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The Effectiveness of a Newly Developed Fluoride-Releasing O-Ring for Prevention of White Spot Lesions: An In-Vitro Study
No full textPreventing white spot lesions (WSLs) in orthodontic patients remains a challenge. An effective method for incorporating calcium fluoride (Ca-F) into polycaprolactone (PCL), widely used for drug delivery, has been established. With this method, an elastomeric ligature (O-ring) is transformed into a Ca-F O-ring capable of consistently releasing therapeutic levels of fluoride ion over a span of seven weeks. The aim of this study is to assess the effectiveness of Ca-F O-ring in preventing WSL in vitro.
A Ca-F solution was combined with 10% PCL to create a mixture of 5% PCL with Ca-F. O-rings were briefly immersed in this mixture to generate the Ca-F O-rings. 60 premolars with sound enamel were bonded and randomly allocated into three groups for pH cycling: 1) ordinary O-ring with topical over-the-counter fluoridated toothpaste application (O-F); 2) ordinary O-ring (O-R); 3) Ca-F O-ring (O-CaF). Acid-resistant nail polish was applied to surrounding tooth surface, leaving a 4x2 mm2 treatment window of exposed enamel adjacent to cervical aspect of the bracket. All specimens underwent a 9-day pH cycling process. Lightness (L*) value within the treatment window of each sample was evaluated using spectrophotometer at baseline (T0) and after (T1) pH cycling. Mineral densities were determined after pH cycling for the treatment window, adjacent surface enamel layer, and deep enamel layer.
No significant differences in L* values were found between groups at T0 and T1. At T1, L* in group O-CaF was lower than other groups, but not significantly. Group O-CaF had significantly lower mineral densities in treatment window regions than the other groups at T1. For all groups, mineral density increased in the treatment window after pH cycling when compared to adjacent surface enamel control regions.
Use of Ca-F O-rings for prevention of WSLs in orthodontic patients is promising. When compared to controls with and without topical fluoride, the group O-CaF exhibited potentially more effective remineralization after pH cycling and less of a hypermineralized surface seen with WSLs. Future studies with SEM analysis and with increased pH cycling time are needed to confirm the ability of these Ca-F O-rings to effectively remineralize enamel after pH cycling
Ira Greenbaum field notebook: GK4001-GK4500.pdf
No full textBound book, each page corresponds to a karyotype slide data.Data pages for GK4001-GK4500 corresponding to unique identifiers of specimens/samples examined for biological research. Specimens are primarily housed at Texas A&M University; Biodiverstiy Research and Teaching Collection
John Bickham field notebook: AK24001-AK24500.pdf
No full textBound book, each page corresponds to a karyotype slide data.Data pages for AK24501-AK25000 corresponding to unique identifiers of specimens/samples examined for biological research. Specimens are primarily housed at Texas A&M University; Biodiverstiy Research and Teaching Collection
The Mental Well-Being of Students Enrolled in Dual Credit Courses at a West Texas Early College High School
No full textThe mental well-being of any adolescent is critical to how they think, feel and act in any environment. The purpose of the study was to measure the level of satisfaction with life of students enrolled in dual credit courses in a West Texas Early College High School (ECHS). The focus domains of life satisfaction were in these five areas: Family, Friends, School, Living Environment, and Self. The sample consisted of 152 ECHS students. The tool used was the Multidimensional Student Life Satisfaction Scale (MSLSS). The MSLSS revealed that although overall ECHS students have a positive satisfaction with life, ECHS students had a low satisfaction with the School domain, below 4.0, indicating a lower life satisfaction in this area. There was no statistically significant difference in life satisfaction among students between grade levels, but there was a statistical difference between genders in the Family domain. An intervention course that integrates resilience-building and social-emotional learning (SEL) is recommended to address these findings. Further research is also recommended towards the adolescent well-being of ECHS students enrolled in dual credit
Essays on the Causal Effects of Retailer Strategic Actions on Sales, Omnichannel Shopping, and Mobile App Engagement
No full textRetailers engage in strategic actions such as store closure and the introduction of new features in mobile apps. Each action has the potential to change shoppers��� omnichannel shopping behavior and engagement. Empirical analysis of the causal effects of these strategic actions is challenging because field experiments are often expensive and infeasible. In the two essays of my dissertation, I focus on the strategic actions of a large U.S. retailer of video games and consumer electronics and analyze the causal effects of these actions. I use the difference-in-differences (DID) framework, controlling for potential endogeneity, to causally estimate the effects of the strategic actions. I apply machine learning algorithms to explore treatment effect heterogeneity and analyze unstructured app clickstream data.
In Essay 1, I study the impact of store closure on the retail chain���s aggregate sales, customers��� omnichannel shopping, and mobile app usage. The results show that store closures led to a significant loss of $209,317 in net monthly sales per county, surpassing the average sales of the closed stores. Both offline and online sales dropped after the closure of a store. These results highlight that retailers should re-examine their closure plans and account for the negative spillover effect.
Essay 2 examines the causal effect of in-app payment introduction on omnichannel shopping and mobile app usage behavior, uncovers individual-level treatment effect heterogeneity, and investigates the underlying mechanisms. I find that adopting in-app payment significantly boosts overall purchases. As a result, overall spending net of returns is 25.3% (33.6%) higher for Apple Pay (PayPal) adopters than nonadopters. Mechanisms driving these results include increased spending both offline and online, reduced friction, lower mobile cart abandonment rate, increased Buy-Online-and-Pickup-In-Store (BOPIS) orders, heightened app usage near stores, greater store visits due to increased product returns and trade-ins, and more impulse purchases
Impact of Astaxanthin Supplementation on Markers of Cardiometabolic Health and Tactical Performance Among Firefighters
No full textFirefighters are at risk for cardiovascular disease (CVD) due to increased oxidative stress, inflammation, and poor cardiorespiratory fitness (CRF). Astaxanthin (AX) possesses antioxidant/anti-inflammatory and purported ergogenic properties. This study examined the impact of 12 mg/d for four weeks of AX supplementation on markers of oxidative stress, inflammation, cardiometabolic health, cardiorespiratory fitness, and occupational performance in career firefighters. In a randomized, double-blinded, placebo-controlled, crossover fashion, 15 male career firefighters (34.5��7.4 years; 177.7��7.0 cm; 95.6��12.0 kg; 30.1��2.9 kg/m��; 11.03��6.85 years of service) ingested 12 mg/d of AX (AstaReal��, Burlington, NJ, USA) or placebo for four weeks while following a standardized resistance training program. After each treatment, testing sessions were completed to assess 1) blood cardiometabolic health, oxidative stress, and inflammatory and CRF parameters, and 2) salivary oxidative stress and inflammatory responses and tactical performance to fire suppressive activities. Data were analyzed using general linear model multivariate analysis with repeated measures (GLM). Clinical significance was assessed via mean changes from baseline (BL) with 95% confidence intervals (mean [LL, UL]). Analysis of mean changes from BL revealed AX lessened the inflammatory response to a cardiopulmonary exercise test. Additionally, the percent ventilatory anaerobic threshold (%VANT) was higher following AX compared to placebo (4.84 [0.27, 9.41] %, p<0.039, ����_p^2=0.114). Analysis of mean changes from BL revealed AX may lessen increases in IL-1��, cortisol, and UA response to fire suppressive activities. Cardiometabolic health markers were not affected in a statistically significant manner. These findings provide some evidence that AX supplementation may help mediate occupation-related inflammation and oxidative stress in response to high-intensity, short-duration exercise in firefighters. More research is warranted to determine if long-term supplementation can improve cardiometabolic risk in this population
Selective Aryl Hydrocarbon Receptor Modulators as a Potential Treatment for Major Depressive Disorder
No full textMajor depressive disorder (MDD) is a worldwide public health concern, and although treatments exist, many people still suffer from treatment resistant depression. The projects in this dissertation aimed to evaluate the feasibility of using selective aryl hydrocarbon modulators (SAhRMs) as a treatment for MDD. The aryl hydrocarbon receptor (AhR) is a ligand-activated intracellular transcription factor that is involved in numerous biological processes which are linked to potential causes of MDD. Two SAhRMs, 3,3���-diindolylmethane (DIM) and 1,4-dihydroxy-2-napthoic acid (DHNA) were tested for their ability to prevent and treat MDD-like behavior in female mice using unpredictable chronic mild stress (UCMS). Depression- and anxiety-like behaviors were examined using a battery of behavioral tests. In the first project, both SAhRMs prevented and reversed depression-like behavior but had little effect on anxiety like behavior. An isomer of DHNA, which is inactive at the AhR, did not prevent depression-like behavior, hinting at a role for AhR activity in the antidepressant action of DHNA. In the second project, male mice were examined, and SAhRMs did not act as antidepressants but had some effects on anxiety-like behavior in males. There was no effect of SAhRMs on spatial learning or on weight gain in stressed or unstressed male or female mice. The third project tested mice which do not express the AhR in the internal epithelium (AhR��IEC). AhR��IEC mice were resilient to the effects of stress on depression-like behavior, suggesting a role for intestinal AhR in maintaining depression- like states. Additionally, SAhRMs prevented depression-like behavior in these mice, effectively eliminating the intestinal epithelium as a potential site of action for SAhRMs. Limitations, possible mechanisms, and applications are discussed. The results of these studies indicate a potential for SAhRMs to be developed as a treatment for MDD and highlight the need to further investigate the role of AhR in MDD
Soil Temperature and Moisture Control in Ground Source Heat Pump Systems
No full textThis numerical study focuses on exploring passive methods to control soil temperature rise and restore favorable thermal conditions in ground source heat pump (GSHP) systems. The three methods investigated were soil moisture control, presence of thermosiphon (TS), and effects of soil type. A single U-loop of a GSHP system was modeled in a soil domain using a finite element analysis (FEA) software Ansys Mechanical. The Backward Euler formulation and the Sparse Direct Solver were used to discretize and solve the governing heat conduction equation. Four moisture contents (high, low-to-high, high-to-low, low) and two soil types (sandy loam, clay loam) were considered, along with the presence (TS case) and absence (non-TS case) of a single thermosiphon. Soil temperature profiles were plotted at multiple points to examine the effects of moisture level and soil type, and the temperature difference between TS- and non-TS cases was plotted to study the thermosiphon effect. Curve-fitting of soil temperature profiles was done to quantify the rate of soil temperature rise at different depths. The results showed that soil temperatures decreased with moisture content. Soil temperatures were lower for TS cases than for non-TS cases, and the TS effect also decreased with moisture content. Moreover, clay loam resulted in higher soil temperatures than sandy loam at all moisture levels considered. In summary, to maintain and restore soil thermal conditions favorable to GSHP systems, moisture control is recommended for GSHPs in high thermal diffusivity soils, while thermosiphon use is preferred for GSHPs in low thermal diffusivity and dry (low moisture content) soils
How Are Standards Developed? An Analysis of the Science Standards Revision Process in Texas
No full textThis study aimed to determine how science education policy is developed and the expertise employed throughout the process. Texas was selected as a historical case due to the recent revision of the science standards, their large impact, and documentation availability. A historical perspective informed the research questions: 1) What are the key positions, underlying justifications, and factors that contributed to the development of science standards in the state of Texas? 2) What expertise do official and unofficial actors possess in the science standards revision process? 3) To what extent were Schwab���s commonplaces (subject matter, teachers, learners, and milieu) considered during the revision process for science standards? and 4) What is the State Board of Education review process followed when revising science standards? State Board of Education meetings were analyzed using naturalistic inquiry and within-case methods.
Findings indicate that several points of failure occurred throughout the revision process that may affect the viability and implementation of the resulting standards. These points of failure included flawed process design, transparency issues, and limited representation of expertise domains. Notably, the learner was not represented during the revision process. As a result, the standards risk being developmentally inappropriate for students; initial evidence suggests this is the case for several standards. To ensure standards are scientifically accurate, developmentally appropriate, can be implemented by teachers, and respectful of the environment in which it is enacted, expertise from the subject matter, the learner/learning, the teacher, and the milieu must be equally considered. Additionally, research, development, and diffusion (RD&D) should be utilized to ensure the standards and curriculum materials are appropriately tested before being required for teachers and students
Assessing Orthodontic Compliance with Tailored vs Generic Reminders
No full textThe purpose of this study is to evaluate the effect of daily automated tailored reminders compared to generic ones on the improvement of oral hygiene compliance.
A blinded, prospective, randomized controlled trial was designed to evaluate the effects of the content of reminders. Subjects were recruited from patients undergoing orthodontic treatment at the Texas A&M University College of Dentistry, Department of Orthodontics and were treated with fixed full appliances in both arches. Subjects were randomly assigned to either a tailored text message group or a generic text message group. There were 68 subjects recruited who were 12 to 17 years of age. Oral hygiene was measured at the beginning of the study and again 8 weeks later.
The generic reminder group had significant improvements in oral hygiene compliance from timepoint 1 to timepoint 2. Decreases from T1 to T2 were 1.20 to 0.59, 1.88 to 1.10, and 3.56 to 2.90 for bleeding index (BI), gingival index (GI), and plaque index (PI), respectively (p<0.001). The tailored reminder group had significant improvements in oral hygiene compliance from timepoint 1 to timepoint 2 as well. Decreases from T1 to T2 were 1.33 to 0.58, 2.02 to 1.12, and 3.75 to 2.81 for bleeding index (BI), gingival index (GI), and plaque index (PI), respectively (p<0.001). All initial values in the tailored group and total decreases for all three periodontal tests were higher than in the generic group but were not statistically significant.
Tailored daily reminders are not more effective at improving oral hygiene compliance than generic daily reminders