1,113 research outputs found

    Effects of Livestock Grazing Management on Grassland Bird Abundance in the Northern Mixed-Grass Prairie

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    Grassland bird populations have been declining throughout a majority of their range in the United States and Canada over the past 40 years, and currently have the most accelerated declines of any guild of terrestrial birds in this region. Rangelands used for domestic cattle grazing are important for maintaining large tracts of native grassland that may otherwise be converted to agricultural use or other human development. In addition, grassland birds respond well to livestock grazing systems that increase habitat heterogeneity by mimicking historic grassland disturbance, such as fire and bison grazing. Montana Department of Fish, Wildlife, and Parks (FWP) implements a rest-rotation grazing system within conservation easements to increase structural heterogeneity of grassland vegetation on the landscape. However, the rest-rotation grazing system administered by Montana FWP was developed for more arid, bunchgrass-dominated rangelands and has not been evaluated as a management tool for creating structurally diverse wildlife habitat in the northern mixed-grass prairie. This study examines the effect of a rest-rotation grazing system on breeding season habitat selection and abundance of four native grassland songbird species, Baird’s sparrow (Ammodramus bairdii), grasshopper sparrow (Ammodramus savannarum), vesper sparrow (Pooecetes gramineus), and western meadowlark (Sturnella neglecta), relative to traditional season-long or rotational grazing systems on a Montana FWP conservation easement in eastern Montana. Our objectives for the study are: 1) evaluate how abundance and spaceuse of four focal grassland bird species are affected by grazing treatment; 2) estimate the importance of habitat and vegetation characteristics for focal species within pasture treatments; 3) offer management recommendations to agencies and private landowners for improving grassland bird abundance and habitat quality

    Monte Carlo Comparisons to a Cryogenic Dark Matter Search Detector with low Transition-Edge-Sensor Transition Temperature

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    We present results on phonon quasidiffusion and Transition Edge Sensor (TES) studies in a large, 3 inch diameter, 1 inch thick [100] high purity germanium crystal, cooled to 50 mK in the vacuum of a dilution refrigerator, and exposed with 59.5 keV gamma-rays from an Am-241 calibration source. We compare calibration data with results from a Monte Carlo which includes phonon quasidiffusion and the generation of phonons created by charge carriers as they are drifted across the detector by ionization readout channels. The phonon energy is then parsed into TES based phonon readout channels and input into a TES simulator

    Gravitomagnetism and the Clock Effect

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    The main theoretical aspects of gravitomagnetism are reviewed. It is shown that the gravitomagnetic precession of a gyroscope is intimately connected with the special temporal structure around a rotating mass that is revealed by the gravitomagnetic clock effect. This remarkable effect, which involves the difference in the proper periods of a standard clock in prograde and retrograde circular geodesic orbits around a rotating mass, is discussed in detail. The implications of this effect for the notion of ``inertial dragging'' in the general theory of relativity are presented. The theory of the clock effect is developed within the PPN framework and the possibility of measuring it via spaceborne clocks is examined.Comment: 27 pages, LaTeX, submitted to Proc. Bad Honnef Meeting on: GYROS, CLOCKS, AND INTERFEROMETERS: TESTING GENERAL RELATIVITY IN SPACE (22 - 27 August 1999; Bad Honnef, Germany

    Triangleland. I. Classical dynamics with exchange of relative angular momentum

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    In Euclidean relational particle mechanics, only relative times, relative angles and relative separations are meaningful. Barbour--Bertotti (1982) theory is of this form and can be viewed as a recovery of (a portion of) Newtonian mechanics from relational premises. This is of interest in the absolute versus relative motion debate and also shares a number of features with the geometrodynamical formulation of general relativity, making it suitable for some modelling of the problem of time in quantum gravity. I also study similarity relational particle mechanics (`dynamics of pure shape'), in which only relative times, relative angles and {\sl ratios of} relative separations are meaningful. This I consider firstly as it is simpler, particularly in 1 and 2 d, for which the configuration space geometry turns out to be well-known, e.g. S^2 for the `triangleland' (3-particle) case that I consider in detail. Secondly, the similarity model occurs as a sub-model within the Euclidean model: that admits a shape--scale split. For harmonic oscillator like potentials, similarity triangleland model turns out to have the same mathematics as a family of rigid rotor problems, while the Euclidean case turns out to have parallels with the Kepler--Coulomb problem in spherical and parabolic coordinates. Previous work on relational mechanics covered cases where the constituent subsystems do not exchange relative angular momentum, which is a simplifying (but in some ways undesirable) feature paralleling centrality in ordinary mechanics. In this paper I lift this restriction. In each case I reduce the relational problem to a standard one, thus obtain various exact, asymptotic and numerical solutions, and then recast these into the original mechanical variables for physical interpretation.Comment: Journal Reference added, minor updates to References and Figure

    Foundations of Relational Particle Dynamics

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    Relational particle dynamics include the dynamics of pure shape and cases in which absolute scale or absolute rotation are additionally meaningful. These are interesting as regards the absolute versus relative motion debate as well as discussion of conceptual issues connected with the problem of time in quantum gravity. In spatial dimension 1 and 2 the relative configuration spaces of shapes are n-spheres and complex projective spaces, from which knowledge I construct natural mechanics on these spaces. I also show that these coincide with Barbour's indirectly-constructed relational dynamics by performing a full reduction on the latter. Then the identification of the configuration spaces as n-spheres and complex projective spaces, for which spaces much mathematics is available, significantly advances the understanding of Barbour's relational theory in spatial dimensions 1 and 2. I also provide the parallel study of a new theory for which positon and scale are purely relative but orientation is absolute. The configuration space for this is an n-sphere regardless of the spatial dimension, which renders this theory a more tractable arena for investigation of implications of scale invariance than Barbour's theory itself.Comment: Minor typos corrected; references update

    Phonon Quasidiffusion in Cryogenic Dark Matter Search Large Germanium Detectors

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    We present results on quasidiffusion studies in large, 3 inch diameter, 1 inch thick [100] high purity germanium crystals, cooled to 50 mK in the vacuum of a dilution refrigerator, and exposed with 59.5 keV gamma-rays from an Am-241 calibration source. We compare data obtained in two different detector types, with different phonon sensor area coverage, with results from a Monte Carlo. The Monte Carlo includes phonon quasidiffusion and the generation of phonons created by charge carriers as they are drifted across the detector by ionization readout channels.Comment: 13 pages, 12 figures, PHONONS201 conference proceedings; http://psroc.phys.ntu.edu.tw/cjp/download.php?d=4&pid=271

    A Demonstration of using Partnerships and Private Lands Conservation to Evaluate Livestock Grazing as a Management Tool for Greater Sage Grouse in Central Montana

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    Partnerships across agencies and land ownerships established to maintain wildlife-compatible “working landscapes” are critical for conserving and managing wildlife in the West.  Preliminary results from the first three years of a 10-yr study in central Montana demonstrate this management approach.  We are evaluating prescribed grazing systems implemented by NRCS’s Sage Grouse Initiative (SGI) that are designed to improve hiding cover and food availability for Greater sage grouse (Centrocercus urophasianus) during critical life stages via voluntary, incentive-based modifications of livestock grazing management.  Extensive vegetation sampling across 8 SGI-enrolled ranches and 20 non-enrolled ranches in 2013 revealed significant increases in residual grass height, live grass height, and herbaceous vegetation cover on SGI-enrolled lands. In 2011-2013, we monitored adult female sage-grouse and chicks with radiotelemetry to measure vital rates and habitat use. Annual hen survival ranged from 57-74 percent, nest success ranged from 12-61 percent, and chick survival ranged from 9-23 percent.  Using an information theoretic approach in program MARK, the top-ranked nest success model showed that grass height was positively correlated with nest success.   During late nesting to early brood rearing periods of 2012 and 2013 we used pitfall traps to collected ground-dwelling arthropods from cattle grazed and rest-rotation phase pastures enrolled in the SGI program. Collected arthropods were identified and appropriate specimens were classified as sage grouse chick food items. During both years of study, food item catches were greatest (P < 0.03) in rested versus grazed pastures indicating that strategic pasture rest may increase the availability of sage grouse chick food resources

    Relativistic MHD with Adaptive Mesh Refinement

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    This paper presents a new computer code to solve the general relativistic magnetohydrodynamics (GRMHD) equations using distributed parallel adaptive mesh refinement (AMR). The fluid equations are solved using a finite difference Convex ENO method (CENO) in 3+1 dimensions, and the AMR is Berger-Oliger. Hyperbolic divergence cleaning is used to control the ∇⋅B=0\nabla\cdot {\bf B}=0 constraint. We present results from three flat space tests, and examine the accretion of a fluid onto a Schwarzschild black hole, reproducing the Michel solution. The AMR simulations substantially improve performance while reproducing the resolution equivalent unigrid simulation results. Finally, we discuss strong scaling results for parallel unigrid and AMR runs.Comment: 24 pages, 14 figures, 3 table

    Miura-type transformations for lattice equations and Lie group actions associated with Darboux-Lax representations

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    Miura-type transformations (MTs) are an essential tool in the theory of integrable nonlinear partial differential and difference equations. We present a geometric method to construct MTs for differential-difference (lattice) equations from Darboux–Lax representations (DLRs) of such equations. The method is applicable to parameter-dependent DLRs satisfying certain conditions. We construct MTs and modified lattice equations from invariants of some Lie group actions on manifolds associated with such DLRs. Using this construction, from a given suitable DLR one can obtain many MTs of different orders. The main idea behind this method is closely related to the results of Drinfeld and Sokolov on MTs for the partial differential KdV equation. Considered examples include the Volterra, Narita–Itoh–Bogoyavlensky, Toda, and Adler–Postnikov lattices. Some of the constructed MTs and modified lattice equations seem to be new
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