525 research outputs found
Semi-selective media for the isolation of Phaeomoniella chlamydospora from soil and vine wood
Two semi-selective culture media, F10S (PDA + folpet 10 ppm + streptomycin sulphate 1 g l-1) and RB150S (PDA +
rose bengal 150 ppm + streptomycin sulphate 1 g l-1), were developed for the isolation of the phytopathogenic fungus Phaeomoniella chlamydospora from soil samples and vine tissues. The media were selected so that they would allow proper growth of the pathogen and would partially inhibit eleven other common fungal genera. Eight antifungal agents were tested: Folpan (a.i. folpet), Captazel (a.i. captan), Benlate (a.i. benomyl), Chipco (a.i. iprodione), Switch (a.i. cyprodinil + fl udioxonil), rose bengal, and the bactericidal antibiotic streptomycin sulphate at several doses. Recovery of Pa. chlamydospora from wood samples was 40% better on RB150S and 50% better on F10S than on PDA, while the contaminants were reduced by 42% with RB150S, and by 48% with F10S. Pathogen reisolation from artificially contaminated soil samples was improved with F10S, while RB150S facilitated pathogen detection in samples containing moderate amounts of Rhizopus, Trichoderma, Penicillium, Alternaria or Trichoderma or in soils heavily contaminated with bacteria. F10S and RB150S improved the isolation of Pa. chlamydospora from wood and soil and can be used as alternatives to current culture media
CpG-ODN-induced sustained expression of BTLA mediating selective inhibition of human B cells.
BTLA (B- and T-lymphocyte attenuator) is a prominent co-receptor that is structurally and functionally related to CTLA-4 and PD-1. In T cells, BTLA inhibits TCR-mediated activation. In B cells, roles and functions of BTLA are still poorly understood and have never been studied in the context of B cells activated by CpG via TLR9. In this study, we evaluated the expression of BTLA depending on activation and differentiation of human B cell subsets in peripheral blood and lymph nodes. Stimulation with CpG upregulated BTLA, but not its ligand: herpes virus entry mediator (HVEM), on B cells in vitro and sustained its expression in vivo in melanoma patients after vaccination. Upon ligation with HVEM, BTLA inhibited CpG-mediated B cell functions (proliferation, cytokine production, and upregulation of co-stimulatory molecules), which was reversed by blocking BTLA/HVEM interactions. Interestingly, chemokine secretion (IL-8 and MIP1β) was not affected by BTLA/HVEM ligation, suggesting that BTLA-mediated inhibition is selective for some but not all B cell functions. We conclude that BTLA is an important immune checkpoint for B cells, as similarly known for T cells
Damage analysis and fracture toughness evaluation in a thin woven composite laminate under static tension using infrared thermography
This work deals with the issue of damage growth in thin woven composite laminates subjected to tensile loading. The conducted tensile tests were monitored on-line with an infrared camera, and tested specimens were analysed using Scanning Electron Microscopy (SEM). Combined with SEM micrographs, observation of heat source fields enabled us to assess the damage sequence. Transverse weft cracking was confirmed to be the main damage mode and fiber breakage was the final damage leading to failure. For cracks which induce little variation of specimen stiffness, the classic “Compliance method” could not be used to compute energy release rate. Hence, we present here a new procedure based on the estimation of heat source fields to calculate the energy release rate associated with transverse weft cracking. The results are then compared to those computed with a simple 3D inverse model of the heat diffusion problem and those presented in the literature
A model for cascading failures in complex networks
Large but rare cascades triggered by small initial shocks are present in most
of the infrastructure networks. Here we present a simple model for cascading
failures based on the dynamical redistribution of the flow on the network. We
show that the breakdown of a single node is sufficient to collapse the
efficiency of the entire system if the node is among the ones with largest
load. This is particularly important for real-world networks with an highly
hetereogeneous distribution of loads as the Internet and electrical power
grids.Comment: 4 pages, 4 figure
Cascade-based attacks on complex networks
We live in a modern world supported by large, complex networks. Examples
range from financial markets to communication and transportation systems. In
many realistic situations the flow of physical quantities in the network, as
characterized by the loads on nodes, is important. We show that for such
networks where loads can redistribute among the nodes, intentional attacks can
lead to a cascade of overload failures, which can in turn cause the entire or a
substantial part of the network to collapse. This is relevant for real-world
networks that possess a highly heterogeneous distribution of loads, such as the
Internet and power grids. We demonstrate that the heterogeneity of these
networks makes them particularly vulnerable to attacks in that a large-scale
cascade may be triggered by disabling a single key node. This brings obvious
concerns on the security of such systems.Comment: 4 pages, 4 figures, Revte
Anomalous scaling and Lee-Yang zeroes in Self-Organized Criticality
We show that the generating functions of avalanche observables in SOC models
exhibits a Lee-Yang phenomenon. This establishes a new link between the
classical theory of critical phenomena and SOC. A scaling theory of the
Lee-Yang zeroes is proposed including finite sampling effects.Comment: 33 pages, 19 figures, submitte
Edge overload breakdown in evolving networks
We investigate growing networks based on Barabasi and Albert's algorithm for
generating scale-free networks, but with edges sensitive to overload breakdown.
the load is defined through edge betweenness centrality. We focus on the
situation where the average number of connections per vertex is, as the number
of vertices, linearly increasing in time. After an initial stage of growth, the
network undergoes avalanching breakdowns to a fragmented state from which it
never recovers. This breakdown is much less violent if the growth is by random
rather than preferential attachment (as defines the Barabasi and Albert model).
We briefly discuss the case where the average number of connections per vertex
is constant. In this case no breakdown avalanches occur. Implications to the
growth of real-world communication networks are discussed.Comment: To appear in Phys. Rev.
Enhancement of the magnetic anisotropy of nanometer-sized Co clusters: influence of the surface and of the inter-particle interactions
We study the magnetic properties of spherical Co clusters with diameters
between 0.8 nm and 5.4 nm (25 to 7500$ atoms) prepared by sequential sputtering
of Co and Al2O3. The particle size distribution has been determined from the
equilibrium susceptibility and magnetization data and it is compared to
previous structural characterizations. The distribution of activation energies
was independently obtained from a scaling plot of the ac susceptibility.
Combining these two distributions we have accurately determined the effective
anisotropy constant Keff. We find that Keff is enhanced with respect to the
bulk value and that it is dominated by a strong anisotropy induced at the
surface of the clusters. Interactions between the magnetic moments of adjacent
layers are shown to increase the effective activation energy barrier for the
reversal of the magnetic moments. Finally, this reversal is shown to proceed
classically down to the lowest temperature investigated (1.8 K).Comment: 13 figures submitted to Phys. Rev.
Can forest management based on natural disturbances maintain ecological resilience?
Given the increasingly global stresses on forests, many ecologists argue that managers must maintain ecological resilience: the capacity of ecosystems to absorb disturbances without undergoing fundamental change. In this review we ask: Can the emerging paradigm of natural-disturbance-based management (NDBM) maintain ecological resilience in managed forests? Applying resilience theory requires careful articulation of the ecosystem state under consideration, the disturbances and stresses that affect the persistence of possible alternative states, and the spatial and temporal scales of management relevance. Implementing NDBM while maintaining resilience means recognizing that (i) biodiversity is important for long-term ecosystem persistence, (ii) natural disturbances play a critical role as a generator of structural and compositional heterogeneity at multiple scales, and (iii) traditional management tends to produce forests more homogeneous than those disturbed naturally and increases the likelihood of unexpected catastrophic change by constraining variation of key environmental processes. NDBM may maintain resilience if silvicultural strategies retain the structures and processes that perpetuate desired states while reducing those that enhance resilience of undesirable states. Such strategies require an understanding of harvesting impacts on slow ecosystem processes, such as seed-bank or nutrient dynamics, which in the long term can lead to ecological surprises by altering the forest's capacity to reorganize after disturbance
The reproductive capacity of Monk Parakeets Myiopsitta monachus is higher in their invasive range
Breeding parameters for Monk Parakeets Myiopsitta monachus nesting in Barcelona, Spain, were collected for 651 nests over five breeding seasons. This invasive population has a high reproductive capacity compared with the species in the native range: fledging success was double, the percentage of pairs attempting second broods three times higher and 55% of first-year birds bred compared with almost zero in South America
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