34 research outputs found

    Polarization phenomena in open charm photoproduction processes

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    We analyze polarization effects in associative photoproduction of pseudoscalar (Dˉ\bar{D}) charmed mesons in exclusive processes γ+N→Yc+Dˉ\gamma+ N\to Y_c +\bar{D}, Yc=Λc+Y_c=\Lambda_c^+, Σc\Sigma_c. Circularly polarized photons induce nonzero polarization of the YcY_c-hyperon with xx- and zz-components (in the reaction plane) and non vanishing asymmetries Ax{\cal A}_x and Az{\cal A}_z for polarized nucleon target. These polarization observables can be predicted in model-independent way for exclusive Dˉ\bar{D}-production processes in collinear kinematics. The T-even YcY_c-polarization and asymmetries for non-collinear kinematics can be calculated in framework of an effective Lagrangian approach. The depolarization coefficients DabD_{ab}, characterizing the dependence of the YcY_c-polarization on the nucleon polarization are also calculated.Comment: 36 pages 13 figure

    Disentangling the response of fishes to recreational fishing over 30 years within a fringing coral reef reserve network

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    Few studies assess the effects of recreational fishing in isolation from commercial fishing. We used meta-analysis to synthesise 4444 samples from 30 years (1987–2017) of fish surveys inside and outside a large network of highly protected reserves in the Ningaloo Marine Park, Western Australia, where the major fishing activity is recreational. Data were collected by different agencies, using varied survey designs and sampling methods. We contrasted the relative abundance and biomass of target and non-target fish groups between fished and reserve locations. We considered the influence of, and possible interactions between, seven additional variables: age and size of reserve, one of two reserve network configurations, reef habitat type, recreational fishing activity, shore-based fishing regulations and survey method. Taxa responded differently: the abundance and biomass inside reserves relative to outside was higher for targeted lethrinids, while other targeted (and non-targeted) fish groups were indistinguishable. Reef habitat was important for explaining lethrinid response to protection, and this factor interacted with reserve size, such that larger reserves were demonstrably more effective in the back reef and lagoon habitats. There was little evidence of changes in relative abundance and biomass of fishes with reserve age, or after rezoning and expansion of the reserve network. Our study demonstrates the complexities in quantifying fishing effects, highlighting some of the key factors and interactions that likely underlie the varied results in reserve assessments that should be considered in future reserve design and assessment

    Bright spots in coastal marine ecosystem restoration

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    The United Nations General Assembly calls for ecosystem restoration to be a primary intervention strategy used to counter the continued loss of natural habitats worldwide, while supporting human health and wellbeing globally. Restoration of coastal marine ecosystems is perceived by many to be expensive and prone to failure, in part explaining its low rates of implementation compared with terrestrial ecosystems. Yet, marine ecosystem restoration is a relatively new field, and we argue that assessments of its potential to answer this call should not rely on typical outcomes, but also to learn from successful outliers. Here, we review successful restoration efforts across a suite of metrics in coastal marine systems to highlight ‘bright spots’. We find that, similar to terrestrial systems, restoration interventions can be effective over large spatial expanses (1,000s–100,000s ha), persist for decades, rapidly expand in size, be cost-effective, and generate social and economic benefits. These bright spots clearly demonstrate restoration of coastal marine systems can be used as a nature-based solution to improve biodiversity and support human health and wellbeing. Examining coastal marine restoration through a historical lens shows that it has developed over a shorter period than restoration in terrestrial systems, partially explaining lower efficiencies. Given these bright spots and the relative immaturity of coastal marine ecosystem restoration, it is likely to advance rapidly over the coming decades and become a common intervention strategy that can reverse marine degradation, contribute to local economies, and improve human wellbeing at a scale relevant to addressing global threats
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