Dissertation Defense Announcements

The orbital angular momentum of light is a promising candidate as an information carrier in optical communication systems to enhance the capacity of data channels. However, the effects of atmospheric turbulence significantly degrade the quality of light beams, thereby imposing limitations on the range of reliable data transmission. To address this issue, researchers have been actively seeking methods to enhance the resilience of light against fluctuations of refractive index due to the atmospheric turbulence. It has long been recognized that partially coherent beams exhibit greater robustness in propagation through turbulence. Consequently, transitioning from full coherence to partial coherence has been suggested as a solution. Conversely, in OAM-based communications, reducing coherence results in broadening of the OAM spectrum, thus increasing cross-talk between adjacent channels. Therefore, utilizing partially coherent beams in free space communications entails both Benefits and drawbacks.
The main objective of this dissertation is to explore various classes of partially coherent beams through analytical approaches in order to identify a robust OAM spectrum in the presence of atmospheric turbulence. The results are presented in three different articles. The first article introduces a simplified version of the extended Huygens-Fresnel principle which is a widely used method of turbulence propagation. The discoveries outlined in the first article substantially alleviate the mathematical complexity associated with propagation in random media, thereby enabling analytical exploration of the propagation of partially coherent beams in random media.
The second article presents an optimization criterion associated with a specific class of partially coherent beams, substantially enhancing their resistance against turbulence. Finally, the third article thoroughly investigates the behavior of three categories of partially coherent beams in interaction with atmosphere, providing a detailed comparison of their respective resistance. The compilation of these three articles presents a comprehensive study of the impact of atmospheric fluctuations on the orbital angular momentum spectrum of partially coherent beams.

Coral reef ecosystems are supported by diverse mutualisms formed between cnidarians such as corals, sea anemones, and jellyfish and dinoflagellate algae in the family Symbiodiniaceae. These dynamic symbiotic relationships rely on the successful establishment of algal endosymbionts, often from the surrounding seawater, within cnidarian host tissues. Due to the current limitations in cellular and molecular tools in the field of cnidarian-Symbiodiniaceae symbiosis, the mechanisms of symbiosis establishment including infection, proliferation, and maintenance are poorly understood. The aim of this thesis is to uncover the cellular processes essential to cnidarian-algal symbiosis by developing in vitro and in hospite assays across Symbiodiniaceae and cnidarian species. In chapter two, the trophic flexibility of Symbiodiniaceae was explored. Symbiodiniaceae Breviolum minutum grown in vitro with organic nutrients showed stable growth and photosynthetic function when compared to limited nutrient conditions; this suggests that the oligotrophic waters of coral reef ecosystems may drive free-living Symbiodiniaceae into symbiosis with cnidarians. Next in chapter three, a new protocol for single-cell dissociation of cnidarian hosts is introduced and used to determine the localization of the first Symbiodiniaceae photosynthesis mutant ora1. Here, ora1 was found to retain its ability to form symbiosis in cnidarians, indicating that photosynthesis is not required for symbiosis establishment. Finally, the newly generated Symbiodiniaceae green mutant, gr02, is introduced and co-inoculated with the brown wild type B. minutum in the sea anemone Aiptasia to uncover the cellular events contributing to symbiont proliferation. For the first time, two algal genotypes (gr02 and wild type B. minutum) were observed co-localized in a single host cell via dissociation and microscopy but were rare in frequency. These results suggest that algal cell division and primary infections drive the proliferation of symbionts in hospite. Furthermore, the co-inoculation of gr02 with other species of Symbiodiniaceae in three cnidarian hosts (coral, sea anemone, and jellyfish) reveals intracellular localization and possible interaction between symbionts in host tissues. Together, this work lays the foundation for future cellular biological research using Symbiodiniaceae mutants to answer pressing questions surrounding cnidarian-Symbiodiniaceae symbiosis.

The primary objective of this study is to evaluate the influence of multi-dimensional legitimacy on consumer adoption of autonomous vehicles. This study used a survey to evaluate the results. These findings reflected that legitimacy positively and negatively influences the relationships between UTAUT2 determinants and intention to use. These effects are noted in this study showing the influence of legitimacy on consumer intention to use AV. Legitimacy warrants further investigation.

Novice programmers are known for holding incomplete and inconsistent mental models. A mental model stores knowledge that reflects a person's belief system, helps determine actions, and facilitates learning. Mental model correctness and consistency are two criteria that make a mental model useful. Though the literature on mental models is rich with more than two decades of research, novice programmers' mental model is understudied in the CS education research community. Guided by the mental model theories from psychology and cognitive science, I investigated novice programmers' mental models of arrays before and after CS1 course instruction. Furthermore, I explored the gap that might exist between students with varying levels of prior programming experience. To that end, by following the theories of mental models, I defined the mental models for Java arrays, including assertions of the array's parts and state changes. I further decomposed the array's parts and state changes into four sub-components each (parts: name, index, type, elements}; state changes: declaration, instantiation, assigning literals, assignment). To elicit the mental model assertions of novice programmers from large CS1 classrooms, I adopted a multiple choice-based questionnaire approach (the Mental Model Test) covering each array's component. I collected responses from novice programmers as they entered a CS1 course and transitioned into a CS2 course. I analyzed participants' mental model assertions based on their correctness and consistency.

The results show that participants' mental model correctness and consistency improved after formal classroom instruction. Moreover, even though improved, I found evidence that the mental model components of the array's state changes were less accurate and consistent than the parts. In addition, participants with prior programming experience had significantly lower mental model correctness and consistency than those with prior programming experience before classroom instruction on arrays. The mental model test highlighted several novice programmers' misconceptions. Over half of our participants held at least one misconception before and after learning arrays in classrooms. Novice programmers mostly held misconceptions about the arrays’ declarations (state change) as incoming CS1 students and when transitioning into CS2. After classroom instruction, the number of students holding misconceptions about the parts components decreased. However, for the state changes components, in most cases, the number of students holding misconceptions remained almost the same even after classroom instruction. I close my dissertation by summarizing the overall findings while investigating novice programmers' mental models in their different learning trajectories. Lastly, I discuss the implications of my research in designing instructional materials for CS educators on possible solutions to mitigate the mental model gap of novice programmers.