Research and Scholarship Repository
The Research and Scholarship Institutional Repository collects, preserves, and showcases the scholarly achievements of Texas State University's academic community. It provides open access to the diverse array of research and scholarship materials created at Texas State including articles, presentations, posters, electronic theses and dissertations, capstones, multimedia presentations, and more.
More information: https://guides.library.txstate.edu/institutional-repository
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- Research centers and institutes supporting scholarly and creative activities across the university.
- Research, creative, and scholarly works created by the university community organized by college.
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- Academic publications and conference proceedings from members of the university community.
- Electronic theses and dissertations, and graduate and undergraduate Capstones and Directed Research.
Recent Submissions
Evidence for five types of fixation during a random saccade eye tracking task: Implications for the study of oculomotor fatigue
(2024-04) Friedman, Lee; Komogortsev, Oleg V.
Our interest was to evaluate changes in fixation duration as a function of time-on-task (TOT) during a random saccade task. We employed a large, publicly available dataset. The frequency histogram of fixation durations was multimodal and modelled as a Gaussian mixture. We found five fixation types. The “ideal” response would be a single accurate saccade after each target movement, with a typical saccade latency of 200-250 msec, followed by a long fixation (> 800 msec) until the next target jump. We found fixations like this, but they comprised only 10% of all fixations and were the first fixation after target movement only 23.4% of the time. More frequently (57.4% of the time), the first fixation after target movement was short (117.7 msec mean) and was commonly followed by a corrective saccade. Across the entire 100 sec of the task, median total fixation duration decreased. This decrease was approximated with a power law fit with R2 = 0.94. A detailed examination of the frequency of each of our five fixation types over time on task (TOT) revealed that the three shortest duration fixation types became more and more frequent with TOT whereas the two longest fixations became less and less frequent. In all cases, the changes over TOT followed power law relationships, with R2 values between 0.73 and 0.93. We concluded that, over the 100 second duration of our task, long fixations are common in the first 15 to 22 seconds but become less common after that. Short fixations are relatively uncommon in the first 15 to 22 seconds but become more and more common as the task progressed. Apparently. the ability to produce an ideal response, although somewhat likely in the first 22 seconds, rapidly declines. This might be related to a noted decline in saccade accuracy over time.
Insights into (Cs0.22FA0.78)Pb(I0.85Br0.15)3 Triple Halide Perovskite films: Stability Investigations via Angle-Resolved XPS Analysis
(2024-04) Mahamudujjaman, Md; Scolfaro, Luisa M.; Geerts, Wilhelmus J.
Perovskite materials have garnered significant attention from researchers due to their promising photovoltaic properties and cost-effective production processes. These films can be deposited using solvent-based techniques close to room temperature, such as spin-casting, blade-coating, slot-die printing, and inkjet printing. Triple halide perovskites, with their tunable wide bandgap, offer promising applications in tandem solar cells, particularly when paired with silicon-based cells. Despite their enhanced efficiencies and reduced production costs, the commercial viability of perovskite solar cells remains constrained by their limited stability. In our study, we employed angle-resolved X-ray photoelectron spectroscopy (XPS) to examine a spin- coated absorber layer formulated from (Cs0.22FA0.78)Pb(I0.85Br0.15)3 with an added 3 mol % MAPbCl3, also referred to as Cs22Br15. The inks, based on DMF, were prepared in a glovebox, and applied to plasma-cleaned glass substrates. Following deposition, the wet films were annealed at 100°C for 30 minutes. X-ray diffraction (XRD) analysis revealed that the annealed samples transitioned to a photo-active α-phase, whereas the unannealed samples retained a photo-inactive δ-phase. The surface chemical composition of the perovskite films was analyzed using angle-resolved XPS, an effective technique for investigating the photochemical and thermal decomposition of perovskite materials. The samples were pre-cleaned using a low-energy ion/cluster beam to prevent damage to the perovskite layers. The survey spectrum of the freshly prepared perovskite/glass samples displayed characteristic peaks, including Pb4f, Br3d, I3d, Cs3d, and C1s. Closer examination between 283 eV and 287 eV identified a peak at approximately 286 eV and a secondary peak at around 284 eV, corresponding to C-N and C-C bonds, respectively. The Pb XPS spectra that were taken 625 hours later of sample preparation and sample treatment show larger Pbo peaks. So, degradation does not stop upon removing the heat and humidity stresses and storing the sample in a nitrogen filled glovebox. We also explored the impact of heat and moisture on the triple halide perovskite. To our knowledge, this is the first report of an XPS study on Cs22Br15.
Analysis of Reflectograms of Pile Integrity Test Using Image Processing Technique
(2024-04) Debnath, Picasso Kumar
Pile foundations are typically used for major constructions and in cases when the soil at shallow depths is insufficient to withstand excessive settlement, uplift, and so on. Excavating a hole in the ground and filling it with concrete with various types of reinforcement is how cast-in-situ piles are constructed. It has become clear that even the most advanced piling technique can't guarantee flawless results. Integrity testing identifies areas with reduced cross-sections (necking) or poor material qualities. Minor faults, such as microscopic cracks, can often be predicted, but their nature must be confirmed through visual inspection. The main objective of this thesis work is to identify the condition of the cast-in-situ pile and to identify the faulty piles. From recent studies, Sonic Integrity Testing (SIT) is a type of low-strain testing that is an effective instrument for detecting faults and estimating pile length. The success of integrity testing in its current state is dependent on two key factors: the quality of gathered signals and the interpreter's experience. A computer-based analysis of the test results is required to determine the best result in place of the human.
As highlighted in the ICE manual handbook, CIRIA 144 (1997), proposes a taxonomy of three types (Type 0, 1, and 2) of Reflectogram signal responses. Here, MATLAB is used to create an image-based analysis that digitally represents the signal type. After that, the data is sorted in an Excel file for numerical analysis. The created method was used on 204 signals of 68 piles at SKS LPG Mongla, with 2 piles classified as Type 0, 171 piles classified as Type 1, and 31 piles classified as Type 2. The image-based algorithm and expert judgment were found to be almost identical. Because the analysis is so good, it's more practical to apply it instead of the traditional approaches for pile testing mechanisms.
Optimizing Learning: How a Minimal Time Investment in Active Learning Boosts Precalculus Mastery
(2024-04-01) Buber, Zafer
Despite various efforts and initiatives to improve the success rates in precalculus courses across the United States, the statistics have not shown significant improvement over the last four decades. The research identifies poor instructional practices as one of the main factors contributing to this issue and finds them to be associated with overloaded curricula and fast-paced instruction in precalculus classes. Given that the primary instructional method in most college mathematics courses is direct instruction, this quasi-experimental study aims to investigate the impact of a low-time commitment active learning strategy on students’ achievement and participation in college precalculus classes. The proposed intervention aims to slow down the instructional pace, especially for the students who need more time for conceptual advancement, and create more opportunities to provide students with more time to reason and think. The findings indicate that this intervention has the potential to improve student achievement and increase participation in college precalculus classes.
Development of a New Method for Rapid Purification and Analysis of Circular Plasmid DNAs from Yeast Cells
(2024-04) Ali, Ahmed Wajahat; Sowersby, Drew S.; Okoye, Linda C.; Lewis, L. Kevin
It is common practice to purify circular plasmid DNAs from small cultures of E. coli bacterial cells for subsequent analysis by gel electrophoresis. By contrast, extraction and electrophoretic analysis of circular DNAs from small cultures of yeast and other eukaryotic cells is difficult because of the small numbers of these molecules inside cells. Existing methods employed in budding yeast (S. cerevisiae) require extraction from a large volume of cultured cells; the partially purified plasmids are then typically transformed into E. coli cells and extracted via plasmid DNA minipreps for gel analysis. In the current study, we have developed a new method for extracting plasmids from small yeast cell cultures that permits visualization of the circular DNAs by electrophoresis. The new approach was shown to be superior to two other common yeast DNA extraction methods, as it produced more plasmid DNA and less contaminating chromosomal DNA and RNA. The method was tested by cloning a RAD52 gene-containing fragment into an expression vector inside yeast cells. DNAs from the transformants were then analyzed directly by gel electrophoresis after performing yeast minipreps. The new method allows yeast plasmids to be analyzed quickly, eliminating the requirement for subsequent transformation into E. coli cells.