TY - JOUR A1 - Stange, Maike A1 - Hintsche, Marius A1 - Sachse, Kirsten A1 - Gerhardt, Matthias A1 - Valleriani, Angelo A1 - Beta, Carsten T1 - Analyzing the spatial positioning of nuclei in polynuclear giant cells JF - Journal of Physics D: Applied Physics N2 - How cells establish and maintain a well-defined size is a fundamental question of cell biology. Here we investigated to what extent the microtubule cytoskeleton can set a predefined cell size, independent of an enclosing cell membrane. We used electropulse-induced cell fusion to form giant multinuclear cells of the social amoeba Dictyostelium discoideum. Based on dual-color confocal imaging of cells that expressed fluorescent markers for the cell nucleus and the microtubules, we determined the subcellular distributions of nuclei and centrosomes in the giant cells. Our two- and three-dimensional imaging results showed that the positions of nuclei in giant cells do not fall onto a regular lattice. However, a comparison with model predictions for random positioning showed that the subcellular arrangement of nuclei maintains a low but still detectable degree of ordering. This can be explained by the steric requirements of the microtubule cytoskeleton, as confirmed by the effect of a microtubule degrading drug. KW - Dictyostelium KW - cell nucleus KW - positioning KW - imaging KW - spatial poisson distribution Y1 - 2017 U6 - https://doi.org/10.1088/1361-6463/aa8da0 SN - 0022-3727 SN - 1361-6463 VL - 50 IS - 46 PB - IOP Publ. Ltd. CY - Bristol ER - TY - JOUR A1 - Kurzke, Henning A1 - Kiethe, Jan A1 - Heuer, Axel A1 - Jechow, Andreas T1 - Frequency doubling of incoherent light from a superluminescent diode in a periodically poled lithium niobate waveguide crystal JF - Laser physics letters N2 - The amplified spontaneous emission from a superluminescent diode was frequency doubled in a periodically poled lithium niobate waveguide crystal. The temporally incoherent radiation of such a superluminescent diode is characterized by a relatively broad spectral bandwidth and thermal-like photon statistics, as the measured degree of second order coherence, g((2))(0)= 1.9 +/- 0.1, indicates. Despite the non-optimized scenario in the spectral domain, we achieve six orders of magnitude higher conversion efficiency than previously reported with truly incoherent light. This is possible by using single spatial mode radiation and quasi phase matched material with a waveguide architecture. This work is a principle step towards efficient frequency conversion of temporally incoherent radiation in one spatial mode to access wavelengths where no radiation from superluminescent diodes is available, especially with tailored quasi phase matched crystals. The frequency doubled light might find application in imaging, metrology and quantum optics experiments. KW - nonlinear frequency conversion KW - periodically poled material KW - waveguides KW - incoherent radiation Y1 - 2017 U6 - https://doi.org/10.1088/1612-202X/aa6889 SN - 1612-2011 SN - 1612-202X VL - 14 PB - IOP Publ. CY - Bristol ER - TY - JOUR A1 - Kamann, Sebastian A1 - Husser, T. -O. A1 - Dreizler, S. A1 - Emsellem, E. A1 - Weilbacher, Peter Michael A1 - Martens, S. A1 - Bacon, R. A1 - den Brok, M. A1 - Giesers, B. A1 - Krajnovic, Davor A1 - Roth, Martin M. A1 - Wendt, Martin A1 - Wisotzki, Lutz T1 - A stellar census in globular clusters with MUSE BT - the contribution of rotation to cluster dynamics studied with 200 000 stars JF - Monthly notices of the Royal Astronomical Society N2 - This is the first of a series of papers presenting the results from our survey of 25 Galactic globular clusters with the MUSE integral-field spectrograph. In combination with our dedicated algorithm for source deblending, MUSE provides unique multiplex capabilities in crowded stellar fields and allows us to acquire samples of up to 20 000 stars within the half-light radius of each cluster. The present paper focuses on the analysis of the internal dynamics of 22 out of the 25 clusters, using about 500 000 spectra of 200 000 individual stars. Thanks to the large stellar samples per cluster, we are able to perform a detailed analysis of the central rotation and dispersion fields using both radial profiles and two-dimensional maps. The velocity dispersion profiles we derive show a good general agreement with existing radial velocity studies but typically reach closer to the cluster centres. By comparison with proper motion data, we derive or update the dynamical distance estimates to 14 clusters. Compared to previous dynamical distance estimates for 47 Tuc, our value is in much better agreement with other methods. We further find significant (>3 sigma) rotation in the majority (13/22) of our clusters. Our analysis seems to confirm earlier findings of a link between rotation and the ellipticities of globular clusters. In addition, we find a correlation between the strengths of internal rotation and the relaxation times of the clusters, suggesting that the central rotation fields are relics of the cluster formation that are gradually dissipated via two-body relaxation. KW - techniques: imaging spectroscopy KW - stars: kinematics and dynamics KW - globular clusters: general Y1 - 2017 U6 - https://doi.org/10.1093/mnras/stx2719 SN - 0035-8711 SN - 1365-2966 VL - 473 IS - 4 SP - 5591 EP - 5616 PB - Oxford Univ. Press CY - Oxford ER - TY - GEN A1 - Javanainen, Matti A1 - Martinez-Seara, Hector A1 - Metzler, Ralf A1 - Vattulainen, Ilpo Tapio T1 - Diffusion of Proteins and Lipids in Protein-Rich Membranesa T2 - Biophysical journal Y1 - 2018 U6 - https://doi.org/10.1016/j.bpj.2017.11.3009 SN - 0006-3495 SN - 1542-0086 VL - 114 IS - 3 SP - 551A EP - 551A PB - Cell Press CY - Cambridge ER - TY - JOUR A1 - Shprits, Yuri Y. A1 - Angelopoulos, V. A1 - Russell, C. T. A1 - Strangeway, R. J. A1 - Runov, A. A1 - Turner, D. A1 - Caron, R. A1 - Cruce, P. A1 - Leneman, D. A1 - Michaelis, I. A1 - Petrov, V. A1 - Panasyuk, M. A1 - Yashin, I. A1 - Drozdov, Alexander Y. A1 - Russell, C. L. A1 - Kalegaev, V. A1 - Nazarkov, I. A1 - Clemmons, J. H. T1 - Scientific Objectives of Electron Losses and Fields INvestigation Onboard Lomonosov Satellite JF - Space science reviews N2 - The objective of the Electron Losses and Fields INvestigation on board the Lomonosov satellite ( ELFIN-L) project is to determine the energy spectrum of precipitating energetic electrons and ions and, together with other polar-orbiting and equatorial missions, to better understand the mechanisms responsible for scattering these particles into the atmosphere. This mission will provide detailed measurements of the radiation environment at low altitudes. The 400-500 km sun-synchronous orbit of Lomonosov is ideal for observing electrons and ions precipitating into the atmosphere. This mission provides a unique opportunity to test the instruments. Similar suite of instruments will be flown in the future NSF-and NASA-supported spinning CubeSat ELFIN satellites which will augment current measurements by providing detailed information on pitch-angle distributions of precipitating and trapped particles. KW - Magnetospheric physics KW - Observations KW - Particles precipitating KW - Particles trapped KW - Radiation belts Y1 - 2017 U6 - https://doi.org/10.1007/s11214-017-0455-4 SN - 0038-6308 SN - 1572-9672 VL - 214 IS - 1 PB - Springer CY - Dordrecht ER - TY - GEN A1 - Gudowska-Nowak, Ewa A1 - Lindenberg, Katja A1 - Metzler, Ralf T1 - Preface: Marian Smoluchowski’s 1916 paper—a century of inspiration T2 - Journal of physics : A, Mathematical and theoretical Y1 - 2017 U6 - https://doi.org/10.1088/1751-8121/aa8529 SN - 1751-8113 SN - 1751-8121 VL - 50 IS - 38 PB - IOP Publ. Ltd. CY - Bristol ER - TY - JOUR A1 - Hani, Maan H. A1 - Sparre, Martin A1 - Ellison, Sara L. A1 - Torrey, Paul A1 - Vogelsberger, Mark T1 - Galaxy mergers moulding the circum-galactic medium BT - I. The impact of a major merger JF - Monthly notices of the Royal Astronomical Society N2 - Galaxies are surrounded by sizeable gas reservoirs which host a significant amount of metals: the circum-galactic medium (CGM). The CGM acts as a mediator between the galaxy and the extragalactic medium. However, our understanding of how galaxy mergers, a major evolutionary transformation, impact the CGM remains deficient. We present a theoretical study of the effect of galaxy mergers on the CGM. We use hydrodynamical cosmological zoom-in simulations of a major merger selected from the Illustris project such that the z = 0 descendant has a halo mass and stellar mass comparable to the Milky Way. To study the CGM we then re-simulated this system at a 40 times better mass resolution, and included detailed post-processing ionization modelling. Our work demonstrates the effect the merger has on the characteristic size of the CGM, its metallicity, and the predicted covering fraction of various commonly observed gas-phase species, such as H I, C IV, and O VI. We show that merger-induced outflows can increase the CGM metallicity by 0.2-0.3 dex within 0.5 Gyr post-merger. These effects last up to 6 Gyr post-merger. While the merger increases the total metal covering fractions by factors of 2-3, the covering fractions of commonly observed UV ions decrease due to the hard ionizing radiation from the active galactic nucleus, which we model explicitly. Our study of the single simulated major merger presented in this work demonstrates the significant impact that a galaxy interaction can have on the size, metallicity, and observed column densities of the CGM. KW - methods: numerical KW - galaxies: evolution KW - galaxies: haloes KW - galaxies: interactions Y1 - 2017 U6 - https://doi.org/10.1093/mnras/stx3252 SN - 0035-8711 SN - 1365-2966 VL - 475 IS - 1 SP - 1160 EP - 1176 PB - Oxford Univ. Press CY - Oxford ER - TY - GEN A1 - Benini, Marco A1 - Schenkel, Alexander T1 - Quantum field theories on categories fibered in groupoids T2 - Postprints der Universität Potsdam : Mathematisch-Naturwissenschaftliche Reihe N2 - We introduce an abstract concept of quantum field theory on categories fibered in groupoids over the category of spacetimes. This provides us with a general and flexible framework to study quantum field theories defined on spacetimes with extra geometric structures such as bundles, connections and spin structures. Using right Kan extensions, we can assign to any such theory an ordinary quantum field theory defined on the category of spacetimes and we shall clarify under which conditions it satisfies the axioms of locally covariant quantum field theory. The same constructions can be performed in a homotopy theoretic framework by using homotopy right Kan extensions, which allows us to obtain first toy-models of homotopical quantum field theories resembling some aspects of gauge theories. T3 - Zweitveröffentlichungen der Universität Potsdam : Mathematisch-Naturwissenschaftliche Reihe - 895 KW - C-asterisk-algebra KW - observables KW - covariance KW - locality Y1 - 2020 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus4-431541 SN - 1866-8372 IS - 895 ER - TY - GEN A1 - Parsons, R. D. A1 - Schüssler, F. A1 - Garrigoux, T. A1 - Balzer, A. A1 - Füssling, Matthias A1 - Hoischen, Clemens A1 - Holler, M. A1 - Mitchell, A. A1 - Pühlhofer, G. A1 - Rowell, G. A1 - Wagner, S. A1 - Bissaldi, E. A1 - Tam, P. H. T. T1 - The HESS II GRB Observation Scheme T2 - AIP conference proceedings / American Institute of Physics N2 - Gamma-ray bursts (GRBs) are some of the Universe’s most enigmatic and exotic events. However, at energies above 10 GeV their behaviour remains largely unknown. Although space based telescopes such as the Fermi-LAT have been able to detect GRBs in this energy range, their photon statistics are limited by the small detector size. Such limitations are not present in ground based gamma-ray telescopes such as the H.E.S.S. experiment, which has now entered its second phase with the addition of a large 600 m2 telescope to the centre of the array. Such a large telescope allows H.E.S.S. to access the sub 100-GeV energy range while still maintaining a large effective collection area, helping to potentially probe the short timescale emission of these events. We present a description of the H.E.S.S. GRB observation programme, summarising the performance of the rapid GRB repointing system and the conditions under which GRB observations are initiated. Additionally we will report on the GRB follow-ups made during the 2014-15 observation campaigns. Y1 - 2017 SN - 978-0-7354-1456-3 U6 - https://doi.org/10.1063/1.4968980 SN - 0094-243X SN - 1551-7616 VL - 1792 IS - 1 PB - American Institute of Physics CY - Melville ER - TY - GEN A1 - Angüner, Ekrem Oǧuzhan A1 - Aharonian, Felix A. A1 - Bordas, Pol A1 - Casanova, Sabrina A1 - Hoischen, Clemens A1 - Oya, I. A1 - Ziegler, A. T1 - HESS J1826-130 BT - a very hard gamma-Ray spectrum source in the Galactic Plane T2 - AIP conference proceedings / American Institute of Physics N2 - HESS J1826-130 is an unidentified hard spectrum source discovered by H.E.S.S. along the Galactic plane, the spectral index being Gamma = 1.6 with an exponential cut-off at about 12 TeV. While the source does not have a clear counterpart at longer wavelengths, the very hard spectrum emission at TeV energies implies that electrons or protons accelerated up to several hundreds of TeV are responsible for the emission. In the hadronic case, the VHE emission can be produced by runaway cosmic-rays colliding with the dense molecular clouds spatially coincident with the H.E.S.S. source. Y1 - 2017 SN - 978-0-7354-1456-3 U6 - https://doi.org/10.1063/1.4968928 SN - 0094-243X SN - 1551-7616 VL - 1792 IS - 1 PB - American Institute of Physics CY - Melville ER - TY - JOUR A1 - Beta, Carsten A1 - Kruse, Karsten T1 - Intracellular oscillations and waves JF - Annual review of condensed matter physics N2 - Dynamic processes in living cells are highly organized in space and time. Unraveling the underlying molecular mechanisms of spatiotemporal pattern formation remains one of the outstanding challenges at the interface between physics and biology. A fundamental recurrent pattern found in many different cell types is that of self-sustained oscillations. They are involved in a wide range of cellular functions, including second messenger signaling, gene expression, and cytoskeletal dynamics. Here, we review recent developments in the field of cellular oscillations and focus on cases where concepts from physics have been instrumental for understanding the underlying mechanisms. We consider biochemical and genetic oscillators as well as oscillations that arise from chemo-mechanical coupling. Finally, we highlight recent studies of intracellular waves that have increasingly moved into the focus of this research field. KW - self-sustained oscillations KW - biochemical oscillators KW - genetic networks KW - chemomechanical coupling KW - actin waves Y1 - 2017 SN - 978-0-8243-5008-6 U6 - https://doi.org/10.1146/annurev-conmatphys-031016-025210 SN - 1947-5454 VL - 8 SP - 239 EP - 264 PB - Annual Reviews CY - Palo Alto ER - TY - GEN A1 - Thoelert, Steffen A1 - Hörmann, Ulrich A1 - Antreich, Felix A1 - Meurer, Michael T1 - Ionospheric effects on high gain antenna GNSS measurements BT - TEC estimation and correction T2 - Proceedings of the 30th International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GNSS+ 2017) N2 - The ionospheric delay of global navigation satellite systems (GNSS) signals typically is compensated by adding a single correction value to the pseudorange measurement of a GNSS receiver. Yet, this neglects the dispersive nature of the ionosphere. In this context we analyze the ionospheric signal distortion beyond a constant delay. These effects become increasingly significant with the signal bandwidth and hence more important for new broadband navigation signals. Using measurements of the Galileo E5 signal, captured with a high gain antenna, we verify that the expected influence can indeed be observed and compensated. A new method to estimate the total electron content (TEC) from a single frequency high gain antenna measurement of a broadband GNSS signal is proposed and described in detail. The received signal is de facto unaffected by multi-path and interference because of the narrow aperture angle of the used antenna which should reduce the error source of the result in general. We would like to point out that such measurements are independent of code correlation, like in standard receiver applications. It is therefore also usable without knowledge of the signal coding. Results of the TEC estimation process are shown and discussed comparing to common TEC products like TEC maps and dual frequency receiver estimates. Y1 - 2017 U6 - https://doi.org/10.33012/2017.15343 SN - 2331-5911 SN - 2331-5954 SP - 3368 EP - 3374 PB - Instituite of Navigation CY - Washington ER - TY - THES A1 - Shenar, Tomer T1 - Comprehensive analyses of massive binaries and implications on stellar evolution T1 - Umfassende Analysen massereicher Doppelsterne und Implikationen für die Sternentwicklung N2 - Via their powerful radiation, stellar winds, and supernova explosions, massive stars (Mini & 8 M☉) bear a tremendous impact on galactic evolution. It became clear in recent decades that the majority of massive stars reside in binary systems. This thesis sets as a goal to quantify the impact of binarity (i.e., the presence of a companion star) on massive stars. For this purpose, massive binary systems in the Local Group, including OB-type binaries, high mass X-ray binaries (HMXBs), and Wolf-Rayet (WR) binaries, were investigated by means of spectral, orbital, and evolutionary analyses. The spectral analyses were performed with the non-local thermodynamic equillibrium (non-LTE) Potsdam Wolf-Rayet (PoWR) model atmosphere code. Thanks to critical updates in the calculation of the hydrostatic layers, the code became a state-of-the-art tool applicable for all types of hot massive stars (Chapter 2). The eclipsing OB-type triple system δ Ori served as an intriguing test-case for the new version of the PoWR code, and provided key insights regarding the formation of X-rays in massive stars (Chapter 3). We further analyzed two prototypical HMXBs, Vela X-1 and IGR J17544-2619, and obtained fundamental conclusions regarding the dichotomy of two basic classes of HMXBs (Chapter 4). We performed an exhaustive analysis of the binary R 145 in the Large Magellanic Cloud (LMC), which was claimed to host the most massive stars known. We were able to disentangle the spectrum of the system, and performed an orbital, polarimetric, and spectral analysis, as well as an analysis of the wind-wind collision region. The true masses of the binary components turned out to be significantly lower than suggested, impacting our understanding of the initial mass function and stellar evolution at low metallicity (Chapter 5). Finally, all known WR binaries in the Small Magellanic Cloud (SMC) were analyzed. Although it was theoretical predicted that virtually all WR stars in the SMC should be formed via mass-transfer in binaries, we find that binarity was not important for the formation of the known WR stars in the SMC, implying a strong discrepancy between theory and observations (Chapter 6). N2 - Durch ihre intensive Strahlung, Sternwinde und Supernovaexplosionen tragen massereiche Sterne (Minitial & 8 M☉) erheblich zur Entwicklung von Galaxien bei. In den letzten Jahren wurde es immer klarer, dass sich die Mehrheit der massereichen Sterne in Doppelsternsystemen befindet. Die vorliegende Doktorarbeit hat das Ziel, den Einfluss dieser Tatsache auf die Entwicklung massereicher Sterne quantitativ zu untersuchen. Um dies zu erreichen, haben wir eine Analyse der Umläufe, Spektren und Entwicklung verschiedener Doppelsternsysteme in der lokalen Gruppe durchgeführt, die OB-Sterne, massereicher Röntgendoppelsterne (HMXBs) und Wolf-Rayet-(WR)-Doppelsterne einschließt. Die Spektralanalyse wurde mithilfe des Potsdam-Wolf-Rayet-(PoWR)-Modellatmosphären-Programms für Strahlungstransport in Abwesenheit von lokalem thermodynamischen Gleichgewicht (non-LTE) durchgeführt. Das PoWR-Programm wurde im Laufe der Arbeit aktualisiert, sodass die Berechnung der hydrostatischen Schichten des Sternes nun wesentlich genauer erfolgt, was die Verwendung dieses Programms für alle Typen heißer massereicher Sterne erlaubte (Kapitel 2). Das bedeckungsveränderliche Dreifachsternsystem δ Ori diente als Test für diese neue Version von PoWR, und lieferte wesentliche Informationen bezüglich der Entstehung von Röntgenstrahlung in massereichen Sternen (Kapitel 3). Die Analyse zweier prototypischer massereicher Röntgendoppelsterne, Vela X-1 und IGR J17544-2619, machte den Ursprung der Dichotomie der zwei Hauptklassen der Röntgendoppelsterne deutlich (Kapitel 4). Eine umfassende Analyse des Doppelsterns R145 in der Großen Magellanschen Wolke (LMC), der angeblich aus den massereichsten uns bekannten Sternen besteht, wurde durchgeführt. Mithilfe einer Dekomposition des Spektrums, einer Orbital- und Spektralanalyse, sowie einer Analyse der Kollision von Sternwinden in diesem System konnten wir zeigen, dass die Massen der Komponenten wesentlich kleiner sind als bisher angenommen. Dies ist ein wichtiger Beitrag zu unserem Verständnis der Anfangsmassenfunktion und der Entwicklung massereicher Sterne in Umgebungen geringer Metalizität (Kapitel 5). Schließlich wurde die Gesamtpopulation der WR-Doppelsterne in der Kleinen Magellanschen Wolke (SMC) analysiert. Im Widerspruch zur theoretischen Vorhersage, alle WR-Doppelsterne in der SMC seien dank Massentransfer in Doppelsternsystemen entstanden, finden wir, dass Massentransfer unerheblich für die Entstehung der uns bekannten WR-Sterne in der SMC war (Kapitel 6). KW - massive stars KW - Wolf-Rayet KW - stellar evolution KW - stellar winds KW - binary stars KW - massereiche Sterne KW - Wolf-Rayet KW - Sternentwicklung KW - Sternwinde KW - Doppelsterne Y1 - 2017 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus4-104857 ER - TY - JOUR A1 - Laquai, Frederic A1 - Andrienko, Denis A1 - Deibel, Carsten A1 - Neher, Dieter T1 - Charge carrier generation, recombination, and extraction in polymer-fullerene bulk heterojunction organic solar cells JF - Elementary processes in organic photovoltaics N2 - In this chapter we review the basic principles of photocurrent generation in bulk heterojunction organic solar cells, discuss the loss channels limiting their efficiency, and present case studies of several polymer-fullerene blends. Using steady-state and transient, optical, and electrooptical techniques, we create a precise picture of the fundamental processes that ultimately govern solar cell efficiency. KW - Charge extraction KW - Charge generation KW - Charge recombination KW - Organic solar cells KW - PBT7 KW - PBTTT KW - PCPDTBT Y1 - 2026 SN - 978-3-319-28338-8 SN - 978-3-319-28336-4 U6 - https://doi.org/10.1007/978-3-319-28338-8_11 SN - 0065-3195 VL - 272 SP - 267 EP - 291 PB - Springer CY - Berlin ER - TY - JOUR A1 - Mardoukhi, Ahmad A1 - Mardoukhi, Yousof A1 - Hokka, Mikko A1 - Kuokkala, Veli-Tapani T1 - Effects of strain rate and surface cracks on the mechanical behaviour of Balmoral Red granite JF - Philosophical Transactions of the Royal Society of London, Series A : Mathematical, Physical and Engineering Sciences N2 - This work presents a systematic study on the effects of strain rate and surface cracks on the mechanical properties and behaviour of Balmoral Red granite. The tensile behaviour of the rock was studied at low and high strain rates using Brazilian disc samples. Heat shocks were used to produce samples with different amounts of surface cracks. The surface crack patterns were analysed using optical microscopy, and the complexity of the patterns was quantified by calculating the fractal dimensions of the patterns. The strength of the rock clearly drops as a function of increasing fractal dimensions in the studied strain rate range. However, the dynamic strength of the rock drops significantly faster than the quasi-static strength, and, because of this, also the strain rate sensitivity of the rock decreases with increasing fractal dimensions. This can be explained by the fracture behaviour and fragmentation during the dynamic loading, which is more strongly affected by the heat shock than the fragmentation at low strain rates. KW - split Hopkinson pressure bar KW - rock KW - granite KW - dynamic loading KW - fractal dimension KW - surface cracks Y1 - 2017 U6 - https://doi.org/10.1098/rsta.2016.0179 SN - 1364-503X SN - 1471-2962 VL - 375 IS - 2085 PB - Royal Society CY - London ER - TY - JOUR A1 - Roland, Steffen A1 - Yan, Liang A1 - Zhang, Qianqian A1 - Jiao, Xuechen A1 - Hunt, Adrian A1 - Ghasemi, Masoud A1 - Ade, Harald A1 - You, Wei A1 - Neher, Dieter T1 - Charge Generation and Mobility-Limited Performance of Bulk Heterojunction Solar Cells with a Higher Adduct Fullerene JF - The journal of physical chemistry : C, Nanomaterials and interfaces N2 - Alternative electron acceptors are being actively explored in order to advance the development of bulk-heterojunction (BHJ) organic solar cells (OSCs). The indene-C-60 bisadduct (ICBA) has been regarded as a promising candidate, as it provides high open-circuit voltage in BHJ solar cells; however, the photovoltaic performance of such ICBA-based devices is often inferior when compared to cells with the omnipresent PCBM electron acceptor. Here, by pairing the high performance polymer (FTAZ) as the donor with either PCBM or ICBA as the acceptor, we explore the physical mechanism behind the reduced performance of the ICBA-based device. Time delayed collection field (TDCF) experiments reveal reduced, yet field-independent free charge generation in the FTAZ:ICBA system, explaining the overall lower photocurrent in its cells. Through the analysis of the photoluminescence, photogeneration, and electroluminescence, we find that the lower generation efficiency is neither caused by inefficient exciton splitting, nor do we find evidence for significant energy back-transfer from the CT state to singlet excitons. In fact, the increase in open circuit voltage when replacing PCBM by ICBA is entirely caused by the increase in the CT energy, related to the shift in the LUMO energy, while changes in the radiative and nonradiative recombination losses are nearly absent. On the other hand, space charge limited current (SCLC) and bias-assisted charge extraction (BACE) measurements consistently reveal a severely lower electron mobilitiy in the FTAZ:ICBA blend. Studies of the blends with resonant soft X-ray scattering (R-SoXS), grazing incident wide-angle X-ray scattering (GIWAXS), and scanning transmission X-ray microscopy (STXM) reveal very little differences in the mesoscopic morphology but significantly less nanoscale molecular ordering of the fullerene domains in the ICBA based blends, which we propose as the main cause for the lower generation efficiency and smaller electron mobility. Calculations of the JV curves with an analytical model, using measured values, show good agreement with the experimentally determined JV characteristics, proving that these devices suffer from slow carrier extraction, resulting in significant bimolecular recombination losses. Therefore, this study highlights the importance of high charge carrier mobility for newly synthesized acceptor materials, in addition to having suitable energy levels. Y1 - 2017 U6 - https://doi.org/10.1021/acs.jpcc.7b02288 SN - 1932-7447 VL - 121 SP - 10305 EP - 10316 PB - American Chemical Society CY - Washington ER - TY - JOUR A1 - Ahnen, M. L. A1 - Ansoldi, S. A1 - Antonelli, L. A. A1 - Antoranz, P. A1 - Babic, A. A1 - Banerjee, B. A1 - Bangale, P. A1 - de Almeida, U. Barres A1 - Barrio, J. A. A1 - Gonzalez, J. Becerra A1 - Bednarek, W. A1 - Bernardini, E. A1 - Berti, A. A1 - Biasuzzi, B. A1 - Biland, A. A1 - Blanch, O. A1 - Bonnefoy, S. A1 - Bonnoli, G. A1 - Borracci, F. A1 - Bretz, T. A1 - Buson, S. A1 - Carosi, A. A1 - Chatterjee, A. A1 - Clavero, R. A1 - Colin, P. A1 - Colombo, E. A1 - Contreras, J. L. A1 - Cortina, J. A1 - Covino, S. A1 - Da Vela, P. A1 - Dazzi, F. A1 - De Angelis, A. A1 - De Lotto, B. A1 - Wilhelmi, E. de Ona A1 - Di Pierro, F. A1 - Doert, M. A1 - Dominguez, A. A1 - Prester, D. Dominis A1 - Dorner, D. A1 - Doro, M. A1 - Einecke, S. A1 - Glawion, D. Eisenacher A1 - Elsaesser, D. A1 - Engelkemeier, M. A1 - Ramazani, V. Fallah A1 - Fernandez-Barral, A. A1 - Fidalgo, D. A1 - Fonseca, M. V. A1 - Font, L. A1 - Frantzen, K. A1 - Fruck, C. A1 - Galindo, D. A1 - Lopez, R. J. Garcia A1 - Garczarczyk, M. A1 - Terrats, D. Garrido A1 - Gaug, M. A1 - Giammaria, P. A1 - Godinovic, N. A1 - Gonzalez Munoz, A. A1 - Gora, D. A1 - Guberman, D. A1 - Hadasch, D. A1 - Hahn, A. A1 - Hanabata, Y. A1 - Hayashida, M. A1 - Herrera, J. A1 - Hose, J. A1 - Hrupec, D. A1 - Hughes, G. A1 - Idec, W. A1 - Kodani, K. A1 - Konno, Y. A1 - Kubo, H. A1 - Kushida, J. A1 - La Barbera, A. A1 - Lelas, D. A1 - Lindfors, E. A1 - Lombardi, S. A1 - Longo, F. A1 - Lopez, M. A1 - Lopez-Coto, R. A1 - Majumdar, P. A1 - Makariev, M. A1 - Mallot, K. A1 - Maneva, G. A1 - Manganaro, M. A1 - Mannheim, K. A1 - Maraschi, L. A1 - Marcote, B. A1 - Mariotti, M. A1 - Martinez, M. A1 - Mazin, D. A1 - Menzel, U. A1 - Miranda, J. M. A1 - Mirzoyan, R. A1 - Moralejo, A. A1 - Moretti, E. A1 - Nakajima, D. A1 - Neustroev, V. A1 - Niedzwiecki, A. A1 - Rosillo, M. Nievas A1 - Nilsson, K. A1 - Nishijima, K. A1 - Noda, K. A1 - Nogues, L. A1 - Overkemping, A. A1 - Paiano, S. A1 - Palacio, J. A1 - Palatiello, M. A1 - Paneque, D. A1 - Paoletti, R. A1 - Paredes, J. M. A1 - Paredes-Fortuny, X. A1 - Pedaletti, G. A1 - Peresano, M. A1 - Perri, L. A1 - Persic, M. A1 - Poutanen, J. A1 - Moroni, P. G. Prada A1 - Prandini, E. A1 - Puljak, I. A1 - Reichardt, I. A1 - Rhode, W. A1 - Ribo, M. A1 - Rico, J. A1 - Rodriguez Garcia, J. A1 - Saito, T. A1 - Satalecka, K. A1 - Schroder, S. A1 - Schultz, C. A1 - Schweizer, T. A1 - Shore, S. N. A1 - Sillanpaa, A. A1 - Sitarek, J. A1 - Snidaric, I. A1 - Sobczynska, D. A1 - Stamerra, A. A1 - Steinbring, T. A1 - Strzys, M. A1 - Suric, T. A1 - Takalo, L. A1 - Tavecchio, F. A1 - Temnikov, P. A1 - Terzic, T. A1 - Tescaro, D. A1 - Teshima, M. A1 - Thaele, J. A1 - Torres, D. F. A1 - Toyama, T. A1 - Treves, A. A1 - Vanzo, G. A1 - Verguilov, V. A1 - Vovk, I. A1 - Ward, J. E. A1 - Will, M. A1 - Wu, M. H. A1 - Zanin, R. A1 - Abeysekara, A. U. A1 - Archambault, S. A1 - Archer, A. A1 - Benbow, W. A1 - Bird, R. A1 - Buchovecky, M. A1 - Buckley, J. H. A1 - Bugaev, V. A1 - Connolly, M. P. A1 - Cui, W. A1 - Dickinson, H. J. A1 - Falcone, A. A1 - Feng, Q. A1 - Finley, J. P. A1 - Fleischhack, H. A1 - Flinders, A. A1 - Fortson, L. A1 - Gillanders, G. H. A1 - Griffin, S. A1 - Grube, J. A1 - Huetten, M. A1 - Hanna, D. A1 - Holder, J. A1 - Humensky, T. B. A1 - Kaaret, P. A1 - Kar, P. A1 - Kelley-Hoskins, N. A1 - Kertzman, M. A1 - Kieda, D. A1 - Krause, M. A1 - Krennrich, F. A1 - Lang, M. J. A1 - Maier, G. A1 - McCann, A. A1 - Moriarty, P. A1 - Mukherjee, R. A1 - Nieto, D. A1 - Ong, R. A. A1 - Otte, N. A1 - Park, N. A1 - Perkins, J. A1 - Pichel, A. A1 - Pohl, M. A1 - Popkow, A. A1 - Pueschel, Elisa A1 - Quinn, J. A1 - Ragan, K. A1 - Reynolds, P. T. A1 - Richards, G. T. A1 - Roache, E. A1 - Rovero, A. C. A1 - Rulten, C. A1 - Sadeh, I. A1 - Santander, M. A1 - Sembroski, G. H. A1 - Shahinyan, K. A1 - Telezhinsky, Igor O. A1 - Tucci, J. V. A1 - Tyler, J. A1 - Wakely, S. P. A1 - Weinstein, A. A1 - Wilcox, P. A1 - Wilhelm, Alina A1 - Williams, D. A. A1 - Zitzer, B. A1 - Razzaque, S. A1 - Villata, M. A1 - Raiteri, C. M. A1 - Aller, H. D. A1 - Aller, M. F. A1 - Larionov, V. M. A1 - Arkharov, A. A. A1 - Blinov, D. A. A1 - Efimova, N. V. A1 - Grishina, T. S. A1 - Hagen-Thorn, V. A. A1 - Kopatskaya, E. N. A1 - Larionova, L. V. A1 - Larionova, E. G. A1 - Morozova, D. A. A1 - Troitsky, I. S. A1 - Ligustri, R. A1 - Calcidese, P. A1 - Berdyugin, A. A1 - Kurtanidze, O. M. A1 - Nikolashvili, M. G. A1 - Kimeridze, G. N. A1 - Sigua, L. A. A1 - Kurtanidze, S. O. A1 - Chigladze, R. A. A1 - Chen, W. P. A1 - Koptelova, E. A1 - Sakamoto, T. A1 - Sadun, A. C. A1 - Moody, J. W. A1 - Pace, C. A1 - Pearson, R. A1 - Yatsu, Y. A1 - Mori, Y. A1 - Carraminyana, A. A1 - Carrasco, L. A1 - de la Fuente, E. A1 - Norris, J. P. A1 - Smith, P. S. A1 - Wehrle, A. A1 - Gurwell, M. A. A1 - Zook, A. A1 - Pagani, C. A1 - Perri, M. A1 - Capalbi, M. A1 - Cesarini, A. A1 - Krimm, H. A. A1 - Kovalev, Y. Y. A1 - Kovalev, Yu. A. A1 - Ros, E. A1 - Pushkarev, A. B. A1 - Lister, M. L. A1 - Sokolovsky, K. V. A1 - Kadler, M. A1 - Piner, G. A1 - Lahteenmaki, A. A1 - Tornikoski, M. A1 - Angelakis, E. A1 - Krichbaum, T. P. A1 - Nestoras, I. A1 - Fuhrmann, L. A1 - Zensus, J. A. A1 - Cassaro, P. A1 - Orlati, A. A1 - Maccaferri, G. A1 - Leto, P. A1 - Giroletti, M. A1 - Richards, J. L. A1 - Max-Moerbeck, W. A1 - Readhead, A. C. S. T1 - Multiband variability studies and novel broadband SED modeling of Mrk 501 in 2009 JF - Astronomy and astrophysics : an international weekly journal N2 - Aims. We present an extensive study of the BL Lac object Mrk 501 based on a data set collected during the multi-instrument campaign spanning from 2009 March 15 to 2009 August 1, which includes, among other instruments, MAGIC, VERITAS, Whipple 10 m, and Fermi-LAT to cover the gamma-ray range from 0.1 GeV to 20 TeV; RXTE and Swift to cover wavelengths from UV to hard X-rays; and GASP-WEBT, which provides coverage of radio and optical wavelengths. Optical polarization measurements were provided for a fraction of the campaign by the Steward and St. Petersburg observatories. We evaluate the variability of the source and interband correlations, the gamma-ray flaring activity occurring in May 2009, and interpret the results within two synchrotron self-Compton (SSC) scenarios. Methods. The multiband variability observed during the full campaign is addressed in terms of the fractional variability, and the possible correlations are studied by calculating the discrete correlation function for each pair of energy bands where the significance was evaluated with dedicated Monte Carlo simulations. The space of SSC model parameters is probed following a dedicated grid-scan strategy, allowing for a wide range of models to be tested and offering a study of the degeneracy of model-to-data agreement in the individual model parameters, hence providing a less biased interpretation than the "single-curve SSC model adjustment" typically reported in the literature. Results. We find an increase in the fractional variability with energy, while no significant interband correlations of flux changes are found on the basis of the acquired data set. The SSC model grid-scan shows that the flaring activity around May 22 cannot be modeled adequately with a one-zone SSC scenario (using an electron energy distribution with two breaks), while it can be suitably described within a two (independent) zone SSC scenario. Here, one zone is responsible for the quiescent emission from the averaged 4.5-month observing period, while the other one, which is spatially separated from the first, dominates the flaring emission occurring at X-rays and very-high-energy (> 100 GeV, VHE) gamma-rays. The flaring activity from May 1, which coincides with a rotation of the electric vector polarization angle (EVPA), cannot be satisfactorily reproduced by either a one-zone or a two-independent-zone SSC model, yet this is partially affected by the lack of strictly simultaneous observations and the presence of large flux changes on sub-hour timescales (detected at VHE gamma rays). Conclusions. The higher variability in the VHE emission and lack of correlation with the X-ray emission indicate that, at least during the 4.5-month observing campaign in 2009, the highest energy (and most variable) electrons that are responsible for the VHE gamma rays do not make a dominant contribution to the similar to 1 keV emission. Alternatively, there could be a very variable component contributing to the VHE gamma-ray emission in addition to that coming from the SSC scenario. The studies with our dedicated SSC grid-scan show that there is some degeneracy in both the one-zone and the two-zone SSC scenarios probed, with several combinations of model parameters yielding a similar model-to-data agreement, and some parameters better constrained than others. The observed gamma-ray flaring activity, with the EVPA rotation coincident with the first gamma-ray flare, resembles those reported previously for low frequency peaked blazars, hence suggesting that there are many similarities in the flaring mechanisms of blazars with different jet properties. KW - BL Lacertae objects: individual: Markarian 501 KW - methods: data analysis Y1 - 2017 U6 - https://doi.org/10.1051/0004-6361/201629540 SN - 1432-0746 VL - 603 PB - EDP Sciences CY - Les Ulis ER - TY - JOUR A1 - Stete, Felix A1 - Koopman, Wouter-Willem Adriaan A1 - Bargheer, Matias T1 - Signatures of strong coupling on nanoparticles BT - revealing absorption anticrossing by tuning the dielectric environment JF - ACS Photonics N2 - In the strong coupling regime, exciton and plasmon excitations are hybridized into combined system excitations. The correct identification of the coupling regime in these systems is currently debated, from both experimental and theoretical perspectives. In this article we show that the extinction spectra may show a large peak splitting, although the energy loss encoded in the absorption spectra clearly rules out the strong coupling regime. We investigate the coupling of J-aggregate excitons to the localized surface plasmon polaritons on gold nanospheres and nanorods by fine-tuning the plasmon resonance via layer-by-layer deposition of polyelectrolytes. While both structures show a characteristic anticrossing in extinction and scattering experiments, the careful assessment of the systems’ light absorption reveals that strong coupling of the plasmon to the exciton is not present in the nanosphere system. In a phenomenological model of two classical coupled oscillators, a Fano-like regime causes only the resonance of the light-driven oscillator to split up, while the other one still dissipates energy at its original frequency. Only in the strong-coupling limit do both oscillators split up the frequencies at which they dissipate energy, qualitatively explaining our experimental finding. KW - hybrid nanoparticles KW - exciton plasmon coupling KW - layer-by-layer deposition KW - strong coupling KW - absorption measurements Y1 - 2017 U6 - https://doi.org/10.1021/acsphotonics.7b00113 SN - 2330-4022 VL - 4 SP - 1669 EP - 1676 PB - American Chemical Society CY - Washington ER - TY - JOUR A1 - Benduhn, Johannes A1 - Tvingstedt, Kristofer A1 - Piersimoni, Fortunato A1 - Ullbrich, Sascha A1 - Fan, Yeli A1 - Tropiano, Manuel A1 - McGarry, Kathryn A. A1 - Zeika, Olaf A1 - Riede, Moritz K. A1 - Douglas, Christopher J. A1 - Barlow, Stephen A1 - Marder, Seth R. A1 - Neher, Dieter A1 - Spoltore, Donato A1 - Vandewal, Koen T1 - Intrinsic non-radiative voltage losses in fullerene-based organic solar cells JF - Nature Energy N2 - Organic solar cells demonstrate external quantum efficiencies and fill factors approaching those of conventional photovoltaic technologies. However, as compared with the optical gap of the absorber materials, their open-circuit voltage is much lower, largely due to the presence of significant non-radiative recombination. Here, we study a large data set of published and new material combinations and find that non-radiative voltage losses decrease with increasing charge-transfer-state energies. This observation is explained by considering non-radiative charge-transfer-state decay as electron transfer in the Marcus inverted regime, being facilitated by a common skeletal molecular vibrational mode. Our results suggest an intrinsic link between non-radiative voltage losses and electron-vibration coupling, indicating that these losses are unavoidable. Accordingly, the theoretical upper limit for the power conversion efficiency of single-junction organic solar cells would be reduced to about 25.5% and the optimal optical gap increases to (1.45-1.65) eV, that is, (0.2-0.3) eV higher than for technologies with minimized non-radiative voltage losses. Y1 - 2017 U6 - https://doi.org/10.1038/nenergy.2017.53 SN - 2058-7546 VL - 2 PB - Nature Publ. Group CY - London ER - TY - JOUR A1 - Xiong, Hui A1 - Mignolet, Benoit A1 - Fang, Li A1 - Osipov, Timur A1 - Wolf, Thomas J. A. A1 - Sistrunk, Emily A1 - Gühr, Markus A1 - Remacle, Francoise A1 - Berrah, Nora T1 - The Role of Super-Atom Molecular Orbitals in Doped Fullerenes in a Femtosecond Intense Laser Field JF - Scientific reports N2 - The interaction of gas phase endohedral fullerene Ho3N@C-80 with intense (0.1-5 x 10(14) W/cm(2)), short (30 fs), 800 nm laser pulses was investigated. The power law dependence of Ho3N@C-80(q+), q = 1-2, was found to be different from that of C-60. Time-dependent density functional theory computations revealed different light-induced ionization mechanisms. Unlike in C-60, in doped fullerenes, the breaking of the cage spherical symmetry makes super atomic molecular orbital (SAMO) states optically active. Theoretical calculations suggest that the fast ionization of the SAMO states in Ho3N@C-80 is responsible for the n = 3 power law for singly charged parent molecules at intensities lower than 1.2 x 10(14) W/cm(2). Y1 - 2017 U6 - https://doi.org/10.1038/s41598-017-00124-9 SN - 2045-2322 VL - 7 PB - Nature Publ. Group CY - London ER -