Heterogeneous Coupling Research Articles

One node driving synchronisation.

Abrupt changes of behaviour in complex networks can be triggered by a single node. This work describes the dynamical fundamentals of how the behaviour of one node affects the whole network formed by coupled phase-oscillators with heterogeneous coupling strengths. The synchronisation of phase-oscillators is independent of the distribution of the natural frequencies, weakly depends on the network size, but highly depends on only one key oscillator whose ratio between its natural frequency in a rotating frame and its coupling strength is maximum. This result is based on a novel method to calculate the critical coupling strength with which the phase-oscillators emerge into frequency synchronisation. In addition, we put forward an analytical method to approximately calculate the phase-angles for the synchronous oscillators.

POPd/TBAB co-catalyzed Suzuki cross-coupling reaction of heteroaryl chlorides/bromides with 4-fluorophenylboronic acid in water

An organic solvent free and efficient heterogeneous synthesis for bridging heteroaryl halides and 4-fluorophenylboronic acid was studied in aqueous media according to the Suzuki cross-coupling protocol. High yields of heteroaryl-aryl fluorides were successfully obtained with: chloro-/bromo-substituted pyridine, thiophene, indole, and inzole in neat water using palladium phosphinous acid complexes (POPd)/tetrabutylammonium bromide (TBAB) as co-catalysts. A possible mechanism for the heterogeneous coupling reaction is proposed and discussed according to the function of the TBAB interphases. The notable properties of the reported method are highly co-catalytic activity, hetero-atom tolerance, simple separating procedure and little environmental disposal impact.

Erosion of synchronization: Coupling heterogeneity and network structure

We study the dynamics of network-coupled phase oscillators in the presence of coupling frustration. It was recently demonstrated that in heterogeneous network topologies, the presence of coupling frustration causes perfect phase synchronization to become unattainable even in the limit of infinite coupling strength. Here, we consider the important case of heterogeneous coupling functions and extend previous results by deriving analytical predictions for the total erosion of synchronization. Our analytical results are given in terms of basic quantities related to the network structure and coupling frustration. In addition to fully heterogeneous coupling, where each individual interaction is allowed to be distinct, we also consider partially heterogeneous coupling and homogeneous coupling in which the coupling functions are either unique to each oscillator or identical for all network interactions, respectively. We demonstrate the validity of our theory with numerical simulations of multiple network models, and highlight the interesting effects that various coupling choices and network models have on the total erosion of synchronization. Finally, we consider some special network structures with well-known spectral properties, which allows us to derive further analytical results.

Analytical Results for Frequency-Weighted Kuramoto-Oscillator Networks**Supported by the National Natural Science Foundation of China under Grant Grant Nos 11162019 and 11047003.

The Kuramoto model for an ensemble of coupled oscillators provides a paradigmatic example of non-equilibrium transitions between an incoherent and a synchronized state. A frequency-weighted network of Kuramoto oscillators is proposed, where the oscillators are asymmetrically coupled with the weights depending on their own native frequencies. Moreover, the characteristics of the whole network can be described by a single weighting exponent β. To obtain some analytical results, we focus on three special values of the weighting exponent β. Obviously, the network of oscillators in connection with the heterogeneous coupling scheme turns out to exhibit richer dynamics. Our findings indicate that the weighting exponents should be of importance to affect the network's synchronization ability.

A heterogeneous copper(I)-catalyzed aerobic oxidative cross-dehydrogenative coupling of terminal alkynes with thiols leading to alkynyl sulfides

A heterogeneous copper-catalyzed direct oxidative cross-dehydrogenative coupling of terminal alkynes with thiols was achieved in DMSO at 70°C in the presence of an MCM-41-supported bidentate nitrogen copper(I) complex [MCM-41-2N-CuCl] and K2CO3 under an atmosphere of O2, yielding selectively a variety of alkynyl sulfides in good to excellent yields. This heterogeneous copper catalyst can be easily recovered by a simple filtration and recycled 10 times without any decreases in activity.

Phase-lag synchronization in networks of coupled chemical oscillators.

Chemical oscillators with a broad frequency distribution are photochemically coupled in network topologies. Experiments and simulations show that the network synchronization occurs by phase-lag synchronization of clusters of oscillators with zero- or nearly zero-lag synchronization. Symmetry also plays a role in the synchronization, the extent of which is explored as a function of coupling strength, frequency distribution, and the highest frequency oscillator location. The phase-lag synchronization occurs through connected synchronized clusters, with the highest frequency node or nodes setting the frequency of the entire network. The synchronized clusters successively "fire," with a constant phase difference between them. For low heterogeneity and high coupling strength, the synchronized clusters are made up of one or more clusters of nodes with the same permutation symmetries. As heterogeneity is increased or coupling strength decreased, the phase-lag synchronization occurs partially through clusters of nodes sharing the same permutation symmetries. As heterogeneity is further increased or coupling strength decreased, partial synchronization and, finally, independent unsynchronized oscillations are observed. The relationships between these classes of behavior are explored with numerical simulations, which agree well with the experimentally observed behavior.

Heterogeneous Coupling between Interdependent Lattices Promotes the Cooperation in the Prisoner's Dilemma Game.

In the research realm of game theory, interdependent networks have extended the content of spatial reciprocity, which needs the suitable coupling between networks. However, thus far, the vast majority of existing works just assume that the coupling strength between networks is symmetric. This hypothesis, to some extent, seems inconsistent with the ubiquitous observation of heterogeneity. Here, we study how the heterogeneous coupling strength, which characterizes the interdependency of utility between corresponding players of both networks, affects the evolution of cooperation in the prisoner’s dilemma game with two types of coupling schemes (symmetric and asymmetric ones). Compared with the traditional case, we show that heterogeneous coupling greatly promotes the collective cooperation. The symmetric scheme seems much better than the asymmetric case. Moreover, the role of varying amplitude of coupling strength is also studied on these two interdependent ways. Current findings are helpful for us to understand the evolution of cooperation within many real-world systems, in particular for the interconnected and interrelated systems.

Heterogeneous interplate coupling along the Nankai Trough, Japan, detected by GPS-acoustic seafloor geodetic observation

The recurring devastating earthquake that occurs in the Nankai Trough subduction zone between the Philippine Sea plate and the Eurasian plate has the potential to cause an extremely dangerous natural disaster in the foreseeable future. Many previous studies have assumed interplate-coupling ratios for this region along the trench axis using onshore geodetic data in order to understand this recursive event. However, the offshore region that has the potential to drive a devastating tsunami cannot be resolved sufficiently because the observation network is biased to the land area. Therefore, the Hydrographic and Oceanographic Department of Japan constructed a geodetic observation network on the seafloor along the Nankai Trough using a GPS-acoustic combination technique and has used it to observe seafloor crustal movements directly above the Nankai Trough subduction zone. We have set six seafloor sites and cumulated enough data to determine the displacement rate from 2006 to January 2011. Our seafloor geodetic observations at these sites revealed a heterogeneous interplate coupling that has three particular features. The fast displacement rates observed in the easternmost area indicate strong interplate coupling (>75%) around not only the future Tokai earthquake source region but also the Paleo-Zenisu ridge. The slow displacement rates near the trench axis in the Kumano-nada Sea, a shallow part of the 1944 Tonankai earthquake source region, show a lower coupling ratio (50% to 75%). The slow displacement rate observed in the area shallower than the 1946 Nankaido earthquake source region off Cape Muroto-zaki reflects weakening interplate coupling (about 50%) probably due to a subducting seamount. Our observations above the subducting ridge and seamount indicate that the effect of a subducting seamount on an interplate-coupling region depends on various conditions such as the geometry of the seamount and the friction parameters on the plate boundary.

Statics of FGM circular plate with magneto-electro-elastic coupling: axisymmetric solutions and their relations with those for corresponding rectangular beam

This paper investigates the static behavior of a functionally graded circular plate made of magneto-electro-elastic (MEE) materials under tension and bending. The analysis is directly based on the three-dimensional governing equations for magneto-electro-elasticity, with the boundary conditions on the upper and lower surfaces satisfied exactly and those on the cylindrical surface satisfied approximately (in the Saint Venant sense). The analytical solutions, derived with a direct displacement method, are valid for any functionally graded material (FGM) with its properties varying independently in a continuous manner along the thickness direction. For homogeneous materials, these solutions are degenerated to the ones available in the literature. Interesting relations are also found between the solutions for a functionally graded magneto-electro-elastic (FGMEE) circular plate and those for an FGMEE rectangular beam, and even those for a functionally graded elastic beam when only the elastic displacements are considered. The beam solutions are also derived using a direct displacement method. Numerical examples are presented to verify the present analytical solutions, show the effects of material heterogeneity and multi-field coupling, and indicate the correspondence between the plate solutions and beam solutions.

Multilayer hybrid modeling framework for the performance assessment of interdependent critical infrastructures

The heterogeneity and tight coupling of modern critical infrastructures make it challenging to create tractable descriptions of their emergent behaviors. Classic analytical methods do not provide adequate insights into system behavior and do not fully capture the complexity of infrastructure interdependencies. Meanwhile, modeling approaches developed to represent the diverse physics and operations of critical infrastructures fail to provide a unifying framework for analyzing performance. This paper attempts to address these challenges by proposing a multilayer hybrid modeling framework that supports the detailed understanding and holistic analysis of critical infrastructure systems. A critical infrastructure is viewed as a combination of integrated subsystems structured in interdependent layers: (i) systems under control; (ii) operational control system; and (iii) human-organizational social system. The systems under control and operational control system constitute the technical components of a critical infrastructure. The human-organizational social system is the non-technical component of a critical infrastructure that captures the human and social factors that influence system performance. The modeling framework is demonstrated using the Swiss electric power supply system, which comprises three interdependent layers: the power grid, a supervisory control and data acquisition (SCADA) system and human operators. The framework can help guide the identification of strategies for designing, maintaining and enhancing the performance of critical infrastructures.

Living with a Dam

The paper discusses the issue of safe functioning of large technical systems (LTS) and questions what are the principles of “operating and living together” of heterogeneous communities. It argues that personal interactions between humans, nature, and technology are crucial for the sustainable operation of socio-technical systems. The paper presents some results of an “ethnographic case study” carried out in one of the biggest hydro-energy systems in Bulgaria, that of “Kardzhali dam”. In order to make clear how an ‘intersubjective' (or inter-actantial) space between humans and non-humans is being formed and how it could bring a sustainable functioning of the dam, the paper explores the micro layer of actors' interactions, i.e. the co-existence in everyday life. Particularly, it is focused on the experience of the dam's chief Ivan Delchev who has spent over 40 years (most of his life and the whole life of the dam) in diligent work, living with technology. Such a long lasting habitation in common space and time brings to the formation of a specific “heterogeneous coupling” (), where caring for the Other (non-human) could not be explained just as “trials of strength” (). Searching for pathways of possible dialogue between Actor-Network Theory and phenomenology (Schutz, Levinas), the analysis reveals in what way “growing together” with technology and “feeling its own rhythm and its own breathing”, in the words of the dam's chief, have a crucial contribution to the safe operation of the whole hydroelectric system.

Heterogeneous heck coupling in multivariate metal–organic frameworks for enhanced selectivity

Highly selective heterogeneous Heck coupling has been demonstrated inside a series of metal–organic frameworks (MOFs). These MOFs, Zn4O(BDC-NH2)n(BDC)(3−n) (n=3, 2.4, 1.8, 1.2, 0.9, 0.75, 0.6, 0.3, and 0.15), have been synthesized with different amounts of 1,4-benzenedicarboxylate (BDC) and 2-amino-1,4-benzenedicarboxylate (BDC-NH2) incorporated into their structure. The BDC-NH2 is functionalized by covalent postmodification with salicylic aldehyde for binding catalytically active Pd(II) ions. The catalytic activity of the embedded Pd(II) ions was tested via heterogeneous Heck coupling to produce resveratrol trimethyl ether, a pharmaceutically relevant precursor. It is also found during catalytic testing that a trade-off exists between amount of metalation and pore blocking.

Contagion in an interacting economy

We investigate the credit risk model defined in Hatchett and Kühn (2006 J. Phys. A: Math. Gen. 39 2231) under more general assumptions, in particular using a general degree distribution for sparse graphs. Expanding upon earlier results, we show that the model is exactly solvable in the N → ∞ limit and demonstrate that the exact solution is described by the message-passing approach outlined in Karrer and Newman (2010 Phys. Rev. E 82 016101), generalized to include heterogeneous agents and couplings. We provide comparisons with simulations of graph ensembles with power-law degree distributions.

ChemInform Abstract: Aerobic Oxidative Homocoupling of Aryl Amines Using Heterogeneous Rhodium Catalysts.

The first heterogeneous catalyzed oxidative coupling of aryl amines is reported. Aryl amines were dimerized at room temperature under air using a heterogeneous Rh/C catalyst in the presence of acids. By choosing a suitable acidic solvent, biaryl compounds and carbazoles were selectively prepared in good yields. This reaction is operationally simple and provides an efficient synthetic methodology for the preparation of biaryl diamines via oxidative C–H activation.

Synthesis of soluble conjugated polymeric nanoparticles through heterogeneous Suzuki coupling reaction

Conjugated hyperbranched polyphenylene nanoparticles are fabricated by cross coupling reactions between an A2 type monomer 1,4-phenylenediboronic acid (1) and B3 type monomers 1,3,5-triiodobenzene (2) and 1,3,5-tribromobenzene (3). The Suzuki-type polycondensation was conducted with a highly efficient heterogeneous catalyst to give conjugated polymeric nanoparticles which are soluble in a variety of organic solvents. The growth of the hyperbranched polyphenylenes are controlled and eventually terminated by the decomposition of the boronate terminal groups in basic aqueous media in the heterogeneous catalysis system. This method represents a new approach to produce soluble conjugated polymeric nanoparticles with simple and symmetrical monomers with more than two end groups (Ax + By, x ≥ 2, y > 2).

Distributed H ∞ filtering over sensor networks with heterogeneous Markovian coupling intercommunication delays

This study is concerned with distributed H∞ filtering for continuous-time linear systems over sensor networks with heterogeneous Markovian coupling intercommunication delays. The set of sensor nodes forms a sensing and communication network whose topology is modelled by a directed graph that describes the measurement exchanged among neighbouring sensor nodes. Heterogeneous random coupling delays modelled by a Markov process are considered in the intercommunication between interacting sensor nodes. A refined two-step decoupling technique is presented to deal with the complicated coupling of exchanged measurement in the presence of the delays. A sufficient condition on the existence of desired distributed H∞ filters is derived such that the resultant filtering error system is mean square exponentially stable with prescribed weighting average H∞ performance. Two illustrative examples are given to show the effectiveness of the proposed results.

Highly efficient heterogeneous aerobic cross-dehydrogenative coupling via C-H functionalization of tertiary amines using a nanoporous gold skeleton catalyst.

We report for the first time that zero-valent nanoporous gold (AuNPore) is a robust and green heterogeneous catalyst for α-C-H functionalization of various tertiary amines. AuNPore combines with molecular oxygen at 80 °C or tert-butyl hydrogen peroxide at room temperature and catalyses the heterogeneous cross-dehydrogenative coupling (CDC) reaction efficiently to afford the corresponding C-C and C-heteroatom coupling products in good to excellent yields with excellent reusability.

Heterogeneous Policy-Practice Coupling in an MNE: the Role of Policy Internalization

This paper focuses on subsidiary-level coupling mechanisms through which formal policies are implemented into concrete practices in multinational enterprises (MNEs). We argue that heterogeneous pol...

Intrinsic Islet Heterogeneity and Gap Junction Coupling Determine Spatiotemporal Ca2+ Wave Dynamics

Insulin is released from the islets of Langerhans in discrete pulses that are linked to synchronized oscillations of intracellular free calcium ([Ca2+]i). Associated with each synchronized oscillation is a propagating calcium wave mediated by Connexin36 (Cx36) gap junctions. A computational islet model predicted that waves emerge due to heterogeneity in β-cell function throughout the islet. To test this, we applied defined patterns of glucose stimulation across the islet using a microfluidic device and measured how these perturbations affect calcium wave propagation. We further investigated how gap junction coupling regulates spatiotemporal [Ca2+]i dynamics in the face of heterogeneous glucose stimulation. Calcium waves were found to originate in regions of the islet having elevated excitability, and this heterogeneity is an intrinsic property of islet β-cells. The extent of [Ca2+]i elevation across the islet in the presence of heterogeneity is gap-junction dependent, which reveals a glucose dependence of gap junction coupling. To better describe these observations, we had to modify the computational islet model to consider the electrochemical gradient between neighboring β-cells. These results reveal how the spatiotemporal [Ca2+]i dynamics of the islet depend on β-cell heterogeneity and cell-cell coupling, and are important for understanding the regulation of coordinated insulin release across the islet.

The role of intermediaries in the synchronization of pulse-coupled oscillators

The role of intermediaries in the synchronization of small groups of light controlled oscillators (LCO) is addressed. A single LCO is a two-time-scale phase oscillator. When pulse-coupling two LCOs, the synchronization time decreases monotonously as the coupling strength increases, independent of the initial conditions and frequency detuning. In this work we study numerically the effects that a third LCO induces to the collective behavior of the system. We analyze the new system by dealing with directed heterogeneous couplings among the units. We report a novel and robust phenomenon, absent when coupling two LCOs, which consists of a discontinuous relationship between the synchronization time and coupling strength or initial conditions. The mechanism responsible for the appearance of such discontinuities is discussed.