Scholar Commons - Institutional Repository of the University of South Carolina
Not a member yet
34867 research outputs found
Sort by
The Effects of Implementing a Mindfulness Program in Two Elementary School Math Classrooms
Get PDFThis action research study examined the effects of utilizing trauma-informed social-emotional learning (SEL) teaching practices in two elementary math classrooms located in a Title 1 public school in North Carolina. The classrooms consisted of one third-grade classroom with 18 students and one fifth-grade classroom with 22 students. These classrooms integrated 10 minutes of mindfulness practice which included direct instruction on calming strategies and breathing techniques. This study worked to help foster a learning environment that supported the academic and mental health needs of the student participants and looked at potential relationships between calming strategies and math assessment data. This study followed a mixed-methods approach which allowed the researcher to examine qualitative and quantitative data to determine potential impacts of the mindfulness program. The data indicated that implementing a mindfulness program prior to math class provides students with tools to reduce anxiety and increase focus and engagement. There was not a statistically significant difference in the assessment scores between students who used mindfulness strategies and students who did not. However, the study data showed that students self-reported high levels of satisfaction with a mindfulness program prior to math class
Dust and Metals in Distant Galaxies
Get PDFInterstellar dust causes reddening and dimming of light from background objects. To analyze how different the dust in distant galaxies is compared to dust in nearby galaxies, we look at multiple background quasars and try to fit their spectra with various models for known galaxies that have differing dust grain populations combined with a quasar spectrum template. Through fitting these models, we found that dust in most of the foreground galaxies we analyzed is similar to the SMC bar, a relatively thin area selected from the Small Magellanic Cloud (SMC). However, we note that all the objects we studied did not experience much reddening as most of their E(B-V)\u3c 0, and therefore there was little to no dust extinction occurring in those galaxies. On another note, atomic absorption lines arising in gas clouds in foreground galaxies situated along sightlines to quasars can help with understanding the chemical composition of the galaxies. However, the column densities of elements derived from absorption line spectra depend on the atomic data used for the spectroscopic analysis. Many past column density determinations were based on old values of oscillator strengths. We used updated oscillator strengths of the transitions of the dominant ions of various key elements to calculate the changes in the column densities of these elements. We find that in some cases the column density differences arising from the improvements in oscillator strengths can be significant, even \u3e2 times the measurement uncertainties in the original published values of the column densities
Thermodynamic Study of Ligand Coordination on Lead Halide Perovskite Quantum Dots
No full textInorganic lead halide perovskite (ILHP) has been extensively studied in thin films and bulk crystals as promising materials for their photovoltaic and optoelectronic properties. These are stable enough to be prepared as colloidal quantum dots that can be dispersed, deposited and used to achieve quantum confinement; however, selection of the suitable surface passivating ligand remains challenge for long term stability of the colloidal quantum dots. Several ligand coordination chemistries used to achieve greater stability or specific functions: these can be installed at time of synthesis in some cases they can also be installed to preexisting quantum dots by ligand exchange reactions, which allows NC growth on coordination to be separately optimized and permits quantitative thermodynamic investigations. Different ligands are exchanged with the in situ ligands, among them zwitterionic ligands and quaternary ammonium salts are especially effective to enhance the stability of lead halide perovskite quantum dots. Here we employed isothermal titration calorimetry techniques to study thermodynamics of ligand coordination, which quantify the enthalpy of ligand coordination, number of ligands coordinating, ligand exchange equilibrium constant and provides insight of on variation of these parameter with size of quantum dots. In this work, we analyzed a recently reported room temperature synthesis of CsPbBr3 perovskite quantum dots and their stability with native ligands. From our results, we conclude that if native ligands are not exchanged with the stronger surface passivating ligands, it leads to growth of intermediate dots but introduction of primary amine allowed a stable size series of QDs with chemically similar surfaces to be achieved. These primary amine stabilized perovskite QDs showed potential starting material that can be analyzed using isothermal titration calorimetry to comprehend thermodynamics of zwitterionic ligand exchange
Assessing Relationships Between Water Quality, Precipitation, Land Cover and Stormwater Conveyance Type Across a Range of Sub-Watersheds in the Southeastern Coastal Zone
Get PDFThe expansion of urban land use/cover along the coast may degrade water quality by introducing a plethora of pollutants and pathogens that negatively impact human and ecological health. It is hypothesized that anthropogenic contaminants associated with stormwater runoff increase with increasing urban density and vary with the timing and magnitude of rainfall. In this study, we examined land use/cover change and relationships between Escherichia coli (E. coli), turbidity, nutrients, and the timing and magnitude of rainfall in two different types of stormwater conveyances (ditches and ponds) within Murrells Inlet, SC during the summer of 2023. Our results indicate there has been a 12.5% increase in impervious surface coverage from 1996-2016 in the Murrells Inlet study area. Levels of E. coli generally exceeded state regulatory standards, with ponds having significantly lower E. coli and phosphorus and significantly higher nitrogen concentrations than ditch sites (p \u3c 0.001), supporting the efficacy of ponds in retaining particle associated pollutants. Percent impervious surface relationships with E. coli and nutrient concentrations were more complicated and differed between pond and ditch sites. There were no large-scale patterns between precipitation timing and magnitude with water quality indicators. However, event scale measurements suggest that precipitation contributes to poor water quality in ditch sites. These results underscore the need for targeted best management practices to mitigate further water quality degradation in Murrells Inlet, emphasizing the importance of controlling impervious surface expansion and improving stormwater management systems
Integrated Coastal Science and Dune Management: A South Carolina Perspective
No full textHistorically, coastal dunes have been poorly understood from a societal perspective despite their protective role in attenuating incoming waves to reduce onshore flood risk. As developed coastlines promote strategies to design and maintain managed dune systems, it is necessary to ensure these strategies are optimized for dune health and resilience, particularly given the increasing threat of natural and anthropogenic stressors. This dissertation work aims to identify strategies that influence coastal dune management in South Carolina (SC), USA from an integrated approach, including a current use assessment, a mesoscale field-based study on strategy efficacy, and by incorporating a societal assessment and evaluation. First, a digitized inventory for sand fencing – a common and inexpensive management strategy emplaced for dune building – was created for the coastal zone of SC using Google Earth Pro (GE) imagery, with validation by location assessed using a high-resolution 2020 image. Results identified 8194 fences, an identification error of ≤1%, and an average placement error of 1.8 m. Statistical analysis and the integration of grey literature provided context on the utility of sand fences as a coastal management strategy across the state, suggesting 55.4% were associated with beach nourishment and 87% were installed following state-mandated recommendations.
Next, a field-based experiment was conducted for approximately one year at Debordieu Beach, SC to compare the development and storm response for two managed dune systems: one with sand fences and dune vegetation installed on a nourished dune with a graded stoss slope of ~21% and second “management zone” where the same materials were installed on a flat upper backshore with a gradual stoss slope of ~4%. Field surveys took place every ~6 weeks and included terrestrial LiDAR (TLS) topographic surveys for Digital Elevation Model (DEM) generation, vegetation surveys for Object-Based Image Analysis (OBIA), and sediment samples. Result from this study indicate that the initial rate of accretion was inhibited (0.54 m3/day vs 0.96 m3/day) for the site inclusive of a nourished dune slope during pre-storm conditions. Statistically significant (p\u3c 0.001) accretionary and erosional hotspots indicated site-specific morphologic trends that continued during post-storm conditions in relation to scarp formation, onshore transport potential, and roughness element presence. Data from this study provide additional context on the potential trade-offs between nourished dunes, management zones, and management strategy efficacy when considering the protection of landward infrastructure.
Lastly, the study pivots to assess dune management from a societal lens by distributing an electronic survey instrument to 229 residents within the SC coastal zone to assess literacy to coastal dune hazard impacts (tropical cyclones and high tide flooding) and management strategies. Results from this study support that experiential variables (experience with hazard impact; prior loss and frequency of beach visits per year) were statistically significant (p\u3c 0.05) in predicting respondent cumulative literacy scores as developed through the survey instrument. Further, when evaluating respondent familiarity, propensity to support, and ranking for success by coastal management strategies, results supported that each strategy type should be characterized individually, with experiential and sociodemographic variables being statistically significant (p\u3c 0.05) by management strategy type.
Holistically, the results from this dissertation support that coastal dune management in SC (and additional coastal geographies) should be assessed at the local scale, with expectations for results to vary by location, given community experiences, motivations, policies, and preferences. The influence of hazard impact as a variable for increasing dune management literacy, proactive and reactive dune management strategy implementation, and overall dune resilience is worthy of further investigation. In this aspect, this research has introduced new theoretical and methodological contributions to the field of geography and provides impetus for ongoing investigation and motivation for community-based coastal management and implementation
Relative Performance of MLR, WLSMV, and Bayes Estimators: An Investigation Using Confirmatory Factor Analysis with Ordinal Data
Get PDFThis study investigated the performance of four robust estimators— robust Maximum Likelihood for continuous data (MLR-CON), robust Maximum Likelihood for categorical data (MLR-CAT), robust Weighted Least Squares (WSLMV), and Bayes estimation—in the context of Confirmatory Factor Analysis (CFA) with ordinal data. The objective was to conduct a comprehensive assessment of their efficacy across varied data conditions. A simulation study was designed to comprise conditions that may be encountered with empirical research. The design included 90 cells with two levels of model specification (correct, misspecified), three sample sizes (100, 200, 500), five item distributions (symmetric, moderately asymmetric, moderately asymmetric-alternating, extremely asymmetric, extremely asymmetric-alternating), and three item categories (2, 4, 5). Outcomes included convergence rates, relative bias in parameter estimates (e.g., factor loading, factor correlations, standard errors), model rejection rates, and fit indices.
The findings indicated that categorical estimators such as MLR-CAT, WLSMV, and Bayes were able to yield unbiased factor loadings and factor correlations for ordinal data under correct model specification and adequate convergence, with MLR-CAT providing the most accurate parameter estimates. MLR-CON tended to produce accurate estimates only for ordinal data with at least five categories and a symmetric distribution. In cases of slight model misspecification where two insignificant secondary paths were omitted, a similar pattern is observed in the recovery of factor loadings by the estimators, although all estimators tended to overestimate factor correlations. Model misspecification had little impact on the estimation of standard errors for the parameter estimates. The standard errors yielded by MLR-CON, MLR-CAT and Bayes were largely unbiased with the only exception being asymmetric dichotomous data at a sample size of 100. However, WLSMV only produced satisfactory results for dichotomous data and showed large, negative bias in all other conditions.
Regarding model fit indices, Bayes-based Posterior Predictive P-value (PPP) exhibited no type I error for the correctly specified model and considerable tolerance for minor model misspecification. WLSMV-based χ^2 and alternative fit indices (CFI, TLI, RMSEA) generally recommended retaining a correct model across all sample sizes and demonstrated moderate tolerance for minor model misspecification in small samples. MLR-CON χ^2 and alternative fit indices are considered acceptable only for normally distributed data with a large sample size (N \u3e 200).
Based on the study, the categorical estimators Bayes, MLR-CAT, and WLSMV are generally recommended for ordinal CFA in small to medium sample sizes. If the standard errors of the parameter estimates are a concern, Bayes and MLR-CAT are preferred over WLSMV. MLR-CAT is particularly suitable for obtaining the most accurate parameter estimates when applicable, while Bayes can effectively handle convergence difficulties that other estimators might encounter. MLR-CON is only recommended for symmetric data with at least five response categories, but its results are less accurate than those yielded by the categorical estimators
Explorations of Multi-Carboranyl Thiols and Phosphines
No full textIn order to ascribe the impact of substituent groups on the bis-ortho-carborane, closo-{C2B10}-closo-{C2B10} multi-cluster system, the first sulfur-containing biscarborane derivatives were synthesized. Biscarborane dithiol, disulfide, bis(methyl)thioether, as well as multiple dithiolate salts were structurally characterized. The exceedingly long C–C bonds and shortened C–S bonds in biscarborane dithiol and its doubly deprotonated dithiolate salts are indicative of significant delocalization of electron density from the sulfur atoms into the cluster. Additionally, a new concept of ligand ambiphilicity is described where, instead of the involvement of only a single center in a ligand, this amphiphilicity relies on the redox behavior of the indirectly coordinated boron cluster scaffold. A copper(I) complex of a carborane-based triphosphine [tBuP-closo-{C2B10}-PhP-closo-{C2B10}-tBuP]Cu(CH3CN)BF4 coordinates an exogenous X anion (X = Cl– or N3–) at the phosphorus center of the ligand and not at the cationic metal site forming [tBuP(X)-nido-{C2B10}-PhP-closo-{C2B10}-tBuP]Cu(CH3CN)2. This nontraditional ligation behavior is imparted by an internal two-electron event at the boron cluster, which renders a non-constrained electron-donating phosphine group into an electrophilic coordination site. The observed ligand-centered behavior exhibits reversible solvent dependence, thus representing an unusual case of metal-ligand anion tautomerism promoted by redox-behavior of the carborane backbone
The Influence of Instruction on Underrepresented Stem Leaders on Elementary Students’ Stem Identity and Perceptions of Stem
Get PDFThis action research study explored the influence of exposure to underrepresented STEM leaders on third-grade students’ STEM identity and their interest in STEM careers. Using an integrative STEM approach and guided by both Constructivist Learning Theory and Social Cognitive Career Theory, this convergent mixed methods study consisted of an eight-week intervention with lessons based on different STEM leaders and related activities each week. This eight-week period collected data through weekly researcher field notes, exit tickets and was prefaced and followed by a pre- and post-survey and pre- and post-interviews. Findings from the quantitative data, the Role Identity Survey in STEM (RIS-STEM; Paul et al., 2020), found no statistically significant difference from pre-post intervention within any of the four constructs that assess aspects of one’s identity (competence, interest, self-recognition, and recognition by others). Once converged with qualitative data (i.e. interviews, exit tickets, and researcher’s field notes), themes emerged highlighting student engagement, the importance of prior knowledge, student belief in oneself as a learner, and the importance of diversity. Results exemplified the importance of interest and enthusiasm for students’ perception of their STEM identity and future career aspirations but indicated a possible need for a longer study to find a statistically significant difference. Implications for findings, practice, limitations, and future research are discussed
Stability of Space-Time Finite Element Discretizations of Subdiffusive Time-Fractional Differential Equations
Get PDFThe study of anamolous diffusion, and in particular of subdiffusive time-fractional differential equations, is of great interest for its ability to describe transport of particles through porous media. The time-fractional derivatives in these problems are nonlocal, which notably hinders performance of classical time-stepping methods. As a result, there is significant interest in using simultaneous space-time discretizations for these subdiffusive problems, which have the additional benefit of significantly relaxing the regularity requirements for candidate solutions. These types of Petrov-Galerkin schemes require a careful choice of discretized trial and test spaces in order to guarantee stability; in particular, the usual Galerkin choice is generally unstable.
We propose a stable, nonadaptive Petrov-Galerkin discretization of a model subdiffusive problem. We show how stable pairs of discretized trial and test spaces can be constructed by tensorizing temporal and spatial trial and test spaces with known good properties. We then demonstrate that the discretized Petrov-Galerkin problem can be reformulated quasi-optimally as a minimal functional residual problem, which can be numerically solved by solving an equivalent algebraic residual minimization problem
Gateways to Reading: Action Research with At-Risk Students at an Alternative School
Get PDFThere is no shortage of research on how low levels of literacy disproportionately affect students of color, but this research was interested in how three theoretical models may impact this trend. The purpose of this qualitative case study was to examine the reading experiences and engagement levels of students in an alternative school English class, applying culturally relevant pedagogy (CRP), self-determination theory (SPD), and zone of proximal development (ZPD). CRP is a theoretical model that upholds students’ cultural identities, while pursuing academic success. ZPD is a theoretical model that suggests learning occurs when content is within students’ ability. SDT is the theory that autonomy, competence, and relatedness support individuals’ motivation. These theoretical models were specifically applied to reading in the classroom. Data was collected from student questionnaires, artifacts on what students said about what they chose to read, and interviews. Findings indicated that CRP, ZPD, and SDT positively impacted students\u27 reading engagement and reading experiences. However, data also indicated other factors contributed to students’ positive reading experiences and reading engagement. More research is needed to inform further on matters that can contribute to historically marginalized students’ reading experiences and engagement