Austin College
  • United States
Recent publications
This report describes the experimental investigation and optical modeling of the structural coloration produced from total internal reflection interference within 3D microstructures. Ray tracing simulations coupled with color visualization and spectral analysis techniques are used to model, examine, and rationalize the iridescence generated for a range of micro-geometries, including hemicylinders and truncated hemispheres, under varying illumination conditions. An approach to deconstruct the observed iridescence and complex far-field spectral features into its elementary components and systematically link them to ray trajectories that emanate from the illuminated microstructures is demonstrated. The results are compared with experiments, wherein microstructures are fabricated with methods such as chemical etching, multiphoton lithography, and greyscale lithography. Microstructure arrays patterned on surfaces with varying orientation and size lead to unique color-traveling optical effects and highlight opportunities for how total internal reflection interference can be used to create customizable reflective iridescence. The findings herein provide a robust conceptual framework for rationalizing this multibounce interference mechanism and establish approaches for characterizing and tailoring the optical and iridescent properties of microstructured surfaces.
Élie Cartan’s invariant integral formalism is extended to gauge field theory, including general relativity. This constitutes an alternative procedure, as shown in several examples, that is equivalent when no second class constraints are present to the Rosenfeld, Bergmann, Dirac algorithm. In addition, a Hamilton–Jacobi formalism is developed for constructing explicit phase space functions in general relativity that are invariant under the full four-dimensional diffeomorphism group. These identify equivalence classes of classical solutions of Einstein’s equations. Each member is dependent on intrinsic spatial coordinates and also undergoes non-trivial evolution in intrinsic time. Furthermore, the construction yields series expansion solutions of the field equations for all of the components of the metric tensor, including lapse and shift, in the intrinsic temporal and spatial coordinates. The intrinsic coordinates are determined by the spacetime geometry in terms of Weyl scalars. The implications of this analysis for an eventual quantum theory of gravity are profound.
Throughout the world of higher education, universities and colleges are reconceptualizing how their institutions are organized, especially in terms of faculty size related to overall programming. As adjunct rates increase and faculty positions are eliminated, many programs may be reduced to a single faculty lead. Yet, single faculty member programs are not well understood in the literature, nor are their roles in the larger higher education structure. This qualitative study explores the experiences of 12 university professors in the United States who coordinate single faculty programs, defined as academic programs employing only one tenured or tenure-track faculty member. Using the conceptual frameworks of Role Theory and Social Isolation, we explored the experiences of single faculty and how those experiences were influenced by the policies and practices of their institutions. Participants’ experiences of isolation included disciplinary/collaborative isolation, physical isolation, ownership isolation, and identity isolation. Participants described their roles as complex, unclear, and often unrecognized by others. Results indicate that faculty in single faculty programs may appear invisible within the current structure of academia and that revising existing practices could better support these faculty and their programs. Institutions must question whether single faculty programs should exist and the conditions under which these programs can succeed. Finally, policy and practice recommendations are offered for institutions, and even non-solo faculty peers, to support flying solo professors as they navigate serving their students and keeping their programs afloat.
The asymmetric unit of the title salt, C 21 H 18 N 4 ²⁺ ·2Br ⁻ , comprises half of the molecule and a bromide ion. The chevron-shaped cations stack as columns in the [001] direction with suitable intermolecular distance for π–π interactions. These cationic columns are further stabilized by intercolumnar C—H...N hydrogen bonding with the bromide ions distributed between them.
The chevron-shaped cations of the title hydrated salt, C 25 H 22 N 4 ²⁺ ·2Br ⁻ ·2H 2 O, are arranged in back-to-back alternating directions to form a zigzag ribbon propagating along the [010] direction. Intermolecular interactions comprising these ribbons are π–π interactions between the pyridinium and adjacent pyridyl rings, as well as O—H...O hydrogen bonding between water molecules and two adjacent pyridyl N atoms. Half of the cation is generated by the mirror plane. The water O atoms, the central C atom and one Br atom are located on this mirror plane while the other Br atom is on a twofold screw axis.
Social networking sites (SNS) are increasingly becoming integrated in our daily lives. We surveyed 184 spouses (female =138) to explore whether there is an association between partner’s perception of the quality of available alternatives and SNS infidelity related behaviors. We also explored if mental illness moderated this association. Those with mental and/or emotional illness reported higher levels of SNS infidelity than those without, however, we did not find between-group differences in perceived quality of alternatives or relationship satisfaction. Perceived quality of available alternatives predicted social media infidelity behaviors and this association was moderated by mental illness status. These results suggest that partners with mental illness may face additional challenges when it comes to guarding their relationship against infidelity.
Crystals of the title compound, C 17 H 15 N 2 ⁺ ·BF 4 ⁻ , were unexpectedly grown from crystallization attempts of [Pt(4,4′-bpy) 4 ](BF 4 ) 2 [Smith et al. (2019). Comments Inorg. Chem. 39 , 188–215] using toluene and acetonitrile. The tetrafluoroborate anion and the central pyridinium ring of the cation are disordered, with atomic site occupancies close to ½. The tolyl group of the cation has a 75.31 (11)° twist relative to the unsubstituted pyridyl group. This rotation allows for a centrosymmetric dimer of cations with weak hydrogen bonding between the pyridyl nitrogen atom and a methyl H atom on the neighbouring cation.
Science, Technology, Engineering and Mathematics (STEM) disciplines recognize the need for leadership development, but the lack of a professionally endorsed model has led to a patchwork of programmes across the nation, each with its unique brand of skills development. Leadership programmes in six diverse STEM fields are included.
In the structure of the title solvated complex, [Pt(C 8 H 4 N 2 S 2 ) 2 (C 5 H 6 N 2 ) 2 ]·C 2 H 6 OS or trans -[Pt(4- ap ) 2 (qdt) 2 ]·dmso (4- ap = 4-aminopyridyl, C 5 H 6 N 2 ; qdt = quinoxaline-2,3-dithiolate, C 8 H 4 N 2 S 2 ; dmso = dimethyl sulfoxide, C 2 H 6 OS) the centrosymmetric complex exhibits Pt—S distances in agreement with other Pt IV —S bond lengths found in platinum(IV) dithiolene complexes. The qdt ligands have intermolecular interactions with an amine hydrogen atom on a 4- ap ligand (hydrogen bonding) and have sandwich π–π interactions with a neighboring qdt ligand.
Objectives The study investigated the relationship between electricity access and infant mortality at the subnational level in Ghana, controlling for correlates such as birth interval, children living with both parents, women’s education, and income distribution. Methods The study employed a pooled cross-section regression approach using data from the Ghana Demographic and Health Survey (GDHS) for 10 administrative regions from 1993-2014. The GDHS is a detailed data set that provides comprehensive information on households and their socio-economic and demographic characteristics in Ghana. Results The results show that in regions with low incidence of infant mortality, a 10% improvement in electricity access reduces infant death by 11.8 per 1,000 live births, whereas in high mortality regions, improvement in electricity access has no impact on infant death. Birth interval reduces the risk of infant death in low mortality regions but not in high mortality regions. Children living with both parents have a high probability of survivorship in high mortality regions. Women’s median years of education lowers the likelihood of infant death in high mortality regions but increases the likelihood in low mortality regions. Wealth distribution is inconsequential for infant death in low mortality regions, but in high mortality regions, both the wealthiest and the poorest experienced significant decline in infant death. Conclusions The findings underscore the fruitfulness of investigating the effects of electricity access and other correlates on infant mortality at the subnational level. The study recommends that the provision of reliable access to electricity is needed to improve infant mortality rates. However, policies that seek to improve access to reliable electricity should be implemented together with health infrastructure development policies, especially in the regions with high infant mortality rates, for electricity access to have the desired effect.
Introduction: Undocumented immigrants (UIs) in the United States are less likely to be able to afford health insurance. As a result, UIs often lack family doctors and are rarely involved in annual screening programs, which makes estimating their health status remarkably challenging. This is especially true if the laboratory results from limited screening programs fail to provide sufficient clinical information. Methods: To address this issue, we have developed a machine learning model based on the non-negative matrix factorization technique. The data set we used for model training and testing was obtained from the 2004 cost-free hepatitis B screening program at the Omni Health Center located in Plano, Texas. Total 300 people were involved, with 199 identified as UIs. Results: People in the UIs group have higher cholesterol (219.6 mg/dL, p=0.038) and triglycerides (173.2 mg/dL, p=0.03) level. They also have a lower hepatitis B vaccination rate (38%, p=0.0247). No significant difference in hepatitis B(+) was found (p=0.8823). Using 16 individual clinical measurements as training features, our newly developed model has a 67.56% accuracy in predicting the ratio of cholesterol to high-density lipoprotein; in addition, this newly developed model performs 9.1% better than a comparable multiclass logistic regression model. Conclusions: Elderly UIs have poorer health status compared with permanent residents and citizens in the United States. Our newly developed machine learning model demonstrates a powerful support tool for designing health intervention programs that target UIs in the United States.
Type 1 diabetes (T1D) results from the destruction of pancreatic β-cells caused by an altered immune balance in the pancreatic microenvironment. In humans as well as in mouse models, T cells are well recognized as key orchestrators of T1D, which is characterized by T helper (Th) 1 and Th17 cell bias and/or low/defective T-regulatory cells (Treg), and culminates in cytotoxic T-cell (CTL)-mediated destruction of β-cells. Refitting of immune cells toward the non-inflammatory phenotype in the pancreas may represent a way to prevent/treat T1D. Recently we developed a unique spontaneous humanized mouse model of type 1 diabetes, wherein mouse MHC-II molecules were replaced by human DQ8, and β-cells were made to express human glutamic acid decarboxylase (GAD) 65 auto-antigen. The mice spontaneously developed T1D resembling the human disease. Humanized T1D mice showed hyperglycemic (250–300 mg/dl) symptoms by the 4th week of life. The diabetogenic T cells (CD4, CD8) present in our model are GAD65 antigen-specific in nature. Intermolecular antigen spreading recorded during 3rd–6th week of age is like that observed in the human preclinical period of T1D. In this paper, we tested our hypothesis in our spontaneous humanized T1D mouse model. We targeted two cell-signaling pathways and their inhibitions: eIF5A pathway inhibition influences T helper cell dynamics toward the non-inflammatory phenotype and Notch signaling inhibition enrich Tregs and targets auto-reactive CTLs, rescues the pancreatic islet structure, and increases the functionality of β-cells in terms of insulin production. We report that inhibition of (eIF5A + Notch) signaling mediates suppression of diabetogenic T cells by inducing plasticity in CD4 + T cells co-expressing IL-17 and IFNγ (IL-17 + IFNγ +) toward the Treg cells phenotype.
Introduction: Left atrial (LA) scar, identified by bipolar voltage mapping, is a frequent finding in patients with non-paroxysmal atrial fibrillation (NPAF). We evaluated the most common sites of scar formation in the LA in a series of NPAF patients. Methods: Consecutive NPAF patients undergoing their first catheter ablation at our center were included in this analysis. Voltage mapping was performed in sinus rhythm (SR) using a 3D electro-anatomic mapping system and a 10-pole circular mapping catheter. The LA was divided into following regions: septum, posterior wall, lateral wall, anterior wall and roof. The threshold for low voltage was <0.5 mV (with a color range setting 0.2-0.5 mV). Results: A total of 359 NPAF (224, 62.4% persistent AF) patients undergoing their first ablation procedure with voltage mapping performed in SR were included in this study. Mean number of points taken to map the scar was 281.2±96.3. Low voltage area was detected in 209/359 (58%) cases; 108 (48.62%) persistent AF, 101(74.8%) long-standing persistent AF, p<0.001). The scarring was observed to be located in the anterior septum in 98 (46.9%) and posterior wall of the LA in 136 (65%) patients (FIGURE) Conclusion: In the NPAF population, LA scar was detected in significantly less number of persistent AF patients. Scars were mostly located in the posterior wall of left atrium followed by the antero-septum region. Characterization of the LA scars would be helpful in optimizing the ablation targets.
Introduction: Intramural PVCs are identified by equal but not remarkably early activation on at least two separate sites. The site of origin of these foci is typically determined by a deductive approach using extensive mapping in the surrounding areas. Ablation of the intramural VT is particularly challenging, since conventional ablation strategies often fail to obtain transmural lesion formation. We report the long-term success rate of ablation of the intramural PVCs at our center. Methods: Consecutive patients undergoing VT ablation at our center were screened and 73 patients with intramural PVCs identified by activation mapping and pace mapping were included in the analysis. Pace-mapping was performed at a pacing cycle length equal to the coupling interval of the spontaneous PVCs. If these PVCs could not be eliminated by conventional ablation, bipolar ablation or ablation from multiple sides or ablation using half-normal saline (HNS) was performed. Standardized RF power settings (up to 40W) were used during the procedure. Ablation was performed using 4-mm irrigated tip catheter guided by 3-D mapping system and intra-cardiac echocardiography. Patients were followed with remote monitoring as well as ICD interrogations and office visits every 3 months for 3 years. Results: A total of 73 patients were included in the analysis (mean age 56.2±8.6 years, 69.8% male, LVEF 54±12%). The intramural focus was effectively ablated by bipolar ablation or ablation from multiple sides in 51 (69.8%) and with the use of HNS in the remaining 22 patients. Median RF time was 11.14±8.7 minutes. Acute success (non-inducibility of the VT) was achieved in 71 (97.2%) patients. At 3 years follow-up, 66 (90.4%) remained arrhythmia-free. Conclusion: Intramural PVCs could be successfully ablated using bipolar or multiple-side ablations or utilizing half-normal saline with high long-term success rate.
Accurate prediction of network-level traffic parameters during inclement weather conditions can greatly help in many transportation applications. Rainfall tends to have a quantifiable impact on driving behavior and traffic network performance. This impact is often studied for low-resolution rainfall data on small road networks, whereas this study investigates it in the context of a large traffic network and high-resolution rainfall radar images. First, the impact of rainfall intensity on traffic performance throughout the day and for different road categories is analyzed. Next, it is investigated whether including rainfall information can improve the predictive accuracy of the state-of-the-art traffic forecasting methods. Numerical results show that the impact of rainfall on traffic varies for different rainfall intensities as well as for different times of the day and days of the week. The results also show that incorporating rainfall data into prediction models improves their overall performance. The average reduction in mean absolute percentage error (MAPE) for models with rainfall data is 4.5%. Experiments with downsampled rainfall data were also performed, and it was concluded that incorporating higher resolution weather data does indeed lead to an increase in performance of traffic prediction models.
Objectives Patient-centered care (PCC) experiences can vary by race and ethnicity and likely contribute to cancer care disparities. We compared PCC concepts between Non-Hispanic White (White), Hispanic, and Non-Hispanic Black (Black) cancer patients utilizing Critical Race Theory (CRT) to understand the relationships between racial-ethnic identity and PCC. Methods A thematic analysis and in-depth CRT-informed analysis of individual interviews exploring patient values, unmet needs, preferences, and priorities were performed. Results:Participants were aged > 25 yrs old, 53% male, and included 5 Hispanic, 4 Black and 6 White cancer patients. Unmet needs for time to make decisions, and provider interaction between visits and the value for finding meaning in the illness emerged among Blacks and Whites. The unmet need for a long-term treatment plan emerged among Blacks, and the preference of research participation among Whites. A value for optimism was observed among Hispanics and Whites. Racial-ethnic variations in patient descriptions and experiences of their values, unmet needs, preferences, and priorities were identified. Conclusions Underrepresented groups face subtle but significant challenges in feeling cared for and understood, voicing concerns, and obtaining quality care. Practice Implications: Increased mutual understanding and provider knowledge of unique PCC experiences among underrepresented cancer patients are needed.
This paper investigates the differential effects of oil price shocks on exchange rate, inflation, and monetary policy rate in Ghana. The paper also introduces the trade weighted U.S. dollar-major currencies index as another measure for identifying the speculative component of the real price of oil. To execute its objective, the paper employed a two-step estimation technique and monthly data from 1973 to 2018. The two-step method involves structural VAR in the first step and OLS regressions in the second step. Full sample estimation results indicate that oil price shocks are inconsequential to exchange rate, inflation, and monetary policy rate in Ghana. Furthermore, when the sample is split into two sub-periods, the study did not find the fact that Ghana switching from a net oil-importer to a net oil-exporter have any deferential effect. Taken together, the findings suggest that even in emerging and developing countries, a fading relationship between oil price shocks and macroeconomic indicators could exist.
Tornadoes are nature’s most violent storm and annually cause billions in damage along with the threat of fatalities and injuries. To improve tornado warnings, the National Weather Service is considering a change from a deterministic to a probabilistic paradigm. While studies have been conducted on how individual behavior may change with the new While studies have been conducted on how individual behavior may change with the new businesses. This project is a response to the Weather Research and Forecasting Innovation Act of 2017, H.R. 353, which calls for the use of social and behavioral science to study and improve storm warning systems. The goal is to discuss business response to probabilistic tornado warnings through descriptive and regression-based statistics using a survey administered to businesses in North Texas. Prior to release, the survey was vetted by a focus group comprised of businesses in Grayson County, TX who assisted in the creation of a behavior ranking scale. The scale ranked behaviors from low to high effort. Responses allowed for determining if the business reacted to the warning in a passive or active manner. Returned surveys came from large and small businesses in North Texas and represent a wide variety of industries. Regression analysis explores which variables have the greatest influence on businesses’ behavior and show that beyond increases in probability from the probabilistic warnings, trust in the warning provides the most significant change to behavior.
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454 members
Kevin Mark Simmons
  • Economics and Business Administration
Andra Petrean
  • Department of Physics
D. C. Salisbury
  • Department of Physics
Ivette Vargas-O'Bryan
  • Department of Relgious Studies
Andrew Carr
  • Department of Chemistry
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