512 research outputs found
Estimating nitrogen fluxes at the European scale by upscaling INTEGRATOR model outputs from selected sites
A comparison was made between upscaled model results of nitrogen (N) fluxes to air and water from 450 sites within the EU-27 and results derived for the entire EU-27 area using the model INTEGRATOR. The 450 sites were selected using stratified random sampling, dividing the EU-27 into 150 strata and selecting three sites at random within each stratum. The strata were based on important environmental factors influencing N fluxes. Hierarchical divisive cluster analysis was used to reduce the numerous combinations of environmental factors to the required total of 150, such that the heterogeneity of environmental factors within strata was as small as possible. Modelled NH<sub>3</sub>, N<sub>2</sub>O and NO<sub>x</sub> emissions and N leaching/runoff obtained were scaled up from the 450 sites to the entire EU-27 and were within 10% of results obtained by running the model for the whole of the EU-27 using about 36 500 sites. This implies that a reliable estimate of N fluxes for EU-27 can be made by upscaling results of the 450 selected sites suggesting that dramatic reduction in computation time can be achieved without substantial deterioration of result
Analysis of Bose-Einstein correlations in e+e- -> W+W- events including final state interactions
Recently DELPHI Collaboration reported new data on Bose-Einstein correlations
(BEC) measured in e+e- -> W^+W^- events. Apparently no enhancement has been
observed. We have analyzed these data including final state interactions (FSI)
of both Coulomb and strong (s-wave) origin and found that there is enhancement
in BEC but it is overshadowed by the FSI which are extremely important for
those events. We have found the following values for the size of the
interaction range beta and the degree of coherence lambda: beta=0.87 +/- 0.31fm
and lambda=1.19 +/- 0.48, respectively.Comment: 7pages, 4 figure
I=2 Scattering Phase Shift with two Flavors of Improved Dynamical Quarks
We present a lattice QCD calculation of phase shift including the chiral and
continuum extrapolations in two-flavor QCD. The calculation is carried out for
I=2 S-wave scattering. The phase shift is evaluated for two momentum
systems, the center of mass and laboratory systems, by using the finite volume
method proposed by L\"uscher in the center of mass system and its extension to
general systems by Rummukainen and Gottlieb. The measurements are made at three
different bare couplings , 1.95 and 2.10 using a renormalization
group improved gauge and a tadpole improved clover fermion action, and
employing a set of configurations generated for hadron spectroscopy in our
previous work. The illustrative values we obtain for the phase shift in the
continuum limit are (deg.) , and for , and , which are
consistent with experiment.Comment: 40 page
On the precision of chiral-dispersive calculations of scattering
We calculate the combination (the Olsson sum rule)
and the scattering lengths and effective ranges , and ,
dispersively (with the Froissart--Gribov representation) using, at
low energy, the phase shifts for scattering obtained by Colangelo,
Gasser and Leutwyler (CGL) from the Roy equations and chiral perturbation
theory, plus experiment and Regge behaviour at high energy, or directly, using
the CGL parameters for s and s. We find mismatch, both among the CGL
phases themselves and with the results obtained from the pion form factor. This
reaches the level of several (2 to 5) standard deviations, and is essentially
independent of the details of the intermediate energy region ( GeV) and, in some cases, of the high energy behaviour assumed. We discuss
possible reasons for this mismatch, in particular in connection with an
alternate set of phase shifts.Comment: Version to appear in Phys. Rev. D. Graphs and sum rule added. Plain
TeX fil
Pion Mass Effects in the Large Limit of \chiPT
We compute the large effective action of the non-linear
sigma model including the effect of the pion mass to order
. This action is more complex than the one corresponding
to the chiral limit not only because of the pion propagators but also because
chiral symmetry produce new interactions proportional to .
We renormalize the action by including the appropriate counter terms and find
the renormalization group equations for the corresponding couplings. Then we
estudy the unitarity propierties of the scattering amplitudes. Finally our
results are applied to the particular case of the linear sigma model and also
are used to fit the pion scattering phase shifts.Comment: FT/UCM/18/9
S-wave Meson-Meson Scattering from Unitarized U(3) Chiral Lagrangians
An investigation of the s-wave channels in meson-meson scattering is
performed within a U(3) chiral unitary approach. Our calculations are based on
a chiral effective Lagrangian which includes the eta' as an explicit degree of
freedom and incorporates important features of the underlying QCD Lagrangian
such as the axial U(1) anomaly. We employ a coupled channel Bethe-Salpeter
equation to generate poles from composed states of two pseudoscalar mesons. Our
results are compared with experimental phase shifts up to 1.5 GeV and effects
of the eta' within this scheme are discussed.Comment: 18 pages, 6 figure
Symptom complexes in patients with seropositive arthralgia and in patients newly diagnosed with rheumatoid arthritis: a qualitative exploration of symptom development
Objective: The aim of this study was to explore symptoms and symptom development during the earliest phases of rheumatoid arthritis (RA) in patients with seropositive arthralgia and patients newly diagnosed with RA
WW Cross-sections and Distributions
We present the results obtained by the "WW Cross-sections and Distributions"
working group during the CERN Workshop "Physics at LEP2" (1994/1995)Comment: 61 pages, tar'ed gzip'ed uuencoded files, LaTeX, 4 Postscript
figures. To appear in "Physics at LEP2", G.Altarelli and F.Zwirner eds., CERN
Report 199
A global fit of and elastic scattering in ChPT with dispersion relations
We apply the one-loop results of the ChPT suplemented
with the inverse amplitude method to fit the available experimental data on
and scattering. With esentially only three parameters we
describe accurately data corresponding to six different channels, namely
and . In addition we
reproduce the first resonances of the and channel with the
right mass corresponding to the and the particles.Comment: 19 pages, 5 figures available on request, FT/UCM/10/9
Mapping the spatiotemporal dynamics of calcium signaling in cellular neural networks using optical flow
An optical flow gradient algorithm was applied to spontaneously forming net-
works of neurons and glia in culture imaged by fluorescence optical microscopy
in order to map functional calcium signaling with single pixel resolution.
Optical flow estimates the direction and speed of motion of objects in an image
between subsequent frames in a recorded digital sequence of images (i.e. a
movie). Computed vector field outputs by the algorithm were able to track the
spatiotemporal dynamics of calcium signaling pat- terns. We begin by briefly
reviewing the mathematics of the optical flow algorithm, and then describe how
to solve for the displacement vectors and how to measure their reliability. We
then compare computed flow vectors with manually estimated vectors for the
progression of a calcium signal recorded from representative astrocyte
cultures. Finally, we applied the algorithm to preparations of primary
astrocytes and hippocampal neurons and to the rMC-1 Muller glial cell line in
order to illustrate the capability of the algorithm for capturing different
types of spatiotemporal calcium activity. We discuss the imaging requirements,
parameter selection and threshold selection for reliable measurements, and
offer perspectives on uses of the vector data.Comment: 23 pages, 5 figures. Peer reviewed accepted version in press in
Annals of Biomedical Engineerin
- …