Study of gyrotron synchronization by an external harmonic signal based on a modified quasi-linear theory

Topic. The paper is devoted to the study of synchronization of a gyrotron by an external harmonic signal. A theoretical study of gyrotron synchronization processes by means of a computational experiment based on certain traditional models of microwave electronics does not provide a complete description of the synchronization pattern. Therefore, the goal of the paper is to develop a modified quasi-linear model based on an approximation of the electron susceptibility by rational functions. Methods. The developed model allows for bifurcation analysis of synchronization processes. On its basis, stationary states are determined and their stability analysis is carried out. The results are in good agreement with numerical simulation based on the non-stationary theory of a gyrotron with a fixed Gaussian high-frequency field structure. Results and discussion. Resonance curves and synchronization bounds are built on the plane of parameters “amplitude – frequency of external signal”. The case where the gyrotron is in the hard excitation mode is considered, since the maximum efficiency is usually achieved in the hard excitation mode. In general, the results are in qualitative agreement with the picture described earlier for a simpler quasi-linear model of a oscillator with hard excitation, in the case of a sufficiently strong phase nonlinearity.

Unified treatment of synchronization patterns in generalized networks with higher-order, multilayer, and temporal interactions

When describing complex interconnected systems, one often has to go beyond the standard network description to account for generalized interactions. Here, we establish a unified framework to simplify the stability analysis of cluster synchronization patterns for a wide range of generalized networks, including hypergraphs, multilayer networks, and temporal networks. The framework is based on finding a simultaneous block diagonalization of the matrices encoding the synchronization pattern and the network topology. As an application, we use simultaneous block diagonalization to unveil an intriguing type of chimera states that appear only in the presence of higher-order interactions. The unified framework established here can be extended to other dynamical processes and can facilitate the discovery of emergent phenomena in complex systems with generalized interactions.

The Whi2p-Psr1p/Psr2p complex regulates interference competition and expansion of cells with competitive advantage in yeast colonies

Yeast form complex highly organized colonies in which cells undergo spatiotemporal phenotypic differentiation in response to local gradients of nutrients, metabolites, and specific signaling molecules. Colony fitness depends on cell interactions, cooperation, and the division of labor between differentiated cell subpopulations. Here, we describe the regulation and dynamics of the expansion of papillae that arise during colony aging, which consist of cells that overcome colony regulatory rules and disrupt the synchronized colony structure. We show that papillae specifically expand within the U cell subpopulation in differentiated colonies. Papillae emerge more frequently in some strains than in others. Genomic analyses further revealed that the Whi2p-Psr1p/Psr2p complex (WPPC) plays a key role in papillae expansion. We show that cells lacking a functional WPPC have a sizable interaction-specific fitness advantage attributable to production of and resistance to a diffusible compound that inhibits growth of other cells. Competitive superiority and high relative fitness ofwhi2andpsr1psr2strains are particularly pronounced in dense spatially structured colonies and are independent of TORC1 and Msn2p/Msn4p regulators previously associated with the WPPC function. The WPPC function, described here, might be a regulatory mechanism that balances cell competition and cooperation in dense yeast populations and, thus, contributes to cell synchronization, pattern formation, and the expansion of cells with a competitive fitness advantage.

Effect of Signal-Dependent Noise on Phase Synchrony Pattern

Background: Intermittent phase synchrony is a phenomenon that occurs at subthreshold levels of oscillator coupling, where two oscillators appear to be synchronized at some times and desynchronized at others. Here, periods of “synchrony” are defined by a certain amount of statistically significant correlation between the time series of the oscillators.1 While general synchrony is observable in any number of settings (e.g. coupled pendula), intermittent synchrony has been detected in EEG readings from specific pairs of electrodes from patients with schizophrenia and Parkinson’s Disease.1 However, the extent to which EEG noise impacts synchrony pattern within the Rubchinsky et. al. model has not yet been studied.1 Methods: Using non-experimental data in MATLAB, we propose to run a series of trials to study the effect of signal-dependent multiplicative noise on the patterns of phase synchrony between oscillators. In the first condition, we simulate two completely synchronized signals, add signal-dependent noise to one, and observe the resulting changes to the synchronization pattern. In the second condition, we begin with two completely desynchronized signals. Potential Impact: In studies of intermittent phase synchrony, it has been suggested that this pattern is the result of neuronal circuits which, as the EEG signals synchronize, fire more strongly and as a result become less responsive to outside input. This interpretation has the power to explain some of the symptoms experienced by patients. Thus, the specific pattern of synchronized and de-synchronized episodes is potentially highly significant. Our study is a necessary first step to understanding if the existing model and interpretations are accurate. References: Rubchinsky, L. L., Ahn, S., & Park, C. (2014). Dynamics of desynchronized episodes in intermittent synchronization. Frontiers in Physics, 2. doi:10.3389/fphy.2014.00038

Mutual synchronization pattern as a complementary indicator of the short-term blood pressure – heart rate feedback regulation activity

We suggest a complementary indicator of the blood pressure – heart rate feedback regulation based on their synchronization pattern assessed by Hilbert transform. We determine the synchronization coefficient Sync as the fraction of time fragments where the standard deviation of the differences between instantaneous phases of blood pressure and pulse intervals are below a certain threshold. While BRS characterizes the intensity of the pulse intervals response to the blood pressure changes during observed feedback responses, the Sync likely indicates how often such responses are activated in the first place. Data from 95 tilt test records indicate that in both healthy subjects and patients with moderate autonomic dysfunction BRS and Sync are typically reciprocal suggesting that low intensity of the feedback responses characterized by low BRS is rather compensated by their more frequent activation indicated by higher Sync. In contrast, in diabetes patients with autonomic neuropathy BRS and Sync are positively correlated likely indicating the breakdown of this compensation in some of the diabetic patients. Therefore we suggest that Sync could be used as an additional indicator of the blood pressure – heart rate feedback regulation activity that is complementary to the widely used baroreflex sensitivity (BRS).

Five Breaks Synchrony While Six Keeps Synchrony: Individual Difference in the Coordinated Pattern of Five- and Six-armed Brittle Stars

Physiological experiments and mathematical models have supported that neuronal activity is crucial for coordinating rhythmic movements in animals. On the other hand, robotics studies have suggested the importance of physical properties made by body structure, i.e. morphology. However, it remains unclear how morphology affects movement coordination in animals, independent of neuronal activity. To begin to understand this issue, our study reports a rhythmic movement in the green brittle star. We found this animal moved five radially symmetric parts in a well-ordered unsynchronized pattern. We built a phenomenological model where internal fluid flows between the five body parts to explain the coordinated pattern without considering neuronal activity. Changing the number of the body parts from five to six, we simulated a synchronized pattern, which was demonstrated also by an individual with six symmetric parts. Our model suggests a different number in morphology makes a different fluid flow, leading to a different synchronization pattern in the animal.