1,670 research outputs found

    Incorporating Wildlife Connectivity into Forest Plan Revision Under the United States Forest Service\u27s 2012 Planning Rule

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    The United States Forest Service promulgated new planning regulations under the National Forest Management Act in 2012 (i.e., the Planning Rule). These new regulations include the first requirements in U.S. public land management history for National Forests to evaluate, protect, and/or restore ecological connectivity as they revise their land management plans. Data and resource limitations make single-species, functional connectivity analyses for the myriad species that occur within the 78 million ha the Forest Service manages implausible. We describe an approach that relies on freely available data and generic species, virtual species whose profile consists of ecological requirements designed to reflect the needs of a group of real species, to address the new Planning Rule requirements. We present high-resolution connectivity estimates for 10 different generic species across a 379,000 ha study area centered on the Custer Gallatin National Forest (CGNF) in Montana and South Dakota under two different movement models. We identify locations important for connectivity for multiple species and characterize the role of the CGNF for regional connectivity. Our results informed the Plan Revision process on the CGNF and could be readily exported to other National Forests currently or planning to revise their land management plans under the new Planning Rule

    Limits to Sympathetic Evaporative Cooling of a Two-Component Fermi Gas

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    We find a limit cycle in a quasi-equilibrium model of evaporative cooling of a two-component fermion gas. The existence of such a limit cycle represents an obstruction to reaching the quantum ground state evaporatively. We show that evaporatively the \beta\mu ~ 1. We speculate that one may be able to cool an atomic fermi gas further by photoassociating dimers near the bottom of the fermi sea.Comment: Submitted to Phys. Rev

    A quasi-diagonal approach to the estimation of Lyapunov spectra for spatio-temporal systems from multivariate time series

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    We describe methods of estimating the entire Lyapunov spectrum of a spatially extended system from multivariate time-series observations. Provided that the coupling in the system is short range, the Jacobian has a banded structure and can be estimated using spatially localised reconstructions in low embedding dimensions. This circumvents the ``curse of dimensionality'' that prevents the accurate reconstruction of high-dimensional dynamics from observed time series. The technique is illustrated using coupled map lattices as prototype models for spatio-temporal chaos and is found to work even when the coupling is not strictly local but only exponentially decaying.Comment: 13 pages, LaTeX (RevTeX), 13 Postscript figs, to be submitted to Phys.Rev.

    The Autism Spectrum Disorder Evaluative Education Model: a school-based method of assessing and selecting interventions for classroom use

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    Evaluating educational programs and interventions is generally considered a normal part of curriculum development and improvement, and published findings are readily accessible through peer-reviewed journals. Recently, however, researchers and practicing educators have identified a lack of evaluative research regarding Autism Spectrum Disorder (ASD) educational practices in the peer-reviewed literature. Autism Spectrum Australia (Aspect) has an established evidence-informed ASD curriculum that is constantly reviewed and updated to meet the needs of the students in Aspect schools and classes. Through a methodical evaluative process, all educational interventions and support processes and devices undergo a series of Evidence-Based Research Trials and evaluations before they are implemented in classes. This article demonstrates how a workflow model can deliver a systematic method for identifying, evaluating, implementing, and disseminating the research findings of a program or support intervention. The Autism Spectrum Disorder Evaluative Education (ASDEE) model is discussed

    Evaporative Cooling of a Two-Component Degenerate Fermi Gas

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    We derive a quantum theory of evaporative cooling for a degenerate Fermi gas with two constituents and show that the optimum cooling trajectory is influenced significantly by the quantum statistics of the particles. The cooling efficiency is reduced at low temperatures due to Pauli blocking of available final states in each binary collision event. We compare the theoretical optimum trajectory with experimental data on cooling a quantum degenerate cloud of potassium-40, and show that temperatures as low as 0.3 times the Fermi temperature can now be achieved.Comment: 6 pages, 4 figure

    Microcoil Spring Interconnects for Ceramic Grid Array Integrated Circuits

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    As integrated circuit miniaturization trends continue, they drive the need for smaller higher input/output (I/O) packages. Hermetically sealed ceramic area array parts are the package of choice by the space community for high reliability space flight electronic hardware. Unfortunately, the coefficient of thermal expansion mismatch between the ceramic area array package and the epoxy glass printed wiring board limits the life of the interconnecting solder joint. This work presents the results of an investigation by Marshall Space Flight Center into a method to increase the life of this second level interconnection by the use of compliant microcoil springs. The design of the spring and its attachment process are presented along with thermal cycling results of microcoil springs (MCS) compared with state-of-the-art ball and column interconnections. Vibration testing has been conducted on MCS and high lead column parts. Radio frequency simulation and measurements have been made and the MCS has been modeled and a stress analysis performed. Thermal cycling and vibration testing have shown MCS interconnects to be significantly more reliable than solder columns. Also, MCS interconnects are less prone to handling damage than solder columns. Future work that includes shock testing, incorporation into a digital signal processor board, and process evaluation of expansion from a 400 I/O device to a device with over 1,100 I/O is identified

    Homogenous recycling of transuranium elements from irradiated fast reactor fuel by the EURO-GANEX solvent extraction process

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    The EURO-GANEX process was developed forco-separating transuranium elements from irradiatednuclear fuels. A hot flow-sheet trial was performed in acounter-current centrifugal contactor setup, using a genuinehigh active feed solution. Irradiated mixed (carbide,nitride) U80Pu20 fast reactor fuel containing 20 % Pu wasthermally treated to oxidise it to the oxide form which wasthen dissolved in HNO3. From this solution uranium wasseparated to >99.9 % in a primary solvent extraction cycleusing 1.0 mol/L DEHiBA (N,N-di(2-ethylhexyl)isobutyramidein TPH (hydrogenated tetrapropene) as the organicphase. The raffinate solution from this process, containing10 g/L Pu, was further processed in a second cycle of solventextraction. In this EURO-GANEX flow-sheet, TRU andfission product lanthanides were firstly co-extracted intoa solvent composed of 0.2 mol/L TODGA (N,N,N′,N′-tetran-octyl diglycolamide) and 0.5 mol/L DMDOHEMA (N,N′-dimethyl-N,N′-dioctyl-2-(2-hexyloxy-ethyl) malonamide)dissolved in Exxsol D80, separating them from most otherfission and corrosion products. Subsequently, the TRUwere selectively stripped from the collected loaded solventusing a solution containing 0.055 mol/L SO3-Ph-BTP(2,6-bis(5,6-di(3-sulphophenyl)-1,2,4-triazin-3-yl)pyridinetetrasodium salt) and 1 mol/L AHA (acetohydroxamicacid) in 0.5 mol/L HNO3; lanthanides were finally strippedusing 0.01 mol/L HNO3. Approximately 99.9 % of the TRUand less than 0.1 % of the lanthanides were found in theproduct solution, which also contained the major fractionsof Zr and Mo

    Sympathetic cooling of an atomic Bose-Fermi gas mixture

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    Sympathetic cooling of an atomic Fermi gas by a Bose gas is studied by solution of the coupled quantum Boltzmann equations for the confined gas mixture. Results for equilibrium temperatures and relaxation dynamics are presented, and some simple models developed. Our study illustrate that a combination of sympathetic and forced evaporative cooling enables the Fermi gas to be cooled to the degenerate regime where quantum statistics, and mean field effects are important. The influence of mean field effects on the equilibrium spatial distributions is discussed qualitatively.Comment: 8 pages, 9 figures, accepted for publication in Phys.Rev.Let

    Theory and computation of covariant Lyapunov vectors

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    Lyapunov exponents are well-known characteristic numbers that describe growth rates of perturbations applied to a trajectory of a dynamical system in different state space directions. Covariant (or characteristic) Lyapunov vectors indicate these directions. Though the concept of these vectors has been known for a long time, they became practically computable only recently due to algorithms suggested by Ginelli et al. [Phys. Rev. Lett. 99, 2007, 130601] and by Wolfe and Samelson [Tellus 59A, 2007, 355]. In view of the great interest in covariant Lyapunov vectors and their wide range of potential applications, in this article we summarize the available information related to Lyapunov vectors and provide a detailed explanation of both the theoretical basics and numerical algorithms. We introduce the notion of adjoint covariant Lyapunov vectors. The angles between these vectors and the original covariant vectors are norm-independent and can be considered as characteristic numbers. Moreover, we present and study in detail an improved approach for computing covariant Lyapunov vectors. Also we describe, how one can test for hyperbolicity of chaotic dynamics without explicitly computing covariant vectors.Comment: 21 pages, 5 figure
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