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In the United States (U.S.), Black women are more likely to undergo a cesarean birth in comparison to other racial and ethnic groups. Previous research has identified individual-level factors, such as health behaviors, comorbidities, and socioeconomic status to be associated with cesarean birth among Black women. However, those individual-level factors do not fully account for the variation in cesarean births. The three-manuscript dissertation explores factors that influence cesarean rates among Black women in the US. The first manuscript provided a scoping review of peer reviewed research on the risk and protective factors associated with cesarean birth among Black women in the U.S. In the second manuscript, logistic regression was utilized to examine the association between experiencing racial discrimination and delivery method using data from the 2016-2021 Pregnancy Risk Monitoring System (PRAMS). The third manuscript applied a qualitative, phenomenological approach to understand the experiences, perceptions, and needs of Black women following a cesarean birth. The findings contribute to the understanding of racial disparities in cesarean births and can inform evidence-based practice and research. There is opportunity to provide all women with the chance to receive optimal maternity care and Black women are no exception.
The functionality of manufactured components is intricately linked to their surface topography, a characteristic profoundly shaped by the fabrication process. Repeatable quantitative characterization of surfaces is essential for detecting variations, defects, and predicting performance. However, the plethora of surface descriptors presents challenges in optimal selection of the correct assessment metric. This work addresses two of these aspects: automatic selection of surface descriptors for classification and an application-specific approach targeting scan path strategies in laser-based powder bed fusion (LPBF) additive manufacturing.
A framework, titled Surface Quality and Inspection Descriptors (SQuID), was developed and shown to provide an effective systematic approach for identifying surface descriptions capable of classifying textures based on process or user-defined differences. Using a form of univariate analysis rooted in signal detection theory, the predictive capability of a discriminability value, d', is demonstrated in the classification of mutually exclusive surface states. A discrimination matrix that offers a robust feature selection algorithm for multiclass classification challenges is also introduced. The generality of the approach is validated on two datasets. The first is the open-source Northeastern University dataset consisting of intensity images from six different surface classes commonly found in cold-rolled steel strip operations. The application of signal detection theory's measure, d', proved successful in quantifying a texture parameter's ability to discriminate between surfaces, even amidst violations of normality and equal variance assumptions regarding the data.
To further validate the approach, SQuID is leveraged to classify different grades of surface finish appearances. ISO 25178-2 areal surface metrics extracted from bandpass filtered measurements of a set of ten visual smoothness standards obtained from low magnification coherent scanning interferometry are used to quantify different grades of powder-coated surface finish. The highest classification accuracy is achieved using only five multi-scale descriptions of the surface determined by the SQuID selection algorithm. In this case, spatial and hybrid parameters were selected over commonly prescribed height parameters such as Sa, which proved ineffective in characterizing differences between the surface grades.
Expanding surface metrology capabilities into LPBF additive manufacturing, additional studies developed a methodology to comprehend the relationship between scanning strategies, interlayer residual heat effects, and atypical surface topography formation. Using a single process-informed surface measurement, a critical cooling constant is derived to link surface topography signatures directly to process conditions that can be calculated before part fabrication. Twelve samples were manufactured and measured to validate the approach. Results indicate that the methodology enables accurate isolation of areas within the parts known to elicit heterogeneity in microstructure and surface topography due to overheating. This approach provides not only a new surface measurement technique but also a scalable parameterization of LPBF scan strategies to quantify track-to-track process conditions. The methodology demonstrates a powerful application of surface texture metrology to characterize LPBF surface quality and predict process outcomes.
Overall, this thesis contributes a systematic approach for identifying discriminatory parameters for surface classification and a novel process-informed surface measurement for predicting track-scale overheating during LPBF-AM of a nickel superalloy.
This dissertation advances research on evaluation (RoE) through a trio of studies focusing on the role of context and the innovative use of Linguistic Inquiry and Word Count (LIWC) software in formative evaluation in a qualitative research project. The initial study maps out how evaluation context dimensions—evaluator, stakeholder, organizational/program, and historical/political—affect evaluation, providing a nuanced understanding of these impacts. Subsequent research demonstrates LIWC's potential to monitor and formatively evaluate interviewer effects in data collection using LIWC's summary variable (authenticity and emotional tone), revealing that interviewer-interviewee demographic alignment has no significant effect in this specific qualitative research's data collection process. The final paper broadens LIWC's application, employing all built-in variables to pinpoint linguistic indicators of data richness, thereby refining data collection techniques. Together, these investigations shed light on contextual influences in RoE and validate LIWC as a pivotal tool for evaluators to assess evaluation context and provide strategies to evaluate qualitative data collection efforts ethically and efficiently, advocating for informed and adaptive evaluation practices to enhance research quality.
Key Words: Research on evaluation (RoE), evaluation context, Linguistic Inquiry and Word Count (LIWC), formative evaluation, interviewer effect, data collection, data richness
Computational materials science plays a crucial role in advancing new and improved materials. To leverage the advantages of local and nonlocal methods and aid in the advancement of predictive capabilities for materials, multiscale models have been introduced. Many such methods have been proposed to overcome computational challenges in accuracy and efficiency. In this work, I begin by presenting a review of some multiscale methods for crystalline modeling to provide context for this dissertation.
Together with my advisor Dr. Xingjie Helen Li, we explore the static behavior of a bottom-up nonlocal-to-local coupling method, Atomistic-to-Continuum coupling, and explore the dynamic behavior of a nonlocal method, Peridynamics, to explore a bimaterial interface.
Inspired by the blending method developed by \cite{Seleson2013} for nonlocal-to-local coupling, we create a symmetric and consistent blended force-based Atomistic-to-Continuum (AtC) scheme for one-dimensional atomistic chains. AtC coupling schemes have been introduced to utilize the accuracy of atomistic models near known defects and the computational efficiency of continuum models elsewhere. The conditions for the well-posedness of the underlying model are established by analyzing an optimal blending size and blending type to ensure the stability of the $H^1$ seminorm for the blended force-based operator. We present several numerical experiments to test and confirm the theoretical findings.
Then, we create a Peridynamics-to-Peridynamics scheme to model a bimaterial bar in one dimension. Peridynamics (PD) naturally allows for the simulation of crack propagation in its model due to its use of integro-differentials and time derivatives instead of the spatial derivatives typical of classical models. Although PD can be computationally intensive, its ability to accurately model fracture behavior, especially at material interfaces, makes it a valuable tool for achieving high accuracy in simulations, especially due to the susceptibility of fracture where differing materials meet. We prove the conservation laws, derive the dispersion relation, and estimate the coefficient of reflection near the interface for this nonlocal-to-nonlocal problem. We seek an optimal nonlocal interaction kernel in the governing equation for the cross-material interaction to reduce spurious artifacts when the kernel is assumed to be constant.
Lastly, I discuss potential future development in Atomistic-to-Continuum coupling and Peridynamics.
The COVID-19 pandemic abruptly changed educational institutions globally and challenged teachers and students. This immediate shift was difficult for K12 teachers because they were required to teach their courses online or using a blended learning (BL) model. As BL use continues to grow, concerns about student-content engagement have emerged. This study used a single case study to investigate experiences with facilitating student-content engagement in BL environments. Eleven teachers from two districts were surveyed and individually interviewed with semi-structured interviews. The complex adaptive blended learning systems (CABLS) was used as the theoretical framework to guide the data collection, data analysis, and interpretation of results. Findings of this study revealed that the learner demographics showed a diversity in economic status and academic abilities, with socioeconomic status emerging as a potential indicator affecting students’ access to technology within BL environments. Digital literacy skills varied among students, influencing their student-content engagement in BL environments. Teacher experiences with BL varied from embracing the mix of technology-mediated instruction with traditional F2F methods. Additionally, results showed that the support systems such as instructional coaches and professional learning communities (PLCs) played a crucial role in facilitating student-content engagement and enhancing pedagogical practices. Furthermore, findings showed that districts and institutions have demonstrated commitment to supporting BL environments through multiple layers of support. As technology continues to evolve, addressing challenges and leveraging collaborative efforts will be essential in ensuring that BL environments thrive and promote meaningful student-content engagement. Implications of this study inform the development of best practices, guidelines, and resources to enhance student engagement and foster a culture of continuous improvement in BL environments to improve student learning outcomes.
Plasmonic metamaterials are artificially structured materials with the inclusion of metallic elements regarded as macroscopically uniform mediums. These materials showcase adaptable optical characteristics achieved through manipulation of the materials' intrinsic geometries at scales much finer than the wavelength of the incident electromagnetic radiation under consideration.
This dissertation focuses on the fabrication methodologies and applications of plasmonic metamaterials in perfect absorption and plasmonic sensing. Plasmonic metamaterials, distinguished by their ability to manipulate electromagnetic radiation through engineered subwavelength structures, have garnered significant attention for their potential in various fields, including photonics, sensing, and energy harvesting.
The dissertation examines current fabrication techniques for plasmonic metamaterials, focusing on additive manufacturing approaches. The advantages of two-photon polymerization for the fabrication of plasmonic metamaterials is discussed in detail along with more traditional techniques like electron beam vapor deposition and atomic layer deposition. The advantages and limitations of each approach are scrutinized, laying the groundwork for subsequent investigations into tailored designs for specific applications.
Building upon the foundation of fabrication techniques, two distinct applications of plasmonic metamaterials are examined. Firstly, the concept of perfect absorption, wherein the metamaterial is engineered to efficiently absorb incident electromagnetic radiation across a narrow spectral range. Through theoretical modeling and experimental validation, novel designs for achieving perfect absorption are proposed and characterized. The investigated designs leverage the unique optical properties of plasmonic metamaterials to enhance light-matter interactions.
Subsequently, the utilization of these architectures for sensing applications is demonstrated. By exploiting the sensitivity of surface plasmon resonance to changes in the local refractive index, plasmonic metamaterials offer unprecedented opportunities for label-free, real-time detection of biomolecules, gases, and other analytes.
This dissertation showcases the potential practical applications of plasmonic metamaterials in perfect absorption and plasmonic sensing. It contributes to the ongoing advancement of plasmonic metamaterials and their seamless integration into cutting-edge photonics and sensing technologies.
Rock weathering, or the mechanical and chemical breakdown of rock over time, creates the landscape on which all terrestrial life is built. Here, I quantify the rates and controls over mechanical weathering [rock cracking/fracturing] f surficial boulder deposits in Eastern California using by collecting rock and crack field measurements, clast size distribution data from the field, and rock elastic properties using laboratory testing. I used a chronosequence or space-for-time approach, whereby data are collected from rocks or sediments that have been exposed to natural weathering conditions for a range of times, using the properties of the stable deposits to represent the amount of weathering that occurs over the time span of exposure. I studied rocks at three sites, with rocks being exposed to Earth surface conditions from 0 to 148,00 years [148 ka].
I manually measured 8763 crack lengths, widths, and orientations from 2221 in situ boulders on Earth’s surface and found that that rock cracking is initially fastest when rocks are exposed to Earth’s surface conditions, with rocks accumulating cracks at a rate of 9-1502 mm of cracks per m^2 rock surface over a thousand years, or 0.1-36 individual cracks per m^2 rock surface over a thousand years. After this point, rocks continue to crack, but the rate of crack growth slows down. After about 30 ka, the growth rate is <36 mm of cracks/m^2 of rock surface per ka, or <1 individual cracks/m^2 of rock surface per ka. Using all rock and crack data I determined that age itself has the most consistent, positive, statistically significant correlation with the number of fractures per rock surface area [fracture number density] and the total length of fractures measured per rock surface area [fracture intensity].
From two sites, I collected a granitic boulder from each dated deposit for rock mechanics testing. These data show that rock compliance increases over time while mechanical weathering leads to an increase in microscale cracks, which alter the rock’s strength and elastic strain response under stress. Using the laboratory analyses and local weather station data, I implemented a simple daily stress model applying Paris’ law of subcritical crack growth to predict single crack growth after each day of weather conditions, for a period of 5000 years. Cracking occurred over only a limited number of unusually intense weather days when the daily range of air temperatures was the largest. In the two semi-arid sites, these cracking days were hot, dry summer days; in the arid site, the day when the most crack growth was predicted coincided with summer monsoonal rains. The model is highly sensitive to rock elastic properties, which supports the theory that a gradual increase in bulk compliance allows rocks to withstand stress without cracking over thousands of years.
Finally, I present clast size data to show that for volcanic and carbonate rocks, there is a correlation between the geometry of cracking observed on the rocks and the shape of sediments on older deposits: when many cracks are parallel to the rock surface, older deposits tend to have more flattened rocks on them. This shows that cracking rates and crack geometries can play a strong role in clast size and shape evolution over geologic time, and mechanical weathering should be considered when interpreting sediments in the geologic record.
These findings are directly applicable to geoscientists attempting to understand weathering, landscape evolution, and geological hazards. More broadly, the decreasing rock cracking rates that accompany slow mechanical property changes represent a real-world example of material fatigue vs. material failure.
The quality of life for those who support loved ones living with substance use disorder (SUD) is adversely affected due to destructive behaviors and the impact these behaviors have on the family system (Kaur, 2016). Consequently, primary support persons (PSP) often live their lives in silence and experience disenfranchised losses that impact not just the family unit but also impacts the human system, the most significant system among family units (Howard et al., 2010). This same researcher asserts this circular causality is almost always found among human and family systems as the actions of one person create responses or adaptions from other persons living within that same family unit. This is important because it highlights the way alcohol and other drugs (AOD) impact normal functioning of the addict, their loved ones, and society (Cudak & Pedagogika, 2015).
The purpose of this study was to examine variables that impact of quality of life of caregivers to people living with SUD. Perceived losses due to a loved one’s SUD, perceived social support, one’s own substance (ab)use, and stress were all examined to learn the impact these variables have on QOL. Multiple linear regression was utilized to examine the impact on QOL (n = 114) as predicted by losses, perceived support, substance use, and stress. Results indicated that support, losses, and stress are significantly associated with the dependent variable QOL (r2 = .815) to QOL. Results of this study postulate insight into future treatment approaches with PSP and highlight links to treatment that need to be addressed on behalf of PSP as well as the total family unit. These findings have implications for mental health and substance abuse counselors in terms of working with PSP and examining how improved QOL of support persons impacts those being treated for SUD. Future research is needed to examine how more thorough and more inclusive treatment approaches can include working with families of those who are addicted to substances.
Keywords: Quality of life, primary support person, substance use disorder, families, addiction, losses, depression and stress, support, family support, SUD treatment, family treatment involvement, support person
Sepsis is one of the leading causes of intensive care unit (ICU) transfers and mortality in the inpatient setting due to delayed recognition and untimely management of sepsis symptoms on non-ICU medical-surgical floors. Educating nurses on units with the highest rates of sepsis mortality and ICU transfers is important to increase confidence and knowledge to promote early recognition of sepsis and implementation of initial management guidelines. There is growing evidence of the effectiveness of escape rooms, however, most studies have been completed with students in academic settings. Additionally, sepsis education is traditionally targeted to the ICU and emergency department (ED) settings, not medical-surgical floors. The purpose of this project was to implement interactive escape room education with evidence-based sepsis content to prepare nurses to identify early warning signs of sepsis and clinical deterioration in medical-surgical patients. A two-group pre-/post-test quality improvement project was conducted with a sample of 17 nurses in the non-ICU medical-surgical units within the medicine service line at the project site. After the interactive escape room educational event, a statistically significant improvement in confidence and increased knowledge was demonstrated. Mean knowledge scores increased from 77.4 (SD=13.7) pre-intervention to 82.4 (SD=14.3) post-intervention. Significant improvements were seen in self-reported knowledge and confidence in identifying sepsis patients (z=2.33, p=.02), knowing how and what to monitor in sepsis patients (z=2.714, p=.007), and knowing initial management of patients with sepsis (z=2.646, p=.008). Mean ICU transfers decreased from 13 (SD=1.0) pre-intervention to 8.67 (SD=3.51) post-intervention indicating the project units performed better than the comparison units. Implementing an innovative escape room education intervention for non-ICU medical-surgical nurses is recommended to improve nurse knowledge and confidence in managing sepsis patients. By increasing nurse knowledge and confidence, earlier recognition of clinical signs of deterioration may assist with reducing ICU transfers related to clinical deterioration due to infections and sepsis.
This qualitative study explores the lack of African American students enrolled in AP Calculus courses in North Carolina public high schools. It considered the perception of student-counselor relationships, academic advising practices, and sense of identity of high school counselor participants. In-depth interviews were conducted with three, African American, female high school counselors with five to twenty-four years of experience in high school counseling. The data yielded five domains: characteristics of a school counselor, expected duties of a school counselor, criteria to become an AP Calculus student, student-counselor relationships, and academic advising practices and the outcomes. From the domains, twenty-seven themes were generated: empathetic, open-minded, organized, flexible, creative, knowledgeable, serving the holistic needs of students, classroom guidance activities, non-counselor duties, resource, enrollments, interventions, advocacy, completion of prerequisite courses, exceptions to the rule, teacher recommendation, AP agreement, importance, trust, connections, race, alternatives, methods, encouragement, benefits, awareness, and partnership. Recommendations include universal access to Math I for African American students in 8th grade, update all stakeholders of the role and purpose of school counselors, professional development for school counselors, and an integrated curriculum for school counselors and administrators.
