Impulse-induced optimum signal amplification in scale-free networks

Optimizing information transmission across a network is an essential task for controlling and manipulating generic information-processing systems. Here, we show how topological amplification effects in scale-free networks of signaling devices are optimally enhanced when the impulse transmitted by periodic external signals (time integral over two consecutive zeros) is maximum. This is demonstrated theoretically by means of a star-like network of overdamped bistable systems subjected to generic zero-mean periodic signals and confirmed numerically by simulations of scale-free networks of such systems. Our results show that the enhancer effect of increasing values of the signal's impulse is due to a correlative increase of the energy transmitted by the periodic signals, while it is found to be resonant-like with respect to the topology-induced amplification mechanism.P.J.M. and R.C. acknowledge financial support from the Ministerio de Economía y Competitividad (Spain) through the FIS2014-55867-P and FIS2012-34902 projects, respectively. P.J.M. acknowledges financial support from the Gobierno de Aragon (Spain, E19-Grupo FENOL) and European Social Funds. R.C. acknowledges financial support from the Junta de Extremadura (JEx, Spain) through project GR15146.Peer Reviewe

Drastic disorder-induced reduction of signal amplification in scale-free networks

Understanding information transmission across a network is a fundamental task for controlling and manipulating both biological and manmade information-processing systems. Here we show how topological resonant-like amplification effects in scale-free networks of signaling devices are drastically reduced when phase disorder in the external signals is considered. This is demonstrated theoretically by means of a starlike network of overdamped bistable systems, and confirmed numerically by simulations of scale-free networks of such systems. The taming effect of the phase disorder is found to be sensitive to the amplification's strength, while the topology-induced amplification mechanism is robust against this kind of quenched disorder in the sense that it does not significantly change the values of the coupling strength where amplification is maximum in its absence.R. C. and P. J. M. acknowledge financial support from the Ministerio de Economía y Competitividad (Mineco, Spain) through FIS2012-34902 and FIS2011-25167 projects, respectively. R.C. acknowledges financial support from the Junta de Extremadura (JEx, Spain) through project GR10045.Peer Reviewe

Ratchet universality in the directed motion of spheres by unbiased driving forces in viscous fluids

Directed motion of a sphere immersed in a viscous fluid and subjected solely to a nonlinear drag force and zero-average biharmonic forces is studied in the absence of any periodic substrate potential. We consider the case of two mutually perpendicular sinusoidal forces of periods T and T/2, respectively, which cannot yield any ratchet effect when acting separately, while inducing directed motion by acting simultaneously. Remarkably and unexpectedly, the dependence on the relative amplitude of the two sinusoidal forces of the average terminal velocity is theoretically explained from the theory of ratchet universality, while extensive numerical simulations confirmed its predictions in the adiabatic limit. Additionally, the dependence on the dimensionless driving frequency of the dimensionless average terminal velocity far from the adiabatic limit is qualitatively explained with the aid of the vibrational mechanics approach

Tectonothermal evolution associated with crustal escale extension: an hercynian example from the Tormes gneiss dome (NW Salamanca, Iberian Massif)

[Abstract] The tectonothermal Variscan evolution ofthe Tormes Gneiss Dome is controlled by a subhorizontal ductile shear zone of crustal scale and extensional characteristics, that induced a quick exhumation ofthe deep parts ofthe metamorphic complex during crustal thinning. The shearing affected a broad band of metamorphic rocks but, as the temperature decreased, became progressively concentrated in a low-grade ductile detachment that separates two distinct units, characterized by their lithology and different tectonothermal evolution. Kinematic indicators in non-coaxial fabrics show a displacement of the hangingwall to the SE, i. e., parallel to the trend of the foldbelt. The subhorizontal shearing is related to the extensional collapse ofthe variscan crust, previously thickened during the collision tectonics

de Sitter black hole with a conformally coupled scalar field in four dimensions

A four-dimensional black hole solution of the Einstein equations with a positive cosmological constant, coupled to a conformal scalar field, is given. There is a curvature singularity at the origin, and scalar field diverges inside the event horizon. The electrically charged solution, which has a fixed charge-to-mass ratio is also found. The quartic self-interacting coupling becomes bounded in terms of Newton's and the cosmological constants.Comment: 5 pages, no figures, CECS style, energy conditions are discussed and some references were added. To appear in Phys. Rev.

Role of climate variability on deep-water dynamics and deoxygenation during sapropel deposition: New insights from a palaeoceanographic empirical approach

https://doi.org/10.1016/j.palaeo.2023.111601Modern marine settings are experiencing rapid deoxygenation mainly forced by global warming and anthropogenic eutrophication. Therefore, studies that assess the role of climate variability in large spatiotemporal deoxygenations during past climate changes are needed to better comprehend the consequences of the current global warming and ocean deoxygenation. In this respect, deep marine sediments associated to past oxic-toanoxic transitions are useful palaeoarchives for understanding the interplay between climate variability, deepwater dynamics and large-scale deoxygenation. Moreover, they can offer long-term perspectives to modern marine settings that are suffering oxygen depletion due to climate change and anthropogenic pressure. In particular, sapropel layers from the Middle Pleistocene to the Holocene are excellent palaeoarchives of past large-scale deoxygenation events, since (i) they occurred during a similar Mediterranean hydrogeographic configuration to the present, (ii) have a robust chronological control, and (iii) previous studies have reconstructed the climate conditions that ruled during their deposition. In this work, we have applied empirical palaeoceanographic conceptual models to five sapropels (S1, S5, S6, S7 and S8) in three Eastern Mediterranean (EM) settings. The models suggest that the hydrographic regimes of all studied sapropels can be considered as analogues to those observed in certain modern marine restricted settings. The results obtained support the idea that climate and the degree of surface-water freshening are the primary factors that influence deep-water dynamics in marine restricted settings, that in turn control the frequency and intensity of bottom-water deoxygenation and the stability and depth of the chemocline. The deepest EM sites are the most vulnerable locations to develop bottom-water restriction and deoxygenation. Local hydrogeographic factors play an essential role in the extent and frequency of bottom-water deoxygenation. Particulate shuttling was very intense during sapropel deposition and water-mass exchange between EM and Western Mediterranean controlled the intensity of the basin reservoir effect and Mo budget in EM.Grants PID2019-104624RB-I00, PID2019-104625RB-100TED2021-131697B-C22 funded by MCIN/AEI/ 10.13039/5011000110 33,Grants FEDER/Junta de Andalucía P18-RT-3804P18-RT- 4074Groups RNM-179RNM-178 funded by Junta de AndalucaLausanne University (Switzerland) for Rock-eval analyses and TOC measurementsCenter for Scientific Instrumentation (CIC, University of Granada)XRF Unit of the IACT (CSIC-UGR) for the ICP and XRF analyse