@article{WegenerWirgesGerhardetal.2004,
  author    = {Wegener, Michael and Wirges, Werner and Gerhard, Reimund and Dansachm{\"u}ller, M. and Schw{\"o}diauer, R. and Bauer-Gogonea, Simona and Bauer, Siegfried and Paajanen, Mika and Minkkinen, Hannu and Raukola, J.},
  title     = {Controlled inflation of voids in cellular polymer ferroelectrets : optimizing electromechanical transducer properties},
  year      = {2004},
  abstract  = {When exposed to sufficiently high electric fields, polymer-foam electret materials with closed cells exhibit ferroelectric-like behavior and may therefore be called ferroelectrets. In cellular ferroelectrets, the influence of the cell size and shape distributions on the application-relevant properties is not yet understood. Therefore, controlled inflation experiments were carried out on cellular polypropylene films, and the resulting elastical and electromechanical parameters were determined. The elastic modulus in the thickness direction shows a minimum with a corresponding maximum in the electromechanical transducer coefficient. The resonance frequency shifts as a function of the elastic modulus and the relative density of the inflated cellular films. Therefore, the transducer properties of cellular ferroelectrets can be optimized by means of controlled inflation. (C) 2004 American Institute of Physics},
  language  = {en}
}
@article{AsghariBroegCaroneetal.2004,
  author    = {Asghari, N. and Broeg, C. and Carone, L. and Casas-Miranda, R. and Palacio, J. C. C. and Csillik, I. and Dvorak, R. and Freistetter, F. and Hadjivantsides, G. and Hussmann, H. and Khramova, A. and Khristoforova, M. and Khromova, I. and Kitiashivilli, I. and Kozlowski, S. and Laakso, T. and Laczkowski, T. and Lytvinenko, D. and Miloni, O. and Morishima, R. and Moro-Martin, A. and Paksyutov, V. and Pal, A. and Patidar, V. and Pecnik, B. and Peles, O. and Pyo, J. and Quinn, T. and Rodriguez, A. and Romano, C. and Saikia, E. and Stadel, J. and Thiel, M. and Todorovic, N. and Veras, D. and Neto, E. V. and Vilagi, J. and von Bloh, Werner and Zechner, R. and Zhuchkova, E.},
  title     = {Stability of terrestrial planets in the habitable zone of G1 777 A, HD 72659, G1 614, 47 Uma and HD 4208},
  issn      = {0004-6361},
  doi       = {10.1051/0004-6361:20040390},
  year      = {2004},
  abstract  = {We have undertaken a thorough dynamical investigation of five extrasolar planetary systems using extensive numerical experiments. The systems Gl 777 A, HD 72659, Gl 614, 47 Uma and HD 4208 were examined concerning the question of whether they could host terrestrial-like planets in their habitable zones (HZ). First we investigated the mean motion resonances between fictitious terrestrial planets and the existing gas giants in these five extrasolar systems. Then a fine grid of initial conditions for a potential terrestrial planet within the HZ was chosen for each system, from which the stability of orbits was then assessed by direct integrations over a time interval of 1 million years. For each of the five systems the 2-dimensional grid of initial conditions contained 80 eccentricity points for the Jovian planet and up to 160 semimajor axis points for the fictitious planet. The computations were carried out using a Lie-series integration method with an adaptive step size control. This integration method achieves machine precision accuracy in a highly efficient and robust way, requiring no special adjustments when the orbits have large eccentricities. The stability of orbits was examined with a determination of the Renyi entropy, estimated from recurrence plots, and with a more straightforward method based on the maximum eccentricity achieved by the planet over the 1 million year integration. Additionally, the eccentricity is an indication of the habitability of a terrestrial planet in the HZ; any value of e > 0.2 produces a significant temperature difference on a planet's surface between apoapse and periapse. The results for possible stable orbits for terrestrial planets in habitable zones for the five systems are: for Gl 777 A nearly the entire HZ is stable, for 47 Uma, HD 72659 and HD 4208 terrestrial planets can survive for a sufficiently long time, while for Gl 614 our results exclude terrestrial planets moving in stable orbits within the HZ. Studies such as this one are of primary interest to future space missions dedicated to finding habitable terrestrial planets in other stellar systems. Assessing the likelihood of other habitable planets, and more generally the possibility of other life, is the central question of astrobiology today. Our investigation indicates that, from the dynamical point of view, habitable terrestrial planets seem to be compatible with many of the currently discovered extrasolar systems},
  language  = {en}
}
@article{YangVardenyKoehleretal.2004,
  author    = {Yang, C. and Vardeny, Z. V. and K{\"o}hler, Anna and Wohlgenannt, M. and Al-Suti, Mohammed K. and Khan, Muhammad S.},
  title     = {Spectroscopic study of spin-dependent exciton formation rates in pi-conjugated semiconductors : Comparison with electroluminescence techniques},
  year      = {2004},
  abstract  = {It has been found in recent measurements that the singlet-to-triplet exciton ratio in organic light-emitting diodes (OLEDs) is larger than expected from spin degeneracy, and that singlet excitons form at a larger rate than triplets. We employed the technique of optically detected magnetic resonance to measure the spin-dependent exciton formation rates in films of a polymer and corresponding monomer, and explore the relation between the formation rates and the actual singlet-to-triplet ratio measured previously in OLEDs. We found that the spin-dependent exciton formation rates can indeed quantitatively explain the observed exciton yields, and that singlet formation rates and yields are significantly enhanced only in polymer OLEDs, but not in OLEDs made from the corresponding monomer},
  language  = {en}
}
@article{KhanSreearunothaiHerzetal.2004,
  author    = {Khan, Amena L. T. and Sreearunothai, Paiboon and Herz, Laura M. and Banach, Michael J. and K{\"o}hler, Anna},
  title     = {Morphology-dependent energy transfer within polyfluorene thin films},
  year      = {2004},
  language  = {en}
}
@article{YangJaiserNeheretal.2004,
  author    = {Yang, Xiao Hui and Jaiser, Frank and Neher, Dieter and Lawson, PaDreyia V. and Br{\´e}das, Jean-Luc and Zojer, Egbert and G{\"u}ntner, Roland and Scanduicci de Freitas, Patricia and Forster, Michael and Scherf, Ullrich},
  title     = {Suppression of the keto-emission in polyfluorene light-emitting diodes : Experiments and models},
  issn      = {1616-301X},
  year      = {2004},
  abstract  = {The spectral characteristics of polyfluorene (PF)-based light-emitting diodes (LEDs) containing a defined low concentration of either keto-defects or of the polymer poly(9.9-octylfuorene-co-benzothiadiazole) (F8BT) are preseneted. Both types of blend layers were tested in different device configurations with respect to the relative and absolute intensities of green blue emission components. It is shown that blending hole-transporting molecules into the emission layer at low concentration or incorporation of a suitable hole-transport layer reduces the green emission contribution in the electroluminescence (EL) spectrum of the PF:F8BT blend, which is similar to what is observed for the keto- containing PF layer. We conclude that the keto-defects in PF homopolymer layers mainly constitute weakly emissive electron traps, in agreement with the results of quantum-mechanical calculations},
  language  = {en}
}
@article{TuvalSchneiderPiroetal.2004,
  author    = {Tuval, I. and Schneider, J. and Piro, O. and Tel, Tomas},
  title     = {Opening up fractal structures of three-dimensional flows via leaking},
  issn      = {0295-5075},
  year      = {2004},
  abstract  = {We study the behavior of time-periodic three-dimensional incompressible flows modelled by three-dimensional volume-preserving maps in the presence of a leakage. The distribution of residence times, and the chaotic saddle together with its stable and unstable invariant manifolds are described and characterized. They shed light. on typical filamentation of chaotic flows whose local stable and unstable manifolds are always of different, character (plane or line). We point out that leaking is a useful method which sheds light on typical filamentation of chaotic flows. In particular; the topology depends on the number of local expanding directions, and is the same in the leaked system as in the closed flow},
  language  = {en}
}
@article{SchraderPenzkoferHolzeretal.2004,
  author    = {Schrader, Sigurd and Penzkofer, Alfons and Holzer, W. and Velagapudi, Ramakrishna and Grimm, Bernhard},
  title     = {Laser spectroscopic investigation of a new precursor - type polyparaphenylenevinylene},
  issn      = {0022-2313},
  year      = {2004},
  abstract  = {Optical, structural and morphological properties of thin films of polyparaphenylenevinylene (PPV) formed by an alkyl sulfinyl precursor route have been studied. Thin films were fabricated on an optical glass and on quartz glass either by spin-coating of the precursor solution or by layer-by-layer deposition using Langmuir-Blodgett technique. PPV precursor films were also spin-coated on gold-coated glass in order to study thin-film optical parameters by surface plasmon spectroscopy. We have been successful in forming about 40 precursor mono layers on quartz glass by Langmuir- Blodgett technique using optimized surface pressure and dipping conditions. After thermal conversion of the precursor layers good quality fluorescent PPV films of yellow colour have been obtained. Optical characterization of the films was carried out by linear absorption and emission spectroscopy, ellipsometry, and surface plasmon spectroscopy. Structural and morphological studies on the thin films were carried out by using X-ray scattering and atomic force microscopy. Wave- guided travelling-wave laser action has been achieved in a PPV film on quartz glass. The sample was transversally pumped with picosecond laser pulses (wavelength 347.15 nm, duration 35 ps). Laser emission occurred at 550 nm for pump pulse energy densities above 1 x 10(-4) J cm(-2). (C) 2004 Elsevier B.V. All rights reserved},
  language  = {en}
}
@article{RosenblumPikovskij2004,
  author    = {Rosenblum, Michael and Pikovskij, Arkadij},
  title     = {Delayed feedback control of collective synchrony : an approach to suppression of pathological brain rhythms},
  issn      = {1063-651X},
  year      = {2004},
  abstract  = {We suggest a method for suppression of synchrony in a globally coupled oscillator network, based on the time- delayed feedback via the mean field. Having in mind possible applications for suppression of pathological rhythms in neural ensembles, we present numerical results for different models of coupled bursting neurons. A theory is developed based on the consideration of the synchronization transition as a Hopf bifurcation},
  language  = {en}
}
@article{ZhouKurths2004,
  author    = {Zhou, Changsong and Kurths, J{\"u}rgen},
  title     = {Resonant patterns in noisy active media},
  issn      = {1063-651X},
  year      = {2004},
  abstract  = {We investigate noise-controlled resonant response of active media to weak periodic forcing, both in excitable and oscillatory regimes. In the excitable regime, we find that noise-induced irregular wave structures can be reorganized into frequency-locked resonant patterns by weak signals with suitable frequencies. The resonance occurs due to a matching condition between the signal frequency and the noise-induced inherent time scale of the media. m:1 resonant regions similar to the Arnold tongues in frequency locking of self-sustained oscillatory media are observed. In the self-sustained oscillatory regime, noise also controls the oscillation frequency and reshapes significantly the Arnold tongues. The combination of noise and weak signal thus could provide an efficient tool to manipulate active extended systems in experiments},
  language  = {en}
}
@article{ZbilutMitchellGiulianietal.2004,
  author    = {Zbilut, J. P. and Mitchell, J. C. and Giuliani, A. and Colosimo, A. and Marwan, Norbert and Webber, C. L.},
  title     = {Singular hydrophobicity patterns and net charge : a mesoscopic principle for protein aggregation/folding},
  issn      = {0378-4371},
  year      = {2004},
  abstract  = {A statistical model describing the propensity for protein aggregation is presented. Only amino-acid hydrophobicity values and calculated net charge are used for the model. The combined effects of hydrophobic patterns as computed by the signal analysis technique, recurrence quantification, plus calculated net charge were included in a function emphasizing the effect of singular hydrophobic patches which were found to be statistically significant for predicting aggregation propensity as quantified by fluorescence studies obtained from the literature. These results suggest preliminary evidence for a mesoscopic principle for protein folding/aggregation. (C) 2004 Elsevier B.V. All rights reserved},
  language  = {en}
}