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Peters W.,Wageningen University | Peters W.,University of Colorado at Boulder | Krol M.C.,Wageningen University | van der Werf G.R.,VU University Amsterdam | And 41 more authors.
Global Change Biology | Year: 2010

We present an estimate of net ecosystem exchange (NEE) of CO2 in Europe for the years 2001-2007. It is derived with a data assimilation that uses a large set of atmospheric CO2 mole fraction observations (∼70 000) to guide relatively simple descriptions of terrestrial and oceanic net exchange, while fossil fuel and fire emissions are prescribed. Weekly terrestrial sources and sinks are optimized (i.e., a flux inversion) for a set of 18 large ecosystems across Europe in which prescribed climate, weather, and surface characteristics introduce finer scale gradients. We find that the terrestrial biosphere in Europe absorbed a net average of -165 Tg C yr-1 over the period considered. This uptake is predominantly in non-EU countries, and is found in the northern coniferous (-94 Tg C yr-1) and mixed forests (-30 Tg C yr-1) as well as the forest/field complexes of eastern Europe (-85 Tg C yr-1). An optimistic uncertainty estimate derived using three biosphere models suggests the uptake to be in a range of -122 to -258 Tg C yr-1, while a more conservative estimate derived from the a-posteriori covariance estimates is -165±437 Tg C yr-1. Note, however, that uncertainties are hard to estimate given the nature of the system and are likely to be significantly larger than this. Interannual variability in NEE includes a reduction in uptake due to the 2003 drought followed by 3 years of more than average uptake. The largest anomaly of NEE occurred in 2005 concurrent with increased seasonal cycles of observed CO2. We speculate these changes to result from the strong negative phase of the North Atlantic Oscillation in 2005 that lead to favorable summer growth conditions, and altered horizontal and vertical mixing in the atmosphere. All our results are available through http://www.carbontracker.eu. © 2009 Blackwell Publishing Ltd.


Grant
Agency: Cordis | Branch: FP7 | Program: 0 | Phase: 0 | Award Amount: 4.66M | Year: 2008

ITER is the next generation of fusion devices and is intended to demonstrate the scientific and technical feasibility of fusion as a sustainable energy source for the future. To exploit the full potential of the device and to guarantee optimal operation for the device a high degree of physics modelling and simulation is needed already in the current construction phase of the ITER project. First principles modelling tools that are needed for an adequate description of the underlying physics cover both a wide range of timescales and spatial orderings and are in general very demanding from a computational point of view. Current modelling activities relies on local or national computational resources and an improved access to computing infrastructures will be instrumental in advancing a pan-European modelling activity for ITER to a very competitive status in relation to the ITER partners. The EUFORIA project will provide a comprehensive framework and infrastructure for core and edge transport and turbulence simulation, linking grid and High Performance Computing (HPC), to the fusion modelling community. The project will enhance the modelling capabilities for ITER and DEMO sized plasmas through the adaptation, optimization and integration of a set of critical applications for edge and core transport modelling targeting different computing paradigms as needed (serial and parallel grid computing and HPC). Deployment of both a grid service and a High Performance computing services are essential to the project. A novel aspect is the dynamic coupling and integration of codes and applications running on a set of heterogeneous platforms into a single coupled framework through a workflow engine a mechanism needed to provide the necessary level integration in the physics applications. This strongly enhances the integrated modelling capabilities of fusion plasmas and will at the same time provide new computing infrastructure and tools to the fusion community in general.


Presciuttini S.,University of Pisa | Valbonesi A.,University of Camerino | Apaza N.,INIA | Antonini M.,INIA | And 2 more authors.
BMC Genetics | Year: 2010

Background: Genetic improvement of fibre-producing animal species has often induced transition from double coated to single coated fleece, accompanied by dramatic changes in skin follicles and hair composition, likely implying variation at multiple loci. Huacaya, the more common fleece phenotype in alpaca (Vicugna pacos), is characterized by a thick dense coat growing perpendicularly from the body, whereas the alternative rare and more prized single-coated Suri phenotype is distinguished by long silky fibre that grows parallel to the body and hangs in separate, distinctive pencil locks. A single-locus genetic model has been proposed for the Suri-Huacaya phenotype, where Huacaya is recessive.Results: Two reciprocal experimental test-crosses (Suri × Huacaya) were carried out, involving a total of 17 unrelated males and 149 unrelated females. An additional dataset of 587 offspring of Suri × Suri crosses was analyzed. Segregation ratios, population genotype frequencies, and/or recombination fraction under different genetic models were estimated by maximum likelihood. The single locus model for the Suri/Huacaya phenotype was rejected. In addition, we present two unexpected observations: 1) a large proportion (about 3/4) of the Suri animals are segregating (with at least one Huacaya offspring), even in breeding conditions where the Huacaya trait would have been almost eliminated; 2) a model with two different values of the segregation ratio fit the data significantly better than a model with a single parameter.Conclusions: The data support a genetic model in which two linked loci must simultaneously be homozygous for recessive alleles in order to produce the Huacaya phenotype. The estimated recombination rate between these loci was 0.099 (95% C.L. = 0.029-0.204). Our genetic analysis may be useful for other species whose breeding system produces mainly half-sib families. © 2010 Presciuttini et al; licensee BioMed Central Ltd.


Marinelli A.,University of California at Los Angeles | Marinelli A.,University of Rome La Sapienza | Marinelli A.,National Institute of Nuclear Physics, Italy | Pellegrini C.,University of California at Los Angeles | And 2 more authors.
Physical Review Special Topics - Accelerators and Beams | Year: 2010

In this paper we investigate and compare the properties of two narrow-bandwidth free-electron laser (FEL) schemes, one using self-seeding and the other high gain harmonic generation (HGHG). The two systems have been thoroughly studied analytically and numerically in the past. The aim of this work is to compare their performances when the FEL is driven by an electron beam with nonideal properties, thus including effects such as shot-to-shot energy fluctuations and nonlinear energy chirp. In both cases nonlinearities produce a bandwidth larger than the Fourier transform limited value. However, our analysis indicates that, for approximately the same output power levels, the self-seeding scheme is less affected than the HGHG scheme by quadratic energy chirps in the electron beam longitudinal phase space. This is confirmed by a specific numerical example corresponding to SPARX parameters where the electron beam was optimized to minimize the FEL gain length. The work has been carried out with the aid of the time dependent FEL codes GENESIS 1.3 (3D) and PERSEO (1D). © 2010 The American Physical Society.


Toth B.,European Commission | Bieliauskas A.,European Commission | Bandini G.,Ente per le Nuove Tecnologie | Birchley J.,Paul Scherrer Institute | And 4 more authors.
Nuclear Technology | Year: 2010

This paper presents the results of posttest calculations of thephebus FPT2 experiment. While the exercise concentrates mainly on code-to-code benchmarking, a comparison is also made with selected experimental results. The test scenario with the appropriate initial and boundary conditions was provided by the Institut de Radioprotection et de SÛreté Nucléaire. For the analyses, seven severe accident analysis codes were used: ASTEC, ATHLET-CD, MELCOR, ICARE2, ICARE/CATHARE, SCDAP/RELAP5, and RELAP/SCDAPSIM. The calculations focused on the following phenomena occurring in the FPT2 bundle: thermal behavior; hydrogen production, mainly due to cladding oxidation; severe degradation of irradiated fuel; and the release of fission products, control rod, and structure materials. Using the same postdefined boundary and initial conditions, the code-data differences are typically within 10% for most parameters, and not more than 25%. More importantly, the codes were able to capture the major features of the transient evolution. Given that Phebus FPT2 exhibited almost all of the major low-pressure severe accident phenomena except for core cooling by water injection and late-phase core melt behavior in the lower head, the results engender a degree of confidence in the code predictive capability for sequences similar toFPT2.

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