or cataloged in the database of the website Capes. As a methodological option, from the literature review defined a total of 13 subconstructs for research, which are: age; sex; hearing loss; risk index; training; barriers; safety culture; risk perception; perception of effects; expectation and valuation of results; risk behavior and chemicals ototoxic drugs. This work - focusing on a sample of 278 industrial workers exposed to sound pressure levels above 80 dB (A) - used as a tool for data analysis multivariate analysis by multiple linear techniques Pearson correlation and regression, applied on variables identified. To consolidate the results, the factor analysis yielded an estimate of direct and indirect of a set of factors related to NIHL effects. It was concluded that an effective understanding of employees about occupational exposures to physical agents showed noise influence the use of hearing PPE. It was also found that the perception of the effects generated by PAIR appears to influence the development of this occupational disease, and may also positively influence the development of safety behavior by employees.
356

Incidência de perda auditiva induzida por ruído ocupacional entre trabalhadores de uma mineradora e pelotizadora de minério de ferro / Incidence of hearing loss induced by occupational noise among workers in a company engaged in iron ore mining and pelletizing

Bruno Vianna do Amaral 03 September 2014 (has links)
INTRODUÇÃO: Em consequência da modernização tecnológica e industrial, surgiram novos fatores que originaram estudos específicos e direcionados sobre os possíveis efeitos nocivos desta evolução no trabalhador. Dentre estes, está o ruído, agente físico que pode causar danos ao organismo humano com efeitos de curto e médio prazo. O ruído, ao atuar sobre o trabalhador pode alterar processos internos do organismo, com consequências fisiológicas e emocionais. A diminuição gradual da acuidade auditiva decorrente da exposição continuada a níveis elevados de pressão sonora é denominada perda auditiva induzida pelo ruído (PAIR), segundo o Comitê Nacional de Ruído e Conservação Auditiva. A PAIR é caracterizada por perda neurossensorial, irreversível, quase sempre bilateral e simétrica, não ultrapassando 40dB(NA) nas frequências graves e 75dB(NA) nas frequências agudas; manifesta-se, primeiramente, em 6kHz, 4kHz e/ou 3kHz, progredindo lentamente às frequências de 8kHz, 2kHz, 1kHz, 500Hz e 250Hz. (MTE, Portaria 19, 1998). Entre os fatores que influenciam no desencadeamento da PAIR, destacam-se as características físicas do ruído (tipo, espectro e intensidade da pressão sonora), o tempo de exposição e a suscetibilidade individual. A PAIR está entre as doenças do trabalho de maior prevalência, com agravante de tratar-se de uma doença irreversível. Acomete com mais frequência o setor industrial. Este estudo avalia a incidência de perda auditiva por ruído e a existência de uma associação positiva entre estes diagnósticos e a exposição a diferentes níveis de pressão sonora em trabalhadores de duas unidades de uma mineradora e pelotizadora de minério de ferro. MÉTODOS: Estudo de coorte histórica com 1.069 trabalhadores divididos em dois grupos, tendo como referência os níveis de pressão sonora aos quais estavam expostos (menor ou igual a 88 dB e acima de 88 dB). A avaliação da audição foi realizada por análise dos resultados das audiometrias realizadas nos exames admissionais e periódicos constantes dos prontuários médicos. Foram calculadas as incidências de perda auditiva de acordo com os grupos de exposição e o tempo médio de início das alterações auditivas em cada grupo. Foram realizadas análises descritivas das variáveis, comparação de médias (teste U de Mann-Whitney), teste de associação de qui-quadrado e, para estimar fatores de risco, modelos de regressão logística univariada e múltipla. RESULTADOS: Entre os participantes do estudo foram identificados 128 casos (11,97%) de perda auditiva. No grupo composto pelos trabalhadores que ficaram expostos aos níveis mais altos de pressão sonora encontra-se uma incidência de 11,84% em alterações de exames audiométricos, enquanto no grupo menos exposto obteve-se uma incidência de 12,4%. O tempo médio para o desencadeamento de alterações audiométricas foi de 3,07 anos (desvio padrão = 1,21) no grupo mais exposto e de 2,88 anos (desvio padrão = 1,53) no grupo menos exposto. Estar na faixa etária acima de 28 anos e 8 meses (RC = 3,33; IC 95%: 2,01 - 5,49) e trabalhar na Unidade 1 (RC = 1,64; IC 95%: 1,09 - 2,46) se mostraram fatores de risco robustos para perda auditiva induzida por ruído. CONCLUSÃO: A perda auditiva ocorre de maneira precoce, prioritariamente até o terceiro ano de exposição e faixa etária, e unidade de trabalho se mostraram os fatores de risco mais relevantes para a perda auditiva induzida por ruído. O estudo mostra a necessidade de uma integração maior entre as áreas de saúde ocupacional e segurança do trabalho na busca de ações preventivas e corretivas, que possam minimizar o surgimento de novos casos ou o agravamento dos já identificados. Este é um estudo preliminar que servirá de apoio a pesquisas futuras sobre o assunto / INTRODUCTION: As a result of technological and industrial modernization new factors have arisen which led to specific studies have focused on the possible harmful effects of this evolution on the worker. Among these factors is noise, a physical agent which can harm the human body with short and medium term effects. Noise can alter internal body processes, with physiological and emotional consequences. The gradual reduction of hearing acuity resulting from a continued exposure to high levels of noise pressure is called noise-induced hearing loss (NIHL), according to the National Committee of Noise and Hearing Conservation. NIHL is characterized by a permanent sensorioneural impairment, almost always bilateral and symmetrical, not exceeding 40dB (NA) at lower frequencies and 75dB (NA) at higher frequencies. It first manifests at 6kHz, 4kHz and/or 3kHz, slowly progressing to the frequencies of 8kHz, 2kHz, 1kHz, 500Hz and 250Hz. (MTE, Ruling 19, 1998). Among the factors which trigger NIHL are the physical characteristics of the noise (type, spectrum and intensity of sound pressure), duration of exposure, and individual susceptibility. NIHL is among the most common occupational diseases, with the aggravating aspect of being irreversible. It is most often found in the industrial sector. This study will evaluate the incidence of noise-induced hearing loss and the existence of a positive association between these diagnoses and the exposure to different levels of sound pressure in workers at two operational units of a iron ore mining and pelletizing organization. METHODS: historical cohort study with 1069 workers, divided in two groups, using as baseline the sound pressure levels to which they were exposed (less than or equal to 88 dB and above 88 dB). The hearing assessment was carried out by means of an analysis of the results of the audiometry exam upon induction and at regular intervals, as recorded in the medical history of the individual. A calculation was made of the degree of hearing loss according to the groups of exposure, and the average time it took for hearing changes to be observed in each group. RESULTS: Among the participants in the study, 128 (11.97%) cases of hearing loss were identified. In the group formed by workers who had been exposed to the highest levels of sound pressures, we found an incidence of 11.84% of changes in the audiometry exams, while in the group subject to lesser exposure we observed an incidence of 12.4%. The average time for the development of hearing impairment was 3.07 years (standard deviation = 1.21) in the group with greater exposure, and 2.88 years (standard deviation = 1.53) in the group with lesser exposure. Robust risk factors for noise-induced hearing loss included being aged over 28 years and 8 months (RC = 3,33; IC 95%: 2,01 - 5,49) and working at Unit 1 (RC = 1,64 ; IC 95%: 1,09 - 2,46). CONCLUSION: Early hearing impairment occurs mainly before the end of the third year of exposure, and age bracket and work location proved to be the most relevant risk factors for noise-induced hearing loss. The study showed the need for a greater integration among the occupational health and safety areas to seek the design and implementation of preventive and corrective actions to minimize the development of new cases or the aggravation of those already identified. This is a preliminary study which will serve as a basis for a more detailed subsequent data analysis
357

Systematic chromosome-wide search for novel fetal epigenetic markers for detection of fetal trisomy 13.

January 2010 (has links)
Lam, Yuk Man. / Thesis (M.Phil.)--Chinese University of Hong Kong, 2010. / Includes bibliographical references (leaves 142-157). / Abstracts in English and Chinese. / ABSTRACT --- p.i / 摘要 --- p.iv / ACKNOWLEDGEMENTS --- p.vi / CONTRIBUTORS --- p.viii / PUBLICATIONS --- p.ix / LIST OF TABLES --- p.x / LIST OF FIGURES --- p.xi / LIST OF ABBREVIATIONS --- p.xiii / TABLE OF CONTENTS --- p.xiv / Chapter SECTION I: --- BACKGROUND --- p.1 / Chapter CHAPTER 1: --- PRENATAL DIAGNOSIS OF FETAL ANEUPLOIDIES --- p.2 / Chapter 1.1 --- The need for prenatal screening and diagnosis --- p.2 / Chapter 1.2 --- Patau Syndrome (Trisomy 13) --- p.2 / Chapter 1.3 --- Current methods for fetal aneuploidy detection --- p.4 / Chapter 1.3.1 --- Routine prenatal screening tests --- p.4 / Chapter 1.3.2 --- Definitive prenatal diagnosis by invasive procedures --- p.7 / Chapter 1.4 --- New approach for noninvasive prenatal diagnosis --- p.11 / Chapter 1.4.1 --- Circulating fetal cells --- p.11 / Chapter 1.4.2 --- Cell-free fetal nucleic acids in maternal circulation --- p.12 / Chapter 1.4.3 --- Diagnostic applications of cell-free fetal nucleic acids in maternal plasma --- p.12 / Chapter CHAPTER 2: --- DEVELOPMENT OF FETAL EPIGENETIC MARKERS IN MATERNAL PLASMA --- p.17 / Chapter 2.1 --- Limitations of fetal DNA markers --- p.17 / Chapter 2.2 --- DNA methylation is an actively-researched area under the field of epigenetics --- p.18 / Chapter 2.3 --- Genome-scale DNA methylation analysis brings new insight into epigenetics --- p.20 / Chapter 2.4 --- The first demonstration of using an epigenetic method for detecting maternally-inherited fetal DNA in maternal plasma --- p.22 / Chapter 2.5 --- The first universal marker for fetal DNA in maternal plasma --- p.24 / Chapter 2.6 --- Discovery of more fetal epigenetic markers --- p.25 / Chapter 2.6.1 --- Methylated fetal epigenetic markers are more desirable --- p.25 / Chapter 2.6.2 --- Discovery of hypermethylated fetal epigenetic markers by studying tumor suppressor genes --- p.26 / Chapter 2.6.3 --- Discovery of hypermethylated fetal epigenetic markers on chromosome 21 --- p.28 / Chapter 2.7 --- Noninvasive detection of fetal aneuploidies using fetal epigenetic markers --- p.29 / Chapter 2.7.1 --- Noninvasive detection of fetal trisomy 18 by the epigenetic allelic ratio (EAR) approach --- p.29 / Chapter 2.7.2 --- Noninvasive detection of fetal trisomy 21 by the epigenetic-genetic (EGG) approach --- p.30 / Chapter 2.8 --- Aim of thesis --- p.32 / Chapter SECTION II: --- MATERIALS AND METHODS --- p.34 / Chapter CHAPTER 3: --- METHODS FOR QUANTITATIVE ANALYSIS OF DNA METHYLATION --- p.35 / Chapter 3.1 --- Subject recruitment and sample collection --- p.35 / Chapter 3.2 --- Sample processing --- p.38 / Chapter 3.3 --- DNA extraction --- p.38 / Chapter 3.3.1 --- Placental tissues --- p.38 / Chapter 3.3.2 --- Maternal blood cells --- p.39 / Chapter 3.3.3 --- Maternal plasma --- p.40 / Chapter 3.4 --- Methylated DNA immunoprecipitation and tiling array analysis (MeDIP-chip) --- p.41 / Chapter 3.4.1 --- Principles --- p.41 / Chapter 3.4.2 --- DNA sample and array processing --- p.43 / Chapter 3.4.2.1 --- DNA preparation and target hybridization --- p.43 / Chapter 3.4.2.2 --- Data analysis --- p.44 / Chapter 3.5 --- DNA methylation analysis on randomly-chosen regions on chromosome / Chapter 3.6 --- Bisulfite conversion --- p.46 / Chapter 3.6.1 --- Principles of bisulfite conversion --- p.46 / Chapter 3.6.2 --- Procedures of bisulfite conversion --- p.46 / Chapter 3.7 --- Quantitative analysis of DNA methylation --- p.47 / Chapter 3.7.1 --- Bisulfite PCR and genomic sequencing --- p.47 / Chapter 3.7.1.1 --- Primer design for bisulfite polymerase chain reaction (PCR) --- p.47 / Chapter 3.7.1.2 --- Bisulfite PCR --- p.49 / Chapter 3.7.1.3 --- Cloning --- p.50 / Chapter 3.7.1.4 --- Bisulfite genomic sequencing --- p.52 / Chapter 3.7.1.5 --- Data acquisition and interpretation --- p.53 / Chapter 3.7.2 --- EpiTYPER,a mass-spectrometry-based method --- p.54 / Chapter 3.7.2.1 --- Principles of matrix-assisted laser desorption ionization time-of-flight mass spectrometry (MALDI-TOF MS) --- p.54 / Chapter 3.7.2.2 --- Primer design of the EpiTYPER assay --- p.55 / Chapter 3.7.2.3 --- The EpiTYPER assay and its principle --- p.56 / Chapter 3.8 --- Methylation-sensitive restriction enzyme (MSRE)-mediated real-time quantitative PCR (qPCR) --- p.61 / Chapter 3.9 --- Digital PCR --- p.66 / Chapter 3.9.1 --- Principles of digital PCR --- p.66 / Chapter 3.9.2 --- Poisson distribution --- p.68 / Chapter 3.10 --- Statistical analyses --- p.69 / Chapter SECTION III: --- SYSTEMATIC IDENTIFICATION OF A FETAL DNA METHYLATION MARKER ON CHROMOSOME 13 FOR DETECTION OF FETAL TRISOMY 13 --- p.70 / Chapter CHAPTER 4: --- SYSTEMATIC IDENTIFICATION OF POTENTIAL FETAL EPIGENETIC MARKERS BY MEDIP-CHIP ANALYSIS --- p.71 / Chapter 4.1 --- Systematic discovery of fetal epigenetic markers on chromosome 13 by MeDIP-chip analysis --- p.71 / Chapter 4.2 --- Experimental design --- p.73 / Chapter 4.3 --- Results --- p.76 / Chapter 4.3.1 --- Identification of differentially methylated DNA regions by MeDIP-chip or non-MeDIP-chip approaches followed by EpiTYPER analysis --- p.76 / Chapter 4.3.2 --- Confirmation of differential methylation patterns and exclusion of regions with high inter-individual variations by EpiTYPER analysis --- p.82 / Chapter 4.3.3 --- Confirmation of differential DNA methylation patterns with higher resolution by bisulfite sequencing --- p.85 / Chapter 4.4 --- Discussion --- p.95 / Chapter CHAPTER 5: --- THE APPLICATION OF FETAL EPIGENETIC MARKER ON CHROMSOME 13 FOR DETECTION OF FETAL TRISOMY 13 --- p.98 / Chapter 5.1 --- Identification of a fetal epigenetic marker on chromosome 13 for the detection of fetal trisomy 13 by the epigenetic-genetic (EGG) chromosome dosage approach --- p.98 / Chapter 5.2 --- Experimental design --- p.101 / Chapter 5.3 --- Results --- p.105 / Chapter 5.3.1 --- Optimization of the digestion protocol --- p.105 / Chapter 5.3.2 --- Detection of digestion-resistant EFNB2-3'UTR moleculesin maternal plasma --- p.109 / Chapter 5.3.3 --- Evaluation of the fetal specificity of digestion-resistant EFNB2´ؤ3 'UTR DNA molecules in maternal plasma --- p.111 / Chapter 5.3.4 --- Comparison of EFNB2-3'UTR methylation profiles between the euploid and trisomy 13 placental tissue samples --- p.115 / Chapter 5.3.5 --- Chromosome dosage analysis by the EGG analysis using placental tissue samples --- p.118 / Chapter 5.4 --- Discussion --- p.122 / Chapter SECTION IV: --- CONCLUDING REMARKS --- p.125 / Chapter CHAPTER 6: --- CONCLUSION AND FUTURE PERSPECTIVES --- p.126 / Chapter 6.1 --- Development of fetal epigenetic markers for noninvasive prenatal diagnosis --- p.126 / Chapter 6.2 --- Systematic identification of fetal epigenetic markers on chromosome13 --- p.127 / Chapter 6.3 --- Detection of fetal trisomy 13 by the epigenetic-genetic (EGG) relative chromosome dosage analysis --- p.129 / Chapter 6.4 --- Future perspectives --- p.132 / Appendix I --- p.134 / Appendix II --- p.136 / REFERENCES --- p.142
358

Magnetic field effects in exciplex- and exciton-based organic light emitting diodes and radical-doped devices

Wang, Yifei 01 January 2017 (has links)
Organic semiconductors (OSCs) have already been shown to have great potential to play an important role in the future of clean energy generation (organic solar cells) and provide energy efficient lighting (organic light-emitting diodes, OLED). Prior research has found that the light-emission efficiency of OLED is severely limited by the magnetic state (technically the spin-configuration) of the light-emission process. In this thesis, we work on the processes using external magnetic fields that can overcome these magnetic limitations. A major focus of this research is to enhance the performance of OLED, while at the same time to unravel the scientific mechanisms by which magnetic fields act on OSCs devices. Thermally activated delayed fluorescence (TADF) is a next-generation OLED emission technology which enables nearly 100% light-emission efficiency without using heavy precious metals. TADF characteristics depend on the probability of reverse intersystem crossing (RISC) from the triplet excited states (T1) to singlet excited states (S1). The conversion (T1 to S1) process depends strongly on spin dynamics, thus we predict a dramatic magnetic field effects (MFEs) in such TADF OLED devices. In subsequent experiments we observed that changes in TADF devices due to various forms of electrical stress can lead to enormous increases in magnetic field effects (MFEs) on the current (> 1400%) and electroluminescence (> 4000%). Our work provides a flexible and inexpensive pathway towards magnetic functionality and field sensitivity in current organic devices. Such OLED pave the way for novel magnetic sensitive OSCs devices with integrated optical, electronic and magnetic characteristics. Organic magnetoresistance (OMAR) has been observed to alter the current and efficiency of OLED without any ferromagnetic components. Here we utilizes slight alterations to the device properties, the addition of a radical-doped functional layer, in which the spin-relaxing effects of localized nuclear spins and electronic spins interfere, to address the assumption about the importance of the hyperfine interaction and to attempt to differentiate between the different models for OMAR. A feature where the magnitude of OMAR exhibits a plateau over a wide range of doping fraction was observed at all temperatures investigated. This phenomenon is well explained by a theory in which a single dopant spin strongly interacts, by exchange, with one of the bottleneck sites. A similar can be used to explain the efficiency increases observed in organic solar cells for certain doping fractions.
359

Expanding the Horizons of Educational Pair Programming: A Methodological Review of Pair Programming in Computer Science Education Research

Rimington, Keith B. 01 May 2010 (has links)
Educators and researchers continue to explore the benefits, real or imagined, of implementing pair programming as part of the computer science pedagogy. Current reviews of computer science educational research practices do not focus on educational pair programming. This thesis presents a review of the research methods used in recent educational pair programming research. The primary purpose of this review is to inform the ongoing dialogue about and to provide evidence-based recommendations for improving educational pair programming research. Replicating the design of a previous computer science education methodological review, this study inspected a sample of 108 articles from a population of 129 of articles related to educational pair programming published from 2000 to 2008. Articles were classified using a 112-variable taxonomy, identifying report elements, research methodology, research design, kinds of variables inspected, and statistical practices. Major findings include several differences between the methodological characteristics of educational pair programming research when compared to general computer science education research, including: (a) an increased proportion of studies involving human participants, (b) a decreased proportion of quantitative methodologies, and (c) an increased proportion of controlled research designs. There exists some minor evidence that researchers affiliated with institutions in the United States are more likely than their counterparts outside of the United States to inspect only student attitudes and implement a posttest-only research design, and less likely to implement an experimental or quasi-experimental methodology
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Measurements of the Top Quark Pair Production Cross Section and an Estimate of the DØ Silicon Detector Lifetime

Strandberg, Sara January 2007 (has links)
<p>This thesis presents two measurements of the top quark pair production cross section at sqrt{s} = 1.96 TeV using data from the DØ experiment. Both measurements are performed in the dilepton final state and make use of secondary vertex b-tagging. With 158 pb<sup>-1</sup> of data in the electron-muon final state, the measured cross section is:</p><p>σ(top-antitop) = 11.1 +5.8 -4.3 (stat) +- 1.4 (syst) +- 0.7 (lumi) pb.</p><p>With 425 pb<sup>-1</sup> of data in the electron+track and muon+track final states, the measured cross section is:</p><p>sigma(top-antitop) = 6.3 +2.1 -1.8 (stat) +- 1.1 (syst) +- 0.4 (lumi) pb.</p><p>Both measurements are in agreement with the prediction from perturbative QCD calculations. In addition, an estimate of the DØ silicon detector lifetime is presented. The radiation damage is determined by studying the depletion voltage of the silicon sensors as a function of time. Based on this data the silicon detector is estimated to remain operational up to delivered luminosities of 6-8 fb<sup>-1</sup>.</p>

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