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 - TY - JOUR A1 - Surovyatkina, E. D. A1 - Kravtsov, Y. A. A1 - Kurths, Jürgen T1 - Fluctuation growth and saturation in nonlinear oscillators on the threshold of bifurcation of spontaneous symmetry breaking N2 - We study prebifurcation fluctuation amplification in nonlinear oscillators subject to bifurcations of spontaneous symmetry breaking which are manifest in the doubling of stable equilibrium states. Our theoretical estimates of both the linear growth and the nonlinear saturation of the fluctuations are in good agreement with our results from numerical simulations. We show that in the saturation mode, the fluctuation variance is proportional to the standard deviation of the external noise, whereas in the linear mode, the fluctuation variance is proportional to the noise variance. It is demonstrated that the phenomenon of prebifurcation noise amplification is more pronounced in the case of a slow transition through the bifurcation point. The amplification of fluctuations in this case makes it easier to form a symmetric probability of the final equilibrium states. In contrast, for a fast transition through the bifurcation point, the effect of amplification is much less pronounced. Under backward and forward passages through the bifurcation point, a loop of noise-dependent hysteresis emerges here. We find that for a fast transition of the nonlinear oscillator through the bifurcation point, the probability symmetry of the final equilibrium states is destroyed Y1 - 2005 SN - 1539-3755 ER - TY - JOUR A1 - Schellnhuber, Hans Joachim A1 - Crutzen, P. J. A1 - Clark, W. C. A1 - Hunt, J. T1 - Earth system analysis for sustainability N2 - Anthropogenic interference has resulted in climate change, ocean acidification, eutrophication and toxic pollution of the earth and it's ecosystems. The Earth System Analysis is an international research program on global environmental change to understand these processes in order to work towards global sustainability Y1 - 2005 SN - 0013-9157 ER - TY - JOUR A1 - Zoller, Gert A1 - Holschneider, Matthias A1 - Ben-Zion, Yehuda T1 - The role of heterogeneities as a tuning parameter of earthquake dynamics N2 - We investigate the influence of spatial heterogeneities on various aspects of brittle failure and seismicity in a model of a large strike-slip fault. The model dynamics is governed by realistic boundary conditions consisting of constant velocity motion of regions around the fault, static/kinetic friction laws, creep with depth-dependent coefficients, and 3-D elastic stress transfer. The dynamic rupture is approximated on a continuous time scale using a finite stress propagation velocity ("quasidynamic model''). The model produces a "brittle- ductile'' transition at a depth of about 12.5 km, realistic hypocenter distributions, and other features of seismicity compatible with observations. Previous work suggested that the range of size scales in the distribution of strength-stress heterogeneities acts as a tuning parameter of the dynamics. Here we test this hypothesis by performing a systematic parameter-space study with different forms of heterogeneities. In particular, we analyze spatial heterogeneities that can be tuned by a single parameter in two distributions: ( 1) high stress drop barriers in near- vertical directions and ( 2) spatial heterogeneities with fractal properties and variable fractal dimension. The results indicate that the first form of heterogeneities provides an effective means of tuning the behavior while the second does not. In relatively homogeneous cases, the fault self-organizes to large-scale patches and big events are associated with inward failure of individual patches and sequential failures of different patches. The frequency-size event statistics in such cases are compatible with the characteristic earthquake distribution and large events are quasi-periodic in time. In strongly heterogeneous or near-critical cases, the rupture histories are highly discontinuous and consist of complex migration patterns of slip on the fault. In such cases, the frequency-size and temporal statistics follow approximately power-law relations Y1 - 2005 SN - 0033-4553 ER - TY - JOUR A1 - Shabunin, A. A1 - Astakhov, Vladimir V. A1 - Kurths, Jürgen T1 - Quantitative analysis of chaotic synchronization by means of coherence N2 - We use an index of chaotic synchronization based on the averaged coherence function for the quantitative analysis of the process of the complete synchronization loss in unidirectionally coupled oscillators and maps. We demonstrate that this value manifests different stages of the synchronization breaking. It is invariant to time delay and insensitive to small noise and distortions, which can influence the accessible signals at measurements. Peculiarities of the synchronization destruction in maps and oscillators are investigated Y1 - 2005 SN - 1539-3755 ER - TY - JOUR A1 - Sremcevic, Miodrag A1 - Krivov, Alexander V. A1 - Krüger, Harald A1 - Spahn, Frank T1 - Impact-generated dust clouds around planetary satellites : model versus Galileo N2 - This paper focuses on tenuous dust clouds of Jupiter's Galilean moons Europa, Ganymede and Callisto. In a companion paper (Sremcevic et al., Planet. Space Sci. 51 (2003) 455-471) an analytical model of impact-generated ejecta dust clouds surrounding planetary satellites has been developed. The main aim of the model is to predict the asymmetries in the dust clouds which may arise from the orbital motion of the parent body through a field of impactors. The Galileo dust detector data from flybys at Europa, Ganymede and Callisto are compatible with the model, assuming projectiles to be interplanetary micrometeoroids. The analysis of the data suggests that two interplanetary impactor populations are most likely the source of the measured dust clouds: impactors with isotropically distributed velocities and micrometeoroids in retrograde orbits. Other impactor populations, namely those originating in the Jovian system, or interplanetary projectiles with low orbital eccentricities and inclinations, or interstellar stream particles, can be ruled out by the statistical analysis of the data. The data analysis also suggests that the mean ejecta velocity angle to the normal at the satellite surface is around 30°, which is in agreement with laboratory studies of the hypervelocity impacts. © 2004 Elsevier Ltd. All rights reserved Y1 - 2005 SN - 0032-0633 ER - TY - JOUR A1 - Schneider, M. A1 - Teuchner, Klaus A1 - Leupold, Dieter T1 - Two-photon fluorescence of ocular melanomas. Studies on a new diagnostic method N2 - Choroidal melanoma is the most frequent form of primary neoplasia among malignant ocular tumors. Since it is presumed that metastasis often occurs before the primary tumor is first diagnosed, early detection is exigent. The aim of the studies described in this report was to develop an objective, noninvasive method for the diagnosis of choroidal melanoma. The underlying new principle of fluorescence excitation is presented. This is based on the observation that melanin, due to its unique absorption characteristics, is selectively excited into fluorescence via stepwise absorption of two photons of a femtosecond laser emitting at 800 nm. In the experiment described, the fluorescence of excised tissue from healthy choroidal pigment epithelium was compared to that of excised choroidal melanoma. The fluorescence of choroidal melanomas exhibited a more reddish appearance and less intensity than that of healthy tissue. This implies that the configuration of melanin apparently changes during the process of malignant degeneration. The method described here could thus serve as an evidentiary objective diagnostic technique before initiating treatment for choroidal melanomas Y1 - 2005 SN - 0941-293X ER - TY - JOUR A1 - Sava, Ion A1 - Bruma, Maria A1 - Schulz, Burkhard A1 - Köpnick, Thomas T1 - Comparison of properties of silicon-containing poly(amide-imide)s N2 - New silicon-containing poly(amide-imide)s have been synthesized by direct polycondensation of various aromatic diamines with a dicarboxylic acid containing the dimethylsilylene group and preformed in-tide cycles. These polymers are easily soluble in polar amidic solvents such as N-methylpyrrolidinone (NMP) or dimethylformamide (DMF) and can be cast into thin flexible films or coatings from such solutions. They show high thermal stability, with initial decomposition temperature being above 400 C and glass transition temperature in the range of 220-270 degrees C. Very thin polymer films deposited by spincoating technique onto silicon wafers showed a smooth, pinhole-free surface in atomic force microscopy investigations Y1 - 2005 SN - 0954-0083 ER - TY - JOUR A1 - Tuncer, Enis T1 - Extracting the spectral density function of a binary composite without a priori assumptions N2 - The spectral representation separates the contributions of geometrical arrangement (topology) and intrinsic constituent properties in a composite. The aim of this Brief Report is to present a numerical algorithm based on the Monte Carlo integration and constrained least-squares methods to resolve the spectral density function for a given system. The numerical method is verified by testing it on the well-known Maxwell Garnett expression. Later, it is applied to a well-studied rock-and-brine system to instruct its utility. The presented method yields significant microstructural information in improving our understanding of how microstructure influences the macroscopic behavior of composites without any intricate mathematics Y1 - 2005 SN - 1098-0121 ER - TY - JOUR A1 - Tuncer, Enis T1 - Numerical calculations of effective elastic properties of two cellular structures N2 - Young's moduli of regular two-dimensional truss-like and eye-shaped structures are simulated using the finite element method. The structures are idealizations of soft polymeric materials used in ferro-electret applications. In the simulations, the length scales of the smallest representative units are varied, which changes the dimensions of the cell walls in the structures. A power-law expression with a quadratic as the exponent term is proposed for the effective Young's moduli of the systems as a function of the solid volume fraction. The data are divided into three regions with respect to the volume fraction: low, intermediate and high. The parameters of the proposed power-law expression in each region are later represented as a function of the structural parameters, the unit-cell dimensions. The expression presented can be used to predict a structure/property relationship in materials with similar cellular structures. The contribution of the cell-wall thickness to the elastic properties becomes significant at concentrations > 0.15. The cell-wall thickness is the most significant factor in predicting the effective Young's modulus of regular cellular structures at high volume fractions of solid. At lower concentrations of solid, the eye-shaped structure yields a lower Young's modulus than a truss-like structure with similar anisotropy. Comparison of the numerical results with those of experimental data for poly(propylene) show good aggreement regarding the influence of cell-wall thickness on elastic properties of thin cellular films Y1 - 2005 SN - 0022-3727 ER - TY - JOUR A1 - Tuncer, Enis T1 - Structure-property relationship in dielectric mixtures: application of the spectral density theory N2 - This paper presents numerical simulations performed on dielectric properties of two-dimensional binary composites. The influence of structural differences and intrinsic electrical properties of constituents on the composite's overall electrical properties is investigated. The structural differences are resolved by fitting the dielectric data with an empirical formula and by the spectral density representation approach. At low concentrations of inclusions (concentrations lower than the percolation threshold), the spectral density functions are delta-sequences, which corresponds to the predictions of the general Maxwell-Garnett (MG) mixture formula. At high concentrations of inclusions (close to the percolation threshold) systems exhibit non-Debye-type dielectric dispersions, and the spectral density functions differ from each other and that predicted by the MG expression. The analysis of the dielectric dispersions with an empirical formula also brings out the structural differences between the considered geometries, however, the information is not qualitative. The empirical formula can only be used to compare structures. The spectral representation method on the other hand is a concrete way of characterizing the structures of the dielectric mixtures. Therefore, as in other spectroscopic techniques, a look-up table might be useful to classify/characterize structures of composite materials. This can be achieved by generating dielectric data for known structures by using ab initio calculations, as presented and emphasized in this study. The numerical technique presented here is not based on any a priori assumption methods Y1 - 2005 SN - 0022-3727 ER - TY - JOUR A1 - Tuncer, Enis A1 - Lang, Sidney B. T1 - Numerical extraction of distributions of space-charge and polarization from laser intensity modulation method N2 - The Fredholm integral equation of the laser intensity modulation method is an ill-conditioned problem with multiple solutions. An approach based on an application of the Monte Carlo technique and a least-squares solver is developed and tested on simulated data containing both Gaussian and white noise. Good agreement between the original polarization and the estimated one was found. The influences of bin size and spacing, and errors in material properties, are discussed. It is shown that the presented approach is an alternative to other data analysis techniques in the literature based on regularization algorithms. (C) 2005 American Institute of Physics Y1 - 2005 SN - 0003-6951 ER - TY - JOUR A1 - Saparin, P. I. A1 - Thomsen, J. S. A1 - Prohaska, Steffen A1 - Zaikin, Alexei A1 - Kurths, Jürgen A1 - Hege, H. C. A1 - Gowin, W. T1 - Quantification of spatial structure of human proximal tibial bone biopsies using 3D measures of complexity N2 - Changes in trabecular bone composition during development of osteoporosis are used as a model for bone loss in microgravity conditions during a space flight. Symbolic dynamics and measures of complexity are proposed and applied to assess quantitatively the structural composition of bone tissue from 3D data sets of human tibia bone biopsies acquired by a micro-CT scanner. In order to justify the newly proposed approach, the measures of complexity of the bone architecture were compared with the results of traditional 2D bone histomorphometry. The proposed technique is able to quantify the structural loss of the bone tissue and may help to diagnose and to monitor changes in bone structure of patients on Earth as well as of the space-flying personnel. © 2005 Elsevier Ltd. All rights reserved Y1 - 2005 SN - 0094-5765 ER - TY - JOUR A1 - Penacorada, Florencio A1 - Souto, Jorge A1 - de Saja, J. A. A1 - Brehmer, Ludwig T1 - Brewster angle microscopy and surface potential measurements of Langmuir-Blodgett films of zinc tri(tert-butyl)- 4-sulphophthalocyanine N2 - The formation of a Langmuir monolayer of an amphiphilic derivative of zinc phthalocyanine (Na[(ZnPcSO3)-S-t]) has been studied by means of surface potential technique and Brewster angle microscopy. The experiments were undertaken in order to understand the behaviour of this monolayer with a well-defined surface pressure isotherm. The floating film is described as a truly monomolecular layer formed by very rigid islands in which the phthalocyanine units tend to take on a preferential orientation with their planes perpendicular to the air-water interface, for high values of the surface pressure. (c) 2004 Elsevier B.V. All rights reserved Y1 - 2005 SN - 0169-4332 ER - TY - JOUR A1 - Pietsch, Ullrich A1 - Panzner, Tobias A1 - Leitenberger, Wolfram A1 - Vartanyants, Ivan A. T1 - Coherence experiments using white synchrotron radiation N2 - Experiments at the bending magnet beamline at BESSY II (EDR beamline) profit from the excellent coherence properties of third generation synchrotron sources. Considering the exponentially decaying incident spectrum, and because no optical elements are installed except slits and vacuum windows, coherence experiments can be performed between 5 keV < E < 15 keV. First, the energy dependence of spatial coherence properties were determined measuring diffraction at single and double pinholes. Next, the coherent white radiation was used to probe the morphology of thin films in reflection geometry. The recorded intensity maps (reflectivity versus sample position) provide speckle patterns which reveal the locally varying sample morphology. Setting the incident angle, alpha(i), smaller or larger than the critical angle of total external reflection, alpha(c), one should be able to separate the surface height profile from the subsurface density modulation of a sample. The validity of this approach is verified at the example of reciprocal space maps taken from a polymer surface where we could reconstruct the lateral height profile from speckle data. (C) 2004 Elsevier B.V. All rights reserved Y1 - 2005 ER - TY - JOUR A1 - Poschel, T. A1 - Brilliantov, Nikolai V. A1 - Schwager, T. T1 - Transient clusters in granular gases N2 - The most striking phenomenon in the dynamics of granular gases is the formation of clusters and other structures. We investigate a gas of dissipatively colliding particles with a velocity dependent coefficient of restitution where cluster formation occurs as a transient phenomenon. Although for small impact velocity the particles collide elastically, surprisingly the temperature converges to zero Y1 - 2005 SN - 0953-8984 ER - TY - JOUR A1 - Rappich, J. A1 - Hartig, P. A1 - Nickel, N. H. A1 - Sieber, I. A1 - Schulze, S. A1 - Dittrich, T. T1 - Stable electrochemically passivated Si surfaces by ultra thin benzene-type layers N2 - Ultra thin organic layers of benzene-type molecules are able to passivate Si surfaces. The organic layers were electrochemically deposited on Si surfaces from aqueous solution of diazonium compounds and show a blocking of the charge transfer from Si into the electrolyte after the deposition process. Electron microscopic images reveal a compact and homogeneous organic layer of 4-bromobenzene on the Si. The surface recombination increases only slightly with respect to a well H-passivated Si surface, so that the interface state density is about 10(11) cm(2) or slightly below. Organic layer modified Si surfaces are much longer stable in ambient air than the H-terminated surface as observed by a slower decay of the integrated photoluminescence intensity with time. Thermal desorption measurements show that the organic layer is stable up to about 200 degrees C. Y1 - 2005 SN - 0167-9317 ER - TY - THES A1 - Abel, Markus T1 - Turbulent flows : transport, analysis and modeling Y1 - 2005 CY - Potsdam ER - TY - THES A1 - Kietzke, Thomas T1 - Solar cells based on novel nanostructured blends of semiconducting polymers Y1 - 2005 CY - Potsdam ER - TY - THES A1 - Andersen, Morten I. T1 - Low-mass pre-main-sequence stars in the massive star clusters NGC 3603 and 30 Dor Y1 - 2005 ER - TY - THES A1 - Steuer, Ralf T1 - Nonlinear dynamics an molecular biology : from gene expression to metabolic networks Y1 - 2005 CY - Potsdam ER - TY - JOUR A1 - Abel, Markus A1 - Ahnert, Karsten A1 - Kurths, R. A1 - Mandelj, S. T1 - Additive nonparametric reconstruction of dynamical systems from time series N2 - We present a nonparametric way to retrieve an additive system of differential equations in embedding space from a single time series. These equations can be treated with dynamical systems theory and allow for long-term predictions. We apply our method to a modified chaotic Chua oscillator in order to demonstrate its potential Y1 - 2005 SN - 1063-651X ER - TY - JOUR A1 - Kappe, Philip A1 - Ostermeyer, Martin A1 - Menzel, Ralf T1 - Active mode locking of a phase-conjugating SBS-laser oscillator Y1 - 2005 SN - 0946-2171 ER - TY - JOUR A1 - Ostermeyer, Martin A1 - Klemz, Guido A1 - Kubina, P. A1 - Menzel, Ralf T1 - Enhanced brightness and extraction efficiency of Nd:YAG rod lasers resulting in 180 W output power with M2<1.2 Y1 - 2005 SN - 1-557-52697-4 ER - TY - THES A1 - Wessel, Niels T1 - Data analysis and modeling of the cardiovascular system Y1 - 2005 CY - Potsdam ER - TY - JOUR A1 - Hoffmann, H. A1 - Boström, Kim A1 - Felbinger, Timo T1 - Comment on Secure direct communication with a quantum one-time pad N2 - In the paper [Phys. Rev. A 69, 052319 (2004)], a quantum direct communication protocol is proposed which is claimed to be unconditionally secure even for the case of a noisy channel. We show that this is not the case by giving an undetectable attack scheme Y1 - 2005 ER - TY - JOUR A1 - Pietsch, Ullrich A1 - Panzner, Tobias A1 - Leitenberger, Wolfram A1 - Vartanyants, Ivan A. T1 - Coherence experiments at the EDR-beamline of BESSY II Y1 - 2005 ER - TY - JOUR A1 - Nest, Mathias A1 - Klamroth, Tillmann T1 - Correlated many-electron dynamics : application to inelastic electron scattering at a metal film N2 - The multiconfiguration time-dependent Hartree-Fock and the time-dependent configuration interaction singles method are applied to the correlated many-electron dynamics of a one-dimensional jellium model system. We study the scattering of an initially free electron at a model film in the framework of both approaches. In particular, both methods are compared with regard to how they describe the underlying physical processes, namely inelastic electron scattering, inverse photoemission, and electron impact ionization Y1 - 2005 ER - TY - JOUR A1 - Baptista, Murilo da Silva A1 - Kurths, Jürgen T1 - Chaotic channel N2 - 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 Y1 - 2005 SN - 1539-3755 ER - TY - JOUR A1 - Lang, Sidney B. A1 - Mellinger, Axel T1 - A package of Mathematica programs for training students in the use of LIMM and its analysis N2 - A package of programs written using the symbolic mathematics program, Mathematicatrademark, has been developed. Its principal usage is in teaching the LIMM method to students and demonstrating data analysis by means of the Polynomial Regularization Method (PRM). A large number of variables can be changed in the program and their effects can be shown graphically. Students at the University of Potsdam and Monash University have used the program successfully Y1 - 2005 ER - TY - JOUR A1 - Colin, S A1 - Corbett, J A1 - Durt, T A1 - Gross, David T1 - About SICPOVMs and discrete Wigner distributions N2 - A set of d(2) vectors in a Hilbert space of dimension d is called equiangular if each pair of vectors encloses the same angle. The projection operators onto these vectors define a POVM which is distinguished by its high degree of symmetry. Measures of this kind are called symmetric informationally complete, or SIC POVMs for short, and could be applied for quantum state tomography. Despite its simple geometrical description, the problem of constructing SIC POVMs or even proving their existence seems to be very hard. It is our purpose to introduce two applications of discrete Wigner functions to the analysis of the problem at hand. First, we will present a method for identifying symmetries of SIC POVMs under Clifford operations. This constitutes an alternative approach to a structure described before by Zauner and Appleby. Further, a simple and geometrically motivated construction for an SIC POVM in dimensions two and three is given (which, unfortunately, allows no generalization). Even though no new structures are found, we hope that the re- formulation of the problem may prove useful for future inquiries Y1 - 2005 ER - TY - JOUR A1 - Talalaev, V A1 - Tomm, JW A1 - Elsaesser, T A1 - Zeimer, Ute A1 - Fricke, J A1 - Knauer, A A1 - Kissel, H A1 - Weyers, Markus A1 - Tarasov, GG A1 - Grenzer, Jörg A1 - Pietsch, Ullrich T1 - Carrier dynamics in laterally strain-modulated InGaAs quantum wells N2 - We investigate the transient recombination and transfer properties of nonequilibrium carriers in an In0.16Ga0.84As/GaAs quantum well (QW) with an additional lateral confinement implemented by a patterned stressor layer. The structure thus contains QW- and quantum-wire-like areas. At low excitation densities, photoluminescence (PL) transients from both areas are well described by a rate equation model for a three-level system with a saturable interlevel carrier transfer representing the lateral drift of carriers from the QW regions into the wires. Small-signal carrier lifetimes for QW, wires, and transfer time from QW to wire are 180, 190, and 28 ps, respectively. For high excitation densities the time constants of the observed transients increase, in agreement with the model. In addition, QW and wire PL lines merge indicating a smoothening of the potential difference, i.e., the effective carrier confinement caused by the stressor structure becomes weaker with increasing excitation. (c) 2005 American Institute of Physics Y1 - 2005 ER - TY - JOUR A1 - Blasius, Bernd T1 - Anomalous phase synchronization in two asymmetrically coupled oscillators in the presence of noise N2 - We study the route to synchronization in two noisy, nonisochronous oscillators. Anomalous phase synchronization arises if both oscillators differ in their respective value of nonisochronicity and it is characterized by a strong detuning of the oscillator frequencies with the onset of coupling. Here we show that anomalous synchronization, both in limit-cycle or chaotic oscillators, can considerably be enlarged under the influence of asymmetrical coupling and noise. In these systems we describe a number of noise induced effects, such as an inversion of the natural frequency difference and coupling induced desynchronization of two identical oscillators. Our results can be explained in terms of a noisy particle in a tilted washboard potential Y1 - 2005 ER - TY - JOUR A1 - Seiss, Martin A1 - Spahn, Frank A1 - Sremcevic, Miodrag A1 - Salo, H. T1 - Structures induced by small moonlets in Saturn's rings : implications for the Cassini Mission N2 - Particle simulations are carried out to study density features caused by small moonlets embedded in a dense planetary ring. The creation of a "propeller" like structure is found together with adjacent density wakes. Both features are clear indications for the existence of moonlets in the rings. We confirmed that the propeller scales with the Hill-radius in radial direction whereas its azimuthal extent is determined by the ratio between the moonlet-mass and the ring-viscosity. Our findings bear direct implications for the analysis of the Cassini imaging (ISS) and occultation (UVIS) data: (i) for the detection of embedded larger bodies (>30 m) in Saturn's rings, and (ii) for remotely probing transport properties of the rings. The existence of a moonlet population may point to a catastrophic disruption of a parent body as a formation scenario for rings Y1 - 2005 SN - 0094-8276 ER - TY - THES A1 - Mironova, Irina Aleksandrova T1 - Vlijanie solne˜écnoj aktivnosti na prozra˜écnost˜§ atmosfery i opti˜éceskie svojstva a˜çerozolja Y1 - 2005 PB - Sankt Peterburgskij gos. univ. CY - Sankt Peterburg ER - TY - JOUR A1 - Feudel, Fred A1 - Witt, Annette A1 - Gellert, Marcus A1 - Kurths, Jürgen A1 - Grebogi, Celso A1 - Sanjuan, Miguel Angel Fernandez T1 - Intersections of stable and unstable manifolds : the skeleton of Lagrangian chaos N2 - We study Hamiltonian chaos generated by the dynamics of passive tracers moving in a two-dimensional fluid flow and describe the complex structure formed in a chaotic layer that separates a vortex region from the shear flow. The stable and unstable manifolds of unstable periodic orbits are computed. It is shown that their intersections in the Poincare map as an invariant set of homoclinic points constitute the backbone of the chaotic layer. Special attention is paid to the finite time properties of the chaotic layer. In particular, finite time Lyapunov exponents are computed and a scaling law of the variance of their distribution is derived. Additionally, the box counting dimension as an effective dimension to characterize the fractal properties of the layer is estimated for different duration times of simulation. Its behavior in the asymptotic time limit is discussed. By computing the Lyapunov exponents and by applying methods of symbolic dynamics, the formation of the layer as a function of the external forcing strength, which in turn represents the perturbation of the originally integrable system, is characterized. In particular, it is shown that the capture of KAM tori by the layer has a remarkable influence on the averaged Lyapunov exponents. (C) 2004 Elsevier Ltd. All rights reserved Y1 - 2005 ER - TY - JOUR A1 - Eisert, Jens T1 - Optimizing linear optics quantum gates N2 - In this Letter, the problem of finding optimal success probabilities of linear optics quantum gates is linked to the theory of convex optimization. It is shown that by exploiting this link, upper bounds for the success probability of networks realizing single-mode gates can be derived, which hold in generality for postselected networks of arbitrary size, any number of auxiliary modes, and arbitrary photon numbers. As a corollary, the previously formulated conjecture is proven that the optimal success probability of a nonlinear sign shift without feedforward is 1/4, a gate playing the central role in the scheme of Knill-Laflamme-Milburn for quantum computation. The concept of Lagrange duality is shown to be applicable to provide rigorous proofs for such bounds, although the original problem is a difficult nonconvex problem in infinitely many objective variables. The versatility of this approach is demonstrated Y1 - 2005 SN - 0031-9007 ER - TY - JOUR A1 - Evans, C. J. A1 - Smartt, S. J. A1 - Lee, J. K. A1 - Lennon, D. J. A1 - Kaufer, A. A1 - Dufton, P. L. A1 - Trundle, C. A1 - Herrero, A. A1 - Simon Díaz, Sergio A1 - de Koter, A. A1 - Hamann, Wolf-Rainer A1 - Hendry, M. A. A1 - Hunter, I. A1 - Irwin, M. J. A1 - Korn, A. J. A1 - Kudritzki, R. P. A1 - Langer, Norbert A1 - Mokiem, M. R. A1 - Najarro, F. A1 - Pauldrach, A. W. A. A1 - Przybilla, Norbert A1 - Puls, J. A1 - Ryans, R. S. I. A1 - Urbaneja, M. A. A1 - Venn, K. A. A1 - Villamariz, M. R. T1 - The VLT-FLAMES survey of massive stars : Observations in the Galactic clusters NGC3293, NGC4755 and NGC6611 N2 - We introduce a new survey of massive stars in the Galaxy and the Magellanic Clouds using the Fibre Large Array Multi- Element Spectrograph ( FLAMES) instrument at the Very Large Telescope ( VLT). Here we present observations of 269 Galactic stars with the FLAMES- Giraffe Spectrograph ( R similar or equal to 25 000), in fields centered on the open clusters NGC3293, NGC4755 and NGC6611. These data are supplemented by a further 50 targets observed with the Fibre- Fed Extended Range Optical Spectrograph ( FEROS, R = 48 000). Following a description of our scientific motivations and target selection criteria, the data reduction methods are described; of critical importance the FLAMES reduction pipeline is found to yield spectra that are in excellent agreement with less automated methods. Spectral classifications and radial velocity measurements are presented for each star, with particular attention paid to morphological peculiarities and evidence of binarity. These observations represent a significant increase in the known spectral content of NGC3293 and NGC4755, and will serve as standards against which our subsequent FLAMES observations in the Magellanic Clouds will be compared Y1 - 2005 ER - TY - JOUR A1 - Dimitriev, O. P. A1 - Smertenko, P. S. A1 - Stiller, Burkhard A1 - Brehmer, Ludwig T1 - Polyaniline-transition metal salt complexes: insight into formation mechanisms N2 - Two basic morphologies of emeraldine base of polyaniline-transition metal salt complex films cast from N- methylpyrrolidinone solutions are described. The first morphology consists of grains and the other consists of loose aggregates, respectively. The correlation of the film morphology with formation of precipitate in the complex solution, kinetics of solvent evaporation from the cast film, amount of solvent entrapped in the film, film conductivity, and IR absorption spectra is shown. Two different mechanisms of the complex formation as a result of competition in the polymer- inorganic salt-solvent trio interactions are discussed; the first mechanism results in folding of macromolecules into compact coils being then a core of grains in the complex films, and the second mechanism leads to blending of the polymer chains with solvent giving rise to formation of loose aggregates. (c) 2005 Elsevier B.V. All rights reserved Y1 - 2005 SN - 0379-6779 ER - TY - JOUR A1 - Serafini, A. A1 - Eisert, Jens A1 - Wolf, M. M. T1 - Multiplicativity of maximal output purities of Gaussian channels under Gaussian inputs N2 - We address the question of the multiplicativity of the maximal p-norm output purities of bosonic Gaussian channels under Gaussian inputs. We focus on general Gaussian channels resulting from the reduction of unitary dynamics in larger Hilbert spaces. It is shown that the maximal output purity of tensor products of single-mode channels under Gaussian inputs is multiplicative for any p is an element of (1, infinity) for products of arbitrary identical channels as well as for a large class of products of different channels. In the case of p=2, multiplicativity is shown to be true for arbitrary products of generic channels acting on any number of modes Y1 - 2005 ER - TY - JOUR A1 - Eisert, Jens A1 - Cramer, Marcus T1 - Single-copy entanglement in critical quantum spin chains N2 - We consider the single-copy entanglement as a quantity to assess quantum correlations in the ground state in quantum many-body systems. We show for a large class of models that already on the level of single specimens of spin chains, criticality is accompanied with the possibility of distilling a maximally entangled state of arbitrary dimension from a sufficiently large block deterministically, with local operations and classical communication. These analytical results-which refine previous results on the divergence of block entropy as the rate at which maximally entangled pairs can be distilled from many identically prepared chains-are made quantitative for general isotropic translationally invariant spin chains that can be mapped onto a quasifree fermionic system, and for the anisotropic XY model. For the XX model, we provide the asymptotic scaling of similar to(1/6)log(2)(L), and contrast it with the block entropy Y1 - 2005 ER - TY - JOUR A1 - Cirone, M. A. A1 - Negretti, Antonio A1 - Calarco, T. A1 - Krüger, P. A1 - Schmiedmayer, Jörg T1 - A simple quantum gate with atom chips N2 - We present a simple scheme for implementing an atomic phase gate using two degrees of freedom for each atom and discuss its realization with cold rubidium atoms on atom chips. We investigate the performance of this collisional phase gate and show that gate operations with high fidelity can be realized in magnetic traps that are currently available on atom chips Y1 - 2005 ER - TY - JOUR A1 - Franco, Olga A1 - Orgzall, Ingo A1 - Reck, Günter A1 - Stockhause, Sabine A1 - Schulz, Burkhard T1 - Structure and high-pressure behavior of 2,5-di-(4-aminophenyl)-1,3,4-oxadiazole N2 - The crystalline structures of two modifications of a compound containing the oxadiazole ring, 2,5-di-(4- aminophenyl)-1,3,4-oxadiazole (DAPO) were determined. One of these modifications contains water molecules in the crystal structure, which is observed for the first time for an oxadiazole crystal. Both crystals show an orthorhombic structure. The water free modification, DAPO L belongs to the space group Pbca (61) and has the lattice parameters: a = 13.461(5), b = 7.937(3) and c = 22.816(8) angstrom (CCDC 246608). The water containing pseudo-polymorph, DAPO 11, has the space group Cmcm (63) and the lattice parameters: a = 16.330(5), b = 12.307(2) and c = 6.9978(14) angstrom (CCDC 246609). To gain information on the inter molecular interactions within the crystals, X-ray experiments under compression at ambient temperature and under heating at vacuum conditions were performed. Neither DAPO I nor DAPO II undergo phase transitions in the ressure range up to 5 GPa, as could be concluded from X-ray and Raman experiments. X-ray and calorimetric studies indicate that DAPO II dehydrates into DAPO I under increasing temperature. Structural considerations suggest a two-stage process. The compression behavior of both substances is well described by the Murnaghan equation of state (MEOS) and the values of the bulk modulus and its pressure derivative are determined for these crystals. Additionally, in the case of DAPO I, also the thermal expansion coefficient an was measured. (c) 2005 Elsevier Ltd. All rights reserved Y1 - 2005 SN - 0022-3697 ER - TY - BOOK A1 - Ostermeyer, Martin A1 - Kappe, Philip A1 - Menzel, Ralf A1 - Sommer, S. A1 - Dausinger, Friedrich T1 - Laser drilling in thin materials with bursts of ns-pulses generated by stimulated Brillouin scattering (SBS) N2 - A passively Q-switched laser with a nonlinear mirror on the basis of stimulated Brillouin scattering (SBS), generates bursts of pulses with a few 10 ns pulse duration and a separation between 20-90 mu s. Percussion drilling and trepanning are performed in different materials with 1 mm thickness. The optimum parameter set of these pulse trains with regard to the burr height and ablation rate is investigated. Differences in the processing results between single pulse and multi pulse structures are discussed. In addition the laser allowed for transiently mode locked operation. Results for mode locked and merely Q-switched operation were compared Y1 - 2005 ER - TY - JOUR A1 - Schneider, J. A1 - Fernandez, V. A1 - Hernandez-Garcia, E. T1 - Leaking method approach to surface transport in the Mediterranean Sea from a numerical ocean model N2 - We use Lagrangian diagnostics (the leaking and the exchange methods) to characterize surface transport out of and between selected regions in the Western Mediterranean. Velocity fields are obtained from a numerical model. Residence times of water of Atlantic origin in the Algerian subbasin, with a strong seasonal dependence, are calculated. Exchange rates between these waters and the ones occupying the northern basin are also evaluated. At surface, northward transport is dominant, and involves filamental features and eddy structures that can be identified with the Algerian eddies. The impact on these results of the presence of small scale turbulent motions is evaluated by adding Lagrangian diffusion. (c) 2005 Elsevier B.V. All rights reserved Y1 - 2005 SN - 0924-7963 ER - TY - JOUR A1 - Pietsch, Ullrich A1 - Panzner, Tobias A1 - Pfeiffer, Franz A1 - Robinson, Ian K. T1 - Substrate morphology repetition in "thick" polymer films N2 - Using Grazing-incidence small-angle scattering (GISAXS) technique we investigated the surface morphology of polymer films spin-coated on different silicon substrates. As substrates we used either technologically smooth silicon wafers or the same silicon wafer coated with thin aluminium or gold films which show a granular structure at the surface. Although the polymer thickness exceeds 300 nm the GISAXS pattern of the film shows the same in-plane angle distribution Delta2theta as the underlying substrate. Annealing the polymer films at a temperature above its glass transition temperature Delta2theta changed from a broad to a narrow distribution as it is typically for films on pure silicon. The experiment can be interpreted by roughness replication and density fluctuation within the polymer film created while spin-coating at room temperature. Due to the low segment mobility there are density fluctuations which repeat the surface morphology of the substrate. Above the glass temperature the polymer density can be homogenized independently from the morphology of the substrate. (C) 2004 Elsevier B.V. All rights reserved Y1 - 2005 ER - TY - JOUR A1 - Motter, Adilson E. A1 - Zhou, Changsong A1 - Kurths, Jürgen T1 - Enhancing complex-network synchronization N2 - Heterogeneity in the degree (connectivity) distribution has been shown to suppress synchronization in networks of symmetrically coupled oscillators with uniform coupling strength (unweighted coupling). Here we uncover a condition for enhanced synchronization in weighted networks with asymmetric coupling. We show that, in the optimum regime, synchronizability is solely determined by the average degree and does not depend on the system size and the details of the degree distribution. In scale-free networks, where the average degree may increase with heterogeneity, synchronizability is drastically enhanced and may become positively correlated with heterogeneity, while the overall cost involved in the network coupling is significantly reduced as compared to the case of unwcighted coupling Y1 - 2005 SN - 0295-5075 ER - TY - JOUR A1 - Muzikante, I. A1 - Fonavs, E. A1 - Tokmakov, A. A1 - Cepite, D. A1 - Stiller, Burkhard A1 - Brehmer, Ludwig A1 - Neilands, O. T1 - Optical and electrical properties of oriented thin films of oligomer containing betaine-type moiety in side chain N2 - Non-linear optical and electrical properties of polymer films obtained by dipole orientation of active units are reported. Novel polar oligomer with N-(indan-1,3-dion-2-yl)pyridinium betaine (IPB) as a side group is studied. Orientation of polar groups in oligomer thin films causes an increase of the photo-induced change of surface potential on irradiation in the region of photo-induced electron transfer (PIET) where the IPB group exhibits a reversible change of the value and sign of the dipole moment. At longer wavelengths, the value of the surface potential of the oligomer may be determined by transport of photo-generated charge carriers Y1 - 2005 SN - 0370-1972 ER - TY - JOUR A1 - Negretti, Antonio A1 - Calarco, T. A1 - Cirone, M. A. A1 - Recati, A. T1 - Performance of quantum phase gates with cold trapped atoms N2 - We examine the performance of a quantum phase gate implemented with cold neutral atoms in microtraps, when anharmonic traps are employed and the effects of finite temperature are also taken into account. Both the anharmonicity and the temperature are found to pose limitations to the performance of the quantum gate. We present a quantitative analysis of the problem and show that the phase gate has a high quality performance for the experimental values that are presently or in the near future achievable in the laboratory Y1 - 2005 ER - TY - JOUR A1 - Orgzall, Ingo A1 - Franco, Olga A1 - Reck, Guenter A1 - Schulz, Burkhard T1 - High-pressure studies on fluorine substituted 2,5-di(phenyl)-1,3,4-oxadiazoles N2 - Results are presented from structural and high-pressure investigations on four differently but symmetrically fluorine substituted 2,5di(phenyl)-1,3,4-oxadiazoles. The substitution pattern includes the para-, meta-, or ortho- substitution and the fully fluorinated 2,5-bis(pentafluorophenyl)-1,3,4-oxadiazole. The crystal structure depends on the molecular structure and results in a different high-pressure behavior. Parameters for the Murnaghan equation of state (EOS) are determined for every compound and the anisotropic pressure response of the crystal lattice is discussed. Although the EOS parameters, bulk modulus K. and its pressure derivative K'(o) are of the same order of magnitude for all four compounds, the anisotropy of strain is noticeably different. (c) 2005 Elsevier B.V. All rights reserved Y1 - 2005 SN - 0022-2860 ER - TY - JOUR A1 - Volkov, E. I. A1 - Ullner, Ekkehard A1 - Kurths, Jürgen T1 - Stochastic multiresonance in the coupled relaxation oscillators N2 - We study the noise-dependent dynamics in a chain of four very stiff excitable oscillators of the FitzHugh- Nagumo type locally coupled by inhibitor diffusion. We could demonstrate frequency- and noise-selective signal acceptance which is based on several noise-supported stochastic attractors that arise owing to slow variable diffusion between identical excitable elements. The attractors have different average periods distinct from that of an isolated oscillator and various phase relations between the elements. We explain the correspondence between the noise-supported stochastic attractors and the observed resonance peaks in the curves for the linear response versus signal frequency. (C) 2005 American Institute of Physics Y1 - 2005 SN - 1054-1500 ER -