University of Central Florida
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Motor Unit Control of Maximal Grip Force Among Older Adults: Reliability, Weakness, and Interventions
No full textRecent evidence suggests that grip strength is a critical biomarker of brain, muscle, and metabolic aging. To date, neuromuscular properties related to individual motor unit size and firing rates have not been explored in the context of grip strength assessments in the older adult population. Given the strong correlation between grip strength and all-cause mortality, understanding motor unit characteristics during maximal grip tests will provide novel perspectives and implications regarding healthy aging. The purpose of this dissertation project was to develop an analytical framework to reliably characterize motor unit strategies employed during maximal grip strength tests, and compare these characteristics between weak and non weak older adults. Study 1 explored the reliability of linear and exponential regression model coefficients derived from motor unit peak firing rate and action potential amplitude relationships during maximal grip strength tests. Results demonstrated moderate-to-excellent intrasession and poor-to-good intersession reliability among key model coefficients, despite poor reliability for the number of motor units used to create the regression models. Study 2 sought to compare key regression model coefficients between weak and non-weak older adults in a single grip testing session. Results from this study show significantly higher peak firing rates, slopes, and decay factors for the non-weak group, which may indicate potential down-regulation of higher threshold motor units among weak older adults. Individuals in the non-weak group also reported significantly higher engagement of vigorous exercise activities compared to the weak group. Study 3 employed a randomized-controlled, double-blind design to explore the potential of combined action observation/mental imagery and transcranial direct current stimulation to modulate motor unit firing rates among older adults. Results from this study indicate no group differences, however lower grip strength was observed among all groups following the intervention period
Hetero-cisgender rituals: the oppression of sexual- and gender-minoritized people
No full textAmong the groups that experience health inequalities in the United States, sexual- and gender-minoritized people figure prominently. Medical practitioners are tasked with alleviating these health inequalities, and it has been suggested that through the education of new physicians, we can decrease these inequalities. This perspective, however, neglects that medical students are social actors and their socialization begins long before medical school. In the present study, I develop a framework for understanding hetero-cisgender rituals that medical students experience and participate in before starting their medical training. I answer three research questions: (1) To what extent do medical students witness hetero-cisgender rituals? (2) How do medical students participate in hetero-cisgender rituals? (3) How do medical students disrupt and deritualize messages of heteronormativity and cisnormativity? Via an analysis of medical student narratives, I develop a hetero-cisgender ritual framework to understand their participation in everyday practices that reproduce heterosexuality and cisgenderism. In their narratives, medical students propose what can be done to improve the experiences of sexual- and gender-minoritized people in medicine. I find that medical students both witness and participate in hetero-cisgender rituals performed by family members, religious communities, and healthcare providers. Medical students that participate in hetero-cisgender rituals observe rituals unfold in silence or assist ritual officiants, but some also officiate rituals. While describing their experiences, medical students suggest opportunities for personal growth and changes in clinical practice that can improve the health and health experiences of sexual- and gender-minoritized peopl
Investing in Digital Solutions for Firm Value
No full textDigital investments have become integral to the strategies of hospitality firms, enabling data-driven decision-making, operational efficiency, and financial growth. This dissertation examines the impact of digital investments, specifically IT investment (CAPEX), research and development (R&D) intensity, and digital marketing intensity, on operational and financial performance within hospitality firms, guided by Innovation Diffusion Theory and Agency Theory. A comprehensive empirical analysis utilized financial data from publicly traded U.S. hospitality firms (2013–2023). Advanced econometric methods, including ARIMA, GARCH, and structured panel regressions, were rigorously assessed to evaluate performance dynamics. Findings reveal IT investments significantly enhance operational efficiency, profitability, and liquidity, despite causing short-term volatility in risk-adjusted returns due to elevated capital expenditures. R&D intensity significantly improved market valuation, highlighting the importance of sustained innovation despite initial uncertainty. Digital marketing intensity substantially boosted liquidity and EBIT-to-assets, yet introduced short-term financial volatility, underscoring the need for strategic oversight and careful expenditure management. Firm size emerged as a critical moderator, with larger firms deriving greater benefits from digital investments due to resource advantages and established infrastructure. Theoretically, this research extends Innovation Diffusion Theory by empirically clarifying the temporal progression from initial uncertainty to long-term competitive advantage. It expands Agency Theory by demonstrating how transparent managerial incentives and monitoring reduce agency costs, enhancing shareholder value. Practically, the findings offer hospitality managers actionable insights, advocating incremental digital investments, disciplined oversight, transparent stakeholder communication, and strategic management of expectations to optimize long-term firm value. Despite acknowledged limitations in measurement and generalizability, this dissertation establishes a robust empirical foundation that guides future scholarship and managerial practice in digital transformation within hospitality contexts
Understanding The Mechanism In Shaping Guest Acceptance Of Service Robots In Caribbean Hotels: The Moderating Role Of Cultural Familiarity In The CAC Model
No full textService robots continue to become increasingly popular in the hospitality and tourism industry. Understanding the cognitive and emotional processes is important in explaining the sequential processes of guests accepting new technologies. Especially in regions like the Caribbean, where human-to-human interaction and personalized services are highly valued.
This study investigates how cognitive evaluations of service robots, including utility, coolness, autonomy, courtesy, and interactivity, influence guests\u27 emotional responses and their acceptance of the technology in Caribbean hotels. Additionally, the study explores the moderating role of cultural familiarity in the relationship between emotion and acceptance.
Using the cognitive-affective-conative (CAC) model, 415 responses were collected using a self-administered survey on the platform prolific and targeted US-based travelers over the age of 18. An exploratory factor analysis (EFA) was done to confirm the validity of the study’s key variables, followed by reliability tests. A multiple regression analysis confirmed that UTcoolness and autonomy significantly predicted positive emotion toward the service robot, while courtesy and interactivity did not. A simple regression analysis found that emotion had a significant effect on acceptance. A group difference test based on cultural familiarity revealed a stronger relationship between emotion and acceptance among participants in the low familiarity group with Caribbean culture compared to those with high familiarity.
This study adds to the current literature in hospitality by contextualizing the acceptance of service robots in a cultural setting and adding to the understanding of the role that emotion plays in acceptance. The findings offer strategic insights for hoteliers in the Caribbean and highlight the importance of cognitive features in the successful implementation of service robots
Examining the Feasibility and Influencing Factors of Large Language Models in Source Code Security Analysis
No full textLarge Language Models (LLMs) have recently emerged as promising tools for analyzing source code; however, their capabilities for automated vulnerability detection and localization remain underexplored, particularly given the widespread reliance on closed-source models which introduce significant privacy, security, and transparency risks. This dissertation rigorously examines the feasibility and key influencing factors determining the efficacy of open-source LLMs in source code security analysis. Initially, we investigate the impact of tokenized input length on vulnerability detection accuracy and explicitness across Java vulnerability datasets using ten distinct LLM architectures, identifying robust performance in specific models while others demonstrate considerable accuracy deterioration. Subsequently, we comprehensively evaluate the true vulnerability detection effectiveness of 38 open-source LLM configurations using both vulnerable and non-vulnerable datasets spanning Java and C/C++, applying realistic zero-shot and few-shot prompting scenarios and meticulously assessing model performance by specific vulnerability types. Furthermore, extending beyond mere detection capabilities, we conduct an extensive empirical study involving 66 LLM configurations for Java and 63 for C/C++ to examine hallucination behaviors during vulnerability localization. Our findings highlight that structured, assumption-based prompts substantially mitigate hallucinations, particularly among mid-sized models; nevertheless, precise vulnerability localization remains notably challenging, especially within C/C++ contexts. Finally, by evaluating precision, recall, and F1 metrics for various open-source LLMs at the function-level localization task, we systematically characterize their true effectiveness and practical applicability. Collectively, this dissertation establishes that through strategic prompt engineering, meticulous model selection, and rigorous empirical validation, open-source LLMs can reliably, transparently, and securely enhance vulnerability detection and localization processes, thereby substantially contributing to secure software development practices
Critical State-Based Study on Deformations Due to Construction Activities and Blast Densification
No full textThe behavior of geo-structures and foundation systems in densely populated urban areas relies on the successful performance of the supporting soils when subjected to static (e.g., the weight of the structure or service loads) or dynamic (e.g., earthquake-induced ground motions, construction-induced vibrations, wind loads, or traffic) loading scenarios. Construction-related activities and ground improvement operations can also be responsible to alter the stress-strain-strength behavior of supporting soils by causing vibration-induced ground deformations, excessive vibrations, or mobilizing soil shear strength in relation to in situ or as-built conditions. Construction-related activities and ground improvement operations such as blast densification trigger complex dynamic input energy-soil-foundation interactions that require robust numerical modeling frameworks to be able to simulate the wave propagation, excess pore water pressure generation, and resulting ground deformations and vibrations propagated through the participating soils. This dissertation focuses on studying the suitability of critical-state-based constitutive soil models to evaluate the triggering mechanisms and ground response (i.e., ground deformations and vibrations) during construction vibrations-related problems (e.g., impact pile driving and vibratory roller compaction) and soil stress redistributions induced by blast densification activities. Construction-induced vibrations and ground deformations are first studied via a field monitoring and testing program developed at selected construction sites across Central Florida followed by the study of soil arching, stress redistributions, and ground deformations in a field-testing blast densification program conducted at the Port of Portland, Oregon. These field-testing programs are used to understand expected soil responses and triggering mechanisms and to perform the validation of the proposed numerical modeling approaches presented in this research work. The hypoplasticity constitutive soil model for sands enhanced with the intergranular strain concept is used in this dissertation to model the changes in soil density (or void ratio) due to abovementioned activities. A detailed calibration of the constitutive soil parameters based on expected elemental scale responses is presented herein. Comprehensive parametric studies are performed following numerical modeling validations to study the effect of the variables involved in vibration-induced changes in dynamic soil behavior due to impact pile driving and road compaction activities and in soil arching and ground deformations resulting from excess pore water pressure dissipation in blast densification programs. Summary charts and equations to predict ground deformations and vibrations are proposed herein
Transformative experience design: Exploring the supply-side perspective in the theme park context
No full textThis study investigates how hedonic tourism activities can facilitate personal transformation, particularly in the context of mass tourism. Focusing on theme parks, which draw millions of visitors annually, the research explores the design elements that can foster visitor transformation. The study aims to uncover the design elements embedded in the creation of these activities and the effects they intend to foster in visitors, answering the research question: How do theme park design practices contribute to transformative tourism experiences? This question is significant given the limited empirical work connecting experience design and transformative tourism from the supplier perspective. Using a qualitative compressed ethnography, data were collected through participant observation and 34 semi-structured interviews with theme park designers and academics. The data were analyzed using a three-step theoretical coding process, which enabled the identification of themes and relationships within the participants\u27 perspectives. The findings revealed that physical stimuli play a significant role in the intentional design of transformative experiences, a factor that has often been overlooked. Moreover, unexplored pathways for personal transformation emerged from the data. These findings enhance theoretical knowledge on transformative tourism by extending the research context to include hedonic activities, expanding the conceptual model beyond existential and transformative learning perspectives. A new type of transformative tourism was conceptualized: invitational transformation, which occurs within commercial, unexpected, and co-created contexts, such as theme parks. This study also contributes to the body of tourism experiences by developing a typology of design elements to inform the production of physical, affective, and cognitive stimuli in these activities, identifying new concepts and components related to the contexts, activities, and emotions associated with individual transformation. This study addresses the rise of experiential offers, offering practical guidance for tourism practitioners to design activities that both entertain and facilitate tourist transformation
Investigation Of The Activity Of Cct2 In The Biogenesis Of Breast Cancer Extracellular Vesicles
No full textMetastatic breast cancer has the lowest cancer survival rate among women. 31% of metastatic breast cancer survivors live beyond five years. In comparison, 99% of women with non-metastatic breast cancer lived past the five-year survival rate. Breast cancer can be identified and treated based on the presence of hormone receptors (HR). The problem is that not all forms of breast cancer contain these receptors, so for these types of breast cancer, an effective treatment is not always available. The Khaled Lab identified Chaperonin-Containing TCP-1 (CCT) as a target for the development of breast cancer treatments and diagnostics. CCT is a protein-folding complex formed by eight subunits (CCT1-8) that was shown to fold many of the proteins involved in promoting breast cancer. CCT2 is a subunit of CCT that the Khaled lab found to be essential for the function of the chaperonin complex. CCT2 is also of interest because studies from the Khaled lab identified a relationship with the formation of extracellular vesicles (EVs). EVs are needed for cell-to-cell communications, and their synthesis could be deregulated with alterations of CCT2 expression. This research aims to explore the relationship between CCT2 and EVs. In the process, it was found that CCT2, in addition to being cytosolic, also localizes inside the nucleus of breast cancer cells and may have an unknown activity in nuclear processes. Importantly, exogenous expression of CCT2 in breast cancer cells increased the levels of CD63, an important marker associated with the biogenesis of EVs. Collectively, these results suggest that CCT2 may be essential for making the EVs that promote breast cancer metastasis
Flame Boundary Effects of Hydrogen-Air Premixing
No full textThe objective of this research was to investigate the reaction of hydrogen and heated air premixing when injected into a combusting ethylene-air crossflow, and to study the flame stabilization location with varying premixing levels. The main parameter of this investigation was the flame stabilization diagnosed through chemiluminescence, based on recorded equivalence ratio, temperature, and flame boundaries, and maintaining a constant air temperature, hydrogen and air mass flow, and momentum flux ratios. Testing was conducted at different ratios of hydrogen and air premixing achieved through alternating the distance between the point where hydrogen and air are mixed and the combusting crossflow. The results show a correlation between the amount of premixing with the location of flame stabilization and the flame boundaries. This research helps further understand the characteristics of burning hydrogen, which will be relevant as the use of hydrogen increases in energy generation
Starch Analysis Of Shell Tools From The Penny Plot Site (8BR158) For The Cape Canaveral Archaeological Mitigation Project
No full textShell tools have a history of being used in the processing and usage of plant foods and materials in past cultures. This study looks at starch residue analysis obtained from shell tools retrieved at site 8BR158 during excavations by the Cape Canaveral Archaeological Mitigation Project (CCAMP) in Cape Canaveral, Florida. This research hopes to expand the understanding and usage of shell tools and to gain a clearer picture of plant usage and environmental interactions of earlier inhabitants along the East Coast of Florida through starch grain analysis. Eleven shell tools were analyzed for starch residues, with six showing evidence of plant processing. Bivalve shells showed the lowest amount of starch residue and may have been single use items which were used for meat or fish processing, while whelk type shells showed the most likely evidence for plant food processing. This new information on possible usage of shell tools in the Indian River Lagoon region opens new doors to future studies, such as phytolith analysis and wear analysis, and will be of importance for gained knowledge and understanding of shell tools usage at other sites along Florida’s east coast