Turbulent flow and heat transfer in eccentric annulus

Published versio

Biglobal linear stability analysis for the flow in eccentric annular channels and a related geometry

Recently, it has been observed that simple geometry characterized by a low level of symmetry present interesting peculiarities in the process of transition from laminar Poiseuille flow to turbulent flow. Examples of this type of geometry are eccentric channels and, more generally, parallel channels containing a narrow gap. In the present work, a global linear stability analysis for the flow in this class of geometry has been performed. The problem is discretized through spectral collocation and the eigenvalue problem has been solved with the Arnoldi-method based algorithms and the QZ algorithm. Since no numerical studies of this type have yet been performed to address the issue of transition in this geometry, the codes have been validated toward results obtained in simplified geometries _e.g., concentric annular channel and square channel_. The eigenvalue spectra of the Poiseuille flow in eccentric channels and a U-shaped channel have then been computed and analyzed for a wide range of geometric parameters. After comparison with spectra typical of channel flow and pipe flow it is shown that an additional linear mechanism of instability is present, related to the spanwise variation of the laminar velocity profile

Analysis of immunoexpression and PTEN allelic loss in dysplastic lesions and oral squamous cell carcinomas

Orientadores: Helder Antonio Rebêlo Pontes, Felipe Paiva FonsecaDissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Odontologia de PiracicabaResumo: O Carcinoma epidermoide é a neoplasia maligna mais comum de boca, representando mais de 95% dos casos diagnosticados neste sítio anatômico. Muitos casos de carcinomas epidermoides de boca (CEB) podem ser precedidos ou estão associados a lesões potencialmente malignas, especialmente as leucoplasias. O processo de carcinogênese envolve a aquisição progressiva de alterações irreversíveis de vários genes, com ativação de oncogenes e inativação de genes supressores tumorais e de genes envolvidos no reparo do DNA. A fosfatase homóloga à tensina deletada no cromossomo 10 (PTEN) é um gene supressor tumoral que exerce um importante mecanismo no controle da aquisição do fenótipo maligno ao inibir a expressão da proteína pAkt, sendo importante no controle da via de sinalização intracelular PI3K?AKT, responsável pelo controle da proliferação celular e apoptose. A perda ou inativação de PTEN ativa a via de sinalização PI3K/AKT, encontrada em diversos tipos de tumores. O objetivo deste estudo foi analisar a perda alélica do gene PTEN e avaliar a imunoexpressão da proteína nas lesões displásicas bucais e CEB. As amostras foram coletadas de 153 pacientes (20 casos controle ¿ C, 30 leucoplasias com displasia leve ¿ DL, 30 leucoplasias com displasia moderada a severa ¿ DMS, e 73 amostras de CEB), provenientes do Serviço de Patologia Bucal do Hospital Universitário João de Barros Barreto (HUJBB). A expressão da proteína PTEN foi investigada através da técnica imuno-histoquímica e a perda alélica foi analisada pelo método de hibridização in situ por fluorescência (FISH). Diferenças entre os grupos foram avaliadas usando o teste Qui-quadrado. Os resultados mostraram que houve um aumento na expressão de PTEN, assim como uma maior perda alélica de acordo com a progressão para a malignidade, onde a expressão foi mais alta em DMS (p=0.002) e CEB (p=0.0259) comparados com o grupo C, além disso, foi observada uma maior expressão em DMS (p=0.0035) e CEB (p=0.049) do que em DL; em relação à análise de FISH, uma maior perda hemizigótica (cópia única) foi observada em CEB comparado com C (p=0.0467) e DL (p=0.0175), assim como uma maior deleção homozigótica em CEB comparado com C (p=0.0159) e DL (p=0.0145). Em conclusão, os resultados deste trabalho sugerem que a perda alélica de PTEN é um importante mecanismo nos estágios finais da aquisição do fenótipo maligno, onde a perda alélica foi observada em 34.25% das amostras de CEBAbstract: Oral squamous cell carcinoma (OSCC) is the most common malignant neoplasm in the oral cavity, accounting for more than 95% of the cases diagnosed in this anatomical site. Many cases of OSCC may be preceded by or associated with potentially malignant disorders, such as leukoplakias. The carcinogenesis process involves a progressive evaluation of irreversible changes of several genes, with activation of oncogenes and inactivation of tumour suppressor genes and genes involved in DNA repair. Phosphatase and tensin homolog deleted on chromosome 10 (PTEN) is a tumour suppressor gene that represents an important mechanism for the acquisition of a malignant phenotype by inhibiting the expression of the pAKT protein, which is important in the control of the intracellular signalling pathway PI3K/AKT, which is responsible for the control of cell proliferation and apoptosis. The loss or inactivation of PTEN activates the PI3K/AKT signalling pathway that is found in several types of tumours. The objective of this study was to analyse allelic loss of the PTEN gene and its protein immunoexpression in dysplastic oral lesions and OSCC. The samples were collected from 153 patients (20 ranulas used as a control ¿ C, 30 leukoplakias with mild dysplasia ¿ MD, 30 leukoplakias with moderate to severe dysplasia ¿ MSD, and 73 OSCC) from the Department of Oral Pathology, João de Barros Barreto University Hospital (HUJBB). PTEN protein expression was investigated using immunohistochemistry, and allelic loss was analysed by fluorescence in situ hybridisation (FISH). Differences among groups were evaluated using the Chi-square test. The results showed that there was an increase in PTEN expression, as well as a greater allelic loss, according to progression to malignancy, where expression was higher in MSD (p=0.002) and OSCC (p=0.0259) compared with the C group, additionally, a higher expression was observed in MSD (p=0.0035) and OSCC (p=0.049) than MD; regarding FISH analysis, a higher hemizygous (single copy) loss was observed in OSCC than C (p=0.0467) and MD (p=0.0175), as well as a higher homozygous deletion in OSCC than C (p=0.0159) and MD (p=0.0145). In conclusion, the results of this work suggest that PTEN allelic loss is an important mechanism in the late stage of the development of oral potentially malignant lesions into oral cancer, where allelic loss was observed in 34.25% of OSCC samplesMestradoEstomatologiaMestra em Estomatopatologia33003033009P4CAPE

Preliminary Considerations from the 2nd Phase of Experiments at the SIET/SWAM Facility

Severe accident codes study the thermo-hydraulics of the suppression chamber with a limited numbers of nodes, generally solving mass and energy equations and assuming perfect mixing conditions. In a long station black out the effect of the sparger’s design might create local phenomena (e.g. stratification, hot-spots) which are hardly predicted by the current practices, resulting in mispredictions of the containment pressure evolution. In order to understand the effect of the sparger geometry, steam mass flux, water sub-cooling and air concentration the SWAM facility (Steam Water Air Mixing) at the SIET laboratory was employed performing around twenty different experiments, in conditions close to what is expected during the Fukushima Daiichi accident. The test facility (poll and pipes) is built with polycarbonate (transparent material) to ease the acquisition of the standard and high-speed cameras. Vertically distributed thermocouples and high-frequency pressure measurements are employed to obtain quantitative values for phenomena investigation and future CFD validations. It was shown that experiments with pure steam and relatively large diameter holes induce chugging that enhances mixing in the pool. Once chugging ceases, because of the reduced sub-cooling, a hot water layer is created in the upper part of the pool. The presence of air in the pipe induces large stratification from the condition of large subcooling because of the limited mixing introduced in the region below the pipe mouth

Thermal-hydraulics of internally heated molten salts and application to the Molten Salt Fast Reactor

The Molten Salt Reactors (MSR) are an innovative kind of nuclear reactors and are presently considered in the framework of the Generation IV International Forum (GIF-IV) for their promising performances in terms of low resource utilization, waste minimization and enhanced safety. A unique feature of MSRs is that molten fluoride salts play the distinctive role of both fuel (heat source) and coolant. The presence of an internal heat generation perturbs the temperature field and consequences are to be expected on the heat transfer characteristics of the molten salts. In this paper, the problem of heat transfer for internally heated fluids in a straight circular channel is first faced on a theoretical ground. The effect of internal heat generation is demonstrated to be described by a corrective factor applied to traditional correlations for the Nusselt number. It is shown that the corrective factor can be fully characterized by making explicit the dependency on Reynolds and Prandtl numbers. On this basis, a preliminary correlation is proposed for the case of molten fluoride salts by interpolating the results provided by an analytic approach previously developed at the Politecnico di Milano. The experimental facility and the related measuring procedure for testing the proposed correlation are then presented. Finally, the developed correlation is used to carry out a parametric investigation on the effect of internal heat generation on the main out-of-core components of the Molten Salt Fast Reactor (MSFR), the reference circulating-fuel MSR design in the GIF-IV. The volumetric power determines higher temperatures at the channel wall, but the effect is significant only in case of large diameters and/or low velocities

FOREST DYNAMICS IN THE EASTERN AMAZON WITH SPECIAL REFERENCE TO SAPOTACEAE SPECIES

AbstractSapotaceae species are among the most dominant tree species in the Amazon forest and are high valued timbers. This paper aimed to evaluate the effect of Reduced Impact Logging (RIL) over a dense tropical rain forest with special reference to Sapotaceae species, to generate information helping decision making in forest management. In 1997, out of a 1050 ha forest area located in the municipality of Moju, State of Pará, Brazil, 200 ha were selected to be logged applying a logging intensity of 23 m3 ha-1 and RIL techniques. To monitor forest dynamics, 22 permanent sample plots (11 ha sampling area) were established and all trees with DBH ≥ 10 cm were measured in years 1995, 1998 and 2010. In the whole observation period, mortality and ingrowth of Sapotaceae species were, respectively, 1.5% year-1 and 1.0% year-1. Trees with full overhead light grew 0.39 cm year-1 and those completely shaded grew only 0.16 cm year-1. Mortality higher than ingrowth indicates that the population of Sapotaceae species still need a period longer than 13 years to recover equilibrium after RIL, despite showing increased diametric growth rates.ResumoDinâmica de uma floresta no leste da Amazônia com ênfase às espécies de Sapotaceae. As espécies de Sapotaceae estão entre as mais dominantes na floresta amazônica e possuem alto valor comercial. O trabalho objetivou avaliar o efeito da Exploração de Impacto Reduzido (EIR) sobre uma floresta ombrófila densa com ênfase às espécies de Sapotaceae para gerar informações que possam subsidiar decisões a serem tomadas sobre o manejo de florestas nativas. De uma área florestal de 1.050 ha, situada no município de Moju, PA, foram selecionados 200 ha para EIR com intensidade de 23 m3 ha-1 em 1997. O monitoramento florestal foi feito com 22 parcelas permanentes (11 ha), sendo medidas todas as árvores com DAP ≥ 10 cm, nos anos de 1995, 1998 e 2010. No período total (1995 a 2010) a mortalidade das espécies de Sapotaceae foi de 1,5% ano-1 e o ingresso de 1,0% ano-1. As árvores com copas totalmente expostas à luz tiveram o incremento de 0,39 cm ano-1 e aquelas totalmente cobertas o incremento foi de 0,16 cm ano-1. A mortalidade maior que o ingresso indica que as espécies de Sapotaceae necessitam de um período maior que 13 anos para recuperar o equilíbrio após a EIR, apesar do aumento no crescimento diamétrico.Palavras-chave: Impacto pós-colheita; mortalidade; manejo florestal.AbstractSapotaceae species are among the most dominant tree species in the Amazon forest and are high valued timbers. This paper aimed to evaluate the effect of Reduced Impact Logging (RIL) over a dense tropical rain forest with special reference to Sapotaceae species, to generate information helping decision making in forest management. In 1997, out of a 1050 ha forest area located in the municipality of Moju, State of Pará, Brazil, 200 ha were selected to be logged applying a logging intensity of 23 m3 ha-1 and RIL techniques. To monitor forest dynamics, 22 permanent sample plots (11 ha sampling area) were established and all trees with DBH ≥ 10 cm were measured in years 1995, 1998 and 2010. In the whole observation period, mortality and ingrowth of Sapotaceae species were, respectively, 1.5% year-1 and 1.0% year-1. Trees with full overhead light grew 0.39 cm year-1 and those completely shaded grew only 0.16 cm year-1. Mortality higher than ingrowth indicates that the population of Sapotaceae species still need a period longer than 13 years to recover equilibrium after RIL, despite showing increased diametric growth rates.Keywords: Impact after logging; mortality; forest management. ResumoDinâmica de uma floresta no leste da Amazônia com ênfase às espécies de Sapotaceae. As espécies de Sapotaceae estão entre as mais dominantes na floresta amazônica e possuem alto valor comercial. O trabalho objetivou avaliar o efeito da Exploração de Impacto Reduzido (EIR) sobre uma floresta ombrófila densa com ênfase às espécies de Sapotaceae para gerar informações que possam subsidiar decisões a serem tomadas sobre o manejo de florestas nativas. De uma área florestal de 1.050 ha, situada no município de Moju, PA, foram selecionados 200 ha para EIR com intensidade de 23 m3 ha-1 em 1997. O monitoramento florestal foi feito com 22 parcelas permanentes (11 ha), sendo medidas todas as árvores com DAP ≥ 10 cm, nos anos de 1995, 1998 e 2010. No período total (1995 a 2010) a mortalidade das espécies de Sapotaceae foi de 1,5% ano-1 e o ingresso de 1,0% ano-1. As árvores com copas totalmente expostas à luz tiveram o incremento de 0,39 cm ano-1 e aquelas totalmente cobertas o incremento foi de 0,16 cm ano-1. A mortalidade maior que o ingresso indica que as espécies de Sapotaceae necessitam de um período maior que 13 anos para recuperar o equilíbrio após a EIR, apesar do aumento no crescimento diamétrico.Palavras-chave: Impacto pós-colheita; mortalidade; manejo florestal

Heat transfer of a buoyancy-aided turbulent flow in a trapezoidal annulus

The objective of this paper is to report a numerical investigation into the heat transfer of a buoyancy-aided flow in a rod-bundle-like channel. The flow field is simulated using large eddy simulation (LES) with WALE SGS model and the buoyant force is taken into account using the Boussinesq approximation. The general trend of the effect of buoyancy on the overall heat transfer is similar to that in a pipe flow, but the effect on the regional heat transfer varies greatly. This has resulted from a number of interplaying factors, including, the redistribution of the mass flow in the various sub-channels, the non-uniform buoyancy effects on turbulence in different regions of the domain and the behaviour of the large flow structures in the flow channel. These factors together make the effect of buoyancy on heat transfer in the considered flow channel really complicated, while the last factor has been found to have the most pronounced effect in most cases studied

Malignant transformation of oral leukoplakia:a multicentric retrospective study in Brazilian population

Among the oral potentially malignant disorders, leukoplakia stands out as the most prevalent. The purpose of this study was to analyse the clinical-pathological features of oral leukoplakia in groups of patients from three major pathology centers in two different regions of Brazil, in order to determine which factors would be associated to the clinical risk of malignant transformation. A total of 148 patients was analyzed, and data regarding gender, age, site, classification of the clinical subtype, harmful habits such as use of tobacco and alcohol, time of evolution and presence of dysplasia were collected. The association between risk factors and malignant transformation was investigated using the chi-square test and Fischer's exact test for correlation of variables. A significance level of 5% (p?0.05) was used. The mean age of the patients was 60 years, and 56% were female. Most of the lesions (34,5%) were located in the lateral and ventral regions of the tongue. Of the 148 patients, ninety had clinical follow-up. Malignant transformation occurred in 13 patients (8.8%), with an average of 44 months of follow up. Non-smoker, nonhomogeneous clinical presentation, location at the tongue, and the presence of high degree of dysplasia were statistically relevant factors associated with a higher risk of transformation transformation