@article{StarkBachGuill2021, author = {Stark, Markus and Bach, Moritz and Guill, Christian}, title = {Patch isolation and periodic environmental disturbances have idiosyncratic effects on local and regional population variabilities in meta-food chains}, series = {Theoretical ecology}, volume = {14}, journal = {Theoretical ecology}, number = {3}, publisher = {Springer}, address = {Dordrecht}, issn = {1874-1738}, doi = {10.1007/s12080-021-00510-0}, pages = {489 -- 500}, year = {2021}, abstract = {While habitat loss is a known key driver of biodiversity decline, the impact of other landscape properties, such as patch isolation, is far less clear. When patch isolation is low, species may benefit from a broader range of foraging opportunities, but are at the same time adversely affected by higher predation pressure from mobile predators. Although previous approaches have successfully linked such effects to biodiversity, their impact on local and metapopulation dynamics has largely been ignored. Since population dynamics may also be affected by environmental disturbances that temporally change the degree of patch isolation, such as periodic changes in habitat availability, accurate assessment of its link with isolation is highly challenging. To analyze the effect of patch isolation on the population dynamics on different spatial scales, we simulate a three-species meta-food chain on complex networks of habitat patches and assess the average variability of local populations and metapopulations, as well as the level of synchronization among patches. To evaluate the impact of periodic environmental disturbances, we contrast simulations of static landscapes with simulations of dynamic landscapes in which 30 percent of the patches periodically become unavailable as habitat. We find that increasing mean patch isolation often leads to more asynchronous population dynamics, depending on the parameterization of the food chain. However, local population variability also increases due to indirect effects of increased dispersal mortality at high mean patch isolation, consequently destabilizing metapopulation dynamics and increasing extinction risk. In dynamic landscapes, periodic changes of patch availability on a timescale much slower than ecological interactions often fully synchronize the dynamics. Further, these changes not only increase the variability of local populations and metapopulations, but also mostly overrule the effects of mean patch isolation. This may explain the often small and inconclusive impact of mean patch isolation in natural ecosystems.}, language = {en} } @article{BoersBookhagenMarwanetal.2016, author = {Boers, Niklas and Bookhagen, Bodo and Marwan, Norbert and Kurths, J{\"u}rgen}, title = {Spatiotemporal characteristics and synchronization of extreme rainfall in South America with focus on the Andes Mountain range}, series = {Climate dynamics : observational, theoretical and computational research on the climate system}, volume = {46}, journal = {Climate dynamics : observational, theoretical and computational research on the climate system}, publisher = {Springer}, address = {New York}, issn = {0930-7575}, doi = {10.1007/s00382-015-2601-6}, pages = {601 -- 617}, year = {2016}, abstract = {The South American Andes are frequently exposed to intense rainfall events with varying moisture sources and precipitation-forming processes. In this study, we assess the spatiotemporal characteristics and geographical origins of rainfall over the South American continent. Using high-spatiotemporal resolution satellite data (TRMM 3B42 V7), we define four different types of rainfall events based on their (1) high magnitude, (2) long temporal extent, (3) large spatial extent, and (4) high magnitude, long temporal and large spatial extent combined. In a first step, we analyze the spatiotemporal characteristics of these events over the entire South American continent and integrate their impact for the main Andean hydrologic catchments. Our results indicate that events of type 1 make the overall highest contributions to total seasonal rainfall (up to 50\%). However, each consecutive episode of the infrequent events of type 4 still accounts for up to 20\% of total seasonal rainfall in the subtropical Argentinean plains. In a second step, we employ complex network theory to unravel possibly non-linear and long-ranged climatic linkages for these four event types on the high-elevation Altiplano-Puna Plateau as well as in the main river catchments along the foothills of the Andes. Our results suggest that one to two particularly large squall lines per season, originating from northern Brazil, indirectly trigger large, long-lasting thunderstorms on the Altiplano Plateau. In general, we observe that extreme rainfall in the catchments north of approximately 20 degrees S typically originates from the Amazon Basin, while extreme rainfall at the eastern Andean foothills south of 20 degrees S and the Puna Plateau originates from southeastern South America.}, language = {en} } @article{KuznetsovTurukinaChernyshovetal.2016, author = {Kuznetsov, Alexander P. and Turukina, Ludmila V. and Chernyshov, Nikolai Yu and Sedova, Yuliya V.}, title = {Oscillations and Synchronization in a System of Three Reactively Coupled Oscillators}, series = {International journal of bifurcation and chaos : in applied sciences and engineering}, volume = {26}, journal = {International journal of bifurcation and chaos : in applied sciences and engineering}, publisher = {World Scientific}, address = {Singapore}, issn = {0218-1274}, doi = {10.1142/S0218127416500103}, pages = {31 -- 39}, year = {2016}, abstract = {We consider a system of three interacting van der Pol oscillators with reactive coupling. Phase equations are derived, using proper order of expansion over the coupling parameter. The dynamics of the system is studied by means of the bifurcation analysis and with the method of Lyapunov exponent charts. Essential and physically meaningful features of the reactive coupling are discussed.}, language = {en} } @article{NagornovOsipoyKomarovetal.2016, author = {Nagornov, Roman and Osipoy, Grigory and Komarov, Maxim and Pikovskij, Arkadij and Shilnikov, Andrey}, title = {Mixed-mode synchronization between two inhibitory neurons with post-inhibitory rebound}, series = {Communications in nonlinear science \& numerical simulation}, volume = {36}, journal = {Communications in nonlinear science \& numerical simulation}, publisher = {Elsevier}, address = {Amsterdam}, issn = {1007-5704}, doi = {10.1016/j.cnsns.2015.11.024}, pages = {175 -- 191}, year = {2016}, abstract = {We study an array of activity rhythms generated by a half-center oscillator (HCO), represented by a pair of reciprocally coupled neurons with post-inhibitory rebounds (PIR). Such coupling induced bursting possesses two time scales, one for fast spiking and another for slow quiescent periods, is shown to exhibit an array of synchronization properties. We discuss several HCO configurations constituted by two endogenous bursters, by tonic-spiking and quiescent neurons, as well as mixed-mode configurations composed of neurons of different type. We demonstrate that burst synchronization can be accompanied by complex, often chaotic, interactions of fast spikes within synchronized bursts. (C) 2015 Elsevier B.V. All rights reserved.}, language = {en} } @article{KomarovPikovskij2014, author = {Komarov, Maxim and Pikovskij, Arkadij}, title = {The Kuramoto model of coupled oscillators with a bi-harmonic coupling function}, series = {Physica : D, Nonlinear phenomena}, volume = {289}, journal = {Physica : D, Nonlinear phenomena}, publisher = {Elsevier}, address = {Amsterdam}, issn = {0167-2789}, doi = {10.1016/j.physd.2014.09.002}, pages = {18 -- 31}, year = {2014}, abstract = {We study synchronization in a Kuramoto model of globally coupled phase oscillators with a bi-harmonic coupling function, in the thermodynamic limit of large populations. We develop a method for an analytic solution of self-consistent equations describing uniformly rotating complex order parameters, both for single-branch (one possible state of locked oscillators) and multi-branch (two possible values of locked phases) entrainment. We show that synchronous states coexist with the neutrally linearly stable asynchronous regime. The latter has a finite life time for finite ensembles, this time grows with the ensemble size as a power law. (C) 2014 Elsevier B.V. All rights reserved.}, language = {en} } @article{HuangChenKurths2011, author = {Huang, Tingwen and Chen, Guanrong and Kurths, J{\"u}rgen}, title = {Synchronization of chaotic of chaotic systems with time-varying coup{\"o}ing delays}, series = {Discrete and continuous dynamical systems : a journal bridging mathematics and sciences ; Series B, Mathematical modelling, analysis and computations}, volume = {16}, journal = {Discrete and continuous dynamical systems : a journal bridging mathematics and sciences ; Series B, Mathematical modelling, analysis and computations}, number = {4}, publisher = {American Institute of Mathematical Sciences}, address = {Springfield}, issn = {1531-3492}, doi = {10.3934/dcdsb.2011.16.1071}, pages = {1071 -- 1082}, year = {2011}, abstract = {In this paper, we study the complete synchronization of a class of time-varying delayed coupled chaotic systems using feedback control. In terms of Linear Matrix Inequalities, a sufficient condition is obtained through using a Lyapunov-Krasovskii functional and differential equation in equalities. The conditions can be easily verified and implemented. We present two simulation examples to illustrate the effectiveness of the proposed method.}, language = {en} } @article{SeemuellerMuellerRoesler2012, author = {Seem{\"u}ller, Anna and M{\"u}ller, E. M. and R{\"o}sler, Frank}, title = {EEG-power and -coherence changes in a unimodal and a crossmodal working memory task with visual and kinesthetic stimuli}, series = {International journal of psychophysiology}, volume = {83}, journal = {International journal of psychophysiology}, number = {1}, publisher = {Elsevier}, address = {Amsterdam}, issn = {0167-8760}, doi = {10.1016/j.ijpsycho.2011.10.009}, pages = {87 -- 95}, year = {2012}, abstract = {We investigated EEG-power and EEG-coherence changes in a unimodal and a crossmodal matching-to-sample working memory task with either visual or kinesthetic stimuli. Angle-shaped trajectories were used as stimuli presented either as a moving dot on a screen or as a passive movement of a haptic device. Effects were evaluated during the different phases of encoding, maintenance, and recognition. Alpha power was modulated during encoding by the stimulus modality, and in crossmodal conditions during encoding and maintenance by the expected modality of the upcoming test stimulus. These power modulations were observed over modality-specific cortex regions. Systematic changes of coherence for crossmodal compared to unimodal tasks were not observed during encoding and maintenance but only during recognition. There, coherence in the theta-band increased between electrode sites over left central and occipital cortex areas in the crossmodal compared to the unimodal conditions. The results underline the importance of modality-specific representations and processes in unimodal and crossmodal working memory tasks. Crossmodal recognition of visually and kinesthetically presented object features seems to be related to a direct interaction of somatosensory/motor and visual cortex regions by means of long-range synchronization in the theta-band and such interactions seem to take place at the beginning of the recognition phase, i.e. when crossmodal transfer is actually necessary.}, language = {en} }