Understanding how energy is released in flares is one of the central problems of solar and stellar astrophysics. Observations of high temperature flare plasma hold many potential clues as to the nature of this energy release. It is clear, however, that flares are not composed of a few impulsively heated loops, but are the result of heating on many small-scale threads that are energized over time, making it difficult to compare observations and numerical simulations in detail. Several previous studies have shown that it is possible to reproduce some aspects of the observed emission by considering the flare as a sequence of independently heated loops, but these studies generally focus on small-scale features while ignoring the global features of the flare. In this paper, we develop a multithreaded model that encompasses the time-varying geometry and heating rate for a series of successivelyheated loops comprising an arcade. To validate, we compare with spectral observations of five flares made with the MinXSS CubeSat as well as light curves measured with GOES/XRS and SDO/AIA. We show that this model can successfully reproduce the light curves and quasi-periodic pulsations in GOES/XRS, the soft X-ray spectra seen with MinXSS, and the light curves in various AIA passbands. The AIA light curves are most consistent with long duration heating, but elemental abundances cannot be constrained with the model. Finally, we show how this model can be used to extrapolate to spectra of extreme events that can predict irradiance across a wide wavelength range including unobserved wavelengths.
We introduce an approach for making a quantitative comparison of the item response curves (IRCs) of any two populations on a multiple-choice test instrument. In this study, we employ simulated and actual data. We apply our approach to a dataset of 12,187 participants on the 25-item Science Literacy Concept Inventory (SLCI), which includes ample demographic data of the participants. Prior comparisons of the IRCs of different populations addressed only two populations and were made by visual inspection. Our approach allows for quickly comparing the IRCs for many pairs of populations to identify those items where substantial differences exist. For each item, we compute the IRC dot product, a number between 0 and 1 for which a value of 1 occurs when the IRCs of the two populations are identical. We then determine whether the value of the IRC dot product is indicative of significant differences in populations of real students. Through this process, we can quickly discover bias across demographic groups. As a case example, we apply our metric to illuminate four SLCI items that exhibit gender bias. We further found that gender bias was present for non-science majors on those items but not for science majors.
Inhibition of Trypanosoma cruzi Epimastigotes in vitro by Iron-Chelating Agents.-Twenty new iron-chelating agents are investigated for their trypanosoma cruzi Epimastigotes inhibiting activities. Imines of type ( VI) are generally inactive, whereas the hydroxypyridones (III) show inhibitory activity comparable to the clinically used benznidazole ( VII). -(JONES, M. M.; SINGH, P. K.; LANE, J. E.; RODRIGUES, R. R.; NESSET, A.; SUAREZ, C. C.; BOGITSH, B.
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