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

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

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

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

The thesis examines the establishment size distribution over time and across groups of regions, using data on Swedish establishments during period 1994-2009. The size distribution of establishments is highly skewed and approximates the Pareto distribution. The shape of size distribution is invariant over time and across groups of regions. The distribution of total number of establishments and incumbent distribution are found to rise from the same distribution. Moreover, the invariance of establishment size distribution is highly determined by the invariance of distribution of incumbents, entry and exit distributions. Larger establishments have more chances to survive and higher probability to remain in current size group comparing to smaller ones, whereas higher probabilities of growth would be attached to smaller establishments.

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

The structure of phytoplankton communities was examined seasonally across five rivers with a focus on small cells and their relative importance. Picophytoplankton (0.2-2 μm), previously considered insignificant in rivers, reached densities as high as those observed in lakes and oceans (~ 10e4-10e5 cells/mL). Their relative importance was not a function of trophic state with the highest contribution to algal biomass found in the most eutrophic river. Body size distributions were analyzed from both chlorophyll-a size fractions and taxonomic enumerations; no significant effect of river or season was detected, suggesting that phytoplankton size distribution is not a useful metric of change in rivers. Unlike lake ecosystems, the rivers were uniformly dominated by small cells (< 20 μm). Taxonomic analyses of the seasonal succession did not reveal a common periodicity of particular divisions (e.g. diatoms). However, strong dominance was more typical of eutrophic rivers even though taxa richness was similar.

Bibliography: leaves 208-216. / xxii, 231 leaves : ill. ; 30 cm. / Title page, contents and abstract only. The complete thesis in print form is available from the University Library. / The aim of this thesis is to define optimal centrifuge operating conditions for inclusion body recovery. Special attention is directed to the interaction of the recovery step with upstream and downstream processes. A new Eschenchia coli debris sizing method, Asoc, is developed to overcome the limitations of existing sizing methods. / Thesis (Ph.D.)--University of Adelaide, Dept. of Chemical Engineering, 1997?

Bibliography: leaves 182-198. / xv, 207 leaves : ill. (some col.) ; 30 cm. / Title page, contents and abstract only. The complete thesis in print form is available from the University Library. / Improvements in the current production system of inclusion bodies and the downstream processing sequence are essential to maintain a competitive advantage in the market place. Optimisation of fermentation is considered to improve production yield; then flotation as a possible inclusion body recovery method. / Thesis (Ph.D.)--University of Adelaide, Dept. of Chemical Engineering, 2000?

O desempenho final das argamassas depende das matérias-primas e de suas proporções na formulação, pois estas determinam o comportamento do material na etapa de aplicação e a microestrutura final do material endurecido. Entre as patologias de revestimentos, a falha de aderência é um dos fenômenos mais freqüentes, sendo originada pela incompatibilidade entre o comportamento reológico da argamassa e a energia de lançamento utilizada, resultando em defeitos na interface argamassa substrato. A adequação das características reológicas das argamassas às solicitações envolvidas na aplicação fornece condições de processamento mais favoráveis para a obtenção das máximas propriedades finais do revestimento. Assim, o objetivo do trabalho é desenvolver critérios de formulação, baseados nas características das matérias-primas, nos modelos de empacotamento de partículas e nos comportamentos reológicos, de modo a obter um método de formulação de argamassas. O método de squeeze-flow foi desenvolvido com sucesso para avaliação reológica de argamassas, sendo as principais variáveis experimentais foram estudadas, assim como o efeito do tipo de mistura no comportamento reológico. Procedimento para quantificação da segregação pasta-agregado foi criado, tendo em vista o intenso efeito que este fenômeno exerce sobre o comportamento reológico em squeeze-flow, especialmente em baixas velocidades. Foi ainda comprovado que o squeeze-flow tem boa relação com a percepção do pedreiro, principalmente, nas etapas de lançamento e aperto. Diversas argamassas nacionais e européias foram caracterizadas, resultando em um mapeamento das características de formulação, do comportamento reológico e das propriedades no estado endurecido. Através da aplicação de conceitos de empacotamento e distância de separação de partículas, foi verificado que a otimização do empacotamento de agregados permite um melhor aproveitamento da pasta para promover argamassas com comportamento reológico mais adequado à aplicação ou com menor consumo de finos e água. As correlações estabelecidas entre as características no estado fluido e as propriedades no estado endurecido permitem prever o comportamento das propriedades no estado endurecido com boa confiabilidade. Por fim, são descritas diretrizes sistemáticas para a formulação de argamassas considerando requisitos de desempenho tanto no estado fresco quanto no endurecido. / The in-use performance of rendering mortars depends on the raw materials features and their content in the formulation, since they have major influence on the material behavior during emplacement, as well as, on its final properties. Adherence failure is one of the most frequent problems of this class of building materials, caused by the incompatibility between rheological behavior and the application process, generating mortar/substrate interface flaws. A rheological behavior more suitable to the application demands, provides appropriate conditions to obtain maximum final rendering properties. Therefore, the main goal of this work is to develop mix-design parameters based on raw materials features, particle packing models and rheological behavior, in order to create a mix-design method for mortars. Squeeze-flow technique was successfully adapted for the rheological evaluation of rendering mortars, and the most important experimental parameters were studied. The method is sensitive enough to measure rheological changes as a function of the mixing process applied. Considering that phase segregation plays an important role on the rheological behavior of concentrated suspensions especially at low speeds, a method was developed to measure paste-aggregate segregation. It was also established that the squeeze-flow agrees well with the workers perception during manual emplacement. Several Brazilian and European products were evaluated, and significant differences were determined on the formulation features, rheological behavior and hardened properties. Using models of particle packing and particle distance, it was verified that optimized packing of aggregates enhances rheological behavior and can also allow the reduction of water and fine particles consumption. The experimental relationships established between fresh characteristics, rheological behavior and final properties can be used to predict hardened features and properties with fair confidence. Lastly, mix-design suggestions are made considering both fresh and hardened performance.