Lattices of hydrodynamically interacting flapping swimmers

Fish schools and bird flocks exhibit complex collective dynamics whose self-organization principles are largely unknown. The influence of hydrodynamics on such collectives has been relatively unexplored theoretically, in part due to the difficulty in modeling the temporally long-lived hydrodynamic interactions between many dynamic bodies. We address this through a novel discrete-time dynamical system (iterated map) that describes the hydrodynamic interactions between flapping swimmers arranged in one- and two-dimensional lattice formations. Our 1D results exhibit good agreement with previously published experimental data, in particular predicting the bistability of schooling states and new instabilities that can be probed in experimental settings. For 2D lattices, we determine the formations for which swimmers optimally benefit from hydrodynamic interactions. We thus obtain the following hierarchy: while a side-by-side single-row "phalanx" formation offers a small improvement over a solitary swimmer, 1D in-line and 2D rectangular lattice formations exhibit substantial improvements, with the 2D diamond lattice offering the largest hydrodynamic benefit. Generally, our self-consistent modeling framework may be broadly applicable to active systems in which the collective dynamics is primarily driven by a fluid-mediated memory

A rationale and design of a microcomputer system for schools and colleges

Imperial Users onl

Ready or Not? Protecting the Public's Health in the Age of Bioterrorism, 2004

Examines ten key indicators to evaluate state preparedness to respond to bioterrorist attacks and other public health emergencies. Evaluates the federal government's role and performance, and offers recommendations for improving readiness

A Review and Research Suggestions for Empirical Approaches to Evaluating Reinforcing Effects of Peer Attention vs. Teacher Attention in the General Education Classroom

Behavior management in the general education classroom can be difficult at times for educators. Attention is one reinforcer of children\u27s behavior in the classroom and the child\u27s behavior may be maintained by teacher attention or peer attention. If attentions is implemented appropriately, peer or teacher attention may prove to be an effective reinforcer in maintaining appropriate behaviors in the classroom. Teacher attention is commonly used to maintain student performance (Broussard & Northup, 1997). Educators may not know which is more reinforcing to the typical student in the general education classroom - teacher attention or peer attention. However, evaluating the effectiveness of such a reinforcer involves evaluating the preference for an intervention, rather than a specific stimulus that can be arranged in a traditional stimulus preference assessment (Hagopian, Long, &Rush, 2004; Hanley, Iwata, & Lindberg, 1999). A modified concurrent-chains assessment can be used to determine the reinforcer preference of individuals (Hanley, 2010). This paper will summarize the use of a modified concurrent-chains assessment on typical students in the general education classroom in order to determine students\u27 preference of peer attention vs. teacher attention