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Predicting the Response of an Underactuated, 3D Printed Prosthetic Hand
No full textThe continuing need for hand prostheses has led to incredible developments in this area. However, due to the cost of the most sophisticated models, it is vital to develop simpler, low-cost, underactuated prostheses that can be produced rapidly. 3D printing is an important tool to achieve this goal. In particular, the 3D printed Flexy-Hand 2 has been one of the most common low-cost designs. A key feature of the Flexy-Hand 2 is its use of tendons and thermoplastic polyurethane (TPU) for joints that are strong and flexible. TPUs, however, lack a thorough understanding of their mechanical behavior, which makes it difficult to discern the forces needed to flex the prosthetic hand or to grip an object. The purpose of this research is to develop, and experimentally verify, a model that can predict the relationship between tendon forces and the flexion of the TPU joints of a prosthetic finger. First, a constitutive model for 3D printed TPU, NinjaFlex® was developed. This model accounts for the effect of filament extrusion temperature and material deposition orientations. Next, flexural tests of cantilevered specimens representing the finger joints were conducted to study the bending behavior of the TPU under realistic conditions to simulate finger flexion. Lastly, the results of these two tasks were incorporated in a quasi-static model relating finger flexion to tendon tension inducing it. This model was verified experimentally
Statistical Classification using Selection and Ranking Methodologies with Statistical Learning
No full textThe subject of Statistical Classification is concerned with identifying and allocating future observations into one of the pre-categorized classes based on the characteristics of the objects. Typically, these decisions to classify and categorize the objects have been dependent on identifying a system of classification, and from there, determining attributes for sorting.
In past decades, from discriminant analysis, various methods have been developed for classification. In particular, the rise of artificial intelligence (AI), machine learning, and statistical learning theory has made it possible to consider improving the existing methods along with new developments and more comprehensive schemes in conjunction with data-driven methods.
In this dissertation, we propose innovation using multiple decision-theoretic perspectives, such as the Indifference-Zone (IZ) approach and the Subset Selection (SS) method, to improve and clarify how these classification decisions can be made
Unraveling the Relationship between Social Vulnerability Index and COVID-19 Prevalence in Southern Nevada
No full textThe COVID-19 pandemic was a catastrophic global event that exacerbated public health issues and disparities, especially in socially vulnerable communities. Thus, this study examines areas classified by the CDC\u27s Social Vulnerability Index (SVI) metric, which assesses vulnerable communities experiencing adverse events through sixteen social determinants that impact health. The purpose of this study will be to determine if (1) COVID-19 testing rates and/or COVID-19 vaccination rates mediate SVI and COVID-19 prevalence rates and (2) if COVID-19 testing rate and COVID-19 vaccination rates serially mediate SVI and COVID-19 prevalence rates. In order to achieve this, census tracts within Southern Nevada will be analyzed from January 2020 to June 2022. Mediation analyses with linear regression were employed to examine complex relationships among SVI, COVID-19 testing, vaccination, and prevalence rates. The 95% confidence intervals of indirect effects were particularly computed using a bootstrap technique to determine whether a mediator was statistically significant. Results display that the COVID-19 testing rate (indirect effect = -3.98; 95% CI = -7.43, -0.11), COVID-19 full-vaccination rate (indirect effect = -1.88; 95% CI = -7.54, -0.95), and COVID-19 follow-up vaccination rate (indirect effect = -11.52; 95% CI = -15.97, -6.49) negatively mediates the relationship between SVI and COVID-19 prevalence rate. Our serial mediation analysis showed that an increase in SVI was significantly inversely associated with a significant total indirect effect of -0.02 (95% CI = -0.03, -0.002) from the sequential pathway from COVID-19 testing rate, COVID-19 full vaccination rate, and COVID-19 follow-up vaccination rate as serial mediators. These findings further highlight the impact of infectious outbreaks from access to vaccination and testing resources in socially vulnerable communities, underscoring the need for public health professionals to develop sustainable interventions
The Association Between Food Insecurity and Transportation Insecurity for Older Adults in Clark County, Nevada
No full textDue to the increase in the aging population, it is a public health priority to ensure communities are age-friendly to promote aging in place. However, there is a gap in the literature examining the relationship between food insecurity and transportation insecurity for older adults, who face unique challenges to both. In addition, access to food and transportation is directly influenced by structural/systemic racism, and people of color are overburdened by both insecurities. Because racial and ethnic disparities impact health outcomes, understanding these disparities in transportation and food insecurity is a necessary first step in beginning to address these issues. The study aimed to better understand the association between transportation insecurity and food insecurity for older adults aged 60 and older in Clark County, Nevada while considering racial and ethnic differences. Through a quantitative cross-sectional study, a secondary data analysis was conducted utilizing data from Three Square Food Bank. Through this analysis, it was determined that 18.2% of older adult participants were food insecure and 25.3% were transportation insecure. Logistic regression revealed a significant association between food insecurity and transportation insecurity (ꭔ2=239.418, df=4, n=1,001, p \u3c 0.001); a dose-response relationship shows that the odds of being food insecure increases as the severity of transportation insecurity increases. This association remains after controlling for correlates of food insecurity and transportation insecurity. While racial and ethnic differences in the odds of being food insecure were found in bivariate analysis, statistical significance was lost after controlling for correlates of food insecurity and transportation insecurity (ꭔ2 = 270.987, df = 22, n = 816, p \u3c 0.001). Furthermore, the odds of being transportation insecure were higher for non-white participants in bivariate analysis (ꭔ2=9.324, df = 3, n = 1,001, p = 0.025), but similarly, statistical significance was lost after controlling for correlates of food insecurity and transportation insecurity (ꭔ2 = 143.846, df = 18, n = 816, p = \u3c 0.001). Results from this study suggest that food and transportation insecurity are a public health concern for older adults; an association between food and transportation insecurity indicates a need to address both simultaneously. Interventions and policies aimed at the root causes of food and transportation insecurity are needed to better serve older adults in Clark County, Nevada
Plant-Plant Interaction in Early- Vs. Late-Successional Varieties of the Hawaiian Landscape-Dominant Tree, \u3cem\u3eMetrosideros polymorpha\u3c/em\u3e
No full textPlant-plant interactions play an important role in assembling plant communities. Interactions between neighboring plants can vary as a result of the genetic relatedness of neighbors, impacting rates of growth and patterns of resource allocation. When growing alongside close relatives, some species decrease their growth in a form of cooperation, while others grow faster through facilitation. A complication of plant interaction studies arises because decreased growth in the presence of close relatives can also be due to competition for resources, which increases with phenotypic similarity. Further complicating matters, mycorrhizal fungi, through their connections with plant roots, may strongly influence plant interactions.
My research compares the nature of plant-plant interactions within and between early- and late-successional varieties of Hawaiian trees, Metrosideros polymorpha var. incana (hereafter incana) and var. glaberrima (hereafter glaberrima), that differ in population density and the prevalence of mycorrhizal fungi in their native environments. I predicted that seedlings would respond (grow) differentially in the presence of genetically different neighbors and that the pattern of response would differ between the varieties in the presence/absence of mycorrhizae. Germinants of the two varieties were planted in pairs in experimental pots such that each pot contained a target seedling and a single neighbor, with the genetic relatedness of neighboring seedlings varying among treatments. One-half of the pots were supplemented with mycorrhizal fungi, and all were kept under ambient greenhouse conditions. After ~15 months, growth rates of the target seedlings were measured under the three treatments (sib = sibling neighbor, pop = neighbor derives from a different population of the same variety, and var = neighbor is from the opposite variety) as well as from control seedlings grown alone, both with and without mycorrhizal fungi. Additionally, hyphal growth was quantified in each pot with mycorrhizae to assess the relative roles of cooperation versus competition; cooperating seedlings were expected to increase the flow of photosynthates (i.e., carbohydrates) to their mycorrhizal symbionts, thus increasing hyphal growth.
Based on the results, an increase in nutrient uptake with mycorrhizal fungi seems to be common in both the early- and late-successional varieties, but the seedling behaviors especially towards siblings seem to be different between incana and glaberrima. The overall growth of both varieties of M. polymorpha was increased, and allocation to root length relative to shoot length was reduced in the presence of mycorrhizae compared to the absence of mycorrhizae, suggesting an increase in nutrient uptake with mycorrhizal fungi. Differences among treatments were completely restricted to the sibling treatment versus the pop and var treatments. In the presence of sibling neighbors, target seedlings of incana and glaberrima had lower and higher root:shoot length ratios, respectively, than those grown with more genetically distant neighbors. Interestingly, root:shoot mass ratios did not vary among treatments for either variety. These results imply that seedlings of glaberrima grown with sibling neighbors prioritized vertical root growth over horizontal root growth to obtain nutrients. Also in the sibling treatment, but in the absence of mycorrhizal fungi, higher specific leaf area (SLA) of target seedlings was observed in both incana and glaberrima, but statistically supported only in glaberrima. In glaberrima, both the greater SLA of target seedlings grown with sibling neighbors and the constant shoot length among treatments suggest the ability of seedlings of this variety to increase light capture without shading sibling neighbors. Further, with a single exception, the sizes of target and neighboring seedlings were negatively correlated as expected, due to competition; the exception was the sibling treatment for which there was a significant positive relationship for glaberrima alone, not incana. Finally, the greatest mycorrhizal hyphal length was observed in both varieties in the sibling treatment, suggesting cooperative behavior, yet this increase was statistically significant only in glaberrima. These four lines of evidence suggest that seedlings of late-successional glaberrima may be adapted to recognize and/or respond to genetically different neighbors, while such evidence was minimal or absent in seedlings of early-successional incana. Given that the differential response of seedlings to genetically different neighbors occurred even in the absence of mycorrhizal fungi, mycorrhizal symbionts do not appear to facilitate kin recognition or response in Metrosideros.
Beyond their responses to neighbor genetic relatedness, incana and glaberrima seemingly have different strategies for resource allocation affecting growth of both seedlings and their mycorrhizal symbionts that is consistent with their differential adaptation to early- and late-successional environments. Higher overall growth rates (i.e., final sizes) were observed in seedlings of incana relative to glaberrima regardless of neighbor treatment or the presence or absence of mycorrhizal symbionts. Rapid seedling growth in incana may reflect adaptation of this variety to the harsh conditions of early-successional environments where seedling establishment is likely restricted to occasional, brief periods of favorable conditions. In addition, mycorrhizal hyphal density was higher in incana-target pots relative to glaberrima-target pots. Despite a lack of correlation between total dry mass and hyphal density for incana or glaberrima separately or combined, the relatively higher growth rates of both target seedlings and mycorrhizal fungi in the incana pots may suggest a mutually positive relationship between incana and mycorrhizal fungi. Such a relationship may be expected in incana given the mycorrhizae-limiting nature and low population density characteristic of early-successional environments in Hawaii, where rapid seedling growth may be favored and can occur without intensifying competition among well-spaced neighbors. In contrast, growth of seedlings of glaberrima and their mycorrhizal symbionts may be restricted to minimize competition for resources in the high population densities of late-successional forests. Results of this research provide novel insights into the poorly known world of neighboring interactions in trees affected by genetic relatedness and successional stage, with implications for forest restoration
Identifying Disease-Related Gene-Environment Interactions Based on Method of Moments
No full textHuman diseases are often caused by a complex interplay of multiple factors, including genetics and environmental factors. These factors can play critical roles in the development and progression of diseases. Although genome-wide association studies (GWAS) have successfully identified many genetic variants associated with human diseases, the estimated effects of these variants are small and can explain only a relatively small portion of the heritability of the underlying diseases.
Detecting gene-environment interactions (G × E) can shed light on the biological mechanisms of diseases. However, most existing methods that investigate G × E only look at how one environmental factor interacts with either common or rare genetic variants, not both. In this study, we propose two approaches to detect interaction effects of an environmental factor and a set of genetic markers containing both rare and common variants.
The first approach is derived from the MinQue for Summary statistics (MQS) method and has been adapted in our study to develop two sub-methods: the MArginal Gene-Environment Interaction Test with RANdom or FIXed genetic effects (MAGEIT_RAN or MAGEIT_FIX). Our second approach leverages the Generalized Method of Moments (GMM), leading to the Gene-Environment Interaction Test based on GMM (GEITGMM). Through simulation studies and real data analysis, we evaluate the performance of these methods. Both the MQS-based MAGEIT_RAN and MAGEIT_FIX, and the GMM-based GEITGMM are grounded in moment estimation and offer analytical tools for examining gene-environment interactions
Mixed Methods Approach to Assess ‘Placental Opioid-Enhancing Factor’ Activity Within ‘Alternative’ Health Contexts of Human Maternal Placentophagy
No full textRats with elevated opioid levels experience an even greater increase in pain threshold after placenta or amniotic fluid consumption via placental opioid-enhancing factor (POEF) in the afterbirth. POEF only enhances opioid hypoalgesia; it cannot produce hypoalgesia alone. Although the POEF molecule remains unidentified and its efficacy in humans is unknown, it could be a safe, novel pain treatment. People who consume placenta as an alternative postpartum health practice are ideal for testing POEF bioactivity. Though rat models show that bioactive POEF is highly sensitive, some forms of the practice in humans may conserve POEF.
This project is the first attempt to conduct translational POEF research. For the past few decades, animal-model research has explored the mechanisms and effects of POEF without direct tests on human health. Moreover, human placentophagy research for the past decade has focused almost exclusively on the most common practice, which involves cooking the placenta, which almost assuredly deactivates POEF, because POEF is highly sensitive to temperature. However, some people choose raw and unprocessed placentophagy (RUP), which involves consuming raw, fresh placenta pieces directly after giving birth, or freezing placenta \u27chunks\u27 to consume after delivery. Although this much is known, there has yet to be a study investigating the practice in fine detail.
This dissertation contains the results from two studies. The first is a qualitative analysis of an online survey of, and semi-structured interviews with, birth workers with first-hand knowledge of RUP. The analysis of this study focused on how RUP fits into their birth-work practices, why some clients choose RUP, how they discuss RUP with clients, and the specific procedural steps for how the placenta is handled and prepared for consumption. Overall, the study participants reported using food-hygiene practices to inform their decisions regarding RUP.
The results of the first study informed the methods of the second study. The second tested if human placenta, prepared according to RUP protocols, and \u27raw, dehydrated\u27 placentophagy protocols, could enhance low-dose-morphine hypoalgesia, in rats, using a cold-water tail-flick assay. Despite the absence of a significant POEF effect in both positive controls and test subjects, the findings of the study remain inconclusive because of the small number of subjects
Top Tier 2.0: Student Achievement
No full textStudent Achievement is about our students who come to UNLV with the expectation that their experiences here will help improve their lives. Students are valued and their success is our mission. The work we do is vital as we prepare individuals for success in their personal, civic, and professional lives.https://oasis.library.unlv.edu/top_tier_focus/1033/thumbnail.jp
The Relationship Between Gender and Experienes of Weight Stigma From Healthcare Providers
No full textHealthcare providers are a common source of weight stigma, which is associated with lower physician trust, poorer patient outcomes, and the avoidance of healthcare services. Currently, there is a lack of consensus in research on whether women and men are equally likely to experience weight stigma from healthcare providers. The present study examined whether gender differences exist in weight stigma received from healthcare providers in childhood or adulthood, comfort seeking medical care, and healthcare avoidance. Adult participants (N = 196) reported the frequency at which they experienced stigmatizing experiences in healthcare environments in the past 12 months and during childhood using the Stigma Situations in Health Care (SSHC) Scale. The Measure of Healthcare Avoidance (MHA) was used to investigate reasons participants might avoid seeing a doctor, and two additional survey questions gauged participants’ comfort seeking medical care in the past 12 months. Logistic regressions showed no gender differences in past experiences of weight stigma (X2 = .072, 1 df, p =.789) or current experiences of weight stigma (X2 = 2.112, 1 df, p = .146). Furthermore, point-biserial correlations showed no association between gender and comfort seeking care (rpb = .051, p =.480) or healthcare avoidance (rpb =.005, p =.941). These findings suggest that men are as likely as women to experience weight stigma from healthcare providers in both childhood and adulthood, and exhibit comparable levels of healthcare avoidance and comfort seeking medical care. Future research should further examine the frequency and nuances of weight stigma in men, women, and gender-diverse individuals.https://oasis.library.unlv.edu/durep_posters/1231/thumbnail.jp
Association Between Polygenic Scores for Brain Structure and Alzheimer\u27s Disease
No full textAlzheimer’s disease (AD) is a progressive neurodegenerative condition and the most common type of dementia. Research has shown that volumetric changes in subcortical brain structures, which make up roughly 25% of the brain\u27s total volume and affect many physiological functions. This research project aims to investigate the genetic association between brain structures and AD. GWAS data of eight different brain structures (ICV, accumbens, amygdala, caudate, hippocampus, pallidum, putamen, and thalamus) were used to create polygenic scores (PGSs) in a discovery (cases/controls = 2,651/2,768) and replication dataset (cases/controls = 553/644). We utilized PRSice-2 software to generate PGSs and assess genetic correlations using two models: one adjusted for principal components (PC1 and PC2), and another incorporating sex, age, and APOE e4 allele count. Meta-analyses were conducted for discovery and replication samples using random and fixed-effect models with p\u3c0.05 being significant. Mendelian Randomization (MR) analyses were conducted between brain structures and AD. The PGSs of three brain structures–amygdala, hippocampus, and pallidum–were significantly associated (p\u3c0.0133) with AD in the fixed effects model, showing that a higher volume of these structures is inversely correlated with AD. However, the association did not remain significant for the hippocampus after being adjusted for covariates, suggesting that the association between the hippocampus and AD may depend on these covariates. MR analysis indicated hippocampal volume had an inverse causal effect on the development of AD, underscoring the critical role of the hippocampus in the disease\u27s progression.https://oasis.library.unlv.edu/durep_posters/1250/thumbnail.jp