2,013 research outputs found
Evolving networks by merging cliques
We propose a model for evolving networks by merging building blocks
represented as complete graphs, reminiscent of modules in biological system or
communities in sociology. The model shows power-law degree distributions,
power-law clustering spectra and high average clustering coefficients
independent of network size. The analytical solutions indicate that a degree
exponent is determined by the ratio of the number of merging nodes to that of
all nodes in the blocks, demonstrating that the exponent is tunable, and are
also applicable when the blocks are classical networks such as
Erd\H{o}s-R\'enyi or regular graphs. Our model becomes the same model as the
Barab\'asi-Albert model under a specific condition.Comment: 8 pages, 8 figure
Comparative parasitism of the fish plagioscion squamosissimus in native and invated river basins.
Biological invasions are considered a major threat to biodiversity around the world, but the role of parasites in this process is still little investigated. Here, we compared parasite infections of a host species in the areas where it originated and where it was introduced, and in native and introduced species in the same environment, using the endoparasites of the fish Plagioscion squamosissimus (Sciaenidae) in 3 Brazilian basins. Samples were taken in 2 rivers where the species is native, i.e., Solimões River (SO) and Tocantins River (TO), and where the species was introduced, the upper Parana´ River (PR). In addition, abundances of diplostomids and larval nematodes were compared between P. squamosissimus and 2 native competitors in the PR, Hoplias malabaricus and Raphiodon vulpinus. In total, 13 species of endoparasites were recorded, but only Austrodiplostomum sp. and cestode cysts were present in all localities. Although infracommunity richness was similar, their species composition was slightly different among localities. General linear models using the relative condition factor of fish as response variables, and abundance of the most prevalent parasites as possible predictors showed that the condition of fish is negatively correlated with parasite abundance only in the native range (TO). Abundance of diplostomid eye flukes was higher in the PR, and in the native species H. malabaricus when compared to the invader, which might present an advantage for P. squamosissimus if they compete for prey. However, although P. squamosissimus may have lost some of its native parasites during its introduction to the PR, it is now possibly acting as a host for native generalist parasites
Prospects for the Search for a Standard Model Higgs Boson in ATLAS using Vector Boson Fusion
The potential for the discovery of a Standard Model Higgs boson in the mass
range m_H < 2 m_Z in the vector boson fusion mode has been studied for the
ATLAS experiment at the LHC. The characteristic signatures of additional jets
in the forward regions of the detector and of low jet activity in the central
region allow for an efficient background rejection. Analyses for the H -> WW
and H -> tau tau decay modes have been performed using a realistic simulation
of the expected detector performance. The results obtained demonstrate the
large discovery potential in the H -> WW decay channel and the sensitivity to
Higgs boson decays into tau-pairs in the low-mass region around 120 GeV.Comment: 20 pages, 13 ps figures, uses EPJ style fil
Visualization and Interpretation of Attosecond Electron Dynamics in Laser-Driven Hydrogen Molecular Ion using Bohmian Trajectories
We analyze the attosecond electron dynamics in hydrogen molecular ion driven
by an external intense laser field using ab-initio numerical simulations of the
corresponding time-dependent Schr{\"{o}}dinger equation and Bohmian
trajectories. To this end, we employ a one-dimensional model of the molecular
ion in which the motion of the protons is frozen. The results of the Bohmian
trajectory calculations do agree well with those of the ab-initio simulations
and clearly visualize the electron transfer between the two protons in the
field. In particular, the Bohmian trajectory calculations confirm the recently
predicted attosecond transient localization of the electron at one of the
protons and the related multiple bunches of the ionization current within a
half cycle of the laser field. Further analysis based on the quantum
trajectories shows that the electron dynamics in the molecular ion can be
understood via the phase difference accumulated between the Coulomb wells at
the two protons. Modeling of the dynamics using a simple two-state system leads
us to an explanation for the sometimes counter-intuitive dynamics of an
electron opposing the classical force of the electric field on the electron.Comment: 8 pages, 6 figures. The following article has been submitted to The
Journal of Chemical Physics. After it is published, it will be found at
http://jcp.aip.org
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