@article{CherstvyMetzler2014, author = {Cherstvy, Andrey G. and Metzler, Ralf}, title = {Nonergodicity, fluctuations, and criticality in heterogeneous diffusion processes}, series = {Physical review : E, Statistical, nonlinear and soft matter physics}, volume = {90}, journal = {Physical review : E, Statistical, nonlinear and soft matter physics}, number = {1}, publisher = {American Physical Society}, address = {College Park}, issn = {1539-3755}, doi = {10.1103/PhysRevE.90.012134}, pages = {11}, year = {2014}, abstract = {We study the stochastic behavior of heterogeneous diffusion processes with the power-law dependence D(x) similar to vertical bar x vertical bar(alpha) of the generalized diffusion coefficient encompassing sub- and superdiffusive anomalous diffusion. Based on statistical measures such as the amplitude scatter of the time-averaged mean-squared displacement of individual realizations, the ergodicity breaking and non-Gaussianity parameters, as well as the probability density function P(x, t), we analyze the weakly nonergodic character of the heterogeneous diffusion process and, particularly, the degree of irreproducibility of individual realizations. As we show, the fluctuations between individual realizations increase with growing modulus vertical bar alpha vertical bar of the scaling exponent. The fluctuations appear to diverge when the critical value alpha = 2 is approached, while for even larger alpha the fluctuations decrease, again. At criticality, the power-law behavior of the mean-squared displacement changes to an exponentially fast growth, and the fluctuations of the time-averaged mean-squared displacement do not converge for increasing number of realizations. From a systematic comparison we observe some striking similarities of the heterogeneous diffusion process with the familiar subdiffusive continuous time random walk process with power-law waiting time distribution and diverging characteristic waiting time.}, language = {en} } @article{LevanovaOsipovPikovskij2014, author = {Levanova, T. A. and Osipov, Grigory V. and Pikovskij, Arkadij}, title = {Coherence properties of cycling chaos}, series = {Communications in nonlinear science \& numerical simulation}, volume = {19}, journal = {Communications in nonlinear science \& numerical simulation}, number = {8}, publisher = {Elsevier}, address = {Amsterdam}, issn = {1007-5704}, doi = {10.1016/j.cnsns.2014.01.011}, pages = {2734 -- 2739}, year = {2014}, abstract = {Cycling chaos is a heteroclinic connection between several chaotic attractors, at which switchings between the chaotic sets occur at growing time intervals. Here we characterize the coherence properties of these switchings, considering nearly periodic regimes that appear close to the cycling chaos due to imperfections or to instability. Using numerical simulations of coupled Lorenz, Roessler, and logistic map models, we show that the coherence is high in the case of imperfection (so that asymptotically the cycling chaos is very regular), while it is low close to instability of the cycling chaos. (C) 2014 Elsevier B. V. All rights reserved.}, language = {en} } @article{AlbrechtGrootoonkNeubertetal.2014, author = {Albrecht, Steve and Grootoonk, Bjorn and Neubert, Sebastian and Roland, Steffen and Wordenweber, Jan and Meier, Matthias and Schlatmann, Rutger and Gordijn, Aad and Neher, Dieter}, title = {Efficient hybrid inorganic/organic tandem solar cells with tailored recombination contacts}, series = {Solar energy materials \& solar cells : an international journal devoted to photovoltaic, photothermal, and photochemical solar energy conversion}, volume = {127}, journal = {Solar energy materials \& solar cells : an international journal devoted to photovoltaic, photothermal, and photochemical solar energy conversion}, publisher = {Elsevier}, address = {Amsterdam}, issn = {0927-0248}, doi = {10.1016/j.solmat.2014.04.020}, pages = {157 -- 162}, year = {2014}, abstract = {In this work, the authors present a 7.5\% efficient hybrid tandem solar cell with the bottom cell made of amorphous silicon and a Si-PCPDTBT:PC70BM bulk heterojunction top cell. Loss-free recombination contacts were realized by combing Al-doped ZnO with either the conducting polymer composite PEDOT:PSS or with a bilayer of ultrathin Al and MoO3. Optimization of these contacts results in tandem cells with high fill factors of 70\% and an open circuit voltage close to the sum of those of the sub-cells. This is the best efficiency reported for this type of hybrid tandem cell so far. Optical and electrical device modeling suggests that the efficiency can be increased to similar to 12\% on combining a donor polymer with suitable absorption onset with PCBM. We also describe proof-of-principle studies employing light trapping in hybrid tandem solar cells, suggesting that this device architecture has the potential to achieve efficiencies well above 12\%. (C) 2014 Elsevier B.V. All rights reserved.}, language = {en} } @article{ArcherBarnackaBeilickeetal.2014, author = {Archer, A. and Barnacka, Anna and Beilicke, M. and Benbow, W. and Berger, K. and Bird, R. and Biteau, Jonathan and Buckley, J. H. and Bugaev, V. and Byrum, K. and Cardenzana, J. V. and Cerruti, M. and Chen, W. and Chen, Xiaoming and Ciupik, L. and Connolly, M. P. and Cui, W. and Dickinson, H. J. and Dumm, J. and Eisch, J. D. and Falcone, A. and Federici, Simone and Feng, Q. and Finley, J. P. and Fleischhack, H. and Fortson, L. and Furniss, A. and Galante, N. 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 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 Perkins, J. S. and Pohl, Manuela 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 Telezhinsky, Igor O. and Tucci, J. V. and Tyler, J. and Varlotta, A. and Vincent, S. and Wakely, S. P. and Weinstein, A. and Welsing, R. and Wilhelm, Alina and Williams, D. A. and Zajczyk, A. and Zitzer, B.}, title = {Very-high energy observations of the galactic center region by veritas IN 2010-2012}, series = {The astrophysical journal : an international review of spectroscopy and astronomical physics}, volume = {790}, journal = {The astrophysical journal : an international review of spectroscopy and astronomical physics}, number = {2}, publisher = {IOP Publ. Ltd.}, address = {Bristol}, issn = {0004-637X}, doi = {10.1088/0004-637X/790/2/149}, pages = {9}, year = {2014}, abstract = {The Galactic center is an interesting region for high-energy (0.1-100 GeV) and very-high-energy (E > 100 GeV) gamma-ray observations. Potential sources of GeV/TeV gamma-ray emission have been suggested, e.g., the accretion of matter onto the supermassive black hole, cosmic rays from a nearby supernova remnant (e.g., Sgr A East), particle acceleration in a plerion, or the annihilation of dark matter particles. The Galactic center has been detected by EGRET and by Fermi/LAT in the MeV/GeV energy band. At TeV energies, the Galactic center was detected with moderate significance by the CANGAROO and Whipple 10 m telescopes and with high significance by H.E.S.S., MAGIC, and VERITAS. We present the results from three years of VERITAS observations conducted at large zenith angles resulting in a detection of the Galactic center on the level of 18 standard deviations at energies above similar to 2.5 TeV. The energy spectrum is derived and is found to be compatible with hadronic, leptonic, and hybrid emission models discussed in the literature. Future, more detailed measurements of the high-energy cutoff and better constraints on the high-energy flux variability will help to refine and/or disentangle the individual models.}, language = {en} } @article{GvaramadzeCheneKniazevetal.2014, author = {Gvaramadze, V. V. and Chene, A.-N. and Kniazev, A. Y. and Schnurr, O. and Shenar, Tomer and Sander, Andreas Alexander Christoph and Hainich, Rainer and Langer, N. and Hamann, Wolf-Rainer and Chu, Y.-H. and Gruendl, R. A.}, title = {Discovery of a new Wolf-Rayet star and a candidate star cluster in the Large Magellanic Cloud with Spitzer}, series = {Monthly notices of the Royal Astronomical Society}, volume = {442}, journal = {Monthly notices of the Royal Astronomical Society}, number = {2}, publisher = {Oxford Univ. Press}, address = {Oxford}, issn = {0035-8711}, doi = {10.1093/mnras/stu909}, pages = {929 -- 945}, year = {2014}, abstract = {We report the first-ever discovery of a Wolf-Rayet (WR) star in the Large Magellanic Cloud via detection of a circular shell with the Spitzer Space Telescope. Follow-up observations with Gemini-South resolved the central star of the shell into two components separated from each other by a parts per thousand 2 arcsec (or a parts per thousand 0.5 pc in projection). One of these components turns out to be a WN3 star with H and He lines both in emission and absorption (we named it BAT99 3a using the numbering system based on extending the Breysacher et al. catalogue). Spectroscopy of the second component showed that it is a B0 V star. Subsequent spectroscopic observations of BAT99 3a with the du Pont 2.5-m telescope and the Southern African Large Telescope revealed that it is a close, eccentric binary system, and that the absorption lines are associated with an O companion star. We analysed the spectrum of the binary system using the non-LTE Potsdam WR (powr) code, confirming that the WR component is a very hot (a parts per thousand 90 kK) WN star. For this star, we derived a luminosity of log L/ L-aS (TM) = 5.45 and a mass-loss rate of 10(- 5.8) M-aS (TM) yr(- 1), and found that the stellar wind composition is dominated by helium with 20 per cent of hydrogen. Spectroscopy of the shell revealed an He iii region centred on BAT99 3a and having the same angular radius (a parts per thousand 15 arcsec) as the shell. We thereby add a new example to a rare class of high-excitation nebulae photoionized by WR stars. Analysis of the nebular spectrum showed that the shell is composed of unprocessed material, implying that the shell was swept-up from the local interstellar medium. We discuss the physical relationship between the newly identified massive stars and their possible membership of a previously unrecognized star cluster.}, language = {en} } @article{CherstvyTeif2014, author = {Cherstvy, Andrey G. and Teif, Vladimir B.}, title = {Electrostatic effect of H1-histone protein binding on nucleosome repeat length}, series = {Physical biology : a journal for the fundamental understanding of biological systems}, volume = {11}, journal = {Physical biology : a journal for the fundamental understanding of biological systems}, number = {4}, publisher = {IOP Publ. Ltd.}, address = {Bristol}, issn = {1478-3967}, doi = {10.1088/1478-3975/11/4/044001}, pages = {6}, year = {2014}, abstract = {Within a simple biophysical model we describe the effect of electrostatic binding of H1 histone proteins on the nucleosome repeat length in chromatin. The length of wrapped DNA optimizes its binding energy to the histone core and the elastic energy penalty of DNA wrapping. The magnitude of the effect predicted from our model is in agreement with the systematic experimental data on the linear variation of nucleosome repeat lengths with H1/nucleosome ratio (Woodcock C L et al 2006 Chromos. Res. 14 17-25). We compare our model to the data for different cell types and organisms, with a widely varying ratio of bound H1 histones per nucleosome. We underline the importance of this non-specific histone-DNA charge-balance mechanism in regulating the positioning of nucleosomes and the degree of compaction of chromatin fibers in eukaryotic cells.}, language = {en} } @article{NazeWangChuetal.2014, author = {Naze, Yael and Wang, Q. Daniel and Chu, You-Hua and Gruendl, Robert and Oskinova, Lidia M.}, title = {A deep chandra observation of the giant HII region N11. I. x-ray sorces in the field}, series = {The astrophysical journal : an international review of spectroscopy and astronomical physics ; Supplement series}, volume = {213}, journal = {The astrophysical journal : an international review of spectroscopy and astronomical physics ; Supplement series}, number = {2}, publisher = {IOP Publ. Ltd.}, address = {Bristol}, issn = {0067-0049}, doi = {10.1088/0067-0049/213/2/23}, pages = {20}, year = {2014}, abstract = {A very sensitive X-ray investigation of the giant HII region N11 in the Large Megallanic Cloud was performed using the Chandra X-ray Observatory. The 300 ks observation reveals X-ray sources with luminosities down to 10(32) erg s(-1), increasing the number of known point sources in the field by more than a factor of five. Among these detections are 13 massive stars (3 compact groups of massive stars, 9 O stars, and one early B star) with log(L-X/L-BOL) similar to -6.5 to -7, which may suggest that they are highly magnetic or colliding-wind systems. On the other hand, the stacked signal for regions corresponding to undetected O stars yields log(L-X/L-BOL) similar to -7.3, i.e., an emission level comparable to similar Galactic stars despite the lower metallicity. Other point sources coincide with 11 foreground stars, 6 late-B/A stars in N11, and many background objects. This observation also uncovers the extent and detailed spatial properties of the soft, diffuse emission regions, but the presence of some hotter plasma in their spectra suggests contamination by the unresolved stellar population.}, language = {en} } @article{ProkhorovFoersterHeetal.2014, author = {Prokhorov, Boris E. and Foerster, M. and He, M. and Namgaladze, Alexander A. and Holschneider, Matthias}, title = {Using MFACE as input in the UAM to specify the MIT dynamics}, series = {Journal of geophysical research : Space physics}, volume = {119}, journal = {Journal of geophysical research : Space physics}, number = {8}, publisher = {American Geophysical Union}, address = {Washington}, issn = {2169-9380}, doi = {10.1002/2014JA019981}, pages = {11}, year = {2014}, abstract = {The magnetosphere-ionosphere-thermosphere (MIT) dynamic system significantly depends on the highly variable solar wind conditions, in particular, on changes of the strength and orientation of the interplanetary magnetic field (IMF). The solar wind and IMF interactions with the magnetosphere drive the MIT system via the magnetospheric field-aligned currents (FACs). The global modeling helps us to understand the physical background of this complex system. With the present study, we test the recently developed high-resolution empirical model of field-aligned currents MFACE (a high-resolution Model of Field-Aligned Currents through Empirical orthogonal functions analysis). These FAC distributions were used as input of the time-dependent, fully self-consistent global Upper Atmosphere Model (UAM) for different seasons and various solar wind and IMF conditions. The modeling results for neutral mass density and thermospheric wind are directly compared with the CHAMP satellite measurements. In addition, we perform comparisons with the global empirical models: the thermospheric wind model (HWM07) and the atmosphere density model (Naval Research Laboratory Mass Spectrometer and Incoherent Scatter Extended 2000). The theoretical model shows a good agreement with the satellite observations and an improved behavior compared with the empirical models at high latitudes. Using the MFACE model as input parameter of the UAM model, we obtain a realistic distribution of the upper atmosphere parameters for the Northern and Southern Hemispheres during stable IMF orientation as well as during dynamic situations. This variant of the UAM can therefore be used for modeling the MIT system and space weather predictions.}, language = {en} } @article{YadavalliSaphiannikovaSanter2014, author = {Yadavalli, Nataraja Sekhar and Saphiannikova, Marina and Santer, Svetlana}, title = {Photosensitive response of azobenzene containing films towards pure intensity or polarization interference patterns}, series = {Applied physics letters}, volume = {105}, journal = {Applied physics letters}, number = {5}, publisher = {American Institute of Physics}, address = {Melville}, issn = {0003-6951}, doi = {10.1063/1.4891615}, pages = {5}, year = {2014}, abstract = {In this paper, we report on differences in the response of photosensitive azobenzene containing films upon irradiation with the intensity or polarization interference patterns. Two materials are studied differing in the molecular weight: an azobenzene-containing polymer and a molecular glass formed from a much smaller molecule consisting of three connected azobenzene units. Topography changes occurring along with the changes in irradiation conditions are recorded using a homemade set-up combining an optical part for generation and shaping of interference patterns and an atomic force microscope for acquiring the kinetics of film deformation. In this way, we could reveal the unique behavior of photosensitive materials during the first few minutes of irradiation: the change in topography is initially driven by an increase in the azobenzene free volume along with the transcis isomerization, followed by the mass transport finally resulting in the surface relief grating. This study demonstrates the great potential of our setup to experimentally highlight puzzling processes governing the formation of surface relief gratings. (C) 2014 AIP Publishing LLC.}, language = {en} } @article{YinRajkovicKubiceketal.2014, author = {Yin, Zhong and Rajkovic, Ivan and Kubicek, Katharina and Quevedo, Wilson and Pietzsch, Annette and Wernet, Philippe and F{\"o}hlisch, Alexander and Techert, Simone}, title = {Probing the Hofmeister effect with ultrafast core-hole spectroscopy}, series = {The journal of physical chemistry : B, Condensed matter, materials, surfaces, interfaces \& biophysical chemistry}, volume = {118}, journal = {The journal of physical chemistry : B, Condensed matter, materials, surfaces, interfaces \& biophysical chemistry}, number = {31}, publisher = {American Chemical Society}, address = {Washington}, issn = {1520-6106}, doi = {10.1021/jp504577a}, pages = {9398 -- 9403}, year = {2014}, abstract = {In the current work, X-ray emission spectra of aqueous solutions of different inorganic salts within the Hofmeister series are presented. The results reflect the direct interaction of the ions with the water molecules and therefore, reveal general properties of the salt-water interactions. Within the experimental precision a significant effect of the ions on the water structure has been observed but no ordering according to the structure maker/structure breaker concept could be mirrored in the results indicating that the Hofmeister effect if existent may be caused by more complex interactions.}, language = {en} } @article{RumyantsevSanterKramarenko2014, author = {Rumyantsev, Artem M. and Santer, Svetlana and Kramarenko, Elena Yu.}, title = {Theory of collapse and overcharging of a polyelectrolyte microgel induced by an oppositely charged surfactant}, series = {Macromolecules : a publication of the American Chemical Society}, volume = {47}, journal = {Macromolecules : a publication of the American Chemical Society}, number = {15}, publisher = {American Chemical Society}, address = {Washington}, issn = {0024-9297}, doi = {10.1021/ma500637d}, pages = {5388 -- 5399}, year = {2014}, abstract = {We report on the theoretical study of interaction of ionic surfactants with oppositely charged microgel particles in dilute solutions. Two approaches are proposed. Within the first approach, the micellization of the surfactants inside the microgel is taken into account while the second model focuses on the hydrophobic interactions of the surfactant tails with the hydrophobic parts of microgel subchains. It has been shown that microgels effectively absorb surfactant ions. At low surfactant concentration this absorption is realized due to an ion exchange between microgel counterions and surfactant ions. The ion exchange is significantly affected by the amount of the microgel counterions initially trapped within the microgel particles which depends on the size of the microgel, its ionization degree, cross-linking density as well as polymer concentration in the solution. Increase of the surfactant concentration causes contraction of the microgels, which can be realized as either a continuous shrinking or a jump-like collapse transition depending on the system parameters. In the collapsed state additional absorption of surfactants by microgels takes place due to an energy gain from micellization or hydrophobic interactions. This leads to microgel precipitation and successive microgel overcharging at an excess of the surfactant in the solution. The theoretical results are compared with the existing experimental data, in particular, on photosensitive surfactant/microgel complexes.}, language = {en} } @article{SaleemThungaKolloscheetal.2014, author = {Saleem, H. and Thunga, M. and Kollosche, Matthias and Kessler, M. R. and Laflamme, S.}, title = {Interfacial treatment effects on behavior of soft nano-composites for highly stretchable dielectrics}, series = {Polymer : the international journal for the science and technology of polymers}, volume = {55}, journal = {Polymer : the international journal for the science and technology of polymers}, number = {17}, publisher = {Elsevier}, address = {Oxford}, issn = {0032-3861}, doi = {10.1016/j.polymer.2014.06.054}, pages = {4531 -- 4537}, year = {2014}, abstract = {We investigate the influence of interfacial treatment on the matrix filler interaction using a melt mixing process to fabricate robust and highly stretchable dielectrics. Silicone oil and silane coupling agent are studied as possible solutions to enhance the compatibility between the inorganic fillers and polymer matrix. Morphology, thermomechanical and dielectric behavior of the prepared specimens are studied. Results show that specimens filled with silicone oil coated particles have promising dielectric and thermal properties. The mechanical properties reveal a stiffness enhancement by 67\% with a high strain at break of 900\%. The relative permittivity of the specimens prepared with silicone oil increased by 45\% as observed from the dielectric analysis. (C) 2014 Elsevier Ltd. All rights reserved.}, language = {en} } @article{GoychukKharchenkoMetzler2014, author = {Goychuk, Igor and Kharchenko, Vasyl O. and Metzler, Ralf}, title = {Molecular motors pulling cargos in the viscoelastic cytosol: how power strokes beat subdiffusion}, series = {Physical chemistry, chemical physics : a journal of European Chemical Societies}, volume = {16}, journal = {Physical chemistry, chemical physics : a journal of European Chemical Societies}, number = {31}, publisher = {Royal Society of Chemistry}, address = {Cambridge}, issn = {1463-9076}, doi = {10.1039/c4cp01234h}, pages = {16524 -- 16535}, year = {2014}, abstract = {The discovery of anomalous diffusion of larger biopolymers and submicron tracers such as endogenous granules, organelles, or virus capsids in living cells, attributed to the viscoelastic nature of the cytoplasm, provokes the question whether this complex environment equally impacts the active intracellular transport of submicron cargos by molecular motors such as kinesins: does the passive anomalous diffusion of free cargo always imply its anomalously slow active transport by motors, the mean transport distance along microtubule growing sublinearly rather than linearly in time? Here we analyze this question within the widely used two-state Brownian ratchet model of kinesin motors based on the continuous-state diffusion along microtubules driven by a flashing binding potential, where the cargo particle is elastically attached to the motor. Depending on the cargo size, the loading force, the amplitude of the binding potential, the turnover frequency of the molecular motor enzyme, and the linker stiffness we demonstrate that the motor transport may turn out either normal or anomalous, as indeed measured experimentally. We show how a highly efficient normal active transport mediated by motors may emerge despite the passive anomalous diffusion of the cargo, and study the intricate effects of the elastic linker. Under different, well specified conditions the microtubule-based motor transport becomes anomalously slow and thus significantly less efficient.}, language = {en} } @article{RolandSchubertCollinsetal.2014, author = {Roland, Steffen and Schubert, Marcel and Collins, Brian A. and Kurpiers, Jona and Chen, Zhihua and Facchetti, Antonio and Ade, Harald W. and Neher, Dieter}, title = {Fullerene-free polymer solar cells with highly reduced bimolecular recombination and field-independent charge carrier generation}, series = {The journal of physical chemistry letters}, volume = {5}, journal = {The journal of physical chemistry letters}, number = {16}, publisher = {American Chemical Society}, address = {Washington}, issn = {1948-7185}, doi = {10.1021/jz501506z}, pages = {2815 -- 2822}, year = {2014}, abstract = {Photogeneration, recombination, and transport of free charge carriers in all-polymer bulk heterojunction solar cells incorporating poly(3-hexylthiophene) (P3HT) as donor and poly([N,N'-bis(2-octyldodecyl)-naphthelene-1,4,5,8-bis(dicarboximide)-2,6-diyl]-alt-5,5'-(2,2'-bithiophene)) (P(NDI2OD-T2)) as acceptor polymer have been investigated by the use of time delayed collection field (TDCF) and time-of-flight (TOF) measurements. Depending on the preparation procedure used to dry the active layers, these solar cells comprise high fill factors (FFs) of up to 67\%. A strongly reduced bimolecular recombination (BMR), as well as a field-independent free charge carrier generation are observed, features that are common to high performance fullerene-based solar cells. Resonant soft X-ray measurements (R-SoXS) and photoluminescence quenching experiments (PQE) reveal that the BMR is related to domain purity. Our results elucidate the similarities of this polymeric acceptor with the superior recombination properties of fullerene acceptors.}, language = {en} } @article{GhoshCherstvyMetzler2014, author = {Ghosh, Surya K. and Cherstvy, Andrey G. and Metzler, Ralf}, title = {Deformation propagation in responsive polymer network films}, series = {The journal of chemical physics : bridges a gap between journals of physics and journals of chemistr}, volume = {141}, journal = {The journal of chemical physics : bridges a gap between journals of physics and journals of chemistr}, number = {7}, publisher = {American Institute of Physics}, address = {Melville}, issn = {0021-9606}, doi = {10.1063/1.4893056}, pages = {9}, year = {2014}, abstract = {We study the elastic deformations in a cross-linked polymer network film triggered by the binding of submicron particles with a sticky surface, mimicking the interactions of viral pathogens with thin films of stimulus-responsive polymeric materials such as hydrogels. From extensive Langevin Dynamics simulations we quantify how far the network deformations propagate depending on the elasticity parameters of the network and the adhesion strength of the particles. We examine the dynamics of the collective area shrinkage of the network and obtain some simple relations for the associated characteristic decay lengths. A detailed analysis elucidates how the elastic energy of the network is distributed between stretching and compression modes in response to the particle binding. We also examine the force-distance curves of the repulsion or attraction interactions for a pair of sticky particles in the polymer network film as a function of the particle-particle separation. The results of this computational study provide new insight into collective phenomena in soft polymer network films and may, in particular, be applied to applications for visual detection of pathogens such as viruses via a macroscopic response of thin films of cross-linked hydrogels. (C) 2014 AIP Publishing LLC.}, language = {en} } @article{PapkeYadavalliHenkeletal.2014, author = {Papke, Thomas and Yadavalli, Nataraja Sekhar and Henkel, Carsten and Santer, Svetlana}, title = {Mapping a plasmonic hologram with photosensitive polymer films: standing versus propagating waves}, series = {ACS applied materials \& interfaces}, volume = {6}, journal = {ACS applied materials \& interfaces}, number = {16}, publisher = {American Chemical Society}, address = {Washington}, issn = {1944-8244}, doi = {10.1021/am503501y}, pages = {14174 -- 14180}, year = {2014}, abstract = {We use a photosensitive layer containing azobenzene moieties to map near-field intensity patterns in the vicinity of nanogrids fabricated within a thin silver layer. It is known that azobenzene containing films deform permanently during irradiation, following the pattern of the field intensity. The photosensitive material reacts only to stationary waves whose intensity patterns do not change in time. In this study, we have found a periodic deformation above the silver film outside the nanostructure, even if the latter consists of just one groove. This is in contradiction to the widely accepted viewpoint that propagating surface plasmon modes dominate outside nanogrids. We explain our observation based on an electromagnetic hologram formed by the constructive interference between a propagating surface plasmon wave and the incident light. This hologram contains a stationary intensity and polarization grating that even appears in the absence of the polymer layer.}, language = {en} } @article{KralemannPikovskijRosenblum2014, author = {Kralemann, Bjoern and Pikovskij, Arkadij and Rosenblum, Michael}, title = {Reconstructing effective phase connectivity of oscillator networks from observations}, series = {New journal of physics : the open-access journal for physics}, volume = {16}, journal = {New journal of physics : the open-access journal for physics}, publisher = {IOP Publ. Ltd.}, address = {Bristol}, issn = {1367-2630}, doi = {10.1088/1367-2630/16/8/085013}, pages = {21}, year = {2014}, abstract = {We present a novel approach for recovery of the directional connectivity of a small oscillator network by means of the phase dynamics reconstruction from multivariate time series data. The main idea is to use a triplet analysis instead of the traditional pairwise one. Our technique reveals an effective phase connectivity which is generally not equivalent to a structural one. We demonstrate that by comparing the coupling functions from all possible triplets of oscillators, we are able to achieve in the reconstruction a good separation between existing and non-existing connections, and thus reliably reproduce the network structure.}, language = {en} } @article{KaiserNoackCordieretal.2014, author = {Kaiser, Eurika and Noack, Bernd R. and Cordier, Laurent and Spohn, Andreas and Segond, Marc and Abel, Markus and Daviller, Guillaume and Osth, Jan and Krajnovic, Sinisa and Niven, Robert K.}, title = {Cluster-based reduced-order modelling of a mixing layer}, series = {Journal of fluid mechanics}, volume = {754}, journal = {Journal of fluid mechanics}, publisher = {Cambridge Univ. Press}, address = {New York}, issn = {0022-1120}, doi = {10.1017/jfm.2014.355}, pages = {365 -- 414}, year = {2014}, language = {en} } @article{KurfuerstFeldmeierKrticka2014, author = {Kurfuerst, P. and Feldmeier, Achim and Krticka, Jiri}, title = {Time-dependent modeling of extended thin decretion disks of critically rotating stars}, series = {Astronomy and astrophysics : an international weekly journal}, volume = {569}, journal = {Astronomy and astrophysics : an international weekly journal}, publisher = {EDP Sciences}, address = {Les Ulis}, issn = {0004-6361}, doi = {10.1051/0004-6361/201424272}, pages = {7}, year = {2014}, abstract = {Context. During their evolution massive stars can reach the phase of critical rotation when a further increase in rotational speed is no longer possible. Direct centrifugal ejection from a critically or near-critically rotating surface forms a gaseous equatorial decretion disk. Anomalous viscosity provides the efficient mechanism for transporting the angular momentum outwards. The outer part of the disk can extend up to a very large distance from the parent star. Aims. We study the evolution of density, radial and azimuthal velocity, and angular momentum loss rate of equatorial decretion disks out to very distant regions. We investigate how the physical characteristics of the disk depend on the distribution of temperature and viscosity. Methods. We calculated stationary models using the Newton-Raphson method. For time-dependent hydrodynamic modeling we developed the numerical code based on an explicit finite difference scheme on an Eulerian grid including full Navier-Stokes shear viscosity. Results. The sonic point distance and the maximum angular momentum loss rate strongly depend on the temperature profile and are almost independent of viscosity. The rotational velocity at large radii rapidly drops accordingly to temperature and viscosity distribution. The total amount of disk mass and the disk angular momentum increase with decreasing temperature and viscosity. Conclusions. The time-dependent one-dimensional models basically confirm the results obtained in the stationary models as well as the assumptions of the analytical approximations. Including full Navier-Stokes viscosity we systematically avoid the rotational velocity sign change at large radii. The unphysical drop of the rotational velocity and angular momentum loss at large radii (present in some models) can be avoided in the models with decreasing temperature and viscosity.}, language = {en} } @article{Baushev2014, author = {Baushev, Anton N.}, title = {Relaxation of dark matter halos: how to match observational data?}, series = {Astronomy and astrophysics : an international weekly journal}, volume = {569}, journal = {Astronomy and astrophysics : an international weekly journal}, publisher = {EDP Sciences}, address = {Les Ulis}, issn = {0004-6361}, doi = {10.1051/0004-6361/201322730}, pages = {8}, year = {2014}, abstract = {We show that moderate energy relaxation in the formation of dark matter halos invariably leads to profiles that match those observed in the central regions of galaxies. The density profile of the central region is universal and insensitive to either the seed perturbation shape or the details of the relaxation process. The profile has a central core; the multiplication of the central density by the core radius is almost independent of the halo mass, in accordance with observations. In the core area the density distribution behaves as an Einasto profile with low index (n similar to 0.5); it has an extensive region with rho proportional to r(-2) at larger distances. This is exactly the shape that observations suggest for the central region of galaxies. On the other hand, this shape does not fit the galaxy cluster profiles. A possible explanation of this fact is that the relaxation is violent in the case of galaxy clusters; however, it is not violent enough when galaxies or smaller dark matter structures are considered. We discuss the reasons for this.}, language = {en} }