8,476 research outputs found

    Spatial structures in a simple model of population dynamics for parasite-host interactions

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    Spatial patterning can be crucially important for understanding the behavior of interacting populations. Here we investigate a simple model of parasite and host populations in which parasites are random walkers that must come into contact with a host in order to reproduce. We focus on the spatial arrangement of parasites around a single host, and we derive using analytics and numerical simulations the necessary conditions placed on the parasite fecundity and lifetime for the populations long-term survival. We also show that the parasite population can be pushed to extinction by a large drift velocity, but, counterintuitively, a small drift velocity generally increases the parasite population.Comment: 6 pages, 6 figure

    Recognition of Design Failure by Fourth-Grade Students During an Engineering Design Challenge

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    The practice of persisting and learning from design failures is essential to engineering design and offers unique ways of knowing and learning for K-12 students. To understand how students engage in the practice of persisting and learning from design failures, we must first understand how, if at all, they recognize that a design failure has occurred. We studied a classroom of fourth-grade students engaged in an engineering design challenge and examined the ways in which design failure occurred and how students recognized, neglected to recognize, or misinterpreted design failure. We found that, in addition to anticipating failure, conducting fair tests, and making focused observations, students must have an understanding and awareness of the evolving criteria and constraints of the design problem in order to recognize design failure. If lacking an understanding and awareness of criteria and constraints represents a barrier to recognizing an initial design failure, it also represents a barrier to recognizing any subsequent design failures in the design process and thus a barrier to persisting and learning from design failures
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