438 research outputs found
Collective Influence of Multiple Spreaders Evaluated by Tracing Real Information Flow in Large-Scale Social Networks
Identifying the most influential spreaders that maximize information flow is
a central question in network theory. Recently, a scalable method called
"Collective Influence (CI)" has been put forward through collective influence
maximization. In contrast to heuristic methods evaluating nodes' significance
separately, CI method inspects the collective influence of multiple spreaders.
Despite that CI applies to the influence maximization problem in percolation
model, it is still important to examine its efficacy in realistic information
spreading. Here, we examine real-world information flow in various social and
scientific platforms including American Physical Society, Facebook, Twitter and
LiveJournal. Since empirical data cannot be directly mapped to ideal
multi-source spreading, we leverage the behavioral patterns of users extracted
from data to construct "virtual" information spreading processes. Our results
demonstrate that the set of spreaders selected by CI can induce larger scale of
information propagation. Moreover, local measures as the number of connections
or citations are not necessarily the deterministic factors of nodes' importance
in realistic information spreading. This result has significance for rankings
scientists in scientific networks like the APS, where the commonly used number
of citations can be a poor indicator of the collective influence of authors in
the community.Comment: 11 pages, 4 figure
The Swift X-ray Telescope Cluster Survey III: Cluster Catalog from 2005-2012 Archival Data
We present the Swift X-ray Cluster Survey (SWXCS) catalog obtained using
archival data from the X-ray telescope (XRT) on board the Swift satellite
acquired from 2005 to 2012, extending the first release of the SWXCS. The
catalog provides positions, soft fluxes, and, when possible, optical
counterparts for a flux-limited sample of X-ray group and cluster candidates.
We consider the fields with Galactic latitude |b| > 20 degree to avoid high HI
column densities. We discard all of the observations targeted at groups or
clusters of galaxies, as well as particular extragalactic fields not suitable
to search for faint extended sources. We finally select ~3000 useful fields
covering a total solid angle of ~400 degree^2. We identify extended source
candidates in the soft-band (0.5-2keV) images of these fields using the
software EXSdetect, which is specifically calibrated for the XRT data.
Extensive simulations are used to evaluate contamination and completeness as a
function of the source signal, allowing us to minimize the number of spurious
detections and to robustly assess the selection function. Our catalog includes
263 candidate galaxy clusters and groups down to a flux limit of 7E-15
erg/cm^2/s in the soft band, and the logN-logS is in very good agreement with
previous deep X-ray surveys. The final list of sources is cross-correlated with
published optical, X-ray, and SZ catalogs of clusters. We find that 137 sources
have been previously identified as clusters, while 126 are new detections.
Currently, we have collected redshift information for 158 sources (60% of the
entire sample). Once the optical follow-up and the X-ray spectral analysis of
the sources are complete, the SWXCS will provide a large and well-defined
catalog of groups and clusters of galaxies to perform statistical studies of
cluster properties and tests of cosmological models.Comment: 41 pages, 16 figures, 3 tables, published on ApJS in Jan 201
Existence of Nontrivial Solutions for Generalized Quasilinear Schrödinger Equations with Critical Growth
We study the following generalized quasilinear Schrödinger equations with critical growth -divg2u∇u+gug′u∇u|2+Vxu=λfx,u+guGu|2⁎-2Gu,x∈RN, where λ>0, N≥3, g(s):R→R+ is a C1 even function, g(0)=1, and g′(s)≥0 for all s≥0, where G(u)≔∫0ug(t)dt. Under some suitable conditions, we prove that the equation has a nontrivial solution by variational method
Probing AGN Inner Structure with X-ray Obscured Type 1 AGN
Using the X-ray-selected active galactic nuclei (AGN) from the XMM-XXL north
survey and the SDSS Baryon Oscillation Spectroscopic Survey (BOSS)
spectroscopic follow-up of them, we compare the properties of X-ray unobscured
and obscured broad-line AGN (BLAGN1 and BLAGN2; below and above
cm), including their X-ray luminosity , black hole
mass, Eddington ratio , optical continuum and line
features. We find that BLAGN2 have systematically larger broad line widths and
hence apparently higher (lower) ()
than BLAGN1. We also find that the X-ray obscuration in BLAGN tends to coincide
with optical dust extinction, which is optically thinner than that in
narrow-line AGN (NLAGN) and likely partial-covering to the broad line region.
All the results can be explained in the framework of a multi-component, clumpy
torus model by interpreting BLAGN2 as an intermediate type between BLAGN1 and
NLAGN in terms of an intermediate inclination angle.Comment: 21 pages, 12 figures, published in MNRA
2-(4-Aminophenyl)-1,3-benzoxazole
In the title molecule, C13H10N2O, the dihedral angle between the benzoxazole ring system and the benzene ring is 11.8 (1)°. In the crystal structure, molecules are linked by intermolecular N—H⋯N hydrogen bonds and π⋯π interactions [centroid–centroid distance = 3.6560 (15) Å] to form a two-dimensional network
Experimental Quantum Communication without a Shared Reference Frame
We present an experimental realization of a robust quantum communication
scheme [Phys. Rev. Lett. 93, 220501 (2004)] using pairs of photons entangled in
polarization and time. Our method overcomes errors due to collective rotation
of the polarization modes (e.g., birefringence in optical fiber or
misalignment), is insensitive to the phase's fluctuation of the interferometer,
and does not require any shared reference frame including time reference,
except the need to label different photons. The practical robustness of the
scheme is further shown by implementing a variation of the Bennett-Brassard
1984 quantum key distribution protocol over 1 km optical fiber.Comment: 4 pages, 4 figure
- …