Railway track ballast fouling is an ongoing issue without a clear understanding regarding either the cause for generation or the source of the fouling materials. This study was conducted to determine what physical processes are likely causing ballast fouling, where in the track sub-structure fouling material is concentrating, and what factors affect the severity of ballast fouling. A field investigation on a CN railway track was conducted in Joliette, QC during undercutting maintenance operations. Data for in-situ ballast, sub-ballast, and subgrade samples were gathered from a series of trenches excavated through the track embankment. The geotechnical and mineralogical characteristics of a selected set of ballast samples were gathered through a regime of laboratory testing. Grain size distribution data for the select samples was collected from sieve and hydrometer testing. Three sets of LA abrasion tests were conducted on both in-situ and freshly quarried ballast rock to determine the degradation characteristics of the various ballast types. The petrographic analysis of the sample types was conducted using bulk hand sample characterization, thin-section analysis, and X-Ray Diffraction Analysis. The petrographic, grain size, and LA abrasion combined analysis indicated that ballast fouling was primarily caused through degradation of the ballast. The fouling material within the ballast pores was sourced to the abraded pieces of ballast that had degraded over time through XRD and grain size distribution analysis. It was found with statistical confidence that ballast layers with harder, structureless rock types have less fouling material form within the ballast void spaces compared to ballast rock types that are soft on the Mohs hardness scale or have planes of weakness due to structural factors. Analysis of the grain size data also showed that ballast fouling was generally concentrated within the section of the ballast layer directly underlying the steel rail, within the topmost parts of the ballast layers. Overall it was recommended that the effects of chemical degradation on ballast rock types and the historical operational duration of ballast be incorporated into future ballast fouling studies. / Thesis (Master, Geological Sciences & Geological Engineering) -- Queen's University, 2011-09-27 10:01:46.141

According to traditional theory, superior competitive ability in plants generally requires a relatively large plant body size. Yet, within natural, crowded vegetation, most resident species are small, and species size distributions are right-skewed at virtually all scales. I aim to provide a potential explanation for this paradox: small species are able to coexist with and outcompete larger species because smaller species have greater ‘reproductive economy’—the ability for some seed production despite severe size suppression when under intense competition. Tracey and Aarssen (2011) found an isometric relationship between minimum reproductive threshold size (MRTS) and maximum resident plant size (MAX); however, a more accurate measure of maximum potential body size (MPBS) was needed (without competition), as typically the effects of competition are size-dependent. An isometric relationship, similar to Tracey and Aarssen (2011) was seen. Tracey and Aarssen (2011) also found that, contrary to the predictions of traditional theory, larger species were not more abundant (based on plot occupancy) in an old-field community. A more accurate measure of abundance was obtained by locating random 1 x 1 m plots and counting the number of ramets for each species in the plot. A significant negative relationship was seen between abundance and MRTS. This suggests that the most abundant plants in communities are not those that are bigger, or smaller, they are those with the smallest MRTSs. To test whether this relationship exists in other habitats, plots were located in different old-field, shrub-land and wood-land communities. Ramets for each species within the plots were counted, and the largest plant of each species was measured. Significant negative relationships between abundance and MAX plant body size were seen in the shrub-land and woodland sites; however, no relationship was detected in this old-field site. The data support the idea that smaller species have greater reproductive economy, but the mechanism remains unknown. These results suggest that a smaller plant body size results in more effective gene transmission into future generations in all habitat types and stages of succession and indicates a suggested paradigm shift in the predicted selection effects of competition on the evolution of plant body size. / Thesis (Master, Biology) -- Queen's University, 2012-07-30 11:56:23.999

No description available.

Objective: The purpose of this study is to determine the relationship between cone beam CT (CBCT) voxel size and tooth root fracture detection. Materials and Methods: Vertical and horizontal root fractures were induced in a total of 30 teeth, and 15 teeth were left intact. Teeth were imaged with projection digital radiography and the Kodak 9000 3D CBCT system with a native voxel size of 76 μm. The CBCT voxels were then downsampled to 100 μm, 200 μm and 300 μm. Five blinded observers evaluated both sets of images with a 1 week washout interval between each set of observations. Results: CBCT outperformed the projection images for fracture detection for all voxel sizes except 300 μm (p<0.05). No significant differences were found between the different voxel sizes (p>0.05). Conclusion: Although voxel size does not impact the interpretation of root fractures, in vitro, CBCT outperformed projection imaging for voxel sizes less than 300 μm.

In this thesis, colloidal nanocrystalline silicon (ncSi) capped with allylbenzene (AB) groups, is created using a sol-gel method. This novel material, AB-ncSi, is size separated and its optical, structural, and electrical characteristics are investigated in detail. For optical characterization, the photoluminescence (PL) peak is located for each fraction of the nanoparticles to determine its diameter. The AB-ncSi samples have diameters ranging from 2.89 nm to 7.65 nm. Ellipsometry and scanning electron microscopy (SEM) are used to estimate the film thickness and average distance between the particles, respectively, for structural characterization. No correlation was found between AB-ncSi size and film thickness however the estimated average distance between the particles decreased with decreasing diameter. Finally, for electrical characterization, conductivity of size-separated samples is measured and the temperature dependent conductance is analyzed. The results emerging from these analyses suggest that the charge transport mechanism for AB-ncSi is nearest-neighbor hopping (NNH) albeit VRH is also a potential contributor.

In this thesis, colloidal nanocrystalline silicon (ncSi) capped with allylbenzene (AB) groups, is created using a sol-gel method. This novel material, AB-ncSi, is size separated and its optical, structural, and electrical characteristics are investigated in detail. For optical characterization, the photoluminescence (PL) peak is located for each fraction of the nanoparticles to determine its diameter. The AB-ncSi samples have diameters ranging from 2.89 nm to 7.65 nm. Ellipsometry and scanning electron microscopy (SEM) are used to estimate the film thickness and average distance between the particles, respectively, for structural characterization. No correlation was found between AB-ncSi size and film thickness however the estimated average distance between the particles decreased with decreasing diameter. Finally, for electrical characterization, conductivity of size-separated samples is measured and the temperature dependent conductance is analyzed. The results emerging from these analyses suggest that the charge transport mechanism for AB-ncSi is nearest-neighbor hopping (NNH) albeit VRH is also a potential contributor.

Our ability to predict community responses to environmental stress remains limited. To address this issue, I investigated how species abundance, community composition and food-web structure varied across abiotic gradients (principally disturbance and habitat size) in New Zealand streams. In surveys, community composition, biomass and richness were all strongly influenced by flood-related habitat disturbance, although disturbance influenced each trophic level via different mechanisms. Experiments indicated that macroinvertebrate prey communities were primarily structured by physical disturbance effects, whereas predatory fish communities were structured by physical disturbance effects and disturbance-mediated changes to prey communities. Prey community biomass and composition affected fish species identity and abundance and an in situ stream channel experiment suggested that prey communities were structured by trade-offs between resisting biotic interactions in physically stable environments and successfully exploiting highly disturbed habitats. The prey community traits associated with different disturbance regimes then directly influenced the composition and predatory impact of the resultant fish communities. In addition to disturbance-mediated biotic interactions, abiotic gradients also provided strong selection pressures on predatory fish communities. In particular, disturbance and habitat size strongly influenced predator community responses (e.g., biomass and maximum body size) in surveys and experiments. However, a habitat’s capacity to support predator community biomass was largely determined by its size. Food-web structure changed with habitat size; small streams supported more prey than predator biomass, whereas large streams had inverted biomass pyramids (i.e., more predator than prey biomass). Similar relationships between food-web structure and habitat size were found in grassland and forested streams, but terrestrial invertebrate subsidies meant that forested streams supported more predator biomass per unit area than grassland stream food webs. My results indicate that human actions resulting in habitat loss (e.g., water abstraction or river impoundment) and increases in flood-related disturbance events (e.g., climate change) are likely to have significant impacts on stream food webs, ultimately leading to habitats that support smaller fish communities (i.e., less biomass, smaller body size). This means that ecologists and managers will need to consider the separate, interactive and indirect effects of disturbance and habitat size on ecological communities if we are to accurately predict and manage food-web responses to global environmental change.

The Cameroon Highlands that run along the Cameroon-Nigeria border are an important source of biodiversity. Not only are they rich in species and high in endemics, but biota from West Africa have not been studied as extensively relative to other parts of the Afrotropics, or the tropics in general. Threatening these rare and diverse habitats is anthropogenic pressure, which fragments forests and changes local animal communities. This thesis wished to address the impact of humans on seed dispersal and recruitment processes on selected tree species in forests on the Mambilla Plateau - a montane region in Nigeria's north-east. Research was conducted at Ngel Nyaki Forest Reserve, a conservation area established by the Nigerian Montane Forest Project. The reserve comprises a moderately-large forest patch (Ngel Nyaki Forest) and many small riparian fragments embedded in a grassland matrix. Cattle grazing and burning of this grassland are major threats to the survival of forest in this area.Hunting of local wildlife for bushmeat is also of concern, considering many of the region’s large-mammalian fauna are now locally extirpated (e.g. elephants) or at low abundances (many primate species). Loss of large-bodied frugivorous species has the potential to negatively impact the recruitment of large-seeded tree species that solely rely on them as seed dispersers. In this study, the ability for scatterhoarding rodents to act as surrogate dispersers for large-seeded species is tested. While much research has been carried out on secondary rodent dispersal in the Neotropics, work in the Afrotropics is still in its infancy. Because the outcome of plant-rodent interactions (i.e. predated or dispersed) may vary with season, habitat, or traits of the seed species in question, a number of experiments were established to quantify how local rodents at Ngel Nyaki may or may not be acting as effective dispersers. Additionally, the benefits of rodent dispersal were examined by creating an experiment that simulated secondary dispersal on seedling recruitment. The results of this study demonstrated that rodents can act as effective dispersers in Afromontane forests, but this is influenced by habitat, seasonal abundance of resources, and palatability of seed species. Furthermore, it was demonstrated that burial of seeds by rodents can increase the establishment probability of a seed by protecting it from removal by other rodents. However, while rodents play a strong driver of seed survival, it was also demonstrated that seedling mortality factors (such as herbivory) can also be heavy filters to seedling success. It is hoped that the results of this study will help to inform better management decisions and understand how the composition of the forest might change in the future.

The impact of graded levels of daylength on the productivity, health and behaviour of hens and toms was studied in two experiments to 18 wk of age. Daylength treatments (trt) were 14 (14L), 17 (17L), 20 (20L) and 23 (23L) h and were started at 10 d of age. Turkeys (720 hens and 480 toms) were randomly allocated to 8 rooms (2 rooms per lighting trt) with six pens (3 hen and 3 tom) per room in each experiment. Body weight (BW) and feed consumption (FC) were assessed throughout the trial and feed efficiency (G:F; g of gain/g of feed) calculated from BW and FC values. Birds were checked daily for mortality and culls, and affected birds sent for necropsy. Bird well-being was evaluated by gait score (GS), the incidence of foot pad dermatitis (FPD), breast buttons and blisters, ocular size and pressure, and tom behavioural observations. Data were analyzed using SAS 9.3 based on a completely randomized design nested within four daylengths. Regression analysis established relationships between response criteria and daylength. Differences were considered significant at P≤0.05 and trends noted at P≤0.10. At 21 and 42 d, body weight increased linearly with daylength, but by 84 d tom weights decreased in a quadratic fashion and hen weights were unaffected by daylength. At 126 d, both male and female weights decreased linearly with increasing daylength, with the magnitude of the response gender dependent. Feed consumption corresponded to body weight changes, increasing for d 10-21 and 21-42, and decreasing for d 63-84, 84-105, and 105-126 with increasing daylength. Feed efficiency (G:F) was not affected by daylength for 10-84, 10-105 and 10-126 d periods. The incidence of mortality and culling was not affected by daylength for the 10-84 d period, but increased in a quadratic manner with increasing daylength for the 10-105 and 10-126 d periods. The incidence of skeletal disorders (valgus-varus and rotated tibia), injurious pecking and pendulous crops (females only) increased linearly with increasing daylength. Average GS increased linearly with daylength at 11 and 17 wk for both hens and toms, but the effect was larger in toms. Daylength did not affect FPD, but more lesions and more severe scores were found for hens than toms. The presence of breast buttons and blisters increased linearly with daylength (11 wk) with the effect on blisters predominately seen in toms. Eye weight increased and corneal diameter decreased linearly with increasing daylength at 12 and 18 wk. Dorso-ventral and media-lateral diameter, and anterior to posterior depth exhibited a quadratic relationship with the highest values seen for the 23L trt. Ocular pressure was not affected by daylength. Over 24 h of behavioural observation (both photo- and scotoperiod), resting increased, and walking, and environmental and feather pecking decreased with increasing daylength. During the photoperiod, inactive resting increased and feeding, drinking, standing, walking, preening, and environmental and feather pecking behaviours decreased as daylength increased. To conclude, daylength affects the growth and feed intake of turkeys in an age and gender specific manner, and mortality and culling increase with longer daylength. Health and welfare parameters are also affected by daylength with 23L demonstrating poorest overall bird well-being.

This thesis comprises four empirical papers, each devoted to a specific topic in local political economics. Paper one and two evaluate the importance of the mayor position to the future electoral success of the mayor’s party. In the first paper, the focus is on the party’s electoral outcome in subsequent mayoral elections, while the second paper is concerned with the interdependencies between the mayor’s office and elections on other levels of government. The third paper investigates the causal effect of individual parties on policy in the context of German town council politics. The objective is to measure the impact of political representation in a proportional election system on core fiscal decisions of the municipalities. The final paper studies the specific concerns when using population thresholds in regression discontinuity designs for causal inference (in the German case). The analysis reviews the German evidence on the link between the size of the legislation and government spending. / <p>Diss. Stockholm :  Stockholm School of Economics, 2011. Introduction together with 4 papers.</p>