270 research outputs found

    Repression and recuperation of brood production in Bombus terrestris bumble bees exposed to a pulse of the neonicotinoid pesticide Imidacloprid

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    Currently, there is concern about declining bee populations and some blame the residues of neonicotinoid pesticides in the nectar and pollen of treated crops. Bumble bees are important wild pollinators that are widely exposed to dietary neonicotinoids by foraging in agricultural environments. In the laboratory, we tested the effect of a pulsed exposure (14 days ‘on dose’ followed by 14 days ‘off dose’) to a common neonicotinoid, imidacloprid, on the amount of brood (number of eggs and larvae) produced by Bombus terrestris L. bumble bees in small, standardised experimental colonies (a queen and four adult workers). During the initial ‘on dose’ period we observed a dose-dependent repression of brood production in colonies, with productivity decreasing as dosage increased up to 98 mg kg-1 dietary imidacloprid. During the following ‘off dose’ period, colonies showed a dose-dependent recuperation such that total brood production during the 28-day pulsed exposure was not correlated with imidacloprid up to 98 mg kg-1. Our findings raise further concern about the threat to wild bumble bees from neonicotinoids, but they also indicate some resilience to a pulsed exposure, such as that arising from the transient bloom of a treated mass-flowering crop.Natural Environment Research Council (NERC

    Building a house of C.A.R.D.S.: The practice structures of coaches in a professional rugby union academy

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    This chapter provides insights into the practice structures used by coaches of the Newcastle Falcons Rugby Union academy. It shows how training session activities are organised and adapted to purposefully develop creativity, awareness, resilience, decision-making and self-organisation (C.A.R.D.S.) among players aspiring to compete professionally. The chapter set out to create opportunities for every player in the Newcastle Falcons academy to explore the boundaries of their capabilities and adapt to the changing nature of the game of rugby union by developing C.A.R.D.S. skills. It draws on a range of concepts from dynamical systems theory, representative design, non-linear pedagogy, constraints-led coaching and games-based approaches. Making frequent amendments to the constraints of training activities is itself a form of adversity, as players need to remain aware and quickly adapt to respond to the new challenges posed. Self-organised players will have ‘the skill to use information to effectively coordinate themselves’

    The GALEX View of "Boyajian's Star" (KIC 8462852)

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    The enigmatic star KIC 8462852, informally known as "Boyajian's Star", has exhibited unexplained variability from both short timescale (days) dimming events, and years-long fading in the Kepler mission. No single physical mechanism has successfully explained these observations to date. Here we investigate the ultraviolet variability of KIC 8462852 on a range of timescales using data from the GALEX mission that occurred contemporaneously with the Kepler mission. The wide wavelength baseline between the Kepler and GALEX data provides a unique constraint on the nature of the variability. Using 1600 seconds of photon-counting data from four GALEX visits spread over 70 days in 2011, we find no coherent NUV variability in the system on 10-100 second or months timescales. Comparing the integrated flux from these 2011 visits to the 2012 NUV flux published in the GALEX-CAUSE Kepler survey, we find a 3% decrease in brightness for KIC 8462852. We find this level of variability is significant, but not necessarily unusual for stars of similar spectral type in the GALEX data. This decrease coincides with the secular optical fading reported by Montet & Simon (2016). We find the multi-wavelength variability is somewhat inconsistent with typical interstellar dust absorption, but instead favors a RV_V = 5.0 ±\pm 0.9 reddening law potentially from circumstellar dust.Comment: 8 pages, 4 figures, ApJ Accepte

    On the Spin of the Black Hole in IC 10 X-1

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    The compact X-ray source in the eclipsing X-ray binary IC 10 X–1 has reigned for years as ostensibly the most massive stellar-mass black hole, with a mass estimated to be about twice that of its closest rival. However, striking results presented recently by Laycock et al. reveal that the mass estimate, based on emission-line velocities, is unreliable and that the mass of the X-ray source is essentially unconstrained. Using Chandra and NuSTAR data, we rule against a neutron-star model and conclude that IC 10 X–1 contains a black hole. The eclipse duration of IC 10 X–1 is shorter and its depth shallower at higher energies, an effect consistent with the X-ray emission being obscured during eclipse by a Compton-thick core of a dense wind. The spectrum is strongly disk-dominated, which allows us to constrain the spin of the black hole via X-ray continuum fitting. Three other wind-fed black hole systems are known; the masses and spins of their black holes are high: M ~ 10 - 15M_☉ and ɑ_* > 0.8. If the mass of IC 10 X-1's black hole is comparable, then its spin is likewise high

    Effects of the neonicotinoid pesticide thiamethoxam at field-realistic levels on microcolonies of Bombus terrestris worker bumble bees

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    Copyright © 2013 Elsevier. Notice: this is the author’s version of a work that was accepted for publication in Ecotoxicology and Environmental Safety. Changes resulting from the publishing process, such as peer review, editing, corrections, structural formatting, and other quality control mechanisms may not be reflected in this document. Changes may have been made to this work since it was submitted for publication. A definitive version was subsequently published in Ecotoxicology and Environmental Safety, 2014, Vol. 100, pp. 153-158 at: http://dx.doi.org/10.1016/j.ecoenv.2013.10.027Neonicotinoid pesticides are currently implicated in the decline of wild bee populations. Bumble bees, Bombus spp., are important wild pollinators that are detrimentally affected by ingestion of neonicotinoid residues. To date, imidacloprid has been the major focus of study into the effects of neonicotinoids on bumble bee health, but wild populations are increasingly exposed to alternative neonicotinoids such as thiamethoxam. To investigate whether environmentally realistic levels of thiamethoxam affect bumble bee performance over a realistic exposure period, we exposed queenless microcolonies of Bombus terrestris L. workers to a wide range of dosages up to 98 μg kg−1 in dietary syrup for 17 days. Results showed that bumble bee workers survived fewer days when presented with syrup dosed at 98 μg thiamethoxam kg−1, while production of brood (eggs and larvae) and consumption of syrup and pollen in microcolonies were significantly reduced by thiamethoxam only at the two highest concentrations (39, 98 μg kg−1). In contrast, we found no detectable effect of thiamethoxam at levels typically found in the nectars of treated crops (between 1 and 11 μg kg−1). By comparison with published data, we demonstrate that during an exposure to field-realistic concentrations lasting approximately two weeks, brood production in worker bumble bees is more sensitive to imidacloprid than thiamethoxam. We speculate that differential sensitivity arises because imidacloprid produces a stronger repression of feeding in bumble bees than thiamethoxam, which imposes a greater nutrient limitation on production of brood.Natural Environment Research Council (NERC
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