Understanding the changes occurring in the mechanical properties during martensite tempering is essential in the development of new industrial grades. The aim of this research was to develop new ultra-high strength steels via nanoprecipitation control, which requires an understanding of the processing-microstructure-property relationship in medium carbon (0.5-0.6 wt.%) steels throughout tempering. Much of the work has been centred in understanding the role of silicon at the precipitation level and in the recovery of martensite. By using an existing spring steel grade, the effect of interrupted ageing (IA) in tempered martensite has been studied. In IA, an intermediate step between quenching and tempering is introduced, where quenched martensite is left to rest at room temperature for a defined period of time. By allowing carbon segregation into dislocation cores, the incorporation of IA resulted in a more stable microstructure and hardness improvement. The effect of silicon in the epsilon to cementite carbide transition has also been studied. The classical nucleation theory was applied in order to model cementite formation under paraequilibrium conditions, thus incorporating silicon during nucleation. Characterisation using high energy X-rays showed the inhibiting effect of silicon in the overall cementite precipitation. The second effect of silicon was observed in the martensite recovery. A series of experiments were carried out in order to capture the various microstructural changes taking place during tempering: precipitation, grain size and dislocation density evolution. It was observed that the addition of silicon reduces the rate of martensite recovery, owing to the reduced cross-slip in the ferrite lattice. A plasticity model based on irreversible thermodynamics and EBSD characterisation was applied to identify the effective grain size. The results from these two techniques require further research. Nevertheless, based on the post-failure analysis by TEM, it appears that at relatively early tempering stages, even low angle lath boundaries can contribute to strengthening, where piled-up dislocations have been observed at lath boundaries.

This research into the properties of a 5"x5"x16lb W.F., A 36 Steel, rolled structural member was undertaken to determine the following: i - Yield stress distribution over the cross section of the member as determined by coupon tests. ii - Development of strain over the cross section of the member, as measured by electric strain gauges, when subjected to a) Axial loading, b) Bending Moment. iii - The effect of previous loading of a member as a column into the region of yielding on its subsequent behaviour as a beam loaded to failure. The following results were obtained: i - Yield stress, particularly the upper yield stress was not uniform over the cross section. ii - The strain distribution in the plastic range was not uniform and varied from cross section to cross section and even at closely adjacent points on the same cross section. iii - Failure of the member, due to inadequate lateral support when loaded as a column, occurred before complete yielding was achieved. The effect of this previous loading on the subsequent behaviour of the member as a beam loaded to failure was inconclusive. / Applied Science, Faculty of / Civil Engineering, Department of / Graduate

Cannabis has been used medicinally for millennia, but the cannabinoid (CB) field exploded with the identification of its endogenous receptors and endocannabinoids (eCBs). In vitro experimentation established that eCBs alter synaptic plasticity at presynaptic nerve terminals; however, the characterization of the eCB system (ECS) in vivo remains incomplete. This study aimed to determine the mechanism of in vivo eCB-mediated hippocampal synaptic plasticity and to analyze the effects this plasticity had on spatial working memory (SWM). With in vivo recordings of field excitatory postsynaptic potentials (fEPSPs) in anesthetized mice and rats as well as pharmacological manipulation of the ECS and glutamate receptor antagonism, it was found that eCBs, both anandamide (AEA) and 2-arachnidonyl glycerol (2-AG), caused LTD at hippocampal CA3-CA1 synapses. Induction of eCB-LTD occurs via a sequential activation of cannabinoid type-1 receptor (CB1R) and NR2B-containing NMDA receptor (NR2BR) and is expressed through the endocytosis of AMPA receptors (AMPARs). Increased eCB tone also caused an impairment of SWM for over 24 hours in the Delayed Non-Match-To-Sample (DNMTS) T-maze. This study provides the first evidence that an acute administration of eCB degradative enzyme inhibitors not only produces an in vivo LTD at hippocampal CA3-CA1 synapses that requires CB1R, NR2BR, and AMPAR, but also impairs SWM, a phenomenon also caused by an acute injection of exogenous CBs.

Sigma-1 receptors (σ-1Rs) are chaperone-like proteins that are broadly distributed throughout the central nervous system and in other tissues. They have been implicated in several physiological and pathological processes, primarily by their ability to modulate certain voltage- and ligand-gated ion channels. Growing evidence suggests that σ-1Rs regulate the functions of ion channels, such as voltage-gated K+ 1.2 (Kv 1.2) and the human Ether-à-go-go-Related Gene (hERG) ion channels, by modulating their expression, trafficking, and targeting. While it is well documented that σ-1Rs enhance the function of N-methyl-D-aspartate receptors (NMDARs), the mechanisms of this enhancement remain poorly understood. Using biochemical methods, we show that 90 minutes after intraperitoneal (i.p.) injection of σ-1R agonists such as (+)-SKF 10,047 (SKF) or (+)-Pentazocine (PTZ) (2 mg/kg), there is an increase in the expression of GluN2 subunits of NMDARs and postsynaptic density protein-95 (PSD-95) in the rat hippocampus. Following activation of σ-1Rs, co-immunoprecipitation (Co-IP) experiments reveal an increased interaction between σ-1Rs and NMDAR subunits; sucrose gradient centrifugation demonstrates an increase in the protein levels of GluN2 subunits in vesicular compartment; and biotinylation shows an increase in the surface levels of GluN2A-containing NMDARs. Taken together, our results suggest σ-1Rs may enhance NMDARs function by increasing their expression, trafficking, and surface levels. This σ-1R-mediated increase in NMDAR expression and surface levels might be involved in several physiological processes such as learning and memory. Our findings also suggest that σ-1Rs could form a potential target for designing novel antipsychotics.

Nanoindentation has brought in many features of research over the past decade. This novel technique is capable of producing insights into the small ranges of deformation. This special point has brought a lot of focus in understanding the deformation behavior under the indenter. Nickel, iron, tungsten and copper-niobium alloy system were considered for a surface deformation study. All the samples exhibited a spectrum of residual deformation. The change in behavior with indentation and the materials responses to deformation at low and high loads is addressed in this study. A study on indenter geometry, which has a huge influence on the contact area and subsequently the hardness and modulus value, has been attempted. Deformation mechanisms that govern the plastic flow in materials at low loads of indentation and their sensitivity to the rate of strain imparted has been studied. A transition to elastic, plastic kind of a tendency to an elasto-plastic tendency was seen with an increase in the strain rate. All samples exhibited the same kind of behavior and a special focus is drawn in comparing the FCC nickel with BCC tungsten and iron where the persistence of the elastic, plastic response was addressed. However there is no absolute reason for the inconsistencies in the mechanical properties observed in preliminary testing, more insights can be provided with advanced microscopy techniques where the study can be focused more to understand the deformation behavior under the indenter. These experiments demonstrate that there is a wealth of information in the initial stages of indentation and has led to much more insights into the incipient stages of plasticity.

Orientador: João Alberto Venegas Requena / Dissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia Civil / Made available in DSpace on 2018-07-31T23:17:23Z (GMT). No. of bitstreams: 1 Santos_RogerioMitsuodos_M.pdf: 3363967 bytes, checksum: ca4edb9a262e5fc2478f70d7c7c011ba (MD5) Previous issue date: 2002 / Resumo: Neste trabalho são apresentadas análises de estruturas metálicas planas constituídas de barras deformáveis por flexão, por força cortante e por força axial. Nestas análises é considerado o efeito de não-linearidade física em sistemas não-conservativos. Um programa computacional foi desenvolvido, em teoria dos pequenos deslocamentos, para possibilitar a determinação do comportamento global da estrutura. A técnica empregada foi a matricial, utilizando funções de rigidez. Esta técnica possibilita análises considerando a não-linearidade física de barras, com pouco esforço computacional. Para a resolução dos sistemas não-lineares foi adotado o método incremental-iterativo de Newton-Raphson. O processo incremental de cargas foi adotado para possibilitar o acompanhamento das deformações nas barras da estrutura nos carregamentos, descarregamentos e carregamentos reversos, de acordo com a análise solicitada; sendo que para as estruturas sujeitas a carregamentos reversos foi considerado o efeito Bauschinger no sistema. No carregamento incremental da estrutura as barras seguem o comportamento elástico ou elasto-plástico dependendo do estado de tensões. No descarregamento as barras seguem somente o comportamento elástico fazendo com que apareça um resíduo plástico de deformação. Desta forma, o sistema pode ser considerado não-conservativo aproximando-se do comportamento real. O regime elasto-plástico foi considerado para barras axialmente solicitadas, predominantemente, utilizando curvas de flambagem do CRC14 (Column Research Council) e da AISC-LRFD1 (Load and Resistance Factor Design). São apresentados exemplos numéricos comparando os tipos de análises nos regimes elástico e elasto-plástico / Abstract: In this work, analyses of steel plane framed structures, consisting of deformable frames by bending, shear and axial load are presented. In these analyses the effect of material nonlinearity in nonconservative systems are considered. According to the theory of small displacements, a computational program was developed to make possible the determination of the global structure behavior. The employed technique was the matrix method, using stiffness functions. This technique makes possible analyses considering the material nonlinearity of frames with little computational effort. For the nonlinear systems resolution the Newton-Raphson incremental-iterative method was adopted. The incremental load process was adopted to make possible the accompaniment of the deformations in the frames of the structure in the loading, unloading, and reverse loading, in accordance with the requested analysis. In the structures submited to reverse loading, the acting of Bauschinger effect in the system was considered. In the incrementalloading of the structure the frames follow the elastic or elastic-plastic behavior depending on the stress state. During the unloading of the structure the frames only follow the elastic behavior. Thus, the system can be considered nonconservative coming close to the real behavior. The elastic-plastic behavior was considered mainly for frames under axial loading using the column curve of CRC14 (Column Research Council) and the column curve of AISC-LRFD1 (Load and Resistance Factor Design). Numerical examples are presented comparing the types of analyses, in elastic and elastic-plastic behavior of the frames / Mestrado / Estruturas / Mestre em Engenharia Civil

No description available.

Recently, there has been an explosion of studies focusing on animal “personality”, defined as consistent individual differences in behaviour. Researchers within this field commonly partition phenotypic variation in behavioural traits at the among- and within-individual levels, because significant among-individual variation implies that a behaviour is repeatable and thus can be subject to selection. It is well known that individuals can not only differ in their mean-level behavioural expression, but also in how their phenotype varies over time, known as temporal plasticity. However, another important yet largely overlooked aspect of behavioural variation is that some individuals are consistently more “unpredictable” than others. This level of variance corresponds to (unexplained) variation among successive measurements on a given individual. Personality and behavioural plasticity have both been studied in many different contexts, however research regarding the possible correlations between these two traits and unpredictability is lacking. Here, I repeatedly assayed locomotor activity in wild white-footed mice (Peromyscus leucopus) exposed to a 10-min novel environment test, to determine whether their behavioural reaction norms exhibited consistent among-individual differences in intercept (personality), slope (plasticity), and variance (unpredictability). Using a doubly hierarchical generalized linear mixed model, I found that both the intercept and slope of the temporal reaction norms were significantly repeatable (Rint= 0.39, Rslp= 0.23) and negatively correlated (r=-0.51). Moreover, unpredictability was found to be significantly repeatable (Rsd= 0.20), positively correlated with intercept (r=0.92), and negatively correlated with slope (r=-0.51). To the extent that these correlations reflect the underlying quantitative genetic architecture of behaviour, my results suggest the presence of constraints on the evolution of behaviour across multiple levels of variation.

An aim of the given thesis is creating of a computational model of strain-stress behaviour of shock absorbers made of plastic and hyperelastic material. First step is get ecquaint with theory of large strains, theory of hyperelasticity and plasticity. Next step is get ecquaint with options of commercial programs based on MKP. Based on this knowledge, models of simple shock absorber are made. With created models, crash tests are simulated and property of shock absorbers are compared.

A fundamental question of evolutionary ecology is, what determines body size? In general, the body size of vertebrates is thought to be relatively inflexible, a product of their genes, food, environment, and stress. However, vertebrate growth can be plastic in response to population interactions such as predator-prey and competition. While these relationships can elicit plasticity of vertebrate growth, mutualistic relationships have yet to be investigated. An iconic example of mutualism involving a vertebrate is the relationship between anemone and anemonefish. In this interaction anemonefish size is often positively correlated with anemone size. Here, I test the hypothesis that anemonefish growth is a plastic response to variation in anemone size. Juvenile clownfish (Amphiprion percula) of relatively uniform size were paired with sea anemones (Entacmaea quadricolor) of variable size and monitored over three months. The average anemone size over the course of the month was then used to predict the fish growth each month. Mixed model analyses verified that anemone area is significantly associated with both change in fish standard length and change in fish body depth. Fish in larger anemones grew more than did fish in small anemones. Remarkably, individuals in large anemones achieved this despite receiving the same amount of food as individuals in small anemones. This clownfish growth plasticity in response to anemone size might be adaptive if anemone area is a good indicator of resource availability in the wild, because it would enable the fish to maximize their reproduction without compromising survival. This study extends the understanding of how plasticity of vertebrate species can be influenced by a wide variety of population interactions.