468 research outputs found

    Inferential tests and modelling of functional trait convergence along environmental gradients

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    The motivation for this paper comes from a recent study which indicated that the influence of environmental filtering should increase with decreasing soil fertility, based on the premise that individuals will employ a resource-retentive strategy in a less productive ecosystem. Mean annual temperature (MAT) is one indicator of the productivity of the ecosystem. We aim to build a more accurate model of environmental filter and want to statistically test whether the environmental filter is stronger when the MAT is lower compared to when it is higher. Our findings throw an interesting insight into how the trait variability changes as a function of MAT and how it could be better modelled

    The effect of uniaxial orientation upon the structural properties of polvaniline films

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    The effects of elongation upon the structural and electronic properties of the conducting polymer polyaniline have been investigated. In particular, the properties of high molecular weight (ca. 150 000 Daltons) polyaniline have been examined, and the effects of increased molecular weight assessed. A method has been found to elongate the emeraldine base (EB) form up to 700% (l/l(_o)=8). This induces partial molecular alignment in the polymer which, upon doping, exhibits electrical conductivity of up to 700 Scm(_-1) and electrical anisotropy of almost 4.The mechanical properties of high molecular weight emeraldine base have been investigated as a function of elongation. The breaking stress has been observed to increase by almost one order of magnitude for a 500% elongated film compared with its unoriented counterpart. The breaking strain is found to decrease initially with increasing elongation, though no noticeable change is evident for samples elongated to more than 300%. Similarly, Young's modulus increases by a factor of 2 with increased elongation, but above 300% remains approximately constant. The behaviour has been interpreted in terms of the crystalline fraction of the samples. X-ray diffraction experiments have enabled the crystalline fraction of emeraldine base and emeraldine salt (ES) to be assessed. 300% elongated EB samples exhibit increased crystalhnity compared with as-cast samples. However, no further increase in crystallmity is evident for 600% elongated samples. Unoriented ES samples have a crystalline fraction of approximately 0.3. The crystallinity of 300% and 600% elongated ES samples is slightly less than for unoriented ES. The polarised reflectance spectra of EB and ES have been measured in the region 0.5- 5.6 eV. The results show increased optical anisotropy with increasing elongation for EB samples, but no change in anisotropy for ES samples above 300% elongation. A Kramers-Kronig analysis of the reflectance data reveals near metallic behaviour parallel to the dkection of elongation, and a high degree of localisation perpendicular to this direction

    Systemic: A Testbed For Characterizing the Detection of Extrasolar Planets. I. The Systemic Console Package

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    We present the systemic Console, a new all-in-one, general-purpose software package for the analysis and combined multiparameter fitting of Doppler radial velocity (RV) and transit timing observations. We give an overview of the computational algorithms implemented in the Console, and describe the tools offered for streamlining the characterization of planetary systems. We illustrate the capabilities of the package by analyzing an updated radial velocity data set for the HD128311 planetary system. HD128311 harbors a pair of planets that appear to be participating in a 2:1 mean motion resonance. We show that the dynamical configuration cannot be fully determined from the current data. We find that if a planetary system like HD128311 is found to undergo transits, then self-consistent Newtonian fits to combined radial velocity data and a small number of timing measurements of transit midpoints can provide an immediate and vastly improved characterization of the planet's dynamical state.Comment: 10 pages, 5 figures, accepted for publication on PASP. Additional material at http://www.ucolick.org/~smeschia/systemic.ph

    Aferword: Law, Literature and Ethics

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    Symposium - The Law and Southern Literatur

    Fact sheet: Assessing restoration objectives following a second-entry prescribed fire in an unharvested mixed conifer forest

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    Efforts to restore degraded forest ecosystems often involve thinning small-diameter trees and reintroducing surface fire; however, in some areas, such as national parks, mechanical tree thinning is kept to a minimum. In these situations, prescribed fire is the best tool available to restore historical fire regimes and forest structure over broad spatial scales

    The Lick-Carnegie Exoplanet Survey: A Saturn-Mass Planet in the Habitable Zone of the Nearby M4V Star HIP 57050

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    Precision radial velocities from Keck/HIRES reveal a Saturn-mass planet orbiting the nearby M4V star HIP 57050. The planet has a minimum mass of 0.3 Jupiter-mass, an orbital period of 41.4 days, and an orbital eccentricity of 0.31. V-band photometry reveals a clear stellar rotation signature of the host star with a period of 98 days, well separated from the period of the radial velocity variations and reinforcing a Keplerian origin for the observed velocity variations. The orbital period of this planet corresponds to an orbit in the habitable zone of HIP 57050, with an expected planetary temperature of approximately 230 K. The star has a metallicity of [Fe/H] = 0.32+/-0.06 dex, of order twice solar and among the highest metallicity stars in the immediate solar neighborhood. This newly discovered planet provides further support that the well-known planet-metallicity correlation for F, G, and K stars also extends down into the M-dwarf regime. The a priori geometric probability for transits of this planet is only about 1%. However, the expected eclipse depth is ~7%, considerably larger than that yet observed for any transiting planet. Though long on the odds, such a transit is worth pursuing as it would allow for high quality studies of the atmosphere via transmission spectroscopy with HST. At the expected planetary effective temperature, the atmosphere may contain water clouds.Comment: 20 pages, 5 figures, 3 tables, to appear in the May 20 issue of ApJ

    A determination of the spin-orbit alignment of the anomalously dense planet orbiting HD 149026

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    We report 35 radial velocity measurements of HD 149026 taken with the Keck Telescope. Of these measurements, 15 were made during the transit of the companion planet HD 149026b, which occurred on 2005 June 25. These velocities provide a high-cadence observation of the Rossiter-McLaughlin effect, the shifting of photospheric line profiles that occurs when a planet occults a portion of the rotating stellar surface. We combine these radial velocities with previously published radial velocity and photometric data sets and derive a composite best-fit model for the star-planet system. This model confirms and improves previously published orbital parameters, including the remarkably small planetary radius, the planetary mass, and the orbital inclination, found to be Rp/RJup = 0.718 ± 0.065, Mp/MJup = 0.352 ± 0.025, and I = 86.1° ± 1.4°, respectively. Together the planetary mass and radius determinations imply a mean planetary density of 1.18(-0.30)(+0.38)g cm(-3). The new data also allow for the determination of the angle between the apparent stellar equator and the orbital plane, which we constrain to be λ = -12° ± 15°
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