Dokument-ID Dokumenttyp Verfasser/Autoren Herausgeber Haupttitel Abstract Auflage Verlagsort Verlag Erscheinungsjahr Seitenzahl Schriftenreihe Titel Schriftenreihe Bandzahl ISBN Quelle der Hochschulschrift Konferenzname Quelle:Titel Quelle:Jahrgang Quelle:Heftnummer Quelle:Erste Seite Quelle:Letzte Seite URN DOI Abteilungen OPUS4-43696 misc Schick, Daniel; Eckert, Sebastian Oliver; Pontius, Niko; Mitzner, Rolf; Föhlisch, Alexander; Holldack, Karsten; Sorgenfrei, Florian Versatile soft X-ray-optical cross-correlator for ultrafast applications We present an X-ray-optical cross-correlator for the soft (> 150 eV) up to the hard X-ray regime based on a molybdenum-silicon superlattice. The cross-correlation is done by probing intensity and position changes of superlattice Bragg peaks caused by photoexcitation of coherent phonons. This approach is applicable for a wide range of X-ray photon energies as well as for a broad range of excitation wavelengths and requires no external fields or changes of temperature. Moreover, the cross-correlator can be employed on a 10 ps or 100 fs time scale featuring up to 50% total X-ray reflectivity and transient signal changes of more than 20%. (C) 2016 Author(s). 2016 9 Zweitveröffentlichungen der Universität Potsdam : Mathematisch-Naturwissenschaftliche Reihe 1331 054304-1 054304-8 urn:nbn:de:kobv:517-opus4-436962 10.25932/publishup-43696 Institut für Physik und Astronomie OPUS4-58962 Wissenschaftlicher Artikel Steinmetz, Matthias Die Vermessung des Universums Berlin Berlin-Brandenburgische Akademie der Wissenschaften 2016 13 Vision als Aufgabe : das Leibniz-Universum im 21. Jahrhundert 978-3-939818-67-0 197 210 urn:nbn:de:kobv:b4-opus4-25899 Institut für Physik und Astronomie OPUS4-56365 Wissenschaftlicher Artikel Reindl, Nicole; Rauch, Thomas; Miller Bertolami, Marcelo Miguel; Todt, Helge Tobias; Werner, K. Breaking news from the HST SAO 244567 is a rare example of a star that allows us to witness stellar evolution in real time. Between 1971 and 1990, it changed from a B-type star into the hot central star of the Stingray Nebula. This observed rapid heating has been a mystery for decades, since it is in strong contradiction with the low mass of the star and canonical post-asymptotic giant branch (AGB) evolution. We speculated that SAO 244567 might have suffered from a late thermal pulse (LTP) and obtained new observations with Hubble Space Telescope (HST)/COS to follow the evolution of the surface properties of SAO 244567 and to verify the LTP hypothesis. Our non-LTE spectral analysis reveals that the star cooled significantly since 2002 and that its envelope is now expanding. Therefore, we conclude that SAO 244567 is currently on its way back towards the AGB, which strongly supports the LTP hypothesis. A comparison with state-of-the-art LTP evolutionary calculations shows that these models cannot fully reproduce the evolution of all surface parameters simultaneously, pointing out possible shortcomings of stellar evolution models. Thereby, SAO 244567 keeps on challenging stellar evolution theory and we highly encourage further investigations. Oxford Oxford Univ. Press 2016 5 Monthly notices of the Royal Astronomical Society 464 L51 L55 10.1093/mnrasl/slw175 Institut für Physik und Astronomie OPUS4-45908 Wissenschaftlicher Artikel Zehbe, Rolf; Zaslansky, Paul; Mochales, Carolina; Mueller, Wolf-Dieter; Fleck, Claudia Synchrotron micro tomographic evaluation of multilayered zirconia ceramics-Volumetric effects after indentation Electrophoretic deposition was used to produce zirconia specimen consisting of alternating layers of fully stabilized cubic zirconia and partially stabilized tetragonal zirconia. In this configuration, the tetragonal stabilized zirconia layers can undergo transformation toughening upon mechanical induced stresses, while the cubic stabilized layers can act as confining element. To understand the volumetric changes due to transformation toughening in these layered materials after indentation, we used an advanced synchrotron-based X-ray mu CT setup and compared the results with surface sensitive methods like Raman spectroscopy, AFM and white light interferometry. The high spatial resolution and the adapted beam energy between the absorption edges of zirconia and yttria allowed discriminating between individual layers due to differences in their yttria content. Furthermore we were able to identify single indents and link volume changes to different physical effects in the different stabilized zirconia parts and visualize the three dimensional volume around only few micrometre sized indents. (C) 2015 Elsevier Ltd. All rights reserved. Oxford Elsevier 2016 7 Journal of the European Ceramic Society 36 171 177 10.1016/j.jeurceramsoc.2015.09.015 Institut für Physik und Astronomie OPUS4-45898 Wissenschaftlicher Artikel Zehbe, Rolf; Mochales, Carolina; Radzik, Daniela; Mueller, Wolf-Dieter; Fleck, Claudia Electrophoretic deposition of multilayered (cubic and tetragonal stabilized) zirconia ceramics for adapted crack deflection The electrophoretic deposition process was used to produce multi-layered ceramics consisting of alternating layers of fully stabilized cubic zirconia and partially stabilized tetragonal zirconia to make use of their different mechanical behaviour, investigating the possibility to deflect advancing cracks at the interfaces of the different layers. This crack deflection is apparently impacted by a toughening mechanism only found in the tetragonal stabilized zirconia polymorph and is characterized by the stress induced transformation of the metastable tetragonal phase into the monoclinic one, which is accompanied by a volume increase resulting in a closing mechanism for advancing cracks. While improving the electrophoretic deposition process, we investigated the transformation toughening mechanism at the layer interfaces and their effect on crack propagation. Investigations involved a combination of different imaging methods, including light microscopy, white light interferometry, atomic force microscopy, scanning electron microscopy, energy dispersive X-ray spectroscopy and Raman spectroscopy. (C) 2015 Elsevier Ltd. All rights reserved. Oxford Elsevier 2016 8 Journal of the European Ceramic Society 36 357 364 10.1016/j.jeurceramsoc.2015.08.022 Institut für Physik und Astronomie OPUS4-45893 Wissenschaftlicher Artikel Mengel, Matthias; Feldmann, Johannes; Levermann, Anders Linear sea-level response to abrupt ocean warming of major West Antarctic ice basin Antarctica's contribution to global sea-level rise has recently been increasing1. Whether its ice discharge will become unstable and decouple from anthropogenic forcing2,3,4 or increase linearly with the warming of the surrounding ocean is of fundamental importance5. Under unabated greenhouse-gas emissions, ocean models indicate an abrupt intrusion of warm circumpolar deep water into the cavity below West Antarctica's Filchner-Ronne ice shelf within the next two centuries6,7. The ice basin's retrograde bed slope would allow for an unstable ice-sheet retreat8, but the buttressing of the large ice shelf and the narrow glacier troughs tend to inhibit such instability9,10,11. It is unclear whether future ice loss will be dominated by ice instability or anthropogenic forcing. Here we show in regional and continental-scale ice-sheet simulations, which are capable of resolving unstable grounding-line retreat, that the sea-level response of the Filchner-Ronne ice basin is not dominated by ice instability and follows the strength of the forcing quasi-linearly. We find that the ice loss reduces after each pulse of projected warm water intrusion. The long-term sea-level contribution is approximately proportional to the total shelf-ice melt. Although the local instabilities might dominate the ice loss for weak oceanic warming12, we find that the upper limit of ice discharge from the region is determined by the forcing and not by the marine ice-sheet instability. London Nature Publ. Group 2016 5 Nature climate change 6 71 + 10.1038/NCLIMATE2808 Institut für Physik und Astronomie OPUS4-45854 Wissenschaftlicher Artikel Baushev, Anton N. Can the dark matter annihilation signal be significantly boosted by substructures? A very general cosmological consideration suggests that, along with galactic dark matter halos, much smaller dark matter structures may exist. These structures are usually called `clumps', and their mass extends to 10−6 M ⊙ or even lower. The clumps should give the main contribution into the signal of dark matter annihilation, provided that they have survived until the present time. Recent observations favor a cored profile for low-mass astrophysical halos. We consider cored clumps and show that they are significantly less firm than the standard NFW ones. In contrast to the standard scenario, the cored clumps should have been completely destroyed inside ~ 20 kpc from the Milky Way center. The dwarf spheroidals should not contain any dark matter clumps. On the other hand, even under the most pessimistic assumption about the clump structure, the clumps should have survived in the Milky Way at a distance exceeding 50 kpc from the center, as well as in low-density cosmic structures. There they significantly boost the dark matter annihilation. We show that at least 70% of the clumps endured the primordial structure formation should still exist untouched in the present-day Universe. Bristol IOP Publ. Ltd. 2016 17 Journal of cosmology and astroparticle physics 30 12 18 10.1088/1475-7516/2016/01/018 Institut für Physik und Astronomie OPUS4-45846 Wissenschaftlicher Artikel Kuznetsov, Alexander P.; Turukina, Ludmila V.; Chernyshov, Nikolai Yu; Sedova, Yuliya V. Oscillations and Synchronization in a System of Three Reactively Coupled Oscillators We consider a system of three interacting van der Pol oscillators with reactive coupling. Phase equations are derived, using proper order of expansion over the coupling parameter. The dynamics of the system is studied by means of the bifurcation analysis and with the method of Lyapunov exponent charts. Essential and physically meaningful features of the reactive coupling are discussed. Singapore World Scientific 2016 10 International journal of bifurcation and chaos : in applied sciences and engineering 26 31 39 10.1142/S0218127416500103 Institut für Physik und Astronomie OPUS4-45843 Wissenschaftlicher Artikel Yadavalli, Nataraja Sekhar; Loebner, Sarah; Papke, Thomas; Sava, Elena; Hurduc, Nicolae; Santer, Svetlana A. A comparative study of photoinduced deformation in azobenzene containing polymer films In this paper two groups supporting different views on the mechanism of light induced polymer deformation argue about the respective underlying theoretical conceptions, in order to bring this interesting debate to the attention of the scientific community. The group of Prof. Nicolae Hurduc supports the model claiming that the cyclic isomerization of azobenzenes may cause an athermal transition of the glassy azobenzene containing polymer into a fluid state, the so-called photo-fluidization concept. This concept is quite convenient for an intuitive understanding of the deformation process as an anisotropic flow of the polymer material. The group of Prof. Svetlana Santer supports the re-orientational model where the mass-transport of the polymer material accomplished during polymer deformation is stated to be generated by the light-induced re-orientation of the azobenzene side chains and as a consequence of the polymer backbone that in turn results in local mechanical stress, which is enough to irreversibly deform an azobenzene containing material even in the glassy state. For the debate we chose three polymers differing in the glass transition temperature, 32 degrees C, 87 degrees C and 95 degrees C, representing extreme cases of flexible and rigid materials. Polymer film deformation occurring during irradiation with different interference patterns is recorded using a homemade set-up combining an optical part for the generation of interference patterns and an atomic force microscope for acquiring the kinetics of film deformation. We also demonstrated the unique behaviour of azobenzene containing polymeric films to switch the topography in situ and reversibly by changing the irradiation conditions. We discuss the results of reversible deformation of three polymers induced by irradiation with intensity (IIP) and polarization (PIP) interference patterns, and the light of homogeneous intensity in terms of two approaches: the re-orientational and the photo-fluidization concepts. Both agree in that the formation of opto-mechanically induced stresses is a necessary prerequisite for the process of deformation. Using this argument, the deformation process can be characterized either as a flow or mass transport. Cambridge Royal Society of Chemistry 2016 11 Soft matter 12 2593 2603 10.1039/c6sm00029k Institut für Physik und Astronomie OPUS4-45839 misc Teif, Vladimir B.; Cherstvy, Andrey G. Chromatin and epigenetics: current biophysical views Recent advances in high-throughput sequencing experiments and their theoretical descriptions have determined fast dynamics of the "chromatin and epigenetics" field, with new concepts appearing at high rate. This field includes but is not limited to the study of DNA-protein-RNA interactions, chromatin packing properties at different scales, regulation of gene expression and protein trafficking in the cell nucleus, binding site search in the crowded chromatin environment and modulation of physical interactions by covalent chemical modifications of the binding partners. The current special issue does not pretend for the full coverage of the field, but it rather aims to capture its development and provide a snapshot of the most recent concepts and approaches. Eighteen open-access articles comprising this issue provide a delicate balance between current theoretical and experimental biophysical approaches to uncover chromatin structure and understand epigenetic regulation, allowing free flow of new ideas and preliminary results. Springfield American Institute of Mathematical Sciences 2016 11 AIMS biophysics 3 88 98 10.3934/biophy.2016.1.88 Institut für Physik und Astronomie