782 research outputs found
Degradation and metabolism of fenoxaprop-P-ethyl in sensitive and resistant populations of Alopecurus myosuroides
Blackgrass (Alopecurus myosuroides) is one of the most economically important weeds in Europe. Because of the development and distribution of herbicide resistant populations the control of this weed has become a serious challenge in agriculture. In recent years a reduced efficacy of fenoxaprop-P-ethyl towards A. myosuroides has been observed. To investigate the degradation of the active substance fenoxaprop-P-ethyl in A. myosuroides, four populations were grown in the greenhouse: One herbicide sensitive population, two populations with a non-target-site resistance (NTSR) and one population with a target-site resistance (TSR). For dose response studies the plants were treated with different dosages of fenoxaprop-P-ethyl and dry weight was determined after three weeks. For the NTSR populations resistance factors of 76 and 2 could be calculated based on ED50 values. The development of the TSR plants was not restricted by the herbicide treatment, not even with the highest dosage. For the degradation and metabolism studies plants were treated with fenoxaprop-P-ethyl and harvested for laboratory analysis 2, 8, 24, 48 and 96 hours after treatment. The active substance degraded within 96 hours without any significant differences between the populations. Two hours after herbicide treatment a metabolite could be identified and quantified in all populations. The mean contents at eight and 24 hours after treatment differed significantly between the populations. Results have shown that the metabolism of fenoxaprop-P-ethyl to fenoxaprop-P is very similar in the tested populations although they have different resistance mechanisms. Further studies are intended to show if the populations differ in the formation of other unknown metabolites. Keywords: ACCase resistance, aryloxyphenoxypropionates (AOPPs), herbicide metabolism, non-target-site resistance (NTSR) Abbau und Metabolismus von Fenoxaprop-P-ethyl in sensitiven und resistenten Populationen von Alopecurus myosuroides Zusammenfassung Ackerfuchsschwanz (Alopecurus myosuroides) ist in Europa eines der Ungräser mit der größten wirtschaftlichen Bedeutung. Durch die Entwicklung und Ausbreitung resistenter Populationen wurde die Bekämpfung zu einer ernstzunehmenden Herausforderung in der Landwirtschaft. Seit einigen Jahren wird eine zunehmende Wirkungsschwäche von Fenoxaprop-P-ethyl gegenüber A. myosuroides beobachtet. Um das Abbauverhalten des Wirkstoffes in A. myosuroides zu untersuchen, wurden vier Populationen im Gewächshaus angezogen. Neben einem sensitiven Standard wurden für diese Untersuchung zwei Populationen mit einer nicht-wirkortspezifischen Resistenz (NTSR), sowie eine Population mit einer wirkortspezifischen Resistenz (TSR) verwendet. Für Dosis-Wirkungsversuche wurden die Pflanzen mit unterschiedlichen Konzentrationen des Wirkstoffs Fenoxaprop-P-ethyl behandelt und das Trockengewicht nach drei Wochen ermittelt. Basierend auf ED50-Werten konnten Resistenzfaktoren von 76 und 2 für die NTSR Populationen berechnet werden. Die Entwicklung der TSR Pflanzen wurde durch die Herbizid Behandlung nicht nachweisbar beeinflusst. Für die Abbau- und Metabolismusstudien wurden die Pflanzen mit Fenoxaprop-P-ethyl behandelt und anschließend nach 2, 8, 24, 48 und 96 Stunden geerntet und im Labor aufgearbeitet. Der Wirkstoff wurde nach 96 Stunden fast vollständig abgebaut ohne signifikante Unterschiede zwischen den Populationen. Zwei Stunden nach Herbizid Applikation konnte ein Metabolit des Wirkstoffes in allen Populationen identifiziert und quantifiziert werden. Die Gehalte des Metaboliten in den Populationen unterscheiden sich nach 8 und nach 24 Stunden signifikant voneinander. Die Ergebnisse zeigen, dass der Metabolismus von Fenoxaprop-P-ethyl zu Fenoxaprop-P, unabhängig vom Resistenzmechanismus sehr ähnlich ist. Weitere Studien sollen zeigen, ob sich die Populationen durch die Bildung von anderen, unbekannten Metaboliten unterscheiden. Stichwörter: ACCase-Resistenz, Aryloxyphenoxypropionate (AOPPs), Metabolismus, nicht-wirkortspezifischen Resistenz (NTSR
Oxidation of SiC-SiC CMC cladding tubes for GFR application in impure helium atmosphere and materials interactions with tantalum liner at high temperatures up to 1600°C
Scalar and vector Slepian functions, spherical signal estimation and spectral analysis
It is a well-known fact that mathematical functions that are timelimited (or
spacelimited) cannot be simultaneously bandlimited (in frequency). Yet the
finite precision of measurement and computation unavoidably bandlimits our
observation and modeling scientific data, and we often only have access to, or
are only interested in, a study area that is temporally or spatially bounded.
In the geosciences we may be interested in spectrally modeling a time series
defined only on a certain interval, or we may want to characterize a specific
geographical area observed using an effectively bandlimited measurement device.
It is clear that analyzing and representing scientific data of this kind will
be facilitated if a basis of functions can be found that are "spatiospectrally"
concentrated, i.e. "localized" in both domains at the same time. Here, we give
a theoretical overview of one particular approach to this "concentration"
problem, as originally proposed for time series by Slepian and coworkers, in
the 1960s. We show how this framework leads to practical algorithms and
statistically performant methods for the analysis of signals and their power
spectra in one and two dimensions, and, particularly for applications in the
geosciences, for scalar and vectorial signals defined on the surface of a unit
sphere.Comment: Submitted to the 2nd Edition of the Handbook of Geomathematics,
edited by Willi Freeden, Zuhair M. Nashed and Thomas Sonar, and to be
published by Springer Verlag. This is a slightly modified but expanded
version of the paper arxiv:0909.5368 that appeared in the 1st Edition of the
Handbook, when it was called: Slepian functions and their use in signal
estimation and spectral analysi
Minimally invasive versus open pancreatoduodenectomy (LEOPARD-2): Study protocol for a randomized controlled trial
Background: Data from observational studies suggest that minimally invasive pancreatoduodenectomy (MIPD) is superior to open pancreatoduodenectomy regarding intraoperative blood loss, postoperative morbidity, and length of hospital stay, without increasing total costs. However, several case-matched studies failed to demonstrate superiority of MIPD, and large registry studies from the USA even suggested increased mortality for MIPDs performed in low-volume (< 10 MIPDs annually) centers. Randomized controlled multicenter trials are lacking but clearly required. We hypothesize that time to functional recovery is shorter after MIPD compared with open pancreatoduodenectomy, even in an enhanced recovery setting. Methods/design: LEOPARD-2 is a randomized controlled, parallel-group, patient-blinded, multicenter, phase 2/3, superiority trial in centers that completed the Dutch Pancreatic Cancer Group LAELAPS-2 training program for laparoscopic pancreatoduodenectomy or LAELAPS-3 training program for robot-assisted pancreatoduodenectomy and have performed ≥ 20 MIPDs. A total of 136 patients with symptomatic benign, premalignant, or malignant disease will be randomly assigned to undergo minimally invasive or open pancreatoduodenectomy in an enhan
Experimental and field investigations of exposure, replication and transmission of SARS-CoV-2 in pigs in the Netherlands
In order to assess the risk of SARS-CoV-2 infection, transmission and reservoir development in swine, we combined results of an experimental and two observational studies. First, intranasal and intratracheal challenge of eight pigs did not result in infection, based on clinical signs and PCR on swab and lung tissue samples. Two serum samples returned a low positive result in virus neutralization, in line with findings in other infection experiments in pigs. Next, a retrospective observational study was performed in the Netherlands in the spring of 2020. Serum samples (N =417) obtained at slaughter from 17 farms located in a region with a high human case incidence in the first wave of the pandemic. Samples were tested with protein micro array, plaque reduction neutralization test and receptor-binding-domain ELISA. None of the serum samples was positive in all three assays, although six samples from one farm returned a low positive result in PRNT (titers 40-80). Therefore we conclude that serological evidence for large scale transmission was not observed. Finally, an outbreak of respiratory disease in pigs on one farm, coinciding with recent exposure to SARS-CoV-2 infected animal caretakers, was investigated. Tonsil swabs and paired serum samples were tested. No evidence for infection with SARS-CoV-2 was found. In conclusion, Although in both the experimental and the observational study few samples returned low antibody titer results in PRNT infection with SARS-CoV-2 was not confirmed. It was concluded that sporadic infections in the field cannot be excluded, but large-scale SARS-CoV-2 transmission among pigs is unlikely.info:eu-repo/semantics/publishedVersio
Forward pi^0 Production and Associated Transverse Energy Flow in Deep-Inelastic Scattering at HERA
Deep-inelastic positron-proton interactions at low values of Bjorken-x down
to x \approx 4.10^-5 which give rise to high transverse momentum pi^0 mesons
are studied with the H1 experiment at HERA. The inclusive cross section for
pi^0 mesons produced at small angles with respect to the proton remnant (the
forward region) is presented as a function of the transverse momentum and
energy of the pi^0 and of the four-momentum transfer Q^2 and Bjorken-x.
Measurements are also presented of the transverse energy flow in events
containing a forward pi^0 meson. Hadronic final state calculations based on QCD
models implementing different parton evolution schemes are confronted with the
data.Comment: 27 pages, 8 figures and 3 table
Deep-Inelastic Inclusive ep Scattering at Low x and a Determination of alpha_s
A precise measurement of the inclusive deep-inelastic e^+p scattering cross
section is reported in the kinematic range 1.5<= Q^2 <=150 GeV^2 and
3*10^(-5)<= x <=0.2. The data were recorded with the H1 detector at HERA in
1996 and 1997, and correspond to an integrated luminosity of 20 pb^(-1). The
double differential cross section, from which the proton structure function
F_2(x,Q^2) and the longitudinal structure function F_L(x,Q^2) are extracted, is
measured with typically 1% statistical and 3% systematic uncertainties. The
measured partial derivative (dF_2(x,Q^2)/dln Q^2)_x is observed to rise
continuously towards small x for fixed Q^2. The cross section data are combined
with published H1 measurements at high Q^2 for a next-to-leading order DGLAP
QCD analysis.The H1 data determine the gluon momentum distribution in the range
3*10^(-4)<= x <=0.1 to within an experimental accuracy of about 3% for Q^2 =20
GeV^2. A fit of the H1 measurements and the mu p data of the BCDMS
collaboration allows the strong coupling constant alpha_s and the gluon
distribution to be simultaneously determined. A value of alpha
_s(M_Z^2)=0.1150+-0.0017 (exp) +0.0009-0.0005 (model) is obtained in NLO, with
an additional theoretical uncertainty of about +-0.005, mainly due to the
uncertainty of the renormalisation scale.Comment: 68 pages, 24 figures and 18 table
Measurements of Transverse Energy Flow in Deep-Inelastic Scattering at HERA
Measurements of transverse energy flow are presented for neutral current
deep-inelastic scattering events produced in positron-proton collisions at
HERA. The kinematic range covers squared momentum transfers Q^2 from 3.2 to
2,200 GeV^2, the Bjorken scaling variable x from 8.10^{-5} to 0.11 and the
hadronic mass W from 66 to 233 GeV. The transverse energy flow is measured in
the hadronic centre of mass frame and is studied as a function of Q^2, x, W and
pseudorapidity. A comparison is made with QCD based models. The behaviour of
the mean transverse energy in the central pseudorapidity region and an interval
corresponding to the photon fragmentation region are analysed as a function of
Q^2 and W.Comment: 26 pages, 8 figures, submitted to Eur. Phys.
Searches at HERA for Squarks in R-Parity Violating Supersymmetry
A search for squarks in R-parity violating supersymmetry is performed in e^+p
collisions at HERA at a centre of mass energy of 300 GeV, using H1 data
corresponding to an integrated luminosity of 37 pb^(-1). The direct production
of single squarks of any generation in positron-quark fusion via a Yukawa
coupling lambda' is considered, taking into account R-parity violating and
conserving decays of the squarks. No significant deviation from the Standard
Model expectation is found. The results are interpreted in terms of constraints
within the Minimal Supersymmetric Standard Model (MSSM), the constrained MSSM
and the minimal Supergravity model, and their sensitivity to the model
parameters is studied in detail. For a Yukawa coupling of electromagnetic
strength, squark masses below 260 GeV are excluded at 95% confidence level in a
large part of the parameter space. For a 100 times smaller coupling strength
masses up to 182 GeV are excluded.Comment: 32 pages, 14 figures, 3 table
Multi-Jet Event Rates in Deep Inelastic Scattering and Determination of the Strong Coupling Constant
Jet event rates in deep inelastic ep scattering at HERA are investigated
applying the modified JADE jet algorithm. The analysis uses data taken with the
H1 detector in 1994 and 1995. The data are corrected for detector and
hadronization effects and then compared with perturbative QCD predictions using
next-to-leading order calculations. The strong coupling constant alpha_S(M_Z^2)
is determined evaluating the jet event rates. Values of alpha_S(Q^2) are
extracted in four different bins of the negative squared momentum
transfer~\qq in the range from 40 GeV2 to 4000 GeV2. A combined fit of the
renormalization group equation to these several alpha_S(Q^2) values results in
alpha_S(M_Z^2) = 0.117+-0.003(stat)+0.009-0.013(syst)+0.006(jet algorithm).Comment: 17 pages, 4 figures, 3 tables, this version to appear in Eur. Phys.
J.; it replaces first posted hep-ex/9807019 which had incorrect figure 4
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