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A literatura refere que os estímulos produzidos pelos diferentes tipos de contração no sistema músculo-esquelético geram adaptações específicas. A locomoção em aclive e declive vem sendo utilizada como modelo de treinamento concêntrico e excêntrico para estudos dessas adaptações em animais. Sendo assim este estudo teve o objetivo de avaliar características mecânicas e histológicas do músculo sóleo de ratos submetidos a treinamento em aclive ou declive. Foram avaliados 36 ratos Wistar machos (90 dias de idade no início do treinamento) divididos igualmente em três grupos: aclive (A), declive (D) e controle (C). Os treinamentos foram realizados em uma esteira adaptada com raias individuais e inclinação de + 16° (aclive) ou – 16° (declive). Os animais passaram por um período de adaptação de uma semana na esteira com a inclinação específica e, em seguida, foram avaliados quanto à velocidade máxima suportada. Os treinamentos aconteceram com velocidade (relativa à máxima avaliada) e tempo progressivos ao longo de oito semanas (29 sessões). Dois dias após o último treino os animais foram anestesiados com Tiopental Sódico (± 5 ml), os músculos sóleos direitos e esquerdos foram removidos e os animais decapitados. Os músculos sóleos da pata direita (n = 7C, 8A, 9D) foram submetidos a ensaios de tração em uma máquina EMIC DL2000, com célula de carga de 50 N a velocidade de 1,66 m·s-1. Durante o ensaio, as amostras foram borrifadas com solução salina a cada um minuto. Os músculos sóleos esquerdos foram retirados para contagem de sarcômeros (n = 4A, 4C e 5D) e análise na proteína titina por Western Blot (n = 4 por grupo). Foi verificada a normalidade e homogeneidade dos dados e a confiabilidade das medidas foi avaliada pelo coeficiente Alpha de Cronbach. Comportamentos individuais foram analisados pelo Coeficiente de Correlação Intraclasse (ICC); ANOVA one way e post hoc de Bonferroni e teste não paramétrico Kruskal-Walls foram aplicados para identificação das diferenças entre os grupos. Dos 36 animais, três morreram antes do final do experimento. Os coeficientes Alpha de Cronbach indicaram confiabilidade das medidas com valores próximos a um para todas as variáveis. Os dados mecânicos dos animais que treinaram em declive apresentaram menores valores de ICC, mesmo assim significativos. As comparações entre os grupos indicaram aumento significativo da rigidez da curva tensão X deformação para os animais treinados em aclive e declive, e maior deformação da curva para os animais controle. Foi encontrado aumento da média da tensão passiva dos músculos dos animais treinados (57 ± 5 e 56 ± 11 para A e D; 51,6 ± 7,7 para C), contudo essa diferença não foi estatisticamente significativa, possivelmente devido a grande variabilidade dos dados mecânicos. Em relação ao número de sarcômeros em série os animais que treinaram em declive apresentaram menores comprimentos de sarcômero (2,806 ± 0,059 μm) e maior número de sarcômeros em série (8170 ± 510) quando comparados aos grupos controle (3,06 ± 0,054 μm e 7510 ± 240) e aclive (2,990 ± 0,023 μm e 7390 ± 270). As demais variáveis analisadas não apresentaram diferenças entre os grupos. É possível concluir com este estudo que adaptações estruturais nem sempre acontecem em paralelo às adaptações funcionais, que o treinamento em declive parece produzir resultados com maiores variações e que os diferentes estímulos provocam diferentes adaptações no músculo sóleo de ratos. / The literature states that the stimulus produced by different types of contraction in skeletal muscle generates specific adaptations. Downhill and uphill locomotion have been used as a model of concentric and eccentric training in studies that verify the different adaptations in animals. Therefore this study intended to evaluate mechanical and histological properties of rats’ soleus muscle submitted to uphill or downhill running. We evaluated 36 male Wistar rats (90 days old at the start of training). They were divided equally into three groups: uphill (A), downhill (D) and control (C). Training was performed on a treadmill adapted to individual lanes and +16º (uphill) or -16º (downhill) incline. The animals went through a one week adjustment period on the treadmill with the specific inclines, and then there were evaluated the maximal speeds they reached. The training took place with progressive speed (relative to the maximum tested) and time over 8 weeks (29 sessions). Two days after the last training the animals were anesthetized with sodium thiopental (± 5 ml), the right and left soleus muscles were removed and the animals were decapitated. The right soleus muscles (n = 7C, 8A, 9D) were subjected to tensile tests on one machine EMIC DL2000, with a load cell of 50 N, speed of 1,66 m.s-1. During the test, the samples were sprayed with saline solution every one minute. The left soleus muscles were removed for counting of sarcomeres (n = 4A, 4C, 5D) and the titin Western blot analysis (n = 4 per group). Data normality and homogeneity were verified and reliability of the measures was assessed by Cronbach's Alpha coefficient. Individual behaviors were analyzed by Intraclass Correlation Coefficient (ICC); one-way ANOVA and post hoc Bonferroni test and nonparametric Kruskal-Wallis were applied to identify the differences between the groups. Three out of the 36 animals died before the end of the experiment. The Cronbach's Alpha coefficients indicated reliability of the measures with values close to one for all the analyzed variables. The mechanical data of downhill trained animals had significantly lower ICC, even though significant. Comparisons between groups showed increased rigidity of the muscles of trained animals and greater deformation of the muscles of control animals. It has been found greater passive tension mean for both training groups (57 ± 5 and 56 ± 11 for A and D; 51.6 ± 7.7 for C), but it was not statistically significant probably due to the high mechanical data variability. Regarding the number of sarcomeres in series the downhill trained animals showed smaller sarcomere lengths (2.806 ± 0.059 μm) and greater serial sarcomere number (8170 ± 510) when compared to control (3.06 ± 0.054 μm and 7510 ± 240) and uphill (2.990 ± 0.023 μm e 7390 ± 270) groups. The remaining variables did not differ between groups. It can be concluded from this study that structural adaptations do not happen in parallel with functional adaptations, downhill running appear to produce more variable results and that different stimuli generate different adaptations in rats’ soleus muscle.

Metallic materials have gained much attention recently from the areas of medical devices and orthopaedics. Artificial organs, dental implants, prostheses and implants that replace damaged or malfunctioning parts in the body are, or contain, metal components. Our ageing society poses an increased demand to provide devices and implants that can demonstrate better performance than those presented by traditional solutions. Matching the mechanical properties (i.e. stiffness and strength) of the device to those of the host tissue is a major challenge for the design and manufacture of engineered metal materials for biomedical applications. Failure in doing so provokes implant loosening, patient discomfort and repeated surgeries. Therefore, tailoring physical properties and biocompatibility of those materials is the main final aim of this research programme. This PhD study has focused on the tailoring of the mechanical properties of titanium-based materials and titanium-based alloys. Titanium inertness and the selection of biocompatible alloying elements were set as the baseline. Two approaches were employed to decrease stiffness (i.e. Young s modulus): one, by introducing porosity in a titanium matrix and therefore, reduce its Young s modulus, and two, by designing and manufacturing beta-titanium-based alloys with a reduced Young s modulus. Titanium scaffolds were manufactured using powder metallurgy with space holder technique and a sintering process. Different space holder sizes were used in four different categories to study the effect of pore size and porosity on the mechanical properties of the porosity engineered Ti scaffolds. Ti-based alloys were manufactured using manufacturing techniques such as sintering and arc-melting. The effect of different fabrication processes and the addition of beta-stabilising elements were studied and investigated. The obtained results of mechanical properties for pore size and porosity were within the values that match bone properties. This means these materials are suitable for biomedical application and the beta-Ti alloys results show that the mechanical properties can be decreased via tailoring the crystal structures. The characterisation of the Ti-based alloys helps to develop this material for its use in biomedical application.

The sintering behavior to form TiC-Ni-Mo cermet using a nano-size TiC powders was investigated in flowing Argon gas at 1500°C. Nano-sized titanium carbide powders with high purity, high surface area, and low cost were synthesized from carbon coated Ti containing precursors utilizing a patented process. The sintering studies showed that an increase in theoretical density (TD) with increasing molybdenum content. TiC based cermets were characterized using X-ray diffraction (XRD), Vickers hardness, and scanning electron microscopy (SEM) with energy dispersive X-ray spectroscopy (EDS). Mechanical properties, electrical conductivity and oxidation resistance results shows potential applications as interconnect for Low/Intermediate Temperature Solid Oxide Fuel Cells (SOFC) and machining tool tips.

Hot-dip galvanizing is widely used for corrosion protection of steel structures. However, there has been a plethora of recent reports on premature cracking in galvanized steel structures, which have resulted in some early decommissions or even hazardous collapses. This research focuses on cold-formed Rectangular Hollow Sections (RHS). A total of 108 tensile coupons were tested to investigate the effects of galvanizing as well as different pre-galvanizing treatments on the material properties around the cross sections of the specimens. For the first time, this thesis reports a comprehensive measurement of residual stresses in different directions at the member ends which are directly relevant to the cracking issue. The results were also compared to the residual stresses far away from the member ends, which are relevant to structural stability research. In all, the research provides a better understanding of the characteristics and structural performance of galvanized RHS to facilitate its application. The recommendations can help engineers, fabricators, and galvanizers mitigate the risk of cracking in RHS during galvanizing. / Graduate

Made available in DSpace on 2014-06-11T19:35:03Z (GMT). No. of bitstreams: 0 Previous issue date: 2009-07-22Bitstream added on 2014-06-13T19:44:50Z : No. of bitstreams: 1 lucas_mg_dr_arafo.pdf: 7609787 bytes, checksum: 818d8660089a22ed3354bf205e9bb72b (MD5) / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) / Neste trabalho foram analisadas as alterações nas propriedades físicas e mecânicas de um gesso odontológico do tipo IV após a incorporação de dois agentes desinfetantes (Digluconato e Cloridrato de clorexidina). Foram realizados testes mecânicos para a análise do tempo de presa, reprodução de detalhes, expansão de presa e resistência à compressão, já as alterações físicas foram analisadas através de uma microscopia eletrônica de varredura (MEV) nos aumentos de 375, 750, 1500 e 3000x. Os resultados demonstraram que somente houve alterações significantes no tempo de presa com a incorporação de Digluconato de Clorexidina 2,0% sem diluição e a resistência a compressão que demonstrou valores significantemente inferiores em todas as incorporações, porém todas as alterações dentro do limite estabelecido pela normatização para gessos odontológicos. Pela análise da Microscopia Eletrônica de Varredura, pode-se observar que os cristais obtiveram um aumento pela associação com os agentes derivados da clorexidina diminuindo os microporos existentes. Com isso verificamos que os derivados da clorexidina podem ser uma alternativa para a obtenção de modelos biologicamente seguros. / The purpose of this study was to evaluate the alterations in physical and mechanical properties of a gypsum tipe IV after the incorporation of two disinfectant agents (Chlorhexidine hydrochlooride and Chlorhexidine gluconate). The mechanical tests are made for setting time, reproduction details, setting expansion and compressive tensile, and the physical properties was examinated in a scanning electron microscope (SEM) and photomicrographed are made in 375, 750,1500, 3000x and compared vissually. The results demonstrated were only significant alterations in the setting time with the incorporation of Chlorhexidine gluconate without dilution and the compression resistance that demonstrated under values in all of the incorporations, however all the alterations meet inside of the established limit for I.S.O values. In the analysis of the physical properties, the crystals obtained an increase for the association with the derived agent´s clorhexidine. In conclusion, the incorporation clorhexidine agents can be a alternative to obtained biological models in dentistry.

A literatura refere que os estímulos produzidos pelos diferentes tipos de contração no sistema músculo-esquelético geram adaptações específicas. A locomoção em aclive e declive vem sendo utilizada como modelo de treinamento concêntrico e excêntrico para estudos dessas adaptações em animais. Sendo assim este estudo teve o objetivo de avaliar características mecânicas e histológicas do músculo sóleo de ratos submetidos a treinamento em aclive ou declive. Foram avaliados 36 ratos Wistar machos (90 dias de idade no início do treinamento) divididos igualmente em três grupos: aclive (A), declive (D) e controle (C). Os treinamentos foram realizados em uma esteira adaptada com raias individuais e inclinação de + 16° (aclive) ou – 16° (declive). Os animais passaram por um período de adaptação de uma semana na esteira com a inclinação específica e, em seguida, foram avaliados quanto à velocidade máxima suportada. Os treinamentos aconteceram com velocidade (relativa à máxima avaliada) e tempo progressivos ao longo de oito semanas (29 sessões). Dois dias após o último treino os animais foram anestesiados com Tiopental Sódico (± 5 ml), os músculos sóleos direitos e esquerdos foram removidos e os animais decapitados. Os músculos sóleos da pata direita (n = 7C, 8A, 9D) foram submetidos a ensaios de tração em uma máquina EMIC DL2000, com célula de carga de 50 N a velocidade de 1,66 m·s-1. Durante o ensaio, as amostras foram borrifadas com solução salina a cada um minuto. Os músculos sóleos esquerdos foram retirados para contagem de sarcômeros (n = 4A, 4C e 5D) e análise na proteína titina por Western Blot (n = 4 por grupo). Foi verificada a normalidade e homogeneidade dos dados e a confiabilidade das medidas foi avaliada pelo coeficiente Alpha de Cronbach. Comportamentos individuais foram analisados pelo Coeficiente de Correlação Intraclasse (ICC); ANOVA one way e post hoc de Bonferroni e teste não paramétrico Kruskal-Walls foram aplicados para identificação das diferenças entre os grupos. Dos 36 animais, três morreram antes do final do experimento. Os coeficientes Alpha de Cronbach indicaram confiabilidade das medidas com valores próximos a um para todas as variáveis. Os dados mecânicos dos animais que treinaram em declive apresentaram menores valores de ICC, mesmo assim significativos. As comparações entre os grupos indicaram aumento significativo da rigidez da curva tensão X deformação para os animais treinados em aclive e declive, e maior deformação da curva para os animais controle. Foi encontrado aumento da média da tensão passiva dos músculos dos animais treinados (57 ± 5 e 56 ± 11 para A e D; 51,6 ± 7,7 para C), contudo essa diferença não foi estatisticamente significativa, possivelmente devido a grande variabilidade dos dados mecânicos. Em relação ao número de sarcômeros em série os animais que treinaram em declive apresentaram menores comprimentos de sarcômero (2,806 ± 0,059 μm) e maior número de sarcômeros em série (8170 ± 510) quando comparados aos grupos controle (3,06 ± 0,054 μm e 7510 ± 240) e aclive (2,990 ± 0,023 μm e 7390 ± 270). As demais variáveis analisadas não apresentaram diferenças entre os grupos. É possível concluir com este estudo que adaptações estruturais nem sempre acontecem em paralelo às adaptações funcionais, que o treinamento em declive parece produzir resultados com maiores variações e que os diferentes estímulos provocam diferentes adaptações no músculo sóleo de ratos. / The literature states that the stimulus produced by different types of contraction in skeletal muscle generates specific adaptations. Downhill and uphill locomotion have been used as a model of concentric and eccentric training in studies that verify the different adaptations in animals. Therefore this study intended to evaluate mechanical and histological properties of rats’ soleus muscle submitted to uphill or downhill running. We evaluated 36 male Wistar rats (90 days old at the start of training). They were divided equally into three groups: uphill (A), downhill (D) and control (C). Training was performed on a treadmill adapted to individual lanes and +16º (uphill) or -16º (downhill) incline. The animals went through a one week adjustment period on the treadmill with the specific inclines, and then there were evaluated the maximal speeds they reached. The training took place with progressive speed (relative to the maximum tested) and time over 8 weeks (29 sessions). Two days after the last training the animals were anesthetized with sodium thiopental (± 5 ml), the right and left soleus muscles were removed and the animals were decapitated. The right soleus muscles (n = 7C, 8A, 9D) were subjected to tensile tests on one machine EMIC DL2000, with a load cell of 50 N, speed of 1,66 m.s-1. During the test, the samples were sprayed with saline solution every one minute. The left soleus muscles were removed for counting of sarcomeres (n = 4A, 4C, 5D) and the titin Western blot analysis (n = 4 per group). Data normality and homogeneity were verified and reliability of the measures was assessed by Cronbach's Alpha coefficient. Individual behaviors were analyzed by Intraclass Correlation Coefficient (ICC); one-way ANOVA and post hoc Bonferroni test and nonparametric Kruskal-Wallis were applied to identify the differences between the groups. Three out of the 36 animals died before the end of the experiment. The Cronbach's Alpha coefficients indicated reliability of the measures with values close to one for all the analyzed variables. The mechanical data of downhill trained animals had significantly lower ICC, even though significant. Comparisons between groups showed increased rigidity of the muscles of trained animals and greater deformation of the muscles of control animals. It has been found greater passive tension mean for both training groups (57 ± 5 and 56 ± 11 for A and D; 51.6 ± 7.7 for C), but it was not statistically significant probably due to the high mechanical data variability. Regarding the number of sarcomeres in series the downhill trained animals showed smaller sarcomere lengths (2.806 ± 0.059 μm) and greater serial sarcomere number (8170 ± 510) when compared to control (3.06 ± 0.054 μm and 7510 ± 240) and uphill (2.990 ± 0.023 μm e 7390 ± 270) groups. The remaining variables did not differ between groups. It can be concluded from this study that structural adaptations do not happen in parallel with functional adaptations, downhill running appear to produce more variable results and that different stimuli generate different adaptations in rats’ soleus muscle.

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