There are two serious methodological problems in the research literature on school effectiveness, the ecological problem in the analysis of aggregate data and the problem of not controlling for important confounding variables. This dissertation corrects these errors by using multilevel modeling procedures, specifically Hierarchical Linear Modeling (HLM), and the Canadian Trends in International Mathematics and Science Study (TIMSS) 2007 data, to evaluate the effect of school variables on the students’ academic achievement when a number of theoretically-relevant student variables have been controlled. In this study, I demonstrate that an aggregate analysis gives the most biased results of the schools’ impact on the students’ academic achievement. I also show that a disaggretate analysis gives better results, but HLM gives the most accurate estimates using this nested data set. Using HLM, I show that the physical resources of schools, which have been evaluated by school principals and classroom teachers, actually have no positive impact on the students’ academic achievement. The results imply that the physical resources are important, but an excessive improvement in the physical conditions of schools is unlikely to improve the students’ achievement. Most of the findings in this study are consistent with the best research literature. I conclude the dissertation by suggesting that aggregate analysis should not be used to infer relationships for individual students. Rather, multilevel analysis should be used whenever possible.

Recycled concrete aggregate (RCA) is a construction material, which is being used in the Canadian construction industry more frequently than it was in the past. The environmental benefits associated with RCA use, such as reduced landfilling and natural aggregate (NA) quarrying, have been identified by industry and government agencies. This has resulted in some incentives to use RCA in construction applications. Some properties of RCA are variable and as a result the material is often used as a structural fill, which is a low risk application. The use of RCA in this application is beneficial from an overall sustainability perspective but may not represent the most efficient use of the material. Efficient use of a material means getting the most benefit possible out of that material in a given application. The initial step in efficient material use is evaluating how a material affects its potential applications. In the case of RCA, this includes its use in concrete as a coarse aggregate. RCA is made up of both aggregate and cement mortar from its original application. Its make-up results in absorption capacities, which are higher than NA. Its high absorption capacity indicates that RCA can retain a relatively large proportion of water. Internal curing of concrete is the practice of intentionally entraining reservoirs of water within concrete. This water is drawn into the cement at a beneficial point in the cement hydration process. This water allows for a more complete hydration reaction, less desiccation, a less permeable concrete pore system, and less susceptibility to the negative effects of poor curing. The potential for RCA to act as an internal curing agent was evaluated in this research. Two RCA types were studied in the course of this research, one RCA of high-quality and one low-quality. These were compared to one NA type, which served as experimental control. Neither RCA type was found to desorb significant amounts of entrained water at relative humidity levels between 85% and 93%. This behaviour indicates that they would not behave as a traditional internal curing agent. Within concrete, the initial saturation levels of these RCAs were 0%, 60% and 100% of their full absorption capacity. The mixtures ranged from 30% RCA (by volume of coarse aggregate) to 100% RCA. These mixtures were subjected to two curing regimes, MTO-specified curing conditions and moist curing, in order to gauge the internal curing potential of the RCA. Fully saturated RCA mixtures were found to retain water throughout the course of testing. They were also found to increase the rate of compressive strength gain at early ages in comparison to similarly cured NA mixtures. Full saturation was found to have a negative effect on the thermal expansion behaviour of the concrete at 28 days concrete age. Permeable porosity of concrete was measured as an indicator of more thorough hydration in RCA concrete, but any potential benefits were masked by the increase in permeable porosity associated with permeable RCA. When compared with NA control mixtures and RCA mixtures cured under ideal conditions, it was found that saturated RCA mixtures provided compressive strength benefits. Low-quality RCA, which lost entrained water earlier in the testing period than high-quality RCA, benefitted in terms of early age compressive strength gains under specified curing conditions. High-quality RCA, which retained a relatively higher proportion of its entrained water throughout the early testing period, improved later age compressive strength under spec-curing conditions. Mixtures with 30% RCA (by volume of coarse aggregate) were generally found to not significantly affect the tensile strength, elastic modulus, and permeable porosity of the concrete. Tensile strength and elastic modulus were found to be consistently lower in RCA concretes, while permeable porosity was consistently higher. However, the magnitudes of these changes were not large enough to be statistically significant based on the testing regime employed. Compressive strength was significantly improved at 28 days when the 30% RCA was fully saturated. 30% RCA mixtures significantly reduced the thermal expansion of concrete at 28 days, which could provide particular benefit to concrete pavement applications. Overall, RCA saturation in new concrete had both positive and negative effects on the properties of concrete, which should both be considered in the context of the application for which RCA concrete is being considered. Specifically, concrete applications with the potential for poor curing and the need for reduced thermal expansion could benefit through the inclusion of coarse RCA. For example, these benefits could manifest in reduced thermal cracking at slab joints and reduced thermal stresses due to temperature gradients in pavements.

There are two serious methodological problems in the research literature on school effectiveness, the ecological problem in the analysis of aggregate data and the problem of not controlling for important confounding variables. This dissertation corrects these errors by using multilevel modeling procedures, specifically Hierarchical Linear Modeling (HLM), and the Canadian Trends in International Mathematics and Science Study (TIMSS) 2007 data, to evaluate the effect of school variables on the students’ academic achievement when a number of theoretically-relevant student variables have been controlled. In this study, I demonstrate that an aggregate analysis gives the most biased results of the schools’ impact on the students’ academic achievement. I also show that a disaggretate analysis gives better results, but HLM gives the most accurate estimates using this nested data set. Using HLM, I show that the physical resources of schools, which have been evaluated by school principals and classroom teachers, actually have no positive impact on the students’ academic achievement. The results imply that the physical resources are important, but an excessive improvement in the physical conditions of schools is unlikely to improve the students’ achievement. Most of the findings in this study are consistent with the best research literature. I conclude the dissertation by suggesting that aggregate analysis should not be used to infer relationships for individual students. Rather, multilevel analysis should be used whenever possible.

In this thesis, the results from molecular dynamics (MD) simulations of nanoaerosol clusters are discussed. The connecting link of these studies is the Köhler theory, which is the theory of condensational growth and activation of cloud droplets to form clouds. By investigating parameters such as the surface tension, state of mixture and morphology of nanoaerosol particles, conclusions can be drawn to improve the Köhler theory to include the effects of organic compounds previously unaccounted for. For the terrestrial environment, the simulations show that the natural surfactant cis-pinonic acid, an oxidation product evaporated from boreal trees, spontaneously accumulates at the surface of nanoaerosol clusters and thereby reduces the surface tension. The surface tension depression is related to the concentration of the surfactant and the size of the clusters. Surface tension is an important parameter of the Köhler theory. A decrease of the surface tension can lower the critical water vapour supersaturation needed for cloud droplet activation, giving rise to more, but smaller cloud droplets (Twomey effect) which in turn could change the optical properties of the cloud. It was also shown that the three organic surfactants, being model compounds for so called Humic-like substances (HULIS) have the ability to form aggregates inside the nanoaerosol clusters. These HULIS aggregates can also promote the solubilization of hydrophobic organic carbon in the form of fluoranthene, enabling soot taking part in cloud drop formation. Dissolved intermediately surface-active free amino acids were shown to be of some relevance for cloud formation over remote marine areas. The MD simulations showed differences between the interacting forces for spherical and planar interfaces of amino acids solutions. This thesis has emphasized the surface-active properties of organic compounds, including model HULIS and amino acids and their effect on surface tension and molecular orientation including aggregate formation in nanoaerosol clusters and their activation to form droplets. This thesis shows that the Köhler equation does not fully satisfactory describe the condensational growth of nano-sized droplets containing organic surfactants. Different approaches are suggested as revisions of the Köhler theory. / <p>At the time of the doctoral defense, the following papers were unpublished and had a status as follows: Paper 3: Submitted. Paper 5: Manuscript.</p>