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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.
141

The influence of the C-N⁺ ----- F-C charge dipole interaction in fluoro organic chemistry

Gooseman, Natalie Elizabeth Jane January 2008 (has links)
Chapter 1 introduces the discovery of elemental fluorine by H. Moissan and some uses of inorganic fluoride. Organo fluoro compounds and their place in pharmaceuticals and agrochemicals are also introduced. The general properties of fluorine and the C-F bond are discussed as well as conformational influences such as the fluorine gauche effect. Chapter 2 describes the C-N⁺------F-C charge dipole interactions within protonated amines and explains the influence of a β fluorine on the conformation on various crystalline structures. A number of systems are synthesised which contain this charge dipole interaction, such as four, five and eight membered aza heterocycles. It was demonstrated that these provided a N⁺-C-C-F gauche torsion angle. This electrostatic effect was also observed in the non-protonated N-ethylpyridinium cations possessing a fluorine β to the charged nitrogen. This clearly showed that hydrogen bonding is not playing a part in the observed N⁺-C-C-F gauche interactions and that it is a purely electrostatic effect. Chapter 3 discusses the effort to explore the C-O⁺-------F-C charge dipole interaction and the synthetic approaches that were taken towards candidate substances. However in the event a Grignard reaction on a fluoro cyclohexanone was found to provide an unexpected product where rearrangement followed by fluorine elimination had occurred. Chapter 4 details the experimental procedures for the compounds synthesised in this thesis and an Appendix outlines the detail of 24 crystal structures that were solved during this research.
142

POLYMORPH FORMATION OF TOLFENAMIC ACID: AN INVESTIGATION OF PRE-NUCLEATION ASSOCIATION

Mattei, Alessandra 01 January 2012 (has links)
The majority of pharmaceutical products are formulated as solids in the crystalline state. With the potential to exist in different crystalline modifications or polymorphs, each solid form bears its own physical and chemical properties, influencing directly bioavailability and manufacturability of the final dosage form. In view of the importance of crystalline form selection in the drug development process, it is imperative for pharmaceutical scientists to work arduously on various aspects of polymorphism, ranging from fundamental understanding of the phenomenon at the molecular level to practical utilization of a specific crystalline form. One common feature of organic crystals is the existence of distinct molecular conformations in different polymorphic structures, known as conformational polymorphism. Conformational polymorphs are routinely observed in drug development, produced when crystal growth conditions vary. Crystallization from solution involves nucleation and crystal growth, the mechanisms that influence the polymorphic outcome. The embryonic solute aggregate has been recognized to play a critical role in dictating the final crystal structure, and solution conditions are also known to drastically influence the self-association behavior of solute molecules during crystallization, affecting crystal packing of organic molecules. For the crystal growth of conformational polymorphs, changes in molecular conformation not only determine the growth kinetics, but also influence the nature and strength of interactions present in the crystal structures. How conformation and intermolecular interaction affect each other underlines the intricacy and the wonder of crystal growth of the organic. Thus, the overall goal of this research is to provide the fundamental understanding of the extent to which solution conditions influence the molecular conformation in the solid-state of a model drug, tolfenamic acid. By combining experimental studies with advanced computational tools, this dissertation offers novel insights into solution species during pre-nucleation and molecular packing of conformational polymorphs of tolfenamic acid. In-depth understanding of the underlying connection between molecular conformation and crystal packing will help advance the knowledge required for rational control of crystal growth.
143

La pluridimensionalité de l'efficacité des ligands des récepteurs couplés aux protéines G : les récepteurs B[bêta]₁- et B[bêta]₂-adrénergiques en tant que modèles d'étude

Galandrin, Ségolène January 2007 (has links)
Thèse numérisée par la Direction des bibliothèques de l'Université de Montréal.
144

Gene expression in P. falciparum : statistical patterns and molecular determinants

Lemieux, Jacob E. January 2012 (has links)
This thesis investigates patterns and mechanisms of gene expression in P. falciparum. The rapidly cycling patterns of genes during the asexual stages confounds the analysis of gene expression in culture and in patients. In order to overcome this problem, we develop statistical models to estimate the temporal progression of malaria parasites by using the observed gene expression values and known reference sets. We extend this framework to account for lineage commitment, and show that, similar to asexual development, it is also possible to recover information about parasite sexual differentiation given observed gene expression values. Using datasets from our own lab as well as those available in the literature, we establish that the patterns of expression in patients are similar to those observed in culture but in additive mixtures whose proportions can vary between patients. We then investigate epigenetic and spatial factors that are important in regulating gene expression. Using second-generation DNA sequencing, we generate genomic maps of chromatin state and chromosome interactions. These maps provide the first global view of chromosome folding and locus-specific affinities in malaria. They also highlight the importance of epigenetic modifications in imposing structure on the spatial organization of the genome. After generating an initial set of genomic maps, we apply these tools to study chromatin reconfigurations during var gene switching. We show that when the active var gene changes, reconfigurations can be seen in the local three-dimensional chromatin structure of the activated locus. Overall, our results contribute new methods for analyzing malaria microarray data, highlight the importance of lineage mixtures in patient infections, generate an atlas of spatial interactions in the nucleus at a resolution of approximately 5 kilobases, and establish a link in malaria between the spatial configuration of active loci and the local chromatin environment.
145

Výpočetní studie krátkých peptidů a miniproteinů a vliv prostředí na jejich konformaci. / Computational study of short peptides and miniproteins in different environments

Vymětal, Jiří January 2014 (has links)
Apart from biological functions, peptides are of uttermost importance as models for un- folded, denatured or disordered state of the proteins. Similarly, miniproteins such as Trp-cage have proven their role as simple models of both experimental and theoretical studies of protein folding. Molecular dynamics and computer simulations can provide an unique insight on processes at atomic level. However, simulations of peptides and minipro- teins face two cardinal problems-inaccuracy of force fields and inadequate conformation sampling. Both principal issues were tackled in this theses. Firstly, the differences in several force field for peptides and proteins were questioned. We demonstrated the inability of the used force fields to predict consistently intrinsic conformational preferences of individual amino acids in the form of dipeptides and the source of the discrepancies was traced. In order to shed light on the nature of conformational ensembles under various denatur- ing conditions, we studied host-guest AAXAA peptides. The simulations revealed that thermal and chemical denaturation by urea produces qualitatively different ensembles and shift propensities of individual amino acids to particular conformers. The problem of insufficient conformation sampling was dealt by introducing gyration- and...
146

Intéractions chromatiniennes à longue distance au locus 4q35 dans la pathogenèse de la dystrophie facio-scapulo-humérale

Morere, Julia 24 September 2012 (has links)
La dystrophie Facio-Scapulo-Humérale, ou FSHD, est une maladie d'hérédité autosomique dominante, caractérisée par un affaiblissement des muscles de la face, et progressant de façon asymétrique au reste du corps. Des analyses de liaison ont montré que 95% des cas sont associés à la délétion de D4Z4, macrosatellite polymorphe de 3,3Kb, répété en tandem dans la région subtélomérique du bras long du chromosome 4, mais aucun gène candidat n'a clairement été identifié, et l'existence de patients sans contraction (FSHD2), suggère des mécanismes complexes dans la survenue de la maladie. Parmi ceux-ci, l'implication d'altérations épigénétique a été suggérée. En effet, des changements de marques épigénétiques chez les patients, tels que l'hypométhylation de l'ADN et la diminution de la triméthylation des résidus H3K9, indiquent que des modifications de l'organisation chromatinienne et des altérations épigénétiques interviendraient dans la FSHD. De plus la localisation particulière du locus 4q35 dans le noyau pourrait contribuer à la régulation de ce locus. La disposition et la localisation des gènes n'est pas aléatoire au sein du noyau, c'est un processus dynamique impliqué dans la régulation des gènes au cours de la prolifération cellulaire et la différenciation. L'objectif nos travaux a donc été de comprendre la conformation tridimensionnelle du locus 4q35 chez les malades et les individus non atteints, pour déterminer de potentielles interactions entre séquences, proches ou distantes, impliquées dans la survenue de la FSHD. / Facio-Scapulo-Humeral-Dystrophy (FSHD) is an autosomal dominant, neuromuscular disorder, characterized by facial muscular weakness with an asymmetric progression to the rest of the body. Linkage analyses have shown that 95% of cases are associated with D4Z4 deletion, a 3.3 kb tandemly repeated sequence located in the subtelomeric region of the long arm of chromosome 4, 4q35. However, no candidate gene has been clearly identified, and families with typical FSHD phenotype, but no linkage to 4q35 (FSHD2) suggest complex epigenetic mechanisms. The deletion of a certain number of this repetitive DNA sequence associated to changes in the epigenetic marks across the D4Z4 array such as DNA hypomethylation or decrease in H3K9 trimethylation also indicates that FSHD involves changes in chromatin organization and epigenetic alterations. Among these changes, the positioning of the 4q35 region within the nuclear space might contribute to the regulation of the disease-associated locus. Indeed, DNA sequences are not randomly distributed within the nuclear space and gene localization is a dynamic process that contributes to the control of gene expression during cell proliferation and differentiation. The aim of our study was to compare chromatin conformation of the 4q35 locus in patients and unaffected individuals, and to identify interactions between sequences, in close proximity or distant to the D4Z4 array in FSHD pathogenesis. Therefore, we have developed an immuno-FISH technique in 3D, in different cellular models, in order to study the tridimensional distribution of DNA sequences within the nuclear volume.
147

Aspectos estruturais de proteínas do veneno crotálico modificadas por radiação ionizante / Structural aspects of crotalic venom proteins modified by ionizing radiation

Oliveira, Karina Corleto de 29 January 2010 (has links)
Os acidentes ofídicos representam um sério problema de Saúde Pública, principalmente em países subtropicais. No Brasil, segundo o Ministério da Saúde, foram notificados cerca de 26 000 acidentes em 2008. O gênero Crotalus (cascavéis) é responsável por aproximadamente 7% do total, porém apresenta um alto índice de letalidade, sendo que 72% dos casos de acidentados sem o tratamento adequado com soro específico (soro anticrotálico) chegam ao óbito. A produção de soro no Brasil, único tratamento eficaz nos casos de acidentes ofídicos, utiliza equinos que, apesar do grande porte, apresentam diminuição da longevidade quando comparado com os cavalos não imunizados. A radiação ionizante tem se mostrado como excelente ferramenta na diminuição da toxicidade de venenos e toxinas isoladas e tem resultado na obtenção de melhores imunógenos para a produção de soro, além de contribuir para o bem estar dos animais soro-produtores. Visto que a ação da radiação gama em toxinas ainda não está totalmente esclarecida do ponto de vista estrutural, foi proposto neste trabalho, a caracterização de duas proteínas da espécie Crotalus durissus terrificus: a crotoxina e a crotamina. Após o isolamento das toxinas de interesse por técnicas cromatográficas, estas foram submetidas às análises estruturais com a aplicação das seguintes metodologias: Fluorescência, Dicroísmo Circular, Calorimetria Diferencial e Espectroscopia Infravermelho. Estas análises mostraram que tanto a crotamina como a crotoxina, quando submetidas à radiação gama, apresentaram alterações na conformação estrutural em comparação com as amostras no estado nativo. Tais alterações possivelmente ocorrem na estrutura terciária e secundária das proteínas e podem explicar as modificações quanto à atividade biológica destas toxinas. / Snake bites are a serious public health problem, especially in subtropical countries. In Brazil, the Ministry of Health notified around 26 000 accidents in 2008. The genus Crotalus (rattlesnakes) accounts for approximately 7% of the total, with a high mortality rate of 72% when untreated with the specific serum, the only effective treatment in case of snake bites. In Brazil, the serum is produced in horses which, despite the large size, have a reduced lifespan due to the high toxicity of the antigen. Ionizing radiation has proven to be an excellent tool for reducing the toxicity of venoms and isolated toxins, resulting in better immunogens for serum production, and contributing to the welfare of serumproducing animals. Since the action of gamma radiation on venoms and toxins has not been yet fully clarified from the structural point of view, we proposed in this paper, to characterize two toxins of the species Crotalus durissus terrificus: crotoxin and crotamine. After isolation of the toxins of interest by chromatographic techniques, they were subjected to structural analysis with the application of the following methods: Fluorescence, Circular Dichroism, Differential Calorimetry and Infrared Spectroscopy. These tests showed that both crotamine as crotoxin when subjected to gamma radiation, showed changes in their structural conformation compared with the samples in the native state. Such changes probably occur in the secondary and tertiary structure and may explain the changes on the biological activity of these toxins.
148

Estudo dinâmico conformacional da proteína calgranulina C (S100A12) mediante interação com íons e receptor RAGE / Dynamic and conformational study of protein calgranulin C (S100A12) in interaction with ions and RAGE receptor

Reis, Renata Almeida Garcia 03 May 2012 (has links)
Calgranulina C (S100A12) é membro da família das proteínas S100 \"EF-hands\" que complexam cálcio. A S100A12 humana é expressa predominantemente por granulócitos e é superexpressa em compartimentos inflamatórios. Níveis séricos elevados de S100A12 são encontrados em pacientes acometidos por distúrbios inflamatórios, neurodegenerativos, metabólicos e neoplasias. A S100A12 intracelular existe como um homodímero anti-paralelo. Cada monômero é composto por um \"EF-hand\" clássico, C-terminal (HI - LI - HII), e um \"EF-hand\" N-terminal, o pseudo \"EF-hand\" (HIII - LIII - HIV). Os \"motifs\" são conectados pela região do \"hinge\" (LII). A Calgranulina C também liga íons zinco e cobre em uma região formada pelas duas subunidades do dímero. Mudanças nas concentrações citosólicas de íons regulam uma grande variedade de processos celulares, e as proteínas que complexam íons são moléculas importantes na transdução do sinal, diferenciação e controle do ciclo celular. O mecanismo pelo qual a Calgranulina C modula o curso do processo inflamatório está relacionado à interação com o receptor para produtos finais de glicosilação (RAGE). Para obter detalhes sobre os mecanismos envolvidos nas etapas de sinalização celular das quais a S100A12 participa, nosso objetivo foi qualificar e quantificar a atividade conformacional dos domínios da S100A12 induzida por variações de parâmetros termodinâmicos intensivos, como mudanças nas concentrações de íons. Além disso, nós investigamos os detalhes da interação entre S100A12 e RAGE para elucidar a região do receptor com a qual a S100A12 interage e quais são os resíduos envolvidos nesta interação. Para os estudos da influência da presença de íons na dinâmica conformacional da S100A12, simulações de dinâmica molecular foram realizadas usando o pacote de simulação GROMACS com o campo de força OPLS-AA, no \"ensemble\" NVT. As estruturas iniciais usadas foram as estruturas cristalográficas da S100A12 (PDB ID: 2WCE e 1E8A). Estas foram submetidas a diferentes concentrações de cloreto de sódio, cálcio e zinco em sistemas separados e solvatados com o modelo de água \"SPC\". Nossos resultados sugerem que em baixas concentrações de Ca2+, o LI permanece ocupado pelo Na+. No período entre ondas de Ca2+, este íon tem acesso à proteína exclusivamente pelo LIII (no EF-2). A medida em que há presença de Zn2+, esse contribui para a saída do Na+ do LI, evento que envolve a participação do resíduo Asp25, permitindo que o LI se abra e descomplexe o Na+. Além disso, devido a alta deformabilidade estrutural, a HIII é muito influenciada pelos íons Na+ e Ca2+, sendo que em determinadas concentrações, ambos levam a perda parcial desta hélice e da HIIa (\"Hinge-Region\") e ao aumento da flexibilidade desta região, embora apenas o Ca2+ seja capaz de se complexar, via HIII, a região próxima ao LIII. Com relação aos estudos com o RAGE, foram realizados estudos de \"docking\" molecular e simulações de SMD (\"Steered Molecular Dynamic\"). A análise dos nossos resultados, sugere que a interação da S100A12 com o RAGE ocorre tanto no domínio V, quanto no domínio C1 do RAGE e depende da região de conexão entre estes domínios. Também, observamos que estados oligoméricos maiores, por exemplo, hexâmeros de S100A12 (PDB ID: 1GQM), têm possibilidades maiores de interação com RAGE e que nestes casos, as regiões relevante da interação envolvem, de acordo com nossos resultados, porções N e C-terminal da HI e C-terminal da HIV da S100A12. / Calgranulin C (S100A12) is a member of the S100 family of EF-hand calcium-binding proteins. Human S100A12 is predominantly expressed by granulocytes and is markedly overexpressed in inflammatory compartments. Elevated serum levels of S100A12 are found in patients suffering from various inflammatory, neurodegenerative, metabolic, and neoplasic disorders. Intracellular S100A12 exists as an anti-parallel homodimer. Each monomer is composed of a C-terminal, classic EF-hand (HI - LI - HII), an N-terminal, pseudo EF-hand (HIII - LIII - HIV). The motifs are linked by the hinge-region. Calgranulin C also binds zinc and copper ions in a site formed by both subunits of dimer. Changes in cytosolic ions concentrations regulate a wide variety of cellular process, and ions-binding proteins are the key molecules in signal transduction, differentiation, and cell cycle control. The mechanism by which calgranulin C modulates the course of inflammatory process is related to its interaction with the receptor for advanced glycated products (RAGE). In order to obtain details about the mechanism involved in cell signaling steps in which S100A12 participates, our goal was to qualify and quantify the activity conformational of S100A12 domains, induced by variations of intensive thermodynamic parameters, as changes in the concentration of ions. Furthermore we investigated the details of the interaction between S100A12 and RAGE in order to elucidate the region of the receptor which interacts with S100A12 and what are the residues involved in this interaction. In order to access the influence of the presence of ions over the conformational dynamics of S100A12, molecular dynamics simulations were performed using the GROMACS suite with the OPLS-AA force field and NVT ensemble. The initial structures used were experimentally determined by X-ray crystallography (PDB ID: 2WCE and 1E8A). They were separately submitted to different concentrations of sodium, calcium and zinc chloride and solvated with the SPC water model. Our results suggest that at low concentrations of Ca²?, LI remains occupied by Na?. During calcium-waves, it can reach the protein exclusively through LIII (in EF-2). As the Zn²? concentration rises, it contributes to the Na? unbinding from LI, an event that involves the residue ASP-25, which allows LI to open and the Na? to unbind. Furthermore, because of its high structural deformability, HIII is strongly influenced by both Na? and Ca²? ions which, in certain concentrations, leads to partial loss of this helix and of HIIa (Hinge-Region) and increases in the flexibility of this region, although only Ca²? is able to bind, through HIII, to the region near LIII. Regarding the RAGE studies, molecular docking essays and SMD (Steered Molecular Dynamics) simulations were performed. Our data analysis suggests that the interaction between S100A12 and RAGE takes place through both V and C1 RAGE domains and depends upon the interdomain region. Additionally, we observed that higher oligomeric states, e.g. S100A12 hexamers (PDB ID: 1GQM), have more interaction possibilites with RAGE and that, according to our results, in this case the interacting region of S100A12 comprises the N- and C-terminal portions of HI and Cterminal of HIV.
149

Efeito da conformação mecânica na resistência a corrosão dos aços NBR7008 ZC/Z275 e Galvalume® ASTM A792 CSB/AZM150

Américo, Renato January 2016 (has links)
Os materiais usados nas indústrias de fabricação de máquinas para o setor de armazenagem e secagem de grãos, devem garantir o desempenho requerido, não gerando nenhum prejuízo ou descontentamento do cliente final. Esta pesquisa tem como objetivo principal, avaliar o desempenho do aço Galvalume® em relação ao aço Galvanizado NBR7008 quando conformados, quanto a resistência a corrosão de ambos os materiais. Para isso foram executados testes em amostras de chapas lisas e conformadas nos aços mencionados. As amostras foram avaliadas quanto à resistência à corrosão a partir de ensaio em câmara de névoa salina (chapas lisas) e ensaio de imersão (chapas conformadas). Além disso, as amostras foram caracterizadas quanto à espessura e morfologia dos revestimentos por MEV e perfilometria em (chapas conformadas). Também foi realizado o ensaio de envelhecimento em campo, que consistiu em avaliar o aspecto visual com ambas as chapas, montadas na tampa de um silo em uso na área rural. A partir dos resultados obtidos nos ensaios, antes e após a conformação mecânica, ficou evidenciada a influencia do processo de conformação sobre a resistência à corrosão do aço Galvanizado NBR7008. Observou-se que as áreas submetidas com as dobras das laterais tiveram a taxa de corrosão aumentada. O mesmo não ocorreu para o aço revestido com Galvalume®, o qual apresentou menor taxa de corrosão do que o aço Galvanizado NBR7008. Os resultados obtidos no ensaio de envelhecimento evidenciaram a grande diferença em relação ao aspecto visual dos painéis, observando-se no aço Galvanizado uma perda excessiva do brilho, com a escurecimento da chapa após 3 anos de exposição em zona rural. Já as chapas de aço Galvalume® mantiveram o brilho após todo esse período de exposição na mesma atmosfera evidenciando a sua superioridade quanto as intempéries. O custo inicial do aço Galvalume® é, em média, 12% mais elevado que o custo do aço galvanizado (NBR7008 ZC/Z275). Contudo é importante salientar que essas características quanto ao aspecto visual são determinantes para a aceitação dos silos pelos clientes. / The most used materials in the industry of manufacture of machines for the storage and grain drying department must ensure the required performance, and should not causing any loss or dissatisfaction to the final customer. This research has as main goal measuring the performance of Galvalume® steel compared to the Galvanized steel NBR7008, when conformed, evaluating the corrosion resistance of both materials. For that, tests were made on samples of plain steel sheet and conformed steel sheet with the mentioned kinds of steel. The samples were evaluated taking into consideration the corrosion resistance in immersion test (shaped plate) and salt spray test (flat sheet). Besides, the samples were described according to thickness and coating morphology by MEV and perfilometry. Also, a test of accelerated aging was made, which consisted in measuring visual aspect in both kinds of steel. They were assembled on the cover of a silo that was working, located in the countryside. From the results reached through the tests, before and after the mechanical conformation, the influence of conformed process on the corrosion resistance of the Galvanized steel NBR7008 was evidenced. It could be noted that the areas submitted with lateral folds had corrosion rates increased. But, with the Galvalume® steel was different, this one showed lower corrosion rate than Galvanized steel NBR7008. The results reached with the accelerated aging test showed the big difference related to visual aspects of the panels, in which an excessive brightness loss on the Galvanized steel, with the darkening of the steel sheet after 3 years of exposure in the countryside was observed. Whereas the Galvalume® steel sheet kept the brightness after all this period of exposure to the same atmosphere, showing its superiority in corrosion resistance. The cost of Galvalume® steel is about 12% higher than cost of Galvanized steel (NBR7008 ZC/Z275). However it is important to point these attributes, regarding to visual aspect, which are determinants for good acceptance of silos by the customers.
150

Análise da qualidade de tensões obtidas na simulação de escoamentos de fluidos viscoelásticos usando a formulação log-conformação

Martins, Adam Macedo January 2016 (has links)
Uma das mais recentes abordagens propostas na literatura para tratar o problema do alto número de Weissenberg (We) é a Formulação Log-Conformação (FLC). Nesta formulação, a equação constitutiva viscoelástica utilizada é reescrita em termos de uma variável Ψ, que é o logaritmo do tensor conformação. Apesar do potencial de aplicação da FLC, pouca atenção tem sido dirigida para análise da acurácia da solução obtida para o campo de tensões quando se utiliza esta formulação. Assim, o objetivo do presente trabalho foi estudar a acurácia da solução obtida pela FLC na análise de escoamentos de fluidos viscoelásticos usando duas geometrias padrão de estudo: placas paralelas e cavidade quadrada com tampa móvel. Primeiramente, a FLC foi implementada no pacote de CFD OpenFOAM. Em seguida foram verificados os limites do número de Weissenberg na formulação numérica padrão (Welim,P), onde para a geometria de placas paralelas foi encontrado Welim,P = 0,3 e para a geometria da cavidade quadrada com tampa móvel foi encontrado Welim,P = 0,8. Depois o código implementado foi aplicado em ambas as geometrias, comparando-se a solução obtida pela FLC com aquela da formulação padrão na faixa de We < Welim,P. Os resultados obtidos na geometria de placas paralelas apresentaram boa concordância com a solução padrão e solução analítica. Para a geometria da cavidade quadrada com tampa móvel, que não possui solução analítica, boa concordância dos resultados também foi observada em comparação com a solução padrão. Posteriormente foram comparados os resultados obtidos pela FLC na faixa de We > Welim,P. Na geometria de placas paralelas, além da boa concordância com a solução analítica, obteve-se convergência em todos os casos estudados neste trabalho, com o maior número de Weissenberg utilizado sendo igual a 8 Os resultados da geometria da cavidade quadrada com tampa móvel também apresentaram boa concordância em comparação com dados da literatura, porém a convergência foi obtida até para We = 2. Com respeito à comparação das formulações numéricas com a solução analítica, feita apenas na geometria de placas paralelas, foi observado um erro máximo de 7,57% na solução padrão e de 12,33% na FLC. Em relação à análise da qualidade das tensões usando os resíduos da equação constitutiva viscoelástica como critério de acurácia, foi verificado nas duas geometrias que os valores de tensão obtidos usando a FLC são menos acurados que aqueles obtidos pela formulação explícita no tensor das tensões nos casos em que esta última converge. Também foi observado que a acurácia diminui com o aumento do We. Esse efeito pôde ser melhor notado na geometria de placas paralelas. Uma razão para a perda de acurácia da tensão provavelmente ocorre devido à natureza matemática da transformação algébrica inversa de Ψxx para τxx. O novo solver implementado neste trabalho apresentou convergência e soluções corretas para as duas geometrias, logo foi implementado corretamente. Ele também potencializa o solver de partida viscoelastiFluidFoam ao estender simulações para uma faixa maior do número de Weissenberg. / A recent approach proposed in the literature to deal with the High Weissenberg Number Problem is the Log-Conformation formulation (LCF). In this formulation the viscoelastic constitutive equation is rewritten in terms of the logarithm of the conformation tensor Ψ. Despite the great potential application of the LCF, little attention has been given in the literature to the accuracy of the obtained stress fields. The purpose of this work was to study the solution obtained by LCF in the analysis of viscoelastic flows using two benchmark geometries: parallel plates and lid driven cavity. Firstly, the LCF was implemented in the OpenFOAM CFD package. Then, the limits of Weissenberg number for the standard numerical formulation (Welim,P) were verified, obtaining Welim,P = 0.3 for the parallel plates and Welim,P = 0.8 for the lid driven cavity. When comparing the solution obtained by the LCF with that of the standard formulation in a range of We < Welim,P, the results obtained for the parallel plates geometry showed good agreement with the standard solution and the analytical solution. For the lid driven cavity geometry, for which there is not analytical solution, good agreement with the standard solution was also observed. For We > Welim,P in the parallel plates geometry, in addition to the good agreement with the analytical solution, it was possible to obtain convergence in all the cases studied in this work, with the largest number of Weissenberg used being equal to 8 The results of the lid driven cavity geometry also presented good agreement in comparison with literature data, but convergence was obtained up to We = 2. With respect to the comparison of the numerical formulations with the analytical solution for the parallel plates geometry, a maximum error of 7.57% was observed in the standard solution and of 12.33% in the LCF. When using the residues of the viscoelastic constitutive equation as a criterion of accuracy, it was verified that for the two geometries the stress values obtained using the LCF were less accurate than those obtained by the explicit formulation in the stress tensor. It has also been observed that accuracy decreases with increasing of We. One reason for the loss of stress accuracy probably occurs because of the mathematical nature of the inverse algebraic transformation from Ψxx to τxx. The new solver implemented in this work presented convergence and correct solutions for the two geometries, so it was implemented correctly. It also potentiates the viscoelastiFluidFoam starting solver by extending simulations to a larger range of Weissenberg number.

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