TY  - JOUR
A1  - Zajnulina, Marina
A1  - Böhm, Michael
A1  - Blow, K.
A1  - Rieznik, A. A.
A1  - Giannone, Domenico
A1  - Haynes, Roger
A1  - Roth, Martin M.
T1  - Soliton radiation beat analysis of optical pulses generated from two continuous-wave lasers
JF  - Chaos : an interdisciplinary journal of nonlinear science
N2  - We propose a fibre-based approach for generation of optical frequency combs (OFCs) with the aim of calibration of astronomical spectrographs in the low and medium-resolution range. This approach includes two steps: in the first step, an appropriate state of optical pulses is generated and subsequently moulded in the second step delivering the desired OFC. More precisely, the first step is realised by injection of two continuous-wave (CW) lasers into a conventional single-mode fibre, whereas the second step generates a broad OFC by using the optical solitons generated in step one as initial condition. We investigate the conversion of a bichromatic input wave produced by two initial CW lasers into a train of optical solitons, which happens in the fibre used as step one. Especially, we are interested in the soliton content of the pulses created in this fibre. For that, we study different initial conditions (a single cosine-hump, an Akhmediev breather, and a deeply modulated bichromatic wave) by means of soliton radiation beat analysis and compare the results to draw conclusion about the soliton content of the state generated in the first step. In case of a deeply modulated bichromatic wave, we observed the formation of a collective soliton crystal for low input powers and the appearance of separated solitons for high input powers. An intermediate state showing the features of both, the soliton crystal and the separated solitons, turned out to be most suitable for the generation of OFC for the purpose of calibration of astronomical spectrographs.
Y1  - 2015
U6  - https://doi.org/10.1063/1.4930316
SN  - 1054-1500
SN  - 1089-7682
VL  - 25
IS  - 10
PB  - American Institute of Physics
CY  - Melville
ER  - 
TY  - JOUR
A1  - Richter, Philipp
A1  - de Boer, Klaas S.
A1  - Werner, Klaus
A1  - Rauch, Thomas
T1  - High-velocity gas toward the LMC resides in the Milky Way halo
JF  - Astronomy and astrophysics : an international weekly journal
N2  - Aims. To explore the origin of high-velocity gas in the direction of the Large Magellanic Cloud, (LMC) we analyze absorption lines in the ultraviolet spectrum of a Galactic halo star that is located in front of the LMC at d = 9.2(-7.2)(+4.1) kpc distance.
 Methods. We study the velocity-component structure of low and intermediate metal ions (CII, SiII, SiIII) in the spectrum of RXJ0439.8-6809, as obtained with the Cosmic Origins Spectrograph (COS) onboard the Hubble Space Telescope (HST), and measure equivalent widths and column densities for these ions. We supplement our COS data with a Far-Ultraviolet Spectroscopic Explorer (FUSE) spectrum of the nearby LMC star Sk-69 59 and with Hi 21 cm data from the Leiden-Argentina-Bonn (LAB) survey.
 Results. Metal absorption toward RXJ0439.8-6809 is unambiguously detected in three different velocity components near v(LSR) = 0, + 60, and + 150 km s(-1). The presence of absorption proves that all three gas components are situated in front of the star, thus located in the disk and inner halo of the Milky Way. For the high-velocity cloud (HVC) at v(LSR) = + 150 km s(-1), we derive an oxygen abundance of [O/H] = -0.63 (similar to 0.2 solar) from the neighboring Sk-69 59 sight line, in accordance with previous abundance measurements for this HVC. From the observed kinematics we infer that the HVC hardly participates in the Galactic rotation.
 Conclusions. Our study shows that the HVC toward the LMC represents a Milky Way halo cloud that traces low column density gas with relatively low metallicity. We rule out scenarios in which the HVC represents material close to the LMC that stems from a LMC outflow.
KW  - Galaxy: halo
KW  - Galaxy: evolution
KW  - ISM: abundances
KW  - ISM: structure
Y1  - 2015
U6  - https://doi.org/10.1051/0004-6361/201527451
SN  - 1432-0746
VL  - 584
PB  - EDP Sciences
CY  - Les Ulis
ER  - 
TY  - JOUR
A1  - Metzler, Ralf
A1  - Bauer, Maximilian
A1  - Rasmussen, Emil S.
A1  - Lomholt, Michael A.
T1  - Real sequence effects on the search dynamics of transcription factors on DNA
JF  - Scientific Reports
N2  - Recent experiments show that transcription factors (TFs) indeed use the facilitated diffusion mechanism to locate their target sequences on DNA in living bacteria cells: TFs alternate between sliding motion along DNA and relocation events through the cytoplasm. From simulations and theoretical analysis we study the TF-sliding motion for a large section of the DNA-sequence of a common E. coli strain, based on the two-state TF-model with a fast-sliding search state and a recognition state enabling target detection. For the probability to detect the target before dissociating from DNA the TF-search times self-consistently depend heavily on whether or not an auxiliary operator (an accessible sequence similar to the main operator) is present in the genome section. Importantly, within our model the extent to which the interconversion rates between search and recognition states depend on the underlying nucleotide sequence is varied. A moderate dependence maximises the capability to distinguish between the main operator and similar sequences. Moreover, these auxiliary operators serve as starting points for DNA looping with the main operator, yielding a spectrum of target detection times spanning several orders of magnitude. Auxiliary operators are shown to act as funnels facilitating target detection by TFs.
KW  - gene regulatory networks
KW  - biological physics
Y1  - 2015
U6  - https://doi.org/10.1038/srep10072
SN  - 2045-2322
VL  - 5
IS  - 10072
PB  - Nature Publishing Group
CY  - London
ER  - 
TY  - JOUR
A1  - Kniepert, Juliane
A1  - Lange, Ilja
A1  - Heidbrink, Jan
A1  - Kurpiers, Jona
A1  - Brenner, Thomas J. K.
A1  - Koster, L. Jan Anton
A1  - Neher, Dieter
T1  - Effect of Solvent Additive on Generation, Recombination, and Extraction in PTB7:PCBM Solar Cells: A Conclusive Experimental and Numerical Simulation Study
JF  - The journal of physical chemistry : C, Nanomaterials and interfaces
N2  - Time-delayed collection field (TDCF), bias-assisted charge extraction (BACE), and space charge-limited current (SCLC) measurements are combined with complete numerical device simulations to unveil the effect of the solvent additive 1,8-diiodooctane (DIO) on the performance of PTB7:PCBM bulk heterojunction solar cells. DIO is shown to increase the charge generation rate, reduce geminate and bimolecular recombination, and increase the electron mobility. In total, the reduction of loss currents by processing with the additive raises the power conversion efficiency of the PTB7:PCBM blend by a factor of almost three. The lower generation rates and higher geminate recombination losses in devices without DIO are consistent with a blend morphology comprising large fullerene clusters embedded within a PTB7-rich matrix, while the low electron mobility suggests that these fullerene clusters are themselves composed of smaller pure fullerene aggregates separated by disordered areas. Our device simulations show unambiguously that the effect of the additive on the shape of the currentvoltage curve (J-V) cannot be ascribed to the variation of only the mobility, the recombination, or the field dependence of generation. It is only when the changes of all three parameters are taken into account that the simulation matches the experimental J-V characteristics under all illumination conditions and for a wide range of voltages.
Y1  - 2015
U6  - https://doi.org/10.1021/jp512721e
SN  - 1932-7447
VL  - 119
IS  - 15
SP  - 8310
EP  - 8320
PB  - American Chemical Society
CY  - Washington
ER  - 
TY  - JOUR
A1  - Wernet, Philippe
A1  - Kunnus, Kristjan
A1  - Josefsson, Ida
A1  - Rajkovic, Ivan
A1  - Quevedo, Wilson
A1  - Beye, Martin
A1  - Schreck, Simon
A1  - Gruebel, S.
A1  - Scholz, Mirko
A1  - Nordlund, Dennis
A1  - Zhang, Wenkai
A1  - Hartsock, Robert W.
A1  - Schlotter, William F.
A1  - Turner, Joshua J.
A1  - Kennedy, Brian
A1  - Hennies, Franz
A1  - de Groot, Frank M. F.
A1  - Gaffney, Kelly J.
A1  - Techert, Simone
A1  - Odelius, Michael
A1  - Föhlisch, Alexander
T1  - Orbital-specific mapping of the ligand exchange dynamics of Fe(CO)(5) in solution
JF  - Nature : the international weekly journal of science
N2  - Transition-metal complexes have long attracted interest for fundamental chemical reactivity studies and possible use in solar energy conversion(1,2). Electronic excitation, ligand loss from the metal centre, or a combination of both, creates changes in charge and spin density at the metal site(3-11) that need to be controlled to optimize complexes for photocatalytic hydrogen production(8) and selective carbon-hydrogen bond activation(9-11). An understanding at the molecular level of how transition-metal complexes catalyse reactions, and in particular of the role of the short-lived and reactive intermediate states involved, will be critical for such optimization. However, suitable methods for detailed characterization of electronic excited states have been lacking. Here we show, with the use of X-ray laser-based femtosecond-resolution spectroscopy and advanced quantum chemical theory to probe the reaction dynamics of the benchmark transition-metal complex Fe(CO)(5) in solution, that the photo-induced removal of CO generates the 16-electron Fe(CO)(4) species, a homogeneous catalyst(12,13) with an electron deficiency at the Fe centre(14,15), in a hitherto unreported excited singlet state that either converts to the triplet ground state or combines with a CO or solvent molecule to regenerate a penta-coordinated Fe species on a sub-picosecond timescale. This finding, which resolves the debate about the relative importance of different spin channels in the photochemistry of Fe(CO)(5) (refs 4, 16-20), was made possible by the ability of femtosecond X-ray spectroscopy to probe frontier-orbital interactions with atom specificity. We expect the method to be broadly applicable in the chemical sciences, and to complement approaches that probe structural dynamics in ultrafast processes.
Y1  - 2015
U6  - https://doi.org/10.1038/nature14296
SN  - 0028-0836
SN  - 1476-4687
VL  - 520
IS  - 7545
SP  - 78
EP  - 81
PB  - Nature Publ. Group
CY  - London
ER  - 
TY  - JOUR
A1  - Aleksic, J.
A1  - Ansoldi, S.
A1  - Antonelli, L. A.
A1  - Antoranz, P.
A1  - Babic, A.
A1  - Bangale, P.
A1  - de Almeida, U. Barres
A1  - Barrio, J. A.
A1  - Gonzalez, J. Becerra
A1  - Bednarek, W.
A1  - Berger, K.
A1  - Bernardini, E.
A1  - Bilandli, A.
A1  - Bianch, O.
A1  - Bock, R. K.
A1  - Bonnefoy, S.
A1  - Bonnoli, G.
A1  - Borracci, F.
A1  - Bretz, T.
A1  - Carmona, E.
A1  - Carosi, A.
A1  - Fidalgo, D. Carreto
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 Caneva, G.
A1  - De Lotto, B.
A1  - Delgado Mendez, C.
A1  - Doert, M.
A1  - Dominguez, A.
A1  - Prester, Dijana Dominis
A1  - Dorner, D.
A1  - Doro, M.
A1  - Einecke, S.
A1  - Eisenacher, D.
A1  - Elsaesser, D.
A1  - Farina, E.
A1  - Ferenc, D.
A1  - Fonseca, M. V.
A1  - Font, L.
A1  - Frantzen, K.
A1  - Fruck, C.
A1  - Garcia Lopez, R. J.
A1  - Garczarczyki, M.
A1  - Garrido Terrats, D.
A1  - Gaug, M.
A1  - Giavitto, G.
A1  - Godinovic, N.
A1  - Gonzalez Munoz, A.
A1  - Gozzini, S. R.
A1  - Hadamek, A.
A1  - Hadasch, D.
A1  - Herrero, A.
A1  - Hildebrand, D.
A1  - Hose, J.
A1  - Hrupec, D.
A1  - Idec, W.
A1  - Kadenius, V.
A1  - Kellermann, H.
A1  - Knoetig, M. L.
A1  - Krause, J.
A1  - Kushida, J.
A1  - La Barbera, A.
A1  - Lelas, D.
A1  - Lewandowska, N.
A1  - Lindfors, E.
A1  - Longo, F.
A1  - Lombardi, S.
A1  - Lopez, M.
A1  - Lopez-Coto, R.
A1  - Lopez-Oramas, A.
A1  - Lorenz, E.
A1  - Lozano, I.
A1  - Makariev, M.
A1  - Mallot, K.
A1  - Maneva, G.
A1  - Mankuzhiyil, N.
A1  - Mannheim, K.
A1  - Maraschi, L.
A1  - Marcote, B.
A1  - Mariotti, M.
A1  - Martinez, M.
A1  - Mazin, D.
A1  - Menzel, U.
A1  - Meucci, M.
A1  - Miranda, J. M.
A1  - Mirzoyan, R.
A1  - Moralejo, A.
A1  - Munar-Adrover, P.
A1  - Nakajima, D.
A1  - Niedzwiecki, A.
A1  - Nilsson, K.
A1  - Nowak, N.
A1  - Orito, R.
A1  - Overkemping, A.
A1  - Paiano, S.
A1  - Palatiello, M.
A1  - Paneque, D.
A1  - Paoletti, R.
A1  - Paredes, J. M.
A1  - Paredes-Fortuny, X.
A1  - Partini, S.
A1  - Persic, M.
A1  - Prada, F.
A1  - Moroni, P. G. Prada
A1  - Prandini, E.
A1  - Preziuso, S.
A1  - Puljak, I.
A1  - Reinthal, R.
A1  - Rhode, W.
A1  - Ribo, M.
A1  - Rico, J.
A1  - Garcia, J. Rodriguez
A1  - Ruegamer, S.
A1  - Saggion, A.
A1  - Saito, K.
A1  - Salvati, M.
A1  - Satalecka, K.
A1  - Scalzotto, V.
A1  - Scapin, V.
A1  - Schuliz, C.
A1  - Schweizer, T.
A1  - Shore, S. N.
A1  - Sillanpaa, A.
A1  - Sitarek, J.
A1  - Snidaric, I.
A1  - Sobczynska, D.
A1  - Spanier, F.
A1  - Stamatescu, V.
A1  - Stamerra, A.
A1  - Steinbring, T.
A1  - Storz, J.
A1  - Sun, S.
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  - Tibolla, O.
A1  - Torres, D. F.
A1  - Toyama, T.
A1  - Treves, A.
A1  - Uellenbeck, M.
A1  - Vogler, P.
A1  - Wagner, R. M.
A1  - Zandanel, F.
A1  - Zanin, R.
A1  - Archambault, S.
A1  - Behera, B.
A1  - Beilicke, M.
A1  - Benbow, W.
A1  - Bird, R.
A1  - Buckley, J. H.
A1  - Bugaev, V.
A1  - Cerruti, M.
A1  - Chen, X.
A1  - Ciupik, L.
A1  - Collins-Hughes, E.
A1  - Cui, W.
A1  - Dumm, J.
A1  - Eisch, J. D.
A1  - Falcone, A.
A1  - Federici, S.
A1  - Feng, Q.
A1  - Finley, J. P.
A1  - Fleischhack, H.
A1  - Fortin, P.
A1  - Fortson, L.
A1  - Furniss, A.
A1  - Griffin, S.
A1  - Griffiths, S. T.
A1  - Grube, J.
A1  - Gyuk, G.
A1  - Hanna, D.
A1  - Holder, J.
A1  - Hughes, G.
A1  - Humensky, T. B.
A1  - Johnson, C. A.
A1  - Kaaret, P.
A1  - Kertzman, M.
A1  - Khassen, Y.
A1  - Kieda, D.
A1  - Krawczynski, H.
A1  - Krennrich, F.
A1  - Kumar, S.
A1  - Lang, M. J.
A1  - Maier, G.
A1  - McArthur, S.
A1  - Meagher, K.
A1  - Moriarty, P.
A1  - Mukherjee, R.
A1  - Ong, R. A.
A1  - Otte, A. N.
A1  - Park, N.
A1  - Pichel, A.
A1  - Pohl, M.
A1  - Popkow, A.
A1  - Prokoph, H.
A1  - Quinn, M. J.
A1  - Ragan, K.
A1  - Rajotte, J.
A1  - Reynolds, P. T.
A1  - Richards, G. T.
A1  - Roache, E.
A1  - Rovero, A. C.
A1  - Sembroski, G. H.
A1  - Shahinyan, K.
A1  - Staszak, D.
A1  - Telezhinsky, Igor O.
A1  - Theiling, M.
A1  - Tucci, J. V.
A1  - Tyler, J.
A1  - Varlotta, A.
A1  - Wakely, S. P.
A1  - Weekes, T. C.
A1  - Weinstein, A.
A1  - Welsing, R.
A1  - Wilhelm, Alina
A1  - Williams, D. A.
A1  - Zitzer, B.
A1  - Villata, M.
A1  - Raiteri, C.
A1  - Aller, H. D.
A1  - Aller, M. F.
A1  - Chen, W. P.
A1  - Jordan, B.
A1  - Koptelova, E.
A1  - Kurtanidze, O. M.
A1  - Lahteenmaki, A.
A1  - McBreen, B.
A1  - Larionov, V. M.
A1  - Lin, C. S.
A1  - Nikolashvili, M. G.
A1  - Angelakis, E.
A1  - Capalbi, M.
A1  - Carraminana, A.
A1  - Carrasco, L.
A1  - Cassaro, P.
A1  - Cesarini, A.
A1  - Fuhrmann, L.
A1  - Giroletti, M.
A1  - Hovatta, T.
A1  - Krichbaum, T. P.
A1  - Krimm, H. A.
A1  - Max-Moerbeck, W.
A1  - Moody, J. W.
A1  - Maccaferri, G.
A1  - Mori, Y.
A1  - Nestoras, I.
A1  - Orlati, A.
A1  - Pace, C.
A1  - Pearson, R.
A1  - Perri, M.
A1  - Readhead, A. C. S.
A1  - Richards, J. L.
A1  - Sadun, A. C.
A1  - Sakamoto, T.
A1  - Tammi, J.
A1  - Tornikoski, M.
A1  - Yatsu, Y.
A1  - Zook, A.
T1  - The 2009 multiwavelength campaign on Mrk 421: Variability and correlation studies
JF  - Astronomy and astrophysics : an international weekly journal
N2  - Aims. We perform an extensive characterization of the broadband emission of Mrk 421, as well as its temporal evolution, during the non-flaring (low) state. The high brightness and nearby location (z = 0.031) of Mrk 421 make it an excellent laboratory to study blazar emission. The goal is to learn about the physical processes responsible for the typical emission of Mrk 421, which might also be extended to other blazars that are located farther away and hence are more difficult to study.
 Methods. We performed a 4.5-month multi-instrument campaign on Mrk 421 between January 2009 and June 2009, which included VLBA, F-GAMMA, GASP-WEBT, Swift, RXTE, Fermi-LAT, MAGIC, and Whipple, among other instruments and collaborations. This extensive radio to very-high-energy (VHE; E > 100 GeV) gamma-ray dataset provides excellent temporal and energy coverage, which allows detailed studies of the evolution of the broadband spectral energy distribution.
 Results. Mrk421 was found in its typical (non-flaring) activity state, with a VHE flux of about half that of the Crab Nebula, yet the light curves show significant variability at all wavelengths, the highest variability being in the X-rays. We determined the power spectral densities (PSD) at most wavelengths and found that all PSDs can be described by power-laws without a break, and with indices consistent with pink/red-noise behavior. We observed a harder-when-brighter behavior in the X-ray spectra and measured a positive correlation between VHE and X-ray fluxes with zero time lag. Such characteristics have been reported many times during flaring activity, but here they are reported for the first time in the non-flaring state. We also observed an overall anti-correlation between optical /UV and X-rays extending over the duration of the campaign.
 Conclusions. The harder-when-brighter behavior in the X-ray spectra and the measured positive X-ray/VHE correlation during the 2009 multiwavelength campaign suggests that the physical processes dominating the emission during non-flaring states have similarities with those occurring during flaring activity. In particular, this observation supports leptonic scenarios as being responsible for the emission of Mrk 421 during non-flaring activity. Such a temporally extended X-ray /VHE correlation is not driven by any single flaring event, and hence is difficult to explain within the standard hadronic scenarios. The highest variability is observed in the X-ray band, which, within the one-zone synchrotron self-Compton scenario, indicates that the electron energy distribution is most variable at the highest energies.
KW  - BL Lacertae objects: individual: Mrk 421
Y1  - 2015
U6  - https://doi.org/10.1051/0004-6361/201424216
SN  - 0004-6361
SN  - 1432-0746
VL  - 576
PB  - EDP Sciences
CY  - Les Ulis
ER  - 
TY  - JOUR
A1  - Monreal-Ibero, Ana
A1  - Weilbacher, Peter Michael
A1  - Wendt, Martin
A1  - Selman, Fernando
A1  - Lallement, Rosine
A1  - Brinchmann, Jarle
A1  - Kamann, Sebastian
A1  - Sandin, Christer
T1  - Towards DIB mapping in galaxies beyond 100 Mpc A radial profile of the lambda 5780.5 diffuse interstellar band in AM1353-272 B
JF  - Astronomy and astrophysics : an international weekly journal
N2  - Context. Diffuse interstellar bands (DIBs) are non-stellar weak absorption features of unknown origin found in the spectra of stars viewed through one or several clouds of the interstellar medium (ISM). Research of DIBs outside the Milky Way is currently very limited. In particular, spatially resolved investigations of DIBs outside of the Local Group are, to our knowledge, inexistent.
 Aims. In this contribution, we explore the capability of the high-sensitivity integral field spectrograph, MUSE, as a tool for mapping diffuse interstellar bands at distances larger than 100 Mpc.
 Methods. We used MUSE commissioning data for AM1353-272 B, the member with the highest extinction of the Dentist's Chair, an interacting system of two spiral galaxies. High signal-to-noise spectra were created by co-adding the signal of many spatial elements distributed in a geometry of concentric elliptical half-rings.
 Results. We derived decreasing radial profiles for the equivalent width of the lambda 5780.5 DIB both in the receding and approaching side of the companion galaxy up to distances of similar to 4.6 kpc from the centre of the galaxy. The interstellar extinction as derived from the Ha/H beta line ratio displays a similar trend, with decreasing values towards the external parts. This translates into an intrinsic correlation between the strength of the DIB and the extinction within AM1353-272 B, consistent with the currently existing global trend between these quantities when using measurements for Galactic and extragalactic sightlines.
 Conclusions. It seems feasible to map the DIB strength in the Local Universe, which has up to now only been performed for the Milky Way. This offers a new approach to studying the relationship between DIBs and other characteristics and species of the ISM in addition to using galaxies in the Local Group or sightlines towards very bright targets outside the Local Group.
KW  - dust, extinction
KW  - ISM: lines and bands
KW  - galaxies: ISM
KW  - galaxies: individual: AM1353-272 B
Y1  - 2015
U6  - https://doi.org/10.1051/0004-6361/201525854
SN  - 0004-6361
SN  - 1432-0746
VL  - 576
PB  - EDP Sciences
CY  - Les Ulis
ER  - 
TY  - JOUR
A1  - Martin, Nicolas F.
A1  - Nidever, David L.
A1  - Besla, Gurtina
A1  - Olsen, Knut
A1  - Walker, Alistair R.
A1  - Vivas, A. Katherina
A1  - Gruendl, Robert A.
A1  - Kaleida, Catherine C.
A1  - Munoz, Ricardo R.
A1  - Blum, Robert D.
A1  - Saha, Abhijit
A1  - Conn, Blair C.
A1  - Bell, Eric F.
A1  - Chu, You-Hua
A1  - Cioni, Maria-Rosa L.
A1  - de Boer, Thomas J. L.
A1  - Gallart, Carme
A1  - Jin, Shoko
A1  - Kunder, Andrea
A1  - Majewski, Steven R.
A1  - Martinez-Delgado, David
A1  - Monachesi, Antonela
A1  - Monelli, Matteo
A1  - Monteagudo, Lara
A1  - Noel, Noelia E. D.
A1  - Olszewski, Edward W.
A1  - Stringfellow, Guy S.
A1  - van der Marel, Roeland P.
A1  - Zaritsky, Dennis
T1  - Hydra II: A faint and compact milky way dwarf galaxy found in the survey of the magellanic stellar history
JF  - The astrophysical journal : an international review of spectroscopy and astronomical physics ; Part 2, Letters
N2  - We present the discovery of a new dwarf galaxy, Hydra II, found serendipitously within the data from the ongoing Survey of the Magellanic Stellar History conducted with the Dark Energy Camera on the Blanco 4 m Telescope. The new satellite is compact (r(h) = 68 +/- 11 pc) and faint (MV = -4.8 +/- 0.3), but well within the realm of dwarf galaxies. The stellar distribution of Hydra II in the color-magnitude diagram is well-described by a metal-poor ([Fe/H] = -2.2) and old (13 Gyr) isochrone and shows a distinct blue horizontal branch, some possible red clump stars, and faint stars that are suggestive of blue stragglers. At a heliocentric distance of 134 +/- 10 kpc, Hydra II is located in a region of the Galactic halo that models have suggested may host material from the leading arm of the Magellanic Stream. A comparison with N-body simulations hints that the new dwarf galaxy could be or could have been a satellite of the Magellanic Clouds.
KW  - galaxies: individual (Hydra II)
KW  - Local Group
KW  - Magellanic Clouds
Y1  - 2015
U6  - https://doi.org/10.1088/2041-8205/804/1/L5
SN  - 2041-8205
SN  - 2041-8213
VL  - 804
IS  - 1
PB  - IOP Publ. Ltd.
CY  - Bristol
ER  - 
TY  - JOUR
A1  - Cherstvy, Andrey G.
A1  - Metzler, Ralf
T1  - Ergodicity breaking, ageing, and confinement in generalized diffusion processes with position and time dependent diffusivity
JF  - Journal of statistical mechanics: theory and experiment
N2  - We study generalized anomalous diffusion processes whose diffusion coefficient D(x, t) similar to D-0x(alpha)t(beta) depends on both the position x of the test particle and the process time t. This process thus combines the features of scaled Brownian motion and heterogeneous diffusion parent processes. We compute the ensemble and time averaged mean squared displacements of this generalized diffusion process. The scaling exponent of the ensemble averaged mean squared displacement is shown to be the product of the critical exponents of the parent processes, and describes both subdiffusive and superdiffusive systems. We quantify the amplitude fluctuations of the time averaged mean squared displacement as function of the length of the time series and the lag time. In particular, we observe a weak ergodicity breaking of this generalized diffusion process: even in the long time limit the ensemble and time averaged mean squared displacements are strictly disparate. When we start to observe this process some time after its initiation we observe distinct features of ageing. We derive a universal ageing factor for the time averaged mean squared displacement containing all information on the ageing time and the measurement time. External confinement is shown to alter the magnitudes and statistics of the ensemble and time averaged mean squared displacements.
KW  - diffusion
Y1  - 2015
U6  - https://doi.org/10.1088/1742-5468/2015/05/P05010
SN  - 1742-5468
PB  - IOP Publ. Ltd.
CY  - Bristol
ER  - 
TY  - JOUR
A1  - Bartesaghi, Davide
A1  - Perez, Irene del Carmen
A1  - Kniepert, Juliane
A1  - Roland, Steffen
A1  - Turbiez, Mathieu
A1  - Neher, Dieter
A1  - Koster, L. Jan Anton
T1  - Competition between recombination and extraction of free charges determines the fill factor of organic solar cells
JF  - Nature Communications
N2  - Among the parameters that characterize a solar cell and define its power-conversion efficiency, the fill factor is the least well understood, making targeted improvements difficult. Here we quantify the competition between charge extraction and recombination by using a single parameter theta, and we demonstrate that this parameter is directly related to the fill factor of many different bulk-heterojunction solar cells. Our finding is supported by experimental measurements on 15 different donor: acceptor combinations, as well as by drift-diffusion simulations of organic solar cells in which charge-carrier mobilities, recombination rate, light intensity, energy levels and active-layer thickness are all varied over wide ranges to reproduce typical experimental conditions. The results unify the fill factors of several very different donor: acceptor combinations and give insight into why fill factors change so much with thickness, light intensity and materials properties. To achieve fill factors larger than 0.8 requires further improvements in charge transport while reducing recombination.
Y1  - 2015
U6  - https://doi.org/10.1038/ncomms8083
SN  - 2041-1723
VL  - 6
PB  - Nature Publ. Group
CY  - London
ER  - 
TY  - JOUR
A1  - Zhang, Haocheng
A1  - Chen, Xuhui
A1  - Böttcher, Markus
A1  - Guo, Fan
A1  - Li, Hui
T1  - Polarization swings reveal magnetic energy dissipation in blazars
JF  - The astrophysical journal : an international review of spectroscopy and astronomical physics
N2  - The polarization signatures of blazar emissions are known to be highly variable. In addition to small fluctuations of the polarization angle around a mean value, large (greater than or similar to 180 degrees) polarization angle swings are sometimes observed. We suggest that such phenomena can be interpreted as arising from light travel time effects within an underlying axisymmetric emission region. We present the first simultaneous fitting of the multi-wavelength spectrum, variability, and time-dependent polarization features of a correlated optical and gamma-ray flaring event of the prominent blazar 3C279, which was accompanied by a drastic change in its polarization signatures. This unprecedented combination of spectral, variability, and polarization information in a coherent physical model allows us to place stringent constraints on the particle acceleration and magnetic field topology in the relativistic jet of a blazar, strongly favoring a scenario in which magnetic energy dissipation is the primary driver of the flare event.
KW  - galaxies: active
KW  - galaxies: jets
KW  - gamma-rays: galaxies
KW  - radiation mechanisms: nonthermal
KW  - relativistic processes
Y1  - 2015
U6  - https://doi.org/10.1088/0004-637X/804/1/58
SN  - 0004-637X
SN  - 1538-4357
VL  - 804
IS  - 1
PB  - IOP Publ. Ltd.
CY  - Bristol
ER  - 
TY  - JOUR
A1  - Coumou, Dim
A1  - Lehmann, Jascha
A1  - Beckmann, Johanna
T1  - The weakening summer circulation in the Northern Hemisphere mid-latitudes
JF  - Science
N2  - Rapid warming in the Arctic could influence mid-latitude circulation by reducing the poleward temperature gradient. The largest changes are generally expected in autumn or winter, but whether significant changes have occurred is debated. Here we report significant weakening of summer circulation detected in three key dynamical quantities: (i) the zonal-mean zonal wind, (ii) the eddy kinetic energy (EKE), and (iii) the amplitude of fast-moving Rossby waves. Weakening of the zonal wind is explained by a reduction in the poleward temperature gradient. Changes in Rossby waves and EKE are consistent with regression analyses of climate model projections and changes over the seasonal cycle. Monthly heat extremes are associated with low EKE, and thus the observed weakening might have contributed to more persistent heat waves in recent summers.
Y1  - 2015
U6  - https://doi.org/10.1126/science.1261768
SN  - 0036-8075
SN  - 1095-9203
VL  - 348
IS  - 6232
SP  - 324
EP  - 327
PB  - American Assoc. for the Advancement of Science
CY  - Washington
ER  - 
TY  - JOUR
A1  - Xin, Hong
A1  - LaRue, Jerry
A1  - Oberg, Henrik
A1  - Beye, Martin
A1  - Turner, J. J.
A1  - Gladh, Jörgen
A1  - Ng, May L.
A1  - Sellberg, Jonas A.
A1  - Kaya, Sarp
A1  - Mercurio, G.
A1  - Hieke, F.
A1  - Nordlund, Dennis
A1  - Schlotter, William F.
A1  - Dakovski, Georgi L.
A1  - Minitti, Michael P.
A1  - Föhlisch, Alexander
A1  - Wolf, Martin
A1  - Wurth, Wilfried
A1  - Ogasawara, Hirohito
A1  - Norskov, Jens K.
A1  - Ostrom, Henrik
A1  - Pettersson, Lars G. M.
A1  - Nilsson, Anders
A1  - Abild-Pedersen, Frank
T1  - Strong Influence of Coadsorbate Interaction on CO Desorption Dynamics on Ru(0001) Probed by Ultrafast X-Ray Spectroscopy and Ab Initio Simulations
JF  - Physical review letters
N2  - We show that coadsorbed oxygen atoms have a dramatic influence on the CO desorption dynamics from Ru(0001). In contrast to the precursor-mediated desorption mechanism on Ru(0001), the presence of surface oxygen modifies the electronic structure of Ru atoms such that CO desorption occurs predominantly via the direct pathway. This phenomenon is directly observed in an ultrafast pump-probe experiment using a soft x-ray free-electron laser to monitor the dynamic evolution of the valence electronic structure of the surface species. This is supported with the potential of mean force along the CO desorption path obtained from density-functional theory calculations. Charge density distribution and frozen-orbital analysis suggest that the oxygen-induced reduction of the Pauli repulsion, and consequent increase of the dative interaction between the CO 5 sigma and the charged Ru atom, is the electronic origin of the distinct desorption dynamics. Ab initio molecular dynamics simulations of CO desorption from Ru(0001) and oxygen-coadsorbed Ru(0001) provide further insights into the surface bond-breaking process.
Y1  - 2015
U6  - https://doi.org/10.1103/PhysRevLett.114.156101
SN  - 0031-9007
SN  - 1079-7114
VL  - 114
IS  - 15
PB  - American Physical Society
CY  - College Park
ER  - 
TY  - JOUR
A1  - Cherstvy, Andrey G.
A1  - Metzler, Ralf
T1  - Ergodicity breaking and particle spreading in noisy heterogeneous diffusion processes
JF  - The journal of chemical physics : bridges a gap between journals of physics and journals of chemistr
N2  - We study noisy heterogeneous diffusion processes with a position dependent diffusivity of the form D(x) similar to D-0 vertical bar x vertical bar (alpha 0) in the presence of annealed and quenched disorder of the environment, corresponding to an effective variation of the exponent a in time and space. In the case of annealed disorder, for which effectively alpha(0) = alpha(0)(t), we show how the long time scaling of the ensemble mean squared displacement (MSD) and the amplitude variation of individual realizations of the time averaged MSD are affected by the disorder strength. For the case of quenched disorder, the long time behavior becomes effectively Brownian after a number of jumps between the domains of a stratified medium. In the latter situation, the averages are taken over both an ensemble of particles and different realizations of the disorder. As physical observables, we analyze in detail the ensemble and time averaged MSDs, the ergodicity breaking parameter, and higher order moments of the time averages. (C) 2015 AIP Publishing LLC.
Y1  - 2015
U6  - https://doi.org/10.1063/1.4917077
SN  - 0021-9606
SN  - 1089-7690
VL  - 142
IS  - 14
PB  - American Institute of Physics
CY  - Melville
ER  - 
TY  - JOUR
A1  - Blavatska, Viktoria
A1  - Metzler, Ralf
T1  - Conformational properties of complex polymers: rosette versus star-like structures
JF  - Journal of physics : A, Mathematical and theoretical
N2  - Multiple loop formation in polymer macromolecules is an important feature of the chromatin organization and DNA compactification in the nuclei. We analyse the size and shape characteristics of complex polymer structures, containing in general f(1) loops (petals) and f(2) linear chains (branches). Within the frames of continuous model of Gaussian macromolecule, we apply the path integration method and obtain the estimates for gyration radius R-g and asphericity (A) over cap of typical conformation as functions of parameters f(1), f(2). In particular, our results qualitatively reveal the extent of anisotropy of star-like topologies as compared to the rosette structures of the same total molecular weight.
KW  - polymers
KW  - path integration
KW  - conformational properties
Y1  - 2015
U6  - https://doi.org/10.1088/1751-8113/48/13/135001
SN  - 1751-8113
SN  - 1751-8121
VL  - 48
IS  - 13
PB  - IOP Publ. Ltd.
CY  - Bristol
ER  - 
TY  - JOUR
A1  - Cui, Qianling
A1  - Yashchenok, Alexey
A1  - Li, Lidong
A1  - Moehwald, Helmuth
A1  - Bargheer, Matias
T1  - Mechanistic study on reduction reaction of nitro compounds catalyzed by gold nanoparticles using in situ SERS monitoring
JF  - Colloids and surfaces : an international journal devoted to the principles and applications of colloid and interface science ; A, Physicochemical and engineering aspects
N2  - Surface-enhanced Raman scattering (SERS) spectroscopy has emerged in recent years as a promising and powerful technique to investigate the reaction mechanism of heterogeneous catalysis. In this work, the reduction reaction of 4-nitrothiophenol (4-NTP) to its corresponding amino derivate catalyzed by gold took place between the gold nanoshell and gold nanostar. Due to the strong binding of thiol group to the gold surface, the molecular configuration of 4-NTP was fixed with NO2 group towards outside. The direct contact of NO2 group with catalytic gold nanostars ensured the reduction reaction went smoothly, which was monitored by SERS spectroscopy. The NO2 vibration Raman band showed a unique blue-shift without any appearance of dimerization product, indicating this catalytic reaction might follow a monomolecular mechanistic pathway. (C) 2015 Elsevier B.V. All rights reserved.
KW  - Surface-enhanced Raman scattering
KW  - Heterogeneous catalysis
KW  - Gold nanoparticles
KW  - Reaction mechanism
KW  - Monomolecular reaction
Y1  - 2015
U6  - https://doi.org/10.1016/j.colsurfa.2015.01.075
SN  - 0927-7757
SN  - 1873-4359
VL  - 470
SP  - 108
EP  - 113
PB  - Elsevier
CY  - Amsterdam
ER  - 
TY  - JOUR
A1  - Würfel, Uli
A1  - Neher, Dieter
A1  - Spies, Annika
A1  - Albrecht, Steve
T1  - Impact of charge transport on current-voltage characteristics and power-conversion efficiency of organic solar cells
JF  - Nature Communications
N2  - This work elucidates the impact of charge transport on the photovoltaic properties of organic solar cells. Here we show that the analysis of current-voltage curves of organic solar cells under illumination with the Shockley equation results in values for ideality factor, photo-current and parallel resistance, which lack physical meaning. Drift-diffusion simulations for a wide range of charge-carrier mobilities and illumination intensities reveal significant carrier accumulation caused by poor transport properties, which is not included in the Shockley equation. As a consequence, the separation of the quasi Fermi levels in the organic photoactive layer (internal voltage) differs substantially from the external voltage for almost all conditions. We present a new analytical model, which considers carrier transport explicitly. The model shows excellent agreement with full drift-diffusion simulations over a wide range of mobilities and illumination intensities, making it suitable for realistic efficiency predictions for organic solar cells.
Y1  - 2015
U6  - https://doi.org/10.1038/ncomms7951
SN  - 2041-1723
VL  - 6
PB  - Nature Publ. Group
CY  - London
ER  - 
TY  - JOUR
A1  - Goychuk, Igor
A1  - Goychuk, Andriy
T1  - Stochastic Wilson-Cowan models of neuronal network dynamics with memory and delay
JF  - New journal of physics : the open-access journal for physics
N2  - We consider a simple Markovian class of the stochastic Wilson-Cowan type models of neuronal network dynamics, which incorporates stochastic delay caused by the existence of a refractory period of neurons. From the point of view of the dynamics of the individual elements, we are dealing with a network of non-Markovian stochastic two-state oscillators with memory, which are coupled globally in a mean-field fashion. This interrelation of a higher-dimensional Markovian and lower-dimensional non-Markovian dynamics is discussed in its relevance to the general problem of the network dynamics of complex elements possessing memory. The simplest model of this class is provided by a three-state Markovian neuron with one refractory state, which causes firing delay with an exponentially decaying memory within the two-state reduced model. This basic model is used to study critical avalanche dynamics (the noise sustained criticality) in a balanced feedforward network consisting of the excitatory and inhibitory neurons. Such avalanches emerge due to the network size dependent noise (mesoscopic noise). Numerical simulations reveal an intermediate power law in the distribution of avalanche sizes with the critical exponent around -1.16. We show that this power law is robust upon a variation of the refractory time over several orders of magnitude. However, the avalanche time distribution is biexponential. It does not reflect any genuine power law dependence.
KW  - neuronal networks
KW  - stochastic models
KW  - memory and delay
KW  - critical avalanche dynamics
Y1  - 2015
U6  - https://doi.org/10.1088/1367-2630/17/4/045029
SN  - 1367-2630
VL  - 17
PB  - IOP Publ. Ltd.
CY  - Bristol
ER  - 
TY  - JOUR
A1  - Politi, Antonio
A1  - Rosenblum, Michael
T1  - Equivalence of phase-oscillator and integrate-and-fire models
JF  - Physical review : E, Statistical, nonlinear and soft matter physics
N2  - A quantitative comparison of various classes of oscillators (integrate-and-fire, Winfree, and Kuramoto-Daido type) is performed in the weak-coupling limit for a fully connected network of identical units. An almost perfect agreement is found, with only tiny differences among the models. We also show that the regime of self-consistent partial synchronization is rather general and can be observed for arbitrarily small coupling strength in any model class. As a byproduct of our study, we are able to show that an integrate-and-fire model with a generic pulse shape can be always transformed into a similar model with delta pulses and a suitable phase response curve.
Y1  - 2015
U6  - https://doi.org/10.1103/PhysRevE.91.042916
SN  - 1539-3755
SN  - 1550-2376
VL  - 91
IS  - 4
PB  - American Physical Society
CY  - College Park
ER  - 
TY  - JOUR
A1  - Aleksic, J.
A1  - Ansoldi, S.
A1  - Antonelli, L. A.
A1  - Antoranz, P.
A1  - Babic, A.
A1  - Bangale, P.
A1  - de Almeida, U. Barres
A1  - Barrio, J. A.
A1  - Gonzalez, J. Becerra
A1  - Bednarek, W.
A1  - Bernardini, E.
A1  - Biasuzzi, B.
A1  - Biland, A.
A1  - Blanch Bigas, O.
A1  - Boller, A.
A1  - Bonnefoy, S.
A1  - Bonnoli, G.
A1  - Borracci, F.
A1  - Bretz, T.
A1  - Carmona, E.
A1  - Carosi, A.
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 Caneva, G.
A1  - De Lotto, B.
A1  - Wilhelmi, E. de Ona
A1  - Mendez, C. Delgado
A1  - Prester, Dijana Dominis
A1  - Dorner, D.
A1  - Doro, M.
A1  - Einecke, S.
A1  - Eisenacher, D.
A1  - Elsaesser, 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  - Godinovic, N.
A1  - Munoz, A. Gonzalez
A1  - Gozzini, S. R.
A1  - Hadasch, D.
A1  - Hanabata, Y.
A1  - Hayashida, M.
A1  - Herrera, J.
A1  - Hildebrand, D.
A1  - Hose, J.
A1  - Hrupec, D.
A1  - Hughes, G.
A1  - Idec, W.
A1  - Kadenius, V.
A1  - Kellermann, H.
A1  - Knoetig, M. L.
A1  - Kodani, K.
A1  - Konno, Y.
A1  - Krause, J.
A1  - Kubo, H.
A1  - Kushida, J.
A1  - La Barbera, A.
A1  - Lelas, D.
A1  - Lewandowska, N.
A1  - Lindfors, E.
A1  - Lombardi, S.
A1  - Lopez, M.
A1  - Lopez-Coto, R.
A1  - Lopez-Oramas, A.
A1  - Lorenz, E.
A1  - Lozano, I.
A1  - Makariev, M.
A1  - Mallot, K.
A1  - Maneva, G.
A1  - Mankuzhiyil, N.
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  - Munar-Adrover, P.
A1  - Nakajima, D.
A1  - Niedzwiecki, A.
A1  - Nilsson, K.
A1  - Nishijima, K.
A1  - Noda, K.
A1  - Orito, R.
A1  - Overkemping, A.
A1  - Paiano, S.
A1  - Palatiello, M.
A1  - Paneque, D.
A1  - Paoletti, R.
A1  - Paredes, J. M.
A1  - Paredes-Fortuny, X.
A1  - Persic, M.
A1  - Moroni, P. G. Prada
A1  - Prandini, E.
A1  - Puljak, I.
A1  - Reinthal, R.
A1  - Rhode, W.
A1  - Ribo, M.
A1  - Rico, J.
A1  - Garcia, J. Rodriguez
A1  - Rugamer, S.
A1  - Saito, T.
A1  - Saito, K.
A1  - Satalecka, K.
A1  - Scalzotto, V.
A1  - Scapin, V.
A1  - Schultz, C.
A1  - Schweizer, T.
A1  - Sun, S.
A1  - Shore, S. N.
A1  - Sillanpaa, A.
A1  - Sitarek, J.
A1  - Snidaric, I.
A1  - Sobczynska, D.
A1  - Spanier, F.
A1  - Stamatescu, V.
A1  - Stamerra, A.
A1  - Steinbring, T.
A1  - Steinke, B.
A1  - Storz, J.
A1  - Strzys, M.
A1  - Takalo, L.
A1  - Takami, H.
A1  - Tavecchio, F.
A1  - Temnikov, P.
A1  - Terzic, T.
A1  - Tescaro, D.
A1  - Teshima, M.
A1  - Thaele, J.
A1  - Tibolla, O.
A1  - Torres, D. F.
A1  - Toyama, T.
A1  - Treves, A.
A1  - Uellenbeck, M.
A1  - Vogler, P.
A1  - Zanin, R.
A1  - Archambault, S.
A1  - Archer, A.
A1  - Beilicke, M.
A1  - Benbow, W.
A1  - Berger, K.
A1  - Bird, R.
A1  - Biteau, Jonathan
A1  - Buckley, J. H.
A1  - Bugaev, V.
A1  - Cerruti, M.
A1  - Chen, Xiaoming
A1  - Ciupik, L.
A1  - Collins-Hughes, E.
A1  - Cui, W.
A1  - Eisch, J. D.
A1  - Falcone, A.
A1  - Feng, Q.
A1  - Finley, J. P.
A1  - Fortin, P.
A1  - Fortson, L.
A1  - Furniss, A.
A1  - Galante, N.
A1  - Gillanders, G. H.
A1  - Griffin, S.
A1  - Gyuk, G.
A1  - Hakansson, Nils
A1  - Holder, J.
A1  - Johnson, C. A.
A1  - Kaaret, P.
A1  - Kar, P.
A1  - Kertzman, M.
A1  - Kieda, D.
A1  - Lang, M. J.
A1  - McArthur, S.
A1  - McCann, A.
A1  - Meagher, K.
A1  - Millis, J.
A1  - Moriarty, P.
A1  - Ong, R. A.
A1  - Otte, A. N.
A1  - Perkins, J. S.
A1  - Pichel, A.
A1  - Pohl, Manuela
A1  - Popkow, A.
A1  - Prokoph, H.
A1  - Pueschel, Elisa
A1  - Ragan, K.
A1  - Reyes, L. C.
A1  - Reynolds, P. T.
A1  - Richards, G. T.
A1  - Roache, E.
A1  - Rovero, A. C.
A1  - Sembroski, G. H.
A1  - Shahinyan, K.
A1  - Staszak, D.
A1  - Telezhinsky, Igor O.
A1  - Tucci, J. V.
A1  - Tyler, J.
A1  - Varlotta, A.
A1  - Wakely, S. P.
A1  - Welsing, R.
A1  - Wilhelm, Alina
A1  - Williams, D. A.
A1  - Buson, S.
A1  - Finke, J.
A1  - Villata, M.
A1  - Raiteri, C.
A1  - Aller, H. D.
A1  - Aller, M. F.
A1  - Cesarini, A.
A1  - Chen, W. P.
A1  - Gurwell, M. A.
A1  - Jorstad, S. G.
A1  - Kimeridze, G. N.
A1  - Koptelova, E.
A1  - Kurtanidze, O. M.
A1  - Kurtanidze, S. O.
A1  - Lahteenmaki, A.
A1  - Larionov, V. M.
A1  - Larionova, E. G.
A1  - Lin, H. C.
A1  - McBreen, B.
A1  - Moody, J. W.
A1  - Morozova, D. A.
A1  - Marscher, A. P.
A1  - Max-Moerbeck, W.
A1  - Nikolashvili, M. G.
A1  - Perri, M.
A1  - Readhead, A. C. S.
A1  - Richards, J. L.
A1  - Ros, J. A.
A1  - Sadun, A. C.
A1  - Sakamoto, T.
A1  - Sigua, L. A.
A1  - Smith, P. S.
A1  - Tornikoski, M.
A1  - Troitsky, I. S.
A1  - Wehrle, A. E.
A1  - Jordan, B.
T1  - Unprecedented study of the broadband emission of Mrk 421 during flaring activity in March 2010
JF  - Astronomy and astrophysics : an international weekly journal
N2  - Context. Because of its proximity, Mrk 421 is one of the best sources on which to study the nature of BL Lac objects. Its proximity allows us to characterize its broadband spectral energy distribution (SED).
 Aims. The goal is to better understand the mechanisms responsible for the broadband emission and the temporal evolution of Mrk 421. These mechanisms may also apply to more distant blazars that cannot be studied with the same level of detail.
 Methods. A flare occurring in March 2010 was observed for 13 consecutive days (from MJD 55 265 to MJD 55 277) with unprecedented wavelength coverage from radio to very high energy (VHE; E > 100 GeV) gamma-rays with MAGIC, VERITAS, Whipple, Fermi-LAT, MAXI, RXTE, Swift, GASP-WEBT, and several optical and radio telescopes. We modeled the day-scale SEDs with one-zone and two-zone synchrotron self-Compton (SSC) models, investigated the physical parameters, and evaluated whether the observed broadband SED variability can be associated with variations in the relativistic particle population.
 Results. The activity of Mrk 421 initially was high and then slowly decreased during the 13-day period. The flux variability was remarkable at the X-ray and VHE bands, but it was minor or not significant at the other bands. The variability in optical polarization was also minor. These observations revealed an almost linear correlation between the X-ray flux at the 2-10 keV band and the VHE gamma-ray flux above 200 GeV, consistent with the gamma-rays being produced by inverse-Compton scattering in the Klein-Nishina regime in the framework of SSC models. The one-zone SSC model can describe the SED of each day for the 13 consecutive days reasonably well, which once more shows the success of this standard theoretical scenario to describe the SEDs of VHE BL Lacs such as Mrk 421. This flaring activity is also very well described by a two-zone SSC model, where one zone is responsible for the quiescent emission, while the other smaller zone, which is spatially separated from the first, contributes to the daily variable emission occurring at X-rays and VHE gamma-rays. The second blob is assumed to have a smaller volume and a narrow electron energy distribution with 3 x 10(4) < gamma < 6 x 10(5), where. is the Lorentz factor of the electrons. Such a two-zone scenario would naturally lead to the correlated variability at the X-ray and VHE bands without variability at the optical/UV band, as well as to shorter timescales for the variability at the X-ray and VHE bands with respect to the variability at the other bands.
 Conclusions. Both the one-zone and the two-zone SSC models can describe the daily SEDs via the variation of only four or five model parameters, under the hypothesis that the variability is associated mostly with the underlying particle population. This shows that the particle acceleration and cooling mechanism that produces the radiating particles might be the main mechanism responsible for the broadband SED variations during the flaring episodes in blazars. The two-zone SSC model provides a better agreement with the observed SED at the narrow peaks of the low-and high-energy bumps during the highest activity, although the reported one-zone SSC model could be further improved by varying the parameters related to the emitting region itself (delta, B and R), in addition to the parameters related to the particle population.
KW  - radiation mechanisms: non-thermal
KW  - galaxies: active
KW  - BL Lacertae objects: individual: Mrk 421
KW  - gamma rays: galaxies
Y1  - 2015
U6  - https://doi.org/10.1051/0004-6361/201424811
SN  - 0004-6361
SN  - 1432-0746
VL  - 578
PB  - EDP Sciences
CY  - Les Ulis
ER  - 
TY  - JOUR
A1  - Martinez-Nunez, Silvia
A1  - Sander, Angelika
A1  - Gimenez-Garcia, Angel
A1  - Gonzalez-Galan, Ana
A1  - Torrejon, Jose Miguel
A1  - Gonzalez-Fernandez, Carlos
A1  - Hamann, Wolf-Rainer
T1  - The donor star of the X-ray pulsar X1908+075
JF  - Astronomy and astrophysics : an international weekly journal
N2  - High-mass X-ray binaries consist of a massive donor star and a compact object. While several of those systems have been well studied in X-rays, little is known for most of the donor stars as they are often heavily obscured in the optical and ultraviolet regime. There is an opportunity to observe them at infrared wavelengths, however. The goal of this study is to obtain the stellar and wind parameters of the donor star in the X1908+075 high-mass X-ray binary system with a stellar atmosphere model to check whether previous studies from X-ray observations and spectral morphology lead to a sufficient description of the donor star. We obtained H-and K-band spectra of X1908+075 and analysed them with the Potsdam Wolf-Rayet (PoWR) model atmosphere code. For the first time, we calculated a stellar atmosphere model for the donor star, whose main parameters are: M-spec = 15 +/- 6 M-circle dot, T-* = 23(-3)(+6) kK, log g(eff) = 3.0 +/- 0.2 and log L/L-circle dot = 4.81 +/- 0.25. The obtained parameters point towards an early B-type (B0-B3) star, probably in a supergiant phase. Moreover we determined a more accurate distance to the system of 4.85 +/- 0.50 kpc than the previously reported value.
KW  - binaries: close
KW  - stars: individual: X1908+075
KW  - stars: massive
KW  - stars: winds
KW  - outflows
KW  - X-rays: binaries
Y1  - 2015
U6  - https://doi.org/10.1051/0004-6361/201424823
SN  - 0004-6361
SN  - 1432-0746
VL  - 578
PB  - EDP Sciences
CY  - Les Ulis
ER  - 
TY  - JOUR
A1  - Premont-Schwarz, Mirabelle
A1  - Schreck, Simon
A1  - Iannuzzi, Marcella
A1  - Nibbering, Erik T. J.
A1  - Odelius, Michael
A1  - Wernet, Philippe
T1  - Correlating Infrared and X-ray Absorption Energies for Molecular-Level Insight into Hydrogen Bond Making and Breaking in Solution
JF  - The journal of physical chemistry : B, Condensed matter, materials, surfaces, interfaces & biophysical chemistry
N2  - While ubiquitous, the making and breaking of hydrogen bonds in solution is notoriously difficult to study due to the associated complex changes of nuclear and electronic structures. With the aim to reduce the according uncertainty in correlating experimental observables and hydrogen-bond configurations, we combine the information from proximate methods to study the N-H center dot center dot center dot O hydrogen bond in solution. We investigate hydrogen-bonding of the N-H group of N-methylaniline with oxygen from liquid DMSO and acetone with infrared spectra in the N-H stretching region and X-ray absorption spectra at the N K-edge. We experimentally observe blue shifts of the infrared stretching band and an X-ray absorption pre-edge peak when going from DMSO to acetone. With ab initio molecular dynamics simulations and calculated spectra, we qualitatively reproduce the experimental observables but we do not reach quantitative agreement with experiment. The infrared spectra support the notion of weakening the N-H center dot center dot center dot O hydrogen bond from DMSO to acetone. However, we fail to theoretically reproduce the measured shift of the X-ray absorption pre-edge peak. We discuss possible shortcomings of the simulation models and spectrum calculations. Common features and distinct differences with the O-H center dot center dot center dot O hydrogen bond are highlighted, and the implications for monitoring hydrogen-bond breaking in solution are discussed.
Y1  - 2015
U6  - https://doi.org/10.1021/acs.jpcb.5b02954
SN  - 1520-6106
VL  - 119
IS  - 25
SP  - 8115
EP  - 8124
PB  - American Chemical Society
CY  - Washington
ER  - 
TY  - JOUR
A1  - Zajnulina, Marina
A1  - Boggio, Jose M. Chavez
A1  - Böhm, Michael
A1  - Rieznik, A. A.
A1  - Fremberg, Tino
A1  - Haynes, Roger
A1  - Roth, Martin M.
T1  - Generation of optical frequency combs via four-wave mixing processes for low- and medium-resolution astronomy
JF  - Applied physics : B, Lasers and optics
N2  - We investigate the generation of optical frequency combs through a cascade of four-wave mixing processes in nonlinear fibres with optimised parameters. The initial optical field consists of two continuous-wave lasers with frequency separation larger than 40 GHz (312.7 pm at 1531 nm). It propagates through three nonlinear fibres. The first fibre serves to pulse shape the initial sinusoidal-square pulse, while a strong pulse compression down to sub-100 fs takes place in the second fibre which is an amplifying erbium-doped fibre. The last stage is a low-dispersion highly nonlinear fibre where the frequency comb bandwidth is increased and the line intensity is equalised. We model this system using the generalised nonlinear Schrodinger equation and investigate it in terms of fibre lengths, fibre dispersion, laser frequency separation and input powers with the aim to minimise the frequency comb noise. With the support of the numerical results, a frequency comb is experimentally generated, first in the near infra-red and then it is frequency-doubled into the visible spectral range. Using a MUSE-type spectrograph, we evaluate the comb performance for astronomical wavelength calibration in terms of equidistancy of the comb lines and their stability.
Y1  - 2015
U6  - https://doi.org/10.1007/s00340-015-6121-1
SN  - 0946-2171
SN  - 1432-0649
VL  - 120
IS  - 1
SP  - 171
EP  - 184
PB  - Springer
CY  - New York
ER  - 
TY  - JOUR
A1  - Piatti, Andres E.
A1  - de Grijs, Richard
A1  - Rubele, Stefano
A1  - Cioni, Maria-Rosa L.
A1  - Ripepi, Vincenzo
A1  - Kerber, Leandro
T1  - The VMC survey - XV. The Small Magellanic Cloud-Bridge connection history as traced by their star cluster populations
JF  - Monthly notices of the Royal Astronomical Society
N2  - We present results based on YJK(s) photometry of star clusters located in the outermost, eastern region of the Small Magellanic Cloud (SMC). We analysed a total of 51 catalogued clusters whose colour-magnitude diagrams (CMDs), having been cleaned from field-star contamination, were used to assess the clusters' reality and estimate ages of the genuine systems. Based on CMD analysis, 15 catalogued clusters were found to be possible non-genuine aggregates. We investigated the properties of 80 per cent of the catalogued clusters in this part of the SMC by enlarging our sample with previously obtained cluster ages, adopting a homogeneous scale for all. Their spatial distribution suggests that the oldest clusters, log(t yr(-1)) >= 9.6, are in general located at greater distances to the galaxy's centre than their younger counterparts - 9.0 <= log(t yr(-1)) <= 9.4 - while two excesses of clusters are seen at log(t yr(-1)) similar to 9.2 and log(t yr(-1)) similar to 9.7. We found a trail of younger clusters which follow the wing/bridge components. This long spatial sequence does not only harbour very young clusters, log(t yr(-1)) similar to 7.3, but it also hosts some of intermediate ages, log(t yr(-1)) similar to 9.1. The derived cluster and field-star formation frequencies as a function of age are different. The most surprising feature is an observed excess of clusters with ages of log(t yr(-1)) <9.0, which could have been induced by interactions with the LMC.
KW  - techniques: photometric
KW  - galaxies: individual: SMC
KW  - Magellanic Clouds
Y1  - 2015
U6  - https://doi.org/10.1093/mnras/stv635
SN  - 0035-8711
SN  - 1365-2966
VL  - 450
IS  - 1
SP  - 552
EP  - 563
PB  - Oxford Univ. Press
CY  - Oxford
ER  - 
TY  - JOUR
A1  - Raatz, Michael
A1  - Hintsche, Marius
A1  - Bahrs, Marco
A1  - Theves, Matthias
A1  - Beta, Carsten
T1  - Swimming patterns of a polarly flagellated bacterium in environments of increasing complexity
JF  - European physical journal special topics
N2  - The natural habitat of many bacterial swimmers is dominated by interfaces and narrow interstitial spacings where they frequently interact with the fluid boundaries in their vicinity. To quantify these interactions, we investigated the swimming behavior of the soil bacterium Pseudomonas putida in a variety of confined environments. Using microfluidic techniques, we fabricated structured microchannels with different configurations of cylindrical obstacles. In these environments, we analyzed the swimming trajectories for different obstacle densities and arrangements. Although the overall swimming pattern remained similar to movement in the bulk fluid, we observed a change in the turning angle distribution that could be attributed to collisions with the cylindrical obstacles. Furthermore, a comparison of the mean run length of the bacteria to the mean free path of a billiard particle in the same geometry indicated that, inside a densely packed environment, the trajectories of the bacterial swimmers are efficiently guided along the open spacings.
Y1  - 2015
U6  - https://doi.org/10.1140/epjst/e2015-02454-3
SN  - 1951-6355
SN  - 1951-6401
VL  - 224
IS  - 7
SP  - 1185
EP  - 1198
PB  - Springer
CY  - Heidelberg
ER  - 
TY  - JOUR
A1  - Reverey, Julia F.
A1  - Jeon, Jae-Hyung
A1  - Bao, Han
A1  - Leippe, Matthias
A1  - Metzler, Ralf
A1  - Selhuber-Unkel, Christine
T1  - Superdiffusion dominates intracellular particle motion in the supercrowded cytoplasm of pathogenic Acanthamoeba castellanii
JF  - Scientific reports
N2  - Acanthamoebae are free-living protists and human pathogens, whose cellular functions and pathogenicity strongly depend on the transport of intracellular vesicles and granules through the cytosol. Using high-speed live cell imaging in combination with single-particle tracking analysis, we show here that the motion of endogenous intracellular particles in the size range from a few hundred nanometers to several micrometers in Acanthamoeba castellanii is strongly superdiffusive and influenced by cell locomotion, cytoskeletal elements, and myosin II. We demonstrate that cell locomotion significantly contributes to intracellular particle motion, but is clearly not the only origin of superdiffusivity. By analyzing the contribution of microtubules, actin, and myosin II motors we show that myosin II is a major driving force of intracellular motion in A. castellanii. The cytoplasm of A. castellanii is supercrowded with intracellular vesicles and granules, such that significant intracellular motion can only be achieved by actively driven motion, while purely thermally driven diffusion is negligible.
Y1  - 2015
U6  - https://doi.org/10.1038/srep11690
SN  - 2045-2322
VL  - 5
PB  - Nature Publ. Group
CY  - London
ER  - 
TY  - JOUR
A1  - Bodrova, Anna S.
A1  - Chechkin, Aleksei V.
A1  - Cherstvy, Andrey G.
A1  - Metzler, Ralf
T1  - Ultraslow scaled Brownian motion
JF  - New journal of physics : the open-access journal for physics
N2  - We define and study in detail utraslow scaled Brownian motion (USBM) characterized by a time dependent diffusion coefficient of the form D(t) similar or equal to 1/t. For unconfined motion the mean squared displacement (MSD) of USBM exhibits an ultraslow, logarithmic growth as function of time, in contrast to the conventional scaled Brownian motion. In a harmonic potential the MSD of USBM does not saturate but asymptotically decays inverse-proportionally to time, reflecting the highly non-stationary character of the process. We show that the process is weakly non-ergodic in the sense that the time averaged MSD does not converge to the regular MSD even at long times, and for unconfined motion combines a linear lag time dependence with a logarithmic term. The weakly non-ergodic behaviour is quantified in terms of the ergodicity breaking parameter. The USBM process is also shown to be ageing: observables of the system depend on the time gap between initiation of the test particle and start of the measurement of its motion. Our analytical results are shown to agree excellently with extensive computer simulations.
KW  - anomalous diffusion
KW  - stochastic processes
KW  - ageing
Y1  - 2015
U6  - https://doi.org/10.1088/1367-2630/17/6/063038
SN  - 1367-2630
VL  - 17
PB  - IOP Publ. Ltd.
CY  - Bristol
ER  - 
TY  - JOUR
A1  - Niebuhr, Mario
A1  - Zink, Christof
A1  - Jechow, Andreas
A1  - Heuer, Axel
A1  - Glebov, Leonid B.
A1  - Menzel, Ralf
T1  - Mode stabilization of a laterally structured broad area diode laser using an external volume Bragg grating
JF  - Optics express : the international electronic journal of optics
N2  - An external volume Bragg grating (VBG) is used for transverse and longitudinal mode stabilization of a broad area diode laser (BAL) with an on-chip transverse Bragg resonance (TBR) grating. The internal TBR grating defines a transverse low-loss mode at a specific propagation angle inside the BAL. Selection of the TBR mode was realized via the angular geometry of an external resonator assembly consisting of the TBR BAL and a feedback element. A feedback mirror provides near diffraction limited and spectral narrow output in the TBR mode albeit requiring an intricate alignment procedure. If feedback is provided via a VBG, adjustment proves to be far less critical and higher output powers were achieved. Moreover, additional modulation in the far field distribution became discernible allowing for a better study of the TBR concept. (C) 2015 Optical Society of America
Y1  - 2015
U6  - https://doi.org/10.1364/OE.23.012394
SN  - 1094-4087
VL  - 23
IS  - 9
SP  - 12394
EP  - 12400
PB  - Optical Society of America
CY  - Washington
ER  - 
TY  - JOUR
A1  - Godec, Aljaz
A1  - Metzler, Ralf
T1  - Optimization and universality of Brownian search in a basic model of quenched heterogeneous media
JF  - Physical review : E, Statistical, nonlinear and soft matter physics
N2  - The kinetics of a variety of transport-controlled processes can be reduced to the problem of determining the mean time needed to arrive at a given location for the first time, the so-called mean first-passage time ( MFPT) problem. The occurrence of occasional large jumps or intermittent patterns combining various types of motion are known to outperform the standard random walk with respect to the MFPT, by reducing oversampling of space. Here we show that a regular but spatially heterogeneous random walk can significantly and universally enhance the search in any spatial dimension. In a generic minimal model we consider a spherically symmetric system comprising two concentric regions with piecewise constant diffusivity. The MFPT is analyzed under the constraint of conserved average dynamics, that is, the spatially averaged diffusivity is kept constant. Our analytical calculations and extensive numerical simulations demonstrate the existence of an optimal heterogeneity minimizing the MFPT to the target. We prove that the MFPT for a random walk is completely dominated by what we term direct trajectories towards the target and reveal a remarkable universality of the spatially heterogeneous search with respect to target size and system dimensionality. In contrast to intermittent strategies, which are most profitable in low spatial dimensions, the spatially inhomogeneous search performs best in higher dimensions. Discussing our results alongside recent experiments on single-particle tracking in living cells, we argue that the observed spatial heterogeneity may be beneficial for cellular signaling processes.
Y1  - 2015
U6  - https://doi.org/10.1103/PhysRevE.91.052134
SN  - 1539-3755
SN  - 1550-2376
VL  - 91
IS  - 5
PB  - American Physical Society
CY  - College Park
ER  - 
TY  - JOUR
A1  - Hoffmann, Holger
A1  - Seiss, Martin
A1  - Salo, Heikki
A1  - Spahn, Frank
T1  - Vertical structures induced by embedded moonlets in Saturn's rings
JF  - Icarus : international journal of solar system studies
N2  - We study the vertical extent of propeller structures in Saturn's rings (i) by extending the model of Spahn and Sremcevic (Spahn, F., Sremcevic, M. [2000]. Astron. Astrophys., 358, 368-372) to include the vertical direction and (ii) by performing N-body box simulations of a perturbing moonlet embedded into the rings. We find that the gravitational interaction of ring particles with a non-inclined moonlet does not induce considerable vertical excursions of ring particles, but causes a considerable thermal motion in the ring plane. We expect ring particle collisions to partly convert the lateral induced thermal motion into vertical excursions of ring particles in the course of a quasi-thermalization. The N-body box simulations lead to maximal propeller heights of about 0.6-0.8 Hill radii of the embedded perturbing moonlet. Moonlet sizes estimated by this relation are in good agreement with size estimates from radial propeller scalings for the propellers Bleriot and Earhart. For large propellers, the extended hydrodynamical propeller model predicts an exponential propeller height relaxation, confirmed by N-body box simulations of non-self gravitating ring particles. Exponential cooling constants, calculated from the hydrodynamical propeller model agree fairly well with values from fits to the tail of the azimuthal height decay of the N-body box simulations. From exponential cooling constants, determined from shadows cast by the propeller Earhart and imaged by the Cassini spacecraft, we estimate collision frequencies of about 6 collisions per particle per orbit in the propeller gap region and about 11 collisions per particle per orbit in the propeller wake region. (C) 2015 Elsevier Inc. All rights reserved.
KW  - Planetary rings
KW  - Saturn, rings
KW  - Saturn, satellites
KW  - Disks
Y1  - 2015
U6  - https://doi.org/10.1016/j.icarus.2015.02.003
SN  - 0019-1035
SN  - 1090-2643
VL  - 252
SP  - 400
EP  - 414
PB  - Elsevier
CY  - San Diego
ER  - 
TY  - JOUR
A1  - Anton, Arthur Markus
A1  - Steyrleuthner, Robert
A1  - Kossack, Wilhelm
A1  - Neher, Dieter
A1  - Kremer, Friedrich
T1  - Infrared Transition Moment Orientational Analysis on the Structural Organization of the Distinct Molecular Subunits in Thin Layers of a High Mobility n-Type Copolymer
JF  - Journal of the American Chemical Society
N2  - The IR-based method of infrared transition moment orientational analysis (IR-TMOA) is employed to unravel molecular order in thin layers of the semiconducting polymer poly[N,N'-bis(2-octyldodecyl),-1,4,5,8-naphthalene-diimide-2,6-diyl]-alt-5-5'-(2,2'-bithiophene) (P(NDI2OD-T2)). Structure-specific vibrational bands are analyzed in dependence On polarization and inclination of the sample-With respect to the optical axis. By that the molecular Order parameter tensor for the respective molecular moieties with regard to the sample: coordinate system is deduced. Making use of the specificity of the IR spectral range, we are able to determine separately the orientation of atomistic planes defined through the naphthalenediimide (NDI) and bithiophene (T2) units relative to the substrate, and hence, relative to each other. A pronounced solvent effect is observed While chlorobenzene causes the T2 planes to align preferentially parallel to the substrate at an angle of 29 degrees, using a 1:1 chloronaphthalene:xylene mixture results in a reorientation of the T2 units from a face on into an edge on arrangement. In contrast the NDI unit remains unaffected. Additionally, for both solvents evidence is observed for the aggregation of chains in accord With recently published results obtained by UV-vis absorption spectroscopy.
Y1  - 2015
U6  - https://doi.org/10.1021/jacs.5b01755
SN  - 0002-7863
VL  - 137
IS  - 18
SP  - 6034
EP  - 6043
PB  - American Chemical Society
CY  - Washington
ER  - 
TY  - JOUR
A1  - Förster, Daniel F.
A1  - Lindenau, Bernd
A1  - Leyendecker, Marko
A1  - Janssen, Franz
A1  - Winkler, Carsten
A1  - Schumann, Frank O.
A1  - Kirschner, Juergen
A1  - Holldack, Karsten
A1  - Föhlisch, Alexander
T1  - Phase-locked MHz pulse selector for x-ray sources
JF  - Optics letters : a publication of the Optical Society of America
N2  - Picosecond x-ray pulses are extracted with a phase-locked x-ray pulse selector at 1.25 MHz repetition rate from the pulse trains of the accelerator-driven multiuser x-ray source BESSY II preserving the peak brilliance at high pulse purity. The system consists of a specially designed in-vacuum chopper wheel rotating with approximate to 1 kHz angular frequency. The wheel is driven in an ultrahigh vacuum and is levitated on magnetic bearings being capable of withstanding high centrifugal forces. Pulses are picked by 1252 high-precision slits of 70 mu m width on the outer rim of the wheel corresponding to a temporal opening window of the chopper of 70 ns. We demonstrate how the electronic phase stabilization of +/- 2 ns together with an arrival time jitter of the individual slits of the same order of magnitude allows us to pick short single bunch x-ray pulses out of a 200 ns ion clearing gap in a multibunch pulse train as emitted from a synchrotron facility at 1.25 MHz repetition rate with a pulse purity below the shot noise detection limit. The approach is applicable to any high-repetition pulsed radiation source, in particular in the x-ray spectral range up to 10 keV. The opening window in a real x-ray beamline, its stability, as well as the limits of mechanical pulse picking techniques in the MHz range are discussed. (C) 2015 Optical Society of America
Y1  - 2015
U6  - https://doi.org/10.1364/OL.40.002265
SN  - 0146-9592
SN  - 1539-4794
VL  - 40
IS  - 10
SP  - 2265
EP  - 2268
PB  - Optical Society of America
CY  - Washington
ER  - 
TY  - JOUR
A1  - Corcoran, Michael F.
A1  - Nichols, Joy S.
A1  - Pablo, Herbert
A1  - Shenar, Tomer
A1  - Pollock, Andy M. T.
A1  - Waldron, Wayne L.
A1  - Moffat, Anthony F. J.
A1  - Richardson, Noel D.
A1  - Russell, Christopher M. P.
A1  - Hamaguchi, Kenji
A1  - Huenemoerder, David P.
A1  - Oskinova, Lida
A1  - Hamann, Wolf-Rainer
A1  - Naze, Yael
A1  - Ignace, Richard
A1  - Evans, Nancy Remage
A1  - Lomax, Jamie R.
A1  - Hoffman, Jennifer L.
A1  - Gayley, Kenneth
A1  - Owocki, Stanley P.
A1  - Leutenegger, Maurice
A1  - Gull, Theodore R.
A1  - Hole, Karen Tabetha
A1  - Lauer, Jennifer
A1  - Iping, Rosina C.
T1  - A coordinated X-Ray and optical campaign of the nearest massive eclipsing binary, delta ORIONIS Aa. I. Overview of thr X-Ray spectrum
JF  - The astrophysical journal : an international review of spectroscopy and astronomical physics
N2  - We present an overview of four deep phase-constrained Chandra HETGS X-ray observations of delta Ori A. Delta Ori A is actually a triple system that includes the nearest massive eclipsing spectroscopic binary, delta Ori Aa, the only such object that can be observed with little phase-smearing with the Chandra gratings. Since the fainter star, delta Ori Aa2, has a much lower X-ray luminosity than the brighter primary (delta Ori Aa1), delta Ori Aa provides a unique system with which to test the spatial distribution of the X-ray emitting gas around delta Ori Aa1 via occultation by the photosphere of, and wind cavity around, the X-ray dark secondary. Here we discuss the X-ray spectrum and X-ray line profiles for the combined observation, having an exposure time of nearly 500 ks and covering nearly the entire binary orbit. The companion papers discuss the X-ray variability seen in the Chandra spectra, present new space-based photometry and ground-based radial velocities obtained simultaneously with the X-ray data to better constrain the system parameters, and model the effects of X-rays on the optical and UV spectra. We find that the X-ray emission is dominated by embedded wind shock emission from star Aa1, with little contribution from the tertiary star Ab or the shocked gas produced by the collision of the wind of Aa1 against the surface of Aa2. We find a similar temperature distribution to previous X-ray spectrum analyses. We also show that the line half-widths are about 0.3-0.5 times the terminal velocity of the wind of star Aa1. We find a strong anti-correlation between line widths and the line excitation energy, which suggests that longer-wavelength, lower-temperature lines form farther out in the wind. Our analysis also indicates that the ratio of the intensities of the strong and weak lines of Fe XVII and Ne X are inconsistent with model predictions, which may be an effect of resonance scattering.
KW  - binaries: close
KW  - binaries: eclipsing
KW  - stars: early-type
KW  - stars: individual (Delta Ori)
KW  - stars: mass-loss
KW  - X-rays: stars
Y1  - 2015
U6  - https://doi.org/10.1088/0004-637X/809/2/132
SN  - 0004-637X
SN  - 1538-4357
VL  - 809
IS  - 2
PB  - IOP Publ. Ltd.
CY  - Bristol
ER  - 
TY  - JOUR
A1  - Dzhanoev, Arsen R.
A1  - Spahn, Frank
A1  - Yaroshenko, Victoriya
A1  - Lühr, Hermann
A1  - Schmidt, Jürgen
T1  - Secondary electron emission from surfaces with small structure
JF  - Physical review : B, Condensed matter and materials physics
N2  - It is found that for objects possessing small surface structures with differing radii of curvature the secondary electron emission (SEE) yield may be significantly higher than for objects with smooth surfaces of the same material. The effect is highly pronounced for surface structures of nanometer scale, often providing a more than 100% increase of the SEE yield. The results also show that the SEE yield from surfaces with structure does not show a universal dependence on the energy of the primary, incident electrons as it is found for flat surfaces in experiments. We derive conditions for the applicability of the conventional formulation of SEE using the simplifying assumption of universal dependence. Our analysis provides a basis for studying low-energy electron emission from nanometer structured surfaces under a penetrating electron beam important in many technological applications.
Y1  - 2015
U6  - https://doi.org/10.1103/PhysRevB.92.125430
SN  - 1098-0121
SN  - 1550-235X
VL  - 92
IS  - 12
PB  - American Physical Society
CY  - College Park
ER  - 
TY  - JOUR
A1  - Heuer, Axel
A1  - Menzel, Ralf
A1  - Milonni, P. W.
T1  - Complementarity in biphoton generation with stimulated or induced coherence
JF  - Physical review : A, Atomic, molecular, and optical physics
N2  - Coherence can be induced or stimulated in parametric down-conversion using two or three crystals when, for example, the idler modes of the crystals are aligned. Previous experiments with induced coherence [Phys. Rev. Lett. 114, 053601 (2015)] focused on which-path information and the role of vacuum fields in realizing complementarity via reduced visibility in single-photon interference. Here we describe experiments comparing induced and stimulated coherence. Different single-photon interference experiments were performed by blocking one of the pump beams in a three-crystal setup. Each counted photon is emitted from one of two crystals and which-way information may or not be available, depending on the setup. Distinctly different results are obtained in the induced and stimulated cases, especially when a variable transmission filter is inserted between the crystals. A simplified theoretical model accounts for all the experimental results and is also used to address the question of whether the phases of the signal and idler fields in parametric down-conversion are correlated.
Y1  - 2015
U6  - https://doi.org/10.1103/PhysRevA.92.033834
SN  - 1050-2947
SN  - 1094-1622
VL  - 92
IS  - 3
PB  - American Physical Society
CY  - College Park
ER  - 
TY  - JOUR
A1  - Elsner, Robert
A1  - Puhlmann, Dirk
A1  - Pieplow, Gregor
A1  - Heuer, Axel
A1  - Menzel, Ralf
T1  - Transverse distinguishability of entangled photons with arbitrarily shaped spatial near- and far-field distributions
JF  - Journal of the Optical Society of America : B, Optical physics
N2  - Entangled photons generated by spontaneous parametric downconversion are ubiquitous in quantum optics. In general, they exhibit a complex spatial photon count distribution. This spatial structure is responsible for seemingly surprising results concerning, e.g., complementarity such as the apparent simultaneous observation of interference fringes V and which-way information D at a double slit, as recently reported by Menzel et al. [Proc. Natl. Acad. Sci. USA 109, 9314 (2012)]. We implement a complete quantitative model of the SPDC interaction that fully incorporates the effects of crystal anisotropies, phase matching, and the pump beam structure and allows for arbitrary manipulations of the SPDC light in the near and far fields. This enables us to establish an upper bound D-2 + V-2 <= 1.47 for the experimental parameters reported by Menzel et al. We report new experimental results that agree excellently with these theoretical predictions. The new model enables a detailed quantitative analysis of this surprising result and the fair sampling interpretation of biphotons passing a double slit. (C) 2015 Optical Society of America
Y1  - 2015
U6  - https://doi.org/10.1364/JOSAB.32.001910
SN  - 0740-3224
SN  - 1520-8540
VL  - 32
IS  - 9
SP  - 1910
EP  - 1919
PB  - Optical Society of America
CY  - Washington
ER  - 
TY  - JOUR
A1  - Carpi, Federico
A1  - Anderson, Iain
A1  - Bauer, Siegfried
A1  - Frediani, Gabriele
A1  - Gallone, Giuseppe
A1  - Gei, Massimiliano
A1  - Graaf, Christian
A1  - Jean-Mistral, Claire
A1  - Kaal, William
A1  - Kofod, Guggi
A1  - Kollosche, Matthias
A1  - Kornbluh, Roy
A1  - Lassen, Benny
A1  - Matysek, Marc
A1  - Michel, Silvain
A1  - Nowak, Stephan
A1  - Pei, Qibing
A1  - Pelrine, Ron
A1  - Rechenbach, Bjorn
A1  - Rosset, Samuel
A1  - Shea, Herbert
T1  - Standards for dielectric elastomer transducers
JF  - Smart materials and structures
N2  - Dielectric elastomer transducers consist of thin electrically insulating elastomeric membranes coated on both sides with compliant electrodes. They are a promising electromechanically active polymer technology that may be used for actuators, strain sensors, and electrical generators that harvest mechanical energy. The rapid development of this field calls for the first standards, collecting guidelines on how to assess and compare the performance of materials and devices. This paper addresses this need, presenting standardized methods for material characterisation, device testing and performance measurement. These proposed standards are intended to have a general scope and a broad applicability to different material types and device configurations. Nevertheless, they also intentionally exclude some aspects where knowledge and/or consensus in the literature were deemed to be insufficient. This is a sign of a young and vital field, whose research development is expected to benefit from this effort towards standardisation.
KW  - standard
KW  - dielectric elastomer
KW  - actuator
KW  - electromechanically active polymer
KW  - EAP
KW  - electroactive polymer
KW  - transducer
Y1  - 2015
U6  - https://doi.org/10.1088/0964-1726/24/10/105025
SN  - 0964-1726
SN  - 1361-665X
VL  - 24
IS  - 10
PB  - IOP Publ. Ltd.
CY  - Bristol
ER  - 
TY  - JOUR
A1  - Oberg, H.
A1  - Gladh, Jörgen
A1  - Anniyev, Toyli
A1  - Beye, Martin
A1  - Coffee, Ryan
A1  - Föhlisch, Alexander
A1  - Katayama, T.
A1  - Kaya, Sarp
A1  - LaRue, Jerry
A1  - Mogelhoj, Andreas
A1  - Nordlund, Dennis
A1  - Ogasawara, Hirohito
A1  - Schlotter, William F.
A1  - Sellberg, Jonas A.
A1  - Sorgenfrei, Florian
A1  - Turner, Joshua J.
A1  - Wolf, Martin
A1  - Wurth, W.
A1  - Ostrom, Henrik
A1  - Nilsson, Anders
A1  - Norskov, Jens K.
A1  - Pettersson, Lars G. M.
T1  - Optical laser-induced CO desorption from Ru(0001) monitored with a free-electron X-ray laser: DFT prediction and X-ray confirmation of a precursor state
JF  - Surface science
N2  - We present density functional theory modeling of time-resolved optical pump/X-ray spectroscopic probe data of CO desorption from Ru(0001). The BEEF van der Waals functional predicts a weakly bound state as a precursor to desorption. The optical pump leads to a near-instantaneous (<100 fs) increase of the electronic temperature to nearly 7000 K. The temperature evolution and energy transfer between electrons, substrate phonons and adsorbate is described by the two-temperature model and found to equilibrate on a timescale of a few picoseconds to an elevated local temperature of similar to 2000K. Estimating the free energy based on the computed potential of mean force along the desorption path, we find an entropic barrier to desorption (and by time-reversal also to adsorption). This entropic barrier separates the chemisorbed and precursor states, and becomes significant at the elevated temperature of the experiment (similar to 1.4 eV at 2000 K). Experimental pump-probe X-ray absorption/X-ray emission spectroscopy indicates population of a precursor state to desorption upon laser-excitation of the system (Dell'Angela et al., 2013). Computing spectra along the desorption path confirms the picture of a weakly bound transient state arising from ultrafast heating of the metal substrate. (C) 2015 Elsevier B.V. All rights reserved.
KW  - CO desorption
KW  - Potential of mean force
KW  - Two-temperature model
KW  - Pump-probe
KW  - X-ray spectroscopy
KW  - Density functional theory
Y1  - 2015
U6  - https://doi.org/10.1016/j.susc.2015.03.011
SN  - 0039-6028
SN  - 1879-2758
VL  - 640
SP  - 80
EP  - 88
PB  - Elsevier
CY  - Amsterdam
ER  - 
TY  - JOUR
A1  - Kunnus, Kristjan
A1  - Schreck, Simon
A1  - Föhlisch, Alexander
T1  - Free-electron laser based resonant inelastic X-ray scattering on molecules and liquids
JF  - Journal of electron spectroscopy and related phenomena : the international journal on theoretical and experimental aspects of electron spectroscopy
N2  - The unprecedented beam properties of free-electron laser based X-ray sources enable novel resonant inelastic X-ray scattering (RIXS) experiments. Femtosecond time-resolved RIXS can be used to follow charge, spin and structural dynamics of dilute solute molecules in solution. Ultrashort X-ray pulses allow probing of highly radiation sensitive states of matter such as the metastable phase of supercooled liquid water. Nonlinear X-ray probes like amplified spontaneous emission and stimulated resonant X-ray scattering provide an enhanced selectivity and sensitivity as well as a path to control radiation damage and increase the photon yields in RIXS experiments. (C) 2015 Elsevier B.V. All rights reserved.
KW  - Free-electron laser
KW  - RIXS
KW  - Pump-probe
KW  - Nonlinear X-ray spectroscopy
KW  - Molecules
KW  - Liquids
Y1  - 2015
U6  - https://doi.org/10.1016/j.elspec.2015.08.012
SN  - 0368-2048
SN  - 1873-2526
VL  - 204
SP  - 345
EP  - 355
PB  - Elsevier
CY  - Amsterdam
ER  - 
TY  - JOUR
A1  - Saleem, Hussam
A1  - Downey, Austin
A1  - Laflamme, Simon
A1  - Kollosche, Matthias
A1  - Ubertini, Filippo
T1  - Investigation of Dynamic Properties of a Novel Capacitive-based Sensing Skin for Nondestructive Testing
JF  - Materials evaluation
N2  - A capacitive-based soft elastomeric strain sensor was recently developed by the authors for structural health monitoring applications. Arranged in a network configuration, the sensor becomes a sensing skin, where local deformations can be monitored over a global area. The sensor transduces a change in geometry into a measurable change in capacitance, which can be converted into strain using a previously developed electromechanical model. Prior studies have demonstrated limitations of this electromechanical model for dynamic excitations beyond 15 Hz, because of a loss in linearity in the sensor's response. In this paper, the dynamic behavior beyond 15 Hz is further studied, and a new version of the electromechanical model is proposed to accommodate dynamic strain measurements up to 40 Hz. This behavior is characterized by subjecting the sensor to a frequency sweep and identifying possible sources of nonlinearities beyond 15 Hz. Results show possible frequency dependence of the materials' Poisson's ratios, which are successfully modeled and integrated into the electromechanical model. This demonstrates that the proposed sensor can be used for monitoring and evaluation of structural responses up to 40 Hz, a range covering the vast majority of the dominating frequency responses of civil infrastructures.
KW  - nondestructive testing
KW  - structural health monitoring
KW  - soft elastomeric capacitor
KW  - capacitive sensor
KW  - vibration monitoring
KW  - sensing skin
Y1  - 2015
SN  - 0025-5327
VL  - 73
IS  - 10
SP  - 1390
EP  - 1397
PB  - American Society for Nondestructive Testing
CY  - Columbus
ER  - 
TY  - JOUR
A1  - Shin, Jaeoh
A1  - Cherstvy, Andrey G.
A1  - Kim, Won Kyu
A1  - Metzler, Ralf
T1  - Facilitation of polymer looping and giant polymer diffusivity in crowded solutions of active particles
JF  - New journal of physics : the open-access journal for physics
N2  - We study the dynamics of polymer chains in a bath of self-propelled particles (SPP) by extensive Langevin dynamics simulations in a two-dimensional model system. Specifically, we analyse the polymer looping properties versus the SPP activity and investigate how the presence of the active particles alters the chain conformational statistics. We find that SPPs tend to extend flexible polymer chains, while they rather compactify stiffer semiflexible polymers, in agreement with previous results. Here we show that higher activities of SPPs yield a higher effective temperature of the bath and thus facilitate the looping kinetics of a passive polymer chain. We explicitly compute the looping probability and looping time in a wide range of the model parameters. We also analyse the motion of a monomeric tracer particle and the polymer's centre of mass in the presence of the active particles in terms of the time averaged mean squared displacement, revealing a giant diffusivity enhancement for the polymer chain via SPP pooling. Our results are applicable to rationalising the dimensions and looping kinetics of biopolymers at constantly fluctuating and often actively driven conditions inside biological cells or in suspensions of active colloidal particles or bacteria cells.
KW  - diffusion
KW  - active transport
KW  - polymers
Y1  - 2015
U6  - https://doi.org/10.1088/1367-2630/17/11/113008
SN  - 1367-2630
VL  - 17
PB  - IOP Publ. Ltd.
CY  - Bristol
ER  - 
TY  - JOUR
A1  - Goychuk, Igor
T1  - Modeling magnetosensitive ion channels in the viscoelastic environment of living cells
JF  - Physical review : E, Statistical, nonlinear and soft matter physics
N2  - We propose and study a model of hypothetical magnetosensitive ionic channels which are long thought to be a possible candidate to explain the influence of weak magnetic fields on living organisms ranging from magnetotactic bacteria to fishes, birds, rats, bats, and other mammals including humans. The core of the model is provided by a short chain of magnetosomes serving as a sensor, which is coupled by elastic linkers to the gating elements of ion channels forming a small cluster in the cell membrane. The magnetic sensor is fixed by one end on cytoskeleton elements attached to the membrane and is exposed to viscoelastic cytosol. Its free end can reorient stochastically and subdiffusively in viscoelastic cytosol responding to external magnetic field changes and can open the gates of coupled ion channels. The sensor dynamics is generally bistable due to bistability of the gates which can be in two states with probabilities which depend on the sensor orientation. For realistic parameters, it is shown that this model channel can operate in the magnetic field of Earth for a small number (five to seven) of single-domain magnetosomes constituting the sensor rod, each of which has a typical size found in magnetotactic bacteria and other organisms or even just one sufficiently large nanoparticle of a characteristic size also found in nature. It is shown that, due to the viscoelasticity of the medium, the bistable gating dynamics generally exhibits power law and stretched exponential distributions of the residence times of the channels in their open and closed states. This provides a generic physical mechanism for the explanation of the origin of such anomalous kinetics for other ionic channels whose sensors move in a viscoelastic environment provided by either cytosol or biological membrane, in a quite general context, beyond the fascinating hypothesis of magnetosensitive ionic channels we explore.
Y1  - 2015
U6  - https://doi.org/10.1103/PhysRevE.92.042711
SN  - 1539-3755
SN  - 1550-2376
VL  - 92
IS  - 4
PB  - American Physical Society
CY  - College Park
ER  - 
TY  - JOUR
A1  - Weilbacher, Peter Michael
A1  - Monreal-Ibero, Ana
A1  - Kollatschny, Wolfram
A1  - Ginsburg, Adam
A1  - McLeod, Anna F.
A1  - Kamann, Sebastian
A1  - Sandin, Christer
A1  - Palsa, Ralf
A1  - Wisotzki, Lutz
A1  - Bacon, Roland
A1  - Selman, Fernando
A1  - Brinchmann, Jarle
A1  - Caruana, Joseph
A1  - Kelz, Andreas
A1  - Martinsson, Thomas
A1  - Pecontal-Rousset, Arlette
A1  - Richard, Johan
A1  - Wendt, Martin
T1  - A MUSE map of the central Orion Nebula (M 42)
JF  - Astronomy and astrophysics : an international weekly journal
N2  - We present a new integral field spectroscopic dataset of the central part of the Orion Nebula (M 42), observed with the MUSE instrument at the ESO VLT. We reduced the data with the public MUSE pipeline. The output products are two FITS cubes with a spatial size of similar to 5'9 x 4'9 (corresponding to similar to 0.76 x 0.63 pc(2)) and a contiguous wavelength coverage of 4595 ... 9366 angstrom, spatially sampled at 0 ''.2. We provide two versions with a sampling of 1.25 angstrom and 0.85 angstrom in dispersion direction. Together with variance cubes these files have a size of 75 and 110 GiB on disk. They are the largest integral field mosaics to date in terms of information content. We make them available for use in the community. To validate this dataset, we compare world coordinates, reconstructed magnitudes, velocities, and absolute and relative emission line fluxes to the literature values and find excellent agreement. We derive a 2D map of extinction and present de-reddened flux maps of several individual emission lines and of diagnostic line ratios. We estimate physical properties of the Orion Nebula, using the emission line ratios [N II] and [S III] (for the electron temperature T-e) and [S II] and [Cl III] (for the electron density N-e), and show 2D images of the velocity measured from several bright emission lines.
KW  - H II regions
KW  - ISM: individual objects: M 42
KW  - open clusters and associations: individual: Trapezium cluster
Y1  - 2015
U6  - https://doi.org/10.1051/0004-6361/201526529
SN  - 1432-0746
VL  - 582
PB  - EDP Sciences
CY  - Les Ulis
ER  - 
TY  - JOUR
A1  - Murray, Claire E.
A1  - Stanimirovic, Snezana
A1  - McClure-Griffiths, Naomi M.
A1  - Putman, Mary E.
A1  - Liszt, Harvey S.
A1  - Wong, Tony
A1  - Richter, Philipp
A1  - Dawson, Joanne R.
A1  - Dickey, John M.
A1  - Lindner, Robert R.
A1  - Babler, Brian L.
A1  - Allison, James R.
T1  - First detection of HCO+ absorption in the magellanic system
JF  - The astrophysical journal : an international review of spectroscopy and astronomical physics
N2  - We present the first detection of HCO+ absorption in the Magellanic System. Using the ATCA, we observed nine extragalactic radio continuum sources behind the Magellanic System and detected HCO+ absorption toward one source located behind the leading edge of the Magellanic Bridge. The detection is located at an LSR velocity of v = 214.0 +/- 0.4 km s(-1), with an FWHM of Delta v = 4.5 +/- 1.0 km s(-1), and an optical depth of tau (HCO+) = 0.10 +/- 0.02. Although there is abundant neutral hydrogen (H I) surrounding the sight line in position-velocity space, at the exact location of the absorber the H I column density is low, <10(20) cm(-2), and there is little evidence for dust or CO emission from Planck observations. While the origin and survival of molecules in such a diffuse environment remain unclear, dynamical events such as H I flows and cloud collisions in this interacting system likely play an important role.
KW  - ISM: molecules
KW  - ISM: structure
KW  - Magellanic Clouds
Y1  - 2015
U6  - https://doi.org/10.1088/0004-637X/808/1/41
SN  - 0004-637X
SN  - 1538-4357
VL  - 808
IS  - 1
PB  - IOP Publ. Ltd.
CY  - Bristol
ER  - 
TY  - JOUR
A1  - Krüsemann, Henning
A1  - Godec, Aljaz
A1  - Metzler, Ralf
T1  - Ageing first passage time density in continuous time random walks and quenched energy landscapes
JF  - Journal of physics : A, Mathematical and theoretical
N2  - We study the first passage dynamics of an ageing stochastic process in the continuous time random walk (CTRW) framework. In such CTRW processes the test particle performs a random walk, in which successive steps are separated by random waiting times distributed in terms of the waiting time probability density function Psi (t) similar or equal to t(-1-alpha) (0 <= alpha <= 2). An ageing stochastic process is defined by the explicit dependence of its dynamic quantities on the ageing time t(a), the time elapsed between its preparation and the start of the observation. Subdiffusive ageing CTRWs with 0 < alpha < 1 describe systems such as charge carriers in amorphous semiconducters, tracer dispersion in geological and biological systems, or the dynamics of blinking quantum dots. We derive the exact forms of the first passage time density for an ageing subdiffusive CTRW in the semi-infinite, confined, and biased case, finding different scaling regimes for weakly, intermediately, and strongly aged systems: these regimes, with different scaling laws, are also found when the scaling exponent is in the range 1 < alpha < 2, for sufficiently long ta. We compare our results with the ageing motion of a test particle in a quenched energy landscape. We test our theoretical results in the quenched landscape against simulations: only when the bias is strong enough, the correlations from returning to previously visited sites become insignificant and the results approach the ageing CTRW results. With small bias or without bias, the ageing effects disappear and a change in the exponent compared to the case of a completely annealed landscape can be found, reflecting the build-up of correlations in the quenched landscape.
KW  - first passage
KW  - random walks
KW  - anomalous diffusion
Y1  - 2015
U6  - https://doi.org/10.1088/1751-8113/48/28/285001
SN  - 1751-8113
SN  - 1751-8121
VL  - 48
IS  - 28
PB  - IOP Publ. Ltd.
CY  - Bristol
ER  - 
TY  - JOUR
A1  - Muraveva, Tatiana
A1  - Palmer, Max
A1  - Clementini, Gisella
A1  - Luri, Xavier
A1  - Cioni, Maria-Rosa L.
A1  - Moretti, Maria Ida
A1  - Marconi, Marcella
A1  - Ripepi, Vincenzo
A1  - Rubele, Stefano
T1  - New near-infrared period-luminosity-metallicity relations for RR lyrae stars and the outlock for GAIA
JF  - The astrophysical journal : an international review of spectroscopy and astronomical physics
N2  - We present results of the analysis of 70 RR Lyrae stars located in the bar of the Large Magellanic Cloud (LMC). Combining the spectroscopically determined metallicity of these stars from the literature with precise periods from the OGLE III catalog and multi-epoch K-s photometry from the VISTA survey of the Magellanic Clouds system, we derive a new near-infrared period-luminosity-metallicity (PLKsZ) relation for RR Lyrae variables. In order to fit the relation we use a fitting method developed specifically for this study. The zero-point of the relation is estimated two different ways: by assuming the value of the distance to the LMC and by using Hubble Space Telescope parallaxes of five RR Lyrae stars in the Milky Way (MW). The difference in distance moduli derived by applying these two approaches is similar to 0.2 mag. To investigate this point further we derive the PL(Ks)Z relation based on 23 MW RR Lyrae stars that had been analyzed in Baade-Wesselink studies. We compared the derived PL(Ks)Z relations for RR Lyrae stars in the MW and LMC. Slopes and zero-points are different, but still consistent within the errors. The shallow slope of the metallicity term is confirmed by both LMC and MW variables. The astrometric space mission Gaia is expected to provide a huge contribution to the determination of the RR Lyrae PL(Ks)Z relation; however, calculating an absolute magnitude from the trigonometric parallax of each star and fitting a PL(Ks)Z relation directly to period and absolute magnitude leads to biased results. We present a tool to achieve an unbiased solution by modeling the data and inferring the slope and zero-point of the relation via statistical methods.
KW  - astrometry
KW  - distance scale
KW  - Magellanic Clouds
KW  - methods: data analysis
KW  - stars: statistics
KW  - stars: variables: RR Lyrae
Y1  - 2015
U6  - https://doi.org/10.1088/0004-637X/807/2/127
SN  - 0004-637X
SN  - 1538-4357
VL  - 807
IS  - 2
PB  - IOP Publ. Ltd.
CY  - Bristol
ER  - 
TY  - JOUR
A1  - Dieterich, Peter
A1  - Klages, Rainer
A1  - Chechkin, Aleksei V.
T1  - Fluctuation relations for anomalous dynamics generated by time-fractional Fokker-Planck equations
JF  - New journal of physics : the open-access journal for physics
N2  - Anomalous dynamics characterized by non-Gaussian probability distributions (PDFs) and/or temporal long-range correlations can cause subtle modifications of conventional fluctuation relations (FRs). As prototypes we study three variants of a generic time-fractional Fokker-Planck equation with constant force. Type A generates superdiffusion, type B subdiffusion and type C both super-and subdiffusion depending on parameter variation. Furthermore type C obeys a fluctuation-dissipation relation whereas A and B do not. We calculate analytically the position PDFs for all three cases and explore numerically their strongly non-Gaussian shapes. While for type C we obtain the conventional transient work FR, type A and type B both yield deviations by featuring a coefficient that depends on time and by a nonlinear dependence on the work. We discuss possible applications of these types of dynamics and FRs to experiments.
KW  - fluctuation relations
KW  - anomalous diffusion
KW  - stochastic processes
KW  - stochastic thermodynamics
KW  - Fokker-Planck equations
Y1  - 2015
U6  - https://doi.org/10.1088/1367-2630/17/7/075004
SN  - 1367-2630
VL  - 17
PB  - IOP Publ. Ltd.
CY  - Bristol
ER  - 
TY  - JOUR
A1  - Sandev, Trifce
A1  - Chechkin, Aleksei V.
A1  - Kantz, Holger
A1  - Metzler, Ralf
T1  - Diffusion and fokker-planck-smoluchowski equations with generalized memory kernel
JF  - Fractional calculus and applied analysis : an international journal for theory and applications
N2  - We consider anomalous stochastic processes based on the renewal continuous time random walk model with different forms for the probability density of waiting times between individual jumps. In the corresponding continuum limit we derive the generalized diffusion and Fokker-Planck-Smoluchowski equations with the corresponding memory kernels. We calculate the qth order moments in the unbiased and biased cases, and demonstrate that the generalized Einstein relation for the considered dynamics remains valid. The relaxation of modes in the case of an external harmonic potential and the convergence of the mean squared displacement to the thermal plateau are analyzed.
KW  - continuous time random walk (CTRW)
KW  - Fokker-Planck-Smoluchowski equation
KW  - Mittag-Leffler functions
KW  - anomalous diffusion
KW  - multi-scaling
Y1  - 2015
U6  - https://doi.org/10.1515/fca-2015-0059
SN  - 1311-0454
SN  - 1314-2224
VL  - 18
IS  - 4
SP  - 1006
EP  - 1038
PB  - De Gruyter
CY  - Berlin
ER  - 
TY  - JOUR
A1  - Bauer, Maximilian
A1  - Rasmussen, Emil S.
A1  - Lomholt, Michael A.
A1  - Metzler, Ralf
T1  - Real sequence effects on the search dynamics of transcription factors on DNA
JF  - Scientific reports
N2  - Recent experiments show that transcription factors (TFs) indeed use the facilitated diffusion mechanism to locate their target sequences on DNA in living bacteria cells: TFs alternate between sliding motion along DNA and relocation events through the cytoplasm. From simulations and theoretical analysis we study the TF-sliding motion for a large section of the DNA-sequence of a common E. coli strain, based on the two-state TF-model with a fast-sliding search state and a recognition state enabling target detection. For the probability to detect the target before dissociating from DNA the TF-search times self-consistently depend heavily on whether or not an auxiliary operator (an accessible sequence similar to the main operator) is present in the genome section. Importantly, within our model the extent to which the interconversion rates between search and recognition states depend on the underlying nucleotide sequence is varied. A moderate dependence maximises the capability to distinguish between the main operator and similar sequences. Moreover, these auxiliary operators serve as starting points for DNA looping with the main operator, yielding a spectrum of target detection times spanning several orders of magnitude. Auxiliary operators are shown to act as funnels facilitating target detection by TFs.
Y1  - 2015
U6  - https://doi.org/10.1038/srep10072
SN  - 2045-2322
VL  - 5
PB  - Nature Publ. Group
CY  - London
ER  - 
TY  - JOUR
A1  - Lu, Guanghao
A1  - Koch, Norbert
A1  - Neher, Dieter
T1  - In-situ tuning threshold voltage of field-effect transistors based on blends of poly(3-hexylthiophene) with an insulator electret
JF  - Applied physics letters
N2  - Blending the conjugated polymer poly(3-hexylthiophene) (P3HT) with the insulating electret polystyrene (PS), we show that the threshold voltage V-t of organic field-effect transistors (OFETs) can be easily and reversely tuned by applying a gate bias stress at 130 degrees C. It is proposed that this phenomenon is caused by thermally activated charge injection from P3HT into PS matrix, and that this charge is immobilized within the PS matrix after cooling down to room temperature. Therefore, room-temperature hysteresis-free FETs with desired V-t can be easily achieved. The approach is applied to reversely tune the OFET mode of operation from accumulation to depletion, and to build inverters. (C) 2015 AIP Publishing LLC.
Y1  - 2015
U6  - https://doi.org/10.1063/1.4928554
SN  - 0003-6951
SN  - 1077-3118
VL  - 107
IS  - 6
PB  - American Institute of Physics
CY  - Melville
ER  -