TY - JOUR A1 - Kaiser, Eurika A1 - Noack, Bernd R. A1 - Cordier, Laurent A1 - Spohn, Andreas A1 - Segond, Marc A1 - Abel, Markus A1 - Daviller, Guillaume A1 - Osth, Jan A1 - Krajnovic, Sinisa A1 - Niven, Robert K. T1 - Cluster-based reduced-order modelling of a mixing layer JF - Journal of fluid mechanics KW - low-dimensional models KW - nonlinear dynamical systems KW - shear layers Y1 - 2014 U6 - https://doi.org/10.1017/jfm.2014.355 SN - 0022-1120 SN - 1469-7645 VL - 754 SP - 365 EP - 414 PB - Cambridge Univ. Press CY - New York ER - TY - JOUR A1 - Levanova, T. A. A1 - Osipov, Grigory V. A1 - Pikovskij, Arkadij T1 - Coherence properties of cycling chaos JF - Communications in nonlinear science & numerical simulation N2 - Cycling chaos is a heteroclinic connection between several chaotic attractors, at which switchings between the chaotic sets occur at growing time intervals. Here we characterize the coherence properties of these switchings, considering nearly periodic regimes that appear close to the cycling chaos due to imperfections or to instability. Using numerical simulations of coupled Lorenz, Roessler, and logistic map models, we show that the coherence is high in the case of imperfection (so that asymptotically the cycling chaos is very regular), while it is low close to instability of the cycling chaos. (C) 2014 Elsevier B. V. All rights reserved. KW - Heteroclinic cycle KW - Chaos KW - Coherence Y1 - 2014 U6 - https://doi.org/10.1016/j.cnsns.2014.01.011 SN - 1007-5704 SN - 1878-7274 VL - 19 IS - 8 SP - 2734 EP - 2739 PB - Elsevier CY - Amsterdam ER - TY - JOUR A1 - Godec, Aljaz A1 - Bauer, Maximilian A1 - Metzler, Ralf T1 - Collective dynamics effect transient subdiffusion of inert tracers in flexible gel networks JF - New journal of physics : the open-access journal for physics N2 - Based on extensive Brownian dynamics simulations we study the thermal motion of a tracer bead in a cross-linked, flexible gel in the limit when the tracer particle size is comparable to or even larger than the equilibrium mesh size of the gel. The analysis of long individual trajectories of the tracer demonstrates the existence of pronounced transient anomalous diffusion. From the time averaged mean squared displacement and the time averaged van Hove correlation functions we elucidate the many-body origin of the non-Brownian tracer bead dynamics. Our results shed new light onto the ongoing debate over the physical origin of steric tracer interactions with structured environments. KW - anomalous diffusion KW - gel network KW - van Hove correlation Y1 - 2014 U6 - https://doi.org/10.1088/1367-2630/16/9/092002 SN - 1367-2630 VL - 16 PB - IOP Publ. Ltd. CY - Bristol ER - TY - INPR A1 - Bürger, Gerd T1 - Comment on "Bias correction, quantile mapping, and downscaling: revisiting the inflation issue" T2 - Journal of climate N2 - In a recent paper, Maraun describes the adverse effects of quantile mapping on downscaling. He argues that when large-scale GCM variables are rescaled directly to small-scale fields or even station data, genuine small-scale covariability is lost and replaced by uniform variability inherited from the larger scales. This leads to a misrepresentation mainly of areal means and long-term trends. This comment acknowledges the former point, although the argument is relatively old, but disagrees with the latter, showing that grid-size long-term trends can be different from local trends. Finally, because it is partly incorrectly addressed, some clarification is added regarding the inflation issue, stressing that neither randomization nor inflation is free of unverified assumptions. KW - Climate change KW - Statistics KW - Climate variability Y1 - 2014 U6 - https://doi.org/10.1175/JCLI-D-13-00184.1 SN - 0894-8755 SN - 1520-0442 VL - 27 IS - 4 SP - 1819 EP - 1820 PB - American Meteorological Soc. CY - Boston ER - TY - INPR A1 - Föhlisch, Alexander A1 - de Groot, F. M. F. A1 - Odelius, Michael A1 - Techert, Simone A1 - Wernet, P. T1 - Comment on "state-dependent electron delocalization dynamics at the solute-solvent interface: soft-x-ray absorption spectroscopy and lambda b initio calculations" T2 - Physical review letters Y1 - 2014 U6 - https://doi.org/10.1103/PhysRevLett.112.129302 SN - 0031-9007 SN - 1079-7114 VL - 112 IS - 12 PB - American Physical Society CY - College Park ER - TY - THES A1 - Brem, Patrick T1 - Compact objects in dense astrophysical environments BT - numerical simulations and implications for gravitational wave astronomy Y1 - 2014 ER - TY - THES A1 - Yeldesbay, Azamat T1 - Complex regimes of synchronization T1 - Komplexe Synchronisationszustände BT - modeling and analysis N2 - Synchronization is a fundamental phenomenon in nature. It can be considered as a general property of self-sustained oscillators to adjust their rhythm in the presence of an interaction. In this work we investigate complex regimes of synchronization phenomena by means of theoretical analysis, numerical modeling, as well as practical analysis of experimental data. As a subject of our investigation we consider chimera state, where due to spontaneous symmetry-breaking of an initially homogeneous oscillators lattice split the system into two parts with different dynamics. Chimera state as a new synchronization phenomenon was first found in non-locally coupled oscillators system, and has attracted a lot of attention in the last decade. However, the recent studies indicate that this state is also possible in globally coupled systems. In the first part of this work, we show under which conditions the chimera-like state appears in a system of globally coupled identical oscillators with intrinsic delayed feedback. The results of the research explain how initially monostable oscillators became effectivly bistable in the presence of the coupling and create a mean field that sustain the coexistence of synchronized and desynchronized states. Also we discuss other examples, where chimera-like state appears due to frequency dependence of the phase shift in the bistable system. In the second part, we make further investigation of this topic by modeling influence of an external periodic force to an oscillator with intrinsic delayed feedback. We made stability analysis of the synchronized state and constructed Arnold tongues. The results explain formation of the chimera-like state and hysteric behavior of the synchronization area. Also, we consider two sets of parameters of the oscillator with symmetric and asymmetric Arnold tongues, that correspond to mono- and bi-stable regimes of the oscillator. In the third part, we demonstrate the results of the work, which was done in collaboration with our colleagues from Psychology Department of University of Potsdam. The project aimed to study the effect of the cardiac rhythm on human perception of time using synchronization analysis. From our part, we made a statistical analysis of the data obtained from the conducted experiment on free time interval reproduction task. We examined how ones heartbeat influences the time perception and searched for possible phase synchronization between heartbeat cycles and time reproduction responses. The findings support the prediction that cardiac cycles can serve as input signals, and is used for reproduction of time intervals in the range of several seconds. N2 - Synchronisation ist ein fundamentales Naturphänomen. Es ist die grundlegende Eigenschaft sich selbsterhaltender Oszillatoren, in Gegenwart einer Wechselwirkung, danach zu streben, ihre Rhythmen anzupassen. In dieser Arbeit betrachten wir komplexe Synchronisationszustände sowohl mit Hilfe analytischer Methoden als auch durch numerische Simulation und in experimentellen Daten. Unser Untersuchungsobjekt sind die sogenannten Chimera Zustände, in welchen sich Ensemble von gekoppelten, identischen Oszillatoren auf Grund eines Symmetriebruches spontan in Gruppen mit unterschiedlicher Dynamik aufteilen. Die Entdeckung von Chimeras in zunächst nichtlokal gekoppelten Systemen hat in den letzten zehn Jahren ein großes Interesse an neuartigen Synchronisationsphänomenen geweckt. Neueste Forschungsergebnisse belegen, dass diese Zustände unter bestimmten Bedingungen auch in global gekoppelten Systemen existieren können. Solche Bedingungen werden im ersten Teil der Arbeit in Ensemblen global gekoppelter Oszillatoren mit zusätzlicher, zeitverzögerter Selbstkopplung untersucht. Wir zeigen, wie zunächst monostabile Oszillatoren in Gegenwart von dem Treiben der globalen Kopplung effektiv bistabil werden, und sich so in zwei Gruppen organisieren. Das mittlere Feld, welches durch diese Gruppen aufgebaut wird, ist quasiperiodisch wodurch der Chimera Zustand sich selbst stabilisiert. In einem anderen Beispiel zeigen wir, dass der Chimera Zustand auch durch einen frequenzabhängigen Phasenunterschied in der globalen Kopplung erreicht werden kann. Zur genaueren Untersuchung der Mechanismen, die zur effektiven Bistabilität führen, betrachten wir im zweiten Teil der Arbeit den Einfluss einer externen periodischen Kraft auf einzelne Oszillatoren mit zeitverzögerter Selbstkopplung. Wir führen die Stabilitätanalyse des synchronen Zustands durch, und stellen die Arnoldzunge dar. Im dritten Teil der Arbeit stellen wir die Ergebnisse einer Synchronisationsanalyse vor, welche in Kooperation mit Wissenschaftlern der Psychologischen Fakultät der Universität Potsdam durchgeführt wurde. In dem Projekt wurde die Auswirkung des Herzrhythmus auf die menschliche Zeitwahrnehmung erforscht. Unsere Aufgabe war es, die experimentellen Daten statistisch zu analysieren. Im Experiment sollten Probanden ein gegebenes Zeitintervall reproduzieren während gleichzeitig ihr Herzschlag aufgezeichnet wurde. Durch eine Phasenanalyse haben wir den Zusammenhang zwischen dem Herzschlag und der Start- bzw. Stoppzeit der zu reproduzierenden Zeitintervalle untersucht. Es stellt sich heraus, dass Herzschläge bei Zeitintervallen über einige Sekunden als Taktgeber dienen können. KW - synchronization KW - phase oscillators KW - chimera state KW - time perception KW - Synchronisation KW - Phasen Oszillatoren KW - chimera Zustände KW - zeitverzögerte Selbstkopplung KW - Synchronisationsanalyse KW - Zeitwahrnehmung Y1 - 2014 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus4-73348 ER - TY - JOUR A1 - Di Florio, G. A1 - Bruendermann, E. A1 - Yadavalli, Nataraja Sekhar A1 - Santer, Svetlana A1 - Havenith, Martina T1 - Confocal raman microscopy and AFM study of the interface between the photosensitive polymer layer and multilayer graphene JF - Soft materials N2 - In this paper we report on the interaction between photosensitive azobenzene-containing polymer films and on top adsorbed graphene multilayers. The photosensitive polymer film changes its topography under irradiation with light interference patterns according to their polarization distribution. The multilayer graphene follows the deformation of the polymer film and stretches accordingly. Using confocal Raman microspectroscopy we can detect the appearance of additional peaks in the Raman spectrum of the photosensitive polymer film upon irradiation indicating a molecular interaction at the interface between the graphene multilayer and the polymer matrix. Multi-component analysis of the specific Raman bands shows that the interaction involves the graphene rings and the aromatic rings of the azobenzenes causing the strong adhesion between the two materials. KW - Graphene KW - Multilayer graphene KW - Photosensitive polymer film KW - Confocal Raman microscopy KW - AFM KW - Surface Relief Grating KW - Interfacial molecular interaction Y1 - 2014 U6 - https://doi.org/10.1080/1539445X.2014.945040 SN - 1539-445X SN - 1539-4468 VL - 12 SP - S98 EP - S105 PB - Taylor & Francis Group CY - Philadelphia ER - TY - JOUR A1 - Kang, Yu A1 - Barbirz, Stefanie A1 - Lipowsky, Reinhard A1 - Santer, Mark T1 - Conformational Diversity of O-Antigen Polysaccharides of the Gram-Negative Bacterium Shigella flexneri Serotype Y JF - The journal of physical chemistry : B, Condensed matter, materials, surfaces, interfaces & biophysical chemistry Y1 - 2014 U6 - https://doi.org/10.1021/jp4111713 SN - 1520-6106 VL - 118 IS - 9 SP - 2523 EP - 2534 PB - American Chemical Society CY - Washington ER - TY - JOUR A1 - Wendt, Martin T1 - Constraints on variations of m(p)/m(e) based on UVES observations of H-2 JF - Astronomische Nachrichten = Astronomical notes N2 - This article summarizes the latest results on the proton-to-electron mass ratio derived from H-2 observations at high redshift in the light of possible variations of fundamental physical constants. The focus lies on UVES observations of the past years as enormous progress was achieved since the first positive results on / were published. With the better understanding of systematics, dedicated observation runs, and numerous approaches to improve wavelength calibration accuracy, all current findings are in reasonable good agreement with no variation and provide an upper limit of / < 1 x 10(-5) for the redshift range of 2 < z < 3. (( KW - cosmology: observations KW - early Universe KW - quasars: absorption lines Y1 - 2014 U6 - https://doi.org/10.1002/asna.201312008 SN - 0004-6337 SN - 1521-3994 VL - 335 IS - 1 SP - 106 EP - 112 PB - Wiley-VCH CY - Weinheim ER - TY - JOUR A1 - Aliu, E. A1 - Aune, T. A1 - Barnacka, Anna A1 - Beilicke, M. A1 - Benbow, W. A1 - Berger, K. A1 - Biteau, Jonathan A1 - Buckley, J. H. A1 - Bugaev, V. A1 - Byrum, K. A1 - Cardenzana, J. V. A1 - Cerruti, M. A1 - Chen, Xuhui A1 - Ciupik, L. A1 - Connaughton, V. A1 - Cui, W. A1 - Dickinson, H. 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 - Fortin, P. A1 - Fortson, L. A1 - Furniss, A. A1 - Galante, N. A1 - Gillanders, G. H. 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 - Humensky, T. B. A1 - Johnson, C. A. A1 - Kaaret, P. A1 - Kar, P. A1 - Kertzman, M. A1 - Khassen, Y. A1 - Kieda, D. A1 - Krawczynski, H. A1 - Krennrich, F. 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 - Mukherjee, R. A1 - Nieto, D. A1 - Ong, R. A. A1 - Otte, A. N. A1 - Park, N. 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 - Telezhinsky, Igor O. A1 - Tucci, J. V. A1 - Tyler, J. A1 - Varlotta, A. A1 - Vassiliev, V. V. A1 - Vincent, S. A1 - Wakely, S. P. A1 - Weiner, O. M. A1 - Weinstein, A. A1 - Welsing, R. A1 - Wilhelm, Alina A1 - Williams, D. A. A1 - Zitzer, B. A1 - McEnery, J. E. A1 - Perkins, J. S. A1 - Veres, P. A1 - Zhu, S. T1 - Constraints on very high energy emission from GRB 130427A JF - The astrophysical journal : an international review of spectroscopy and astronomical physics ; Part 2, Letters N2 - Prompt emission from the very fluent and nearby (z = 0.34) gamma-ray burst GRB130427A was detected by several orbiting telescopes and by ground-based, wide-field-of-view optical transient monitors. Apart from the intensity and proximity of this GRB, it is exceptional due to the extremely long-lived high-energy (100 MeV to 100 GeV) gamma-ray emission, which was detected by the Large Area Telescope on the Fermi Gamma-Ray Space Telescope for similar to 70 ks after the initial burst. The persistent, hard-spectrum, high-energy emission suggests that the highest-energy gamma rays may have been produced via synchrotron self-Compton processes though there is also evidence that the high-energy emission may instead be an extension of the synchrotron spectrum. VERITAS, a ground-based imaging atmospheric Cherenkov telescope array, began follow-up observations of GRB130427A similar to 71 ks (similar to 20 hr) after the onset of the burst. The GRB was not detected with VERITAS; however, the high elevation of the observations, coupled with the low redshift of the GRB, make VERITAS a very sensitive probe of the emission from GRB130427A for E > 100 GeV. The non-detection and consequent upper limit derived place constraints on the synchrotron self-Compton model of high-energy gamma-ray emission from this burst. KW - gamma-ray burst: individual (GRB 130427A) Y1 - 2014 U6 - https://doi.org/10.1088/2041-8205/795/1/L3 SN - 2041-8205 SN - 2041-8213 VL - 795 IS - 1 PB - IOP Publ. Ltd. CY - Bristol ER - TY - THES A1 - Steinhaus, Sebastian Peter T1 - Constructing quantum spacetime T1 - Konstruktion der Quantenraumzeit BT - relation to classical gravity BT - Relation zur klassischen Gravitation N2 - Despite remarkable progress made in the past century, which has revolutionized our understanding of the universe, there are numerous open questions left in theoretical physics. Particularly important is the fact that the theories describing the fundamental interactions of nature are incompatible. Einstein's theory of general relative describes gravity as a dynamical spacetime, which is curved by matter and whose curvature determines the motion of matter. On the other hand we have quantum field theory, in form of the standard model of particle physics, where particles interact via the remaining interactions - electromagnetic, weak and strong interaction - on a flat, static spacetime without gravity. A theory of quantum gravity is hoped to cure this incompatibility by heuristically replacing classical spacetime by quantum spacetime'. Several approaches exist attempting to define such a theory with differing underlying premises and ideas, where it is not clear which is to be preferred. Yet a minimal requirement is the compatibility with the classical theory, they attempt to generalize. Interestingly many of these models rely on discrete structures in their definition or postulate discreteness of spacetime to be fundamental. Besides the direct advantages discretisations provide, e.g. permitting numerical simulations, they come with serious caveats requiring thorough investigation: In general discretisations break fundamental diffeomorphism symmetry of gravity and are generically not unique. Both complicates establishing the connection to the classical continuum theory. The main focus of this thesis lies in the investigation of this relation for spin foam models. This is done on different levels of the discretisation / triangulation, ranging from few simplices up to the continuum limit. In the regime of very few simplices we confirm and deepen the connection of spin foam models to discrete gravity. Moreover, we discuss dynamical, e.g. diffeomorphism invariance in the discrete, to fix the ambiguities of the models. In order to satisfy these conditions, the discrete models have to be improved in a renormalisation procedure, which also allows us to study their continuum dynamics. Applied to simplified spin foam models, we uncover a rich, non--trivial fixed point structure, which we summarize in a phase diagram. Inspired by these methods, we propose a method to consistently construct the continuum theory, which comes with a unique vacuum state. N2 - Trotz bemerkenswerter Fortschritte im vergangenen Jahrhundert, die unser Verständnis des Universums revolutioniert haben, gibt es noch zahlreiche ungeklärte Fragen in der theoretischen Physik. Besondere Bedeutung kommt der Tatsache zu, dass die Theorien, welche die fundamentalen Wechselwirkungen der Natur beschreiben, inkompatibel sind. Nach Einsteins allgemeiner Relativitätstheorie wird die Gravitation durch eine dynamische Raumzeit dargestellt, die von Materie gekrümmt wird und ihrerseits durch die Krümmung die Bewegung der Materie bestimmt. Dem gegenüber steht die Quantenfeldtheorie, die die verbliebenen Wechselwirkungen - elektromagnetische, schwache und starke Wechselwirkung - im Standardmodell der Teilchenphysik beschreibt, in dem Teilchen auf einer statischen Raumzeit -- ohne Gravitation -- miteinander interagieren. Die Hoffnung ist, dass eine Theorie der Quantengravitation diese Inkompatibilität beheben kann, indem, heuristisch, die klassische Raumzeit durch eine 'Quantenraumzeit' ersetzt wird. Es gibt zahlreiche Ansätze eine solche Theorie zu definieren, die auf unterschiedlichen Prämissen und Ideen beruhen, wobei a priori nicht klar ist, welche zu bevorzugen sind. Eine Minimalanforderung an diese Theorien ist Kompatibilität mit der klassischen Theorie, die sie verallgemeinern sollen. Interessanterweise basieren zahlreiche Modelle in ihrer Definition auf Diskretisierungen oder postulieren eine fundamentale Diskretheit der Raumzeit. Neben den unmittelbaren Vorteilen, die Diskretisierungen bieten, z.B. das Ermöglichen numerischer Simulationen, gibt es auch gravierende Nachteile, die einer ausführlichen Untersuchung bedürfen: Im Allgemeinen brechen Diskretisierungen die fundamentale Diffeomorphismensymmetrie der Gravitation und sind in der Regel nicht eindeutig definiert. Beides erschwert die Wiederherstellung der Verbindung zur klassischen, kontinuierlichen Theorie. Das Hauptaugenmerk dieser Doktorarbeit liegt darin diese Verbindung insbesondere für Spin-Schaum-Modelle (spin foam models) zu untersuchen. Dies geschieht auf sehr verschiedenen Ebenen der Diskretisierung / Triangulierung, angefangen bei wenigen Simplizes bis hin zum Kontinuumslimes. Im Regime weniger Simplizes wird die bekannte Verbindung von Spin--Schaum--Modellen zu diskreter Gravitation bestätigt und vertieft. Außerdem diskutieren wir dynamische Prinzipien, z.B. Diffeomorphismeninvarianz im Diskreten, um die Ambiguitäten der Modelle zu fixieren. Um diese Bedingungen zu erfüllen, müssen die diskreten Modelle durch Renormierungsverfahren verbessert werden, wodurch wir auch ihre Kontinuumsdynamik untersuchen können. Angewandt auf vereinfachte Spin-Schaum-Modelle finden wir eine reichhaltige, nicht-triviale Fixpunkt-Struktur, die wir in einem Phasendiagramm zusammenfassen. Inspiriert von diesen Methoden schlagen wir zu guter Letzt eine konsistente Konstruktionsmethode für die Kontinuumstheorie vor, die einen eindeutigen Vakuumszustand definiert. KW - Quantengravitation KW - Spin-Schaum-Modelle KW - Regge Kalkül KW - Renormierung KW - Verfeinerungslimes KW - quantum gravity KW - spin foams KW - regge calculus KW - renormalization and refinement limit Y1 - 2014 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus-72558 ER - TY - JOUR A1 - Beim Graben, Peter T1 - Contextual emergence of intentionality JF - Journal of consciousness studies : controversies in science & the humanities ; an international multi-disciplinary journal N2 - By means of an intriguing physical example, magnetic surface swimmers, that can be described in terms of Dennett's intentional stance, I reconstruct a hierarchy of necessary and sufficient conditions for the applicability of the intentional strategy. It turns out that the different levels of the intentional hierarchy are contextually emergent from their respective subjacent levels by imposing stability constraints upon them. At the lowest level of the hierarchy, phenomenal physical laws emerge for the coarse-grained description of open, nonlinear, and dissipative non-equilibrium systems in critical states. One level higher, dynamic patterns, such as, for example, magnetic surface swimmers, are contextually emergent as they are invariant under certain symmetry operations. Again one level up, these patterns behave apparently rationally by selecting optimal pathways for the dissipation of energy that is delivered by external gradients. This is in accordance with the restated Second Law of thermodynamics as a stability criterion. At the highest level, true believers are intentional systems that are stable under exchanging their observation conditions. Y1 - 2014 SN - 1355-8250 VL - 21 IS - 5-6 SP - 75 EP - 96 PB - Imprint Academic CY - Exeter ER - TY - JOUR A1 - van Driel-Gesztelyi, L. A1 - Baker, Daniel N. A1 - Toeroek, T. A1 - Pariat, E. A1 - Green, L. M. A1 - Williams, D. R. A1 - Carlyle, J. A1 - Valori, G. A1 - Demoulin, Pascal A1 - Kliem, Bernhard A1 - Long, D. M. A1 - Matthews, S. A. A1 - Malherbe, J. -M. T1 - Coronal magnetic reconnection driven by CME expansion-the 2011 June 7 event JF - The astrophysical journal : an international review of spectroscopy and astronomical physics N2 - Coronal mass ejections (CMEs) erupt and expand in a magnetically structured solar corona. Various indirect observational pieces of evidence have shown that the magnetic field of CMEs reconnects with surrounding magnetic fields, forming, e.g., dimming regions distant from the CME source regions. Analyzing Solar Dynamics Observatory (SDO) observations of the eruption from AR 11226 on 2011 June 7, we present the first direct evidence of coronal magnetic reconnection between the fields of two adjacent active regions during a CME. The observations are presented jointly with a data-constrained numerical simulation, demonstrating the formation/intensification of current sheets along a hyperbolic flux tube at the interface between the CME and the neighboring AR 11227. Reconnection resulted in the formation of new magnetic connections between the erupting magnetic structure from AR 11226 and the neighboring active region AR 11227 about 200 Mm from the eruption site. The onset of reconnection first becomes apparent in the SDO/AIA images when filament plasma, originally contained within the erupting flux rope, is redirected toward remote areas in AR 11227, tracing the change of large-scale magnetic connectivity. The location of the coronal reconnection region becomes bright and directly observable at SDO/AIA wavelengths, owing to the presence of down-flowing cool, dense (1010 cm(-3)) filament plasma in its vicinity. The high-density plasma around the reconnection region is heated to coronal temperatures, presumably by slow-mode shocks and Coulomb collisions. These results provide the first direct observational evidence that CMEs reconnect with surrounding magnetic structures, leading to a large-scale reconfiguration of the coronal magnetic field. KW - magnetic reconnection KW - magnetohydrodynamics (MHD) KW - Sun: corona KW - Sun: coronal mass ejections (CMEs) KW - Sun: magnetic fields KW - Sun: UV radiation Y1 - 2014 U6 - https://doi.org/10.1088/0004-637X/788/1/85 SN - 0004-637X SN - 1538-4357 VL - 788 IS - 1 PB - IOP Publ. Ltd. CY - Bristol ER - TY - JOUR A1 - Schubert, Marcel A1 - Collins, Brian A. A1 - Mangold, Hannah A1 - Howard, Ian A. A1 - Schindler, Wolfram A1 - Vandewal, Koen A1 - Roland, Steffen A1 - Behrends, Jan A1 - Kraffert, Felix A1 - Steyrleuthner, Robert A1 - Chen, Zhihua A1 - Fostiropoulos, Konstantinos A1 - Bittl, Robert A1 - Salleo, Alberto A1 - Facchetti, Antonio A1 - Laquai, Frederic A1 - Ade, Harald W. A1 - Neher, Dieter T1 - Correlated donor/acceptor crystal orientation controls photocurrent generation in all-polymer solar cells JF - Advanced functional materials N2 - New polymers with high electron mobilities have spurred research in organic solar cells using polymeric rather than fullerene acceptors due to their potential of increased diversity, stability, and scalability. However, all-polymer solar cells have struggled to keep up with the steadily increasing power conversion efficiency of polymer: fullerene cells. The lack of knowledge about the dominant recombination process as well as the missing concluding picture on the role of the semi-crystalline microstructure of conjugated polymers in the free charge carrier generation process impede a systematic optimization of all-polymer solar cells. These issues are examined by combining structural and photo-physical characterization on a series of poly(3-hexylthiophene) (donor) and P(NDI2OD-T2) (acceptor) blend devices. These experiments reveal that geminate recombination is the major loss channel for photo-excited charge carriers. Advanced X-ray and electron-based studies reveal the effect of chloronaphthalene co-solvent in reducing domain size, altering domain purity, and reorienting the acceptor polymer crystals to be coincident with those of the donor. This reorientation correlates well with the increased photocurrent from these devices. Thus, effi cient split-up of geminate pairs at polymer/polymer interfaces may necessitate correlated donor/acceptor crystal orientation, which represents an additional requirement compared to the isotropic fullerene acceptors. Y1 - 2014 U6 - https://doi.org/10.1002/adfm.201304216 SN - 1616-301X SN - 1616-3028 VL - 24 IS - 26 SP - 4068 EP - 4081 PB - Wiley-VCH CY - Weinheim ER - TY - JOUR A1 - Sandev, Trifce A1 - Metzler, Ralf A1 - Tomovski, Zivorad T1 - Correlation functions for the fractional generalized Langevin equation in the presence of internal and external noise JF - Journal of mathematical physics N2 - We study generalized fractional Langevin equations in the presence of a harmonic potential. General expressions for the mean velocity and particle displacement, the mean squared displacement, position and velocity correlation functions, as well as normalized displacement correlation function are derived. We report exact results for the cases of internal and external friction, that is, when the driving noise is either internal and thus the fluctuation-dissipation relation is fulfilled or when the noise is external. The asymptotic behavior of the generalized stochastic oscillator is investigated, and the case of high viscous damping (overdamped limit) is considered. Additional behaviors of the normalized displacement correlation functions different from those for the regular damped harmonic oscillator are observed. In addition, the cases of a constant external force and the force free case are obtained. The validity of the generalized Einstein relation for this process is discussed. The considered fractional generalized Langevin equation may be used to model anomalous diffusive processes including single file-type diffusion. Y1 - 2014 U6 - https://doi.org/10.1063/1.4863478 SN - 0022-2488 SN - 1089-7658 VL - 55 IS - 2 PB - American Institute of Physics CY - Melville ER - TY - THES A1 - Balzer, Arnim T1 - Crab flare observations with H.E.S.S. phase II T1 - Crab Flare Observations with H.E.S.S. Phase II N2 - The H.E.S.S. array is a third generation Imaging Atmospheric Cherenkov Telescope (IACT) array. It is located in the Khomas Highland in Namibia, and measures very high energy (VHE) gamma-rays. In Phase I, the array started data taking in 2004 with its four identical 13 m telescopes. Since then, H.E.S.S. has emerged as the most successful IACT experiment to date. Among the almost 150 sources of VHE gamma-ray radiation found so far, even the oldest detection, the Crab Nebula, keeps surprising the scientific community with unexplained phenomena such as the recently discovered very energetic flares of high energy gamma-ray radiation. During its most recent flare, which was detected by the Fermi satellite in March 2013, the Crab Nebula was simultaneously observed with the H.E.S.S. array for six nights. The results of the observations will be discussed in detail during the course of this work. During the nights of the flare, the new 24 m × 32 m H.E.S.S. II telescope was still being commissioned, but participated in the data taking for one night. To be able to reconstruct and analyze the data of the H.E.S.S. Phase II array, the algorithms and software used by the H.E.S.S. Phase I array had to be adapted. The most prominent advanced shower reconstruction technique developed by de Naurois and Rolland, the template-based model analysis, compares real shower images taken by the Cherenkov telescope cameras with shower templates obtained using a semi-analytical model. To find the best fitting image, and, therefore, the relevant parameters that describe the air shower best, a pixel-wise log-likelihood fit is done. The adaptation of this advanced shower reconstruction technique to the heterogeneous H.E.S.S. Phase II array for stereo events (i.e. air showers seen by at least two telescopes of any kind), its performance using MonteCarlo simulations as well as its application to real data will be described. N2 - Das H.E.S.S. Experiment misst sehr hochenergetische Gammastrahlung im Khomas Hochland von Namibia. Es ist ein sogenanntes abbildendes atmosphärisches Cherenkov-Teleskopsystem welches in der 1. Phase, die im Jahr 2004 mit der Datennahme begann, aus vier identischen 13 m Spiegelteleskopen bestand. Seitdem hat sich H.E.S.S. als das erfolgreichstes Experiment in der bodengebundenen Gammastrahlungsastronomie etabliert. Selbst die älteste der mittlerweile fast 150 entdeckten Quellen von sehr hochenergetischer Gammastrahlung, der Krebsnebel, fasziniert immernoch Wissenschaftler mit neuen bisher unbekannten und unerwarteten Phänomenen. Ein Beispiel dafür sind die vor kurzem entdeckten sehr energiereichen Ausbrüche von hochenergetischer Gammastrahlung. Bei dem letzten deratigen Ausbruch des Krebsnebels im März 2013 hat das H.E.S.S. Experiment für sechs Nächte simultan mit dem Fermi-Satelliten, welcher den Ausbruch entdeckte, Daten genommen. Die Analyse der Daten, deren Ergebnis und deren Interpretation werden im Detail in dieser Arbeit vorgestellt. Während dieser Beobachtungen befand sich ein neues 24 m × 32 m großes Spiegelteleskop, das H.E.S.S. II- Teleskop, noch in seiner Inbetriebnahme, trotzdem hat es für eine dieser sechs Nächte an der Datennahme des gesamten Teleskopsystems teilgenommen. Um die Daten rekonstruieren und analysieren zu können, mussten die für die 1. Phase des Experiments entwickelten Algorithmen und die Software des H.E.S.S.- Experiments angepasst werden. Die fortschrittlichste Schauerrekonstruktionsmethode, welche von de Naurois und Rolland entwickelt wurde, basiert auf dem Vergleich von echten Schauerbildern, die mit Hilfe der Cherenkov-Kameras der einzelnen Teleskope aufgenommen wurden, mit Schauerschablonen die mit Hilfe eines semianalytischen Modells erzeugt wurden. Das am besten passende Bild und damit auch alle relevanten Schauerparameter, wird mit Hilfe einer pixelweisen Loglikelihood-Anpassung ermittelt. Die nötigen Änderungen um Multiteleskopereignisse, welche vom heterogenen H.E.S.S. Phase II Detektor gemessen wurden, mit Hilfe dieser fortschrittlichen Schauerrekonstruktionsmethode analysieren zu können, sowie die resultierenden Ergebnisse von MonteCarlo-Simulationen, als auch die Anwendung auf echte Daten, werden im Rahmen dieser Arbeit präsentiert. KW - Gammastrahlungsastronomie KW - Rekonstruktionsmethoden KW - Datenanalyse KW - Krebsnebel KW - gamma-ray astronomy KW - reconstruction methods KW - data analysis KW - Crab Nebula Y1 - 2014 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus-72545 ER - TY - JOUR A1 - de Carvalho, Sidney J. A1 - Metzler, Ralf A1 - Cherstvy, Andrey G. T1 - Critical adsorption of polyelectrolytes onto charged Janus nanospheres JF - Physical chemistry, chemical physics : a journal of European Chemical Societies N2 - Based on extensive Monte Carlo simulations and analytical considerations we study the electrostatically driven adsorption of flexible polyelectrolyte chains onto charged Janus nanospheres. These net-neutral colloids are composed of two equally but oppositely charged hemispheres. The critical binding conditions for polyelectrolyte chains are analysed as function of the radius of the Janus particle and its surface charge density, as well as the salt concentration in the ambient solution. Specifically for the adsorption of finite-length polyelectrolyte chains onto Janus nanoparticles, we demonstrate that the critical adsorption conditions drastically differ when the size of the Janus particle or the screening length of the electrolyte are varied. We compare the scaling laws obtained for the adsorption-desorption threshold to the known results for uniformly charged spherical particles, observing significant disparities. We also contrast the changes to the polyelectrolyte chain conformations close to the surface of the Janus nanoparticles as compared to those for simple spherical particles. Finally, we discuss experimentally relevant physicochemical systems for which our simulations results may become important. In particular, we observe similar trends with polyelectrolyte complexation with oppositely but heterogeneously charged proteins. Y1 - 2014 U6 - https://doi.org/10.1039/c4cp02207f SN - 1463-9076 SN - 1463-9084 VL - 16 IS - 29 SP - 15539 EP - 15550 PB - Royal Society of Chemistry CY - Cambridge ER - TY - GEN A1 - de Carvalho, Sidney J. A1 - Metzler, Ralf A1 - Cherstvy, Andrey G. T1 - Critical adsorption of polyelectrolytes onto charged Janus nanospheres N2 - Based on extensive Monte Carlo simulations and analytical considerations we study the electrostatically driven adsorption of flexible polyelectrolyte chains onto charged Janus nanospheres. These net-neutral colloids are composed of two equally but oppositely charged hemispheres. The critical binding conditions for polyelectrolyte chains are analysed as function of the radius of the Janus particle and its surface charge density, as well as the salt concentration in the ambient solution. Specifically for the adsorption of finite-length polyelectrolyte chains onto Janus nanoparticles, we demonstrate that the critical adsorption conditions drastically differ when the size of the Janus particle or the screening length of the electrolyte are varied. We compare the scaling laws obtained for the adsorption–desorption threshold to the known results for uniformly charged spherical particles, observing significant disparities. We also contrast the changes to the polyelectrolyte chain conformations close to the surface of the Janus nanoparticles as compared to those for simple spherical particles. Finally, we discuss experimentally relevant physico-chemical systems for which our simulations results may become important. In particular, we observe similar trends with polyelectrolyte complexation with oppositely but heterogeneously charged proteins. T3 - Zweitveröffentlichungen der Universität Potsdam : Mathematisch-Naturwissenschaftliche Reihe - 278 Y1 - 2014 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus4-98783 ER - TY - JOUR A1 - Archambault, S. A1 - Aune, T. A1 - Behera, B. A1 - Beilicke, M. A1 - Benbow, W. A1 - Berger, K. A1 - Bird, R. A1 - Biteau, Jonathan 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, Wei A1 - Dumm, J. 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 - Galante, N. A1 - Gillanders, G. H. A1 - Griffin, S. A1 - Griffiths, S. T. A1 - Grube, J. A1 - Gyuk, G. A1 - Hanna, D. A1 - Holder, J. A1 - Hughes, G. A1 - Humensky, T. B. A1 - Johnson, C. A. A1 - Kaaret, P. A1 - Kertzman, M. A1 - Khassen, Y. A1 - Kieda, D. A1 - Krawczynski, H. A1 - Krennrich, F. A1 - Kumar, S. A1 - Lang, M. J. A1 - Madhavan, A. S. A1 - Maier, G. A1 - McCann, A. A1 - Meagher, K. A1 - Moriarty, P. A1 - Mukherjee, R. A1 - Nieto, Daniel A1 - Ong, R. A. A1 - Otte, A. N. A1 - Park, N. A1 - Pohl, Martin A1 - Popkow, A. A1 - Prokoph, H. 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 - Staszak, D. A1 - Telezhinsky, Igor O. A1 - Tucci, J. V. A1 - Tyler, J. A1 - Varlotta, A. A1 - Vassiliev, V. V. A1 - Vincent, S. A1 - Wakely, S. P. A1 - Weinstein, A. A1 - Welsing, R. A1 - Wilhelm, Alina A1 - Williams, D. A. A1 - Ackermann, Margit A1 - Ajello, M. A1 - Albert, A. A1 - Baldini, L. A1 - Bastieri, D. A1 - Bellazzini, R. A1 - Bissaldi, E. A1 - Bregeon, Johan A1 - Buehler, R. A1 - Buson, S. A1 - Caliandro, G. A. A1 - Cameron, R. A. A1 - Caraveo, P. A. A1 - Cavazzuti, E. A1 - Charles, E. A1 - Chiang, J. A1 - Ciprini, S. A1 - Claus, R. A1 - Cutini, S. A1 - de Angelis, A. A1 - de Palma, F. A1 - Dermer, C. D. A1 - Digel, S. W. A1 - Di Venere, L. A1 - Drell, P. S. A1 - Favuzzi, C. A1 - Franckowiak, A. A1 - Fusco, P. A1 - Gargano, F. A1 - Gasparrini, D. A1 - Giglietto, N. A1 - Giordano, F. A1 - Giroletti, M. A1 - Grenier, I. A. A1 - Guiriec, S. A1 - Jogler, T. A1 - Kuss, M. A1 - Larsson, S. A1 - Latronico, L. A1 - Longo, F. A1 - Loparco, F. A1 - Lubrano, P. A1 - Madejski, G. M. A1 - Mayer, M. A1 - Mazziotta, Mario Nicola A1 - Michelson, P. F. A1 - Mizuno, T. A1 - Monzani, M. E. A1 - Morselli, Aldo A1 - Murgia, S. A1 - Nuss, E. A1 - Ohsugi, T. A1 - Ormes, J. F. A1 - Paneque, D. A1 - Perkins, J. S. A1 - Piron, F. A1 - Pivato, G. A1 - Raino, S. A1 - Razzano, M. A1 - Reimer, A. A1 - Reimer, Olaf A1 - Ritz, S. A1 - Schaal, M. A1 - Sgro, C. A1 - Siskind, E. J. A1 - Spinelli, P. A1 - Takahashi, H. A1 - Tibaldo, L. A1 - Tinivella, M. A1 - Troja, E. A1 - Vianello, G. A1 - Werner, M. A1 - Wood, M. T1 - Deep broadband observations of the distant gamma-ray blazar PKS 1424+240 JF - The astrophysical journal : an international review of spectroscopy and astronomical physics ; Part 2, Letters N2 - We present deep VERITAS observations of the blazar PKS 1424+240, along with contemporaneous Fermi Large Area Telescope, Swift X-ray Telescope, and Swift UV Optical Telescope data between 2009 February 19 and 2013 June 8. This blazar resides at a redshift of z >= 0.6035, displaying a significantly attenuated gamma-ray flux above 100 GeV due to photon absorption via pair-production with the extragalactic background light. We present more than 100 hr of VERITAS observations over three years, a multiwavelength light curve, and the contemporaneous spectral energy distributions. The source shows a higher flux of (2.1 +/- 0.3) x 10(-7) photons m(-2) s(-1) above 120 GeV in 2009 and 2011 as compared to the flux measured in 2013, corresponding to (1.02 +/- 0.08) x 10-7 photons m(-2) s(-1) above 120 GeV. The measured differential very high energy (VHE; E >= 100 GeV) spectral indices are Gamma = 3.8 +/- 0.3, 4.3 +/- 0.6 and 4.5 +/- 0.2 in 2009, 2011, and 2013, respectively. No significant spectral change across the observation epochs is detected. We find no evidence for variability at gamma-ray opacities of greater than tau = 2, where it is postulated that any variability would be small and occur on timescales longer than a year if hadronic cosmic-ray interactions with extragalactic photon fields provide a secondary VHE photon flux. The data cannot rule out such variability due to low statistics. KW - BL Lacertae objects: individual (PKS 1424+240)-cosmic background radiation KW - gamma rays: galaxies Y1 - 2014 U6 - https://doi.org/10.1088/2041-8205/785/1/L16 SN - 2041-8205 SN - 2041-8213 VL - 785 IS - 1 PB - IOP Publ. Ltd. CY - Bristol ER -