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- Puckett, A. J. R., et al.
(author)
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Final analysis of proton form factor ratio data at Q(2)=4.0, 4.8, and 5.6 GeV2
- 2012
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In: Physical Review C (Nuclear Physics). - 0556-2813. ; 85:4
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Journal article (peer-reviewed)abstract
- Precise measurements of the proton electromagnetic form factor ratio R = mu(p)G(E)(p)/G(M)(p) using the polarization transfer method at Jefferson Lab have revolutionized the understanding of nucleon structure by revealing the strong decrease of R with momentum transfer Q(2) for Q(2) greater than or similar to 1 GeV2, in strong disagreement with previous extractions of R from cross-section measurements. In particular, the polarization transfer results have exposed the limits of applicability of the one-photon-exchange approximation and highlighted the role of quark orbital angular momentum in the nucleon structure. The GEp-II experiment in Jefferson Lab's Hall A measured R at four Q(2) values in the range 3.5 GeV2 <= Q(2) <= 5.6 GeV2. A possible discrepancy between the originally published GEp-II results and more recent measurements at higher Q(2) motivated a new analysis of the GEp-II data. This article presents the final results of the GEp-II experiment, including details of the new analysis, an expanded description of the apparatus, and an overview of theoretical progress since the original publication. The key result of the final analysis is a systematic increase in the results for R, improving the consistency of the polarization transfer data in the high-Q(2) region. This increase is the result of an improved selection of elastic events which largely removes the systematic effect of the inelastic contamination, underestimated by the original analysis.
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| 3. |
- Meier, H. E. M., et al.
(author)
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modeling the combined impact of changing climate and changing nutrient loads on the baltic sea environment in an ensemble of transient simulations for 1961 2099
- 2012
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In: Climate Dynamics. - : Springer Science and Business Media LLC. - 0930-7575 .- 1432-0894. ; 39:9-10, s. 2421-2441
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Journal article (peer-reviewed)abstract
- The combined future impacts of climate change and industrial and agricultural practices in the Baltic Sea catchment on the Baltic Sea ecosystem were assessed. For this purpose 16 transient simulations for 1961-2099 using a coupled physical-biogeochemical model of the Baltic Sea were performed. Four climate scenarios were combined with four nutrient load scenarios ranging from a pessimistic business-as-usual to a more optimistic case following the Baltic Sea Action Plan (BSAP). Annual and seasonal mean changes of climate parameters and ecological quality indicators describing the environmental status of the Baltic Sea like bottom oxygen, nutrient and phytoplankton concentrations and Secchi depths were studied. Assuming present-day nutrient concentrations in the rivers, nutrient loads from land increase during the twenty first century in all investigated scenario simulations due to increased volume flows caused by increased net precipitation in the Baltic catchment area. In addition, remineralization rates increase due to increased water temperatures causing enhanced nutrient flows from the sediments. Cause-and-effect studies suggest that both processes may play an important role for the biogeochemistry of eutrophicated seas in future climate partly counteracting nutrient load reduction efforts like the BSAP.
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| 4. |
- Meier, H.E.M., et al.
(author)
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Transient scenario simulations for the Baltic Sea Region during the 21st century
- 2011
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Reports (peer-reviewed)abstract
- The combined future impacts of climate change and industrial and agricultural practices in the Baltic Sea catchment on the Baltic Sea ecosystem were assessed. For this purpose 16 transient simulations for 1961-2099 using a coupled physical-biogeochemical model of the Baltic Sea have been performed. Four climate scenarios were combined with four nutrient load scenarios ranging from a pessimistic business-as-usual to a more optimistic case following the Baltic Sea Action Plan (BSAP). In this study we focussed on annual and seasonal mean changes of ecological quality indicators describing the environmental status of the Baltic Sea. In correspondence with earlier studies we found that the impact of changing climate on the Baltic biogeo-chemistry might be signi cant. Assuming reference loadings the water quality in all climate scenarios is reduced at the end of the century. The impact of nutrient load reductions according to the BSAP will be less e ective in future climate compared to present climate.However, the results of the pessimistic business-as-usual scenario suggest that policy makers should act to avoid much worse environ-mental conditions than today.
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