Classification of coupled dynamical systems with multiple delays: Finding the minimal number of delays

In this article we study networks of coupled dynamical systems with time-delayed connections. If two such networks hold different delays on the connections it is in general possible that they exhibit different dynamical behavior as well. We prove that for particular sets of delays this is not the case. To this aim we introduce a componentwise timeshift transformation (CTT) which allows to classify systems which possess equivalent dynamics, though possibly different sets of connection delays. In particular, we show for a large class of semiflows (including the case of delay differential equations) that the stability of attractors is invariant under this transformation. Moreover we show that each equivalence class which is mediated by the CTT possesses a representative system in which the number of different delays is not larger than the cycle space dimension of the underlying graph. We conclude that the 'true' dimension of the corresponding parameter space of delays is in general smaller than it appears at first glance

Transformations of Energy-Related Small Molecules at Dinuclear Complexes

The urgent need for the development of carbon-neutral energy conversion schemes has inspired chemists worldwide to investigate catalytic water splitting using sunlight as the energy source. A key component for the preparation of devices employing this process is the water oxidation catalyst (WOC), and understanding the factors that govern its catalytic performance is among the major challenges. Herein, two highly water-soluble dinuclear ruthenium complexes were synthesized and proven capable of chemical, electrochemical and photochemical water oxidation, revealing the surprising stability of a bridging DMSO ligand. Dinuclear copper and cobalt complexes were also investigated as WOCs, showing degradation under the catalytic conditions. Magnetic susceptibility measurements on related cobalt complexes further displayed interesting magnetic behavior with a slow relaxation of the magnetization. Moreover, a glance was cast at dioxygen activation. In this regard, the acetate-bridged dicopper(II) complex was first reduced, affording the dicopper(I) compound via a unique mixed-valent Cu(I)Cu(II) intermediate. Subsequent oxygen activation yielded both superoxo and peroxo species. Surprisingly, the reduction of the formate-bridged dicopper(II) compound generated a hexanuclear copper(I) hydride complex after decarboxylation.2021-11-0

Análisis del conflicto en torno a la construcción del Puente Letizia en la ciudad de Córdoba (Argentina)

Este artículo busca analizar las diferentes posiciones que toman dos actores colectivos a partir de la construcción de un puente que conectará a dos barrios de la ciudad de Córdoba (Argentina). Se sostiene que esta intervención pública ilumina un conflicto que une a ambos lados del río contra la gestión local y provincial, unión que se sustenta en reivindicaciones diferentes. Sin embargo, ambos coinciden en la falta de participación en las decisiones que los afectan directamente y el protagonismo de la lógica mercantil en la producción de la ciudad. Teniendo en cuenta que los actores colectivos se constituyen como tal en la medida en que actúan de manera comprometida en relación a cuestiones socialmente problematizadas, la construcción de este puente resulta significativa en términos analíticos puesto que, a partir de los argumentos, procedimientos y reivindicaciones que movilizan a los mismos actores, surgen visiones acerca de la forma en que se construye la política urbana y la ciudad. Palabras claves: conflicto urbano; intervención pública; actores colectivos;renovación urbana; Córdoba (Argentina). Abstract This article analyzes the positions adopted by two collective actors in relation to the construction of a bridge connecting two neighborhoods in the city of Córdoba (Argentina). It is argued that this public works project sheds light on a conflict that unites both sides of the river against the local and provincial administrations. While they make different demands, they coincide in their claim that they have been denied meaningful participation in decisions directly affecting them, and in their rejection of the mercantile logic that prevails in the production of the city. As a case study, the construction of the bridge is analytically valuable because it demonstrates how collective actors are constituted in and through socially engaged forms of action. The arguments, procedures and demands that mobilize these actors give rise to different visions of how urban politics and the city are constructed. Key words: urban conflict; public intervention; collective actors; urban renewal; Córdoba (Argentina)

Analysing the Conflict over the Construction of Letizia Bridge in the City of Cordoba (Argentina)

Este artículo busca analizar las diferentes posiciones que toman dos actores colectivos a partir de la construcción de un puente que conectará a dos barrios de la ciudad de Córdoba (Argentina). Se sostiene que esta intervención pública ilumina un conflicto que une a ambos lados del río contra la gestión local y provincial, unión que se sustenta en reivindicaciones diferentes. Sin embargo, ambos coinciden en la falta de participación en las decisiones que los afectan directamente y el protagonismo de la lógica mercantil en la producción de la ciudad. Teniendo en cuenta que los actores colectivos se constituyen como tal en la medida en que actúan de manera comprometida en relación a cuestiones socialmente problematizadas, la construcción de este puente resulta significativa en términos analíticos puesto que, a partir de los argumentos, procedimientos y reivindicaciones que movilizan a los mismos actores, surgen visiones acerca de la forma en que se construye la política urbana y la ciudad.This article analyzes the positions adopted by two collective actors in relation to the construction of a bridge connecting two neighborhoods in the city of Córdoba (Argentina). It is argued that this public works project sheds light on a conflict that unites both sides of the river against the local and provincial administrations. While they make different demands, they coincide in their claim that they have been denied meaningful participation in decisions directly affecting them, and in their rejection of the mercantile logic that prevails in the production of the city. As a case study, the construction of the bridge is analytically valuable because it demonstrates how collective actors are constituted in and through socially engaged forms of action. The arguments, procedures and demands that mobilize these actors give rise to different visions of how urban politics and the city are constructed.Fil: Von Lücken, Marianne. Universidad de Buenos Aires. Facultad de Ciencias Sociales. Instituto de Investigaciones "Gino Germani"; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentin

Multistable jittering in oscillators with pulsatile delayed feedback

Oscillatory systems with time-delayed pulsatile feedback appear in various applied and theoretical research areas, and received a growing interest in the last years. For such systems, we report a remarkable scenario of destabilization of a periodic regular spiking regime. In the bifurcation point numerous regimes with non-equal interspike intervals emerge simultaneously. We show that this bifurcation is triggered by the steepness of the oscillator's phase resetting curve and that the number of the emerging, so-called "jittering" regimes grows exponentially with the delay value. Although this appears as highly degenerate from a dynamical systems viewpoint, the "multi-jitter" bifurcation occurs robustly in a large class of systems. We observe it not only in a paradigmatic phase-reduced model, but also in a simulated Hodgkin-Huxley neuron model and in an experiment with an electronic circuit

Orientation dependence of recrystallization in aluminum – Simulation and experiment

In this project the orientation dependence of recrystallization in aluminum (99.99%) was studied by means of experimental methods and computer simulation. Samples with columnar grain morphology were deformed in plane strain compression in a channel die setup up to a technical thickness reduction of 50% in several defined steps. After the last deformation step the samples were recrystallized at different temperatures. After each of the deformation steps and each of the recrystallization steps the samples were analyzed by means of electron backscattering diffraction technique. With the orientation data gained from the last deformation step an input file was generated for a recrystallization simulation based on a probabilistic cellular automaton

Detection and storage of multivariate temporal sequences by spiking pattern reverberators

We consider networks of spiking coincidence detectors in continuous time. A single detector is a finite state machine that emits a pulsatile signal whenever the number incoming inputs exceeds a threshold within a time window of some tolerance width. Such finite state models are well-suited for hardware implementations of neural networks, as on integrated circuits (IC) or field programmable arrays (FPGAs) but they also reflect the natural capability of many neurons to act as coincidence detectors. We pay special attention to a recurrent coupling structure, where the delays are tuned to a specific pattern. Applying this pattern as an external input leads to a self-sustained reverberation of the encoded pattern if the tuning is chosen correctly. In terms of the coupling structure, the tolerance and the refractory time of the individual coincidence detectors, we determine conditions for the uniqueness of the sustained activity, i.e., for the funcionality of the network as an unambiguous pattern detector. We also present numerical experiments, where the functionality of the proposed pattern detector is demonstrated replacing the simplistic finite state models by more realistic Hodgkin-Huxley neurons and we consider the possibility of implementing several pattern detectors using a set of shared coincidence detectors. We propose that inhibitory connections may aid to increase the precision of the pattern discrimination