@article{StangeHintscheSachseetal.2017, author = {Stange, Maike and Hintsche, Marius and Sachse, Kirsten and Gerhardt, Matthias and Valleriani, Angelo and Beta, Carsten}, title = {Analyzing the spatial positioning of nuclei in polynuclear giant cells}, series = {Journal of Physics D: Applied Physics}, volume = {50}, journal = {Journal of Physics D: Applied Physics}, number = {46}, publisher = {IOP Publ. Ltd.}, address = {Bristol}, issn = {0022-3727}, doi = {10.1088/1361-6463/aa8da0}, pages = {8}, year = {2017}, abstract = {How cells establish and maintain a well-defined size is a fundamental question of cell biology. Here we investigated to what extent the microtubule cytoskeleton can set a predefined cell size, independent of an enclosing cell membrane. We used electropulse-induced cell fusion to form giant multinuclear cells of the social amoeba Dictyostelium discoideum. Based on dual-color confocal imaging of cells that expressed fluorescent markers for the cell nucleus and the microtubules, we determined the subcellular distributions of nuclei and centrosomes in the giant cells. Our two- and three-dimensional imaging results showed that the positions of nuclei in giant cells do not fall onto a regular lattice. However, a comparison with model predictions for random positioning showed that the subcellular arrangement of nuclei maintains a low but still detectable degree of ordering. This can be explained by the steric requirements of the microtubule cytoskeleton, as confirmed by the effect of a microtubule degrading drug.}, language = {en} } @article{KurzkeKietheHeueretal.2017, author = {Kurzke, Henning and Kiethe, Jan and Heuer, Axel and Jechow, Andreas}, title = {Frequency doubling of incoherent light from a superluminescent diode in a periodically poled lithium niobate waveguide crystal}, series = {Laser physics letters}, volume = {14}, journal = {Laser physics letters}, publisher = {IOP Publ.}, address = {Bristol}, issn = {1612-2011}, doi = {10.1088/1612-202X/aa6889}, pages = {5}, year = {2017}, abstract = {The amplified spontaneous emission from a superluminescent diode was frequency doubled in a periodically poled lithium niobate waveguide crystal. The temporally incoherent radiation of such a superluminescent diode is characterized by a relatively broad spectral bandwidth and thermal-like photon statistics, as the measured degree of second order coherence, g((2))(0)= 1.9 +/- 0.1, indicates. Despite the non-optimized scenario in the spectral domain, we achieve six orders of magnitude higher conversion efficiency than previously reported with truly incoherent light. This is possible by using single spatial mode radiation and quasi phase matched material with a waveguide architecture. This work is a principle step towards efficient frequency conversion of temporally incoherent radiation in one spatial mode to access wavelengths where no radiation from superluminescent diodes is available, especially with tailored quasi phase matched crystals. The frequency doubled light might find application in imaging, metrology and quantum optics experiments.}, language = {en} } @article{KamannHusserDreizleretal.2017, author = {Kamann, Sebastian and Husser, T. -O. and Dreizler, S. and Emsellem, E. and Weilbacher, Peter Michael and Martens, S. and Bacon, R. and den Brok, M. and Giesers, B. and Krajnovic, Davor and Roth, Martin M. and Wendt, Martin and Wisotzki, Lutz}, title = {A stellar census in globular clusters with MUSE}, series = {Monthly notices of the Royal Astronomical Society}, volume = {473}, journal = {Monthly notices of the Royal Astronomical Society}, number = {4}, publisher = {Oxford Univ. Press}, address = {Oxford}, issn = {0035-8711}, doi = {10.1093/mnras/stx2719}, pages = {5591 -- 5616}, year = {2017}, abstract = {This is the first of a series of papers presenting the results from our survey of 25 Galactic globular clusters with the MUSE integral-field spectrograph. In combination with our dedicated algorithm for source deblending, MUSE provides unique multiplex capabilities in crowded stellar fields and allows us to acquire samples of up to 20 000 stars within the half-light radius of each cluster. The present paper focuses on the analysis of the internal dynamics of 22 out of the 25 clusters, using about 500 000 spectra of 200 000 individual stars. Thanks to the large stellar samples per cluster, we are able to perform a detailed analysis of the central rotation and dispersion fields using both radial profiles and two-dimensional maps. The velocity dispersion profiles we derive show a good general agreement with existing radial velocity studies but typically reach closer to the cluster centres. By comparison with proper motion data, we derive or update the dynamical distance estimates to 14 clusters. Compared to previous dynamical distance estimates for 47 Tuc, our value is in much better agreement with other methods. We further find significant (>3 sigma) rotation in the majority (13/22) of our clusters. Our analysis seems to confirm earlier findings of a link between rotation and the ellipticities of globular clusters. In addition, we find a correlation between the strengths of internal rotation and the relaxation times of the clusters, suggesting that the central rotation fields are relics of the cluster formation that are gradually dissipated via two-body relaxation.}, language = {en} } @misc{JavanainenMartinezSearaMetzleretal.2017, author = {Javanainen, Matti and Martinez-Seara, Hector and Metzler, Ralf and Vattulainen, Ilpo Tapio}, title = {Diffusion of Proteins and Lipids in Protein-Rich Membranesa}, series = {Biophysical journal}, volume = {114}, journal = {Biophysical journal}, number = {3}, publisher = {Cell Press}, address = {Cambridge}, issn = {0006-3495}, doi = {10.1016/j.bpj.2017.11.3009}, pages = {551A -- 551A}, year = {2017}, language = {en} } @misc{ShpritsAngelopoulosRusselletal.2017, author = {Shprits, Yuri Y. and Angelopoulos, V. and Russell, C. T. and Strangeway, R. J. and Runov, A. and Turner, D. and Caron, R. and Cruce, P. and Leneman, D. and Michaelis, I. and Petrov, V. and Panasyuk, M. and Yashin, I. and Drozdov, Alexander Y. and Russell, C. L. and Kalegaev, V. and Nazarkov, I. and Clemmons, J. H.}, title = {Scientific Objectives of Electron Losses and Fields INvestigation Onboard Lomonosov Satellite}, series = {Space science reviews}, volume = {214}, journal = {Space science reviews}, number = {1}, publisher = {Springer}, address = {Dordrecht}, issn = {0038-6308}, doi = {10.1007/s11214-017-0455-4}, pages = {19}, year = {2017}, abstract = {The objective of the Electron Losses and Fields INvestigation on board the Lomonosov satellite ( ELFIN-L) project is to determine the energy spectrum of precipitating energetic electrons and ions and, together with other polar-orbiting and equatorial missions, to better understand the mechanisms responsible for scattering these particles into the atmosphere. This mission will provide detailed measurements of the radiation environment at low altitudes. The 400-500 km sun-synchronous orbit of Lomonosov is ideal for observing electrons and ions precipitating into the atmosphere. This mission provides a unique opportunity to test the instruments. Similar suite of instruments will be flown in the future NSF-and NASA-supported spinning CubeSat ELFIN satellites which will augment current measurements by providing detailed information on pitch-angle distributions of precipitating and trapped particles.}, language = {en} } @misc{GudowskaNowakLindenbergMetzler2017, author = {Gudowska-Nowak, Ewa and Lindenberg, Katja and Metzler, Ralf}, title = {Preface: Marian Smoluchowski's 1916 paper—a century of inspiration}, series = {Journal of physics : A, Mathematical and theoretical}, volume = {50}, journal = {Journal of physics : A, Mathematical and theoretical}, number = {38}, publisher = {IOP Publ. Ltd.}, address = {Bristol}, issn = {1751-8113}, doi = {10.1088/1751-8121/aa8529}, pages = {8}, year = {2017}, language = {en} } @article{HaniSparreEllisonetal.2017, author = {Hani, Maan H. and Sparre, Martin and Ellison, Sara L. and Torrey, Paul and Vogelsberger, Mark}, title = {Galaxy mergers moulding the circum-galactic medium}, series = {Monthly notices of the Royal Astronomical Society}, volume = {475}, journal = {Monthly notices of the Royal Astronomical Society}, number = {1}, publisher = {Oxford Univ. Press}, address = {Oxford}, issn = {0035-8711}, doi = {10.1093/mnras/stx3252}, pages = {1160 -- 1176}, year = {2017}, abstract = {Galaxies are surrounded by sizeable gas reservoirs which host a significant amount of metals: the circum-galactic medium (CGM). The CGM acts as a mediator between the galaxy and the extragalactic medium. However, our understanding of how galaxy mergers, a major evolutionary transformation, impact the CGM remains deficient. We present a theoretical study of the effect of galaxy mergers on the CGM. We use hydrodynamical cosmological zoom-in simulations of a major merger selected from the Illustris project such that the z = 0 descendant has a halo mass and stellar mass comparable to the Milky Way. To study the CGM we then re-simulated this system at a 40 times better mass resolution, and included detailed post-processing ionization modelling. Our work demonstrates the effect the merger has on the characteristic size of the CGM, its metallicity, and the predicted covering fraction of various commonly observed gas-phase species, such as H I, C IV, and O VI. We show that merger-induced outflows can increase the CGM metallicity by 0.2-0.3 dex within 0.5 Gyr post-merger. These effects last up to 6 Gyr post-merger. While the merger increases the total metal covering fractions by factors of 2-3, the covering fractions of commonly observed UV ions decrease due to the hard ionizing radiation from the active galactic nucleus, which we model explicitly. Our study of the single simulated major merger presented in this work demonstrates the significant impact that a galaxy interaction can have on the size, metallicity, and observed column densities of the CGM.}, language = {en} } @misc{BeniniSchenkel2017, author = {Benini, Marco and Schenkel, Alexander}, title = {Quantum field theories on categories fibered in groupoids}, series = {Postprints der Universit{\"a}t Potsdam : Mathematisch-Naturwissenschaftliche Reihe}, journal = {Postprints der Universit{\"a}t Potsdam : Mathematisch-Naturwissenschaftliche Reihe}, number = {895}, issn = {1866-8372}, doi = {10.25932/publishup-43154}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus4-431541}, pages = {48}, year = {2017}, abstract = {We introduce an abstract concept of quantum field theory on categories fibered in groupoids over the category of spacetimes. This provides us with a general and flexible framework to study quantum field theories defined on spacetimes with extra geometric structures such as bundles, connections and spin structures. Using right Kan extensions, we can assign to any such theory an ordinary quantum field theory defined on the category of spacetimes and we shall clarify under which conditions it satisfies the axioms of locally covariant quantum field theory. The same constructions can be performed in a homotopy theoretic framework by using homotopy right Kan extensions, which allows us to obtain first toy-models of homotopical quantum field theories resembling some aspects of gauge theories.}, language = {en} } @misc{ParsonsSchuesslerGarrigouxetal.2017, author = {Parsons, R. D. and Sch{\"u}ssler, F. and Garrigoux, T. and Balzer, A. and F{\"u}ssling, Matthias and Hoischen, Clemens and Holler, M. and Mitchell, A. and P{\"u}hlhofer, G. and Rowell, G. and Wagner, S. and Bissaldi, E. and Tam, P. H. T.}, title = {The HESS II GRB Observation Scheme}, series = {AIP conference proceedings / American Institute of Physics}, volume = {1792}, journal = {AIP conference proceedings / American Institute of Physics}, number = {1}, publisher = {American Institute of Physics}, address = {Melville}, organization = {HESS Collaboration}, isbn = {978-0-7354-1456-3}, issn = {0094-243X}, doi = {10.1063/1.4968980}, pages = {5}, year = {2017}, abstract = {Gamma-ray bursts (GRBs) are some of the Universe's most enigmatic and exotic events. However, at energies above 10 GeV their behaviour remains largely unknown. Although space based telescopes such as the Fermi-LAT have been able to detect GRBs in this energy range, their photon statistics are limited by the small detector size. Such limitations are not present in ground based gamma-ray telescopes such as the H.E.S.S. experiment, which has now entered its second phase with the addition of a large 600 m2 telescope to the centre of the array. Such a large telescope allows H.E.S.S. to access the sub 100-GeV energy range while still maintaining a large effective collection area, helping to potentially probe the short timescale emission of these events. We present a description of the H.E.S.S. GRB observation programme, summarising the performance of the rapid GRB repointing system and the conditions under which GRB observations are initiated. Additionally we will report on the GRB follow-ups made during the 2014-15 observation campaigns.}, language = {en} } @misc{AnguenerAharonianBordasetal.2017, author = {Ang{\"u}ner, Ekrem Oǧuzhan and Aharonian, Felix A. and Bordas, Pol and Casanova, Sabrina and Hoischen, Clemens and Oya, I. and Ziegler, A.}, title = {HESS J1826-130}, series = {AIP conference proceedings / American Institute of Physics}, volume = {1792}, journal = {AIP conference proceedings / American Institute of Physics}, number = {1}, publisher = {American Institute of Physics}, address = {Melville}, organization = {HESS Collaboration}, isbn = {978-0-7354-1456-3}, issn = {0094-243X}, doi = {10.1063/1.4968928}, pages = {6}, year = {2017}, abstract = {HESS J1826-130 is an unidentified hard spectrum source discovered by H.E.S.S. along the Galactic plane, the spectral index being Gamma = 1.6 with an exponential cut-off at about 12 TeV. While the source does not have a clear counterpart at longer wavelengths, the very hard spectrum emission at TeV energies implies that electrons or protons accelerated up to several hundreds of TeV are responsible for the emission. In the hadronic case, the VHE emission can be produced by runaway cosmic-rays colliding with the dense molecular clouds spatially coincident with the H.E.S.S. source.}, language = {en} }