58 research outputs found

    Closing Racial Disparity by Dismantling Constructs of Fear - A Practical Methodology for Learning to Swim

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    African American, Black, Hispanic, Latino, and low-socioeconomic communities have lower swimming ability and higher relative drowning rates than White and high-socioeconomic communities, distinguishing the former as high-priority populations to engage with effective learn-to-swim programming. This article demonstrates how prioritizing the reduction of fear-producing brain processes while learning to swim can result in 79.5% of high-priority population non-swimmers being able to jump into deep water, roll onto their backs and either float or tread for 60 seconds, and swim 25 yards after an average of 14 practice sessions. Practical explanations of four key components— water exploration, structured games, emulating coaches, and water safety education—are provided. Three real-world programming examples detail how the curriculum was structured and results for (1) a youth learn-to-swim program, (2) a high school program, and (3) a weekly day camp program

    A resonant-term-based model including a nascent disk, precession, and oblateness: application to GJ 876

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    Investigations of two resonant planets orbiting a star or two resonant satellites orbiting a planet often rely on a few resonant and secular terms in order to obtain a representative quantitative description of the system's dynamical evolution. We present a semianalytic model which traces the orbital evolution of any two resonant bodies in a first- through fourth-order eccentricity or inclination-based resonance dominated by the resonant and secular arguments of the user's choosing. By considering the variation of libration width with different orbital parameters, we identify regions of phase space which give rise to different resonant ''depths,'' and propose methods to model libration profiles. We apply the model to the GJ 876 extrasolar planetary system, quantify the relative importance of the relevant resonant and secular contributions, and thereby assess the goodness of the common approximation of representing the system by just the presumably dominant terms. We highlight the danger in using ''order'' as the metric for accuracy in the orbital solution by revealing the unnatural libration centers produced by the second-order, but not first-order, solution, and by demonstrating that the true orbital solution lies somewhere ''in-between'' the third- and fourth-order solutions. We also present formulas used to incorporate perturbations from central-body oblateness and precession, and a protoplanetary or protosatellite thin disk with gaps, into a resonant system. We quantify these contributions to the GJ 876 system, and thereby highlight the conditions which must exist for multi-planet exosystems to be significantly influenced by such factors. We find that massive enough disks may convert resonant libration into circulation; such disk-induced signatures may provide constraints for future studies of exoplanet systems.Comment: 39 pages of body text, 21 figures, 5 tables, 1 appendix, accepted for publication in Celestial Mechanics and Dynamical Astronom

    Migration-Induced Architectures of Planetary Systems

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