Dissertation Defense Announcements

Candidate Name: Varnika Mittal
Title: Draft genome of hairy sea cucumber Sclerodactyla briareus, a model to study gene families for tissue regeneration and host-viral interactions in echinoderms
 February 16, 2024  9:00 AM
Location: Bioinformatics Building, Room 218
Abstract:

Echinoderms are highly regenerative animals that share a common ancestor with chordates, including humans. While the two phyla share a common ancestor, echinoderms defeat humans when it comes to regeneration. Regeneration is the replacement of damaged cells or regrowth of damaged tissues or organs naturally. Despite the significant differences in the body plan of echinoderms and humans, the similarities in their genome structure, the genes these two groups share, the phylogenetic relationship they have, and the simplicity of experimentation make echinoderms a valuable group to study regeneration. We expect that understanding tissue regeneration in echinoderms can set a stage for improved treatments and provide insights for developing therapeutic approaches to treat human injuries in the future.

Even within such a highly regenerative phylum as echinoderms, some species regenerate more readily than others. Holothurians, commonly known as sea cucumbers, occupy a special place in this regard, as they can fully and rapidly regenerate their body parts and major organs, including: the viscera, central nervous system, body wall, and muscles. However, the available genomic resources are very limited to implement holothuroids as animal models to study regeneration. Moreover, the available genomic resources do not represent diversity within the phylum. Hence, to fill this gap, I have updated an easy-to-use web-based application, EchinoDB, a database resource that includes the genomic and transcriptomic data on 42 unique echinoderm species, spanning the deepest divergences within the five extant classes of the phylum in addition to the 2 new major datasets: the RNA-Seq data of the brittle star Ophioderma brevispinum and the high-quality genomic assembly data of the green sea urchin Lytechinus variegatus.

Among sea cucumbers, the vast majority of molecular studies have been done on a single species, Holothuria glaberrima which do not represent the diversity of various regenerative events, including: regeneration of the gut luminal epithelium (mesodermal to endodermal) and regeneration of the pharyngeal bulb. However, other sea cucumber species, especially, those of the order Dendrochirotida are capable of such exceptional regeneration events. Therefore, I sequenced and annotated the draft genome of a dendrochirotid Sclerodactyla briareus to gain a deeper understanding of the regulatory molecular mechanisms controlling regeneration and genomic aspects behind the diversity of regeneration, seen in echinoderms.

To illustrate the practical utility of the dendrochirotid genome for regeneration studies, key components of the Notch and Wnt signaling pathways were selected and identified in the genome of hairy sea cucumber S. briareus. This is a biologically relevant example as these pathways are crucial for tissue regeneration in echinoderms. They are highly conserved across all multi-cellular animals and are known to coordinate many cellular events, including: cell proliferation, de-differentiation, cell division, and apoptosis. Therefore, I aimed to retrieve 29 selected genes of the Notch pathway and 25 selected genes of the canonical Wnt signaling pathway. Except for Mesp2 (a Notch pathway gene), all other genes were identified in the newly assembled draft genome of S. briareus.

I also studied S. briareus for primordial host-viral interactions and to learn about the evolution of their immune system by looking at the recombination activating genes (RAG) in relation to Strongylocentrotus purpuratus and other echinoderms. The objective was to discover and characterize novel viral sequences within S. briareus alongside the evolution of immune genes (RAG-Like) in marine environment. However, because of the gaps in the assembly, I was unable to find any evidence of viral markers in the genome of S. briareus. The paucity of full-length contigs in the genome assembly also resulted into only 3 protein sequences that may potentially share a sequence homology with RAG1-Like gene, but further investigation is needed. The lack of results require improvements in the genome assembly and the availability of increased data for RAG-Like genes on echinoderms. Nevertheless, this work is still useful for regeneration studies on echinoderms.



Candidate Name: Stephen Parker
Title: A Single Case Study of an Inner-City School During an Era of School Choice
 February 27, 2024  9:30 AM
Location: Zoom: https://charlotte-edu.zoom.us/j/7213332920
Abstract:

With the recent increase in the number of available options for families to consider when selecting a school, diverse publicly funded public schools are now competing for both students and funding. This study intended to contribute to the available research on the changes at inner-city schools during increased school choice options. The purpose of this single case study was to gain additional insights into changes in student demographics, academic achievement, and perceptions of an inner-city high school during an era of increased school choice from 2011-2023. This single case study included both qualitative and quantitative data sources. The researcher’s data for this study involved semi-structured, one-on-one interviews with five participants and publicly available data from the North Carolina Department of Public Instruction and the North Carolina Teacher Working Conditions survey. The researcher also reviewed school yearbooks for the 2011-2023 school years to further develop an understanding of the school changes during the study period. Findings indicate that there has been a decline in enrollment over the past 13 school years, with an increase in the percentage of students of color attending the school. Findings also indicate a decline in the school's academic profile, with only a small improvement over the last two years. Implications included the need for the local school district to review the number of district-supported school choice options, the potential impact of choice programs on non-choice schools, the need to recruit and retain capable leadership, and evaluating the out-of-district application process.



Candidate Name: Nicole Voss
Title: Beyond Behaviors: The Role of Perception in Social Skills Reputation
 February 07, 2024  2:00 PM
Location: Colvard 3027C
Abstract:

This dissertation explores the perception of social skills in structured virtual interviews, with a focus on how verbal, nonverbal, and vocal signals influence Social Skills Perception (SSP). The study explores the impact of specific behaviors on observers' perceptions of social skills and why particular behaviors are associated with low social skills perception scores. A central finding is the "just right" effect, which reveals that both excessive and insufficient displays of certain behaviors can negatively affect SSP, emphasizing the importance of balanced social skills demonstration in structured interviews. The findings contribute to social skills literature by building on the Heggestad et al. (2023) Social Skills Framework and highlight the complex dynamics of SSP in professional settings, particularly in structured interviews. This study suggests that such interviews might not fully capture exceptional social skills, offering insights into interview practices and evaluating social competencies in the workplace. Future research is encouraged to explore SSP across various contexts and cultures to deepen our understanding of these phenomena.



Candidate Name: Devron Kenneth Furr
Title: A Case Study of the Experiences of Beginning Superintendents
 February 22, 2024  1:00 PM
Location: Zoom https://charlotte-edu.zoom.us/j/7213332920
Abstract:

Superintendent turnover in the state of North Carolina is a concern. Through a qualitative multiple case study, the researcher’s goal in conducting this study was to explore the lived experiences of eight first-year superintendents in North Carolina. Using Hambrick and Fukutomi’s (1991) concept of the seasons of a chief executive officer’s tenure, this study explored participants’ pathways to the superintendency and professional and personal challenges while in the role. Additionally, this study sought further understanding of participants’ priorities, successes, and mistakes, along with advice they had for aspiring superintendents. Eight semi-structured interviews were used to gather data for this study. To identify themes from the eight interviews, data were analyzed using a constant comparison analysis (Marshall & Rossman, 2006). The findings of the study align with existing literature about the experiences of superintendents. Common themes from the eight participants illuminated the importance of a productive partnership with the board of education, professional relationships with stakeholders, and the need for professional networking. Additionally, participants commonly felt a sense of professional isolation and struggled to maintain work-life balance. Implications and recommendations included the need to ensure aspiring superintendents closely consider the alignment between their goals and dispositions and those of the board for which they may work. Additionally, networking and long-range planning were emphasized along with proactive measures to address the social and emotional needs of those serving in highly demanding superintendent positions.



Candidate Name: Christopher Jonassen
Title: A Qualitative Study of Principal Perspectives on the Implementation of Restorative Practices
 February 19, 2024  2:30 PM
Location: Zoom: https://charlotte-edu.zoom.us/j/7213332920
Abstract:

With student discipline becoming a growing area of concern in public schools, the staggering number of office referrals and student suspensions following incidents of student misbehavior has caused principals to seek alternative methods. Restorative practices aim to teach students appropriate behaviors by focusing on reflection, repair, and open communication following incidents of misbehavior. The purpose of this basic, interpretive qualitative study was to explore school principals’ perceptions and experiences related to the implementation of restorative practices. The researcher hopes key findings will assist with future implementation efforts in schools and support principals seeking to change their practices from traditional discipline efforts to restorative approaches. The findings from this study revealed numerous implications for future research as well as recommendations for practice. Results from semi-structured one-on-one interviews with six public school principals revealed that there are advantages, processes, and pitfalls that can guide future research and implementation efforts. Participants consistently reported the benefits of implementing restorative practices in their schools to include improved relationships and fewer suspensions. Findings suggest that relationships, expectations, accountability, professional development, and mindset all play an important role in successful implementation. Additional research investigating the balance of restorative practices and traditional consequences and the impact on student academic performance is still needed.



Candidate Name: Lindsay M Merritt
Title: AN EXPLORATORY STUDY OF THE LIVED EXPERIENCES OF FIRST-YEAR, INTERNATIONAL SPANISH-SPEAKING DUAL LANGUAGE TEACHERS IN NORTH CAROLINA
 February 26, 2024  2:30 PM
Location: Zoom Meeting Room: https://charlotte-edu.zoom.us/j/7213332920
Abstract:

As interest in DL/I programs continues to grow in North Carolina, the hiring of international teachers has increased tremendously. These international teachers often have not had the experience or training to address the needs of the students they are serving. In addition, pedagogical challenges such as working with diverse learners' abilities, social constraints, educational practices, and emotional needs are often associated with international teachers' different experiences. Many states, including North Carolina, seek to expand dual language programs but have difficulty hiring sufficient dual language teachers, highlighting the need to hire internationally (Lachance, 2017).
The purpose of this exploratory study was to examine the perceptions and experiences of first-year international Spanish-speaking DL/I teachers in North Carolina, focusing on the supports and barriers these teachers face relative to cultural differences. The results of this study from semi-structured one-on-one interviews indicated that international teachers sometimes feel unsupported as they face barriers in housing, transportation, and healthcare. Emotional isolation was common as they dealt with loneliness and homesickness. Cultural barriers, such as spoken and body language nuances and differences in educational systems, emphasized the multifaceted impact of cultural differences on their teaching experience. Implications reflect the urgent need for comprehensive training for DL/I teachers, focusing on locality. Additionally, there is a call for better pre-arrival support, considering the challenges international teachers face in adjusting to the nuances of North Carolina's educational system as compared to their experiences in their home countries.



Candidate Name: Mahfuja A. Khuda
Title: Modeling and Analysis of the Latent Heat Cold Thermal Energy Storage (LCTES) System Using Salt Hydrate
 February 06, 2024  1:00 PM
Location: Zoom link: https://charlotte-edu.zoom.us/j/99472410689?pwd=TUxIcjVmUkFGR0thMFhOeks5UXc5dz09
Abstract:

Energy storage plays a crucial role in addressing the growing demand for energy and electricity while simultaneously reducing greenhouse gas emissions. Most of the power infrastructure in the U.S. heavily relies on water-cooling technology, leading to significant freshwater withdrawals. To mitigate high water withdrawal rates and the thermal pollution of water sources, an alternative solution involves implementing dry cooling towers (DCT) or air-cooled condensers (ACC). However, the effectiveness of dry cooling techniques depends on the dry bulb temperature of the ambient cooling air, resulting in a plant performance penalty equivalent to approximately a 2%-point efficiency loss compared to wet cooling.
The current research focuses on designing a cost-effective latent heat cold thermal energy storage (LCTES) system to enhance the performance of DCT/ACC during the summer months. This is achieved by storing cold energy during the nighttime in inexpensive materials like phase change materials (PCM), such as CaCl2 hexahydrate or CC6. To guide the LCTES design, a numerical analysis of the melting and solidification processes of PCM within the tube array was conducted. Transient two-dimensional Navier-Stokes equations and a Realizable k-ɛ turbulence model were used to predict fluid flow and heat transfer in LCTES heat storage modules. The enthalpy-porosity technique was employed to model PCM melting and solidification.
The numerical results show excellent agreement with experimentally obtained values. The resulting design successfully met the predefined performance criteria, achieving a cooling effect of 4 °C for a four-hour duration while maintaining a pressure drop of less than 100 Pa. The proposed prototype-scale tube array design can efficiently cool the incoming ambient air, and PCM in the LCTES can be fully frozen overnight. The energy storage density of the system falls within the range of 22 to 27 kWh/m3, with the maximum energy efficiency reaching around 75% during the system charging and discharging processes. Apart from its primary focus on coal power plant dry cooling technology, the suggested concept can also be used for industrial, commercial, and residential applications, including concentrated solar power (CSP).



Candidate Name: Bethani Cogburn
Title: Low Income STEM College Student Experiences of Ecowellness
 February 05, 2024  3:30 PM
Location: COED 246
Abstract:

The rising rates of mental health issues among college students (WHO, 2022) can be compounded by the challenges of STEM (Henry et al., 2022) and any experiences of minority stress (Helling & Chandler, 2019), yet little research has been done on college student wellness (Beauchemin, 2018), in particular low income STEM college students. Moreover, the concept of ecowellness (Reese & Myers, 2012) is still new and growing within the field of counseling, indicating the need for further study and application. Previous authors have asserted the potential for nature-based social groups in supporting wellness (Adams & Morgan, 2018; Reese & Gosling, 2020). The purpose of this research study was to understand the ecowellness experiences of STEM college students who are recipients of a scholarship serving low income students. Using a phenomenological case study design (Vagle, 2018), I collected demographic information and interviewed 9 participants for the study then analyzed the data. Analysis involved constant comparative coding (Dye et al., 2000) followed by final development of the findings through iterative dialogue with two external reviewers. Analysis produced two major findings, ecology of wellness and nature as partner in nourishment, including five themes and 14 sub-themes. Implications of these results for higher education, STEM, and the counseling field are discussed, along with limitations of the study and recommendations for future research. Higher education stakeholders may consider employing nature-based social groups to promote the wellness, academic achievement, and career success of college students. The results of this study add to the understanding of the relationship between nature, access, and wellness for this case study of diverse low income STEM college students.



Candidate Name: Abhishek Shibu
Title: EXCITON MANAGEMENT IN METALLOPORPHYRINS AND THIAZOLOTHIAZOLE-BASED MATERIALS
 January 24, 2024  11:00 AM
Location: Science Building 115
Abstract:

Over the last few decades, optical technologies utilizing organic materials in the solid state have become ubiquitous. In the solid state, contrary to their constituent molecules, organic materials exhibit energy level continuums along which excited-state energy (excitons) can diffuse. Controlled and efficient management of excitons in systems with numerous organic molecules packed in limited degrees of freedom has been the governing principle for organic optoelectronic devices. However, given the net neutral electrical charge of an exciton and the complex excited-state energy landscape in organic molecular aggregates, efficient management of excitons becomes a challenging task.
In this lecture I will present three significant studies that explore the manipulation of exciton behavior in organic solid-state materials through self-assembly techniques. By modulating molecular packing in the solid state, the energetics and photophysical properties of the chromophores can be effectively controlled, opening up avenues for advanced optical and photonic applications. The successful modulation of exciton diffusion in Zn-metalloporphyrin solution-processable thin films and the establishment of a structure-photophysics correlation in disubstituted alkoxyphenyl thiazolo[5,4-d]thiazole (TTz)-based crystals demonstrate the potential of this approach. Furthermore, the controlled formation and relaxation kinetics of excimers in asymmetric TTz films offer a novel route to achieving high luminescence efficiency, paving the way for a new generation of optical and photonic devices. These findings highlight the importance of self-assembly as a powerful tool for tailoring the behavior of excitons in organic chromophores, leading to significant advancements in various fields.



Candidate Name: Md Shifat Us Sami
Title: Co-growth of 3D Si and 2D Si2Te3 Crystals: Roles of Catalysts and Effects of Catalyst Stabilities
 January 29, 2024  1:00 PM
Location: Duke 324
Abstract:

Growth mechanism study is important to achieve high-quality materials growth using more convenient approaches and to realize controlled growth with compositional and structural tunability. In vapor-based deposition, vapor-solid (VS) and vapor-liquid-solid (VLS) processes have been two classic mechanisms for the growth of micro- and nano-scale structures. The VS process is a non-catalyst growth controlled by vapor supersaturation, while the VLS process is a catalyst-assisted growth initiated and guided by eutectic particles. This research reported a co-growth of three-dimensional (3D) Si crystals with two-dimensional (2D) Si2Te3 crystals and explored its growth mechanism. Chemical vapor deposition (CVD) method has been employed using Te and Si powders as the source materials in the presence of a Cu-coated Si substrate. The growth mechanism study reveals that the Te source plays two different roles in the growth. First, it serves as a reactant which vaporizes and reacts with Si powders to yield 2D Si2Te3 growth via the VS mechanism. A unique “liquid epitaxial growth” was discovered that Te droplets formed prior to the Si2Te3 growth could promote a quasi-epitaxial growth of Si2Te3 crystals on a lattice mismatch substrate. Second, the Te serves as an unstable catalyst for the 3D Si growth. The Si growth is promoted by the synergistic effects of Cu and Te: (1) Cu as a stable catalyst facilitates the reaction of Te vapor species with the Si substrate, forming ternary Te-Cu-Si eutectics; (2) due to the instability of Te, the Te-Cu-Si eutectic particles evaporate and release Si vapor as the precursor for the VS growth of Si crystals. This intermediate process is dubbed as a vapor-liquid-vapor (VLV) process which provides a new approach for the material growth with lower growth temperature, lower cost, and higher compatibility for device fabrications.




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