TY - JOUR A1 - Liebig, Ferenc A1 - Sarhan, Radwan Mohamed A1 - Prietzel, Claudia Christina A1 - Reinecke, Antje A1 - Koetz, Joachim T1 - "Green" gold nanotriangles: synthesis, purification by polyelectrolyte/micelle depletion flocculation and performance in surface-enhanced Raman scattering JF - RSC Advances N2 - The aim of this study was to develop a one-step synthesis of gold nanotriangles (NTs) in the presence of mixed phospholipid vesicles followed by a separation process to isolate purified NTs. Negatively charged vesicles containing AOT and phospholipids, in the absence and presence of additional reducing agents (polyampholytes, polyanions or low molecular weight compounds), were used as a template phase to form anisotropic gold nanoparticles. Upon addition of the gold chloride solution, the nucleation process is initiated and both types of particles, i.e., isotropic spherical and anisotropic gold nanotriangles, are formed simultaneously. As it was not possible to produce monodisperse nanotriangles with such a one-step procedure, the anisotropic nanoparticles needed to be separated from the spherical ones. Therefore, a new type of separation procedure using combined polyelectrolyte/micelle depletion flocculation was successfully applied. As a result of the different purification steps, a green colored aqueous dispersion was obtained containing highly purified, well-defined negatively charged flat nanocrystals with a platelet thickness of 10 nm and an edge length of about 175 nm. The NTs produce promising results in surface-enhanced Raman scattering. Y1 - 2016 U6 - https://doi.org/10.1039/c6ra04808k SN - 2046-2069 VL - 6 SP - 33561 EP - 33568 PB - Royal Society of Chemistry CY - Cambridge ER - TY - JOUR A1 - Yadavalli, Nataraja Sekhar A1 - Loebner, Sarah A1 - Papke, Thomas A1 - Sava, Elena A1 - Hurduc, Nicolae A1 - Santer, Svetlana T1 - A comparative study of photoinduced deformation in azobenzene containing polymer films JF - Soft matter N2 - In this paper two groups supporting different views on the mechanism of light induced polymer deformation argue about the respective underlying theoretical conceptions, in order to bring this interesting debate to the attention of the scientific community. The group of Prof. Nicolae Hurduc supports the model claiming that the cyclic isomerization of azobenzenes may cause an athermal transition of the glassy azobenzene containing polymer into a fluid state, the so-called photo-fluidization concept. This concept is quite convenient for an intuitive understanding of the deformation process as an anisotropic flow of the polymer material. The group of Prof. Svetlana Santer supports the re-orientational model where the mass-transport of the polymer material accomplished during polymer deformation is stated to be generated by the light-induced re-orientation of the azobenzene side chains and as a consequence of the polymer backbone that in turn results in local mechanical stress, which is enough to irreversibly deform an azobenzene containing material even in the glassy state. For the debate we chose three polymers differing in the glass transition temperature, 32 degrees C, 87 degrees C and 95 degrees C, representing extreme cases of flexible and rigid materials. Polymer film deformation occurring during irradiation with different interference patterns is recorded using a homemade set-up combining an optical part for the generation of interference patterns and an atomic force microscope for acquiring the kinetics of film deformation. We also demonstrated the unique behaviour of azobenzene containing polymeric films to switch the topography in situ and reversibly by changing the irradiation conditions. We discuss the results of reversible deformation of three polymers induced by irradiation with intensity (IIP) and polarization (PIP) interference patterns, and the light of homogeneous intensity in terms of two approaches: the re-orientational and the photo-fluidization concepts. Both agree in that the formation of opto-mechanically induced stresses is a necessary prerequisite for the process of deformation. Using this argument, the deformation process can be characterized either as a flow or mass transport. Y1 - 2016 U6 - https://doi.org/10.1039/c6sm00029k SN - 1744-683X SN - 1744-6848 VL - 12 SP - 2593 EP - 2603 PB - Royal Society of Chemistry CY - Cambridge ER - TY - JOUR A1 - Clusella, Pau A1 - Politi, Antonio A1 - Rosenblum, Michael T1 - A minimal model of self-consistent partial synchrony JF - NEW JOURNAL OF PHYSICS N2 - We show that self-consistent partial synchrony in globally coupled oscillatory ensembles is a general phenomenon. We analyze in detail appearance and stability properties of this state in possibly the simplest setup of a biharmonic Kuramoto-Daido phase model as well as demonstrate the effect in limit-cycle relaxational Rayleigh oscillators. Such a regime extends the notion of splay state from a uniform distribution of phases to an oscillating one. Suitable collective observables such as the Kuramoto order parameter allow detecting the presence of an inhomogeneous distribution. The characteristic and most peculiar property of self-consistent partial synchrony is the difference between the frequency of single units and that of the macroscopic field. KW - synchronization KW - collective dynamics KW - coupled oscillators Y1 - 2016 U6 - https://doi.org/10.1088/1367-2630/18/9/093037 SN - 1367-2630 VL - 18 PB - IOP Publ. Ltd. CY - Bristol ER - TY - JOUR A1 - Neher, Dieter A1 - Kniepert, Juliane A1 - Elimelech, Arik A1 - Koster, L. Jan Anton T1 - A New Figure of Merit for Organic Solar Cells with Transport-limited Photocurrents JF - Scientific reports N2 - Compared to their inorganic counterparts, organic semiconductors suffer from relatively low charge carrier mobilities. Therefore, expressions derived for inorganic solar cells to correlate characteristic performance parameters to material properties are prone to fail when applied to organic devices. This is especially true for the classical Shockley-equation commonly used to describe current-voltage (JV)-curves, as it assumes a high electrical conductivity of the charge transporting material. Here, an analytical expression for the JV-curves of organic solar cells is derived based on a previously published analytical model. This expression, bearing a similar functional dependence as the Shockley-equation, delivers a new figure of merit a to express the balance between free charge recombination and extraction in low mobility photoactive materials. This figure of merit is shown to determine critical device parameters such as the apparent series resistance and the fill factor. Y1 - 2016 U6 - https://doi.org/10.1038/srep24861 SN - 2045-2322 VL - 6 SP - E2348 EP - E2349 PB - Nature Publ. Group CY - London ER - TY - JOUR A1 - Neher, Dieter A1 - Kniepert, Juliane A1 - Elimelech, Arik A1 - Koster, L. Jan Anton T1 - A New Figure of Merit for Organic Solar Cells with Transport-limited Photocurrents JF - Scientific reports N2 - Compared to their inorganic counterparts, organic semiconductors suffer from relatively low charge carrier mobilities. Therefore, expressions derived for inorganic solar cells to correlate characteristic performance parameters to material properties are prone to fail when applied to organic devices. This is especially true for the classical Shockley-equation commonly used to describe current-voltage (JV)-curves, as it assumes a high electrical conductivity of the charge transporting material. Here, an analytical expression for the JV-curves of organic solar cells is derived based on a previously published analytical model. This expression, bearing a similar functional dependence as the Shockley-equation, delivers a new figure of merit α to express the balance between free charge recombination and extraction in low mobility photoactive materials. This figure of merit is shown to determine critical device parameters such as the apparent series resistance and the fill factor. KW - Electronic and spintronic devices KW - Semiconductors Y1 - 2016 U6 - https://doi.org/10.1038/srep24861 SN - 2045-2322 VL - 6 PB - Nature Publishing Group CY - London ER - TY - GEN A1 - Neher, Dieter A1 - Kniepert, Juliane A1 - Elimelech, Arik A1 - Koster, L. Jan Anton T1 - A New Figure of Merit for Organic Solar Cells with Transport-limited Photocurrents N2 - Compared to their inorganic counterparts, organic semiconductors suffer from relatively low charge carrier mobilities. Therefore, expressions derived for inorganic solar cells to correlate characteristic performance parameters to material properties are prone to fail when applied to organic devices. This is especially true for the classical Shockley-equation commonly used to describe current-voltage (JV)-curves, as it assumes a high electrical conductivity of the charge transporting material. Here, an analytical expression for the JV-curves of organic solar cells is derived based on a previously published analytical model. This expression, bearing a similar functional dependence as the Shockley-equation, delivers a new figure of merit α to express the balance between free charge recombination and extraction in low mobility photoactive materials. This figure of merit is shown to determine critical device parameters such as the apparent series resistance and the fill factor. T3 - Zweitveröffentlichungen der Universität Potsdam : Mathematisch-Naturwissenschaftliche Reihe - 225 KW - Electronic and spintronic devices KW - Semiconductors Y1 - 2016 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus4-91414 ER - TY - THES A1 - Marx, Robert T1 - A quantitative model of spatial correlations in parametric down conversion for investigating complementarity at a double slit Y1 - 2016 ER - TY - JOUR A1 - Abeysekara, A. U. A1 - Archambault, S. A1 - Archer, A. A1 - Benbow, W. A1 - Bird, R. A1 - Buchovecky, M. A1 - Buckley, J. H. A1 - Byrum, K. A1 - Cardenzana, J. V. A1 - Cerruti, M. A1 - Chen, Xuhui A1 - Christiansen, J. L. A1 - Ciupik, L. A1 - Cui, W. A1 - Dickinson, H. J. A1 - Eisch, J. D. A1 - Errando, M. A1 - Falcone, A. A1 - Fegan, D. J. A1 - Feng, Q. A1 - Finley, J. P. A1 - Fleischhack, H. A1 - Fortin, P. A1 - Fortson, L. A1 - Furniss, A. A1 - Gillanders, G. H. A1 - Griffin, S. A1 - Grube, J. A1 - Gyuk, G. A1 - Huetten, M. A1 - Hakansson, Nils A1 - Hanna, D. A1 - Holder, J. A1 - Humensky, T. B. A1 - Johnson, C. A. A1 - Kaaret, P. A1 - Kar, P. A1 - Kelley-Hoskins, N. A1 - Kertzman, M. A1 - Kieda, D. A1 - Krause, M. A1 - Krennrich, F. A1 - Kumar, S. A1 - Lang, M. J. A1 - Lin, T. T. Y. A1 - Maier, G. A1 - McArthur, S. A1 - McCann, A. A1 - Meagher, K. A1 - Moriarty, P. A1 - Mukherjee, R. A1 - Nieto, D. A1 - Ong, R. A. A1 - Otte, A. N. A1 - Park, N. A1 - Perkins, J. S. A1 - Petrashyk, A. A1 - Pohl, Martin A1 - Popkow, A. A1 - Pueschel, Elisa A1 - Quinn, J. A1 - Ragan, K. A1 - Ratliff, G. A1 - Reynolds, P. T. A1 - Richards, G. T. A1 - Roache, E. 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 - Vincent, S. A1 - Wakely, S. P. A1 - Weiner, O. M. A1 - Weinstein, A. A1 - Williams, D. A. A1 - Zitzer, B. T1 - A SEARCH FOR BRIEF OPTICAL FLASHES ASSOCIATED WITH THE SETI TARGET KIC 8462852 JF - The astrophysical journal : an international review of spectroscopy and astronomical physics ; Part 2, Letters N2 - The F-type star KIC. 8462852 has recently been identified as an exceptional target for search for extraterrestrial intelligence (SETI) observations. We describe an analysis methodology for optical SETI, which we have used to analyze nine hours of serendipitous archival observations of KIC. 8462852 made with the VERITAS gamma-ray observatory between 2009 and 2015. No evidence of pulsed optical beacons, above a pulse intensity at the Earth of approximately 1 photon m(-2), is found. We also discuss the potential use of imaging atmospheric Cherenkov telescope arrays in searching for extremely short duration optical transients in general. KW - astrobiology KW - extraterrestrial intelligence KW - methods: observational KW - stars: individual ( KIC 8462852) KW - techniques: photometric Y1 - 2016 U6 - https://doi.org/10.3847/2041-8205/818/2/L33 SN - 2041-8205 SN - 2041-8213 VL - 818 PB - IOP Publ. Ltd. CY - Bristol ER - TY - JOUR A1 - Aliu, E. A1 - Archambault, S. A1 - Archer, A. A1 - Benbow, W. A1 - Bird, R. A1 - Biteau, Jonathan A1 - Buchovecky, M. A1 - Buckley, J. H. A1 - Bugaev, V. A1 - Byrum, K. A1 - Cardenzana, J. V. A1 - Cerruti, M. A1 - Chen, Xuhui A1 - Ciupik, L. A1 - Connolly, M. P. A1 - Cui, W. A1 - Dickinson, H. J. A1 - Eisch, J. D. A1 - Falcone, A. A1 - Feng, Q. A1 - Finley, J. P. A1 - Fleischhack, H. A1 - Flinders, A. A1 - Fortin, P. A1 - Fortson, L. A1 - Furniss, A. A1 - Gillanders, G. H. A1 - Griffin, S. A1 - Grube, J. A1 - Gyuk, G. A1 - Huetten, M. A1 - Hakansson, Nils A1 - Holder, J. A1 - Humensky, T. B. A1 - Johnson, C. A. A1 - Kaaret, P. A1 - Kar, P. A1 - Kelley-Hoskins, N. A1 - Kertzman, M. A1 - Kieda, D. A1 - Krause, M. A1 - Lang, M. J. A1 - Loo, A. 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 - Pandel, D. A1 - Park, N. A1 - Pelassa, V. A1 - Petrashyk, 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 - Rulten, C. A1 - Santander, M. A1 - Sembroski, G. H. A1 - Shahinyan, K. A1 - Smith, A. W. A1 - Staszak, D. A1 - Telezhinsky, Igor O. A1 - Tucci, J. V. A1 - Tyler, J. A1 - Varlotta, A. A1 - Vincent, S. A1 - Wakely, S. P. A1 - Weiner, O. M. A1 - Weinstein, A. A1 - Wilhelm, Alina A1 - Williams, D. A. A1 - Zitzer, B. A1 - Chernyakova, M. A1 - Roberts, M. S. E. T1 - A SEARCH FOR VERY HIGH ENERGY GAMMA RAYS FROM THE MISSING LINK BINARY PULSAR J1023+0038 WITH VERITAS JF - The astrophysical journal : an international review of spectroscopy and astronomical physics N2 - The binary millisecond radio pulsar PSR J1023+0038 exhibits many characteristics similar to the gamma-ray binary system PSR B1259-63/LS 2883, making it an ideal candidate for the study of high-energy nonthermal emission. It has been the subject of multiwavelength campaigns following the disappearance of the pulsed radio emission in 2013 June, which revealed the appearance of an accretion disk around the neutron star. We present the results of very high energy (VHE) gamma-ray observations carried out by the Very Energetic Radiation Imaging Telescope Array System before and after this change of state. Searches for steady and pulsed emission of both data sets yield no significant gamma-ray signal above 100 GeV, and upper limits are given for both a steady and pulsed gamma-ray flux. These upper limits are used to constrain the magnetic field strength in the shock region of the PSR J1023+0038 system. Assuming that VHE gamma rays are produced via an inverse Compton mechanism in the shock region, we constrain the shock magnetic field to be greater than similar to 2 G before the disappearance of the radio pulsar and greater than similar to 10 G afterward. KW - binaries: general KW - gamma rays: general KW - pulsars: general KW - pulsars: individual (PSR J1023+0038) Y1 - 2016 U6 - https://doi.org/10.3847/0004-637X/831/2/193 SN - 0004-637X SN - 1538-4357 VL - 831 PB - IOP Publ. Ltd. CY - Bristol ER - TY - JOUR A1 - Levermann, Anders A1 - Winkelmann, Ricarda T1 - A simple equation for the melt elevation feedback of ice sheets JF - The Cryosphere : TC ; an interactive open access journal of the European Geosciences Union N2 - In recent decades, the Greenland Ice Sheet has been losing mass and has thereby contributed to global sea-level rise. The rate of ice loss is highly relevant for coastal protection worldwide. The ice loss is likely to increase under future warming. Beyond a critical temperature threshold, a meltdown of the Greenland Ice Sheet is induced by the self-enforcing feedback between its lowering surface elevation and its increasing surface mass loss: the more ice that is lost, the lower the ice surface and the warmer the surface air temperature, which fosters further melting and ice loss. The computation of this rate so far relies on complex numerical models which are the appropriate tools for capturing the complexity of the problem. By contrast we aim here at gaining a conceptual understanding by deriving a purposefully simple equation for the self-enforcing feedback which is then used to estimate the melt time for different levels of warming using three observable characteristics of the ice sheet itself and its surroundings. The analysis is purely conceptual in nature. It is missing important processes like ice dynamics for it to be useful for applications to sea-level rise on centennial timescales, but if the volume loss is dominated by the feedback, the resulting logarithmic equation unifies existing numerical simulations and shows that the melt time depends strongly on the level of warming with a critical slow-down near the threshold: the median time to lose 10% of the present-day ice volume varies between about 3500 years for a temperature level of 0.5 degrees C above the threshold and 500 years for 5 degrees C. Unless future observations show a significantly higher melting sensitivity than currently observed, a complete meltdown is unlikely within the next 2000 years without significant ice-dynamical contributions. Y1 - 2016 U6 - https://doi.org/10.5194/tc-10-1799-2016 SN - 1994-0416 SN - 1994-0424 VL - 10 SP - 1799 EP - 1807 PB - Copernicus CY - Göttingen ER - TY - JOUR A1 - Schwarzl, Maria A1 - Godec, Aljaz A1 - Oshanin, Gleb A1 - Metzler, Ralf T1 - A single predator charging a herd of prey: effects of self volume and predator-prey decision-making JF - Journal of physics : A, Mathematical and theoretical N2 - We study the degree of success of a single predator hunting a herd of prey on a two-dimensional square lattice landscape. We explicitly consider the self volume of the prey restraining their dynamics on the lattice. The movement of both predator and prey is chosen to include an intelligent, decision making step based on their respective sighting ranges, the radius in which they can detect the other species (prey cannot recognise each other besides the self volume interaction): after spotting each other the motion of prey and predator turns from a nearest neighbour random walk into directed escape or chase, respectively. We consider a large range of prey densities and sighting ranges and compute the mean first passage time for a predator to catch a prey as well as characterise the effective dynamics of the hunted prey. We find that the prey's sighting range dominates their life expectancy and the predator profits more from a bad eyesight of the prey than from his own good eye sight. We characterise the dynamics in terms of the mean distance between the predator and the nearest prey. It turns out that effectively the dynamics of this distance coordinate can be captured in terms of a simple Ornstein–Uhlenbeck picture. Reducing the many-body problem to a simple two-body problem by imagining predator and nearest prey to be connected by an effective Hookean bond, all features of the model such as prey density and sighting ranges merge into the effective binding constant. KW - first passage process KW - diffusion KW - predator-prey model Y1 - 2016 U6 - https://doi.org/10.1088/1751-8113/49/22/225601 SN - 1751-8113 SN - 1751-8121 VL - 49 PB - IOP Publ. Ltd. CY - Bristol ER - TY - GEN A1 - Levermann, Anders A1 - Petoukhov, Vladimir A1 - Schewe, Jacob A1 - Schellnhuber, Hans Joachim T1 - Abrupt monsoon transitions as seen in paleorecords can be explained by moisture-advection feedback T2 - Proceedings of the National Academy of Sciences of the United States of America Y1 - 2016 U6 - https://doi.org/10.1073/pnas.1603130113 SN - 0027-8424 VL - 113 SP - E2348 EP - E2349 PB - National Acad. of Sciences CY - Washington ER - TY - JOUR A1 - Abramowski, Attila A1 - Aharonian, Felix A. A1 - Benkhali, Faical Ait A1 - Akhperjanian, A. G. A1 - Angüner, Ekrem Oǧuzhan A1 - Backes, Michael A1 - Balzer, Arnim A1 - Becherini, Yvonne A1 - Tjus, J. Becker A1 - Berge, David A1 - Bernhard, Sabrina A1 - Bernlöhr, K. A1 - Birsin, E. A1 - Blackwell, R. A1 - Boettcher, Markus A1 - Boisson, Catherine A1 - Bolmont, J. A1 - Bordas, Pol A1 - Bregeon, Johan A1 - Brun, Francois A1 - Brun, Pierre A1 - Bryan, Mark A1 - Bulik, Tomasz A1 - Carr, John A1 - Casanova, Sabrina A1 - Chakraborty, N. A1 - Chalme-Calvet, R. A1 - Chaves, Ryan C. G. A1 - Chen, Andrew A1 - Chretien, M. A1 - Colafrancesco, Sergio A1 - Cologna, Gabriele A1 - Conrad, Jan A1 - Couturier, C. A1 - Cui, Y. A1 - Davids, I. D. A1 - Degrange, B. A1 - Deil, C. A1 - deWilt, P. A1 - Djannati-Ata, A. A1 - Domainko, W. A1 - Donath, A. A1 - Dubus, G. A1 - Dutson, K. A1 - Dyks, J. A1 - Dyrda, M. A1 - Edwards, T. A1 - Egberts, Kathrin A1 - Eger, P. A1 - Ernenwein, J-P. A1 - Espigat, P. A1 - Farnier, C. A1 - Fegan, S. A1 - Feinstein, F. A1 - Fernandes, M. V. A1 - Fernandez, D. A1 - Fiasson, A. A1 - Fontaine, G. A1 - Foerster, A. 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 - Grudzinska, M. A1 - Hadasch, D. A1 - Haeffner, S. A1 - Hahn, J. A1 - Hawkes, J. A1 - Heinzelmann, G. A1 - Henri, G. A1 - Hermann, G. A1 - Hervet, O. A1 - Hillert, A. A1 - Hinton, James Anthony A1 - Hofmann, W. A1 - Hofverberg, P. A1 - Hoischen, Clemens A1 - Holler, M. A1 - Horns, D. A1 - Ivascenko, A. A1 - Jacholkowska, A. A1 - Jamrozy, M. A1 - Janiak, M. A1 - Jankowsky, F. A1 - Jung-Richardt, I. A1 - Kastendieck, M. A. A1 - Katarzynski, K. A1 - Katz, U. A1 - Kerszberg, D. A1 - Khelifi, B. A1 - Kieffer, M. A1 - Klepser, S. A1 - Klochkov, D. A1 - Kluzniak, W. A1 - Kolitzus, D. A1 - Komin, Nu. A1 - Kosack, K. A1 - Krakau, S. A1 - Krayzel, F. A1 - Krueger, P. P. A1 - Laffon, H. A1 - Lamanna, G. A1 - Lau, J. A1 - Lefaucheur, J. A1 - Lefranc, V. A1 - Lemiere, A. A1 - Lemoine-Goumard, M. A1 - Lenain, J-P. A1 - Lohse, T. A1 - Lopatin, A. A1 - Lu, C-C. A1 - Lui, R. 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 - Menzler, U. A1 - Meyer, M. A1 - Mitchell, A. M. W. A1 - Moderski, R. A1 - Mohamed, M. A1 - Mora, K. A1 - Moulin, Emmanuel A1 - Murach, T. A1 - de Naurois, M. A1 - Niemiec, J. A1 - Oakes, L. A1 - Odaka, H. A1 - Oettl, S. A1 - Ohm, S. A1 - Opitz, B. A1 - Ostrowski, M. A1 - Oya, I. A1 - Panter, M. A1 - Parsons, R. D. A1 - Arribas, M. Paz A1 - Pekeur, N. W. A1 - Pelletier, G. A1 - Petrucci, P-O. A1 - Peyaud, B. A1 - Pita, S. A1 - Poon, H. A1 - Prokoph, H. A1 - Puehlhofer, G. A1 - Punch, M. A1 - Quirrenbach, A. A1 - Raab, S. A1 - Reichardt, I. 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, David M. A1 - Santangelo, A. A1 - Sasaki, M. A1 - Schlickeiser, R. A1 - Schuessler, F. A1 - Schulz, A. A1 - Schwanke, U. A1 - Schwemmer, S. A1 - Seyffert, A. S. A1 - Simoni, R. A1 - Sol, H. A1 - Spanier, F. A1 - Spengler, G. A1 - Spies, F. A1 - Stawarz, L. A1 - Steenkamp, R. A1 - Stegmann, Christian A1 - Stinzing, F. A1 - Stycz, K. A1 - Sushch, Iurii A1 - Tavernet, J-P. A1 - Tavernier, T. A1 - Taylor, A. M. A1 - Terrier, R. A1 - Tluczykont, M. A1 - Trichard, C. A1 - Tuffs, R. A1 - Valerius, K. A1 - van der Walt, J. A1 - van Eldik, 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 - Wagner, S. J. A1 - Wagner, P. A1 - Wagner, R. M. A1 - Weidinger, M. A1 - Weitzel, Q. 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 - Zywucka, N. T1 - Acceleration of petaelectronvolt protons in the Galactic Centre JF - Nature : the international weekly journal of science N2 - Galactic cosmic rays reach energies of at least a few petaelectronvolts (of the order of 1015 electronvolts). This implies that our Galaxy contains petaelectronvolt accelerators (‘PeVatrons’), but all proposed models of Galactic cosmic-ray accelerators encounter difficulties at exactly these energies. Dozens of Galactic accelerators capable of accelerating particles to energies of tens of teraelectronvolts (of the order of 1013 electronvolts) were inferred from recent γ-ray observations3. However, none of the currently known accelerators—not even the handful of shell-type supernova remnants commonly believed to supply most Galactic cosmic rays—has shown the characteristic tracers of petaelectronvolt particles, namely, power-law spectra of γ-rays extending without a cut-off or a spectral break to tens of teraelectronvolts4. Here we report deep γ-ray observations with arcminute angular resolution of the region surrounding the Galactic Centre, which show the expected tracer of the presence of petaelectronvolt protons within the central 10 parsecs of the Galaxy. We propose that the supermassive black hole Sagittarius A* is linked to this PeVatron. Sagittarius A* went through active phases in the past, as demonstrated by X-ray outbursts5and an outflow from the Galactic Centre6. Although its current rate of particle acceleration is not sufficient to provide a substantial contribution to Galactic cosmic rays, Sagittarius A* could have plausibly been more active over the last 106–107 years, and therefore should be considered as a viable alternative to supernova remnants as a source of petaelectronvolt Galactic cosmic rays. Y1 - 2016 U6 - https://doi.org/10.1038/nature17147 SN - 0028-0836 SN - 1476-4687 VL - 531 SP - 476 EP - + PB - Nature Publ. Group CY - London ER - TY - JOUR A1 - Godec, Aljaz A1 - Metzler, Ralf T1 - Active transport improves the precision of linear long distance molecular signalling JF - Journal of physics : A, Mathematical and theoretical N2 - Molecular signalling in living cells occurs at low copy numbers and is thereby inherently limited by the noise imposed by thermal diffusion. The precision at which biochemical receptors can count signalling molecules is intimately related to the noise correlation time. In addition to passive thermal diffusion, messenger RNA and vesicle-engulfed signalling molecules can transiently bind to molecular motors and are actively transported across biological cells. Active transport is most beneficial when trafficking occurs over large distances, for instance up to the order of 1 metre in neurons. Here we explain how intermittent active transport allows for faster equilibration upon a change in concentration triggered by biochemical stimuli. Moreover, we show how intermittent active excursions induce qualitative changes in the noise in effectively one-dimensional systems such as dendrites. Thereby they allow for significantly improved signalling precision in the sense of a smaller relative deviation in the concentration read-out by the receptor. On the basis of linear response theory we derive the exact mean field precision limit for counting actively transported molecules. We explain how intermittent active excursions disrupt the recurrence in the molecular motion, thereby facilitating improved signalling accuracy. Our results provide a deeper understanding of how recurrence affects molecular signalling precision in biological cells and novel medical-diagnostic devices. KW - noise in biochemical signalling KW - Brownian motion KW - active transport KW - linear response theory KW - fluctuation-dissipation theorem KW - generalised Langevin equation KW - recurrence Y1 - 2016 U6 - https://doi.org/10.1088/1751-8113/49/36/364001 SN - 1751-8113 SN - 1751-8121 VL - 49 PB - IOP Publ. Ltd. CY - Bristol ER - TY - GEN A1 - Bürger, Andreas A1 - Magdans, Uta A1 - Gies, Hermann T1 - Adsorption of amino acids on the magnetite-(111)-surface: a force field study (vol 19, 851, 2013) T2 - Journal of molecular modeling Y1 - 2016 U6 - https://doi.org/10.1007/s00894-016-3124-8 SN - 1610-2940 SN - 0948-5023 VL - 22 PB - Springer CY - New York ER - TY - JOUR A1 - Fischer, Jost Leonhardt A1 - Bader, Rolf A1 - Abel, Markus T1 - Aeroacoustical coupling and synchronization of organ pipes JF - The journal of the Acoustical Society of America N2 - A synchronization experiment on two mutual interacting organ pipes is compared with a theoretical model which takes into account the coupling mechanisms by the underlying first principles of fluid mechanics and aeroacoustics. The focus is on the Arnold-tongue, a mathematical object in the parameter space of detuning and coupling strength which quantitatively captures the interaction of the synchronized sound sources. From the experiment, a nonlinearly shaped Arnold-tongue is obtained, describing the coupling of the synchronized pipe-pipe system. This is in contrast to the linear shaped Arnold-tongue found in a preliminary experiment of the coupled system pipe-loudspeaker. To understand the experimental result, a coarse-grained model of two nonlinear coupled self-sustained oscillators is developed. The model, integrated numerically, is in very good agreement with the synchronization experiment for separation distances of the pipes in the far field and in the intermediate field. The methods introduced open the door for a deeper understanding of the fundamental processes of sound generation and the coupling mechanisms on mutual interacting acoustic oscillators. (C) 2016 Acoustical Society of America. Y1 - 2016 U6 - https://doi.org/10.1121/1.4964135 SN - 0001-4966 SN - 1520-8524 VL - 140 SP - 2344 EP - 2351 PB - American Institute of Physics CY - Melville ER - TY - JOUR A1 - Kruesemann, Henning A1 - Schwarzl, Richard A1 - Metzler, Ralf T1 - Ageing Scher-Montroll Transport JF - Transport in Porous Media N2 - We study the properties of ageing Scher-Montroll transport in terms of a biased subdiffusive continuous time random walk in which the waiting times between consecutive jumps of the charge carriers are distributed according to the power law probability with . As we show, the dynamical properties of the Scher-Montroll transport depend on the ageing time span between the initial preparation of the system and the start of the observation. The Scher-Montroll transport theory was originally shown to describe the photocurrent in amorphous solids in the presence of an external electric field, but it has since been used in many other fields of physical sciences, in particular also in the geophysical context for the description of the transport of tracer particles in subsurface aquifers. In the absence of ageing () the photocurrent of the classical Scher-Montroll model or the breakthrough curves in the groundwater context exhibit a crossover between two power law regimes in time with the scaling exponents and . In the presence of ageing a new power law regime and an initial plateau regime of the current emerge. We derive the different power law regimes and crossover times of the ageing Scher-Montroll transport and show excellent agreement with simulations of the process. Experimental data of ageing Scher-Montroll transport in polymeric semiconductors are shown to agree well with the predictions of our theory. KW - Anomalous diffusion KW - Ageing KW - Scher-Montroll transport Y1 - 2016 U6 - https://doi.org/10.1007/s11242-016-0686-y SN - 0169-3913 SN - 1573-1634 VL - 115 SP - 327 EP - 344 PB - Springer CY - New York ER - TY - JOUR A1 - Kuik, Friderike A1 - Lauer, Axel A1 - Churkina, Galina A1 - Van der Gon, Hugo A. C. Denier A1 - Fenner, Daniel A1 - Mar, Kathleen A. A1 - Butler, Tim M. T1 - Air quality modelling in the Berlin-Brandenburg region using WRF-Chem v3.7.1: sensitivity to resolution of model grid and input data JF - Geoscientific model development : an interactive open access journal of the European Geosciences Union N2 - Air pollution is the number one environmental cause of premature deaths in Europe. Despite extensive regulations, air pollution remains a challenge, especially in urban areas. For studying summertime air quality in the Berlin–Brandenburg region of Germany, the Weather Research and Forecasting Model with Chemistry (WRF-Chem) is set up and evaluated against meteorological and air quality observations from monitoring stations as well as from a field campaign conducted in 2014. The objective is to assess which resolution and level of detail in the input data is needed for simulating urban background air pollutant concentrations and their spatial distribution in the Berlin–Brandenburg area. The model setup includes three nested domains with horizontal resolutions of 15, 3 and 1 km and anthropogenic emissions from the TNO-MACC III inventory. We use RADM2 chemistry and the MADE/SORGAM aerosol scheme. Three sensitivity simulations are conducted updating input parameters to the single-layer urban canopy model based on structural data for Berlin, specifying land use classes on a sub-grid scale (mosaic option) and downscaling the original emissions to a resolution of ca. 1 km × 1 km for Berlin based on proxy data including traffic density and population density. The results show that the model simulates meteorology well, though urban 2 m temperature and urban wind speeds are biased high and nighttime mixing layer height is biased low in the base run with the settings described above. We show that the simulation of urban meteorology can be improved when specifying the input parameters to the urban model, and to a lesser extent when using the mosaic option. On average, ozone is simulated reasonably well, but maximum daily 8 h mean concentrations are underestimated, which is consistent with the results from previous modelling studies using the RADM2 chemical mechanism. Particulate matter is underestimated, which is partly due to an underestimation of secondary organic aerosols. NOx (NO + NO2) concentrations are simulated reasonably well on average, but nighttime concentrations are overestimated due to the model's underestimation of the mixing layer height, and urban daytime concentrations are underestimated. The daytime underestimation is improved when using downscaled, and thus locally higher emissions, suggesting that part of this bias is due to deficiencies in the emission input data and their resolution. The results further demonstrate that a horizontal resolution of 3 km improves the results and spatial representativeness of the model compared to a horizontal resolution of 15 km. With the input data (land use classes, emissions) at the level of detail of the base run of this study, we find that a horizontal resolution of 1 km does not improve the results compared to a resolution of 3 km. However, our results suggest that a 1 km horizontal model resolution could enable a detailed simulation of local pollution patterns in the Berlin–Brandenburg region if the urban land use classes, together with the respective input parameters to the urban canopy model, are specified with a higher level of detail and if urban emissions of higher spatial resolution are used. Y1 - 2016 U6 - https://doi.org/10.5194/gmd-9-4339-2016 SN - 1991-959X SN - 1991-9603 VL - 9 SP - 4339 EP - 4363 PB - Copernicus CY - Göttingen ER - TY - JOUR A1 - Vafin, Sergei A1 - Schlickeiser, R. A1 - Yoon, P. H. T1 - AMPLIFICATION OF COLLECTIVE MAGNETIC FLUCTUATIONS IN MAGNETIZED BI-MAXWELLIAN PLASMAS FOR PARALLEL WAVE VECTORS. I. ELECTRON-PROTON PLASMA JF - The astrophysical journal : an international review of spectroscopy and astronomical physics N2 - The general electromagnetic fluctuation theory is a powerful tool to analyze the magnetic fluctuation spectrum of a plasma. Recent works utilizing this theory for a magnetized non-relativistic isotropic Maxwellian electron-proton plasma have demonstrated that the equilibrium ratio of vertical bar delta B vertical bar/B-0 can be as high as 10(-12). This value results from the balance between spontaneous emission of fluctuations and their damping, and it is considerably smaller than the observed value vertical bar delta B vertical bar/B-0 in the solar wind at 1 au, where 10(-3) less than or similar to vertical bar delta B vertical bar/B-0 less than or similar to 10(-1). In the present manuscript, we consider an anisotropic bi-Maxwellian distribution function to investigate the effect of plasma instabilities on the magnetic field fluctuations. We demonstrate that these instabilities strongly amplify the magnetic field fluctuations and provide a sufficient mechanism to explain the observed value of vertical bar delta B vertical bar/B-0 in the solar wind at 1 au. KW - instabilities KW - magnetic fields KW - solar wind KW - turbulence KW - waves Y1 - 2016 U6 - https://doi.org/10.3847/0004-637X/829/1/41 SN - 0004-637X SN - 1538-4357 VL - 829 PB - IOP Publ. Ltd. CY - Bristol ER - TY - JOUR A1 - Aldoretta, E. J. A1 - St-Louis, N. A1 - Richardson, N. D. A1 - Moffat, Anthony F. J. A1 - Eversberg, T. A1 - Hill, G. M. A1 - Shenar, Tomer A1 - Artigau, E. A1 - Gauza, B. A1 - Knapen, J. H. A1 - Kubat, Jiří A1 - Kubatova, Brankica A1 - Maltais-Tariant, R. A1 - Munoz, M. A1 - Pablo, H. A1 - Ramiaramanantsoa, T. A1 - Richard-Laferriere, A. A1 - Sablowski, D. P. A1 - Simon-Diaz, S. A1 - St-Jean, L. A1 - Bolduan, F. A1 - Dias, F. M. A1 - Dubreuil, P. A1 - Fuchs, D. A1 - Garrel, T. A1 - Grutzeck, G. A1 - Hunger, T. A1 - Kuesters, D. A1 - Langenbrink, M. A1 - Leadbeater, R. A1 - Li, D. A1 - Lopez, A. A1 - Mauclaire, B. A1 - Moldenhawer, T. A1 - Potter, M. A1 - dos Santos, E. M. A1 - Schanne, L. A1 - Schmidt, J. A1 - Sieske, H. A1 - Strachan, J. A1 - Stinner, E. A1 - Stinner, P. A1 - Stober, B. A1 - Strandbaek, K. A1 - Syder, T. A1 - Verilhac, D. A1 - Waldschlaeger, U. A1 - Weiss, D. A1 - Wendt, A. T1 - An extensive spectroscopic time series of three Wolf-Rayet stars - I. The lifetime of large-scale structures in the wind of WR 134 JF - Monthly notices of the Royal Astronomical Society N2 - During the summer of 2013, a 4-month spectroscopic campaign took place to observe the variabilities in three Wolf-Rayet stars. The spectroscopic data have been analysed for WR 134 (WN6b), to better understand its behaviour and long-term periodicity, which we interpret as arising from corotating interaction regions (CIRs) in the wind. By analysing the variability of the He ii lambda 5411 emission line, the previously identified period was refined to P = 2.255 +/- 0.008 (s.d.) d. The coherency time of the variability, which we associate with the lifetime of the CIRs in the wind, was deduced to be 40 +/- 6 d, or similar to 18 cycles, by cross-correlating the variability patterns as a function of time. When comparing the phased observational grey-scale difference images with theoretical grey-scales previously calculated from models including CIRs in an optically thin stellar wind, we find that two CIRs were likely present. A separation in longitude of Delta I center dot a parts per thousand integral 90A degrees was determined between the two CIRs and we suggest that the different maximum velocities that they reach indicate that they emerge from different latitudes. We have also been able to detect observational signatures of the CIRs in other spectral lines (C iv lambda lambda 5802,5812 and He i lambda 5876). Furthermore, a DAC was found to be present simultaneously with the CIR signatures detected in the He i lambda 5876 emission line which is consistent with the proposed geometry of the large-scale structures in the wind. Small-scale structures also show a presence in the wind, simultaneously with the larger scale structures, showing that they do in fact co-exist. KW - instabilities KW - methods: data analysis KW - techniques: spectroscopic KW - stars: individual: WR 134 KW - stars: massive KW - stars: Wolf-Rayet Y1 - 2016 U6 - https://doi.org/10.1093/mnras/stw1188 SN - 0035-8711 SN - 1365-2966 VL - 460 SP - 3407 EP - 3417 PB - Oxford Univ. Press CY - Oxford ER - TY - JOUR A1 - Richter, Philipp A1 - Wakker, Bart P. A1 - Fechner, Cora A1 - Herenz, Peter A1 - Tepper-Garcia, T. A1 - Fox, Andrew J. T1 - An HST/COS legacy survey of intervening Si III absorption in the extended gaseous halos of low-redshift galaxies JF - Climate : open access journal N2 - Aims. Doubly ionized silicon (Si III) is a powerful tracer of diffuse ionized gas inside and outside of galaxies. It can be observed in the local Universe in ultraviolet (UV) absorption against bright extragalactic background sources. We here present an extensive study of intervening Si III-selected absorbers and study the properties of the warm circumgalactic medium (CGM) around low-redshift (z <= 0.1) galaxies. Methods. We analyzed the UV absorption spectra of 303 extragalactic background sources, as obtained with the Cosmic Origins Spectrograph (COS) on-board the Hubble Space Telescope (HST). We developed a geometrical model for the absorption-cross section of the CGM around the local galaxy population and compared the observed Si III absorption statistics with predictions provided by the model. We also compared redshifts and positions of the absorbers with those of similar to 64 000 galaxies using archival galaxy-survey data to investigate the relation between intervening Si III absorbers and the CGM. Results. Along a total redshift path of Delta z approximate to 24, we identify 69 intervening Si III systems that all show associated absorption from other low and high ions (e.g., H I, Si II, Si IV, C II, C IV). We derive a bias-corrected number density of dN/dz(Si III) = 2.5 +/- 0.4 for absorbers with column densities log N(Si III) > 12.2, which is similar to 3 times the number density of strong Mg II systems at z = 0. This number density matches the expected cross section of a Si III absorbing CGM around the local galaxy population with a mean covering fraction of < f(c)> = 0.69. For the majority (similar to 60 percent) of the absorbers, we identify possible host galaxies within 300 km s(-1) of the absorbers and derive impact parameters rho < 200 kpc, demonstrating that the spatial distributions of Si III absorbers and galaxies are highly correlated. Conclusions. Our study indicates that the majority of Si III-selected absorbers in our sample trace the CGM of nearby galaxies within their virial radii at a typical covering fraction of similar to 70 percent. We estimate that diffuse gas in the CGM around galaxies, as traced by Si III, contains substantially more (more than twice as much) baryonic mass than their neutral interstellar medium. KW - galaxies: halos KW - galaxies: formation KW - intergalactic medium KW - quasars: absorption lines Y1 - 2016 U6 - https://doi.org/10.1051/0004-6361/201527038 SN - 1432-0746 VL - 590 PB - EDP Sciences CY - Les Ulis ER - TY - JOUR A1 - Schick, Daniel A1 - Le Guyader, Loic A1 - Pontius, Niko A1 - Radu, Ilie A1 - Kachel, Torsten A1 - Mitzner, Rolf A1 - Zeschke, Thomas A1 - Schuessler-Langeheine, Christian A1 - Föhlisch, Alexander A1 - Holldack, Karsten T1 - Analysis of the halo background in femtosecond slicing experiments JF - Journal of synchrotron radiation N2 - The slicing facility FemtoSpeX at BESSY II offers unique opportunities to study photo-induced dynamics on femtosecond time scales by means of X-ray magnetic circular dichroism, resonant and non-resonant X-ray diffraction, and X-ray absorption spectroscopy experiments in the soft X-ray regime. Besides femtosecond X-ray pulses, slicing sources inherently also produce a so-called `halo' background with a different time structure, polarization and pointing. Here a detailed experimental characterization of the halo radiation is presented, and a method is demonstrated for its correct and unambiguous removal from femtosecond time-resolved data using a special laser triggering scheme as well as analytical models. Examples are given for time-resolved measurements with corresponding halo correction, and errors of the relevant physical quantities caused by either neglecting or by applying a simplified model to describe this background are estimated. KW - femtosecond slicing KW - halo KW - pump-probe KW - XMCD KW - X-ray scattering Y1 - 2016 U6 - https://doi.org/10.1107/S160057751600401X SN - 1600-5775 VL - 23 SP - 700 EP - 711 PB - International Union of Crystallography CY - Chester ER - TY - JOUR A1 - Steinke, Martin A1 - Oskinova, Lida A1 - Hamann, Wolf-Rainer A1 - Sander, Andreas Alexander Christoph A1 - Liermann, A. A1 - Todt, Helge Tobias T1 - Analysis of the WN star WR102c, its WR nebula, and the associated cluster of massive stars in the Sickle Nebula JF - Tectonophysics : international journal of geotectonics and the geology and physics of the interior of the earth N2 - Context. The massive Wolf-Rayet type star WR102c is located near the Quintuplet Cluster, one of the three massive star clusters in the Galactic centre region. Previous studies indicated that WR102c may have a dusty circumstellar nebula and is among the main ionising sources of the Sickle Nebula associated with the Quintuplet Cluster. Aims. The goals of our study are to derive the stellar parameters of WR102c from the analysis of its spectrum and to investigate its stellar and nebular environment. Methods. We obtained observations with the ESO VLT integral field spectrograph SINFONI in the K-band, extracted the stellar spectra, and analysed them by means of stellar atmosphere models. Results. Our new analysis supersedes the results previously reported for WR102c. We significantly decrease its bolometric luminosity and hydrogen content. We detect four early OB type stars close to WR102c. These stars have radial velocities similar to that of WR102c. We suggest that together with WR102c these stars belong to a distinct star cluster with a total mass of similar to 1000 M-circle dot. We identify a new WR nebula around WR102c in the SINFONI map of the di ff use Br gamma emission and in the HST Pa ff images. The Br gamma line at di ff erent locations is not significantly broadened and similar to the width of nebular emission elsewhere in the H i i region around WR102c. Conclusions. The massive star WR102c located in the Galactic centre region resides in a star cluster containing additional early-type stars. The stellar parameters of WR102c are typical for hydrogen-free WN6 stars. We identify a nebula surrounding WR102c that has a morphology similar to other nebulae around hydrogen-free WR stars, and propose that the formation of this nebula is linked to interaction of the fast stellar wind with the matter ejected at a previous evolutionary stage of WR102c. KW - stars: early-type KW - stars: individual: WR 102c KW - stars: Wolf KW - Rayet KW - Galaxy: center KW - HII regions KW - infrared: stars Y1 - 2016 U6 - https://doi.org/10.1051/0004-6361/201527692 SN - 1432-0746 VL - 588 PB - EDP Sciences CY - Les Ulis ER - TY - JOUR A1 - Cherstvy, Andrey G. A1 - Metzler, Ralf T1 - Anomalous diffusion in time-fluctuating non-stationary diffusivity landscapes JF - Physical chemistry, chemical physics : PCCP ; a journal of European chemical societies N2 - We investigate the ensemble and time averaged mean squared displacements for particle diffusion in a simple model for disordered media by assuming that the local diffusivity is both fluctuating in time and has a deterministic average growth or decay in time. In this study we compare computer simulations of the stochastic Langevin equation for this random diffusion process with analytical results. We explore the regimes of normal Brownian motion as well as anomalous diffusion in the sub- and superdiffusive regimes. We also consider effects of the inertial term on the particle motion. The investigation of the resulting diffusion is performed for unconfined and confined motion. Y1 - 2016 U6 - https://doi.org/10.1039/C6CP03101C SN - 1463-9084 SN - 1463-9076 VL - 18 SP - 23840 EP - 23852 PB - RSC Publ. CY - Cambridge ER - TY - GEN A1 - Cherstvy, Andrey G. A1 - Metzler, Ralf T1 - Anomalous diffusion in time-fluctuating non-stationary diffusivity landscapes N2 - We investigate the ensemble and time averaged mean squared displacements for particle diffusion in a simple model for disordered media by assuming that the local diffusivity is both fluctuating in time and has a deterministic average growth or decay in time. In this study we compare computer simulations of the stochastic Langevin equation for this random diffusion process with analytical results. We explore the regimes of normal Brownian motion as well as anomalous diffusion in the sub- and superdiffusive regimes. We also consider effects of the inertial term on the particle motion. The investigation of the resulting diffusion is performed for unconfined and confined motion. T3 - Zweitveröffentlichungen der Universität Potsdam : Mathematisch-Naturwissenschaftliche Reihe - 257 Y1 - 2016 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus4-95901 SP - 23840 EP - 23852 ER - TY - JOUR A1 - Cherstvy, Andrey G. A1 - Metzler, Ralf T1 - Anomalous diffusion in time-fluctuating non-stationary diffusivity landscapes JF - Physical chemistry, chemical physics : a journal of European Chemical Societies N2 - We investigate the ensemble and time averaged mean squared displacements for particle diffusion in a simple model for disordered media by assuming that the local diffusivity is both fluctuating in time and has a deterministic average growth or decay in time. In this study we compare computer simulations of the stochastic Langevin equation for this random diffusion process with analytical results. We explore the regimes of normal Brownian motion as well as anomalous diffusion in the sub- and superdiffusive regimes. We also consider effects of the inertial term on the particle motion. The investigation of the resulting diffusion is performed for unconfined and confined motion. Y1 - 2016 U6 - https://doi.org/10.1039/c6cp03101c SN - 1463-9076 SN - 1463-9084 VL - 18 SP - 23840 EP - 23852 PB - Royal Society of Chemistry CY - Cambridge ER - TY - JOUR A1 - Poeschke, Patrick A1 - Sokolov, Igor M. A1 - Nepomnyashchy, Alexander A. A1 - Zaks, Michael A. T1 - Anomalous transport in cellular flows: The role of initial conditions and aging JF - Physical review : E, Statistical, nonlinear and soft matter physics N2 - We consider the diffusion-advection problem in two simple cellular flow models ( often invoked as examples of subdiffusive tracer motion) and concentrate on the intermediate time range, in which the tracer motion indeed may show subdiffusion. We perform extensive numerical simulations of the systems under different initial conditions and show that the pure intermediate-time subdiffusion regime is only evident when the particles start at the border between different cells, i.e., at the separatrix, and is less pronounced or absent for other initial conditions. The motion moreover shows quite peculiar aging properties, which are also mirrored in the behavior of the time-averaged mean squared displacement for single trajectories. This kind of behavior is due to the complex motion of tracers trapped inside the cell and is absent in classical models based on continuous-time random walks with no dynamics in the trapped state. Y1 - 2016 U6 - https://doi.org/10.1103/PhysRevE.94.032128 SN - 2470-0045 SN - 2470-0053 VL - 94 PB - American Physical Society CY - College Park ER - TY - JOUR A1 - Ghosh, Surya K. A1 - Cherstvy, Andrey G. A1 - Grebenkov, Denis S. A1 - Metzler, Ralf T1 - Anomalous, non-Gaussian tracer diffusion in crowded two-dimensional environments JF - NEW JOURNAL OF PHYSICS N2 - A topic of intense current investigation pursues the question of how the highly crowded environment of biological cells affects the dynamic properties of passively diffusing particles. Motivated by recent experiments we report results of extensive simulations of the motion of a finite sized tracer particle in a heterogeneously crowded environment made up of quenched distributions of monodisperse crowders of varying sizes in finite circular two-dimensional domains. For given spatial distributions of monodisperse crowders we demonstrate how anomalous diffusion with strongly non-Gaussian features arises in this model system. We investigate both biologically relevant situations of particles released either at the surface of an inner domain or at the outer boundary, exhibiting distinctly different features of the observed anomalous diffusion for heterogeneous distributions of crowders. Specifically we reveal an asymmetric spreading of tracers even at moderate crowding. In addition to the mean squared displacement (MSD) and local diffusion exponent we investigate the magnitude and the amplitude scatter of the time averaged MSD of individual tracer trajectories, the non-Gaussianity parameter, and the van Hove correlation function. We also quantify how the average tracer diffusivity varies with the position in the domain with a heterogeneous radial distribution of crowders and examine the behaviour of the survival probability and the dynamics of the tracer survival probability. Inter alia, the systems we investigate are related to the passive transport of lipid molecules and proteins in two-dimensional crowded membranes or the motion in colloidal solutions or emulsions in effectively two-dimensional geometries, as well as inside supercrowded, surface adhered cells. KW - anomalous diffusion KW - crowded fluids KW - stochastic processes Y1 - 2016 U6 - https://doi.org/10.1088/1367-2630/18/1/013027 SN - 1367-2630 VL - 18 PB - IOP Publ. Ltd. CY - Bristol ER - TY - JOUR A1 - Kunnus, Kristjan A1 - Josefsson, Ida A1 - Rajkovic, Ivan A1 - Schreck, Simon A1 - Quevedo, Wilson A1 - Beye, Martin A1 - Grübel, Sebastian A1 - Scholz, Mirko A1 - Nordlund, Dennis A1 - Zhang, Wenkai A1 - Hartsock, Robert W. A1 - Gaffney, Kelly J. A1 - Schlotter, William F. A1 - Turner, Joshua J. A1 - Kennedy, Brian A1 - Hennies, Franz A1 - Techert, Simone A1 - Wernet, Philippe A1 - Odelius, Michael A1 - Föhlisch, Alexander T1 - Anti-Stokes resonant x-ray Raman scattering for atom specific and excited state selective dynamics JF - NEW JOURNAL OF PHYSICS N2 - Ultrafast electronic and structural dynamics of matter govern rate and selectivity of chemical reactions, as well as phase transitions and efficient switching in functional materials. Since x-rays determine electronic and structural properties with elemental, chemical, orbital and magnetic selectivity, short pulse x-ray sources have become central enablers of ultrafast science. Despite of these strengths, ultrafast x-rays have been poor at picking up excited state moieties from the unexcited ones. With time-resolved anti-Stokes resonant x-ray Raman scattering (AS-RXRS) performed at the LCLS, and ab initio theory we establish background free excited state selectivity in addition to the elemental, chemical, orbital and magnetic selectivity of x-rays. This unparalleled selectivity extracts low concentration excited state species along the pathway of photo induced ligand exchange of Fe(CO)(5) in ethanol. Conceptually a full theoretical treatment of all accessible insights to excited state dynamics with AS-RXRS with transform-limited x-ray pulses is given-which will be covered experimentally by upcoming transform-limited x-ray sources. KW - ultrafast photochemistry KW - excited state selectivity KW - anti-Stokes resonant x-ray raman scattering KW - free electron lasers KW - resonant inelastic x-ray scattering Y1 - 2016 U6 - https://doi.org/10.1088/1367-2630/18/10/103011 SN - 1367-2630 VL - 18 PB - IOP Publ. Ltd. CY - Bristol ER - TY - JOUR A1 - Zhelavskaya, Irina A1 - Spasojevic, M. A1 - Shprits, Yuri Y. A1 - Kurth, William S. T1 - Automated determination of electron density from electric field measurements on the Van Allen Probes spacecraft JF - Journal of geophysical research : Space physics N2 - We present the Neural-network-based Upper hybrid Resonance Determination (NURD) algorithm for automatic inference of the electron number density from plasma wave measurements made on board NASA's Van Allen Probes mission. A feedforward neural network is developed to determine the upper hybrid resonance frequency, fuhr, from electric field measurements, which is then used to calculate the electron number density. In previous missions, the plasma resonance bands were manually identified, and there have been few attempts to do robust, routine automated detections. We describe the design and implementation of the algorithm and perform an initial analysis of the resulting electron number density distribution obtained by applying NURD to 2.5 years of data collected with the Electric and Magnetic Field Instrument Suite and Integrated Science (EMFISIS) instrumentation suite of the Van Allen Probes mission. Densities obtained by NURD are compared to those obtained by another recently developed automated technique and also to an existing empirical plasmasphere and trough density model. KW - Van Allen Probes KW - electron number density KW - neural networks Y1 - 2016 U6 - https://doi.org/10.1002/2015JA022132 SN - 2169-9380 SN - 2169-9402 VL - 121 SP - 4611 EP - 4625 PB - American Geophysical Union CY - Washington ER - TY - JOUR A1 - Pavlenko, Elena S. A1 - Sander, Mathias A1 - Mitzscherling, S. A1 - Pudell, Jan-Etienne A1 - Zamponi, Flavio A1 - Roessle, M. A1 - Bojahr, Andre A1 - Bargheer, Matias T1 - Azobenzene - functionalized polyelectrolyte nanolayers as ultrafast optoacoustic transducers JF - Nanoscale N2 - We introduce azobenzene-functionalized polyelectrolyte multilayers as efficient, inexpensive optoacoustic transducers for hyper-sound strain waves in the GHz range. By picosecond transient reflectivity measurements we study the creation of nanoscale strain waves, their reflection from interfaces, damping by scattering from nanoparticles and propagation in soft and hard adjacent materials like polymer layers, quartz and mica. The amplitude of the generated strain epsilon similar to 5 x 10(-4) is calibrated by ultrafast X-ray diffraction. Y1 - 2016 U6 - https://doi.org/10.1039/c6nr01448h SN - 2040-3364 SN - 2040-3372 VL - 8 SP - 13297 EP - 13302 PB - Royal Society of Chemistry CY - Cambridge ER - TY - GEN A1 - Pavlenko, Elena S. A1 - Sander, Mathias A1 - Mitzscherling, Steffen A1 - Pudell, Jan-Etienne A1 - Zamponi, Flavio A1 - Rössle, Matthias A1 - Bojahr, Andre A1 - Bargheer, Matias T1 - Azobenzene – functionalized polyelectrolyte nanolayers as ultrafast optoacoustic transducers N2 - We introduce azobenzene-functionalized polyelectrolyte multilayers as efficient, inexpensive optoacoustic transducers for hyper-sound strain waves in the GHz range. By picosecond transient reflectivity measurements we study the creation of nanoscale strain waves, their reflection from interfaces, damping by scattering from nanoparticles and propagation in soft and hard adjacent materials like polymer layers, quartz and mica. The amplitude of the generated strain ε ∼ 5 × 10−4 is calibrated by ultrafast X-ray diffraction. T3 - Zweitveröffentlichungen der Universität Potsdam : Mathematisch-Naturwissenschaftliche Reihe - 297 Y1 - 2016 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus4-101996 VL - 8 SP - 13297 EP - 13302 ER - TY - JOUR A1 - Przybilla, Norbert A1 - Fossati, Luca A1 - Hubrig, Swetlana A1 - Nieva, M. -F. A1 - Jaervinen, S. P. A1 - Castro, Norberto A1 - Schoeller, M. A1 - Ilyin, Ilya A1 - Butler, Keith A1 - Schneider, F. R. N. A1 - Oskinova, Lida A1 - Morel, T. A1 - Langer, N. A1 - de Koter, A. T1 - B fields in OB stars (BOB): Detection of a magnetic field in the He-strong star CPD-57 degrees 3509 JF - Organic letters N2 - Methods. Spectropolarimetric observations with FORS2 and HARPSpol are analysed using two independent approaches to quantify the magnetic field strength. A high-S/N FLAMES/GIRAFFE spectrum is analysed using a hybrid non-LTE model atmosphere technique. Comparison with stellar evolution models constrains the fundamental parameters of the star. Results. We obtain a firm detection of a surface averaged longitudinal magnetic field with a maximum amplitude of about 1 kG. Assuming a dipolar configuration of the magnetic field, this implies a dipolar field strength larger than 3.3 kG. Moreover, the large amplitude and fast variation (within about 1 day) of the longitudinal magnetic field implies that CPD-57 degrees 3509 is spinning very fast despite its apparently slow projected rotational velocity. The star should be able to support a centrifugal magnetosphere, yet the spectrum shows no sign of magnetically confined material; in particular, emission in H alpha is not observed. Apparently, the wind is either not strong enough for enough material to accumulate in the magnetosphere to become observable or, alternatively, some leakage process leads to loss of material from the magnetosphere. The quantitative spectroscopic analysis of the star yields an effective temperature and a logarithmic surface gravity of 23 750 +/- 250 K and 4.05 +/- 0.10, respectively, and a surface helium fraction of 0.28 +/- 0.02 by number. The surface abundances of C, N, O, Ne, S, and Ar are compatible with the cosmic abundance standard, whereas Mg, Al, Si, and Fe are depleted by about a factor of 2. This abundance pattern can be understood as the consequence of a fractionated stellar wind. CPD-57 degrees 3509 is one of the most evolved He-strong stars known with an independent age constraint due to its cluster membership. KW - stars: abundances KW - stars: atmospheres KW - stars: evolution KW - stars: magnetic field KW - stars: individual: CPD-57 degrees 3509 KW - stars: massive Y1 - 2016 U6 - https://doi.org/10.1051/0004-6361/201527646 SN - 1432-0746 VL - 587 PB - EDP Sciences CY - Les Ulis ER - TY - JOUR A1 - Reindl, Nicole A1 - Rauch, Thomas A1 - Miller Bertolami, Marcelo Miguel A1 - Todt, Helge Tobias A1 - Werner, K. T1 - Breaking news from the HST BT - the central star of the Stingray Nebula is now returning towards the AGB JF - Monthly notices of the Royal Astronomical Society N2 - SAO 244567 is a rare example of a star that allows us to witness stellar evolution in real time. Between 1971 and 1990, it changed from a B-type star into the hot central star of the Stingray Nebula. This observed rapid heating has been a mystery for decades, since it is in strong contradiction with the low mass of the star and canonical post-asymptotic giant branch (AGB) evolution. We speculated that SAO 244567 might have suffered from a late thermal pulse (LTP) and obtained new observations with Hubble Space Telescope (HST)/COS to follow the evolution of the surface properties of SAO 244567 and to verify the LTP hypothesis. Our non-LTE spectral analysis reveals that the star cooled significantly since 2002 and that its envelope is now expanding. Therefore, we conclude that SAO 244567 is currently on its way back towards the AGB, which strongly supports the LTP hypothesis. A comparison with state-of-the-art LTP evolutionary calculations shows that these models cannot fully reproduce the evolution of all surface parameters simultaneously, pointing out possible shortcomings of stellar evolution models. Thereby, SAO 244567 keeps on challenging stellar evolution theory and we highly encourage further investigations. KW - stars: AGB and post-AGB KW - stars: atmospheres KW - stars: evolution Y1 - 2016 U6 - https://doi.org/10.1093/mnrasl/slw175 SN - 0035-8711 SN - 1365-2966 VL - 464 SP - L51 EP - L55 PB - Oxford Univ. Press CY - Oxford ER - TY - JOUR A1 - Baushev, Anton N. T1 - Can the dark matter annihilation signal be significantly boosted by substructures? JF - Journal of cosmology and astroparticle physics N2 - A very general cosmological consideration suggests that, along with galactic dark matter halos, much smaller dark matter structures may exist. These structures are usually called `clumps', and their mass extends to 10−6 M ⊙ or even lower. The clumps should give the main contribution into the signal of dark matter annihilation, provided that they have survived until the present time. Recent observations favor a cored profile for low-mass astrophysical halos. We consider cored clumps and show that they are significantly less firm than the standard NFW ones. In contrast to the standard scenario, the cored clumps should have been completely destroyed inside ~ 20 kpc from the Milky Way center. The dwarf spheroidals should not contain any dark matter clumps. On the other hand, even under the most pessimistic assumption about the clump structure, the clumps should have survived in the Milky Way at a distance exceeding 50 kpc from the center, as well as in low-density cosmic structures. There they significantly boost the dark matter annihilation. We show that at least 70% of the clumps endured the primordial structure formation should still exist untouched in the present-day Universe. KW - dark matter theory KW - particle physics - cosmology connection KW - supersymmetry and cosmology KW - cosmic ray theory Y1 - 2016 U6 - https://doi.org/10.1088/1475-7516/2016/01/018 SN - 1475-7516 VL - 30 SP - 12 EP - 18 PB - IOP Publ. Ltd. CY - Bristol ER - TY - JOUR A1 - Leonhardt, Helmar A1 - Gerhardt, Matthias A1 - Hoeppner, Nadine A1 - Krüger, Kirsten A1 - Tarantola, Marco A1 - Beta, Carsten T1 - Cell-substrate impedance fluctuations of single amoeboid cells encode cell-shape and adhesion dynamics JF - Physical review : E, Statistical, nonlinear and soft matter physics N2 - We show systematic electrical impedance measurements of single motile cells on microelectrodes. Wild-type cells and mutant strains were studied that differ in their cell-substrate adhesion strength. We recorded the projected cell area by time-lapse microscopy and observed irregular oscillations of the cell shape. These oscillations were correlated with long-term variations in the impedance signal. Superposed to these long-term trends, we observed fluctuations in the impedance signal. Their magnitude clearly correlated with the adhesion strength, suggesting that strongly adherent cells display more dynamic cell-substrate interactions. Y1 - 2016 U6 - https://doi.org/10.1103/PhysRevE.93.012414 SN - 2470-0045 SN - 2470-0053 VL - 93 PB - American Physical Society CY - College Park ER - TY - THES A1 - Lehmann, Jascha In-su T1 - Changes in extratropical storm track activity and their implications for extreme weather events Y1 - 2016 ER - TY - JOUR A1 - Puhlmann, Dirk A1 - Henkel, Carsten A1 - Heuer, Axel A1 - Pieplow, Gregor A1 - Menzel, Ralf T1 - Characterization of a remote optical element with bi-photons JF - Physica scripta : an international journal for experimental and theoretical physics N2 - We present a simple setup that exploits the interference of entangled photon pairs. 'Signal' photons are sent through a Mach–Zehnder-like interferometer, while 'idlers' are detected in a variable polarization state. Two-photon interference (in coincidence detection) is observed with very high contrast and for significant time delays between signal and idler detection events. This is explained by quantum erasure of the polarization tag and a delayed choice protocol involving a non-local virtual polarizer. The phase of the two-photon fringes is scanned by varying the path length in the signal beam or by rotating a birefringent crystal in the idler beam. We exploit this to characterize one beam splitter of the signal photon interferometer (reflection and transmission amplitudes including losses), using only information about coincidences and control parameters in the idler path. This is possible because our bi-photon state saturates the Greenberger–Yelin–Englert inequality between contrast and predictability. KW - quantum optics KW - quantum eraser KW - entanglement KW - bi-photons Y1 - 2016 U6 - https://doi.org/10.1088/0031-8949/91/2/023006 SN - 0031-8949 SN - 1402-4896 VL - 91 SP - 113 EP - 114 PB - IOP Publ. Ltd. CY - Bristol ER - TY - JOUR A1 - Sander, Mathias A1 - Koc, A. A1 - Kwamen, C. T. A1 - Michaels, H. A1 - von Reppert, Alexander A1 - Pudell, Jan-Etienne A1 - Zamponi, Flavio A1 - Bargheer, Matias A1 - Sellmann, J. A1 - Schwarzkopf, J. A1 - Gaal, P. T1 - Characterization of an ultrafast Bragg-Switch for shortening hard x-ray pulses JF - Journal of applied physics N2 - We present a nanostructured device that functions as photoacoustic hard x-ray switch. The device is triggered by femtosecond laser pulses and allows for temporal gating of hard x-rays on picosecond (ps) timescales. It may be used for pulse picking or even pulse shortening in 3rd generation synchrotron sources. Previous approaches mainly suffered from insufficient switching contrasts due to excitation-induced thermal distortions. We present a new approach where thermal distortions are spatially separated from the functional switching layers in the structure. Our measurements yield a switching contrast of 14, which is sufficient for efficient hard x-ray pulse shortening. The optimized structure also allows for utilizing the switch at high repetition rates of up to 208 kHz. Published by AIP Publishing. Y1 - 2016 U6 - https://doi.org/10.1063/1.4967835 SN - 0021-8979 SN - 1089-7550 VL - 120 PB - American Institute of Physics CY - Melville ER - TY - JOUR A1 - Paulke, Andreas A1 - Stranks, Samuel D. A1 - Kniepert, Juliane A1 - Kurpiers, Jona A1 - Wolff, Christian Michael A1 - Schön, Natalie A1 - Snaith, Henry J. A1 - Brenner, Thomas J. K. A1 - Neher, Dieter T1 - Charge carrier recombination dynamics in perovskite and polymer solar cells JF - Applied physics letters N2 - Time-delayed collection field experiments are applied to planar organometal halide perovskite (CH3NH3PbI3) based solar cells to investigate charge carrier recombination in a fully working solar cell at the nanosecond to microsecond time scale. Recombination of mobile (extractable) charges is shown to follow second-order recombination dynamics for all fluences and time scales tested. Most importantly, the bimolecular recombination coefficient is found to be time-dependent, with an initial value of ca. 10(-9) cm(3)/s and a progressive reduction within the first tens of nanoseconds. Comparison to the prototypical organic bulk heterojunction device PTB7:PC71BM yields important differences with regard to the mechanism and time scale of free carrier recombination. (C) 2016 AIP Publishing LLC. Y1 - 2016 U6 - https://doi.org/10.1063/1.4944044 SN - 0003-6951 SN - 1077-3118 VL - 108 SP - 252 EP - 262 PB - American Institute of Physics CY - Melville ER - TY - JOUR A1 - Mueller, Lars A1 - Nanova, Diana A1 - Glaser, Tobias A1 - Beck, Sebastian A1 - Pucci, Annemarie A1 - Kast, Anne K. A1 - Schroeder, Rasmus R. A1 - Mankel, Eric A1 - Pingel, Patrick A1 - Neher, Dieter A1 - Kowalsky, Wolfgang A1 - Lovrincic, Robert T1 - Charge-Transfer-Solvent Interaction Predefines Doping Efficiency in p-Doped P3HT Films JF - Chemistry of materials : a publication of the American Chemical Society N2 - Efficient electrical doping of organic semiconductors is a necessary prerequisite for the fabrication of high performance organic electronic devices. In this work, we study p-type doping of poly(3-hexylthiophene) (P3HT) with 2,3,5,6-tetrafluoro-7,7,8,8-tetracyanoquinodimethane (F(4)TCNQ) spin-cast from two different solvents. Using electron diffraction, we find strong dopant-induced pi-pi-stacking for films from the solvent chloroform, but not from chlorobenzene. This image is confirmed and expanded by the analysis of vibrational features of P3HT and polaron absorptions using optical spectroscopy. Here, a red-shifted polaron absorption is found in doped films from chloroform, caused by a higher conjugation length of the polymer backbone. These differences result in a higher conductivity of films from chloroform. We use optical spectroscopy on the corresponding blend solutions to shed light on the origin of this effect and propose a model to explain why solutions of doped P3HT reveal more aggregation of charged molecules in chlorobenzene, whereas more order is finally observed in dried films from chloroform. Our study emphasizes the importance of solvent parameters exceeding the bare solubility of pure dopant and host material for the preparation of highly conductive doped films. Y1 - 2016 U6 - https://doi.org/10.1021/acs.chemmater.6b01629 SN - 0897-4756 SN - 1520-5002 VL - 28 SP - 4432 EP - 4439 PB - American Chemical Society CY - Washington ER - TY - JOUR A1 - Dzhanoev, Arsen R. A1 - Schmidt, J. A1 - Liu, X. A1 - Spahn, Frank T1 - Charging of small grains in a space plasma: Application to Jovian stream particles JF - International psychogeriatrics N2 - Context. Most theoretical investigations of dust charging processes in space have treated the current balance condition as independent of grain size. However, for small grains, since they are often observed in space environments, a dependence on grain size is expected owing to secondary electron emission (SEE). Here, by the term "small" we mean a particle size comparable to the typical penetration depth for given primary electron energy. The results are relevant for the dynamics of small, charged dust particles emitted by the volcanic moon Io, which forms the Jovian dust streams. Aims. We revise the theory of charging of small (submicron sized) micrometeoroids to take into account a high production of secondary electrons for small grains immersed in an isotropic flux of electrons. We apply our model to obtain an improved estimate for the charge of the dust streams leaving the Jovian system, detected by several spacecraft. Methods. We apply a continuum model to describe the penetration of primary electrons in a grain and the emission of secondary electrons along the path. Averaging over an isotropic flux of primaries, we derive a new expression for the secondary electron yield, which can be used to express the secondary electron current on a grain. Results. For the Jupiter plasma environment we derive the surface potential of grains composed of NaCl (believed to be the major constituent of Jovian dust stream particles) or silicates. For small particles, the potential depends on grain size and the secondary electron current induces a sensitivity to material properties. As a result of the small particle effect, the estimates for the charging times and for the fractional charge fluctuations of NaCl grains obtained using our general approach to SEE give results qualitatively different from the analogous estimates derived from the traditional approach to SEE. We find that for the charging environment considered in this paper field emission does not limit the charging of NaCl grains. KW - plasmas KW - planets and satellites: individual: Jupiter Y1 - 2016 U6 - https://doi.org/10.1051/0004-6361/201527891 SN - 1432-0746 VL - 591 SP - 647 EP - 684 PB - EDP Sciences CY - Les Ulis ER - TY - JOUR A1 - Beye, Martin A1 - Öberg, Henrik A1 - Xin, Hongliang A1 - Dakovski, Georgi L. A1 - Föhlisch, Alexander A1 - Gladh, Jorgen A1 - Hantschmann, Markus A1 - Hieke, Florian A1 - Kaya, Sarp A1 - Kühn, Danilo A1 - LaRue, Jerry A1 - Mercurio, Giuseppe A1 - Minitti, Michael P. A1 - Mitra, Ankush A1 - Moeller, Stefan P. A1 - Ng, May Ling A1 - Nilsson, Anders A1 - Nordlund, Dennis A1 - Norskov, Jens A1 - Öström, Henrik A1 - Ogasawara, Hirohito A1 - Persson, Mats A1 - Schlotter, William F. A1 - Sellberg, Jonas A. A1 - Wolf, Martin A1 - Abild-Pedersen, Frank A1 - Pettersson, Lars G. M. A1 - Wurth, Wilfried T1 - Chemical Bond Activation Observed with an X-ray Laser JF - The journal of physical chemistry letters N2 - The concept of bonding and antibonding orbitals is fundamental in chemistry. The population of those orbitals and the energetic difference between the two reflect the strength of the bonding interaction. Weakening the bond is expected to reduce this energetic splitting, but the transient character of bond-activation has so far prohibited direct experimental access. Here we apply time-resolved soft X-ray spectroscopy at a free electron laser to directly observe the decreased bonding antibonding splitting following bond-activation using an ultrashort optical laser pulse. Y1 - 2016 U6 - https://doi.org/10.1021/acs.jpclett.6b01543 SN - 1948-7185 VL - 7 SP - 3647 EP - 3651 PB - American Chemical Society CY - Washington ER - TY - THES A1 - Brauer, Dorothée T1 - Chemo-kinematic constraints on Milky Way models from the spectroscopic surveys SEGUE & RAVE T1 - Beschränkungen von Modellen der Milchstraße auf Basis der chemisch-kinematischen Analyse von Beobachtungsdaten der spektroskopischen Himmelsdurchmusterungen SEGUE und RAVE N2 - The Milky Way is only one out of billions of galaxies in the universe. However, it is a special galaxy because it allows to explore the main mechanisms involved in its evolution and formation history by unpicking the system star-by-star. Especially, the chemical fingerprints of its stars provide clues and evidence of past events in the Galaxy’s lifetime. These information help not only to decipher the current structure and building blocks of the Milky Way, but to learn more about the general formation process of galaxies. In the past decade a multitude of stellar spectroscopic Galactic surveys have scanned millions of stars far beyond the rim of the solar neighbourhood. The obtained spectroscopic information provide unprecedented insights to the chemo-dynamics of the Milky Way. In addition analytic models and numerical simulations of the Milky Way provide necessary descriptions and predictions suited for comparison with observations in order to decode the physical properties that underlie the complex system of the Galaxy. In the thesis various approaches are taken to connect modern theoretical modelling of galaxy formation and evolution with observations from Galactic stellar surveys. With its focus on the chemo-kinematics of the Galactic disk this work aims to determine new observational constraints on the formation of the Milky Way providing also proper comparisons with two different models. These are the population synthesis model TRILEGAL based on analytical distribution functions, which aims to simulate the number and distribution of stars in the Milky Way and its different components, and a hybrid model (MCM) that combines an N-body simulation of a Milky Way like galaxy in the cosmological framework with a semi-analytic chemical evolution model for the Milky Way. The major observational data sets in use come from two surveys, namely the “Radial Velocity Experiment” (RAVE) and the “Sloan Extension for Galactic Understanding and Exploration” (SEGUE). In the first approach the chemo-kinematic properties of the thin and thick disk of the Galaxy as traced by a selection of about 20000 SEGUE G-dwarf stars are directly compared to the predictions by the MCM model. As a necessary condition for this, SEGUE's selection function and its survey volume are evaluated in detail to correct the spectroscopic observations for their survey specific selection biases. Also, based on a Bayesian method spectro-photometric distances with uncertainties below 15% are computed for the selection of SEGUE G-dwarfs that are studied up to a distance of 3 kpc from the Sun. For the second approach two synthetic versions of the SEGUE survey are generated based on the above models. The obtained synthetic stellar catalogues are then used to create mock samples best resembling the compiled sample of observed SEGUE G-dwarfs. Generally, mock samples are not only ideal to compare predictions from various models. They also allow validation of the models' quality and improvement as with this work could be especially achieved for TRILEGAL. While TRILEGAL reproduces the statistical properties of the thin and thick disk as seen in the observations, the MCM model has shown to be more suitable in reproducing many chemo-kinematic correlations as revealed by the SEGUE stars. However, evidence has been found that the MCM model may be missing a stellar component with the properties of the thick disk that the observations clearly show. While the SEGUE stars do indicate a thin-thick dichotomy of the stellar Galactic disk in agreement with other spectroscopic stellar studies, no sign for a distinct metal-poor disk is seen in the MCM model. Usually stellar spectroscopic surveys are limited to a certain volume around the Sun covering different regions of the Galaxy’s disk. This often prevents to obtain a global view on the chemo-dynamics of the Galactic disk. Hence, a suitable combination of stellar samples from independent surveys is not only useful for the verification of results but it also helps to complete the picture of the Milky Way. Therefore, the thesis closes with a comparison of the SEGUE G-dwarfs and a sample of RAVE giants. The comparison reveals that the chemo-kinematic relations agree in disk regions where the samples of both surveys show a similar number of stars. For those parts of the survey volumes where one of the surveys lacks statistics they beautifully complement each other. This demonstrates that the comparison of theoretical models on the one side, and the combined observational data gathered by multiple surveys on the other side, are key ingredients to understand and disentangle the structure and formation history of the Milky Way. N2 - Die Milchstraße ist nur eine unter Milliarden von Galaxien im Universum, dennoch ist sie besonders. Sie bietet die einzigartige Möglichkeit anhand ihrer einzeln auflösbaren Sterne und deren im Detail beobachtbaren Eigenschaften die Mechanismen ihrer Evolutions- und Entstehungsgeschichte genau zu studieren und damit Rückschlüsse auf die Entwicklungsprozesse von Galaxien im Allgemeinen zu ziehen. Insbesondere der chemische Fingerabdruck ihrer Sterne liefert dabei Indizien und Beweise für Ereignisse im Leben der Galaxie. In den letzten 15 Jahren wurden daher in einer Vielzahl von Himmeldurchmusterungen Millionen von Sternen in der Milchstraße spektroskopisch beobachtet. Die so gewonnenen Informationen bieten detaillierte Einblicke in die Substrukturen unserer Galaxie und deren chemisch-kinematische Struktur. Ergänzend dazu liefern analytische Modelle und numerische Simulationen der Milchstraße wichtige Beschreibungen, die sich zum Vergleich mit Beobachtungen eignen, um die dem komplexen System der Galaxie zugrunde liegenden exakten physikalischen Eigenschaften entschlüsseln zu können. Die vorliegende Arbeit nutzt verschiedene Ansätze, um moderne theoretische Modelle der Galaxienentstehung und -evolution mit Daten aus stellaren Beobachtungskampagnen zu vergleichen. Die dazu analysierten Beobachtungsdatensätze stammen aus zwei großen Himmelsdurchmusterungen, dem „Radial Velocity Experiment“ (RAVE) und dem „Sloan Extension for Galactic Understanding and Exploration“ (SEGUE). Mit dem Fokus auf der chemisch-kinematischen Struktur der galaktischen Scheibe geht es im Wesentlichen darum, zwei Modelle der Milchstraße zu testen, nämlich ein Populationssynthesemodell (TRILEGAL) und ein Hybridmodell (MCM). Während TRILEGAL auf analytischen Verteilungsfunktionen basiert und zum Ziel hat, die Anzahl und Verteilung der Sterne innerhalb der Galaxie und ihrer unterschiedlichen Komponenten zu simulieren, verbindet das MCM Modell eine kosmologische N-Körper Simulation einer der Milchstraße ähnlichen Galaxie mit einem semi-analytischen Modell zur Beschreibung der chemischen Evolution der Milchstraße. Auf Grundlage einer Auswahl von etwa 20000 SEGUE G-Zwergsternen werden in einem ersten Ansatz die aus den Messdaten gewonnenen chemisch-kinematischen Eigenschaften der dünnen und dicken Scheibe der Milchstraße mit den direkten Vorhersagen des MCM Modells verglichen. Eine notwendige Bedingung dafür ist die Korrektur der Beobachtungsdaten für systematische Fehler bei der Objektauswahl der Beobachtungskampagne. Zudem werden mittels einer Bayesischen Methode spektro-photometrische Distanzen mit Fehlern kleiner als 15% für die Auswahl an SEGUE Sternen berechnet, die sich in einer Entfernung von bis zu 3 kpc von der Sonne befinden. Für den zweiten Ansatz werden basierend auf den oben genannten Modellen zwei synthetische Versionen der SEGUE Himmelsdurchmusterung generiert. Diese künstlichen stellaren Kataloge werden dann verwendet, um Vergleichspseudodatensätze für die verwendeten Zwergsterndaten anzufertigen. Solche synthetischen Testdatensätze eignen sich nicht nur, um die Vorhersagen verschiedener Modelle zu vergleichen, sie können auch zur Validierung der Qualität einzelner Modelle herangezogen werden. Während sich in der Analyse zeigt, dass TRILEGAL sich besonders gut eignet, statistische Eigenschaften der dünnen und dicken galaktischen Scheibe zu reproduzieren, spiegelt das MCM Modell viele der in der Milchstraße beobachtbaren chemisch-kinematischen Korrelationen gut wieder. Trotzdem finden sich Beweise dafür, dass dem MCM Modell eine stellare Komponente fehlt, deren Eigenschaften der in den Beobachtungen sichtbaren dicken Scheibe ähnlich sind. Meist sind spektroskopische Beobachtungskampagnen auf ein bestimmtes Volumen um die Sonne beschränkt. Oftmals verhindert dies die Möglichkeit einen globalen Blick auf die chemisch-kinematischen Eigenschaften der galaktischen Scheibe zu erlangen. Die Kombination von stellaren Daten unabhängiger Kampagnen ist daher nicht nur nützlich für die Verifikation von Ergebnissen, es hilft auch ein ganzheitlicheres Bild der Galaxie zu erlangen. Die vorliegende Arbeit schließt daher mit einem Vergleich der SEGUE G-Zwergsterne und einer Auswahl von RAVE Riesensternen. Es zeigt sich eine gute Übereinstimmung bzgl. der chemisch-kinematischen Struktur der galaktischen Scheibe besonders in denjenigen Regionen, die von einer Vielzahl von SEGUE und RAVE Objekten abgedeckt werden. Für Regionen des Beobachtungsvolumens, in dem die eine oder die andere der beiden Beobachtungskampagnen eine geringere Statistik von beobachteten Sternen aufweist, ergänzen sich RAVE und SEGUE gut. Dies zeigt, dass nicht nur der Vergleich von Beobachtungen und theoretischen Modellen, sondern auch die Kombination von Messdaten aus verschiedenen Himmelsdurchmusterungen wichtig ist, um die Struktur und die Entstehungsgeschichte der Milchstraße zu verstehen und zu entschlüsseln. KW - galaktische Astronomie KW - galactic astronomy KW - Entstehung der Milchstraße KW - Milky Way formation KW - Evolution der Milchstraße KW - Milky Way evolution KW - Milky Way chemo-kinematics KW - Chemokinematik der Milchstraße KW - SEGUE survey KW - SEGUE Beobachtungskampagne KW - RAVE survey KW - RAVE Beobachtungskampagne KW - mock data catalogues KW - Pseudodatensätze Y1 - 2016 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus4-403968 ER - TY - GEN A1 - Teif, Vladimir B. A1 - Cherstvy, Andrey G. T1 - Chromatin and epigenetics: current biophysical views T2 - AIMS biophysics N2 - Recent advances in high-throughput sequencing experiments and their theoretical descriptions have determined fast dynamics of the "chromatin and epigenetics" field, with new concepts appearing at high rate. This field includes but is not limited to the study of DNA-protein-RNA interactions, chromatin packing properties at different scales, regulation of gene expression and protein trafficking in the cell nucleus, binding site search in the crowded chromatin environment and modulation of physical interactions by covalent chemical modifications of the binding partners. The current special issue does not pretend for the full coverage of the field, but it rather aims to capture its development and provide a snapshot of the most recent concepts and approaches. Eighteen open-access articles comprising this issue provide a delicate balance between current theoretical and experimental biophysical approaches to uncover chromatin structure and understand epigenetic regulation, allowing free flow of new ideas and preliminary results. KW - chromatin KW - epigenetics KW - linker histones KW - nucleosome KW - DNA-protein binding KW - histone modifications KW - remodelers KW - topologically associated domains KW - DNA methylation KW - DNA supercoiling Y1 - 2016 U6 - https://doi.org/10.3934/biophy.2016.1.88 SN - 2377-9098 VL - 3 SP - 88 EP - 98 PB - American Institute of Mathematical Sciences CY - Springfield ER - TY - THES A1 - Wenz, Leonie T1 - Climate change impacts in an increasingly connected world Y1 - 2016 ER - TY - JOUR A1 - Bozzo, Enrico A1 - Oskinova, Lida A1 - Feldmeier, Achim A1 - Falanga, M. T1 - Clumpy wind accretion in supergiant neutron star high mass X-ray binaries JF - BMC neuroscience N2 - The accretion of the stellar wind material by a compact object represents the main mechanism powering the X-ray emission in classical supergiant high mass X-ray binaries and supergiant fast X-ray transients. In this work we present the first attempt to simulate the accretion process of a fast and dense massive star wind onto a neutron star, taking into account the effects of the centrifugal and magnetic inhibition of accretion ("gating") due to the spin and magnetic field of the compact object. We made use of a radiative hydrodynamical code to model the nonstationary radiatively driven wind of an O-B supergiant star and then place a neutron star characterized by a fixed magnetic field and spin period at a certain distance from the massive companion. Our calculations follow, as a function of time (on a total timescale of several hours), the transitions of the system through all different accretion regimes that are triggered by the intrinsic variations in the density and velocity of the nonstationary wind. The X-ray luminosity released by the system is computed at each time step by taking into account the relevant physical processes occurring in the different accretion regimes. Synthetic lightcurves are derived and qualitatively compared with those observed from classical supergiant high mass X-ray binaries and supergiant fast X-ray transients. Although a number of simplifications are assumed in these calculations, we show that taking into account the effects of the centrifugal and magnetic inhibition of accretion significantly reduces the average X-ray luminosity expected for any neutron star wind-fed binary. The present model calculations suggest that long spin periods and stronger magnetic fields are favored in order to reproduce the peculiar behavior of supergiant fast X-ray transients in the X-ray domain. KW - stars: neutron KW - X-rays: binaries KW - supergiants Y1 - 2016 U6 - https://doi.org/10.1051/0004-6361/201628341 SN - 1432-0746 VL - 589 SP - 369 EP - 389 PB - EDP Sciences CY - Les Ulis ER - TY - JOUR A1 - Schleussner, Carl-Friedrich A1 - Donges, Jonathan Friedemann A1 - Engemann, Denis A. A1 - Levermann, Anders T1 - Clustered marginalization of minorities during social transitions induced by co-evolution of behaviour and network structure JF - Scientific reports N2 - Large-scale transitions in societies are associated with both individual behavioural change and restructuring of the social network. These two factors have often been considered independently, yet recent advances in social network research challenge this view. Here we show that common features of societal marginalization and clustering emerge naturally during transitions in a co-evolutionary adaptive network model. This is achieved by explicitly considering the interplay between individual interaction and a dynamic network structure in behavioural selection. We exemplify this mechanism by simulating how smoking behaviour and the network structure get reconfigured by changing social norms. Our results are consistent with empirical findings: The prevalence of smoking was reduced, remaining smokers were preferentially connected among each other and formed increasingly marginalized clusters. We propose that self-amplifying feedbacks between individual behaviour and dynamic restructuring of the network are main drivers of the transition. This generative mechanism for co-evolution of individual behaviour and social network structure may apply to a wide range of examples beyond smoking. Y1 - 2016 U6 - https://doi.org/10.1038/srep30790 SN - 2045-2322 VL - 6 SP - 3407 EP - 3417 PB - Nature Publ. Group CY - London ER - TY - JOUR A1 - Sandev, Trifce A1 - Iomin, Alexander A1 - Kantz, Holger A1 - Metzler, Ralf A1 - Chechkin, Aleksei V. T1 - Comb Model with Slow and Ultraslow Diffusion JF - Mathematical modelling of natural phenomena N2 - We consider a generalized diffusion equation in two dimensions for modeling diffusion on a comb-like structures. We analyze the probability distribution functions and we derive the mean squared displacement in x and y directions. Different forms of the memory kernels (Dirac delta, power-law, and distributed order) are considered. It is shown that anomalous diffusion may occur along both x and y directions. Ultraslow diffusion and some more general diffusive processes are observed as well. We give the corresponding continuous time random walk model for the considered two dimensional diffusion-like equation on a comb, and we derive the probability distribution functions which subordinate the process governed by this equation to the Wiener process. KW - comb-like model KW - anomalous diffusion KW - mean squared displacement KW - probability density function Y1 - 2016 U6 - https://doi.org/10.1051/mmnp/201611302 SN - 0973-5348 SN - 1760-6101 VL - 11 SP - 18 EP - 33 PB - EDP Sciences CY - Les Ulis ER - TY - GEN A1 - Berenstein, Igal A1 - Beta, Carsten A1 - De Decker, Yannick T1 - Comment on "Flow-induced arrest of spatiotemporal chaos and transition to a stationary pattern in the Gray-Scott model" T2 - Physical review : E, Statistical, nonlinear and soft matter physics N2 - In this Comment, we review the results of pattern formation in a reaction-diffusion-advection system following the kinetics of the Gray-Scott model. A recent paper by Das [Phys. Rev. E 92, 052914 (2015)] shows that spatiotemporal chaos of the intermittency type can disappear as the advective flow is increased. This study, however, refers to a single point in the space of kinetic parameters of the original Gray-Scott model. Here we show that the wealth of patterns increases substantially as some of these parameters are changed. In addition to spatiotemporal intermittency, defect-mediated turbulence can also be found. In all cases, however, the chaotic behavior is seen to disappear as the advective flow is increased, following a scenario similar to what was reported in our earlier work [I. Berenstein and C. Beta, Phys. Rev. E 86, 056205 (2012)] as well as by Das. We also point out that a similar phenomenon can be found in other reaction-diffusion-advection models, such as the Oregonator model for the Belousov-Zhabotinsky reaction under flow conditions. Y1 - 2016 U6 - https://doi.org/10.1103/PhysRevE.94.046201 SN - 2470-0045 SN - 2470-0053 VL - 94 PB - American Physical Society CY - College Park ER - TY - JOUR A1 - Sebek, Michael A1 - Tönjes, Ralf A1 - Kiss, Istvan Z. T1 - Complex Rotating Waves and Long Transients in a Ring Network of Electrochemical Oscillators with Sparse Random Cross-Connections JF - Physical review letters N2 - We perform experiments and phase model simulations with a ring network of oscillatory electrochemical reactions to explore the effect of random connections and nonisochronicity of the interactions on the pattern formation. A few additional links facilitate the emergence of the fully synchronized state. With larger nonisochronicity, complex rotating waves or persistent irregular phase dynamics can derail the convergence to global synchronization. The observed long transients of irregular phase dynamics exemplify the possibility of a sudden onset of hypersynchronous behavior without any external stimulus or network reorganization. Y1 - 2016 U6 - https://doi.org/10.1103/PhysRevLett.116.068701 SN - 0031-9007 SN - 1079-7114 VL - 116 SP - 3001 EP - 3009 PB - American Physical Society CY - College Park ER - TY - GEN A1 - Battiston, Stefano A1 - Farmer, J. Doyne A1 - Flache, Andreas A1 - Garlaschelli, Diego A1 - Haldane, Andrew G. A1 - Heesterbeek, Hans A1 - Hommes, Cars A1 - Jaeger, Carlo A1 - May, Robert A1 - Scheffer, Marten T1 - COMPLEX SYSTEMS Complexity theory and financial regulation T2 - Science N2 - Traditional economic theory could not explain, much less predict, the near collapse of the financial system and its long-lasting effects on the global economy. Since the 2008 crisis, there has been increasing interest in using ideas from complexity theory to make sense of economic and financial markets. Concepts, such as tipping points, networks, contagion, feedback, and resilience have entered the financial and regulatory lexicon, but actual use of complexity models and results remains at an early stage. Recent insights and techniques offer potential for better monitoring and management of highly interconnected economic and financial systems and, thus, may help anticipate and manage future crises. Y1 - 2016 U6 - https://doi.org/10.1126/science.aad0299 SN - 0036-8075 SN - 1095-9203 VL - 351 SP - 818 EP - 819 PB - American Assoc. for the Advancement of Science CY - Washington ER - TY - JOUR A1 - Clark, Peter U. A1 - Shakun, Jeremy D. A1 - Marcott, Shaun A. A1 - Mix, Alan C. A1 - Eby, Michael A1 - Kulp, Scott A1 - Levermann, Anders A1 - Milne, Glenn A. A1 - Pfister, Patrik L. A1 - Santer, Benjamin D. A1 - Schrag, Daniel P. A1 - Solomon, Susan A1 - Stocker, Thomas F. A1 - Strauss, Benjamin H. A1 - Weaver, Andrew J. A1 - Winkelmann, Ricarda A1 - Archer, David A1 - Bard, Edouard A1 - Goldner, Aaron A1 - Lambeck, Kurt A1 - Pierrehumbert, Raymond T. A1 - Plattner, Gian-Kasper T1 - Consequences of twenty-first-century policy for multi-millennial climate and sea-level change JF - Nature climate change N2 - Most of the policy debate surrounding the actions needed to mitigate and adapt to anthropogenic climate change has been framed by observations of the past 150 years as well as climate and sea-level projections for the twenty-first century. The focus on this 250-year window, however, obscures some of the most profound problems associated with climate change. Here, we argue that the twentieth and twenty-first centuries, a period during which the overwhelming majority of human-caused carbon emissions are likely to occur, need to be placed into a long-term context that includes the past 20 millennia, when the last Ice Age ended and human civilization developed, and the next ten millennia, over which time the projected impacts of anthropogenic climate change will grow and persist. This long-term perspective illustrates that policy decisions made in the next few years to decades will have profound impacts on global climate, ecosystems and human societies - not just for this century, but for the next ten millennia and beyond. Y1 - 2016 U6 - https://doi.org/10.1038/NCLIMATE2923 SN - 1758-678X SN - 1758-6798 VL - 6 SP - 360 EP - 369 PB - Nature Publ. Group CY - London ER - TY - JOUR A1 - Kronberg, Elena A. A1 - Rashev, M. V. A1 - Daly, P. W. A1 - Shprits, Yuri Y. A1 - Turner, D. L. A1 - Drozdov, Alexander A1 - Dobynde, M. A1 - Kellerman, Adam C. A1 - Fritz, T. A. A1 - Pierrard, V. A1 - Borremans, K. A1 - Klecker, B. A1 - Friedel, R. T1 - Contamination in electron observations of the silicon detector on board JF - Space Weather: The International Journal of Research and Applications N2 - Since more than 15 years, the Cluster mission passes through Earth's radiation belts at least once every 2 days for several hours, measuring the electron intensity at energies from 30 to 400 keV. These data have previously been considered not usable due to contamination caused by penetrating energetic particles (protons at >100 keV and electrons at >400 keV). In this study, we assess the level of distortion of energetic electron spectra from the Research with Adaptive Particle Imaging Detector (RAPID)/Imaging Electron Spectrometer (IES) detector, determining the efficiency of its shielding. We base our assessment on the analysis of experimental data and a radiation transport code (Geant4). In simulations, we use the incident particle energy distribution of the AE9/AP9 radiation belt models. We identify the Roederer L values, L⋆, and energy channels that should be used with caution: at 3≤L⋆≤4, all energy channels (40–400 keV) are contaminated by protons (≃230 to 630 keV and >600 MeV); at L⋆≃1 and 4–6, the energy channels at 95–400 keV are contaminated by high-energy electrons (>400 keV). Comparison of the data with electron and proton observations from RBSP/MagEIS indicates that the subtraction of proton fluxes at energies ≃ 230–630 keV from the IES electron data adequately removes the proton contamination. We demonstrate the usefulness of the corrected data for scientific applications. Y1 - 2016 U6 - https://doi.org/10.1002/2016SW001369 SN - 1542-7390 VL - 14 SP - 449 EP - 462 PB - American Geophysical Union CY - Washington ER - TY - JOUR A1 - Di Pietro, Riccardo A1 - Nasrallah, Iyad A1 - Carpenter, Joshua A1 - Gann, Eliot A1 - Kölln, Lisa Sophie A1 - Thomsen, Lars A1 - Venkateshvaran, Deepak A1 - Sadhanala, Aditya A1 - Chabinyc, Michael A1 - McNeill, Christopher R. A1 - Facchetti, Antonio A1 - Ade, Harald W. A1 - Sirringhaus, Henning A1 - Neher, Dieter T1 - Coulomb Enhanced Charge Transport in Semicrystalline Polymer Semiconductors JF - Advanced functional materials Y1 - 2016 U6 - https://doi.org/10.1002/adfm.201602080 SN - 1616-301X SN - 1616-3028 VL - 26 SP - 8011 EP - 8022 PB - Wiley-VCH CY - Weinheim ER - TY - JOUR A1 - de Carvalho, Sidney J. A1 - Metzler, Ralf A1 - Cherstvy, Andrey G. T1 - Critical adsorption of polyelectrolytes onto planar and convex highly charged surfaces BT - the nonlinear Poisson–Boltzmann approach JF - New journal of physics : the open-access journal for physics N2 - We study the adsorption–desorption transition of polyelectrolyte chains onto planar, cylindrical and spherical surfaces with arbitrarily high surface charge densities by massive Monte Carlo computer simulations. We examine in detail how the well known scaling relations for the threshold transition—demarcating the adsorbed and desorbed domains of a polyelectrolyte near weakly charged surfaces—are altered for highly charged interfaces. In virtue of high surface potentials and large surface charge densities, the Debye–Hückel approximation is often not feasible and the nonlinear Poisson–Boltzmann approach should be implemented. At low salt conditions, for instance, the electrostatic potential from the nonlinear Poisson–Boltzmann equation is smaller than the Debye–Hückel result, such that the required critical surface charge density for polyelectrolyte adsorption σc increases. The nonlinear relation between the surface charge density and electrostatic potential leads to a sharply increasing critical surface charge density with growing ionic strength, imposing an additional limit to the critical salt concentration above which no polyelectrolyte adsorption occurs at all. We contrast our simulations findings with the known scaling results for weak critical polyelectrolyte adsorption onto oppositely charged surfaces for the three standard geometries. Finally, we discuss some applications of our results for some physical–chemical and biophysical systems. KW - polyelectrolyte adsorption KW - electrostatic interactions KW - critical phenomena KW - Debye screening Y1 - 2016 U6 - https://doi.org/10.1088/1367-2630/18/8/083037 SN - 1367-2630 VL - 18 PB - IOP Publ. CY - London ER - TY - GEN A1 - de Carvalho, Sidney J. A1 - Metzler, Ralf A1 - Cherstvy, Andrey G. T1 - Critical adsorption of polyelectrolytes onto planar and convex highly charged surfaces BT - the nonlinear Poisson–Boltzmann approach N2 - We study the adsorption–desorption transition of polyelectrolyte chains onto planar, cylindrical and spherical surfaces with arbitrarily high surface charge densities by massive Monte Carlo computer simulations. We examine in detail how the well known scaling relations for the threshold transition—demarcating the adsorbed and desorbed domains of a polyelectrolyte near weakly charged surfaces—are altered for highly charged interfaces. In virtue of high surface potentials and large surface charge densities, the Debye–Hückel approximation is often not feasible and the nonlinear Poisson–Boltzmann approach should be implemented. At low salt conditions, for instance, the electrostatic potential from the nonlinear Poisson–Boltzmann equation is smaller than the Debye–Hückel result, such that the required critical surface charge density for polyelectrolyte adsorption σc increases. The nonlinear relation between the surface charge density and electrostatic potential leads to a sharply increasing critical surface charge density with growing ionic strength, imposing an additional limit to the critical salt concentration above which no polyelectrolyte adsorption occurs at all. We contrast our simulations findings with the known scaling results for weak critical polyelectrolyte adsorption onto oppositely charged surfaces for the three standard geometries. Finally, we discuss some applications of our results for some physical–chemical and biophysical systems. T3 - Zweitveröffentlichungen der Universität Potsdam : Mathematisch-Naturwissenschaftliche Reihe - 292 KW - polyelectrolyte adsorption KW - electrostatic interactions KW - critical phenomena KW - Debye screening Y1 - 2016 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus4-100295 ER - TY - JOUR A1 - de Carvalho, Sidney J. A1 - Metzler, Ralf A1 - Cherstvy, Andrey G. T1 - Critical adsorption of polyelectrolytes onto planar and convex highly charged surfaces: the nonlinear Poisson-Boltzmann approach JF - NEW JOURNAL OF PHYSICS N2 - We study the adsorption-desorption transition of polyelectrolyte chains onto planar, cylindrical and spherical surfaces with arbitrarily high surface charge densities by massive Monte Carlo computer simulations. We examine in detail how the well known scaling relations for the threshold transition demarcating the adsorbed and desorbed domains of a polyelectrolyte near weakly charged surfaces-are altered for highly charged interfaces. In virtue of high surface potentials and large surface charge densities, the Debye-Huckel approximation is often not feasible and the nonlinear Poisson-Boltzmann approach should be implemented. At low salt conditions, for instance, the electrostatic potential from the nonlinear Poisson-Boltzmann equation is smaller than the Debye-Huckel result, such that the required critical surface charge density for polyelectrolyte adsorption sigma(c) increases. The nonlinear relation between the surface charge density and electrostatic potential leads to a sharply increasing critical surface charge density with growing ionic strength, imposing an additional limit to the critical salt concentration above which no polyelectrolyte adsorption occurs at all. We contrast our simulations findings with the known scaling results for weak critical polyelectrolyte adsorption onto oppositely charged surfaces for the three standard geometries. Finally, we discuss some applications of our results for some physical-chemical and biophysical systems. KW - polyelectrolyte adsorption KW - electrostatic interactions KW - critical phenomena KW - Debye screening Y1 - 2016 U6 - https://doi.org/10.1088/1367-2630/18/8/083037 SN - 1367-2630 VL - 18 PB - IOP Publ. Ltd. CY - Bristol ER - TY - JOUR A1 - Ganopolski, A. A1 - Winkelmann, Ricarda A1 - Schellnhuber, Hans Joachim T1 - Critical insolation-CO2 relation for diagnosing past and future glacial inception JF - Nature : the international weekly journal of science N2 - The past rapid growth of Northern Hemisphere continental ice sheets, which terminated warm and stable climate periods, is generally attributed to reduced summer insolation in boreal latitudes(1-3). Yet such summer insolation is near to its minimum at present(4), and there are no signs of a new ice age(5). This challenges our understanding of the mechanisms driving glacial cycles and our ability to predict the next glacial inception(6). Here we propose a critical functional relationship between boreal summer insolation and global carbon dioxide (CO2) concentration, which explains the beginning of the past eight glacial cycles and might anticipate future periods of glacial inception. Using an ensemble of simulations generated by an Earth system model of intermediate complexity constrained by palaeoclimatic data, we suggest that glacial inception was narrowly missed before the beginning of the Industrial Revolution. The missed inception can be accounted for by the combined effect of relatively high late-Holocene CO2 concentrations and the low orbital eccentricity of the Earth(7). Additionally, our analysis suggests that even in the absence of human perturbations no substantial build-up of ice sheets would occur within the next several thousand years and that the current interglacial would probably last for another 50,000 years. However, moderate anthropogenic cumulative CO2 emissions of 1,000 to 1,500 gigatonnes of carbon will postpone the next glacial inception by at least 100,000 years(8,9). Our simulations demonstrate that under natural conditions alone the Earth system would be expected to remain in the present delicately balanced interglacial climate state, steering clear of both large-scale glaciation of the Northern Hemisphere and its complete deglaciation, for an unusually long time. Y1 - 2016 U6 - https://doi.org/10.1038/nature16494 SN - 0028-0836 SN - 1476-4687 VL - 529 SP - 200 EP - U159 PB - Nature Publ. Group CY - London ER - TY - JOUR A1 - Xu, Siyao A1 - Yan, Huirong A1 - Lazarian, A. T1 - DAMPING OF MAGNETOHYDRODYNAMIC TURBULENCE IN PARTIALLY IONIZED PLASMA: IMPLICATIONS FOR COSMIC RAY PROPAGATION JF - The astrophysical journal : an international review of spectroscopy and astronomical physics N2 - We study the damping processes of both incompressible and compressible magnetohydrodynamic (MHD) turbulence in a partially ionized medium. We start from the linear analysis of MHD waves, applying both single-fluid and two-fluid treatments. The damping rates derived from the linear analysis are then used in determining the damping scales of MHD turbulence. The physical connection between the damping scale of MHD turbulence and the cutoff boundary of linear MHD waves is investigated. We find two branches of slow modes propagating in ions and neutrals, respectively, below the damping scale of slow MHD turbulence, and offer a thorough discussion of their propagation and dissipation behavior. Our analytical results are shown to be applicable in a variety of partially ionized interstellar medium (ISM) phases and the solar chromosphere. The importance of neutral viscosity in damping the Alfvenic turbulence in the interstellar warm neutral medium and the solar chromosphere is demonstrated. As a significant astrophysical utility, we introduce damping effects to the propagation of cosmic rays in partially ionized ISM. The important role of turbulence damping in both transit-time damping and gyroresonance is identified. KW - cosmic rays KW - magnetohydrodynamics (MHD) KW - turbulence Y1 - 2016 U6 - https://doi.org/10.3847/0004-637X/826/2/166 SN - 0004-637X SN - 1538-4357 VL - 826 PB - IOP Publ. Ltd. CY - Bristol ER - TY - JOUR A1 - Frieler, Katja A1 - Mengel, M. A1 - Levermann, Anders T1 - Delaying future sea-level rise by storing water in Antarctica JF - Earth system dynamics N2 - Even if greenhouse gas emissions were stopped today, sea level would continue to rise for centuries, with the long-term sea-level commitment of a 2 degrees C warmer world significantly exceeding 2 m. In view of the potential implications for coastal populations and ecosystems worldwide, we investigate, from an ice-dynamic perspective, the possibility of delaying sea-level rise by pumping ocean water onto the surface of the Antarctic ice sheet. We find that due to wave propagation ice is discharged much faster back into the ocean than would be expected from a pure advection with surface velocities. The delay time depends strongly on the distance from the coastline at which the additional mass is placed and less strongly on the rate of sea-level rise that is mitigated. A millennium-scale storage of at least 80% of the additional ice requires placing it at a distance of at least 700 km from the coastline. The pumping energy required to elevate the potential energy of ocean water to mitigate the currently observed 3 mmyr(-1) will exceed 7% of the current global primary energy supply. At the same time, the approach offers a comprehensive protection for entire coastlines particularly including regions that cannot be protected by dikes. Y1 - 2016 U6 - https://doi.org/10.5194/esd-7-203-2016 SN - 2190-4979 SN - 2190-4987 VL - 7 SP - 203 EP - 210 PB - Copernicus CY - Göttingen ER - TY - THES A1 - Amaro-Seoane, Pau T1 - Dense stellar systems and massive black holes T1 - Dichte stellare Systeme und massive Schwarze Löcher BT - sources of gravitational radiation and tidal disruptions BT - Quellen von Gravitationsstrahlung und Gezeiten-Sternzerissereignissen N2 - Gravity dictates the structure of the whole Universe and, although it is triumphantly described by the theory of General Relativity, it is the force that we least understand in nature. One of the cardinal predictions of this theory are black holes. Massive, dark objects are found in the majority of galaxies. Our own galactic center very contains such an object with a mass of about four million solar masses. Are these objects supermassive black holes (SMBHs), or do we need alternatives? The answer lies in the event horizon, the characteristic that defines a black hole. The key to probe the horizon is to model the movement of stars around a SMBH, and the interactions between them, and look for deviations from real observations. Nuclear star clusters harboring a massive, dark object with a mass of up to ~ ten million solar masses are good testbeds to probe the event horizon of the potential SMBH with stars. The channel for interactions between stars and the central MBH are the fact that (a) compact stars and stellar-mass black holes can gradually inspiral into the SMBH due to the emission of gravitational radiation, which is known as an “Extreme Mass Ratio Inspiral” (EMRI), and (b) stars can produce gases which will be accreted by the SMBH through normal stellar evolution, or by collisions and disruptions brought about by the strong central tidal field. Such processes can contribute significantly to the mass of the SMBH. These two processes involve different disciplines, which combined will provide us with detailed information about the fabric of space and time. In this habilitation I present nine articles of my recent work directly related with these topics. N2 - Die Gravitation bestimmt die Struktur des ganzen Universums und ist, obwohl sie mit großem Erfolg durch die Theorie der Allgemeinen Relativitätstheorie beschrieben wird, die am wenigsten verstandene Kraft in der Natur. Eine der grundsätzlichsten Vorhersagen dieser Theorie sind Schwarze Löcher. Massive, dunkle Objekte befinden sich in einem Großteil aller Galaxien. Das Zentrum unserer eigenen Galaxis enthält solch ein Objekt mit einer Masse von etwa vier Millionen Sonnenmassen. Sind diese Objekte supermassive Schwarze Löcher oder brauchen wir Alternativen? Die Antwort liegt im Ereignishorizont, der Eigenschaft, die ein Schwarzes Loch definiert. Der Schlüssel um den Ereignishorizont zu untersuchen ist, die Bewegungen der Sterne um eine Supermassives Schwarzes Loch zu modellieren, sowie deren Interaktionen, und nach Abweichungen von unseren Erwartungen in echten Beobachtungen zu suchen. Zentrale Sternhaufen, die ein massives, dunkles Objekt mit einer Masse bis zu ∼ zehn Millionen Sonnenmassen enthalten, sind gute Laborarien um den Ereignishorizont eines möglichen supermassiven Schwarzen Lochs mit Hilfe von Sternen zu untersuchen. Die Kanäle für mögliche Wechselwirkungen zwischen Sternen und einem zentralen Schwarzen Loch sind: (a) Kompakte Sternreste und stellare Schwarze Löcher können durch die Emission von Gravitationswellen allmählich auf spiralförmigen Orbits in das supermassive Schwarze Loch fallen, was als “Extreme Mass Ratio Inspiral” (EMRI) bezeichent wird. (b) Durch normale Sternentwicklung (Sternwinde) sowie durch Sternkollisionen oder Zerstörung von Sternen im starken zentralen Gezeitenfeld kann Gas freigesetzt werden, welches anschließend vom supermassiven Schwarzen Loch akkretiert werden kann. Solche Prozesse können wesentlich zur Masse eines Supermassiven Schwarzen Lochs beitragen. Die beiden Prozesse (a und b) beinhalten verschiedene astrophysikalische Aspekte, welche uns in ihrer Kombination mit detaillierter Information über die Beschaffenheit der Raumzeit versorgen. In dieser Habilitationsschrift präsentiere ich neun Artikel aus meiner jüngeren Forschungsarbeit, welche direkt Probleme aus diesen Themenbereichen behandeln. KW - stellar dynamics KW - massive black holes KW - gravitational waves KW - general relativity KW - Stellardynamik KW - massive Schwarze Löcher KW - Gravitationswellen KW - allgemeine Relativitätstheorie Y1 - 2016 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus4-95439 ER - TY - GEN A1 - Niskanen, Johannes A1 - Kooser, Kuno A1 - Koskelo, Jaakko A1 - Käämbre, Tanel A1 - Kunnus, Kristjan A1 - Pietzsch, Annette A1 - Quevedo, Wilson A1 - Hakala, Mikko A1 - Föhlisch, Alexander A1 - Huotari, Simo A1 - Kukk, Edwin T1 - Density functional simulation of resonant inelastic X-ray scattering experiments in liquids: acetonitrile N2 - In this paper we report an experimental and computational study of liquid acetonitrile (H3C–C[triple bond, length as m-dash]N) by resonant inelastic X-ray scattering (RIXS) at the N K-edge. The experimental spectra exhibit clear signatures of the electronic structure of the valence states at the N site and incident-beam-polarization dependence is observed as well. Moreover, we find fine structure in the quasielastic line that is assigned to finite scattering duration and nuclear relaxation. We present a simple and light-to-evaluate model for the RIXS maps and analyze the experimental data using this model combined with ab initio molecular dynamics simulations. In addition to polarization-dependence and scattering-duration effects, we pinpoint the effects of different types of chemical bonding to the RIXS spectrum and conclude that the H2C–C[double bond, length as m-dash]NH isomer, suggested in the literature, does not exist in detectable quantities. We study solution effects on the scattering spectra with simulations in liquid and in vacuum. The presented model for RIXS proved to be light enough to allow phase-space-sampling and still accurate enough for identification of transition lines in physical chemistry research by RIXS. T3 - Zweitveröffentlichungen der Universität Potsdam : Mathematisch-Naturwissenschaftliche Reihe - 331 Y1 - 2016 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus4-395133 ER - TY - THES A1 - Herenz, Edmund Christian T1 - Detecting and understanding extragalactic Lyman α emission using 3D spectroscopy T1 - Detektion und Interpretation extragalaktischer Lyman Alpha Emission mittels 3D Spektroskopie N2 - In this thesis we use integral-field spectroscopy to detect and understand of Lyman α (Lyα) emission from high-redshift galaxies. Intrinsically the Lyα emission at λ = 1216 Å is the strongest recombination line from galaxies. It arises from the 2p → 1s transition in hydrogen. In star-forming galaxies the line is powered by ionisation of the interstellar gas by hot O- and B- stars. Galaxies with star-formation rates of 1 - 10 Msol/year are expected to have Lyα luminosities of 42 dex - 43 dex (erg/s), corresponding to fluxes ~ -17 dex - -18 dex (erg/s/cm²) at redshifts z~3, where Lyα is easily accessible with ground-based telescopes. However, star-forming galaxies do not show these expected Lyα fluxes. Primarily this is a consequence of the high-absorption cross-section of neutral hydrogen for Lyα photons σ ~ -14 dex (cm²). Therefore, in typical interstellar environments Lyα photons have to undergo a complex radiative transfer. The exact conditions under which Lyα photons can escape a galaxy are poorly understood. Here we present results from three observational projects. In Chapter 2, we show integral field spectroscopic observations of 14 nearby star-forming galaxies in Balmer α radiation (Hα, λ = 6562.8 Å). These observations were obtained with the Potsdam Multi Aperture Spectrophotometer at the Calar-Alto 3.5m Telescope}. Hα directly traces the intrinsic Lyα radiation field. We present Hα velocity fields and velocity dispersion maps spatially registered onto Hubble Space Telescope Lyα and Hα images. From our observations, we conjecture a causal connection between spatially resolved Hα kinematics and Lyα photometry for individual galaxies. Statistically, we find that dispersion-dominated galaxies are more likely to emit Lyα photons than galaxies where ordered gas-motions dominate. This result indicates that turbulence in actively star-forming systems favours an escape of Lyα radiation. Not only massive stars can power Lyα radiation, but also non-thermal emission from an accreting super-massive black hole in the galaxy centre. If a galaxy harbours such an active galactic nucleus, the rate of hydrogen-ionising photons can be more than 1000 times higher than that of a typical star-forming galaxy. This radiation can potentially ionise large regions well outside the main stellar body of galaxies. Therefore, it is expected that the neutral hydrogen from these circum-galactic regions shines fluorescently in Lyα. Circum-galactic gas plays a crucial role in galaxy formation. It may act as a reservoir for fuelling star formation, and it is also subject to feedback processes that expel galactic material. If Lyα emission from this circum-galactic medium (CGM) was detected, these important processes could be studied in-situ around high-z galaxies. In Chapter 3, we show observations of five radio-quiet quasars with PMAS to search for possible extended CGM emission in the Lyα line. However, in four of the five objects, we find no significant traces of this emission. In the fifth object, there is evidence for a weak and spatially quite compact Lyα excess at several kpc outside the nucleus. The faintness of these structures is consistent with the idea that radio-quiet quasars typically reside in dark matter haloes of modest masses. While we were not able to detect Lyα CGM emission, our upper limits provide constraints for the new generation of IFS instruments at 8--10m class telescopes. The Multi Unit Spectroscopic Explorer (MUSE) at ESOs Very Large Telescopeis such an unique instrument. One of the main motivating drivers in its construction was the use as a survey instrument for Lyα emitting galaxies at high-z. Currently, we are conducting such a survey that will cover a total area of ~100 square arcminutes with 1 hour exposures for each 1 square arcminute MUSE pointing. As a first result from this survey we present in Chapter 5 a catalogue of 831 emission-line selected galaxies from a 22.2 square arcminute region in the Chandra Deep Field South. In order to construct the catalogue, we developed and implemented a novel source detection algorithm -- LSDCat -- based on matched filtering for line emission in 3D spectroscopic datasets (Chapter 4). Our catalogue contains 237 Lyα emitting galaxies in the redshift range 3 ≲ z ≲ 6. Only four of those previously had spectroscopic redshifts in the literature. We conclude this thesis with an outlook on the construction of a Lyα luminosity function based on this unique sample (Chapter 6). N2 - In der vorliegenden Doktorarbeit präsentieren wir Resultate aus drei integralfeldspektroskopischen Beobachtungskampagnen die mit der Intention Lyman α (Lyα) Strahlung von hoch-rotverschobenen Galaxien zu detektieren und zu verstehen durchgeführt wurden. Die Lyα Emissionslinie im ultravioletten Teil des elektromagnetischen Spektrums (λ = 1216 Å) ist intrinsisch die stärkste Rekombinationslinie im Linienspektrum sternbildender Galaxien. Die Linie ist eine Folge der Ionisation des interstellaren Gases durch heiße O- und B- Sterne. Man erwartet von Galaxien mit Sternentstehungsraten 1 - 10 Msol/Jahr intrinsische Lyα Leuchtkräfte von 42 dex - 43 dex (erg/s), was bei Rotverschiebungen von z~3, bei denen Lyα mit bodengebundenen Teleskopen zu beobachten ist, einem Strahlungsstrom von ~ -17 dex - -18 dex (erg/s/cm²) entspricht. Allerdings werden nicht von allen sternbildenen Galaxien derartige Lyα Strahlungsströme gemessen. Dies ist in erster Linie eine direkte Konsequenz des hohen Absorptionsquerschnitts von neutralem Wasserstoff für Lyα Photonen. Deshalb erfahren Lyα Photonen einen komplexen Strahlungstransportprozess in typischen interstellaren Umgebungen. Die exakten Bedingungen bei denen Lyα Strahlung eine Galaxie verlassen sind noch nicht hinreichend gut verstanden. Diesbezüglich werden in Kapitel 2 dieser Arbeit integralfeldspektroskopische Beobachtungsergebnisse der Balmer α Strahlung (Hα, λ = 6562.8 Å) von 14 nahen sternbildenden Galaxien gezeigt. Die Beobachtungsdaten wurden mit dem Potsdam Multi Aperture Spectrophotometer (PMAS) am Calar Alto 3.5m Teleskop gewonnen. Hα Strahlung ist eine direkte Kopie des intrinischen Lyα Strahlungsfeldes der Galaxien. Wir zeigen unsere Hα Geschwindigkeitsfelder und Geschwindigkeitsdispersionsfelder räumlich überlagert zu Hubble-Weltraumteleskop-Bildaufnahmen der Lyα und Hα Strahlungsströme. Aus diesen Beobachtungen können wir schlussfolgern, dass in einigen Galaxien kausale Zusammenhänge zwischen der Hα-Kinematik und der Lyα-Photometrie bestehen. Statistisch signifikant finden wir, dass Galaxien, bei denen chaotische Dispersionsbewegungen dominieren, wahrscheinlicher Lyα Strahlung abgeben als Galaxien bei denen die Gasbewegungen durch geordnete Bewegungen dominiert sind. Dieses Resultat ist ein Indiz dafür, dass Turbulenz im interstellaren Medium aktiv sternbildender Galaxien schafft, welche ein Austreten der Lyα-Strahlung begünstigen. Neben massereichen Sternen kann nicht-thermische Strahlung eines akretierenden supermassereichen schwarzen Loches eine weitere Energiequelle zur Erzeugung von Lyα Strahlung sein. Wenn eine Galaxie einen solchen aktiven Galaxienkern enthält, kann die Rate der ionisierenden Photonen 1000-mal höher sein als bei einer normalen sternbildenden Galaxie. Diese Strahlung hat das Potential große Bereiche weit ausserhalb der Sternansammlungen der Galaxien zu ionisieren. Deshalb ist zu erwarten, dass der neutrale Wasserstoff in diesen zirkum-galaktischen Gebieten in Lyα-Strahlung fluoresziert. Dieses zirkum-galaktische Gas spielt eine wesentliche Rolle bei der Entwicklung von Galaxien. Zum Einen ist es das Reservoir aus denen Sternentstehungsprozesse ihr Gas beziehen, zum Anderen ist es Wechselwirkungsprozessen ausgesetzt, bei denen Gas aus der Galaxie hinausgeschleudert wird. Wenn Lyα-Strahlung dieses zirkum-galaktischen Mediums detektiert werden könnte, ließen sich diese fundamentalen Prozesse der Galaxienentwicklung detaillierter studieren. In Kapitel 3 dieser Arbeit zeigen wir PMAS Beobachtungsdaten von 5 radio-leisen Quasaren in denen wir nach dieser ausgedehnten Lyα-Strahlung gesucht haben. Jedoch haben wir für 4 unserer Quasare keine signifikanten Spuren dieser ausgedehnten Strahlung entdecken können. Im fünften Objekt finden wir in Entfernung von einigen Kiloparsec zum Kern Anzeichen für eine schwache und räumlich eher kompakte Quelle. Deartig schwache Flüsse von solchen Strukturen erscheinen konsistent mit der Annahme, dass radio-leise Quasare sich in Halos aus dunkler Materie mit eher moderaten Massen befinden. Obwohl wir nicht direkt Lyα-Strahlung vom zirkum-galaktischen Medium detektieren konnten, sind unsere Detektionsgrenzen von Nutzem bei der Planung von diesbezüglichen Beobachtungen mit der neuen Generation von Integralfeldspektrographen an 8--10m Teleskopen. Ein derartiges Instrument ist der Multi Unit Spectroscopic Explorer (MUSE) am ESO Very Large Telescope. Einer der Hauptbeweggründe für dessen Konstruktion war die Verwendung als Durchmusterungsinstrument für Lyα emittierende Galaxien bei hohen Rotverschiebungen. Aktuell führen wir eine derartige Durchmusterungskampagne durch. Nach deren Abschluss, werden wir eine Fläche von 100 Quadratbogenminuten durchmustert haben. In Kapitel 5 dieser Arbeit präsentieren wir als erstes Resultat einen Katalog von 831 Emissionslinienselektierten Galaxien in einer 22.2 Quadratbogenminuten großen Region im Chandra Deep Field South. Um diesen Katalog zu erzeugen, haben wir eine neuartige Quellendetektionsmethode für integralfeldspektroskopische Datensätze entwickelt und implementiert (Kapitel 4). Unser Katalog enthält 237 Lyα emittierende Galaxien bei Rotverschiebungen 3 ≲ z ≲ 6. Aufgrund ihrer geringen Kontinuumsflussdichten existierten zuvor nur von 4 dieser Galaxien spektroskopische Rotverschiebungen. Als Abschluss dieser Arbeit präsentieren wir einen Ausbick bezüglich der Konstruktion einer Leuchtkraftfunktion dieser einzigartigen Lyα Galaxienstichprobe (Kapitel 6). KW - astrophysics KW - galaxies KW - high redshift galaxies KW - integral field spectroscopy KW - quasars KW - Astrophysik KW - Galaxien KW - Galaxien bei hoher Rotverschiebung KW - Integralfeldspektroskopie KW - Quasare Y1 - 2016 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus4-102341 ER - TY - JOUR A1 - Steinmetz, Matthias T1 - Die Vermessung des Universums JF - Vision als Aufgabe : das Leibniz-Universum im 21. Jahrhundert Y1 - 2016 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:b4-opus4-25899 SN - 978-3-939818-67-0 SP - 197 EP - 210 PB - Berlin-Brandenburgische Akademie der Wissenschaften CY - Berlin ER - TY - JOUR A1 - Yang, Jie A1 - Gühr, Markus A1 - Vecchione, Theodore A1 - Robinson, Matthew Scott A1 - Li, Renkai A1 - Hartmann, Nick A1 - Shen, Xiaozhe A1 - Coffee, Ryan A1 - Corbett, Jeff A1 - Fry, Alan A1 - Gaffney, Kelly A1 - Gorkhover, Tais A1 - Hast, Carsten A1 - Jobe, Keith A1 - Makasyuk, Igor A1 - Reid, Alexander A1 - Robinson, Joseph A1 - Vetter, Sharon A1 - Wang, Fenglin A1 - Weathersby, Stephen A1 - Yoneda, Charles A1 - Centurion, Martin A1 - Wang, Xijie T1 - Diffractive imaging of a rotational wavepacket in nitrogen molecules with femtosecond megaelectronvolt electron pulses JF - Nature Communications N2 - Imaging changes in molecular geometries on their natural femtosecond timescale with sub-Angstrom spatial precision is one of the critical challenges in the chemical sciences, as the nuclear geometry changes determine the molecular reactivity. For photoexcited molecules, the nuclear dynamics determine the photoenergy conversion path and efficiency. Here we report a gas-phase electron diffraction experiment using megaelectronvolt (MeV) electrons, where we captured the rotational wavepacket dynamics of nonadiabatically laser-aligned nitrogen molecules. We achieved a combination of 100 fs root-mean-squared temporal resolution and sub-Angstrom (0.76 angstrom) spatial resolution that makes it possible to resolve the position of the nuclei within the molecule. In addition, the diffraction patterns reveal the angular distribution of the molecules, which changes from prolate (aligned) to oblate (anti-aligned) in 300 fs. Our results demonstrate a significant and promising step towards making atomically resolved movies of molecular reactions. Y1 - 2016 U6 - https://doi.org/10.1038/ncomms11232 SN - 2041-1723 VL - 7 PB - Nature Publ. Group CY - London ER - TY - JOUR A1 - Yang, Jie A1 - Guehr, Markus A1 - Shen, Xiaozhe A1 - Li, Renkai A1 - Vecchione, Theodore A1 - Coffee, Ryan A1 - Corbett, Jeff A1 - Fry, Alan A1 - Hartmann, Nick A1 - Hast, Carsten A1 - Hegazy, Kareem A1 - Jobe, Keith A1 - Makasyuk, Igor A1 - Robinson, Joseph A1 - Robinson, Matthew Scott A1 - Vetter, Sharon A1 - Weathersby, Stephen A1 - Yoneda, Charles A1 - Wang, Xijie A1 - Centurion, Martin T1 - Diffractive Imaging of Coherent Nuclear Motion in Isolated Molecules JF - Physical review letters N2 - Observing the motion of the nuclear wave packets during a molecular reaction, in both space and time, is crucial for understanding and controlling the outcome of photoinduced chemical reactions. We have imaged the motion of a vibrational wave packet in isolated iodine molecules using ultrafast electron diffraction with relativistic electrons. The time-varying interatomic distance was measured with a precision 0.07 angstrom and temporal resolution of 230 fs full width at half maximum. The method is not only sensitive to the position but also the shape of the nuclear wave packet. Y1 - 2016 U6 - https://doi.org/10.1103/PhysRevLett.117.153002 SN - 0031-9007 SN - 1079-7114 VL - 117 PB - American Physical Society CY - College Park ER - TY - JOUR A1 - Hamaguchi, K. A1 - Oskinova, Lida A1 - Russell, C. M. P. A1 - Petre, R. A1 - Enoto, T. A1 - Morihana, K. A1 - Ishida, M. T1 - DISCOVERY OF RAPIDLY MOVING PARTIAL X-RAY ABSORBERS WITHIN GAMMA CASSIOPEIAE JF - The astrophysical journal : an international review of spectroscopy and astronomical physics N2 - detected six rapid X-ray spectral hardening events called "softness dips" in a similar to 100 ks observation in 2011. All the softness dip events show symmetric softness-ratio variations, and some of them have flat bottoms apparently due to saturation. The softness dip spectra are best described by either similar to 40% or similar to 70% partial covering absorption to kT similar to 12 keV plasma emission by matter with a neutral hydrogen column density of similar to(2-8) x 10(21) cm(-2), while the spectrum outside these dips is almost free of absorption. This result suggests the presence of two distinct X-ray-emitting spots in the.. Cas system, perhaps on a white dwarf (WD) companion with dipole mass accretion. The partial covering absorbers may be blobs in the Be stellar wind, the Be disk, or rotating around the WD companion. Weak correlations of the softness ratios to the hard X-ray flux suggest the presence of stable plasmas at kT similar to 0.9 and 5 keV, which may originate from the Be or WD winds. The formation of a Be star and WD binary system requires mass transfer between two stars; gamma Cas may have experienced such activity in the past. KW - blue stragglers KW - stars: emission-line, Be KW - stars: individual (gamma Cassiopeiae) KW - stars: winds, outflows KW - white dwarfs KW - X-rays: stars Y1 - 2016 U6 - https://doi.org/10.3847/0004-637X/832/2/140 SN - 0004-637X SN - 1538-4357 VL - 832 SP - 33 EP - 49 PB - IOP Publ. Ltd. CY - Bristol ER - TY - JOUR A1 - Archambault, S. A1 - Archer, A. A1 - Barnacka, Anna A1 - Behera, B. A1 - Beilicke, M. A1 - Benbow, W. A1 - Berger, K. A1 - Bird, R. A1 - Böttcher, Markus A1 - Buckley, J. H. A1 - Bugaev, V. A1 - Cardenzana, J. V. A1 - Cerruti, M. A1 - Chen, Xuhui A1 - Christiansen, J. L. A1 - Ciupik, L. A1 - Collins-Hughes, E. A1 - Connolly, M. P. A1 - Cui, W. A1 - Dickinson, H. J. A1 - Dumm, J. A1 - Eisch, J. D. A1 - Errando, M. A1 - Falcone, A. A1 - Federici, Simone A1 - Feng, Q. A1 - Finley, J. P. A1 - Fleischhack, H. A1 - Fortson, L. A1 - Furniss, A. A1 - Gillanders, G. H. A1 - Godambe, S. A1 - Griffin, S. A1 - Griffiths, S. T. A1 - Grube, J. A1 - Gyuk, G. A1 - Hakansson, Nils A1 - Hanna, D. A1 - Holder, J. A1 - Hughes, G. A1 - Johnson, C. A. A1 - Kaaret, P. A1 - Kar, P. A1 - Kertzman, M. A1 - Khassen, Y. A1 - Kieda, D. A1 - Krawczynski, H. A1 - Kumar, S. A1 - Lang, M. J. A1 - Madhavan, A. S. A1 - Maier, G. A1 - McArthur, S. A1 - McCann, A. A1 - Meagher, K. A1 - Millis, J. A1 - Moriarty, P. A1 - Nelson, T. A1 - Nieto, D. A1 - Ong, R. A. A1 - Otte, A. N. A1 - Park, N. A1 - Perkins, J. S. A1 - Pohl, Martin A1 - Popkow, A. A1 - Prokoph, H. A1 - Pueschel, Elisa A1 - Quinn, J. A1 - Ragan, K. A1 - Rajotte, J. A1 - Reyes, L. C. A1 - Reynolds, P. T. A1 - Richards, G. T. A1 - Roache, E. A1 - Sembroski, G. H. A1 - Shahinyan, K. A1 - Smith, A. W. A1 - Staszak, D. A1 - Sweeney, K. A1 - Telezhinsky, Igor O. A1 - Tucci, J. V. A1 - Tyler, J. A1 - Varlotta, A. A1 - Vassiliev, V. V. A1 - Wakely, S. P. A1 - Welsing, R. A1 - Wilhelm, Alina A1 - Williams, D. A. A1 - Zitzer, B. T1 - Discovery of very high energy gamma rays from 1ES 1440+122 JF - Monthly notices of the Royal Astronomical Society KW - BL Lacertae objects: general KW - gamma-rays: general Y1 - 2016 U6 - https://doi.org/10.1093/mnras/stw1319 SN - 0035-8711 SN - 1365-2966 VL - 461 SP - 202 EP - 208 PB - Oxford Univ. Press CY - Oxford ER - TY - JOUR A1 - Kurpiers, Jona A1 - Neher, Dieter T1 - Dispersive Non-Geminate Recombination in an Amorphous Polymer: Fullerene Blend JF - Scientific reports N2 - Recombination of free charge is a key process limiting the performance of solar cells. For low mobility materials, such as organic semiconductors, the kinetics of non-geminate recombination (NGR) is strongly linked to the motion of charges. As these materials possess significant disorder, thermalization of photogenerated carriers in the inhomogeneously broadened density of state distribution is an unavoidable process. Despite its general importance, knowledge about the kinetics of NGR in complete organic solar cells is rather limited. We employ time delayed collection field (TDCF) experiments to study the recombination of photogenerated charge in the high-performance polymer: fullerene blend PCDTBT:PCBM. NGR in the bulk of this amorphous blend is shown to be highly dispersive, with a continuous reduction of the recombination coefficient throughout the entire time scale, until all charge carriers have either been extracted or recombined. Rapid, contact-mediated recombination is identified as an additional loss channel, which, if not properly taken into account, would erroneously suggest a pronounced field dependence of charge generation. These findings are in stark contrast to the results of TDCF experiments on photovoltaic devices made from ordered blends, such as P3HT:PCBM, where non-dispersive recombination was proven to dominate the charge carrier dynamics under application relevant conditions. Y1 - 2016 U6 - https://doi.org/10.1038/srep26832 SN - 2045-2322 VL - 6 PB - Nature Publ. Group CY - London ER - TY - JOUR A1 - Kurpiers, Jona A1 - Neher, Dieter T1 - Dispersive Non-Geminate Recombination in an Amorphous Polymer:Fullerene Blend JF - Scientific reports N2 - Recombination of free charge is a key process limiting the performance of solar cells. For low mobility materials, such as organic semiconductors, the kinetics of non-geminate recombination (NGR) is strongly linked to the motion of charges. As these materials possess significant disorder, thermalization of photogenerated carriers in the inhomogeneously broadened density of state distribution is an unavoidable process. Despite its general importance, knowledge about the kinetics of NGR in complete organic solar cells is rather limited. We employ time delayed collection field (TDCF) experiments to study the recombination of photogenerated charge in the high-performance polymer:fullerene blend PCDTBT:PCBM. NGR in the bulk of this amorphous blend is shown to be highly dispersive, with a continuous reduction of the recombination coefficient throughout the entire time scale, until all charge carriers have either been extracted or recombined. Rapid, contact-mediated recombination is identified as an additional loss channel, which, if not properly taken into account, would erroneously suggest a pronounced field dependence of charge generation. These findings are in stark contrast to the results of TDCF experiments on photovoltaic devices made from ordered blends, such as P3HT:PCBM, where non-dispersive recombination was proven to dominate the charge carrier dynamics under application relevant conditions. Y1 - 2016 U6 - https://doi.org/10.1038/srep26832 SN - 2045-2322 VL - 6 PB - Nature Publishing Group CY - London ER - TY - GEN A1 - Kurpiers, Jona A1 - Neher, Dieter T1 - Dispersive Non-Geminate Recombination in an Amorphous Polymer:Fullerene Blend N2 - Recombination of free charge is a key process limiting the performance of solar cells. For low mobility materials, such as organic semiconductors, the kinetics of non-geminate recombination (NGR) is strongly linked to the motion of charges. As these materials possess significant disorder, thermalization of photogenerated carriers in the inhomogeneously broadened density of state distribution is an unavoidable process. Despite its general importance, knowledge about the kinetics of NGR in complete organic solar cells is rather limited. We employ time delayed collection field (TDCF) experiments to study the recombination of photogenerated charge in the high-performance polymer:fullerene blend PCDTBT:PCBM. NGR in the bulk of this amorphous blend is shown to be highly dispersive, with a continuous reduction of the recombination coefficient throughout the entire time scale, until all charge carriers have either been extracted or recombined. Rapid, contact-mediated recombination is identified as an additional loss channel, which, if not properly taken into account, would erroneously suggest a pronounced field dependence of charge generation. These findings are in stark contrast to the results of TDCF experiments on photovoltaic devices made from ordered blends, such as P3HT:PCBM, where non-dispersive recombination was proven to dominate the charge carrier dynamics under application relevant conditions. T3 - Zweitveröffentlichungen der Universität Potsdam : Mathematisch-Naturwissenschaftliche Reihe - 228 Y1 - 2016 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus4-91541 ER - TY - JOUR A1 - Lu, Guanghao A1 - Di Pietro, Riccardo A1 - Kölln, Lisa Sophie A1 - Nasrallah, Iyad A1 - Zhou, Ling A1 - Mollinger, Sonya A1 - Himmelberger, Scott A1 - Koch, Norbert A1 - Salleo, Alberto A1 - Neher, Dieter T1 - Dual-Characteristic Transistors Based on Semiconducting Polymer Blends JF - Advanced electronic materials N2 - A dual-characteristic polymer field-effect transistor has markedly different characteristics in low and high voltage operations. In the low-voltage range (<5 V) it shows sharp subthreshold slopes (0.3–0.4 V dec−1), using which a low-voltage inverter with gain 8 is realized, while high-voltage (>5 V) induces symmetric current with regard to drain and gate voltages, leading to discrete differential (trans) conductances. KW - charge accumulation KW - crystalline ordering KW - field-effect-transistor KW - semiconducting polymers Y1 - 2016 U6 - https://doi.org/10.1002/aelm.201600267 SN - 2199-160X VL - 2 SP - 2344 EP - 2351 PB - Wiley-Blackwell CY - Hoboken ER - TY - JOUR A1 - Guber, Christoph R. A1 - Richter, Philipp T1 - Dust depletion of Ca and Ti in QSO absorption-line systems JF - Wiley Interdisciplinary Reviews : Water N2 - Aims. To explore the role of titanium-and calcium-dust depletion in gas in and around galaxies, we systematically study Ti/Ca abundance ratios in intervening absorption-line systems at low and high redshift. Methods. We investigate high-resolution optical spectra obtained by the UVES instrument at the Very Large Telescope (VLT) and spectroscopically analyze 34 absorption-line systems at z <= 0.5 to measure column densities (or limits) for Ca II and Ti II. We complement our UVES data set with previously published absorption-line data on Ti/Ca for redshifts up to z similar to 3.8. Our absorber sample contains 110 absorbers including damped Lyman alpha systems (DLAs), sub-DLAs, and Lyman-Limit systems (LLS). We compare our Ti/Ca findings with results from the MilkyWay and the Magellanic Clouds and discuss the properties of Ti/Ca absorbers in the general context of quasar absorption-line systems. Results. Our analysis indicates that there are two distinct populations of absorbers with either high or low Ti/Ca ratios with a separation at [Ti/Ca] approximate to 1. While the calcium-dust depletion in most of the absorbers appears to be severe, the titanium depletions are mild in systems with high Ti/Ca ratios. The derived trend indicates that absorbers with high Ti/Ca ratios have dust-to-gas ratios that are substantially lower than in the Milky Way. We characterize the overall nature of the absorbers by correlating Ti/Ca with other observables (e.g., metallicity, velocity-component structure) and by modeling the ionization properties of singly-ionized Ca and Ti in different environments. Conclusions. We conclude that Ca II and Ti II bearing absorption-line systems trace predominantly neutral gas in the disks and inner halo regions of galaxies, where the abundance of Ca and Ti reflects the local metal and dust content of the gas. Our study suggests that the Ti/Ca ratio represents a useful measure for the gas-to-dust ratio and overall metallicity in intervening absorption-line systems. KW - quasars: absorption lines KW - dust, extinction KW - galaxies: abundances KW - galaxies: ISM KW - intergalactic medium Y1 - 2016 U6 - https://doi.org/10.1051/0004-6361/201628466 SN - 1432-0746 VL - 591 PB - EDP Sciences CY - Les Ulis ER - TY - JOUR A1 - Liu, Xiaodong A1 - Sachse, Manuel A1 - Spahn, Frank A1 - Schmidt, Jurgen T1 - Dynamics and distribution of Jovian dust ejected from the Galilean satellites JF - Journal of geophysical research, Planets N2 - In this paper, the dynamical analysis of the Jovian dust originating from the four Galilean moons is presented. High-accuracy orbital integrations of dust particles are used to determine their dynamical evolution. A variety of forces are taken into account, including the Lorentz force, solar radiation pressure, Poynting-Robertson drag, solar gravity, the satellites' gravity, plasma drag, and gravitational effects due to nonsphericity of Jupiter. More than 20,000 dust particles from each source moon in the size range from 0.05 μm to 1 cm are simulated over 8000 (Earth) years until each dust grain hits a sink (moons, Jupiter, or escape from the system). Configurations of dust number density in the Jovicentric equatorial inertial frame are calculated and shown. In a Jovicentric frame rotating with the Sun the dust distributions are found to be asymmetric. For certain small particle sizes, the dust population is displaced towards the Sun, while for certain larger sizes, the dust population is displaced away from the Sun. The average lifetime as a function of particle size for ejecta from each source moon is derived, and two sharp jumps in the average lifetime are analyzed. Transport of dust between the Galilean moons and to Jupiter is investigated. Most of the orbits for dust particles from Galilean moons are prograde, while, surprisingly, a small fraction of orbits are found to become retrograde mainly due to solar radiation pressure and Lorentz force. The distribution of orbital elements is also analyzed. Y1 - 2016 U6 - https://doi.org/10.1002/2016JE004999 SN - 2169-9097 SN - 2169-9100 VL - 121 SP - 1141 EP - 1173 PB - American Geophysical Union CY - Washington ER - TY - THES A1 - Fournier, Yori T1 - Dynamics of the rise of magnetic flux tubes in stellar interiors BT - a numerical study of compressible non-axisymmetric flux tubes N2 - In sonnenähnlichen Sternen erhält ein Dynamo-Mechanismus die Magnetfelder. Der Babcock-Leighton-Dynamo beruht auf einem solchen Mechanismus und erfordert insbesondere die Existenz von magnetischen Flussröhren. Man nimmt an, dass magnetische Flussröhren am Boden der Konvetionszone entstehen und durch Auftrieb bis zur Oberfläche steigen. Es wird ein spezielles Dynamomodell vorgeschlagen, in dem der Verzögerungseffekt durch das Aufsteigen der Flussröhren berücksichtigt wird. Die vorliegende Dissertation beschäftigt sich mit der Anwendbarkeit des Babcock-Leighton-Dynamos auf andere Sterne. Zu diesem Zweck versuchen wir, die Aufstiegszeiten von magnetischen Flussröhren mit Hilfe von kompressiblen MHD-Simulationen in spärischen Kugelschalen mit Dichteschichtung zu bestimmen und einzugrenzen. Derartige Simulationen sind allerdings nur in einem unrealistischen Parameterbereich möglich. Deshalb ist eine Skalierungsrelation nötig, die die Ergebnisse auf realistische physikalische Regimes überträgt. Wir erweitern frühere Arbeiten zu Skalierungsrelationen in 2D und leiten ein allgemeines Skalierungsgesetz ab, das für 2D- und 3D-Flussröhren gültig ist. In einem umfangreichen Satz von numerischen Simulationen zeigen wir, dass die abgeleitete Skalierungsrelation auch im vollständig nichtlinearen Fall gilt. Wir haben damit ein Gesetz für die Aufstiegszeit von magnetischen Flussröhren gefunden, dass in jedem sonnenähnlichen Stern Gültigkeit hat. Schließlich implementieren wir dieses Gesetz in einem Dynamomodell mit Verzögerungsterm. Die Simulationen eines solchen verzögerten Flussröhren/Babcock-Leighton-Dynamos auf der Basis der Meanfield-Formulierung führten auf ein neues Dynamo-Regime, das nur bei Anwesenheit der Verzögerung existiert. Die erforderlichen Verzögerungen sind von der Gröÿenordnung der Zykluslänge, die resultierenden Magnetfelder sind schwächer als die Äquipartitions-Feldstärke. Dieses neue Regime zeigt, dass auch bei sehr langen Aufstiegszeiten der Flussröhren/Babcock-Leighton-Dynamo noch nichtzerfallende Lösungen liefern und daher auf ein breites Spektrum von Sternen anwendbar sein kann. N2 - Solar-like stars maintain their magnetic fields thanks to a dynamo mechanism. The Babcock-Leighton dynamo is one possible dynamo that has the particularity to require magnetic flux tubes. Magnetic flux tubes are assumed to form at the bottom of the convective zone and rise buoyantly to the surface. A delayed dynamo model has been suggested, where the delay accounts for the rise time of the magnetic flux tubes; a time, that has been ignored by former studies. The present thesis aims to study the applicability of the flux tube/Babcock-Leighton dynamo to other stars. To do so, we attempt to constrain the rise time of magnetic flux tubes thanks to the first fully compressible MHD simulations of rising magnetic flux tubes in stratified rotating spherical shells. Such simulations are limited to an unrealistic parameter space, therefore, a scaling relation is required to scale the results to realistic physical regimes. We extended earlier works on 2D scaling relations and derived a general scaling law valid for both 2D and 3D. We then carried out two large series of numerical experiments and verified that the scaling law we have derived indeed applies to the fully non-linear case. It allowed us to extract a constraint for the rise time of magnetic flux tubes that is valid for any solar-like star. We finally introduced this constraint to a delayed dynamo model. By carrying out simulations of a mean-field, delayed, flux tube/Babcock-Leighton dynamo, we were able to identify a new dynamo regime resulting from the delay. This regime requires delays about an entire cycle and exhibits subequipartition magnetic activity. Revealing this new regime shows that even for long delays the flux tube/Babcock-Leighton dynamo can still deliver non-decaying solutions and remains a good candidate for a wide range of solar-like stars. KW - astrophysics KW - stellar physics KW - magnetohydrodynamics (MHD) KW - numerical experiments KW - magnetic flux tubes KW - dynamo theory Y1 - 2016 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus4-394533 ER - TY - JOUR A1 - Vlasov, Vladimir A1 - Rosenblum, Michael A1 - Pikovskij, Arkadij T1 - Dynamics of weakly inhomogeneous oscillator populations: perturbation theory on top of Watanabe-Strogatz integrability JF - Journal of physics : A, Mathematical and theoretical N2 - As has been shown by Watanabe and Strogatz (WS) (1993 Phys. Rev. Lett. 70 2391), a population of identical phase oscillators, sine-coupled to a common field, is a partially integrable system: for any ensemble size its dynamics reduce to equations for three collective variables. Here we develop a perturbation approach for weakly nonidentical ensembles. We calculate corrections to the WS dynamics for two types of perturbations: those due to a distribution of natural frequencies and of forcing terms, and those due to small white noise. We demonstrate that in both cases, the complex mean field for which the dynamical equations are written is close to the Kuramoto order parameter, up to the leading order in the perturbation. This supports the validity of the dynamical reduction suggested by Ott and Antonsen (2008 Chaos 18 037113) for weakly inhomogeneous populations. KW - Kuramoto model KW - oscillator populations KW - integrability KW - perturbation theory Y1 - 2016 U6 - https://doi.org/10.1088/1751-8113/49/31/31LT02 SN - 1751-8113 SN - 1751-8121 VL - 49 PB - IOP Publ. Ltd. CY - Bristol ER - TY - JOUR A1 - Love, John A. A1 - Chou, Shu-Hua A1 - Huang, Ye A1 - Bazan, Guillermo C. A1 - Thuc-Quyen Nguyen, T1 - Effects of solvent additive on "s-shaped" curves in solution-processed small molecule solar cells JF - Beilstein journal of organic chemistry N2 - A novel molecular chromophore, p-SIDT(FBTThCA8)(2), is introduced as an electron-donor material for bulk heterojunction (BHJ) solar cells with broad absorption and near ideal energy levels for the use in combination with common acceptor materials. It is found that films cast from chlorobenzene yield devices with strongly s-shaped current-voltage curves, drastically limiting performance. We find that addition of the common solvent additive diiodooctane, in addition to facilitating crystallization, leads to improved vertical phase separation. This yields much better performing devices, with improved curve shape, demonstrating the importance of morphology control in BHJ devices and improving the understanding of the role of solvent additives. KW - current voltage analysis KW - morphology KW - organic solar cells Y1 - 2016 U6 - https://doi.org/10.3762/bjoc.12.249 SN - 1860-5397 VL - 12 SP - 2543 EP - 2555 PB - Beilstein-Institut zur Förderung der Chemischen Wissenschaften CY - Frankfurt, Main ER - TY - JOUR A1 - Ge, J. X. A1 - He, J. H. A1 - Yan, Huirong T1 - Effects of turbulent dust grain motion to interstellar chemistry JF - Monthly notices of the Royal Astronomical Society N2 - Theoretical studies have revealed that dust grains are usually moving fast through the turbulent interstellar gas, which could have significant effects upon interstellar chemistry by modifying grain accretion. This effect is investigated in this work on the basis of numerical gas-grain chemical modelling. Major features of the grain motion effect in the typical environment of dark clouds (DC) can be summarized as follows: (1) decrease of gas-phase (both neutral and ionic) abundances and increase of surface abundances by up to 2-3 orders of magnitude; (2) shifts of the existing chemical jumps to earlier evolution ages for gas-phase species and to later ages for surface species by factors of about 10; (3) a few exceptional cases in which some species turn out to be insensitive to this effect and some other species can show opposite behaviours too. These effects usually begin to emerge from a typical DC model age of about 10(5) yr. The grain motion in a typical cold neutral medium (CNM) can help overcome the Coulomb repulsive barrier to enable effective accretion of cations on to positively charged grains. As a result, the grain motion greatly enhances the abundances of some gas-phase and surface species by factors up to 2-6 or more orders of magnitude in the CNM model. The grain motion effect in a typical molecular cloud (MC) is intermediate between that of the DC and CNM models, but with weaker strength. The grain motion is found to be important to consider in chemical simulations of typical interstellar medium. KW - astrochemistry KW - turbulence KW - ISM: abundances KW - ISM: clouds KW - dust, extinction KW - ISM: molecules Y1 - 2016 U6 - https://doi.org/10.1093/mnras/stv2560 SN - 0035-8711 SN - 1365-2966 VL - 455 SP - 3570 EP - 3587 PB - Oxford Univ. Press CY - Oxford ER - TY - JOUR A1 - Kumph, Muir A1 - Henkel, Carsten A1 - Rabl, Peter A1 - Brownnutt, Michael A1 - Blatt, Rainer T1 - Electric-field noise above a thin dielectric layer on metal electrodes JF - NEW JOURNAL OF PHYSICS N2 - The electric-field noise above a layered structure composed of a planar metal electrode covered by a thin dielectric is evaluated and it is found that the dielectric film considerably increases the noise level, in proportion to its thickness. Importantly, even a thin (mono) layer of a low-loss dielectric can enhance the noise level by several orders of magnitude compared to the noise above a bare metal. Close to this layered surface, the power spectral density of the electric field varies with the inverse fourth power of the distance to the surface, rather than with the inverse square, as it would above a bare metal surface. Furthermore, compared to a clean metal, where the noise spectrum does not vary with frequency (in the radio-wave and microwave bands), the dielectric layer can generate electricfield noise which scales in inverse proportion to the frequency. For various realistic scenarios, the noise levels predicted from this model are comparable to those observed in trapped-ion experiments. Thus, these findings are of particular importance for the understanding and mitigation of unwanted heating and decoherence in miniaturized ion traps. KW - ion trap KW - electric field noise KW - fluctuation dissipation Y1 - 2016 U6 - https://doi.org/10.1088/1367-2630/18/2/023020 SN - 1367-2630 VL - 18 SP - 1125 EP - 1136 PB - IOP Publ. Ltd. CY - Bristol ER - TY - JOUR A1 - Zehbe, Rolf A1 - Mochales, Carolina A1 - Radzik, Daniela A1 - Mueller, Wolf-Dieter A1 - Fleck, Claudia T1 - Electrophoretic deposition of multilayered (cubic and tetragonal stabilized) zirconia ceramics for adapted crack deflection JF - Journal of the European Ceramic Society N2 - The electrophoretic deposition process was used to produce multi-layered ceramics consisting of alternating layers of fully stabilized cubic zirconia and partially stabilized tetragonal zirconia to make use of their different mechanical behaviour, investigating the possibility to deflect advancing cracks at the interfaces of the different layers. This crack deflection is apparently impacted by a toughening mechanism only found in the tetragonal stabilized zirconia polymorph and is characterized by the stress induced transformation of the metastable tetragonal phase into the monoclinic one, which is accompanied by a volume increase resulting in a closing mechanism for advancing cracks. While improving the electrophoretic deposition process, we investigated the transformation toughening mechanism at the layer interfaces and their effect on crack propagation. Investigations involved a combination of different imaging methods, including light microscopy, white light interferometry, atomic force microscopy, scanning electron microscopy, energy dispersive X-ray spectroscopy and Raman spectroscopy. (C) 2015 Elsevier Ltd. All rights reserved. KW - Electrophoretic deposition KW - Yttria stabilized zirconia KW - Transformation toughening KW - Multilayer KW - Crack deflection Y1 - 2016 U6 - https://doi.org/10.1016/j.jeurceramsoc.2015.08.022 SN - 0955-2219 SN - 1873-619X VL - 36 SP - 357 EP - 364 PB - Elsevier CY - Oxford ER - TY - JOUR A1 - Romita, Krista A1 - Lada, Elizabeth A1 - Cioni, Maria-Rosa L. T1 - EMBEDDED CLUSTERS IN THE LARGE MAGELLANIC CLOUD USING THE VISTA MAGELLANIC CLOUDS SURVEY JF - The astrophysical journal : an international review of spectroscopy and astronomical physics N2 - We present initial results of the first large-scale survey of embedded star clusters in molecular clouds in the Large Magellanic Cloud (LMC) using near-infrared imaging from the Visible and Infrared Survey Telescope for Astronomy Magellanic Clouds Survey. We explored a ~1.65 deg2 area of the LMC, which contains the well-known star-forming region 30 Doradus as well as ~14% of the galaxy's CO clouds, and identified 67 embedded cluster candidates, 45 of which are newly discovered as clusters. We have determined the sizes, luminosities, and masses for these embedded clusters, examined the star formation rates (SFRs) of their corresponding molecular clouds, and made a comparison between the LMC and the Milky Way. Our preliminary results indicate that embedded clusters in the LMC are generally larger, more luminous, and more massive than those in the local Milky Way. We also find that the surface densities of both embedded clusters and molecular clouds is ~3 times higher than in our local environment, the embedded cluster mass surface density is ~40 times higher, the SFR is ~20 times higher, and the star formation efficiency is ~10 times higher. Despite these differences, the SFRs of the LMC molecular clouds are consistent with the SFR scaling law presented in Lada et al. This consistency indicates that while the conditions of embedded cluster formation may vary between environments, the overall process within molecular clouds may be universal. KW - galaxies: star clusters: general KW - Magellanic Clouds KW - stars: formation Y1 - 2016 U6 - https://doi.org/10.3847/0004-637X/821/1/51 SN - 0004-637X SN - 1538-4357 VL - 821 PB - IOP Publ. Ltd. CY - Bristol ER - TY - JOUR A1 - Wenz, Leonie A1 - Levermann, Anders T1 - Enhanced economic connectivity to foster heat stress-related losses JF - Science Advances N2 - Assessing global impacts of unexpected meteorological events in an increasingly connected world economy is important for estimating the costs of climate change. We show that since the beginning of the 21st century, the structural evolution of the global supply network has been such as to foster an increase of climate-related production losses. We compute first- and higher-order losses from heat stress-induced reductions in productivity under changing economic and climatic conditions between 1991 and 2011. Since 2001, the economic connectivity has augmented in such a way as to facilitate the cascading of production loss. The influence of this structural change has dominated over the effect of the comparably weak climate warming during this decade. Thus, particularly under future warming, the intensification of international trade has the potential to amplify climate losses if no adaptation measures are taken. Y1 - 2016 U6 - https://doi.org/10.1126/sciadv.1501026 SN - 2375-2548 VL - 2 PB - American Assoc. for the Advancement of Science CY - Washington ER - TY - JOUR A1 - Nishikawa, Ken-Ichi A1 - Frederiksen, J. T. A1 - Nordlund, A. A1 - Mizuno, Y. A1 - Hardee, P. E. A1 - Niemiec, J. A1 - Gomez, J. L. A1 - Dutan, I. A1 - Meli, A. A1 - Sol, H. A1 - Pohl, Martin A1 - Hartmann, D. H. T1 - EVOLUTION OF GLOBAL RELATIVISTIC JETS: COLLIMATIONS AND EXPANSION WITH kKHI AND THE WEIBEL INSTABILITY JF - The astrophysical journal : an international review of spectroscopy and astronomical physics N2 - In the study of relativistic jets one of the key open questions is their interaction with the environment. Here. we study the initial evolution of both electron-proton (e(-) - p(+)) and electron-positron (e(+/-)) relativistic jets, focusing on their lateral interaction with ambient plasma. We follow the evolution of toroidal magnetic fields generated by both the kinetic Kelvin-Helmholtz and Mushroom instabilities. For an e(-) - p(+) jet, the induced magnetic field collimates the jet and electrons are perpendicularly accelerated. As the instabilities saturate and subsequently weaken, the magnetic polarity switches from clockwise to counterclockwise in the middle of the jet. For an e(+/-) jet, we find strong mixing of electrons and positrons with the ambient plasma, resulting in the creation of a bow shock. The merging of current filaments generates density inhomogeneities that. initiate a forward shock. Strong jet-ambient plasma mixing prevents a full development of the jet (on the scale studied), revealing evidence for both jet collimation and particle acceleration in the forming bow shock. Differences in the magnetic field structure generated by e(-) - p(+) and e(+/-) jets may contribute to the polarization properties of the observed emission in AGN jets and gamma-ray bursts. KW - acceleration of particles KW - plasmas KW - radiation mechanisms: non-thermal KW - relativistic processes KW - stars: jets KW - Sun: magnetic fields Y1 - 2016 U6 - https://doi.org/10.3847/0004-637X/820/2/94 SN - 0004-637X SN - 1538-4357 VL - 820 PB - IOP Publ. Ltd. CY - Bristol ER - TY - JOUR A1 - Archambault, S. A1 - Archer, A. A1 - Aune, T. A1 - Barnacka, Anna A1 - Benbow, W. A1 - Bird, R. A1 - Buchovecky, M. A1 - Buckley, J. H. A1 - Bugaev, V. A1 - Byrum, K. A1 - Cardenzana, J. V. A1 - Cerruti, M. A1 - Chen, Xuhui A1 - Ciupik, L. A1 - Collins-Hughes, E. A1 - Connolly, M. P. A1 - Cui, W. A1 - Dickinson, H. J. A1 - Dumm, J. A1 - Eisch, J. D. A1 - Falcone, A. A1 - Feng, Q. A1 - Finley, J. P. A1 - Fleischhack, H. A1 - Flinders, A. A1 - Fortin, P. A1 - Fortson, L. A1 - Furniss, A. A1 - Gillanders, G. H. A1 - Griffin, S. A1 - Grube, J. A1 - Gyuk, G. A1 - Huetten, M. A1 - Hakansson, Nils A1 - Hanna, D. A1 - Holder, J. A1 - Humensky, T. B. A1 - Johnson, C. A. A1 - Kaaret, P. A1 - Kar, P. A1 - Kelley-Hoskins, N. A1 - Kertzman, M. A1 - Khassen, Y. 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 - Millis, J. A1 - Moriarty, P. A1 - Mukherjee, R. A1 - Nieto, D. A1 - Ong, R. A. A1 - Otte, A. N. A1 - Pandel, D. 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 - Rousselle, J. A1 - Rulten, C. A1 - Santander, M. A1 - Sembroski, G. H. A1 - Shahinyan, K. A1 - Smith, A. W. A1 - Staszak, D. A1 - Telezhinsky, Igor O. A1 - Tucci, J. V. A1 - Tyler, J. A1 - Vincent, S. A1 - Wakely, S. P. A1 - Weiner, O. M. A1 - Weinstein, A. A1 - Wilhelm, Alina A1 - Williams, D. A. A1 - Zitzer, B. T1 - EXCEPTIONALLY BRIGHT TEV FLARES FROM THE BINARY LS I+61 degrees 303 JF - The astrophysical journal : an international review of spectroscopy and astronomical physics ; Part 2, Letters N2 - The TeV binary system LS I +61 degrees 303 is known for its regular, non-thermal emission pattern that traces the orbital period of the compact object in its 26.5 day orbit around its B0 Ve star companion. The system typically presents elevated TeV emission around apastron passage with flux levels between 5% and 15% of the steady flux from the Crab Nebula (> 300 GeV). In this article, VERITAS observations of LS I + 61 degrees. 303 taken in late 2014 are presented, during which bright TeV flares around apastron at flux levels peaking above 30% of the Crab Nebula flux were detected. This is the brightest such activity from this source ever seen in the TeV regime. The strong outbursts have rise and fall times of less than a day. The short timescale of the flares, in conjunction with the observation of 10 TeV photons from LS I + 61 degrees 303 during the flares, provides constraints on the properties of the accelerator in the source. KW - binaries: general KW - gamma-rays: general KW - stars: individual (LS I+61 degrees 303, VER J0240+612) KW - X-rays: binaries Y1 - 2016 U6 - https://doi.org/10.3847/2041-8205/817/1/L7 SN - 2041-8205 SN - 2041-8213 VL - 817 PB - IOP Publ. Ltd. CY - Bristol ER - TY - JOUR A1 - Wisotzki, Lutz A1 - Bacon, Roland A1 - Blaizot, J. A1 - Brinchmann, Jarle A1 - Herenz, Edmund Christian A1 - Schaye, Joop A1 - Bouche, Nicolas A1 - Cantalupo, Sebastiano A1 - Contini, Thierry A1 - Carollo, C. M. A1 - Caruana, Joseph A1 - Courbot, J. -B. A1 - Emsellem, E. A1 - Kamann, S. A1 - Kerutt, Josephine Victoria A1 - Leclercq, F. A1 - Lilly, S. J. A1 - Patricio, V. A1 - Sandin, C. A1 - Steinmetz, Matthias A1 - Straka, Lorrie A. A1 - Urrutia, Tanya A1 - Verhamme, A. A1 - Weilbacher, Peter Michael A1 - Wendt, Martin T1 - Extended Lyman alpha haloes around individual high-redshift galaxies revealed by MUSE JF - Science N2 - We report the detection of extended Ly alpha emission around individual star-forming galaxies at redshifts z = 3-6 in an ultradeep exposure of the Hubble Deep Field South obtained with MUSE on the ESO-VLT. The data reach a limiting surface brightness (1 sigma) of similar to 1 x 10(-19) erg s(-1) cm(-2) arcsec(-2) in azimuthally averaged radial profiles, an order of magnitude improvement over previous narrowband imaging. Our sample consists of 26 spectroscopically confirmed Ly alpha-emitting, but mostly continuum-faint (m(AB) greater than or similar to 27) galaxies. In most objects the Ly alpha emission is considerably more extended than the UV continuum light. While five of the faintest galaxies in the sample show no significantly detected Ly alpha haloes, the derived upper limits suggest that this is due to insufficient S/N. Ly alpha haloes therefore appear to be ubiquitous even for low-mass (similar to 10(8)-10(9) M-circle dot) star-forming galaxies at z > 3. We decompose the Ly alpha emission of each object into a compact component tracing the UV continuum and an extended halo component, and infer sizes and luminosities of the haloes. The extended Ly alpha emission approximately follows an exponential surface brightness distribution with a scale length of a few kpc. While these haloes are thus quite modest in terms of their absolute sizes, they are larger by a factor of 5-15 than the corresponding rest-frame UV continuum sources as seen by HST. They are also much more extended, by a factor similar to 5, than Ly alpha haloes around low-redshift star-forming galaxies. Between similar to 40% and greater than or similar to 90% of the observed Ly alpha flux comes from the extended halo component, with no obvious correlation of this fraction with either the absolute or the relative size of the Ly alpha halo. Our observations provide direct insights into the spatial distribution of at least partly neutral gas residing in the circumgalactic medium of low to intermediate mass galaxies at z > 3. KW - galaxies: high-redshift KW - galaxies: evolution KW - galaxies: formation KW - cosmology: observations KW - intergalactic medium Y1 - 2016 U6 - https://doi.org/10.1051/0004-6361/201527384 SN - 1432-0746 VL - 587 PB - EDP Sciences CY - Les Ulis ER - TY - JOUR A1 - Intravaia, F. A1 - Behunin, R. O. A1 - Henkel, Carsten A1 - Busch, K. A1 - Dalvit, D. A. R. T1 - Failure of Local Thermal Equilibrium in Quantum Friction JF - Physical review letters N2 - Recent progress in manipulating atomic and condensed matter systems has instigated a surge of interest in nonequilibrium physics, including many-body dynamics of trapped ultracold atoms and ions, near-field radiative heat transfer, and quantum friction. Under most circumstances the complexity of such nonequilibrium systems requires a number of approximations to make theoretical descriptions tractable. In particular, it is often assumed that spatially separated components of a system thermalize with their immediate surroundings, although the global state of the system is out of equilibrium. This powerful assumption reduces the complexity of nonequilibrium systems to the local application of well-founded equilibrium concepts. While this technique appears to be consistent for the description of some phenomena, we show that it fails for quantum friction by underestimating by approximately 80% the magnitude of the drag force. Our results show that the correlations among the components of driven, but steady-state, quantum systems invalidate the assumption of local thermal equilibrium, calling for a critical reexamination of this approach for describing the physics of nonequilibrium systems. Y1 - 2016 U6 - https://doi.org/10.1103/PhysRevLett.117.100402 SN - 0031-9007 SN - 1079-7114 VL - 117 SP - 989 EP - 1010 PB - American Physical Society CY - College Park ER - TY - JOUR A1 - Kim, Kyung-Chan A1 - Shprits, Yuri Y. A1 - Blake, J. Bernard T1 - Fast injection of the relativistic electrons into the inner zone and the formation of the split-zone structure during the Bastille Day storm in July 2000 JF - Journal of geophysical research : Space physics N2 - During the July 2000 geomagnetic storm, known as the Bastille Day storm, Solar, Anomalous, and Magnetospheric Particle Explorer (SAMPEX)/Heavy Ion Large Telescope (HILT) observed a strong injection of similar to 1MeV electrons into the slot region (L similar to 2.5) during the storm main phase. Then, during the following month, electrons were clearly seen diffusing inward down to L=2 and forming a pronounced split structure encompassing a narrow, newly formed slot region around L=3. SAMPEX observations are first compared with electron and proton observations on HEO-3 and NOAA-15 to validate that the observed unusual dynamics was not caused by proton contamination of the SAMPEX instrument. The time-dependent 3-D Versatile Electron Radiation Belt (VERB) simulation of 1MeV electron flux evolution is compared with the SAMPEX/HILT observations. The results show that the VERB code predicts overall time evolution of the observed split structure. The simulated split structure is produced by pitch angle scattering into the Earth atmosphere of similar to 1MeV electrons by plasmaspheric hiss. KW - inner radiation zone and slot region KW - Bastille Day geomagnetic storm KW - 3-D diffusion simulation KW - plasmaspheric hiss Y1 - 2016 U6 - https://doi.org/10.1002/2015JA022072 SN - 2169-9380 SN - 2169-9402 VL - 121 SP - 8329 EP - 8342 PB - American Geophysical Union CY - Washington ER - TY - GEN A1 - Yang, Jie A1 - Guehr, Markus A1 - Vecchione, Theodore A1 - Robinson, Matthew Scott A1 - Li, Renkai A1 - Hartmann, Nick A1 - Shen, Xiaozhe A1 - Coffee, Ryan A1 - Corbett, Jeff A1 - Fry, Alan A1 - Gaffney, Kelly A1 - Gorkhover, Tais A1 - Hast, Carsten A1 - Jobe, Keith A1 - Makasyuk, Igor A1 - Reid, Alexander A1 - Robinson, Joseph A1 - Vetter, Sharon A1 - Wang, Fenglin A1 - Weathersby, Stephen A1 - Yoneda, Charles A1 - Wang, Xijie A1 - Centurion, Martin T1 - Femtosecond gas phase electron diffraction with MeV electrons N2 - We present results on ultrafast gas electron diffraction (UGED) experiments with femtosecond resolution using the MeV electron gun at SLAC National Accelerator Laboratory. UGED is a promising method to investigate molecular dynamics in the gas phase because electron pulses can probe the structure with a high spatial resolution. Until recently, however, it was not possible for UGED to reach the relevant timescale for the motion of the nuclei during a molecular reaction. Using MeV electron pulses has allowed us to overcome the main challenges in reaching femtosecond resolution, namely delivering short electron pulses on a gas target, overcoming the effect of velocity mismatch between pump laser pulses and the probe electron pulses, and maintaining a low timing jitter. At electron kinetic energies above 3 MeV, the velocity mismatch between laser and electron pulses becomes negligible. The relativistic electrons are also less susceptible to temporal broadening due to the Coulomb force. One of the challenges of diffraction with relativistic electrons is that the small de Broglie wavelength results in very small diffraction angles. In this paper we describe the new setup and its characterization, including capturing static diffraction patterns of molecules in the gas phase, finding time-zero with sub-picosecond accuracy and first time-resolved diffraction experiments. The new device can achieve a temporal resolution of 100 fs root-mean-square, and sub-angstrom spatial resolution. The collimation of the beam is sufficient to measure the diffraction pattern, and the transverse coherence is on the order of 2 nm. Currently, the temporal resolution is limited both by the pulse duration of the electron pulse on target and by the timing jitter, while the spatial resolution is limited by the average electron beam current and the signal-to-noise ratio of the detection system. We also discuss plans for improving both the temporal resolution and the spatial resolution. T3 - Zweitveröffentlichungen der Universität Potsdam : Mathematisch-Naturwissenschaftliche Reihe - 326 Y1 - 2016 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus4-394989 ER - TY - JOUR A1 - Yang, Jie A1 - Gühr, Markus A1 - Vecchione, Theodore A1 - Robinson, Matthew Scott A1 - Li, Renkai A1 - Hartmann, Nick A1 - Shen, Xiaozhe A1 - Coffee, Ryan A1 - Corbett, Jeff A1 - Fry, Alan A1 - Gaffney, Kelly A1 - Gorkhover, Tais A1 - Hast, Carsten A1 - Jobe, Keith A1 - Makasyuk, Igor A1 - Reid, Alexander A1 - Robinson, Joseph A1 - Vetter, Sharon A1 - Wang, Fenglin A1 - Weathersby, Stephen A1 - Yoneda, Charles A1 - Wang, Xijie A1 - Centurion, Martin T1 - Femtosecond gas phase electron diffraction with MeV electrons JF - Faraday discussions N2 - We present results on ultrafast gas electron diffraction (UGED) experiments with femtosecond resolution using the MeV electron gun at SLAC National Accelerator Laboratory. UGED is a promising method to investigate molecular dynamics in the gas phase because electron pulses can probe the structure with a high spatial resolution. Until recently, however, it was not possible for UGED to reach the relevant timescale for the motion of the nuclei during a molecular reaction. Using MeV electron pulses has allowed us to overcome the main challenges in reaching femtosecond resolution, namely delivering short electron pulses on a gas target, overcoming the effect of velocity mismatch between pump laser pulses and the probe electron pulses, and maintaining a low timing jitter. At electron kinetic energies above 3 MeV, the velocity mismatch between laser and electron pulses becomes negligible. The relativistic electrons are also less susceptible to temporal broadening due to the Coulomb force. One of the challenges of diffraction with relativistic electrons is that the small de Broglie wavelength results in very small diffraction angles. In this paper we describe the new setup and its characterization, including capturing static diffraction patterns of molecules in the gas phase, finding time-zero with sub-picosecond accuracy and first time-resolved diffraction experiments. The new device can achieve a temporal resolution of 100 fs root-mean-square, and sub-angstrom spatial resolution. The collimation of the beam is sufficient to measure the diffraction pattern, and the transverse coherence is on the order of 2 nm. Currently, the temporal resolution is limited both by the pulse duration of the electron pulse on target and by the timing jitter, while the spatial resolution is limited by the average electron beam current and the signal-to-noise ratio of the detection system. We also discuss plans for improving both the temporal resolution and the spatial resolution. Y1 - 2016 U6 - https://doi.org/10.1039/c6fd00071a SN - 1359-6640 SN - 1364-5498 VL - 194 SP - 563 EP - 581 PB - Royal Society of Chemistry CY - Cambridge ER - TY - GEN A1 - Battiston, Stefano A1 - Farmer, Doyne A1 - Flache, Andreas A1 - Garlaschelli, Diego A1 - Haldane, Andy A1 - Heesterbeek, Hans A1 - Hommes, Cars A1 - Jaeger, Carlo A1 - May, Robert A1 - Scheffer, Marten T1 - Financial complexity: Accounting for fraud Response T2 - Science Y1 - 2016 U6 - https://doi.org/10.1126/science.352.6283.302 SN - 0036-8075 SN - 1095-9203 VL - 352 SP - 302 EP - 302 PB - American Assoc. for the Advancement of Science CY - Washington ER - TY - THES A1 - Krüsemann, Henning T1 - First passage phenomena and single-file motion in ageing continuous time random walks and quenched energy landscapes N2 - In der Physik gibt es viele Prozesse, die auf Grund ihrer Komplexität nicht durch physikalische Gleichungen beschrieben werden können, beispielsweise die Bewegung eines Staubkorns in der Luft. Durch die vielen Stöße mit Luftmolekülen führt es eine Zufallsbewegung aus, die so genannte Diffusion. Auch Moleküle in biologischen Zellen diffundieren, jedoch befinden sich in einer solchen Zelle im selben Volumen viel mehr oder viel größere Moleküle. Das beobachtete Teilchen stößt dementsprechend öfter mit anderen zusammen und die Diffusion wird langsamer, sie wird subdiffusiv. Mit der Zeit kann sich die Charakteristik der Subdiffusion ändern; dies wird als (mikroskopisches) Altern bezeichnet. Ich untersuche in der vorliegenden Arbeit zwei mathematische Modelle für eindimensionale Subdiffusion, einmal den continuous time random walk (CTRW) und einmal die Zufallsbewegung in einer eingefrorenen Energielandschaft (QEL=quenched energy landscape). Beide sind Sprungprozesse, das heißt, sie sind Abfolgen von räumlichen Sprüngen, die durch zufallsverteilte Wartezeiten getrennt sind. Die Wartezeiten in der QEL sind räumlich korrelliert, während sie im CTRW unkorrelliert sind. Ich untersuche in der vorliegenden Arbeit verschiedene statistische Größen in beiden Modellen. Zunächst untersuche ich den Einfluss des Alters und den Einfluss der Korrellationen einer QEL auf die Verteilung der Zeiten, die das diffundierendes Teilchen benötigt, um eine (räumliche) Schwelle zu überqueren. Ausserdem bestimme ich den Effekt des Alters auf Ströme von (sub)diffundierenden Partikeln, die sich auf eine absorbierende Barriere zubewegen. Zuletzt beschäftige ich mich mit der Diffusion einer eindimensionalen Anordnung von Teilchen in einer QEL, in der diese als harte Kugeln miteinander wechselwirken. Dabei vergleiche ich die gemeinsame Bewegung in einer QEL und als individuelle CTRWs miteinander über die Standartabweichung von der Startposition, für die ich das Mittel über mehrere QELs untersuche. Meine Arbeit setzt sich zusammen aus theoretischen Überlegungen und Berechnungen sowie der Simulation der Zufallsprozesse. Die Ergebnisse der Simulation und, soweit vorhanden, experimentelle Daten werden mit der Theorie verglichen. N2 - In the first part of my work I have investigated the ageing properties of the first passage time distributions in a one-dimensional subdiffusive continuous time random walk with power law distributed waiting times of the form $\psi(\tau) \sim \tau^{-1-\alpha}$ with $0<\alpha<1$ and $1<\alpha<2$. The age or ageing time $t_a$ is the time span from the start of the stochastic process to the start of the observation of this process (at $t=0$). I have calculated the results for a single target and two targets, also including the biased case, where the walker is driven towards the boundary by a constant force. I have furthermore refined the previously derived results for the non-ageing case and investigated the changes that occur when the walk is performed in a discrete quenched energy landscape, where the waiting times are fixed for every site. The results include the exact Laplace space densities and infinite (converging) series as exact results in the time space. The main results are the dominating long time power law behavior regimes, which depend on the ageing time. For the case of unbiased subdiffusion ($\alpha < 1$) in the presence of one target, I find three different dominant terms for ranges of $t$ separated by $t_a$ and another crossover time $t^{\star}$, which depends on $t_a$ as well as on the anomalous exponent $\alpha$ and the anomalous diffusion coefficient $K_{\alpha}$. In all three regimes ($t \ll t_a$, $t_a \ll t \ll t^{\star}$, $t \gg t^{\star}$) one finds power law decay with exponents depending on $\alpha$. The middle regime only exists for $t_a \ll t^{\star}$. The dominant terms in the first two regimes (ageing regimes) come from the probability distribution of the forward waiting time, the time one has to wait for the stochastic process to make the first step during the observation. When the observation time is larger than the second crossover time $t^{\star}$, the first passage time density does not show ageing and the non-ageing first passage time dominates. The power law exponents in the respective regimes are $-\alpha$ for strong ageing, $-1-\alpha$ in the intermediate regime, and $-1-\alpha/2$ in the final non-ageing regime. A similar split into three regimes can be found for $1<\alpha<2$, only with a different second crossover time $t^*$. In this regime the diffusion is normal but also age-dependent. For the diffusion in quenched energy landscapes one cannot detect ageing. The first passage time density shows a quenched power law $^\sim t^{-(1+2\alpha)/(1+\alpha)}$. For diffusion between two target sites and the biased diffusion towards a target only two scaling regimes emerge, separated by the ageing time. In the ageing case $t \ll t_a$ the forward waiting time is again dominant with power law exponent $-\alpha$, while the non-ageing power law $-1-\alpha$ is found for all times $t \gg t_a$. An intermediate regime does not exist. The bias and the confinement have similar effects on the first passage time density. For quenched diffusion, the biased case is interesting, as the bias reduces correlations due to revisiting of the same waiting time. As a result, CTRW like behavior is observed, including ageing. Extensive computer simulations support my findings. The second part of my research was done on the subject of ageing Scher-Montroll transport, which is in parts closely related to the first passage densities. It explains the electrical current in an amorphous material. I have investigated the effect of the width of a given initial distribution of charge carriers on the transport coefficients as well as the ageing effect on the emerging power law regimes and a constant initial regime. While a spread out initial distribution has only little impact on the Scher-Montroll current, ageing alters the behavior drastically. Instead of the two classical power laws one finds four current regimes, up to three of which can appear in a single experiment. The dominant power laws differ for $t \ll t_a, t_c$, $t_a \ll t \ll t_c$, $t_c \ll t \ll t_a$, and $t \gg t_a,t_c$. Here, $t_c$ is the crossover time of the non-aged Scher-Montroll current. For strongly aged systems one can observe a constant current in the first regime while the others are dominated by decaying power laws with exponents $\alpha -1$, $-\alpha$, and $-1-\alpha$. The ageing regimes are the 1st and 3rd one, while the classical regimes are the 2nd and the 4th. I have verified the theory using numerical integration of the exact integrals and applied the new results to experimental data. In the third part I considered a single file of subdiffusing particles in an energy landscape. Every occupied site of the landscape acts as a boundary, from which a particle is immediately reflected to its previous site, if it tries to jump there. I have analysed the effects single-file diffusion a quenched landscape compared to an annealed landscape and I have related these results to the number of steps and related quantities. The diffusion changes from ultraslow logarithmic diffusion in the annealed or CTRW case to subdiffusion with an anomalous exponent $\alpha/(1+\alpha)$ in the quenched landscape. The behavior is caused by the forward waiting time, which changes drastically from the quenched to the annealed case. Single-file effects in the quenched landscape are even more complicated to consider in the ensemble average, since the diffusion in individual landscapes shows extremely diverse behavior. Extensive simulations support my theoretical arguments, which consider mainly the long time evolution of the mean square displacement of a bulk particle. KW - continuous time random walk KW - quenched energy landscape KW - first passage time KW - Scher-Montroll transport KW - single-file motion KW - Zufallsbewegung KW - Diffusion KW - eingefrorene Energielandschaft KW - Scher-Montroll Transport KW - Wartezeitverteilung Y1 - 2016 ER - TY - JOUR A1 - Godec, Aljaz A1 - Metzler, Ralf T1 - First passage time distribution in heterogeneity controlled kinetics: going beyond the mean first passage time JF - Scientific reports N2 - The first passage is a generic concept for quantifying when a random quantity such as the position of a diffusing molecule or the value of a stock crosses a preset threshold (target) for the first time. The last decade saw an enlightening series of new results focusing mostly on the so-called mean and global first passage time (MFPT and GFPT, respectively) of such processes. Here we push the understanding of first passage processes one step further. For a simple heterogeneous system we derive rigorously the complete distribution of first passage times (FPTs). Our results demonstrate that the typical FPT significantly differs from the MFPT, which corresponds to the long time behaviour of the FPT distribution. Conversely, the short time behaviour is shown to correspond to trajectories connecting directly from the initial value to the target. Remarkably, we reveal a previously overlooked third characteristic time scale of the first passage dynamics mirroring brief excursion away from the target. Y1 - 2016 U6 - https://doi.org/10.1038/srep20349 SN - 2045-2322 VL - 6 PB - Nature Publ. Group CY - London ER - TY - JOUR A1 - Gonzalez Manrique, Sergio Javier A1 - Kuckein, Christoph A1 - Pastor Yabar, A. A1 - Collados Vera, M. A1 - Denker, Carsten A1 - Fischer, C. E. A1 - Gömöry, P. A1 - Diercke, Andrea A1 - Gonzalez, N. Bello A1 - Schlichenmaier, R. A1 - Balthasar, H. A1 - Berkefeld, T. A1 - Feller, A. A1 - Hoch, S. A1 - Hofmann, A. A1 - Kneer, F. A1 - Lagg, A. A1 - Nicklas, H. A1 - Orozco Suarez, D. A1 - Schmidt, D. A1 - Schmidt, W. A1 - Sigwarth, M. A1 - Sobotka, M. A1 - Solanki, S. K. A1 - Soltau, D. A1 - Staude, J. A1 - Strassmeier, Klaus G. A1 - Verma, Meetu A1 - Volkmer, R. A1 - von der Lühe, O. A1 - Waldmann, T. T1 - Fitting peculiar spectral profiles in He I 10830 angstrom absorption features JF - Astronomische Nachrichten = Astronomical notes N2 - The new generation of solar instruments provides better spectral, spatial, and temporal resolution for a better understanding of the physical processes that take place on the Sun. Multiple-component profiles are more commonly observed with these instruments. Particularly, the He i 10830 triplet presents such peculiar spectral profiles, which give information on the velocity and magnetic fine structure of the upper chromosphere. The purpose of this investigation is to describe a technique to efficiently fit the two blended components of the He i 10830 triplet, which are commonly observed when two atmospheric components are located within the same resolution element. The observations used in this study were taken on 2015 April 17 with the very fast spectroscopic mode of the GREGOR Infrared Spectrograph (GRIS) attached to the 1.5-m GREGOR solar telescope, located at the Observatorio del Teide, Tenerife, Spain. We apply a double-Lorentzian fitting technique using Levenberg-Marquardt least-squares minimization. This technique is very simple and much faster than inversion codes. Line-of-sight Doppler velocities can be inferred for a whole map of pixels within just a few minutes. Our results show sub-and supersonic downflow velocities of up to 32 km s(-1) for the fast component in the vicinity of footpoints of filamentary structures. The slow component presents velocities close to rest. (C) 2016 WILEY-VCH Verlag GmbH& Co. KGaA, Weinheim KW - Sun: chromosphere KW - methods: data analysis KW - techniques: spectroscopic KW - line: profiles Y1 - 2016 U6 - https://doi.org/10.1002/asna.201512433 SN - 0004-6337 SN - 1521-3994 VL - 337 SP - 1057 EP - 1063 PB - Wiley-VCH CY - Weinheim ER - TY - JOUR A1 - Verma, Meetu A1 - Denker, Carsten A1 - Böhm, F. A1 - Balthasar, H. A1 - Fischer, C. E. A1 - Kuckein, Christoph A1 - Gonzalez, N. Bello A1 - Berkefeld, T. A1 - Collados Vera, M. A1 - Diercke, Andrea A1 - Feller, A. A1 - Gonzalez Manrique, Sergio Javier A1 - Hofmann, A. A1 - Lagg, A. A1 - Nicklas, H. A1 - Orozco Suarez, D. A1 - Pator Yabar, A. A1 - Rezaei, R. A1 - Schlichenmaier, R. A1 - Schmidt, D. A1 - Schmidt, W. A1 - Sigwarth, M. A1 - Sobotka, M. A1 - Solanki, S. K. A1 - Soltau, D. A1 - Staude, J. A1 - Strassmeier, Klaus G. A1 - Volkmer, R. A1 - von der Lühe, O. A1 - Waldmann, T. T1 - Flow and magnetic field properties in the trailing sunspots of active region NOAA 12396 JF - Astronomische Nachrichten = Astronomical notes N2 - Improved measurements of the photospheric and chromospheric three-dimensional magnetic and flow fields are crucial for a precise determination of the origin and evolution of active regions. We present an illustrative sample of multi-instrument data acquired during a two-week coordinated observing campaign in August 2015 involving, among others, the GREGOR solar telescope (imaging and near-infrared spectroscopy) and the space missions Solar Dynamics Observatory (SDO) and Interface Region Imaging Spectrograph (IRIS). The observations focused on the trailing part of active region NOAA 12396 with complex polarity inversion lines and strong intrusions of opposite polarity flux. The GREGOR Infrared Spectrograph (GRIS) provided Stokes IQUV spectral profiles in the photospheric Si i.1082.7 nm line, the chromospheric He I lambda 1083.0 nm triplet, and the photospheric Ca I lambda 1083.9 nm line. Carefully calibrated GRIS scans of the active region provided maps of Doppler velocity and magnetic field at different atmospheric heights. We compare quick-look maps with those obtained with the " Stokes Inversions based on Response functions" (SIR) code, which furnishes deeper insight into the magnetic properties of the region. We find supporting evidence that newly emerging flux and intruding opposite polarity flux are hampering the formation of penumbrae, i.e., a penumbra fully surrounding a sunspot is only expected after cessation of flux emergence in proximity to the sunspots. (C) 2016 WILEY-VCH Verlag GmbH& Co.KGaA, Weinheim KW - Sun: magnetic fields KW - sunspots KW - methods: data analysis KW - techniques: polarimetric KW - techniques: spectroscopic Y1 - 2016 U6 - https://doi.org/10.1002/asna.201612447 SN - 0004-6337 SN - 1521-3994 VL - 337 SP - 1090 EP - 1098 PB - Wiley-VCH CY - Weinheim ER - TY - JOUR A1 - Fang, Lijia A1 - Holzmueller, Felix A1 - Matulaitis, Tomas A1 - Baasner, Anne A1 - Hauenstein, Christoph A1 - Benduhn, Johannes A1 - Schwarze, Martin A1 - Petrich, Annett A1 - Piersimoni, Fortunato A1 - Scholz, Reinhard A1 - Zeika, Olaf A1 - Koerner, Christian A1 - Neher, Dieter A1 - Vandewal, Koen A1 - Leo, Karl T1 - Fluorine-containing low-energy-gap organic dyes with low voltage losses for organic solar cells JF - Synthetic metals : the journal of electronic polymers and electronic molecular materials N2 - Fluorine-containing donor molecules TFTF, CNTF and PRTF are designed and isomer selectively synthesized for application in vacuum-deposited organic solar cells. These molecules comprise a donor acceptor molecular architecture incorporating thiophene and benzothiadiazole derivatives as the electron-donating and electron-withdrawing moieties, respectively. As opposed to previously reported materials from this class, PRTF can be purified by vacuum sublimation at moderate to high yields because of its higher volatility and better stabilization due to a stronger intramolecular hydrogen bond, as compared to TFTF and CNTF. The UV-vis absorption spectra of the three donors show an intense broadband absorption between 500 nm and 800 nm with, similar positions of their frontier energy levels. The photophysical properties of the three donor molecules are thoroughly tested and optimized in bulk heterojunction solar cells with C-60 as acceptor. PRTF shows the best performance, yielding power conversion efficiencies of up to 3.8%. Moreover, the voltage loss for the PRTF device due to the non radiative recombination of free charge carriers is exceptionally low (0.26 V) as compared to typical values for organic solar cells (>0.34V). (C) 2016 Published by Elsevier B.V. KW - (Z)-isomer KW - Donor materials KW - CH center dot center dot center dot F hydrogen bonds KW - Sublimation with good yield KW - Low voltage losses Y1 - 2016 U6 - https://doi.org/10.1016/j.synthmet.2016.10.025 SN - 0379-6779 VL - 222 SP - 232 EP - 239 PB - Elsevier CY - Lausanne ER - TY - JOUR A1 - Hic, Ceren A1 - Pradhan, Prajal A1 - Rybski, Diego A1 - Kropp, Jürgen T1 - Food Surplus and Its Climate Burdens JF - Geological Society of America bulletin N2 - Avoiding food loss and waste may counteract the increasing food demand and reduce greenhouse gas (GHG) emissions from the agricultural sector. This is crucial because of limited options available to increase food production. In the year 2010, food availability was 20% higher than was required on a global scale. Thus, a more sustainable food production and adjusted consumption would have positive environmental effects. This study provides a systematic approach to estimate consumer level food waste on a country scale and globally, based on food availability and requirements. The food requirement estimation considers demographic development, body weights, and physical activity levels. Surplus between food availability and requirements of a given country is considered as food waste. The global food requirement changed from 2,300 kcal/cap/day to 2,400 kcal/cap/day during the last 50 years, while food surplus grew from 310 kcal/cap/day to 510 kcal/cap/day. Similarly, GHG emissions related to the food surplus increased from 130 Mt CO2eq/yr to 530 Mt CO2eq/yr, an increase of more than 300%. Moreover, the global food surplus may increase up to 850 kcal/cap/day, while the total food requirement will increase only by 2%-20% by 2050. Consequently, GHG emissions associated with the food waste may also increase tremendously to 1.9-2.5 Gt CO2eq/yr. Y1 - 2016 U6 - https://doi.org/10.1021/acs.est.5b05088 SN - 0013-936X SN - 1520-5851 VL - 50 SP - 4269 EP - 4277 PB - American Chemical Society CY - Washington ER - TY - JOUR A1 - Parezanovic, Vladimir A1 - Cordier, Laurent A1 - Spohn, Andreas A1 - Duriez, Thomas A1 - Noack, Bernd R. A1 - Bonnet, Jean-Paul A1 - Segond, Marc A1 - Abel, Markus A1 - Brunton, Steven L. T1 - Frequency selection by feedback control in a turbulent shear flow JF - Journal of fluid mechanics N2 - Many previous studies have shown that the turbulent mixing layer under periodic forcing tends to adopt a lock-on state, where the major portion of the fluctuations in the flow are synchronized at the forcing frequency. The goal of this experimental study is to apply closed-loop control in order to provoke the lock-on state, using information from the flow itself. We aim to determine the range of frequencies for which the closed-loop control can establish the lock-on, and what mechanisms are contributing to the selection of a feedback frequency. In order to expand the solution space for optimal closed-loop control laws, we use the genetic programming control (CPC) framework. The best closed-loop control laws obtained by CPC are analysed along with the associated physical mechanisms in the mixing layer flow. The resulting closed-loop control significantly outperforms open-loop forcing in terms of robustness to changes in the free-stream velocities. In addition, the selection of feedback frequencies is not locked to the most amplified local mode, but rather a range of frequencies around it. KW - free shear layers KW - instability control KW - turbulence control Y1 - 2016 U6 - https://doi.org/10.1017/jfm.2016.261 SN - 0022-1120 SN - 1469-7645 VL - 797 SP - 247 EP - 283 PB - Cambridge Univ. Press CY - New York ER - TY - JOUR A1 - Thiem, A. A1 - Bagheri, M. A1 - Grosse-Siestrup, C. A1 - Zehbe, Rolf T1 - Gelatin-poly(lactic-co-glycolic acid) scaffolds with oriented pore channel architecture - From in vitro to in vivo testing JF - Vision research : an international journal for functional aspects of vision. N2 - A gelatin-poly(lactic-co-glycolic acid), PLGA, composite scaffold, featuring a highly oriented pore channel structure, was developed as a template for articular cartilage regeneration. As a design principle the composite scaffold was optimized to contain only medical grade educts and accordingly no chemical cross linking agents or other toxicological relevant substances or methods were used. Scaffolds were synthesized using a freeze structuring method combined with an electrochemical process followed by freeze-drying. Finally, cross linking was performed using dehydrothermal treatment, which was simultaneously used for sterilization purposes. These composite scaffolds were analyzed in regard to structural and biomechanical properties, and to their degradation behavior. Furthermore, cell culture performance was tested using chondrocytes originated from joint articular cartilage tissue from 6 to 10 months old domestic pigs. Finally, the scaffolds were tested for tissue biocompatibility and their ability for tissue integration in a rat model. The scaffolds showed both excellent functional performance and high biocompatibility in vitro and in vivo. We expect that these gelatin-PLGA scaffolds can effectively support chondrogenesis in vivo demonstrating great potential for the use in cartilage defect treatment. (C) 2016 Elsevier B.V. All rights reserved. KW - Gelatin-PLGA Scaffold KW - Dehydrothermal cross linking KW - Cartilage tissue engineering KW - Biomechanics KW - Rat model Y1 - 2016 U6 - https://doi.org/10.1016/j.msec.2016.02.019 SN - 0928-4931 SN - 1873-0191 VL - 62 SP - 585 EP - 595 PB - Elsevier CY - Amsterdam ER - TY - THES A1 - Dionysopoulou, Kyriaki T1 - General-relativistic magnetohydrodynamics in compact objects BT - a resistive-magnetohydrodynamics approach Y1 - 2016 ER -