@article{PereiraBaptistaReyesetal.2009, author = {Pereira, Tiago and Baptista, Murilo da Silva and Reyes, Marcelo B. and Caldas, Ibere Luiz and Sartorelli, Jos{\´e} Carlos and Kurths, J{\"u}rgen}, title = {A scenario for torus T-2 destruction via a global bifurcation}, issn = {0960-0779}, doi = {10.1016/j.chaos.2007.06.115}, year = {2009}, abstract = {We show a scenario of a two-frequeney torus breakdown, in which a global bifurcation occurs due to the collision of a quasi-periodic torus T-2 with saddle points, creating a heteroclinic saddle connection. We analyze the geometry of this torus-saddle collision by showing the local dynamics and the invariant manifolds (global dynamics) of the saddle points. Moreover, we present detailed evidences of a heteroclinic saddle-focus orbit responsible for the type- if intermittency induced by this global bifurcation. We also characterize this transition to chaos by measuring the Lyapunov exponents and the scaling laws.}, language = {en} } @article{ZaikinKurths2000, author = {Zaikin, Alexei A. and Kurths, J{\"u}rgen}, title = {Additive noise and noise-induced nonequilibrium phase transitions}, isbn = {1-563-96826-6}, year = {2000}, language = {en} } @article{ZaikinKurths2001, author = {Zaikin, Alexei A. and Kurths, J{\"u}rgen}, title = {Additive noise in noise-induced nonequilibrium transitions}, issn = {1054-1500}, year = {2001}, language = {en} } @article{ParkRosenblumKurthsetal.1999, author = {Park, Eun Hyoung and Rosenblum, Michael and Kurths, J{\"u}rgen and Zaks, Michael A.}, title = {Alternating locking ratios in imperfect phase synchronization}, year = {1999}, language = {en} } @article{KolodnerAbelKurthsetal.1999, author = {Kolodner, P. and Abel, Markus and Kurths, J{\"u}rgen and Voss, Henning U.}, title = {Amplitude equations from spatiotemporal binary-fluid convection data}, year = {1999}, language = {en} } @article{AllefeldKurths2004, author = {Allefeld, Carsten and Kurths, J{\"u}rgen}, title = {An approach to multivariate phase synchronization analysis and its application to event-related potentials}, issn = {0218-1274}, year = {2004}, abstract = {A method for the multivariate analysis of statistical phase synchronization phenomena in empirical data is presented. A first statistical approach is complemented by a stochastic dynamic model, to result in a data analysis algorithm which can in a specific sense be shown to be a generic multivariate statistical phase synchronization analysis. The method is applied to EEG data from a psychological experiment, obtaining results which indicate the relevance of this method in the context of cognitive science as well as in other fields}, language = {en} } @misc{AllefeldKurths2004, author = {Allefeld, Carsten and Kurths, J{\"u}rgen}, title = {An approach to multivariate phase synchronization analysis and its application to event-related potentials}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus-20106}, year = {2004}, abstract = {A method for the multivariate analysis of statistical phase synchronization phenomena in empirical data is presented. A first statistical approach is complemented by a stochastic dynamic model, to result in a data analysis algorithm which can in a specific sense be shown to be a generic multivariate statistical phase synchronization analysis. The method is applied to EEG data from a psychological experiment, obtaining results which indicate the relevance of this method in the context of cognitive science as well as in other fields.}, language = {en} } @misc{CiemerRehmKurthsetal.2020, author = {Ciemer, Catrin and Rehm, Lars and Kurths, J{\"u}rgen and Donner, Reik Volker and Winkelmann, Ricarda and Boers, Niklas}, title = {An early-warning indicator for Amazon droughts exclusively based on tropical Atlantic sea surface temperatures}, series = {Postprints der Universit{\"a}t Potsdam : Mathematisch-Naturwissenschaftliche Reihe}, journal = {Postprints der Universit{\"a}t Potsdam : Mathematisch-Naturwissenschaftliche Reihe}, number = {9}, issn = {1866-8372}, doi = {10.25932/publishup-52586}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus4-525863}, pages = {12}, year = {2020}, abstract = {Droughts in tropical South America have an imminent and severe impact on the Amazon rainforest and affect the livelihoods of millions of people. Extremely dry conditions in Amazonia have been previously linked to sea surface temperature (SST) anomalies in the adjacent tropical oceans. Although the sources and impacts of such droughts have been widely studied, establishing reliable multi-year lead statistical forecasts of their occurrence is still an ongoing challenge. Here, we further investigate the relationship between SST and rainfall anomalies using a complex network approach. We identify four ocean regions which exhibit the strongest overall SST correlations with central Amazon rainfall, including two particularly prominent regions in the northern and southern tropical Atlantic. Based on the time-dependent correlation between SST anomalies in these two regions alone, we establish a new early-warning method for droughts in the central Amazon basin and demonstrate its robustness in hindcasting past major drought events with lead-times up to 18 months.}, language = {en} } @article{CiemerRehmKurthsetal.2020, author = {Ciemer, Catrin and Rehm, Lars and Kurths, J{\"u}rgen and Donner, Reik Volker and Winkelmann, Ricarda and Boers, Niklas}, title = {An early-warning indicator for Amazon droughts exclusively based on tropical Atlantic sea surface temperatures}, series = {Environmental Research Letters}, volume = {15}, journal = {Environmental Research Letters}, number = {9}, publisher = {IOP - Institute of Physics Publishing}, address = {Bristol}, pages = {10}, year = {2020}, abstract = {Droughts in tropical South America have an imminent and severe impact on the Amazon rainforest and affect the livelihoods of millions of people. Extremely dry conditions in Amazonia have been previously linked to sea surface temperature (SST) anomalies in the adjacent tropical oceans. Although the sources and impacts of such droughts have been widely studied, establishing reliable multi-year lead statistical forecasts of their occurrence is still an ongoing challenge. Here, we further investigate the relationship between SST and rainfall anomalies using a complex network approach. We identify four ocean regions which exhibit the strongest overall SST correlations with central Amazon rainfall, including two particularly prominent regions in the northern and southern tropical Atlantic. Based on the time-dependent correlation between SST anomalies in these two regions alone, we establish a new early-warning method for droughts in the central Amazon basin and demonstrate its robustness in hindcasting past major drought events with lead-times up to 18 months.}, language = {en} } @article{ZakharovaKurthsVadivasovaetal.2011, author = {Zakharova, Anna and Kurths, J{\"u}rgen and Vadivasova, Tatyana and Koseska, Aneta}, title = {Analysing dynamical behavior of cellular networks via stochastic bifurcations}, series = {PLoS one}, volume = {6}, journal = {PLoS one}, number = {5}, publisher = {PLoS}, address = {San Fransisco}, issn = {1932-6203}, doi = {10.1371/journal.pone.0019696}, pages = {12}, year = {2011}, abstract = {The dynamical structure of genetic networks determines the occurrence of various biological mechanisms, such as cellular differentiation. However, the question of how cellular diversity evolves in relation to the inherent stochasticity and intercellular communication remains still to be understood. Here, we define a concept of stochastic bifurcations suitable to investigate the dynamical structure of genetic networks, and show that under stochastic influence, the expression of given proteins of interest is defined via the probability distribution of the phase variable, representing one of the genes constituting the system. Moreover, we show that under changing stochastic conditions, the probabilities of expressing certain concentration values are different, leading to different functionality of the cells, and thus to differentiation of the cells in the various types.}, language = {en} } @article{KomalapriyaRomanoBlascoThieletal.2009, author = {Komalapriya, Chandrasekaran and Romano Blasco, Maria Carmen and Thiel, Marco and Schwarz, Udo and Kurths, J{\"u}rgen and Simonotto, Jennifer and Furman, Michael and Ditto, William L. and Carney, Paul R.}, title = {Analysis of high-resulution microelectrode EEG recordings in an animal model of spontaneous limbic seizures}, issn = {0218-1274}, doi = {10.1142/S0218127409023226}, year = {2009}, language = {en} } @article{MalikBookhagenMarwanetal.2012, author = {Malik, Nishant and Bookhagen, Bodo and Marwan, Norbert and Kurths, J{\"u}rgen}, title = {Analysis of spatial and temporal extreme monsoonal rainfall over South Asia using complex networks}, series = {Climate dynamics : observational, theoretical and computational research on the climate system}, volume = {39}, journal = {Climate dynamics : observational, theoretical and computational research on the climate system}, number = {3-4}, publisher = {Springer}, address = {New York}, issn = {0930-7575}, doi = {10.1007/s00382-011-1156-4}, pages = {971 -- 987}, year = {2012}, abstract = {We present a detailed analysis of summer monsoon rainfall over the Indian peninsular using nonlinear spatial correlations. This analysis is carried out employing the tools of complex networks and a measure of nonlinear correlation for point processes such as rainfall, called event synchronization. This study provides valuable insights into the spatial organization, scales, and structure of the 90th and 94th percentile rainfall events during the Indian summer monsoon (June-September). We furthermore analyse the influence of different critical synoptic atmospheric systems and the impact of the steep Himalayan topography on rainfall patterns. The presented method not only helps us in visualising the structure of the extreme-event rainfall fields, but also identifies the water vapor pathways and decadal-scale moisture sinks over the region. Furthermore a simple scheme based on complex networks is presented to decipher the spatial intricacies and temporal evolution of monsoonal rainfall patterns over the last 6 decades.}, language = {en} } @article{ZhouKurthsHu2001, author = {Zhou, Changsong and Kurths, J{\"u}rgen and Hu, B.}, title = {Array-enhanced coherence resonance: Nontrivial effects of heterogeneity and spatial independence of noise}, year = {2001}, language = {en} } @article{OsipovRosenblumPikovskijetal.1997, author = {Osipov, Grigory V. and Rosenblum, Michael and Pikovskij, Arkadij and Zaks, Michael A. and Kurths, J{\"u}rgen}, title = {Attractor-repeller collision and eyelet intermittency at the transition to phase synchronization}, year = {1997}, abstract = {The chaotically driven circle map is considered as the simplest model ofphase synchronization of a chaotic continuous-time oscillator by external periodic force. The phase dynamics is analyzed via phase-locking regions of the periodic cycles embedded in the strange attractor. It is shown that full synchronization, where all the periodic cycles are phase locked, disappears via the attractor-repeller collision. Beyond the transition an intermittent regime with exponentially rare phase slips, resulting from the trajectory's hits on an eyelet, is observed.}, language = {en} } @article{AnishchenkoVadivasovaKurthsetal.2004, author = {Anishchenko, Vadim S. and Vadivasova, T. E. and Kurths, J{\"u}rgen and Okrokvertskhov, G. A. and Strelkova, G. I.}, title = {Autocorrelation function and spectral linewidth of spiral chaos in a physical experiment}, issn = {1063-651X}, year = {2004}, abstract = {We present results of physical experiments where we measure the autocorrelation function (ACF) and the spectral linewidth of the basic frequency of a spiral chaotic attractor in a generator with inertial nonlinearity both without and in the presence of external noise. It is shown that the ACF of spiral attractors decays according to an exponential law with a decrement which is defined by the phase diffusion coefficient. It is also established that the evolution of the instantaneous phase can be approximated by a Wiener random process}, language = {en} } @article{BelykhOsipovKucklaenderetal.2005, author = {Belykh, Vladimir N. and Osipov, Grigory V. and Kuckl{\"a}nder, Nina and Blasius, Bernd and Kurths, J{\"u}rgen}, title = {Automatic control of phase synchronization in coupled complex oscillators}, year = {2005}, abstract = {We present an automatic control method for phase locking of regular and chaotic non-identical oscillations, when all subsystems interact via feedback. This method is based on the well known principle of feedback control which takes place in nature and is successfully used in engineering. In contrast to unidirectional and bidirectional coupling, the approach presented here supposes the existence of a special controller, which allows to change the parameters of the controlled systems. First we discuss general principles of automatic phase synchronization (PS) for arbitrary coupled systems with a controller whose input is given by a special quadratic form of coordinates of the individual systems and its output is a result of the application of a linear differential operator. We demonstrate the effectiveness of our approach for controlled PS on several examples: (i) two coupled regular oscillators, (ii) coupled regular and chaotic oscillators, (iii) two coupled chaotic R"ossler oscillators, (iv) two coupled foodweb models, (v) coupled chaotic R"ossler and Lorenz oscillators, (vi) ensembles of locally coupled regular oscillators, (vii) ensembles of locally coupled chaotic oscillators, and (viii) ensembles of globally coupled chaotic oscillators.}, language = {en} } @article{FrascaBergnerKurthsetal.2012, author = {Frasca, Mattia and Bergner, Andre and Kurths, J{\"u}rgen and Fortuna, Luigi}, title = {Bifurcations in a star-like network of Stuart-Landau oscillators}, series = {International journal of bifurcation and chaos : in applied sciences and engineering}, volume = {22}, journal = {International journal of bifurcation and chaos : in applied sciences and engineering}, number = {7}, publisher = {World Scientific}, address = {Singapore}, issn = {0218-1274}, doi = {10.1142/S0218127412501738}, pages = {13}, year = {2012}, abstract = {In this paper, we analytically study a star motif of Stuart-Landau oscillators, derive the bifurcation diagram and discuss the different forms of synchronization arising in such a system. Despite the parameter mismatch between the central node and the peripheral ones, an analytical approach independent of the number of units in the system has been proposed. The approach allows to calculate the separatrices between the regions with distinct dynamical behavior and to determine the nature of the different transitions to synchronization appearing in the system. The theoretical analysis is supported by numerical results.}, language = {en} } @article{GowinSaparinKurthsetal.2001, author = {Gowin, W. and Saparin, Peter and Kurths, J{\"u}rgen and Felsenberg, D.}, title = {Bone Architecture assessment with Measures of Complexity}, year = {2001}, language = {en} } @article{GowinSaparinKurths2001, author = {Gowin, W. and Saparin, Peter and Kurths, J{\"u}rgen}, title = {Bone architecture quantification: Measures of complexity compared to failure lead results}, year = {2001}, language = {en} } @article{VianaGrebogiPintoetal.2005, author = {Viana, R. L. and Grebogi, Celso and Pinto, S. E. D. and Lopes, S. R. and Batista, A. M. and Kurths, J{\"u}rgen}, title = {Bubbling bifurcation : loss of synchronization and shadowing breakdown in complex systems}, year = {2005}, abstract = {Complex dynamical systems with many degrees of freedom may exhibit a wealth of collective phenomena related to high-dimensional chaos. This paper focuses on a lattice of coupled logistic maps to investigate the relationship between the loss of chaos synchronization and the onset of shadowing breakdown via unstable dimension variability in complex systems. In the neighborhood of the critical transition to strongly non-hyperbolic behavior, the system undergoes on-off intermittency with respect to the synchronization manifold. This has been confirmed by numerical diagnostics of synchronization and non-hyperbolic behavior, the latter using the statistical properties of finite-time Lyapunov exponents. (c) 2005 Elsevier B.V. All rights reserved}, language = {en} } @article{BaptistaKurths2005, author = {Baptista, Murilo da Silva and Kurths, J{\"u}rgen}, title = {Chaotic channel}, issn = {1539-3755}, year = {2005}, abstract = {This work combines the theory of chaotic synchronization with the theory of information in order to introduce the chaotic channel, an active medium formed by connected chaotic systems. This subset of a large chaotic net represents the path along which information flows. We show that the possible amount of information exchange between the transmitter, where information enters the net, and the receiver, the destination of the information, is proportional to the level of synchronization between these two special subsystems}, language = {en} } @article{SenthilkumarKurths2010, author = {Senthilkumar, Dharmapuri Vijayan and Kurths, J{\"u}rgen}, title = {Characteristics and synchronization of time-delay systems driven by a common noise}, issn = {1951-6355}, doi = {10.1140/epjst/e2010-01273-4}, year = {2010}, abstract = {We investigate the characteristics of time-delay systems in the presence of Gaussian noise. We show that the delay time embedded in the time series of time-delay system with constant delay cannot be estimated in the presence noise for appropriate values of noise intensity thereby forbidding any possibility of phase space reconstruction. We also demonstrate the existence of complete synchronization between two independent identical time-delay systems driven by a common noise without explicitly establishing any external coupling between them.}, language = {en} } @unpublished{WittNeimanKurths1997, author = {Witt, Annette and Neiman, Alexander and Kurths, J{\"u}rgen}, title = {Characterizing the dynamics of stochastic bistable systems by measures of complexity}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus-14556}, year = {1997}, abstract = {The dynamics of noisy bistable systems is analyzed by means of Lyapunov exponents and measures of complexity. We consider both the classical Kramers problem with additive white noise and the case when the barrier fluctuates due to additional external colored noise. In case of additive noise we calculate the Lyapunov exponents and all measures of complexity analytically as functions of the noise intensity resp. the mean escape time. For the problem of fluctuating barrier the usual description of the dynamics with the mean escape time is not sufficient. The application of the concept of measures of complexity allows to describe the structures of motion in more detail. Most complexity measures sign the value of correlation time at which the phenomenon of resonant activation occurs with an extremum.}, language = {en} } @book{WittNeimanKurths1997, author = {Witt, Annette and Neiman, Alexander and Kurths, J{\"u}rgen}, title = {Characterizing the dynamics of stochastic bistable systems by measures of complexity}, series = {Preprint NLD}, volume = {36}, journal = {Preprint NLD}, publisher = {Univ. Potsdam}, address = {Potsdam}, issn = {1432-2935}, pages = {20 S. : graph. Darst.}, year = {1997}, language = {en} } @article{WittNeimanKurths1997, author = {Witt, Annette and Neiman, Alexander and Kurths, J{\"u}rgen}, title = {Charakterizing the dynamics of stochastic bistable systems by measures of complexity}, year = {1997}, language = {en} } @article{MarwanTrauthSchwarzetal.1999, author = {Marwan, Norbert and Trauth, Martin H. and Schwarz, Udo and Kurths, J{\"u}rgen and Strecker, Manfred}, title = {Climate dynamics of varved pleistocene lake sediments in nw Argentina}, issn = {1029-7006}, year = {1999}, language = {en} } @article{SpahnKatzorkePetzschmannetal.1997, author = {Spahn, Frank and Katzorke, Ines and Petzschmann, Olaf and Schwarz, Udo and Kurths, J{\"u}rgen}, title = {Cluster instabiliy of granular assemblies}, year = {1997}, language = {en} } @article{SpahnSchwarzKurths1997, author = {Spahn, Frank and Schwarz, Udo and Kurths, J{\"u}rgen}, title = {Clustering of granular assemblies with temperature dependent restitution under Keplerian differential rotation}, year = {1997}, language = {en} } @article{PikovskijKurths1997, author = {Pikovskij, Arkadij and Kurths, J{\"u}rgen}, title = {Coherence Resonance in a Noise-Driven Excitable System}, year = {1997}, abstract = {We study the dynamics of the excitable Fitz Hugh-Nagumo system under external noisy driving. Noise activates the system producing a sequence of pulses. The coherence of these noise-induced oscillations is shown to be maximal for a certain noise amplitude. This new effect of coherence resonance is explained by different noise dependencies of the activation and the excursion times. A simple one-dimensional model based on the Langevin dynamics is proposed for the quantitative description of this phenomenon.}, language = {en} } @article{PikovskijKurths1997, author = {Pikovskij, Arkadij and Kurths, J{\"u}rgen}, title = {Coherence resonance in a noise-driven excitable system}, year = {1997}, language = {en} } @article{KopitzkiWarnkeSaparinetal.2002, author = {Kopitzki, K. and Warnke, P. C. and Saparin, Peter and Kurths, J{\"u}rgen and Timmer, Jens}, title = {Comment on "Kullback-Leibler and renormalized entropies: Applications to electroencephalograms of epilepsy patients"}, year = {2002}, language = {en} } @article{RosenblumKurthsPikovskij2001, author = {Rosenblum, Michael and Kurths, J{\"u}rgen and Pikovskij, Arkadij}, title = {Comment on "Phase synchronization in discrete chaotic systems"}, year = {2001}, abstract = {Chen et al. [Phys. Rev. E 61, 2559 (2000)] recently proposed an extension of the concept of phase for discrete chaotic systems. Using the newly introduced definition of phase they studied the dynamics of coupled map lattices and compared these dynamics with phase synchronization of coupled continuous-time chaotic systems. In this paper we illustrate by two simple counterexamples that the angle variable introduced by Chen et al. fails to satisfy the basic requirements to the proper phase. Furthermore, we argue that an extension of the notion of phase synchronization to generic discrete maps is doubtful.}, language = {en} } @article{MarwanTrauthVuilleetal.2003, author = {Marwan, Norbert and Trauth, Martin H. and Vuille, Mathias and Kurths, J{\"u}rgen}, title = {Comparing modern and Pleistocene ENSO-like influences in NW Argentina using nonlinear time series analysis methods}, year = {2003}, abstract = {Higher variability in rainfall and river discharge could be of major importance in landslide generation in the north-western Argentine Andes. Annual layered (varved) deposits of a landslide dammed lake in the Santa Maria Basin (26°S, 66°W) with an age of 30,000 14C years provide an archive of precipitation variability during this time. The comparison of these data with present-day rainfall observations tests the hypothesis that increased rainfall variability played a major role in landslide generation. A potential cause of such variability is the El Ni{\~n}o/ Southern Oscillation (ENSO). The causal link between ENSO and local rainfall is quantified by using a new method of nonlinear data analysis, the quantitative analysis of cross recurrence plots (CRP). This method seeks similarities in the dynamics of two different processes, such as an ocean-atmosphere oscillation and local rainfall. Our analysis reveals significant similarities in the statistics of both modern and palaeo-precipitation data. The similarities in the data suggest that an ENSO-like influence on local rainfall was present at around 30,000 14C years ago. Increased rainfall, which was inferred from a lake balance modeling in a previous study, together with ENSO-like cyclicities could help to explain the clustering of landslides at around 30,000 14C years ago.}, language = {en} } @article{HassanKurths2001, author = {Hassan, M. K. and Kurths, J{\"u}rgen}, title = {Competitive random sequential adsorption of point and fixed-sized particles: analytical results}, year = {2001}, language = {en} } @article{OzturkMarwanKorupetal.2018, author = {Ozturk, Ugur and Marwan, Norbert and Korup, Oliver and Saito, H. and Agarwa, Ankit and Grossman, M. J. and Zaiki, M. and Kurths, J{\"u}rgen}, title = {Complex networks for tracking extreme rainfall during typhoons}, series = {Chaos : an interdisciplinary journal of nonlinear science}, volume = {28}, journal = {Chaos : an interdisciplinary journal of nonlinear science}, number = {7}, publisher = {American Institute of Physics}, address = {Melville}, issn = {1054-1500}, doi = {10.1063/1.5004480}, pages = {8}, year = {2018}, abstract = {Reconciling the paths of extreme rainfall with those of typhoons remains difficult despite advanced forecasting techniques. We use complex networks defined by a nonlinear synchronization measure termed event synchronization to track extreme rainfall over the Japanese islands. Directed networks objectively record patterns of heavy rain brought by frontal storms and typhoons but mask out contributions of local convective storms. We propose a radial rank method to show that paths of extreme rainfall in the typhoon season (August-November, ASON) follow the overall southwest-northeast motion of typhoons and mean rainfall gradient of Japan. The associated eye-of-the-typhoon tracks deviate notably and may thus distort estimates of heavy typhoon rainfall. We mainly found that the lower spread of rainfall tracks in ASON may enable better hindcasting than for westerly-fed frontal storms in June and July.}, language = {en} } @article{DongesZouMarwanetal.2009, author = {Donges, Jonathan and Zou, Yong and Marwan, Norbert and Kurths, J{\"u}rgen}, title = {Complex networks in climate dynamics : comparing linear and nonlinear network construction methods}, issn = {1951-6355}, doi = {10.1140/epjst/e2009-01098-2}, year = {2009}, abstract = {Complex network theory provides a powerful framework to statistically investigate the topology of local and non- local statistical interrelationships, i.e. teleconnections, in the climate system. Climate networks constructed from the same global climatological data set using the linear Pearson correlation coefficient or the nonlinear mutual information as a measure of dynamical similarity between regions, are compared systematically on local, mesoscopic and global topological scales. A high degree of similarity is observed on the local and mesoscopic topological scales for surface air temperature fields taken from AOGCM and reanalysis data sets. We find larger differences on the global scale, particularly in the betweenness centrality field. The global scale view on climate networks obtained using mutual information offers promising new perspectives for detecting network structures based on nonlinear physical processes in the climate system.}, language = {en} } @article{ChenShiauTsengetal.2010, author = {Chen, Jin-Long and Shiau, Yuo-Hsien and Tseng, Yin-Jiun and Chiu, Hung-Wen and Hsiao, Tzu-Chien and Wessel, Niels and Kurths, J{\"u}rgen and Chu, Woei-Chyn}, title = {Concurrent sympathetic activation and vagal withdrawal in hyperthyroidism : evidence from detrended fluctuation analysis of heart rate variability}, issn = {0378-4371}, doi = {10.1016/j.physa.2009.12.062}, year = {2010}, abstract = {Despite many previous Studies on the association between hyperthyroidism and the hyperadrenergic state, controversies still exist. Detrended fluctuation analysis (DFA) is a well recognized method in the nonlinear analysis of heart rate variability (HRV), and it has physiological significance related to the autonomic nervous system. In particular, an increased short-term scaling exponent alpha 1 calculated from DFA is associated with both increased sympathetic activity and decreased vagal activity. No study has investigated the DFA of HRV in hyperthyroidism. This study was designed to assess the sympathovagal balance in hyperthyroidism. We performed the DFA along with the linear analysis of HRV in 36 hyperthyroid Graves' disease patients (32 females and 4 males; age 30 +/- 1 years, means +/- SE) and 36 normal controls matched by sex, age and body mass index. Compared with the normal controls, the hyperthyroid patients revealed a significant increase (P < 0.001) in alpha 1 (hyperthyroid 1.28 +/- 0.04 versus control 0.91 +/- 0.02), long-term scaling exponent alpha 2 (1.05 +/- 0.02 versus 0.90 +/- 0.01), overall scaling exponent alpha (1.11 +/- 0.02 versus 0.89 +/- 0.01), low frequency power in normalized units (LF\%) and the ratio of low frequency power to high frequency power (LF/HF); and a significant decrease (P < 0.001) in the standard deviation of the R-R intervals (SDNN) and high frequency power (HF). In conclusion, hyperthyroidism is characterized by concurrent sympathetic activation and vagal withdrawal. This sympathovagal imbalance state in hyperthyroidism helps to explain the higher prevalence of atrial fibrillation and exercise intolerance among hyperthyroid patients.}, language = {en} } @article{SteuerZhouKurths2003, author = {Steuer, Ralf and Zhou, Changsong and Kurths, J{\"u}rgen}, title = {Constructive effects of fluctuations in genetic and biochemical regulatory systems}, issn = {0303-2647}, year = {2003}, abstract = {Biochemical and genetic regulatory systems that involve low concentrations of molecules are inherently noisy. This intrinsic stochasticity, has received considerable interest recently, leading to new insights about the sources and consequences of noise in complex systems of genetic regulation. However, most prior work was devoted to the reduction of fluctuation and the robustness of cellular function with respect to intrinsic noise. Here, we focus on several scenarios in which the inherent molecular fluctuations are not merely a nuisance, but act constructively and bring about qualitative changes in the dynamics of the system. It will be demonstrated that in many typical situations biochemical and genetic regulatory systems may utilize intrinsic noise to their advantage. (C) 2002 Elsevier Ireland Ltd. All rights reserved}, language = {en} } @article{ZaikinRosenblumLandaetal.1997, author = {Zaikin, Alexei A. and Rosenblum, Michael and Landa, Polina S. and Kurths, J{\"u}rgen}, title = {Control of noise-induced oscillations of a pendulum with a rondomly vibrating suspension axis}, year = {1997}, language = {en} } @article{LindTitzKuhlbrodtetal.2004, author = {Lind, P. G. and Titz, Sven Holger and Kuhlbrodt, Till and Corte-Real, J. A. M. and Kurths, J{\"u}rgen and Gallas, J. A. C. and Feudel, Ulla}, title = {Coupled bistable maps : a tool to study convection parameterization in ocean models}, issn = {0218-1274}, year = {2004}, abstract = {We present a study of ocean convection parameterization based on a novel approach which includes both eddy diffusion and advection and consists of a two-dimensional lattice of bistable maps. This approach retains important features of usual grid models and allows to assess the relative roles of diffusion and advection in the spreading of convective cells. For large diffusion our model exhibits a phase transition from convective patterns to a homogeneous state over the entire lattice. In hysteresis experiments we find staircase behavior depending on stability thresholds of local convection patterns. This nonphysical behavior is suspected to induce spurious abrupt changes in the spreading of convection in ocean models. The final steady state of convective cells depends not only on the magnitude of the advective velocity but also on its direction, implying a possible bias in the development of convective patterns. Such bias points to the need for an appropriate choice of grid geometry in ocean modeling}, language = {en} } @article{MarwanNowaczykKurthsetal.2001, author = {Marwan, Norbert and Nowaczyk, Norbert R. and Kurths, J{\"u}rgen and Thiel, Marco}, title = {Cross recurrence plot based rescaling of geological time series}, issn = {1029-7006}, year = {2001}, abstract = {The rescaling of geological data series to a geological reference time series is of major interest in many investigations. For example, geophysical borehole data should be correlated to a given data series whose time scale is known in order to achieve an age-depth function or the sedimentation rate for the borehole data. Usually this synchronization is performed visually and by hand. Instead of using this wiggle matching by eye, we present the application of cross recurrence plots for such tasks. Using this method, the synchronization and rescaling of geological data to a given time scale is much easier and faster than by hand.}, language = {en} } @article{MaraunKurths2004, author = {Maraun, Douglas and Kurths, J{\"u}rgen}, title = {Cross wavelet analysis: significance testing and pitfalls}, issn = {1023-5809}, year = {2004}, abstract = {In this paper, we present a detailed evaluation of cross wavelet analysis of bivariate time series. We develop a statistical test for zero wavelet coherency based on Monte Carlo simulations. If at least one of the two processes considered is Gaussian white noise, an approximative formula for the critical value can be utilized. In a second part, typical pitfalls of wavelet cross spectra and wavelet coherency are discussed. The wavelet cross spectrum appears to be not suitable for significance testing the interrelation between two processes. Instead, one should rather apply wavelet coherency. Furthermore we investigate problems due to multiple testing. Based on these results, we show that coherency between ENSO and NAO is an artefact for most of the time from 1900 to 1995. However, during a distinct period from around 1920 to 1940, significant coherency between the two phenomena occurs}, language = {en} } @article{GozolchianiMoshelHausdorffetal.2006, author = {Gozolchiani, Avi and Moshel, Shay and Hausdorff, Jeffrey M. and Simon, Ely and Kurths, J{\"u}rgen and Havlin, Shlomo}, title = {Decaying of phase synchronization in parkinsonian tremor}, issn = {0378-4371}, doi = {10.1016/j.physa.2005.10.033}, year = {2006}, abstract = {We describe effects of the asymmetry of cycles and non-stationarity in time series on the phase synchronization method which may lead to artifacts. We develop a modified method that overcomes these effects and apply it to study parkinsonian tremor. Our results indicate that there is synchronization between two different hands and provide information about the time delay separating their dynamics. These findings suggest that this method may be useful for detecting and quantifying weak synchronization between two non-stationary signals.}, language = {en} } @article{KimKurthsKimetal.1998, author = {Kim, G. G. and Kurths, J{\"u}rgen and Kim, S. and Cao, L. Y.}, title = {Detecting determinism in human posture control data}, year = {1998}, language = {en} } @unpublished{ThiessenhusenEspositoKurthsetal.1995, author = {Thiessenhusen, Kai-Uwe and Esposito, Larry W. and Kurths, J{\"u}rgen and Spahn, Frank}, title = {Detection of hidden resonances in Saturn's B-ring}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus-13618}, year = {1995}, abstract = {The Voyager 2 Photopolarimeter experiment has yielded the highest resolved data of Saturn's rings, exhibiting a wide variety of features. The B-ring region between 105000 km and 110000 km distance from Saturn has been investigated. It has a high matter density and contains no significance features visible by eye. Analysis with statistical methods has let us to the detection of two significant events. These features are correlated with the inner 3:2 resonances of the F-ring shepherd satellites Pandora and Prometheus, and may be evidence of large ring paricles caught in the corotation resonances.}, language = {en} } @article{TassRosenblumWeuleetal.1998, author = {Tass, Peter and Rosenblum, Michael and Weule, J. and Kurths, J{\"u}rgen and Pikovskij, Arkadij and Volkmann, J. and Schnitzler, A. and Freund, H.-J.}, title = {Detection of n:m phase locking from noisy data : application to magnetoencephalography}, year = {1998}, abstract = {We use the concept of phase synchronization for the analysis of noisy nonstationary bivariate data. Phase synchronization is understood in a statistical sense as an existence of preferred values of the phase difference, and two techniques are proposed for a reliable detection of synchronous epochs. These methods are applied to magnetoencephalograms and records of muscle activity of a Parkinsonian patient. We reveal that}, language = {en} } @article{RomanoThielKurthsetal.2005, author = {Romano, Maria Carmen and Thiel, M. and Kurths, J{\"u}rgen and Kiss, Istvan Z. and Hudson, J. L.}, title = {Detection of synchronization for non-phase-coherent and non-stationary data}, issn = {0295-5075}, year = {2005}, abstract = {We present a new method to detect phase as well as generalized synchronization in a wide class of complex systems. It is based on the recurrences of the system's trajectory to the neighborhood of a former state in phase space. We illustrate the applicability of the algorithm for the paradigmatic chaotic Rossler system in the funnel regime and for noisy data, where other methods to detect phase synchronization fail. Furthermore, we demonstrate for electrochemical experiments that the method can easily detect phase and generalized synchronization in non-phase- coherent and even non-stationary time series}, language = {en} } @article{KoseskaVolkovKurths2009, author = {Koseska, Aneta and Volkov, Evgenij and Kurths, J{\"u}rgen}, title = {Detuning-dependent dominance of oscillation death in globally coupled synthetic genetic oscillators}, issn = {0295-5075}, doi = {10.1209/0295-5075/85/28002}, year = {2009}, abstract = {We study dynamical regimes of globally coupled genetic relaxation oscillators in the presence of small detuning. Using bifurcation analysis, we find that under strong coupling via the slow variable, the detuning can eliminate standard oscillatory solutions in a large region of the parameter space, providing the dominance of oscillation death. This result is substantially different from previous results on oscillation quenching, where for homogeneous populations, the coexistence of oscillation death and limit cycle oscillations is always present. We propose further that this effect of detuning-dependent dominance could be a powerful regulator of genetic network's dynamics.}, language = {en} } @article{SaparinKurthsGowinetal.1997, author = {Saparin, Peter and Kurths, J{\"u}rgen and Gowin, P. and Felsenberg, D.}, title = {Die quantitative Beurteilung trabecul{\"a}rer Knochenstrukturen der Lendenwirbelk{\"o}rper durch Meßmethoden der nicht-linearen Dynamik}, year = {1997}, language = {de} } @article{ZaikinKurthsSchimanskyGeier2000, author = {Zaikin, Alexei A. and Kurths, J{\"u}rgen and Schimansky-Geier, Lutz}, title = {Doubly stochastic resonance}, year = {2000}, abstract = {We report the effect of doubly stochastic resonance which appears in nonlinear extended systems if the influence of noise is twofold: A multiplicative noise induces bimodality of the mean field of the coupled network and an independent additive noise governs the dynamic behavior in response to small periodic driving. For optimally selected values of the additive noise intensity stochastic resonance is observed, which is manifested by a maximal coherence between the dynamics of the mean field and the periodic input. Numerical simulations of the signal-to-noise ratio and theoretical results from an effective two state model are in good quantitative agreement.}, language = {en} }