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Block copolymers have attracted interests for potential application ranging from dynamic photonic sensors to solid-state ion conductors. However, due to nucleation and growth mechanism, block copolymer inherently forms granular microstructure with defects such as grain boundaries. Understanding the microstructure of block copolymer is thus crucial in many applications because the microstructure determines the transport property of functional fillers such as ions in block copolymer template. Previous research has shown that athermal filler segregated to grain boundary of lamellae block copolymer and retards the grain coarsening. However, the kinetics of this grain boundary segregation during thermal annealing has not been revealed. Polystyrene-b-polyisoprene blended with deuterated polystyrene is used for neutron scattering study on studying the kinetics of grain boundary segregation. Deuterated polystyrene will segregate to grain boundaries, therefore, decorate grain boundary. The filler segregation behavior will be studied by comparing neutron scattering of polystyrene-b-polyisoprene/deuterated polystyrene with different annealing times (at T=130 deg C, duration of 0hr, 3hr, 1day, 3day and 7day, respectively). Invariant (Q) analysis along with grain mapping is conducted to quantitatively analyze the kinetics of grain boundary segregation. This kinetic was in good agreement with the McLean’s kinetic model for grain boundary segregation in metals. By applying Langmuir-Mclean’s segregation isotherm equation, we have predicted the equilibrium concentration of filler in grain boundary by calculating the strain energy stored in grain boundary.

Seed development, germination and dormancy, considered as the most important phenomena in seeds, are regulated by several plant hormones; gibberellin (GA) and abscisic acid (ABA) being the major players acting antagonistically. The regulation of these seed related processes by GA and ABA is dependent partly on the endogenous levels of the two hormones, which in turn are determined by the balance between their biosynthesis and catabolism. This thesis investigated the spatial and temporal expression patterns of several members of the GA and ABA biosynthetic and catabolic gene families during grain development using a non-dormant cultivar and during imbibition using grains collected from dormant and non-dormant cultivars of barley. In addition, the thesis examined the effect of exogenous ABA treatment, and after-ripening of seeds collected from dormant cultivars on the expression patterns GA and ABA metabolism genes during grain development and imbibition, respectively. The results suggest that specific members of the gene families related to the metabolic pathways of the two hormones exhibit distinct spatial and temporal roles in the regulation of barley grain development, dormancy and germination. / October 2015

Typescript. / Digitized by Kansas Correctional Industries

Thesis (M. Sc. (Agricultural Management)) -- University of LImpopo, 2002 / Refer to document / NRF (National Research Foundation) and WRC (Water Research Commission)

This thesis is concerned with an investigation into current on-farm grain storage practice and with ascertaining what educational interventions, if any, are appropriate for future and more detailed consideration. The Australian grain growing, handling, and marketing industry has changed in recent times. A few years ago (1989), the grain growers only essential contact with grain marketing was through the bulk handling authorities and the Australian Wheat Board. Advice was freely available from state departments of agriculture, and the only requirement to store grain on-farm was that necessary for the grower's own needs. Now (1994), there is a possible advantage that grain stored on-farm may be used for a wide range of selling options, amongst other reasons, and market requirements are much more complex and stringent. There is a substantial body of research on grain storage techniques. At the same time there is a significant gap between researched knowledge and the use of this knowledge for on-farm storage. A major purpose of this study is to identify an improved approach to extension and farmer education that may help to reduce this gap. This thesis contains a review of the general literature on extension followed by an overview of extension in the developed world to establish the international context for Australia. Then the historical context of extension is examined briefly to understand the current situation in each state. Some educational models are reviewed to identify relationships between stakeholders and the opportunities available for and constraints to development of educational strategies. Information channels are reviewed to comprehend extension interaction and grain storage technologies are reviewed to ensure comprehension of techniques. On the basis of the literature review a field study was designed to investigate current on-farm storage practice, current extension sources for storage information and preferences for future educational interventions. This was done by a survey using a stratified random sample of grain growers and cluster selection of individuals for personal interviews. This information was complemented by informal discussion with farmers at field days. The results of the study confirmed the gap between research knowledge and on-farm implementation of this knowledge. They also demonstrated that grain growers wanted more information and gave some indicators of how this might be achieved. Major findings of the research included the need for extension coalitions and the desirability for active involvement of the grain grower. Major conclusions, for on-farm storage and extension, are drawn to form a basis for development of future extension interventions. These are aimed at ensuring grain growers have available the information needed for good storage practice. This includes an essential understanding the grain growers' needs and perceptions, early, in any planning process. It also includes the necessity for coordination of extension/education activities at local, regional and national levels. The research has some major implications for an improved approach to extension and on-farm storage. These include the establishment of a farmers-as-researcher program to implement grain storage innovations and the recognition that implemented change will need long term maintenance; often more resource intensive than the original intervention.

No description available.

Changes in the federal farm program, in rainfall pattern and quantity, and increased incidence of herbicide resistant weeds and diseases have generated increased interest in spring grains in the Pacific Northwest. However, spring grains have traditionally been treated as minor crops in this region, thus little research has been done on them. Complicating the situation is the diversity in spring growing conditions as well as crops grown. This study was conducted to a) assess the impact of seeding date on the growth and development of the spring grains and b) to determine the differences or extent of differences among genetically diverse grains. Planting date and cultivar had significant effects on number of leaves and tillers as well as dry matter production. The differences among planting dates were mainly as a result of variations in temperature, though soil moisture was of significance in some cases. Among the cultivars, Alpowa had a high tillering rate, while Westbred936 was poor. The leaves of the cultivars generally emerged at a constant rate (with a few exceptions) within a given planting date, but rates differed among planting dates. Though significant differences in rate of leaf emergence were observed among cultivars, rate of leaf emergence in wheat as a group was not significantly different from that of the barley or oat cultivar evaluated. Phyllochron decreased with later sowing in only the first year. In the second year, no consistent increase or decrease in phyllochron with planting date was observed. Rate of dry matter production followed an inverse quadratic polynomial trend. Rate increased slowly during early growth and later rising sharply as plant matured regardless of planting date. Among the cultivars, barley plants showed clear superiority in dry matter accumulation. This is likely the reason why barleys seemed to show superior growth to all the other cultivars. A relationship between vegetative growth and grain yields was observed; however, assimilate redistribution was also found to play significant role. Results obtained were a clear reflection of differences in environmental conditions for each year. / Graduation date: 2000

Revised

No description available.