323 research outputs found
Uncovering the dynamics of citations of scientific papers
We demonstrate a comprehensive framework that accounts for citation dynamics
of scientific papers and for the age distribution of references. We show that
citation dynamics of scientific papers is nonlinear and this nonlinearity has
far-reaching consequences, such as diverging citation distributions and runaway
papers. We propose a nonlinear stochastic dynamic model of citation dynamics
based on link copying/redirection mechanism. The model is fully calibrated by
empirical data and does not contain free parameters. This model can be a basis
for quantitative probabilistic prediction of citation dynamics of individual
papers and of the journal impact factor.Comment: 18 pages, 7 figure
Hysteresis measurement of anomalous microwave surface resistance in superconducting thin films
The anomalous decrease in microwave surface resistance, R_{s}, of
superconducting YBa_{2}Cu_{3}O_{7-d} (YBCO) thin films in the presence of a low
dc magnetic field is studied using a microstrip resonator technique. We have
done a dc field hysteresis measurement of R_{s} to study the effects of vortex
penetration on the anomalous effect. It is shown that the anomaly happens at a
field level far below the low critical field, H_{c1,strip}, of the
superconducting microstrip and vortex (Abrikosov) penetration would eliminate
the anomalous effect observed at low field. This implies that the anomalous
effect is not contributed by vortices.Comment: 2 pages, 1 figure, submitted to Physica C for M2S-HTSC-VI Proceeding
Structure of MnO nanoparticles embedded into channel-type matrices
X-ray diffraction experiments were performed on MnO confined in mesoporous
silica SBA-15 and MCM-41 matrices with different channel diameters. The
measured patterns were analyzed by profile analysis and compared to numerical
simulations of the diffraction from confined nanoparticles. From the lineshape
and the specific shift of the diffraction reflections it was shown that the
embedded objects form ribbon-like structures in the SBA-15 matrices with
channels diameters of 47-87 {\AA}, and nanowire-like structures in the MCM-41
matrices with channels diameters of 24-35 {\AA}. In the latter case the
confined nanoparticles appear to be narrower than the channel diameters. The
physical reasons for the two different shapes of the confined nanoparticles are
discussed.Comment: 8 pages, including 9 postscript figures, uses revtex4.cl
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