41 research outputs found

    Perceptions of emotional abuse in the coach-athlete relationship in youth sport: The influence of competitive level and outcome

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    Emotional abuse has been highlighted as a key issue within the youth sport context. The present study investigated how perceptions of emotional abuse are influenced by situational factors. Two hundred and eight participants (107 athletes and 101 coaches) were shown a series of vignettes depicting emotionally abusive behaviour by a coach towards a 14 year old athlete. Differences in perceptions were explored in relation to the level of competition (elite, county and club) and performance outcome (successful/unsuccessful) depicted in the vignette. Participants rated each vignette on a 5 point scale in terms of the extent to which the coach’s behaviour had an impact on the athlete’s performance and wellbeing as well as the perceived commonality and acceptability of the behaviour. Two-way ANOVAs revealed that competitive level and performance outcome, both as main effects and as an interaction, significantly influenced perceptions. These findings can inform policy and practice to change attitudes and behaviours which support and justify emotionally abusive behaviours in youth sport contexts

    π+\pi^+ photoproduction on the proton for photon energies from 0.725 to 2.875 GeV

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    Differential cross sections for the reaction γpnπ+\gamma p \to n \pi^+ have been measured with the CEBAF Large Acceptance Spectrometer (CLAS) and a tagged photon beam with energies from 0.725 to 2.875 GeV. Where available, the results obtained here compare well with previously published results for the reaction. Agreement with the SAID and MAID analyses is found below 1 GeV. The present set of cross sections has been incorporated into the SAID database, and exploratory fits have been made up to 2.7 GeV. Resonance couplings have been extracted and compared to previous determinations. With the addition of these cross sections to the world data set, significant changes have occurred in the high-energy behavior of the SAID cross-section predictions and amplitudes.Comment: 18 pages, 10 figure

    Exclusive ρ0\rho^0 electroproduction on the proton at CLAS

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    The epepρ0e p\to e^\prime p \rho^0 reaction has been measured, using the 5.754 GeV electron beam of Jefferson Lab and the CLAS detector. This represents the largest ever set of data for this reaction in the valence region. Integrated and differential cross sections are presented. The WW, Q2Q^2 and tt dependences of the cross section are compared to theoretical calculations based on tt-channel meson-exchange Regge theory on the one hand and on quark handbag diagrams related to Generalized Parton Distributions (GPDs) on the other hand. The Regge approach can describe at the \approx 30% level most of the features of the present data while the two GPD calculations that are presented in this article which succesfully reproduce the high energy data strongly underestimate the present data. The question is then raised whether this discrepancy originates from an incomplete or inexact way of modelling the GPDs or the associated hard scattering amplitude or whether the GPD formalism is simply inapplicable in this region due to higher-twists contributions, incalculable at present.Comment: 29 pages, 29 figure

    A measurement of the differential cross section for the reaction γnπp\gamma n \to \pi^{-} p from deuterium

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    We report a measurement of the differential cross section for the γnπp\gamma n \to \pi^- p process from the CLAS detector at Jefferson Lab in Hall B for photon energies between 1.0 and 3.5 GeV and pion center-of-mass (c.m.) angles (θc.m.\theta_{c.m.}) between 50^\circ and 115^\circ. We confirm a previous indication of a broad enhancement around a c.m. energy (s\sqrt{s}) of 2.2 GeV at θc.m.=90\theta_{c.m.}=90^\circ in the scaled differential cross section, s7dσdts^7 {\frac{d\sigma}{dt}}. Our data show the angular dependence of this enhancement as the scaling region is approached in the kinematic region from 70^\circ to 105^\circ.Comment: 6 pages, 3 figures. submitted to PR

    The extraction of ϕN\phi-N total cross section from d(γ,pK+K)nd(\gamma,pK^{+}K^{-})n

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    We report on the first measurement of the differential cross section of ϕ\phi-meson photoproduction for the d(γ,pK+K)nd(\gamma,pK^{+}K^{-})n exclusive reaction channel. The experiment was performed using a \textcolor{black}{tagged-photon} beam and the CEBAF Large Acceptance Spectrometer (CLAS) at Jefferson Lab. A combined analysis using data from the d(γ,pK+K)nd(\gamma,pK^{+}K^{-})n channel and those from a previous publication on coherent ϕ\phi production on the deuteron has been carried out to extract the ϕN\phi-N total cross section, σϕN\sigma_{\phi N}. The extracted ϕN\phi-N total cross section favors a value above 20 mb. This value is larger than the value extracted using vector-meson dominance models for ϕ\phi photoproduction on the proton.Comment: 7 pages 4 figure

    First measurement of target and double spin asymmetries for polarized e- polarized p --> e p pi0 in the nucleon resonance region above the Delta(1232)

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    The exclusive channel polarized proton(polarized e,e prime p)pi0 was studied in the first and second nucleon resonance regions in the Q2 range from 0.187 to 0.770 GeV2 at Jefferson Lab using the CEBAF Large Acceptance Spectrometer (CLAS). Longitudinal target and beam-target asymmetries were extracted over a large range of center-of-mass angles of the pi0 and compared to the unitary isobar model MAID, the dynamic model by Sato and Lee, and the dynamic model DMT. A strong sensitivity to individual models was observed, in particular for the target asymmetry and in the higher invariant mass region. This data set, once included in the global fits of the above models, is expected to place strong constraints on the electrocoupling amplitudes A_{1/2} and S_{1/2} for the Roper resonance N(1400)P11, and the N(1535)S11 and N(1520)D13 states.Comment: 13 pages, 13 figure

    Genetic correlations between temperature-induced plasticity of life-history traits in a soil arthropod.

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    Temperature is considered one of the most important mediators of phenotypic plasticity in ectotherms. However, the costs and benefits shaping the evolution of different thermal responses are poorly elucidated. One of the possible constraints to phenotypic plasticity is its intrinsic genetic cost, such as genetic linkage or pleiotropy. Genetic coupling of the thermal response curves for different life history traits may significantly affect the evolution of thermal sensitivity in thermally fluctuating environments. We used the collembolan Orchesella cincta to study if there is genetic variation in temperature-induced phenotypic plasticity in life history traits, and if the degree of temperature-induced plasticity is correlated across traits. Egg development rate, juvenile growth rate and egg size of 19 inbred isofemale lines were measured at two temperatures. Our results show that temperature was a highly significant factor for all three traits. Egg development rate and juvenile growth rate increased with increasing temperature, while egg size decreased. Line by temperature interaction was significant for all traits tested; indicating that genetic variation for temperature-induced plasticity existed. The degree of plasticity was significantly positively correlated between egg development rate and growth rate, but plasticity in egg size was not correlated to the other two plasticity traits. The findings suggest that the thermal plasticities of egg development rate and growth rate are partly under the control of the same genes or genetic regions. Hence, evolution of the thermal plasticity of traits cannot be understood in isolation of the response of other traits. If traits have similar and additive effects on fitness, genetic coupling between these traits may well facilitate the evolution of optimal phenotypes. However, for this we need to know the selective forces under field conditions. © 2010 Springer Science+Business Media B.V

    Adaptive responses of animals to climate change are most likely insufficient

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    Biological responses to climate change have been widely documented across taxa and regions, but it remains unclear whether species are maintaining a good match between phenotype and environment, i.e. whether observed trait changes are adaptive. Here we reviewed 10,090 abstracts and extracted data from 71 studies reported in 58 relevant publications, to assess quantitatively whether phenotypic trait changes associated with climate change are adaptive in animals. A meta-analysis focussing on birds, the taxon best represented in our dataset, suggests that global warming has not systematically affected morphological traits, but has advanced phenological traits. We demonstrate that these advances are adaptive for some species, but imperfect as evidenced by the observed consistent selection for earlier timing. Application of a theoretical model indicates that the evolutionary load imposed by incomplete adaptive responses to ongoing climate change may already be threatening the persistence of species
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