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1
Stephens, D. G. "Residual stresses in ring stiffened cylinders." Thesis, University of Cambridge, 1987. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.384531.
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Rashid, Asim. "MINIMIZING CONTACT STRESSES IN AN ELASTIC RING BY RESPONSE SURFACE OPTIMIZATION." Thesis, Högskolan i Jönköping, Tekniska Högskolan, 2010. http://urn.kb.se/resolve?urn=urn:nbn:se:hj:diva-13023.
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Jerabek, Jakub, Allessandra Keil, Jens Schoene, Rostislav Chudoba, Josef Hegger, and Michael Raupach. "Experimental and Numerical Analysis of Spalling Effect in TRC Specimens." Saechsische Landesbibliothek- Staats- und Universitaetsbibliothek Dresden, 2009. http://nbn-resolving.de/urn:nbn:de:bsz:14-ds-1244046893347-05461.
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The paper presents the study of spalling effect occurring under tensile loading in thin-walled TRC specimens. The experimentally observed failure patterns are first classified and the performed experiment design is explained and discussed. A parameter study of spalling effect with varied thickness of concrete cover and reinforcement configurations including both the textile fabrics and the yarns provided the basis for numerical analysis of the effect. The applied numerical model was designed in order to capture the initiation and propagation of longitudinal cracks leading to the separation of concrete blocks from the textile fabrics. A meso-scopic material resolution in a single crack bridge is used for the simulation exploiting the periodic structure of the crack bridges both in the lateral and in the longitudinal direction of the TRC specimens. The matrix was modeled using an anisotropic damage model falling in the microplane-category of material models. The bond between yarn and matrix follows a non-linear bond-law calibrated using pull-out tests. The epoxy-impregnated reinforcement is considered as a homogeneous bar.
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Travis, David J., Vernon Meentemeyer, and Roger P. Belanger. "Stressed Trees Produce a Better Climatic Signal than Healthy Trees." Tree-Ring Society, 1990. http://hdl.handle.net/10150/261930.
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The basis for the selection of trees to be used in the production of dendrochronologies has long been an issue (Douglass 1946; Fritts 1976). In humid regions the common practice has been to use trees that appear to be in good health. As a part of a larger study involving the impact of ice storms on tree-ring increments (Travis 1989), we show that trees stressed as a result of ice damage produced a stronger climatic signal than nondamaged trees.
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Aleong, Chris J. "Experimental determination of residual stresses in filament wound composite rings." Thesis, University of Ottawa (Canada), 1986. http://hdl.handle.net/10393/4818.
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Watson, Emma, and Brian H. Luckman. "The Development of a Moisture-Stressed Tree-Ring Chronology Network for the Southern Canadian Cordillera." Tree-Ring Society, 2001. http://hdl.handle.net/10150/251652.
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Fifty-three ring-width chronologies have been developed from open-grown, low-elevation stands of Pseudotsuga menziesii (Douglas-fir) and Pinar ponderosa (ponderosa pine) in the southern Canadian Cordillera. These chronologies will be used to develop precipitation reconstructions for the region. The sites are unevenly distributed across the interior valleys from east of the Coast Ranges to the Canadian Rockies and from the Canada-U.S. border to the northern limits of both species. The chronologies range from 123-691 years (mean = 383 years) and, on average, have a strong within-chronology common signal (Expressed Population Signal > 0.85) with as few as eight trees. A Rotated Principal Components Analysis (RPCA) identified three regions within which annual ring-width chronologies covary similarly. A preliminary assessment of regional chronologies and patterns of extreme narrow and wide marker rings demonstrates that common growth variations exist in the chronology network that are probably precipitation related. Both the RPCA and marker ring analyses suggest distinctive regional patterns of growth on both interannual and longer timescales that vary through time and are possibly linked to persistent large scale climatic anomalies.
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Gonzalez-Mendez, Jose Luis. "Prediction of Geometric Distortions and Residual Stresses on Heat Treated Hot Rolled Rings." The Ohio State University, 2011. http://rave.ohiolink.edu/etdc/view?acc_num=osu1322064630.
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Seeley, Kathryn E. "Evaluation and Validation of Measures of Chronic Stress in Ring-tailed Lemurs (Lemur catta)." The Ohio State University, 2017. http://rave.ohiolink.edu/etdc/view?acc_num=osu1492536480829096.
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She, Dawei. "Analysis of Ni and Fe-based Alloys for Turbine Seal Ring Applications." Scholar Commons, 2018. http://scholarcommons.usf.edu/etd/7229.
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Metal sealing rings have been used widely in compressors, turbines and hydraulic devices. Such rings can extend out due to elasticity, and keep close contact with the valve wall, resulting in the formation of a functional seal under pressure. In this project, the failure of metal sealing rings is considered. Sealing component failure due to stress relaxation can threaten the safety of the whole steam turbine. The object of this study was to examine the stress relaxation response and corresponding changes in microstructure of metal sealing rings used in nuclear steam turbine under high temperature and applied stress. The two kinds of sealing ring samples were selected for GH4145 and GH2132.
In this paper, all samples were tested by accelerated simulation experiment. The test temperature was controlled at 400℃, 600℃, and 800℃. The 400℃ experiments lasted for 10, 20, 30 and 40 hours, while the 600℃ and 800℃ experiments lasted for 5, 10, 15 and 20 hours. The surface morphology was observed by metallographic analysis. It was found that the two kinds of sealing ring samples presented with a continuous development of grain coarsening and a decrease of the twins when time and test temperature were increased. The prolongation of time and increase of test temperature will drive the grain coarsening and reduce the twins faster. Many precipitates and inclusions were observed on the surface. The composition of precipitation was examined by scanning electron microscopy (SEM). It was further studied by testing samples with applied stress. The differences between the two tests and their influence on mechanical properties are discussed. The grain coarsening and twinning in the alloy will reduce the stress relaxation resistance of the material. Additionally, the precipitates and inclusions in the alloy may adversely affect the stress relaxation performance. Sealing rings using the nickel-based superalloys have stronger anti-stress relaxation performance than sealing rings made of iron-based superalloys.
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Yang, Kang. "Numerical and semi analytical models for electromagnetic ring expansion test." Thesis, Compiègne, 2017. http://www.theses.fr/2017COMP2350.
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Le taux de déformation des matériaux est élevé pendant le soudage / formage à grande vitesse, le découpage, le sertissage, etc. Les propriétés des matériaux sous déformation à grande vitesse ne suivent pas la même loi que dans le cas de chargement quasi statiques. La caractérisation des matériaux à taux de déformation important est assez difficile et nécessite des équipements sophistiqués. Grâce au développement de la technologie de formage électromagnétique, le test d'expansion d'anneau électromagnétique présente un grand potentiel à utiliser pour caractériser les matériaux à haute vitesse de déformation. Pendant le test d’expansion de l’anneau électromagnétique, la pièce à usiner peut atteindre une vitesse d’expansion de l’ordre de 100m/s et une vitesse de déformation de 104 s-1. Par conséquent, ce test peut être utilisé pour prédire les paramètres du matériau, tels que la dureté et la ductilité à déformation à grande vitesse. Pour d’atteindre cet objectif, un modèle approprié décrivant le processus est nécessaire. Ce modèle doit contenir un couplage électromagnétique-mécanique-thermique pour bien décrire le problème multi-physique. Il existe deux méthodes principales de modélisation dans la littérature, viz. Les méthodes semi-analytiques et les méthodes des éléments finis (parfois combinées avec la méthode des éléments limitants). Les méthodes semi-analytiques nécessitent un temps de calcul court mais offrent une faible précision par rapport aux méthodes des éléments finis. Cependant, en raison de la complexité du couplage multi-physique, l’erreur de calcul est difficile à estimer. De plus, les déformations hétérogènes ainsi que les états de contrainte compliqués peuvent influencer l’identification. Dans ce sens, cette thèse s’est principalement concentrée sur les méthodes d’analyse et de modélisation du test d’expansion d’anneau électromagnétique, incluant les comportements locaux et les phénomènes dynamiques à l’aide des outils expérimentaux et numériques. Par ailleurs, cette thèse comprend aussi le développement d’un méthode semi-analytique permettant le couplage multi-physique, ce qui a été validé par un modèle numérique idéal et par des tests expérimentaux. Les résultats expérimentaux ont été obtenus à l’aide d’une caméra à grande vitesse et du vélocimétrie photovoltaïque Doppler (PDV) pour différents cas tests. Ils ont été utilisés pour déterminer les paramètres du processus et du matériau à l’aide des modèles numériques. Les modèles adaptés pour analyser les états de contrainte et de déformation durant le test d’expansion d’anneau montrent que ce dernier n’est pas un test de traction uniaxial pur comme revendiqué par les chercheurs. En outre, le phénomène de vibration qui se produise de la récupération élastique a été étudié par simulations multi-physiques et par systèmes PDV. Cette étude de récupération élastique permet de mieux comprendre les paramètres influençant du test, ce qui pourrait être utilisé pour contrôler le rebond dans d’autres processus électromagnétique. La méthode de modélisation semi-analytique pour le test d’expansion de l’anneau électromagnétique, qui comprend quatre parties de calcul (partie mécanique, thermique, force de Lorentz et courant de Foucault), a été analysée à l’aide de simulations numériques. Les résultats obtenus ressemblent étroitement aux résultats obtenus par un test idéal et un test expérimental. L’analyse d’erreur des différents aspects physiques permet d’améliorer la précision de calcul semi-analytique, ce qui pourrait être utilisé comme outil supplémentaire d’obtention rapide des paramètres de contrôle dans les tests. Il pourrait aussi être utilisé pour l’identification des paramètres des matériels à déformation à grande vitesseHigh stain rate material deformations are prevalent during high speed impacts, high speed forming/welding, cutting, crimping, blast etc. Characteristics of materials under high strain rate deformation do not follow the same as it occurs under the quasi-static loading conditions. However, characterization of materials under high strain rate deformation is always challenging and it requires sophisticated equipment. Thanks to the development in electromagnetic forming technology, the electromagnetic ring expansion test shows a great potential to be used to characterize materials under high strain rate conditions. During the electromagnetic ring expansion test, the workpiece can reach deformation velocities in the order of 100 m/s and a strain rate of up to 104 s-1. Consequently, this test can be used to predict the material parameters such as the strain rate hardening and ductility under extremely high strain rates (strain rates in the order of 103 – 104 s-1). In order to achieve this goal, an appropriate model is required to describe the process. The model should contain an electromagnetic-mechanical-thermal coupling to obtain the accurate multi-physics nature of the problem. There exist two main modeling methods in literature, viz., the semi-analytical methods and finite element methods (sometime combined with boundary element method). Normally, the semi-analytical methods require short calculation time while it provides lower accuracy in comparison with finite element methods. However, due to the complexity of multi-physics coupling, the calculation error is difficult to be analyzed. Moreover, errors in calculation and identification assumptions may also result from heterogeneous deformations or localized specific phenomena (such as local necking at multi points or electric current localization, skin effect, edge effect of Lorentz force etc.) that could influence identification work as well as stress and strain states. Therefore, this thesis mainly focused on the analysis and modeling methods of ring expansion test including local behaviors and dynamic phenomena with the help of experimental and numerical tools. Moreover, this thesis also includes a development of a semi-analytical method with multi-physics coupling capabilities, which has been validated using a theoretical model and experimental frameworks. Experimental measurements were obtained using high-speed cameras and photonic Doppler velocimetry (PDV) for various test cases are used together with numerical models to investigate the process and material parameters. The models used to analyze the stress and stain states during a ring expansion test show that the ring expansion test is not a pure uniaxial tensile test as claimed by researchers. Besides, another potential process behavior, the vibration phenomena that occurs during the elastic recovery was investigated using multi-physics simulations and PDV systems. This investigation of the elastic recovery helps to understand the potential influencing parameters of the test those are applicable and could be used to control the springback phenomenon during other electromagnetic forming processes. The semi-analytical modeling method for ring expansion test including four calculation parts (mechanical part, eddy current, Lorentz force calculation, thermal part) were analyzed with the help of numerical simulations. The results obtained from analytical work closely resemble with the numerical simulations for both theoretical model and an experimental case study. The error analysis of various physical aspects allows improving the accuracy of semi-analytical calculation that could be used as an additional platform to obtain rapid calculation of the test conditions. This semi-analytical method could be extended in the future to identify material parameters under high strain rate deformations
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Fernandes, Rafael Queirós. "Polimorfismos da região promotora do gene ELANE em doentes com doença renal terminal." Master's thesis, Universidade de Aveiro, 2015. http://hdl.handle.net/10773/14897.
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Mestrado em Bioquímica - Bioquímica ClínicaA doença renal crónica (DRC) é um problema de saúde pública com uma prevalência mundial crescente. Os doentes terminais apresentam uma taxa de mortalidade que excede a da população em geral. A inflamação é uma característica clínica comum dos doentes em terapia de hemodiálise, não havendo, no entanto, um conhecimento claro sobre os mecanismos bioquímicos subjacentes. Foi demonstrado que o procedimento hemodialítico promove a ativação de neutrófilos, com libertação de elastase, podendo desempenhar um papel importante na resposta inflamatória, e no desenvolvimento de stress oxidativo, dois fatores que, em conjunto, podem agravar a anemia e o risco de doenças cardiovasculares, que são a principal causa de mortalidade desta população. A elastase neutrofílica, uma protease capaz de degradar várias proteínas da matriz extracelular, é codificada pelo gene ELANE, que foi associado ao desenvolvimento de várias patologias e ao aumento do risco de desenvolvimento de cancro do pulmão. A presença de mutações e polimorfismos neste gene parecem determinar modificações ao nível da expressão da elastase, promovendo distúrbios proteolíticos. Este trabalho teve como objetivos identificar e avaliar o impacto dos polimorfismos da região promotora do gene ELANE nos níveis circulantes de elastase, a sua associação com alterações hematológicas, inflamatórias, nutricionais e de adequação da diálise, e com o risco de mortalidade na DRC. Para isso, realizou-se um estudo transversal com 123 doentes renais terminais portugueses em hemodiálise. Estudaram-se os polimorfismos no promotor do gene ELANE, por PCR-sequenciação direta. Os níveis plasmáticos de elastase foram determinados por ELISA. Avaliou-se a correlação de cada polimorfismo com vários parâmetros clínicos, marcadores hematológicos e inflamatórios, de metabolismo do ferro, do estado nutricional e de adequação da diálise, recolhidos dos registos dos doentes. Dos cinco polimorfismos já descritos na literatura, identificaram-se três neste grupo de doentes: c.-903T>G, c.-741G>A, e a presença de uma sequência extra de 52 pb. Além disso, identificaram-se dois novos polimorfismos: c.-801G>A, e a presença de um bloco extra, composto pela quarta e pela quinta repetição que compõem a região promotora do gene. Estes polimorfismos não parecem influenciar significativamente os níveis circulantes de elastase, nem o processo inflamatório dos doentes, não apresentando influência sobre o prognóstico da doença.
End-stage renal disease (ESRD) is a growing public health problem with an increasing worldwide prevalence. ESRD patients present a high mortality rate that far exceeds the mortality rate for the non-ESRD population. Inflammation is a common feature of the patients under hemodialysis; however, the mechanisms/factors triggering the inflammatory process are still poorly clarified. It has been recently demonstrated that hemodialysis procedure induces neutrophil activation and elastase release, which might have an important role in the inflammatory process and in the development of oxidative stress, two factors that can increase the anemia and the risk of cardiovascular diseases, which are the leading cause of mortality in this population. Neutrophil elastase, a protease capable of degrading several extracellular matrix proteins, is encoded by ELANE gene that has been shown to be related with the development of several pathologies and with the higher risk of developing lung cancer. The presence of mutations and polymorphisms in this gene appear to influence the level of elastase expression, promoting proteolytic imbalances. This study aimed to identify and assess the impact of polymorphisms of the promoter region of the ELANE gene in the circulating levels of elastase, their association with hematological, inflammatory and nutritional alterations, dialysis adequacy and with mortality in DRC. To accomplish these objectives, we performed a cross-sectional study with 123 ESRD patients on regular hemodialysis. The promoter region of the ELANE gene was screened for all patients using PCR-direct sequencing and elastase quantification was performed by ELISA. We evaluated the correlation of each polymorphism with various clinical and hematological data, inflammatory and iron metabolism markers, nutritional status and dialysis adequacy, collected from patient records. Of the five polymorphisms already described in the literature, we identified three in this group of patients: c.-903T>G, C-741G>A and the presence of an extra sequence of 52 bp. In addition, we identified two new polymorphisms: c.-801G>A and the presence of an extra block composed of the fourth and the fifth repeat that make up the promoter region of the gene. These polymorphisms do not appear to significantly influence circulating levels of elastase or the infl
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Rodeiro, Pablo Filgueira. "Análise de distribuição de temperaturas e tensões residuais em soldas do tipo ring-weld." Universidade de São Paulo, 2003. http://www.teses.usp.br/teses/disponiveis/3/3135/tde-21052003-080734/.
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Este estudo apresenta uma abordagem para a determinação do campo de temperaturas e tensões residuais desenvolvidos durante a soldagem de uma solda do tipo ring-weld. Devido à complexidade da junta soldada e à velocidade de deposição, um modelo de elementos finitos sólido-tridimensional foi elaborado para a solução do campo de temperaturas e tensões residuais. As características não-lineares do fenômeno tais como a dependência das propriedades físicas e mecânicas com a temperatura e a deposição de material ao longo da soldagem foram consideradas neste estudo. Um ensaio com termopares foi realizado com a finalidade de comparação e validação do modelo térmico utilizado. Os resultados obtidos mostraram uma boa correlação entre o ensaio e o modelo numérico, permitindo uma maior confiabilidade para a execução do modelo mecânico subseqüente. Os resultados do modelo mecânico para a determinação das tensões residuais não foram comprovados por ensaio, porém os resultados se apresentaram qualitativamente satisfatórios.This study presents an approach to determine the temperature field and residual stresses developed during the welding of a ring-weld. Due to the complexity of the welded joint and its deposition speed, a 3D solid finite element model was constructed for solving the temperature and residual stress fields. The non-linear characteristics of the phenomenon such as, the temperature dependence of the physical properties and the material deposition through the welding process were taken into account. A thermocouple test was performed in order to compare and validate the thermal model used. The results obtained have shown a good correlation between the test and numerical model results, allowing a greater reliability to the execution of the subsequent mechanical model. The results of the mechanical model used for determining the residual stresses were not verified by testing, but the results were qualitatively adequate.
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Hudson, Laura Elizabeth. "Limber pine sensitivity to climatic and biological stressors evidence from dendrochronology and carbon isotopes /." Laramie, Wyo. : University of Wyoming, 2007. http://proquest.umi.com/pqdweb?did=1495959111&sid=1&Fmt=2&clientId=18949&RQT=309&VName=PQD.
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Silva, Alisson Duarte da. "Prediction and control of geometric distortion and residual stresses in hot rolled and heat treated large rings." Universidade Federal de Minas Gerais, 2012. http://hdl.handle.net/1843/BUOS-8XTQPN.
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Seamless rings are produced by hot rolling and heat treatment processes. The heat treatment is used to enhance the material properties of a wide range of mechanical steel components, according to their final application. Quenching is a common step in these heat treatments, involving the fast cooling of previously austenitized parts and leading to a phase transformation from austenite to hard martensite in the material. Quenching commonly causes a geometric distortion in the parts, associated with the thermal contraction and with the change in the mechanical and geometrical properties of the material phases. For the manufacturing of large thin-walled rings, the control of the distortion during the quench process is not possible. The high production rate, the range of rings sizes and all the quench conditions inside the tank represent a very complex system. It is of importance to predict these distortions, so that one can design corrective post-heat treatment shape corrections, leading to a final part with adequate shape and dimensions. This doctoral thesis develops a methodology to predict and correct the ring distortion so-called ovality. This methodology is based on finite element (FE) simulations of the heat treatment (normalizing and quenching) and straightening of an AISI 4140 steel hot rolled ring. The heat treatment simulation is validated using a Navy C-Ring Test. The straightening process uses a compressing machine with flat tools, and an experimental procedure is defined and performed through out simulationAnéis sem costura são fabricados através de processos como a laminação a quente e o tratamento térmico. O tratamento térmico é utilizado para aprimorar as propriedades do material, podendo ser conferido a uma grande variedade de componentes mecânicos em aço, conforme a sua aplicação. A têmpera é um estágio bastante comum no tratamento térmico de componentes mecânicos, o qual consiste no resfriamento rápido de peças austenitizadas, provocando a transformação da fase austenita para a martensita. Normalmente, a têmpera causa distorções geométricas, as quais estão associadas com a contração térmica e a modificação das propriedades mecânicas e geométricas. Para o processo de grandes anéis com espessura fina, o controle da distorção durante a têmpera representa uma tarefa complexa e praticamente impossível. A necessidade de uma alta produtividade, a variedade de tamanho dos anéis, além de todas as condições existentes dentro do tanque de têmpera, representam um sistema complexo de processo. Neste caso, torna-se necessário prever estas distorções, visando-se o projeto de sistemas de correção pós-tratamento térmico, buscando-se obter formas e dimensões adequadas. Esta tese de doutorado desenvolve uma metodologia para prever e corrigir a distorção de anéis denominada ovalização. Esta metodologia é baseada em simulação por elementos finitos do tratamento térmico (normalização e têmpera) e do processo de desempeno de um anel laminado a quente de aço AISI 4140. A simulação por tratamento térmico é validada usando-se o Teste do Anel em C. A etapa de desempeno utiliza um equipamento de compressão, provido por duas ferramentas planas. Um procedimento experimental é definido e numericamente simulado para o processo de desempeno.
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Alpay, Ceyda. "Investigation Of Geometrical Factors For Determining Fracture Toughness With The Modified Ring Test." Master's thesis, METU, 2008. http://etd.lib.metu.edu.tr/upload/12609883/index.pdf.
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Modified Ring specimens are of the shape of discs having a hole inside and
flattened ends. These specimens are used for determination of Mode I fracture
toughness. Finite element program, named ABAQUS, is used for numerical
modeling for finding stress intensity factors. Varying disc geometries were used
for the experiments and numerical modeling in which size of the flat ends,
radius of the hole inside, and external radius of the specimen were varied.
Experiments were done by using pink Ankara andesite. Effects of internal hole
radius, external disc radius and size of the flat ends on both stress intensity
factor and fracture toughness were studied. In order to compare the results,
fracture tests with semi-circular specimens under three point bending (SCB)
were also performed. From a similar previous study, fracture toughness values
of gray andesite were recalculated and compared to the fracture toughness
values of pink andesite for varying geometrical factors. Size effect studies were
performed as well for varying diameter of core specimens.Fracture toughness values of andesite were found to increase with increasing
specimen size. Fracture toughness of 100 mm specimens was determined as
1.11±0.07 MPa&
#8730
m, whereas fracture toughness of 75 mm specimens was 0.96±
0.08 MPa&
#8730
m. 100 mm or larger diameter specimens were suggested for the fracture toughness determination with the modified ring tests.
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Dang, Quang Khang. "DEVELOPMENT OF A NEW HIGH-STRESS DYNAMIC-LOADING RING-SHEAR APPARATUS AND ITS APPLICATION TO LARGE-SCALE LANDSLIDES." 京都大学 (Kyoto University), 2015. http://hdl.handle.net/2433/202690.
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Lindhout, Katina, and Lynette Brown@latrobe edu au. "Physiology of Chilling-Related Postharvest Rind Breakdown of Navel Oranges (Citrus Sinensis (L.) Osbeck)." La Trobe University. School of Life Sciences, 2007. http://www.lib.latrobe.edu.au./thesis/public/adt-LTU20080526.093527.
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Chilling-related postharvest rind breakdown of navel oranges is a significant economic problem worldwide.
Chilling injury (CI) symptoms on navel orange fruit vary, and descriptive classification is generally ad hoc, making inter-study comparisons difficult. In this study, external symptoms of CI were related to patterns of cellular collapse in affected flavedo tissue, and a classification system developed to aid consistent symptom identification and improve communication within the supply chain.
Potential markers of senescence were evaluated because older fruit were found to be more susceptible to CI. Electrolyte leakage, moisture content and protein content of flavedo tissue were ineffective indicators of both senescence and chilling stress. Rind colour and internal maturity were generally good indicators of fruit age, but lacked sensitivity over short time periods to be of use.
Although there was a strong seasonal effect on CI incidence, pre-storage treatments, including hot water and methyl jasmonate, generally reduced the incidence of CI. Because these treatments elicit defence responses that protect tissue from chilling stress, the response and efficiency of plant defence systems is probably an important factor in chilling tolerance.
The concentration of lipid hydroperoxides (LOOH) in flavedo tissue was lower in fruit that were stored at a chilling temperature (1�C) compared to fruit that were stored at a non-chilling temperature (12�C) and lipid peroxidation did not increase during storage at 1�C. There was also a lower concentration of LOOH in the chilling sensitive variety than in the chilling tolerant variety. Therefore, increased lipid peroxidation is not related to chilling stress and subsequent injury but the results do suggest a role for LOOH in stress signalling. Antioxidant activity in the lipophilic fraction of flavedo tissue extracts increased as fruit senesced and was strongly correlated with carotenoid content. LOOH concentrations in flavedo tissue also increased as fruit senesced. The antioxidant activity of both the lipophilic and hydrophilic fractions of flavedo tissue extracts was higher in fruit stored at 12�C than in fruit stored at 1�C.
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Biancalana, Neto Américo [UNESP]. "Alívio de tensões em tubos a partir da aplicação de vibração mecânica." Universidade Estadual Paulista (UNESP), 2016. http://hdl.handle.net/11449/143972.
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Os processos tradicionais de produção de tubos API 5CT N80Q envolvem processos de bobinamento e desbobinamento, conformação por dobramento, soldagem, etapas de usinagem e expansão dos diâmetros interno e externo, tratamentos térmicos de têmpera e revenimento e endireitamento. Essas etapas são responsáveis por introduzir tensões residuais no material constituinte do tubo. Estas tensões residuais podem alcançar valores próximos aos do limite de escoamento do material base do tubo, podendo produzir distorções geométricas, falhas prematuras, baixa resistência à corrosão, e diminuição na sua capacidade de absorção de cargas em trabalho. O método mais utilizado para alívio de tensões é o tratamento térmico. Porém, a aplicação de vibrações mecânicas, (Vibratory Stress Rielif) para reduzir e redistribuir as tensões residuais em estruturas conformadas a frio e em estruturas soldadas, tem sido utilizada com sucesso em várias partes do mundo, principalmente nos Estados Unidos, China e Canada. Para verificar a viabilidade deste processo, como um método alternativo para o alivio de tensões, selecionamos um tubo API 5CT 80NQ, com diâmetro de 178 mm com 8,05 mm de espessura e 3000 mm de comprimento. Os ensaios de vibração foram executados na frequência de ressonância do tubo, através de um indutor de vibração montado no seu comprimento médio, dentro de um intervalo de tempo correspondente ao seu peso. Comparando os valores de tensões residuais existentes no tubo antes e após o tratamento de vibração conseguimos uma redução média de 16% no valor das mesmas. Para a caracterização mecânica do tubo, antes e depois do processo vibratório, foram realizados os seguintes ensaios conforme a norma API 5CT 2001: impacto Charpy “V”, ensaios de tração e dureza Rockwell C, tanto no metal base do tubo, como na região da solda. Foi realizada, também, a sua caracterização micro estrutural através, microscopia ótica, antes e depois dos ensaios de vibração. Para avaliação das tensões residuais, antes e após os ensaios de vibração, foi utilizado o método de secção longitudinal de um anel (splitting ring test) conforme a norma ASTM EN 1928-13.
The traditional production processes API 5CT N80Q pipes involve coiling and uncoiling processes the plate, conformation by bending, welding, machining steps and expansion of its internal and external diameters, heat treatment of quenching and tempering and straightening. These steps are responsible for introducing residual stresses in the material of the tube. These residual stresses can reach values close to the yield strength of the pipe`s base material and may produce geometric distortions, premature failure, low corrosion resistance and reduction its capacity of absorption loads in the work. The most widely used method for relieving stress is the heat treatment. The application of mechanical vibrations, Vibratory stress relief ( VSR), to reduce and redistribute the residual stresses in cold shaped structures and welded structures, has been used with success in various parts of the world, especially the United States, China and Canada. Thus, the mechanical vibration, Vibratory stress relief (VSR), can prove to be an interesting process to relieve stress in the tubes. To verify the feasibility of this process, as an alternative method for the relief of stresses, we selected an API 5CT 80NQ tube with a diameter of 178 mm, with 8.05 mm thickness and 3000 mm in length. Vibration tests were performed in pipe resonance frequency, via a vibration-inducing mounted at its mid-length, within a time corresponding to their weight. Comparing the values of residual stress existing in the tube before and after the vibration treatment achieved a mean reduction of 16 % in the amount thereof. For the mechanical characterization of the pipe, before and after the vibration process, the following tests were conducted according to API standard 5CT 2001: Charpy 'V', tensile tests and hardness Rockwell C, both in the metal base tube, and in the weld region. It was also carried out their microstructural characterization through optical microscopy before and after the vibration tests. To evaluate the residual stress before and after the vibration tests, we used the ring splitting test according to ASTM E1928-13.
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Cavitt, Marchello Alfonzo. "Stress relief: Exercising Lewis acid catalysis for donor-acceptor cyclopropane ring-opening annulations, a basis for new reaction methodologies." Diss., Georgia Institute of Technology, 2015. http://hdl.handle.net/1853/54448.
Full textAbstract:
Nature’s biodiversity is complex and filled with beauty and wonder which are all observable on the macroscopic scale. This exquisiteness of nature’s intricacies are mirrored on the molecular level such that substances, large or small, are assembled to serve as signaling molecules, protective agents, and fundamental composites of higher-order frameworks for the operation and survival of life. Over the years, chemists have isolated and synthesized these molecules, known as natural products, to understand and evaluate their functions in biology and potential for medicinal applications.
Although bioactive natural products demonstrate medicinal promise, poor pharmacological effects require further derivatization because semisynthesis is not sufficient to refine adverse pharmacokinetics. For some active molecules, isolation results in poor yields. In addition to small quantity isolation, many natural products, reflecting the immense complexity of biology itself, pose difficult synthetic challenges to organic chemists because of skeletal heterogeneity, stereochemical complexity, and substitution divergence. As a result of these synthetic obstacles to natural product utilization, improvements are needed in current chemical approaches, and new innovative methodologies for synthesis and chemical space exploration are necessary.
Pharmaceutically relevant frameworks, natural products, and synthetic biologically active molecules are comprised of polycarbocyclic and heterocyclic scaffolds. Traditionally, cycloadditions, transannular transformations, and annulation reactions serve as powerful methods for polycyclic formation. In order to assemble diverse polycycles, donor-acceptor cyclopropanes are useful, versatile synthetic equivalents for C-C bond formations. By taking advantage of the strain within these unique, polarized systems, differing molecular architectures can be accessed directly to perform contemporary organic synthesis. Moreover, the donor-acceptor cyclopropanes initially utilized in these studies provided a fundamental basis for new methods to synthesize other relevant scaffolds. Unique, efficient, Lewis acid-catalyzed intramolecular cyclization strategies for the construction of functionalized polycycles using Friedel-Crafts-type alkylation sequences are presented to expand the reaction repertoire of the molecular architect. Generally, products were formed from commercially-available starting materials in high yields with broad scope. The methodologies were demonstrated to be modular, operationally simple, and amenable to different substitution patterns and functional groups to afford tetrahydroindolizines, heteroaromatic cyclohexenones, hydropyrido[1,2-a]indoles, pyrrolo[1,2-a]indoles, pyrrolo[3,2,1-ij]quinolines, pyrrolizines, and tetrahydrobenzo[ij]quinolizines. To demonstrate the utility of the methodologies devised, progress toward, (±)-rhazinicine, a natural product, is discussed.
This dissertation is organized into six chapters: (1) an introduction, paradoxical stress and molecular strain’s utility in synthesis; (2) annulation reactions for the formation of heteroaromatic cyclohexenones; (3) hydropyrido[1,2-a]indole formation via an In(III)-catalyzed cyclopropane ring-opening/Friedel-Crafts alkylation sequence; (4) tetrahydroindolizine formation and progress toward the total synthesis of (±)-rhazinicine (5) pyrrolo[1,2-a]indole synthesis using a Michael-type Friedel-Crafts cyclization approach; and (6) a versatile protocol for the intramolecular formation of functionalized pyrrolo[3,2,1-ij]quinolines.
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Martin-Benito, Dario, Kevin Anchukaitis, Michael Evans, Río Miren del, Hans Beeckman, and Isabel Cañellas. "Effects of Drought on Xylem Anatomy and Water-Use Efficiency of Two Co-Occurring Pine Species." MDPI AG, 2017. http://hdl.handle.net/10150/625999.
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Exploring how drought influences growth, performance, and survival in different species is crucial to understanding the impacts of climate change on forest ecosystems. Here, we investigate the responses of two co-occurring pines (Pinus nigra and Pinus sylvestris) to interannual drought in east-central Spain by dendrochronological and wood anatomical features integrated with isotopic ratios of carbon (delta C-13) and oxygen (delta O-18) in tree rings. Our results showed that drought induces both species to allocate less carbon to build tracheid cell-walls but increases tracheid lumen diameters, particularly in the transition wood between early and latewood, potentially maximizing hydraulic conductivity but reducing resistance to embolism at a critical phase during the growing season. The thicker cell-wall-to-lumen ratio in P. nigra could imply that its xylem may be more resistant to bending stress and drought-induced cavitation than P. sylvestris. In contrast, the higher intrinsic water-use efficiency (iWUE) in P. sylvestris suggests that it relies more on a water-saving strategy. Our results suggest that narrower cell-walls and reduced growth under drought are not necessarily linked to increased iWUE. At our site P. nigra showed a higher growth plasticity, grew faster and was more competitive than P. sylvestris. In the long term, these sustained differences in iWUE and anatomical characters could affect forest species performance and composition, particularly under increased drought stress.
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Nau, Andreas [Verfasser]. "A Contribution to Enlarge the Application Limits of Residual Stress Analyses by the Hole-Drilling and the Ring-Core Method / Andreas Nau." Kassel : Kassel University Press, 2016. http://d-nb.info/1084604221/34.
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Keen, Rachel M. "Using Tree-Ring Growth and Stable Isotopes to Explore Ponderosa Pine Ecophysiological Responses to Climate Variability and the 2012-2015 California Drought." DigitalCommons@USU, 2019. https://digitalcommons.usu.edu/etd/7511.
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Climate warming in recent decades has resulted in more frequent and severe drought events in the western United States. These changes are projected to continue, making it exceedingly important to understand how forests respond to severe drought stress, and how we can manage these forests to reduce mortality during future events. The 2012-2015 California drought is a recent example of a severe, multi-year drought that was coupled with an epidemic-scale outbreak of western pine beetle, killing nearly 90% of ponderosa pines in the central and southern Sierra Nevadas. In the first portion of this study, we compared pairs of surviving and dead ponderosa pines following this drought event to determine how the surviving trees were able to survive. We were also interested in how closely ponderosa pine tree-rings were recording ecosystem responses to this drought event. In the second portion of this study, we compared tree-ring growth rates and stable isotopes to data from an on-site flux tower to determine whether tree-rings were recording important information regarding ecosystem carbon and water fluxes during this severe drought event. Overall, we sought to better understand how the 2012- 2015 California drought event affected ponderosa pines to inform future management practices in forests of the western United States.
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Pierine, Damiana Tortolero [UNESP]. "Influência da suplementação sobre estresse oxidativo e processo inflamatório renal de animais com sobrecarga nutricional." Universidade Estadual Paulista (UNESP), 2014. http://hdl.handle.net/11449/123252.
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000816201.pdf: 414593 bytes, checksum: 55fcbfa486e7feb7d6425d16f8b32b2c (MD5)Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)
Os mecanismos que relacionam a obesidade aos danos renais são desconhecidos. O rim é um órgão alvo para lesões causadas por AGEs. O receptor de AGEs (RAGE) tem estímulo pró inflamatório e parece desempenhar um papel na patogênese da doença renal. O estudo objetivou verificar o efeito da obesidade sobre o dano renal e o efeito do licopeno sobre essas complicações. Ratos Wistar machos foram randomicamente divididos para receberem dieta controle (C, n =7) ou hiperlipídica mais sacarose (DH+S, n =14) por 6 semanas. Após este período, os animais DH+S foram randomizados em 2 grupos: DH+S (n=7) e DH+S suplementado com licopeno (DH+S+L, n=7). Os animais receberam óleo de milho (C e DH+S) ou licopeno (DH+S+L, 10 mg/kg peso/5 vezes por semana) por 6 semanas. Ao final do período urina de 24hs foi coletada, os animais eutanasiados e amostras de sangue e rim foram obtidas para as análises. Foram avaliados parâmetros bioquímicos, hemodinâmico, função renal, marcadores de estresse oxidativo e inflamação. O índice de adiposidade aumentou nos grupos DH+S e DH+S+L (C: 5,8±1,8 < DH+S: 9,4±1,6 = DH+S+L: 9,7±1,7 %; p<0,001). Os animais DH+S e DH+S+L apresentaram resistência insulínica (Glicemia OGTT após 150 min.; C: 117,6±3,9 < DH+S: 138,1±5,1 = DH+S+L: 137,8±5,2 mg/dL; p=0,01), porém, sem alterações em glicemia de jejum, lipidemia, PAS e função renal. As concentrações renais de RAGE e TNF-α aumentaram no grupo DH+S e a suplementação de licopeno restaurou estes níveis aumentados para valores semelhantes ao grupo controle (RAGE - C: 3,1±0,3 = DH+S+L: 3,1±0,3 < DH+S: 3,6±0,4 μg/g; p=0,014; TNF- α - C: 227,8±2,7 = DH+S+L: 227,4±2,2 < DH+S: 238,7±3,0 ρg/mL; p=0,014). O licopeno foi capaz de diminuir RAGE e TNF- α no rim. Assim, esse carotenóide pode ser benéfico para a prevenção e terapia do estresse oxidativo e inflamação nos rins decorrente da obesidade
The mechanisms linking obesity to kidney damage are unknown. The kidney is a target organ lesions caused by AGEs. The receptor of AGEs (RAGE) has proinflammatory stimuli and appears to play a role in the pathogenesis of renal disease. The study aimed to verify the effect of obesity on renal damage and the effect of lycopene on these complications. Male Wistar rats were randomly assigned to receive control diet (C, n = 7) or high fat plus sucrose (HD+S, n = 14) for 6 weeks. After this period, the HD+S animals were randomized into two groups: HD+S (n = 7) and HD+S supplemented with lycopene (HD+S+L, n = 7). The animals received corn oil (C and HD+S+L) and lycopene (HD+S+L, 10 mg/kg/5 times per week) for 6 weeks. At the end of the period 24h urine was collected, the animals euthanized and samples of blood and kidney were obtained for analysis. Biochemical, hemodynamic parameters, renal function, markers of oxidative stress and inflammation were assessed. The adiposity index increased in groups HD+S and HD+S+L (C: 5.8±1.8 < HD+S: 9.4±1.6 = HD+S+L: 9.7±1.7%, p <0.001). The HD+S and HD+S+L animals had insulin resistance (OGTT glucose levels after 150 min, C: 117.6±3.9 < HD+S: 138.1±5.1 = HD+S+L: 137.8±5.2 mg / dL, p = 0.01), but no changes in fasting glucose, lipids, SBP and renal function. Renal concentrations of RAGE and TNF-α increased in the HD+S group and lycopene supplementation restored these increased levels similar to the control group (RAGE values - C: 3.1±0.3 = HD+S+L: 3.1±0.3 < DH+S: 3.6±0.4 mg/g , p = 0.014; TNF-α - C: 227.8±2.7 = HD+S+L: 227.4±2 , 2 < HD+S: 238.7±3.0 ρg/mL, p = 0.014). Lycopene was able to decrease TNF-α RAGE and kidney. Thus, this carotenoid can be beneficial for the prevention and therapy of oxidative stress and inflammation in the kidneys resulting from obesity
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Silva, Luciana Carandina da [UNESP]. "Dopplerfluxometria renal em macao-prego (Sapajus apella) de cativeiro." Universidade Estadual Paulista (UNESP), 2013. http://hdl.handle.net/11449/105877.
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000743147.pdf: 1282780 bytes, checksum: 10f5cc91ce14bf5131e10583be6d5653 (MD5)O macaco prego se encontra amplamente distribuído no Brasil. Ainda são poucos os estudos realizados nesta espécie, não obtendo um padrão de normalidade para diversos parâmetros, entre eles a dopplerfluxometria renal. Realizou-se um estudo ultrassonográfico em modo B e Doppler dos rins de 10 macacos- prego, com o objetivo de padronizar os valores ultrassonográficos modo B e valores dopplervelocimétricos renais da espécie. Estes animais foram anestesiados com Ketamina e Miadzolam como medicação pré anestésica e Isoflurano para manutenção. Na análise Doppler, os valores obtidos do índice de resistividade, apresentaram diferenças estatísticas entre rim esquerdo e rim direito nas artérias arqueadas, renal e interlobares. A velocidade de pico sistólico também mostrou diferença estatística entre as artérias interlobares e artérias arqueadas. A velocidade diastólica final não apresentou diferença estatística entre rim esquerdo e direito. A diferença destes valores foi atribuída ao tempo de anestesia e ao estresse que os animais apresentavam logo após a captura. Desta forma, conclui-se que o exame ultrassonográfico Doppler é útil para monitorar alterações renais, porém quando submetidos à anestesia, o protocolo anestésico e o grau de estresse do animal pode influenciar diretamente no cálculo do índice de resistividade
The capuchin monkeys are widely distributed in Brazil. There are only few studies on this species, that do not allow a normal range on various parameters, including renal Doppler. This study evaluated ten capuchin monkeys on ultrasound B-mode and Doppler, in order to standardize ultrasound B-mode and Doppler renal values of this specie. The animals were anesthetized with Ketamine and Miadzolam as premedication and Isoflurane for maintenance. On Doppler analysis, resistivity index values presented statistical differences between the left and right kidney on renal, inrterlobar and arcuate arteries. VPS also showed statistical difference between the interlobar arteries and arcuate arteries. VDF showed no statistical difference between left and right kidney. The difference between these values was attributed to anesthesia time and capture related stress. Thus, it is concluded that Doppler ultrasonography is useful in monitoring renal diseases. However, when undergoing anesthesia, the anesthetic protocol and the level of stress can directly influence the calculation of the resistivity index
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Pierine, Damiana Tortolero. "Influência da suplementação com licopeno sobre estresse oxidativo e processo inflamatório renal de animais com sobrecarga nutricional /." Botucatu, 2014. http://hdl.handle.net/11449/123252.
Full textAbstract:
Orientador: Camila Renata CorrêaCoorientador: Renata de Azevedo Melo Luvizotto
Banca: Denise Rangel da Silva Sartori
Banca: Isaías Dichi
Banca: Vanessa dos Santos Silva
Banca: Ana Paula Bazanelli
Resumo: Os mecanismos que relacionam a obesidade aos danos renais são desconhecidos. O rim é um órgão alvo para lesões causadas por AGEs. O receptor de AGEs (RAGE) tem estímulo pró inflamatório e parece desempenhar um papel na patogênese da doença renal. O estudo objetivou verificar o efeito da obesidade sobre o dano renal e o efeito do licopeno sobre essas complicações. Ratos Wistar machos foram randomicamente divididos para receberem dieta controle (C, n =7) ou hiperlipídica mais sacarose (DH+S, n =14) por 6 semanas. Após este período, os animais DH+S foram randomizados em 2 grupos: DH+S (n=7) e DH+S suplementado com licopeno (DH+S+L, n=7). Os animais receberam óleo de milho (C e DH+S) ou licopeno (DH+S+L, 10 mg/kg peso/5 vezes por semana) por 6 semanas. Ao final do período urina de 24hs foi coletada, os animais eutanasiados e amostras de sangue e rim foram obtidas para as análises. Foram avaliados parâmetros bioquímicos, hemodinâmico, função renal, marcadores de estresse oxidativo e inflamação. O índice de adiposidade aumentou nos grupos DH+S e DH+S+L (C: 5,8±1,8 < DH+S: 9,4±1,6 = DH+S+L: 9,7±1,7 %; p<0,001). Os animais DH+S e DH+S+L apresentaram resistência insulínica (Glicemia OGTT após 150 min.; C: 117,6±3,9 < DH+S: 138,1±5,1 = DH+S+L: 137,8±5,2 mg/dL; p=0,01), porém, sem alterações em glicemia de jejum, lipidemia, PAS e função renal. As concentrações renais de RAGE e TNF-α aumentaram no grupo DH+S e a suplementação de licopeno restaurou estes níveis aumentados para valores semelhantes ao grupo controle (RAGE - C: 3,1±0,3 = DH+S+L: 3,1±0,3 < DH+S: 3,6±0,4 μg/g; p=0,014; TNF- α - C: 227,8±2,7 = DH+S+L: 227,4±2,2 < DH+S: 238,7±3,0 ρg/mL; p=0,014). O licopeno foi capaz de diminuir RAGE e TNF- α no rim. Assim, esse carotenóide pode ser benéfico para a prevenção e terapia do estresse oxidativo e inflamação nos rins decorrente da obesidade
Abstract: The mechanisms linking obesity to kidney damage are unknown. The kidney is a target organ lesions caused by AGEs. The receptor of AGEs (RAGE) has proinflammatory stimuli and appears to play a role in the pathogenesis of renal disease. The study aimed to verify the effect of obesity on renal damage and the effect of lycopene on these complications. Male Wistar rats were randomly assigned to receive control diet (C, n = 7) or high fat plus sucrose (HD+S, n = 14) for 6 weeks. After this period, the HD+S animals were randomized into two groups: HD+S (n = 7) and HD+S supplemented with lycopene (HD+S+L, n = 7). The animals received corn oil (C and HD+S+L) and lycopene (HD+S+L, 10 mg/kg/5 times per week) for 6 weeks. At the end of the period 24h urine was collected, the animals euthanized and samples of blood and kidney were obtained for analysis. Biochemical, hemodynamic parameters, renal function, markers of oxidative stress and inflammation were assessed. The adiposity index increased in groups HD+S and HD+S+L (C: 5.8±1.8 < HD+S: 9.4±1.6 = HD+S+L: 9.7±1.7%, p <0.001). The HD+S and HD+S+L animals had insulin resistance (OGTT glucose levels after 150 min, C: 117.6±3.9 < HD+S: 138.1±5.1 = HD+S+L: 137.8±5.2 mg / dL, p = 0.01), but no changes in fasting glucose, lipids, SBP and renal function. Renal concentrations of RAGE and TNF-α increased in the HD+S group and lycopene supplementation restored these increased levels similar to the control group (RAGE values - C: 3.1±0.3 = HD+S+L: 3.1±0.3 < DH+S: 3.6±0.4 mg/g, p = 0.014; TNF-α - C: 227.8±2.7 = HD+S+L: 227.4±2, 2 < HD+S: 238.7±3.0 ρg/mL, p = 0.014). Lycopene was able to decrease TNF-α RAGE and kidney. Thus, this carotenoid can be beneficial for the prevention and therapy of oxidative stress and inflammation in the kidneys resulting from obesity
Doutor
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Silva, Luciana Carandina da. "Dopplerfluxometria renal em macao-prego (Sapajus apella) de cativeiro /." Botucatu, 2013. http://hdl.handle.net/11449/105877.
Full textAbstract:
Orientador: Vânis Maria de Vasconcelos MachadoBanca: Roberto Carlos Teixeira
Banca: Milton Kolber
Resumo: O macaco prego se encontra amplamente distribuído no Brasil. Ainda são poucos os estudos realizados nesta espécie, não obtendo um padrão de normalidade para diversos parâmetros, entre eles a dopplerfluxometria renal. Realizou-se um estudo ultrassonográfico em modo B e Doppler dos rins de 10 macacos- prego, com o objetivo de padronizar os valores ultrassonográficos modo B e valores dopplervelocimétricos renais da espécie. Estes animais foram anestesiados com Ketamina e Miadzolam como medicação pré anestésica e Isoflurano para manutenção. Na análise Doppler, os valores obtidos do índice de resistividade, apresentaram diferenças estatísticas entre rim esquerdo e rim direito nas artérias arqueadas, renal e interlobares. A velocidade de pico sistólico também mostrou diferença estatística entre as artérias interlobares e artérias arqueadas. A velocidade diastólica final não apresentou diferença estatística entre rim esquerdo e direito. A diferença destes valores foi atribuída ao tempo de anestesia e ao estresse que os animais apresentavam logo após a captura. Desta forma, conclui-se que o exame ultrassonográfico Doppler é útil para monitorar alterações renais, porém quando submetidos à anestesia, o protocolo anestésico e o grau de estresse do animal pode influenciar diretamente no cálculo do índice de resistividade
Abstract: The capuchin monkeys are widely distributed in Brazil. There are only few studies on this species, that do not allow a normal range on various parameters, including renal Doppler. This study evaluated ten capuchin monkeys on ultrasound B-mode and Doppler, in order to standardize ultrasound B-mode and Doppler renal values of this specie. The animals were anesthetized with Ketamine and Miadzolam as premedication and Isoflurane for maintenance. On Doppler analysis, resistivity index values presented statistical differences between the left and right kidney on renal, inrterlobar and arcuate arteries. VPS also showed statistical difference between the interlobar arteries and arcuate arteries. VDF showed no statistical difference between left and right kidney. The difference between these values was attributed to anesthesia time and capture related stress. Thus, it is concluded that Doppler ultrasonography is useful in monitoring renal diseases. However, when undergoing anesthesia, the anesthetic protocol and the level of stress can directly influence the calculation of the resistivity index
Doutor
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Bossowski, Józef Piotr. "Induction d’une réponse immunitaire anti-tumorale par un régime pauvre en protéines." Thesis, Université Côte d'Azur (ComUE), 2018. http://www.theses.fr/2018AZUR4105/document.
Full textAbstract:
Plusieurs arguments de la littérature suggèrent l’importance de l’alimentation dans le développement tumoral et l’efficacité des traitements anti-cancereux. Dans différents modèles animaux, la restriction calorique (CR) supprime la prolifération des cellules tumorales et les sensibilise aux thérapies ciblées. Par conséquent, des approches non-pharmacologiques comme la restriction calorique ont un intérêt grandissant en clinique. Considérant l’addiction des cellules tumorales aux nutriments, nous nous sommes demandé quels macronutriments pouvaient avoir des propriétés anticancéreuses. A partir d’un modèle murin de lymphomes B (modèle transgénique Eµ-Myc) nous avons testé l’impact de deux régimes alimentaires : l’un pauvre en glucides (Low CHO, 25% de réduction en glucides) et l’autre pauvre en protéines (Low PROT, 25% de réduction en protéines). Des souris syngéniques C57BL/6 ont été injectées par voie intraveineuse avec des cellules primaires Eμ-Myc. Malgré un apport alimentaire équivalent entre les groupes, nous avons observé que le régime pauvre en protéines augmente la survie globale des souris C57BL/6 développant un lymphome B Eµ-Myc. De manière intéressante, nous avons démontré que cet effet pro-survie est dépendant du système immunitaire. En effet, la déplétion des cellules T CD8+ ou l’utilisation d’un modèle murin immunodéficient NSG (NOD-SCID il2rγ), empêche l’effet bénéfique du régime pauvre en protéines sur le développement tumoral. Nous avons reproduit et étendu nos observations en utilisant des lignées modèles de cancéreuses colorectaux (CT26) et de mélanome (B16) injectée dans des souris syngéniques, immunocompétente. Les cellules tumorales étant fortement dépendantes des nutriments, nous avons émis l’hypothèse qu’un régime pauvre en protéines pourrait induire un stress du réticulum endoplasmique (RE) dans ces dernières. En effet, nous avons observé une augmentation des protéines impliquées dans la signalisation du RE : CHOP et sXBP1. Par conséquent, nous avons traité les souris nourries en régime pauvre en protéines avec deux inhibiteurs du stress du RE : TUDCA, inhibiteur générique et MKC4485 qui cible l’activité ribonucléase d’IRE1. Dans les deux cas, ces inhibiteurs ont bloqué l’effet du régime faible en protéines sur le développement tumoral et l’infiltration des T CD8+ au sein de la tumeur. Pour s’affranchir, des potentiels effets secondaires des inhibiteurs chimiques, nous avons invalidé IRE1 dans la lignée CT26 et nous avons obtenus des résultats similaires, démontrant que la voie IRE1 dans les cellules tumorales est une voie centrale dans la réponse immunitaire anticancéreuse induite par un régime pauvre en protéines. En outre, nous avons découvert que l’activation de RIG-I est un événement en aval de l’activation d’IRE1 et que, par analyse bio-informatique nous avons pu corréler une signature IRE1 à une infiltration immunitaire élevée et à une immunogénicité accrue du cancer chez les patients atteints de mélanome, glioblastome et cancer colorectal. De ce fait, nous avons démontré que la réponse du système immunitaire induite par un régime pauvre en protéines est une conséquence de l’activation accrue de IRE1 dans les cellules cancéreusesSeveral arguments from the literature suggested the importance of diets in cancer development and in the efficacy of anti-cancer therapies. Calorie restriction (CR) suppresses cancer growth in various animal models and sensitizes tumor cells to targeted therapies (Meynet & Ricci, 2014). Thus, non-pharmacologic approaches such as CR have a growing interest in the clinic. Considering the nutrient addiction of cancer cells, we wondered which specific macronutrients contribute the most to anti-cancer effects. Therefore, we tested the reduction in specific macronutrient without decrease in general calorie intake on tumor development. We used two diets: reduced in carbohydrates (Low CHO, -25% carbohydrates) and diet reduced in protein (Low PROT, -25% proteins) on the Eµ-Myc transgenic mouse model of B-cell lymphoma. Syngeneic C57BL/6 mice were intravenously injected with primary Eμ-Myc cells. We observed that low PROT-diet, in spite of equal calorie intake among the groups, resulted in increase of the overall survival of Eµ-Myc-bearing C57BL/6 mice. Very importantly, we established that this pro-survival effect is immune system-dependent as both depletion of CD8+ T cells and use of immunodeficient NSG (NOD-SCID il2rγ) mouse model prevented the beneficial effect of the low PROT-diet on the tumor development. We reproduced and further extended our observations using subcutaneous injection of CT26 colorectal cancer cells in syngeneic immunocompetent BALB/c mice and B16 melanoma in C57BL/6 mice. As tumor cells are highly dependent on nutrients, we speculated that low PROT diet could induce ER stress in tumor cells. Indeed, we observed increase in proteins implicated in ER stress signaling – CHOP and sXBP1. Therefore, we treated low PROT-diet fed mice with two ER stress inhibitors, the general inhibitor TUDCA or MKC4485, which targets IRE1 RNAse activity. In both cases, inhibitors significantly prevented the effect of the Low PROT-diet on tumor development and on intratumoral number of CD8+ T cells. To eliminate any side effects of chemical inhibitors, we invalidated IRE1 in CT26 cells and obtained similar results, demonstrating that IRE1 signaling in tumor cells is a central event in the low PROT-diet induced anti-cancer immune response. In addition, we have uncovered RIG-I activation as a downstream event of IRE1 activation and by bioinformatic analysis correlated high-IRE1 signature with high immune infiltration and enhanced immunogenicity of cancer in patients bearing melanoma, glioblastoma and colorectal cancer. Hence, we have shown that the immune system response elicited under a Low PROT diet is a consequence of increased IRE1 activation in cancer cells
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Zahn, Nadine. "Stoffwechseluntersuchung bei klinisch gesunden Kühen unter besonderer Berücksichtigung der Superoxid-Dismutase." Doctoral thesis, Universitätsbibliothek Leipzig, 2006. http://nbn-resolving.de/urn:nbn:de:swb:15-20070117-145638-6.
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Seit Anfang der Siebzigerjahre werden weltweit in Rinderbetrieben in vielfältigen Variationen und Anwendungen Stoffwechseluntersuchungen durchgeführt. Das Hauptaugenmerk lag dabei stets auf Seiten der Energie- und Mineralstoffversorgung. Die Superoxid-Dismutase (SOD) fand hier bislang keine Berücksichtigung. Ziel der vorliegenden Untersuchung war es, die SOD-Aktivität in Stoffwechsel-untersuchungen bei klinisch gesunden Kühen mit ein zu beziehen sowie den Einfluss von Laktation und Jahreszeit zu prüfen. Versuchsanordnung: Insgesamt wurden bei 125 SB/HF-Kühen (7990 kg fettkorregierte Milch/Jahr) folgende drei Gruppen analysiert: Gruppe 1: Im Verlauf eines Jahres wurden im Abstand von 6 Wochen jeweils 10 gesunde Kühe, die sich alle 1-2 Wochen post partum (pp) befanden, untersucht. Zusätzlich wurden die Stall- und die Außentemperaturen berücksichtigt. Gruppe 2: Zur Kontrolle des Laktationsverlaufes wurden 10 Kühe zum Zeitpunkt 4-5 Wochen ante partum (ap), 1 Woche ap, 1-2 Wochen pp, 4 Wochen pp und 8-12 Wochen pp untersucht. Gruppe 3: Um jahreszeitlich bedingte Schwankungen des Stoffwechsels und der SOD-Aktivität in Gruppe 2 auszuschließen, wurden an einem Entnahmetag jeweils sieben verschiedene Kühe zum Zeitpunkt 4-5 Wochen ap, 1 Woche ap, 1-2 Wochen pp, 4 Wochen pp, und 8-12 Wochen pp geprüft. Die Tiere aller drei Gruppen wurden nach der klinischen Untersuchung hämatologisch sowie klinisch-chemisch (SOD, β-Hydroxybutyrat (BHB), Glucose, Cholesterol, Bilirubin, Glutamat-Dehydrogenase (GLDH), Aspartat-aminotransferase (ASAT), Creatinkinase (CK), Protein, Albumin, Harnstoff, Calcium, anorganisches Phosphat, Magnesium, Natrium, Kalium, Chlorid, Eisen) getestet. Auch die Fütterung fand durch Anfertigung einer Rationsberechnung Berücksichtigung. Ergebnisse: Die Ergebnisse der Stoffwechseluntersuchungen und der SOD-Aktivität im Jahresverlauf (Gruppe 1) deuten auf eine verminderte Futteraufnahme in den Sommermonaten infolge Hitzestresses hin. Vor allem ein Absinken der Harnstoff-, Glucose- (positive Korrelation zur SOD-Aktivität), Phosphat- (positive Korrelation zur SOD-Aktivität) und Cholesterolkonzentrationen bei gleichzeitig ansteigenden BHB- (negative Korrelation zur SOD-Aktivität) und Bilirubinkonzentrationen weisen auf eine negative Energiebilanz in diesen Monaten hin. Die Calcium- und Magnesiumkonzentrationen liegen bei allen Tieren im unteren Referenzbereich. Die SOD-Aktivität klinisch gesunder Kühe im Jahresverlauf beträgt 501 bis 978 U/ml Erythrozytenlysat (Interzentilbereich). In Gruppen 2 und Gruppe 3 sind ebenfalls deutliche Schwankungen der Stoffwechselparameter Protein, Harnstoff, Bilirubin, Glucose, BHB und Cholesterol zu beobachten, wobei die stärksten Schwankungen im Zeitraum 1 Woche ap bis 4 Wochen pp vorhanden sind. Auch dies ist durch die reduzierte Futteraufnahme peripartal sowie steigende Futteraufnahme in der Frühlaktation zu erklären. Die SOD-Aktivität der Kühe aus Gruppe 2 zeigt die entsprechenden Schwankungen mit niedrigen Aktivitäten 4-5 Wochen ap bis 1-2 Wochen pp und einen deutlichen Anstieg bis 4 Wochen pp. Die Calcium- und Magnesiumkonzentrationen befinden sich auch in dieser Gruppe im unteren Referenzbereich. In der Gruppe 3 fällt bei den Kühen 4 Wochen pp eine deutliche Stoffwechselbelastung mit erhöhten Bilirubin- und BHB-Konzentrationen sowie ASAT- und GLDH-Aktivitäten auf. In dieser Gruppe sind die Calcium- und Magnesiumkonzentrationen physiologisch. Die SOD-Aktivitäten differieren nur gering mit einer tendenziell höheren Aktivität 4 Wochen pp. Insgesamt fallen im Vergleich zu Gruppe 1 und 2 deutlich höhere SOD-Aktivitäten zwischen 835 und 1758 U/ml Erythrozytenlysat (Interzentilbereich) auf, welche mit den höheren Calcium- und Magnesiumkonzentrationen in Beziehung stehen können. Schlussfolgerungen: Schwankungen von Stoffwechselparametern im Jahres- und Laktationsverlauf betreffen vor allem fütterungsabhängige Parameter. Die SOD-Aktivität verhält sich entsprechend dieser fütterungsabhängigen Parameter mit niedrigerer Aktivität bei längeren Belastungsphasen sowie im geburtsnahen Zeitraum. Statistisch gesicherte Korrelationen ergaben sich mit folgenden fütterungs-abhängigen Parametern: im Jahresverlauf mit BHB, Glucose und anorganischem Phosphat, im Laktationsverlauf in Gruppe 2 mit BHB, Cholesterol, Protein, Glucose, Magnesium und Milchharnstoff und in Gruppe 3 zu BHB und Magnesium. Die Analyse der SOD-Aktivität bereichert die Informationen bei Stoffwechselkontrollen sinnvoll.
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Yoo, Ji Seung. "INVESTIGATIONS INTO THE ROLES OF PKR-INDUCED ANTIVIRAL STRESS GRANULE AND DHX36 IN RIG-I SIGNALING." 京都大学 (Kyoto University), 2014. http://hdl.handle.net/2433/189378.
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Gaffney, Charles. "Topographic microclimate influence on radial growth responses of sugar maple (acer saccharum marsh.) and white oak (quercus alba L.) to regional climate stresses." Virtual Press, 1995. http://liblink.bsu.edu/uhtbin/catkey/941379.
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Tree-rings were analyzed to assess the relative importance of slope position and aspect as determinants of the climate-sensitivity of sugar maple and white oak radial growth. Tree size, crown condition, forest and soil composition, and site indices were assessed to document environmental differences between site-types and to verify similarity of stands within the same site-type. Climate-sensitivity was assessed using mean between-tree correlation, principal components analysis, mean sensitivity, regression analysis, and analysis of radial growth decline after severe drought. Ecological differences were found between high and low sites on north and south facing aspects. Sugar maple did not exhibit greater climate-sensitivity than white oak. Both species showed greater climate-sensitivity on upper and south-facing slopes.Department of Biology
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Aydın, Levent Altundağ Artem H. Seçil. "Investigation of stress intensity factors in an elastic cylinder under axial tension with a crack of ring-shape/Levent Aydın; thesis advisor H. Seçil Altundağ Artem." [s.l.]: [s.n.], 2005. http://library.iyte.edu.tr/tezlerengelli/master/makinamuh/T000361.pdf.
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Assis, Renata Pires de [UNESP]. "Efeito dos solutos urêmicos sobre espécies reativas de oxigênio em sistemas-modelo in vitro." Universidade Estadual Paulista (UNESP), 2012. http://hdl.handle.net/11449/87972.
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Universidade Estadual Paulista (UNESP)
Em pacientes com doença renal crônica é observado à presença de estresse oxidativo e a exacerbação desse estresse com o tratamento hemodialítico, bem como tem se postulado a ação antioxidante de alguns solutos urêmicos. Esse contexto instigou-nos explorar, a ação antioxidante dos solutos urêmicos: L-arginina, Ácido Úrico, Ácido Hipúrico, Creatinina, Fenol, Metilguanidina, p-Cresol, L-tirosina e Uréia, utilizando sistemas-modelo in vitro. Quatro desses solutos mostraram eficiência (expressa via o IC50 em µmol/L) para os sistemas-modelo: Capacidade de captura sobre o ABTS + , p-Cresol (3,99 ± 0,01), L-tirosina (5,23 ± 0,02), Fenol (12,98 ± 0,09) e o Ácido Úrico (16,75 ± 0,14); Capacidade de captura sobre o HOCl / OCl -, L-tirosina (2,83 ± 0,04), Ácido Úrico (5,75 ± 0,13), Fenol (8,95 ± 0,10) e p- Cresol (15,75 ± 0,12), e o bleaching da crocina (lipoperoxidação), Ácido Úrico (6,90), Fenol (1125,81) e p-Cresol (1162,31). Em relação à capacidade de captura sobre o Ânion Radical Superóxido e o Peróxido de Hidrogênio nenhum dos solutos apresentou atividade significativa. Em todos os ensaios onde não foi observada atividade antioxidante, investigou-se desde concentrações fisiológicas, urêmicas e até 10 vezes maior que as concentrações urêmicas médias. Como os solutos urêmicos, Ácido Úrico, p-Cresol, Fenol e L-tirosina capturaram significativamente as espécies reativas, ABTS + , HOCl / OCl - e ROO , estudou-se o comportamento da mistura desses solutos, tendo como referência o IC50 de cada soluto. Obteve-se nos ensaios de captura do ABTS + e do HOCl / OCl - os IC50, como uma fração de concentração de 26 e 27%, respectivamente, para cada soluto na mistura, o que demonstrou um efeito aditivo...
Patients with chronic kidney disease suffer from oxidative stress and this stress is exacerbated by hemodialysis. It has been postulated that some uremic solutes have antioxidant effects. This context prompted us to explore the antioxidant action of the uremic solutes: L-arginine, uric acid, hippuric acid, creatinine, phenol, methylguanidine, p-cresol, L-tyrosine and urea, by means of 5 in vitro model systems. Only four of these solutes were effective antioxidants (assessed by their IC50 in µmol/L) in 3 model systems: ABTS + scavenging: p-cresol (3.99±0.01), L-tyrosine (5.23±0.02), phenol (12.98±0.09) and uric acid (16.75±0.14); hypochlorous acid scavenging: L-tyrosine (2.83±0.04), uric acid (5.75±0.13), phenol (8.95±0.10) and p-cresol (15.75±0.12); and crocin bleaching (lipoperoxidation): uric acid (6.90), phenol (1,125.81) and p-cresol (1,162.31). In tests with the superoxide radical anion and hydrogen peroxide, none of the solutes showed antioxidant activity. In each of the assays in which no activity was detected, tests were carried out over a range of solute concentrations, from normal physiological levels, through typical uremic up to ten times higher than mean uremic concentrations. As the 4 uremic solutes, uric acid, p-cresol, phenol and L-tyrosine showed significant scavenging activity for 3 reactive species, ABTS + , HOCl / OCl - and ROO , the behavior of mixture of these solutes was investigated, with reference to the IC50 of each solute. In the ABTS + and HOCl / OCl - scavenging assays, the IC50 involved a concentration of 26% and 27%, respectively, of each solute in the mixture, demonstrating... (Complete abstract click electronic access below)
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Silva, Ana Carolina Almeida da. "Estresse oxidativo em rins de ratas reprodutoras e não reprodutoras ao longo do envelhecimento." reponame:Biblioteca Digital de Teses e Dissertações da UFRGS, 2013. http://hdl.handle.net/10183/78149.
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A reprodução é um processo dispendioso da vida, e o investimento reprodutivo parece ser maior para fêmeas do que para os machos em muitas espécies. Neste trabalho analisamos os efeitos do investimento reprodutivo durante o envelhecimento com relação aos parâmetros de estresse oxidativo em rins de ratas Wistar. Medimos a atividade da glutationa peroxidase, glutationa S-transferase, superóxido dismutase e aconitase. O consumo de peróxido de hidrogénio, a carbonilação de proteínas, peroxidação lipídica, nitrito e nitrato, os níveis de vitamina C e E e de hormônios sexuais foram também mensurados. Traçamos o perfil oxidativo nas idades de 3, 6, 12 e 24 meses. Os animais foram agrupados de acordo com a experiência reprodutiva: em reprodutores e não reprodutores. Os animais não reprodutores exibiram um aumento nos parâmetros estudados aos 6 e 24 meses, enquanto que os animais reprodutores exibiram um perfil semelhante aos 3 e 12 meses. Aos seis meses de idade, durante o período que representa o pico reprodutivo, os animais não reprodutores apresentaram maiores níveis de MDA, vitamina C, consumo de peróxido de hidrogênio e atividades de GPx, aconitase e SOD. Em ratos idosos não reprodutores, observou-se um aumento nos marcadores de dano oxidativo e um aumento nas defesas antioxidantes enzimáticas e não enzimáticas, com a exceção do consumo de peróxido de hidrogênio e vitamina C. Em longo prazo, pode-se inferir que o investimento reprodutivo não foi suficiente para interferir com a capacidade antioxidante, e não contribuiu para o dano oxidativo em rins de ratas Wistar.Reproduction is a costly life process, and the reproductive investment by females appears to be greater than males in many species. We have analyzed the effects of reproductive investment during aging with respect to oxidative stress parameters in kidneys of female Wistar rats. We measured the activity glutathione peroxidase, glutathione S-transferase, superoxide dismutase, consumption of hydrogen peroxide, protein carbonylation, lipid peroxidation, nitrite and nitrate levels, and vitamin C and E levels. We traced oxidative profiles at ages 3, 6, 12, and 24 months. Animals were grouped according to reproductive experience: experienced or naïve with respect to reproductive activity. We measured aconitase activity and sex hormone levels. The naïve animals exhibited an increase in the parameters studied at 6 and 24 months, whereas experienced animals exhibited a similar increase at 3 and 12 months. At six months of age, during the period that would represent peak reproductive activity, naïve animals showed higher levels of MDA, Vitamin C, consumption of hydrogen peroxide and GPx, aconitase, and SOD activities. In naïve elderly rats, we observed an increase in oxidative damage markers and an increase in enzymatic and non-enzymatic antioxidants, with the exception of consumption of hydrogen peroxide and vitamin C. In the long term, the reproductive investment was not sufficient to interfere with antioxidant capacity, and did not contribute to oxidative damage in kidneys of female Wistar rats.
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Oh, Seong-Wook. "Functional Analysis of RIG-I and RNP Complexes in the Antiviral Interferon System." 京都大学 (Kyoto University), 2016. http://hdl.handle.net/2433/215973.
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Fukuoka, Hiroshi. "Variation of the Friction Angle of Granular Materials in the High-Speed High-Stress Ring Shear Apparatus-Influence of Re-orientation,Alignment and Crushing of Grains during Shear-." 京都大学 (Kyoto University), 1992. http://hdl.handle.net/2433/86440.
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Werneck, Marilia Lacerda. "Estresse nitro-oxidativo induzido por soro urêmico in vivo e in vitro / Marilia Lacerda Werneck ; orientadora, Lia Sumie Nakao ; co-orientador, Roberto Pecoits-Filho." reponame:Biblioteca Digital de Teses e Dissertações da PUC_PR, 2007. http://www.biblioteca.pucpr.br/tede/tde_busca/arquivo.php?codArquivo=1132.
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Dissertação (mestrado) - Pontifícia Universidade Católica do Paraná, Curitiba, 2007Bibliografia: f. 55-59
Pacientes de doença renal crônica (DRC) apresentam maiores riscos de desenvolver doença cardiovascular (DCV) que pacientes com função renal normal. Dentre vários fatores quem contribuem para patologia vascular, inflamação, calcificação e estresse oxidativ
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Jonsson, Åsa, and Grim Skarsgård. "Synchrotron tomography of pressboard during in-situ compression loading : Construction of compression rig, image acquisition procedure and methods for image processing." Thesis, Uppsala universitet, Tillämpad mekanik, 2015. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-257276.
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Pressboard, a high density cellulose-based material used for insulation in high voltage power transformers, exhibits stress relaxation during compressive loading. Investigating the micro-mechanical mechanisms responsible for the relaxation can lead to modifications of the production process to control the behaviour of the material. This investigation can be done using Synchrotron X-ray micro Computed Tomography which provides sufficient temporal and spatial resolutions to capture the stress relaxation process. In the present thesis, a compression rig for in-situ mechanical loading during X-ray micro Computed Tomography was designed and constructed. Local tomography scans with sub-micrometre resolution were obtained at the TOMCAT beamline at the Swiss Light Source, Paul Scherrer Institut, Switzerland. Several fibre segmentation techniques are analysed, together with Optical Flow and Digital Volume Correlation (DVC), methods used for estimating displacement, strain and velocity vector fields. Suitability of the tested methods is evaluated, and it is found that segmentation of individual fibres in a cellulose material of such a high density is probably not possible using currently available segmentation techniques. The movements during relaxation are measurable at the used resolution, and can be estimated using Optical Flow. Further work into correction of image shift due to rig movement between scans, as well as image artefact reduction should allow for measurement and comparisons of displacement during relaxation as well as DVC-computed strain measurements during compression, recreating earlier results.
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Dongare, Vishal S. "Hot Extrusion of Carbon Nanotube - Magnesium Matrix Composite Wire." Ohio University / OhioLINK, 2014. http://rave.ohiolink.edu/etdc/view?acc_num=ohiou1415975904.
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Assis, Renata Pires de. "Efeito dos solutos urêmicos sobre espécies reativas de oxigênio em sistemas-modelo in vitro /." Araraquara : [s.n.], 2012. http://hdl.handle.net/11449/87972.
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Orientador: Iguatemy Lourenço BrunettiBanca: Mariza Pires de Melo
Banca: Eduardo Maffud Cilli
Resumo: Em pacientes com doença renal crônica é observado à presença de estresse oxidativo e a exacerbação desse estresse com o tratamento hemodialítico, bem como tem se postulado a ação antioxidante de alguns solutos urêmicos. Esse contexto instigou-nos explorar, a ação antioxidante dos solutos urêmicos: L-arginina, Ácido Úrico, Ácido Hipúrico, Creatinina, Fenol, Metilguanidina, p-Cresol, L-tirosina e Uréia, utilizando sistemas-modelo in vitro. Quatro desses solutos mostraram eficiência (expressa via o IC50 em µmol/L) para os sistemas-modelo: Capacidade de captura sobre o ABTS + , p-Cresol (3,99 ± 0,01), L-tirosina (5,23 ± 0,02), Fenol (12,98 ± 0,09) e o Ácido Úrico (16,75 ± 0,14); Capacidade de captura sobre o HOCl / OCl -, L-tirosina (2,83 ± 0,04), Ácido Úrico (5,75 ± 0,13), Fenol (8,95 ± 0,10) e p- Cresol (15,75 ± 0,12), e o bleaching da crocina (lipoperoxidação), Ácido Úrico (6,90), Fenol (1125,81) e p-Cresol (1162,31). Em relação à capacidade de captura sobre o Ânion Radical Superóxido e o Peróxido de Hidrogênio nenhum dos solutos apresentou atividade significativa. Em todos os ensaios onde não foi observada atividade antioxidante, investigou-se desde concentrações fisiológicas, urêmicas e até 10 vezes maior que as concentrações urêmicas médias. Como os solutos urêmicos, Ácido Úrico, p-Cresol, Fenol e L-tirosina capturaram significativamente as espécies reativas, ABTS + , HOCl / OCl - e ROO , estudou-se o comportamento da mistura desses solutos, tendo como referência o IC50 de cada soluto. Obteve-se nos ensaios de captura do ABTS + e do HOCl / OCl - os IC50, como uma fração de concentração de 26 e 27%, respectivamente, para cada soluto na mistura, o que demonstrou um efeito aditivo... (Resumo completo, clicar acesso eletrônico abaixo)
Abstract: Patients with chronic kidney disease suffer from oxidative stress and this stress is exacerbated by hemodialysis. It has been postulated that some uremic solutes have antioxidant effects. This context prompted us to explore the antioxidant action of the uremic solutes: L-arginine, uric acid, hippuric acid, creatinine, phenol, methylguanidine, p-cresol, L-tyrosine and urea, by means of 5 in vitro model systems. Only four of these solutes were effective antioxidants (assessed by their IC50 in µmol/L) in 3 model systems: ABTS + scavenging: p-cresol (3.99±0.01), L-tyrosine (5.23±0.02), phenol (12.98±0.09) and uric acid (16.75±0.14); hypochlorous acid scavenging: L-tyrosine (2.83±0.04), uric acid (5.75±0.13), phenol (8.95±0.10) and p-cresol (15.75±0.12); and crocin bleaching (lipoperoxidation): uric acid (6.90), phenol (1,125.81) and p-cresol (1,162.31). In tests with the superoxide radical anion and hydrogen peroxide, none of the solutes showed antioxidant activity. In each of the assays in which no activity was detected, tests were carried out over a range of solute concentrations, from normal physiological levels, through typical uremic up to ten times higher than mean uremic concentrations. As the 4 uremic solutes, uric acid, p-cresol, phenol and L-tyrosine showed significant scavenging activity for 3 reactive species, ABTS + , HOCl / OCl - and ROO , the behavior of mixture of these solutes was investigated, with reference to the IC50 of each solute. In the ABTS + and HOCl / OCl - scavenging assays, the IC50 involved a concentration of 26% and 27%, respectively, of each solute in the mixture, demonstrating... (Complete abstract click electronic access below)
Mestre
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Braz, Fabiano. "Avaliação do impacto do pneumoperitônio e do estresse oxidativo renal de ratos pré-tratados com citrato de sildenafil." Botucatu, 2016. http://hdl.handle.net/11449/144645.
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Orientador: Juliany Gomes QuitzanResumo: A laparoscopia tem sido cada vez mais empregada na rotina médica e veterinária com o intuito de promover intervenções cirúrgicas e diagnósticas menos invasivas. Apesar de seus benefícios, há evidências de que a insuflação abdominal pode levar à isquemia dos órgãos, seguida pela injúria de reperfusão. Algumas medicações tem sido utilizadas na tentativa de prevenir ou minimizar os danos que podem ser causados pela injúria isquemia/reperfusão. O presente estudo teve por objetivo avaliar se o uso do sildenafil via oral, antes da realização do pneumoperitôneo, seria capaz de atenuar estes efeitos da isquemia/reperfusão. Foram utilizados 26 ratos Wistar machos, divididos em 3 grupos: controle (6), Sham (10) e S/P (10). O grupo S/P foi suplementado com 1mg/kg de citrato de sildenafil via oral. Os animais dos grupos Sham e S/P foram submetidos ao pneumoperitônio por 60 minutos, com pressão intra-abdominal de 12mmHg. A artéria carótida direita foi dissecada e canulada para que fossem colhidas amostras sanguíneas e avaliadas variáveis de oxigenação e ventilação (pressão parcial de oxigênio, pressão parcial de gás carbônico e saturação de oxigênio). Durante o procedimento também foram avaliadas variáveis hemodinâmicas (frequência cardíaca, frequência respiratória e pressão arterial média). Após 24 horas os animais foram submetidos à eutanásia e foram colhidos os rins para dosagem do estresse oxidativo, através da mensuração da atividade das enzimas antioxidantes superóxido dismutase, glutationaperoxidase e catalase, além do subproduto da peroxidação lipídica, o hidroperóxido. Os resultados observados em relação às variáveis hemodinâmicas e também de oxigenação e ventilação, não apresentaram diferença quando comparados os diferentes momentos dentro de um mesmo grupo, e na comparação entre os... (Resumo completo, clicar acesso eletrônico abaixo)
Abstract: Laparoscopy has been increasingly used in medical and veterinary routine in order to promote less invasive surgical and diagnostic interventions. Despite its benefits, there is evidence that abdominal insufflation can lead to ischemia of the organs, followed by reperfusion injury. Some medications have been used in attempts to prevent or minimize the damage that can be caused by injury ischemia/reperfusion. This study aimed to assess whether the use of oral sildenafil, prior to the pneumoperitoneum, was able to mitigate these effects of ischemia/reperfusion. We used 26 male Wistar rats, divided in 3 groups: control (6) Sham (10) and S/P (10). The S/P group was supplemented with 1 mg/kg of oral sildenafil citrate. The animals of the sham group and S/P were subjected to pneumoperitoneum for 60 minutes with intra-abdominal pressure of 12mmHg. The right carotid artery was dissected and cannulated in order to collect blood samples and evaluated oxygenation and ventilation variables (partial pressure of oxygen, partial pressure of carbon dioxide and oxygen saturation). During the procedure, hemodynamic variables were also evaluated (heart rate, respiratory rate and mean arterial pressure). After 24 hours the animals were euthanized and their kidneys were collected for dosage of oxidative stress by measuring the activity of antioxidant enzymes superoxide dismutase, catalase and glutationaperoxidase, besides the byproduct of lipid peroxidation, hydroperoxide. The results observed for the hemodynamic variables and also oxygenation and ventilation, showed no difference when comparing the diferente times whithin the same group, and compared between groups. The values found for the antioxidant enzyme activity were similar in the S/P and control group. It was observed that the activities of the enzymes glutathione peroxidase and catalase were markedly increased, while... (Complete abstract click electronic access below)
Mestre
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Shirahatti, Anilkumar. "A novel test rig to study the effects of elastic follow-up, long range residual stress and applied load on creep crack initiation." Thesis, University of Bristol, 2014. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.649366.
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One of the many challenges in the behaviour of structures is to understand if the presence of residual stress plays an important role in contributing to failure of a structure operating at high temperature. Structural integrity assessments of components operating at high temperature require an accurate prediction of the creep crack initiation. In general, assessments are based on experiments carried out using standard laboratory scale creep test specimens tested under either displacement or load controlled conditions. In practice, structures are subjected to combinations of residual and applied stresses which in turn lead to mixed boundary conditions. Conventional laboratory creep tests do not represent these circumstances. This dissertation considers the effects of elastic follow-up , long-range residual stress and applied load on creep crack initiation of Type 316H stainless steel. Novel test rigs are designed for the purpose of investigating. The concept of rig is based on a three bar structure with an initial misfit introduced into the central bar to represent a long range residual stress and could be characterised easily without using time consuming residual stress measurement techniques. Initial results demonstrated that the magnitude and the interaction of the residual stress with the applied loading is a function of the initial misfit displacements and the relative stiffness of the components of the system. Additionally, the subsequent behaviour of the system, with and without the application of additional loading, is governed by (a) the degree to which the misfit is accommodated by plastic and creep strain and (b) the elastic follow-up provided by the system.
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Rini, Dwi Setyo [Verfasser], Erwin [Akademischer Betreuer] Grill, and Ruiz Ramón Angel [Akademischer Betreuer] Torres. "Positional cloning and physiological analysis of novel Arabidopsis mutants involved in drought stress signalling / Dwi Setyo Rini. Gutachter: Ramón Angel Torres Ruiz ; Erwin Grill. Betreuer: Erwin Grill." München : Universitätsbibliothek der TU München, 2015. http://d-nb.info/1072224798/34.
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Westrin, Pontus, and Nils Melin. "Slope processes and strength of material in silt rich ravines in Säterdalen, Sweden." Thesis, Uppsala universitet, Institutionen för geovetenskaper, 2015. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-239978.
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Slope processes are important to understand if we are to protect fragile environments. Every year slope development in weak soils put nearby infrastructure in risk zones of sliding and ravine erosion takes away field areal from farmers as they grow even larger. Many methods for doing a risk analysis of a slope and its soil are complicated and require a lot of equipment. A simple way to do a slope investigation is explained in this report, along with its advantages and disadvantages. The authors construct a shear ring, an apparatus to measure peak shear stress of soils before fracturing. LIDAR scanning of two small ravines are also made to illustrate how laser scanning can be used to accurately measure denudation in slopes. The results vary, the shear ring is mostly a success aside from errors caused by difficulty in taking representative samples and disturbance. Some of the laboratory work made to determine material properties fail at giving good results, often a result of bad samples or disturbance in the tests. The LIDAR is determined to be a good instrument when working with slope development.Sluttningsprocesser är viktiga att förstå och studera om vi ska kunna skydda känsliga områden. Varje år så sätter svaga jordar i sluttningar närliggande infrastruktur i riskzonen för att ligga på ett glidplan som snabbt kan släppa om jorden blir för blöt eller om för mycket tyngd läggs ovanpå. Samtidigt så tar ravinerosion bort åkerareal från bönder varje år medan ravinerna blir större och större. Många metoder för att göra riskanalyser av sluttningar är komplicerade och kräver mycket utrustning. I denna rapport så testas ett enkelt sätt att göra en sluttningsanalys med tillhörande diskussion kring dess fördelar och nackdelar. Författarna konstruerar en shear ring, en apparat som används för att testa jordens möjlighet att motstå en applicerad kraft. Två sidoraviner scannas även med LIDAR som en bas för att studera denudation i sluttningar. Resultaten varierar, shear ring-apparaturen bestäms som väl fungerande med undantag från vissa utförda tester, där svårigheter uppstod då jordproverna var störda eller mindre representativa. Vissa av laborationerna på jorden misslyckas med att ge bra värden, vilket ofta är ett resultat av dåliga eller störda prover. Laserscanningar av raviner med LIDAR bestäms som ett bra sätt att studera utvecklingen i sluttningar samt att mäta erosion.
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Costa, Cristiane Aguiar da. "Efeito do extrato de Euterpe oleracea Mart.(Açaí) sobre a disfunção endotelial, estresse oxidativo e alterações vasculares e renais associados à hipertensão renovascular dois rins, 1 clip (2R,1C)." Universidade do Estado do Rio de Janeiro, 2012. http://www.bdtd.uerj.br/tde_busca/arquivo.php?codArquivo=9241.
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Fundação Carlos Chagas Filho de Amparo a Pesquisa do Estado do Rio de JaneiroEstudos recentes mostram que o açaí é rico em polifenóis e uma dieta rica em polifenóis pode estar envolvida na proteção contra o risco cardiovascular. O objetivo deste estudo foi avaliar o efeito do tratamento crônico de animais hipertensos 2R,1C com extrato hidroalcoólico do caroço do açaí (ASE) sobre o desenvolvimento da hipertensão e disfunção endotelial; estresse oxidativo e sobre as alterações vasculares e renais. Ratos Wistar machos foram utilizados para obtenção da hipertensão renovascular 2R,1C e ratos controles 2R (sham) foram somente submetidos à laparotomia e receberam tratamento diário com veículo ou ASE (200 mg/Kg/dia) durante 40 dias. A pressão arterial sistólica (PAS) foi aferida por pletismografia de cauda e os efeitos vasodilatadores da acetilcolina (ACh) e nitroglicerina (NG) foram estudados em leito arterial mesentérico (LAM) perfundido e pré-contraído com norepinefrina. A atividade das enzimas SOD, CAT, GPx, os níveis de MDA, a carbonilação de proteínas e os níveis de nitrito foram avaliados por espectrofotometria. As expressões de enzimas pró e antioxidantes foram avaliadas por western blot. A atividade de MMP-2 foi avaliada por zimografia. Os níveis séricos de creatinina foram avaliados através de kit, por espectrofotometria. As alterações vasculares e renais foram avaliadas por microscopia de luz. A PAS foi maior nos animais 2R,1C, e o tratamento com ASE preveniu o desenvolvimento da hipertensão. O efeito vasodilatador reduzido da ACh em animais 2R,1C foi recuperado pelo ASE. O efeito vasodilatador da NG não foi diferente entre os grupos. O dano oxidativo avaliado pela peroxidação lipídica e carbonilação de proteínas foi maior nos animais 2R,1C, e reduzido pelo tratamento com ASE. As atividades da SOD, CAT e GPx foram menores em amostras de mesentério, plasma, rim e coração de animais 2R,1C e o tratamento com ASE aumentou estas atividades. A produção de NO foi menor no plasma, mesentério e rim dos animais 2R,1C, e o tratamento com ASE aumentou a produção de NO somente no rim e mesentério destes animais. A expressão de SOD-1, 2, eNOS e TIMP-1 foram menores nos animais 2R,1C e o tratamento com ASE aumentou a expressão destas enzimas. A expressão de NOX-4 e MMP-2 e a atividade de MMP-2 foram maiores nos animais 2R,1C e o tratamento com ASE reduziu a expressão destas enzimas e a atividade de MMP-2. Os animais 2R,1C apresentaram um aumento na espessura da camada média da aorta e artéria mesentérica e um aumento na relação média/lúmen da aorta, e estas alterações foram prevenidas pelo ASE. Os níveis séricos aumentados de creatinina nos animais 2R,1C foram reduzidos por ASE. As alterações morfológicas renais nos animais 2R,1C foram prevenidas pelo ASE. Portanto, o tratamento com ASE previne o desenvolvimento da hipertensão, melhora a disfunção endotelial e previne as alterações vasculares e renais em ratos 2R,1C. A redução da atividade antioxidante e o aumento na peroxidação lipídica e carbonilação de proteínas sugerem o envolvimento de um mecanismo deficiente da defesa antioxidante e de um dano oxidativo aumentado, os quais foram revertidos pelo ASE.
Studies show that açai is rich in polyphenols and a diet rich in polyphenols may be involved in protection against cardiovascular risk. The aim this study was assessed the effect of chronic treatment of hypertensive animals 2K,1C with hydroalcoholic extract the stone of açaí (ASE) on the development of hypertension and endothelial dysfunction, oxisative stress and renal and vascular changes. Male Wistar rats used to obtain the renovascular hypertension 2K,1C and control rats 2K (sham) were only subjected to laparotomy, were treated daily with vehicle or ASE (200mg/Kg/dia) for 40 days, and had a systolic blood pressure (SBP) measured plethysmography by the tail. The vasodilatory effects of acetylcholine (ACh) and nitroglycerin (NG) were studied in mesenteric arterial bed (LAM) perfused and pre-contracted with norepinephrine. The activity of enzymes SOD, CAT, GPx, malondialdehyde (MDA) levels, carbonyl protein and levels of nitrite were measured by spectrophotometry. The expressions of pro and antioxidant enzymes were assessed by western blot. The activity of MMP-2 was analyzed by zymography. The serum creatinine levels were assessed using a kit by spectrophotometry. The vascular and renal changes were evaluated by light microscopy. The SBP was higher in 2K,1C animals, and treatment with ASE prevent the development of hypertension. The effect of reduced vasodilator ACh in 2K,1C animals was recovered by ASE. The vasodilator effect of NG was not different between groups. Oxidative damage assessed by lipid peroxidation and protein carbonylation was greater in 2K,1C animals, and reduced by treatment with ASE. The activities of SOD, CAT and GPx were lower in samples of mesentery, plasma, kidney and heart of 2K,1C animals and ASE treatment increased these activities. The production of NO was lower in plasma, mesentery, kidney of 2K,1C animals and treatment with ASE increased the production of NO only in the kidney and mesentery of these animals. Expression of SOD-1, 2, TIMP-1 and eNOS was lower in 2K,1C animals and ASE treatment increased the expression of these enzymes. The expression for NOX-4, MMP-2 and MMP-2 activity were increased in the 2K,1C animals and ASE treatment reduced expression of these enzymes and activity of MMP-2. 2K,1C animals showed an increase in medial thickness of aorta and mesenteric artery and an increase in the ratio media/lumen of the aorta, and these changes were prevented by ASE. Serum levels of creatinine increased in 2K,1C animals were reduced by ASE. The renal morphological changes in 2K,1C animals were prevented by ASE. Therefore, treatment with ASE prevents the development of hypertension, improves endothelial dysfunction and prevents the renal and vascular changes in 2K,1C rats. The reduction in antioxidant activity and increased lipid peroxidation and protein carbonyls suggest the involvement of a mechanism of impaired antioxidant defense and increased oxidative damage, which was reversed by ASE.
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Hassan, Mohamed K. I. "Novel Elastomers, Characterization Techniques, and Improvements in the Mechanical Properties of Some Thermoplastic Biodegradable Polymers and Their Nanocomposites." University of Cincinnati / OhioLINK, 2004. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1086633832.
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Poduška, Jan. "Popis residuálních napětí v polymerních trubkách." Master's thesis, Vysoké učení technické v Brně. Fakulta strojního inženýrství, 2014. http://www.nusl.cz/ntk/nusl-231705.
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This thesis is dealing with the issue of residual stress present in the wall of a polymer pipe and the influence on its lifetime. Experimental data obtained by the ring slitting method are evaluated and the tangential residual stress in the wall of polypropylene pipe is determined. The evaluation is carried out using a new methodology based on the curved beam theory. The method is verified using numerical simulation. 3D numerical model is used to verify the behavior of the pipe, when there are both tangential and axial residual stresses present in the pipe wall, because the presence of axial stress causes a rise in the magnitude of tangential residual stress. A correction of the tangential stress values corresponding to the pipe length is then proposed. It is shown, that the distribution of the tangential residual stress does not depend significantly on the dimensions or ma-terial of the extruded pipe and a general equation is proposed to describe the distribution. This general distribution is then involved in the calculations of the pipe lifetime that are carried out using a method based on the linear elastic fracture mechanics. A significantly lower lifetimes are obtained when taking the residual stress into account.
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Lundqvist, Nina, and Carolina Hansson. "Kartläggning av studier kring psykosociala konsekvenser av plötslig idiopatisk hörselnedsättning." Thesis, Örebro University, Department of Health Sciences, 2006. http://urn.kb.se/resolve?urn=urn:nbn:se:oru:diva-690.
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Uppsatsen kartlägger forskning kring psykosociala konsekvenser av plötslig idiopatisk hörselnedsättning och en studie beskrivs närmare. Definitionen av plötslig idiopatisk hörselnedsättning är vanligen en sensorineural hörselnedsättning som uppkommit inom 3 dagar på 3 frekvenser i följd och är mer än 30 dB HL. Vid en hörselskada måste uppmärksamhet riktas mot de psykosociala konsekvenserna som kan uppkomma i arbetslivet och äktenskapet samt leda till isolering. Det finns skillnader i den psykologiska anpassningen till en hörselskada beroende på vilken sorts skada det är, samt individuella skillnader i upplevelsen av de konsekvenser en hörselskada ger. Syftet med uppsatsen var att genom en systematisk litteraturstudie kartlägga den forskning som finns kring de psykosociala konsekvenser som plötslig hörselnedsättning kan medföra. Litteratursökning har skett via databaser och manuellt. En studie kunde inkluderas i den djupare analysen. Resultatet visade att personer med unilateral plötslig idiopatisk hörselnedsättning upplevde psykologiska och sociala konsekvenser på grund av symtomen tinnitus och hörselnedsättning. Några slutsatser kunde inte dras då underlaget var för litet. Men det kan tänkas att plötslig idiopatisk hörselnedsättning faktiskt leder till psykosociala konsekvenser. Den slutsats som kunde dras är att det finns få studier gjorda och därmed lite kunskap kring området, och att mer forskning behövs.
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Racanelli, Claudio. "Analysis of flowability of bulk solids in a pilot scale Silo." Master's thesis, Alma Mater Studiorum - Università di Bologna, 2017. http://amslaurea.unibo.it/12864/.
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Il seguente lavoro di tesi ha lo scopo di verificare una procedura di dimensionamento per silo contenenti polveri solide - Jenike's procedure - che è utilizzata al fine di ottenere, durante lo svuotamento degli impianti, il mass flow come regime di flusso.
Tale verifica della procedura consiste nel confrontare i valori calcolati dell'angolo di inclinazione rispetto alla verticale della tramoggia del silo e della dimensione principale della sezione d'uscita con i valori direttamente misurati in un silo di piccole dimensioni. L'esecuzione della Jenike's procedure richiede una caratterizzazione della flowability delle polveri indagate: chalk, sawdust, perlite e potato starch. La misurazione delle flow properties delle polveri solide è stata effettuata utilizzando una RST-XS (Ring Shear Tester). Le prove svolte con tale strumento sono lo yield locus test e il wall yield locus test, permettendo di misurare così yield loci, wall yield loci e flow fuctions. In parallelo a questo lavoro sono state effettuate misurazioni dell'AOR (Angle of Repose) al fine di cercare una correlazione diretta con l'angolo di inclinazione della tramoggia dell'impianto pilota. Durante lo svolgimento del progetto è inoltre stato implementato uno stress sensor all'interno del silo con lo scopo di effettuare misurazioni dello stato degli stress agenti in pianta.
E' stato ottenuto che la Jenike's procedure sovradimensiona di un certo valore il silo pilota. Ulteriori indagini riguardanti il metodo adottato per effettuare il dimensionamento potrebbero presumibilmente permettere la riduzione del sovradimensionamento.
Per quanto riguarda il confronto tra AOR e l'angolo di inclinazione della tramoggia non è stata invece trovata alcuna correlazione. Mentre i valori dello stress misurati con lo stress sensor sono emersi conformi con i valori attesi dalle relazioni teoriche (Janssen's equation e method of Arnold and McLean).
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Oliveira, Vitor Antunes de. "Toxicidade do mercúrio em ratas virgens, gestantes e lactantes: efeito protetor do zinco e da N-acetilcisteína." Universidade Federal de Santa Maria, 2016. http://repositorio.ufsm.br/handle/1/4501.
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Coordenação de Aperfeiçoamento de Pessoal de Nível SuperiorMercury (Hg) is a divalent metal found liquid at room temperature without biological functions and anthropogenically released in industrial, agricultural activities and burning of fossil fuels. Toxic effects caused by exposure to this metal are related to the interaction of different biochemical processes due to its affinity for sulfhydryl groups (SH). This damage depends on the time of exposure and the development period in which the individuals are exposed. Thus, the aim of this study was to evaluate the effects of a single subcutaneous dose of inorganic Hg in virgin, pregnant and lactating rats, as well as the protective effect of zinc (Zn) and N-acetylcysteine (NAC). For this, three experimental protocols were used: I) Virgin female rats were treated with ZnCl2 (27 mg/kg) and/or NAC (5 mg/kg) or saline (0.9%) and 24 hours after with HgCl2 (5 mg/kg) or saline (Article 1). II) Pregnant or lactating rats were treated with ZnCl2 (27 mg/kg) and/or NAC (5 mg/kg) or saline (0.9%) and 24 hours after with HgCl2 (10 mg/kg) or saline (manuscript I). III) Renal and hepatic analysis of virgin, pregnant and lactating rats exposed to a dose of HgCl2 (5 mg/kg) or saline (manuscript II). In all protocols euthanasia was performed 24 hours after the last treatment and the tissues removed and prepared for analysis. Protocols I and II focused primarily on biochemical parameters in different tissues and protocol III in morphological evaluations and protein expression in the kidneys and liver. Virgin rats exposed to Hg showed inhibition of the δ-aminolevulinic acid dehydratase (δ-ALA-D) activity in all tissues analyzed, changes in serum markers of hepatic (alanine aminotransferase [ALT] and aspartate aminotransferase [AST]) and renal (creatinine and urea) damage, morphological damage, and changes in proteins related to oxidative stress expression, for instance, mitofusin 2 (MFN2), inducible nitric oxide synthase (iNOS), heat shock protein 27 (HSP27) and glucose regulated protein 75 (GRP75). Pregnant and lactating rats exposed to mercury showed milder changes than virgin rats, including no inhibition of hepatic δ-ALA-D or alterations of proteins related to oxidative stress and few morphological damage. Pregnant and lactating rats still showed physiologically higher levels of metallothionein (MT) in the liver and larger glomerulus diameter than virgin rats. The results suggest greater resistance of pregnant and lactating rats to Hg compared with virgin rats. This difference may be related to increase of hepatic MT levels induced by pregnancy and lactation. This protein is synthesized in the liver and plays an important chelator role,. making substances, such as Hg, less harmful. The treatment with Zn and NAC showed promising results against damage caused by Hg, probably by induction of MT synthesis caused by Zn and by chelating action of NAC. In both situations occur the capture of Hg. The metal bound to MT or NAC is neutralized and consequently has lower toxicity effects.
O mercúrio (Hg) é um metal bivalente encontrado líquido a temperatura ambiente, sem funções biológicas e antropogenicamente liberado em atividades industriais, agricultura e queima de combustíveis fósseis. Os efeitos tóxicos causados pela exposição a esse metal estão relacionados à sua interação com diferentes processos bioquímicos devido a sua afinidade por grupos sulfidrílicos (SH). Estes danos dependem do tempo de exposição e do período de desenvolvimento em que os indivíduos são expostos. Com isso, o objetivo deste trabalho foi avaliar os efeitos do Hg inorgânico, em dose única subcutânea, em ratas virgens, gestantes e lactantes, bem como, a capacidade protetora do zinco (Zn) e da N-acetilcisteína (NAC). Para isso, adotamos três protocolos experimentais: I) Ratas virgens foram tratadas com ZnCl2 (27 mg/kg) e/ou NAC (5 mg/kg) ou salina (0,9%) e 24 horas após com HgCl2 (5 mg/kg) ou salina (artigo 1). II) Ratas gestantes e lactantes tratadas com ZnCl2 (27 mg/kg) e/ou NAC (5 mg/kg) ou salina (0,9%) e 24 horas após com HgCl2 (10 mg/kg) ou salina (manuscrito I). III) Análise renal e hepática de ratas virgens, gestantes e lactantes expostas a uma dose de HgCl2 (5 mg/kg) ou salina (manuscrito II). Em todos os protocolos a eutanásia foi realizada 24 horas após o último tratamento e os tecidos retirados e preparados para as análises. Os protocolos I e II tiveram como foco principal parâmetros bioquímicos em diferentes tecidos e o protocolo III em avaliações morfológicas, expressão proteica em rins e fígado. Ratas virgens expostas ao Hg apresentaram inibição da atividade da δ-aminolevulinato desidratase (δ-ALA-D) em todos os tecidos analisados, alterações em marcadores hepáticos (alanina aminotransferase [ALT] e aspartato aminotransferase [AST]) e renais (creatinina e ureia), além de danos morfológicos e alteração na expressão de proteínas relacionadas ao estresse oxidativo, como a mitofusina 2 (MFN2), óxido nítrico sintetase induzível (iNOS), proteína de choque térmico 27 (HSP27) e proteína reguladora de glicose 75 (GRP75). Ratas gestantes e lactantes expostas ao Hg apresentaram alterações mais brandas que ratas virgens, inclusive sem inibição da δ-ALA-D hepática ou distúrbios em proteínas relacionadas com dano oxidativo, bem como poucos danos morfológicos em rins e fígado. Ratas gestantes e lactantes apresentaram altos níveis hepáticos de metalotioneínas (MT) e aumento no diâmetro glomerular em relação as ratas virgens. Os resultados sugerem maior resistência de ratas gestantes e lactantes ao Hg quando comparadas com ratas virgens. Esta diferença pode ser relacionada ao aumento nos níveis hepáticos de MT induzidos pela gestação e lactação. Essa proteína é sintetizada principalmente no fígado e desempenha importante função quelante, tornando substâncias como o Hg, menos nocivas. Os tratamentos com Zn e NAC, mostraram resultados promissores contra os danos causados pelo Hg, provavelmente pela indução da síntese de MT causada pelo Zn, e pela ação quelante da NAC. Em ambas as situações ocorre a captura do Hg. O metal ligado a MT ou a NAC é neutralizado e consequentemente apresenta menor toxicidade.
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Zumdieck, Alexander. "Dynamics of Active Filament Systems." Doctoral thesis, Saechsische Landesbibliothek- Staats- und Universitaetsbibliothek Dresden, 2006. http://nbn-resolving.de/urn:nbn:de:swb:14-1139849910030-68242.
Full textAbstract:
Aktive Filament-Systeme, wie zum Beispiel das Zellskelett, sind Beispiele einer interessanten Klasse neuartiger Materialien, die eine wichtige Rolle in der belebten Natur spielen. Viele wichtige Prozesse in lebenden Zellen wie zum Beispiel die Zellbewegung oder Zellteilung basieren auf dem Zellskelett. Das Zellskelett besteht aus Protein-Filamenten, molekularen Motoren und einer großen Zahl weiterer Proteine, die an die Filamente binden und diese zu einem Netz verbinden können. Die Filamente selber sind semifexible Polymere, typischerweise einige Mikrometer lang und bestehen aus einigen hundert bis tausend Untereinheiten, typischerweise Mono- oder Dimeren. Die Filamente sind strukturell polar, d.h. sie haben eine definierte Richtung, ähnlich einer Ratsche. Diese Polarität begründet unterschiedliche Polymerisierungs- und Depolymerisierungs-Eigenschaften der beiden Filamentenden und legt außerdem die Bewegungsrichtung molekularer Motoren fest. Die Polymerisation von Filamenten sowie Krafterzeugung und Bewegung molekularer Motoren sind aktive Prozesse, die kontinuierlich chemische Energie benötigen. Das Zellskelett ist somit ein aktives Gel, das sich fern vom thermodynamischen Gleichgewicht befindet. In dieser Arbeit präsentieren wir Beschreibungen solcher aktiven Filament-Systeme und wenden sie auf Strukturen an, die eine ähnliche Geometrie wie zellulare Strukturen haben. Beispiele solcher zellularer Strukturen sind Spannungsfasern, kontraktile Ringe oder mitotische Spindeln. Spannungsfasern sind für die Zellbewegung essentiell; sie können kontrahieren und so die Zelle vorwärts bewegen. Die mitotische Spindel trennt Kopien der Erbsubstanz DNS vor der eigentlichen Zellteilung. Der kontraktile Ring schließlich trennt die Zelle am Ende der Zellteilung. In unserer Theorie konzentrieren wir uns auf den Einfluß der Polymerisierung und Depolymerisierung von Filamenten auf die Dynamik dieser Strukturen. Wir zeigen, dass der kontinuierliche Umschlag (d.h. fortwährende Polymerisierung und Depolymerisierung) von Filamenten unabdingbar ist für die kontraktion eines Rings mit konstanter Geschwindigkeit, so wie in Experimenten mit Hefezellen beobachtet. Mit Hilfe einer mikroskopisch motivierten Beschreibung zeigen wir, wie "filament treadmilling", also Filament Polymerisierung an einem Ende mit der gleichen Rate wie Depolymerisierung am anderen Ende, zur Spannung in Filament Bündeln und Ringen beitragen kann. Ein zentrales Ergebnis ist, dass die Depolymerisierung von Filamenten in Anwesenheit von filamentverbindenden Proteinen das Zusammenziehen dieser Bündel sogar in Abwesenheit molekulare Motoren herbeiführen kann. Ferner entwickeln wir eine generische Kontinuumsbeschreibung aktiver Filament-Systeme, die ausschließlich auf Symmetrien der Systeme beruht und von mikroskopischen Details unabhängig ist. Diese Theorie erlaubt uns eine komplementäre Sichtweise auf solche aktiven Filament-Systeme. Sie stellt ein wichtiges Werkzeug dar, um die physikalischen Mechanismen z.B. in Filamentbündeln aber auch bei der Bildung von Filamentringen im Zellkortex zu untersuchen. Schließlich entwickeln wir eine auf einem Kräftegleichgewicht basierende Beschreibung für bipolare Strukturen aktiver Filamente und wenden diese auf die mitotische Spindel an. Wir diskutieren Bedingungen für die Bildung und Stabilität von SpindelnActive filament systems such as the cell cytoskeleton represent an intriguing class of novel materials that play an important role in nature. The cytoskeleton for example provides the mechanical basis for many central processes in living cells, such as cell locomotion or cell division. It consists of protein filaments, molecular motors and a host of related proteins that can bind to and cross-link the filaments. The filaments themselves are semiflexible polymers that are typically several micrometers long and made of several hundreds to thousands of subunits. The filaments are structurally polar, i.e. they possess a directionality. This polarity causes the two distinct filament ends to exhibit different properties regarding polymerization and depolymerization and also defines the direction of movement of molecular motors. Filament polymerization as well as force generation and motion of molecular motors are active processes, that constantly use chemical energy. The cytoskeleton is thus an active gel, far from equilibrium. We present theories of such active filament systems and apply them to geometries reminiscent of structures in living cells such as stress fibers, contractile rings or mitotic spindles. Stress fibers are involved in cell locomotion and propel the cell forward, the mitotic spindle mechanically separates the duplicated sets of chromosomes prior to cell division and the contractile ring cleaves the cell during the final stages of cell division. In our theory, we focus in particular on the role of filament polymerization and depolymerization for the dynamics of these structures. Using a mean field description of active filament systems that is based on the microscopic processes of filaments and motors, we show how filament polymerization and depolymerization contribute to the tension in filament bundles and rings. We especially study filament treadmilling, an ubiquitous process in cells, in which one filament end grows at the same rate as the other one shrinks. A key result is that depolymerization of filaments in the presence of linking proteins can induce bundle contraction even in the absence of molecular motors. We extend this description and apply it to the mitotic spindle. Starting from force balance considerations we discuss conditions for spindle formation and stability. We find that motor binding to filament ends is essential for spindle formation. Furthermore we develop a generic continuum description that is based on symmetry considerations and independent of microscopic details. This theory allows us to present a complementary view on filament bundles, as well as to investigate physical mechanisms behind cell cortex dynamics and ring formation in the two dimensional geometry of a cylinder surface. Finally we present a phenomenological description for the dynamics of contractile rings that is based on the balance of forces generated by active processes in the ring with forces necessary to deform the cell. We find that filament turnover is essential for ring contraction with constant velocities such as observed in experiments with fission yeast