Organizational commitment has been recognized as a multiple foci phenomenon with two of the more important foci being the work team and the organization as a whole. That organizational and team commitment can vary differentially has been established. However, research has not attempted to determine the antecedents that may cause them to do so. At the same time, a number of constructs that have been explored as antecedents of organizational commitment have also been recognized as having particular salience in a self-directed work team environment. The purpose of this research is to test a model in which it has been hypothesized that certain antecedents will have differential effects on organizational commitment and team commitment. The model was developed employing constructs that are antecedents of commitment in the workplace and are of particular importance in a self-directed work team environment. All but one of the hypotheses were supported indicating that factors that are important in a self-directed work team environment have differential effects on organizational and team commitment. The results are discussed in terms of both theory and praxis. Implications for practicing managers and future research are presented along with the limitations of the study. / Ph. D.

Stagnant student achievement in science education in the United States has placed an increased emphasis on teacher professional development. Since many elementary educators could benefit from improved science content knowledge—and given the challenge of providing this at a level scalable and sustainable through face-to-face delivery alone—this study sought to understand what types of online self-directed content-interaction strategies are of greatest learner satisfaction and provide the highest learning impact for teachers in grades three–six. Employing Anderson's Equivalency of Interaction Theorem, and looking at age, years teaching experience, and learning preferences via Kolb and Kolb's Learning Style Inventory 3.1 (2005), this descriptive study non-randomly sampled 85 educators who passed a series of self-paced interactive web modules to rate their preferences for five different types of content-interactive strategies: (a) simulations, (b) interactive reference, (c) hands-on, (d) personal feedback, and (e) pedagogical implications. Using an online survey and a pre- and postassessment instrument it was found that (a) as age and years teaching experience increase, teachers' preferences for personal feedback, interactive reference, and simulations increased, (b) teachers' content knowledge increased significantly after completing the web modules, (c) teachers' learning style moderately aligned with their preferences for content-interaction strategies, and (d) teachers least preferred the pedagogical implications component. Instructional designers and education administrators selecting professional development for teachers may find this informative. Data from this research support Anderson's theory that if the content interaction is rich, human interaction may be provided in diminished capacities. / Ph. D.

The present study was designed to investigate whether infants prefer their fathers’ voices over an unfamiliar male voice within the context of normal father-infant interaction, i.e., infant-directed (ID) speech. Twenty Caucasian male and female four-month-olds were tested in a visual-fixation preference procedure. Attentional preference was measured by the amount of time the infants watched a visual stimulus. It was found that infants did not show greater attentional or affective responsiveness to paternal ID over unfamiliar male ID speech samples. However, mothers and fathers appear to be very similar in their perception of father-infant interaction. According to these results, four-month-olds do not prefer their fathers’ voices to that of an unfamiliar male. This finding contrast sharply with the literature on maternal voice preference. The data was interpreted as supporting the hypothesis that multimodal stimulus cues are necessary for paternal voice recognition in infancy. / Master of Science

The purpose of my dissertation study is to better understand the educational experiences of undergraduate engineering students within non-curricular learning environments, specifically in the form of extracurricular engineering groups or programs. I first conducted a content analysis of engineering education literature to identify where engineering design learning occurs, and to synthesize the implications of studies regarding engineering design learning. Aiming to fill a gap in the literature regarding non-curricular learning contexts, this study investigated what extracurricular groups and programs can educationally provide undergraduate engineering students by observing and interviewing students engaging in these environments. This study also aimed to identify if and how engineering students find navigational flexibility within engineering curricula, and how non-curricular learning environments might provide navigational flexibility. With regard to where engineering design learning occurs, the literature points to various educational contexts that effectively deliver engineering design education. Strategies that involve authentic and longer-term engineering design experiences tend to be the most impactful in terms of student outcomes and perceptions, however those experiences are not always implementable at larger scale. More traditional educational approaches to engineering design learning, though less impactful, are still effective delivery methods for introducing key aspects of engineering design education (e.g. modeling, global/societal/economic/environmental factors, communication skills). However, there was limited literature regarding more non-curricular learning experiences, such as learning in designed settings, outreach learning, learning media, and everyday informal learning. This literature review is one of the first attempts towards synthesizing where and how engineering design learning occurs, and has identified a significant gap in the literature regarding non-curricular educational settings. Addressing the identified gap in engineering education literature regarding non-curricular learning experiences, this dissertation study investigated five non-curricular engineering learning sites for undergraduate engineering students at a large research-driven state institution. Informed by the preliminary findings of a pilot study, I first investigated the salient features of engineering-related non-curricular activities from the students' perspectives using a self-directed learner autonomy framework to guide the study. Students participating in extracurricular engineering environments exhibited strong attributes of self-directed learners, particularly a willingness and ability to be challenged and to learn. The educational environments of the extracurricular opportunities cultivated these self-directed learning attributes by providing students a space to be exposed to an engineering community, authentic engineering work, and accessible resources. Findings from this portion of the dissertation indicated necessary modifications to the self-directed learner autonomy framework used to guide this study. The modified framework contributes a possible approach towards future assessment or research pursuits regarding non-curricular learning experiences in engineering. I also investigated the role non-curricular activities play in providing engineering students navigational flexibility through engineering curricula. Extracurricular engineering environments afford navigational flexibility by offering students opportunities to work on motivating challenges with and among supportive communities. By providing a space for students to express their engineering selves in primarily self-directed ways, extracurricular engineering experiences cultivate students' drive to find and pursue personally meaningful curricular and non-curricular educational experiences. However, institutional barriers, particularly time constraints and institutionally recognized achievements, stifle students' flexibility and willingness to pursue personally meaningful experiences. The findings of this study have helped uncover the various affordances non-curricular learning experiences provide engineering students, but more importantly, have identified the institutional barriers that prevent students from taking full advantage of non-curricular learning experiences. Based on these findings, I recommend that university and program level structures be reevaluated to encourage and provide students with more flexibility to find personalized learning experiences in and out of the classroom. / Ph. D.

Disease outbreaks caused by oomycetes can be catastrophic. The first part of this dissertation describes development of a system to identify potential new and durable resistance (R) genes against P. sojae in soybean germplasm. We developed a system to screen soybean germplasm for genes that recognize core Phytophthora sojae RXLR effectors that are conserved within the pathogen species and essential for virulence. R genes that recognize these effectors will likely be effective and durable against diverse P. sojae isolates. We developed a system to deliver individual P. sojae effectors by Type III secretion into soybean using the bacterium Pseudomonas, and we screened 12 core effectors on a collection of 30 G. max lines that likely contain new resistance genes against P. sojae. We identified candidate R genes against 10 effectors. Genetic segregation ratios from crosses indicated that three of these genes have a simple inheritance pattern and would be amenable to breeding into elite cultivars. The second part of the dissertation involves use of a model plant-oomycete system to study the genetic basis of susceptibility to oomycete diseases. We compared host transcriptomes from a resistant and a susceptible infection of Arabidopsis thaliana by the downy mildew pathogen Hyaloperonospora arabidopsidis (Hpa). We identified five gene clusters with expression patterns specific to the susceptible interaction. Genes from each cluster were selected and null mutants were tested for altered susceptibility to virulent Hpa. Most A. thaliana null mutants showed enhanced disease susceptibility, suggesting their involvement in pattern-triggered immunity (PTI). A knockout mutant in the AtGcn5 gene was completely resistant to Hpa Emco5 suggesting that the gene/protein is necessary for Hpa to successfully colonize the plant. This study provided new molecular insights into plant-oomycete interaction and revealed a plant gene that could potentially be engineered to provide enhanced resistance to oomycete pathogens. / Ph. D.

The goals of this research were 1) to produce hydrogen in high yields from cellulosic materials and water by synthetic pathway biotranformation (SyPaB), and 2) to increase the hydrogen production rate to a level comparable to microbe-based methods (~ 5 mmol H2/L/h). Cell-free SyPaB is a new biocatalysis technology that integrates a number of enzymatic reactions from four different metabolic pathways, e.g. glucan phosphorylation, pentose phosphate pathway, gluconeogenesis, and hydrogenase-catalyzed hydrogen production, so as to release 12 mol hydrogen per mol glucose equivalent. To ensure the artificial enzymatic pathway would work for hydrogen production, thermodynamic analysis was firstly conducted, suggesting that the artificial enzymatic pathway would spontaneously release hydrogen from cellulosic materials. A kinetic model was constructed to assess the rate-limited step(s) through metabolic control analysis. Three phosphorylases, i.e. α-glucan phosphorylase, cellobiose phosphorylase, and cellodextrin phosphorylase, were cloned from a thermophile Clostridium thermocellum, and heterologously expressed in Escherichia coli, purified and characterized in detail. Finally, up to 93% of hydrogen was produced from cellulosic materials (11.2 mol H2/mol glucose equivalent). A nearly 20-fold enhancement in hydrogen production rates has been achieved by increasing the rate-limiting hydrogenase concentration, increasing the substrate loading, and elevating the reaction temperature slightly from 30 to 32°C. The hydrogen production rates were higher than those of photobiological systems and comparable to the rates reported in dark fermentations. Now the hydrogen production is limited by the low stabilities and low activities of various phosphorylases. Therefore, non-biologically based methods have been applied to prolong the stability of α-glucan phosphorylases. The catalytic potential of cellodextrin phosphorylase has been improved to degrade insoluble cellulose by fusion of a carbohydrate-binding module (CBM) family 9 from Thermotoga maritima Xyn10A. The inactivation halftime of C. thermocellum cellobiose phosphorylase has been enhanced by three-fold at 70°C via a combination of rational design and directed evolution. The phosphorylases with improved properties would work as building blocks for SyPaB and enabled large-scale enzymatic production of cellulosic hydrogen. / Ph. D.

Ncd is a member of the kinesin family of motor proteins. Ncd is involved in the processes of meiosis and early mitosis in <i>D. melanogaster</i>. PCR-mediated site-directed mutagenesis was utilized to introduce specific mutations into pET/MC6, a construct containing the motor domain of ncd. Six mutations were generated, two at glutamic acid residue 656, two at proline residue 649, one at arginine residue 623, and one double mutant at arginine residue 623 and threonine residue 632. Mutants proteins were expressed in bacteria and further characterized. Mutagenesis of the proline or glutamic acid residues resulted in insoluble proteins. The one exception is the mutagenesis of glutamic acid residue 656 into a glutamine, which resulted in a partially soluble protein. Mutagenesis of the arginine residue into an alanine (MC6-A623) resulted in a soluble protein while the double mutation of the arginine and threonine was insoluble. MC6-A623 exhibited a similar S-sepharose ion exchange chromatography binding and elution profile as MC6. Peptide antibodies made to conserved ncd motor domain sequences also recognized MC6- A623. The affinity of MC6-A623 (under the conditions tested) for microtubules was less than MC6. Most interestingly, under the conditions tested, MC6-A623 did not exhibit an increased ATPase rate in the presence of microtubules, a hallmark of the kinesin family of microtubule motor proteins. Analysis of the published ncd crystal structure, other motor protein sequences, and the experimental results of the mutagenesis of arginine residue 623, suggest that this residue is involved in the binding of MC6 to microtubules. / Master of Science

Thesis advisor: Abhishek Chatterjee / Thesis advisor: Jia Niu / Directed Evolution has emerged as an invaluable tool for advancing protein functions in both research and industry. Our lab has pioneered a directed evolution platform in mammalian cells, utilizing an AAV delivery vector to package a DNA library and linking the biomolecule of interest to AAV production. During my tenure in Prof. Chatterjee's lab, I focused on harnessing our lab’s directed evolution platform, known as Virus-Assisted Directed Evolution of tRNA (VADER), to develop highly efficient tRNAs for genetic code expansion. Additionally, I contributed to the development of the AAV-based selection platform, termed Virus-Assisted Mutational Profiling (VAMP), as a profiling tool. Through the utilization of VAMP, I conducted comprehensive profiling of tRNA and RNA polymerase III promoter sequences. This enabled me to gain insights into regions of flexibility and evolution, ultimately leading to the construction of improved constructs with enhanced activity relative to the starting sequence. / Thesis (PhD) — Boston College, 2024. / Submitted to: Boston College. Graduate School of Arts and Sciences. / Discipline: Chemistry.

From 1959 -1964, the Prince Edward County, VA School Board closed down its public schools to circumvent the 1954 Brown v. Board of Education Supreme Court ruling declaring separate public schools for Black and White students "inherently unequal" and the 1955 Brown II ruling to desegregate public schools with "all deliberate speed." For five years, more than 1700 African American children received no public education in the county, as White children attended a newly-constructed and private Prince Edward Academy. While some students left Prince Edward to reside with relatives, others were placed with families by the American Friends Service Committee. However, the majority of Black children remained in the county without formalized public instruction. This study investigated the perceived impact of The Closing on adult self-directed learning, lifelong learning, occupational choices and success within a family with sixteen of its twenty-one children forced from school. Via audio-/video-taped interviews, three participants reflected upon their "lived experiences" during and since The Closing. Transcribed data were coded and analyzed based upon the major and underlying research questions guiding the study. Nine major conclusions were drawn from its findings: (a) The Closing perceivably impacted immediate educational goals of participants differently, (b) The Closing perceivably impacted specific and general long-range educational goals, (c) Participants have pursued educational goals via supportive spouses/family members and adult self-directed/lifelong learning measures, (d) Following the re-opening of schools, all respondents graduated high school, and two later enrolled in academic learning centers, (e) Self-directed learning has played an essential role in the lives of all participants, (f) All participants considered themselves life-long learners, (g) The Closing perceivably impacted the career plans of one participant, (h) Respondents acquired manufacturing and/or labor positions and were successfully employed throughout their adult lives, (i) Literacy assistance from family members, self-directed learning, on-the-job training and formalized coursework were perceived as having had a positive bearing on occupational success. The implications of this study suggested resiliency, family dynamics, family values, and narratological significance. Study participants, driven to live productive and successful lives, appeared to have emulated Adult Learning Theory tenets of self-directed, lifelong quests for formally-delivered and informally-acquired knowledge. Recommendations emerging from this study included investigations of School Closing survivors' motivations for adult learning, the role of faith in Closing survivors' lives, The Closing's perceived impact on the Next Generation, ancestral discourse, male birth order relationships, 1951 strikers' guilt, education vs. vocation and growth under adversity. / Ph. D.

In nature, many social species demonstrate collective behavior ranging from coordinated motion in flocks of birds and schools of fish to collective decision making in humans. Such distinct behavioral patterns at the group level are the consequence of local interactions among the individuals. We can learn from these biological systems, which have successfully evolved to operate in noisy and fault-prone environments, and understand how these complex interactions can be applied to engineered systems where robustness remains a major challenge. This dissertation addresses a two-scale approach to study these interactions- one in larger scale, where we are interested in the information exchange in a group and how it enables the group to reach a common decision, and the other in a smaller scale, where we are focused in the presence and directionality in the information exchange in a pair of individuals. To understand the interactions at large scale, we use a graph theoretic approach to study consensus or synchronization protocols over two types of biologically-inspired interaction networks. The first network captures both collaborative and antagonistic interactions and the second considers the impact of dynamic leaders in presence of purely collaborative interactions. To study the interactions at small scale, we use an information theoretic approach to understand the directionality of information transfer in a pair of individual using a real-world data-set of animal group motion. Finally, we choose the issue of same-sex marriage in the United States to demonstrate that collective opinion formation is not only a result of negotiations among the individuals, but also reflects inherent spatial and political similarities and temporal delays. / Ph. D. / Social animals exhibit coordination often referred to as ‘collective behavior’ that results from interactions among individuals in the group. This dissertation has demonstrated how interactions can be studied using mathematical modeling, at the same time reveals that real-world interactions are even more complex. Mathematical modeling provides capabilities to introduce biologically inspired phenomena, for example, the implementation of both friendly and hostile interactions that may coexist; and the presence of leader-follower interactions, which is another determinant of collective behavior. The results may find applications in real-world networks, where hostile and leader-follower interactions are prevalent, for example international relations, online social media sites, neural networks, and biologically inspired robotic interactions. We further extend our knowledge regarding interactions by choosing real world systems, the first to understand human decision making, for example in public policies; and the second in animal group motion. Public policy adoption is generally complex and depends on a variety of factors, and no exception is same-sex marriage in the United States which has been a volatile subject for decades until nationwide legalization on June 26, 2015. We target this timely issue and explore the opinion formation of senators and state-law as they evolve over two decades to identify factors that may have affected the dynamics. We unravel geographic proximity, and state-government ideology are significant contributors to the senators opinions and the state-law adoption. Moreover, we build a state-law adoption model which captures these driving factors, and demonstrates predictive power. This study will help to understand or model other public policies that propagate via social and political change. Next we choose the system of bats to investigate navigational leadership roles as they fly in pairs from direct observation of bat swarms in flight. Pairs of bats were continuously tracked in a mountain cave in Shandong Province, China, from which three-dimensional path points are extracted and converted to one-dimensional curvature time series. The study allows us to answer the question of whether individuals fly independently of each other or interact to plan flight paths.