published_or_final_version / Ecology and Biodiversity / Doctoral / Doctor of Philosophy

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Hong, Wei = 膠體玻璃化相變的實驗及理論研究 / 洪偉. / Thesis (M.Phil.)--Chinese University of Hong Kong, 2011. / Includes bibliographical references (leaves 89-91). / Abstracts in English and Chinese. / Hong, Wei = Jiao ti bo li hua xiang bian de shi yan ji li lun yan jiu / Hong Wei. / Abstract --- p.i / Chapter 1 --- Introduction --- p.1 / Chapter 1.1 --- Experimental background --- p.2 / Chapter 1.1.1 --- What is a colloidal system? --- p.2 / Chapter 1.1.2 --- Single particle diffusion --- p.5 / Chapter 1.1.3 --- Inter-particle interaction --- p.9 / Chapter 1.1.4 --- Colloidal phase transition --- p.14 / Chapter 1.2 --- Glass transition --- p.16 / Chapter 1.2.1 --- Vibrational modes --- p.18 / Chapter 1.2.2 --- Dynamics --- p.21 / Chapter 2 --- Experimental setup and methods --- p.29 / Chapter 2.1 --- Sample and setup --- p.29 / Chapter 2.1.1 --- Sample preparation --- p.29 / Chapter 2.1.2 --- Setup --- p.32 / Chapter 2.2 --- Resolution enhancement --- p.36 / Chapter 2.2.1 --- Alignment --- p.36 / Chapter 2.2.2 --- Lens resolution --- p.37 / Chapter 2.2.3 --- Lens combination --- p.38 / Chapter 2.2.4 --- LED light source and filter --- p.39 / Chapter 2.3 --- Image preprocessing --- p.42 / Chapter 2.3.1 --- Background subtraction --- p.42 / Chapter 2.3.2 --- Noise filter --- p.43 / Chapter 2.3.3 --- Particle recognition and tracking --- p.45 / Chapter 2.3.4 --- Dedrift --- p.47 / Chapter 3 --- Measurement --- p.50 / Chapter 3.1 --- Dynamical characteristics --- p.50 / Chapter 3.1.1 --- Mean squared displacement --- p.50 / Chapter 3.1.2 --- Diffusion coefficient versus area fraction --- p.56 / Chapter 3.2 --- Structural characteristics --- p.58 / Chapter 3.2.1 --- Pair correlation function --- p.58 / Chapter 3.2.2 --- Cluster statistics --- p.62 / Chapter 4 --- Dynamical heterogeneity and structural properties --- p.67 / Chapter 4.1 --- Dynamical heterogeneity --- p.67 / Chapter 4.2 --- Structural properties --- p.71 / Chapter 4.2.1 --- The general picture --- p.71 / Chapter 4.2.2 --- Identification of the slow particles --- p.72 / Chapter 4.2.3 --- Growing clusters of slow particles --- p.80 / Chapter 5 --- Discussion --- p.81 / Chapter 5.1 --- Percolation model --- p.81 / Chapter 6 --- Summary and conclusion --- p.87 / Bibliography --- p.89

As a study organism, annual killifish (Austrofundulus limnaeus) provide a well suited study system for examining the effects of environmental temperature fluctuations at the cellular level. A. limnaeus persist in the harsh high desert climate of the Maracaibo Basin, Venezuela where they live in small, ephemeral freshwater pools. Temperatures in these waters can vary as much as 20 degrees C daily and reach maximums of over 40 degrees C due to the semi-arid climate. Previous cDNA microarray studies on killifish revealed the mRNA pattern for High Mobility Group Protein 1 (HMGB1) to be strongly affected by temperature perturbations. Specifically, peaks in hmgb1 transcript abundance were negatively correlated with temperature during temperature cycling, and experienced over a 10 fold difference in expression in response to the temperature cycle. Using the same temperature cycling experimental setup, this study's aim was three-fold: (1) to characterize the total amount of HMGB1 protein in adult male killifish livers, (2) to describe the subcellular localization of the HMGB1 protein in adult male killifish livers and (3) to sequence the 5' upstream region of the hmgb1 gene to identify possible stress responsive elements. We detected no significant difference in total HMGB1 protein levels as a consequence of temperature cycling. The data for subcellular localization of HGMB1 protein do not support a strong change in subcellular localization of the protein in response to temperature cycling; most of the HMGB1 protein is found in the cytoplasmic compartment in liver tissue. Although overall patterns of subcellular localization did not change significantly, we found a significant difference between nuclear HMGB1 protein levels in temperature cycled fish versus control (constant temperature) fish. This could suggest a muting of the natural translocation of HMGB1 into the nucleus observed in control fish at around 9:00 at night. Finally, the upstream region of the hgmb1 gene does reveal a number of putative stress responsive transcription factor binding sites.

Controlling the placement and hydration temperature of concrete is important to concrete durability. Thermal gradients and delayed ettringite formation (DEF) result in cracking when concrete in the plastic state becomes too hot. Cooler placement temperatures slow hydration reaction, increase working time, reduce the maximum temperature in the concrete member, and reduce thermal gradients. Furthermore, cooler concrete achieves better long-term strength and microstructural development. Concrete producers have been using multiple methods of reducing the placement temperature of concrete, such as cooling mixtures with ice or chilled water, shading aggregate piles, placing concrete at night, and using evaporative cooling of aggregate piles. More recently, concrete producers have turned to liquid nitrogen for cooling fresh concrete. The objective of this research was to determine the effects of liquid nitrogen on concrete hydration, microstructural development, and performance. The following concrete mixture properties and methods were investigated: cement type, the effects of selected supplementary cementing materials and chemical admixtures, placement temperature, and the time at which liquid nitrogen dosing occurs (delayed dosing). Concrete performance was tested in terms of slump, setting time, yield, compressive and splitting tensile strength, elastic modulus, rapid chloride permeability, and hardened and fresh air void analysis. Hydration and microstructural development were monitored by isothermal calorimetry, semi-adiabatic calorimetry, x-ray diffractometry, inductively coupled plasma, and environmental scanning electron microscopy. Additional testing was performed on concrete mixing drums to determine the effects of liquid nitrogen on the durability of steel mixing drums. The results indicate that performance, hydration, and microstructural development of fresh concrete are relatively unaffected when cooled with liquid nitrogen to room temperatures. Significant findings show that the slump of liquid nitrogen cooled concrete is similar to hot concrete mixtures and not room temperature mixtures. Additionally, setting time results show that liquid nitrogen dosing of hot concrete can be delayed for up to 1 hour and setting times will still be similar to room temperature mixtures. Based on findings from this research study, liquid nitrogen is recommended as a primary cooling option to reduce the placement temperature of fresh concrete.

published_or_final_version / Civil Engineering / Master / Master of Philosophy

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Thesis (M.S.)--University of Hawaii at Manoa, 2006. / Includes bibliographical references (leaves 62-70). / ix, 70 leaves, bound ill. 29 cm