@phdthesis{Sorce2014,
  author    = {Sorce, Jenny},
  title     = {From Spitzer mid-infrared observations and measurements of peculiar velocities to constrained simulations of the local universe},
  url       = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus-72486},
  school      = {Universit{\"a}t Potsdam},
  pages     = {xx, 303},
  year      = {2014},
  abstract  = {Galaxies are observational probes to study the Large Scale Structure. Their gravitational motions are tracers of the total matter density and therefore of the Large Scale Structure. Besides, studies of structure formation and galaxy evolution rely on numerical cosmological simulations. Still, only one universe observable from a given position, in time and space, is available for comparisons with simulations. The related cosmic variance affects our ability to interpret the results. Simulations constrained by observational data are a perfect remedy to this problem. Achieving such simulations requires the projects Cosmic flows and CLUES. Cosmic flows builds catalogs of accurate distance measurements to map deviations from the expansion. These measures are mainly obtained with the galaxy luminosity-rotation rate correlation. We present the calibration of that relation in the mid-infrared with observational data from Spitzer Space Telescope. Resulting accurate distance estimates will be included in the third catalog of the project. In the meantime, two catalogs up to 30 and 150 Mpc/h have been released. We report improvements and applications of the CLUES' method on these two catalogs. The technique is based on the constrained realization algorithm. The cosmic displacement field is computed with the Zel'dovich approximation. This latter is then reversed to relocate reconstructed three-dimensional constraints to their precursors' positions in the initial field. The size of the second catalog (8000 galaxies within 150 Mpc/h) highlighted the importance of minimizing the observational biases. By carrying out tests on mock catalogs, built from cosmological simulations, a method to minimize observational bias can be derived. Finally, for the first time, cosmological simulations are constrained solely by peculiar velocities. The process is successful as resulting simulations resemble the Local Universe. The major attractors and voids are simulated at positions approaching observational positions by a few megaparsecs, thus reaching the limit imposed by the linear theory.},
  language  = {en}
}
@article{SpahnVieiraNetoGuimaraesetal.2014,
  author    = {Spahn, Frank and Vieira Neto, E. and Guimaraes, A. H. F. and Gorban, A. N. and Brilliantov, Nikolai V.},
  title     = {A statistical model of aggregate fragmentation},
  series = {New journal of physics : the open-access journal for physics},
  volume    = {16},
  journal   = {New journal of physics : the open-access journal for physics},
  publisher = {IOP Publ. Ltd.},
  address   = {Bristol},
  issn      = {1367-2630},
  doi       = {10.1088/1367-2630/16/1/013031},
  pages     = {11},
  year      = {2014},
  abstract  = {A statistical model of fragmentation of aggregates is proposed, based on the stochastic propagation of cracks through the body. The propagation rules are formulated on a lattice and mimic two important features of the process-a crack moves against the stress gradient while dissipating energy during its growth. We perform numerical simulations of the model for two-dimensional lattice and reveal that the mass distribution for small-and intermediate-size fragments obeys a power law, F(m) proportional to m(-3/2), in agreement with experimental observations. We develop an analytical theory which explains the detected power law and demonstrate that the overall fragment mass distribution in our model agrees qualitatively with that one observed in experiments.},
  language  = {en}
}
@article{SteffenHubrigTodtetal.2014,
  author    = {Steffen, M. and Hubrig, Swetlana and Todt, Helge Tobias and Schoeller, M. and Hamann, Wolf-Rainer and Sandin, Christer and Sch{\"o}nberner, Detlef},
  title     = {Weak magnetic fields in central stars of planetary nebulae?},
  series = {Astronomy and astrophysics : an international weekly journal},
  volume    = {570},
  journal   = {Astronomy and astrophysics : an international weekly journal},
  publisher = {EDP Sciences},
  address   = {Les Ulis},
  issn      = {0004-6361},
  doi       = {10.1051/0004-6361/201423842},
  pages     = {15},
  year      = {2014},
  abstract  = {Context. It is not yet clear whether magnetic fields play an essential role in shaping planetary nebulae (PNe), or whether stellar rotation alone and/or a close binary companion, stellar or substellar, can account for the variety of the observed nebular morphologies. Aims. In a quest for empirical evidence verifying or disproving the role of magnetic fields in shaping planetary nebulae, we follow up on previous attempts to measure the magnetic field in a representative sample of PN central stars. Methods. We obtained low-resolution polarimetric spectra with FORS2 installed on the Antu telescope of the VLT for a sample of 12 bright central stars of PNe with different morphologies, including two round nebulae, seven elliptical nebulae, and three bipolar nebulae. Two targets are Wolf-Rayet type central stars. Results. For the majority of the observed central stars, we do not find any significant evidence for the existence of surface magnetic fields. However, our measurements may indicate the presence of weak mean longitudinal magnetic fields of the order of 100 Gauss in the central star of the young elliptical planetary nebula IC 418 as well as in the Wolf-Rayet type central star of the bipolar nebula Hen 2-113 and the weak emission line central star of the elliptical nebula Hen 2-131. A clear detection of a 250 G mean longitudinal field is achieved for the A-type companion of the central star of NGC 1514. Some of the central stars show a moderate night-to-night spectrum variability, which may be the signature of a variable stellar wind and/or rotational modulation due to magnetic features. Conclusions. Since our analysis indicates only weak fields, if any, in a few targets of our sample, we conclude that strong magnetic fields of the order of kG are not widespread among PNe central stars. Nevertheless, simple estimates based on a theoretical model of magnetized wind bubbles suggest that even weak magnetic fields below the current detection limit of the order of 100 G may well be sufficient to contribute to the shaping of the surrounding nebulae throughout their evolution. Our current sample is too small to draw conclusions about a correlation between nebular morphology and the presence of stellar magnetic fields.},
  language  = {en}
}
@phdthesis{Steinhaus2014,
  author    = {Steinhaus, Sebastian Peter},
  title     = {Constructing quantum spacetime},
  url       = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus-72558},
  school      = {Universit{\"a}t Potsdam},
  year      = {2014},
  abstract  = {Despite remarkable progress made in the past century, which has revolutionized our understanding of the universe, there are numerous open questions left in theoretical physics. Particularly important is the fact that the theories describing the fundamental interactions of nature are incompatible. Einstein's theory of general relative describes gravity as a dynamical spacetime, which is curved by matter and whose curvature determines the motion of matter. On the other hand we have quantum field theory, in form of the standard model of particle physics, where particles interact via the remaining interactions - electromagnetic, weak and strong interaction - on a flat, static spacetime without gravity. A theory of quantum gravity is hoped to cure this incompatibility by heuristically replacing classical spacetime by quantum spacetime'. Several approaches exist attempting to define such a theory with differing underlying premises and ideas, where it is not clear which is to be preferred. Yet a minimal requirement is the compatibility with the classical theory, they attempt to generalize. Interestingly many of these models rely on discrete structures in their definition or postulate discreteness of spacetime to be fundamental. Besides the direct advantages discretisations provide, e.g. permitting numerical simulations, they come with serious caveats requiring thorough investigation: In general discretisations break fundamental diffeomorphism symmetry of gravity and are generically not unique. Both complicates establishing the connection to the classical continuum theory. The main focus of this thesis lies in the investigation of this relation for spin foam models. This is done on different levels of the discretisation / triangulation, ranging from few simplices up to the continuum limit. In the regime of very few simplices we confirm and deepen the connection of spin foam models to discrete gravity. Moreover, we discuss dynamical, e.g. diffeomorphism invariance in the discrete, to fix the ambiguities of the models. In order to satisfy these conditions, the discrete models have to be improved in a renormalisation procedure, which also allows us to study their continuum dynamics. Applied to simplified spin foam models, we uncover a rich, non--trivial fixed point structure, which we summarize in a phase diagram. Inspired by these methods, we propose a method to consistently construct the continuum theory, which comes with a unique vacuum state.},
  language  = {en}
}
@article{Stephan2014,
  author    = {Stephan, Christoph A.},
  title     = {A dark sector extension of the almost-commutative standard model},
  series = {International journal of modern physics : A, Particles and fields, gravitation, cosmology, nuclear physics},
  volume    = {29},
  journal   = {International journal of modern physics : A, Particles and fields, gravitation, cosmology, nuclear physics},
  number    = {1},
  publisher = {World Scientific},
  address   = {Singapore},
  issn      = {0217-751X},
  doi       = {10.1142/S0217751X14500055},
  pages     = {30},
  year      = {2014},
  abstract  = {We consider an extension of the Standard Model within the framework of Noncommutative Geometry. The model is based on an older model [C. A. Stephan, Phys. Rev. D 79, 065013 (2009)] which extends the Standard Model by new fermions, a new U(1)-gauge group and, crucially, a new scalar field which couples to the Higgs field. This new scalar field allows to lower the mass of the Higgs mass from similar to 170 GeV, as predicted by the Spectral Action for the Standard Model, to a value of 120-130 GeV. The shortcoming of the previous model lay in its inability to meet all the constraints on the gauge couplings implied by the Spectral Action. These shortcomings are cured in the present model which also features a "dark sector" containing fermions and scalar particles.},
  language  = {en}
}
@phdthesis{Steyrleuthner2014,
  author    = {Steyrleuthner, Robert},
  title     = {Korrelation von Struktur, optischen Eigenschaften und Ladungstransport in einem konjugierten Naphthalindiimid-Bithiophen Copolymer mit herausragender Elektronenmobilit{\"a}t},
  url       = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus-71413},
  school      = {Universit{\"a}t Potsdam},
  year      = {2014},
  abstract  = {Organische Halbleiter besitzen neue, bemerkenswerte Materialeigenschaften, die sie f{\"u}r die grundlegende Forschung wie auch aktuelle technologische Entwicklung (bsw. org. Leuchtdioden, org. Solarzellen) interessant werden lassen. Aufgrund der starken konformative Freiheit der konjugierten Polymerketten f{\"u}hrt die Vielzahl der m{\"o}glichen Anordnungen und die schwache intermolekulare Wechselwirkung f{\"u}r gew{\"o}hnlich zu geringer struktureller Ordnung im Festk{\"o}rper. Die Morphologie hat gleichzeitig direkten Einfluss auf die elektronische Struktur der organischen Halbleiter, welches sich meistens in einer deutlichen Reduktion der Ladungstr{\"a}gerbeweglichkeit gegen{\"u}ber den anorganischen Verwandten zeigt. So stellt die Beweglichkeit der Ladungen im Halbleiter einen der limitierenden Faktoren f{\"u}r die Leistungsf{\"a}higkeit bzw. den Wirkungsgrad von funktionellen organischen Bauteilen dar. Im Jahr 2009 wurde ein neues auf Naphthalindiimid und Bithiophen basierendes Dornor/Akzeptor Copolymer vorgestellt [P(NDI2OD‑T2)], welches sich durch seine außergew{\"o}hnlich hohe Ladungstr{\"a}germobilit{\"a}t auszeichnet. In dieser Arbeit wird die Ladungstr{\"a}germobilit{\"a}t in P(NDI2OD‑T2) bestimmt, und der Transport durch eine geringe energetischer Unordnung charakterisiert. Obwohl dieses Material zun{\"a}chst als amorph beschrieben wurde zeigt eine detaillierte Analyse der optischen Eigenschaften von P(NDI2OD‑T2), dass bereits in L{\"o}sung geordnete Vorstufen supramolekularer Strukturen (Aggregate) existieren. Quantenchemische Berechnungen belegen die beobachteten spektralen {\"A}nderungen. Mithilfe der NMR-Spektroskopie kann die Bildung der Aggregate unabh{\"a}ngig von optischer Spektroskopie best{\"a}tigt werden. Die Analytische Ultrazentrifugation an P(NDI2OD‑T2) L{\"o}sungen legt nahe, dass sich die Aggregation innerhalb der einzelnen Ketten unter Reduktion des hydrodynamischen Radius vollzieht. Die Ausbildung supramolekularen Strukturen nimmt auch eine signifikante Rolle bei der Filmbildung ein und verhindert gleichzeitig die Herstellung amorpher P(NDI2OD‑T2) Filme. Durch chemische Modifikation der P(NDI2OD‑T2)-Kette und verschiedener Prozessierungs-Methoden wurde eine {\"A}nderung des Kristallinit{\"a}tsgrades und gleichzeitig der Orientierung der kristallinen Dom{\"a}nen erreicht und mittels R{\"o}ntgenbeugung quantifiziert. In hochaufl{\"o}senden Elektronenmikroskopie-Messungen werden die Netzebenen und deren Einbettung in die semikristallinen Strukturen direkt abgebildet. Aus der Kombination der verschiedenen Methoden erschließt sich ein Gesamtbild der Nah- und Fernordnung in P(NDI2OD‑T2). {\"U}ber die Messung der Elektronenmobilit{\"a}t dieser Schichten wird die Anisotropie des Ladungstransports in den kristallographischen Raumrichtungen von P(NDI2OD‑T2) charakterisiert und die Bedeutung der intramolekularen Wechselwirkung f{\"u}r effizienten Ladungstransport herausgearbeitet. Gleichzeitig wird deutlich, wie die Verwendung von gr{\"o}ßeren und planaren funktionellen Gruppen zu h{\"o}heren Ladungstr{\"a}germobilit{\"a}ten f{\"u}hrt, welche im Vergleich zu klassischen semikristallinen Polymeren weniger sensitiv auf die strukturelle Unordnung im Film sind.},
  language  = {de}
}
@article{SteyrleuthnerDiPietroCollinsetal.2014,
  author    = {Steyrleuthner, Robert and Di Pietro, Riccardo and Collins, Brian A. and Polzer, Frank and Himmelberger, Scott and Schubert, Marcel and Chen, Zhihua and Zhang, Shiming and Salleo, Alberto and Ade, Harald W. and Facchetti, Antonio and Neher, Dieter},
  title     = {The Role of Regioregularity, Crystallinity, and Chain Orientation on Electron Transport in a High-Mobility n-Type Copolymer},
  series = {Journal of the American Chemical Society},
  volume    = {136},
  journal   = {Journal of the American Chemical Society},
  number    = {11},
  publisher = {American Chemical Society},
  address   = {Washington},
  issn      = {0002-7863},
  doi       = {10.1021/ja4118736},
  pages     = {4245 -- 4256},
  year      = {2014},
  language  = {en}
}
@article{TalukderSenChakrabortietal.2014,
  author    = {Talukder, Srijeeta and Sen, Shrabani and Chakraborti, Prantik and Metzler, Ralf and Banik, Suman K. and Chaudhury, Pinaki},
  title     = {Breathing dynamics based parameter sensitivity analysis of hetero-polymeric DNA},
  series = {The journal of chemical physics : bridges a gap between journals of physics and journals of chemistr},
  volume    = {140},
  journal   = {The journal of chemical physics : bridges a gap between journals of physics and journals of chemistr},
  number    = {12},
  publisher = {American Institute of Physics},
  address   = {Melville},
  issn      = {0021-9606},
  doi       = {10.1063/1.4869112},
  pages     = {10},
  year      = {2014},
  abstract  = {We study the parameter sensitivity of hetero-polymeric DNA within the purview of DNA breathing dynamics. The degree of correlation between the mean bubble size and the model parameters is estimated for this purpose for three different DNA sequences. The analysis leads us to a better understanding of the sequence dependent nature of the breathing dynamics of hetero-polymeric DNA. Out of the 14 model parameters for DNA stability in the statistical Poland-Scheraga approach, the hydrogen bond interaction epsilon(hb)(AT) for an AT base pair and the ring factor. turn out to be the most sensitive parameters. In addition, the stacking interaction epsilon(st)(TA-TA) for an TA-TA nearest neighbor pair of base-pairs is found to be the most sensitive one among all stacking interactions. Moreover, we also establish that the nature of stacking interaction has a deciding effect on the DNA breathing dynamics, not the number of times a particular stacking interaction appears in a sequence. We show that the sensitivity analysis can be used as an effective measure to guide a stochastic optimization technique to find the kinetic rate constants related to the dynamics as opposed to the case where the rate constants are measured using the conventional unbiased way of optimization. (c) 2014 AIP Publishing LLC.},
  language  = {en}
}
@misc{TalukderSenChakrabortietal.2014,
  author    = {Talukder, Srijeeta and Sen, Shrabani and Chakraborti, Prantik and Metzler, Ralf and Banik, Suman K. and Chaudhury, Pinaki},
  title     = {Breathing dynamics based parameter sensitivity analysis of hetero-polymeric DNA},
  series = {The journal of chemical physics : bridges a gap between journals of physics and journals of chemistr},
  volume    = {140},
  journal   = {The journal of chemical physics : bridges a gap between journals of physics and journals of chemistr},
  number    = {14},
  publisher = {American Institute of Physics},
  address   = {Melville},
  issn      = {0021-9606},
  doi       = {10.1063/1.4871297},
  pages     = {1},
  year      = {2014},
  abstract  = {We study the parameter sensitivity of hetero-polymeric DNA within the purview of DNA breathing dynamics. The degree of correlation between the mean bubble size and the model parameters is estimated for this purpose for three different DNA sequences. The analysis leads us to a better understanding of the sequence dependent nature of the breathing dynamics of hetero-polymeric DNA. Out of the 14 model parameters for DNA stability in the statistical Poland-Scheraga approach, the hydrogen bond interaction epsilon(hb)(AT) for an AT base pair and the ring factor. turn out to be the most sensitive parameters. In addition, the stacking interaction epsilon(st)(TA-TA) for an TA-TA nearest neighbor pair of base-pairs is found to be the most sensitive one among all stacking interactions. Moreover, we also establish that the nature of stacking interaction has a deciding effect on the DNA breathing dynamics, not the number of times a particular stacking interaction appears in a sequence. We show that the sensitivity analysis can be used as an effective measure to guide a stochastic optimization technique to find the kinetic rate constants related to the dynamics as opposed to the case where the rate constants are measured using the conventional unbiased way of optimization.},
  language  = {en}
}
@article{TobieTeanbyCoustenisetal.2014,
  author    = {Tobie, G. and Teanby, N. A. and Coustenis, A. and Jaumann, Ralf and Raulin, E. and Schmidt, J. and Carrasco, N. and Coates, Andrew J. and Cordier, D. and De Kok, R. and Geppert, W. D. and Lebreton, J. -P. and Lefevre, A. and Livengood, T. A. and Mandt, K. E. and Mitri, G. and Nimmo, F. and Nixon, C. A. and Norman, L. and Pappalardo, R. T. and Postberg, F. and Rodriguez, S. and SchuizeMakuch, D. and Soderblom, J. M. and Solomonidou, A. and Stephan, K. and Stofan, E. R. and Turtle, E. P. and Wagner, R. J. and West, R. A. and Westlake, J. H.},
  title     = {Science goals and mission concept for the future exploration of Titan and Enceladus},
  series = {Planetary and space science},
  volume    = {104},
  journal   = {Planetary and space science},
  publisher = {Elsevier},
  address   = {Oxford},
  issn      = {0032-0633},
  doi       = {10.1016/j.pss.2014.10.002},
  pages     = {59 -- 77},
  year      = {2014},
  language  = {en}
}
@article{ToenjesSokolovPostnikov2014,
  author    = {Toenjes, Ralf and Sokolov, Igor M. and Postnikov, Eugene B.},
  title     = {Spectral properties of the fractional Fokker-Planck operator for the Levy flight in a harmonic potential},
  series = {The European physical journal},
  volume    = {87},
  journal   = {The European physical journal},
  number    = {12},
  publisher = {Springer},
  address   = {New York},
  issn      = {1434-6028},
  doi       = {10.1140/epjb/e2014-50558-5},
  pages     = {11},
  year      = {2014},
  abstract  = {We present a detailed analysis of the eigenfunctions of the Fokker-Planck operator for the LevyOrnstein- Uhlenbeck process, their asymptotic behavior and recurrence relations, explicit expressions in coordinate space for the special cases of the Ornstein-Uhlenbeck process with Gaussian and with Cauchy white noise and for the transformation kernel, which maps the fractional Fokker-Planck operator of the Cauchy-Ornstein-Uhlenbeck process to the non-fractional Fokker-Planck operator of the usual Gaussian Ornstein-Uhlenbeck process. We also describe how non-spectral relaxation can be observed in bounded random variables of the Levy-Ornstein-Uhlenbeck process and their correlation functions.},
  language  = {en}
}
@article{ToeroekKliemBergeretal.2014,
  author    = {Toeroek, T. and Kliem, Bernhard and Berger, M. A. and Linton, M. G. and Demoulin, Pascal and van Driel-Gesztelyi, L.},
  title     = {The evolution of writhe in kink-unstable flux ropes and erupting filaments},
  series = {Plasma physics and controlled fusion},
  volume    = {56},
  journal   = {Plasma physics and controlled fusion},
  number    = {6},
  publisher = {IOP Publ. Ltd.},
  address   = {Bristol},
  issn      = {0741-3335},
  doi       = {10.1088/0741-3335/56/6/064012},
  pages     = {7},
  year      = {2014},
  abstract  = {The helical kink instability of a twisted magnetic flux tube has been suggested as a trigger mechanism for solar filament eruptions and coronal mass ejections (CMEs). In order to investigate if estimations of the pre-emptive twist can be obtained from observations of writhe in such events, we quantitatively analyze the conversion of twist into writhe in the course of the instability, using numerical simulations. We consider the line tied, cylindrically symmetric Gold-Hoyle flux rope model and measure the writhe using the formulae by Berger and Prior which express the quantity as a single integral in space. We find that the amount of twist converted into writhe does not simply scale with the initial flux rope twist, but depends mainly on the growth rates of the instability eigenmodes of higher longitudinal order than the basic mode. The saturation levels of the writhe, as well as the shapes of the kinked flux ropes, are very similar for considerable ranges of initial flux rope twists, which essentially precludes estimations of pre-eruptive twist from measurements of writhe. However, our simulations suggest an upper twist limit of similar to 6 pi for the majority of filaments prior to their eruption.},
  language  = {en}
}
@article{ToeroekLeakeTitovetal.2014,
  author    = {Toeroek, T. and Leake, J. E. and Titov, Viacheslav S. and Archontis, V. and Mikic, Z. and Linton, M. G. and Dalmasse, K. and Aulanier, Guillaume and Kliem, Bernhard},
  title     = {Distribution of electric currents in solar active regions},
  series = {The astrophysical journal : an international review of spectroscopy and astronomical physics ; Part 2, Letters},
  volume    = {782},
  journal   = {The astrophysical journal : an international review of spectroscopy and astronomical physics ; Part 2, Letters},
  number    = {1},
  publisher = {IOP Publ. Ltd.},
  address   = {Bristol},
  issn      = {2041-8205},
  doi       = {10.1088/2041-8205/782/1/L10},
  pages     = {6},
  year      = {2014},
  language  = {en}
}
@phdthesis{Trabant2014,
  author    = {Trabant, Christoph},
  title     = {Ultrafast photoinduced phase transitions in complex materials probed by time-resolved resonant soft x-ray diffraction},
  url       = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus-71377},
  school      = {Universit{\"a}t Potsdam},
  year      = {2014},
  abstract  = {In processing and data storage mainly ferromagnetic (FM) materials are being used. Approaching physical limits, new concepts have to be found for faster, smaller switches, for higher data densities and more energy efficiency. Some of the discussed new concepts involve the material classes of correlated oxides and materials with antiferromagnetic coupling. Their applicability depends critically on their switching behavior, i.e., how fast and how energy efficient material properties can be manipulated. This thesis presents investigations of ultrafast non-equilibrium phase transitions on such new materials. In transition metal oxides (TMOs) the coupling of different degrees of freedom and resulting low energy excitation spectrum often result in spectacular changes of macroscopic properties (colossal magneto resistance, superconductivity, metal-to-insulator transitions) often accompanied by nanoscale order of spins, charges, orbital occupation and by lattice distortions, which make these material attractive. Magnetite served as a prototype for functional TMOs showing a metal-to-insulator-transition (MIT) at T = 123 K. By probing the charge and orbital order as well as the structure after an optical excitation we found that the electronic order and the structural distortion, characteristics of the insulating phase in thermal equilibrium, are destroyed within the experimental resolution of 300 fs. The MIT itself occurs on a 1.5 ps timescale. It shows that MITs in functional materials are several thousand times faster than switching processes in semiconductors. Recently ferrimagnetic and antiferromagnetic (AFM) materials have become interesting. It was shown in ferrimagnetic GdFeCo, that the transfer of angular momentum between two opposed FM subsystems with different time constants leads to a switching of the magnetization after laser pulse excitation. In addition it was theoretically predicted that demagnetization dynamics in AFM should occur faster than in FM materials as no net angular momentum has to be transferred out of the spin system. We investigated two different AFM materials in order to learn more about their ultrafast dynamics. In Ho, a metallic AFM below T ≈ 130 K, we found that the AFM Ho can not only be faster but also ten times more energy efficiently destroyed as order in FM comparable metals. In EuTe, an AFM semiconductor below T ≈ 10 K, we compared the loss of magnetization and laser-induced structural distortion in one and the same experiment. Our experiment shows that they are effectively disentangled. An exception is an ultrafast release of lattice dynamics, which we assign to the release of magnetostriction. The results presented here were obtained with time-resolved resonant soft x-ray diffraction at the Femtoslicing source of the Helmholtz-Zentrum Berlin and at the free-electron laser in Stanford (LCLS). In addition the development and setup of a new UHV-diffractometer for these experiments will be reported.},
  language  = {en}
}
@article{TremelFischerKayunkidetal.2014,
  author    = {Tremel, Kim and Fischer, Florian S. U. and Kayunkid, Navaphun and Di Pietro, Riccardo and Tkachov, Roman and Kiriy, Anton and Neher, Dieter and Ludwigs, Sabine and Brinkmann, Martin},
  title     = {Charge transport anisotropy in highly oriented thin films of the acceptor polymer P(NDI2OD-T2)},
  series = {dvanced energy materials},
  volume    = {4},
  journal   = {dvanced energy materials},
  number    = {10},
  publisher = {Wiley-VCH},
  address   = {Weinheim},
  issn      = {1614-6832},
  doi       = {10.1002/aenm.201301659},
  pages     = {13},
  year      = {2014},
  abstract  = {The nanomorphology of the high mobility polymer poly{[N,N'-bis(2-octyldodecyl)-1,4,5,8-naphthalenedicarboximide-2,6-diyl]-alt-5,5'-(2,2'-bithiophene)} P(NDI2OD-T2) in thin films is explored as a function of different annealing conditions and correlated to optical and electrical properties. While nanofibrils with face-on orientation in form I are obtained directly after spin-coating and annealing below the melt transition temperature, clear evidence of lamellar structures is found after melt-annealing followed by slow cooling to room temperature. Interestingly these structural changes are accompanied by distinct changes in the absorption patterns. Electron diffraction measurements further show clear transitions towards predominant edge-on oriented chains in form II upon melt-annealing. Large-scale alignment with dichroic ratios up to 10 and improved order is achieved by high temperature rubbing and subsequent post-rubbing annealing. These highly oriented morphologies allow anisotropic in-plane charge transport to be probed with top-gate transistors parallel and perpendicular to the polymer chain direction. Mobilities up to 0.1 cm(2) V-1 s(-1) are observed parallel to the polymer chain, which is up to 10 times higher than those perpendicular to the polymer chain.},
  language  = {en}
}
@article{TuWang2014,
  author    = {Tu, Rui and Wang, Li},
  title     = {Real-time coseismic wave retrieving by integrated Kalman filter with observations of GPS, Glonass and strong-motion sensor},
  series = {Advances in space research},
  volume    = {53},
  journal   = {Advances in space research},
  number    = {1},
  publisher = {Elsevier},
  address   = {Oxford},
  issn      = {0273-1177},
  doi       = {10.1016/j.asr.2013.10.011},
  pages     = {130 -- 137},
  year      = {2014},
  abstract  = {A method of real-time coseismic wave retrieving was proposed based on the tight integration of GPS, Glonass and strong-motion sensor observations, the validation and precision analysis have been made by an experimental data. The series of results have been shown that: by the integrated Kalman filter and multi-sensors, the coseismic waves can be optimally recovered by complement the advantages of each other, especially when the observation conditions are very bad. In additional, the results are not significantly effected by different receiver clock error processes for the integration solution.},
  language  = {en}
}
@article{vanDrielGesztelyiBakerToeroeketal.2014,
  author    = {van Driel-Gesztelyi, L. and Baker, Daniel N. and Toeroek, T. and Pariat, E. and Green, L. M. and Williams, D. R. and Carlyle, J. and Valori, G. and Demoulin, Pascal and Kliem, Bernhard and Long, D. M. and Matthews, S. A. and Malherbe, J. -M.},
  title     = {Coronal magnetic reconnection driven by CME expansion-the 2011 June 7 event},
  series = {The astrophysical journal : an international review of spectroscopy and astronomical physics},
  volume    = {788},
  journal   = {The astrophysical journal : an international review of spectroscopy and astronomical physics},
  number    = {1},
  publisher = {IOP Publ. Ltd.},
  address   = {Bristol},
  issn      = {0004-637X},
  doi       = {10.1088/0004-637X/788/1/85},
  pages     = {12},
  year      = {2014},
  abstract  = {Coronal mass ejections (CMEs) erupt and expand in a magnetically structured solar corona. Various indirect observational pieces of evidence have shown that the magnetic field of CMEs reconnects with surrounding magnetic fields, forming, e.g., dimming regions distant from the CME source regions. Analyzing Solar Dynamics Observatory (SDO) observations of the eruption from AR 11226 on 2011 June 7, we present the first direct evidence of coronal magnetic reconnection between the fields of two adjacent active regions during a CME. The observations are presented jointly with a data-constrained numerical simulation, demonstrating the formation/intensification of current sheets along a hyperbolic flux tube at the interface between the CME and the neighboring AR 11227. Reconnection resulted in the formation of new magnetic connections between the erupting magnetic structure from AR 11226 and the neighboring active region AR 11227 about 200 Mm from the eruption site. The onset of reconnection first becomes apparent in the SDO/AIA images when filament plasma, originally contained within the erupting flux rope, is redirected toward remote areas in AR 11227, tracing the change of large-scale magnetic connectivity. The location of the coronal reconnection region becomes bright and directly observable at SDO/AIA wavelengths, owing to the presence of down-flowing cool, dense (1010 cm(-3)) filament plasma in its vicinity. The high-density plasma around the reconnection region is heated to coronal temperatures, presumably by slow-mode shocks and Coulomb collisions. These results provide the first direct observational evidence that CMEs reconnect with surrounding magnetic structures, leading to a large-scale reconfiguration of the coronal magnetic field.},
  language  = {en}
}
@article{VandewalAlbrechtHokeetal.2014,
  author    = {Vandewal, Koen and Albrecht, Steve and Hoke, Eric T. and Graham, Kenneth R. and Widmer, Johannes and Douglas, Jessica D. and Schubert, Marcel and Mateker, William R. and Bloking, Jason T. and Burkhard, George F. and Sellinger, Alan and Frechet, Jean M. J. and Amassian, Aram and Riede, Moritz K. and McGehee, Michael D. and Neher, Dieter and Salleo, Alberto},
  title     = {Efficient charge generation by relaxed charge-transfer states at organic interfaces},
  series = {Nature materials},
  volume    = {13},
  journal   = {Nature materials},
  number    = {1},
  publisher = {Nature Publ. Group},
  address   = {London},
  issn      = {1476-1122},
  doi       = {10.1038/NMAT3807},
  pages     = {63 -- 68},
  year      = {2014},
  abstract  = {carriers on illumination. Efficient organic solar cells require a high yield for this process, combined with a minimum of energy losses. Here, we investigate the role of the lowest energy emissive interfacial charge-transfer state (CT1) in the charge generation process. We measure the quantum yield and the electric field dependence of charge generation on excitation of the charge-transfer (CT) state manifold viaweakly allowed, low-energy optical transitions. For a wide range of photovoltaic devices based on polymer: fullerene, small-molecule:C-60 and polymer: polymer blends, our study reveals that the internal quantum efficiency (IQE) is essentially independent of whether or not D, A or CT states with an energy higher than that of CT1 are excited. The best materials systems show an IQE higher than 90\% without the need for excess electronic or vibrational energy.},
  language  = {en}
}
@article{VlasovMacauPikovskij2014,
  author    = {Vlasov, Vladimir and Macau, Elbert E. N. and Pikovskij, Arkadij},
  title     = {Synchronization of oscillators in a Kuramoto-type model with generic coupling},
  series = {Chaos : an interdisciplinary journal of nonlinear science},
  volume    = {24},
  journal   = {Chaos : an interdisciplinary journal of nonlinear science},
  number    = {2},
  publisher = {American Institute of Physics},
  address   = {Melville},
  issn      = {1054-1500},
  doi       = {10.1063/1.4880835},
  pages     = {7},
  year      = {2014},
  abstract  = {We study synchronization properties of coupled oscillators on networks that allow description in terms of global mean field coupling. These models generalize the standard Kuramoto-Sakaguchi model, allowing for different contributions of oscillators to the mean field and to different forces from the mean field on oscillators. We present the explicit solutions of self-consistency equations for the amplitude and frequency of the mean field in a parametric form, valid for noise-free and noise-driven oscillators. As an example, we consider spatially spreaded oscillators for which the coupling properties are determined by finite velocity of signal propagation. (C) 2014 AIP Publishing LLC.},
  language  = {en}
}
@article{Wendt2014,
  author    = {Wendt, Martin},
  title     = {Constraints on variations of m(p)/m(e) based on UVES observations of H-2},
  series = {Astronomische Nachrichten = Astronomical notes},
  volume    = {335},
  journal   = {Astronomische Nachrichten = Astronomical notes},
  number    = {1},
  publisher = {Wiley-VCH},
  address   = {Weinheim},
  issn      = {0004-6337},
  doi       = {10.1002/asna.201312008},
  pages     = {106 -- 112},
  year      = {2014},
  abstract  = {This article summarizes the latest results on the proton-to-electron mass ratio derived from H-2 observations at high redshift in the light of possible variations of fundamental physical constants. The focus lies on UVES observations of the past years as enormous progress was achieved since the first positive results on / were published. With the better understanding of systematics, dedicated observation runs, and numerous approaches to improve wavelength calibration accuracy, all current findings are in reasonable good agreement with no variation and provide an upper limit of / < 1 x 10(-5) for the redshift range of 2 < z < 3. ((},
  language  = {en}
}
@misc{WinklerCherstvy2014,
  author    = {Winkler, Roland G. and Cherstvy, Andrey G.},
  title     = {Strong and weak polyelectrolyte adsorption onto oppositely charged curved surfaces},
  series = {Advances in polymer science},
  volume    = {255},
  journal   = {Advances in polymer science},
  editor    = {Muller, M.},
  publisher = {Springer},
  address   = {Berlin},
  isbn      = {978-3-642-40734-5; 978-3-642-40733-8},
  issn      = {0065-3195},
  doi       = {10.1007/12_2012_183},
  pages     = {1 -- 56},
  year      = {2014},
  abstract  = {Polyelectrolytes are macromolecules composed of charged monomers and exhibit unique properties due to the interplay of their flexibility and electrostatic interactions. In solution, they are attracted to oppositely charged surfaces and interfaces and exhibit a transition to an adsorbed state when certain conditions are met concerning the charge densities of the polymer and surface and the properties of the solution. In this review, we discuss two limiting cases for adsorption of flexible polyelectrolytes on curved surfaces: weak and strong adsorption. In the first case, adsorption is strongly influenced by the entropic degrees of freedom of a flexible polyelectrolyte. By contrast, in the strong adsorption limit, electrostatic interactions dominate, which leads to particular adsorption patterns, specifically on spherical surfaces. We discuss the corresponding theoretical approaches, applying a mean-field description for the polymer and the polymer-surface interaction. For weak adsorption, we discuss the critical adsorption behavior by exactly solvable models for planar and spherical geometries and a generic approximation scheme, which is additionally applied to cylindrical surfaces. For strong adsorption, we investigate various polyelectrolyte patterns on cylinders and spheres and evaluate their stability. The results are discussed in the light of experimental results, mostly of DNA adsorption experiments.},
  language  = {en}
}
@article{XuBrennerChabanneetal.2014,
  author    = {Xu, Jingsan and Brenner, Thomas J. K. and Chabanne, Laurent and Neher, Dieter and Antonietti, Markus and Shalom, Menny},
  title     = {Liquid-Based growth of polymeric carbon nitride layers and their use in a mesostructured polymer solar cell with V-oc exceeding 1 V},
  series = {Journal of the American Chemical Society},
  volume    = {136},
  journal   = {Journal of the American Chemical Society},
  number    = {39},
  publisher = {American Chemical Society},
  address   = {Washington},
  issn      = {0002-7863},
  doi       = {10.1021/ja508329c},
  pages     = {13486 -- 13489},
  year      = {2014},
  abstract  = {Herein we report a general liquid-mediated pathway for the growth of continuous polymeric carbon nitride (C3N4) thin films. The deposition method consists of the use of supramolecular complexes that transform to the liquid state before direct thermal condensation into C3N4 solid films. The resulting films exhibit continuous porous C3N4 networks on various substrates. Moreover, the optical absorption can be easily tuned to cover the solar spectrum by the insertion of an additional molecule into the starting complex. The strength of the deposition method is demonstrated by the use of the C3N4 layer as the electron acceptor in a polymer solar cell that exhibits a remarkable open-circuit voltage exceeding 1 V. The easy, safe, and direct synthesis of carbon nitride in a continuous layered architecture on different functional substrates opens new possibilities for the fabrication of many energy-related devices.},
  language  = {en}
}
@article{XuBrennerChenetal.2014,
  author    = {Xu, Jingsan and Brenner, Thomas J. K. and Chen, Zupeng and Neher, Dieter and Antonietti, Markus and Shalom, Menny},
  title     = {Upconversion-agent induced improvement of g-C3N4 photocatalyst under visible light},
  series = {ACS applied materials \& interfaces},
  volume    = {6},
  journal   = {ACS applied materials \& interfaces},
  number    = {19},
  publisher = {American Chemical Society},
  address   = {Washington},
  issn      = {1944-8244},
  doi       = {10.1021/am5051263},
  pages     = {16481 -- 16486},
  year      = {2014},
  abstract  = {Herein, we report the use of upconversion agents to modify graphite carbon nitride (g-C3N4) by direct thermal condensation of a mixture of ErCl3 center dot 6H(2)O and the supramolecular precursor cyanuric acid-melamine. We show the enhancement of g-C3N4 photoactivity after Er3+ doping by monitoring the photodegradation of Rhodamine B dye under visible light. The contribution of the upconversion agent is demonstrated by measurements using only a red laser. The Er3+ doping alters both the electronic and the chemical properties of g-C3N4. The Er3+ doping reduces emission intensity and lifetime, indicating the formation of new, nonradiative deactivation pathways, probably involving charge-transfer processes.},
  language  = {en}
}
@phdthesis{Yadavalli2014,
  author    = {Yadavalli, Nataraja Sekhar},
  title     = {Advances in experimental methods to probe surface relief grating formation mechanism in photosensitive materials},
  url       = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus-71213},
  school      = {Universit{\"a}t Potsdam},
  year      = {2014},
  abstract  = {When azobenzene-modified photosensitive polymer films are irradiated with light interference patterns, topographic variations in the film develop that follow the electric field vector distribution resulting in the formation of surface relief grating (SRG). The exact correspondence of the electric field vector orientation in interference pattern in relation to the presence of local topographic minima or maxima of SRG is in general difficult to determine. In my thesis, we have established a systematic procedure to accomplish the correlation between different interference patterns and the topography of SRG. For this, we devise a new setup combining an atomic force microscope and a two-beam interferometer (IIAFM). With this set-up, it is possible to track the topography change in-situ, while at the same time changing polarization and phase of the impinging interference pattern. To validate our results, we have compared two photosensitive materials named in short as PAZO and trimer. This is the first time that an absolute correspondence between the local distribution of electric field vectors of interference pattern and the local topography of the relief grating could be established exhaustively. In addition, using our IIAFM we found that for a certain polarization combination of two orthogonally polarized interfering beams namely SP (↕, ↔) interference pattern, the topography forms SRG with only half the period of the interference patterns. Exploiting this phenomenon we are able to fabricate surface relief structures below diffraction limit with characteristic features measuring only 140 nm, by using far field optics with a wavelength of 491 nm. We have also probed for the stresses induced during the polymer mass transport by placing an ultra-thin gold film on top (5-30 nm). During irradiation, the metal film not only deforms along with the SRG formation, but ruptures in regular and complex manner. The morphology of the cracks differs strongly depending on the electric field distribution in the interference pattern even when the magnitude and the kinetic of the strain are kept constant. This implies a complex local distribution of the opto-mechanical stress along the topography grating. The neutron reflectivity measurements of the metal/polymer interface indicate the penetration of metal layer within the polymer resulting in the formation of bonding layer that confirms the transduction of light induced stresses in the polymer layer to a metal film.},
  language  = {en}
}
@article{YadavalliKorolkovMoulinetal.2014,
  author    = {Yadavalli, Nataraja Sekhar and Korolkov, Denis and Moulin, Jean-Francois and Krutyeva, Margarita and Santer, Svetlana},
  title     = {Probing opto-mechanical stresses within azobenzene-containing photosensitive polymer films by a thin metal film placed above},
  series = {ACS applied materials \& interfaces},
  volume    = {6},
  journal   = {ACS applied materials \& interfaces},
  number    = {14},
  publisher = {American Chemical Society},
  address   = {Washington},
  issn      = {1944-8244},
  doi       = {10.1021/am501870t},
  pages     = {11333 -- 11340},
  year      = {2014},
  abstract  = {Azo-modified photosensitive polymers offer the interesting possibility to reshape bulk polymers and thin films by UV-irradiation while being in the solid glassy state. The polymer undergoes considerable mass transport under irradiation with a light interference pattern resulting in the formation of surface relief grating (SRG). The forces inscribing this SRG pattern into a thin film are hard to assess experimentally directly. In the current study, we are proposing a method to probe opto-mechanical stresses within polymer films by characterizing the mechanical response of thin metal films (10 nm) deposited on the photosensitive polymer. During irradiation, the metal film not only deforms along with the SRG formation but ruptures in a regular and complex manner. The morphology of the cracks differs strongly depending on the electrical field distribution in the interference pattern, even when the magnitude and the kinetics of the strain are kept constant. This implies a complex local distribution of the opto-mechanical stress along the topography grating. In addition, the neutron reflectivity measurements of the metal/polymer interface indicate the penetration of a metal layer within the polymer, resulting in a formation of a bonding layer that confirms the transduction of light-induced stresses in the polymer layer to a metal film.},
  language  = {en}
}
@article{YadavalliSaphiannikovaSanter2014,
  author    = {Yadavalli, Nataraja Sekhar and Saphiannikova, Marina and Santer, Svetlana},
  title     = {Photosensitive response of azobenzene containing films towards pure intensity or polarization interference patterns},
  series = {Applied physics letters},
  volume    = {105},
  journal   = {Applied physics letters},
  number    = {5},
  publisher = {American Institute of Physics},
  address   = {Melville},
  issn      = {0003-6951},
  doi       = {10.1063/1.4891615},
  pages     = {5},
  year      = {2014},
  abstract  = {In this paper, we report on differences in the response of photosensitive azobenzene containing films upon irradiation with the intensity or polarization interference patterns. Two materials are studied differing in the molecular weight: an azobenzene-containing polymer and a molecular glass formed from a much smaller molecule consisting of three connected azobenzene units. Topography changes occurring along with the changes in irradiation conditions are recorded using a homemade set-up combining an optical part for generation and shaping of interference patterns and an atomic force microscope for acquiring the kinetics of film deformation. In this way, we could reveal the unique behavior of photosensitive materials during the first few minutes of irradiation: the change in topography is initially driven by an increase in the azobenzene free volume along with the transcis isomerization, followed by the mass transport finally resulting in the surface relief grating. This study demonstrates the great potential of our setup to experimentally highlight puzzling processes governing the formation of surface relief gratings. (C) 2014 AIP Publishing LLC.},
  language  = {en}
}
@phdthesis{Yeldesbay2014,
  author    = {Yeldesbay, Azamat},
  title     = {Complex regimes of synchronization},
  url       = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus4-73348},
  school      = {Universit{\"a}t Potsdam},
  pages     = {ii, 60},
  year      = {2014},
  abstract  = {Synchronization is a fundamental phenomenon in nature. It can be considered as a general property of self-sustained oscillators to adjust their rhythm in the presence of an interaction. In this work we investigate complex regimes of synchronization phenomena by means of theoretical analysis, numerical modeling, as well as practical analysis of experimental data. As a subject of our investigation we consider chimera state, where due to spontaneous symmetry-breaking of an initially homogeneous oscillators lattice split the system into two parts with different dynamics. Chimera state as a new synchronization phenomenon was first found in non-locally coupled oscillators system, and has attracted a lot of attention in the last decade. However, the recent studies indicate that this state is also possible in globally coupled systems. In the first part of this work, we show under which conditions the chimera-like state appears in a system of globally coupled identical oscillators with intrinsic delayed feedback. The results of the research explain how initially monostable oscillators became effectivly bistable in the presence of the coupling and create a mean field that sustain the coexistence of synchronized and desynchronized states. Also we discuss other examples, where chimera-like state appears due to frequency dependence of the phase shift in the bistable system. In the second part, we make further investigation of this topic by modeling influence of an external periodic force to an oscillator with intrinsic delayed feedback. We made stability analysis of the synchronized state and constructed Arnold tongues. The results explain formation of the chimera-like state and hysteric behavior of the synchronization area. Also, we consider two sets of parameters of the oscillator with symmetric and asymmetric Arnold tongues, that correspond to mono- and bi-stable regimes of the oscillator. In the third part, we demonstrate the results of the work, which was done in collaboration with our colleagues from Psychology Department of University of Potsdam. The project aimed to study the effect of the cardiac rhythm on human perception of time using synchronization analysis. From our part, we made a statistical analysis of the data obtained from the conducted experiment on free time interval reproduction task. We examined how ones heartbeat influences the time perception and searched for possible phase synchronization between heartbeat cycles and time reproduction responses. The findings support the prediction that cardiac cycles can serve as input signals, and is used for reproduction of time intervals in the range of several seconds.},
  language  = {en}
}
@article{YeldesbayPikovskijRosenblum2014,
  author    = {Yeldesbay, Azamat and Pikovskij, Arkadij and Rosenblum, Michael},
  title     = {Chimeralike states in an ensemble of globally coupled oscillators},
  series = {Physical review letters},
  volume    = {112},
  journal   = {Physical review letters},
  number    = {14},
  publisher = {American Physical Society},
  address   = {College Park},
  issn      = {0031-9007},
  doi       = {10.1103/PhysRevLett.112.144103},
  pages     = {5},
  year      = {2014},
  abstract  = {We demonstrate the emergence of a complex state in a homogeneous ensemble of globally coupled identical oscillators, reminiscent of chimera states in nonlocally coupled oscillator lattices. In this regime some part of the ensemble forms a regularly evolving cluster, while all other units irregularly oscillate and remain asynchronous. We argue that the chimera emerges because of effective bistability, which dynamically appears in the originally monostable system due to internal delayed feedback in individual units. Additionally, we present two examples of chimeras in bistable systems with frequency-dependent phase shift in the global coupling.},
  language  = {en}
}
@article{YinRajkovicKubiceketal.2014,
  author    = {Yin, Zhong and Rajkovic, Ivan and Kubicek, Katharina and Quevedo, Wilson and Pietzsch, Annette and Wernet, Philippe and F{\"o}hlisch, Alexander and Techert, Simone},
  title     = {Probing the Hofmeister effect with ultrafast core-hole spectroscopy},
  series = {The journal of physical chemistry : B, Condensed matter, materials, surfaces, interfaces \& biophysical chemistry},
  volume    = {118},
  journal   = {The journal of physical chemistry : B, Condensed matter, materials, surfaces, interfaces \& biophysical chemistry},
  number    = {31},
  publisher = {American Chemical Society},
  address   = {Washington},
  issn      = {1520-6106},
  doi       = {10.1021/jp504577a},
  pages     = {9398 -- 9403},
  year      = {2014},
  abstract  = {In the current work, X-ray emission spectra of aqueous solutions of different inorganic salts within the Hofmeister series are presented. The results reflect the direct interaction of the ions with the water molecules and therefore, reveal general properties of the salt-water interactions. Within the experimental precision a significant effect of the ions on the water structure has been observed but no ordering according to the structure maker/structure breaker concept could be mirrored in the results indicating that the Hofmeister effect if existent may be caused by more complex interactions.},
  language  = {en}
}
@article{ZakrevskyyRoxlauBrezesinskietal.2014,
  author    = {Zakrevskyy, Yuriy and Roxlau, Julian and Brezesinski, Gerald and Lomadze, Nino and Santer, Svetlana},
  title     = {Photosensitive surfactants: Micellization and interaction with DNA},
  series = {The journal of chemical physics : bridges a gap between journals of physics and journals of chemistr},
  volume    = {140},
  journal   = {The journal of chemical physics : bridges a gap between journals of physics and journals of chemistr},
  number    = {4},
  publisher = {American Institute of Physics},
  address   = {Melville},
  issn      = {0021-9606},
  doi       = {10.1063/1.4862678},
  pages     = {8},
  year      = {2014},
  abstract  = {Recently, photosensitive surfactants have re-attracted considerable attention. It has been shown that their association with oppositely charged biologically important polyelectrolytes, such as DNA or microgels, can be efficiently manipulated simply by light exposure. In this article, we investigate the self-assembly of photosensitive surfactants as well as their interactions with DNA by calorimetric and spectroscopic methods. Critical micelle concentration (CMC), standard micellization enthalpy, entropy, and Gibbs energy were determined in different conditions (ionic strengths and temperatures) for a series of cationic surfactants with an azobenzene group in their tail. It is shown, that aggregation forces of photosensitive units play an important role in the micellization giving the major contribution to the micellization enthalpy. The onset of the aggregation can be traced from shift of the absorption peak position in the UV-visible spectrum. Titration UV-visible spectroscopy is used as an alternative, simple, and sensitive approach to estimate CMC. The titration UV-visible spectroscopy was also employed to investigate interactions (CAC: critical aggregation concentration, precipitation, and colloidal stabilization) in the DNA-surfactant complex.},
  language  = {en}
}
@article{ZakrevskyyTitovLomadzeetal.2014,
  author    = {Zakrevskyy, Yuriy and Titov, Evgenii and Lomadze, Nino and Santer, Svetlana},
  title     = {Phase diagrams of DNA-photosensitive surfactant complexes: Effect of ionic strength and surfactant structure},
  series = {The journal of chemical physics : bridges a gap between journals of physics and journals of chemistr},
  volume    = {141},
  journal   = {The journal of chemical physics : bridges a gap between journals of physics and journals of chemistr},
  number    = {16},
  publisher = {American Institute of Physics},
  address   = {Melville},
  issn      = {0021-9606},
  doi       = {10.1063/1.4899281},
  pages     = {8},
  year      = {2014},
  abstract  = {Realization of all-optically controlled and efficient DNA compaction is the major motivation in the study of interactions between DNA and photosensitive surfactants. In this article, using recently published approach of phase diagram construction [Y. Zakrevskyy, P. Cywinski, M. Cywinska, J. Paasche, N. Lomadze, O. Reich, H.-G. Lohmannsroben, and S. Santer, J. Chem. Phys. 140, 044907 (2014)], a strategy for substantial reduction of compaction agent concentration and simultaneous maintaining the light-induced decompaction efficiency is proposed. The role of ionic strength (NaCl concentration), as a very important environmental parameter, and surfactant structure (spacer length) on the changes of positions of phase transitions is investigated. Increase of ionic strength leads to increase of the surfactant concentration needed to compact DNA molecule. However, elongation of the spacer results to substantial reduction of this concentration. DNA compaction by surfactants with longer tails starts to take place in diluted solutions at charge ratios Z < 1 and is driven by azobenzene-aggregation compaction mechanism, which is responsible for efficient decompaction. Comparison of phase diagrams for different DNA-photosensitive surfactant systems allowed explanation and proposal of a strategy to overcome previously reported limitations of the light-induced decompaction for complexes with increasing surfactant hydrophobicity. (C) 2014 AIP Publishing LLC.},
  language  = {en}
}
@article{ZamponiPenfoldNachtegaaletal.2014,
  author    = {Zamponi, Flavio and Penfold, Thomas J. and Nachtegaal, Maarten and Luebcke, Andrea and Rittmann, Jochen and Milne, Chris J. and Chergui, Majed and van Bokhoven, Jeroen A.},
  title     = {Probing the dynamics of plasmon-excited hexanethiol-capped gold nanoparticles by picosecond X-ray absorption spectroscopy},
  series = {Physical chemistry, chemical physics : a journal of European Chemical Societies},
  volume    = {16},
  journal   = {Physical chemistry, chemical physics : a journal of European Chemical Societies},
  number    = {42},
  publisher = {Royal Society of Chemistry},
  address   = {Cambridge},
  issn      = {1463-9076},
  doi       = {10.1039/c4cp03301a},
  pages     = {23157 -- 23163},
  year      = {2014},
  abstract  = {Picosecond X-ray absorption spectroscopy (XAS) is used to investigate the electronic and structural dynamics initiated by plasmon excitation of 1.8 nm diameter Au nanoparticles (NPs) functionalised with 1-hexanethiol. We show that 100 ps after photoexcitation the transient XAS spectrum is consistent with an 8\% expansion of the Au-Au bond length and a large increase in disorder associated with melting of the NPs. Recovery of the ground state occurs with a time constant of similar to 1.8 ns, arising from thermalisation with the environment. Simulations reveal that the transient spectrum exhibits no signature of charge separation at 100 ps and allows us to estimate an upper limit for the quantum yield (QY) of this process to be <0.1.},
  language  = {en}
}
@article{ZaritskyCourtoisMunozMateosetal.2014,
  author    = {Zaritsky, Dennis and Courtois, Helene and Munoz-Mateos, Juan-Carlos and Sorce, Jenny and Erroz-Ferrer, S. and Comeron, S. and Gadotti, D. A. and Gil De Paz, A. and Hinz, J. L. and Laurikainen, E. and Kim, T. and Laine, J. and Menendez-Delmestre, K. and Mizusawa, T. and Regan, M. W. and Salo, H. and Seibert, M. and Sheth, K. and Athanassoula, E. and Bosma, A. and Cisternas, M. and Ho, Luis C. and Holwerda, B.},
  title     = {The baryonic Tully-Fisher relationship for S(4)G galaxies and the "condensed" baryon fraction of galaxies},
  series = {The astronomical journal},
  volume    = {147},
  journal   = {The astronomical journal},
  number    = {6},
  publisher = {IOP Publ. Ltd.},
  address   = {Bristol},
  issn      = {0004-6256},
  doi       = {10.1088/0004-6256/147/6/134},
  pages     = {11},
  year      = {2014},
  abstract  = {We combine data from the Spitzer Survey for Stellar Structure in Galaxies, a recently calibrated empirical stellar mass estimator from Eskew et al., and an extensive database of Hi spectral line profiles to examine the baryonic Tully-Fisher (BTF) relation. We find (1) that the BTF has lower scatter than the classic Tully-Fisher (TF) relation and is better described as a linear relationship, confirming similar previous results, (2) that the inclusion of a radial scale in the BTF decreases the scatter but only modestly, as seen previously for the TF relation, and (3) that the slope of the BTF, which we find to be 3.5 +/- 0.2 (Delta log M-baryon/Delta log v(c)), implies that on average a nearly constant fraction (similar to 0.4) of all baryons expected to be in a halo are "condensed" onto the central region of rotationally supported galaxies. The condensed baryon fraction, M-baryon/M-total, is, to our measurement precision, nearly independent of galaxy circular velocity (our sample spans circular velocities, vc, between 60 and 250 km s(-1), but is extended to v(c) similar to 10 km s(-1) using data from the literature). The observed galaxy-to-galaxy scatter in this fraction is generally <= a factor of 2 despite fairly liberal selection criteria. These results imply that cooling and heating processes, such as cold versus hot accretion, mass loss due to stellar winds, and active galactic nucleus driven feedback, to the degree that they affect the global galactic properties involved in the BTF, are independent of halo mass for galaxies with 10 < v(c) < 250 km s(-1) and typically introduce no more than a factor of two range in the resulting M-baryon/M-total. Recent simulations by Aumer et al. of a small sample of disk galaxies are in excellent agreement with our data, suggesting that current simulations are capable of reproducing the global properties of individual disk galaxies. More detailed comparison to models using the BTF holds great promise, but awaits improved determinations of the stellar masses.},
  language  = {en}
}
@article{ZhangChenBoettcher2014,
  author    = {Zhang, Haocheng and Chen, Xuhui and Boettcher, Markus},
  title     = {Synchrotron polarization in blazars},
  series = {The astrophysical journal : an international review of spectroscopy and astronomical physics},
  volume    = {789},
  journal   = {The astrophysical journal : an international review of spectroscopy and astronomical physics},
  number    = {1},
  publisher = {IOP Publ. Ltd.},
  address   = {Bristol},
  issn      = {0004-637X},
  doi       = {10.1088/0004-637X/789/1/66},
  pages     = {16},
  year      = {2014},
  abstract  = {We present a detailed analysis of time-and energy-dependent synchrotron polarization signatures in a shock-in-jet model for gamma-ray blazars. Our calculations employ a full three-dimensional radiation transfer code, assuming a helical magnetic field throughout the jet. The code considers synchrotron emission from an ordered magnetic field, and takes into account all light-travel-time and other relevant geometric effects, while the relevant synchrotron self-Compton and external Compton effects are handled with the two-dimensional Monte-Carlo/Fokker-Planck (MCFP) code. We consider several possible mechanisms through which a relativistic shock propagating through the jet may affect the jet plasma to produce a synchrotron and high-energy flare. Most plausibly, the shock is expected to lead to a compression of the magnetic field, increasing the toroidal field component and thereby changing the direction of the magnetic field in the region affected by the shock. We find that such a scenario leads to correlated synchrotron + synchrotron-self-Compton flaring, associated with substantial variability in the synchrotron polarization percentage and position angle. Most importantly, this scenario naturally explains large polarization angle rotations by greater than or similar to 180 degrees, as observed in connection with gamma-ray flares in several blazars, without the need for bent or helical jet trajectories or other nonaxisymmetric jet features.},
  language  = {en}
}
@article{ZhangZhangYouetal.2014,
  author    = {Zhang, Xiaoqing and Zhang, Xinwu and You, Qiong and Sessler, Gerhard M.},
  title     = {Low- cost, large- area, stretchable piezoelectric films based on irradiation- crosslinked poly ( propylene)},
  series = {Macromolecular materials and engineering},
  volume    = {299},
  journal   = {Macromolecular materials and engineering},
  number    = {3},
  publisher = {Wiley-VCH},
  address   = {Weinheim},
  issn      = {1438-7492},
  doi       = {10.1002/mame.201300161},
  pages     = {290 -- 295},
  year      = {2014},
  abstract  = {Low cost, large area, lightweight, stretchable piezoelectric films, based on space-charge electret with a foam structure (i.e., ferroelectrets or piezoelectrets), have been fabricated by using commercially available irradiation cross-linked poly(propylene) (IXPP) foam sheets. Piezoelectric d(33) coefficients are as high as 100pCN(-1). The piezoelectric performance in such IXPP films is well preserved for repeated strains of less than 10\%. Piezoelectric d(33) coefficients are frequency independent in the range from 2 to 100Hz. Such new class materials may be applied in sensory skins, smart clothing, bio-inspired systems, microenergy harvesters, and so on.},
  language  = {en}
}
@article{ZhaoDunlopQiuetal.2014,
  author    = {Zhao, Qiang and Dunlop, John William Chapman and Qiu, Xunlin and Huang, Feihe and Zhang, Zibin and Heyda, Jan and Dzubiella, Joachim and Antonietti, Markus and Yuan, Jiayin},
  title     = {An instant multi-responsive porous polymer actuator driven by solvent molecule sorption},
  series = {Nature Communications},
  volume    = {5},
  journal   = {Nature Communications},
  publisher = {Nature Publ. Group},
  address   = {London},
  issn      = {2041-1723},
  doi       = {10.1038/ncomms5293},
  pages     = {8},
  year      = {2014},
  abstract  = {Fast actuation speed, large-shape deformation and robust responsiveness are critical to synthetic soft actuators. A simultaneous optimization of all these aspects without trade-offs remains unresolved. Here we describe porous polymer actuators that bend in response to acetone vapour (24 kPa, 20 degrees C) at a speed of an order of magnitude faster than the state-of-the-art, coupled with a large-scale locomotion. They are meanwhile multi-responsive towards a variety of organic vapours in both the dry and wet states, thus distinctive from the traditional gel actuation systems that become inactive when dried. The actuator is easy-to-make and survives even after hydrothermal processing (200 degrees C, 24 h) and pressing-pressure (100 MPa) treatments. In addition, the beneficial responsiveness is transferable, being able to turn 'inert' objects into actuators through surface coating. This advanced actuator arises from the unique combination of porous morphology, gradient structure and the interaction between solvent molecules and actuator materials.},
  language  = {en}
}
@phdthesis{Zhou2014,
  author    = {Zhou, Xu},
  title     = {Atmospheric interactions with land surface in the arctic based on regional climate model solutions},
  pages     = {143},
  year      = {2014},
  language  = {en}
}
@article{ZinkNiebuhrJechowetal.2014,
  author    = {Zink, Christof and Niebuhr, Mario and Jechow, Andreas and Heuer, Axel and Menzel, Ralf},
  title     = {Broad area diode laser with on-chip transverse Bragg grating stabilized in an off-axis external cavity},
  series = {Optics express : the international electronic journal of optics},
  volume    = {22},
  journal   = {Optics express : the international electronic journal of optics},
  number    = {12},
  publisher = {Optical Society of America},
  address   = {Washington},
  issn      = {1094-4087},
  doi       = {10.1364/OE.22.014108},
  pages     = {14108 -- 14113},
  year      = {2014},
  abstract  = {The emission characteristics of a novel, specially designed broad area diode laser (BAL) with on-chip transversal Bragg resonance (TBR) grating in lateral direction were investigated in an off-axis external cavity setup. The internal TBR grating defines a low loss transversal mode at a specific angle of incidence and a certain wavelength. By providing feedback at this specific angle with an external mirror, it is possible to select this low loss transverse mode and stabilize the BAL. Near diffraction limited emission with an almost single lobed far field pattern could be realized, in contrast to the double lobed far field pattern of similar setups using standard BALs or phase-locked diode laser arrays. Furthermore, we could achieve a narrow bandwidth emission with a simplified setup without external frequency selective elements. (C) 2014 Optical Society of America},
  language  = {en}
}
@article{ZinkWernerJechowetal.2014,
  author    = {Zink, Christof and Werner, Nils and Jechow, Andreas and Heuer, Axel and Menzel, Ralf},
  title     = {Multi-wavelength operation of a single broad area diode laser by spectral beam combining},
  series = {IEEE photonics technology letters},
  volume    = {26},
  journal   = {IEEE photonics technology letters},
  number    = {3},
  publisher = {Inst. of Electr. and Electronics Engineers},
  address   = {Piscataway},
  issn      = {1041-1135},
  doi       = {10.1109/LPT.2013.2291963},
  pages     = {253 -- 256},
  year      = {2014},
  abstract  = {Stabilized multi-wavelength emission from a single emitter broad area diode laser (BAL) is realized by utilizing an external cavity with a spectral beam combining architecture. Self-organized emitters that are equidistantly spaced across the slow axis are enforced by the spatially distributed wavelength selectivity of the external cavity. This resulted in an array like near-field emission although the BAL is physically a single emitter without any epitaxial sub-structuring and only one electrical contact. Each of the self-organized emitters is operated at a different wavelength and the emission is multiplexed into one spatial mode with near-diffraction limited beam quality. With this setup, multi-line emission of 31 individual spectral lines centered around and a total spectral width of 3.6 nm is realized with a 1000 mu m wide BAL just above threshold. To the best of our knowledge, this is the first demonstration of such a self-organization of emitters by optical feedback utilizing a spectral beam combining architecture.},
  language  = {en}
}