TY - JOUR A1 - Javanainen, Matti A1 - Hammaren, Henrik A1 - Monticelli, Luca A1 - Jeon, Jae-Hyung A1 - Miettinen, Markus S. A1 - Martinez-Seara, Hector A1 - Metzler, Ralf A1 - Vattulainen, Ilpo T1 - Anomalous and normal diffusion of proteins and lipids in crowded lipid membranes JF - Faraday discussions N2 - Lateral diffusion plays a crucial role in numerous processes that take place in cell membranes, yet it is quite poorly understood in native membranes characterized by, e.g., domain formation and large concentration of proteins. In this article, we use atomistic and coarse-grained simulations to consider how packing of membranes and crowding with proteins affect the lateral dynamics of lipids and membrane proteins. We find that both packing and protein crowding have a profound effect on lateral diffusion, slowing it down. Anomalous diffusion is observed to be an inherent property in both protein-free and protein-rich membranes, and the time scales of anomalous diffusion and the exponent associated with anomalous diffusion are found to strongly depend on packing and crowding. Crowding with proteins also has a striking effect on the decay rate of dynamical correlations associated with lateral single-particle motion, as the transition from anomalous to normal diffusion is found to take place at macroscopic time scales: while in protein-poor conditions normal diffusion is typically observed in hundreds of nanoseconds, in protein-rich conditions the onset of normal diffusion is tens of microseconds, and in the most crowded systems as large as milliseconds. The computational challenge which results from these time scales is not easy to deal with, not even in coarse-grained simulations. We also briefly discuss the physical limits of protein motion. Our results suggest that protein concentration is anything but constant in the plane of cell membranes. Instead, it is strongly dependent on proteins' preference for aggregation. Y1 - 2013 U6 - https://doi.org/10.1039/c2fd20085f SN - 1359-6640 VL - 161 IS - 1 SP - 397 EP - 417 PB - Royal Society of Chemistry CY - Cambridge ER - TY - JOUR A1 - Sliusarenko, O. Yu. A1 - Surkov, D. A. A1 - Gonchar, V. Yu. A1 - Chechkin, Aleksei V. T1 - Stationary states in bistable system driven by Levy noise JF - European physical journal special topics N2 - We study the properties of the probability density function (PDF) of a bistable system driven by heavy tailed white symmetric L,vy noise. The shape of the stationary PDF is found analytically for the particular case of the L,vy index alpha = 1 (Cauchy noise). For an arbitrary L,vy index we employ numerical methods based on the solution of the stochastic Langevin equation and space fractional kinetic equation. In contrast to the bistable system driven by Gaussian noise, in the L,vy case, the positions of maxima of the stationary PDF do not coincide with the positions of minima of the bistable potential. We provide a detailed study of the distance between the maxima and the minima as a function of the depth of the potential and the L,vy noise parameters. Y1 - 2013 U6 - https://doi.org/10.1140/epjst/e2013-01736-0 SN - 1951-6355 VL - 216 IS - 1 SP - 133 EP - 138 PB - Springer CY - Heidelberg ER - TY - JOUR A1 - Li, Hongguang A1 - Babu, Sukumaran Santhosh A1 - Turner, Sarah T. A1 - Neher, Dieter A1 - Hollamby, Martin J. A1 - Seki, Tomohiro A1 - Yagai, Shiki A1 - Deguchi, Yonekazu A1 - Möhwald, Helmuth A1 - Nakanishi, Takashi T1 - Alkylated-C-60 based soft materials regulation of self-assembly and optoelectronic properties by chain branching JF - Journal of materials chemistry : C, Materials for optical and electronic devices N2 - Derivatization of fullerene (C-60) with branched aliphatic chains softens C-60-based materials and enables the formation of thermotropic liquid crystals and room temperature nonvolatile liquids. This work demonstrates that by carefully tuning parameters such as type, number and substituent position of the branched chains, liquid crystalline C-60 materials with mesophase temperatures suited for photovoltaic cell fabrication and room temperature nonvolatile liquid fullerenes with tunable viscosity can be obtained. In particular, compound 1, with branched chains, exhibits a smectic liquid crystalline phase extending from 84 degrees C to room temperature. Analysis of bulk heterojunction (BHJ) organic solar cells with a ca. 100 nm active layer of compound 1 and poly(3-hexylthiophene) (P3HT) as an electron acceptor and an electron donor, respectively, reveals an improved performance (power conversion efficiency, PCE: 1.6 + 0.1%) in comparison with another compound, 10 (PCE: 0.5 + 0.1%). The latter, in contrast to 1, carries linear aliphatic chains and thus forms a highly ordered solid lamellar phase at room temperature. The solar cell performance of 1 blended with P3HT approaches that of PCBM/P3HT for the same active layer thickness. This indicates that C-60 derivatives bearing branched tails are a promising class of electron acceptors in soft (flexible) photovoltaic devices. Y1 - 2013 U6 - https://doi.org/10.1039/c3tc00066d SN - 2050-7526 VL - 1 IS - 10 SP - 1943 EP - 1951 PB - Royal Society of Chemistry CY - Cambridge ER - TY - JOUR A1 - Marwan, Norbert A1 - Schinkel, Stefan A1 - Kurths, Jürgen T1 - Recurrence plots 25 years later -Gaining confidence in dynamical transitions JF - epl : a letters journal exploring the frontiers of physics N2 - Recurrence-plot-based time series analysis is widely used to study changes and transitions in the dynamics of a system or temporal deviations from its overall dynamical regime. However, most studies do not discuss the significance of the detected variations in the recurrence quantification measures. In this letter we propose a novel method to add a confidence measure to the recurrence quantification analysis. We show how this approach can be used to study significant changes in dynamical systems due to a change in control parameters, chaos-order as well as chaos-chaos transitions. Finally we study and discuss climate transitions by analysing a marine proxy record for past sea surface temperature. This paper is dedicated to the 25th anniversary of the introduction of recurrence plots. Y1 - 2013 U6 - https://doi.org/10.1209/0295-5075/101/20007 SN - 0295-5075 VL - 101 IS - 2 PB - EDP Sciences CY - Mulhouse ER - TY - JOUR A1 - Menzel, Ralf A1 - Heuer, Axel A1 - Puhlmann, Dirk A1 - Dechoum, K. A1 - Hillery, M. A1 - Spaehn, M. J. A. A1 - Schleich, W. P. T1 - A two-photon double-slit experiment JF - Journal of modern optics N2 - We employ a photon pair created by spontaneous parametric down conversion (SPDC) where the pump laser is in the TEM01 mode to perform a Young's double-slit experiment. The signal photon illuminates the two slits and displays interference fringes in the far-field while the idler photon measured in the near-field in coincidence with the signal photon provides us with which-slit' information. We explain the results of these experiments with the help of an analytical expression for the second-order correlation function derived from an elementary model of SPDC. Our experiment emphasizes the crucial role of the mode function in the quantum theory of radiation. KW - complementarity KW - wave-particle dualism KW - Young's double-slit experiment KW - spontaneous parametric down conversion KW - TEM01 mode Y1 - 2013 U6 - https://doi.org/10.1080/09500340.2012.746400 SN - 0950-0340 VL - 60 IS - 1 SP - 86 EP - 94 PB - Routledge, Taylor & Francis Group CY - Abingdon ER - TY - JOUR A1 - Bindschadler, Robert A. A1 - Nowicki, Sophie A1 - Abe-Ouchi, Ayako A1 - Aschwanden, Andy A1 - Choi, Hyeungu A1 - Fastook, Jim A1 - Granzow, Glen A1 - Greve, Ralf A1 - Gutowski, Gail A1 - Herzfeld, Ute A1 - Jackson, Charles A1 - Johnson, Jesse A1 - Khroulev, Constantine A1 - Levermann, Anders A1 - Lipscomb, William H. A1 - Martin, Maria A. A1 - Morlighem, Mathieu A1 - Parizek, Byron R. A1 - Pollard, David A1 - Price, Stephen F. A1 - Ren, Diandong A1 - Saito, Fuyuki A1 - Sato, Tatsuru A1 - Seddik, Hakime A1 - Seroussi, Helene A1 - Takahashi, Kunio A1 - Walker, Ryan A1 - Wang, Wei Li T1 - Ice-sheet model sensitivities to environmental forcing and their use in projecting future sea level (the SeaRISE project) JF - Journal of glaciology N2 - Ten ice-sheet models are used to study sensitivity of the Greenland and Antarctic ice sheets to prescribed changes of surface mass balance, sub-ice-shelf melting and basal sliding. Results exhibit a large range in projected contributions to sea-level change. In most cases, the ice volume above flotation lost is linearly dependent on the strength of the forcing. Combinations of forcings can be closely approximated by linearly summing the contributions from single forcing experiments, suggesting that nonlinear feedbacks are modest. Our models indicate that Greenland is more sensitive than Antarctica to likely atmospheric changes in temperature and precipitation, while Antarctica is more sensitive to increased ice-shelf basal melting. An experiment approximating the Intergovernmental Panel on Climate Change's RCP8.5 scenario produces additional first-century contributions to sea level of 22.3 and 8.1 cm from Greenland and Antarctica, respectively, with a range among models of 62 and 14 cm, respectively. By 200 years, projections increase to 53.2 and 26.7 cm, respectively, with ranges of 79 and 43 cm. Linear interpolation of the sensitivity results closely approximates these projections, revealing the relative contributions of the individual forcings on the combined volume change and suggesting that total ice-sheet response to complicated forcings over 200 years can be linearized. Y1 - 2013 U6 - https://doi.org/10.3189/2013JoG12J125 SN - 0022-1430 VL - 59 IS - 214 SP - 195 EP - 224 PB - International Glaciological Society CY - Cambridge ER - TY - JOUR A1 - Pattyn, Frank A1 - Perichon, Laura A1 - Durand, Gael A1 - Favier, Lionel A1 - Gagliardini, Olivier A1 - Hindmarsh, Richard C. A. A1 - Zwinger, Thomas A1 - Albrecht, Torsten A1 - Cornford, Stephen A1 - Docquier, David A1 - Furst, Johannes J. A1 - Goldberg, Daniel A1 - Gudmundsson, Gudmundur Hilmar A1 - Humbert, Angelika A1 - Huetten, Moritz A1 - Huybrechts, Philippe A1 - Jouvet, Guillaume A1 - Kleiner, Thomas A1 - Larour, Eric A1 - Martin, Daniel A1 - Morlighem, Mathieu A1 - Payne, Anthony J. A1 - Pollard, David A1 - Rueckamp, Martin A1 - Rybak, Oleg A1 - Seroussi, Helene A1 - Thoma, Malte A1 - Wilkens, Nina T1 - Grounding-line migration in plan-view marine ice-sheet models: results of the ice2sea MISMIP3d intercomparison JF - Journal of glaciology N2 - Predictions of marine ice-sheet behaviour require models able to simulate grounding-line migration. We present results of an intercomparison experiment for plan-view marine ice-sheet models. Verification is effected by comparison with approximate analytical solutions for flux across the grounding line using simplified geometrical configurations (no lateral variations, no buttressing effects from lateral drag). Perturbation experiments specifying spatial variation in basal sliding parameters permitted the evolution of curved grounding lines, generating buttressing effects. The experiments showed regions of compression and extensional flow across the grounding line, thereby invalidating the boundary layer theory. Steady-state grounding-line positions were found to be dependent on the level of physical model approximation. Resolving grounding lines requires inclusion of membrane stresses, a sufficiently small grid size (<500 m), or subgrid interpolation of the grounding line. The latter still requires nominal grid sizes of <5 km. For larger grid spacings, appropriate parameterizations for ice flux may be imposed at the grounding line, but the short-time transient behaviour is then incorrect and different from models that do not incorporate grounding-line parameterizations. The numerical error associated with predicting grounding-line motion can be reduced significantly below the errors associated with parameter ignorance and uncertainties in future scenarios. Y1 - 2013 U6 - https://doi.org/10.3189/2013JoG12J129 SN - 0022-1430 VL - 59 IS - 215 SP - 410 EP - 422 PB - International Glaciological Society CY - Cambridge ER - TY - JOUR A1 - Schleussner, Carl-Friedrich A1 - Feulner, G. T1 - A volcanically triggered regime shift in the subpolar North Atlantic Ocean as a possible origin of the Little Ice Age JF - Climate of the past : an interactive open access journal of the European Geosciences Union N2 - Among the climatological events of the last millennium, the Northern Hemisphere Medieval Climate Anomaly succeeded by the Little Ice Age are of exceptional importance. The origin of these regional climate anomalies remains a subject of debate and besides external influences like solar and volcanic activity, internal dynamics of the climate system might have also played a dominant role. Here, we present transient last millennium simulations of the fully coupled model of intermediate complexity Climber 3a forced with stochastically reconstructed wind-stress fields. Our results indicate that short-lived volcanic eruptions might have triggered a cascade of sea ice ocean feedbacks in the North Atlantic, ultimately leading to a persistent regime shift in the ocean circulation. We find that an increase in the Nordic Sea sea-ice extent on decadal timescales as a consequence of major volcanic eruptions in our model leads to a spin-up of the subpolar gyre and a weakened Atlantic meridional overturning circulation, eventually causing a persistent, basin-wide cooling. These results highlight the importance of regional climate feedbacks such as a regime shift in the subpolar gyre circulation for understanding the dynamics of past and future climate. Y1 - 2013 U6 - https://doi.org/10.5194/cp-9-1321-2013 SN - 1814-9324 SN - 1814-9332 VL - 9 IS - 3 SP - 1321 EP - 1330 PB - Copernicus CY - Göttingen ER - TY - JOUR A1 - Inal, Sahika A1 - Koelsch, Jonas D. A1 - Chiappisi, Leonardo A1 - Janietz, Dietmar A1 - Gradzielski, Michael A1 - Laschewsky, André A1 - Neher, Dieter T1 - Structure-related differences in the temperature-regulated fluorescence response of LCST type polymers JF - Journal of materials chemistry : C, Materials for optical and electronic devices N2 - We demonstrate new fluorophore-labelled materials based on acrylamide and on oligo(ethylene glycol) (OEG) bearing thermoresponsive polymers for sensing purposes and investigate their thermally induced solubility transitions. It is found that the emission properties of the polarity-sensitive (solvatochromic) naphthalimide derivative attached to three different thermoresponsive polymers are highly specific to the exact chemical structure of the macromolecule. While the dye emits very weakly below the LCST when incorporated into poly(N-isopropylacrylamide) (pNIPAm) or into a polyacrylate backbone bearing only short OEG side chains, it is strongly emissive in polymethacrylates with longer OEG side chains. Heating of the aqueous solutions above their cloud point provokes an abrupt increase of the fluorescence intensity of the labelled pNIPAm, whereas the emission properties of the dye are rather unaffected as OEG-based polyacrylates and methacrylates undergo phase transition. Correlated with laser light scattering studies, these findings are ascribed to the different degrees of pre-aggregation of the chains at low temperatures and to the extent of dehydration that the phase transition evokes. It is concluded that although the temperature-triggered changes in the macroscopic absorption characteristics, related to large-scale alterations of the polymer chain conformation and aggregation, are well detectable and similar for these LCST-type polymers, the micro-environment provided to the dye within each polymer network differs substantially. Considering sensing applications, this finding is of great importance since the temperature-regulated fluorescence response of the polymer depends more on the macromolecular architecture than the type of reporter fluorophore. Y1 - 2013 U6 - https://doi.org/10.1039/c3tc31304b SN - 2050-7526 VL - 1 IS - 40 SP - 6603 EP - 6612 PB - Royal Society of Chemistry CY - Cambridge ER - TY - JOUR A1 - Nishikawa, Ken-Ichi A1 - Hardee, P. A1 - Zhang, B. A1 - Dutan, I. A1 - Medvedev, M. A1 - Choi, E. J. A1 - Min, K. W. A1 - Niemiec, J. A1 - Mizuno, Y. A1 - Nordlund, Ake A1 - Frederiksen, Jacob Trier A1 - Sol, H. A1 - Pohl, Martin A1 - Hartmann, D. H. T1 - Magnetic field generation in a jet-sheath plasma via the kinetic Kelvin-Helmholtz instability JF - Annales geophysicae N2 - We have investigated the generation of magnetic fields associated with velocity shear between an unmagnetized relativistic jet and an unmagnetized sheath plasma. We have examined the strong magnetic fields generated by kinetic shear (Kelvin-Helmholtz) instabilities. Compared to the previous studies using counter-streaming performed by Alves et al. (2012), the structure of the kinetic Kelvin-Helmholtz instability (KKHI) of our jet-sheath configuration is slightly different, even for the global evolution of the strong transverse magnetic field. In our simulations the major components of growing modes are the electric field E-z, perpendicular to the flow boundary, and the magnetic field B-y, transverse to the flow direction. After the B-y component is excited, an induced electric field E-x, parallel to the flow direction, becomes significant. However, other field components remain small. We find that the structure and growth rate of KKHI with mass ratios m(i)/m(e) = 1836 and m(i)/m(e) = 20 are similar. In our simulations in the nonlinear stage is not as clear as in counter-streaming cases. The growth rate for a mildly-relativistic jet case (gamma(j) = 1.5) is larger than for a relativistic jet case (gamma(j) = 15). KW - Solar physics KW - astrophysics KW - astronomy (Energetic particles) Y1 - 2013 U6 - https://doi.org/10.5194/angeo-31-1535-2013 SN - 0992-7689 VL - 31 IS - 9 SP - 1535 EP - 1541 PB - Copernicus CY - Göttingen ER - TY - JOUR A1 - Cherstvy, Andrey G. A1 - Metzler, Ralf T1 - Population splitting, trapping, and non-ergodicity in heterogeneous diffusion processes JF - Physical chemistry, chemical physics : a journal of European Chemical Societies N2 - We consider diffusion processes with a spatially varying diffusivity giving rise to anomalous diffusion. Such heterogeneous diffusion processes are analysed for the cases of exponential, power-law, and logarithmic dependencies of the diffusion coefficient on the particle position. Combining analytical approaches with stochastic simulations, we show that the functional form of the space-dependent diffusion coefficient and the initial conditions of the diffusing particles are vital for their statistical and ergodic properties. In all three cases a weak ergodicity breaking between the time and ensemble averaged mean squared displacements is observed. We also demonstrate a population splitting of the time averaged traces into fast and slow diffusers for the case of exponential variation of the diffusivity as well as a particle trapping in the case of the logarithmic diffusivity. Our analysis is complemented by the quantitative study of the space coverage, the diffusive spreading of the probability density, as well as the survival probability. Y1 - 2013 U6 - https://doi.org/10.1039/c3cp53056f SN - 1463-9076 SN - 1463-9084 VL - 15 IS - 46 SP - 20220 EP - 20235 PB - Royal Society of Chemistry CY - Cambridge ER - TY - JOUR A1 - Inal, Sahika A1 - Kölsch, Jonas D. A1 - Sellrie, Frank A1 - Schenk, Jörg A. A1 - Wischerhoff, Erik A1 - Laschewsky, André A1 - Neher, Dieter T1 - A water soluble fluorescent polymer as a dual colour sensor for temperature and a specific protein JF - Journal of materials chemistry : B, Materials for biology and medicine N2 - We present two thermoresponsive water soluble copolymers prepared via free radical statistical copolymerization of N-isopropylacrylamide (NIPAm) and of oligo(ethylene glycol) methacrylates (OEGMAs), respectively, with a solvatochromic 7-(diethylamino)-3-carboxy-coumarin (DEAC)-functionalized monomer. In aqueous solutions, the NIPAm-based copolymer exhibits characteristic changes in its fluorescence profile in response to a change in solution temperature as well as to the presence of a specific protein, namely an anti-DEAC antibody. This polymer emits only weakly at low temperatures, but exhibits a marked fluorescence enhancement accompanied by a change in its emission colour when heated above its cloud point. Such drastic changes in the fluorescence and absorbance spectra are observed also upon injection of the anti-DEAC antibody, attributed to the specific binding of the antibody to DEAC moieties. Importantly, protein binding occurs exclusively when the polymer is in the well hydrated state below the cloud point, enabling a temperature control on the molecular recognition event. On the other hand, heating of the polymer-antibody complexes releases a fraction of the bound antibody. In the presence of the DEAC-functionalized monomer in this mixture, the released antibody competitively binds to the monomer and the antibody-free chains of the polymer undergo a more effective collapse and inter-aggregation. In contrast, the emission properties of the OEGMA-based analogous copolymer are rather insensitive to the thermally induced phase transition or to antibody binding. These opposite behaviours underline the need for a carefully tailored molecular design of responsive polymers aimed at specific applications, such as biosensing. Y1 - 2013 U6 - https://doi.org/10.1039/c3tb21245a SN - 2050-750X SN - 2050-7518 VL - 1 IS - 46 SP - 6373 EP - 6381 PB - Royal Society of Chemistry CY - Cambridge ER - TY - JOUR A1 - Barbosa Pfannes, Eva Katharina A1 - Anielski, Alexander A1 - Gerhardt, Matthias A1 - Beta, Carsten T1 - Intracellular photoactivation of caged cGMP induces myosin II and actin responses in motile cells JF - Integrative biology N2 - Cyclic GMP (cGMP) is a ubiquitous second messenger in eukaryotic cells. It is assumed to regulate the association of myosin II with the cytoskeleton of motile cells. When cells of the social amoeba Dictyostelium discoideum are exposed to chemoattractants or to increased osmotic stress, intracellular cGMP levels rise, preceding the accumulation of myosin II in the cell cortex. To directly investigate the impact of intracellular cGMP on cytoskeletal dynamics in a living cell, we released cGMP inside the cell by laser-induced photo-cleavage of a caged precursor. With this approach, we could directly show in a live cell experiment that an increase in intracellular cGMP indeed induces myosin II to accumulate in the cortex. Unexpectedly, we observed for the first time that also the amount of filamentous actin in the cell cortex increases upon a rise in the cGMP concentration, independently of cAMP receptor activation and signaling. We discuss our results in the light of recent work on the cGMP signaling pathway and suggest possible links between cGMP signaling and the actin system. Y1 - 2013 U6 - https://doi.org/10.1039/c3ib40109j SN - 1757-9694 SN - 1757-9708 VL - 5 IS - 12 SP - 1456 EP - 1463 PB - Royal Society of Chemistry CY - Cambridge ER - TY - JOUR A1 - Menon, Arathy A1 - Levermann, Anders A1 - Schewe, Jacob A1 - Lehmann, J. A1 - Frieler, Katja T1 - Consistent increase in Indian monsoon rainfall and its variability across CMIP-5 models JF - Earth system dynamics N2 - The possibility of an impact of global warming on the Indian monsoon is of critical importance for the large population of this region. Future projections within the Coupled Model Intercomparison Project Phase 3 (CMIP-3) showed a wide range of trends with varying magnitude and sign across models. Here the Indian summer monsoon rainfall is evaluated in 20 CMIP-5 models for the period 1850 to 2100. In the new generation of climate models, a consistent increase in seasonal mean rainfall during the summer monsoon periods arises. All models simulate stronger seasonal mean rainfall in the future compared to the historic period under the strongest warming scenario RCP-8.5. Increase in seasonal mean rainfall is the largest for the RCP-8.5 scenario compared to other RCPs. Most of the models show a northward shift in monsoon circulation by the end of the 21st century compared to the historic period under the RCP-8.5 scenario. The interannual variability of the Indian monsoon rainfall also shows a consistent positive trend under unabated global warming. Since both the long-term increase in monsoon rainfall as well as the increase in interannual variability in the future is robust across a wide range of models, some confidence can be attributed to these projected trends. Y1 - 2013 U6 - https://doi.org/10.5194/esd-4-287-2013 SN - 2190-4979 SN - 2190-4987 VL - 4 IS - 2 SP - 287 EP - 300 PB - Copernicus CY - Göttingen ER - TY - JOUR A1 - Basso, Heitor Cury A1 - Qiu, Xunlin A1 - Wirges, Werner A1 - Gerhard, Reimund T1 - Temporal evolution of the re-breakdown voltage in small gaps from nanoseconds to milliseconds JF - Applied physics letters N2 - A detailed understanding of electric breakdown in dielectrics is of scientific and technological interest. In gaseous dielectrics, a so-called re-breakdown is sometimes observed after extinction of the previous discharge. Although time-dependent re-breakdown voltage is essentially known, its behavior immediately after the previous discharge is not precisely understood. We present an electronic circuit for accurate measurements of the time-dependent re-breakdown voltage in small gaps from tens of nanoseconds to several milliseconds after the previous spark. Results from such experiments are compared with earlier findings, and relevant physical mechanisms such as heating of the gas, decay of the plasma, and ionization of excited atoms and molecules are discussed. It is confirmed that the thermal model is not valid at times below several microseconds. Y1 - 2013 U6 - https://doi.org/10.1063/1.4773518 SN - 0003-6951 VL - 102 IS - 1 PB - American Institute of Physics CY - Melville ER - TY - JOUR A1 - Schulz, Johannes H. P. A1 - Barkai, Eli A1 - Metzler, Ralf T1 - Aging effects and population splitting in single-particle trajectoryaverages JF - Physical review letters N2 - We study time averages of single particle trajectories in scale-free anomalous diffusion processes, in which the measurement starts at some time t(a) > 0 after initiation of the process at t = 0. Using aging renewal theory, we show that for such nonstationary processes a large class of observables are affected by a unique aging function, which is independent of boundary conditions or the external forces. Moreover, we discuss the implications of aging induced population splitting: with growing age ta of the process, an increasing fraction of particles remains motionless in a measurement of fixed duration. Consequences for single biomolecule tracking in live cells are discussed. Y1 - 2013 U6 - https://doi.org/10.1103/PhysRevLett.110.020602 SN - 0031-9007 SN - 1079-7114 VL - 110 IS - 2 PB - American Physical Society CY - College Park ER - TY - JOUR A1 - Arlen, T. A1 - Aune, T. A1 - Beilicke, M. A1 - Benbow, W. A1 - Bouvier, A. A1 - Buckley, J. H. A1 - Bugaev, V. A1 - Cesarini, A. A1 - Ciupik, L. A1 - Connolly, M. P. A1 - Cui, W. A1 - Dickherber, R. A1 - Dumm, J. A1 - Errando, M. A1 - Falcone, A. A1 - Federici, S. A1 - Feng, Q. A1 - Finley, J. P. A1 - Finnegan, G. A1 - Fortson, L. A1 - Furniss, A. A1 - Galante, N. A1 - Gall, D. A1 - Griffin, S. A1 - Grube, J. A1 - Gyuk, G. A1 - Hanna, D. A1 - Holder, J. A1 - Humensky, T. B. A1 - Kaaret, P. A1 - Karlsson, N. A1 - Kertzman, M. A1 - Khassen, Y. A1 - Kieda, D. A1 - Krawczynski, H. A1 - Krennrich, F. A1 - Maier, G. A1 - Moriarty, P. A1 - Mukherjee, R. A1 - Nelson, T. A1 - de Bhroithe, A. O'Faolain A1 - Ong, R. A. A1 - Orr, M. 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 - Saxon, D. B. A1 - Schroedter, M. A1 - Sembroski, G. H. A1 - Staszak, D. A1 - Telezhinsky, Igor O. A1 - Tesic, G. A1 - Theiling, M. A1 - Tsurusaki, K. A1 - Varlotta, A. A1 - Vincent, S. A1 - Wakely, S. P. A1 - Weekes, T. C. A1 - Weinstein, A. A1 - Welsing, R. A1 - Williams, D. A. A1 - Zitzer, B. A1 - Jorstad, S. G. A1 - MacDonald, N. R. A1 - Marscher, A. P. A1 - Smith, P. S. A1 - Walker, R. C. A1 - Hovatta, T. A1 - Richards, J. A1 - Max-Moerbeck, W. A1 - Readhead, A. A1 - Lister, M. L. A1 - Kovalev, Y. Y. A1 - Pushkarev, A. B. A1 - Gurwell, M. A. A1 - Lahteenmaki, A. A1 - Nieppola, E. A1 - Tornikoski, M. A1 - Jarvela, E. T1 - Rapid TeV Gamma-Ray flaring of bl lacertae JF - The astrophysical journal : an international review of spectroscopy and astronomical physics N2 - We report on the detection of a very rapid TeV gamma-ray flare from BL Lacertae on 2011 June 28 with the Very Energetic Radiation Imaging Telescope Array System (VERITAS). The flaring activity was observed during a 34.6 minute exposure, when the integral flux above 200 GeV reached (3.4 +/- 0.6) x 10(-6) photons m(-2) s(-1), roughly 125% of the Crab Nebula flux measured by VERITAS. The light curve indicates that the observations missed the rising phase of the flare but covered a significant portion of the decaying phase. The exponential decay time was determined to be 13 +/- 4 minutes, making it one of the most rapid gamma-ray flares seen from a TeV blazar. The gamma-ray spectrum of BL Lacertae during the flare was soft, with a photon index of 3.6 +/- 0.4, which is in agreement with the measurement made previously by MAGIC in a lower flaring state. Contemporaneous radio observations of the source with the Very Long Baseline Array revealed the emergence of a new, superluminal component from the core around the time of the TeV gamma-ray flare, accompanied by changes in the optical polarization angle. Changes in flux also appear to have occurred at optical, UV, and GeV gamma-ray wavelengths at the time of the flare, although they are difficult to quantify precisely due to sparse coverage. A strong flare was seen at radio wavelengths roughly four months later, which might be related to the gamma-ray flaring activities. We discuss the implications of these multiwavelength results. KW - galaxies: active KW - galaxies: individual (BL Lacertae, VER J2202+422) KW - gamma rays: galaxies Y1 - 2013 U6 - https://doi.org/10.1088/0004-637X/762/2/92 SN - 0004-637X VL - 762 IS - 2 PB - IOP Publ. Ltd. CY - Bristol ER - TY - JOUR A1 - Godec, Aljaz A1 - Metzler, Ralf T1 - Finite-Time effects and ultraweak ergodicity breaking in superdiffusive dynamics JF - Physical review letters N2 - We study the ergodic properties of superdiffusive, spatiotemporally coupled Levy walk processes. For trajectories of finite duration, we reveal a distinct scatter of the scaling exponents of the time averaged mean squared displacement (delta x(2)) over bar around the ensemble value 3 - alpha (1 < alpha < 2) ranging from ballistic motion to subdiffusion, in strong contrast to the behavior of subdiffusive processes. In addition we find a significant dependence of the average of (delta x(2)) over bar over an ensemble of trajectories as a function of the finite measurement time. This so-called finite-time amplitude depression and the scatter of the scaling exponent is vital in the quantitative evaluation of superdiffusive processes. Comparing the long time average of the second moment with the ensemble mean squared displacement, these only differ by a constant factor, an ultraweak ergodicity breaking. Y1 - 2013 U6 - https://doi.org/10.1103/PhysRevLett.110.020603 SN - 0031-9007 VL - 110 IS - 2 PB - American Physical Society CY - College Park ER - TY - JOUR A1 - Schubert, Marcel A1 - Preis, Eduard A1 - Blakesley, James C. A1 - Pingel, Patrick A1 - Scherf, Ullrich A1 - Neher, Dieter T1 - Mobility relaxation and electron trapping in a donor/acceptor copolymer JF - Physical review : B, Condensed matter and materials physics N2 - To address the nature of charge transport and the origin of severe (intrinsic) trapping in electron-transporting polymers, transient and steady-state charge transport measurements have been conducted on the prototype donor/acceptor copolymer poly[2,7-(9,9-dialkyl-fluorene)-alt-5,5-(4',7'-di-2-thienyl-2',1',3'-benzothiadiazole)] (PFTBTT). A charge-generation layer technique is used to selectively address transport of the desired charge carrier type, to perform time-of-flight measurements on samples with < 200 nm thickness, and to combine the time-of-flight and the photocharge extraction by linearly increasing voltage (photo-CELIV) techniques to investigate charge carrier dynamics over a wide time range. Significant trapping of free electrons is observed in the bulk of dioctyl-substituted PFTBTT (alt-PF8TBTT), introducing a strong relaxation of the charge carrier mobility with time. We used Monte-Carlo simulation to simulate the measured transient data and found that all measurements can be modeled with a single parameter set, with the charge transport behavior determined by multiple trapping and detrapping of electrons in an exponential trap distribution. The influence of the concomitant mobility relaxation on the transient photocurrent characteristics in photo-CELIV experiments is discussed and shown to explain subtle features that were seen in former publications but were not yet assigned to electron trapping. Comparable studies on PFTBTT copolymers with chemical modifications of the side chains and backbone suggest that the observed electron trapping is not caused by a distinct chemical species but rather is related to interchain interactions. Y1 - 2013 U6 - https://doi.org/10.1103/PhysRevB.87.024203 SN - 1098-0121 VL - 87 IS - 2 PB - American Physical Society CY - College Park ER - TY - JOUR A1 - Bauer, Maximilian A1 - Metzler, Ralf T1 - In vivo facilitated diffusion model JF - PLoS one N2 - Under dilute in vitro conditions transcription factors rapidly locate their target sequence on DNA by using the facilitated diffusion mechanism. However, whether this strategy of alternating between three-dimensional bulk diffusion and one-dimensional sliding along the DNA contour is still beneficial in the crowded interior of cells is highly disputed. Here we use a simple model for the bacterial genome inside the cell and present a semi-analytical model for the in vivo target search of transcription factors within the facilitated diffusion framework. Without having to resort to extensive simulations we determine the mean search time of a lac repressor in a living E. coli cell by including parameters deduced from experimental measurements. The results agree very well with experimental findings, and thus the facilitated diffusion picture emerges as a quantitative approach to gene regulation in living bacteria cells. Furthermore we see that the search time is not very sensitive to the parameters characterizing the DNA configuration and that the cell seems to operate very close to optimal conditions for target localization. Local searches as implied by the colocalization mechanism are only found to mildly accelerate the mean search time within our model. Y1 - 2013 U6 - https://doi.org/10.1371/journal.pone.0053956 SN - 1932-6203 VL - 8 IS - 1 PB - PLoS CY - San Fransisco ER - TY - JOUR A1 - Huebener, R. A1 - Mari, Andrea A1 - Eisert, Jens T1 - Wick's theorem for matrix product states JF - Physical review letters N2 - Matrix product states and their continuous analogues are variational classes of states that capture quantum many-body systems or quantum fields with low entanglement; they are at the basis of the density-matrix renormalization group method and continuous variants thereof. In this work we show that, generically, N-point functions of arbitrary operators in discrete and continuous translation invariant matrix product states are completely characterized by the corresponding two- and three-point functions. Aside from having important consequences for the structure of correlations in quantum states with low entanglement, this result provides a new way of reconstructing unknown states from correlation measurements, e. g., for one-dimensional continuous systems of cold atoms. We argue that such a relation of correlation functions may help in devising perturbative approaches to interacting theories. Y1 - 2013 U6 - https://doi.org/10.1103/PhysRevLett.110.040401 SN - 0031-9007 VL - 110 IS - 4 PB - American Physical Society CY - College Park ER - TY - JOUR A1 - Abramowski, Attila A1 - Acero, F. A1 - Aharonian, Felix A. A1 - Akhperjanian, A. G. A1 - Anton, Gisela A1 - Balenderan, Shangkari A1 - Balzer, Arnim A1 - Barnacka, Anna A1 - Becherini, Yvonne A1 - Tjus, J. Becker A1 - Bernlöhr, K. A1 - Birsin, E. A1 - Biteau, Jonathan A1 - Bochow, A. A1 - Boisson, Catherine A1 - Bolmont, J. A1 - Bordas, Pol A1 - Brucker, J. A1 - Brun, Francois A1 - Brun, Pierre A1 - Bulik, Tomasz A1 - Carrigan, Svenja A1 - Casanova, Sabrina A1 - Cerruti, M. A1 - Chadwick, Paula M. A1 - Chaves, Ryan C. G. A1 - Cheesebrough, A. A1 - Colafrancesco, Sergio A1 - Cologna, Gabriele A1 - Conrad, Jan A1 - Couturier, C. A1 - Dalton, M. A1 - Daniel, M. K. A1 - Davids, I. D. A1 - Degrange, B. A1 - Deil, C. A1 - deWilt, P. A1 - Dickinson, H. J. A1 - Djannati-Ataï, A. A1 - Domainko, W. A1 - Drury, L. O'C. A1 - Dubus, G. A1 - Dutson, K. A1 - Dyks, J. A1 - Dyrda, M. A1 - Egberts, Kathrin A1 - Eger, P. A1 - Espigat, P. A1 - Fallon, L. A1 - Farnier, C. A1 - Fegan, S. A1 - Feinstein, F. A1 - Fernandes, M. V. A1 - Fernandez, D. A1 - Fiasson, A. A1 - Fontaine, G. A1 - Foerster, A. A1 - Fussling, Matthias A1 - Gajdus, M. A1 - Gallant, Y. A. A1 - Garrigoux, T. A1 - Gast, H. A1 - Giebels, B. A1 - Glicenstein, J. F. A1 - Glueck, B. A1 - Goering, D. A1 - Grondin, M. -H. A1 - Haeffner, S. A1 - Hague, J. D. A1 - Hahn, J. A1 - Hampf, D. A1 - Harris, J. A1 - Heinz, S. A1 - Heinzelmann, G. A1 - Henri, G. A1 - Hermann, G. A1 - Hillert, A. A1 - Hinton, James Anthony A1 - Hofmann, W. A1 - Hofverberg, P. A1 - Holler, M. A1 - Horns, D. A1 - Jacholkowska, A. A1 - Jahn, C. A1 - Jamrozy, M. A1 - Jung, I. A1 - Kastendieck, M. A. A1 - Katarzynski, K. A1 - Katz, U. A1 - Kaufmann, S. A1 - Khelifi, B. A1 - Klepser, S. A1 - Klochkov, D. A1 - Kluzniak, W. A1 - Kneiske, T. A1 - Komin, Nu A1 - Kosack, K. A1 - Kossakowski, R. A1 - Krayzel, F. A1 - Krueger, P. P. A1 - Laffon, H. A1 - Lamanna, G. A1 - Lefaucheur, J. A1 - Lemoine-Goumard, M. A1 - Lenain, J. -P. A1 - Lennarz, D. A1 - Lohse, T. A1 - Lopatin, A. A1 - Lu, C. -C. A1 - Marandon, V. A1 - Marcowith, Alexandre A1 - Masbou, J. A1 - Maurin, G. A1 - Maxted, N. A1 - Mayer, M. A1 - McComb, T. J. L. A1 - Medina, M. C. A1 - Mehault, J. A1 - Menzler, U. A1 - Moderski, R. A1 - Mohamed, M. A1 - Moulin, Emmanuel A1 - Naumann, C. L. A1 - Naumann-Godo, M. A1 - de Naurois, M. A1 - Nedbal, D. A1 - Nekrassov, D. A1 - Nguyen, N. A1 - Niemiec, J. A1 - Nolan, S. J. A1 - Ohm, S. A1 - Awilhelmi, E. de Ona A1 - Opitz, B. A1 - Ostrowski, M. A1 - Oya, I. A1 - Panter, M. A1 - Parsons, R. D. A1 - Arribas, M. Paz A1 - Pekeur, N. W. A1 - Pelletier, G. A1 - Perez, J. A1 - Petrucci, P. -O. A1 - Peyaud, B. A1 - Pita, S. A1 - Puehlhofer, G. A1 - Punch, M. A1 - Quirrenbach, A. A1 - Raue, M. A1 - Reimer, A. A1 - Reimer, O. A1 - Renaud, M. A1 - de los Reyes, R. A1 - Rieger, F. A1 - Ripken, J. A1 - Rob, L. A1 - Rosier-Lees, S. A1 - Rowell, G. A1 - Rudak, B. A1 - Rulten, C. B. A1 - Sahakian, V. A1 - Sanchez, David M. A1 - Santangelo, Andrea A1 - Schlickeiser, R. A1 - Schulz, A. A1 - Schwanke, U. A1 - Schwarzburg, S. A1 - Schwemmer, S. A1 - Sheidaei, F. A1 - Skilton, J. L. A1 - Sol, H. A1 - Spengler, G. A1 - Stawarz, L. A1 - Steenkamp, R. A1 - Stegmann, Christian A1 - Stinzing, F. A1 - Stycz, K. A1 - Sushch, Iurii A1 - Szostek, A. A1 - Tavernet, J. -P. A1 - Terrier, R. A1 - Tluczykont, M. A1 - Trichard, C. A1 - Valerius, K. A1 - van Eldik, C. A1 - Vasileiadis, G. A1 - Venter, C. A1 - Viana, A. A1 - Vincent, P. A1 - Voelk, H. J. A1 - Volpe, F. A1 - Vorobiov, S. A1 - Vorster, M. A1 - Wagner, S. J. A1 - Ward, M. A1 - White, R. A1 - Wierzcholska, A. A1 - Wouters, D. A1 - Zacharias, M. A1 - Zajczyk, A. A1 - Zdziarski, A. A. A1 - Zech, Alraune A1 - Zechlin, H. -S. T1 - Search for Photon-Linelike Signatures from Dark Matter Annihilations with H.E.S.S. JF - Physical review letters N2 - Gamma-ray line signatures can be expected in the very-high-energy (E-gamma > 100 GeV) domain due to self-annihilation or decay of dark matter (DM) particles in space. Such a signal would be readily distinguishable from astrophysical gamma-ray sources that in most cases produce continuous spectra that span over several orders of magnitude in energy. Using data collected with the H. E. S. S. gamma-ray instrument, upper limits on linelike emission are obtained in the energy range between similar to 500 GeV and similar to 25 TeV for the central part of the Milky Way halo and for extragalactic observations, complementing recent limits obtained with the Fermi-LAT instrument at lower energies. No statistically significant signal could be found. For monochromatic gamma-ray line emission, flux limits of (2 x 10(-7)-2 x 10(-5)) m(-2)s(-1)sr(-1) and (1 x 10(-8)- 2 x 10(-6)) m(-2)s(-1)sr(-1) are obtained for the central part of the Milky Way halo and extragalactic observations, respectively. For a DM particle mass of 1 TeV, limits on the velocity- averaged DM annihilation cross section (chi chi ->gamma gamma) reach similar to 10(-27)cm(3)s(-1), based on the Einasto parametrization of the Galactic DM halo density profile. DOI: 10.1103/PhysRevLett.110.041301 Y1 - 2013 U6 - https://doi.org/10.1103/PhysRevLett.110.041301 SN - 0031-9007 VL - 110 IS - 4 PB - American Physical Society CY - College Park ER - TY - JOUR A1 - Stoyanov, Hristiyan A1 - Kollosche, Matthias A1 - Risse, Sebastian A1 - Wache, Remi A1 - Kofod, Guggi T1 - Soft conductive elastomer materials for stretchable electronics and voltage controlled artificial muscles JF - Advanced materials N2 - Block copolymer elastomer conductors (BEC) are mixtures of block copolymers grafted with conducting polymers, which are found to support very large strains, while retaining a high level of conductivity. These novel materials may find use in stretchable electronics. The use of BEC is demonstrated in a capacitive strain sensor and in an artificial muscle of the dielectric elastomer actuator type, supporting more than 100% actuation strain and capacity strain sensitivity up to 300%. KW - soft electrical connections KW - stretchable electronics KW - elastic conductor KW - compliant electrodes Y1 - 2013 U6 - https://doi.org/10.1002/adma.201202728 SN - 0935-9648 VL - 25 IS - 4 SP - 578 EP - 583 PB - Wiley-VCH CY - Weinheim ER - TY - JOUR A1 - Ohliger, Matthias A1 - Nesme, V. A1 - Eisert, J. T1 - Efficient and feasible state tomography of quantum many-body systems JF - New journal of physics : the open-access journal for physics N2 - We present a novel method for performing quantum state tomography for many-particle systems, which are particularly suitable for estimating the states in lattice systems such as of ultra-cold atoms in optical lattices. We show that the need to measure a tomographically complete set of observables can be overcome by letting the state evolve under some suitably chosen random circuits followed by the measurement of a single observable. We generalize known results about the approximation of unitary two-designs, i.e. certain classes of random unitary matrices, by random quantum circuits and connect our findings to the theory of quantum compressed sensing. We show that for ultra-cold atoms in optical lattices established experimental techniques such as optical super-lattices, laser speckles and time-of-flight measurements are sufficient to perform fully certified, assumption-free tomography. This is possible without the need to address single sites in any step of the procedure. Combining our approach with tensor network methods-in particular, the theory of matrix product states-we identify situations where the effort of reconstruction is even constant in the number of lattice sites, allowing, in principle, to perform tomography on large-scale systems readily available in present experiments. Y1 - 2013 U6 - https://doi.org/10.1088/1367-2630/15/1/015024 SN - 1367-2630 VL - 15 IS - 5 PB - IOP Publ. Ltd. CY - Bristol ER - TY - JOUR A1 - Naze, Yael A1 - Oskinova, Lida A1 - Gosset, Eric T1 - A detailed x-ray investigation of zeta puppis - II. the variability on short and long timescales JF - The astrophysical journal : an international review of spectroscopy and astronomical physics N2 - Stellar winds are a crucial component of massive stars, but their exact properties still remain uncertain. To shed some light on this subject, we have analyzed an exceptional set of X-ray observations of zeta Puppis, one of the closest and brightest massive stars. The sensitive light curves that were derived reveal two major results. On the one hand, a slow modulation of the X-ray flux (with a relative amplitude of up to 15% over 16 hr in the 0.3-4.0 keV band) is detected. Its characteristic timescale cannot be determined with precision, but amounts from one to several days. It could be related to corotating interaction regions, known to exist in zeta Puppis from UV observations. Hour-long changes, linked to flares or to the pulsation activity, are not observed in the last decade covered by the XMM observations; the 17 hr tentative period, previously reported in a ROSAT analysis, is not confirmed either and is thus transient, at best. On the other hand, short-term changes are surprisingly small (<1% relative amplitude for the total energy band). In fact, they are compatible solely with the presence of Poisson noise in the data. This surprisingly low level of short-term variability, in view of the embedded wind-shock origin, requires a very high fragmentation of the stellar wind, for both absorbing and emitting features (>10(5) parcels, comparing with a two-dimensional wind model). This is the first time that constraints have been placed on the number of clumps in an O-type star wind and from X-ray observations. KW - stars: early-type KW - stars: individual (zeta Pup) KW - X-rays: stars Y1 - 2013 U6 - https://doi.org/10.1088/0004-637X/763/2/143 SN - 0004-637X VL - 763 IS - 2 PB - IOP Publ. Ltd. CY - Bristol ER - TY - JOUR A1 - Trinh, Christopher Q. A1 - Ellis, Simon C. A1 - Bland-Hawthorn, Joss A1 - Lawrence, Jon S. A1 - Horton, Anthony J. A1 - Leon-Saval, Sergio G. A1 - Shortridge, Keith A1 - Bryant, Julia A1 - Case, Scott A1 - Colless, Matthew A1 - Couch, Warrick A1 - Freeman, Kenneth A1 - Löhmannsröben, Hans-Gerd A1 - Gers, Luke A1 - Glazebrook, Karl A1 - Haynes, Roger A1 - Lee, Steve A1 - O'Byrne, John A1 - Miziarski, Stan A1 - Roth, Martin M. A1 - Schmidt, Brian A1 - Tinney, Christopher G. A1 - Zheng, Jessica T1 - Gnosis - the first instrument to use fiber bragg gratings for OH suppression JF - The astronomical journal N2 - The near-infrared is an important part of the spectrum in astronomy, especially in cosmology because the light from objects in the early universe is redshifted to these wavelengths. However, deep near-infrared observations are extremely difficult to make from ground-based telescopes due to the bright background from the atmosphere. Nearly all of this background comes from the bright and narrow emission lines of atmospheric hydroxyl (OH) molecules. The atmospheric background cannot be easily removed from data because the brightness fluctuates unpredictably on short timescales. The sensitivity of ground-based optical astronomy far exceeds that of near-infrared astronomy because of this long-standing problem. GNOSIS is a prototype astrophotonic instrument that utilizes "OH suppression fibers" consisting of fiber Bragg gratings and photonic lanterns to suppress the 103 brightest atmospheric emission doublets between 1.47 and 1.7 mu m. GNOSIS was commissioned at the 3.9 m Anglo-Australian Telescope with the IRIS2 spectrograph to demonstrate the potential of OH suppression fibers, but may be potentially used with any telescope and spectrograph combination. Unlike previous atmospheric suppression techniques GNOSIS suppresses the lines before dispersion and in a manner that depends purely on wavelength. We present the instrument design and report the results of laboratory and on-sky tests from commissioning. While these tests demonstrated high throughput (approximate to 60%) and excellent suppression of the skylines by the OH suppression fibers, surprisingly GNOSIS produced no significant reduction in the interline background and the sensitivity of GNOSIS+IRIS2 is about the same as IRIS2. It is unclear whether the lack of reduction in the interline background is due to physical sources or systematic errors as the observations are detector noise dominated. OH suppression fibers could potentially impact ground-based astronomy at the level of adaptive optics or greater. However, until a clear reduction in the interline background and the corresponding increasing in sensitivity is demonstrated optimized OH suppression fibers paired with a fiber-fed spectrograph will at least provide a real benefit at low resolving powers. KW - atmospheric effects KW - infrared: diffuse background KW - instrumentation: miscellaneous Y1 - 2013 U6 - https://doi.org/10.1088/0004-6256/145/2/51 SN - 0004-6256 VL - 145 IS - 2 PB - IOP Publ. Ltd. CY - Bristol ER - TY - JOUR A1 - Salert, Beatrice Ch. D. A1 - Krueger, Hartmut A1 - Bagnich, Sergey A. A1 - Unger, Thomas A1 - Jaiser, Frank A1 - Al-Sa'di, Mahmoud A1 - Neher, Dieter A1 - Hayer, Anna A1 - Eberle, Thomas T1 - New polymer matrix system for phosphorescent organic light-emitting diodes and the role of the small molecular co-host JF - Journal of polymer science : A, Polymer chemistry N2 - A new matrix system for phosphorescent organic light-emitting diodes (OLEDs) based on an electron transporting component attached to an inert polymer backbone, an electronically neutral co-host, and a phosphorescent dye that serves as both emitter and hole conductor are presented. The inert co-host is used either as small molecules or covalently connected to the same chain as the electron-transporting host. The use of a small molecular inert co-host in the active layer is shown to be highly advantageous in comparison to a purely polymeric matrix bearing the same functionalities. Analysis of the dye phosphorescence decay in pure polymer, small molecular co-host film, and their blend lets to conclude that dye molecules distribute mostly in the small molecular co-host phase, where the co-host prevents agglomeration and self-quenching of the phosphorescence as well as energy transfer to the electron transporting units. In addition, the co-host accumulates at the anode interface where it acts as electron blocking layer and improves hole injection. This favorable phase separation between polymeric and small molecular components results in devices with efficiencies of about 47 cd/A at a luminance of 1000 cd/m(2). Investigation of OLED degradation demonstrates the presence of two time regimes: one fast component that leads to a strong decrease at short times followed by a slower decrease at longer times. Unlike the long time degradation, the efficiency loss that occurs at short times is reversible and can be recovered by annealing of the device at 180 degrees C. We also show that the long-time degradation must be related to a change of the optical and electrical bulk properties. KW - charge transport KW - conducting polymer KW - degradation KW - host-guest systems KW - light-emitting diodes KW - random copolymer KW - synthesis KW - UV-vis spectroscopy Y1 - 2013 U6 - https://doi.org/10.1002/pola.26409 SN - 0887-624X VL - 51 IS - 3 SP - 601 EP - 613 PB - Wiley-Blackwell CY - Hoboken ER - TY - JOUR A1 - van Loon, Jacco Th. A1 - Bailey, M. A1 - Tatton, B. L. A1 - Apellaniz, Jesus Maiz A1 - Crowther, P. A. A1 - de Koter, A. A1 - Evans, C. J. A1 - Henault-Brunet, V. A1 - Howarth, I. D. A1 - Richter, Philipp A1 - Sana, Hugues A1 - Simon Díaz, Sergio A1 - Taylor, W. A1 - Walborn, N. R. T1 - The VLT-FLAMES tarantula survey IX. - the interstellar medium seen through diffuse interstellar bands and neutral sodium JF - Astronomy and astrophysics : an international weekly journal N2 - Context. The Tarantula Nebula (a.k.a. 30 Dor) is a spectacular star-forming region in the Large Magellanic Cloud (LMC), seen through gas in the Galactic disc and halo. Diffuse interstellar bands (DIBs) offer a unique probe of the diffuse, cool-warm gas in these regions. Aims. The aim is to use DIBs as diagnostics of the local interstellar conditions, whilst at the same time deriving properties of the yet-unknown carriers of these enigmatic spectral features. Methods. Spectra of over 800 early-type stars from the Very Large Telescope Flames Tarantula Survey (VFTS) were analysed. Maps were created, separately, for the Galactic and LMC absorption in the DIBs at 4428 and 6614 angstrom and - in a smaller region near the central cluster R 136 - neutral sodium (the Na ID doublet); we also measured the DIBs at 5780 and 5797 angstrom. Results. The maps show strong 4428 and 6614 angstrom DIBs in the quiescent cloud complex to the south of 30 Dor but weak absorption in the harsher environments to the north (bubbles) and near the OB associations. The Na maps show at least five kinematic components in the LMC and a shell-like structure surrounding R 136, and small-scale structure in the Milky Way. The strengths of the 4428, 5780, 5797 and 6614 angstrom DIBs are correlated, also with Na absorption and visual extinction. The strong 4428 angstrom DIB is present already at low Na column density but the 6614, 5780 and 5797 angstrom DIBs start to be detectable at subsequently larger Na column densities. Conclusions. The carriers of the 4428, 6614, 5780 and 5797 angstrom DIBs are increasingly prone to removal from irradiated gas. The relative strength of the 5780 and 5797 angstrom DIBs clearly confirm the Tarantula Nebula as well as Galactic high-latitude gas to represent a harsh radiation environment. The resilience of the 4428 angstrom DIB suggests its carrier is large, compact and neutral. Structure is detected in the distribution of cool-warm gas on scales between one and > 100 pc in the LMC and as little as 0.01 pc in the Sun's vicinity. Stellar winds from the central cluster R 136 have created an expanding shell; some infalling gas is also detected, reminiscent of a galactic "fountain". KW - ISM: individual objects: Tarantula Nebula (30 Doradus Nebula) KW - ISM: molecules KW - ISM: kinematics and dynamics KW - ISM: lines and bands KW - ISM: structure KW - local insterstellar matter Y1 - 2013 U6 - https://doi.org/10.1051/0004-6361/201220210 SN - 0004-6361 VL - 550 IS - 9 PB - EDP Sciences CY - Les Ulis ER - TY - JOUR A1 - Herenz, Peter A1 - Richter, Philipp A1 - Charlton, Jane C. A1 - Masiero, Joseph R. T1 - The milky way halo as a QSO absorption-line system new results from an HST/STIS absorption-line catalogue of galactic high-velocity clouds JF - Astronomy and astrophysics : an international weekly journal N2 - We use archival UV absorption-line data from HST/STIS to statistically analyse the absorption characteristics of the high-velocity clouds (HVCs) in the Galactic halo towards more than 40 extragalactic background sources. We determine absorption covering fractions of low-and intermediate ions (Oi, Cii, Si ii, Mgii, Feii, Si iii, Civ, and Si iv) in the range f(c) = 0.20-0.70. For detailed analysis we concentrate on Si ii absorption components in HVCs, for which we investigate the distribution of column densities, b-values, and radial velocities. Combining information for Si ii and Mg II, and using a geometrical HVC model we investigate the contribution of HVCs to the absorption cross section of strong Mg ii absorbers in the local Universe. We estimate that the Galactic HVCs would contribute on average similar to 52 percent to the total strong Mg ii cross section of the Milky Way, if our Galaxy were to be observed from an exterior vantage point. We further estimate that the mean projected covering fraction of strong Mg ii absorption in the Milky Way halo and disc from an exterior vantage point is < f(c,sMgII)> = 0.31 for a halo radius of R = 61 kpc. These numbers, together with the observed number density of strong Mg ii absorbers at low redshift, indicate that the contribution of infalling gas clouds (i.e., HVC analogues) in the halos of Milky Way-type galaxies to the cross section of strong Mgii absorbers is < 34 percent. These findings are in line with the idea that outflowing gas (e. g., produced by galactic winds) in the halos of more actively star-forming galaxies dominate the absorption-cross section of strong Mgii absorbers in the local Universe. KW - ISM: structure KW - Galaxy: halo KW - galaxies: halos Y1 - 2013 U6 - https://doi.org/10.1051/0004-6361/201220531 SN - 0004-6361 VL - 550 PB - EDP Sciences CY - Les Ulis ER - TY - JOUR A1 - Ignace, Richard A1 - Oskinova, Lida A1 - Massa, D. T1 - A report on the X-ray properties of the tau Sco-like stars JF - Monthly notices of the Royal Astronomical Society N2 - An increasing number of OB stars have been shown to possess magnetic fields. Although the sample remains small, it is surprising that the magnetic and X-ray properties of these stars appear to be far less correlated than expected. This contradicts model predictions, which generally indicate that the X-rays from magnetic stars are harder and more luminous than their non-magnetic counterparts. Instead, the X-ray properties of magnetic OB stars are quite diverse. tau Sco is one example where the expectations are better met. This bright main-sequence, early B star has been studied extensively in a variety of wavebands. It has a surface magnetic field of around 500 G, and Zeeman Doppler tomography has revealed an unusual field configuration. Furthermore, tau Sco displays an unusually hard X-ray spectrum, much harder than similar, non-magnetic OB stars. In addition, the profiles of its UV P Cygni wind lines have long been known to possess a peculiar morphology. Recently, two stars, HD 66665 and HD 63425, whose spectral types and UV wind line profiles are similar to those of tau Sco, have also been determined to be magnetic. In the hope of establishing a magnetic field - X-ray connection for at least a subset of the magnetic stars, we obtained XMM-Newton European Photon Imaging Camera spectra of these two objects. Our results for HD 66665 are somewhat inconclusive. No especially strong hard component is detected; however, the number of source counts is insufficient to rule out hard emission. Longer exposure is needed to assess the nature of the X-rays from this star. On the other hand, we do find that HD 63425 has a substantial hard X-ray component, thereby bolstering its close similarity to tau Sco. KW - stars: early-type KW - stars: individual: HD 63425 KW - stars: individual: HD 66665 KW - stars: magnetic field KW - X-rays: stars Y1 - 2013 U6 - https://doi.org/10.1093/mnras/sts358 SN - 0035-8711 VL - 429 IS - 1 SP - 516 EP - 522 PB - Oxford Univ. Press CY - Oxford ER - TY - JOUR A1 - Meibom, S. A1 - Barnes, Sydney A. A1 - Covey, K. A1 - Jeffries, R. D. A1 - Matt, S. A1 - Morin, J. A1 - Palacios, A. A1 - Reiners, A. A1 - Sicilia-Aguilar, A. A1 - Irwin, J. T1 - Angular momentum evolution of cool stars: Toward a synthesis of observations and theory before and after the ZAMS JF - Astronomische Nachrichten = Astronomical notes N2 - The coexistence of fast and slowly rotating cool stars in ZAMS clusters - forming distinct sequences in the color vs. rotation period plane - is providing clues to differences in their pre main-sequence angular momentum evolution. This Cool Stars 17 splinter was dedicated to a discussion of new observational and theoretical results that may help discriminate between proposed mechanisms for early angular momentum regulation and help us explain the observed ZAMS dichotomy. KW - circumstellar matter KW - stars: late-type KW - stars: magnetic fields KW - stars: pre-main sequence KW - stars: rotation Y1 - 2013 U6 - https://doi.org/10.1002/asna.201211777 SN - 0004-6337 SN - 1521-3994 VL - 334 IS - 1-2 SP - 168 EP - 171 PB - Wiley-VCH CY - Weinheim ER - TY - JOUR A1 - Pieplow, Gregor A1 - Henkel, Carsten T1 - Fully covariant radiation force on a polarizable particle JF - New journal of physics : the open-access journal for physics N2 - The electromagnetic force on a polarizable particle is calculated in a covariant framework. Local equilibrium temperatures for the electromagnetic field and the particle's dipole moment are assumed, using a relativistic formulation of the fluctuation-dissipation theorem. Two examples illustrate radiative friction forces: a particle moving through a homogeneous radiation background and above a planar interface. Previous results for arbitrary relative velocities are recovered in a compact way. Y1 - 2013 U6 - https://doi.org/10.1088/1367-2630/15/2/023027 SN - 1367-2630 VL - 15 IS - 4 PB - IOP Publ. Ltd. CY - Bristol ER - TY - JOUR A1 - Schick, Daniel A1 - Bojahr, Andre A1 - Herzog, Marc A1 - Gaal, P. A1 - Vrejoiu, I. A1 - Bargheer, Matias T1 - Following Strain-Induced Mosaicity Changes of Ferroelectric Thin Films by Ultrafast Reciprocal Space Mapping JF - Physical review letters N2 - We investigate coherent phonon propagation in a thin film of ferroelectric PbZr0.2Ti0.8O3 (PZT) by ultrafast x-ray diffraction experiments, which are analyzed as time-resolved reciprocal space mapping in order to observe the in-and out-of-plane structural dynamics, simultaneously. The mosaic structure of the PZT leads to a coupling of the excited out-of-plane expansion to in-plane lattice dynamics on a picosecond time scale, which is not observed for out-of-plane compression. Y1 - 2013 U6 - https://doi.org/10.1103/PhysRevLett.110.095502 SN - 0031-9007 SN - 1079-7114 VL - 110 IS - 9 PB - American Physical Society CY - College Park ER - TY - JOUR A1 - Eliazar, Iddo A1 - Metzler, Ralf T1 - Anomalous statistics of random relaxations in random environments JF - Physical review : E, Statistical, nonlinear and soft matter physics N2 - We comprehensively analyze the emergence of anomalous statistics in the context of the random relaxation ( RARE) model [Eliazar and Metzler, J. Chem. Phys. 137, 234106 ( 2012)], a recently introduced versatile model of random relaxations in random environments. The RARE model considers excitations scattered randomly across a metric space around a reaction center. The excitations react randomly with the center, the reaction rates depending on the excitations' distances from this center. Relaxation occurs upon the first reaction between an excitation and the center. Addressing both the relaxation time and the relaxation range, we explore when these random variables display anomalous statistics, namely, heavy tails at zero and at infinity that manifest, respectively, exceptionally high occurrence probabilities of very small and very large outliers. A cohesive set of closed-form analytic results is established, determining precisely when such anomalous statistics emerge. Y1 - 2013 U6 - https://doi.org/10.1103/PhysRevE.87.022141 SN - 1539-3755 SN - 1550-2376 VL - 87 IS - 2 PB - American Physical Society CY - College Park ER - TY - JOUR A1 - Feudel, Fred A1 - Seehafer, Norbert A1 - Tuckerman, Laurette S. A1 - Gellert, Marcus T1 - Multistability in rotating spherical shell convection JF - Physical review : E, Statistical, nonlinear and soft matter physics N2 - The multiplicity of stable convection patterns in a rotating spherical fluid shell heated from the inner boundary and driven by a central gravity field is presented. These solution branches that arise as rotating waves (RWs) are traced for varying Rayleigh number while their symmetry, stability, and bifurcations are studied. At increased Rayleigh numbers all the RWs undergo transitions to modulated rotating waves (MRWs) which are classified by their spatiotemporal symmetry. The generation of a third frequency for some of the MRWs is accompanied by a further loss of symmetry. Eventually a variety of MRWs, three-frequency solutions, and chaotic saddles and attractors control the dynamics for higher Rayleigh numbers. Y1 - 2013 U6 - https://doi.org/10.1103/PhysRevE.87.023021 SN - 1539-3755 VL - 87 IS - 2 PB - American Physical Society CY - College Park ER - TY - JOUR A1 - Oskinova, Lida A1 - Sun, W. A1 - Evans, C. J. A1 - Henault-Brunet, V. A1 - Chu, Y.-H. A1 - Gallagher, J. S. A1 - Guerrero, Martín A. A1 - Gruendl, R. A. A1 - Güdel, M. A1 - Silich, S. A1 - Chen, Y. A1 - Naze, Y. A1 - Hainich, Rainer A1 - Reyes-Iturbide, J. T1 - Discovery of x-ray emission from young suns in the small magellanic cloud JF - The astrophysical journal : an international review of spectroscopy and astronomical physics N2 - We report the discovery of extended X-ray emission within the young star cluster NGC 602a in the Wing of the Small Magellanic Cloud (SMC) based on observations obtained with the Chandra X-Ray Observatory. X-ray emission is detected from the cluster core area with the highest stellar density and from a dusty ridge surrounding the H II region. We use a census of massive stars in the cluster to demonstrate that a cluster wind or wind-blown bubble is unlikely to provide a significant contribution to the X-ray emission detected from the central area of the cluster. We therefore suggest that X-ray emission at the cluster core originates from an ensemble of low-and solar-mass pre-main-sequence (PMS) stars, each of which would be too weak in X-rays to be detected individually. We attribute the X-ray emission from the dusty ridge to the embedded tight cluster of the newborn stars known in this area from infrared studies. Assuming that the levels of X-ray activity in young stars in the low-metallicity environment of NGC 602a are comparable to their Galactic counterparts, then the detected spatial distribution, spectral properties, and level of X-ray emission are largely consistent with those expected from low-and solar-mass PMS stars and young stellar objects (YSOs). This is the first discovery of X-ray emission attributable to PMS stars and YSOs in the SMC, which suggests that the accretion and dynamo processes in young, low-mass objects in the SMC resemble those in the Galaxy. KW - Magellanic Clouds KW - ISM: bubbles KW - H II regions KW - stars: winds, outflows KW - stars: pre-main sequence KW - X-rays: stars Y1 - 2013 U6 - https://doi.org/10.1088/0004-637X/765/1/73 SN - 0004-637X VL - 765 IS - 1 PB - IOP Publ. Ltd. CY - Bristol ER - TY - JOUR A1 - Hoffmann, H. A1 - Seiß, Martin A1 - Spahn, Frank T1 - Vertical relaxation of a moonlet propeller in Saturn's a ring JF - The astrophysical journal : an international review of spectroscopy and astronomical physics ; Part 2, Letters N2 - Two images, taken by the Cassini spacecraft near Saturn's equinox in 2009 August, show the Earhart propeller casting a 350 km long shadow, offering the opportunity to watch how the ring height, excited by the propeller moonlet, relaxes to an equilibrium state. From the shape of the shadow cast and a model of the azimuthal propeller height relaxation, we determine the exponential cooling constant of this process to be lambda = 0.07 +/- 0.02 km(-1), and thereby determine the collision frequency of the ring particles in the vertically excited region of the propeller to be omega(c)/Omega = 0.9 +/- 0.2. KW - planets and satellites: individual (Saturn) KW - planets and satellites: rings Y1 - 2013 U6 - https://doi.org/10.1088/2041-8205/765/1/L4 SN - 2041-8205 VL - 765 IS - 1 PB - IOP Publ. Ltd. CY - Bristol ER - TY - JOUR A1 - Lange, J. A1 - Pohl, Martin T1 - The average GeV-band emission from gamma-ray bursts JF - Astronomy and astrophysics : an international weekly journal N2 - Aims. We analyze the emission in the 0.3-30 GeV energy range of gamma-ray bursts detected with the Fermi Gamma-ray Space Telescope. We concentrate on bursts that were previously only detected with the Gamma-Ray Burst Monitor in the keV energy range. These bursts will then be compared to the bursts that were individually detected with the Large Area Telescope at higher energies. Methods. To estimate the emission of faint GRBs we used nonstandard analysis methods and sum over many GRBs to find an average signal that is significantly above background level. We used a subsample of 99 GRBs listed in the Burst Catalog from the first two years of observation. Results. Although most are not individually detectable, the bursts not detected by the Large Area Telescope on average emit a significant flux in the energy range from 0.3 GeV to 30 GeV, but their cumulative energy fluence is only 8% of that of all GRBs. Likewise, the GeV-to-MeV flux ratio is less and the GeV-band spectra are softer. We confirm that the GeV-band emission lasts much longer than the emission found in the keV energy range. The average allsky energy flux from GRBs in the GeV band is 6.4 x 10(-4) erg cm(-2) yr(-1) or only similar to 4% of the energy flux of cosmic rays above the ankle at 10(18.6) eV. KW - methods: statistical KW - surveys KW - gamma-ray burst: general Y1 - 2013 U6 - https://doi.org/10.1051/0004-6361/201220652 SN - 0004-6361 VL - 551 IS - 1 PB - EDP Sciences CY - Les Ulis ER - TY - JOUR A1 - Hubrig, Swetlana A1 - Schoeller, M. A1 - Ilyin, Ilya A1 - Kharchenko, N. V. A1 - Oskinova, Lida A1 - Langer, N. A1 - Gonzalez, J. F. A1 - Kholtygin, A. F. A1 - Briquet, Maryline T1 - Exploring the origin of magnetic fields in massive stars - II. New magnetic field measurements in cluster and field stars JF - Astronomy and astrophysics : an international weekly journal N2 - Context. Theories on the origin of magnetic fields in massive stars remain poorly developed, because the properties of their magnetic field as function of stellar parameters could not yet be investigated. Additional observations are of utmost importance to constrain the conditions that are conducive to magnetic fields and to determine first trends about their occurrence rate and field strength distribution. Aims. To investigate whether magnetic fields in massive stars are ubiquitous or appear only in stars with a specific spectral classification, certain ages, or in a special environment, we acquired 67 new spectropolarimetric observations for 30 massive stars. Among the observed sample, roughly one third of the stars are probable members of clusters at different ages, whereas the remaining stars are field stars not known to belong to any cluster or association. Methods. Spectropolarimetric observations were obtained during four different nights using the low-resolution spectropolarimetric mode of FOcal Reducer low dispersion Spectrograph (FORS 2) mounted on the 8-m Antu telescope of the VLT. Furthermore, we present a number of follow-up observations carried out with the high-resolution spectropolarimeters SOFIN mounted at the Nordic Optical Telescope (NOT) and HARPS mounted at the ESO 3.6 m between 2008 and 2011. To assess the membership in open clusters and associations, we used astrometric catalogues with the highest quality kinematic and photometric data currently available. Results. The presence of a magnetic field is confirmed in nine stars previously observed with FORS 1/2: HD36879, HD47839, CPD-28 2561, CPD-47 2963, HD93843, HD148937, HD149757, HD328856, and HD164794. New magnetic field detections at a significance level of at least 3 sigma were achieved in five stars: HD92206c, HD93521, HD93632, CPD-46 8221, and HD157857. Among the stars with a detected magnetic field, five stars belong to open clusters with high membership probability. According to previous kinematic studies, five magnetic O-type stars in our sample are candidate runaway stars. KW - polarization KW - stars: early-type KW - stars: kinematics and dynamics KW - stars: magnetic field KW - stars: massive KW - open clusters and associations: general Y1 - 2013 U6 - https://doi.org/10.1051/0004-6361/201220721 SN - 0004-6361 VL - 551 PB - EDP Sciences CY - Les Ulis ER - TY - JOUR A1 - Abramowski, Attila A1 - Acero, F. A1 - Aharonian, Felix A. A1 - Akhperjanian, A. G. A1 - Anton, Gisela A1 - Balenderan, Shangkari A1 - Balzer, Arnim A1 - Barnacka, Anna A1 - Becherini, Yvonne A1 - Tjus, J. Becker A1 - Bernlöhr, K. A1 - Birsin, E. A1 - Biteau, Jonathan A1 - Boisson, Catherine A1 - Bolmont, J. A1 - Bordas, Pol A1 - Brucker, J. A1 - Brun, Francois A1 - Brun, Pierre A1 - Bulik, Tomasz A1 - Carrigan, Svenja A1 - Casanova, Sabrina A1 - Cerruti, M. A1 - Chadwick, Paula M. A1 - Chaves, Ryan C. G. A1 - Cheesebrough, A. A1 - Colafrancesco, Sergio A1 - Cologna, Gabriele A1 - Conrad, Jan A1 - Couturier, C. A1 - Dalton, M. A1 - Daniel, M. K. A1 - Davids, I. D. A1 - Degrange, B. A1 - Deil, C. A1 - deWilt, P. A1 - Dickinson, H. J. A1 - Djannati-Ataï, A. A1 - Domainko, W. A1 - Drury, L. O'C. A1 - Dubus, G. A1 - Dutson, K. A1 - Dyks, J. A1 - Dyrda, M. A1 - Egberts, Kathrin A1 - Eger, P. A1 - Espigat, P. A1 - Fallon, L. A1 - Farnier, C. A1 - Fegan, S. A1 - Feinstein, F. A1 - Fernandes, M. V. A1 - Fernandez, D. A1 - Fiasson, A. A1 - Fontaine, G. A1 - Foerster, A. A1 - Fuessling, M. A1 - Gajdus, M. A1 - Gallant, Y. A. A1 - Garrigoux, T. A1 - Gast, H. A1 - Giebels, B. A1 - Glicenstein, J. F. A1 - Glueck, B. A1 - Goering, D. A1 - Grondin, M. -H. A1 - Grudzinska, M. A1 - Haeffner, S. A1 - Hague, J. D. A1 - Hahn, J. A1 - Hampf, D. A1 - Harris, J. A1 - Heinz, S. A1 - Heinzelmann, G. A1 - Henri, G. A1 - Hermann, G. A1 - Hillert, A. A1 - Hinton, James Anthony A1 - Hofmann, W. A1 - Hofverberg, P. A1 - Holler, Markus A1 - Horns, D. A1 - Jacholkowska, A. A1 - Jahn, C. A1 - Jamrozy, M. A1 - Jung, I. A1 - Kastendieck, M. A. A1 - Katarzynski, K. A1 - Katz, U. A1 - Kaufmann, S. A1 - Khelifi, B. A1 - Klepser, S. A1 - Klochkov, D. A1 - Kluzniak, W. A1 - Kneiske, T. A1 - Kolitzus, D. A1 - Komin, Nu A1 - Kosack, K. A1 - Kossakowski, R. A1 - Krayzel, F. A1 - Krueger, P. P. A1 - Laffon, H. A1 - Lamanna, G. A1 - Lefaucheur, J. A1 - Lemoine-Goumard, M. A1 - Lenain, J. -P. A1 - Lennarz, D. A1 - Lohse, T. A1 - Lopatin, A. A1 - Lu, C. -C. A1 - Marandon, V. A1 - Marcowith, Alexandre A1 - Masbou, J. A1 - Maurin, G. A1 - Maxted, N. A1 - Mayer, M. A1 - McComb, T. J. L. A1 - Medina, M. C. A1 - Mehault, J. A1 - Menzler, U. A1 - Moderski, R. A1 - Mohamed, M. A1 - Moulin, Emmanuel A1 - Naumann, C. L. A1 - Naumann-Godo, M. A1 - de Naurois, M. A1 - Nedbal, D. A1 - Nguyen, N. A1 - Niemiec, J. A1 - Nolan, S. J. A1 - Oakes, L. A1 - Ohm, S. A1 - Wilhelmi, E. de Ona A1 - Opitz, B. A1 - Ostrowski, M. A1 - Oya, I. A1 - Panter, M. A1 - Parsons, R. D. A1 - Arribas, M. Paz A1 - Pekeur, N. W. A1 - Pelletier, G. A1 - Perez, J. A1 - Petrucci, P. -O. A1 - Peyaud, B. A1 - Pita, S. A1 - Puehlhofer, G. A1 - Punch, M. A1 - Quirrenbach, A. A1 - Raab, S. A1 - Raue, M. A1 - Reimer, A. A1 - Reimer, O. A1 - Renaud, M. A1 - de los Reyes, R. A1 - Rieger, F. A1 - Ripken, J. A1 - Rob, L. A1 - Rosier-Lees, S. A1 - Rowell, G. A1 - Rudak, B. A1 - Rulten, C. B. A1 - Sahakian, V. A1 - Sanchez, David M. A1 - Santangelo, Andrea A1 - Schlickeiser, R. A1 - Schulz, A. A1 - Schwanke, U. A1 - Schwarzburg, S. A1 - Schwemmer, S. A1 - Sheidaei, F. A1 - Skilton, J. L. A1 - Sol, H. A1 - Spengler, G. A1 - Stawarz, L. A1 - Steenkamp, R. A1 - Stegmann, Christian A1 - Stinzing, F. A1 - Stycz, K. A1 - Sushch, Iurii A1 - Szostek, A. A1 - Tavernet, J. -P. A1 - Terrier, R. A1 - Tluczykont, M. A1 - Trichard, C. A1 - Valerius, K. A1 - van Eldik, C. A1 - Vasileiadis, G. A1 - Venter, C. A1 - Viana, A. A1 - Vincent, P. A1 - Voelk, H. J. A1 - Volpe, F. A1 - Vorobiov, S. A1 - Vorster, M. A1 - Wagner, S. J. A1 - Ward, M. A1 - White, R. A1 - Wierzcholska, A. A1 - Willmann, P. A1 - Wouters, D. A1 - Zacharias, M. A1 - Zajczyk, A. A1 - Zdziarski, A. A. A1 - Zech, Alraune A1 - Zechlin, H. -S. T1 - HESS observations of the binary system PSR B1259-63/LS 2883 around the 2010/2011 periastron passage JF - Astronomy and astrophysics : an international weekly journal N2 - Aims. We present very high energy (VHE; E > 100 GeV) data from the gamma-ray binary system PSR B1259-63/LS 2883 taken around its periastron passage on 15th of December 2010 with the High Energy Stereoscopic System (H. E. S. S.) of Cherenkov Telescopes. We aim to search for a possible TeV counterpart of the GeV flare detected by the Fermi LAT. In addition, we aim to study the current periastron passage in the context of previous observations taken at similar orbital phases, testing the repetitive behaviour of the source. Methods. Observations at VHEs were conducted with H.E.S.S. from 9th to 16th of January 2011. The total dataset amounts to similar to 6 h of observing time. The data taken around the 2004 periastron passage were also re-analysed with the current analysis techniques in order to extend the energy spectrum above 3 TeV to fully compare observation results from 2004 and 2011. Results. The source is detected in the 2011 data at a significance level of 11.5 sigma revealing an averaged integral flux above 1 TeV of (1.01 +/- 0.18(stat) +/- 0.20(sys)) x 10(-12) cm(-2) s(-1). The differential energy spectrum follows a power-law shape with a spectral index Gamma = 2.92 +/- 0.30(stat) +/- 0.20(sys) and a flux normalisation at 1 TeV of N-0 = (1.95 +/- 0.32(stat) +/- 0.39(sys)) x 10(-12) TeV-1 cm(-2) s(-1). The measured light curve does not show any evidence for variability of the source on the daily scale. The re-analysis of the 2004 data yields results compatible with the published ones. The differential energy spectrum measured up to similar to 10 TeV is consistent with a power law with a spectral index Gamma = 2.81 +/- 0.10(stat) +/- 0.20(sys) and a flux normalisation at 1 TeV of N-0 = (1.29 +/- 0.08(stat) +/- 0.26(sys)) x 10(-12) TeV-1 cm(-2) s(-1). Conclusions. The measured integral flux and the spectral shape of the 2011 data are compatible with the results obtained around previous periastron passages. The absence of variability in the H.E.S.S. data indicates that the GeV flare observed by Fermi LAT in the time period covered also by H.E.S.S. observations originates in a different physical scenario than the TeV emission. Moreover, the comparison of the new results to the results from the 2004 observations made at a similar orbital phase provides a stronger evidence of the repetitive behaviour of the source. KW - gamma rays: general KW - pulsars: individual: PSR B1259-63 KW - X-rays: binaries KW - stars: individual: LS 2883 Y1 - 2013 U6 - https://doi.org/10.1051/0004-6361/201220612 SN - 0004-6361 VL - 551 PB - EDP Sciences CY - Les Ulis ER - TY - INPR A1 - Acharya, B. S. A1 - Actis, M. A1 - Aghajani, T. A1 - Agnetta, G. A1 - Aguilar, J. A1 - Aharonian, Felix A. A1 - Ajello, M. A1 - Akhperjanian, A. G. A1 - Alcubierre, M. A1 - Aleksic, J. A1 - Alfaro, R. A1 - Aliu, E. A1 - Allafort, A. J. A1 - Allan, D. A1 - Allekotte, I. A1 - Amato, E. A1 - Anderson, J. A1 - Angüner, Ekrem Oǧuzhan A1 - Antonelli, L. A. A1 - Antoranz, P. A1 - Aravantinos, A. A1 - Arlen, T. A1 - Armstrong, T. A1 - Arnaldi, H. A1 - Arrabito, L. A1 - Asano, K. A1 - Ashton, T. A1 - Asorey, H. G. A1 - Awane, Y. A1 - Baba, H. A1 - Babic, A. A1 - Baby, N. A1 - Baehr, J. A1 - Bais, A. A1 - Baixeras, C. A1 - Bajtlik, S. A1 - Balbo, M. A1 - Balis, D. A1 - Balkowski, C. A1 - Bamba, A. A1 - Bandiera, R. A1 - Barber, A. A1 - Barbier, C. A1 - Barcelo, M. A1 - Barnacka, Anna A1 - Barnstedt, Jürgen A1 - Barres de Almeida, U. A1 - Barrio, J. A. A1 - Basili, A. A1 - Basso, S. A1 - Bastieri, D. A1 - Bauer, C. A1 - Baushev, Anton N. A1 - Becerra Gonzalez, J. A1 - Becherini, Yvonne A1 - Bechtol, K. C. A1 - Tjus, J. Becker A1 - Beckmann, Volker A1 - Bednarek, W. A1 - Behera, B. A1 - Belluso, M. A1 - Benbow, W. A1 - Berdugo, J. A1 - Berger, K. A1 - Bernard, F. A1 - Bernardino, T. A1 - Bernlöhr, K. A1 - Bhat, N. A1 - Bhattacharyya, S. A1 - Bigongiari, C. A1 - Biland, A. A1 - Billotta, S. A1 - Bird, T. A1 - Birsin, E. A1 - Bissaldi, E. A1 - Biteau, Jonathan A1 - Bitossi, M. A1 - Blake, S. A1 - Blanch Bigas, O. A1 - Blasi, P. A1 - Bobkov, A. A. A1 - Boccone, V. A1 - Boettcher, Markus A1 - Bogacz, L. A1 - Bogart, J. A1 - Bogdan, M. A1 - Boisson, Catherine A1 - Boix Gargallo, J. A1 - Bolmont, J. A1 - Bonanno, G. A1 - Bonardi, A. A1 - Bonev, T. A1 - Bonifacio, P. A1 - Bonnoli, G. A1 - Bordas, Pol A1 - Borgland, A. W. A1 - Borkowski, Janett A1 - Bose, R. A1 - Botner, O. A1 - Bottani, A. A1 - Bouchet, L. A1 - Bourgeat, M. A1 - Boutonnet, C. A1 - Bouvier, A. A1 - Brau-Nogue, S. A1 - Braun, I. A1 - Bretz, T. A1 - Briggs, M. S. A1 - Bringmann, T. A1 - Brook, P. A1 - Brun, Pierre A1 - Brunetti, L. A1 - Buanes, T. A1 - Buckley, J. H. A1 - Buehler, R. A1 - Bugaev, V. A1 - Bulgarelli, A. A1 - Bulik, Tomasz A1 - Busetto, G. A1 - Buson, S. A1 - Byrum, K. A1 - Cailles, M. A1 - Cameron, R. A. A1 - Camprecios, J. A1 - Canestrari, R. A1 - Cantu, S. A1 - Capalbi, M. A1 - Caraveo, P. A. A1 - Carmona, E. A1 - Carosi, A. A1 - Carr, John A1 - Carton, P. H. A1 - Casanova, Sabrina A1 - Casiraghi, M. A1 - Catalano, O. A1 - Cavazzani, S. A1 - Cazaux, S. A1 - Cerruti, M. A1 - Chabanne, E. A1 - Chadwick, Paula M. A1 - Champion, C. A1 - Chen, Andrew A1 - Chiang, J. A1 - Chiappetti, L. A1 - Chikawa, M. A1 - Chitnis, V. R. A1 - Chollet, F. A1 - Chudoba, J. A1 - Cieslar, M. A1 - Cillis, A. N. A1 - Cohen-Tanugi, J. A1 - Colafrancesco, Sergio A1 - Colin, P. A1 - Calome, J. A1 - Colonges, S. A1 - Compin, M. A1 - Conconi, P. A1 - Conforti, V. A1 - Connaughton, V. A1 - Conrad, Jan A1 - Contreras, J. L. A1 - Coppi, P. A1 - Corona, P. A1 - Corti, D. A1 - Cortina, J. A1 - Cossio, L. A1 - Costantini, H. A1 - Cotter, G. A1 - Courty, B. A1 - Couturier, S. A1 - Covino, S. A1 - Crimi, G. A1 - Criswell, S. J. A1 - Croston, J. A1 - Cusumano, G. A1 - Dafonseca, M. A1 - Dale, O. A1 - Daniel, M. A1 - Darling, J. A1 - Davids, I. A1 - Dazzi, F. A1 - De Angelis, A. A1 - De Caprio, V. A1 - De Frondat, F. A1 - de Gouveia Dal Pino, E. M. A1 - de la Calle, I. A1 - De La Vega, G. A. A1 - Lopez, R. de los Reyes A1 - De Lotto, B. A1 - De Luca, A. A1 - de Mello Neto, J. R. T. A1 - de Naurois, M. A1 - de Oliveira, Y. A1 - de Ona Wilhelmi, E. A1 - de Souza, V. A1 - Decerprit, G. A1 - Decock, G. A1 - Deil, C. A1 - Delagnes, E. A1 - Deleglise, G. A1 - Delgado, C. A1 - Della Volpe, D. A1 - Demange, P. A1 - Depaola, G. 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A1 - Trifoglio, M. A1 - Troyano, I. A1 - Tsinganos, K. A1 - Ueno, H. A1 - Umehara, K. A1 - Upadhya, S. S. A1 - Usher, T. A1 - Uslenghi, M. A1 - Valdes-Galicia, J. F. A1 - Vallania, P. A1 - Vallejo, G. A1 - van Driel, W. A1 - van Eldik, C. A1 - Vandenbrouke, J. A1 - Vanderwalt, J. A1 - Vankov, H. A1 - Vasileiadis, G. A1 - Vassiliev, V. A1 - Veberic, D. A1 - Vegas, I. A1 - Vercellone, S. A1 - Vergani, S. A1 - Veyssiere, C. A1 - Vialle, J. P. A1 - Viana, A. A1 - Videla, M. A1 - Vincent, P. A1 - Vincent, S. A1 - Vink, J. A1 - Vlahakis, N. A1 - Vlahos, L. A1 - Vogler, P. A1 - Vollhardt, A. A1 - von Gunten, H. P. A1 - Vorobiov, S. A1 - Vuerli, C. A1 - Waegebaert, V. A1 - Wagner, R. A1 - Wagner, R. G. A1 - Wagner, S. A1 - Wakely, S. P. A1 - Walter, R. A1 - Walther, T. A1 - Warda, K. 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 - Werner, M. A1 - Wetteskind, H. A1 - White, R. A1 - Wierzcholska, A. A1 - Wiesand, S. A1 - Wilkinson, M. A1 - Williams, D. A. A1 - Willingale, R. A1 - Winiarski, K. A1 - Wischnewski, R. A1 - Wisniewski, L. A1 - Wood, M. A1 - Woernlein, A. A1 - Xiong, Q. A1 - Yadav, K. K. A1 - Yamamoto, H. A1 - Yamamoto, T. A1 - Yamazaki, R. A1 - Yanagita, S. A1 - Yebras, J. M. A1 - Yelos, D. A1 - Yoshida, A. A1 - Yoshida, T. A1 - Yoshikoshi, T. A1 - Zabalza, V. A1 - Zacharias, M. A1 - Zajczyk, A. A1 - Zanin, R. A1 - Zdziarski, A. A1 - Zech, Alraune A1 - Zhao, A. A1 - Zhou, X. A1 - Zietara, K. A1 - Ziolkowski, J. A1 - Ziolkowski, P. A1 - Zitelli, V. A1 - Zurbach, C. A1 - Zychowski, P. T1 - Introducing the CTA concept T2 - Astroparticle physics N2 - The Cherenkov Telescope Array (CTA) is a new observatory for very high-energy (VHE) gamma rays. CTA has ambitions science goals, for which it is necessary to achieve full-sky coverage, to improve the sensitivity by about an order of magnitude, to span about four decades of energy, from a few tens of GeV to above 100 TeV with enhanced angular and energy resolutions over existing VHE gamma-ray observatories. An international collaboration has formed with more than 1000 members from 27 countries in Europe, Asia, Africa and North and South America. In 2010 the CTA Consortium completed a Design Study and started a three-year Preparatory Phase which leads to production readiness of CTA in 2014. In this paper we introduce the science goals and the concept of CTA, and provide an overview of the project. KW - TeV gamma-ray astronomy KW - Air showers KW - Cherenkov Telescopes Y1 - 2013 U6 - https://doi.org/10.1016/j.astropartphys.2013.01.007 SN - 0927-6505 SN - 1873-2852 VL - 43 IS - 2 SP - 3 EP - 18 PB - Elsevier CY - Amsterdam ER - TY - JOUR A1 - Burgemeister, S. A1 - Gvaramadze, Visily V. A1 - Stringfellow, G. S. A1 - Kniazev, Alexei Y. A1 - Todt, Helge Tobias A1 - Hamann, Wolf-Rainer T1 - WR 120bb and WR 120bc: a pair of WN9h stars with possibly interacting circumstellar shells JF - Monthly notices of the Royal Astronomical Society N2 - Two optically obscured Wolf-Rayet (WR) stars have been recently discovered by means of their infrared (IR) circumstellar shells, which show signatures of interaction with each other. Following the systematics of the WR star catalogues, these stars obtain the names WR 120bb and WR 120bc. In this paper, we present and analyse new near-IR, J-, H- and K-band spectra using the Potsdam Wolf-Rayet model atmosphere code. For that purpose, the atomic data base of the code has been extended in order to include all significant lines in the near-IR bands. The spectra of both stars are classified as WN9h. As their spectra are very similar the parameters that we obtained by the spectral analyses hardly differ. Despite their late spectral subtype, we found relatively high stellar temperatures of 63 kK. The wind composition is dominated by helium, while hydrogen is depleted to 25 per cent by mass. Because of their location in the Scutum-Centaurus Arm, WR 120bb and WR 120bc appear highly reddened, A(Ks) approximate to 2 mag. We adopt a common distance of 5.8 kpc to both stars, which complies with the typical absolute K-band magnitude for the WN9h subtype of -6.5 mag, is consistent with their observed extinction based on comparison with other massive stars in the region, and allows for the possibility that their shells are interacting with each other. This leads to luminosities of log(L/L-circle dot) = 5.66 and 5.54 for WR 120bb and WR 120bc, with large uncertainties due to the adopted distance. The values of the luminosities of WR 120bb and WR 120bc imply that the immediate precursors of both stars were red supergiants (RSG). This implies in turn that the circumstellar shells associated with WR 120bb and WR 120bc were formed by interaction between the WR wind and the dense material shed during the preceding RSG phase. KW - line: identification KW - circumstellar matter KW - stars: fundamental parameters KW - stars: massive KW - stars: Wolf-Rayet Y1 - 2013 U6 - https://doi.org/10.1093/mnras/sts588 SN - 0035-8711 SN - 1365-2966 VL - 429 IS - 4 SP - 3305 EP - 3315 PB - Oxford Univ. Press CY - Oxford ER - TY - JOUR A1 - Lu, Guanghao A1 - Blakesley, James C. A1 - Himmelberger, Scott A1 - Pingel, Patrick A1 - Frisch, Johannes A1 - Lieberwirth, Ingo A1 - Salzmann, Ingo A1 - Oehzelt, Martin A1 - Di Pietro, Riccardo A1 - Salleo, Alberto A1 - Koch, Norbert A1 - Neher, Dieter T1 - Moderate doping leads to high performance of semiconductor/insulator polymer blend transistors JF - Nature Communications N2 - Polymer transistors are being intensively developed for next-generation flexible electronics. Blends comprising a small amount of semiconducting polymer mixed into an insulating polymer matrix have simultaneously shown superior performance and environmental stability in organic field-effect transistors compared with the neat semiconductor. Here we show that such blends actually perform very poorly in the undoped state, and that mobility and on/off ratio are improved dramatically upon moderate doping. Structural investigations show that these blend layers feature nanometre-scale semiconductor domains and a vertical composition gradient. This particular morphology enables a quasi three-dimensional spatial distribution of semiconductor pathways within the insulating matrix, in which charge accumulation and depletion via a gate bias is substantially different from neat semiconductor, and where high on-current and low off-current are simultaneously realized in the stable doped state. Adding only 5 wt% of a semiconducting polymer to a polystyrene matrix, we realized an environmentally stable inverter with gain up to 60. Y1 - 2013 U6 - https://doi.org/10.1038/ncomms2587 SN - 2041-1723 VL - 4 IS - 1-2 PB - Nature Publ. Group CY - London ER - TY - JOUR A1 - Westendorf, Christian A1 - Negrete, Jose A1 - Bae, Albert J. A1 - Sandmann, Rabea A1 - Bodenschatz, Eberhard A1 - Beta, Carsten T1 - Actin cytoskeleton of chemotactic amoebae operates close to the onset of oscillations JF - Proceedings of the National Academy of Sciences of the United States of America N2 - The rapid reorganization of the actin cytoskeleton in response to external stimuli is an essential property of many motile eukaryotic cells. Here, we report evidence that the actin machinery of chemotactic Dictyostelium cells operates close to an oscillatory instability. When averaging the actin response of many cells to a short pulse of the chemoattractant cAMP, we observed a transient accumulation of cortical actin reminiscent of a damped oscillation. At the single-cell level, however, the response dynamics ranged from short, strongly damped responses to slowly decaying, weakly damped oscillations. Furthermore, in a small subpopulation, we observed self-sustained oscillations in the cortical F-actin concentration. To substantiate that an oscillatory mechanism governs the actin dynamics in these cells, we systematically exposed a large number of cells to periodic pulse trains of different frequencies. Our results indicate a resonance peak at a stimulation period of around 20 s. We propose a delayed feedback model that explains our experimental findings based on a time-delay in the regulatory network of the actin system. To test the model, we performed stimulation experiments with cells that express GFP-tagged fusion proteins of Coronin and actin-interacting protein 1, as well as knockout mutants that lack Coronin and actin-interacting protein 1. These actin-binding proteins enhance the disassembly of actin filaments and thus allow us to estimate the delay time in the regulatory feedback loop. Based on this independent estimate, our model predicts an intrinsic period of 20 s, which agrees with the resonance observed in our periodic stimulation experiments. KW - Dictyostelium discoideum KW - microfluidics KW - caged cAMP KW - delay-differential equation Y1 - 2013 U6 - https://doi.org/10.1073/pnas.1216629110 SN - 0027-8424 VL - 110 IS - 10 SP - 3853 EP - 3858 PB - National Acad. of Sciences CY - Washington ER - TY - JOUR A1 - Beye, Martin A1 - Föhlisch, Alexander T1 - Soft X-ray probes of ultrafast dynamics for heterogeneous catalysis JF - Chemical physics : a journal devoted to experimental and theoretical research involving problems of both a chemical and physical nature N2 - Soft X-ray spectroscopy is one of the best tools to directly address the electronic structure, the driving force of chemical reactions. It enables selective studies on sample surfaces to single out reaction centers in heterogeneous catalytic reactions. With core-hole clock methods, specific dynamics are related to the femtosecond life time of a core-hole. Typically, this method is used with photoemission spectroscopy, but advancements in soft X-ray emission techniques render more specific studies possible. With the advent of bright femtosecond pulsed soft X-ray sources, highly selective pump-probe X-ray emission studies are enabled with temporal resolutions down to tens of femtoseconds. This finally allows to study dynamics in the electronic structure of adsorbed reaction centers on the whole range of relevant time scales - closing the gap between kinetic soft X-ray studies and the atto- to femtosecond core-hole clock techniques. KW - Core-hole clock KW - Resonant inelastic X-ray scattering KW - Ultrafast surface science KW - Photoelectron spectroscopy Y1 - 2013 U6 - https://doi.org/10.1016/j.chemphys.2012.03.023 SN - 0301-0104 SN - 1873-4421 VL - 414 IS - 5 SP - 130 EP - 138 PB - Elsevier CY - Amsterdam ER - TY - JOUR A1 - Jechow, Andreas A1 - Norton, B. G. A1 - Händel, S. A1 - Blums, V. A1 - Streed, E. W. A1 - Kielpinski, D. T1 - Controllable optical phase shift over one radian from a single isolated atom JF - Physical review letters N2 - Fundamental optics such as lenses and prisms work by applying phase shifts of several radians to incoming light, and rapid control of such phase shifts is crucial to telecommunications. However, large, controllable optical phase shifts have remained elusive for isolated quantum systems. We have used a single trapped atomic ion to induce and measure a large optical phase shift of 1.3 +/- 0.1 radians in light scattered by the atom. Spatial interferometry between the scattered light and unscattered illumination light enables us to isolate the phase shift in the scattered component. The phase shift achieves the maximum value allowed by atomic theory over the accessible range of laser frequencies, pointing out new opportunities in microscopy and nanophotonics. Single-atom phase shifts of this magnitude open up new quantum information protocols, in particular long-range quantum phase-shift-keying cryptography. DOI: 10.1103/PhysRevLett.110.113605 Y1 - 2013 U6 - https://doi.org/10.1103/PhysRevLett.110.113605 SN - 0031-9007 VL - 110 IS - 11 PB - American Physical Society CY - College Park ER - TY - JOUR A1 - Dell'Angela, M. A1 - Anniyev, Toyli A1 - Beye, Martin A1 - Coffee, Ryan A1 - Föhlisch, Alexander A1 - Gladh, J. A1 - Katayama, T. A1 - Kaya, S. A1 - Krupin, O. A1 - LaRue, J. A1 - Mogelhoj, A. A1 - Nordlund, D. A1 - Norskov, J. K. A1 - Oberg, H. A1 - Ogasawara, H. A1 - Ostrom, H. A1 - Pettersson, Lars G. M. A1 - Schlotter, W. F. A1 - Sellberg, J. A. A1 - Sorgenfrei, Nomi A1 - Turner, J. J. A1 - Wolf, M. A1 - Wurth, W. A1 - Nilsson, A. T1 - Real-time observation of surface bond breaking with an X-ray Laser JF - Science N2 - We used the Linac Coherent Light Source free-electron x-ray laser to probe the electronic structure of CO molecules as their chemisorption state on Ru(0001) changes upon exciting the substrate by using a femtosecond optical laser pulse. We observed electronic structure changes that are consistent with a weakening of the CO interaction with the substrate but without notable desorption. A large fraction of the molecules (30%) was trapped in a transient precursor state that would precede desorption. We calculated the free energy of the molecule as a function of the desorption reaction coordinate using density functional theory, including van der Waals interactions. Two distinct adsorption wells-chemisorbed and precursor state separated by an entropy barrier-explain the anomalously high prefactors often observed in desorption of molecules from metals. Y1 - 2013 U6 - https://doi.org/10.1126/science.1231711 SN - 0036-8075 VL - 339 IS - 6125 SP - 1302 EP - 1305 PB - American Assoc. for the Advancement of Science CY - Washington ER - TY - JOUR A1 - Pohl, Martin A1 - Eichler, David T1 - Understanding TeV-band cosmic-ray anistropy JF - The astrophysical journal : an international review of spectroscopy and astronomical physics N2 - We investigate the temporal and spectral correlations between flux and anisotropy fluctuations of TeV-band cosmic rays in light of recent data taken with IceCube. We find that for a conventional distribution of cosmic-ray sources, the dipole anisotropy is higher than observed, even if source discreteness is taken into account. Moreover, even for a shallow distribution of galactic cosmic-ray sources and a reacceleration model, fluctuations arising from source discreteness provide a probability only of the order of 10% that the cosmic-ray anisotropy limits of the recent IceCube analysis are met. This probability estimate is nearly independent of the exact choice of source rate, but generous for a large halo size. The location of the intensity maximum far from the Galactic Center is naturally reproduced. KW - cosmic rays Y1 - 2013 U6 - https://doi.org/10.1088/0004-637X/766/1/4 SN - 0004-637X VL - 766 IS - 1 PB - IOP Publ. Ltd. CY - Bristol ER - TY - JOUR A1 - Kuptsov, Pavel V. A1 - Kuznetsov, Sergey P. A1 - Pikovskij, Arkadij T1 - Hyperbolic chaos at blinking coupling of noisy oscillators JF - Physical review : E, Statistical, nonlinear and soft matter physics N2 - We study an ensemble of identical noisy phase oscillators with a blinking mean-field coupling, where onecluster and two-cluster synchronous states alternate. In the thermodynamic limit the population is described by a nonlinear Fokker-Planck equation. We show that the dynamics of the order parameters demonstrates hyperbolic chaos. The chaoticity manifests itself in phases of the complex mean field, which obey a strongly chaotic Bernoulli map. Hyperbolicity is confirmed by numerical tests based on the calculations of relevant invariant Lyapunov vectors and Lyapunov exponents. We show how the chaotic dynamics of the phases is slightly smeared by finite-size fluctuations. DOI: 10.1103/PhysRevE.87.032912 Y1 - 2013 U6 - https://doi.org/10.1103/PhysRevE.87.032912 SN - 1539-3755 VL - 87 IS - 3 PB - American Physical Society CY - College Park ER - TY - JOUR A1 - Komarov, Maxim A1 - Pikovskij, Arkadij T1 - Dynamics of multifrequency oscillator communities JF - Physical review letters N2 - We consider a generalization of the Kuramoto model of coupled oscillators to the situation where communities of oscillators having essentially different natural frequencies interact. General equations describing possible resonances between the communities' frequencies are derived. The simplest situation of three resonantly interacting groups is analyzed in detail. We find conditions for the mutual coupling to promote or suppress synchrony in individual populations and present examples where the interaction between communities leads to their synchrony or to a partially asynchronous state or to a chaotic dynamics of order parameters. DOI: 10.1103/PhysRevLett.110.134101 Y1 - 2013 U6 - https://doi.org/10.1103/PhysRevLett.110.134101 SN - 0031-9007 VL - 110 IS - 13 PB - American Physical Society CY - College Park ER - TY - JOUR A1 - Pingel, P. A1 - Neher, Dieter T1 - Comprehensive picture of p-type doping of P3HT with the molecular acceptor F(4)TCNQ JF - Physical review : B, Condensed matter and materials physics N2 - By means of optical spectroscopy, Kelvin probe, and conductivity measurements, we study the p-type doping of the donor polymer poly(3-hexylthiophene), P3HT, with the molecular acceptor tetrafluorotetracyanoquin-odimethane, F(4)TCNQ, covering a broad range of molar doping ratios from the ppm to the percent regime. Thorough quantitative analysis of the specific near-infrared absorption bands of ionized F(4)TCNQ reveals that almost every F(4)TCNQ dopant undergoes integer charge transfer with a P3HT site. However, only about 5% of these charge carrier pairs are found to dissociate and contribute a free hole for electrical conduction. The nonlinear behavior of the conductivity on doping ratio is rationalized by a numerical mobility model that accounts for the broadening of the energetic distribution of transport sites by the Coulomb potentials of ionized F(4)TCNQ dopants. DOI: 10.1103/PhysRevB.87.115209 Y1 - 2013 U6 - https://doi.org/10.1103/PhysRevB.87.115209 SN - 1098-0121 VL - 87 IS - 11 PB - American Physical Society CY - College Park ER - TY - JOUR A1 - Eschenlohr, Andrea A1 - Battiato, Marco A1 - Maldonado, R. A1 - Pontius, N. A1 - Kachel, T. A1 - Holldack, K. A1 - Mitzner, Rolf A1 - Föhlisch, Alexander A1 - Oppeneer, P. M. A1 - Stamm, C. T1 - Ultrafast spin transport as key to femtosecond demagnetization JF - Nature materials N2 - Irradiating a ferromagnet with a femtosecond laser pulse is known to induce an ultrafast demagnetization within a few hundred femtoseconds. Here we demonstrate that direct laser irradiation is in fact not essential for ultrafast demagnetization, and that electron cascades caused by hot electron currents accomplish it very efficiently. We optically excite a Au/Ni layered structure in which the 30 nm Au capping layer absorbs the incident laser pump pulse and subsequently use the X-ray magnetic circular dichroism technique to probe the femtosecond demagnetization of the adjacent 15 nm Ni layer. A demagnetization effect corresponding to the scenario in which the laser directly excites the Ni film is observed, but with a slight temporal delay. We explain this unexpected observation by means of the demagnetizing effect of a superdiffusive current of non-equilibrium, non-spin-polarized electrons generated in the Au layer. Y1 - 2013 U6 - https://doi.org/10.1038/NMAT3546 SN - 1476-1122 VL - 12 IS - 4 SP - 332 EP - 336 PB - Nature Publ. Group CY - London ER - TY - JOUR A1 - Dieckmann, M. E. A1 - Ahmed, H. A1 - Sarri, G. A1 - Doria, D. A1 - Kourakis, I. A1 - Romagnani, L. A1 - Pohl, Martin A1 - Borghesi, M. T1 - Parametric study of non-relativistic electrostatic shocks and the structure of their transition layer JF - Physics of plasmas N2 - Nonrelativistic electrostatic unmagnetized shocks are frequently observed in laboratory plasmas and they are likely to exist in astrophysical plasmas. Their maximum speed, expressed in units of the ion acoustic speed far upstream of the shock, depends only on the electron-to-ion temperature ratio if binary collisions are absent. The formation and evolution of such shocks is examined here for a wide range of shock speeds with particle-in-cell simulations. The initial temperatures of the electrons and the 400 times heavier ions are equal. Shocks form on electron time scales at Mach numbers between 1.7 and 2.2. Shocks with Mach numbers up to 2.5 form after tens of inverse ion plasma frequencies. The density of the shock-reflected ion beam increases and the number of ions crossing the shock thus decreases with an increasing Mach number, causing a slower expansion of the downstream region in its rest frame. The interval occupied by this ion beam is on a positive potential relative to the far upstream. This potential pre-heats the electrons ahead of the shock even in the absence of beam instabilities and decouples the electron temperature in the foreshock ahead of the shock from the one in the far upstream plasma. The effective Mach number of the shock is reduced by this electron heating. This effect can potentially stabilize nonrelativistic electrostatic shocks moving as fast as supernova remnant shocks. Y1 - 2013 U6 - https://doi.org/10.1063/1.4801447 SN - 1070-664X VL - 20 IS - 4 PB - American Institute of Physics CY - Melville ER - TY - JOUR A1 - Heydari, Esmaeil A1 - Flehr, Roman A1 - Stumpe, Joachim T1 - Influence of spacer layer on enhancement of nanoplasmon-assisted random lasing JF - Applied physics letters N2 - Threshold reduction and emission enhancement are reported for a gold nanoparticle-based waveguided random laser, exploiting the localized surface plasmon resonance excitation. It was experimentally found that a proper thickness of the spacer layer between the gold nanoparticles and the gain layer enhances the random laser performance. It tunes the coupling between the gain polymer and the gold nanoparticles and avoids the quenching of emission in close contact to the gold nanoparticles which is considered as one of the main sources of loss in the current laser system. (C) 2013 American Institute of Physics. [http://dx.doi.org/10.1063/1.4800776] Y1 - 2013 U6 - https://doi.org/10.1063/1.4800776 SN - 0003-6951 VL - 102 IS - 13 PB - American Institute of Physics CY - Melville ER - TY - JOUR A1 - Todt, Helge Tobias A1 - Kniazev, A. Y. A1 - Gvaramadze, V. V. A1 - Hamann, Wolf-Rainer A1 - Buckley, D. A1 - Crause, L. A1 - Crawford, S. M. A1 - Gulbis, A. A. S. A1 - Hettlage, C. A1 - Hooper, E. A1 - Husser, T. -O. A1 - Kotze, P. A1 - Loaring, N. A1 - Nordsieck, K. H. A1 - O'Donoghue, D. A1 - Pickering, T. A1 - Potter, S. A1 - Romero-Colmenero, E. A1 - Vaisanen, P. A1 - Williams, T. A1 - Wolf, M. T1 - Abell 48-a rare WN-type central star of a planetary nebula JF - Monthly notices of the Royal Astronomical Society N2 - A considerable fraction of the central stars of planetary nebulae (CSPNe) are hydrogen-deficient. Almost all of these H-deficient central stars (CSs) display spectra with strong carbon and helium lines. Most of them exhibit emission-line spectra resembling those of massive WC stars. Therefore these stars are classed as CSPNe of spectral type [WC]. Recently, quantitative spectral analysis of two emission-line CSs, PB 8 and IC 4663, revealed that these stars do not belong to the [WC] class. Instead PB 8 has been classified as [WN/WC] type and IC 4663 as [WN] type. In this work we report the spectroscopic identification of another rare [WN] star, the CS of Abell 48. We performed a spectral analysis of Abell 48 with the Potsdam Wolf-Rayet (PoWR) models for expanding atmospheres. We find that the expanding atmosphere of Abell 48 is mainly composed of helium (85 per cent by mass), hydrogen (10 per cent) and nitrogen (5 per cent). The residual hydrogen and the enhanced nitrogen abundance make this object different from the other [WN] star IC 4663. We discuss the possible origin of this atmospheric composition. KW - stars: abundances KW - stars: AGB and post-AGB KW - stars: mass-loss KW - stars: Wolf-Rayet KW - planetary nebulae: general KW - planetary nebulae: individual: PN G029.0+00.4 Y1 - 2013 U6 - https://doi.org/10.1093/mnras/stt056 SN - 0035-8711 SN - 1365-2966 VL - 430 IS - 3 SP - 2302 EP - 2312 PB - Oxford Univ. Press CY - Oxford ER - TY - JOUR A1 - Katayama, T. A1 - Anniyev, Toyli A1 - Beye, Martin A1 - Coffee, Ryan A1 - Dell'Angela, M. A1 - Föhlisch, Alexander A1 - Gladh, J. A1 - Kaya, S. A1 - Krupin, O. A1 - Nilsson, A. A1 - Nordlund, D. A1 - Schlotter, W. F. A1 - Sellberg, J. A. A1 - Sorgenfrei, Nomi A1 - Turner, J. J. A1 - Wurth, W. A1 - Öström, H. A1 - Ogasawara, H. T1 - Ultrafast soft X-ray emission spectroscopy of surface adsorbates using an X-ray free electron laser JF - Journal of electron spectroscopy and related phenomena : the international journal on theoretical and experimental aspects of electron spectroscopy N2 - We report on an experimental system designed to probe chemical reactions on solid surfaces on a sub-picosecond timescale using soft X-ray emission spectroscopy at the Linac Coherent Light Source (LCLS) free electron laser (FEL) at the SLAC National Accelerator Laboratory. We analyzed the O 1s X-ray emission spectra recorded from atomic oxygen adsorbed on a Ru(0001) surface at a synchrotron beamline (SSRL, BL13-2) and an FEL beamline (LCLS, SXR). We have demonstrated conditions that provide negligible amount of FEL induced damage of the sample. In addition we show that the setup is capable of tracking the temporal evolution of electronic structure during a surface reaction of submonolayer quantities of CO molecules desorbing from the surface. KW - X-ray emission spectroscopy KW - Surface science KW - Free electron laser KW - Ultrafast Y1 - 2013 U6 - https://doi.org/10.1016/j.elspec.2013.03.006 SN - 0368-2048 VL - 187 IS - 1 SP - 9 EP - 14 PB - Elsevier CY - Amsterdam ER - TY - CHAP A1 - Santer, Svetlana A1 - Zakrevskyy, Yuriy T1 - Reversible light-controlled compaction of soft colloids by azobenzene containing surfactant T2 - Abstracts of papers : joint conference / The Chemical Institute of Cananda, CIC, American Chemical Society, ACS Y1 - 2013 SN - 0065-7727 VL - 245 PB - American Chemical Society CY - Washington ER - TY - JOUR A1 - Toenjes, Ralf A1 - Sokolov, Igor M. A1 - Postnikov, E. B. T1 - Non-spectral relaxation in one dimensional Ornstein-Uhlenbeck processes JF - Physical review letters N2 - The relaxation of a dissipative system to its equilibrium state often shows a multiexponential pattern with relaxation rates, which are typically considered to be independent of the initial condition. The rates follow from the spectrum of a Hermitian operator obtained by a similarity transformation of the initial Fokker-Planck operator. However, some initial conditions are mapped by this similarity transformation to functions which growat infinity. These cannot be expanded in terms of the eigenfunctions of a Hermitian operator, and show different relaxation patterns. Considering the exactly solvable examples of Gaussian and generalized Levy Ornstein-Uhlenbeck processes (OUPs) we show that the relaxation rates belong to the Hermitian spectrum only if the initial condition belongs to the domain of attraction of the stable distribution defining the noise. While for an ordinary OUP initial conditions leading to nonspectral relaxation can be considered exotic, for generalized OUPs driven by Levy noise, such initial conditions are the rule. DOI: 10.1103/PhysRevLett.110.150602 Y1 - 2013 U6 - https://doi.org/10.1103/PhysRevLett.110.150602 SN - 0031-9007 VL - 110 IS - 15 PB - American Physical Society CY - College Park ER - TY - JOUR A1 - Jeon, Jae-Hyung A1 - Leijnse, Natascha A1 - Oddershede, Lene B. A1 - Metzler, Ralf T1 - Anomalous diffusion and power-law relaxation of the time averaged mean squared displacement in worm-like micellar solutions JF - New journal of physics : the open-access journal for physics N2 - We report the results of single tracer particle tracking by optical tweezers and video microscopy in micellar solutions. From careful analysis in terms of different stochastic models, we show that the polystyrene tracer beads of size 0.52-2.5 mu m after short-time normal diffusion turn over to perform anomalous diffusion of the form < r(2)(t)> similar or equal to t(alpha) with alpha approximate to 0.3. This free anomalous diffusion is ergodic and consistent with a description in terms of the generalized Langevin equation with a power-law memory kernel. With optical tweezers tracking, we unveil a power-law relaxation over several decades in time to the thermal plateau value under the confinement of the harmonic tweezer potential, as predicted previously (Phys. Rev. E 85 021147 (2012)). After the subdiffusive motion in the millisecond range, the motion becomes faster and turns either back to normal Brownian diffusion or to even faster superdiffusion, depending on the size of the tracer beads. Y1 - 2013 U6 - https://doi.org/10.1088/1367-2630/15/4/045011 SN - 1367-2630 VL - 15 IS - 4 PB - IOP Publ. Ltd. CY - Bristol ER - TY - JOUR A1 - Isaeva, Olga B. A1 - Kuznetsov, Alexey S. A1 - Kuznetsov, Sergey P. T1 - Hyperbolic chaos of standing wave patterns generated parametrically by a modulated pump source JF - Physical review : E, Statistical, nonlinear and soft matter physics N2 - We outline a possibility of hyperbolic chaotic dynamics associated with the expanding circle map for spatial phases of parametrically excited standing wave patterns. The model system is governed by a one-dimensional wave equation with nonlinear dissipation. The phenomenon arises due to the pump modulation providing the alternating excitation of modes with the ratio of characteristic scales 1 : 3. DOI: 10.1103/PhysRevE.87.040901 Y1 - 2013 U6 - https://doi.org/10.1103/PhysRevE.87.040901 SN - 1539-3755 VL - 87 IS - 4 PB - American Physical Society CY - College Park ER - TY - JOUR A1 - Tiscareno, Matthew S. A1 - Mitchell, Colin J. A1 - Murray, Carl D. A1 - Di Nino, Daiana A1 - Hedman, Matthew M. A1 - Schmidt, Jürgen A1 - Burns, Joseph A. A1 - Cuzzi, Jeffrey N. A1 - Porco, Carolyn C. A1 - Beurle, Kevin A1 - Evans, Michael W. T1 - Observations of Ejecta clouds produced by impacts onto Saturn's rings JF - Science N2 - We report observations of dusty clouds in Saturn's rings, which we interpret as resulting from impacts onto the rings that occurred between 1 and 50 hours before the clouds were observed. The largest of these clouds was observed twice; its brightness and cant angle evolved in a manner consistent with this hypothesis. Several arguments suggest that these clouds cannot be due to the primary impact of one solid meteoroid onto the rings, but rather are due to the impact of a compact stream of Saturn-orbiting material derived from previous breakup of a meteoroid. The responsible interplanetary meteoroids were initially between 1 centimeter and several meters in size, and their influx rate is consistent with the sparse prior knowledge of smaller meteoroids in the outer solar system. Y1 - 2013 U6 - https://doi.org/10.1126/science.1233524 SN - 0036-8075 VL - 340 IS - 6131 SP - 460 EP - 464 PB - American Assoc. for the Advancement of Science CY - Washington ER - TY - JOUR A1 - Vahabi, Mahsa A1 - Schulz, Johannes H. P. A1 - Shokri, Babak A1 - Metzler, Ralf T1 - Area coverage of radial Levy flights with periodic boundary conditions JF - Physical review : E, Statistical, nonlinear and soft matter physics N2 - We consider the area coverage of radial Levy flights in a finite square area with periodic boundary conditions. From simulations we show how the fractal path dimension d(f) and thus the degree of area coverage depends on the number of steps of the trajectory, the size of the area, and the resolution of the applied box counting algorithm. For sufficiently long trajectories and not too high resolution, the fractal dimension returned by the box counting method equals two, and in that sense the Levy flight fully covers the area. Otherwise, the determined fractal dimension equals the stable index of the distribution of jump lengths of the Levy flight. We provide mathematical expressions for the turnover between these two scaling regimes. As complementary methods to analyze confined Levy flights we investigate fractional order moments of the position for which we also provide scaling arguments. Finally, we study the time evolution of the probability density function and the first passage time density of Levy flights in a square area. Our findings are of interest for a general understanding of Levy flights as well as for the analysis of recorded trajectories of animals searching for food or for human motion patterns. Y1 - 2013 U6 - https://doi.org/10.1103/PhysRevE.87.042136 SN - 1539-3755 VL - 87 IS - 4 PB - American Physical Society CY - College Park ER - TY - JOUR A1 - König, Tobias A1 - Papke, Thomas A1 - Kopyshev, Alexey A1 - Santer, Svetlana T1 - Atomic force microscopy nanolithography fabrication of metallic nano-slits using silicon nitride tips JF - Journal of materials science N2 - In this paper, we report on the properties of nano-slits created in metal thin films using atomic force microscope (AFM) nanolithography (AFM-NL). We demonstrate that instead of expensive diamond AFM tips, it is also possible to use low cost silicon nitride tips. It is shown that depending on the direction of scratching, nano-slits of different widths and depths can be fabricated at constant load force. We elucidate the reasons for this behavior and identify an optimal direction and load force for scratching a gold layer. Y1 - 2013 U6 - https://doi.org/10.1007/s10853-013-7188-x SN - 0022-2461 VL - 48 IS - 10 SP - 3863 EP - 3869 PB - Springer CY - New York ER - TY - JOUR A1 - Beye, Martin A1 - Anniyev, Toyli A1 - Coffee, Ryan A1 - Dell'Angela, Martina A1 - Föhlisch, Alexander A1 - Gladh, J. A1 - Katayama, T. A1 - Kaya, S. A1 - Krupin, O. A1 - Mogelhoj, A. A1 - Nilsson, A. A1 - Nordlund, D. A1 - Norskov, J. K. A1 - Oberg, H. A1 - Ogasawara, H. A1 - Pettersson, Lars G. M. A1 - Schlotter, W. F. A1 - Sellberg, J. A. A1 - Sorgenfrei, Nomi A1 - Turner, J. J. A1 - Wolf, M. A1 - Wurth, Wilfried A1 - Ostrom, H. T1 - Selective ultrafast probing of transient hot chemisorbed and precursor States of CO on Ru(0001) JF - Physical review letters N2 - We have studied the femtosecond dynamics following optical laser excitation of CO adsorbed on a Ru surface by monitoring changes in the occupied and unoccupied electronic structure using ultrafast soft x-ray absorption and emission. We recently reported [M. Dell'Angela et al. Science 339, 1302 (2013)] a phonon-mediated transition into a weakly adsorbed precursor state occurring on a time scale of >2 ps prior to desorption. Here we focus on processes within the first picosecond after laser excitation and show that the metal-adsorbate coordination is initially increased due to hot-electron-driven vibrational excitations. This process is faster than, but occurs in parallel with, the transition into the precursor state. With resonant x-ray emission spectroscopy, we probe each of these states selectively and determine the respective transient populations depending on optical laser fluence. Ab initio molecular dynamics simulations of CO adsorbed on Ru(0001) were performed at 1500 and 3000 K providing insight into the desorption process. Y1 - 2013 U6 - https://doi.org/10.1103/PhysRevLett.110.186101 SN - 0031-9007 VL - 110 IS - 18 PB - American Physical Society CY - College Park ER - TY - JOUR A1 - Valori, Gherarod A1 - Demoulin, Pascal A1 - Pariat, E. A1 - Masson, S. T1 - Accuracy of magnetic energy computations JF - Astronomy and astrophysics : an international weekly journal N2 - Context. For magnetically driven events, the magnetic energy of the system is the prime energy reservoir that fuels the dynamical evolution. In the solar context, the free energy (i.e., the energy in excess of the potential field energy) is one of the main indicators used in space weather forecasts to predict the eruptivity of active regions. A trustworthy estimation of the magnetic energy is therefore needed in three-dimensional (3D) models of the solar atmosphere, e. g., in coronal fields reconstructions or numerical simulations. Aims. The expression of the energy of a system as the sum of its potential energy and its free energy (Thomson's theorem) is strictly valid when the magnetic field is exactly solenoidal. For numerical realizations on a discrete grid, this property may be only approximately fulfilled. We show that the imperfect solenoidality induces terms in the energy that can lead to misinterpreting the amount of free energy present in a magnetic configuration. Methods. We consider a decomposition of the energy in solenoidal and nonsolenoidal parts which allows the unambiguous estimation of the nonsolenoidal contribution to the energy. We apply this decomposition to six typical cases broadly used in solar physics. We quantify to what extent the Thomson theorem is not satisfied when approximately solenoidal fields are used. Results. The quantified errors on energy vary from negligible to significant errors, depending on the extent of the nonsolenoidal component of the field. We identify the main source of errors and analyze the implications of adding a variable amount of divergence to various solenoidal fields. Finally, we present pathological unphysical situations where the estimated free energy would appear to be negative, as found in some previous works, and we identify the source of this error to be the presence of a finite divergence. Conclusions. We provide a method of quantifying the effect of a finite divergence in numerical fields, together with detailed diagnostics of its sources. We also compare the efficiency of two divergence-cleaning techniques. These results are applicable to a broad range of numerical realizations of magnetic fields. KW - magnetic fields KW - methods: numerical KW - Sun: surface magnetism KW - Sun: corona Y1 - 2013 U6 - https://doi.org/10.1051/0004-6361/201220982 SN - 0004-6361 VL - 553 IS - 2 PB - EDP Sciences CY - Les Ulis ER - TY - JOUR A1 - Abboud, Ali A1 - Send, Sebastian A1 - Pashniak, N. A1 - Leitenberger, Wolfram A1 - Ihle, Sebastian A1 - Huth, M. A1 - Hartmann, Robert A1 - Strüder, Lothar A1 - Pietsch, Ullrich T1 - Sub-pixel resolution of a pnCCD for X-ray white beam applications JF - Journal of instrumentation N2 - A new approach to achieve sub-pixel spatial resolution in a pnCCD detector with 75 x 75 mu m(2) pixel size is proposed for X-ray applications in single photon counting mode. The approach considers the energy dependence of the charge cloud created by a single photon and its split probabilities between neighboring pixels of the detector based on a rectangular model for the charge cloud density. For cases where the charge of this cloud becomes distributed over three or four pixels the center position of photon impact can be reconstructed with a precision better than 2 mu m. The predicted charge cloud sizes are tested at selected X-ray fluorescence lines emitting energies between 6.4 keV and 17.4 keV and forming charge clouds with size (rms) varying between 8 mu m and 10 mu m respectively. The 2 mu m enhanced spatial resolution of the pnCCD is verified by means of an x-ray transmission experiment throughout an optical grating. KW - Solid state detectors KW - Interaction of radiation with matter KW - Detector modelling and simulations II (electric fields, charge transport, multiplication and induction, pulse formation, electron emission, etc) Y1 - 2013 U6 - https://doi.org/10.1088/1748-0221/8/05/P05005 SN - 1748-0221 VL - 8 IS - 3 PB - IOP Publ. Ltd. CY - Bristol ER - TY - JOUR A1 - Shayduk, Roman A1 - Herzog, Marc A1 - Bojahr, Andre A1 - Schick, Daniel A1 - Gaal, Peter A1 - Leitenberger, Wolfram A1 - Navirian, Hengameh A1 - Sander, Mathias A1 - Goldshteyn, Jevgenij A1 - Vrejoiu, Ionela A1 - Bargheer, Matias T1 - Direct time-domain sampling of subterahertz coherent acoustic phonon spectra in SrTiO3 using ultrafast x-ray diffraction JF - Physical review : B, Condensed matter and materials physics N2 - We synthesize sub-THz longitudinal quasimonochromatic acoustic phonons in a SrTiO3 single crystal using a SrRuO3/SrTiO3 superlattice as an optical-acoustic transducer. The generated acoustic phonon spectrum is determined using ultrafast x-ray diffraction. The analysis of the generated phonon spectrum in the time domain reveals a k-vector dependent phonon lifetime. It is observed that even at sub-THz frequencies the phonon lifetime agrees with the 1/omega(2) power law known from Akhiezer's model for hyper sound attenuation. The observed shift of the synthesized spectrum to the higher q is discussed in the framework of nonlinear effects appearing due to the high amplitude of the synthesized phonons. Y1 - 2013 U6 - https://doi.org/10.1103/PhysRevB.87.184301 SN - 1098-0121 VL - 87 IS - 18 PB - American Physical Society CY - College Park ER - TY - JOUR A1 - Mulansky, Mario A1 - Pikovskij, Arkadij T1 - Energy spreading in strongly nonlinear disordered lattices JF - New journal of physics : the open-access journal for physics N2 - We study the scaling properties of energy spreading in disordered strongly nonlinear Hamiltonian lattices. Such lattices consist of nonlinearly coupled local linear or nonlinear oscillators, and demonstrate a rather slow, subdiffusive spreading of initially localized wave packets. We use a fractional nonlinear diffusion equation as a heuristic model of this process, and confirm that the scaling predictions resulting from a self-similar solution of this equation are indeed applicable to all studied cases. We show that the spreading in nonlinearly coupled linear oscillators slows down compared to a pure power law, while for nonlinear local oscillators a power law is valid in the whole studied range of parameters. Y1 - 2013 U6 - https://doi.org/10.1088/1367-2630/15/5/053015 SN - 1367-2630 VL - 15 IS - 5 PB - IOP Publ. Ltd. CY - Bristol ER - TY - JOUR A1 - Kralemann, Björn A1 - Pikovskij, Arkadij A1 - Rosenblum, Michael T1 - Detecting triplet locking by triplet synchronization indices JF - Physical review : E, Statistical, nonlinear and soft matter physics N2 - We discuss the effect of triplet synchrony in oscillatory networks. In this state the phases and the frequencies of three coupled oscillators fulfill the conditions of a triplet locking, whereas every pair of systems remains asynchronous. We suggest an easy to compute measure, a triplet synchronization index, which can be used to detect such states from experimental data. Y1 - 2013 U6 - https://doi.org/10.1103/PhysRevE.87.052904 SN - 1539-3755 VL - 87 IS - 5 PB - American Physical Society CY - College Park ER - TY - JOUR A1 - Pulkkinen, Otto A1 - Metzler, Ralf T1 - Distance matters the impact of gene proximity in bacterial gene regulation JF - Physical review letters N2 - Following recent discoveries of colocalization of downstream-regulating genes in living cells, the impact of the spatial distance between such genes on the kinetics of gene product formation is increasingly recognized. We here show from analytical and numerical analysis that the distance between a transcription factor (TF) gene and its target gene drastically affects the speed and reliability of transcriptional regulation in bacterial cells. For an explicit model system, we develop a general theory for the interactions between a TF and a transcription unit. The observed variations in regulation efficiency are linked to the magnitude of the variation of the TF concentration peaks as a function of the binding site distance from the signal source. Our results support the role of rapid binding site search for gene colocalization and emphasize the role of local concentration differences. Y1 - 2013 U6 - https://doi.org/10.1103/PhysRevLett.110.198101 SN - 0031-9007 VL - 110 IS - 19 PB - American Physical Society CY - College Park ER - TY - JOUR A1 - Schwabedal, Justus T. C. A1 - Pikovskij, Arkadij T1 - Phase description of stochastic oscillations JF - Physical review letters N2 - We introduce an invariant phase description of stochastic oscillations by generalizing the concept of standard isophases. The average isophases are constructed as sections in the state space, having a constant mean first return time. The approach allows us to obtain a global phase variable of noisy oscillations, even in the cases where the phase is ill defined in the deterministic limit. A simple numerical method for finding the isophases is illustrated for noise-induced switching between two coexisting limit cycles, and for noise-induced oscillation in an excitable system. We also discuss how to determine isophases of observed irregular oscillations, providing a basis for a refined phase description in data analysis. Y1 - 2013 U6 - https://doi.org/10.1103/PhysRevLett.110.204102 SN - 0031-9007 VL - 110 IS - 20 PB - American Physical Society CY - College Park ER - TY - JOUR A1 - Lomholt, Michael A. A1 - Lizana, Ludvig A1 - Metzler, Ralf A1 - Ambjoernsson, Tobias T1 - Microscopic origin of the logarithmic time evolution of aging processes in complex systems JF - Physical review letters N2 - There exists compelling experimental evidence in numerous systems for logarithmically slow time evolution, yet its full theoretical understanding remains elusive. We here introduce and study a generic transition process in complex systems, based on nonrenewal, aging waiting times. Each state n of the system follows a local clock initiated at t = 0. The random time tau between clock ticks follows the waiting time density psi (tau). Transitions between states occur only at local clock ticks and are hence triggered by the local forward waiting time, rather than by psi (tau). For power-law forms psi (tau) similar or equal to tau(-1-alpha) (0 < alpha < 1) we obtain a logarithmic time evolution of the state number < n(t)> similar or equal to log(t/t(0)), while for alpha > 2 the process becomes normal in the sense that < n(t)> similar or equal to t. In the intermediate range 1 < alpha < 2 we find the power-law growth < n(t)> similar or equal to t(alpha-1). Our model provides a universal description for transition dynamics between aging and nonaging states. Y1 - 2013 U6 - https://doi.org/10.1103/PhysRevLett.110.208301 SN - 0031-9007 VL - 110 IS - 20 PB - American Physical Society CY - College Park ER - TY - JOUR A1 - Kharchenko, Vasyl O. A1 - Goychuk, Igor T1 - Subdiffusive rocking ratchets in viscoelastic media transport optimization and thermodynamic efficiency in overdamped regime JF - Physical review : E, Statistical, nonlinear and soft matter physics N2 - We study subdiffusive overdamped Brownian ratchets periodically rocked by an external zero-mean force in viscoelastic media within the framework of a non-Markovian generalized Langevin equation approach and associated multidimensional Markovian embedding dynamics. Viscoelastic deformations of the medium caused by the transport particle are modeled by a set of auxiliary Brownian quasiparticles elastically coupled to the transport particle and characterized by a hierarchy of relaxation times which obey a fractal scaling. The most slowly relaxing deformations which cannot immediately follow to the moving particle imprint long-range memory about its previous positions and cause subdiffusion and anomalous transport on a sufficiently long time scale. This anomalous behavior is combined with normal diffusion and transport on an initial time scale of overdamped motion. Anomalously slow directed transport in a periodic ratchet potential with broken space inversion symmetry emerges due to a violation of the thermal detailed balance by a zero-mean periodic driving and is optimized with frequency of driving, its amplitude, and temperature. Such optimized anomalous transport can be low dispersive and characterized by a large generalized Peclet number. Moreover, we show that overdamped subdiffusive ratchets can sustain a substantial load and do useful work. The corresponding thermodynamic efficiency decays algebraically in time since the useful work done against a load scales sublinearly with time following to the transport particle position, but the energy pumped by an external force scales with time linearly. Nevertheless, it can be transiently appreciably high and compare well with the thermodynamical efficiency of the normal diffusion overdamped ratchets on sufficiently long temporal and spatial scales. Y1 - 2013 U6 - https://doi.org/10.1103/PhysRevE.87.052119 SN - 1539-3755 VL - 87 IS - 5 PB - American Physical Society CY - College Park ER - TY - JOUR A1 - Send, Sebastian A1 - Abboud, Ali A1 - Hartmann, Robert A1 - Huth, M. A1 - Leitenberger, Wolfram A1 - Pashniak, N. A1 - Schmidt, J. A1 - Strüder, Lothar A1 - Pietsch, Ullrich T1 - Characterization of a pnCCD for applications with synchrotron radiation JF - Nuclear instruments & methods in physics research : a journal on accelerators, instrumentation and techniques applied to research in nuclear and atomic physics, materials science and related fields in physics ; A, Accelerators, spectrometers, detectors and associated equipment N2 - In this work we study the response of a pnCCD by means of X-ray spectroscopy in the energy range between 6 key and 20 key and by Laue diffraction techniques. The analyses include measurements of characteristic detector parameters like energy resolution, count rate capability and effects of different gain settings. The limit of a single photon counting operation in white beam X-ray diffraction experiments is discussed with regard to the occurrence of pile-up events, for which the energy information about individual photons is lost. In case of monochromatic illumination the pnCCD can be used as a fast conventional CCD with a charge handling capacity (CHC) of about 300,000 electrons per pixel. If the CHC is exceeded, any surplus charge will spill to neighboring pixels perpendicular to the transfer direction due to electrostatic repulsion. The possibilities of increasing the number of storable electrons are investigated for different voltage settings by exposing a single pixel with X-rays generated by a microfocus X-ray source. The pixel binning mode is tested as an alternative approach that enables a pnCCD operation with significantly shorter readout times. KW - pnCCD KW - X-ray spectroscopy KW - X-ray imaging KW - Energy-dispersive Laue diffraction Y1 - 2013 U6 - https://doi.org/10.1016/j.nima.2013.01.044 SN - 0168-9002 VL - 711 IS - 5 SP - 132 EP - 142 PB - Elsevier CY - Amsterdam ER - TY - JOUR A1 - Born, Andreas A1 - Stocker, Thomas F. A1 - Raible, Christoph C. A1 - Levermann, Anders T1 - Is the Atlantic subpolar gyre bistable in comprehensive coupled climate models? JF - Climate dynamics : observational, theoretical and computational research on the climate system N2 - The Atlantic subpolar gyre (SPG) is one of the main drivers of decadal climate variability in the North Atlantic. Here we analyze its dynamics in pre-industrial control simulations of 19 different comprehensive coupled climate models. The analysis is based on a recently proposed description of the SPG dynamics that found the circulation to be potentially bistable due to a positive feedback mechanism including salt transport and enhanced deep convection in the SPG center. We employ a statistical method to identify multiple equilibria in time series that are subject to strong noise and analyze composite fields to assess whether the bistability results from the hypothesized feedback mechanism. Because noise dominates the time series in most models, multiple circulation modes can unambiguously be detected in only six models. Four of these six models confirm that the intensification is caused by the positive feedback mechanism. Y1 - 2013 U6 - https://doi.org/10.1007/s00382-012-1525-7 SN - 0930-7575 VL - 40 IS - 11-12 SP - 2993 EP - 3007 PB - Springer CY - New York ER - TY - JOUR A1 - Eichler, David A1 - Kumar, Rahul A1 - Pohl, Martin T1 - Is the galatic cosmic-ray spectrum constant in time? JF - The astrophysical journal : an international review of spectroscopy and astronomical physics N2 - The hypothesis is considered that the present, local Galactic cosmic-ray spectrum is, due to source intermittency, softer than average over time and over the Galaxy. Measurements of muogenic nuclides underground could provide an independent measurement of the time-averaged spectrum. Source intermittency could also account for the surprising low anisotropy reported by the IceCube Collaboration. Predictions for Galactic emission of ultrahigh-energy (UHE) quanta, such as UHE gamma rays and neutrinos, might be higher or lower than previously estimated. KW - cosmic rays Y1 - 2013 U6 - https://doi.org/10.1088/0004-637X/769/2/138 SN - 0004-637X VL - 769 IS - 2 PB - IOP Publ. Ltd. CY - Bristol ER - TY - JOUR A1 - Cherstvy, Andrey G. A1 - Teif, V. B. T1 - Structure-driven homology pairing of chromatin fibers the role of electrostatics and protein-induced bridging JF - Journal of biological physics : emphasizing physical principles in biological research ; an international journal for the formulation and application of mathematical models in the biological sciences N2 - Chromatin domains formed in vivo are characterized by different types of 3D organization of interconnected nucleosomes and architectural proteins. Here, we quantitatively test a hypothesis that the similarities in the structure of chromatin fibers (which we call "structural homology") can affect their mutual electrostatic and protein-mediated bridging interactions. For example, highly repetitive DNA sequences in heterochromatic regions can position nucleosomes so that preferred inter-nucleosomal distances are preserved on the surfaces of neighboring fibers. On the contrary, the segments of chromatin fiber formed on unrelated DNA sequences have different geometrical parameters and lack structural complementarity pivotal for stable association and cohesion. Furthermore, specific functional elements such as insulator regions, transcription start and termination sites, and replication origins are characterized by strong nucleosome ordering that might induce structure-driven iterations of chromatin fibers. We propose that shape-specific protein-bridging interactions facilitate long-range pairing of chromatin fragments, while for closely-juxtaposed fibers electrostatic forces can in addition yield fine-tuned structure-specific recognition and pairing. These pairing effects can account for some features observed for mitotic and inter-phase chromatins. KW - Chromatin pairing KW - Homology KW - Electrostatics KW - Shape recognition KW - Long-range bridging Y1 - 2013 U6 - https://doi.org/10.1007/s10867-012-9294-4 SN - 0092-0606 SN - 1573-0689 VL - 39 IS - 3 SP - 363 EP - 385 PB - Springer CY - Dordrecht ER - TY - JOUR A1 - Hempel, Sabrina A1 - Koseska, Aneta A1 - Nikoloski, Zoran T1 - Data-driven reconstruction of directed networks JF - The European physical journal : B, Condensed matter and complex systems N2 - We investigate the properties of a recently introduced asymmetric association measure, called inner composition alignment (IOTA), aimed at inferring regulatory links (couplings). We show that the measure can be used to determine the direction of coupling, detect superfluous links, and to account for autoregulation. In addition, the measure can be extended to infer the type of regulation (positive or negative). The capabilities of IOTA to correctly infer couplings together with their directionality are compared against Kendall's rank correlation for time series of different lengths, particularly focussing on biological examples. We demonstrate that an extended version of the measure, bidirectional inner composition alignment (biIOTA), increases the accuracy of the network reconstruction for short time series. Finally, we discuss the applicability of the measure to infer couplings in chaotic systems. Y1 - 2013 U6 - https://doi.org/10.1140/epjb/e2013-31111-8 SN - 1434-6028 VL - 86 IS - 6 PB - Springer CY - New York ER - TY - JOUR A1 - Abramowski, Attila A1 - Acero, F. A1 - Aharonian, Felix A. A1 - Akhperjanian, A. G. A1 - Anton, Gisela A1 - Balenderan, Shangkari A1 - Balzer, Arnim A1 - Barnacka, Anna A1 - Becherini, Yvonne A1 - Tjus, J. Becker A1 - Behera, B. A1 - Bernlöhr, K. A1 - Birsin, E. A1 - Biteau, Jonathan A1 - Bochow, A. A1 - Boisson, Catherine A1 - Bolmont, J. A1 - Bordas, Pol A1 - Brucker, J. A1 - Brun, Francois A1 - Brun, Pierre A1 - Bulik, Tomasz A1 - Carrigan, Svenja A1 - Casanova, Sabrina A1 - Cerruti, M. A1 - Chadwick, Paula M. A1 - Chaves, Ryan C. G. A1 - Cheesebrough, A. A1 - Colafrancesco, Sergio A1 - Cologna, Gabriele A1 - Conrad, Jan A1 - Couturier, C. A1 - Dalton, M. A1 - Daniel, M. K. A1 - Davids, I. D. A1 - Degrange, B. A1 - Deil, C. A1 - deWilt, P. A1 - Dickinson, H. J. A1 - Djannati-Ataï, A. A1 - Domainko, W. A1 - Drury, L. O'C. A1 - Dubus, G. A1 - Dutson, K. A1 - Dyks, J. A1 - Dyrda, M. A1 - Egberts, Kathrin A1 - Eger, P. A1 - Espigat, P. A1 - Fallon, L. A1 - Farnier, C. A1 - Fegan, S. A1 - Feinstein, F. A1 - Fernandes, M. V. A1 - Fernandez, D. A1 - Fiasson, A. A1 - Fontaine, G. A1 - Foester, A. A1 - Fuessling, M. A1 - Gajdus, M. A1 - Gallant, Y. A. A1 - Garrigoux, T. A1 - Gast, H. A1 - Giebels, B. A1 - Glicenstein, J. F. A1 - Glueck, B. A1 - Goeing, D. A1 - Grondin, M. -H. A1 - Grudzinska, M. A1 - Haeffner, S. A1 - Hague, J. D. A1 - Hahn, J. A1 - Hampf, D. A1 - Harris, J. A1 - Hauser, M. A1 - Heinz, S. A1 - Heinzelmann, G. A1 - Henri, G. A1 - Hermann, G. A1 - Hillert, A. A1 - Hinton, James Anthony A1 - Hofmann, W. A1 - Hofverberg, P. A1 - Holler, Markus A1 - Horns, D. A1 - Jacholkowska, A. A1 - Jahn, C. A1 - Jamrozy, M. A1 - Jung, I. A1 - Kastendieck, M. A. A1 - Katarzynski, K. A1 - Katz, U. A1 - Kaufmann, S. A1 - Khelifi, B. A1 - Klepser, S. A1 - Klochkov, D. A1 - Kluzniak, W. A1 - Kneiske, T. A1 - Komin, Nu. A1 - Kosack, K. A1 - Kossakowski, R. A1 - Krayzel, F. A1 - Krueger, P. P. A1 - Laffon, H. A1 - Lamanna, G. A1 - Lefaucheur, J. A1 - Lemoine-Goumard, M. A1 - Lenain, J. -P. A1 - Lennarz, D. A1 - Lohse, T. A1 - Lopatin, A. A1 - Lu, C. -C. A1 - Marandon, V. A1 - Marcowith, Alexandre A1 - Masbou, J. A1 - Maurin, G. A1 - Maxted, N. A1 - Mayer, M. A1 - McComb, T. J. L. A1 - Medina, M. C. A1 - Mehault, J. A1 - Menzler, U. A1 - Moderski, R. A1 - Mohamed, M. A1 - Moulin, Emmanuel A1 - Naumann, C. L. A1 - Naumann-Godo, M. A1 - de Naurois, M. A1 - Nedbal, D. A1 - Nguyen, N. A1 - Niemiec, J. A1 - Nolan, S. J. A1 - Ohm, S. A1 - Wilhelmi, E. de Ona A1 - Opitz, B. A1 - Ostrowski, M. A1 - Oya, I. A1 - Panter, M. A1 - Parsons, R. D. A1 - Arribas, M. Paz A1 - Pekeur, N. W. A1 - Pelletier, G. A1 - Perez, J. A1 - Petrucci, P. -O. A1 - Peyaud, B. A1 - Pita, S. A1 - Puehlhofer, G. A1 - Punch, M. A1 - Quirrenbach, A. A1 - Raab, S. A1 - Raue, M. A1 - Reimer, A. A1 - Reimer, O. A1 - Renaud, M. A1 - de los Reyes, R. A1 - Rieger, F. A1 - Ripken, J. A1 - Rob, L. A1 - Rosier-Lees, S. A1 - Rowell, G. A1 - Rudak, B. A1 - Rulten, C. B. A1 - Sahakian, V. A1 - Sanchez, David M. A1 - Santangelo, Andrea A1 - Schlickeiser, R. A1 - Schulz, A. A1 - Schwanke, U. A1 - Schwarzburg, S. A1 - Schwemmer, S. A1 - Sheidaei, F. A1 - Skilton, J. L. A1 - Sol, H. A1 - Spengler, G. A1 - Stawarz, L. A1 - Steenkamp, R. A1 - Stegmann, Christian A1 - Stinzing, F. A1 - Stycz, K. A1 - Sushch, Iurii A1 - Szostek, A. A1 - Tavernet, J. -P. A1 - Terrier, R. A1 - Tluczykont, M. A1 - Trichard, C. A1 - Valerius, K. A1 - van Eldik, C. A1 - Vasileiadis, G. A1 - Venter, C. A1 - Viana, A. A1 - Vincent, P. A1 - Voelk, H. J. A1 - Volpe, F. A1 - Vorobiov, S. A1 - Vorster, M. A1 - Wagner, S. J. A1 - Ward, M. A1 - White, R. A1 - Wierzcholska, A. A1 - Wouters, D. A1 - Zacharias, M. A1 - Zajczyk, A. A1 - Zdziarski, A. A. A1 - Zech, Alraune A1 - Zechlin, H. S. T1 - HESS discovery of VHE gamma-rays from the quasar PKS 1510-089 JF - Astronomy and astrophysics : an international weekly journal N2 - The quasar PKS 1510-089 (z = 0.361) was observed with the H.E.S.S. array of imaging atmospheric Cherenkov telescopes during high states in the optical and GeV bands, to search for very high energy (VHE, defined as E >= 0.1 TeV) emission. VHE gamma-rays were detected with a statistical significance of 9.2 standard deviations in 15.8 h of H. E. S. S. data taken during March and April 2009. A VHE integral flux of I(0.15 TeV < E < 1.0TeV) = (1.0 +/- 0.2(stat) +/- 0.2(sys)) x 10(-11) cm(-2) s(-1) is measured. The best-fit power law to the VHE data has a photon index of G = 5.4 +/- 0.7(stat) +/- 0.3(sys). The GeV and optical light curves show pronounced variability during the period of H.E.S.S. observations. However, there is insufficient evidence to claim statistically significant variability in the VHE data. Because of its relatively high redshift, the VHE flux from PKS 1510-089 should suffer considerable attenuation in the intergalactic space due to the extragalactic background light (EBL). Hence, the measured gamma-ray spectrum is used to derive upper limits on the opacity due to EBL, which are found to be comparable with the previously derived limits from relatively-nearby BL Lac objects. Unlike typical VHE-detected blazars where the broadband spectrum is dominated by nonthermal radiation at all wavelengths, the quasar PKS 1510-089 has a bright thermal component in the optical to UV frequency band. Among all VHE detected blazars, PKS 1510-089 has the most luminous broad line region. The detection of VHE emission from this quasar indicates a low level of gamma - gamma absorption on the internal optical to UV photon field. KW - gamma rays: galaxies KW - quasars: individual: PKS 1510-089 KW - infrared: diffuse background Y1 - 2013 U6 - https://doi.org/10.1051/0004-6361/201321135 SN - 0004-6361 VL - 554 IS - 6 PB - EDP Sciences CY - Les Ulis ER - TY - JOUR A1 - Abramowski, Attila A1 - Acero, F. A1 - Aharonian, Felix A. A1 - Akhperjanian, A. G. A1 - Angüner, Ekrem Oǧuzhan A1 - Anton, Gisela A1 - Balenderan, Shangkari A1 - Balzer, Arnim A1 - Barnacka, Anna A1 - Becherini, Yvonne A1 - Tjus, J. Becker A1 - Bernlöhr, K. A1 - Birsin, E. A1 - Bissaldi, E. A1 - Biteau, Jonathan A1 - Boisson, Catherine A1 - Bolmont, J. A1 - Bordas, Pol A1 - Brucker, J. A1 - Brun, Francois A1 - Brun, Pierre A1 - Bulik, Tomasz A1 - Carrigan, Svenja A1 - Casanova, Sabrina A1 - Cerruti, M. A1 - Chadwick, Paula M. A1 - Chalme-Calvet, R. A1 - Chaves, Ryan C. G. A1 - Cheesebrough, A. A1 - Chretien, M. A1 - Colafrancesco, Sergio A1 - Cologna, Gabriele A1 - Conrad, Jan A1 - Couturier, C. A1 - Dalton, M. A1 - Daniel, M. K. A1 - Davids, I. D. A1 - Degrange, B. A1 - Deil, C. A1 - deWilt, P. A1 - Dickinson, H. J. A1 - Djannati-Ataï, A. A1 - Domainko, W. A1 - Drury, L. O'C. A1 - Dubus, G. A1 - Dutson, K. A1 - Dyks, J. A1 - Dyrda, M. A1 - Edwards, T. A1 - Egberts, Kathrin A1 - Eger, P. A1 - Espigat, P. A1 - Farnier, C. A1 - Fegan, S. A1 - Feinstein, F. A1 - Fernandes, M. V. A1 - Fernandez, D. A1 - Fiasson, A. A1 - Fontaine, G. A1 - Foerster, A. A1 - Fuessling, M. A1 - Gajdus, M. A1 - Gallant, Y. A. A1 - Garrigoux, T. A1 - Gast, H. A1 - Giebels, B. A1 - Glicenstein, J. F. A1 - Goering, D. A1 - Grondin, M. -H. A1 - Grudzinska, M. A1 - Haeffner, S. A1 - Hague, J. D. A1 - Hahn, J. A1 - Harris, J. A1 - Heinzelmann, G. A1 - Henri, G. A1 - Hermann, G. A1 - Hervet, O. A1 - Hillert, A. A1 - Hinton, James Anthony A1 - Hofmann, W. A1 - Hofverberg, P. A1 - Holler, Markus A1 - Horns, D. A1 - Jacholkowska, A. A1 - Jahn, C. A1 - Jamrozy, M. A1 - Janiak, M. A1 - Jankowsky, F. A1 - Jung, I. A1 - Kastendieck, M. A. A1 - Katarzynski, K. A1 - Katz, U. A1 - Kaufmann, S. A1 - Khelifi, B. A1 - Kieffer, M. A1 - Klepser, S. A1 - Klochkov, D. A1 - Kluzniak, W. A1 - Kneiske, T. A1 - Kolitzus, D. A1 - Komin, Nu. A1 - Kosack, K. A1 - Krakau, S. A1 - Krayzel, F. A1 - Krueger, P. P. A1 - Laffon, H. A1 - Lamanna, G. A1 - Lefaucheur, J. A1 - Lemoine-Goumard, M. A1 - Lenain, J. -P. A1 - Lennarz, D. A1 - Lohse, T. A1 - Lopatin, A. A1 - Lu, C. -C. A1 - Marandon, V. A1 - Marcowith, Alexandre A1 - Maxted, N. A1 - Mayer, M. A1 - McComb, T. J. L. A1 - Medina, M. C. A1 - Mehault, J. A1 - Menzler, U. A1 - Meyer, M. A1 - Moderski, R. A1 - Mohamed, M. A1 - Moulin, Emmanuel A1 - Murach, T. A1 - Naumann, C. L. A1 - de Naurois, M. A1 - Nedbal, D. A1 - Niemiec, J. A1 - Nolan, S. J. A1 - Oakes, L. A1 - Ohm, S. A1 - Wilhelmi, E. de Ona A1 - Opitz, B. A1 - Ostrowski, M. A1 - Oya, I. A1 - Panter, M. A1 - Parsons, R. D. A1 - Arribas, M. Paz A1 - Pekeur, N. W. A1 - Pelletier, G. A1 - Perez, J. A1 - Petrucci, P. -O. A1 - Peyaud, B. A1 - Pita, S. A1 - Poon, H. A1 - Punch, M. A1 - Quirrenbach, A. A1 - Raab, S. A1 - Raue, M. A1 - Reimer, A. A1 - Reimer, O. A1 - Renaud, M. A1 - de los Reyes, R. A1 - Rieger, F. A1 - Rob, L. A1 - Rosier-Lees, S. A1 - Rowell, G. A1 - Rudak, B. A1 - Rulten, C. B. A1 - Sahakian, V. A1 - Sanchez, David M. A1 - Santangelo, Andrea A1 - Schlickeiser, R. A1 - Schuessler, F. A1 - Schulz, A. A1 - Schwanke, U. A1 - Schwarzburg, S. A1 - Schwemmer, S. A1 - Sol, H. A1 - Spengler, G. A1 - Spiess, F. A1 - Stawarz, L. A1 - Steenkamp, R. A1 - Stegmann, Christian A1 - Stinzing, F. A1 - Stycz, K. A1 - Sushch, Iurii A1 - Szostek, A. A1 - Tavernet, J. -P. A1 - Terrier, R. A1 - Tluczykont, M. A1 - Trichard, C. A1 - Valerius, K. A1 - van Eldik, C. A1 - Vasileiadis, G. A1 - Venter, C. A1 - Viana, A. A1 - Vincent, P. A1 - Voelk, H. J. A1 - Volpe, F. A1 - Vorster, M. A1 - Wagner, S. J. A1 - Wagner, P. A1 - Ward, M. A1 - Weidinger, M. A1 - White, R. A1 - Wierzcholska, A. A1 - Willmann, P. A1 - Woernlein, A. A1 - Wouters, D. A1 - Zacharias, M. A1 - Zajczyk, A. A1 - Zdziarski, A. A. A1 - Zech, Alraune A1 - Zechlin, H. -S. T1 - Discovery of high and very high-energy emission from the BL Lacertae object SHBL J001355.9-185406 JF - Astronomy and astrophysics : an international weekly journal N2 - The detection of the high-frequency peaked BL Lac object (HBL) SHBL J001355.9-185406 (z = 0.095) at high (HE; 100 MeV < E < 300 GeV) and very high-energy (VHE; E > 100 GeV) with the Fermi Large Area Telescope (LAT) and the High Energy Stereoscopic System (H.E.S.S.) is reported. Dedicated observations were performed with the H. E. S. S. telescopes, leading to a detection at the 5.5 sigma significance level. The measured flux above 310 GeV is (8.3 +/- 1.7(stat) +/- 1.7(sys)) x 10(-13) photons cm(-2) s(-1) (about 0.6% of that of the Crab Nebula), and the power-law spectrum has a photon index of Gamma = 3.4 +/- 0.5(stat) +/- 0.2(sys). Using 3.5 years of publicly available Fermi-LAT data, a faint counterpart has been detected in the LAT data at the 5.5 sigma significance level, with an integrated flux above 300 MeV of (9.3 +/- 3.4(stat) +/- 0.8(sys)) x 10(-10) photons cm(-2) s(-1) and a photon index of Gamma = 1.96 +/- 0.20(stat) +/- 0.08(sys). X-ray observations with Swift-XRT allow the synchrotron peak energy in vF(v) representation to be located at similar to 1.0 keV. The broadband spectral energy distribution is modelled with a one-zone synchrotron self-Compton (SSC) model and the optical data by a black-body emission describing the thermal emission of the host galaxy. The derived parameters are typical of HBLs detected at VHE, with a particle-dominated jet. KW - BL Lacertae objects: individual: SHBL J001355.9-185406 KW - gamma rays: general Y1 - 2013 U6 - https://doi.org/10.1051/0004-6361/201220996 SN - 0004-6361 VL - 554 PB - EDP Sciences CY - Les Ulis ER - TY - JOUR A1 - Beye, Martin A1 - Wernet, Ph. A1 - Schüßler-Langeheine, Christian A1 - Föhlisch, Alexander T1 - Time resolved resonant inelastic X-ray scattering: a supreme tool to understand dynamics in solids and molecules JF - Journal of electron spectroscopy and related phenomena : the international journal on theoretical and experimental aspects of electron spectroscopy N2 - Dynamics in materials typically involve different degrees of freedom, like charge, lattice, orbital and spin in a complex interplay. Time-resolved resonant inelastic X-ray scattering (RIXS) as a highly selective tool can provide unique insight and follow the details of dynamical processes while resolving symmetries, chemical and charge states, momenta, spin configurations, etc. In this paper, we review examples where the intrinsic scattering duration time is used to study femtosecond phenomena. Free-electron lasers access timescales starting in the sub-ps range through pump-probe methods and synchrotrons study the time scales longer than tens of ps. In these examples, time-resolved resonant inelastic X-ray scattering is applied to solids as well as molecular systems. KW - Resonant inelastic X-ray scattering KW - Ultrafast spectroscopy KW - Phase transitions KW - Molecular dynamics Y1 - 2013 U6 - https://doi.org/10.1016/j.elspec.2013.04.013 SN - 0368-2048 VL - 188 IS - 3 SP - 172 EP - 182 PB - Elsevier CY - Amsterdam ER - TY - JOUR A1 - Könnecke, Rene A1 - Follath, R. A1 - Pontius, N. A1 - Schlappa, J. A1 - Eggenstein, F. A1 - Zeschke, T. A1 - Bischoff, P. A1 - Schmidt, J. -S. A1 - Noll, T. A1 - Trabant, C. A1 - Schreck, S. A1 - Wernet, Ph. A1 - Eisebitt, S. A1 - Senf, F. A1 - Schuessler-Langeheine, Christian A1 - Erko, A. A1 - Föhlisch, Alexander T1 - The confocal plane grating spectrometer at BESSY II JF - Journal of electron spectroscopy and related phenomena : the international journal on theoretical and experimental aspects of electron spectroscopy N2 - At BESSY II a confocal plane grating spectrometer for resonant inelastic X-ray scattering (RIXS) is currently under commissioning. The new endstation operates with a source size of 4 x 1 mu m(2) provided by its dedicated beamline. The RIXS-spectrometer covers an energy range from 50 eV to 1000 eV, providing a resolving power E/Delta E of 5000-15,000. The beamline allows full polarization control and gives a photon flux of up to 7 x 10(14) photons/s/0.1 A/0.1%bandwidth by offering a resolving power E/Delta E of 4000-12,000. KW - Resonant inelastic X-ray scattering KW - Soft X-ray monochromator KW - High transmission micro focus beamline KW - Plane grating emission spectrometer Y1 - 2013 U6 - https://doi.org/10.1016/j.elspec.2012.11.003 SN - 0368-2048 VL - 188 SP - 133 EP - 139 PB - Elsevier CY - Amsterdam ER - TY - JOUR A1 - Nowicki, Sophie A1 - Bindschadler, Robert A. A1 - Abe-Ouchi, Ayako A1 - Aschwanden, Andy A1 - Bueler, Ed A1 - Choi, Hyeungu A1 - Fastook, Jim A1 - Granzow, Glen A1 - Greve, Ralf A1 - Gutowski, Gail A1 - Herzfeld, Ute A1 - Jackson, Charles A1 - Johnson, Jesse A1 - Khroulev, Constantine A1 - Larour, Eric A1 - Levermann, Anders A1 - Lipscomb, William H. A1 - Martin, Maria A. A1 - Morlighem, Mathieu A1 - Parizek, Byron R. A1 - Pollard, David A1 - Price, Stephen F. A1 - Ren, Diandong A1 - Rignot, Eric A1 - Saito, Fuyuki A1 - Sato, Tatsuru A1 - Seddik, Hakime A1 - Seroussi, Helene A1 - Takahashi, Kunio A1 - Walker, Ryan A1 - Wang, Wei Li T1 - Insights into spatial sensitivities of ice mass response to environmental change from the SeaRISE ice sheet modeling project II Greenland JF - Journal of geophysical research : Earth surface N2 - The Sea-level Response to Ice Sheet Evolution (SeaRISE) effort explores the sensitivity of the current generation of ice sheet models to external forcing to gain insight into the potential future contribution to sea level from the Greenland and Antarctic ice sheets. All participating models simulated the ice sheet response to three types of external forcings: a change in oceanic condition, a warmer atmospheric environment, and enhanced basal lubrication. Here an analysis of the spatial response of the Greenland ice sheet is presented, and the impact of model physics and spin-up on the projections is explored. Although the modeled responses are not always homogeneous, consistent spatial trends emerge from the ensemble analysis, indicating distinct vulnerabilities of the Greenland ice sheet. There are clear response patterns associated with each forcing, and a similar mass loss at the full ice sheet scale will result in different mass losses at the regional scale, as well as distinct thickness changes over the ice sheet. All forcings lead to an increased mass loss for the coming centuries, with increased basal lubrication and warmer ocean conditions affecting mainly outlet glaciers, while the impacts of atmospheric forcings affect the whole ice sheet. KW - Greenland KW - ice-sheet KW - sea-level KW - model KW - ensemble Y1 - 2013 U6 - https://doi.org/10.1002/jgrf.20076 SN - 2169-9003 VL - 118 IS - 2 SP - 1025 EP - 1044 PB - American Geophysical Union CY - Washington ER - TY - JOUR A1 - Yadavalli, Nataraja Sekhar A1 - Santer, Svetlana T1 - In-situ atomic force microscopy study of the mechanism of surface relief grating formation in photosensitive polymer films JF - Journal of applied physics N2 - When photosensitive azobenzene-containing polymer films are irradiated with light interference patterns, topographic variations in the film develop that follow the local distribution of the electric field vector. The exact correspondence of e.g., the vector orientation in relation to the presence of local topographic minima or maxima is in general difficult to determine. Here, we report on a systematic procedure how this can be accomplished. For this, we devise a new set-up combining an atomic force microscope and two-beam interferometry. With this set-up, it is possible to track the topography change in-situ, while at the same time changing polarization and phase of the impinging interference pattern. This is the first time that an absolute correspondence between the local distribution of electric field vectors and the local topography of the relief grating could be established exhaustively. Our setup does not require a complex mathematical post-processing and its simplicity renders it interesting for characterizing photosensitive polymer films in general. Y1 - 2013 U6 - https://doi.org/10.1063/1.4809640 SN - 0021-8979 SN - 1089-7550 VL - 113 IS - 22 PB - American Institute of Physics CY - Melville ER - TY - JOUR A1 - Qiu, Xunlin A1 - Holländer, Lars A1 - Wirges, Werner A1 - Gerhard, Reimund A1 - Basso, Heitor Cury T1 - Direct hysteresis measurements on ferroelectret films by means of a modified Sawyer-Tower circuit JF - Journal of applied physics N2 - Ferro- and piezo-electrets are non-polar polymer foams or film systems with internally charged cavities. Since their invention more than two decades ago, ferroelectrets have become a welcome addition to the range of piezo-, pyro-, and ferro-electric materials available for device applications. A polarization-versus-electric-field hysteresis is an essential feature of a ferroelectric material and may also be used for determining some of its main properties. Here, a modified Sawyer-Tower circuit and a combination of unipolar and bipolar voltage waveforms are employed to record hysteresis curves on cellular-foam polypropylene ferroelectret films and on tubular-channel fluoroethylenepropylene copolymer ferroelectret film systems. Internal dielectric barrier discharges (DBDs) are required for depositing the internal charges in ferroelectrets. The true amount of charge transferred during the internal DBDs is obtained from voltage measurements on a standard capacitor connected in series with the sample, but with a much larger capacitance than the sample. Another standard capacitor with a much smaller capacitance-which is, however, still considerably larger than the sample capacitance-is also connected in series as a high-voltage divider protecting the electrometer against destructive breakdown. It is shown how the DBDs inside the polymer cavities lead to phenomenological hysteresis curves that cannot be distinguished from the hysteresis loops found on other ferroic materials. The physical mechanisms behind the hysteresis behavior are described and discussed. Y1 - 2013 U6 - https://doi.org/10.1063/1.4809556 SN - 0021-8979 VL - 113 IS - 22 PB - American Institute of Physics CY - Melville ER - TY - JOUR A1 - tAliu, E. A1 - Archambault, S. A1 - Arlen, T. A1 - Aune, T. A1 - Beilicke, M. A1 - Benbow, W. A1 - Bird, R. A1 - Bouvier, A. 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 - Dumm, J. A1 - Dwarkadas, Vikram V. A1 - Errando, M. A1 - Falcone, A. A1 - Federici, Simone A1 - Feng, Q. 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 - Gotthelf, E. V. A1 - Griffin, S. A1 - Grube, J. A1 - Gyuk, G. A1 - Hanna, D. A1 - Holder, J. A1 - Huan, H. A1 - Hughes, G. A1 - Humensky, T. B. A1 - Kaaret, P. A1 - Karlsson, N. A1 - Kertzman, M. A1 - Khassen, Y. A1 - Kieda, D. A1 - Krawczynski, H. A1 - Krennrich, F. A1 - Lang, M. J. A1 - Lee, K. A1 - Madhavan, A. S. A1 - Maier, G. A1 - Majumdar, P. A1 - McArthur, S. A1 - McCann, A. A1 - Millis, J. A1 - Moriarty, P. A1 - Mukherjee, R. A1 - Nelson, T. A1 - de Bhroithe, A. O'Faolain A1 - Ong, R. A. A1 - Orr, M. A1 - Otte, A. N. A1 - Pandel, D. A1 - Park, N. A1 - Perkins, J. S. A1 - Pohl, Martin A1 - Popkow, A. 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, Jens A1 - Saxon, D. B. A1 - Schroedter, M. A1 - Sembroski, G. H. A1 - Sentuerk, G. D. A1 - Skole, C. A1 - Telezhinsky, Igor O. 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 - Wakely, S. P. A1 - Ward, J. E. A1 - Weekes, T. C. A1 - Weinstein, A. A1 - Weisgarber, T. A1 - Welsing, R. A1 - Williams, D. A. A1 - Zitzer, B. T1 - Discovery of TeV Gamma-Ray emission toward supernova remnant SNR G78.2+2.1 JF - The astrophysical journal : an international review of spectroscopy and astronomical physics N2 - We report the discovery of an unidentified, extended source of very-high-energy gamma-ray emission, VER J2019+407, within the radio shell of the supernova remnant SNR G78.2+2.1, using 21.4 hr of data taken by the VERITAS gamma-ray observatory in 2009. These data confirm the preliminary indications of gamma-ray emission previously seen in a two-year (2007-2009) blind survey of the Cygnus region by VERITAS. VER J2019+407, which is detected at a post-trials significance of 7.5 standard deviations in the 2009 data, is localized to the northwestern rim of the remnant in a region of enhanced radio and X-ray emission. It has an intrinsic extent of 0 degrees.23 +/- 0 degrees.03(stat-0 degrees.02sys)(+0 degrees.04) and its spectrum is well-characterized by a differential power law (dN/dE = N-0 x (E/TeV)-Gamma) with a photon index of Gamma = 2.37 +/- 0.14(stat) +/- 0.20(sys) and a flux normalization of N-0 = 1.5 +/- 0.2(stat) +/- 0.4(sys) x 10(-12) photon TeV-1 cm(-2) s(-1). This yields an integral flux of 5.2 +/- 0.8(stat) +/- 1.4(sys) x 10(-12) photon cm(-2) s(-1) above 320 GeV, corresponding to 3.7% of the Crab Nebula flux. We consider the relationship of the TeV gamma-ray emission with the GeV gamma-ray emission seen from SNR G78.2+2.1 as well as that seen from a nearby cocoon of freshly accelerated cosmic rays. Multiple scenarios are considered as possible origins for the TeV gamma-ray emission, including hadronic particle acceleration at the SNR shock. KW - acceleration of particles KW - cosmic rays KW - gamma rays: general KW - ISM: supernova remnants Y1 - 2013 U6 - https://doi.org/10.1088/0004-637X/770/2/93 SN - 0004-637X VL - 770 IS - 2 PB - IOP Publ. Ltd. CY - Bristol ER - TY - JOUR A1 - Temirbayev, Amirkhan A. A1 - Nalibayev, Yerkebulan D. A1 - Zhanabaev, Zeinulla Zh. A1 - Ponomarenko, Vladimir I. A1 - Rosenblum, Michael T1 - Autonomous and forced dynamics of oscillator ensembles with global nonlinear coupling an experimental study JF - Physical review : E, Statistical, nonlinear and soft matter physics N2 - We perform experiments with 72 electronic limit-cycle oscillators, globally coupled via a linear or nonlinear feedback loop. While in the linear case we observe a standard Kuramoto-like synchronization transition, in the nonlinear case, with increase of the coupling strength, we first observe a transition to full synchrony and then a desynchronization transition to a quasiperiodic state. However, in this state the ensemble remains coherent so that the amplitude of the mean field is nonzero, but the frequency of the mean field is larger than frequencies of all oscillators. Next, we analyze effects of common periodic forcing of the linearly or nonlinearly coupled ensemble and demonstrate regimes when the mean field is entrained by the force whereas the oscillators are not. Y1 - 2013 U6 - https://doi.org/10.1103/PhysRevE.87.062917 SN - 1539-3755 SN - 1550-2376 VL - 87 IS - 6 PB - American Physical Society CY - College Park ER - TY - JOUR A1 - Menon, Arathy A1 - Levermann, Anders A1 - Schewe, Jacob T1 - Enhanced future variability during India's rainy season JF - Geophysical research letters N2 - The Indian summer monsoon shapes the livelihood of a large share of the world's population. About 80% of annual precipitation over India occurs during the monsoon season from June through September. Next to its seasonal mean rainfall, the day-to-day variability is crucial for the risk of flooding, national water supply, and agricultural productivity. Here we show that the latest ensemble of climate model simulations, prepared for the AR-5 of the Intergovernmental Panel on Climate Change, consistently projects significant increases in day-to-day rainfall variability under unmitigated climate change. The relative increase by the period 2071-2100 with respect to the control period 1871-1900 ranges from 13% to 50% under the strongest scenario (Representative Concentration Pathways, RCP-8.5), in the 10 models with the most realistic monsoon climatology; and 13% to 85% when all the 20 models are considered. The spread across models reduces when variability increase per degree of global warming is considered, which is independent of the scenario in most models, and is 8% +/- 4%/K on average. This consistent projection across 20 comprehensive climate models provides confidence in the results and suggests the necessity of profound adaptation measures in the case of unmitigated climate change. KW - monsoon KW - variability KW - CMIP-5 Y1 - 2013 U6 - https://doi.org/10.1002/grl.50583 SN - 0094-8276 VL - 40 IS - 12 SP - 3242 EP - 3247 PB - American Geophysical Union CY - Washington ER - TY - JOUR A1 - Goswami, Bedartha A1 - Marwan, Norbert A1 - Feulner, Georg A1 - Kurths, Jürgen T1 - How do global temperature drivers influence each other? JF - European physical journal special topics N2 - We investigate a network of influences connected to global mean temperature. Considering various climatic factors known to influence global mean temperature, we evaluate not only the impacts of these factors on temperature but also the directed dependencies among the factors themselves. Based on an existing recurrence-based connectivity measure, we propose a new and more general measure that quantifies the level of dependence between two time series based on joint recurrences at a chosen time delay. The measures estimated in the analysis are tested for statistical significance using twin surrogates. We find, in accordance with earlier studies, the major drivers for global mean temperature to be greenhouse gases, ENSO, volcanic activity, and solar irradiance. We further uncover a feedback between temperature and ENSO. Our results demonstrate the need to involve multiple, delayed interactions within the drivers of temperature in order to develop a more thorough picture of global temperature variations. Y1 - 2013 U6 - https://doi.org/10.1140/epjst/e2013-01889-8 SN - 1951-6355 VL - 222 IS - 3-4 SP - 861 EP - 873 PB - Springer CY - Heidelberg ER - TY - JOUR A1 - Malyar, Ivan V. A1 - Santer, Svetlana A1 - Stetsyura, Svetlana V. T1 - The effect of illumination on the parameters of the polymer layer deposited from solution onto a semiconductor substrate JF - Technical physics letters : letters to the Russian journal of applied physics N2 - The effect of illumination on the thickness and roughness of monolayers of polycationic molecules of polyethyleneimine deposited from solution onto a silicon substrate was discovered and investigated. The super-bandgap illumination of the substrate during polyethyleneimine adsorption causes a decrease in both the roughness and integral thickness of the organic layer on n- and p-Si substrates. Y1 - 2013 U6 - https://doi.org/10.1134/S1063785013070183 SN - 1063-7850 VL - 39 IS - 7 SP - 656 EP - 659 PB - Pleiades Publ. CY - New York ER - TY - JOUR A1 - Molaro, P. A1 - Centurion, Martin A1 - Whitmore, J. B. A1 - Evans, T. M. A1 - Murphy, M. T. A1 - Agafonova, I. I. A1 - Bonifacio, P. A1 - D'Odorico, S. A1 - Levshakov, S. A. A1 - Lopez, S. A1 - Martins, C. J. A. P. A1 - Petitjean, P. A1 - Rahmani, H. A1 - Reimers, D. A1 - Srianand, R. A1 - Vladilo, G. A1 - Wendt, Martin T1 - The UVES Large Program for testing fundamental physics I. Bounds on a change in alpha towards quasar HE 221-2818 JF - Astronomy and astrophysics : an international weekly journal N2 - Context. Absorption-line systems detected in quasar spectra can be used to compare the value of the fine-structure constant, alpha, measured today on Earth with its value in distant galaxies. In recent years, some evidence has emerged of small temporal and also spatial variations in alpha on cosmological scales. These variations may reach a fractional level of approximate to 10 ppm (parts per million). Aims. To test these claims we are conducting a Large Program of observations with the Very Large Telescope's Ultraviolet and Visual Echelle Spectrograph (UVES), and are obtaining high-resolution (R approximate to 60 000) and high signal-to-noise ratio (S/N approximate to 100) UVES spectra calibrated specifically for this purpose. Here we analyse the first complete quasar spectrum from this programme, that of HE 2217-2818. Methods. We applied the many multiplet method to measure alpha in five absorption systems towards this quasar: z(abs) = 0.7866, 0.9424, 1.5558, 1.6279, and 1.6919. Results. The most precise result is obtained for the absorber at z(abs) = 1.6919 where 3 Fe II transitions and Al II lambda 1670 have high S/N and provide a wide range of sensitivities to alpha. The absorption profile is complex with several very narrow features, and it requires 32 velocity components to be fitted to the data. We also conducted a range of tests to estimate the systematic error budget. Our final result for the relative variation in alpha in this system is Delta alpha/alpha = +1.3 +/- 2.4(stat) +/- 1.0(sys) ppm. This is one of the tightest current bounds on alpha-variation from an individual absorber. A second, separate approach to the data reduction, calibration, and analysis of this system yielded a slightly different result of -3.8 +/- 2.1(stat) ppm, possibly suggesting a larger systematic error component than our tests indicated. This approach used an additional 3 Fe II transitions, parts of which were masked due to contamination by telluric features. Restricting this analysis to the Fe II transitions alone and using a modified absorption profile model gave a result that is consistent with the first approach, Delta alpha/alpha = +1.1 +/- 2.6(stat) ppm. The four other absorbers have simpler absorption profiles, with fewer and broader features, and offer transitions with a narrower range of sensitivities to alpha. They therefore provide looser bounds on Delta alpha/alpha at the greater than or similar to 10 ppm precision level. Conclusions. The absorbers towards quasar HE 2217-2818 reveal no evidence of any variation in alpha at the 3-ppm precision level (1 sigma confidence). If the recently reported 10-ppm dipolar variation in alpha across the sky is correct, the expectation at this sky position is (3.2-5.4) +/- 1.7 ppm depending on dipole model used. Our constraint of Delta alpha/alpha = +1.3 +/- 2.4(stat) +/- 1.0(sys) ppm is not inconsistent with this expectation. KW - quasars: absorption lines KW - quasars: individual: HE 2217-2818 KW - intergalactic medium KW - cosmology: miscellaneous cosmology KW - observations Y1 - 2013 U6 - https://doi.org/10.1051/0004-6361/201321351 SN - 0004-6361 VL - 555 IS - 4 PB - EDP Sciences CY - Les Ulis ER - TY - JOUR A1 - Laflamme, Simon A1 - Kollosche, Matthias A1 - Connor, Jerome J. A1 - Kofod, Guggi T1 - Robust flexible capacitive surface sensor for structural health monitoring applications JF - Journal of engineering mechanics N2 - Early detection of possible defects in civil infrastructure is vital to ensuring timely maintenance and extending structure life expectancy. The authors recently proposed a novel method for structural health monitoring based on soft capacitors. The sensor consisted of an off-the-shelf flexible capacitor that could be easily deployed over large surfaces, the main advantages being cost-effectiveness, easy installation, and allowing simple signal processing. In this paper, a capacitive sensor with tailored mechanical and electrical properties is presented, resulting in greatly improved robustness while retaining measurement sensitivity. The sensor is fabricated from a thermoplastic elastomer mixed with titanium dioxide and sandwiched between conductive composite electrodes. Experimental verifications conducted on wood and concrete specimens demonstrate the improved robustness, as well as the ability of the sensing method to diagnose and locate strain. KW - Strain gages KW - Structural health monitoring KW - Monitoring KW - Probe instruments KW - Strain gauge KW - Structural health monitoring KW - Strain monitoring KW - Capacitive sensor KW - Dielectric polymer KW - Stretchable sensor KW - Flexible membrane KW - Sensing skin Y1 - 2013 U6 - https://doi.org/10.1061/(ASCE)EM.1943-7889.0000530 SN - 0733-9399 SN - 1943-7889 VL - 139 IS - 7 SP - 879 EP - 885 PB - American Society of Civil Engineers CY - Reston ER - TY - JOUR A1 - Baushev, Anton N. T1 - Extragalactic dark matter and direct detection experiments JF - The astrophysical journal : an international review of spectroscopy and astronomical physics N2 - Recent astronomical data strongly suggest that a significant part of the dark matter content of the Local Group and Virgo Supercluster is not incorporated into the galaxy halos and forms diffuse components of these galaxy clusters. A portion of the particles from these components may penetrate the Milky Way and make an extragalactic contribution to the total dark matter containment of our Galaxy. We find that the particles of the diffuse component of the Local Group are apt to contribute similar to 12% to the total dark matter density near Earth. The particles of the extragalactic dark matter stand out because of their high speed (similar to 600 km s(-1)), i.e., they are much faster than the galactic dark matter. In addition, their speed distribution is very narrow (similar to 20 km s(-1)). The particles have an isotropic velocity distribution (perhaps, in contrast to the galactic dark matter). The extragalactic dark matter should provide a significant contribution to the direct detection signal. If the detector is sensitive only to the fast particles (v > 450 km s(-1)), then the signal may even dominate. The density of other possible types of the extragalactic dark matter (for instance, of the diffuse component of the Virgo Supercluster) should be relatively small and comparable with the average dark matter density of the universe. However, these particles can generate anomaly high-energy collisions in direct dark matter detectors. KW - astroparticle physics KW - dark matter KW - elementary particles KW - Local Group Y1 - 2013 U6 - https://doi.org/10.1088/0004-637X/771/2/117 SN - 0004-637X VL - 771 IS - 2 PB - IOP Publ. Ltd. CY - Bristol ER - TY - JOUR A1 - Koenig, Tobias A1 - Tsukruk, Vladimir V. A1 - Santer, Svetlana T1 - Controlled topography change of subdiffraction structures based on photosensitive polymer films induced by surface plasmon polaritons JF - ACS applied materials & interfaces N2 - We discuss the controlled subdiffraction modulations of photosensitive polymer films that are induced by surface plasmon interference in striking contrast to well-known conventional microscopic gratings. The near-field light intensity patterns were generated at the nanoslits fabricated in a silver layer with the photosensitive polymer film placed above. We observed that the topographical modulations can be excited only when the polarization is perpendicular to the nanoslits. Moreover, we have shown that light with certain wavelengths resulted in a characteristic topographical pattern with the periodicity three times smaller than the wavelength of incoming light. A combination of experimental observations with simulations showed that the unique subdiffraction topographical patterns are caused by constructive interference between two counter-propagating surface plasmon waves generated at neighboring nanoslits in the metal layer beneath the photosensitive polymer film. The light intensity distribution was simulated to demonstrate strong dependency upon the slit array periodicity as well as wavelength and polarization of incoming light. KW - azobenzene photosensitive polymer films KW - surface plasm on polaritons KW - silver nanoslits Y1 - 2013 U6 - https://doi.org/10.1021/am400712r SN - 1944-8244 VL - 5 IS - 13 SP - 6009 EP - 6016 PB - American Chemical Society CY - Washington ER - TY - JOUR A1 - Nezhadhaghighi, M. Ghasemi A1 - Rajabpour, M. A. T1 - Quantum entanglement entropy and classical mutual information in long-range harmonic oscillators JF - Physical review : B, Condensed matter and materials physics N2 - We study different aspects of quantum von Neumann and Renyi entanglement entropy of one-dimensional long-range harmonic oscillators that can be described by well-defined nonlocal field theories. We show that the entanglement entropy of one interval with respect to the rest changes logarithmically with the number of oscillators inside the subsystem. This is true also in the presence of different boundary conditions. We show that the coefficients of the logarithms coming from different boundary conditions can be reduced to just two different universal coefficients. We also study the effect of the mass and temperature on the entanglement entropy of the system in different situations. The universality of our results is also confirmed by changing different parameters in the coupled harmonic oscillators. We also show that more general interactions coming from general singular Toeplitz matrices can be decomposed to our long-range harmonic oscillators. Despite the long-range nature of the couplings, we show that the area law is valid in two dimensions and the universal logarithmic terms appear if we consider subregions with sharp corners. Finally, we study analytically different aspects of the mutual information such as its logarithmic dependence to the subsystem, effect of mass, and influence of the boundary. We also generalize our results in this case to general singular Toeplitz matrices and higher dimensions. Y1 - 2013 U6 - https://doi.org/10.1103/PhysRevB.88.045426 SN - 1098-0121 SN - 1550-235X VL - 88 IS - 4 PB - American Physical Society CY - College Park ER - TY - JOUR A1 - Proctor, Christopher M. A1 - Kim, Chunki A1 - Neher, Dieter A1 - Thuc-Quyen Nguyen, T1 - Nongeminate recombination and charge transport limitations in diketopyrrolopyrrole-based solution-processed small molecule solar cells JF - Advanced functional materials N2 - Charge transport and nongeminate recombination are investigated in two solution-processed small molecule bulk heterojunction solar cells consisting of diketopyrrolopyrrole (DPP)-based donor molecules, mono-DPP and bis-DPP, blended with [6,6]-phenyl-C71-butyric acid methyl ester (PCBM). While the bis-DPP system exhibits a high fill factor (62%) the mono-DPP system suffers from pronounced voltage dependent losses, which limit both the fill factor (46%) and short circuit current. A method to determine the average charge carrier density, recombination current, and effective carrier lifetime in operating solar cells as a function of applied bias is demonstrated. These results and light intensity measurements of the current-voltage characteristics indicate that the mono-DPP system is severely limited by nongeminate recombination losses. Further analysis reveals that the most significant factor leading to the difference in fill factor is the comparatively poor hole transport properties in the mono-DPP system (2 x 10(-5) cm(2) V-1 s(-1) versus 34 x 10(-5) cm(2) V-1 s(-1)). These results suggest that future design of donor molecules for organic photovoltaics should aim to increase charge carrier mobility thereby enabling faster sweep out of charge carriers before they are lost to nongeminate recombination. KW - charge transport KW - solar cells KW - photovoltaic devices KW - organic electronics KW - characterization tools Y1 - 2013 U6 - https://doi.org/10.1002/adfm.201202643 SN - 1616-301X SN - 1616-3028 VL - 23 IS - 28 SP - 3584 EP - 3594 PB - Wiley-VCH CY - Weinheim ER - TY - JOUR A1 - Rychkov, Dmitry A1 - Rychkov, A. A1 - Efimov, N. A1 - Malygin, A. A1 - Gerhard, Reimund T1 - Higher stabilities of positive and negative charge on tetrafluoroethylene-hexafluoropropylene copolymer (FEP) electrets treated with titanium-tetrachloride vapor JF - Applied physics : A, Materials science & processing N2 - Tetrafluoroethylene-hexafluoropropylene copolymer (FEP) films were treated with titanium-tetrachloride vapor in a molecular-layer deposition process. As a result of the surface treatment, significant improvements of the thermal and temporal charge stability were observed. Charge-decay measurements revealed enhancements of the half-value temperatures and the relaxation times of positively charged FEP electrets by at least 120 A degrees C and two orders of magnitude, respectively. Beyond previous publications on fluoropolymer electrets with surface modification, we here report enhanced charge stabilities of the FEP films charged in negative as well as in positive corona discharges. Even though the improvement for negatively charged FEP films is moderate (half-value temperature about 20 A degrees C higher), our experiments show that the asymmetry in positive and negative charge stability that is typical for FEP electrets can be overcome by means of chemical surface treatments. The results are discussed in the context of the formation of modified surface layers with enhanced charge-trapping properties. Y1 - 2013 U6 - https://doi.org/10.1007/s00339-013-7821-1 SN - 0947-8396 VL - 112 IS - 2 SP - 283 EP - 287 PB - Springer CY - New York ER - TY - JOUR A1 - Poghossian, A. A1 - Weil, M. A1 - Cherstvy, Andrey G. A1 - Schöning, M. J. T1 - Electrical monitoring of polyelectrolyte multilayer formation by means of capacitive field-effect devices JF - Analytical & bioanalytical chemistry N2 - The semiconductor field-effect platform represents a powerful tool for detecting the adsorption and binding of charged macromolecules with direct electrical readout. In this work, a capacitive electrolyte-insulator-semiconductor (EIS) field-effect sensor consisting of an Al-p-Si-SiO2 structure has been applied for real-time in situ electrical monitoring of the layer-by-layer formation of polyelectrolyte (PE) multilayers (PEM). The PEMs were deposited directly onto the SiO2 surface without any precursor layer or drying procedures. Anionic poly(sodium 4-styrene sulfonate) and cationic weak polyelectrolyte poly(allylamine hydrochloride) have been chosen as a model system. The effect of the ionic strength of the solution, polyelectrolyte concentration, number and polarity of the PE layers on the characteristics of the PEM-modified EIS sensors have been studied by means of capacitance-voltage and constant-capacitance methods. In addition, the thickness, surface morphology, roughness and wettabilityof the PE mono- and multilayers have been characterised by ellipsometry, atomic force microscopy and water contact-angle methods, respectively. To explain potential oscillations on the gate surface and signal behaviour of the capacitive field-effect EIS sensor modified with a PEM, a simplified electrostatic model that takes into account the reduced electrostatic screening of PE charges by mobile ions within the PEM has been proposed and discussed. KW - Field-effect KW - Capacitive sensor KW - Polyelectrolyte multilayer KW - Electrical monitoring KW - ConCap Y1 - 2013 U6 - https://doi.org/10.1007/s00216-013-6951-9 SN - 1618-2642 VL - 405 IS - 20 SP - 6425 EP - 6436 PB - Springer CY - Heidelberg ER - TY - JOUR A1 - Richter, Philipp A1 - Fox, Andrew J. A1 - Wakker, Bart P. A1 - Lehner, Nicolas A1 - Howk, J. Christopher A1 - Bland-Hawthorn, Joss A1 - Ben Bekhti, Nadya A1 - Fechner, Cora T1 - The COS/UVES absorption survey of the magellanic stream - II. Evidence for a complex enrichment history of the stream from the fairall 9 sightline JF - The astrophysical journal : an international review of spectroscopy and astronomical physics N2 - We present a multi-wavelength study of the Magellanic Stream (MS), a massive gaseous structure in the Local Group that is believed to represent material stripped from the Magellanic Clouds. We use ultraviolet, optical and radio data obtained with HST/COS, VLT/UVES, FUSE, GASS, and ATCA to study metal abundances and physical conditions in the Stream toward the quasar Fairall 9. Line absorption in the MS from a large number of metal ions and from molecular hydrogen is detected in up to seven absorption components, indicating the presence of multi-phase gas. From the analysis of unsaturated S II absorption, in combination with a detailed photoionization model, we obtain a surprisingly high alpha abundance in the Stream toward Fairall 9 of [S/H] = -0.30 +/- 0.04 (0.50 solar). This value is five times higher than what is found along other MS sightlines based on similar COS/UVES data sets. In contrast, the measured nitrogen abundance is found to be substantially lower ([N/H] = -1.15 +/- 0.06), implying a very low [N/alpha] ratio of -0.85 dex. The substantial differences in the chemical composition of MS toward Fairall 9 compared to other sightlines point toward a complex enrichment history of the Stream. We favor a scenario, in which the gas toward Fairall 9 was locally enriched with a elements by massive stars and then was separated from the Magellanic Clouds before the delayed nitrogen enrichment from intermediate-mass stars could set in. Our results support (but do not require) the idea that there is a metal-enriched filament in the Stream toward Fairall 9 that originates in the LMC. KW - Galaxy: evolution KW - Galaxy: halo KW - ISM: abundances KW - Magellanic Clouds KW - quasars: absorption lines Y1 - 2013 U6 - https://doi.org/10.1088/0004-637X/772/2/111 SN - 0004-637X VL - 772 IS - 2 PB - IOP Publ. Ltd. CY - Bristol ER - TY - JOUR A1 - Fox, Andrew J. A1 - Richter, Philipp A1 - Wakker, Bart P. A1 - Lehner, Nicolas A1 - Howk, J. Christopher A1 - Ben Bekhti, Nadya A1 - Bland-Hawthorn, Joss A1 - Lucas, Stephen T1 - The COS/UVES absorption survey of the magellanic stream - I. One-tenth solar abundances along the body of the stream JF - The astrophysical journal : an international review of spectroscopy and astronomical physics N2 - The Magellanic Stream (MS) is a massive and extended tail of multi-phase gas stripped out of the Magellanic Clouds and interacting with the Galactic halo. In this first paper of an ongoing program to study the Stream in absorption, we present a chemical abundance analysis based on HST/COS and VLT/UVES spectra of four active galactic nuclei (RBS 144, NGC 7714, PHL 2525, and HE 0056-3622) lying behind the MS. Two of these sightlines yield good MS metallicity measurements: toward RBS 144 we measure a low MS metallicity of [S/H] = [S II/H I] = -1.13 +/- 0.16 while toward NGC 7714 we measure [O/H] = [O I/H I] = -1.24 +/- 0.20. Taken together with the published MS metallicity toward NGC 7469, these measurements indicate a uniform abundance of approximate to 0.1 solar along the main body of the Stream. This provides strong support to a scenario in which most of the Stream was tidally stripped from the SMC approximate to 1.5-2.5 Gyr ago (a time at which the SMC had a metallicity of approximate to 0.1 solar), as predicted by several N-body simulations. However, in Paper II of this series, we report a much higher metallicity (S/H = 0.5 solar) in the inner Stream toward Fairall 9, a direction sampling a filament of the MS that Nidever et al. claim can be traced kinematically to the Large Magellanic Cloud, not the Small Magellanic Cloud. This shows that the bifurcation of the Stream is evident in its metal enrichment, as well as its spatial extent and kinematics. Finally we measure a similar low metallicity [O/H] = [O I/H I] = -1.03 +/- 0.18 in the v(LSR) = 150 km s(-1) cloud toward HE 0056-3622, which belongs to a population of anomalous velocity clouds near the south Galactic pole. This suggests these clouds are associated with the Stream or more distant structures (possibly the Sculptor Group, which lies in this direction at the same velocity), rather than tracing foreground Galactic material. KW - Galaxy: evolution KW - Galaxy: halo KW - ISM: abundances KW - Magellanic Clouds KW - ultraviolet: ISM Y1 - 2013 U6 - https://doi.org/10.1088/0004-637X/772/2/110 SN - 0004-637X VL - 772 IS - 2 PB - IOP Publ. Ltd. CY - Bristol ER -