The studies reported in this thesis aim to provide insights on the process of navigation while driving. Driving requires processing and monitoring multiple tasks and sources of information. Navigation while driving increases the cognitive load of the driving task. Offloading the task of navigation to navigation aid systems such as GPS has potential disadvantages for our spatial memory skills. In this thesis, we introduce useful cues and skills to improve the performance of drivers in a variety of situations where they must navigate without the help of GPS. We used a motion simulator with six degrees of freedom to simulate various virtual reality driving scenarios that combine both visual and vestibular cues. In the following chapters, we report the effects of landmark cues, vestibular cues, self-reported mood disorders (e.g., depression, anxiety, and stress), individual differences at the visual spatial level (e.g., working memory span and mental rotation skills), age, and self-reported navigation skills on drivers’ route learning. We showed that successful navigation in various navigational situations depends on the type of landmarks available in the environment and the specific visual-spatial skills of drivers. We showed that vestibular self-motion cues improve egocentric route learning. Depression, anxiety, and stress affected drivers' route learning ability and dependency on GPS. We observed no deficit in age-related navigation performance when older drivers were able to use an egocentric frame of reference, however there was less optimal navigation performance of older drivers when wayfinding required an allocentric frame of reference. Overall, the application of the findings of this thesis may lead to an increase in efficacy and success in navigation performance and wayfinding while driving. / Thesis / Candidate in Philosophy / This thesis focuses on enhancing our understanding of wayfinding while driving in young and older adults. Using a driving simulator, we ran various virtual reality experiments to examine the underlying mechanisms of navigation while driving and ways to improve wayfinding of drivers. We identified useful cues for route learning in different environments where there were no navigation aid systems. We examined correlations between various spatial skills and performance that may improve drivers' wayfinding in unfamiliar environments. Furthermore, we assessed age-related effects on route learning and potential interventions to improve navigation in older drivers. The findings from the experiments reported in this thesis introduce the principle of route learning while driving in terms of how various internal and external factors can affect it. Drivers can incorporate these findings into their navigation tasks to overcome the wayfinding challenges that they encounter when driving in unfamiliar environments.

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Ribonuclease III is a highly-conserved bacterial enzyme that cleaves double-stranded (ds) RNA structures, and participates in diverse RNA maturation and decay pathways. Essential insight on the RNase III mechanism of dsRNA cleavage has been provided by crystallographic studies of the enzyme from the hyperthermophilic bacterium, Aquifex aeolicus. However, those crystals involved complexes containing either cleaved RNA, or a mutant RNase III that is catalytically inactive. In addition, neither the biochemical properties of A. aeolicus (Aa)-RNase III, nor the reactivity epitopes of its cognate substrates are known. The goal of this project is to use Aa-RNase III, for which there is atomic-level structural information, to determine how RNase III recognizes its substrates and selects the target site. I first purified recombinant Aa-RNase III and defined the conditions that support its optimal in vitro catalytic activity. The catalytic activity of purified recombinant Aa-RNase III exhibits a temperature optimum of 70-85°C, a pH optimum of 8.0, and with either Mg2+ or Mn2+ supports efficient catalysis. Cognate substrates for Aa-RNase III were identified and their reactivity epitopes were characterized, including the specific bp sequence elements that determine processing reactivity and selectivity. Small RNA hairpins, based on the double-stranded structures associated with the Aquifex 16S and 23S rRNA precursors, are cleaved in vitro at sites that are consistent with production of the immediate precursors to the mature rRNAs. Third, the role of the dsRBD in scissile bond selection was examined by a mutational analysis of the conserved interactions of RNA binding motif 1 (RBM1) with the substrate proximal box (pb). The individual contributions towards substrate recognition were determined for conserved amino acid side chains in the RBM1. It also was shown that the dsRBD plays key dual roles in both binding energy and selectivity, through RBM1 responsiveness to proximal box bp sequence. The dsRBD is specifically responsive to an antideterminant (AD) bp in pb position 2. The relative structural rigidity of both dsRNA and dsRBD rationalizes the strong effect of an inhibitory bp at pb position 2: disruption of one RBM1 side chain interaction can effectively disrupt the other RBM1 side chain interactions. Finally, a cis-acting model was developed for subunit involvement in substrate recognition by RNase III. Structurally asymmetric mutant heterodimers of Escherichia coli (Ec)-RNase III were constructed, and asymmetric substrates were employed to reveal how RNase III can bind and deliver hairpin substrates to the active site cleft in a pathway that requires specific binding configurations of both enzyme and substrate. / Chemistry

Yes / Students of education encounter a range of pedagogies yet how future teachers’ appropriate moral principles are little understood. We conducted an investigation into this process with 10 international students of education attending an intensive course on ‘dialogic pedagogy’ in a university in Finland. The data comprising student learning journals and essays were coded for the level of questioning, acceptance and irreverence. In the findings, reverential acceptance was more frequent than questioning and irreverence; however, our qualitative analysis also found a large number of micro-transitions between questioning, acceptance and irreverence suggesting a dynamic interplay. Recognising this vacillation as part of a moral journey may support better understanding of what it means to engage with a different pedagogy.

The adsorption of cationic and zwitterionic surfactants is studied in aqueous electrolyte solutions. A Maxwell relation is applied to Atomic Force Microscopy (AFM) data to obtain changes in surfactant adsorption as a function of the separation between two glass surfaces. In addition, self-consistent field theory (SCF) is used to calculate the adsorption profiles and interaction energies when two solid surfaces are brought into close proximity. Addition of surfactant is shown to affect the surface forces when lateral surfactant chain interactions are significant. The surfactant adsorbs and desorbs in response to over-lapping electric double-layers, with the adsorption being affected at larger solid-solid separations when the double-layer force is longer ranged. Furthermore, elimination off the surface charge or net surfactant charge eliminates adsorption with decreased solid-solid separation. The magnitude of the changes in surfactant adsorption at decreased separations is shown to scale with the chain length of the surfactant. Surfactant adsorption exceeds that required to regulate the surface charge according to the constant potential boundary condition in Poisson-Boltzmann theory. An equation of state including short-ranged (contact) tail interactions is proposed to describe both the adsorption of surfactant and the surface forces at small separations, where the double-layers overlap. Furthermore, SCF calculations show confinement-induced phase transitions when the surfactant layers on opposite surfaces merge. These phase transitions lead to further surfactant adsorption and a corresponding attractive force. / Ph. D.

Soil organic matter (SOM) is the largest terrestrial pool of organic carbon (C), and potential carbon-climate feedbacks involving SOM decomposition could exacerbate anthropogenic climate change. Despite the importance of SOM in the global C cycle, our understanding of the controls on SOM stabilization and decomposition is still developing, and as such, SOM dynamics are a source of major uncertainty in current Earth system models (ESMs), which reduces the effectiveness of these models in predicting the efficacy of climate change mitigation strategies. To improve our understanding of controls on SOM decomposition at scales relevant to such modeling efforts, A and upper B horizon soil samples from 22 National Ecological Observatory Network (NEON) sites spanning the conterminous U.S. were incubated for 52 weeks under conditions representing site-specific mean summer temperature and horizon-specific field capacity (-33 kPa) water potential. Cumulative CO2 respired was periodically measured and normalized by soil organic C content to obtain cumulative specific respiration (CSR). A two-pool decomposition model was fitted to the CSR data to calculate decomposition rates of fast- (kfast) and slow-cycling pools (kslow). Post-LASSO best subsets multiple linear regression was used to construct horizon-specific models of significant predictors for CSR, kfast, and kslow. Significant predictors for all three response variables consisted mostly of proximal factors related to clay-sized fraction mineralogy and SOM composition. Non-crystalline minerals and lower SOM lability negatively affected CSR for both A and B horizons. Significant predictors for decomposition rates varied by horizon and pool. B horizon decomposition rates were positively influenced by nitrogen (N) availability, while an index of pyrogenic C had a negative effect on kfast in both horizons. These results reinforce the recognized need to explicitly represent SOM stabilization via interactions with non-crystalline minerals in ESMs, and they also suggest that increased N inputs could enhance SOM decomposition in the subsoil, highlighting another mechanism beyond shifts in temperature and precipitation regimes that could alter SOM decomposition rates. / Master of Science / Soils contain a large amount of carbon (C) in the form of soil organic matter (SOM), and there is the potential for the increased decomposition of SOM due to warmer temperatures to cause climate change to become worse through the release of additional CO₂ into the atmosphere. However, we still do not know exactly what is most important for predicting how vulnerable SOM is to decomposition at continental scales, and this results in a substantial amount of uncertainty in Earth system models used to predict climate change. To address this question, the proportion of organic C decomposed in soil samples from the topsoil and subsoil from 22 sites across the conterminous U.S. was monitored over the course of a year under optimal moisture conditions and at site-specific summer temperature. Additionally, a mathematical model was fitted to the proportion of organic C decomposed over time to estimate decomposition rates of a quickly decomposing pool of SOM and a slowly decomposing pool of SOM. The proportion of organic C decomposed and decomposition rates were related to soil and site properties using multiple linear regression to find which soil and site properties were most important for predicting these response variables. The type of clay-sized mineral and SOM chemical composition were found to be important predictors of the proportion of organic C decomposed for both topsoil and subsoil samples. The important predictors for decomposition rates varied by pool and by topsoil vs. subsoil. For subsoil decomposition rates, it was found that a greater availability of nitrogen (N) increased decomposition rates, and in the quickly decomposing pool, it was found that fire-derived organic matter slowed decomposition rates. The results of this study showed the general importance of local factors for controlling SOM decomposition. Specifically, it showed that the type of clay-sized mineral present at a site needs to be considered as well as the fact that N might increase SOM decomposition in the subsoil.

The goal of this research project was to determine the content of the discourse occurring in grade-level meetings and coaching sessions and participants' perceptions of how the conversations in these two venues impacted learning and practice for individual teachers. Learning Forward's Standard for Professional Learning (2001) recommended that teachers organize into learning communities providing continuous learning opportunities to enhance adult learning and collaboration. Little (2003a) found that research was lacking that described the dynamics of communities of practice that promote teacher learning. It was in the content of the discourse that a proxy for evidence was found that the actions of the instructional coaches and grade-level meetings impact teacher growth. A case study was utilized to examine these structures and processes for job-embedded professional development at a school located in the eastern United States. Research questions focused on the nature of the discourse among teachers and coaches in the grade-level meetings and in individual coaching conversations. Teachers reported what they felt that they learned in the grade-level meetings and the coaching discussions. Additionally, teachers stated what they did differently as a result of this method of professional learning occurring in grade-level meetings and coaching discussions. Finally, the school's improvement plans were compared with the conversations in the grade-level meetings and coaching sessions. Verbatim transcriptions of recordings of grade-level meetings and coaching sessions provided data which revealed categories of content, coaching roles, and patterns of discourse. The goals of the meetings and coaching were to ensure communication about school district policies and to set expectations for teacher performance and student learning. Assertions generated provided patterns of discourse that identified roles of the principal, coaches, and teachers. This investigation utilized a descriptive content discourse analysis and found support for the finding that the actions of this emerging community of practice were directed by federal, state, and local polices for teacher performance and student learning. Patterns of discourse revealed roles of administration, coaches, and teachers as they collaborated to negotiate meaning through the building of a shared repertoire. Interview data revealed that these dynamics enhanced teacher growth in many cases; however, lack of teacher input may have limited some potential opportunities. / Ed. D.