TY - JOUR A1 - Navirian, Hengameh A. A1 - Herzog, Marc A1 - Goldshteyn, J. A1 - Leitenberger, Wolfram A1 - Vrejoiu, Ionella A1 - Khakhulin, D. A1 - Wulff, M. A1 - Shayduk, Roman A1 - Gaal, P. A1 - Bargheer, Matias T1 - Shortening x-ray pulses for pump-probe experiments at synchrotrons JF - Journal of applied physics N2 - We implemented an experimental scheme for ultrafast x-ray diffraction at storage rings based on a laser-driven Bragg-switch that shortens the x-ray pulses emitted from an undulator. The increased time-resolution is demonstrated by observing changes of intensity, position and width of the diffraction peaks of a La(0.7)Sr(0.3)MnO(3)/SrTiO(3) superlattice sample after optical excitation, i.e., by quantitatively measuring the propagation of an expansion wave through the sample. These experimental transients with timescales of 35 to 60 ps evidence a reduction of the x-ray pulse duration by a factor of two. Y1 - 2011 U6 - https://doi.org/10.1063/1.3601057 SN - 0021-8979 VL - 109 IS - 12 PB - American Institute of Physics CY - Melville ER - TY - JOUR A1 - Kar, Parimal A1 - Lipowsky, Reinhard A1 - Knecht, Volker T1 - Importance of polar solvation for cross-reactivity of antibody and its variants with steroids JF - The journal of physical chemistry : B, Condensed matter, materials, surfaces, interfaces & biophysical chemistry N2 - Understanding the factors determining the binding of ligands to receptors in detail is essential for rational drug design. Here, the free energies of binding of the steroids progesterone (PRG) and 5 beta-androstane-3,17-dione (SAD) to the Diels-Alderase antibody 1E9, as well as the Leu(H47)Trp/Arg(H100)Trp 1E9 double mutant (1E9dm) and the corresponding single mutants, have been estimated and decomposed using the molecular mechanics-Poisson-Boltzmann surface area (MM-PBSA) method. Also the difference in binding free energies between the PRG-1E9dm complex and the complex of PRG with the antiprogesterone antibody DB3 have been evaluated and decomposed. The steroids bind less strongly to 1E9 than to DB3, but the mutations tend to improve the steroid affinity, in quantitative agreement with experimental data. Although the complexes formed by PRG or SAD with 1E9dm and by PRG with DB3 have similar affinity, the binding mechanisms are different. Reduced Waals for SAD-1E9dm versus PRG-1E9dm or for PRG-1E9dm versus PRG-DB3 are energetically compensated by an increased solvation of polar groups, partly contrasting previous conclusions based on structural inspection. Our study illustrates that deducing binding mechanisms from structural models alone can be misleading. Therefore, taking into account solvation effects as in MM-PBSA calculations is essential to elucidate molecular recognition. Y1 - 2011 U6 - https://doi.org/10.1021/jp201538t SN - 1520-6106 VL - 115 IS - 23 SP - 7661 EP - 7669 PB - American Chemical Society CY - Washington ER - TY - JOUR A1 - Postberg, Frank A1 - Schmidt, J. A1 - Hillier, J. A1 - Kempf, Sascha A1 - Srama, Ralf T1 - A salt-water reservoir as the source of a compositionally stratified plume on Enceladus JF - Nature : the international weekly journal of science N2 - The discovery of a plume of water vapour and ice particles emerging from warm fractures ('tiger stripes') in Saturn's small, icy moon Enceladus(1-6) raised the question of whether the plume emerges from a subsurface liquid source(6-8) or from the decomposition of ice(9-12). Previous compositional analyses of particles injected by the plume into Saturn's diffuse E ring have already indicated the presence of liquid water(8), but the mechanisms driving the plume emission are still debated(13). Here we report an analysis of the composition of freshly ejected particles close to the sources. Salt-rich ice particles are found to dominate the total mass flux of ejected solids (more than 99 per cent) but they are depleted in the population escaping into Saturn's E ring. Ice grains containing organic compounds are found to be more abundant in dense parts of the plume. Whereas previous Cassini observations were compatible with a variety of plume formation mechanisms, these data eliminate or severely constrain non-liquid models and strongly imply that a salt-water reservoir with a large evaporating surface(7,8) provides nearly all of the matter in the plume. Y1 - 2011 U6 - https://doi.org/10.1038/nature10175 SN - 0028-0836 VL - 474 IS - 7353 SP - 620 EP - 622 PB - Nature Publ. Group CY - London ER - TY - JOUR A1 - Baumgärtel, Hellmut T1 - A Characteristic decay semigroup for the resonances of trace class perturbations with analyticity conditions of semibounded hamiltonians JF - International journal of theoretical physic N2 - To asymptotic complete scattering systems {M(+) + V, M(+)} on H(+) := L(2)(R(+), K, d lambda), where M(+) is the multiplication operator on H(+) and V is a trace class operator with analyticity conditions, a decay semigroup is associated such that the spectrum of the generator of this semigroup coincides with the set of all resonances (poles of the analytic continuation of the scattering matrix into the lower half plane across the positive half line), i.e. the decay semigroup yields a "time-dependent" characterization of the resonances. As a counterpart a "spectral characterization" is mentioned which is due to the "eigenvalue-like" properties of resonances. KW - Resonances KW - Scattering theory KW - Lax-Phillips theory KW - Decay semigroups Y1 - 2011 U6 - https://doi.org/10.1007/s10773-010-0533-9 SN - 0020-7748 VL - 50 IS - 7 SP - 2002 EP - 2008 PB - Springer CY - New York ER - TY - JOUR A1 - Delahaye, T. A1 - Fiasson, A. A1 - Pohl, Martin A1 - Salati, P. T1 - The GeV-TeV Galactic gamma-ray diffuse emission I. Uncertainties in the predictions of the hadronic component JF - Astronomy and astrophysics : an international weekly journal N2 - Context. The Galactic gamma-ray diffuse emission is currently observed in the GeV-TeV energy range with unprecedented accuracy by the Fermi satellite. Understanding this component is crucial because it provides a background to many different signals, such as extragalactic sources or annihilating dark matter. It is timely to reinvestigate how it is calculated and to assess the various uncertainties that are likely to affect the accuracy of the predictions. Aims. The Galactic gamma-ray diffuse emission is mostly produced above a few GeV by the interactions of cosmic ray primaries impinging on the interstellar material. The theoretical error on that component is derived by exploring various potential sources of uncertainty. Particular attention is paid to cosmic ray propagation. Nuclear cross sections, the proton and helium fluxes at the Earth's position, the Galactic radial profile of supernova remnants, and the hydrogen distribution can also severely affect the signal. Methods. The propagation of cosmic ray species throughout the Galaxy is described in the framework of a semi-analytic two-zone diffusion/convection model. The gamma-ray flux is reliably and quickly determined. This allows conversion of the constraints set by the boron-to-carbon data into a theoretical uncertainty on the diffuse emission. New deconvolutions of the HI and CO sky maps are also used to get the hydrogen distribution within the Galaxy. Results. The thickness of the cosmic ray diffusive halo is found to have a significant effect on the Galactic gamma-ray diffuse emission, while the interplay between diffusion and convection has little influence on the signal. The uncertainties related to nuclear cross sections and to the primary cosmic ray fluxes at the Earth are significant. The radial distribution of supernova remnants along the Galactic plane turns out to be a key ingredient. As expected, the predictions are extremely sensitive to the spatial distribution of hydrogen within the Milky Way. Conclusions. Most of the sources of uncertainty are likely to be reduced in the near future. The stress should be put (i) on better determination of the thickness of the cosmic ray diffusive halo; and (ii) on refined observations of the radial profile of supernova remnants. KW - gamma rays: diffuse background KW - cosmic rays KW - methods: analytical KW - gamma rays: ISM Y1 - 2011 U6 - https://doi.org/10.1051/0004-6361/201116647 SN - 0004-6361 VL - 531 IS - 4 PB - EDP Sciences CY - Les Ulis ER - TY - JOUR A1 - Kappel, Marcel A1 - Abel, Markus A1 - Gerhard, Reimund T1 - Characterization and calibration of piezoelectric polymers in situ measurements of body vibrations JF - Review of scientific instruments : a monthly journal devoted to scientific instruments, apparatus, and techniques N2 - Piezoelectric polymers are known for their flexibility in applications, mainly due to their bending ability, robustness, and variable sensor geometry. It is an optimal material for minimal-invasive investigations in vibrational systems, e.g., for wood, where acoustical impedance matches particularly well. Many applications may be imagined, e. g., monitoring of buildings, vehicles, machinery, alarm systems, such that our investigations may have a large impact on technology. Longitudinal piezoelectricity converts mechanical vibrations normal to the polymer-film plane into an electrical signal, and the respective piezoelectric coefficient needs to be carefully determined in dependence on the relevant material parameters. In order to evaluate efficiency and durability for piezopolymers, we use polyvinylidene fluoride and measure the piezoelectric coefficient with respect to static pressure, amplitude of the dynamically applied force, and long-term stability. A known problem is the slow relaxation of the material towards equilibrium, if the external pressure changes; here, we demonstrate how to counter this problem with careful calibration. Since our focus is on acoustical measurements, we determine accurately the frequency response curve - for acoustics probably the most important characteristic. Eventually, we show that our piezopolymer transducers can be used as a calibrated acoustical sensors for body vibration measurements on a wooden musical instrument, where it is important to perform minimal-invasive measurements. A comparison with the simultaneously recorded airborne sound yields important insight of the mechanism of sound radiation in comparison with the sound propagating in the material. This is especially important for transient signals, where not only the long-living eigenmodes contribute to the sound radiation. Our analyses support that piezopolymer sensors can be employed as a general tool for the determination of the internal dynamics of vibrating systems. KW - acoustic transducers KW - calibration KW - durability KW - electric sensing devices KW - piezoelectricity KW - polymers Y1 - 2011 U6 - https://doi.org/10.1063/1.3607435 SN - 0034-6748 VL - 82 IS - 7 PB - American Institute of Physics CY - Melville ER - TY - JOUR A1 - Lueck, S. A1 - Pikovskij, Arkadij T1 - Dynamics of multi-frequency oscillator ensembles with resonant coupling JF - Modern physics letters : A, Particles and fields, gravitation, cosmology, nuclear physics N2 - We study dynamics of populations of resonantly coupled oscillators having different frequencies. Starting from the coupled van der Pol equations we derive the Kuramoto-type phase model for the situation, where the natural frequencies of two interacting subpopulations are in relation 2 : 1. Depending on the parameter of coupling, ensembles can demonstrate fully synchronous clusters, partial synchrony (only one subpopulation synchronizes), or asynchrony in both subpopulations. Theoretical description of the dynamics based on the Watanabe-Strogatz approach is developed. KW - Oscillator populations KW - Kuramoto model KW - Resonant interaction Y1 - 2011 U6 - https://doi.org/10.1016/j.physleta.2011.06.016 SN - 0375-9601 VL - 375 IS - 28-29 SP - 2714 EP - 2719 PB - Elsevier CY - Amsterdam ER - TY - JOUR A1 - Levnajic, Zoran A1 - Pikovskij, Arkadij T1 - Network reconstruction from random phase resetting JF - Physical review letters N2 - We propose a novel method of reconstructing the topology and interaction functions for a general oscillator network. An ensemble of initial phases and the corresponding instantaneous frequencies is constructed by repeating random phase resets of the system dynamics. The desired details of network structure are then revealed by appropriately averaging over the ensemble. The method is applicable for a wide class of networks with arbitrary emergent dynamics, including full synchrony. Y1 - 2011 U6 - https://doi.org/10.1103/PhysRevLett.107.034101 SN - 0031-9007 VL - 107 IS - 3 PB - American Physical Society CY - College Park ER - TY - JOUR A1 - Rivnay, Jonathan A1 - Steyrleuthner, Robert A1 - Jimison, Leslie H. A1 - Casadei, Alberto A1 - Chen, Zhihua A1 - Toney, Michael F. A1 - Facchetti, Antonio A1 - Neher, Dieter A1 - Salleo, Alberto T1 - Drastic control of texture in a high performance n-Type polymeric semiconductor and implications for charge transport JF - Macromolecules : a publication of the American Chemical Society N2 - Control of crystallographic texture from mostly face-on to edge-on is observed for the film morphology of the n-type semicrystalline polymer [N,N-9-bis(2-octyldodecyl)naphthalene-1,4,5,8-bis(dicarboximide)-2,6-diy1]alt-5,59-(2,29-bithiophene)}, P(NDI2OD-T2), when annealing the film to the polymer melting point followed by slow cooling to ambient temperature. A variety of X-ray diffraction analyses, including pole figure construction and Fourier transform peak shape deconvolution, are employed to quantify the texture change, relative degree of crystallinity and lattice order. We find that annealing the polymer film to the melt leads to a shift from 77.5% face-on to 94.6% edge-on lamellar texture as well as to a 2-fold increase in crystallinity and a 40% decrease in intracrystallite cumulative disorder. The texture change results in a significant drop in the electron-only diode current density through the film thickness upon melt annealing while little change is observed in the in-plane transport of bottom gated thin film transistors. This suggests that the texture change is prevalent in the film interior and that either the (bottom) surface structure is different from the interior structure or the intracrystalline order and texture play a secondary role in transistor transport for this material. Y1 - 2011 U6 - https://doi.org/10.1021/ma200864s SN - 0024-9297 VL - 44 IS - 13 SP - 5246 EP - 5255 PB - American Chemical Society CY - Washington ER - TY - JOUR A1 - Gerhardt, Matthias A1 - Groeger, Gillian A1 - MacCarthy, Niall T1 - Monopolar vs. bipolar subretinal stimulation-An in vitro study JF - Journal of neuroscience methods N2 - This study uses an in vitro rd10 mouse model to quantify and compare the ability of the monopolar and the (concentric) bipolar electrode configurations for subretinal stimulation. To allow for results which can be directly compared an identical region of the retina was stimulated due to the circumstance that the bipolar electrode configuration allows also for monopolar stimulation, if the concentric counter-electrode is set potential-free (floating). A ganglion cell, located centrally over the bipolar electrode configuration was selected to extracellularly record action potentials during stimulation. To analyse the recorded action potentials, we introduce a new method which combines the advantages of (a) singular value decomposition (SVD) for weighting similar modulation patterns with which the recorded action potentials are characterized and (b) multi curve fitting to identify a common threshold level, required to finally assemble a strength-duration relationship (SDR). By directly comparing the obtained SDR curves, we found that the efficiency of stimulation with the monopolar electrode configuration is significantly higher than with the bipolar electrode configuration. All obtained SDR curves were fitted using the Lapicque model to estimate the chronaxie times and the rheobase currents. Liquid inclusions, eventually separating the retina from the electrodes are discussed to be a major cause for low ganglion cell responses during stimulation with the bipolar electrode configuration. KW - SVD KW - Subretinal KW - Electrodes KW - Monopolar KW - Bipolar KW - Retina KW - Ganglion KW - Cells Y1 - 2011 U6 - https://doi.org/10.1016/j.jneumeth.2011.04.017 SN - 0165-0270 VL - 199 IS - 1 SP - 26 EP - 34 PB - Elsevier CY - Amsterdam ER - TY - JOUR A1 - Qiu, Xunlin A1 - Wirges, Werner A1 - Gerhard, Reimund T1 - Beneficial and detrimental fatigue effects of dielectric barrier discharges on the piezoelectricity of polypropylene ferroelectrets JF - Journal of applied physics N2 - Cellular polypropylene (PP) ferroelectrets combine a large piezoelectricity with mechanical flexibility and elastic compliance. Their charging process represents a series of dielectric barrier discharges (DBDs) that generate a cold plasma with numerous active species and thus modify the inner polymer surfaces of the foam cells. Both the threshold for the onset of DBDs and the piezoelectricity of ferroelectrets are sensitive to repeated DBDs in the voids. It is found that the threshold voltage is approximately halved and the charging efficiency is clearly improved after only 10(3) DBD cycles. However, plasma modification of the inner surfaces from repeated DBDs deteriorates the chargeability of the voids, leading to a significant reduction of the piezoelectricity in ferroelectrets. After a significant waiting period, the chargeability of previously fatigued voids shows a partial recovery. The plasma modification is, however, detrimental to the stability of the deposited charges and thus also of the macroscopic dipoles and of the piezoelectricity. Fatigue from only 10(3) DBD cycles already results in significantly less stable piezoelectricity in cellular PP ferroelectrets. The fatigue rate as a function of the number of voltage cycles follows a stretched exponential. Fatigue from repeated DBDs can be avoided if most of the gas molecules inside the voids are removed via a suitable evacuation process. Y1 - 2011 U6 - https://doi.org/10.1063/1.3610507 SN - 0021-8979 SN - 1089-7550 VL - 110 IS - 2 PB - American Institute of Physics CY - Melville ER - TY - JOUR A1 - Komarov, Maxim A1 - Pikovskij, Arkadij T1 - Effects of nonresonant interaction in ensembles of phase oscillators JF - Physical review : E, Statistical, nonlinear and soft matter physics N2 - We consider general properties of groups of interacting oscillators, for which the natural frequencies are not in resonance. Such groups interact via nonoscillating collective variables like the amplitudes of the order parameters defined for each group. We treat the phase dynamics of the groups using the Ott-Antonsen ansatz and reduce it to a system of coupled equations for the order parameters. We describe different regimes of cosynchrony in the groups. For a large number of groups, heteroclinic cycles, corresponding to a sequential synchronous activity of groups and chaotic states where the order parameters oscillate irregularly, are possible. Y1 - 2011 U6 - https://doi.org/10.1103/PhysRevE.84.016210 SN - 1539-3755 VL - 84 IS - 1 PB - American Physical Society CY - College Park ER - TY - JOUR A1 - Ilnytskyi, Jaroslav M. A1 - Neher, Dieter A1 - Saphiannikova, Marina T1 - Opposite photo-induced deformations in azobenzene-containing polymers with different molecular architecture molecular dynamics study JF - The journal of chemical physics : bridges a gap between journals of physics and journals of chemistr N2 - Photo-induced deformations in azobenzene-containing polymers (azo-polymers) are central to a number of applications, such as optical storage and fabrication of diffractive elements. The microscopic nature of the underlying opto-mechanical coupling is yet not clear. In this study, we address the experimental finding that the scenario of the effects depends on molecular architecture of the used azo-polymer. Typically, opposite deformations in respect to the direction of light polarization are observed for liquid crystalline and amorphous azo-polymers. In this study, we undertake molecular dynamics simulations of two different models that mimic these two types of azo-polymers. We employ hybrid force field modeling and consider only trans-isomers of azobenzene, represented as Gay-Berne sites. The effect of illumination on the orientation of the chromophores is considered on the level of orientational hole burning and emphasis is given to the resulting deformation of the polymer matrix. We reproduce deformations of opposite sign for the two models being considered here and discuss the relevant microscopic mechanisms in both cases. KW - amorphous state KW - light polarisation KW - liquid crystal polymers KW - molecular dynamics method KW - optical hole burning KW - photochemistry Y1 - 2011 U6 - https://doi.org/10.1063/1.3614499 SN - 0021-9606 VL - 135 IS - 4 PB - American Institute of Physics CY - Melville ER - TY - JOUR A1 - Levnajic, Zoran T1 - Emergent multistability and frustration in phase-repulsive networks of oscillators JF - Physical review : E, Statistical, nonlinear and soft matter physics N2 - The collective dynamics of oscillator networks with phase-repulsive coupling is studied, considering various network sizes and topologies. The notion of link frustration is introduced to characterize and quantify the network dynamical states. In opposition to widely studied phase-attractive case, the properties of final dynamical states in our model critically depend on the network topology. In particular, each network's total frustration value is intimately related to its topology. Moreover, phase-repulsive networks in general display multiple final frustration states, whose statistical and stability properties are uniquely identifying them. Y1 - 2011 U6 - https://doi.org/10.1103/PhysRevE.84.016231 SN - 1539-3755 VL - 84 IS - 1 PB - American Physical Society CY - College Park ER - TY - JOUR A1 - Grass, T. D. A1 - dos Santos, Francisca E. A. A1 - Pelster, Axel T1 - Real-time Ginzburg-Landau theory for bosons in optical lattices JF - Laser physics N2 - Within the Schwinger-Keldysh formalism we derive a Ginzburg-Landau theory for the Bose-Hubbard model which describes the real-time dynamics of the complex order parameter field. Analyzing the excitations in the vicinity of the quantum phase transitions it turns out that particle/hole dispersions in the Mott phase map continuously onto corresponding amplitude/phase excitations in the superfluid phase. Furthermore, in the superfluid phase we find a sound mode, which is in accordance with recent Bragg spectroscopy measurements in the Bogoliubov regime, as well as an additional gapped mode, which seems to have been detected via lattice modulation. Y1 - 2011 U6 - https://doi.org/10.1134/S1054660X11150096 SN - 1054-660X SN - 1555-6611 VL - 21 IS - 8 SP - 1459 EP - 1463 PB - IOP Publ. Ltd. CY - Bristol ER - TY - JOUR A1 - Fechner, Cora T1 - Reconstructing the intergalactic UV background with QSO absorption lines JF - Astronomy and astrophysics : an international weekly journal N2 - We present a new approach to observationally constraining the spectral energy distribution of the intergalactic UV background by studying metal absorption systems. We study single-component metal line systems that exhibit various well-measured species. Among the observed transitions, at least two ratios of ionization stages from the same element are required, e. g. C III/C IV and Si III/Si IV. For each system photoionization models are constructed by varying the spectrum of the ionizing radiation. The spectral energy distribution can then be constrained by comparing the models with the observed column density ratios. Extensive tests with artificial absorbers show that the spectrum of the ionizing radiation cannot be reconstructed unambiguously, but it is possible to constrain the main characteristics of the spectrum. Furthermore, the resulting physical parameters of the absorber, such as ionization parameter, metallicity, and relative abundances, may depend strongly on the adopted ionizing spectrum. Even in case of well-fitting models, the uncertainties can be as high as similar to 0.5 dex for the ionization parameter and up to similar to 1.5 dex for the metallicity. Therefore, it is essential to know the hardness of the UV background when estimating the metallicity of the intergalactic medium. Applying the procedure to a small sample of 3 observed single-component metal line systems yields a soft ionizing radiation at z > 2 and a slightly harder spectrum at z < 2. The resulting energy distributions exhibit strong He II Lya re-emission features, suggesting that reprocessing by intergalactic He II is important. Comparing the observed systems to UV background spectra from the literature indicates that a recent model that includes sawtooth modulation due to reprocessing by intergalactic He II with delayed helium reionization fits the investigated systems very well. KW - intergalactic medium KW - quasars: absorption lines KW - diffuse radiation Y1 - 2011 U6 - https://doi.org/10.1051/0004-6361/201117080 SN - 0004-6361 VL - 532 IS - 2 PB - EDP Sciences CY - Les Ulis ER - TY - JOUR A1 - Bagnich, Sergey A. A1 - Unger, Th. A1 - Jaiser, Frank A1 - Neher, Dieter A1 - Thesen, M. W. A1 - Krüger, H. T1 - Efficient green electrophosphorescence based on ambipolar nonconjugated polymers evaluation of transport and emission properties JF - Journal of applied physics N2 - New materials for polymer organic light-emitting diodes based on a polymer matrix doped with phosphorescent dyes are presented. The matrix system is based on a polystyrene backbone bearing either electron or hole transporting units at the 4-position of each repeat unit. Random copolymers and polymer blend systems of the homopolymers are prepared, both with 62 wt.% electron transporting and 38 wt.% hole transporting moieties. Adding a green electrophosphorescent dye to the polymer matrix leads to efficient electroluminescence with a maximum current efficiency of 35 cd/A and a maximum external quantum efficiency of up to 10%. The mobilities of electrons and holes in the dye-doped copolymer, as measured by transient electroluminescence, are around 5 x 10(-5) and 5 x 10(-6) cm(2)/Vs, respectively, while the blend of the two homopolymers exhibits slightly lower mobilities of both types of carriers. Despite the pronounced imbalance of charge transport, the device performance is almost entirely limited by the phosphorescence efficiency of the dye, implying balanced flow of holes and electrons into the active region. Also, devices made with either the copolymer or the blend yielded very similar device efficiencies, despite the noticeable difference in electron and hole mobility. It is proposed that electrons are efficiently blocked at the interlayer and that the so-formed space charge assists the balanced injection of holes. Y1 - 2011 U6 - https://doi.org/10.1063/1.3618681 SN - 0021-8979 SN - 1089-7550 VL - 110 IS - 3 PB - American Institute of Physics CY - Melville ER - TY - JOUR A1 - Prosen, Tomaz A1 - Ilievski, Enej T1 - Nonequilibrium phase transition in a periodically driven XY spin chain JF - Physical review letters N2 - We present a general formulation of Floquet states of periodically time-dependent open Markovian quasifree fermionic many-body systems in terms of a discrete Lyapunov equation. Illustrating the technique, we analyze periodically kicked XY spin-1/2 chain which is coupled to a pair of Lindblad reservoirs at its ends. A complex phase diagram is reported with reentrant phases of long range and exponentially decaying spin-spin correlations as some of the system's parameters are varied. The structure of phase diagram is reproduced in terms of counting nontrivial stationary points of Floquet quasiparticle dispersion relation. Y1 - 2011 U6 - https://doi.org/10.1103/PhysRevLett.107.060403 SN - 0031-9007 VL - 107 IS - 6 PB - American Physical Society CY - College Park ER - TY - JOUR A1 - Zakrevskyy, Yuriy A1 - Kopyshev, Alexey A1 - Lomadze, Nino A1 - Morozova, Elena A1 - Lysyakova, Liudmila A1 - Kasyanenko, Nina A1 - Santer, Svetlana T1 - DNA compaction by azobenzene-containing surfactant JF - Physical review : E, Statistical, nonlinear and soft matter physics N2 - We report on the interaction of cationic azobenzene-containing surfactant with DNA investigated by absorption and fluorescence spectroscopy, dynamic light scattering, and atomic force microscopy. The properties of the surfactant can be controlled with light by reversible switching of the azobenzene unit, incorporated into the surfactant tail, between a hydrophobic trans (visible irradiation) and a hydrophilic cis (UV irradiation) configuration. The influence of the trans-cis isomerization of the azobenzene on the compaction process of DNA molecules and the role of both isomers in the formation and colloidal stability of DNA-surfactant complexes is discussed. It is shown that the trans isomer plays a major role in the DNA compaction process. The influence of the cis isomer on the DNA coil configuration is rather small. The construction of a phase diagram of the DNA concentration versus surfactant/DNA charge ratio allows distancing between three major phases: colloidally stable and unstable compacted globules, and extended coil conformation. There is a critical concentration of DNA above which the compacted globules can be hindered from aggregation and precipitation by adding an appropriate amount of the surfactant in the trans configuration. This is because of the compensation of hydrophobicity of the globules with an increasing amount of the surfactant. Below the critical DNA concentration, the compacted globules are colloidally stable and can be reversibly transferred with light to an extended coil state. Y1 - 2011 U6 - https://doi.org/10.1103/PhysRevE.84.021909 SN - 1539-3755 VL - 84 IS - 2 PB - American Physical Society CY - College Park ER - TY - JOUR A1 - Schütz, Nadine A1 - Holschneider, Matthias T1 - Detection of trend changes in time series using Bayesian inference JF - Physical review : E, Statistical, nonlinear and soft matter physics N2 - Change points in time series are perceived as isolated singularities where two regular trends of a given signal do not match. The detection of such transitions is of fundamental interest for the understanding of the system's internal dynamics or external forcings. In practice observational noise makes it difficult to detect such change points in time series. In this work we elaborate on a Bayesian algorithm to estimate the location of the singularities and to quantify their credibility. We validate the performance and sensitivity of our inference method by estimating change points of synthetic data sets. As an application we use our algorithm to analyze the annual flow volume of the Nile River at Aswan from 1871 to 1970, where we confirm a well-established significant transition point within the time series. Y1 - 2011 U6 - https://doi.org/10.1103/PhysRevE.84.021120 SN - 1539-3755 SN - 1550-2376 VL - 84 IS - 2 PB - American Physical Society CY - College Park ER - TY - JOUR A1 - Blakesley, James C. A1 - Neher, Dieter T1 - Relationship between energetic disorder and open-circuit voltage in bulk heterojunction organic solar cells JF - Physical review : B, Condensed matter and materials physics N2 - We simulate organic bulk heterojunction solar cells. The effects of energetic disorder are incorporated through a Gaussian or exponential model of density of states. Analytical models of open-circuit voltage (V(OC)) are derived from the splitting of quasi-Fermi potentials. Their predictions are backed up by more complex numerical device simulations including effects such as carrier-density-dependent charge-carrier mobilities. It is predicted that the V(OC) depends on: (1) the donor-acceptor energy gap; (2) charge-carrier recombination rates; (3) illumination intensity; (4) the contact work functions (if not in the pinning regime); and (5) the amount of energetic disorder. A large degree of energetic disorder, or a high density of traps, is found to cause significant reductions in V(OC). This can explain why V(OC) is often less than expected in real devices. Energetic disorder also explains the nonideal temperature and intensity dependence of V(OC) and the superbimolecular recombination rates observed in many real bulk heterojunction solar cells. Y1 - 2011 U6 - https://doi.org/10.1103/PhysRevB.84.075210 SN - 1098-0121 VL - 84 IS - 7 PB - American Physical Society CY - College Park ER - TY - JOUR A1 - Burylko, Oleksandr A1 - Pikovskij, Arkadij T1 - Desynchronization transitions in nonlinearly coupled phase oscillators JF - Physica :D, Nonlinear phenomena N2 - We consider the nonlinear extension of the Kuramoto model of globally coupled phase oscillators where the phase shift in the coupling function depends on the order parameter. A bifurcation analysis of the transition from fully synchronous state to partial synchrony is performed. We demonstrate that for small ensembles it is typically mediated by stable cluster states, that disappear with creation of heteroclinic cycles, while for a larger number of oscillators a direct transition from full synchrony to a periodic or a quasiperiodic regime occurs. KW - Coupled oscillators KW - Oscillator ensembles KW - Kuramoto model KW - Nonlinear coupling KW - Bifurcations Y1 - 2011 U6 - https://doi.org/10.1016/j.physd.2011.05.016 SN - 0167-2789 VL - 240 IS - 17 SP - 1352 EP - 1361 PB - Elsevier CY - Amsterdam ER - TY - JOUR A1 - Sun, Y-P A1 - Pietzsch, Annette A1 - Hennies, Franz A1 - Rinkevicius, Z. A1 - Karlsson, Hans O. A1 - Schmitt, Thorsten A1 - Strocov, Vladimir N. A1 - Andersson, Joakim A1 - Kennedy, B. A1 - Schlappa, J. A1 - Föhlisch, Alexander A1 - Gel'mukhanov, F. A1 - Rubensson, Jan-Erik T1 - Internal symmetry and selection rules in resonant inelastic soft x-ray scattering JF - Journal of physics : B, Atomic, molecular and optical physics N2 - Resonant inelastic soft x-ray scattering spectra excited at the dissociative 1 sigma(g) -> 3 sigma(u) resonance in gas-phase O(2) are presented and discussed in terms of state-of-the-art molecular theory. A new selection rule due to internal spin coupling is established, facilitating a deep analysis of the valence excited final states. Furthermore, it is found that a commonly accepted symmetry selection rule due to orbital parity breaks down, as the core hole and excited electron swap parity, thereby opening the symmetry forbidden 3 sigma(g) decay channel. Y1 - 2011 U6 - https://doi.org/10.1088/0953-4075/44/16/161002 SN - 0953-4075 VL - 44 IS - 16 PB - IOP Publ. Ltd. CY - Bristol ER - TY - JOUR A1 - Acciari, V. A. A1 - Aliu, E. A1 - Arlen, T. A1 - Aune, T. A1 - Beilicke, M. A1 - Benbow, W. A1 - Bradbury, S. M. A1 - Buckley, J. H. A1 - Bugaev, V. A1 - Byrum, K. A1 - Cannon, A. A1 - Cesarini, A. A1 - Ciupik, L. A1 - Collins-Hughes, E. A1 - Connolly, M. P. A1 - Cui, W. A1 - Dickherber, R. A1 - Duke, C. A1 - Errando, M. A1 - Falcone, A. A1 - Finley, J. P. A1 - Finnegan, G. A1 - Fortson, L. A1 - Furniss, A. A1 - Galante, N. A1 - Gall, D. A1 - Gillanders, G. H. A1 - Godambe, S. A1 - Griffin, S. A1 - Grube, J. A1 - Guenette, R. A1 - Gyuk, G. A1 - Hanna, D. A1 - Holder, J. A1 - Hughes, G. A1 - Hui, C. M. A1 - Humensky, T. B. A1 - Kaaret, P. A1 - Karlsson, N. A1 - Kertzman, M. A1 - Kieda, D. A1 - Krawczynski, H. A1 - Krennrich, F. A1 - Lang, M. J. A1 - LeBohec, S. A1 - Maier, G. A1 - Majumdar, P. A1 - McArthur, S. A1 - McCann, A. A1 - Moriarty, P. A1 - Mukherjee, R. A1 - Ong, R. A. A1 - Orr, M. A1 - Otte, A. N. A1 - Park, N. A1 - Perkins, J. S. A1 - Pohl, Martin A1 - Prokoph, H. A1 - Quinn, J. A1 - Ragan, K. A1 - Reyes, L. C. A1 - Reynolds, P. T. A1 - Roache, E. A1 - Rose, H. J. A1 - Ruppel, J. A1 - Saxon, D. B. A1 - Schroedter, M. A1 - Sembroski, G. H. A1 - Senturk, G. D. A1 - Smith, A. W. A1 - Staszak, D. A1 - Tesic, G. A1 - Theiling, M. A1 - Thibadeau, S. A1 - Tsurusaki, K. A1 - Varlotta, A. A1 - Vassiliev, V. V. A1 - Vincent, S. A1 - Vivier, M. A1 - Wakely, S. P. A1 - Ward, J. E. A1 - Weekes, T. C. A1 - Weinstein, A. A1 - Weisgarber, T. A1 - Williams, D. A. A1 - Zitzer, B. T1 - VERITAS OBSERVATIONS OF THE TeV BINARY LS I+61 degrees 303 DURING 2008-2010 JF - The astrophysical journal : an international review of spectroscopy and astronomical physics N2 - We present the results of observations of the TeV binary LS I + 61 degrees 303 with the VERITAS telescope array between 2008 and 2010, at energies above 300 GeV. In the past, both ground-based gamma-ray telescopes VERITAS and MAGIC have reported detections of TeV emission near the apastron phases of the binary orbit. The observations presented here show no strong evidence for TeV emission during these orbital phases; however, during observations taken in late 2010, significant emission was detected from the source close to the phase of superior conjunction (much closer to periastron passage) at a 5.6 standard deviation (5.6 sigma) post-trials significance. In total, between 2008 October and 2010 December a total exposure of 64.5 hr was accumulated with VERITAS on LS I + 61 degrees 303, resulting in an excess at the 3.3 sigma significance level for constant emission over the entire integrated data set. The flux upper limits derived for emission during the previously reliably active TeV phases (i.e., close to apastron) are less than 5% of the Crab Nebula flux in the same energy range. This result stands in apparent contrast to previous observations by both MAGIC and VERITAS which detected the source during these phases at 10% of the Crab Nebula flux. During the two year span of observations, a large amount of X-ray data were also accrued on LS I + 61 degrees 303 by the Swift X-ray Telescope and the Rossi X-ray Timing Explorer Proportional Counter Array. We find no evidence for a correlation between emission in the X-ray and TeV regimes during 20 directly overlapping observations. We also comment on data obtained contemporaneously by the Fermi Large Area Telescope. KW - binaries: general KW - gamma rays: general KW - X-rays: binaries Y1 - 2011 U6 - https://doi.org/10.1088/0004-637X/738/1/3 SN - 0004-637X VL - 738 IS - 1 PB - IOP Publ. Ltd. CY - Bristol ER - TY - JOUR A1 - Stich, Michael A1 - Beta, Carsten T1 - Standing waves in a complex Ginzburg-Landau equation with time-delay feedback JF - Discrete and continuous dynamical systems : a journal bridging mathematics and sciences N2 - Standing waves are studied as solutions of a complex Ginsburg-Landau equation subjected to local and global time-delay feedback terms. The onset of standing waves is studied at the instability of the homogeneous periodic solution with respect to spatially periodic perturbations. The solution of this spatiotemporal wave pattern is given and is compared to the homogeneous periodic solution. KW - pattern formation KW - reaction-diffusion system KW - control Y1 - 2011 SN - 1078-0947 SN - 1553-5231 IS - 1 SP - 1329 EP - 1334 PB - American Institute of Mathematical Sciences CY - Springfield ER - TY - JOUR A1 - Hübener, Robert A1 - Kruszynska, Caroline A1 - Hartmann, Lorenz A1 - Duer, Wolfgang A1 - Plenio, Martin B. A1 - Eisert, Jens T1 - Tensor network methods with graph enhancement JF - Physical review : B, Condensed matter and materials physics N2 - We present applications of the renormalization algorithm with graph enhancement (RAGE). This analysis extends the algorithms and applications given for approaches based on matrix product states introduced in [Phys. Rev. A 79, 022317 (2009)] to other tensor-network states such as the tensor tree states (TTS) and projected entangled pair states. We investigate the suitability of the bare TTS to describe ground states, showing that the description of certain graph states and condensed-matter models improves. We investigate graph-enhanced tensor-network states, demonstrating that in some cases (disturbed graph states and for certain quantum circuits) the combination of weighted graph states with TTS can greatly improve the accuracy of the description of ground states and time-evolved states. We comment on delineating the boundary of the classically efficiently simulatable states of quantum many-body systems. Y1 - 2011 U6 - https://doi.org/10.1103/PhysRevB.84.125103 SN - 1098-0121 VL - 84 IS - 12 PB - American Physical Society CY - College Park ER - TY - JOUR A1 - Schmah, Tanya A1 - Marwan, Norbert A1 - Thomsen, Jesper Skovhus A1 - Saparin, Peter T1 - Long range node-strut analysis of trabecular bone microarchitecture JF - Medical physics : the international journal of medical physics research and practice N2 - Purpose: We present a new morphometric measure of trabecular bone microarchitecture, called mean node strength (NdStr), which is part of a newly developed approach called long range nodestrut analysis. Our general aim is to describe and quantify the apparent "latticelike" microarchitecture of the trabecular bone network. Methods: Similar in some ways to the topological node-strut analysis introduced by Garrahan et al. [J. Microsc. 142, 341-349 (1986)], our method is distinguished by an emphasis on long-range trabecular connectivity. Thus, while the topological classification of a pixel (after skeletonization) as a node, strut, or terminus, can be determined from the 3 x 3 neighborhood of that pixel, our method, which does not involve skeletonization, takes into account a much larger neighborhood. In addition, rather than giving a discrete classification of each pixel as a node, strut, or terminus, our method produces a continuous variable, node strength. The node strength is averaged over a region of interest to produce the mean node strength of the region. Results: We have applied our long range node-strut analysis to a set of 26 high-resolution peripheral quantitative computed tomography (pQCT) axial images of human proximal tibiae acquired 17 mm below the tibial plateau. We found that NdStr has a strong positive correlation with trabecular volumetric bone mineral density (BMD). After an exponential transformation, we obtain a Pearson's correlation coefficient of r - 0.97. Qualitative comparison of images with similar BMD but with very different NdStr values suggests that the latter measure has successfully quantified the prevalence of the "latticelike" microarchitecture apparent in the image. Moreover, we found a strong correlation (r - 0.62) between NdStr and the conventional node-terminus ratio (Nd/Tm) of Garrahan et al. The Nd/Tm ratios were computed using traditional histomorphometry performed on bone biopsies obtained at the same location as the pQCT scans. Conclusions: The newly introduced morphometric measure allows a quantitative assessment of the long-range connectivity of trabecular bone. One advantage of this method is that it is based on pQCT images that can be obtained noninvasively from patients, i.e., without having to obtain a bone biopsy from the patient. KW - trabecular bone KW - osteoporosis KW - structure analysis KW - histomorphometry KW - pQCT Y1 - 2011 U6 - https://doi.org/10.1118/1.3622600 SN - 0094-2405 VL - 38 IS - 9 SP - 5003 EP - 5011 PB - American Association of Physicists in Medicine CY - Melville ER - TY - JOUR A1 - Oskinova, Lida A1 - Todt, Helge Tobias A1 - Ignace, Richard A1 - Brown, John C. A1 - Cassinelli, Joseph P. A1 - Hamann, Wolf-Rainer T1 - Early magnetic B-type stars X-ray emission and wind properties JF - Monthly notices of the Royal Astronomical Society N2 - We present a comprehensive study of X-ray emission by, and wind properties of, massive magnetic early B-type stars. Dedicated XMM-Newton observations were obtained for three early-type B-type stars, xi(1) CMa, V2052 Oph and zeta Cas, with recently discovered magnetic fields. We report the first detection of X-ray emission from V2052 Oph and zeta Cas. The latter is one the softest X-ray sources among the early-type stars, while the former is one of the X-ray faintest. The observations show that the X-ray spectra of our programme stars are quite soft with the bulk of X-ray emitting material having a temperature of about 1 MK. We compile the complete sample of early B-type stars with detected magnetic fields to date and existing X-ray measurements, in order to study whether the X-ray emission can be used as a general proxy for stellar magnetism. We find that the X-ray properties of early massive B-type magnetic stars are diverse, and that hard and strong X-ray emission does not necessarily correlate with the presence of a magnetic field, corroborating similar conclusions reached earlier for the classical chemically peculiar magnetic Bp-Ap stars. We analyse the ultraviolet (UV) spectra of five non-supergiant B stars with magnetic fields (tau Sco, beta Cep, xi(1) CMa, V2052 Oph and zeta Cas) by means of non-local thermodynamic equilibrium (non-LTE) iron-blanketed model atmospheres. The latter are calculated with the Potsdam Wolf-Rayet (PoWR) code, which treats the photosphere as well as the wind, and also accounts for X-rays. With the exception of t Sco, this is the first analysis of these stars by means of stellar wind models. Our models accurately fit the stellar photospheric spectra in the optical and the UV. The parameters of X-ray emission, temperature and flux are included in the model in accordance with observations. We confirm the earlier findings that the filling factors of X-ray emitting material are very high. Our analysis reveals that the magnetic early-type B stars studied here have weak winds with velocities not significantly exceeding upsilon(esc). The mass-loss rates inferred from the analysis of UV lines are significantly lower than predicted by hydrodynamically consistent models. We find that, although the X-rays strongly affect the ionization structure of the wind, this effect is not sufficient in reducing the total radiative acceleration. When the X-rays are accounted for at the intensity and temperatures observed, there is still sufficient radiative acceleration to drive a stronger mass-loss than we empirically infer from the UV spectral lines. KW - techniques: spectroscopic KW - stars: magnetic field KW - stars: massive KW - stars: mass loss KW - X-rays: stars Y1 - 2011 U6 - https://doi.org/10.1111/j.1365-2966.2011.19143.x SN - 0035-8711 VL - 416 IS - 2 SP - 1456 EP - 1474 PB - Wiley-Blackwell CY - Hoboken ER - TY - JOUR A1 - Winkel, B. A1 - Ben Bekhti, Nadya A1 - Darmstaedter, V. A1 - Floeer, L. A1 - Kerp, J. A1 - Richter, Philipp T1 - The high-velocity cloud complex Galactic center negative as seen by EBHIS and GASS I. Cloud catalog and global properties JF - Astronomy and astrophysics : an international weekly journal N2 - Using Milky Way data of the new Effelsberg-Bonn HI Survey (EBHIS) and the Galactic All-Sky Survey (GASS), we present a revised picture of the high-velocity cloud (HVC) complex Galactic center negative (GCN). Owing to the higher angular resolution of these surveys compared to previous studies (e.g., the Leiden Dwingeloo Survey), we resolve complex GCN into lots of individual tiny clumps, that mostly have relatively broad line widths of more than 15 km s(-1). We do not detect a diffuse extended counterpart, which is unusual for an HVC complex. In total 243 clumps were identified and parameterized which allows us to statistically analyze the data. Cold-line components (i.e.,Delta upsilon(fwhm) < 7.5 km s(-1)) are found in about 5% only of the identified cloudlets. Our analysis reveals that complex GCN is likely built up of several subpopulations that do not share a common origin. Furthermore, complex GCN might be a prime example for warm-gas accretion onto the Milky Way, where neutral HI clouds are not stable against interaction with the Milky Way gas halo and become ionized prior to accretion. KW - ISM: clouds KW - Galaxy: halo Y1 - 2011 U6 - https://doi.org/10.1051/0004-6361/201117357 SN - 0004-6361 VL - 533 IS - 18 PB - EDP Sciences CY - Les Ulis ER - TY - JOUR A1 - Sun, Zhongkui A1 - Yang, Xiaoli T1 - Generating and enhancing lag synchronization of chaotic systems by white noise JF - Chaos : an interdisciplinary journal of nonlinear science N2 - In this paper, we study the crucial impact of white noise on lag synchronous regime in a pair of time-delay unidirectionally coupled systems. Our result demonstrates that merely via white-noise-based coupling lag synchronization could be achieved between the coupled systems (chaotic or not). And it is also demonstrated that a conventional lag synchronous regime can be enhanced by white noise. Sufficient conditions are further proved mathematically for noise-inducing and noise-enhancing lag synchronization, respectively. Additionally, the influence of parameter mismatch on the proposed lag synchronous regime is studied, by which we announce the robustness and validity of the new strategy. Two numerical examples are provided to illustrate the validity and some possible applications of the theoretical result. Y1 - 2011 U6 - https://doi.org/10.1063/1.3623440 SN - 1054-1500 SN - 1089-7682 VL - 21 IS - 3 PB - American Institute of Physics CY - Melville ER - TY - JOUR A1 - Schuh, Christian A1 - Lomadze, Nino A1 - Rühe, Jürgen A1 - Kopyshev, Alexey A1 - Santer, Svetlana T1 - Photomechanical degrafting of Azo-functionalized Poly(methacrylic acid) (PMAA) brushes JF - The journal of physical chemistry : B, Condensed matter, materials, surfaces, interfaces & biophysical chemistry N2 - We report on the preparation and characterization of photosensitive polymer brushes. The brushes are synthesized through polymer analogous attachment of azobenzene groups to surface-attached poly(methacrylic acid) (PMAA) chains. The topography of the photosensitive brushes shows a strong reaction upon irradiation with UV light. While homogeneous illumination leaves the polymer topography unchanged, irradiation of the samples with interference patterns with periodically varying light intensity leads to the formation of surface relief gratings (SRG). The height of the stripes of the grating can be controlled by adjusting the irradiation time. The SRG pattern can be erased through solvent treatment when the periodicity of the stripe pattern is less than the length of the fully stretched polymer chains. In the opposite case, photomechanical scission of receding polymer chains is observed during SRG formation, and the inscribed patterns are permanent. Y1 - 2011 U6 - https://doi.org/10.1021/jp2041229 SN - 1520-6106 VL - 115 IS - 35 SP - 10431 EP - 10438 PB - American Chemical Society CY - Washington ER - TY - JOUR A1 - Schuch, Norbert A1 - Harrison, Sarah K. A1 - Osborne, Tobias J. A1 - Eisert, Jens T1 - Information propagation for interacting-particle systems JF - Physical review : A, Atomic, molecular, and optical physics N2 - We study the speed at which information propagates through systems of interacting quantum particles moving on a regular lattice and show that for a certain class of initial conditions there exists a maximum speed of sound at which information can propagate. Our argument applies equally to quantum spins, bosons such as in the Bose-Hubbard model, fermions, anyons, and general mixtures thereof, on arbitrary lattices of any dimension. It also pertains to dissipative dynamics on the lattice, and generalizes to the continuum for quantum fields. Our result can be seen as an analog of the Lieb-Robinson bound for strongly correlated models. Y1 - 2011 U6 - https://doi.org/10.1103/PhysRevA.84.032309 SN - 1050-2947 VL - 84 IS - 3 PB - American Physical Society CY - College Park ER - TY - JOUR A1 - Eichler, David A1 - Pohl, Martin T1 - Can ultrahigh-energy cosmic rays come from Gamma-ray bursts? - cosmic rays below the ankle and galactic gamma-ray bursts JF - The astrophysical journal : an international review of spectroscopy and astronomical physics ; Part 2, Letters N2 - The maximum cosmic-ray energy achievable by acceleration by a relativistic blast wave is derived. It is shown that forward shocks from long gamma-ray bursts (GRBs) in the interstellar medium accelerate protons to large enough energies, and have a sufficient energy budget, to produce the Galactic cosmic-ray component just below the ankle at 4 x 10(18) eV, as per an earlier suggestion. It is further argued that, were extragalactic long GRBs responsible for the component above the ankle as well, the occasional Galactic GRB within the solar circle would contribute more than the observational limits on the outward flux from the solar circle, unless an avoidance scenario, such as intermittency and/or beaming, allows the present-day local flux to be less than 10(-3) of the average. Difficulties with these avoidance scenarios are noted. KW - cosmic rays KW - galaxies: general KW - gamma-ray burst: general Y1 - 2011 U6 - https://doi.org/10.1088/2041-8205/738/2/L21 SN - 2041-8205 VL - 738 IS - 2 PB - IOP Publ. Ltd. CY - Bristol ER - TY - JOUR A1 - Aliu, E. A1 - Arlen, T. A1 - Aune, T. A1 - Beilicke, M. A1 - Benbow, W. A1 - Boettcher, Markus A1 - Bouvier, A. A1 - Bradbury, S. M. A1 - Buckley, J. H. A1 - Bugaev, V. A1 - Cannon, A. A1 - Cesarini, A. A1 - Ciupik, L. A1 - Collins-Hughes, E. A1 - Connolly, M. P. A1 - Cui, W. A1 - Dickherber, R. A1 - Errando, M. A1 - Falcone, A. A1 - Finley, J. P. A1 - Fortson, L. A1 - Furniss, A. A1 - Galante, N. A1 - Gall, D. A1 - Gillanders, G. H. A1 - Godambe, S. A1 - Griffin, S. A1 - Grube, J. A1 - Gyuk, G. A1 - Hanna, D. A1 - Holder, J. A1 - Huan, H. A1 - Hughes, G. A1 - Hui, C. M. A1 - Humensky, T. B. A1 - Kaaret, P. A1 - Karlsson, N. A1 - Kertzman, M. A1 - Kieda, D. A1 - Krawczynski, H. A1 - Krennrich, F. A1 - Madhavan, A. S. A1 - Maier, G. A1 - Majumdar, P. A1 - McArthur, S. A1 - McCann, A. A1 - Moriarty, P. A1 - Mukherjee, R. A1 - Ong, R. A. A1 - Orr, M. A1 - Otte, A. N. A1 - Park, N. A1 - Perkins, J. S. A1 - Pichel, A. A1 - Pohl, Martin A1 - Prokoph, H. A1 - Quinn, J. A1 - Ragan, K. A1 - Reyes, L. C. A1 - Reynolds, P. T. A1 - Roache, E. A1 - Rose, H. J. A1 - Ruppel, J. A1 - Saxon, D. B. A1 - Schroedter, M. A1 - Sembroski, G. H. A1 - Skole, C. A1 - Smith, A. W. A1 - Staszak, D. A1 - Tesic, G. A1 - Theiling, M. A1 - Thibadeau, S. A1 - Tsurusaki, K. A1 - Tyler, J. A1 - Varlotta, A. A1 - Vincent, S. A1 - Vivier, M. A1 - Wakely, S. P. A1 - Ward, J. E. A1 - Weinstein, A. A1 - Weisgarber, T. A1 - Williams, D. A. T1 - Veritas observations of unusual extragalactic transient swift J164449.3+573451 JF - The astrophysical journal : an international review of spectroscopy and astronomical physics ; Part 2, Letters N2 - We report on very high energy (>100 GeV) gamma-ray observations of Swift J164449.3+573451, an unusual transient object first detected by the Swift Observatory and later detected by multiple radio, optical, and X-ray observatories. A total exposure of 28 hr was obtained on Swift J164449.3+573451 with the Very Energetic Radiation Imaging Telescope Array System ( VERITAS) during 2011 March 28-April 15. We do not detect the source and place a differential upper limit on the emission at 500 GeV during these observations of 1.4 x 10(-12) erg cm(-2) s(-1) (99% confidence level). We also present time-resolved upper limits and use a flux limit averaged over the X-ray flaring period to constrain various emission scenarios that can accommodate both the radio-through-X-ray emission detected from the source and the lack of detection by VERITAS. KW - accretion, accretion disks KW - galaxies: active KW - gamma rays: galaxies KW - radiation mechanisms: non-thermal Y1 - 2011 U6 - https://doi.org/10.1088/2041-8205/738/2/L30 SN - 2041-8205 VL - 738 IS - 2 PB - IOP Publ. Ltd. CY - Bristol ER - TY - JOUR A1 - Kliesch, Martin A1 - Barthel, Thomas A1 - Gogolin, C. A1 - Kastoryano, M. A1 - Eisert, J. T1 - Dissipative quantum church-turing theorem JF - Physical review letters N2 - We show that the time evolution of an open quantum system, described by a possibly time dependent Liouvillian, can be simulated by a unitary quantum circuit of a size scaling polynomially in the simulation time and the size of the system. An immediate consequence is that dissipative quantum computing is no more powerful than the unitary circuit model. Our result can be seen as a dissipative Church-Turing theorem, since it implies that under natural assumptions, such as weak coupling to an environment, the dynamics of an open quantum system can be simulated efficiently on a quantum computer. Formally, we introduce a Trotter decomposition for Liouvillian dynamics and give explicit error bounds. This constitutes a practical tool for numerical simulations, e.g., using matrix-product operators. We also demonstrate that most quantum states cannot be prepared efficiently. Y1 - 2011 U6 - https://doi.org/10.1103/PhysRevLett.107.120501 SN - 0031-9007 VL - 107 IS - 12 PB - American Physical Society CY - College Park ER - TY - JOUR A1 - Shayduk, Roman A1 - Navirian, Hengameh A1 - Leitenberger, Wolfram A1 - Goldshteyn, Jevgenij A1 - Vrejoiu, Ionela A1 - Weinelt, Martin A1 - Gaal, Peter A1 - Herzog, Marc A1 - von Korff Schmising, Clemens A1 - Bargheer, Matias T1 - Nanoscale heat transport studied by high-resolution time-resolved x-ray diffraction JF - New journal of physics : the open-access journal for physics N2 - We report on synchrotron-based high-repetition rate ultrafast x-ray diffraction (UXRD) experiments monitoring the transport of heat from an epitaxial La(0.7)Sr(0.3)MnO(3)/SrTiO(3) superlattice (SL) into the substrate on timescales from 100 ps to 4 mu s. Transient thermal lattice expansion was determined with an accuracy of 10(-7), corresponding to a sensitivity to temperature changes down to 0.01 K. We follow the heat flow within the SL and into the substrate after the impulsive laser heating leads to a small temperature rise of Delta T = 6 K. The transient lattice temperature can be simulated very well using the bulk heat conductivities. This contradicts the interpretation of previous UXRD measurements, which predicted a long-lasting expansion of SrRuO(3) for more than 200 ps. The disagreement could be resolved by assuming that the heat conductivity changes in the first hundred picoseconds. Y1 - 2011 U6 - https://doi.org/10.1088/1367-2630/13/9/093032 SN - 1367-2630 VL - 13 IS - 11 PB - IOP Publ. Ltd. CY - Bristol ER - TY - JOUR A1 - Lomadze, Nino A1 - Kopyshev, Alexey A1 - Rühe, Jürgen A1 - Santer, Svetlana T1 - Light-Induced chain scission in photosensitive polymer brushes JF - Macromolecules : a publication of the American Chemical Society N2 - We report on a process inducing photomechanical fracture of chemical bonds in photosensitive PMAA polymer brushes. The photosensitive PMAA polymer brushes were prepared by covalent attachment of azobenzene groups to poly(methylacrylic acid) (PMAA) chains generated by surface-initiated polymerization. While homogeneous irradiation leaves the polymer topography unchanged, the azo-PMAA brushes show a strong response upon irradiation with UV interference patterns. The photoisomerization process in the surface-attached polymer films results in the irreversible formation of surface relief gratings (SRG), which are strongly enhanced upon washing with a good solvent for the polymer. The photomechanical forces during mass transport induced by the irradiation lead to the scission of covalent bounds and accordingly to a degrafting of the polymer chains in areas where the polymer is receding from. It is observed that the number of ruptured chains depends strongly on the amount of azo side chains in the polymer. Y1 - 2011 U6 - https://doi.org/10.1021/ma201016q SN - 0024-9297 VL - 44 IS - 18 SP - 7372 EP - 7377 PB - American Chemical Society CY - Washington ER - TY - JOUR A1 - Sun, Zhuanlan A1 - Zhang, Xiaoqing A1 - Xia, Zhongfu A1 - Qiu, Xunlin A1 - Wirges, Werner A1 - Gerhard, Reimund A1 - Zeng, Changchun A1 - Zhang, Chuck A1 - Wang, Ben T1 - Polarization and piezoelectricity in polymer films with artificial void structure JF - Applied physics : A, Materials science & processing N2 - Laminated polymer-film systems with well-defined void structures were prepared from fluoroethylenepropylene (FEP) and polytetrafluoroethylene (PTFE) layers. First the PTFE films were patterned and then fusion-bonded with the FEP films. The laminates were subjected to either corona or contact charging in order to obtain the desired piezoelectricity. The build-up of the "macro-dipoles" in the laminated films was studied by recording the electric hysteresis loops. The resulting electro-mechanical properties were investigated by means of dielectric resonance spectroscopy (DRS) and direct measurements of the stress-strain relationship. Moreover, the thermal stability of the piezoelectric d (33) coefficient was investigated at elevated temperatures and via thermally stimulated discharge (TSD) current measurements in short circuit. For 150 mu m thick laminated films, consisting of one 25 mu m thick PTFE layer, two 12.5 mu m thick FEP layers, and a void of 100 mu m height, the critical voltage necessary for the build-up of the "macro-dipoles" in the inner voids was approximately 1400 V, which agrees with the value calculated from the Paschen Law. A quasi-static piezoelectric d (33) coefficient up to 300 pC/N was observed after corona charging. The mechanical properties of the film systems are highly anisotropic. At room temperature, the Young's moduli of the laminated film system are around 0.37 MPa in the thickness direction and 274 MPa in the lateral direction, respectively. Using these values, the theoretical shape anisotropy ratio of the void was calculated, which agrees well with experimental observation. Compared with films that do not exhibit structural regularity, the laminates showed improved thermal stability of the d (33) coefficients. The thermal stability of d (33) can be further improved by pre-aging. E.g., the reduction of the d (33) value in the sample pre-aged at 150A degrees C for 5 h was less than 5% after annealing for 30 h at a temperature of 90A degrees C. Y1 - 2011 U6 - https://doi.org/10.1007/s00339-011-6481-2 SN - 0947-8396 VL - 105 IS - 1 SP - 197 EP - 205 PB - Springer CY - New York ER - TY - JOUR A1 - Koseska, Aneta A1 - Volkov, Evgenii A1 - Kurths, Jürgen T1 - Synthetic multicellular oscillatory systems controlling protein dynamics with genetic circuits JF - Physica scripta : an international journal for experimental and theoretical physics N2 - Synthetic biology is a relatively new research discipline that combines standard biology approaches with the constructive nature of engineering. Thus, recent efforts in the field of synthetic biology have given a perspective to consider cells as 'programmable matter'. Here, we address the possibility of using synthetic circuits to control protein dynamics. In particular, we show how intercellular communication and stochasticity can be used to manipulate the dynamical behavior of a population of coupled synthetic units and, in this manner, finely tune the expression of specific proteins of interest, e.g. in large bioreactors. Y1 - 2011 U6 - https://doi.org/10.1088/0031-8949/84/04/045007 SN - 0031-8949 VL - 84 IS - 4 PB - IOP Publ. Ltd. CY - Bristol ER - TY - JOUR A1 - Baushev, Anton N. T1 - Principal properties of the velocity distribution of dark matter particles on the outskirts of the Solar system JF - Monthly notices of the Royal Astronomical Society N2 - The velocity distribution of the dark matter particles on the outskirts of the Solar system remains unclear. We suggest to determine it using experimentally found properties of the oldest halo objects. Indeed, the oldest halo stars and globular clusters form a collisionless system, as well as dark matter particles do, and they evolved in the same gravitational field. If we accept this analogy, we can show that the velocity distribution of the dark matter particles should be highly anisotropic and have a sharp maximum near upsilon similar to 500 km s(-1). The distribution is totally different from the Maxwell one. We analyse the influence of the distribution function on the results of dark matter detection experiments. It is found that the direct detection signal should differ noticeably from the one calculated from the Maxwell distribution with similar or equal to 220 km s(-1), which is conventional for direct detection experiments (the ratio depends on the detector properties and typically falls within the range between 6 and 0.2). Moreover, the sharp distinction from the Maxwell distribution can be very essential to the observations of dark matter annihilation. KW - elementary particles KW - methods: analytical KW - dark matter Y1 - 2011 U6 - https://doi.org/10.1111/j.1745-3933.2011.01125.x SN - 0035-8711 VL - 417 IS - 1 SP - L83 EP - L87 PB - Wiley-Blackwell CY - Malden ER - TY - JOUR A1 - Döring, Sebastian A1 - Kollosche, Matthias A1 - Rabe, Torsten A1 - Stumpe, Joachim A1 - Kofod, Guggi T1 - Electrically tunable polymer DFB laser JF - Advanced materials Y1 - 2011 U6 - https://doi.org/10.1002/adma.201102465 SN - 0935-9648 VL - 23 IS - 37 SP - 4265 EP - 4269 PB - Wiley-VCH CY - Weinheim ER - TY - JOUR A1 - Blaha, Karen A. A1 - Pikovskij, Arkadij A1 - Rosenblum, Michael A1 - Clark, Matthew T. A1 - Rusin, Craig G. A1 - Hudson, John L. T1 - Reconstruction of two-dimensional phase dynamics from experiments on coupled oscillators JF - Physical review : E, Statistical, nonlinear and soft matter physics N2 - Phase models are a powerful method to quantify the coupled dynamics of nonlinear oscillators from measured data. We use two phase modeling methods to quantify the dynamics of pairs of coupled electrochemical oscillators, based on the phases of the two oscillators independently and the phase difference, respectively. We discuss the benefits of the two-dimensional approach relative to the one-dimensional approach using phase difference. We quantify the dependence of the coupling functions on the coupling magnitude and coupling time delay. We show differences in synchronization predictions of the two models using a toy model. We show that the two-dimensional approach reveals behavior not detected by the one-dimensional model in a driven experimental oscillator. This approach is broadly applicable to quantify interactions between nonlinear oscillators, especially where intrinsic oscillator sensitivity and coupling evolve with time. Y1 - 2011 U6 - https://doi.org/10.1103/PhysRevE.84.046201 SN - 1539-3755 VL - 84 IS - 4 PB - American Physical Society CY - College Park ER - TY - JOUR A1 - Tremblay, Jean Christophe A1 - Monturet, Serge A1 - Saalfrank, Peter T1 - The Effects of electron-hole pair coupling on the infrared laser-controlled vibrational excitation of NO on Au(111) JF - The journal of physical chemistry : A, Molecules, spectroscopy, kinetics, environment & general theory N2 - In this work, we present theoretical simulations of laser-driven vibrational control of NO adsorbed on a gold surface. Our goal is to tailor laser pulses to selectively excite specific modes and vibrational eigenstates, as well as to favor photodesorption of the adsorbed molecule. To this end, various control schemes and algorithms are applied. For adsorbates at metallic surfaces, the creation of electron hole pairs in the substrate is known to play a dominant role in the transfer of energy from the system to the surroundings. These nonadiabatic couplings are included perturbatively in our reduced density matrix simulations using a generalization of the state-resolved position-dependent anharmonic rate model we recently introduced. An extension of the reduced density matrix is also proposed to provide a sound model for photodesorption in dissipative systems. Y1 - 2011 U6 - https://doi.org/10.1021/jp205902k SN - 1089-5639 VL - 115 IS - 39 SP - 10698 EP - 10707 PB - American Chemical Society CY - Washington ER - TY - JOUR A1 - Aliu, E. A1 - Arlen, T. A1 - Aune, T. A1 - Beilicke, M. A1 - Benbow, W. A1 - Bouvier, A. A1 - Bradbury, S. M. A1 - Buckley, J. H. A1 - Bugaev, V. A1 - Byrum, K. A1 - Cannon, A. A1 - Cesarini, A. A1 - Christiansen, J. L. A1 - Ciupik, L. A1 - Collins-Hughes, E. A1 - Connolly, M. P. A1 - Cui, W. A1 - Dickherber, R. A1 - Duke, C. A1 - Errando, M. A1 - Falcone, A. A1 - Finley, J. P. A1 - Finnegan, G. A1 - Fortson, L. A1 - Furniss, A. A1 - Galante, N. A1 - Gall, D. A1 - Gibbs, K. A1 - Gillanders, G. H. A1 - Godambe, S. A1 - Griffin, S. A1 - Grube, J. A1 - Guenette, R. A1 - Gyuk, G. A1 - Hanna, D. A1 - Holder, J. A1 - Huan, H. A1 - Hughes, G. A1 - Hui, C. M. A1 - Humensky, T. B. A1 - Imran, A. A1 - Kaaret, P. A1 - Karlsson, N. A1 - Kertzman, M. A1 - Kieda, D. A1 - Krawczynski, H. A1 - Krennrich, F. A1 - Lang, M. J. A1 - Lyutikov, M. A1 - Madhavan, A. S. A1 - Maier, G. A1 - Majumdar, P. A1 - McArthur, S. A1 - McCann, A. A1 - McCutcheon, M. A1 - Moriarty, P. A1 - Mukherjee, R. A1 - Nunez, P. A1 - Ong, R. A. A1 - Orr, M. A1 - Otte, A. N. A1 - Park, N. A1 - Perkins, J. S. A1 - Pizlo, F. A1 - Pohl, Martin A1 - Prokoph, H. A1 - Quinn, J. A1 - Ragan, K. A1 - Reyes, L. C. A1 - Reynolds, P. T. A1 - Roache, E. A1 - Rose, H. J. A1 - Ruppel, J. A1 - Saxon, D. B. A1 - Schroedter, M. A1 - Sembroski, G. H. A1 - Sentuerk, G. D. A1 - Smith, A. W. A1 - Staszak, D. A1 - Tesic, G. A1 - Theiling, M. A1 - Thibadeau, S. A1 - Tsurusaki, K. A1 - Tyler, J. A1 - Varlotta, A. A1 - Vassiliev, V. V. A1 - Vincent, S. A1 - Vivier, M. A1 - Wakely, S. P. A1 - Ward, J. E. A1 - Weekes, T. C. A1 - Weinstein, A. A1 - Weisgarber, T. A1 - Williams, D. A. A1 - Zitzer, B. T1 - Detection of pulsed Gamma Rays Above 100 GeV from the Crab Pulsar JF - Science N2 - We report the detection of pulsed gamma rays from the Crab pulsar at energies above 100 giga-electron volts (GeV) with the Very Energetic Radiation Imaging Telescope Array System (VERITAS) array of atmospheric Cherenkov telescopes. The detection cannot be explained on the basis of current pulsar models. The photon spectrum of pulsed emission between 100 mega-electron volts and 400 GeV is described by a broken power law that is statistically preferred over a power law with an exponential cutoff. It is unlikely that the observation can be explained by invoking curvature radiation as the origin of the observed gamma rays above 100 GeV. Our findings require that these gamma rays be produced more than 10 stellar radii from the neutron star. Y1 - 2011 U6 - https://doi.org/10.1126/science.1208192 SN - 0036-8075 VL - 334 IS - 6052 SP - 69 EP - 72 PB - American Assoc. for the Advancement of Science CY - Washington ER - TY - JOUR A1 - Sun, Y. -P. A1 - Hennies, Franz A1 - Pietzsch, Annette A1 - Kennedy, B. A1 - Schmitt, Thorsten A1 - Strocov, Vladimir N. A1 - Andersson, Joakim A1 - Berglund, Martin A1 - Rubensson, Jan-Erik A1 - Aidas, K. A1 - Gel'mukhanov, F. A1 - Odelius, Michael A1 - Föhlisch, Alexander T1 - Intramolecular soft modes and intermolecular interactions in liquid acetone JF - Physical review : B, Condensed matter and materials physics N2 - Resonant inelastic x-ray scattering spectra excited at the O1s(-1)pi* resonance of liquid acetone are presented. Scattering to the electronic ground state shows a resolved vibrational progression where the dominant contribution is due to the C-O stretching mode, thus demonstrating a unique sensitivity of the method to the local potential energy surface in complex molecular systems. For scattering to electronically excited states, soft vibrational modes and, to a smaller extent, intermolecular interactions give a broadening, which blurs the vibrational fine structure. It is predicted that environmental broadening is dominant in aqueous acetone. Y1 - 2011 U6 - https://doi.org/10.1103/PhysRevB.84.132202 SN - 1098-0121 VL - 84 IS - 13 PB - American Physical Society CY - College Park ER - TY - JOUR A1 - Kiel, Mareike A1 - Möhwald, Helmuth A1 - Bargheer, Matias T1 - Broadband measurements of the transient optical complex dielectric function of a nanoparticle/polymer composite upon ultrafast excitation JF - Physical review : B, Condensed matter and materials physics N2 - We determined experimentally the complex transient optical dielectric function of a well-characterized polyelectrolyte/gold-nanoparticle composite system over a broad spectral range upon short pulse laser excitation by simultaneously measuring the time-dependent reflectance and transmittance of white light pulses with femtosecond pump-probe spectroscopy. We extracted directly the ultrafast changes in the real and imaginary parts of the effective dielectric function, epsilon(eff)(r) (omega,t)and epsilon(eff)(i) (omega,t), from the experiment. This complete experimental set of information on the time-dependent complex dielectric function challenges theories modeling the transient dielectric function of gold particles and the effective medium. Y1 - 2011 U6 - https://doi.org/10.1103/PhysRevB.84.165121 SN - 1098-0121 VL - 84 IS - 16 PB - American Physical Society CY - College Park ER - TY - JOUR A1 - Berenstein, Igal A1 - Beta, Carsten T1 - Flow-induced control of chemical turbulence JF - The journal of chemical physics : bridges a gap between journals of physics and journals of chemistr N2 - We report spatiotemporal chaos in the Oregonator model of the Belousov-Zhabotinsky reaction. Spatiotemporal chaos spontaneously develops in a regime, where the underlying local dynamics show stable limit cycle oscillations (diffusion-induced turbulence). We show that spatiotemporal chaos can be suppressed by a unidirectional flow in the system. With increasing flow velocity, we observe a transition scenario from spatiotemporal chaos via a regime of travelling waves to a stationary steady state. At large flow velocities, we recover the known regime of flow distributed oscillations. KW - chaos KW - chemical equilibrium KW - chemically reactive flow KW - reaction kinetics theory KW - spatiotemporal phenomena KW - turbulence Y1 - 2011 U6 - https://doi.org/10.1063/1.3656248 SN - 0021-9606 VL - 135 IS - 16 PB - American Institute of Physics CY - Melville ER - TY - JOUR A1 - Blakesley, James C. A1 - Schubert, Marcel A1 - Steyrleuthner, Robert A1 - Chen, Zhihua A1 - Facchetti, Antonio A1 - Neher, Dieter T1 - Time-of-flight measurements and vertical transport in a high electron-mobility polymer JF - Applied physics letters N2 - We investigate charge transport in a high-electron mobility polymer, poly(N, N-bis 2-octyldodecyl-naphthalene-1,4,5,8-bis dicarboximide-2,6-diyl-alt-5,5-2,2-bithiophene) [P(NDI2OD-T2), Polyera ActivInk (TM) N2200]. Time-of-flight measurements reveal electron mobilities approaching those measured in field-effect transistors, the highest ever recorded in a conjugated polymer using this technique. The modest temperature dependence and weak dispersion of the transients indicate low energetic disorder in this material. Steady-state electron-only current measurements reveal a barrier to injection of about 300 meV. We propose that this barrier is located within the P(NDI2OD-T2) film and arises from molecular orientation effects. Y1 - 2011 U6 - https://doi.org/10.1063/1.3657827 SN - 0003-6951 VL - 99 IS - 18 PB - American Institute of Physics CY - Melville ER - TY - JOUR A1 - Huang, Tingwen A1 - Chen, Guanrong A1 - Kurths, Jürgen T1 - Synchronization of chaotic of chaotic systems with time-varying coupöing delays JF - Discrete and continuous dynamical systems : a journal bridging mathematics and sciences ; Series B, Mathematical modelling, analysis and computations N2 - In this paper, we study the complete synchronization of a class of time-varying delayed coupled chaotic systems using feedback control. In terms of Linear Matrix Inequalities, a sufficient condition is obtained through using a Lyapunov-Krasovskii functional and differential equation in equalities. The conditions can be easily verified and implemented. We present two simulation examples to illustrate the effectiveness of the proposed method. KW - Synchronization KW - Chaotic System KW - Time-varying Delay Y1 - 2011 U6 - https://doi.org/10.3934/dcdsb.2011.16.1071 SN - 1531-3492 VL - 16 IS - 4 SP - 1071 EP - 1082 PB - American Institute of Mathematical Sciences CY - Springfield ER - TY - JOUR A1 - Khader, Patrick H. A1 - Pachur, Thorsten A1 - Meier, Stefanie A1 - Bien, Siegfried A1 - Jost, Kerstin A1 - Roesler, Frank T1 - Memory-based decision-making with heuristics evidence for a controlled activation of memory representations JF - Journal of cognitive neuroscience N2 - Many of our daily decisions are memory based, that is, the attribute information about the decision alternatives has to be recalled. Behavioral studies suggest that for such decisions we often use simple strategies (heuristics) that rely on controlled and limited information search. It is assumed that these heuristics simplify decision-making by activating long-term memory representations of only those attributes that are necessary for the decision. However, from behavioral studies alone, it is unclear whether using heuristics is indeed associated with limited memory search. The present study tested this assumption by monitoring the activation of specific long-term-memory representations with fMRI while participants made memory-based decisions using the "take-the-best" heuristic. For different decision trials, different numbers and types of information had to be retrieved and processed. The attributes consisted of visual information known to be represented in different parts of the posterior cortex. We found that the amount of information required for a decision was mirrored by a parametric activation of the dorsolateral PFC. Such a parametric pattern was also observed in all posterior areas, suggesting that activation was not limited to those attributes required for a decision. However, the posterior increases were systematically modulated by the relative importance of the information for making a decision. These findings suggest that memory-based decision-making is mediated by the dorsolateral PFC, which selectively controls posterior storage areas. In addition, the systematic modulations of the posterior activations indicate a selective boosting of activation of decision-relevant attributes. Y1 - 2011 SN - 0898-929X VL - 23 IS - 11 SP - 3540 EP - 3554 PB - MIT Press CY - Cambridge ER - TY - JOUR A1 - Sanhueza-Pino, Katia A1 - Korup, Oliver A1 - Hetzel, Ralf A1 - Munack, Henry A1 - Weidinger, Johannes T. A1 - Dunning, Stuart A. A1 - Ormukov, Cholponbek A1 - Kubik, Peter W. T1 - Glacial advances constrained by Be-10 exposure dating of bedrock landslides, Kyrgyz Tien Shan JF - Quaternary research : an interdisciplinary journal N2 - Numerous large landslide deposits occur in the Tien Shan, a tectonically active intraplate orogen in Central Asia. Yet their significance in Quaternary landscape evolution and natural hazard assessment remains unresolved due to the lack of "absolute" age constraints. Here we present the first Be-10 exposure ages for three prominent (>10(7) m(3)) bedrock landslides that blocked major rivers and formed lakes, two of which subsequently breached, in the northern Kyrgyz Tien Shan. Three Be-10 ages reveal that one landslide in the Alamyedin River occurred at 11-15 ka, which is consistent with two C-14 ages of gastropod shells from reworked loess capping the landslide. One large landslide in Aksu River is among the oldest documented in semi-arid continental interiors, with a Be-10 age of 63-67 ka. The Ukok River landslide deposit(s) yielded variable Be-10 ages, which may result from multiple landslides, and inheritance of Be-10. Two Be-10 ages of 8.2 and 5.9 ka suggest that one major landslide occurred in the early to mid-Holocene, followed by at least one other event between 1.5 and 0.4 ka. Judging from the regional glacial chronology, all three landslides have occurred between major regional glacial advances. Whereas Alamyedin and Ukok can be considered as postglacial in this context, Aksu is of interglacial age. None of the landslide deposits show traces of glacial erosion, hence their locations and I Be ages mark maximum extents and minimum ages of glacial advances, respectively. Using toe-to-headwall altitude ratios of 0.4-0.5, we reconstruct minimum equilibrium-line altitudes that exceed previous estimates by as much as 400 m along the moister northern fringe of the Tien Shan. Our data show that deposits from large landslides can provide valuable spatio-temporal constraints for glacial advances in landscapes where moraines and glacial deposits have low preservation potential. (C) 2011 University of Washington. Published by Elsevier Inc. All rights reserved. KW - Landslide KW - Rock avalanche KW - Be-10 exposure dating KW - Quaternary glaciations KW - Tien Shan Y1 - 2011 U6 - https://doi.org/10.1016/j.yqres.2011.06.013 SN - 0033-5894 VL - 76 IS - 3 SP - 295 EP - 304 PB - Elsevier CY - San Diego ER - TY - JOUR A1 - Lisso, Janina A1 - Schröder, Florian A1 - Fisahn, Joachim A1 - Muessig, Carsten T1 - NFX1-LIKE2 (NFXL2) Suppresses Abscisic Acid Accumulation and Stomatal Closure in Arabidopsis thaliana JF - PLoS one N2 - The NFX1-LIKE1 (NFXL1) and NFXL2 genes were identified as regulators of salt stress responses. The NFXL1 protein is a nuclear factor that positively affects adaptation to salt stress. The nfxl1-1 loss-of-function mutant displayed reduced survival rates under salt and high light stress. In contrast, the nfxl2-1 mutant, defective in the NFXL2 gene, and NFXL2-antisense plants exhibited enhanced survival under these conditions. We show here that the loss of NFXL2 function results in abscisic acid (ABA) overaccumulation, reduced stomatal conductance, and enhanced survival under drought stress. The nfxl2-1 mutant displayed reduced stomatal aperture under all conditions tested. Fusicoccin treatment, exposition to increasing light intensities, and supply of decreasing CO2 concentrations demonstrated full opening capacity of nfxl2-1 stomata. Reduced stomatal opening presumably is a consequence of elevated ABA levels. Furthermore, seedling growth, root growth, and stomatal closure were hypersensitive to exogenous ABA. The enhanced ABA responses may contribute to the improved drought stress resistance of the mutant. Three NFXL2 splice variants were cloned and named NFXL2-78, NFXL2-97, and NFXL2-100 according to the molecular weight of the putative proteins. Translational fusions to the green fluorescent protein suggest nuclear localisation of the NFXL2 proteins. Stable expression of the NFXL2-78 splice variant in nfxl2-1 plants largely complemented the mutant phenotype. Our data show that NFXL2 controls ABA levels and suppresses ABA responses. NFXL2 may prevent unnecessary and costly stress adaptation under favourable conditions. Y1 - 2011 U6 - https://doi.org/10.1371/journal.pone.0026982 SN - 1932-6203 VL - 6 IS - 11 PB - PLoS CY - San Fransisco ER - TY - JOUR A1 - Ackermann, Margit A1 - Ajello, M. A1 - Allafort, A. J. A1 - Baldini, L. A1 - Ballet, J. A1 - Barbiellini, G. A1 - Bastieri, D. A1 - Belfiore, A. A1 - Bellazzini, R. A1 - Berenji, B. A1 - Blandford, R. D. A1 - Bloom, E. D. A1 - Bonamente, E. A1 - Borgland, A. W. A1 - Bottacini, E. A1 - Brigida, M. A1 - Bruel, P. A1 - Buehler, R. A1 - Buson, S. A1 - Caliandro, G. A. A1 - Cameron, R. A. A1 - Caraveo, P. A. A1 - Casandjian, J. M. A1 - Cecchi, C. A1 - Chekhtman, A. A1 - Cheung, C. C. A1 - Chiang, J. A1 - Ciprini, S. A1 - Claus, R. A1 - Cohen-Tanugi, J. A1 - de Angelis, A. A1 - de Palma, F. A1 - Dermer, C. D. A1 - do Couto e Silva, E. A1 - Drell, P. S. A1 - Dumora, D. A1 - Favuzzi, C. A1 - Fegan, S. J. A1 - Focke, W. B. A1 - Fortin, P. A1 - Fukazawa, Y. A1 - Fusco, P. A1 - Gargano, F. A1 - Germani, S. A1 - Giglietto, N. A1 - Giordano, F. A1 - Giroletti, M. A1 - Glanzman, T. A1 - Godfrey, G. A1 - Grenier, I. A. A1 - Guillemot, L. A1 - Guiriec, S. A1 - Hadasch, D. A1 - Hanabata, Y. A1 - Harding, A. K. A1 - Hayashida, M. A1 - Hayashi, K. A1 - Hays, E. A1 - Johannesson, G. A1 - Johnson, A. S. A1 - Kamae, T. A1 - Katagiri, H. A1 - Kataoka, J. A1 - Kerr, M. A1 - Knoedlseder, J. A1 - Kuss, M. A1 - Lande, J. A1 - Latronico, L. A1 - Lee, S. -H. A1 - Longo, F. A1 - Loparco, F. A1 - Lott, B. A1 - Lovellette, M. N. A1 - Lubrano, P. A1 - Martin, P. A1 - Mazziotta, Mario Nicola A1 - McEnery, J. E. A1 - Mehault, J. A1 - Michelson, P. F. A1 - Mitthumsiri, W. A1 - Mizuno, T. A1 - Monte, C. A1 - Monzani, M. E. A1 - Morselli, A. A1 - Moskalenko, I. V. A1 - Murgia, S. A1 - Naumann-Godo, M. A1 - Nolan, P. L. A1 - Norris, J. P. A1 - Nuss, E. A1 - Ohsugi, T. A1 - Okumura, A. A1 - Orlando, E. A1 - Ormes, J. F. A1 - Ozaki, M. A1 - Paneque, D. A1 - Parent, D. A1 - Pesce-Rollins, M. A1 - Pierbattista, M. A1 - Piron, F. A1 - Pohl, Martin A1 - Prokhorov, D. A1 - Raino, S. A1 - Rando, R. A1 - Razzano, M. A1 - Reposeur, T. A1 - Ritz, S. A1 - Parkinson, P. M. Saz A1 - Sgro, C. A1 - Siskind, E. J. A1 - Smith, P. D. A1 - Spinelli, P. A1 - Strong, A. W. A1 - Takahashi, H. A1 - Tanaka, T. A1 - Thayer, J. G. A1 - Thayer, J. B. A1 - Thompson, D. J. A1 - Tibaldo, L. A1 - Torres, D. F. A1 - Tosti, G. A1 - Tramacere, A. A1 - Troja, E. A1 - Uchiyama, Y. A1 - Vandenbroucke, J. A1 - Vasileiou, V. A1 - Vianello, G. A1 - Vitale, V. A1 - Waite, A. P. A1 - Wang, P. A1 - Winer, B. L. A1 - Wood, K. S. A1 - Yang, Z. A1 - Zimmer, S. A1 - Bontemps, S. T1 - A cocoon of freshly accelerated cosmic rays detected by fermi in the cygnus superbubble JF - Science N2 - The origin of Galactic cosmic rays is a century-long puzzle. Indirect evidence points to their acceleration by supernova shockwaves, but we know little of their escape from the shock and their evolution through the turbulent medium surrounding massive stars. Gamma rays can probe their spreading through the ambient gas and radiation fields. The Fermi Large Area Telescope (LAT) has observed the star-forming region of Cygnus X. The 1- to 100-gigaelectronvolt images reveal a 50-parsec-wide cocoon of freshly accelerated cosmic rays that flood the cavities carved by the stellar winds and ionization fronts from young stellar clusters. It provides an example to study the youth of cosmic rays in a superbubble environment before they merge into the older Galactic population. Y1 - 2011 U6 - https://doi.org/10.1126/science.1210311 SN - 0036-8075 VL - 334 IS - 6059 SP - 1103 EP - 1107 PB - American Assoc. for the Advancement of Science CY - Washington ER - TY - JOUR A1 - Pohl, Martin A1 - Eichler, David T1 - Origin of ultra-high-energy galactic cosmic rays the isotropy problem JF - The astrophysical journal : an international review of spectroscopy and astronomical physics N2 - We study the propagation of ultra-high-energy cosmic rays (UHECRs) in the Galaxy, concentrating on the energy range below the ankle in the spectrum at 4 EeV. A Monte Carlo method, based on analytical solutions to the time-dependent diffusion problem, is used to account for intermittency by placing sources at random locations. Assuming a source population that scales with baryon mass density or star formation (e.g., long GRB), we derive constraints arising from intermittency and the observational limits on the composition and anisotropy. It is shown that the composition and anisotropy at 10(18) eV are difficult to reproduce and require that either (1) the particle mean free path is much smaller than a gyroradius, implying the escape time is very long, (2) the composition is heavier than suggested by recent Auger data, (3) the ultra-high-energy sub-ankle component is mostly extragalactic, or (4) we are living in a rare lull in the UHECR production, and the current UHECR intensity is far below the Galactic time average. We therefore recommend a strong observational focus on determining the UHECR composition around 10(18) eV. KW - cosmic rays KW - gamma-ray burst: general Y1 - 2011 U6 - https://doi.org/10.1088/0004-637X/742/2/114 SN - 0004-637X VL - 742 IS - 2 PB - IOP Publ. Ltd. CY - Bristol ER - TY - JOUR A1 - Aliu, E. A1 - Aune, T. A1 - Beilicke, M. A1 - Benbow, W. A1 - Boettcher, Markus A1 - Bouvier, A. A1 - Bradbury, S. M. A1 - Buckley, J. H. A1 - Bugaev, V. A1 - Cannon, A. A1 - Cesarini, A. A1 - Ciupik, L. A1 - Connolly, M. P. A1 - Cui, W. A1 - Decerprit, G. A1 - Dickherber, R. A1 - Duke, C. A1 - Errando, M. A1 - Falcone, A. A1 - Feng, Q. A1 - Finnegan, G. A1 - Fortson, L. A1 - Furniss, A. A1 - Galante, N. A1 - Gall, D. A1 - Gillanders, G. H. A1 - Godambe, S. A1 - Griffin, S. A1 - Grube, J. A1 - Gyuk, G. A1 - Hanna, D. A1 - Hivick, B. A1 - Holder, J. A1 - Huan, H. A1 - Hughes, G. A1 - Hui, C. M. A1 - Humensky, T. B. A1 - Kaaret, P. A1 - Karlsson, N. A1 - Kertzman, M. A1 - Kieda, D. A1 - Krawczynski, H. A1 - Krennrich, F. A1 - Maier, G. A1 - Majumdar, P. A1 - McArthur, S. A1 - McCann, A. A1 - Moriarty, P. A1 - Mukherjee, R. A1 - Nelson, T. A1 - Ong, R. A. A1 - Orr, M. A1 - Otte, A. N. A1 - Park, N. A1 - Perkins, J. S. A1 - Pichel, A. A1 - Pohl, Martin A1 - Prokoph, H. A1 - Quinn, J. A1 - Ragan, K. A1 - Reyes, L. C. A1 - Reynolds, P. T. A1 - Roache, E. A1 - Rose, H. J. A1 - Ruppel, J. A1 - Saxon, D. B. A1 - Sembroski, G. H. A1 - Skole, C. A1 - Smith, A. W. A1 - Staszak, D. A1 - Tesic, G. A1 - Theiling, M. A1 - Thibadeau, S. A1 - Tsurusaki, K. A1 - Tyler, J. A1 - Varlotta, A. A1 - Vassiliev, V. V. A1 - Wakely, S. P. A1 - Weekes, T. C. A1 - Weinstein, A. A1 - Williams, D. A. A1 - Zitzer, B. A1 - Ciprini, S. A1 - Fumagalli, M. A1 - Kaplan, K. A1 - Paneque, D. A1 - Prochaska, J. X. T1 - Multiwavelenght observations of the previously unidentified blzar RX J0648.7+1516 JF - The astrophysical journal : an international review of spectroscopy and astronomical physics N2 - We report on the VERITAS discovery of very high energy (VHE) gamma-ray emission above 200 GeV from the high-frequency-peaked BL Lac (HBL) object RX J0648.7+1516 (GB J0648+1516), associated with 1FGL J0648.8+1516. The photon spectrum above 200 GeV is fitted by a power law dN/dE = F-0(E/E-0)(-Gamma) with a photon index Gamma of 4.4 +/- 0.8(stat) +/- 0.3(syst) and a flux normalization F-0 of (2.3 +/- 0.5(stat) +/- 1.2(sys)) x 10(-11) TeV-1 cm(-2) s(-1) with E-0 = 300 GeV. No VHE variability is detected during VERITAS observations of RX J0648.7+1516 between 2010 March 4 and April 15. Following the VHE discovery, the optical identification and spectroscopic redshift were obtained using the Shane 3 m Telescope at the Lick Observatory, showing the unidentified object to be a BL Lac type with a redshift of z = 0.179. Broadband multiwavelength observations contemporaneous with the VERITAS exposure period can be used to subclassify the blazar as an HBL object, including data from the MDM observatory, Swift-UVOT, and X-Ray Telescope, and continuous monitoring at photon energies above 1 GeV from the Fermi Large Area Telescope (LAT). We find that in the absence of undetected, high-energy rapid variability, the one-zone synchrotron self-Compton (SSC) model overproduces the high-energy gamma-ray emission measured by the Fermi-LAT over 2.3 years. The spectral energy distribution can be parameterized satisfactorily with an external-Compton or lepto-hadronic model, which have two and six additional free parameters, respectively, compared to the one-zone SSC model. KW - BL Lacertae objects: individual (RX J0648.7+1516, 1FGL J0648.8+1516, VER J0648+152) KW - gamma rays: galaxies Y1 - 2011 U6 - https://doi.org/10.1088/0004-637X/742/2/127 SN - 0004-637X VL - 742 IS - 2 PB - IOP Publ. Ltd. CY - Bristol ER - TY - JOUR A1 - Mulansky, Mario A1 - Ahnert, Karsten A1 - Pikovskij, Arkadij A1 - Shepelyansky, Dima L. T1 - Strong and weak chaos in weakly nonintegrable many-body hamiltonian systems JF - Journal of statistical physics N2 - We study properties of chaos in generic one-dimensional nonlinear Hamiltonian lattices comprised of weakly coupled nonlinear oscillators by numerical simulations of continuous-time systems and symplectic maps. For small coupling, the measure of chaos is found to be proportional to the coupling strength and lattice length, with the typical maximal Lyapunov exponent being proportional to the square root of coupling. This strong chaos appears as a result of triplet resonances between nearby modes. In addition to strong chaos we observe a weakly chaotic component having much smaller Lyapunov exponent, the measure of which drops approximately as a square of the coupling strength down to smallest couplings we were able to reach. We argue that this weak chaos is linked to the regime of fast Arnold diffusion discussed by Chirikov and Vecheslavov. In disordered lattices of large size we find a subdiffusive spreading of initially localized wave packets over larger and larger number of modes. The relations between the exponent of this spreading and the exponent in the dependence of the fast Arnold diffusion on coupling strength are analyzed. We also trace parallels between the slow spreading of chaos and deterministic rheology. KW - Lyapunov exponent KW - Arnold diffusion KW - Chaos spreading Y1 - 2011 U6 - https://doi.org/10.1007/s10955-011-0335-3 SN - 0022-4715 VL - 145 IS - 5 SP - 1256 EP - 1274 PB - Springer CY - New York ER - TY - JOUR A1 - Schoeller, M. A1 - Hubrig, Swetlana A1 - Ilyin, Ilya A1 - Kharchenko, N. V. A1 - Briquet, Maryline A1 - Gonzalez, J. F. A1 - Langer, Norbert A1 - Oskinova, Lida T1 - Magnetic field studies of massive main sequence stars JF - Astronomische Nachrichten = Astronomical notes N2 - We report on the status of our spectropolarimetric observations of massive stars. During the last years, we have discovered magnetic fields in many objects of the upper main sequence, including Be stars, beta Cephei and Slowly Pulsating B stars, and a dozen O stars. Since the effects of those magnetic fields have been found to be substantial by recent models, we are looking into their impact on stellar rotation, pulsation, stellar winds, and chemical abundances. Accurate studies of the age, environment, and kinematic characteristics of the magnetic stars are also promising to give us new insight into the origin of the magnetic fields. Furthermore, longer time series of magnetic field measurements allow us to observe the temporal variability of the magnetic field and to deduce the stellar rotation period and the magnetic field geometry. Studies of the magnetic field in massive stars are indispensable to understand the conditions controlling the presence of those fields and their implications on the stellar physical parameters and evolution. KW - stars: early-type KW - stars: magnetic fields KW - stars: kinematics KW - techniques: polarimetric Y1 - 2011 U6 - https://doi.org/10.1002/asna.201111606 SN - 0004-6337 VL - 332 IS - 9-10 SP - 994 EP - 997 PB - Wiley-Blackwell CY - Malden ER - TY - JOUR A1 - Oskinova, Lida A1 - Hamann, Wolf-Rainer A1 - Cassinelli, Joseph P. A1 - Brown, John C. A1 - Todt, Helge Tobias T1 - X-ray emission from massive stars with magnetic fields JF - Astronomische Nachrichten = Astronomical notes N2 - We investigate the connections between the magnetic fields and the X-ray emission from massive stars. Our study shows that the X-ray properties of known strongly magnetic stars are diverse: while some comply to the predictions of the magnetically confined wind model, others do not. We conclude that strong, hard, and variable X-ray emission may be a sufficient attribute of magnetic massive stars, but it is not a necessary one. We address the general properties of X-ray emission from "normal" massive stars, especially the long standing mystery about the correlations between the parameters of X-ray emission and fundamental stellar properties. The recent development in stellar structure modeling shows that small-scale surface magnetic fields may be common. We suggest a "hybrid" scenario which could explain the X-ray emission from massive stars by a combination of magnetic mechanisms on the surface and shocks in the stellar wind. The magnetic mechanisms and the wind shocks are triggered by convective motions in sub-photospheric layers. This scenario opens the door for a natural explanation of the well established correlation between bolometric and X-ray luminosities. KW - stars: magnetic fields KW - stars: mass-loss KW - stars: winds, outflows KW - stars: Wolf-Rayet KW - techniques: spectroscopic KW - X-rays: stars Y1 - 2011 U6 - https://doi.org/10.1002/asna.201111602 SN - 0004-6337 VL - 332 IS - 9-10 SP - 988 EP - 993 PB - Wiley-Blackwell CY - Malden ER - TY - JOUR A1 - Abel, M. W. A1 - Shepelyansky, Dima L. T1 - Google matrix of business process management JF - The European physical journal : B, Condensed matter and complex systems N2 - Development of efficient business process models and determination of their characteristic properties are subject of intense interdisciplinary research. Here, we consider a business process model as a directed graph. Its nodes correspond to the units identified by the modeler and the link direction indicates the causal dependencies between units. It is of primary interest to obtain the stationary flow on such a directed graph, which corresponds to the steady-state of a firm during the business process. Following the ideas developed recently for the World Wide Web, we construct the Google matrix for our business process model and analyze its spectral properties. The importance of nodes is characterized by PageRank and recently proposed CheiRank and 2DRank, respectively. The results show that this two-dimensional ranking gives a significant information about the influence and communication properties of business model units. We argue that the Google matrix method, described here, provides a new efficient tool helping companies to make their decisions on how to evolve in the exceedingly dynamic global market. Y1 - 2011 U6 - https://doi.org/10.1140/epjb/e2010-10710-y SN - 1434-6028 VL - 84 IS - 4 SP - 493 EP - 500 PB - Springer CY - New York ER - TY - JOUR A1 - Müller, Matthias M. A1 - Haakh, Harald R. A1 - Calarco, Tommaso A1 - Koch, Christiane P. A1 - Henkel, Carsten T1 - Prospects for fast Rydberg gates on an atom chip JF - Quantum information processing N2 - Atom chips are a promising candidate for a scalable architecture for quantum information processing provided a universal set of gates can be implemented with high fidelity. The difficult part in achieving universality is the entangling two-qubit gate. We consider a Rydberg phase gate for two atoms trapped on a chip and employ optimal control theory to find the shortest gate that still yields a reasonable gate error. Our parameters correspond to a situation where the Rydberg blockade regime is not yet reached. We discuss the role of spontaneous emission and the effect of noise from the chip surface on the atoms in the Rydberg state. KW - Optimal control KW - Phase gate KW - Rydberg atoms KW - Cavity quantum electrodynamics Y1 - 2011 U6 - https://doi.org/10.1007/s11128-011-0296-0 SN - 1570-0755 VL - 10 IS - 6 SP - 771 EP - 792 PB - Springer CY - New York ER - TY - JOUR A1 - Kuznetsov, Sergey P. T1 - Plykin type attractor in electronic device simulated in MULTISIM JF - Chaos : an interdisciplinary journal of nonlinear science N2 - An electronic device is suggested representing a non-autonomous dynamical system with hyperbolic chaotic attractor of Plykin type in the stroboscopic map, and the results of its simulation with software package NI MULTISIM are considered in comparison with numerical integration of the underlying differential equations. A main practical advantage of electronic devices of this kind is their structural stability that means insensitivity of the chaotic dynamics in respect to variations of functions and parameters of elements constituting the system as well as to interferences and noises. Y1 - 2011 U6 - https://doi.org/10.1063/1.3646903 SN - 1054-1500 VL - 21 IS - 4 PB - American Institute of Physics CY - Melville ER - TY - JOUR A1 - Actis, M. A1 - Agnetta, G. A1 - Aharonian, Felix A. A1 - Akhperjanian, A. G. A1 - Aleksic, J. A1 - Aliu, E. A1 - Allan, D. A1 - Allekotte, I. A1 - Antico, F. A1 - Antonelli, L. A. A1 - Antoranz, P. A1 - Aravantinos, A. A1 - Arlen, T. A1 - Arnaldi, H. A1 - Artmann, S. A1 - Asano, K. A1 - Asorey, H. G. A1 - Baehr, J. A1 - Bais, A. A1 - Baixeras, C. A1 - Bajtlik, S. A1 - Balis, D. A1 - Bamba, A. A1 - Barbier, C. A1 - Barcelo, M. A1 - Barnacka, Anna A1 - Barnstedt, Jürgen A1 - de Almeida, U. Barres A1 - Barrio, J. A. A1 - Basso, S. A1 - Bastieri, D. A1 - Bauer, C. A1 - Becerra Gonzalez, J. A1 - Becherini, Yvonne A1 - Bechtol, K. C. A1 - Becker, J. A1 - Beckmann, Volker A1 - Bednarek, W. A1 - Behera, B. A1 - Beilicke, M. A1 - Belluso, M. A1 - Benallou, M. A1 - Benbow, W. A1 - Berdugo, J. A1 - Berger, K. A1 - Bernardino, T. A1 - Bernlöhr, K. A1 - Biland, A. A1 - Billotta, S. A1 - Bird, T. A1 - Birsin, E. A1 - Bissaldi, E. A1 - Blake, S. A1 - Blanch Bigas, O. A1 - Bobkov, A. A. A1 - Bogacz, L. A1 - Bogdan, M. A1 - Boisson, Catherine A1 - Boix Gargallo, J. A1 - Bolmont, J. A1 - Bonanno, G. A1 - Bonardi, A. A1 - Bonev, T. A1 - Borkowski, Janett A1 - Botner, O. A1 - Bottani, A. A1 - Bourgeat, M. A1 - Boutonnet, C. A1 - Bouvier, A. A1 - Brau-Nogue, S. A1 - Braun, I. A1 - Bretz, T. A1 - Briggs, M. S. A1 - Brun, Pierre A1 - Brunetti, L. A1 - Buckley, H. A1 - Bugaev, V. A1 - Buehler, R. A1 - Bulik, Tomasz A1 - Busetto, G. A1 - Buson, S. A1 - Byrum, K. A1 - Cailles, M. A1 - Cameron, R. A. A1 - Canestrari, R. A1 - Cantu, S. A1 - Carmona, E. A1 - Carosi, A. A1 - Carr, John A1 - Carton, P. H. A1 - Casiraghi, M. A1 - Castarede, H. A1 - Catalano, O. A1 - Cavazzani, S. A1 - Cazaux, S. A1 - Cerruti, B. A1 - Cerruti, M. A1 - Chadwick, M. A1 - Chiang, J. A1 - Chikawa, M. A1 - Cieslar, M. A1 - Ciesielska, M. A1 - Cillis, A. N. A1 - Clerc, C. A1 - Colin, P. A1 - Colome, J. A1 - Compin, M. A1 - Conconi, P. A1 - Connaughton, V. A1 - Conrad, Jan A1 - Contreras, J. L. A1 - Coppi, P. A1 - Corlier, M. A1 - Corona, P. A1 - Corpace, O. A1 - Corti, D. A1 - Cortina, J. A1 - Costantini, H. A1 - Cotter, G. A1 - Courty, B. A1 - Couturier, S. A1 - Covino, S. A1 - Croston, J. A1 - Cusumano, G. A1 - Daniel, M. K. A1 - Dazzi, F. A1 - Deangelis, A. A1 - de Cea del Pozo, E. A1 - Dal Pino, E. M. de Gouveia A1 - de Jager, O. A1 - de la Calle Perez, I. A1 - De La Vega, G. A1 - De Lotto, B. A1 - de Naurois, M. A1 - Wilhelmi, E. de Ona A1 - de Souza, V. A1 - Decerprit, B. A1 - Deil, C. A1 - Delagnes, E. A1 - Deleglise, G. A1 - Delgado, C. A1 - Dettlaff, T. A1 - Di Paolo, A. A1 - Di Pierro, F. A1 - Diaz, C. A1 - Dick, J. A1 - Dickinson, H. A1 - Digel, S. W. A1 - Dimitrov, D. A1 - Disset, G. A1 - Djannati-Ataï, A. A1 - Doert, M. A1 - Domainko, W. A1 - Dorner, D. A1 - Doro, M. A1 - Dournaux, J. -L. A1 - Dravins, D. A1 - Drury, L. A1 - Dubois, F. A1 - Dubois, R. A1 - Dubus, G. A1 - Dufour, C. A1 - Durand, D. A1 - Dyks, J. A1 - Dyrda, M. A1 - Edy, E. A1 - Egberts, Kathrin A1 - Eleftheriadis, C. A1 - Elles, S. A1 - Emmanoulopoulos, D. A1 - Enomoto, R. A1 - Ernenwein, J. -P. A1 - Errando, M. A1 - Etchegoyen, A. A1 - Falcone, A. D. A1 - Farakos, K. A1 - Farnier, C. A1 - Federici, S. A1 - Feinstein, F. A1 - Ferenc, D. A1 - Fillin-Martino, E. A1 - Fink, D. A1 - Finley, C. A1 - Finley, J. P. A1 - Firpo, R. A1 - Florin, D. A1 - Foehr, C. A1 - Fokitis, E. A1 - Font, Ll. A1 - Fontaine, G. A1 - Fontana, A. A1 - Foerster, A. A1 - Fortson, L. A1 - Fouque, N. A1 - Fransson, C. A1 - Fraser, G. W. A1 - Fresnillo, L. A1 - Fruck, C. A1 - Fujita, Y. A1 - Fukazawa, Y. A1 - Funk, S. A1 - Gaebele, W. A1 - Gabici, S. A1 - Gadola, A. A1 - Galante, N. A1 - Gallant, Y. A1 - Garcia, B. A1 - Garcia Lopez, R. J. A1 - Garrido, D. A1 - Garrido, L. A1 - Gascon, D. A1 - Gasq, C. A1 - Gaug, M. A1 - Gaweda, J. A1 - Geffroy, N. A1 - Ghag, C. A1 - Ghedina, A. A1 - Ghigo, M. A1 - Gianakaki, E. A1 - Giarrusso, S. A1 - Giavitto, G. A1 - Giebels, B. A1 - Giro, E. A1 - Giubilato, P. A1 - Glanzman, T. A1 - Glicenstein, J. -F. A1 - Gochna, M. A1 - Golev, V. A1 - Gomez Berisso, M. A1 - Gonzalez, A. A1 - Gonzalez, F. A1 - Granena, F. A1 - Graciani, R. A1 - Granot, J. A1 - Gredig, R. A1 - Green, A. A1 - Greenshaw, T. A1 - Grimm, O. A1 - Grube, J. A1 - Grudzinska, M. A1 - Grygorczuk, J. A1 - Guarino, V. A1 - Guglielmi, L. A1 - Guilloux, F. A1 - Gunji, S. A1 - Gyuk, G. A1 - Hadasch, D. A1 - Haefner, D. A1 - Hagiwara, R. A1 - Hahn, J. A1 - Hallgren, A. A1 - Hara, S. A1 - Hardcastle, M. J. A1 - Hassan, T. A1 - Haubold, T. A1 - Hauser, M. A1 - Hayashida, M. A1 - Heller, R. A1 - Henri, G. A1 - Hermann, G. A1 - Herrero, A. A1 - Hinton, James Anthony A1 - Hoffmann, D. A1 - Hofmann, W. A1 - Hofverberg, P. A1 - Horns, D. A1 - Hrupec, D. A1 - Huan, H. A1 - Huber, B. A1 - Huet, J. -M. A1 - Hughes, G. A1 - Hultquist, K. A1 - Humensky, T. B. A1 - Huppert, J. -F. A1 - Ibarra, A. A1 - Illa, J. M. A1 - Ingjald, J. A1 - Inoue, S. A1 - Inoue, Y. A1 - Ioka, K. A1 - Jablonski, C. A1 - Jacholkowska, A. A1 - Janiak, M. A1 - Jean, P. A1 - Jensen, H. A1 - Jogler, T. A1 - Jung, I. A1 - Kaaret, P. A1 - Kabuki, S. A1 - Kakuwa, J. A1 - Kalkuhl, C. A1 - Kankanyan, R. A1 - Kapala, M. A1 - Karastergiou, A. A1 - Karczewski, M. A1 - Karkar, S. A1 - Karlsson, N. A1 - Kasperek, J. A1 - Katagiri, H. A1 - Katarzynski, K. A1 - Kawanaka, N. A1 - Kedziora, B. A1 - Kendziorra, E. A1 - Khelifi, B. A1 - Kieda, D. A1 - Kifune, T. A1 - Kihm, T. A1 - Klepser, S. A1 - Kluzniak, W. A1 - Knapp, J. A1 - Knappy, A. R. A1 - Kneiske, T. A1 - Knoedlseder, J. A1 - Koeck, F. A1 - Kodani, K. A1 - Kohri, K. A1 - Kokkotas, K. A1 - Komin, N. A1 - Konopelko, A. A1 - Kosack, K. A1 - Kossakowski, R. A1 - Kostka, P. A1 - Kotula, J. A1 - Kowal, G. A1 - Koziol, J. A1 - Kraehenbuehl, T. A1 - Krause, J. A1 - Krawczynski, H. A1 - Krennrich, F. A1 - Kretzschmann, A. A1 - Kubo, H. A1 - Kudryavtsev, V. A. A1 - Kushida, J. A1 - La Barbera, N. A1 - La Parola, V. A1 - La Rosa, G. A1 - Lopez, A. A1 - Lamanna, G. A1 - Laporte, P. A1 - Lavalley, C. A1 - Le Flour, T. A1 - Le Padellec, A. A1 - Lenain, J. -P. A1 - Lessio, L. A1 - Lieunard, B. A1 - Lindfors, E. A1 - Liolios, A. A1 - Lohse, T. A1 - Lombardi, S. A1 - Lopatin, A. A1 - Lorenz, E. A1 - Lubinski, P. A1 - Luz, O. A1 - Lyard, E. A1 - Maccarone, M. C. A1 - Maccarone, T. A1 - Maier, G. A1 - Majumdar, P. A1 - Maltezos, S. A1 - Malkiewicz, P. A1 - Mana, C. A1 - Manalaysay, A. A1 - Maneva, G. A1 - Mangano, A. A1 - Manigot, P. A1 - Marin, J. A1 - Mariotti, M. A1 - Markoff, S. A1 - Martinez, G. A1 - Martinez, M. A1 - Mastichiadis, A. A1 - Matsumoto, H. A1 - Mattiazzo, S. A1 - Mazin, D. A1 - McComb, T. J. L. A1 - McCubbin, N. A1 - McHardy, I. A1 - Medina, C. A1 - Melkumyan, D. A1 - Mendes, A. A1 - Mertsch, P. A1 - Meucci, M. A1 - Michalowski, J. A1 - Micolon, P. A1 - Mineo, T. A1 - Mirabal, N. A1 - Mirabel, F. A1 - Miranda, J. M. A1 - Mirzoyan, R. A1 - Mizuno, T. A1 - Moal, B. A1 - Moderski, R. A1 - Molinari, E. A1 - Monteiro, I. A1 - Moralejo, A. A1 - Morello, C. A1 - Mori, K. A1 - Motta, G. A1 - Mottez, F. A1 - Moulin, Emmanuel A1 - Mukherjee, R. A1 - Munar, P. A1 - Muraishi, H. A1 - Murase, K. A1 - Murphy, A. Stj. A1 - Nagataki, S. A1 - Naito, T. A1 - Nakamori, T. A1 - Nakayama, K. A1 - Naumann, C. L. A1 - Naumann, D. A1 - Nayman, P. A1 - Nedbal, D. A1 - Niedzwiecki, A. A1 - Niemiec, J. A1 - Nikolaidis, A. A1 - Nishijima, K. A1 - Nolan, S. J. A1 - Nowak, N. A1 - O'Brien, P. T. A1 - Ochoa, I. A1 - Ohira, Y. A1 - Ohishi, M. A1 - Ohka, H. A1 - Okumura, A. A1 - Olivetto, C. A1 - Ong, R. A. A1 - Orito, R. A1 - Orr, M. A1 - Osborne, J. P. A1 - Ostrowski, M. A1 - Otero, L. A1 - Otte, A. N. A1 - Ovcharov, E. A1 - Oya, I. A1 - Ozieblo, A. A1 - Paiano, S. A1 - Pallota, J. A1 - Panazol, J. L. A1 - Paneque, D. A1 - Panter, M. A1 - Paoletti, R. A1 - Papyan, G. A1 - Paredes, J. M. A1 - Pareschi, G. A1 - Parsons, R. D. A1 - Arribas, M. Paz A1 - Pedaletti, G. A1 - Pepato, A. A1 - Persic, M. A1 - Petrucci, P. O. A1 - Peyaud, B. A1 - Piechocki, W. A1 - Pita, S. A1 - Pivato, G. A1 - Platos, L. A1 - Platzer, R. A1 - Pogosyan, L. A1 - Pohl, Martin A1 - Pojmanski, G. A1 - Ponz, J. D. A1 - Potter, W. A1 - Prandini, E. A1 - Preece, R. A1 - Prokoph, H. A1 - Puehlhofer, G. A1 - Punch, M. A1 - Quel, E. A1 - Quirrenbach, A. A1 - Rajda, P. A1 - Rando, R. A1 - Rataj, M. A1 - Raue, M. A1 - Reimann, C. A1 - Reimann, O. A1 - Reimer, A. A1 - Reimer, O. A1 - Renaud, M. A1 - Renner, S. A1 - Reymond, J. -M. A1 - Rhode, W. A1 - Ribo, M. A1 - Ribordy, M. A1 - Rico, J. A1 - Rieger, F. A1 - Ringegni, P. A1 - Ripken, J. A1 - Ristori, P. A1 - Rivoire, S. A1 - Rob, L. A1 - Rodriguez, S. A1 - Roeser, U. A1 - Romano, Patrizia A1 - Romero, G. E. A1 - Rosier-Lees, S. A1 - Rovero, A. C. A1 - Roy, F. A1 - Royer, S. A1 - Rudak, B. A1 - Rulten, C. B. A1 - Ruppel, J. A1 - Russo, F. A1 - Ryde, F. A1 - Sacco, B. A1 - Saggion, A. A1 - Sahakian, V. A1 - Saito, K. A1 - Saito, T. A1 - Sakaki, N. A1 - Salazar, E. A1 - Salini, A. A1 - Sanchez, F. A1 - Sanchez Conde, M. A. A1 - Santangelo, Andrea A1 - Santos, E. M. A1 - Sanuy, A. A1 - Sapozhnikov, L. A1 - Sarkar, S. A1 - Scalzotto, V. A1 - Scapin, V. A1 - Scarcioffolo, M. A1 - Schanz, T. A1 - Schlenstedt, S. A1 - Schlickeiser, R. A1 - Schmidt, T. A1 - Schmoll, J. A1 - Schroedter, M. A1 - Schultz, C. A1 - Schultze, J. A1 - Schulz, A. A1 - Schwanke, U. A1 - Schwarzburg, S. A1 - Schweizer, T. A1 - Seiradakis, J. A1 - Selmane, S. A1 - Seweryn, K. A1 - Shayduk, M. A1 - Shellard, R. C. A1 - Shibata, T. A1 - Sikora, M. A1 - Silk, J. A1 - Sillanpaa, A. A1 - Sitarek, J. A1 - Skole, C. A1 - Smith, N. A1 - Sobczynska, D. A1 - Sofo Haro, M. A1 - Sol, H. A1 - Spanier, F. A1 - Spiga, D. A1 - Spyrou, S. A1 - Stamatescu, V. A1 - Stamerra, A. A1 - Starling, R. L. C. A1 - Stawarz, L. A1 - Steenkamp, R. A1 - Stegmann, Christian A1 - Steiner, S. A1 - Stergioulas, N. A1 - Sternberger, R. A1 - Stinzing, F. A1 - Stodulski, M. A1 - Straumann, U. A1 - Suarez, A. A1 - Suchenek, M. A1 - Sugawara, R. A1 - Sulanke, K. H. A1 - Sun, S. A1 - Supanitsky, A. D. A1 - Sutcliffe, P. A1 - Szanecki, M. A1 - Szepieniec, T. A1 - Szostek, A. A1 - Szymkowiak, A. A1 - Tagliaferri, G. A1 - Tajima, H. A1 - Takahashi, H. A1 - Takahashi, K. A1 - Takalo, L. A1 - Takami, H. A1 - Talbot, R. G. A1 - Tam, P. H. A1 - Tanaka, M. A1 - Tanimori, T. A1 - Tavani, M. A1 - Tavernet, J. -P. A1 - Tchernin, C. A1 - Tejedor, L. A. A1 - Telezhinsky, Igor O. A1 - Temnikov, P. A1 - Tenzer, C. A1 - Terada, Y. A1 - Terrier, R. A1 - Teshima, M. A1 - Testa, V. A1 - Tibaldo, L. A1 - Tibolla, O. A1 - Tluczykont, M. A1 - Peixoto, C. J. Todero A1 - Tokanai, F. A1 - Tokarz, M. A1 - Toma, K. A1 - Torres, D. F. A1 - Tosti, G. A1 - Totani, T. A1 - Toussenel, F. A1 - Vallania, P. A1 - Vallejo, G. A1 - van der Walt, J. A1 - van Eldik, C. A1 - Vandenbroucke, J. A1 - Vankov, H. A1 - Vasileiadis, G. A1 - Vassiliev, V. V. A1 - Vegas, I. A1 - Venter, L. A1 - Vercellone, S. A1 - Veyssiere, C. A1 - Vialle, J. P. A1 - Videla, M. A1 - Vincent, P. A1 - Vink, J. A1 - Vlahakis, N. A1 - Vlahos, L. A1 - Vogler, P. A1 - Vollhardt, A. A1 - Volpe, F. A1 - Von Gunten, H. P. A1 - Vorobiov, S. A1 - Wagner, S. A1 - Wagner, R. M. A1 - Wagner, B. A1 - Wakely, S. P. A1 - Walter, P. A1 - Walter, R. A1 - Warwick, R. A1 - Wawer, P. A1 - Wawrzaszek, R. A1 - Webb, N. A1 - Wegner, P. A1 - Weinstein, A. A1 - Weitzel, Q. A1 - Welsing, R. A1 - Wetteskind, H. A1 - White, R. A1 - Wierzcholska, A. A1 - Wilkinson, M. I. A1 - Williams, D. A. A1 - Winde, M. A1 - Wischnewski, R. A1 - Wisniewski, L. A1 - Wolczko, A. A1 - Wood, M. A1 - Xiong, Q. A1 - Yamamoto, T. A1 - Yamaoka, K. A1 - Yamazaki, R. A1 - Yanagita, S. A1 - Yoffo, B. A1 - Yonetani, M. A1 - Yoshida, A. A1 - Yoshida, T. A1 - Yoshikoshi, T. A1 - Zabalza, V. A1 - Zagdanski, A. A1 - Zajczyk, A. A1 - Zdziarski, A. A1 - Zech, Alraune A1 - Zietara, K. A1 - Ziolkowski, P. A1 - Zitelli, V. A1 - Zychowski, P. T1 - Design concepts for the Cherenkov Telescope Array CTA an advanced facility for ground-based high-energy gamma-ray astronomy JF - Experimental astronomy : an international journal on astronomical instrumentation and data analysis N2 - Ground-based gamma-ray astronomy has had a major breakthrough with the impressive results obtained using systems of imaging atmospheric Cherenkov telescopes. Ground-based gamma-ray astronomy has a huge potential in astrophysics, particle physics and cosmology. CTA is an international initiative to build the next generation instrument, with a factor of 5-10 improvement in sensitivity in the 100 GeV-10 TeV range and the extension to energies well below 100 GeV and above 100 TeV. CTA will consist of two arrays (one in the north, one in the south) for full sky coverage and will be operated as open observatory. The design of CTA is based on currently available technology. This document reports on the status and presents the major design concepts of CTA. KW - Ground based gamma ray astronomy KW - Next generation Cherenkov telescopes KW - Design concepts Y1 - 2011 U6 - https://doi.org/10.1007/s10686-011-9247-0 SN - 0922-6435 SN - 1572-9508 VL - 32 IS - 3 SP - 193 EP - 316 PB - Springer CY - Dordrecht ER - TY - JOUR A1 - Kussmaul, Bjoern A1 - Risse, Sebastian A1 - Kofod, Guggi A1 - Wache, Remi A1 - Wegener, Michael A1 - McCarthy, Denis N. A1 - Krüger, Hartmut A1 - Gerhard, Reimund T1 - Enhancement of dielectric permittivity and electromechanical response in silicone elastomers molecular grafting of organic dipoles to the macromolecular Network JF - Advanced functional materials N2 - A novel method is established for permittivity enhancement of a silicone matrix for dielectric elastomer actuators (DEAs) by molecular level modifications of the elastomer matrix. A push-pull dipole is synthesized to be compatible with the silicone crosslinking chemistry, allowing for direct grafting to the crosslinker molecules in a one-step film formation process. This method prevents agglomeration and yields elastomer films that are homogeneous down to the molecular level. The dipole-to-silicone network grafting reaction is studied by FTIR. The chemical, thermal, mechanical and electrical properties of films with dipole contents ranging from 0 wt% to 13.4 wt% were thoroughly characterized. The grafting of dipoles modifies the relative permittivity and the stiffness, resulting in the actuation strain at a given electrical field being improved by a factor of six. KW - dipole grafting KW - silicone based dielectric elastomer actuators KW - permittivity enhancement Y1 - 2011 U6 - https://doi.org/10.1002/adfm.201100884 SN - 1616-301X VL - 21 IS - 23 SP - 4589 EP - 4594 PB - Wiley-VCH CY - Weinheim ER - TY - JOUR A1 - DiGuglielmo, J. A1 - Samblowski, A. A1 - Hage, B. A1 - Pineda, Carlos A1 - Eisert, Jens A1 - Schnabel, R. T1 - Experimental Unconditional Preparation and Detection of a Continuous Bound Entangled State of Light JF - Physical review letters N2 - Among the possibly most intriguing aspects of quantum entanglement is that it comes in free and bound instances. The existence of bound entangled states certifies an intrinsic irreversibility of entanglement in nature and suggests a connection with thermodynamics. In this Letter, we present a first unconditional, continuous-variable preparation and detection of a bound entangled state of light. We use convex optimization to identify regimes rendering its bound character well certifiable, and continuously produce a distributed bound entangled state with an extraordinary and unprecedented significance of more than 10 standard deviations away from both separability and distillability. Our results show that the approach chosen allows for the efficient and precise preparation of multimode entangled states of light with various applications in quantum information, quantum state engineering, and high precision metrology. Y1 - 2011 U6 - https://doi.org/10.1103/PhysRevLett.107.240503 SN - 0031-9007 VL - 107 IS - 24 PB - American Physical Society CY - College Park ER - TY - JOUR A1 - Acciari, V. A. A1 - Aliu, E. A1 - Arlen, T. A1 - Aune, T. A1 - Beilicke, M. A1 - Benbow, W. A1 - Bradbury, S. M. A1 - Buckley, J. H. A1 - Bugaev, V. A1 - Byrum, K. A1 - Cannon, A. A1 - Cesarini, A. A1 - Christiansen, J. L. A1 - Ciupik, L. A1 - Collins-Hughes, E. A1 - Connolly, M. P. A1 - Cui, W. A1 - Duke, C. A1 - Errando, M. A1 - Falcone, A. A1 - Finley, J. P. A1 - Finnegan, G. A1 - Fortson, L. A1 - Furniss, A. A1 - Galante, N. A1 - Gall, D. A1 - Godambe, S. A1 - Griffin, S. A1 - Grube, J. A1 - Guenette, R. A1 - Gyuk, G. A1 - Hanna, D. A1 - Holder, J. A1 - Hughes, G. A1 - Hui, C. M. A1 - Humensky, T. B. A1 - Jackson, D. J. A1 - Kaaret, P. A1 - Karlsson, N. A1 - Kertzman, M. A1 - Kieda, D. A1 - Krawczynski, H. A1 - Krennrich, F. A1 - Lang, M. J. A1 - Madhavan, A. S. A1 - Maier, G. A1 - McArthur, S. A1 - McCann, A. A1 - Moriarty, P. A1 - Newbold, M. D. A1 - Ong, R. A. A1 - Orr, M. A1 - Otte, A. N. A1 - Park, N. A1 - Perkins, J. S. A1 - Pohl, Martin A1 - Prokoph, H. A1 - Quinn, J. A1 - Ragan, K. A1 - Reyes, L. C. A1 - Reynolds, P. T. A1 - Roache, E. A1 - Rose, H. J. A1 - Ruppel, J. A1 - Saxon, D. B. A1 - Schroedter, M. A1 - Sembroski, G. H. A1 - Sentuerk, G. D. A1 - Smith, A. W. A1 - Staszak, D. A1 - Swordy, S. P. A1 - Tesic, G. A1 - Theiling, M. A1 - Thibadeau, S. A1 - Tsurusaki, K. A1 - Varlotta, A. A1 - Vassiliev, V. V. A1 - Vincent, S. A1 - Vivier, M. A1 - Wakely, S. P. A1 - Ward, J. E. A1 - Weekes, T. C. A1 - Weinstein, A. A1 - Weisgarber, T. A1 - Williams, D. A. A1 - Wood, M. T1 - Veritas observations of gamma-ray bursts detected by swift JF - The astrophysical journal : an international review of spectroscopy and astronomical physics N2 - We present the results of 16 Swift-triggered Gamma-ray burst (GRB) follow-up observations taken with the Very Energetic Radiation Imaging Telescope Array System (VERITAS) telescope array from 2007 January to 2009 June. The median energy threshold and response time of these observations were 260 GeV and 320 s, respectively. Observations had an average duration of 90 minutes. Each burst is analyzed independently in two modes: over the whole duration of the observations and again over a shorter timescale determined by the maximum VERITAS sensitivity to a burst with a t(-1.5) time profile. This temporal model is characteristic of GRB afterglows with high-energy, long-lived emission that have been detected by the Large Area Telescope on board the Fermi satellite. No significant very high energy (VHE) gamma-ray emission was detected and upper limits above the VERITAS threshold energy are calculated. The VERITAS upper limits are corrected for gamma-ray extinction by the extragalactic background light and interpreted in the context of the keV emission detected by Swift. For some bursts the VHE emission must have less power than the keV emission, placing constraints on inverse Compton models of VHE emission. KW - astroparticle physics KW - gamma-ray burst: general Y1 - 2011 U6 - https://doi.org/10.1088/0004-637X/743/1/62 SN - 0004-637X VL - 743 IS - 1 PB - IOP Publ. Ltd. CY - Bristol ER - TY - JOUR A1 - Gruber, W. A1 - Chakravarty, S. A1 - Baehtz, C. A1 - Leitenberger, Wolfram A1 - Bruns, M. A1 - Kobler, A. A1 - Kübel, Christian A1 - Schmidt, H. T1 - Strain relaxation and vacancy creation in thin platinum films JF - Physical review letters N2 - Synchrotron based combined in situ x-ray diffractometry and reflectometry is used to investigate the role of vacancies for the relaxation of residual stress in thin metallic Pt films. From the experimentally determined relative changes of the lattice parameter a and of the film thickness L the modification of vacancy concentration and residual strain was derived as a function of annealing time at 130 degrees C. The results indicate that relaxation of strain resulting from compressive stress is accompanied by the creation of vacancies at the free film surface. This proves experimentally the postulated dominant role of vacancies for stress relaxation in thin metal films close to room temperature. Y1 - 2011 U6 - https://doi.org/10.1103/PhysRevLett.107.265501 SN - 0031-9007 VL - 107 IS - 26 PB - American Physical Society CY - College Park ER - TY - JOUR A1 - Donges, Jonathan A1 - Donner, Reik Volker A1 - Trauth, Martin H. A1 - Marwan, Norbert A1 - Schellnhuber, Hans Joachim A1 - Kurths, Jürgen T1 - Nonlinear detection of paleoclimate-variability transitions possibly related to human evolution JF - Proceedings of the National Academy of Sciences of the United States of America N2 - Potential paleoclimatic driving mechanisms acting on human evolution present an open problem of cross-disciplinary scientific interest. The analysis of paleoclimate archives encoding the environmental variability in East Africa during the past 5 Ma has triggered an ongoing debate about possible candidate processes and evolutionary mechanisms. In this work, we apply a nonlinear statistical technique, recurrence network analysis, to three distinct marine records of terrigenous dust flux. Our method enables us to identify three epochs with transitions between qualitatively different types of environmental variability in North and East Africa during the (i) Middle Pliocene (3.35-3.15 Ma B. P.), (ii) Early Pleistocene (2.25-1.6 Ma B. P.), and (iii) Middle Pleistocene (1.1-0.7 Ma B. P.). A deeper examination of these transition periods reveals potential climatic drivers, including (i) large-scale changes in ocean currents due to a spatial shift of the Indonesian throughflow in combination with an intensification of Northern Hemisphere glaciation, (ii) a global reorganization of the atmospheric Walker circulation induced in the tropical Pacific and Indian Ocean, and (iii) shifts in the dominating temporal variability pattern of glacial activity during the Middle Pleistocene, respectively. A reexamination of the available fossil record demonstrates statistically significant coincidences between the detected transition periods and major steps in hominin evolution. This result suggests that the observed shifts between more regular and more erratic environmental variability may have acted as a trigger for rapid change in the development of humankind in Africa. KW - African climate KW - Plio-Pleistocene KW - climate-driven evolution KW - dynamical transitions KW - nonlinear time series analysis Y1 - 2011 U6 - https://doi.org/10.1073/pnas.1117052108 SN - 0027-8424 VL - 108 IS - 51 SP - 20422 EP - 20427 PB - National Acad. of Sciences CY - Washington ER - TY - JOUR A1 - Turner, Sarah T. A1 - Pingel, Patrick A1 - Steyrleuthner, Robert A1 - Crossland, Edward J. W. A1 - Ludwigs, Sabine A1 - Neher, Dieter T1 - Quantitative analysis of bulk heterojunction films using linear absorption spectroscopy and solar cell performance JF - Advanced functional materials N2 - A fundamental understanding of the relationship between the bulk morphology and device performance is required for the further development of bulk heterojunction organic solar cells. Here, non-optimized (chloroform cast) and nearly optimized (solvent-annealed o-dichlorobenzene cast) P3HT:PCBM blend films treated over a range of annealing temperatures are studied via optical and photovoltaic device measurements. Parameters related to the P3HT aggregate morphology in the blend are obtained through a recently established analytical model developed by F. C. Spano for the absorption of weakly interacting H-aggregates. Thermally induced changes are related to the glass transition range of the blend. In the chloroform prepared devices, the improvement in device efficiency upon annealing within the glass transition range can be attributed to the growth of P3HT aggregates, an overall increase in the percentage of chain crystallinity, and a concurrent increase in the hole mobilities. Films treated above the glass transition range show an increase in efficiency and fill factor not only associated with the change in chain crystallinity, but also with a decrease in the energetic disorder. On the other hand, the properties of the P3HT phase in the solvent-annealed o-dichlorobenzene cast blends are almost indistinguishable from those of the corresponding pristine P3HT layer and are only weakly affected by thermal annealing. Apparently, slow drying of the blend allows the P3HT chains to crystallize into large domains with low degrees of intra- and interchain disorder. This morphology appears to be most favorable for the efficient generation and extraction of charges. KW - Organic electronics KW - morphology KW - solar cells KW - mobility KW - absorption spectroscopy Y1 - 2011 U6 - https://doi.org/10.1002/adfm.201101583 SN - 1616-301X VL - 21 IS - 24 SP - 4640 EP - 4652 PB - Wiley-VCH CY - Weinheim ER - TY - JOUR A1 - Abdolvahab, Rouhollah Haji A1 - Metzler, Ralf A1 - Ejtehadi, Mohammad Reza T1 - First passage time distribution of chaperone driven polymer translocation through a nanopore homopolymer and heteropolymer cases JF - The journal of chemical physics : bridges a gap between journals of physics and journals of chemistr N2 - Combining the advection-diffusion equation approach with Monte Carlo simulations we study chaperone driven polymer translocation of a stiff polymer through a nanopore. We demonstrate that the probability density function of first passage times across the pore depends solely on the Peclet number, a dimensionless parameter comparing drift strength and diffusivity. Moreover it is shown that the characteristic exponent in the power-law dependence of the translocation time on the chain length, a function of the chaperone-polymer binding energy, the chaperone concentration, and the chain length, is also effectively determined by the Peclet number. We investigate the effect of the chaperone size on the translocation process. In particular, for large chaperone size, the translocation progress and the mean waiting time as function of the reaction coordinate exhibit pronounced sawtooth-shapes. The effects of a heterogeneous polymer sequence on the translocation dynamics is studied in terms of the translocation velocity, the probability distribution for the translocation progress, and the monomer waiting times. (C) 2011 American Institute of Physics. Y1 - 2011 U6 - https://doi.org/10.1063/1.3669427 SN - 0021-9606 VL - 135 IS - 24 PB - American Institute of Physics CY - Melville ER - TY - JOUR A1 - Fuhrmann, Marcel A1 - Seehafer, Norbert A1 - Valori, Gherardo A1 - Wiegelmann, Thomas T1 - A comparison of preprocessing methods for solar force-free magnetic field extrapolation Y1 - 2011 UR - http://www.aanda.org/index.php?option=com_article&access=standard&Itemid=129&url=/articles/aa/full_html/ 2011/02/aa15453-10/aa15453-10.html SN - 0004-6361 ER -