Methods designed for incorporation into multiscale modeling polycrystals are presented in this work in two tasks. This work contains mesoscale methods for capturing the effects of both the interactions of slip dislocations encountering twin grain boundaries and the simultaneous growth of multiple twin grain volume fractions on mechanical hardening and texture evolution. These are implemented in a crystal plasticity framework using the Los Alamos visco-plastic self consistent code, VPSC-7. Presented here, the effects of simultaneous growth in multiple twin variants on textural evolution is tracked using a Kalidindi-type twin volume transfer scheme. In Task 1, the implementation of this scheme in order to simulate the texture of Twinning Induced Plasticity steels (TWIP) subjected to Equal Channel Angular Pressing (ECAP) are summarized. In Task 2, the hardening effects of two types of interactions between slip dislocations and encountered twin grain boundaries, namely dislocation transmutation and dissociation, are captured by way of modifying the dislocation density based hardening model of [14]. Interactions of the first type are presented in a constitutive relation calculating the amount of dislocation density apportioned to a given slip system contained within the encountered twin volume fraction from each interacting slip system in the parent volume fraction. The amount transmuted from each interacting slip system described using the Correspondence Method, an onto mapping of slip systems in a parent grain to slip systems in considered twin grains. Interactions of the second type are then introduced into this constitutive relation as a disassociation parameter, the value of which is established by observations gleaned from the results of the molecular dynamics simulations of [11] and [36]. These methods are implanted to simulate the anisotropic hardening behavior of HCP magnesium under multiple load paths.

No description available.

Environmental variation, an important source of phenotypic variation, can influence phenotypes, fitness and even rates of evolution. My thesis explores the effects of evolutionary change on the response to different types of environmental variation. In the first study, I examined the evolution of environmental canalization in adaptively diverged populations of Drosophila melanogaster that vary in degree of genetic canalization. I use these populations to test the congruence hypothesis which predicts that genetic canalization is a co-product of the evolution of environmental canalization and thus should be correlated. My results show that, despite adaptive evolutionary changes in morphology and genetic canalization, these populations have similar degree of variability due to environmental variation. In the second study, I explore how both variation in temperature and food quality during development influence patterns of sexual dimorphism in wing morphology in adaptively diverged populations of Drosophila melanogaster. I compare the relative contributions of adaptation, food availability and temperature on sexual size and shape dimorphism of the Drosophila wing. In particular, I focus on how these factors influence size-shape allometry both in general and in a sex-specific manner. My results show that despite the large adaptive divergence and a strong influence of environmental manipulation on wing size and shape, sex-specific patterns of condition dependence remain relatively consistent between the two populations. In the third study, I explore the evolutionary patterns of condition-dependent sexual size dimorphism among 27 different species from the melanogaster species group with varying degrees of sexual size dimorphism. Using food availability manipulations during development, I examine how sexual size dimorphism changes in response to condition at both the intra-specific and the inter-specific level. The results of this study suggest that, although we see a correlation between sexual size dimorphism and condition dependence among traits within most species, sexual dimorphism and condition dependence do not seem to have a correlated evolution among species of the melanogaster species group. / Dissertation / Doctor of Philosophy (PhD)

Short-term facilitation, a form of synaptic plasticity, takes place at GABAergic synapses between cerebellar Purkinje cells (PCs). We studied the mechanism of this short-term facilitation by directly patch-clamp recording from a PC axon terminal in cerebellar cultures. We show that the Ca2+ currents elicited by high-frequency action potentials were augmented depending on intracellular [Ca2+] on the terminal. The facilitation of synaptic transmission showed 4-5th power dependence on the Ca2+ current facilitation, and was abolished when the Ca2+ current facilitation was supressed. We conclude that short-term facilitation of Ca2+ currents predominantly mediates short-term facilitation at synapses between PCs. / 博士(理学) / Doctor of Philosophy in Science / 同志社大学 / Doshisha University

博士(理学) / Doctor of Philosophy in Science / 同志社大学 / Doshisha University

Phenotypic plasticity and developmental instability in leaf traits are common in oak species but the role of environmental factors is not well understood. To decipher possible correlations between different leaf traits and effects of the position of leaves within the tree canopy, we quantified the plasticity of three leaf traits of 30 trees of Quercus alba L., Quercus palustris Muench and Quercus velutina Lam. We hypothesized that trees could modify the shape of their leaves for better adaptation to the variable microclimate within the canopy. Our results demonstrated that the south and north outer leaves were significantly smaller, more lobed and denser than those situated in the inner canopy. The order of leaves on the branch accounted for the plasticity of leaf traits in Q. alba only. Plasticity of lobing in Q. alba and Q. velutina depended on the height of the trees. We detected fluctuating asymmetry (FA) in all three species, but the source of variation depended on branch position in Q. velutina only. FA was more pronounced in north-facing leaves. Plasticity of the leaf traits ranged from small to medium. Plasticity of leaf area and leaf mass per area (LMA) depended on the branch position. However, the plasticity of lobation was not affected by the location of a branch within the tree canopy. Quercus alba and Q. palustris had similar plastic responses but the plasticity of Q. velutina was significantly smaller. We concluded that individual plants detect and cope with environmental stress through vegetative organ modification.

No description available.

No description available.

The ability to adjust behaviors to a particular environment has been well documented across taxa. Our understanding of behavioral plasticity is largely based on experiments in which individuals have a single exposure to an environment. Observed behavioral changes are then traditionally measured in small windows of responsiveness in a single population or species. In this project I investigated the effects of prolonged exposure to predator cues in Gryllodes sigillatus and also tested for the presence of trans-generational effects of this prolonged exposure. I found there were no differences in anti-predator behaviors when measured in subsequent assays compared to control individuals. These results were paired with a comparison of differences in average expressions of behaviors, differences in variances, and behavioral correlations of five closely related cricket species, including G. sigillatus. Our results showed that species differ in average behaviors and plasticity but did not significantly differ in behavioral correlations.

The objective of this research was to compare the efficacy of portland cement to that of lime for improving the strength and durability of plastic clays. The scope of work associated with this research involved laboratory strength and durability testing of three plastic clays treated with portland cement or lime. To ensure a broad application of the work, the clays were obtained from three different regions of the United States, specifically from project sites near Bloomington, Indiana; San Antonio, Texas; and Monticello, Utah. Laboratory testing included evaluation of selected properties of the three clays in the untreated condition and in the treated condition. For the untreated condition, testing included measurements of soluble sulfate concentration, analysis of particle-size distribution, determination of treatment concentration using the Eades and Grim test, determination of Atterberg limits, development of moisture-density relationships, and measurement of California bearing ratio. In the treated condition, each clay sample was treated with either portland cement or lime, and testing included determination of Atterberg limits, development of moisture-density relationships, measurement of unconfined compressive strength (UCS), evaluation under wet-dry cycling, and evaluation under freeze-thaw cycling. For each of the three clay types, statistical analysis was performed to compare the strength and durability of the cement-treated specimens and the lime-treated specimens at each treatment concentration. Across all three clays, lime-treated specimens exhibited greater reductions in the plasticity index when compared to cement-treated specimens. In general, increased treatment concentrations corresponded to increased strength and strength retention. Percent strength retention of the cement-treated specimens was higher, on average, than that of the lime-treated specimens for the Indiana and Texas clays at low and medium concentrations. Similar strength retention was observed for cement-treated specimens and lime-treated specimens at high stabilizer concentrations across all three clays. In general, similar or significantly higher strengths were observed for specimens treated with cement than specimens treated with lime after 7 days, 28 days, and freeze-thaw cycling. Cement-treated specimens retained similar or greater mass after wet-dry cycling than lime-treated specimens. Cement-treated specimens also retained similar or greater strength after freeze-thaw cycling than lime-treated specimens, except for the Texas clay treated at the high concentration and the Utah clay treated at the medium concentration.