Synchronization in Dynamically Coupled Fractional-Order Chaotic Systems: Studying the Effects of Fractional Derivatives

This study presents the effectiveness of dynamic coupling as a synchronization strategy for fractional chaotic systems. Using an auxiliary system as a link between the oscillators, we investigate the onset of synchronization in the coupled systems and we analytically determine the regions where both systems achieve complete synchronization. In the analysis, the integration order is considered as a key parameter affecting the onset of full synchronization, considering the stability conditions for fractional systems. The local stability of the synchronous solution is studied using the linearized error dynamics. Moreover, some statistical metrics such as the average synchronization error and Pearson’s correlation are used to numerically identify the synchronous behavior. Two particular examples are considered, namely, the fractional-order Rössler and Chua systems. By using bifurcation diagrams, it is also shown that the integration order has a strong influence not only on the onset of full synchronization but also on the individual dynamic behavior of the uncoupled systems.

Synchronous RNA conformational changes trigger ordered phase transitions in crystals

Time-resolved studies of biomacromolecular crystals have been limited to systems involving only minute conformational changes within the same lattice. Ligand-induced changes greater than several angstroms, however, are likely to result in solid-solid phase transitions, which require a detailed understanding of the mechanistic interplay between conformational and lattice transitions. Here we report the synchronous behavior of the adenine riboswitch aptamer RNA in crystal during ligand-triggered isothermal phase transitions. Direct visualization using polarized video microscopy and atomic force microscopy shows that the RNA molecules undergo cooperative rearrangements that maintain lattice order, whose cell parameters change distinctly as a function of time. The bulk lattice order throughout the transition is further supported by time-resolved diffraction data from crystals using an X-ray free electron laser. The synchronous molecular rearrangements in crystal provide the physical basis for studying large conformational changes using time-resolved crystallography and micro/nanocrystals.

Uniform-in-time continuum limit of the lattice Winfree model and emergent dynamics

<p style='text-indent:20px;'>We study a uniform-in-time continuum limit of the lattice Winfree model(LWM) and its asymptotic dynamics which depends on system functions such as natural frequency function and coupling strength function. The continuum Winfree model(CWM) is an integro-differential equation for the temporal evolution of Winfree phase field. The LWM describes synchronous behavior of weakly coupled Winfree oscillators on a lattice lying in a compact region. For bounded measurable initial phase field, we establish a global well-posedness of classical solutions to the CWM under suitable assumptions on coupling function, and we also show that a classical solution to the CWM can be obtained as a <inline-formula><tex-math id="M1">\begin{document}$ L^1 $\end{document}</tex-math></inline-formula>-limit of a sequence of lattice solutions. Moreover, in the presence of frustration effect, we show that stationary states and bump states can emerge from some admissible class of initial data in a large and intermediate coupling regimes, respectively. We also provide several numerical examples and compare them with analytical results.</p>

Influence of Autapses on Synchronization in Neural Networks With Chemical Synapses

A great deal of research has been devoted on the investigation of neural dynamics in various network topologies. However, only a few studies have focused on the influence of autapses, synapses from a neuron onto itself via closed loops, on neural synchronization. Here, we build a random network with adaptive exponential integrate-and-fire neurons coupled with chemical synapses, equipped with autapses, to study the effect of the latter on synchronous behavior. We consider time delay in the conductance of the pre-synaptic neuron for excitatory and inhibitory connections. Interestingly, in neural networks consisting of both excitatory and inhibitory neurons, we uncover that synchronous behavior depends on their synapse type. Our results provide evidence on the synchronous and desynchronous activities that emerge in random neural networks with chemical, inhibitory and excitatory synapses where neurons are equipped with autapses.

Synchronous Behavior for Memristive Synapse-Connected Chay Twin-Neuron Network and Hardware Implementation

Synchronous behavior can be responsible for the function or dysfunction of a neural network. To employ a memristor with threshold memductance as a bidirectional synapse, a memristive synapse-connected Chay twin-neuron network is constructed. This paper numerically presents the synchronous behavior for four representative firing activities in the memristive twin-neuron network by utilizing time-domain waveforms, synchronized transition states (STSs), and mean synchronization errors (MSEs). Indeed, the synchronous behaviors are truly related to the coupling strength and initial condition of the memristor. Besides, utilizing the powerful XC7Z020 FPGA, a digitally circuit-implemented electro-neuron and the memristive synapse-connected Chay twin-neuron network are made. Thereafter, the four representative firing activities and their STSs are experimentally captured to further confirm the numerical simulations.

Investigation of Sub Synchronous Vibration of Very High Speed Turbocharger Semi-Floating Bearing System: Prediction vs Test

Automotive engines are facing increased design focus towards downsizing, higher performance and lower emissions, in the process, challenging turbocharger (TC) technology to their limits. Downsizing of the engine needs smaller compressor and turbine wheels to achieve the critical flow requirements that leads to very high TC operating speeds of more 300k rpm. In general, TC rotor is most commonly supported by hydrodynamic fully floating (RFRB) or semi-floating bearing (SFRB) systems. For such high-speed applications, SFRB could be preferred bearing system where inner and outer bearing clearances act as a plain journal bearing and a squeeze film damper. These hydrodynamic bearings, exhibit non-linear oil whirl/whip phenomena in the inner bearing that leads to higher sub-synchronous vibration and overall deflection of the shaft. Sub-synchronous behavior of the SFRB is evaluated both numerically and experimentally (hot gas stand) for two design variants and results are published in this paper. TCs were run up in hot gas stand and were recorded using NVH Data Acquisition System (DAQ) with frequency analyzers and eddy current displacement sensors. In numerical simulations, multi-body dynamics (MBD) of flexible rotor and housing structures are coupled with elasto-hydrodynamics (EHD) of the inner and outer oil films. The energy equation is considered for calculation of oil film temperature in EHD using thermal boundary condition obtained from 3D FE simulation. Detailed numerical investigation was conducted using EHD joint definitions in the above bearing system. Good agreement was obtained between test and prediction, and finer source characterization was achieved using simulation.

Developmental social pragmatic interventions for preschoolers with autism spectrum disorder: A systematic review

Background and aims Developmental social pragmatic interventions are one treatment option for supporting the social communication and language skills of preschool children with autism spectrum disorder. Our first aim was to differentiate interventions using a developmental social pragmatic model from other developmental or naturalistic behavioral approaches. We applied explicit criteria outlining core features of developmental social pragmatic interventions to identify programs that use these core features. We then systematically reviewed studies examining the impact of developmental social pragmatic interventions in supporting (a) foundational social communication and language skills of preschool children with autism spectrum disorder and (b) caregiver interaction style. Additionally, we reviewed results exploring mediators and potential factors influencing children’s response to developmental social pragmatic interventions. Methods A multistep comprehensive search strategy was used to identify developmental social pragmatic treatments and studies examining their effectiveness for preschool children with autism spectrum disorder. The characteristics of each study and their outcomes were then reviewed, and a modified Critical Appraisal Skills Programme tool was used to evaluate rigor. Main contribution/Results Six interventions that met criteria to be classified as developmental social pragmatic are examined within this review. Ten studies of varying methodological rigor met criteria for inclusion and collectively reported on the outcomes of 716 preschool-aged children with autism spectrum disorder. All of the studies examined foundational communication outcomes and all but one reported positive outcomes for at least one of the measures. Seven studies examined language outcomes. While results were positive for language use within natural contexts, they were mixed for overall, receptive, and expressive language. Parents’ interaction styles significantly changed postintervention, namely in terms of increased responsiveness, synchronous behavior, use of affect, and decreased directiveness. Only two studies conducted formal mediation analysis and found that parent responsiveness and synchronous behavior were related to children’s positive response to treatment. Conclusions This review suggests that developmental social pragmatic treatments positively impact children’s foundational communication capacities (i.e. attention, social referencing, joint attention, initiation, reciprocity). Positive findings were not consistently found for supporting children’s language. Further, methodologically rigorous studies are needed to draw definitive conclusions. Additional research exploring components of developmental social pragmatic treatments that might mediate response to treatment is needed. Implications This review provides synthesized information for clinicians, families, and researchers on the effectiveness of developmental social pragmatic interventions for improving children’s foundational communication. It also suggests directions for future research and provides ideas for enhancing methodological rigor and promoting more homogeneity among treatment implementation and outcome assessments.