6,332 research outputs found
The Effects of Reducing Sanitary and Phytosanitary (SPS) Barriers to Trade on the Washington State Apple Industry
Health Economics and Policy,
: three-body final state interactions and isospin states
Final state interactions are considered to formulate the meson decay
amplitude for the channel. The Faddeev decomposition of the
Bethe-Salpeter equation is used in order to build a relativistic three-body
model within the light-front framework. The S-wave scattering amplitude for the
system is considered in the and isospin channels with the
set of inhomogeneous integral equations solved perturbatively. In comparison
with previous results for the meson decay in the same channel, one has to
consider the different partonic processes, which build the source amplitudes,
and the larger absorption to other decay channels appears, that are important
features to be addressed. As in the decay case, the convergence of the
rescattering perturbative series is also achieved with two-loop contributions.Comment: 10 pages, 4 figure
Quantum electrodynamics in 2+1 dimensions, confinement, and the stability of U(1) spin liquids
Compact quantum electrodynamics in 2+1 dimensions often arises as an
effective theory for a Mott insulator, with the Dirac fermions representing the
low-energy spinons. An important and controversial issue in this context is
whether a deconfinement transition takes place. We perform a renormalization
group analysis to show that deconfinement occurs when , where is the number of fermion replica. For , however, there
are two stable fixed points separated by a line containing a unstable
non-trivial fixed point: a fixed point corresponding to the scaling limit of
the non-compact theory, and another one governing the scaling behavior of the
compact theory. The string tension associated to the confining interspinon
potential is shown to exhibit a universal jump as . Our results
imply the stability of a spin liquid at the physical value N=2 for Mott
insulators.Comment: 4 pages; 1 figure; v4: version accepted for publication in PRL.
Additional material: the detailed derivation of the RG equations appearing in
this preprint can be downloaded from
http://www.physik.fu-berlin.de/~nogueira/cqed3.htm
Growth kinetics of environmental Legionella pneumophila isolated from industrial wastewater
Wastewater treatment plants are environmental niches for Legionella pneumophila, the most commonly identified causative agent of severe pneumonia known as Legionnaire's disease. In the present study, Legionella pneumophila's concentrations were monitored in an industrial wastewater treatment plant and environmental isolates were characterized concerning their growth kinetics with respect to temperature and their inhibition by organic acids and ammonium. The results of the monitoring study showed that Legionella pneumophila occurs in activated sludge tanks operated with very different sludge retention times, 2.5 days in a complete-mix reactor, and 10 days in a membrane bioreactor, indicating that this bacterium can grow at different rates, despite the same wastewater temperature of 35 degrees C. The morphology of Legionella cells is different in both reactors; in the membrane bioreactor, the bacteria grow in clusters, while in the complete-mix reactor, filaments predominate demonstrating a faster growth rate. Legionella pneumophila concentrations in the complete-mix reactor and in the membrane bioreactor were within the range 3 x 10(1) to 4.8 x 10(3) GU/mL and 3 x 10(2) to 4.7 x 10(3) GU/mL, respectively. Environmental Legionella pneumophila SG2-14 isolates showed distinct temperature preferences. The lowest growth rate was observed at 28 degrees C, and the highest 0.34 d(-1) was obtained at 42 degrees C. The presence of high concentrations of organic acids and ammonium found in anaerobically pre-treated wastewater caused growth inhibition. Despite the increasing research efforts, the mechanisms governing the growth of Legionella pneumophila in wastewater treatment plants are still unclear. New innovative strategies to prevent the proliferation of this bacterium in wastewater are in demand
Color-suppression of non-planar diagrams in bosonic bound states
We study the suppression of non-planar diagrams in a scalar QCD model of a
meson system in space-time dimensions due to the inclusion of the color
degrees of freedom. As a prototype of the color-singlet meson, we consider a
flavor-nonsinglet system consisting of a scalar-quark and a scalar-antiquark
with equal masses exchanging a scalar-gluon of a different mass, which is
investigated within the framework of the homogeneous Bethe-Salpeter equation.
The equation is solved by using the Nakanishi representation for the manifestly
covariant bound-state amplitude and its light-front projection. The resulting
non-singular integral equation is solved numerically. The damping of the impact
of the cross-ladder kernel on the binding energies are studied in detail. The
color-suppression of the cross-ladder effects on the light-front wave function
and the elastic electromagnetic form factor are also discussed. As our results
show, the suppression appears significantly large for , which supports
the use of rainbow-ladder truncations in practical nonperturbative calculations
within QCD.Comment: 12 pages, 7 figures. To appear in Physics Letters
Solving the three-body bound-state Bethe-Salpeter equation in Minkowski space
The scalar three-body Bethe-Salpeter equation, with zero-range interaction,
is solved in Minkowski space by direct integration of the four-dimensional
integral equation. The singularities appearing in the propagators are treated
properly by standard analytical and numerical methods, without relying on any
ansatz or assumption. The results for the binding energies and transverse
amplitudes are compared with the results computed in Euclidean space. A fair
agreement between the calculations is found.Comment: 10 pages, 2 figures, version accepted for publication in Phys. Lett.
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