Studies of the exhaust products from solid propellant rocket motors

This study was undertaken to determine the feasibility of conducting environmental chamber tests on the physical processes which occur when a solid rocket motor exhaust mixes with the ambient atmosphere. Of particular interest was the interaction between hydrogen chloride, aluminum oxide, and water vapor. The program consisted of three phases: (1) building a small rocket motor and using it to provide the exhaust species in a controlled environment; (2) evaluating instruments used to detect and measure HCl concentrations and if possible determining whether the HCl existed in the gaseous state or as an acid aerosol; (3) monitoring a series of 6.4-percent scale space shuttle motor tests and comparing the results to the environmental chamber studies. Eighteen firings were conducted in an environmental chamber with the initial ambient relative humidity set at values from 29 to 100 percent. Two additional firings were made in a large shed, and four were made on an open concrete apron. Six test firings at MSFC were monitored, and the ground level concentrations are reported. Evidence is presented which shows that the larger Al2O3 (5 to 50 micrometers) particles from the rocket motor can act as condensation nuclei. Under appropriate ambient conditions where there is sufficient water vapor this results in the formation of an acid aerosol. Droplets of this acid were detected both in the environmental chamber and in the scaled shuttle engine tests

Force-matched embedded-atom method potential for niobium

Large-scale simulations of plastic deformation and phase transformations in alloys require reliable classical interatomic potentials. We construct an embedded-atom method potential for niobium as the first step in alloy potential development. Optimization of the potential parameters to a well-converged set of density-functional theory (DFT) forces, energies, and stresses produces a reliable and transferable potential for molecular dynamics simulations. The potential accurately describes properties related to the fitting data, and also produces excellent results for quantities outside the fitting range. Structural and elastic properties, defect energetics, and thermal behavior compare well with DFT results and experimental data, e.g., DFT surface energies are reproduced with less than 4% error, generalized stacking-fault energies differ from DFT values by less than 15%, and the melting temperature is within 2% of the experimental value.Comment: 17 pages, 13 figures, 7 table

Association of Polymorphisms in Oxidative Stress Genes with Clinical Outcomes for Bladder Cancer Treated with Bacillus Calmette-Guérin

Genetic polymorphisms in oxidative stress pathway genes may contribute to carcinogenesis, disease recurrence, treatment response, and clinical outcomes. We applied a pathway-based approach to determine the effects of multiple single nucleotide polymorphisms (SNPs) within this pathway on clinical outcomes in non-muscle-invasive bladder cancer (NMIBC) patients treated with Bacillus Calmette-Guérin (BCG). We genotyped 276 SNPs in 38 genes and evaluated their associations with clinical outcomes in 421 NMIBC patients. Twenty-eight SNPs were associated with recurrence in the BCG-treated group (P<0.05). Six SNPs, including five in NEIL2 gene from the overall and BCG group remained significantly associated with recurrence after multiple comparison adjustments (q<0.1). Cumulative unfavorable genotype analysis showed that the risk of recurrence increased with increasing number of unfavorable genotypes. In the analysis of risk factors associated with progression to disease, rs3890995 in UNG, remained significant after adjustment for multiple comparison (q<0.1). These results support the hypothesis that genetic variations in host oxidative stress genes in NMIBC patients may affect response to therapy with BCG

Insights into the Second Law of Thermodynamics from Anisotropic Gas-Surface Interactions

Thermodynamic implications of anisotropic gas-surface interactions in a closed molecular flow cavity are examined. Anisotropy at the microscopic scale, such as might be caused by reduced-dimensionality surfaces, is shown to lead to reversibility at the macroscopic scale. The possibility of a self-sustaining nonequilibrium stationary state induced by surface anisotropy is demonstrated that simultaneously satisfies flux balance, conservation of momentum, and conservation of energy. Conversely, it is also shown that the second law of thermodynamics prohibits anisotropic gas-surface interactions in "equilibrium", even for reduced dimensionality surfaces. This is particularly startling because reduced dimensionality surfaces are known to exhibit a plethora of anisotropic properties. That gas-surface interactions would be excluded from these anisotropic properties is completely counterintuitive from a causality perspective. These results provide intriguing insights into the second law of thermodynamics and its relation to gas-surface interaction physics.Comment: 28 pages, 11 figure

Resegregation: A case study of the failure of the color blind ideal in K–12 schooling policy

Given the current trend for school districts to reorganize once unitary status is achieved, a cultural ethnography was conducted to determine how high school students experienced the inevitable resegregation in their school system. The findings of this study reinforced and extended the arguments Kenneth Clark presented about the deleterious effects of social and school segregation on Black children in the court cases leading up to Brown v. Board of Education. Like the child participants in his famous doll experiments, students assigned to the all Black high school internalized a type of social deficit theory about themselves, which they explained through race, geographic, and to a lesser extent, class identity—revealing a clear social text that marked them as less in virtually every aspect of their schooling experience. The study highlights the negative consequences of the Supreme Court’s color blind ideology, as realized in the assignment of students to neighborhood schools. Despite promises of equity by school leaders resegregation has a profoundly negative effect on students, the vast majority of those involved clearly believing they were second class citizens within a caste system. Resegregated students especially noted newly created barriers to academic, social, and other curricular experiences important for their post-secondary aspirations. The meaning of racial separation was especially significant due to hidden messages associated with diversity on the emotional, psychological, and intellectual development of adolescents. It was concluded that given the racialized meaning of inequitable educational opportunities produced by resegregation, there is an urgent need to reconsider the color blind ideology undergirding the received reading of the Fourteenth Amendment to adopt more color conscious policies sensitive to the damaging effects Black students now experience through policies that unintentionally or intentionally produce racially isolated schools

Learning integrated work : inter-organisational collaborators reflect on provision of authentic virtual multimedia project experience

This discussion paper outlines the experience of initiating and sustaining an authentic, team based, work integrated learning experience for advanced level, undergraduate students of collaborative multimedia design and production. It is a reflective account of how the needs of both organisations involved came to be addressed, creating a win-win-win outcome for the industry partner, the students and the university. Unusual aspects to do with the distance study mode of the students and the requirement for virtual collaboration are showcased. In the analysis, the difficulties experienced in initiating and sustaining such an inter-organisational relationship, especially where there is no direct vocational interdependency and so, no supportive administrative framework, are highlighted

Measurement of Socio-Scientific Reasoning (SSR) and Exploration of SSR as a Progression of Competencies

Socio-scientific reasoning (SSR) is key to helping students take informed positions around socio-scientific issues (SSI). SSR comprises four competencies: recognising complexity of SSI’s, multiple perspectives around SSI’s, the need for ongoing inquiry around SSI’s, and skepticism around different parties’ claims made about SSI’s. The Quantitative Assessment of SSR (QuASSR) provides a promising measurement framework, but there are still important questions around the ability of this instrument to measure transfer across different scenarios and change in SSR over an intervention. Further, prior work suggests that the four competencies may constitute a progression. We explored the ability of the QuASSR to measure transfer of SSR across three different SSI’s using 2-faceted and multi-faceted Rasch models. We used path analysis to test the hypothesis that competencies associated with SSR formed a progression. We found transfer or neartransfer of SSR across the three scenarios, and that the competencies comprise a unidimensional hierarchy. Perspective-taking is a necessary bridge between students’ understanding of complexity and the higher-level competencies of inquiry and skepticism. Inquiry and skepticism were found to be conditionally independent upon accounting for perspective-taking, supporting the idea that seeing multiple perspectives around SSI’s is central to development of the other SSR competencies. (PsycInfo Database Record (c) 2021 APA, all rights reserved

Measurement of Socio-Scientific Reasoning (SSR) and Exploration of SSR as a Progression of Competencies

Socio-scientific reasoning (SSR) is key to helping students take informed positions around socio-scientific issues (SSI). SSR comprises four competencies: recognising complexity of SSI’s, multiple perspectives around SSI’s, the need for ongoing inquiry around SSI’s, and skepticism around different parties’ claims made about SSI’s. The Quantitative Assessment of SSR (QuASSR) provides a promising measurement framework, but there are still important questions around the ability of this instrument to measure transfer across different scenarios and change in SSR over an intervention. Further, prior work suggests that the four competencies may constitute a progression. We explored the ability of the QuASSR to measure transfer of SSR across three different SSI’s using 2-faceted and multi-faceted Rasch models. We used path analysis to test the hypothesis that competencies associated with SSR formed a progression. We found transfer or neartransfer of SSR across the three scenarios, and that the competencies comprise a unidimensional hierarchy. Perspective-taking is a necessary bridge between students’ understanding of complexity and the higher-level competencies of inquiry and skepticism. Inquiry and skepticism were found to be conditionally independent upon accounting for perspective-taking, supporting the idea that seeing multiple perspectives around SSI’s is central to development of the other SSR competencies. (PsycInfo Database Record (c) 2021 APA, all rights reserved