@article{SchubertSteyrleuthnerBangeetal.2009,
  author    = {Schubert, Marcel and Steyrleuthner, Robert and Bange, Sebastian and Sellinger, Alan and Neher, Dieter},
  title     = {Charge transport and recombination in bulk heterojunction solar cells containing a dicyanoimidazole-based molecular acceptor},
  issn      = {1862-6300},
  doi       = {10.1002/pssa.200925312},
  year      = {2009},
  abstract  = {Carrier transport and recombination have been studied in single component layers and blends of the soluble PPV- derivative poly[2,5-dimethoxy-1,4-phenylenevinylene-2-methoxy-5-(2-ethyl-hexyloxy)- 1,4-phenylenevinylene] (M3EH-PPV) and the small molecule acceptor 4,7-bis(2-(1-hexyl-4,5-dicyanoimidazole-2-yl)vinyl) benzo[c][1,2,5]-thiadiazole (HV-BT). Measurements on single carrier devices show significantly smaller electron mobility in the blend compared to the pure HV- BT layer, which is suggestive of the formation of isolated clusters of the acceptor in a continuous polymer matrix. The significant change in fill factor (FF) with increasing illumination intensity is consistently explained by a model taking into account bimolecular recombination and space charge effects. The decay of the carrier density after photoexcitation has been studied by performing photo-CELIV measurements on pure and blend layers. It is found that the decay at long delay times follows a power-law dependence, which is, however, not consistent with a Langevin-type bimolecular recombination of free charges. A good description of the data is obtained by assuming trimolecular recombination to govern the charge carrier dynamics in these systems.},
  language  = {en}
}
@article{ZamponiAnsarivonKorffSchmisingetal.2009,
  author    = {Zamponi, Flavio and Ansari, Zunaira and von Korff Schmising, Clemens and Rothhardt, Philip and Zhavoronkov, Nickolai and Woerner, Michael and Elsaesser, Thomas and Bargheer, Matias and Trobitzsch-Ryll, Timo and Haschke, Michael},
  title     = {Femtosecond hard X-ray plasma sources with a kilohertz repetition rate},
  issn      = {0947-8396},
  doi       = {10.1007/s00339-009-5171-9},
  year      = {2009},
  abstract  = {Laser-driven plasma sources of femtosecond hard X-ray pulses have found widespread application in ultrafast X- ray diffraction. The recent development of plasma sources working at kilohertz repetition rates has allowed for diffraction experiments with strongly improved sensitivity, now revealing subtle fully reversible changes of the geometry of crystal lattices. We provide a brief review of this development and present a novel plasma source with an optimized mechanical and optical design, providing a high flux of several 10(10) photons/s at the Cu-K alpha energy of 8.04 keV and a pulse duration of a parts per thousand currency sign300 fs. First experiments, including the generation of Debye-Scherrer diffraction patterns from Si powder, demonstrate the high performance of this source.},
  language  = {en}
}
@article{YangEisert2009,
  author    = {Yang, Dong and Eisert, Jens},
  title     = {Entanglement combing},
  issn      = {0031-9007},
  doi       = {10.1103/Physrevlett.103.220501},
  year      = {2009},
  abstract  = {We show that all multipartite pure states can, under local operations, be transformed into bipartite pairwise entangled states in a "lossless fashion": An arbitrary distinguished party will keep pairwise entanglement with all other parties after the asymptotic protocol-decorrelating all other parties from each other-in a way that the degree of entanglement of this party with respect to the rest will remain entirely unchanged. The set of possible entanglement distributions of bipartite pairs is also classified. Finally, we point out several applications of this protocol as a useful primitive in quantum information theory.},
  language  = {en}
}
@article{WoernervonKorffSchmisingBargheeretal.2009,
  author    = {Woerner, Michael and von Korff Schmising, Clemens and Bargheer, Matias and Zhavoronkov, Nickolai and Vrejoiu, Ionela and Hesse, Dietrich and Alexe, Marin and Elsaesser, Thomas},
  title     = {Ultrafast structural dynamics of perovskite superlattices},
  issn      = {0947-8396},
  doi       = {10.1007/s00339-009-5174-6},
  year      = {2009},
  abstract  = {Femtosecond x-ray diffraction provides direct insight into the ultrafast reversible lattice dynamics of materials with a perovskite structure. Superlattice (SL) structures consisting of a sequence of nanometer-thick layer pairs allow for optically inducing a tailored stress profile that drives the lattice motions and for limiting the influence of strain propagation on the observed dynamics. We demonstrate this concept in a series of diffraction experiments with femtosecond time resolution, giving detailed information on the ultrafast lattice dynamics of ferroelectric and ferromagnetic superlattices. Anharmonically coupled lattice motions in a SrRuO3/PbZr0.2Ti0.8O3 (SRO/ PZT) SL lead to a switch-off of the electric polarizations on a time scale of the order of 1 ps. Ultrafast magnetostriction of photoexcited SRO layers is demonstrated in a SRO/SrTiO3 (STO) SL.},
  language  = {en}
}
@article{WangMuglachKliem2009,
  author    = {Wang, Yi-Ming and Muglach, Karin and Kliem, Bernhard},
  title     = {Endpoint brightenings in erupting filaments},
  issn      = {0004-637X},
  doi       = {10.1088/0004-637x/699/1/133},
  year      = {2009},
  abstract  = {Two well known phenomena associated with erupting filaments are the transient coronal holes that form on each side of the filament channel and the bright post-event arcade with its expanding double row of footpoints. Here we focus on a frequently overlooked signature of filament eruptions: the spike- or fan-shaped brightenings that appear to mark the far endpoints of the filament. From a sample of non-active-region filament events observed with the Extreme- Ultraviolet Imaging Telescope on the Solar and Heliospheric Observatory, we find that these brightenings usually occur near the outer edges of the transient holes, in contrast to the post-event arcades, which define their inner edges. The endpoints are often multiple and are rooted in and around strong network flux well outside the filament channel, a result that is consistent with the axial field of the filament being much stronger than the photospheric field inside the channel. The extreme ultraviolet brightenings, which are most intense at the time of maximum outward acceleration of the filament, can be used to determine unambiguously the direction of the axial field component from longitudinal magnetograms. Their location near the outer boundary of the transient holes suggests that we are observing the footprints of the current sheet formed at the leading edge of the erupting filament, as distinct from the vertical current sheet behind the filament which is the source of the post-event arcade.},
  language  = {en}
}
@article{ToenjesBlasius2009,
  author    = {Toenjes, Ralf and Blasius, Bernd},
  title     = {Perturbation analysis of the Kuramoto phase-diffusion equation subject to quenched frequency disorder},
  issn      = {1539-3755},
  doi       = {10.1103/Physreve.79.016112},
  year      = {2009},
  abstract  = {The Kuramoto phase-diffusion equation is a nonlinear partial differential equation which describes the spatiotemporal evolution of a phase variable in an oscillatory reaction-diffusion system. Synchronization manifests itself in a stationary phase gradient where all phases throughout a system evolve with the same velocity, the synchronization frequency. The formation of concentric waves can be explained by local impurities of higher frequency which can entrain their surroundings. Concentric waves in synchronization also occur in heterogeneous systems, where the local frequencies are distributed randomly. We present a perturbation analysis of the synchronization frequency where the perturbation is given by the heterogeneity of natural frequencies in the system. The nonlinearity in the form of dispersion leads to an overall acceleration of the oscillation for which the expected value can be calculated from the second-order perturbation terms. We apply the theory to simple topologies, like a line or sphere, and deduce the dependence of the synchronization frequency on the size and the dimension of the oscillatory medium. We show that our theory can be extended to include rotating waves in a medium with periodic boundary conditions. By changing a system parameter, the synchronized state may become quasidegenerate. We demonstrate how perturbation theory fails at such a critical point.},
  language  = {en}
}
@article{ToenjesBlasius2009,
  author    = {Toenjes, Ralf and Blasius, Bernd},
  title     = {Perturbation analysis of complete synchronization in networks of phase oscillators},
  issn      = {1539-3755},
  doi       = {10.1103/Physreve.80.026202},
  year      = {2009},
  abstract  = {The behavior of weakly coupled self-sustained oscillators can often be well described by phase equations. Here we use the paradigm of Kuramoto phase oscillators which are coupled in a network to calculate first- and second-order corrections to the frequency of the fully synchronized state for nonidentical oscillators. The topology of the underlying coupling network is reflected in the eigenvalues and eigenvectors of the network Laplacian which influence the synchronization frequency in a particular way. They characterize the importance of nodes in a network and the relations between them. Expected values for the synchronization frequency are obtained for oscillators with quenched random frequencies on a class of scale-free random networks and for a Erdoumls-Reacutenyi random network. We briefly discuss an application of the perturbation theory in the second order to network structural analysis.},
  language  = {en}
}
@article{SunLuKurthsetal.2009,
  author    = {Sun, Xiaojuan and Lu, Qishao and Kurths, J{\"u}rgen and Wang, Qingyun},
  title     = {Spatiotemporal coherence resonance in a map lattice},
  issn      = {0218-1274},
  doi       = {10.1142/S021812740902310X},
  year      = {2009},
  abstract  = {We study the effects of parametric noise on a lattice network, which is locally modeled by a two-dimensional Rulkov map. We conclude that at some intermediate noise intensity, parametric noise can induce ordered circular patterns, which indicates the appearance of spatiotemporal coherence resonance in the studied lattice. With the observation of coherence-like manner in linear spatial cross-correlation, the coherence phenomena can be analyzed quantitatively.},
  language  = {en}
}
@article{StoyanovMcCarthyKolloscheetal.2009,
  author    = {Stoyanov, Hristiyan and Mc Carthy, Denis N. and Kollosche, Matthias and Kofod, Guggi},
  title     = {Dielectric properties and electric breakdown strength of a subpercolative composite of carbon black in thermoplastic copolymer},
  issn      = {0003-6951},
  doi       = {10.1063/1.3154553},
  year      = {2009},
  abstract  = {We investigate the dielectric properties and electric breakdown strength of subpercolative composites of conductive carbon black particles in a rubber insulating matrix. A significant increase in the permittivity in the vicinity of the insulator to conductor transition was observed, with relatively low increases in dielectric loss; however, a rapid decrease in electric breakdown strength was inevitable. A steplike feature was ascribed to agglomeration effects. The low ultimate values of the electric field strength of such composites appear to prohibit practical use.},
  language  = {en}
}
@article{SteyrleuthnerBangeNeher2009,
  author    = {Steyrleuthner, Robert and Bange, Sebastian and Neher, Dieter},
  title     = {Reliable electron-only devices and electron transport in n-type polymers},
  issn      = {0021-8979},
  doi       = {10.1063/1.3086307},
  year      = {2009},
  abstract  = {Current-voltage analysis of single-carrier transport is a popular method for the determination of charge carrier mobilities in organic semiconductors. Although in widespread use for the analysis of hole transport, only a few reports can be found where the method was applied to electron transport. Here, we summarize the experimental difficulties related to the metal electrode leakage currents and nonlinear differential resistance (NDR) effects and explain their origin. We present a modified preparation technique for the metal electrodes and show that it significantly increases the reliability of such measurements. It allows to produce test devices with low leakage currents and without NDR even for thin organic layers. Metal oxides were often discussed as a possible cause of NDR. Our measurements on forcibly oxidized metal electrodes demonstrate that oxide layers are not exclusively responsible for NDR effects. We present electron transport data for two electron-conducting polymers often applied in all-polymer solar cells for a large variety of layer thicknesses and temperatures. The results can be explained by established exponential trapping models.},
  language  = {en}
}
@article{ShklyaevStraube2009,
  author    = {Shklyaev, Sergey and Straube, Arthur V.},
  title     = {The impact of bubble diffusivity on confined oscillated bubbly liquid},
  issn      = {1070-6631},
  doi       = {10.1063/1.3157237},
  year      = {2009},
  abstract  = {We consider the dynamics of monodisperse bubbly liquid confined by two plane solid walls and subject to small- amplitude high-frequency transverse oscillations. The period of these oscillations is assumed small in comparison with typical relaxation times for a single bubble but comparable with the period of volume eigenoscillations. The time- averaged description accounting for the two-way coupling between the liquid and the bubbles and for the diffusivity of bubbles is applied. We find nonuniform steady states with the liquid quiescent on average. At relatively low frequencies, accumulation of bubbles either at the walls or in planes parallel to the walls is detected. These one- dimensional states are shown to be unstable. At relatively high frequencies, this accumulation is found at the central plane and the solution is stable.},
  language  = {en}
}
@article{ShepelyanskyPikovskijSchmidtetal.2009,
  author    = {Shepelyansky, Dima L. and Pikovskij, Arkadij and Schmidt, J{\"u}rgen and Spahn, Frank},
  title     = {Synchronization mechanism of sharp edges in rings of Saturn},
  issn      = {0035-8711},
  doi       = {10.1111/j.1365-2966.2009.14719.x},
  year      = {2009},
  abstract  = {We propose a new mechanism which explains the existence of enormously sharp edges in the rings of Saturn. This mechanism is based on the synchronization phenomenon due to which the epicycle rotational phases of particles in the ring, under certain conditions, become synchronized with the phase of external satellite, e. g. with the phase of Mimas in the case of the outer B ring edge. This synchronization eliminates collisions between particles and suppresses the diffusion induced by collisions by orders of magnitude. The minimum of the diffusion is reached at the centre of the synchronization regime corresponding to the ratio 2:1 between the orbital frequency at the edge of B ring and the orbital frequency of Mimas. The synchronization theory gives the sharpness of the edge in a few tens of meters that is in agreement with available observations.},
  language  = {en}
}
@article{SchulzDietzelOrgzalletal.2009,
  author    = {Schulz, Burkhard and Dietzel, Birgit and Orgzall, Ingo and Diez, Isabel and Xu, Chenggang},
  title     = {Aspects of morphology control during the oxidative synthesis of electrically conducting polymers},
  issn      = {0954-0083},
  doi       = {10.1177/0954008309339933},
  year      = {2009},
  abstract  = {The formation of micro- and nanostructures during the oxidative polymerization of polypyrrole and polyaniline is investigated using different sulfonic acid dopants. Rod- or tube-like structures are found in polypyrrole as well as in polyaniline without addition of further compounds to the initial reaction mixture of monomer, dopant and oxidant. In these cases, always a crystalline precursor complex composed of a dopand molecule and the pure monomer (aniline) or a trimeric moiety (pyrrole) serves as in-situ template. In most cases the surface of the growing polymer is covered by secondary structures with much smaller sizes so that a hierarchical order of structures at different length scales results. Corresponding model considerations for the polymerization process are outlined. Additionally, unusual structures like platelets, frames, rings, or ribbons are observed in the polypyrrole synthesis in the presence of fluorosurfactants.},
  language  = {en}
}
@article{SchubertYinCastellanietal.2009,
  author    = {Schubert, Marcel and Yin, Chunhong and Castellani, Mauro and Bange, Sebastian and Tam, Teck Lip and Sellinger, Alan and Hoerhold, Hans-Heinrich and Kietzke, Thomas and Neher, Dieter},
  title     = {Heterojunction topology versus fill factor correlations in novel hybrid small-molecular/polymeric solar cells},
  issn      = {0021-9606},
  doi       = {10.1063/1.3077007},
  year      = {2009},
  abstract  = {The authors present organic photovoltaic (OPV) devices comprising a small molecule electron acceptor based on 2- vinyl-4,5-dicyanoimidazole (Vinazene (TM)) and a soluble poly(p-phenylenevinylene) derivative as the electron donor. A strong dependence of the fill factor (FF) and the external quantum efficiency [incident photons converted to electrons (IPCE)] on the heterojunction topology is observed. As-prepared blends provided relatively low FF and IPCE values of 26\% and 4.5\%, respectively, which are attributed to significant recombination of geminate pairs and free carriers in a highly intermixed blend morphology. Going to an all-solution processed bilayer device, the FF and IPCE dramatically increased to 43\% and 27\%, respectively. The FF increases further to 57\% in devices comprising thermally deposited Vinazene layers where there is virtually no interpenetration at the donor/acceptor interface. This very high FF is comparable to values reported for OPV using fullerenes as the electron acceptor. Furthermore, the rather low electron affinity of Vinazene compound near 3.5 eV enabled a technologically important open circuit voltage (V-oc) of 1.0 V.},
  language  = {en}
}
@article{SchlemmerBetzBerchtoldetal.2009,
  author    = {Schlemmer, Christian and Betz, Wolfgang and Berchtold, Bernd and R{\"u}he, J{\"u}rgen and Santer, Svetlana},
  title     = {The design of thin polymer membranes filled with magnetic particles on a microstructured silicon surface},
  issn      = {0957-4484},
  doi       = {10.1088/0957-4484/20/25/255301},
  year      = {2009},
  abstract  = {In this paper we present the fabrication and characterization of polymer nanomembranes filled with magnetic nanoparticles and attached covalently to a periodic array of free-standing silicon walls, forming an array of micro- channels with the membrane as a cover. The width of a micro-channel of about 1.4 mu m sets a characteristic lateral size and the thickness of the polymer membrane ranges between 100 and 300 nm. The membrane is made of cross-linked hydrophilic polymers possessing a Young's modulus of only a few MPa. The presence of the magnetic particles within the membrane makes the film responsive to external magnetic fields. The mechanical and magnetic properties of the membrane are characterized by bulge tests and with atomic force microscopy.},
  language  = {en}
}
@article{SchiefeleHenkel2009,
  author    = {Schiefele, J{\"u}rgen and Henkel, Carsten},
  title     = {Casimir energy of a BEC : from moderate interactions to the ideal gas},
  issn      = {1751-8113},
  doi       = {10.1088/1751-8113/42/4/045401},
  year      = {2009},
  abstract  = {Considering the Casimir effect due to phononic excitations of a weakly interacting dilute Bose-Einstein condensate ( BEC), we derive a renormalized expression for the zero-temperature Casimir energy E-C of a BEC confined to a parallel plate geometry with periodic boundary conditions. Our expression is formally equivalent to the free energy of a bosonic field at finite temperature, with a nontrivial density of modes that we compute analytically. As a function of the interaction strength, E-C smoothly describes the transition from the weakly interacting Bogoliubov regime to the non- interacting ideal BEC. For the weakly interacting case, E-C reduces to leading order to the Casimir energy due to zero- point fluctuations of massless phonon modes. In the limit of an ideal Bose gas, our result correctly describes the Casimir energy going to zero.},
  language  = {en}
}
@article{SaracGencturkGilsingetal.2009,
  author    = {Sarac, A. Sezai and Gencturk, Asli and Gilsing, Hans-Detlev and Schulz, Burkhard and Turhan, C. Metehan},
  title     = {Effect of electrolyte on the electropolymerization of 2,2-dibutyl-3,4-propylenedioxythiophene on carbon fiber microelectrodes},
  issn      = {1533-4880},
  doi       = {10.1166/Jnn.2009.027},
  year      = {2009},
  abstract  = {Electrocoating of 2,2 dibutylpropylene dioxythiophene on carbon fiber microelectrodes (CFMEs) in different electrolytes in acetonitrile was performed, and surface morphology and electrochemical impedance spectroscopic investigation has been carried out. Impedance spectra showed the typical form of Z(IM) versus Z(RE) for transmission- line at frequencies 10 Hz, with transition to almost pure capacitive behaviour down to 10 mHz (the lower limit of frequency scan).},
  language  = {en}
}
@article{RusconiVallerianiDunlopetal.2009,
  author    = {Rusconi, Marco and Valleriani, Angelo and Dunlop, John William Chapman and Kurths, J{\"u}rgen and Weinkamer, Richard},
  title     = {Insights into the control of trabecular bone remodelling obtained by a Markov model},
  issn      = {8756-3282},
  doi       = {10.1016/j.bone.2009.03.467},
  year      = {2009},
  language  = {en}
}
@article{RichterCharltonFanganoetal.2009,
  author    = {Richter, Philipp and Charlton, Jane C. and Fangano, Alessio P. M. and Ben Bekhti, Nadya and Masiero, Joseph R.},
  title     = {A population of weak metal-line absorbers surrounding the Milky Way},
  issn      = {0004-637X},
  doi       = {10.1088/0004-637x/695/2/1631},
  year      = {2009},
  abstract  = {We report on the detection of a population of weak metal-line absorbers in the halo or nearby intergalactic environment of the Milky Way. Using high-resolution ultraviolet absorption-line spectra of bright quasars (QSO) obtained with the Space Telescope Imaging Spectrograph (STIS), along six sight lines we have observed unsaturated, narrow absorption in O I and Si II, together with mildly saturated C II absorption at high radial velocities (vertical bar v(LSR)vertical bar = 100-320 km s(-1)). The measured O I column densities lie in the range N(O I) 2 x 10(14) cm(-2) implying that these structures represent Lyman limit Systems and sub-Lyman limit System with H I column densities between 10(16) and 3 x 10(18) cm(-2), thus below the detection limits of current 21 cm all-sky surveys of high-velocity clouds (HVCs). The absorbers apparently are not directly associated with any of the large high column density HVC complexes, but rather represent isolated, partly neutral gas clumps embedded in a more tenuous, ionized gaseous medium situated in the halo or nearby intergalactic environment of the Galaxy. Photoionization modeling of the observed low ion ratios suggests typical hydrogen volume densities of n(H) > 0.02 cm(-3) and characteristic thicknesses of a several parsec down to subparsec scales. For three absorbers, metallicities are constrained in the range of 0.1-1.0 solar, implying that these gaseous structures may have multiple origins inside and outside the Milky Way. Using supplementary optical absorption-line data, we find for two other absorbers Ca II/O I column-density ratios that correspond to solar Ca/O abundance ratios. This finding indicates that these clouds do not contain significant amounts of dust. This population of low column density gas clumps in the circumgalactic environment of the Milky Way is indicative of the various processes that contribute to the circulation of neutral gas in the extended halos of spiral galaxies. These processes include the accretion of gas from the intergalactic medium and satellite galaxies, galactic fountains, and outflows. We speculate that this absorber population represents the local analog of weak Mg II systems that are commonly observed in the circumgalactic environment of low- and high-redshift galaxies.},
  language  = {en}
}
@article{ReinholdGeueHuberetal.2009,
  author    = {Reinhold, Beate and Geue, Thomas and Huber, Patrick and Sant, Tushar and Pietsch, Ullrich and Sztucki, Michael},
  title     = {In situ and ex situ SAXS investigation of colloidal sedimentation onto laterally patterned support},
  issn      = {0743-7463},
  doi       = {10.1021/La803078b},
  year      = {2009},
  abstract  = {We report on in situ investigations of colloidal ordering during gravity sedimentation from a colloidal suspension onto a prepatterned support using a polymeric surface relief grating (SRG) as the support. The ordering of colloids with a diameter of 420 nm was investigated by means of grazing-incidence small-angle X-ray scattering (GISAXS) and transmission SAXS using a preparation cell guaranteeing stable temperature and humidity. GISAXS was used for in situ monitoring of the time evolution of colloidal ordering within the whole illuminated sample area. The onset of ordering was indicated by the increase of integrated intensity within a small time frame shortly before complete evaporation of the dispersant. Single domains of coated samples were investigated ex situ by SAXS in transmission geometry where the irradiated sample area was 200 x 200 mu m(2) only. Domains with the typical size of a few millimeters were observed varying in orientation and crystallographic structure for various positions at the sample. They were mainly oriented along the grooves of the grating, confirming the influence of the underlying grating on colloidal ordering.},
  language  = {en}
}
@article{ReddyGuptaGomeetal.2009,
  author    = {Reddy, Raghavendra V. and Gupta, Ajay and Gome, Anil and Leitenberger, Wolfram and Pietsch, Ullrich},
  title     = {In situ x-ray reflectivity and grazing incidence x-ray diffraction study of L1(0) ordering in Fe-57/Pt multilayers},
  issn      = {0953-8984},
  doi       = {10.1088/0953-8984/21/18/186002},
  year      = {2009},
  abstract  = {In situ high temperature x-ray reflectivity and grazing incidence x-ray diffraction measurements in the energy dispersive mode are used to study the ordered face-centered tetragonal (fct) L1(0) phase formation in [Fe(19 angstrom)/ Pt(25 angstrom)](x10) multilayers prepared by ion beam sputtering. With the in situ x-ray measurements it is observed that (i) the multilayer structure first transforms to a disordered FePt and subsequently to an ordered fct L1(0) phase, (ii) the ordered fct L1(0) FePt peaks start to appear at 320°C annealing, (iii) the activation energy of the interdiffusion is 0.8 eV and (iv) ordered fct FePt grains have preferential out-of-plane texture. The magneto-optical Kerr effect and conversion electron Mossbauer spectroscopies are used to study the magnetic properties of the as- deposited and 400°C annealed multilayers. The magnetic data for the 400°C annealed sample indicate that the magnetization is at an angle of ~50° from the plane of the film.},
  language  = {en}
}
@article{PrasadWittKieneletal.2009,
  author    = {Prasad, Sushama and Witt, Annette and Kienel, Ulrike and Dulski, Peter and Bauer, Eva and Yancheva, Gergana},
  title     = {The 8.2 ka event : evidence for seasonal differences and the rate of climate change in western Europe},
  issn      = {0921-8181},
  doi       = {10.1016/j.gloplacha.2009.03.011},
  year      = {2009},
  abstract  = {Recent studies have drawn attention to differences in the seasonal impact of the 8.2 ka event, with longer cooler summers and shorter cooler/drier winters. However, there are no data available on the simultaneity or the rate of onset of the seasonal changes in Europe. Based on the microfacies and geochemical analyses of seasonally laminated varved sediments from Holzmaar, we present evidence of differences in duration and onset time of changes in summer temperature and winter rainfall during the 8.2 ka event. Since both summer and winter climate signals are co-registered within a single varve, there can be no ambiguity about the phasing and duration of the signals. Our data show that the onset and withdrawal of the 8.2 ka summer cooling occurred within a year, and that summer rains were reduced or absent during the investigated period. The onset of cooler summers preceded the onset of winter dryness by ca. 28 years. In view of the differences in nature and duration of the impact of the 8.2 ka event we suggest that a clearer definition of the 8.2 ka event (summer cooling or winter cooling/dryness) needs to be developed. Based on regional comparison and available modelling studies we also discuss the roles of solar variability, changes in North Atlantic Thermohaline circulation, and North Atlantic Circulation (NAO) during the period under consideration. Wavelet analyses of seasonal laminae indicates that the longer NAO cycles, linked to changes in the N. Atlantic temperatures, were more frequent during the drier periods.},
  language  = {en}
}
@article{PostbergKempfSchmidtetal.2009,
  author    = {Postberg, Frank and Kempf, Sascha and Schmidt, J{\"u}rgen and Brilliantov, Nikolai V. and Beinsen, Alexander and Abel, Bernd and Buck, Udo and Srama, Ralf},
  title     = {Sodium salts in E-ring ice grains from an ocean below the surface of Enceladus},
  issn      = {0028-0836},
  doi       = {10.1038/Nature08046},
  year      = {2009},
  abstract  = {Saturn's moon Enceladus emits plumes of water vapour and ice particles from fractures near its south pole(1-5), suggesting the possibility of a subsurface ocean(5-7). These plume particles are the dominant source of Saturn's E ring(7,8). A previous in situ analysis(9) of these particles concluded that the minor organic or siliceous components, identified in many ice grains, could be evidence for interaction between Enceladus' rocky core and liquid water(9,10). It was not clear, however, whether the liquid is still present today or whether it has frozen. Here we report the identification of a population of E-ring grains that are rich in sodium salts (similar to 0.5- 2\% by mass), which can arise only if the plumes originate from liquid water. The abundance of various salt components in these particles, as well as the inferred basic pH, exhibit a compelling similarity to the predicted composition of a subsurface Enceladus ocean in contact with its rock core(11). The plume vapour is expected to be free of atomic sodium. Thus, the absence of sodium from optical spectra(12) is in good agreement with our results. In the E ring the upper limit for spectroscopy(12) is insufficiently sensitive to detect the concentrations we found.},
  language  = {en}
}
@article{PingelZenNeheretal.2009,
  author    = {Pingel, Patrick and Zen, Achmad and Neher, Dieter and Lieberwirth, Ingo and Wegner, Gerhard and Allard, Sybille and Scherf, Ullrich},
  title     = {Unexpectedly high field-effect mobility of a soluble, low molecular weight oligoquaterthiophene fraction with low polydispersity},
  issn      = {0947-8396},
  doi       = {10.1007/s00339-008-4994-0},
  year      = {2009},
  abstract  = {Layers made from soluble low molecular weight polythiophene PQT-12 with low polydispersity exhibit a highly ordered structure and charge-carrier mobilities of the order of 10(-3) cm(2)/(V s), which we attribute to its proximity to monodispersity. We propose that polydispersity is a decisive factor with regard to structure formation and transport properties of soluble low molecular weight polythiophenes.},
  language  = {en}
}
@article{PikovskijRosenblum2009,
  author    = {Pikovskij, Arkadij and Rosenblum, Michael},
  title     = {Self-organized partially synchronous dynamics in populations of nonlinearly coupled oscillators},
  issn      = {0167-2789},
  doi       = {10.1016/j.physd.2008.08.018},
  year      = {2009},
  abstract  = {We analyze a minimal model of a population of identical oscillators with a nonlinear coupling-a generalization of the popular Kuramoto model. In addition to well-known for the Kuramoto model regimes of full synchrony, full asynchrony, and integrable neutral quasiperiodic states, ensembles of nonlinearly coupled oscillators demonstrate two novel nontrivial types of partially synchronized dynamics: self-organized bunch states and self-organized quasiperiodic dynamics. The analysis based on the Watanabe-Strogatz ansatz allows us to describe the self-organized bunch states in any finite ensemble as a set of equilibria, and the self-organized quasiperiodicity as a two-frequency quasiperiodic regime. An analytic solution in the thermodynamic limit of infinitely many oscillators is also discussed.},
  language  = {en}
}
@article{PhamPetreBerquezetal.2009,
  author    = {Pham, Cong Duc and Petre, Anca and Berquez, Laurent and Flores Su{\´a}rez, Rosaura and Mellinger, Axel and Wirges, Werner and Gerhard, Reimund},
  title     = {3D high-resolution mapping of polarization profiles in thin poly(vinylidenefluoride-trifluoroethylene) (PVDF- TrFE) films using two thermal techniques},
  issn      = {1070-9878},
  doi       = {10.1109/TDEI.2009.5128505},
  year      = {2009},
  abstract  = {In this paper, two non-destructive thermal methods are used in order to determine, with a high degree of accuracy, three-dimensional polarization distributions in thin films (12 mu m) of poly(vinylidenefluoride- trifluoroethylene) (PVDF-TrFE). The techniques are the frequency-domain Focused Laser Intensity Modulation Method (FLIMM) and time-domain Thermal-Pulse Tomography (TPT). Samples were first metalized with grid-shaped electrode and poled. 3D polarization mapping yielded profiles which reproduce the electrode-grid shape. The polarization is not uniform across the sample thickness. Significant polarization values are found only at depths beyond 0.5 mu m from the sample surface. Both methods provide similar results, TPT method being faster, whereas the FLIMM technique has a better lateral resolution.},
  language  = {en}
}
@article{PereiraBaptistaReyesetal.2009,
  author    = {Pereira, Tiago and Baptista, Murilo da Silva and Reyes, Marcelo B. and Caldas, Ibere Luiz and Sartorelli, Jos{\´e} Carlos and Kurths, J{\"u}rgen},
  title     = {A scenario for torus T-2 destruction via a global bifurcation},
  issn      = {0960-0779},
  doi       = {10.1016/j.chaos.2007.06.115},
  year      = {2009},
  abstract  = {We show a scenario of a two-frequeney torus breakdown, in which a global bifurcation occurs due to the collision of a quasi-periodic torus T-2 with saddle points, creating a heteroclinic saddle connection. We analyze the geometry of this torus-saddle collision by showing the local dynamics and the invariant manifolds (global dynamics) of the saddle points. Moreover, we present detailed evidences of a heteroclinic saddle-focus orbit responsible for the type- if intermittency induced by this global bifurcation. We also characterize this transition to chaos by measuring the Lyapunov exponents and the scaling laws.},
  language  = {en}
}
@article{OstermeyerWaltingerGregor2009,
  author    = {Ostermeyer, Martin and Waltinger, Thomas and Gregor, Markus},
  title     = {Frequency stabilization of a Q-switched Nd:YAG laser oscillator with stability better 300 kHz following an rf- sideband scheme},
  issn      = {0030-4018},
  doi       = {10.1016/j.optcom.2009.04.063},
  year      = {2009},
  abstract  = {A frequency stabilization scheme following the Pound-Drever-Hall technique modified with a sample and hold circuit has been applied to a Q-switched diode-pumped Nd:YAG ring oscillator. The high-power ring is injection seeded by a monolithic non-planar ring laser oscillator (NPRO). The slave oscillator emits pulses of 23 ns duration and 20 mJ pulse energy with almost diffraction limited beam quality (M-2 = 1.2) at a repetition rate of 400 Hz. The short-term fluctuation of the center frequency from pulse to pulse is 290 kHz. The oscillator is designed for applications within lidar measurements.},
  language  = {en}
}
@article{OstermeyerPuhlmannKorn2009,
  author    = {Ostermeyer, Martin and Puhlmann, Dirk and Korn, Dietmar},
  title     = {Quantum diffraction of biphotons at a blazed grating},
  issn      = {0740-3224},
  year      = {2009},
  abstract  = {Correlations between photons are interesting for a number of applications and concepts in metrology, in particular for resolution improvements in different methods of quantum imaging. We demonstrate the application of a blazed grating for the characterization of the degree of spatial correlation of biphotons. The biphotons are generated by type II parametric downconversion. Compared to an ordinary transmission grating, a blazed grating shows a high diffraction efficiency only for a single order of diffraction. Thus, higher intensities in the Fraunhofer far field behind the grating, and easier photon counting, can be achieved. The distribution of the two-photon rate in the Fraunhofer far field of the blazed grating can show one additional order of diffraction with a visibility related to the degree of correlation of the biphotons. The number of spatial modes that are populated by the biphoton beam can be directly altered in our experiments. The relation of the spatial mode order of the photon propagation to the observable degree of spatial correlation of the biphotons is investigated and related to the Schmidt number of spatially entangled modes.},
  language  = {en}
}
@article{OstermeyerKornPuhlmannetal.2009,
  author    = {Ostermeyer, Martin and Korn, Dietmar and Puhlmann, Dirk and Henkel, Carsten and Eisert, Jens},
  title     = {Two-dimensional characterization of spatially entangled photon pairs},
  issn      = {0950-0340},
  doi       = {10.1080/09500340903359962},
  year      = {2009},
  abstract  = {We characterize the entanglement in position and momentum of photon pairs generated in type-II parametric down- conversion. Coincidence maps of the photon positions in the near-field and far-field planes are observed in two transverse dimensions using scanning fiber probes. We estimate the covariance matrix of an effective two-mode system and apply criteria for entanglement based on covariance matrices to certify space-momentum entanglement. The role of higher- order spatial modes for observing spatial entanglement between the two photons is discussed.},
  language  = {en}
}
@article{OskinovaHamannFeldmeieretal.2009,
  author    = {Oskinova, Lida and Hamann, Wolf-Rainer and Feldmeier, Achim and Ignace, Richard and Chu, You-Hua},
  title     = {Discovery of X-ray emission from the Wolf-Rayet star WR 142 of oxygen subtype},
  issn      = {0004-637X},
  doi       = {10.1088/0004-637x/693/1/L44},
  year      = {2009},
  abstract  = {We report the discovery of weak yet hard X-ray emission from the Wolf-Rayet (WR) star WR 142 with the XMM- Newton X-ray telescope. Being of spectral subtype WO2, WR 142 is a massive star in a very advanced evolutionary stage shortly before its explosion as a supernova or. gamma-ray burst. This is the first detection of X-ray emission from a WO- type star. We rule out any serendipitous X-ray sources within approximate to 1 '' of WR 142. WR 142 has an X- ray luminosity of L-X approximate to 7 x 10(30) erg s(-1), which constitutes only less than or similar to 10(-8) of its bolometric luminosity. The hard X-ray spectrum suggests a plasma temperature of about 100 MK. Commonly, X-ray emission from stellar winds is attributed to embedded shocks due to the intrinsic instability of the radiation driving. From qualitative considerations we conclude that this mechanism cannot account for the hardness of the observed radiation. There are no hints for a binary companion. Therefore the only remaining, albeit speculative explanation must refer to magnetic activity. Possibly related, WR 142 seems to rotate extremely fast, as indicated by the unusually round profiles of its optical emission lines. Our detection implies that the wind of WR 142 must be relatively transparent to X-rays, which can be due to strong wind ionization, wind clumping, or nonspherical geometry from rapid rotation.},
  language  = {en}
}
@article{MulanskyAhnertPikovskijetal.2009,
  author    = {Mulansky, Mario and Ahnert, Karsten and Pikovskij, Arkadij and Shepelyansky, Dima L.},
  title     = {Dynamical thermalization of disordered nonlinear lattices},
  issn      = {1539-3755},
  doi       = {10.1103/Physreve.80.056212},
  year      = {2009},
  abstract  = {We study numerically how the energy spreads over a finite disordered nonlinear one-dimensional lattice, where all linear modes are exponentially localized by disorder. We establish emergence of dynamical thermalization characterized as an ergodic chaotic dynamical state with a Gibbs distribution over the modes. Our results show that the fraction of thermalizing modes is finite and grows with the nonlinearity strength.},
  language  = {en}
}
@article{MofidiAliofkhazraeiRouhaghdametal.2009,
  author    = {Mofidi, Seyed Haman Hedayat and Aliofkhazraei, Mahmood and Rouhaghdam, Alireza Sabour and Ghobadi, Ehsan and Mohsenian, Ehsan},
  title     = {Improvement of surface characteristics by electroplating hard chromium coating post treated by nanocrystalline plasma electrolytic carbonitriding},
  issn      = {1612-8850},
  doi       = {10.1002/ppap.200930702},
  year      = {2009},
  abstract  = {Nanocrystalline carbonitrides were performed by pulsed plasma electrolytic carbonitriding on hard chromium coating deposited on AISI 1035 substrate by electroplating. The electroplated samples were connected cathodically to a high-current pulsed power supply and biased to a negative voltage. The treatment times were 30, 60 and 60 min. A thick compound layer was formed on the surface of Cr coating with microhardness of about 1200 HV0.15. The nanostructure of the treated layers depends strongly on the applied voltage. The wear resistance of the treated layers depended on process parameters. Overall mechanical properties of treated samples show strong relation to morphology and distribution of complex carbonitride nanocrystallites.},
  language  = {en}
}
@article{McCarthyRisseKatekomoletal.2009,
  author    = {Mc Carthy, Denis N. and Risse, Stefan and Katekomol, Phisan and Kofod, Guggi},
  title     = {The effect of dispersion on the increased relative permittivity of TiO2/SEBS composites},
  issn      = {0022-3727},
  doi       = {10.1088/0022-3727/42/14/145406},
  year      = {2009},
  abstract  = {Polymer composites are currently suggested for use as improved dielectric materials in many applications. Here, the effect of particle size and dispersion on the electrical properties of composites of rutile TiO2 and poly(styrene- ethylene-butadiene-styrene) (SEBS) are investigated. Both 15 and 300 nm particles are mixed with SEBS, with amounts of sorbitan monopalmitate surfactant from 0 to 3.3 vol\%, and their dielectric and mechanical properties are measured. Composites with the 300 nm TiO2 particles result in increases of 170\% in relative permittivity over the pure polymer, far above those predicted by standard theories, such as Bruggeman (140\%) and Yamada (114\%), and improving dispersion with surfactant has little effect. The composites with 15 nm particles showed surprisingly large relative permittivity increases (350\%), but improving the dispersion by the addition of any surfactant causes the relative permittivity to decrease to 240\% of the pure polymer value. We suggest that the increase is due to the formation of a highly conductive layer in the polymer around the TiO2 particles.},
  language  = {en}
}
@article{MarzoliTombesiCiaramicolietal.2009,
  author    = {Marzoli, Irene and Tombesi, Paolo and Ciaramicoli, Giacomo and Werth, Guenther and Bushev, Pavel and Stahl, S. and Schmidt-Kaler, Ferdinand and Hellwig, Michael and Henkel, Carsten and Marx, Gerrit and Jex, Igor and Stachowska, Ewa and Szawiola, Gustaw and Walaszyk, Adrian},
  title     = {Experimental and theoretical challenges for the trapped electron quantum computer},
  issn      = {0953-4075},
  doi       = {10.1088/0953-4075/42/15/154010},
  year      = {2009},
  abstract  = {We discuss quantum information processing with trapped electrons. After recalling the operation principle of planar Penning traps, we sketch the experimental conditions to load, cool and detect single electrons. Here we present a detailed investigation of a scalable scheme including feasibility studies and the analysis of all important elements, relevant for the experimental stage. On the theoretical side, we discuss different methods to couple electron qubits. We estimate the relevant qubit coherence times and draw implications for the experimental setting. A critical assessment of quantum information processing with trapped electrons concludes the paper.},
  language  = {en}
}
@article{MarzeionLevermann2009,
  author    = {Marzeion, Benjamin and Levermann, Anders},
  title     = {Stratification-dependent mixing may increase sensitivity of a wind-driven Atlantic overturning to surface freshwater flux},
  issn      = {0094-8276},
  doi       = {10.1029/2009gl039947},
  year      = {2009},
  abstract  = {Stratification-dependent mixing is employed in a coupled climate model of intermediate complexity with a 3- dimensional ocean component. Oceanic vertical diffusivity is calculated as kappa similar to N-alpha, where N is the local buoyancy frequency. The sensitivity of the Atlantic meridional overturning circulation (AMOC) to freshwater forcing is tested for exponents 0 <= a <= 2 by first slowly increasing, then decreasing the freshwater forcing over the North Atlantic, keeping the model close to equilibrium. The surface fresh anomaly imposed between 20 degrees N and 50 degrees N in the Atlantic reaches the deep ocean by vertical diffusion, and by AMOC advection via the northern convection sites. The fresh anomaly leads to enhanced stratification and thereby reduces vertical mixing stronger for higher values of a. Consequently, the freshwater anomaly reaches the northern deep water formation regions less diluted, and reduces the AMOC more strongly compared to lower values of a. Our findings indicate that modeled changes in the AMOC depend critically on the details of the mixing parameterization employed in the model.},
  language  = {en}
}
@article{MariEisert2009,
  author    = {Mari, Andrea and Eisert, Jens},
  title     = {Gently modulating optomechanical systems},
  issn      = {0031-9007},
  doi       = {10.1103/Physrevlett.103.213603},
  year      = {2009},
  abstract  = {We introduce a framework of optomechanical systems that are driven with a mildly amplitude-modulated light field, but that are not subject to classical feedback or squeezed input light. We find that in such a system one can achieve large degrees of squeezing of a mechanical micromirror-signifying quantum properties of optomechanical systems- without the need of any feedback and control, and within parameters reasonable in experimental settings. Entanglement dynamics is shown of states following classical quasiperiodic orbits in their first moments. We discuss the complex time dependence of the modes of a cavity-light field and a mechanical mode in phase space. Such settings give rise to certifiable quantum properties within experimental conditions feasible with present technology.},
  language  = {en}
}
@article{MaraunRustOsborn2009,
  author    = {Maraun, Douglas and Rust, Henning W. and Osborn, Tim J.},
  title     = {The annual cycle of heavy precipitation across the United Kingdom : a model based on extreme value statistics},
  issn      = {0899-8418},
  doi       = {10.1002/Joc.1811},
  year      = {2009},
  abstract  = {The annual cycle of extreme I-day precipitation events across the UK is investigated by developing a statistical model and fitting it to data from 689 rain gauges A generalized extrerne-value distribution (GEV) is fit to the time series of monthly maxima, across all months of the year simultaneously, by approximating, the annual cycles of the location and scale parameters by harmonic functions, while keeping the shape parameter constant throughout the year We average the shape parameter of neighbouring rain gauges to decrease uncertainties. and also Interpolate values of all model parameters to give complete coverage of (lie UK. The model reveals distinct spatial patterns the estimated parameters The annual mean of the location and scale parameter is highly correlated with orography. The annual cycle of the location parameter is strong in the northwest UK (peaking in late autumn or winter) and in East Anglia (where it peaks HI late summer), and low in the Midlands The annual cycle of the scale parameter exhibits a similar pattern with strongest amplitudes in East Anglia The spatial patterns of the annual cycle phase suggest that they are linked to the dominance of frontal precipitation for generating extreme precipitation in the west and convective precipitation in the southeast of the UK The shape parameter shows a gradient from Positive Values in the east to negative values in some areas of the west We also estimate 10-year and 100-year return levels at each rain gauge, and interpolated across the UK.},
  language  = {en}
}
@article{MaranhaoSartorelliBaptista2009,
  author    = {Maranh{\~a}o, D. M. and Sartorelli, Jose Carlos and Baptista, Murilo da Silva},
  title     = {Experimental identification of chaotic fibers},
  issn      = {0960-0779},
  doi       = {10.1016/j.chaos.2007.01.131},
  year      = {2009},
  abstract  = {In a 2D parameter space, by using nine experimental time series of a Clitia's circuit, we characterized three codimension-1 chaotic fibers parallel to a period-3 window. To show the local preservation of the properties of the chaotic attractors in each fiber, we applied the closed return technique and two distinct topological methods. With the first topological method we calculated the linking, numbers in the sets of unstable periodic orbits, and with the second one we obtained the symbolic planes and the topological entropies by applying symbolic dynamic analysis.},
  language  = {en}
}
@article{LiChenWuetal.2009,
  author    = {Li, Ping and Chen, Maoyin and Wu, Ye and Kurths, J{\"u}rgen},
  title     = {Matrix-measure criterion for synchronization in coupled-map networks},
  issn      = {1539-3755},
  doi       = {10.1103/Physreve.79.067102},
  year      = {2009},
  abstract  = {We present conditions for the local and global synchronizations in coupled-map networks using the matrix measure approach. In contrast to many existing synchronization conditions, the proposed synchronization criteria do not depend on the solution of the synchronous state and give less limitation on the network connections. Numerical simulations of the coupled quadratic maps demonstrate the potentials of our main results.},
  language  = {en}
}
@article{KoseskaVolkovKurths2009,
  author    = {Koseska, Aneta and Volkov, Evgenij and Kurths, J{\"u}rgen},
  title     = {Detuning-dependent dominance of oscillation death in globally coupled synthetic genetic oscillators},
  issn      = {0295-5075},
  doi       = {10.1209/0295-5075/85/28002},
  year      = {2009},
  abstract  = {We study dynamical regimes of globally coupled genetic relaxation oscillators in the presence of small detuning. Using bifurcation analysis, we find that under strong coupling via the slow variable, the detuning can eliminate standard oscillatory solutions in a large region of the parameter space, providing the dominance of oscillation death. This result is substantially different from previous results on oscillation quenching, where for homogeneous populations, the coexistence of oscillation death and limit cycle oscillations is always present. We propose further that this effect of detuning-dependent dominance could be a powerful regulator of genetic network's dynamics.},
  language  = {en}
}
@article{KofodMcCarthyKrissleretal.2009,
  author    = {Kofod, Guggi and Mc Carthy, Denis N. and Krissler, Jan and Lang, G{\"u}nter and Jordan, Grace},
  title     = {Electroelastic optical fiber positioning with submicrometer accuracy : model and experiment},
  issn      = {0003-6951},
  doi       = {10.1063/1.3134002},
  year      = {2009},
  abstract  = {We present accurate electromechanical measurements on a balanced push-pull dielectric elastomer actuator, demonstrating submicrometer accurate position control. An analytical model based on a simplified pure-shear dielectric elastomer film with prestretch is found to capture the voltage-displacement behavior, with reduced output due to the boundary conditions. Two complementary experiments show that actuation coefficients of 0.5-1 nm/V-2 are obtainable with the demonstrated device, enabling motion control with submicrometer accuracy in a voltage range below 200 V.},
  language  = {en}
}
@article{JoshiPingelGrigorianetal.2009,
  author    = {Joshi, Siddharth and Pingel, Patrick and Grigorian, Souren and Panzner, Tobias and Pietsch, Ullrich and Neher, Dieter and Forster, Michael and Scherf, Ullrich},
  title     = {Bimodal temperature behavior of structure and mobility in high molecular weight p3ht thin films},
  issn      = {0024-9297},
  doi       = {10.1021/Ma900021w},
  year      = {2009},
  abstract  = {We report a temperature dependent crystalline structure of spin-coated thin films of high molecular weight regioregular poly(3-hexylthiophene) (P3HT) (M-n similar to 30000 g/mol) and its correlation with charge carrier mobility. These investigations show a reversible change of the crystalline structure, where the interlayer lattice spacing (100)along the alkyl side chains continuously increases up to a temperature of about 220 degrees C; in contrast, the in-plane pi-pi distance reduces with increasing temperature. These changes in structure are reversible and can be repeated several times. The temperature-induced structural properties differ for thick and thin films, pointing to a surface/interface role in stabilization of the layer morphology. In contrast to the structural changes, the carrier mobility is rather constant in the temperature range from room temperature up to 100-120 degrees C, followed by a continuous decrease. For thick layers this drop is significant and the transistor performance almost vanishes at high temperature, however, it completely recovers upon cooling back to roorn temperature. The drop of the charge carrier mobility at higher temperatures is in contrast with expectations front the structural studies, considering the increase of crystalline fraction of the polycrystalline layer. our electrical measurements Underscore that the reduction of the macroscopic mobility is mostly caused by it pronounced decrease of the intergrain transport. The thermally induced crystallization along(100) direction and the creation of numerous small crystallites at the film-substrate interface reduce the number of long polymer chain, bridging crystalline domains, which ultimately limits the macroscopic charge transport.},
  language  = {en}
}
@article{JechowLichtnerMenzeletal.2009,
  author    = {Jechow, Andreas and Lichtner, Mark and Menzel, Ralf and Radziunas, Mindaugas and Skoczowsky, Danilo and Vladimirov, Andrei G.},
  title     = {Stripe-array diode-laser in an off-axis external cavity : theory and experiment},
  issn      = {1094-4087},
  doi       = {10.1364/OE.17.019599},
  year      = {2009},
  abstract  = {Stripe-array diode lasers naturally operate in an anti-phase supermode. This produces a sharp double lobe far field at angles +/-alpha depending on the period of the array. In this paper a 40 emitter gain guided stripe-array laterally coupled by off-axis filtered feedback is investigated experimentally and numerically. We predict theoretically and confirm experimentally that at doubled feedback angle 2 alpha a stable higher order supermode exists with twice the number of emitters per array period. The theoretical model is based on time domain traveling wave equations for optical fields coupled to the carrier density equation taking into account diffusion of carriers. Feedback from the external reflector is modeled using Fresnel integration.},
  language  = {en}
}
@article{IntravaiaHenkel2009,
  author    = {Intravaia, Francesco and Henkel, Carsten},
  title     = {Casimir interaction from magnetically coupled eddy currents},
  issn      = {0031-9007},
  doi       = {10.1103/Physrevlett.103.130405},
  year      = {2009},
  abstract  = {We study the quantum and thermal fluctuations of eddy (Foucault) currents in thick metallic plates. A Casimir interaction between two plates arises from the coupling via quasistatic magnetic fields. As a function of distance, the relevant eddy current modes cross over from a quantum to a thermal regime. These modes alone reproduce previously discussed thermal anomalies of the electromagnetic Casimir interaction between good conductors. In particular, they provide a physical picture for the Casimir entropy whose nonzero value at zero temperature arises from a correlated, glassy state.},
  language  = {en}
}
@article{InalCastellaniSellingeretal.2009,
  author    = {Inal, Sahika and Castellani, Mauro and Sellinger, Alan and Neher, Dieter},
  title     = {Relationship of photophysical properties and the device performance of novel hybrid small-molecular/polymeric solar cells},
  issn      = {1022-1336},
  doi       = {10.1002/marc.200900221},
  year      = {2009},
  abstract  = {We investigate solar cells comprised of a vinazene derivative (HV-BT) as the electron acceptor and the well- known polymer poly(3-hexylthiophene) as the electron donor. In the as-prepared blend, most of the excited state species, including the excimers on HV-BT, are quenched at the heterojunction. Although the photophysical properties of the blends change upon annealing, the blend solar cells largely remain uninfluenced by such treatments. A significant improvement is, however, observed when inducing phase separation at a longer length scale, for example, in solution-processed bilayer devices. Hereby, both the fill factor (FF) and the open circuit voltage are considerably increased, pointing to the importance of the heterojunction topology and the layer composition at the charge extracting contacts. An optimized device exhibits a power conversion efficiency of close to 1\%.},
  language  = {en}
}
@article{HuebenerKruszynskaHartmannetal.2009,
  author    = {H{\"u}bener, Robert and Kruszynska, Caroline and Hartmann, Lorenz and Duer, Wolfgang and Verstraete, Frank and Eisert, Jens and Plenio, Martin B.},
  title     = {Renormalization algorithm with graph enhancement},
  issn      = {1050-2947},
  doi       = {10.1103/Physreva.79.022317},
  year      = {2009},
  abstract  = {We introduce a class of variational states to describe quantum many-body systems. This class generalizes matrix product states which underlie the density-matrix renormalization-group approach by combining them with weighted graph states. States within this class may (i) possess arbitrarily long-ranged two-point correlations, (ii) exhibit an arbitrary degree of block entanglement entropy up to a volume law, (iii) be taken translationally invariant, while at the same time (iv) local properties and two-point correlations can be computed efficiently. This variational class of states can be thought of as being prepared from matrix product states, followed by commuting unitaries on arbitrary constituents, hence truly generalizing both matrix product and weighted graph states. We use this class of states to formulate a renormalization algorithm with graph enhancement and present numerical examples, demonstrating that improvements over density-matrix renormalization-group simulations can be achieved in the simulation of ground states and quantum algorithms. Further generalizations, e.g., to higher spatial dimensions, are outlined.},
  language  = {en}
}
@article{GvaramadzeFabrikaHamannetal.2009,
  author    = {Gvaramadze, Vasily V. and Fabrika, Sergei Nikolaevich and Hamann, Wolf-Rainer and Sholukhova, Olga N. and Valeev, Azamat F. and Goranskij, Vitaly P. and Cherepashchuk, Anatol M. and Bomans, Dominik J. and Oskinova, Lida},
  title     = {Discovery of a new Wolf-Rayet star and its ring nebula in Cygnus},
  issn      = {0035-8711},
  doi       = {10.1111/j.1365-2966.2009.15492.x},
  year      = {2009},
  abstract  = {We report the serendipitous discovery of a ring nebula around a candidate Wolf-Rayet (WR) star, HBHA 4202-22, in Cygnus using the Spitzer Space Telescope archival data. Our spectroscopic follow-up observations confirmed the WR nature of this star (we named it WR 138a) and showed that it belongs to the WN8-9h subtype. We thereby add a new example to the known sample of late WN stars with circumstellar nebulae. We analysed the spectrum of WR 138a by using the Potsdam Wolf-Rayet (PoWR) model atmospheres, obtaining a stellar temperature of 40 kK. The stellar wind composition is dominated by helium with 20 per cent of hydrogen. The stellar spectrum is highly reddened and absorbed (EB- V = 2.4 mag, A(V) = 7.4 mag). Adopting a stellar luminosity of log L/L-circle dot = 5.3, the star has a mass-loss rate of 10-4.7 M- circle dot yr-1, and resides in a distance of 4.2 kpc. We measured the proper motion for WR 138a and found that it is a runaway star with a peculiar velocity of similar or equal to 50 km s-1. Implications of the runaway nature of WR 138a for constraining the mass of its progenitor star and understanding the origin of its ring nebula are discussed.},
  language  = {en}
}
@article{GrossFlammiaEisert2009,
  author    = {Gross, David and Flammia, Steven T. and Eisert, Jens},
  title     = {Most quantum states are too entangled to be useful as computational resources},
  issn      = {0031-9007},
  doi       = {10.1103/Physrevlett.102.190501},
  year      = {2009},
  abstract  = {It is often argued that entanglement is at the root of the speedup for quantum compared to classical computation, and that one needs a sufficient amount of entanglement for this speedup to be manifest. In measurement- based quantum computing, the need for a highly entangled initial state is particularly obvious. Defying this intuition, we show that quantum states can be too entangled to be useful for the purpose of computation, in that high values of the geometric measure of entanglement preclude states from offering a universal quantum computational speedup. We prove that this phenomenon occurs for a dramatic majority of all states: the fraction of useful n-qubit pure states is less than exp(-n(2)). This work highlights a new aspect of the role entanglement plays for quantum computational speedups.},
  language  = {en}
}
@article{GoldobinZaikin2009,
  author    = {Goldobin, Denis S. and Zaikin, Alexey},
  title     = {Towards quantitative prediction of proteasomal digestion patterns of proteins},
  issn      = {1742-5468},
  doi       = {10.1088/1742-5468/2009/01/P01009},
  year      = {2009},
  abstract  = {We discuss the problem of proteasomal degradation of proteins. Though proteasomes are important for all aspects of cellular metabolism, some details of the physical mechanism of the process remain unknown. We introduce a stochastic model of the proteasomal degradation of proteins, which accounts for the protein translocation and the topology of the positioning of cleavage centers of a proteasome from first principles. For this model we develop a mathematical description based on a master equation and techniques for reconstruction of the cleavage specificity inherent to proteins and the proteasomal translocation rates, which are a property of the proteasome species, from mass spectroscopy data on digestion patterns. With these properties determined, one can quantitatively predict digestion patterns for new experimental set-ups. Additionally we design an experimental set-up for a synthetic polypeptide with a periodic sequence of amino acids, which enables especially reliable determination of translocation rates.},
  language  = {en}
}