6,235 research outputs found

    Patch-Scale Movement Dynamics in the Iowa Grassland Butterflies \u3ci\u3eSpeyeria Cybele\u3c/i\u3e and \u3ci\u3eMegisto Cymela\u3c/i\u3e (Lepidoptera: Nymphalidae)

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    An understanding of the movement dynamics of invertebrates can be critical to their conservation, especially when managing relatively small, isolated habitats. Most studies of butterfly movement have focused on metapopulation dynamics at relatively large spatial scales, and the results from these studies may not translate well for patchy populations within a single nature preserve. In this work we use individual mark and recapture (IMR) methods to follow the movements of two species of butterfly, Megisto cymela (Cramer) and Speyeria cybele F. (Lepidoptera: Nymphalidae) within a 240 hectare forest and grassland preserve in central Iowa, USA. Significant redistribution was seen in both species, with 55.7% of S. cybele and 31.1% of M. cymela undergoing interpatch movement. Median movement rates during the study were 105 m/day for S. cybele and 38 m/day for M. cymela, with the top decile moving at a rate of over five times these values. This movement did not appear to be random. S. cybele exhibited directed movement towards patches with high nectaring potential, although not all such patches were selected. M. cymela aggregated in particular prairie patches, especially those with high edge to area ratios, although the reason for aggregation is not clear

    Evaluation of Risk Management Methods for Satsuma Mandarin

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    Simulation of production budgets were used to compare net discounted returns and the distribution of returns under alternative risk-mitigation scenarios. Results indicate that the combination of freeze protection and crop insurance increases expected net discounted 20-year returns while decreasing the downside risk. Break-even prices ranged from .257to.257 to .289 per pound. Crop insurance returns were constant across price.Satsuma oranges, freeze protection, crop insurance, production budget, simulation, Crop Production/Industries, Farm Management, Risk and Uncertainty, C63, D81, Q12,

    A Reactive Molecular Dynamics Model for Uranium/Hydrogen Containing Systems

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    Uranium-based materials are valuable assets in the energy, medical, and military industries. However, understanding their sensitivity to hydrogen embrittlement is particularly challenging due to the toxicity of uranium and computationally expensive nature of the quantum-based methods generally required to study such processes. In this regard, we have developed a Chebyshev Interaction Model for Efficient Simulation (ChIMES) model that can be employed to compute energies and forces of U and UH3 bulk structures with vacancies and hydrogen interstitials with similar accuracy to Density Functional Theory (DFT) while yielding linear scaling and orders of magnitude improvement in computational efficiency. We show that that the bulk structural parameters, uranium and hydrogen vacancy formation energies, and diffusion barriers predicted by the ChIMES potential are in strong agreement with the reference DFT data. We then use ChIMES to conduct molecular dynamics simulations of the temperature-dependent diffusion of a hydrogen interstitial and determine the corresponding diffusion activation energy. Our model has particular significance in studies of actinides and other high-Z materials, where there is a strong need for computationally efficient methods to bridge length and time scales between experiments and quantum theory.Comment: Reactive molecular dynamics model for U/H systems based on the ChIMES reactive force fiel

    Theoretical modeling of propagation of magneto-acoustic waves in magnetic regions below sunspots

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    We use 2D numerical simulations and eikonal approximation, to study properties of MHD waves traveling below the solar surface through the magnetic structure of sunspots. We consider a series of magnetostatic models of sunspots of different magnetic field strengths, from 10 Mm below the photosphere to the low chromosphere. The purpose of these studies is to quantify the effect of the magnetic field on local helioseismology measurements by modeling waves excited by sub-photospheric sources. Time-distance propagation diagrams and wave travel times are calculated for models of various field strength and compared to the non-magnetic case. The results clearly indicate that the observed time-distance helioseismology signals in sunspot regions correspond to fast MHD waves. The slow MHD waves form a distinctly different pattern in the time-distance diagram, which has not been detected in observations. The numerical results are in good agreement with the solution in the short-wavelength (eikonal) approximation, providing its validation. The frequency dependence of the travel times is in a good qualitative agreement with observations.Comment: accepted by Ap

    Athletic Training Student and Student Aide Clinical Task Allowance in the Secondary School Setting

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    Purpose: Athletic training student aides (SA) are minors in high school that participate in an athletic training experience under the supervision of secondary school athletic trainers (SSAT). The NATA published an official statement on the proper supervision of SAs related to task allowance. As SSATs may also supervise athletic training students (ATSs), it is important to understand the differences in both. Therefore, the objective was to explore the training, task allowance, and perspectives of SAs and ATSs by SSATs during clinical experiences. Methods: We used a cross-sectional, web-based survey for this study. SSATs (n=3,567) from the ATLAS database were recruited and 614 participants (age=39±11years, years credentialed=12±9years) completed the study. An online survey was developed to reflect the NATA official statement for task allowance and supervision of SAs and ATSs. Dependent variables included requirements and task allowance of the SA and ATS based on supervision (direct, autonomous, and restricted), and the personal perceptions from SSATs. Results: 76.5% of SSATs reported having SAs involved in their clinical practice. Less than 50% of SSATs implemented recommended trainings related to emergency preparedness, first aid, and patient privacy. When exploring task allowance, most SSATs were following best practice guidelines for job-related tasks. Additionally, SSATs were allowing ATSs to perform more tasks autonomously as compared to SAs. Conclusions: SSATs are mostly following best practice recommendations for task allowance, whereby they are providing supervision to SAs in the appropriate areas and not allowing certain duties. However, 100% compliance was not met, thus increasing risks to patients and the profession. SSATs should improve training and preparedness for the SAs involved in their clinical practice Additionally, SSATs are allowing ATSs to perform job-related tasks autonomously or with directed supervision during clinical experiences with the exception to administrative tasks and autonomous clinical-decision making

    Letter from the Nuclear Security Women Editors

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    Letter from the Nuclear Security Women Editors for the IJNS and NSW Special Issue: Women in Nuclear Securit

    Simulation to Support Local Search in Trajectory Optimization Planning

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    NASA and the international community are investing in the development of a commercial transportation infrastructure that includes the increased use of rotorcraft, specifically helicopters and civil tilt rotors. However, there is significant concern over the impact of noise on the communities surrounding the transportation facilities. One way to address the rotorcraft noise problem is by exploiting powerful search techniques coming from artificial intelligence coupled with simulation and field tests to design low-noise flight profiles which can be tested in simulation or through field tests. This paper investigates the use of simulation based on predictive physical models to facilitate the search for low-noise trajectories using a class of automated search algorithms called local search. A novel feature of this approach is the ability to incorporate constraints directly into the problem formulation that addresses passenger safety and comfort

    Adaptive windowing in contrast-enhanced intravascular ultrasound imaging

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    Intravascular ultrasound (IVUS) is one of the most commonly-used interventional imaging techniques and has seen recent innovations which attempt to characterize the risk posed by atherosclerotic plaques. One such development is the use of microbubble contrast agents to image vasa vasorum, fine vessels which supply oxygen and nutrients to the walls of coronary arteries and typically have diameters less than 200 µm. The degree of vasa vasorum neovascularization within plaques is positively correlated with plaque vulnerability. Having recently presented a prototype dual-frequency transducer for contrast agent-specific intravascular imaging, here we describe signal processing approaches based on minimum variance (MV) beamforming and the phase coherence factor (PCF) for improving the spatial resolution and contrast-to-tissue ratio (CTR) in IVUS imaging. These approaches are examined through simulations, phantom studies, ex vivo studies in porcine arteries, and in vivo studies in chicken embryos. In phantom studies, PCF processing improved CTR by a mean of 4.2 dB, while combined MV and PCF processing improved spatial resolution by 41.7%. Improvements of 2.2 dB in CTR and 37.2% in resolution were observed in vivo. Applying these processing strategies can enhance image quality in conventional B-mode IVUS or in contrast-enhanced IVUS, where signal-to-noise ratio is relatively low and resolution is at a premium
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