Generalized synchronization in a tritrophic food web metacommunity.

Complete synchronization among the metacommunity is known to elevate the risk of their extinction due to stochasticity and other environmental perturbations. Owing to the inherent heterogeneous nature of the metacommunity, we demonstrate the emergence of generalized synchronization among the patches of dispersally connected tritrophic food web using the framework of an auxiliary system approach and the mutual false nearest neighbor. We find that the critical value of the dispersal rate increases significantly with the size of the metacommunity for both unidirectional and bidirectional dispersals, which in turn corroborates that larger metacommunities are more stable than smaller ones. Further, we find that the critical value of the dispersal for the onset of generalized synchronization is smaller(larger) for bidirectional dispersal than that for unidirectional dispersal for smaller(larger) metacommunities. Most importantly, complete synchronization error remains finite even after the onset of generalized synchronization in a wider range of dispersal rate elucidating that the latter can serve as an early warning signal for the extinction of the metacommunity.

Effect of higher-order interactions on chimera states in two populations of Kuramoto oscillators.

We investigate the effect of the fraction of pairwise and higher-order interactions on the emergent dynamics of the two populations of globally coupled Kuramoto oscillators with phase-lag parameters. We find that the stable chimera exists between saddle-node and Hopf bifurcations, while the breathing chimera lives between Hopf and homoclinic bifurcations in the two-parameter phase diagrams. The higher-order interaction facilitates the onset of the bifurcation transitions at a much lower disparity between the inter- and intra-population coupling strengths. Furthermore, the higher-order interaction facilitates the spread of breathing chimera in a large region of the parameter space while suppressing the spread of the stable chimera. A low degree of heterogeneity among the phase-lag parameters promotes the spread of both stable chimera and breathing chimera to a large region of the parameter space for a large fraction of the higher-order coupling. In contrast, a large degree of heterogeneity is found to decrease the spread of both chimera states for a large fraction of the higher-order coupling. A global synchronized state is observed above a critical value of heterogeneity among the phase-lag parameters. We have deduced the low-dimensional evolution equations for the macroscopic order parameters using the Ott-Antonsen Ansatz. We have also deduced the analytical saddle-node and Hopf bifurcation curves from the evolution equations for the macroscopic order parameters and found them to match with the bifurcation curves obtained using the software XPPAUT and with the simulation results.

Highly pathogenic avian influenza (H5N1) infection in crows through ingestion of infected crow carcasses.

The present study was aimed to investigate the role of cannibalism in transmission of H5N1 avian influenza virus to house crows (Corvus splendens). Four crows were intranasally inoculated with 108.0 EID50 (A/crow/India/01CA249/2021) H5N1 highly pathogenic avian influenza (HPAI) virus and were observed for 14 days for any overt signs of illness. Two of the infected crows showed signs of wing paralysis, incoordination, and torticollis. For cannibalism experiment, two crows showing clinical signs were euthanized on 14th day post-infection (dpi) and were kept in the isolator and four naïve healthy crows were introduced along with the euthanized crows. The viscera from the infected carcasses were eaten by all the four crows. Oropharyngeal and cloacal swabs were collected up to 14 days to assess virus excretion. All four crows showed clinical signs viz., dullness, reluctance to move with ruffled feathers on 6th day post cannibalism along with neurological signs including incoordination and paralysis of the wings. All the crows gradually recovered after showing clinical signs and were euthanized on 21st day of observation period. Virus excretion was observed from 3rd to 11th day post cannibalism through both oropharyngeal and cloacal routes with maximum shedding through oropharyngeal route. The virus was isolated from lungs and trachea of one the infected crows at 21st day after euthanasia. All the four crows seroconverted against H5N1 virus infection at 14th day post cannibalism. Our study confirms the transmission of H5N1 virus in crows through cannibalism and highlights how H5N1 virus might circulate in a crow colony once they become infected.

Solvable Dynamics of Coupled High-Dimensional Generalized Limit-Cycle Oscillators.

We introduce a new model consisting of globally coupled high-dimensional generalized limit-cycle oscillators, which explicitly incorporates the role of amplitude dynamics of individual units in the collective dynamics. In the limit of weak coupling, our model reduces to the D-dimensional Kuramoto phase model, akin to a similar classic construction of the well-known Kuramoto phase model from weakly coupled two-dimensional limit-cycle oscillators. For the practically important case of D=3, the incoherence of the model is rigorously proved to be stable for negative coupling (K<0) but unstable for positive coupling (K>0); the locked states are shown to exist if K>0; in particular, the onset of amplitude death is theoretically predicted. For D≥2, the discrete and continuous spectra for both locked states and amplitude death are governed by two general formulas. Our proposed D-dimensional model is physically more reasonable, because it is no longer constrained by fixed amplitude dynamics, which puts the recent studies of the D-dimensional Kuramoto phase model on a stronger footing by providing a more general framework for D-dimensional limit-cycle oscillators.

Oscillation quenching in diffusively coupled dynamical networks with inertial effects.

Self-sustained oscillations are ubiquitous and of fundamental importance for a variety of physical and biological systems including neural networks, cardiac dynamics, and circadian rhythms. In this work, oscillation quenching in diffusively coupled dynamical networks including "inertial" effects is analyzed. By adding inertia to diffusively coupled first-order oscillatory systems, we uncover that even small inertia is capable of eradicating the onset of oscillation quenching. We consolidate the generality of inertia in eradicating oscillation quenching by extensively examining diverse quenching scenarios, where macroscopic oscillations are extremely deteriorated and even completely lost in the corresponding models without inertia. The presence of inertia serves as an additional scheme to eradicate the onset of oscillation quenching, which does not need to tailor the coupling functions. Our findings imply that inertia of a system is an enabler against oscillation quenching in coupled dynamical networks, which, in turn, is helpful for understanding the emergence of rhythmic behaviors in complex coupled systems with amplitude degree of freedom.

Symmetry breaking dynamics induced by mean-field density and low-pass filter.

The phenomenon of spontaneous symmetry breaking facilitates the onset of a plethora of nontrivial dynamical states/patterns in a wide variety of dynamical systems. Spontaneous symmetry breaking results in amplitude and phase variations in a coupled identical oscillator due to the breaking of the prevailing permutational/translational symmetry of the coupled system. Nevertheless, the role and the competing interaction of the low-pass filter and the mean-field density parameter on the symmetry breaking dynamical states are unclear and yet to be explored explicitly. The effect of low pass filtering along with the mean-field parameter is explored in conjugately coupled Stuart-Landau oscillators. The dynamical transitions are examined via bifurcation analysis. We show the emergence of a spontaneous symmetry breaking (asymmetric) oscillatory state, which coexists with a nontrivial amplitude death state. Through the basin of attraction, the multi-stable nature of the spontaneous symmetry breaking state is examined, which reveals that the asymmetric distribution of the initial state favors the spontaneous symmetry breaking dynamics, while the symmetric distribution of initial states gives rise to the nontrivial amplitude death state. In addition, the trade-off between the cut-off frequency of the low-pass filter along with the mean-field density induces and enhances the symmetry breaking dynamical states. Global dynamical transitions are discussed as a function of various system parameters. Analytical stability curves corresponding to the nontrivial amplitude death and oscillation death states are deduced.

Experimental infection and pathology of two highly pathogenic avian influenza H5N1 viruses isolated from crow and chicken in house crows (Corvus splendens).

We investigated the experimental infection of two highly pathogenic avian influenza H5N1 viruses isolated from crow (A/crow/Assam/142119/2008) and chicken (A/chicken/Sikkim/151466/2009) in house crows (Corvus splendens). Both viruses caused infection in crows, where four out of six and three out of six crows succumbed to H5N1 infection within 11 days post challenge by crow and chicken viruses, respectively. The major clinical signs in crows were wing paralysis, circling and torticollis. The virus shedding detected from swabs was not persistent in both crow nor chicken viruses. Both viruses were isolated more frequently from oral swabs than from cloacal swabs. Both virus strains were isolated from brain, lungs, heart, liver, pancreas, spleen, large intestines of crows that succumbed to H5N1 infection. The surviving birds seroconverted in response to H5N1 virus infection. Microscopically, both viruses caused coagulative necrosis in pancreas and kidneys. Brain showed gliosis and neuronal degeneration. This experimental study highlights that crows could be infected with H5N1 viruses from different hosts with minor differences in pathogenicity. Therefore, it is imperative to carry out surveillance of highly pathogenic avian influenza H5N1 virus in synanthropic birds along with biosecurity measures to mitigate the H5N1 spread in poultry population. Keywords: chicken virus; crow virus; highly pathogenic avian influenza; house crows.

Porcine reproductive and respiratory syndrome virus induces concurrent elevation of High Mobility Group Box-1 protein and pro-inflammatory cytokines in experimentally infected piglets.

Porcine Reproductive and Respiratory Syndrome (PRRS), caused by PRRS virus (PRRSV), is one of the most important devastating diseases of pigs, characterized by reproductive failure in sows, and respiratory disease with heavy mortality in piglets. PRRS virus has been reported to elevate the levels of proinflammatory cytokines in the serum of infected pigs. High Mobility Group Box-1 (HMGB-1) protein is a cellular biomolecule belonging to the Danger Associated Molecular Patterns (DAMP) family, which stimulates immune cells to release pro-inflammatory cytokines upon release out of cells. The role of HMGB-1 in the pathogenesis of PRRSV remains largely unknown. In the present study, HMGB-1 levels in serum samples collected from six-week-old piglets infected intra-nasally with 2 × 105.75 TCID50/mL of Indian PRRSV (Ind-297221/2013) was estimated by ELISA up to 21 days post infection (dpi). Pro-inflammatory cytokine mRNA (IL-1ß, IL-6 and TNF- α) expression in PBL was estimated by SYBR green based real time PCR. Mean HMGB-1 concentration in serum was found to be significantly elevated in PRRSV infected piglets on 6 dpi as compared to uninfected control piglets. At mRNA level, significant increase in expression of HMGB-1 was observed from 4 to 5 dpi and from 11 to 13 dpi. IL-1ß and IL-6 mRNA were significantly upregulated between 4 and 6 dpi. Significant increase in TNF-α gene expression was seen only on 7 and 9 dpi. Higher levels of pro-inflammatory cytokines and HMGB-1 could be correlated with fever which was observed within 7 dpi in all the infected piglets and additionally around 13 dpi in the animal that died on 17 dpi. Thus, elevated HMGB-1 level in PRRSV infected piglets could be correlated with concurrent increase in pro-inflammatory cytokine (IL-6) mRNA. In-vitro studies were conducted in PRRSV infected Porcine Pulmonary Alveolar Macrophages (PAM) to ascertain HMGB-1 role in PRRS pathogenesis. The results of both in-vivo and in-vitro studies showed that HMGB-1 plays an important role in mediating the pro-inflammatory cytokine responses in PRRS pathogenesis.

Aging transition in the absence of inactive oscillators.

The role of counter-rotating oscillators in an ensemble of coexisting co- and counter-rotating oscillators is examined by increasing the proportion of the latter. The phenomenon of aging transition was identified at a critical value of the ratio of the counter-rotating oscillators, which was otherwise realized only by increasing the number of inactive oscillators to a large extent. The effect of the mean-field feedback strength in the symmetry preserving coupling is also explored. The parameter space of aging transition was increased abruptly even for a feeble decrease in the feedback strength, and, subsequently, aging transition was observed at a critical value of the feedback strength surprisingly without any counter-rotating oscillators. Further, the study was extended to symmetry breaking coupling using conjugate variables, and it was observed that the symmetry breaking coupling can facilitate the onset of aging transition even in the absence of counter-rotating oscillators and for the unit value of the feedback strength. In general, the parameter space of aging transition was found to increase by increasing the frequency of oscillators and by increasing the proportion of the counter-rotating oscillators in both symmetry preserving and symmetry breaking couplings. Further, the transition from oscillatory to aging occurs via a Hopf bifurcation, while the transition from aging to oscillation death state emerges via the pitchfork bifurcation. Analytical expressions for the critical ratio of the counter-rotating oscillators are deduced to find the stable boundaries of the aging transition.

Elevated level of pro inflammatory cytokine and chemokine expression in chicken bone marrow and monocyte derived dendritic cells following LPS induced maturation.

The study was designed to characterize and compare chicken bone marrow and peripheral blood monocyte derived dendritic cells (chBM-DC and chMoDC) and to evaluate inflammatory cytokine and chemokine alterations in response upon LPS stimulation. Typical morphology was observed in DCs from 48h of culture using recombinant chicken GM-CSF and IL-4. Maturation of DCs with LPS (1µg/ml) showed significant up regulation of mRNA of surface markers (CD40, CD80, CD83, CD86, MHC-II and DC-LAMP (CD208)), pro-inflammatory cytokines (IL-1ß, IL-6, TNF-α (LITAF)), iNOS, chemokine CXCli2 and TLRs4 and 15. Basal level of TLR1 mRNA expression was higher followed by TLR15 in both DCs irrespective of their origin. Expression of iNOS and CXCLi2 mRNA in mature DCs of both origins were higher than other surface molecules and cytokines studied. Hence, its level of expression can also be used as an additional maturation marker for LPS induced chicken dendritic cell maturation along with CD83 and CD40. LPS matured DCs of both origins upregulated IL-12 and IFN-γ. Based on CD40 and CD83 mRNA expression, it was observed that LPS induced the maturation in both DCs, but chMoDCs responded better in expression of surface markers and inflammatory mediator genes.

Experimental demonstration of revival of oscillations from death in coupled nonlinear oscillators.

We experimentally demonstrate that a processing delay, a finite response time, in the coupling can revoke the stability of the stable steady states, thereby facilitating the revival of oscillations in the same parameter space where the coupled oscillators suffered the quenching of oscillation. This phenomenon of reviving of oscillations is demonstrated using two different prototype electronic circuits. Further, the analytical critical curves corroborate that the spread of the parameter space with stable steady state is diminished continuously by increasing the processing delay. Finally, the death state is completely wiped off above a threshold value by switching the stability of the stable steady state to retrieve sustained oscillations in the same parameter space. The underlying dynamical mechanism responsible for the decrease in the spread of the stable steady states and the eventual reviving of oscillation as a function of the processing delay is explained using analytical results.

Disparity-driven heterogeneous nucleation in finite-size adaptive networks.

Phase transitions are crucial in shaping the collective dynamics of a broad spectrum of natural systems across disciplines. Here, we report two distinct heterogeneous nucleation facilitating single step and multistep phase transitions to global synchronization in a finite-size adaptive network due to the trade off between time scale adaptation and coupling strength disparities. Specifically, small intracluster nucleations coalesce either at the population interface or within the populations resulting in the two distinct phase transitions depending on the degree of the disparities. We find that the coupling strength disparity largely controls the nature of phase transition in the phase diagram irrespective of the adaptation disparity. We provide a mesoscopic description for the cluster dynamics using the collective coordinates approach that brilliantly captures the multicluster dynamics among the populations leading to distinct phase transitions. Further, we also deduce the upper bound for the coupling strength for the existence of two intraclusters explicitly in terms of adaptation and coupling strength disparities. These insights may have implications across domains ranging from neurological disorders to segregation dynamics in social networks.

Hebbian and anti-Hebbian adaptation-induced dynamical states in adaptive networks.

We investigate the interplay of an external forcing and an adaptive network, whose connection weights coevolve with the dynamical states of the phase oscillators. In particular, we consider the Hebbian and anti-Hebbian adaptation mechanisms for the evolution of the connection weights. The Hebbian adaptation manifests several interesting partially synchronized states, such as phase and frequency clusters, bump state, bump frequency phase clusters, and forced entrained clusters, in addition to the completely synchronized and forced entrained states. Anti-Hebbian adaptation facilitates the manifestation of the itinerant chimera characterized by randomly evolving coherent and incoherent domains along with some of the aforementioned dynamical states induced by the Hebbian adaptation. We introduce three distinct measures for the strength of incoherence based on the local standard deviations of the time-averaged frequency and the instantaneous phase of each oscillator, and the time-averaged mean frequency for each bin to corroborate the distinct dynamical states and to demarcate the two parameter phase diagrams. We also arrive at the existence and stability conditions for the forced entrained state using the linear stability analysis, which is found to be consistent with the simulation results.

Exotic swarming dynamics of high-dimensional swarmalators.

Swarmalators are oscillators that can swarm as well as sync via a dynamic balance between their spatial proximity and phase similarity. Swarmalator models employed so far in the literature comprise only one-dimensional phase variables to represent the intrinsic dynamics of the natural collectives. Nevertheless, the latter can indeed be represented more realistically by high-dimensional phase variables. For instance, the alignment of velocity vectors in a school of fish or a flock of birds can be more realistically set up in three-dimensional space, while the alignment of opinion formation in population dynamics could be multidimensional, in general. We present a generalized D-dimensional swarmalator model, which more accurately captures self-organizing behaviors of a plethora of real-world collectives by self-adaptation of high-dimensional spatial and phase variables. For a more sensible visualization and interpretation of the results, we restrict our simulations to three-dimensional spatial and phase variables. Our model provides a framework for modeling complicated processes such as flocking, schooling of fish, cell sorting during embryonic development, residential segregation, and opinion dynamics in social groups. We demonstrate its versatility by capturing the maneuvers of a school of fish, qualitatively and quantitatively, by a suitable extension of the original model to incorporate appropriate features besides a gallery of its intrinsic self-organizations for various interactions. We expect the proposed high-dimensional swarmalator model to be potentially useful in describing swarming systems and programmable and reconfigurable collectives in a wide range of disciplines, including the physics of active matter, developmental biology, sociology, and engineering.

Reviving oscillations in coupled nonlinear oscillators.

By introducing a processing delay in the coupling, we find that it can effectively annihilate the quenching of oscillation, amplitude death (AD), in a network of coupled oscillators by switching the stability of AD. It revives the oscillation in the AD regime to retain sustained rhythmic functioning of the networks, which is in sharp contrast to the propagation delay with the tendency to induce AD. This processing delay-induced phenomenon occurs both with and without the propagation delay. Further this effect is rather general from two coupled to networks of oscillators in all known scenarios that can exhibit AD, and it has a wide range of applications where sustained oscillations should be retained for proper functioning of the systems.

Abrupt symmetry-preserving transition from the chimera state.

We consider two populations of the globally coupled Sakaguchi-Kuramoto model with the same intra- and interpopulations coupling strengths. The oscillators constituting the intrapopulation are identical whereas the interpopulations are nonidentical with a frequency mismatch. The asymmetry parameters ensure the permutation symmetry among the oscillators constituting the intrapopulation and a reflection symmetry among the oscillators constituting the interpopulation. We show that the chimera state manifests by spontaneously breaking the reflection symmetry and also exists in almost in the entire explored range of the asymmetry parameter without restricting to the near π/2 values of it. The saddle-node bifurcation mediates the abrupt transition from the symmetry breaking chimera state to the symmetry-preserving synchronized oscillatory state in the reverse trace, whereas the homoclinic bifurcation mediates the transition from the synchronized oscillatory state to synchronized steady state in the forward trace. We deduce the governing equations of motion for the macroscopic order parameters employing the finite-dimensional reduction by Watanabe and Strogatz. The analytical saddle-node and homoclinic bifurcation conditions agree well with the simulations results and the bifurcation curves.

Monkeypox: a model-free analysis.

Monkeypox is a zoonotic disease caused by a virus that is a member of the orthopox genus, which has been causing an outbreak since May 2022 around the globe outside of its country of origin Democratic Republic of the Congo, Africa. Here we systematically analyze the data of cumulative infection per day adapting model-free analysis, in particular, statistically using the power law distribution, and then separately we use reservoir computing-based Echo state network (ESN) to predict and forecast the disease spread. We also use the power law to characterize the country-specific infection rate which will characterize the growth pattern of the disease spread such as whether the disease spread reached a saturation state or not. The results obtained from power law method were then compared with the outbreak of the smallpox virus in 1907 in Tokyo, Japan. The results from the machine learning-based method are also validated by the power law scaling exponent, and the correlation has been reported.

Multistable chimera states in a smallest population of three coupled oscillators.

We uncover the emergence of distinct sets of multistable chimera states in addition to chimera death and synchronized states in a smallest population of three globally coupled oscillators with mean-field diffusive coupling. Sequence of torus bifurcations result in the manifestation of distinct periodic orbits as a function of the coupling strength, which in turn result in the genesis of distinct chimera states constituted by two synchronized oscillators coexisting with an asynchronous oscillator. Two subsequent Hopf bifurcations result in homogeneous and inhomogeneous steady states resulting in desynchronized steady states and chimera death state among the coupled oscillators. The periodic orbits and the steady states lose their stability via a sequence of saddle-loop and saddle-node bifurcations finally resulting in a stable synchronized state. We have generalized these results to N coupled oscillators and also deduced the variational equations corresponding to the perturbation transverse to the synchronization manifold and corroborated the synchronized state in the two-parameter phase diagrams using its largest eigenvalue. Chimera states in three coupled oscillators emerge as a solitary state in N coupled oscillator ensemble.

Phase transitions in an adaptive network with the global order parameter adaptation.

We consider an adaptive network of Kuramoto oscillators with purely dyadic coupling, where the adaption is proportional to the degree of the global order parameter. We find only the continuous transition to synchronization via the pitchfork bifurcation, an abrupt synchronization (desynchronization) transition via the pitchfork (saddle-node) bifurcation resulting in the bistable region R_{1}. This is a smooth continuous transition to a weakly synchronized state via the pitchfork bifurcation followed by a subsequent abrupt transition to a strongly synchronized state via a second saddle-node bifurcation along with an abrupt desynchronization transition via the first saddle-node bifurcation resulting in the bistable region R_{2} between the weak and strong synchronization. The transition goes from the bistable region R_{1} to the bistable region R_{2}, and transition from the incoherent state to the bistable region R_{2} as a function of the coupling strength for various ranges of the degree of the global order parameter and the adaptive coupling strength. We also find that the phase-lag parameter enlarges the spread of the weakly synchronized state and the bistable states R_{1} and R_{2} to a large region of the parameter space. We also derive the low-dimensional evolution equations for the global order parameters using the Ott-Antonsen ansatz. Further, we also deduce the pitchfork, first and second saddle-node bifurcation conditions, which is in agreement with the simulation results.

Impact of connection delays on noise-induced spatiotemporal patterns in neuronal networks.

In the present work, we investigate the nontrivial roles of independent Gaussian noise and time-delayed coupling on the synchronous dynamics and coherence property of Fitz Hugh-Nagumo neurons on small-world networks by numerical simulations. First, it is shown that an intermediate level of noise in the neuronal networks can optimally induce a temporal coherence state when the delay in the coupling is absent. We find that this phenomenon is robust to changes of the coupling strength and the rewiring probability of small-world networks. Then, when appropriately tuned delays with moderate values are included in the coupling, the neurons on the networks can reach higher ordered spatiotemporal patterns which are the most coherent in time and almost synchronized in space. Moreover, the tuned delays are within a range, and the period of the firing activity is delay-dependent which equals nearly to the length of the coupling delay. This result implies that the higher ordered spatiotemporal dynamics induced by intermediate delays could be the result of a locking between the period-1 neuronal spiking activity and the delay. The performance of moderate delays in enhancing the ordered spatiotemporal patterns is also examined to be robust against variations of the network randomness.