TY  - JOUR
A1  - Stange, Maike
A1  - Hintsche, Marius
A1  - Sachse, Kirsten
A1  - Gerhardt, Matthias
A1  - Valleriani, Angelo
A1  - Beta, Carsten
T1  - Analyzing the spatial positioning of nuclei in polynuclear giant cells
JF  - Journal of Physics D: Applied Physics
N2  - How cells establish and maintain a well-defined size is a fundamental question of cell biology. Here we investigated to what extent the microtubule cytoskeleton can set a predefined cell size, independent of an enclosing cell membrane. We used electropulse-induced cell fusion to form giant multinuclear cells of the social amoeba Dictyostelium discoideum. Based on dual-color confocal imaging of cells that expressed fluorescent markers for the cell nucleus and the microtubules, we determined the subcellular distributions of nuclei and centrosomes in the giant cells. Our two- and three-dimensional imaging results showed that the positions of nuclei in giant cells do not fall onto a regular lattice. However, a comparison with model predictions for random positioning showed that the subcellular arrangement of nuclei maintains a low but still detectable degree of ordering. This can be explained by the steric requirements of the microtubule cytoskeleton, as confirmed by the effect of a microtubule degrading drug.
KW  - Dictyostelium
KW  - cell nucleus
KW  - positioning
KW  - imaging
KW  - spatial poisson distribution
Y1  - 2017
U6  - https://doi.org/10.1088/1361-6463/aa8da0
SN  - 0022-3727
SN  - 1361-6463
VL  - 50
IS  - 46
PB  - IOP Publ. Ltd.
CY  - Bristol
ER  - 
TY  - JOUR
A1  - Kurzke, Henning
A1  - Kiethe, Jan
A1  - Heuer, Axel
A1  - Jechow, Andreas
T1  - Frequency doubling of incoherent light from a superluminescent diode in a periodically poled lithium niobate waveguide crystal
JF  - Laser physics letters
N2  - The amplified spontaneous emission from a superluminescent diode was frequency doubled in a periodically poled lithium niobate waveguide crystal. The temporally incoherent radiation of such a superluminescent diode is characterized by a relatively broad spectral bandwidth and thermal-like photon statistics, as the measured degree of second order coherence, g((2))(0)= 1.9 +/- 0.1, indicates. Despite the non-optimized scenario in the spectral domain, we achieve six orders of magnitude higher conversion efficiency than previously reported with truly incoherent light. This is possible by using single spatial mode radiation and quasi phase matched material with a waveguide architecture. This work is a principle step towards efficient frequency conversion of temporally incoherent radiation in one spatial mode to access wavelengths where no radiation from superluminescent diodes is available, especially with tailored quasi phase matched crystals. The frequency doubled light might find application in imaging, metrology and quantum optics experiments.
KW  - nonlinear frequency conversion
KW  - periodically poled material
KW  - waveguides
KW  - incoherent radiation
Y1  - 2017
U6  - https://doi.org/10.1088/1612-202X/aa6889
SN  - 1612-2011
SN  - 1612-202X
VL  - 14
PB  - IOP Publ.
CY  - Bristol
ER  - 
TY  - JOUR
A1  - Kamann, Sebastian
A1  - Husser, T. -O.
A1  - Dreizler, S.
A1  - Emsellem, E.
A1  - Weilbacher, Peter Michael
A1  - Martens, S.
A1  - Bacon, R.
A1  - den Brok, M.
A1  - Giesers, B.
A1  - Krajnovic, Davor
A1  - Roth, Martin M.
A1  - Wendt, Martin
A1  - Wisotzki, Lutz
T1  - A stellar census in globular clusters with MUSE
BT  - the contribution of rotation to cluster dynamics studied with 200 000 stars
JF  - Monthly notices of the Royal Astronomical Society
N2  - This is the first of a series of papers presenting the results from our survey of 25 Galactic globular clusters with the MUSE integral-field spectrograph. In combination with our dedicated algorithm for source deblending, MUSE provides unique multiplex capabilities in crowded stellar fields and allows us to acquire samples of up to 20 000 stars within the half-light radius of each cluster. The present paper focuses on the analysis of the internal dynamics of 22 out of the 25 clusters, using about 500 000 spectra of 200 000 individual stars. Thanks to the large stellar samples per cluster, we are able to perform a detailed analysis of the central rotation and dispersion fields using both radial profiles and two-dimensional maps. The velocity dispersion profiles we derive show a good general agreement with existing radial velocity studies but typically reach closer to the cluster centres. By comparison with proper motion data, we derive or update the dynamical distance estimates to 14 clusters. Compared to previous dynamical distance estimates for 47 Tuc, our value is in much better agreement with other methods. We further find significant (>3 sigma) rotation in the majority (13/22) of our clusters. Our analysis seems to confirm earlier findings of a link between rotation and the ellipticities of globular clusters. In addition, we find a correlation between the strengths of internal rotation and the relaxation times of the clusters, suggesting that the central rotation fields are relics of the cluster formation that are gradually dissipated via two-body relaxation.
KW  - techniques: imaging spectroscopy
KW  - stars: kinematics and dynamics
KW  - globular clusters: general
Y1  - 2017
U6  - https://doi.org/10.1093/mnras/stx2719
SN  - 0035-8711
SN  - 1365-2966
VL  - 473
IS  - 4
SP  - 5591
EP  - 5616
PB  - Oxford Univ. Press
CY  - Oxford
ER  - 
TY  - JOUR
A1  - Hani, Maan H.
A1  - Sparre, Martin
A1  - Ellison, Sara L.
A1  - Torrey, Paul
A1  - Vogelsberger, Mark
T1  - Galaxy mergers moulding the circum-galactic medium
BT  - I. The impact of a major merger
JF  - Monthly notices of the Royal Astronomical Society
N2  - Galaxies are surrounded by sizeable gas reservoirs which host a significant amount of metals: the circum-galactic medium (CGM). The CGM acts as a mediator between the galaxy and the extragalactic medium. However, our understanding of how galaxy mergers, a major evolutionary transformation, impact the CGM remains deficient. We present a theoretical study of the effect of galaxy mergers on the CGM. We use hydrodynamical cosmological zoom-in simulations of a major merger selected from the Illustris project such that the z = 0 descendant has a halo mass and stellar mass comparable to the Milky Way. To study the CGM we then re-simulated this system at a 40 times better mass resolution, and included detailed post-processing ionization modelling. Our work demonstrates the effect the merger has on the characteristic size of the CGM, its metallicity, and the predicted covering fraction of various commonly observed gas-phase species, such as H I, C IV, and O VI. We show that merger-induced outflows can increase the CGM metallicity by 0.2-0.3 dex within 0.5 Gyr post-merger. These effects last up to 6 Gyr post-merger. While the merger increases the total metal covering fractions by factors of 2-3, the covering fractions of commonly observed UV ions decrease due to the hard ionizing radiation from the active galactic nucleus, which we model explicitly. Our study of the single simulated major merger presented in this work demonstrates the significant impact that a galaxy interaction can have on the size, metallicity, and observed column densities of the CGM.
KW  - methods: numerical
KW  - galaxies: evolution
KW  - galaxies: haloes
KW  - galaxies: interactions
Y1  - 2017
U6  - https://doi.org/10.1093/mnras/stx3252
SN  - 0035-8711
SN  - 1365-2966
VL  - 475
IS  - 1
SP  - 1160
EP  - 1176
PB  - Oxford Univ. Press
CY  - Oxford
ER  - 
TY  - JOUR
A1  - Beta, Carsten
A1  - Kruse, Karsten
T1  - Intracellular oscillations and waves
JF  - Annual review of condensed matter physics
N2  - Dynamic processes in living cells are highly organized in space and time. Unraveling the underlying molecular mechanisms of spatiotemporal pattern formation remains one of the outstanding challenges at the interface between physics and biology. A fundamental recurrent pattern found in many different cell types is that of self-sustained oscillations. They are involved in a wide range of cellular functions, including second messenger signaling, gene expression, and cytoskeletal dynamics. Here, we review recent developments in the field of cellular oscillations and focus on cases where concepts from physics have been instrumental for understanding the underlying mechanisms. We consider biochemical and genetic oscillators as well as oscillations that arise from chemo-mechanical coupling. Finally, we highlight recent studies of intracellular waves that have increasingly moved into the focus of this research field.
KW  - self-sustained oscillations
KW  - biochemical oscillators
KW  - genetic networks
KW  - chemomechanical coupling
KW  - actin waves
Y1  - 2017
SN  - 978-0-8243-5008-6
U6  - https://doi.org/10.1146/annurev-conmatphys-031016-025210
SN  - 1947-5454
VL  - 8
SP  - 239
EP  - 264
PB  - Annual Reviews
CY  - Palo Alto
ER  - 
TY  - JOUR
A1  - Mardoukhi, Ahmad
A1  - Mardoukhi, Yousof
A1  - Hokka, Mikko
A1  - Kuokkala, Veli-Tapani
T1  - Effects of strain rate and surface cracks on the mechanical behaviour of Balmoral Red granite
JF  - Philosophical Transactions of the Royal Society of London, Series A : Mathematical, Physical and Engineering Sciences
N2  - This work presents a systematic study on the effects of strain rate and surface cracks on the mechanical properties and behaviour of Balmoral Red granite. The tensile behaviour of the rock was studied at low and high strain rates using Brazilian disc samples. Heat shocks were used to produce samples with different amounts of surface cracks. The surface crack patterns were analysed using optical microscopy, and the complexity of the patterns was quantified by calculating the fractal dimensions of the patterns. The strength of the rock clearly drops as a function of increasing fractal dimensions in the studied strain rate range. However, the dynamic strength of the rock drops significantly faster than the quasi-static strength, and, because of this, also the strain rate sensitivity of the rock decreases with increasing fractal dimensions. This can be explained by the fracture behaviour and fragmentation during the dynamic loading, which is more strongly affected by the heat shock than the fragmentation at low strain rates.
KW  - split Hopkinson pressure bar
KW  - rock
KW  - granite
KW  - dynamic loading
KW  - fractal dimension
KW  - surface cracks
Y1  - 2017
U6  - https://doi.org/10.1098/rsta.2016.0179
SN  - 1364-503X
SN  - 1471-2962
VL  - 375
IS  - 2085
PB  - Royal Society
CY  - London
ER  - 
TY  - JOUR
A1  - Ahnen, M. L.
A1  - Ansoldi, S.
A1  - Antonelli, L. A.
A1  - Antoranz, P.
A1  - Babic, A.
A1  - Banerjee, B.
A1  - Bangale, P.
A1  - de Almeida, U. Barres
A1  - Barrio, J. A.
A1  - Gonzalez, J. Becerra
A1  - Bednarek, W.
A1  - Bernardini, E.
A1  - Berti, A.
A1  - Biasuzzi, B.
A1  - Biland, A.
A1  - Blanch, O.
A1  - Bonnefoy, S.
A1  - Bonnoli, G.
A1  - Borracci, F.
A1  - Bretz, T.
A1  - Buson, S.
A1  - Carosi, A.
A1  - Chatterjee, A.
A1  - Clavero, R.
A1  - Colin, P.
A1  - Colombo, E.
A1  - Contreras, J. L.
A1  - Cortina, J.
A1  - Covino, S.
A1  - Da Vela, P.
A1  - Dazzi, F.
A1  - De Angelis, A.
A1  - De Lotto, B.
A1  - Wilhelmi, E. de Ona
A1  - Di Pierro, F.
A1  - Doert, M.
A1  - Dominguez, A.
A1  - Prester, D. Dominis
A1  - Dorner, D.
A1  - Doro, M.
A1  - Einecke, S.
A1  - Glawion, D. Eisenacher
A1  - Elsaesser, D.
A1  - Engelkemeier, M.
A1  - Ramazani, V. Fallah
A1  - Fernandez-Barral, A.
A1  - Fidalgo, D.
A1  - Fonseca, M. V.
A1  - Font, L.
A1  - Frantzen, K.
A1  - Fruck, C.
A1  - Galindo, D.
A1  - Lopez, R. J. Garcia
A1  - Garczarczyk, M.
A1  - Terrats, D. Garrido
A1  - Gaug, M.
A1  - Giammaria, P.
A1  - Godinovic, N.
A1  - Gonzalez Munoz, A.
A1  - Gora, D.
A1  - Guberman, D.
A1  - Hadasch, D.
A1  - Hahn, A.
A1  - Hanabata, Y.
A1  - Hayashida, M.
A1  - Herrera, J.
A1  - Hose, J.
A1  - Hrupec, D.
A1  - Hughes, G.
A1  - Idec, W.
A1  - Kodani, K.
A1  - Konno, Y.
A1  - Kubo, H.
A1  - Kushida, J.
A1  - La Barbera, A.
A1  - Lelas, D.
A1  - Lindfors, E.
A1  - Lombardi, S.
A1  - Longo, F.
A1  - Lopez, M.
A1  - Lopez-Coto, R.
A1  - Majumdar, P.
A1  - Makariev, M.
A1  - Mallot, K.
A1  - Maneva, G.
A1  - Manganaro, M.
A1  - Mannheim, K.
A1  - Maraschi, L.
A1  - Marcote, B.
A1  - Mariotti, M.
A1  - Martinez, M.
A1  - Mazin, D.
A1  - Menzel, U.
A1  - Miranda, J. M.
A1  - Mirzoyan, R.
A1  - Moralejo, A.
A1  - Moretti, E.
A1  - Nakajima, D.
A1  - Neustroev, V.
A1  - Niedzwiecki, A.
A1  - Rosillo, M. Nievas
A1  - Nilsson, K.
A1  - Nishijima, K.
A1  - Noda, K.
A1  - Nogues, L.
A1  - Overkemping, A.
A1  - Paiano, S.
A1  - Palacio, J.
A1  - Palatiello, M.
A1  - Paneque, D.
A1  - Paoletti, R.
A1  - Paredes, J. M.
A1  - Paredes-Fortuny, X.
A1  - Pedaletti, G.
A1  - Peresano, M.
A1  - Perri, L.
A1  - Persic, M.
A1  - Poutanen, J.
A1  - Moroni, P. G. Prada
A1  - Prandini, E.
A1  - Puljak, I.
A1  - Reichardt, I.
A1  - Rhode, W.
A1  - Ribo, M.
A1  - Rico, J.
A1  - Rodriguez Garcia, J.
A1  - Saito, T.
A1  - Satalecka, K.
A1  - Schroder, S.
A1  - Schultz, C.
A1  - Schweizer, T.
A1  - Shore, S. N.
A1  - Sillanpaa, A.
A1  - Sitarek, J.
A1  - Snidaric, I.
A1  - Sobczynska, D.
A1  - Stamerra, A.
A1  - Steinbring, T.
A1  - Strzys, M.
A1  - Suric, T.
A1  - Takalo, L.
A1  - Tavecchio, F.
A1  - Temnikov, P.
A1  - Terzic, T.
A1  - Tescaro, D.
A1  - Teshima, M.
A1  - Thaele, J.
A1  - Torres, D. F.
A1  - Toyama, T.
A1  - Treves, A.
A1  - Vanzo, G.
A1  - Verguilov, V.
A1  - Vovk, I.
A1  - Ward, J. E.
A1  - Will, M.
A1  - Wu, M. H.
A1  - Zanin, R.
A1  - Abeysekara, A. U.
A1  - Archambault, S.
A1  - Archer, A.
A1  - Benbow, W.
A1  - Bird, R.
A1  - Buchovecky, M.
A1  - Buckley, J. H.
A1  - Bugaev, V.
A1  - Connolly, M. P.
A1  - Cui, W.
A1  - Dickinson, H. J.
A1  - Falcone, A.
A1  - Feng, Q.
A1  - Finley, J. P.
A1  - Fleischhack, H.
A1  - Flinders, A.
A1  - Fortson, L.
A1  - Gillanders, G. H.
A1  - Griffin, S.
A1  - Grube, J.
A1  - Huetten, M.
A1  - Hanna, D.
A1  - Holder, J.
A1  - Humensky, T. B.
A1  - Kaaret, P.
A1  - Kar, P.
A1  - Kelley-Hoskins, N.
A1  - Kertzman, M.
A1  - Kieda, D.
A1  - Krause, M.
A1  - Krennrich, F.
A1  - Lang, M. J.
A1  - Maier, G.
A1  - McCann, A.
A1  - Moriarty, P.
A1  - Mukherjee, R.
A1  - Nieto, D.
A1  - Ong, R. A.
A1  - Otte, N.
A1  - Park, N.
A1  - Perkins, J.
A1  - Pichel, A.
A1  - Pohl, M.
A1  - Popkow, A.
A1  - Pueschel, Elisa
A1  - Quinn, J.
A1  - Ragan, K.
A1  - Reynolds, P. T.
A1  - Richards, G. T.
A1  - Roache, E.
A1  - Rovero, A. C.
A1  - Rulten, C.
A1  - Sadeh, I.
A1  - Santander, M.
A1  - Sembroski, G. H.
A1  - Shahinyan, K.
A1  - Telezhinsky, Igor O.
A1  - Tucci, J. V.
A1  - Tyler, J.
A1  - Wakely, S. P.
A1  - Weinstein, A.
A1  - Wilcox, P.
A1  - Wilhelm, Alina
A1  - Williams, D. A.
A1  - Zitzer, B.
A1  - Razzaque, S.
A1  - Villata, M.
A1  - Raiteri, C. M.
A1  - Aller, H. D.
A1  - Aller, M. F.
A1  - Larionov, V. M.
A1  - Arkharov, A. A.
A1  - Blinov, D. A.
A1  - Efimova, N. V.
A1  - Grishina, T. S.
A1  - Hagen-Thorn, V. A.
A1  - Kopatskaya, E. N.
A1  - Larionova, L. V.
A1  - Larionova, E. G.
A1  - Morozova, D. A.
A1  - Troitsky, I. S.
A1  - Ligustri, R.
A1  - Calcidese, P.
A1  - Berdyugin, A.
A1  - Kurtanidze, O. M.
A1  - Nikolashvili, M. G.
A1  - Kimeridze, G. N.
A1  - Sigua, L. A.
A1  - Kurtanidze, S. O.
A1  - Chigladze, R. A.
A1  - Chen, W. P.
A1  - Koptelova, E.
A1  - Sakamoto, T.
A1  - Sadun, A. C.
A1  - Moody, J. W.
A1  - Pace, C.
A1  - Pearson, R.
A1  - Yatsu, Y.
A1  - Mori, Y.
A1  - Carraminyana, A.
A1  - Carrasco, L.
A1  - de la Fuente, E.
A1  - Norris, J. P.
A1  - Smith, P. S.
A1  - Wehrle, A.
A1  - Gurwell, M. A.
A1  - Zook, A.
A1  - Pagani, C.
A1  - Perri, M.
A1  - Capalbi, M.
A1  - Cesarini, A.
A1  - Krimm, H. A.
A1  - Kovalev, Y. Y.
A1  - Kovalev, Yu. A.
A1  - Ros, E.
A1  - Pushkarev, A. B.
A1  - Lister, M. L.
A1  - Sokolovsky, K. V.
A1  - Kadler, M.
A1  - Piner, G.
A1  - Lahteenmaki, A.
A1  - Tornikoski, M.
A1  - Angelakis, E.
A1  - Krichbaum, T. P.
A1  - Nestoras, I.
A1  - Fuhrmann, L.
A1  - Zensus, J. A.
A1  - Cassaro, P.
A1  - Orlati, A.
A1  - Maccaferri, G.
A1  - Leto, P.
A1  - Giroletti, M.
A1  - Richards, J. L.
A1  - Max-Moerbeck, W.
A1  - Readhead, A. C. S.
T1  - Multiband variability studies and novel broadband SED modeling of Mrk 501 in 2009
JF  - Astronomy and astrophysics : an international weekly journal
N2  - Aims. We present an extensive study of the BL Lac object Mrk 501 based on a data set collected during the multi-instrument campaign spanning from 2009 March 15 to 2009 August 1, which includes, among other instruments, MAGIC, VERITAS, Whipple 10 m, and Fermi-LAT to cover the gamma-ray range from 0.1 GeV to 20 TeV; RXTE and Swift to cover wavelengths from UV to hard X-rays; and GASP-WEBT, which provides coverage of radio and optical wavelengths. Optical polarization measurements were provided for a fraction of the campaign by the Steward and St. Petersburg observatories. We evaluate the variability of the source and interband correlations, the gamma-ray flaring activity occurring in May 2009, and interpret the results within two synchrotron self-Compton (SSC) scenarios. Methods. The multiband variability observed during the full campaign is addressed in terms of the fractional variability, and the possible correlations are studied by calculating the discrete correlation function for each pair of energy bands where the significance was evaluated with dedicated Monte Carlo simulations. The space of SSC model parameters is probed following a dedicated grid-scan strategy, allowing for a wide range of models to be tested and offering a study of the degeneracy of model-to-data agreement in the individual model parameters, hence providing a less biased interpretation than the "single-curve SSC model adjustment" typically reported in the literature. Results. We find an increase in the fractional variability with energy, while no significant interband correlations of flux changes are found on the basis of the acquired data set. The SSC model grid-scan shows that the flaring activity around May 22 cannot be modeled adequately with a one-zone SSC scenario (using an electron energy distribution with two breaks), while it can be suitably described within a two (independent) zone SSC scenario. Here, one zone is responsible for the quiescent emission from the averaged 4.5-month observing period, while the other one, which is spatially separated from the first, dominates the flaring emission occurring at X-rays and very-high-energy (> 100 GeV, VHE) gamma-rays. The flaring activity from May 1, which coincides with a rotation of the electric vector polarization angle (EVPA), cannot be satisfactorily reproduced by either a one-zone or a two-independent-zone SSC model, yet this is partially affected by the lack of strictly simultaneous observations and the presence of large flux changes on sub-hour timescales (detected at VHE gamma rays). Conclusions. The higher variability in the VHE emission and lack of correlation with the X-ray emission indicate that, at least during the 4.5-month observing campaign in 2009, the highest energy (and most variable) electrons that are responsible for the VHE gamma rays do not make a dominant contribution to the similar to 1 keV emission. Alternatively, there could be a very variable component contributing to the VHE gamma-ray emission in addition to that coming from the SSC scenario. The studies with our dedicated SSC grid-scan show that there is some degeneracy in both the one-zone and the two-zone SSC scenarios probed, with several combinations of model parameters yielding a similar model-to-data agreement, and some parameters better constrained than others. The observed gamma-ray flaring activity, with the EVPA rotation coincident with the first gamma-ray flare, resembles those reported previously for low frequency peaked blazars, hence suggesting that there are many similarities in the flaring mechanisms of blazars with different jet properties.
KW  - BL Lacertae objects: individual: Markarian 501
KW  - methods: data analysis
Y1  - 2017
U6  - https://doi.org/10.1051/0004-6361/201629540
SN  - 1432-0746
VL  - 603
PB  - EDP Sciences
CY  - Les Ulis
ER  - 
TY  - JOUR
A1  - Xiong, Hui
A1  - Mignolet, Benoit
A1  - Fang, Li
A1  - Osipov, Timur
A1  - Wolf, Thomas J. A.
A1  - Sistrunk, Emily
A1  - Gühr, Markus
A1  - Remacle, Francoise
A1  - Berrah, Nora
T1  - The Role of Super-Atom Molecular Orbitals in Doped Fullerenes in a Femtosecond Intense Laser Field
JF  - Scientific reports
N2  - The interaction of gas phase endohedral fullerene Ho3N@C-80 with intense (0.1-5 x 10(14) W/cm(2)), short (30 fs), 800 nm laser pulses was investigated. The power law dependence of Ho3N@C-80(q+), q = 1-2, was found to be different from that of C-60. Time-dependent density functional theory computations revealed different light-induced ionization mechanisms. Unlike in C-60, in doped fullerenes, the breaking of the cage spherical symmetry makes super atomic molecular orbital (SAMO) states optically active. Theoretical calculations suggest that the fast ionization of the SAMO states in Ho3N@C-80 is responsible for the n = 3 power law for singly charged parent molecules at intensities lower than 1.2 x 10(14) W/cm(2).
Y1  - 2017
U6  - https://doi.org/10.1038/s41598-017-00124-9
SN  - 2045-2322
VL  - 7
PB  - Nature Publ. Group
CY  - London
ER  - 
TY  - JOUR
A1  - Archambault, S.
A1  - Archer, A.
A1  - Benbow, W.
A1  - Bird, R.
A1  - Bourbeau, E.
A1  - Brantseg, T.
A1  - Buchovecky, M.
A1  - Buckley, J. H.
A1  - Bugaev, V.
A1  - Byrum, K.
A1  - Cerruti, M.
A1  - Christiansen, J. L.
A1  - Connolly, M. P.
A1  - Cui, W.
A1  - Daniel, M. K.
A1  - Feng, Q.
A1  - Finley, J. P.
A1  - Fleischhack, H.
A1  - Fortson, L.
A1  - Furniss, A.
A1  - Geringer-Sameth, A.
A1  - Griffin, S.
A1  - Grube, J.
A1  - Hütten, M.
A1  - Hakansson, N.
A1  - Hanna, D.
A1  - Hervet, O.
A1  - Holder, J.
A1  - Hughes, G.
A1  - Hummensky, B.
A1  - Johnson, C. A.
A1  - Kaaret, P.
A1  - Kar, P.
A1  - Kelley-Hoskins, N.
A1  - Kertzman, M.
A1  - Kieda, D.
A1  - Koushiappas, S.
A1  - Krause, M.
A1  - Krennrich, F.
A1  - Lang, M. J.
A1  - Lin, T. T. Y.
A1  - McArthur, S.
A1  - Moriarty, P.
A1  - Mukherjee, R.
A1  - Nieto, D.
A1  - Ong, R. A.
A1  - Otte, A. N.
A1  - Park, N.
A1  - Pohl, M.
A1  - Popkow, A.
A1  - Pueschel, Elisa
A1  - Quinn, J.
A1  - Ragan, K.
A1  - Reynolds, P. T.
A1  - Richards, G. T.
A1  - Roache, E.
A1  - Rulten, C.
A1  - Sadeh, I.
A1  - Santander, M.
A1  - Sembroski, G. H.
A1  - Shahinyan, K.
A1  - Smith, A. W.
A1  - Staszak, D.
A1  - Telezhinsky, Igor O.
A1  - Trepanier, S.
A1  - Tucci, J. V.
A1  - Tyler, J.
A1  - Wakely, S. P.
A1  - Weinstein, A.
A1  - Wilcox, P.
A1  - Williams, D. A.
A1  - Zitzer, B.
T1  - Dark matter constraints from a joint analysis of dwarf Spheroidal galaxy observations with VERITAS
JF  - Physical review : D, Particles, fields, gravitation, and cosmology
N2  - We present constraints on the annihilation cross section of weakly interacting massive particles dark matter based on the joint statistical analysis of four dwarf galaxies with VERITAS. These results are derived from an optimized photon weighting statistical technique that improves on standard imaging atmospheric Cherenkov telescope (IACT) analyses by utilizing the spectral and spatial properties of individual photon events. We report on the results of similar to 230 hours of observations of five dwarf galaxies and the joint statistical analysis of four of the dwarf galaxies. We find no evidence of gamma-ray emission from any individual dwarf nor in the joint analysis. The derived upper limit on the dark matter annihilation cross section from the joint analysis is 1.35 x 10(-23) cm(3) s(-1) at 1 TeV for the bottom quark (b (b) over bar) final state, 2.85 x 10(-24) cm(3) s(-1) at 1 TeV for the tau lepton (tau+tau(-)) final state and 1.32 x 10-25 cm(3) s(-1) at 1 TeV for the gauge boson (gamma gamma) final state.
Y1  - 2017
U6  - https://doi.org/10.1103/PhysRevD.95.082001
SN  - 2470-0010
SN  - 2470-0029
VL  - 95
IS  - 8
PB  - American Physical Society
CY  - College Park
ER  - 
TY  - JOUR
A1  - Leussu, R.
A1  - Usoskin, IIlya G.
A1  - Valliappan, Senthamizh Pavai
A1  - Diercke, Andrea
A1  - Arlt, Rainer
A1  - Denker, Carsten
A1  - Mursula, K.
T1  - Wings of the butterfly
BT  - sunspot groups for 1826-2015
JF  - Astronomy and astrophysics : an international weekly journal
N2  - The spatio-temporal evolution of sunspot activity, the so-called Maunder butterfly diagram, has been continously available since 1874 using data from the Royal Greenwich Observatory, extended by SOON network data after 1976. Here we present a new extended butterfly diagram of sunspot group occurrence since 1826, using the recently digitized data from Schwabe (1826-1867) and Sporer (1866-1880). The wings of the diagram are separated using a recently developed method based on an analysis of long gaps in sunspot group occurrence in different latitude bands. We define characteristic latitudes, corresponding to the start, end, and the largest extent of the wings (the F, L, and H latitudes). The H latitudes (30 degrees-45 degrees) are highly significantly correlated with the strength of the wings (quantified by the total sum of the monthly numbers of sunspot groups). The F latitudes (20 degrees-30 degrees) depict a weak tendency, especially in the southern hemisphere, to follow the wing strength. The L latitudes (2 degrees-10 degrees) show no clear relation to the wing strength. Overall, stronger cycle wings tend to start at higher latitudes and have a greater wing extent. A strong (5-6)-cycle periodic oscillation is found in the start and end times of the wings and in the overlap and gaps between successive wings of one hemisphere. While the average wing overlap is zero in the southern hemisphere, it is two to three months in the north. A marginally significant oscillation of about ten solar cycles is found in the asymmetry of the L latitudes. The new long database of butterfly wings provides new observational constraints to solar dynamo models that discuss the spatio-temporal distribution of sunspot occurrence over the solar cycle and longer.
KW  - Sun: activity
KW  - sunspots
KW  - history and philosophy of astronomy
Y1  - 2017
U6  - https://doi.org/10.1051/0004-6361/201629533
SN  - 1432-0746
VL  - 599
PB  - EDP Sciences
CY  - Les Ulis
ER  - 
TY  - JOUR
A1  - Rätzel, Dennis
A1  - Wilkens, Martin
A1  - Menzel, Ralf
T1  - Effect of polarization entanglement in photon-photon scattering
JF  - Physical review : A, Atomic, molecular, and optical physics
N2  - It is found that the differential cross section of photon-photon scattering is a function of the degree of polarization entanglement of the two-photon state. A reduced general expression for the differential cross section of photon-photon scattering is derived by applying simple symmetry arguments. An explicit expression is obtained for the example of photon-photon scattering due to virtual electron-positron pairs in quantum electrodynamics. It is shown how the effect in this explicit example can be explained as an effect of quantum interference and that it fits with the idea of distance-dependent forces.
Y1  - 2017
U6  - https://doi.org/10.1103/PhysRevA.95.012101
SN  - 2469-9926
SN  - 2469-9934
VL  - 95
IS  - 1
PB  - American Physical Society
CY  - College Park
ER  - 
TY  - JOUR
A1  - Gong, Chen Chris
A1  - Klumpp, Stefan
T1  - Modeling sRNA-Regulated Plasmid Maintenance
JF  - PLoS one
N2  - We study a theoretical model for the toxin-antitoxin (hok/sok) mechanism for plasmid maintenance in bacteria. Toxin-antitoxin systems enforce the maintenance of a plasmid through post-segregational killing of cells that have lost the plasmid. Key to their function is the tight regulation of expression of a protein toxin by an sRNA antitoxin. Here, we focus on the nonlinear nature of the regulatory circuit dynamics of the toxin-antitoxin mechanism. The mechanism relies on a transient increase in protein concentration rather than on the steady state of the genetic circuit. Through a systematic analysis of the parameter dependence of this transient increase, we confirm some known design features of this system and identify new ones: for an efficient toxin-antitoxin mechanism, the synthesis rate of the toxin’s mRNA template should be lower that of the sRNA antitoxin, the mRNA template should be more stable than the sRNA antitoxin, and the mRNA-sRNA complex should be more stable than the sRNA antitoxin. Moreover, a short half-life of the protein toxin is also beneficial to the function of the toxin-antitoxin system. In addition, we study a therapeutic scenario in which a competitor mRNA is introduced to sequester the sRNA antitoxin, causing the toxic protein to be expressed.
Y1  - 2017
U6  - https://doi.org/10.1371/journal.pone.0169703
SN  - 1932-6203
VL  - 12
PB  - PLoS
CY  - San Fransisco
ER  - 
TY  - JOUR
A1  - Fandrich, Artur
A1  - Buller, Jens
A1  - Memczak, Henry
A1  - Stoecklein, W.
A1  - Hinrichs, K.
A1  - Wischerhoff, E.
A1  - Schulz, B.
A1  - Laschewsky, André
A1  - Lisdat, Fred
T1  - Responsive Polymer-Electrode Interface-Study of its Thermo- and pH-Sensitivity and the Influence of Peptide Coupling
JF  - Electrochimica acta : the journal of the International Society of Electrochemistry (ISE)
N2  - This study introduces a thermally responsive, polymer-based electrode system. The key component is a surface-attached, temperature-responsive poly(oligoethylene glycol) methacrylate (poly(OEGMA)) type polymer bearing photoreactive benzophenone and carboxy groups containing side chains. The responsive behavior of the polymer in aqueous media has been investigated by turbidimetry measurements. Polymer films are formed on gold substrates by means of the photoreactive 2(dicyclohexylphosphino)benzophenone (DPBP) through photocrosslinking. The electrochemical behavior of the resulting polymer-substrate interface has been investigated in buffered [Fe(CN)6](3-)/[Fe (CN)6](4-)solutions at room temperature and under temperature variation by cyclic voltammetry (CV). The CV experiments show that with increasing temperature structural changes of the polymer layer occur, which alter the output of the electrochemical measurement. Repeated heating/cooling cycles analyzed by CV measurements and pH changes analyzed by quartz crystal microbalance with dissipation monitoring (QCM-D) reveal the reversible nature of the restructuring process. The immobilized films are further modified by covalent coupling of two small biomolecules - a hydrophobic peptide and a more hydrophilic one. These attached components influence the hydrophobicity of the layer in a different way the resulting change of the temperature-caused behavior has been studied by CV indicating a different state of the polymer after coupling of the hydrophobic peptide.
KW  - Stimuli-responsive materials
KW  - electroanalysis
KW  - modified electrode
KW  - bioreceptors
KW  - peptides
KW  - surface modification
KW  - cyclic voltammetry
KW  - IR ellipsometry
KW  - quartz crystal microbalance
Y1  - 2017
U6  - https://doi.org/10.1016/j.electacta.2017.01.080
SN  - 0013-4686
SN  - 1873-3859
VL  - 229
SP  - 325
EP  - 333
PB  - Elsevier
CY  - Oxford
ER  - 
TY  - JOUR
A1  - Zacharias, Michael
A1  - Chen, Xuhui
A1  - Wagner, Stefan
T1  - Attenuation of TeV gamma-rays by the starlight photon field of the host galaxy
JF  - Monthly notices of the Royal Astronomical Society
N2  - The absorption of TeV gamma-ray photons produced in relativistic jets by surrounding soft photon fields is a long-standing problem of jet physics. In some cases, the most likely emission site close to the central black hole is ruled out because of the high opacity caused by strong optical and infrared photon sources, such as the broad-line region. Mostly neglected for jet modelling is the absorption of gamma-rays in the starlight photon field of the host galaxy. Analysing the absorption for arbitrary locations and observation angles of the gamma-ray emission site within the host galaxy, we find that the distance to the galaxy centre, the observation angle, and the distribution of starlight in the galaxy are crucial for the amount of absorption. We derive the absorption value for a sample of 20 TeV-detected blazars with a redshift z(r) < 0.2. The absorption value of the gamma-ray emission located in the galaxy centre may be as high as 20 per cent, with an average value of 6 per cent. This is important in order to determine the intrinsic blazar parameters. We see no significant trends in our sample between the degree of absorption and host properties, such as starlight emissivity, galactic size, half-light radius, and redshift. While the uncertainty of the spectral properties of the extragalactic background light exceeds the effect of absorption by stellar light from the host galaxy in distant objects, the latter is a dominant effect in nearby sources. It may also be revealed in a differential comparison of sources with similar redshifts.
KW  - opacity
KW  - radiation mechanisms: non-thermal
KW  - galaxies: active
KW  - gamma-rays: galaxies
Y1  - 2016
U6  - https://doi.org/10.1093/mnras/stw3032
SN  - 0035-8711
SN  - 1365-2966
VL  - 465
IS  - 3
SP  - 3767
EP  - 3774
PB  - Oxford Univ. Press
CY  - Oxford
ER  - 
TY  - JOUR
A1  - Anielski, Alexander
A1  - Barbosa Pfannes, Eva Katharina
A1  - Beta, Carsten
T1  - Adaptive microfluidic gradient generator for quantitative chemotaxis experiments
JF  - Review of scientific instruments : a monthly journal devoted to scientific instruments, apparatus, and techniques
N2  - Chemotactic motion in a chemical gradient is an essential cellular function that controls many processes in the living world. For a better understanding and more detailed modelling of the underlying mechanisms of chemotaxis, quantitative investigations in controlled environments are needed. We developed a setup that allows us to separately address the dependencies of the chemotactic motion on the average background concentration and on the gradient steepness of the chemoattractant. In particular, both the background concentration and the gradient steepness can be kept constant at the position of the cell while it moves along in the gradient direction. This is achieved by generating a well-defined chemoattractant gradient using flow photolysis. In this approach, the chemoattractant is released by a light-induced reaction from a caged precursor in a microfluidic flow chamber upstream of the cell. The flow photolysis approach is combined with an automated real-time cell tracker that determines changes in the cell position and triggers movement of the microscope stage such that the cell motion is compensated and the cell remains at the same position in the gradient profile. The gradient profile can be either determined experimentally using a caged fluorescent dye or may be alternatively determined by numerical solutions of the corresponding physical model. To demonstrate the function of this adaptive microfluidic gradient generator, we compare the chemotactic motion of Dictyostelium discoideum cells in a static gradient and in a gradient that adapts to the position of the moving cell. Published by AIP Publishing.
Y1  - 2017
U6  - https://doi.org/10.1063/1.4978535
SN  - 0034-6748
SN  - 1089-7623
VL  - 88
PB  - American Institute of Physics
CY  - Melville
ER  - 
TY  - JOUR
A1  - Koopman, Wouter-Willem Adriaan
A1  - Natali, Marco
A1  - Donati, Giovanni P.
A1  - Muccini, Michele
A1  - Toffanin, Stefano
T1  - Charge-exciton interaction rate in organic field-effect transistors by means of transient photoluminescence electromodulated spectroscopy
JF  - ACS photonics
N2  - Organic light-emitting transistors (OLETs) offer a huge potential for the design of highly integrated multifunctional optoelectronic systems and of intense nano scale light sources, such as the long-searched-for electrically pumped organic laser. In order to fulfill these promises, the efficiency and brightness of the current state-of-the-art devices have to be increased significantly. The dominating quenching process limiting the external quantum efficiency in OLETs is charge-exciton interaction. A comprehensive understanding of this quenching process is therefore of paramount importance. The present article reports a systematic investigation of charge-exciton interaction in organic transistors employing time resolved photoluminescence electro-modulation (PLEM) spectroscopy on the picosecond time scale. The results show that the injected charges reduce the exciton radiative recombination in two ways: (i) charges may prevent the generation of excitons and (ii) charges activate a further nonradiative channel for the exciton decay. Moreover, the transient PLEM measurements clearly reveal that not only trapped charges, as already reported in literature, but rather the entire injected charge density contributes to the quenching of the exciton population.
KW  - photoluminescence quenching
KW  - charge density
KW  - exciton dynamics
KW  - organic
KW  - field-effect transistor
KW  - light emission
KW  - optical spectroscopy
Y1  - 2017
U6  - https://doi.org/10.1021/acsphotonics.6b00573
SN  - 2330-4022
VL  - 4
IS  - 2
SP  - 282
EP  - 291
PB  - American Chemical Society
CY  - Washington, DC
ER  - 
TY  - JOUR
A1  - Sun, Ning-Chen
A1  - de Grijs, Richard
A1  - Subramanian, Smitha
A1  - Cioni, Maria-Rosa L.
A1  - Rubele, Stefano
A1  - Bekki, Kenji
A1  - Ivanov, Valentin D.
A1  - Piatti, Andrés E.
A1  - Ripepi, Vincenzo
T1  - The VMC Survey. XXII. Hierarchical star formation in the 30 Doradus-N158-N159-N160 star-forming complex
JF  - The astrophysical journal : an international review of spectroscopy and astronomical physics
N2  - We study the hierarchical stellar structures in a similar to 1.5 deg(2) area covering the 30. Doradus-N158-N159-N160 starforming complex with the VISTA Survey of. Magellanic Clouds. Based on the young upper main-sequence stars, we find that the surface densities cover a wide range of values, from log(Sigma.pc(2))less than or similar to -2.0 to log(Sigma. pc(2)) greater than or similar to 0.0. Their distributions are highly non-uniform, showing groups that frequently have subgroups inside. The sizes of the stellar groups do not exhibit characteristic values, and range continuously from several parsecs to more than 100. pc; the cumulative size distribution can be well described by a single power law, with the power-law index indicating a projected fractal dimension D-2 = 1.6 +/- 0.3. We suggest that the phenomena revealed here support a scenario of hierarchical star formation. Comparisons with other star-forming regions and galaxies are also discussed.
KW  - galaxies: clusters: general
KW  - infrared: stars
KW  - Magellanic Clouds
KW  - stars: formation
Y1  - 2017
U6  - https://doi.org/10.3847/1538-4357/835/2/171
SN  - 0004-637X
SN  - 1538-4357
VL  - 835
IS  - 2
PB  - Institute of Physics Publ.
CY  - Bristol
ER  - 
TY  - JOUR
A1  - Warren, Donald C.
A1  - Ellison, Donald C.
A1  - Barkov, Maxim V.
A1  - Nagataki, Shigehiro
T1  - Nonlinear Particle Acceleration and Thermal Particles in GRB Afterglows
JF  - The astrophysical journal : an international review of spectroscopy and astronomical physics
N2  - The standard model for GRB afterglow emission treats the accelerated electron population as a simple power law, N(E) proportional to E-p for p greater than or similar to 2. However, in standard Fermi shock acceleration, a substantial fraction of the swept-up particles do not enter the acceleration process at all. Additionally, if acceleration is efficient, then the nonlinear back-reaction of accelerated particles on the shock structure modifies the shape of the nonthermal tail of the particle spectra. Both of these modifications to the standard synchrotron afterglow impact the luminosity, spectra, and temporal variation of the afterglow. To examine the effects of including thermal particles and nonlinear particle acceleration on afterglow emission, we follow a hydrodynamical model for an afterglow jet and simulate acceleration at numerous points during the evolution. When thermal particles are included, we find that the electron population is at no time well fitted by a single power law, though the highest-energy electrons are; if the acceleration is efficient, then the power-law region is even smaller. Our model predicts hard-soft-hard spectral evolution at X-ray energies, as well as an uncoupled X-ray and optical light curve. Additionally, we show that including emission from thermal particles has drastic effects (increases by factors of 100 and 30, respectively) on the observed flux at optical and GeV energies. This enhancement of GeV emission makes afterglow detections by future gamma-ray observatories, such as CTA, very likely.
KW  - acceleration of particles
KW  - cosmic rays
KW  - gamma-ray burst: general
KW  - shock waves
KW  - turbulence
Y1  - 2017
U6  - https://doi.org/10.3847/1538-4357/aa56c3
SN  - 0004-637X
SN  - 1538-4357
VL  - 835
IS  - 2
PB  - IOP Publ. Ltd.
CY  - Bristol
ER  - 
TY  - JOUR
A1  - Liu, Lin
A1  - Cherstvy, Andrey G.
A1  - Metzler, Ralf
T1  - Facilitated Diffusion of Transcription Factor Proteins with Anomalous Bulk Diffusion
JF  - The journal of physical chemistry : B, Condensed matter, materials, surfaces, interfaces & biophysical chemistry
N2  - What are the physical laws of the diffusive search of proteins for their specific binding sites on DNA in the presence of the macromolecular crowding in cells? We performed extensive computer simulations to elucidate the protein target search on DNA. The novel feature is the viscoelastic non-Brownian protein bulk diffusion recently observed experimentally. We examine the influence of the protein-DNA binding affinity and the anomalous diffusion exponent on the target search time. In all cases an optimal search time is found. The relative contribution of intermittent three-dimensional bulk diffusion and one-dimensional sliding of proteins along the DNA is quantified. Our results are discussed in the light of recent single molecule tracking experiments, aiming at a better understanding of the influence of anomalous kinetics of proteins on the facilitated diffusion mechanism.
Y1  - 2017
U6  - https://doi.org/10.1021/acs.jpcb.6b12413
SN  - 1520-6106
VL  - 121
SP  - 1284
EP  - 1289
PB  - American Chemical Society
CY  - Washington
ER  - 
TY  - JOUR
A1  - Almeida, Leonardo A.
A1  - Sana, H.
A1  - Taylor, W.
A1  - Barbá, Rodolfo
A1  - Bonanos, Alceste Z.
A1  - Crowther, Paul
A1  - Damineli, Augusto
A1  - de Koter, A.
A1  - de Mink, Selma E.
A1  - Evans, C. J.
A1  - Gieles, Mark
A1  - Grin, Nathan J.
A1  - Hénault-Brunet, V.
A1  - Langer, Norbert
A1  - Lennon, D.
A1  - Lockwood, Sean
A1  - Maíz Apellániz, Jesús
A1  - Moffat, A. F. J.
A1  - Neijssel, C.
A1  - Norman, C.
A1  - Ramírez-Agudelo, O. H.
A1  - Richardson, N. D.
A1  - Schootemeijer, Abel
A1  - Shenar, Tomer
A1  - Soszyński, Igor
A1  - Tramper, Frank
A1  - Vink, J. S.
T1  - The tarantula massive binary monitoring
BT  - I. Observational campaign and OB-type spectroscopic binaries
JF  - Astronomy and astrophysics : an international weekly journal
N2  - Context:
Massive binaries play a crucial role in the Universe. Knowing the distributions of their orbital parameters is important for a wide range of topics from stellar feedback to binary evolution channels and from the distribution of supernova types to gravitational wave progenitors, yet no direct measurements exist outside the Milky Way.
Aims:
The Tarantula Massive Binary Monitoring project was designed to help fill this gap by obtaining multi-epoch radial velocity (RV) monitoring of 102 massive binaries in the 30 Doradus region.
Methods: 
In this paper we analyze 32 FLAMES/GIRAFFE observations of 93 O- and 7 B-type binaries. We performed a Fourier analysis and obtained orbital solutions for 82 systems: 51 single-lined (SB1) and 31 double-lined (SB2) spectroscopic binaries.
Results: 
Overall, the binary fraction and orbital properties across the 30 Doradus region are found to be similar to existing Galactic samples. This indicates that within these domains environmental effects are of second order in shaping the properties of massive binary systems. A small difference is found in the distribution of orbital periods, which is slightly flatter (in log space) in 30 Doradus than in the Galaxy, although this may be compatible within error estimates and differences in the fitting methodology. Also, orbital periods in 30 Doradus can be as short as 1.1 d, somewhat shorter than seen in Galactic samples. Equal mass binaries (q> 0.95) in 30 Doradus are all found outside NGC 2070, the central association that surrounds R136a, the very young and massive cluster at 30 Doradus’s core. Most of the differences, albeit small, are compatible with expectations from binary evolution. One outstanding exception, however, is the fact that earlier spectral types (O2–O7) tend to have shorter orbital periods than later spectral types (O9.2–O9.7).
Conclusions: 
Our results point to a relative universality of the incidence rate of massive binaries and their orbital properties in the metallicity range from solar (Z⊙) to about half solar. This provides the first direct constraints on massive binary properties in massive star-forming galaxies at the Universe’s peak of star formation at redshifts z ~ 1 to 2 which are estimated to have Z ~ 0.5 Z⊙.
KW  - stars: early-type
KW  - stars: massive
KW  - binaries: spectroscopic
KW  - binaries: close
Y1  - 2017
U6  - https://doi.org/10.1051/0004-6361/201629844
SN  - 1432-0746
VL  - 598
PB  - EDP Sciences
CY  - Les Ulis
ER  - 
TY  - JOUR
A1  - Gorobtsov, O. Yu.
A1  - Mercurio, G.
A1  - Brenner, G.
A1  - Lorenz, Ulf
A1  - Gerasimova, N.
A1  - Kurta, R. P.
A1  - Hieke, F.
A1  - Skopintsev, P.
A1  - Zaluzhnyy, I.
A1  - Lazarev, S.
A1  - Dzhigaev, D.
A1  - Rose, M.
A1  - Singer, A.
A1  - Wurth, W.
A1  - Vartanyants, I. A.
T1  - Statistical properties of a free-electron laser revealed by Hanbury Brown-Twiss interferometry
JF  - Physical review : A, Atomic, molecular, and optical physics
N2  - We present a comprehensive experimental analysis of statistical properties of the self-amplified spontaneous emission free-electron laser (FEL) FLASH by means of Hanbury Brown and Twiss interferometry. The experiments were performed at FEL wavelengths of 5.5, 13.4, and 20.8 nm. We determined the second-order intensity correlation function for all wavelengths and different operation conditions of FLASH. In all experiments a high degree of spatial coherence (above 50%) was obtained. Our analysis performed in spatial and spectral domains provided us with the independent measurements of an average pulse duration of the FEL that were below 60 fs. To explain the complicated behavior of the second-order intensity correlation function we developed an advanced theoretical model that includes the presence of multiple beams and external positional jitter of the FEL pulses. By this analysis we determined that in one of the experiments external positional jitter was about 25% of the beam size. We envision that methods developed in our study will be used widely for analysis and diagnostics of FEL radiation.
Y1  - 2017
U6  - https://doi.org/10.1103/PhysRevA.95.023843
SN  - 2469-9926
SN  - 2469-9934
VL  - 95
IS  - 2
PB  - American Physical Society
CY  - College Park
ER  - 
TY  - JOUR
A1  - Godec, Aljaž
A1  - Metzler, Ralf
T1  - First passage time statistics for two-channel diffusion
JF  - Journal of physics : A, Mathematical and theoretical
N2  - We present rigorous results for the mean first passage time and first passage time statistics for two-channel Markov additive diffusion in a 3-dimensional spherical domain. Inspired by biophysical examples we assume that the particle can only recognise the target in one of the modes, which is shown to effect a non-trivial first passage behaviour. We also address the scenario of intermittent immobilisation. In both cases we prove that despite the perfectly non-recurrent motion of two-channel Markov additive diffusion in 3 dimensions the first passage statistics at long times do not display Poisson-like behaviour if none of the phases has a vanishing diffusion coefficient. This stands in stark contrast to the standard (one-channel) Markov diffusion counterpart. We also discuss the relevance of our results in the context of cellular signalling.
KW  - first passage time
KW  - Markov additive processes
KW  - Fokker-Planck equation
KW  - random search processes
KW  - coupled initial boundary value problem
KW  - cellular signalling
KW  - asymptotic analysis
Y1  - 2017
U6  - https://doi.org/10.1088/1751-8121/aa5204
SN  - 1751-8113
SN  - 1751-8121
VL  - 50
IS  - 8
PB  - IOP Publ. Ltd.
CY  - Bristol
ER  - 
TY  - JOUR
A1  - Goychuk, Igor
T1  - Quantum ergodicity breaking in semi-classical electron transfer dynamics
JF  - Physical chemistry, chemical physics : a journal of European Chemical Societies
N2  - Can the statistical properties of single-electron transfer events be correctly predicted within a common equilibrium ensemble description? This fundamental in nanoworld question of ergodic behavior is scrutinized within a very basic semi-classical curve-crossing problem. It is shown that in the limit of non-adiabatic electron transfer (weak tunneling) well-described by the Marcus-Levich-Dogonadze (MLD) rate the answer is yes. However, in the limit of the so-called solvent-controlled adiabatic electron transfer, a profound breaking of ergodicity occurs. Namely, a common description based on the ensemble reduced density matrix with an initial equilibrium distribution of the reaction coordinate is not able to reproduce the statistics of single-trajectory events in this seemingly classical regime. For sufficiently large activation barriers, the ensemble survival probability in a state remains nearly exponential with the inverse rate given by the sum of the adiabatic curve crossing (Kramers) time and the inverse MLD rate. In contrast, near to the adiabatic regime, the single-electron survival probability is clearly non-exponential, even though it possesses an exponential tail which agrees well with the ensemble description. Initially, it is well described by a Mittag-Leffler distribution with a fractional rate. Paradoxically, the mean transfer time in this classical on the ensemble level regime is well described by the inverse of the nonadiabatic quantum tunneling rate on a single particle level. An analytical theory is developed which perfectly agrees with stochastic simulations and explains our findings.
Y1  - 2016
U6  - https://doi.org/10.1039/c6cp07206b
SN  - 1463-9076
SN  - 1463-9084
VL  - 19
SP  - 3056
EP  - 3066
PB  - Royal Society of Chemistry
CY  - Cambridge
ER  - 
TY  - JOUR
A1  - Kunnus, Kristjan
A1  - Josefsson, I.
A1  - Schreck, Simon Frederik
A1  - Quevedo, W.
A1  - Miedema, P. S.
A1  - Techert, S.
A1  - de Groot, F. M. F.
A1  - Föhlisch, Alexander
A1  - Odelius, M.
A1  - Wernet, Ph.
T1  - Quantifying covalent interactions with resonant inelastic soft X-ray scattering
BT  - case study of Ni2+ aqua complex
JF  - Chemical physics letters
N2  - We analyze the effects of covalent interactions in Ni 2p3d resonant inelastic X-ray scattering (RIXS) spectra from aqueous Ni2+ ions and find that the relative RIXS intensities of ligand-to-metal charge-transfer final states with respect to the ligand-field final states reflect the covalent mixing between Ni 3d and water orbitals. Specifically, the experimental intensity ratio at the Ni L-3-edge allows to determine that the Ni 3d orbitals have on average 5.5% of water character. We propose that 2p3d RIXS at the Ni L-3-edge can be utilized to quantify covalency in Ni complexes without the use of external references or simulations.
KW  - Transition-metal ion
KW  - Aqueous solution
KW  - Covalent interaction
KW  - Resonant inelastic X-ray scattering
KW  - Ligand-field state
KW  - Charge-transfer state
Y1  - 2016
U6  - https://doi.org/10.1016/j.cplett.2016.12.046
SN  - 0009-2614
SN  - 1873-4448
VL  - 669
SP  - 196
EP  - 201
PB  - Elsevier
CY  - Amsterdam
ER  - 
TY  - JOUR
A1  - Olson, R.
A1  - An, Soon-Il
A1  - Fan, Y.
A1  - Evans, J. P.
A1  - Caesar, Levke
T1  - North Atlantic observations sharpen meridional overturning projections
JF  - Climate dynamics : observational, theoretical and computational research on the climate system
N2  - Atlantic Meridional Overturning Circulation (AMOC) projections are uncertain due to both model errors, as well as internal climate variability. An AMOC slowdown projected by many climate models is likely to have considerable effects on many aspects of global and North Atlantic climate. Previous studies to make probabilistic AMOC projections have broken new ground. However, they do not drift-correct or cross-validate the projections, and do not fully account for internal variability. Furthermore, they consider a limited subset of models, and ignore the skill of models at representing the temporal North Atlantic dynamics. We improve on previous work by applying Bayesian Model Averaging to weight 13 Coupled Model Intercomparison Project phase 5 models by their skill at modeling the AMOC strength, and its temporal dynamics, as approximated by the northern North-Atlantic temperature-based AMOC Index. We make drift-corrected projections accounting for structural model errors, and for the internal variability. Cross-validation experiments give approximately correct empirical coverage probabilities, which validates our method. Our results present more evidence that AMOC likely already started slowing down. While weighting considerably moderates and sharpens our projections, our results are at low end of previously published estimates. We project mean AMOC changes between periods 1960-1999 and 2060-2099 of -4.0 Sv and -6.8 Sv for RCP4.5 and RCP8.5 emissions scenarios respectively. The corresponding average 90% credible intervals for our weighted experiments are [-7.2, -1.2] and [-10.5, -3.7] Sv respectively for the two scenarios.
KW  - Atlantic Meridional Overturning Circulation
KW  - Climate modeling
KW  - Bayesian Model Averaging
KW  - Model structural error
KW  - Probabilistic projections
Y1  - 2017
U6  - https://doi.org/10.1007/s00382-017-3867-7
SN  - 0930-7575
SN  - 1432-0894
VL  - 50
IS  - 11-12
SP  - 4171
EP  - 4188
PB  - Springer
CY  - New York
ER  - 
TY  - JOUR
A1  - Kayser, Markus
A1  - Maturilli, Marion
A1  - Graham, Robert M.
A1  - Hudson, Stephen R.
A1  - Rinke, Annette
A1  - Cohen, Lana
A1  - Kim, Joo-Hong
A1  - Park, Sang-Jong
A1  - Moon, Woosok
A1  - Granskog, Mats A.
T1  - Vertical thermodynamic structure of the troposphere during the Norwegian young sea ICE expedition (N-ICE2015)
JF  - Journal of geophysical research-atmosheres
N2  - The Norwegian young sea ICE (N-ICE2015) expedition was designed to investigate the atmosphere-snow-ice-ocean interactions in the young and thin sea ice regime north of Svalbard. Radiosondes were launched twice daily during the expedition from January to June 2015. Here we use these upper air measurements to study the multiple cyclonic events observed during N-ICE2015 with respect to changes in the vertical thermodynamic structure, moisture content, and boundary layer characteristics. We provide statistics of temperature inversion characteristics, static stability, and boundary layer extent. During winter, when radiative cooling is most effective, we find the strongest impact of synoptic cyclones. Changes to thermodynamic characteristics of the boundary layer are associated with transitions between the radiatively "clear" and "opaque" atmospheric states. In spring, radiative fluxes warm the surface leading to lifted temperature inversions and a statically unstable boundary layer. Further, we compare the N-ICE2015 static stability distributions to corresponding profiles from ERA-Interim reanalysis, from the closest land station in the Arctic North Atlantic sector, Ny-Alesund, and to soundings from the SHEBA expedition (1997/1998). We find similar stability characteristics for N-ICE2015 and SHEBA throughout the troposphere, despite differences in location, sea ice thickness, and snow cover. For Ny-Alesund, we observe similar characteristics above 1000 m, while the topography and ice-free fjord surrounding Ny-Alesund generate great differences below. The long-term radiosonde record (1993-2014) from Ny-Alesund indicates that during the N-ICE2015 spring period, temperatures were close to the climatological mean, while the lowest 3000 m were 1-3 degrees C warmer than the climatology during winter. Plain Language Summary The Norwegian young sea ICE (N-ICE2015) expedition was designed to investigate the atmosphere-snow-ice-ocean interactions in the young and thin sea ice regime north of Svalbard. Radiosondes were launched twice daily during the expedition from January to June 2015. Here we use these upper air measurements to study the multiple cyclonic events observed during N-ICE2015 with respect to changes in the vertical thermodynamic structure, moisture content, and the atmospheric boundary layer characteristics. During winter, we find the strongest impact of synoptic cyclones, which transport warm and moist air into the cold and dry Arctic atmosphere. In spring, incoming solar radiation warms the surface. This leads to very different thermodynamic conditions and higher moisture content, which reduces the contrast between stormy and calm periods. Further, we compare the N-ICE2015 measurements to corresponding profiles from ERA-Interim reanalysis, from the closest land station in the Arctic North Atlantic sector, Ny-Alesund, and to soundings from the SHEBA expedition (1997/1998). We find similar stability characteristics for N-ICE2015 and SHEBA throughout the troposphere, despite differences in location, sea ice thickness, and snow cover. The comparisons highlight the value of the N-ICE2015 observation and show the importance of winter time observations in the Arctic North Atlantic sector.
Y1  - 2017
U6  - https://doi.org/10.1002/2016JD026089
SN  - 2169-897X
SN  - 2169-8996
VL  - 122
IS  - 20
SP  - 10855
EP  - 10872
PB  - American Geophysical Union
CY  - Washington
ER  - 
TY  - JOUR
A1  - Mardoukhi, Ahmad
A1  - Mardoukhi, Yousof
A1  - Hokka, Mikko
A1  - Kuokkala, Veli-Tapani
T1  - Effects of heat shock on the dynamic tensile behavior of granitic rocks
JF  - Rock mechanics and rock engineering
N2  - This paper presents a new experimental method for the characterization of the surface damage caused by a heat shock on a Brazilian disk test sample. Prior to mechanical testing with a Hopkinson Split Pressure bar device, the samples were subjected to heat shock by placing a flame torch at a fixed distance from the sample’s surface for periods of 10, 30, and 60 s. The sample surfaces were studied before and after the heat shock using optical microscopy and profilometry, and the images were analyzed to quantify the damage caused by the heat shock. The complexity of the surface crack patterns was quantified using fractal dimension of the crack patterns, which were used to explain the results of the mechanical testing. Even though the heat shock also causes damage below the surface which cannot be quantified from the optical images, the presented surface crack pattern analysis can give a reasonable estimate on the drop rate of the tension strength of the rock.
KW  - SHPB
KW  - Rock
KW  - Granite
KW  - DIC
KW  - Dynamic loading
KW  - Fractal dimension
Y1  - 2017
U6  - https://doi.org/10.1007/s00603-017-1168-4
SN  - 0723-2632
SN  - 1434-453X
VL  - 50
SP  - 1171
EP  - 1182
PB  - Springer
CY  - Wien
ER  - 
TY  - JOUR
A1  - Heydari, Esmaeil
A1  - Pastoriza-Santos, Isabel
A1  - Liz-Marzan, Luis M.
A1  - Stumpe, Joachim
T1  - Nanoplasmonically-engineered random lasing in organic semiconductor thin films
JF  - Nanoscale horizons
N2  - We demonstrate plasmonically nano-engineered coherent random lasing and stimulated emission enhancement in a hybrid gainmedium of organic semiconductors doped with core-shell plasmonic nanoparticles. The gain medium is composed of a 300 +/- 2 nm thin waveguide of an organic semiconductor, doped with 53 nm gold nanoparticle cores, isolated within silica shells. Upon loading the nanoparticles, the threshold of amplified spontaneous emission is reduced from 1.75 mu J cm(-2) x 10(2) for an undoped gain medium, to 0.35 mu J cm(-2) x 10(2) for a highly concentrated gain medium, and lasing spikes narrower than 0.1 nm are obtained. Most importantly, selection of silica shells with thicknesses of 10, 17 and 21 nm enables engineering of the plasmon-exciton energy coupling and consequently tuning of the laser slope efficiency. With this approach, the slope efficiency is increased by two times by decreasing the silica shell from 21 nm down to 10 nm, due to the enhancement of the localized electric field.
Y1  - 2017
U6  - https://doi.org/10.1039/c7nh00054e
SN  - 2055-6756
SN  - 2055-6764
VL  - 2
SP  - 261
EP  - 266
PB  - Royal Society of Chemistry
CY  - Cambridge
ER  - 
TY  - JOUR
A1  - Gout, Julien
A1  - Quade, Markus
A1  - Shafi, Kamran
A1  - Niven, Robert K.
A1  - Abel, Markus
T1  - Synchronization control of oscillator networks using symbolic regression
JF  - Nonlinear Dynamics
N2  - Networks of coupled dynamical systems provide a powerful way to model systems with enormously complex dynamics, such as the human brain. Control of synchronization in such networked systems has far-reaching applications in many domains, including engineering and medicine. In this paper, we formulate the synchronization control in dynamical systems as an optimization problem and present a multi-objective genetic programming-based approach to infer optimal control functions that drive the system from a synchronized to a non-synchronized state and vice versa. The genetic programming-based controller allows learning optimal control functions in an interpretable symbolic form. The effectiveness of the proposed approach is demonstrated in controlling synchronization in coupled oscillator systems linked in networks of increasing order complexity, ranging from a simple coupled oscillator system to a hierarchical network of coupled oscillators. The results show that the proposed method can learn highly effective and interpretable control functions for such systems.
KW  - Dynamical systems
KW  - Synchronization control
KW  - Genetic programming
Y1  - 2017
U6  - https://doi.org/10.1007/s11071-017-3925-z
SN  - 0924-090X
SN  - 1573-269X
VL  - 91
IS  - 2
SP  - 1001
EP  - 1021
PB  - Springer
CY  - Dordrecht
ER  - 
TY  - JOUR
A1  - Kegeles, Alexander
A1  - Oriti, Daniele
T1  - Continuous point symmetries in group field theories
JF  - Journal of physics : A, Mathematical and theoretical
N2  - We discuss the notion of symmetries in non-local field theories characterized by integro-differential equations of motion, from a geometric perspective. We then focus on group field theory (GFT) models of quantum gravity and provide a general analysis of their continuous point symmetry transformations, including the generalized conservation laws following from them.
KW  - group field theory
KW  - quantum field theory
KW  - conservation laws
KW  - continuous symmetries
Y1  - 2017
U6  - https://doi.org/10.1088/1751-8121/aa5c14
SN  - 1751-8113
SN  - 1751-8121
VL  - 50
IS  - 12
PB  - IOP Publishing Ltd
CY  - Bristol
ER  - 
TY  - JOUR
A1  - Feudel, Fred
A1  - Tuckerman, Laurette S.
A1  - Zaks, Michael
A1  - Hollerbach, Rainer
T1  - Hysteresis of dynamos in rotating spherical shell convection
JF  - Physical review fluids / American Physical Society
N2  - Bifurcations of dynamos in rotating and buoyancy-driven spherical Rayleigh-Benard convection in an electrically conducting fluid are investigated numerically. Both nonmagnetic and magnetic solution branches comprised of rotating waves are traced by path-following techniques, and their bifurcations and interconnections for different Ekman numbers are determined. In particular, the question of whether the dynamo branches bifurcate super- or sub-critically and whether a direct link to the primary pure convective states exists is answered.
Y1  - 2017
U6  - https://doi.org/10.1103/PhysRevFluids.2.053902
SN  - 2469-990X
VL  - 2
PB  - American Physical Society
CY  - College Park
ER  - 
TY  - JOUR
A1  - Morgner, Frank
A1  - Bennemann, Mark
A1  - Cywiński, Piotr J.
A1  - Kollosche, Matthias
A1  - Górski, Krzysztof
A1  - Pietraszkiewicz, Marek
A1  - Geßner, André
A1  - Löhmannsröben, Hans-Gerd
T1  - Elastic FRET sensors for contactless pressure measurement
JF  - RSC Advances : an international journal to further the chemical sciences
N2  - Contactless pressure monitoring based on Forster resonance energy transfer between donor/acceptor pairs immobilized within elastomers is demonstrated. The donor/acceptor energy transfer is employed by dispersing terbium(III) tris[(2-hydroxybenzoyl)-2-aminoethyl] amine complex (LLC, donor) and CdSe/ZnS quantum dots (QD655, acceptor) in styrene-ethylene/buthylene-styrene (SEBS) and poly(dimethylsiloxane) (PDMS). The continuous monitoring of QD luminescence showed a reversible intensity change as the pressure signal is alternated between two stable states indicating a pressure sensitivity of 6350 cps kPa(-1). Time-resolved measurements show the pressure impact on the FRET signal due to an increase of decay time (270 ms up to 420 ms) for the donor signal and parallel drop of decay time (170 mu s to 155 mu s) for the acceptor signal as the net pressure applied. The LLC/QD655 sensors enable a contactless readout as well as space resolved monitoring to enable miniaturization towards smaller integrated stretchable opto-electronics. Elastic FRET sensors can potentially lead to developing profitable analysis systems capable to outdo conventional wired electronic systems (inductive, capacitive, ultrasonic and photoelectric sensors) especially for point-of-care diagnostics, biological monitoring required for wearable electronics.
Y1  - 2017
U6  - https://doi.org/10.1039/c7ra06379b
SN  - 2046-2069
VL  - 7
SP  - 50578
EP  - 50583
PB  - RSC Publishing
CY  - Cambridge
ER  - 
TY  - JOUR
A1  - Dahlke, Sandro
A1  - Maturilli, Marion
T1  - Contribution of atmospheric advection to the amplified winter warming in the arctic north atlantic region
JF  - Advances in meteorology
N2  - Arctic Amplification of climate warming is caused by various feedback processes in the atmosphere-ocean-ice system and yields the strongest temperature increase during winter in the Arctic North Atlantic region. In our study, we attempt to quantify the advective contribution to the observed atmospheric warming in the Svalbard area. Based on radiosonde measurements from Ny-Ålesund, a strong dependence of the tropospheric temperature on the synoptic flow direction is revealed. Using FLEXTRA backward trajectories, an increase of advection from the lower latitude Atlantic region towards Ny-Ålesund is found that is attributed to a change in atmospheric circulation patterns. We find that about one-quarter (0.45 K per decade) of the observed atmospheric winter near surface warming trend in the North Atlantic region of the Arctic (2 K per decade) is due to increased advection of warm and moist air from the lower latitude Atlantic region, affecting the entire troposphere.
Y1  - 2017
U6  - https://doi.org/10.1155/2017/4928620
SN  - 1687-9309
SN  - 1687-9317
PB  - Hindawi Publ. Corp.
CY  - New York
ER  - 
TY  - JOUR
A1  - Kiethe, Jan
A1  - Heuer, Axel
A1  - Jechow, Andreas
T1  - Second-order coherence properties of amplified spontaneous emission from a high-power tapered superluminescent diode
JF  - Laser physics letters
N2  - We study the degree of second-order coherence of the emission of a high-power multi-quantum well superluminescent diode with a lateral tapered amplifier section with and without optical feedback. When operated in an external cavity, the degree of second-order coherence changed from the almost thermal case of g((2))(0)approximate to 1.9 towards the mostly coherent case of g((2)) (0) approximate to 1.2 when the injection current at the tapered section was increased. We found good agreement with semi-classical laser theory near and below threshold while above laser threshold a slightly higher g((2))(0) was observed. As a free running device, the superluminescent diode yielded more than 400 mW of optical output power with good spatial beam quality of M-slow(2) < 1.6. In this case, the degree of second-order coherence dropped only slightly from 1.9 at low powers to 1.6 at the maximum output power. To our knowledge, this is the first investigation of a high-power tapered superluminescent diode concerning the degree of second-order coherence. Such a device might be useful for real-world applications probing the second order coherence function, such as ghost imaging.
KW  - photon statistics
KW  - incoherent light
KW  - superluminescent diodes
Y1  - 2017
U6  - https://doi.org/10.1088/1612-202X/aa772c
SN  - 1612-2011
SN  - 1612-202X
VL  - 14
PB  - IOP Publ. Ltd.
CY  - Bristol
ER  - 
TY  - JOUR
A1  - Park, Jaeheung
A1  - Lühr, Hermann
A1  - Kervalishvili, Guram
A1  - Rauberg, Jan
A1  - Stolle, Claudia
A1  - Kwak, Young-Sil
A1  - Lee, Woo Kyoung
T1  - Morphology of high-latitude plasma density perturbations as deduced from the total electron content measurements onboard the Swarm constellation
JF  - Journal of geophysical research : A, Space physics
N2  - In this study, we investigate the climatology of high-latitude total electron content (TEC) variations as observed by the dual-frequency Global Navigation Satellite Systems (GNSS) receivers onboard the Swarm satellite constellation. The distribution of TEC perturbations as a function of geographic/magnetic coordinates and seasons reasonably agrees with that of the Challenging Minisatellite Payload observations published earlier. Categorizing the high-latitude TEC perturbations according to line-of-sight directions between Swarm and GNSS satellites, we can deduce their morphology with respect to the geomagnetic field lines. In the Northern Hemisphere, the perturbation shapes are mostly aligned with the L shell surface, and this anisotropy is strongest in the nightside auroral (substorm) and subauroral regions and weakest in the central polar cap. The results are consistent with the well-known two-cell plasma convection pattern of the high-latitude ionosphere, which is approximately aligned with L shells at auroral regions and crossing different L shells for a significant part of the polar cap. In the Southern Hemisphere, the perturbation structures exhibit noticeable misalignment to the local L shells. Here the direction toward the Sun has an additional influence on the plasma structure, which we attribute to photoionization effects. The larger offset between geographic and geomagnetic poles in the south than in the north is responsible for the hemispheric difference.
Y1  - 2017
U6  - https://doi.org/10.1002/2016JA023086
SN  - 2169-9380
SN  - 2169-9402
VL  - 122
IS  - 1
SP  - 1338
EP  - 1359
PB  - American Geophysical Union
CY  - Washington
ER  - 
TY  - JOUR
A1  - Niebuhr, Mario
A1  - Heuer, Axel
T1  - Phase measurement and far-field reconstruction on externally coupled laser diode arrays
JF  - Optics express
N2  - Passive coherent combination of several discrete low power laser diodes is a promising way to overcome the issue of degrading beam quality when scaling single emitters to > 10W output power. Such systems would be an efficient alternative to current high power sources, yet they suffer from fatal coherence loss when operated well above threshold. We present a new way to obtain detailed coherence information for laser diode arrays using a spatial light modulator to help identify the underlying decoherence processes. Reconstruction tests of the emitted far-field distribution are conducted to evaluate the performance of our setup.
Y1  - 2017
U6  - https://doi.org/10.1364/OE.25.014317
SN  - 1094-4087
VL  - 25
IS  - 13
SP  - 14317
EP  - 14322
PB  - Optical Society of America
CY  - Washington, DC
ER  - 
TY  - JOUR
A1  - Buschhüter, David
A1  - Spoden, Christian
A1  - Borowski, Andreas
T1  - Physics knowledge of first semester physics students in Germany
BT  - a comparison of 1978 and 2013 cohorts
JF  - International journal of science education
N2  - Over the last decades, the percentage of the age group choosing to pursue university studies has increased significantly across the world. At the same time, there are university teachers who believe that the standards have fallen. There is little research on whether students nowadays demonstrate knowledge or abilities similar to that of the preceding cohorts. However, in times of educational expansion, empirical evidence on student test performance is extremely helpful in evaluating how well educational systems cope with the increasing numbers of students. In this study, we compared a sample of 2322 physics freshmen from 2013 with another sample of 2718 physics freshmen from 1978 at universities in Germany with regard to their physics knowledge based on their results in the same entrance test. Previous results on mathematics knowledge and abilities in the same sample of students indicated that there was no severe decline in their average achievement. This paper compares the physics knowledge of the same two samples of students. Contrary to their mathematics results, their physics results showed a substantial decrease in physics knowledge as measured by the test.
KW  - University physics
KW  - entrance test
KW  - generational comparison
Y1  - 2017
U6  - https://doi.org/10.1080/09500693.2017.1318457
SN  - 0950-0693
SN  - 1464-5289
VL  - 39
IS  - 9
SP  - 1109
EP  - 1132
PB  - Routledge, Taylor & Francis Group
CY  - Abingdon
ER  - 
TY  - JOUR
A1  - Nadammal, Naresh
A1  - Cabeza, Sandra
A1  - Mishurova, Tatiana
A1  - Thiede, Tobias
A1  - Kromm, Arne
A1  - Seyfert, Christoph
A1  - Farahbod, Lena
A1  - Haberland, Christoph
A1  - Schneider, Judith Ann
A1  - Portella, Pedro Dolabella
A1  - Bruno, Giovanni
T1  - Effect of hatch length on the development of microstructure, texture and residual stresses in selective laser melted superalloy Inconel 718
JF  - Materials & Design
N2  - In the present study, samples fabricated by varying the deposition hatch length during selective laser melting of nickel based superalloy Inconel 718 were investigated. Microstructure and texture of these samples was characterized using scanning electron microscopy, combined with electron back-scattered diffraction, and residual stress assessment, using neutron diffraction method. Textured columnar grains oriented along the sample building direction were observed in the shorter hatch length processed sample. A ten-fold increase in the hatch length reduced the texture intensity by a factor of two attributed to the formation of finer grains in the longer hatch length sample. Larger gradients of transverse residual stress in the longer hatch length sample were also observed. Along the build direction, compressive stresses in the shorter hatch length and negligible stresses for the longer hatch length specimen were observed. Changes to the temperature gradient (G) in response to the hatch length variation, influenced the G to growth rate (R) ratio and the product GxR, in agreement with the microstructures and textures formed. For the residual stress development, geometry of the part also played an important role. In summary, tailored isotropy could be induced in Inconel 718 by a careful selection of parameters during selective laser melting.
KW  - Additive manufacturing
KW  - Nickel-based superalloy
KW  - Microstructure and texture
KW  - Residual stress
KW  - Electron back-scattered diffraction
KW  - Neutron diffraction
Y1  - 2017
U6  - https://doi.org/10.1016/j.matdes.2017.08.049
SN  - 0264-1275
SN  - 1873-4197
VL  - 134
SP  - 139
EP  - 150
PB  - Elsevier
CY  - Oxford
ER  - 
TY  - JOUR
A1  - Müller, B. R.
A1  - Cooper, R. C.
A1  - Lange, A.
A1  - Kupsch, Andreas
A1  - Wheeler, M.
A1  - Hentschel, M. P.
A1  - Staude, A.
A1  - Pandey, A.
A1  - Shyam, A.
A1  - Bruno, Giovanni
T1  - Stress-induced microcrack density evolution in beta-eucryptite ceramics
BT  - experimental observations and possible route to strain hardening
JF  - Acta materialia
N2  - In order to investigate their microcracking behaviour, the microstructures of several beta-eucryptite ceramics, obtained from glass precursor and cerammed to yield different grain sizes and microcrack densities, were characterized by laboratory and synchrotron x-ray refraction and tomography. Results were compared with those obtained from scanning electron microscopy (SEM). In SEM images, the characterized materials appeared fully dense but computed tomography showed the presence of pore clusters. Uniaxial tensile testing was performed on specimens while strain maps were recorded and analyzed by Digital Image Correlation (DIC). X-ray refraction techniques were applied on specimens before and after tensile testing to measure the amount of the internal specific surface (i.e., area per unit volume). X-ray refraction revealed that (a) the small grain size (SGS) material contained a large specific surface, originating from the grain boundaries and the interfaces of TiO2 precipitates; (b) the medium (MGS) and large grain size (LGS) materials possessed higher amounts of specific surface compared to SGS material due to microcracks, which decreased after tensile loading; (c) the precursor glass had negligible internal surface. The unexpected decrease in the internal surface of MGS and LGS after tensile testing is explained by the presence of compressive regions in the DIC strain maps and further by theoretical arguments. It is suggested that while some microcracks merge via propagation, more close mechanically, thereby explaining the observed X-ray refraction results. The mechanisms proposed would allow the development of a strain hardening route in ceramics.
KW  - Beta-eucryptite
KW  - Microcracked ceramics
KW  - X-ray refraction
KW  - Tensile load
KW  - Strain hardening
Y1  - 2017
U6  - https://doi.org/10.1016/j.actamat.2017.10.030
SN  - 1359-6454
SN  - 1873-2453
VL  - 144
SP  - 627
EP  - 641
PB  - Elsevier
CY  - Oxford
ER  - 
TY  - JOUR
A1  - Cooper, Ryan C.
A1  - Bruno, Giovanni
A1  - Wheeler, M. R.
A1  - Pandey, A.
A1  - Watkins, T. R.
A1  - Shyarn, A.
T1  - Effect of microcracking on the uniaxial tensile response of beta-eucryptite ceramics
BT  - Experiments and constitutive model
JF  - Acta Materialia
N2  - A constitutive model for the nonlinear or "pseudoplastic" mechanical behavior in a linear-elastic solid with thermally induced microcracks is developed and applied to experimental results. The model is termed strain dependent microcrack density approximation (SDMDA) and is an extension of the modified differential scheme that describes the slope of the stress-strain curves of microcracked solids. SDMDA allows a continuous variation in the microcrack density with tensile loading. Experimental uniaxial tensile response of beta-eucryptite glass and ceramics with controlled levels of microcracking is reported. It is demonstrated that SDMDA can well describe the extent of non-linearity in the experimental uniaxial tensile response of beta-eucryptite with varying levels of microcracking. The advantages of the SDMDA are discussed in regard to tensile loading.
KW  - behavior
Y1  - 2017
U6  - https://doi.org/10.1016/j.actamat.2017.06.033
SN  - 1359-6454
SN  - 1873-2453
VL  - 135
SP  - 361
EP  - 371
PB  - Elsevier
CY  - Oxford
ER  - 
TY  - JOUR
A1  - Waldrip, S. H.
A1  - Niven, Robert K.
A1  - Abel, Markus
A1  - Schlegel, M.
T1  - Reduced-Parameter Method for Maximum Entropy Analysis of Hydraulic Pipe Flow Networks
JF  - Journal of hydraulic engineering
N2  - A maximum entropy (MaxEnt) method is developed to predict flow rates or pressure gradients in hydraulic pipe networks without sufficient information to give a closed-form (deterministic) solution. This methodology substantially extends existing deterministic flow network analysis methods. It builds on the MaxEnt framework previously developed by the authors. This study uses a continuous relative entropy defined on a reduced parameter set, here based on the external flow rates. This formulation ensures consistency between different representations of the same network. The relative entropy is maximized subject to observable constraints on the mean values of a subset of flow rates or potential differences, the frictional properties of each pipe, and physical constraints arising from Kirchhoff’s first and second laws. The new method is demonstrated by application to a simple one-loop network and a 1,123-node, 1,140-pipe water distribution network in the suburb of Torrens, Australian Capital Territory, Australia.
KW  - Maximum entropy method
KW  - Water distribution systems
KW  - Hydraulic networks
KW  - Pipe networks
KW  - Hydraulic models
KW  - Nonlinear analysis
KW  - Probability
Y1  - 2017
U6  - https://doi.org/10.1061/(ASCE)HY.1943-7900.0001379
SN  - 0733-9429
SN  - 1943-7900
VL  - 144
IS  - 2
PB  - American Society of Civil Engineers
CY  - Reston
ER  - 
TY  - JOUR
A1  - Juaristi, J. I.
A1  - Alducin, Maite
A1  - Saalfrank, Peter
T1  - Femtosecond laser induced desorption of H-2, D-2, and HD from Ru(0001)
BT  - dynamical promotion and suppression studied with ab initio molecular dynamics with electronic friction
JF  - Physical review : B, Condensed matter and materials physics
N2  - We perform ab initio molecular dynamics simulations to study the femtosecond laser induced desorption of H-2, D-2, and HD from a H: D-saturated Ru(0001) surface. To this aim we have extended the ab initio molecular dynamics with electronic friction (AIMDEF) scheme to include a random force that is a function of a timedependent electronic temperature. The latter characterizes the action of the ultrashort laser pulse according to a two temperature model. This allows us to perform multidimensional, hot-electron driven reaction dynamics and investigate the dependence of the desorption yields on the relative H: D isotope concentration on the surface. Our AIMDEF simulations show that the desorption process takes place in the presence of a heated adsorbate system that clearly influences the desorption dynamics. The heating of the adsorbate system is more (less) pronounced the larger is the concentration of the lighter (heavier) isotope. As a result, we conclude that the presence of H on the surface favors the desorption of molecules, whereas the presence of D hampers it, in agreement with previous experimental observations in which the phenomenon of "dynamical promotion" of a surface reaction had been postulated.
Y1  - 2017
U6  - https://doi.org/10.1103/PhysRevB.95.125439
SN  - 2469-9950
SN  - 2469-9969
VL  - 95
IS  - 12
PB  - American Physical Society
CY  - College Park
ER  - 
TY  - JOUR
A1  - Henkel, Carsten
T1  - Nanoscale Thermal Transfer
BT  - an Invitation to Fluctuation Electrodynamics
JF  - Zeitschrift für Naturforschung A
N2  - An electromagnetic theory of thermal radiation is outlined, based on the fluctuation electrodynamics of Rytov and co-workers. We discuss the basic concepts and the status of different approximations. The physical content is illustrated with a few examples on near-field heat transfer.
KW  - Heat Transfer
KW  - Near-Field Optics
KW  - Thermal Radiation
Y1  - 2017
U6  - https://doi.org/10.1515/zna-2016-0372
SN  - 0932-0784
SN  - 1865-7109
VL  - 72
IS  - 2
SP  - 99
EP  - 108
PB  - De Gruyter
CY  - Berlin
ER  - 
TY  - JOUR
A1  - Herrmann, Carl J. J.
A1  - Metzler, Ralf
T1  - A self-avoiding walk with neural delays as a model of fixational eye movements
JF  - Scientific reports
N2  - Fixational eye movements show scaling behaviour of the positional mean-squared displacement with a characteristic transition from persistence to antipersistence for increasing time-lag. These statistical patterns were found to be mainly shaped by microsaccades (fast, small-amplitude movements). However, our re-analysis of fixational eye-movement data provides evidence that the slow component (physiological drift) of the eyes exhibits scaling behaviour of the mean-squared displacement that varies across human participants. These results suggest that drift is a correlated movement that interacts with microsaccades. Moreover, on the long time scale, the mean-squared displacement of the drift shows oscillations, which is also present in the displacement auto-correlation function. This finding lends support to the presence of time-delayed feedback in the control of drift movements. Based on an earlier non-linear delayed feedback model of fixational eye movements, we propose and discuss different versions of a new model that combines a self-avoiding walk with time delay. As a result, we identify a model that reproduces oscillatory correlation functions, the transition from persistence to antipersistence, and microsaccades.
Y1  - 2017
U6  - https://doi.org/10.1038/s41598-017-13489-8
SN  - 2045-2322
VL  - 7
SP  - 1
EP  - 17
PB  - Springer Nature
CY  - London
ER  - 
TY  - JOUR
A1  - Menzel, Ralf
A1  - Puhlmann, Dirk
A1  - Heuer, Axel
T1  - Complementarity in single photon interference – the role of the mode function and vacuum fields
JF  - Journal of the European Optical Society-Rapid
N2  - Background
In earlier experiments the role of the vacuum fields could be demonstrated as the source of complementarity with respect to the temporal properties (Heuer et al., Phys. Rev. Lett. 114:053601, 2015).

Methods
Single photon first order interferences of spatially separated regions from the cone structure of spontaneous parametric down conversion allow for analyzing the role of the mode function in quantum optics regarding the complementarity principle.

Results
Here the spatial coherence properties of these vacuum fields are demonstrated as the physical reason for complementarity in these single photon quantum optical experiments. These results are directly connected to the mode picture in classical optics.

Conclusion
The properties of the involved vacuum fields selected via the measurement process are the physical background of the complementarity principle in quantum optics.
KW  - Quantum optics
KW  - Complementarity
KW  - Mode function
KW  - Vacuum fields
Y1  - 2017
U6  - https://doi.org/10.1186/s41476-017-0036-x
SN  - 1990-2573
VL  - 13
PB  - Springer
ER  - 
TY  - JOUR
A1  - Cherstvy, Andrey G.
A1  - Vinod, Deepak
A1  - Aghion, Erez
A1  - Chechkin, Aleksei V.
A1  - Metzler, Ralf
T1  - Time averaging, ageing and delay analysis of financial time series
JF  - New journal of physics
N2  - We introduce three strategies for the analysis of financial time series based on time averaged observables. These comprise the time averaged mean squared displacement (MSD) as well as the ageing and delay time methods for varying fractions of the financial time series. We explore these concepts via statistical analysis of historic time series for several Dow Jones Industrial indices for the period from the 1960s to 2015. Remarkably, we discover a simple universal law for the delay time averaged MSD. The observed features of the financial time series dynamics agree well with our analytical results for the time averaged measurables for geometric Brownian motion, underlying the famed Black–Scholes–Merton model. The concepts we promote here are shown to be useful for financial data analysis and enable one to unveil new universal features of stock market dynamics.
KW  - time averaging
KW  - diffusion
KW  - geometric Brownian motion
KW  - financial time series
Y1  - 2017
U6  - https://doi.org/10.1088/1367-2630/aa7199
SN  - 1367-2630
VL  - 19
SP  - 1
EP  - 11
PB  - IOP
CY  - London
ER  - 
TY  - JOUR
A1  - Wolf, Thomas J. A.
A1  - Holzmeier, Fabian
A1  - Wagner, Isabella
A1  - Berrah, Nora
A1  - Bostedt, Christoph
A1  - Bozek, John
A1  - Bucksbaum, Philip H.
A1  - Coffee, Ryan
A1  - Cryan, James
A1  - Farrell, Joe
A1  - Feifel, Raimund
A1  - Martinez, Todd J.
A1  - McFarland, Brian
A1  - Mucke, Melanie
A1  - Nandi, Saikat
A1  - Tarantelli, Francesco
A1  - Fischer, Ingo
A1  - Gühr, Markus
T1  - Observing Femtosecond Fragmentation Using Ultrafast X-ray-Induced Auger Spectra
JF  - Applied Sciences
N2  - Molecules often fragment after photoionization in the gas phase. Usually, this process can only be investigated spectroscopically as long as there exists electron correlation between the photofragments. Important parameters, like their kinetic energy after separation, cannot be investigated. We are reporting on a femtosecond time-resolved Auger electron spectroscopy study concerning the photofragmentation dynamics of thymine. We observe the appearance of clearly distinguishable signatures from thymine′s neutral photofragment isocyanic acid. Furthermore, we observe a time-dependent shift of its spectrum, which we can attribute to the influence of the charged fragment on the Auger electron. This allows us to map our time-dependent dataset onto the fragmentation coordinate. The time dependence of the shift supports efficient transformation of the excess energy gained from photoionization into kinetic energy of the fragments. Our method is broadly applicable to the investigation of photofragmentation processes.
KW  - ultrafast dynamics
KW  - Auger electron spectroscopy
KW  - photofragmentation
KW  - photochemistry
Y1  - 2017
U6  - https://doi.org/10.3390/app7070681
SN  - 2076-3417
VL  - 7
IS  - 7
PB  - MDPI
CY  - Basel
ER  - 
TY  - JOUR
A1  - Schwarzl, Maria
A1  - Godec, Aljaž
A1  - Metzler, Ralf
T1  - Quantifying non-ergodicity of anomalous diffusion with higher order moments
JF  - Scientific reports
N2  - Anomalous diffusion is being discovered in a fast growing number of systems. The exact nature of this anomalous diffusion provides important information on the physical laws governing the studied system. One of the central properties analysed for finite particle motion time series is the intrinsic variability of the apparent diffusivity, typically quantified by the ergodicity breaking parameter EB. Here we demonstrate that frequently EB is insufficient to provide a meaningful measure for the observed variability of the data. Instead, important additional information is provided by the higher order moments entering by the skewness and kurtosis. We analyse these quantities for three popular anomalous diffusion models. In particular, we find that even for the Gaussian fractional Brownian motion a significant skewness in the results of physical measurements occurs and needs to be taken into account. Interestingly, the kurtosis and skewness may also provide sensitive estimates of the anomalous diffusion exponent underlying the data. We also derive a new result for the EB parameter of fractional Brownian motion valid for the whole range of the anomalous diffusion parameter. Our results are important for the analysis of anomalous diffusion but also provide new insights into the theory of anomalous stochastic processes.
Y1  - 2017
U6  - https://doi.org/10.1038/s41598-017-03712-x
VL  - 7
PB  - Macmillan Publishers Limited
CY  - London
ER  - 
TY  - JOUR
A1  - Zhang, Kai
A1  - Chen, Zhiming
A1  - Armin, Ardalan
A1  - Dong, Sheng
A1  - Xia, Ruoxi
A1  - Yip, Hin-Lap
A1  - Shoaee, Safa
A1  - Huang, Fei
A1  - Cao, Yong
T1  - Efficient large area organic solar cells processed by blade-coating with single-component green solvent
JF  - Solar Rrl
N2  - While the performance of laboratory-scale organic solar cells (OSCs) continues to grow, development of high efficiency large area OSCs remains a big challenge. Although a few attempts to produce large area organic solar cells (OSCs) have been reported, there are still challenges on the way to realizing efficient module devices, such as the low compatibility of the thickness-sensitive active layer with large area coating techniques, the frequent need for toxic solvents and tedious optimization processes used during device fabrication. In this work, highly efficient thickness-insensitive OSCs based on PTB7-Th:PC71BM that processed with single-component green solvent 2-methylanisole are presented, in which both junction thickness limitation and solvent toxicity issues are simultaneously addressed. Careful investigation reveals that this green solvent prevents the evolution of PC71BM into large area clusters resulting in reduced charge carrier recombination, and largely eliminates trapping centers, and thus improves the thickness tolerance of the films. These findings enable us to address the scalability and solvent toxicity issues and to fabricate a 16 cm(2) OSC with doctor-blade coating with a state-of-the-art power conversion efficiency of 7.5% using green solvent.
KW  - doctor-blade coating
KW  - green solvents
KW  - large area devices
KW  - organic solar cells
KW  - thickness insensitive active layers
Y1  - 2017
U6  - https://doi.org/10.1002/solr.201700169
SN  - 2367-198X
VL  - 2
IS  - 1
PB  - Wiley-VCH
CY  - Weinheim
ER  - 
TY  - JOUR
A1  - Sysoev, Ilya V.
A1  - Ponomarenko, Vladimir I.
A1  - Pikovskij, Arkadij
T1  - Reconstruction of coupling architecture of neural field networks from vector time series
JF  - Communications in nonlinear science & numerical simulation
N2  - We propose a method of reconstruction of the network coupling matrix for a basic voltage-model of the neural field dynamics. Assuming that the multivariate time series of observations from all nodes are available, we describe a technique to find coupling constants which is unbiased in the limit of long observations. Furthermore, the method is generalized for reconstruction of networks with time-delayed coupling, including the reconstruction of unknown time delays. The approach is compared with other recently proposed techniques.
KW  - Network reconstruction
KW  - Time series
KW  - Neurooscillators
KW  - Time delay
Y1  - 2017
U6  - https://doi.org/10.1016/j.cnsns.2017.10.006
SN  - 1007-5704
SN  - 1878-7274
VL  - 57
SP  - 342
EP  - 351
PB  - Elsevier
CY  - Amsterdam
ER  -