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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.
An in-depth analysis of a distinctive electric machine topology characterized by a doubly salient structure and integrated permanent magnets within the stator is presented in this dissertation. The machine demonstrates high power density (up to 50 kW/L) with capabilities such as a rated torque of 95 Nm at 12,500 rpm and a maximum speed of 37,500 rpm. An analytical model using lumped parameter magnetic equivalent circuits (LPMEC) is developed, examining spatial harmonics and validating results through finite element analysis. A high-fidelity model-based motor drive system employs a field-oriented control approach and introduces a complex vector current (CVC) regulation strategy, enhancing stability compared to classical methods. Comparative analyses highlight the robustness of CVC regulation. Experimental tests have been conducted to validate the analytical outcomes and proposed control methodologies employing an open frame laboratory prototype (OFLP) of the proposed machine and SiC based traction inverter.
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.
There is growing concern about the pervasive underrepresentation of qualified Black women superintendents. despite women significantly outnumbering men in public education. This study sought to shed light on the lived experiences of Black women superintendents in North Carolina. The purpose of this basic interpretive qualitative study was to gain an understanding of the perceptions about inhibiting and enabling factors Black women leaders faced when ascending to the superintendency and while serving in the role. Specifically, this study sought to contribute to the existing body of scholarly work and inform aspiring Black women superintendents about the experiences of Black women superintendents in the role, as this area has not been explored. By considering the intersectionality of race and gender for Black women superintendents, the study findings were grounded in the theoretic frameworks of Black feminist theory and the glass ceiling effect. These informed current practices related to hiring superintendents to create career advancement opportunities for aspiring Black women leaders. Results of the study from semi-structured individual interviews with five Black women superintendents in North Carolina indicated a substantial discrepancy between the number of women, particularly Black women, and men in the superintendent’s role. Implications included the need for career pathway training for prospective Black women superintendents, further research on the topic, new school board policies related to fair hiring and recruitment, and preventing suppression of opportunities by White power structures.
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).
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.
Graph coloring is commonly used to schedule computations on parallel systems. Given a good estimation of the computational requirement for each task, one can refine the model by adding a weight to each vertex. Instead of coloring each vertex with a single color, the problem is to color each vertex with an interval of colors.
Stencil graphs appear naturally in the parallelization of applications, where the location of an object in a space affects the state of neighboring objects. Rectilinear decompositions of a space generate conflict graphs that are 9-pt stencils for 2D problems and 27-pt stencils for 3D problems. We show that the 5-pt stencil and 7-pt stencil relaxations of the problem can be solved in polynomial time. We prove that the decision problem on 27-pt stencil is NP-Complete. We evaluate the effectiveness of several different algorithms experimentally.
Executing graph algorithms in a parallel or distributed context is a challenging problem. It is possible that the algorithm picks a partial order with long chains, which limits its utility to parallel applications. We investigate how distributed dataflow graph algorithms obtain a partial order and how one could favor orders with shorter long chains. We study the behavior of these different algorithms on randomly generated RMAT graphs and real-world graphs. We show that our ordering methods can significantly reduce the length of the longest chain.
Approximately 25% of United States mental health practitioners are employed in private practice settings (BLS Data Viewer, 2021). However, the Council for Accreditation of Counseling and Related Educational Programs, which sets standards for graduate level counseling programs, neither specifies private practice settings as a specialization nor an area for graduate programs to emphasize. In addition, research specific to private practice counselors is limited to the challenges of working in the setting (Harrington, 2013; Legge, 2017). The purpose of this study was to explore the career development and current work experiences of new licensed counselors who earned the required direct client and supervision hours in the private practice setting. Basic qualitative research design, as described by Merriam and Tisdell (2016), was paired with Braun and Clarke’s (2021) Reflexive Thematic Analysis for this exploration. Due to the limited empirical research, Krumboltz’s (1979) Social Learning Theory of Career Decision Making was used as a theoretical framework. Supporting evidence from eight participants was analyzed and five patterns emerged: (1) Non-Counseling Experience is an Asset, (2) Graduate School Does a Great Job Giving you a Foundation to Build On, (3) Practical Experience Makes Up for Academic Gaps, (4) I’m Going to Start Private Practice and See What I Can Do, and (5) Private Practice Yields for My Career Development. These patterns and the accompanying ten subpatterns are discussed in alignment with extant literature and the theoretical framework. A private practice counselor development model was proposed amongst the other implications of the findings.
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.
