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Development of an Anisotropic Hyperelastic Material Model for Porcine Colorectal Tissues
No full textMany colonic surgeries include colorectal anastomoses whose leaks may be life-threatening, affecting thousands of patients annually. Various studies propose that mechanical interaction between the staples and neighboring tissues may play an important role in anastomotic leakage. Therefore, understanding the mechanical behavior of colorectal tissue is essential to characterizing the reasons for this type of failure. So far, experimental data characterizing the mechanical properties of colorectal tissue have been few and inconsistent, which has significantly limited understanding their behavior. This research proposes an approach to developing an anisotropic hyperelastic material model for colorectal tissues based on uniaxial testing of freshly harvested porcine specimens, which were collected from several age- and weight-matched pigs. The specimens were extracted from the same colon tract of each pig along their circumferential and longitudinal orientations. We propose a constitutive model combining Yeoh isotropic hyperelastic material with fibers oriented in two directions to account for the hyperelastic and anisotropic nature of colorectal tissues. Experimental data were used to accurately determine the model’s coefficients (circumferential, R2 = 0.9968; longitudinal, R2 = 0.9675). The results show that the proposed model can be incorporated into a finite element model that can simulate procedures such as colorectal anastomoses reliably
Charging During the Stay: The Effects of EV Chargers’ Availability and Pricing on Consumer Perceived Utilitarian Value and Behavioral Intentions
No full textHotels are increasingly hosting EV chargers. Yet, scant research examines the effects of EV chargers on consumer behavioral intentions toward the hotel. This study draws on the expectancy theory and examines the effect of EV chargers availability and the availability of surrounding chargers on consumer hotel booking intentions and willingness to pay a price premium. The results of two scenario-based experiments showed that free or paid EV chargers enhance consumers’ perceived utilitarian value and behavioral intentions. The effects are partially amplified when the availability of surrounding chargers is limited. This research contributes to the literature on hotel add-on services and offers practical guidance on EV charger implementations at hotels
Making College Worth It: Inequalities In Higher Education and How to Solve Them
No full textMost students who graduate from college go on to earn higher wages, have more employment stability, and enjoy better health. While posted tuitions are high, a “high price, high aid” approach to college pricing means that the average cost of college has actually declined in recent years. Yet, public confidence in higher education is at an all-time low. What explains this tension? Who gains from going to college and who does not? What can colleges do to change perceptions about the value of a college education? This lecture by Brookings Institution scholar Katharine Meyer highlights trends in college enrollment and completion and offers solutions for how states can hold colleges accountable and align student support with the needs of the 21st century learner
The Cost of Long-Term Care in the Mountain West, 2023
No full textThis fact sheet examines data on the cost of long-term care for the Mountain West states of Arizona, Colorado, Nevada, New Mexico, and Utah from the Genworth “Cost of Care Survey.” Data on long-term care includes home health care, adult day health care facilities, licensed assisted living facilities, and certified and licensed nursing homes
Music’s Influence on Focus and Concentration: A Puzzle-Solving Task Study
No full texthttps://oasis.library.unlv.edu/spectra_images/1009/thumbnail.jp
Characterizing the Molecular and Cellular Changes of Senescent Cells Induced by Diverse Stressors in 2D and 3D Microenvironments
No full textAging is a risk factor for myriad diseases and is often associated with the accumulation of senescent cells. Cellular senescence, a process of irreversible cell cycle arrest, is associated with various changes in cellular morphology and function. While senescence will occur naturally in a time-dependent manner, it can be prematurely induced by various extrinsic and intrinsic factors. Most senescence studies model cell behavior in two-dimensional (2D) microenvironments; however, these models are not physiologically relevant. In this study, the effects of naturally occurring reactive oxygen species (ROS) hydrogen peroxide (H2O2) and commonly used chemotherapy drugs, doxorubicin and palbociclib, on cellular senescence are modeled and compared in 2D and 3D replicas of skin tissue using human foreskin fibroblasts (HFF). This study shows that senescence associated cellular changes are not only stressor-dependent, but also environment dependent
Using Student Voices to Inform Educational Reform: Exploring High School Educational Desires to Improve Curricular Decisions
No full textIn the education system, the integration of student perspectives into effective pedagogical strategies is gaining momentum. This dissertation delves into the concept of \u27Student Voice\u27 and its role in shaping educational frameworks. Recognizing the growing gap in soft skill proficiency among newly recruited employees, contrasted with the emphasis on hard skills within current educational standards, this study analyzes what those skill gaps are in the education and what skills students perceive are necessary to integrate into a high school education to better prepare students for life, the workforce, and higher education. Focused on recent high school graduates in Nevada, the research explores their educational experiences with a specific emphasis on soft skill cultivation. By amplifying student voices, the study aims to understand how students perceive their high school education in terms of soft skill development. Through mixed methods, the research seeks to identify the skills students consider essential for personal and professional growth, aligning these aspirations with broader educational objectives
Understanding Stress and Coping Among Adults in the United States During the COVID-19 Pandemic
No full textSince the COVID-19 pandemic started, individuals in the United States (U.S.) and across the globe have experienced unprecedented levels of stress. The purpose of this study is to understand the stress experienced among adults in the U.S. and which coping processes affect their overall emotional well-being. Guided by Lazarus and Folkman’s (1987) Transactional Model of Stress and Coping (TMSC), this study conducted a secondary data analysis (n=404) of adults across the U.S who completed an online survey examining their experiences with stress and coping. A Pearson correlation was utilized to explore the relationship between stress and depressive symptoms. Paired samples t-tests were conducted to evaluate stress, resilience, and depressive symptoms before and since COVID-19. Multiple regressions were calculated to understand the impact of cognitive appraisal on the eight types of coping. Participants primarily self-identified as White (40.3%), female (77.6%), with a mean age of 30.61 (13.76%), and Christian (43.1%). Results revealed gender, age, and racial differences in how adults cope with the stress of COVID-19. Male adults primarily utilized planful problem-solving (M = 5.6, SD = 3.5), while female adults primarily employed escape avoidance (M = 4.54, SD = 3.0). Adults aged 36–55 years old (M = 4.3, SD = 2.5) as well as 55 and older (M = 4.0, SD = 3.0) predominantly used planful problem solving compared to younger adults (18–35) who utilized escape avoidance (M = 5.0, SD = 2.9). Whites (M = 4.4, SD = 3.0), American Indians/Alaska Natives (M = 5.9 SD = 3.0), Asians (M = 5.1, SD = 2.9), Other (M = 4.3, SD = 3.4), and Multiracial groups (M = 4.6, SD = 3.1) predominantly used escape avoidance, while Black/African Americans (M = 4.9, SD = 2.5) and Pacific Islanders (M = 5.4, SD = 2.5) primarily used planful problem-solving. A small, positive correlation between COVID-19 stressors and depression symptoms (r = 0.251, n = 397,
Seasonal Climate and Environmental Conditions Associated with Physiological Variations of Southwestern United States Pines
No full textJuvenile and adult conifers in the southwestern United States are vulnerable to a range of different abiotic and biotic factors, yet it is unclear how their stress tolerance varies across environments. Predicted increases in the frequency and intensity of disturbance as well as greater climate and weather variability across the region highlight the potential for differential physiological responses across tree species and populations. This thesis focuses on two physiologic mechanisms, hydraulic vulnerability and mortality, that could be altered by climate change in two broadly distributed southwestern United States conifers: ponderosa pine and pinyon pine.
In chapter 2, I measured the hydraulic vulnerability of juvenile (~20-30 years old) ponderosa pines (Pinus ponderosa) in six climatically-varying locations (northern and central Arizona, southern and northern New Mexico, southern Colorado, and southern Nevada) of the southwestern United States (SWUS). I evaluated hydraulic vulnerability using the p50 value of stem conduits. P50 is the pressure (MPa) at which 50% of xylem conductance is lost, and lower p50 values correspond to lower tree vulnerability to soil moisture limitation. I then contrasted the climate and environmental conditions of our sampling sites from 1990-2020 using site characterization data, gridded meteorological estimates (DayMet), soil estimates (POLARIS), and soil water balance modeling (SOILWAT2). My objectives were to determine if hydraulic vulnerability varied between juvenile ponderosa pines growing in different subregional locations, and to determine if climate and environmental variables were associated with these differences. Juvenile ponderosa pines in southern Nevada had more negative p50 values (-5.05 ± 1.16 MPa) than juveniles in southern Colorado (-4.26 ± 0.79 MPa), southern New Mexico (-3.72 ± 0.86 MPa), and central Arizona (-4.06 ± 0.96 MPa; ANOVA, p \u3c 0.05). Compared to all other SWUS locations, southern Nevada also had significantly more severe warm season (April-September) meteorological moisture deficit, lower cool season (October-March) and warm season soil water potential [ψp: MPa], and lower soil water holding capacity (p \u3c 0.05). Thus, lower p, imparted by low warm season precipitation and physical soil characteristics, was associated with higher stress tolerance found in juvenile ponderosa pines growing in southern Nevada. Although future research is required to determine the reason for their higher stress tolerance – which could include acclimation, adaptation, and/or environmental control – my results provide new evidence for physiological differences at early stages of ponderosa pine development in the SWUS.
In chapter 3, I used the Cox Proportional Hazards (PH) model to evaluate background mortality hazard for adult pinyon pines in three climatically-varying locations (Colorado, Arizona, and Nevada) of the southwestern United States (SWUS). Life status (living/dead) and tree size were recorded for Pinus edulis (Colorado pinyon; Colorado, Arizona) and Pinus monophylla (single-leaf pinyon; Nevada) over multiple 10-year periods from 2001-2019 (USFS FIA). I then contrasted the climate and environmental conditions of each location using gridded meteorological estimates (DayMet) and soil simulations (POLARIS). My objectives were to determine if background mortality varied between adult pinyon pines growing in different sub-regional locations over a 10-year period, and to analyze associated variables and their potential time-dependent effects for P. edulis and P. monophylla. 10-year background mortality ranged from 4-6% across locations and was lower than previously reported for P. monophylla. Adult P. edulis in Arizona had the greatest cumulative hazard and lowest overall survival probability over a 10-year period. Based on my results, factors influencing background mortality varied between study locations. The probability of mortality significantly decreased with greater cool and warm season precipitation, % soil organic matter (30-100 cm), and % soil silt content (100-200 cm; p \u3c 0.05). The probability of mortality significantly increased with greater tree size (height and diameter), soil pH (30-100 cm), and cool season maximum air temperature (p \u3c 0.05). My results show that the mechanisms driving background mortality in adult pinyon pines differ between and among species occupying different climate regimes, and provide further evidence that greater tree size increases the probability of mortality pinyon pine
Experiment Development and Validation of a Granular Jamming Robotic Gripper
No full textA granular jamming gripper (GJG) is widely known as a Universal Gripper because of the wide range of objects that it can grasp and the simplicity of control, design, and manufacturing. Despite multitude of research improving the GJG, here, we focus on the base version of the GJG and attempt to glean the range of objects that it may reliably grasp. Despite the limited range of objects, which were a sphere, rectangular prism, and cylinder, we gleaned geometric properties as it relates to successful and unsuccessful grasping. This was based on the two types of testing: push and pull testing that measured the grasp ability, and grasp strength, respectively. The experiment results were surprising because we used the load cell in different orientations, but we attained the expected results as if the load cell was in the same orientation. These experiments attempt to validate and build upon current research by economically developing and testing the apparatus and gripper. From these experiments, we validated that the gripper grasp ability depends on the gripper diameter, and the contact angle with the object via introducing a “pressure” parameter that is the force by the surface area contact. Since a cartesian machine was used, we can nearly guarantee the depth into the object and therefore calculate the surface area contact using the 3D model