2,209 research outputs found
PathOrganic - Identification of Critical Control Points for organic vegetable crops
The aim of this work is the identification of Critical Control Points1 (CCPs) for organic farms, which use manure for the production of organic lettuce, cabbage, carrots and spinach in Austria, Switzerland, Sweden, and Denmark. Due to the application of manure, vegetables are at risk to be contaminated with enteropathogens such as Escherichia coli pathogenic strains (i. e. O157:H7), Salmonella enterica serovar Typhimurium, Campylobacter jejuni, Listeria monocyto-genes, and Staphylococcus aureus.
This work applies part of the principles and steps described for HACCP2 to identify the CCPs. The steps described hereafter are reported in the course guidance document âHACCP in agri-culture â Organic milk productionâ (1) and were adapted to the agricultural production of field vegetables.
The hazard analysis is based on the characteristics of the above mentioned enteropathogens and the agricultural practices applied by the organic farmers in the four countries when growing lettuce, cabbage, carrots, and spinach. The assessment of the actual agricultural practices uses the evaluation of interviews conducted with organic farmers growing these vegetables and using manure as fertiliser. In total were interviewed 16 farmers in Austria, 16 farmers in Switzerland, 13 farmers in Sweden, and 9 farmers in Denmark. In general terms, there is no agricultural practice common to the majority of organic farmers concerning the management of animal ma-nure, fertilisation, irrigation, harvest and postharvest management when growing lettuce, cab-bage, spinach, and carrots in Austria, Switzerland, Denmark, and Sweden.
Using the decision tree of the HACCP system, CCPs were identified for the primary production of organic field vegetables. Where appropriate, instead of CCPs were defined PRP-CPs3 or OP-PRPs4. Four CCPs were identified for the process steps âstorage of animal manureâ, âfertilisation practicesâ, âprevention of runoff and floodingâ, and âirrigation practicesâ
On the linear dispersion--linear potential quantum oscillator
We solve the bi-linear quantum oscillator H=v|p|+F|x| both quasi-classically
and numerically.Comment: 5 pages, 3 figure
Gauge invariance and wave packet simulations in the presence of dipole fields
A method for performing wave packet simulations in dipole fields is
presented. Starting from a Hamiltonian with non commuting terms, a gauge
transformation leads to a new Hamiltonian which allows to calculate explicitly
the evolution operator. In this new gauge, the dipole field is fully included
in the {\it vector} potential. The method of Goldberg, Schwartz and Schey based
on the Caley form of the evolution operator is then generalized, and the
resulting scheme is applied to describe a switching device based on Rabi
oscillations. The probability to tunnel in the free region exhibits a plateaux
structure as the wave function is emitted by ``bursts'' after each Rabi
oscillation has been completed.Comment: 4 pages (Revtex 3.0), figures upon request, LA-UR-94-303
Spheroidal nanoparticles as thermal near-field sensors
We suggest to exploit the shape-dependence of the near-field heat transfer
for nanoscale thermal imaging. By utilizing strongly prolate or oblate
nanoparticles as sensors one can assess individual components of the
correlation tensors characterizing the thermal near field close to a
nanostructured surface, and thus obtain directional information beyond the
local density of states. Our theoretical considerations are backed by idealized
numerical model calculations
Scattering of electromagnetic waves by many thin cylinders
Electromagnetic wave scattering by many parallel infinite cylinders is
studied asymptotically as . Here is the radius of the cylinders. It
is assumed that the points are distributed so that
where
is the number of points in an
arbitrary open subset of the plane , the axes of the cylinders are passing
through points , these axes are parallel to the z-axis. The function
is a given continuous function. An equation for the
self-consistent (efficient) field is derived as . The cylinders are
assumed perfectly conducting. Formula is derived for the effective refraction
coefficient in the medium in which many cylinders are distributed
- Z interferometry at a -factory
We analyze the possibilities that the proposed -factories offer to
measure interference. In the unpolarized beam case, we study
different signatures in the channel, taking advantage of the
presence of the near-by resonance. We build a C-odd forward-backward
asymmetry, estimated to be around , and (P-even, T-even) and (P-odd,
T-odd) alignments of the , to be seen from the angular distribution of
its decay products. With polarized electrons a left-right asymmetry
around is present in all channels. At leading order this
asymmetry is independent of hadronic matrix elements and is sensitive to the
vector coupling. In the channel, a combined
left-right forward-backward asymmetry is considered.Comment: 29 pages + 6 figures. Some changes concerning observables,
especially related with possible 2 contribution
Statistical Error in Particle Simulations of Hydrodynamic Phenomena
We present predictions for the statistical error due to finite sampling in
the presence of thermal fluctuations in molecular simulation algorithms.
Specifically, we establish how these errors depend on Mach number, Knudsen
number, number of particles, etc. Expressions for the common hydrodynamic
variables of interest such as flow velocity, temperature, density, pressure,
shear stress and heat flux are derived using equilibrium statistical mechanics.
Both volume-averaged and surface-averaged quantities are considered.
Comparisons between theory and computations using direct simulation Monte Carlo
for dilute gases, and molecular dynamics for dense fluids, show that the use of
equilibrium theory provides accurate results.Comment: 24 pages postscript (including 16 figures
Attitudes toward conflict and aggression
Depto. de PsicobiologĂa y MetodologĂa en Ciencias del ComportamientoFac. de PsicologĂaTRUEpu
Topology induced anomalous defect production by crossing a quantum critical point
We study the influence of topology on the quench dynamics of a system driven
across a quantum critical point. We show how the appearance of certain edge
states, which fully characterise the topology of the system, dramatically
modifies the process of defect production during the crossing of the critical
point. Interestingly enough, the density of defects is no longer described by
the Kibble-Zurek scaling, but determined instead by the non-universal
topological features of the system. Edge states are shown to be robust against
defect production, which highlights their topological nature.Comment: Phys. Rev. Lett. (to be published
Gravitational radiation from monopoles connected by strings
Monopole-antimonopole pairs connected by strings can be formed as topological
defects in a sequence of cosmological phase transitions. Such hybrid defects
typically decay early in the history of the universe but can still generate an
observable background of gravitational waves. We study the spectrum of
gravitational radiation from these objects both analytically and numerically,
concentrating on the simplest case of an oscillating pair connected by a
straight string.Comment: 18 pages, RevTex and 2 postscript figures. Submitted to Phys. Rev.
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