26,971 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 ‘Discovery’ and ‘Conference’ 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
On the nonlinear statistics of range image patches
In [A. B. Lee, K. S. Pedersen, and D. Mumford, Int. J. Comput. Vis., 54 (2003), pp. 83–103], the authors study the distributions of 3 × 3 patches from optical images and from range images. In [G. Carlsson, T. Ishkanov, V. de Silva, and A. Zomorodian, Int. J. Comput. Vis., 76 (2008), pp.
1–12], the authors apply computational topological tools to the data set of optical patches studied by Lee, Pedersen, and Mumford and find geometric structures for high density subsets. One high density subset is called the primary circle and essentially consists of patches with a line separating a light and a dark region. In this paper, we apply the techniques of Carlsson et al. to range patches.
By enlarging to 5×5 and 7×7 patches, we find core subsets that have the topology of the primary circle, suggesting a stronger connection between optical patches and range patches than was found by Lee, Pedersen, and Mumford
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Sand Penetration By High-Speed Projectiles
Tungsten projectiles were shot into sand at velocities between 600 and 2200 m/s. Penetration was maximum at about 775 m/s. Below that velocity, projectiles were apparently stabilized by a fin set. Above that velocity, projectiles were broken by transverse loads. High-speed penetration resulted in comminution of sand particles, reducing their size by about 1000 times.Mechanical Engineerin
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
Stability of supercooled binary liquid mixtures
Recently the supercooled Wahnstrom binary Lennard-Jones mixture was partially
crystallized into phase crystals in lengthy Molecular Dynamics
simulations. We present Molecular Dynamics simulations of a modified
Kob-Andersen binary Lennard-Jones mixture that also crystallizes in lengthy
simulations, here however by forming pure fcc crystals of the majority
component. The two findings motivate this paper that gives a general
thermodynamic and kinetic treatment of the stability of supercooled binary
mixtures, emphasizing the importance of negative mixing enthalpy whenever
present. The theory is used to estimate the crystallization time in a
Kob-Andersen mixture from the crystallization time in a series of relared
systems. At T=0.40 we estimate this time to be 5 time units
(). A new binary Lennard-Jones mixture is proposed that is not
prone to crystallization and faster to simulate than the two standard binary
Lennard-Jones mixtures; this is obtained by removing the like-particle
attractions by switching to Weeks-Chandler-Andersen type potentials, while
maintaining the unlike-particle attraction
Are all hosts created equal? Partitioning host species contributions to parasite persistence in multihost communities
Many parasites circulate endemically within communities of multiple host species. To understand disease persistence within these communities, it is essential to know the contribution each host species makes to parasite transmission and maintenance. However, quantifying those contributions is challenging. We present a conceptual framework for classifying multihost sharing, based on key thresholds for parasite persistence. We then develop a generalized technique to quantify each species’ contribution to parasite persistence, allowing natural systems to be located within the framework. We illustrate this approach using data on gastrointestinal parasites circulating within rodent communities and show that, although many parasites infect several host species, parasite persistence is often driven by just one host species. In some cases, however, parasites require multiple host species for maintenance. Our approach provides a quantitative method for differentiating these cases using minimal reliance on system-specific parameters, enabling informed decisions about parasite management within poorly understood multihost communities
Crystallization of the Wahnstr\"om Binary Lennard-Jones Liquid
We report observation of crystallization of the glass-forming binary
Lennard-Jones liquid first used by Wahnstr\"om [G. Wahnstr\"om, Phys. Rev. A
44, 3752 (1991)]. Molecular dynamics simulations of the metastable liquid on a
timescale of microseconds were performed. The liquid crystallized
spontaneously. The crystal structure was identified as MgZn_2. Formation of
transient crystallites is observed in the liquid. The crystallization is
investigate at different temperatures and compositions. At high temperature the
rate of crystallite formation is the limiting factor, while at low temperature
the limiting factor is growth rate. The melting temperature of the crystal is
estimated to be T_m=0.93 at rho=0.82. The maximum crystallization rate of the
A_2B composition is T=0.60+/-0.02.Comment: 4 pages, 4 figures; corrected typo
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
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