3,145 research outputs found

    MACS: Multi-agent COTR system for Defense Contracting

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    The field of intelligent multi-agent systems has expanded rapidly in the recent past. Multi-agent architectures and systems are being investigated and continue to develop. To date, little has been accomplished in applying multi-agent systems to the defense acquisition domain. This paper describes the design, development, and related considerations of a multi-agent system in the area of procurement and contracting for the defense acquisition community

    The mechanical response of semiflexible networks to localized perturbations

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    Previous research on semiflexible polymers including cytoskeletal networks in cells has suggested the existence of distinct regimes of elastic response, in which the strain field is either uniform (affine) or non-uniform (non-affine) under external stress. Associated with these regimes, it has been further suggested that a new fundamental length scale emerges, which characterizes the scale for the crossover from non-affine to affine deformations. Here, we extend these studies by probing the response to localized forces and force dipoles. We show that the previously identified nonaffinity length [D.A. Head et al. PRE 68, 061907 (2003).] controls the mesoscopic response to point forces and the crossover to continuum elastic behavior at large distances.Comment: 16 pages, 18 figures; substantial changes to text and figures to clarify the crossover to continuum elasticity and the role of finite-size effect

    The probable, possible, and novel functions of ERp29

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    The luminal endoplasmic reticulum (ER) protein of 29 kDa (ERp29) is a ubiquitously expressed cellular agent with multiple critical roles. ERp29 regulates the biosynthesis and trafficking of several transmembrane and secretory proteins, including the cystic fibrosis transmembrane conductance regulator (CFTR), the epithelial sodium channel (ENaC), thyroglobulin, connexin 43 hemichannels, and proinsulin. ERp29 is hypothesized to promote ER t

    Are superflares on solar analogues caused by extra-solar planets?

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    Stellar flares with 102107{10^2-10^7} times more energy than the largest solar flare have been detected from 9 normal F and G main sequence stars (Schaefer, King & Deliyannis 1999). These superflares have durations of hours to days and are visible from at least x-ray to optical frequencies. The absence of world-spanning aurorae in historical records and of anomalous extinctions in the geological record indicate that our Sun likely does not suffer superflares. In seeking to explain this new phenomenon, we are struck by its similarity to large stellar flares on RS Canum Venaticorum binary systems, which are caused by magnetic reconnection events associated with the tangling of magnetic fields between the two stars. The superflare stars are certainly not of this class, although we propose a similar flare mechanism. That is, superflares are caused by magnetic reconnection between fields of the primary star and a close-in Jovian planet. Thus, by only invoking known planetary properties and reconnection scenarios, we can explain the energies, durations, and spectra of superflares, as well as explain why our Sun does not have such events.Comment: 13 pages, Accepted for publication in Ap

    Coupled dynamics of voltage and calcium in paced cardiac cells

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    We investigate numerically and analytically the coupled dynamics of transmembrane voltage and intracellular calcium cycling in paced cardiac cells using a detailed physiological model and its reduction to a three-dimensional discrete map. The results provide a theoretical framework to interpret various experimentally observed modes of instability ranging from electromechanically concordant and discordant alternans to quasiperiodic oscillations of voltage and calcium

    Cardiac Troponin Assessment Following Atrial Fibrillation Ablation: Implications for Chest Pain Evaluation

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    Background: The range of elevation of troponin I (tI) that is within expected limits from left atrial radiofrequency ablation for atrial fibrillation (AF) is not well described, though such information may be of clinical value. Objectives: Identify the expected range of tI values post-atrial fibrillation (AF) ablation. Methods: 31 patients undergoing AF ablation had a single tI level drawn the day following the procedure. Clinical variables were also collected, such as ablation type and radiofrequency (RF) time. Results: Paroxysmal AF was present in 23 patients, and 8 had chronic AF. The average RF time was 2627.8 ± 737.5 seconds. The mean RF power was 61.7 ± 4.3W (range 55-70W). The mean RF temperature limit was 53.6 ± 2.0°C (range 50-55°C). There was no clinical or electrocardiographic evidence of coronary ischemia in this population. The mean tI the following day was 3.21 ± 1.5 (range 1.48-8.41). There was no correlation between RF time, ablation type, ablation catheter size, and ablation temperature or ablation power and tI levels. Conclusions: Troponin I elevation post-ablation was ubiquitous. Knowledge of expected post-ablation tI levels may be helpful in the evaluation of post-procedure chest pain
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