902 research outputs found

    Herbivore performance and plant defense after sequential attacks by inducing and suppressing herbivores

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    It is well known that herbivore‐induced plant defenses alter host plant quality and can affect the behavior and performance of later arriving herbivores. Effects of sequential attacks by herbivores that either suppress or induce plant defenses are less well studied. We sequentially infested leaves of tomato plants with a strain of the phytophagous spider mite Tetranychus urticae that induces plant defenses and the closely related Tetranychus evansi, which suppresses plant defenses. Plant quality was quantified through oviposition of both spider mite species and by measuring proteinase inhibitor activity using plant material that had been sequentially attacked by both herbivore species. Spider‐mite oviposition data show that T. evansi could suppress an earlier induction of plant defenses by T. urticae, and T. urticae could induce defenses in plants previously attacked by T. evansi in 1 day. Longer attacks by the second species did not result in further changes in oviposition. Proteinase inhibitor activity levels showed that T. evansi suppressed the high activity levels induced by T. urticae to constitutive levels in 1 day, and further suppressed activity to levels similar to those in plants attacked by T. evansi alone. Attacks by T. urticae induced proteinase inhibitor activity in plants previously attacked by T. evansi, eventually to similar levels as induced by T. urticae alone. Hence, plant quality and plant defenses were significantly affected by sequential attacks and the order of attack does not affect subsequent performance, but does affect proteinase inhibitor activity levels. Based on our results, we discuss the evolution of suppression of plant defenses

    An efficient multi-objective evolutionary approach for solving the operation of multi-reservoir system scheduling in hydro-power plants

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    This paper tackles the short-term hydro-power unit commitment problem in a multi-reservoir system ? a cascade-based operation scenario. For this, we propose a new mathematical modeling in which the goal is to maximize the total energy production of the hydro-power plant in a sub-daily operation, and, simultaneously, to maximize the total water content (volume) of reservoirs. For solving the problem, we discuss the Multi-objective Evolutionary Swarm Hybridization (MESH) algorithm, a recently proposed multi-objective swarm intelligence-based optimization method which has obtained very competitive results when compared to existing evolutionary algorithms in specific applications. The MESH approach has been applied to find the optimal water discharge and the power produced at the maximum reservoir volume for all possible combinations of turbines in a hydro-power plant. The performance of MESH has been compared with that of well-known evolutionary approaches such as NSGA-II, NSGA-III, SPEA2, and MOEA/D in a realistic problem considering data from a hydro-power energy system with two cascaded hydro-power plants in Brazil. Results indicate that MESH showed a superior performance than alternative multi-objective approaches in terms of efficiency and accuracy, providing a profit of $412,500 per month in a projection analysis carried out.European CommissionMinisterio de Economía y CompetitividadComunidad de Madri

    Head Orientation in CBCT-generated Cephalograms

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    To determine the reliability of obtaining two-dimensional cephalometric measurements using two virtual head orientations from cone-beam computed tomography (CBCT) models

    Benchmark Parameters for CMB Polarization Experiments

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    The recently detected polarization of the cosmic microwave background (CMB) holds the potential for revealing the physics of inflation and gravitationally mapping the large-scale structure of the universe, if so called B-mode signals below 10^{-7}, or tenths of a uK, can be reliably detected. We provide a language for describing systematic effects which distort the observed CMB temperature and polarization fields and so contaminate the B-modes. We identify 7 types of effects, described by 11 distortion fields, and show their association with known instrumental systematics such as common mode and differential gain fluctuations, line cross-coupling, pointing errors, and differential polarized beam effects. Because of aliasing from the small-scale structure in the CMB, even uncorrelated fluctuations in these effects can affect the large-scale B modes relevant to gravitational waves. Many of these problems are greatly reduced by having an instrumental beam that resolves the primary anisotropies (FWHM << 10'). To reach the ultimate goal of an inflationary energy scale of 3 \times 10^{15} GeV, polarization distortion fluctuations must be controlled at the 10^{-2}-10^{-3} level and temperature leakage to the 10^{-4}-10^{-3} level depending on effect. For example pointing errors must be controlled to 1.5'' rms for arcminute scale beams or a percent of the Gaussian beam width for larger beams; low spatial frequency differential gain fluctuations or line cross-coupling must be eliminated at the level of 10^{-4} rms.Comment: 11 pages, 5 figures, submitted to PR

    First record of Eufriesea laniventris (Ducke, 1902) (Hymenoptera, Apidae, Euglossini) in the state of Amazonas, Brazil

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    The first record of Eufriesea laniventris in the state of Amazonas is here reported. Attracted to 1.8 cineole and methyl salicylate fragrances, six specimens were colected in the region of Manaus (2º 36' S 60º 02' W) during the year 2000.", 'enÉ registrada pela primeira vez a ocorrência de Eufriesea laniventris no Amazonas. No ano 2000, foram coletados seis exemplares na região de Manaus (2º 36' S e 60º 02' W) atraídos pelas substâncias odoríferas 1,8 cineol e salicilato de metila

    Tidal Dwarf Galaxies at Intermediate Redshifts

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    We present the first attempt at measuring the production rate of tidal dwarf galaxies (TDGs) and estimating their contribution to the overall dwarf population. Using HST/ACS deep imaging data from GOODS and GEMS surveys in conjunction with photometric redshifts from COMBO-17 survey, we performed a morphological analysis for a sample of merging/interacting galaxies in the Extended Chandra Deep Field South and identified tidal dwarf candidates in the rest-frame optical bands. We estimated a production rate about 1.4 {\times} 10^{-5} per Gyr per comoving volume for long-lived TDGs with stellar mass 3 {\times} 10^{8-9} solar mass at 0.5<z<1.1. Together with galaxy merger rates and TDG survival rate from the literature, our results suggest that only a marginal fraction (less than 10%) of dwarf galaxies in the local universe could be tidally-originated. TDGs in our sample are on average bluer than their host galaxies in the optical. Stellar population modelling of optical to near-infrared spectral energy distributions (SEDs) for two TDGs favors a burst component with age 400/200 Myr and stellar mass 40%/26% of the total, indicating that a young stellar population newly formed in TDGs. This is consistent with the episodic star formation histories found for nearby TDGs.Comment: 9 pages, 5 figures, Accepted for publication in Astrophysics & Space Scienc
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