TY - JOUR A1 - Christensen, Lise Bech A1 - Schulte-Ladbeck, R. E. A1 - Sanchez, Sebastian F. A1 - Becker, Thomas A1 - Jahnke, Knud A1 - Kelz, A. A1 - Roth, Martin M. A1 - Wisotzki, Lutz T1 - Abundances and kinematics of a candidate sub-damped Lymana galaxy toward PHL 1226 N2 - The spectrum of the quasar PHL 1226 is known to have a strong Mg II and sub-damped Lymanalpha (sub-DLA) absorption line system with N(H I) = (5 +/- 2) x 10(19) cm(-2) at z = 0.1602. Using integral field spectra from the Potsdam Multi Aperture Spectrophotometer (PMAS) we investigate a galaxy at an impact parameter of 6".4 which is most probably responsible for the absorption lines. A fainter galaxy at a similar redshift and a slightly larger distance from the QSO is known to exist, but we assume that the absorption is caused by the more nearby galaxy. From optical Balmer lines we estimate an intrinsic reddening consistent with 0, and a moderate star formation rate of 0.5 M-circle dot yr(-1) is inferred from the Ha luminosity. Using nebular emission line ratios we find a solar oxygen abundance 12 + log (O/H) = 8.7 +/- 0.1 and a solar nitrogen to oxygen abundance ratio log (N/O) = -1.0 +/- 0.2. This abundance is larger than those of all known sub-DLA systems derived from analyses of metal absorption lines in quasar spectra. On the other hand, the properties are compatible with the most metal rich galaxies responsible for strong Mg II absorption systems. These two categories can be reconciled if we assume an abundance gradient similar to local galaxies. Under that assumption we predict abundances 12 + log (O/H) = 7.1 and log (N/O) = -1.9 for the sub-DLA cloud, which is similar to high redshift DLA and sub-DLA systems. We find evidence for a rotational velocity of similar to200 km s(-1) over a length of similar to7 kpc. From the geometry and kinematics of the galaxy we estimate that the absorbing cloud does not belong to a rotating disk, but could originate in a rotating halo Y1 - 2005 ER - TY - THES A1 - Brezesinski, Torsten T1 - Herstellung und Charakterisierung funktioneller Mesostrukturierter Metalloxidfilme Y1 - 2005 CY - Potsdam ER - TY - JOUR A1 - Witt, Annette A1 - Schumann, A. Y. T1 - Holocene climate variability on millennial scales recorded in Greenland ice cores Y1 - 2005 SN - 1023-5809 ER - TY - JOUR A1 - Bragard, Jean A1 - Montbrio, Ernest A1 - Mendoza, C. A1 - Boccaletti, Stefano A1 - Blasius, Bernd T1 - Defect-enhanced anomaly in frequency synchronization of asymmetrically coupled spatially extended systems N2 - We analytically establish and numerically show that anomalous frequency synchronization occurs in a pair of asymmetrically coupled chaotic space extended oscillators. The transition to anomalous behaviors is crucially dependent on asymmetries in the coupling configuration, while the presence of phase defects has the effect of enhancing the anomaly in frequency synchronization with respect to the case of merely time chaotic oscillators. Y1 - 2005 UR - http://www.agnld.uni-potsdam.de/~bernd/papers/pre4.pdf ER - TY - JOUR A1 - Fussmann, Gregor F. A1 - Blasius, Bernd T1 - Community response to enrichment is highly sensitive to model structure N2 - Biologists use mathematical functions to model, understand, and predict nature. For most biological processes, however, the exact analytical form is not known. This is also true for one of the most basic life processes, the uptake of food or resources. We show that the use of a number of nearly indistinguishable functions, which can serve as phenomenological descriptors of resource uptake, may lead to alarmingly different dynamical behaviour in a simple community model. More specifically, we demonstrate that the degree of resource enrichment needed to destabilize the community dynamics depends critically on the mathematical nature of the uptake function. Y1 - 2005 UR - http://www.agnld.uni-potsdam.de/~bernd/papers/BiolLett1.pdf ER - TY - JOUR A1 - Blasius, Bernd A1 - Toenjes, Ralf T1 - Quasiregular concentric waves in heterogeneous lattices of coupled oscillators N2 - We study the pattern formation in a lattice of locally coupled phase oscillators with quenched disorder. In the synchronized regime quasi regular concentric waves can arise which are induced by the disorder of the system. Maximal regularity is found at the edge of the synchronization regime. The emergence of the concentric waves is related to the symmetry breaking of the interaction function. An explanation of the numerically observed phenomena is given in a one- dimensional chain of coupled phase oscillators. Scaling properties, describing the target patterns are obtained. Y1 - 2005 UR - http://www.agnld.uni-potsdam.de/~bernd/papers/prl1.pdf ER - TY - JOUR A1 - Huppert, Amit A1 - Blasius, Bernd A1 - Olinky, Ronen A1 - Stone, Lewi T1 - A Model for Seasonal Phytoplankton Blooms N2 - We analyse a generic bottom-up nutrient phytoplankton model to help understand the dynamics of seasonally recurring algae blooms. The deterministic model displays a wide spectrum of dynamical behaviours, from simple cyclical blooms which trigger annually, to irregular chaotic blooms in which both the time between outbreaks and their magnitudes are erratic. Unusually, despite the persistent seasonal forcing, it is extremely difficult to generate blooms that are both annually recurring and also chaotic or irregular (i.e. in amplitude) even though this characterizes many real time series. Instead the model has a tendency to `skip' with outbreaks often being suppressed from one year to the next. This behaviour is studied in detail and we develop an analytical expression to describe the model's flow in phase space, yielding insights into the mechanism of the bloom recurrence. We also discuss how modifications to the equations through the inclusion of appropriate functional forms can generate more realistic dynamics. Y1 - 2005 UR - http://www.agnld.uni-potsdam.de/~bernd/papers/jtb2.pdf ER - TY - THES A1 - Herrmann, Frank T1 - Evolution and analysis of binary black hole spacetimes Y1 - 2005 CY - Potsdam ER - TY - THES A1 - Mechau, Norman T1 - Lichtinduziertes Erweichen azobenzolhaltiger Polymerfilme Y1 - 2005 CY - Potsdam ER - TY - THES A1 - Saha, Subodh Kumar T1 - The influence of an improved soil scheme on the arctic climate in a RCM Y1 - 2005 CY - Potsdam ER - TY - JOUR A1 - Hayer, Anna A1 - Khan, A. L. T. A1 - Friend, Richard H. A1 - Köhler, Anna T1 - Morphology dependence of the triplet excited state formation and absorption in polyfluorene Y1 - 2005 ER - TY - THES A1 - Leisner, Antje T1 - Entwicklung von Modellkompetenz im Physikunterricht T2 - Studien zum Physik- und Chemielernen Y1 - 2005 SN - 3-8325-1020-6 SN - 1614-8967 VL - 44 PB - Logos-Verl. CY - Berlin ER - TY - JOUR A1 - Wichmann, Matthias A1 - Johst, Karin A1 - Schwager, Monika A1 - Jeltsch, Florian A1 - Blasius, Bernd T1 - Extinction risk, coloured noise and the scaling of variance N2 - The impact of temporally correlated fluctuating environments (coloured noise) on the extinction risk of populations has become a main focus in theoretical population ecology. In this study we particularly focus on the extinction risk in strongly autocorrelated environments. Here, in contrast to moderate autocorrelation, we found the extinction risk to be highly dependent on the process of noise generation, in particular on the method of variance scaling. Such variance scaling is commonly applied to avoid variance-driven biases when comparing the extinction risk for white and coloured noise. In this study we found an often-used scaling technique to lead to high variability in the resulting variances of different time series for strong auto-correlation eventually leading to deviations in the projected extinction risk. Therefore, we present an alternative method that always delivers the target variance, even in the case of strong temporal correlation. Furthermore, in contrast to the earlier method, our very intuitive method is not bound to auto-regressive processes but can be applied to all types of coloured noises. We recommend the method introduced here to be used when the target of interest is the effect of noise colour on extinction risk not obscured by any variance effects. Y1 - 2005 UR - http://www.agnld.uni-potsdam.de/~bernd/papers/tpb1.pdf ER - TY - THES A1 - Dittrich, Bianca T1 - Aspects of classical and quantum dynamics of canonical general relativity Y1 - 2005 CY - Potsdam ER - TY - THES A1 - Mishra, Narayan Chandra T1 - Interactions in and stability of thin liquid films Y1 - 2005 CY - Potsdam ER - TY - THES A1 - Aulbert, Carsten T1 - Finding millisecond binary pulsars in 47 tucanae by applying the hough transformation to radio data Y1 - 2005 CY - Potsdam ER - TY - JOUR A1 - Li, L. A1 - Möhwald, Helmuth A1 - Spitz, Christian A1 - von Seggern, David A1 - Mucke, M. A1 - Menzel, Ralf T1 - Long-lived photoinduced charge separation inside polarity gradient capsules Y1 - 2005 ER - TY - THES A1 - Diez San Jose, Isabel Maria T1 - Shaping of conductive polypyrrole during polymerization Y1 - 2005 CY - Potsdam ER - TY - THES A1 - Schwarzer, Rolf T1 - Identification of REDDI and TRB3 as novel transcriptional targets of PI 3-kinase signalling and analysis of their involvement in growth of cancer cells Y1 - 2005 CY - Potsdam ER - TY - JOUR A1 - Brilliantov, Nikolai V. A1 - Poschel, T. T1 - Self-diffusion in granular gases : Green-Kubo versus Chapman-Enskog N2 - We study the diffusion of tracers (self-diffusion) in a homogeneously cooling gas of dissipative particles, using the Green-Kubo relation and the Chapman-Enskog approach. The dissipative particle collisions are described by the coefficient of restitution epsilon which for realistic material properties depends on the impact velocity. First, we consider self-diffusion using a constant coefficient of restitution, epsilon=const, as frequently used to simplify the analysis. Second, self-diffusion is studied for a simplified (stepwise) dependence of epsilon on the impact velocity. Finally, diffusion is considered for gases of realistic viscoelastic particles. We find that for epsilon=const both methods lead to the same result for the self-diffusion coefficient. For the case of impact-velocity dependent coefficients of restitution, the Green-Kubo method is, however, either restrictive or too complicated for practical application, therefore we compute the diffusion coefficient using the Chapman-Enskog method. We conclude that in application to granular gases, the Chapman-Enskog approach is preferable for deriving kinetic coefficients. (C) 2005 American Institute of Physics Y1 - 2005 SN - 1054-1500 ER - TY - JOUR A1 - Carvajal, R. A1 - Wessel, Niels A1 - Vallverdu, M. A1 - Caminal, P. A1 - Voss, Andreas T1 - Correlation dimension analysis of heart rate variability in patients with dilated cardiomyopathy N2 - A correlation dimension analysis of heart rate variability (HRV) was applied to a group of 55 patients with dilated cardiomyopathy (DCM) and 55 healthy subjects as controls. The 24-h RR time series for each subject was divided into segments of 10,000 beats to determine the correlation dimension (CD) per segment. A study of the influence of the time delay (tag) in the calculation of CD was performed. Good discrimination between both groups (p < 0.005) was obtained with tag values of 5 or greater. CD values of DCM patients (8.4 ± 1.9) were significantly lower than CD values for controls (9.5 ± 1.9). An analysis of CD values of HRV showed that for healthy people, CD night values (10.6 ± 1.8) were significant greater than CD day values (9.2 ± 1.9), revealing a circadian rhythm. In DCM patients, this circadian rhythm was lost and there were no differences between CD values in day (8.8 ± 2.4) and night (8.9 ± 2. 1). © 2005 Elsevier Ireland Ltd. All rights reserved Y1 - 2005 SN - 0169-2607 ER - TY - JOUR A1 - Chambodut, Aude A1 - Mandea, Mioara T1 - Evidence for geomagnetic jerks in comprehensive models N2 - The rate of secular variation occasionally undergoes a sudden, sharp change, called a geomagnetic jerk. Such jerks have been detected in geomagnetic time series, centered-over the last four decades-around 1971, 1980, 1991, and 1999; others have been inferred from historical records. The geomagnetic jerks represent a reorganization of the secular variation, implying an internal origin, as established through spherical harmonic and wavelet analysis. However, some characteristics of jerks are not well understood. Here we estimate the occurrence dates for geomagnetic jerks, as they can be detected from a global geomagnetic model. This choice makes the present study novel, for two reasons. First, utilizing the comprehensive modelling approach allows for the use of a secular variation signal free of time-varying external fields and their corresponding induced counterpart, and observatory biases. Second, the model utilizes satellite data when available, in addition to observatory data. Indeed, POGO (1967 to 1971), MAGSAT (1979 to 1980), Orsted (1999 to present time) and CHAMP (2000 to present time) satellite measurements help to separate the different magnetic sources. In this study the CM4 comprehensive model is used for a global search of geomagnetic jerks and their occurrence dates. Our first result indicates that found geomagnetic jerks might not have been worldwide in occurrence. Moreover, the obtained dates suggest that jerks detected in the CM4 model over the last four decades occurred not simultaneously but at slightly different times around 1971, 1980 and 1991 Y1 - 2005 SN - 1343-8832 ER - TY - JOUR A1 - Pietsch, Ullrich A1 - Bodenthin, Yves A1 - Grenzer, Jörg A1 - Geue, Thomas A1 - Möhwald, Helmuth A1 - Kurth, Dirk G. T1 - Structure and temperature behavior of metallo-supramolecular assemblies N2 - A detailed structural analysis of a Langmuir-Blodgett (LB) multilayer composed of a polyelectrolyte-amphiphile complex (PAC) is presented. The PAC is self-assembled from metal ions, ditopic bis-terpyridines, and amphiphiles. The vertical structure of the LB multilayer is investigated by X-ray reflectometry. The multilayer has a periodicity of 57 A, which corresponds to an architecture of flat lying metallo-supramolecular coordination polyelectrolyte (MEPE) rods and upright-standing amphiphiles (dihexadecyl phosphate, DHP). In-plane diffraction reveals hexagonal packing of the DHP molecules. Using extended X-ray absorption fine structure (EXAFS) experiments, we prove that the central metal ion is coordinated to the terpyridine moieties in a pseudo-octahedral coordination environment. The Fe-N bond distances are 1.82 and 2.0 angstrom, respectively. Temperature resolved measurements indicate a reversible phase transition in a temperature range up to 55 degrees C. EXAFS measurements indicate a lengthening of the average Fe-N bond distance from 1.91 to 1.95 angstrom. The widening of the coordination cage upon heating is expected to lower the ligand field stabilization, thus giving rise to spin transitions in these composite materials Y1 - 2005 ER - TY - JOUR A1 - Barden, Marco A1 - Rix, Hans-Walter A1 - Somerville, Rachel S. A1 - Bell, Eric F. A1 - Häußler, Boris A1 - Peng, Chen Y. A1 - Borch, Andrea A1 - Beckwith, Steven V. W. A1 - Caldwell, John A. R. A1 - Heymans, Catherine A1 - Jahnke, Knud A1 - Jogee, Shardha A1 - McIntosh, Daniel H. A1 - Meisenheimer, Klaus A1 - Sanchez, Sebastian F. A1 - Wisotzki, Lutz A1 - Wolf, C. T1 - GEMS : the surface brightness and surface mass density evolution of disk galaxies N2 - We combine HST imaging from the GEMS ( Galaxy Evolution from Morphologies and SEDs) survey with photometric redshifts from COMBO-17 to explore the evolution of disk-dominated galaxies since z less than or similar to 1.1. The sample is composed of all GEMS galaxies with Sersic indices n < 2.5, derived from fits to the galaxy images. We account fully for selection effects through careful analysis of image simulations; we are limited by the depth of the redshift and HST data to the study of galaxies with M-V less than or similar to -20, or equivalently, log (M/M-circle dot) greater than or similar to 10. We find strong evolution in the magnitude-size scaling relation for galaxies with M-V less than or similar to -20, corresponding to a brightening of similar to 1 mag arcsec(-2) in rest-frame V band by z similar to 1. Yet disks at a given absolute magnitude are bluer and have lower stellar mass-to-light ratios at z similar to 1 than at the present day. As a result, our findings indicate weak or no evolution in the relation between stellar mass and effective disk size for galaxies with log (M/M-circle dot) greater than or similar to 10 over the same time interval. This is strongly inconsistent with the most naive theoretical expectation, in which disk size scales in proportion to the halo virial radius, which would predict that disks are a factor of 2 denser at fixed mass at z similar to 1. The lack of evolution in the stellar mass-size relation is consistent with an "inside-out'' growth of galaxy disks on average (galaxies increasing in size as they grow more massive), although we cannot rule out more complex evolutionary scenarios Y1 - 2005 ER - TY - JOUR A1 - Mermer, Ö. A1 - Veeraraghavan, G. A1 - Francis, T. L. A1 - Sheng, Y. A1 - Nguyen, D. T. A1 - Wohlgenannt, M. A1 - Köhler, Anna A1 - Al-Suti, Mohammed K. T1 - Large magnetoresistance in nonmagnetic pi-conjugated semiconductor thin film devices N2 - Following the recent observation of large magnetoresistance at room temperature in polyfluorene sandwich devices, we have performed a comprehensive magnetoresistance study on a set of organic semiconductor sandwich devices made from different pi-conjugated polymers and small molecules. The study includes a range of materials that show greatly different chemical structure, mobility, and spin-orbit coupling strength. We study both hole and electron transporters at temperatures ranging from 10 K to 300 K. We observe large negative or positive magnetoresistance (up to 10% at 300 K and 10 mT) depending on material and device operating conditions. We discuss our results in the framework of known magnetoresistance mechanisms and find that none of the existing models can explain our results. Y1 - 2005 ER - TY - JOUR A1 - Baptista, Murilo da Silva A1 - Pereira, Tiago A1 - Sartorelli, J. C. A1 - Caldas, Ibere Luiz A1 - Kurths, Jürgen T1 - Non-transitive maps in phase synchronization N2 - Concepts from Ergodic Theory are used to describe the existence of special non-transitive maps in attractors of phase synchronous chaotic oscillators. In particular, it is shown that, for a class of phase-coherent oscillators, these special maps imply phase synchronization. We illustrate these ideas in the sinusoidally forced Chua's circuit and two coupled Rossler oscillators. Furthermore, these results are extended to other coupled chaotic systems. In addition, a phase for a chaotic attractor is defined from the tangent vector of the flow. Finally, it is discussed how these maps can be used for the real-time detection of phase synchronization in experimental systems. (c) 2005 Elsevier B.V. All rights reserved Y1 - 2005 ER - TY - JOUR A1 - Baptista, Murilo da Silva A1 - Kraut, Suso A1 - Grebogi, Celso T1 - Poincare recurrence and measure of hyperbolic and nonhyperbolic chaotic attractors N2 - We study Poincare recurrence of chaotic attractors for regions of finite size. Contrary to the standard case, where the size of the recurrent regions tends to zero, the measure is no longer supported solely by unstable periodic orbits of finite length inside it, but also by other special recurrent trajectories, located outside that region. The presence of the latter leads to a deviation of the distribution of the Poincare first return times from a Poissonian. Consequently, by taking into account the contribution of these special recurrent trajectories, a corrected estimate of the measure is obtained. This has wide experimental implications, as in the laboratory all returns can exclusively be observed for regions of finite size, and only unstable periodic orbits of finite length can be detected Y1 - 2005 SN - 0031-9007 ER - TY - JOUR A1 - Pietsch, Ullrich A1 - Bhattacharya, M. K. A1 - Sanyal, M. K. A1 - Geue, Thomas T1 - Glass transition in Ultrathin Polymer Films : a Thermal Expansion Study N2 - The glass transition process gets affected in ultrathin films having thickness comparable to the size of the molecules. We observe systematic broadening of the glass transition temperature (T-g) as the thickness of an ultrathin polymer film reduces below the radius of gyration but the change in the average T-g was found to be very small. The existence of reversible negative and positive thermal expansion below and above T-g increased the sensitivity of our thickness measurements performed using energy-dispersive x-ray reflectivity. A simple model of the T-g variation as a function of depth expected from sliding motion could explain the results Y1 - 2005 ER - TY - JOUR A1 - Kitajima, H. A1 - Kurths, Jürgen T1 - Synchronized firing of FitzHugh-Nagumo neurons by noise N2 - We investigate the influence of noise on synchronization between the spiking activities of neurons with external impulsive forces. We first analyze the dependence of the synchronized firing on the amplitude and the angular frequency of the impulsive force in the noise-free system. Three cases (regular spiking, traveling wave, and chaotic spiking) with low synchronized firing are chosen to study effects due to noise. In each case we find that small noise can be a promoter of synchronization phenomena in neural activities, by choosing an appropriate noise intensity acting on some of the neurons. (C) 2005 American Institute of Physics Y1 - 2005 SN - 1054-1500 ER - TY - JOUR A1 - Claussen, M. A1 - Brovkin, Victor A1 - Calov, R. A1 - Ganopolski, A. A1 - Kubatzki, C. T1 - Did humankind prevent a Holocene glaciation? N2 - Recently, W.F. Ruddiman (2003, Climatic Change, Vol. 61, pp. 261-293) suggested that the anthropocene, the geological epoch of significant anthropospheric interference with the natural Earth system, has started much earlier than previously thought (P. I. Crutzen and E. F. Stoermer, 2000, IGBP Newsletter, Vol. 429, pp. 623-628). Ruddiman proposed that due to human land use, atmospheric concentrations of CO2 and CH4 began to deviate from their natural declining trends some 8000 and 5000 years ago, respectively. Furthermore, Ruddiman concluded that greenhouse gas concentrations grew anomalously thereby preventing natural large-scale glaciation of northern North America that should have occurred some 4000-5000 years ago without human interference. Here we would like to comment on (a) natural changes in atmospheric CO2 concentration during the Holocene and (b) on the possibility of a Holocene glacial inception. We substantiate our comments by modelling results which suggest that the last three interglacials are not a proper analogue for Holocene climate variations. In particular, we show that our model does not yield a glacial inception during the last several thousand years even if a declining trend in atmospheric CO2 was assumed Y1 - 2005 SN - 0165-0009 ER - TY - JOUR A1 - Dominis, Dijana A1 - Mimica, P. A1 - Pavlovski, K. A1 - Tamajo, E. T1 - In between beta Lyrae and Algol : the case of V356 Sgr N2 - The eclipsing binary system V356 Sgr is of considerable interest, since it is probably at the very end of its mass transfer phase, i.e. between beta Lyrae and Algol. Hence, the binary provides an opportunity to directly examine the exposed core of a star for signatures of nuclear burning, and to test stellar evolution models. The system is composed of an early B star accreting matter from a Roche-lobe filling A2 II star. Recently, with progress in the UV spectral region, significant revision of previous values for absolute parameters has been made. Therefore, we find it justified and important to present a new photometric solution. Our model is compared to an early disk model, and is discussed in the framework of mass transfer processes in this binary system Y1 - 2005 SN - 0004-640X ER - TY - JOUR A1 - Breu, J. A1 - Stossel, P. A1 - Schrader, Sigurd A1 - Starukhin, A. A1 - Finkenzeller, W. J. A1 - Yersin, H. T1 - Crystal structure of fac-Ir(ppy)(3) and emission properties under ambient conditions and at high pressure N2 - Solution and refinement of the crystal structure of fac-Ir(ppy)(3) is severely hampered by systematic twinning and pseudo-symmetry.fac-Ir(ppy)(3) Crystallizes in the centrosymmetric space group P (3) over bar as has been deduced from single-crystal structure refinement and investigations of the second harmonic generation (SHG) of fac-Ir(ppy)(3) powder as compared to two standard materials. The topology of the molecular packing of fac-Ir(ppy)(3) is identical to the packing observed for [Ru(bpy)(3)](0), however, the site symmetry of all Ir(ppy)(3) molecules is necessarily lowered from D-3 to C-3. Packing motifs with intermolecular "pi-pi interactions" of T-shaped and "shifted pi stack" geometry are realized. The systematic twinning leads to the occurrence of crystalline domains with rigorously alternating chirality within the bulk of the domains but with homochiral fac-Ir(ppy)(3) contacts at the domain interfaces. These differences in packing motifs are displayed in the emission spectra and in the high-pressure-induced shifts of the emission. The emission maximum of the bulk material at 18 350 cm(-1) (545 nm) and of the domain interfaces at 19 700 cm-1 (507 nm) experience for p < 25 kbar and T = 295 K red shifts of Delta nu/Delta p = -(12 +/- 2) cm(-1)/kbar, and -(22 +/- 4) cm(- 1)/kbar, respectively Y1 - 2005 SN - 0897-4756 ER - TY - JOUR A1 - Gräfener, Götz A1 - Hamann, Wolf-Rainer T1 - Hydrodynamic model atmospheres for WR stars : self-consistent modeling of a WC star wind N2 - We present the first non-LTE atmosphere models for WRstars that incorporate a self-consistent solution of the hydrodynamic equations. The models take iron-group line-blanketing and clumping into account, and compute the hydrodynamic structure of a radiatively driven wind consistently with the non-LTE radiation transport in the co-moving frame. We construct a self-consistent wind model that reproduces all observed properties of an early-type WCstar (WC5). We find that the WR-type mass-loss is initiated at high optical depth by the so-called "Hot Iron Bump" opacities (Fe IX- XVI). The acceleration of the outer wind regions is due to iron-group ions of lower excitation in combination with C and O. Consequently, the wind structure shows two acceleration regions, one close to the hydrostatic wind base in the optically thick part of the atmosphere, and another farther out in the wind. In addition to the radiative acceleration, the "Iron Bump" opacities are responsible for an intense heating of deep atmospheric layers. We find that the observed narrow O VI emission lines in the optical spectra of WC stars originate from this region. From their dependence on the clumping factor we gain important information about the location where the density inhomogeneities in WR-winds start to develop Y1 - 2005 SN - 0004-6361 ER - TY - JOUR A1 - Pietsch, Ullrich A1 - Grenzer, Jörg A1 - Bischoff, Lothar T1 - Grazing-incidence diffraction strain analysis of a laterally patterned Si wafer treated by focused Ge and An ion beam implantation N2 - Strain analysis of a laterally patterned Si-wafer was carried out utilizing X-ray grazing-incidence diffraction with synchrotron radiation. The lateral patterning was done by focused ion beam implantation using an ion source of liquid AuGeSi alloy. Samples were prepared by either 35 keV Au+ ions (dose: 0.2, 2 x 10(14) cm(-2)) or 70 keV Ge++ ions (dose: 8 X 10(14) cm(-1)). It was shown that due to implantation a periodical defect structure is created consisting of both implanted and not implanted stripes. The evaluated depth distribution of defects within the implanted stripes corresponds to that obtained by TRIM calculation. The induced strain distribution, however, shows no periodicity. This can be explained by an overlap of the strain fields created in each implanted stripe. (c) 2005 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim Y1 - 2005 ER - TY - JOUR A1 - Mortonson, M. J. A1 - Schechter, P. L. A1 - Wambsganss, Joachim T1 - Size is everything : universal features of quasar microlensing with extended sources N2 - We examine the effect that the shape of the source brightness profile has on the magnitude fluctuations of images in quasar lens systems due to microlensing. We do this by convolving a variety of accretion disk models (including Gaussian disks, uniform disks, "cones," and a Shakura-Sunyaev thermal model) with two magnification maps in the source plane, one with convergence kappa = 0.4 and shear gamma = 0.4 (positive parity) and the other with kappa = gamma = 0.6 ( negative parity). By looking at magnification histograms of the convolutions and using chi(2) tests to determine the number of observations that would be necessary to distinguish histograms associated with different disk models, we find that, for circular disk models, the microlensing fluctuations are relatively insensitive to all properties of the models except the half-light radius of the disk. Shakura-Sunyaev models are sufficiently well constrained by observed quasar properties that we can estimate the half-light radius at optical wavelengths for a typical quasar. If Shakura-Sunyaev models are appropriate, the half-light radii are very much smaller than the Einstein rings of intervening stars, and the quasar can be reasonably taken to be a point source except in the immediate vicinity of caustic-crossing events Y1 - 2005 SN - 0004-637X ER - TY - JOUR A1 - Poschel, T. A1 - Brilliantov, Nikolai V. A1 - Zaikin, Alexei T1 - Bistability and noise-enhanced velocity of rolling motion N2 - We investigate the motion of a hard cylinder rolling down a soft, inclined plane. The cylinder is subjected to a viscous drag force and stochastic fluctuations due to the surrounding rnedium. In a wide range of parameters we observe bistability of the rolling velocity. In dependence on the parameters, increasing noise level may lead to increasing or decreasing average velocity of the cylinder. The approximative analytical theory agrees with numerical results Y1 - 2005 ER - TY - JOUR A1 - Ostermeyer, Martin A1 - Kappe, Philip A1 - Menzel, Ralf A1 - Wulfmeyer, Volker T1 - Diode-pumped Nd : YAG master oscillator power amplifier with high pulse energy, excellent beam quality, and frequency-stabilized master oscillator as a basis for a next-generation lidar system N2 - In the original publication [Ostermeyer et al., Appl. Opt., 44, 582-590 (2005)], Fig. 5 appeared twice as Figs. 4 and 5. This inaccuracy is corrected here. (c) 2005 Optical Society of America Y1 - 2005 SN - 0003-6935 ER - TY - JOUR A1 - Borger, V. A1 - Kuliskovska, O. A1 - Hubmann, K. G. A1 - Stumpe, Joachim A1 - Huber, M. A1 - Menzel, Henning T1 - Novel polymers to study the influence of the azobenzene content on the photo-induced surface relief grating formation N2 - The influence of the azobenzene concentration on the photo-induced surface relief grating (SRG) formation in polymer films was investigated. Two series of polymers with 4-alkoxy-4'-cyanoazobenzene side groups were synthesized. In series A, the degree of substitution was varied, while in series B, azobenzene and biphenyl groups were introduced in varying composition, but the concentration of non-reacted HEMA-groups was kept constant. Photo-induction of the dichroism and the SRG was studied as function of the azobenzene concentration. An optimum was found for the SRG formation (76%), while the highest dichroism was induced at the lowest azobenzene concentration of 20%. The restriction of rotational and translational molecular motions observed at higher azobenzene concentration was explained by pi-pi stacking of the azobenzene moieties and interaction of unreacted HEMA groups Y1 - 2005 SN - 1022-1352 ER - TY - JOUR A1 - Brehm-Jurish, Eva Ute A1 - Saddy, Douglas T1 - On cohesion and coherence in text processing : two ERP studies Y1 - 2005 SN - 0898-929X ER - TY - JOUR A1 - Allefeld, Carsten T1 - Phase vs. amplitude correlations in event-related potentials Y1 - 2005 SN - 0898-929X ER - TY - JOUR A1 - Pietsch, Ullrich A1 - Bodenthin, Yves A1 - Möhwald, Helmuth A1 - Kurth, Dirk G. T1 - Inducing spin crossover in metallo-supramolecular polyelectrolytes through an amphiphilic phase transition N2 - A phase transition in an amphiphilic mesophase is explored to deliberately induce mechanical strain in an assembly of tightly coupled metal ion coordination centers. Melting of the alkyl chains in the amphiphilic mesophase causes distortion of the coordination geometry around the central transition metal ion. As a result, the crystal field splitting of the d-orbital subsets decreases resulting in a spin transition from a low-spin to a high-spin state. The diamagnetic-paramagnetic transition is reversible. This concept is demonstrated in a metallo-supramolecular coordination polyelectrolyte-amphiphile complex self-assembled from ditopic bis-terpyridines, Fe(II) as central transition metal, and dialkyl phosphates as amphiphiles. The magnetic properties are studied in a Langmuir-Blodgett multilayer. The modularity of this concept provides extensive control of structure and function from molecular to macroscopic length scales and gives access to a wide range of new molecular magnetic architectures such as nanostructures, thin films, and liquid crystals Y1 - 2005 ER - TY - JOUR A1 - Heringer-Walther, Silvia A1 - Moreira, M. C. V. A1 - Wessel, Niels A1 - Saliba, J. L. A1 - Silvia-Barra, J. A1 - Pena, J. L. B. A1 - Becker, S. A1 - Siems, W. E. A1 - Schultheiss, H. P. A1 - Walther, T. T1 - Brain natriuretic peptide predicts survival in Chagas' disease more effectively than atrial natriuretic peptide Y1 - 2005 SN - 1355-6037 ER - TY - JOUR A1 - Gorfman, S. V. A1 - Tsirelson, Vladimir G. A1 - Pietsch, Ullrich T1 - X-ray diffraction by a crystal in a permanent external electric field : general considerations N2 - The variations of X-ray diffraction intensities from a crystal in the presence of a permanent external electric field is modeled analytically using a first-order stationary perturbation theory. The change in a crystal, induced by an external electric field, is separated into two contributions. The first one is related to a pure polarization of an electron subsystem, while the second contribution can be reduced to the displacements of the rigid pseudoatoms from their equilibrium positions. It is shown that a change of the X-ray diffraction intensities mainly originates from the second contribution, while the influence of the pure polarization of a crystal electron subsystem is negligibly small. The quantities restored from an X-ray diffraction experiment in the presence of an external electric field were analyzed in detail in terms of a rigid pseudoatomic model of electron density and harmonic approximation for the atomic thermal motion. Explicit relationships are derived that link the properties of phonon spectra with E-field-induced variations of a structure factor, pseudoatomic displacements and piezoelectric strains. The displacements can be numerically estimated using a model of independent atomic motion if the Debye - Waller factors and pseudoatomic charges are known either from a previous single-crystal X-ray diffraction study or from density functional theory calculations. The above estimations can be used to develop an optimum strategy for a data collection that avoids the measurements of reflections insensitive to the electric-field-induced variations Y1 - 2005 SN - 0108-7673 ER - TY - JOUR A1 - Holzer, Wolfgang A1 - Penzkofer, Alfons A1 - Schrader, Sigurd A1 - Grimm, Bernhard T1 - Photo-physical and lasing characterisation of a polyparaphenylenevinylene (PPV) neat film N2 - The wave-guided travelling-wave laser action (amplified spontaneous emission) of a neat film of poly(p- phenylenevinylene) (PPV) on a quartz glass substrate prepared by a sulfinyl precursor technique is studied. The samples are transversally pumped with picosecond excitation pulses (wavelength 347.15 nm, duration 35 ps). Lasing occurs at 550 nm. The optical constants of the neat films are determined by transmittance measurements exploiting the multiple beam interference in the transparency region. A fluorescence spectroscopic characterisation is carried out determining the fluorescence quantum distribution, fluorescence quantum yield, degree of fluorescence polarisation, and fluorescence lifetime. The emitting chromophore size (emitting singlet exciton extension) is determined by the ratio of exciton radiative lifetime to repeat-unit based radiative lifetime. The obtained size of about two repeat units is discussed in a disordered solid-state polymer model Y1 - 2005 SN - 0306-8919 ER - TY - JOUR A1 - Huber, C. A1 - Klamroth, Tillmann T1 - Simulation of two-photon-photoelectron spectra at a jellium-vacuum interface N2 - In this paper we report on time dependent configuration interaction singles (TD-CIS) calculations aimed at simulating two-photon-photoelectron emission (2PPE) spectra of metal films, the latter treated within a one-dimensional jellium model. The method is based on a many-electron approach in which electron-electron-scattering is approximately accounted for and no artificial lifetimes have to be assumed for excited electrons. This contrasts with one-electron models where lifetimes and "dissipation" have to be introduced. The driving force for the photoelectron ejection in 2PPE experiments is the electric field of two laser pulses that are generally separated by a delay time, Delta t. To compute energy- and time-resolved 2PPE signals P(E, Delta t), a new scheme based on the time-energy method is proposed to analyze electronic wave packets in asymptotic regions of the potential Y1 - 2005 ER - TY - JOUR A1 - Jarosz, Grazyna A1 - Quinn, P. D. A1 - Stephan, Niels A1 - Brehmer, Ludwig T1 - Dielectric properties of zinc phthalocyanine thin films : effects of annealing in air and in N-2 N2 - This work presents the effects of ambient conditions, in particular oxygen and humidity, on the dielectric spectra of thin zinc phthalocyanine (ZnPc) films equipped with interdigitated electrodes and the effect of annealing in dry N-2 or in ambient air. The measurements were performed in the frequency range 10(-2)-10(5) Hz. The results indicate that the electric properties of ZnPc films are not only affected by oxygen but also by water vapour the presence of which always leads to the drop in alternating current conductance (ac-conductance). Moreover, at room temperature, the ac-conductance of ZnPc films previously exposed to air exhibits a reversible change with humidity, which makes these films attractive for humidity sensing applications. (C) 2004 Elsevier B.V. All rights reserved Y1 - 2005 SN - 0040-6090 ER - TY - JOUR A1 - Makuch, Martin A1 - Krivov, Alexander V. A1 - Spahn, Frank T1 - Long-term dynamical evolution of dusty ejecta from Deimos N2 - We re-assess expected properties of the presumed dust belt of Mars formed by impact ejecta from Deimos. Previous studies have shown that dynamics of Deimos particles are dominated by two perturbing forces: radiation pressure (RP) and Mars' oblateness (J2). At the same time, they have demonstrated that lifetimes of particles, especially of grains about ten of micrometers in size, may reach more than 10(4) years. On such timescales, the Poynting-Robertson drag (PR) becomes important. Here we provide a study of the dynamics under the combined action of all three perturbing forces. We show that a PR decay of the semimajor axes leads to an adiabatic decrease of amplitudes and periods of oscillations in orbital inclinations predicted in the framework of the underlying RP+J2 problem. Furthermore, we show that smallest of the long-lived Deimos grains (radius approximate to 5-10 mum) may reach a chaotic regime, resulting in unpredictable and abrupt changes of their dynamics. The particles just above that size (approximate to 10- 15 mum) should be the most abundant in the Deimos torus. Our dynamical analysis, combined with a more accurate study of the particle lifetimes, provides corrections to earlier predictions about the dimensions and geometry of the Deimos torus. In addition to a population, appreciably inclined and shifted towards the Sun, the torus should contain a more contracted, less asymmetric, and less tilted component between the orbits of Phobos and Deimos. (C) 2004 Elsevier Ltd. All rights reserved Y1 - 2005 SN - 0032-0633 ER - TY - JOUR A1 - Hainzl, Sebastian A1 - Ogata, Y. T1 - Detecting fluid signals in seismicity data through statistical earthquake modeling N2 - [1] According to the well-known Coulomb failure criterion the variation of either stress or pore pressure can result in earthquake rupture. Aftershock sequences characterized by the Omori law are often assumed to be the consequence of varying stress, whereas earthquake swarms are thought to be triggered by fluid intrusions. The role of stress triggering can be analyzed by modeling solely three-dimensional (3-D) elastic stress changes in the crust, but fluid flows which initiate seismicity cannot be investigated without considering complex seismicity patterns resulting from both pore pressure variations and earthquake-connected stress field changes. We show that the epidemic-type aftershock sequence (ETAS) model is an appropriate tool to extract the primary fluid signal from such complex seismicity patterns. We analyze a large earthquake swarm that occurred in 2000 in Vogtland/NW Bohemia, central Europe. By fitting the stochastic ETAS model, we find that stress triggering is dominant in creating the observed seismicity patterns and explains the observed fractal interevent time distribution. External forcing, identified with pore pressure changes due to fluid intrusion, is found to directly trigger only a few percent of the total activity. However, temporal deconvolution indicates that a pronounced fluid signal initiated the swarm. These results are confirmed by our analogous investigation of model simulations in which earthquakes are triggered by fluid intrusion as well as stress transfers on a fault plane embedded in a 3-D elastic half-space. The deconvolution procedure based on the ETAS model is able to reveal the underlying pore pressure variations Y1 - 2005 SN - 0148-0227 ER - TY - JOUR A1 - Krivov, Alexander V. A1 - Sremcevic, Miodrag A1 - Spahn, Frank T1 - Evolution of a Keplerian disk of colliding and fragmenting particles: a kinetic model with application to the Edgeworth-Kuiper belt N2 - We present a kinetic model of a disk of solid particles, orbiting a primary and experiencing inelastic collisions. In distinction to other collisional models that use a 2D (mass-sernimajor axis) binning and perform a separate analysis of the velocity (eccentricity, inclination) evolution, we choose mass and orbital elements as independent variables of a phase space. The distribution function in this space contains full information on the combined mass, spatial, and velocity distributions of particles. A general kinetic equation for the distribution function is derived, valid for any set of orbital elements and for any collisional outcome, specified by a single kernel function. The first implementation of the model utilizes a 3D phase space (mass-semimajor axis-eccentricity) and involves averages over the inclination and all angular elements. We assume collisions to be destructive, simulate them with available material- and size-dependent scaling laws, and include collisional damping. A closed set of kinetic equations for a mass-semimajor axis-eccentricity distribution is written and transformation rules to usual mass and spatial distributions of the disk material are obtained. The kinetic "core" of our approach is generic. It is possible to add inclination as an additional phase space variable, to include cratering collisions and agglomeration, dynamical friction and viscous stirring, gravity of large perturbers, drag forces, and other effects into the model. As a specific application, we address the collisional evolution of the classical population in the Edgeworth-Kuiper belt (EKB). We run the model for different initial disk's masses and radial profiles and different impact strengths of objects. Our results for the size distribution, collisional timescales, and mass loss are in agreement with previous studies. In particular, collisional evolution is found to be most substantial in the inner part of the EKB, where the separation size between the survivors over EKB ' s age and fragments of earlier collisions lies between a few and several tens of km. The size distribution in the EKB is not a single Dohnanyi-type power law, reflecting the size dependence of the critical specific energy in both strength and gravity regimes. The net mass loss rate of an evolved disk is nearly constant and is dominated by disruption of larger objects. Finally, assuming an initially uniform distribution of orbital eccentricities, we show that an evolved disk contains more objects in orbits with intermediate eccentricities than in nearly circular or more eccentric orbits. This property holds for objects of any size and is explained in terms of collisional probabilities. The effect should modulate the eccentricity distribution shaped by dynamical mechanisms, such as resonances and truncation of perihelia by Neptune. (c) 2004 Elsevier Inc. All rights reserved Y1 - 2005 SN - 0019-1035 ER - TY - JOUR A1 - Kappe, Philip A1 - Ostermeyer, Martin A1 - Menzel, Ralf T1 - Active mode locking of a phase-conjugating SBS-laser oscillator N2 - We present a flashlamp-pumped Nd: YAG laser simultaneously emitting pulse structures on microsecond, nanosecond and picosecond time scales. Within a microsecond flashlamp pump pulse a nonlinear reflector based on stimulated Brillouin scattering (SBS) generates several Q-switch pulses. The phase-conjugating effect of the SBS reflector provides a compensation of phase distortions generated inside the laser rod, resulting in transverse fundamental mode operation. Additional acousto-optic loss modulation inside the resonator leads to mode locking. As a result, each Q-switch pulse is subdivided into several picosecond pulses. Energies of up to 2 mJ for the mode-locked pulses with durations between 220 and 800 ps are demonstrated. The wide variability of the laser's temporal output parameters as well as its high beam quality make it a splendid tool for fundamental research in laser materials processing Y1 - 2005 SN - 0946-2171 ER -