Quantification of methane oxidation in the rice rhizosphere using 13C-labelled methane

In this paper isotope ratio mass spectrometry is used to determine the methane (CH4) oxidation fraction in the rhizosphere of intact rice plant-soil systems. Earlier studies on quantification of the methane oxidation were based on inhibition or incubation procedures which strongly interfered with the plant-soil system and resulted in a large variability of the reported fractions, while other studies considered stable isotopes at natural abundance levels to investigate methanotrophy in the rhizosphere of rice. The current work is the first that used 13C-labelled CH4 as additive and calculated the oxidation fraction from the ratio between the added 13C-labelled CH4 and its oxidation product 13CO2. Both labelled gases could be distinguished from the natural abundance percentages. The oxidation fraction for methane was found to be smaller than 7%, suggesting that former approaches overestimate the methane oxidation fraction.

Sensorgerichte bespuitingen van de hoofdscheut van vruchtbomen in de opkweek

De arbeidsbehoefte van vruchtboom scheuttoppen spuiten is te hoog omdat iedere scheuttop individueel handmatig bespoten moet worden. De oorzaak hiervan ligt in de tijdigheid van de bespuitingen, en in de benodigde accuratesse. Door de tijdigheid en de accuratesse is de benodigde effectiviteit van de bespuitingen in gevaar. In de gewenste situatie worden alle vruchtbomen accuraat en op tijd bespoten. In dit project werd succesvol een geautomatiseerde sensorgerichte spuitunit voor de productie van vruchtbomen ontworpen. Het automatisch herkennen en precies bespuiten van de scheuttop is op dit moment realistisch en haalbaar voor praktijkonderzoek en implementatie in de vruchtboomkwekerij. Huidige sensoren bieden na implementatie in de vruchtboomkwekerij de mogelijkheid de bespuitingen gericht en precies gedoseerd en vergaand gemechaniseerd uit te voeren. Daarmee wordt flink bespaard op arbeid en wordt de snelheid van werkgangen vergroot

Het effect van spuitboombeweging en windvector op de drift : Randvariatie metingen 2007-2008

Spray drift measurements have been performed to quantify the effect of variations in wind angle and wind speed during application and the sprayer boom movement alongside the sprayed edge of the field on spray drift deposition alongside a sprayed potato field (2007-2008). Results of these spray drift measurements are used to develop spray drift models incorporating the effects of wind variability and sprayer boom movement on spray drift deposition. Measured spray drift deposition patterns are analysed based on the wind field and sprayer boom movements measured during the spray drift experiments. Models have been developed incorporating the variability of the windfield and the sprayer boom movement calculating the trajectories of individual packages of spray drift from discrete nozzle positions in time during the spraying of the edge of the field. The addition of sprayer boom movement in the spray drift model over wind field alone improved the calculated results of spray drift deposition variation alongside the field

Analyse van de Spotspray van een PWM-spuitdop

Sensor gestuurde spuitsystemen waarmee door middel van een sensor kwantitatief een aantasting of hoeveelheid onkruid (biomassa) in het veld gemeten kan worden vragen om spuitsystemen met een variabele dosering. Eén methode om dat te realiseren is met een Pulse Width Modulation (PWM) techniek het debiet van de spuitdop te variëren. Dit PWM-systeem bestaat uit een dophouder met daarin een klep die tijdens de bespuiting met een hoge frequentie (PWM-cyclus) open en dicht wordt gezet. Met deze debietinstellingen kunnen spotsprays worden gegenereerd om individuele planten een plantafhankelijke of specifieke dosis aan gewasbeschermingsmiddel te geven. Bij een spotspray wordt de dop meerdere PWM-cycli opengezet. Er is dus sprake van een PWM-cyclustijd die veel korter is dan de lengte van de spotspray. In dit onderzoek wordt de druppelverdeling van een PWM-gemoduleerde dop (Rometron WeedIt, Steenderen), voor een debiet van 20% en 50% van het maximale debiet bij een druk van 2 en 3 bar, onderzocht

Anomalous Effects of "Guest" Charges Immersed in Electrolyte: Exact 2D Results

We study physical situations when one or two "guest" arbitrarily-charged particles are immersed in the bulk of a classical electrolyte modelled by a Coulomb gas of positive/negative unit point-like charges, the whole system being in thermal equilibrium. The models are treated as two-dimensional with logarithmic pairwise interactions among charged constituents; the (dimensionless) inverse temperature $\beta$ is considered to be smaller than 2 in order to ensure the stability of the electrolyte against the collapse of positive-negative pairs of charges. Based on recent progress in the integrable (1+1)-dimensional sine-Gordon theory, exact formulas are derived for the chemical potential of one guest charge and for the asymptotic large-distance behavior of the effective interaction between two guest charges. The exact results imply, under certain circumstances, anomalous effects such as an effective attraction (repulsion) between like-charged (oppositely-charged) guest particles and the charge inversion in the electrolyte vicinity of a highly-charged guest particle. The adequacy of the concept of renormalized charge is confirmed in the whole stability region of inverse temperatures and the related saturation phenomenon is revised.Comment: 21 pages, 1 figur

Search for direct production of charginos and neutralinos in events with three leptons and missing transverse momentum in √s = 7 TeV pp collisions with the ATLAS detector

A search for the direct production of charginos and neutralinos in final states with three electrons or muons and missing transverse momentum is presented. The analysis is based on 4.7 fb−1 of proton–proton collision data delivered by the Large Hadron Collider and recorded with the ATLAS detector. Observations are consistent with Standard Model expectations in three signal regions that are either depleted or enriched in Z-boson decays. Upper limits at 95% confidence level are set in R-parity conserving phenomenological minimal supersymmetric models and in simplified models, significantly extending previous results

Jet size dependence of single jet suppression in lead-lead collisions at sqrt(s(NN)) = 2.76 TeV with the ATLAS detector at the LHC

Measurements of inclusive jet suppression in heavy ion collisions at the LHC provide direct sensitivity to the physics of jet quenching. In a sample of lead-lead collisions at sqrt(s) = 2.76 TeV corresponding to an integrated luminosity of approximately 7 inverse microbarns, ATLAS has measured jets with a calorimeter over the pseudorapidity interval |eta| < 2.1 and over the transverse momentum range 38 < pT < 210 GeV. Jets were reconstructed using the anti-kt algorithm with values for the distance parameter that determines the nominal jet radius of R = 0.2, 0.3, 0.4 and 0.5. The centrality dependence of the jet yield is characterized by the jet "central-to-peripheral ratio," Rcp. Jet production is found to be suppressed by approximately a factor of two in the 10% most central collisions relative to peripheral collisions. Rcp varies smoothly with centrality as characterized by the number of participating nucleons. The observed suppression is only weakly dependent on jet radius and transverse momentum. These results provide the first direct measurement of inclusive jet suppression in heavy ion collisions and complement previous measurements of dijet transverse energy imbalance at the LHC.Comment: 15 pages plus author list (30 pages total), 8 figures, 2 tables, submitted to Physics Letters B. All figures including auxiliary figures are available at http://atlas.web.cern.ch/Atlas/GROUPS/PHYSICS/PAPERS/HION-2011-02

Search for displaced vertices arising from decays of new heavy particles in 7 TeV pp collisions at ATLAS

We present the results of a search for new, heavy particles that decay at a significant distance from their production point into a final state containing charged hadrons in association with a high-momentum muon. The search is conducted in a pp-collision data sample with a center-of-mass energy of 7 TeV and an integrated luminosity of 33 pb^-1 collected in 2010 by the ATLAS detector operating at the Large Hadron Collider. Production of such particles is expected in various scenarios of physics beyond the standard model. We observe no signal and place limits on the production cross-section of supersymmetric particles in an R-parity-violating scenario as a function of the neutralino lifetime. Limits are presented for different squark and neutralino masses, enabling extension of the limits to a variety of other models.Comment: 8 pages plus author list (20 pages total), 8 figures, 1 table, final version to appear in Physics Letters

Measurement of the polarisation of W bosons produced with large transverse momentum in pp collisions at sqrt(s) = 7 TeV with the ATLAS experiment

This paper describes an analysis of the angular distribution of W->enu and W->munu decays, using data from pp collisions at sqrt(s) = 7 TeV recorded with the ATLAS detector at the LHC in 2010, corresponding to an integrated luminosity of about 35 pb^-1. Using the decay lepton transverse momentum and the missing transverse energy, the W decay angular distribution projected onto the transverse plane is obtained and analysed in terms of helicity fractions f0, fL and fR over two ranges of W transverse momentum (ptw): 35 < ptw < 50 GeV and ptw > 50 GeV. Good agreement is found with theoretical predictions. For ptw > 50 GeV, the values of f0 and fL-fR, averaged over charge and lepton flavour, are measured to be : f0 = 0.127 +/- 0.030 +/- 0.108 and fL-fR = 0.252 +/- 0.017 +/- 0.030, where the first uncertainties are statistical, and the second include all systematic effects.Comment: 19 pages plus author list (34 pages total), 9 figures, 11 tables, revised author list, matches European Journal of Physics C versio

Observation of a new chi_b state in radiative transitions to Upsilon(1S) and Upsilon(2S) at ATLAS

The chi_b(nP) quarkonium states are produced in proton-proton collisions at the Large Hadron Collider (LHC) at sqrt(s) = 7 TeV and recorded by the ATLAS detector. Using a data sample corresponding to an integrated luminosity of 4.4 fb^-1, these states are reconstructed through their radiative decays to Upsilon(1S,2S) with Upsilon->mu+mu-. In addition to the mass peaks corresponding to the decay modes chi_b(1P,2P)->Upsilon(1S)gamma, a new structure centered at a mass of 10.530+/-0.005 (stat.)+/-0.009 (syst.) GeV is also observed, in both the Upsilon(1S)gamma and Upsilon(2S)gamma decay modes. This is interpreted as the chi_b(3P) system.Comment: 5 pages plus author list (18 pages total), 2 figures, 1 table, corrected author list, matches final version in Physical Review Letter