Sun, Guanqing. / Thesis (M.Phil.)--Chinese University of Hong Kong, 2011. / Includes bibliographical references. / Abstracts in English and Chinese. / 摘要 --- p.I / ABSTRACT --- p.III / TABLE OF CONTENTS --- p.V / ACKNOWLEDGEMENT --- p.VIII / CHAPTER 1 --- p.1 / Chapter 1.1 --- Definition of Emulsions --- p.1 / Chapter 1.2 --- Emulsion Instability --- p.3 / Chapter 1.3 --- Stabilization of Emulsions by Surfactants --- p.6 / Chapter 1.4 --- Types of Emulsions --- p.8 / Chapter 1.5. --- Particle-Stabilized Emulsions (Pickering Emulsions) --- p.10 / Chapter 1.5.1 --- The Adhesion of Colloidal Nanoparticles at an Interface --- p.10 / Chapter 1.5.2 --- An Overview of Particle-Stabilized Emulsions --- p.13 / Chapter 1.5.3 --- Particle-Stabilized HIPEs --- p.16 / Chapter 1.6 --- Objective of the research --- p.17 / Chapter 1.7 --- References --- p.18 / CHAPTER 2 --- p.21 / Chapter 2.1 --- Introduction to Particle-Stabilized HIPEs --- p.21 / Chapter 2.2 --- Experimental Part --- p.22 / Chapter 2.2.1 --- Materials --- p.22 / Chapter 2.2.2 --- Polystyrene-co-PMAA Particle Synthesis and Characterization --- p.23 / Chapter 2.2.3 --- Particle-Stabilized Emulsion Preparation and Characterization --- p.26 / Chapter 2.3 --- Results and Discussion --- p.27 / Chapter 2.3.1 --- pH-Triggered Inversion --- p.27 / Chapter 2.3.2 --- Salt-Triggered Inversion --- p.31 / Chapter 2.3.3 --- Phase Diagram and Rhcological Properties --- p.34 / Chapter 2.4 --- Conclusions --- p.38 / Chapter 2.5 --- References --- p.38 / CHAPTER 3 --- p.40 / Chapter 3.1 --- Introduction --- p.40 / Chapter 3.2 --- Experiments and Discussion --- p.42 / Chapter 3.2.1 --- Materials --- p.42 / Chapter 3.2.2. --- PS-co-AEMH Particles Synthesis and Characterization --- p.42 / Chapter 3.3.3 --- Particle-Stabilized Emulsion Formation --- p.45 / Chapter 3.3 --- Conclusions --- p.45 / Chapter 3.4 --- References --- p.46 / FUTURE PERSPECTIVES --- p.47 / PUBLICATION --- p.48

DNA single strand breaks (SSBs) are one of the most common lesions to genomic DNA, arising from various endogenous and exogenous sources. Single strand break repair (SSBR) constitutes a biochemical pathway whereby SSBs are detected, enzymatically processed and ligated. Whilst the general mechanisms of SSBR are relatively well described in vitro, there are remaining questions concerning how the pathway operates in vivo. For example, an early step in SSBR is thought to be the poly(ADP-ribose) polymerase (PARP)-dependent modification of SSB-proximal proteins with ADP-ribose, which is a signal for the recruitment of downstream repair factors, including the central scaffold XRCC1. Yet, the presence of multiple DNA-dependent PARP genes (PARP1, PARP2 and PARP3) has caused confusion regarding their specific roles in SSBR. This thesis potentially clarifies some contentious aspects of PARP function in the repair of SSBs induced by reactive oxygen species (ROS) and by Topoisomerase 1 (Top1). By employing PARP1-/-/PARP2-/- cells generated herein using CRISPR-Cas9 technology, in combination with preextraction immunofluorescence imaging and high-content analysis, I demonstrate that both PARP1 and PARP2 contribute towards ROS-induced ADP-ribosylation and XRCC1 chromatin-localization, but that in response to Top1-SSBs, these functions are specifically supported by PARP1 alone. Furthermore, using TDP1-/- and XRCC1-/-/TDP1-/- cells also generated herein, I characterize a striking hyper-ADP-ribosylation phenotype in response to Top1-SSBs. The clinical significance of this was confirmed by co-workers, who observed a similar phenotype in an XRCC1-deficient patient, where mutations in XRCC1 underlie a novel cerebellar neurodegenerative disease. This phenotype could be utilized in future to screen for genes with novel functions in SSBR. Finally, I investigate the functional implications of disrupted SSBR genes for rates of repair and cellular viability using alkaline single-cell electrophoresis and clonogenic survival assay. In doing so, I unexpectedly discovered that deletion of PARP1 suppresses CPT-induced comet tail moments of WT and XRCC1-/- cells.

Faculty of Science 0207022d / The United Arab Emirates (UAE) is a country that has developed rapidly over the past thirty years. Future development is going to be hampered by the enormous shortage of fresh water in the country. It is critically important that a strategic management plan for water resource management be developed to avoid a water crisis for the population and environment. The first step in managing water resources is to understand the sources and sinks of fresh water. Clearly, one of the most important sources of water to any environment is precipitation and the atmospheric processes and characteristics that promote or diminish the likelihood of rainfall over an area. The synoptic circulation of a region, as well as the thermodynamic structure of the atmosphere, are important for both frontal and convectively activated rainfall. In the past little detailed research has been conducted over the UAE and surrounding regions to classify and characterise atmospheric processes. This study represents the first attempt to develop a synoptic circulation climatology for the region. Synoptic circulation patterns have been classified at both the surface and 500 hPa layer over a period of seven years (1995-2001). In addition, the UAE is located under the descending limb of the Hadley circulation. As in other parts of the globe, this has severe implications for the vertical thermodynamic structure of the atmosphere. Atmospheric stability over the UAE has been evaluated for the period of seven years. The implications of descending air have been determined with respect to the thermodynamic structure of the atmosphere as a function of time and space. Vertical Radiosonde data collected over the same seven year period at the Abu Dhabi International Airport have been analysed to determine the frequency of occurrence and nature of absolutely stable layers in the atmosphere. Six circulation patterns that dominate the flow at both the surface and in the upper atmosphere at 500 hPa have been identified from the synoptic climatology. The dominant circulation pattern at the surface and upper atmosphere are the Siberian high and the Subtropical high, respectively. The Siberian high occurs at the surface predominantly during the winter season with a maximum frequency of occurrence in January (48%). The Subtropical high occurs in the upper atmosphere throughout the year, however, it is dominant during the summer months occurring 80 % of the time in August. Absolute stable layers are a permanent feature of the atmosphere over the UAE. A maximum of six layers have been identified in the atmosphere at a given time. Surface inversions occur throughout the year. Absolute stable layers have been identified at 850, 700, 600, 500 and 400 hPa. The surface inversions as well as the layers at 850 and 700 hPa have a distinctly seasonal pattern of occurrence. The absolute stable layers at the remaining pressure layers do not vary significantly with season. The surface and 600 hPa layers are by far the most dominant in the atmosphere and certainly have the most important control on vertical movement and accumulation of pollutants in the atmosphere.

Necessary conditions for stability of coupled autonomous vehicles in R are established in this thesis. The focus is on linear arrays with decentralized vehicles, where each vehicle interacts with only a few of its neighbors. Decentralized means that there is no central authority governing the motion. Instead, each vehicle registers only velocity and position relative to itself and bases its acceleration only on those data. Explicit expressions are obtained for necessary conditions for asymptotic stability in the cases that a system consists of a periodic arrangement of two or three different types of vehicles, i.e. configurations as follows: ...2-1-2-1 or ...3-2-1-3-2-1. Previous literature indicated that the (necessary) condition for stability in the case of a single vehicle type (...1-1-1) held that the first moment of certain coefficients of the interactions between vehicles has to be zero. Here, we show that that does not generalize. Instead, the (necessary) condition in the cases considered is that the first moment plus a nonlinear correction term must be zero.

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The effectiveness of the passive anti-roll tank system aboard the R/V YAQUINA was determined. Measurements of ship roll, effective waveslope and tank water transfer were analyzed using a systems analysis technique. Time series of the inputs and outputs of the ship/tank system and of the tank itself were processed using spectral analysis methods in order to obtain system transfer functions for stabilized and unstabilized configurations. Comparison of these transfer functions showed that the anti-roll tank system has a significant and beneficial effect on the rolling performance of the vessel. / Graduation date: 1971

Intuitively, we expect that averaging --- or bagging --- different regressors with low correlation should smooth their behavior and be somewhat similar to regularization. In this note we make this intuition precise. Using an almost classical definition of stability, we prove that a certain form of averaging provides generalization bounds with a rate of convergence of the same order as Tikhonov regularization --- similar to fashionable RKHS-based learning algorithms.

It is critical to consider the balance between the catalytic capabilities of an enzyme and the inherent structural stability of the protein when developing enzymes for specific applications. Rational site directed mutagenesis has been used to explore the role of residues 254 and 257 in the global stability and catalytic specificities of organophosphorus hydrolase (OPH, EC 3.1.8.1). Substitution of residues H254 and H257, which are located near the active site, had a marked effect on both the global stability and substrate specificity of the enzyme. For example, the for the double mutation CoTGΔ2+ H254R H257L (RL) enzyme variant was 19.6 kcal/mol, 5.7 kcal/mol less than that of the wild type enzyme. At the same time, the altered enzyme was catalytically more effective against VX and VR (Russian VX), as compared to the wild type enzyme. Limited proteolysis verified the importance of residues 254 and 257 for functional stability, evidenced by enhanced resistance to irreversible unfolding associated with thermal denaturation. It has been possible to construct third generation OPH variants, which are more stable than the wild type enzyme, with a 10 °C increase in the apparent melting temperature (TM app), yet retained desirable catalytic properties. It appeared that aromatic stacking and cation-π interactions involving near active site residues not only affected activity but significantly contributed to the chemical and thermal stability of OPH. Rational design was used to develop an enzyme with an optimized orientation on a catalytically active biosensor surface. In these studies, lysine side chains located on the surface of OPH were used to create attachment sites to a surface plasmon resonance sensor resulting in an ensemble of enzyme orientations. Some of these orientations could be functionally restrictive if the active site is oriented toward the sensor surface. Substitution of a lysine near the active site resulted in 20% more activity with 53% less enzyme immobilized, thus increasing the specific activity of the decorated surface 2.5 fold.

Copper is a widely used conductor in the manufacture of printed wiring boards (PWB). The trends in miniaturization of electronic devices create increasing challenges to all electronic industries. In particular PWB manufacturers face great challenges because the increasing demands in greater performance and device miniaturization pose enormous difficulties in manufacturing and product reliability. Nanocrystalline and ultrafine grain copper can potentially offer increased reliability and functionality of the PWB due to the increases in strength and achievable wiring density by reduction in grain size. The first part of this thesis is concerned with the synthesis and characterization of nanocrystalline and ultra-fine grain-sized copper for potential applications in the PWB industry. Nanocrystalline copper with different amounts of sulfur impurities (25- 230ppm) and grain sizes (31-49nm) were produced and their hardness, electrical resistivity and etchability were determined. To study the thermal stability of nanocrystalline copper, differential scanning calorimetry and isothermal heat treatments combined with electron microscopy techniques for microstructural analysis were used. Differential scanning calorimetry was chosen to continuously monitor the grain growth process in the temperature range from 40C to 400C. During isothermal annealing experiments samples were annealed at 23C, 100C and 300C to study various potential thermal issues for these materials in PWB applications such as the long-term room temperature thermal stability as well as for temperature excursions above the operation temperature and peak temperature exposure during the PWB manufacturing process. From all annealing experiments the various grain growth events and the overall stability of these materials were analyzed in terms of driving and dragging forces. Experimental evidence is presented which shows that the overall thermal stability, grain boundary character and texture evolution of copper is greatly related to changes in driving and dragging forces, which in turn, are strongly depended on parameters such as annealing temperature and time, total sulfur impurity content and the distribution of the impurities within the material. It was shown that a simple increase in the sulfur impurity level does not necessarily improve the thermal stability of nanocrystalline copper.