Atranorin is a secondary metabolite found in many lichens. This compound can act as a photo-buffer, supporting its use as a marker of metabolic response to changes in light. In preliminary trials, atranorin was found to be unstable over time when in solution, potentially precluding its usefulness in this capacity. The present study tests the stability of atranorin in different extraction solvents and at different pH values over time using HPLC analysis. We found that atranorin is most stable in acetonitrile, among six tested solvents, and that the presence of strong acid or a strong base destabilizes the compound. We propose that atranorin breaks down through transesterification in methanol and ethanol until an equilibrium is reached, while a strong base breaks down atranorin through saponification and under acidic conditions, atranorin concentration significantly increases with time. Although atranorin levels were found to be stable in whole thallus extracts from fresh lichens using a leaching method, chemicals isolated using chromatographic separation showed similar breakdown to an atranorin standard. In future work on lichens atranorin should be extracted in acetonitrile or acetone without an added base or acid to yield the greatest stability and thus provide more accurate concentration values of atranorin with time using HPLC. The interactions of atranorin with acid and with chloroform need further study.
Two approaches, Linear Discriminant Analysis, and Logistic Regression are used and compared to predict success or failure for first-time freshmen in the first calculus course at a medium-sized public, 4-year institution prior to Fall registration. The predictor variables are high school GPA, the number, and GPA's of college prep mathematics courses taken in grades 9 to 12, ACT math scores, and the score on a calculus readiness test. First-time freshmen who are predicted to fail are advised to take a precalculus course prior to attempting the first calculus course. Using a prediction model for 2012 based on data from 2010 and 2011, 73.9% of students were classified correctly as either passing or failing Calculus I. Of students predicted to fail, 77% did in fact fail which was almost three times as high as the failure rate for students predicted to pass. The study also found that both precollege achievement factors, (specifically high school math GPA), and a placement test (the calculus readiness test) were significant predictors of success in Calculus I.
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