The western United States has experienced increases in wildfire occurrence, total fire area burned, and fire size over the previous four decades, leading to worse summer air quality (

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Previous nationwide studies have reported links between long-term PM2.5 concentrations and COVID-19 infection and mortality rates. In order to translate these results to the state level, we use Bayesian hierarchical models to explore potential links between long-term PM2.5 concentrations and census tract-level rates of COVID-19 outcomes (infections, hospitalizations, and deaths) in Colorado. We explicitly consider how the uncertainty in PM2.5 estimates affect our results by comparing four different PM2.5 surfaces from academic and governmental organizations. After controlling for 20 census tract-level covariates, we find that our results depend heavily on the choice of PM2.5 surface. Using PM2.5 estimates from the United States EPA, we find that a 1 μg/m 3 increase in long term PM2.5 concentrations is associated with a statistically significant 26% increase in the relative risk of hospitalizations and a 34% increase in mortality. Results for all other surfaces and outcomes were not statistically significant. At the same time, we find a clear association between communities of color and COVID-19 outcomes at the Colorado census tract level that is minimally affected by the choice of PM2.5 surface. A per-interquartile range (IQR) increase in the percent of non-African American people of color was associated with a 31%, 43%, and 56% increase in the relative risk of infection, hospitalization, and mortality respectively, while a per-IQR increase in the proportion of non-Hispanic African Americans was associated with a 4% and 7% increase in the relative risk of infections and hospitalizations. The current disagreement among the different PM2.5 estimates is a key factor limiting our ability to link environmental exposures and health outcomes at the census tract level. These results have strong implications for the implementation of an equitable public health response during the crisis and suggest targeted areas for additional air monitoring in Colorado.

Historical case studies of scientific concepts are a useful medium for showing how scientific ideas originate and how they change over time. They are thus a useful tool for conveying knowledge about the nature of science. This paper focuses on the concepts of heat and temperature and discusses some issues related to choosing the content for a historical case study which incorporates not only nature of science perspectives but understandings related to what we know about the teaching and learning of these concepts. The case study is designed for first-year university chemistry students as an introduction to their study of thermodynamics. The paper includes a general chemistry textbook analysis of the heat and temperature concepts and a discussion of the caloric theory of heat, thermometry, and a brief survey of how the energy concept transformed our understanding of heat and temperature.

PV = c Syringe J PlVl =P2V2 19 PV constant, lab. 1 P,VI =P,V2 3 Note: J represents the presence of a feature represents the absence of a feature Blank space means no laboratory exercises from which to choose. P, PV = c V 1 V J PlV, =P,V, 6