290 research outputs found

    Linking manure properties to phosphorus solubility in calcareous soils: Importance of the manure carbon to phosphorus ratio

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    Land application of manure can increase P transfer in runoff, although the risk depends in part on the characteristics of the manure. We assessed this for calcareous soils using manures from swine (Sus domesticus) fed one of five barley varieties (Hordeum vulgare L.), including four low phytate mutants and a normal variety, to produce manures with a range of total P (6.8-4.9 g P water-soluble P (4.3-8.0 g P kg-'), total N/P ratios (2.5:1-5.5:1), and total C/P ratios (31:1-67:1). Two experiments were conducted. First, manures were incorporated into three soils on a N (150 mg N kg-' soil) or P (27.5 mg P kg-1 soil) basis three times during a 7-wk incubation. Second, 10 additional soils were incubated for 2 wk following a single P-based manure application (82.5 mg P kg-i soil). Water and NaHCO3 (Olsen) extractable P were determined at regular intervals, with microbial P determined by fumigation-extraction after each incubation. For N-based application (i.e., variable P amendment), extractable P increased with total P applied. For P-based applications, the increase in soil P was more closely correlated to microbial P concentration than manure P composition or soil properties. These results suggest that stimulation of the microbial biomass by added organic C is important in determining soil P solubility following manure application

    A Kinematically Complete Measurement of the Proton Structure Function F2 in the Resonance Region and Evaluation of Its Moments

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    We measured the inclusive electron-proton cross section in the nucleon resonance region (W < 2.5 GeV) at momentum transfers Q**2 below 4.5 (GeV/c)**2 with the CLAS detector. The large acceptance of CLAS allowed for the first time the measurement of the cross section in a large, contiguous two-dimensional range of Q**2 and x, making it possible to perform an integration of the data at fixed Q**2 over the whole significant x-interval. From these data we extracted the structure function F2 and, by including other world data, we studied the Q**2 evolution of its moments, Mn(Q**2), in order to estimate higher twist contributions. The small statistical and systematic uncertainties of the CLAS data allow a precise extraction of the higher twists and demand significant improvements in theoretical predictions for a meaningful comparison with new experimental results.Comment: revtex4 18 pp., 12 figure

    Search for Single Top Production at LEP

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    Single top production in e+e- annihilations is searched for in data collected by the L3 detector at centre-of-mass energies from 189 to 209 GeV, corresponding to a total integrated luminosity of 634 pb-1. Investigating hadronic and semileptonic top decays, no evidence of single top production at LEP is obtained and upper limits on the single top cross section as a function of the centre-of-mass energy are derived. Limits on possible anomalous couplings, as well as on the scale of contact interactions responsible for single top production are determined

    Flavour Independent Search for Neutral Higgs Bosons at LEP

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    A flavour independent search for the CP-even and CP-odd neutral Higgs bosons h and A is performed in 624/pb of data collected with the L3 detector at LEP at centre-of-mass energies between 189 and 209GeV. Higgs boson production through the e^+e^- -> Z h and the e^+e^- ->h A processes is considered and decays of the Higgs bosons into hadrons are studied. No significant signal is observed and 95% confidence level limits on the hZZ and hAZ couplings are derived as a function of the Higgs boson masses. Assuming the Standard Model cross section for the Higgs-strahlung process and a 100% branching fraction into hadrons, a 95% confidence level lower limit on the mass of the Higgs boson is set at 110.3GeV

    Measurement of the Probability of Gluon Splitting into Charmed Quarks in Hadronic Z Decays

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    We have measured the probability, n(g->cc~), of a gluon splitting into a charm-quark pair using 1.7 million hadronic Z decays collected by the L3 detector. Two independent methods have been applied to events with a three-jet topology. One method relies on tagging charmed hadrons by identifying a lepton in the lowest energy jet. The other method uses a neural network based on global event shape parameters. Combining both methods, we measure n(g->cc~)= [2.45 +/- 0.29 +/- 0.53]%

    Search for Neutral Higgs Bosons of the Minimal Supersymmetric Standard Model in e+e- Interactions at root(s)=192-202GeV

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    A search for the lightest neutral CP-even and the neutral CP-odd Higgs bosons of the Minimal Supersymmetric Standard Model is performed using 233.2 pb-1 of integrated luminosity collected with the L3 detector at LEP at centre-of-mass energies 192-202 GeV. No signal is observed and lower mass limits are given as a function of tan(beta) for two scalar top mixing hypotheses. For tan(beta) greater than 0.8, they are mh > 83.4 GeV and mA > 83.8 GeV at 95 % confidence level

    Barium in twilight zone suspended matter as a potential proxy for particulate organic carbon remineralization : results for the North Pacific

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    Author Posting. © Elsevier B.V., 2008. This is the author's version of the work. It is posted here by permission of Elsevier B.V. for personal use, not for redistribution. The definitive version was published in Deep Sea Research Part II: Topical Studies in Oceanography 55 (2008): 1673-1683, doi:10.1016/j.dsr2.2008.04.020.This study focuses on the fate of exported organic carbon in the twilight zone at two contrasting environments in the North Pacific: the oligotrophic ALOHA site (22°45' N 158°W; Hawaii; studied during June–July 2004) and the mesotrophic Subarctic Pacific K2 site (47°N, 161°W; studied during July-August 2005). Earlier work has shown that non-lithogenic, excess particulate Ba (Baxs) in the mesopelagic water column is a potential proxy of organic carbon remineralization. In general Baxs contents were significantly larger at K2 than at ALOHA. At ALOHA the Baxs profiles from repeated sampling (5 casts) showed remarkable consistency over a period of three weeks, suggesting that the system was close to being at steady state. In contrast, more variability was observed at K2 (6 casts sampled) reflecting the more dynamic physical and biological conditions prevailing in this environment. While for both sites Baxs concentrations increased with depth, at K2 a clear maximum was present between the base of the mixed layer at around 50m and 500m, reflecting production and release of Baxs. Larger mesopelagic Baxs contents and larger bacterial production in the twilight zone at the K2 site indicate that more material was exported from the upper mixed layer for bacterial degradation deeper, compared to the ALOHA site. Furthermore, application of a published transfer function (Dehairs et al., 1997) relating oxygen consumption to the observed Baxs data indicated that the latter were in good agreement with bacterial respiration, calculated from bacterial production. These results corroborate earlier findings highlighting the potential of Baxs as a proxy for organic carbon remineralization. The range of POC remineralization rates calculated from twilight zone excess particulate Ba contents did also compare well with the depth dependent POC flux decrease as recorded by neutrally buoyant sediment traps, except in 1 case (out of 4). This discrepancy could indicate that differences in sinking velocities cause an 3 uncoupling of the processes occurring in the fine suspended particle pool from those affecting the larger particle pool which sustains the vertical flux, thus rendering comparison between both approaches risky.This research was supported by Federal Science Policy Office, Brussels through contracts EV/03/7A, SD/CA/03A, the Research Foundation Flanders through grant G.0021.04 and Vrije Universiteit Brussel via grant GOA 22, as well as the US National Science Foundation programs in Chemical and Biological Oceanography
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