Dissertation Defense Announcements

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.

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.

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.

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).