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- Burkhardt, J., et al.
(författare)
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Modelling the dynamic chemical interactions of atmospheric ammonia with leaf surface wetness in a managed grassland canopy
- 2009
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Ingår i: Biogeosciences. - Göttingen : Copernicus Publications. - 1726-4170 .- 1726-4189. ; 6:1, s. 67-84
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Tidskriftsartikel (refereegranskat)abstract
- Ammonia exchange fluxes between grassland and the atmosphere were modelled on the basis of stomatal compensation points and leaf surface chemistry, and compared with measured fluxes during the GRAMINAE intensive measurement campaign in spring 2000 near Braunschweig, Germany. Leaf wetness and dew chemistry in grassland were measured together with ammonia fluxes and apoplastic NH4+ and H+ concentration, and the data were used to apply, validate and further develop an existing model of leaf surface chemistry and ammonia exchange. Foliar leaf wetness which is known to affect ammonia fluxes may be persistent after the end of rainfall, or sustained by recondensation of water vapour originating from the ground or leaf transpiration, so measured leaf wetness values were included in the model. pH and ammonium concentrations of dew samples collected from grass were compared to modelled values.The measurement period was divided into three phases: a relatively wet phase followed by a dry phase in the first week before the grass was cut, and a second drier week after the cut. While the first two phases were mainly characterised by ammonia deposition and occasional short emission events, regular events of strong ammonia emissions were observed during the post-cut period. A single-layer resistance model including dynamic cuticular and stomatal exchange could describe the fluxes well before the cut, but after the cut the stomatal compensation points needed to numerically match measured fluxes were much higher than the ones measured by bioassays, suggesting another source of ammonia fluxes. Considerably better agreement both in the direction and the size range of fluxes were obtained when a second layer was introduced into the model, to account for the large additional ammonia source inherent in the leaf litter at the bottom of the grass canopy. Therefore, this was found to be a useful extension of the mechanistic dynamic chemistry model by keeping the advantage of requiring relatively little site-specific information.
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- Knot, J, et al.
(författare)
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How to set up an effective national primary angioplasty network : Lessons learned from five European countries
- 2009
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Ingår i: EuroIntervention. - 1774-024X. ; 3:299, s. 301-309
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Tidskriftsartikel (refereegranskat)abstract
- AIMS: Percutaneous coronary interventions (PCI) are used to treat acute and chronic forms of coronary artery disease. While in chronic forms the main goal of PCI is to improve the quality of life, in acute coronary syndromes (ACS) timely PCI is a life-saving procedure - especially in the setting of ST-elevation myocardial infarction (STEMI). The aim of this study was to describe the experience of countries with successful nationwide implementation of PCI in STEMI, and to provide general recommendations for other countries. METHODS AND RESULTS: The European Association of Percutaneous Cardiovascular Interventions (EAPCI) recenty launched the Stent For Life Initiative (SFLI). The initial phase of this pan-European project was focused on the positive experience of five countries to provide the best practice examples. The Netherlands, the Czech Republic, Sweden, Denmark and Austria were visited and the logistics of ACS treatment was studied. Public campaigns improved patient access to acute PCI. Regional networks involving emergency medical services (EMS), non-PCI hospitals and PCI centres are useful in providing access to acute PCI for most patients. Direct transfer from the first medical contact site to the cathlab is essential to minimise the time delays. Cathlab staff work is organised to provide acute PCI services 24 hours a day / seven days a week (24/7). Even in those regions where thrombolysis is still used due to long transfer distances to PCI, patients should still be transferred to a PCI centre (after thrombolysis). The highest risk non-ST elevation acute myocardial infarction patients should undergo emergency coronary angiography within two hours of hospital admission, i.e. similar to STEMI patients. CONCLUSIONS: Three realistic goals for other countries were defined based on these experiences: 1) primary PCI should be used for >70% of all STEMI patients, 2) primary PCI rates should reach >600 per million inhabitants per year and 3) existing PCI centres should treat all their STEMI patients by primary PCI, i.e. should offer a 24/7 service
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- Sutton, M. A., et al.
(författare)
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Dynamics of ammonia exchange with cut grassland : Strategy and implementation of the GRAMINAE Integrated Experiment
- 2009
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Ingår i: Biogeosciences. - : Copernicus Publications (on behalf of the European Geosciences Union). - 1726-4170 .- 1726-4189. ; 6:3, s. 309-331
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Tidskriftsartikel (refereegranskat)abstract
- A major international experiment on ammonia (NH3) biosphere-atmosphere exchange was conducted over intensively managed grassland at Braunschweig, Germany. The experimental strategy was developed to allow an integrated analysis of different features of NH3 exchange including: a) quantification of nearby emissions and advection effects, b) estimation of net NH3 fluxes with the canopy by a range of micrometeorological measurements, c) analysis of the sources and sinks of NH3 within the plant canopy, including soils and bioassay measurements, d) comparison of the effects of grassland management options on NH3 fluxes and e) assessment of the interactions of NH3 fluxes with aerosol exchange processes. Additional technical objectives included the inter-comparison of different estimates of sensible and latent heat fluxes, as well as continuous-gradient and Relaxed Eddy Accumulation (REA) systems for NH3 fluxes. The prior analysis established the spatial and temporal design of the experiment, allowing significant synergy between these objectives. The measurements were made at 7 measurement locations, thereby quantifying horizontal and vertical profiles, and covered three phases: a) tall grass canopy prior to cutting (7 days), b) short grass after cutting (7 days) and c) re-growing sward following fertilization with ammonium nitrate (10 days). The sequential management treatments allowed comparison of sources-sinks, advection and aerosol interactions under a wide range of NH3 fluxes. This paper describes the experimental strategy and reports the grassland management history, soils, environmental conditions and air chemistry during the experiment, finally summarizing how the results are coordinated in the accompanying series of papers.
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