3,570 research outputs found
On the formation of structure in growing networks
Based on the formation of triad junctions, the proposed mechanism generates
networks that exhibit extended rather than single power law behavior. Triad
formation guarantees strong neighborhood clustering and community-level
characteristics as the network size grows to infinity. The asymptotic behavior
is of interest in the study of directed networks in which (i) the formation of
links cannot be described according to the principle of preferential
attachment; (ii) the in-degree distribution fits a power law for nodes with a
high degree and an exponential form otherwise; (iii) clustering properties
emerge at multiple scales and depend on both the number of links that newly
added nodes establish and the probability of forming triads; and (iv) groups of
nodes form modules that feature less links to the rest of the nodes.Comment: 17 pages, 9 figures, we apply the proposed mechanism to generate
network realizations that resemble the degree distribution and clustering
properties of an empirical network with no directed cycles (i.e., when the
model parameter n=0), updated reference
Power-law weighted networks from local attachments
This letter introduces a mechanism for constructing, through a process of
distributed decision-making, substrates for the study of collective dynamics on
extended power-law weighted networks with both a desired scaling exponent and a
fixed clustering coefficient. The analytical results show that the connectivity
distribution converges to the scaling behavior often found in social and
engineering systems. To illustrate the approach of the proposed framework we
generate network substrates that resemble steady state properties of the
empirical citation distributions of (i) publications indexed by the Institute
for Scientific Information from 1981 to 1997; (ii) patents granted by the U.S.
Patent and Trademark Office from 1975 to 1999; and (iii) opinions written by
the Supreme Court and the cases they cite from 1754 to 2002.Comment: 18 pages, 3 figures; Proceedings of the IEEE Conference on Decision
and Control and the European Control Conference, Orlando, FL, Dec. 2011;
Added references; We modified the model in order to take into account
extended power-law distributions which better fit to the citations data sets;
Added proofs of theorems; Shorten version; Updated plo
What pops out in positional priming of pop-out: insights from event-related EEG lateralizations
It is well established that, in visual pop-out search, reaction time (RT) performance is influenced by cross-trial repetitions versus changes of target-defining attributes. One instance of this is referred to as “positional priming of pop-out” (pPoP; Maljkovic and Nakayama, 1996). In positional PoP paradigms, the processing of the current target is examined depending on whether it occurs at the previous target or a previous distractor location, relative to a previously empty location (“neutral” baseline), permitting target facilitation and distractor inhibition to be dissociated. The present study combined RT measures with specific sensory- and motor-driven event-related lateralizations to track the time course of four distinct processing levels as a function of the target’s position across consecutive trials. The results showed that, relative to targets at previous target and “neutral” locations, the appearance of a target at a previous distractor location was associated with a delayed build-up of the posterior contralateral negativity wave, indicating that distractor positions are suppressed at early stages of visual processing. By contrast, presentation of a target at a previous target, relative to “neutral” and distractor locations, modulated the elicitation of the subsequent stimulus-locked lateralized readiness potential wave, indicating that post-selective response selection is facilitated if the target occurred at the same position as on the previous trial. Overall, the results of present study provide electrophysiological evidence for the idea that target location priming (RT benefits) does not originate from an enhanced coding of target saliency at repeated (target) locations; instead, they arise (near-) exclusively from processing levels subsequent to focal-attentional target selection
Bedrijfsnetwerk op weg naar minder antibiotica
Steeds meer (biologische) melkveehouders ontdekken dat hun bedrijfsvoering toe kan met minder antibiotica. Geïnteresseerde veehouders hebben de afgelopen jaren veel van elkaar geleerd binnen het ‘Bedrijfsnetwerk Antibioticavrije Bedrijfsvoering’. Als alternatief voor antibiotica zijn meestal meerdere strategieën en oplossingen mogelijk. Het is de kunst om een strategie te kiezen die past bij de veehouder, het bedrijf, de veestapel en de individuele koe. In dit bioKennisbericht meer informatie uit het bedrijfsnetwerk
Investigating powerful jets in radio-loud Narrow Line Seyfert 1s
We report results on multiband observations from radio to gamma-rays of the
two radio-loud narrow-line Seyfert 1 (NLSy1) galaxies PKS 2004-447 and
J1548+3511. Both sources show a core-jet structure on parsec scale, while they
are unresolved at the arcsecond scale. The high core dominance and the high
variability brightness temperature make these NLSy1 galaxies good gamma-ray
source candidates. Fermi-LAT detected gamma-ray emission only from PKS
2004-447, with a gamma-ray luminosity comparable to that observed in blazars.
No gamma-ray emission is observed for J1548+3511. Both sources are variable in
X-rays. J1548+3511 shows a hardening of the spectrum during high activity
states, while PKS 2004-447 has no spectral variability. A spectral steepening
likely related to the soft excess is hinted below 2 keV for J1548+3511, while
the X-ray spectra of PKS 2004-447 collected by XMM-Newton in 2012 are described
by a single power-law without significant soft excess. No additional absorption
above the Galactic column density or the presence of an Fe line is detected in
the X-ray spectra of both sources.Comment: 16 pages, 8 figures, accepted for publication in MNRA
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