1,101 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
Daniel Geary / Camilla Schofield / Jennifer Sutton (eds.): Global White Nationalism. From Apartheid to Trump, Manchester: Manchester University Press, 2020, 338 pp.
The refractive index and wave vector in passive or active media
Materials that exhibit loss or gain have a complex valued refractive index
. Nevertheless, when considering the propagation of optical pulses, using a
complex is generally inconvenient -- hence the standard choice of
real-valued refractive index, i.e. n_s = \RealPart (\sqrt{n^2}). However, an
analysis of pulse propagation based on the second order wave equation shows
that use of results in a wave vector \emph{different} to that actually
exhibited by the propagating pulse. In contrast, an alternative definition n_c
= \sqrt{\RealPart (n^2)}, always correctly provides the wave vector of the
pulse. Although for small loss the difference between the two is negligible, in
other cases it is significant; it follows that phase and group velocities are
also altered. This result has implications for the description of pulse
propagation in near resonant situations, such as those typical of metamaterials
with negative (or otherwise exotic) refractive indices.Comment: Phys. Rev. A, to appear (2009
Description de schizontes de rechute chez un nouvel Haemoproteidae, Hepatocystis perronae n.sp. parasite de mégachiroptÚres africains
The Stochastic Dynamics of Rectangular and V-shaped Atomic Force Microscope Cantilevers in a Viscous Fluid and Near a Solid Boundary
Using a thermodynamic approach based upon the fluctuation-dissipation theorem
we quantify the stochastic dynamics of rectangular and V-shaped microscale
cantilevers immersed in a viscous fluid. We show that the stochastic cantilever
dynamics as measured by the displacement of the cantilever tip or by the angle
of the cantilever tip are different. We trace this difference to contributions
from the higher modes of the cantilever. We find that contributions from the
higher modes are significant in the dynamics of the cantilever tip-angle. For
the V-shaped cantilever the resulting flow field is three-dimensional and
complex in contrast to what is found for a long and slender rectangular
cantilever. Despite this complexity the stochastic dynamics can be predicted
using a two-dimensional model with an appropriately chosen length scale. We
also quantify the increased fluid dissipation that results as a V-shaped
cantilever is brought near a solid planar boundary.Comment: 10 pages, 15 images, corrected equation (8
Forcing function control of Faraday wave instabilities in viscous shallow fluids
We investigate the relationship between the linear surface wave instabilities
of a shallow viscous fluid layer and the shape of the periodic,
parametric-forcing function (describing the vertical acceleration of the fluid
container) that excites them. We find numerically that the envelope of the
resonance tongues can only develop multiple minima when the forcing function
has more than two local extrema per cycle. With this insight, we construct a
multi-frequency forcing function that generates at onset a non-trivial harmonic
instability which is distinct from a subharmonic response to any of its
frequency components. We measure the corresponding surface patterns
experimentally and verify that small changes in the forcing waveform cause a
transition, through a bicritical point, from the predicted harmonic
short-wavelength pattern to a much larger standard subharmonic pattern. Using a
formulation valid in the lubrication regime (thin viscous fluid layer) and a
WKB method to find its analytic solutions, we explore the origin of the
observed relation between the forcing function shape and the resonance tongue
structure. In particular, we show that for square and triangular forcing
functions the envelope of these tongues has only one minimum, as in the usual
sinusoidal case.Comment: 12 pages, 10 figure
A Multidimensional Relativistic Hydrodynamics Code with a General Equation of State
The ideal gas equation of state with a constant adiabatic index, although
commonly used in relativistic hydrodynamics, is a poor approximation for most
relativistic astrophysical flows. Here we propose a new general equation of
state for a multi-component relativistic gas which is consistent with the Synge
equation of state for a relativistic perfect gas and is suitable for numerical
(special) relativistic hydrodynamics. We also present a multidimensional
relativistic hydrodynamics code incorporating the proposed general equation of
state, based on the HLL scheme, which does not make use of a full
characteristic decomposition of the relativistic hydrodynamic equations. The
accuracy and robustness of this code is demonstrated in multidimensional
calculations through several highly relativistic test problems taking into
account nonvanishing tangential velocities. Results from three-dimensional
simulations of relativistic jets show that the morphology and dynamics of the
relativistic jets are significantly influenced by the different equation of
state and by different compositions of relativistic perfect gases. Our new
numerical code, combined with our proposed equation of state is very efficient
and robust, and unlike previous codes, it gives very accurate results for
thermodynamic variables in relativistic astrophysical flows.Comment: 32 pages, 9 figures, accepted by ApJ
Capillary origami: spontaneous wrapping of a droplet with an elastic sheet
The interaction between elasticity and capillarity is used to produce three
dimensional structures, through the wrapping of a liquid droplet by a planar
sheet. The final encapsulated 3D shape is controlled by tayloring the initial
geometry of the flat membrane. A 2D model shows the evolution of open sheets to
closed structures and predicts a critical length scale below which
encapsulation cannot occur, which is verified experimentally. This {\it
elastocapillary length} is found to depend on the thickness as , a
scaling favorable to miniaturization which suggests a new way of mass
production of 3D micro- or nano-scale objects.Comment: 5 pages, 5 figure
The stochastic dynamics of micron and nanoscale elastic cantilevers in fluid: fluctuations from dissipation
The stochastic dynamics of micron and nanoscale cantilevers immersed in a
viscous fluid are quantified. Analytical results are presented for long slender
cantilevers driven by Brownian noise. The spectral density of the noise force
is not assumed to be white and the frequency dependence is determined from the
fluctuation-dissipation theorem. The analytical results are shown to be useful
for the micron scale cantilevers that are commonly used in atomic force
microscopy. A general thermodynamic approach is developed that is valid for
cantilevers of arbitrary geometry as well as for arrays of multiple cantilevers
whose stochastic motion is coupled through the fluid. It is shown that the
fluctuation-dissipation theorem permits the calculation of stochastic
quantities via straightforward deterministic methods. The thermodynamic
approach is used with deterministic finite element numerical simulations to
quantify the autocorrelation and noise spectrum of cantilever fluctuations for
a single micron scale cantilever and the cross-correlations and noise spectra
of fluctuations for an array of two experimentally motivated nanoscale
cantilevers as a function of cantilever separation. The results are used to
quantify the noise reduction possible using correlated measurements with two
closely spaced nanoscale cantilevers.Comment: Submitted to Nanotechnology April 26, 200
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