Synchronization Properties of Network Motifs

We address the problem of understanding the variable abundance of 3-node and 4-node subgraphs (motifs) in complex networks from a dynamical point of view. As a criterion in the determination of the functional significance of a n-node subgraph, we propose an analytic method to measure the stability of the synchronous state (SSS) the subgraph displays. We show that, for undirected graphs, the SSS is correlated with the relative abundance, while in directed graphs the correlation exists only for some specific motifs.Comment: 7 pages, 3 figure

Relay synchronization in multiplex networks

Relay (or remote) synchronization between two not directly connected oscillators in a network is an important feature allowing distant coordination. In this work, we report a systematic study of this phenomenon in multiplex networks, where inter-layer synchronization occurs between distant layers mediated by a relay layer that acts as a transmitter. We show that this transmission can be extended to higher order relay configurations, provided symmetry conditions are preserved. By first order perturbative analysis, we identify the dynamical and topological dependencies of relay synchronization in a multiplex. We find that the relay synchronization threshold is considerably reduced in a multiplex configuration, and that such synchronous state is mostly supported by the lower degree nodes of the outer layers, while hubs can be de-multiplexed without affecting overall coherence. Finally, we experimentally validated the analytical and numerical findings by means of a multiplex of three layers of electronic circuits.the analytical and numerical findings by means of a multiplex of three layers of electronic circuits

The red- or violet-shift of quasars without any source motion

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Searching for sub-stellar companion into the LkCa15 proto-planetary disk

Recent sub-millimetric observations at the Plateau de Bure interferometer evidenced a cavity at ~ 46 AU in radius into the proto-planetary disk around the T Tauri star LkCa15 (V1079 Tau), located in the Taurus molecular cloud. Additional Spitzer observations have corroborated this result possibly explained by the presence of a massive (>= 5 MJup) planetary mass, a brown dwarf or a low mass star companion at about 30 AU from the star. We used the most recent developments of high angular resolution and high contrast imaging to search directly for the existence of this putative companion, and to bring new constraints on its physical and orbital properties. The NACO adaptive optics instrument at VLT was used to observe LkCa15 using a four quadrant phase mask coronagraph to access small angular separations at relatively high contrast. A reference star at the same parallactic angle was carefully observed to optimize the quasi-static speckles subtraction (limiting our sensitivity at less than 1.0). Although we do not report any positive detection of a faint companion that would be responsible for the observed gap in LkCa15's disk (25-30 AU), our detection limits start constraining its probable mass, semi-major axis and eccentricity. Using evolutionary model predictions, Monte Carlo simulations exclude the presence of low eccentric companions with masses M >= 6 M Jup and orbiting at a >= 100 AU with significant level of confidence. For closer orbits, brown dwarf companions can be rejected with a detection probability of 90% down to 80 AU (at 80% down to 60 AU). Our detection limits do not access the star environment close enough to fully exclude the presence of a brown dwarf or a massive planet within the disk inner activity (i.e at less than 30 AU). Only, further and higher contrast observations should unveil the existence of this putative companion inside the LkCa15 disk.Comment: 6 pages, 4 figures, accepted for publication in A&

Synchronization of Chaotic Oscillators due to Common Delay Time Modulation

We have found a synchronization behavior between two identical chaotic systems^M when their delay times are modulated by a common irregular signal. ^M This phenomenon is demonstrated both in two identical chaotic maps whose delay times are driven by a common^M chaotic or random signal and in two identical chaotic oscillators whose delay times are driven by^M a signal of another chaotic oscillator. We analyze the phenomenon by using^M the Lyapunov exponents and discuss it in relation with generalized synchronization.^MComment: 5 pages, 4 figures (to be published in PRE

Generalized Synchronization in Ginzburg-Landau Equations with Local Coupling

The establishment of generalized chaotic synchronization in Ginzburg-Landau equations unidirectionally coupled at discrete points of space (local coupling) has been studied. It is shown that generalized syn-chronization regimes are also established with this type of coupling, but the necessary intensity of coupling issignificantly higher than that in the case of a spatially homogeneous couplingComment: 4 pages, 2 figure

Familial Uncombable Hair Syndrome: Ultrastructural Hair Study and Response toBiotin

Abstract: We report a family affected to the fourth generation by uncombable hair syndrome. This syndrome is characterized by unruly, dry, blond hair with a tangled appearance. The family pedigree strongly supports the hypothesis of autosomal dominant inheritance; some members of the family had, apart from uncombable hair, minor signs of atopy and ectodermal dysplasia, such as abnormalities of the nails. The diagnosis was confirmed by means of extensive scanning electron microscopy. A trial with oral biotin 5 mg/daywas started on two young patients with excellent results as regards the hair appearance, although scanning electron microscopy did not show structural changes in the hair. After a 2-year-period of follow-up, hair normality was maintained without biotin, while nail fragility still required biotin supplementation for control