@article{MuellerNanovaGlaseretal.2016, author = {Mueller, Lars and Nanova, Diana and Glaser, Tobias and Beck, Sebastian and Pucci, Annemarie and Kast, Anne K. and Schroeder, Rasmus R. and Mankel, Eric and Pingel, Patrick and Neher, Dieter and Kowalsky, Wolfgang and Lovrincic, Robert}, title = {Charge-Transfer-Solvent Interaction Predefines Doping Efficiency in p-Doped P3HT Films}, series = {Chemistry of materials : a publication of the American Chemical Society}, volume = {28}, journal = {Chemistry of materials : a publication of the American Chemical Society}, publisher = {American Chemical Society}, address = {Washington}, issn = {0897-4756}, doi = {10.1021/acs.chemmater.6b01629}, pages = {4432 -- 4439}, year = {2016}, abstract = {Efficient electrical doping of organic semiconductors is a necessary prerequisite for the fabrication of high performance organic electronic devices. In this work, we study p-type doping of poly(3-hexylthiophene) (P3HT) with 2,3,5,6-tetrafluoro-7,7,8,8-tetracyanoquinodimethane (F(4)TCNQ) spin-cast from two different solvents. Using electron diffraction, we find strong dopant-induced pi-pi-stacking for films from the solvent chloroform, but not from chlorobenzene. This image is confirmed and expanded by the analysis of vibrational features of P3HT and polaron absorptions using optical spectroscopy. Here, a red-shifted polaron absorption is found in doped films from chloroform, caused by a higher conjugation length of the polymer backbone. These differences result in a higher conductivity of films from chloroform. We use optical spectroscopy on the corresponding blend solutions to shed light on the origin of this effect and propose a model to explain why solutions of doped P3HT reveal more aggregation of charged molecules in chlorobenzene, whereas more order is finally observed in dried films from chloroform. Our study emphasizes the importance of solvent parameters exceeding the bare solubility of pure dopant and host material for the preparation of highly conductive doped films.}, language = {en} } @article{NagornovOsipoyKomarovetal.2016, author = {Nagornov, Roman and Osipoy, Grigory and Komarov, Maxim and Pikovskij, Arkadij and Shilnikov, Andrey}, title = {Mixed-mode synchronization between two inhibitory neurons with post-inhibitory rebound}, series = {Communications in nonlinear science \& numerical simulation}, volume = {36}, journal = {Communications in nonlinear science \& numerical simulation}, publisher = {Elsevier}, address = {Amsterdam}, issn = {1007-5704}, doi = {10.1016/j.cnsns.2015.11.024}, pages = {175 -- 191}, year = {2016}, abstract = {We study an array of activity rhythms generated by a half-center oscillator (HCO), represented by a pair of reciprocally coupled neurons with post-inhibitory rebounds (PIR). Such coupling induced bursting possesses two time scales, one for fast spiking and another for slow quiescent periods, is shown to exhibit an array of synchronization properties. We discuss several HCO configurations constituted by two endogenous bursters, by tonic-spiking and quiescent neurons, as well as mixed-mode configurations composed of neurons of different type. We demonstrate that burst synchronization can be accompanied by complex, often chaotic, interactions of fast spikes within synchronized bursts. (C) 2015 Elsevier B.V. All rights reserved.}, language = {en} } @article{ShenarHainichTodtetal.2016, author = {Shenar, Tomer and Hainich, Rainer and Todt, Helge Tobias and Sander, Andreas Alexander Christoph and Hamann, Wolf-Rainer and Moffat, Anthony F. J. and Eldridge, J. J. and Pablo, H. and Oskinova, Lida and Richardson, N. D.}, title = {Wolf-Rayet stars in the Small Magellanic Cloud II. Analysis of the binaries}, series = {American mineralogist : an international journal of earth and planetary materials}, volume = {591}, journal = {American mineralogist : an international journal of earth and planetary materials}, publisher = {EDP Sciences}, address = {Les Ulis}, issn = {1432-0746}, doi = {10.1051/0004-6361/201527916}, pages = {25}, year = {2016}, abstract = {Context. Massive Wolf-Rayet (WR) stars are evolved massive stars (M-i greater than or similar to 20 M-circle dot) characterized by strong mass-loss. Hypothetically, they can form either as single stars or as mass donors in close binaries. About 40\% of all known WR stars are confirmed binaries, raising the question as to the impact of binarity on the WR population. Studying WR binaries is crucial in this context, and furthermore enable one to reliably derive the elusive masses of their components, making them indispensable for the study of massive stars. Aims. By performing a spectral analysis of all multiple WR systems in the Small Magellanic Cloud (SMC), we obtain the full set of stellar parameters for each individual component. Mass-luminosity relations are tested, and the importance of the binary evolution channel is assessed. Methods. The spectral analysis is performed with the PotsdamWolf-Rayet (PoWR) model atmosphere code by superimposing model spectra that correspond to each component. Evolutionary channels are constrained using the Binary Population and Spectral Synthesis (BPASS) evolution tool. Results. Significant hydrogen mass fractions (0.1 < X-H < 0.4) are detected in all WN components. A comparison with mass-luminosity relations and evolutionary tracks implies that the majority of the WR stars in our sample are not chemically homogeneous. The WR component in the binary AB6 is found to be very luminous (log L approximate to 6.3 [L-circle dot]) given its orbital mass (approximate to 10 M-circle dot), presumably because of observational contamination by a third component. Evolutionary paths derived for our objects suggest that Roche lobe overflow had occurred in most systems, affecting their evolution. However, the implied initial masses (greater than or similar to 60 M-circle dot) are large enough for the primaries to have entered the WR phase, regardless of binary interaction. Conclusions. Together with the results for the putatively single SMC WR stars, our study suggests that the binary evolution channel does not dominate the formation of WR stars at SMC metallicity.}, language = {en} } @article{GuberRichter2016, author = {Guber, Christoph R. and Richter, Philipp}, title = {Dust depletion of Ca and Ti in QSO absorption-line systems}, series = {Wiley Interdisciplinary Reviews : Water}, volume = {591}, journal = {Wiley Interdisciplinary Reviews : Water}, publisher = {EDP Sciences}, address = {Les Ulis}, issn = {1432-0746}, doi = {10.1051/0004-6361/201628466}, pages = {16}, year = {2016}, abstract = {Aims. To explore the role of titanium-and calcium-dust depletion in gas in and around galaxies, we systematically study Ti/Ca abundance ratios in intervening absorption-line systems at low and high redshift. Methods. We investigate high-resolution optical spectra obtained by the UVES instrument at the Very Large Telescope (VLT) and spectroscopically analyze 34 absorption-line systems at z <= 0.5 to measure column densities (or limits) for Ca II and Ti II. We complement our UVES data set with previously published absorption-line data on Ti/Ca for redshifts up to z similar to 3.8. Our absorber sample contains 110 absorbers including damped Lyman alpha systems (DLAs), sub-DLAs, and Lyman-Limit systems (LLS). We compare our Ti/Ca findings with results from the MilkyWay and the Magellanic Clouds and discuss the properties of Ti/Ca absorbers in the general context of quasar absorption-line systems. Results. Our analysis indicates that there are two distinct populations of absorbers with either high or low Ti/Ca ratios with a separation at [Ti/Ca] approximate to 1. While the calcium-dust depletion in most of the absorbers appears to be severe, the titanium depletions are mild in systems with high Ti/Ca ratios. The derived trend indicates that absorbers with high Ti/Ca ratios have dust-to-gas ratios that are substantially lower than in the Milky Way. We characterize the overall nature of the absorbers by correlating Ti/Ca with other observables (e.g., metallicity, velocity-component structure) and by modeling the ionization properties of singly-ionized Ca and Ti in different environments. Conclusions. We conclude that Ca II and Ti II bearing absorption-line systems trace predominantly neutral gas in the disks and inner halo regions of galaxies, where the abundance of Ca and Ti reflects the local metal and dust content of the gas. Our study suggests that the Ti/Ca ratio represents a useful measure for the gas-to-dust ratio and overall metallicity in intervening absorption-line systems.}, language = {en} } @article{GimenezGarciaShenarTorrejonetal.2016, author = {Gimenez-Garcia, Ana and Shenar, Tomer and Torrejon, J. M. and Oskinova, Lida and Martinez-Nunez, S. and Hamann, Wolf-Rainer and Rodes-Roca, J. J. and Gonz{\´a}lez-Galan, A. and Alonso-Santiago, J. and Gonz{\´a}lez-Fern{\´a}ndez, C. and Bernabeu, Guillermo and Sander, Andreas Alexander Christoph}, title = {Measuring the stellar wind parameters in IGR J17544-2619 and Vela X-1 constrains the accretion physics in supergiant fast X-ray transient and classical supergiant X-ray binaries}, series = {Siberian Mathematical Journal}, volume = {591}, journal = {Siberian Mathematical Journal}, publisher = {EDP Sciences}, address = {Les Ulis}, issn = {1432-0746}, doi = {10.1051/0004-6361/201527551}, pages = {25}, year = {2016}, abstract = {Aims. To close this gap, we perform a comparative analysis of the optical companion in two important systems: IGR J175442619 (SFXT) and Vela X-1 (SGXB). We analyze the spectra of each star in detail and derive their stellar and wind properties. As a next step, we compare the wind parameters, giving us an excellent chance of recognizing key differences between donor winds in SFXTs and SGXBs. Methods. We use archival infrared, optical and ultraviolet observations, and analyze them with the non-local thermodynamic equilibrium (NLTE) Potsdam Wolf-Rayet model atmosphere code. We derive the physical properties of the stars and their stellar winds, accounting for the influence of X-rays on the stellar winds. Results. We find that the stellar parameters derived from the analysis generally agree well with the spectral types of the two donors: O9I (IGR J17544-2619) and B0.5Iae (Vela X-1). The distance to the sources have been revised and also agree well with the estimations already available in the literature. In IGR J17544-2619 we are able to narrow the uncertainty to d = 3.0 +/- 0.2 kpc. From the stellar radius of the donor and its X-ray behavior, the eccentricity of IGR J17544-2619 is constrained to e < 0.25. The derived chemical abundances point to certain mixing during the lifetime of the donors. An important difference between the stellar winds of the two stars is their terminal velocities (v(infinity) = 1500 km s(-1) in IGR J17544-2619 and v(infinity) = 700 km s(-1) in Vela X-1), which have important consequences on the X-ray luminosity of these sources. Conclusions. The donors of IGR J17544-2619 and Vela X-1 have similar spectral types as well as similar parameters that physically characterize them and their spectra. In addition, the orbital parameters of the systems are similar too, with a nearly circular orbit and short orbital period. However, they show moderate differences in their stellar wind velocity and the spin period of their neutron star which has a strong impact on the X-ray luminosity of the sources. This specific combination of wind speed and pulsar spin favors an accretion regime with a persistently high luminosity in Vela X-1, while it favors an inhibiting accretion mechanism in IGR J17544-2619. Our study demonstrates that the relative wind velocity is critical in class determination for the HMXBs hosting a supergiant donor, given that it may shift the accretion mechanism from direct accretion to propeller regimes when combined with other parameters.}, language = {en} } @article{DzhanoevSchmidtLiuetal.2016, author = {Dzhanoev, Arsen R. and Schmidt, J. and Liu, X. and Spahn, Frank}, title = {Charging of small grains in a space plasma: Application to Jovian stream particles}, series = {International psychogeriatrics}, volume = {591}, journal = {International psychogeriatrics}, publisher = {EDP Sciences}, address = {Les Ulis}, issn = {1432-0746}, doi = {10.1051/0004-6361/201527891}, pages = {647 -- 684}, year = {2016}, abstract = {Context. Most theoretical investigations of dust charging processes in space have treated the current balance condition as independent of grain size. However, for small grains, since they are often observed in space environments, a dependence on grain size is expected owing to secondary electron emission (SEE). Here, by the term "small" we mean a particle size comparable to the typical penetration depth for given primary electron energy. The results are relevant for the dynamics of small, charged dust particles emitted by the volcanic moon Io, which forms the Jovian dust streams. Aims. We revise the theory of charging of small (submicron sized) micrometeoroids to take into account a high production of secondary electrons for small grains immersed in an isotropic flux of electrons. We apply our model to obtain an improved estimate for the charge of the dust streams leaving the Jovian system, detected by several spacecraft. Methods. We apply a continuum model to describe the penetration of primary electrons in a grain and the emission of secondary electrons along the path. Averaging over an isotropic flux of primaries, we derive a new expression for the secondary electron yield, which can be used to express the secondary electron current on a grain. Results. For the Jupiter plasma environment we derive the surface potential of grains composed of NaCl (believed to be the major constituent of Jovian dust stream particles) or silicates. For small particles, the potential depends on grain size and the secondary electron current induces a sensitivity to material properties. As a result of the small particle effect, the estimates for the charging times and for the fractional charge fluctuations of NaCl grains obtained using our general approach to SEE give results qualitatively different from the analogous estimates derived from the traditional approach to SEE. We find that for the charging environment considered in this paper field emission does not limit the charging of NaCl grains.}, language = {en} } @article{AbeysekaraArchambaultArcheretal.2016, author = {Abeysekara, A. U. and Archambault, S. and Archer, A. and Benbow, W. and Bird, R. and Biteau, Jonathan and Buchovecky, M. and Buckley, J. H. and Bugaev, V. and Byrum, K. and Cardenzana, J. V. and Cerruti, M. and Chen, Xuhui and Christiansen, J. L. and Ciupik, L. and Connolly, M. P. and Cui, W. and Dickinson, H. J. and Dumm, J. and Eisch, J. D. and Errando, M. and Falcone, A. and Feng, Q. and Finley, J. P. and Fleischhack, H. and Flinders, A. and Fortin, P. and Fortson, L. and Furniss, A. and Gillanders, G. H. and Griffin, S. and Grube, J. and Gyuk, G. and Huetten, M. and Hanna, D. and Holder, J. and Humensky, T. B. and Johnson, C. A. and Kaaret, P. and Kar, P. and Kelley-Hoskins, N. and Kertzman, M. and Kieda, D. and Krause, M. and Krennrich, F. and Lang, M. J. and Maier, G. and McArthur, S. and McCann, A. and Meagher, K. and Moriarty, P. and Mukherjee, R. and Nieto, D. and Ong, R. A. and Otte, A. N. and Park, N. and Pelassa, V. and Petrashyk, A. and Petry, D. and Pohl, Martin and Popkow, A. and Pueschel, Elisa and Quinn, J. and Ragan, K. and Ratliff, G. and Reyes, L. C. and Reynolds, P. T. and Reynolds, K. and Richards, G. T. and Roache, E. and Rulten, C. and Santander, M. and Sembroski, G. H. and Shahinyan, K. and Smith, A. W. and Staszak, D. and Telezhinsky, Igor O. and Tucci, J. V. and Tyler, J. and Vincent, S. and Wakely, S. P. and Weiner, O. M. and Weinstein, A. and Wilhelm, Alina and Williams, D. A. and Zitzer, B.}, title = {VERITAS and multiwavelength observations of the BL Lacertae object 1ES 1741+196}, series = {Monthly notices of the Royal Astronomical Society}, volume = {459}, journal = {Monthly notices of the Royal Astronomical Society}, publisher = {Oxford Univ. Press}, address = {Oxford}, issn = {0035-8711}, doi = {10.1093/mnras/stw664}, pages = {2550 -- 2557}, year = {2016}, abstract = {We present results from multiwavelength observations of the BL Lacertae object 1ES 1741 + 196, including results in the very high energy gamma-ray regime using the Very Energetic Radiation Imaging Telescope Array System (VERITAS). The VERITAS time-averaged spectrum, measured above 180 GeV, is well modelled by a power law with a spectral index of 2.7 +/- 0.7(stat) +/- 0.2(syst). The integral flux above 180 GeV is (3.9 +/- 0.8(stat) +/- 1.0(syst)) x 10(-8) m(-2) s(-1), corresponding to 1.6 per cent of the Crab nebula flux on average. The multiwavelength spectral energy distribution of the source suggests that 1ES 1741+196 is an extreme-high-frequency-peaked BL Lacertae object. The observations analysed in this paper extend over a period of six years, during which time no strong flares were observed in any band. This analysis is therefore one of the few characterizations of a blazar in a non-flaring state.}, language = {en} } @article{LiuSachseSpahnetal.2016, author = {Liu, Xiaodong and Sachse, Manuel and Spahn, Frank and Schmidt, Jurgen}, title = {Dynamics and distribution of Jovian dust ejected from the Galilean satellites}, series = {Journal of geophysical research, Planets}, volume = {121}, journal = {Journal of geophysical research, Planets}, publisher = {American Geophysical Union}, address = {Washington}, issn = {2169-9097}, doi = {10.1002/2016JE004999}, pages = {1141 -- 1173}, year = {2016}, abstract = {In this paper, the dynamical analysis of the Jovian dust originating from the four Galilean moons is presented. High-accuracy orbital integrations of dust particles are used to determine their dynamical evolution. A variety of forces are taken into account, including the Lorentz force, solar radiation pressure, Poynting-Robertson drag, solar gravity, the satellites' gravity, plasma drag, and gravitational effects due to nonsphericity of Jupiter. More than 20,000 dust particles from each source moon in the size range from 0.05 \&\#956;m to 1 cm are simulated over 8000 (Earth) years until each dust grain hits a sink (moons, Jupiter, or escape from the system). Configurations of dust number density in the Jovicentric equatorial inertial frame are calculated and shown. In a Jovicentric frame rotating with the Sun the dust distributions are found to be asymmetric. For certain small particle sizes, the dust population is displaced towards the Sun, while for certain larger sizes, the dust population is displaced away from the Sun. The average lifetime as a function of particle size for ejecta from each source moon is derived, and two sharp jumps in the average lifetime are analyzed. Transport of dust between the Galilean moons and to Jupiter is investigated. Most of the orbits for dust particles from Galilean moons are prograde, while, surprisingly, a small fraction of orbits are found to become retrograde mainly due to solar radiation pressure and Lorentz force. The distribution of orbital elements is also analyzed.}, language = {en} } @article{PedatellaFangJinetal.2016, author = {Pedatella, Nick M. and Fang, T. -W. and Jin, Hao and Sassi, F. and Schmidt, H. and Chau, Jorge Luis and Siddiqui, Tarique Adnan and Goncharenko, L.}, title = {Multimodel comparison of the ionosphere variability during the 2009 sudden stratosphere warming}, series = {Journal of geophysical research : Space physics}, volume = {121}, journal = {Journal of geophysical research : Space physics}, publisher = {American Geophysical Union}, address = {Washington}, issn = {2169-9380}, doi = {10.1002/2016JA022859}, pages = {7204 -- 7225}, year = {2016}, abstract = {A comparison of different model simulations of the ionosphere variability during the 2009 sudden stratosphere warming (SSW) is presented. The focus is on the equatorial and low-latitude ionosphere simulated by the Ground-to-topside model of the Atmosphere and Ionosphere for Aeronomy (GAIA), Whole Atmosphere Model plus Global Ionosphere Plasmasphere (WAM+GIP), and Whole Atmosphere Community Climate Model eXtended version plus Thermosphere-Ionosphere-Mesosphere-Electrodynamics General Circulation Model (WACCMX+TIMEGCM). The simulations are compared with observations of the equatorial vertical plasma drift in the American and Indian longitude sectors, zonal mean Fregion peak density (NmF2) from the Constellation Observing System for Meteorology, Ionosphere, and Climate (COSMIC) satellites, and ground-based Global Positioning System (GPS) total electron content (TEC) at 75 degrees W. The model simulations all reproduce the observed morning enhancement and afternoon decrease in the vertical plasma drift, as well as the progression of the anomalies toward later local times over the course of several days. However, notable discrepancies among the simulations are seen in terms of the magnitude of the drift perturbations, and rate of the local time shift. Comparison of the electron densities further reveals that although many of the broad features of the ionosphere variability are captured by the simulations, there are significant differences among the different model simulations, as well as between the simulations and observations. Additional simulations are performed where the neutral atmospheres from four different whole atmosphere models (GAIA, HAMMONIA (Hamburg Model of the Neutral and Ionized Atmosphere), WAM, and WACCMX) provide the lower atmospheric forcing in the TIME-GCM. These simulations demonstrate that different neutral atmospheres, in particular, differences in the solar migrating semidiurnal tide, are partly responsible for the differences in the simulated ionosphere variability in GAIA, WAM+GIP, and WACCMX+TIMEGCM.}, language = {en} } @article{QuadeAbelShafietal.2016, author = {Quade, Markus and Abel, Markus and Shafi, Kamran and Niven, Robert K. and Noack, Bernd R.}, title = {Prediction of dynamical systems by symbolic regression}, series = {Physical review : E, Statistical, nonlinear and soft matter physics}, volume = {94}, journal = {Physical review : E, Statistical, nonlinear and soft matter physics}, publisher = {American Society for Pharmacology and Experimental Therapeutics}, address = {Bethesda}, issn = {2470-0045}, doi = {10.1103/PhysRevE.94.012214}, pages = {15}, year = {2016}, abstract = {We study the modeling and prediction of dynamical systems based on conventional models derived from measurements. Such algorithms are highly desirable in situations where the underlying dynamics are hard to model from physical principles or simplified models need to be found. We focus on symbolic regression methods as a part of machine learning. These algorithms are capable of learning an analytically tractable model from data, a highly valuable property. Symbolic regression methods can be considered as generalized regression methods. We investigate two particular algorithms, the so-called fast function extraction which is a generalized linear regression algorithm, and genetic programming which is a very general method. Both are able to combine functions in a certain way such that a good model for the prediction of the temporal evolution of a dynamical system can be identified. We illustrate the algorithms by finding a prediction for the evolution of a harmonic oscillator based on measurements, by detecting an arriving front in an excitable system, and as a real-world application, the prediction of solar power production based on energy production observations at a given site together with the weather forecast.}, language = {en} } @article{PiattiIvanovRubeleetal.2016, author = {Piatti, Andres E. and Ivanov, Valentin D. and Rubele, Stefano and Marconi, Marcella and Ripepi, Vincenzo and Cioni, Maria-Rosa L. and Oliveira, Joana M. and Bekki, Kenji}, title = {The VMC Survey - XXI. New star cluster candidates discovered from infrared photometry in the Small Magellanic Cloud}, series = {Monthly notices of the Royal Astronomical Society}, volume = {460}, journal = {Monthly notices of the Royal Astronomical Society}, publisher = {Oxford Univ. Press}, address = {Oxford}, issn = {0035-8711}, doi = {10.1093/mnras/stw1000}, pages = {383 -- 395}, year = {2016}, language = {en} } @article{BodrovaChechkinCherstvyetal.2016, author = {Bodrova, Anna S. and Chechkin, Aleksei V. and Cherstvy, Andrey G. and Safdari, Hadiseh and Sokolov, Igor M. and Metzler, Ralf}, title = {Underdamped scaled Brownian motion: (non-)existence of the overdamped limit in anomalous diffusion}, series = {Scientific reports}, volume = {6}, journal = {Scientific reports}, publisher = {Nature Publ. Group}, address = {London}, issn = {2045-2322}, doi = {10.1038/srep30520}, pages = {16}, year = {2016}, abstract = {It is quite generally assumed that the overdamped Langevin equation provides a quantitative description of the dynamics of a classical Brownian particle in the long time limit. We establish and investigate a paradigm anomalous diffusion process governed by an underdamped Langevin equation with an explicit time dependence of the system temperature and thus the diffusion and damping coefficients. We show that for this underdamped scaled Brownian motion (UDSBM) the overdamped limit fails to describe the long time behaviour of the system and may practically even not exist at all for a certain range of the parameter values. Thus persistent inertial effects play a non-negligible role even at significantly long times. From this study a general questions on the applicability of the overdamped limit to describe the long time motion of an anomalously diffusing particle arises, with profound consequences for the relevance of overdamped anomalous diffusion models. We elucidate our results in view of analytical and simulations results for the anomalous diffusion of particles in free cooling granular gases.}, language = {en} } @article{KopyshevGalvinPatiletal.2016, author = {Kopyshev, Alexey and Galvin, Casey J. and Patil, Rohan R. and Genzer, Jan and Lomadze, Nino and Feldmann, David and Zakrevski, Juri and Santer, Svetlana}, title = {Light-Induced Reversible Change of Roughness and Thickness of Photosensitive Polymer Brushes}, series = {Applied physics : A, Materials science \& processing}, volume = {8}, journal = {Applied physics : A, Materials science \& processing}, publisher = {American Chemical Society}, address = {Washington}, issn = {1944-8244}, doi = {10.1021/acsami.6b06881}, pages = {19175 -- 19184}, year = {2016}, abstract = {We investigate light-induced changes in thickness and roughness of photosensitive polymer brushes containing azobenzene cationic surfactants by atomic force microscopy (AFM) in real time during light irradiation. Because the cis-state of azobenzene unit requires more free volume than its trans counterpart, the UV light-induced expansion of polymer thin films associated with the trans-to-cis isomerism of azobenzene groups is expected to occur. This phenomenon is well documented in physisorbed polymer films containing azobenzene groups. In contrast, photosensitive polymer brushes show a decrease in thickness under UV irradiation. We have found that the azobenzene surfactants in their trans-state form aggregates within the brush. Under irradiation, the surfactants undergo photoisomerization to the cis-state, which is more hydrophilic. As a consequence, the aggregates within the brush are disrupted, and the polymer brush contracts. When subsequently irradiated with blue light the polymer brush thickness returns back to its initial value. This behavior is related to isomerization of the surfactant to the more hydrophobic trans-state and subsequent formation of surfactant aggregates within the polymer brush. The photomechanical function of the dry polymer brush, i.e., contraction and expansion, was found to be reversible with repeated irradiation cycles and requires only a few seconds for switching. In addition to the thickness change, the roughness of the brush also changes reversibly between a few Angstroms (blue light) and several nanometers (UV light). Photosensitive polymer brushes represent smart films with light responsive thickness and roughness that could be used for generating dynamic fluctuating surfaces, the function of which can be turned on and off in a controllable manner on a nanometer length scale.}, language = {en} } @article{KunnusZhangDelceyetal.2016, author = {Kunnus, Kristjan and Zhang, Wenkai and Delcey, Mickael G. and Pinjari, Rahul V. and Miedema, Piter S. and Schreck, Simon and Quevedo, Wilson and Schr{\"o}der, Henning and F{\"o}hlisch, Alexander and Gaffney, Kelly J. and Lundberg, Marcus and Odelius, Michael and Wernet, Philippe}, title = {Viewing the Valence Electronic Structure of Ferric and Ferrous Hexacyanide in Solution from the Fe and Cyanide Perspectives}, series = {The journal of physical chemistry : B, Condensed matter, materials, surfaces, interfaces \& biophysical chemistry}, volume = {120}, journal = {The journal of physical chemistry : B, Condensed matter, materials, surfaces, interfaces \& biophysical chemistry}, publisher = {American Chemical Society}, address = {Washington}, issn = {1520-6106}, doi = {10.1021/acs.jpcb.6b04751}, pages = {7182 -- 7194}, year = {2016}, abstract = {The valence-excited states of ferric and ferrous hexacyanide ions in aqueous solution were mapped by resonant inelastic X-ray scattering (RIXS) at the Fe L-2,L-3 and N K edges. Probing of both the central Fe and the ligand N atoms enabled identification of the metal-and ligand-centered excited states, as well as ligand-to-metal and metal-to-ligand charge-transfer excited states. Ab initio calculations utilizing the RASPT2 method were used to simulate the Fe L-2,L-3-edge RIXS spectra and enabled quantification of the covalencies of both occupied and empty orbitals of pi and sigma symmetry. We found that pi back-donation in the ferric complex is smaller than that in the ferrous complex. This is evidenced by the relative amounts of Fe 3d character in the nominally 2 pi CN- molecular orbital of 7\% and 9\% in ferric and ferrous hexacyanide, respectively. Utilizing the direct sensitivity of Fe L-3-edge RIXS to the Fe 3d character in the occupied molecular orbitals, we also found that the donation interactions are dominated by sigma bonding. The latter was found to be stronger in the ferric complex, with an Fe 3d contribution to the nominally 5 sigma CN- molecular orbitals of 29\% compared to 20\% in the ferrous complex. These results are consistent with the notion that a higher charge at the central metal atom increases donation and decreases back-donation.}, language = {en} } @article{ThomasFeldmeier2016, author = {Thomas, Timon and Feldmeier, Achim}, title = {Radiative waves in stellar winds with line scattering}, series = {Monthly notices of the Royal Astronomical Society}, volume = {460}, journal = {Monthly notices of the Royal Astronomical Society}, publisher = {Oxford Univ. Press}, address = {Oxford}, issn = {0035-8711}, doi = {10.1093/mnras/stw1008}, pages = {1923 -- 1933}, year = {2016}, abstract = {Photospheric radiation can drive winds from hot, massive stars by direct momentum transfer through scattering in bound-bound transitions of atmospheric ions. The line radiation force should cause a new radiative wave mode. The dispersion relation from perturbations of the line force was analysed so far either in Sobolev approximation or for pure line absorption. The former does not include the line-driven instability, and the latter cannot account for upstream propagating, radiative waves. We consider a non-Sobolev line force that includes scattering in a simplified way, accounting however for the important line-drag effect. We derive a new dispersion relation for radiative waves, and analyse wave propagation using Fourier methods, and by numerical solution of an integro-differential equation. The existence of an upstream propagating, dispersive radiative wave mode is demonstrated.}, language = {en} } @article{GeigerFrielerLevermann2016, author = {Geiger, Tobias and Frieler, Katja and Levermann, Anders}, title = {High-income does not protect against hurricane losses}, series = {Environmental research letters}, volume = {11}, journal = {Environmental research letters}, publisher = {IOP Publ. Ltd.}, address = {Bristol}, issn = {1748-9326}, doi = {10.1088/1748-9326/11/8/084012}, pages = {10}, year = {2016}, abstract = {Damage due to tropical cyclones accounts for more than 50\% of all meteorologically-induced economic losses worldwide. Their nominal impact is projected to increase substantially as the exposed population grows, per capita income increases, and anthropogenic climate change manifests. So far, historical losses due to tropical cyclones have been found to increase less than linearly with a nation's affected gross domestic product (GDP). Here we show that for the United States this scaling is caused by a sub-linear increase with affected population while relative losses scale super-linearly with per capita income. The finding is robust across a multitude of empirically derived damage models that link the storm's wind speed, exposed population, and per capita GDP to reported losses. The separation of both socio-economic predictors strongly affects the projection of potential future hurricane losses. Separating the effects of growth in population and per-capita income, per hurricane losses with respect to national GDP are projected to triple by the end of the century under unmitigated climate change, while they are estimated to decrease slightly without the separation.}, language = {en} } @article{RoshchupkinOrtegaPlotitcynaetal.2016, author = {Roshchupkin, Dmitry and Ortega, Luc and Plotitcyna, Olga and Erko, Alexei and Zizak, Ivo and Vadilonga, Simone and Irzhak, Dmitry and Emelin, Evgenii and Buzanov, Oleg and Leitenberger, Wolfram}, title = {Piezoelectric Ca3NbGa3Si2O14 crystal: crystal growth, piezoelectric and acoustic properties}, series = {Journal of geophysical research : Space physics}, volume = {122}, journal = {Journal of geophysical research : Space physics}, publisher = {Springer}, address = {New York}, issn = {0947-8396}, doi = {10.1007/s00339-016-0279-1}, pages = {2803 -- 2812}, year = {2016}, abstract = {Ca3NbGa3Si2O14 (CNGS), a five-component crystal of lanthanum-gallium silicate group, was grown by the Czochralski method. The parameters of the elementary unit cell of the crystal were measured by powder diffraction. The independent piezoelectric strain coefficients d(11) and d(14) were determined by the triple-axis X-ray diffraction in the Bragg and Laue geometries. Excitation and propagation of surface acoustic waves (SAW) were studied by high-resolution X-ray diffraction at BESSY II synchrotron radiation source. The velocity of SAW propagation and power flow angles in the Y-, X-and yxl/+36 degrees-cuts of the CNGS crystal were determined from the analysis of the diffraction spectra. The CNGS crystal was found practically isotropic by its acoustic properties.}, language = {en} } @article{XuYanLazarian2016, author = {Xu, Siyao and Yan, Huirong and Lazarian, A.}, title = {DAMPING OF MAGNETOHYDRODYNAMIC TURBULENCE IN PARTIALLY IONIZED PLASMA: IMPLICATIONS FOR COSMIC RAY PROPAGATION}, series = {The astrophysical journal : an international review of spectroscopy and astronomical physics}, volume = {826}, journal = {The astrophysical journal : an international review of spectroscopy and astronomical physics}, publisher = {IOP Publ. Ltd.}, address = {Bristol}, issn = {0004-637X}, doi = {10.3847/0004-637X/826/2/166}, pages = {32}, year = {2016}, abstract = {We study the damping processes of both incompressible and compressible magnetohydrodynamic (MHD) turbulence in a partially ionized medium. We start from the linear analysis of MHD waves, applying both single-fluid and two-fluid treatments. The damping rates derived from the linear analysis are then used in determining the damping scales of MHD turbulence. The physical connection between the damping scale of MHD turbulence and the cutoff boundary of linear MHD waves is investigated. We find two branches of slow modes propagating in ions and neutrals, respectively, below the damping scale of slow MHD turbulence, and offer a thorough discussion of their propagation and dissipation behavior. Our analytical results are shown to be applicable in a variety of partially ionized interstellar medium (ISM) phases and the solar chromosphere. The importance of neutral viscosity in damping the Alfvenic turbulence in the interstellar warm neutral medium and the solar chromosphere is demonstrated. As a significant astrophysical utility, we introduce damping effects to the propagation of cosmic rays in partially ionized ISM. The important role of turbulence damping in both transit-time damping and gyroresonance is identified.}, language = {en} } @article{RipollLoridanCunninghametal.2016, author = {Ripoll, Jean-Fran{\c{c}}ois and Loridan, Vivien and Cunningham, G. S. and Reeves, Geoffrey D. and Shprits, Yuri Y.}, title = {On the time needed to reach an equilibrium structure of the radiation belts}, series = {Journal of geophysical research : Space physics}, volume = {121}, journal = {Journal of geophysical research : Space physics}, publisher = {American Geophysical Union}, address = {Washington}, issn = {2169-9380}, doi = {10.1002/2015JA022207}, pages = {7684 -- 7698}, year = {2016}, abstract = {In this study, we complement the notion of equilibrium states of the radiation belts with a discussion on the dynamics and time needed to reach equilibrium. We solve for the equilibrium states obtained using 1-D radial diffusion with recently developed hiss and chorus lifetimes at constant values of Kp = 1, 3, and 6. We find that the equilibrium states at moderately low Kp, when plotted versus L shell (L) and energy (E), display the same interesting S shape for the inner edge of the outer belt as recently observed by the Van Allen Probes. The S shape is also produced as the radiation belts dynamically evolve toward the equilibrium state when initialized to simulate the buildup after a massive dropout or to simulate loss due to outward diffusion from a saturated state. Physically, this shape, intimately linked with the slot structure, is due to the dependence of electron loss rate (originating from wave-particle interactions) on both energy and L shell. Equilibrium electron flux profiles are governed by the Biot number (tau(Diffusion)/tau(loss)), with large Biot number corresponding to low fluxes and low Biot number to large fluxes. The time it takes for the flux at a specific (L, E) to reach the value associated with the equilibrium state, starting from these different initial states, is governed by the initial state of the belts, the property of the dynamics (diffusion coefficients), and the size of the domain of computation. Its structure shows a rather complex scissor form in the (L, E) plane. The equilibrium value (phase space density or flux) is practically reachable only for selected regions in (L, E) and geomagnetic activity. Convergence to equilibrium requires hundreds of days in the inner belt for E>300 keV and moderate Kp (<= 3). It takes less time to reach equilibrium during disturbed geomagnetic conditions (Kp = 3), when the system evolves faster. Restricting our interest to the slot region, below L = 4, we find that only small regions in (L, E) space can reach the equilibrium value: E similar to [200, 300] keV for L= [3.7, 4] at Kp= 1, E similar to[0.6, 1] MeV for L = [3, 4] at Kp = 3, and E similar to 300 keV for L = [3.5, 4] at Kp = 6 assuming no new incoming electrons.}, language = {en} } @article{BoydSpenceHuangetal.2016, author = {Boyd, A. J. and Spence, Harlan E. and Huang, Chia-Lin and Reeves, Geoffrey D. and Baker, Daniel N. and Turner, D. L. and Claudepierre, Seth G. and Fennell, Joseph F. and Blake, J. Bernard and Shprits, Yuri Y.}, title = {Statistical properties of the radiation belt seed population}, series = {Journal of geophysical research : Space physics}, volume = {121}, journal = {Journal of geophysical research : Space physics}, publisher = {American Geophysical Union}, address = {Washington}, issn = {2169-9380}, doi = {10.1002/2016JA022652}, pages = {7636 -- 7646}, year = {2016}, abstract = {We present a statistical analysis of phase space density data from the first 26 months of the Van Allen Probes mission. In particular, we investigate the relationship between the tens and hundreds of keV seed electrons and >1 MeV core radiation belt electron population. Using a cross-correlation analysis, we find that the seed and core populations are well correlated with a coefficient of approximate to 0.73 with a time lag of 10-15 h. We present evidence of a seed population threshold that is necessary for subsequent acceleration. The depth of penetration of the seed population determines the inner boundary of the acceleration process. However, we show that an enhanced seed population alone is not enough to produce acceleration in the higher energies, implying that the seed population of hundreds of keV electrons is only one of several conditions required for MeV electron radiation belt acceleration.}, language = {en} } @article{XiongStolleLuehr2016, author = {Xiong, Chao and Stolle, Claudia and L{\"u}hr, Hermann}, title = {The Swarm satellite loss of GPS signal and its relation to ionospheric plasma irregularities}, series = {Space Weather: The International Journal of Research and Applications}, volume = {14}, journal = {Space Weather: The International Journal of Research and Applications}, publisher = {American Geophysical Union}, address = {Washington}, issn = {1542-7390}, doi = {10.1002/2016SW001439}, pages = {563 -- 577}, year = {2016}, abstract = {In this study we investigated conditions for loss of GPS signals observed by the Swarm satellites during a 2 year period, from December 2013 to November 2015. Our result shows that the Swarm satellites encountered most of the total loss of GPS signal at the ionization anomaly crests, between +/- 5 degrees and +/- 20 degrees magnetic latitude, forming two bands along the magnetic equator, and these low-latitude events mainly appear around postsunset hours from 19: 00 to 22: 00 local time. By further checking the in situ electron density measurements of Swarm, we found that practically, all the total loss of GPS signal events at low latitudes are related to equatorial plasma irregularities (EPIs) that show absolute density depletions larger than 10 x 10(11) m(-3); then, the Swarm satellites encountered for up to 95\% loss of GPS signal for at least one channel and up to 45\% tracked less than four GPS satellites (making precise orbit determination impossible). For those EPIs with density depletions less than 10 x 10(11) m(-3), the chance of tracked GPS signals less than four reduces to only 1.0\%. Swarm also observed total loss of all GPS signal at high latitudes, mainly around local noon, and these events are related to large spatial density gradients due to polar patches or increased geomagnetic/auroral activities. We further found that the loss of GPS signals were less frequent after appropriate settings of the Swarm GPS receivers had been updated. However, the more recent period of the mission, e.g., after the GPS receiver settings have been updated, also coincides with less severe electron density depletions due to the declining solar cycle, making GPS loss events less likely. We conclude that both lower electron density gradients and appropriate GPS receiver settings reduce the probability for Swarm satellites loss of GPS signals.}, language = {en} } @misc{WuesthoffSohl2016, author = {Wuesthoff, Martin and Sohl, F.}, title = {Obliquity tides have an impact in diurnal tidal stresses on the Moon.}, series = {Macromolecules : a publication of the American Chemical Society}, volume = {51}, journal = {Macromolecules : a publication of the American Chemical Society}, publisher = {Wiley-Blackwell}, address = {Hoboken}, issn = {1086-9379}, pages = {A672 -- A672}, year = {2016}, language = {en} } @article{VlasovRosenblumPikovskij2016, author = {Vlasov, Vladimir and Rosenblum, Michael and Pikovskij, Arkadij}, title = {Dynamics of weakly inhomogeneous oscillator populations: perturbation theory on top of Watanabe-Strogatz integrability}, series = {Journal of physics : A, Mathematical and theoretical}, volume = {49}, journal = {Journal of physics : A, Mathematical and theoretical}, publisher = {IOP Publ. Ltd.}, address = {Bristol}, issn = {1751-8113}, doi = {10.1088/1751-8113/49/31/31LT02}, pages = {8}, year = {2016}, abstract = {As has been shown by Watanabe and Strogatz (WS) (1993 Phys. Rev. Lett. 70 2391), a population of identical phase oscillators, sine-coupled to a common field, is a partially integrable system: for any ensemble size its dynamics reduce to equations for three collective variables. Here we develop a perturbation approach for weakly nonidentical ensembles. We calculate corrections to the WS dynamics for two types of perturbations: those due to a distribution of natural frequencies and of forcing terms, and those due to small white noise. We demonstrate that in both cases, the complex mean field for which the dynamical equations are written is close to the Kuramoto order parameter, up to the leading order in the perturbation. This supports the validity of the dynamical reduction suggested by Ott and Antonsen (2008 Chaos 18 037113) for weakly inhomogeneous populations.}, language = {en} } @article{SchleussnerDongesEngemannetal.2016, author = {Schleussner, Carl-Friedrich and Donges, Jonathan and Engemann, Denis A. and Levermann, Anders}, title = {Clustered marginalization of minorities during social transitions induced by co-evolution of behaviour and network structure}, series = {Scientific reports}, volume = {6}, journal = {Scientific reports}, publisher = {Nature Publ. Group}, address = {London}, issn = {2045-2322}, doi = {10.1038/srep30790}, pages = {3407 -- 3417}, year = {2016}, abstract = {Large-scale transitions in societies are associated with both individual behavioural change and restructuring of the social network. These two factors have often been considered independently, yet recent advances in social network research challenge this view. Here we show that common features of societal marginalization and clustering emerge naturally during transitions in a co-evolutionary adaptive network model. This is achieved by explicitly considering the interplay between individual interaction and a dynamic network structure in behavioural selection. We exemplify this mechanism by simulating how smoking behaviour and the network structure get reconfigured by changing social norms. Our results are consistent with empirical findings: The prevalence of smoking was reduced, remaining smokers were preferentially connected among each other and formed increasingly marginalized clusters. We propose that self-amplifying feedbacks between individual behaviour and dynamic restructuring of the network are main drivers of the transition. This generative mechanism for co-evolution of individual behaviour and social network structure may apply to a wide range of examples beyond smoking.}, language = {en} } @article{AldorettaStLouisRichardsonetal.2016, author = {Aldoretta, E. J. and St-Louis, N. and Richardson, N. D. and Moffat, Anthony F. J. and Eversberg, T. and Hill, G. M. and Shenar, Tomer and Artigau, E. and Gauza, B. and Knapen, J. H. and Kubat, Jiř{\´i} and Kubatova, Brankica and Maltais-Tariant, R. and Munoz, M. and Pablo, H. and Ramiaramanantsoa, T. and Richard-Laferriere, A. and Sablowski, D. P. and Simon-Diaz, S. and St-Jean, L. and Bolduan, F. and Dias, F. M. and Dubreuil, P. and Fuchs, D. and Garrel, T. and Grutzeck, G. and Hunger, T. and Kuesters, D. and Langenbrink, M. and Leadbeater, R. and Li, D. and Lopez, A. and Mauclaire, B. and Moldenhawer, T. and Potter, M. and dos Santos, E. M. and Schanne, L. and Schmidt, J. and Sieske, H. and Strachan, J. and Stinner, E. and Stinner, P. and Stober, B. and Strandbaek, K. and Syder, T. and Verilhac, D. and Waldschlaeger, U. and Weiss, D. and Wendt, A.}, title = {An extensive spectroscopic time series of three Wolf-Rayet stars - I. The lifetime of large-scale structures in the wind of WR 134}, series = {Monthly notices of the Royal Astronomical Society}, volume = {460}, journal = {Monthly notices of the Royal Astronomical Society}, publisher = {Oxford Univ. Press}, address = {Oxford}, issn = {0035-8711}, doi = {10.1093/mnras/stw1188}, pages = {3407 -- 3417}, year = {2016}, abstract = {During the summer of 2013, a 4-month spectroscopic campaign took place to observe the variabilities in three Wolf-Rayet stars. The spectroscopic data have been analysed for WR 134 (WN6b), to better understand its behaviour and long-term periodicity, which we interpret as arising from corotating interaction regions (CIRs) in the wind. By analysing the variability of the He ii lambda 5411 emission line, the previously identified period was refined to P = 2.255 +/- 0.008 (s.d.) d. The coherency time of the variability, which we associate with the lifetime of the CIRs in the wind, was deduced to be 40 +/- 6 d, or similar to 18 cycles, by cross-correlating the variability patterns as a function of time. When comparing the phased observational grey-scale difference images with theoretical grey-scales previously calculated from models including CIRs in an optically thin stellar wind, we find that two CIRs were likely present. A separation in longitude of Delta I center dot a parts per thousand integral 90A degrees was determined between the two CIRs and we suggest that the different maximum velocities that they reach indicate that they emerge from different latitudes. We have also been able to detect observational signatures of the CIRs in other spectral lines (C iv lambda lambda 5802,5812 and He i lambda 5876). Furthermore, a DAC was found to be present simultaneously with the CIR signatures detected in the He i lambda 5876 emission line which is consistent with the proposed geometry of the large-scale structures in the wind. Small-scale structures also show a presence in the wind, simultaneously with the larger scale structures, showing that they do in fact co-exist.}, language = {en} } @article{SantosdeLimaYandeGouveiaDalPinoetal.2016, author = {Santos de Lima, Reinaldo and Yan, Huirong and de Gouveia Dal Pino, E. M. and Lazarian, A.}, title = {Limits on the ion temperature anisotropy in the turbulent intracluster medium}, series = {Monthly notices of the Royal Astronomical Society}, volume = {460}, journal = {Monthly notices of the Royal Astronomical Society}, publisher = {Oxford Univ. Press}, address = {Oxford}, issn = {0035-8711}, doi = {10.1093/mnras/stw1079}, pages = {2492 -- 2504}, year = {2016}, abstract = {Turbulence in the weakly collisional intracluster medium (ICM) of galaxies is able to generate strong thermal velocity anisotropies in the ions (with respect to the local magnetic field direction), if the magnetic moment of the particles is conserved in the absence of Coulomb collisions. In this scenario, the anisotropic pressure magnetohydrodynamic (AMHD) turbulence shows a very different statistical behaviour from the standard MHD one and is unable to amplify seed magnetic fields. This is in contrast to previous cosmological MHD simulations that are successful in explaining the observed magnetic fields in the ICM. On the other hand, temperature anisotropies can also drive plasma instabilities that can relax the anisotropy. This work aims to compare the relaxation rate with the growth rate of the anisotropies driven by the turbulence. We employ quasi-linear theory to estimate the ion scattering rate resulting from the parallel firehose, mirror and ion-cyclotron instabilities, for a set of plasma parameters resulting from AMHD simulations of the turbulent ICM. We show that the ICM turbulence can sustain only anisotropy levels very close to the instability thresholds. We argue that the AMHD model that bounds the anisotropies at the marginal stability levels can describe the Alfv,nic turbulence cascade in the ICM.}, language = {en} } @article{FeldmannLevermann2016, author = {Feldmann, Johannes and Levermann, Anders}, title = {Similitude of ice dynamics against scaling of geometry and physical parameters}, series = {The Cryosphere : TC ; an interactive open access journal of the European Geosciences Union}, volume = {10}, journal = {The Cryosphere : TC ; an interactive open access journal of the European Geosciences Union}, publisher = {Copernicus}, address = {G{\"o}ttingen}, issn = {1994-0416}, doi = {10.5194/tc-10-1753-2016}, pages = {1753 -- 1769}, year = {2016}, abstract = {The concept of similitude is commonly employed in the fields of fluid dynamics and engineering but rarely used in cryospheric research. Here we apply this method to the problem of ice flow to examine the dynamic similitude of isothermal ice sheets in shallow-shelf approximation against the scaling of their geometry and physical parameters. Carrying out a dimensional analysis of the stress balance we obtain dimensionless numbers that characterize the flow. Requiring that these numbers remain the same under scaling we obtain conditions that relate the geometric scaling factors, the parameters for the ice softness, surface mass balance and basal friction as well as the ice-sheet intrinsic response time to each other. We demonstrate that these scaling laws are the same for both the (two-dimensional) flow-line case and the three-dimensional case. The theoretically predicted ice-sheet scaling behavior agrees with results from numerical simulations that we conduct in flow-line and three-dimensional conceptual setups. We further investigate analytically the implications of geometric scaling of ice sheets for their response time. With this study we provide a framework which, under several assumptions, allows for a fundamental comparison of the ice-dynamic behavior across different scales. It proves to be useful in the design of conceptual numerical model setups and could also be helpful for designing laboratory glacier experiments. The concept might also be applied to real-world systems, e.g., to examine the response times of glaciers, ice streams or ice sheets to climatic perturbations.}, language = {en} } @article{deCarvalhoMetzlerCherstvy2016, author = {de Carvalho, Sidney J. and Metzler, Ralf and Cherstvy, Andrey G.}, title = {Critical adsorption of polyelectrolytes onto planar and convex highly charged surfaces: the nonlinear Poisson-Boltzmann approach}, series = {NEW JOURNAL OF PHYSICS}, volume = {18}, journal = {NEW JOURNAL OF PHYSICS}, publisher = {IOP Publ. Ltd.}, address = {Bristol}, issn = {1367-2630}, doi = {10.1088/1367-2630/18/8/083037}, pages = {17}, year = {2016}, abstract = {We study the adsorption-desorption transition of polyelectrolyte chains onto planar, cylindrical and spherical surfaces with arbitrarily high surface charge densities by massive Monte Carlo computer simulations. We examine in detail how the well known scaling relations for the threshold transition demarcating the adsorbed and desorbed domains of a polyelectrolyte near weakly charged surfaces-are altered for highly charged interfaces. In virtue of high surface potentials and large surface charge densities, the Debye-Huckel approximation is often not feasible and the nonlinear Poisson-Boltzmann approach should be implemented. At low salt conditions, for instance, the electrostatic potential from the nonlinear Poisson-Boltzmann equation is smaller than the Debye-Huckel result, such that the required critical surface charge density for polyelectrolyte adsorption sigma(c) increases. The nonlinear relation between the surface charge density and electrostatic potential leads to a sharply increasing critical surface charge density with growing ionic strength, imposing an additional limit to the critical salt concentration above which no polyelectrolyte adsorption occurs at all. We contrast our simulations findings with the known scaling results for weak critical polyelectrolyte adsorption onto oppositely charged surfaces for the three standard geometries. Finally, we discuss some applications of our results for some physical-chemical and biophysical systems.}, language = {en} } @article{LevermannWinkelmann2016, author = {Levermann, Anders and Winkelmann, Ricarda}, title = {A simple equation for the melt elevation feedback of ice sheets}, series = {The Cryosphere : TC ; an interactive open access journal of the European Geosciences Union}, volume = {10}, journal = {The Cryosphere : TC ; an interactive open access journal of the European Geosciences Union}, publisher = {Copernicus}, address = {G{\"o}ttingen}, issn = {1994-0416}, doi = {10.5194/tc-10-1799-2016}, pages = {1799 -- 1807}, year = {2016}, abstract = {In recent decades, the Greenland Ice Sheet has been losing mass and has thereby contributed to global sea-level rise. The rate of ice loss is highly relevant for coastal protection worldwide. The ice loss is likely to increase under future warming. Beyond a critical temperature threshold, a meltdown of the Greenland Ice Sheet is induced by the self-enforcing feedback between its lowering surface elevation and its increasing surface mass loss: the more ice that is lost, the lower the ice surface and the warmer the surface air temperature, which fosters further melting and ice loss. The computation of this rate so far relies on complex numerical models which are the appropriate tools for capturing the complexity of the problem. By contrast we aim here at gaining a conceptual understanding by deriving a purposefully simple equation for the self-enforcing feedback which is then used to estimate the melt time for different levels of warming using three observable characteristics of the ice sheet itself and its surroundings. The analysis is purely conceptual in nature. It is missing important processes like ice dynamics for it to be useful for applications to sea-level rise on centennial timescales, but if the volume loss is dominated by the feedback, the resulting logarithmic equation unifies existing numerical simulations and shows that the melt time depends strongly on the level of warming with a critical slow-down near the threshold: the median time to lose 10\% of the present-day ice volume varies between about 3500 years for a temperature level of 0.5 degrees C above the threshold and 500 years for 5 degrees C. Unless future observations show a significantly higher melting sensitivity than currently observed, a complete meltdown is unlikely within the next 2000 years without significant ice-dynamical contributions.}, language = {en} } @article{KopyshevGalvinGenzeretal.2016, author = {Kopyshev, Alexey and Galvin, Casey J. and Genzer, Jan and Lomadze, Nino and Santer, Svetlana}, title = {Polymer brushes modified by photosensitive azobenzene containing polyamines}, series = {Polymer : the international journal for the science and technology of polymers}, volume = {98}, journal = {Polymer : the international journal for the science and technology of polymers}, publisher = {Elsevier}, address = {Oxford}, issn = {0032-3861}, doi = {10.1016/j.polymer.2016.03.050}, pages = {421 -- 428}, year = {2016}, abstract = {This paper describes a strategy for preparing photosensitive polymeric grafts on flat solid surfaces by loading diblock-copolymer or homopolymer brushes with cationic azobenzene-containing surfactants. In contrast to previous work, we utilize photosensitive surfactants that bear positively-charged polyamine head groups whose charge varies between 1(+) and 3(+). Poly(methylmethacrylate-b-methacrylic acid) (PMMA-b-PMAA) brushes were prepared by employing atom transfer radical polymerization, where the bottom poly(methyl methacrylate) block was grown first followed by the synthesis of t-butyl methacrylate block that after de-protection yielded poly(methacrylic acid). We used PMMA-b-PMAA brushes with constant grafting density and length of the PMMA block, and three different lengths of the PMAA block. The azobenzene-based surfactants attached only to the PMAA block. The degree of binding (i.e., the number of surfactant molecules per binding site on the brush backbone) of the surfactants to the brush depends strongly on the valence of the surfactant head-group; within the brushes the concentration of the surfactant carrying unit charge is larger than that of multivalent surfactants. We detect pronounced response of the brush topography on irradiation with UV interference pattern even at very low degree of binding (as small as 0.08) of multi-valence surfactant. Areas on the sample that receive the highest UV dose exhibit chain scission. By removing the ruptured chains from the substrate via good solvent, one uncovers a surface topographical relief grating, whose spatial arrangement follows the intensity distribution of the UV light on the sample during irradiation. Due to strong coupling of the multi-valence surfactants to the polymer brush, it was possible in some cases to completely remove the polyelectrolyte block from the PMMA layer. The application of multi-valence azobenzene surfactants for triggering brush photosensitive has important advantage over usage of surfactant with unit charge because relative to single-valence surfactants much lower concentrations of the multivalent surfactant are needed to achieve comparable response upon UV irradiation. (C) 2016 Elsevier Ltd. All rights reserved.}, language = {en} } @article{Oskinova2016, author = {Oskinova, Lida}, title = {X-ray diagnostics of massive star winds}, series = {Advances in space research}, volume = {58}, journal = {Advances in space research}, publisher = {Elsevier}, address = {Oxford}, issn = {0273-1177}, doi = {10.1016/j.asr.2016.06.030}, pages = {739 -- 760}, year = {2016}, abstract = {Nearly all types of massive stars with radiatively driven stellar winds are X-ray sources that can be observed by the presently operating powerful X-ray telescopes. In this review I briefly address recent advances in our understanding of stellar winds obtained from X-ray observations. X-rays may strongly influence the dynamics of weak winds of main sequence B-type stars. X-ray pulsations were detected in a beta Cep type variable giving evidence of tight photosphere-wind connections. The winds of OB dwarfs with subtypes later than O9V may be predominantly in a hot phase, and X-ray observations offer the best window for their studies. The X-ray properties of OB super giants are largely determined by the effects of radiative transfer in their clumped stellar winds. The recently suggested method to directly measure mass-loss rates of O stars by fitting the shapes of X-ray emission lines is considered but its validity cannot be confirmed. To obtain robust quantitative information on stellar wind parameters from X-ray spectroscopy, a multiwavelength analysis by means of stellar atmosphere models is required. Independent groups are now performing such analyses with encouraging results. Joint analyses of optical, UV, and X-ray spectra of OB supergiants yield consistent mass-loss rates. Depending on the adopted clumping parameters, the empirically derived mass-loss rates are a factor of a few smaller or comparable to those predicted by standard recipes (Vink et al., 2001). All sufficiently studied O stars display variable X-ray emission that might be related to corotating interaction regions in their winds. In the latest stages of stellar evolution, single red supergiants (RSG) and luminous blue variable (LBV) stars do not emit observable amounts of X-rays. On the other hand, nearly all types of Wolf-Rayet (WR) stars are X-ray sources. X-ray spectroscopy allows a sensitive probe of WR wind abundances and opacities. (C) 2016 COSPAR. Published by Elsevier Ltd. All rights reserved.}, language = {en} } @misc{Oskinova2016, author = {Oskinova, Lida}, title = {Preface: X-ray emission from hot stars and their winds}, series = {Advances in space research}, volume = {58}, journal = {Advances in space research}, publisher = {Elsevier}, address = {Oxford}, issn = {0273-1177}, doi = {10.1016/j.asr.2016.06.031}, pages = {679 -- 679}, year = {2016}, language = {en} } @article{IurchukSchickBranetal.2016, author = {Iurchuk, V. and Schick, D. and Bran, J. and Colson, D. and Forget, A. and Halley, D. and Koc, Azize and Reinhardt, Mathias and Kwamen, C. and Morley, N. A. and Bargheer, Matias and Viret, M. and Gumeniuk, R. and Schmerber, G. and Doudin, B. and Kundys, B.}, title = {Optical Writing of Magnetic Properties by Remanent Photostriction}, series = {Physical review letters}, volume = {117}, journal = {Physical review letters}, publisher = {American Physical Society}, address = {College Park}, issn = {0031-9007}, doi = {10.1103/PhysRevLett.117.107403}, pages = {5}, year = {2016}, abstract = {We present an optically induced remanent photostriction in BiFeO3, resulting from the photovoltaic effect, which is used to modify the ferromagnetism of Ni film in a hybrid BiFeO3/Ni structure. The 75\% change in coercivity in the Ni film is achieved via optical and nonvolatile control. This photoferromagnetic effect can be reversed by static or ac electric depolarization of BiFeO3. Hence, the strain dependent changes in magnetic properties are written optically, and erased electrically. Light-mediated straintronics is therefore a possible approach for low-power multistate control of magnetic elements relevant for memory and spintronic applications.}, language = {en} } @article{IntravaiaBehuninHenkeletal.2016, author = {Intravaia, F. and Behunin, R. O. and Henkel, Carsten and Busch, K. and Dalvit, D. A. R.}, title = {Failure of Local Thermal Equilibrium in Quantum Friction}, series = {Physical review letters}, volume = {117}, journal = {Physical review letters}, publisher = {American Physical Society}, address = {College Park}, issn = {0031-9007}, doi = {10.1103/PhysRevLett.117.100402}, pages = {989 -- 1010}, year = {2016}, abstract = {Recent progress in manipulating atomic and condensed matter systems has instigated a surge of interest in nonequilibrium physics, including many-body dynamics of trapped ultracold atoms and ions, near-field radiative heat transfer, and quantum friction. Under most circumstances the complexity of such nonequilibrium systems requires a number of approximations to make theoretical descriptions tractable. In particular, it is often assumed that spatially separated components of a system thermalize with their immediate surroundings, although the global state of the system is out of equilibrium. This powerful assumption reduces the complexity of nonequilibrium systems to the local application of well-founded equilibrium concepts. While this technique appears to be consistent for the description of some phenomena, we show that it fails for quantum friction by underestimating by approximately 80\% the magnitude of the drag force. Our results show that the correlations among the components of driven, but steady-state, quantum systems invalidate the assumption of local thermal equilibrium, calling for a critical reexamination of this approach for describing the physics of nonequilibrium systems.}, language = {en} } @article{SchleussnerRogeljSchaefferetal.2016, author = {Schleussner, Carl-Friedrich and Rogelj, Joeri and Schaeffer, Michiel and Lissner, Tabea and Licker, Rachel and Fischer, Erich M. and Knutti, Reto and Levermann, Anders and Frieler, Katja and Hare, William}, title = {Science and policy characteristics of the Paris Agreement temperature goal}, series = {Nature climate change}, volume = {6}, journal = {Nature climate change}, publisher = {Nature Publ. Group}, address = {London}, issn = {1758-678X}, doi = {10.1038/NCLIMATE3096}, pages = {827 -- 835}, year = {2016}, language = {en} } @article{WaldripNivenAbeletal.2016, author = {Waldrip, S. H. and Niven, R. K. and Abel, Markus and Schlegel, M.}, title = {Maximum Entropy Analysis of Hydraulic Pipe Flow Networks}, series = {Journal of hydraulic engineering}, volume = {142}, journal = {Journal of hydraulic engineering}, publisher = {American Society of Civil Engineers}, address = {Reston}, issn = {0733-9429}, doi = {10.1061/(ASCE)HY.1943-7900.0001126}, pages = {332 -- 347}, year = {2016}, language = {en} } @article{ArchambaultArcherBarnackaetal.2016, author = {Archambault, S. and Archer, A. and Barnacka, Anna and Behera, B. and Beilicke, M. and Benbow, W. and Berger, K. and Bird, R. and B{\"o}ttcher, Markus and Buckley, J. H. and Bugaev, V. and Cardenzana, J. V. and Cerruti, M. and Chen, Xuhui and Christiansen, J. L. and Ciupik, L. and Collins-Hughes, E. and Connolly, M. P. and Cui, W. and Dickinson, H. J. and Dumm, J. and Eisch, J. D. and Errando, M. and Falcone, A. and Federici, Simone and Feng, Q. and Finley, J. P. and Fleischhack, H. and Fortson, L. and Furniss, A. and Gillanders, G. H. and Godambe, S. and Griffin, S. and Griffiths, S. T. and Grube, J. and Gyuk, G. and Hakansson, Nils and Hanna, D. and Holder, J. and Hughes, G. and Johnson, C. A. and Kaaret, P. and Kar, P. and Kertzman, M. and Khassen, Y. and Kieda, D. and Krawczynski, H. and Kumar, S. and Lang, M. J. and Madhavan, A. S. and Maier, G. and McArthur, S. and McCann, A. and Meagher, K. and Millis, J. and Moriarty, P. and Nelson, T. and Nieto, D. and Ong, R. A. and Otte, A. N. and Park, N. and Perkins, J. S. and Pohl, Martin and Popkow, A. and Prokoph, H. and Pueschel, Elisa and Quinn, J. and Ragan, K. and Rajotte, J. and Reyes, L. C. and Reynolds, P. T. and Richards, G. T. and Roache, E. and Sembroski, G. H. and Shahinyan, K. and Smith, A. W. and Staszak, D. and Sweeney, K. and Telezhinsky, Igor O. and Tucci, J. V. and Tyler, J. and Varlotta, A. and Vassiliev, V. V. and Wakely, S. P. and Welsing, R. and Wilhelm, Alina and Williams, D. A. and Zitzer, B.}, title = {Discovery of very high energy gamma rays from 1ES 1440+122}, series = {Monthly notices of the Royal Astronomical Society}, volume = {461}, journal = {Monthly notices of the Royal Astronomical Society}, publisher = {Oxford Univ. Press}, address = {Oxford}, issn = {0035-8711}, doi = {10.1093/mnras/stw1319}, pages = {202 -- 208}, year = {2016}, language = {en} } @article{ShpritsDrozdovSpasojevicetal.2016, author = {Shprits, Yuri Y. and Drozdov, Alexander and Spasojevic, Maria and Kellerman, Adam C. and Usanova, Maria E. and Engebretson, Mark J. and Agapitov, Oleksiy V. and Zhelavskaya, Irina and Raita, Tero J. and Spence, Harlan E. and Baker, Daniel N. and Zhu, Hui and Aseev, Nikita}, title = {Wave-induced loss of ultra-relativistic electrons in the Van Allen radiation belts}, series = {Nature Communications}, volume = {7}, journal = {Nature Communications}, publisher = {Nature Publ. Group}, address = {London}, issn = {2041-1723}, doi = {10.1038/ncomms12883}, pages = {7}, year = {2016}, language = {en} } @article{KimShpritsBlake2016, author = {Kim, Kyung-Chan and Shprits, Yuri Y. and Blake, J. Bernard}, title = {Fast injection of the relativistic electrons into the inner zone and the formation of the split-zone structure during the Bastille Day storm in July 2000}, series = {Journal of geophysical research : Space physics}, volume = {121}, journal = {Journal of geophysical research : Space physics}, publisher = {American Geophysical Union}, address = {Washington}, issn = {2169-9380}, doi = {10.1002/2015JA022072}, pages = {8329 -- 8342}, year = {2016}, abstract = {During the July 2000 geomagnetic storm, known as the Bastille Day storm, Solar, Anomalous, and Magnetospheric Particle Explorer (SAMPEX)/Heavy Ion Large Telescope (HILT) observed a strong injection of similar to 1MeV electrons into the slot region (L similar to 2.5) during the storm main phase. Then, during the following month, electrons were clearly seen diffusing inward down to L=2 and forming a pronounced split structure encompassing a narrow, newly formed slot region around L=3. SAMPEX observations are first compared with electron and proton observations on HEO-3 and NOAA-15 to validate that the observed unusual dynamics was not caused by proton contamination of the SAMPEX instrument. The time-dependent 3-D Versatile Electron Radiation Belt (VERB) simulation of 1MeV electron flux evolution is compared with the SAMPEX/HILT observations. The results show that the VERB code predicts overall time evolution of the observed split structure. The simulated split structure is produced by pitch angle scattering into the Earth atmosphere of similar to 1MeV electrons by plasmaspheric hiss.}, language = {en} } @article{ReppertPudellKocetal.2016, author = {Reppert, Alexander von and Pudell, Jan-Etienne and Koc, A. and Reinhardt, M. and Leitenberger, Wolfram and Dumesnil, K. and Zamponi, Flavio and Bargheer, Matias}, title = {Persistent nonequilibrium dynamics of the thermal energies in the spin and phonon systems of an antiferromagnet}, series = {Structural dynamics}, volume = {3}, journal = {Structural dynamics}, publisher = {American Institute of Physics}, address = {Melville}, issn = {2329-7778}, doi = {10.1063/1.4961253}, pages = {11}, year = {2016}, abstract = {We present a temperature and fluence dependent Ultrafast X-Ray Diffraction study of a laser-heated antiferromagnetic dysprosium thin film. The loss of antiferromagnetic order is evidenced by a pronounced lattice contraction. We devise a method to determine the energy flow between the phonon and spin system from calibrated Bragg peak positions in thermal equilibrium. Reestablishing the magnetic order is much slower than the cooling of the lattice, especially around the Neel temperature. Despite the pronounced magnetostriction, the transfer of energy from the spin system to the phonons in Dy is slow after the spin-order is lost. (C) 2016 Author(s).}, language = {en} } @article{SchickEckertPontiusetal.2016, author = {Schick, Daniel and Eckert, Sebastian and Pontius, Niko and Mitzner, Rolf and F{\"o}hlisch, Alexander and Holldack, Karsten and Sorgenfrei, Nomi}, title = {Versatile soft X-ray-optical cross-correlator for ultrafast applications}, series = {Structural dynamics}, volume = {3}, journal = {Structural dynamics}, publisher = {American Institute of Physics}, address = {Melville}, issn = {2329-7778}, doi = {10.1063/1.4964296}, pages = {054304-1 -- 054304-8}, year = {2016}, abstract = {We present an X-ray-optical cross-correlator for the soft (> 150 eV) up to the hard X-ray regime based on a molybdenum-silicon superlattice. The cross-correlation is done by probing intensity and position changes of superlattice Bragg peaks caused by photoexcitation of coherent phonons. This approach is applicable for a wide range of X-ray photon energies as well as for a broad range of excitation wavelengths and requires no external fields or changes of temperature. Moreover, the cross-correlator can be employed on a 10 ps or 100 fs time scale featuring up to 50\% total X-ray reflectivity and transient signal changes of more than 20\%. (C) 2016 Author(s).}, language = {en} } @article{BroseTelezhinskyPohl2016, author = {Brose, Robert and Telezhinsky, Igor O. and Pohl, Martin}, title = {Transport of magnetic turbulence in supernova remnants}, series = {Physical review letters}, volume = {593}, journal = {Physical review letters}, publisher = {EDP Sciences}, address = {Les Ulis}, issn = {1432-0746}, doi = {10.1051/0004-6361/201527345}, pages = {8}, year = {2016}, abstract = {Context. Supernova remnants are known as sources of Galactic cosmic rays for their nonthermal emission of radio waves, X-rays, and gamma rays. However, the observed soft broken power-law spectra are hard to reproduce within standard acceleration theory based on the assumption of Bohm diffusion and steady-state calculations. Aims. We point out that a time-dependent treatment of the acceleration process together with a self-consistent treatment of the scattering turbulence amplification is necessary. Methods. We numerically solve the coupled system of transport equations for cosmic rays and isotropic Alfvenic turbulence. The equations are coupled through the growth rate of turbulence determined by the cosmic-ray gradient and the spatial diffusion coefficient of cosmic rays determined by the energy density of the turbulence. The system is solved on a comoving expanding grid extending upstream for dozens of shock radii, allowing for the self-consistent study of cosmic-ray diffusion in the vicinity of their acceleration site. The transport equation for cosmic rays is solved in a test-particle approach. Results. We demonstrate that the system is typically not in a steady state. In fact, even after several thousand years of evolution, no equilibrium situation is reached. The resulting time-dependent particle spectra strongly differ from those derived assuming a steady state and Bohm diffusion. Our results indicate that proper accounting for the evolution of the scattering turbulence and hence the particle diffusion coefficient is crucial for the formation of the observed soft spectra. In any case, the need to continuously develop magnetic turbulence upstream of the shock introduces nonlinearity in addition to that imposed by cosmic-ray feedback.}, language = {en} } @article{RaetzelWilkensMenzel2016, author = {R{\"a}tzel, Dennis and Wilkens, Martin and Menzel, Ralf}, title = {The effect of entanglement in gravitational photon-photon scattering}, series = {epl : a letters journal exploring the frontiers of physics}, volume = {115}, journal = {epl : a letters journal exploring the frontiers of physics}, publisher = {EDP Sciences}, address = {Mulhouse}, issn = {0295-5075}, doi = {10.1209/0295-5075/115/51002}, pages = {S12 -- S13}, year = {2016}, abstract = {The differential cross-section for gravitational photon-photon scattering calculated in perturbative quantum gravity is shown to depend on the degree of polarization entanglement of the two photons. The interaction between photons in the symmetric Bell state is stronger than between not entangled photons. In contrast, the interaction between photons in the anti-symmetric Bell state is weaker than between not entangled photons. The results are interpreted in terms of quantum interference, and it is shown how they fit into the idea of distance-dependent forces. Copyright (C) EPLA, 2016}, language = {en} } @article{AbdallaAbramowskiAharonianetal.2016, author = {Abdalla, Hassan E. and Abramowski, Attila and Aharonian, Felix A. and Benkhali, Fai{\c{c}}al Ait and Akhperjanian, A. G. and Ang{\"u}ner, Ekrem Oǧuzhan and Arrieta, M. and Aubert, Pierre and Backes, Michael and Balzer, Arnim and Barnard, Michelle and Becherini, Yvonne and Tjus, Julia Becker and Berge, David and Bernhard, Sabrina and Bernl{\"o}hr, K. and Birsin, E. and Blackwell, R. and Bottcher, Markus and Boisson, Catherine and Bolmont, J. and Bordas, Pol and Bregeon, Johan and Brun, Francois and Brun, Pierre and Bryan, Mark and Bulik, Tomasz and Capasso, M. and Carr, John and Casanova, Sabrina and Chakraborty, N. and Chalme-Calvet, R. and Chaves, Ryan C. G. and Chen, Andrew and Chevalier, J. and Chretien, M. and Colafrancesco, Sergio and Cologna, Gabriele and Condon, B. and Conrad, Jan and Couturier, C. and Cui, Y. and Davids, I. D. and Degrange, B. and Deil, Christoph and deWilt, P. and Djannati-Atai, Arache and Domainko, Wilfried and Donath, Axel and Dubus, Guillaume and Dutson, Kate and Dyks, J. and Dyrda, M. and Edwards, T. and Egberts, Kathrin and Eger, P. and Ernenwein, J. -P. and Eschbach, S. and Farnier, C. and Fegan, Stuart and Fernandes, M. V. and Fiasson, A. and Fontaine, G. and Foerster, A. and Funk, S. and F{\"u}ßling, Matthias and Gabici, Stefano and Gajdus, M. and Gallant, Y. A. and Garrigoux, T. and Giavitto, Gianluca and Giebels, B. and Glicenstein, J. F. and Gottschall, Daniel and Goyal, A. and Grondin, M. -H. and Grudzinska, M. and Hadasch, Daniela and Hahn, J. and Hawkes, J. and Heinzelmann, G. and Henri, Gilles and Hermann, G. and Hervet, Olivier and Hillert, A. and Hinton, James Anthony and Hofmann, Werner and Hoischen, Clemens and Holler, M. and Horns, D. and Ivascenko, Alex and Jacholkowska, A. and Jamrozy, Marek and Janiak, M. and Jankowsky, D. and Jankowsky, Felix and Jingo, M. and Jogler, Tobias and Jouvin, Lea and Jung-Richardt, Ira and Kastendieck, M. A. and Katarzynski, Krzysztof and Katz, Uli and Kerszberg, D. and Khelifi, B. and Kieffer, M. and King, J. and Klepser, S. and Klochkov, Dmitry and Kluzniak, W. and Kolitzus, D. and Komin, Nu. and Kosack, K. and Krakau, S. and Kraus, Michael and Krayzel, F. and Kruger, P. P. and Laffon, H. and Lamanna, G. and Lau, Jeanie and Lees, J. -P. and Lefaucheur, J. and Lefranc, V. and Lemiere, A. and Lemoine-Goumard, M. and Lenain, J. -P. and Leser, Eva and Lohse, Thomas and Lorentz, M. and Lui, R. and Lypova, Iryna and Marandon, Vincent and Marcowith, Alexandre and Mariaud, C. and Marx, R. and Maurin, G. and Maxted, N. and Mayer, Michael and Meintjes, Petrus Johannes and Menzler, U. and Meyer, Manuel and Mitchell, A. M. W. and Moderski, R. and Mohamed, M. and Mora, K. and Moulin, Emmanuel and Murach, T. and de Naurois, Mathieu and Niederwanger, F. and Niemiec, J. and Oakes, L. and Odaka, Hirokazu and Ohm, Stefan and Oettl, S. and Ostrowski, M. and Oya, I. and Padovani, Marco and Panter, M. and Parsons, R. D. and Arribas, M. Paz and Pekeur, N. W. and Pelletier, G. and Petrucci, P. -O. and Peyaud, B. and Pita, S. and Poon, Helen and Prokhorov, Dmitry and Prokoph, Heike and Puehlhofer, Gerd and Punch, Michael and Quirrenbach, Andreas and Raab, S. and Reimer, Anita and Reimer, Olaf and Renaud, M. and de los Reyes, R. and Rieger, Frank and Romoli, Carlo and Rosier-Lees, S. and Rowell, G. and Rudak, B. and Rulten, C. B. and Sahakian, V. and Salek, David and Sanchez, David A. and Santangelo, Andrea and Sasaki, Manami and Schlickeiser, Reinhard and Schussler, F. and Schulz, Andreas and Schwanke, U. and Schwemmer, S. and Seyffert, A. S. and Shafi, N. and Simoni, R. and Sol, H. and Spanier, Felix and Spengler, G. and Spiess, F. and Stawarz, Lukasz and Steenkamp, R. and Stegmann, Christian and Stinzing, F. and Stycz, K. and Sushch, Iurii and Tavernet, J. -P. and Tavernier, T. and Taylor, A. M. and Terrier, R. and Tluczykont, Martin and Trichard, C. and Tuffs, R. and van der Walt, Johan and van Eldik, Christopher and van Soelen, Brian and Vasileiadis, Georges and Veh, J. and Venter, C. and Viana, A. and Vincent, P. and Vink, Jacco and Voisin, F. and Voelk, Heinrich J. and Vuillaume, Thomas and Wadiasingh, Z. and Wagner, Stefan J. and Wagner, P. and Wagner, R. M. and White, R. and Wierzcholska, Alicja and Willmann, P. and Woernlein, A. and Wouters, Denis and Yang, R. and Zabalza, Victor and Zaborov, D. and Zacharias, M. and Zdziarski, A. A. and Zech, Andreas and Zefi, F. and Ziegler, A. and Zywucka, Natalia}, title = {Search for Dark Matter Annihilations towards the Inner Galactic Halo from 10 Years of Observations with HESS}, series = {Physical review letters}, volume = {117}, journal = {Physical review letters}, publisher = {American Physical Society}, address = {College Park}, organization = {HESS Collaboration}, issn = {0031-9007}, doi = {10.1103/PhysRevLett.117.111301}, pages = {6}, year = {2016}, abstract = {The inner region of the Milky Way halo harbors a large amount of dark matter (DM). Given its proximity, it is one of the most promising targets to look for DM. We report on a search for the annihilations of DM particles using gamma-ray observations towards the inner 300 pc of the Milky Way, with the H.E.S.S. array of ground-based Cherenkov telescopes. The analysis is based on a 2D maximum likelihood method using Galactic Center (GC) data accumulated by H.E.S.S. over the last 10 years (2004-2014), and does not show any significant gamma-ray signal above background. Assuming Einasto and Navarro-Frenk-White DM density profiles at the GC, we derive upper limits on the annihilation cross section . These constraints are the strongest obtained so far in the TeV DM mass range and improve upon previous limits by a factor 5. For the Einasto profile, the constraints reach values of 6 x 10(-26) cm(3) s(-1) in the W+W- channel for a DM particle mass of 1.5 TeV, and 2 x 10(-26) cm(3) s(-1) in the tau(+)tau(-) channel for a 1 TeV mass. For the first time, ground-based gamma-ray observations have reached sufficient sensitivity to probe values expected from the thermal relic density for TeV DM particles.}, language = {en} } @article{GodecMetzler2016, author = {Godec, Aljaz and Metzler, Ralf}, title = {Active transport improves the precision of linear long distance molecular signalling}, series = {Journal of physics : A, Mathematical and theoretical}, volume = {49}, journal = {Journal of physics : A, Mathematical and theoretical}, publisher = {IOP Publ. Ltd.}, address = {Bristol}, issn = {1751-8113}, doi = {10.1088/1751-8113/49/36/364001}, pages = {11}, year = {2016}, abstract = {Molecular signalling in living cells occurs at low copy numbers and is thereby inherently limited by the noise imposed by thermal diffusion. The precision at which biochemical receptors can count signalling molecules is intimately related to the noise correlation time. In addition to passive thermal diffusion, messenger RNA and vesicle-engulfed signalling molecules can transiently bind to molecular motors and are actively transported across biological cells. Active transport is most beneficial when trafficking occurs over large distances, for instance up to the order of 1 metre in neurons. Here we explain how intermittent active transport allows for faster equilibration upon a change in concentration triggered by biochemical stimuli. Moreover, we show how intermittent active excursions induce qualitative changes in the noise in effectively one-dimensional systems such as dendrites. Thereby they allow for significantly improved signalling precision in the sense of a smaller relative deviation in the concentration read-out by the receptor. On the basis of linear response theory we derive the exact mean field precision limit for counting actively transported molecules. We explain how intermittent active excursions disrupt the recurrence in the molecular motion, thereby facilitating improved signalling accuracy. Our results provide a deeper understanding of how recurrence affects molecular signalling precision in biological cells and novel medical-diagnostic devices.}, language = {en} } @article{ZersonNeumannSteyrleuthneretal.2016, author = {Zerson, Mario and Neumann, Martin and Steyrleuthner, Robert and Neher, Dieter and Magerle, Robert}, title = {Surface Structure of Semicrystalline Naphthalene Diimide-Bithiophene Copolymer Films Studied with Atomic Force Microscopy}, series = {Macromolecules : a publication of the American Chemical Society}, volume = {49}, journal = {Macromolecules : a publication of the American Chemical Society}, publisher = {American Chemical Society}, address = {Washington}, issn = {0024-9297}, doi = {10.1021/acs.macromol.6b00988}, pages = {6549 -- 6557}, year = {2016}, language = {en} } @article{CherstvyMetzler2016, author = {Cherstvy, Andrey G. and Metzler, Ralf}, title = {Anomalous diffusion in time-fluctuating non-stationary diffusivity landscapes}, series = {Physical chemistry, chemical physics : a journal of European Chemical Societies}, volume = {18}, journal = {Physical chemistry, chemical physics : a journal of European Chemical Societies}, publisher = {Royal Society of Chemistry}, address = {Cambridge}, issn = {1463-9076}, doi = {10.1039/c6cp03101c}, pages = {23840 -- 23852}, year = {2016}, abstract = {We investigate the ensemble and time averaged mean squared displacements for particle diffusion in a simple model for disordered media by assuming that the local diffusivity is both fluctuating in time and has a deterministic average growth or decay in time. In this study we compare computer simulations of the stochastic Langevin equation for this random diffusion process with analytical results. We explore the regimes of normal Brownian motion as well as anomalous diffusion in the sub- and superdiffusive regimes. We also consider effects of the inertial term on the particle motion. The investigation of the resulting diffusion is performed for unconfined and confined motion.}, language = {en} } @article{SchreckWernet2016, author = {Schreck, Simon and Wernet, Philippe}, title = {Isotope effects in liquid water probed by transmission mode x-ray absorption spectroscopy at the oxygen K-edge}, series = {The journal of chemical physics : bridges a gap between journals of physics and journals of chemistr}, volume = {145}, journal = {The journal of chemical physics : bridges a gap between journals of physics and journals of chemistr}, publisher = {American Institute of Physics}, address = {Melville}, issn = {0021-9606}, doi = {10.1063/1.4962237}, pages = {24 -- 32}, year = {2016}, abstract = {The effects of isotope substitution in liquid water are probed by x-ray absorption spectroscopy at the O K-edge as measured in transmission mode. Confirming earlier x-ray Raman scattering experiments, the D2O spectrum is found to be blue shifted with respect to H2O, and the D2O spectrum to be less broadened. Following the earlier interpretations of UV and x-ray Raman spectra, the shift is related to the difference in ground-state zero-point energies between D2O and H2O, while the difference in broadening is related to the difference in ground-state vibrational zero-point distributions. We demonstrate that the transmission-mode measurements allow for determining the spectral shapes with unprecedented accuracy. Owing in addition to the increased spectral resolution and signal to noise ratio compared to the earlier measurements, the new data enable the stringent determination of blue shift and broadening in the O K-edge x-ray absorption spectrum of liquid water upon isotope substitution. The results are compared to UV absorption data, and it is discussed to which extent they reflect the differences in zero-point energies and vibrational zero-point distributions in the ground-states of the liquids. The influence of the shape of the final-state potential, inclusion of the Franck-Condon structure, and differences between liquid H2O and D2O resulting from different hydrogen-bond environments in the liquids are addressed. The differences between the O K-edge absorption spectra of water from our transmission-mode measurements and from the state-of-the-art x-ray Raman scattering experiments are discussed in addition. The experimentally extracted values of blue shift and broadening are proposed to serve as a test for calculations of ground-state zero-point energies and vibrational zero-point distributions in liquid H2O and D2O. This clearly motivates the need for new calculations of the O K-edge x-ray absorption spectrum of liquid water. Published by AIP Publishing.}, language = {en} } @article{BeyeOebergXinetal.2016, author = {Beye, Martin and {\"O}berg, Henrik and Xin, Hongliang and Dakovski, Georgi L. and F{\"o}hlisch, Alexander and Gladh, Jorgen and Hantschmann, Markus and Hieke, Florian and Kaya, Sarp and K{\"u}hn, Danilo and LaRue, Jerry and Mercurio, Giuseppe and Minitti, Michael P. and Mitra, Ankush and Moeller, Stefan P. and Ng, May Ling and Nilsson, Anders and Nordlund, Dennis and Norskov, Jens and {\"O}str{\"o}m, Henrik and Ogasawara, Hirohito and Persson, Mats and Schlotter, William F. and Sellberg, Jonas A. and Wolf, Martin and Abild-Pedersen, Frank and Pettersson, Lars G. M. and Wurth, Wilfried}, title = {Chemical Bond Activation Observed with an X-ray Laser}, series = {The journal of physical chemistry letters}, volume = {7}, journal = {The journal of physical chemistry letters}, publisher = {American Chemical Society}, address = {Washington}, issn = {1948-7185}, doi = {10.1021/acs.jpclett.6b01543}, pages = {3647 -- 3651}, year = {2016}, abstract = {The concept of bonding and antibonding orbitals is fundamental in chemistry. The population of those orbitals and the energetic difference between the two reflect the strength of the bonding interaction. Weakening the bond is expected to reduce this energetic splitting, but the transient character of bond-activation has so far prohibited direct experimental access. Here we apply time-resolved soft X-ray spectroscopy at a free electron laser to directly observe the decreased bonding antibonding splitting following bond-activation using an ultrashort optical laser pulse.}, language = {en} } @article{MoradiZakrevskyyJavadietal.2016, author = {Moradi, N. and Zakrevskyy, Yuriy and Javadi, A. and Aksenenko, E. V. and Fainerman, V. B. and Lomadze, Nino and Santer, Svetlana and Miller, R.}, title = {Surface tension and dilation rheology of DNA solutions in mixtures with azobenzene-containing cationic surfactant}, series = {Colloids and surfaces : an international journal devoted to the principles and applications of colloid and interface science ; A, Physicochemical and engineering aspects}, volume = {505}, journal = {Colloids and surfaces : an international journal devoted to the principles and applications of colloid and interface science ; A, Physicochemical and engineering aspects}, publisher = {Elsevier}, address = {Amsterdam}, issn = {0927-7757}, doi = {10.1016/j.colsurfa.2016.04.021}, pages = {186 -- 192}, year = {2016}, abstract = {The surface tension and dilational surface visco-elasticity of the individual solutions of the biopolymer DNA and the azobenzene-containing cationic surfactant AzoTAB, as well as their mixtures were measured using the drop profile analysis tensiometry. The negatively charged DNA molecules form complexes with the cationic surfactant AzoTAB. Mixed DNA + AzoTAB solutions exhibit high surface activity and surface layer elasticity. Extremes in the dependence of these characteristics on the AzoTAB concentration exist within the concentration range of 3 x 10(-6)-5 x 10(-5) M. The surface tension of the mixture shows a minimum with a subsequent maximum. In the same concentration range the elasticity shows first a maximum and then a subsequent minimum. A recently developed thermodynamic model was modified to account for the dependence of the adsorption equilibrium constant of the adsorbed complex on the cationic surfactant concentration. This modified theory shows good agreement with the experimental data both for the surface tension and the elasticity values over the entire range of studied AzoTAB concentrations. (C) 2016 Elsevier B.V. All rights reserved.}, language = {en} }