We investigate evolution of mountain channel morphology and riverbed surface roughness by conducting laboratory experiments. The experimental flume is 4m long by 0.1m wide with a working length of 2.5m. We control initial sediment size distribution, flume slope, water discharge, and sediment feed rate. Measurements include topographic profiles, flow depth, surficial grain-size distribution, sediment transport rate, and sediment size distribution. Experiments begin with a gravel bed of a broad sediment size distribution, at two initial flume slopes: 8.2% and 12.4%. Discharge is held constant until transport rates and topographic changes indicate the system is at near steady state. Coarse sand is then fed into the channel at 1,000 g/min as a means to perturb the system. Sediment feed is held constant until the perturbed bed reach steady-state conditions. The feed is subsequently ceased and measurements continue until sediment transport rates and topography stabilize. These laboratory experiments provide first-hand observations of channel systems evolving after perturbations. Transport rates decay exponentially following perturbations and remain very low when the channel bed is stabilized. The introduction of coarse sand acts to smooth the channel bed by filling in topographic lows in the 8.2% sloped channel. At a 12.4% slope, increased mobility of sand allows steady state conditions to be met with little smoothing of the bed. The sand also increases the mobility of coarser sediment that was previously stable, likely due to local surface smoothing at grain scale. The increased fraction of surface sand cover maintains increased scouring and mobilization of coarser grains. These post-perturbation mechanisms are interpreted to be responsible for topographic adjustments as the system readjusts towards new steady-state conditions. Surface sorting and transporting distributions reflect high sand fractions well after perturbations have ceased. This suggests that brief pulses of fine sediment can increase coarse sediment mobility for prolonged periods. / text

Folivores do not exhibit a direct relationship between group size and daily path length and are consequently believed to experience little feeding competition. However, previous studies lacked sufficient control for ecological variation and did not account for the underlying hierarchical structure inherent in closely related taxa (phylogeny). The present analysis examined daily path length and relative ranging cost in 37 primate species, including 18 folivores, while controlling for ecological variation and phylogeny. Group size effects on group spread, changes in activity budget, and infant to female ratios were similarly investigated as these have been found to indicate feeding competition in folivorous primates. Although relative ranging cost was a not a significant predictor of folivore group size, large groups traveled significantly farther per day, increased group spread per individual, and had lower infant to female ratios than small groups. Large groups spent more time feeding and less time resting than small groups; however, these trends were not significant. A strong phylogenetic signal was detected among species’ mean values for average group size (λ = 0.827). Because primate group size and behavior represent the combination of adapting to present-day environments and phylogenetic inertia, future comparative analyses of feeding competition should account for both current ecological conditions and the phylogenetic signals inherent in the taxa being compared. As suggested by the current study, folivorous primates may utilize a number of foraging strategies, other than increasing daily path length, to alleviate feeding competition. To better assess feeding competition, future research should include alternative correlates of feeding competition such as increased group spread, changes in activity budgets, and decreased female fecundity. The information gained from such research may improve our current interpretations of the ‘folivore paradox’ and redefine the competitive regime of leaf eating primates. / text

The infraorbital nerve (ION) transmits sensory information from mechanoreceptors of the upper lip and vibrissae (whiskers) to the brain via the infraorbital foramen (IOF). Vibrissae are special sensory hairs used by mammals to explore their surroundings. Researchers have used the size of the IOF to infer vibrissa count, which in turn has been incorporated into phylogenetic and ecological interpretations of fossil taxa. However, these interpretations are based on untested assumptions linking IOF size, ION size, vibrissae, and ecology. The purpose of this dissertation is to determine the functional significance of IOF size and to apply the results to the fossil record. It is hypothesized that ecological differences among mammals affects maxillary mechanoreceptivity (touch sensitivity of the rostrum), and that IOF area may be used as a measure of maxillary mechanoreceptivity. Three questions are posed to appraise this hypothesis: (1) Does IOF area correlate with ION area and vibrissa count? (2) How do the IOFs of primates differ from those of other mammals? (3) How do diet, substrate preference, and activity pattern affect IOF size? IOF area, ION area, and vibrissa count were collected from cadaver of extant mammals as well as museum osteological specimens. Results indicate that: (1) IOF and ION areas show a strong positive correlation. Based on this finding, it is hypothesized that IOF area may be a good measure of maxillary mechanoreception. (2) Vibrissae count significantly correlates with IOF area. (3) Euarchontans have relatively smaller IOFs than most other mammals. (4) The IOFs of primates co-vary with diet, where frugivores have relatively larger IOFs than both insectivores and folivores. Infraorbital foramen areas of 14 adapoid, six omomyoid, and 15 plesiadapiform species were measured. Two questions were addressed: (1) Do the sampled fossils share a similar reduction in IOF area to extant primates? (2) Do extinct frugivores have larger IOFs than insectivores and folivores? Results show that, adapoids and omomyoids have relatively small IOFs similar to euarchontans, but plesiadapiforms retain larger IOFs, comparable to most non-euarchontan mammals. Dietary analyses indicate that both frugivorous adapoids and omomyoids have larger IOFs than both insectivorous and folivorous species. / text

Within a polymer thin film, free-volume elements have a wide range of size and topology. This broad range of free-volume element sizes determines the ability for a polymer to perform molecular separations. Herein, the free volume and transport properties (diffusion, permeability, and selectivity) in both rubbery and glassy polymers were simulated using fully atomistic models. Extension of the computational tool to study the void structure in proteins is also included in this thesis. Six permeable thermally rearranged (TR) polymers and their precursors were studied. Using atomistic models, cavity size (free volume) distributions determined by a combination of molecular dynamics and Monte Carlo methods were consistent with experimental observation that TR polymers are more permeable than their precursors. The cavity size distributions determined by simulation were also consistent with free volume distributions determined by positron annihilation lifetime spectroscopy. The diffusion, solubility and permeation of gases in TR polymers and their precursors were also simulated at 308 K, with results that agree qualitatively with experimental data. A new hybrid Monte Carlo/Molecular Dynamics method is developed for estimating the slow diffusion processes of light gases transporting in glassy polymers. Diffusion coefficients, as small as 10⁻⁵ to 10⁻⁹ cm²/s are estimated for penetrants in four different polymers at 298 K. In all cases, agreement between literature experimental data and values obtained from the fast hybrid molecular dynamics method ranges from good to excellent. A new technique is developed using Monte Carlo methods to characterize the cavity size distribution and surface atoms in globular proteins. New statistical metrics have been defined for the structural characterization of globular proteins. Some of these metrics include volume, surface area, asymmetry ratio, interior cavity size distribution, and the identification of percolation channels. Wild-type (WT) myoglobin (Mb) and 5 Mb mutants have been studied in this research as examples. An analysis of cavity statistics provides an efficient method to quantify local properties such as packing density and transport pathways. The average cavity sizes of WT Mb and its mutants are around 4.0-5.0 Å. / text

published_or_final_version / Politics and Public Administration / Master / Master of Public Administration

In the recent decade or so, the phenomenon of enrollment decline of secondary schools has been clearly observed in Hong Kong. The significance of this phenomenon has grown over time such that the number of public sector schools has had to be reduced. Meanwhile, an alternative to school closure is to reduce the class size of schools which is however not less controversial. On the surface, the arguments against class size reduction include perceived extra cost per student and ineffectiveness of small class teaching in secondary schools. Hidden in the agenda of the Government could be, arguably, the political difficulty to reverse such class size reduction trend when the enrollment rebounds eventually. This dissertation reviews how the Government has reacted to the changing situation and developing public concern on the issue, and cautiously evaluates the effectiveness of the Government’s responses. Then, this dissertation explores the literature in public administration in relation to school retrenchment policies, and hence addresses the Hong Kong case accordingly. Finally, recommendations are made along with rationale for the betterment of managing enrollment decline by means of controlled class size subject to a mechanism to be agreed on. In making these recommendations, it is hoped that the policy direction should point to the future, with an aim to look for positive management opportunities while solving problematic phenomenon at the same time. / published_or_final_version / Politics and Public Administration / Master / Master of Public Administration

Bread owes its appeal to its aerated structure which directly relies on the bubbles entrained into the dough during mixing. If the bubble size distribution (BSD) in the dough can be determined at the end of mixing, then the resulting loaf quality could be predicted before bread is fully manufactured. However, non-invasively monitoring the structure of a fragile opaque soft solid such as dough is challenging. This thesis addressed the challenge by determining dough’s BSD and its evolution using ultrasound and X-ray microtomography. Using a resonant scattering model and the frequency dependence of the ultrasonic parameters measured in the dough, the change in the BSD in dough (made without yeast) with time as a result of disproportionation was determined. At 30 min after mixing, the median radius (R0) of the lognormal BSD was 6.5 microns. Converting the BSD to the radius dependence of bubble volume fraction (BVF(R)), R0V (the median radius of BVF(R)) was 66.4 microns and increased 18 % in the succeeding 90 min. In order to validate the bubble sizes determined ultrasonically, X-rays from a synchrotron source were utilized to examine dough’s microstructure. Large numbers of very small bubbles were discovered and it was apparent that lognormality did not describe the BSDs. Nevertheless, lognormal characterization of the BVF(R) was appropriate. At 30 min after mixing R0V of the BVF(R) was 32.5 microns and it increased by 20 % in the succeeding 90 min, supporting the ultrasonic quantification of bubble volume changes due to disproportionation. Changes in the mode, median and mean of the BVF(R) with time after mixing had the same trend for ultrasound and for X-ray microtomography. The time evolution of the mode of the BVF(R) obtained by ultrasound and X-ray microtomography matched very well; both increasing linearly as a function of time. Ultrasonic assessments of bubble sizes and their changes with time are very encouraging, but the ultrasonic model should use distribution functions that precisely define the empirical data, perhaps not making ‘pre-assumptions’ of lognormality for the BSD data. / February 2015

Malaria is a deadly disease that causes nearly one million deaths each year. Understanding the demographic history of the malaria parasite Plasmodium falciparum and the genetic basis of its adaptations to antimalarial treatments and the human immune system is important for developing methods to control and eradicate malaria. To study the long-term demographic history and recent effective size of the population in order to identify genes under selection more efficiently and predict the effectiveness of selection, in Chapter 2 we sequenced the complete genomes of 25 cultured P. falciparum isolates from Senegal. In addition, in Chapter 3 we estimated temporal allele frequencies in 24 loci among 528 strains from the same population across six years. Based on genetic diversity of the genome sequences, we estimate the long-term effective population size to be approximately 100,000, and a major population expansion of the parasite population approximately 20,000-40,000 years ago. Based on temporal changes in allele frequencies, however, the recent effective size is estimated to be less than 100 from 2007-2011. The discrepancy may reflect recent aggressive efforts to control malaria in Senegal or migration between populations.

A remarkable property of developing organisms is the consistency and robustness within the formation of the body plan. In many animals, morphological pattern formation is orchestrated by conserved signaling pathways, through a process of strict spatio-temporal regulation of cell fate specification. Although morphological patterns have been the focus of both classical and recent studies, little is known about how this robust process is modified throughout evolution to accomodate different morphological adaptations.

In this dissertation, I will look into the size distribution of silver nanoparticles produced by laser ablation of microparticles (LAM). I will investigate the role of both pulsed and continuously operating nozzles on the size distribution. In addition, I will examine any deviations from the previously observed log-normal size distribution for silver nanoparticles comparing previous collection techniques involving supersonic jet impaction with a current time of flight mass spectrometer (TOF-MS). These new observations will be made in situ using a Wiley-McLaren TOF-MS with a reflector and multiphoton ionization and will mainly focus on the smaller sized nanoparticles. An introduction to enhancing a second harmonic optically generated signal will also be investigated involving silver nanocomposites while utilizing a polarized crossed-beam femtosecond laser technique. / text