An optimal non-linear method for simulating relic neutrinos

Cosmology places the strongest current limits on the sum of neutrino masses. Future observations will further improve the sensitivity and this will require accurate cosmological simulations to quantify possible systematic uncertainties and to make predictions for non-linear scales, where much information resides. However, shot noise arising from neutrino thermal motions limits the accuracy of simulations. In this paper, we introduce a new method for simulating large-scale structure formation with neutrinos that accurately resolves the neutrinos down to small scales and significantly reduces the shot noise. The method works by tracking perturbations to the neutrino phase-space distribution with particles and reduces shot noise in the power spectrum by a factor of O (102) at z = 0 for minimal neutrino masses and significantly more at higher redshifts, without neglecting the back-reaction caused by neutrino clustering. We prove that the method is part of a family of optimal methods that minimize shot noise subject to a maximum deviation from the non-linear solution. Compared to other methods, we find per mille level agreement in the matter power spectrum and per cent level agreement in the large-scale neutrino bias, but large differences in the neutrino component on small scales. A basic version of the method can easily be implemented in existing N-body codes and allows neutrino simulations with significantly reduced particle load. Further gains are possible by constructing background models based on perturbation theory. A major advantage of this technique is that it works well for all masses, enabling a consistent exploration of the full neutrino parameter space

Financial Evaluation of Different Vaccination Strategies for Controlling the Bluetongue Virus Serotype 8 Epidemic in the Netherlands in 2008

Background: Bluetongue (BT) is a vector-borne disease of ruminants caused by bluetongue virus that is transmitted by biting midges (Culicoides spp.). In 2006, the introduction of BTV serotype 8 (BTV-8) caused a severe epidemic in Western and Central Europe. The principal effective veterinary measure in response to BT was believed to be vaccination accompanied by other measures such as movement restrictions and surveillance. As the number of vaccine doses available at the start of the vaccination campaign was rather uncertain, the Dutch Ministry of Agriculture, Nature and Food Quality and the Dutch agricultural industry wanted to evaluate several different vaccination strategies. This study aimed to rank eight vaccination strategies based on their efficiency (i.e. net costs in relation to prevented losses or benefits) for controlling the bluetongue virus serotype 8 epidemic in 2008 Methodology/Principal Findings: An economic model was developed that included the Dutch professional cattle, sheep and goat sectors together with the hobby farms. Strategies were evaluated based on the least cost - highest benefit frontier, the benefit-cost ratio and the total net returns. Strategy F, where all adult sheep at professional farms in the Netherlands would be vaccinated was very efficient at lowest costs, whereas strategy D, where additional to all adult sheep at professional farms also all adult cattle in the four Northern provinces would be vaccinated, was also very efficient but at a little higher costs. Strategy C, where all adult sheep and cattle at professional farms in the whole of the Netherlands would be vaccinated was also efficient but again at higher costs. Conclusions/Significance: This study demonstrates that a financial analysis differentiates between vaccination strategies and indicates important decision rules based on efficienc

Quality control of CarboEurope flux data ? Part II: Inter-comparison of eddy-covariance software

International audienceAs part of the quality assurance and quality control activities within the CarboEurope-IP network, a comparison of eddy-covariance software was conducted. For four five-day datasets, CO2 flux estimates were calculated by seven commonly used software packages to assess the uncertainty of CO2 flux estimates due to differences in post-processing. The datasets originated from different sites representing different commonly applied instrumentation and different canopy structures to cover a wide range of realistic conditions. Data preparation, coordinate rotation and the implementation of the correction for high frequency spectral losses were identified as crucial processing steps leading to significant discrepancies in the CO2 flux results. The overall comparison indicated a good although not yet perfect agreement among the different software within 5?10% difference for 30-min CO2 flux values. Conceptually different ideas about the selection and application of processing steps were a main reason for the differences in the CO2 flux estimates observed. A balance should be aspired between scientific freedom on the one hand, in order to advance methodical issues, and standardisation of procedures on the other hand, in order to obtain comparable fluxes for multi-site synthesis studies

Hydrologie en waterhuishouding van bosgebieden in Nederland; fase 2: meetopzet en eerste resultaten

Verdampings-, voelbarewarmte- en impulsflux, bodemvochtgehalte, weervariabelen en doorval zijn op vier boslocaties (populier, lariks, grove den, gemengd naald- en loofbos) in 1995 nagenoeg continu gemeten. In de zomer nam het interceptieverlies als percentage van de brutoneerslag af in de volgorde lariks (32,2%), populier (26,7%) en grove den (21,5%). De transpiratie nam af in de volgorde populier (422 mm), lariks (375 mm) en grove den (283 mm). Dit is een eerste schatting uit de metingen van de totale verdamping en interceptie voor het groeiseizoen van dag 120 tot en met dag 275. Het totale waterverbruik van populier (655 mm) en lariks (651 mm) is vrijwel gelijk, en hoger dan dat van grove den (539 mm)

De waterbalans van grove den op de Veluwe 1995

De interceptiepercentages van douglasspar zijn twee keer zo hoog als in 1995 voor grove den is gemeten. De transpiratie voor grove den is 100 mm lager dan die berekend voor douglasspar. Verlovingsscenarios voor de Veluwe, waarbij de totale oppervlaktewordt verondersteld uit douglasspar te bestaan, geven dus een vertekend beeld van de regionale waterbalans. Het verdampingsverlies van grove den komt meer overeen met dat van eikenbos. De verdamping van drie opstanden populieren, grove den en lariks verschilt nauwelijks in de winter van 1995. In de hydrologisch belangrijke winterperiode zal er weinig verschil in de grondwatertoelevering van deze drie opstanden bestaan