Dokument-ID Dokumenttyp Verfasser/Autoren Herausgeber Haupttitel Abstract Auflage Verlagsort Verlag Erscheinungsjahr Seitenzahl Schriftenreihe Titel Schriftenreihe Bandzahl ISBN Quelle der Hochschulschrift Konferenzname Quelle:Titel Quelle:Jahrgang Quelle:Heftnummer Quelle:Erste Seite Quelle:Letzte Seite URN DOI Abteilungen OPUS4-55324 Wissenschaftlicher Artikel Abeysekara, A. U.; Archambault, S.; Archer, A.; Benbow, Wystan; Bird, Ralph; Buchovecky, M.; Buckley, J. H.; Bugaev, V.; Byrum, K.; Cerruti, M.; Chen, X.; Ciupik, L.; Cui, W.; Dickinson, H. J.; Eisch, J. D.; Errando, M.; Falcone, A.; Feng, Q.; Finley, J. P.; Fleischhack, H.; Fortson, L.; Furniss, A.; Gillanders, G. H.; Griffin, S.; Grube, J.; Hutten, M.; Hakansson, N.; Hanna, D.; Holder, J.; Humensky, T. B.; Johnson, C. A.; Kaaret, P.; Kar, P.; Kertzman, M.; Kieda, D.; Krause, M.; Krennrich, F.; Kumar, S.; Lang, M. J.; Maier, G.; McArthur, S.; McCann, A.; Meagher, K.; Moriarty, P.; Mukherjee, R.; Nguyen, T.; Nieto, D.; Ong, R. A.; Otte, A. N.; Park, N.; Pelassa, V.; Pohl, Martin; Popkow, A.; Pueschel, Elisa; Quinn, J.; Ragan, K.; Reynolds, P. T.; Richards, G. T.; Roache, E.; Rulten, C.; Santander, M.; Sembroski, G. H.; Shahinyan, K.; Staszak, D.; Telezhinsky, Igor O.; Tucci, J. V.; Tyler, J.; Wakely, S. P.; Weiner, O. M.; Weinstein, A.; Wilhelm, Alina; Williams, D. A.; Fegan, S.; Giebels, B.; Horan, D.; Berdyugin, A.; Kuan, J.; Lindfors, E.; Nilsson, K.; Oksanen, A.; Prokoph, H.; Reinthal, R.; Takalo, L.; Zefi, F. A Luminous and Isolated Gamma-Ray Flare from the Blazar B2 1215+30 B2 1215+30 is a BL-Lac-type blazar that was first detected at TeV energies by the MAGIC atmospheric Cherenkov telescopes and subsequently confirmed by the Very Energetic Radiation Imaging Telescope Array System (VERITAS) observatory with data collected between 2009 and 2012. In 2014 February 08, VERITAS detected a large-amplitude flare from B2. 1215+30 during routine monitoring observations of the blazar 1ES. 1218+304, located in the same field of view. The TeV flux reached 2.4 times the Crab Nebula flux with a variability timescale of <3.6 hr. Multiwavelength observations with Fermi-LAT, Swift, and the Tuorla Observatory revealed a correlated high GeV flux state and no significant optical counterpart to the flare, with a spectral energy distribution where the gamma-ray luminosity exceeds the synchrotron luminosity. When interpreted in the framework of a onezone leptonic model, the observed emission implies a high degree of beaming, with Doppler factor delta > 10, and an electron population with spectral index p < 2.3. Bristol IOP Publ. Ltd. 2017 6 The astrophysical journal : an international review of spectroscopy and astronomical physics 836 2 10.3847/1538-4357/836/2/205 Institut für Physik und Astronomie OPUS4-52181 Wissenschaftlicher Artikel Hintsche, Marius; Waljor, Veronika; Grossmann, Robert; Kühn, Marco J.; Thormann, Kai M.; Peruani, Fernando; Beta, Carsten A polar bundle of flagella can drive bacterial swimming by pushing, pulling, or coiling around the cell body Bacteria swim in sequences of straight runs that are interrupted by turning events. They drive their swimming locomotion with the help of rotating helical flagella. Depending on the number of flagella and their arrangement across the cell body, different run-and-turn patterns can be observed. Here, we present fluorescence microscopy recordings showing that cells of the soil bacterium Pseudomonas putida that are decorated with a polar tuft of helical flagella, can alternate between two distinct swimming patterns. On the one hand, they can undergo a classical push-pull-push cycle that is well known from monopolarly flagellated bacteria but has not been reported for species with a polar bundle of multiple flagella. Alternatively, upon leaving the pulling mode, they can enter a third slow swimming phase, where they propel themselves with their helical bundle wrapped around the cell body. A theoretical estimate based on a random-walk model shows that the spreading of a population of swimmers is strongly enhanced when cycling through a sequence of pushing, pulling, and wrapped flagellar configurations as compared to the simple push-pull-push pattern. London Macmillan Publishers Limited, part of Springer Nature 2017 10 Scientific reports 7 10.1038/s41598-017-16428-9 Institut für Physik und Astronomie OPUS4-55353 Wissenschaftlicher Artikel Postnov, K.; Oskinova, Lida M.; Torrejon, J. M. A propelling neutron star in the enigmatic Be-star gamma Cassiopeia gamma Cassiopeia (gamma Cas), is known to be a binary system consisting of a Be-type star and a low-mass (M similar to 1M(circle dot)) companion of unknown nature orbiting in the Be-disc plane. Here, we apply the quasi-spherical accretion theory on to a compact magnetized star and show that if the low-mass companion of gamma Cas is a fast spinning neutron star, the key observational signatures of. Cas are remarkably well reproduced. Direct accretion on to this fast rotating neutron star is impeded by the propeller mechanism. In this case, around the neutron star magnetosphere a hot shell is formed which emits thermal X-rays in qualitative and quantitative agreement with observed properties of the X-ray emission from gamma Cas. We suggest that gamma Cas and its analogues constitute a new subclass of Be-type X-ray binaries hosting rapidly rotating neutron stars formed in supernova explosions with small kicks. The subsequent evolutionary stage of gamma Cas and its analogues should be the X Per-type binaries comprising low-luminosity slowly rotating X-ray pulsars. The model explains the enigmatic X-ray emission from gamma Cas, and also establishes evolutionary connections between various types of rotating magnetized neutron stars in Be-binaries. Oxford Oxford Univ. Press 2017 5 Monthly notices of the Royal Astronomical Society 465 1 L119 L123 10.1093/mnrasl/slw223 Institut für Physik und Astronomie OPUS4-40373 Wissenschaftlicher Artikel Herrmann, Carl J. J.; Metzler, Ralf A self-avoiding walk with neural delays as a model of fixational eye movements Fixational eye movements show scaling behaviour of the positional mean-squared displacement with a characteristic transition from persistence to antipersistence for increasing time-lag. These statistical patterns were found to be mainly shaped by microsaccades (fast, small-amplitude movements). However, our re-analysis of fixational eye-movement data provides evidence that the slow component (physiological drift) of the eyes exhibits scaling behaviour of the mean-squared displacement that varies across human participants. These results suggest that drift is a correlated movement that interacts with microsaccades. Moreover, on the long time scale, the mean-squared displacement of the drift shows oscillations, which is also present in the displacement auto-correlation function. This finding lends support to the presence of time-delayed feedback in the control of drift movements. Based on an earlier non-linear delayed feedback model of fixational eye movements, we propose and discuss different versions of a new model that combines a self-avoiding walk with time delay. As a result, we identify a model that reproduces oscillatory correlation functions, the transition from persistence to antipersistence, and microsaccades. London Springer Nature 2017 16 Scientific reports 7 1 17 10.1038/s41598-017-13489-8 Institut für Physik und Astronomie OPUS4-53756 Wissenschaftlicher Artikel Kamann, Sebastian; Husser, T. -O.; Dreizler, S.; Emsellem, E.; Weilbacher, Peter Michael; Martens, S.; Bacon, R.; den Brok, M.; Giesers, B.; Krajnovic, Davor; Roth, Martin M.; Wendt, Martin; Wisotzki, Lutz A stellar census in globular clusters with MUSE This is the first of a series of papers presenting the results from our survey of 25 Galactic globular clusters with the MUSE integral-field spectrograph. In combination with our dedicated algorithm for source deblending, MUSE provides unique multiplex capabilities in crowded stellar fields and allows us to acquire samples of up to 20 000 stars within the half-light radius of each cluster. The present paper focuses on the analysis of the internal dynamics of 22 out of the 25 clusters, using about 500 000 spectra of 200 000 individual stars. Thanks to the large stellar samples per cluster, we are able to perform a detailed analysis of the central rotation and dispersion fields using both radial profiles and two-dimensional maps. The velocity dispersion profiles we derive show a good general agreement with existing radial velocity studies but typically reach closer to the cluster centres. By comparison with proper motion data, we derive or update the dynamical distance estimates to 14 clusters. Compared to previous dynamical distance estimates for 47 Tuc, our value is in much better agreement with other methods. We further find significant (>3 sigma) rotation in the majority (13/22) of our clusters. Our analysis seems to confirm earlier findings of a link between rotation and the ellipticities of globular clusters. In addition, we find a correlation between the strengths of internal rotation and the relaxation times of the clusters, suggesting that the central rotation fields are relics of the cluster formation that are gradually dissipated via two-body relaxation. Oxford Oxford Univ. Press 2017 26 Monthly notices of the Royal Astronomical Society 473 4 5591 5616 10.1093/mnras/stx2719 Institut für Physik und Astronomie OPUS4-55442 Wissenschaftlicher Artikel Vandewal, Koen; Benduhn, Johannes; Schellhammer, Karl Sebastian; Vangerven, Tim; Rückert, Janna E.; Piersimoni, Fortunato; Scholz, Reinhard; Zeika, Olaf; Fan, Yeli; Barlow, Stephen; Neher, Dieter; Marder, Seth R.; Manca, Jean; Spoltore, Donato; Cuniberti, Gianaurelio; Ortmann, Frank Absorption Tails of Donor In disordered organic semiconductors, the transfer of a rather localized charge carrier from one site to another triggers a deformation of the molecular structure quantified by the intramolecular relaxation energy. A similar structural relaxation occurs upon population of intermolecular charge-transfer (CT) states formed at organic electron donor (D)-acceptor (A) interfaces. Weak CT absorption bands for D A complexes occur at photon energies below the optical gaps of both the donors and the C-60 acceptor as a result of optical transitions from the neutral ground state to the ionic CT state. In this work, we show that temperature-activated intramolecular vibrations of the ground state play a major role in determining the line shape of such CT absorption bands. This allows us to extract values for the relaxation energy related to the geometry change from neutral to ionic CT complexes. Experimental values for the relaxation energies of 20 D:C-60 CT complexes correlate with values calculated within density functional theory. These results provide an experimental method for determining the polaron relaxation energy in solid-state organic D-A blends and show the importance of a reduced relaxation energy, which we introduce to characterize thermally activated CT processes. Washington American Chemical Society 2017 6 Journal of the American Chemical Society 139 4 1699 1704 10.1021/jacs.6b12857 Institut für Physik und Astronomie OPUS4-55245 Wissenschaftlicher Artikel Anielski, Alexander; Barbosa Pfannes, Eva Katharina; Beta, Carsten Adaptive microfluidic gradient generator for quantitative chemotaxis experiments Chemotactic motion in a chemical gradient is an essential cellular function that controls many processes in the living world. For a better understanding and more detailed modelling of the underlying mechanisms of chemotaxis, quantitative investigations in controlled environments are needed. We developed a setup that allows us to separately address the dependencies of the chemotactic motion on the average background concentration and on the gradient steepness of the chemoattractant. In particular, both the background concentration and the gradient steepness can be kept constant at the position of the cell while it moves along in the gradient direction. This is achieved by generating a well-defined chemoattractant gradient using flow photolysis. In this approach, the chemoattractant is released by a light-induced reaction from a caged precursor in a microfluidic flow chamber upstream of the cell. The flow photolysis approach is combined with an automated real-time cell tracker that determines changes in the cell position and triggers movement of the microscope stage such that the cell motion is compensated and the cell remains at the same position in the gradient profile. The gradient profile can be either determined experimentally using a caged fluorescent dye or may be alternatively determined by numerical solutions of the corresponding physical model. To demonstrate the function of this adaptive microfluidic gradient generator, we compare the chemotactic motion of Dictyostelium discoideum cells in a static gradient and in a gradient that adapts to the position of the moving cell. Published by AIP Publishing. Melville American Institute of Physics 2017 10 Review of scientific instruments : a monthly journal devoted to scientific instruments, apparatus, and techniques 88 10.1063/1.4978535 Institut für Physik und Astronomie OPUS4-55503 Wissenschaftlicher Artikel Safdari, Hadiseh; Cherstvy, Andrey G.; Chechkin, Aleksei V.; Bodrova, Anna; Metzler, Ralf Aging underdamped scaled Brownian motion We investigate both analytically and by computer simulations the ensemble- and time-averaged, nonergodic, and aging properties of massive particles diffusing in a medium with a time dependent diffusivity. We call this stochastic diffusion process the (aging) underdamped scaled Brownian motion (UDSBM). We demonstrate how the mean squared displacement (MSD) and the time-averaged MSD of UDSBM are affected by the inertial term in the Langevin equation, both at short, intermediate, and even long diffusion times. In particular, we quantify the ballistic regime for the MSD and the time-averaged MSD as well as the spread of individual time-averaged MSD trajectories. One of the main effects we observe is that, both for the MSD and the time-averaged MSD, for superdiffusive UDSBM the ballistic regime is much shorter than for ordinary Brownian motion. In contrast, for subdiffusive UDSBM, the ballistic region extends to much longer diffusion times. Therefore, particular care needs to be taken under what conditions the overdamped limit indeed provides a correct description, even in the long time limit. We also analyze to what extent ergodicity in the Boltzmann-Khinchin sense in this nonstationary system is broken, both for subdiffusive and superdiffusive UDSBM. Finally, the limiting case of ultraslow UDSBM is considered, with a mixed logarithmic and power-law dependence of the ensemble-and time-averaged MSDs of the particles. In the limit of strong aging, remarkably, the ordinary UDSBM and the ultraslow UDSBM behave similarly in the short time ballistic limit. The approaches developed here open ways for considering other stochastic processes under physically important conditions when a finite particle mass and aging in the system cannot be neglected. College Park American Physical Society 2017 15 Physical review : E, Statistical, nonlinear and soft matter physics 95 10.1103/PhysRevE.95.012120 Institut für Physik und Astronomie OPUS4-49317 Wissenschaftlicher Artikel Stange, Maike; Hintsche, Marius; Sachse, Kirsten; Gerhardt, Matthias; Valleriani, Angelo; Beta, Carsten Analyzing the spatial positioning of nuclei in polynuclear giant cells How cells establish and maintain a well-defined size is a fundamental question of cell biology. Here we investigated to what extent the microtubule cytoskeleton can set a predefined cell size, independent of an enclosing cell membrane. We used electropulse-induced cell fusion to form giant multinuclear cells of the social amoeba Dictyostelium discoideum. Based on dual-color confocal imaging of cells that expressed fluorescent markers for the cell nucleus and the microtubules, we determined the subcellular distributions of nuclei and centrosomes in the giant cells. Our two- and three-dimensional imaging results showed that the positions of nuclei in giant cells do not fall onto a regular lattice. However, a comparison with model predictions for random positioning showed that the subcellular arrangement of nuclei maintains a low but still detectable degree of ordering. This can be explained by the steric requirements of the microtubule cytoskeleton, as confirmed by the effect of a microtubule degrading drug. Bristol IOP Publ. Ltd. 2017 8 Journal of Physics D: Applied Physics 50 46 10.1088/1361-6463/aa8da0 Institut für Physik und Astronomie OPUS4-54877 Wissenschaftlicher Artikel Stolterfoht, Martin; Wolff, Christian Michael; Amir, Yohai; Paulke, Andreas; Perdigon-Toro, Lorena; Caprioglio, Pietro; Neher, Dieter Approaching the fill factor Shockley-Queisser limit in stable, dopant-free triple cation perovskite solar cells Perovskite solar cells now compete with their inorganic counterparts in terms of power conversion efficiency, not least because of their small open-circuit voltage (V-OC) losses. A key to surpass traditional thin-film solar cells is the fill factor (FF). Therefore, more insights into the physical mechanisms that define the bias dependence of the photocurrent are urgently required. In this work, we studied charge extraction and recombination in efficient triple cation perovskite solar cells with undoped organic electron/hole transport layers (ETL/HTL). Using integral time of flight we identify the transit time through the HTL as the key figure of merit for maximizing the fill factor (FF) and efficiency. Complementarily, intensity dependent photocurrent and V-OC measurements elucidate the role of the HTL on the bias dependence of non-radiative and transport-related loss channels. We show that charge transport losses can be completely avoided under certain conditions, yielding devices with FFs of up to 84%. Optimized cells exhibit power conversion efficiencies of above 20% for 6 mm(2) sized pixels and 18.9% for a device area of 1 cm(2). These are record efficiencies for hybrid perovskite devices with dopant-free transport layers, highlighting the potential of this device technology to avoid charge-transport limitations and to approach the Shockley-Queisser limit. Cambridge Royal Society of Chemistry 2017 10 Energy & Environmental Science 10 1530 1539 10.1039/c7ee00899f Institut für Physik und Astronomie OPUS4-55272 Wissenschaftlicher Artikel Zacharias, Michael; Chen, Xuhui; Wagner, Stefan Attenuation of TeV gamma-rays by the starlight photon field of the host galaxy The absorption of TeV gamma-ray photons produced in relativistic jets by surrounding soft photon fields is a long-standing problem of jet physics. In some cases, the most likely emission site close to the central black hole is ruled out because of the high opacity caused by strong optical and infrared photon sources, such as the broad-line region. Mostly neglected for jet modelling is the absorption of gamma-rays in the starlight photon field of the host galaxy. Analysing the absorption for arbitrary locations and observation angles of the gamma-ray emission site within the host galaxy, we find that the distance to the galaxy centre, the observation angle, and the distribution of starlight in the galaxy are crucial for the amount of absorption. We derive the absorption value for a sample of 20 TeV-detected blazars with a redshift z(r) < 0.2. The absorption value of the gamma-ray emission located in the galaxy centre may be as high as 20 per cent, with an average value of 6 per cent. This is important in order to determine the intrinsic blazar parameters. We see no significant trends in our sample between the degree of absorption and host properties, such as starlight emissivity, galactic size, half-light radius, and redshift. While the uncertainty of the spectral properties of the extragalactic background light exceeds the effect of absorption by stellar light from the host galaxy in distant objects, the latter is a dominant effect in nearby sources. It may also be revealed in a differential comparison of sources with similar redshifts. Oxford Oxford Univ. Press 2017 8 Monthly notices of the Royal Astronomical Society 465 3 3767 3774 10.1093/mnras/stw3032 Institut für Physik und Astronomie OPUS4-53549 Wissenschaftlicher Artikel Bolotov, Maxim I.; Smirnov, Lev A.; Osipov, Grigory V.; Pikovskij, Arkadij Breathing chimera in a system of phase oscillators Chimera states consisting of synchronous and asynchronous domains in a medium of nonlinearly coupled phase oscillators have been considered. Stationary inhomogeneous solutions of the Ott-Antonsen equation for a complex order parameter that correspond to fundamental chimeras have been constructed. The direct numerical simulation has shown that these structures under certain conditions are transformed to oscillatory (breathing) chimera regimes because of the development of instability. New York Pleiades Publ. 2017 7 JETP Letters 106 393 399 10.1134/S0021364017180059 Institut für Physik und Astronomie OPUS4-55303 Wissenschaftlicher Artikel Petereit, Johannes; Pikovskij, Arkadij Chaos synchronization by nonlinear coupling We study synchronization properties of three nonlinearly coupled chaotic maps. Coupling is introduced in such a way, that it cannot be reduced to pairwise terms, but includes combined action of all interacting units. For two models of nonlinear coupling we characterize the transition to complete synchrony, as well as partially synchronized states. Relation to hypernetworks of chaotic units is also discussed. Amsterdam Elsevier 2017 8 Communications in nonlinear science & numerical simulation 44 344 351 10.1016/j.cnsns.2016.09.002 Institut für Physik und Astronomie OPUS4-54885 Wissenschaftlicher Artikel Roland, Steffen; Yan, Liang; Zhang, Qianqian; Jiao, Xuechen; Hunt, Adrian; Ghasemi, Masoud; Ade, Harald; You, Wei; Neher, Dieter Charge Generation and Mobility-Limited Performance of Bulk Heterojunction Solar Cells with a Higher Adduct Fullerene Alternative electron acceptors are being actively explored in order to advance the development of bulk-heterojunction (BHJ) organic solar cells (OSCs). The indene-C-60 bisadduct (ICBA) has been regarded as a promising candidate, as it provides high open-circuit voltage in BHJ solar cells; however, the photovoltaic performance of such ICBA-based devices is often inferior when compared to cells with the omnipresent PCBM electron acceptor. Here, by pairing the high performance polymer (FTAZ) as the donor with either PCBM or ICBA as the acceptor, we explore the physical mechanism behind the reduced performance of the ICBA-based device. Time delayed collection field (TDCF) experiments reveal reduced, yet field-independent free charge generation in the FTAZ:ICBA system, explaining the overall lower photocurrent in its cells. Through the analysis of the photoluminescence, photogeneration, and electroluminescence, we find that the lower generation efficiency is neither caused by inefficient exciton splitting, nor do we find evidence for significant energy back-transfer from the CT state to singlet excitons. In fact, the increase in open circuit voltage when replacing PCBM by ICBA is entirely caused by the increase in the CT energy, related to the shift in the LUMO energy, while changes in the radiative and nonradiative recombination losses are nearly absent. On the other hand, space charge limited current (SCLC) and bias-assisted charge extraction (BACE) measurements consistently reveal a severely lower electron mobilitiy in the FTAZ:ICBA blend. Studies of the blends with resonant soft X-ray scattering (R-SoXS), grazing incident wide-angle X-ray scattering (GIWAXS), and scanning transmission X-ray microscopy (STXM) reveal very little differences in the mesoscopic morphology but significantly less nanoscale molecular ordering of the fullerene domains in the ICBA based blends, which we propose as the main cause for the lower generation efficiency and smaller electron mobility. Calculations of the JV curves with an analytical model, using measured values, show good agreement with the experimentally determined JV characteristics, proving that these devices suffer from slow carrier extraction, resulting in significant bimolecular recombination losses. Therefore, this study highlights the importance of high charge carrier mobility for newly synthesized acceptor materials, in addition to having suitable energy levels. Washington American Chemical Society 2017 12 The journal of physical chemistry : C, Nanomaterials and interfaces 121 10305 10316 10.1021/acs.jpcc.7b02288 Institut für Physik und Astronomie OPUS4-55376 Wissenschaftlicher Artikel Koopman, Wouter-Willem Adriaan; Natali, Marco; Donati, Giovanni P.; Muccini, Michele; Toffanin, Stefano Charge-exciton interaction rate in organic field-effect transistors by means of transient photoluminescence electromodulated spectroscopy Organic light-emitting transistors (OLETs) offer a huge potential for the design of highly integrated multifunctional optoelectronic systems and of intense nano scale light sources, such as the long-searched-for electrically pumped organic laser. In order to fulfill these promises, the efficiency and brightness of the current state-of-the-art devices have to be increased significantly. The dominating quenching process limiting the external quantum efficiency in OLETs is charge-exciton interaction. A comprehensive understanding of this quenching process is therefore of paramount importance. The present article reports a systematic investigation of charge-exciton interaction in organic transistors employing time resolved photoluminescence electro-modulation (PLEM) spectroscopy on the picosecond time scale. The results show that the injected charges reduce the exciton radiative recombination in two ways: (i) charges may prevent the generation of excitons and (ii) charges activate a further nonradiative channel for the exciton decay. Moreover, the transient PLEM measurements clearly reveal that not only trapped charges, as already reported in literature, but rather the entire injected charge density contributes to the quenching of the exciton population. Washington, DC American Chemical Society 2017 10 ACS photonics 4 2 282 291 10.1021/acsphotonics.6b00573 Institut für Physik und Astronomie OPUS4-55322 Wissenschaftlicher Artikel Smirnov, Lev A.; Osipov, Grigory V.; Pikovskij, Arkadij Chimera patterns in the Kuramoto-Battogtokh model Kuramoto and Battogtokh (2002 Nonlinear Phenom. Complex Syst. 5 380) discovered chimera states represented by stable coexisting synchrony and asynchrony domains in a lattice of coupled oscillators. After a reformulation in terms of a local order parameter, the problem can be reduced to partial differential equations. We find uniformly rotating, spatially periodic chimera patterns as solutions of a reversible ordinary differential equation, and demonstrate a plethora of such states. In the limit of neutral coupling they reduce to analytical solutions in the form of one-and two-point chimera patterns as well as localized chimera solitons. Patterns at weakly attracting coupling are characterized by virtue of a perturbative approach. Stability analysis reveals that only the simplest chimeras with one synchronous region are stable. Bristol IOP Publ. Ltd. 2017 10 Journal of physics : A, Mathematical and theoretical 50 8 10.1088/1751-8121/aa55f1 Institut für Physik und Astronomie OPUS4-40216 Wissenschaftlicher Artikel Zaks, Michael A.; Pikovskij, Arkadij Chimeras and complex cluster states in arrays of spin-torque oscillators We consider synchronization properties of arrays of spin-torque nano-oscillators coupled via an RC load. We show that while the fully synchronized state of identical oscillators may be locally stable in some parameter range, this synchrony is not globally attracting. Instead, regimes of different levels of compositional complexity are observed. These include chimera states (a part of the array forms a cluster while other units are desynchronized), clustered chimeras (several clusters plus desynchronized oscillators), cluster state (all oscillators form several clusters), and partial synchronization (no clusters but a nonvanishing mean field). Dynamically, these states are also complex, demonstrating irregular and close to quasiperiodic modulation. Remarkably, when heterogeneity of spin-torque oscillators is taken into account, dynamical complexity even increases: close to the onset of a macroscopic mean field, the dynamics of this field is rather irregular. London Macmillan Publishers Limited 2017 Scientific reports 7 10.1038/s41598-017-04918-9 Institut für Physik und Astronomie OPUS4-39520 Wissenschaftlicher Artikel Menzel, Ralf; Puhlmann, Dirk; Heuer, Axel Complementarity in single photon interference - the role of the mode function and vacuum fields Background In earlier experiments the role of the vacuum fields could be demonstrated as the source of complementarity with respect to the temporal properties (Heuer et al., Phys. Rev. Lett. 114:053601, 2015). Methods Single photon first order interferences of spatially separated regions from the cone structure of spontaneous parametric down conversion allow for analyzing the role of the mode function in quantum optics regarding the complementarity principle. Results Here the spatial coherence properties of these vacuum fields are demonstrated as the physical reason for complementarity in these single photon quantum optical experiments. These results are directly connected to the mode picture in classical optics. Conclusion The properties of the involved vacuum fields selected via the measurement process are the physical background of the complementarity principle in quantum optics. Springer 2017 7 Journal of the European Optical Society-Rapid 13 10.1186/s41476-017-0036-x Institut für Physik und Astronomie OPUS4-55171 Wissenschaftlicher Artikel Kegeles, Alexander; Oriti, Daniele Continuous point symmetries in group field theories We discuss the notion of symmetries in non-local field theories characterized by integro-differential equations of motion, from a geometric perspective. We then focus on group field theory (GFT) models of quantum gravity and provide a general analysis of their continuous point symmetry transformations, including the generalized conservation laws following from them. Bristol IOP Publishing Ltd 2017 36 Journal of physics : A, Mathematical and theoretical 50 12 10.1088/1751-8121/aa5c14 Institut für Physik und Astronomie OPUS4-55704 Wissenschaftlicher Artikel Dahlke, Sandro; Maturilli, Marion Contribution of atmospheric advection to the amplified winter warming in the arctic north atlantic region Arctic Amplification of climate warming is caused by various feedback processes in the atmosphere-ocean-ice system and yields the strongest temperature increase during winter in the Arctic North Atlantic region. In our study, we attempt to quantify the advective contribution to the observed atmospheric warming in the Svalbard area. Based on radiosonde measurements from Ny-Ålesund, a strong dependence of the tropospheric temperature on the synoptic flow direction is revealed. Using FLEXTRA backward trajectories, an increase of advection from the lower latitude Atlantic region towards Ny-Ålesund is found that is attributed to a change in atmospheric circulation patterns. We find that about one-quarter (0.45 K per decade) of the observed atmospheric winter near surface warming trend in the North Atlantic region of the Arctic (2 K per decade) is due to increased advection of warm and moist air from the lower latitude Atlantic region, affecting the entire troposphere. New York Hindawi Publ. Corp. 2017 8 Advances in meteorology 10.1155/2017/4928620 Institut für Physik und Astronomie OPUS4-55332 Wissenschaftlicher Artikel Garakani, Tayebeh Mirzaei; Richter, Marina Juliane; Böker, Alexander Controlling the bio-inspired synthesis of silica The influence of different parameters on the silicification procedure using lysozyme is reported. When polyethoxysiloxane (PEOS), an internally crosslinked silica reservoir, is used, regular structures with a narrow size distribution could be obtained only via introducing the silica precursor in two steps including initial dropping and subsequent addition of residual oil phase in one portion. We found that mixing sequence of mineralizing agents in the presence of a positively charged surfactant plays a key role in terms of silica precipitation when tetraethoxyorthosilicate (TEOS) is the oil phase. In contrast, well mineralized crumpled features with high specific surface area could be synthesized in the presence of PEOS as a silica precursor polymer, regardless of mixing sequence. Moreover, introducing sodium dodecyl sulfate (SDS) as a negatively charged surfactant resulted in regular silica sphere formation only in combination with hexylene glycol (MPD) as a specific co-solvent. Finally, it is demonstrated that by inclusion of different nanoparticles even more sophisticated hybrid materials can be generated. San Diego Elsevier 2017 13 Journal of colloid and interface science 488 322 334 10.1016/j.jcis.2016.10.069 Institut für Physik und Astronomie OPUS4-55140 Wissenschaftlicher Artikel Archambault, S.; Archer, A.; Benbow, W.; Bird, R.; Bourbeau, E.; Brantseg, T.; Buchovecky, M.; Buckley, J. H.; Bugaev, V.; Byrum, K.; Cerruti, M.; Christiansen, J. L.; Connolly, M. P.; Cui, W.; Daniel, M. K.; Feng, Q.; Finley, J. P.; Fleischhack, H.; Fortson, L.; Furniss, A.; Geringer-Sameth, A.; Griffin, S.; Grube, J.; Hütten, M.; Hakansson, N.; Hanna, D.; Hervet, O.; Holder, J.; Hughes, G.; Hummensky, B.; Johnson, C. A.; Kaaret, P.; Kar, P.; Kelley-Hoskins, N.; Kertzman, M.; Kieda, D.; Koushiappas, S.; Krause, M.; Krennrich, F.; Lang, M. J.; Lin, T. T. Y.; McArthur, S.; Moriarty, P.; Mukherjee, R.; Nieto, D.; Ong, R. A.; Otte, A. N.; Park, N.; Pohl, M.; Popkow, A.; Pueschel, Elisa; Quinn, J.; Ragan, K.; Reynolds, P. T.; Richards, G. T.; Roache, E.; Rulten, C.; Sadeh, I.; Santander, M.; Sembroski, G. H.; Shahinyan, K.; Smith, A. W.; Staszak, D.; Telezhinsky, Igor O.; Trepanier, S.; Tucci, J. V.; Tyler, J.; Wakely, S. P.; Weinstein, A.; Wilcox, P.; Williams, D. A.; Zitzer, B. Dark matter constraints from a joint analysis of dwarf Spheroidal galaxy observations with VERITAS We present constraints on the annihilation cross section of weakly interacting massive particles dark matter based on the joint statistical analysis of four dwarf galaxies with VERITAS. These results are derived from an optimized photon weighting statistical technique that improves on standard imaging atmospheric Cherenkov telescope (IACT) analyses by utilizing the spectral and spatial properties of individual photon events. We report on the results of similar to 230 hours of observations of five dwarf galaxies and the joint statistical analysis of four of the dwarf galaxies. We find no evidence of gamma-ray emission from any individual dwarf nor in the joint analysis. The derived upper limit on the dark matter annihilation cross section from the joint analysis is 1.35 x 10(-23) cm(3) s(-1) at 1 TeV for the bottom quark (b (b) over bar) final state, 2.85 x 10(-24) cm(3) s(-1) at 1 TeV for the tau lepton (tau+tau(-)) final state and 1.32 x 10-25 cm(3) s(-1) at 1 TeV for the gauge boson (gamma gamma) final state. College Park American Physical Society 2017 14 Physical review : D, Particles, fields, gravitation, and cosmology 95 8 10.1103/PhysRevD.95.082001 Institut für Physik und Astronomie OPUS4-45921 Wissenschaftlicher Artikel Hofacker, Andreas; Neher, Dieter Dispersive and steady-state recombination in organic disordered semiconductors Charge carrier recombination in organic disordered semiconductors is strongly influenced by the thermalization of charge carriers in the density of states (DOS). Measurements of recombination dynamics, conducted under transient or steady-state conditions, can easily be misinterpreted when a detailed understanding of the interplay of thermalization and recombination is missing. To enable adequate measurement analysis, we solve the multiple-trapping problem for recombining charge carriers and analyze it in the transient and steady excitation paradigm for different DOS distributions. We show that recombination rates measured after pulsed excitation are inherently time dependent since recombination gradually slows down as carriers relax in the DOS. When measuring the recombination order after pulsed excitation, this leads to an apparent high-order recombination at short times. As times goes on, the recombination order approaches an asymptotic value. For the Gaussian and the exponential DOS distributions, this asymptotic value equals the recombination order of the equilibrated system under steady excitation. For a more general DOS distribution, the recombination order can also depend on the carrier density, under both transient and steady-state conditions. We conclude that transient experiments can provide rich information about recombination in and out of equilibrium and the underlying DOS occupation provided that consistent modeling of the system is performed. College Park American Physical Society 2017 11 Physical review : B, Condensed matter and materials physics 96 10.1103/PhysRevB.96.245204 Institut für Physik und Astronomie OPUS4-49318 Wissenschaftlicher Artikel Nadammal, Naresh; Cabeza, Sandra; Mishurova, Tatiana; Thiede, Tobias; Kromm, Arne; Seyfert, Christoph; Farahbod, Lena; Haberland, Christoph; Schneider, Judith Ann; Portella, Pedro Dolabella; Bruno, Giovanni Effect of hatch length on the development of microstructure, texture and residual stresses in selective laser melted superalloy Inconel 718 In the present study, samples fabricated by varying the deposition hatch length during selective laser melting of nickel based superalloy Inconel 718 were investigated. Microstructure and texture of these samples was characterized using scanning electron microscopy, combined with electron back-scattered diffraction, and residual stress assessment, using neutron diffraction method. Textured columnar grains oriented along the sample building direction were observed in the shorter hatch length processed sample. A ten-fold increase in the hatch length reduced the texture intensity by a factor of two attributed to the formation of finer grains in the longer hatch length sample. Larger gradients of transverse residual stress in the longer hatch length sample were also observed. Along the build direction, compressive stresses in the shorter hatch length and negligible stresses for the longer hatch length specimen were observed. Changes to the temperature gradient (G) in response to the hatch length variation, influenced the G to growth rate (R) ratio and the product GxR, in agreement with the microstructures and textures formed. For the residual stress development, geometry of the part also played an important role. In summary, tailored isotropy could be induced in Inconel 718 by a careful selection of parameters during selective laser melting. Oxford Elsevier 2017 12 Materials & Design 134 139 150 10.1016/j.matdes.2017.08.049 Institut für Physik und Astronomie OPUS4-54742 Wissenschaftlicher Artikel Cooper, Ryan C.; Bruno, Giovanni; Wheeler, M. R.; Pandey, A.; Watkins, T. R.; Shyarn, A. Effect of microcracking on the uniaxial tensile response of beta-eucryptite ceramics A constitutive model for the nonlinear or "pseudoplastic" mechanical behavior in a linear-elastic solid with thermally induced microcracks is developed and applied to experimental results. The model is termed strain dependent microcrack density approximation (SDMDA) and is an extension of the modified differential scheme that describes the slope of the stress-strain curves of microcracked solids. SDMDA allows a continuous variation in the microcrack density with tensile loading. Experimental uniaxial tensile response of beta-eucryptite glass and ceramics with controlled levels of microcracking is reported. It is demonstrated that SDMDA can well describe the extent of non-linearity in the experimental uniaxial tensile response of beta-eucryptite with varying levels of microcracking. The advantages of the SDMDA are discussed in regard to tensile loading. Oxford Elsevier 2017 11 Acta Materialia 135 361 371 10.1016/j.actamat.2017.06.033 Institut für Physik und Astronomie OPUS4-55528 Wissenschaftlicher Artikel Rätzel, Dennis; Wilkens, Martin; Menzel, Ralf Effect of polarization entanglement in photon-photon scattering It is found that the differential cross section of photon-photon scattering is a function of the degree of polarization entanglement of the two-photon state. A reduced general expression for the differential cross section of photon-photon scattering is derived by applying simple symmetry arguments. An explicit expression is obtained for the example of photon-photon scattering due to virtual electron-positron pairs in quantum electrodynamics. It is shown how the effect in this explicit example can be explained as an effect of quantum interference and that it fits with the idea of distance-dependent forces. College Park American Physical Society 2017 6 Physical review : A, Atomic, molecular, and optical physics 95 1 10.1103/PhysRevA.95.012101 Institut für Physik und Astronomie OPUS4-55093 Wissenschaftlicher Artikel Mardoukhi, Ahmad; Mardoukhi, Yousof; Hokka, Mikko; Kuokkala, Veli-Tapani Effects of heat shock on the dynamic tensile behavior of granitic rocks This paper presents a new experimental method for the characterization of the surface damage caused by a heat shock on a Brazilian disk test sample. Prior to mechanical testing with a Hopkinson Split Pressure bar device, the samples were subjected to heat shock by placing a flame torch at a fixed distance from the sample's surface for periods of 10, 30, and 60 s. The sample surfaces were studied before and after the heat shock using optical microscopy and profilometry, and the images were analyzed to quantify the damage caused by the heat shock. The complexity of the surface crack patterns was quantified using fractal dimension of the crack patterns, which were used to explain the results of the mechanical testing. Even though the heat shock also causes damage below the surface which cannot be quantified from the optical images, the presented surface crack pattern analysis can give a reasonable estimate on the drop rate of the tension strength of the rock. Wien Springer 2017 12 Rock mechanics and rock engineering 50 1171 1182 10.1007/s00603-017-1168-4 Institut für Physik und Astronomie OPUS4-55460 Wissenschaftlicher Artikel Mardoukhi, Ahmad; Mardoukhi, Yousof; Hokka, Mikko; Kuokkala, Veli-Tapani Effects of strain rate and surface cracks on the mechanical behaviour of Balmoral Red granite This work presents a systematic study on the effects of strain rate and surface cracks on the mechanical properties and behaviour of Balmoral Red granite. The tensile behaviour of the rock was studied at low and high strain rates using Brazilian disc samples. Heat shocks were used to produce samples with different amounts of surface cracks. The surface crack patterns were analysed using optical microscopy, and the complexity of the patterns was quantified by calculating the fractal dimensions of the patterns. The strength of the rock clearly drops as a function of increasing fractal dimensions in the studied strain rate range. However, the dynamic strength of the rock drops significantly faster than the quasi-static strength, and, because of this, also the strain rate sensitivity of the rock decreases with increasing fractal dimensions. This can be explained by the fracture behaviour and fragmentation during the dynamic loading, which is more strongly affected by the heat shock than the fragmentation at low strain rates. London Royal Society 2017 11 Philosophical Transactions of the Royal Society of London, Series A : Mathematical, Physical and Engineering Sciences 375 2085 10.1098/rsta.2016.0179 Institut für Physik und Astronomie OPUS4-40371 Wissenschaftlicher Artikel Grebenkov, Denis S.; Metzler, Ralf; Oshanin, Gleb Effects of the target aspect ratio and intrinsic reactivity onto diffusive search in bounded domains Westudy the mean first passage time (MFPT) to a reaction event on a specific site in a cylindrical geometry—characteristic, for instance, for bacterial cells, with a concentric inner cylinder representing the nuclear region of the bacterial cell. Asimilar problem emerges in the description of a diffusive search by a transcription factor protein for a specific binding region on a single strand of DNA.We develop a unified theoretical approach to study the underlying boundary value problem which is based on a self-consistent approximation of the mixed boundary condition. Our approach permits us to derive explicit, novel, closed-form expressions for the MFPT valid for a generic setting with an arbitrary relation between the system parameters.Weanalyse this general result in the asymptotic limits appropriate for the above-mentioned biophysical problems. Our investigation reveals the crucial role of the target aspect ratio and of the intrinsic reactivity of the binding region, which were disregarded in previous studies. Theoretical predictions are confirmed by numerical simulations. London IOP 2017 10 New journal of physics 19 1 11 10.1088/1367-2630/aa8ed9 Institut für Physik und Astronomie OPUS4-54313 Wissenschaftlicher Artikel Zhang, Kai; Chen, Zhiming; Armin, Ardalan; Dong, Sheng; Xia, Ruoxi; Yip, Hin-Lap; Shoaee, Safa; Huang, Fei; Cao, Yong Efficient large area organic solar cells processed by blade-coating with single-component green solvent While the performance of laboratory-scale organic solar cells (OSCs) continues to grow, development of high efficiency large area OSCs remains a big challenge. Although a few attempts to produce large area organic solar cells (OSCs) have been reported, there are still challenges on the way to realizing efficient module devices, such as the low compatibility of the thickness-sensitive active layer with large area coating techniques, the frequent need for toxic solvents and tedious optimization processes used during device fabrication. In this work, highly efficient thickness-insensitive OSCs based on PTB7-Th:PC71BM that processed with single-component green solvent 2-methylanisole are presented, in which both junction thickness limitation and solvent toxicity issues are simultaneously addressed. Careful investigation reveals that this green solvent prevents the evolution of PC71BM into large area clusters resulting in reduced charge carrier recombination, and largely eliminates trapping centers, and thus improves the thickness tolerance of the films. These findings enable us to address the scalability and solvent toxicity issues and to fabricate a 16 cm(2) OSC with doctor-blade coating with a state-of-the-art power conversion efficiency of 7.5% using green solvent. Weinheim Wiley-VCH 2017 9 Solar Rrl 2 1 10.1002/solr.201700169 Institut für Physik und Astronomie OPUS4-55082 Wissenschaftlicher Artikel Jošt, Marko; Albrecht, Steve; Kegelmann, Lukas; Wolff, Christian Michael; Lang, Felix; Lipovšek, Benjamin; Krč, Janez; Korte, Lars; Neher, Dieter; Rech, Bernd; Topič, Marko Efficient light management by textured nanoimprinted layers for perovskite solar cells Inorganic-organic perovskites like methylammonium-lead-iodide have proven to be an effective class of 17 materials for fabricating efficient solar cells. To improve their performance, light management techniques using textured surfaces, similar to those used in established solar cell technologies, should be considered. Here, we apply a light management foil created by UV nanoimprint lithography on the glass side of an inverted (p-i-n) perovskite solar cell with 16.3% efficiency. The obtained 1 mA cm(-2) increase in the short-circuit current density translates to a relative improvement in cell performance of 5%, which results in a power conversion efficiency of 17.1%. Optical 3D simulations based on experimentally obtained parameters were used to support the experimental findings. A good match between the simulated and experimental data was obtained, validating the model. Optical simulations reveal that the main improvement in device performance is due to a reduction in total reflection and that relative improvement in the short-circuit current density of up to 10% is possible for large-area devices. Therefore, our results present the potential of light management foils for improving the device performance of perovskite solar cells and pave the way for further use of optical simulations in the field of perovskite solar cells. Washington American Chemical Society 2017 8 ACS photonics 4 1232 1239 10.1021/acsphotonics.7b00138 Institut für Physik und Astronomie OPUS4-55593 Wissenschaftlicher Artikel Morgner, Frank; Bennemann, Mark; Cywiński, Piotr J.; Kollosche, Matthias; Górski, Krzysztof; Pietraszkiewicz, Marek; Geßner, André; Löhmannsröben, Hans-Gerd Elastic FRET sensors for contactless pressure measurement Contactless pressure monitoring based on Forster resonance energy transfer between donor/acceptor pairs immobilized within elastomers is demonstrated. The donor/acceptor energy transfer is employed by dispersing terbium(III) tris[(2-hydroxybenzoyl)-2-aminoethyl] amine complex (LLC, donor) and CdSe/ZnS quantum dots (QD655, acceptor) in styrene-ethylene/buthylene-styrene (SEBS) and poly(dimethylsiloxane) (PDMS). The continuous monitoring of QD luminescence showed a reversible intensity change as the pressure signal is alternated between two stable states indicating a pressure sensitivity of 6350 cps kPa(-1). Time-resolved measurements show the pressure impact on the FRET signal due to an increase of decay time (270 ms up to 420 ms) for the donor signal and parallel drop of decay time (170 mu s to 155 mu s) for the acceptor signal as the net pressure applied. The LLC/QD655 sensors enable a contactless readout as well as space resolved monitoring to enable miniaturization towards smaller integrated stretchable opto-electronics. Elastic FRET sensors can potentially lead to developing profitable analysis systems capable to outdo conventional wired electronic systems (inductive, capacitive, ultrasonic and photoelectric sensors) especially for point-of-care diagnostics, biological monitoring required for wearable electronics. Cambridge RSC Publishing 2017 6 RSC Advances : an international journal to further the chemical sciences 7 50578 50583 10.1039/c7ra06379b Institut für Physik und Astronomie OPUS4-54703 Wissenschaftlicher Artikel Fang, Peng; Ma, Xingchen; Li, Xiangxin; Qiu, Xunlin; Gerhard, Reimund; Zhang, Xiaoqing; Li, Guanglin Fabrication, Structure Characterization, and Performance Testing of Piezoelectret-Film Sensors for Recording Body Motion During muscle contractions, radial-force distributions are generated on muscle surfaces due to muscle-volume changes, from which the corresponding body motions can be recorded by means of so-called force myography (FMG). Piezo- or ferroelectrets are flexible piezoelectric materials with attractive materials and sensing properties. In addition to several other applications, they are suitable for detecting force variations by means of wearable devices. In this paper, we prepared piezoelectrets from cellular polypropylene films by optimizing the fabrication procedures, and developed an FMG-recording system based on piezoelectret sensors. Different hand and wrist movements were successfully detected on able-bodied subjects with the FMG system. The FMG patterns were evaluated and identified by means of linear discriminant analysis and artificial neural network algorithms, and average motion-classification accuracies of 96.1% and 94.8%, respectively, were obtained. This paper demonstrates the feasibility of using piezoelectret-film sensors for FMG and may thus lead to alternative methods for detecting body motion and to related applications, e.g., in biomedical engineering or structural-health monitoring. Piscataway Inst. of Electr. and Electronics Engineers 2017 12 IEEE Sensors Journal 18 1 401 412 10.1109/JSEN.2017.2766663 Institut für Physik und Astronomie OPUS4-55328 Wissenschaftlicher Artikel Liu, Lin; Cherstvy, Andrey G.; Metzler, Ralf Facilitated Diffusion of Transcription Factor Proteins with Anomalous Bulk Diffusion What are the physical laws of the diffusive search of proteins for their specific binding sites on DNA in the presence of the macromolecular crowding in cells? We performed extensive computer simulations to elucidate the protein target search on DNA. The novel feature is the viscoelastic non-Brownian protein bulk diffusion recently observed experimentally. We examine the influence of the protein-DNA binding affinity and the anomalous diffusion exponent on the target search time. In all cases an optimal search time is found. The relative contribution of intermittent three-dimensional bulk diffusion and one-dimensional sliding of proteins along the DNA is quantified. Our results are discussed in the light of recent single molecule tracking experiments, aiming at a better understanding of the influence of anomalous kinetics of proteins on the facilitated diffusion mechanism. Washington American Chemical Society 2017 6 The journal of physical chemistry : B, Condensed matter, materials, surfaces, interfaces & biophysical chemistry 121 1284 1289 10.1021/acs.jpcb.6b12413 Institut für Physik und Astronomie OPUS4-55156 Wissenschaftlicher Artikel Juaristi, J. I.; Alducin, Maite; Saalfrank, Peter Femtosecond laser induced desorption of H-2, D-2, and HD from Ru(0001) We perform ab initio molecular dynamics simulations to study the femtosecond laser induced desorption of H-2, D-2, and HD from a H: D-saturated Ru(0001) surface. To this aim we have extended the ab initio molecular dynamics with electronic friction (AIMDEF) scheme to include a random force that is a function of a timedependent electronic temperature. The latter characterizes the action of the ultrashort laser pulse according to a two temperature model. This allows us to perform multidimensional, hot-electron driven reaction dynamics and investigate the dependence of the desorption yields on the relative H: D isotope concentration on the surface. Our AIMDEF simulations show that the desorption process takes place in the presence of a heated adsorbate system that clearly influences the desorption dynamics. The heating of the adsorbate system is more (less) pronounced the larger is the concentration of the lighter (heavier) isotope. As a result, we conclude that the presence of H on the surface favors the desorption of molecules, whereas the presence of D hampers it, in agreement with previous experimental observations in which the phenomenon of "dynamical promotion" of a surface reaction had been postulated. College Park American Physical Society 2017 7 Physical review : B, Condensed matter and materials physics 95 12 10.1103/PhysRevB.95.125439 Institut für Physik und Astronomie OPUS4-55321 Wissenschaftlicher Artikel Godec, Aljaž; Metzler, Ralf First passage time statistics for two-channel diffusion We present rigorous results for the mean first passage time and first passage time statistics for two-channel Markov additive diffusion in a 3-dimensional spherical domain. Inspired by biophysical examples we assume that the particle can only recognise the target in one of the modes, which is shown to effect a non-trivial first passage behaviour. We also address the scenario of intermittent immobilisation. In both cases we prove that despite the perfectly non-recurrent motion of two-channel Markov additive diffusion in 3 dimensions the first passage statistics at long times do not display Poisson-like behaviour if none of the phases has a vanishing diffusion coefficient. This stands in stark contrast to the standard (one-channel) Markov diffusion counterpart. We also discuss the relevance of our results in the context of cellular signalling. Bristol IOP Publ. Ltd. 2017 17 Journal of physics : A, Mathematical and theoretical 50 8 10.1088/1751-8121/aa5204 Institut für Physik und Astronomie OPUS4-55095 Wissenschaftlicher Artikel Kurzke, Henning; Kiethe, Jan; Heuer, Axel; Jechow, Andreas Frequency doubling of incoherent light from a superluminescent diode in a periodically poled lithium niobate waveguide crystal The amplified spontaneous emission from a superluminescent diode was frequency doubled in a periodically poled lithium niobate waveguide crystal. The temporally incoherent radiation of such a superluminescent diode is characterized by a relatively broad spectral bandwidth and thermal-like photon statistics, as the measured degree of second order coherence, g((2))(0)= 1.9 +/- 0.1, indicates. Despite the non-optimized scenario in the spectral domain, we achieve six orders of magnitude higher conversion efficiency than previously reported with truly incoherent light. This is possible by using single spatial mode radiation and quasi phase matched material with a waveguide architecture. This work is a principle step towards efficient frequency conversion of temporally incoherent radiation in one spatial mode to access wavelengths where no radiation from superluminescent diodes is available, especially with tailored quasi phase matched crystals. The frequency doubled light might find application in imaging, metrology and quantum optics experiments. Bristol IOP Publ. 2017 5 Laser physics letters 14 10.1088/1612-202X/aa6889 Institut für Physik und Astronomie OPUS4-53438 Wissenschaftlicher Artikel Hani, Maan H.; Sparre, Martin; Ellison, Sara L.; Torrey, Paul; Vogelsberger, Mark Galaxy mergers moulding the circum-galactic medium Galaxies are surrounded by sizeable gas reservoirs which host a significant amount of metals: the circum-galactic medium (CGM). The CGM acts as a mediator between the galaxy and the extragalactic medium. However, our understanding of how galaxy mergers, a major evolutionary transformation, impact the CGM remains deficient. We present a theoretical study of the effect of galaxy mergers on the CGM. We use hydrodynamical cosmological zoom-in simulations of a major merger selected from the Illustris project such that the z = 0 descendant has a halo mass and stellar mass comparable to the Milky Way. To study the CGM we then re-simulated this system at a 40 times better mass resolution, and included detailed post-processing ionization modelling. Our work demonstrates the effect the merger has on the characteristic size of the CGM, its metallicity, and the predicted covering fraction of various commonly observed gas-phase species, such as H I, C IV, and O VI. We show that merger-induced outflows can increase the CGM metallicity by 0.2-0.3 dex within 0.5 Gyr post-merger. These effects last up to 6 Gyr post-merger. While the merger increases the total metal covering fractions by factors of 2-3, the covering fractions of commonly observed UV ions decrease due to the hard ionizing radiation from the active galactic nucleus, which we model explicitly. Our study of the single simulated major merger presented in this work demonstrates the significant impact that a galaxy interaction can have on the size, metallicity, and observed column densities of the CGM. Oxford Oxford Univ. Press 2017 17 Monthly notices of the Royal Astronomical Society 475 1 1160 1176 10.1093/mnras/stx3252 Institut für Physik und Astronomie OPUS4-55339 Wissenschaftlicher Artikel Archambault, S.; Archer, A.; Benbow, Wystan; Bird, Ralph; Bourbeau, E.; Buchovecky, M.; Buckley, J. H.; Bugaev, V.; Cerruti, M.; Connolly, M. P.; Cui, W.; Dwarkadas, Vikram V.; Errando, M.; Falcone, A.; Feng, Q.; Finley, J. P.; Fleischhack, H.; Fortson, L.; Furniss, A.; Griffin, S.; Huetten, M.; Hanna, D.; Holder, J.; Johnson, C. A.; Kaaret, P.; Kar, P.; Kelley-Hoskins, N.; Kertzman, M.; Kieda, D.; Krause, M.; Kumar, S.; Lang, M. J.; Maier, G.; McArthur, S.; McCann, A.; Moriarty, P.; Mukherjee, R.; Nieto, D.; Ong, R. A.; Otte, A. N.; Park, Nahee; Pohl, Martin; Popkow, A.; Pueschel, Elisa; Quinn, J.; Ragan, K.; Reynolds, P. T.; Richards, G. T.; Roache, E.; Sadeh, I.; Santander, M.; Sembroski, G. H.; Shahinyan, K.; Slane, P.; Staszak, D.; Telezhinsky, Igor O.; Trepanier, S.; Tyler, J.; Wakely, S. P.; Weinstein, A.; Weisgarber, T.; Wilcox, P.; Wilhelm, Alina; Williams, D. A.; Zitzer, B. Gamma-ray Observations of Tycho's Supernova Remnant with VERITAS and Fermi Bristol IOP Publ. Ltd. 2017 8 The astrophysical journal : an international review of spectroscopy and astronomical physics 836 1 10.3847/1538-4357/836/1/23 Institut für Physik und Astronomie OPUS4-55040 Wissenschaftlicher Artikel Archambault, S.; Archer, A.; Benbow, W.; Bird, Ralph; Bourbeau, E.; Bouvier, A.; Buchovecky, M.; Bugaev, V.; Cardenzana, J. V.; Cerruti, M.; Ciupik, L.; Connolly, M. P.; Cui, W.; Daniel, M. K.; Errando, M.; Falcone, A.; Feng, Q.; Finley, J. P.; Fleischhack, H.; Fortson, L.; Furniss, A.; Gillanders, G. H.; Griffin, S.; Hanna, D.; Hervet, O.; Holder, J.; Hughes, G.; Humensky, T. B.; Hutten, M.; Johnson, C. A.; Kaaret, P.; Kar, P.; Kertzman, M.; Kieda, D.; Krause, M.; Lang, M. J.; Lin, T. T. Y.; Maier, G.; McArthur, S.; Moriarty, P.; Mukherjee, R.; Nieto, D.; Ong, R. A.; Otte, A. N.; Park, N.; Pohl, Martin; Popkow, A.; Pueschel, Elisa; Quinn, J.; Ragan, K.; Reynolds, P. T.; Richards, G. T.; Roache, E.; Rulten, C.; Sadeh, I.; Sembroski, G. H.; Shahinyan, K.; Staszak, D.; Telezhinsky, Igor O.; Trepanier, S.; Wakely, S. P.; Weinstein, A.; Wilcox, P.; Williams, D. A.; Zitzer, B. Gamma-ray observations under bright moonlight with VERITAS Imaging atmospheric Cherenkov telescopes (IACTs) are equipped with sensitive photomultiplier tube (PMT) cameras. Exposure to high levels of background illumination degrades the efficiency of and potentially destroys these photo-detectors over time, so IACTs cannot be operated in the same configuration in the presence of bright moonlight as under dark skies. Since September 2012, observations have been carried out with the VERITAS IACTs under bright moonlight (defined as about three times the night-sky-background (NSB) of a dark extragalactic field, typically occurring when Moon illumination > 35%) in two observing modes, firstly by reducing the voltage applied to the PMTs and, secondly, with the addition of ultra-violet (UV) bandpass filters to the cameras. This has allowed observations at up to about 30 times previous NSB levels (around 80% Moon illumination), resulting in 30% more observing time between the two modes over the course of a year. These additional observations have already allowed for the detection of a flare from the 1ES 1727 + 502 and for an observing program targeting a measurement of the cosmic-ray positron fraction. We provide details of these new observing modes and their performance relative to the standard VERITAS observations. (C) 2017 Elsevier B.V. All rights reserved. Amsterdam Elsevier 2017 10 Astroparticle physics 91 34 43 10.1016/j.astropartphys.2017.03.001 Institut für Physik und Astronomie OPUS4-54941 Wissenschaftlicher Artikel Feudel, Fred; Tuckerman, Laurette S.; Zaks, Michael; Hollerbach, Rainer Hysteresis of dynamos in rotating spherical shell convection Bifurcations of dynamos in rotating and buoyancy-driven spherical Rayleigh-Benard convection in an electrically conducting fluid are investigated numerically. Both nonmagnetic and magnetic solution branches comprised of rotating waves are traced by path-following techniques, and their bifurcations and interconnections for different Ekman numbers are determined. In particular, the question of whether the dynamo branches bifurcate super- or sub-critically and whether a direct link to the primary pure convective states exists is answered. College Park American Physical Society 2017 11 Physical review fluids / American Physical Society 2 10.1103/PhysRevFluids.2.053902 Institut für Physik und Astronomie OPUS4-56985 Wissenschaftlicher Artikel Beta, Carsten; Kruse, Karsten Intracellular oscillations and waves Dynamic processes in living cells are highly organized in space and time. Unraveling the underlying molecular mechanisms of spatiotemporal pattern formation remains one of the outstanding challenges at the interface between physics and biology. A fundamental recurrent pattern found in many different cell types is that of self-sustained oscillations. They are involved in a wide range of cellular functions, including second messenger signaling, gene expression, and cytoskeletal dynamics. Here, we review recent developments in the field of cellular oscillations and focus on cases where concepts from physics have been instrumental for understanding the underlying mechanisms. We consider biochemical and genetic oscillators as well as oscillations that arise from chemo-mechanical coupling. Finally, we highlight recent studies of intracellular waves that have increasingly moved into the focus of this research field. Palo Alto Annual Reviews 2017 26 Annual review of condensed matter physics 8 978-0-8243-5008-6 239 264 10.1146/annurev-conmatphys-031016-025210 Institut für Physik und Astronomie OPUS4-54827 Wissenschaftlicher Artikel Benduhn, Johannes; Tvingstedt, Kristofer; Piersimoni, Fortunato; Ullbrich, Sascha; Fan, Yeli; Tropiano, Manuel; McGarry, Kathryn A.; Zeika, Olaf; Riede, Moritz K.; Douglas, Christopher J.; Barlow, Stephen; Marder, Seth R.; Neher, Dieter; Spoltore, Donato; Vandewal, Koen Intrinsic non-radiative voltage losses in fullerene-based organic solar cells Organic solar cells demonstrate external quantum efficiencies and fill factors approaching those of conventional photovoltaic technologies. However, as compared with the optical gap of the absorber materials, their open-circuit voltage is much lower, largely due to the presence of significant non-radiative recombination. Here, we study a large data set of published and new material combinations and find that non-radiative voltage losses decrease with increasing charge-transfer-state energies. This observation is explained by considering non-radiative charge-transfer-state decay as electron transfer in the Marcus inverted regime, being facilitated by a common skeletal molecular vibrational mode. Our results suggest an intrinsic link between non-radiative voltage losses and electron-vibration coupling, indicating that these losses are unavoidable. Accordingly, the theoretical upper limit for the power conversion efficiency of single-junction organic solar cells would be reduced to about 25.5% and the optimal optical gap increases to (1.45-1.65) eV, that is, (0.2-0.3) eV higher than for technologies with minimized non-radiative voltage losses. London Nature Publ. Group 2017 6 Nature Energy 2 10.1038/nenergy.2017.53 Institut für Physik und Astronomie OPUS4-49704 Wissenschaftlicher Artikel Bouakline, Foudhil; Lorenz, Ulrich J.; Melani, Giacomo; Paramonov, Guennaddi K.; Saalfrank, Peter Isotopic effects in vibrational relaxation dynamics of H on a Si(100) surface In a recent paper [U. Lorenz and P. Saalfrank, Chem. Phys. 482, 69 (2017)], we proposed a robust scheme to set up a system-bath model Hamiltonian, describing the coupling of adsorbate vibrations (system) to surface phonons (bath), from first principles. The method is based on an embedded cluster approach, using orthogonal coordinates for system and bath modes, and an anharmonic phononic expansion of the system-bath interaction up to second order. In this contribution, we use this model Hamiltonian to calculate vibrational relaxation rates of H-Si and D-Si bending modes, coupled to a fully H(D)-covered Si(100)-(2×1) surface, at zero temperature. The D-Si bending mode has an anharmonic frequency lying inside the bath frequency spectrum, whereas the H-Si bending mode frequency is outside the bath Debye band. Therefore, in the present calculations, we only take into account one-phonon system-bath couplings for the D-Si system and both one- and two-phonon interaction terms in the case of H-Si. The computation of vibrational lifetimes is performed with two different approaches, namely, Fermi's golden rule, and a generalized Bixon-Jortner model built in a restricted vibrational space of the adsorbate-surface zeroth-order Hamiltonian. For D-Si, the Bixon-Jortner Hamiltonian can be solved by exact diagonalization, serving as a benchmark, whereas for H-Si, an iterative scheme based on the recursive residue generation method is applied, with excellent convergence properties. We found that the lifetimes obtained with perturbation theory, albeit having almost the same order of magnitude—a few hundred fs for D-Si and a couple of ps for H-Si—, are strongly dependent on the discretized numerical representation of the bath spectral density. On the other hand, the Bixon-Jortner model is free of such numerical deficiencies, therefore providing better estimates of vibrational relaxation rates, at a very low computational cost. The results obtained with this model clearly show a net exponential decay of the time-dependent survival probability for the H-Si initial vibrational state, allowing an easy extraction of the bending mode "lifetime." This is in contrast with the D-Si system, whose survival probability exhibits a non-monotonic decay, making it difficult to define such a lifetime. This different behavior of the vibrational decay is rationalized in terms of the power spectrum of the adsorbate-surface system. In the case of D-Si, it consists of several, non-uniformly distributed peaks around the bending mode frequency, whereas the H-Si spectrum exhibits a single Lorentzian lineshape, whose width corresponds to the calculated lifetime. The present work gives some insight into mechanisms of vibration-phonon coupling at surfaces. It also serves as a benchmark for multidimensional system-bath quantum dynamics, for comparison with approximate schemes such as reduced, open-system density matrix theory (where the bath is traced out and a Liouville-von Neumann equation is solved) or approximate wavefunction methods to solve the combined system-bath Schrödinger equation. Melville American Institute of Physics 2017 11 The journal of chemical physics : bridges a gap between journals of physics and journals of chemistr 147 14 10.1063/1.4994635 Institut für Physik und Astronomie OPUS4-55129 Wissenschaftlicher Artikel Ortiz-Amezcua, Pablo; Guerrero-Rascado, Juan Luis; Jose Granados-Munoz, Maria; Benavent-Oltra, Jose Antonio; Böckmann, Christine; Samaras, Stefanos; Stachlewska, Iwona S.; Janicka, Lucja; Baars, Holger; Bohlmann, Stephanie; Alados-Arboledas, Lucas Microphysical characterization of long-range transported biomass burning particles from North America at three EARLINET stations Strong events of long-range transported biomass burning aerosol were detected during July 2013 at three EARLINET (European Aerosol Research Lidar Network) stations, namely Granada (Spain), Leipzig (Germany) and Warsaw (Poland). Satellite observations from MODIS (Moderate Resolution Imaging Spectroradiometer) and CALIOP (Cloud-Aerosol Lidar with Orthogonal Polarization) instruments, as well as modeling tools such as HYSPLIT (Hybrid Single-Particle Lagrangian Integrated Trajectory) and NAAPS (Navy Aerosol Analysis and Prediction System), have been used to estimate the sources and transport paths of those North American forest fire smoke particles. A multiwavelength Raman lidar technique was applied to obtain vertically resolved particle optical properties, and further inversion of those properties with a regularization algorithm allowed for retrieving microphysical information on the studied particles. The results highlight the presence of smoke layers of 1-2 km thickness, located at about 5 km a.s.l. altitude over Granada and Leipzig and around 2.5 km a.s.l. at Warsaw. These layers were intense, as they accounted for more than 30% of the total AOD (aerosol optical depth) in all cases, and presented optical and microphysical features typical for different aging degrees: color ratio of lidar ratios (LR532/LR355) around 2, alpha-related angstrom exponents of less than 1, effective radii of 0.3 mu m and large values of single scattering albedos (SSA), nearly spectrally independent. The intensive microphysical properties were compared with columnar retrievals form co-located AERONET (Aerosol Robotic Network) stations. The intensity of the layers was also characterized in terms of particle volume concentration, and then an experimental relationship between this magnitude and the particle extinction coefficient was established. Göttingen Copernicus 2017 16 Atmospheric Chemistry and Physics 17 5931 5946 10.5194/acp-17-5931-2017 Institut für Physik und Astronomie OPUS4-55502 Wissenschaftlicher Artikel Gong, Chen Chris; Klumpp, Stefan Modeling sRNA-Regulated Plasmid Maintenance We study a theoretical model for the toxin-antitoxin (hok/sok) mechanism for plasmid maintenance in bacteria. Toxin-antitoxin systems enforce the maintenance of a plasmid through post-segregational killing of cells that have lost the plasmid. Key to their function is the tight regulation of expression of a protein toxin by an sRNA antitoxin. Here, we focus on the nonlinear nature of the regulatory circuit dynamics of the toxin-antitoxin mechanism. The mechanism relies on a transient increase in protein concentration rather than on the steady state of the genetic circuit. Through a systematic analysis of the parameter dependence of this transient increase, we confirm some known design features of this system and identify new ones: for an efficient toxin-antitoxin mechanism, the synthesis rate of the toxin's mRNA template should be lower that of the sRNA antitoxin, the mRNA template should be more stable than the sRNA antitoxin, and the mRNA-sRNA complex should be more stable than the sRNA antitoxin. Moreover, a short half-life of the protein toxin is also beneficial to the function of the toxin-antitoxin system. In addition, we study a therapeutic scenario in which a competitor mRNA is introduced to sequester the sRNA antitoxin, causing the toxic protein to be expressed. San Fransisco PLoS 2017 19 PLoS one 12 10.1371/journal.pone.0169703 Institut für Physik und Astronomie OPUS4-57388 Wissenschaftlicher Artikel Park, Jaeheung; Lühr, Hermann; Kervalishvili, Guram; Rauberg, Jan; Stolle, Claudia; Kwak, Young-Sil; Lee, Woo Kyoung Morphology of high-latitude plasma density perturbations as deduced from the total electron content measurements onboard the Swarm constellation In this study, we investigate the climatology of high-latitude total electron content (TEC) variations as observed by the dual-frequency Global Navigation Satellite Systems (GNSS) receivers onboard the Swarm satellite constellation. The distribution of TEC perturbations as a function of geographic/magnetic coordinates and seasons reasonably agrees with that of the Challenging Minisatellite Payload observations published earlier. Categorizing the high-latitude TEC perturbations according to line-of-sight directions between Swarm and GNSS satellites, we can deduce their morphology with respect to the geomagnetic field lines. In the Northern Hemisphere, the perturbation shapes are mostly aligned with the L shell surface, and this anisotropy is strongest in the nightside auroral (substorm) and subauroral regions and weakest in the central polar cap. The results are consistent with the well-known two-cell plasma convection pattern of the high-latitude ionosphere, which is approximately aligned with L shells at auroral regions and crossing different L shells for a significant part of the polar cap. In the Southern Hemisphere, the perturbation structures exhibit noticeable misalignment to the local L shells. Here the direction toward the Sun has an additional influence on the plasma structure, which we attribute to photoionization effects. The larger offset between geographic and geomagnetic poles in the south than in the north is responsible for the hemispheric difference. Washington American Geophysical Union 2017 22 Journal of geophysical research : A, Space physics 122 1 1338 1359 10.1002/2016JA023086 Institut für Mathematik OPUS4-55329 Wissenschaftlicher Artikel Shprits, Yuri Y.; Kellerman, Adam C .; Aseev, Nikita A.; Drozdov, Alexander Y.; Michaelis, Ingo Multi-MeV electron loss in the heart of the radiation belts Significant progress has been made in recent years in understanding acceleration mechanisms in the Earth's radiation belts. In particular, a number of studies demonstrated the importance of the local acceleration by analyzing the radial profiles of phase space density (PSD) and observing building up peaks in PSD. In this study, we focus on understanding of the local loss using very similar tools. The profiles of PSD for various values of the first adiabatic invariants during the previously studied 17 January 2013 storm are presented and discussed. The profiles of PSD show clear deepening minimums consistent with the scattering by electromagnetic ion cyclotron waves. Long-term evolution shows that local minimums in PSD can persist for relatively long times. During considered interval of time the deepening minimums were observed around L* = 4 during 17 January 2013 storm and around L* = 3.5 during 1 March 2013 storm. This study shows a new method that can help identify the location, magnitude, and time of the local loss and will help quantify local loss in the future. This study also provides additional clear and definitive evidence that local loss plays a major role for the dynamics of the multi-MeV electrons. Washington American Geophysical Union 2017 6 Geophysical research letters 44 3 1204 1209 10.1002/2016GL072258 Institut für Physik und Astronomie OPUS4-54802 Wissenschaftlicher Artikel Ahnen, M. L.; Ansoldi, S.; Antonelli, L. A.; Antoranz, P.; Babic, A.; Banerjee, B.; Bangale, P.; de Almeida, U. Barres; Barrio, J. A.; Gonzalez, J. Becerra; Bednarek, W.; Bernardini, E.; Berti, A.; Biasuzzi, B.; Biland, A.; Blanch, O.; Bonnefoy, S.; Bonnoli, G.; Borracci, F.; Bretz, T.; Buson, S.; Carosi, A.; Chatterjee, A.; Clavero, R.; Colin, P.; Colombo, E.; Contreras, J. L.; Cortina, J.; Covino, S.; Da Vela, P.; Dazzi, F.; De Angelis, A.; De Lotto, B.; Wilhelmi, E. de Ona; Di Pierro, F.; Doert, M.; Dominguez, A.; Prester, D. Dominis; Dorner, D.; Doro, M.; Einecke, S.; Glawion, D. Eisenacher; Elsaesser, D.; Engelkemeier, M.; Ramazani, V. Fallah; Fernandez-Barral, A.; Fidalgo, D.; Fonseca, M. V.; Font, L.; Frantzen, K.; Fruck, C.; Galindo, D.; Lopez, R. J. Garcia; Garczarczyk, M.; Terrats, D. Garrido; Gaug, M.; Giammaria, P.; Godinovic, N.; Gonzalez Munoz, A.; Gora, D.; Guberman, D.; Hadasch, D.; Hahn, A.; Hanabata, Y.; Hayashida, M.; Herrera, J.; Hose, J.; Hrupec, D.; Hughes, G.; Idec, W.; Kodani, K.; Konno, Y.; Kubo, H.; Kushida, J.; La Barbera, A.; Lelas, D.; Lindfors, E.; Lombardi, S.; Longo, F.; Lopez, M.; Lopez-Coto, R.; Majumdar, P.; Makariev, M.; Mallot, K.; Maneva, G.; Manganaro, M.; Mannheim, K.; Maraschi, L.; Marcote, B.; Mariotti, M.; Martinez, M.; Mazin, D.; Menzel, U.; Miranda, J. M.; Mirzoyan, R.; Moralejo, A.; Moretti, E.; Nakajima, D.; Neustroev, V.; Niedzwiecki, A.; Rosillo, M. Nievas; Nilsson, K.; Nishijima, K.; Noda, K.; Nogues, L.; Overkemping, A.; Paiano, S.; Palacio, J.; Palatiello, M.; Paneque, D.; Paoletti, R.; Paredes, J. M.; Paredes-Fortuny, X.; Pedaletti, G.; Peresano, M.; Perri, L.; Persic, M.; Poutanen, J.; Moroni, P. G. Prada; Prandini, E.; Puljak, I.; Reichardt, I.; Rhode, W.; Ribo, M.; Rico, J.; Rodriguez Garcia, J.; Saito, T.; Satalecka, K.; Schroder, S.; Schultz, C.; Schweizer, T.; Shore, S. N.; Sillanpaa, A.; Sitarek, J.; Snidaric, I.; Sobczynska, D.; Stamerra, A.; Steinbring, T.; Strzys, M.; Suric, T.; Takalo, L.; Tavecchio, F.; Temnikov, P.; Terzic, T.; Tescaro, D.; Teshima, M.; Thaele, J.; Torres, D. F.; Toyama, T.; Treves, A.; Vanzo, G.; Verguilov, V.; Vovk, I.; Ward, J. E.; Will, M.; Wu, M. H.; Zanin, R.; Abeysekara, A. U.; Archambault, S.; Archer, A.; Benbow, W.; Bird, R.; Buchovecky, M.; Buckley, J. H.; Bugaev, V.; Connolly, M. P.; Cui, W.; Dickinson, H. J.; Falcone, A.; Feng, Q.; Finley, J. P.; Fleischhack, H.; Flinders, A.; Fortson, L.; Gillanders, G. H.; Griffin, S.; Grube, J.; Huetten, M.; Hanna, D.; Holder, J.; Humensky, T. B.; Kaaret, P.; Kar, P.; Kelley-Hoskins, N.; Kertzman, M.; Kieda, D.; Krause, M.; Krennrich, F.; Lang, M. J.; Maier, G.; McCann, A.; Moriarty, P.; Mukherjee, R.; Nieto, D.; Ong, R. A.; Otte, N.; Park, N.; Perkins, J.; Pichel, A.; Pohl, M.; Popkow, A.; Pueschel, Elisa; Quinn, J.; Ragan, K.; Reynolds, P. T.; Richards, G. T.; Roache, E.; Rovero, A. C.; Rulten, C.; Sadeh, I.; Santander, M.; Sembroski, G. H.; Shahinyan, K.; Telezhinsky, Igor O.; Tucci, J. V.; Tyler, J.; Wakely, S. P.; Weinstein, A.; Wilcox, P.; Wilhelm, Alina; Williams, D. A.; Zitzer, B.; Razzaque, S.; Villata, M.; Raiteri, C. M.; Aller, H. D.; Aller, M. F.; Larionov, V. M.; Arkharov, A. A.; Blinov, D. A.; Efimova, N. V.; Grishina, T. S.; Hagen-Thorn, V. A.; Kopatskaya, E. N.; Larionova, L. V.; Larionova, E. G.; Morozova, D. A.; Troitsky, I. S.; Ligustri, R.; Calcidese, P.; Berdyugin, A.; Kurtanidze, O. M.; Nikolashvili, M. G.; Kimeridze, G. N.; Sigua, L. A.; Kurtanidze, S. O.; Chigladze, R. A.; Chen, W. P.; Koptelova, E.; Sakamoto, T.; Sadun, A. C.; Moody, J. W.; Pace, C.; Pearson, R.; Yatsu, Y.; Mori, Y.; Carraminyana, A.; Carrasco, L.; de la Fuente, E.; Norris, J. P.; Smith, P. S.; Wehrle, A.; Gurwell, M. A.; Zook, A.; Pagani, C.; Perri, M.; Capalbi, M.; Cesarini, A.; Krimm, H. A.; Kovalev, Y. Y.; Kovalev, Yu. A.; Ros, E.; Pushkarev, A. B.; Lister, M. L.; Sokolovsky, K. V.; Kadler, M.; Piner, G.; Lahteenmaki, A.; Tornikoski, M.; Angelakis, E.; Krichbaum, T. P.; Nestoras, I.; Fuhrmann, L.; Zensus, J. A.; Cassaro, P.; Orlati, A.; Maccaferri, G.; Leto, P.; Giroletti, M.; Richards, J. L.; Max-Moerbeck, W.; Readhead, A. C. S. Multiband variability studies and novel broadband SED modeling of Mrk 501 in 2009 Aims. We present an extensive study of the BL Lac object Mrk 501 based on a data set collected during the multi-instrument campaign spanning from 2009 March 15 to 2009 August 1, which includes, among other instruments, MAGIC, VERITAS, Whipple 10 m, and Fermi-LAT to cover the gamma-ray range from 0.1 GeV to 20 TeV; RXTE and Swift to cover wavelengths from UV to hard X-rays; and GASP-WEBT, which provides coverage of radio and optical wavelengths. Optical polarization measurements were provided for a fraction of the campaign by the Steward and St. Petersburg observatories. We evaluate the variability of the source and interband correlations, the gamma-ray flaring activity occurring in May 2009, and interpret the results within two synchrotron self-Compton (SSC) scenarios. Methods. The multiband variability observed during the full campaign is addressed in terms of the fractional variability, and the possible correlations are studied by calculating the discrete correlation function for each pair of energy bands where the significance was evaluated with dedicated Monte Carlo simulations. The space of SSC model parameters is probed following a dedicated grid-scan strategy, allowing for a wide range of models to be tested and offering a study of the degeneracy of model-to-data agreement in the individual model parameters, hence providing a less biased interpretation than the "single-curve SSC model adjustment" typically reported in the literature. Results. We find an increase in the fractional variability with energy, while no significant interband correlations of flux changes are found on the basis of the acquired data set. The SSC model grid-scan shows that the flaring activity around May 22 cannot be modeled adequately with a one-zone SSC scenario (using an electron energy distribution with two breaks), while it can be suitably described within a two (independent) zone SSC scenario. Here, one zone is responsible for the quiescent emission from the averaged 4.5-month observing period, while the other one, which is spatially separated from the first, dominates the flaring emission occurring at X-rays and very-high-energy (> 100 GeV, VHE) gamma-rays. The flaring activity from May 1, which coincides with a rotation of the electric vector polarization angle (EVPA), cannot be satisfactorily reproduced by either a one-zone or a two-independent-zone SSC model, yet this is partially affected by the lack of strictly simultaneous observations and the presence of large flux changes on sub-hour timescales (detected at VHE gamma rays). Conclusions. The higher variability in the VHE emission and lack of correlation with the X-ray emission indicate that, at least during the 4.5-month observing campaign in 2009, the highest energy (and most variable) electrons that are responsible for the VHE gamma rays do not make a dominant contribution to the similar to 1 keV emission. Alternatively, there could be a very variable component contributing to the VHE gamma-ray emission in addition to that coming from the SSC scenario. The studies with our dedicated SSC grid-scan show that there is some degeneracy in both the one-zone and the two-zone SSC scenarios probed, with several combinations of model parameters yielding a similar model-to-data agreement, and some parameters better constrained than others. The observed gamma-ray flaring activity, with the EVPA rotation coincident with the first gamma-ray flare, resembles those reported previously for low frequency peaked blazars, hence suggesting that there are many similarities in the flaring mechanisms of blazars with different jet properties. Les Ulis EDP Sciences 2017 30 Astronomy and astrophysics : an international weekly journal 603 10.1051/0004-6361/201629540 Institut für Physik und Astronomie OPUS4-54734 Wissenschaftlicher Artikel Heydari, Esmaeil; Pastoriza-Santos, Isabel; Liz-Marzan, Luis M.; Stumpe, Joachim Nanoplasmonically-engineered random lasing in organic semiconductor thin films We demonstrate plasmonically nano-engineered coherent random lasing and stimulated emission enhancement in a hybrid gainmedium of organic semiconductors doped with core-shell plasmonic nanoparticles. The gain medium is composed of a 300 +/- 2 nm thin waveguide of an organic semiconductor, doped with 53 nm gold nanoparticle cores, isolated within silica shells. Upon loading the nanoparticles, the threshold of amplified spontaneous emission is reduced from 1.75 mu J cm(-2) x 10(2) for an undoped gain medium, to 0.35 mu J cm(-2) x 10(2) for a highly concentrated gain medium, and lasing spikes narrower than 0.1 nm are obtained. Most importantly, selection of silica shells with thicknesses of 10, 17 and 21 nm enables engineering of the plasmon-exciton energy coupling and consequently tuning of the laser slope efficiency. With this approach, the slope efficiency is increased by two times by decreasing the silica shell from 21 nm down to 10 nm, due to the enhancement of the localized electric field. Cambridge Royal Society of Chemistry 2017 6 Nanoscale horizons 2 261 266 10.1039/c7nh00054e Institut für Physik und Astronomie OPUS4-55430 Wissenschaftlicher Artikel Henkel, Carsten Nanoscale Thermal Transfer An electromagnetic theory of thermal radiation is outlined, based on the fluctuation electrodynamics of Rytov and co-workers. We discuss the basic concepts and the status of different approximations. The physical content is illustrated with a few examples on near-field heat transfer. Berlin De Gruyter 2017 10 Zeitschrift für Naturforschung A 72 2 99 108 10.1515/zna-2016-0372 Institut für Physik und Astronomie OPUS4-55354 Wissenschaftlicher Artikel Warren, Donald C.; Ellison, Donald C.; Barkov, Maxim V.; Nagataki, Shigehiro Nonlinear Particle Acceleration and Thermal Particles in GRB Afterglows The standard model for GRB afterglow emission treats the accelerated electron population as a simple power law, N(E) proportional to E-p for p greater than or similar to 2. However, in standard Fermi shock acceleration, a substantial fraction of the swept-up particles do not enter the acceleration process at all. Additionally, if acceleration is efficient, then the nonlinear back-reaction of accelerated particles on the shock structure modifies the shape of the nonthermal tail of the particle spectra. Both of these modifications to the standard synchrotron afterglow impact the luminosity, spectra, and temporal variation of the afterglow. To examine the effects of including thermal particles and nonlinear particle acceleration on afterglow emission, we follow a hydrodynamical model for an afterglow jet and simulate acceleration at numerous points during the evolution. When thermal particles are included, we find that the electron population is at no time well fitted by a single power law, though the highest-energy electrons are; if the acceleration is efficient, then the power-law region is even smaller. Our model predicts hard-soft-hard spectral evolution at X-ray energies, as well as an uncoupled X-ray and optical light curve. Additionally, we show that including emission from thermal particles has drastic effects (increases by factors of 100 and 30, respectively) on the observed flux at optical and GeV energies. This enhancement of GeV emission makes afterglow detections by future gamma-ray observatories, such as CTA, very likely. Bristol IOP Publ. Ltd. 2017 15 The astrophysical journal : an international review of spectroscopy and astronomical physics 835 2 10.3847/1538-4357/aa56c3 Institut für Physik und Astronomie OPUS4-52858 Wissenschaftlicher Artikel Olson, R.; An, Soon-Il; Fan, Y.; Evans, J. P.; Caesar, Levke North Atlantic observations sharpen meridional overturning projections Atlantic Meridional Overturning Circulation (AMOC) projections are uncertain due to both model errors, as well as internal climate variability. An AMOC slowdown projected by many climate models is likely to have considerable effects on many aspects of global and North Atlantic climate. Previous studies to make probabilistic AMOC projections have broken new ground. However, they do not drift-correct or cross-validate the projections, and do not fully account for internal variability. Furthermore, they consider a limited subset of models, and ignore the skill of models at representing the temporal North Atlantic dynamics. We improve on previous work by applying Bayesian Model Averaging to weight 13 Coupled Model Intercomparison Project phase 5 models by their skill at modeling the AMOC strength, and its temporal dynamics, as approximated by the northern North-Atlantic temperature-based AMOC Index. We make drift-corrected projections accounting for structural model errors, and for the internal variability. Cross-validation experiments give approximately correct empirical coverage probabilities, which validates our method. Our results present more evidence that AMOC likely already started slowing down. While weighting considerably moderates and sharpens our projections, our results are at low end of previously published estimates. We project mean AMOC changes between periods 1960-1999 and 2060-2099 of -4.0 Sv and -6.8 Sv for RCP4.5 and RCP8.5 emissions scenarios respectively. The corresponding average 90% credible intervals for our weighted experiments are [-7.2, -1.2] and [-10.5, -3.7] Sv respectively for the two scenarios. New York Springer 2017 18 Climate dynamics : observational, theoretical and computational research on the climate system 50 11-12 4171 4188 10.1007/s00382-017-3867-7 Institut für Physik und Astronomie OPUS4-40268 Wissenschaftlicher Artikel Wolf, Thomas J. A.; Holzmeier, Fabian; Wagner, Isabella; Berrah, Nora; Bostedt, Christoph; Bozek, John; Bucksbaum, Philip H.; Coffee, Ryan; Cryan, James; Farrell, Joe; Feifel, Raimund; Martinez, Todd J.; McFarland, Brian; Mucke, Melanie; Nandi, Saikat; Tarantelli, Francesco; Fischer, Ingo; Gühr, Markus Observing Femtosecond Fragmentation Using Ultrafast X-ray-Induced Auger Spectra Molecules often fragment after photoionization in the gas phase. Usually, this process can only be investigated spectroscopically as long as there exists electron correlation between the photofragments. Important parameters, like their kinetic energy after separation, cannot be investigated. We are reporting on a femtosecond time-resolved Auger electron spectroscopy study concerning the photofragmentation dynamics of thymine. We observe the appearance of clearly distinguishable signatures from thymine′s neutral photofragment isocyanic acid. Furthermore, we observe a time-dependent shift of its spectrum, which we can attribute to the influence of the charged fragment on the Auger electron. This allows us to map our time-dependent dataset onto the fragmentation coordinate. The time dependence of the shift supports efficient transformation of the excess energy gained from photoionization into kinetic energy of the fragments. Our method is broadly applicable to the investigation of photofragmentation processes. Basel MDPI 2017 Applied Sciences 7 7 10.3390/app7070681 Institut für Physik und Astronomie OPUS4-40213 Wissenschaftlicher Artikel Niebuhr, Mario; Heuer, Axel Phase measurement and far-field reconstruction on externally coupled laser diode arrays Passive coherent combination of several discrete low power laser diodes is a promising way to overcome the issue of degrading beam quality when scaling single emitters to > 10W output power. Such systems would be an efficient alternative to current high power sources, yet they suffer from fatal coherence loss when operated well above threshold. We present a new way to obtain detailed coherence information for laser diode arrays using a spatial light modulator to help identify the underlying decoherence processes. Reconstruction tests of the emitted far-field distribution are conducted to evaluate the performance of our setup. Washington, DC Optical Society of America 2017 5 Optics express 25 13 14317 14322 10.1364/OE.25.014317 Institut für Physik und Astronomie OPUS4-55167 Wissenschaftlicher Artikel Malyar, Ivan V.; Gorin, Dmitry A.; Santer, Svetlana A.; Stetsyura, Svetlana V. Photo-assisted adsorption of gold nanoparticles onto a silicon substrate We report on a photo-assisted adsorption of gold nanoparticles on a silicon substrate studied using atomic-force microscopy and secondary ion mass-spectrometry. Depending on a silicon conductivity type (n-Si or p-Si), the amount of photo-assisted adsorbed gold nanoparticles either increases (n-Si) or decreases (p-Si) on irradiation. In addition, the impacts of a cationic polyelectrolyte monolayer and adsorption time were also revealed. The polyelectrolyte layer enhances the adsorption of the gold nanoparticles but decreases the influence of light. The results of the photo-assisted adsorption on two types of silicon wafer were explained by electron processes at the substrate/solution interface. This work was supported by the German-Russian Interdisciplinary Science Center (G-RISC) funded by the German Federal Foreign Office via the German Academic Exchange Service (DAAD), Project No. P-2014b-1, and Russian foundation for basic research, Project No. 16-08-00524_a. Melville American Institute of Physics 2017 4 Applied physics letters 110 10.1063/1.4979082 Institut für Physik und Astronomie OPUS4-55511 Wissenschaftlicher Artikel Schimka, Selina; Lomadze, Nino; Rabe, Maren; Kopyshev, Alexey; Lehmann, Maren; von Klitzing, Regine; Rumyantsev, Artem M.; Kramarenko, Elena Yu.; Santer, Svetlana A. Photosensitive microgels containing azobenzene surfactants of different charges We report on light sensitive microgel particles that can change their volume reversibly in response to illumination with light of different wavelengths. To make the anionic microgels photosensitive we add surfactants with a positively charged polyamine head group and an azobenzene containing tail. Upon illumination, azobenzene undergoes a reversible photo-isomerization reaction from a trans- to a cis-state accompanied by a change in the hydrophobicity of the surfactant. Depending on the isomerization state, the surfactant molecules are either accommodated within the microgel (trans- state) resulting in its shrinkage or desorbed back into water (cis-isomer) letting the microgel swell. We have studied three surfactants differing in the number of amino groups, so that the number of charges of the surfactant head varies between 1 and 3. We have found experimentally and theoretically that the surfactant concentration needed for microgel compaction increases with decreasing number of charges of the head group. Utilization of polyamine azobenzene containing surfactants for the light triggered remote control of the microgel size opens up a possibility for applications of light responsive microgels as drug carriers in biology and medicine. Cambridge Royal Society of Chemistry 2017 10 Physical chemistry, chemical physics : a journal of European Chemical Societies 19 108 117 10.1039/c6cp04555c Institut für Physik und Astronomie OPUS4-55779 Wissenschaftlicher Artikel Buschhüter, David; Spoden, Christian; Borowski, Andreas Physics knowledge of first semester physics students in Germany Over the last decades, the percentage of the age group choosing to pursue university studies has increased significantly across the world. At the same time, there are university teachers who believe that the standards have fallen. There is little research on whether students nowadays demonstrate knowledge or abilities similar to that of the preceding cohorts. However, in times of educational expansion, empirical evidence on student test performance is extremely helpful in evaluating how well educational systems cope with the increasing numbers of students. In this study, we compared a sample of 2322 physics freshmen from 2013 with another sample of 2718 physics freshmen from 1978 at universities in Germany with regard to their physics knowledge based on their results in the same entrance test. Previous results on mathematics knowledge and abilities in the same sample of students indicated that there was no severe decline in their average achievement. This paper compares the physics knowledge of the same two samples of students. Contrary to their mathematics results, their physics results showed a substantial decrease in physics knowledge as measured by the test. Abingdon Routledge, Taylor & Francis Group 2017 24 International journal of science education 39 9 1109 1132 10.1080/09500693.2017.1318457 Institut für Physik und Astronomie OPUS4-54942 Wissenschaftlicher Artikel Acero, F.; Aloisio, R.; Amans, J.; Amato, Elena; Antonelli, L. A.; Aramo, C.; Armstrong, T.; Arqueros, F.; Asano, Katsuaki; Ashley, M.; Backes, M.; Balazs, C.; Balzer, A.; Bamba, Aya; Barkov, Maxim; Barrio, J. A.; Benbow, Wystan; Bernloehr, K.; Beshley, V.; Bigongiari, C.; Biland, A.; Bilinsky, A.; Bissaldi, Elisabetta; Biteau, J.; Blanch, O.; Blasi, P.; Blazek, J.; Boisson, C.; Bonanno, G.; Bonardi, A.; Bonavolonta, C.; Bonnoli, G.; Braiding, C.; Brau-Nogue, S.; Bregeon, J.; Brown, A. M.; Bugaev, V.; Bulgarelli, A.; Bulik, T.; Burton, Michael; Burtovoi, A.; Busetto, G.; Bottcher, M.; Cameron, R.; Capalbi, M.; Caproni, Anderson; Caraveo, P.; Carosi, R.; Cascone, E.; Cerruti, M.; Chaty, Sylvain; Chen, A.; Chen, X.; Chernyakova, M.; Chikawa, M.; Chudoba, J.; Cohen-Tanugi, J.; Colafrancesco, S.; Conforti, V.; Contreras, J. L.; Costa, A.; Cotter, G.; Covino, Stefano; Covone, G.; Cumani, P.; Cusumano, G.; Daniel, M.; Dazzi, F.; De Angelis, A.; De Cesare, G.; De Franco, A.; De Frondat, F.; Dal Pino, E. M. de Gouveia; De Lisio, C.; Lopez, R. de los Reyes; De Lotto, B.; de Naurois, M.; De Palma, F.; Del Santo, M.; Delgado, C.; della Volpe, D.; Di Girolamo, T.; Di Giulio, C.; Di Pierro, F.; Di Venere, L.; Doro, M.; Dournaux, J.; Dumas, D.; Dwarkadas, Vikram V.; Diaz, C.; Ebr, J.; Egberts, Kathrin; Einecke, S.; Elsaesser, D.; Eschbach, S.; Falceta-Goncalves, D.; Fasola, G.; Fedorova, E.; Fernandez-Barral, A.; Ferrand, Gilles; Fesquet, M.; Fiandrini, E.; Fiasson, A.; Filipovic, Miroslav D.; Fioretti, V.; Font, L.; Fontaine, Gilles; Franco, F. J.; Freixas Coromina, L.; Fujita, Yutaka; Fukui, Y.; Funk, S.; Forster, A.; Gadola, A.; Lopez, R. Garcia; Garczarczyk, M.; Giglietto, N.; Giordano, F.; Giuliani, A.; Glicenstein, J.; Gnatyk, R.; Goldoni, P.; Grabarczyk, T.; Graciani, R.; Graham, J.; Grandi, P.; Granot, Jonathan; Green, A. J.; Griffiths, S.; Gunji, S.; Hakobyan, H.; Hara, S.; Hassan, T.; Hayashida, M.; Heller, M.; Helo, J. C.; Hinton, J.; Hnatyk, B.; Huet, J.; Huetten, M.; Humensky, T. B.; Hussein, M.; Horandel, J.; Ikeno, Y.; Inada, T.; Inome, Y.; Inoue, S.; Inoue, T.; Inoue, Y.; Ioka, K.; Iori, Maurizio; Jacquemier, J.; Janecek, P.; Jankowsky, D.; Jung, I.; Kaaret, P.; Katagiri, H.; Kimeswenger, S.; Kimura, Shigeo S.; Knodlseder, J.; Koch, B.; Kocot, J.; Kohri, K.; Komin, N.; Konno, Y.; Kosack, K.; Koyama, S.; Kraus, Michaela; Kubo, Hidetoshi; Mezek, G. Kukec; Kushida, J.; La Palombara, N.; Lalik, K.; Lamanna, G.; Landt, H.; Lapington, J.; Laporte, P.; Lee, S.; Lees, J.; Lefaucheur, J.; Lenain, J. -P.; Leto, Giuseppe; Lindfors, E.; Lohse, T.; Lombardi, S.; Longo, F.; Lopez, M.; Lucarelli, F.; Luque-Escamilla, Pedro Luis; Lopez-Coto, R.; Maccarone, M. C.; Maier, G.; Malaguti, G.; Mandat, D.; Maneva, G.; Mangano, S.; Marcowith, A.; Marti, J.; Martinez, M.; Martinez, G.; Masuda, S.; Maurin, G.; Maxted, N.; Melioli, Claudio; Mineo, T.; Mirabal, N.; Mizuno, T.; Moderski, R.; Mohammed, M.; Montaruli, T.; Moralejo, A.; Mori, K.; Morlino, G.; Morselli, A.; Moulin, E.; Mukherjee, R.; Mundell, C.; Muraishi, H.; Murase, Kohta; Nagataki, Shigehiro; Nagayoshi, T.; Naito, T.; Nakajima, D.; Nakamori, T.; Nemmen, R.; Niemiec, Jacek; Nieto, D.; Nievas-Rosillo, M.; Nikolajuk, M.; Nishijima, K.; Noda, K.; Nogues, L.; Nosek, D.; Novosyadlyj, B.; Nozaki, S.; Ohira, Yutaka; Ohishi, M.; Ohm, S.; Okumura, A.; Ong, R. A.; Orito, R.; Orlati, A.; Ostrowski, M.; Oya, I.; Padovani, Marco; Palacio, J.; Palatka, M.; Paredes, Josep M.; Pavy, S.; Persic, M.; Petrucci, P.; Petruk, Oleh; Pisarski, A.; Pohl, Martin; Porcelli, A.; Prandini, E.; Prast, J.; Principe, G.; Prouza, M.; Pueschel, Elisa; Puelhofer, G.; Quirrenbach, A.; Rameez, M.; Reimer, O.; Renaud, M.; Ribo, M.; Rico, J.; Rizi, V.; Rodriguez, J.; Fernandez, G. Rodriguez; Rodriguez Vazquez, J. J.; Romano, P.; Romeo, G.; Rosado, J.; Rousselle, J.; Rowell, G.; Rudak, B.; Sadeh, I.; Safi-Harb, S.; Saito, T.; Sakaki, N.; Sanchez, D.; Sangiorgi, P.; Sano, H.; Santander, M.; Sarkar, S.; Sawada, M.; Schioppa, E. J.; Schoorlemmer, H.; Schovanek, P.; Schussler, F.; Sergijenko, O.; Servillat, M.; Shalchi, A.; Shellard, R. C.; Siejkowski, H.; Sillanpaa, A.; Simone, D.; Sliusar, V.; Sol, H.; Stanic, S.; Starling, R.; Stawarz, L.; Stefanik, S.; Stephan, M.; Stolarczyk, T.; Szanecki, M.; Szepieniec, T.; Tagliaferri, G.; Tajima, H.; Takahashi, M.; Takeda, J.; Tanaka, M.; Tanaka, S.; Tejedor, L. A.; Telezhinsky, Igor O.; Temnikov, P.; Terada, Y.; Tescaro, D.; Teshima, M.; Testa, V.; Thoudam, S.; Tokanai, F.; Torres, D. F.; Torresi, E.; Tosti, G.; Townsley, C.; Travnicek, P.; Trichard, C.; Trifoglio, M.; Tsujimoto, S.; Vagelli, V.; Vallania, P.; Valore, L.; van Driel, W.; van Eldik, C.; Vandenbroucke, Justin; Vassiliev, V.; Vecchi, M.; Vercellone, Stefano; Vergani, S.; Vigorito, C.; Vorobiov, S.; Vrastil, M.; Vazquez Acosta, M. L.; Wagner, S. J.; Wagner, R.; Wakely, S. P.; Walter, R.; Ward, J. E.; Watson, J. J.; Weinstein, A.; White, M.; White, R.; Wierzcholska, A.; Wilcox, P.; Williams, D. A.; Wischnewski, R.; Wojcik, P.; Yamamoto, T.; Yamamoto, H.; Yamazaki, Ryo; Yanagita, S.; Yang, L.; Yoshida, T.; Yoshida, M.; Yoshiike, S.; Yoshikoshi, T.; Zacharias, M.; Zampieri, L.; Zanin, R.; Zavrtanik, M.; Zavrtanik, D.; Zdziarski, A.; Zech, Alraune; Zechlin, Hannes; Zhdanov, V.; Ziegler, A.; Zorn, J. Prospects for Cherenkov Telescope Array Observations of the Young Supernova Remnant RX J1713.7-3946 We perform simulations for future Cherenkov Telescope Array (CTA) observations of RX J1713.7-3946, a young supernova remnant (SNR) and one of the brightest sources ever discovered in very high energy (VHE) gamma rays. Special attention is paid to exploring possible spatial (anti) correlations of gamma rays with emission at other wavelengths, in particular X-rays and CO/H I emission. We present a series of simulated images of RX J1713.7-3946 for CTA based on a set of observationally motivated models for the gamma-ray emission. In these models, VHE gamma rays produced by high-energy electrons are assumed to trace the nonthermal X-ray emission observed by XMM-Newton, whereas those originating from relativistic protons delineate the local gas distributions. The local atomic and molecular gas distributions are deduced by the NANTEN team from CO and H I observations. Our primary goal is to show how one can distinguish the emission mechanism(s) of the gamma rays (i.e., hadronic versus leptonic, or a mixture of the two) through information provided by their spatial distribution, spectra, and time variation. This work is the first attempt to quantitatively evaluate the capabilities of CTA to achieve various proposed scientific goals by observing this important cosmic particle accelerator. Bristol IOP Publ. Ltd. 2017 14 The astrophysical journal : an international review of spectroscopy and astronomical physics 840 2 10.3847/1538-4357/aa6d67 Institut für Physik und Astronomie OPUS4-55206 Wissenschaftlicher Artikel Popovych, Oleksandr V.; Lysyansky, Borys; Rosenblum, Michael; Pikovskij, Arkadij; Tass, Peter A. Pulsatile desynchronizing delayed feedback for closed-loop deep brain stimulation High-frequency (HF) deep brain stimulation (DBS) is the gold standard for the treatment of medically refractory movement disorders like Parkinson's disease, essential tremor, and dystonia, with a significant potential for application to other neurological diseases. The standard setup of HF DBS utilizes an open-loop stimulation protocol, where a permanent HF electrical pulse train is administered to the brain target areas irrespectively of the ongoing neuronal dynamics. Recent experimental and clinical studies demonstrate that a closed-loop, adaptive DBS might be superior to the open-loop setup. We here combine the notion of the adaptive high-frequency stimulation approach, that aims at delivering stimulation adapted to the extent of appropriately detected biomarkers, with specifically desynchronizing stimulation protocols. To this end, we extend the delayed feedback stimulation methods, which are intrinsically closed-loop techniques and specifically designed to desynchronize abnormal neuronal synchronization, to pulsatile electrical brain stimulation. We show that permanent pulsatile high-frequency stimulation subjected to an amplitude modulation by linear or nonlinear delayed feedback methods can effectively and robustly desynchronize a STN-GPe network of model neurons and suggest this approach for desynchronizing closed-loop DBS. San Fransisco PLoS 2017 29 PLoS one 12 10.1371/journal.pone.0173363 Institut für Physik und Astronomie OPUS4-55449 Wissenschaftlicher Artikel Kunnus, Kristjan; Josefsson, I.; Schreck, Simon Frederik; Quevedo, W.; Miedema, P. S.; Techert, S.; de Groot, F. M. F.; Föhlisch, Alexander; Odelius, M.; Wernet, Ph. Quantifying covalent interactions with resonant inelastic soft X-ray scattering We analyze the effects of covalent interactions in Ni 2p3d resonant inelastic X-ray scattering (RIXS) spectra from aqueous Ni2+ ions and find that the relative RIXS intensities of ligand-to-metal charge-transfer final states with respect to the ligand-field final states reflect the covalent mixing between Ni 3d and water orbitals. Specifically, the experimental intensity ratio at the Ni L-3-edge allows to determine that the Ni 3d orbitals have on average 5.5% of water character. We propose that 2p3d RIXS at the Ni L-3-edge can be utilized to quantify covalency in Ni complexes without the use of external references or simulations. Amsterdam Elsevier 2017 6 Chemical physics letters 669 196 201 10.1016/j.cplett.2016.12.046 Institut für Physik und Astronomie OPUS4-40209 Wissenschaftlicher Artikel Schwarzl, Maria; Godec, Aljaž; Metzler, Ralf Quantifying non-ergodicity of anomalous diffusion with higher order moments Anomalous diffusion is being discovered in a fast growing number of systems. The exact nature of this anomalous diffusion provides important information on the physical laws governing the studied system. One of the central properties analysed for finite particle motion time series is the intrinsic variability of the apparent diffusivity, typically quantified by the ergodicity breaking parameter EB. Here we demonstrate that frequently EB is insufficient to provide a meaningful measure for the observed variability of the data. Instead, important additional information is provided by the higher order moments entering by the skewness and kurtosis. We analyse these quantities for three popular anomalous diffusion models. In particular, we find that even for the Gaussian fractional Brownian motion a significant skewness in the results of physical measurements occurs and needs to be taken into account. Interestingly, the kurtosis and skewness may also provide sensitive estimates of the anomalous diffusion exponent underlying the data. We also derive a new result for the EB parameter of fractional Brownian motion valid for the whole range of the anomalous diffusion parameter. Our results are important for the analysis of anomalous diffusion but also provide new insights into the theory of anomalous stochastic processes. London Macmillan Publishers Limited 2017 18 Scientific reports 7 10.1038/s41598-017-03712-x Institut für Physik und Astronomie OPUS4-50106 Wissenschaftlicher Artikel Matzka, Jürgen; Siddiqui, Tarique Adnan; Lilienkamp, Henning; Stolle, Claudia; Veliz, Oscar Quantifying solar flux and geomagnetic main field influence on the equatorial ionospheric current system at the geomagnetic observatory Huancayo In order to analyse the sensitivity of the equatorial ionospheric current system, i.e. the solar quiet current system and the equatorial electrojet, to solar cycle variations and to the secular variation of the geomagnetic main field, we have analysed 51 years (1935-1985) of geomagnetic observatory data from Huancayo, Peru. This period is ideal to analyse the influence of the main field strength on the amplitude of the quiet daily variation, since the main field decreases significantly from 1935 to 1985, while the distance of the magnetic equator to the observatory remains stable. To this end, we digitised some 19 years of hourly mean values of the horizontal component (H), which have not been available digitally at the World Data Centres. Then, the sensitivity of the amplitude Ali of the quiet daily variation to both solar cycle variations (in terms of sunspot numbers and solar flux F10.7) and changes of the geomagnetic main field strength (due to secular variation) was determined. We confirm an increase of Delta H for the decreasing main field in this period, as expected from physics based models (Cnossen, 2016), but with a somewhat smaller rate of 4.4% (5.8% considering one standard error) compared with 6.9% predicted by the physics based model. Oxford Elsevier 2017 6 Journal of Atmospheric and Solar-Terrestrial Physics 163 120 125 10.1016/j.jastp.2017.04.014 Institut für Umweltwissenschaften und Geographie OPUS4-55457 Wissenschaftlicher Artikel Goychuk, Igor Quantum ergodicity breaking in semi-classical electron transfer dynamics Can the statistical properties of single-electron transfer events be correctly predicted within a common equilibrium ensemble description? This fundamental in nanoworld question of ergodic behavior is scrutinized within a very basic semi-classical curve-crossing problem. It is shown that in the limit of non-adiabatic electron transfer (weak tunneling) well-described by the Marcus-Levich-Dogonadze (MLD) rate the answer is yes. However, in the limit of the so-called solvent-controlled adiabatic electron transfer, a profound breaking of ergodicity occurs. Namely, a common description based on the ensemble reduced density matrix with an initial equilibrium distribution of the reaction coordinate is not able to reproduce the statistics of single-trajectory events in this seemingly classical regime. For sufficiently large activation barriers, the ensemble survival probability in a state remains nearly exponential with the inverse rate given by the sum of the adiabatic curve crossing (Kramers) time and the inverse MLD rate. In contrast, near to the adiabatic regime, the single-electron survival probability is clearly non-exponential, even though it possesses an exponential tail which agrees well with the ensemble description. Initially, it is well described by a Mittag-Leffler distribution with a fractional rate. Paradoxically, the mean transfer time in this classical on the ensemble level regime is well described by the inverse of the nonadiabatic quantum tunneling rate on a single particle level. An analytical theory is developed which perfectly agrees with stochastic simulations and explains our findings. Cambridge Royal Society of Chemistry 2017 11 Physical chemistry, chemical physics : a journal of European Chemical Societies 19 3056 3066 10.1039/c6cp07206b Institut für Physik und Astronomie OPUS4-53228 Wissenschaftlicher Artikel Sysoev, Ilya V.; Ponomarenko, Vladimir I.; Pikovskij, Arkadij Reconstruction of coupling architecture of neural field networks from vector time series We propose a method of reconstruction of the network coupling matrix for a basic voltage-model of the neural field dynamics. Assuming that the multivariate time series of observations from all nodes are available, we describe a technique to find coupling constants which is unbiased in the limit of long observations. Furthermore, the method is generalized for reconstruction of networks with time-delayed coupling, including the reconstruction of unknown time delays. The approach is compared with other recently proposed techniques. Amsterdam Elsevier 2017 10 Communications in nonlinear science & numerical simulation 57 342 351 10.1016/j.cnsns.2017.10.006 Institut für Physik und Astronomie OPUS4-54996 Wissenschaftlicher Artikel Ramos, Antonio M. T.; Builes-Jaramillo, Alejandro; Poveda, German; Goswami, Bedartha; Macau, Elbert E. N.; Kurths, Jürgen; Marwan, Norbert Recurrence measure of conditional dependence and applications Identifying causal relations from observational data sets has posed great challenges in data-driven causality inference studies. One of the successful approaches to detect direct coupling in the information theory framework is transfer entropy. However, the core of entropy-based tools lies on the probability estimation of the underlying variables. Herewe propose a data-driven approach for causality inference that incorporates recurrence plot features into the framework of information theory. We define it as the recurrence measure of conditional dependence (RMCD), and we present some applications. The RMCD quantifies the causal dependence between two processes based on joint recurrence patterns between the past of the possible driver and present of the potentially driven, excepting the contribution of the contemporaneous past of the driven variable. Finally, it can unveil the time scale of the influence of the sea-surface temperature of the Pacific Ocean on the precipitation in the Amazonia during recent major droughts. College Park American Physical Society 2017 8 Physical review : E, Statistical, nonlinear and soft matter physics 95 10.1103/PhysRevE.95.052206 Institut für Physik und Astronomie OPUS4-53812 Wissenschaftlicher Artikel Waldrip, S. H.; Niven, Robert K.; Abel, Markus; Schlegel, M. Reduced-Parameter Method for Maximum Entropy Analysis of Hydraulic Pipe Flow Networks A maximum entropy (MaxEnt) method is developed to predict flow rates or pressure gradients in hydraulic pipe networks without sufficient information to give a closed-form (deterministic) solution. This methodology substantially extends existing deterministic flow network analysis methods. It builds on the MaxEnt framework previously developed by the authors. This study uses a continuous relative entropy defined on a reduced parameter set, here based on the external flow rates. This formulation ensures consistency between different representations of the same network. The relative entropy is maximized subject to observable constraints on the mean values of a subset of flow rates or potential differences, the frictional properties of each pipe, and physical constraints arising from Kirchhoff's first and second laws. The new method is demonstrated by application to a simple one-loop network and a 1,123-node, 1,140-pipe water distribution network in the suburb of Torrens, Australian Capital Territory, Australia. Reston American Society of Civil Engineers 2017 10 Journal of hydraulic engineering 144 2 10.1061/(ASCE)HY.1943-7900.0001379 Institut für Physik und Astronomie OPUS4-55271 Wissenschaftlicher Artikel Fandrich, Artur; Buller, Jens; Memczak, Henry; Stoecklein, W.; Hinrichs, K.; Wischerhoff, E.; Schulz, B.; Laschewsky, André; Lisdat, Fred Responsive Polymer-Electrode Interface-Study of its Thermo- and pH-Sensitivity and the Influence of Peptide Coupling This study introduces a thermally responsive, polymer-based electrode system. The key component is a surface-attached, temperature-responsive poly(oligoethylene glycol) methacrylate (poly(OEGMA)) type polymer bearing photoreactive benzophenone and carboxy groups containing side chains. The responsive behavior of the polymer in aqueous media has been investigated by turbidimetry measurements. Polymer films are formed on gold substrates by means of the photoreactive 2(dicyclohexylphosphino)benzophenone (DPBP) through photocrosslinking. The electrochemical behavior of the resulting polymer-substrate interface has been investigated in buffered [Fe(CN)6](3-)/[Fe (CN)6](4-)solutions at room temperature and under temperature variation by cyclic voltammetry (CV). The CV experiments show that with increasing temperature structural changes of the polymer layer occur, which alter the output of the electrochemical measurement. Repeated heating/cooling cycles analyzed by CV measurements and pH changes analyzed by quartz crystal microbalance with dissipation monitoring (QCM-D) reveal the reversible nature of the restructuring process. The immobilized films are further modified by covalent coupling of two small biomolecules - a hydrophobic peptide and a more hydrophilic one. These attached components influence the hydrophobicity of the layer in a different way the resulting change of the temperature-caused behavior has been studied by CV indicating a different state of the polymer after coupling of the hydrophobic peptide. Oxford Elsevier 2017 9 Electrochimica acta : the journal of the International Society of Electrochemistry (ISE) 229 325 333 10.1016/j.electacta.2017.01.080 Institut für Physik und Astronomie OPUS4-50101 Wissenschaftlicher Artikel Mahata, Khadak Singh; Panday, Arnico Kumar; Rupakheti, Maheswar; Singh, Ashish; Naja, Manish; Lawrence, Mark G. Seasonal and diurnal variations in methane and carbon dioxide in the Kathmandu Valley in the foothills of the central Himalayas The SusKat-ABC (Sustainable Atmosphere for the Kathmandu Valley-Atmospheric Brown Clouds) international air pollution measurement campaign was carried out from December 2012 to June 2013 in the Kathmandu Valley and surrounding regions in Nepal. The Kathmandu Valley is a bowl-shaped basin with a severe air pollution problem. This paper reports measurements of two major greenhouse gases (GHGs), methane (CH4) and carbon dioxide (CO2), along with the pollutant CO, that began during the campaign and were extended for 1 year at the SusKat-ABC supersite in Bode, a semi-urban location in the Kathmandu Valley. Simultaneous measurements were also made during 2015 in Bode and a nearby rural site (Chanban) similar to 25 km (aerial distance) to the southwest of Bode on the other side of a tall ridge. The ambient mixing ratios of methane (CH4), carbon dioxide (CO2), water vapor, and carbon monoxide (CO) were measured with a cavity ring-down spectrometer (G2401; Picarro, USA) along with meteorological parameters for 1 year (March 2013-March 2014). These measurements are the first of their kind in the central Himalayan foothills. At Bode, the annual average mixing ratios of CO2 and CH4 were 419.3 (+/- 6.0) ppm and 2.192 (+/- 0.066) ppm, respectively. These values are higher than the levels observed at background sites such as Mauna Loa, USA (CO2: 396.8 +/- 2.0 ppm, CH4: 1.831 +/- 0.110 ppm) and Waliguan, China (CO2: 397.7 +/- 3.6 ppm, CH4: 1.879 +/- 0.009 ppm) during the same period and at other urban and semi-urban sites in the region, such as Ahmedabad and Shadnagar (India). They varied slightly across the seasons at Bode, with seasonal average CH4 mixing ratios of 2.157 (+/- 0.230) ppm in the pre-monsoon season, 2.199 (+/- 0.241) ppm in the monsoon, 2.210 (+/- 0.200) ppm in the post-monsoon, and 2.214 (+/- 0.209) ppm in the winter season. The average CO2 mixing ratios were 426.2 (+/- 25.5) ppm in the pre-monsoon, 413.5 (+/- 24.2) ppm in the monsoon, 417.3 (+/- 23.1) ppm in the postmonsoon, and 421.9 (+/- 20.3) ppm in the winter season. The maximum seasonal mean mixing ratio of CH4 in winter was only 0.057 ppm or 2.6% higher than the seasonal minimum during the pre-monsoon period, while CO2 was 12.8 ppm or 3.1% higher during the pre-monsoon period (seasonal maximum) than during the monsoon (seasonal minimum). On the other hand, the CO mixing ratio at Bode was 191% higher during the winter than during the monsoon season. The enhancement in CO2 mixing ratios during the pre-monsoon season is associated with additional CO2 emissions from forest fires and agro-residue burning in northern South Asia in addition to local emissions in the Kathmandu Valley. Published CO = CO2 ratios of different emission sources in Nepal and India were compared with the observed CO = CO2 ratios in this study. This comparison suggested that the major sources in the Kathmandu Valley were residential cooking and vehicle exhaust in all seasons except winter. In winter, brick kiln emissions were a major source. Simultaneous measurements in Bode and Chanban (15 July-3 October 2015) revealed that the mixing ratios of CO2, CH4, and CO were 3.8, 12, and 64% higher in Bode than Chanban. The Kathmandu Valley thus has significant emissions from local sources, which can also be attributed to its bowl-shaped geography that is conducive to pollution build-up. At Bode, all three gas species (CO2, CH4, and CO) showed strong diurnal patterns in their mixing ratios with a pronounced morning peak (ca. 08:00), a dip in the afternoon, and a gradual increase again through the night until the next morning. CH4 and CO at Chanban, however, did not show any noticeable diurnal variations. These measurements provide the first insights into the diurnal and seasonal variation in key greenhouse gases and air pollutants and their local and regional sources, which is important information for atmospheric research in the region. Göttingen Copernicus 2017 24 Atmospheric Chemistry and Physics 17 20 12573 12596 10.5194/acp-17-12573-2017 Institut für Physik und Astronomie OPUS4-54757 Wissenschaftlicher Artikel Kiethe, Jan; Heuer, Axel; Jechow, Andreas Second-order coherence properties of amplified spontaneous emission from a high-power tapered superluminescent diode We study the degree of second-order coherence of the emission of a high-power multi-quantum well superluminescent diode with a lateral tapered amplifier section with and without optical feedback. When operated in an external cavity, the degree of second-order coherence changed from the almost thermal case of g((2))(0)approximate to 1.9 towards the mostly coherent case of g((2)) (0) approximate to 1.2 when the injection current at the tapered section was increased. We found good agreement with semi-classical laser theory near and below threshold while above laser threshold a slightly higher g((2))(0) was observed. As a free running device, the superluminescent diode yielded more than 400 mW of optical output power with good spatial beam quality of M-slow(2) < 1.6. In this case, the degree of second-order coherence dropped only slightly from 1.9 at low powers to 1.6 at the maximum output power. To our knowledge, this is the first investigation of a high-power tapered superluminescent diode concerning the degree of second-order coherence. Such a device might be useful for real-world applications probing the second order coherence function, such as ghost imaging. Bristol IOP Publ. Ltd. 2017 4 Laser physics letters 14 10.1088/1612-202X/aa772c Institut für Physik und Astronomie OPUS4-55482 Wissenschaftlicher Artikel Couto, Rafael C.; Cruz, Vinicius V.; Ertan, Emelie; Eckert, Sebastian Oliver; Fondell, Mattis; Dantz, Marcus; Kennedy, Brian; Schmitt, Thorsten; Pietzsch, Annette; Guimaraes, Freddy F.; Agren, Hans; Odelius, Michael; Kimberg, Victor; Föhlisch, Alexander Selective gating to vibrational modes through resonant X-ray scattering The dynamics of fragmentation and vibration of molecular systems with a large number of coupled degrees of freedom are key aspects for understanding chemical reactivity and properties. Here we present a resonant inelastic X-ray scattering (RIXS) study to show how it is possible to break down such a complex multidimensional problem into elementary components. Local multimode nuclear wave packets created by X-ray excitation to different core-excited potential energy surfaces (PESs) will act as spatial gates to selectively probe the particular ground-state vibrational modes and, hence, the PES along these modes. We demonstrate this principle by combining ultra-high resolution RIXS measurements for gas-phase water with state-of-the-art simulations. London Nature Publ. Group 2017 7 Nature Communications 8 10.1038/ncomms14165 Institut für Physik und Astronomie OPUS4-54807 Wissenschaftlicher Artikel Stete, Felix; Koopman, Wouter-Willem Adriaan; Bargheer, Matias Signatures of strong coupling on nanoparticles In the strong coupling regime, exciton and plasmon excitations are hybridized into combined system excitations. The correct identification of the coupling regime in these systems is currently debated, from both experimental and theoretical perspectives. In this article we show that the extinction spectra may show a large peak splitting, although the energy loss encoded in the absorption spectra clearly rules out the strong coupling regime. We investigate the coupling of J-aggregate excitons to the localized surface plasmon polaritons on gold nanospheres and nanorods by fine-tuning the plasmon resonance via layer-by-layer deposition of polyelectrolytes. While both structures show a characteristic anticrossing in extinction and scattering experiments, the careful assessment of the systems' light absorption reveals that strong coupling of the plasmon to the exciton is not present in the nanosphere system. In a phenomenological model of two classical coupled oscillators, a Fano-like regime causes only the resonance of the light-driven oscillator to split up, while the other one still dissipates energy at its original frequency. Only in the strong-coupling limit do both oscillators split up the frequencies at which they dissipate energy, qualitatively explaining our experimental finding. Washington American Chemical Society 2017 8 ACS Photonics 4 1669 1676 10.1021/acsphotonics.7b00113 OPUS4-55317 Wissenschaftlicher Artikel Gorobtsov, O. Yu.; Mercurio, G.; Brenner, G.; Lorenz, Ulf; Gerasimova, N.; Kurta, R. P.; Hieke, F.; Skopintsev, P.; Zaluzhnyy, I.; Lazarev, S.; Dzhigaev, D.; Rose, M.; Singer, A.; Wurth, W.; Vartanyants, I. A. Statistical properties of a free-electron laser revealed by Hanbury Brown-Twiss interferometry We present a comprehensive experimental analysis of statistical properties of the self-amplified spontaneous emission free-electron laser (FEL) FLASH by means of Hanbury Brown and Twiss interferometry. The experiments were performed at FEL wavelengths of 5.5, 13.4, and 20.8 nm. We determined the second-order intensity correlation function for all wavelengths and different operation conditions of FLASH. In all experiments a high degree of spatial coherence (above 50%) was obtained. Our analysis performed in spatial and spectral domains provided us with the independent measurements of an average pulse duration of the FEL that were below 60 fs. To explain the complicated behavior of the second-order intensity correlation function we developed an advanced theoretical model that includes the presence of multiple beams and external positional jitter of the FEL pulses. By this analysis we determined that in one of the experiments external positional jitter was about 25% of the beam size. We envision that methods developed in our study will be used widely for analysis and diagnostics of FEL radiation. College Park American Physical Society 2017 16 Physical review : A, Atomic, molecular, and optical physics 95 2 10.1103/PhysRevA.95.023843 Institut für Physik und Astronomie OPUS4-53599 Wissenschaftlicher Artikel Müller, B. R.; Cooper, R. C.; Lange, A.; Kupsch, Andreas; Wheeler, M.; Hentschel, M. P.; Staude, A.; Pandey, A.; Shyam, A.; Bruno, Giovanni Stress-induced microcrack density evolution in beta-eucryptite ceramics In order to investigate their microcracking behaviour, the microstructures of several beta-eucryptite ceramics, obtained from glass precursor and cerammed to yield different grain sizes and microcrack densities, were characterized by laboratory and synchrotron x-ray refraction and tomography. Results were compared with those obtained from scanning electron microscopy (SEM). In SEM images, the characterized materials appeared fully dense but computed tomography showed the presence of pore clusters. Uniaxial tensile testing was performed on specimens while strain maps were recorded and analyzed by Digital Image Correlation (DIC). X-ray refraction techniques were applied on specimens before and after tensile testing to measure the amount of the internal specific surface (i.e., area per unit volume). X-ray refraction revealed that (a) the small grain size (SGS) material contained a large specific surface, originating from the grain boundaries and the interfaces of TiO2 precipitates; (b) the medium (MGS) and large grain size (LGS) materials possessed higher amounts of specific surface compared to SGS material due to microcracks, which decreased after tensile loading; (c) the precursor glass had negligible internal surface. The unexpected decrease in the internal surface of MGS and LGS after tensile testing is explained by the presence of compressive regions in the DIC strain maps and further by theoretical arguments. It is suggested that while some microcracks merge via propagation, more close mechanically, thereby explaining the observed X-ray refraction results. The mechanisms proposed would allow the development of a strain hardening route in ceramics. Oxford Elsevier 2017 15 Acta materialia 144 627 641 10.1016/j.actamat.2017.10.030 Institut für Physik und Astronomie OPUS4-54268 Wissenschaftlicher Artikel Gout, Julien; Quade, Markus; Shafi, Kamran; Niven, Robert K.; Abel, Markus Synchronization control of oscillator networks using symbolic regression Networks of coupled dynamical systems provide a powerful way to model systems with enormously complex dynamics, such as the human brain. Control of synchronization in such networked systems has far-reaching applications in many domains, including engineering and medicine. In this paper, we formulate the synchronization control in dynamical systems as an optimization problem and present a multi-objective genetic programming-based approach to infer optimal control functions that drive the system from a synchronized to a non-synchronized state and vice versa. The genetic programming-based controller allows learning optimal control functions in an interpretable symbolic form. The effectiveness of the proposed approach is demonstrated in controlling synchronization in coupled oscillator systems linked in networks of increasing order complexity, ranging from a simple coupled oscillator system to a hierarchical network of coupled oscillators. The results show that the proposed method can learn highly effective and interpretable control functions for such systems. Dordrecht Springer 2017 21 Nonlinear Dynamics 91 2 1001 1021 10.1007/s11071-017-3925-z Institut für Physik und Astronomie OPUS4-54698 Wissenschaftlicher Artikel Dzhanoev, Arsen R.; Sokolov, Igor M. The effect of the junction model on the anomalous diffusion in the 3D comb structure The diffusion in the comb structures is a popular model of geometrically induced anomalous diffusion. In the present work we concentrate on the diffusion along the backbone in a system where sidebranches are planes, and the diffusion thereon is anomalous and described by continuous time random walks (CTRW). We show that the mean squared displacement (MSD) in the backbone of the comb behaves differently depending on whether the waiting time periods in the sidebranches are reset after the step in the backbone is done (a rejuvenating junction model), or not (a non-rejuvenating junction model). In the rejuvenating case the subdiffusion in the sidebranches only changes the prefactor in the ultra-slow (logarithmic) diffusion along the backbone, while in the non-rejuvenating case the ultraslow, logarithmic subdiffusion is changed to a much faster power-law subdiffusion (with a logarithmic correction) as it was found earlier by Iomin and Mendez [25]. Moreover, in the first case the result does not change if the diffusion in the backbone is itself anomalous, while in the second case it does. Two of the special cases of the considered models (the non-rejuvenating junction under normal diffusion in the backbone, and rejuvenating junction for the same waiting time distribution in the sidebranches and in junction points) were also investigated within the approach based on the corresponding generalized Fokker-Planck equations. (c) 2017 Elsevier Ltd. All rights reserved. Oxford Elsevier 2017 7 Chaos, solitons & fractals : applications in science and engineering ; an interdisciplinary journal of nonlinear science 106 330 336 10.1016/j.chaos.2017.12.001 Institut für Physik und Astronomie OPUS4-54262 Wissenschaftlicher Artikel Reese, Ronja; Gudmundsson, Gudmundur Hilmar; Levermann, Anders; Winkelmann, Hilke Ricarda The far reach of ice-shelf thinning in Antarctica Floating ice shelves, which fringe most of Antarctica's coastline, regulate ice flow into the Southern Ocean1,2,3. Their thinning4,5,6,7 or disintegration8,9 can cause upstream acceleration of grounded ice and raise global sea levels. So far the effect has not been quantified in a comprehensive and spatially explicit manner. Here, using a finite-element model, we diagnose the immediate, continent-wide flux response to different spatial patterns of ice-shelf mass loss. We show that highly localized ice-shelf thinning can reach across the entire shelf and accelerate ice flow in regions far from the initial perturbation. As an example, this 'tele-buttressing' enhances outflow from Bindschadler Ice Stream in response to thinning near Ross Island more than 900 km away. We further find that the integrated flux response across all grounding lines is highly dependent on the location of imposed changes: the strongest response is caused not only near ice streams and ice rises, but also by thinning, for instance, well-within the Filchner-Ronne and Ross Ice Shelves. The most critical regions in all major ice shelves are often located in regions easily accessible to the intrusion of warm ocean waters10,11,12, stressing Antarctica's vulnerability to changes in its surrounding ocean. London Nature Publ. Group 2017 7 Nature climate change 8 1 53 57 10.1038/s41558-017-0020-x Institut für Physik und Astronomie OPUS4-55202 Wissenschaftlicher Artikel Xiong, Hui; Mignolet, Benoit; Fang, Li; Osipov, Timur; Wolf, Thomas J. A.; Sistrunk, Emily; Gühr, Markus; Remacle, Francoise; Berrah, Nora The Role of Super-Atom Molecular Orbitals in Doped Fullerenes in a Femtosecond Intense Laser Field The interaction of gas phase endohedral fullerene Ho3N@C-80 with intense (0.1-5 x 10(14) W/cm(2)), short (30 fs), 800 nm laser pulses was investigated. The power law dependence of Ho3N@C-80(q+), q = 1-2, was found to be different from that of C-60. Time-dependent density functional theory computations revealed different light-induced ionization mechanisms. Unlike in C-60, in doped fullerenes, the breaking of the cage spherical symmetry makes super atomic molecular orbital (SAMO) states optically active. Theoretical calculations suggest that the fast ionization of the SAMO states in Ho3N@C-80 is responsible for the n = 3 power law for singly charged parent molecules at intensities lower than 1.2 x 10(14) W/cm(2). London Nature Publ. Group 2017 8 Scientific reports 7 10.1038/s41598-017-00124-9 Institut für Physik und Astronomie OPUS4-55367 Wissenschaftlicher Artikel Almeida, Leonardo A.; Sana, H.; Taylor, W.; Barbá, Rodolfo; Bonanos, Alceste Z.; Crowther, Paul; Damineli, Augusto; de Koter, A.; de Mink, Selma E.; Evans, C. J.; Gieles, Mark; Grin, Nathan J.; Hénault-Brunet, V.; Langer, Norbert; Lennon, D.; Lockwood, Sean; Maíz Apellániz, Jesús; Moffat, A. F. J.; Neijssel, C.; Norman, C.; Ramírez-Agudelo, O. H.; Richardson, N. D.; Schootemeijer, Abel; Shenar, Tomer; Soszyński, Igor; Tramper, Frank; Vink, J. S. The tarantula massive binary monitoring Context: Massive binaries play a crucial role in the Universe. Knowing the distributions of their orbital parameters is important for a wide range of topics from stellar feedback to binary evolution channels and from the distribution of supernova types to gravitational wave progenitors, yet no direct measurements exist outside the Milky Way. Aims: The Tarantula Massive Binary Monitoring project was designed to help fill this gap by obtaining multi-epoch radial velocity (RV) monitoring of 102 massive binaries in the 30 Doradus region. Methods: In this paper we analyze 32 FLAMES/GIRAFFE observations of 93 O- and 7 B-type binaries. We performed a Fourier analysis and obtained orbital solutions for 82 systems: 51 single-lined (SB1) and 31 double-lined (SB2) spectroscopic binaries. Results: Overall, the binary fraction and orbital properties across the 30 Doradus region are found to be similar to existing Galactic samples. This indicates that within these domains environmental effects are of second order in shaping the properties of massive binary systems. A small difference is found in the distribution of orbital periods, which is slightly flatter (in log space) in 30 Doradus than in the Galaxy, although this may be compatible within error estimates and differences in the fitting methodology. Also, orbital periods in 30 Doradus can be as short as 1.1 d, somewhat shorter than seen in Galactic samples. Equal mass binaries (q> 0.95) in 30 Doradus are all found outside NGC 2070, the central association that surrounds R136a, the very young and massive cluster at 30 Doradus's core. Most of the differences, albeit small, are compatible with expectations from binary evolution. One outstanding exception, however, is the fact that earlier spectral types (O2-O7) tend to have shorter orbital periods than later spectral types (O9.2-O9.7). Conclusions: Our results point to a relative universality of the incidence rate of massive binaries and their orbital properties in the metallicity range from solar (Z⊙) to about half solar. This provides the first direct constraints on massive binary properties in massive star-forming galaxies at the Universe's peak of star formation at redshifts z ~ 1 to 2 which are estimated to have Z ~ 0.5 Z⊙. Les Ulis EDP Sciences 2017 36 Astronomy and astrophysics : an international weekly journal 598 10.1051/0004-6361/201629844 Institut für Physik und Astronomie OPUS4-55368 Wissenschaftlicher Artikel Shenar, Tomer; Richardson, N. D.; Sablowski, Daniel P.; Hainich, Rainer; Sana, H.; Moffat, A. F. J.; Todt, Helge Tobias; Hamann, Wolf-Rainer; Oskinova, Lida M.; Sander, Andreas Alexander Christoph; Tramper, Frank; Langer, Norbert; Bonanos, Alceste Z.; de Mink, Selma E.; Gräfener, G.; Crowther, Paul; Vink, J. S.; Almeida, Leonardo A.; de Koter, A.; Barbá, Rodolfo; Herrero, A.; Ulaczyk, Krzysztof The tarantula massive binary monitoring We present the first SB2 orbital solution and disentanglement of the massive Wolf-Rayet binary R145 (P = 159 d) located in the Large Magellanic Cloud. The primary was claimed to have a stellar mass greater than 300 M-circle dot, making it a candidate for being the most massive star known to date. While the primary is a known late-type, H-rich Wolf-Rayet star (WN6h), the secondary has so far not been unambiguously detected. Using moderate-resolution spectra, we are able to derive accurate radial velocities for both components. By performing simultaneous orbital and polarimetric analyses, we derive the complete set of orbital parameters, including the inclination. The spectra are disentangled and spectroscopically analyzed, and an analysis of the wind-wind collision zone is conducted. The disentangled spectra and our models are consistent with a WN6h type for the primary and suggest that the secondary is an O3.5 If*/WN7 type star. We derive a high eccentricity of e = 0 : 78 and minimum masses of M-1 sin(3) i approximate to M-2 sin(3) i = 13 +/- 2 M-circle dot, with q = M-2/M-1 = 1.01 +/- 0.07. An analysis of emission excess stemming from a wind-wind collision yields an inclination similar to that obtained from polarimetry (i = 39 +/- 6 degrees). Our analysis thus implies M-1 = 53(-20)(+40) and M2 = 54(-20)(+40) M-circle dot, excluding M-1 > 300 M-circle dot. A detailed comparison with evolution tracks calculated for single and binary stars together with the high eccentricity suggests that the components of the system underwent quasi-homogeneous evolution and avoided mass-transfer. This scenario would suggest current masses of approximate to 80 M-circle dot and initial masses of M-i,M-1 approximate to 10(5) and M-i,M-2 approximate to 90 M-circle dot, consistent with the upper limits of our derived orbital masses, and would imply an age of approximate to 2.2 Myr. Les Ulis EDP Sciences 2017 16 Astronomy and astrophysics : an international weekly journal 598 10.1051/0004-6361/201629621 Institut für Physik und Astronomie OPUS4-55377 Wissenschaftlicher Artikel Sun, Ning-Chen; de Grijs, Richard; Subramanian, Smitha; Cioni, Maria-Rosa L.; Rubele, Stefano; Bekki, Kenji; Ivanov, Valentin D.; Piatti, Andrés E.; Ripepi, Vincenzo The VMC Survey. XXII. Hierarchical star formation in the 30 Doradus-N158-N159-N160 star-forming complex We study the hierarchical stellar structures in a similar to 1.5 deg(2) area covering the 30. Doradus-N158-N159-N160 starforming complex with the VISTA Survey of. Magellanic Clouds. Based on the young upper main-sequence stars, we find that the surface densities cover a wide range of values, from log(Sigma.pc(2))less than or similar to -2.0 to log(Sigma. pc(2)) greater than or similar to 0.0. Their distributions are highly non-uniform, showing groups that frequently have subgroups inside. The sizes of the stellar groups do not exhibit characteristic values, and range continuously from several parsecs to more than 100. pc; the cumulative size distribution can be well described by a single power law, with the power-law index indicating a projected fractal dimension D-2 = 1.6 +/- 0.3. We suggest that the phenomena revealed here support a scenario of hierarchical star formation. Comparisons with other star-forming regions and galaxies are also discussed. Bristol Institute of Physics Publ. 2017 10 The astrophysical journal : an international review of spectroscopy and astronomical physics 835 2 10.3847/1538-4357/835/2/171 Institut für Physik und Astronomie OPUS4-40053 Wissenschaftlicher Artikel Cherstvy, Andrey G.; Vinod, Deepak; Aghion, Erez; Chechkin, Aleksei V.; Metzler, Ralf Time averaging, ageing and delay analysis of financial time series We introduce three strategies for the analysis of financial time series based on time averaged observables. These comprise the time averaged mean squared displacement (MSD) as well as the ageing and delay time methods for varying fractions of the financial time series. We explore these concepts via statistical analysis of historic time series for several Dow Jones Industrial indices for the period from the 1960s to 2015. Remarkably, we discover a simple universal law for the delay time averaged MSD. The observed features of the financial time series dynamics agree well with our analytical results for the time averaged measurables for geometric Brownian motion, underlying the famed Black-Scholes-Merton model. The concepts we promote here are shown to be useful for financial data analysis and enable one to unveil new universal features of stock market dynamics. London IOP 2017 11 New journal of physics 19 1 11 10.1088/1367-2630/aa7199 Institut für Physik und Astronomie OPUS4-57027 Wissenschaftlicher Artikel Schubert, Marcel; Frisch, Johannes; Allard, Sybille; Preis, Eduard; Scherf, Ullrich; Koch, Norbert; Neher, Dieter Tuning side chain and main chain order in a prototypical donor-acceptor copolymer The recent development of donor-acceptor copolymers has led to an enormous improvement in the performance of organic solar cells and organic field-effect transistors. Here we describe the synthesis, detailed characterisation, and application of a series of structurally modified copolymers to investigate fundamental structure-property relationships in this class of conjugated polymers. The interplay between chemical structure and optoelectronic properties is investigated. These are further correlated to the charge transport and solar cell performance, which allows us to link their chemical structure to the observed physical properties. Berlin Springer 2017 23 Elementary Processes in Organic Photovoltaics 272 978-3-319-28338-8 243 265 10.1007/978-3-319-28338-8_10 Institut für Physik und Astronomie OPUS4-49700 Wissenschaftlicher Artikel Kayser, Markus; Maturilli, Marion; Graham, Robert M.; Hudson, Stephen R.; Rinke, Annette; Cohen, Lana; Kim, Joo-Hong; Park, Sang-Jong; Moon, Woosok; Granskog, Mats A. Vertical thermodynamic structure of the troposphere during the Norwegian young sea ICE expedition (N-ICE2015) The Norwegian young sea ICE (N-ICE2015) expedition was designed to investigate the atmosphere-snow-ice-ocean interactions in the young and thin sea ice regime north of Svalbard. Radiosondes were launched twice daily during the expedition from January to June 2015. Here we use these upper air measurements to study the multiple cyclonic events observed during N-ICE2015 with respect to changes in the vertical thermodynamic structure, moisture content, and boundary layer characteristics. We provide statistics of temperature inversion characteristics, static stability, and boundary layer extent. During winter, when radiative cooling is most effective, we find the strongest impact of synoptic cyclones. Changes to thermodynamic characteristics of the boundary layer are associated with transitions between the radiatively "clear" and "opaque" atmospheric states. In spring, radiative fluxes warm the surface leading to lifted temperature inversions and a statically unstable boundary layer. Further, we compare the N-ICE2015 static stability distributions to corresponding profiles from ERA-Interim reanalysis, from the closest land station in the Arctic North Atlantic sector, Ny-Alesund, and to soundings from the SHEBA expedition (1997/1998). We find similar stability characteristics for N-ICE2015 and SHEBA throughout the troposphere, despite differences in location, sea ice thickness, and snow cover. For Ny-Alesund, we observe similar characteristics above 1000 m, while the topography and ice-free fjord surrounding Ny-Alesund generate great differences below. The long-term radiosonde record (1993-2014) from Ny-Alesund indicates that during the N-ICE2015 spring period, temperatures were close to the climatological mean, while the lowest 3000 m were 1-3 degrees C warmer than the climatology during winter. Plain Language Summary The Norwegian young sea ICE (N-ICE2015) expedition was designed to investigate the atmosphere-snow-ice-ocean interactions in the young and thin sea ice regime north of Svalbard. Radiosondes were launched twice daily during the expedition from January to June 2015. Here we use these upper air measurements to study the multiple cyclonic events observed during N-ICE2015 with respect to changes in the vertical thermodynamic structure, moisture content, and the atmospheric boundary layer characteristics. During winter, we find the strongest impact of synoptic cyclones, which transport warm and moist air into the cold and dry Arctic atmosphere. In spring, incoming solar radiation warms the surface. This leads to very different thermodynamic conditions and higher moisture content, which reduces the contrast between stormy and calm periods. Further, we compare the N-ICE2015 measurements to corresponding profiles from ERA-Interim reanalysis, from the closest land station in the Arctic North Atlantic sector, Ny-Alesund, and to soundings from the SHEBA expedition (1997/1998). We find similar stability characteristics for N-ICE2015 and SHEBA throughout the troposphere, despite differences in location, sea ice thickness, and snow cover. The comparisons highlight the value of the N-ICE2015 observation and show the importance of winter time observations in the Arctic North Atlantic sector. Washington American Geophysical Union 2017 18 Journal of geophysical research-atmosheres 122 20 10855 10872 10.1002/2016JD026089 Institut für Physik und Astronomie OPUS4-55213 Wissenschaftlicher Artikel Leussu, R.; Usoskin, IIlya G.; Valliappan, Senthamizh Pavai; Diercke, Andrea; Arlt, Rainer; Denker, Carsten; Mursula, K. Wings of the butterfly The spatio-temporal evolution of sunspot activity, the so-called Maunder butterfly diagram, has been continously available since 1874 using data from the Royal Greenwich Observatory, extended by SOON network data after 1976. Here we present a new extended butterfly diagram of sunspot group occurrence since 1826, using the recently digitized data from Schwabe (1826-1867) and Sporer (1866-1880). The wings of the diagram are separated using a recently developed method based on an analysis of long gaps in sunspot group occurrence in different latitude bands. We define characteristic latitudes, corresponding to the start, end, and the largest extent of the wings (the F, L, and H latitudes). The H latitudes (30 degrees-45 degrees) are highly significantly correlated with the strength of the wings (quantified by the total sum of the monthly numbers of sunspot groups). The F latitudes (20 degrees-30 degrees) depict a weak tendency, especially in the southern hemisphere, to follow the wing strength. The L latitudes (2 degrees-10 degrees) show no clear relation to the wing strength. Overall, stronger cycle wings tend to start at higher latitudes and have a greater wing extent. A strong (5-6)-cycle periodic oscillation is found in the start and end times of the wings and in the overlap and gaps between successive wings of one hemisphere. While the average wing overlap is zero in the southern hemisphere, it is two to three months in the north. A marginally significant oscillation of about ten solar cycles is found in the asymmetry of the L latitudes. The new long database of butterfly wings provides new observational constraints to solar dynamo models that discuss the spatio-temporal distribution of sunspot occurrence over the solar cycle and longer. Les Ulis EDP Sciences 2017 8 Astronomy and astrophysics : an international weekly journal 599 10.1051/0004-6361/201629533 Institut für Physik und Astronomie