TY - JOUR A1 - Perrin, Helene A1 - Colombe, Yves A1 - Mercier, Brigitte A1 - Lorent, Vincent A1 - Henkel, Carsten T1 - Diffuse reflection of a Bose-Einstein condensate from a rough evanescent wave mirror JF - Journal of physics : B, Atomic, molecular and optical physics N2 - We present experimental results showing the diffuse reflection of a Bose Einstein condensate from a rough mirror, consisting of a dielectric substrate supporting a blue-detuned evanescent wave. The scattering is anisotropic, more pronounced in the direction of the surface propagation of the evanescent wave. These results agree very well with theoretical predictions. Y1 - 2006 U6 - https://doi.org/10.1088/0953-4075/39/22/009 SN - 0953-4075 VL - 39 SP - 4649 EP - 4658 PB - IOP Publ. CY - Bristol ER - TY - JOUR A1 - Landa, Polina S. A1 - Ushakov, Vladimir A1 - Kurths, Jürgen T1 - Rigorous theory of stochastic resonance in overdamped bistable oscillators for weak signals JF - Chaos, solitons & fractals : applications in science and engineering N2 - The results of the theoretical consideration of stochastic resonance in overdamped bistable oscillators are given. These results are founded not on the model of two states as in [McNamara B, Wiesenfeld K. Theory of stochastic resonance. Phys Rev A 1989;39:4854-69], but on splitting of motion into regular and random and the rigorous solution of the Fokker-Planck equation for the random component. We show that this resonance is caused by a change, under the influence of noise, of the system's effective stiffness and damping factor contained in the equation for the regular component. For a certain value of the noise intensity the effective stiffness is minimal, and this fact causes non-monotonic change of the output signal amplitude as the noise intensity changes. It is important that the location of the minimum and its value depend essentially on the signal frequency. Y1 - 2006 UR - http://www.sciencedirect.com/science/journal/09600779 U6 - https://doi.org/10.1016/j.chaos.2005.08.116 SN - 0960-0779 VL - 30 IS - 3 SP - 574 EP - 578 PB - Elsevier CY - Amsterdam ER - TY - JOUR A1 - Gandhimathi, V. M. A1 - Rajasekar, S. A1 - Kurths, Jürgen T1 - Vibrational and stochastic resonances in two coupled overdamped anharmonic oscillators JF - Modern physics letters : A, Particles and fields, gravitation, cosmology, nuclear physics N2 - We study the overdamped version of two coupled anharmonic oscillators under the influence of both low- and high-frequency forces respectively and a Gaussian noise term added to one of the two state variables of the system. The dynamics of the system is first studied in the presence of both forces separately without noise. In the presence of only one of the forces, no resonance behaviour is observed, however, hysteresis happens there. Then the influence of the high-frequency force in the presence of a low-frequency, i.e. biharmonic forcing, is studied. Vibrational resonance is found to occur when the amplitude of the high-frequency force is varied. The resonance curve resembles a stochastic resonance-like curve. It is maximum at the value of g at which the orbit lies in one well during one half of the drive cycle of the low-frequency force and in the other for the remaining half cycle. Vibrational resonance is characterized using the response amplitude and mean residence time. We show the occurrence of stochastic resonance behaviour in the overdamped system by replacing the high-frequency force by Gaussian noise. Similarities and differences between both types of resonance are presented. (c) 2006 Elsevier B.V. All rights reserved. KW - vibrational resonance KW - low-frequency force KW - high-frequency force KW - stochastic resonance KW - noise KW - mean residence time Y1 - 2006 U6 - https://doi.org/10.1016/j.physleta.2006.08.051 SN - 0375-9601 VL - 360 IS - 2 SP - 279 EP - 286 PB - Elsevier CY - Amsterdam ER - TY - JOUR A1 - Zou, Yong A1 - Thiel, M. A1 - Romano, Maria Carmen A1 - Kurths, Jürgen A1 - Bi, Q. T1 - Shrimp structure and associated dynamics in parametrically excited oscillators JF - International journal of bifurcation and chaos : in applied sciences and engineering N2 - We investigate the bifurcation structures in a two-dimensional parameter space (PS) of a parametrically excited system with two degrees of freedom both analytically and numerically. By means of the Renyi entropy of second order K-2, which is estimated from recurrence plots, we uncover that regions of chaotic behavior are intermingled with many complex periodic windows, such as shrimp structures in the PS. A detailed numerical analysis shows that, the stable solutions lose stability either via period doubling, or via intermittency when the parameters leave these shrimps in different directions, indicating different bifurcation properties of the boundaries. The shrimps of different sizes offer promising ways to control the dynamics of such a complex system. KW - bifurcation analysis KW - recurrence plot KW - period doubling KW - intermittency Y1 - 2006 U6 - https://doi.org/10.1142/S0218127406016987 SN - 0218-1274 VL - 16 IS - 12 SP - 3567 EP - 3579 PB - World Scientific Publ. Co CY - Singapore ER - TY - JOUR A1 - Heringer-Walther, Silvia A1 - Moreira, Maria da Consolacao V. A1 - Wessel, Niels A1 - Wang, Yong A1 - Ventura, Pago Moreira A1 - Schultheiss, Heinz-Peter A1 - Walther, Thomas T1 - Does the C-type natriuretic peptide have prognostic value in Chagas disease and other dilated cardiomyopathies JF - Journal of cardiovascular pharmacology N2 - Atrial natriuretic peptides (ANP) and brain natriuretic peptides (BNP) are powerful neurohormonal indicators of left-ventricular function and prognosis in heart failure (HF). Chagas disease (CD) caused by the protozoan Trypanosoma cruzi. remains a major cause of HF in Latin America. We assessed whether the plasma concentration of the third natriuretic peptide, C-type natnuretic peptide (CNP), also has diagnostic and prognostic properties in patients with CD or other dilated cardiomyopathies (DCM). Blood samples were obtained from 66 patients with CD, 50 patients with DCM from other causes, and 30 gender- and age-matched healthy subjects. Patients were subdivided according to the New York Heart Association (NYHA) class. The CNP concentration was determined by radioimmunoassay (Immundiagnostik, Bensheim, Germany). The main duration of follow-up was 31.4 months (range 13 to 54 months), 19 patients had died and 11 patients received a heart transplant. CNP concentrations were only significantly altered in patients with DCM or CD of the NYHA classes III and IV (P < 0.05). The Pearson correlation of echocardiographic data with CNP revealed an association only with the left-ventricular end systolic volume (P = 0.03) in patients with DCM. Furthermore, CNP did not predict mortality or the necessity for heart transplant. Our data are the first to demonstrate the raised levels of the third natriuretic peptide CNP in CD and other DCM Whereas ANP and BNP have a high predictive value for mortality in both diseases, CNP is without any predictive potency. KW - cardiomyopathy KW - heart failure KW - natriuretic peptide system KW - Trypanosoma cruzi Y1 - 2006 U6 - https://doi.org/10.1097/01.fjc.0000249892.22635.46 SN - 0160-2446 VL - 48 IS - 6 SP - 293 EP - 298 PB - Lippincott Williams & Wilkins CY - Philadelphia ER - TY - JOUR A1 - Zhou, Changsong A1 - Zemanova, Lucia A1 - Zamora, Gorka A1 - Hilgetag, Claus C. A1 - Kurths, Jürgen T1 - Hierarchical organization unveiled by functional connectivity in complex brain networks JF - Physical review letters N2 - How do diverse dynamical patterns arise from the topology of complex networks? We study synchronization dynamics in the cortical brain network of the cat, which displays a hierarchically clustered organization, by modeling each node (cortical area) with a subnetwork of interacting excitable neurons. We find that in the biologically plausible regime the dynamics exhibits a hierarchical modular organization, in particular, revealing functional clusters coinciding with the anatomical communities at different scales. Our results provide insights into the relationship between network topology and functional organization of complex brain networks. Y1 - 2006 U6 - https://doi.org/10.1103/PhysRevLett.97.238103 SN - 0031-9007 SN - 1079-7114 VL - 97 PB - American Physical Society CY - College Park ER - TY - JOUR A1 - Emmerling, Franziska A1 - Orgzall, Ingo A1 - Reck, Günter A1 - Schulz, Burkhard W. A1 - Stockhause, Sabine A1 - Schulz, Burkhard T1 - Structures of substituted di-aryl-1, 3,4-oxadiazole derivatives: 2,5-bis(pyridyl)- and 2,5-bis(aminophenyl)-substitution JF - Journal of molecular structure N2 - Crystal structures of four different di-aryl-1,3,4-oxadiazole compounds (aryl = 2-pyridyl-, 3-pyridyl-, 2-aminophenyl-, 3-aminophenyl-) are determined. Crystallization of di(2-pyridyl)-1,3,4-oxadiazole yielded monoclinic and triclinic polymorphs. The structures are characterized by the occurrence of pi-pi interactions. Additionally, in case of the aminophenyl compounds intra- as well as intermolecular hydrogen bonds are found that influence the packing motif as well. Since these molecules are often used as ligands in metal-organic complexes similarities and differences of the molecular conformation between the molecules in the pure crystals and that of the ligands in the complexes are discussed. (c) 2006 Elsevier B.V. All rights reserved. KW - crystal structure KW - 1,3,4-oxadiazole KW - molecular conformation KW - hydrogen bonds Y1 - 2006 U6 - https://doi.org/10.1016/j.molstruc.2006.03.076 SN - 0022-2860 VL - 800 IS - 1-3 SP - 74 EP - 84 PB - Elsevier CY - Amsterdam ER - TY - JOUR A1 - Medrano-T., R. O. A1 - Baptista, Murilo da Silva A1 - Caldas, Ibere Luiz T1 - Shilnikov homoclinic orbit bifurcations in the Chua’s circuit JF - Chaos : an interdisciplinary journal of nonlinear science N2 - We analytically describe the complex scenario of homoclinic bifurcations in the Chua’s circuit. We obtain a general scaling law that gives the ratio between bifurcation parameters of different nearby homoclinic orbits. As an application of this theoretical approach, we estimate the number of higher order subsidiary homoclinic orbits that appear between two consecutive lower order subsidiary orbits. Our analytical finds might be valid for a large class of dynamical systems and are numerically confirmed in the parameter space of the Chua’s circuit. Shilnikov homoclinic orbits are trajectories that depart from a fixed saddle-focus point, with specific eigenvalues, and return to it after an infinite amount of time (that is also true to time reversal evolution). That results in an orbit that is unstable and has an infinite period. These two main characteristics contribute in the hardness for its observation in a dynamical system as well as in nature. However, its presence reveals fundamental characteristics of the system involved, as the existence of unstable periodic orbits embedded in a chaotic set. Once the unstable periodic orbits give invariants quantities of this set,1 the Shilnikov homoclinic orbits are also related to the characteristics of the chaotic set. Their connection with the fundamental dynamical properties is verified in a wide variety of systems. A series of numerical and experimental investigations reveal how Shilnikov homoclinic orbits, in the vicinity of a chaotic attractor, determine its dynamical and topological properties.4 Thus, the Shilnikov orbits are related to the returning time of the trajectory of a CO2 laser,5 also to the topology of a glow-discharge system.6 Moreover, some class of spiking neurons are modeled by chaos governed by such orbits,7,8 and their presence are connected to the intermittence present in rabbit arteries.9 These orbits are shown to be behind the mechanism of noise-induced phenomena,10 and they are also responsible for the dynamics of an electrochemical oscillator.11 In this work, we contribute to the understanding of how Shilnikov homoclinic orbits appear on the parameter space of systems as the ones above mentioned, by showing that these orbits are not only distributed following an universal rule but also exist for large parameter variations. We then confirm our previsions in the Chua’s circuit system Y1 - 2006 U6 - https://doi.org/10.1063/1.2401060 SN - 1054-1500 VL - 16 IS - 4 PB - American Institute of Physics CY - Melville ER - TY - JOUR A1 - Montbrio, Ernest A1 - Pazo, Diego A1 - Schmidt, Jürgen T1 - Time delay in the Kuramoto model with bimodal frequency distribution JF - Physical review : E, Statistical, nonlinear and soft matter physics N2 - We investigate the effects of a time-delayed all-to-all coupling scheme in a large population of oscillators with natural frequencies following a bimodal distribution. The regions of parameter space corresponding to synchronized and incoherent solutions are obtained both numerically and analytically for particular frequency distributions. In particular, we find that bimodality introduces a new time scale that results in a quasiperiodic disposition of the regions of incoherence. Y1 - 2006 U6 - https://doi.org/10.1103/PhysRevE.74.056201 SN - 1539-3755 VL - 74 PB - APS CY - College Park ER - TY - JOUR A1 - Akpo, Claudia A1 - Weber, Edwin A1 - Reiche, Jürgen T1 - Synthesis, Langmuir and Langmuir-Blodgett film behaviour of new dendritic amphiphiles JF - New journal of chemistry N2 - New amphiphilic compounds 1-9 that feature a construction with dendronized hydrophilic and hydrophobic segment groups connected to a specific aromatic or aliphatic spacer unit have been synthesized, following a modular building block strategy. The hydrophilic dendrons are typically branched elements with peripheral carboxylic groups, unlike the hydrophobic dendrons that contain peripheral alkyl chains as part of respective amide functions. The hydrophilic dendrons are in different generations of branching, while the hydrophobic dendrons are all in the first generation of branching (three terminal branching), but differ in the length of the alkyl chains, thus giving rise to designed structure and amphiphilic properties in the new compounds. The resulting surfactants are capable of forming well-defined Langmuir films of remarkable stability when spread from a solution onto an aqueous subphase. Nevertheless, specific packing behaviour and orientation of the amphiphilic molecules were found, depending on the molecular structure, as determined using analysis of the surface pressure-area (pi-A) isotherms. Langmuir-Blodgett transfer of the first monolayer from a pure water subphase to a clean silicon wafer proved possible for the amphiphiles of peripheral alkyl chain length C-12, while the amphiphiles with the longer alkyl chains failed, possibly due to the more rigid monolayers they form, impeding the transfer. Y1 - 2006 U6 - https://doi.org/10.1039/b609645j SN - 1144-0546 SN - 1369-9261 VL - 30 SP - 1820 EP - 1833 PB - RSC CY - Cambridge ER -