@article{JoštAlbrechtKegelmannetal.2017,
  author    = {Jošt, Marko and Albrecht, Steve and Kegelmann, Lukas and Wolff, Christian Michael and Lang, Felix and Lipovšek, Benjamin and Krč, Janez and Korte, Lars and Neher, Dieter and Rech, Bernd and Topič, Marko},
  title     = {Efficient light management by textured nanoimprinted layers for perovskite solar cells},
  series = {ACS photonics},
  volume    = {4},
  journal   = {ACS photonics},
  publisher = {American Chemical Society},
  address   = {Washington},
  issn      = {2330-4022},
  doi       = {10.1021/acsphotonics.7b00138},
  pages     = {1232 -- 1239},
  year      = {2017},
  abstract  = {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.},
  language  = {en}
}
@article{MardoukhiMardoukhiHokkaetal.2017,
  author    = {Mardoukhi, Ahmad and Mardoukhi, Yousof and Hokka, Mikko and Kuokkala, Veli-Tapani},
  title     = {Effects of heat shock on the dynamic tensile behavior of granitic rocks},
  series = {Rock mechanics and rock engineering},
  volume    = {50},
  journal   = {Rock mechanics and rock engineering},
  publisher = {Springer},
  address   = {Wien},
  issn      = {0723-2632},
  doi       = {10.1007/s00603-017-1168-4},
  pages     = {1171 -- 1182},
  year      = {2017},
  abstract  = {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.},
  language  = {en}
}
@article{KurzkeKietheHeueretal.2017,
  author    = {Kurzke, Henning and Kiethe, Jan and Heuer, Axel and Jechow, Andreas},
  title     = {Frequency doubling of incoherent light from a superluminescent diode in a periodically poled lithium niobate waveguide crystal},
  series = {Laser physics letters},
  volume    = {14},
  journal   = {Laser physics letters},
  publisher = {IOP Publ.},
  address   = {Bristol},
  issn      = {1612-2011},
  doi       = {10.1088/1612-202X/aa6889},
  pages     = {5},
  year      = {2017},
  abstract  = {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.},
  language  = {en}
}
@article{ArchambaultArcherBenbowetal.2017,
  author    = {Archambault, S. and Archer, A. and Benbow, W. and Bird, Ralph and Bourbeau, E. and Bouvier, A. and Buchovecky, M. and Bugaev, V. and Cardenzana, J. V. and Cerruti, M. and Ciupik, L. and Connolly, M. P. and Cui, W. and Daniel, M. K. and Errando, M. and Falcone, A. and Feng, Q. and Finley, J. P. and Fleischhack, H. and Fortson, L. and Furniss, A. and Gillanders, G. H. and Griffin, S. and Hanna, D. and Hervet, O. and Holder, J. and Hughes, G. and Humensky, T. B. and Hutten, M. and Johnson, C. A. and Kaaret, P. and Kar, P. and Kertzman, M. and Kieda, D. and Krause, M. and Lang, M. J. and Lin, T. T. Y. and Maier, G. and McArthur, S. and Moriarty, P. and Mukherjee, R. and Nieto, D. and Ong, R. A. and Otte, A. N. and Park, N. and Pohl, Martin and Popkow, A. and Pueschel, Elisa and Quinn, J. and Ragan, K. and Reynolds, P. T. and Richards, G. T. and Roache, E. and Rulten, C. and Sadeh, I. and Sembroski, G. H. and Shahinyan, K. and Staszak, D. and Telezhinsky, Igor O. and Trepanier, S. and Wakely, S. P. and Weinstein, A. and Wilcox, P. and Williams, D. A. and Zitzer, B.},
  title     = {Gamma-ray observations under bright moonlight with VERITAS},
  series = {Astroparticle physics},
  volume    = {91},
  journal   = {Astroparticle physics},
  publisher = {Elsevier},
  address   = {Amsterdam},
  issn      = {0927-6505},
  doi       = {10.1016/j.astropartphys.2017.03.001},
  pages     = {34 -- 43},
  year      = {2017},
  abstract  = {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.},
  language  = {en}
}
@article{RamosBuilesJaramilloPovedaetal.2017,
  author    = {Ramos, Antonio M. T. and Builes-Jaramillo, Alejandro and Poveda, German and Goswami, Bedartha and Macau, Elbert E. N. and Kurths, J{\"u}rgen and Marwan, Norbert},
  title     = {Recurrence measure of conditional dependence and applications},
  series = {Physical review : E, Statistical, nonlinear and soft matter physics},
  volume    = {95},
  journal   = {Physical review : E, Statistical, nonlinear and soft matter physics},
  publisher = {American Physical Society},
  address   = {College Park},
  issn      = {2470-0045},
  doi       = {10.1103/PhysRevE.95.052206},
  pages     = {8},
  year      = {2017},
  abstract  = {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.},
  language  = {en}
}
@article{AceroAloisioAmansetal.2017,
  author    = {Acero, F. and Aloisio, R. and Amans, J. and Amato, Elena and Antonelli, L. A. and Aramo, C. and Armstrong, T. and Arqueros, F. and Asano, Katsuaki and Ashley, M. and Backes, M. and Balazs, C. and Balzer, A. and Bamba, Aya and Barkov, Maxim and Barrio, J. A. and Benbow, Wystan and Bernloehr, K. and Beshley, V. and Bigongiari, C. and Biland, A. and Bilinsky, A. and Bissaldi, Elisabetta and Biteau, J. and Blanch, O. and Blasi, P. and Blazek, J. and Boisson, C. and Bonanno, G. and Bonardi, A. and Bonavolonta, C. and Bonnoli, G. and Braiding, C. and Brau-Nogue, S. and Bregeon, J. and Brown, A. M. and Bugaev, V. and Bulgarelli, A. and Bulik, T. and Burton, Michael and Burtovoi, A. and Busetto, G. and Bottcher, M. and Cameron, R. and Capalbi, M. and Caproni, Anderson and Caraveo, P. and Carosi, R. and Cascone, E. and Cerruti, M. and Chaty, Sylvain and Chen, A. and Chen, X. and Chernyakova, M. and Chikawa, M. and Chudoba, J. and Cohen-Tanugi, J. and Colafrancesco, S. and Conforti, V. and Contreras, J. L. and Costa, A. and Cotter, G. and Covino, Stefano and Covone, G. and Cumani, P. and Cusumano, G. and Daniel, M. and Dazzi, F. and De Angelis, A. and De Cesare, G. and De Franco, A. and De Frondat, F. and Dal Pino, E. M. de Gouveia and De Lisio, C. and Lopez, R. de los Reyes and De Lotto, B. and de Naurois, M. and De Palma, F. and Del Santo, M. and Delgado, C. and della Volpe, D. and Di Girolamo, T. and Di Giulio, C. and Di Pierro, F. and Di Venere, L. and Doro, M. and Dournaux, J. and Dumas, D. and Dwarkadas, Vikram V. and Diaz, C. and Ebr, J. and Egberts, Kathrin and Einecke, S. and Elsaesser, D. and Eschbach, S. and Falceta-Goncalves, D. and Fasola, G. and Fedorova, E. and Fernandez-Barral, A. and Ferrand, Gilles and Fesquet, M. and Fiandrini, E. and Fiasson, A. and Filipovic, Miroslav D. and Fioretti, V. and Font, L. and Fontaine, Gilles and Franco, F. J. and Freixas Coromina, L. and Fujita, Yutaka and Fukui, Y. and Funk, S. and Forster, A. and Gadola, A. and Lopez, R. Garcia and Garczarczyk, M. and Giglietto, N. and Giordano, F. and Giuliani, A. and Glicenstein, J. and Gnatyk, R. and Goldoni, P. and Grabarczyk, T. and Graciani, R. and Graham, J. and Grandi, P. and Granot, Jonathan and Green, A. J. and Griffiths, S. and Gunji, S. and Hakobyan, H. and Hara, S. and Hassan, T. and Hayashida, M. and Heller, M. and Helo, J. C. and Hinton, J. and Hnatyk, B. and Huet, J. and Huetten, M. and Humensky, T. B. and Hussein, M. and Horandel, J. and Ikeno, Y. and Inada, T. and Inome, Y. and Inoue, S. and Inoue, T. and Inoue, Y. and Ioka, K. and Iori, Maurizio and Jacquemier, J. and Janecek, P. and Jankowsky, D. and Jung, I. and Kaaret, P. and Katagiri, H. and Kimeswenger, S. and Kimura, Shigeo S. and Knodlseder, J. and Koch, B. and Kocot, J. and Kohri, K. and Komin, N. and Konno, Y. and Kosack, K. and Koyama, S. and Kraus, Michaela and Kubo, Hidetoshi and Mezek, G. Kukec and Kushida, J. and La Palombara, N. and Lalik, K. and Lamanna, G. and Landt, H. and Lapington, J. and Laporte, P. and Lee, S. and Lees, J. and Lefaucheur, J. and Lenain, J. -P. and Leto, Giuseppe and Lindfors, E. and Lohse, T. and Lombardi, S. and Longo, F. and Lopez, M. and Lucarelli, F. and Luque-Escamilla, Pedro Luis and Lopez-Coto, R. and Maccarone, M. C. and Maier, G. and Malaguti, G. and Mandat, D. and Maneva, G. and Mangano, S. and Marcowith, Alexandre and Marti, J. and Martinez, M. and Martinez, G. and Masuda, S. and Maurin, G. and Maxted, N. and Melioli, Claudio and Mineo, T. and Mirabal, N. and Mizuno, T. and Moderski, R. and Mohammed, M. and Montaruli, T. and Moralejo, A. and Mori, K. and Morlino, G. and Morselli, A. and Moulin, Emmanuel and Mukherjee, R. and Mundell, C. and Muraishi, H. and Murase, Kohta and Nagataki, Shigehiro and Nagayoshi, T. and Naito, T. and Nakajima, D. and Nakamori, T. and Nemmen, R. and Niemiec, Jacek and Nieto, D. and Nievas-Rosillo, M. and Nikolajuk, M. and Nishijima, K. and Noda, K. and Nogues, L. and Nosek, D. and Novosyadlyj, B. and Nozaki, S. and Ohira, Yutaka and Ohishi, M. and Ohm, S. and Okumura, A. and Ong, R. A. and Orito, R. and Orlati, A. and Ostrowski, M. and Oya, I. and Padovani, Marco and Palacio, J. and Palatka, M. and Paredes, Josep M. and Pavy, S. and Persic, M. and Petrucci, P. and Petruk, Oleh and Pisarski, A. and Pohl, Martin and Porcelli, A. and Prandini, E. and Prast, J. and Principe, G. and Prouza, M. and Pueschel, Elisa and Puelhofer, G. and Quirrenbach, A. and Rameez, M. and Reimer, O. and Renaud, M. and Ribo, M. and Rico, J. and Rizi, V. and Rodriguez, J. and Fernandez, G. Rodriguez and Rodriguez Vazquez, J. J. and Romano, Patrizia and Romeo, G. and Rosado, J. and Rousselle, J. and Rowell, G. and Rudak, B. and Sadeh, I. and Safi-Harb, S. and Saito, T. and Sakaki, N. and Sanchez, D. and Sangiorgi, P. and Sano, H. and Santander, M. and Sarkar, S. and Sawada, M. and Schioppa, E. J. and Schoorlemmer, H. and Schovanek, P. and Schussler, F. and Sergijenko, O. and Servillat, M. and Shalchi, A. and Shellard, R. C. and Siejkowski, H. and Sillanpaa, A. and Simone, D. and Sliusar, V. and Sol, H. and Stanic, S. and Starling, R. and Stawarz, L. and Stefanik, S. and Stephan, M. and Stolarczyk, T. and Szanecki, M. and Szepieniec, T. and Tagliaferri, G. and Tajima, H. and Takahashi, M. and Takeda, J. and Tanaka, M. and Tanaka, S. and Tejedor, L. A. and Telezhinsky, Igor O. and Temnikov, P. and Terada, Y. and Tescaro, D. and Teshima, M. and Testa, V. and Thoudam, S. and Tokanai, F. and Torres, D. F. and Torresi, E. and Tosti, G. and Townsley, C. and Travnicek, P. and Trichard, C. and Trifoglio, M. and Tsujimoto, S. and Vagelli, V. and Vallania, P. and Valore, L. and van Driel, W. and van Eldik, C. and Vandenbroucke, Justin and Vassiliev, V. and Vecchi, M. and Vercellone, Stefano and Vergani, S. and Vigorito, C. and Vorobiov, S. and Vrastil, M. and Vazquez Acosta, M. L. and Wagner, S. J. and Wagner, R. and Wakely, S. P. and Walter, R. and Ward, J. E. and Watson, J. J. and Weinstein, A. and White, M. and White, R. and Wierzcholska, A. and Wilcox, P. and Williams, D. A. and Wischnewski, R. and Wojcik, P. and Yamamoto, T. and Yamamoto, H. and Yamazaki, Ryo and Yanagita, S. and Yang, L. and Yoshida, T. and Yoshida, M. and Yoshiike, S. and Yoshikoshi, T. and Zacharias, M. and Zampieri, L. and Zanin, R. and Zavrtanik, M. and Zavrtanik, D. and Zdziarski, A. and Zech, Alraune and Zechlin, Hannes and Zhdanov, V. and Ziegler, A. and Zorn, J.},
  title     = {Prospects for Cherenkov Telescope Array Observations of the Young Supernova Remnant RX J1713.7-3946},
  series = {The astrophysical journal : an international review of spectroscopy and astronomical physics},
  volume    = {840},
  journal   = {The astrophysical journal : an international review of spectroscopy and astronomical physics},
  number    = {2},
  publisher = {IOP Publ. Ltd.},
  address   = {Bristol},
  issn      = {0004-637X},
  doi       = {10.3847/1538-4357/aa6d67},
  pages     = {14},
  year      = {2017},
  abstract  = {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.},
  language  = {en}
}
@article{FeudelTuckermanZaksetal.2017,
  author    = {Feudel, Fred and Tuckerman, Laurette S. and Zaks, Michael and Hollerbach, Rainer},
  title     = {Hysteresis of dynamos in rotating spherical shell convection},
  series = {Physical review fluids / American Physical Society},
  volume    = {2},
  journal   = {Physical review fluids / American Physical Society},
  publisher = {American Physical Society},
  address   = {College Park},
  issn      = {2469-990X},
  doi       = {10.1103/PhysRevFluids.2.053902},
  pages     = {11},
  year      = {2017},
  abstract  = {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.},
  language  = {en}
}
@article{RolandYanZhangetal.2017,
  author    = {Roland, Steffen and Yan, Liang and Zhang, Qianqian and Jiao, Xuechen and Hunt, Adrian and Ghasemi, Masoud and Ade, Harald and You, Wei and Neher, Dieter},
  title     = {Charge Generation and Mobility-Limited Performance of Bulk Heterojunction Solar Cells with a Higher Adduct Fullerene},
  series = {The journal of physical chemistry : C, Nanomaterials and interfaces},
  volume    = {121},
  journal   = {The journal of physical chemistry : C, Nanomaterials and interfaces},
  publisher = {American Chemical Society},
  address   = {Washington},
  issn      = {1932-7447},
  doi       = {10.1021/acs.jpcc.7b02288},
  pages     = {10305 -- 10316},
  year      = {2017},
  abstract  = {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.},
  language  = {en}
}
@article{StolterfohtWolffAmiretal.2017,
  author    = {Stolterfoht, Martin and Wolff, Christian Michael and Amir, Yohai and Paulke, Andreas and Perdig{\´o}n-Toro, Lorena and Caprioglio, Pietro and Neher, Dieter},
  title     = {Approaching the fill factor Shockley-Queisser limit in stable, dopant-free triple cation perovskite solar cells},
  series = {Energy \& Environmental Science},
  volume    = {10},
  journal   = {Energy \& Environmental Science},
  publisher = {Royal Society of Chemistry},
  address   = {Cambridge},
  issn      = {1754-5692},
  doi       = {10.1039/c7ee00899f},
  pages     = {1530 -- 1539},
  year      = {2017},
  abstract  = {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.},
  language  = {en}
}
@article{BenduhnTvingstedtPiersimonietal.2017,
  author    = {Benduhn, Johannes and Tvingstedt, Kristofer and Piersimoni, Fortunato and Ullbrich, Sascha and Fan, Yeli and Tropiano, Manuel and McGarry, Kathryn A. and Zeika, Olaf and Riede, Moritz K. and Douglas, Christopher J. and Barlow, Stephen and Marder, Seth R. and Neher, Dieter and Spoltore, Donato and Vandewal, Koen},
  title     = {Intrinsic non-radiative voltage losses in fullerene-based organic solar cells},
  series = {Nature Energy},
  volume    = {2},
  journal   = {Nature Energy},
  publisher = {Nature Publ. Group},
  address   = {London},
  issn      = {2058-7546},
  doi       = {10.1038/nenergy.2017.53},
  pages     = {6},
  year      = {2017},
  abstract  = {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.},
  language  = {en}
}
@article{AhnenAnsoldiAntonellietal.2017,
  author    = {Ahnen, M. L. and Ansoldi, S. and Antonelli, L. A. and Antoranz, P. and Babic, A. and Banerjee, B. and Bangale, P. and de Almeida, U. Barres and Barrio, J. A. and Gonzalez, J. Becerra and Bednarek, W. and Bernardini, E. and Berti, A. and Biasuzzi, B. and Biland, A. and Blanch, O. and Bonnefoy, S. and Bonnoli, G. and Borracci, F. and Bretz, T. and Buson, S. and Carosi, A. and Chatterjee, A. and Clavero, R. and Colin, P. and Colombo, E. and Contreras, J. L. and Cortina, J. and Covino, S. and Da Vela, P. and Dazzi, F. and De Angelis, A. and De Lotto, B. and Wilhelmi, E. de Ona and Di Pierro, F. and Doert, M. and Dominguez, A. and Prester, D. Dominis and Dorner, D. and Doro, M. and Einecke, S. and Glawion, D. Eisenacher and Elsaesser, D. and Engelkemeier, M. and Ramazani, V. Fallah and Fernandez-Barral, A. and Fidalgo, D. and Fonseca, M. V. and Font, L. and Frantzen, K. and Fruck, C. and Galindo, D. and Lopez, R. J. Garcia and Garczarczyk, M. and Terrats, D. Garrido and Gaug, M. and Giammaria, P. and Godinovic, N. and Gonzalez Munoz, A. and Gora, D. and Guberman, D. and Hadasch, D. and Hahn, A. and Hanabata, Y. and Hayashida, M. and Herrera, J. and Hose, J. and Hrupec, D. and Hughes, G. and Idec, W. and Kodani, K. and Konno, Y. and Kubo, H. and Kushida, J. and La Barbera, A. and Lelas, D. and Lindfors, E. and Lombardi, S. and Longo, F. and Lopez, M. and Lopez-Coto, R. and Majumdar, P. and Makariev, M. and Mallot, K. and Maneva, G. and Manganaro, M. and Mannheim, K. and Maraschi, L. and Marcote, B. and Mariotti, M. and Martinez, M. and Mazin, D. and Menzel, U. and Miranda, J. M. and Mirzoyan, R. and Moralejo, A. and Moretti, E. and Nakajima, D. and Neustroev, V. and Niedzwiecki, A. and Rosillo, M. Nievas and Nilsson, K. and Nishijima, K. and Noda, K. and Nogues, L. and Overkemping, A. and Paiano, S. and Palacio, J. and Palatiello, M. and Paneque, D. and Paoletti, R. and Paredes, J. M. and Paredes-Fortuny, X. and Pedaletti, G. and Peresano, M. and Perri, L. and Persic, M. and Poutanen, J. and Moroni, P. G. Prada and Prandini, E. and Puljak, I. and Reichardt, I. and Rhode, W. and Ribo, M. and Rico, J. and Rodriguez Garcia, J. and Saito, T. and Satalecka, K. and Schroder, S. and Schultz, C. and Schweizer, T. and Shore, S. N. and Sillanpaa, A. and Sitarek, J. and Snidaric, I. and Sobczynska, D. and Stamerra, A. and Steinbring, T. and Strzys, M. and Suric, T. and Takalo, L. and Tavecchio, F. and Temnikov, P. and Terzic, T. and Tescaro, D. and Teshima, M. and Thaele, J. and Torres, D. F. and Toyama, T. and Treves, A. and Vanzo, G. and Verguilov, V. and Vovk, I. and Ward, J. E. and Will, M. and Wu, M. H. and Zanin, R. and Abeysekara, A. U. and Archambault, S. and Archer, A. and Benbow, W. and Bird, R. and Buchovecky, M. and Buckley, J. H. and Bugaev, V. and Connolly, M. P. and Cui, W. and Dickinson, H. J. and Falcone, A. and Feng, Q. and Finley, J. P. and Fleischhack, H. and Flinders, A. and Fortson, L. and Gillanders, G. H. and Griffin, S. and Grube, J. and Huetten, M. and Hanna, D. and Holder, J. and Humensky, T. B. and Kaaret, P. and Kar, P. and Kelley-Hoskins, N. and Kertzman, M. and Kieda, D. and Krause, M. and Krennrich, F. and Lang, M. J. and Maier, G. and McCann, A. and Moriarty, P. and Mukherjee, R. and Nieto, D. and Ong, R. A. and Otte, N. and Park, N. and Perkins, J. and Pichel, A. and Pohl, M. and Popkow, A. and Pueschel, Elisa and Quinn, J. and Ragan, K. and Reynolds, P. T. and Richards, G. T. and Roache, E. and Rovero, A. C. and Rulten, C. and Sadeh, I. and Santander, M. and Sembroski, G. H. and Shahinyan, K. and Telezhinsky, Igor O. and Tucci, J. V. and Tyler, J. and Wakely, S. P. and Weinstein, A. and Wilcox, P. and Wilhelm, Alina and Williams, D. A. and Zitzer, B. and Razzaque, S. and Villata, M. and Raiteri, C. M. and Aller, H. D. and Aller, M. F. and Larionov, V. M. and Arkharov, A. A. and Blinov, D. A. and Efimova, N. V. and Grishina, T. S. and Hagen-Thorn, V. A. and Kopatskaya, E. N. and Larionova, L. V. and Larionova, E. G. and Morozova, D. A. and Troitsky, I. S. and Ligustri, R. and Calcidese, P. and Berdyugin, A. and Kurtanidze, O. M. and Nikolashvili, M. G. and Kimeridze, G. N. and Sigua, L. A. and Kurtanidze, S. O. and Chigladze, R. A. and Chen, W. P. and Koptelova, E. and Sakamoto, T. and Sadun, A. C. and Moody, J. W. and Pace, C. and Pearson, R. and Yatsu, Y. and Mori, Y. and Carraminyana, A. and Carrasco, L. and de la Fuente, E. and Norris, J. P. and Smith, P. S. and Wehrle, A. and Gurwell, M. A. and Zook, A. and Pagani, C. and Perri, M. and Capalbi, M. and Cesarini, A. and Krimm, H. A. and Kovalev, Y. Y. and Kovalev, Yu. A. and Ros, E. and Pushkarev, A. B. and Lister, M. L. and Sokolovsky, K. V. and Kadler, M. and Piner, G. and Lahteenmaki, A. and Tornikoski, M. and Angelakis, E. and Krichbaum, T. P. and Nestoras, I. and Fuhrmann, L. and Zensus, J. A. and Cassaro, P. and Orlati, A. and Maccaferri, G. and Leto, P. and Giroletti, M. and Richards, J. L. and Max-Moerbeck, W. and Readhead, A. C. S.},
  title     = {Multiband variability studies and novel broadband SED modeling of Mrk 501 in 2009},
  series = {Astronomy and astrophysics : an international weekly journal},
  volume    = {603},
  journal   = {Astronomy and astrophysics : an international weekly journal},
  publisher = {EDP Sciences},
  address   = {Les Ulis},
  organization    = {MAGIC Collaboration;VERITAS Collaboration},
  issn      = {1432-0746},
  doi       = {10.1051/0004-6361/201629540},
  pages     = {30},
  year      = {2017},
  abstract  = {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.},
  language  = {en}
}
@article{KietheHeuerJechow2017,
  author    = {Kiethe, Jan and Heuer, Axel and Jechow, Andreas},
  title     = {Second-order coherence properties of amplified spontaneous emission from a high-power tapered superluminescent diode},
  series = {Laser physics letters},
  volume    = {14},
  journal   = {Laser physics letters},
  publisher = {IOP Publ. Ltd.},
  address   = {Bristol},
  issn      = {1612-2011},
  doi       = {10.1088/1612-202X/aa772c},
  pages     = {4},
  year      = {2017},
  abstract  = {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.},
  language  = {en}
}
@article{CooperBrunoWheeleretal.2017,
  author    = {Cooper, Ryan C. and Bruno, Giovanni and Wheeler, M. R. and Pandey, A. and Watkins, T. R. and Shyarn, A.},
  title     = {Effect of microcracking on the uniaxial tensile response of beta-eucryptite ceramics},
  series = {Acta Materialia},
  volume    = {135},
  journal   = {Acta Materialia},
  publisher = {Elsevier},
  address   = {Oxford},
  issn      = {1359-6454},
  doi       = {10.1016/j.actamat.2017.06.033},
  pages     = {361 -- 371},
  year      = {2017},
  abstract  = {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.},
  language  = {en}
}
@article{KrivenkovGoliasMarchenkoetal.2017,
  author    = {Krivenkov, Maxim and Golias, Evangelos and Marchenko, Dmitry and Sanchez-Barriga, Jaime and Bihlmayer, Gustav and Rader, Oliver and Varykhalov, Andrei},
  title     = {Nanostructural origin of giant Rashba effect in intercalated graphene},
  series = {2D Materials},
  volume    = {4},
  journal   = {2D Materials},
  number    = {3},
  publisher = {IOP Publ. Ltd.},
  address   = {Bristol},
  issn      = {2053-1583},
  doi       = {10.1088/2053-1583/aa7ad8},
  pages     = {11},
  year      = {2017},
  abstract  = {To enhance the spin-orbit interaction in graphene by a proximity effect without compromising the quasi-free-standing dispersion of the Dirac cones means balancing the opposing demands for strong and weak graphene-substrate interaction. So far, only the intercalation of Au under graphene/Ni(111) has proven successful, which was unexpected since graphene prefers a large separation (similar to 3.3 angstrom) from a Au monolayer in equilibrium. Here, we investigate this system and find the solution in a nanoscale effect. We reveal that the Au largely intercalates as nanoclusters. Our density functional theory calculations show that the graphene is periodically stapled to the Ni substrate, and this attraction presses graphene and Au nanoclusters together. This, in turn, causes a Rashba effect of the giant magnitude observed in experiment. Our findings show that nanopatterning of the substrate can be efficiently used for engineering of spin-orbit effects in graphene.},
  language  = {en}
}
@article{HeydariPastorizaSantosLizMarzanetal.2017,
  author    = {Heydari, Esmaeil and Pastoriza-Santos, Isabel and Liz-Marzan, Luis M. and Stumpe, Joachim},
  title     = {Nanoplasmonically-engineered random lasing in organic semiconductor thin films},
  series = {Nanoscale horizons},
  volume    = {2},
  journal   = {Nanoscale horizons},
  publisher = {Royal Society of Chemistry},
  address   = {Cambridge},
  issn      = {2055-6756},
  doi       = {10.1039/c7nh00054e},
  pages     = {261 -- 266},
  year      = {2017},
  abstract  = {We demonstrate plasmonically nano-engineered coherent random lasing and stimulated emission enhancement in a hybrid gainmedium of organic semiconductors doped with core-shell plasmonic nanoparticles. The gain medium is composed of a 300 +/- 2 nm thin waveguide of an organic semiconductor, doped with 53 nm gold nanoparticle cores, isolated within silica shells. Upon loading the nanoparticles, the threshold of amplified spontaneous emission is reduced from 1.75 mu J cm(-2) x 10(2) for an undoped gain medium, to 0.35 mu J cm(-2) x 10(2) for a highly concentrated gain medium, and lasing spikes narrower than 0.1 nm are obtained. Most importantly, selection of silica shells with thicknesses of 10, 17 and 21 nm enables engineering of the plasmon-exciton energy coupling and consequently tuning of the laser slope efficiency. With this approach, the slope efficiency is increased by two times by decreasing the silica shell from 21 nm down to 10 nm, due to the enhancement of the localized electric field.},
  language  = {en}
}
@misc{GeigerFrielerLevermann2017,
  author    = {Geiger, Tobias and Frieler, Katja and Levermann, Anders},
  title     = {Reply to Comment on: High-income does not protect against hurricane losses (Environmental research letters. - 12 (2017))},
  series = {Environmental research letters},
  volume    = {12},
  journal   = {Environmental research letters},
  publisher = {IOP Publ. Ltd.},
  address   = {Bristol},
  issn      = {1748-9326},
  doi       = {10.1088/1748-9326/aa88d6},
  pages     = {2},
  year      = {2017},
  abstract  = {Recently a multitude of empirically derived damage models have been applied to project future tropical cyclone (TC) losses for the United States. In their study (Geiger et al 2016 Environ. Res. Lett. 11 084012) compared two approaches that differ in the scaling of losses with socio-economic drivers: the commonly-used approach resulting in a sub-linear scaling of historical TC losses with a nation's affected gross domestic product (GDP), and the disentangled approach that shows a sub-linear increase with affected population and a super-linear scaling of relative losses with per capita income. Statistics cannot determine which approach is preferable but since process understanding demands that there is a dependence of the loss on both GDP per capita and population, an approach that accounts for both separately is preferable to one which assumes a specific relation between the two dependencies. In the accompanying comment, Rybski et al argued that there is no rigorous evidence to reach the conclusion that high-income does not protect against hurricane losses. Here we affirm that our conclusion is drawn correctly and reply to further remarks raised in the comment, highlighting the adequateness of our approach but also the potential for future extension of our research.},
  language  = {en}
}
@article{FangMaLietal.2017,
  author    = {Fang, Peng and Ma, Xingchen and Li, Xiangxin and Qiu, Xunlin and Gerhard, Reimund and Zhang, Xiaoqing and Li, Guanglin},
  title     = {Fabrication, Structure Characterization, and Performance Testing of Piezoelectret-Film Sensors for Recording Body Motion},
  series = {IEEE Sensors Journal},
  volume    = {18},
  journal   = {IEEE Sensors Journal},
  number    = {1},
  publisher = {Inst. of Electr. and Electronics Engineers},
  address   = {Piscataway},
  issn      = {1530-437X},
  doi       = {10.1109/JSEN.2017.2766663},
  pages     = {401 -- 412},
  year      = {2017},
  abstract  = {During muscle contractions, radial-force distributions are generated on muscle surfaces due to muscle-volume changes, from which the corresponding body motions can be recorded by means of so-called force myography (FMG). Piezo- or ferroelectrets are flexible piezoelectric materials with attractive materials and sensing properties. In addition to several other applications, they are suitable for detecting force variations by means of wearable devices. In this paper, we prepared piezoelectrets from cellular polypropylene films by optimizing the fabrication procedures, and developed an FMG-recording system based on piezoelectret sensors. Different hand and wrist movements were successfully detected on able-bodied subjects with the FMG system. The FMG patterns were evaluated and identified by means of linear discriminant analysis and artificial neural network algorithms, and average motion-classification accuracies of 96.1\% and 94.8\%, respectively, were obtained. This paper demonstrates the feasibility of using piezoelectret-film sensors for FMG and may thus lead to alternative methods for detecting body motion and to related applications, e.g., in biomedical engineering or structural-health monitoring.},
  language  = {en}
}
@article{DzhanoevSokolov2017,
  author    = {Dzhanoev, Arsen R. and Sokolov, Igor M.},
  title     = {The effect of the junction model on the anomalous diffusion in the 3D comb structure},
  series = {Chaos, solitons \& fractals : applications in science and engineering ; an interdisciplinary journal of nonlinear science},
  volume    = {106},
  journal   = {Chaos, solitons \& fractals : applications in science and engineering ; an interdisciplinary journal of nonlinear science},
  publisher = {Elsevier},
  address   = {Oxford},
  issn      = {0960-0779},
  doi       = {10.1016/j.chaos.2017.12.001},
  pages     = {330 -- 336},
  year      = {2017},
  abstract  = {The diffusion in the comb structures is a popular model of geometrically induced anomalous diffusion. In the present work we concentrate on the diffusion along the backbone in a system where sidebranches are planes, and the diffusion thereon is anomalous and described by continuous time random walks (CTRW). We show that the mean squared displacement (MSD) in the backbone of the comb behaves differently depending on whether the waiting time periods in the sidebranches are reset after the step in the backbone is done (a rejuvenating junction model), or not (a non-rejuvenating junction model). In the rejuvenating case the subdiffusion in the sidebranches only changes the prefactor in the ultra-slow (logarithmic) diffusion along the backbone, while in the non-rejuvenating case the ultraslow, logarithmic subdiffusion is changed to a much faster power-law subdiffusion (with a logarithmic correction) as it was found earlier by Iomin and Mendez [25]. Moreover, in the first case the result does not change if the diffusion in the backbone is itself anomalous, while in the second case it does. Two of the special cases of the considered models (the non-rejuvenating junction under normal diffusion in the backbone, and rejuvenating junction for the same waiting time distribution in the sidebranches and in junction points) were also investigated within the approach based on the corresponding generalized Fokker-Planck equations. (c) 2017 Elsevier Ltd. All rights reserved.},
  language  = {en}
}
@article{RamachandranHainichHamannetal.2017,
  author    = {Ramachandran, Varsha and Hainich, Rainer and Hamann, Wolf-Rainer and Oskinova, Lidia M. and Shenar, T. and Sander, Andreas Alexander Christoph and Todt, Helge Tobias and Gallagher, John S.},
  title     = {Stellar population of the superbubble N206 in the LMC I. Analysis of the Of-type stars},
  series = {Astronomy and astrophysics : an international weekly journal},
  volume    = {609},
  journal   = {Astronomy and astrophysics : an international weekly journal},
  publisher = {EDP Sciences},
  address   = {Les Ulis},
  issn      = {1432-0746},
  doi       = {10.1051/0004-6361/201731093},
  pages     = {26},
  year      = {2017},
  abstract  = {Context. Massive stars severely influence their environment by their strong ionizing radiation and by the momentum and kinetic energy input provided by their stellar winds and supernovae. Quantitative analyses of massive stars are required to understand how their feedback creates and shapes large scale structures of the interstellar medium. The giant H II region N206 in the Large Magellanic Cloud contains an OB association that powers a superbubble filled with hot X-ray emitting gas, serving as an ideal laboratory in this context. Aims. We aim to estimate stellar and wind parameters of all OB stars in N206 by means of quantitative spectroscopic analyses. In this first paper, we focus on the nine Of-type stars located in this region. We determine their ionizing flux and wind mechanical energy. The analysis of nitrogen abundances in our sample probes rotational mixing. Methods. We obtained optical spectra with the multi-object spectrograph FLAMES at the ESO-VLT. When possible, the optical spectroscopy was complemented by UV spectra from the HST, IUE, and FUSE archives. Detailed spectral classifications are presented for our sample Of-type stars. For the quantitative spectroscopic analysis we used the Potsdam Wolf-Rayet model atmosphere code. We determined the physical parameters and nitrogen abundances of our sample stars by fitting synthetic spectra to the observations. Results. The stellar and wind parameters of nine Of-type stars, which are largely derived from spectral analysis are used to construct wind momentum luminosity relationship. We find that our sample follows a relation close to the theoretical prediction, assuming clumped winds. The most massive star in the N206 association is an Of supergiant that has a very high mass-loss rate. Two objects in our sample reveal composite spectra, showing that the Of primaries have companions of late O subtype. All stars in our sample have an evolutionary age of less than 4 million yr, with the O2-type star being the youngest. All these stars show a systematic discrepancy between evolutionary and spectroscopic masses. All stars in our sample are nitrogen enriched. Nitrogen enrichment shows a clear correlation with increasing projected rotational velocities. Conclusions. The mechanical energy input from the Of stars alone is comparable to the energy stored in the N206 superbubble as measured from the observed X-ray and H alpha emission.},
  language  = {en}
}
@article{ShenarOskinovaJaervinenetal.2017,
  author    = {Shenar, Tomer and Oskinova, Lidia M. and Jaervinen, S. P. and Luckas, P. and Hainich, Rainer and Todt, Helge Tobias and Hubrig, Swetlana and Sander, Andreas Alexander Christoph and Ilyin, Ilya and Hamann, Wolf-Rainer},
  title     = {Constraining the weak-wind problem},
  series = {Contributions Of The Astronomical Observatory Skalnate Pleso},
  volume    = {48},
  journal   = {Contributions Of The Astronomical Observatory Skalnate Pleso},
  number    = {1},
  publisher = {Astronomick{\´y} {\´U}stav SAV},
  address   = {Tatransk{\´a} Lomnica},
  issn      = {1335-1842},
  doi       = {10.1051/0004-6361/201731291},
  pages     = {139 -- 143},
  year      = {2017},
  abstract  = {Mass-loss rates of massive, late type main sequence stars are much weaker than currently predicted, but their true values are very difficult to measure. We suggest that confined stellar winds of magnetic stars can be exploited to constrain the true mass-loss rates M of massive main sequence stars. We acquired UV, X-ray, and optical amateur data of HD 54879 (09.7 V), one of a few O-type stars with a detected atmospheric magnetic field (B-d greater than or similar to 2 kG). We analyze these data with the Potsdam Wolf-Rayet (PoWR) and XSPEC codes. We can roughly estimate the mass-loss rate the star would have in the absence of a magnetic field as log M-B=0 approximate to -9.0 M-circle dot yr(-1). Since the wind is partially trapped within the Alfven radius rA greater than or similar to 12 R-*,, the true mass-loss rate of HD 54879 is log M less than or similar to -10.2 M-circle dot yr(-1). Moreover, we find that the microturbulent, macroturbulent, and projected rotational velocities are lower than previously suggested (< 4 km s(-1)). An initial mass of 16 M-circle dot and an age of 5 Myr are inferred. We derive a mean X-ray emitting temperature of log T-x = 6.7 K and an X-ray luminosity of log L-x = 32 erg s(-1). The latter implies a significant X-ray excess (log L-x/L-Bol approximate to - 6.0), most likely stemming from collisions at the magnetic equator. A tentative period of P approximate to 5 yr is derived from variability of the Ha line. Our study confirms that strongly magnetized stars lose little or no mass, and supplies important constraints on the weak-wind problem of massive main sequence stars.},
  language  = {en}
}