19,990 research outputs found
Combined production of broilers and fruits
Combined production of broilers and fruit trees is a subject often discussed in organic fruit
production in Denmark. Very little research has been carried out on this type of production
system. In organic production in Denmark, nearly no pesticides are allowed, so the need
for alternative pest control is large. Apple sawfly (Hoplocampa testudinea) and pear midge
(Contarinia pyrivora) cause big crop losses in apples and pears respectively, in unsprayed
organic fruit production. Both insects infest fruitlets and cause these to drop prematurely
after which the pests pupate in the topsoil. In the present experiment a research orchard
with the varieties âDiscoveryâ and âConferenceâ were used as outdoor area for broilers to
minimise the population of sawflies and pear midges, and to reduce the need for weeding
and manuring. The trees were kept unsprayed. Fruit yield and fruit quality were assessed
at harvest. White sticky traps were placed in the test area in order to measure the
occurrence of sawfly over time. The infestation of pear midge was investigated counting
the infested fruitlets in clusters on trees at the centre of the plots. The catch of apple
sawflies was reduced in the combined apple and broiler production, but no significant
effect on the yield or the fruit quality was seen. Experiences from on-farm research show
that combining fruit and egg-production is one way to reduce the problem with apple
sawfly, but poultry alone is not a sufficient way of controlling sawflies. The welfare and
health of the broilers were excellent under fruit trees
The ac-Driven Motion of Dislocations in a Weakly Damped Frenkel-Kontorova Lattice
By means of numerical simulations, we demonstrate that ac field can support
stably moving collective nonlinear excitations in the form of dislocations
(topological solitons, or kinks) in the Frenkel-Kontorova (FK) lattice with
weak friction, which was qualitatively predicted by Bonilla and Malomed [Phys.
Rev. B{\bf 43}, 11539 (1991)]. Direct generation of the moving dislocations
turns out to be virtually impossible; however, they can be generated initially
in the lattice subject to an auxiliary spatial modulation of the on-site
potential strength. Gradually relaxing the modulation, we are able to get the
stable moving dislocations in the uniform FK lattice with the periodic boundary
conditions, provided that the driving frequency is close to the gap frequency
of the linear excitations in the uniform lattice. The excitations have a large
and noninteger index of commensurability with the lattice (suggesting that its
actual value is irrational). The simulations reveal two different types of the
moving dislocations: broad ones, that extend, roughly, to half the full length
of the periodic lattice (in that sense, they cannot be called solitons), and
localized soliton-like dislocations, that can be found in an excited state,
demonstrating strong persistent internal vibrations. The minimum (threshold)
amplitude of the driving force necessary to support the traveling excitation is
found as a function of the friction coefficient. Its extrapolation suggests
that the threshold does not vanish at the zero friction, which may be explained
by radiation losses. The moving dislocation can be observed experimentally in
an array of coupled small Josephson junctions in the form of an {\it inverse
Josephson effect}, i.e., a dc-voltage response to the uniformly applied ac bias
current.Comment: Plain Latex, 13 pages + 9 PostScript figures. to appear on Journal of
Physics: condensed matte
A mapping approach to synchronization in the "Zajfman trap": stability conditions and the synchronization mechanism
We present a two particle model to explain the mechanism that stabilizes a
bunch of positively charged ions in an "ion trap resonator" [Pedersen etal,
Phys. Rev. Lett. 87 (2001) 055001]. The model decomposes the motion of the two
ions into two mappings for the free motion in different parts of the trap and
one for a compressing momentum kick. The ions' interaction is modelled by a
time delay, which then changes the balance between adjacent momentum kicks.
Through these mappings we identify the microscopic process that is responsible
for synchronization and give the conditions for that regime.Comment: 12 pages, 9 figures; submitted to Phys Rev
Inflammation and changes in cytokine levels in neurological feline infectious peritonitis.
Feline infectious peritonitis (FIP) is a progressive, fatal, predominantly Arthus-type immune-mediated disease that is triggered when cats are infected with a mutant enteric coronavirus. The disease presents variably with multiple organ failure, seizures, generalized effusion, or shock. Neurological FIP is clinically and pathologically more homogeneous than systemic 'wet' or 'dry' FIP; thus, comparison of cytokine profiles from cats with neurological FIP, wet FIP, and non-FIP neurological disease may provide insight into some baseline characteristics relating to the immunopathogenesis of neurological FIP. This study characterizes inflammation and changes in cytokines in the brain tissue of FIP-affected cats. Cellular infiltrates in cats with FIP included lymphocytes, plasma cells, neutrophils, macrophages, and eosinophils. IL-1 beta, IL-6, IL-12, IL-18, TNF-alpha, macrophage inhibitory protein (MIP)-1 alpha, and RANTES showed no upregulation in the brains of control cats, moderate upregulation in neurological FIP cats, and very high upregulation in generalized FIP cats. Transcription of IFN-gamma appeared upregulated in cats with systemic FIP and slightly downregulated in neurological FIP. In most cytokines tested, variance was extremely high in generalized FIP and much less in neurological FIP. Principal components analysis was performed in order to find the least number of 'components' that would summarize the cytokine profiles in cats with neurological FIP. A large component of the variance (91.7%) was accounted for by levels of IL-6, MIP-1 alpha, and RANTES. These findings provide new insight into the immunopathogenesis of FIP and suggest targets for immune therapy of this disease
Slow-light enhanced light-matter interactions with applications to gas sensing
Optical gas detection in microsystems is limited by the short micron scale
optical path length available. Recently, the concept of slow-light enhanced
absorption has been proposed as a route to compensate for the short path length
in miniaturized absorption cells. We extend the previous perturbation theory to
the case of a Bragg stack infiltrated by a spectrally strongly dispersive gas
with a narrow and distinct absorption peak. We show that considerable signal
enhancement is possible. As an example, we consider a Bragg stack consisting of
PMMA infiltrated by O2. Here, the required optical path length for visible to
near-infrared detection (~760 nm) can be reduced by at least a factor of 10^2,
making a path length of 1 mm feasible. By using this technique, optical gas
detection can potentially be made possible in microsystems
Inducing spin-dependent tunneling to probe magnetic correlations in optical lattices
We suggest a simple experimental method for probing antiferromagnetic spin
correlations of two-component Fermi gases in optical lattices. The method
relies on a spin selective Raman transition to excite atoms of one spin species
to their first excited vibrational mode where the tunneling is large. The
resulting difference in the tunneling dynamics of the two spin species can then
be exploited, to reveal the spin correlations by measuring the number of doubly
occupied lattice sites at a later time. We perform quantum Monte Carlo
simulations of the spin system and solve the optical lattice dynamics
numerically to show how the timed probe can be used to identify
antiferromagnetic spin correlations in optical lattices.Comment: 5 pages, 5 figure
Antiferromagnetic noise correlations in optical lattices
We analyze how noise correlations probed by time-of-flight (TOF) experiments
reveal antiferromagnetic (AF) correlations of fermionic atoms in
two-dimensional (2D) and three-dimensional (3D) optical lattices. Combining
analytical and quantum Monte Carlo (QMC) calculations using experimentally
realistic parameters, we show that AF correlations can be detected for
temperatures above and below the critical temperature for AF ordering. It is
demonstrated that spin-resolved noise correlations yield important information
about the spin ordering. Finally, we show how to extract the spin correlation
length and the related critical exponent of the AF transition from the noise.Comment: 4 pages, 4 figure
Joint estimation of Doppler frequency and directions in channel sounding using switched Tx and Rx arrays
Ptychographic X-ray computed tomography of extended colloidal networks in food emulsions
As a main structural level in colloidal food materials, extended colloidal
networks are important for texture and rheology. By obtaining the 3D
microstructure of the network, macroscopic mechanical properties of the
material can be inferred. However, this approach is hampered by the lack of
suitable non-destructive 3D imaging techniques with submicron resolution.
We present results of quantitative ptychographic X-ray computed tomography
applied to a palm kernel oil based oil-in-water emulsion. The measurements were
carried out at ambient pressure and temperature. The 3D structure of the
extended colloidal network of fat globules was obtained with a resolution of
around 300 nm. Through image analysis of the network structure, the fat globule
size distribution was computed and compared to previous findings. In further
support, the reconstructed electron density values were within 4% of reference
values.Comment: 19 pages, 4 figures, to be published in Food Structur
Investigations of the ambiguity effect in the estimation of Doppler frequency and directions in channel sounding using switched Tx and Rx arrays
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