TY  - JOUR
A1  - Abdo, A. A.
A1  - Ackermann, Margit
A1  - Ajello, M.
A1  - Allafort, A. J.
A1  - Baldini, L.
A1  - Ballet, J.
A1  - Barbiellini, G.
A1  - Baring, M. G.
A1  - Bastieri, D.
A1  - Bechtol, K. C.
A1  - Bellazzini, R.
A1  - Berenji, B.
A1  - Blandford, R. D.
A1  - Bloom, E. D.
A1  - Bonamente, E.
A1  - Borgland, A. W.
A1  - Bouvier, A.
A1  - Brandt, T. J.
A1  - Bregeon, Johan
A1  - Brez, A.
A1  - Brigida, M.
A1  - Bruel, P.
A1  - Buehler, R.
A1  - Buson, S.
A1  - Caliandro, G. A.
A1  - Cameron, R. A.
A1  - Cannon, A.
A1  - Caraveo, P. A.
A1  - Carrigan, Svenja
A1  - Casandjian, J. M.
A1  - Cavazzuti, E.
A1  - Cecchi, C.
A1  - Celik, O.
A1  - Charles, E.
A1  - Chekhtman, A.
A1  - Cheung, C. C.
A1  - Chiang, J.
A1  - Ciprini, S.
A1  - Claus, R.
A1  - Cohen-Tanugi, J.
A1  - Conrad, Jan
A1  - Cutini, S.
A1  - Dermer, C. D.
A1  - de Palma, F.
A1  - do Couto e Silva, E.
A1  - Drell, P. S.
A1  - Dubois, R.
A1  - Dumora, D.
A1  - Favuzzi, C.
A1  - Fegan, S. J.
A1  - Ferrara, E. C.
A1  - Focke, W. B.
A1  - Fortin, P.
A1  - Frailis, M.
A1  - Fuhrmann, L.
A1  - Fukazawa, Y.
A1  - Funk, S.
A1  - Fusco, P.
A1  - Gargano, F.
A1  - Gasparrini, D.
A1  - Gehrels, N.
A1  - Germani, S.
A1  - Giglietto, N.
A1  - Giordano, F.
A1  - Giroletti, M.
A1  - Glanzman, T.
A1  - Godfrey, G.
A1  - Grenier, I. A.
A1  - Guillemot, L.
A1  - Guiriec, S.
A1  - Hayashida, M.
A1  - Hays, E.
A1  - Horan, D.
A1  - Hughes, R. E.
A1  - Johannesson, G.
A1  - Johnson, A. S.
A1  - Johnson, W. N.
A1  - Kadler, M.
A1  - Kamae, T.
A1  - Katagiri, H.
A1  - Kataoka, J.
A1  - Knoedlseder, J.
A1  - Kuss, M.
A1  - Lande, J.
A1  - Latronico, L.
A1  - Lee, S. -H.
A1  - Lemoine-Goumard, M.
A1  - Longo, F.
A1  - Loparco, F.
A1  - Lott, B.
A1  - Lovellette, M. N.
A1  - Lubrano, P.
A1  - Madejski, G. M.
A1  - Makeev, A.
A1  - Max-Moerbeck, W.
A1  - Mazziotta, Mario Nicola
A1  - McEnery, J. E.
A1  - Mehault, J.
A1  - Michelson, P. F.
A1  - Mitthumsiri, W.
A1  - Mizuno, T.
A1  - Moiseev, A. A.
A1  - Monte, C.
A1  - Monzani, M. E.
A1  - Morselli, A.
A1  - Moskalenko, I. V.
A1  - Murgia, S.
A1  - Naumann-Godo, M.
A1  - Nishino, S.
A1  - Nolan, P. L.
A1  - Norris, J. P.
A1  - Nuss, E.
A1  - Ohsugi, T.
A1  - Okumura, A.
A1  - Omodei, N.
A1  - Orlando, E.
A1  - Ormes, J. F.
A1  - Paneque, D.
A1  - Panetta, J. H.
A1  - Parent, D.
A1  - Pavlidou, V.
A1  - Pearson, T. J.
A1  - Pelassa, V.
A1  - Pepe, M.
A1  - Pesce-Rollins, M.
A1  - Piron, F.
A1  - Porter, T. A.
A1  - Raino, S.
A1  - Rando, R.
A1  - Razzano, M.
A1  - Readhead, A.
A1  - Reimer, A.
A1  - Reimer, O.
A1  - Richards, J. L.
A1  - Ripken, J.
A1  - Ritz, S.
A1  - Roth, M.
A1  - Sadrozinski, H. F. -W.
A1  - Sanchez, D.
A1  - Sander, A.
A1  - Scargle, J. D.
A1  - Sgro, C.
A1  - Siskind, E. J.
A1  - Smith, P. D.
A1  - Spandre, G.
A1  - Spinelli, P.
A1  - Stawarz, L.
A1  - Stevenson, M.
A1  - Strickman, M. S.
A1  - Sokolovsky, K. V.
A1  - Suson, D. J.
A1  - Takahashi, H.
A1  - Takahashi, T.
A1  - Tanaka, T.
A1  - Thayer, J. B.
A1  - Thayer, J. G.
A1  - Thompson, D. J.
A1  - Tibaldo, L.
A1  - Torres, F.
A1  - Tosti, G.
A1  - Tramacere, A.
A1  - Uchiyama, Y.
A1  - Usher, T. L.
A1  - Vandenbroucke, J.
A1  - Vasileiou, V.
A1  - Vilchez, N.
A1  - Vitale, V.
A1  - Waite, A. P.
A1  - Wang, P.
A1  - Wehrle, A. E.
A1  - Winer, B. L.
A1  - Wood, K. S.
A1  - Yang, Z.
A1  - Ylinen, T.
A1  - Zensus, J. A.
A1  - Ziegler, M.
A1  - Aleksic, J.
A1  - Antonelli, L. A.
A1  - Antoranz, P.
A1  - Backes, Michael
A1  - Barrio, J. A.
A1  - Gonzalez, J. Becerra
A1  - Bednarek, W.
A1  - Berdyugin, A.
A1  - Berger, K.
A1  - Bernardini, E.
A1  - Biland, A.
A1  - Blanch Bigas, O.
A1  - Bock, R. K.
A1  - Boller, A.
A1  - Bonnoli, G.
A1  - Bordas, Pol
A1  - Tridon, D. Borla
A1  - Bosch-Ramon, Valentin
A1  - Bose, D.
A1  - Braun, I.
A1  - Bretz, T.
A1  - Camara, M.
A1  - Carmona, E.
A1  - Carosi, A.
A1  - Colin, P.
A1  - Colombo, E.
A1  - Contreras, J. L.
A1  - Cortina, J.
A1  - Covino, S.
A1  - Dazzi, F.
A1  - de Angelis, A.
A1  - del Pozo, E. De Cea
A1  - De Lotto, B.
A1  - De Maria, M.
A1  - De Sabata, F.
A1  - Mendez, C. Delgado
A1  - Ortega, A. Diago
A1  - Doert, M.
A1  - Dominguez, A.
A1  - Prester, Dijana Dominis
A1  - Dorner, D.
A1  - Doro, M.
A1  - Elsaesser, D.
A1  - Ferenc, D.
A1  - Fonseca, M. V.
A1  - Font, L.
A1  - Lopen, R. J. Garcia
A1  - Garczarczyk, M.
A1  - Gaug, M.
A1  - Giavitto, G.
A1  - Godinovi, N.
A1  - Hadasch, D.
A1  - Herrero, A.
A1  - Hildebrand, D.
A1  - Hoehne-Moench, D.
A1  - Hose, J.
A1  - Hrupec, D.
A1  - Jogler, T.
A1  - Klepser, S.
A1  - Kraehenbuehl, T.
A1  - Kranich, D.
A1  - Krause, J.
A1  - La Barbera, A.
A1  - Leonardo, E.
A1  - Lindfors, E.
A1  - Lombardi, S.
A1  - Lopez, M.
A1  - Lorenz, E.
A1  - Majumdar, P.
A1  - Makariev, E.
A1  - Maneva, G.
A1  - Mankuzhiyil, N.
A1  - Mannheim, K.
A1  - Maraschi, L.
A1  - Mariotti, M.
A1  - Martinez, M.
A1  - Mazin, D.
A1  - Meucci, M.
A1  - Miranda, J. M.
A1  - Mirzoyan, R.
A1  - Miyamoto, H.
A1  - Moldon, J.
A1  - Moralejo, A.
A1  - Nieto, D.
A1  - Nilsson, K.
A1  - Orito, R.
A1  - Oya, I.
A1  - Paoletti, R.
A1  - Paredes, J. M.
A1  - Partini, S.
A1  - Pasanen, M.
A1  - Pauss, F.
A1  - Pegna, R. G.
A1  - Perez-Torres, M. A.
A1  - Persic, M.
A1  - Peruzzo, J.
A1  - Pochon, J.
A1  - Moroni, P. G. Prada
A1  - Prada, F.
A1  - Prandini, E.
A1  - Puchades, N.
A1  - Puljak, I.
A1  - Reichardt, T.
A1  - Reinthal, R.
A1  - Rhode, W.
A1  - Ribo, M.
A1  - Rico, J.
A1  - Rissi, M.
A1  - Ruegamer, S.
A1  - Saggion, A.
A1  - Saito, K.
A1  - Saito, T. Y.
A1  - Salvati, M.
A1  - Sanchez-Conde, M.
A1  - Satalecka, K.
A1  - Scalzotto, V.
A1  - Scapin, V.
A1  - Schultz, C.
A1  - Schweizer, T.
A1  - Shayduk, M.
A1  - Shore, S. N.
A1  - Sierpowska-Bartosik, A.
A1  - Sillanpaa, A.
A1  - Sitarek, J.
A1  - Sobczynska, D.
A1  - Spanier, F.
A1  - Spiro, S.
A1  - Stamerra, A.
A1  - Steinke, B.
A1  - Storz, J.
A1  - Strah, N.
A1  - Struebig, J. C.
A1  - Suric, T.
A1  - Takalo, L. O.
A1  - Tavecchio, F.
A1  - Temnikov, P.
A1  - Terzic, T.
A1  - Tescaro, D.
A1  - Teshima, M.
A1  - Vankov, H.
A1  - Wagner, R. M.
A1  - Weitzel, Q.
A1  - Zabalza, V.
A1  - Zandanel, F.
A1  - Zanin, R.
A1  - Acciari, V. A.
A1  - Arlen, T.
A1  - Aune, T.
A1  - Benbow, W.
A1  - Boltuch, D.
A1  - Bradbury, S. M.
A1  - Buckley, J. H.
A1  - Bugaev, V.
A1  - Cannon, A.
A1  - Cesarini, A.
A1  - Ciupik, L.
A1  - Cui, W.
A1  - Dickherber, R.
A1  - Errando, M.
A1  - Falcone, A.
A1  - Finley, J. P.
A1  - Finnegan, G.
A1  - Fortson, L.
A1  - Furniss, A.
A1  - Galante, N.
A1  - Gall, D.
A1  - Gillanders, G. H.
A1  - Godambe, S.
A1  - Grube, J.
A1  - Guenette, R.
A1  - Gyuk, G.
A1  - Hanna, D.
A1  - Holder, J.
A1  - Huang, D.
A1  - Hui, C. M.
A1  - Humensky, T. B.
A1  - Kaaret, P.
A1  - Karlsson, N.
A1  - Kertzman, M.
A1  - Kieda, D.
A1  - Konopelko, A.
A1  - Krawczynski, H.
A1  - Krennrich, F.
A1  - Lang, M. J.
A1  - Maier, G.
A1  - McArthur, S.
A1  - McCann, A.
A1  - McCutcheon, M.
A1  - Moriarty, P.
A1  - Mukherjee, R.
A1  - Ong, R.
A1  - Otte, N.
A1  - Pandel, D.
A1  - Perkins, J. S.
A1  - Pichel, A.
A1  - Pohl, M.
A1  - Quinn, J.
A1  - Ragan, K.
A1  - Reyes, L. C.
A1  - Reynolds, P. T.
A1  - Roache, E.
A1  - Rose, H. J.
A1  - Rovero, A. C.
A1  - Schroedter, M.
A1  - Sembroski, G. H.
A1  - Senturk, G. D.
A1  - Steele, D.
A1  - Swordy, S. P.
A1  - Tesic, G.
A1  - Theiling, M.
A1  - Thibadeau, S.
A1  - Varlotta, A.
A1  - Vincent, S.
A1  - Wakely, S. P.
A1  - Ward, J. E.
A1  - Weekes, T. C.
A1  - Weinstein, A.
A1  - Weisgarber, T.
A1  - Williams, D. A.
A1  - Wood, M.
A1  - Zitzer, B.
A1  - Villata, M.
A1  - Raiteri, C. M.
A1  - Aller, H. D.
A1  - Aller, M. F.
A1  - Arkharov, A. A.
A1  - Blinov, D. A.
A1  - Calcidese, P.
A1  - Chen, W. P.
A1  - Efimova, N. V.
A1  - Kimeridze, G.
A1  - Konstantinova, T. S.
A1  - Kopatskaya, E. N.
A1  - Koptelova, E.
A1  - Kurtanidze, O. M.
A1  - Kurtanidze, S. O.
A1  - Lahteenmaki, A.
A1  - Larionov, V. M.
A1  - Larionova, E. G.
A1  - Larionova, L. V.
A1  - Ligustri, R.
A1  - Morozova, D. A.
A1  - Nikolashvili, M. G.
A1  - Sigua, L. A.
A1  - Troitsky, I. S.
A1  - Angelakis, E.
A1  - Capalbi, M.
A1  - Carraminana, A.
A1  - Carrasco, L.
A1  - Cassaro, P.
A1  - de la Fuente, E.
A1  - Gurwell, M. A.
A1  - Kovalev, Y. Y.
A1  - Kovalev, Yu. A.
A1  - Krichbaum, T. P.
A1  - Krimm, H. A.
A1  - Leto, Paolo
A1  - Lister, M. L.
A1  - Maccaferri, G.
A1  - Moody, J. W.
A1  - Mori, Y.
A1  - Nestoras, I.
A1  - Orlati, A.
A1  - Pagani, C.
A1  - Pace, C.
A1  - Pearson, R.
A1  - Perri, M.
A1  - Piner, B. G.
A1  - Pushkarev, A. B.
A1  - Ros, E.
A1  - Sadun, A. C.
A1  - Sakamoto, T.
A1  - Tornikoski, M.
A1  - Yatsu, Y.
A1  - Zook, A.
T1  - Insights into the high-energy gamma-Ray emission of markarian 501 fromextensive multifrequency observations in the fermi era
JF  - The astrophysical journal : an international review of spectroscopy and astronomical physics
N2  - We report on the gamma-ray activity of the blazar Mrk 501 during the first 480 days of Fermi operation. We find that the average Large Area Telescope (LAT) gamma-ray spectrum of Mrk 501 can be well described by a single power-law function with a photon index of 1.78 +/- 0.03. While we observe relatively mild flux variations with the Fermi-LAT (within less than a factor of two), we detect remarkable spectral variability where the hardest observed spectral index within the LAT energy range is 1.52 +/- 0.14, and the softest one is 2.51 +/- 0.20. These unexpected spectral changes do not correlate with the measured flux variations above 0.3 GeV. In this paper, we also present the first results from the 4.5 month long multifrequency campaign (2009 March 15-August 1) on Mrk 501, which included the Very Long Baseline Array (VLBA), Swift, RXTE, MAGIC, and VERITAS, the F-GAMMA, GASP-WEBT, and other collaborations and instruments which provided excellent temporal and energy coverage of the source throughout the entire campaign. The extensive radio to TeV data set from this campaign provides us with the most detailed spectral energy distribution yet collected for this source during its relatively low activity. The average spectral energy distribution of Mrk 501 is well described by the standard one-zone synchrotron self-Compton (SSC) model. In the framework of this model, we find that the dominant emission region is characterized by a size less than or similar to 0.1 pc (comparable within a factor of few to the size of the partially resolved VLBA core at 15-43 GHz), and that the total jet power (similar or equal to 10(44) erg s(-1)) constitutes only a small fraction (similar to 10(-3)) of the Eddington luminosity. The energy distribution of the freshly accelerated radiating electrons required to fit the time-averaged data has a broken power-law form in the energy range 0.3 GeV-10 TeV, with spectral indices 2.2 and 2.7 below and above the break energy of 20 GeV. We argue that such a form is consistent with a scenario in which the bulk of the energy dissipation within the dominant emission zone of Mrk 501 is due to relativistic, proton-mediated shocks. We find that the ultrarelativistic electrons and mildly relativistic protons within the blazar zone, if comparable in number, are in approximate energy equipartition, with their energy dominating the jet magnetic field energy by about two orders of magnitude.
KW  - acceleration of particles
KW  - BL Lacertae objects: general
KW  - BL Lacertae objects: individual (Mrk 501)
KW  - galaxies: active
KW  - gamma rays: general
KW  - radiation mechanisms: non-thermal
Y1  - 2011
U6  - https://doi.org/10.1088/0004-637X/727/2/129
SN  - 0004-637X
VL  - 727
IS  - 2
PB  - IOP Publ. Ltd.
CY  - Bristol
ER  - 
TY  - BOOK
A1  - Rabe, Thorid
T1  - Physikdidaktische Lehrerprofessionalisierung zwischen Anspruch und Wirklichkeit : Antrittsvorlesung 2011-06-08
N2  - Physiklehrer bestimmen durch die Gestaltung des Unterrichts und damit durch ihr professionelles Handeln maßgeblich mit, wie die individuellen Lernprozesse der Schüler zu Inhalten der Physik ablaufen. Für die Entwicklung ihrer professionellen Handlungskompetenz müssen zukünftige Physiklehrer einerseits physikalisches, physikdidaktisches und pädagogisches Wissen erwerben und andererseits motiviert sein, dieses Wissen auch anzuwenden. In ihrer Vorlesung geht Thorid Rabe der Frage nach, welche physikdidaktischen Kompetenzen Studierende im Rahmen der universitären Ausbildung erwerben sollten. Am Beispiel der Lehrveranstaltung "Physikalische Schulexperimente" zeigt sie, wie physikdidaktische Theorie und praktisches Lehrerhandeln aufeinander bezogen werden können. Zudem wird sie ein Forschungsprojekt vorstellen, das einem bisher vernachlässigten Aspekt professioneller Handlungskompetenz nachgeht, nämlich den domänenspezifischen Selbstwirksamkeitserwartungen - dem Zutrauen in sich selbst, als Physiklehrer angemessen und erfolgreich handeln zu können.
Y1  - 2011
UR  - http://info.ub.uni-potsdam.de/multimedia/show_multimediafile.php?mediafile_id=548
PB  - Univ.-Bibl.
CY  - Potsdam
ER  - 
TY  - THES
A1  - Partl, Adrian M.
T1  - Cosmological radiative transfer and the lonisation of the integalactic medium
Y1  - 2011
CY  - Potsdam
ER  - 
TY  - THES
A1  - Osterloh, Lukas
T1  - Retrieving aerosol microphysical properties from multiwavelength Lidar Data
Y1  - 2011
CY  - Potsdam
ER  - 
TY  - THES
A1  - Matthes, Heidrun
T1  - Interaction of land surface processes and the atmophere in the Arctic - senitivities and extremes
Y1  - 2011
CY  - Potsdam
ER  - 
TY  - THES
A1  - Dosche, Carsten
T1  - Funktionale Farbstoffe und ihre Photophysik und Anwendung in komplexen Matrizes
Y1  - 2011
CY  - Potsdam
ER  - 
TY  - BOOK
A1  - Brehmer, Ludwig
T1  - Die Brandeburgische Landeshochschule zu Potsdam im Jahre eins : die Hochschule in Potsdamer Schulen ; Daten und Fakten ; Kommentare und Dokumente
Y1  - 2011
SN  - 978-3-00-034135-9
VL  - 4
PB  - Eigenverl. des Verf
CY  - Potsdam
ER  - 
TY  - THES
A1  - Schewe, Jacob
T1  - Basic physical mechanisms for monsoon failure in past and future climate
Y1  - 2011
CY  - Potsdam
ER  - 
TY  - THES
A1  - Mielke, Moritz
T1  - Atmosphärische Prozesstudien auf der Basis von Beobachtungen und regionalen Klimamodellsimulationen in der Arktis
Y1  - 2011
CY  - Potsdam
ER  - 
TY  - THES
A1  - Koseska, Aneta
T1  - Dynamics of biological networks : data analysis, modeling and bifurcations
Y1  - 2011
CY  - Potsdam
ER  - 
TY  - JOUR
A1  - Janotta, Peter
A1  - Gogolin, Christian
A1  - Barrett, Jonathan
A1  - Brunner, Nicolas
T1  - Limits on nonlocal correlations from the structure of the local state space
JF  - New journal of physics : the open-access journal for physics
N2  - The outcomes of measurements on entangled quantum systems can be nonlocally correlated. However, while it is easy to write down toy theories allowing arbitrary nonlocal correlations, those allowed in quantum mechanics are limited. Quantum correlations cannot, for example, violate a principle known as macroscopic locality, which implies that they cannot violate Tsirelson's bound. This paper shows that there is a connection between the strength of nonlocal correlations in a physical theory and the structure of the state spaces of individual systems. This is illustrated by a family of models in which local state spaces are regular polygons, where a natural analogue of a maximally entangled state of two systems exists. We characterize the nonlocal correlations obtainable from such states. The family allows us to study the transition between classical, quantum and super-quantum correlations by varying only the local state space. We show that the strength of nonlocal correlations-in particular whether the maximally entangled state violates Tsirelson's bound or not-depends crucially on a simple geometric property of the local state space, known as strong self-duality. This result is seen to be a special case of a general theorem, which states that a broad class of entangled states in probabilistic theories-including, by extension, all bipartite classical and quantum states-cannot violate macroscopic locality. Finally, our results show that models exist that are locally almost indistinguishable from quantum mechanics, but can nevertheless generate maximally nonlocal correlations.
Y1  - 2011
U6  - https://doi.org/10.1088/1367-2630/13/6/063024
SN  - 1367-2630
VL  - 13
IS  - 23
PB  - IOP Publ. Ltd.
CY  - Bristol
ER  - 
TY  - JOUR
A1  - Brandao, F. G. S. L.
A1  - Eisert, Jens
A1  - Horodecki, M.
A1  - Yang, Dong
T1  - Entangled inputs cannot make imperfect quantum channels perfect
JF  - Physical review letters
N2  - Entangled inputs can enhance the capacity of quantum channels, this being one of the consequences of the celebrated result showing the nonadditivity of several quantities relevant for quantum information science. In this work, we answer the converse question (whether entangled inputs can ever render noisy quantum channels to have maximum capacity) to the negative: No sophisticated entangled input of any quantum channel can ever enhance the capacity to the maximum possible value, a result that holds true for all channels both for the classical as well as the quantum capacity. This result can hence be seen as a bound as to how "nonadditive quantum information can be.'' As a main result, we find first practical and remarkably simple computable single-shot bounds to capacities, related to entanglement measures. As examples, we discuss the qubit amplitude damping and identify the first meaningful bound for its classical capacity.
Y1  - 2011
U6  - https://doi.org/10.1103/PhysRevLett.106.230502
SN  - 0031-9007
VL  - 106
IS  - 23
PB  - American Physical Society
CY  - College Park
ER  - 
TY  - JOUR
A1  - Schmidt, Hans-Jürgen
T1  - Perihelion advance for orbits with large eccentricities in the Schwarzschild black hole
JF  - Physical review : D, Particles, fields, gravitation, and cosmology
N2  - We deduce a new formula for the perihelion advance Theta of a test particle in the Schwarzschild black hole by applying a newly developed nonlinear transformation within the Schwarzschild space-time. By this transformation we are able to apply the well-known formula valid in the weak-field approximation near infinity also to trajectories in the strong-field regime near the horizon of the black hole. The resulting formula has the structure Theta = c(1) - c(2) ln(c(3)(2) - e(2)) with positive constants c(1,2,3) depending on the angular momentum of the test particle. It is especially useful for orbits with large eccentricities e < c(3) < 1 showing that Theta -> infinity as e -> c(3).
Y1  - 2011
U6  - https://doi.org/10.1103/PhysRevD.83.124010
SN  - 1550-7998
VL  - 83
IS  - 12
PB  - American Physical Society
CY  - College Park
ER  - 
TY  - JOUR
A1  - Worseck, Gabor
A1  - Prochaska, J. Xavier
A1  - McQuinn, Matthew
A1  - Dall'Aglio, Aldo
A1  - Fechner, Cora
A1  - Hennawi, Joseph F.
A1  - Reimers, Dieter
A1  - Richter, Philipp
A1  - Wisotzki, Lutz
T1  - The end of Helium Reionization at z similar or equal to 2.7 Inferred  from cosmic variance in HST/COS He II Ly alpha Absorption spectra
JF  - The astrophysical journal : an international review of spectroscopy and astronomical physics ; Part 2, Letters
N2  - We report on the detection of strongly varying intergalactic He II absorption in HST/COS spectra of two z(em) similar or equal to 3 quasars. From our homogeneous analysis of the He II absorption in these and three archival sightlines, we find a marked increase in the mean He II effective optical depth from <tau(eff, He II)> similar or equal to 1 at z similar or equal to 2.3 to <tau(eff, He II)> greater than or similar to 5 at z similar or equal to 3.2, but with a large scatter of 2 less than or similar to tau(eff, He II) less than or similar to 5 at 2.7 < z < 3 on scales of similar to 10 proper Mpc. This scatter is primarily due to fluctuations in the He II fraction and the He II-ionizing background, rather than density variations that are probed by the coeval Hi forest. Semianalytic models of He II absorption require a strong decrease in the He II-ionizing background to explain the strong increase of the absorption at z greater than or similar to 2.7, probably indicating He II reionization was incomplete at z(reion) greater than or similar to 2.7. Likewise, recent three-dimensional numerical simulations of He II reionization qualitatively agree with the observed trend only if He II reionization completes at z(reion) similar or equal to 2.7 or even below, as suggested by a large tau(eff, He II) greater than or similar to 3 in two of our five sightlines at z < 2.8. By doubling the sample size at 2.7 less than or similar to z less than or similar to 3, our newly discovered He II sightlines for the first time probe the diversity of the second epoch of reionization when helium became fully ionized.
KW  - dark ages, reionization, first stars
KW  - diffuse radiation
KW  - intergalactic medium
KW  - quasars: absorption lines
KW  - quasars: individual (SDSS J092447.36+485242.8, SDSS J110155.74+105302.3)
Y1  - 2011
U6  - https://doi.org/10.1088/2041-8205/733/2/L24
SN  - 2041-8205
VL  - 733
IS  - 2
PB  - IOP Publ. Ltd.
CY  - Bristol
ER  - 
TY  - JOUR
A1  - Lange, Ilja
A1  - Blakesley, James C.
A1  - Frisch, Johannes
A1  - Vollmer, Antje
A1  - Koch, Norbert
A1  - Neher, Dieter
T1  - Band bending in conjugated polymer layers
JF  - Physical review letters
N2  - We use the Kelvin probe method to study the energy-level alignment of four conjugated polymers deposited on various electrodes. Band bending is observed in all polymers when the substrate work function exceeds critical values. Through modeling, we show that the band bending is explained by charge transfer from the electrodes into a small density of states that extends several hundred meV into the band gap. The energetic spread of these states is correlated with charge-carrier mobilities, suggesting that the same states also govern charge transport in the bulk of these polymers.
Y1  - 2011
U6  - https://doi.org/10.1103/PhysRevLett.106.216402
SN  - 0031-9007
VL  - 106
IS  - 21
PB  - American Physical Society
CY  - College Park
ER  - 
TY  - JOUR
A1  - Zakharova, Anna
A1  - Kurths, Jürgen
A1  - Vadivasova, Tatyana
A1  - Koseska, Aneta
T1  - Analysing dynamical behavior of cellular networks via stochastic bifurcations
JF  - PLoS one
N2  - The dynamical structure of genetic networks determines the occurrence of various biological mechanisms, such as cellular differentiation. However, the question of how cellular diversity evolves in relation to the inherent stochasticity and intercellular communication remains still to be understood. Here, we define a concept of stochastic bifurcations suitable to investigate the dynamical structure of genetic networks, and show that under stochastic influence, the expression of given proteins of interest is defined via the probability distribution of the phase variable, representing one of the genes constituting the system. Moreover, we show that under changing stochastic conditions, the probabilities of expressing certain concentration values are different, leading to different functionality of the cells, and thus to differentiation of the cells in the various types.
Y1  - 2011
U6  - https://doi.org/10.1371/journal.pone.0019696
SN  - 1932-6203
VL  - 6
IS  - 5
PB  - PLoS
CY  - San Fransisco
ER  - 
TY  - JOUR
A1  - Jewitt, David
A1  - Weaver, Harold
A1  - Mutchler, Max
A1  - Larson, Stephen
A1  - Agarwal, Jessica
T1  - Hubble space telescope observations of main-belt comet (596) scheila
JF  - The astrophysical journal : an international review of spectroscopy and astronomical physics ; Part 2, Letters
N2  - We present Hubble Space Telescope Observations of (596) Scheila during its recent dust outburst. The nucleus remained point-like with absolute magnitude H(V) = 8.85 +/- 0.02 in our data, equal to the pre-outburst value, with no secondary fragments of diameter >= 100m (for assumed albedos 0.04). We find a coma having a peak scattering cross section similar to 2.2x10(4) km(2), corresponding to a mass in micron-sized particles of similar to 4x10(7) kg. The particles are deflected by solar radiation pressure on projected spatial scales similar to 2x10(4) km, in the sunward direction, and swept from the vicinity of the nucleus on timescales of weeks. The coma fades by similar to 30% between observations on UT 2010 December 27 and 2011 January 4. The observed mass loss is inconsistent with an origin either by rotational instability of the nucleus or by electrostatic ejection of regolith charged by sunlight. Dust ejection could be caused by the sudden but unexplained exposure of buried ice. However, the data are most simply explained by the impact, at similar to 5 km s(-1), of a previously unknown asteroid similar to 35m in diameter.
KW  - comets: general
KW  - comets: individual ((596) Scheila)
KW  - minor planets, asteroids: general
Y1  - 2011
U6  - https://doi.org/10.1088/2041-8205/733/1/L4
SN  - 2041-8205
VL  - 733
IS  - 1
PB  - IOP Publ. Ltd.
CY  - Bristol
ER  - 
TY  - JOUR
A1  - Postberg, Frank
A1  - Schmidt, J.
A1  - Hillier, J.
A1  - Kempf, Sascha
A1  - Srama, Ralf
T1  - A salt-water reservoir as the source of a compositionally stratified plume on Enceladus
JF  - Nature : the international weekly journal of science
N2  - The discovery of a plume of water vapour and ice particles emerging from warm fractures ('tiger stripes') in Saturn's small, icy moon Enceladus(1-6) raised the question of whether the plume emerges from a subsurface liquid source(6-8) or from the decomposition of ice(9-12). Previous compositional analyses of particles injected by the plume into Saturn's diffuse E ring have already indicated the presence of liquid water(8), but the mechanisms driving the plume emission are still debated(13). Here we report an analysis of the composition of freshly ejected particles close to the sources. Salt-rich ice particles are found to dominate the total mass flux of ejected solids (more than 99 per cent) but they are depleted in the population escaping into Saturn's E ring. Ice grains containing organic compounds are found to be more abundant in dense parts of the plume. Whereas previous Cassini observations were compatible with a variety of plume formation mechanisms, these data eliminate or severely constrain non-liquid models and strongly imply that a salt-water reservoir with a large evaporating surface(7,8) provides nearly all of the matter in the plume.
Y1  - 2011
U6  - https://doi.org/10.1038/nature10175
SN  - 0028-0836
VL  - 474
IS  - 7353
SP  - 620
EP  - 622
PB  - Nature Publ. Group
CY  - London
ER  - 
TY  - JOUR
A1  - Kar, Parimal
A1  - Lipowsky, Reinhard
A1  - Knecht, Volker
T1  - Importance of polar solvation for cross-reactivity of antibody and its variants with steroids
JF  - The journal of physical chemistry : B, Condensed matter, materials, surfaces, interfaces & biophysical chemistry
N2  - Understanding the factors determining the binding of ligands to receptors in detail is essential for rational drug design. Here, the free energies of binding of the steroids progesterone (PRG) and 5 beta-androstane-3,17-dione (SAD) to the Diels-Alderase antibody 1E9, as well as the Leu(H47)Trp/Arg(H100)Trp 1E9 double mutant (1E9dm) and the corresponding single mutants, have been estimated and decomposed using the molecular mechanics-Poisson-Boltzmann surface area (MM-PBSA) method. Also the difference in binding free energies between the PRG-1E9dm complex and the complex of PRG with the antiprogesterone antibody DB3 have been evaluated and decomposed. The steroids bind less strongly to 1E9 than to DB3, but the mutations tend to improve the steroid affinity, in quantitative agreement with experimental data. Although the complexes formed by PRG or SAD with 1E9dm and by PRG with DB3 have similar affinity, the binding mechanisms are different. Reduced Waals for SAD-1E9dm versus PRG-1E9dm or for PRG-1E9dm versus PRG-DB3 are energetically compensated by an increased solvation of polar groups, partly contrasting previous conclusions based on structural inspection. Our study illustrates that deducing binding mechanisms from structural models alone can be misleading. Therefore, taking into account solvation effects as in MM-PBSA calculations is essential to elucidate molecular recognition.
Y1  - 2011
U6  - https://doi.org/10.1021/jp201538t
SN  - 1520-6106
VL  - 115
IS  - 23
SP  - 7661
EP  - 7669
PB  - American Chemical Society
CY  - Washington
ER  - 
TY  - JOUR
A1  - Navirian, Hengameh A.
A1  - Herzog, Marc
A1  - Goldshteyn, J.
A1  - Leitenberger, Wolfram
A1  - Vrejoiu, Ionella
A1  - Khakhulin, D.
A1  - Wulff, M.
A1  - Shayduk, Roman
A1  - Gaal, P.
A1  - Bargheer, Matias
T1  - Shortening x-ray pulses for pump-probe experiments at synchrotrons
JF  - Journal of applied physics
N2  - We implemented an experimental scheme for ultrafast x-ray diffraction at storage rings based on a laser-driven Bragg-switch that shortens the x-ray pulses emitted from an undulator. The increased time-resolution is demonstrated by observing changes of intensity, position and width of the diffraction peaks of a La(0.7)Sr(0.3)MnO(3)/SrTiO(3) superlattice sample after optical excitation, i.e., by quantitatively measuring the propagation of an expansion wave through the sample. These experimental transients with timescales of 35 to 60 ps evidence a reduction of the x-ray pulse duration by a factor of two.
Y1  - 2011
U6  - https://doi.org/10.1063/1.3601057
SN  - 0021-8979
VL  - 109
IS  - 12
PB  - American Institute of Physics
CY  - Melville
ER  - 
TY  - JOUR
A1  - Masanes, Lluis
A1  - Müller, Markus P.
T1  - A derivation of quantum theory from physical requirements
JF  - New journal of physics : the open-access journal for physics
N2  - Quantum theory (QT) is usually formulated in terms of abstract mathematical postulates involving Hilbert spaces, state vectors and unitary operators. In this paper, we show that the full formalism of QT can instead be derived from five simple physical requirements, based on elementary assumptions regarding preparations, transformations and measurements. This is very similar to the usual formulation of special relativity, where two simple physical requirements-the principles of relativity and light speed invariance-are used to derive the mathematical structure of Minkowski space-time. Our derivation provides insights into the physical origin of the structure of quantum state spaces (including a group-theoretic explanation of the Bloch ball and its three dimensionality) and suggests several natural possibilities to construct consistent modifications of QT.
Y1  - 2011
U6  - https://doi.org/10.1088/1367-2630/13/6/063001
SN  - 1367-2630
VL  - 13
IS  - 1
PB  - IOP Publ. Ltd.
CY  - Bristol
ER  - 
TY  - JOUR
A1  - Makhmudo, K. O.
A1  - Makhmudov, O. I.
A1  - Tarkhanov, Nikolai Nikolaevich
T1  - Equations of Maxwell type
JF  - Journal of mathematical analysis and applications
N2  - For an elliptic complex of first order differential operators on a smooth manifold X, we define a system of two equations which can be thought of as abstract Maxwell equations. The formal theory of this system proves to be very similar to that of classical Maxwell's equations. The paper focuses on boundary value problems for the abstract Maxwell equations, especially on the Cauchy problem.
KW  - Electromagnetic waves
KW  - Scattering
KW  - Elliptic complex
KW  - Green formulas
KW  - Stratton-Chu formulas
KW  - Cauchy problem
Y1  - 2011
U6  - https://doi.org/10.1016/j.jmaa.2011.01.012
SN  - 0022-247X
VL  - 378
IS  - 1
SP  - 64
EP  - 75
PB  - Elsevier
CY  - San Diego
ER  - 
TY  - JOUR
A1  - Pontius, N.
A1  - Kachel, T.
A1  - Schüssler-Langeheine, C.
A1  - Schlotter, W. F.
A1  - Beye, Martin
A1  - Sorgenfrei, Florian
A1  - Chang, C. F.
A1  - Föhlisch, Alexander
A1  - Wurth, W.
A1  - Metcalf, P.
A1  - Leonov, I.
A1  - Yaresko, A.
A1  - Stojanovic, N.
A1  - Berglund, Martin
A1  - Guerassimova, N.
A1  - Duesterer, S.
A1  - Redlin, H.
A1  - Duerr, H. A.
T1  - Time-resolved resonant soft x-ray diffraction with free-electron lasers  femtosecond dynamics across the Verwey transition in magnetite
JF  - Applied physics letters
N2  - Resonant soft x-ray diffraction (RSXD) with femtosecond (fs) time resolution is a powerful tool for disentangling the interplay between different degrees of freedom in strongly correlated electron materials. It allows addressing the coupling of particular degrees of freedom upon an external selective perturbation, e. g., by an optical or infrared laser pulse. Here, we report a time-resolved RSXD experiment from the prototypical correlated electron material magnetite using soft x-ray pulses from the free-electron laser FLASH in Hamburg. We observe ultrafast melting of the charge-orbital order leading to the formation of a transient phase, which has not been observed in equilibrium.
Y1  - 2011
U6  - https://doi.org/10.1063/1.3584855
SN  - 0003-6951
VL  - 98
IS  - 18
PB  - American Institute of Physics
CY  - Melville
ER  - 
TY  - JOUR
A1  - Baumgärtel, Hellmut
T1  - A Characteristic decay semigroup for the resonances of trace class perturbations with analyticity conditions of semibounded hamiltonians
JF  - International journal of theoretical physic
N2  - To asymptotic complete scattering systems {M(+) + V, M(+)} on H(+) := L(2)(R(+), K, d lambda), where M(+) is the multiplication operator on H(+) and V is a trace class operator with analyticity conditions, a decay semigroup is associated such that the spectrum of the generator of this semigroup coincides with the set of all resonances (poles of the analytic continuation of the scattering matrix into the lower half plane across the positive half line), i.e. the decay semigroup yields a "time-dependent" characterization of the resonances. As a counterpart a "spectral characterization" is mentioned which is due to the "eigenvalue-like" properties of resonances.
KW  - Resonances
KW  - Scattering theory
KW  - Lax-Phillips theory
KW  - Decay semigroups
Y1  - 2011
U6  - https://doi.org/10.1007/s10773-010-0533-9
SN  - 0020-7748
VL  - 50
IS  - 7
SP  - 2002
EP  - 2008
PB  - Springer
CY  - New York
ER  - 
TY  - JOUR
A1  - Grass, T. D.
A1  - dos Santos, Francisca E. A.
A1  - Pelster, Axel
T1  - Real-time Ginzburg-Landau theory for bosons in optical lattices
JF  - Laser physics
N2  - Within the Schwinger-Keldysh formalism we derive a Ginzburg-Landau theory for the Bose-Hubbard model which describes the real-time dynamics of the complex order parameter field. Analyzing the excitations in the vicinity of the quantum phase transitions it turns out that particle/hole dispersions in the Mott phase map continuously onto corresponding amplitude/phase excitations in the superfluid phase. Furthermore, in the superfluid phase we find a sound mode, which is in accordance with recent Bragg spectroscopy measurements in the Bogoliubov regime, as well as an additional gapped mode, which seems to have been detected via lattice modulation.
Y1  - 2011
U6  - https://doi.org/10.1134/S1054660X11150096
SN  - 1054-660X
SN  - 1555-6611
VL  - 21
IS  - 8
SP  - 1459
EP  - 1463
PB  - IOP Publ. Ltd.
CY  - Bristol
ER  - 
TY  - JOUR
A1  - Levnajic, Zoran
T1  - Emergent multistability and frustration in phase-repulsive networks of oscillators
JF  - Physical review : E, Statistical, nonlinear and soft matter physics
N2  - The collective dynamics of oscillator networks with phase-repulsive coupling is studied, considering various network sizes and topologies. The notion of link frustration is introduced to characterize and quantify the network dynamical states. In opposition to widely studied phase-attractive case, the properties of final dynamical states in our model critically depend on the network topology. In particular, each network's total frustration value is intimately related to its topology. Moreover, phase-repulsive networks in general display multiple final frustration states, whose statistical and stability properties are uniquely identifying them.
Y1  - 2011
U6  - https://doi.org/10.1103/PhysRevE.84.016231
SN  - 1539-3755
VL  - 84
IS  - 1
PB  - American Physical Society
CY  - College Park
ER  - 
TY  - JOUR
A1  - Ilnytskyi, Jaroslav M.
A1  - Neher, Dieter
A1  - Saphiannikova, Marina
T1  - Opposite photo-induced deformations in azobenzene-containing polymers with different molecular architecture molecular dynamics study
JF  - The journal of chemical physics : bridges a gap between journals of physics and journals of chemistr
N2  - Photo-induced deformations in azobenzene-containing polymers (azo-polymers) are central to a number of applications, such as optical storage and fabrication of diffractive elements. The microscopic nature of the underlying opto-mechanical coupling is yet not clear. In this study, we address the experimental finding that the scenario of the effects depends on molecular architecture of the used azo-polymer. Typically, opposite deformations in respect to the direction of light polarization are observed for liquid crystalline and amorphous azo-polymers. In this study, we undertake molecular dynamics simulations of two different models that mimic these two types of azo-polymers. We employ hybrid force field modeling and consider only trans-isomers of azobenzene, represented as Gay-Berne sites. The effect of illumination on the orientation of the chromophores is considered on the level of orientational hole burning and emphasis is given to the resulting deformation of the polymer matrix. We reproduce deformations of opposite sign for the two models being considered here and discuss the relevant microscopic mechanisms in both cases.
KW  - amorphous state
KW  - light polarisation
KW  - liquid crystal polymers
KW  - molecular dynamics method
KW  - optical hole burning
KW  - photochemistry
Y1  - 2011
U6  - https://doi.org/10.1063/1.3614499
SN  - 0021-9606
VL  - 135
IS  - 4
PB  - American Institute of Physics
CY  - Melville
ER  - 
TY  - JOUR
A1  - Fechner, Cora
T1  - Reconstructing the intergalactic UV background with QSO absorption lines
JF  - Astronomy and astrophysics : an international weekly journal
N2  - We present a new approach to observationally constraining the spectral energy distribution of the intergalactic UV background by studying metal absorption systems. We study single-component metal line systems that exhibit various well-measured species. Among the observed transitions, at least two ratios of ionization stages from the same element are required, e. g. C III/C IV and Si III/Si IV. For each system photoionization models are constructed by varying the spectrum of the ionizing radiation. The spectral energy distribution can then be constrained by comparing the models with the observed column density ratios. Extensive tests with artificial absorbers show that the spectrum of the ionizing radiation cannot be reconstructed unambiguously, but it is possible to constrain the main characteristics of the spectrum. Furthermore, the resulting physical parameters of the absorber, such as ionization parameter, metallicity, and relative abundances, may depend strongly on the adopted ionizing spectrum. Even in case of well-fitting models, the uncertainties can be as high as similar to 0.5 dex for the ionization parameter and up to similar to 1.5 dex for the metallicity. Therefore, it is essential to know the hardness of the UV background when estimating the metallicity of the intergalactic medium. Applying the procedure to a small sample of 3 observed single-component metal line systems yields a soft ionizing radiation at z > 2 and a slightly harder spectrum at z < 2. The resulting energy distributions exhibit strong He II Lya re-emission features, suggesting that reprocessing by intergalactic He II is important. Comparing the observed systems to UV background spectra from the literature indicates that a recent model that includes sawtooth modulation due to reprocessing by intergalactic He II with delayed helium reionization fits the investigated systems very well.
KW  - intergalactic medium
KW  - quasars: absorption lines
KW  - diffuse radiation
Y1  - 2011
U6  - https://doi.org/10.1051/0004-6361/201117080
SN  - 0004-6361
VL  - 532
IS  - 2
PB  - EDP Sciences
CY  - Les Ulis
ER  - 
TY  - JOUR
A1  - Gerhardt, Matthias
A1  - Groeger, Gillian
A1  - MacCarthy, Niall
T1  - Monopolar vs. bipolar subretinal stimulation-An in vitro study
JF  - Journal of neuroscience methods
N2  - This study uses an in vitro rd10 mouse model to quantify and compare the ability of the monopolar and the (concentric) bipolar electrode configurations for subretinal stimulation. To allow for results which can be directly compared an identical region of the retina was stimulated due to the circumstance that the bipolar electrode configuration allows also for monopolar stimulation, if the concentric counter-electrode is set potential-free (floating). A ganglion cell, located centrally over the bipolar electrode configuration was selected to extracellularly record action potentials during stimulation. To analyse the recorded action potentials, we introduce a new method which combines the advantages of (a) singular value decomposition (SVD) for weighting similar modulation patterns with which the recorded action potentials are characterized and (b) multi curve fitting to identify a common threshold level, required to finally assemble a strength-duration relationship (SDR). By directly comparing the obtained SDR curves, we found that the efficiency of stimulation with the monopolar electrode configuration is significantly higher than with the bipolar electrode configuration. All obtained SDR curves were fitted using the Lapicque model to estimate the chronaxie times and the rheobase currents. Liquid inclusions, eventually separating the retina from the electrodes are discussed to be a major cause for low ganglion cell responses during stimulation with the bipolar electrode configuration.
KW  - SVD
KW  - Subretinal
KW  - Electrodes
KW  - Monopolar
KW  - Bipolar
KW  - Retina
KW  - Ganglion
KW  - Cells
Y1  - 2011
U6  - https://doi.org/10.1016/j.jneumeth.2011.04.017
SN  - 0165-0270
VL  - 199
IS  - 1
SP  - 26
EP  - 34
PB  - Elsevier
CY  - Amsterdam
ER  - 
TY  - JOUR
A1  - Rivnay, Jonathan
A1  - Steyrleuthner, Robert
A1  - Jimison, Leslie H.
A1  - Casadei, Alberto
A1  - Chen, Zhihua
A1  - Toney, Michael F.
A1  - Facchetti, Antonio
A1  - Neher, Dieter
A1  - Salleo, Alberto
T1  - Drastic control of texture in a high performance n-Type polymeric semiconductor and implications for charge transport
JF  - Macromolecules : a publication of the American Chemical Society
N2  - Control of crystallographic texture from mostly face-on to edge-on is observed for the film morphology of the n-type semicrystalline polymer [N,N-9-bis(2-octyldodecyl)naphthalene-1,4,5,8-bis(dicarboximide)-2,6-diy1]alt-5,59-(2,29-bithiophene)}, P(NDI2OD-T2), when annealing the film to the polymer melting point followed by slow cooling to ambient temperature. A variety of X-ray diffraction analyses, including pole figure construction and Fourier transform peak shape deconvolution, are employed to quantify the texture change, relative degree of crystallinity and lattice order. We find that annealing the polymer film to the melt leads to a shift from 77.5% face-on to 94.6% edge-on lamellar texture as well as to a 2-fold increase in crystallinity and a 40% decrease in intracrystallite cumulative disorder. The texture change results in a significant drop in the electron-only diode current density through the film thickness upon melt annealing while little change is observed in the in-plane transport of bottom gated thin film transistors. This suggests that the texture change is prevalent in the film interior and that either the (bottom) surface structure is different from the interior structure or the intracrystalline order and texture play a secondary role in transistor transport for this material.
Y1  - 2011
U6  - https://doi.org/10.1021/ma200864s
SN  - 0024-9297
VL  - 44
IS  - 13
SP  - 5246
EP  - 5255
PB  - American Chemical Society
CY  - Washington
ER  - 
TY  - JOUR
A1  - Prosen, Tomaz
A1  - Ilievski, Enej
T1  - Nonequilibrium phase transition in a periodically driven XY spin chain
JF  - Physical review letters
N2  - We present a general formulation of Floquet states of periodically time-dependent open Markovian quasifree fermionic many-body systems in terms of a discrete Lyapunov equation. Illustrating the technique, we analyze periodically kicked XY spin-1/2 chain which is coupled to a pair of Lindblad reservoirs at its ends. A complex phase diagram is reported with reentrant phases of long range and exponentially decaying spin-spin correlations as some of the system's parameters are varied. The structure of phase diagram is reproduced in terms of counting nontrivial stationary points of Floquet quasiparticle dispersion relation.
Y1  - 2011
U6  - https://doi.org/10.1103/PhysRevLett.107.060403
SN  - 0031-9007
VL  - 107
IS  - 6
PB  - American Physical Society
CY  - College Park
ER  - 
TY  - JOUR
A1  - Bagnich, Sergey A.
A1  - Unger, Th.
A1  - Jaiser, F.
A1  - Neher, Dieter
A1  - Thesen, M. W.
A1  - Krüger, H.
T1  - Efficient green electrophosphorescence based on ambipolar nonconjugated polymers evaluation of transport and emission properties
JF  - Journal of applied physics
N2  - New materials for polymer organic light-emitting diodes based on a polymer matrix doped with phosphorescent dyes are presented. The matrix system is based on a polystyrene backbone bearing either electron or hole transporting units at the 4-position of each repeat unit. Random copolymers and polymer blend systems of the homopolymers are prepared, both with 62 wt.% electron transporting and 38 wt.% hole transporting moieties. Adding a green electrophosphorescent dye to the polymer matrix leads to efficient electroluminescence with a maximum current efficiency of 35 cd/A and a maximum external quantum efficiency of up to 10%. The mobilities of electrons and holes in the dye-doped copolymer, as measured by transient electroluminescence, are around 5 x 10(-5) and 5 x 10(-6) cm(2)/Vs, respectively, while the blend of the two homopolymers exhibits slightly lower mobilities of both types of carriers. Despite the pronounced imbalance of charge transport, the device performance is almost entirely limited by the phosphorescence efficiency of the dye, implying balanced flow of holes and electrons into the active region. Also, devices made with either the copolymer or the blend yielded very similar device efficiencies, despite the noticeable difference in electron and hole mobility. It is proposed that electrons are efficiently blocked at the interlayer and that the so-formed space charge assists the balanced injection of holes.
Y1  - 2011
U6  - https://doi.org/10.1063/1.3618681
SN  - 0021-8979
SN  - 1089-7550
VL  - 110
IS  - 3
PB  - American Institute of Physics
CY  - Melville
ER  - 
TY  - JOUR
A1  - DiGuglielmo, J.
A1  - Samblowski, A.
A1  - Hage, B.
A1  - Pineda, Carlos
A1  - Eisert, Jens
A1  - Schnabel, R.
T1  - Experimental Unconditional Preparation and Detection of a Continuous Bound Entangled State of Light
JF  - Physical review letters
N2  - Among the possibly most intriguing aspects of quantum entanglement is that it comes in free and bound instances. The existence of bound entangled states certifies an intrinsic irreversibility of entanglement in nature and suggests a connection with thermodynamics. In this Letter, we present a first unconditional, continuous-variable preparation and detection of a bound entangled state of light. We use convex optimization to identify regimes rendering its bound character well certifiable, and continuously produce a distributed bound entangled state with an extraordinary and unprecedented significance of more than 10 standard deviations away from both separability and distillability. Our results show that the approach chosen allows for the efficient and precise preparation of multimode entangled states of light with various applications in quantum information, quantum state engineering, and high precision metrology.
Y1  - 2011
U6  - https://doi.org/10.1103/PhysRevLett.107.240503
SN  - 0031-9007
VL  - 107
IS  - 24
PB  - American Physical Society
CY  - College Park
ER  - 
TY  - JOUR
A1  - Lisso, Janina
A1  - Schröder, Florian
A1  - Fisahn, Joachim
A1  - Muessig, Carsten
T1  - NFX1-LIKE2 (NFXL2) Suppresses Abscisic Acid Accumulation and Stomatal Closure in Arabidopsis thaliana
JF  - PLoS one
N2  - The NFX1-LIKE1 (NFXL1) and NFXL2 genes were identified as regulators of salt stress responses. The NFXL1 protein is a nuclear factor that positively affects adaptation to salt stress. The nfxl1-1 loss-of-function mutant displayed reduced survival rates under salt and high light stress. In contrast, the nfxl2-1 mutant, defective in the NFXL2 gene, and NFXL2-antisense plants exhibited enhanced survival under these conditions. We show here that the loss of NFXL2 function results in abscisic acid (ABA) overaccumulation, reduced stomatal conductance, and enhanced survival under drought stress. The nfxl2-1 mutant displayed reduced stomatal aperture under all conditions tested. Fusicoccin treatment, exposition to increasing light intensities, and supply of decreasing CO2 concentrations demonstrated full opening capacity of nfxl2-1 stomata. Reduced stomatal opening presumably is a consequence of elevated ABA levels. Furthermore, seedling growth, root growth, and stomatal closure were hypersensitive to exogenous ABA. The enhanced ABA responses may contribute to the improved drought stress resistance of the mutant. Three NFXL2 splice variants were cloned and named NFXL2-78, NFXL2-97, and NFXL2-100 according to the molecular weight of the putative proteins. Translational fusions to the green fluorescent protein suggest nuclear localisation of the NFXL2 proteins. Stable expression of the NFXL2-78 splice variant in nfxl2-1 plants largely complemented the mutant phenotype. Our data show that NFXL2 controls ABA levels and suppresses ABA responses. NFXL2 may prevent unnecessary and costly stress adaptation under favourable conditions.
Y1  - 2011
U6  - https://doi.org/10.1371/journal.pone.0026982
SN  - 1932-6203
VL  - 6
IS  - 11
PB  - PLoS
CY  - San Fransisco
ER  - 
TY  - JOUR
A1  - Abel, M. W.
A1  - Shepelyansky, Dima L.
T1  - Google matrix of business process management
JF  - The European physical journal : B, Condensed matter and complex systems
N2  - Development of efficient business process models and determination of their characteristic properties are subject of intense interdisciplinary research. Here, we consider a business process model as a directed graph. Its nodes correspond to the units identified by the modeler and the link direction indicates the causal dependencies between units. It is of primary interest to obtain the stationary flow on such a directed graph, which corresponds to the steady-state of a firm during the business process. Following the ideas developed recently for the World Wide Web, we construct the Google matrix for our business process model and analyze its spectral properties. The importance of nodes is characterized by PageRank and recently proposed CheiRank and 2DRank, respectively. The results show that this two-dimensional ranking gives a significant information about the influence and communication properties of business model units. We argue that the Google matrix method, described here, provides a new efficient tool helping companies to make their decisions on how to evolve in the exceedingly dynamic global market.
Y1  - 2011
U6  - https://doi.org/10.1140/epjb/e2010-10710-y
SN  - 1434-6028
VL  - 84
IS  - 4
SP  - 493
EP  - 500
PB  - Springer
CY  - New York
ER  - 
TY  - JOUR
A1  - Abdolvahab, Rouhollah Haji
A1  - Metzler, Ralf
A1  - Ejtehadi, Mohammad Reza
T1  - First passage time distribution of chaperone driven polymer translocation through a nanopore homopolymer and heteropolymer cases
JF  - The journal of chemical physics : bridges a gap between journals of physics and journals of chemistr
N2  - Combining the advection-diffusion equation approach with Monte Carlo simulations we study chaperone driven polymer translocation of a stiff polymer through a nanopore. We demonstrate that the probability density function of first passage times across the pore depends solely on the Peclet number, a dimensionless parameter comparing drift strength and diffusivity. Moreover it is shown that the characteristic exponent in the power-law dependence of the translocation time on the chain length, a function of the chaperone-polymer binding energy, the chaperone concentration, and the chain length, is also effectively determined by the Peclet number. We investigate the effect of the chaperone size on the translocation process. In particular, for large chaperone size, the translocation progress and the mean waiting time as function of the reaction coordinate exhibit pronounced sawtooth-shapes. The effects of a heterogeneous polymer sequence on the translocation dynamics is studied in terms of the translocation velocity, the probability distribution for the translocation progress, and the monomer waiting times. (C) 2011 American Institute of Physics.
Y1  - 2011
U6  - https://doi.org/10.1063/1.3669427
SN  - 0021-9606
VL  - 135
IS  - 24
PB  - American Institute of Physics
CY  - Melville
ER  - 
TY  - JOUR
A1  - Turner, Sarah T.
A1  - Pingel, Patrick
A1  - Steyrleuthner, Robert
A1  - Crossland, Edward J. W.
A1  - Ludwigs, Sabine
A1  - Neher, Dieter
T1  - Quantitative analysis of bulk heterojunction films using linear absorption spectroscopy and solar cell performance
JF  - Advanced functional materials
N2  - A fundamental understanding of the relationship between the bulk morphology and device performance is required for the further development of bulk heterojunction organic solar cells. Here, non-optimized (chloroform cast) and nearly optimized (solvent-annealed o-dichlorobenzene cast) P3HT:PCBM blend films treated over a range of annealing temperatures are studied via optical and photovoltaic device measurements. Parameters related to the P3HT aggregate morphology in the blend are obtained through a recently established analytical model developed by F. C. Spano for the absorption of weakly interacting H-aggregates. Thermally induced changes are related to the glass transition range of the blend. In the chloroform prepared devices, the improvement in device efficiency upon annealing within the glass transition range can be attributed to the growth of P3HT aggregates, an overall increase in the percentage of chain crystallinity, and a concurrent increase in the hole mobilities. Films treated above the glass transition range show an increase in efficiency and fill factor not only associated with the change in chain crystallinity, but also with a decrease in the energetic disorder. On the other hand, the properties of the P3HT phase in the solvent-annealed o-dichlorobenzene cast blends are almost indistinguishable from those of the corresponding pristine P3HT layer and are only weakly affected by thermal annealing. Apparently, slow drying of the blend allows the P3HT chains to crystallize into large domains with low degrees of intra- and interchain disorder. This morphology appears to be most favorable for the efficient generation and extraction of charges.
KW  - Organic electronics
KW  - morphology
KW  - solar cells
KW  - mobility
KW  - absorption spectroscopy
Y1  - 2011
U6  - https://doi.org/10.1002/adfm.201101583
SN  - 1616-301X
VL  - 21
IS  - 24
SP  - 4640
EP  - 4652
PB  - Wiley-VCH
CY  - Weinheim
ER  - 
TY  - JOUR
A1  - Donges, Jonathan Friedemann
A1  - Donner, Reik Volker
A1  - Trauth, Martin H.
A1  - Marwan, Norbert
A1  - Schellnhuber, Hans Joachim
A1  - Kurths, Jürgen
T1  - Nonlinear detection of paleoclimate-variability transitions possibly related to human evolution
JF  - Proceedings of the National Academy of Sciences of the United States of America
N2  - Potential paleoclimatic driving mechanisms acting on human evolution present an open problem of cross-disciplinary scientific interest. The analysis of paleoclimate archives encoding the environmental variability in East Africa during the past 5 Ma has triggered an ongoing debate about possible candidate processes and evolutionary mechanisms. In this work, we apply a nonlinear statistical technique, recurrence network analysis, to three distinct marine records of terrigenous dust flux. Our method enables us to identify three epochs with transitions between qualitatively different types of environmental variability in North and East Africa during the (i) Middle Pliocene (3.35-3.15 Ma B. P.), (ii) Early Pleistocene (2.25-1.6 Ma B. P.), and (iii) Middle Pleistocene (1.1-0.7 Ma B. P.). A deeper examination of these transition periods reveals potential climatic drivers, including (i) large-scale changes in ocean currents due to a spatial shift of the Indonesian throughflow in combination with an intensification of Northern Hemisphere glaciation, (ii) a global reorganization of the atmospheric Walker circulation induced in the tropical Pacific and Indian Ocean, and (iii) shifts in the dominating temporal variability pattern of glacial activity during the Middle Pleistocene, respectively. A reexamination of the available fossil record demonstrates statistically significant coincidences between the detected transition periods and major steps in hominin evolution. This result suggests that the observed shifts between more regular and more erratic environmental variability may have acted as a trigger for rapid change in the development of humankind in Africa.
KW  - African climate
KW  - Plio-Pleistocene
KW  - climate-driven evolution
KW  - dynamical transitions
KW  - nonlinear time series analysis
Y1  - 2011
U6  - https://doi.org/10.1073/pnas.1117052108
SN  - 0027-8424
VL  - 108
IS  - 51
SP  - 20422
EP  - 20427
PB  - National Acad. of Sciences
CY  - Washington
ER  - 
TY  - JOUR
A1  - Gruber, W.
A1  - Chakravarty, S.
A1  - Baehtz, C.
A1  - Leitenberger, Wolfram
A1  - Bruns, M.
A1  - Kobler, A.
A1  - Kübel, Christian
A1  - Schmidt, H.
T1  - Strain relaxation and vacancy creation in thin platinum films
JF  - Physical review letters
N2  - Synchrotron based combined in situ x-ray diffractometry and reflectometry is used to investigate the role of vacancies for the relaxation of residual stress in thin metallic Pt films. From the experimentally determined relative changes of the lattice parameter a and of the film thickness L the modification of vacancy concentration and residual strain was derived as a function of annealing time at 130 degrees C. The results indicate that relaxation of strain resulting from compressive stress is accompanied by the creation of vacancies at the free film surface. This proves experimentally the postulated dominant role of vacancies for stress relaxation in thin metal films close to room temperature.
Y1  - 2011
U6  - https://doi.org/10.1103/PhysRevLett.107.265501
SN  - 0031-9007
VL  - 107
IS  - 26
PB  - American Physical Society
CY  - College Park
ER  - 
TY  - JOUR
A1  - Kuznetsov, Sergey P.
T1  - Plykin type attractor in electronic device simulated in MULTISIM
JF  - Chaos : an interdisciplinary journal of nonlinear science
N2  - An electronic device is suggested representing a non-autonomous dynamical system with hyperbolic chaotic attractor of Plykin type in the stroboscopic map, and the results of its simulation with software package NI MULTISIM are considered in comparison with numerical integration of the underlying differential equations. A main practical advantage of electronic devices of this kind is their structural stability that means insensitivity of the chaotic dynamics in respect to variations of functions and parameters of elements constituting the system as well as to interferences and noises.
Y1  - 2011
U6  - https://doi.org/10.1063/1.3646903
SN  - 1054-1500
VL  - 21
IS  - 4
PB  - American Institute of Physics
CY  - Melville
ER  - 
TY  - JOUR
A1  - Feudel, Fred
A1  - Bergemann, Kay
A1  - Tuckerman, Laurette S.
A1  - Egbers, C.
A1  - Futterer, B.
A1  - Gellert, Marcus
A1  - Hollerbach, Rainer
T1  - Convection patterns in a spherical fluid shell
JF  - Physical review : E, Statistical, nonlinear and soft matter physics
N2  - Symmetry-breaking bifurcations have been studied for convection in a nonrotating spherical shell whose outer radius is twice the inner radius, under the influence of an externally applied central force field with a radial dependence proportional to 1/r(5). This work is motivated by the GeoFlow experiment, which is performed under microgravity condition at the International Space Station where this particular central force can be generated. In order to predict the observable patterns, simulations together with path-following techniques and stability computations have been applied. Branches of axisymmetric, octahedral, and seven-cell solutions have been traced. The bifurcations producing them have been identified and their stability ranges determined. At higher Rayleigh numbers, time-periodic states with a complex spatiotemporal symmetry are found, which we call breathing patterns.
Y1  - 2011
U6  - https://doi.org/10.1103/PhysRevE.83.046304
SN  - 1539-3755
VL  - 83
IS  - 4
PB  - American Physical Society
CY  - College Park
ER  - 
TY  - JOUR
A1  - Richter, Philipp
A1  - Krause, F.
A1  - Fechner, Cora
A1  - Charlton, Jane C.
A1  - Murphy, M. T.
T1  - The neutral gas extent of galaxies as derived from weak intervening Ca II absorbers
JF  - Astronomy and astrophysics : an international weekly journal
N2  - We present a systematic study of weak intervening CaII absorbers at low redshift (z < 0.5), based on the analysis of archival high-resolution (R >= 45 000) optical spectra of 304 quasars and active galactic nuclei observed with VLT/UVES. Along a total redshift path of Delta z approximate to 100 we detected 23 intervening CaII absorbers in both the CaII H & K lines, with rest frame equivalent widths W-r,W-3934 = 15-799 m angstrom and column densities log N(CaII) = 11.25-13.04 (obtained by fitting Voigt-profile components). We obtain a bias-corrected number density of weak intervening CaII absorbers of dN/dz = 0.117 +/- 0.044 at < z(abs)> = 0.35 for absorbers with log N(CaII) >= 11.65 (W-r,W-3934 >= 32 m angstrom). This is similar to 2.6 times the value obtained for damped Lyman alpha absorbers (DLAs) at low redshift. All CaII absorbers in our sample show associated absorption by other low ions such as MgII and FeII; 45 percent of them have associated NaI absorption. From ionization modelling we conclude that intervening CaII absorption with log N(CaII) >= 11.5 arises in DLAs, sub-DLAs and Lyman-limit systems (LLS) at HI column densities of log N(HI) >= 17.4. Using supplementary HI information for nine of the absorbers we find that the CaII/HI ratio decreases strongly with increasing HI column density, indicating a column-density-dependent dust depletion of Ca. The observed column density distribution function of CaII absorption components follows a relatively steep power law, f(N) proportional to N-beta, with a slope of -beta = -1.68, which again points towards an enhanced dust depletion in high column density systems. The relatively large cross section of these absorbers together with the frequent detection of CaII absorption in high-velocity clouds (HVCs) in the halo of the Milky Way suggests that a considerable fraction of the intervening CaII systems trace (partly) neutral gas structures in the halos and circumgalactic environment of galaxies (i.e., they are HVC analogs). Based on the recently measured detection rate of CaII absorption in the Milky Way HVCs we estimate that the mean (projected) CaII covering fraction of galaxies and their gaseous halos is < f(c,CaII)> = 0.33. Using this value and considering all galaxies with luminosities L >= 0.05 L-star we calculate that the characteristic radial extent of (partly) neutral gas clouds with log N(HI) >= 17.4 around low-redshift galaxies is R-HVC approximate to 55 kpc.
KW  - galaxies: halos
KW  - galaxies: formation
KW  - galaxies: ISM
KW  - intergalactic medium
KW  - quasars: absorption lines
Y1  - 2011
U6  - https://doi.org/10.1051/0004-6361/201015566
SN  - 0004-6361
VL  - 528
IS  - 4
PB  - EDP Sciences
CY  - Les Ulis
ER  - 
TY  - JOUR
A1  - Müller, Markus P.
A1  - Gross, David
A1  - Eisert, Jens
T1  - Concentration of Measure for Quantum States with a Fixed Expectation Value
JF  - Communications in mathematical physics
N2  - Given some observable H on a finite-dimensional quantum system, we investigate the typical properties of random state vectors vertical bar psi >> that have a fixed expectation value < psi vertical bar H vertical bar psi > = E with respect to H. Under some conditions on the spectrum, we prove that this manifold of quantum states shows a concentration of measure phenomenon: any continuous function on this set is almost everywhere close to its mean. We also give a method to estimate the corresponding expectation values analytically, and we prove a formula for the typical reduced density matrix in the case that H is a sum of local observables. We discuss the implications of our results as new proof tools in quantum information theory and to study phenomena in quantum statistical mechanics. As a by-product, we derive a method to sample the resulting distribution numerically, which generalizes the well-known Gaussian method to draw random states from the sphere.
Y1  - 2011
U6  - https://doi.org/10.1007/s00220-011-1205-1
SN  - 0010-3616
VL  - 303
IS  - 3
SP  - 785
EP  - 824
PB  - Springer
CY  - New York
ER  - 
TY  - JOUR
A1  - Mann, R. B.
A1  - Young, M. B.
A1  - Fuüntes-Schuller, I.
T1  - A perturbative approach to inelastic collisions in a Bose-Einstein condensate
JF  - Journal of physics : B, Atomic, molecular and optical physics
N2  - It has recently been discovered that for certain rates of mode-exchange collisions analytic solutions can be found for a Hamiltonian describing the two-mode Bose-Einstein condensate. We proceed to study the behaviour of the system using perturbation theory if the coupling constants only approximately match these parameter constraints. We find that the model is robust to such perturbations. We study the effects of degeneracy on the perturbations and find that the induced changes differ greatly from the non-degenerate case. We also model inelastic collisions that result in particle loss or condensate decay as external perturbations and use this formalism to examine the effects of three-body recombination and background collisions.
Y1  - 2011
U6  - https://doi.org/10.1088/0953-4075/44/8/085301
SN  - 0953-4075
VL  - 44
IS  - 8
PB  - IOP Publ. Ltd.
CY  - Bristol
ER  - 
TY  - JOUR
A1  - Valleriani, Angelo
A1  - Zhang, Gong
A1  - Nagar, Apoorva
A1  - Ignatova, Zoya
A1  - Lipowsky, Reinhard
T1  - Length-dependent translation of messenger RNA by ribosomes
JF  - Physical review : E, Statistical, nonlinear and soft matter physics
N2  - A simple measure for the efficiency of protein synthesis by ribosomes is provided by the steady state amount of protein per messenger RNA (mRNA), the so-called translational ratio, which is proportional to the translation rate. Taking the degradation of mRNA into account, we show theoretically that both the translation rate and the translational ratio decrease with increasing mRNA length, in agreement with available experimental data for the prokaryote Escherichia coli. We also show that, compared to prokaryotes, mRNA degradation in eukaryotes leads to a less rapid decrease of the translational ratio. This finding is consistent with the fact that, compared to prokaryotes, eukaryotes tend to have longer proteins.
Y1  - 2011
U6  - https://doi.org/10.1103/PhysRevE.83.042903
SN  - 1539-3755
VL  - 83
IS  - 4
PB  - American Physical Society
CY  - College Park
ER  - 
TY  - JOUR
A1  - Tepper-Garcia, Thorsten
A1  - Richter, Philipp
A1  - Schaye, Joop
A1  - Booth, C. M.
A1  - Vecchia, Claudio Dalla
A1  - Theuns, Tom
A1  - Wiersma, Robert P. C.
T1  - Absorption signatures of warm-hot gas at low redshift o vi
JF  - Monthly notices of the Royal Astronomical Society
N2  - We investigate the origin and physical properties of O vi absorbers at low redshift (z = 0.25) using a subset of cosmological, hydrodynamical simulations from the OverWhelmingly Large Simulations (OWLS) project. Intervening O vi absorbers are believed to trace shock-heated gas in the warm-hot intergalactic medium (WHIM) and may thus play a key role in the search for the missing baryons in the present-day Universe. When compared to observations, the predicted distributions of the different O vi line parameters (column density, Doppler parameter, rest equivalent width W-r) from our simulations exhibit a lack of strong O vi absorbers, a discrepancy that has also been found by Oppenheimer & Dave. This suggests that physical processes on subgrid scales (e.g. turbulence) may strongly influence the observed properties of O vi systems. We find that the intervening O vi absorption arises mainly in highly metal enriched (10-1 < Z/Z(circle dot) less than or similar to 1) gas at typical overdensities of 1 < /<<>> less than or similar to 102. One-third of the O vi absorbers in our simulation are found to trace gas at temperatures T < 105 K, while the rest arises in gas at higher temperatures, most of them around T = 105.3 +/- 0.5 K. These temperatures are much higher than inferred by Oppenheimer & Dave, probably because that work did not take the suppression of metal-line cooling by the photoionizing background radiation into account. While the O vi resides in a similar region of (, T)-space as much of the shock-heated baryonic matter, the vast majority of this gas has a lower metal content and does not give rise to detectable O vi absorption. As a consequence of the patchy metal distribution, O vi absorbers in our simulations trace only a very small fraction of the cosmic baryons (< 2 per cent) and the cosmic metals. Instead, these systems presumably trace previously shock-heated, metal-rich material from galactic winds that is now mixing with the ambient gas and cooling. The common approach of comparing O vi and H i column densities to estimate the physical conditions in intervening absorbers from QSO observations may be misleading, as most of the H i (and most of the gas mass) is not physically connected with the high-metallicity patches that give rise to the O vi absorption.
KW  - methods: numerical
KW  - galaxies: formation
KW  - intergalactic medium
KW  - quasars: absorption lines
KW  - cosmology: theory
Y1  - 2011
U6  - https://doi.org/10.1111/j.1365-2966.2010.18123.x
SN  - 0035-8711
VL  - 413
IS  - 1
SP  - 190
EP  - 212
PB  - Wiley-Blackwell
CY  - Hoboken
ER  - 
TY  - JOUR
A1  - Schmidt, Hans-Jürgen
T1  - Gauss-Bonnet lagrangian G lnG and cosmological exact solutions
JF  - Physical review : D, Particles, fields, gravitation, and cosmology
N2  - For the Lagrangian L = G lnG where G is the Gauss-Bonnet curvature scalar we deduce the field equation and solve it in closed form for 3-flat Friedmann models using a state-finder parametrization. Further we show that among all Lagrangians F(G) this L is the only one not having the form G(r) with a real constant r but possessing a scale-invariant field equation. This turns out to be one of its analogies to f(R) theories in two-dimensional space-time. In the appendix, we systematically list several formulas for the decomposition of the Riemann tensor in arbitrary dimensions n, which are applied in the main deduction for n = 4.
Y1  - 2011
U6  - https://doi.org/10.1103/PhysRevD.83.083513
SN  - 1550-7998
VL  - 83
IS  - 8
PB  - American Physical Society
CY  - College Park
ER  - 
TY  - JOUR
A1  - Kniepert, Juliane
A1  - Schubert, Marcel
A1  - Blakesley, James C.
A1  - Neher, Dieter
T1  - Photogeneration and recombination in P3HT/PCBM solar cells probed by time-delayed collection field experiments
JF  - The journal of physical chemistry letters
N2  - Time-delayed collection field (TDCF) experiments are performed on bulk heterojunction solar cells comprised of a blend of poly(3-hexylthiophene) and [6,6]-phenyl C-71 butyric acid methyl ester. TDCF is analogous to a pump-probe experiment using optical excitation and an electrical probe with a resolution of < 100 ns. The number of free charge carriers extracted after a short delay is found to be independent of the electric field during illumination. Also, experiments performed with a variable delay between the optical excitation and the electrical probe do not reveal any evidence for the generation of charge via field-assisted dissociation of bound long-lived polaron pairs. Photocurrent transients are well fitted by computational drift diffusion simulations with only direct generation of free charge carriers. With increasing delay times between pump and probe, two loss mechanisms are identified; first, charge-carriers are swept out of the device by the internal electric field, and second, bimolecular recombination of the remaining carriers takes place with a reduced recombination coefficient.
Y1  - 2011
U6  - https://doi.org/10.1021/jz200155b
SN  - 1948-7185
VL  - 2
IS  - 7
SP  - 700
EP  - 705
PB  - American Chemical Society
CY  - Washington
ER  - 
TY  - JOUR
A1  - Beye, Martin
A1  - Föhlisch, Alexander
T1  - A soft X-ray approach to electron-phonon interactions beyond the Born-Oppenheimer approximation
JF  - Journal of electron spectroscopy and related phenomena : the international journal on theoretical and experimental aspects of electron spectroscopy
N2  - With modern soft X-ray methods, the whole field of electron-phonon interactions becomes accessible directly in the ultrafast time domain with ultrashort pulsed X-ray sources, as well as in the energy domain through modern highly resolving spectrometers. The well-known core-hole clock approach plays an intermediate role, resolving energetic and temporal features at the same time. In this perspective paper, we review several experiments to illustrate the modern advances in the selective study of electron-phonon interactions as fundamentally determining ingredients for materials properties. We present the different complementary approaches that can be taken with soft X-ray methods to conquer this field beyond the Born-Oppenheimer approximation.
KW  - Electron-phonon coupling
KW  - Resonant inelastic X-ray scattering
KW  - X-ray emission spectroscopy
KW  - Near edge X-ray absorption fine structure
Y1  - 2011
U6  - https://doi.org/10.1016/j.elspec.2010.12.032
SN  - 0368-2048
VL  - 184
IS  - 3-6
SP  - 313
EP  - 317
PB  - Elsevier
CY  - Amsterdam
ER  - 
TY  - JOUR
A1  - Campbell, Earl T.
T1  - Catalysis and activation of magic states in fault-tolerant architectures
JF  - Physical review : A, Atomic, molecular, and optical physics
N2  - In many architectures for fault-tolerant quantum computing universality is achieved by a combination of Clifford group unitary operators and preparation of suitable nonstabilizer states, the so-called magic states. Universality is possible even for some fairly noisy nonstabilizer states, as distillation can convert many noisy copies into fewer purer magic states. Here we propose protocols that exploit multiple species of magic states in surprising ways. These protocols provide examples of previously unobserved phenomena that are analogous to catalysis and activation well known in entanglement theory.
Y1  - 2011
U6  - https://doi.org/10.1103/PhysRevA.83.032317
SN  - 1050-2947
VL  - 83
IS  - 3
PB  - American Physical Society
CY  - College Park
ER  - 
TY  - JOUR
A1  - Schaefer, Edith
A1  - Westendorf, Christian
A1  - Bodenschatz, Eberhard
A1  - Beta, Carsten
A1  - Geil, Burkhard
A1  - Janshoff, Andreas
T1  - Shape oscillations of dictyostelium discoideum cells on ultramicroelectrodes monitored by impedance analysis
JF  - Small
Y1  - 2011
U6  - https://doi.org/10.1002/smll.201001955
SN  - 1613-6810
VL  - 7
IS  - 6
SP  - 723
EP  - 726
PB  - Wiley-Blackwell
CY  - Malden
ER  - 
TY  - JOUR
A1  - Prosen, Tomaz
T1  - Complexity and nonseparability of classical Liouvillian dynamics
JF  - Physical review : E, Statistical, nonlinear and soft matter physics
N2  - We propose a simple complexity indicator of classical Liouvillian dynamics, namely the separability entropy, which determines the logarithm of an effective number of terms in a Schmidt decomposition of phase space density with respect to an arbitrary fixed product basis. We show that linear growth of separability entropy provides a stricter criterion of complexity than Kolmogorov-Sinai entropy, namely it requires that the dynamics be exponentially unstable, nonlinear, and non-Markovian.
Y1  - 2011
U6  - https://doi.org/10.1103/PhysRevE.83.031124
SN  - 1539-3755
VL  - 83
IS  - 3
PB  - American Physical Society
CY  - College Park
ER  - 
TY  - JOUR
A1  - Stich, Michael
A1  - Beta, Carsten
T1  - Standing waves in a complex Ginzburg-Landau equation with time-delay  feedback
JF  - Discrete and continuous dynamical systems : a journal bridging mathematics and sciences
N2  - Standing waves are studied as solutions of a complex Ginsburg-Landau equation subjected to local and global time-delay feedback terms. The onset of standing waves is studied at the instability of the homogeneous periodic solution with respect to spatially periodic perturbations. The solution of this spatiotemporal wave pattern is given and is compared to the homogeneous periodic solution.
KW  - pattern formation
KW  - reaction-diffusion system
KW  - control
Y1  - 2011
SN  - 1078-0947
SN  - 1553-5231
IS  - 1
SP  - 1329
EP  - 1334
PB  - American Institute of Mathematical Sciences
CY  - Springfield
ER  - 
TY  - JOUR
A1  - Kliesch, Martin
A1  - Barthel, Thomas
A1  - Gogolin, C.
A1  - Kastoryano, M.
A1  - Eisert, J.
T1  - Dissipative quantum church-turing theorem
JF  - Physical review letters
N2  - We show that the time evolution of an open quantum system, described by a possibly time dependent Liouvillian, can be simulated by a unitary quantum circuit of a size scaling polynomially in the simulation time and the size of the system. An immediate consequence is that dissipative quantum computing is no more powerful than the unitary circuit model. Our result can be seen as a dissipative Church-Turing theorem, since it implies that under natural assumptions, such as weak coupling to an environment, the dynamics of an open quantum system can be simulated efficiently on a quantum computer. Formally, we introduce a Trotter decomposition for Liouvillian dynamics and give explicit error bounds. This constitutes a practical tool for numerical simulations, e.g., using matrix-product operators. We also demonstrate that most quantum states cannot be prepared efficiently.
Y1  - 2011
U6  - https://doi.org/10.1103/PhysRevLett.107.120501
SN  - 0031-9007
VL  - 107
IS  - 12
PB  - American Physical Society
CY  - College Park
ER  - 
TY  - JOUR
A1  - Schuch, Norbert
A1  - Harrison, Sarah K.
A1  - Osborne, Tobias J.
A1  - Eisert, Jens
T1  - Information propagation for interacting-particle systems
JF  - Physical review : A, Atomic, molecular, and optical physics
N2  - We study the speed at which information propagates through systems of interacting quantum particles moving on a regular lattice and show that for a certain class of initial conditions there exists a maximum speed of sound at which information can propagate. Our argument applies equally to quantum spins, bosons such as in the Bose-Hubbard model, fermions, anyons, and general mixtures thereof, on arbitrary lattices of any dimension. It also pertains to dissipative dynamics on the lattice, and generalizes to the continuum for quantum fields. Our result can be seen as an analog of the Lieb-Robinson bound for strongly correlated models.
Y1  - 2011
U6  - https://doi.org/10.1103/PhysRevA.84.032309
SN  - 1050-2947
VL  - 84
IS  - 3
PB  - American Physical Society
CY  - College Park
ER  - 
TY  - JOUR
A1  - Schmah, Tanya
A1  - Marwan, Norbert
A1  - Thomsen, Jesper Skovhus
A1  - Saparin, Peter
T1  - Long range node-strut analysis of trabecular bone microarchitecture
JF  - Medical physics : the international journal of medical physics research and practice
N2  - Purpose: We present a new morphometric measure of trabecular bone microarchitecture, called mean node strength (NdStr), which is part of a newly developed approach called long range nodestrut analysis. Our general aim is to describe and quantify the apparent "latticelike" microarchitecture of the trabecular bone network.
 Methods: Similar in some ways to the topological node-strut analysis introduced by Garrahan et al. [J. Microsc. 142, 341-349 (1986)], our method is distinguished by an emphasis on long-range trabecular connectivity. Thus, while the topological classification of a pixel (after skeletonization) as a node, strut, or terminus, can be determined from the 3 x 3 neighborhood of that pixel, our method, which does not involve skeletonization, takes into account a much larger neighborhood. In addition, rather than giving a discrete classification of each pixel as a node, strut, or terminus, our method produces a continuous variable, node strength. The node strength is averaged over a region of interest to produce the mean node strength of the region.
 Results: We have applied our long range node-strut analysis to a set of 26 high-resolution peripheral quantitative computed tomography (pQCT) axial images of human proximal tibiae acquired 17 mm below the tibial plateau. We found that NdStr has a strong positive correlation with trabecular volumetric bone mineral density (BMD). After an exponential transformation, we obtain a Pearson's correlation coefficient of r - 0.97. Qualitative comparison of images with similar BMD but with very different NdStr values suggests that the latter measure has successfully quantified the prevalence of the "latticelike" microarchitecture apparent in the image. Moreover, we found a strong correlation (r - 0.62) between NdStr and the conventional node-terminus ratio (Nd/Tm) of Garrahan et al. The Nd/Tm ratios were computed using traditional histomorphometry performed on bone biopsies obtained at the same location as the pQCT scans.
 Conclusions: The newly introduced morphometric measure allows a quantitative assessment of the long-range connectivity of trabecular bone. One advantage of this method is that it is based on pQCT images that can be obtained noninvasively from patients, i.e., without having to obtain a bone biopsy from the patient.
KW  - trabecular bone
KW  - osteoporosis
KW  - structure analysis
KW  - histomorphometry
KW  - pQCT
Y1  - 2011
U6  - https://doi.org/10.1118/1.3622600
SN  - 0094-2405
VL  - 38
IS  - 9
SP  - 5003
EP  - 5011
PB  - American Association of Physicists in Medicine
CY  - Melville
ER  - 
TY  - JOUR
A1  - Hübener, Robert
A1  - Kruszynska, Caroline
A1  - Hartmann, Lorenz
A1  - Duer, Wolfgang
A1  - Plenio, Martin B.
A1  - Eisert, Jens
T1  - Tensor network methods with graph enhancement
JF  - Physical review : B, Condensed matter and materials physics
N2  - We present applications of the renormalization algorithm with graph enhancement (RAGE). This analysis extends the algorithms and applications given for approaches based on matrix product states introduced in [Phys. Rev. A 79, 022317 (2009)] to other tensor-network states such as the tensor tree states (TTS) and projected entangled pair states. We investigate the suitability of the bare TTS to describe ground states, showing that the description of certain graph states and condensed-matter models improves. We investigate graph-enhanced tensor-network states, demonstrating that in some cases (disturbed graph states and for certain quantum circuits) the combination of weighted graph states with TTS can greatly improve the accuracy of the description of ground states and time-evolved states. We comment on delineating the boundary of the classically efficiently simulatable states of quantum many-body systems.
Y1  - 2011
U6  - https://doi.org/10.1103/PhysRevB.84.125103
SN  - 1098-0121
VL  - 84
IS  - 12
PB  - American Physical Society
CY  - College Park
ER  - 
TY  - GEN
A1  - Qiu, Xunlin
T1  - Patterned piezo-, pyro-, and ferroelectricity of poled polymer electrets
T2  - Journal of applied physics
Y1  - 2011
U6  - https://doi.org/10.1063/1.3638069
SN  - 0021-8979
VL  - 110
IS  - 5
PB  - American Institute of Physics
CY  - Melville
ER  - 
TY  - JOUR
A1  - Lokstein, Heiko
A1  - Krikunova, Maria
A1  - Teuchner, Klaus
A1  - Voigt, Bernd
T1  - Elucidation of structure-function relationships in photosynthetic light-harvesting antenna complexes by non-linear polarization spectroscopy in the frequency domain (NLPF)
JF  - Journal of plant physiology : biochemistry, physiology, molecular biology and biotechnology of plants
N2  - Photosynthetically active pigments are usually organized into pigment-protein complexes. These include light-harvesting antenna complexes (LHCs) and reaction centers. Site energies of the bound pigments are determined by interactions with their environment, i.e., by pigment-protein as well as pigment-pigment interactions. Thus, resolution of spectral substructures of the pigment-protein complexes may provide valuable insight into structure-function relationships.
 By means of conventional (linear) and time-resolved spectroscopic techniques, however, it is often difficult to resolve the spectral substructures of complex pigment-protein assemblies. Nonlinear polarization spectroscopy in the frequency domain (NLPF) is shown to be a valuable technique in this regard. Based on initial experimental work with purple bacterial antenna complexes as well as model systems NLPF has been extended to analyse the substructure(s) of very complex spectra, including analyses of interactions between chlorophylls and "optically dark" states of carotenoids in LHCs. The paper reviews previous work and outlines perspectives regarding the application of NLPF spectroscopy to disentangle structure-function relationships in pigment-protein complexes.
KW  - Excitonic interactions
KW  - Laser spectroscopy
KW  - Light-harvesting complex
KW  - Nonlinear polarization spectroscopy in the frequency domain
KW  - Pigment-pigment interactions
Y1  - 2011
U6  - https://doi.org/10.1016/j.jplph.2010.12.012
SN  - 0176-1617
VL  - 168
IS  - 12
SP  - 1488
EP  - 1496
PB  - Elsevier
CY  - Jena
ER  - 
TY  - JOUR
A1  - Blakesley, James C.
A1  - Neher, Dieter
T1  - Relationship between energetic disorder and open-circuit voltage in bulk heterojunction organic solar cells
JF  - Physical review : B, Condensed matter and materials physics
N2  - We simulate organic bulk heterojunction solar cells. The effects of energetic disorder are incorporated through a Gaussian or exponential model of density of states. Analytical models of open-circuit voltage (V(OC)) are derived from the splitting of quasi-Fermi potentials. Their predictions are backed up by more complex numerical device simulations including effects such as carrier-density-dependent charge-carrier mobilities. It is predicted that the V(OC) depends on: (1) the donor-acceptor energy gap; (2) charge-carrier recombination rates; (3) illumination intensity; (4) the contact work functions (if not in the pinning regime); and (5) the amount of energetic disorder. A large degree of energetic disorder, or a high density of traps, is found to cause significant reductions in V(OC). This can explain why V(OC) is often less than expected in real devices. Energetic disorder also explains the nonideal temperature and intensity dependence of V(OC) and the superbimolecular recombination rates observed in many real bulk heterojunction solar cells.
Y1  - 2011
U6  - https://doi.org/10.1103/PhysRevB.84.075210
SN  - 1098-0121
VL  - 84
IS  - 7
PB  - American Physical Society
CY  - College Park
ER  - 
TY  - JOUR
A1  - Schütz, Nadine
A1  - Holschneider, Matthias
T1  - Detection of trend changes in time series using Bayesian inference
JF  - Physical review : E, Statistical, nonlinear and soft matter physics
N2  - Change points in time series are perceived as isolated singularities where two regular trends of a given signal do not match. The detection of such transitions is of fundamental interest for the understanding of the system's internal dynamics or external forcings. In practice observational noise makes it difficult to detect such change points in time series. In this work we elaborate on a Bayesian algorithm to estimate the location of the singularities and to quantify their credibility. We validate the performance and sensitivity of our inference method by estimating change points of synthetic data sets. As an application we use our algorithm to analyze the annual flow volume of the Nile River at Aswan from 1871 to 1970, where we confirm a well-established significant transition point within the time series.
Y1  - 2011
U6  - https://doi.org/10.1103/PhysRevE.84.021120
SN  - 1539-3755
SN  - 1550-2376
VL  - 84
IS  - 2
PB  - American Physical Society
CY  - College Park
ER  - 
TY  - JOUR
A1  - Sun, Zhongkui
A1  - Yang, Xiaoli
T1  - Generating and enhancing lag synchronization of chaotic systems by white noise
JF  - Chaos : an interdisciplinary journal of nonlinear science
N2  - In this paper, we study the crucial impact of white noise on lag synchronous regime in a pair of time-delay unidirectionally coupled systems. Our result demonstrates that merely via white-noise-based coupling lag synchronization could be achieved between the coupled systems (chaotic or not). And it is also demonstrated that a conventional lag synchronous regime can be enhanced by white noise. Sufficient conditions are further proved mathematically for noise-inducing and noise-enhancing lag synchronization, respectively. Additionally, the influence of parameter mismatch on the proposed lag synchronous regime is studied, by which we announce the robustness and validity of the new strategy. Two numerical examples are provided to illustrate the validity and some possible applications of the theoretical result.
Y1  - 2011
U6  - https://doi.org/10.1063/1.3623440
SN  - 1054-1500
SN  - 1089-7682
VL  - 21
IS  - 3
PB  - American Institute of Physics
CY  - Melville
ER  - 
TY  - JOUR
A1  - Winkel, B.
A1  - Ben Bekhti, Nadya
A1  - Darmstaedter, V.
A1  - Floeer, L.
A1  - Kerp, J.
A1  - Richter, Philipp
T1  - The high-velocity cloud complex Galactic center negative as seen by EBHIS and GASS I. Cloud catalog and global properties
JF  - Astronomy and astrophysics : an international weekly journal
N2  - Using Milky Way data of the new Effelsberg-Bonn HI Survey (EBHIS) and the Galactic All-Sky Survey (GASS), we present a revised picture of the high-velocity cloud (HVC) complex Galactic center negative (GCN). Owing to the higher angular resolution of these surveys compared to previous studies (e.g., the Leiden Dwingeloo Survey), we resolve complex GCN into lots of individual tiny clumps, that mostly have relatively broad line widths of more than 15 km s(-1). We do not detect a diffuse extended counterpart, which is unusual for an HVC complex. In total 243 clumps were identified and parameterized which allows us to statistically analyze the data. Cold-line components (i.e.,Delta upsilon(fwhm) < 7.5 km s(-1)) are found in about 5% only of the identified cloudlets. Our analysis reveals that complex GCN is likely built up of several subpopulations that do not share a common origin. Furthermore, complex GCN might be a prime example for warm-gas accretion onto the Milky Way, where neutral HI clouds are not stable against interaction with the Milky Way gas halo and become ionized prior to accretion.
KW  - ISM: clouds
KW  - Galaxy: halo
Y1  - 2011
U6  - https://doi.org/10.1051/0004-6361/201117357
SN  - 0004-6361
VL  - 533
IS  - 18
PB  - EDP Sciences
CY  - Les Ulis
ER  - 
TY  - JOUR
A1  - Green, Luci M.
A1  - Kliem, Bernhard
A1  - Wallace, A. J.
T1  - Photospheric flux cancellation and associated flux rope formation and eruption
JF  - Astronomy and astrophysics : an international weekly journal
N2  - Aims. We study an evolving bipolar active region that exhibits flux cancellation at the internal polarity inversion line, the formation of a soft X-ray sigmoid along the inversion line and a coronal mass ejection. The aim is to investigate the quantity of flux cancellation that is involved in flux rope formation in the time period leading up to the eruption.
 Methods. The active region is studied using its extreme ultraviolet and soft X-ray emissions as it evolves from a sheared arcade to flux rope configuration. The evolution of the photospheric magnetic field is described and used to estimate how much flux is reconnected into the flux rope.
 Results. About one third of the active region flux cancels at the internal polarity inversion line in the 2.5 days leading up to the eruption. In this period, the coronal structure evolves from a weakly to a highly sheared arcade and then to a sigmoid that crosses the inversion line in the inverse direction. These properties suggest that a flux rope has formed prior to the eruption. The amount of cancellation implies that up to 60% of the active region flux could be in the body of the flux rope. We point out that only part of the cancellation contributes to the flux in the rope if the arcade is only weakly sheared, as in the first part of the evolution. This reduces the estimated flux in the rope to similar to 30% or less of the active region flux. We suggest that the remaining discrepancy between our estimate and the limiting value of similar to 10% of the active region flux, obtained previously by the flux rope insertion method, results from the incomplete coherence of the flux rope, due to nonuniform cancellation along the polarity inversion line. A hot linear feature is observed in the active region which rises as part of the eruption and then likely traces out the field lines close to the axis of the flux rope. The flux cancellation and changing magnetic connections at one end of this feature suggest that the flux rope reaches coherence by reconnection immediately before and early in the impulsive phase of the associated flare. The sigmoid is destroyed in the eruption but reforms quickly, with the amount of cancellation involved being much smaller than in the course of its original formation.
KW  - Sun: activity
KW  - Sun: coronal mass ejections (CMEs)
KW  - magnetic fields
KW  - magnetic reconnection
KW  - Sun: photosphere
KW  - Sun: magnetic topology
Y1  - 2011
U6  - https://doi.org/10.1051/0004-6361/201015146
SN  - 0004-6361
VL  - 526
IS  - 2
PB  - EDP Sciences
CY  - Les Ulis
ER  - 
TY  - JOUR
A1  - Hoffmann, Katrin
A1  - Dietzel, Birgit
A1  - Schulz, Burkhard
A1  - Reck, Guenter
A1  - Hoffmann, Angelika
A1  - Orgzall, Ingo
A1  - Resch-Genger, Ute
A1  - Emmerling, Franziska
T1  - Combined structural and fluorescence studies of methyl-substituted 2,5-diphenyl-1,3,4-oxadiazoles - Relation between electronic properties and packing motifs
JF  - Journal of molecular structure
N2  - Prerequisite for the rational design of functional organic materials with tailor-made electronic properties is the knowledge of the structure-property relationship for the specific class of molecules under consideration. This encouraged us to systematically study the influence of the molecular structure and substitution pattern of aromatically substituted 1,3,4-oxadiazoles on the electronic properties and packing motifs of these molecules and on the interplay of these factors. For this purpose, seven diphenyl-oxadiazoles equipped with methyl substituents in the ortho- and meta-position(s) were synthesized and characterized. Absorption and fluorescence spectra in solution served here as tools to monitor substitution-induced changes in the electronic properties of the individual molecules whereas X-ray and optical measurements in the solid state provided information on the interplay of electronic and packing effects. In solution, the spectral position of the absorption maximum, the size of Stokes shift, and the fluorescence quantum yield are considerably affected by ortho-substitution in three or four ortho-positions. This results in blue shifted absorption bands, increased Stokes shifts, and reduced fluorescence quantum yields whereas the spectral position and vibrational structure of the emission bands remain more or less unaffected. In the crystalline state, however, the spectral position and shape of the emission bands display a strong dependence on the molecular structure and/or packing motifs that seem to control the amount of dye-dye-interactions. These observations reveal the limited value of commonly reported absorption and fluorescence measurements in solution for a straightforward comparison of spectroscopic results with single X-ray crystallography. This underlines the importance of solid state spectroscopic studies for a better understanding of the interplay of electronic effects and molecular order.
KW  - Diphenyl-oxadiazoles
KW  - X-ray structure
KW  - Packing motif
KW  - Optical properties
KW  - Fluorescence quantum yield
Y1  - 2011
U6  - https://doi.org/10.1016/j.molstruc.2010.11.071
SN  - 0022-2860
VL  - 988
IS  - 1-3
SP  - 35
EP  - 46
PB  - Elsevier
CY  - Amsterdam
ER  - 
TY  - JOUR
A1  - Kuehn, Sergei
A1  - Pingel, Patrick
A1  - Breusing, Markus
A1  - Fischer, Thomas
A1  - Stumpe, Joachim
A1  - Neher, Dieter
A1  - Elsaesser, Thomas
T1  - High-Resolution Near-Field Optical Investigation of Crystalline Domains in Oligomeric PQT-12 Thin Films
JF  - Advanced functional materials
N2  - The structure and morphology on different length scales dictate both the electrical and optical properties of organic semiconductor thin films. Using a combination of spectroscopic methods, including scanning near-field optical microscopy, we study the domain structure and packing quality of highly crystalline thin films of oligomeric PQT-12 with 100 nanometer spatial resolution. The pronounced optical anisotropy of these layers measured by polarized light microscopy facilitates the identification of regions with uniform molecular orientation. We find that a hierarchical order on three different length scales exists in these layers, made up of distinct well-ordered dichroic areas at the ten-micrometer-scale, which are sub-divided into domains with different molecular in-plane orientation. These serve as a template for the formation of smaller needle-like crystallites at the layer surface. A high degree of crystalline order is believed to be the cause of the rather high field-effect mobility of these layers of 10(-3) cm 2 V(-1) s(-1), whereas it is limited by the presence of domain boundaries at macroscopic distances.
Y1  - 2011
U6  - https://doi.org/10.1002/adfm.201001978
SN  - 1616-301X
VL  - 21
IS  - 5
SP  - 860
EP  - 868
PB  - Wiley-Blackwell
CY  - Malden
ER  - 
TY  - JOUR
A1  - Hoban, Matty J.
A1  - Campbell, Earl T.
A1  - Loukopoulos, Klearchos
A1  - Browne, Dan E.
T1  - Non-adaptive measurement-based quantum computation and multi-party Bell inequalities
JF  - New journal of physics : the open-access journal for physics
N2  - Quantum correlations exhibit behaviour that cannot be resolved with a local hidden variable picture of the world. In quantum information, they are also used as resources for information processing tasks, such as measurement-based quantum computation (MQC). In MQC, universal quantum computation can be achieved via adaptive measurements on a suitable entangled resource state. In this paper, we look at a version of MQC in which we remove the adaptivity of measurements and aim to understand what computational abilities remain in the resource. We show that there are explicit connections between this model of computation and the question of non-classicality in quantum correlations. We demonstrate this by focusing on deterministic computation of Boolean functions, in which natural generalizations of the Greenberger-Horne-Zeilinger paradox emerge; we then explore probabilistic computation via, which multipartite Bell inequalities can be defined. We use this correspondence to define families of multi-party Bell inequalities, which we show to have a number of interesting contrasting properties.
Y1  - 2011
U6  - https://doi.org/10.1088/1367-2630/13/2/023014
SN  - 1367-2630
VL  - 13
IS  - 1
PB  - IOP Publ. Ltd.
CY  - Bristol
ER  - 
TY  - JOUR
A1  - Reiche, Jürgen
A1  - Kratz, Karl
A1  - Hofmann, Dieter
A1  - Lendlein, Andreas
T1  - Current status of Langmuir monolayer degradation of polymeric biomaterials
JF  - The international journal of artificial organs
N2  - Langmuir monolayer degradation (LMD) experiments with polymers possessing outstanding biomedical application potential yield information regarding the kinetics of their hydrolytic or enzymatic chain scission under well-defined and adjustable degradation conditions. A brief review is given of LMD investigations, including the author's own work on 2-dimensional (2D) polymer systems, providing chain scission data, which are not disturbed by simultaneously occurring transport phenomena, such as water penetration into the sample or transport of scission fragments out of the sample.
 A knowledge-based approach for the description and simulation of polymer hydrolytic and enzymatic degradation based on a combination of fast LMD experiments and computer simulation of the water penetration is briefly introduced. Finally, the advantages and disadvantages of this approach are discussed.
KW  - Monolayer
KW  - Hydrolytic degradation
KW  - Enzymatic degradation
KW  - Biomaterial
KW  - Degradable polymer
Y1  - 2011
U6  - https://doi.org/10.5301/IJAO.2011.6401
SN  - 0391-3988
VL  - 34
IS  - 2
SP  - 123
EP  - 128
PB  - Wichtig
CY  - Milano
ER  - 
TY  - JOUR
A1  - Giewekemeyer, K.
A1  - Krueger, S. P.
A1  - Kalbfleisch, S.
A1  - Bartels, Meike
A1  - Beta, Carsten
A1  - Salditt, T.
T1  - X-ray propagation microscopy of biological cells using waveguides as a quasipoint source
JF  - Physical review : A, Atomic, molecular, and optical physics
N2  - We have used x-ray waveguides as highly confining optical elements for nanoscale imaging of unstained biological cells using the simple geometry of in-line holography. The well-known twin-image problem is effectively circumvented by a simple and fast iterative reconstruction. The algorithm which combines elements of the classical Gerchberg-Saxton scheme and the hybrid-input-output algorithm is optimized for phase-contrast samples, well-justified for imaging of cells at multi-keV photon energies. The experimental scheme allows for a quantitative phase reconstruction from a single holographic image without detailed knowledge of the complex illumination function incident on the sample, as demonstrated for freeze-dried cells of the eukaryotic amoeba Dictyostelium discoideum. The accessible resolution range is explored by simulations, indicating that resolutions on the order of 20 nm are within reach applying illumination times on the order of minutes at present synchrotron sources.
Y1  - 2011
U6  - https://doi.org/10.1103/PhysRevA.83.023804
SN  - 1050-2947
VL  - 83
IS  - 2
PB  - American Physical Society
CY  - College Park
ER  - 
TY  - JOUR
A1  - Kofod, Guggi
A1  - Risse, Sebastian
A1  - Stoyanov, Hristiyan
A1  - McCarthy, Denis N.
A1  - Sokolov, Sergey
A1  - Krähnert, Ralph
T1  - Broad-spectrum enhancement of polymer composite dielectric constant at ultra low volume fractions of silica-supported copper nanoparticles
JF  - ACS nano
N2  - A new strategy for the synthesis of high permittivity polymer composites is demonstrated based on well-defined spatial distribution of ultralow amounts of conductive nanoparticles. The spatial distribution Was realized by immobilizing Cu nanoparticles within the pore system of Alia microspheres, preventing direct contact between individual Cu particles. Both Cu-loaded and unloaded silica microspheres were-then used as fillers in polymer composites prepared with thermoplastic SEBS rubber is the matrix. With a metallic Cu content of about 0.26 vol % In the compoilte, a relative increase of 94% In real permittivity was obtained. No Cu-induced relaxations were observed in the dielectric spectrum within the studied frequency range of 0.1 Hz to 1 MHz. When related to the amount of conductive nanoparticles, the obtained composites achieve the highest broad spectrum enhancement of permittivity ever reported for a polymer based composite.
KW  - nanocomposite
KW  - broad-spectrum permittivity enhancement
KW  - metal nanoparticles
KW  - uniform spatial arrangement
Y1  - 2011
U6  - https://doi.org/10.1021/nn103097q
SN  - 1936-0851
VL  - 5
IS  - 3
SP  - 1623
EP  - 1629
PB  - American Chemical Society
CY  - Washington
ER  - 
TY  - JOUR
A1  - Lachmuth, Susanne
A1  - Durka, Walter
A1  - Schurr, Frank Martin
T1  - Differentiation of reproductive and competitive ability in the invaded range of Senecio inaequidens  the role of genetic Allee effects, adaptive and nonadaptive evolution
JF  - New phytologist : international journal of plant science
N2  - Genetic differentiation in the competitive and reproductive ability of invading populations can result from genetic Allee effects or r/K selection at the local or range-wide scale. However, the neutral relatedness of populations may either mask or falsely suggest adaptation and genetic Allee effects.
 In a common-garden experiment, we investigated the competitive and reproductive ability of invasive Senecio inaequidens populations that vary in neutral genetic diversity, population age and field vegetation cover. To account for population relatedness, we analysed the experimental results with 'animal models' adopted from quantitative genetics.
 Consistent with adaptive r/K differentiation at local scales, we found that genotypes from low-competition environments invest more in reproduction and are more sensitive to competition. By contrast, apparent effects of large-scale r/K differentiation and apparent genetic Allee effects can largely be explained by neutral population relatedness.
 Invading populations should not be treated as homogeneous groups, as they may adapt quickly to small-scale environmental variation in the invaded range. Furthermore, neutral population differentiation may strongly influence invasion dynamics and should be accounted for in analyses of common-garden experiments.
KW  - animal models
KW  - biological invasions
KW  - genetic Allee effects
KW  - interspecific competition
KW  - life history evolution
KW  - nonadaptive evolution
KW  - r and K selection
KW  - reproduction
Y1  - 2011
U6  - https://doi.org/10.1111/j.1469-8137.2011.03808.x
SN  - 0028-646X
VL  - 192
IS  - 2
SP  - 529
EP  - 541
PB  - Wiley-Blackwell
CY  - Malden
ER  - 
TY  - JOUR
A1  - Hundertmark, Michaela
A1  - Dimova, Rumiana
A1  - Lengefeld, Jan
A1  - Seckler, Robert
A1  - Hincha, Dirk K.
T1  - The intrinsically disordered late embryogenesis abundant protein LEA18 from Arabidopsis thaliana modulates membrane stability through binding and folding
JF  - Biochimica et biophysica acta : Biomembranes
N2  - Intrinsically disordered proteins (IDPs) constitute a substantial part of cellular proteomes. late embryogenesis abundant (LEA) proteins are mostly predicted to be IDPs associated with dehydration tolerance in many plant, animal and bacterial species. Their functions, however, are largely unexplored and also their structure and interactions with potential target molecules have only recently been experimentally investigated in a small number of proteins. Here, we report on the structure and interactions with membranes of the Pfam LEA_1 protein LEA18 from the higher plant Arabidopsis thaliana. This functionally uncharacterized positively charged protein specifically aggregated and destabilized negatively charged liposomes. Isothermal titration calorimetry showed binding of the protein to both charged and uncharged membranes. LEA18 alone was largely unstructured in solution. While uncharged membranes had no influence on the secondary structure of LEA18, the protein partially folded into beta-sheet structure in the presence of negatively charged liposomes. These data suggest that LEA18 does not function as a membrane stabilizing protein, as suggested for other LEA proteins. Instead, a possible function of LEA18 could be the composition-dependent modulation of membrane stability, e.g., during signaling or vesicle-mediated transport.
KW  - Intrinsically disordered protein
KW  - Late embryogenesis abundant protein
KW  - Membrane stability
KW  - Protein-membrane interaction
KW  - Protein folding
Y1  - 2011
U6  - https://doi.org/10.1016/j.bbamem.2010.09.010
SN  - 0005-2736
VL  - 1808
IS  - 1
SP  - 446
EP  - 453
PB  - Elsevier
CY  - Amsterdam
ER  - 
TY  - JOUR
A1  - Belova, Valentina
A1  - Shchukin, Dmitry G.
A1  - Gorin, Dmitry A.
A1  - Kopyshev, Alexey
A1  - Moehwald, Helmuth
T1  - A new approach to nucleation of cavitation bubbles at chemically modified surfaces
JF  - Physical chemistry, chemical physics : a journal of European Chemical Societies
N2  - Cavitation at the solid surface normally begins with nucleation, in which defects or assembled molecules located at a liquid-solid interface act as nucleation centers and are actively involved in the evolution of cavitation bubbles. Here, we propose a simple approach to evaluate the behavior of cavitation bubbles formed under high intensity ultrasound (20 kHz, 51.3 W cm (2)) at solid surfaces, based on sonication of patterned substrates with a small roughness (less than 3 nm) and controllable surface energy. A mixture of octadecylphosphonic acid (ODTA) and octadecanethiol (ODT) was stamped on the Si wafer coated with different thicknesses of an aluminium layer (20-500 nm). We investigated the growth mechanism of cavitation bubble nuclei and the evolution of individual pits (defects) formed under sonication on the modified surface. A new activation behavior as a function of Al thickness, sonication time, ultrasonic power and temperature is reported. In this process cooperativity is introduced, as initially formed pits further reduce the energy to form bubbles. Furthermore, cavitation on the patterns is a controllable process, where up to 40-50 min of sonication time only the hydrophobic areas are active nucleation sites. This study provides a convincing proof of our theoretical approach on nucleation.
Y1  - 2011
U6  - https://doi.org/10.1039/c1cp20218a
SN  - 1463-9076
VL  - 13
IS  - 17
SP  - 8015
EP  - 8023
PB  - Royal Society of Chemistry
CY  - Cambridge
ER  - 
TY  - JOUR
A1  - Robinson, Alexander
A1  - Calov, Reinhard
A1  - Ganopolski, Andrey
T1  - Greenland ice sheet model parameters constrained using simulations of the Eemian Interglacial
JF  - Climate of the past : an interactive open access journal of the European Geosciences Union
N2  - Using a new approach to force an ice sheet model, we performed an ensemble of simulations of the Greenland Ice Sheet evolution during the last two glacial cycles, with emphasis on the Eemian Interglacial. This ensemble was generated by perturbing four key parameters in the coupled regional climate-ice sheet model and by introducing additional uncertainty in the prescribed "background" climate change. The sensitivity of the surface melt model to climate change was determined to be the dominant driver of ice sheet instability, as reflected by simulated ice sheet loss during the Eemian Interglacial period. To eliminate unrealistic parameter combinations, constraints from present-day and paleo information were applied. The constraints include (i) the diagnosed present-day surface mass balance partition between surface melting and ice discharge at the margin, (ii) the modeled present-day elevation at GRIP; and (iii) the modeled elevation reduction at GRIP during the Eemian. Using these three constraints, a total of 360 simulations with 90 different model realizations were filtered down to 46 simulations and 20 model realizations considered valid. The paleo constraint eliminated more sensitive melt parameter values, in agreement with the surface mass balance partition assumption. The constrained simulations resulted in a range of Eemian ice loss of 0.4-4.4m sea level equivalent, with a more likely range of about 3.7-4.4m sea level if the GRIP delta O-18 isotope record can be considered an accurate proxy for the precipitation-weighted annual mean temperatures.
Y1  - 2011
U6  - https://doi.org/10.5194/cp-7-381-2011
SN  - 1814-9324
VL  - 7
IS  - 2
SP  - 381
EP  - 396
PB  - Copernicus
CY  - Göttingen
ER  - 
TY  - JOUR
A1  - Baushev, Anton N.
T1  - Principal properties of the velocity distribution of dark matter particles on the outskirts of the Solar system
JF  - Monthly notices of the Royal Astronomical Society
N2  - The velocity distribution of the dark matter particles on the outskirts of the Solar system remains unclear. We suggest to determine it using experimentally found properties of the oldest halo objects. Indeed, the oldest halo stars and globular clusters form a collisionless system, as well as dark matter particles do, and they evolved in the same gravitational field. If we accept this analogy, we can show that the velocity distribution of the dark matter particles should be highly anisotropic and have a sharp maximum near upsilon similar to 500 km s(-1). The distribution is totally different from the Maxwell one.
 We analyse the influence of the distribution function on the results of dark matter detection experiments. It is found that the direct detection signal should differ noticeably from the one calculated from the Maxwell distribution with <upsilon > similar or equal to 220 km s(-1), which is conventional for direct detection experiments (the ratio depends on the detector properties and typically falls within the range between 6 and 0.2). Moreover, the sharp distinction from the Maxwell distribution can be very essential to the observations of dark matter annihilation.
KW  - elementary particles
KW  - methods: analytical
KW  - dark matter
Y1  - 2011
U6  - https://doi.org/10.1111/j.1745-3933.2011.01125.x
SN  - 0035-8711
VL  - 417
IS  - 1
SP  - L83
EP  - L87
PB  - Wiley-Blackwell
CY  - Malden
ER  - 
TY  - JOUR
A1  - Blakesley, James C.
A1  - Schubert, Marcel
A1  - Steyrleuthner, Robert
A1  - Chen, Zhihua
A1  - Facchetti, Antonio
A1  - Neher, Dieter
T1  - Time-of-flight measurements and vertical transport in a high electron-mobility polymer
JF  - Applied physics letters
N2  - We investigate charge transport in a high-electron mobility polymer, poly(N, N-bis 2-octyldodecyl-naphthalene-1,4,5,8-bis dicarboximide-2,6-diyl-alt-5,5-2,2-bithiophene) [P(NDI2OD-T2), Polyera ActivInk (TM) N2200]. Time-of-flight measurements reveal electron mobilities approaching those measured in field-effect transistors, the highest ever recorded in a conjugated polymer using this technique. The modest temperature dependence and weak dispersion of the transients indicate low energetic disorder in this material. Steady-state electron-only current measurements reveal a barrier to injection of about 300 meV. We propose that this barrier is located within the P(NDI2OD-T2) film and arises from molecular orientation effects.
Y1  - 2011
U6  - https://doi.org/10.1063/1.3657827
SN  - 0003-6951
VL  - 99
IS  - 18
PB  - American Institute of Physics
CY  - Melville
ER  - 
TY  - JOUR
A1  - Berenstein, Igal
A1  - Beta, Carsten
T1  - Flow-induced control of chemical turbulence
JF  - The journal of chemical physics : bridges a gap between journals of physics and journals of chemistr
N2  - We report spatiotemporal chaos in the Oregonator model of the Belousov-Zhabotinsky reaction. Spatiotemporal chaos spontaneously develops in a regime, where the underlying local dynamics show stable limit cycle oscillations (diffusion-induced turbulence). We show that spatiotemporal chaos can be suppressed by a unidirectional flow in the system. With increasing flow velocity, we observe a transition scenario from spatiotemporal chaos via a regime of travelling waves to a stationary steady state. At large flow velocities, we recover the known regime of flow distributed oscillations.
KW  - chaos
KW  - chemical equilibrium
KW  - chemically reactive flow
KW  - reaction kinetics theory
KW  - spatiotemporal phenomena
KW  - turbulence
Y1  - 2011
U6  - https://doi.org/10.1063/1.3656248
SN  - 0021-9606
VL  - 135
IS  - 16
PB  - American Institute of Physics
CY  - Melville
ER  - 
TY  - JOUR
A1  - Kiel, Mareike
A1  - Möhwald, Helmuth
A1  - Bargheer, Matias
T1  - Broadband measurements of the transient optical complex dielectric function of a nanoparticle/polymer composite upon ultrafast excitation
JF  - Physical review : B, Condensed matter and materials physics
N2  - We determined experimentally the complex transient optical dielectric function of a well-characterized polyelectrolyte/gold-nanoparticle composite system over a broad spectral range upon short pulse laser excitation by simultaneously measuring the time-dependent reflectance and transmittance of white light pulses with femtosecond pump-probe spectroscopy. We extracted directly the ultrafast changes in the real and imaginary parts of the effective dielectric function, epsilon(eff)(r) (omega,t)and epsilon(eff)(i) (omega,t), from the experiment. This complete experimental set of information on the time-dependent complex dielectric function challenges theories modeling the transient dielectric function of gold particles and the effective medium.
Y1  - 2011
U6  - https://doi.org/10.1103/PhysRevB.84.165121
SN  - 1098-0121
VL  - 84
IS  - 16
PB  - American Physical Society
CY  - College Park
ER  - 
TY  - JOUR
A1  - Khader, Patrick H.
A1  - Pachur, Thorsten
A1  - Meier, Stefanie
A1  - Bien, Siegfried
A1  - Jost, Kerstin
A1  - Roesler, Frank
T1  - Memory-based decision-making with heuristics evidence for a controlled activation of memory representations
JF  - Journal of cognitive neuroscience
N2  - Many of our daily decisions are memory based, that is, the attribute information about the decision alternatives has to be recalled. Behavioral studies suggest that for such decisions we often use simple strategies (heuristics) that rely on controlled and limited information search. It is assumed that these heuristics simplify decision-making by activating long-term memory representations of only those attributes that are necessary for the decision. However, from behavioral studies alone, it is unclear whether using heuristics is indeed associated with limited memory search. The present study tested this assumption by monitoring the activation of specific long-term-memory representations with fMRI while participants made memory-based decisions using the "take-the-best" heuristic. For different decision trials, different numbers and types of information had to be retrieved and processed. The attributes consisted of visual information known to be represented in different parts of the posterior cortex. We found that the amount of information required for a decision was mirrored by a parametric activation of the dorsolateral PFC. Such a parametric pattern was also observed in all posterior areas, suggesting that activation was not limited to those attributes required for a decision. However, the posterior increases were systematically modulated by the relative importance of the information for making a decision. These findings suggest that memory-based decision-making is mediated by the dorsolateral PFC, which selectively controls posterior storage areas. In addition, the systematic modulations of the posterior activations indicate a selective boosting of activation of decision-relevant attributes.
Y1  - 2011
SN  - 0898-929X
VL  - 23
IS  - 11
SP  - 3540
EP  - 3554
PB  - MIT Press
CY  - Cambridge
ER  - 
TY  - JOUR
A1  - Huang, Tingwen
A1  - Chen, Guanrong
A1  - Kurths, Jürgen
T1  - Synchronization of chaotic of chaotic systems with time-varying coupöing delays
JF  - Discrete and continuous dynamical systems : a journal bridging mathematics and sciences ; Series B, Mathematical modelling, analysis and computations
N2  - In this paper, we study the complete synchronization of a class of time-varying delayed coupled chaotic systems using feedback control. In terms of Linear Matrix Inequalities, a sufficient condition is obtained through using a Lyapunov-Krasovskii functional and differential equation in equalities. The conditions can be easily verified and implemented. We present two simulation examples to illustrate the effectiveness of the proposed method.
KW  - Synchronization
KW  - Chaotic System
KW  - Time-varying Delay
Y1  - 2011
U6  - https://doi.org/10.3934/dcdsb.2011.16.1071
SN  - 1531-3492
VL  - 16
IS  - 4
SP  - 1071
EP  - 1082
PB  - American Institute of Mathematical Sciences
CY  - Springfield
ER  - 
TY  - JOUR
A1  - Shayduk, Roman
A1  - Navirian, Hengameh
A1  - Leitenberger, Wolfram
A1  - Goldshteyn, Jevgenij
A1  - Vrejoiu, Ionela
A1  - Weinelt, Martin
A1  - Gaal, Peter
A1  - Herzog, Marc
A1  - von Korff Schmising, Clemens
A1  - Bargheer, Matias
T1  - Nanoscale heat transport studied by high-resolution time-resolved x-ray diffraction
JF  - New journal of physics : the open-access journal for physics
N2  - We report on synchrotron-based high-repetition rate ultrafast x-ray diffraction (UXRD) experiments monitoring the transport of heat from an epitaxial La(0.7)Sr(0.3)MnO(3)/SrTiO(3) superlattice (SL) into the substrate on timescales from 100 ps to 4 mu s. Transient thermal lattice expansion was determined with an accuracy of 10(-7), corresponding to a sensitivity to temperature changes down to 0.01 K. We follow the heat flow within the SL and into the substrate after the impulsive laser heating leads to a small temperature rise of Delta T = 6 K. The transient lattice temperature can be simulated very well using the bulk heat conductivities. This contradicts the interpretation of previous UXRD measurements, which predicted a long-lasting expansion of SrRuO(3) for more than 200 ps. The disagreement could be resolved by assuming that the heat conductivity changes in the first hundred picoseconds.
Y1  - 2011
U6  - https://doi.org/10.1088/1367-2630/13/9/093032
SN  - 1367-2630
VL  - 13
IS  - 11
PB  - IOP Publ. Ltd.
CY  - Bristol
ER  - 
TY  - JOUR
A1  - Beta, Carsten
A1  - Bodenschatz, Eberhard
T1  - Microfluidic tools for quantitative studies of eukaryotic chemotaxis
JF  - European journal of cell biology
N2  - Over the past decade, microfluidic techniques have been established as a versatile platform to perform live cell experiments under well-controlled conditions. To investigate the directional responses of cells, stable concentration profiles of chemotactic factors can be generated in microfluidic gradient mixers that provide a high degree of spatial control. However, the times for built-up and switching of gradient profiles are in general too slow to resolve the intracellular protein translocation events of directional sensing of eukaryotes. Here, we review an example of a conventional microfluidic gradient mixer as well as the novel flow photolysis technique that achieves an increased temporal resolution by combining the photo-activation of caged compounds with the advantages of microfluidic chambers.
KW  - Eukaryotic chemotaxis
KW  - Dictyostelium discoideum
KW  - Microfluidics
KW  - Caged compounds
KW  - Numerical simulations
Y1  - 2011
U6  - https://doi.org/10.1016/j.ejcb.2011.05.006
SN  - 0171-9335
VL  - 90
IS  - 10
SP  - 811
EP  - 816
PB  - Elsevier
CY  - Jena
ER  - 
TY  - JOUR
A1  - Koseska, Aneta
A1  - Volkov, Evgenii
A1  - Kurths, Jürgen
T1  - Synthetic multicellular oscillatory systems controlling protein dynamics with genetic circuits
JF  - Physica scripta : an international journal for experimental and theoretical physics
N2  - Synthetic biology is a relatively new research discipline that combines standard biology approaches with the constructive nature of engineering. Thus, recent efforts in the field of synthetic biology have given a perspective to consider cells as 'programmable matter'. Here, we address the possibility of using synthetic circuits to control protein dynamics. In particular, we show how intercellular communication and stochasticity can be used to manipulate the dynamical behavior of a population of coupled synthetic units and, in this manner, finely tune the expression of specific proteins of interest, e.g. in large bioreactors.
Y1  - 2011
U6  - https://doi.org/10.1088/0031-8949/84/04/045007
SN  - 0031-8949
VL  - 84
IS  - 4
PB  - IOP Publ. Ltd.
CY  - Bristol
ER  - 
TY  - JOUR
A1  - Döring, Sebastian
A1  - Kollosche, Matthias
A1  - Rabe, Torsten
A1  - Stumpe, Joachim
A1  - Kofod, Guggi
T1  - Electrically tunable polymer DFB laser
JF  - Advanced materials
Y1  - 2011
U6  - https://doi.org/10.1002/adma.201102465
SN  - 0935-9648
VL  - 23
IS  - 37
SP  - 4265
EP  - 4269
PB  - Wiley-VCH
CY  - Weinheim
ER  - 
TY  - JOUR
A1  - Stoyanov, Hristiyan
A1  - Kollosche, Matthias
A1  - Risse, Sebastian
A1  - McCarthy, Denis N.
A1  - Kofod, Guggi
T1  - Elastic block copolymer nanocomposites with controlled interfacial interactions for artificial muscles with direct voltage control
JF  - Soft matter
N2  - Soft, physically crosslinking, block copolymer elastomers were filled with surface-treated nanoparticles, in order to evaluate the possibility for improvement of their properties when used as soft dielectric actuators. The nanoparticles led to improvements in dielectric properties, however they also reinforced the elastomer matrix. Comparing dielectric spectra of composites with untreated and surface-treated particles showed a measurable influence of the surface on the dielectric loss behaviour for high filler amounts, strongly indicating an improved host-guest interaction for the surface-treated particles. Breakdown strength was measured using a test bench and was found to be in good agreement with the results from the actuation measurements. Actuation responses predicted by a model for prestrained actuators agreed well with measurements up to a filler amount of 20%(vol). Strong improvements in actuation behaviour were observed, with an optimum near 15%(vol) nanoparticles, corresponding to a reduction in electrical field of 27% for identical actuation strains. The use of physically crosslinking elastomer ensured the mechanical properties of the matrix elastomer were unchanged by nanoparticles effecting the crosslinking reaction, contrary to similar experiments performed with chemically crosslinking elastomers. This allows for a firm conclusion about the positive effects of surface-treated nanoparticles on actuation behavior.
Y1  - 2011
U6  - https://doi.org/10.1039/c0sm00715c
SN  - 1744-683X
SN  - 1744-6848
VL  - 7
IS  - 1
SP  - 194
EP  - 202
PB  - Royal Society of Chemistry
CY  - Cambridge
ER  - 
TY  - JOUR
A1  - Schenk, Paul
A1  - Hamilton, Douglas P.
A1  - Johnson, Robert E.
A1  - McKinnon, William B.
A1  - Paranicas, Chris
A1  - Schmidt, Jürgen
A1  - Showalter, Mark R.
T1  - Plasma, plumes and rings saturn system dynamics as recorded in global color patterns on its midsize icy satellites
JF  - Icarus : international journal of solar system studies
N2  - New global maps of the five inner midsize icy saturnian satellites, Mimas, Enceladus, Tethys, Dione, and Rhea, have been constructed in three colors (UV, Green and near-IR) at resolutions of 1 km/pixel. The maps reveal prominent global patterns common to several of these satellites but also three major color features unique to specific satellites or satellite subgroups. The most common features among the group are first-order global asymmetries in color properties. This pattern, expressed on Tethys, Dione and Rhea, takes the form of a similar to 1.4-1.8 times enhancement in redness (expressed as IR/UV ratio) of the surface at the center of the trailing hemisphere of motion, and a similar though significantly weaker IR/UV enhancement at the center of the leading hemisphere. The peak in redness on the trailing hemisphere also corresponds to a known decrease in albedo. These double hemispheric asymmetries are attributable to plasma and E-ring grain bombardment on the trailing and leading hemispheres, respectively, for the outer three satellites Tethys, Dione and Rhea, whereas as E-ring bombardment may be focused on the trailing hemisphere of Mimas due to its orbital location interior to Enceladus. The maps also reveal three major deviations from these basic global patterns. We observe the previously known dark bluish leading hemisphere equatorial band on Tethys but have also discovered a similar band on Mimas. Similar in shape, both features match the surface patterns expected for irradiation of the surface by incident MeV electrons that drift in a direction opposite to the plasma flow. The global asymmetry on Enceladus is offset similar to 40 degrees to the west compared to the other satellites. We do not consider Enceladus in detail here, but the global distribution of bluish material can be shown to match the deposition pattern predicted for plume fallback onto the surface (Kempf, S., Beckmann, U., Schmidt, S. [2010]. Icarus 206, 446-457. doi:10.1016/j.icarus.2009.09.016). E-ring deposition on Enceladus thus appears to mask or prevent the formation of the lenses and hemispheric asymmetries we see on the other satellites. Finally, we observe a chain of discrete bluish splotches along the equator of Rhea. Unlike the equatorial bands of Tethys and Mimas, these splotches form a very narrow great circle <= 10-km wide (north-to-south) and appear to be related to surface disruption, exposing fresh, bluish ice on older crater rims. This feature is unique to Rhea and may have formed by impact onto its surface of orbiting material.
KW  - Satellites, Surfaces
KW  - Saturn, Satellites
KW  - Saturn, Rings
KW  - Enceladus
KW  - Satellites, Composition
KW  - Magnetospheres
Y1  - 2011
U6  - https://doi.org/10.1016/j.icarus.2010.08.016
SN  - 0019-1035
VL  - 211
IS  - 1
SP  - 740
EP  - 757
PB  - Elsevier
CY  - San Diego
ER  - 
TY  - JOUR
A1  - Mari, Andrea
A1  - Kieling, Konrad
A1  - Nielsen, B. Melholt
A1  - Polzik, E. S.
A1  - Eisert, Jens
T1  - Directly estimating nonclassicality
JF  - Physical review letters
N2  - We establish a method of directly measuring and estimating nonclassicality-operationally defined in terms of the distinguishability of a given state from one with a positive Wigner function. It allows us to certify nonclassicality, based on possibly much fewer measurement settings than necessary for obtaining complete tomographic knowledge, and is at the same time equipped with a full certificate. We find that even from measuring two conjugate variables alone, one may infer the nonclassicality of quantum mechanical modes. This method also provides a practical tool to eventually certify such features in mechanical degrees of freedom in opto-mechanics. The proof of the result is based on Bochner's theorem characterizing classical and quantum characteristic functions and on semidefinite programming. In this joint theoretical-experimental work we present data from experimental optical Fock state preparation.
Y1  - 2011
U6  - https://doi.org/10.1103/PhysRevLett.106.010403
SN  - 0031-9007
VL  - 106
IS  - 1
PB  - American Physical Society
CY  - College Park
ER  - 
TY  - JOUR
A1  - Lemr, Karel
A1  - Cernoch, A.
A1  - Soubusta, Jan
A1  - Kieling, Konrad
A1  - Eisert, Jens
A1  - Dusek, M.
T1  - Experimental implementation of the optimal linear-optical controlled phase gate
JF  - Physical review letters
N2  - We report on the first experimental realization of optimal linear-optical controlled phase gates for arbitrary phases. The realized scheme is entirely flexible in that the phase shift can be tuned to any given value. All such controlled phase gates are optimal in the sense that they operate at the maximum possible success probabilities that are achievable within the framework of postselected linear-optical implementations with vacuum ancillas. The quantum gate is implemented by using bulk optical elements and polarization encoding of qubit states. We have experimentally explored the remarkable observation that the optimum success probability is not monotone in the phase.
Y1  - 2011
U6  - https://doi.org/10.1103/PhysRevLett.106.013602
SN  - 0031-9007
VL  - 106
IS  - 1
PB  - American Physical Society
CY  - College Park
ER  - 
TY  - JOUR
A1  - Gogolin, Christian
A1  - Müller, Markus P.
A1  - Eisert, Jens
T1  - Absence of thermalization in nonintegrable systems
JF  - Physical review letters
N2  - We establish a link between unitary relaxation dynamics after a quench in closed many-body systems and the entanglement in the energy eigenbasis. We find that even if reduced states equilibrate, they can have memory on the initial conditions even in certain models that are far from integrable. We show that in such situations the equilibrium states are still described by a maximum entropy or generalized Gibbs ensemble, regardless of whether a model is integrable or not, thereby contributing to a recent debate. In addition, we discuss individual aspects of the thermalization process, comment on the role of Anderson localization, and collect and compare different notions of integrability.
Y1  - 2011
U6  - https://doi.org/10.1103/PhysRevLett.106.040401
SN  - 0031-9007
VL  - 106
IS  - 4
PB  - American Physical Society
CY  - College Park
ER  - 
TY  - JOUR
A1  - Jordan, Grace
A1  - McCarthy, Denis N.
A1  - Schlepple, N.
A1  - Krissler, Jan
A1  - Schroeder, H.
A1  - Kofod, Guggi
T1  - Actuated micro-optical submount using a dielectric elastomer actuator
JF  - IEEE ASME transactions on mechatronics
N2  - Analysis of the operating characteristics of a dielectric elastomer actuator (DEA) submount for the high-precision positioning of optical components in one dimension is presented. Precise alignment of a single-mode fiber is demonstrated and variation of the sensitivity of the submount motion by changing the bias voltage is confirmed. A comparison of the performance of the DEA submount with a piezoelectric alignment stage is made, which demonstrates that DEAs could present a very attractive, low-cost alternative to currently used manual technologies in overcoming the hurdle of expensive packaging of single-mode optical components.
KW  - Actuators
KW  - manufacturing automation
KW  - optical interconnections
KW  - packaging
KW  - position control
Y1  - 2011
U6  - https://doi.org/10.1109/TMECH.2010.2089991
SN  - 1083-4435
VL  - 16
IS  - 1
SP  - 98
EP  - 102
PB  - Inst. of Electr. and Electronics Engineers
CY  - Piscataway
ER  - 
TY  - JOUR
A1  - Rychkov, Dmitry
A1  - Kuznetsov, Alexey
A1  - Rychkov, Andrey
T1  - Electret properties of polyethylene and polytetrafluoroethylene films with chemically modified surface
JF  - IEEE transactions on dielectrics and electrical insulation
N2  - This paper investigates the effect of chemical surface modification of polytetrafluoroethylene (PTFE) and low density polyethylene (LDPE) films on their electret properties. PTFE films were subjected to wet treatment with three different chemicals: orthophosphoric acid, tetrabutyl titanate and tetraethoxysilane. The technique based on the principles of molecular layer deposition (MLD) method was used to modify the surface of LDPE films with phosphorus trichloride vapors. The surfaces of the films were then corona charged, and the electret charge stability was studied by means of isothermal and thermally stimulated surface potential decay. Both PTFE and LDPE films, after the surface treatment, displayed a considerable enhancement in the charge stability compared to the virgin samples. It is important to note that the enhancement of the charge stability was achieved in the positively charged PTFE films, a result important to practical applications. We attribute this effect of charge stabilization to the formation of new energetically deep traps on the modified surface. Decrease in molecular mobility, due to attachment of new chemical structures to the surface macromolecules, may also contribute to the overall growth of the charge stability.
KW  - Electrets
KW  - surface treatment
KW  - charge stability
KW  - charge carrier processes
KW  - polytetrafluoroethylene
KW  - polyethylene
Y1  - 2011
U6  - https://doi.org/10.1109/TDEI.2011.5704487
SN  - 1070-9878
VL  - 18
IS  - 1
SP  - 8
EP  - 14
PB  - Inst. of Electr. and Electronics Engineers
CY  - Piscataway
ER  - 
TY  - JOUR
A1  - Mellinger, Axel
A1  - Mellinger, Olena
T1  - Breakdown threshold of dielectric barrier discharges in ferroelectrets  where Paschen's law fails
JF  - IEEE transactions on dielectrics and electrical insulation
N2  - The piezoelectric activity of charged cellular foams (so-called ferroelectrets) is compared against simulations based on a multi-layer electromechanical model and Townsend's model of Paschen breakdown, with the distribution of void heights determined from scanning electron micrographs. While the calculated space charge hysteresis curves are in good agreement with experimental data, the onset of piezoelectric activity is observed at significantly higher electric fields than predicted by Paschen's law. One likely explanation is that the commonly accepted Paschen curve for electric breakdown in air poorly describes the critical electric field for dielectric barrier discharges in micrometer-size cavities.
KW  - Ferroelectrets
KW  - dielectric barrier discharges
KW  - piezoelectricity
KW  - Paschen's law
Y1  - 2011
U6  - https://doi.org/10.1109/TDEI.2011.5704491
SN  - 1070-9878
VL  - 18
IS  - 1
SP  - 43
EP  - 48
PB  - Inst. of Electr. and Electronics Engineers
CY  - Piscataway
ER  - 
TY  - JOUR
A1  - Fiehler, Katja
A1  - Bannert, Michael M.
A1  - Bischoff, Matthias
A1  - Blecker, Carlo
A1  - Stark, Rudolf
A1  - Vaitl, Dieter
A1  - Franz, Volker H.
A1  - Roesler, Frank
T1  - Working memory maintenance of grasp-target information in the human posterior parietal cortex
JF  - NeuroImage : a journal of brain function
N2  - Event-related functional magnetic resonance imaging was applied to identify cortical areas involved in maintaining target information in working memory used for an upcoming grasping action. Participants had to grasp with their thumb and index finger of the dominant right hand three-dimensional objects of different size and orientation. Reaching-to-grasp movements were performed without visual feedback either immediately after object presentation or after a variable delay of 2-12 s. The right inferior parietal cortex demonstrated sustained neural activity throughout the delay, which overlapped with activity observed during encoding of the grasp target. Immediate and delayed grasping activated similar motor-related brain areas and showed no differential activity. The results suggest that the right inferior parietal cortex plays an important functional role in working memory maintenance of grasp-related information. Moreover, our findings confirm the assumption that brain areas engaged in maintaining information are also involved in encoding the same information, and thus extend previous findings on working memory function of the posterior parietal cortex in saccadic behavior to reach-to-grasp movements.
Y1  - 2011
U6  - https://doi.org/10.1016/j.neuroimage.2010.09.080
SN  - 1053-8119
VL  - 54
IS  - 3
SP  - 2401
EP  - 2411
PB  - Elsevier
CY  - San Diego
ER  - 
TY  - JOUR
A1  - Seiss, Martin
A1  - Spahn, Frank
T1  - Hydrodynamics of saturn's dense rings
JF  - Mathematical modelling of natural phenomena
N2  - The space missions Voyager and Cassini together with earthbound observations revealed a wealth of structures in Saturn's rings. There are, for example, waves being excited at ring positions which are in orbital resonance with Saturn's moons. Other structures can be assigned to embedded moons like empty gaps, moon induced wakes or S-shaped propeller features. Furthermore, irregular radial structures are observed in the range from 10 meters until kilometers. Here some of these structures will be discussed in the frame of hydrodynamical modeling of Saturn's dense rings. For this purpose we will characterize the physical properties of the ring particle ensemble by mean field quantities and point to the special behavior of the transport coefficients. We show that unperturbed rings can become unstable and how diffusion acts in the rings. Additionally, the alternative streamline formalism is introduced to describe perturbed regions of dense rings with applications to the wake damping and the dispersion relation of the density waves.
KW  - granular gas
KW  - instabilities
KW  - hydrodynamics
KW  - planetary rings
Y1  - 2011
U6  - https://doi.org/10.1051/mmnp/20116409
SN  - 0973-5348
SN  - 1760-6101
VL  - 6
IS  - 4
SP  - 191
EP  - 218
PB  - EDP Sciences
CY  - Les Ulis
ER  - 
TY  - JOUR
A1  - Kollosche, Matthias
A1  - Stoyanov, Hristiyan
A1  - Laflamme, Simon
A1  - Kofod, Guggi
T1  - Strongly enhanced sensitivity in elastic capacitive strain sensors
JF  - Journal of materials chemistry
N2  - Strain sensors based on dielectric elastomer capacitors function by the direct coupling of mechanical deformations with the capacitance. The coupling can be improved by enhancing the relative permittivity of the dielectric elastomer. Here, this is carried out through the grafting of conducting polymer (poly-aniline) to the elastomer backbone, leading to molecular composites. An enhancement in capacitance response of 46 times is observed. This could help to extend the possible range of miniaturization towards even smaller device features.
Y1  - 2011
U6  - https://doi.org/10.1039/c0jm03786a
SN  - 0959-9428
VL  - 21
IS  - 23
SP  - 8292
EP  - 8294
PB  - Royal Society of Chemistry
CY  - Cambridge
ER  - 
TY  - JOUR
A1  - Sepp, T.
A1  - Tempel, E.
A1  - Gramann, M.
A1  - Nurmi, P.
A1  - Haupt, Michael
T1  - Studying the patterns of the universe
JF  - Baltic astronomy
N2  - The SDSS galaxy catalog is one of the best databases for galaxy distribution studies. The SDSS DR8 data is used to construct the galaxy cluster catalog. We construct the clusters from the calculated luminosity density field and identify denser regions. Around these peak regions we construct galaxy clusters. Another interesting question in cosmology is how observable galaxy structures are connected to underlying dark matter distribution. To study this we compare the SDSS DR7 galaxy group catalog with galaxy groups obtained from the semi-analytical Millennium N-Body simulation. Specifically, we compare the group richness, virial radius, maximum separation and velocity dispersion distributions and find a relatively good agreement between the mock catalog and observations. This strongly supports the idea, that the dark matter distribution and galaxies in the semi-analytical models and observations are very closely linked.
KW  - galaxies: groups, clusters
KW  - cosmology: dark matter, large-scale structure of the Universe
Y1  - 2011
SN  - 1392-0049
VL  - 20
IS  - 2
SP  - 309
EP  - 312
PB  - Institute of Theoretical Physics and Astronomy
CY  - Moletai
ER  - 
TY  - JOUR
A1  - Sanhueza-Pino, Katia
A1  - Korup, Oliver
A1  - Hetzel, Ralf
A1  - Munack, Henry
A1  - Weidinger, Johannes T.
A1  - Dunning, Stuart A.
A1  - Ormukov, Cholponbek
A1  - Kubik, Peter W.
T1  - Glacial advances constrained by Be-10 exposure dating of bedrock landslides, Kyrgyz Tien Shan
JF  - Quaternary research : an interdisciplinary journal
N2  - Numerous large landslide deposits occur in the Tien Shan, a tectonically active intraplate orogen in Central Asia. Yet their significance in Quaternary landscape evolution and natural hazard assessment remains unresolved due to the lack of "absolute" age constraints. Here we present the first Be-10 exposure ages for three prominent (>10(7) m(3)) bedrock landslides that blocked major rivers and formed lakes, two of which subsequently breached, in the northern Kyrgyz Tien Shan. Three Be-10 ages reveal that one landslide in the Alamyedin River occurred at 11-15 ka, which is consistent with two C-14 ages of gastropod shells from reworked loess capping the landslide. One large landslide in Aksu River is among the oldest documented in semi-arid continental interiors, with a Be-10 age of 63-67 ka. The Ukok River landslide deposit(s) yielded variable Be-10 ages, which may result from multiple landslides, and inheritance of Be-10. Two Be-10 ages of 8.2 and 5.9 ka suggest that one major landslide occurred in the early to mid-Holocene, followed by at least one other event between 1.5 and 0.4 ka. Judging from the regional glacial chronology, all three landslides have occurred between major regional glacial advances. Whereas Alamyedin and Ukok can be considered as postglacial in this context, Aksu is of interglacial age. None of the landslide deposits show traces of glacial erosion, hence their locations and I Be ages mark maximum extents and minimum ages of glacial advances, respectively. Using toe-to-headwall altitude ratios of 0.4-0.5, we reconstruct minimum equilibrium-line altitudes that exceed previous estimates by as much as 400 m along the moister northern fringe of the Tien Shan. Our data show that deposits from large landslides can provide valuable spatio-temporal constraints for glacial advances in landscapes where moraines and glacial deposits have low preservation potential. (C) 2011 University of Washington. Published by Elsevier Inc. All rights reserved.
KW  - Landslide
KW  - Rock avalanche
KW  - Be-10 exposure dating
KW  - Quaternary glaciations
KW  - Tien Shan
Y1  - 2011
U6  - https://doi.org/10.1016/j.yqres.2011.06.013
SN  - 0033-5894
VL  - 76
IS  - 3
SP  - 295
EP  - 304
PB  - Elsevier
CY  - San Diego
ER  - 
TY  - JOUR
A1  - Fuhrmann, Marcel
A1  - Seehafer, Norbert
A1  - Valori, Gherardo
A1  - Wiegelmann, Thomas
T1  - A comparison of preprocessing methods for solar force-free magnetic field extrapolation
Y1  - 2011
UR  - http://www.aanda.org/index.php?option=com_article&access=standard&Itemid=129&url=/articles/aa/full_html/ 2011/02/aa15453-10/aa15453-10.html
SN  - 0004-6361
ER  - 
TY  - JOUR
A1  - Fuhrmann, Marcel
A1  - Seehafer, Norbert
A1  - Valori, Gherardo
A1  - Wiegelmann, T.
T1  - A comparison of preprocessing methods for solar force-free magnetic field extrapolation
JF  - Astronomy and astrophysics : an international weekly journal
N2  - Context. Extrapolations of solar photospheric vector magnetograms into three-dimensional magnetic fields in the chromosphere and corona are usually done under the assumption that the fields are force-free. This condition is violated in the photosphere itself and a thin layer in the lower atmosphere above. The field calculations can be improved by preprocessing the photospheric magnetograms. The intention here is to remove a non-force-free component from the data.
 Aims. We compare two preprocessing methods presently in use, namely the methods of Wiegelmann et al. (2006, Sol. Phys., 233, 215) and Fuhrmann et al. (2007, A&A, 476, 349).
 Methods. The two preprocessing methods were applied to a vector magnetogram of the recently observed active region NOAA AR 10 953. We examine the changes in the magnetogram effected by the two preprocessing algorithms. Furthermore, the original magnetogram and the two preprocessed magnetograms were each used as input data for nonlinear force-free field extrapolations by means of two different methods, and we analyze the resulting fields.
 Results. Both preprocessing methods managed to significantly decrease the magnetic forces and magnetic torques that act through the magnetogram area and that can cause incompatibilities with the assumption of force-freeness in the solution domain. The force and torque decrease is stronger for the Fuhrmann et al. method. Both methods also reduced the amount of small-scale irregularities in the observed photospheric field, which can sharply worsen the quality of the solutions. For the chosen parameter set, the Wiegelmann et al. method led to greater changes in strong-field areas, leaving weak-field areas mostly unchanged, and thus providing an approximation of the magnetic field vector in the chromosphere, while the Fuhrmann et al. method weakly changed the whole magnetogram, thereby better preserving patterns present in the original magnetogram. Both preprocessing methods raised the magnetic energy content of the extrapolated fields to values above the minimum energy, corresponding to the potential field. Also, the fields calculated from the preprocessed magnetograms fulfill the solenoidal condition better than those calculated without preprocessing.
KW  - Sun: magnetic topology
KW  - Sun: atmosphere
KW  - magnetohydrodynamics (MHD)
Y1  - 2011
U6  - https://doi.org/10.1051/0004-6361/201015453
SN  - 0004-6361
VL  - 526
PB  - EDP Sciences
CY  - Les Ulis
ER  - 
TY  - JOUR
A1  - Cockburn, S. P.
A1  - Negretti, Antonio
A1  - Proukakis, N. P.
A1  - Henkel, Carsten
T1  - Comparison between microscopic methods for finite-temperature Bose gases
JF  - Physical review : A, Atomic, molecular, and optical physics
N2  - We analyze the equilibrium properties of a weakly interacting, trapped quasi-one-dimensional Bose gas at finite temperatures and compare different theoretical approaches. We focus in particular on two stochastic theories: a number-conserving Bogoliubov (NCB) approach and a stochastic Gross-Pitaevskii equation (SGPE) that have been extensively used in numerical simulations. Equilibrium properties like density profiles, correlation functions, and the condensate statistics are compared to predictions based upon a number of alternative theories. We find that due to thermal phase fluctuations, and the corresponding condensate depletion, the NCB approach loses its validity at relatively low temperatures. This can be attributed to the change in the Bogoliubov spectrum, as the condensate gets thermally depleted, and to large fluctuations beyond perturbation theory. Although the two stochastic theories are built on different thermodynamic ensembles (NCB, canonical; SGPE, grand-canonical), they yield the correct condensate statistics in a large Bose-Einstein condensate (BEC) (strong enough particle interactions). For smaller systems, the SGPE results are prone to anomalously large number fluctuations, well known for the grand-canonical, ideal Bose gas. Based on the comparison of the above theories to the modified Popov approach, we propose a simple procedure for approximately extracting the Penrose-Onsager condensate from first-and second-order correlation functions that is both computationally convenient and of potential use to experimentalists. This also clarifies the link between condensate and quasicondensate in the Popov theory of low-dimensional systems.
Y1  - 2011
U6  - https://doi.org/10.1103/PhysRevA.83.043619
SN  - 1050-2947
SN  - 1094-1622
VL  - 83
IS  - 4
PB  - American Physical Society
CY  - College Park
ER  -