@article{CramerEisert2010,
  author    = {Cramer, Marcus and Eisert, Jens},
  title     = {A quantum central limit theorem for non-equilibrium systems : exact local relaxation of correlated states},
  issn      = {1367-2630},
  doi       = {10.1088/1367-2630/12/5/055020},
  year      = {2010},
  abstract  = {We prove that quantum many-body systems on a one-dimensional lattice locally relax to Gaussian states under non- equilibrium dynamics generated by a bosonic quadratic Hamiltonian. This is true for a large class of initial states-pure or mixed-which have to satisfy merely weak conditions concerning the decay of correlations. The considered setting is a proven instance of a situation where dynamically evolving closed quantum systems locally appear as if they had truly relaxed, to maximum entropy states for fixed second moments. This furthers the understanding of relaxation in suddenly quenched quantum many-body systems. The proof features a non-commutative central limit theorem for non-i.i.d. random variables, showing convergence to Gaussian characteristic functions, giving rise to trace-norm closeness. We briefly link our findings to the ideas of typicality and concentration of measure.},
  language  = {en}
}
@article{CuzziBurnsCharnozetal.2010,
  author    = {Cuzzi, Jeff N. and Burns, Joseph A. and Charnoz, S{\´e}bastien and Clark, Roger N. and Colwell, Josh E. and Dones, Luke and Esposito, Larry W. and Filacchione, Gianrico and French, Richard G. and Hedman, Matthew M. and Kempf, Sascha and Marouf, Essam A. and Murray, Carl D. and Nicholson, Phillip D. and Porco, Carolyn C. and Schmidt, J{\"u}rgen and Showalter, Mark R. and Spilker, Linda J. and Spitale, Joseph N. and Srama, Ralf and Sremcević, Miodrag and Tiscareno, Matthew Steven and Weiss, John},
  title     = {An evolving view of Saturn's dynamic rings},
  issn      = {0036-8075},
  doi       = {10.1126/science.1179118},
  year      = {2010},
  abstract  = {We review our understanding of Saturn's rings after nearly 6 years of observations by the Cassini spacecraft. Saturn's rings are composed mostly of water ice but also contain an undetermined reddish contaminant. The rings exhibit a range of structure across many spatial scales; some of this involves the interplay of the fluid nature and the self-gravity of innumerable orbiting centimeter- to meter-sized particles, and the effects of several peripheral and embedded moonlets, but much remains unexplained. A few aspects of ring structure change on time scales as short as days. It remains unclear whether the vigorous evolutionary processes to which the rings are subject imply a much younger age than that of the solar system. Processes on view at Saturn have parallels in circumstellar disks.},
  language  = {en}
}
@article{EisertPlenio2010,
  author    = {Eisert, Jens and Plenio, Martin B.},
  title     = {Focus on quantum information and many-body theory},
  issn      = {1367-2630},
  doi       = {10.1088/1367-2630/12/2/025001},
  year      = {2010},
  abstract  = {Quantum many-body models describing natural systems or materials and physical systems assembled piece by piece in the laboratory for the purpose of realizing quantum information processing share an important feature: intricate correlations that originate from the coherent interaction between a large number of constituents. In recent years it has become manifest that the cross-fertilization between research devoted to quantum information science and to quantum many- body physics leads to new ideas, methods, tools, and insights in both fields. Issues of criticality, quantum phase transitions, quantum order and magnetism that play a role in one field find relations to the classical simulation of quantum systems, to error correction and fault tolerance thresholds, to channel capacities and to topological quantum computation, to name but a few. The structural similarities of typical problems in both fields and the potential for pooling of ideas then become manifest. Notably, methods and ideas from quantum information have provided fresh approaches to long-standing problems in strongly correlated systems in the condensed matter context, including both numerical methods and conceptual insights.},
  language  = {en}
}
@article{deBeaudrap2010,
  author    = {de Beaudrap, Niel},
  title     = {On restricted unitary Cayley graphs and symplectic transformations modulo n},
  issn      = {1077-8926},
  year      = {2010},
  abstract  = {We present some observations on a restricted variant of unitary Cayley graphs modulo n, and implications for a decomposition of elements of symplectic operators over the integers modulo n. We define quadratic unitary Cayley graphs G(n), whose vertex set is the ring Z(n), and where residues a, b modulo n are adjacent if and only if their difference is a quadratic residue. By bounding the diameter of such graphs, we show an upper bound on the number of elementary operations (symplectic scalar multiplications, symplectic row swaps, and row additions or subtractions) required to decompose a symplectic matrix over Z(n). We also characterize the conditions on n for G(n) to be a perfect graph.},
  language  = {en}
}
@article{deBeaudrap2010,
  author    = {de Beaudrap, Niel},
  title     = {Unitary-circuit semantics for measurement-based computations},
  issn      = {0219-7499},
  doi       = {10.1142/S0219749910006113},
  year      = {2010},
  abstract  = {One-way measurement based quantum computations (1WQC) may describe unitary transformations, via a composition of CPTP maps which are not all unitary themselves. This motivates the following decision problems. Is it possible to determine whether a "quantum-to-quantum" 1WQC procedure (having non-trivial input and output subsystems) performs a unitary transformation? Is it possible to describe precisely how such computations transform quantum states, by translation to a quantum circuit of comparable complexity? In this article, we present an efficient algorithm for transforming certain families of measurement-based computations into a reasonable unitary circuit model, in particular without employing the principle of deferred measurement.},
  language  = {en}
}
@article{deBeaudrapOhligerOsborneetal.2010,
  author    = {de Beaudrap, Niel and Ohliger, Matthias and Osborne, Tobias J. and Eisert, Jens},
  title     = {Solving frustration-free spin systems},
  issn      = {0031-9007},
  doi       = {10.1103/Physrevlett.105.060504},
  year      = {2010},
  abstract  = {We identify a large class of quantum many-body systems that can be solved exactly: natural frustration-free spin-1/2 nearest-neighbor Hamiltonians on arbitrary lattices. We show that the entire ground-state manifold of such models can be found exactly by a tensor network of isometries acting on a space locally isomorphic to the symmetric subspace. Thus, for this wide class of models, real-space renormalization can be made exact. Our findings also imply that every such frustration-free spin model satisfies an area law for the entanglement entropy of the ground state, establishing a novel large class of models for which an area law is known. Finally, we show that our approach gives rise to an ansatz class useful for the simulation of almost frustration-free models in a simple fashion, outperforming mean- field theory.},
  language  = {en}
}
@article{deBeaudrapOsborneEisert2010,
  author    = {de Beaudrap, Niel and Osborne, Tobias J. and Eisert, Jens},
  title     = {Ground states of unfrustrated spin Hamiltonians satisfy an area law},
  issn      = {1367-2630},
  doi       = {10.1088/1367-2630/12/9/095007},
  year      = {2010},
  abstract  = {We show that ground states of unfrustrated quantum spin-1/2 systems on general lattices satisfy an entanglement area law, provided that the Hamiltonian can be decomposed into nearest-neighbor interaction terms that have entangled excited states. The ground state manifold can be efficiently described as the image of a low-dimensional subspace of low Schmidt measure, under an efficiently contractible tree-tensor network. This structure gives rise to the possibility of efficiently simulating the complete ground space (which is in general degenerate). We briefly discuss 'non- generic' cases, including highly degenerate interactions with product eigenbases, using a relationship to percolation theory. We finally assess the possibility of using such tree tensor networks to simulate almost frustration- free spin models.},
  language  = {en}
}
@article{Mikelskis2010,
  author    = {Mikelskis, Helmut F.},
  title     = {Physics schoolbooks - their history and future},
  isbn      = {978-3-8309-2018-2},
  year      = {2010},
  language  = {en}
}
@phdthesis{Neumeyer2010,
  author    = {Neumeyer, Steffen},
  title     = {Entwicklung und Evaluation eines Lernortes Praktikum f{\"u}r die Schule},
  address   = {Potsdam},
  pages     = {253 Bl. : Ill., graph. Darst.},
  year      = {2010},
  language  = {de}
}
@phdthesis{Tambornino2010,
  author    = {Tambornino, Johannes},
  title     = {An analysis of the low energy regime of loop quantum gravity},
  address   = {Potsdam},
  pages     = {ix, 169 S.},
  year      = {2010},
  language  = {en}
}
@phdthesis{Lara2010,
  author    = {Lara, Luc{\´i}a Santamar{\´i}a},
  title     = {Coalescence of black-hole binaries : from theoretical source models to applications in gravitational-wave astronomy},
  address   = {Potsdam},
  pages     = {xxii, 172 S. : graph. Darst.},
  year      = {2010},
  language  = {en}
}
@phdthesis{Krobath2010,
  author    = {Krobath, Heinrich},
  title     = {Binding cooperativity and domain energies of membrane adhesion receptors},
  address   = {Potsdam},
  pages     = {106 S. : graph. Darst.},
  year      = {2010},
  language  = {en}
}
@article{BlakesleyClubbGreenham2010,
  author    = {Blakesley, James C. and Clubb, Helen S. and Greenham, Neil C.},
  title     = {Temperature-dependent electron and hole transport in disordered semiconducting polymers : analysis of energetic disorder},
  issn      = {1098-0121},
  doi       = {10.1103/Physrevb.81.045210},
  year      = {2010},
  abstract  = {We have used space-charge limited current measurements to study the mobility of holes and electrons in two fluorene-based copolymers for temperatures from 100 to 300 K. Interpreting the results using the standard analytical model produced an Arrhenius-type temperature dependence for a limited temperature range only and mobility was found to be apparently dependent on the thickness of the polymer film. To improve on this, we have interpreted our data using a numerical model that takes into account the effects of the carrier concentration and energetic disorder on transport. This accounted for the thickness dependence and gave a more consistent temperature dependence across the full range of temperatures, giving support to the extended Gaussian disorder model for transport in disordered polymers. Furthermore, we find that the same model adequately describes both electron and hole transport without the need to explicitly include a distribution of electron traps. Room-temperature mobilities were found to be in the region of 4 x 10(-8) and 2 x 10(- 8) cm(2) V-1 s(-1) in the limit of zero field and zero carrier density with disorders of 110+/-10 and 100+/-10 meV for polymers poly{9,9-dioctylfluorene-co-bis[N,N'-(4-butylphenyl)]bis(N, N'-phenyl-1,4-phenylene)diamine} and poly(9,9-dioctylfluorene-co-benzothiadiazole), respectively.},
  language  = {en}
}
@article{BoedekerBetaFranketal.2010,
  author    = {Boedeker, Hendrik Ulrich and Beta, Carsten and Frank, Till D. and Bodenschatz, Eberhard},
  title     = {Quantitative analysis of random ameboid motion},
  issn      = {0295-5075},
  doi       = {10.1209/0295-5075/90/28005},
  year      = {2010},
  abstract  = {We quantify random migration of the social ameba Dictyostelium discoideum. We demonstrate that the statistics of cell motion can be described by an underlying Langevin-type stochastic differential equation. An analytic expression for the velocity distribution function is derived. The separation into deterministic and stochastic parts of the movement shows that the cells undergo a damped motion with multiplicative noise. Both contributions to the dynamics display a distinct response to external physiological stimuli. The deterministic component depends on the developmental state and ambient levels of signaling substances, while the stochastic part does not.},
  language  = {en}
}
@article{BordyugovFischerEngeletal.2010,
  author    = {Bordyugov, Grigory and Fischer, Nils and Engel, Harald and Manz, Niklas and Steinbock, Oliver},
  title     = {Anomalous dispersion in the Belousov-Zhabotinsky reaction : experiments and modeling},
  issn      = {0167-2789},
  doi       = {10.1016/j.physd.2009.10.022},
  year      = {2010},
  abstract  = {We report results on dispersion relations and instabilities of traveling waves in excitable systems. Experiments employ solutions of the 1,4-cyclohexanedione Belousov-Zhabotinsky reaction confined to thin capillary tubes which create a pseudo-one-dimensional system. Theoretical analyses focus on a three-variable reaction-diffusion model that is known to reproduce qualitatively many of the experimentally observed dynamics. Using continuation methods, we show that the transition from normal, monotonic to anomalous, single-overshoot dispersion curves is due to an orbit flip bifurcation of the solitary pulse homoclinics. In the case of "wave stacking", this anomaly induces attractive pulse interaction, slow solitary pulses, and faster wave trains. For "wave merging", wave trains break up in the wake of the slow solitary pulse due to an instability of wave trains at small wavelength. A third case, "wave tracking" is characterized by the non-existence of solitary waves but existence of periodic wave trains. The corresponding dispersion curve is a closed curve covering a finite band of wavelengths.},
  language  = {en}
}
@article{BalažVidanovicBogojevićetal.2010,
  author    = {Balaž, Antun and Vidanovic, Ivana and Bogojević, Aleksandar and Pelster, Axel},
  title     = {Ultra-fast converging path-integral approach for rotating ideal Bose-Einstein condensates},
  issn      = {0375-9601},
  doi       = {10.1016/j.physleta.2010.01.034},
  year      = {2010},
  abstract  = {A recently developed efficient recursive approach for analytically calculating the short-time evolution of the one-particle propagator to extremely high orders is applied here for numerically studying the thermodynamical and dynamical properties of a rotating ideal Bose gas of Rb-87 atoms in an anharmonic trap. At first, the one-particle energy spectrum of the system is obtained by diagonalizing the discretized short-time propagator. Using this, many-boson properties such as the condensation temperature, the ground-state occupancy, density profiles, and time-of-flight absorption pictures are calculated for varying rotation frequencies. The obtained results improve previous semiclassical calculations, in particular for smaller particle numbers. Furthermore, we find that typical time scales for a free expansion are increased by an order of magnitude for the delicate regime of both critical and overcritical rotation.},
  language  = {en}
}
@article{BarthelKlieschEisert2010,
  author    = {Barthel, Thomas and Kliesch, Martin and Eisert, Jens},
  title     = {Real-space renormalization yields finite correlations},
  issn      = {0031-9007},
  doi       = {10.1103/Physrevlett.105.010502},
  year      = {2010},
  abstract  = {Real-space renormalization approaches for quantum lattice systems generate certain hierarchical classes of states that are subsumed by the multiscale entanglement renormalization Ansatz (MERA). It is shown that, with the exception of one spatial dimension, MERA states are actually states with finite correlations, i.e., projected entangled pair states (PEPS) with a bond dimension independent of the system size. Hence, real-space renormalization generates states which can be encoded with local effective degrees of freedom, and MERA states form an efficiently contractible class of PEPS that obey the area law for the entanglement entropy. It is further pointed out that there exist other efficiently contractible schemes violating the area law.},
  language  = {en}
}
@article{WinterWinterFernandesGuimaraesetal.2010,
  author    = {Winter, Silvia Maria Giuliatti and Winter, Othon Cabo and Fernandes Guimar{\~a}es, Ana Helena and Silva, Maria Rita},
  title     = {Exploring S-type orbits in the Pluto-Charon binary system},
  issn      = {0035-8711},
  doi       = {10.1111/j.1365-2966.2010.16302.x},
  year      = {2010},
  abstract  = {This work generates, through a sample of numerical simulations of the restricted three-body problem, diagrams of semimajor axis and eccentricity which defines stable and unstable zones for particles in S-type orbits around Pluto and Charon. Since we consider initial conditions with 0 <= e <= 0.99, we found several new stable regions. We also identified the nature of each one of these newly found stable regions. They are all associated to families of periodic orbits derived from the planar circular restricted three-body problem. We have shown that a possible eccentricity of the Pluto-Charon system slightly reduces, but does not destroy, any of the stable regions.},
  language  = {en}
}
@article{WuZhouXiaoetal.2010,
  author    = {Wu, Ye Wu and Zhou, Changsong and Xiao, Jinghua and Kurths, J{\"u}rgen and Schellnhuber, Hans Joachim},
  title     = {Evidence for a bimodal distribution in human communication},
  issn      = {0027-8424},
  doi       = {10.1073/pnas.1013140107},
  year      = {2010},
  abstract  = {Interacting human activities underlie the patterns of many social, technological, and economic phenomena. Here we present clear empirical evidence from Short Message correspondence that observed human actions are the result of the interplay of three basic ingredients: Poisson initiation of tasks and decision making for task execution in individual humans as well as interaction among individuals. This interplay leads to new types of interevent time distribution, neither completely Poisson nor power-law, but a bimodal combination of them. We show that the events can be separated into independent bursts which are generated by frequent mutual interactions in short times following random initiations of communications in longer times by the individuals. We introduce a minimal model of two interacting priority queues incorporating the three basic ingredients which fits well the distributions using the parameters extracted from the empirical data. The model can also embrace a range of realistic social interacting systems such as e-mail and letter communications when taking the time scale of processing into account. Our findings provide insight into various human activities both at the individual and network level. Our analysis and modeling of bimodal activity in human communication from the viewpoint of the interplay between processes of different time scales is likely to shed light on bimodal phenomena in other complex systems, such as interevent times in earthquakes, rainfall, forest fire, and economic systems, etc.},
  language  = {en}
}
@article{ZakharovaVadivasovaAnishchenkoetal.2010,
  author    = {Zakharova, Anna and Vadivasova, Tatjana and Anishchenko, Vadim S. and Koseska, Aneta and Kurths, J{\"u}rgen},
  title     = {Stochastic bifurcations and coherencelike resonance in a self-sustained bistable noisy oscillator},
  issn      = {1539-3755},
  doi       = {10.1103/Physreve.81.011106},
  year      = {2010},
  abstract  = {We investigate the influence of additive Gaussian white noise on two different bistable self-sustained oscillators: Duffing-Van der Pol oscillator with hard excitation and a model of a synthetic genetic oscillator. In the deterministic case, both oscillators are characterized with a coexistence of a stable limit cycle and a stable equilibrium state. We find that under the influence of noise, their dynamics can be well characterized through the concept of stochastic bifurcation, consisting in a qualitative change of the stationary amplitude distribution. For the Duffing-Van der Pol oscillator analytical results, obtained for a quasiharmonic approach, are compared with the result of direct computer simulations. In particular, we show that the dynamics is different for isochronous and anisochronous systems. Moreover, we find that the increase of noise intensity in the isochronous regime leads to a narrowing of the spectral line. This effect is similar to coherence resonance. However, in the case of anisochronous systems, this effect breaks down and a new phenomenon, anisochronous-based stochastic bifurcation occurs.},
  language  = {en}
}
@article{SenthilkumarMuruganandamLakshmanan2010,
  author    = {Senthilkumar, Dharmapuri Vijayan and Muruganandam, Paulsamy and Lakshmanan, Muthusamy},
  title     = {Scaling and synchronization in a ring of diffusively coupled nonlinear oscillators},
  issn      = {1539-3755},
  doi       = {10.1103/Physreve.81.066219},
  year      = {2010},
  abstract  = {Chaos synchronization in a ring of diffusively coupled nonlinear oscillators driven by an external identical oscillator is studied. Based on numerical simulations we show that by introducing additional couplings at (mN(c) + 1)-th oscillators in the ring, where m is an integer and N-c is the maximum number of synchronized oscillators in the ring with a single coupling, the maximum number of oscillators that can be synchronized can be increased considerably beyond the limit restricted by size instability. We also demonstrate that there exists an exponential relation between the number of oscillators that can support stable synchronization in the ring with the external drive and the critical coupling strength epsilon(c) with a scaling exponent gamma. The critical coupling strength is calculated by numerically estimating the synchronization error and is also confirmed from the conditional Lyapunov exponents of the coupled systems. We find that the same scaling relation exists for m couplings between the drive and the ring. Further, we have examined the robustness of the synchronous states against Gaussian white noise and found that the synchronization error exhibits a power-law decay as a function of the noise intensity indicating the existence of both noise-enhanced and noise-induced synchronizations depending on the value of the coupling strength epsilon. In addition, we have found that epsilon(c) shows an exponential decay as a function of the number of additional couplings. These results are demonstrated using the paradigmatic models of Rossler and Lorenz oscillators.},
  language  = {en}
}
@article{ZhuStoyanovKofodetal.2010,
  author    = {Zhu, Jian and Stoyanov, Hristiyan and Kofod, Guggi and Suo, Zhigang},
  title     = {Large deformation and electromechanical instability of a dielectric elastomer tube actuator},
  issn      = {0021-8979},
  doi       = {10.1063/1.3490186},
  year      = {2010},
  abstract  = {This paper theoretically analyzes a dielectric elastomer tube actuator (DETA). Subject to a voltage difference between the inner and outer surfaces, the actuator reduces in thickness and expands in length, so that the same voltage will induce an even higher electric field. This positive feedback may cause the actuator to thin down drastically, resulting in electrical breakdown. We obtain an analytical solution of the actuator undergoing finite deformation when the elastomer obeys the neo-Hookean model. The critical strain of actuation is calculated in terms of various parameters of design. We also discuss the effect of the strain-stiffening on electromechanical behavior of DETAs by using the model of freely joined links. (C) 2010 American Institute of Physics. [doi:10.1063/1.3490186]},
  language  = {en}
}
@article{ZunkovicProsen2010,
  author    = {Zunkovic, Bojan and Prosen, Tomaz},
  title     = {Explicit solution of the Lindblad equation for nearly isotropic boundary driven XY spin 1/2 chain},
  issn      = {1742-5468},
  doi       = {10.1088/1742-5468/2010/08/P08016},
  year      = {2010},
  abstract  = {Explicit solution for the two-point correlation function in a non-equilibrium steady state of a nearly isotropic boundary driven open XY spin 1/2 chain in the Lindblad formulation is provided. A non-equilibrium quantum phase transition from exponentially decaying correlations to long range order is discussed analytically. In the regime of long range order a new phenomenon of correlation resonances is reported, where the correlation response of the system is unusually high for certain discrete values of the external bulk parameter, e.g. the magnetic field.},
  language  = {en}
}
@article{ZykovBordyugovLentzetal.2010,
  author    = {Zykov, Vladimir and Bordyugov, Grigory and Lentz, Hartmut and Engel, Harald},
  title     = {Hysteresis phenomenon in the dynamics of spiral waves rotating around a hole},
  issn      = {0167-2789},
  doi       = {10.1016/j.physd.2009.07.018},
  year      = {2010},
  abstract  = {Hysteresis in the pinning-depinning transitions of spiral waves rotating around a hole in a circular shaped two- dimensional excitable medium is studied both by use of the continuation software AUTO and by direct numerical integration of the reaction-diffusion equations for the FitzHugh-Nagumo model. In order to clarify the role of different factors in this phenomenon, a kinematical description is applied. It is found that the hysteresis phenomenon computed for the reaction-diffusion model can be reproduced qualitatively only when a nonlinear eikonal equation (i.e. velocity- curvature relationship) is assumed. However, to obtain quantitative agreement, the dispersion relation has to be taken into account.},
  language  = {en}
}
@article{Hamann2010,
  author    = {Hamann, Wolf-Rainer},
  title     = {Stellar winds from hot low-mass stars},
  issn      = {0004-640X},
  doi       = {10.1007/s10509-010-0344-8},
  year      = {2010},
  abstract  = {Stellar winds appear as a persistent feature of hot stars, irrespective of their wide range of different luminosities, masses, and chemical composition. Among the massive stars, the Wolf-Rayet types show considerably stronger mass loss than the O stars. Among hot low-mass stars, stellar winds are seen at central stars of planetary nebulae, where again the hydrogen-deficient stars show much stronger winds than those central stars with "normal" composition. We also studied mass-loss from a few extreme helium stars and sdOs. Their mass-loss rate roughly follows the same proportionality with luminosity to the power 1.5 as the massive O stars. This relation roughly marks a lower limit for the mass loss from hot stars of all kinds, and provides evidence that radiation pressure on spectral lines is the basic mechanism at work. For certain classes of stars the mass-loss rates lie significantly above this relation, for reasons that are not yet fully understood. Mass loss from low-mass stars may affect their evolution, by reducing the envelope mass, and can easily prevent diffusion from establishing atmospheric abundance patterns. In close binary systems, their winds can feed the accretion onto a companion.},
  language  = {en}
}
@article{GrossEisert2010,
  author    = {Gross, David and Eisert, Jens},
  title     = {Quantum computational webs},
  issn      = {1050-2947},
  doi       = {10.1103/Physreva.82.040303},
  year      = {2010},
  abstract  = {We discuss the notion of quantum computational webs: These are quantum states universal for measurement-based computation, which can be built up from a collection of simple primitives. The primitive elements-reminiscent of building blocks in a construction kit-are (i) one-dimensional states (computational quantum wires) with the power to process one logical qubit and (ii) suitable couplings, which connect the wires to a computationally universal web. All elements are preparable by nearest-neighbor interactions in a single pass, of the kind accessible in a number of physical architectures. We provide a complete classification of qubit wires, a physically well-motivated class of universal resources that can be fully understood. Finally, we sketch possible realizations in superlattices and explore the power of coupling mechanisms based on Ising or exchange interactions.},
  language  = {en}
}
@article{GrossLiuFlammiaetal.2010,
  author    = {Gross, David and Liu, Yi-Kai and Flammia, Steven T. and Becker, Stephen and Eisert, Jens},
  title     = {Quantum state tomography via compressed sensing},
  issn      = {0031-9007},
  doi       = {10.1103/Physrevlett.105.150401},
  year      = {2010},
  abstract  = {We establish methods for quantum state tomography based on compressed sensing. These methods are specialized for quantum states that are fairly pure, and they offer a significant performance improvement on large quantum systems. In particular, they are able to reconstruct an unknown density matrix of dimension d and rank r using O(rdlog(2)d) measurement settings, compared to standard methods that require d(2) settings. Our methods have several features that make them amenable to experimental implementation: they require only simple Pauli measurements, use fast convex optimization, are stable against noise, and can be applied to states that are only approximately low rank. The acquired data can be used to certify that the state is indeed close to pure, so no a priori assumptions are needed.},
  language  = {en}
}
@article{GrossMuellerColbecketal.2010,
  author    = {Gross, David and Mueller, Markus and Colbeck, Roger and Dahlsten, Oscar C. O.},
  title     = {All reversible dynamics in maximally nonlocal theories are trivial},
  issn      = {0031-9007},
  doi       = {10.1103/Physrevlett.104.080402},
  year      = {2010},
  abstract  = {A remarkable feature of quantum theory is nonlocality ( Bell inequality violations). However, quantum correlations are not maximally nonlocal, and it is natural to ask whether there are compelling reasons for rejecting theories in which stronger violations are possible. To shed light on this question, we consider post-quantum theories in which maximally nonlocal states ( nonlocal boxes) occur. We show that reversible transformations in such theories are trivial: they consist solely of local operations and permutations of systems. In particular, no correlations can be created; nonlocal boxes cannot be prepared from product states and classical computers can efficiently simulate all such processes.},
  language  = {en}
}
@article{GvaramadzeKniazevHamannetal.2010,
  author    = {Gvaramadze, Vasily V. and Kniazev, Alexei Y. and Hamann, Wolf-Rainer and Berdnikov, Leonid N. and Fabrika, Sergei Nikolaevich and Valeev, Azamat F.},
  title     = {A new Wolf-Rayet star and its circumstellar nebula in Aquila},
  issn      = {0035-8711},
  doi       = {10.1111/j.1365-2966.2009.16126.x},
  year      = {2010},
  abstract  = {We report the discovery of a new Wolf-Rayet star in Aquila via detection of its circumstellar nebula (reminiscent of ring nebulae associated with late WN stars) using the Spitzer Space Telescope archival data. Our spectroscopic follow-up of the central point source associated with the nebula showed that it is a WN7h star (we named it WR121b). We analysed the spectrum of WR 121b by using the Potsdam Wolf-Rayet model atmospheres, obtaining a stellar temperature of similar or equal to 50 kK. The stellar wind composition is dominated by helium with similar to 20 per cent of hydrogen. The stellar spectrum is highly reddened [E(B - V) = 2.85 mag]. Adopting an absolute magnitude of M-v = 5.7, the star has a luminosity of log L/L-circle dot = 5.75 and a mass-loss rate of 10(-4.7)M(circle dot)yr(-1), and resides at a distance of 6.3 kpc. We searched for a possible parent cluster of WR 121b and found that this star is located at similar or equal to 1 degrees from the young star cluster embedded in the giant HII region W43 (containing a WN7+a/OB? star - WR121a). We also discovered a bow shock around the O9.5III star ALS 9956, located at similar or equal to 0 degrees.5 from the cluster. We discuss the possibility that WR121b and ALS 9956 are runaway stars ejected from the cluster in W43.},
  language  = {en}
}
@article{SenthilkumarKurths2010,
  author    = {Senthilkumar, Dharmapuri Vijayan and Kurths, J{\"u}rgen},
  title     = {Characteristics and synchronization of time-delay systems driven by a common noise},
  issn      = {1951-6355},
  doi       = {10.1140/epjst/e2010-01273-4},
  year      = {2010},
  abstract  = {We investigate the characteristics of time-delay systems in the presence of Gaussian noise. We show that the delay time embedded in the time series of time-delay system with constant delay cannot be estimated in the presence noise for appropriate values of noise intensity thereby forbidding any possibility of phase space reconstruction. We also demonstrate the existence of complete synchronization between two independent identical time-delay systems driven by a common noise without explicitly establishing any external coupling between them.},
  language  = {en}
}
@article{StichBeta2010,
  author    = {Stich, Michael and Beta, Carsten},
  title     = {Control of pattern formation by time-delay feedback with global and local contributions},
  issn      = {0167-2789},
  doi       = {10.1016/j.physd.2010.05.001},
  year      = {2010},
  abstract  = {We consider the suppression of spatiotemporal chaos in the complex Ginzburg-Landau equation by a combined global and local time-delay feedback. Feedback terms are implemented as a control scheme, i.e., they are proportional to the difference between the time-delayed state of the system and its current state. We perform a linear stability analysis of uniform oscillations with respect to space-dependent perturbations and compare with numerical simulations. Similarly, for the fixed-point solution that corresponds to amplitude death in the spatially extended system, a linear stability analysis with respect to space-dependent perturbations is performed and complemented by numerical simulations.},
  language  = {en}
}
@phdthesis{Klasczyk2010,
  author    = {Klasczyk, Benjamin},
  title     = {Interactions of ions with membranes},
  address   = {Potsdam},
  pages     = {116 S.},
  year      = {2010},
  language  = {en}
}
@phdthesis{Fix2010,
  author    = {Fix, Dmitri},
  title     = {Lokalkorrosion auf Aluminium: Nicht-invasive in-situ-Observation von Lochkorrosion},
  address   = {Potsdam},
  pages     = {124 S.},
  year      = {2010},
  language  = {de}
}
@book{Foehlisch2010,
  author    = {F{\"o}hlisch, Alexander},
  title     = {Phasen{\"u}berg{\"a}nge und Ultrakurzzeitdynamik : Antrittsvorlesung 2010-05-12},
  publisher = {Univ.-Bibl.},
  address   = {Potsdam},
  year      = {2010},
  abstract  = {F{\"o}hlisch wird in seinem Vortrag die großen Zukunftsthemen der Mensch streifen: Energie, Umwelt und Struktur der Materie. Die Komplexit{\"a}t ihrer elementaren Prozesse erfordert die komplement{\"a}re Betrachtung der damit verbundene Dimensionen von Energie, Zeit und Raum. Dies l{\"a}sst sich inzwischen mit Synchrotronstrahlungsquellen in gr{\"o}ßter Pr{\"a}ision darstellen.},
  language  = {de}
}
@phdthesis{Schwabedal2010,
  author    = {Schwabedal, Justus Tilmann Caspar},
  title     = {Phase dynamics of irregular oscillations},
  url       = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus-50115},
  school      = {Universit{\"a}t Potsdam},
  year      = {2010},
  abstract  = {In der vorliegenden Dissertation wird eine Beschreibung der Phasendynamik irregul{\"a}rer Oszillationen und deren Wechselwirkungen vorgestellt. Hierbei werden chaotische und stochastische Oszillationen autonomer dissipativer Systeme betrachtet. F{\"u}r eine Phasenbeschreibung stochastischer Oszillationen m{\"u}ssen zum einen unterschiedliche Werte der Phase zueinander in Beziehung gesetzt werden, um ihre Dynamik unabh{\"a}ngig von der gew{\"a}hlten Parametrisierung der Oszillation beschreiben zu k{\"o}nnen. Zum anderen m{\"u}ssen f{\"u}r stochastische und chaotische Oszillationen diejenigen Systemzust{\"a}nde identifiziert werden, die sich in der gleichen Phase befinden. Im Rahmen dieser Dissertation werden die Werte der Phase {\"u}ber eine gemittelte Phasengeschwindigkeitsfunktion miteinander in Beziehung gesetzt. F{\"u}r stochastische Oszillationen sind jedoch verschiedene Definitionen der mittleren Geschwindigkeit m{\"o}glich. Um die Unterschiede der Geschwindigkeitsdefinitionen besser zu verstehen, werden auf ihrer Basis effektive deterministische Modelle der Oszillationen konstruiert. Hierbei zeigt sich, dass die Modelle unterschiedliche Oszillationseigenschaften, wie z. B. die mittlere Frequenz oder die invariante Wahrscheinlichkeitsverteilung, nachahmen. Je nach Anwendung stellt die effektive Phasengeschwindigkeitsfunktion eines speziellen Modells eine zweckm{\"a}ßige Phasenbeziehung her. Wie anhand einfacher Beispiele erkl{\"a}rt wird, kann so die Theorie der effektiven Phasendynamik auch kontinuierlich und pulsartig wechselwirkende stochastische Oszillationen beschreiben. Weiterhin wird ein Kriterium f{\"u}r die invariante Identifikation von Zust{\"a}nden gleicher Phase irregul{\"a}rer Oszillationen zu sogenannten generalisierten Isophasen beschrieben: Die Zust{\"a}nde einer solchen Isophase sollen in ihrer dynamischen Entwicklung ununterscheidbar werden. F{\"u}r stochastische Oszillationen wird dieses Kriterium in einem mittleren Sinne interpretiert. Wie anhand von Beispielen demonstriert wird, lassen sich so verschiedene Typen stochastischer Oszillationen in einheitlicher Weise auf eine stochastische Phasendynamik reduzieren. Mit Hilfe eines numerischen Algorithmus zur Sch{\"a}tzung der Isophasen aus Daten wird die Anwendbarkeit der Theorie anhand eines Signals regelm{\"a}ßiger Atmung gezeigt. Weiterhin zeigt sich, dass das Kriterium der Phasenidentifikation f{\"u}r chaotische Oszillationen nur approximativ erf{\"u}llt werden kann. Anhand des R{\"o}ssleroszillators wird der tiefgreifende Zusammenhang zwischen approximativen Isophasen, chaotischer Phasendiffusion und instabilen periodischen Orbits dargelegt. Gemeinsam erm{\"o}glichen die Theorien der effektiven Phasendynamik und der generalisierten Isophasen eine umfassende und einheitliche Phasenbeschreibung irregul{\"a}rer Oszillationen.},
  language  = {de}
}
@phdthesis{Ahnert2010,
  author    = {Ahnert, Karsten},
  title     = {Compactons in strongly nonlinear lattices},
  url       = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus-48539},
  school      = {Universit{\"a}t Potsdam},
  year      = {2010},
  abstract  = {In the present work, we study wave phenomena in strongly nonlinear lattices. Such lattices are characterized by the absence of classical linear waves. We demonstrate that compactons - strongly localized solitary waves with tails decaying faster than exponential - exist and that they play a major role in the dynamics of the system under consideration. We investigate compactons in different physical setups. One part deals with lattices of dispersively coupled limit cycle oscillators which find various applications in natural sciences such as Josephson junction arrays or coupled Ginzburg-Landau equations. Another part deals with Hamiltonian lattices. Here, a prominent example in which compactons can be found is the granular chain. In the third part, we study systems which are related to the discrete nonlinear Schr{\"o}dinger equation describing, for example, coupled optical wave-guides or the dynamics of Bose-Einstein condensates in optical lattices. Our investigations are based on a numerical method to solve the traveling wave equation. This results in a quasi-exact solution (up to numerical errors) which is the compacton. Another ansatz which is employed throughout this work is the quasi-continuous approximation where the lattice is described by a continuous medium. Here, compactons are found analytically, but they are defined on a truly compact support. Remarkably, both ways give similar qualitative and quantitative results. Additionally, we study the dynamical properties of compactons by means of numerical simulation of the lattice equations. Especially, we concentrate on their emergence from physically realizable initial conditions as well as on their stability due to collisions. We show that the collisions are not exactly elastic but that a small part of the energy remains at the location of the collision. In finite lattices, this remaining part will then trigger a multiple scattering process resulting in a chaotic state.},
  language  = {en}
}
@phdthesis{Kralemann2010,
  author    = {Kralemann, Bj{\"o}rn Christian},
  title     = {Die Rekonstruktion invarianter Phasenmodelle aus Daten},
  url       = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus-45057},
  school      = {Universit{\"a}t Potsdam},
  year      = {2010},
  abstract  = {Ziel dieser Arbeit ist die {\"U}berwindung einer Differenz, die zwischen der Theorie der Phase bzw. der Phasendynamik und ihrer Anwendung in der Zeitreihenanalyse besteht: W{\"a}hrend die theoretische Phase eindeutig bestimmt und invariant unter Koordinatentransformationen bzw. gegen{\"u}ber der jeweils gew{\"a}hlten Observable ist, f{\"u}hren die Standardmethoden zur Absch{\"a}tzung der Phase aus gegebenen Zeitreihen zu Resultaten, die einerseits von den gew{\"a}hlten Observablen abh{\"a}ngen und so andererseits das jeweilige System keineswegs in eindeutiger und invarianter Weise beschreiben. Um diese Differenz deutlich zu machen, wird die terminologische Unterscheidung von Phase und Protophase eingef{\"u}hrt: Der Terminus Phase wird nur f{\"u}r Variablen verwendet, die dem theoretischen Konzept der Phase entsprechen und daher das jeweilige System in invarianter Weise charakterisieren, w{\"a}hrend die observablen-abh{\"a}ngigen Absch{\"a}tzungen der Phase aus Zeitreihen als Protophasen bezeichnet werden. Der zentrale Gegenstand dieser Arbeit ist die Entwicklung einer deterministischen Transformation, die von jeder Protophase eines selbsterhaltenden Oszillators zur eindeutig bestimmten Phase f{\"u}hrt. Dies erm{\"o}glicht dann die invariante Beschreibung gekoppelter Oszillatoren und ihrer Wechselwirkung. Die Anwendung der Transformation bzw. ihr Effekt wird sowohl an numerischen Beispielen demonstriert - insbesondere wird die Phasentransformation in einem Beispiel auf den Fall von drei gekoppelten Oszillatoren erweitert - als auch an multivariaten Messungen des EKGs, des Pulses und der Atmung, aus denen Phasenmodelle der kardiorespiratorischen Wechselwirkung rekonstruiert werden. Abschließend wird die Phasentransformation f{\"u}r autonome Oszillatoren auf den Fall einer nicht vernachl{\"a}ssigbaren Amplitudenabh{\"a}ngigkeit der Protophase erweitert, was beispielsweise die numerischen Bestimmung der Isochronen des chaotischen R{\"o}ssler Systems erm{\"o}glicht.},
  language  = {de}
}
@article{SchwabedalPikovskij2010,
  author    = {Schwabedal, Justus T. C. and Pikovskij, Arkadij},
  title     = {Effective phase description of noise-perturbed and noise-induced oscillations},
  issn      = {1951-6355},
  doi       = {10.1140/epjst/e2010-01271-6},
  year      = {2010},
  abstract  = {An effective dynamical description of a general class of stochastic phase oscillators is presented. For this, the effective phase velocity is defined either by the stochastic phase oscillators invariant probability density or its first passage times. Using the first approach the effective phase exhibits the correct frequency and invariant distribution density, whereas the second approach models the proper phase resetting curve. The discrepancy of the effective models is most pronounced for noise-induced oscillations and is related to non-monotonicity of the stochastic phase variable due to fluctuations.},
  language  = {en}
}
@article{SchwabedalPikovskij2010,
  author    = {Schwabedal, Justus T. C. and Pikovskij, Arkadij},
  title     = {Effective phase dynamics of noise-induced oscillations in excitable systems},
  issn      = {1539-3755},
  doi       = {10.1103/Physreve.81.046218},
  year      = {2010},
  abstract  = {We develop an effective description of noise-induced oscillations based on deterministic phase dynamics. The phase equation is constructed to exhibit correct frequency and distribution density of noise-induced oscillations. In the simplest one-dimensional case the effective phase equation is obtained analytically, whereas for more complex situations a simple method of data processing is suggested. As an application an effective coupling function is constructed that quantitatively describes periodically forced noise-induced oscillations.},
  language  = {en}
}
@article{BaibolatovRosenblumZhanabaevetal.2010,
  author    = {Baibolatov, Yernur and Rosenblum, Michael and Zhanabaev, Zeinulla Zh. and Pikovskij, Arkadij},
  title     = {Complex dynamics of an oscillator ensemble with uniformly distributed natural frequencies and global nonlinear coupling},
  issn      = {1539-3755},
  doi       = {10.1103/Physreve.82.016212},
  year      = {2010},
  abstract  = {We consider large populations of phase oscillators with global nonlinear coupling. For identical oscillators such populations are known to demonstrate a transition from completely synchronized state to the state of self-organized quasiperiodicity. In this state phases of all units differ, yet the population is not completely incoherent but produces a nonzero mean field; the frequency of the latter differs from the frequency of individual units. Here we analyze the dynamics of such populations in case of uniformly distributed natural frequencies. We demonstrate numerically and describe theoretically (i) states of complete synchrony, (ii) regimes with coexistence of a synchronous cluster and a drifting subpopulation, and (iii) self-organized quasiperiodic states with nonzero mean field and all oscillators drifting with respect to it. We analyze transitions between different states with the increase of the coupling strength; in particular we show that the mean field arises via a discontinuous transition. For a further illustration we compare the results for the nonlinear model with those for the Kuramoto-Sakaguchi model.},
  language  = {en}
}
@article{BordyugovPikovskijRosenblum2010,
  author    = {Bordyugov, Grigory and Pikovskij, Arkadij and Rosenblum, Michael},
  title     = {Self-emerging and turbulent chimeras in oscillator chains},
  issn      = {1539-3755},
  doi       = {10.1103/Physreve.82.035205},
  year      = {2010},
  abstract  = {We report on a self-emerging chimera state in a homogeneous chain of nonlocally and nonlinearly coupled oscillators. This chimera, i.e., a state with coexisting regions of complete and partial synchrony, emerges via a supercritical bifurcation from a homogeneous state. We develop a theory of chimera based on the Ott-Antonsen equations for the local complex order parameter. Applying a numerical linear stability analysis, we also describe the instability of the chimera and transition to phase turbulence with persistent patches of synchrony.},
  language  = {en}
}
@article{HenniesPietzschBerglundetal.2010,
  author    = {Hennies, Franz and Pietzsch, Annette and Berglund, Martin and F{\"o}hlisch, Alexander and Schmitt, Thorsten and Strocov, Vladimir and Karlsson, Hans O. and Andersson, Joakim and Rubensson, Jan-Erik},
  title     = {Resonant inelastic scattering spectra of free molecules with vibrational resolution},
  issn      = {0031-9007},
  doi       = {10.1103/Physrevlett.104.193002},
  year      = {2010},
  abstract  = {Inelastic x-ray scattering spectra excited at the 1s(-1) pi* resonance of gas phase O-2 have been recorded with an overall energy resolution that allows for well-resolved vibrational progressions. The nuclear wave packet dynamics in the intermediate state is reflected in vibrational excitations of the electronic ground state, and by fine-tuning the excitation energy the dissociation dynamics in the predissociative B' (3) Pi(g) final state is controlled.},
  language  = {en}
}
@article{TodtPenaHamannetal.2010,
  author    = {Todt, Helge Tobias and Pena, Maria A. and Hamann, Wolf-Rainer and Gr{\"a}fener, G{\"o}tz},
  title     = {The central star of the planetary nebula PB8 : a Wolf-Rayet-type wind of an unusual WN/WC chemical composition},
  issn      = {0004-6361},
  doi       = {10.1051/0004-6361/200912183},
  year      = {2010},
  abstract  = {A considerable fraction of the central stars of planetary nebulae (CSPNe) are hydrogen-deficient. As a rule, these CSPNe exhibit a chemical composition of helium, carbon, and oxygen with the majority showing Wolf-Rayet-like emission line spectra. These stars are classified as CSPNe of a spectral type [WC]. We perform a spectral analysis of CSPN PB 8 with the Potsdam Wolf-Rayet (PoWR) models for expanding atmospheres. The source PB8 displays wind-broadened emission lines from strong mass loss. Most strikingly, we find that its surface composition is hydrogen-deficient, but not carbon-rich. With mass fractions of 55\% helium, 40\% hydrogen, 1.3\% carbon, 2\% nitrogen, and 1.3\% oxygen, it differs greatly from the 30-50\% of carbon which are typically seen in [WC]-type central stars. The atmospheric mixture in PB8 has an analogy in the WN/WC transition type among the massive Wolf-Rayet stars. Therefore we suggest to introduce a new spectral type [WN/WC] for CSPNe, with PB8 as its first member. The central star of PB8 has a relatively low temperature of T-* = 52 kK, as expected for central stars in their early evolutionary stages. Its surrounding nebula is less than 3000 years old, i.e. relatively young. Existing calculations for the post-AGB evolution can produce hydrogen-deficient stars of the [WC] type, but do not predict the composition found in PB8. We discuss various scenarios that might explain the origin of this unique object.},
  language  = {en}
}
@phdthesis{SanchezBarriga2010,
  author    = {S{\´a}nchez-Barriga, Jaime},
  title     = {A photoemission study of quasiparticle excitations, electron-correlation effects and magnetization dynamics in thin magnetic systems},
  url       = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus-48499},
  school      = {Universit{\"a}t Potsdam},
  year      = {2010},
  abstract  = {This thesis is focused on the electronic, spin-dependent and dynamical properties of thin magnetic systems. Photoemission-related techniques are combined with synchrotron radiation to study the spin-dependent properties of these systems in the energy and time domains. In the first part of this thesis, the strength of electron correlation effects in the spin-dependent electronic structure of ferromagnetic bcc Fe(110) and hcp Co(0001) is investigated by means of spin- and angle-resolved photoemission spectroscopy. The experimental results are compared to theoretical calculations within the three-body scattering approximation and within the dynamical mean-field theory, together with one-step model calculations of the photoemission process. From this comparison it is demonstrated that the present state of the art many-body calculations, although improving the description of correlation effects in Fe and Co, give too small mass renormalizations and scattering rates thus demanding more refined many-body theories including nonlocal fluctuations. In the second part, it is shown in detail monitoring by photoelectron spectroscopy how graphene can be grown by chemical vapour deposition on the transition-metal surfaces Ni(111) and Co(0001) and intercalated by a monoatomic layer of Au. For both systems, a linear E(k) dispersion of massless Dirac fermions is observed in the graphene pi-band in the vicinity of the Fermi energy. Spin-resolved photoemission from the graphene pi-band shows that the ferromagnetic polarization of graphene/Ni(111) and graphene/Co(0001) is negligible and that graphene on Ni(111) is after intercalation of Au spin-orbit split by the Rashba effect. In the last part, a time-resolved x-ray magnetic circular dichroic-photoelectron emission microscopy study of a permalloy platelet comprising three cross-tie domain walls is presented. It is shown how a fast picosecond magnetic response in the precessional motion of the magnetization can be induced by means of a laser-excited photoswitch. From a comparision to micromagnetic calculations it is demonstrated that the relatively high precessional frequency observed in the experiments is directly linked to the nature of the vortex/antivortex dynamics and its response to the magnetic perturbation. This includes the time-dependent reversal of the vortex core polarization, a process which is beyond the limit of detection in the present experiments.},
  language  = {en}
}
@article{FilimonKopfBalloutetal.2010,
  author    = {Filimon, Marlena and Kopf, Ilona and Ballout, Fuad and Schmidt, Dietrich A. and Bruendermann, Erik and R{\"u}he, J{\"u}rgen and Santer, Svetlana and Havenith, Martina},
  title     = {Smart polymer surfaces : mapping chemical landscapes on the nanometre scale},
  issn      = {1744-683X},
  doi       = {10.1039/C0sm00098a},
  year      = {2010},
  abstract  = {We show that Scattering Infrared Near-field Microscopy (SNIM) allows chemical mapping of polymer monolayers that can serve as designed nanostructured surfaces with specific surface chemistry properties on a nm scale. Using s- SNIM a minimum volume of 100 nm x 100 nm x 15 nm is sufficient for a recording of a "chemical'' IR signature which corresponds to an enhancement of at least four orders of magnitudes compared to conventional FT-IR microscopy. We could prove that even in cases where it is essentially difficult to distinguish between distinct polymer compositions based solely on topography, nanophase separated polymers can be clearly distinguished according to their characteristic near-field IR response.},
  language  = {en}
}
@article{ChinagliaGregorioStefanelloetal.2010,
  author    = {Chinaglia, Dante Luis and Gregorio, Rinaldo and Stefanello, Josiani Cristina and Altafim, Ruy Alberto Pisani and Wirges, Werner and Wang, Feipeng and Gerhard, Reimund},
  title     = {Influence of the solvent evaporation rate on the crystalline phases of solution-cast poly(vinylidene fluoride) films},
  issn      = {0021-8995},
  doi       = {10.1002/App.31488},
  year      = {2010},
  abstract  = {The influence of the solvent-evaporation rate on the formation of of. and P crystalline phases in solution-cast poly(vinylidene fluoride) (PVDF) films was systematically investigated. Films were crystallized from PVDF/N,N- dimethylformamide solutions with concentrations of 2.5, 5.0, 10, and 20 wt \% at different temperatures. During crystallization, the solvent evaporation rate was monitored in situ by means of a semianalytic balance. With this system, it was possible to determine the evaporation rate for different concentrations and temperatures of the solution under specific ambient conditions (pressure, temperature, and humidity). Fourier-Transform InfraRed spectroscopy with Attenuated Total Reflectance revealed the P-phase content in the PVDF films and its dependence on previous evaporation rates. Based on the relation between the evaporation rate and the PVDF phase composition, a consistent explanation for the different amounts of P phase observed at the upper and lower sample surfaces is achieved. Furthermore, the role of the sample thickness has also been studied. The experimental results show that not only the temperature but also the evaporation rate have to be controlled to obtain the desired crystalline phases in solution-cast PVDF films.},
  language  = {en}
}
@article{FloresSuarezGanesanWirgesetal.2010,
  author    = {Flores Su{\´a}rez, Rosaura and Ganesan, Lakshmi Meena and Wirges, Werner and Gerhard, Reimund and Mellinger, Axel},
  title     = {Imaging liquid crystals dispersed in a ferroelectric polymer matrix by means of thermal-pulse tomography},
  issn      = {1070-9878},
  doi       = {10.1109/TDEI.2010.5539683},
  year      = {2010},
  abstract  = {A new arrangement of the optical elements in a Thermal-Pulse-Tomography (TPT) setup allows to scan micrometer structures in composite and heterogeneous samples such as polymer-dispersed liquid crystals (PDLCs). The non-destructive TPT technique allows the determination of three-dimensional profiles of polarization and space charge in dielectrics. The samples under study were 12 mu m thick films of a copolymer of vinylidene fluoride with trifluoroethylene P(VDF- TrFE) (65/35) with embedded liquid-crystal droplets. The poling process was performed in direct contact well above the coercive field of the copolymer. The 3D map obtained from scanning with a 10 mu m wide spot shows elliptically shaped areas with liquid-crystal droplets. Considering the droplets as oblate spheroids, their major axis lies in the x-y plane, while their minor axis in the z direction measures 0.5 mu m or more. This result is in good agreement with scanning electron micrographs. It is believed that the major axis is overestimated due to imaging of liquid-crystal clusters.},
  language  = {en}
}
@article{GrecoWangWegener2010,
  author    = {Greco, Tonino and Wang, Feipeng and Wegener, Michael},
  title     = {Multifunctional silver poly(vinylidene fluoride) nanocomposites : nanoparticle synthesis, film processing, and structural characterization},
  issn      = {0015-0193},
  doi       = {10.1080/00150193.2010.482896},
  year      = {2010},
  abstract  = {Scope of this work was the synthesis of homogeneously dispersed silver nanoparticles in the ferroelectric polymer poly(vinylidene fluoride) (PVDF) and the study of the resulting properties affecting both the electro-active matrix and the optically-active nanofiller. In the nanocomposites surface plasmon resonances can be tuned across the UV- vis to the NIR spectral range. From IR spectra and DSC measurements it is concluded that the - to -phase transformation is observed and no degradation of the polymer matrix occurs. Finally, electrical poling was performed in order to investigate the influence of the embedded silver particles on the polarization behavior of the ferroelectric polymer.},
  language  = {en}
}
@article{FangQiuWirgesetal.2010,
  author    = {Fang, Peng and Qiu, Xunlin and Wirges, Werner and Gerhard, Reimund and Zirkel, Larissa},
  title     = {Polyethylene-naphthalate (PEN) ferroelectrets : cellular structure, piezoelectricity and thermal stability},
  issn      = {1070-9878},
  doi       = {10.1109/TDEI.2010.5539678},
  year      = {2010},
  abstract  = {Cellular polyethylene-naphthalate (PEN) ferroelectrets are useful as soft and flexible electromechanical transducer materials. Improved cellular PEN foams are prepared by means of a "voiding + inflation + stretching" process and investigated with respect to their structure and their applications-relevant properties. It is found that most of the cellular voids have heights below 8 mu m. The polymer walls do not allow sufficient gas exchange between the voids and the ambient atmosphere, when the cellular films are exposed to atmospheric pressures between a millibar and a few bars. As expected for ferroelectrets, a threshold voltage for charging is observed: A reasonable piezoelectric coefficient d(33) is only found when the charging voltage is higher than 4 kV. Furthermore, d(33) increases with charging voltage and reaches saturation at approximately 8 kV. Annealing after charging or charging at elevated temperatures may enhance the thermal stability of the PEN ferroelectrets. The d(33) of properly annealed samples is stable up to the respective annealing temperatures, but the annealing process reduces the piezoelectric activity of charged ferroelectret films to some extent. Samples charged at suitable elevated temperatures show much better thermal stability than those charged at room temperature, but the charging temperature should be limited to values below the material's glass-transition temperature T-g. Furthermore, the relevant elastic modulus c(33) of PEN ferroelectrets may decrease upon thermal treatment.},
  language  = {en}
}
@phdthesis{Fang2010,
  author    = {Fang, Peng},
  title     = {Preparation and investigation of polymer-foam films and polymer-layer systems for ferroelectrets},
  url       = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus-48412},
  school      = {Universit{\"a}t Potsdam},
  year      = {2010},
  abstract  = {Piezoelectric materials are very useful for applications in sensors and actuators. In addition to traditional ferroelectric ceramics and ferroelectric polymers, ferroelectrets have recently become a new group of piezoelectrics. Ferroelectrets are functional polymer systems for electromechanical transduction, with elastically heterogeneous cellular structures and internal quasi-permanent dipole moments. The piezoelectricity of ferroelectrets stems from linear changes of the dipole moments in response to external mechanical or electrical stress. Over the past two decades, polypropylene (PP) foams have been investigated with the aim of ferroelectret applications, and some products are already on the market. PP-foam ferroelectrets may exhibit piezoelectric d33 coefficients of 600 pC/N and more. Their operating temperature can, however, not be much higher than 60 °C. Recently developed polyethylene-terephthalate (PET) and cyclo-olefin copolymer (COC) foam ferroelectrets show slightly better d33 thermal stabilities, but usually at the price of smaller d33 values. Therefore, the main aim of this work is the development of new thermally stable ferroelectrets with appreciable piezoelectricity. Physical foaming is a promising technique for generating polymer foams from solid films without any pollution or impurity. Supercritical carbon dioxide (CO2) or nitrogen (N2) are usually employed as foaming agents due to their good solubility in several polymers. Polyethylene propylene (PEN) is a polyester with slightly better properties than PET. A "voiding + inflation + stretching" process has been specifically developed to prepare PEN foams. Solid PEN films are saturated with supercritical CO2 at high pressure and then thermally voided at high temperatures. Controlled inflation (Gas-Diffusion Expansion or GDE) is applied in order to adjust the void dimensions. Additional biaxial stretching decreases the void heights, since it is known lens-shaped voids lead to lower elastic moduli and therefore also to stronger piezoelectricity. Both, contact and corona charging are suitable for the electric charging of PEN foams. The light emission from the dielectric-barrier discharges (DBDs) can be clearly observed. Corona charging in a gas of high dielectric strength such as sulfur hexafluoride (SF6) results in higher gas-breakdown strength in the voids and therefore increases the piezoelectricity. PEN foams can exhibit piezoelectric d33 coefficients as high as 500 pC/N. Dielectric-resonance spectra show elastic moduli c33 of 1 - 12 MPa, anti-resonance frequencies of 0.2 - 0.8 MHz, and electromechanical coupling factors of 0.016 - 0.069. As expected, it is found that PEN foams show better thermal stability than PP and PET. Samples charged at room temperature can be utilized up to 80 - 100 °C. Annealing after charging or charging at elevated temperatures may improve thermal stabilities. Samples charged at suitable elevated temperatures show working temperatures as high as 110 - 120 °C. Acoustic measurements at frequencies of 2 Hz - 20 kHz show that PEN foams can be well applied in this frequency range. Fluorinated ethylene-propylene (FEP) copolymers are fluoropolymers with very good physical, chemical and electrical properties. The charge-storage ability of solid FEP films can be significantly improved by adding boron nitride (BN) filler particles. FEP foams are prepared by means of a one-step procedure consisting of CO2 saturation and subsequent in-situ high-temperature voiding. Piezoelectric d33 coefficients up to 40 pC/N are measured on such FEP foams. Mechanical fatigue tests show that the as-prepared PEN and FEP foams are mechanically stable for long periods of time. Although polymer-foam ferroelectrets have a high application potential, their piezoelectric properties strongly depend on the cellular morphology, i.e. on size, shape, and distribution of the voids. On the other hand, controlled preparation of optimized cellular structures is still a technical challenge. Consequently, new ferroelectrets based on polymer-layer system (sandwiches) have been prepared from FEP. By sandwiching an FEP mesh between two solid FEP films and fusing the polymer system with a laser beam, a well-designed uniform macroscopic cellular structure can be formed. Dielectric resonance spectroscopy reveals piezoelectric d33 coefficients as high as 350 pC/N, elastic moduli of about 0.3 MPa, anti-resonance frequencies of about 30 kHz, and electromechanical coupling factors of about 0.05. Samples charged at elevated temperatures show better thermal stabilities than those charged at room temperature, and the higher the charging temperature, the better is the stability. After proper charging at 140 °C, the working temperatures can be as high as 110 - 120 °C. Acoustic measurements at frequencies of 200 Hz - 20 kHz indicate that the FEP layer systems are suitable for applications at least in this range.},
  language  = {en}
}