TY - JOUR A1 - Gong, Chen Chris A1 - Klumpp, Stefan T1 - Modeling sRNA-Regulated Plasmid Maintenance JF - PLoS one N2 - We study a theoretical model for the toxin-antitoxin (hok/sok) mechanism for plasmid maintenance in bacteria. Toxin-antitoxin systems enforce the maintenance of a plasmid through post-segregational killing of cells that have lost the plasmid. Key to their function is the tight regulation of expression of a protein toxin by an sRNA antitoxin. Here, we focus on the nonlinear nature of the regulatory circuit dynamics of the toxin-antitoxin mechanism. The mechanism relies on a transient increase in protein concentration rather than on the steady state of the genetic circuit. Through a systematic analysis of the parameter dependence of this transient increase, we confirm some known design features of this system and identify new ones: for an efficient toxin-antitoxin mechanism, the synthesis rate of the toxin’s mRNA template should be lower that of the sRNA antitoxin, the mRNA template should be more stable than the sRNA antitoxin, and the mRNA-sRNA complex should be more stable than the sRNA antitoxin. Moreover, a short half-life of the protein toxin is also beneficial to the function of the toxin-antitoxin system. In addition, we study a therapeutic scenario in which a competitor mRNA is introduced to sequester the sRNA antitoxin, causing the toxic protein to be expressed. Y1 - 2017 U6 - https://doi.org/10.1371/journal.pone.0169703 SN - 1932-6203 VL - 12 PB - PLoS CY - San Fransisco ER - TY - JOUR A1 - Couto, Rafael C. A1 - Cruz, Vinicius V. A1 - Ertan, Emelie A1 - Eckert, Sebastian A1 - Fondell, Mattis A1 - Dantz, Marcus A1 - Kennedy, Brian A1 - Schmitt, Thorsten A1 - Pietzsch, Annette A1 - Guimaraes, Freddy F. A1 - Agren, Hans A1 - Odelius, Michael A1 - Kimberg, Victor A1 - Föhlisch, Alexander T1 - Selective gating to vibrational modes through resonant X-ray scattering JF - Nature Communications N2 - The dynamics of fragmentation and vibration of molecular systems with a large number of coupled degrees of freedom are key aspects for understanding chemical reactivity and properties. Here we present a resonant inelastic X-ray scattering (RIXS) study to show how it is possible to break down such a complex multidimensional problem into elementary components. Local multimode nuclear wave packets created by X-ray excitation to different core-excited potential energy surfaces (PESs) will act as spatial gates to selectively probe the particular ground-state vibrational modes and, hence, the PES along these modes. We demonstrate this principle by combining ultra-high resolution RIXS measurements for gas-phase water with state-of-the-art simulations. Y1 - 2017 U6 - https://doi.org/10.1038/ncomms14165 SN - 2041-1723 VL - 8 PB - Nature Publ. Group CY - London ER - TY - JOUR A1 - Mardoukhi, Ahmad A1 - Mardoukhi, Yousof A1 - Hokka, Mikko A1 - Kuokkala, Veli-Tapani T1 - Effects of strain rate and surface cracks on the mechanical behaviour of Balmoral Red granite JF - Philosophical Transactions of the Royal Society of London, Series A : Mathematical, Physical and Engineering Sciences N2 - This work presents a systematic study on the effects of strain rate and surface cracks on the mechanical properties and behaviour of Balmoral Red granite. The tensile behaviour of the rock was studied at low and high strain rates using Brazilian disc samples. Heat shocks were used to produce samples with different amounts of surface cracks. The surface crack patterns were analysed using optical microscopy, and the complexity of the patterns was quantified by calculating the fractal dimensions of the patterns. The strength of the rock clearly drops as a function of increasing fractal dimensions in the studied strain rate range. However, the dynamic strength of the rock drops significantly faster than the quasi-static strength, and, because of this, also the strain rate sensitivity of the rock decreases with increasing fractal dimensions. This can be explained by the fracture behaviour and fragmentation during the dynamic loading, which is more strongly affected by the heat shock than the fragmentation at low strain rates. KW - split Hopkinson pressure bar KW - rock KW - granite KW - dynamic loading KW - fractal dimension KW - surface cracks Y1 - 2017 U6 - https://doi.org/10.1098/rsta.2016.0179 SN - 1364-503X SN - 1471-2962 VL - 375 IS - 2085 PB - Royal Society CY - London ER - TY - JOUR A1 - Goychuk, Igor T1 - Quantum ergodicity breaking in semi-classical electron transfer dynamics JF - Physical chemistry, chemical physics : a journal of European Chemical Societies N2 - Can the statistical properties of single-electron transfer events be correctly predicted within a common equilibrium ensemble description? This fundamental in nanoworld question of ergodic behavior is scrutinized within a very basic semi-classical curve-crossing problem. It is shown that in the limit of non-adiabatic electron transfer (weak tunneling) well-described by the Marcus-Levich-Dogonadze (MLD) rate the answer is yes. However, in the limit of the so-called solvent-controlled adiabatic electron transfer, a profound breaking of ergodicity occurs. Namely, a common description based on the ensemble reduced density matrix with an initial equilibrium distribution of the reaction coordinate is not able to reproduce the statistics of single-trajectory events in this seemingly classical regime. For sufficiently large activation barriers, the ensemble survival probability in a state remains nearly exponential with the inverse rate given by the sum of the adiabatic curve crossing (Kramers) time and the inverse MLD rate. In contrast, near to the adiabatic regime, the single-electron survival probability is clearly non-exponential, even though it possesses an exponential tail which agrees well with the ensemble description. Initially, it is well described by a Mittag-Leffler distribution with a fractional rate. Paradoxically, the mean transfer time in this classical on the ensemble level regime is well described by the inverse of the nonadiabatic quantum tunneling rate on a single particle level. An analytical theory is developed which perfectly agrees with stochastic simulations and explains our findings. Y1 - 2016 U6 - https://doi.org/10.1039/c6cp07206b SN - 1463-9076 SN - 1463-9084 VL - 19 SP - 3056 EP - 3066 PB - Royal Society of Chemistry CY - Cambridge ER - TY - JOUR A1 - Kunnus, Kristjan A1 - Josefsson, I. A1 - Schreck, Simon Frederik A1 - Quevedo, W. A1 - Miedema, P. S. A1 - Techert, S. A1 - de Groot, F. M. F. A1 - Föhlisch, Alexander A1 - Odelius, M. A1 - Wernet, Ph. T1 - Quantifying covalent interactions with resonant inelastic soft X-ray scattering BT - case study of Ni2+ aqua complex JF - Chemical physics letters N2 - We analyze the effects of covalent interactions in Ni 2p3d resonant inelastic X-ray scattering (RIXS) spectra from aqueous Ni2+ ions and find that the relative RIXS intensities of ligand-to-metal charge-transfer final states with respect to the ligand-field final states reflect the covalent mixing between Ni 3d and water orbitals. Specifically, the experimental intensity ratio at the Ni L-3-edge allows to determine that the Ni 3d orbitals have on average 5.5% of water character. We propose that 2p3d RIXS at the Ni L-3-edge can be utilized to quantify covalency in Ni complexes without the use of external references or simulations. KW - Transition-metal ion KW - Aqueous solution KW - Covalent interaction KW - Resonant inelastic X-ray scattering KW - Ligand-field state KW - Charge-transfer state Y1 - 2016 U6 - https://doi.org/10.1016/j.cplett.2016.12.046 SN - 0009-2614 SN - 1873-4448 VL - 669 SP - 196 EP - 201 PB - Elsevier CY - Amsterdam ER - TY - JOUR A1 - Vandewal, Koen A1 - Benduhn, Johannes A1 - Schellhammer, Karl Sebastian A1 - Vangerven, Tim A1 - Rückert, Janna E. A1 - Piersimoni, Fortunato A1 - Scholz, Reinhard A1 - Zeika, Olaf A1 - Fan, Yeli A1 - Barlow, Stephen A1 - Neher, Dieter A1 - Marder, Seth R. A1 - Manca, Jean A1 - Spoltore, Donato A1 - Cuniberti, Gianaurelio A1 - Ortmann, Frank T1 - Absorption Tails of Donor BT - C-60 Blends Provide Insight into Thermally Activated Charge-Transfer Processes and Polaron Relaxation JF - Journal of the American Chemical Society N2 - In disordered organic semiconductors, the transfer of a rather localized charge carrier from one site to another triggers a deformation of the molecular structure quantified by the intramolecular relaxation energy. A similar structural relaxation occurs upon population of intermolecular charge-transfer (CT) states formed at organic electron donor (D)-acceptor (A) interfaces. Weak CT absorption bands for D A complexes occur at photon energies below the optical gaps of both the donors and the C-60 acceptor as a result of optical transitions from the neutral ground state to the ionic CT state. In this work, we show that temperature-activated intramolecular vibrations of the ground state play a major role in determining the line shape of such CT absorption bands. This allows us to extract values for the relaxation energy related to the geometry change from neutral to ionic CT complexes. Experimental values for the relaxation energies of 20 D:C-60 CT complexes correlate with values calculated within density functional theory. These results provide an experimental method for determining the polaron relaxation energy in solid-state organic D-A blends and show the importance of a reduced relaxation energy, which we introduce to characterize thermally activated CT processes. Y1 - 2017 U6 - https://doi.org/10.1021/jacs.6b12857 SN - 0002-7863 VL - 139 IS - 4 SP - 1699 EP - 1704 PB - American Chemical Society CY - Washington ER - TY - JOUR A1 - Henkel, Carsten T1 - Nanoscale Thermal Transfer BT - an Invitation to Fluctuation Electrodynamics JF - Zeitschrift für Naturforschung A N2 - An electromagnetic theory of thermal radiation is outlined, based on the fluctuation electrodynamics of Rytov and co-workers. We discuss the basic concepts and the status of different approximations. The physical content is illustrated with a few examples on near-field heat transfer. KW - Heat Transfer KW - Near-Field Optics KW - Thermal Radiation Y1 - 2017 U6 - https://doi.org/10.1515/zna-2016-0372 SN - 0932-0784 SN - 1865-7109 VL - 72 IS - 2 SP - 99 EP - 108 PB - De Gruyter CY - Berlin ER - TY - JOUR A1 - Sun, Ning-Chen A1 - de Grijs, Richard A1 - Subramanian, Smitha A1 - Cioni, Maria-Rosa L. A1 - Rubele, Stefano A1 - Bekki, Kenji A1 - Ivanov, Valentin D. A1 - Piatti, Andrés E. A1 - Ripepi, Vincenzo T1 - The VMC Survey. XXII. Hierarchical star formation in the 30 Doradus-N158-N159-N160 star-forming complex JF - The astrophysical journal : an international review of spectroscopy and astronomical physics N2 - We study the hierarchical stellar structures in a similar to 1.5 deg(2) area covering the 30. Doradus-N158-N159-N160 starforming complex with the VISTA Survey of. Magellanic Clouds. Based on the young upper main-sequence stars, we find that the surface densities cover a wide range of values, from log(Sigma.pc(2))less than or similar to -2.0 to log(Sigma. pc(2)) greater than or similar to 0.0. Their distributions are highly non-uniform, showing groups that frequently have subgroups inside. The sizes of the stellar groups do not exhibit characteristic values, and range continuously from several parsecs to more than 100. pc; the cumulative size distribution can be well described by a single power law, with the power-law index indicating a projected fractal dimension D-2 = 1.6 +/- 0.3. We suggest that the phenomena revealed here support a scenario of hierarchical star formation. Comparisons with other star-forming regions and galaxies are also discussed. KW - galaxies: clusters: general KW - infrared: stars KW - Magellanic Clouds KW - stars: formation Y1 - 2017 U6 - https://doi.org/10.3847/1538-4357/835/2/171 SN - 0004-637X SN - 1538-4357 VL - 835 IS - 2 PB - Institute of Physics Publ. CY - Bristol ER - TY - JOUR A1 - Koopman, Wouter-Willem Adriaan A1 - Natali, Marco A1 - Donati, Giovanni P. A1 - Muccini, Michele A1 - Toffanin, Stefano T1 - Charge-exciton interaction rate in organic field-effect transistors by means of transient photoluminescence electromodulated spectroscopy JF - ACS photonics N2 - Organic light-emitting transistors (OLETs) offer a huge potential for the design of highly integrated multifunctional optoelectronic systems and of intense nano scale light sources, such as the long-searched-for electrically pumped organic laser. In order to fulfill these promises, the efficiency and brightness of the current state-of-the-art devices have to be increased significantly. The dominating quenching process limiting the external quantum efficiency in OLETs is charge-exciton interaction. A comprehensive understanding of this quenching process is therefore of paramount importance. The present article reports a systematic investigation of charge-exciton interaction in organic transistors employing time resolved photoluminescence electro-modulation (PLEM) spectroscopy on the picosecond time scale. The results show that the injected charges reduce the exciton radiative recombination in two ways: (i) charges may prevent the generation of excitons and (ii) charges activate a further nonradiative channel for the exciton decay. Moreover, the transient PLEM measurements clearly reveal that not only trapped charges, as already reported in literature, but rather the entire injected charge density contributes to the quenching of the exciton population. KW - photoluminescence quenching KW - charge density KW - exciton dynamics KW - organic KW - field-effect transistor KW - light emission KW - optical spectroscopy Y1 - 2017 U6 - https://doi.org/10.1021/acsphotonics.6b00573 SN - 2330-4022 VL - 4 IS - 2 SP - 282 EP - 291 PB - American Chemical Society CY - Washington, DC ER - TY - JOUR A1 - Almeida, Leonardo A. A1 - Sana, H. A1 - Taylor, W. A1 - Barbá, Rodolfo A1 - Bonanos, Alceste Z. A1 - Crowther, Paul A1 - Damineli, Augusto A1 - de Koter, A. A1 - de Mink, Selma E. A1 - Evans, C. J. A1 - Gieles, Mark A1 - Grin, Nathan J. A1 - Hénault-Brunet, V. A1 - Langer, Norbert A1 - Lennon, D. A1 - Lockwood, Sean A1 - Maíz Apellániz, Jesús A1 - Moffat, A. F. J. A1 - Neijssel, C. A1 - Norman, C. A1 - Ramírez-Agudelo, O. H. A1 - Richardson, N. D. A1 - Schootemeijer, Abel A1 - Shenar, Tomer A1 - Soszyński, Igor A1 - Tramper, Frank A1 - Vink, J. S. T1 - The tarantula massive binary monitoring BT - I. Observational campaign and OB-type spectroscopic binaries JF - Astronomy and astrophysics : an international weekly journal N2 - Context: Massive binaries play a crucial role in the Universe. Knowing the distributions of their orbital parameters is important for a wide range of topics from stellar feedback to binary evolution channels and from the distribution of supernova types to gravitational wave progenitors, yet no direct measurements exist outside the Milky Way. Aims: The Tarantula Massive Binary Monitoring project was designed to help fill this gap by obtaining multi-epoch radial velocity (RV) monitoring of 102 massive binaries in the 30 Doradus region. Methods: In this paper we analyze 32 FLAMES/GIRAFFE observations of 93 O- and 7 B-type binaries. We performed a Fourier analysis and obtained orbital solutions for 82 systems: 51 single-lined (SB1) and 31 double-lined (SB2) spectroscopic binaries. Results: Overall, the binary fraction and orbital properties across the 30 Doradus region are found to be similar to existing Galactic samples. This indicates that within these domains environmental effects are of second order in shaping the properties of massive binary systems. A small difference is found in the distribution of orbital periods, which is slightly flatter (in log space) in 30 Doradus than in the Galaxy, although this may be compatible within error estimates and differences in the fitting methodology. Also, orbital periods in 30 Doradus can be as short as 1.1 d, somewhat shorter than seen in Galactic samples. Equal mass binaries (q> 0.95) in 30 Doradus are all found outside NGC 2070, the central association that surrounds R136a, the very young and massive cluster at 30 Doradus’s core. Most of the differences, albeit small, are compatible with expectations from binary evolution. One outstanding exception, however, is the fact that earlier spectral types (O2–O7) tend to have shorter orbital periods than later spectral types (O9.2–O9.7). Conclusions: Our results point to a relative universality of the incidence rate of massive binaries and their orbital properties in the metallicity range from solar (Z⊙) to about half solar. This provides the first direct constraints on massive binary properties in massive star-forming galaxies at the Universe’s peak of star formation at redshifts z ~ 1 to 2 which are estimated to have Z ~ 0.5 Z⊙. KW - stars: early-type KW - stars: massive KW - binaries: spectroscopic KW - binaries: close Y1 - 2017 U6 - https://doi.org/10.1051/0004-6361/201629844 SN - 1432-0746 VL - 598 PB - EDP Sciences CY - Les Ulis ER - TY - JOUR A1 - Shenar, Tomer A1 - Richardson, N. D. A1 - Sablowski, Daniel P. A1 - Hainich, Rainer A1 - Sana, H. A1 - Moffat, A. F. J. A1 - Todt, Helge Tobias A1 - Hamann, Wolf-Rainer A1 - Oskinova, Lidia M. A1 - Sander, Andreas Alexander Christoph A1 - Tramper, Frank A1 - Langer, Norbert A1 - Bonanos, Alceste Z. A1 - de Mink, Selma E. A1 - Gräfener, G. A1 - Crowther, Paul A1 - Vink, J. S. A1 - Almeida, Leonardo A. A1 - de Koter, A. A1 - Barbá, Rodolfo A1 - Herrero, A. A1 - Ulaczyk, Krzysztof T1 - The tarantula massive binary monitoring BT - II. First SB2 orbital and spectroscopic analysis for the Wolf-Rayet binary R145 JF - Astronomy and astrophysics : an international weekly journal N2 - We present the first SB2 orbital solution and disentanglement of the massive Wolf-Rayet binary R145 (P = 159 d) located in the Large Magellanic Cloud. The primary was claimed to have a stellar mass greater than 300 M-circle dot, making it a candidate for being the most massive star known to date. While the primary is a known late-type, H-rich Wolf-Rayet star (WN6h), the secondary has so far not been unambiguously detected. Using moderate-resolution spectra, we are able to derive accurate radial velocities for both components. By performing simultaneous orbital and polarimetric analyses, we derive the complete set of orbital parameters, including the inclination. The spectra are disentangled and spectroscopically analyzed, and an analysis of the wind-wind collision zone is conducted. The disentangled spectra and our models are consistent with a WN6h type for the primary and suggest that the secondary is an O3.5 If*/WN7 type star. We derive a high eccentricity of e = 0 : 78 and minimum masses of M-1 sin(3) i approximate to M-2 sin(3) i = 13 +/- 2 M-circle dot, with q = M-2/M-1 = 1.01 +/- 0.07. An analysis of emission excess stemming from a wind-wind collision yields an inclination similar to that obtained from polarimetry (i = 39 +/- 6 degrees). Our analysis thus implies M-1 = 53(-20)(+40) and M2 = 54(-20)(+40) M-circle dot, excluding M-1 > 300 M-circle dot. A detailed comparison with evolution tracks calculated for single and binary stars together with the high eccentricity suggests that the components of the system underwent quasi-homogeneous evolution and avoided mass-transfer. This scenario would suggest current masses of approximate to 80 M-circle dot and initial masses of M-i,M-1 approximate to 10(5) and M-i,M-2 approximate to 90 M-circle dot, consistent with the upper limits of our derived orbital masses, and would imply an age of approximate to 2.2 Myr. KW - binaries: spectroscopic KW - stars: Wolf-Rayet KW - stars: massive KW - Magellanic Clouds KW - stars: individual: R 145 KW - stars: atmospheres Y1 - 2017 U6 - https://doi.org/10.1051/0004-6361/201629621 SN - 1432-0746 VL - 598 PB - EDP Sciences CY - Les Ulis ER - TY - JOUR A1 - Abdalla, H. A1 - Abramowski, A. A1 - Aharonian, Felix A. A1 - Benkhali, F. Ait A1 - Akhperjanian, A. G. A1 - Andersson, T. A1 - Anguener, E. O. A1 - Arrieta, M. A1 - Aubert, P. A1 - Backes, M. A1 - Balzer, A. A1 - Barnard, M. A1 - Becherini, Y. A1 - Tjus, J. Becker A1 - Berge, D. A1 - Bernhard, S. A1 - Bernlorhr, K. A1 - Blackwell, R. A1 - Bottcher, M. A1 - Boisson, C. A1 - Bolmont, J. A1 - Bordas, Pol A1 - Bregeon, J. A1 - Brun, F. A1 - Brun, P. A1 - Bryan, M. A1 - Bulik, T. A1 - Capasso, M. A1 - Carr, J. A1 - Casanova, Sabrina A1 - Cerruti, M. A1 - Chakraborty, N. A1 - Chalme-Calvet, R. A1 - Chaves, R. C. G. A1 - Chen, A. A1 - Chevalier, J. A1 - Chretien, M. A1 - Colafrancesco, S. A1 - Cologna, G. A1 - Condon, B. A1 - Conrad, J. A1 - Cui, Y. A1 - Davids, I. D. A1 - Decock, J. A1 - Degrange, B. A1 - Deil, C. A1 - Devin, J. A1 - deWilt, P. A1 - Dirson, L. A1 - Djannati-Atai, A. A1 - Domainko, W. A1 - Donath, A. A1 - Dubus, G. A1 - Dutson, K. A1 - Dyks, J. A1 - Edwards, T. A1 - Egberts, Kathrin A1 - Eger, P. A1 - Ernenwein, J. -P. A1 - Eschbach, S. A1 - Farnier, C. A1 - Fegan, S. A1 - Fernandes, M. V. A1 - Fiasson, A. A1 - Fontaine, G. A1 - Foerster, A. A1 - Funk, S. A1 - Fuessling, M. A1 - Gabici, S. A1 - Gajdus, M. A1 - Gallant, Y. A. A1 - Garrigoux, T. A1 - Giavitto, G. A1 - Giebels, B. A1 - Glicenstein, J. F. A1 - Gottschall, D. A1 - Goyal, A. A1 - Grondin, M. -H. A1 - Hadasch, D. A1 - Hahn, J. A1 - Haupt, M. A1 - Hawkes, J. A1 - Heinzelmann, G. A1 - Henri, G. A1 - Hermann, G. A1 - Hervet, O. A1 - Hinton, J. A. A1 - Hofmann, W. A1 - Hoischen, Clemens A1 - Holler, M. A1 - Horns, D. A1 - Ivascenko, A. A1 - Jacholkowska, A. A1 - Jamrozy, M. A1 - Janiak, M. A1 - Jankowsky, D. A1 - Jankowsky, F. A1 - Jingo, M. A1 - Jogler, T. A1 - Jouvin, L. A1 - Jung-Richardt, I. A1 - Kastendieck, M. A. A1 - Katarzynski, K. A1 - Katz, U. A1 - Kerszberg, D. A1 - Khelifi, B. A1 - Er, M. Kie Ff A1 - King, J. A1 - Klepser, S. A1 - Klochkov, D. A1 - Kluzniak, W. A1 - Kolitzus, D. A1 - Komin, Nu. A1 - Kosack, K. A1 - Krakau, S. A1 - Kraus, M. A1 - Krayzel, F. A1 - Kruger, P. P. A1 - Laffon, H. A1 - Lamanna, G. A1 - Lau, J. A1 - Lees, J. -P. A1 - Lefaucheur, J. A1 - Lefranc, V. A1 - Lemiere, A. A1 - Lemoine-Goumard, M. A1 - Lenain, J. -P. A1 - Leser, E. A1 - Lohse, T. A1 - Lorentz, M. A1 - Liu, R. A1 - Lopez-Coto, R. A1 - Lypova, I. A1 - Marandon, V. A1 - Marcowith, Alexandre A1 - Mariaud, C. A1 - Marx, R. A1 - Maurin, G. A1 - Maxted, N. A1 - Mayer, M. A1 - Meintjes, P. J. A1 - Meyer, M. A1 - Mitchell, A. M. W. A1 - Moderski, R. A1 - Mohamed, M. A1 - Mohrmann, L. A1 - Mora, K. A1 - Moulin, Emmanuel A1 - Murach, T. A1 - de Naurois, M. A1 - Niederwanger, F. A1 - Niemiec, J. A1 - Oakes, L. A1 - Odaka, H. A1 - Oettl, S. A1 - Ohm, S. A1 - Ostrowski, M. A1 - Oya, I. A1 - Padovani, M. A1 - Panter, M. A1 - Parsons, R. D. A1 - Pekeur, N. W. A1 - Pelletier, G. A1 - Perennes, C. A1 - Petrucci, P. -O. A1 - Peyaud, B. A1 - Piel, Q. A1 - Pita, S. A1 - Poon, H. A1 - Prokhorov, D. A1 - Prokoph, H. A1 - Puehlhofer, G. A1 - Punch, M. A1 - Quirrenbach, A. A1 - Raab, S. A1 - Reimer, A. A1 - Reimer, O. A1 - Renaud, M. A1 - de los Reyes, R. A1 - Rieger, F. A1 - Romoli, C. A1 - Rosier-Lees, S. A1 - Rowell, G. A1 - Rudak, B. A1 - Rulten, C. B. A1 - Sahakian, V. A1 - Salek, D. A1 - Sanchez, D. A. A1 - Santangelo, Andrea A1 - Sasaki, M. A1 - Schlickeiser, R. A1 - Schussler, F. A1 - Schulz, A. A1 - Schwanke, U. A1 - Schwemmer, S. A1 - Settimo, M. A1 - Seyffert, A. S. A1 - Shafi, N. A1 - Shilon, I. A1 - Simoni, R. A1 - Sol, H. A1 - Spanier, F. A1 - Spengler, G. A1 - Spies, F. A1 - Ert, Ff A1 - Stawarz, L. A1 - Steenkamp, R. A1 - Stegmann, Christian Michael A1 - Stinzing, F. A1 - Stycz, K. A1 - Sushch, I. A1 - Tavernet, J. -P. A1 - Tavernier, T. A1 - Taylor, A. M. A1 - Terrier, R. A1 - Tibaldo, L. A1 - Tiziani, D. A1 - Tluczykont, M. A1 - Trichard, C. A1 - Tuffs, R. A1 - Uchiyama, Y. A1 - van der Walt, D. J. A1 - van Eldik, C. A1 - van Rensburg, C. A1 - van Soelen, B. A1 - Vasileiadis, G. A1 - Veh, J. A1 - Venter, C. A1 - Viana, A. A1 - Vincent, P. A1 - Vink, J. A1 - Voisin, F. A1 - Voelk, H. J. A1 - Vuillaume, T. A1 - Wadiasingh, Z. A1 - Wagner, S. J. A1 - Wagner, P. A1 - Wagner, R. M. A1 - White, R. A1 - Wierzcholska, A. A1 - Willmann, P. A1 - Woernlein, A. A1 - Wouters, D. A1 - Yang, R. A1 - Zabalza, V. A1 - Zaborov, D. A1 - Zacharias, M. A1 - Zdziarski, A. A. A1 - Zech, Alraune A1 - Zefi, F. A1 - Ziegler, A. A1 - Zywucka, N. T1 - Characterizing the gamma-ray long-term variability of PKS2155 304 with HESS and Fermi-LAT JF - Astronomy and astrophysics : an international weekly journal N2 - Studying the temporal variability of BL Lac objects at the highest energies provides unique insights into the extreme physical processes occurring in relativistic jets and in the vicinity of super-massive black holes. To this end, the long-term variability of the BL Lac object PKS 2155 304 is analyzed in the high (HE, 100MeV < E < 300 GeV) and very high energy (VHE, E > 200 GeV) gamma-ray domain. Over the course of similar to 9 yr of H. E. S. S. observations the VHE light curve in the quiescent state is consistent with a log-normal behavior. The VHE variability in this state is well described by flicker noise (power-spectral-density index beta(VHE) = 1 .10(+ 0 : 10) (0 : 13)) on timescales larger than one day. An analysis of similar to 5.5 yr of HE Fermi-LAT data gives consistent results (beta(HE) = 1 : 20(+ 0 : 21) (0 : 23), on timescales larger than 10 days) compatible with the VHE findings. The HE and VHE power spectral densities show a scale invariance across the probed time ranges. A direct linear correlation between the VHE and HE fluxes could neither be excluded nor firmly established. These long-term-variability properties are discussed and compared to the red noise behavior (beta similar to 2) seen on shorter timescales during VHE-flaring states. The difference in power spectral noise behavior at VHE energies during quiescent and flaring states provides evidence that these states are influenced by different physical processes, while the compatibility of the HE and VHE long-term results is suggestive of a common physical link as it might be introduced by an underlying jet-disk connection. KW - galaxies: active KW - BL Lacertae objects: individual: PKS 2155-304 KW - gamma rays: galaxies KW - galaxies: jets KW - galaxies: nuclei KW - radiation mechanisms: non-thermal Y1 - 2017 U6 - https://doi.org/10.1051/0004-6361/201629419 SN - 1432-0746 SN - 0004-6361 VL - 598 PB - EDP Sciences CY - Les Ulis ER - TY - JOUR A1 - Archambault, S. A1 - Archer, A. A1 - Benbow, W. A1 - Buchovecky, M. A1 - Bugaev, V. A1 - Cerruti, M. A1 - Connolly, M. P. A1 - Cui, W. A1 - Falcone, A. A1 - Alonso, M. Fernandez A1 - Finley, J. P. A1 - Fleischhack, H. A1 - Fortson, L. A1 - Furniss, A. A1 - Griffin, S. A1 - Hutten, M. A1 - Hervet, O. A1 - Holder, J. A1 - Humensky, T. B. A1 - Johnson, C. A. A1 - Kaaret, P. A1 - Kar, P. A1 - Kieda, D. A1 - Krause, M. A1 - Krennrich, F. A1 - Lang, M. J. A1 - Lin, T. T. Y. A1 - Maier, G. A1 - McArthur, S. A1 - Moriarty, P. A1 - Nieto, D. A1 - Ong, R. A. A1 - Otte, A. N. A1 - Pohl, M. A1 - Popkow, A. A1 - Pueschel, Elisa A1 - Quinn, J. A1 - Ragan, K. A1 - Reynolds, P. T. A1 - Richards, G. T. A1 - Roache, E. A1 - Rovero, A. C. A1 - Sadeh, I. A1 - Shahinyan, K. A1 - Staszak, D. A1 - Telezhinsky, Igor O. A1 - Tyler, J. A1 - Wakely, S. P. A1 - Weinstein, A. A1 - Weisgarber, T. A1 - Wilcox, P. A1 - Wilhelm, Alina A1 - Williams, D. A. A1 - Zitzer, B. T1 - Search for Magnetically Broadened Cascade Emission from Blazars with VERITAS JF - The astrophysical journal : an international review of spectroscopy and astronomical physics N2 - We present a search for magnetically broadened gamma-ray emission around active galactic nuclei (AGNs), using VERITAS observations of seven hard-spectrum blazars. A cascade process occurs when multi-TeV gamma-rays from an AGN interact with extragalactic background light (EBL) photons to produce electron-positron pairs, which then interact with cosmic microwave background photons via inverse-Compton scattering to produce gamma-rays. Due to the deflection of the electron- positron pairs, a non-zero intergalactic magnetic field (IGMF) would potentially produce detectable effects on the angular distribution of the cascade emission. In particular, an angular broadening compared to the unscattered emission could occur. Through non-detection of angularly broadened emission from 1ES 1218 vertical bar 304, the source with the largest predicted cascade fraction, we exclude a range of IGMF strengths around 10(-14) G at the 95% confidence level. The extent of the exclusion range varies with the assumptions made about the intrinsic spectrum of 1ES. 1218+304 and the EBL model used in the simulation of the cascade process. All of the sources are used to set limits on the flux due to extended emission. KW - BL Lacertae objects: general KW - galaxies: active KW - gamma rays: galaxies KW - magnetic fields Y1 - 2017 U6 - https://doi.org/10.3847/1538-4357/835/2/288 SN - 0004-637X SN - 1538-4357 VL - 835 IS - 2 PB - IOP Publ. Ltd. CY - Bristol ER - TY - JOUR A1 - Warren, Donald C. A1 - Ellison, Donald C. A1 - Barkov, Maxim V. A1 - Nagataki, Shigehiro T1 - Nonlinear Particle Acceleration and Thermal Particles in GRB Afterglows JF - The astrophysical journal : an international review of spectroscopy and astronomical physics N2 - The standard model for GRB afterglow emission treats the accelerated electron population as a simple power law, N(E) proportional to E-p for p greater than or similar to 2. However, in standard Fermi shock acceleration, a substantial fraction of the swept-up particles do not enter the acceleration process at all. Additionally, if acceleration is efficient, then the nonlinear back-reaction of accelerated particles on the shock structure modifies the shape of the nonthermal tail of the particle spectra. Both of these modifications to the standard synchrotron afterglow impact the luminosity, spectra, and temporal variation of the afterglow. To examine the effects of including thermal particles and nonlinear particle acceleration on afterglow emission, we follow a hydrodynamical model for an afterglow jet and simulate acceleration at numerous points during the evolution. When thermal particles are included, we find that the electron population is at no time well fitted by a single power law, though the highest-energy electrons are; if the acceleration is efficient, then the power-law region is even smaller. Our model predicts hard-soft-hard spectral evolution at X-ray energies, as well as an uncoupled X-ray and optical light curve. Additionally, we show that including emission from thermal particles has drastic effects (increases by factors of 100 and 30, respectively) on the observed flux at optical and GeV energies. This enhancement of GeV emission makes afterglow detections by future gamma-ray observatories, such as CTA, very likely. KW - acceleration of particles KW - cosmic rays KW - gamma-ray burst: general KW - shock waves KW - turbulence Y1 - 2017 U6 - https://doi.org/10.3847/1538-4357/aa56c3 SN - 0004-637X SN - 1538-4357 VL - 835 IS - 2 PB - IOP Publ. Ltd. CY - Bristol ER - TY - JOUR A1 - Postnov, K. A1 - Oskinova, Lidia M. A1 - Torrejon, J. M. T1 - A propelling neutron star in the enigmatic Be-star gamma Cassiopeia JF - Monthly notices of the Royal Astronomical Society N2 - gamma Cassiopeia (gamma Cas), is known to be a binary system consisting of a Be-type star and a low-mass (M similar to 1M(circle dot)) companion of unknown nature orbiting in the Be-disc plane. Here, we apply the quasi-spherical accretion theory on to a compact magnetized star and show that if the low-mass companion of gamma Cas is a fast spinning neutron star, the key observational signatures of. Cas are remarkably well reproduced. Direct accretion on to this fast rotating neutron star is impeded by the propeller mechanism. In this case, around the neutron star magnetosphere a hot shell is formed which emits thermal X-rays in qualitative and quantitative agreement with observed properties of the X-ray emission from gamma Cas. We suggest that gamma Cas and its analogues constitute a new subclass of Be-type X-ray binaries hosting rapidly rotating neutron stars formed in supernova explosions with small kicks. The subsequent evolutionary stage of gamma Cas and its analogues should be the X Per-type binaries comprising low-luminosity slowly rotating X-ray pulsars. The model explains the enigmatic X-ray emission from gamma Cas, and also establishes evolutionary connections between various types of rotating magnetized neutron stars in Be-binaries. KW - stars: emission-line, Be KW - stars: neutron Y1 - 2017 U6 - https://doi.org/10.1093/mnrasl/slw223 SN - 0035-8711 SN - 1365-2966 VL - 465 IS - 1 SP - L119 EP - L123 PB - Oxford Univ. Press CY - Oxford ER - TY - JOUR A1 - Archambault, S. A1 - Archer, A. A1 - Benbow, Wystan A1 - Bird, Ralph A1 - Bourbeau, E. A1 - Buchovecky, M. A1 - Buckley, J. H. A1 - Bugaev, V. A1 - Cerruti, M. A1 - Connolly, M. P. A1 - Cui, W. A1 - Dwarkadas, Vikram V. A1 - Errando, M. A1 - Falcone, A. A1 - Feng, Q. A1 - Finley, J. P. A1 - Fleischhack, H. A1 - Fortson, L. A1 - Furniss, A. A1 - Griffin, S. A1 - Huetten, M. A1 - Hanna, D. A1 - Holder, J. A1 - Johnson, C. A. A1 - Kaaret, P. A1 - Kar, P. A1 - Kelley-Hoskins, N. A1 - Kertzman, M. A1 - Kieda, D. A1 - Krause, M. A1 - Kumar, S. A1 - Lang, M. J. A1 - Maier, G. A1 - McArthur, S. A1 - McCann, A. A1 - Moriarty, P. A1 - Mukherjee, R. A1 - Nieto, D. A1 - Ong, R. A. A1 - Otte, A. N. A1 - Park, Nahee A1 - Pohl, Martin A1 - Popkow, A. A1 - Pueschel, Elisa A1 - Quinn, J. A1 - Ragan, K. A1 - Reynolds, P. T. A1 - Richards, G. T. A1 - Roache, E. A1 - Sadeh, I. A1 - Santander, M. A1 - Sembroski, G. H. A1 - Shahinyan, K. A1 - Slane, P. A1 - Staszak, D. A1 - Telezhinsky, Igor O. A1 - Trepanier, S. A1 - Tyler, J. A1 - Wakely, S. P. A1 - Weinstein, A. A1 - Weisgarber, T. A1 - Wilcox, P. A1 - Wilhelm, Alina A1 - Williams, D. A. A1 - Zitzer, B. T1 - Gamma-ray Observations of Tycho's Supernova Remnant with VERITAS and Fermi JF - The astrophysical journal : an international review of spectroscopy and astronomical physics KW - material KW - data behind figure Y1 - 2017 U6 - https://doi.org/10.3847/1538-4357/836/1/23 SN - 0004-637X SN - 1538-4357 VL - 836 IS - 1 PB - IOP Publ. Ltd. CY - Bristol ER - TY - JOUR A1 - Garakani, Tayebeh Mirzaei A1 - Richter, Marina Juliane A1 - Böker, Alexander T1 - Controlling the bio-inspired synthesis of silica JF - Journal of colloid and interface science N2 - The influence of different parameters on the silicification procedure using lysozyme is reported. When polyethoxysiloxane (PEOS), an internally crosslinked silica reservoir, is used, regular structures with a narrow size distribution could be obtained only via introducing the silica precursor in two steps including initial dropping and subsequent addition of residual oil phase in one portion. We found that mixing sequence of mineralizing agents in the presence of a positively charged surfactant plays a key role in terms of silica precipitation when tetraethoxyorthosilicate (TEOS) is the oil phase. In contrast, well mineralized crumpled features with high specific surface area could be synthesized in the presence of PEOS as a silica precursor polymer, regardless of mixing sequence. Moreover, introducing sodium dodecyl sulfate (SDS) as a negatively charged surfactant resulted in regular silica sphere formation only in combination with hexylene glycol (MPD) as a specific co-solvent. Finally, it is demonstrated that by inclusion of different nanoparticles even more sophisticated hybrid materials can be generated. KW - Silicification KW - Lysozyme KW - Polyetlioxysiloxane KW - High specific surface area KW - Surfactant KW - Nanoparticles KW - Hybrid materials Y1 - 2016 U6 - https://doi.org/10.1016/j.jcis.2016.10.069 SN - 0021-9797 SN - 1095-7103 VL - 488 SP - 322 EP - 334 PB - Elsevier CY - San Diego ER - TY - JOUR A1 - Shprits, Yuri A1 - Kellerman, Adam C . A1 - Aseev, Nikita A1 - Drozdov, Alexander A1 - Michaelis, Ingo T1 - Multi-MeV electron loss in the heart of the radiation belts JF - Geophysical research letters N2 - Significant progress has been made in recent years in understanding acceleration mechanisms in the Earth's radiation belts. In particular, a number of studies demonstrated the importance of the local acceleration by analyzing the radial profiles of phase space density (PSD) and observing building up peaks in PSD. In this study, we focus on understanding of the local loss using very similar tools. The profiles of PSD for various values of the first adiabatic invariants during the previously studied 17 January 2013 storm are presented and discussed. The profiles of PSD show clear deepening minimums consistent with the scattering by electromagnetic ion cyclotron waves. Long-term evolution shows that local minimums in PSD can persist for relatively long times. During considered interval of time the deepening minimums were observed around L* = 4 during 17 January 2013 storm and around L* = 3.5 during 1 March 2013 storm. This study shows a new method that can help identify the location, magnitude, and time of the local loss and will help quantify local loss in the future. This study also provides additional clear and definitive evidence that local loss plays a major role for the dynamics of the multi-MeV electrons. Y1 - 2017 U6 - https://doi.org/10.1002/2016GL072258 SN - 0094-8276 SN - 1944-8007 VL - 44 IS - 3 SP - 1204 EP - 1209 PB - American Geophysical Union CY - Washington ER - TY - JOUR A1 - Liu, Lin A1 - Cherstvy, Andrey G. A1 - Metzler, Ralf T1 - Facilitated Diffusion of Transcription Factor Proteins with Anomalous Bulk Diffusion JF - The journal of physical chemistry : B, Condensed matter, materials, surfaces, interfaces & biophysical chemistry N2 - What are the physical laws of the diffusive search of proteins for their specific binding sites on DNA in the presence of the macromolecular crowding in cells? We performed extensive computer simulations to elucidate the protein target search on DNA. The novel feature is the viscoelastic non-Brownian protein bulk diffusion recently observed experimentally. We examine the influence of the protein-DNA binding affinity and the anomalous diffusion exponent on the target search time. In all cases an optimal search time is found. The relative contribution of intermittent three-dimensional bulk diffusion and one-dimensional sliding of proteins along the DNA is quantified. Our results are discussed in the light of recent single molecule tracking experiments, aiming at a better understanding of the influence of anomalous kinetics of proteins on the facilitated diffusion mechanism. Y1 - 2017 U6 - https://doi.org/10.1021/acs.jpcb.6b12413 SN - 1520-6106 VL - 121 SP - 1284 EP - 1289 PB - American Chemical Society CY - Washington ER - TY - JOUR A1 - Smirnov, Lev A. A1 - Osipov, Grigory V. A1 - Pikovskij, Arkadij T1 - Chimera patterns in the Kuramoto-Battogtokh model JF - Journal of physics : A, Mathematical and theoretical N2 - Kuramoto and Battogtokh (2002 Nonlinear Phenom. Complex Syst. 5 380) discovered chimera states represented by stable coexisting synchrony and asynchrony domains in a lattice of coupled oscillators. After a reformulation in terms of a local order parameter, the problem can be reduced to partial differential equations. We find uniformly rotating, spatially periodic chimera patterns as solutions of a reversible ordinary differential equation, and demonstrate a plethora of such states. In the limit of neutral coupling they reduce to analytical solutions in the form of one-and two-point chimera patterns as well as localized chimera solitons. Patterns at weakly attracting coupling are characterized by virtue of a perturbative approach. Stability analysis reveals that only the simplest chimeras with one synchronous region are stable. KW - nonlocal coupled oscillators KW - chimera state KW - coarse-grained order parameter KW - Ott-Antonsen reduction KW - perturbation approach KW - linear stability analysis Y1 - 2017 U6 - https://doi.org/10.1088/1751-8121/aa55f1 SN - 1751-8113 SN - 1751-8121 VL - 50 IS - 8 PB - IOP Publ. Ltd. CY - Bristol ER - TY - JOUR A1 - Abeysekara, A. U. A1 - Archambault, S. A1 - Archer, A. A1 - Benbow, Wystan A1 - Bird, Ralph A1 - Buchovecky, M. A1 - Buckley, J. H. A1 - Bugaev, V. A1 - Byrum, K. A1 - Cerruti, M. A1 - Chen, X. A1 - Ciupik, L. A1 - Cui, W. A1 - Dickinson, H. J. A1 - Eisch, J. D. A1 - Errando, M. A1 - Falcone, A. A1 - Feng, Q. A1 - Finley, J. P. A1 - Fleischhack, H. A1 - Fortson, L. A1 - Furniss, A. A1 - Gillanders, G. H. A1 - Griffin, S. A1 - Grube, J. A1 - Hutten, M. A1 - Hakansson, N. A1 - Hanna, D. A1 - Holder, J. A1 - Humensky, T. B. A1 - Johnson, C. A. A1 - Kaaret, P. A1 - Kar, P. A1 - Kertzman, M. A1 - Kieda, D. A1 - Krause, M. A1 - Krennrich, F. A1 - Kumar, S. A1 - Lang, M. J. A1 - Maier, G. A1 - McArthur, S. A1 - McCann, A. A1 - Meagher, K. A1 - Moriarty, P. A1 - Mukherjee, R. A1 - Nguyen, T. A1 - Nieto, D. A1 - Ong, R. A. A1 - Otte, A. N. A1 - Park, N. A1 - Pelassa, V. A1 - Pohl, Martin A1 - Popkow, A. A1 - Pueschel, Elisa A1 - Quinn, J. A1 - Ragan, K. A1 - Reynolds, P. T. A1 - Richards, G. T. A1 - Roache, E. A1 - Rulten, C. A1 - Santander, M. A1 - Sembroski, G. H. A1 - Shahinyan, K. A1 - Staszak, D. A1 - Telezhinsky, Igor O. A1 - Tucci, J. V. A1 - Tyler, J. A1 - Wakely, S. P. A1 - Weiner, O. M. A1 - Weinstein, A. A1 - Wilhelm, Alina A1 - Williams, D. A. A1 - Fegan, S. A1 - Giebels, B. A1 - Horan, D. A1 - Berdyugin, A. A1 - Kuan, J. A1 - Lindfors, E. A1 - Nilsson, K. A1 - Oksanen, A. A1 - Prokoph, H. A1 - Reinthal, R. A1 - Takalo, L. A1 - Zefi, F. T1 - A Luminous and Isolated Gamma-Ray Flare from the Blazar B2 1215+30 JF - The astrophysical journal : an international review of spectroscopy and astronomical physics N2 - B2 1215+30 is a BL-Lac-type blazar that was first detected at TeV energies by the MAGIC atmospheric Cherenkov telescopes and subsequently confirmed by the Very Energetic Radiation Imaging Telescope Array System (VERITAS) observatory with data collected between 2009 and 2012. In 2014 February 08, VERITAS detected a large-amplitude flare from B2. 1215+30 during routine monitoring observations of the blazar 1ES. 1218+304, located in the same field of view. The TeV flux reached 2.4 times the Crab Nebula flux with a variability timescale of <3.6 hr. Multiwavelength observations with Fermi-LAT, Swift, and the Tuorla Observatory revealed a correlated high GeV flux state and no significant optical counterpart to the flare, with a spectral energy distribution where the gamma-ray luminosity exceeds the synchrotron luminosity. When interpreted in the framework of a onezone leptonic model, the observed emission implies a high degree of beaming, with Doppler factor delta > 10, and an electron population with spectral index p < 2.3. KW - BL Lacertae objects: individual (B2 1215+30, VER J1217+301) KW - galaxies: active KW - galaxies: jets KW - galaxies: nuclei KW - gamma rays: galaxies Y1 - 2017 U6 - https://doi.org/10.3847/1538-4357/836/2/205 SN - 0004-637X SN - 1538-4357 VL - 836 IS - 2 PB - IOP Publ. Ltd. CY - Bristol ER - TY - JOUR A1 - Godec, Aljaž A1 - Metzler, Ralf T1 - First passage time statistics for two-channel diffusion JF - Journal of physics : A, Mathematical and theoretical N2 - We present rigorous results for the mean first passage time and first passage time statistics for two-channel Markov additive diffusion in a 3-dimensional spherical domain. Inspired by biophysical examples we assume that the particle can only recognise the target in one of the modes, which is shown to effect a non-trivial first passage behaviour. We also address the scenario of intermittent immobilisation. In both cases we prove that despite the perfectly non-recurrent motion of two-channel Markov additive diffusion in 3 dimensions the first passage statistics at long times do not display Poisson-like behaviour if none of the phases has a vanishing diffusion coefficient. This stands in stark contrast to the standard (one-channel) Markov diffusion counterpart. We also discuss the relevance of our results in the context of cellular signalling. KW - first passage time KW - Markov additive processes KW - Fokker-Planck equation KW - random search processes KW - coupled initial boundary value problem KW - cellular signalling KW - asymptotic analysis Y1 - 2017 U6 - https://doi.org/10.1088/1751-8121/aa5204 SN - 1751-8113 SN - 1751-8121 VL - 50 IS - 8 PB - IOP Publ. Ltd. CY - Bristol ER - TY - JOUR A1 - Gorobtsov, O. Yu. A1 - Mercurio, G. A1 - Brenner, G. A1 - Lorenz, Ulf A1 - Gerasimova, N. A1 - Kurta, R. P. A1 - Hieke, F. A1 - Skopintsev, P. A1 - Zaluzhnyy, I. A1 - Lazarev, S. A1 - Dzhigaev, D. A1 - Rose, M. A1 - Singer, A. A1 - Wurth, W. A1 - Vartanyants, I. A. T1 - Statistical properties of a free-electron laser revealed by Hanbury Brown-Twiss interferometry JF - Physical review : A, Atomic, molecular, and optical physics N2 - We present a comprehensive experimental analysis of statistical properties of the self-amplified spontaneous emission free-electron laser (FEL) FLASH by means of Hanbury Brown and Twiss interferometry. The experiments were performed at FEL wavelengths of 5.5, 13.4, and 20.8 nm. We determined the second-order intensity correlation function for all wavelengths and different operation conditions of FLASH. In all experiments a high degree of spatial coherence (above 50%) was obtained. Our analysis performed in spatial and spectral domains provided us with the independent measurements of an average pulse duration of the FEL that were below 60 fs. To explain the complicated behavior of the second-order intensity correlation function we developed an advanced theoretical model that includes the presence of multiple beams and external positional jitter of the FEL pulses. By this analysis we determined that in one of the experiments external positional jitter was about 25% of the beam size. We envision that methods developed in our study will be used widely for analysis and diagnostics of FEL radiation. Y1 - 2017 U6 - https://doi.org/10.1103/PhysRevA.95.023843 SN - 2469-9926 SN - 2469-9934 VL - 95 IS - 2 PB - American Physical Society CY - College Park ER - TY - JOUR A1 - Petereit, Johannes A1 - Pikovskij, Arkadij T1 - Chaos synchronization by nonlinear coupling JF - Communications in nonlinear science & numerical simulation N2 - We study synchronization properties of three nonlinearly coupled chaotic maps. Coupling is introduced in such a way, that it cannot be reduced to pairwise terms, but includes combined action of all interacting units. For two models of nonlinear coupling we characterize the transition to complete synchrony, as well as partially synchronized states. Relation to hypernetworks of chaotic units is also discussed. KW - Chaos synchronization KW - Partial synchrony KW - Intermittency KW - Hypernetwork Y1 - 2016 U6 - https://doi.org/10.1016/j.cnsns.2016.09.002 SN - 1007-5704 SN - 1878-7274 VL - 44 SP - 344 EP - 351 PB - Elsevier CY - Amsterdam ER - TY - JOUR A1 - Ramachandran, Varsha A1 - Das, S. R. A1 - Tej, A. A1 - Vig, S. A1 - Ghosh, S. K. A1 - Ojha, D. K. T1 - Radio and infrared study of the star-forming region IRAS 20286+4105 JF - Monthly notices of the Royal Astronomical Society N2 - In this paper, we present a multi wavelength investigation of the star-forming complex IRAS 20286+4105, located in the Cygnus X region. Near-infrared K-band data are used to revisit the cluster/stellar group identified in previous studies. Radio continuum observations at 610 and 1280 MHz show the presence of a H II region possibly powered by a star of spectral type B0-B0.5. The cometary morphology of the ionized region is explained by invoking the bowshock model, where the likely association with a nearby supernova remnant is also explored. A compact radio knot with a non-thermal spectral index is detected towards the centre of the cloud. Mid-infrared data from the Spitzer Legacy Survey of the Cygnus X region show the presence of six Class I young stellar objects inside the cloud. Thermal dust emission in this complex is modelled using Herschel far-infrared data to generate dust temperature and column density maps. Herschel images also show the presence of two clumps in this region, the masses of which are estimated to be similar to 175 and 30 M-circle dot. The mass-radius relation and the surface density of the clumps mean that they do not qualify as massive star-forming sites. An overall picture of a runaway star ionizing the cloud and a triggered population of intermediatemass, Class I sources located towards the cloud centre emerges from this multiwavelength study. Variation in the dust emissivity spectral index is shown to exist in this region and is seen to have an inverse relation with the dust temperature. KW - stars: formation KW - H II regions KW - ISM: individual objects: IRAS 20286+4105 KW - radio continuum: ISM Y1 - 2016 U6 - https://doi.org/10.1093/mnras/stw2906 SN - 0035-8711 SN - 1365-2966 VL - 465 IS - 4 SP - 4753 EP - 4771 PB - Oxford Univ. Press CY - Oxford ER - TY - JOUR A1 - Zacharias, Michael A1 - Chen, Xuhui A1 - Wagner, Stefan T1 - Attenuation of TeV gamma-rays by the starlight photon field of the host galaxy JF - Monthly notices of the Royal Astronomical Society N2 - The absorption of TeV gamma-ray photons produced in relativistic jets by surrounding soft photon fields is a long-standing problem of jet physics. In some cases, the most likely emission site close to the central black hole is ruled out because of the high opacity caused by strong optical and infrared photon sources, such as the broad-line region. Mostly neglected for jet modelling is the absorption of gamma-rays in the starlight photon field of the host galaxy. Analysing the absorption for arbitrary locations and observation angles of the gamma-ray emission site within the host galaxy, we find that the distance to the galaxy centre, the observation angle, and the distribution of starlight in the galaxy are crucial for the amount of absorption. We derive the absorption value for a sample of 20 TeV-detected blazars with a redshift z(r) < 0.2. The absorption value of the gamma-ray emission located in the galaxy centre may be as high as 20 per cent, with an average value of 6 per cent. This is important in order to determine the intrinsic blazar parameters. We see no significant trends in our sample between the degree of absorption and host properties, such as starlight emissivity, galactic size, half-light radius, and redshift. While the uncertainty of the spectral properties of the extragalactic background light exceeds the effect of absorption by stellar light from the host galaxy in distant objects, the latter is a dominant effect in nearby sources. It may also be revealed in a differential comparison of sources with similar redshifts. KW - opacity KW - radiation mechanisms: non-thermal KW - galaxies: active KW - gamma-rays: galaxies Y1 - 2016 U6 - https://doi.org/10.1093/mnras/stw3032 SN - 0035-8711 SN - 1365-2966 VL - 465 IS - 3 SP - 3767 EP - 3774 PB - Oxford Univ. Press CY - Oxford ER - TY - JOUR A1 - Fandrich, Artur A1 - Buller, Jens A1 - Memczak, Henry A1 - Stoecklein, W. A1 - Hinrichs, K. A1 - Wischerhoff, E. A1 - Schulz, B. A1 - Laschewsky, André A1 - Lisdat, Fred T1 - Responsive Polymer-Electrode Interface-Study of its Thermo- and pH-Sensitivity and the Influence of Peptide Coupling JF - Electrochimica acta : the journal of the International Society of Electrochemistry (ISE) N2 - This study introduces a thermally responsive, polymer-based electrode system. The key component is a surface-attached, temperature-responsive poly(oligoethylene glycol) methacrylate (poly(OEGMA)) type polymer bearing photoreactive benzophenone and carboxy groups containing side chains. The responsive behavior of the polymer in aqueous media has been investigated by turbidimetry measurements. Polymer films are formed on gold substrates by means of the photoreactive 2(dicyclohexylphosphino)benzophenone (DPBP) through photocrosslinking. The electrochemical behavior of the resulting polymer-substrate interface has been investigated in buffered [Fe(CN)6](3-)/[Fe (CN)6](4-)solutions at room temperature and under temperature variation by cyclic voltammetry (CV). The CV experiments show that with increasing temperature structural changes of the polymer layer occur, which alter the output of the electrochemical measurement. Repeated heating/cooling cycles analyzed by CV measurements and pH changes analyzed by quartz crystal microbalance with dissipation monitoring (QCM-D) reveal the reversible nature of the restructuring process. The immobilized films are further modified by covalent coupling of two small biomolecules - a hydrophobic peptide and a more hydrophilic one. These attached components influence the hydrophobicity of the layer in a different way the resulting change of the temperature-caused behavior has been studied by CV indicating a different state of the polymer after coupling of the hydrophobic peptide. KW - Stimuli-responsive materials KW - electroanalysis KW - modified electrode KW - bioreceptors KW - peptides KW - surface modification KW - cyclic voltammetry KW - IR ellipsometry KW - quartz crystal microbalance Y1 - 2017 U6 - https://doi.org/10.1016/j.electacta.2017.01.080 SN - 0013-4686 SN - 1873-3859 VL - 229 SP - 325 EP - 333 PB - Elsevier CY - Oxford ER - TY - JOUR A1 - Schöller, Markus A1 - Hubrig, Swetlana A1 - Fossati, L. A1 - Carroll, Thorsten Anthony A1 - Briquet, Maryline A1 - Oskinova, Lida A1 - Järvinen, S. A1 - Ilyin, Ilya A1 - Castro, N. A1 - Morel, T. A1 - Langer, N. A1 - Przybilla, N. A1 - Nieva, M. -F. A1 - Kholtygin, A. F. A1 - Sana, H. A1 - Herrero, A. A1 - Barba, R. H. A1 - de Koter, A. T1 - B fields in OB stars (BOB) BT - Concluding the FORS2 observing campaign JF - Astronomy and astrophysics : an international weekly journal N2 - Aims. The B fields in OB stars (BOB) Collaboration is based on an ESO Large Programme to study the occurrence rate, properties, and ultimately the origin of magnetic fields in massive stars. Methods. In the framework of this program, we carried out low-resolution spectropolarimetric observations of a large sample of massive stars using FORS2 installed at the ESO VLT 8m telescope. Results. We determined the magnetic field values with two completely independent reduction and analysis pipelines. Our in-depth study of the magnetic field measurements shows that differences between our two pipelines are usually well within 3 sigma errors. From the 32 observations of 28 OB stars, we were able to monitor the magnetic fields in CPD -57 degrees 3509 and HD164492C, confirm the magnetic field in HD54879, and detect a magnetic field in CPD -62 degrees 2124. We obtain a magnetic field detection rate of 6 +/- 3% for the full sample of 69 OB stars observed with FORS 2 within the BOB program. For the preselected objects with a nu sin i below 60 km s(-1), we obtain a magnetic field detection rate of 5 +/- 5%. We also discuss X-ray properties and multiplicity of the objects in our FORS2 sample with respect to the magnetic field detections. KW - polarization KW - stars: early-type KW - stars: magnetic field KW - stars: massive Y1 - 2017 U6 - https://doi.org/10.1051/0004-6361/201628905 SN - 1432-0746 VL - 599 PB - EDP Sciences CY - Les Ulis ER - TY - JOUR A1 - Anielski, Alexander A1 - Barbosa Pfannes, Eva Katharina A1 - Beta, Carsten T1 - Adaptive microfluidic gradient generator for quantitative chemotaxis experiments JF - Review of scientific instruments : a monthly journal devoted to scientific instruments, apparatus, and techniques N2 - Chemotactic motion in a chemical gradient is an essential cellular function that controls many processes in the living world. For a better understanding and more detailed modelling of the underlying mechanisms of chemotaxis, quantitative investigations in controlled environments are needed. We developed a setup that allows us to separately address the dependencies of the chemotactic motion on the average background concentration and on the gradient steepness of the chemoattractant. In particular, both the background concentration and the gradient steepness can be kept constant at the position of the cell while it moves along in the gradient direction. This is achieved by generating a well-defined chemoattractant gradient using flow photolysis. In this approach, the chemoattractant is released by a light-induced reaction from a caged precursor in a microfluidic flow chamber upstream of the cell. The flow photolysis approach is combined with an automated real-time cell tracker that determines changes in the cell position and triggers movement of the microscope stage such that the cell motion is compensated and the cell remains at the same position in the gradient profile. The gradient profile can be either determined experimentally using a caged fluorescent dye or may be alternatively determined by numerical solutions of the corresponding physical model. To demonstrate the function of this adaptive microfluidic gradient generator, we compare the chemotactic motion of Dictyostelium discoideum cells in a static gradient and in a gradient that adapts to the position of the moving cell. Published by AIP Publishing. Y1 - 2017 U6 - https://doi.org/10.1063/1.4978535 SN - 0034-6748 SN - 1089-7623 VL - 88 PB - American Institute of Physics CY - Melville ER - TY - JOUR A1 - Leussu, R. A1 - Usoskin, IIlya G. A1 - Valliappan, Senthamizh Pavai A1 - Diercke, Andrea A1 - Arlt, Rainer A1 - Denker, Carsten A1 - Mursula, K. T1 - Wings of the butterfly BT - sunspot groups for 1826-2015 JF - Astronomy and astrophysics : an international weekly journal N2 - The spatio-temporal evolution of sunspot activity, the so-called Maunder butterfly diagram, has been continously available since 1874 using data from the Royal Greenwich Observatory, extended by SOON network data after 1976. Here we present a new extended butterfly diagram of sunspot group occurrence since 1826, using the recently digitized data from Schwabe (1826-1867) and Sporer (1866-1880). The wings of the diagram are separated using a recently developed method based on an analysis of long gaps in sunspot group occurrence in different latitude bands. We define characteristic latitudes, corresponding to the start, end, and the largest extent of the wings (the F, L, and H latitudes). The H latitudes (30 degrees-45 degrees) are highly significantly correlated with the strength of the wings (quantified by the total sum of the monthly numbers of sunspot groups). The F latitudes (20 degrees-30 degrees) depict a weak tendency, especially in the southern hemisphere, to follow the wing strength. The L latitudes (2 degrees-10 degrees) show no clear relation to the wing strength. Overall, stronger cycle wings tend to start at higher latitudes and have a greater wing extent. A strong (5-6)-cycle periodic oscillation is found in the start and end times of the wings and in the overlap and gaps between successive wings of one hemisphere. While the average wing overlap is zero in the southern hemisphere, it is two to three months in the north. A marginally significant oscillation of about ten solar cycles is found in the asymmetry of the L latitudes. The new long database of butterfly wings provides new observational constraints to solar dynamo models that discuss the spatio-temporal distribution of sunspot occurrence over the solar cycle and longer. KW - Sun: activity KW - sunspots KW - history and philosophy of astronomy Y1 - 2017 U6 - https://doi.org/10.1051/0004-6361/201629533 SN - 1432-0746 VL - 599 PB - EDP Sciences CY - Les Ulis ER - TY - JOUR A1 - Popovych, Oleksandr V. A1 - Lysyansky, Borys A1 - Rosenblum, Michael A1 - Pikovskij, Arkadij A1 - Tass, Peter A. T1 - Pulsatile desynchronizing delayed feedback for closed-loop deep brain stimulation JF - PLoS one N2 - High-frequency (HF) deep brain stimulation (DBS) is the gold standard for the treatment of medically refractory movement disorders like Parkinson’s disease, essential tremor, and dystonia, with a significant potential for application to other neurological diseases. The standard setup of HF DBS utilizes an open-loop stimulation protocol, where a permanent HF electrical pulse train is administered to the brain target areas irrespectively of the ongoing neuronal dynamics. Recent experimental and clinical studies demonstrate that a closed-loop, adaptive DBS might be superior to the open-loop setup. We here combine the notion of the adaptive high-frequency stimulation approach, that aims at delivering stimulation adapted to the extent of appropriately detected biomarkers, with specifically desynchronizing stimulation protocols. To this end, we extend the delayed feedback stimulation methods, which are intrinsically closed-loop techniques and specifically designed to desynchronize abnormal neuronal synchronization, to pulsatile electrical brain stimulation. We show that permanent pulsatile high-frequency stimulation subjected to an amplitude modulation by linear or nonlinear delayed feedback methods can effectively and robustly desynchronize a STN-GPe network of model neurons and suggest this approach for desynchronizing closed-loop DBS. Y1 - 2017 U6 - https://doi.org/10.1371/journal.pone.0173363 SN - 1932-6203 VL - 12 PB - PLoS CY - San Fransisco ER - TY - JOUR A1 - Xiong, Hui A1 - Mignolet, Benoit A1 - Fang, Li A1 - Osipov, Timur A1 - Wolf, Thomas J. A. A1 - Sistrunk, Emily A1 - Gühr, Markus A1 - Remacle, Francoise A1 - Berrah, Nora T1 - The Role of Super-Atom Molecular Orbitals in Doped Fullerenes in a Femtosecond Intense Laser Field JF - Scientific reports N2 - The interaction of gas phase endohedral fullerene Ho3N@C-80 with intense (0.1-5 x 10(14) W/cm(2)), short (30 fs), 800 nm laser pulses was investigated. The power law dependence of Ho3N@C-80(q+), q = 1-2, was found to be different from that of C-60. Time-dependent density functional theory computations revealed different light-induced ionization mechanisms. Unlike in C-60, in doped fullerenes, the breaking of the cage spherical symmetry makes super atomic molecular orbital (SAMO) states optically active. Theoretical calculations suggest that the fast ionization of the SAMO states in Ho3N@C-80 is responsible for the n = 3 power law for singly charged parent molecules at intensities lower than 1.2 x 10(14) W/cm(2). Y1 - 2017 U6 - https://doi.org/10.1038/s41598-017-00124-9 SN - 2045-2322 VL - 7 PB - Nature Publ. Group CY - London ER - TY - JOUR A1 - Kegeles, Alexander A1 - Oriti, Daniele T1 - Continuous point symmetries in group field theories JF - Journal of physics : A, Mathematical and theoretical N2 - We discuss the notion of symmetries in non-local field theories characterized by integro-differential equations of motion, from a geometric perspective. We then focus on group field theory (GFT) models of quantum gravity and provide a general analysis of their continuous point symmetry transformations, including the generalized conservation laws following from them. KW - group field theory KW - quantum field theory KW - conservation laws KW - continuous symmetries Y1 - 2017 U6 - https://doi.org/10.1088/1751-8121/aa5c14 SN - 1751-8113 SN - 1751-8121 VL - 50 IS - 12 PB - IOP Publishing Ltd CY - Bristol ER - TY - JOUR A1 - Malyar, Ivan V. A1 - Gorin, Dmitry A. A1 - Santer, Svetlana A1 - Stetsyura, Svetlana V. T1 - Photo-assisted adsorption of gold nanoparticles onto a silicon substrate JF - Applied physics letters N2 - We report on a photo-assisted adsorption of gold nanoparticles on a silicon substrate studied using atomic-force microscopy and secondary ion mass-spectrometry. Depending on a silicon conductivity type (n-Si or p-Si), the amount of photo-assisted adsorbed gold nanoparticles either increases (n-Si) or decreases (p-Si) on irradiation. In addition, the impacts of a cationic polyelectrolyte monolayer and adsorption time were also revealed. The polyelectrolyte layer enhances the adsorption of the gold nanoparticles but decreases the influence of light. The results of the photo-assisted adsorption on two types of silicon wafer were explained by electron processes at the substrate/solution interface. This work was supported by the German-Russian Interdisciplinary Science Center (G-RISC) funded by the German Federal Foreign Office via the German Academic Exchange Service (DAAD), Project No. P-2014b-1, and Russian foundation for basic research, Project No. 16-08-00524_a. Y1 - 2017 U6 - https://doi.org/10.1063/1.4979082 SN - 0003-6951 SN - 1077-3118 VL - 110 PB - American Institute of Physics CY - Melville ER - TY - JOUR A1 - Juaristi, J. I. A1 - Alducin, Maite A1 - Saalfrank, Peter T1 - Femtosecond laser induced desorption of H-2, D-2, and HD from Ru(0001) BT - dynamical promotion and suppression studied with ab initio molecular dynamics with electronic friction JF - Physical review : B, Condensed matter and materials physics N2 - We perform ab initio molecular dynamics simulations to study the femtosecond laser induced desorption of H-2, D-2, and HD from a H: D-saturated Ru(0001) surface. To this aim we have extended the ab initio molecular dynamics with electronic friction (AIMDEF) scheme to include a random force that is a function of a timedependent electronic temperature. The latter characterizes the action of the ultrashort laser pulse according to a two temperature model. This allows us to perform multidimensional, hot-electron driven reaction dynamics and investigate the dependence of the desorption yields on the relative H: D isotope concentration on the surface. Our AIMDEF simulations show that the desorption process takes place in the presence of a heated adsorbate system that clearly influences the desorption dynamics. The heating of the adsorbate system is more (less) pronounced the larger is the concentration of the lighter (heavier) isotope. As a result, we conclude that the presence of H on the surface favors the desorption of molecules, whereas the presence of D hampers it, in agreement with previous experimental observations in which the phenomenon of "dynamical promotion" of a surface reaction had been postulated. Y1 - 2017 U6 - https://doi.org/10.1103/PhysRevB.95.125439 SN - 2469-9950 SN - 2469-9969 VL - 95 IS - 12 PB - American Physical Society CY - College Park ER - TY - JOUR A1 - Archambault, S. A1 - Archer, A. A1 - Benbow, W. A1 - Bird, R. A1 - Bourbeau, E. A1 - Brantseg, T. A1 - Buchovecky, M. A1 - Buckley, J. H. A1 - Bugaev, V. A1 - Byrum, K. A1 - Cerruti, M. A1 - Christiansen, J. L. A1 - Connolly, M. P. A1 - Cui, W. A1 - Daniel, M. K. A1 - Feng, Q. A1 - Finley, J. P. A1 - Fleischhack, H. A1 - Fortson, L. A1 - Furniss, A. A1 - Geringer-Sameth, A. A1 - Griffin, S. A1 - Grube, J. A1 - Hütten, M. A1 - Hakansson, N. A1 - Hanna, D. A1 - Hervet, O. A1 - Holder, J. A1 - Hughes, G. A1 - Hummensky, B. A1 - Johnson, C. A. A1 - Kaaret, P. A1 - Kar, P. A1 - Kelley-Hoskins, N. A1 - Kertzman, M. A1 - Kieda, D. A1 - Koushiappas, S. A1 - Krause, M. A1 - Krennrich, F. A1 - Lang, M. J. A1 - Lin, T. T. Y. A1 - McArthur, S. A1 - Moriarty, P. A1 - Mukherjee, R. A1 - Nieto, D. A1 - Ong, R. A. A1 - Otte, A. N. A1 - Park, N. A1 - Pohl, M. A1 - Popkow, A. A1 - Pueschel, Elisa A1 - Quinn, J. A1 - Ragan, K. A1 - Reynolds, P. T. A1 - Richards, G. T. A1 - Roache, E. A1 - Rulten, C. A1 - Sadeh, I. A1 - Santander, M. A1 - Sembroski, G. H. A1 - Shahinyan, K. A1 - Smith, A. W. A1 - Staszak, D. A1 - Telezhinsky, Igor O. A1 - Trepanier, S. A1 - Tucci, J. V. A1 - Tyler, J. A1 - Wakely, S. P. A1 - Weinstein, A. A1 - Wilcox, P. A1 - Williams, D. A. A1 - Zitzer, B. T1 - Dark matter constraints from a joint analysis of dwarf Spheroidal galaxy observations with VERITAS JF - Physical review : D, Particles, fields, gravitation, and cosmology N2 - We present constraints on the annihilation cross section of weakly interacting massive particles dark matter based on the joint statistical analysis of four dwarf galaxies with VERITAS. These results are derived from an optimized photon weighting statistical technique that improves on standard imaging atmospheric Cherenkov telescope (IACT) analyses by utilizing the spectral and spatial properties of individual photon events. We report on the results of similar to 230 hours of observations of five dwarf galaxies and the joint statistical analysis of four of the dwarf galaxies. We find no evidence of gamma-ray emission from any individual dwarf nor in the joint analysis. The derived upper limit on the dark matter annihilation cross section from the joint analysis is 1.35 x 10(-23) cm(3) s(-1) at 1 TeV for the bottom quark (b (b) over bar) final state, 2.85 x 10(-24) cm(3) s(-1) at 1 TeV for the tau lepton (tau+tau(-)) final state and 1.32 x 10-25 cm(3) s(-1) at 1 TeV for the gauge boson (gamma gamma) final state. Y1 - 2017 U6 - https://doi.org/10.1103/PhysRevD.95.082001 SN - 2470-0010 SN - 2470-0029 VL - 95 IS - 8 PB - American Physical Society CY - College Park ER - TY - JOUR A1 - Ortiz-Amezcua, Pablo A1 - Guerrero-Rascado, Juan Luis A1 - Jose Granados-Munoz, Maria A1 - Benavent-Oltra, Jose Antonio A1 - Böckmann, Christine A1 - Samaras, Stefanos A1 - Stachlewska, Iwona Sylwia A1 - Janicka, Lucja A1 - Baars, Holger A1 - Bohlmann, Stephanie A1 - Alados-Arboledas, Lucas T1 - Microphysical characterization of long-range transported biomass burning particles from North America at three EARLINET stations JF - Atmospheric Chemistry and Physics N2 - Strong events of long-range transported biomass burning aerosol were detected during July 2013 at three EARLINET (European Aerosol Research Lidar Network) stations, namely Granada (Spain), Leipzig (Germany) and Warsaw (Poland). Satellite observations from MODIS (Moderate Resolution Imaging Spectroradiometer) and CALIOP (Cloud-Aerosol Lidar with Orthogonal Polarization) instruments, as well as modeling tools such as HYSPLIT (Hybrid Single-Particle Lagrangian Integrated Trajectory) and NAAPS (Navy Aerosol Analysis and Prediction System), have been used to estimate the sources and transport paths of those North American forest fire smoke particles. A multiwavelength Raman lidar technique was applied to obtain vertically resolved particle optical properties, and further inversion of those properties with a regularization algorithm allowed for retrieving microphysical information on the studied particles. The results highlight the presence of smoke layers of 1-2 km thickness, located at about 5 km a.s.l. altitude over Granada and Leipzig and around 2.5 km a.s.l. at Warsaw. These layers were intense, as they accounted for more than 30% of the total AOD (aerosol optical depth) in all cases, and presented optical and microphysical features typical for different aging degrees: color ratio of lidar ratios (LR532/LR355) around 2, alpha-related angstrom exponents of less than 1, effective radii of 0.3 mu m and large values of single scattering albedos (SSA), nearly spectrally independent. The intensive microphysical properties were compared with columnar retrievals form co-located AERONET (Aerosol Robotic Network) stations. The intensity of the layers was also characterized in terms of particle volume concentration, and then an experimental relationship between this magnitude and the particle extinction coefficient was established. Y1 - 2017 U6 - https://doi.org/10.5194/acp-17-5931-2017 SN - 1680-7316 SN - 1680-7324 VL - 17 SP - 5931 EP - 5946 PB - Copernicus CY - Göttingen ER - TY - JOUR A1 - Jošt, Marko A1 - Albrecht, Steve A1 - Kegelmann, Lukas A1 - Wolff, Christian Michael A1 - Lang, Felix A1 - Lipovšek, Benjamin A1 - Krč, Janez A1 - Korte, Lars A1 - Neher, Dieter A1 - Rech, Bernd A1 - Topič, Marko T1 - Efficient light management by textured nanoimprinted layers for perovskite solar cells JF - ACS photonics N2 - Inorganic-organic perovskites like methylammonium-lead-iodide have proven to be an effective class of 17 materials for fabricating efficient solar cells. To improve their performance, light management techniques using textured surfaces, similar to those used in established solar cell technologies, should be considered. Here, we apply a light management foil created by UV nanoimprint lithography on the glass side of an inverted (p-i-n) perovskite solar cell with 16.3% efficiency. The obtained 1 mA cm(-2) increase in the short-circuit current density translates to a relative improvement in cell performance of 5%, which results in a power conversion efficiency of 17.1%. Optical 3D simulations based on experimentally obtained parameters were used to support the experimental findings. A good match between the simulated and experimental data was obtained, validating the model. Optical simulations reveal that the main improvement in device performance is due to a reduction in total reflection and that relative improvement in the short-circuit current density of up to 10% is possible for large-area devices. Therefore, our results present the potential of light management foils for improving the device performance of perovskite solar cells and pave the way for further use of optical simulations in the field of perovskite solar cells. KW - perovskite solar cells KW - antireflection KW - light management KW - UV nanoimprint lithography KW - optical simulations Y1 - 2017 U6 - https://doi.org/10.1021/acsphotonics.7b00138 SN - 2330-4022 VL - 4 SP - 1232 EP - 1239 PB - American Chemical Society CY - Washington ER - TY - JOUR A1 - Mardoukhi, Ahmad A1 - Mardoukhi, Yousof A1 - Hokka, Mikko A1 - Kuokkala, Veli-Tapani T1 - Effects of heat shock on the dynamic tensile behavior of granitic rocks JF - Rock mechanics and rock engineering N2 - This paper presents a new experimental method for the characterization of the surface damage caused by a heat shock on a Brazilian disk test sample. Prior to mechanical testing with a Hopkinson Split Pressure bar device, the samples were subjected to heat shock by placing a flame torch at a fixed distance from the sample’s surface for periods of 10, 30, and 60 s. The sample surfaces were studied before and after the heat shock using optical microscopy and profilometry, and the images were analyzed to quantify the damage caused by the heat shock. The complexity of the surface crack patterns was quantified using fractal dimension of the crack patterns, which were used to explain the results of the mechanical testing. Even though the heat shock also causes damage below the surface which cannot be quantified from the optical images, the presented surface crack pattern analysis can give a reasonable estimate on the drop rate of the tension strength of the rock. KW - SHPB KW - Rock KW - Granite KW - DIC KW - Dynamic loading KW - Fractal dimension Y1 - 2017 U6 - https://doi.org/10.1007/s00603-017-1168-4 SN - 0723-2632 SN - 1434-453X VL - 50 SP - 1171 EP - 1182 PB - Springer CY - Wien ER - TY - JOUR A1 - Kurzke, Henning A1 - Kiethe, Jan A1 - Heuer, Axel A1 - Jechow, Andreas T1 - Frequency doubling of incoherent light from a superluminescent diode in a periodically poled lithium niobate waveguide crystal JF - Laser physics letters N2 - The amplified spontaneous emission from a superluminescent diode was frequency doubled in a periodically poled lithium niobate waveguide crystal. The temporally incoherent radiation of such a superluminescent diode is characterized by a relatively broad spectral bandwidth and thermal-like photon statistics, as the measured degree of second order coherence, g((2))(0)= 1.9 +/- 0.1, indicates. Despite the non-optimized scenario in the spectral domain, we achieve six orders of magnitude higher conversion efficiency than previously reported with truly incoherent light. This is possible by using single spatial mode radiation and quasi phase matched material with a waveguide architecture. This work is a principle step towards efficient frequency conversion of temporally incoherent radiation in one spatial mode to access wavelengths where no radiation from superluminescent diodes is available, especially with tailored quasi phase matched crystals. The frequency doubled light might find application in imaging, metrology and quantum optics experiments. KW - nonlinear frequency conversion KW - periodically poled material KW - waveguides KW - incoherent radiation Y1 - 2017 U6 - https://doi.org/10.1088/1612-202X/aa6889 SN - 1612-2011 SN - 1612-202X VL - 14 PB - IOP Publ. CY - Bristol ER - TY - JOUR A1 - Archambault, S. A1 - Archer, A. A1 - Benbow, W. A1 - Bird, Ralph A1 - Bourbeau, E. A1 - Bouvier, A. A1 - Buchovecky, M. A1 - Bugaev, V. A1 - Cardenzana, J. V. A1 - Cerruti, M. A1 - Ciupik, L. A1 - Connolly, M. P. A1 - Cui, W. A1 - Daniel, M. K. A1 - Errando, M. A1 - Falcone, A. A1 - Feng, Q. A1 - Finley, J. P. A1 - Fleischhack, H. A1 - Fortson, L. A1 - Furniss, A. A1 - Gillanders, G. H. A1 - Griffin, S. A1 - Hanna, D. A1 - Hervet, O. A1 - Holder, J. A1 - Hughes, G. A1 - Humensky, T. B. A1 - Hutten, M. A1 - Johnson, C. A. A1 - Kaaret, P. A1 - Kar, P. A1 - Kertzman, M. A1 - Kieda, D. A1 - Krause, M. A1 - Lang, M. J. A1 - Lin, T. T. Y. A1 - Maier, G. A1 - McArthur, S. A1 - Moriarty, P. A1 - Mukherjee, R. A1 - Nieto, D. A1 - Ong, R. A. A1 - Otte, A. N. A1 - Park, N. A1 - Pohl, Martin A1 - Popkow, A. A1 - Pueschel, Elisa A1 - Quinn, J. A1 - Ragan, K. A1 - Reynolds, P. T. A1 - Richards, G. T. A1 - Roache, E. A1 - Rulten, C. A1 - Sadeh, I. A1 - Sembroski, G. H. A1 - Shahinyan, K. A1 - Staszak, D. A1 - Telezhinsky, Igor O. A1 - Trepanier, S. A1 - Wakely, S. P. A1 - Weinstein, A. A1 - Wilcox, P. A1 - Williams, D. A. A1 - Zitzer, B. T1 - Gamma-ray observations under bright moonlight with VERITAS JF - Astroparticle physics N2 - Imaging atmospheric Cherenkov telescopes (IACTs) are equipped with sensitive photomultiplier tube (PMT) cameras. Exposure to high levels of background illumination degrades the efficiency of and potentially destroys these photo-detectors over time, so IACTs cannot be operated in the same configuration in the presence of bright moonlight as under dark skies. Since September 2012, observations have been carried out with the VERITAS IACTs under bright moonlight (defined as about three times the night-sky-background (NSB) of a dark extragalactic field, typically occurring when Moon illumination > 35%) in two observing modes, firstly by reducing the voltage applied to the PMTs and, secondly, with the addition of ultra-violet (UV) bandpass filters to the cameras. This has allowed observations at up to about 30 times previous NSB levels (around 80% Moon illumination), resulting in 30% more observing time between the two modes over the course of a year. These additional observations have already allowed for the detection of a flare from the 1ES 1727 + 502 and for an observing program targeting a measurement of the cosmic-ray positron fraction. We provide details of these new observing modes and their performance relative to the standard VERITAS observations. (C) 2017 Elsevier B.V. All rights reserved. KW - Instrumentation KW - Moonlight KW - Observing methods KW - VERITAS KW - IACT Y1 - 2017 U6 - https://doi.org/10.1016/j.astropartphys.2017.03.001 SN - 0927-6505 SN - 1873-2852 VL - 91 SP - 34 EP - 43 PB - Elsevier CY - Amsterdam ER - TY - JOUR A1 - Ramos, Antonio M. T. A1 - Builes-Jaramillo, Alejandro A1 - Poveda, German A1 - Goswami, Bedartha A1 - Macau, Elbert E. N. A1 - Kurths, Jürgen A1 - Marwan, Norbert T1 - Recurrence measure of conditional dependence and applications JF - Physical review : E, Statistical, nonlinear and soft matter physics N2 - Identifying causal relations from observational data sets has posed great challenges in data-driven causality inference studies. One of the successful approaches to detect direct coupling in the information theory framework is transfer entropy. However, the core of entropy-based tools lies on the probability estimation of the underlying variables. Herewe propose a data-driven approach for causality inference that incorporates recurrence plot features into the framework of information theory. We define it as the recurrence measure of conditional dependence (RMCD), and we present some applications. The RMCD quantifies the causal dependence between two processes based on joint recurrence patterns between the past of the possible driver and present of the potentially driven, excepting the contribution of the contemporaneous past of the driven variable. Finally, it can unveil the time scale of the influence of the sea-surface temperature of the Pacific Ocean on the precipitation in the Amazonia during recent major droughts. Y1 - 2017 U6 - https://doi.org/10.1103/PhysRevE.95.052206 SN - 2470-0045 SN - 2470-0053 VL - 95 PB - American Physical Society CY - College Park ER - TY - JOUR A1 - Acero, F. A1 - Aloisio, R. A1 - Amans, J. A1 - Amato, Elena A1 - Antonelli, L. A. A1 - Aramo, C. A1 - Armstrong, T. A1 - Arqueros, F. A1 - Asano, Katsuaki A1 - Ashley, M. A1 - Backes, M. A1 - Balazs, C. A1 - Balzer, A. A1 - Bamba, Aya A1 - Barkov, Maxim A1 - Barrio, J. A. A1 - Benbow, Wystan A1 - Bernloehr, K. A1 - Beshley, V. A1 - Bigongiari, C. A1 - Biland, A. A1 - Bilinsky, A. A1 - Bissaldi, Elisabetta A1 - Biteau, J. A1 - Blanch, O. A1 - Blasi, P. A1 - Blazek, J. A1 - Boisson, C. A1 - Bonanno, G. A1 - Bonardi, A. A1 - Bonavolonta, C. A1 - Bonnoli, G. A1 - Braiding, C. A1 - Brau-Nogue, S. A1 - Bregeon, J. A1 - Brown, A. M. A1 - Bugaev, V. A1 - Bulgarelli, A. A1 - Bulik, T. A1 - Burton, Michael A1 - Burtovoi, A. A1 - Busetto, G. A1 - Bottcher, M. A1 - Cameron, R. A1 - Capalbi, M. A1 - Caproni, Anderson A1 - Caraveo, P. A1 - Carosi, R. A1 - Cascone, E. A1 - Cerruti, M. A1 - Chaty, Sylvain A1 - Chen, A. A1 - Chen, X. A1 - Chernyakova, M. A1 - Chikawa, M. A1 - Chudoba, J. A1 - Cohen-Tanugi, J. A1 - Colafrancesco, S. A1 - Conforti, V. A1 - Contreras, J. L. A1 - Costa, A. A1 - Cotter, G. A1 - Covino, Stefano A1 - Covone, G. A1 - Cumani, P. A1 - Cusumano, G. A1 - Daniel, M. A1 - Dazzi, F. A1 - De Angelis, A. A1 - De Cesare, G. A1 - De Franco, A. A1 - De Frondat, F. A1 - Dal Pino, E. M. de Gouveia A1 - De Lisio, C. A1 - Lopez, R. de los Reyes A1 - De Lotto, B. A1 - de Naurois, M. A1 - De Palma, F. A1 - Del Santo, M. A1 - Delgado, C. A1 - della Volpe, D. A1 - Di Girolamo, T. A1 - Di Giulio, C. A1 - Di Pierro, F. A1 - Di Venere, L. A1 - Doro, M. A1 - Dournaux, J. A1 - Dumas, D. A1 - Dwarkadas, Vikram V. A1 - Diaz, C. A1 - Ebr, J. A1 - Egberts, Kathrin A1 - Einecke, S. A1 - Elsaesser, D. A1 - Eschbach, S. A1 - Falceta-Goncalves, D. A1 - Fasola, G. A1 - Fedorova, E. A1 - Fernandez-Barral, A. A1 - Ferrand, Gilles A1 - Fesquet, M. A1 - Fiandrini, E. A1 - Fiasson, A. A1 - Filipovic, Miroslav D. A1 - Fioretti, V. A1 - Font, L. A1 - Fontaine, Gilles A1 - Franco, F. J. A1 - Freixas Coromina, L. A1 - Fujita, Yutaka A1 - Fukui, Y. A1 - Funk, S. A1 - Forster, A. A1 - Gadola, A. A1 - Lopez, R. Garcia A1 - Garczarczyk, M. A1 - Giglietto, N. A1 - Giordano, F. A1 - Giuliani, A. A1 - Glicenstein, J. A1 - Gnatyk, R. A1 - Goldoni, P. A1 - Grabarczyk, T. A1 - Graciani, R. A1 - Graham, J. A1 - Grandi, P. A1 - Granot, Jonathan A1 - Green, A. J. A1 - Griffiths, S. A1 - Gunji, S. A1 - Hakobyan, H. A1 - Hara, S. A1 - Hassan, T. A1 - Hayashida, M. A1 - Heller, M. A1 - Helo, J. C. A1 - Hinton, J. A1 - Hnatyk, B. A1 - Huet, J. A1 - Huetten, M. A1 - Humensky, T. B. A1 - Hussein, M. A1 - Horandel, J. A1 - Ikeno, Y. A1 - Inada, T. A1 - Inome, Y. A1 - Inoue, S. A1 - Inoue, T. A1 - Inoue, Y. A1 - Ioka, K. A1 - Iori, Maurizio A1 - Jacquemier, J. A1 - Janecek, P. A1 - Jankowsky, D. A1 - Jung, I. A1 - Kaaret, P. A1 - Katagiri, H. A1 - Kimeswenger, S. A1 - Kimura, Shigeo S. A1 - Knodlseder, J. A1 - Koch, B. A1 - Kocot, J. A1 - Kohri, K. A1 - Komin, N. A1 - Konno, Y. A1 - Kosack, K. A1 - Koyama, S. A1 - Kraus, Michaela A1 - Kubo, Hidetoshi A1 - Mezek, G. Kukec A1 - Kushida, J. A1 - La Palombara, N. A1 - Lalik, K. A1 - Lamanna, G. A1 - Landt, H. A1 - Lapington, J. A1 - Laporte, P. A1 - Lee, S. A1 - Lees, J. A1 - Lefaucheur, J. A1 - Lenain, J. -P. A1 - Leto, Giuseppe A1 - Lindfors, E. A1 - Lohse, T. A1 - Lombardi, S. A1 - Longo, F. A1 - Lopez, M. A1 - Lucarelli, F. A1 - Luque-Escamilla, Pedro Luis A1 - Lopez-Coto, R. A1 - Maccarone, M. C. A1 - Maier, G. A1 - Malaguti, G. A1 - Mandat, D. A1 - Maneva, G. A1 - Mangano, S. A1 - Marcowith, Alexandre A1 - Marti, J. A1 - Martinez, M. A1 - Martinez, G. A1 - Masuda, S. A1 - Maurin, G. A1 - Maxted, N. A1 - Melioli, Claudio A1 - Mineo, T. A1 - Mirabal, N. A1 - Mizuno, T. A1 - Moderski, R. A1 - Mohammed, M. A1 - Montaruli, T. A1 - Moralejo, A. A1 - Mori, K. A1 - Morlino, G. A1 - Morselli, A. A1 - Moulin, Emmanuel A1 - Mukherjee, R. A1 - Mundell, C. A1 - Muraishi, H. A1 - Murase, Kohta A1 - Nagataki, Shigehiro A1 - Nagayoshi, T. A1 - Naito, T. A1 - Nakajima, D. A1 - Nakamori, T. A1 - Nemmen, R. A1 - Niemiec, Jacek A1 - Nieto, D. A1 - Nievas-Rosillo, M. A1 - Nikolajuk, M. A1 - Nishijima, K. A1 - Noda, K. A1 - Nogues, L. A1 - Nosek, D. A1 - Novosyadlyj, B. A1 - Nozaki, S. A1 - Ohira, Yutaka A1 - Ohishi, M. A1 - Ohm, S. A1 - Okumura, A. A1 - Ong, R. A. A1 - Orito, R. A1 - Orlati, A. A1 - Ostrowski, M. A1 - Oya, I. A1 - Padovani, Marco A1 - Palacio, J. A1 - Palatka, M. A1 - Paredes, Josep M. A1 - Pavy, S. A1 - Persic, M. A1 - Petrucci, P. A1 - Petruk, Oleh A1 - Pisarski, A. A1 - Pohl, Martin A1 - Porcelli, A. A1 - Prandini, E. A1 - Prast, J. A1 - Principe, G. A1 - Prouza, M. A1 - Pueschel, Elisa A1 - Puelhofer, G. A1 - Quirrenbach, A. A1 - Rameez, M. A1 - Reimer, O. A1 - Renaud, M. A1 - Ribo, M. A1 - Rico, J. A1 - Rizi, V. A1 - Rodriguez, J. A1 - Fernandez, G. Rodriguez A1 - Rodriguez Vazquez, J. J. A1 - Romano, Patrizia A1 - Romeo, G. A1 - Rosado, J. A1 - Rousselle, J. A1 - Rowell, G. A1 - Rudak, B. A1 - Sadeh, I. A1 - Safi-Harb, S. A1 - Saito, T. A1 - Sakaki, N. A1 - Sanchez, D. A1 - Sangiorgi, P. A1 - Sano, H. A1 - Santander, M. A1 - Sarkar, S. A1 - Sawada, M. A1 - Schioppa, E. J. A1 - Schoorlemmer, H. A1 - Schovanek, P. A1 - Schussler, F. A1 - Sergijenko, O. A1 - Servillat, M. A1 - Shalchi, A. A1 - Shellard, R. C. A1 - Siejkowski, H. A1 - Sillanpaa, A. A1 - Simone, D. A1 - Sliusar, V. A1 - Sol, H. A1 - Stanic, S. A1 - Starling, R. A1 - Stawarz, L. A1 - Stefanik, S. A1 - Stephan, M. A1 - Stolarczyk, T. A1 - Szanecki, M. A1 - Szepieniec, T. A1 - Tagliaferri, G. A1 - Tajima, H. A1 - Takahashi, M. A1 - Takeda, J. A1 - Tanaka, M. A1 - Tanaka, S. A1 - Tejedor, L. A. A1 - Telezhinsky, Igor O. A1 - Temnikov, P. A1 - Terada, Y. A1 - Tescaro, D. A1 - Teshima, M. A1 - Testa, V. A1 - Thoudam, S. A1 - Tokanai, F. A1 - Torres, D. F. A1 - Torresi, E. A1 - Tosti, G. A1 - Townsley, C. A1 - Travnicek, P. A1 - Trichard, C. A1 - Trifoglio, M. A1 - Tsujimoto, S. A1 - Vagelli, V. A1 - Vallania, P. A1 - Valore, L. A1 - van Driel, W. A1 - van Eldik, C. A1 - Vandenbroucke, Justin A1 - Vassiliev, V. A1 - Vecchi, M. A1 - Vercellone, Stefano A1 - Vergani, S. A1 - Vigorito, C. A1 - Vorobiov, S. A1 - Vrastil, M. A1 - Vazquez Acosta, M. L. A1 - Wagner, S. J. A1 - Wagner, R. A1 - Wakely, S. P. A1 - Walter, R. A1 - Ward, J. E. A1 - Watson, J. J. A1 - Weinstein, A. A1 - White, M. A1 - White, R. A1 - Wierzcholska, A. A1 - Wilcox, P. A1 - Williams, D. A. A1 - Wischnewski, R. A1 - Wojcik, P. A1 - Yamamoto, T. A1 - Yamamoto, H. A1 - Yamazaki, Ryo A1 - Yanagita, S. A1 - Yang, L. A1 - Yoshida, T. A1 - Yoshida, M. A1 - Yoshiike, S. A1 - Yoshikoshi, T. A1 - Zacharias, M. A1 - Zampieri, L. A1 - Zanin, R. A1 - Zavrtanik, M. A1 - Zavrtanik, D. A1 - Zdziarski, A. A1 - Zech, Alraune A1 - Zechlin, Hannes A1 - Zhdanov, V. A1 - Ziegler, A. A1 - Zorn, J. T1 - Prospects for Cherenkov Telescope Array Observations of the Young Supernova Remnant RX J1713.7-3946 JF - The astrophysical journal : an international review of spectroscopy and astronomical physics N2 - We perform simulations for future Cherenkov Telescope Array (CTA) observations of RX J1713.7-3946, a young supernova remnant (SNR) and one of the brightest sources ever discovered in very high energy (VHE) gamma rays. Special attention is paid to exploring possible spatial (anti) correlations of gamma rays with emission at other wavelengths, in particular X-rays and CO/H I emission. We present a series of simulated images of RX J1713.7-3946 for CTA based on a set of observationally motivated models for the gamma-ray emission. In these models, VHE gamma rays produced by high-energy electrons are assumed to trace the nonthermal X-ray emission observed by XMM-Newton, whereas those originating from relativistic protons delineate the local gas distributions. The local atomic and molecular gas distributions are deduced by the NANTEN team from CO and H I observations. Our primary goal is to show how one can distinguish the emission mechanism(s) of the gamma rays (i.e., hadronic versus leptonic, or a mixture of the two) through information provided by their spatial distribution, spectra, and time variation. This work is the first attempt to quantitatively evaluate the capabilities of CTA to achieve various proposed scientific goals by observing this important cosmic particle accelerator. KW - cosmic rays KW - gamma rays: ISM KW - ISM: individual objects (RX J1713.7-3946, G347.3-0.5) Y1 - 2017 U6 - https://doi.org/10.3847/1538-4357/aa6d67 SN - 0004-637X SN - 1538-4357 VL - 840 IS - 2 PB - IOP Publ. Ltd. CY - Bristol ER - TY - JOUR A1 - Feudel, Fred A1 - Tuckerman, Laurette S. A1 - Zaks, Michael A1 - Hollerbach, Rainer T1 - Hysteresis of dynamos in rotating spherical shell convection JF - Physical review fluids / American Physical Society N2 - Bifurcations of dynamos in rotating and buoyancy-driven spherical Rayleigh-Benard convection in an electrically conducting fluid are investigated numerically. Both nonmagnetic and magnetic solution branches comprised of rotating waves are traced by path-following techniques, and their bifurcations and interconnections for different Ekman numbers are determined. In particular, the question of whether the dynamo branches bifurcate super- or sub-critically and whether a direct link to the primary pure convective states exists is answered. Y1 - 2017 U6 - https://doi.org/10.1103/PhysRevFluids.2.053902 SN - 2469-990X VL - 2 PB - American Physical Society CY - College Park ER - TY - JOUR A1 - Roland, Steffen A1 - Yan, Liang A1 - Zhang, Qianqian A1 - Jiao, Xuechen A1 - Hunt, Adrian A1 - Ghasemi, Masoud A1 - Ade, Harald A1 - You, Wei A1 - Neher, Dieter T1 - Charge Generation and Mobility-Limited Performance of Bulk Heterojunction Solar Cells with a Higher Adduct Fullerene JF - The journal of physical chemistry : C, Nanomaterials and interfaces N2 - Alternative electron acceptors are being actively explored in order to advance the development of bulk-heterojunction (BHJ) organic solar cells (OSCs). The indene-C-60 bisadduct (ICBA) has been regarded as a promising candidate, as it provides high open-circuit voltage in BHJ solar cells; however, the photovoltaic performance of such ICBA-based devices is often inferior when compared to cells with the omnipresent PCBM electron acceptor. Here, by pairing the high performance polymer (FTAZ) as the donor with either PCBM or ICBA as the acceptor, we explore the physical mechanism behind the reduced performance of the ICBA-based device. Time delayed collection field (TDCF) experiments reveal reduced, yet field-independent free charge generation in the FTAZ:ICBA system, explaining the overall lower photocurrent in its cells. Through the analysis of the photoluminescence, photogeneration, and electroluminescence, we find that the lower generation efficiency is neither caused by inefficient exciton splitting, nor do we find evidence for significant energy back-transfer from the CT state to singlet excitons. In fact, the increase in open circuit voltage when replacing PCBM by ICBA is entirely caused by the increase in the CT energy, related to the shift in the LUMO energy, while changes in the radiative and nonradiative recombination losses are nearly absent. On the other hand, space charge limited current (SCLC) and bias-assisted charge extraction (BACE) measurements consistently reveal a severely lower electron mobilitiy in the FTAZ:ICBA blend. Studies of the blends with resonant soft X-ray scattering (R-SoXS), grazing incident wide-angle X-ray scattering (GIWAXS), and scanning transmission X-ray microscopy (STXM) reveal very little differences in the mesoscopic morphology but significantly less nanoscale molecular ordering of the fullerene domains in the ICBA based blends, which we propose as the main cause for the lower generation efficiency and smaller electron mobility. Calculations of the JV curves with an analytical model, using measured values, show good agreement with the experimentally determined JV characteristics, proving that these devices suffer from slow carrier extraction, resulting in significant bimolecular recombination losses. Therefore, this study highlights the importance of high charge carrier mobility for newly synthesized acceptor materials, in addition to having suitable energy levels. Y1 - 2017 U6 - https://doi.org/10.1021/acs.jpcc.7b02288 SN - 1932-7447 VL - 121 SP - 10305 EP - 10316 PB - American Chemical Society CY - Washington ER - TY - JOUR A1 - Stolterfoht, Martin A1 - Wolff, Christian Michael A1 - Amir, Yohai A1 - Paulke, Andreas A1 - Perdigón-Toro, Lorena A1 - Caprioglio, Pietro A1 - Neher, Dieter T1 - Approaching the fill factor Shockley-Queisser limit in stable, dopant-free triple cation perovskite solar cells JF - Energy & Environmental Science N2 - Perovskite solar cells now compete with their inorganic counterparts in terms of power conversion efficiency, not least because of their small open-circuit voltage (V-OC) losses. A key to surpass traditional thin-film solar cells is the fill factor (FF). Therefore, more insights into the physical mechanisms that define the bias dependence of the photocurrent are urgently required. In this work, we studied charge extraction and recombination in efficient triple cation perovskite solar cells with undoped organic electron/hole transport layers (ETL/HTL). Using integral time of flight we identify the transit time through the HTL as the key figure of merit for maximizing the fill factor (FF) and efficiency. Complementarily, intensity dependent photocurrent and V-OC measurements elucidate the role of the HTL on the bias dependence of non-radiative and transport-related loss channels. We show that charge transport losses can be completely avoided under certain conditions, yielding devices with FFs of up to 84%. Optimized cells exhibit power conversion efficiencies of above 20% for 6 mm(2) sized pixels and 18.9% for a device area of 1 cm(2). These are record efficiencies for hybrid perovskite devices with dopant-free transport layers, highlighting the potential of this device technology to avoid charge-transport limitations and to approach the Shockley-Queisser limit. Y1 - 2017 U6 - https://doi.org/10.1039/c7ee00899f SN - 1754-5692 SN - 1754-5706 VL - 10 SP - 1530 EP - 1539 PB - Royal Society of Chemistry CY - Cambridge ER - TY - JOUR A1 - Benduhn, Johannes A1 - Tvingstedt, Kristofer A1 - Piersimoni, Fortunato A1 - Ullbrich, Sascha A1 - Fan, Yeli A1 - Tropiano, Manuel A1 - McGarry, Kathryn A. A1 - Zeika, Olaf A1 - Riede, Moritz K. A1 - Douglas, Christopher J. A1 - Barlow, Stephen A1 - Marder, Seth R. A1 - Neher, Dieter A1 - Spoltore, Donato A1 - Vandewal, Koen T1 - Intrinsic non-radiative voltage losses in fullerene-based organic solar cells JF - Nature Energy N2 - Organic solar cells demonstrate external quantum efficiencies and fill factors approaching those of conventional photovoltaic technologies. However, as compared with the optical gap of the absorber materials, their open-circuit voltage is much lower, largely due to the presence of significant non-radiative recombination. Here, we study a large data set of published and new material combinations and find that non-radiative voltage losses decrease with increasing charge-transfer-state energies. This observation is explained by considering non-radiative charge-transfer-state decay as electron transfer in the Marcus inverted regime, being facilitated by a common skeletal molecular vibrational mode. Our results suggest an intrinsic link between non-radiative voltage losses and electron-vibration coupling, indicating that these losses are unavoidable. Accordingly, the theoretical upper limit for the power conversion efficiency of single-junction organic solar cells would be reduced to about 25.5% and the optimal optical gap increases to (1.45-1.65) eV, that is, (0.2-0.3) eV higher than for technologies with minimized non-radiative voltage losses. Y1 - 2017 U6 - https://doi.org/10.1038/nenergy.2017.53 SN - 2058-7546 VL - 2 PB - Nature Publ. Group CY - London ER - TY - JOUR A1 - Ahnen, M. L. A1 - Ansoldi, S. A1 - Antonelli, L. A. A1 - Antoranz, P. A1 - Babic, A. A1 - Banerjee, B. A1 - Bangale, P. A1 - de Almeida, U. Barres A1 - Barrio, J. A. A1 - Gonzalez, J. Becerra A1 - Bednarek, W. A1 - Bernardini, E. A1 - Berti, A. A1 - Biasuzzi, B. A1 - Biland, A. A1 - Blanch, O. A1 - Bonnefoy, S. A1 - Bonnoli, G. A1 - Borracci, F. A1 - Bretz, T. A1 - Buson, S. A1 - Carosi, A. A1 - Chatterjee, A. A1 - Clavero, R. A1 - Colin, P. A1 - Colombo, E. A1 - Contreras, J. L. A1 - Cortina, J. A1 - Covino, S. A1 - Da Vela, P. A1 - Dazzi, F. A1 - De Angelis, A. A1 - De Lotto, B. A1 - Wilhelmi, E. de Ona A1 - Di Pierro, F. A1 - Doert, M. A1 - Dominguez, A. A1 - Prester, D. Dominis A1 - Dorner, D. A1 - Doro, M. A1 - Einecke, S. A1 - Glawion, D. Eisenacher A1 - Elsaesser, D. A1 - Engelkemeier, M. A1 - Ramazani, V. Fallah A1 - Fernandez-Barral, A. A1 - Fidalgo, D. A1 - Fonseca, M. V. A1 - Font, L. A1 - Frantzen, K. A1 - Fruck, C. A1 - Galindo, D. A1 - Lopez, R. J. Garcia A1 - Garczarczyk, M. A1 - Terrats, D. Garrido A1 - Gaug, M. A1 - Giammaria, P. A1 - Godinovic, N. A1 - Gonzalez Munoz, A. A1 - Gora, D. A1 - Guberman, D. A1 - Hadasch, D. A1 - Hahn, A. A1 - Hanabata, Y. A1 - Hayashida, M. A1 - Herrera, J. A1 - Hose, J. A1 - Hrupec, D. A1 - Hughes, G. A1 - Idec, W. A1 - Kodani, K. A1 - Konno, Y. A1 - Kubo, H. A1 - Kushida, J. A1 - La Barbera, A. A1 - Lelas, D. A1 - Lindfors, E. A1 - Lombardi, S. A1 - Longo, F. A1 - Lopez, M. A1 - Lopez-Coto, R. A1 - Majumdar, P. A1 - Makariev, M. A1 - Mallot, K. A1 - Maneva, G. A1 - Manganaro, M. A1 - Mannheim, K. A1 - Maraschi, L. A1 - Marcote, B. A1 - Mariotti, M. A1 - Martinez, M. A1 - Mazin, D. A1 - Menzel, U. A1 - Miranda, J. M. A1 - Mirzoyan, R. A1 - Moralejo, A. A1 - Moretti, E. A1 - Nakajima, D. A1 - Neustroev, V. A1 - Niedzwiecki, A. A1 - Rosillo, M. Nievas A1 - Nilsson, K. A1 - Nishijima, K. A1 - Noda, K. A1 - Nogues, L. A1 - Overkemping, A. A1 - Paiano, S. A1 - Palacio, J. A1 - Palatiello, M. A1 - Paneque, D. A1 - Paoletti, R. A1 - Paredes, J. M. A1 - Paredes-Fortuny, X. A1 - Pedaletti, G. A1 - Peresano, M. A1 - Perri, L. A1 - Persic, M. A1 - Poutanen, J. A1 - Moroni, P. G. Prada A1 - Prandini, E. A1 - Puljak, I. A1 - Reichardt, I. A1 - Rhode, W. A1 - Ribo, M. A1 - Rico, J. A1 - Rodriguez Garcia, J. A1 - Saito, T. A1 - Satalecka, K. A1 - Schroder, S. A1 - Schultz, C. A1 - Schweizer, T. A1 - Shore, S. N. A1 - Sillanpaa, A. A1 - Sitarek, J. A1 - Snidaric, I. A1 - Sobczynska, D. A1 - Stamerra, A. A1 - Steinbring, T. A1 - Strzys, M. A1 - Suric, T. A1 - Takalo, L. A1 - Tavecchio, F. A1 - Temnikov, P. A1 - Terzic, T. A1 - Tescaro, D. A1 - Teshima, M. A1 - Thaele, J. A1 - Torres, D. F. A1 - Toyama, T. A1 - Treves, A. A1 - Vanzo, G. A1 - Verguilov, V. A1 - Vovk, I. A1 - Ward, J. E. A1 - Will, M. A1 - Wu, M. H. A1 - Zanin, R. A1 - Abeysekara, A. U. A1 - Archambault, S. A1 - Archer, A. A1 - Benbow, W. A1 - Bird, R. A1 - Buchovecky, M. A1 - Buckley, J. H. A1 - Bugaev, V. A1 - Connolly, M. P. A1 - Cui, W. A1 - Dickinson, H. J. A1 - Falcone, A. A1 - Feng, Q. A1 - Finley, J. P. A1 - Fleischhack, H. A1 - Flinders, A. A1 - Fortson, L. A1 - Gillanders, G. H. A1 - Griffin, S. A1 - Grube, J. A1 - Huetten, M. A1 - Hanna, D. A1 - Holder, J. A1 - Humensky, T. B. A1 - Kaaret, P. A1 - Kar, P. A1 - Kelley-Hoskins, N. A1 - Kertzman, M. A1 - Kieda, D. A1 - Krause, M. A1 - Krennrich, F. A1 - Lang, M. J. A1 - Maier, G. A1 - McCann, A. A1 - Moriarty, P. A1 - Mukherjee, R. A1 - Nieto, D. A1 - Ong, R. A. A1 - Otte, N. A1 - Park, N. A1 - Perkins, J. A1 - Pichel, A. A1 - Pohl, M. A1 - Popkow, A. A1 - Pueschel, Elisa A1 - Quinn, J. A1 - Ragan, K. A1 - Reynolds, P. T. A1 - Richards, G. T. A1 - Roache, E. A1 - Rovero, A. C. A1 - Rulten, C. A1 - Sadeh, I. A1 - Santander, M. A1 - Sembroski, G. H. A1 - Shahinyan, K. A1 - Telezhinsky, Igor O. A1 - Tucci, J. V. A1 - Tyler, J. A1 - Wakely, S. P. A1 - Weinstein, A. A1 - Wilcox, P. A1 - Wilhelm, Alina A1 - Williams, D. A. A1 - Zitzer, B. A1 - Razzaque, S. A1 - Villata, M. A1 - Raiteri, C. M. A1 - Aller, H. D. A1 - Aller, M. F. A1 - Larionov, V. M. A1 - Arkharov, A. A. A1 - Blinov, D. A. A1 - Efimova, N. V. A1 - Grishina, T. S. A1 - Hagen-Thorn, V. A. A1 - Kopatskaya, E. N. A1 - Larionova, L. V. A1 - Larionova, E. G. A1 - Morozova, D. A. A1 - Troitsky, I. S. A1 - Ligustri, R. A1 - Calcidese, P. A1 - Berdyugin, A. A1 - Kurtanidze, O. M. A1 - Nikolashvili, M. G. A1 - Kimeridze, G. N. A1 - Sigua, L. A. A1 - Kurtanidze, S. O. A1 - Chigladze, R. A. A1 - Chen, W. P. A1 - Koptelova, E. A1 - Sakamoto, T. A1 - Sadun, A. C. A1 - Moody, J. W. A1 - Pace, C. A1 - Pearson, R. A1 - Yatsu, Y. A1 - Mori, Y. A1 - Carraminyana, A. A1 - Carrasco, L. A1 - de la Fuente, E. A1 - Norris, J. P. A1 - Smith, P. S. A1 - Wehrle, A. A1 - Gurwell, M. A. A1 - Zook, A. A1 - Pagani, C. A1 - Perri, M. A1 - Capalbi, M. A1 - Cesarini, A. A1 - Krimm, H. A. A1 - Kovalev, Y. Y. A1 - Kovalev, Yu. A. A1 - Ros, E. A1 - Pushkarev, A. B. A1 - Lister, M. L. A1 - Sokolovsky, K. V. A1 - Kadler, M. A1 - Piner, G. A1 - Lahteenmaki, A. A1 - Tornikoski, M. A1 - Angelakis, E. A1 - Krichbaum, T. P. A1 - Nestoras, I. A1 - Fuhrmann, L. A1 - Zensus, J. A. A1 - Cassaro, P. A1 - Orlati, A. A1 - Maccaferri, G. A1 - Leto, P. A1 - Giroletti, M. A1 - Richards, J. L. A1 - Max-Moerbeck, W. A1 - Readhead, A. C. S. T1 - Multiband variability studies and novel broadband SED modeling of Mrk 501 in 2009 JF - Astronomy and astrophysics : an international weekly journal N2 - Aims. We present an extensive study of the BL Lac object Mrk 501 based on a data set collected during the multi-instrument campaign spanning from 2009 March 15 to 2009 August 1, which includes, among other instruments, MAGIC, VERITAS, Whipple 10 m, and Fermi-LAT to cover the gamma-ray range from 0.1 GeV to 20 TeV; RXTE and Swift to cover wavelengths from UV to hard X-rays; and GASP-WEBT, which provides coverage of radio and optical wavelengths. Optical polarization measurements were provided for a fraction of the campaign by the Steward and St. Petersburg observatories. We evaluate the variability of the source and interband correlations, the gamma-ray flaring activity occurring in May 2009, and interpret the results within two synchrotron self-Compton (SSC) scenarios. Methods. The multiband variability observed during the full campaign is addressed in terms of the fractional variability, and the possible correlations are studied by calculating the discrete correlation function for each pair of energy bands where the significance was evaluated with dedicated Monte Carlo simulations. The space of SSC model parameters is probed following a dedicated grid-scan strategy, allowing for a wide range of models to be tested and offering a study of the degeneracy of model-to-data agreement in the individual model parameters, hence providing a less biased interpretation than the "single-curve SSC model adjustment" typically reported in the literature. Results. We find an increase in the fractional variability with energy, while no significant interband correlations of flux changes are found on the basis of the acquired data set. The SSC model grid-scan shows that the flaring activity around May 22 cannot be modeled adequately with a one-zone SSC scenario (using an electron energy distribution with two breaks), while it can be suitably described within a two (independent) zone SSC scenario. Here, one zone is responsible for the quiescent emission from the averaged 4.5-month observing period, while the other one, which is spatially separated from the first, dominates the flaring emission occurring at X-rays and very-high-energy (> 100 GeV, VHE) gamma-rays. The flaring activity from May 1, which coincides with a rotation of the electric vector polarization angle (EVPA), cannot be satisfactorily reproduced by either a one-zone or a two-independent-zone SSC model, yet this is partially affected by the lack of strictly simultaneous observations and the presence of large flux changes on sub-hour timescales (detected at VHE gamma rays). Conclusions. The higher variability in the VHE emission and lack of correlation with the X-ray emission indicate that, at least during the 4.5-month observing campaign in 2009, the highest energy (and most variable) electrons that are responsible for the VHE gamma rays do not make a dominant contribution to the similar to 1 keV emission. Alternatively, there could be a very variable component contributing to the VHE gamma-ray emission in addition to that coming from the SSC scenario. The studies with our dedicated SSC grid-scan show that there is some degeneracy in both the one-zone and the two-zone SSC scenarios probed, with several combinations of model parameters yielding a similar model-to-data agreement, and some parameters better constrained than others. The observed gamma-ray flaring activity, with the EVPA rotation coincident with the first gamma-ray flare, resembles those reported previously for low frequency peaked blazars, hence suggesting that there are many similarities in the flaring mechanisms of blazars with different jet properties. KW - BL Lacertae objects: individual: Markarian 501 KW - methods: data analysis Y1 - 2017 U6 - https://doi.org/10.1051/0004-6361/201629540 SN - 1432-0746 VL - 603 PB - EDP Sciences CY - Les Ulis ER - TY - JOUR A1 - Kiethe, Jan A1 - Heuer, Axel A1 - Jechow, Andreas T1 - Second-order coherence properties of amplified spontaneous emission from a high-power tapered superluminescent diode JF - Laser physics letters N2 - We study the degree of second-order coherence of the emission of a high-power multi-quantum well superluminescent diode with a lateral tapered amplifier section with and without optical feedback. When operated in an external cavity, the degree of second-order coherence changed from the almost thermal case of g((2))(0)approximate to 1.9 towards the mostly coherent case of g((2)) (0) approximate to 1.2 when the injection current at the tapered section was increased. We found good agreement with semi-classical laser theory near and below threshold while above laser threshold a slightly higher g((2))(0) was observed. As a free running device, the superluminescent diode yielded more than 400 mW of optical output power with good spatial beam quality of M-slow(2) < 1.6. In this case, the degree of second-order coherence dropped only slightly from 1.9 at low powers to 1.6 at the maximum output power. To our knowledge, this is the first investigation of a high-power tapered superluminescent diode concerning the degree of second-order coherence. Such a device might be useful for real-world applications probing the second order coherence function, such as ghost imaging. KW - photon statistics KW - incoherent light KW - superluminescent diodes Y1 - 2017 U6 - https://doi.org/10.1088/1612-202X/aa772c SN - 1612-2011 SN - 1612-202X VL - 14 PB - IOP Publ. Ltd. CY - Bristol ER - TY - JOUR A1 - Cooper, Ryan C. A1 - Bruno, Giovanni A1 - Wheeler, M. R. A1 - Pandey, A. A1 - Watkins, T. R. A1 - Shyarn, A. T1 - Effect of microcracking on the uniaxial tensile response of beta-eucryptite ceramics BT - Experiments and constitutive model JF - Acta Materialia N2 - A constitutive model for the nonlinear or "pseudoplastic" mechanical behavior in a linear-elastic solid with thermally induced microcracks is developed and applied to experimental results. The model is termed strain dependent microcrack density approximation (SDMDA) and is an extension of the modified differential scheme that describes the slope of the stress-strain curves of microcracked solids. SDMDA allows a continuous variation in the microcrack density with tensile loading. Experimental uniaxial tensile response of beta-eucryptite glass and ceramics with controlled levels of microcracking is reported. It is demonstrated that SDMDA can well describe the extent of non-linearity in the experimental uniaxial tensile response of beta-eucryptite with varying levels of microcracking. The advantages of the SDMDA are discussed in regard to tensile loading. KW - behavior Y1 - 2017 U6 - https://doi.org/10.1016/j.actamat.2017.06.033 SN - 1359-6454 SN - 1873-2453 VL - 135 SP - 361 EP - 371 PB - Elsevier CY - Oxford ER -